氢燃料发动机性能参数的研究

针对氢作为发动机燃料的优越性以及氢燃料发动机的特点、技术发展趋势进行了简要概括,并在此基础上,结合实验研究,对压缩比、当量比、过量空气系数对氢燃料发动机性能的影响进行了分析研究.     

Characteristics of Listeria monocytogenes strains isolated in Russia and their typing using pulse electrophoresis

On the basis of specially developed scheme for the isolation of Listeria strains comprising 2 enrichment stages and the use of growth inhibitors, 128 L. monocytogenes cultures were isolated from clinical material, foodstuffs and sewage water. Highly virulent L.monocytogenes strains isolated from clinical material belonged to serovar 4b (54%) and 1/2a (38%), while those isolated from foodstuffs and sewage water belonged to 4b (74%). The restriction analysis of the chromosomal DNA of the isolated cultures with the use of restrictase EcoR1 on the basis of pulsed-field gel electrophoresis (PFGE) made it possible to distinguish Listeria strains in accordance with 5 types of restrictograms. The restrictograms of highly virulent L. monocytogenes strains, serovar 4b, belonged to types 1 and 2, while those of L. monocytogenes strains, serovar 1/2a, belonged to types 2 and 3. The comparative use of different methods for typing L. monocytogenes (sero-, phago-, bio- and resistotyping, the analysis of plasmid composition and restriction analysis) revealed that the combination of serotyping and restriction analysis on the basis of PFGE proved to be most promising for the characterization of the isolated L. monocytogenes strains and the assessment of their epidemic importance.     

Identification of residues 99, 220, and 221 of human cytochrome P450 2C19 as key determinants of omeprazole activity

Human P450 2C19 is selective for 4'-hydroxylation of S-mephenytoin and 5-hydroxylation of omeprazole, while the structurally homologous P450 2C9 has low activity toward these substrates. To identify the critical amino acids that determine the specificity of human amino acids that determine the specificity of human P450 2C19, we constructed chimeras of p450 2C9 replacing various proposed substrate binding sites (SRS) with those of P450 2C19 and then replaced individual residues of P450 2C19 and then replaced individual residues of P450 2C9 by site-directed mutagenesis. The 339 NH2-terminal amino acid residues (SRS-1-SRS-4) and amino acids 160-383 (SRS-2-SRS-5) of P450 2C19 conferred omeprazole 5-hydroxylase activity to P450 2C9. In contract, the COOH terminus of P450 2C19 (residues 340-490 including SRS-5 and SRS-6), residues 228-339 (SRS-3 and SRS-4) and residues 292-383 (part of SRS-4 and SRS-5) conferred only modest increases in activity. A single mutation Ile99 --> His increased omeprazole 5-hydroxylase to approximately 51% of that of P450 2C19. A chimera spanning residues 160-227 of P450 2C19 also exhibited omeprazole 5-hydroxylase activity which was dramatically enhanced by the mutation Ile99 --> His. A combination of two mutations, Ile99 --> His and Ser200 --> Pro, converted P450 2C9 to an enzyme with a turnover number of omeprazole 5-hyrdroxylation, which resembled that of P450 /c19. Mutation of Pro221 --> Thr enhanced this activity. Residue 99 is within SRS-1, but amino acids 220 and 221 are in the F-G loop and outside any known SRS. Mutation of these three amino acids did not confer significant S-mephenytoin 4'-hydroxylase activity to P450 2C9, although chimeras containing SRS-1-SRS-4 and SRS-2-SRS-5 of P450 2C19 exhibited activity toward this substrate. Our results thus indicate that amino acids 99, 220, and 221 are key residues that determine the specificity of P450 2C19 for omeprazole.     

Modulation of interferon-gamma-induced macrophage activation by phosphotyrosine phosphatases inhibition. Effect on murine Leishmaniasis progression

Phagocyte functions are markedly inhibited after infection with the intracellular protozoan parasite Leishmania. This situation strongly favors the installation and propagation of this pathogen within its mammalian host. Previous findings by us and others have established that alteration of several signaling pathways (protein kinase C-, Ca2+- and protein-tyrosine kinases-dependent signaling events) were directly responsible for Leishmania-induced macrophage (MO) dysfunctions. Here we report that modulation of phosphotyrosine-dependent events with a protein tyrosine phosphatases (PTP) inhibitor, the peroxovanadium (pV) compound bpV(phen) (potassium bisperoxo(1,10-phenanthroline)oxovanadate(Vi)), can control host-pathogen interactions by different mechanisms. We observed that the inhibition of parasite PTP resulted in an arrest of proliferation and death of the latter in coincidence with cyclin-dependent kinase (CDK1) tyrosine 15 phosphorylation. Moreover the treatment of MO with bpV(phen) resulted in an increased sensitivity to interferon-gamma stimulation, which was reflected by enhanced nitric oxide (NO) production. This enhanced IFN-gamma-induced NO generation was accompanied by a marked increase of inducible nitric oxide synthase (iNOS) mRNA gene and protein expression. Finally we have verified the in vivo potency of bpV(phen) over a 6-week period of daily administration of a sub-toxic dose. The results revealed its effectiveness in controlling the progression of visceral and cutaneous leishmaniasis. Therefore PTP inhibition of Leishmania and MO by the pV compound bpV(phen) can differentially affect these eukaryotic cells. This strongly suggests that PTP plays an important role in the progression of Leishmania infection and pathogenesis. The apparent potency of pV compounds along with their relatively simple and versatile structure render them attractive pharmacological agents for the management of parasitic infections.     

无线信道动态树碰撞解决算法的性能分析

一般的随机访问信道(RACH)，延时特性只有均值，很难有明确的上限保证，所以对部分实时业务性能难以保证。树型算法则可以对日前处理的业务提供明确的延时上限，然而一般的固定树型算法对于无线信道的业务波动情况没有适应能力，例如树型分支固定，只能适合一定强度的到达业务，其他情况下会导致信道利用率下降和延时增加。本文针对随机访问信道协议，在固定树型算法的基础上，结合随机接续协议，给出了一种混合动态树型算法，目的是提高一般树型算法的信道利用率，保证延时指标的上限。     

座式水轮机调速器机械液压随动系统的研制与应用

 针对传统的水轮机调速器机械液压系统布置方式上的不足，采取将机械液压系统安装在水轮机层的方案，研制了DJT-80WZ型电动集成座式调速器，并成功应用于尼泊尔波迪·科西电站。研究结果表明，该型机械液压随动系统不仅结构简单，安装方便，操作维护量小，而且性能指标得到提高，转速死区ix≤0.030；空载转速摆动值自动时为±0.06%，手动时为±0.08%；接力器不动时间Tq=0.14 s；甩最大负荷时Tp=36 s。同时，结合当前国内调速器技术发展现状，阐述了推广应用座式调速器的必要性。     

基于SA605和AD9850的接收电路设计及应用

本文介绍了一款Philips公司生产的通信专用芯片SA605的基本功能及特性，并基于SA605，与当前飞速发展的DDS技术相结合，设计了一种简洁实用的RF信号接收方案。该方案可用于空间信号检测仪接收端。本文较详细地阐述了电路实现中的若干问题以及解决方法。     

非线性编辑中场序的判断及处理

非线性技术与电视领域在场方式处理方面的差异常导致一些问题的发生,这些问题往往会导致原本"完美"的电视画面变得不完美.下面就此问题进行分析并探讨解决方法.     

丹江口大坝加高工程贴坡新老混凝土结合施工技术

论述了南水北调中线水源工程丹江口大坝加高工程贴坡新老混凝土结合施工的技术要求、施工程序、施工方法及质量控制措施等。