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101.
Entropic effects in carbon nanotubes-templated crystallization of Poly(3-alkyl thiophenes,P3HT,P3OT)
A significant increase in polymer crystallinity is reported in composites of carbon-nanotubes (CNT) and Poly(3-octylthiophene-2,5-diyl), P3HT and Poly(3-octylthiophene-2,5-diyl), P3OT; Differential scanning calorimetry (DSC) reveal an increase from about 40% crystallinity of the native P3HT to ∼62% in composites containing 25 wt% MWNT. A similar behavior is observed in P3OT with ∼68% crystallinity, a double crystallization peak and higher melting temperature than the native polymers. The effect is unique to CNT and is not induced by fullerenes or graphene layers. High-resolution transmission electron microscopy, (HRTEM) of CNT-polymer dispersions reveal chains stacked upon the CNT in an elongated, stretched conformation. Following a detailed molecular study by Bernardi et al. and the HRTEM observations the DSC results are attributed to a CNT-mediated entropic effect: due to their intrinsic, 1D cylindrical shape the CNT impose an increased conjugation length on chains adsorbed and stacked upon dispersed CNT. Crystallization thus commences from a heterogeneous mixture of native chains and chains with a longer persistence length (higher effective rigidity) and consequentially a lower effective height of the entropic barrier for crystallization. The findings offer a new insight into the origins of CNT-induced polymer nucleation. 相似文献
102.
Rachel Wang 《中外葡萄与葡萄酒》2011,(3):94-95
首先声明,这绝对不是个玩笑!
其次,红雷司令(Roter Riesling)也并非由享誉全球的德国盖森海姆研究院Gaisenheim Institute培育出的新的克隆品种。相反,这是一个存在了几个世纪的古老品种。据了解,几个世纪来红雷司令葡萄串中常常能发现白色变种,至于为何红皮最终被白皮取而代之,这是个很有意思的问题... 相似文献
103.
Philip M. Delaforce Julie A. Yeomans Neil C. Filkin Gary J. Wright Rachel C. Thomson 《Journal of the American Ceramic Society》2007,90(3):918-924
Nickel oxide (NiO) was screen printed onto the surfaces of 3 and 8 mol% yttria-stabilized zirconia (YSZ) dense pre-fired substrates and then heat treated at temperatures from 1350° to 1550°C. The effect of NiO was dependent on the yttria content of the substrate. In 3 mol% YSZ, it was found to alter the phase composition from predominantly tetragonal with a small amount of cubic phase to one consisting of approximately equal amounts of cubic and monoclinic phase. The cubic grains were much larger than the monoclinic ones and contained more nickel. Furthermore, nickel was observed to migrate through the thickness of the tile, a distance of approximately 200 μm. In the 8 mol% YSZ substrates, the phase composition was unaltered, although large grains developed under the printed NiO layer and the nickel migration was confined to the extent of these large grains. 相似文献
104.
Helen F. Nahrung Rachel Waugh Richard Andrew Hayes 《Journal of chemical ecology》2009,35(9):1043-1053
Hybridization is an important biological phenomenon that can be used to understand the evolutionary process of speciation
of plants and their associated pests and diseases. Interactions between hybrid plants and the herbivores of the parental taxa
may be used to elucidate the various cues being used by the pests for host location or other processes. The chemical composition
of plants, and their physical foliar attributes, including leaf thickness, trichome density, moisture content and specific
leaf weight were compared between allopatric pure and commercial hybrid species of Corymbia, an important subtropical hardwood taxon. The leaf-eating beetle Paropsis atomaria, to which the pure taxa represented host (C. citriodora subsp. variegata) and non-host (C. torelliana) plants, was used to examine patterns of herbivory in relation to these traits. Hybrid physical foliar traits, chemical profiles,
and field and laboratory beetle feeding preference, while showing some variability, were generally intermediate to those exhibited
by parent taxa, thus suggesting an additive inheritance pattern. The hybrid susceptibility hypothesis was not supported by
our field or laboratory studies, and there was no strong relationship between adult preference and larval performance. The
most-preferred adult host was the sympatric taxon, although this species supported the lowest larval survival, while the hybrid
produced significantly smaller pupae than the pure species. The results are discussed in relation to plant chemistry and physical
characteristics. The findings suggest a chemical basis for host selection behavior and indicate that it may be possible to
select for resistance to this insect pest in these commercially important hardwood trees. 相似文献
105.
Suldo Shannon M.; Mihalas Stephanie; Powell Heather; French Rachel 《Canadian Metallurgical Quarterly》2008,23(3):373
The current study examined important predictors of substance use during early adolescence. The authors hypothesized that adolescents' relationships with key adults (i.e., teachers and parents) influence their choices to use substances indirectly through links with their decisions regarding peer groups. A total of 461 middle school students from an affluent suburban community completed self-report measures of authoritative parenting, perceived social support from teachers, affiliation with rule-breaking and substance-using peers, and frequency of alcohol, cigarette, and drug use. Results of structural equation modeling supported the hypothesized model. Authoritative parenting and teacher support accounted for 31% of the variance in affiliation with deviant peers which, in turn, accounted for 27% of the variance in adolescent substance use; direct paths from parenting and teacher support to substance use were not indicated. Implications for school psychologists' involvement in substance use prevention and intervention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
Salekin Randall T.; Yff Rachel M. A.; Neumann Craig S.; Leistico Anne-Marie R.; Zalot Alecia A. 《Canadian Metallurgical Quarterly》2002,8(4):373
Juvenile court judges are often required to make distinctions as to whether certain adolescents should remain in the juvenile justice system or be transferred to adult courts. Typically, 3 broad factors weigh into juvenile court judges' decision making: (a) the level of danger the juvenile poses to the community, (b) the level of sophistication-maturity of the juvenile, and (c) the extent to which the juvenile is viewed as treatable. In an earlier study, knowledge of forensic and child psychologists was tapped to elucidate core characteristics related to the transfer process (R. T. Salekin et al, 2001). The current study augments that investigation. Judges provided (a) their perspective regarding the core criteria for dangerousness, sophistication-maturity, and amenability to treatment, and (b) data on the core characteristics of juveniles who were evaluated and subsequently judged to be appropriate for transfer to adult criminal courts. Policy implications for this increasingly critical interface between law and psychology are threefold: (a) Individualized assessments are key; (b) the adoption of a national standard for transfer to adult court is required; and (c) the development of treatment programs to improve the socialization of youth is necessary. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
This paper focuses on the distinction between the selection process in a computer command menu and in an information retrieval menu. We argue that the cognitive processes involved in these two tasks are different and consequently, that performance cannot be explained by the same factors. Preliminary experimental results are presented to support this claim. 相似文献
108.
K. Rachel Makinson 《纺织学会志》2013,104(11):587-589
109.
This study evaluated the production of biodiesel using fish oil as raw material. Two-stage alkaline-catalysis transesterification
was performed with 6/1 molar ratio of methanol to oil at 55°C in the presence of 1 wt. % base amount of potassium hydroxide
(KOH). The fuel properties of the biodiesel were further analyzed. The characterizations of the produced biodiesel showed
that it met ASTM D 6751 standard with respect to acid number, flash point, water and sediment, free and total glycerin, sulfur
content, distillation temperature, etc. It was found that cold soak and oxidative stability were out spec due to the high
amount of polyunsaturated fatty acid present in the fish oil. However, through blending with used cooking oil biodiesel, in
spec biodiesel fuel could be achieved. 相似文献
110.
Jimmieson Nerina L.; McKimmie B. M.; Hannam Rachel L.; Gallagher Jenifer 《Canadian Metallurgical Quarterly》2010,14(4):350
This study explored how the social context influences the stress-buffering effects of social support on employee adjustment. It was anticipated that the positive relationship between support from colleagues and employee adjustment would be more marked for those strongly identifying with their work team. Furthermore, as part of a three-way interactive effect, it was predicted that high identification would increase the efficacy of coworker support as a buffer of two role stressors (role overload and role ambiguity). One hundred and 55 employees recruited from first-year psychology courses enrolled at two Australian universities were surveyed. Hierarchical multiple regression analyses revealed that the negative main effect of role ambiguity on job satisfaction was significant for those employees with low levels of team identification, whereas high team identifiers were buffered from the deleterious effect of role ambiguity on job satisfaction. There also was a significant interaction between coworker support and team identification. The positive effect of coworker support on job satisfaction was significant for high team identifiers, whereas coworker support was not a source of satisfaction for those employees with low levels of team identification. A three-way interaction emerged among the focal variables in the prediction of psychological well-being, suggesting that the combined benefits of coworker support and team identification under conditions of high demand may be limited and are more likely to be observed when demands are low. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献