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排序方式: 共有1144条查询结果,搜索用时 468 毫秒
941.
942.
刘驰 《西安工程科技学院学报》2009,23(2)
开发了一种微薄型压力传感器.传感器精确测量所穿服装施加在人体上的压力,并且将其作为一种方法用来决定在各种不同款式的服装中所需要的适当的放松量的大小.实验结果显示,传感器可以测试在不同变化姿势时服装的压力. 相似文献
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诺贝尔奖走过的一个世纪 总被引:1,自引:0,他引:1
最近 ,几位科学家看到了他们的名字已经与世人瞩目的成就、与永远不会失去的名誉相提并论。公众正探究着这些新出现的名人是怎样达到事业顶峰的 :他们克服了什么障碍、是站在什么人的肩膀上才看得如此之远。不计今年的得奖者 ,自诺贝尔在 1 0 0年前设奖至今 ,在 3个科学领域———物理学、化学和生理学或医学———中已经颁发了 2 80个奖项。艰苦的研究和献身未必能取得作为在这个独一无二的“俱乐部”中的一个成员的资格。斯德哥尔摩的诺贝尔博物馆馆长斯万特·林德奎斯特 (SvanteLindqvist)说 :“诺贝尔奖不是为终身的成就… 相似文献
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Seandel M James D Shmelkov SV Falciatori I Kim J Chavala S Scherr DS Zhang F Torres R Gale NW Yancopoulos GD Murphy A Valenzuela DM Hobbs RM Pandolfi PP Rafii S 《Nature》2007,449(7160):346-350
Adult mammalian testis is a source of pluripotent stem cells. However, the lack of specific surface markers has hampered identification and tracking of the unrecognized subset of germ cells that gives rise to multipotent cells. Although embryonic-like cells can be derived from adult testis cultures after only several weeks in vitro, it is not known whether adult self-renewing spermatogonia in long-term culture can generate such stem cells as well. Here, we show that highly proliferative adult spermatogonial progenitor cells (SPCs) can be efficiently obtained by cultivation on mitotically inactivated testicular feeders containing CD34+ stromal cells. SPCs exhibit testicular repopulating activity in vivo and maintain the ability in long-term culture to give rise to multipotent adult spermatogonial-derived stem cells (MASCs). Furthermore, both SPCs and MASCs express GPR125, an orphan adhesion-type G-protein-coupled receptor. In knock-in mice bearing a GPR125-beta-galactosidase (LacZ) fusion protein under control of the native Gpr125 promoter (GPR125-LacZ), expression in the testis was detected exclusively in spermatogonia and not in differentiated germ cells. Primary GPR125-LacZ SPC lines retained GPR125 expression, underwent clonal expansion, maintained the phenotype of germline stem cells, and reconstituted spermatogenesis in busulphan-treated mice. Long-term cultures of GPR125+ SPCs (GSPCs) also converted into GPR125+ MASC colonies. GPR125+ MASCs generated derivatives of the three germ layers and contributed to chimaeric embryos, with concomitant downregulation of GPR125 during differentiation into GPR125- cells. MASCs also differentiated into contractile cardiac tissue in vitro and formed functional blood vessels in vivo. Molecular bookmarking by GPR125 in the adult mouse and, ultimately, in the human testis could enrich for a population of SPCs for derivation of GPR125+ MASCs, which may be employed for genetic manipulation, tissue regeneration and revascularization of ischaemic organs. 相似文献
948.
Participants in laboratory games are often willing to alter others' incomes at a cost to themselves, and this behaviour has the effect of promoting cooperation. What motivates this action is unclear: punishment and reward aimed at promoting cooperation cannot be distinguished from attempts to produce equality. To understand costly taking and costly giving, we create an experimental game that isolates egalitarian motives. The results show that subjects reduce and augment others' incomes, at a personal cost, even when there is no cooperative behaviour to be reinforced. Furthermore, the size and frequency of income alterations are strongly influenced by inequality. Emotions towards top earners become increasingly negative as inequality increases, and those who express these emotions spend more to reduce above-average earners' incomes and to increase below-average earners' incomes. The results suggest that egalitarian motives affect income-altering behaviours, and may therefore be an important factor underlying the evolution of strong reciprocity and, hence, cooperation in humans. 相似文献
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950.
Bv8 regulates myeloid-cell-dependent tumour angiogenesis 总被引:1,自引:0,他引:1
Shojaei F Wu X Zhong C Yu L Liang XH Yao J Blanchard D Bais C Peale FV van Bruggen N Ho C Ross J Tan M Carano RA Meng YG Ferrara N 《Nature》2007,450(7171):825-831
Bone-marrow-derived cells facilitate tumour angiogenesis, but the molecular mechanisms of this facilitation are incompletely understood. We have previously shown that the related EG-VEGF and Bv8 proteins, also known as prokineticin 1 (Prok1) and prokineticin 2 (Prok2), promote both tissue-specific angiogenesis and haematopoietic cell mobilization. Unlike EG-VEGF, Bv8 is expressed in the bone marrow. Here we show that implantation of tumour cells in mice resulted in upregulation of Bv8 in CD11b+Gr1+ myeloid cells. We identified granulocyte colony-stimulating factor as a major positive regulator of Bv8 expression. Anti-Bv8 antibodies reduced CD11b+Gr1+ cell mobilization elicited by granulocyte colony-stimulating factor. Adenoviral delivery of Bv8 into tumours was shown to promote angiogenesis. Anti-Bv8 antibodies inhibited growth of several tumours in mice and suppressed angiogenesis. Anti-Bv8 treatment also reduced CD11b+Gr1+ cells, both in peripheral blood and in tumours. The effects of anti-Bv8 antibodies were additive to those of anti-Vegf antibodies or cytotoxic chemotherapy. Thus, Bv8 modulates mobilization of CD11b+Gr1+ cells from the bone marrow during tumour development and also promotes angiogenesis locally. 相似文献