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951.
Jesús Rodríguez-Sánchez Barbara Myszka Aldo Roberto Boccaccini Dag Kristian Dysthe 《Journal of the American Ceramic Society》2019,102(11):6980-6990
Calcium carbonate cements have emerged in the last few years as an attractive candidate for biomedical applications. They can be easily prepared by mixing water with two metastable calcium carbonate phases––amorphous calcium carbonate (ACC) and vaterite––which (re)crystallize into calcite during setting reaction. The transformation kinetics (and therefore the final surface cement composition) strongly depends on the initial mixture design and is controlled by the dissolution of ACC, whereas calcite nucleation typically controls their recrystallization in fluid batch experiments. Novel compositions are presented in this paper by incorporating organic molecules as a proxy to test their capability to carry on other biomolecules like proteins or antibiotics. The hardened samples are microporous and show excellent bioactivity rates, although their mechanical properties still remain poor. However, this would not be a handicap for in-vivo applications such as bone filling, especially in low mechanical stress locations. 相似文献
952.
Diana B. Peckys Daniel Gaa Dalia Alansary Barbara A. Niemeyer Niels de Jonge 《International journal of molecular sciences》2021,22(2)
The Ca2+ selective channel ORAI1 and endoplasmic reticulum (ER)-resident STIM proteins form the core of the channel complex mediating store operated Ca2+ entry (SOCE). Using liquid phase electron microscopy (LPEM), the distribution of ORAI1 proteins was examined at rest and after SOCE-activation at nanoscale resolution. The analysis of over seven hundred thousand ORAI1 positions revealed a number of ORAI1 channels had formed STIM-independent distinct supra-molecular clusters. Upon SOCE activation and in the presence of STIM proteins, a fraction of ORAI1 assembled in micron-sized two-dimensional structures, such as the known puncta at the ER plasma membrane contact zones, but also in divergent structures such as strands, and ring-like shapes. Our results thus question the hypothesis that stochastically migrating single ORAI1 channels are trapped at regions containing activated STIM, and we propose instead that supra-molecular ORAI1 clusters fulfill an amplifying function for creating dense ORAI1 accumulations upon SOCE-activation. 相似文献
953.
Experimental thermal conditions conducive to the production of high levels of hydrogen cyanide (HCN) from flexible polyurethane foam were determined. In these experiments the material was exposed to relatively low-temperature non-flaming oxidative conditions for a short time period, during which a char was formed. Further heating of the char to temperature above 500°C generated the increased HCN levels. Upon exposure to this same two-step decomposition process, a fire-retarded flexible polyurethane foam produced twice as much char and twice as much HCN. Elemental analyses indicated that the HCN concentration was directly related to the amount of char formed and its nitrogen content. Room burns of slabs of flexible polyurethane foam and chairs containing flexible polyurethane foam indicated that this same phenomenon occurs in large-scale experiments. In these NBS tests, increased concentrations of HCN were produced when the material underwent flaming combustion following a period of smoldering, presumably from heating the char that was formed during smoldering. Investigation of the molecular mechanisms responsible for the increased HCN concentrations was attempted using ion chromatography, electron spectroscopy for chemical analysis (ESCA), Fourier transform infrared (FTIR), pyrolysis/mass spectrometry and 13C solid-state nuclear magnetic resonance (NMR) techniques. While the molecular structures of the nitrogen-containing compounds in the char were not elucidated, these analyses provided evidence of multiple compounds containing amine, amide, imine and nitrile functional groups as the most likely sources of the observed HCN. 相似文献
954.
The notion of modeling particle motion in fluidized beds by stochastic methods is extended to include non-Markovian behavior. The inclusion of such “memory” terms should more adequately represent the key physical considerations. A general memory equation is first introduced. Two expressions for the so-called memory function are then suggested and subsequently used to generate autocorrelation functions which favorably represent the available experimental data. 相似文献
955.
G Bassotti R De Giorgio V Stanghellini M Tonini G Barbara B Salvioli S Fiorella R Corinaldesi 《Canadian Metallurgical Quarterly》1998,30(5):542-548
Constipation is a frequent complaint among patients with different neurological diseases. This review provides a brief account of the numerous conditions affecting the central, peripheral and intrinsic (enteric) nervous systems in which constipation can be the only clinical manifestation or a component of a complex syndrome. Recent neuropathophysiological acquisitions show that any structural or functional impairment of the intrinsic innervation of the gut, including both developmental (i.e., Hirschsprung's disease and intestinal neuronal dysplasia) and acquired (i.e., either degenerative or inflammatory neuropathies) disorders, can be associated with constipation. Constipation may also arise from derangements of the peripheral nervous system, including diabetes and primary chronic autonomic failure (pandysautonomias). Finally, in the central nervous system, a wide array of disorders (post-traumatic, degenerative, ischaemic or neoplastic) are recognized to determine bowel dysfunction, ultimately leading to constipation. Further understanding of the fine pathophysiological mechanisms through which the intrinsic and extrinsic nerve supplies to the digestive system are involved in idiopathic constipation or in diseases generating this symptom will hopefully lead to a better treatment of this frequent pathological condition. 相似文献
956.
Shisslak Catherine M.; Crago Marjorie; Neal Mary E.; Swain Barbara 《Canadian Metallurgical Quarterly》1987,55(5):660
Eating disorders have increased dramatically over the past two decades, but the primary prevention of these disorders has received little attention. This article summarizes our current understanding of anorexia nervosa and bulimia and offers some suggestions for the primary prevention of these disorders at the individual, family, and community levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
957.
Stacy Alan W.; Leigh Barbara C.; Weingardt Kenneth R. 《Canadian Metallurgical Quarterly》1994,2(3):269
Theoretical predictions involving memory associations between alcohol use and its positive outcomes were examined. In 2 preliminary studies, the availability from memory of outcomes from drinking was investigated. In subsequent studies, a measurement paradigm was used that decreased the accessibility of the association between drinking behavior and positive outcomes so that individual differences in drinking frequency might predict the accessibility of memory responses. In a final study, this paradigm was refined further by manipulating various types of alcohol-related cues. The results converge on a class of theory of memory association in which repeated drinking experiences influence the accessibility of thoughts about alcohol use and its most normatively frequent outcomes. The increased association of this behavior and its outcomes in memory has important implications for the cognitive mediation of alcohol use and abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
958.
959.
Summary A modification of a theoretical model for the determination of the number average molecular weight between crosslinks, ¯Mc, is presented for the case of multifunctional junction functionalities in highly crosslinked, macromolecular systems. 相似文献
960.
The National Bureau of Standards toxicity test method 总被引:1,自引:0,他引:1
Barbara Chernov Levin 《Fire Technology》1985,21(2):134-145