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排序方式: 共有760条查询结果,搜索用时 15 毫秒
1.
J Westhuyzen AD Cochrane PJ Tesar T Mau DB Cross MP Frenneaux FA Khafagi SJ Fleming 《Canadian Metallurgical Quarterly》1997,113(5):942-948
Augmentation of antioxidant defenses may help protect tissues against ischemia-reperfusion injury associated with operations involving cardiopulmonary bypass. In this study we examined the effect of pretreating patients with alpha-tocopherol (vitamin E) and ascorbic acid (vitamin C) or placebo on injury to the myocardium. Seventy-six subjects undergoing elective coronary artery bypass grafting participated in a prospective, double-blind, placebo-controlled randomized trial, receiving either placebo or both 750 IU dl-alpha-tocopherol per day for 7 to 10 days and 1 gm ascorbic acid 12 hours before the operation. Plasma alpha-tocopherol concentrations, raised fourfold by supplementation, fell by 70% after the operation in the supplemented group and to negligible levels in the placebo group. There were no significant differences between the groups with respect to release of creatine kinase MB isoenzyme over 72 hours, nor in the reduction of the myocardial perfusion defect determined by thallium 201 uptake. Electrocardiography provided no evidence of a benefit from antioxidant supplementation. Thus the supplementation regimen prevented the depletion of the primary lipid soluble antioxidant in plasma, but provided no measurable reduction in myocardial injury after the operation. 相似文献
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We have examined the formation of hydroxyphenols, nitrophenols, and the minor products 4-nitrosophenol, benzoquinone, 2,2'-biphenol, and 4,4'-biphenol from the reaction of peroxynitrite with phenol in the presence and absence of added carbonate. In the absence of added carbonate, the product yields of nitrophenols and hydroxyphenols have different pH profiles. The rates of nitration and hydroxylation also have different pH profiles and match the trends observed for the product yields. At a given pH, the sum of the rate constants for nitration and hydroxylation is nearly identical to the rate constant for the spontaneous decomposition of peroxynitrite. The reaction of peroxynitrite with phenol is zero-order in phenol, both in the presence and absence of added carbonate. In the presence of added carbonate, hydroxylation is inhibited, whereas the rate of formation and yield of nitrophenols increase. The combined maximum yield of o- and p-nitrophenols is 20 mol% (based on the initial concentration of peroxynitrite) and is about fourfold higher than the maximal yield obtained in the absence of added carbonate. The o/p ratio of nitrophenols is the same in the presence and absence of added carbonate. These results demonstrate that hydroxylation and nitration occur via two different intermediates. We suggest that the activated intermediate formed in the isomerization of peroxynitrous acid to nitrate, ONOOH*, is the hydroxylating species. We propose that intermediate 1, O=N-OO-CO2-, or secondary products derived from it, is (are) responsible for the nitration of phenol. The possible mechanisms responsible for nitration are discussed. 相似文献
4.
Bruce M. Cross 《Renewable Energy》1996,9(1-4)
A methodology of the design of solar energy test facilities is presented. In the design of the test facilities, careful attention has been paid to the availability of local materials and skilled labour to perform tests on solar energy equipment to international standards. Outdoor test results are presented for collector tests performed to ASHRAE standards on site in Egypt. The results are compared with indoor tests from the UK National Test Laboratory using the SERC solar simulator at University of Wales College of Cardiff, UK. Data analysis has been carried out on the outdoor and indoor results to determine the performance of these collectors. The indoor and outdoor results agreed very well. The indoor results have been corrected in accordance with International Standards to yield an ‘equivalent outdoor’ peformance characteristic. The emerging international standards for solar thermal testing are discussed, particularly in a developing country context. 相似文献
5.
Cross Susan E.; Gore Jonathan S.; Morris Michael L. 《Canadian Metallurgical Quarterly》2003,85(5):933
Examination of the assumptions underlying consistency perspectives in social and personality psychology reveals that they are based on an independent, individualistic view of the self. If the self is constructed as relational or interdependent with others, consistency may be less important in social behavior and well-being. Using a variety of measures of well-being, the studies showed that there is a weaker relation between consistency and well-being for individuals with a highly relational self-construal than for those with a low relational self-construal. Study 3 examined the association between the self-construal, consistency, authenticity, and well-being. These findings reveal the importance of a cultural analysis of theories of the self, personality, and well-being for further theory development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing. 相似文献
7.
The purpose of this study was to determine if prostate specific antigen density (PSAD) is a predictor of outcome following external beam radiotherapy for prostate cancer, and to compare it with other prognostic factors. Between January 1990 and December 1993, 205 patients with T1-T3 adenocarcinoma of the prostate received a radical course of external beam irradiation, with no prior or adjuvant hormonal therapy. All patients had pre- and post-treatment serum prostate specific antigen (PSA) evaluation. They were followed up for at least 24 months. PSAD was defined as the ratio of pre-treatment serum PSA to the prostate volume, as determined from CT treatment planning scans. Prostate volumes were calculated using the prostate ellipse formula. Median PSA density was 0.37, with a range 0.01-6.7. Biochemical failure was defined as three consecutive rises in serum PSA, regardless of the magnitude of elevation. 4-year biochemical disease-free survival (BDFS) for patients with PSAD < or = 0.3 was 60%, compared with 22% for patients with PSAD > 0.3 (p = < 0.001). In a multivariate analysis, pre-treatment PSA (p = < 0.001), Gleason score (p = 0.002), and stage (p = 0.03) were independent predictors of BDFS, while PSAD was not an important prognosticator (p = 0.62). Pre-treatment serum PSA is the most important prognosticator of BDFS, following external beam radiotherapy, for patients with prostate cancer. PSA density did not predict treatment outcome. 相似文献
8.
TK Held ME Mielke M Chedid M Unger M Trautmann D Huhn AS Cross 《Canadian Metallurgical Quarterly》1998,91(7):2525-2535
Besides its well-established effects on granulocytopoiesis, granulocyte colony-stimulating factor (G-CSF) has been shown to have direct effects on the recruitment and bactericidal ability of neutrophils, resulting in improved survival of experimentally infected animals. We studied the effect of G-CSF on the course of experimental pneumonia induced by Klebsiella pneumoniae, an important gram-negative bacillary pulmonary pathogen. Using a highly reproducible murine model, we here show the paradoxical finding that mortality from infection was significantly increased when animals received G-CSF before induction of pneumonia. Administration of G-CSF promoted replication of bacteria in the liver and spleen, thus indicating an impairment rather than an enhancement of antibacterial mechanisms. By contrast, a monoclonal antibody against Klebsiella K2 capsule significantly reduced bacterial multiplication in the lung, liver, and spleen, and abrogated the increased mortality caused by G-CSF. In vitro studies showed a direct effect of G-CSF on K pneumoniae resulting in increased capsular polysaccharide (CPS) production. When bacteria were coincubated with therapeutically achievable concentrations of G-CSF, phagocytic uptake and killing by neutrophils was impaired. Western blot analysis showed three binding sites of G-CSF to K pneumoniae. Binding of 125I-G-CSF to K pneumoniae was displaced by an excess of unlabeled G-CSF, whereas an unrelated cytokine, interleukin-1alpha, did not compete with G-CSF binding to the bacteria. Thus, in this model, the direct effect of G-CSF on a bacterial virulence factor, CPS production, outweighed any beneficial effect of G-CSF on recruitment and stimulation of leukocytes. 相似文献
9.
JA Teresi RR Golden P Cross B Gurland M Kleinman D Wilder 《Canadian Metallurgical Quarterly》1995,48(4):473-483
A study of item bias in standard cognitive screening measures was conducted in a sample of Afro-American, Hispanic and non-Hispanic white elderly respondents who were part of a dementia case registry study. The methods of item-response theory were applied to identify biased items. Both cross-cultural and high and low education groups were examined to determine which items were biased. Out of 50 cognitive items examined from six widely used cognitive screening measures, 16 were identified as biased for either high and low education groups or ethnic/racial group membership. 相似文献
10.
To probe for a lever arm action in the kinesin stepping mechanism, we engineered a rodlike extension piece into the tail of rat kinesin at various points close to the head-tail junction and measured its effects on the temperature dependence of velocity in microtubule gliding assays. The insert comprised two contiguous alpha-actinin triple-coil repeats and was predicted to fold into a stiff rodlike module about 11 nm long. The effects of this module were greater the closer it was placed to the head-tail junction. When inserted distal to the head-tail junction, at Asn401 in the dimeric K partial differential401GST, the insert had no effect. When inserted closer to the heads at Val376 into K partial differential376GST, the insert slowed progress below 22 degreesC but accelerated progress to approximately 125% of wild type above 22 degreesC. The most dramatic effect of the synthetic lever occurred when it was inserted very close to the head-neck junction, at Glu340 into the single-headed construct K partial differential340GST. This construct was immotile without the insert, but motile with it, at about 30% of the velocity of the dimeric control. The alpha-actinin module thus confers some gain-of-function when inserted close to the head-neck junction but not when placed distal to it. The data exclude the presence of a lever arm C-terminal to Val376 in the kinesin tail but suggest that a short-throw lever arm may be present, N-terminal to Val376 and contiguous with the head-neck junction at Ala339. 相似文献