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排序方式: 共有1103条查询结果,搜索用时 17 毫秒
1.
IC Wilson TJ Gardner JM DiNatale AM Gillinov WE Curtis DE Cameron 《Canadian Metallurgical Quarterly》1993,106(5):805-810
Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation. 相似文献
2.
FV Elmslie M Rees MP Williamson M Kerr MJ Kjeldsen KA Pang A Sundqvist ML Friis D Chadwick A Richens A Covanis M Santos A Arzimanoglou CP Panayiotopoulos D Curtis WP Whitehouse RM Gardiner 《Canadian Metallurgical Quarterly》1997,6(8):1329-1334
The epilepsies are a group of disorders characterised by recurrent seizures caused by episodes of abnormal neuronal hyperexcitability involving the brain. Up to 60 million people are affected worldwide and genetic factors may contribute to the aetiology in up to 40% of patients. The most common human genetic epilepsies display a complex pattern of inheritance. These are categorised as idiopathic in the absence of detectable structural or metabolic abnormalities. Juvenile myoclonic epilepsy (JME) is a distinctive and common variety of familial idiopathic generalised epilepsy (IGE) with a prevalence of 0.5-1.0 per 1000 and a ratio of sibling risk to population prevalence (lambda(s)) of 42. The molecular genetic basis of these familial idiopathic epilepsies is entirely unknown, but a mutation in the gene CHRNA4, encoding the alpha4 subunit of the neuronal nicotinic acetylcholine receptor (nAChR), was recently identified in a rare Mendelian variety of idiopathic epilepsy. Chromosomal regions harbouring genes for nAChR subunits were therefore tested for linkage to the JME trait in 34 pedigrees. Significant evidence for linkage with heterogeneity was found to polymorphic loci encompassing the region in which the gene encoding the alpha7 subunit of nAChR (CHRNA7) maps on chromosome 15q14 (HLOD = 4.4 at alpha = 0.65; Z(all) = 2.94, P = 0.0005). This major locus contributes to genetic susceptibility to JME in a majority of the families studied. 相似文献
3.
4.
This paper deals with the trajectory planning problem for redundant manipulators. A genetic algorithm (GA) using a floating point representation is proposed to search for the optimal end-effector trajectory for a redundant manipulator. An evaluation function is defined based on multiple criteria, including the total displacement of the end-effector, the total angular displacement of all the joints, as well as the uniformity of Cartesian and joint space velocities. These criteria result in minimized, smooth end-effector motions. Simulations are carried out for path planning in free space and in a workspace with obstacles. Results demonstrate the effectiveness and capability of the proposed method in generating optimized collision-free trajectories. 相似文献
5.
JeremyCurtis 《今日电子》2003,(12):30-31
移动终端是一种采用先进通信协议栈的复杂系统,它需要具有与许多网络供应商设备的互操作性、支持先进而丰富的多媒体应用程序,而且,所有这些都必需在一个资源有限的嵌入式系统的约束条件下实现。提供一个满足上述要求的软件解决方案需要考虑许多方面的问题并经历诸多阶段。成功的要素是:平台质量、应用程序集成质量和产品质量。平台质量能让制造商用来生成多种设计方案的移动手机参考设计,必须提供一个用于制造高品质终端用户产品的优质平台。移动手机软件包括三个关键部分——协议栈、应用程序架构和应用程序。协议栈毫无疑问是最为复杂的… 相似文献
6.
During a longitudinal study of vector biology and malaria transmission in western Venezuela, adult mosquitoes were collected by different methods and their efficiency was compared with human landing catches. CDC light traps, a double-net, a calf-baited trap and collection of resting mosquitoes on vegetation were tested. These methods did not prove to be effective substitutes for human landing catches. 相似文献
7.
Braver Sanford L.; Wolchik Sharlene A.; Sandler Irwin N.; Sheets Virgil L.; Fogas Bruce; Bay R. Curtis 《Canadian Metallurgical Quarterly》1993,7(1):9
Reports the results of a 3-wave longitudinal study of a sizable, regionally representative sample of both noncustodial and custodial parents interviewed initially before their divorce was final. A model was tested that predicted the noncustodial parent's postdivorce contact with the child and the payment of child support from a series of factors related to a social exchange orientation. This orientation highlights the noncustodial parent's implicit calculation of the rewards vs the costs of continuing involvement and support of the child. It was found that noninvolvement was, in general, well-predicted, both cross-sectionally and longitudinally, by the model. The most powerful factor in the model was the noncustodial parent's perception that he or she had some control over the child's upbringing. Among fully employed noncustodial parents who reported high perceived control, there was an excellent record of involvement and child support payment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
James Rodgers Kaye Wolf Norm Willis Don Hamilton Ralph Ledbetter Curtis Stewart 《Color research and application》1994,19(5):322-331
A multiplant Quality Improvement Team [QIT] was firmed to develop and implement an evaluation program for various color measurement .systems as potential replacements for the then-current aging systems. The emphasis qf this article is the analytical methodology utilized to evaluate the various color systems. The evaluation program consisted cf two phases. Phase I was a general overview/review of several systems, while Phase II was an extensive internal comparative evaluation measurement systems. These were Milton-Roy's ColorMate HDS, HunterLab's Ultrascan, Datacolor's CS-5, and BYK-Gardner's The Color Sphere [TCS]. The main comparison criteria were interinstrument agreement [agreement between two instruments ofthe same system], user-friendly software and computer interface capability, vendor amenability to a long-term logistical and maintenance relationship, and price. All systems were evaluated by duplicate measurements on various color tiles, yarns, and polymer flakes-over 1600 measurements on each system. The systems were compared with an instrument matrix, a decision matrix, and a product matrix. The instrument matrix was a comparison qfinstrument parameters, software/math treatments, and economics. The decision matrix was a forced ranking of each system by each criteria category [1–4 scale, with 1 representing the best and 4 representing the worst]. The product matrix accentuated the relative importance ofone criterion category over another by multiplying the forced ranking by the criticality of the category. The criticality of a given category wus determined by consensus within the QIT. Thr combination qf the three matrices allowed the evaluator[.s] t o select the color rneasuremmt system that best satixfied the color measurement needs and requirements of their facility and their products. For this evaluation, all ofthe evaluated systems were superior to the then-current agingsystems. As a result of this methodology, one instrument emerged as clearly superior. © 1994 John Wrley & Sons, Inc. 相似文献
9.
ML Price AL Curtis LG Kirby RJ Valentino I Lucki 《Canadian Metallurgical Quarterly》1998,18(6):492-502
The serotonergic dorsal raphe nucleus is innervated by corticotropin-releasing factor (CRF) and expresses CRF receptors, suggesting that endogenous CRF impacts on this system. The present study characterized interactions between CRF and the dorsal raphe serotonin (5-HT) system. The effects of intracerebroventricularly (i.c.v.) administered CRF on microdialysate concentrations of 5-HT in the lateral striatum of freely moving rats were determined. CRF had biphasic effects, with 0.1 and 0.3 microgram decreasing, and 3.0 micrograms increasing 5-HT dialysate concentrations. i.c.v. administration of CRF inhibited neuronal activity of the majority of dorsal raphe neurons at both low (0.3 microgram) and high (3 micrograms) doses. Likewise, intraraphe administration of CRF (0.3 and 1.0 ng) had predominantly inhibitory effects on discharge rate. Together, these results suggest that CRF is positioned to regulate the function of the dorsal raphe serotonergic system via actions within the cell body region. This regulation may play a role in stress-related psychiatric disorders in which 5-HT has been implicated. 相似文献
10.
Frank E. Curtis Nicholas I.M. Gould Hao Jiang Daniel P. Robinson 《Optimization methods & software》2016,31(1):157-186
In this paper, we consider augmented Lagrangian (AL) algorithms for solving large-scale nonlinear optimization problems that execute adaptive strategies for updating the penalty parameter. Our work is motivated by the recently proposed adaptive AL trust region method by Curtis et al. [An adaptive augmented Lagrangian method for large-scale constrained optimization, Math. Program. 152 (2015), pp. 201–245.]. The first focal point of this paper is a new variant of the approach that employs a line search rather than a trust region strategy, where a critical algorithmic feature for the line search strategy is the use of convexified piecewise quadratic models of the AL function for computing the search directions. We prove global convergence guarantees for our line search algorithm that are on par with those for the previously proposed trust region method. A second focal point of this paper is the practical performance of the line search and trust region algorithm variants in Matlab software, as well as that of an adaptive penalty parameter updating strategy incorporated into the Lancelot software. We test these methods on problems from the CUTEst and COPS collections, as well as on challenging test problems related to optimal power flow. Our numerical experience suggests that the adaptive algorithms outperform traditional AL methods in terms of efficiency and reliability. As with traditional AL algorithms, the adaptive methods are matrix-free and thus represent a viable option for solving large-scale problems. 相似文献