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851.
Summary The macrocyclic compounds occurring in animal glandular secretions are reviewed. Early hypotheses for their biogenesis from fatty acids via and -oxidations are found to be inadequate. Radio-active acetate was incorporated into macrocyclic ketones of muskrat (Ondatra sp.) preputial glandular secretion, but radiolabelled stearate, oleate, anda, -octadecandioic acid were not incorporated.Acknowledgment. We wish to thank Dr.W.J. Doude van Troostwijk, Research Institute for Nature Management, Arnhem, for his assistance in obtaining muskrats, and Mr J. Vellekoop, Leiden, for the Shakespeare quotations. 相似文献
852.
Improvements to the dynamic programming (DP) strategy for partitioning (nonhierarchical classification) as discussed in Hubert, Arabie, and Meulman (2001) are proposed. First, it is shown how the number of evaluations in the DP process can be decreased
without affecting generality. Both a completely nonredundant and a quasi-nonredundant
method are proposed. Second, an efficient implementation of both approaches is discussed.
This implementation is shown to have a dramatic increase in speed over the original program.
The flexibility of the approach is illustrated by analyzing three data sets. 相似文献
853.
潘江 《科技情报开发与经济》2004,14(6):9-10
引入研究型大学及其图书馆的定义,阐述了研究型大学图书馆进行人力资源管理的重要意义。进而提出了研究型大学图书馆人力资源管理的策略,包括改变人力资源管理理念,建立以人为本的人才管理机制,注重人才的使用和培养,充分调动馆员的积极性等。 相似文献
854.
庞晓青 《科技情报开发与经济》2004,14(6):250-251
人才是提高综合国力的关键要素。为用好人才,一是要辨证地把握好识别人才、起用人才的标准,既要选拔出德才兼备的人才,又不可求全责备;二是用人要讲究方法。做到公平竞争、择优录用、知人善用,同时鼓励人才合理流动;三是用人要遵循讲正气、讲民主、讲大度的原则,大胆使用人才。 相似文献
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857.
C. H. W. Horne A. W. Thomson C. B. J. Hunter V. van Heyningen D. L. Deane C. M. Steel 《Cellular and molecular life sciences : CMLS》1979,35(3):411-412
Summary 2-PAG is present on the surface of mononuclear blood leucocytes and can be demonstrated predominantly on B-lymphocytes and monocytes. Pretreatment of cells with antibody to 2-PAG leads to a marked reduction in Fc-rosette formation. Competitive blocking experiments with specific antisera reveal a particularly close asociation between 2-PAG and MLR (mixed leucocyte reaction) determinants on the cell surface. These findings suggest one mechanism whereby 2-PAG may modify cell-mediated immune responses. 相似文献
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859.
D'Angelo G Polishchuk E Di Tullio G Santoro M Di Campli A Godi A West G Bielawski J Chuang CC van der Spoel AC Platt FM Hannun YA Polishchuk R Mattjus P De Matteis MA 《Nature》2007,449(7158):62-67
The molecular machinery responsible for the generation of transport carriers moving from the Golgi complex to the plasma membrane relies on a tight interplay between proteins and lipids. Among the lipid-binding proteins of this machinery, we previously identified the four-phosphate adaptor protein FAPP2, the pleckstrin homology domain of which binds phosphatidylinositol 4-phosphate and the small GTPase ARF1. FAPP2 also possesses a glycolipid-transfer-protein homology domain. Here we show that human FAPP2 is a glucosylceramide-transfer protein that has a pivotal role in the synthesis of complex glycosphingolipids, key structural and signalling components of the plasma membrane. The requirement for FAPP2 makes the whole glycosphingolipid synthetic pathway sensitive to regulation by phosphatidylinositol 4-phosphate and ARF1. Thus, by coupling the synthesis of glycosphingolipids with their export to the cell surface, FAPP2 emerges as crucial in determining the lipid identity and composition of the plasma membrane. 相似文献
860.
Trench-parallel flow and seismic anisotropy in the Mariana and Andean subduction systems 总被引:2,自引:0,他引:2
Shear-wave splitting measurements above the mantle wedge of the Mariana and southern Andean subduction zones show trench-parallel seismically fast directions close to the trench and abrupt rotations to trench-perpendicular anisotropy in the back arc. These patterns of seismic anisotropy may be caused by three-dimensional flow associated with along-strike variations in slab geometry. The Mariana and Andean subduction systems are associated with the largest along-strike variations of slab geometry observed on Earth and are ideal for testing the link between slab geometry and solid-state creep processes in the mantle. Here we show, with fully three-dimensional non-newtonian subduction zone models, that the strong curvature of the Mariana slab and the transition to shallow slab dip in the Southern Andes give rise to strong trench-parallel stretching in the warm-arc and warm-back-arc mantle and to abrupt rotations in stretching directions that are accompanied by strong trench-parallel stretching. These models show that the patterns of shear-wave splitting observed in the Mariana and southern Andean systems may be caused by significant three-dimensional flow induced by along-strike variations in slab geometry. 相似文献