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171.
Shiheng Tao Xiaoming Liu Jianhua Chu Rongmei Zhang Liping Du Zewei Luo 《科学通报(英文版)》2001,46(5):358-363
Modeling linkage disequilibria (LD) between genes usually observed in admixed natural populations has been shown an effective approach in high-resolution mapping of disease genes in humans. A prerequisite to obtain accurate estimation of recombination fraction between genes at a marker locus and the disease locus using the approach is a reliable prediction of the proportion of the admixture populations. The present study suggested the use of gene frequencies to predict the estimate of the admixture proportion based on the observation that the gene frequencies are much more stable quantities than the haplotype frequencies over evolution of the population. In this paper, we advanced the theory and methods by which the decay rate of nonlinear term of LD in admixed population may be used to estimate the recombination fraction between the genes. Theoretical analysis and simulation study indicate that, the larger the difference of gene frequencies between parental populations and the more closely the admixture proportion approaches 0.5, the more important the nonlinear term of the LD in the admixed population, and hence the more informative such admixed populations in the high-resolution gene mapping practice. 相似文献
172.
氘化、氟化对塑料光纤损耗性能的影响 总被引:2,自引:0,他引:2
利用Morse势能理论,计算了不同化学键C-X(X分别为H、D、F)的振动吸收损耗,发现在波长小于3000nm时,C-H键的损耗最大,C-D键的次之,C-F键的最小;在波长大于3000nm时,C-F键的损耗超过C-D键的,因为塑料光纤本征损耗主要是C-H的振动吸收损耗,如果用D、F替代塑料光纤材料中C-H的H,C-X在可见光区及红外光区的振动吸收损耗就能显著降低,利用氘化、氟化的聚合物材料可制备出损耗小于10dB/km的低损耗塑料光纤,研究结果为降低塑料光纤损耗提供了新的理论依据。 相似文献
173.
A defined range of guard cell calcium oscillation parameters encodes stomatal movements. 总被引:59,自引:0,他引:59
G J Allen S P Chu C L Harrington K Schumacher T Hoffmann Y Y Tang E Grill J I Schroeder 《Nature》2001,411(6841):1053-1057
Oscillations in cytosolic calcium concentration ([Ca2+]cyt) are central regulators of signal transduction cascades, although the roles of individual [Ca2+]cyt oscillation parameters in regulating downstream physiological responses remain largely unknown. In plants, guard cells integrate environmental and endogenous signals to regulate the aperture of stomatal pores and [Ca2+]cyt oscillations are a fundamental component of stomatal closure. Here we systematically vary [Ca2+]cyt oscillation parameters in Arabidopsis guard cells using a 'calcium clamp' and show that [Ca2+]cyt controls stomatal closure by two mechanisms. Short-term 'calcium-reactive' closure occurred rapidly when [Ca2+]cyt was elevated, whereas the degree of long-term steady-state closure was 'calcium programmed' by [Ca2+]cyt oscillations within a defined range of frequency, transient number, duration and amplitude. Furthermore, in guard cells of the gca2 mutant, [Ca2+]cyt oscillations induced by abscisic acid and extracellular calcium had increased frequencies and reduced transient duration, and steady-state stomatal closure was abolished. Experimentally imposing [Ca2+]cyt oscillations with parameters that elicited closure in the wild type restored long-term closure in gca2 stomata. These data show that a defined window of guard cell [Ca2+]cyt oscillation parameters programs changes in steady-state stomatal aperture. 相似文献
174.
175.
简要介绍核级蓄电池模拟地震试验的试件选择、安装环境的模拟以及试验的基本程序,重点讨论地震荷载作用期间蓄电池连续放电特性,以及试验前后蓄电池容量的考核等特性问题。验证了样机设计的可靠性及合理性,为改进设计及现场安装提供了依据。还论证了国产蓄电池应用在核电领域中的可行性。 相似文献
176.
CREB is activated in EPO induced HEL cells 总被引:1,自引:0,他引:1
177.
With the 2.16 m telescope at Beijing Astronomical Observatory, it is identified that a compact X-ray source detected by ROSAT
located in the vicinity of 5′.9 from the LINER galaxy NGC4579 is a quasar with a redshift z = 0.106. A further analysis indicates
that this quasar is possibly ejected from NGC4579. 相似文献
178.
The two-step monsoon changes of the last deglaciation recorded in tropical Maar Lake Huguangyan, southern China 总被引:3,自引:0,他引:3
Wenyuan Wang Jiaqi Liu Dongsheng Liu Tungsheng Liu Ping’an Peng Houyuan Lu Zhaoyan Gu Guoqiang Chu J. Negendank Xiangjun Luo J. Mingram 《科学通报(英文版)》2000,45(16):1529-1532
The concentrations of biogenic silica, total organic carbon, total nitrogen and total hydrogen inferred from the sediments
of tropical Maar Lake Huguangyan, southern China, provide a climate record of the last déglaciation with century resolution.
The records fully demonstrate the existence of the two-step shape of the last déglaciation in tropic East Asia, and they point
out noticeable differences between the low and high latitudes in the Northern Hemisphere. Thus, the Boiling first warming
at the last deglaciation in the low latitude may have preceded that of the high latitude, whereas the cooling of the Younger
Dryas occurred synchronously in the two regions. These results likely suggest that the links between the low and high latitude
climates in the Northern Hemisphere during this period are complexity. 相似文献
179.
新型炎症显像剂的初步研究 总被引:1,自引:1,他引:0
对柠檬酸(Cit)、酒石酸(Tar)、DL-苹果酸(DL-Mal)、L-苹果酸(L-Mal)和D-葡萄糖二酸(D-Gca)等5种含有羟基和羟在的小分子化合物的^99mTc标记条件以及亲炎症的生物性能进行了初步研究。根据它们的最佳标记条件,分别对其进行标记。标记率均大于90%,这5种配合物和^99mTcO4^-4(P)的松节油致炎小鼠中的生物分布结果表明,炎症模型脓肿与肌肉的质量活度分数之比值(am 相似文献
180.
在物化实验中用自编程序实现计算机数据处理 总被引:1,自引:0,他引:1
在我们所开设的物理化学实验中有许多电化学实验,用扫描恒电位仪发出信号,X-Y记录仪接收信号,因为普通扫描情怀电位仪没有计算机接口,所以不能用计算机采集数据及处理。本文通过采用信号处理仪代替X-Y记录仪采用数据并通过自编软件帝现数据转换,再用美国EG&G-PAR公司提供的电化学软件包解析数据,实现数据采集及处理的计算机化,减小了数据记录及处理的误差,求得了相应的电化学参数。 相似文献