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321.
研究了用伯胺N_(1928)从Ha_2S_2O_3-Na_2SO_3介质中萃取银的机理.由于S_2O_3~(2-)易被氧化.因此萃取时不应有氧化性离子如NO_8~-等存在,并且要加入Na_2SO_3作稳定剂.此外,有机相伯胺的硫代硫酸盐也是临用时制备的.萃取的最适合pH在3.5~6.0.萃合物的组成用4种方法测定:即Job氏法,饱和容量法,斜率法与饱和有机相的化学分析.它们都表明萃合物组成为(RNH_3)_5Aga(S_2O_3)_4.用红外光谱研究了被萃阴离子的结构,说明该阴离子为折线状,测得该反应的热力学函数为logKex=27.05.△H°=-49.3J/mol,△G°=-141.3/kJmol与△S°=517.1J/mol·K。 相似文献
322.
323.
以HTTA为端基与乙二胺、二乙三胺及丙二胺缩合制得H2TTAen,H2TTAdien,H2TTAPn3种Schiff碱.它们既类似于聚酸可作多齿螯合配体,又与p-二酮类似,其羰其可以异构成烯醇式,为一个二元酸.用多种近代分析测试方法对其组成和基本性质进行了表征,用PH电位法和光度法测定了酸离解常数. 相似文献
324.
325.
Skinner W. A. Tong H. Johnson H. Maibach H. Skidmore D. 《Cellular and molecular life sciences : CMLS》1968,24(7):679-680
Zusammenfassung Es wird gezeigt, dass menschliche Schweissabsonderungen verschiedener Versuchspersonen auf weibliche Moskitos (Aedes aegypti) verschieden attraktiv sind. Mit Diethyläther (pH 1) lassen sich im Schweiss sowohl «anlockende» wie auch «abschreckende» Bestandteile extrahieren. Für den «repellent effect» sind teilweise gleiche Mischungen von Milchsäure und Milchsäureanhydrid verantwortlich. Zwei weitere, noch nicht identifizierte Substanzen zeigten im Zwei-Kammer-Olfaktometer identische «repellent» Wirkungen.
This study was supported by U.S. Army Medical Research and Development Command, Dept. of the Army, Contracts No. DA 49-193-MD-2465 (W. Skinner) and No. DA 49-193-MD-2466 (H. Maibach). We thank Dr.L. Pope, Superintendent, and the inmates of the California Medical Faculty, Vacaville, California, USA, for their cooperation in this study. 相似文献
This study was supported by U.S. Army Medical Research and Development Command, Dept. of the Army, Contracts No. DA 49-193-MD-2465 (W. Skinner) and No. DA 49-193-MD-2466 (H. Maibach). We thank Dr.L. Pope, Superintendent, and the inmates of the California Medical Faculty, Vacaville, California, USA, for their cooperation in this study. 相似文献
326.
Evidence for dynamically organized modularity in the yeast protein-protein interaction network 总被引:1,自引:0,他引:1
Han JD Bertin N Hao T Goldberg DS Berriz GF Zhang LV Dupuy D Walhout AJ Cusick ME Roth FP Vidal M 《Nature》2004,430(6995):88-93
In apparently scale-free protein-protein interaction networks, or 'interactome' networks, most proteins interact with few partners, whereas a small but significant proportion of proteins, the 'hubs', interact with many partners. Both biological and non-biological scale-free networks are particularly resistant to random node removal but are extremely sensitive to the targeted removal of hubs. A link between the potential scale-free topology of interactome networks and genetic robustness seems to exist, because knockouts of yeast genes encoding hubs are approximately threefold more likely to confer lethality than those of non-hubs. Here we investigate how hubs might contribute to robustness and other cellular properties for protein-protein interactions dynamically regulated both in time and in space. We uncovered two types of hub: 'party' hubs, which interact with most of their partners simultaneously, and 'date' hubs, which bind their different partners at different times or locations. Both in silico studies of network connectivity and genetic interactions described in vivo support a model of organized modularity in which date hubs organize the proteome, connecting biological processes--or modules--to each other, whereas party hubs function inside modules. 相似文献
327.
BMP signaling inhibits intestinal stem cell self-renewal through suppression of Wnt-beta-catenin signaling 总被引:21,自引:0,他引:21
He XC Zhang J Tong WG Tawfik O Ross J Scoville DH Tian Q Zeng X He X Wiedemann LM Mishina Y Li L 《Nature genetics》2004,36(10):1117-1121
In humans, mutations in BMPR1A, SMAD4 and PTEN are responsible for juvenile polyposis syndrome, juvenile intestinal polyposis and Cowden disease, respectively. The development of polyposis is a common feature of these diseases, suggesting that there is an association between BMP and PTEN pathways. The mechanistic link between BMP and PTEN pathways and the related etiology of juvenile polyposis is unresolved. Here we show that conditional inactivation of Bmpr1a in mice disturbs homeostasis of intestinal epithelial regeneration with an expansion of the stem and progenitor cell populations, eventually leading to intestinal polyposis resembling human juvenile polyposis syndrome. We show that BMP signaling suppresses Wnt signaling to ensure a balanced control of stem cell self-renewal. Mechanistically, PTEN, through phosphatidylinosital-3 kinase-Akt, mediates the convergence of the BMP and Wnt pathways on control of beta-catenin. Thus, BMP signaling may control the duplication of intestinal stem cells, thereby preventing crypt fission and the subsequent increase in crypt number. 相似文献
328.
Immunogenicity of recombinant fowl-pox virus co-expressing structural protein precursor P1-2A and proteinase 3C of FMDV 总被引:1,自引:0,他引:1
JINNingyi ZHANGHongyong YINGefeng ZHENGMin LIUTong JIANGWenzheng LIZijian 《科学通报(英文版)》2004,49(8):823-823
Two recombinant plasmids, pUTA2P1 and pUTAL3CP1, were constructed by inserting structural protein precursor P1-2A and proteinase 3C of foot-and-mouth disease virus (FMDV) into fowl-pox virus (FPV) recombinant vectors pUTA-2 and pUTA-16-LacZ respectively, and two recombinant FPVs (vUTA2P1 and vUTAL3CP1) screened by the RT-PCR, IFA assay and Western blotting assay were obtained successfully. Mice injected respectively with rFPVs were induced high level specific anti-FMDV antibodies, increasing of T subtypes, and higher cytotoxicities of splenocytes than those of control groups. These results indicated that a new method was used to construct a potential candidate vaccine of FMDV. 相似文献
329.
Twenty Yongzheng copper coins were fast dat-ing by X-ray energy dispersive spectrometer with scanning electron microscope (SEM-EDS) according to official ingredient. The 20 coins were classified in two groups according to the results. Group 1 represents the coins minted before AD 1 728 and group 2 represents the coins minted after AD 1 728. At concentration range (0.00%-5.13%), the distribution of lead is not homogeneous in the coins, and the largest diameter of lead inclusion is less than 15 μm. The official fineness degrade is supported. 相似文献
330.
目前在空调专业各种教材及设计手册中,有关湿空气的各项状态参数,都是以“焓湿图”的形式给出,查看时既不方便又不精确。本运用FoxPro编程方法,将“焓湿图”变换成“湿空气状态参数表”。 相似文献