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51.
We observe that daily highs and lows of stock prices do not diverge over time and, hence, adopt the cointegration concept and the related vector error correction model (VECM) to model the daily high, the daily low, and the associated daily range data. The in‐sample results attest to the importance of incorporating high–low interactions in modeling the range variable. In evaluating the out‐of‐sample forecast performance using both mean‐squared forecast error and direction of change criteria, it is found that the VECM‐based low and high forecasts offer some advantages over alternative forecasts. The VECM‐based range forecasts, on the other hand, do not always dominate—the forecast rankings depend on the choice of evaluation criterion and the variables being forecast. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
52.
Steidl C Shah SP Woolcock BW Rui L Kawahara M Farinha P Johnson NA Zhao Y Telenius A Neriah SB McPherson A Meissner B Okoye UC Diepstra A van den Berg A Sun M Leung G Jones SJ Connors JM Huntsman DG Savage KJ Rimsza LM Horsman DE Staudt LM Steidl U Marra MA Gascoyne RD 《Nature》2011,471(7338):377-381
53.
Comparative Study on Shearing Edge Quality Influence of the Change of Tool Geometry in Fine-Blanking for Non-homogeneous Materials 总被引:1,自引:0,他引:1
Excellent quality of shearing edge implies that a s mo oth cutting edge without tearing will be observed on the whole edge surface. Thi s is one of the most significant features of the Fine-blanking process. To achi eve such a superb blanking edge quality in fine-blanking, there actually involv es quite a large number of factors, such as blanking speed, processing material, product shape, lubrication and tool geometry, to be considered simultaneously d uring the operation. Nevertheless, the thorough invest... 相似文献
54.
This paper describes an investigation in the fabric longi-tudinal compressibility of thirty-one suiting and trouse-ring materials using a newly developed device attached to the advanced Instron extensometer Model4466.The at-tachment was designed mainly to ensure a correct align-meat of fabric plane at the start of compression.Usingthe newly developed testing method,fabric longitudinalcompression curve was obtained and the results of longi-tudinal compressibility measured by two different com-pression load ranges(from 0 to 0.5 N/m width and 0 to1 N/m width)were examined.In addition,their rela-tionships with the fabric low-stress mechanical proper-ties measured by the KES-F system were investigatedusing statistical analysis.The results clearly indicatedthat significant differences existed when substituting fab-ric longitudinal compressibility with fabric extensibilitymeasured using the KES-F system under a low-load.Significant infiuence of yarn rotational movement in fab-ric on the longitudinal compressibi 相似文献
55.
Bmi1 is essential for cerebellar development and is overexpressed in human medulloblastomas 总被引:1,自引:0,他引:1
Leung C Lingbeek M Shakhova O Liu J Tanger E Saremaslani P Van Lohuizen M Marino S 《Nature》2004,428(6980):337-341
Overexpression of the polycomb group gene Bmi1 promotes cell proliferation and induces leukaemia through repression of Cdkn2a (also known as ink4a/Arf) tumour suppressors. Conversely, loss of Bmi1 leads to haematological defects and severe progressive neurological abnormalities in which de-repression of the ink4a/Arf locus is critically implicated. Here, we show that Bmi1 is strongly expressed in proliferating cerebellar precursor cells in mice and humans. Using Bmi1-null mice we demonstrate a crucial role for Bmi1 in clonal expansion of granule cell precursors both in vivo and in vitro. Deregulated proliferation of these progenitor cells, by activation of the sonic hedgehog (Shh) pathway, leads to medulloblastoma development. We also demonstrate linked overexpression of BMI1 and patched (PTCH), suggestive of SHH pathway activation, in a substantial fraction of primary human medulloblastomas. Together with the rapid induction of Bmi1 expression on addition of Shh or on overexpression of the Shh target Gli1 in cerebellar granule cell cultures, these findings implicate BMI1 overexpression as an alternative or additive mechanism in the pathogenesis of medulloblastomas, and highlight a role for Bmi1-containing polycomb complexes in proliferation of cerebellar precursor cells. 相似文献
56.
Nucleolar proteome dynamics 总被引:2,自引:0,他引:2
The nucleolus is a key organelle that coordinates the synthesis and assembly of ribosomal subunits and forms in the nucleus around the repeated ribosomal gene clusters. Because the production of ribosomes is a major metabolic activity, the function of the nucleolus is tightly linked to cell growth and proliferation, and recent data suggest that the nucleolus also plays an important role in cell-cycle regulation, senescence and stress responses. Here, using mass-spectrometry-based organellar proteomics and stable isotope labelling, we perform a quantitative analysis of the proteome of human nucleoli. In vivo fluorescent imaging techniques are directly compared to endogenous protein changes measured by proteomics. We characterize the flux of 489 endogenous nucleolar proteins in response to three different metabolic inhibitors that each affect nucleolar morphology. Proteins that are stably associated, such as RNA polymerase I subunits and small nuclear ribonucleoprotein particle complexes, exit from or accumulate in the nucleolus with similar kinetics, whereas protein components of the large and small ribosomal subunits leave the nucleolus with markedly different kinetics. The data establish a quantitative proteomic approach for the temporal characterization of protein flux through cellular organelles and demonstrate that the nucleolar proteome changes significantly over time in response to changes in cellular growth conditions. 相似文献
57.
Expression of human immune interferon cDNA in E. coli and monkey cells 总被引:118,自引:0,他引:118
P W Gray D W Leung D Pennica E Yelverton R Najarian C C Simonsen R Derynck P J Sherwood D M Wallace S L Berger A D Levinson D V Goeddel 《Nature》1982,295(5849):503-508
58.
A new gene like the alpha-globin gene has been identified in higher primates at the 3' end of the alpha-globin gene cluster. There is some controversy as to whether this gene, theta, is a functional globin gene or a non-functional pseudogene. The high degree of sequence conservation displayed by theta between primates and various mammals, such as horse and rabbit, suggests that this gene is functional in some species. Furthermore, theta encodes a 141-amino-acid polypeptide in sequence similar to alpha-globin and appears to possess functional RNA-processing signals. But the promoter region of theta is unlike the other globin genes because its CCAAT and ATA box sequences are displaced from the coding sequence by the insertion of a 200-base-pair GC-rich sequence. We demonstrate here the presence of theta-globin messenger RNA in human fetal erythroid tissue, but not in adult erythroid or other non-erythroid tissues. Furthermore, theta-globin mRNA is detectable in significant amounts in a human erythroleukaemic cell line. These results predict that theta-globin protein will be found in the early stages of human fetal development. Surprisingly, the promoter sequence of theta-globin does not correspond to the CCAAT and ATA box sequences of the gene but rather lies within the adjacent GC-rich sequence, resulting in a heterogeneous series of mRNA 5' ends 50-10 base pairs to 5' of the initiation codon. This type of promoter is reminiscent of that found in housekeeping genes such as adenine deaminase and hypoxanthine-guanine phosphoribosyl-transferase. 相似文献
59.
60.
在某些信号处理和通信应用中要求非均匀抽样。本文描述一种新的切匹雪夫非均匀抽样模式的特性和利用脉动阵列结构相应的实现方案。本文证明切匹雪夫非均匀抽样模式具有简单、规则和快速重构的优点。 相似文献