排序方式: 共有63条查询结果,搜索用时 15 毫秒
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Familial and abnormality. 总被引:1,自引:0,他引:1
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Nagaraj Ekabote Krishnaraja G. Kodancha T. M. Yunus Khan Irfan Anjum Badruddin 《Materials》2022,15(4)
AA2050-T84 alloy is widely used in primary structures of modern transport aircraft. AA2050-T84 is established as a low-density aluminum alloy with improved Young’s modulus, less anisotropy, and temperature-dependent mechanical properties. During flights, loading rate and temperature variation in aircraft engine subsequent parts are commonly observed. The present work focuses on the effect of loading rate and temperature on tensile and fracture properties of the 50 mm thick (2-inch) AA2050-T84 alloy plate. Quasi-static strain rates of 0.01, 0.1, and 1 s−1 at −20 °C, 24 °C and 200 °C are considered. Tensile test results revealed the sensitivity of mechanical properties towards strain rate variations for considered temperatures. The key tensile properties, yield, and ultimate tensile stresses were positive strain rate dependent. However, Young’s modulus and elongation showed negative strain rate dependency. Experimental fracture toughness tests exhibited the lower Plane Strain Fracture Toughness (KIC) at −20 °C compared to 24 °C. Elastic numerical fracture analysis revealed that the crack driving and constraint parameters are positive strain rate dependent and maximum at −20 °C, if plotted and analyzed over the stress ratio. The current results concerning strain rates and temperatures will help in understanding the performance-related issues of AA2050-T84 alloy reported in aircraft applications. 相似文献
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P J Harris G S Roubin N N Sadick C Y Choong G Bautovich D T Kelly 《The American journal of cardiology》1983,52(2):113A-118A
Intravascular pressures, cardiac output and left ventricular function were measured at rest and during exercise in 14 patients with stable angina pectoris before and during an intravenous nitroglycerin infusion. Nitroglycerin was infused at a rate sufficient to reduce mean arterial pressure at rest by 15 to 25 mm Hg.At rest, the end-diastolic volume index decreased from 57 ± 13 to 39 ± 3 ml/m2, stroke volume index from 32 ± 6 to 24 ± 5 ml/m2 and mean arterial pressure from 112 ± 16 to 91 ± 14 mm Hg. The cardiac output was maintained by an increase in heart rate from 73 ± 9 to 92 ± 37 beats/min. The left ventricular ejection fraction increased from 57 ± 7 to 62 ± 9% because the stroke volume decreased less than the end-diastolic volume.All 14 patients were limited by angina in the prenitroglycerin exercise study, and the mean ST-segment depression at maximal work load was 2.2 ± 1.2 mm. At identical work loads in the nitroglycerin study, only 4 patients had angina, and the mean ST-segment depression was 0.3 ± 0.5 mm. Ten of the 14 patients improved their exercise performance by at least 30 W.Comparing the 2 exercise studies at the maximal work load achieved in the prenitroglycerin study, the mean pulmonary artery wedge pressure was decreased from 23 ± 6 to 6 ± 4 mm Hg, the end-diastolic volume index from 38 ± 15 to 27 ± 12 ml/m2, and the mean arterial pressure from 132 ± 8 to 114 ±13 mm Hg. The stroke volume index and the heart rate were not significantly altered and the ejection fraction increased from 56 ± 8% to 66 ± 8%.Thus, in the high dose administered, nitroglycerin decreased left ventricular filling pressure, heart size, and stroke volume at rest and increased the ejection fraction. During exercise, nitroglycerin decreased myocardial ischemia and improved exercise tolerance. An increase in exercise ejection fraction was associated with an increase in the ratio of systolic pressure to end-systolic volume, suggesting that there was an improvement in contractile performance. 相似文献
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Arthur T.H. Tan Norman Sadick David T. Kelly Phillip J. Harris S.Benedict Freedman George Bautovich 《The American journal of cardiology》1982,49(2):425-430
A double blind placebo-controlled study was performed in 12 patients with stable angina pectoris to evaluate the effects of oral verapamil (320 mg/day) on left ventricular function, as measured at rest and during exercise with gated equilibrium radionuclide ventriculography. On verapamil, patients had a lower heart rate-blood pressure product at each work load than with placebo. Anginal threshold increased by 28 ± 19 watts (p < 3.005), and maximal exercise capacity increased by 20 ± 14 watts (p < 0.001) with verapamil, but the rate-pressure product at the onset of angina and at maximal exercise was unchanged. Left ventricular ejection fraction at rest during verapamil therapy was the same as with placebo therapy. On exercise during placebo therapy, the ejection fraction decreased from 40 ± 9 to 35 ± 11 percent (p < 0.025) because end-systolic volume increased disproportionately compared with end-diastolic volume. On exercise during verapamil therapy, the ejection fraction did not decrease (44 ± 8 versus 45 ± 12 percent) and was significantly higher at identical work loads than on placebo because of a smaller increase in end-systolic volume. Oral verapamil is effective treatment for effort angina and may prevent the decrease in left ventricular ejection fraction due to exercise-induced ischemia. 相似文献
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The QRS scoring system for estimating myocardial infarct size: clinical, angiographic and prognostic correlations 总被引:2,自引:0,他引:2
G S Roubin W F Shen D T Kelly P J Harris 《Journal of the American College of Cardiology》1983,2(1):38-44
The relation between a QRS score derived from the routine electrocardiogram and left ventricular function was investigated in 181 patients after myocardial infarction. Patients with left ventricular hypertrophy and conduction defects were excluded. The QRS score correlated closely with the severity of wall motion abnormalities and left ventricular ejection fraction. The more severe the dyssynergy, the higher the QRS score (hypokinesia = 3.0; akinesia = 5.4; dyskinesia = 9.1). The left ventricular ejection fraction (percent) = 66 - (3.3 x QRS score) (correlation coefficient [r] = -0.81, probability [p] less than 0.001). With use of this regression equation, the QRS score predicted angiographic left ventricular ejection fraction to within 12% of the angiographic ejection fraction in 29 of 30 additional patients studied prospectively. The QRS score was also related to clinical functional class. The worse the clinical manifestation of left ventricular dysfunction, the higher the QRS score (Killip class I = 3.5; class II = 6.5; class III = 7.1). A QRS score greater than or equal to 7 had a specificity of 97% and a sensitivity of 59% for predicting an ejection fraction of less than 45%. Patients with a QRS score of 7 or greater had severe wall motion abnormalities, higher peak serum creatine kinase levels, higher prevalence of multivessel coronary disease, poor clinical functional class and an unfavorable outcome. The QRS score provides an inexpensive, clinically useful estimate of left ventricular function after myocardial infarction and can identify patients at high risk. 相似文献
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P. Joy Ho Elizabeth M. Moore Zoe K. McQuilten Cameron Wellard Krystal Bergin Bradley Augustson Hilary Blacklock Simon J. Harrison Noemi Horvath Tracy King Peter Mollee Hang Quach Christopher Reid Brian Rosengarten Patricia Walker Erica M. Wood Andrew Spencer 《Clinical Lymphoma, Myeloma & Leukemia》2019,19(8):e415-e424
BackgroundRenal impairment (RI) is a common complication of multiple myeloma (MM) and remains a poor prognostic factor despite improved survival with newer therapies.Patients and MethodsWe evaluated baseline characteristics, treatment, and outcomes of newly diagnosed MM patients with RI at diagnosis in the Australia and New Zealand Myeloma and Related Diseases Registry over 5 years to April 2018; we compared patients with RI (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m2) with those with eGFR ≥60. In autologous stem cell transplantation (ASCT) analyses, patients aged 70 years and younger and ≥1 year from diagnosis were included.ResultsOverall, 36% of patients with newly diagnosed MM had RI; they were older, had more advanced disease and comorbidities, and worse performance status. Bortezomib-based induction therapy was most commonly used, although administered to fewer RI patients, despite similar response rates. Patients with RI were less likely to receive ASCT; however, recipients had longer progression-free survival (PFS) and overall survival (OS). Patients with RI had shorter OS and PFS after adjusting for age. In ASCT recipients with RI versus no RI, there was no difference in PFS and OS.ConclusionOur findings in “real world” MM patients with RI confirm that patient-, disease-, and treatment-related factors (such as suboptimal bortezomib and ASCT use), and delays in commencing therapy, might contribute to poorer outcomes, and support the use of ASCT in patients with RI. 相似文献
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