**5. Conclusions**

The meshless Galerkin method (MGM) is an effective solution for problems related to supernormal and irregular particles. Without gridding the supernormal particles in the computational domain, the dynamic movement process of supernormal particles such as transportation, collision, throwing, and tumbling can be described only by constructing approximate weight functions and solving partial differential equations with the field function (particle force, particle movement velocity, and displacement value). In this paper, the meshless Galerkin method (MGM) and the method of combining numerical simulation and experimental verification are employed to study the influence of jujube branch size (particle size), the total number of feeds (number of particles), and the gear rotation speed and shape (particle force) on the picking rate of jujube branches.

**Author Contributions:** Formal analysis, J.H.; Funding acquisition, W.W.; Investigation, X.Y.; Project administration, W.W.; Software, D.R.; Supervision, W.W.; Validation, Y.G.; Writing—original draft, R.Z. and G.W.; Writing—review and editing, W.W. and M.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by National Nature Science Foundation of China, grant number 32171900.

**Institutional Review Board Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank the research team members for their contributions to this work.

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


*Article* **Impact of Potentially Toxic Compounds in Cow Milk: How Industrial Activities Affect Animal Primary Productions**

**Sergio Forcada 1,\*, Mario Menéndez-Miranda 1, Carlos Boente 2, José Luis Rodríguez Gallego 3, José M. Costa-Fernández 4, Luis J. Royo 1,5 and Ana Soldado 4,\***

**Abstract:** Potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) frequently coexist in soils near industrial areas and sometimes in environmental compartments directly linked to feed (forage) and food (milk) production. However, the distribution of these pollutants along the dairy farm production chain is unclear. Here, we analyzed soil, forage, and milk samples from 16 livestock farms in Spain: several PTEs and PAHs were quantified. Farms were compared in terms of whether they were close to (<5 km) or far away from (>5 km) industrial areas. The results showed that PTEs and PAHs were enriched in the soils and forages from farms close to industrial areas, but not in the milk. In the soil, the maximum concentrations of PTEs reached 141, 46.1, 3.67, 6.11, and 138 mg kg−1 for chromium, arsenic, cadmium, mercury, and lead, respectively, while fluoranthene (172.8 μg kg−1) and benzo(b)fluoranthene (177.4 μg kg−1) were the most abundant PAHs. Principal component analysis of the soil PTEs suggested common pollution sources for iron, arsenic, and lead. In the forage, the maximum contents of chromium, arsenic, cadmium, mercury, and lead were 32.8, 7.87, 1.31, 0.47, and 7.85 mg kg−1, respectively. The PAH found in the highest concentration in the feed forage was pyrene (120 μg kg−1). In the milk, the maximum PTE levels were much lower than in the soil or the feed forages: 74.1, 16.1, 0.12, 0.28, and 2.7 μg kg−1 for chromium, arsenic, cadmium, mercury, and lead, respectively. Neither of the two milk samples exceeded the 20 μg kg−1 limit for lead set in EU 1881/2006. Pyrene was the most abundant PAH found in the milk (39.4 μg kg−1), while high molecular weight PAHs were not detected. For PTEs, the results showed that soil–forage transfer factors were higher than forage–milk ratios. Our results suggest that soils and forages around farms near industries, as well as the milk produced from those farms, have generally low levels of PTE and PAH contaminants.

**Keywords:** pollution; soil; forage; milk; polycyclic aromatic hydrocarbon; potentially toxic element


**Social Innovation in Sustainable Urban Development**

Editor

**Harald A. Mieg**

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

*Editor* Harald A. Mieg Humboldt-Universitat zu ¨ Berlin Germany

*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 *Sustainability* (ISSN 2071-1050) (available at: https://www.mdpi.com/journal/sustainability/ special issues/Social Innovation Sustainable Urban Development).

For citation purposes, cite each article independently as indicated on the article page online and as indicated below:

LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. *Journal Name* **Year**, *Volume Number*, Page Range.

**ISBN 978-3-0365-4173-0 (Hbk) ISBN 978-3-0365-4174-7 (PDF)**

© 2022 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications.

The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND.


**Factors Influencing Consumers' Perceptions of Food: A Study of Apple Juice Using Sensory and Visual Attention Methods**

#### **Katarzyna Włodarska 1, Katarzyna Pawlak-Lema ´nska 1, Tomasz Górecki 2 and Ewa Sikorska 1,\***

Received: 28 September 2019; Accepted: 1 November 2019; Published: 3 November 2019

**Abstract:** The aim of this study was to evaluate the influence of intrinsic product characteristics and extrinsic packaging-related factors on the food quality perception. Sensory and visual attention methods were used to study how consumers perceive the quality of commercial apple juices from four product categories: clear juices from concentrate, cloudy juices from concentrate, pasteurized cloudy juices not from concentrate, and fresh juices. Laboratory tests included the assessment of sensory liking in blind and informed conditions and expected liking based on packages only. The results showed that brand and package information have a large impact on consumers' sensory perceptions and generate high sensory expectations. An innovative visual attention tracking technique was used in online experiments to identify packages and label areas on individual packages, which attracted consumer attention. During an online shelf test, consumers mostly focused on not from concentrate juices from local producers, which were perceived as more natural, healthy, and expensive than juices reconstituted from concentrate. When individual labels were analyzed, consumers predominantly focused on nutritional data, brand name, and information about the type of product. The present results confirm a large impact of information and visual stimuli related to packaging on product perception.

**Keywords:** apple juice; consumer perception; internal preference mapping; visual attention; packaging; label

#### **1. Introduction**

The sources that consumers use to form their impression of a product are typically classified as intrinsic or extrinsic cues [1,2]. The intrinsic cues are those characteristics that are part of the physical product. Some of these may be assessed before consumption (e.g., color, size, damage), while others may only be experienced through consumption, i.e., sensory properties. There is no single defined set of sensory attributes that are important across all of the food products. The importance of flavor, texture, and appearance attributes is product-dependent [3]. The extrinsic sources of information are those that are related to the product, but are not a part of it physically, such as brand name, label, packaging, price, the location where it is sold, and marketing communications [3,4]. These external cues generate consumer expectations about food products and affect their choices, sensory perception, and hedonic liking [5,6]. For these reasons, both sensory and non-sensory aspects should be included into the consumer research of food quality perception.

Sensory consumer research has confirmed that extrinsic product cues affect consumer perception of the food product sensory quality [4,7,8]. It has been reported that the brand name shown on a package influences consumer liking of taste of various food products [9,10]. The nutritional labeling also affects the estimation of taste [11]. In contrast, little is known about the relative effect of the extrinsic cues on the informed product evaluation when multiple cues are present [4].

The consumer perception of food packages and labels has been traditionally based on the self-reported estimates, although these estimates are subject to different biases and are reportedly only a poor indicator of the consumer behavior in real-life situations [6]. Some recent studies demonstrated that eye-tracking methodology is adequate for examining the effect of the package features on the consumer attention [12]. Food packages and nutrition labels were investigated with eye-tracking tools to monitor consumer visual attention to the respective product and nutritional information [13–15]. The eye-tracking technology precisely tracks the location and duration of gaze, providing detailed information on the consumer's visual attention and is more and more widely used in product marketing and consumer science, and recently also in consumer sensory studies [16,17].

Apple juice is one of the most popular products among juices all over the world, due to its pleasant sensory qualities and high nutritional value. Presently, the juice market offers a wide range of differently processed products. New trends in the juice market are determined by the consumer demand [18,19]. One of the fastest growing trends is that for minimally processed products, characterized by sensory properties similar to those of the fresh material and preserving valuable components of the fresh fruit. Apple juices available on the market include natural juices obtained directly from fruit by squeezing, not from concentrate (NFC) juices, both pasteurized and unpasteurized, and juices reconstituted from concentrate (FC), clear varieties and pulp-enriched cloudy varieties. Within each of the groups, one can distinguish ecological and conventional products. According to the European Fruit Juice Association (AIJN) Liquid Fruit Market Report [20], the consumption of non-concentrate fruit juices has increased significantly over the last five years in the European Union. The information on the production process is mandatory on the juice package. The results of previous studies showed varied consumer preferences for apple juices from different product categories [21,22].

Commercial apple juices are available in a variety of packages, including glass or plastic bottles and cartons. Food packaging is primarily used to protect food products from environmental contamination and other influences, and to ensure food quality and safety [23]. However, the packaging also has an important communicative role. The effective communication of product advantages through the packaging design determines consumer impressions of the product quality [24]. Thus, consumers mostly prefer products that attract their visual attention; therefore, food packaging must also be attractive or eye-catching. Both shape, material, color, and layout of the packaging elements have been shown to impact consumer perception [25]. Therefore, more research is needed in order to identify the packaging features that attract attention and enhance the buying potential.

The aim of the present work was to study the influence of the intrinsic product properties and the extrinsic cues related to packaging upon the food quality perception and liking. We studied commercially available apple juices from various product categories. We investigated the influence of the intrinsic cues and packages on liking and expectations using a consumer sensory study. Consumer visual attention to the apple juice packages and labels was examined with the use of an online visual attention tracking technique.

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

#### *2.1. Apple Juice Samples*

Eight apple juices from four product categories available on the Polish market were evaluated in this study. Two representative juices produced in Poland were selected in each of the four market categories, based on our previous studies of the physicochemical and sensory properties of a large number of juices and public recognition of their brands [26,27]. The selected products included juices reconstituted from concentrate (clear and cloudy varieties) and direct naturally cloudy juices (pasteurized and freshly squeezed varieties). Taking into account the type of production, the package, and the price, the juices studied may be classified into the standard and premium market segments. The detailed description of the samples is presented in Table 1.

**Table 1.** Description of the apple juices used in the study.

1 The set of A–H juices was the same as studied previously [28]. 2 FC—from concentrate, NFC—not from concentrate.

#### *2.2. Consumer Studies*

Two experiments were performed to evaluate consumer perceptions of the commercial apple juices using different complementary methodologies. All of the participants declared to consume apple juices at least several times a month and to have apple juice as the first preference among fruit juices. No ethical approval was required for this study. The first experiment was performed in laboratory conditions and the second experiment online. The experiments were conducted as follows:

Experiment 1. A group of 96 consumers of apple juices participated in the laboratory sensory study (64.6% female and 35.4% male). The participants were recruited from staff and students of the Pozna ´n University of Economics and Business based on their availability and interest in participation in the study. Of this number, 55.2% were under 25 years old, 36.5% were between 26 and 45 years old, and 8.3% were over 45 years old. The same group of consumers examined the quality of apple juice samples in different exposure conditions. To prevent communications between the members of the consumer panel, they were informed about the rules of the experiment, each person occupied a separate cubicle, and the sessions were supervised.

Two sessions were held over two consecutive weeks. Three types of data were gathered with the same group of consumers: (1) overall liking of the samples in blind-testing conditions, (2) expected liking of juices in packages, and (3) overall liking of the samples in an informed testing conditions; all samples were evaluated on 9-point hedonic scales (1 = dislike extremely, 5 = neither like nor dislike, and 9 = like extremely). The samples were presented to the consumers following a balanced rotation scheme. In blind-testing experiments, juices were coded by three-digit random numbers.

Fifty milliliters of each beverage were served to consumers at 20 ◦C in transparent plastic containers in blind and informed sensory evaluations, respectively, without and with packages. Mineral water was available during studies. The results of this experiment were already presented in our previous paper [28], where blind liking scores were discussed in detail and the relationships between the consumer liking and the physicochemical and sensory properties of juices were determined.

In an expected liking evaluation, consumers were asked to inspect full packages of eight apple juices and to score their expected sensory liking. To evaluate spontaneous perception of the labels, without making participants focus on specific aspects, they were asked to answer check-all-that-apply (CATA) questions with terms describing the product characteristics: natural, artificial, tasty, tasteless, not very healthy, very healthy, expensive, inexpensive, a familiar product, an innovative product, and a trendy product. Consumers were asked to check all the terms they considered appropriate to describe each of the products.

Experiment 2. A group of 171 consumers (68.8% female and 31.2% male) participated in the online study using Attensee software (https://www.attensee.com). Of these, 72.9% were under 25 years old, 23.0% were between 26 and 45 years old, and 4.1% were over 45 years old.

Attensee is an application used for the study of visual attention, that mimics an eye-tracker [29]; it provides an interface for computers and tablets and does not require any special hardware. This innovative approach to record human information lets one see what consumers look at on labels, packaging, or pictures. To get the required information, the reference areas (RA) on packaging and labels should be marked, and the percentage of consumers focusing their attention on these RA are recorded [30]. Based on these results, final calculations of the visual path tracking parameters may be made. The following RA were used in our experiments: brand names, logos, pictograms, photos, tables and lists of nutritional values, slogans regarding the content of pro-health ingredients, eco/bio labeling, and packaging size statement.

This experiment was conducted online. Consumers were asked to take part in the study via social media, and after agreeing, they received an individual link to the online experiment and were informed that the study involved the simulation of visual perception on a computer screen by means of cursor movements. The participants used the mouse pointer to bring certain parts of the screen into clarity (focused circle 2 cm in diameter). The software updated the information in real time as participants changed their area of focus and the way of exploration. After receiving instructions and doing some trial runs, participants performed the actual test. First, an image of all of the analyzed products on the shop shelf was presented on a computer screen for 45 s, and then the images of individual juice labels were presented, each for 30 s. The sequence of showing the individual labels was proportional and randomized across participants to eliminate the order effects. Each of the participants examined an image with all of the products (shelf picture), and randomly selected four of the eight individual product images. The photographic images of juice packages (with 4592 × 3056 pixels resolution) were captured using a digital camera (Sony A3056, Tokyo, Japan).

The Attensee software can also produce different types of questionnaires. Thus, the participants were asked to answer a check-all-that-apply questionnaire with the terms describing the product, the same as in Experiment 1.

#### *2.3. Data Analysis*

Consumer liking data were analyzed by multivariate analysis of variance (MANOVA). When a significant difference (*p* < 0.05) was detected, a *t*-test with Holm correction was applied to evaluate the difference between the samples. Pearson coefficients were calculated to evaluate the correlations between the consumer liking scores gained in different evaluation conditions. Principal component analysis (PCA) was performed on the individual consumer scores in three different conditions using the correlation matrix. PCA models were validated using the full cross-validation procedure. The correspondence analysis (CA) was performed on the frequency table containing responses to the check-all-that-apply questions. Statistical analyses were performed using the R-language and XLSTAT software (Addinsoft, Paris, France) packages.

#### **3. Results**

#### *3.1. Consumer Liking of Apple Juices in Di*ff*erent Evaluation Conditions*

The same consumer group evaluated the quality of eight apple juices in three testing conditions in our laboratory study. The results of consumer evaluations expressed on the 9-point hedonic scale are presented in Table 2.

**Table 2.** Mean consumer liking scores1 of apple juices evaluated in blind, expected, and informed conditions.

1 Evaluated on a nine-point hedonic scale. 2 The consumer ratings in blind conditions were available from our previous study [28]. Different lowercase superscripts (a–e) within a column indicate significant differences according to the *t*-test (*p* < 0.05). Different capital superscripts (A–C) within a row indicate significant differences according to the *t*-test (*p* < 0.05).

The results of the consumer study in blind condition were described in detail and discussed in a previous paper, as regards physicochemical and sensory characteristics of juices [28]. Presently, we used these results to compare them with the consumer ratings in expected and informed conditions. The consumers reacted differently to the sensory characteristics of the juices. The overall liking scores in blind conditions ranged from 4.1 corresponding to dislike slightly to 6.2 corresponding to like slightly. Significant differences were found in consumer liking of the samples assessed in a blind test (*p* < 0.05). Freshly squeezed juices (samples G and H) and reconstituted cloudy juices (samples C and D) were the most liked juices, while cloudy NFC juices (samples E and F) and reconstituted clear juices were the most disliked. The results are in line with those reported earlier [31], where average consumer ratings of the studied apple juice were at 5.5–6.0 on a 9-point scale, and these rather low ratings were explained by consumer habits for certain products.

The expected liking scores were in the range of 5.8–7.1 and higher than blind scores. These results indicate that the package with its product information, including brand, type of production, nutritional value, etc., generates high consumer expectations. Significant differences were observed in mean consumer scores; fresh juices (G, H) and cloudy FC juice (D) gained the highest ratings, while clear juice (A) and naturally cloudy (E) the lowest. The NFC juice (E) which is an organic product (information on the package) received the lowest rating among the studied juices, as it had a large amount of natural sediment. Note that sediment and turbidity of fruit juice may be perceived negatively by consumers as a product defect [32]. On the other hand, consumers were reported to have higher expectations for local apple juices as opposed to the mainstream juices available on the market, and also expected the higher quality of fresh apple juices as opposed to juices subject to thermal, high hydrostatic pressure, or pulsed-electric field treatment [21,22].

Our present study explored consumer perceptions of apple juices based on the comprehensive product information available on the label. The consumers, knowing the product brand and product information available on the package, rated the sensory quality of fresh juices (G, H) the highest. Significantly lower scores were obtained by clear juices (A, B) and naturally cloudy NFC (E, F) juices. Similar results were reported by Lee, Lusk, Mirosa, and Oey [22], indicating that consumers mostly valued the untreated apple juices.

When comparing consumer liking of juices in various testing conditions, the highest influence of product information on liking was observed for NFC juices (E, F). These samples correspond to the premium brands available in glass bottles. Clear FC juices (A, B) and fresh ones (G, H) were also assessed higher in informed as compared to blind tests. The blind and informed liking did not differ significantly only for cloudy FC juices (C, D). These latter juices were available in cartons and received high ratings for sensory quality at the first stage of the study. On the other hand, the expected quality scores were higher than the sensory scores for coded samples for six of the eight juices tested (except samples C and G, which received high sensory evaluation). The expected liking scores were significantly higher than the informed liking scores for clear (A, B) and naturally cloudy NFC (E, F) juices. The discrepancy between these assessments indicates that the sensory profiles of these juices do not meet consumer expectations generated by the product information contained on the packaging.

The mean consumer liking scores are useful for determining the overall trends, but do not provide information on the formation of the consumer groups (segments) with similar preferences [33]. Consumer liking data were analyzed using principal component analysis (PCA), performed on the individual consumer scores obtained in three different conditions. Internal preference maps were generated, illustrating the main preference directions [34], presented as biplots in Figure 1.

**Figure 1.** *Cont.*

**Figure 1.** Internal preference maps for different testing conditions: (**a**) blind, (**b**) expected, (**c**) informed. A,B—clear FC juices; C,D—cloudy FC juices; E,F—cloudy NFC juices; G,H—fresh juices. Red dots correspond to the individual consumers. PC1 and PC2 correspond to the first and second principal component, respectively.

The distribution of individual consumer scores varied depending on the testing conditions. Regardless of the testing conditions, the two juices in each of the pairs belonging to a certain product category were rated similarly by consumers; thus, the points corresponding to these juices are located close together in the two-dimensional space.

Most of the consumers preferred cloudy FC and freshly squeezed juices in the blind test (Figure 1a). The first PC1 component distinctly differentiated the juices according to sensory preferences (direct vs. reconstituted juices). A very different distribution of consumers and juices was obtained for expected liking (Figure 1b), where two main groups of the consumers may be distinguished. The first group assigned higher ratings to NFC juices, available in glass bottles. The second group, more scattered, rated FC juices, clear and cloudy varieties, available in 1 L boxes higher. As shown in Figure 1c, combined internal and external attributes provided poorer differentiation of the juices studied. Note that PC1 clearly differentiated clear FC juices from fresh juices, but not pasteurized cloudy FC and NFC juices. Most consumers, basing on sensory quality and external attributes, assessed the quality of fresh juices (G, H) as higher. The preference map for informed testing differed significantly from that for blind testing. These results confirmed the strong influence of the external attributes on the sensory evaluation of apple juice. Similar results were obtained by Lee, Lusk, Mirosa, and Oey [22].

There was a strong positive correlation (*p* < 0.05) between the expected and informed liking scores (*r* = 0.944) and between the blind and informed consumer scores (*r* = 0.800). No correlation was observed between blind and expected liking, indicating that the two approaches measure different aspects of product quality. These results are in agreement with the findings reported by Varela, Ares, Giménez, and Gámbaro [35].

#### *3.2. Perception of Apple Juices Based on External Attributes*

In order to gather supplementary data on the consumer perception of the juices studied, a check-all-that-apply (CATA) questionnaire with terms related to characteristics of the product and the brand image was used. CATA questions are increasingly more often used in consumer research to investigate the perceptions of a variety of attributes perceived by consumers and to obtain a rapid product profile from consumers [36–38].

Consumers used between one and seven terms to describe the apple juices in both laboratory and online studies. The most frequently used terms were natural and tasty; the least used term was tasteless. Most consumers indicated both cloudy NFC (E, F) and fresh (G, H) juices as natural. These juices were rated also as very healthy and expensive. The differences between FC and NFC juices

in their naturalness were clearer in the laboratory as compared to the online study. This may be due to increased attention of the respondents and the lack of a time limit in the laboratory testing. Furthermore, consumers perceived the juices studied as more innovative and trendier in the classic laboratory study as compared to the online experiment. This may be due to the fact that the photos did not fully reflect the differences between the products. Based on the results obtained, we concluded that apple juices are generally perceived by the consumers as natural and healthy products.

The correspondence analysis was used to visualize and interpret the results of the check-all-that-apply questions [39]. The plots of the first two factors for the consumer laboratory study and the online study data are shown in Figure 2.

**Figure 2.** Correspondence analysis of check-all-that-apply responses: (**a**) laboratory consumer study, (**b**) online consumer study. A,B—clear FC juices; C,D—cloudy FC juices; E,F—cloudy NFC juices; G,H—fresh juices.

A two-dimensional representation of the data was obtained, describing respectively 92.05% and 92.31% of the variability of laboratory and online consumer data. The results of the correspondence analysis showed that the external attributes differentiated the studied juices. The first direction differentiating the products was related to the perceived naturalness. The second dimension was related to the expected taste of the juice and was positively correlated to tasteless and negatively to tasty. As shown in Figure 2, the first and the second dimensions sorted the samples into the two main groups, according to consumer expectations: the first group contained FC juices (A, B, C, D) and the second group direct juices (E, F, G, H). The sample distribution was distinctly different from that obtained for blind and informed liking scores, while similar to the distribution of expected liking scores (Figure 2). As a result of both experiments, FC juices were perceived as more artificial, quite healthy, and inexpensive, whereas NFC juices were perceived as more healthy, natural, innovative, and expensive. These characteristics may be explained by the type of packaging and the production information declared by the manufacturer on the package. Note that NFC juices are available in glass bottles, which makes the natural sediment more visible.

CATA results obtained in the laboratory and online studies were convergent. This suggests that an online experiment could be an effective alternative to the classic consumer laboratory study, being a faster and cheaper way of obtaining consumer perception data.

#### *3.3. Visual Attention to Product Labels*

To examine the labels' zones that attract consumer attention, an online study was conducted using the innovative Attensee.com application. Based on the defined reference areas (RA), the application generated three types of data which are similar to the data obtained by the eye-tracking tool: (1) path of engagement specifying locations on packaging which attracted the attention of the respondents; (2) heatmap for time, showing the average time that respondents focused on an area; and (3) heatmap for attention, specifying the number of people who focused on a particular area of an image.

Firstly, the image of all the analyzed products was presented to consumers. The purpose of this presentation was to investigate which products attract the most consumer attention during the decision process on the store shelf.

During the on-shelf product recognition survey, consumers mostly focused on NFC juices (samples E and F) from local producers and focused the least on FC juices from well-known brands. According to the CATA questionnaire results discussed above (Section 3.2), it can be presumed that customers were focusing longer on products that they considered more attractive (healthy, natural, innovative) and from the premium segment (expensive). Consumer interest could also be due to the fact that NFC juices produced by local producers are less recognized than FC juices from well-known brands available nationwide. This feature may be seen by consumers as positive. Hempel and Hamm [40] examined consumer preferences for different food products of varying places of origin and observed that consumers prefer locally produced food.

Based on our results, we may distinguish the packaging elements that attract consumer attention. First of all, consumers paid attention to brand names of products, but it should be emphasized that they focused more attention on local juices as opposed to well-known brands. Subsequently, consumers noticed the information about product type and quality. More specifically, over 99% of consumers noticed the green BIO-label on NFC juice E. Studies show that consumers have a high preference for ethical or 'green' products and favor environmentally labeled packaging as the most important criteria in food choice [41,42]. Furthermore, consumers focused for over 2 s on average on the area of NFC juice F informing about type of product ("pressed apple juice").

One more experimental survey concerned the individual label pictures of juices from different product categories. Table 3 presents the aggregated results of this study.

**Table 3.** Average percentage of consumers who focused their attention on the label's specified reference area defined individually for each type of label, and the average time of attention for apple juices assessed using a visual attention tracking tool.

Generally, the longest average attention time (1.2 s) was devoted to the part of labels with nutritional information and involved almost 94% of consumers. Based on a detailed analysis of the consumer results and reference areas for the individual products, we noticed that the more clearly designed and sharply outlined nutritional information caused shorter attention time to this part of the label.

The brand names of juices were explored by almost 90% of the consumers who focused on this part of the label for an average of 0.5 s. Analyzing the percentage of consumers who focused their attention on the label's specified reference area, we found that the products from the better-known brands (clear and cloudy FC juices) attracted less attention than little-known craft brands (freshly squeezed and NFC juices).

The third main area of the consumer interest was the part of the label describing the type of product. About 87% of consumers focused their attention on that area for 0.8 s on average. In this case, the differences in the time of gaze fixation for all of the studied products was not significant and fluctuated between 0.7 and 1.2 s.

The next two areas, also important from the consumer point of view, were the information about the manufacturer/producer and places with special pictograms and signs including certificates and pictograms describing social action. The interest in manufacturer information was visible especially in the case of the NFC juices (samples F and E)—88% and 78% of consumers visited these areas and spent about 0.5 and 0.9 s, respectively, focusing on it. Special signs about sports and social action available on the package of juice D attracted the attention of 59% consumers, who spent about 0.7 s focusing on it. Furthermore, the culinary certificate on the label of juice F was noticed by 59% consumers who focused their gaze on it for 0.7 s on average.

When analyzing the heatmaps of a single juice label, we noted that consumers did not study some parts of the product information. This suggests that consumers did not assess the presented information comprehensively. These observations are in agreement with findings published by Oliveira et al. [15]. Generally, consumers mainly turn their attention to the information given in larger letters, information presented in an intense color (especially red), and special pictograms like certificates. It should be emphasized that we presented the labels to the consumers on a computer screen one by one. The consumers had possibility to also investigate the information presented on the sides and back of the packages. The consumer attention to product information in real-life conditions is expected to be even lower than presently reported.

It was previously reported that regardless of the type of product and the label design, consumers direct their attention to selected label zones such as brand, ingredients, and nutritional information [15,43]. The results obtained in the present study for real market products are convergent

with those reports. The proposed approach would be useful for assessing the effects of a variety of commercial juice packaging designs on consumer perception.

#### **4. Conclusions**

The present study combined sensory evaluation and visual attention experiments to investigate how intrinsic and extrinsic factors affected consumers' perceptions of apple juice quality. Eight commercial apple juices were studied, representing the four product categories currently available on the Polish market, which were evaluated by consumers. In a blind test, consumers rated the experienced quality of fresh and cloudy FC juices as the highest and the quality of cloudy NFC juices as the lowest. The packages with the product description not only generated high consumer expectations, but also impacted the sensory liking in a markedly positive way. For most of the tested juices, consumers rated the expected quality higher than the experienced quality of the coded samples. The product information influenced the rating of the quality of NFC juices, fresh juices, and clear FC juices in a significant and positive manner. These results confirmed the importance of the information presented on the packaging. On the other hand, they indicated the need to improve the sensory quality of juices to meet consumer expectations and encourage them to buy the product again.

An innovative online visual attention tracking technique was used for a more detailed analysis of the perception of packaging and labels. The online shelf test revealed that consumers focused the most on NFC juices from local producers. Additional information about the perceived juice quality in both the laboratory and online studies was provided by CATA questionnaires. The results obtained in all experiments were convergent and revealed that consumers perceived NFC juices as more natural, healthy, and expensive than juices reconstituted from concentrate.

The study of individual packaging enabled to identify zones that attracted consumers' visual attention. The consumers predominantly focused on nutritional data, brand name, and information about the type of product. This knowledge may be of practical utility for packaging and label design, to improve the attractiveness and competitiveness of the product. However, the observed effects might be modified by many factors including participants' previous knowledge of the product, text information presented with the image, and the level of congruency of the images. These aspects will be explored more fully in future research.

We conclude that the experimental approach proposed in this study provided a comprehensive view of the influence of the product information presented on packaging on the consumer expectations and sensory perception; moreover, it enabled to identify the important features of the packaging and labels. The results confirmed the effect of intrinsic and extrinsic factors on the product quality perception.

**Author Contributions:** Conceptualization, K.W., K.P.-L., and E.S.; Data curation, T.G.; Formal analysis, K.W., T.G., and E.S.; Investigation, K.W., and K.P.-L.; Methodology, K.W., K.P.-L., T.G., and E.S.; Supervision, E.S.; Validation, K.W., K.P.-L., and E.S.; Visualization, K.W.; Writing–original draft, K.W., and K.P.-L.; Writing–review & editing, K.W., K.P.-L., T.G., and E.S.

**Funding:** This research received no external funding. The APC was funded by Pozna ´n University of Economics and Business.

**Acknowledgments:** The authors thank Dawid Wiener (Cogision Ltd.) for the opportunity to use the Attensee.com software. The authors are very grateful to all consumers participating in the study.

**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/).


4.2.4. Applications to Antihypertensive Treatment in Humans

Our results on animals clearly show the advantages of an early start of an effective antihypertensive therapy, in particular with respect to preventing cardiac remodeling and thus transition into cardiac failure. This emphasizes the importance of starting BP control during early adulthood. Important aspects of antihypertensive treatment in humans are fast achievement of target BP values and adequate persistence and adherence to therapy. A combination of two or three drugs from different drug classes facilitates the adjustment of treatment to the individual patient as it allows dose reduction of the single drugs and minimization of adverse drug effects, thus ensuring the patient's adherence to therapy. Consequently, a combination of two or more, ideally as fixed-dose single-pill administration, as initial therapy of hypertension is currently recommended in most guidelines [4,22].


*4.1. Chemicals and Other Reagents*

10-hydroxyoleoside 11-methyl ester (**1**, C17 H24 O12, CAS No. 131836-11-8, MW 420.37, purity 98%), 10-hydroxyoleoside dimethyl ester (**2**, C18 H26 O12, CAS No. 91679-27-5, MW 434.39, purity 98%), 10-hydroxyligustroside (**3**, C25 H32 O13, CAS No. 35897-94-0, MW 540.51, purity 97%) and multifloroside (**4**, C32 H38 O16, CAS No. 131836-10-7, MW 678.64, purity 98%) (Figure 1) were purchased from BioBioPha Co., Ltd. (Kunming, China). MTT was from Merck Millipore. The Annexin V-FITC/PI double staining apoptosis assay kit and Cell Cycle Detection Kit were from KeyGEN Bio Tech (Nanjing, China). MitoSox Red mitochondrial superoxide indicator was obtained from Thermo Fisher (Shanghai, China). The JC-10 Mitochondrial Membrane Potential Assay Kit was from Mybiotech, (Xi'an, China). Dulbecco's Modified Eagle's Medium (DMEM) and fetal bovine serum (FBS) were purchased from Gibco (Carlsbad, California, USA). Trypsin, penicillin, streptomycin and l-glutamate were purchased from MP Biomedicals, LLC (Santa Ana, CA, USA). All other chemicals used in this work were analytical grade and were purchased from local commercial suppliers and used without further purification unless otherwise noted.


**5. Conclusion**

Chinese people believe that "sages" can be cultivated through self-reflection and deliberate

Moreover, the dark side of leadership can be more harmful in Asian cultures than that in Western cultures. This is because how people react to the dark side of leadership differs across different cultures. A recent study by Zhuang et al. [49] revealed that Chinese tend to be unwilling to report the unethical behavior of leader than peers. The authors suggested that a low tolerance of the unethical acts of peers may be attributed to collective loyalty to the organization, while the unwilling to report the unethical behaviors of leaders may be due to the respect for authority [49]. As stated earlier, the respect for authority has been linked to paternalistic leadership, which is a legacy of Confucian values and prevalent in Chinese cultures [38]. More specifically, the norms of individual behaviors and relationships are ruled by five cardinal relationships of Confucianism, which include emperorminister, father-son, husband-wife, elder-young and friend-friend relationships. As such, Chinese followers seldom challenge their leaders. An extreme case is that Chinese would even tolerate the corrupted leaders in late Qing dynasty. We could argue that the absence of fatherly benevolence, authoritarian supervision and moral integrity will deeply disappoint the followers in a Confucian society. Meanwhile if the followers obey destructive leaders possessing authorities, they may experience strong moral conflicts [38]. In **Table 5**, we summarize the Confucian virtues with reference to the related work in the leadership

practice if one strives for excellence.

140 Dark Sides of Organizational Behavior and Leadership

**Confucian virtues Related leadership literature** Loyalty ("zhong", 忠) Organization loyalty [40]

Trustworthiness ("xin", 信) Reliability [52]

Harmony ("he", 和) Harmony [42]

Integrity ("lian", 廉) Integrity [45]

Righteousness ("yi", 义) Fairness and justice [53]

Propriety ("li", 礼) Propriety, politeness [42]

Shame ("chi", 耻) Self-reflection and social emotion [48]

Committed to organization [50]

Affection ("ai", 爱) Paternalistic leadership [44], authentic transformational leadership [32]

Filial piety ("xiao", 孝) Respect of authority, paternalistic leadership [38, 44] Benevolence ("ren", 仁) Paternalistic leadership [44], servant leadership [51]

Integrity [42]

Conformity [43] Peace ("ping", 平) Agreeableness (tendency to be peaceful and gentle) [54]

**Table 5.** Summary of Confucian virtues with reference to the western scientific literature.

literature.

According to Chung and Bell [10], the Anna Karenina principle makes clear that no quantity of "good deeds" can make up for or prevent the consequences of one devastating error. Hence, a lack of any of the three fundamental qualities, namely competence, character and care, can constitute the dark side of leadership. Viruses arising from the POS also constitute to the dark side of leadership.

In the scientific literature, there are different conceptions of the dark side of leadership. Interestingly, most of the conceptions are related to the lack of competencies, character and care, echoing the emphases of the Service Leadership Theory, which highlight the lack of these qualities as well as the emergence of viruses as the dark side of leadership. Empirically, the negative outcomes brought by the dark side of leadership have also been well discussed in research studies. Finally, through the lens of Confucian virtues, one can further understand the dark side of leadership. In particular, linking the dark side of leadership to Confucianism allows us to understand this issue in a specific cultural and social context. Sim [55] argued that Confucian ethics can supplement Aristotle's insufficient discussion on human relations. In addition, the framework of the Service Leadership Theory addresses the limitations of many contemporary leadership theories, which often neglect the importance of cultural values [56].


*<IP_ADDRESS> Working of a solar cell*

Because the p-type layer is so thin, light photons can easily access the p-n junction. This allows light to go through the material more quickly. A sufficient quantity of energy is supplied to the circuit by the photons of light, which enables the circuit to

#### **Figure 2.** *Construction of solar cell.*

generate a significant number of electron-hole pairs. Because of the light, the link is no longer in a condition of thermal equilibrium. This is because of the light. Free electrons have an easier time making their way to the n-type side of the junction when they are located in an area that is deficient in electrons. The depletion produces holes that have the capability of rushing to the P-type side of the link, where they can cause further damage. The barrier potential of the junction halts the freshly formed free electrons in their tracks as soon as they reach the n-type side, rendering them unable to continue crossing the junction. This occurs as soon as the electrons reach the n-type side.

Once they have reached the p-type side of the junction, newly generated holes are unable to continue crossing the junction because of the constant barrier potential that exists between the two sides of the junction. When the number of electrons on one side of a p-n junction (the n-type side) is greater than the number of holes on the opposite side of the junction, the p-n junction behaves like a small battery cell. This occurs when the number of electrons on the n-type side of the junction is greater than the number of holes on the other side of the junction (the p-type side). The voltage that is generated is known as "photovoltage," which is only another word for what it is. When there is only a light load placed across the junction, there will only be a very small amount of current flowing through it.


*Psychotherapeutic Interventions for Type 2 Diabetes Mellitus DOI: http://dx.doi.org/10.5772/intechopen.97653*

### *Psychology and Pathophysiological Outcomes of Eating*

#### *Psychotherapeutic Interventions for Type 2 Diabetes Mellitus DOI: http://dx.doi.org/10.5772/intechopen.97653*

#### *Psychology and Pathophysiological Outcomes of Eating*

## *Psychotherapeutic Interventions for Type 2 Diabetes Mellitus DOI: http://dx.doi.org/10.5772/intechopen.97653*

#### *Psychology and Pathophysiological Outcomes of Eating*

### *Psychotherapeutic Interventions for Type 2 Diabetes Mellitus DOI: http://dx.doi.org/10.5772/intechopen.97653*

#### *Psychology and Pathophysiological Outcomes of Eating*

#### **Table 1.**

*Summary of reviewed randomized controlled trials.*


4. Discussion of some higher dimensional solutions

With this aim, we follow the method developed by Tang and Lou [32] for generating some families of diverse pattern formations while using the arbitrary functions g expressed previously.

Let us mention that for some convenience, we rewrite the variables X, Y, and T into their lower cases. Paying particular attention to fractal pattern formations, based upon the previous works carried out on the subject, we classify the above waves according to the different expressions of the generic lower dimensional function Θ of two generalized coordinates ð Þ ξ; t as defined by [33].

1. Nonlocal fractal pattern: we have the following

$$\Theta(\xi, t) = \sum\_{j=1}^{2} \lambda\_j \theta\_j |\theta\_j| \left\{ \left\{ a\_j \sin \left[ \ln \left( \theta\_j^2 \right) \right] + \beta\_j \cos \left[ \ln \left( \theta\_j^2 \right) \right] \right\} \right\}, \tag{47}$$

provided quantities θ0j, λj, αj, and βj being arbitrary parameters. Also, θj � kjξ � vjt þ θ0j. Variables ξ, kj, and vj are spacelike-defined, wave number, and velocity of the j-wave component, respectively.

2. Fractal dromiom pattern: the dromion-like (lump-like) structure is exponentially (algebraically) localized on a large scale and possesses self-similar structure near the center of the pattern. The function Θ can be expressed as

$$\Theta(\xi, t) = \exp\left\{-|\theta|\overline{N}\{r + \mathfrak{s}\sin\left[\ln\left(\theta^2\right)\right] + w\cos\left[\ln\left(\theta^2\right)\right]\}\right\},\tag{48}$$

with θj � kξ � vt þ θ0j, θ0 being an arbitrary parameter, and constants N, r, w, and s are arbitrary parameters. But also we can find

$$\Theta(\xi, t) = |\theta| \left\{ \overline{a} \sin \left[ \ln \left( \theta^2 \right) \right] + \overline{\beta} \cos \left[ \ln \left( \theta^2 \right) \right] \right\} \dot{N} / \left( 1 + \theta^4 \right), \tag{49}$$

for fractal lump solution. Constants α, β, and N~ are arbitrary parameters.

3. Stochastic fractal pattern: Such typical excitation is expressed through the differentiable Weierstrass function ℘ defined as

$$\otimes(\xi, t) = \sum\_{j=0}^{N} a^{-j/2} \sin \left( \beta^j \theta \right), N \to \infty,\tag{50}$$

with constants α and β being arbitrary parameters. A stochastic fractal excitation can be expressed as

$$\Theta(\xi,\mathfrak{t}) = \sum\_{i,j} R\_i(\theta\_i) R\_j(\theta\_j),\tag{51}$$

Depiction of Nonlocal fractal patterns at t ¼ 0. The parameters are chosen as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , λ1 ¼ 1=4, λ2 ¼ 0, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , λ1 ¼ 1=4, λ2 ¼ 0, θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α1 ¼ 1 and β1 ¼ 0. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and �2:32 � 10�10; 2:32 � 10�10 2 , respectively.

Figure 3.

Figure 4.

93

�2:32 � 10�10; 2:32 � 10�10 2

Fractal lump excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 2 such that: For p xð Þ¼ ; t Θð Þ x; t , θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 1, and β ¼ 0. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d)

Fractal stochastic nonlocal excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , λ1 ¼ 1=4, λ2 ¼ 0, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , λ1 ¼ 1=4, λ2 ¼ 0, θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities

, respectively.

represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and �2:32 � 10�10; 2:32 � 10�10 2

are their corresponding densities represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and

, respectively.

Fractal Structures of the Carbon Nanotube System Arrays

DOI: http://dx.doi.org/10.5772/intechopen.82306

#### Figure 2.

Fractal dromiom excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , r ¼ 3=2, s ¼ 1, w ¼ 0, N ¼ 1, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �7 � 10�3; 7 � 10�3 2 and �2:8 � 10�8; 2:8 � 10�8 2 , respectively.

Fractal Structures of the Carbon Nanotube System Arrays DOI: http://dx.doi.org/10.5772/intechopen.82306

#### Figure 3.

Figure 1.

Fractal Analysis

Figure 2.

92

�2:8 � 10�8; 2:8 � 10�8 2

, respectively.

Depiction of Nonlocal fractal patterns at t ¼ 0. The parameters are chosen as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , λ1 ¼ 1=4, λ2 ¼ 0, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , λ1 ¼ 1=4, λ2 ¼ 0, θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α1 ¼ 1 and β1 ¼ 0. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities

Fractal dromiom excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , r ¼ 3=2, s ¼ 1, w ¼ 0, N ¼ 1, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �7 � 10�3; 7 � 10�3 2 and

, respectively.

represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and �2:32 � 10�10; 2:32 � 10�10 2

Fractal lump excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 2 such that: For p xð Þ¼ ; t Θð Þ x; t , θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 1, and β ¼ 0. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and �2:32 � 10�10; 2:32 � 10�10 2 , respectively.

#### Figure 4.

Fractal stochastic nonlocal excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , λ1 ¼ 1=4, λ2 ¼ 0, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , λ1 ¼ 1=4, λ2 ¼ 0, θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �3:6 � 10�2; 3:6 � 10�2 2 and �2:32 � 10�10; 2:32 � 10�10 2 , respectively.

where Ri ¼ ℘ð Þþ θi θ2 i þ μi, with μi standing for arbitrary parameter.

Stochastic fractal dromion/solitoff excitations: such structures are obtained by including the Weierstrass function into the dromiom solution. Especially for solitoff excitations, we can try the following:

$$\Theta(\xi, t) = k + \sum\_{j=0} \eta\_j \otimes (\theta\_j) \tanh^{\mu\_j}(\theta\_j), \tag{52}$$

provided quantities k, ηj, and μj being arbitrary parameters. Stochastic fractal lump pattern: Eq. (51) is reduced as

$$\Theta(\xi, t) = \sum\_{i, j} \rho\_j R\_j(\theta\_j), \tag{53}$$

Next, in Figure 3, we obtain the fractal lump which shows self-similar structures

In addition to the above self-similar regular fractal dromion and lump excitations, by using the lower dimensional stochastic fractal functions, we construct some other higher dimensional stochastic fractal patterns. Thus, in Figure 4, we generate a typical stochastic fractal nonlocal pattern with self-similarity in structure.

Besides, in Figure 5, with the selecting parameters and suitable choices of lower dimensional arbitrary stochastic fractal dromion function as presented in the captions of these figures, we obtain higher dimensional stochastic dromion excitations. The self-similarity in structure of the observable I � ∣B∣ shows how the peaks are

In Figure 6, we construct the fractal solitoff excitations. By reducing the region

In Figure 7 with the selecting parameters and suitable choices of lower dimensional arbitrary stochastic fractal lump function as presented in the captions of the figure, we obtain higher dimensional stochastic lump excitations. Through the panels (7(a) and 7(b)) depicting the variations of ∣B∣�observable, at t ¼ 0, the selfsimilarity in structure of this observable shows how the peaks are distributed

; 7 � 10�3 2 and

Fractal stochastic solitoff excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , κ ¼ 2, M ¼ 1, η0 ¼ 0, η1 ¼ 1=2, ηm ¼ 0ð Þ m ≥2 , μ1 ¼ 1, θ01 ¼ �20, k1 ¼ 4, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , κ ¼ 0, M ¼ 2, η0 ¼ 0, η1 ¼ 1=5, η2 ¼ 1=4, ηm ¼ 0ð Þ m ≥3 , μ1 ¼ μ1 ¼ 1, θ02 ¼ �15, k2 ¼ 2, and v2 ¼ 2. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities

represented within the square regions �1:2 � 10�2; 1:2 � 10�2 � �½ � 5; 10 and

�1:5 � 10�8; 1:5 � 10�8 � �½ � 5; 10 , respectively.

; 1:2 � 10�2 � �½ � 5; 10 of panel 6ð Þ a to �1:5 � 10�8; 1:5 � 10�8 � �½ � 5; 10 of panel 6ð Þc , we obtain a totally similar structure with density plots represented

; 1 � 10�2 2 and

. In the above configurations, the stochastic fractal solitoff

distributed stochastically within the regions �1 � 10�2

Fractal Structures of the Carbon Nanotube System Arrays

DOI: http://dx.doi.org/10.5772/intechopen.82306

�2:6 � 10�8; 2:6 � 10�8 2 for stochastic fractal dromion.

in panels ð Þc and ð Þ d .

�1:2 � 10�2

Figure 6.

95

in panels (b) and (d), respectively.

�2:1 � 10�10; 2:1 � 10�10 2

stochastically within the regions �7 � 10�3

where quantities ηj and ρj being arbitrary parameter.

Now, let us analyze different figures with respect to the previous classifications. Thus, in Figure 1, we depict the variations of the ∣B∣-observable with space at t ¼ 0.

In a 3D�representation, the features presented in panel 1ð Þ a within the space region �3:6 � 10�2 ; 3:6 � 10�2 2 � ∣B∣ and those depicted in ð Þc within region �2:32 � 10�10; 2:32 � 10�10 2 � ∣B∣ are self-similar nonlocal.

Following the above figure, in Figure 2, we generate the fractal dromiom depicting self-similar structure with density plots represented in panels ð Þ b and ð Þ d , respectively. In comparison to the previous nonlocal fractal patterns, it appears that the fractal dromions have relatively high amplitudes.

#### Figure 5.

Fractal stochastic dromion excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , r ¼ 3=2, s ¼ 1, w ¼ 0, N ¼ 1, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �1 � 10�2; 1 � 10�2 2 and �2:6 � 10�8; 2:6 � 10�8 2 , respectively.

Fractal Structures of the Carbon Nanotube System Arrays DOI: http://dx.doi.org/10.5772/intechopen.82306

where Ri ¼ ℘ð Þþ θi θ2

Fractal Analysis

region �3:6 � 10�2

respectively.

Figure 5.

94

�2:32 � 10�10; 2:32 � 10�10 2

excitations, we can try the following:

; 3:6 � 10�2 2

i þ μi, with μi standing for arbitrary parameter.

tanhμj θj

� ∣B∣ and those depicted in ð Þc within region

� ∣B∣ are self-similar nonlocal. Such a similarity in the

, (52)

, respectively.

, (53)

Stochastic fractal dromion/solitoff excitations: such structures are obtained by including the Weierstrass function into the dromiom solution. Especially for solitoff

> j¼0 ηj ℘ θj

Θð Þ¼ ξ; t Σ

profiles is clearly shown in panels ð Þ b and ð Þ d standing for their density plots,

Following the above figure, in Figure 2, we generate the fractal dromiom depicting self-similar structure with density plots represented in panels ð Þ b and ð Þ d , respectively. In comparison to the previous nonlocal fractal patterns, it appears that

Fractal stochastic dromion excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , r ¼ 3=2, s ¼ 1, w ¼ 0, N ¼ 1, θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities

represented within the square regions �1 � 10�2; 1 � 10�2 2 and �2:6 � 10�8; 2:6 � 10�8 2

i,j

Now, let us analyze different figures with respect to the previous classifications. Thus, in Figure 1, we depict the variations of the ∣B∣-observable with space at t ¼ 0. In a 3D�representation, the features presented in panel 1ð Þ a within the space

ρjRj θj

Θð Þ¼ ξ; t k þ Σ

provided quantities k, ηj, and μj being arbitrary parameters.

Stochastic fractal lump pattern: Eq. (51) is reduced as

where quantities ηj and ρj being arbitrary parameter.

the fractal dromions have relatively high amplitudes.

Next, in Figure 3, we obtain the fractal lump which shows self-similar structures in panels ð Þc and ð Þ d .

In addition to the above self-similar regular fractal dromion and lump excitations, by using the lower dimensional stochastic fractal functions, we construct some other higher dimensional stochastic fractal patterns. Thus, in Figure 4, we generate a typical stochastic fractal nonlocal pattern with self-similarity in structure.

Besides, in Figure 5, with the selecting parameters and suitable choices of lower dimensional arbitrary stochastic fractal dromion function as presented in the captions of these figures, we obtain higher dimensional stochastic dromion excitations. The self-similarity in structure of the observable I � ∣B∣ shows how the peaks are distributed stochastically within the regions �1 � 10�2 ; 1 � 10�2 2 and

�2:6 � 10�8; 2:6 � 10�8 2 for stochastic fractal dromion.

In Figure 6, we construct the fractal solitoff excitations. By reducing the region �1:2 � 10�2 ; 1:2 � 10�2 � �½ � 5; 10 of panel 6ð Þ a to �1:5 � 10�8; 1:5 � 10�8 � �½ � 5; 10 of panel 6ð Þc , we obtain a totally similar structure with density plots represented in panels (b) and (d), respectively.

In Figure 7 with the selecting parameters and suitable choices of lower dimensional arbitrary stochastic fractal lump function as presented in the captions of the figure, we obtain higher dimensional stochastic lump excitations. Through the panels (7(a) and 7(b)) depicting the variations of ∣B∣�observable, at t ¼ 0, the selfsimilarity in structure of this observable shows how the peaks are distributed stochastically within the regions �7 � 10�3 ; 7 � 10�3 2 and

�2:1 � 10�10; 2:1 � 10�10 2 . In the above configurations, the stochastic fractal solitoff

#### Figure 6.

Fractal stochastic solitoff excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 1 such that: For p xð Þ¼ ; t Θð Þ x; t , κ ¼ 2, M ¼ 1, η0 ¼ 0, η1 ¼ 1=2, ηm ¼ 0ð Þ m ≥2 , μ1 ¼ 1, θ01 ¼ �20, k1 ¼ 4, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , κ ¼ 0, M ¼ 2, η0 ¼ 0, η1 ¼ 1=5, η2 ¼ 1=4, ηm ¼ 0ð Þ m ≥3 , μ1 ¼ μ1 ¼ 1, θ02 ¼ �15, k2 ¼ 2, and v2 ¼ 2. Note that α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �1:2 � 10�2; 1:2 � 10�2 � �½ � 5; 10 and �1:5 � 10�8; 1:5 � 10�8 � �½ � 5; 10 , respectively.

system is Painlevé integrable [15]. We derived another important properties, namely the Bäcklund transformation and the Hirota bilinearization [27–30] while

took advantage of the existence of some arbitrary functions to construct some interesting solutions such as fractals. Actually, following the investigation of fractals in many physical systems [31–33], we constructed some localized nonlinear excitations with some fractal support. As a result, we found the following typical features: the fractal dromion, the fractal lump, the stochastic and nonlocal fractal excitations. One of the advantages of the WTC method discussed in this work is the generation of arbitrary functions useful in constructing many kinds and different solutions to the governing system. From such property endowing the method with the powerfulness, it would be rather interesting again to construct other types of nonlinear excitations such as the bubbles, the solitoffs, the dromions, the peakons, the fractals, among others [34–37]. These typical excitations would be useful in the understanding, more deeply, of the interaction between light incident excitations and carbon nanotubes for some practical issues in nanomechanical, nanoelectronic, and nanophotonic devices, alongside some emerging applications exploiting the good thermal and electronic conductivities of carbon nanotubes in some flat panel

In the wake of the result obtained from the WTC approach of integrability, we

Also, we intend using the WTC method in order to discover more other interesting properties still unknown in the carbon nanotube arrays. Previously, we discovered the properties of compactons in CNT [38]. The different properties will allow us in the future to improve the different uses of carbon nanotube in different areas of life. Moreover, because of these electrical and mechanical properties (very resistant, flexible, and lightweight), they are very suitable for the design of pressure sensors. These could be used by engineers to prevent structural collapses in civil engineering. They will have to measure either the pressure or the shear. Similarly, these sensors can be used in medicine while incorporating the system in textiles for better follow-up of patients or in a shoe sole. In another view, the sensors will have to be able to perform a good measure of the desired size. So to refine the design of these sensors, it will be essential to get even more information about this material. By discovering more properties of the material, we will know more how to exploit it in a safe way in all the various disciplines combining research and innovation.

National Advanced School of Engineering, University of Yaounde I, Cameroon

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

establishing the complete integrability of the system.

Fractal Structures of the Carbon Nanotube System Arrays

DOI: http://dx.doi.org/10.5772/intechopen.82306

displays and field-effect transistors, among others.

Author details

97

Raïssa S. Noule and Victor K. Kuetche\*

provided the original work is properly cited.

\*Address all correspondence to<EMAIL_ADDRESS>
Figure 7.

Fractal stochastic lump excitations depicted at t ¼ 0 by the observable ∣B∣ � I which expression is given by Eq. (40). In this case, the parameters are selected as a0 ¼ 1, a1 ¼ 1, a2 ¼ 1, and a3 ¼ 2 such that: For p xð Þ¼ ; t Θð Þ x; t , θ01 ¼ 0, k1 ¼ 1, and v1 ¼ 1. For q y ð Þ¼ ; t Θð Þ y; t , θ02 ¼ 0, k2 ¼ 1, and v2 ¼ 1. Note that α ¼ 1, β ¼ 0, N~ ¼ 2 associated to α ¼ 3=2, β ¼ 3=2, and N ¼ 100. Panels (a) and (c) represent the pattern formations depicted in 3D-perspective, and the two others (b) and (d) are their corresponding densities represented within the square regions �7 � 10�3; 7 � 10�3 2 and �2:1 � 10�10; 2:1 � 10�10 2 , respectively.

and stochastic fractal lump excitations appear to be the waves with greater amplitudes in comparison to the previous ones.

From a physical viewpoint, the observable B which has the meaning of the dimensionless electric field shows that its intensity ∣B∣ can be nonlocal or rather selfconfined. Actually, the intensity of the electromagnetic wave propagating along the carbon nanotube arrays is compact within the arrays. The previous study has revealed that the light bullet intensity describes a fractal-like excitation which provides more insights into the structural dynamics of the system under investigation.

#### 5. Summary

Throughout the present work, we investigated the formation of fractal ultrashort spatiotemporal optical waveforms in arrays of carbon nanotubes. We followed the short-wave approximation to derive a generic (2+1)-dimensional coupled system. Such a coupled system was constructed via the use of the reductive perturbation analysis for the Maxwell equations and for the corresponding Boltzmann kinetic equation of the distribution function of electrons in the carbon nanotubes. Prior to the construction of different solutions to the previous coupled equations, we first studied the integrability of the governing system within the viewpoint of WTC formalism [15]. Thus, we investigated the singularity structure of the system. In this analysis, we expanded the different observables in the form of the Laurent series. Therefore, we found the leading order terms useful to solve the recurrent system. Solving this last system, we unearthed the different resonances of the governing equations. At the end, we found that the number of resonances balances seemingly the number of arbitrary functions in such a way that the governing system has sufficient and enough arbitrary functions. Hence, we derived that the

#### Fractal Structures of the Carbon Nanotube System Arrays DOI: http://dx.doi.org/10.5772/intechopen.82306

system is Painlevé integrable [15]. We derived another important properties, namely the Bäcklund transformation and the Hirota bilinearization [27–30] while establishing the complete integrability of the system.

In the wake of the result obtained from the WTC approach of integrability, we took advantage of the existence of some arbitrary functions to construct some interesting solutions such as fractals. Actually, following the investigation of fractals in many physical systems [31–33], we constructed some localized nonlinear excitations with some fractal support. As a result, we found the following typical features: the fractal dromion, the fractal lump, the stochastic and nonlocal fractal excitations.

One of the advantages of the WTC method discussed in this work is the generation of arbitrary functions useful in constructing many kinds and different solutions to the governing system. From such property endowing the method with the powerfulness, it would be rather interesting again to construct other types of nonlinear excitations such as the bubbles, the solitoffs, the dromions, the peakons, the fractals, among others [34–37]. These typical excitations would be useful in the understanding, more deeply, of the interaction between light incident excitations and carbon nanotubes for some practical issues in nanomechanical, nanoelectronic, and nanophotonic devices, alongside some emerging applications exploiting the good thermal and electronic conductivities of carbon nanotubes in some flat panel displays and field-effect transistors, among others.

Also, we intend using the WTC method in order to discover more other interesting properties still unknown in the carbon nanotube arrays. Previously, we discovered the properties of compactons in CNT [38]. The different properties will allow us in the future to improve the different uses of carbon nanotube in different areas of life. Moreover, because of these electrical and mechanical properties (very resistant, flexible, and lightweight), they are very suitable for the design of pressure sensors. These could be used by engineers to prevent structural collapses in civil engineering. They will have to measure either the pressure or the shear. Similarly, these sensors can be used in medicine while incorporating the system in textiles for better follow-up of patients or in a shoe sole. In another view, the sensors will have to be able to perform a good measure of the desired size. So to refine the design of these sensors, it will be essential to get even more information about this material. By discovering more properties of the material, we will know more how to exploit it in a safe way in all the various disciplines combining research and innovation.


*Blockchain from a Modern Perspective: An Evolution to Health Science DOI: http://dx.doi.org/10.5772/intechopen.109178*

To begin with, the cryptographic approval of every exchange guarantees information honesty [11]. This is basic for guaranteeing information truthfulness — forestalling information creation, information "beautification," and, here and there, information innovation. Second, one of the principal abilities of Blockchain is information discernibility and accuracy: every exchange is timestamped [12]. This information is available to people in general; any client can get a duplicate of the time-stepped information. **Figure 4** portrays the mind boggling progressions of heterogeneous information and metadata that circle in a clinical report, proposing countless medical care partners and all records whose presence might be confirmed utilizing Blockchain. Accordingly, the presence of information becomes evident while the information stays private.

Rundown of non-thorough instances of key data that can favorably "sit on the top" of the Blockchain:

**Figure 4.** *Clinical trial complex data workflow encoded in Blockchain.*


4.4.2. Mutations in ATP Synthase Nuclear Structural Subunits

At present, only a small number of mitochondrial pathologies have been attributed to mutations in nuclear genes coding for subunits of the ATP synthase and for chaperones that function in assembly of the enzyme. Several studies found that patients with lactic acidosis, persisting 3-methylglutaconic aciduria, cardiomyopathy, and early death were correlated with severe deficiencies in ATP synthase, but the genetic lesions in these studies were not identified [209–211]. *ATP5F1E* and *ATP5F1D*, the human homologs of the yeast *ATP15* and *ATP16*, code for the ε and δ subunits, respectively, of the central stalk of F1. A homozygous missense mutation in *ATP5F1E* was the first reported instance of a patient with an ATP synthase defect stemming from a mutation in a nuclear encoded subunit of the enzyme. The mutation caused mild mental retardation and the patient developed peripheral neuropathy [6]. The mitochondrial synthesis of ATP, the oligomycin ATPase activity and the ATP synthase content were reduced by 60–70%. The residual enzyme with the mutated ε subunit had normal activity, indicating that the primary effect of the mutation was on assembly of the synthase. Interestingly, this mutation, when introduced in the ε subunit of yeast ATP synthase, did not elicit any detectable effect on either the activity of assembly of the enzyme [212]. This suggested that the mutation in the human ε subunit, perhaps because of a weaker physical interaction with the c ring, exerted a deleterious effect on assembly of the human but not of the yeast enzyme [212]. In a more recent report, two patients with homozygous mutations in *ATP5F1D* were shown to suffer from metabolic disorders in one case and from encephalopathy in another [213]. *ATP5F1A,* coding for human α subunit of F1, is the third nuclear ATP synthase gene identified in two patients presenting fatal neonatal encephalopathy with intractable seizures [5]. Interestingly, reduced levels of cellular ATP5F1 were also shown to correlate significantly with earlier-onset prostate cancer [214]. Indeed, transitioning from oxidative phosphorylation to anaerobic glycolysis for energy production occurs in many types of tumors, and could explain the pathophysiology of the disease.

**Table 7.** Pathologies resulting from mutations in genes encoding ATP synthase subunits and assembly factors, and their yeast homologs.

**Table 7.** *Cont.*

1 Review describing many mutations. 2 In different patients. 3 In the same patient.

None of the patients with mutations in the nuclear ATP synthase genes discussed in this and the next sections exhibit the clinical NARP and Leigh syndrome phenotypes characteristic of patients with mutations in the two mitochondrially-encoded genes of the enzyme.

#### 4.4.3. Nuclear ATP Synthase Assembly Gene Mutations

A substantial number of nuclear gene products of *S. cerevisiae* are known to regulate and chaperone different steps of ATP synthase assembly [215]. At present, however, the only known human regulatory factors with identified mutations in a small number of patients are TMEM70, a protein essential for ATP synthase assembly and ATPAF2, the homolog of the yeast Atp12 chaperone that interacts with the α subunit of F1 during assembly of this ATP synthase module [216]. TMEM70 does not have a yeast homolog. The phenotypes associated with mutations in TMEM70 and the role of its product in ATP synthase assembly have been reviewed elsewhere [217,218].

A study in which two patients, ascertained to have nuclear mutations that affected mitochondrial ATP synthase assembly, were screened by sequencing human homologs of yeast genes previously shown to affect F1 biogenesis led to the identification in one patient of a mutation in *ATPAF2*. This patient, diagnosed with lactic acidosis, glutaconic aciduria, encephalomyopathy and a range of different developmental problems, was found to have a homozygous W94R amino acid substitution that resulted in severe deficits of ATP synthase in the heart, liver and to a lesser degree in skeletal muscle, resulting in death at 14 months of age [219]. The deleterious effect of the W94R substitution in a highly conserved region of *ATPAF2* on ATP synthase assembly was confirmed by Meulemans et al. [7], who showed that the wild-type, but not the mutant human gene, restored the ATP synthase activity of a yeast *atp12* mutant. The *atp12* mutant also failed to be complemented by the yeast *ATP12* harboring the equivalent W102R mutation expressed from a low copy yeast CEN, but not from a high-copy plasmid. The rescue by the W102R, however, depended on the presence of wild-type *FMC1*, a gene implicated in regulating the activity of yeast Atp12 [220].

#### *4.5. Coenzyme Q*

Coenzyme Q (ubiquinone, CoQ or CoQ10 in humans) is a lipophilic redox molecule found in virtually all eukaryotic organisms and most bacteria. It is composed of a quinone ring connected to a polyisoprenoid side chain of variable length. Coenzyme Q serves several crucial functions in mitochondria, including transfer of electrons from Complexes I and II to Complex III, acting as an essential cofactor in the uncoupler protein mediated transfer of protons to the matrix, prevention of lipid peroxidation, biosynthesis of uridine, beta-oxidation of fatty acids, and binding to and regulating the permeability transition of the voltage-dependent anion channel [221].

The CoQ biosynthetic pathway in eukaryotes has been studied in yeast *coq* mutants arrested at different steps of the pathway [222,223]. Like human cells, yeast relies on de novo synthesis of CoQ; and any deficiency in the biosynthetic pathway results in a growth arrest on media containing non-fermentable carbon sources [3,224]. Most enzymes of the CoQ biosynthetic pathway are organized in a multi-subunit complex known as the CoQ synthome [222,225]. The CoQ synthome is spatially linked to the endoplasmic reticulum–mitochondria contact sites, providing optimal CoQ production with an efficient intracellular distribution as well as minimizing the escape of toxic intermediates [226,227]. Expression of functional CoQ in yeast depends on at least 14 nuclear gene products (Coq1-Coq11, Yah1, Arh1, and Hfd1), all located in mitochondria [227].

CoQ biosynthesis is achieved by three separate and highly conserved pathways:

(1) Synthesis of the quinone ring from 4- hydroxybenzoate (4HB), derived from tyrosine [228], or from p-aminobenzoic acid (pABA), in yeast but not in humans [225,227,229]. The early steps of 4HB formation are still to be determined but deamination of tyrosine starts with Aro8 or Aro9 catalyzed transamination [230]. The formation of the final intermediate 4-hydroxybenzaldehyde (4 HBz) is catalyzed by the aldehyde dehydrogenase Hfd1 [230,231].

(2) Synthesis of isopentenyl pyrophosphate (IPP) and dimethylally pyrophosphate (DMAPP), catalyzed by Coq1 in yeast [232] and PDSS1 and PDSS2 in humans.

(3) Prenylation of parahydroxybenzoate by the polisoprenyl transferase Coq2 [233] and further modifications of the benzoquinone ring by hydroxylases and methyl transferases. The isoprenoid side chain is important for proper CoQ localization at the mid-plane of phospholipid bilayers. Yeast coenzyme Q contains 6 isopentenyl units (CoQ6) while in humans the major coenzyme Q isoform contains 10 isopentenyl units (CoQ10).

The benzoquinone head group is modified by hydroxylations catalyzed by Coq6 and Coq7 [234–236], methylation of the resultant hydroxyls by the Coq3 methyl transferase [237], methylation of the ring by Coq5 [238] and a decarboxylation step catalyzed by a still unidentified enzyme of this pathway. Other gene products linked to coenzyme Q biosynthesis and utilization include Coq4 and Coq9, that have been assigned a role in assembly and stability of the CoQ synthome, and Coq8, a member of a protein family that includes kinases and ATP-dependent ligases. Coq8 has been implicated in the phosphorylation state of Coq3, Coq5 and Coq7 [239–241]. The steady-state concentrations of Coq4, 6, 7, and 9 are markedly decreased in a *coq8* null mutant, as a result of which assembly of the CoQ synthome is abrogated [242]. The *coq8* null mutant, however, contains a complex of Coq6 and Coq7 thought to be an early intermediate of the synthome [243]. Coq10 is a low molecular weight member of the START protein family that binds coenzyme Q. Although Coq10 is required for respiration, its synthesis is only partially affected in log but not in stationary phase yeast cells, suggesting that its function is related to the delivery of coenzyme Q from the synthome located at the endoplasmic-mitochondrial contact sites to the regions of the inner membrane containing the respiratory chain complexes [226,244]. The respiratory deficiency of *coq10* mutants is partially rescued in a *coq11* mutant, which codes for a component of the synthome that has been proposed to down- regulate the synthesis of coenzyme Q [244]. Coq11 (human NDUFA9), a separate protein in yeast, is a component of the CoQ synthome [245] and appears to regulate its formation and stability [244]. CoQ yeast and human genes are listed in Table 8.

**Table 8.** Coenzyme Q genes required for functional expression of CoQ and their yeast homologs.

**Table 8.** *Cont.*

#### Mutations in COQ Genes

CoQ10 deficiency, a biochemical lesion first described over three decades ago by Ogasahara et al. [246], is subdivided into primary CoQ10 deficiency, when caused by a pathogenic mutation in one of the genes required for the coenzyme's biosynthesis, and secondary CoQ10 deficiency, when the mutated gene is not directly related to the biosynthetic pathway [247]. Of the two, the latter has been reported more frequently in patients, with phenotypes including mitochondrial myopathies, mitochondrial DNA depletion syndrome and multiple acyl-CoA dehydrogenase deficiency (MADD) [248]. However, the pathogenic mechanisms linking these disorders with the observed CoQ10 deficiency have yet to be elucidated.

Primary CoQ10 deficiency is far rarer [248]. Emmanuele et al. [247] first classified the clinical manifestations of primary CoQ10 deficiency into five distinct phenotypes: encephalomyopathy, isolated myopathy, nephropathy, infantile multisystemic disease, and cerebellar ataxia. However, it has been argued that this subdivision should be updated, as new cases have been discovered with novel mutations presenting a wide range of other clinical phenotypes, as well as different combinations of the previously described symptoms [248]. To date, mutations in ten genes have been associated with primary CoQ10 deficiency (Table 9).

With the exception of Coq3, patients have been reported with mutations in all other components of the CoQ multi-subunit complex [249,250]. These patients can be treated with CoQ10 supplementation with partial success. Early treatment based on early diagnosis is critical for the best outcome [251]. Because of its poor solubility, CoQ10 is only administrated in oral formulations, despite its destitute bioavailability [252,253]. Similarly, uptake of CoQ6 in yeast *coq* mutants is inefficient [254,255].

Due to the striking homology between human and yeast COQ genes [227], studies of CoQ proteins in *S. cerevisiae* may provide insight into human homologs, leading to the identification of residues critical for protein function and, therefore, with higher pathogenic potential [256]. Indeed, yeast *coq3*, *coq8*, *coq9*, and *coq10* mutants are complemented by the human counterparts [239,257–259], while yeast *coq5* null mutants are complemented by human *COQ5* combined with overexpression of *COQ8* [260]. Furthermore, studies of pathogenic mutations in *COQ* genes have been validated in yeast *coq1* [261], *coq2* [261,262], *coq4* [263], *coq6* [264], *coq8* [241], and *coq9* mutants [265].

*PDSS1* and *PDSS2*, both human homologs of yeast *COQ1*, encode two proteins that form a heterotetramer that catalyzes the elongation of the isoprenoid side chain. *PDSS1* does not complement the yeast *coq1* null mutant [261]. Mutations in both of these genes lead to infantile multisystemic disease, a heterogeneous disorder characterized by psychomotor regression, encephalopathy, optic atrophy, retinopathy, hearing loss, renal dysfunction and heart valvulopathy [247,261]. Mutations in *PDSS2* have been associated with additional phenotypes, including Leigh syndrome, steroid resistant nephrotic syndrome (SRNS)—an atypical manifestation for other mitochondrial disorders but quite common for CoQ10 deficiencies; and hepatocellular carcinoma [247,266,267]. It has been shown that the downregulation of *PDSS2* can induce a shift from aerobic metabolism to anaerobic glycolysis, as well as increased chromosomal instability—a possible pathogenic mechanism for hepatocellular carcinoma [267].

Pathogenic mutations in *COQ2*, encoding a parahydroxybenzoate-polyprenyltransferase that catalyzes the addition of the isoprenoid chain to the benzoquinone ring, were the first to be associated with primary CoQ10 deficiency [268]. Pathogenic mutations in human *COQ2* have been confirmed in yeast by complementation studies of the yeast *coq2* null mutant [261,262]. Clinical manifestations of these mutations include isolated SRNS, SRNS with encephalomyopathy resembling MELAS, fatal infantile multisystemic disease, and late-onset multiple-system atrophy and retinopathy [247,248].

The first pathogenic mutation in *COQ4*, required for the stability of the CoQ synthome, was found as a haploinsufficiency, with a phenotype similar to that of a heterozygous yeast mutant [263]. The patient presented facial dysmorphism and muscle hypotonia, which improved significantly with CoQ10 supplementation [263]. Since then, a total of 19 patients, all infants, have been identified with mutations in *COQ4*, with clinical phenotypes that included cerebellar atrophy, lactic acidosis, seizures, muscle weakness, cardiomyopathy, ataxia, and Leigh syndrome [269,270]. None of the patients suffered from nephropathy, typically found in primary CoQ10 deficiency.

To date, only three cases of pathogenic mutations in the methyltransferase encoded by *COQ5*, have been recorded. The affected individuals were three female siblings presenting with non-progressive cerebellar ataxia, dysarthria, and mild to moderate cognitive disability [250]. Two of the three siblings exhibited myoclonic jerks and generalized tonic-clonic seizures in adolescence and early 20s. Next-generation sequencing identified a tandem duplication of the last four exons of *COQ5*, while biochemical studies showed a 33% reduction of CoQ10 in skeletal muscle—sufficient to sustain a basal rate but insufficient to reach maximal efficiency of respiration [250].

Mutations in *COQ6*, encoding an enzyme involved in hydroxylation and deamination reactions during CoQ biosynthesis, have been primarily associated with SRNS [264], characterized by significant proteinuria with resulting hypoalbuminemia and edema and presenting with focal segmental glomerulosclerosis [248]. The pathogenicity of the first six *COQ6* mutations in human patients was confirmed by complementation studies using the yeast *coq6* null mutant [264]. Three patients harboring a *COQ6* mutation also suffered from infantile multisystemic disease [247]. Based on in vitro and in vivo studies of renal podocyte cell lines, it has been hypothesized that the pathogenicity of *COQ6* mutations relates to respiratory chain deficiency, ROS generation, disruption of podocyte cytoskeleton and induction of cellular apoptosis, ultimately resulting in SRNS [271].

Three cases of primary CoQ10 deficiency caused by mutations in *COQ7*, responsible for the penultimate step of CoQ biosynthesis, have been reported in two children with similar phenotypes of spasticity, sensorineural hearing loss and muscle hypotonia; and a third more severe case of fatal mitochondrial encephalo-myo-nephro-cardiopathy, persistent lactic acidosis, and basal ganglia lesions [272–274]. In one of the patients, treatment with the unnatural biosynthesis precursor 2,4-dihydroxybenzoate (DHB), a hydroxylated variant of the native 4-hydroxybenzoic acid (4-HB) normally modified by COQ7, increased CoQ10 levels and partially restored mitochondrial respiration [273].

The human genes *ADCK3* and *ADCK4*, also known as *COQ8A* and *COQ8B*, are both homologs of yeast *COQ8*. Mutations in *COQ8A* have mostly been associated with autosomal recessive progressive cerebellar ataxia (ARCA), often accompanied by childhood onset cerebellar atrophy, with and without seizures, and exercise intolerance [241,248,275]. The pathogenic nature of the *ADCK3* mutations was corroborated using the yeast counterpart system [241]. However, isolated cases of psychiatric disorders, seizures, migraines, and dysarthria have been reported [248]. Studies of fibroblast cell lines isolated from ARCA patients showed an increased sensitivity to oxidative stress induced by hydrogen peroxide, high levels of oxidative stress and changes in mitochondrial homeostasis as a result of loss-of-function mutations in *COQ8A* [275]. Interestingly, concomitant with the upregulation of ROS production, increased respiratory supercomplex stability and basal respiratory rate were observed, suggesting that the loss of ADCK3 could result in a compensatory elevation of respirasome formation [275]. The relationship between the two human paralogs *COQ8A* and *COQ8B* is unclear. However, pathogenic mutations in the two genes lead to completely different clinical phenotypes. Indeed, all patients with *COQ8B* mutations suffered from SNRS, with only a single case of neurological involvement reported [248,276].

**Table 9.** Pathologies resulting from mutations in Coenzyme Q genes and their yeast homologs.

1 Review describing many mutations. 2 In different patients.

Primary CoQ10 deficiency caused by mutations in *COQ9* is extremely rare, with only seven cases from four families having been reported. The *COQ9* gene product binds to the polyprenyl tail of CoQ intermediates with high specificity, allowing the modification of the benzene ring by Coq7 and other components of the CoQ synthome [259,277]. The reported cases include an infant suffering from lethal lactic acidosis, seizures, cerebral atrophy, HCM, and renal dysfunction [248,265], a boy diagnosed with neonatal Leigh-like syndrome who died at 18 days of age from cardio-respiratory failure [278], four siblings with an unknown and ultimately lethal condition characterized by dilated cardiomyopathy, anemia, abnormal appearing kidney, and suspected Leigh syndrome [279]; and a nine-month old girl presenting with microcephaly, truncal hypotonia, and dysmorphic features [280].

It has been shown that the pathogenicity of primary and secondary CoQ10 deficiencies is linked to the impairment of electron transfer to Complex III, ultimately resulting in decreased mitochondrial respiration and ATP synthesis [248,281]. It has also been noted that the neurological presentation of CoQ10 deficiency is likely associated with oxidative damage and caspase-independent apoptotic cell death in the brain, as a result of mitochondrial impairment [281]. While renal dysfunction is not uncharacteristic of mitochondrial deficiencies, the glomerular involvement, as opposed to the tubular damage seen in other mitochondrial cytopathies, is perplexing and could be a result of impaired CoQ10 antioxidant function [248]. Equally puzzling is the remarkable diversity of clinical phenotypes resulting from mutations in different COQ genes. Based on in vivo studies of mouse models harboring *COQ9* mutations, Luna-Sánchez et al. [281] have hypothesized that a key factor in determining the degree of severity and particular clinical phenotypes of CoQ10 deficiencies is the stability of the CoQ synthome. Lastly, decreased CoQ10 levels impair the activity of sulfide:quinone oxidoreductase, an enzyme involved in the catabolism of H2S [282]. While at physiological conditions H2S serves as an electron donor to the mitochondrial respiratory chain, at elevated levels it inhibits Complex IV activity, resulting in reduced cellular respiration. Over-physiological levels of H2S could therefore participate in the pathogenic mechanism of CoQ10 deficiency [282].