Operant behavior of pre and post pubertal rats irradiated with I131 in the last trimester of gestation

Résumé Les petits de rates irradiées au 14^e jour de leur gestation, avec 3000 µC/kg de¹³¹I i.p. ont montré une plus grande réduction de leur capacité à presser sur un levier lorsqu'ls l'ont appris avant la puberté. Cet effet fut d'autant plus manifeste chez les animaux qui avaient été conditionnés lentement et qui ont généralement tendance à améliorer leur performance avec l'âge.

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Supported by NIMH Grant No. NS-07889.     

关于关联BCK-代数

本文建立了有限初始段关联BCK-代数与无限初始段关联BCK-代数的概念。获得三个主要结果:任一有限初始段关联BCK-代数与的某一子代数同构;对任一关联BCK-代数,规定X_0={x|x∈X,A(x)是有限集},则X_0是X的理想;当X_0是有限集且X_0≠X时,商代数X/X_0是无限初始段关联BCK-代数。     

An Indentation Method for Nanoprecision Measurement of Diamond Tool Edge Radius

In ductile mode cutting of brittle materials using di amond tools, such as ductile cutting of silicon and quartz for wafer fabrication , one of the key conditions for achieving ductile chip formation is to get the r ight ratio of tool cutting edge radius to the undeformed chip thickness. It has been shown that the undeformed chip thickness has to be in the order of nanomete rs and that the tool cutting edge radius has to be smaller than the undeformed c hip thickness. Therefore, nanoprecision measurement ...     

Autoinhibition of juvenile hormone production. The case of the cockroachBlattella germanica (L.)

In 6-day-old females ofBlattella germanica, the activity of corpora allata (CA) was inhibited in vitro by juvenile hormone III (JH III). Effective doses (281.5 and 375.4 M in the medium) were somewhat higher than (although of the same order of magnitude as) the estimated intraglandular concentration of JH III at this age, and they induced about 45% inhibition of hormonal release and a significant intraglandular accumulation of JH III and methyl farnesoate. The results suggest that autoinhibitory mechanisms operate in the CA to constrain the upper limit of JH III production at the end of the gonadotrophic cycle.     

A negative inotropic effect of acetylcholine in the presence of several phosphodiesterase inhibitors

Summary The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine (IBMX) reveal a negative inotropic effect of acetylcholine in cat ventricular heart muscle. This effect is unrelated to -adrenoceptor stimulation and possibly mediated by the accumulation of cyclic GMP.I thank Mrs Petra Lauck for help. This work was supported by the Deutsche Forschungsgemeinschaft.     

In vivo incorporation of14C-phenylalanine into ascidian tunichrome

Ascidia ceratodes exposed to¹⁴C-phenylalanine in the surrounding seawater incorporates the radiolabel into newly biosynthesized tunichrome molecules. Radioactivity can be detected in tunichrome extracted from circulating blood cells within one day following initial exposure to the radiolabel; weak activity (4 Ci/mol tunichrome=22 nmol phenylalanine/mol tunichrome) is detected in 1 to 10 days; significantly higher amounts of radiolabel (57 Ci/mol tunichrome=318 nmol phenylalanine/mol tunichrome) appear 20 days after seawater exposure. Therefore, phenylalanine can function as a precursor in the biosynthesis of tunichrome.     

我国数字图书馆建设的必要性及主要任务

论述了我国数字图书馆建设的必要性，认为建设数字图书馆是加快社会信息化步伐的需要，是弘扬中华文化的需要，是提高国民素质的需要，是我国图书馆事业发展的需要。指出我国数字图书馆建设的主要任务包括数字资源建设、系统开发、标准规范的制定和人才培养等方面。