248 research outputs found
Origin of atomic clusters during ion sputtering
Previous studies have shown that the size distributions of small clusters ( n<=40 n = number of atoms/cluster) generated by sputtering obey an inverse power law with an exponent between -8 and -4. Here we report electron microscopy studies of the size distributions of larger clusters ( n>=500) sputtered by high-energy ion impacts. These new measurements also yield an inverse power law, but one with an exponent of -2 and one independent of sputtering yield, indicating that the large clusters are produced when shock waves, generated by subsurface displacement cascades, ablate the surface
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Molecular mechanisms of intercellular communication: transmembrane signaling
This short discussion of transmembrane signaling depicts a particular class of signaling devices whose functional characteristics may well be representative of broader classes of membrane switches. These multicomponent aggregates are characterized by tight organization of interacting components which function by conformational interactions to provide sensitive, amplified, rapid, and modulated responses. It is clear that the essential role of such switches in cell-cell interactions necessitated their appearance early in the history of the development of multicellular organisms. It also seems clear that once such devices made their appearance, the conformationally interactive moieties were firmly locked into a regulatory relationship. Since modification of interacting components could perturb or interfere with the functional integrity of the whole switch, genetic drift was only permitted at the input and outflow extremes. However, the GTP binding moiety and its interacting protein domains on contiguous portions of the receptor and readout components were highly conserved. The observed stringent evolutionary conservation of the molecular features of these membrane switches thus applies primarily to the central (GTP binding) elements. An extraordinary degree of variation was permitted within the domains of signal recognition and enzymatic output. Thus, time and evolution have adapted the central logic of the regulatory algorithm to serve a great variety of cellular purposes and to recognize a great variety of chemical and physical signals. This is exemplified by the richness of the hormonal and cellular dialogues found in primates such as man. Here the wealth of intercellular communiation can support the composition and performance of symphonies and the study of cellular immunology
Vitamin K Supplementation in Postmenopausal Women with Osteopenia (ECKO Trial): A Randomized Controlled Trial
Angela Cheung and colleagues investigate whether vitamin K1 can prevent bone loss among postmenopausal women with osteopenia
Overview of the assessment practices of occupational therapists working in Quebec
Description. L'Ă©valuation du client est primordiale dans la pratique de l'ergothĂ©rapie, notamment pour Ă©tablir les prioritĂ©s de traitement et pour vĂ©rifier l'efficacitĂ© des interventions. Les pratiques Ă©valuatives des ergothĂ©rapeutes sont cependant peu documentĂ©es. But. Dresser un portrait des pratiques Ă©valuatives des ergothĂ©rapeutes du QuĂ©bec selon les dimensions personne-environnement-occupation et les clientĂšles. MĂ©thodologie. Une enquĂȘte transversale a Ă©tĂ© rĂ©alisĂ©e Ă l'aide d'un sondage en ligne envoyĂ© aux ergothĂ©rapeutes du QuĂ©bec. RĂ©sultats. En pĂ©diatrie, les ergothĂ©rapeutes utilisent majoritairement
des outils standardisĂ©s des aptitudes physiques et neurologiques. L'Ă©valuation d'adultes cible principalement les aptitudes physiques et la productivitĂ©. AuprĂšs des aĂźnĂ©s, l'Ă©valuation repose surtout sur les aspects fonctionnels, particuliĂšrement les aptitudes physiques, les soins personnels et la sĂ©curitĂ© Ă domicile, et sur le dĂ©pistage des difficultĂ©s cognitives. Implications pour la pratique. L'Ă©valuation ergothĂ©rapique serait gĂ©nĂ©ralement axĂ©e sur les aptitudes physiques. Pour assurer une approche holistique, l'occupation et l'environnement devraient ĂȘtre davantage considĂ©rĂ©s dans l'Ă©valuation.Abstract : Background. In occupational therapy practice, client assessments are essential for establishing treatment priorities and determining the effectiveness of interventions. However, occupational therapists' assessment practices are not well documented. Purpose. This work aimed to provide an overview of the assessment practices of Quebec occupational therapists based on the personâenvironmentâoccupation components and clienteles. Method. A cross-sectional survey was conducted using an online survey that was sent to occupational therapists in Quebec. Findings. In paediatrics, occupational
therapists tend to use standardized tools to assess physical and neurological abilities. Adult assessment focuses mainly on physical abilities and productivity. For seniors, assessment focuses mainly on functional aspects (physical abilities, personal care, and home safety) and screening for cognitive difficulties. Implications. Occupational therapy assessment mostly focuses on physicial abilities. To ensure a holistic approach, more occupational and environmental components should be included in the assessment practices
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Safe extension of red blood cell storage life at 4{degree}C
The project sought to develop methods to extend the storage life of red blood cells. Extended storage would allow donor to self or autologous transfusion, expand and stabilize the blood supply, reduce the cost of medical care and eliminate the risk of transfusion related infections, including a spectrum of hepatitides (A, B and C) and HIV. The putative cause of red blood cell spoilage at 4 C has been identified as oxidative membrane damage resulting from deoxyhemoglobin and its denaturation products including hemichrome, hemin and Fe{sup 3+}. Trials with carbon monoxide, which is a stabilizer of hemoglobin, have produced striking improvement of red blood cell diagnostics for cells stored at 4 C. Carbonmonoxy hemoglobin is readily converted to oxyhemoglobin by light in the presence of oxygen. These findings have generated a working model and an approach to identify the best protocols for optimal red cell storage and hemoglobin regeneration
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