负载型丝光沸石催化剂的催化性能研究

运用二元碱氮置换吸附红外光谱法、分子筛孔径分布测定技术、XPS技术,考察了丝光沸石表面酸性与孔结构的相互关系、钯在丝光沸石上分布情况和价态及其与沸石的相互作用。结果表明,随着丝光沸石脱铝程度的增加,表面出现大量不规整晶格,存在较多的次级孔道。强质子酸中心主要分布在它的“外表面”。钯在其表面富集,并与“外表面”上的质子酸中心协同作用,促进了轻质烷烃异构化反应。     

Postembryonic sensory axon guidance in Drosophila

The peripheral sensory system of the Drosophila adult has been used for the genetic analysis of axon guidance because of its accessibility for experimental manipulation and mutant screens. Wing, leg, antenna, or eye sensory axons are able to pathfind normally under different perturbations, indicating that sensory axon guidance is a highly canalized process. Similarly to other model systems, sensory growth cones seem to use multiple, simultaneous cues for guidance. In addition, sensory axons from peripheral structures seem to be capable of using alternative substrates for pathfinding. Developmental regulation could account for the high stability of axon guidance under experimental and natural perturbation conditions. Despite this flexibility, functional characterization of genes involved in sensory axon guidance is being carried out in situations where there appears to be less system redundancy.     

Separation of specific fractions of synaptosomes by affinity chromatography

Summary The authors describe a new technique for isolation of specific fractions of synaptosomes, on the basis of their surface glycoproteins, by affinity chromatography using lectin-Sepharose columns.     

Alteration in the SAT-chromosome ofAllium cepa affecting the size of the nucleolus

Resumen Se describe el hallazgo de un bulbo deAllium cepa en el cual los dos nucleolos de cada nÚcleo muestran una clara diferencia de tamaño. El nucleolo menor posee aproximadamente la mitad del diámetro del nucleolo normal. Esta alteración de la morfología nucleolar se correlaciona con la ausencia de satélite en uno de los dos cromosomas normalmente satelizados.

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The work reported in this paper was undertaken during the tenure of a Research Training Fellowship awarded by the International Agency for Research on Cancer.     

Effect of copulation or vaginal stimulation on melanocyte-stimulating hormone content of the hypophysis

Résumé Dans le rat, 1 h après la copulation, la concentration de l'MSH de l'hypophyse présente une diminution statistiquement significative, autant chez le mâle que chez la femelle. La stimulation vaginale avec une baguette de verre provoqua 60 et 120 min plus tard une diminution de la concentration de plus de 50% de l'MSH de l'hypophyse. Au bout de 30 min, on n'a observé aucun changement. On en déduit que la copulation ou la stimulation vaginale libère l'MSH.

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This investigation was supported by grant No. NB 04732-03 from the NIH, US. Public health Service.     

Studies on the quaternary structure of the first enzyme for histidine biosynthesis

Resumen Se han realizado estudios de asociación-disociación por filtración en gel con el primer enzima de la biosíntesis de histidina enEscherichia coli, en presencia de sustratos y ligandos. Se observa una interconversión reversible entre las formas dímero, tetrámero y exámero, y una agregación irreversible de orden superior.