1,619 research outputs found

    Surface Geometry of C60 on Ag(111)

    Get PDF
    The geometry of adsorbed C60 influences its collective properties. We report the first dynamical low-energy electron diffraction study to determine the geometry of a C60 monolayer, Ag(111)-(23×23)30°-C60, and related density functional theory calculations. The stable monolayer has C60 molecules in vacancies that result from the displacement of surface atoms. C60 bonds with hexagons down, with their mirror planes parallel to that of the substrate. The results indicate that vacancy structures are the rule rather than the exception for C60 monolayers on close-packed metal surfaces. © 2009 The American Physical Society

    Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange NMR

    Full text link
    We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas in the pore space and 129Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.Comment: 14 pages of text, 4 figure

    A functional-cognitive framework for attitude research

    Get PDF
    In attitude research, behaviours are often used as proxies for attitudes and attitudinal processes. This practice is problematic because it conflates the behaviours that need to be explained (explanandum) with the mental constructs that are used to explain these behaviours (explanans). In the current chapter we propose a meta-theoretical framework that resolves this problem by distinguishing between two levels of analysis. According to the proposed framework, attitude research can be conceptualised as the scientific study of evaluation. Evaluation is defined not in terms of mental constructs but in terms of elements in the environment, more specifically, as the effect of stimuli on evaluative responses. From this perspective, attitude research provides answers to two questions: (1) Which elements in the environment moderate evaluation? (2) What mental processes and representations mediate evaluation? Research on the first question provides explanations of evaluative responses in terms of elements in the environment (functional level of analysis); research on the second question offers explanations of evaluation in terms of mental processes and representations (cognitive level of analysis). These two levels of analysis are mutually supportive, in that better explanations at one level lead to better explanations at the other level. However, their mutually supportive relation requires a clear distinction between the concepts of their explanans and explanandum, which are conflated if behaviours are treated as proxies for mental constructs. The value of this functional-cognitive framework is illustrated by applying it to four central questions of attitude research

    A test of the automaticity assumption of compliance tactics: discouraging undergraduate binge drinking by appealing to consistency and reciprocity

    Get PDF
    The mindfulness of compliance with requests making use of the commitment/consistency or the reciprocity principle was investigated. Participants (N = 129) received a foot-in-the-door (FITD) request (commitment/consistency application), a door-in-the-face (DITF) request (reciprocity application), or no request. Next, participants read either a weak or neutral message about the importance of moderate alcohol consumption then reported the likelihood of not drinking excessively for one week (target request). When accompanied by a weak message, the target request elicited less compliance if preceded by the DITF or FITD requests than by no initial request, suggesting compliance tactics sometimes increase thoughtfulness

    Understanding the management challenges associated with the implementation of the physically active teaching and learning (PATL) pedagogy: a case study of three Isle of Wight primary schools

    Get PDF
    Enabled partly by government policies by the Department for Culture Media and Sport, some schools are beginning to shift towards promoting a physical activity culture which complements the traditional PE and school sports provision. For many, this entails using physical activity as a modality to promote academic performance. Physically Active Teaching and Learning (PATL) is one approach which has been adopted by schools on the Isle of Wight (UK) as part of a holistic island-wide intervention aimed at increasing pupil’s educational attainment, health and wellbeing. To gain an in-depth understanding of PATL and examine the management implications of its implementation, this paper draws on qualitative data collected from three primary schools on the Isle of Wight. Overall, the paper supports PATL pedagogies as a holistic and joined-up policy response, however, critical conversations are crucial for unravelling and unlocking collaborative solutions when discussing physical activity in schools

    Influence of Nanoparticle Size and Shape on Oligomer Formation of an Amyloidogenic Peptide

    Full text link
    Understanding the influence of macromolecular crowding and nanoparticles on the formation of in-register β\beta-sheets, the primary structural component of amyloid fibrils, is a first step towards describing \emph{in vivo} protein aggregation and interactions between synthetic materials and proteins. Using all atom molecular simulations in implicit solvent we illustrate the effects of nanoparticle size, shape, and volume fraction on oligomer formation of an amyloidogenic peptide from the transthyretin protein. Surprisingly, we find that inert spherical crowding particles destabilize in-register β\beta-sheets formed by dimers while stabilizing β\beta-sheets comprised of trimers and tetramers. As the radius of the nanoparticle increases crowding effects decrease, implying smaller crowding particles have the largest influence on the earliest amyloid species. We explain these results using a theory based on the depletion effect. Finally, we show that spherocylindrical crowders destabilize the ordered β\beta-sheet dimer to a greater extent than spherical crowders, which underscores the influence of nanoparticle shape on protein aggregation
    corecore