The Small-Is-Very-Small Principle

The central result of this paper is the small-is-very-small principle for restricted sequential theories. The principle says roughly that whenever the given theory shows that a property has a small witness, i.e. a witness in every definable cut, then it shows that the property has a very small witness: i.e. a witness below a given standard number. We draw various consequences from the central result. For example (in rough formulations): (i) Every restricted, recursively enumerable sequential theory has a finitely axiomatized extension that is conservative w.r.t. formulas of complexity $\leq n$. (ii) Every sequential model has, for any $n$, an extension that is elementary for formulas of complexity $\leq n$, in which the intersection of all definable cuts is the natural numbers. (iii) We have reflection for $\Sigma^0_2$-sentences with sufficiently small witness in any consistent restricted theory $U$. (iv) Suppose $U$ is recursively enumerable and sequential. Suppose further that every recursively enumerable and sequential $V$ that locally inteprets $U$, globally interprets $U$. Then, $U$ is mutually globally interpretable with a finitely axiomatized sequential theory. The paper contains some careful groundwork developing partial satisfaction predicates in sequential theories for the complexity measure depth of quantifier alternations

Testing mechanisms of Bergmann’s rule: Phenotypic decline but no genetic change in body size in three posserine bird populations

Bergmann’s rule predicts a decrease in body size with increasing temperature and has much empirical support. Surprisingly, we know very little about whether “Bergmann size clines” are due to a genetic response or are a consequence of phenotypic plasticity. Here, we use data on body size (mass and tarsus length) from three long-term (1979–2008) study populations of great tits (Parus major) that experienced a temperature increase to examine mechanisms behind Bergmann’s rule. We show that adult body mass decreased over the study period in all populations and that tarsus length increased in one population. Both body mass and tarsus length were heritable and under weak positive directional selection, predicting an increase, rather than a decrease, in body mass. There was no support for microevolutionary change, and thus the observed declines in body mass were likely a result of phenotypic plasticity. Interestingly, this plasticity was not in direct response to temperature changes but seemed to be due to changes in prey dynamics. Our results caution against interpreting recent phenotypic body size declines as adaptive evolutionary responses to temperature changes and highlight the importance of considering alternative environmental factors when testing size clines.

Muon localization site in U(Pt,Pd)3

The angular and temperature (10-250 K) variation of the Knight shift of single-crystalline U(Pt0.95Pd0.05)3 has been measured in transverse field (B=0.6 T) mSR experiments. By analysing the temperature variation of the Knight shift with a modified Curie-Weiss expression the muon localization site in this hexagonal material is determined at (0,0,0).Comment: 12 pages (including 4 figures); postscript file; Proc. 8th Int. Conf. on Muon Spin Rotation, Relaxation and Resonance (Aug.30-Sept.3, Les Diablerets); 2nd version with minor correction

How do people make sense of their recovery from academic burnout during their undergraduate studies? An interpretative phenomenological inquiry into the experience of young adults

Academic (student) burnout involves a rise in absenteeism, lack of motivation to meet coursework requirements and a higher student dropout rate. Its symptoms manifest on an emotional, social, cognitive and physical level. The aim of this study was to explore young people’s experience of recovering from burnout during their undergraduate studies, with the purpose of contributing to the very limited phenomenological research on both student burnout and recovery from student burnout. Semi-structured interviews were conducted with eight participants and analysed using Interpretative Phenomenological Analysis (IPA). The analysis produced three superordinate themes. Firstly, Falling Behind, Falling Short captures the academic, social and personal challenges that promoted burnout. Secondly, Getting Stuck depicts burnout as a state of psychological distress that led to social withdrawal and disengagement from studies. Thirdly, Finding a Way Out Through Personal Growth presents recovery from burnout as a turning point marking the start of new attitudes and behaviours, followed by deepening self-understanding, cultivation of support and increasing self-regulation. For counselling psychologists, the research sheds light on the subjective and interpersonal dimensions of academic burnout, the different manifestations of student burnout and the role of personal growth in recovering from burnout. The study also points to the role of negative coping responses and negative attitudes to help-seeking in the development and perpetuation of burnout. Further research on academic burnout during university and pre-university education is called for. Phenomenological research exploring the student’s experience of learning, seeking support and coping with stress arising from the undergraduate environment is recommended

Tolman wormholes violate the strong energy condition

For an arbitrary Tolman wormhole, unconstrained by symmetry, we shall define the bounce in terms of a three-dimensional edgeless achronal spacelike hypersurface of minimal volume. (Zero trace for the extrinsic curvature plus a "flare-out" condition.) This enables us to severely constrain the geometry of spacetime at and near the bounce and to derive general theorems regarding violations of the energy conditions--theorems that do not involve geodesic averaging but nevertheless apply to situations much more general than the highly symmetric FRW-based subclass of Tolman wormholes. [For example: even under the mildest of hypotheses, the strong energy condition (SEC) must be violated.] Alternatively, one can dispense with the minimal volume condition and define a generic bounce entirely in terms of the motion of test particles (future-pointing timelike geodesics), by looking at the expansion of their timelike geodesic congruences. One re-confirms that the SEC must be violated at or near the bounce. In contrast, it is easy to arrange for all the other standard energy conditions to be satisfied.Comment: 8 pages, ReV-TeX 3.

Hybridized polymer matrix composite

Under certain conditions of combined fire and impact, graphite fibers are released to the atmosphere by graphite fiber composites. The retention of graphite fibers in these situations is investigated. Hybrid combinations of graphite tape and cloth, glass cloth, and resin additives are studied with resin systems. Polyimide resins form the most resistant composites and resins based on simple novolac epoxies the least resistant of those tested. Great improvement in the containment of the fibers is obtained in using graphite/glass hybrids, and nearly complete prevention of individual fiber release is made possible by the use of resin additives

Young men's ambivalence toward alcohol

There is widespread concern about the health and social consequences of excessive alcohol consumption among young men. Interventions to reduce alcohol-related harm will be affected by ambivalence toward alcohol, because ambivalent attitudes are worse predictors of behaviour than are homogeneous attitudes. It is therefore important to identify aspects of alcohol consumption about which young men are not ambivalent. In-depth interviews were conducted with a socioeconomically diverse sample of 31 men, aged 18–21 living in London, UK. Ambivalence toward alcohol was widespread. None of the drinkers who were interviewed had uncomplicated positive evaluations of drinking: all mentioned compelling reasons not to drink. Most motives for drinking were also identified as reasons for not drinking if consumption became excessive. However, three motives for not drinking were not also motives for drinking: violence, alcoholism, and cost. These findings should be considered during the design of interventions to reduce the health and social consequences of excessive alcohol consumption amongst young men

High pressure transport study of non-Fermi liquid behaviour in U2Pt2In and U3Ni3Sn4

The strongly correlated metals U2Pt2In and U3Ni3Sn4 show pronounced non-Fermi liquid (NFL) phenomena at ambient pressure. Here we review single-crystal electrical resistivity measurements under pressure (p <= 1.8 GPa) conducted to investigate the stability of the NFL phase. For tetragonal U2Pt2In (I||a) we observe a rapid recovery of the Fermi-liquid T^2-term with pressure. The Fermi-liquid temperature varies as T_FL ~ p-p_c, where p_c= 0 is a critical pressure. The analysis within the magnetotransport theory of Rosch provides evidence for the location of U2Pt2In at a zero pressure antiferromagnetic quantum critical point (QCP). In the case of cubic U3Ni3Sn4 we find T_FL ~ (p-p_c)^1/2. The analysis provides evidence for an antiferromagnetic QCP in U3Ni3Sn4 at a negative pressure p_c= -0.04+-0.04 GPa.Comment: 6 pages (4 figures); to appear in Proc. of Int. Conf. PPHMF-IV (20-25 Oct. 2001, Santa Fe

Time-resolved FRET fluorescence spectroscopy of visible fluorescent protein pairs

Förster resonance energy transfer (FRET) is a powerful method for obtaining information about small-scale lengths between biomacromolecules. Visible fluorescent proteins (VFPs) are widely used as spectrally different FRET pairs, where one VFP acts as a donor and another VFP as an acceptor. The VFPs are usually fused to the proteins of interest, and this fusion product is genetically encoded in cells. FRET between VFPs can be determined by analysis of either the fluorescence decay properties of the donor molecule or the rise time of acceptor fluorescence. Time-resolved fluorescence spectroscopy is the technique of choice to perform these measurements. FRET can be measured not only in solution, but also in living cells by the technique of fluorescence lifetime imaging microscopy (FLIM), where fluorescence lifetimes are determined with the spatial resolution of an optical microscope. Here we focus attention on time-resolved fluorescence spectroscopy of purified, selected VFPs (both single VFPs and FRET pairs of VFPs) in cuvette-type experiments. For quantitative interpretation of FRET–FLIM experiments in cellular systems, details of the molecular fluorescence are needed that can be obtained from experiments with isolated VFPs. For analysis of the time-resolved fluorescence experiments of VFPs, we have utilised the maximum entropy method procedure to obtain a distribution of fluorescence lifetimes. Distributed lifetime patterns turn out to have diagnostic value, for instance, in observing populations of VFP pairs that are FRET-inactiv