Strain-Rate Frequency Superposition in Large-Amplitude Oscillatory Shear

In a recent work, Wyss, {\it et.al.} [Phys. Rev. Lett., {\bf 98}, 238303 (2007)] have noted a property of `soft solids' under oscillatory shear, the so-called strain-rate frequency superposition (SRFS). We extend this study to the case of soft solids under large-amplitude oscillatory shear (LAOS). We show results from LAOS studies in a monodisperse hydrogel suspension, an aqueous gel, and a biopolymer suspension, and show that constant strain-rate frequency sweep measurements with soft solids can be superimposed onto master curves for higher harmonic moduli, with the {\it same} shift factors as for the linear viscoelastic moduli. We show that the behavior of higher harmonic moduli at low frequencies in constant strain-rate frequency sweep measurements is similar to that at large strain amplitudes in strain-amplitude sweep tests. We show surface plots of the harmonic moduli and the energy dissipation rate per unit volume in LAOS for soft solids, and show experimentally that the energy dissipated per unit volume depends on the first harmonic loss modulus alone, in both the linear and the nonlinear viscoelastic regime.Comment: 10 pages, 25 figures, accepted for publication in Physical Review E. Incorporates referee comment

Research on physical and physiological aspects of visual optics in space flight

Physical and physiological aspects of visual optics in space fligh

Non-adaptive phenotypic plasticity: the effects of terrestrial and aquatic herbicides on larval salamander morphology and swim speed

Department of Biology, University of North Carolina, Chapel Hill, NC, USAPhenotypic plasticity, although ubiquitous, may not always be advantageous. Non-adaptive plasticity is likely to occur in response to novel environmental stress. Anthropogenic contaminants, such as herbicides, are novel stressors that are not present in the evolutionary history of most species. We investigated the pattern and consequences of phenotypic plasticity induced by four glyphosate-based herbicides (two terrestrial and two aquatic) in larvae of the spotted salamander, , by determining (1) whether the herbicides induced different morphologies; (2) if different morphologies translated to differences in burst swim performance; and (3) how induced individuals performed relative to non-induced controls. Different herbicide formulations led to the production of significantly different head and tail morphologies, and tail morphology correlated with fastest escape speed. However, escape speed did not vary among treatments. In addition, three out of four herbicide treatments experienced accelerated growth rates, in terms of the lateral size of tails, although the tail shapes were either similar to preliminary controls or intermediate between preliminary and final controls. These observations suggest that herbicide-induced morphology is a case of non-adaptive phenotypic plasticity, and that there is potentially a trade-off between growth and development for larvae exposed to different formulations. Understanding the functional significance of induced phenotypes is important for determining their importance in shaping an organism's ecological interactions and evolutionary trajectories. Furthermore, under different conditions, the morphological changes that we observed in response to exposure to herbicides might affect salamander fitness and influence population dynamics

Fundamental solutions to moment equations for the simulation of microscale gas flows

Fundamental solutions (Green's functions) to Grad's steady-state linearised 13-moment equations for non-equilibrium gas ows are derived. The creeping microscale gas ows, to which they pertain, are important to understanding the behaviour of atmospheric particulate and the performance of many potential micro/nano technologies. Fundamental solutions are also derived for the regularised form of the steady-state linearised 13- moment equations, due to Struchtrup & Torrilhon (2003). The solutions are compared to their classical and ubiquitous counterpart: the Stokeslet. For an illustration of their utility, the fundamental solution to Grad's equations are implemented in a linear superposition approach to modelling external ows. Such schemes are mesh free, and bene t from not having to truncate and discretise an in nite three-dimensional domain. The high accuracy of the technique is demonstrated for creeping non-equilibrium gas ow around a sphere, for which an analytical solution exists for comparison. Finally, to demonstrate the method's geometrical exibility, the ow generated between adjacent spheres held at a xed uniform temperature di erence is explored

Activation of the Unfolded Protein Response Enhances Motor Recovery after Spinal Cord Injury

Spinal cord injury (SCI) is a major cause of paralysis, and involves multiple cellular and tissular responses including demyelination, inflammation, cell death and axonal degeneration. Recent evidence suggests that perturbation on the homeostasis of the endoplasmic reticulum (ER) is observed in different SCI models; however, the functional contribution of this pathway to this pathology is not known. Here we demonstrate that SCI triggers a fast ER stress reaction (1–3 h) involving the upregulation of key components of the unfolded protein response (UPR), a process that propagates through the spinal cord. Ablation of X-box-binding protein 1 (XBP1) or activating transcription factor 4 (ATF4) expression, two major UPR transcription factors, leads to a reduced locomotor recovery after experimental SCI. The effects of UPR inactivation were associated with a significant increase in the number of damaged axons and reduced amount of oligodendrocytes surrounding the injury zone. In addition, altered microglial activation and pro-inflammatory cytokine expression were observed in ATF4 deficient mice after SCI. Local expression of active XBP1 into the spinal cord using adeno-associated viruses enhanced locomotor recovery after SCI, and was associated with an increased number of oligodendrocytes. Altogether, our results demonstrate a functional role of the UPR in SCI, offering novel therapeutic targets to treat this invalidating condition

Believing is achieving: a longitudinal study of self-efficacy and positive affect in resettled refugees

Research has shown that self-efficacy can play an important role in recovery from trauma (Benight and Bandura 2004). We hypothesised that for refugees, whose (often traumatic) experiences pre- and post-resettlement have been linked to a decrease in their wellbeing (e.g., Aspinall and Watters 2010), self-efficacy would play a key role in improving wellbeing. This paper investigates the link between self-efficacy and positive affect among resettled refugees (N = 180). Research used mixed methods. The longitudinal survey with three time points confirmed that higher levels of general self-efficacy were consistently associated with better positive affect at later time points. The reverse effects, from positive affect to later self-efficacy, were not significant. In addition, qualitative interviews with a subsample provide suggestions as to how self-efficacy of refugees might be improved: that is, by improving access to employment and language classes, by clarifying how British social and cultural systems work, including the practical information necessary to navigate daily life, and by providing more opportunities to increase social networks, all suggesting the necessity of a proactive role of the receiving society

Patterns of self–other overlap in children

Self–other overlap is a multi-dimensional construct; however, little is known about the characterization of these dimensions through early to middle childhood. The present work introduced several adapted measures for investigating the early development of two self–other overlap dimensions: Perceived Closeness (claimed similarity with a target other) and Overlapping Representations (cognitive confusion or merging of self and other). Children aged 5-6 (n = 45) and 7-8 (n = 45) completed measures of these dimensions of overlap between themselves and a close (best friend) and distant (acquaintance) target other. Children in both age groups had higher Perceived Closeness for a close than a distant target other, with larger distinction between the target others by the older group than the younger group. No Target Relationship differences were found for Overlapping Representations measures; however, exploratory analyses revealed patterns of self-enhancement in ratings of self and others, as well as a tendency for younger children to make more favorable misattributions to the self than to others in a trait memory game. An Age effect for one Overlapping Representations measure suggested that younger children have higher Overlapping Representations with others than do older children. These patterns are discussed in terms of the emergence of self-concept and cognitive abilities, the development of implicit personality theories, and self–other overlap’s relations with person perception and biases, as well as considerations for future measurement