Fresnel arrays for the study of Lamb waves in laser ultrasonics

An experimental technique is proposed to analyze and control laser-generated Lamb waves propagating in aluminum plates. The technique consists in forming on the surface of the specimen an array of concentric arc sources by passing the laser beam through a Fresnel lens. The spacing between the illuminated arcs produces a forcing wavelength for which only a few specific frequencies (those which satisfy the dispersion relation) can propagate in the sample. Dispersion curves can be obtained by measuring the frequency content of the received signals for a range of wavenumbers. The technique offers a relatively high signal-to-noise ratio because of the narrow-band nature of the method and because of the confocal geometry of the source distribution. Reasonably good agreement is obtained between theoretical and experimental dispersion curves especially for the lower modes, thus showing that the proposed technique may have some potential for some specific applications in laser ultrasonic nondestructive evaluation.     

Interactive effects of menarcheal status and dating on dieting and disordered eating among adolescent girls.

The effects of menarcheal status and opposite-sex socializing (mixed-sex social activity, dating, and noncoital sexual involvement with boyfriends) on dieting and disordered eating among early adolescent girls are examined. In all, 89 12- and 13-year-old girls reported their menarcheal status, dieting behaviors and attitudes, and involvement in dating and other heterosocial activities. Girls who are more involved in mixed-sex social activities are more likely to exhibit disordered eating tendencies, and this effect is stronger among girls who have experienced menarche. Also, girls who are dating and are more physically involved with boyfriends are more likely to report dieting and disordered eating than are their peers. An interaction between dating and menarcheal status was observed in the prediction of dieting and disordered eating, with dating more strongly linked to dieting and disordered eating among girls who have recently experienced menarche. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rheological characterization of mechanical properties of chemically crosslinked microspheres

This work presents a rheological method to characterize degradation of microspheres made of chemically crosslinked hydrogels. Conditions to measure rheological properties of microspheres, remaining as individual microspheres during measurement, were established. Relevant and reproducible measurements could be obtained with a rheometer equipped with a parallel plate geometry in which a homogenous and continuous monolayer of microspheres was inserted in a gap between the plates. The storage modulus of microspheres was determined under an imposed strain of 0.04% with an oscillatory measurement mode at various frequencies. The microspheres showed almost purely elastic behavior while their storage modulus was affected by the degree of crosslinking. In the second part of the work, the rheological method was applied to investigate the degradation of microspheres made of a hydrolyzable crosslinked hydrogel. The method was found suitable by measuring the storage modulus over time. A good correlation was identified between acidification of the incubation medium because of the release of degradation products and the decrease of the storage modulus of the microspheres indicating a reduction in the crosslinking of the hydrogel resulting from the degradation process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The Importance of Bridging Points for Charge Transport in Webs of Conjugated Polymer Nanofibers

Electrical characterizations on webs of highly ordered semiconducting polymer nanofibers (NFs) are often performed with large electrodes devices (millimeter scale) for which the carrier transport is an average between transport within isolated NFs and transport at the intersection of two or more NFs. In order to assess the nanoscale electrical properties of the NFs, a field‐effect transistor based on conductive atomic force microscopy is introduced that allows the visualization of the current distribution at the nanometer scale within a web of poly(3‐butylthiophene) NFs. The contact resistance is evaluated to be ≈4 kΩ cm, which does not limit the charge transport process, and the mobility in one single NF is μ_NF = 0.07 ± 0.03 cm² V^?1 s^?1. One NF can carry a current density of 20 kA cm^?2 without being destroyed. Moreover, by observing the current maps in detail, it is found that the electrical resistance associated with the bridging of two or more individual NFs does not reduce the charge transport inside the web of NFs. Finally, different kinds of bridging geometries are shown and the role of tie molecules is discussed.     

Applications and implications of nanotechnologies for the food sector

A review of current and projected nanotechnology-derived food ingredients, food additives and food contact materials is presented in relation to potential implications for consumer safety and regulatory controls. Nanotechnology applications are expected to bring a range of benefits to the food sector, including new tastes, textures and sensations, less use of fat, enhanced absorption of nutrients, improved packaging, traceability and security of food products. The review has shown that nanotechnology-derived food and health food products are set to grow worldwide and, moreover, a variety of food ingredients, additives, carriers for nutrients/supplements and food contact materials is already available in some countries. The current level of applications in the European food sector is at an elementary stage; however, it is widely expected that more and more products will be available in the EU over the coming years. The toxicological nature of hazard, likelihood of exposure and risk to consumers from nanotechnology-derived food/food packaging are largely unknown and this review highlights major gaps in knowledge that require further research. A number of uncertainties and gaps in relevant regulatory frameworks have also been identified and ways of addressing them proposed.     

When frames of reference lag perception of reality: Managing senior careers in the first ten years of the 21st century.

This article summarizes a review of the careers of 50 executives who have been outstanding in traversing the careers of their professional lives. In a world of short job tenure-elongated middle age, most executives will have to simultaneously manage two separate careers. One career is called full-time assignment work and is the traditional "job." The other career is called project assignment work, also known as interim or consulting work. Many think these two careers will occur sequentially. This typical framework sets leaders up for perceived failure because this sequential model is no longer realistic. Leaders will be traversing between full time and project based work through their professional lives. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using portable datafiles in the construction supply chain

Portable datafile technologies such as high density bar coding and electronic tagging now permit very high information storage capacities. Aside from anecdotal evidence, there are few examples of these technologies being used within construction. This paper explores the potential advantages of using portable datafiles for storing and transmitting information relating to construction materials and components. A structured methodology is presented to aid the definition of (1) information which could be encoded within labels or tags; and (2) the stages within the supply chain where such a device would most fruitfully be employed. A case study is presented which demonstrates both the operational and financial feasibility of using portable datafiles within the scenario of a live project. Recommendations are made for the development of a construction industry standard for portable datafiles as part of a framework to promote more widespread deployment of the technologies. Les fichiers de donnees portables comme les codes a barres et l'etiquetage electronique sont des technologies qui autorisent de tres hautes capacites de stockage de l'information. A part l'evidence anecdotique, on compte peu d'exemples de l'utilisation de ces technologies dans le secteur de la construction. Dans cet article l'auteur explore les avantages potentiels de l'utilisation des fichiers de donnees portables pour le stockage et la transmission des informations se rapportant aux materiaux et equipements de construction. Il expose une methodologie structuree destinee a faciliter la definition de l'information qui peut etre codee dans des etiquettes ainsi que des etapes dans la chaine d'approvisionnement ou de tels systemes seraient particulierement utiles. Une etude de cas est presentee demontrant la faisabilite operationnelle et financiere de l'utilisation de fichiers de donnees portables dans le cadre d'un projet concret. L'auteur fait des recommandations en vue de l'elaboration d'une norme industrielle portant sur l'utilisation de fichiers portables dans le secteur de la construction, l'objectif etant de promouvoir davantage encore le deploiement de ces technologies.