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421.
Banach空间X称为具有正规结构,如果对每个非平凡有界凸子集K,存在p∈K,使 sup{‖p-x‖;彩x∈tr}相似文献
422.
Beauchamp GK Keast RS Morel D Lin J Pika J Han Q Lee CH Smith AB Breslin PA 《Nature》2005,437(7055):45-46
Newly pressed extra-virgin olive oil contains oleocanthal--a compound whose pungency induces a strong stinging sensation in the throat, not unlike that caused by solutions of the non-steroidal anti-inflammatory drug ibuprofen. We show here that this similar perception seems to be an indicator of a shared pharmacological activity, with oleocanthal acting as a natural anti-inflammatory compound that has a potency and profile strikingly similar to that of ibuprofen. Although structurally dissimilar, both these molecules inhibit the same cyclooxygenase enzymes in the prostaglandin-biosynthesis pathway. 相似文献
423.
Emison ES McCallion AS Kashuk CS Bush RT Grice E Lin S Portnoy ME Cutler DJ Green ED Chakravarti A 《Nature》2005,434(7035):857-863
The identification of common variants that contribute to the genesis of human inherited disorders remains a significant challenge. Hirschsprung disease (HSCR) is a multifactorial, non-mendelian disorder in which rare high-penetrance coding sequence mutations in the receptor tyrosine kinase RET contribute to risk in combination with mutations at other genes. We have used family-based association studies to identify a disease interval, and integrated this with comparative and functional genomic analysis to prioritize conserved and functional elements within which mutations can be sought. We now show that a common non-coding RET variant within a conserved enhancer-like sequence in intron 1 is significantly associated with HSCR susceptibility and makes a 20-fold greater contribution to risk than rare alleles do. This mutation reduces in vitro enhancer activity markedly, has low penetrance, has different genetic effects in males and females, and explains several features of the complex inheritance pattern of HSCR. Thus, common low-penetrance variants, identified by association studies, can underlie both common and rare diseases. 相似文献
424.
Regulation of polarized extension and planar cell polarity in the cochlea by the vertebrate PCP pathway 总被引:1,自引:0,他引:1
Wang J Mark S Zhang X Qian D Yoo SJ Radde-Gallwitz K Zhang Y Lin X Collazo A Wynshaw-Boris A Chen P 《Nature genetics》2005,37(9):980-985
The mammalian auditory sensory organ, the organ of Corti, consists of sensory hair cells with uniformly oriented stereocilia on the apical surfaces and has a distinct planar cell polarity (PCP) parallel to the sensory epithelium. It is not certain how this polarity is achieved during differentiation. Here we show that the organ of Corti is formed from a thicker and shorter postmitotic primordium through unidirectional extension, characteristic of cellular intercalation known as convergent extension. Mutations in the PCP pathway interfere with this extension, resulting a shorter and wider cochlea as well as misorientation of stereocilia. Furthermore, parallel to the homologous pathway in Drosophila melanogaster, a mammalian PCP component Dishevelled2 shows PCP-dependent polarized subcellular localization across the organ of Corti. Taken together, these data suggest that there is a conserved molecular mechanism for PCP pathways in invertebrates and vertebrates and indicate that the mammalian PCP pathway might directly couple cellular intercalations to PCP establishment in the cochlea. 相似文献
425.
Borisenko SV Kordyuk AA Koitzsch A Knupfer M Fink J Berger H Lin CT 《Nature》2004,431(7004):1 p following 39
One of the mysteries of modern condensed-matter physics is the nature of the pseudogap state of the superconducting cuprates. Kaminski et al. claim to have observed signatures of time-reversal symmetry breaking in the pseudogap regime in underdoped Bi2Sr2CaCu2O8+delta (Bi2212). Here we argue that the observed circular dichroism is due to the 51 superstructure replica of the electronic bands and therefore cannot be considered as evidence for spontaneous time-reversal symmetry breaking in cuprates. 相似文献
426.
Vitamin K epoxide reductase (VKOR) is the target of warfarin, the most widely prescribed anticoagulant for thromboembolic disorders. Although estimated to prevent twenty strokes per induced bleeding episode, warfarin is under-used because of the difficulty of controlling dosage and the fear of inducing bleeding. Although identified in 1974 (ref. 2), the enzyme has yet to be purified or its gene identified. A positional cloning approach has become possible after the mapping of warfarin resistance to rat chromosome 1 (ref. 3) and of vitamin K-dependent protein deficiencies to the syntenic region of human chromosome 16 (ref. 4). Localization of VKOR to 190 genes within human chromosome 16p12-q21 narrowed the search to 13 genes encoding candidate transmembrane proteins, and we used short interfering RNA (siRNA) pools against individual genes to test their ability to inhibit VKOR activity in human cells. Here, we report the identification of the gene for VKOR based on specific inhibition of VKOR activity by a single siRNA pool. We confirmed that MGC11276 messenger RNA encodes VKOR through its expression in insect cells and sensitivity to warfarin. The expressed enzyme is 163 amino acids long, with at least one transmembrane domain. Identification of the VKOR gene extends our understanding of blood clotting, and should facilitate development of new anticoagulant drugs. 相似文献
427.
α-diketones and β-diketones react with Grignard reagents in the presence of a catalytic amount of Cp2TiCl2 to yield α-ketols and corresponding ketones respectively. Sulfoxides can be deoxygenated by Cp2TiCl2/Al system. The possible mechanisms are also discussed. 相似文献
428.
Scalable synthesis of A2S3 (A=Sb, Bi) submicro/nanowires using their powders via solvothermal proceeding 总被引:1,自引:0,他引:1
JI Tianhao LIU Guanrao QI Xingyi YANG Qinglin DENG Yuan GUO Lin 《科学通报(英文版)》2006,51(6):655-660
One-dimensional (1D) nanostructural materials of semiconductors are being widely studied due to their unusual opto-electronic properties and potential im-plementation as nanodevices[1―6]. The nanowires of A2S3 (A=Sb, Bi) are one of the most interesting 1… 相似文献
429.
Chien-Yuan Tseng Houng-Yi Yang WAN Yusheng LIU Dunyi Da-Jen Wen Tzung-Chi Lin Kuo-An Tung 《科学通报(英文版)》2006,51(8):963-970
The Qilian Mountain is considered a part of the Cen- tral Orogenic Belt of China[1]. The Central Orogenic Belt of China, extending for a distance of about 4000 km long in the E-W direction from the east coast west- ward through the mainland China all the … 相似文献
430.
In this paper, the structure and operating principle of the dye-sensitized nanocrystalline solar cells (DSSC) are discussed. The electrolytes can be divided into three types: liquid electrolyte, quasi-solid electrolyte and solid electrolyte. Based on the relevant study of our group, we summarized mainly the research progress of the quasi-solid electrolyte and solid electrolyte in solid-state DSSC. 相似文献