Tomas Bata University in Zlín
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Grafting well-defined polymers onto unsaturated PVDF using thiol-ene reactions
Get PDFPoly(vinylidene fluoride) (PVDF) is commonly used in membranes, lithium-ion battery binders, and coatings due to its thermal and chemical robustness. Nevertheless, PVDF-based copolymers can broaden the application scope and performance capabilities of pristine PVDF. PVDF has been modified via grafting-from reactions. However, grafting density and graft length, two important properties of graft copolymers, cannot be accurately determined. Herein, we used grafting-onto thiol-ene reactions as a method to modify PVDF. The molar mass of pre-synthesized, thiol-terminated polymers were accurately determined, and grafting densities were calculated. Unsaturated sites were generated through dehydrofluorination and dehydrochlorination in PVDF and P(VDF-co-chlorotrifluoroethylene) (PVDF-CTFE). Various conditions were studied, including the molar mass and chemical structure of grafts, the degree of thiol substitution, and thiol-ene reaction mechanisms. Base-catalyzed Michael addition with secondary thiols performed best, with the highest grafting density calculated to be about 4 chains per PVDF chain. Despite the low grafting density, changes in material properties between the product and starting materials were observed, validating this controlled method for PVDF modification.National Science Foundation, NSF, (DMR 2202747); US-UK Fulbright Commission, (2022-21-1, RP/CPS/2022/007); Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF, (194385); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (CHE-0130903, CHE-1039870, CHE-1726525)NSF [DMR 2202747, CHE-0130903, CHE-1039870, CHE-1726525]; Swiss National Science Foundations (SNSF) [194385]; J. W. Fulbright Commission [2022-21-1]; DKRVO - MEYS of the Czech Republic [RP/CPS/2022/007
Moderating effect of social media in shaping ecotourism loyalty: A two-stage-cross-sectional study
Get PDFThis study aims to evaluate the moderating role of social media influence before and after the trip in Vietnam and Czech Republic. Primary data, gathered during time lag data surveys conducted among international tourists travelling to the Czech Republic and Vietnam, was analyzed with the Structural Equation Modelling (SEM) in R. The findings revealed that social media influence with higher level positively strengthened the connection between tourist motivation and the post trip destination image. Furthermore, social media had a significant moderating effect on the relationship between tourist satisfaction and ecotourism loyalty. However, there are strong differences between the destinations of developed and emerging economies. For Czech Republic, as developed economy, social media influence plays a more important role as a value-expressive mechanism at the post-trip stage whereas for the developing economy of Vietnam, social media plays a more important role as an information source before the trip. This study extends the Expectation Confirmation Theory (ECT) by introducing the moderating effect of social media influence, which first time measures this moderating effect before and after the trip accounting for the dynamic nature of the destination image as an antecedent of ecotourism loyalty. Limitations, theoretical implications, and recommendations for practice and further research are addressed
Pharmacological Significance of Boraginaceae with Special Insights into Shikonin and Its Potential in the Food Industry
Get PDFShikonin is a naphthoquinone pigment present in the hairy roots of the plant species from the Boraginaceae family. The compound has been well investigated for its highly efficient medicinal, antioxidant, and antimicrobial properties. Various extraction methodologies have been employed to maximise yield while minimising waste production of shikonin and its derivatives. Despite substantial research on shikonin and Boraginaceae plants, a research gap persists in the food industry and extraction technologies. This review addresses crucial aspects of shikonin deserving of further exploration. It begins by elucidating the attributes of the Boraginaceae plants and their medicinal traits in folklore. It proceeds to focus on the roots of the plant and its medicinal properties, followed by extraction procedures explored in the last fifteen years, emphasising the novel technologies that have been chosen to improve the yield extract while minimising extraction times. Furthermore, this review briefly outlines studies employing cell culture techniques to enhance in vitro shikonin production. Lastly, attention is directed towards research in the food industry, particularly on shikonin-loaded biodegradable films and the antioxidant activity of shikonin. This review concludes by summarising the future potential in food science and prominent research gaps in this field.Tomas Bata University in Zlín, TBU, (IGA/FT/2024/005); Tomas Bata University in Zlín, TBUTomas Bata University in Zli
Comparison of the bending behavior of cylindrically shaped lattice specimens with radially and orthogonally arranged cells made of ABS
Get PDFThe article deals with the comparison of the bending behavior of cylindrical lattice samples with radially and orthogonally arranged cells made of ABS material. The structures were designed in PTC Creo Parametric 8 software, while four types of lattice structures were evaluated: Rhombus, Cuboidal BCC, Octagon, and Starry, in three material volume fractions: 44, 57, and 70%, together with tubular and rod-shaped samples. The Fused Filament Fabrication (FFF) technique was chosen for the production of ABS plastic samples. Based on the bending tests, the dependences of the force on the deflection were recorded and the obtained data were statistically processed to identify outliers using the Grubbs test. The maximum stresses were calculated and the dependences of the stresses on the volume fractions were plotted. Along with energy absorption, ductility indices were also specified. Although the Rhombus structure appears to be the best based on the ductility indices obtained, on the other hand, the structure showed the lowest values of bending stresses (in the range from 10.6 to 12.6 MPa for volume fractions ranging from 44 to 70%, respectively). Therefore, from a synergic point of view of both factors, stress and ductility, the Starry structure exhibits the best flexural properties among those investigated.Ministry of Education, Science, Research and Sport; Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky, (APVV-19-0550); Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA, (005TUKE-4/2021, 032TUKE-4/2022)Ministry of Education, Science, Research and Sport of the Slovak Republic; KEGA [032TUKE-4/2022]; [APVV-19-0550]; [KEGA 005TUKE-4/2021
The influence of brand avoidance on consumers purchasing decision
Get PDFOne of the most important factors affecting a company's capacity to achieve a competitive advantage over its rivals is its brand. This paper seeks to examine the impact of brand avoidance on consumer purchasing decisions. Consumers are more likely to be satisfied and have higher expectations when brand managers can offer them high-quality products. Additionally, quality brands have a favourable impact on the consumer's purchasing decision. This study uses a qualitative methodology, notably document analysis, to uncover relevant sources on the subject to achieve the study's aim. Furthermore, a keyword-based search of the databases of Web of Science, Google Scholar, and Scopus was carried out to find seventeen useful scientific papers to reach the study's objective. The findings of the study showed that identity avoidance, moral avoidance, and deficit-value avoidance all had a significant impact on consumers' purchasing decisions through the literature reviewed. As a result, the study offers both theoretical and practical directions on how to succeed in getting away from the underlying reasons for disregard for brands so that consumers make insightful purchase decisions.American Spinal Injury Association, ASI
Influence of polymer flow on polypropylene morphology, micro-mechanical, and tribological properties of injected part
Get PDFThis research investigates the micro-mechanical and tribological properties of injection-molded parts made from polypropylene. The tribological properties of polymers are a very interesting area of research. Understanding tribological processes is very crucial. Considering that the mechanical and tribological properties of injected parts are not uniform at various points of the part, this research was conducted to explain the non-homogeneity of properties along the flow path. Non-homogeneity can be influenced by numerous factors, including distance from the gate, mold and melt temperature, injection pressure, crystalline structure, cooling rate, the surface of the mold, and others. The key factor from the micro-mechanical and tribological properties point of view is the polymer morphology (degree of crystallinity and size of the skin and core layers). The morphology is influenced by polymer flow and the injection molding process conditions. Gained results indicate that the indentation method was sufficiently sensitive to capture the changes in polypropylene morphology, which is a key parameter for the resulting micro-mechanical and tribological properties of the part. It was proven that the mechanical and tribological properties are not equal in varying regions of the part. Due to cooling and process parameters, the difference in the indentation modulus in individual measurement points was up to 55%, and the tribological properties, in particular the friction coefficient, showed a difference of up to 20%. The aforementioned results indicate the impact this finding signifies for injection molding technology in technical practice. Tribological properties are a key property of the part surface and, together with micro-mechanical properties, characterize the resistance of the surface to mechanical failure of the plastic part when used in engineering applications. A suitable choice of gate location, finishing method of the cavity surface, and process parameters can ensure the improvement of mechanical and tribological properties in stressed regions of the part. This will increase the stiffness and wear resistance of the surface.TBU at Zlin Internal Grant Agency, (IGA/FT/2024/003)Project TBU at Zlin Internal Grant Agency [IGA/FT/2024/003
Changes in preferences and attitudes towards university selection in the post-COVID era
Get PDFGeneral societal developments show that the COVID-19 pandemic has brought about lasting changes in attitudes towards education and lifestyle, among others. The presented study aims to verify, using a quantitative questionnaire survey method on a sample of 500 respondents each, whether there have been changes in the preferences of potential students at a selected university in the Czech Republic between pre-Covid (2017) and post-Covid (2022) years. Current studies show that the post-COVID decision-making process is, among other things, generally more affected by the relationships with family and friends. Also, the paper’s goal is to verify whether this fact also applies to the area of preferences of university applicants and whether it is differentiated by gender. Based on the statistical testing and interpretation of the data, recommendations will be formulated for the marketing management of universities concerning how to adapt to changes in the preferences of applicants and how to effectively adjust the communication mix and message to the given target group, thereby increasing its interest in studying at the university. The proposed measures will thus contribute to increasing the competitiveness of universities, as they identify opportunities to target potential students more effectively.Long-term conceptual development of research at the Faculty of Multimedia Communications at TBU in Zli
Online learning platforms and resources in adult education and training: new findings from four European countries
Get PDFDigitisation represents one of the key directions of adult education and training in the post-COVID-19 times, but direct empirical evidence of its scope among learners is rather scarce after 2021. Therefore, the general aim of this article is to investigate the current state of the use of online learning platforms and resources in adult education and training throughout Europe. For this purpose, we utilise data from a dedicated survey in the Czech Republic, Germany, Sweden, and the United Kingdom (n = 4,000) from 2022, which cover a wide range of digitalisation as measured by the Digital Economy and Society Index (DESI). Our findings are consistent with DESI in the overall levels of online learning across the four countries. Beyond this, we provide two main findings. First, the patterns of digitalisation are different in formal (FAE) and non-formal adult education (NFE). We identify two corresponding modes of platformization based on how and how much online learning platforms and resources are used. Second, factors of participation in online learning differ in some regards from factors of participation in AET in general. Therefore, online learning seems to constitute a new layer mediating participation in AET, possibly introducing new forms of inequalities
The impact of selected financial factors on business ethics in the SMEs segment in the V4 countries
Get PDFThis paper aimed to quantify the impact of selected financial management factors on business ethics in the segment of small and medium-sized enterprises (SMEs) in the Visegrad Four countries (Czech Republic, Slovakia, Poland, and Hungary). The empirical research, which was aimed at ascertaining the attitudes of SMEs, was conducted in June 2022 in the Visegrad Four countries. The selection of respondents was carried out by random sampling using the CAWI method. In the Czech Republic, the total number of respondents was 347, in the Slovak Republic, the total number of respondents was 322, in Poland, the total number of respondents was 381 and in Hungary, the total number of respondents was 348. The scientific hypotheses were verified through regression and correlation analysis. The empirical research yielded a number of interesting and stimulating scientific findings. The results showed that the selected factors in the financial management of SMEs have a significant impact on the formation of entrepreneurs' attitudes in the field of business ethics. Knowledge of the most important aspects of the firm's financial management represents the most significant factor influencing the implementation of ethical aspects in the management process of SMEs and positive perceptions of business ethics in the context of financial performance. Other financial factors, namely entrepreneurs' belief that they can appropriately manage financial risks in the firm, a correct understanding of financial risk, and belief in the firm's survival in the medium term, have also shown a significant impact on business ethics. A surprising finding was that a positive assessment of a firm's current financial performance does not have any impact on the formation of attitudes towards business ethics. The representation and intensity of the effect of financial management factors on business ethics varies across the V4 countries. While the attitudes of SMEs in the Czech Republic, Slovakia and Poland have similar characteristics, Hungarian SMEs differ significantly from them
Poloxamer-based mixed micelles loaded with thymol or eugenol for topical applications
Get PDFPoloxamers (P184, P188, and P407) have been investigated as the carrier system for eugenol or thymol. A synergic effect of mixed Poloxamers was proved by enhanced micellar parameters, with a lower critical micelle concentration (about 0.06 mM) and the highest surface adsorption of 9 × 10-7 mol m-2 for P188/P407. Dynamic light scattering revealed a decrease in micellar size after loading with biomolecules. Three mathematical models were applied to study the release kinetics, of which Korsmeyer-Peppas was the best fitted model. Higher relative release was observed for Poloxamer/eugenol samples, up to a value of 0.8. Poloxamer micelles with thymol were highly influential in bacterial reduction. Single P407/eugenol micelles proved to be bacteriostatic for up to 6 h for S. aureus or up to 48 h for E. coli. Mixed micelles were confirmed to have prolonged bacteriostatic activity for up to 72 h against both bacteria. This trend was also proven by the modified Gompertz model. An optimized P188/P407/eugenol micelle was successfully used as a model system for release study with a particle size of less than 30 nm and high encapsulation efficiency surpassing 90%. The developed mixed micelles were proved to have antibiofilm activity, and thus they provide an innovative approach for controlled release with potential in topical applications.European Cooperation in Science and Technology, COSTEuropean Cooperation in Science and Technology [CA19124]; COST (European Cooperation in Science and Technology