text
stringlengths 1
6.27k
| id
int64 0
3.07M
| raw_id
stringlengths 2
9
| shard_id
int64 0
0
| num_shards
int64 16
16
|
|---|---|---|---|---|
as oxaliplatin, to inhibit colorectal cancer cell proliferation. 409 Hypoxia in the TME provides a special environment for the effects of some drugs, called hypoxia-activated prodrugs (HAPs). 395 For instance, evofosfamide (TH-302) and tarloxotinib-effector inhibited cancer growth by suppressing signaling and cell proliferation in patient-derived cancer cells in vitro and in mouse xenograft models. 410,411 However, there is controversy in the clinical treatment of advanced soft tissue sarcoma. 412,413 Mechanistically, DNA dioxygenase ten-eleven translocation (TET)2 is recruited by Fig. 8 Hypoxia enhances the ability of the tumor to resist radiotherapy. Radiotherapy induces cancer cell death by directly damaging DNA through the production of free radicals such as OH• and H•. SPINK1, secreted by hypoxic cancer cells, upregulates EGFR and NRF2 antioxidant response in adjacent cancer cells to reduce radiation-induced DNA damage, thereby inducing cancer radioresistance. VEGF, FGF and PDGF secreted by hypoxic cancer cells enhanced the radiation resistance of ECs. HIF-1α stimulates DNA-PK expression and repairs DNA DSB Fig. 7 Hypoxia enhances tumor chemotherapy resistance. IL-6 stimulates HIF-1α expression, which increases PGP expression through upregulation of miR-27a. Chemotherapeutic agents are transported by HIF-1α-induced intracellular MRP1 and excreted from cells via PGP and BCRP. HIF-1α induces OLFM4 to enhance cancer cell chemoresistance. HIF-1α enhances chemotherapeutic resistance in cancer cells by promoting PKM1, enhancing mitochondrial OXPHOS. Under hypoxic conditions, cancer cells induce enhanced autophagy and inhibit the chemotherapeutic drug-induced BNIP3 death pathway to resist drug toxicity. HIF-1α synergizes with TGF-β to promote GLI2 expression through SMAD3, inducing cancer cell stemness and chemoresistance. HIF-2α upregulation promotes the ability of
| 1,100 |
256905742
| 0 | 16 |
hypoxic cancer cells to resist drug toxicity by activating the TGF-α/EGFR pathway and COX-2. In addition, CDD and SLC play important roles in the drug resistance of cancer cells, the effect of hypoxic conditions on CDD and SLC is unclear the transcription factor (HNF4α) to activate FBP1 expressions, thereby antagonizing the functions of HIF-1/2α) in metabolic reprogramming to suppress clear cell renal cell carcinoma growth. 414 Clinical trials regarding hypoxia-targeted therapy are summarized in Table 2. These clinical trials were designed using hypoxia tracers, hypoxia-activated prodrugs, and drugs targeting HIF and downstream targets. Hypoxia tracers can visualize and quantify tumor hypoxia, assisting clinicians in the non-invasive detection and assessment of tumor hypoxia levels, and with the aid of PET imaging can be used to monitor the dynamic response of patients to treatment, potentially allowing for individualized patient treatment. 415,416 Hypoxia-activated prodrugs can selectively target hypoxic tumor cells, have hypoxia-selective cytotoxicity, and exhibit broad antitumor activity. 412,417,418 HIF and downstream gene-targeted drugs effectively inhibited tumor even, significantly improved patient survival, and phenocopied better tolerability. [419][420][421] However, these drugs have certain toxic side effects, and common adverse events include headache, fatigue, nausea, vomiting, diarrhea and dehydration, and serious adverse events include Gastrointestinal bleeding, blood clots/deep vein thrombosis, lymphocytopenia, febrile neutropenia, anemia and triggering secondary infections. Some clinical trials do not have sufficient data to analyze the safety and efficacy of drugs. Hypoxia and immunotherapy Hypoxia inhibits anti-cancer immune sensitivity. 422 Reduction of the hypoxic environment in the TME increases the efficacy of immune checkpoint blockade (ICB) against cancers
| 1,101 |
256905742
| 0 | 16 |
in vivo. The rational use of the pulsatile system of the TME can ameliorate hypoxia. Increasing the oxygen partial pressure through intravenous oxygenation can reverse hypoxia in the TME. 423 However, some of the vessels in cancer are abnormal and non-functional. Therefore, vascular remodeling in the TME is necessary to ameliorate hypoxia. Elevated levels of Delta-like 1 (DLL1) in breast and lung cancer induce long-term cancer vascular normalization to alleviate cancer hypoxia, promote the accumulation of IFN-γexpressing CD8 + T cells, and enhance macrophage polarization toward the M1-phenotype. 424 Hyperoxia upregulates MHC-I expression in cancer cells, enhances T cell-mediated cytotoxicity, 398 promotes the anti-cancer activities of NK cells, 235 reduces the immunosuppressive effects of Tregs in the TME, and inhibits the production of MDSC-derived exosomes to reduce cancer cell stemness. 235,281 Pro-oxidants can also be used to increase oxygen levels in the TME. Wu et al. 396 developed nanoparticle-stabilized oxygen microcapsules that could be precisely targeted to pancreatic ductal adenocarcinoma (PDAC), improving hypoxia and significantly increasing the efficacy of anti-PD-1 antibodies against PDAC. Treatment with oxygen microcapsules combined with anti-PD-1 antibodies alleviates TAM infiltration, polarizes macrophages from the pro-cancer M2 phenotype to the anticancer M1 phenotype, and increases the proportion of TME Th1 cells and CTLs to enhance anti-cancer immune effects. 396 The oxygenating agent (TH-302) eliminates hypoxia in cancers and promotes T-cell infiltration. 425 The pro-oxidant adaptor (p66SHC) reduces ATP production in B cells by limiting glycolysis and compromising mitochondrial integrity, while activating AMPK to promote B cell mitochondrial autophagy and limiting plasma cell differentiation.
| 1,102 |
256905742
| 0 | 16 |
426 Suppression of HIF pathway-mediated PD-L1 is an important measure for enhancing cancer immune responses. Inhibition of HIF-1α synthesis suppresses PD-L1 expression and induces lysosomal degradation of PD-L1, enhancing the ability of CTLs to kill cancer cells. 427 The deletion of HIF-1α in NK cells significantly inhibits cancer growth and improves patient survival outcomes by activating the NF-κB pathway and stimulating the expression of effector molecules, such as IL-18. 428 Single inhibition of HIF-1α in immune cells restores immune cytotoxicity; however, it also induces PD-L1 expression in cancer cells, impairing anticancer immunity. 234 Therefore, multichannel combination therapy is vital for cancer treatment. Hypoxia leads to the increased expression of immune checkpoints and promotes fibrosis, thereby suppressing the efficacy of cancer immunotherapy. Increasing the oxygen concentration affects cancer immune responses by altering the extracellular matrix. For instance, hyperbaric oxygen (HBO) promotes PD-1 antibody delivery and T cell infiltration into the cancer parenchyma by depleting major components of the extracellular matrix, such as collagen and fibronectin. 429 Genetic engineering approaches can be used to construct high-affinity NK (haNK) cells, which can express highaffinity CD16 receptors and IL-2, improve tolerance against acute hypoxia, and maintain the functions of NK cells to kill cancer cells. 430 Hypoxia and radiotherapy Radiotherapy is a non-invasive oncologic treatment approach for drug-resistant cancers. 431 It is based on the principle of targeting cancer tissues with X-rays or gamma rays, which directly or indirectly damage biomolecules to ionize the surrounding water and generate ROS, inducing DNA damage and apoptosis. 432,433 Oxygen in the TME can
| 1,103 |
256905742
| 0 | 16 |
anchor broken ends of DNA and form stable organic peroxide groups that inhibit further DNA repair. 434 However, local hypoxia in the TME markedly reduces the therapeutic efficacy of radiation therapy. In addition, radiotherapy requires high doses of X-rays to treat cancers, which can cause serious side effects. 435 By utilizing the sustainable production of O 2 from endogenous H 2 O 2 decomposition, cancer hypoxia can be improved and the efficacy of radiotherapy is enhanced. 436 Chai et al. found that under continuous external irradiation with a 660 nm laser and X-ray beams, cyanobacteria continuously photosynthesized and released oxygen, and the large amount of ROS produced by the two-dimensional (2D) bismuth radiosensitizer greatly enhanced the efficacy of radiation therapy and inhibited cancer growth in vivo. 437 Improving hypoxia increases the sensitivity of cancer cells to radiotherapy, 437 which may be related to HIF-1α inhibition in cancer cells by changing the optical redox status. 438 The mechanisms involved in hypoxia-induced tolerance to radiotherapy in cancer cells should be investigated further. Nano application therapy Nanoparticles are characterized by small sizes, large surface areas, high bioavailability, and good biocompatibility, and have great potential for safely and efficiently transporting external oxygen to the hypoxic TME. 439 The nanocomposite "oxygen bomb" PSPP-Au980-D is used to precisely locate the hypoxic microenvironment of pancreatic cancer, and through different nm laser irradiation, it can improve hypoxia, generate singlet oxygen, and enhance the efficacy of photodynamic therapy (PDT). 440 The use of an acidic microenvironment to generate oxygen is a feasible method. For instance,
| 1,104 |
256905742
| 0 | 16 |
an acidic environment triggers a reaction between MnO 2 and H 2 O 2 , releasing large amounts of oxygen to alleviate intratumoral hypoxia. Fragmented human-induced pluripotent stem cells (iPSCs) release cancer-sharing antigens, which trigger strong innate and adaptive immune responses against cancers, promote dendritic cell maturation, and activate effector T and NK cells. Meanwhile, they also decreased the amount of Treg cells. iPS-MnO2@Ce6 significantly inhibited cancer growth, metastasis and reduced mortality in cancer-bearing mice models. 441 Nanoparticles can also host various drugs, such as oxygenating agents, chemotherapeutic agents and immune-boosting drugs, improving the anti-cancer effects. 442 Manganese dioxide based nanocarriers can enhance the anticancer effects of piggyback paclitaxel by alleviating the degree of hypoxia in the in situ glioma microenvironment. 442 Porous Au@Pt core-shell nanostructures inhibit the expressions of HIF-1α and MDR1 gene by oxidizing the TME, thereby reducing the extracellular secretion of adriamycin (DOX) and enhancing the efficacy of chemophotothermal therapy. 443 When hybrid nanospheres containing Fe 3+ , aggregation-induced emission (AIE) photosensitizer, and Bcl-2 inhibitor of sabutoclax were consumed by cancer cells, they increased intratumoral oxygen concentration through Fe 3+mediated Fenton reactions, and intracellular PDT resistance of the AIE photosensitizer was mitigated by sabutoclax. 444 Remodeling the tumor immune microenvironment by nanoparticle technology can achieve efficient cancer therapy. Mesoporous silica nanoparticles (MSNs) in combination with pro-oxidants and mitochondrial respiration inhibitors can alleviate the hypoxic environment and inhibit MDSCs infiltration. 445 TK-M@Man-HMPB/ HCQ alleviated hypoxic microenvironment-induced TAM polarization, promoted CTL infiltration, and significantly inhibited cancer growth. 446 Novel poly (vinylpyrrolidone) (PVP)-modified BiFeO3/ Bi2 WO6
| 1,105 |
256905742
| 0 | 16 |
(BFO/BWO) with a p-n type heterojunction reshapes the immunosuppressive TME. It triggers H 2 O 2 catabolism to generate O 2 to alleviate cancer hypoxia, enhance PDT and radiotherapy sensitivity, promote TAM polarization from the M2 to the M1 phenotype, and inhibit HIF-1α expression. This photo-activated nanoconjugated radiotherapy can activate and recruit T cells and stimulate TAMs toward the M1 phenotype, significantly reversing the immunosuppressive TME to immunoreactive TME and further enhancing the immune memory response. 447 Advances in nanotechnology to improve the hypoxic TME, or to combine chemotherapy, radiotherapy, and immunotherapy, have achieved satisfactory outcomes, compared to traditional treatments, and may become a treatment measure with great potential in the future. Biotherapy Accumulating evidence suggests that microbiota play an important role in cancer by damaging cellular DNA, inducing transformation, activating and altering stromal cell components in the TME, and influencing cellular metabolism. 448,449 The microbiota characteristics under hypoxic conditions are currently not fully understood. Recent research has demonstrated that a combination of live bacteria and treatment modalities such as surgery, chemotherapy, and radiotherapy can produce good clinical outcomes. Certain bacteria have the potential to gravitate to the hypoxic core of cancer cells and can spread and proliferate. Spores of the anaerobic bacterium Clostridium novyi-NT were used to treat the transplanted tumors in mice. In several mouse models including colorectal cancer, biliary cancer, melanoma and squamous cell carcinoma, this bacterium was found to significantly improve the efficacy of radiotherapy. 450 The use of the attenuated pathogenic anaerobe Salmonella VNP20009 to target the cancer hypoxic region, equipped
| 1,106 |
256905742
| 0 | 16 |
with photosensitizers and bromodomain and extra terminal domain (BET) protein inhibitors with mitochondrial targeting properties improved the heat elimination abilities of photothermal therapy (PTT) and significantly inhibited the expressions of PD-L1 in cancer cells, thereby enhancing and maintaining a durable immune response. 451 Bioluminescent bacteria designed by transforming attenuated Salmonella typhimurium strains effectively increased PDT and promoted inflammation by converting macrophages M2 to M1, activated NK cells, CD4 + Th cells and CD8 + T cells in the TME, reduced intratumoral immunosuppressive Tregs, and upregulated the expressions of various effector cytokines. 452 Salmonella preferentially localizes sites and proliferates in hypoxic cancers, due to this advantage, Salmonella is also used as a cancer targeting vector to deliver different therapeutic agents and to achieve synergistic anticancer effects. However, colonized Salmonella recruits a large number of neutrophils, thus favoring cancer growth. 315,316 The elimination of Salmonella-recruited neutrophils facilitates complete cancer eradication and reduces side effects. 453 Delivery of peroxidase is an effective strategy for reducing resistance to radiotherapy. The peroxidase membrane vesicles (EMs) of Escherichia coli have higher peroxidase activity than free peroxidase, which decomposes H 2 O 2 into oxygen to alleviate cancer hypoxia. Combined with their immunostimulatory properties, EMs can effectively enhance the effects of radiation therapy and induce anticancer immune memory. 391 Maximizing the use of live bacteria under hypoxic conditions has the potential to be a therapeutic modality for the treatment of cancer. CONCLUSIONS AND PERSPECTIVES Over the last 60 years, extensive progress has been made in the understanding of hypoxia-mediated signaling pathways. Hypoxiabased research
| 1,107 |
256905742
| 0 | 16 |
has provided new insights into how hypoxia works and has laid the foundation for the development of targeted therapies that can improve patient prognosis. Carcinogenic factors and mature cancer characteristics promote hypoxia in the TME, and cancer cells adapt to hypoxia by changing their own metabolism through key genes such as HIFs. With advances in analytical tools and genomic technologies, such as pan-genomic analysis, are important for in-depth studies of HIFs. 454,455 Hypoxiainduced pathways can alter the malignant behavior of cancer cells. Under hypoxic conditions, most downstream targets are HIFdependent. Whether there are other key genes independent of HIFs requires further investigation. For instance, hypoxia-induced RNA editing by endogenous RNA editing enzyme can be mimicked by inhibiting mitochondrial respiration and occurs independently of HIF-1α to facilitate adaptation to hypoxic stress. 225 Moreover, hypoxia reshapes the stromal cell properties of the TME, especially with the rise of immunotherapy, and both innate and adaptive immune cells in hypoxic environments have received extensive attention. However, despite significant breakthroughs, some results remain controversial. The reasons for this may be related to tissue specificity in addition to the experimental tools used and design bias, and mature modeling is also critical. The composition of the TME is diverse, and in addition to its own components, other foreign components may be present, such as microbiota, an emerging field that plays an important role in various cancers. Microbiota in the TME is one of the factors that form and maintain chronic hypoxia, activates HIF-1α in a nonhypoxic manner, increases HIF-1α mRNA levels, stabilizes HIF-1α
| 1,108 |
256905742
| 0 | 16 |
protein, and induces the expression of HIF-1α regulatory genes. 288,456,457 Changes in the characteristics of the microbiota in hypoxic environments and their effects on tumors are interesting and deserve further exploration. Therapeutic measures based on these characteristics, including targeted therapy, immunotherapy, chemotherapy, radiotherapy, radiotherapy, and biotherapy, offer good prospects. However, the complexity of the tumor relationship makes it inefficient to treat cancer from a single perspective. Multidisciplinary combination therapy, such as biology, chemistry, materials, machinery, electronics, artificial intelligence, and other multidisciplinary approaches for cancer (especially refractory cancer), is an interesting trend. Extensive study is still required before the development and implementation of efficacious and robust hypoxia-related precision treatment. ADDITIONAL INFORMATION Competing interests: The authors declare no competing interests. Ethics declarations: Not applicable.
| 1,109 |
256905742
| 0 | 16 |
Positive site selection bias in meta-analyses comparing natural regeneration to active forest restoration Selection bias calls into question whether natural regeneration is really more successful than active tropical forest restoration. How and where to restore tropical forests have become topics of global importance for addressing the interrelated challenges of climate change, biodiversity loss, and desertification (1)(2)(3). A suite of recent meta-analyses have attempted to advance the state of the science by comparing active forest restoration or reforestation approaches (for example, tree planting) to natural regeneration (that is, forest regeneration with little or no intervention by humans) (4)(5)(6). On the basis of comparisons across many studies, these meta-analyses find little to no advantage in actively intervening to catalyze forest succession. For example, Crouzeilles et al. (6) determined that naturally regenerated tropical forests have higher plant diversity, tree density, and tree height than forests established by active restoration, and they concluded that tropical forest restoration is more successful using the former approach. However, this and other metaanalytical data sets contain an inherent, positive selection bias for naturally regenerated forests that casts doubt on the robustness of these conclusions. The bias in these meta-analyses arises from a mismatch between the pool of studies that contain data about active forest restoration and the pool of studies that contain data about natural forest regeneration ( Fig. 1). With few exceptions, studies of natural regeneration and active restoration have been conducted at separate locations. Most studies evaluating natural regeneration, for instance, occurred in sites where secondary forest was present at the start
| 1,110 |
21706017
| 0 | 16 |
of the study [for example, (7)(8)(9)(10)]. In contrast, active tree planting studies are typically initiated on entirely deforested sites [for example, (11)(12)(13)], including sites that likely would not have established at all without assistance (for example, strip mines). Hence, many natural regeneration studies focus on forests that have already passed through a filter that excludes less resilient, more degraded sites where forest succession would be slow or stalled. Active restoration studies are not exposed to the same site selection filter, so it is hardly surprising that active restoration should perform weakly in meta-analyses when compared to secondary forests that had already established. For example, take a tree plantation where seedlings were planted on degraded agricultural land, and compare that plantation to a 10-yearold secondary forest discovered on post-agricultural land. All else being equal, the plantation has the opportunity to fail to establish, but if the secondary forest had not already established it would never have been considered as a study site. Documented cases of slow or arrested forest succession are widespread throughout the tropics [for example, (14)(15)(16)(17)(18)]. These and other studies attribute slow or stalled recovery to a suite of factors including the severity of prior land use, the distance to propagule sources, and the intrinsic resilience of species that make up a given community (19). Meta-analyses comparing active restoration and natural forest regeneration have sometimes attempted to statistically control for some of these factors, but what limits forest growth at a given site can be idiosyncratic and there may not be enough replication in the
| 1,111 |
21706017
| 0 | 16 |
literature to conduct a rigorous meta-analysis. A few of these factors include soil quality (20,21), fire (22), presence of seed-dispersing animals (23), competition from exotic grasses (24), and herbivory (25). Moreover, statistical controls still fail to establish a counterfactual; a rigorous metaanalysis would have to select only those natural regeneration studies in which failed regeneration was a possibility. In some cases, meta-analyses are further complicated by questionable categorizations of actions that qualify as active restoration or natural regeneration. For instance, Parrota and Knowles (26) heavy machinery to level the overburden and replace 15 cm of topsoil and woody debris from a stockpile. This treatment was considered to be "natural regeneration" by Crouzeilles et al. (6), but without this expensive human intervention, it is doubtful that forest would have regenerated on the bare, mined surface. Likewise, Crouzeilles et al. (6) considered plantations of exotic, agroforestry trees to be active restoration (27,28) and compared these to the rapid, natural regeneration of selectively logged forests (29); neither treatment is widely representative of projects seeking to restore native tropical forests. The complexity of conditions that can influence whether natural regeneration will be slow or stalled highlights the need for paired evaluations of active restoration and natural regeneration at the same site (30). The relatively small number of studies where this has been done highlights the fact that the process of natural regeneration can be highly variable, sometimes producing a secondary forest quickly (31) and sometimes not (32). Similar conclusions are reported from a largescale analysis of >2000 Brazilian forest restoration
| 1,112 |
21706017
| 0 | 16 |
projects spanning nearly 700,000 ha. Comparing passive and active restoration at sites that were all initially deforested, Brancalion et al. (33) found that, although active restoration and natural regeneration both had variable outcomes, tree planting generally increased canopy cover and tree and shrub diversity. Given the discrepancies between meta-analyses and site-based comparisons, definitive evaluation of the effects of tree planting on the pace of tropical forest recovery would benefit from a systematic review using formal quality assessment (34). For restoration practitioners seeking evidence-based management strategies, a take-home message from the empirical literature is that it is often worthwhile to observe natural forest recovery for a year or two to assess if natural regeneration will accomplish management objectives before deciding whether some form of active intervention is needed (19). If an adaptive management process indicates that action is warranted, possible interventions range from low-intensity assisted natural regeneration to higher-intensity plantations (35). Despite the implication by recent meta-analyses that active restoration and natural regeneration are competitive and mutually exclusive strategies, in reality, human interventions to restore tropical forests fall on a continuous gradient of intensity and are often synergistic.
| 1,113 |
21706017
| 0 | 16 |
Finite size effects in the phase transition patterns of coupled scalar field systems It is considered in this work the phase transition patterns for a coupled two-scalar field system model under the combined effects of finite sizes and temperature. The scalar fields are taken as propagating in a D=4 Euclidean space with the usual periodic compactification in the Euclidean time direction (with dimension given by the inverse of the temperature) and also under a compact dimension in the space direction, which is restricted to size L. In the latter case, a Dirichlet boundary condition is considered. Finite-size variation of the critical temperature for the cases of symmetry restoration and inverse symmetry breaking are studied. At fixed finite-temperature values, the variation of the inverse correlation lengths with the size L might display a behavior analogous to reentrant phase transitions. Possible applications of our results to physical systems of interest are also discussed. It is considered in this work the phase transition patterns for a coupled two-scalar field system model under the combined effects of finite sizes and temperature. The scalar fields are taken as propagating in a D = 4 Euclidean space with the usual periodic compactification in the Euclidean time direction (with dimension given by the inverse of the temperature) and also under a compact dimension in the space direction, which is restricted to size L. In the latter case, a Dirichlet boundary condition is considered. Finite-size variation of the critical temperature for the cases of symmetry restoration and inverse symmetry breaking are studied. At fixed
| 1,114 |
254366527
| 0 | 16 |
finite-temperature values, the variation of the inverse correlation lengths with the size L might display a behavior analogous to reentrant phase transitions. Possible applications of our results to physical systems of interest are also discussed. I. INTRODUCTION Studies of phase transitions under different conditions, like temperature, external fields and chemical potential, just to cite a few examples, have always been of relevance. Modeling and describing these phase transitions through effective field theories with, e.g., scalar fields, find applications in a variety of physical systems of interest, ranging from condensed matter to cosmology. Studying the properties of quantum field theory models involving multiple scalar fields and understanding how symmetries change in these models when undergoing phase transitions have gained relevance recently. The reason for this interest is that these type of models can have connections ranging from statistical physics and condensed matter [1][2][3][4][5] to high-energy physics [6][7][8][9][10][11][12][13][14][15][16]. A model that has been of particular interest is a multiple scalar field system with a O(N φ ) × O(N χ ), for a Lagrangian density containing scalar fields φ ≡ (φ 1 , . . . , φ N φ ) and χ ≡ (χ 1 , . . . , χ Nχ ), with N φ and N χ components, respectively. This type of model has long been of interest and have also been studied before in different contexts [17][18][19][20][21][22][23][24][25][26][27][28][29]. Those studies mostly focused on how symmetries in these type of systems change with the temperature. The interest on these type of models derives from the fact
| 1,115 |
254366527
| 0 | 16 |
that they can display a rich phase structure depending on the parameter space available for them. In particular, it is known since the work done by Weinberg in Ref. [30] that nontrivial phase transition patterns can be displayed by these type of models. These phase transitions are, for example, related to inverse symmetry breaking (ISB), i.e., the breaking of symmetries at high temperatures, as well as symmetry nonrestoration (SNR), namely, the persistence of symmetry breaking at high temperatures. In this work, we are interested in investigating the patterns of phase transitions in the above multiple scalar field model, but including the effects of a finite boundary along a space dimension in addition to the known effects of temperature. Studies of finite-size effects in quantum field theory have long been of importance, like, for example, in understanding the questions related to vacuum energy, e.g., in the Casimir energy in different topologies [31][32][33][34][35]. Finitesize effects have also been shown to lead to phase transitions (see, e.g., Ref. [36] and references there in). This can happen since space compactifications work similarly to the introduction of temperature in the Matsubara formalism of finite-temperature quantum field theory in Euclidean spacetime and where the Euclidean time direction is compactified to a finite dimension given by the inverse of the temperature [37]. Space compactifications can then modify the effective masses of the fields in quantum field theory and affect the symmetry properties of these fields [38]. In a practical context, like in most experiments under laboratory conditions, the limitation of the system size
| 1,116 |
254366527
| 0 | 16 |
can produce important boundary effects. The thermodynamic limit in these cases might not give a reliable result and, in fact alter many critical behaviors of the system [39,40]. Likewise, in the studies of heavy ion collisions performed, e.g., at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC), it has been indicated that the mean-free path of quarks and gluons formed is not much smaller than the typical fireball radius [41]. This indicates that the thermodynamics of the quark-gluon plasma (QGP) can have sizable effects from the boundaries of the system and which has motivated many studies of finite-size effects towards understanding their contributions [42][43][44][45][46][47]. In this paper, we will be interested in studying how the introduction of a boundary affects the thermodynamics of a coupled two scalar field system. In particular, we want to focus on the possible emergence of reentrant phases and symmetry persistence in systems of this type. This study complements the many previous studies on similar systems, which, however, up to our knowledge, have not explored how a boundary might eventually affect the phase transition in this context. Even though we do not focus on a particular application, this study arXiv:2212.03336v2 [hep-ph] 29 Mar 2023 might be of relevance in understanding condensed matter systems that can be well modeled by these type of models in an effective description, besides, as already cited earlier, of also being of theoretical interest in general. In the present study, we make use of the nonperturbative resummation of the one-loop order terms, i.e.,
| 1,117 |
254366527
| 0 | 16 |
in the ring (bubble) resummed approximation [48][49][50][51][52]. Similar techniques were also previously used to study ISB and SNR, but in the absence of space boundaries [22,23,27,28]. The results obtained here are also compared in the context of the large-N approximation for the model. For definiteness, we will also consider the case of a Dirichlet boundary condition, which is motivated by both condensed matter type of systems where the wave function vanishes at the surface of the material and does not propagate beyond it. This type of boundary condition has also been claimed to be the appropriate one to consider for finite-size effects on the thermodynamics of the QGP [46]. As an additional advantage of using a Dirichlet boundary condition is that it allows to obtain simple analytical approximate equations, which facilitate the analysis and interpretation of the results. As we are going to show, besides of the ISB and SNR phenomena, behavior analogous to reentrant symmetry breaking, with double transition points, can also manifest when space dimensions are constrained to finite sizes. The remainder of this paper is organized as follows. In Sec. II, we review the basics of ISB/SNR for a O(N φ ) × O(N χ ) invariant relativistic scalar field model in the context of perturbation theory (PT) in the hightemperature approximation. In Sec. III, the self-energy corrections to the fields and that are dependent on the temperature and finite size are derived. The effective masses entering in our calculations are then computed. In Sec. IV the renormalized parameters of the model are
| 1,118 |
254366527
| 0 | 16 |
discussed and the bubble (ring) resummed masses are given along also the tadpole equations that give the expectation values for the fields. Our results are discussed in Sec. V and the possibility of behavior analogous to reentrant phase transitions at high temperatures and under the effects of the boundary are studied. In Sec. VI the large-N approximation is implemented in the model and the results are again compared by varying the number of components for the fields. Finally, in Sec. VII our conclusions are given and possible applications of our results are discussed. II. THE PERTURBATIVE DESCRIPTION OF ISB AND SNR AT FINITE TEMPERATURE The prototype model we consider is that of a O(N φ ) × O(N χ ) invariant relativistic scalar field model, with φ and χ consisting of scalar fields with N φ and N χ components, respectively. The interactions are given by the standard self-interactions among each field species, with quartic couplings λ φ and λ χ , respectively and by a quadratic (inter) cross-coupling λ between φ and χ The Lagrangian density is given by The potential is always bounded for positive couplings, but the overall boundness of the potential is still maintained even when the intercoupling λ is negative, provided that (2.2) and in this case ISB and SNR can emerge at finite temperature, as first shown in the seminal work in Ref. [30]. For instance, restricting to the one-loop approximation and in the high-temperature approximation (m φ /T, m χ /T 1), the thermal masses for the φ and
| 1,119 |
254366527
| 0 | 16 |
χ fields are simply 3) shows that ISB/SNR can emerge for λ < 0, if, for example, m 2 i,j > 0, i.e., we have a symmetric theory at T = 0 in both φ and χ directions initially and ISB can take place in the direction of one of the fields if In this case, the symmetry changing scheme is A natural question to ask is whether these nonusual symmetry patterns at high temperature would not be just artifacts of the naive one-loop approximation and high-temperature approximation. In principle, it could well be the case that higher-order terms could restore the usual SR patterns expected commonly. However, many previous papers using a variety of nonperturbative methods give support for ISB/SNR [19][20][21][22][23][24][25][26][27][28] and also in more recent works, like e.g., in Refs. [12,53,54]. In the next sections we will explore this problem when in addition to temperature, finite-size effects are also included. III. EFFECTIVE MASSES DEPENDENCE ON T AND L We want to extend the above analysis when now there is a compactification in one of the space dimensions. In other words, we want to study the above picture of ISB/SNR when in the presence of finite-size effects. Following the quantum field theory formalism in toroidal topologies [36], the finite-size effects can be included by defining the space in a topology Γ d where D is the space-time dimension and d is the number of compactified dimensions, such that d ≤ D. Let us see how this can be generalized to the present problem. For this,
| 1,120 |
254366527
| 0 | 16 |
let us return to a moment to the one-loop perturbative Eq. (2.3) and express it in terms of the original momentum integrals. In Euclidean D-dimensional momentum space, we then have that where i, j represent either φ or χ. For each compactified dimension, with finite lengths L a , a ≤ d, the corresponding momentum p a in that direction is replaced in terms of discrete frequencies ω na , p a → ω na . The discrete frequencies ω na depend on the boundary condition (BC). Some well know BCs used in the literature under different contexts are, for example, the periodic, antiperiodic, Neumann and Dirichlet boundary conditions. For a periodic BC we have for an antiperiodic BC, for a Neumann BC, while for a Dirichlet BC, The periodic and antiperiodic BCs are well known in the context of quantum field theory at finite temperature, where the (Euclidean) time gets compactified with size L → 1/T , where T is the temperature and the corresponding frequencies are given in terms of the Matsubara's frequencies for bosons (periodic BC) or fermions (antiperiodic BC). Neumann BC applies when, e.g., the derivative of the wave function vanishes at the boundaries, while for Dirichlet BC the wave function (or field) is identically zero at the boundaries and outside the bulk. A Dirichlet boundary condition (DBC) can be seen then like an impenetrable barrier. Thus, for each compactified space dimension, with finite-lengths L a , we can write the momentum integral in the corresponding direction as and for d <
| 1,121 |
254366527
| 0 | 16 |
D compactifications, the momentum integrals, which we will be interested in this work, they are all of the form where ν = α − (D − d)/2, µ is an arbitrary mass regularization scale (in the MS-scheme) and γ E is the Euler-Mascheroni constant. Performing the sum on the right hand side of Eq. (3.8) is arduous in general. However, the job can get simplified by expressing those type of sums in terms of an Epstein-Hurwitz zeta function [35] (3.9) where, for example, we can identify c = m i , a j (j = 1, . . . d) are coefficients that depend on the BCs (see, e.g., Eqs. (3.2)-(3.5)) and ν = α − δ/2. Following, e.g., Ref. [55], we can also express Eq. (3.9) in the form where K α (x) is the modified Bessel function of the second kind. For definiteness, in this work we will focus in the case of boundaries satisfying DBC. With DBC, at the boundaries the fields vanish (i.e., the fields should not "leak" beyond the boundaries). Hence, φ( The discrete frequencies associated with the DBC are then given by Eq. (3.5). Recalling that temperature is accounted for through a periodic compactification (for bosons) in Euclidean time and considering the case of one compactified space dimension using DBC, with length L (i.e., along this work we consider a slab geometry in the three-dimensional space: Note that Eq. (3.11) can also be written as 12) and the last term is then of the form of Eq. (3.10), while the
| 1,122 |
254366527
| 0 | 16 |
first term in Eq. (3.12), under analytic continuation with the zeta-function method, is obtained by using the result [35] n∈Z in the case of DBC is explicitly given by (3.14) The divergent term appearing in Eq. (3.14) is the standard divergence for the two-point Green function for a scalar field in the bulk. Thus, as far as regularization and renormalization are concerned, the (mass square) divergence can be removed by adding the standard counterterm of mass in the vacuum. We note, however, that more generally, when working with finite-size effects at the level of the effective action, additional renormalization counterterms are required as surface divergences also appear [56][57][58]. In the present work we will not have to deal with these more general renormalization and, thus, we will only require the standard renormalization coun-terterms in the bulk (see also Ref. [59] for details on the renormalization under the finite-size effects in general). Thus, by adding to the Lagrangian density Eq. (2.1) the appropriate mass counterterms of renormalization, e.g., by redefining the masses of the fields such that m 2 φ → m 2 φ + δm 2 φ and m 2 χ → m 2 χ + δm 2 χ , the mass counterterms are, respectively, given by and The renormalized masses at one-loop order for the φ and χ fields then become and where I 2,R (m i , T, L) is the result obtained in Eq. (3.14) when the divergence is subtracted. It is also illustrative to work in the approximation of small masses, i.e.,
| 1,123 |
254366527
| 0 | 16 |
m i /T 1 and m i L 1. In this case, it is more convenient to return to Eq. (3.11). Isolating the thermal zero mode (n = 0) from it, we have that n∈Z l1∈N>0 The first term in Eq. (3.19) can be written in a similar form as in Eq. (3.13), which, as also in according to Ref. [35], can be expressed as The second term in Eq. (3.19) can now be written as 2 n∈N>0 l1∈N>0 where in the last part in Eq. (3.21) we have expanded for m i /T 1. We can now use the following result for the twodimensional Epstein zeta-function representation [60] ∞ n1,n2=1 In Eq. (3.22) we can choose a 1 and a 2 to be either 1/(2T L) 2 or 1. Obviously the two choices are completely equivalent, however, in the cases where m i /T 1 and T L > 1/2, the choice a 1 = 1/(2T L) 2 and a 2 = 1 turns out to be the suitable one, as it display better convergence properties in this case. Alternatively, we could also make the expansion in terms of m i L 1, which then the choice a 1 = 1 and a 2 = 1/(2T L) 2 is the one that will exhibit better convergence properties when T L < 1/2. Given this, in practice, in all our numerical results, we work with an interpolated version of these expressions, favoring one case or the other depending on the value of T L. This strategy
| 1,124 |
254366527
| 0 | 16 |
is similar to the one used in Ref. [46]. Using the above expressions, we then obtain the small masses expansions for Eq. (3.14) and, when |m i |/T 1 and T L ≥ 1/2 and keeping terms up to quadratic order in the masses, it is explicitly given by while for |m i |L 1 and T L < 1/2, we have that where in the above expressions η(x) is the Dedekind eta function, defined as [61] η(x) = e iπx/12 As a cross-check of Eq. (3.23), let us consider the bulk limit L → ∞ of it. Using the identities, which is the correct expression for the thermal integral I (1) in the high-temperature approximation [62]. It is also useful to work the limiting case where Eq. (3.24) applies. Considering now the different dimensional parameters satisfy m T 1/L and applying again the identities (3.26) and (3.27) now to Eq. (3.24), we obtain The limiting case shown in Eq. (3.28), by dropping the divergent and mass dependent terms, leads automatically to the perturbative quadratic mass as given by Eq. (2.3). On the other hand, for m T 1/L, we get similarly that (3.30) Hence, the roles played by T and L get reversed. Therefore, we expect that for sufficiently small values for L, an initially broken symmetry will get restored whenever As an immediate consequence of the behavior of I (1),DBC 2,R as a function of T and L will be the possibility of having behavior analogous to reentrant phase transitions as we will demonstrate
| 1,125 |
254366527
| 0 | 16 |
in Sec. V. IV. RENORMALIZED MASSES AND COUPLINGS AND RESUMMATION PROCEDURE Let us discuss in this section both the dependence of the renormalized masses and couplings with the scale and also the resummation procedure we have adopted to analyze the phase transition patterns at both finite temperature and size. A. Dependence of the masses and couplings with the renormalization scale Before presenting our results, let us discuss the dependence of the masses and coupling in our model with the renormalization scale µ. As already mentioned in the previous section, it is enough for us here to work the renormalization of the system in the bulk. Working at the one-loop level, the renormalized masses and coupling constants can then be readily computed (see, for instance Ref. [63]) and they are given by with the above equations depending on the renormalization scale µ through the MS parameters of the renormalized Lagrangian. Note that in the above equations we are expressing all bare quantities (which does not depend on the scale µ), and that appears on the right-hand side of the equations, as a barred quantity. The renormalized parameters, on the other hand, are all dependent on the scale µ. Finally, note that the above equations apply to the symmetry restored case wherem 2 i > 0. In the symmetry broken case, the procedure is well-known (see, for instance Refs. [64][65][66] for details of the corresponding renormalization group (RG) procedure): the fields are shifted around the true mininum, leading to bare and renormalized masses, when in the vacuum, replaced
| 1,126 |
254366527
| 0 | 16 |
by m 2 i → 2|m 2 i | and m 2 i → 2|m 2 i |, respectively. The renormalization scale dependence on both masses and couplings are given in terms of their respective RG expressions, given in terms of the RG functions β and γ m given, respectively, by [63] and which, for our respective masses and couplings and at one-loop ( ) order, give Equations (4.8)-(4.12) form a coupled set of flow equations determining how the masses and couplings change under different renormalization scales. In particular, we can also see from, e.g., Eqs. (4.10), (4.11) and (4.12), that their solution is also equivalent to solving the coupled set of linear equations, (4.14) which also make apparent how the renormalized couplings are related through a change of the scale from, e.g., µ 0 to µ. The results obtained from the flow equations given above give the standard way of nonperturbatively resumming through the RG equations the leading order corrections (in this case the leading log-dependent corrections) to the coupling constants. These equations also show that the couplings evolve with the scale in a logarithmic way. Suitable choices of the scale can minimize these logarithmic contributions. It is common in the literature in general that at high temperatures to take the scale proportional to the temperature, µ ∼ T . In particular, a suitable choice of scale has been shown to be given by [50] µ = 2πT . The typical strategy is followed: for example, in the hard-thermal loop analysis of the thermodynamics (see,
| 1,127 |
254366527
| 0 | 16 |
for example, Ref. [67]), we can express all physical quantities in terms of the renormalized, scale-dependent, parameters. Working similarly here, this means, for instance, the set of renormalized parameters are given at the reference scale µ 0 . By a change of the scale (e.g., with the temperature, or, in our present problem can also be with L), the new set of renormalized parameters related to the original ones fixed at the reference scale µ 0 are then obtained by solving the coupled flow equations, Eqs. (4.8)-(4.12), for the new value µ. The bare parameters are then finally determined by inverting the set of equations (4.1)-(4.5), gettingm φ (m φ , m χ , λ φ , λ χ , λ), etc. At finite sizes, we also see from the equations derived earlier, Eqs. (3.23) and (3.24), that those equations suggest that a more suitable scale might be µ ∼ 1/L when T L < 1/2. In practice, in all of our numerical analy-sis, we will adopt for the reference scale µ 0 = 2πT or µ 0 = 2π/L, depending whether the temperature or the (inverse of the) length size dominates the loop integrals. As typically adopted in the literature to check the variation of the results with the scale µ, we will then vary µ in a range α = µ/µ 0 = [1/2, 2]. Either way, the logarithmic dependence on the scale will imply that all of our results will be weakly dependent on the particular choice of µ, provided that the couplings,
| 1,128 |
254366527
| 0 | 16 |
T and 1/L are not too large. In the parameters we will be working with our examples in Sec. V, this will always be the case. B. The bubble (ring) resummed gap equations for the masses and field expectation values We want to investigate the full phase structure for the multiple field system. However, it is well known that PT breaks down at high temperatures and, in particular close to critical points [37]. Here, we go beyond the perturbation theory by using the bubble (or ring) dressed method for finite-temperature scalar fields [48]. In the bubble resummation procedure, the one-loop terms with the temperature and finite-size effects are self-consistently resummed by using the gap equations for the masses, which is similar as previously considered in ISB/SNR earlier studies [22,27,28,68]. In this case, this is equivalent of solving the coupled system of gap equations for the renormalized masses 1 , where the renormalized one-loop function I 2,R is given by Eq. (3.14) with the divergence subtracted. The fields are shifted around their expectation values, φ →φ + φ and χ →χ + χ , whereφ ≡ φ andχ ≡ χ , while φ = 0 and χ = 0. The expectation values for the fields are then defined through their respective coupled tadpole equations, given by, respectively, in terms of the one-particle irreducible (1PI) one-point functions Γ (1) φ ≡ 0 and Γ (1) χ ≡ 0. At the one-loop level and re-1 Note that these equations can also be seen as the extension to multiple fields
| 1,129 |
254366527
| 0 | 16 |
of the foam diagram resummation defined, e.g., in Ref. [50]. summed bubble approximation, we have that whereΩ φ andΩ χ are defined, respectively, bỹ We now have the complete set of necessary equations to analyze the phase structure of the coupled two-scalar field system. V. RESULTS Let us now consider the combined effects of temperature and finite size in the phase transition patterns in the two-scalar field model. But before studying the coupled two-field system, it is instructive to first analyze the case of only one field, e.g., φ, which can be easily obtained by setting the intercoupling λ to zero in the equations defined in the previous section. From Figs. 2(a) and 2(c) we can see that the effect of the compact dimension allows the system to have a double critical point, where the symmetry can get broken in between two values of critical length L c . This is a reentrant phase transition, which might be of interest in condensed matter systems [27,28,69,70]. These type of transitions are also of interest for understanding, for example, phase transitions in superconducting films, as studied previously in Ref. [71], which considered finite-size effects in a Ginzburg-Landau model with periodic boundary conditions. The same trend of transitions also is seen to happen here in the context of DBC. In Figs. 2(b) and 2(d) the SR behavior as a function of temperature is shown for some fixed values of length L. Here we note that although there seems to be no multiple critical points in the temperature (e.g., the
| 1,130 |
254366527
| 0 | 16 |
appearance of two critical values of temperature), it shows instead that for small values of L the critical temperature tends to grow as L increases, but then T c starts to decrease beyond some value of L. Note that the phase transition points agree between the results shown for either the effective gap mass or the field expectation value, as they should. We can also notice from the results displayed in the panels of Fig. 2 that the transition is always continuous, which characterize a second-order phase transitions for all the cases displayed in Fig. 2. At this point, it becomes useful to analyze the dependence of any of these results with the variation of the scale. Let us remainder that a sensitive of the results with the renormalization scale µ can also be seen as an indicator of the reliability of the approximation method which is being used in our study, i.e., the bubble resummation scheme explained in Sec. IV B. For instance, the effective mass here is directly related to the 1PI two-point function at zero momentum, Γ (2) i (0, 0) ≡ −M 2 i and Γ (2) i must satisfy the RG equation [72], Of course, since we cannot evaluate Γ (2) i to arbitrary precision, the level of sensitive of it on the renormalization scale gives us an indication of the level of accuracy of the method used in its derivation. As already explained at the end of Sec. IV A, we follow the standard procedure usually adopted in many of
| 1,131 |
254366527
| 0 | 16 |
the studies in the context of the hard thermal loop and vary µ with respect to the reference scale by a factor of two, µ/µ 0 ≡ α = [1 /2, 2]. This typically gives a good indicator of how relevant thermodynamical quantities (like the pressure) are sensitive to the scale [67]. Taking for instance the example shown in Fig. 2 zooming in around each of the critical points shown in there. Our results show that the considered variation of the renormalization scale leads to a change in the critical points by around the one percent level and smaller. This is in a sense consistent with the fact that we are considering not large couplings neither is the temperature is too large to cause a significant change here (recalling from the flow equations that variations with the scale are logarithmic). Figure 3 shows the behavior for the effective mass M φ close to the transition points in the temperature and length. The same can be done also for the field expectation value φ shown in Figs. 2(c) and 2(d). Let us recall that the inverse of the effective mass is equivalent to the correlation length of the field, ξ φ = 1/M φ , while φ makes the role of the order parameter for the phase transition, much the same way as the correlation length and magnetization, respectively, for an Ising system in three spatial dimensions in the context of statistical physics [73]. The way these quantities approach the critical point are specified by the critical
| 1,132 |
254366527
| 0 | 16 |
exponents ν and β, which can be defined as where, in the usual prescription, τ denotes the reduced temperature, τ = (T − T c )/T c and T c is the critical temperature. In the present problem, the critical point can be approached by varying either the temperature or the length L. Hence, we can define τ with respect to either T or L, according to the equivalence between T and 1/L already discussed at the end of Sec. III, and make estimates concerning the critical exponents ν and β. Already from Fig. 3 we can see that the effective mass square always approaches the critical point in a linear way. Since we expect that M 2 φ ∝ |τ | 2ν as τ → 0, hence, ν = 1/2. The same can be studied for how the expectation value of the field approaches the critical points. Taking sufficiently small values for τ , we verify that here too we get β = 1/2. These are the mean-field critical exponents and which are expected for the level of approximation we are presently considering. Deviations from the mean-field values are only expected to happen when the full twoloop order terms are also resummed and to approach the expected critical exponents for this problem can only be achieved through a three-loop and higher-order resummation scheme (see, e.g., Ref. [63] for some examples). Finally, for illustration, the different transition behaviors displayed in Fig. 2 are shown in the phase diagram depicted in Fig. 4, where the regions of
| 1,133 |
254366527
| 0 | 16 |
symmetry breaking, φ = 0, and symmetry restored, φ = 0, are shown in the plane (L, T ). The variation of the renormalization scale in the same range considered in Fig. 3 only leads to very small changes (at most at the one percent level) in the critical curve shown in Fig. 4 and, therefore, it is not shown explicitly. The phase diagram depicted in Fig. 4 shows that the critical temperature fast increases when L is increased when starting from very small values (mL 0.03), reaches a maximum at mL 0.05 and then decreases towards large L. The horizontal dashed line indicates the critical temperature in the case of the absence of finite-size effects (L → ∞), whose value for the parameters used in Fig. 4 is found to be T c (L → ∞)/m 15.5. The behavior analogous to reentrant phase transitions as a function of L are clearly visible when taking constant temperature values and that happens with temperatures in the range 15.5 T /m 28. The phase structure behavior displayed in Fig. 4 is easy to understand when we look at the temperature and size dependence of the loop integral I ∝ T 2 , eventually SR is realized. Finally, when L is decreased with fixed T , again we see that since now I (1) 2 ∝ 1/L 2 , then the symmetry will also be restored for sufficiently small values of L, as it is explicitly seen in Fig. 4. B. The two-scalar field case Let us now study
| 1,134 |
254366527
| 0 | 16 |
the multiscalar field case, i.e., including both φ and χ with a nonvanishing intercoupling λ between them. We are mainly interested in exploring a parameter space where the usual SR can happen at high temperatures along a given field direction, while the other field experiences ISB. Let us first recall that from the PT estimates from Sec. II, considering a negative intercoupling λ, when Eq. (2.4) is observed, but still satisfying the boundness condition Eq. (2.2), we expected an ISB phase transition in the i-field direction, when m 2 i > 0, or, equivalently, a SNR, when m 2 i < 0. According to the previous discussions, these phase transition patterns are expected at either at high temperatures (at fixed L), or, likewise, at small values of the length, L 1/m, 1/T (at fixed T ). By focus on the ISB case, let us investigate first the parameter space that leads to this phase transition pattern. Without loss of generality, we can consider, for example, the two sets of renormalized couplings 2 : Set I: 2 Unless stated otherwise, we work with all parameters defined at the reference scale µ 0 . We could likewise work directly with the 2). Then, with the perturbation equations in the high-temperature approximation, e.g., Eq. (2.3), they predict an ISB phase transition along the direction of the χ field whenever m 2 χ > 0. On the other hand, for m 2 χ < 0, SNR should manifest, in which case the χ-field expectation value should always remain as nonvanishing,
| 1,135 |
254366527
| 0 | 16 |
χ = 0. The symmetry behavior along the φ field direction depends only on the sign of its mass square term entering in the Lagrangian density. For m 2 φ > 0, it (in the φ field direction) remains in a symmetry restored phase, φ = 0, while considering initially (at T = 0) a symmetry broken (SB) phase along the φ field direction, i.e., m 2 φ < 0, the usual symmetry restoration at high temperatures is expected. Of course, had we chosen different assignments for the couplings, the roles of the φ and χ fields are expected to be reversed under the phenomena scale independent parameters, the barred quantities of Sec. III. For the coupling constants that we will be considering the difference between the barred parameters and unbarred ones (which explicitly depend on the scale) are always very small and the use of one or another set of parameters does not affect our results in any qualitative or significant quantitative way. of SB/SR and ISB/SNR. For definiteness, in the analysis that follow, we will consider that φ suffers the usual SR at high temperatures, while χ should experience ISB, i.e., we choose the mass renormalized parameters such that m 2 φ < 0 and m 2 χ > 0 and under the above given choice of representative values for the two sets of coupling constants. Of course, other combinations of parameters could be used but the results could be similarly interpreted. It is useful to show the two sets of couplings that we
| 1,136 |
254366527
| 0 | 16 |
are considering here in a given plane in the coupling constants parameter space. With λ φ = 0.8. in Fig. 5, we present the parameter available for ISB. The location of the sets I and II are represented by the black dot and white (open) points, respectively. The region in between the solid and dotted lines is the region for ISB predicted by PT according to Eq. (2.4) and when L → ∞. The region for ISB according to the nonperturbative results coming from the solution of the gap equations is, however, delimited by the solid and dashed lines (also when L → ∞). Note that there is reduction of the parameter region available for ISB when compared to PT 3 . The dash-dotted line delimits the region for ISB for the case of finite L, which is taken as L = 0.075/m in the example shown in Fig. 5. Note that the finite-size effect is to enlarge the region for ISB when compared to the result at L → ∞. In both parameter sets I and II we expect that the field φ will experience the usual SR as the temperature increases. Also, as in the one-field case studied in the previous subsection, as we decrease L, SR is also expected. This is explicitly illustrated in Fig. 6, where the transition pattern for φ in both sets of parameters is shown. Figure 6 shows again the characteristic reentrant (double transition point) like behavior as the compactification size L is changed and a maximum critical temperature
| 1,137 |
254366527
| 0 | 16 |
that can be reached when L changes. Note that in the results shown in Fig. 6 and the next ones, we have verified explicitly that the change in the scale µ only leads to small corrections, just like in the one-field case, and causes no change in our conclusions regarding the phase transition patterns reported here. Thus, all the following results are presented only at the reference scale µ 0 . The situation becomes more interesting when we now analyze the transition pattern for the field ψ. In the parameter set I we expect the field ψ to display ISB just 3 This figure can be compared for instance to the similar one of Ref. [23] (given by Fig. 1 in that reference), which considered instead the method of the exact renormalization group to analyze ISB. The reduction of the parameter region is equivalent to the one we obtain here. like in the case of the bulk case (L → ∞). This is indeed the case as shown in Fig. 7(a) when L is increased. However, as expected, ISB also manifests in the small L region, for the same reason as discussed for the transition in the φ direction (though now instead of SR, we have ISB) and it is again due to the behavior displayed by the loop function in terms of L and T . Note that now, we have a reentrant transition to a symmetry restored phase in between the two extremes. However, for the parameter set II, which resides in between the
| 1,138 |
254366527
| 0 | 16 |
dashed line (L → ∞) and the finite L region shown in Fig. 5, we do not expect ISB to persist for large values of L, as the dash-dotted line moves towards the dashed line and the point will reside in the SR phase. Thus, here, ISB is truly only a consequence of the finite-size effect as illustrated in Fig. 7(b). VI. FINITE N EFFECTS AND COMPARISON WITH THE LARGE-N APPROXIMATION So far, in the previous section we have restricted to cases where N φ = N χ = 1, i.e., in the context of a twofield model with symmetry Z 2 × Z 2 . Let us now investigate how those results might get affected by finite N effects. It is useful in this context to compare the finite N results with the ones derived in the context of the large-N approximation. In the large-N (LN) approximation (for a review, see, e.g., Ref. [74]) both coupling constants and fields are normalized by N , such that, for instance, λ i → λ i /N i , λ → λ/ N φ N χ , φ → N φ φ and χ → N χ χ, while the rescaled coupling are kept fixed as N i → ∞. Without loss of generality, we will consider N φ = N χ ≡ N . Note that in the LN approximation, the simple one-loop expressions, e.g., Eqs. (3.17) and (3.18), become exact, since higher order terms become suppressed by factors of 1/N i . Next, we will compare
| 1,139 |
254366527
| 0 | 16 |
the LN approximation result for the phase diagram in the plane (L, T ) for φ and χ with the corresponding finite N ones constructed in this approach. In Fig. 8(a) we show the result for the phase diagram for φ, while in Fig. 8(b) it is shown the result for χ. We have used the values N = 2, N = 3 and N = 4 for comparison, which can be motivated by, e.g., coupled complex scalar fields with O(2) × O(2) symmetry, coupled Heisenberg type of models with O(3) × O(3) symmetry, or a coupled linear σ-model with O(4) × O(4) symmetry, respectively. The set of parameters considered was set II, which was used in previous subsection. We note that for the large-N case, as also for the finite N examples shown in Fig. 8, the point represented by the parameter set II moves to the ISB inner region shown in Fig. 5. Hence, as oppositely seen in Fig. 7 in the case of N φ = N χ = 1, here ISB persists even at larger values of L. We also note from the results shown in Figs. 8 that in the LN approximation we still observe reentrant phases with double critical values for L in both the φ and χ directions. VII. CONCLUSIONS In this work we have investigated the possible phase transitions patterns in a two-field multicomponent scalar model with symmetry O(N φ ) × O(N χ ) when both thermal and finite-size effects are present. While in the bulk (in
| 1,140 |
254366527
| 0 | 16 |
the absence of space boundaries) phenomena like ISB have shown to be present at high temperatures, when the intercoupling between the fields is negative, the phase transition patterns when finite-size effects are present become more involved. The finite-size effects allow the system to display behavior analogous to reentrant symmetry breaking (which can happen in between two phases of symmetry restoration) and vice versa, where symmetry restoration can happen in between two phases of symmetry breaking. These type of phenomena can happen for both fields depending on the choice of parameters and they are a consequence of the behavior of the oneloop integral as a function of T and L, which presents a minimum depending on the choice of temperature and length. In this work we have analyzed these phase transition phenomena with the use of the bubble (or ring) resummed gap equations for both the effective masses for the fields and for their expectation values, φ and χ . The results were also compared with the large-N approximation. The behavior analogous to reentrant symmetry breaking for the fields was shown to be present in both cases. We have considered in this paper the Dirichlet boundary condition for the space compactification in a slab geometry in the three-dimensional space, R 2 × [0, L]. The Dirichlet boundary condition is a well-motivated condition for different physical systems as has been argued in the recent literature. For practical purposes, it is also computationally convenient since there are no zero modes when working with the discrete frequencies and, consequently, direct
| 1,141 |
254366527
| 0 | 16 |
simple equations in the limit of large temperature can be derived. We have obtained the expressions for the two-point one-loop self-energy correction contributing to the effective masses and we have also made use of the renormalized parameters (masses and coupling constants). We have shown that typical variations of the scale around a reference value do not change in any significant way the transition patterns describe and found in this work, with the variations with the scale remaining small. This fact can be used as an additional argument concerning the reliability of the approximation used. Our results can, in principle, also be extended to higher loops, which would allow eventually to explore regions of larger couplings than the ones we have considered here. Other types of geometries can also be considered as future developments of this work. But still, the simpler slab geometry here considered can be of interest in practical physical applications, most notably, like in condensed matter problems where, for example, the thickness of thin films are important [75][76][77][78][79]. With the advent of even more miniaturized electronic devices, it is extremely relevant to analyze how the size and interface effects change the properties and performances of nanomaterials. In particular, similar phase transition behaviors as a function of the thickness that resembles the ones we have seen here, have also been observed in different materials. For instance, a rapid grow of the critical temperature with the thickness and then a smooth decrease of T c , as it appears in Figs. 2, 6 and 8, for
| 1,142 |
254366527
| 0 | 16 |
example, have been experimentally measured in different materials displaying superconductivity transitions (see, e.g., Ref. [80]). In this context, even though we have here considered a relativistic type of model, our results can still be of interest in applications in the condensed matter context. For instance, excitons type of systems exhibit a relativistic dispersion relation [81] and, furthermore, are effectively modeled as a multifield scalar model for which our results can be directly applied to. Our results can also be of interest for high-energy relativistic systems. Relativistic type of systems typically modeled by multifield scalar models with both inter and intracouplings include for example those in the context of color-flavor superconductivity [82][83][84], which the study of the effect of space compactifications can be of relevance. In addition, other applications are also possible, like, for example, to infer possible finitesize effects in the transition from a quark-gluon plasma to hadronic matter in the case of the fireball formed in the collision of heavy ions. The pancake like shape of the formed plasma (for a review, see, e.g.. Ref. [85]) suggest that at the central region our slablike geometry might be relevant and these consequent finite-size effects to be important in the interpretation of the transition and thermodynamics of the plasma, as suggested, e.g., in Ref. [46,86,87]. In addition, other system of possible relevance could be in the physics of compact stars. The structure of hybrid type of stars typically involves crust like structures which is important in the description of the stability and structure of these type of
| 1,143 |
254366527
| 0 | 16 |
compact stellar objects (see, e.g., Ref. [88] and references therein). It is conceivable that in the presence of more than one crust type of structure, if thin enough, finite-size effects as the ones studied here can also be important. Finally, while we have investigate the transition patterns in a thermal environment, the same can also be performed in the context of quantum phase transitions, which also find applications in the context of multifield type of models like the one studied here [89]. The study of finite sizes in these type of systems can also be of interest as well. Applications in the context of any of the above mentioned type of systems and others require, of course, a separate dedicated study. Other extensions of our work can also include the uses of other boundary conditions and the analysis under different nonperturbative methods. These further developments are clearly of interest and we hope to address some of them in the future.
| 1,144 |
254366527
| 0 | 16 |
Perceptions of health promoters about health promotion programmes for families with adolescents orphaned as a result of AIDS in the rural Hammanskraal region in South Africa Providing health promotion in the communities is one of the many strategies that were introduced by the Government of South Africa in an attempt to combat the increasing numbers of people South African communities are still greatly affected by the high rate of infection with HIV or who are living with AIDS, mirrored in the 2008 overall national HIV prevalence of 29.3% (UNAIDS 2010:10). In addressing the challenge, the health system is dependent on community care level workers such as caregivers to render health promotion and education in the homes and communities. The caregivers based in the communities are the ones with first-hand information on what is needed for the success of health promotion programmes. This study, aimed at exploring the challenges faced by the health promoters, described their perceptions regarding a health promotion programme for families with adolescents orphaned as a result of AIDS. Data were collected on the purposively selected participants at the rural Hammanskraal region in South Africa and the research question: ‘What is your perception regarding health promotion programmes for families with adolescents orphaned as a result of AIDS’ was asked and discussed by participants in a focus group interview. Data were analysed using the adapted Tesch method to organize and isolate the main categories, sub-categories and themes. The following main categories were isolated: attitudes of adolescents, effectiveness of home visits, need for health education and
| 1,145 |
72793345
| 0 | 16 |
limited resources. Based on the findings, it was therefore recommended that health care planners assist in the improvement of health promotion and education by using the community and national media, providing information material and providing access to the internet in order to allow more people, including young people, to access the information. Introduction Problem statement Providing health promotion in the communities is one of the many strategies that were introduced by the Government of South Africa in an attempt to combat the increasing numbers of people South African communities are still greatly affected by the high rate of infection with HIV or who are living with AIDS, mirrored in the 2008 overall national HIV prevalence of 29.3% (UNAIDS 2010:10).In addressing the challenge, the health system is dependent on community care level workers such as caregivers to render health promotion and education in the homes and communities.The caregivers based in the communities are the ones with first-hand information on what is needed for the success of health promotion programmes.This study, aimed at exploring the challenges faced by the health promoters, described their perceptions regarding a health promotion programme for families with adolescents orphaned as a result of AIDS.Data were collected on the purposively selected participants at the rural Hammanskraal region in South Africa and the research question: 'What is your perception regarding health promotion programmes for families with adolescents orphaned as a result of AIDS' was asked and discussed by participants in a focus group interview.Data were analysed using the adapted Tesch method to organize and isolate
| 1,146 |
72793345
| 0 | 16 |
the main categories, sub-categories and themes.The following main categories were isolated: attitudes of adolescents, effectiveness of home visits, need for health education and limited resources.Based on the findings, it was therefore recommended that health care planners assist in the improvement of health promotion and education by using the community and national media, providing information material and providing access to the internet in order to allow more people, including young people, to access the information. Suid-Afrikaanse gemeenskappe word steeds grootliks beïnvloed deur die hoë vlak van MIV en vigs, soos weerspieël in die algehele nasionale MIV-syfer in 2008 van 29.3% (UNAIDS 2010:10).In die aanspreek van hierdie uitdaging is die gesondheidstelsel afhanklik van gemeenskapsorgwerkers om gesondheidsbevordering en -opleiding aan huise en gemeenskappe te voorsien.Die versorgers wat in die gemeenskap werk, het eerstehandse inligting oor wat nodig is om die sukses van programme vir gesondheidsbevordering te verseker.Hierdie studie, wat ten doel het om die uitdagings van gesondheidspromotors te verken, beskryf hul persepsie ten opsigte van 'n gesondheidsbevorderingsprogram vir families met adolessente wat wees gelaat is as gevolg van vigs.Data is op die doelbewus geselekteerde deelnemers in die landelike Hammanskraal-streek in Suid-Afrika ingesamel en die volgende navorsingvraag is in 'n fokusgroep-onderhoud gevra en bespreek: 'Wat is jou persepsie oor die gesondheidsbevorderingsprogram vir families met adolessente wat ouerloos gelaat is as gevolg van MIV en vigs?' Die data is met behulp van die aangepaste Tesch-metode geanaliseer om die hoof-en sub-kategorieë, asook die temas te organiseer en isoleer.Die volgende hoof-kategorieë is uitgesonder: die houdings van adolessente, die doeltreffendheid van huisbesoeke, die behoefte
| 1,147 |
72793345
| 0 | 16 |
aan gesondheidsopvoeding en beperkte hulpbronne.Gebaseer op hierdie bevindinge is die aanbeveling dat die gesondheidsorgbeplanners bydra tot die verbetering van gesondheidsbevordering en -opvoeding deur die gebruik van gemeenskapsen nasionale media, die beskikbaarstelling van inligtingsmateriaal en die voorsiening van internet om meer mense, insluitende jongmense, die geleentheid te bied om toegang tot die inligting te verkry.living with HIV and AIDS.However Peu, Van Wyk and Botha (2008:16) did acknowledge the fact that there were no formal written health promotion guidelines for families with adolescents orphaned as a result of AIDS.The same study reaffirms that lack of health resources such as health care services, lack of information on health care and poor access to health care services makes health promotion inevitable (Peu et al. 2008:16), hence the study of this nature was needed to accumulate adequate information from the sole beneficiaries of the programme; to assist in closing the health promotion gap and render the effective health promotion to the families with adolescents orphaned as a result of AIDS. Aims of the study This study aimed at exploring and describing the challenges met by the health promoters whilst rendering health promotion to the communities.The findings of this study will therefore assist in improving and developing health promotion guidelines for families with adolescents orphaned as a result of AIDS. Trends South Africa is rated as having the second highest orphan rate in the sub-Saharan region with an estimated 1 900 000 in 2009, led by Nigeria at 2 400 000 (Avert Stats 2009).The proportion of orphanhood in South Africa had shown
| 1,148 |
72793345
| 0 | 16 |
to increase faster amongst children after the age of 12 years, which marked the beginning of the adolescent stage (Doctor & Radasi 2007).Studies had shown a steady but increasing trend of orphans in the North West Province as compared to the higher rates in KwaZulu-Natal and Eastern Cape (ibid. 2007).However, it is alarming to learn that orphaned children are more likely to contribute to high rates of not going to school (ibid.2007); fall under duress due to the loss of a parent or even an ailing parent, endure economic hardship, malnutrition and illness, and increased risk of abuse (Maqoko & Dreyer 2007:718).A health care need was emphasized as the major need for orphaned adolescents in the study conducted by Peu et al. (2008:23) hence the study of this nature. Research objectives The following objective guided the research process: to explore and describe the perception of health promoters on health promotion programme for families with adolescents orphaned as a result of AIDS. Definition of key concepts The following operational definitions are discussed: adolescents; health promotion; health education; perception and orphans. Adolescents: is the process of developing from child into an adult between the ages of 10 and 17 years (Peu et al. 2008: 16). Health promotion: defined by O'Donnel as 'the science and art of helping people to change their lifestyle and move towards a state of optimal health' (Edelman & Mandle 2000:16).World Health Organization (WHO) 1987:12 views health promotion as 'a unifying concept for those who recognise the need for change in the ways and conditions
| 1,149 |
72793345
| 0 | 16 |
of living, in order to promote health' (Dennil, King & Swanepoel 2007:122).In addition, health promotion is also defined as 'the process of enabling people (individuals) to increase control over the determinants of health, and thereby improve it' (Dennil et al. 2007:122).In this study, the art of helping people to change their lifestyle will be directed at families with adolescents orphaned as a result of AIDS. Health education: is defined by Tone and Tilfort 'as any intentional activity which is designed to achieve health or illness, related learning in an individual's capability or disposition' (cited in Dennill et al. 2007:149).The activity will assist the individual in attaining the state of good health. Perception: is an interpretation or impression based on one's understanding of something (Thompson 1996(Thompson :1014)).In this study, the health promoter's impression or interpretation is explored and described. Orphan: is defined by United Nations as a child who has lost one or both parents (Avert 2009).In this study, the loss will be due to HIV and AIDS-related diseases. Significance of the study There are possible factors that seemed to constrain the effective rendering of health promotion services to the growing trends of families with adolescents orphaned as a result of AIDS.The study aims to explore the view as expressed by the executor of health promotion in the community on the challenges they face whilst rendering health promotion services to these families.The results of this study will assist health planners in closing gaps in health promotion programmes to enhance their efficiency for their recipients. Literature review South
| 1,150 |
72793345
| 0 | 16 |
Africa has been recorded as the world's largest population living with HIV, as UNAIDS estimated 5.7 million people are living with HIV, more than 3 m of them being women and about 280 000 being children aged 0-14 years (UNAIDS, SA 2010: 20).According to the ASA model 2003, over 500 000 people were newly infected with HIV in 2009, and nearly 400 000 people died of AIDS-related illnesses (UNAIDS, SA 2010:11).Therefore, health promotion is seen as a strategy that attempts to relieve the burden of diseases on the presently overloaded health system in South Africa.Hence, the South African government invited all the stakeholders, from governmental and non-governmental organisations as well as communities, to participate in the rendering of health promotion in the home-based care sector in order, amongst other objectives, to prevent health complications (Department of Health 2001;Peu, van Wyk & Botha 2008:15).The Home Based Community Care and Support reported 411 867 orphans and vulnerable children in 2008 and 2009 and 449 732 children in the first three quarter of 2009 (UNAIDS, SA 2010:45).Furthermore, there is an increasing trend of orphans with one or both parents deceased.This is now estimated at 1.5 m to 3 m (UNAIDS, SA 2010:46).Health promotion plays a major role in rendering healthcare to families and communities, especially to the vulnerable groups.The SA Country Progress Report noted that the country needed five times the number of available social workers just to deal with the orphans and vulnerable children (UNAIDS, SA 2010:33).With the increasing rate of children who are orphaned as a result
| 1,151 |
72793345
| 0 | 16 |
of AIDS, health promoters are faced with the challenge of rendering health care to the families with adolescents orphaned as a result of AIDS.In promoting a healthy lifestyle, campaigns that will empower communities with the self-help skills and knowledge necessary for proactive community participation in health promotion behaviour are needed, especially in families with adolescents orphaned as a result of AIDS.A healthy life style in respect of HIV and AIDS-affected families would involve, amongst other things, the promotion of eating nutritious food, physical exercise, and avoiding activities that may lead to opportunistic infections and re-infection by HIV. Estimates from the South African National HIV prevalence rates of 2008 (released 2009) amongst antenatal attendees stand at 29.3%, which represents a stable number compared to 2006 and 2007 at 29.0% and 29.4% respectively (UNAIDS, SA 2010:10).The South African provincial reports on HIV prevalence amongst antenatal clinic attendees do show a report on four provinces recording higher prevalence than the national average of 29.3% (UNAIDS, SA 2010:23).The KwaZulu-Natal province still maintains its highest rate of 39.5% in 2009, Mpumalanga 34.7%, Free State 30.1%, and North West 30.0%(Sastats 2009).It is, however, disturbing that the infection rate in the North West province remains unchanged over a period of 3 years.The infection rate ranges from 29.0% in 2006, 29.0% in 2007and 30.0% in 2008(UNAIDS, SA 2010:25), which prompted the research question to explore the challenges and barriers of the people rendering health promotion services.The purpose of this study was to explore and describe the experiences of health promoters in their field of
| 1,152 |
72793345
| 0 | 16 |
work whilst rendering health promotion to orphaned adolescents who are not only affected by the loss of parents due to HIV and AIDS, but also have to thrive in life whilst taking care of their siblings. According to Stanhope and Lancaster (2008:679) it is during the teen years that a young girl learns the basic health promoting behaviour that she will carry into adulthood.Orphaned adolescents find themselves compelled to implement health promotion activities at home without prior training.It is the responsibility of health promoters to provide a comprehensive health promotion strategy to teach and endorse correct health promotion activities in such cases.Healthy attitudes and practices that include regular exercise and mental health promotion must be incorporated at early ages to have lasting positive benefits throughout a woman's (man's) life (Allender & Spradley 2005:679).It is during the teen years that the prevention strategies such as providing health and safety education and encouraging both males and females to keep their immunisation up-to-date are learned (Allender & Spradley 2005:693).The significance of this study is to identify the possible factors that constrain the effectiveness of a health promotion programme and to assist the health planners to close any possible gaps regarding the effectiveness of health promotion, especially in this new growing trend of orphaned adolescents. Design The research methodology was qualitative in nature.Focus group interview was the method used to collect a rich descriptive data from the study participants.The researcher chose focus group methods for its ability to obtain many viewpoints of many individual in a short time (Polit &
| 1,153 |
72793345
| 0 | 16 |
Beck 2008:395), whilst observing, describing and documenting the situation in the setting of the study participants (Polit & Beck 2008:326, 752). Research population and sampling The population of this study consisted of government and non-governmental health promoters, males and females working under the North West Department of Health around rural Hammanskraal in South Africa, directly and indirectly involved in promoting health care to families with adolescents orphaned as a result of AIDS.A total of ten participants, which included four males and six females with ages ranging from 19-38 years, were purposively selected as they met the criteria of the population required.All participants had high school education and two had tertiary education (Table 1).Two people assisted in handpicking the study participants, namely the health promotion coordinator from the hospital in Hammanskraal, and the social worker working closely with the health promoters involved in the families with adolescents orphaned as a result of AIDS. Data collection methods Data were collected at the participants' area of work, and the researcher facilitated the focus group interviews.During the first briefing session, participants were educated on their ethical rights, the purpose of this research and the process of data collection.The information leaflet and the consent forms were presented on the same day for the participants to read and sign at home and bring to the next meeting as arranged.Following the briefing session, two focus group discussions were conducted with the study participants on different days.The research question 'what is your perception regarding health promotion for families with adolescents orphaned as a result
| 1,154 |
72793345
| 0 | 16 |
of AIDS?' was asked and the participants elaborated on their feelings.The interviews were conducted for 40-60 minutes with the researcher probing, following up on clues and constantly encouraging the participants to continue with the discussion until no new data were elicited from the participants.A total attendance of ten participants on both interviews was maintained as the researcher was in constant communication with them on their availability.The researcher used the tape recorder to record the interview and kept field notes, which were then transcribed and analysed. Data analysis Data were analysed using the adapted Tesch version as described in De Vos (2005:334) and Cresswell (2003:192). Tesch method provides eight detailed guidance for the coding process which aided the researcher in a systematic process of analysing textual data (Cresswell 2003:193). As the researcher collected data using the tape recorder, transcriptions of the interviews were done regularly and accurately according to the descriptive method.Both the researchers and the senior researcher discussed and agreed on the categories, sub-categories and themes to be included in the analysis.Direct quotations were used to support every category and sub-category as themes. The researcher read through the transcribed information and got a sense of what was said and made a list of topics whilst reading through the transcription.The researcher then clustered together the similar topics into columns, and arranged them as major topics and unique topics.The researcher, using a highlighter, coloured the topics with similar meaning with the same colour, finding the most descriptive word for those topics, turning them into categories.Each category was assembled
| 1,155 |
72793345
| 0 | 16 |
with the topics similar to the category as sub-categories, and each subcategory with a theme that represented the quote of exact words from the transcription.The supervisor and the researcher met and discussed the findings, and reached a consensus about the categories, subcategories and themes that have been identified. Context of the study This study was conducted in the rural Hammanskraal region situated in the North West Province.The study participants are working for the non-profit organization Sunrise Hospice Centre based in the region and the interviews were conducted at the hospice centre. Results Four categories and fourteen sub-categories that emerged from the data analysis assisted the researcher in exploring and describing the perception of health promoters regarding health promotion programmes for families with adolescents orphaned as a result of AIDS.The four categories identified in this regard were attitude of adolescents, effectiveness of home visits, need for health education and limited resources (Figure 1). Attitude of adolescents Attitude of adolescents emerged as a category with ignorance, resistance and lack of motivation as sub-categories.The adolescents and the community at large showed no interest in the participants' attempt to educate them and provide health promotion activities for them.Adolescents could not associate themselves with the health promoters, as they already knew what they were going to say and therefore ignored them when approached: '… people are so used to our services they tend to ignore us.' (Participant 3, Female, Health Promoter, 23 years, Matric) The adult community is also still ashamed to talk about safe sexual activities in the presence of
| 1,156 |
72793345
| 0 | 16 |
their children, which is The participants are working in this type of conditions, and earn next to nothing, which puts a strain on their commitment to perform their duties: '…no increment on what we are earning, any incentives or bonuses.This is so discouraging to us and we are not motivated at all.' (Participant 1, Male, Health Promoter, 25 years, Matric) Effectiveness of home visits The effectiveness of home visits were identified with the following sub-categories: door-to-door campaigns, and follow-up.The participants took part in door-to-door campaigns as part of their services to the community where they issue information leaflets and health education to the families, and this elicited good results: 'People do get the message and we find a number of people coming to the centre for more.' (Participant 3,Female,Health Promoter,23 years,Matric) During these door-to-door campaigns, participants identify cases that need follow up, refer cases that need professional help and provide health advice to those who welcome it.They also conduct daily home visits where they render health care to the frail and ill clients.The participants' main challenge in doing home visits and follow up was lack of transport, which made their clients lost to follow-up and became worse in their health state: 'We never find time to go back to check on clients due to lack of transport.'(Participant 2, Male, HIV Counsellor, 28 years, Matric) Need for health education Lack of information and source of information emerged from this category need for health education.The participants felt that young people lacked information on HIV and AIDS as is
| 1,157 |
72793345
| 0 | 16 |
evident that there are a lot of pregnant teenagers in the community: '…What worries me is the fact that they still become pregnant even after the health talks.' (Participant 5, Female, Health Promoter, 29 years, Matric) However the participants regard themselves as the source of information since the young people come to them whenever they need HIV and AIDS information.They felt proud and important that they are contributing to the wellbeing of the community: Participants reckoned that an information corner from which the communities -especially young people -could access information without being associated with community health workers, could be beneficial in distributing the health education materials. Limited resources Limited resources are described as lack of funds, shortage of staff and lack of facilities.Participants expressed their concerns on the sustainability of the health promotion programme.There are periods where the centre runs out of funding and the participants have to go without their monthly payments, which leaves them financially distressed and hungry: 'At times there is a delay in funding which leads to late payment or even no payment to us as health promoters'.(Participant 4,Female,Health Care Provider,28 years,Diploma) They felt that the workload is increasing and requires a larger workforce adequately to cover the burden of care.In addition, they requested that a doctor be appointed at their centre to minimize the referral route to government clinics: 'For the programme to be successful, we need to address the staff shortages…' (Participant 7, Male, Health Promoter (working as an administrator, 32 years, Matric) '…If we had our own doctor who
| 1,158 |
72793345
| 0 | 16 |
will diagnose, prescribe and manage our clients at the centre, people will get relevant treatment for their conditions'.(Participant 4,Female,Health Care Provider,28 years,Diploma) The participants added the need for resources such as a daycare and youth centre, so that those adolescents who are left to care for their siblings could leave them at the centre whilst they go to school or work: 'We also need the day-care centre for children'.'I think if we had a youth centre, we will attract a lot of young people.' (Participant 6, Female, Health Promoter, 19 years, Matric) Ethical consideration Ethics is the branch of philosophy that deals with morality (Burns & Groove 2005:62).This study was conducted for academic purposes; ethical clearance to conduct this study was obtained from the University of Pretoria Research Ethics Committee.Permission to conduct the study was also obtained from the North West Department of Health. Regarding participants this study used the following principles to protect them from ethical misconducts: beneficence, respect for human dignity and justice.Participants' rights were discussed in the first contact meeting as they were given a full preview of the study stating the purpose, objectives and the research method to be used.Following this debriefing process, an information leaflet with the consent forms was given to participants to read, understand and sign at home.Participants were advised to withdraw at any point, should they feel emotionally drained.The purpose of this study was to explore and describe the perception of health promoters in rendering health promotion services.The outcome of this study will benefit the recipients of health
| 1,159 |
72793345
| 0 | 16 |
promotion services, and specifically those families headed by adolescents orphaned as a result of AIDS. Confidentiality was maintained throughout the research process.Participants were treated fairly and with respect and dignity.Those who chose not to participate were treated with respect and without discrimination.The involvement of the supervisor was explained to the participants in order for them to give a full, informed consent.The data collected were saved on the audio cassettes and in the field notes, which were only accessible to the researcher and the senior researcher (Polit & Beck 2008:173). Trustworthiness Trustworthiness refers to the degree of confidence qualitative researchers have in their data using the criteria of credibility, dependability, confirmability and transferability (Polit & Beck 2008:196).The strategies applied in ensuring trustworthiness are outlined (Table 2). Outline of the results Four categories and 14 sub-categories that emerged from the data analysis assisted the researcher in exploring and describing the perception of health promoters regarding health promotion programmes for families with adolescents orphaned as a result of AIDS.The four categories identified in this regard were attitude of adolescents, effectiveness of home visits, need for health education, limited resources.The findings of this research concur with findings of other researchers. The participants experienced ignorance from the young people when provided with health education about HIV and AIDS.They met a lot of resistance from the community at large, especially religious people.Talking about safe sex, condom use and the transmission of HIV was regarded as a taboo to their religion and by older people.Similarly, Norman et al. (2009:141) identified ignorance and misconception
| 1,160 |
72793345
| 0 | 16 |
about the disease as the two primary reasons for discrimination towards people living with HIV and AIDS.Wang, Meier, Shah, and Li (2007:47) identified six activities to provide health education, namely distribution of educational materials; showing of educational videos; delivery of lectures; facilitation of peer group discussions; and provision of reproductive health services and counselling.The counsellors and health workers are experiencing stigma and resistance surrounding HIV and AIDS enacted by the community whilst caring for HIVpositive patients (Delobelle et al. 2009(Delobelle et al. :1067)).Also, in a study conducted by Dhavanna-Maselesele, Lalendle and Useh (2007:18) parents and church leaders were rated amongst the least-consulted sources of information, mainly because most parents and church leaders do not create an environment that allows for free discussion of sex-related issues, including HIV and AIDS.Doing the door-to-door campaign in the community assisted the participants to identify families with health needs and affected families headed by children and adolescents.Participants were faced with challenges such as increased workloads and transport problems when supposed to follow up on their clients.Tolle (2009:669) recommended that an extensive outreach programme utilising the communitybased services should be a priority to regularly assess the families' unmet needs.Similar studies confirmed that home visits are a necessity to the under-resourced communities with limited access to healthcare services (Mtshali 2005:9).The purpose of home healthcare nurses is to provide direct clinical and preventive care to ill and/or injured patients in a home setting (Williamson 2007:133).The study on the Iranian community reveals that male community workers were charged with activities mainly outside the health houses,
| 1,161 |
72793345
| 0 | 16 |
such as making follow-up visits to patients and identifying them in surrounding villages (Bulletin of the World Health Organization 2008:586).Williamson (2007:145) further advises homecare nurses in the field that it is imperative that communication be effective in order to keep in touch with clients. During their services in the community, participants noticed a lack of information amongst young and older people as evidenced by the increased teenage pregnancy.Young people would ask questions from the participants when given assignments on HIV and AIDS at school.For the same reasons, participants issued HIV and AIDS information materials to the young people to read on their own to gain information.Similar studies reported limited information concerning HIV knowledge and attitude towards HIV testing in underserved communities (Djokic et al. 2009:23). Page 6 of 8 Credibility Prolonged engagement Two sessions were held for 45-60 minutes per session with the participants on different days. Persistent observation The tape recorder was used to record all data during the interviews, whilst the researcher collected field notes on the nonverbal communication and/or signals and gestures during the interview. Triangulation Multiple data sources were used to validate the conclusion. The same researcher collected data on all occasions to confirm consistency. Member checking The researcher constantly checked with the participants after transcription. The results were taken to participants for confirmation post analysis. Peer debriefing The researcher used own peers to discuss issues of concern and the senior researcher was directly and/or fully supervising the process of data collection. Dependability Descriptive data Data were recorded on tape and transcribed,
| 1,162 |
72793345
| 0 | 16 |
in addition to the field notes. The researcher and the supervisor reached consensus on the accurate description of findings and results. Confirmability audit The use of field notes, the interview report, and the taped data confirmed the neutrality of the study. The presence of the senior researcher to supervise the data collection confirmed the objectivity of the study. Transferability Descriptive data Follow-up visits to collect more data from the participants until no new information was elicited. Selected sample The use of purposive sampling to select participants who have knowledge of the topic under study. The study conducted of a rural African population confirmed that young people were at risk of adolescent pregnancy and sexually transmitted deseases, with a low incidence of condom use (Ross 2007(Ross :1943)).Also the study by Djokic et al. (2009:23) reported that Black women are at a high risk for contracting HIV, as related to risk behaviour of their sexual partner or by having multiple partners.However, the majority (75.0%-85.0%) of the surveyed community wanted to learn about HIV risk factors, testing, treatment choices and AIDS-related disease through pamphlets, videos, classes or neighbourhood meetings (Djokic et al. 2009:25).The researchers concluded that exposure to branded messages was significantly more likely to be effective in adolescents who are at a higher risk of acquiring HIV and AIDS (Yoo et al. 2005:396).In a similar study, the most commonly reported source of information for both male and female students was the media (newspapers, magazines and television), friends and clinics (James, Reddy & Jinabhai 2004:266). Delayed funding impacted negatively
| 1,163 |
72793345
| 0 | 16 |
on the participants' morale and motivation to work, as they are greatly dependant on the stipend they receive monthly to support their families.Participants also identified resources such as staff, and facilities such as a day-care centre and youth centre, which could add value to health promotion in the community.Participants reckoned that peer education at the youth centre would attract young people and encourage their participation.In similar studies participants reported being overworked, demoralised and emotionally distressed due to seeing patients with incurable diseases deteriorate over time (Delobelle et al. 2009(Delobelle et al. :1066)).The researchers concluded that, in order to retain personnel, very serious attention needs to be given to the needs of nurses regarding salaries, workload and working conditions, as well as to the recognition of nurses for their contribution (Selebi & Minnaar 2007:59).In addition and by virtue of their positions, managers have the ability to motivate subordinates by empowering them occasionally with increasing responsibility and implementing a rewards system that reflects an individual and collective value system (Marquis & Huston 2006:458-459). The World Health Organisation acknowledges the fact that a lack of long-term sustained funding threatens efforts to achieve universal access to HIV prevention, treatment and care (WHO 2008).Programme sustainability is a process of intervention to continue to deliver benefits or health gains beyond the initial funding or demonstrating the project stage (Herman and Saxena & Moodie 2005:20).The staff shortage was regarded as the most urgent threat to the early success of the ART treatment (Van Oosterhood et al. 2007:1245), whilst infrastructure was seen as a
| 1,164 |
72793345
| 0 | 16 |
long-term investment in caring for the HIV and AIDS clients (Tolle 2009:669). A children's day-care centre at the hospice facilities has proven to be a necessity for different needs as observed at Trinity Hospice and Palliative Care Services.There is a link between children orphaned as a result of AIDS and a lower school enrolment rate (Cluver, Gardner & Operario 2009:735). The relationship reveals the overall school attendance of children orphaned as a result of AIDs as 93.9%, compared to the 97.1% of other orphaned or non-orphaned children's overall school attendance (Cluver et al. 2009:735).Given this rate, it is vital to have a day-care centre for children aged 0-6 years for the child-headed family with young siblings, an after-school programme for older children, and supportive care for chronically ill children (Heymann & Kidman 2009:39).These measures would assist in poverty alleviation, as the older family members will go to work or school to be able to take care of the family (Hermann & Kidman 2009:39). Limitation of the study The study was conducted and limited to health promoters in a rural area, and the results cannot be generalised to all health promoters, especially those in urban areas.The sample size used in one province cannot be generalised to health promoters of other provinces.However, health policy makers could make use of these findings to improve the distribution of resources, and to attend to the challenges faced by health promoters in the communities as part of establishing an effective health promotion programme. Recommendations Based on the findings of this study, it
| 1,165 |
72793345
| 0 | 16 |
was therefore recommended that health care planners assist in the improvement of health promotion and education through community and national media, availability of information material and easy access via the Internet in order to attract more people, including young people, to access information.Equal distribution of resources including medicine, equipment and finances should be maintained in order to ensure uninterrupted services.Availability of infrastructure for people living with HIV and AIDS and other chronic diseases, such as terminally ill cancer patients and any form of paralysed clients who need specialised care, should form the basis of the intervention.The establishment of improved peer education programmes that are accessible to all communities should be considered. Conclusion A qualitative study was conducted and followed an exploratory, descriptive and contextual design.Based on the research questions, the results of this study, namely attitude of adolescents, effectiveness of home visits, need for health education and limited resources, demonstrated that multiple factors are responsible in limiting the effective rendering of health promotion; hence of our country struggles in reducing the HIV infection rate.Even though these results cannot be generalised to all the provinces, it is clear that there is still a challenge in the rollout of health promotion by the community health care workers.By considering new alternatives, namely additional resources and working with the young people of our communities, effective health promotion programmes could be developed. FIGURE 1 : FIGURE 1: Results on the perception of health promoters. TABLE 1 : Demographic presentation of participants. TABLE 2 : Strategies to establish trustworthiness.
| 1,166 |
72793345
| 0 | 16 |
Students’ Learning Outcomes and Activities: The Use of Video Conference during COVID-19 Pandemic This research was motivated by problems during the covid-19 pandemic, it showed that the students’ activity and learning outcomes of the topic of Ecosystem at Public High School 10 Palembang remain low. Based on observations of the electronic learning process carried out at the school, the teacher mostly applies asynchronous learning, thus the interactivity between teacher and students is not performed well. This study aimed to find out the effect of using video conferencing on the topic of Ecosystem toward the activities and learning outcomes of students. This study was set up as a quasiexperiment, using a nonequivalent control group design with two groups. The experimental group (Grade 10 of MIA 2) which do e-learning using video conference and the control group (Grade 10 of MIA 4) where e-learning without using video conference. Both groups were selected randomly. Data collection instruments were learning activity observation sheets and biology learning outcomes tests. Learning activity was analyzed quantitatively, while the learning outcomes data were also run quantitatively on a prerequisite test, hypothesis testing and the N-gain test. The results show the average percentage of experimental class learning activities increased from 39.5% to 42.5% while the control class did not increase. The Ancova test showed a significance value of 0.000 or less than = 0.05 and the N-gain test was 0.36. Based on the results, the use of video conferencing on the topic of Ecosystem significantly affected the learning outcomes improvement. This is an open-access article
| 1,167 |
239702977
| 0 | 16 |
under the CC-BY-SA license Introduction Coronavirus Disease has become a trending topic of conversation around the world. The Ministry of Education and Culture gave instructions to conduct distance learning for schools and universities by spreading a Decree No. 36962/MPK.A/HK/2020 (Kementerian Pendidikan dan Kebudayaan RI, 2020). Education in the industrial era 4.0 can ward off education that is feared to be hampered during this pandemic. The industrial revolution 4.0 era requires people to be able to adapt to the existing challenges and changes, especially in using information technology to support the success of distance learning. This demand requires schools to be able to implement electronic learning optimally. Thus, students are expected to be able to better understand concepts in the field of science, which is biology. However, the facts based on several studies show that the activities and learning outcomes of students are still less than the minimum criteria. Learning activities are activities of students who use ideas, intelligence, and interest in the learning process to develop cognitive, norms, affective, and psychomotor (Nurmala et al., 2014;Rosiana et al., 2012). A good learning activity is when students process and respond to the information conveyed by the teacher actively (Anggreiny et al., 2020). Therefore, good learning activities can result in cognitive and psychomotor formation leading to improved learning outcomes. Based on the results of initial observations carried out with class X biology teachers at SMAN 10 Palembang, she stated that during the Covid-19 pandemic biology learning activities were carried out using asynchronous learning assisted by the Google Classroom platform.
| 1,168 |
239702977
| 0 | 16 |
The method that educators use is by sending materials, media, and assignments to be studied and done by students. Meanwhile, educators use links from Google Forms that are distributed to students through Google Classroom to learn evaluation. The results of learning activities at SMAN 10 Palembang on biology learning show the percentage of learning activity scores that are less than optimal. During the learning process on ecosystem materials, students also quickly feel bored and indifferent when e-learning. It will prevent students from having a good understanding and can affect their learning outcomes. Learning outcomes are the outputs of students' learning activities in terms of cognitive, affective, and psychomotor aspects which are measured through assessment/evaluation. Learning outcomes are very important for the process of determining the success of the implementation of learning. Student learning outcomes show the cognitive aspects that students have regarding learning materials (Mitrayani et al., 2018). Initial observation of e-learning during Covid-19 pandemic shows that the achievement of learning outcomes in ecosystem material is relatively low. One class at SMAN 10 Palembang, Grade 10 of MIA 2, with 40 students, there were only 7 students who completed the minimum completeness criteria on ecosystem materials, so the classical completeness reached 18%. Ecosystem material is too hard to learn because students do not understand and connect it with daily life. One of the parts that are considered hard to understand by students is the material cycle (Çimer, 2012). The material cycle is part of an ecosystem that learns about biogeochemical cycles and energy flow consisting of
| 1,169 |
239702977
| 0 | 16 |
concept materials. They compared fact and principal materials that make it difficult for students to understand ecosystem materials. This problem will have an impact on learning outcomes obtained by students. The low learning outcomes indicate that the learning that educators apply has not been fully successful and research needs to be done. Electronic learning (e-learning) is the use of various electronic media to carry out educational or learning activities that can be used anytime and anywhere, so as to solve the problems of space and time in learning (Aryaningrum, 2016;Haske & Wulan, 2015). The use of e-learning helps us to save time, to reduce tuition fees, to cover a wider area, and to educate students acquiring knowledge more independently. However, electronic learning does not provide a clear picture of the information conveyed because of the low interactivity between educators and students in asynchronous learning (Yazdi, 2012). Early models of asynchronous learning were not effective because the system lacked student-teacher interaction as well as student-to-student interaction. it may lead to misinterpretation of other people's ideas. On the other hand, in synchronous learning the teacher and the students could interact with each other at a given time and place. The advantage of utilizing synchronous learning is that it facilitates real time collaboration, the student and the teacher may interact spontaneously, and the participants can have immediate feedback from each other (Lim, 2017;Shahabadi & Uplane, 2015). Therefore, the solution to this problem is the implementation of synchronous learning using video conferencing. Video conferencing is an example of synchronous learning.
| 1,170 |
239702977
| 0 | 16 |
The main benefit of synchronous learning is that it allows students to get rid of feelings of isolation because they can interact with educators or other students during learning activities. Video conferencing is an interactive telecommunications technology tool that is used to interact and conduct learning through audio and video simultaneously by students and educators in distance learning (Sandiwarno, 2016;Silitonga & V, 2012). So, through video conferencing, it is expected to be able to make learning fun, increase the element of interactivity and improve student learning outcomes. Therefore, to overcome these problems, synchronous learning is applied using video conferencing. This study aimed to find out the effect of using video conferencing on the activities and learning outcomes of students in class X ecosystem material. Methods This research took place at SMAN 10 Palembang which was held from October 2020 to July 2021. This study used a quantitative approach with the Quasi-experimental method. The method used is the nonequivalent control group design where the researcher will divide the students into two groups, namely the control group and the experimental group. The following table shows the research design used: The population in this study were students of class X MIA SMAN 10 Palembang. The sample in this study were students in class X MIA 2 as the experimental group and students in class X MIA 4 as the control group. Class X MIA 2 and X MIA 4 each consist of 20 students. The sample selection in this study was carried out using a simple random sampling technique.
| 1,171 |
239702977
| 0 | 16 |
In this study, data collection used test and non-test instruments. The test instrument is in the form of a cognitive test of biology learning outcomes, while the non-test instrument is a learning activity observation sheet. The learning outcomes measured are limited to cognitive biology learning outcomes in ecosystem materials. The biology learning outcomes test given is in the form of multiple-choice objective tests related to ecosystem materials totaling 20 questions that have validity and reliability requirements based on cognitive aspects including knowledge level (C1), understanding (C2), application (C3) and analysis (C4). Then, observations were made using an observation sheet containing indicators about student learning activities during the learning process. Observation of learning activities include visual activities; oral activities; writing activities; and mental activities. The indicators of visual activities are students reading the material that has been uploaded and paying attention to the teacher's explanation. The indicators of oral activities are students asking questions and expressing their opinions. The indicators of writing activities are students taking notes on the material or important points explained by the teacher, working on, and collecting the student's worksheet. The indicators of mental activities are students answering questions and concluding the material bravely. Learning activity data is obtained from qualitative data in the form of observations about teaching and learning situations, namely for data from observations of student learning activities, it is calculated using the equation below (Aminoto & Pathoni, 2014). = × 100% Note: A = Students' activities Na = Number of active students N = Number of all students The
| 1,172 |
239702977
| 0 | 16 |
interpretation of the value of student learning activities used the criteria shown in Table 2. (Aminoto & Pathoni, 2014) While the data obtained from the results of the pre-test and post-test were analyzed to determine the increase in learning outcomes. Related to the analysis of learning outcomes data, a prerequisite test is carried out in the form of a homogeneity test and a normality test. Then proceed with hypothesis testing using the Analysis of Covariance (Ancova) test and the Ngain test. Ancova aimed to determine the effect of treatment on the dependent variable by controlling for other variables (Sudaryono, 2016). The hypothesis in this study is: H0: The use of video conferencing has no significant effect on improving the learning outcomes of students' ecosystem materials in class X SMAN 10 Palembang. H1: The use of video conferencing has a significant effect on improving the learning outcomes of students' ecosystem materials in class X SMAN 10 Palembang. Students' Learning Activities During the lesson, researchers taught ecosystem materials to the control class using the announcement feature in google classroom and the experimental class using video conferencing by utilizing the screen sharing feature in Zoom Cloud Meeting. Learning using video conferencing at Zoom Cloud Meeting is equipped with HD video features so that students and researchers can listen to the material more clearly. Researchers also take advantage of presentation features that help in explaining because we can point the cursor, write, and make highlights during presentations. Researchers also interact with students such as finding out the students' initial understanding,
| 1,173 |
239702977
| 0 | 16 |
conducting questions and answers to providing learning reflections. In the control class, the researcher utilizes the comments and chat rooms in Google Classroom, while the experimental class uses the online synchronous zoom feature which allows educators and students to interact in real time. This feature is also equipped with clear audio, which can be turned on and off to make the class more conducive. Researcher also takes advantage of the task feature in Google Classroom to send assignments to the control class and experimental class. The types of learning activities observed in the control class and experimental class include visual activities, oral activities, writing activities and mental activities. The percentage of student learning activity results for each type of learning activity can be seen in Figure 1. Control Class Experimental Class In Figure 1 the learning activities of students in the control class and the experimental class for the activity of paying attention are very active with an average score of 100% and 96.6%. For oral activities, the results of the average percentage of students in the control class showed 4% which was categorized as inactive. Meanwhile, with an average percentage difference of 10%, the results of the oral activity of students in the experimental class which showed 14% were also categorized as inactive. Then for writing activities, the results of the average percentage score of students in the control class showed 36% which was categorized as less active. Meanwhile, for the experimental class, the percentage of writing activity was 42% with quite active category. Finally,
| 1,174 |
239702977
| 0 | 16 |
the mental activity of students in the control class and the experimental class were both categorized as inactive with a difference in the average percentage score of 4.6% with details of mental activity in the control class at 8% and mental activity in the experimental class at 12. 6%. The results of the data on student learning activities from both classes can be illustrated in graphical form. The comparison graph of the results of student learning activities at first, second and third meetings is shown in Figure 2. Figure 2 by utilizing the features of video conferencing for electronic learning, the results of the average percentage of student learning activities in the experimental class first meeting showed 39.5% in the less active category and increased 2% on second meeting to 42% in the quite active. Then on third meeting, there was an increase of 0.5% in learning activities of students in the experimental class, so it became 42.5% categorized as quite active. While the control class did not increase with an average percentage of learning activities in amount of 37% categorized as less active. Based on this explanation, it can be concluded that the learning activities of students in the experimental class using video conferencing is more active than the learning activities of students in the control class. Through the observations of the two classes, it can be concluded that the use of video conferencing can increase learning activities. This is supported by the results of observations showing that the activities of students in the experimental
| 1,175 |
239702977
| 0 | 16 |
class is more active, so that teaching and learning activities become more meaningful. Using video conference allows students and educators to interact or do learning through audio and video simultaneously (Fitriyani et al., 2020). Video conferencing is also able to make teaching and learning activities not boring and have a high element of interactivity. Meanwhile, the control class with educators did not Control class Experimental Class provide a clear picture of the information conveyed because of the low interactivity of asynchronous learning. Students also tend to passively accept the material that has been shared and are not motivated to ask questions and express opinions when learning. Students' Learning Outcomes In this study, the initial conditions of the students' abilities were tested by distributing pretests and after the treatment were carried out followed by posttests in the control class (X MIA 4) and experimental class (X MIA 2) related to ecosystem material. The results of the students' pretest and posttest can be seen in Figure 3. 1. Pretest 2. Posttest Based on Figure 3 shows the cognitive learning outcomes of students in the control class and the experimental class which is the pretest data in the control class reached an average of 55.2 and in the experimental class reached an average of 50.4. Then, there was an increase in learning outcomes of the control class and the experimental class. The results of the posttest data for the control class increased to 57.6, while the experimental class increased to 68.6. The following table 3 shows the Gain and
| 1,176 |
239702977
| 0 | 16 |
N-gain values obtained in this study. Table 3 shows that the control class has a gain of 2.4 and an N-gain of 0.053 in the low category. Meanwhile, the experimental class has a gain of 18.2 and an N-gain Control Class Experimental Class of 0.36 in the medium category. So, it can be concluded that the highest increase in learning outcomes is in the experimental class by conducting learning using video conferencing. The prerequisite test results used the normality test and the homogeneity test. The normality test used is the Kolmogorov-Smirnov and Shapiro-Wilk. Calculation of normality test data using SPSS 20.0 can be seen in Table 4. Based on the results of the normality test calculation using the SPSS application, the learning outcomes scores (pretest and posttest) in the control class and the experimental class have a P-value of the Lilliefors (Kosmogorov-Smirnov) normality test in amount to 0.2 which is greater than = 0.05, so that the learning outcomes of the two classes come from a normally distributed population. Then the Shapiro-Wilk normality test also shows a P-value greater than = 0.05, so that the learning outcomes of the two classes come from a normally distributed population. Then proceed with the homogeneity test. The results of the homogeneity calculation using the Levene test are shown in Table 5. Based on the calculation results, the homogeneity significance value is 0.656, which means more than = 0.05, so that the learning outcomes data come from a homogeneous population. From the results obtained, it can be determined that the
| 1,177 |
239702977
| 0 | 16 |
learning outcomes of the control and experimental classes are homogeneous. Analysis of research data used to test the hypothesis is using analysis of covariance (ANCOVA). Based on the results of the classical assumption test, it was determined that the data collected was homogeneous and normally distributed. So, for the hypothesis testing stage, analysis of covariance (ANCOVA) can be used. Calculation of data using SPSS 20.0 produces the results shown in Table 6. The results of the Ancova test obtained a significance value of 0.000 which is less than 0, = 0.05, so the null hypothesis is rejected, and the alternative hypothesis is accepted, and it can be concluded if the use of video conferencing has a significant effect on improving student learning outcomes of ecosystem materials in class X SMAN 10 Palembang. Then the Partial eta squared value √0.430 = 0.655 which is greater than = 0.05 indicating that there is no interaction between the pretest and posttest scores, so students are not affected by the pretest when doing the posttest. The results of this study are in line with the research conducted by Ismawati and Prasetyo, the results of the research are learning using video conferencing in early childhood achieves a Gain of 10,313 and it is concluded that video conferencing has a significant effect on learning outcomes (Ismawati & Prasetyo, 2020). This research is also in line with the research results obtained by Liu and Ilyas, namely that video conferencing also has a significant effect on the learning outcomes of students of physics education
| 1,178 |
239702977
| 0 | 16 |
at the University of Flores. This statement is supported by the gain of 6.0741 (Liu & Ilyas, 2020). The research that conducted by Correia et all explained that video conferencing can be used as an effective teaching and communication tool in synchronous distance education. Moreover, due to the multimedia capabilities of web-based video conferencing technology, teachers and students can express themselves using audio, visual, and verbal communication with others. This reduces the ambiguity caused by text only communication and enhances psychological engagement, which potentially leads to a performance level in collaborative tasks comparable to face-to-face communication (Correia et al., 2020). According to studies, it can be concluded that learning using video conferencing has a significant effect on student learning outcomes. Learning using video conferencing can improve learning outcomes higher than the control class because the online synchronous zoom feature on video conferencing allows educators to convey material and provide an overview of information to students through audio and video (Kusuma & Hamidah, 2020) more clearly. Learning using video conferencing at Zoom Cloud Meeting is equipped with HD video features so that students and educators can listen to the material more clearly. Educators also take advantage of presentation features that help in explaining because educators can point the cursor, write to highlight when presenting. With learning using video conferencing, interactivity is higher because students and educators can interact and provide feedback directly and quickly, and educators can more easily manage classes, reach out and observe all students (Elyas, 2018). Communication using video conferencing between the educator and
| 1,179 |
239702977
| 0 | 16 |
the students is visual, audio, and data based. The educator and the other students can hear the student who has been given the floor by the educator (Malik et al., 2017). With respect to data communication, the educator can present media such as PowerPoint to the students, ask them to answer the questions by pressing an appropriate button on the satellite phone, and immediately present the distribution of answers to the students. Learners may also need to ask questions to the instructor and/or share comments with the learning community because of their own reflections. Along the same lines, the chat feature, which is supported by all four systems and virtual hand-raising, which is only supported by Zoom Cloud Meeting, may be useful as well. Additionally, the annotation tools offered are useful to capture reflections and keep comments. (Correia et al., 2020). Conclusion According to the findings, it is shown that the use of video conferencing on ecosystem materials can improve student learning activities in class X SMAN 10 Palembang. Students' learning activities using video conferencing is 39.5% on first meeting, 42% on second meeting and 42.5% on third meeting, while in the control class is 37% and did not show an increase. Results of this research is also shown that the use of video conferencing has a significant effect on improving the learning outcomes of students' ecosystem materials in class X SMAN 10 Palembang. The use of video conferencing on ecosystem materials can improve student learning outcomes in class X SMAN 10 Palembang with an N-gain
| 1,180 |
239702977
| 0 | 16 |
of 0.36, while the control class is only improved learning outcomes with an N-gain of 0.053. Future researchers should be able to conduct research using video conferencing on other learning materials and record the learning process.
| 1,181 |
239702977
| 0 | 16 |
Treatment of severe acetaminophen-induced hepatocellular injury with prostaglandin E : Two case reports ALL HEPATIC DISEASES BEGIN WIth injury to liver cells. Depending on the extent of damage to the hepatocytes, the injury may, at one extreme, be minor and clinically inapparent or it may lead to severe impairment of hepatocellular function associated with encephalopathy and coagulopathy – a condition known as fulminant hepatic failure (1). Similarly, the prognosis of liver disease may be quite favourable with minor insult or it may culminate in mortality of over 90% with stage IV encephalopathy in fulminant hepatic failure (2). Etiological agents in the development of hepatic disease include drugs and toxins, viral hepatitis and vascular injury (3). Acetaminophen is one example of a commonly used over-thecounter drug that may cause severe centrolobular hepatic necrosis when ingested in large amounts in suicide attempts or accidental overdoses. Traditional principles in the management of liver injury include supportive measures, such as fluid and electrolyte resuscitation, repletion of coagulation factors, and glucose infusion, as well as treatment of secondary sepsis (4). Liver transplantation may be life-saving, particularly early in the course of massive hepatocyte damage in a previously healthy organ (5). BRIEF COMMUNICATION – HEPATOLOGY In recent years, a family of bioactive lipids in the form of prostaglandins (PG) have been evaluated in the therapy of fulminant hepatic failure.Preliminary reports of biochemical and clinical response of fulminant viral hepatitis to PGE have been promising (9,10).This report describes two cases of severe acetaminophen-induced hepatocellular injury that improved rapidly after treatment with PGE 1
| 1,182 |
74103931
| 0 | 16 |
. CASE 1 PRESENTATION A 39-year-old female was admitted with acetaminophen, codeine and doxylamine succinate overdose after attempted suicide.She had been diagnosed with multiple personality disorder three years earlier and had two prior episodes of drug overdose. On the night preceding admission, she ingested 32.5 g acetaminophen accompanied by 126 g of alcohol (beer).Over the 12 h before presentation she felt nauseated but denied other symptoms.Medication history was otherwise unremarkable, but she admitted to consuming, on average, 216 g of alcohol (beer) a week. Physical examination upon presentation revealed a well nourished female with blood pressure 140/85 mmHg, pulse 75 beats/min, respiratory rate 18/min and temperature 37.5°C.There was no scleral icterus.Liver span was normal and there was neither splenomegaly nor any stigmata of chronic liver disease.She was alert, fully oriented and no asterixis was elicited.The remainder of the physical examination was within normal limits. Admission laboratory data revealed normal electrolytes, renal function and complete blood count.Pertinent biochemical and hematological data are shown in Table 1.Hepatitis A immunoglobulin M, hepatitis B (HB) surface antigen, anti-HB surface, anti-HB core, as well as antihepatitis C (HC) virus were negative.Acetaminophen level 24 h following overdose was 117 mmol/ L. The remainder of the drug screen was negative. At presentation, an intravenous solution of 5% dextrose/water was initiated.An infusion of N-acetyl cysteine was started as per usual protocol (11).Vitamin K 10 mg orally was administered.Twenty-four hours following admission, the patient was transferred to an intensive care setting to initiate PGE 1 infusion as per the manufacturer's protocol (Upjohn) (Appendix). As the
| 1,183 |
74103931
| 0 | 16 |
liver enzymes and coagulopathy began to normalize, the PGE 1 infusion was tapered and stopped.The patient was assessed and discharged by the psychiatry service. CASE 2 PRESENTATION A 32-year-old single Chilean-born male factory worker was admitted with unintentional overdose of acetaminophen taken for severe toothache.There was no history of other medications but he consumed 54 g alcohol (beer) per week.Two days before admission he ingested 15 g acetaminophen over 90 mins.This was preceded by ingestion of 90 g of alcohol (beer).The day before admission he felt nauseous and weak; over the ensuing 4 to 5 h symptoms progressed to repeated bilious emesis and diffuse abdominal pain.He consulted his family physician who promptly referred him to the emergency department. Physical examination upon presentation revealed a young male in mild to moderate distress due to abdominal discomfort.Blood pressure was 130/80 mmHg, pulse 72 beats/min, respiratory rate 16/min and temperature 37°C.There was no scleral icterus and dental examination showed evidence of pulpitis in an upper molar tooth on the left.There was diffuse abdominal tenderness without rebound, most prominent in the epigastrium.The liver edge was boggy and tender but the span was normal.He was somnolent but arousable and fully oriented without asterixis.classique de la lésion hépatique imputable à l'acétaminophène repose sur le maintien des fonctions vitales et la prévention de toute autre absorption du médicament.De plus, chez les patients dont les concentrations plasmatiques d'acétaminophène sont élevées, la gravité de la nécrose semble s'atténuer lors de l'administration de composés de sulfhydryle, comme la N-acétyl-cystéine.Le présent article décrit deux cas d'hépatotoxicité liée
| 1,184 |
74103931
| 0 | 16 |
à l'acétaminophène traités avec succès par prostaglandine E 1 . There were no stigmata of chronic liver disease. Laboratory investigation on admission showed normal electrolytes, mildly elevated blood urea nitrogen (BUN) at 8.5 mmol/L with creatinine at 102 mmol/L.BUN normalized with hydration.Relevant laboratory data are outlined in Table 2. Serum acetaminophen level 48 h postingestion was less than 66 mmol/L.The drug screen was otherwise unremarkable.Screen for HB and HC was negative. N-acetyl cysteine was administered as per the standard protocol (11), together with intravenous dextrose and saline.The patient was admitted to the intensive care unit for initiation of PGE 1 (for protocol see Appendix).Vitamin K 10 mg subcutaneously was given daily over three days.Potassium phosphate was administered intravenously to correct a serum phosphate of 0.35 mmol/L.Beginning two days following admission, PGE 1 infusion was slowly tapered and stopped as liver enzymes and coagulopathy progressively improved.The patient was discharged in stable condition with dental followup for tooth extraction. DISCUSSION Acetaminophen, a widely used antipyretic analgesic, can cause severe liver injury when ingested in large quantities.It is rapidly absorbed from the gastrointestinal tract and significant firstpass metabolism occurs in the luminal cells of the intestine and in the hepatocytes (12).The drug diffuses quickly into most tissues and concentrates mainly in the liver.A single dose of 10 to 15 g may produce clinical evidence of liver damage, whereas fulminant fatal disease is usually (although not invariably) associated with ingestion of 25 g or more. Acetaminophen hepatotoxicity is mediated by a toxic reactive metabolite formed from the parent compound by
| 1,185 |
74103931
| 0 | 16 |
the cytochrome P450 mixed-function oxidase system of the hepatocyte.Under normal circumstances the metabolite reacts with glutathione to form a harmless end-product.However, the consumption of large doses of acetaminophen depletes glutathione and the metabolite is covalently bound to nucleophilic hepatocyte molecules; this process is believed to lead to hepatocyte necrosis (12).The precise sequence and mechanisms are unclear but it is well known that liver injury may be potentiated by prior alcohol intake ( 13), the so-called alcohol-acetaminophen syndrome.Moreover, combinations of two or more single agents used together may have synergistic toxicity, for example acetaminophen used with isoniazid (14). Treatment of acetaminophen toxicity involves supportive measures and prevention of further drug absorption Based on the cases presented and published data on PG use in fulminant viral hepatitis, the use of PG as adjunctive therapy in acetaminophen-induced hepatic toxicity is an attractive concept.The mechanisms of this beneficial effect remain to be elucidated, yet initiation of PG therapy appears to result in a marked and sustained decrease in transaminases (9,10).The immunosuppressive properties of PG may be instrumental in reversing the liver injury in cases of drug-induced damage.It has been shown that PG decreases expression of class I and II antigens known to be induced in liver disease (15)(16)(17) and that PGE 1 inhibits T cell-mediated cytotoxicity against isolated murine he-patocytes (18).Moreover, several groups have demonstrated beneficial effects of PG in animal models of hepatic failure due to a variety of toxins including acetaminophen (19). CONCLUSIONS We describe two cases in which PGE 1 was used to treat acute acetaminophen-induced hepatotoxicity
| 1,186 |
74103931
| 0 | 16 |
successfully.Controlled and randomized clinical trials are undoubtedly fundamental in establishing efficacy and benefit of this therapy, and in extending the use of PG to other forms of hepatotoxicity.
| 1,187 |
74103931
| 0 | 16 |
Automaticity in reading isiZulu Automaticity, or instant recognition of combinations of letters as units of language, is essential for proficient reading in any language. The article explores automaticity amongst competent adult first-language readers of isiZulu, and the factors associated with it or its opposite - active decoding. Whilst the transparent spelling patterns of isiZulu aid learner readers, some of its orthographical features may militate against their gaining automaticity. These features are agglutination; a conjoined writing system; comparatively long, complex words; and a high rate of recurring strings of particular letters. This implies that optimal strategies for teaching reading in orthographically opaque languages such as English should not be assumed to apply to languages with dissimilar orthographies. Keywords: Orthography; Eye movement; Reading; isiZulu Introduction Recent years have seen a surge of policy supporting the use of indigenous languages in Africa (Trudell 2010), but literature about reading in African languages is sparse.The article reports on indications of automaticity in a study of competent readers of isiZulu, the most widely spoken indigenous South African language. Automaticity in reading 'Reading is arguably the most complex cognitive activity in which humans routinely engage' (Reichle, Warren & McConnell 2009), and yet it is taken for granted by millions of experienced readers who barely notice the fine combination of elements of perception and cognitive activity that cohere during reading.In brief, these are that as we read, we shift our focus along lines of text, processing symbols and their locations to generate visual representations of letters and words and select some of these to
| 1,188 |
55002387
| 0 | 16 |
convert to concepts.As we glean information from each point of focus, we use unclear images in the parafoveal view that suggest word boundaries to plan the next focus shift.Simultaneously, we integrate lexical information gained with semantic and syntactic information from text already read to construct meaning of the text. This complex combination of skills can become automatically integrated into a relaxed, swift exercise.When this happens, we have developed automaticity and can use brief visual perceptions of symbol clusters to automatically access associated pieces of language and meanings without additional active cognitive decoding (Penner-Wilger 2008).We can then engage imaginatively with meaning, making inferences, links with remembered information and judgements on what the writer has communicated.Without automaticity, it is extremely difficult for readers to construct a growing interpretation of texts as they read, to use context to aid comprehension (Marinelli, Martelli & Zoccolotti 2010), to gain new information from the text (Verhoeven, Reitsma & Siegel 2011), or to perform any higher order skills associated with reading (Abadzi 2012). Attaining automaticity Automaticity is regarded as crucial for reading by Helen Abadzi whose work in neuroscience has brought new insight to understanding reading processes.Abadzi describes automaticity as a 'vaccine' and an 'on-off switch' for literacy (2011); without it, competent reading is not possible.Confirming psycholinguistic evidence, neuroscience indicates that to read effectively, readers must move through text fluently and swiftly because human working memory has a capacity of about 12 seconds (Abadzi 2012).To understand messages in text, we must construct them as wholes, and so must read rapidly enough to get
| 1,189 |
55002387
| 0 | 16 |
from the beginning to the end of each message within 12 seconds.In English, a minimum reading rate of 45-60 words per minute (wpm) appears necessary for reading at a basic level (Abadzi 2012).Complex tasks, like searching for information, require speeds of about 250 wpm (Abadzi 2010).This reading rate can be achieved only through automatic, instantaneous recognition of a significant proportion of words, and to establish Automaticity, or instant recognition of combinations of letters as units of language, is essential for proficient reading in any language.The article explores automaticity amongst competent adult first-language readers of isiZulu, and the factors associated with it or its opposite -active decoding.Whilst the transparent spelling patterns of isiZulu aid learner readers, some of its orthographical features may militate against their gaining automaticity.These features are agglutination; a conjoined writing system; comparatively long, complex words; and a high rate of recurring strings of particular letters.This implies that optimal strategies for teaching reading in orthographically opaque languages such as English should not be assumed to apply to languages with dissimilar orthographies.automaticity clusters of letters must be perceived as whole words or units rather than groups of characters.This develops only through extensive exposure to text and repeated association of particular clusters with words or units they represent. Children who are included in literacy-related practices early and have explicit instruction in developing reading skills and plenty of supported reading practice usually achieve automaticity easily.In contrast, children who have little exposure to literacy practices, mediocre instruction and infrequent reading practice may never achieve it (Abadzi 2012).People who learn
| 1,190 |
55002387
| 0 | 16 |
to read after adolescence rarely achieve automaticity, and adults learning to read a new script report that although they see all the letters, they must consciously work out what words they represent (Abadzi 1996).In a new script, a word needs to be decoded approximately 3000 times before it is automatically recognised (Abadzi 2012). Automaticity in different languages and orthographies Learning to read appears to be easier in languages with consistent orthographies, that is where letters always represent the same sounds.Inconsistent orthographies compel readers to seek cues in large groupings of letters -in other words, in large-grain size units of text (Georgiou, Parrila & Papadopoulos 2008), which assists in the automatic recognition of whole words.Amongst languages used in Europe, the ability to read words accurately takes longest to develop in English, which has the most opaque orthography amongst them (Georgiou et al. 2008;Seymour, Aro & Erskine 2003).Children learning to read languages with consistent, transparent orthographies (e.g.Italian, German, Greek, Spanish and Finnish) read words accurately at the end of grade one (Ziegler et al. 2010).In comparison, children reading Portuguese, French and Danish (which are orthographically inconsistent and less transparent) cannot read words as accurately.Children learning to read in English, with the least transparent and least consistent orthography in Europe, achieve only 34% accuracy at the end of grade one (Ziegler et al. 2010) and lag behind German children in accurately reading words even at age 12, suggesting that English is 'the hardest European orthography to acquire' (Hutzler et al. 2004).Comparable information on learning to read in African languages
| 1,191 |
55002387
| 0 | 16 |
is not available. Children who read orthographically consistent languages are better at reading pseudo words (pronounceable non-words) than children who read English (Seymour et al. 2003).This suggests that they are decoding graphemes directly to phonemes 1 , using small grain size orthographic cues (Ziegler & Goswami 2005).This means that they rapidly reconstruct speech sounds on the basis of letter-sound correlation.In contrast, beginner readers of English must learn letter-sound 1.A phoneme is a single speech sound.A grapheme is a representation of a single speech sound and can be a single letter (e.g.'o' and 'm') or a pair of letters (e.g.'th' and 'ng') or a cluster of letters (e.g.'ough').Phonemes and graphemes differ between languages. correlation and develop a mental lexicon based on larger grain size orthographic cues (Seymour et al. 2003).Also, readers of opaque orthographies may use knowledge of syntax, vocabulary and contextual cues more than readers of transparent orthographies (Share 2008).This combination of strategies apparently enables readers to cope with contradictory rules as they learn to read words that are visually similar but phonologically distinct, for example 'tough', 'though', 'thought' and 'through'. In languages whose orthography features clusters of consonants and graphemes of groups of letters, it is relatively difficult to learn decoding skills (Seymour et al. 2003). Unsurprisingly, automatic recognition is most easily established where simple visual patterns consistently represent particular word sounds (Abadzi 2011). Thus, automaticity is likely to develop more easily in orthographies whose printed word forms are obviously dissimilar to one another and with more difficulty in orthographies where unrelated words can look
| 1,192 |
55002387
| 0 | 16 |
similar.This has particular relevance here because agglutinated isiZulu words may be visually complex and similar, yet not semantically related. Eye movement and automaticity Fixations are strongly related to readers' direction of attention (Miellet, O'Donnell & Seren 2009;Paulson 2005), and cognitive procedures of text comprehension and ease or difficulty in identifying words influence eye movements (Paterson, Alcock & Liversedge 2011).This implies that eye movement records can show which units of text are automatically recognised and which are processed only after refixations, indicating that they are decoded with cognitive effort. Eye movements indicating established automaticity Word recognition might not always happen exactly in parallel with eye movements (Rayner, Juhasz & Pollatsek 2007).However, in eye movement records of silent reading of continuous alphabetic text, brief fixations separated by wide saccades, plus a reader's good understanding of text point unequivocally to a high level of automaticity.Successive, fleeting fixations without regressions indicate that a reader's focus has moved steadily along lines of text, and visual stimuli have been smoothly transformed into the 'flow of phonetic imagery through the mind' (Coulmas 2003) that characterises fluent silent reading.Elements recognised could be single words, words in a familiar or predictable string or parts of complex single words. Word recognition Instant recognition of a word may be an instant response to seeing the printed form [Perfetti & Ehri, cited in Castles and Nation (2008)], but in text passages, short, familiar, predictable words are often skipped by efficient readers (Paterson et al. 2011;Rayner 2009).This suggests that readers use anticipated meaning or word collocations to predict words
| 1,193 |
55002387
| 0 | 16 |
to the right of their point of focus, and if the indefinite shape perceived matches the prediction, they take the word as read without fixating directly on it (Paterson et al. 2011).Word recognition is probably also influenced by a reader's prior knowledge, suppositions activated during reading and construction of meaning of text read so far (Rapp & van den Broek 2005).Within a sentence, complex words are more easily recognised if preceded by semantically related words (Paterson et al. 2011).These factors inevitably differ between readers and contexts. Eye movements indicating absence of automaticity A high frequency of refixations and regressions implies that a reader is not automatically recognising many words.In English, readers take longer to recognise multisyllabic words than short ones; words incorporating more than nine letters are often read with more than one fixation, and each syllable adds on average 20 milliseconds to recognition time in studies of lexical decision making (New et al. 2006).This reflects Paterson's observation (2011) that visual recognition of English words composed of multiple morphemes (e.g.'multisyllabic') is likely to depend on breakdown into constituent morphemes. Regressions show that a reader is referring to areas of difficulty in text read (Paulson 2005).Causes of regression include syntactic or semantic complexities, low-frequency words, confusion, disconfirmation of an interpretation, difficulties in word identification, overshooting or undershooting the beginning of a line or returning to words skipped on a first reading (Paulson 2005).Paterson et al. (2011) note readers' tendency to regress on the second of two related morphologically complex words in a sentence and suggest similar word
| 1,194 |
55002387
| 0 | 16 |
forms can inhibit recognition.When regressing, readers seem to maintain a sense of the spatial arrangement of words in text understood so far and can return their point of focus to points that were problematic for them (Rayner, Fischer & Pollatsek 1998).Because readers redirect their focus to points that caused them difficulty, analysis of eye movement records could reveal features in text that attract regressions most frequently. Reading and Zulu orthography Literature on reading African languages is minimal compared with English (Pretorius & Mampuru 2007), but comparison of reading skills in isiZulu and English is appropriate because they are the most used languages in KwaZulu-Natal (van der Merwe & van der Merwe 2006) and isiZulu speakers need to learn to read in both of them at school. Findings from reading research in English cannot be assumed to apply across languages (Share 2008), and readers of English and isiZulu may have to develop contrasting skills for each orthography.In terms of psycholinguistic grain size theory, because isiZulu orthography is consistent and transparent, its readers probably process relatively small-grain size units of text, as do readers of other orthographically consistent languages (Ziegler & Goswami 2005).This small grain size processing might be the optimal strategy for reading isiZulu not only because of its orthographic consistency but also because of its agglutinative nature and conjoined writing system.These features make many words long and complex, composed of short morphemes clustered round central word sterns.To illustrate, one isiZulu word is often the equivalent of four or five words in disjunctive languages such as English,
| 1,195 |
55002387
| 0 | 16 |
as in the starting sentence of one of the texts used in this study: Wawunezindlu ezingamaqhugwana amathathu wakhiwe ngaphansi kwegquma (He had three houses that were [grass] huts built at the base of a hill) (Literal translation: He-had-houses that-were-huts three built at-the-base of-a-hill). These six isiZulu words translate into 14 English words, but use more line space. Because long complex words occur frequently even in fairly simple isiZulu text, word length is unlikely to be a salient determining factor of reading difficulty in isiZulu (as explained below).In contrast, in the disjunctive languages of Europe, it is central to measures of reading difficulty (Readability Formulas 2013). There are high-frequency, short, unagglutinated isiZulu words that have a constant form, for example nouns such as umuntu/abantu (person/people), adverbs such as kahle (well or slowly), and conjunctives such as kodwa (but).Proficient isiZulu readers are likely to automatically recognise these words instantly.They probably also automatically recognise commonly recurring parts of long agglutinated words as 'multiletter units' as suggested by Verhoeven et al. (2011).For example, in a word from the sentence above, Wawunezindlu, a reader may automatically recognise any or all of the morphemes wa wu ne zi or ndlu. This study Based on recordings of eye movements of proficient readers of isiZulu, and their recall of reading processes, this study seeks to discover their patterns of automaticity.It asks the following questions: Which words were instantly recognised and which needed active decoding by nearly all the most proficient readers? To what extent is their treatment of recurring words consistent? What can their
| 1,196 |
55002387
| 0 | 16 |
immediate recollection of reading experiences reveal about processes that combine in reading isiZulu text? Instruments According to Shuter & Shooter Educational Publishers, who have published isiZulu novels, poetry and textbooks since the 1930s, no official grading system exists for isiZulu texts; publishers rely 'on gut feel to gauge the language level for any grade' (S.Zulu, pers. comm., 12 April 2013).So to select texts for this study, three first-language isiZulu lecturers in education at the University of KwaZulu-Natal were asked to judge the readability of excerpts from novels written in (as opposed to translated into) isiZulu (Appendix 1).Notably, their 'gut feel' judgement matched sentence length and complexity.Two texts judged to be easy to read consisted of 19 sentences with an average of 1.4 clauses per sentence and 15 sentences with an average of 1.8 clauses per sentence, respectively.One of two texts judged to be more difficult had 10 sentences with an average of 2.7 clauses per sentence, and the other only six sentences with an average of 4.2 clauses per sentence.Average word length differs by less than one letter across the four texts, and so it is unlikely to have influenced the perceived reading difficulty.The easy texts were seen to reflect current urban isiZulu, whilst the more difficult texts included words and expressions characteristic of 'deep isiZulu' spoken in remote rural areas and formally studied at academic institutions. The Visagraph eye movement recording system used in this study records fixations, regressions, reading rate and intereye coordination (Compevo 2012).The system uses infrared differential reflectivity to detect eye movement
| 1,197 |
55002387
| 0 | 16 |
and samples eye position 60× per second (Compevo 2012).Some systems sample eye position at higher rates than this.However, competent readers in other languages 2 make up to 5.2 fixations per second (Hutzler, Braun & Jacobs 2008), so even at this rate, the Visagraph's recording rate would enable each fixation to be recorded approximately 11.5 times.The advantage of Visagraph here is that it operates in natural light, allows free head movement and uses text printed on normal sheets of A4 paper held by readers at reading distances they found comfortable.Thus, although readers wore a mask and knew that their eye movements were being recorded, the reading experience was natural at least in that the text read was authentic continuous text printed on normal paper, and readers sat in ordinary chairs in a natural reading posture. Sample Measures of reading proficiency in isiZulu have yet to be standardised (Van Rooy & Pretorius 2013), so selection and screening of participants was necessarily innovative.Sampling was purposive and encouraged competent readers of isiZulu text to self-select.An invitation to proficient readers of isiZulu was inserted in an isiZulu newspaper in Pietermaritzburg and sent to isiZulu-speaking academics, journalists, publishers and high-performing learners at a local high school. Approximately 150 respondents underwent a reading test 3 .On the basis of their speed and accuracy, the most efficient 25% of respondents (38 of them) were selected, and their eye movements recorded as they silently read four texts described above.Five participants were excluded because of imperfect recordings.The remaining group of 33 included: • 15 women and
| 1,198 |
55002387
| 0 | 16 |
18 men • 24 professionals, 5 full-time university students and 4 high school students. Participants' ages ranged from 16-61, with 25 of them between the ages of 20 and 49. Because the article focuses particularly on automaticity and the orthography of isiZulu, the analysis and discussion below is based on the 10 swiftest recordings of each text (i.e.40 recordings).This selection increased the likelihood that the recorded eye movements demonstrated established automaticity.An analysis of the reading patterns of the whole group is discussed in another article (Land 2015). Data collection This took approximately one hour for each participant.The mask of the recording system was fitted to the reader's head, its receptors aligned with the pupils of their eyes and their eye movements recorded as they silently read each text. Immediately after reading each text, each reader gave an account of the content to show the extent of their understanding. The Visagraph system allows recorded eye movements to be viewed in various forms, one of which allows the replay of the movement of the reader's point of focus represented by a moving cursor on an electronic copy of the text read.This was possible through an isiZulu language package using the selected texts, and designed particularly for this research by Reading Plus, an organisation that offers computer-based reading improvement programmes.With the reading experience fresh in her mind, each reader joined the researcher in following and discussing the recorded movement of her point of focus on the text.The purpose of this exercise was not to try and recapture the subconscious
| 1,199 |
55002387
| 0 | 16 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.