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排序方式: 共有1778条查询结果,搜索用时 14 毫秒
91.
Suska F Källtorp M Esposito M Gretzer C Tengvall P Thomsen P 《Journal of materials science. Materials in medicine》2001,12(10-12):939-944
Machined, commercially pure titanium (Ti) disks were coated with approximately 400 nm copper (Cu) by physical vapor deposition or left uncoated. The kinetics of inflammatory cell recruitment, distribution and viability was evaluated around Ti, Cu, and in sham sites after 1, 3, 12, 18, 24, and 48 h in a rat subcutaneous (s.c.) model. Further analysis of the cells on implant surfaces was performed by ex vivo incubation of the disks. Ti and Cu stimulated an increased recruitment of inflammatory cells in comparison with sham sites. A markedly higher amount of cells, predominantly polymorpho-nuclear granulocytes (PMN), was detected around Cu after 18 h and onwards. More cells were found at the implant surfaces than in the surrounding exudates after 18 h. The total amount of lactate dehydrogenase (LDH), an indicator of plasma membrane injury, was higher in Cu exudates after 18 h in comparison with Ti and sham. In contrast, no differences in the proportion of dead cells (trypan blue dye uptake) were detected in the exudates. Further, LDH levels were higher around Ti than Cu during the initial 18 h of ex vivo incubation. The results of this study indicate that the early inflammatory process associated with a cytotoxic material in soft tissues is largely attributed to the induction of a markedly strong and prolonged chemotactic response. In contrast, this process is characterized by a higher amount of inflammatory cells around a biocompatible material than in sham sites, but with a transient course and total LDH similar to sham sites. 相似文献
92.
J. Jakobsen E. Bozhevolnaya O.T. Thomsen 《Composites Science and Technology》2007,67(15-16):3378-3385
The paper addresses the damage tolerance of sandwich structures, where the prevention and limitation of delamination failure are highly important design issues. Due to the layered composition of sandwich structures, face–core interface delamination is a commonly observed failure mode, often referred to as peeling failure. Peeling between the sandwich face sheets and the core material drastically diminishes the structural integrity of the structure. This paper presents a new peel stopper concept for sandwich structures. Its purpose is to effectively stop the development of debonding/delamination by rerouting the delamination, and to confine it to a predefined zone in the sandwich structure. The suggested design was experimentally tested for different material compositions of sandwich beams subjected to three-point bending loading. For all the tested sandwich configurations the suggested peel stopper was able to stop face–core delamination and to limit the delamination damage to restricted zones. 相似文献
93.
Nonresponse to surveys, which seems to plague work environment studies and studies of health care personnel in particular, may pose problems of generalizability and validity. The aim of this study was to provide an estimate of nonresponse error in a self-administered survey concerning the work environment of psychiatric health care personnel. A random sample of 10% of the original survey population (N?=?693) was selected to participate in a telephone follow-up of a postal survey that had a response rate of 51%. There were no differences between the responders and nonresponders to the postal survey on the exposure or outcome variables. There was no evidence of nonresponse bias in this study, although recall bias may have been a problem. In those cases in which generalizability is deemed important, it is recommended that nonresponse studies be regularly carried out when response rates are less than 100%. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
95.
Digital dermatitis is a serious problem in dairy production in many countries. In many settings, it is important to evaluate the digital dermatitis status of individual cows or an entire dairy herd. Such an evaluation has traditionally been done in a hoof trimming chute. An evaluation in the milking parlor can take place without disturbing the cows to a large extent, it can be done using less labor compared with an evaluation in a hoof trimming chute, and is cheaper than using a chute. The objective was to evaluate the sensitivity and specificity of a rapid screening method for digital dermatitis in the milking parlor, without using any specialized tools and taking approximately 15 s/cow. All lactating cows in 3 commercial Danish dairy herds were included. Cows were first scored for the presence of digital dermatitis during milking and the next day all cows were scored during hoof trimming. A 6-point nominal scoring system based on a visual inspection of the digital dermatitis lesions was used. For the analysis, the scores were dichotomized (digital dermatitis positive or digital dermatitis negative). Additionally, lesions were classified as small (diameter ≤ 2 cm) or large (diameter >2 cm). Sensitivity and specificity were calculated using observations from the hoof trimming chute as the “gold standard” and observations during milking as the diagnostic test. Relatively large variation was found between herds with an overall sensitivity of 0.65 (95% confidence interval: 0.59 to 0.72) and a specificity of 0.84 (0.81 to 0.87). The sensitivity increased to 0.69 (0.62 to 0.76), when only large lesions were assessed. The method has several advantages compared with evaluation in a chute and may be a useful tool in the daily hoof health management in dairy herds. 相似文献
96.
97.
Hans Erhorn Tomasz Mroz Ove Mørck Fritz Schmidt Lorenz Schoff Kirsten Engelund Thomsen 《Energy and Buildings》2008,40(4):419-428
Educational buildings such as kindergartens, schools and universities display many similar design, operation and maintenance features in most countries. The two most noteworthy similarities amongst these building types are the high energy consumption and the necessity for retrofitting many buildings within this sector. However, studies have shown that during retrofit, energy saving measures are only rarely applied, because the decision-makers lack knowledge of investments and the efficiency of potential energy saving measures. The main goal of the International Energy Agency ECBCS Annex 36 is to provide the educational building decision-makers with sufficient data, information and tools to improve their learning and teaching environments by improving the energy efficiency of their buildings. 相似文献
98.
A 27-year-old woman was admitted with an abdominal mass in the right hypochondrium. Ultrasound, intravenous urography and scintigraphy revealed a giant non-functioning hydronephrosis. Because she refused surgery, a percutaneous aspiration with instillation of doxycycline was performed. One year thereafter, the patient was still without recurrence of any symptoms or hydronephrosis. 相似文献
99.
J H?glund BL Ljungstr?m O Nilsson H Lundquist E Osterman A Uggla 《Canadian Metallurgical Quarterly》1997,38(2):157-165
The biological accuracy of a nonlinear compartmental model describing the in vivo kinetics of L-3,4-dihydroxy-6-[18F]fluorophenylalanine ([18F]FDOPA) metabolism was investigated. Tissue activities for [18F]FDOPA and its labeled metabolites 3-O-methyl-[18F]FDOPA ([18F]OMFD), 6-[18F]fluorodopamine ([18F]FDA), L-3,4-dihydroxy-6-[18F]fluorophenylacetic acid ([18F]FDOPAC), and 6-[18F]fluorohomovanillic acid ([18F]FHVA) were calculated using a plasma [18F]FDOPA input function, and kinetic constants estimated previously by chromatographic fractionation of 18F-labeled compounds in plasma and brain extracts from rat. Present data accurately reflected the measured radiochemical composition in rat brain for tracer circulation times past 10 min. We formulated the hypothesis that the discrepancy between calculated and measured fractions of [18F]FDOPA and the deaminated metabolite [18F]FDOPAC at times earlier than 10 min reflected storage of [18F]FDA in vesicles without monoamine oxidase. This hypothesis explained the initially rapid appearance of [18F]FDOPAC in striatum by delayed transfer of [18F]FDA from cytosol into vesicles. We conclude that the simpler model of [18F]FDOPA compartmentation is accurate when the cytosolic and vesicular fractions of [18F]FDA are at steady-state; the approach to equilibrium has a time constant of 15-30 min. The present model is valid for positron emission tomography studies of [18F]FDOPA metabolism in living brain. 相似文献
100.
In order to evaluate hypotheses regarding production constraints on final consonants in babbling, 721 utterance-final consonants produced by 6 infants in consonant-vowel-consonant (CVC) syllables were examined and compared with the preceding consonant in the CVC. Consistent with earlier studies, major patterns were observed for each of the three main consonantal properties--place and manner of articulation and voicing. These patterns included a strong tendency for final consonants to repeat the place of articulation of nonfinal consonants and a tendency for relatively more fricative, nasal and voiceless consonants to occur in final position than in nonfinal position. The high frequency with which final consonants shared place of articulation with the preceding consonant was considered to reflect 'frame dominance' or the tendency of a relatively constant mandibular cycle (the frame) to determine the structure of utterances with very little contribution from other active articulators. The manner and voicing effects were attributed to an overall terminal energy decrease in the vocal production system. 相似文献