Reflection of structural waves at a solid/liquid interface

This paper investigates the reflection characteristics of structural or guided waves in rods at a solid/liquid interface. Structural waves, whose wavelengths are much larger than the diameter of the rod, are described in a first approximation by classical one-dimensional wave theory. The reflection characteristics of such waves at a solid/liquid (melting) interface has been reported by two different ultrasonic measurement techniques: first, measuring the fast regression rate of a melting interface during the burning of metal rod samples in an oxygen-enriched environment, and second, monitoring the propagation of the solid/liquid interface during the slow melting and solidification of a rod sample in a furnace. The second work clearly shows that the major reflection occurs from the solid/liquid interface and not the liquid/gas interface as predicted by plane longitudinal wave reflectivity theory. The present work confirms this observation by reporting on the results of some specially designed experiments to identify the main interface of reflection for structural waves in rods. Hence, it helps in explaining the fundamental discrepancy between the reflection characteristics at a solid/liquid interface between low frequency structural waves and high frequency bulk waves, and confirms that the detected echo within a burning metallic rod clearly represents a reflection from the solid/liquid interface. (C) 2003 Elsevier Science B.V. All rights reserved.

A new principle for tight junction modulation based on occludin peptides

The aim of this study was to investigate whether peptides from the extracellular loops of the tight junction protein occludin could be used as a new principle for tight junction modulation. Peptides of 4 to 47 amino acids in length and covering the two extracellular loops of the tight junction protein occludin were synthesized, and their effect on the tight junction permeability in Caco-2 cells was investigated using [C-14] mannitol as a paracellular marker. Lipopeptide derivatives of one of the active occludin peptides (OPs), synthesized by adding a lipoamino acid containing 14 carbon atoms (C-14-) to the N terminus of the peptide, were also investigated. Peptides corresponding to the N terminus of the first extracellular loop of occludin increased the permeability of the tight junctions without causing short-term toxicity. However, the peptides had an effect only when added to the basolateral side of the cells, which could be partly explained by degradation by apical peptidases and aggregate formation. By contrast, the lipopeptide C-14-OP90-103, which protects the peptide from degradation and aggregation, displayed a rapid apical effect. The L- and D-diastereomers of C-14-OP90-103 had distinctly different effects. The D-isomer, which releases intact OP90-103 from the lipoamino acid, displayed a rapid and transient increase in tight junction permeability. The L- isomer, which releases OP90-103 more rapidly, gave a more sustained increase in tight junction permeability. In conclusion, C-14-OP90-103 represents a prototype of a new class of tight junction modulators that act on the extracellular domains of tight junction proteins.

Solution of the dual reflection equation for A(n-1)((1)) solid-on-solid model

We obtain a diagonal solution of the dual reflection equation for the elliptic A(n-1)((1)) solid-on-solid model. The isomorphism between the solutions of the reflection equation and its dual is studied. (C) 2004 American Institute of Physics.

First-principle density-functional calculation of the Raman spectra of BEDT-TTF

We present a first-principles density-functional calculation for the Raman spectra of a neutral BEDT-TTF molecule. Our results are in excellent agreement with experimental results. We show that a planar Structure is not a stable state of a neutral BEDT-TTF molecule. We consider three possible conformations and discuss their relation to disorder in these systems.

Reflective analysis: Techniques for facilitating reflection

This paper describes a number of techniques for facilitating reflective critical analysis as a means of eliciting in-depth reflections on practice. The authors have previously used similar techniques in the research context, to assist practitioners to identify and analyse the basis of their work with clients. The techniques presented in this paper have been adapted for use in social work education, including in class-based and field education contexts, and to professional supervision.

Coadaptation: A unifying principle in evolutionary thermal biology

Over the last 50 yr, thermal biology has shifted from a largely physiological science to a more integrated science of behavior, physiology, ecology, and evolution. Today, the mechanisms that underlie responses to environmental temperature are being scrutinized at levels ranging from genes to organisms. From these investigations, a theory of thermal adaptation has emerged that describes the evolution of thermoregulation, thermal sensitivity, and thermal acclimation. We review and integrate current models to form a conceptual model of coadaptation. We argue that major advances will require a quantitative theory of coadaptation that predicts which strategies should evolve in specific thermal environments. Simply combining current models, however, is insufficient to understand the responses of organisms to thermal heterogeneity; a theory of coadaptation must also consider the biotic interactions that influence the net benefits of behavioral and physiological strategies. Such a theory will be challenging to develop because each organism's perception of and response to thermal heterogeneity depends on its size, mobility, and life span. Despite the challenges facing thermal biologists, we have never been more pressed to explain the diversity of strategies that organisms use to cope with thermal heterogeneity and to predict the consequences of thermal change for the diversity of communities.