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461.
The effect of alkalinity, transition metals and oxygen on alkali darkening of mechanical pulp, and its relations to subsequent peroxide bleaching were investigated. The chromophores generated under mild conditions of an alkaline treatment can be destroyed in a subsequent peroxide stage.Peroxide-resistant chromophores are generated only under severe conditions. The results also show that a short alkaline pretreatment can improve the performance of a peroxide bleaching stage. 相似文献
462.
IntroductionIt is reasonable to expect the fibre distribution in across-section of a blended yarn to have an influence on theperfor mance of the yarn. This is particularly so if one ofthe components has specific inherent property of interest .In this paper ,the specific property is fire retardancy (FR)in conex fibre . The objective is establishing the fibredistribution resulting fromvarious input sliver arrangementin friction spinning .The distribution of fibres in blended yarns has beenthes… 相似文献
463.
464.
Structure and transcription of human papillomavirus sequences in cervical carcinoma cells 总被引:36,自引:0,他引:36
E Schwarz U K Freese L Gissmann W Mayer B Roggenbuck A Stremlau H zur Hausen 《Nature》1985,314(6006):111-114
465.
Primary structure of the precursor to the three major surface antigens of Plasmodium falciparum merozoites 总被引:12,自引:0,他引:12
A A Holder M J Lockyer K G Odink J S Sandhu V Riveros-Moreno S C Nicholls Y Hillman L S Davey M L Tizard R T Schwarz 《Nature》1985,317(6034):270-273
Recently, a class of protein antigens of high relative molecular mass (Mt) which can induce protective immunity against blood-stage malaria has been identified. In Plasmodium falciparum the protein has a Mr of approximately 195,000 (P195). It is the precursor of three proteins of Mr 83,000 (83K), 42K and 19K which are the major surface antigens of merozoites; thus it may also be useful for immunization against P. falciparum. Three studies describing the isolation of single short complementary DNA clones for part of the P195 gene sequence have been reported. Here we describe the complete structure of the P195 gene determined from further DNA clones, its organization within genomic DNA and the location of the specific processing fragments within the primary amino-acid sequence. 相似文献
466.
Michael K. Berkowitz Nancy T. Gallini Eric J. Miller Robert A. Wolfe 《Journal of forecasting》1987,6(4):249-269
A case study in which a three-stage choice model of Canadian household vehicle holdings and usage is used to generate short-run forecasts of changes in household vehicle usage and gasoline consumption in response to a range of energy-related policies. The objectives of this case study are to (1) demonstrate the application of disaggregate choice modelling methods to the generation of policy-relevant forecasts of travel behaviour; (2) draw implications from this forecasting exercise concerning the likely impacts of various energy-related policies; and (3) assess some of the strengths and weaknesses of the current state-of-the-art of forecasting with disaggregate choice models, using the presented study as a case in point. 相似文献
467.
468.
本研究通过显微注射技术将TRPV1 cRNA(1ng/nL)注射至非洲爪蟾卵母细胞(20nL/个)体内,放置于G-ORi培养液中,并在(19±1)℃的恒温培养箱内表达.同时利用灌流技术将不同浓度梯度的大黄素、辣椒素按照设计顺序依次灌流进入流动腔,同时控制流速保证非洲爪蟾卵母细胞完全浸没于流动腔内.使用双电极电压钳技术记录0.1,1.0,10.0,50.0μmol/L浓度梯度的大黄素对500nmol/L浓度的辣椒素激活TRPV1电流的影响.得到大黄素作用辣椒素激活TRPV1通道的抑制作用表现出浓度依耐性和电压非依赖性,IC50=38μmol/L,Hill系数n=0.5.结果表明了大黄素对TRPV1位点的相互作用是负协同的,在天然药物里面是一类比较弱的拮抗剂,且大黄素在ORi溶液中开始析出沉淀的浓度在50~60μmol/L之间.我们首次发现了大黄素能够抑制TRPV1通道电流,这可能为开发新的镇痛药物提供理论基础. 相似文献
469.
A molecular signature of metastasis in primary solid tumors 总被引:54,自引:0,他引:54
Metastasis is the principal event leading to death in individuals with cancer, yet its molecular basis is poorly understood. To explore the molecular differences between human primary tumors and metastases, we compared the gene-expression profiles of adenocarcinoma metastases of multiple tumor types to unmatched primary adenocarcinomas. We found a gene-expression signature that distinguished primary from metastatic adenocarcinomas. More notably, we found that a subset of primary tumors resembled metastatic tumors with respect to this gene-expression signature. We confirmed this finding by applying the expression signature to data on 279 primary solid tumors of diverse types. We found that solid tumors carrying the gene-expression signature were most likely to be associated with metastasis and poor clinical outcome (P < 0.03). These results suggest that the metastatic potential of human tumors is encoded in the bulk of a primary tumor, thus challenging the notion that metastases arise from rare cells within a primary tumor that have the ability to metastasize. 相似文献
470.
Cell-specific mitotic defect and dyserythropoiesis associated with erythroid band 3 deficiency 总被引:11,自引:0,他引:11
Paw BH Davidson AJ Zhou Y Li R Pratt SJ Lee C Trede NS Brownlie A Donovan A Liao EC Ziai JM Drejer AH Guo W Kim CH Gwynn B Peters LL Chernova MN Alper SL Zapata A Wickramasinghe SN Lee MJ Lux SE Fritz A Postlethwait JH Zon LI 《Nature genetics》2003,34(1):59-64
Most eukaryotic cell types use a common program to regulate the process of cell division. During mitosis, successful partitioning of the genetic material depends on spatially coordinated chromosome movement and cell cleavage. Here we characterize a zebrafish mutant, retsina (ret), that exhibits an erythroid-specific defect in cell division with marked dyserythropoiesis similar to human congenital dyserythropoietic anemia. Erythroblasts from ret fish show binuclearity and undergo apoptosis due to a failure in the completion of chromosome segregation and cytokinesis. Through positional cloning, we show that the ret mutation is in a gene (slc4a1) encoding the anion exchanger 1 (also called band 3 and AE1), an erythroid-specific cytoskeletal protein. We further show an association between deficiency in Slc4a1 and mitotic defects in the mouse. Rescue experiments in ret zebrafish embryos expressing transgenic slc4a1 with a variety of mutations show that the requirement for band 3 in normal erythroid mitosis is mediated through its protein 4.1R-binding domains. Our report establishes an evolutionarily conserved role for band 3 in erythroid-specific cell division and illustrates the concept of cell-specific adaptation for mitosis. 相似文献