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排序方式: 共有232条查询结果,搜索用时 15 毫秒
141.
ON Semiconductor 《电源世界》2013,(5):46-50
低压降线性稳压器(LDO)是任何电源系统常用的构建模块,其选择对系统总体能耗有重要影响。本文介绍了设计人员在选择LDO时应该考虑的一些因素,对不同类型超低IQLDO的性能特点进行分析。 相似文献
142.
ON Krogmann J Traber M Jakob J Schneider M Turina OM Hess 《Canadian Metallurgical Quarterly》1998,9(5):239-248
The genotoxic activities of 8-methoxypsoralen (8-MOP) and 4,4',5'-trimethylazapsoralen (4,4',5'-TMAP) on plasmid DNA have been compared. In a previous work, 4,4',5'-TMAP, a methyl derivative of a psoralen isoster, had shown potential photochemotherapeutic activity. The mutagenic activity of mono- and bifunctional lesions caused by these compounds was evaluated both after UVA irradiation, which causes the formation of both kinds of lesions, and after a two-step irradiation procedure of the psoralen-plasmid DNA complex, which allowed monoadducts and interstrand crosslinks to be studied separately. Furthermore, we used a procedure that allowed us to evaluate both the mutagenic and recombinogenic activity of the two compounds. Results indicate that the most important difference between 8-MOP and 4,4',5'-TMAP consists in their mode of photoreaction with DNA rather than in their mutagenic potential. In fact, in all of the experimental procedures, 4,4',5'-TMAP shows a lower ability than 8-MOP to generate interstrand crosslinks. However, when comparable toxicity levels are reached, the two compounds show the same mutagenic potentiality. 相似文献
143.
AV Levin GM Kagalovski? AG Smetanin AM Samu?lenkov ON Ananko AA Maksimenko AP Semitko 《Canadian Metallurgical Quarterly》1998,46(4):32-33
Two new methods for elimination of bronchial fistulas in postresectional empyemas were tested in 40 patients. The most effective procedure was transbronchial diathermocoagulation of the draining (fistular) bronchus, with a full clinical effect being in 100% of patients), and selective foam rubber obturation in 80%. 相似文献
144.
AN Murashev OR Kunduzova ON Khokhlova NA Medvedeva OS Medvedev 《Canadian Metallurgical Quarterly》1997,60(4):32-34
The aim of the study was estimation of the incidence rate of complications arising in the course of fractional plasmapheresis (FPA), the analysis of their causes and design of prophylactic measures. 139 courses comprising 410 FPA sessions were delivered in 118 patients with various diseases. The highest rate of complications was 4.7%. If put on FPA without previous preparation, the patient experienced marked hypotension because of fast escape from circulation of 500 ml of blood. Induction of short-term hypervolemia in patients with low arterial pressure prevents emergence of cardiovascular complications in the course of blood exfusion. 相似文献
145.
C Cruz R Correa-Rotter C Mézquita ON Medina-Campos J Pedraza-Chaverrí 《Canadian Metallurgical Quarterly》1998,25(7-8):568-571
1. The concentration of renin and angiotensinogen (Ao) and the activity of angiotensin I-converting enzyme (ACE) was measured in the ascites fluid of nephrotic rats obtained 8 days after puromycin aminonucleoside (PAN) injection. 2. Ascites fluid, serum and urine proteins of these rats were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). 3. Renin, Ao and ACE were found in the ascites fluid and the percentage of the ratio ascites fluid/(plasma or serum) ranged from 5.9 to 9.9%. The electrophoretic analysis revealed that the ascites fluid contained low (Mr < 66 kDa) and high (Mr < 66 kDa) molecular weight proteins. Albumin and six proteins higher than 66 kDa were present both in the ascites fluid and in serum from nephrotic rats. 4. Data from the study suggest that some proteins in the ascites fluid, including renin, Ao and ACE, come from the plasma. It is possible that the loss of renin, Ao and ACE to the ascites fluid may be playing a role in the metabolic alterations of these three proteins in PAN-nephrotic rats. 相似文献
146.
Z Weng AC Fluckiger S Nisitani MI Wahl LQ Le CA Hunter AA Fernal MM Le Beau ON Witte 《Canadian Metallurgical Quarterly》1998,95(21):12334-12339
Cell cycle progression is monitored by highly coordinated checkpoint machinery, which is activated to induce cell cycle arrest until defects like DNA damage are corrected. We have isolated an anti-proliferative cell cycle regulator named G2A (for G2 accumulation), which is predominantly expressed in immature T and B lymphocyte progenitors and is a member of the seven membrane-spanning G protein-coupled receptor family. G2A overexpression attenuates the transformation potential of BCR-ABL and other oncogenes, and leads to accumulation of cells at G2/M independently of p53 and c-Abl. G2A can be induced in lymphocytes and to a lesser extent in nonlymphocyte cell lines or tissues by multiple stimuli including different classes of DNA-damaging agents and serves as a response to damage and cellular stimulation which functions to slow cell cycle progression. 相似文献
147.
148.
149.
ML Pardue ON Danilevskaya KL Traverse K Lowenhaupt 《Canadian Metallurgical Quarterly》1997,100(1-3):73-84
Transposable elements are abundant in the genomes of higher organisms but are usually thought to affect cells only incidentally, by transposing in or near a gene and influencing its expression. Telomeres of Drosophila chromosomes are maintained by two non-LTR retrotransposons, HeT-A and TART. These are the first transposable elements with identified roles in chromosome structure. We suggest that these elements may be evolutionarily related to telomerase; in both cases an enzyme extends the end of a chromosome by adding DNA copied from an RNA template. The evolution of transposable elements from chromosomal replication mechanisms may have occurred multiple times, although in other organisms the new products have not replaced the endogenous telomerase, as they have in Drosophila. This is somewhat reminiscent of the oncogenes that have arisen from cellular genes. Perhaps the viruses that carry oncogenes have also arisen from cellular genetic systems. 相似文献
150.
AB Satterthwaite CA Lowell WN Khan P Sideras FW Alt ON Witte 《Canadian Metallurgical Quarterly》1998,188(5):833-844
Transphosphorylation by Src family kinases is required for the activation of Bruton's tyrosine kinase (Btk). Differences in the phenotypes of Btk-/- and lyn-/- mice suggest that these kinases may also have independent or opposing functions. B cell development and function were examined in Btk-/-lyn-/- mice to better understand the functional interaction of Btk and Lyn in vivo. The antigen-independent phase of B lymphopoiesis was normal in Btk-/-lyn-/- mice. However, Btk-/-lyn-/- animals had a more severe immunodeficiency than Btk-/- mice. B cell numbers and response to T cell-dependent antigens were reduced. Btk and Lyn therefore play independent or partially redundant roles in the maintenance and function of peripheral B cells. Autoimmunity, hypersensitivity to B cell receptor (BCR) cross-linking, and splenomegaly caused by myeloerythroid hyperplasia were alleviated by Btk deficiency in lyn-/- mice. A transgene expressing Btk at approximately 25% of endogenous levels (Btklo) was crossed onto Btk-/- and Btk-/-lyn-/- backgrounds to demonstrate that Btk is limiting for BCR signaling in the presence but not in the absence of Lyn. These observations indicate that the net outcome of Lyn function in vivo is to inhibit Btk-dependent pathways in B and myeloid cells, and that Btklo mice are a useful sensitized system to identify regulatory components of Btk signaling pathways. 相似文献