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排序方式: 共有862条查询结果,搜索用时 15 毫秒
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N. Nikbakht J. C. McLachlan 《Proceedings. Biological sciences / The Royal Society》1999,266(1424):1101
The precise identification of the digits of the avian wing is of importance in evolutionary studies. If the digits are numbered two, three and four, this has been taken to suggest that birds are not descended directly from dinosaurs. If the digits are numbered one, two and three, dinosaur origins become more plausible. Studies of the development of the avian wing have failed to resolve this dilemma. However, in some instances, it is possible to deduce information about evolutionary morphologies by manipulating development experimentally. We grafted beads loaded with fibroblast growth factor 4 into the distal tip of chick wing buds at times when the apical ectodermal ridge is regressing. The consequence was that the cartilage structure conventionally labelled ''element 5'' increased dramatically in size and acquired a digit-like morphology in some instances. Corresponding changes in soft tissue morphology were also observed. We conclude that it may be possible to resolve the issue of avian digit homology by the induction of experimental atavisms of this kind. 相似文献
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Mohsen A. Jafari 《Flexible Services and Manufacturing Journal》1989,2(1):63-86
We consider a flexible manufacturing system with a number of workstations, a single material transporter, and a common storage space of finite capacity. The material handling delay times are explicitly considered in the model and assumed to follow a two-stage Coxian distribution. The material processing times on a workstation also have a two-stage Coxian distribution. The routing of parts within the system follows a Markov chain. An approximate performance model is developed and the results are compared with the exact or simulation results. We also investigate how this performance model compares to a simulation with deterministic routing and processing times. Finally, we study the effect, on the performance measures, of ignoring the material transporter or of modeling the transporter as a central server with aggregation of routing information. 相似文献
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Mohsen A. F. El-Hazmi Hassan M. Bahakim Arjumand S. Warsy Abdulkarim Al-Momen Abdullah Al-Wazzan Ibrahim Al-Fawwaz Sameer Huraib Mohammad Harakati 《Molecular and cellular biochemistry》1993,124(1):17-22
Sickle cell anaemia (SCA) exhibits significant variations in clinical presentation in different populations for which several genetic factors including SCA-associated -and -thalassaemias, G-6-PD deficiency and elevated Hb F level have been implicated as possible ameliorating factors. Saudi Arabia is unique in that mild and severe forms of the disease occur at a high frequency. We investigated the G/A ratio and Hb F level and correlated these values with the severity of SCA. The results showed that Hb F level varies significantly in both groups of patients with no evident correlation with the mild clinical manifestations. However, G/A ratio correlated significantly with the disease severity where a high ratio was observed in patients with the mild and a low ratio in patients with the severe disease. The results are evaluated and discussed in the light of correlation studies and regression analysis. 相似文献
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This report describes the cases of three mentally and physically well-developed siblings, 12, 10, and 8 years of age, with varying degrees of isolated valvular pulmonic stenosis not related to age. The severest lesion occurred in the middle patient and was associated with a right-to-left shunt through a patent foramen ovale. The three children had no other siblings, and there was no history of congenital heart disease among close relatives. These cases support the conclusion that genetic factors play a significant role in the development of certain congenital cardiac disorders. 相似文献
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Amir Ali Rahsepar Asadollah Mirzaee Fatemeh Moodi Mohsen Moohebati Shima Tavallaie Fatemeh Khorashadizadeh Ali Eshraghi Maryam-Sadat Alavi Laya Zarrabi Mostafa Sajjadian Maral Amini Roshanak Khojasteh Roghayeh Paydar Somayeh Mousavi Majid Ghayour-Mobarhan Gordon A. Ferns 《Cell stress & chaperones》2013,18(1):65-74
The relationship between serum anti-heat shock protein (Hsp)27 antibody and high sensitive C-reactive protein (hs-CRP) levels and indices of cardiac function were investigated in patients undergoing coronary artery bypass grafting (CABG) or heart valve replacement. The changes in anti-Hsp27 antibody titers and hs-CRP levels were compared among patients undergoing off-pump and on-pump CABG or valvular heart replacement. Fifty-three patients underwent off-pump, on-pump CABG, and heart valvular replacement in each group. Serum anti-Hsp27 titers and hs-CRP values were measured 24 h before and after the operation and at discharge. Echocardiography was performed before surgery and before discharge. The results were compared with values from 83 healthy controls. hs-CRP levels increased and anti-Hsp27 antibody decreased following surgery (P < 0.001 and P < 0.05, respectively), although these changes were independent of operative procedure (P = 0.361 and P = 0.120, respectively). Anti-Hsp27 antibody levels were higher at the time of discharge (P = 0.016). Only in coronary patients were anti-Hsp27 antibody levels negatively associated with E/E′ (r = −0.268, P = 0.022), a marker of pulmonary capillary wedge pressure. In conclusions, anti-Hsp27 antibody levels are associated with indices of cardiac function in coronary patients. Cardiopulmonary bypass had no significant effect on the induction of changes in anti-Hsp27 levels. Moreover, anti-Hsp27 antibody levels fell in all groups postoperatively; this may be due to the formation of immune complexes of antigen–antibody, and antibody levels were higher at the time of discharge.
Electronic supplementary material
The online version of this article (doi:10.1007/s12192-012-0358-y) contains supplementary material, which is available to authorized users. 相似文献8.
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Mohsen Akbari Mehran Torki Keyomars Kaviani 《International journal of biometeorology》2016,60(3):447-454
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