浅析地理大发现在国际贸易形成中的作用

地理大发现使世界各国相互联结为一个整体,加强了彼此相互了解和商品的相互往来,打破了相互隔绝的局面.欧洲及北美国家的世界市场竞争和殖民掠夺,使世界市场分工明确,联系更紧密,商品交换更频繁,最终导致国际贸易的形成.     

严格预不变拟凸函数的新性质

在严格预不变拟凸函数和半严格预不变拟凸函数定义基础上,研究了关于严格预不变凸函数的两个新性质,得到了关于严格预不变拟凸函数的新性质.这些性质可用于判定严格预不变拟凸函数.     

严格预不变拟凸函数的新性质

在严格预不变拟凸函数和半严格预不变拟凸函数定义基础上,研究了关于严格预不变凸函数的两个新性质,得到了关于严格预不变拟凸函数的新性质。这些性质可用于判定严格预不变拟凸函数。     

Combinational electroporation and transplantation approach to studying gene functions in avian embryos

Gene transfection is an indispensable approach for studying gene function since it provides important information on gain- and/or loss-of-function. Chick embryos are also extensively employed for studying bio- logical function since they are easily accessible and can be maintained alive after manipulation. The combination of both techniques presents a powerful approach to under- standing how genes regulate embryo development. Fur- thermore, combining these approaches with tissue transplant techniques make even more attractive for elu- cidate gene function. Electroporation, employing parallelly fashioned electrodes, has been widely used in chick embryos. However, experimenters have been frustrated by unsuccessfully transfection in some embryonic tissue of interest because the electrodes were improperly positioned.We presently demonstrated the different patterns of orga- nizing and positioning the electrodes, in combination with tissue transplantation, to efficiently and specifically trans- fect the chick embryonic head, trunk neural tube, heart tube, somites and neural crest cells with the GFP reporter gene.     

Inhibition of platelet thrombus formation by chlorpromazine acting to diminish haemolysis.

There is increasing evidence that the sudden, unpredicatable event initiating myocardial infarction is fissuring of an atherosclerotic plaque. The resulting haemorrhage into the arterial wall produces obstructive platelet thrombi, just as arterial haemorrhages elsewhere produce haemostatic platelet plugs. It has been suggested that such platelet aggregation depends on ADP originating in red cells which are subjected to excessive haemodynamic stress at the site of haemorrhage. The release of ADP from red cells has been demonstrated in vitro in equivalent condtions of shear stress; and other mechansims, such as activation by collagen, cannot account for the rapidity with which the platelets react. One of us (G.V.R.B.) has suggested that drugs capable of counteracting haemolysis might diminish the activating effect of erythrocytes on platelets and so inhibit their aggregation as thrombi. Thus, chlorpromazine, added to human blood at concentrations which diminish haemoylsis but do not directly affect platelet aggregation, prolonged the 'bleeding time' from small holes in artificial vessels where extravasation is terminated, as in living arterioles, by aggregated platelets. The bleeding time was also prolonged by apyrase, consistent with the conclusion that the chlorpromazine acted through decreasing plasma ADP. We show here that this occurs through the anti-haemolytic action of chlorpromazine.     

一种新型多功能晶闸管触发电路

介绍了一种自行开发的由单片微处理器控制的多功能晶闸管移相触发器。对触发电路的原理和软件进行了分析 ,在不改动电路和软件的情况下 ,该触发电路能适用于多种主电路类型的晶闸管变流电路     

密码函数安全准则的一种新刻划

为了更好地认识密码函数的性质,引入了一些新的指标,讨论了这些指标之间的关系,用这些指标刻划了密码函数的一些安全准则,给出了非线性度新的上界,说明了这些上界与一般上界之间的关系,最后给出了Bent函数的新定义及其它等阶定义。     

The Drosophila posterior-group gene nanos functions by repressing hunchback activity

The development of the body plan in the Drosophila embryo depends on the activity of maternal determinants localized at the anterior and posterior of the egg. These activities define both the polarity of the anterior-posterior (AP) axis and the spatial domains of expression of the zygotic gap genes, which in turn control the subsequent steps in segmentation. The nature and mode of action of one anterior determinant, the bicoid(bcd) gene product, has recently been defined, but the posterior determinants are less well characterized. At least seven maternally acting genes are required for posterior development. Mutations in these maternal posterior-group genes result in embryos lacking all abdominal segments. Cytoplasmic transplantation studies indicate that the maternally encoded product of the nanos(nos) gene may act as an abdominal determinant, whereas the other maternal posterior-group genes appear to be required for the appropriate localization and stabilization of this signal. Here we show that the lack of the nos gene product can be compensated for by eliminating the maternal activity of the gap gene hunchback (hb). Embryos lacking both of these maternally derived gene products are viable and can survive as fertile adults. These results suggest that the nos gene product functions by repressing the activity of the maternal hb products in the posterior of the egg.     

Cloning of the T gene required in mesoderm formation in the mouse

The murine developmental mutation T identifies an essential gene in mesoderm formation. Embryos lacking normal gene activity fail to form the notochord, the entire posterior region and the allantois, and die at about 10 days of gestation. We have isolated the T gene using a combination of molecular and genetic techniques, thus making molecular tools available to study processes underlying mesoderm formation in the mouse.     

凝集素的分离纯化、基因克隆及功能研究进展

凝集素(lectin)研究近年来发展迅速,尤其在植物基因工程中,植物外源凝集素基因越来越受到重视。本文从凝集素的分离纯化、基因克隆、理化性质和功能等方面进行了综述。此外还讨论了凝集素基因在植物基因工程中的应用。     

Clifford分析中的k-超正则函数和二次k-超正则函数

研究了Clifford分析中k-超正则函数的一些性质,首次定义了二次k-超正则函数及拟二次k-超正则函数,并讨论了k-超正则函数和二次k-超正则函数之间的一些关系．     

Expression pattern of the mouse T gene and its role in mesoderm formation.

Formation of mesoderm is a crucial event in vertebrate development, establishing many of the important features of the body. Recent studies have implicated molecules that are similar to growth factors in mesoderm formation in Xenopus, but other gene products involved in this process have yet to be identified. Genetic evidence indicates that in the mouse the T gene (Brachyury) has a role in the formation and organization of mesoderm. Mice homozygous for mutant alleles of the T gene do not generate enough mesoderm, and show severe disruption in morphogenesis of mesoderm-derived structures, in particular the notochord. The cloning of the T gene has now allowed us to examine its expression pattern. We report that T-gene expression occurs in both early stage mesoderm and its epithelial progenitor, and then becomes restricted to the notochord. This expression pattern correlates with the tissues affected in the T-gene mutant, and indicates that the T gene has a direct role in the early events of mesoderm formation and in the morphogenesis of the notochord.     

关于preinvex函数和pseudoinvex函数

本文讨论了可微的强invex函数和强pseudoinvex函数分别与其梯度的强不变单调和强不变伪单调的关系,得到了pseudoinvex函数在某些条件下可以等价prequasiinvex函数.证明了:若f关于向量值函数η是preinvex函数,且满足lipschitz条件,则y为f(x)的全局极小点等价于0∈(e)0f(y).     

EDA中实现MAX PLUS内附函数的扩展

随着科技的不断进步,现代技术中新产品、新元件不断问世,利用OrCAD PSpice技术中元件库扩充功能,实现EDA技术中MAX PLUS中内附函数的功能扩展,以增加起对于电路的开发能力,为EDA技术的不断创新提出了新的想法。通过对实际芯片的外观的相应修改,观察其修改过后的仿真波形,并与原来的仿真波形相比较,发现两波形完全相同,以此验证该方法是完全可行的。     

Nucleotide sequence and formation of the transforming gene of a mouse sarcoma virus

The complete nucleotide sequence of the transforming gene of a mouse sarcoma virus has been determined. It codes for a protein of 374 amino acids. The nucleotide sequence of the junctions between a murine leukaemia virus and cellular sequences leading to the formation of the viral transforming gene have also been elucidated. The viral transforming sequence and its cellular homologue share an uninterrupted stretch of 1,159 nucleotides, with few base substitutions. The predicted amino acid sequence of the mouse sarcoma virus transforming gene was found to share considerable homology with the proposed amino acid sequence of the avian sarcoma virus oncogene (src) product.     

凸函数与超加函数的关系研究

应用积分理论，研究了在整数规划中具有重要应用的凸函数及其超加函数的关系。利用超加函数的有关结论，证明了任何过原点的凸函数必为超加函数，并得到了此类凸函数的若干推论。     

区问值和模糊数值函数的Choquet积分

定义和讨论了区间值函数和模糊数值函数关于非可加Sugeno测度的Choquet积分及其性质,并利用传统的模糊数值函数的Kaleva积分对其进行了刻划;同时,讨论了区间值函数和模糊数值函数的Choquet不定积分,发现该集函数对于原有测度的性质具有遗传性,分别是一种区间值和模糊数值模糊测度.所有结果不难推广到定义域为高维空间或取值域为高维模糊数空间的情形.     

关于E-凸集，E-凸函数和半-E-凸函数性质的研究

在文献[1-4]已经对E-凸集，E-凸函数，半-E-凸函数进行了研究，本文在此基础上对它们进行了再次研究，得出了一些新的性质，完善这类非凸集和非凸函数。