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811.
Interval Time Series Analysis with an Application to the Sterling-Dollar Exchange Rate 总被引:2,自引:0,他引:2
Traditional econometrics has long employed "points" to measure time series data. In real life situations, however, it suffers the loss of volatility information, since many variables are bounded by intervals in a given period. To address this issue, this paper provides a new methodology for interval time series analysis. The concept of "interval stochastic process" is formally defined as a counterpart of "stochastic process" in point-based econometrics. The authors introduce the concepts of interval stationarity, interval statistics (including interval mean, interval variance, etc.) and propose an interval linear model to investigate the dynamic relationships between interval processes. A new interval-based optimization approach for estimation is proposed, and corresponding evaluation criteria are derived. To demonstrate that the new interval method provides valid results, an empirical example on the sterling-dollar exchange rate is presented. 相似文献
812.
A major portion of the mammalian genome is transcribed to produce large numbers of noncoding RNAs(ncRNAs).During the past decade,the discovery of small RNAs,including the microRNAs(miRNA) and small interfering RNAs(siRNA),has led to important advances in biology.The breadth of the ncRNA field of study has substantially expanded and many recent results have revealed a range of functions that can be attributed to the miRNAs and other ncRNAs.For example,H19 RNA,HOTAIR RNA,transcribed ultraconserved regions(T-UCRs),natural antisense RNA,transfer RNA and mitochondrial noncoding RNA have been suggested to play important roles in cancers and other diseases as well as in diverse cellular processes.In this review,we focus on the current status of several classes of ncRNAs associated with cancer with the emphasis on those that are not microRNAs. 相似文献
813.
ChuanDeng Yi ShuZhu Tang Yong Zhou GuoHua Liang ZhiYun Gong MingHong Gu 《科学通报(英文版)》2008,53(19):2973-2980
Oryza sativa and O. latifolia belong to the AA and CCDD genomes of Oryza, respectively. In this study, interspecific hybrids of these species were obtained using the embryo rescue technique. Hybrid panicle traits, such as long awns, small grain, exoteric large purple stigma, grain shattering and dispersed panicles, resemble that of the paternal parent, O. latifolia, whereas there is obvious heterosis in such respects as plant height, tillering ability and vegetative vigor. Chromosome pairing and the genomic components of the hybrid were subsequently investigated using genomic in situ hybridization (GISH) and fluorescent in situ hybridization (FISH) analysis. Based on the mitotic metaphase chromosome numbers of the root tips investigated, the hybrid is a triploid with 36 chromosomes. The genomic constitution of the hybrid is ACD. In the meiotic metaphase Ⅰ of the hybrid pollen mother cell, poor chromosome pairing was identified and most of the chromosomes were univalent, which resulted in complete male sterility in the hybrid. 相似文献
814.
815.
从内生经济增长理论出发,探讨了基于卢卡斯人力资本模型的人力资本对经济增长的贡献,可以分解为直接贡献和间接贡献。为了说明这个理论,从人力资本要素这个角度,以改革开放以来的上海为对象进行实证研究分析,通过对各种要素在不同时期对经济增长的贡献进行分解,发现上海经济快速增长有其内生性原因,其中人力资本的作用明显,尤其是人力资本的间接贡献作用要大于直接贡献。在实证中,创造性地通过带约束的回归检验,验证了人力资本间接贡献的显著性。 相似文献
816.
Jian Wang Yu Li Yonglie Chen Zhaoxi Liang Ying Xiang Ziyang Lin Longpei Shi Zhiren Qiu 《科学通报(英文版)》2001,46(8):647-649
4[4'-(phenylazo)phenylazo]phenol was synthesized and characterized. Optical-induced Freedericksz transition of 5CB liquid crystal doped with trace diazophenyl was studied. It was observed that the doped 5CB dramatically decreased the optical field threshold, and the Freedericksz transition threshold occurred at optical intensity level of 0.3 mW/mm2 for the 12.5 μm thickness planar alignment doped 5CB, which is three orders of magnitude lower than that for the pure 5CB. This new phenomenon indicated that trans-cis isomerization of diazophenyl plays an important role in the decrease of the Freedericksz transition threshold. 相似文献
817.
针对小基高比立体匹配中的"黏合"现象和深度精度问题,提出一种小基高比立体匹配方法.该方法通过将自适应窗口技术和多窗口策略相结合为参考图像确定匹配窗口;然后根据规范化互相关函数和"胜者全取"策略计算整数级视差;再以整数级视差为基础利用基于二分法的亚像素匹配方法计算亚像级视差;最后采用基于图像分割的迭代传播方法以获得稠密视差图.实验结果表明:该立体匹配算法减少了小基高比匹配中的"黏合"现象,同时获得了稠密的高精度亚像素级视差,其亚像素精度可优于1/20个像元. 相似文献
818.
LI YiPing HE LangChong 《科学通报(英文版)》2007,52(7):922-928
A model of vascular endothelial cell membrane chromatography was established by using an ECV304 cell membrane stationary phase (ECV304 CMSP) prepared by immobilizing the ECV304 cell membrane onto the surface of silica carrier. The surface and chromatographic characteristics of ECV304 CMSP were studied. The active component from Caulophyllum robustum was screened by using the model of vascular endothelial cell membrane chromatography. The interaction between the active component and membrane receptor was determined by using a replace experiments. The effect of the active component was tested by using tube formation of ECV304 cell. The results indicated that the model of ECV304 cell membrane chromatograph (ECV304 CMC) can stimulate the interaction between drug and receptor in vitro and the retention characteristics of taspine as active component was similar to that of model molecule in the model of ECV304 CMC. And therefore, taspine acted on VEGFR2 and inhibited the tube formation of ECV304 cell induced by VEGF. This model can be used to screen definite active component as a screening model. 相似文献
819.
以亚硫酸盐与光化学反应产生碘的反应, 用于某些食品中痕量亚硫酸盐的测定. 标准加入回收率在 98% ~105% 之间, 相对标准偏差低于 4% 相似文献
820.
HuiTong Wang Na Weng ShuiChang Zhang GuangYou Zhu JianPing Chen CaiYun Wei 《科学通报(英文版)》2010,55(19):2039-2045
Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) is com-mercially available in the 1990s, with the characteristics of large peak capacity, high resolution, high sensitivity, etc. However, its application to the petroleum and geological analyses is just emerging in China and overseas. In this research, the analytical method for petroleum aromatic fraction using GC×GC-TOFMS is set up, via the choice of the column system and optimization of setting parameters, such as temperature programming, modulation time, hot pulse time, flow rate of carrier gas, data acquisition rate and data processing. The results indicate that different polar compounds of aromatic fraction distribute as bands on structured GC×GC chromatogram. Within each band, homologous compounds appear as a roof-tile structure based on the number of substituent residues. The aromatic compounds are identified and characterized according to the GC×GC chromatogram and mass spectra. According to the polarity and the number of rings, aromatic compounds are spatially present on one chromatogram, which directly reflects the distribution characteristics of complex compounds of aromatic hydrocarbons. In addition, quantitative analysis is favored as some overlapped peaks on traditional GC-MS chromatogram have been separated completely on GC×GC. Some heterocyclic atom aromatic compounds at trace level can be clearly identified using this method, for polarity differences from other interfered aromatic compounds. The development of this method and chromatogram recognition offer petroleum geologists a practical example for the application performance of GC×GC-TOFMS. 相似文献