桁架结构拓扑优化设计的模拟退火算法

研究了平面桁架结构拓扑优化设计的模拟退火算法．构造了一个双重控制Ｍｅｔｒｏｐｏｌｉｓ准则处理应力约束,提出了一个基于力平衡的启发式准则,以实现优化过程中单元的自动增删．算例表明,该方法能够克服桁架结构拓扑优化中因存在非凸星形可行域而造成的拓扑优化求解困难．     

一种子带适应的图象恢复最小二乘迭代算法

研究了基于子波变换的图象最小二乘恢复技术,提出了一种具有子带适应性的选代算法实验结果表明,采用该算法的恢复图象的质量和迭代收敛的速率均优于常规的空域解法．     

A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean

The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability.     

Insect motion detectors matched to visual ecology

To detect motion, primates, birds and insects all use local detectors to correlate signals sampled at one location in the image with those sampled after a delay at adjacent locations. These detectors can adapt to high image velocities by shortening the delay. To investigate whether they use long delays for detecting low velocities, we compared motion-sensitive neurons in ten species of fast-flying insects, some of which encounter low velocities while hovering. Neurons of bee-flies and hawkmoths, which hover, are tuned to lower temporal frequencies than those of butterflies and bumblebees, which do not. Tuning to low frequencies indicates longer delays and extends sensitivity to lower velocities. Hoverflies retain fast temporal tuning but use their high spatial acuity for sensing low-velocity motion. Thus an unexpectedly wide range of spatio-temporal tuning matches motion detection to visual ecology.     

21世纪前夕世界经济所面临的问题

通过对二战后世界经济发展的回顾与分析,论述了技术革命与全球化和在此进程中产生的问题：“精简”,以及由此带来的社会影响。介绍了西方国家学者关于解决上述问题的不同建议和主张,进而提出了自己的观点和对策。     

Nα-quinaldyl-L-arginine·HCl,a new defensive alkaloid fromSubcoccinella-24-punctata (Coleoptera,Coccinellidae)

The isolation of N-quinaldyl-L-arginine·HCl (1) from the CoccinellidaeSubcoccinella-24-punctata is reported. The structure, first established on the basis of the analysis of the spectral properties of1, has been confirmed by synthesis. The alkaloid is of endogenous origin and markedly deterrent to ants.     

混凝土复合外加剂复合理论和复合设计

以分子结构有无条件形成氢键作为分类标准,将基准外加剂分成两类：一类能形成氢键;一类不能形成氢键,提出复合外加剂是由能形成氢键的基准外加剂和不能形成氢键的基准外加剂两部分组成的新观点,以此观点为基础,作者用数学模式表述复合外加剂和它的复合,将复合外加剂的“组成－结构－功能－名称”有机地联系起来。     

Cyclophosphamide-impaired regulation of hepatic heme metabolism

Summary Im male rats hepatic cytochromes b₅ and P-450 were reduced at different times after treatment with cyclophosphamide (CP) (200 mg/kg i.p. for 3 days). In contrast, microsomal heme did not change until 48 h after the last dose of CP, leading to accumulation of heme in a non-cytochromal form. Parallel to the above changes the heme metabolism showed derangement: -aminolaevulinate synthase, the rate-limiting enzyme in heme synthesis, was depressed and heme oxygenase, the enzyme which catalyzes the oxidative degradation of heme, was increased.     

Pineal-related changes in cyclic AMP levels of rat medial basal hypothalamus

Summary Pinealectomy (Px) in adult male rats resulted in increased cyclic AMP accumulation by medial basal hypothalamic (MBH) explants 3 and 7 days after surgery. 24 h after superior cervical ganglionectomy (Gx) an augmented MBH cyclic AMP accumulation was observed. The effects of Px and Gx were additive, as revealed in animals subjected to Gx 3 days after Px.This study was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (N^o 6638) and from the Fundación Alberto J. Roemmers, Argentina.     

‘Chloride-cell’ — like mitochondria-rich cells of salamander larva gill epithelium

Summary Two types of mitochondria-rich cells (MRC) are described ultrastructurally in the gill epithelium of salamander larva. They resemble MRC found in larval ventral epidermis. Histochemical localization of carbonic anhydrase indicated numerous positive reacting cells, most of them flask-shaped. Morphological and functional similarities to fish chloride cells are discussed.