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Echocardiographic assessment of flow across continuous-flow ventricular assist devices at low speeds
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M. S. Yeoman B. D. Reddy H. C. Bowles P. Zilla D. Bezuidenhout T. Franz 《Annals of biomedical engineering》2009,37(11):2266-2287
The mechanics of arteries result from the properties of the soft tissue constituents and the interaction of the wall layers,
predominantly media and adventitia. This concept was adopted in this study for the design of a tissue regenerative vascular
graft. To achieve the desired structural properties of the graft, most importantly a diametric compliance of 6%/100 mmHg,
finite element methods and genetic algorithms were used in an integrated approach to identify the mechanical properties of
an adventitial fabric layer that were required to optimally complement an intimal/medial polyurethane layer with interconnected
porosity of three different size classes. The models predicted a compliance of 16.0, 19.2, and 31.5%/100 mmHg for the non-reinforced
grafts and 5.3, 5.5, and 6.0%/100 mmHg for the fabric-reinforced grafts. The latter, featuring fabrics manufactured according
to the required non-linear mechanical characteristics numerically predicted, exhibited an in vitro compliance of 2.1 ± 0.8, 3.0 ± 2.4, and 4.0 ± 0.7% /100 mmHg. The combination of finite element methods and genetic algorithms
was shown to be able to successfully optimize the mechanical design of the composite graft. The method offers potential for
the application to alternative concepts of modular vascular grafts and the incorporation of tissue ingrowth and biodegradation. 相似文献
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Catrine Tudor-Locke Hidde P van der Ploeg Heather R Bowles Michael Bittman Kimberly Fisher Dafna Merom Jonathan Gershuny Adrian Bauman Muriel Egerton 《The international journal of behavioral nutrition and physical activity》2007,4(1):45-9
Background
The American Heritage Time Use Study (AHTUS) represents a harmonised historical data file of time use by adults, amalgamating surveys collected in 1965–66, 1975–76, 1985, 1992–94, and 2003. The objectives of time-use studies have ranged from evaluating household and other unpaid production of goods and services, to monitoring of media use, to comparing lifestyles of more and less privileged social groups, or to tracking broad shifts in social behaviour. The purpose of this paper is to describe the process and utility of identifying and compiling data from the AHTUS to describe a range of walking behaviours collected using time-use survey methods over almost 40 years in the USA. 相似文献37.
The authors detail the process of developing four specific tools for student evaluation of faculty performance at the master's and baccalaureate levels. To accomplish the desired goal of improving instruction, these authors believe student evaluation tools should be tailor-made to the educational setting and mode of delivery. The tools described in this article were developed to evaluate faculty performance in clinical-direct, on-campus laboratory, clinically precepted, and didactic settings. 相似文献
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Alpha adrenergic agonists (e.g. vasoconstrictors) represent one of the most commonly used drug classes in dentistry. Although adrenergic agonists have potent vascular effects, recent studies suggest that capsaicin-sensitive nociceptors may express adrenoceptors, suggesting that these drugs may directly modulate the function of an important class of pain-signaling neurons in peripheral tissues. In this study, we tested the hypothesis that adrenergic agonists inhibit activation of peripheral terminals of capsaicin-sensitive fibers innervating dental pulp. Pretreatment with epinephrine or clonidine significantly inhibited capsaicin-evoked release of immunoreactive calcitonin gene-related peptide from superfused bovine dental pulp. These studies suggest that adrenergic agonists may reduce postoperative pain in part via a direct inhibition of capsaicin-sensitive nociceptors. This finding may lead to the development of selective, peripherally acting, adrenergic analgesics. Moreover, because neuropeptide release alters blood flow, it is possible that the vascular effects of these drugs are caused by both vasoconstriction and inhibition of peripheral neuropeptide release. 相似文献
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Bowles KC Bianchini A Brauner CJ Kramer JR Wood CM 《Environmental toxicology and chemistry / SETAC》2002,21(6):1286-1293
Experiments were designed to assess the potential protective effect of the presence of sulfide against the acute (48-h) toxicity of silver(I) to Daphnia magna. Tests were conducted in borosilicate glass beakers (250 ml) in moderately hard synthetic water. Toxicity solutions were replaced after 24 h by static renewal method. This paper describes the chemical system, and the acute toxicity results are presented in a companion paper. Sulfide was below detection limit (<5 nM) in controls with no sulfide added. Sulfide, added as zinc sulfide clusters at approximately 35- or approximately 350-nM concentration, dropped in concentration to approximately 25 and 250 nM, respectively, over the 24-h period of measurements. Silver also decreased in concentration during the experiment (up to 59%), and the rate of loss was greater in the absence of sulfide compared with the presence of sulfide. A filtration experiment indicated a 1:1 binding ratio of silver to sulfide and a conditional stability constant for the Ag(I)-zinc sulfide complex of log K' = 8.9. The losses of sulfide and silver during the experiments highlighted the need for regular monitoring of the important chemical components of the system, even during short (48-h) toxicity tests. 相似文献