冷成型不锈钢部件力学性能的精确预测

冷加工截面构件的制作过程导致材料的力学性能和强度有明显的改变．本文提出了精确预测不锈钢材料和冷加工材料力学性能的研究结果．首先,本文对不锈钢材料提出了一种新的应力-应变关系模型,这种模型可以精确预测全范围内的拉应变和压应变．新的应力-应变模型采用3个基本的Ramberg—Osgood参数,并基于对已有试验数据的详细分析来定义．在论文的第二部分,提出了预测冷加工材料的应力-应变性能的有限元模型．该方法中,通过对压弯成形截面制作过程的数值模拟,以及在随后对Coupon测试的有限元模拟中以加工过程中所导致的残余应力和等效塑性应变作为初始状态,解释了冷加工材料的应力-应变性能．这种方法能够预测冷加工材料的拉伸和压缩的应力-应变性能．新提出的应力-应变模型以及有限元方法的精度通过和试验得到的应力-应变曲线的对比进行了验证．所提出的有限元方法和新的应力-应变模型可以在将来应用到原始材料和冷加工材料的关系中．     

Glycogenolysis induced by serotonin in brain: identification of a new class of receptor

Serotonin-containing neurones in brain have been proposed to have a role in the control of physiological mechanisms such as sleep, thermoregulation, pain perception and endocrine secretions as well as in the physiopathology of migraine or depressive illness. One difficulty in testing these possibilities lies in the scarcity of pharmacological agents able to interact selectively with the probably multiple classes of serotonin receptors in the central nervous system. Development of such agents would be facilitated by simple in vitro models in which biological responses to serotonin in mammalian brain could be quantified. Thus a serotonin-sensitive adenylate cyclase has been characterized in rat brain, but the response to serotonin is weak in newborn and practically absent in adult animals. In addition, two pharmacologically distinct classes of serotoninergic binding site have been identified using 3H-serotonin and 3H-spiperone as ligands, but their identification as receptors remains to be established. More recently, serotonin has been shown to stimulate phosphorylation of a neuronal protein in slices from the facial motor nucleus, although the receptors mediating this action were not characterized. We now report that serotonin stimulates glycogen hydrolysis in slices of cerebral cortex, that this action is mediated by a novel class of receptors and that tricyclic antidepressants are among the best competitive antagonists of the indolamine.     

Modeling large reversible electric-field-induced strain in ferroelectric materials using 90° orientation switching

Reversible large electric-field-induced strain caused by reversible orientation switchings in BaTiO3 is modeled using the Landau's theory of phase transition.A triple well free energy function is constructed.Each of its minima is associated with one of the polarization orientations involved.Nonlinear constitutive laws accounting for reversible orientation switchings and electrostriction effects are obtained by using thermodynamic equilibrium conditions.Hysteretic dynamics of onedimensional structures is des...     

Probing Local Lattice Fluctautions in Cuprates and Manganites by High k—Resolution EXAFS

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｈｉｇｈＴｃｓｕｐｅｒｃｏｎｄｕｃｔｏｒｓａｒｅｌａｙｅｒｅｄｍａｔｅｒｉａｌｓｗｉｔｈＣｕＯ2 ｐｌａｎｅｓ ,ｓｅｐａｒａｔｅｄｂｙｉｎｓｕｌａｔｉｎｇｒｏｃｋ ｓａｌｔｏｘｉｄｅｌａｙｅｒｓ.ＴｈｅｉｍｐｏｒｔａｎｃｅｏｆｔｈｅＣｕＯ2 ｐｌａｎｅｓｈａｓｃｒｅａｔｅｄｍａｊｏｒｉｎｔｅｒｅｓｔｔｏｓｔｕｄｙｔｈｅｅｌｅｃｔｒｏｎｉｃａｎｄｓｔｒｕｃｔｕｒａｌｂｅｈａｖｉｏｕｒｏｆｔｈｅｓｅｓｔｒｕｃｔｕｒａｌｅｌｅｍｅｎｔｓｓｉｎｃｅｔｈｅｄｉｓｃｏｖｅｒｙｏｆｔｈ…     

Natural selection has driven population differentiation in modern humans

The considerable range of observed phenotypic variation in human populations may reflect, in part, distinctive processes of natural selection and adaptation to variable environmental conditions. Although recent genome-wide studies have identified candidate regions under selection, it is not yet clear how natural selection has shaped population differentiation. Here, we have analyzed the degree of population differentiation at 2.8 million Phase II HapMap single-nucleotide polymorphisms. We find that negative selection has globally reduced population differentiation at amino acid-altering mutations, particularly in disease-related genes. Conversely, positive selection has ensured the regional adaptation of human populations by increasing population differentiation in gene regions, primarily at nonsynonymous and 5'-UTR variants. Our analyses identify a fraction of loci that have contributed, and probably still contribute, to the morphological and disease-related phenotypic diversity of current human populations.     

Mutations of the X-linked genes encoding neuroligins NLGN3 and NLGN4 are associated with autism

Many studies have supported a genetic etiology for autism. Here we report mutations in two X-linked genes encoding neuroligins NLGN3 and NLGN4 in siblings with autism-spectrum disorders. These mutations affect cell-adhesion molecules localized at the synapse and suggest that a defect of synaptogenesis may predispose to autism.