Influence of Elastic Strains on the Adsorption Process in Porous Materials. An Experimental Approach

The experimental results presented in this paper show the influence of the elastic deformation of porous solids on the adsorption process. With p+-type porous silicon formed on highly boron doped (100) Si single crystal, we can make identical porous layers, either supported by or detached from the substrate. The pores are perpendicular to the substrate. The adsorption isotherms corresponding to these two layers are distinct. In the region preceding capillary condensation, the adsorbed amount is lower for the membrane than for the supported layer and the hysteresis loop is observed at higher pressure. We attribute this phenomenon to different elastic strains undergone by the two layers during the adsorption process. For the supported layer, the planes perpendicular to the substrate are constrained to have the same interatomic spacing as that of the substrate so that the elastic deformation is unilateral, at an atomic scale, and along the pore axis. When the substrate is removed, tridimensional deformations occur and the porous system can find a new configuration for the solid atoms which decreases the free energy of the system adsorbate-solid. This results in a decrease of the adsorbed amount and in an increase of the condensation pressure. The isotherms for the supported porous layers shift toward that of the membrane when the layer thickness is increased from 30 to 100 microns. This is due to the relaxation of the stress exerted by the substrate as a result of the breaking of Si-Si bonds at the interface between the substrate and the porous layer. The membrane is the relaxed state of the supported layer.Comment: Accepted in Langmui

Law Reform: A Saskatchewan Viewpoint

The term law reform has a positive connotation. It indicates that those engaged in the process are at least optimistic to the extent that law can indeed be reformed and not merely changed. A variety of legislative shapes and administrative forms of law reform agencies has been created in this country over the last ten years. The objectives of law reform have been widely discussed in law review articles and in the daily press. There emerges a sense that reforming the law by way of a permanent law reform commission is a viable endeavour. Yet there is some difference of opinion about the approach to be taken and the objectives to be achieved. The words law reform have different meanings depending upon one\u27s point of view. An attempt is made here to illustrate three points of view, each having important ramifications in terms of the work undertaken and the goals achieved. Three simplistic hypothetical models are put forward in order to highlight, in a broad way, different meanings attributed to the term law reform . In addition, the activities of the Law Reform Commission of Saskatchewan will be outlined

How can ten fingers shape a pot? Evidence for equivalent function in culturally distinct motor skills

Behavioural variability is likely to emerge when a particular task is performed in different cultural settings, assuming that part of human motor behaviour is influenced by culture. In analysing motor behaviour it is useful to distinguish how the action is performed from the result achieved. Does cultural environment lead to specific cultural motor skills? Are there differences between cultures both in the skills themselves and in the corresponding outcomes? Here we analyse the skill of pottery wheel-throwing in French and Indian cultural environments. Our specific goal was to examine the ability of expert potters from distinct cultural settings to reproduce a common model shape (a sphere). The operational aspects of motor performance were captured through the analysis of the hand positions used by the potters during the fashioning process. In parallel, the outcomes were captured by the geometrical characteristics of the vessels produced. As expected, results revealed a cultural influence on the operational aspects of the potters' motor skill. Yet, the marked cultural differences in hand positions used did not give rise to noticeable differences in the shapes of the vessels produced. Hence, for the simple model form studied, the culturally-specific motor traditions of the French and Indian potters gave rise to an equivalent outcome, that is shape uniformity. Further work is needed to test whether such equivalence is also observed in more complex ceramic shapes

Adsorption in non interconnected pores open at one or at both ends: A reconsideration of the origin of the hysteresis phenomenon

We report on an experimental study of adsorption isotherme of nitrogen onto porous silicon with non interconnected pores open at one or at both ends in order to check for the first time the old (1938) but always current idea based on Cohan's description which suggests that the adsorption of gaz should occur reversibly in the first case and irreversibly in the second one. Hysteresis loops, the shape of which is usually associated to interconnections in porous media, are observed whether the pores are open at one or at both ends in contradiction with Cohan's model.Comment: 5 pages, 4 EPS figure

Adsorption-Induced Deformation in Nanopores: Unexpected Results Obtained by Molecular Simulations

International audienceThe adsorption of a fluid in a nanoporous material induces deformations of the solid. The saturating regime, where the solid is filled with liquid, generally exhibits a linear relationship between the liquid pressure and the solid strain. This provides an experimental way to measure the elastic moduli of the solid walls. For large pores, the strain is determined by the pressure of the liquid saturating the pores and the mechanical properties of the porous solid. What happens at the nanometric scale, where liquid/matrix interfacial effects dominate? We have performed molecular simulations of a simple Lennard-Jones fluid confined between deformable nanoplatelets. The simulations provide the deformation of the nanopore as a function of the liquid pressure, in a way similar to what is done experimentally. The results show unexpected interface effects, which could be relevant to experimental data analysis

Bestrijding van rouwmuggen en oevervliegen

Rouwmuggen zijn zeer algemeen in kassen, en meestal talrijker dan de typische plaag-insecten. De meeste soorten voeden zich met schimmels en met organisch materiaal, en zijn onschadelijke voor planten. Enkele soorten kunnen schadelijk zijn in zaaibedden, aan stekmateriaal en aan jonge planten. Veel breedwerkende insecticiden hebben een effect op de muggen en hun larven, maar het probleem blijft dat de populaties zich echter snel herstellen. Van de twintig geteste producten gaven Trigard (cyromazine), Nomolt (teflubenzuron) en de nematode Steinernema feltiae de beste resultaten. Geen van de insectenpathogene schimmels en ook niet de kortschildkever Atheta coriaria en de nematode Heterorhabditis bacteriophora hadden effect op het aantal rouwmuggen. Bodemroofmijten waren op korte termijn niet effectief

Transmission of vortex electrons through a solenoid

We argue that it is generally nonstationary Laguerre-Gaussian states (NSLG) rather than the Landau ones that appropriately describe electrons with orbital angular momentum both in their dynamics at a hard-edge boundary between a solenoid and vacuum and inside the magnetic field. It is shown that the r.m.s. radius of the NSLG state oscillates in time and its period-averaged value can significantly exceed the r.m.s. radius of the Landau state, even far from the boundary. We propose to study the unconventional features of quantum dynamics inside a solenoid in several experimental scenarios with vortex electrons described by the NSLG states. Relevance for processes in scanning and transmission electron microscopes, as well as for particle accelerators with relativistic beams is emphasized.Comment: 6 pages, 2 figure