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31.
Polymers derived from natural, minimally‐processed materials have recently emerged as a more sustainable alternative to synthetic polymers, with promising applications in biocompatible and biodegradable devices. Plasma‐enhanced deposition is well‐suited to one‐step, fast, and efficient synthesis of highly crosslinked inert polymers directly from natural resources, however, fabrication of biologically active polymers remains a challenge. Plasma processing parameters influence the properties such as surface energy, roughness, morphology, and chemical composition of deposited polymers and thus their final applications. This article reports on the important role of substrate temperature (TS) in the chemical composition, wettability, refractive index, and crosslinking density of plasma polymers derived from terpenoids. Experiments are conducted as a function of deposition power Pd, and substrate temperature, TS. TS varied from 40 to 280 °C and is externally controlled. Atomic force microscopy analysis reveals the change in deposition mechanism attributed to shadowing effect at higher TS and Pd. Increase in band gap (Eg) with high Ts deposition for terpenoid based plasma polymers is observed. Swelling behavior analyzed by in situ ellipsometry affirms the enhanced crosslink density with increasing deposition rate. Fourier transform infrared analysis exhibits the formation of additional chemical moieties with increasing TS. Increase in deposition rate with increasing TS at higher Pd supports the theory of direct incorporation of depositing particles as dominant mechanism of plasma polymerization in this study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45771. 相似文献
32.
Kateryna Kuksenok Cecilia Aragon James Fogarty Charlotte P. Lee Gina Neff 《Computer Supported Cooperative Work (CSCW)》2017,26(4-6):663-691
Computing affects how scientific knowledge is constructed, verified, and validated. Rapid changes in hardware capability, and software flexibility, are coupled with a volatile tool and skill set, particularly in the interdisciplinary scientific contexts of oceanography. Existing research considers the role of scientists as both users and producers of code. We focus on how an intentional, individually-initiated but socially-situated, process of uptake influences code written by scientists. We present an 18-month interview and observation study of four oceanography teams, with a focus on ethnographic shadowing of individuals undertaking code work. Through qualitative analysis, we developed a framework of deliberate individual change, which builds upon prior work on programming practices in science through the lens of sociotechnical infrastructures. We use qualitative vignettes to illustrate how our theoretical framework helps to understand changing programming practices. Our findings suggest that scientists use and produce software in a way that deliberately mitigates the potential pitfalls of their programming practice. In particular, the object and method of visualization is subject to restraint intended to prevent accidental misuse. 相似文献
33.
Parker James D. A.; Keefer Kateryna V.; Taylor Graeme J.; Bagby R. Michael 《Canadian Metallurgical Quarterly》2008,20(4):385
Despite a wealth of research on the validity of alexithymia and its association with a number of common medical and psychiatric disorders, the fundamental question of whether alexithymia is best conceptualized as a dimensional or categorical construct remains unresolved. In the current investigation, taxometric analysis is used to examine the nature of the latent structure of alexithymia. Several nonredundant taxometric procedures were performed with item sets from the 20-item Toronto Alexithymia Scale (R. M. Bagby, J. D. A. Parker, & G. J. Taylor, 1994) as indicators. These procedures were applied separately in large community (n = 1,933) and undergraduate (n = 1,948) samples and in a smaller sample of psychiatric outpatients (n = 302). The results across various taxometric procedures and the different samples provide strong support that alexithymia is a dimensional construct. Some theoretical implications of these findings for research on the alexithymia construct are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
Kateryna Sybirna Pierre Ezanno Carole Baffert Christophe Léger Hervé Bottin 《International Journal of Hydrogen Energy》2013
[Fe–Fe] hydrogenases, with hydrogen evolution activities outperforming [Ni–Fe] hydrogenases by 3–4 orders of magnitude, are still the most promising enzyme class for hydrogen production purposes. For Chlamydomonas reinhardtii [Fe–Fe] hydrogenase HydA1 the question of catalytic activity and electron transport is of main importance. Here we report the characterization of two mutant forms of C. reinhardtii HydA1. An aspartic acid in place of arginine171 leads to a six-fold increase of the catalytic activity in comparison to the wild type protein during methyl viologen-dependent hydrogen production. Tryptophan in position 171 does not result in any change in methyl viologen-induced activity. At the same time these mutations lead to a strong decrease in ferredoxin-dependent hydrogen production while the catalytic center of mutant forms stays intact. The localization of this amino acid (arginine171) in the environment of CrHydA1 H-cluster indicates that the limitation of the catalytic activity of this hydrogenase is due to the electron transfer step to the catalytic center where the reduction of protons takes place. 相似文献
35.
Antimicrobial properties and thermal stability of polycarbonate modified with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids
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Sergiy Rogalsky Kateryna Fatyeyeva Lyudmila Lyoshina Oksana Tarasyuk Olga Bulko Sofiia Lobok 《应用聚合物科学杂志》2014,131(7)
Four water immiscible ionic liquids (ILs): 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, 1‐heptyl‐3‐methylimidazolium tetrafluoroborate, 1‐octyl‐3‐methylimidazolium tetrafluoroborate and 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate have been synthesized. Polycarbonate (PC) films containing ILs were prepared by solvent casting from methylene chloride solutions. Scanning electron microscopy measurements showed the high homogeneity of PC/IL films with the IL content up to 4 wt %. The tendency to IL aggregation was observed for polymeric films with higher IL content (5%). PC/IL composites were found to have the reduced thermal decomposition temperature under both an air and a nitrogen atmosphere in comparison with the neat PC. The effect of IL content on the antimicrobial activity of PC films against Escherichia coli bacteria was studied. Pronounced antimicrobial efficacy was revealed for PC/IL films for all studied ILs starting from 3 wt % of IL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40050. 相似文献
36.
Mei-xian Wang Fan Xu Hong-fang Sun Qi Liu Kateryna Artyushkova Eric A. Stach Jian Xie 《Electrochimica acta》2011,(5):2566
The nanoscale graphite particles were prepared and the Pt catalysts supported on such graphites were developed for oxygen reduction in the polymer electrolyte membrane fuel cells. Catalytic activity and carbon corrosion of the developed catalysts were evaluated using rotating disc electrode techniques and results were compared with those of a state-of-the-art commercial E-TEK Pt catalyst supported on carbon black Vulcan XC72. The results showed that the particle distribution and the structure of the developed Pt nanoparticles supported on the nanoscale graphite were similar to those of the commercial catalyst. The accelerated degradation testing results showed that the electrochemical active surface area losses after 1500 cycles were 46.92% and 62.2% for the developed catalyst and the commercial catalyst, respectively, while mass activity losses were 45.3% and 84.2%, respectively. The temperature-programmed oxidation results suggest that the developed catalysts had better corrosion resistance than the commercial catalyst. The developed Pt catalysts had similar catalytic performance to the commercial catalyst; however, the developed catalysts had much better corrosion resistance than the commercial catalyst. Overall, nanoscale graphite can be a promising electrocatalyst support to replace the currently used Vulcan XC72 carbon black. 相似文献
37.
Kaiyi Luo Qiuping Zhang Huan Yuan Yutong Liu Xiaoyi Wang Jiaxi Zhang Wenyu Hu Ming Xu Shuyan Xu Igor Levchenko Kateryna Bazaka 《Ceramics International》2021,47(1):48-56
By carefully balancing synergies and antagonisms that arise from incorporating Cu and Ag within a single ZnO-based catalytic platform, the photocatalytic activity of Ag/ZnO based on three-dimensional modified ceramic structures can be further significantly enhanced. The performance of Ag/ZnO heterostructure (Z0) was significantly improved by only 0.2 mol% Cu incorporation (Z0.2) and the first-order degradation kinetics constants (K) of Z0.2 were 2 and 1.5 times higher than that of Z0 under simulated sunlight and UV light. The synergies between Cu dopants and metallic Ag were mainly the significantly enhanced visible light absorption capacity and the prolonged photo-excited charge lifetime. However, with the excessive introduction of Cu precursors, the surface Cu2+ was found to inhibit the interfacial charge transfer between Ag and ZnO NPs under UV and visible light irradiation, but the transformation from Cu2+ to Cu+ was also presumed to be a driving factor for the improvement of photocatalytic efficiency. These interactions may provide a useful pathway for enhancing photocatalytic efficiency of low-cost ZnO-based catalytic platforms. 相似文献
38.
Juho‐Jooel Nissil Kateryna Savelieva Jussi Lampi Sari Ung‐Lanki Marko Elovainio Juha Pekkanen 《Indoor air》2019,29(5):865-873
Poor indoor air quality (IAQ) in schools is related to increased symptom reporting in students. We investigated whether parental worry about school IAQ influences this association. Data came from survey collected from five Finnish primary schools with observed IAQ problems and five control schools. Parents (n = 1868) of primary school students reported worry about IAQ in schools and symptoms of their children. Associations between observed IAQ problems, worry, and five symptom scores (ie, respiratory, lower respiratory, eye, skin, and general symptoms) were analyzed using multivariate logistic regression and mediation analysis. Parents were on average more worried in schools with observed IAQ problems. Observed IAQ problems were strongly associated with increased worry and all symptoms under study (unadjusted ORs ranged between 1.48 [95% CI 1.48‐2.16] and 2.70 [95% CI 1.52‐5.17]). Parental worry was associated with all symptoms (unadjusted ORs ranged between 2.49 [95% CI 1.75‐3.60] and 4.92 [95% CI 2.77‐9.40]). Mediation analyses suggested that parental worry might partially explain the association between observed IAQ problems and symptom reporting (proportion mediated ranged between 67% and 84% for the different symptoms). However, prospective studies are needed to assess causal relationships between observed IAQ problems, worry, and symptom reporting in schools. 相似文献
39.
Ulrich Krings Kateryna Zelena Shimin Wu Ralf G. Berger 《European Food Research and Technology》2006,223(5):675-681
The volatile fraction of commercial cocoa powders was isolated using thin-layer high-vacuum distillation (TLHVD) of Soxhlet extracts. Calculated and experimental recovery of the internal standard n-undecanoic acid methylester did agree, and a good reproducibility was found for the procedure. Around 70 volatile compounds were identified and semi-quantified using internal standard-based gas chromatography (GC), coupled GC–mass spectrometry (GC–MS) and GC-olfactometry (GC-O). Dehydromevalonic acid lactone, (R)-(−)-pantolactone and two diastereomer solerols were identified for the first time after purification by micropreparative GC and re-analysis using GC–MS and chiral GC. Strong sensory contributions also came from acetic acid, 2/3-methyl butanoic acid, phenylacetaldehyde, furaneol, dihydroxymaltol, vanillin and phenylacetic acid. 相似文献
40.
Kateryna Lyakhova A. Catarina C. Esteves Marcel W. P. van de Put Leo G. J. van der Ven Rolf A. T. M. van Benthem Gijsbertus de With 《Advanced Materials Interfaces》2014,1(3)
To investigate self‐replenishing on surface‐structured composite coatings a dual simulation‐experimental approach is employed to study the decisive role of polymer‐air and polymer‐particle interfaces. Experimentally, the composite system consists of a cross‐linked polymer network with fluorinated‐dangling chains, embedding colloidal SiO2 nanoparticles which are incorporated in the network via covalent bonding. These particles provide the desired surface structure at the air‐interface before and after damage. Any damage replicates the rough surface, while the polymer layer on top of the particles serves as source of low surface energy groups which are able to reorient towards the new air‐interfaces. Using coarse‐grained simulations details of these self‐replenishing composite systems are revealed such as the minimum thickness of the polymer layer necessary for providing optimal self‐replenishing ability and the distribution profile of the dangling chains at the various interfaces. The principles and dual approach reported here may be applied to other self‐healing composite systems with applications in self‐cleaning, anti‐fouling or low adhesion materials. 相似文献