*Article* **The Chemical Composition and Surface Texture of Transparent Heavy Minerals from Core LQ24 in the Changjiang Delta**

#### **Wei Yue 1,2,\*, Xiyuan Yue 3, Sugandha Panwar 2, Lingmin Zhang 2 and Bingfu Jin 4**

Received: 12 May 2019; Accepted: 19 July 2019; Published: 22 July 2019

**Abstract:** The assessment of textural and compositional modifications of detrital sediments is required to reconstruct past source to sink dynamics. The Changjiang Delta is an ideal location to study the sedimentary environment from the Pliocene to Quaternary transition. In the present study, we aim to decipher the response of heavy minerals to mechanical wear and chemical weathering since the Pliocene. With the application of a scanning electron microscope and an electron probe, the geochemistry and surface texture of different heavy minerals (amphibole, epidote, and tourmaline groups) with grain-size fractions of 32–63 μm and 63–125 μm were studied. The result shows that the surface texture of unstable minerals (amphibole, epidote) changed under strong chemical weathering in the Pliocene sediments. By contrast, unstable minerals of the Pleistocene sediments are relatively fresh and similar to those of the modern Changjiang sediment. The stable mineral tourmaline does not exhibit morphology changes in different chemical weathering conditions. No effect of grain size on geochemical composition is noticed. The single minerals of very fine sand and coarse silt show similar geochemical and morphological features. The integration of mineralogy, geochemical data, and grain size parameters yield a more precise understanding of the physical and chemical response of heavy minerals to different weathering conditions. The outcome of the study is also helpful in deciphering sediment provenance changes and environmental changes in the Changjiang basin.

**Keywords:** heavy mineral; Pliocene; the Changjiang Delta; amphibole; surface texture

#### **1. Introduction**

The study of source to sink dynamics of large river systems such as Changjiang are vital to understand the hydrological, geomorphological, ecological, and anthropogenic modifications in the ever-changing climatic conditions [1–3]. The pre-dam (Three Gorges Dam) sediment yield of the Changjiang River was >300 × 106 tons per year, whereas, at present, it is ~120 × 106 tons [4]. The reconstruction of the source and distribution patterns of the delta sediments can help to unravel the history of erosion processes, source area characteristics, and the factors controlling and determining the production (source), transport, dispersal and accumulation (sink), and reworking (number of burial-erosion cycles during sediment transport) at different temporal and spatial scales [5–7].

The identification and quantification of heavy minerals is one of the most sensitive approaches to classify the various provenance terrains and depositional environment conditions [8,9]. However, heavy mineral assemblages are affected by hydraulic sorting during transportation, chemical weathering during deposition, and dissolution during diagenesis [10–13]. Moreover, physical and chemical

etching and corrosion processes intensify with burial depth due to intrastratal dissolution, resulting in the depletion of unstable minerals (like amphibole and epidote) and the enrichment of stable minerals (ZTR) in core sediments [8,14]. To overcome this bias, several provenance-sensitive heavy mineral ratios (e.g., the garnet-zircon (GZi), ZTR, and stability indexes) are widely used [11,15]. Moreover, in situ geochemical analysis of heavy minerals is also widely applied in geoscience and adds a considerable complexity of interpretation [16–18]. Chemical analysis on single-grain minerals (e.g., zircon, tourmaline, apatite, rutile, monazite, amphibole, and garnet) has promoted the study of sediment source to sink [19–21]. However, there are only a few studies that deal with the relationship between the physical and chemical parameters of single heavy minerals and address these significant research lacunae: (i) How do different minerals respond to different sedimentary environments in the deltaic area? (ii) Do the physical and chemical properties of stable and unstable heavy minerals change depending on depth?

Thicknesses of 150–400 m sediments have been deposited in the Changjiang Delta since the Pliocene [22]. This area is a natural laboratory that can be used to carry out studies on sediment provenance, tectonic evolution, sedimentary environment, and river evolution [23–25]. With the application of clay minerals, geochemistry, and heavy mineral analyses, researchers have documented different sedimentary environments during the Pliocene to Pleistocene transition [26,27]. Heavy mineral analysis evinces the presence of high contents of zircon and extremely low contents of amphibole (5%) in Pliocene sediments of the Changjiang Delta, which is related to strong chemical weathering or diagenesis during this time (Figure 1). In contrast, high proportions of unstable mineral (amphibole 40%) in the Pleistocene strata indicate relatively weak chemical weathering or minor diagenetic effects [3,27]. The high heavy mineral concentration (HMC) values in some of the Pleistocene samples define a placer trend, probably due to hydraulic sorting [13,20]. The different chemical weathering and sedimentary conditions at the Pliocene to Quaternary transition make the Changjiang Delta an ideal location to document the physical and geochemical response of single minerals to different sedimentary environments [23,27].

**Figure 1.** Stable minerals (ZTR) vs. heavy mineral concentration of Pliocene and Pleistocene sediments from the Core LQ24 of the Changjiang Delta. HMC = Heavy mineral concentration; the ZTR index [11] is the percentage of relatively durable zircon, tourmaline, and rutile among the transparent heavy minerals. The high HMC values in some of the Pleistocene samples define a placer trend [13], and diagenetic dissolution in the Pliocene sand produces a decrease in HMC and an increase in ZTR.

In this study, unstable (amphibole, epidote) and stable (tourmaline) heavy mineral in grain size fractions of 32–63 μm and 63–125 μm were analyzed by using a scanning electron microscope (SEM) and an electron probe (EP). Through the assessment of the surface texture and chemical composition of different transparent heavy minerals, we aim to study the physical and chemical response of different single minerals and discuss their influence on provenance discrimination.

#### **2. Materials and Methods**

One continuous Late Cenozoic borehole (LQ24, 400 m in length) was extracted from Chongming Island in the Changjiang Delta. The bottom (400–337.2 m) of LQ24 is constrained to the Pliocene according to the paleomagnetic analysis results, which disclosed that the boundary of Gauss/Matuyama (G/M) is located at a core depth of 337.2 m (Figure 2). The Pliocene strata above the bedrocks consisted of stiff clay. There were many calcareous and iron-manganese nodules (Figure 2). Moreover, a block of grey calcareous sand was found in the bottom strata (Figure 2). No microfossils were found in the Pliocene sediments. In addition, poorly sorted gravels can be found, which indicate the origin of sedimentary facies as an alluvial fan or a meandering river [22]. The Quaternary strata comprised several sedimentary sequences, which were composed of sand at the bottom and clayey silt at the top, suggesting a fluvial environment (Figure 2). In some mid–late Quaternary sediments, foraminifera and shell debris were easily found, implying marine transgression since then [3,23,27]. In-depth detailed stratigraphic information, including magnetostratigraphy, grain size, sedimentary facies, magnetic susceptibility, and foraminifera have been documented by [3]. In the present study, two Pliocene sediment samples (core depth of 378 m and 355 m), and three Pleistocene samples (core depth of 320, 259, and 178 m) were selected (Figure 2).

**Figure 2.** The Plio-Pleistocene magneto-stratigraphy of Core LQ24 from the Changjiang Delta. Paleo-magnetic dating, lithology, and grain size parameters were from [3]. N = Pliocene, Q = Pleistocene.

In order to make a comparison with the Changjiang Delta sediment, one modern sediment sample was collected from its estuary levee (Figure 3).

**Figure 3.** Sampling locations of the core and modern Changjiang River sediment.

For each sample (1 kg each), the very fine sand (63–125 μm) and coarse silt (32–63 μm) fractions were separated and selected for single mineral analyses. These size fractions were wet-sieved through 125, 63, and 32 μm nylon meshes, respectively. After drying in the oven with a temperature of <40 ◦C, the very fine sand and coarse silt fractions were then put into a sodium polytungstate solution (2.90 kg/dm3 at 20 ◦C; e.g., [5,21,28]) and heavy minerals were separated from the light fraction by the gravity separation method (e.g., [14,29]). The content of the heavy minerals (HMC) is calculated as the total mass of the heavy mineral fraction contained in the analyzed fraction [30].

After heavy liquid separation, >100 mineral grains (amphibole, epidote, and tourmaline) were handpicked randomly under a stereoscopic microscope. Further, all the handpicked minerals were observed and checked under a polarizing microscope. All of the amphibole grains of the Pliocene samples were selected due to their low concentrations. At least 30 single mineral grains were measured randomly by SEM analysis. After SEM analysis, single mineral grains were then embedded in epoxy, polished, and coated with carbon to carry out electron probe analysis. A uniform flat surface of each grain was selected as a test spot. Single mineral grains were photographed by a scanning electron microscope (XL-30 ESEM, Philips Company, Eindhoven, The Netherlands), and the mineral chemical composition was measured by an electron probe microanalysis (JXA-8230 electron probe system, JEOL, Kyoto, Japan) at the State Key Laboratory of Marine Geology, Tongji University. The measurement conditions were a 15 kV accelerating voltage, a 10 nA probe current, and a 5 μm beam diameter. The analysis time of each element was 30 s for Si, Mg, Al, Fe, Ca, and Mn; 10 s for Na; 12 s for K; and 60 s for Ti. Natural and synthetic mineral standards (SPI) were used to calibrate all quantitative analyses, and a ZAF correction was used for data reduction.

#### **3. Results**

#### *3.1. Geochemical Characteristics of Di*ff*erent Single Minerals in Core LQ24*

#### 3.1.1. Geochemical Characteristics of Unstable Minerals in Core LQ24

No change in the composition content (TFeO, CaO, MgO, Al2O3, K2O, TiO2, MnO, Cr2O3, and V2O3) of the amphibole derived from very fine sand and the coarse silt fractions was noticed (Figure 4). The detailed EPMA results of this study are presented in Table 1.

Further classification of the amphiboles was made in Figure 5. Results show that members of the amphibole group in all of the Changjiang sediment samples belong to the calcic–amphibole group [31], in which ten different kinds of hornblendes were included. These hornblendes were dominated by magnesio-hornblende, followed by actinolite, tschermakite, and edenite (Figure 5). Other amphibole species, including ferrotschermakite, ferroedenite, magnesio hastingsite, and ferropargasite, were low in content. Moreover, amphibole compositions in very fine sand and coarse silt fractions were very similar (Figure 5).

Similar to the characteristics of the amphibole in Core LQ24, the epidote geochemistry of the Pliocene is almost the same with the Pleistocene and modern Changjiang samples (Figure 6). No difference in the composition (main element content) of the epidote between 63–125 μm and 32–63 μm size fractions was found.

**Figure 4.** The mean element compositions of the amphibole of Core LQ24 and modern Changjiang River. A very fine sand fraction (63–125 μm) is indicated by full lines and coarse silt (32–63 μm) is indicated by dashed lines. Core depth is set in the vertical axis. CJ = Changjiang River. Core samples that were sampled from different depths of burial are marked in a red and light blue color. The red one is representative of the Pliocene; the light blue is representative of Pleistocene; N = Pliocene, Q = Pleistocene. Please see Table 1 for the numbers of grains analysed per sample.

**Figure 5.** Amphibole classification diagrams for Core LQ24 and the modern Changjing River. CJ = Changjiang, N = Pliocene, Q = Pleistocene. Ca-amphibole classification was performed according to [31].

**Figure 6.** Mean element compositions of the epidote of Core LQ24 and the modern Changjiang River. A very fine sand fraction (63–125 μm) is indicated by full lines and coarse silt (32–63 μm) is indicated by dashed lines. Core depth is set in the vertical axis. CJ = Changjiang River. Core samples that were sampled from different depths of burial are marked in a red and light blue color. The red one is representative of the Pliocene; the light blue is representative of the Pleistocene; N = Pliocene, Q = Pleistocene. Please see Table 1 for the numbers of grains analysed per sample.

3.1.2. Geochemical Characteristics of Stable Mineral in Core LQ24

The element composition (Al2O3, TFeO, MgO, Na2O, CaO, K2O, TiO2, MnO, Cr2O3, and V2O3) of stable tourmaline is shown in Figure 7. Similar to the geochemical characteristics of amphibole and epidote in Core LQ24, the element characteristics of tourmaline are also the same at different core depths and the same as the modern Changjiang river samples (Figure 7).

**Figure 7.** The mean element compositions of the tourmaline of Core LQ24 and the modern Changjiang River. A very fine sand fraction (63–125 μm) is indicated by full lines and coarse silt (32–63 μm) is indicated by dashed lines. The core depth is set in the vertical axis. CJ = Changjiang River. Core samples that were sampled from different depths of burial are marked in a red and light blue color. The red one is representative of the Pliocene; the light blue is representative of the Pleistocene; N = Pliocene, Q = Pleistocene. Please see Table 1 for the numbers of grains analysed per sample.

#### *3.2. Surface Texture of Di*ff*erent Transparent Heavy Minerals in Core Sediment of the Changjiang Delta*

The surface texture characteristic of unstable heavy minerals are different for the Pliocene and Pleistocene sediment samples (Figure 8). The corroded unstable mineral grains were abundant in the Pliocene sediment compared to the Pleistocene samples. The corroded amphibole accounted for about 30% in the Pliocene sediment and 15% in the Pleistocene samples. On the other hand, corroded epidote grains accounted for about 50% in Pliocene sediments, which was approximately twice that of the Pleistocene samples. In contrast to the unstable minerals, the surface texture of the stable minerals did not exhibit an obvious change in the depth of the core. The corroded tourmaline grains were about 10% on average, which was less than that of unstable minerals. For the same single mineral, the surface texture characteristic of the very fine sand was similar to that of the coarse silt (Figure 8).

**Figure 8.** Percentage of corroded single mineral grains in the Core LQ24 of Changjiang Delta. A very fine sand fraction (63–125 μm) is indicated by full lines and coarse silt (32–63 μm) is indicated by dashed lines. N = Pliocene, Q = Pleistocene.

#### 3.2.1. Crystal Morphology of Unstable Heavy Minerals in Core LQ24

SEM results showed that the surface texture of the unstable heavy minerals was different in the Pliocene and Pleistocene samples. For the Pliocene sediment of Core LQ24, both the amphibole and epidote displayed evidence of chemical etching (Figures 9 and 10). Etch pits on the crystal surfaces of these single mineral grains were visible. The crystal corrosion along the cleavage plane and fuzzy edges were readily visible. Microscope observation found that the transparency of some mineral grains was significantly reduced. Due to strong dissolution, some amphibole grains were found to be deeply etched (Figure 9).

**Figure 9.** Surface texture of the amphibole in the Core LQ24 of the Changjiang Delta. s = Very fine sand fraction (63–125 μm), cs = coarse silt fraction (32–63 μm). N = Pliocene, Q = Pleistocene.

Unlike the sample of the Pliocene strata, the surface texture of the unstable heavy minerals in the Pleistocene sample displayed different characteristics. Amphibole and epidote grains generally had an irregular-angular shape, and their crystal surfaces were relatively fresh (Figures 9 and 10). Two systems of cleavage were obvious at a specific angle. Only a few particles had a fuzzy crystal surface and plane due to dissolution and abrasion (Figures 9 and 10). The crystal morphology of the different grain size displayed little surface texture difference between the very fine sand and coarse silt.

**Figure 10.** Surface texture of the epidote in the Core LQ24 of the Changjiang Delta. s = Very fine sand fraction (63–125 μm), cs = coarse silt fraction (32–63 μm). N = Pliocene, Q = Pleistocene.

#### 3.2.2. Surface Texture of Stable Heavy Mineral

The SEM images of the stable heavy mineral of tourmaline showed that crystal particles in the Pliocene and Pleistocene sediments had short prismatic or granular morphologies, and were mostly sub-angular or sub-rounded in shape (Figure 11). The edges of the tourmaline crystal were clear with generally flat crystal surfaces. Etch pits were noticed in a few particles (Figure 11). Similar crystal morphologies were observed in the Pleistocene and Pliocene samples of tourmaline. The tourmaline grain size in the very fine sand and coarse silt has a similar surface texture. In general, the unstable heavy minerals of the Pliocene samples show signs of weathering, while these minerals in the Quaternary strata are relatively fresh. A slight alteration or dissolution was found in the crystal morphology of the stable mineral from the Changjiang Delta, and no variations were seen in the Pliocene and Pleistocene samples.

**Figure 11.** Surface texture of the tourmaline in the Core LQ24 of the Changjiang Delta. s = Very fine sand fraction (63–125 μm), cs = coarse silt fraction (32–63 μm). N = Pliocene, Q = Pleistocene.

#### **4. Discussion**

#### *4.1. The Factors Which may Cause Variations in Surface Texture of Di*ff*erent Single Minerals*

The corrosion signature of heavy minerals indicates different transportation, sedimentation, and burial conditions [32–34]. The SEM images of Core LQ24 revealed that the amphibole and epidote in the Pliocene strata were more corroded than the tourmaline mineral present in both the Pliocene and Pleistocene sediments (Figures 9–11). In our interpretation, weathering is the main factor influencing the dissolution of unstable minerals in the analyzed sediment samples. In the warm-humid climate, chemical weathering proceeds at a faster rate and can result in the progressive corrosion and depletion of unstable minerals [35,36]. Previous studies have documented a drastic environment change in the Changjiang Delta during the Pliocene to Pleistocene transition [23,27]. Then, warm and wet climate conditions were prevalent in East China, along with a low deposition rate in the Changjiang Delta [24,37,38]. Before deposition, weathering may have been responsible for the surface texture variation in amphibole, epidote, and tourmaline. In such strong weathering conditions, unstable minerals are progressively corroded and finally depleted.

The abundance of apatite is a reliable indicator of surface weathering. This mineral is susceptible to dissolution during weathering but remains stable in deep burial [8,13,15]. In order to reflect the weathering intensity, we used the ATi (Apatite-Tourmaline index), whose value is calculated as (100 × Apatite%)/(Apatite% + tourmaline%) [39]. In this parameter, two minerals (Apatite and tourmaline) possess identical densities but show contrasting behaviours in weathering, thereby reducing the effect of hydrodynamics. Furthermore, apatite fertility and erosion rates may have an impact on the content of apatite [20,21]. In the present study, low ATi and apatite content in the Pliocene imply stronger weathering scenarios (Figure 12). Moreover, a strong enrichment of ZTR and a significant loss of unstable minerals (amphibole <5%) also suggest that weathering was much stronger during the Pliocene than during the Quaternary time (Figure 12).

**Figure 12.** Heavy mineral distribution for Core LQ24 of the Changjiang Delta. Heavy mineral data are from [3]. The analyzed size fraction is very fine sand (63–125 μm). N = Pliocene, Q = Pleistocene. Systematic mineral abbreviation list: ATi (Apatite-Tourmaline index) = (100 × Apatite%)/(Apatite% + tourmaline%). Amp = Amphibole, Ep = Epidote, Ilm = Ilmenite, Mgt = Magnetite, Px = Pyroxene, Ap = Apatite, Zrn = Zircon; Tur = Tourmaline, Grt = Garnet, Others = Other heavy minerals and mineral aggregate, including limonite, fluorite, titanite, rutile, anatase, kyanite, andalusite, un-identified grains, rock fragments, etc.

Strong weathering conditions resulted in a decline in the concentration of unstable heavy minerals [8,27], and amphibole and epidote developed etched surfaces, as shown in Figures 9 and 10. As an unstable heavy mineral, amphibole is dissolved in strong weathering conditions [10,27]. In such environments, unstable minerals were easily etched during the Pliocene. SEM images show that amphibole and epidote were corroded along the direction of the crystal cleavage and left tiny holes on the crystal face after dissolution (Figures 9 and 10). At the same time, the crystal's transparency reduced.

Amphibole and epidote etching were found to be comparable to previously published studies [9,10,32]. In modern sediments of subequatorial regions, surface textures of detrital minerals ranged from incipient corrosion to deep etching, reflecting a progressive increase in the degree of alteration [9]. In addition, some studies show that etching developed from mamillations, through facetted grains, to skeletal grains [32]. Therefore, we infer that the etching of amphibole and epidote grains would have occurred during the sediment transport process before deposition in the sink area of the Changjiang Delta. In this process, the least stable mineral, amphibole, dissolved faster and decreased in the bottom of Core LQ24. On the other hand, the more stable minerals of ZTR dissolved at slower rates and thus were relatively enriched.

The intrastratal dissolution during the diagenetic process may also be listed as a major factor that promotes unstable mineral dissolution in a core sediment. For ancient sediments, temperatures and pressures that increase with burial depth cause the intrastratal dissolution of unstable heavy minerals [14]. Being a depocenter since the Pliocene, the Changjiang Delta has a deposition of a ~300 m thick siliciclastic sedimentary sequence. Affected by compaction and diagenesis, a block of calcite-cemented sand formed at the core bottom of the Changjiang Delta [3,27]. However, the burial depths involved in this study area are modest (the deepest thickness = ca. 400 m), and the sediments of the Changjiang Delta are very young (Neogene) [22,38]. Calcite-cemented sands in the bottom strata are not fully diagenized. Environmental magnetic parameters have shown that diagenesis has not erased the detrital magnetic signal in the Changjiang Delta. This observation suggests weak post-depositional diagenesis [38]. Compared to similar studies in other parts of the world, the process of dissolution during burial diagenesis needs a deeper burial and higher temperatures. Studies in older (Paleocene) sandstones of the North Sea show that amphibole and epidote dissolutions are not complete until they reach a 600 m and 1100 m burial depth, respectively [40]. Walderhaug and Porten suggest that amphibole and epidote dissolution requires pore water temperatures of 40 and 95 ◦C, respectively [41]. These studies suggest that the process of burial diagenesis did not play a significant role in the single mineral dissolution in the Changjiang Delta.

#### *4.2. Chemical Responses of Di*ff*erent Single Minerals to Di*ff*erent Weathering Environments*

Irrespective of the corroded surface texture of susceptible heavy minerals in the Pliocene strata (as a result of strong weathering conditions), no change in the major element composition of single minerals was observed (Figures 4–7). The EPMA results show the prevalence of a similar geochemical character in single minerals extracted from the Pliocene, Pleistocene, and modern Changjiang sediments. The result of amphibole classification showed that all amphibole grains in the boreholes and river samples were mainly composed of magnesio-hornblende, actinolite, tschermakite, and edenite (Table 2, Figure 5). For different samples, the percentage of the same amphibole species varied slightly (Table 2). This bias might have been introduced by natural processes, such as hydraulic sorting, mechanical abrasion, and weathering, or by inaccurate procedures during sampling, laboratory treatment, and analysis [20,28]. Furthermore, for the same type of heavy mineral, the geochemical characteristics are similar in the size fractions of 63–125 μm and 32–63 μm.

**Table 2.** Amphibole species (%) for Core LQ24 and the modern Changjing River. s = Very fine sand fraction (63–125 μm), cs = coarse silt fraction (32–63 μm). CJ = Changjiang River. Others = other amphibole species, including Ferrotschermakite, Ferroedenite, Magnesio Hastingsite, and Ferropargasite.

Under a strong weathering environment, unstable minerals are easily corroded due to their crystal lattice feature. As chemical weathering proceeds, unstable minerals gradually disappear, thereby resulting in an extremely low (about 5%) content of amphibole in the Pliocene strata. Unstable mineral dissolution further affected the HMC. Studies show that the HMC of most Pliocene samples is only 0.5% (Figure 2), which is much lower than that of the modern river sediment samples [27,42].

#### **5. Conclusions**

**Author Contributions:** Conceptualization, W.Y.; Methodology, L.Z. and B.J.; Writing—original draft preparation, W.Y; Writing—review and editing, W.Y., S.P. and X.Y.

**Funding:** This research was funded by a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, the National Science Foundation of China (Grant No. 41706048; 41730531; 41576057), and the Natural Science Foundation of Shandong Province, China (No: ZR2019MD009).

**Acknowledgments:** Special thanks to Sergio Andò and three anonymous reviewers for their constructive comments that helped improve the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).


Preface

This book brings new research knowledge insights to the properties and behavior of gamma-rays. It encompasses a wide range of options, including gamma applications in nuclear physics, medical physics, industrial processes, environmental sciences, radiation biology, radiation chemistry, radiotherapy, agriculture and forestry, sterilization, and the food industry, as well as a review of both advantages and problems that are present in these applications. The book is primarily intended for scientific workers who have contacts with gamma-rays, such as staff working in nuclear power plants, manufacturing industries, civil engineers, medical equipment manufacturers, oncologists, radiation therapists, dental professionals, universities, and the military, as well as those who intend to enter the world of applications and problems of gamma-rays. Because of the global importance of gamma-rays, the content of this book will be interesting to a wider audience.

**II**

**Chapter 8 129**

**Chapter 9 139**

**Chapter 10 157** Gamma Radiation in the Vicinity of the Entrance to Linac Radiotherapy Room

**Chapter 11 175** The Secondary Photoelectron Effect: Gamma Ray Ionisation Enhancement in

Irradiation **199**

**Chapter 12 201**

**Chapter 13 215**

**Chapter 14 233**

Gamma Irradiation Causes Variation and Stability of Artemisinin Content in

*by Thongchai Koobkokkruad, Praderm Wanichananan, Chalermpol Kirdmanee*

*by Nicholas Kamyshanchenko, Vladimir Krasil'nikov, Alexander Parkhomenko*

Application of Radiation and Genetic Engineering Techniques to Improve

*by Seyed Mahyar Mirmajlessi, Hossein Ahari Mostafavi, Evelin Loit,*

Study of Bio-Based Foams Prepared from PBAT/PLA Reinforced with Bio-Calcium Carbonate and Compatibilized with Gamma Radiation *by Elizabeth C.L. Cardoso, Duclerc F. Parra, Sandra R. Scagliusi, Ricardo M. Sales, Fernando Caviquioli and Ademar B. Lugão*

*by Kinga Polaczek-Grelik, Aneta Kawa-Iwanicka, Marek Rygielski*

Biocontrol Agent Performance: A Short Review

Tissues from High Atomic Number Elements

Modeling Plastic Deformation in Irradiated Materials

Influence of Gamma Radiation on Gas-Filled Surge Arresters *by Luka Rubinjoni, Katarina Karadžić and Boris Lončar*

*Neda Najdabbasi and Marika Mänd*

*and Łukasz Michalecki*

**Section 4**

*and Victor Robuk*

*Artemisia annua* Plants

*and Wanchai De-Eknamkul*

*by Christopher Charles Busby*

**Dr. Basim A. Almayahi** Professor, University of Kufa, Najaf, Iraq

**1**

Section 1

Natural Radioactivity

Section 1


**4. Conclusions**

We investigated the deformation index of various patterns such as circular, finger-like, and annular-like patterns during fluid displacement, while changing the progression of phase separation using the newly defined dimensionless number, Bf. The fully miscible cases under the hydrodynamically stable displacement condition, where the more viscous PEG solution displaces the less viscous Na2SO4 solution, show constant circular patterns. For the partially miscible systems, phase separation occurs at the interface between displacing and displaced solutions, creating a separated region with domain growth for the annular patterns and creating a deformed interface for the finger pattern. Moreover, the deformation index of the patterns can be scaled with Bf, which involves viscous dissipation, molecular diffusion, and phase separation. Therefore, the patterns in the partially miscible systems are proved to be formed by the competition of viscous dissipation and phase separation. Bf is a crucial factor to describe the complex morphologies induced by the fluid displacement in partially miscible systems. The investigated morphologies and Bf will directly contribute to predicting and/or controlling CO2-enhanced oil recovery, where more viscous water displaces less viscous CO2 under the ground, the conditions of which are partially miscible.

**Author Contributions:** Experiments, R.T. and R.X.S.; discussion and review, R.X.S., R.T., Y.N., M.M., and T.B.; writing, R.X.S. and T.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This is study was supported by JSPS KAKENHI Grant No. 19J12553.

**Conflicts of Interest:** The authors declare no conflict of interest.


**2. Urbanization**

Urbanization is a metropolitan development that is a response to often less understood implications of technological, economic, social, and political forces and to the physical geography of an area. The pattern of urbanization in India is characterized by a continuous concentration of population and activities in large cities. Kingsley Davis used the term "over-urbanization," "where in urban misery and rural poverty exist side by side with the result that city can hardly be called dynamic" and where inefficient, unproductive informal sector becomes increasingly apparent [7]. Another scholar, Breese, depicts urbanization in India as pseudo urbanization where people arrive in cities not due to urban pull but due to rural push [8].

The considerable economic and livelihood opportunities in urban areas and an increase in accommodating immigrating populations result in greater urbanization. It is never seen as a vulnerability to environmental growth, but it is the accidental urban area and energetic urban growth, or the sprawl that influences the land use of any area that becomes a substance of concern through its habit in the loss of major farming lands. It is very important to study and determine the information and suggestions interrelated with the problem of unexpected urban growth ensuing sprawl.

Urbanization is a global process in which most developing nations experience that has led to the rise of great metropolitans along with slums and squatter. At the same time, a notice concern is also about the exhaustion of natural resources, increasing pollution and environmental hazards apart from the development of urban-rural fringes and suburban divisions, a host of ecological and socioeconomic factors that have become remarkable challenges of the current era. Chandna highlighted these factors [9].

### **3. Characteristics of urbanizations**

Urbanization is a universal phenomenon. It is a process of enrich growth in a country's urban inhabitants accompanied by an even huge development in the financial, political, and cultural importance of cities associated with rural areas. In "The Origin and Growth of Urbanization in the World," Davis explains and gives the world growth of population and the way of urbanization and growth stages.

The term "urbanization" illustrates a development in the human population associated with the development of energy and resource consumption and widespread land use. Since the rise of population becomes more enrich, the need for goods and services is often driven by addition rather than just rapid population growth. Urbanization refers to a growth in the percentage of a population living in urban areas of an exact size.

The rapid growth of the population is a result of the sparing scientific and medical knowledge and is the fundamental reason for urban growth and population. However, the rapid development of the population in urban centers is also disturbed by economic development, which is decreasing the percentage of the population engaged in agricultural areas. Structural change in employment, especially the growth of the tertiary (service) sector, has led to an improved number of employments in urban areas. Most service firms need to be central business districts (CBDs) to obtain benefits from close communication with each other.

**179**

*Urban Sprawl*

**5. Migration**

development of a town.

various sources of entertainment.

**6. Urban sprawl**

*DOI: http://dx.doi.org/10.5772/intechopen.92383*

The central business district (CBD) is the main part of the city that contains the major commercial streets and main commercial buildings. Throughout history, the Central Business District has been characterized by land classification and land use changes that include residential, commercial, industrial, and administration purposes. These spatial changes have been used to support Central Business District development. However, in the wake of post war decentralization and the growth popularity of polycentric regions in both Europe and the US, much of this work has itself come under criticism. The main force of the criticism proposes that Central Business Districts are now more likely to practice for the development of suburban lifestyles. However, similar developments, such as core city regeneration, propose that CBDs are now at the heartbeat of a more extensive back to the city movement that (re)promotes the pleasant appearance of city area living through residential expansion, delightful cultural districts, and an urban cool cultural social scene. The beginning of the 21st century, the Central Business District had turned into a discrete area of the metropolitan city and built-in residencies, retail shops, commercial malls, Central universities, recreational, government, financial institutions, health care centers, and culture centers. The urban area is located at workplaces or educational institutions in the CBD for regular movement. This includes students, doctors, academics, government officials and civil servants, business peoples, formers, and financiers. In the current era, the rapid development of residential expansion and the growth of shopping malls have given a new life to the Central Business District. In addition, multi residential buildings, mega-malls with theaters, Kochi Lulu international shopping mall is an example of a business district area as an entertainment and shopping center. City walk malls are also familiar in central business districts in an attempt to make the CBD a 24 × 7-hour working destination.

Migration is the movement of people from one place to another place for various purposes. Immigrants go away their nation, while migrate peoples enter a country. Migration impacts two nations and places where migrants enter settle. [9] addressed urbanization, migration and economic development and explained the primary stages of urban growth based on the migration of the population and the economic

People have so many reasons why they force to move from one nation to another nation. The reasons behind this movement are employment opportunity, economic, education, globalization, and political or environmental condition. Migration is classified as 'push factor' and 'pull factor.' Push factors force people to migrate; for example, unemployment, lack of infrastructure (such as hospital, education institutions, etc.), natural disasters (such as floods, droughts, earthquakes, cyclones, etc.), local conflicts, war, etc. The people get experience of life and move one place which gives them good life. Pull factors attract people from different places, such as better opportunities for education and employment, better health facilities, and

In India, rapid population growth and migration, greater than before urban population and urbanization, is not predictable. Barnes et al. highlight sprawl

**4. Central business district**


**3. Conclusions**

Throughout the chapter, examples were provided of organizations that are considered to be innovative. The conclusion of the chapter focuses on specifying commonalities between innovative organizations. We believe themes emerge in the five profiles highlighting linkages between HRD, KM, and innovation. The identification of similar practices and processes may not make it easier for organizations to be innovative, but it does facilitate understanding by practitioners and researchers of some organizational antecedents necessary for innovation to flourish.

We hope this chapter also accomplishes a secondary goal to solidify and clarify where the pres‐ ence of HRD together with KM establishes conditions necessary for innovation. HRD looks to develop and unleash human expertise and creativity with its focus on career development, train‐ ing, and organizational development. HRD at these five cases contribute to facilitating a learning culture, providing a broad spectrum of learning and development (L&D) opportunities, and providing employees a broad spectrum of opportunities and encouraging diversity of thought and new ideas. On the other hand, KM focuses on the development of communities of practices, organizational knowledge sharing through lesson learned process, and the utilization of tech‐ nology to create infrastructure for storing and sharing expertise and best practices. These KM processes facilitate and sustain individual and collective activities to help manage the flow of knowledge (to acquire, create, store, share, use, and assess) throughout the organization. When and where there is expertise and creativity coupled with methods of harnessing, sharing, and growing knowledge and ideas, we believe an organizational environment or culture can exist for innovation. **Figure 1** captures the relation between HRD, KM, and innovative organization.


Rule 16. If SI high and AMo high and LTV slow and STV slow, then there is loss of fetal wellbeing.

IF SI↑ AND AMo↑ AND LTV↓ AND STV↓ THEN FETAL DISTRESS.

#### 4. Results

The results of the fuzzy diagnosis for 188 datasets are shown in Figure 8. Two well-defined clusters can be observed, corresponding to those who were clinically diagnosed as healthy pregnancies (+) and those who presented loss of fetal well-being (o). Can be observed that a

Figure 8. Scatter plot for fuzzy outputs of the 188 records.

fuzzy output from a high-risk pregnancy record with fetal distress was incorrectly evaluated by fuzzy system, fuzzy output of 0.183 classifies it as normal pregnancy.

Table 6 shows 6 of the 49 records, the values for their descriptors, the fuzzy output, and the clinical diagnosis. The records N16, N6, FGR6, FGR29, N27 are well evaluated by the fuzzy inference system, but the record FGR20, which corresponds to a fetal growth restricted pregnancy with fetal distress, is classified by fuzzy system as normal pregnancy. The ROC curve and confusion matrix for the 188 cases evaluated are shown in Figure 9.

Of the 188 records, 84 with fetal distress were correctly evaluated (true positives) and only one was diagnosed as normal (false negative). On the other hand, the 103 normal cases were

Table 6. SI, AMo, LTV, and STV values for fuzzy input descriptors, fuzzy assessment, and clinic diagnosis.

Fuzzy Detection of Fetal Distress for Antenatal Monitoring in Pregnancy with Fetal Growth Restriction… 21 http://dx.doi.org/10.5772/intechopen.80223

Figure 9. (a) ROC curve of the overall fuzzy system evaluation and (b) confusion matrix for 188 data evaluated.

diagnosed correctly (true negatives) by the fuzzy system. The global sensitivity was 0.9882 and global specificity was 1.

Finally, fuzzy inference system was evaluated with 21 new records of 30 minutes, classified as distress: D1-D3, and normal pregnancy: N1-N18. Each record was sampled at 2-minute interval. Figure 10 shows the fuzzy evaluation of three records of patients with emergency

Figure 10. Fuzzy evaluation of three 30-minutes records of patients with emergency pregnancy.

Figure 11. Fuzzy evaluation of eighteen 30-minute records of patients with normal pregnancy.

pregnancy. D1 and D2 were classified with fetal distress correctly, but D3 is shown with a normal fetal well-being state.

Figure 11 shows the fuzzy inference of 18 patients with normal pregnancy. Records N2-N4, N6-N16, and N18 show a normal fetal well-being during the 30-minute recording. The record N1 shows an indeterminate state, except for periods of 3–5 and 8–10 minutes, where the assessment of fetal well-being is normal. The record N5 was classified by the fuzzy system as indeterminate. N17 shows fetal distress from minutes 3 to 9, between minutes 15 and 21 the fetal state changes to normal, returning to distress after minute 27.

#### 5. Conclusions

A combination of fetal HRV and CTG descriptors was proposed for discrimination between fetuses with loss of fetal well-being and normal fetuses, both in pregnancies with intrauterine growth restriction and healthy pregnancies.

The feasibility of the selected descriptors, SI, AMo, STV, and LTV was evaluated by sensitivity, specificity, and Spearman's correlation analysis, so that these parameters can be considered as evident markers of fetal well-being status in the case of FGR.

Since SI and AMo are relevant to the sympathetic part of the autonomic regulation, the opinion on the involvement of the sympathetic mechanisms in fetal distress is supported [1]. The predictive value of the parasympathetic regulation variables was lower. The growing activity of this division of the autonomic function is a marker of fetal neurological maturation [5]. The relation found between maternal and fetal HRV parameters was a sign of fetal and maternal coupling in healthy pregnancy. Maternal respiratory sinus arrhythmia was speculated as a reason of this regularity. It was disturbed in preeclampsia [11]. Fetal growth is known to be impacted by maternal organism [6, 13]. The investigation of the possible relations between maternal and fetal HRV and its fractal components will create a novel concept of the management of women with growth-restricted fetuses.

Formerly, the most sensitive and specific for fetal distress T/QRS ratio obtained from fetal noninvasive ECG tracing was found [1, 12]. Since peaks and intervals are detectable on fetalaveraged PQRST complex, the subsequent investigation of their clinical significance is of great prospect. But the study population of the abovementioned research was suffered from preeclampsia. Thus, preeclampsia could change fetal cardiac conductivity. But will T/QRS ratio be of use in diagnosing fetal distress among all pregnant women is still a question?

The main criterion of fetal well-being is a reactivity to its motile activity by accelerating the heart rate during nonstress test [2, 3]. The obtained results could make it possible to think that SI and AMo will become an alternative to the Dawes-Redman criteria. The assessment of shortterm variations (STV) and long-term variations (LTV) was found to be of use in diagnosing fetal compromise. These variables used in CTG monitors are known as the most evident markers of fetal distress [4, 9]. But the duration of the recording should be not less than 1 hour or, at least, 30 minutes. This time interval is known to be associated with better sleep/awake fetal status ratio [2, 4]. Therefore, the application of the proposed fetal HRV variables will help to use fetal noninvasive ECG tracing of the only 10 minutes long. It will be more convenient in clinical practice. Another advantage is the possibility to support or neglect fetal distress in case of negative (areactive) or false-negative nonstress test.

The hypothesis of the intrauterine programming of the diseases determines that any abnormalities during fetal life will have a subsequent clinical manifestation afterward. The cardiac signals proceeding is a convenient approach to the assessment of fetal autonomic maturation [6, 13]. Fetal HRV variables are disturbed in growth-restricted fetuses. Therefore, the investigation of fetal neurobehavioral response in case of intrauterine growth restriction is a possible way for the fetal well-being screening. But fetal growth restriction is not always associated with fetal distress and still stimulating obstetrical aggression in its projections on the term and the mode of delivery. That is why the outcome of our research in future is an advanced protocol of management of pregnant women with fetal growth restriction.

The findings of this work are based on fetal noninvasive ECG investigation. This method is still a challenge for the clinician [9]. The main problem is a low signal-to-noise ratio [1]. But fetal noninvasive ECG could be used for fetal Holter monitoring. The possibility for the creation of the system for fetal wireless distant monitoring will contribute to the better diagnosing of fetal compromise and cardiac arrhythmias.

HRV and CTG proposed descriptors can be used in an assessment system, for discrimination or prediction between fetuses with loss of fetal well-being and normal fetuses, both in pregnancies with intrauterine growth restriction and pregnancies of healthy fetuses.

Finally, a system based on fuzzy logic was designed with these descriptors in order to obtain an evaluation of the fetal well-being status. Only one false negative was obtained in the diagnosis using 188 data, which represents an accuracy of 98.8% in fetal distress prediction, and 100% in healthy pregnancy.

#### Author details

Igor V. Lakhno1 , Bertha Patricia Guzmán-Velázquez1,2\* and José Alejandro Díaz-Méndez1,2

\*Address all correspondence to<EMAIL_ADDRESS>
1 Obstetrics and Gynecology Department of Kharkiv Medical Academy of Postgraduate Education, Kharkiv, Ukraine

2 Electronics Department of National Institute of Astrophysics, Optics and Electronics, Puebla, México

#### References

**Section 3**

**Biomedical Images Analysis**


*4.2. Preparation of Essential Oil*

The aerial part of *Chrysanthemum boreale* (Asteraceae) was collected in October in Wonju city, Gangwon-do, Korea. This plant was identified by Sang-Cheol Lim (Department of Horticulture and Landscape, Sangji University, Korea). The voucher specimen (natchem# 38) was deposited at the Laboratory of Natural Products Chemistry, Department of Pharmaceutical Engineering, Sangji University, Korea. ECB was extracted using the method of steam distillation. The plant material (300 g) was distilled for 3 h by a steam distillation apparatus. The distilled liquid was fractionated three times with diethyl ether (each 400 mL). The diethyl ether layer was subjected to dehydration with anhydrous sodium sulfate, and then evaporated to give the essential oil (weight 14.1 g; volume 14.2 mL).


Computer Graphics and Imaging

*Edited by Branislav Sobota*

Published in London, United Kingdom

## *Supporting open minds since 2005*

Computer Graphics and Imaging http://dx.doi.org/10.5772/intechopen.75340 Edited by Branislav Sobota

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First published in London, United Kingdom, 2019 by IntechOpen IntechOpen is the global imprint of INTECHOPEN LIMITED, registered in England and Wales, registration number: 11086078, The Shard, 25th floor, 32 London Bridge Street London, SE19SG – United Kingdom Printed in Croatia

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**Rheumatic Diseases: Pathophysiology, Targeted Therapy, Focus on Vascular and Pulmonary Manifestations**

Editors

**Barbara Ruaro Francesco Salton Paola Confalonieri**

MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade • Manchester • Tokyo • Cluj • Tianjin

*Editors* Barbara Ruaro SC Pneumoogia, Cattinara Hospital, University of Trieste Trieste, Italy

Paola Confalonieri SC Pneumoogia, Cattinara Hospital, University of Trieste Trieste, Italy

Francesco Salton SC Pneumoogia, Cattinara Hospital, University of Trieste Trieste, Italy

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

This is a reprint of articles from the Special Issue published online in the open access journal *Pharmaceuticals* (ISSN 1424-8247) (available at: https://www.mdpi.com/journal/pharmaceuticals/ special issues/Rheumatic Diseases).

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**7. Pathogenicity**

Pathogenicity of *Salmonella* is dependent on the serovar and the host. However, factors that influencing serovar–host specificity are not well known [56]. The basic of *Salmonella* virulence mechanism is associated with the invasion of intestinal mucosa and multiplication in gut-associated lymphoid tissue (GALT). *Salmonella* will invade non-phagocytic cells in the intestine by promoting their self-uptake in a complicated and dynamic process similar to phagocytosis [57].

*Salmonella* infection in human can cause either systemic disease with rare association with food poisoning or one that can cause enteritis or localised disease. In oral infection, *Salmonella* must go through a variety of host defence mechanisms and different environments in the stomach during the progression of infection before successfully entering the intestinal tract. *Salmonella* adapted to these settings by using a broad variety of genes that may be reflected as virulence determinants, including *Salmonella*-specific virulence genes, housekeeping genes and regulatory genes. Virulence genes involved in invasion and critical for intracellular survival are grouped in large chromosomal DNA regions termed as *Salmonella* pathogenicity islands (SPIs). SPIs often exist in huge clusters of genes that are found in the vast chromosomal DNA regions that contribute to a certain virulence phenotype that manifests at a given period during infection [58].

Significant pathogenicity islands in *Salmonella* are SPI-1 and SPI-2. SPI-1 being the most well-defined SPI and required for virulence encodes the type III protein secretion system (T3SS), which injects effector proteins into host cells and provides the essential

mechanism for intestinal invasion and enteritis formation [59]. The T3SS is the most significant *Salmonella* virulence factor. SPI-1 genes are involved in host cell invasion, immune cell recruitment, apoptosis, and biofilm formation, while other transcription factors encoded outside SPI-1 engage in the expression of SPI-1-encoded genes. SPI-1's regulatory network is intricate and extremely important [37]. SPI-1's ubiquity is conserved and essential for *Salmonella* pathogenicity, as shown by its direct role in invasion. The T3SS of SPI-1 and SPI-2 has been suggested to be inversely regulated [52, 53].

This is an appealing hypothesis as *Salmonella* systemic infection to a host must first infiltrate M cells, where SPI-1 expression is required, and then replicate within macrophages, where SPI-2 expression is required. Mutations in SPI-2 genes encoding the type III secretion apparatus, on the other hand, diminish the expression of genes encoding a transcriptional activator of SPI-1 (*sipC*, *prgK* and *hilA*), suggesting the interaction between SPI-1 and SPI-2 [60]. Over the previous decade, around 30 SPI-2 T3SS effectors have been discovered. Thirteen of them are involved in the regulation of *Salmonella*-containing vacuole (SCV) membrane dynamics, the location of *Salmonella*-containing vacuole (SCV) inside host cells, immunological modulation, cytoskeletal changes and the motility of infected cells, among other things [61].


2.2.2. Indentation

Similar to the strain rate effect under uniaxial loading, an increase in loading rate in indentation tests leads to a rise of transformation stress. Moreover, a higher loading rate brings a smaller indentation depth and a drop in the recoverable deformation [36]. The interpretation in most studies [35,36,82] is that the underlying mechanism can be attributed to the increased release rate of latent heat during transformation with increasing strain rate and the strong temperature dependence of NiTi SMAs.

Considering the effect of the released latent heat conduction within the material, Amini et al. [35] adopted a normalized loading rate parameter to represent the rate effect in the experiment. The normalized loading rate was defined as a ratio of the loading rate . F to the transformation stress *σy*0 times the conduction coefficient *k*, and the normalized indentation depth was defined as a ratio of the indentation depth *h* to the radius of the tip *R*, as shown in Figure 7. Based on the level of the normalized loading rate, the indentation process could be roughly classified into isothermal, adiabatic, and a transition between

them, which resembles the strain-rate-dependent ranges under uniaxial loads. Amini et al. compared NiTi SMA with copper and quartz showing that the indentation depth of NiTi SMA decreased more rapidly with the loading rate. This can be explained by the enhanced transformation hardening caused by the latent heat accumulation around the indentation.

**Figure 7.** The rate dependence of the normalized indentation depth on the normalized loading rate parameter. A sketch of the heat transfer during indentation is drawn at the top right corner [35]. (Reprinted from Ref. [35], Figure 3, 2011, with permission from Elsevier.)

However, Farhat et al. [82] developed a simple heat model to predict the impact of temperature in indentation and suggested that the decrease of the indentation depth was not because of the temperature accumulation during transformation. Farhat et al. argued that the indentation depth decreased with the strain rate even at extremely low loading rates, where the generated heat could hardly accumulate. The loss of superelasticity might be due to the retardation of the transformation process during indentation, though more studies are needed to prove this claim.

#### 2.2.3. Cyclic Loading

The thermomechanical cyclic behaviors of NiTi SMA have been widely studied under strain- or stress-controlled uniaxial loading mode [37,38,83–85]. The rate-dependence under quasi-static cyclic strain-controlled loadings was systematically investigated by Kan et al. [37]. Impact fatigue tests were conducted less frequently than quasi-static ones [38]. Superelasticity degeneration and temperature variations were found strongly dependent on the strain rate, while the cyclic transformation path did not changed with strain rate.

Superelasticity degeneration indicated by transformation stress decrease, residual strain accumulation, and hysteresis loss takes place at all strain rates. Generally, the start and peak of transformation stress decrease with increasing number of cycles [37,38,83]. In Kan's experiments, cyclic tests were performed at six strain rates ranging from 10−4 s−1 to 10−2 s−1 with the maximum strain fixed at 9%. The corresponding stress-strain curves in different cycles are shown in Figure 8. The drop of transformation stress at each cycle becomes more conspicuous with increasing strain rate. Residual strain accumulation during cyclic loadings increases remarkably with increasing strain rate. The dissipation energy, i.e., the area of the stress-strain hysteresis loop, decreases with cycles, but the rate-dependence of the dissipation energy loss could be more complicated.

**Figure 8.** Rate-dependent stress–strain curves in different cycles: (**a**) 1st cycle; (**b**) 2nd cycle; (**c**) 5th cycle; (**d**) 10th cycle; (**e**) 20th cycle; (**f**) 50th cycle [37]. (Reprinted from Ref. [37], Figure 3, 2016, with permission from Elsevier.)

Superelasticity degeneration of NiTi SMA is mainly attributed to the interactions between transformation and dislocations [37,84,85]. Dislocations can be nucleated by high local stress near the phase interface and accumulate with the loading cycles. The internal stress caused by the dislocations assists stress-induced martensitic transformation, accounting for a decreasing critical transformation stress, and hindering the reverse martensitic transformation, resulting in an increasing residual strain. Therefore, superelasticity degeneration is speeded up by high strain rates.

Temperature variations during the cyclic deformation are also greatly influenced by the strain rate [37,84,85]. The evolution of temperature at five different strain rates in the 1st and 20th cycle are shown in Figure 9. In the loading part the temperature increases due to the release of transformation latent heat, while in the unloading part the temperature decreases first since the latent heat is absorbed in the reverse transformation and finally returns to the initial ambient temperature. Higher strain rates bring higher average temperatures. Generally, the amplitude of temperature oscillation decreases with increasing number of cycles; however, it increases with increasing strain rate.

**Figure 9.** Temperature records at various strain rates in the 1st cycle (**a**) and 20th cycle (**b**) [37]. (Reprinted from Ref. [37], Figure 9, 2016, with permission from Elsevier.)

Due to the temperature effect, the transformation hardening is enhanced as the strain rate grows [37]. The driving force in forward transformation progressively increases as the temperature rises. At a strain rate below 10−2 s−1, the heat generated by latent heat has to compete with heat conduction and convection in order to raise the temperature. This is similar to the mechanism under monotonic uniaxial loadings.

The number of impact fatigue tests is fewer than that of quasi-static ones. Zurbitu et al. [38] investigated the superelastic repeated-impact behaviors of NiTi SMA wires at a strain rate of 10 s−1. They discovered that the critical transformation stress decreased with increasing cycles in both quasi-static and impact fatigue situations. However, the transformation stress dropped more slowly with cycles in the impact condition since rapid deformation caused a high level of dislocation density which hindered the reduction of martensitic transformation stress. Furthermore, Fitzka et al. [86] found that the intermediate R-phase still occurred in both forward and reverse martensitic transformation when the test frequency was increased to ultrasonic (102 s−1). Therefore, the cyclic transformation path is independent of the strain rate.

In summary, the cyclic deformation of NiTi SMA is strongly dependent on the strain rate in the range from 10−4 s−1 to 102 s−1. As the strain rate increases, the superelasticity degenerates more rapidly and the sample temperature increases. The thermo-mechanical coupling effect determines the rate-dependent cyclic behaviors of NiTi SMA.

#### *2.3. Dependence of the Strain Rate Effect on Microstructure*

In addition to the loading condition, microstructure also have an important effect on the strain-rate dependent behaviors of NiTi SMAs. For general NiTi SMAs, the strain rate effect of R-phase transformation should be taken into consideration when the total strain is less than 2%. Precipitated phases, such as Ni4Ti3 precipitates, could improve the pseudoelasticity. A smaller grain size of austinite could neutralize the strain rate effect since the temperature effect decreases with a smaller latent heat. Porous SMAs are found with a similar strain rate effect, while SMA composites exhibit excellent impact-resisting performance.

### 2.3.1. General SMAs

#### a. R-phase

A rhombohedral (R) phase transformation is much more sensitive to the strain rate compared to martensitic transformation. Since the elongation strain caused by R-phase is usually less than 1% (total martensitic transformation strain is 8%), the R-phase effect can be ignored in most situations. However, when the total strain is less than 2%, the influence of R-phase is worth considering carefully. Helbert et al. [39] built a three-phase pseudodiagram and took R-phase transformation into consideration in explaining the strain effect on sensitivity of NiTi SMA wires. They found that the temperature sensitiveness of R- phase transformation stress was more than 10 MPa/K, which was approximately twice the sensitiveness of martensite phase, as shown in Figure 10. As the strain rate influences the temperature, R-phase transformation stress increases with the strain rate more rapidly than that of martensitic transformation.

**Figure 10.** Pseudo-diagram of the studied NiTi alloy. The stress-temperature slope of R-phase is twice that of martensite phase. [39]. (Reprinted from Ref. [39], Figure 7, 2014, with permission from Elsevier.)

## b. Precipitated phase

The influence of precipitates on the transformation behaviors of Ni-rich NiTi SMAs has been investigated by a large number of researchers [42,43,87–89]. The precipitated phase of Ni-rich NiTi SMAs is highly dependent on the aging temperature and time, among which the most studied are Ni4Ti3 precipitates. The Ni4Ti3 precipitates usually introduce R-phase transformation and result in a multistage transformation behavior [87]. Experimental results have shown that the precipitate influence varies with the strain rate.

The precipitation evolution and transformation behavior at quasi-static strain rates were studied and characterized by Fan et al. [42]. The critical transformation stress found was mainly determined by the magnitude of martensitic transformation temperature rather than the appearance of precipitates after aging treatment. Generally, the transformation temperature increases with decreasing aging temperature and increasing aging time.

A recent study by Yu et al. [43] showed that Ni4Ti3 precipitates could improve the pseudoelasticity of NiTi SMAs under impact loading. The critical transformation stress increases with increasing size and volume fraction of precipitates. The best performance in strength is found in the sample with the precipitates dispersed homogeneously within the grains. However, a more comprehensive study on the dependence of the strain rate effect on the precipitated phase is still needed.

c. Grain size

Smaller grains typically reduce the rate-sensitivity of the transformation behavior. Ahadi and Sun [40] studied the rate-dependence of NiTi SMAs on the grain size systematically. Weaker rate dependence was found with smaller grain size, i.e., the difference between the transformation stresses at high and low strain rates diminished as the grain size became smaller. As shown in Figure 11, when the grain shrinks from 90 nm to 10 nm, Δ*σ* decreases from 135 MPa to zero. Such decreased rate dependence can be explained by smaller temperature variations due to the reduction of latent heat.

**Figure 11.** The effect of five Grain Sizes (GS) on the *σ* − *ε* curves under monotonic loading–unloading in the strain rate range from 4 × 10−5s−1 to 10−1s−1 [40]. (Reprinted from Ref. [40], Figure 5, 2014, with permission from Elsevier.)

#### 2.3.2. Porous SMAs and Composites

The rate dependence of porous SMAs is similar to general solid NiTi SMAs [25], as greater transformation stress is found at higher strain rates.

SMA composites commonly have lamellar structures with NiTi SMAs embedded and exhibit excellent impact-resisting performance [41]. For example, Pappadà et al. dropped a heavy ball on a composite plate to test the impact effect around the strain rate of 10 s−1. They compared the SMA-embedded and steel-embedded plates and showed that the SMA-embedded composites had a better performance in absorbing the impact energy.


**4. Discussion**

The effects of initial xylose concentration and aeration (OTR) on maximum xylitol yield, maximum xylitol volumetric productivity, and xylitol yield after 24 h were investigated first in this study, by using *Candida boidinii* NCAIM Y.01308 in a semi-defined xylose medium. Vandeska et al. [45] investigated the effect of the initial xylose concentration on the achievable xylitol yield during fermentation on a model xylose medium by *C. boidinii* NRRL Y17213. They varied the initial xylose concentration between 20 and 200 g/L under the same aeration conditions (50 mL medium in 125 mL-flask, 150 rpm shaking), and concluded that the xylitol yield of 14 days fermentation continuously increased from 6% to the maximum value of 52% by increasing the initial xylose concentration from 20 g/L to 150 g/L. Interestingly, initial xylose concentration of 200 g/L significantly inhibited the xylitol fermentation. Vongsuvanlert and Tani [46] reported that a xylose concentration of 150 g/L resulted in lower xylitol production than that of 100 g/L, when *C. boidinii* no. 2201 was used on xylose basal medium. They performed the fermentations in 500 mL-flasks filled with 100 mL medium at 100 rpm shaking. Those studies showed that under given conditions of aeration, increasing xylose concentration increased the xylitol production until a certain value above which it had a negative effect. Osmotic stress on the cells is often hypothesized as a possible reason for the negative effect of high xylose concentration [46,47]. However, in our study, a decreasing tendency in the xylitol yield was observed by increasing the xylose concentration under the investigated range of xylose concentration and aeration. Oxygen availability during xylitol fermentation is a key factor due to its

influence on the intracellular redox balance. The key enzymes for assimilation of D-xylose in yeasts are the xylose reductase (XR), which catalyses the reduction of D-xylose to xylitol requiring NAD(P)H as cofactor, and the NAD-dependent xylitol dehydrogenase (XDH) catalysing the xylitol conversion to xylulose [48]. Xylitol accumulation under microaerobic conditions is the result of a deficient NAD regeneration by the respiratory chain which leads to diminished XDH activity [45,48]. In addition, formation of certain by-products during the xylitol fermentation can also contribute to maintaining the intracellular cofactor balance [49]. Winkelhausen et al. [50] investigated the effect of different kLa values on the xylitol production of *C. boidinni* NRRL Y17213 in a xylose model medium using shake flasks (50 g/L initial xylose concentration) and fermenter (130 g/L initial xylose concentration). The kLa values were varied between 0 and 46 1/h in shake flasks, and it was concluded that increasing kLa resulted in decreasing xylitol and increasing cell mass production. Interestingly, the highest specific xylitol yield (0.3 g/g) was achieved under anaerobic conditions (0 1/h kLa). As a comparison, Winkelhasuen et al. [50] achieved a specific xylitol yield of 0.16 g/g at 50 g/L initial xylose concentration and 16 1/h kLa after 96 h, which is lower than that of obtained in our study (0.43 g/g) at an initial xylose concentration of 55 g/L and kLa of 15 1/h (3.1 mmol O2/(L × h) OTR) after 72 h. The lower initial cell concentration (1.3 g/L) applied by Winkelhasuen et al. [50] compared to that of used in our study (5 g/L) could be one of the reasons for that. However, it is clear that xylitol producing capability can significantly differ with the subspecies of *Candida boidinii* also. Subspecies isolated from different environmental conditions might have XR and XDH enzymes with different characteristics, and different metabolic pathways for co-factors regeneration might have been activated in them, resulting in variable capability in xylitol fermentation under certain fermentation conditions. During the fermentations in a bioreactor using 130 g/L initial xylose and 5 g/L initial cell concentrations, Winkelhasuen et al. [50] achieved the highest specific xylitol yield (around 0.45 g/g) and xylitol volumetric productivity (around 0.26 g/(L × h)) at kLa of 47 1/h. It seemed that the increase in xylose and aeration together caused an increase in xylitol yield and productivity, however the increased initial cell mass could also have a positive effect on that. In our study, it was concluded that both initial xylose concentration and OTR had significant effects on the maximum xylitol yield and xylitol yield achieved after one day. However the interaction between xylose concentration and OTR had no significant effect within the investigated experimental range. It is worth it to note that the extent of their effects and their significant terms were different when the achievable maximum xylitol yield and the xylitol yield after a certain fermentation time (e.g., one day) was examined. In contrast, when the maximum xylitol volumetric productivity was evaluated, a clear interaction between OTR and initial xylose concentration was observed.

Xylitol fermentation on lignocellulosic hydrolysates by using *Candida boidinii* was previously tested by other studies. Santana et al. [51] investigated *Candida boidinii* XM02G (4 g/L initial cell mass) on cocoa pod husk hemicellulose hydrolysate detoxified by activated carbon, and a specific xylitol yield of 0.52 g/g was achieved after 372 h of fermentation. Fehér et al. [39] published a xylitol yield of 53% of theoretical and a xylitol volumetric productivity of 0.14 g/(L × h) reached after 72 h of fermentation by using *C. boidinii* NCAIM Y.01308 (5 g/L initial cell mass) on corn fibre hydrolysate detoxified by activated carbon. Lopez-Linares et al. [52] investigated the xylitol production of *C. boidinii* NCAIM Y.01308. (5 g/L initial mass) on exhausted olive pomace hydrolysate detoxified by ion-exchange resin and achieved 0.43 g/g specific xylitol yield and 0.07 g/(L × h) volumetric productivity after 96 h. In this study, the xylitol yield, the specific xylitol yield, and the volumetric productivity were 60%, 0.72 g/g, and 0.58 g/(L × h), respectively, on WB1/S after 24 h. Those results exceeded the ones mentioned before. It is also important to note that in the case of WB1/S, no detoxification step was required prior to the fermentation. In our previous study, xylitol fermentation was performed by using *Ogataea zsoltii* NCAIM Y.01540 on xylose-rich wheat bran hydrolysate [17]. Comparing the maximum xylitol yields and volumetric productivities achieved under the same conditions by using

*O. zsoltii* NCAIM Y.01540 (56% and 0.24 g/(L × h)) and *C. boidinii* NCAIM Y.01308 (60% and 0.58 g/(L × h)), xylitol production of *C. boidinii* NCAIM Y.01308 was found to be more advantageous. Based on these results, this study confirms that the xylose-rich hydrolysate of wheat bran is a suitable medium for xylitol fermentation without detoxification.

Mayerhoff et al. [53] investigated different yeast strains to ferment xylitol on sulfuric acid treated rice straw hydrolysate. In their work, the initial xylose concentration was 53.9 g/L and 50 mL medium was used in 125 mL-flasks at 200 rpm shaking. High specific xylitol yields (>0.6 g/g) were achieved after 75 h by several *Candida* strains such as *C. guilliermondii* FTI-20037, *C. mogii* NRRL Y-17032, *C. parapsilosis* IZ-1710, and *C. veronae* IZ-945. However, it was only 0.17 g/g by using *C. boidinii* NRRL Y-17213. Compared to that, a higher specific xylitol yield was achieved by *C. boidinii* NCAIM Y.01308 in our study (0.26 g/g after 72 h). Nitrogen source in the fermentation media is also an important factor influencing the xylitol production. Since rice straw hydrolysates contained very low amount of proteins, supplementation by ammonium-sulphate and peptone was tested in this study. Generally, organic nitrogen sources (e.g., yeast extract and urea) result in higher xylitol yield compared to the inorganic ones [54]. In accord with that, higher maximum xylitol yield was achieved on peptone-supplemented GRS/S (25%) compared to GRS/S (20%). Silvia and Roberto [55] also investigated the effect of the nutrient supplementation (2 g/L (NH4)2SO4, 0.1 g/L CaCl2\*2H2O and 10 g/L rice bran extract) of rice straw hydrolysate in order to improve the xylitol production of *C. guilliermondii* FTI 20037. They found that the nitrogen supplementation had no effect on the specific xylitol yield (0.36–0.37 g/g) achieved. In this study, a similar result was obtained, supplementation of GRS/S with peptone did not improve the specific xylitol yield (0.35 g/g after 24 h); however it increased the maximum xylitol yield from 20% to 25% of theoretical. Zeid et al. [56] investigated the effects of activated carbon treatment on xylitol production by *C. tropicalis* and *C. guilliermondii* using rice straw hydrolysate. After the activated carbon treatment, specific xylitol yields were increased from 0.25 g/g and 0.47 g/g to 0.61 g/g and 0.69 g/g in the cases of *C. tropicalis* and *C. guilliermondii*, respectively. Similarly, as a result of the activated carbon treatment of GRS/S, the maximum xylitol yield was increased from 25% to 30% in this study. Lopez Linares et al. [52] published a specific xylitol yield of 0.36 g/g achieved on exhausted olive pomace hydrolysate treated by activated carbon after 72 h of fermentation by *C. boidinii* NCAIM Y.01308 (5 g/L initial cell mass, 50 mL medium in 100 mL-flask, 150 rpm shaking). That is slightly lower than that obtained in our study (0.38 g/g) using peptone-supplemented GRS/S treated by activated carbon and the same yeast strain. One of the reasons for the low xylitol yields obtained in our study on rice straw hydrolysates is probably the presence of considerable amount of glucose (glucose/xylose ratio of 0.29 in GRS/S). A glucose/xylose ratio that is higher than 0.1 could negatively affect xylitol fermentation [52]. Moreover, the activated carbon treatment was not effective in removing the organic acids from GRS/S, which could also contribute to the insufficient bioconversion of xylose into xylitol. Bio-purification processes selectively removing organic acids and glucose from lignocellulosic hydrolysates [57,58] or appropriate genetic modifications of the xylose-fermenting microorganisms [59,60] are promising ways to overcome these kinds of obstacles.


*3.5. Differential Scanning Calorimetry (DSC)*

The down peak in the graph represents an endothermic reaction, and the up peak represents an exothermic reaction (Figure 3). In mancozeb-loaded chitosan–gum acacia NPs, a sharp endothermic peak is observed at 190.95 ◦C with an enthalpy change (ΔH) of 99.406 J/g, which may be attributed to the melting of mancozeb [33]. Commercial mancozeb around 180 ◦C has a ΔH of 159.8806 J/g (Figure 3e). In contrast, blank and drug-loaded polymeric NPs have lower ΔH of 33.3051 J/g and 99.406 J/g, respectively (Figure 3c,d), which may be due to the glass transition of CSGA nanocomposites [34]. The lower ΔH, as compared to commercial mancozeb, makes both nanoformulations (blank and mancozeb-loaded NPs) more thermally stable than commercial mancozeb [29].

**Figure 3.** DSC thermograms of raw biopolymeric materials, (**a**) chitosan, (**b**) gum acacia and test samples, (**c**) CSGA blank, NPs (**d**) CSGA-1.0 NPs, (**e**) mancozeb.