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901.
本文研究了陕北神府矿区大柳塔井田2~(-2)煤层中煤样的显微组成,岩石类型及煤的300℃前氧化放热与燃点的关系。实验中发现,丝质组以及丝炭氧化放热量最大而燃点最低,镜质组以及镜煤氧化放热量最小,而燃点最高。随着各煤岩类型中丝质组含量的增高,其氧化放热量增加,燃点降低。因此丝质组及丝炭是最易自燃的显微组分和煤岩类型,并对其易自燃的原因进行了探讨。 相似文献
902.
本文介绍了一种实用的数字超声电视测井实验模拟系统,该系统用EP ROM存贮特定的图样作为回波信号的幅度信息,用逻辑电路产生回波信号的时间信息和各种同步控制信号,并处理为4PSK信号传送.该系统可对超声电视测井系统的主要电性能进行实验模拟研究,也可以作为诊断设备对井上检测设备及图象处理系统的工作状态进行诊断. 相似文献
903.
本文详细讨论了描述量子系统的动力学行为的三种图象,即Schrodinger图象,Heisenberg图象和相互作用图象。 相似文献
904.
Chromosome instability and immunodeficiency syndrome caused by mutations in a DNA methyltransferase gene 总被引:71,自引:0,他引:71
Xu GL Bestor TH Bourc'his D Hsieh CL Tommerup N Bugge M Hulten M Qu X Russo JJ Viegas-Péquignot E 《Nature》1999,402(6758):187-191
The recessive autosomal disorder known as ICF syndrome (for immunodeficiency, centromere instability and facial anomalies; Mendelian Inheritance in Man number 242860) is characterized by variable reductions in serum immunoglobulin levels which cause most ICF patients to succumb to infectious diseases before adulthood. Mild facial anomalies include hypertelorism, low-set ears, epicanthal folds and macroglossia. The cytogenetic abnormalities in lymphocytes are exuberant: juxtacentromeric heterochromatin is greatly elongated and thread-like in metaphase chromosomes, which is associated with the formation of complex multiradiate chromosomes. The same juxtacentromeric regions are subject to persistent interphase self-associations and are extruded into nuclear blebs or micronuclei. Abnormalities are largely confined to tracts of classical satellites 2 and 3 at juxtacentromeric regions of chromosomes 1, 9 and 16. Classical satellite DNA is normally heavily methylated at cytosine residues, but in ICF syndrome it is almost completely unmethylated in all tissues. ICF syndrome is the only genetic disorder known to involve constitutive abnormalities of genomic methylation patterns. Here we show that five unrelated ICF patients have mutations in both alleles of the gene that encodes DNA methyltransferase 3B (refs 5, 6). Cytosine methylation is essential for the organization and stabilization of a specific type of heterochromatin, and this methylation appears to be carried out by an enzyme specialized for the purpose. 相似文献
905.
Obtaining transgenic rice resistant to rice fungal blast disease by controlled cell death strategy 总被引:1,自引:0,他引:1
MAOShengji GUHongya QULijia CHENZhangliang 《科学通报(英文版)》2003,48(16):1753-1759
The strategy of the two-component system,composed of Barnase and Barstar which encode RNase and a specific inhibitor to the RNase respectively, is adopted to obtain transgenic rice resistant to rice fungal blast disease. In this study, two chimeric promoters, induced by rice blast fungus pathogen (Magnaporthe grisea), are fused with Barnase respectively to construct two plant expression vectors, pWBNBS and pPBNBS together with the Barstar driven by CaMV 35S promoter. The resistance of the transgenic rice lines to rice blast fungus disease and rice blight disease are evaluated. The results show that (1) the expression of Barnase is induced in rice leaves when inoculated with the spores of Magnaporthe grisea; (2) the induced expression level of Barnase surpasses the level of Barstar, which elicits a similar hypersensitive response (HR) in the leaves, and the transgenic plant shows high resistance to the rice fungal blast disease; and (3) transgenic rice plants also show obvious resistance to rice bacterial blight disease. Taken together, these results suggest that the transgenic rice plants harboring this two-component system acquire relatively broad spectrum resistance against pathogens, especially high resistance to rice fungal pathogen. 相似文献
906.
Microtubule associated protein tau binds to double-stranded but not single-stranded DNA 总被引:3,自引:0,他引:3
Hua Q He RQ Haque N Qu MH del Carmen Alonso A Grundke-Iqbal I Iqbal K 《Cellular and molecular life sciences : CMLS》2003,60(2):413-421
Tau, a major microtubule-associated protein of the neuron, which is known to promote the assembly of and to stabilize microtubules,
has also been seen associated with chromatin in neuronal cell lines, but its role in this subcellular compartment is still
unknown. In this study, the binding of tau to DNA was investigated using the electrophoretic mobility shift assay. Using polynucleotide
as probe, we found that tau bound to double-stranded but not to single-stranded DNA. Formation of tau-polynucleotide complex
was disrupted by alkaline pH and a high concentration of NaCl, but was not affected by dithiothreitol. Electron microscopy
revealed that the protein associated with the nucleic acid in a necklacelike manner. DNA-cellulose chromatography and radioimmunodot-blot
analyses showed that calf thymus histones VI-S, VII-S and VIII-S could replace both recombinant human brain tau352 (tau-23) and tau441 (tau-40) from DNA. Thus, tau appears to bind to DNA reversibly in the presence of histones.
Received 24 November 2002; received after revision 28 December 2002; accepted 30 December 2002
RID="*"
ID="*"Corresponding author. 相似文献
907.
Photoelectrochemical synergetic degradation of Acid Orange II with TiO2 modified β-PbO2 electrode 总被引:1,自引:0,他引:1
LIGuoting QUJiuhui WURongcheng 《科学通报(英文版)》2005,50(12):1185-1190
Electrochemically assisted photocatalysis is an effective approach to improve photocatalytic efficiency. In this paper, modified β-PbO2 electrode was prepared by TiO2 co-deposition and characterized by SEM and XRD. Then 2.0g TiO2 modified β-PbO2 electrode (2.0 g TiO2 involved in the 200 mL co-deposition solution) was used in electrochemically assisted photocatalytic degradation of Acid Orange II and the influence of initial pH values was investigated when the potential applied across the electrodes was 1.5 V. When the potential applied was 2.5 V, the difference of the degradation process and the final products were studied. The results indicated that 2.0 g TiO2 modified β-PbO2 electrode was different from the unmodified one in that the β-PbO2 crystals became finer and the electrode became more compact and more uniform. The synergetic effect in electrochemically assisted photocatalytic degradation of Acid Orange Ⅱ was observed and degradation efficiency and TOC removal were the highest at initial solution pH 2.0. By UV-visible spectral analysis, it was proved that photoelectrochemical synergetic degradation of Acid Orange Ⅱ went through the step of producing main product maleic acid for the solution at the initial pH 2.0 within 2 h, but the degradation was slow for the solution at the initial pH 12.0. 相似文献
908.
纳米固体超强酸SO4^2-/TiO2的制备及其催化活性 总被引:5,自引:0,他引:5
以廉价的无机盐TiCl4为原料,采用溶胶-凝胶法结合超临界流体干燥技术制备出纳米TiO2粉末,经硫酸溶液浸泡、活化后制成纳米固体超强酸SO4^2-/TiO2.着重探讨了纳米固体超强酸的制备条件,并将其用于乙酸正丁酯的合成反应以考察其催化活性.结果表明:该法制备的纳米固体超强酸SO4^2-/TiO2具有很强的催化活性,且制备成本低,反应时间短,酯化率高. 相似文献
909.
严宣辉 《福建师范大学学报(自然科学版)》2005,21(1):20-24
给出一种智能神经网络与证据组合推理相结合的网络入侵检测方法,将神经网络检测结果认为是"证据",并引入D-S证据理论进行组合推理,为解决连续时间序列入侵行为判别的问题提供了一种新方法,并且能提高入侵检测的判别精度。 相似文献
910.
针对三维荧光显微镜成像中的光致漂白效应导致的图像质量下降问题,提出了一种荧光衰减曲线测量方法,并基于测量的荧光衰减曲线给出双指数曲线拟合,将拟合曲线用于活体细胞的三维荧光图像恢复.在此基础上给出期望最大化算法国像恢复结果,并对恢复结果做出分析.结果显示本文的方法可以对三维荧光显微成像中存在的荧光衰减进行有效补偿. 相似文献