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B. L. van der Waerden 《Archive for History of Exact Sciences》1978,18(4):343-357
Ohne Zusammenfassung 相似文献
114.
Résumé Dans une publication antérieure, nous avions signalé que le coefficient de température de la résistance électrique des films en nickel était négatif en dessous d'une certaine épaisseur critique (40 mµ). Au-dessus de 40 mµ, la courbe «Résistance en fonction de la température» présentait un minimum aux basses températures. A la suite de nouvelles expériences, nous avons constaté que ce phénomène est accompagné d'une déviation de la loi d'Ohm: la résistance diminue quand le courant de mesure augmente. Nous avons pu conclure que ces deux particularités ne sont qu'indirectement provoquées par la minceur des films. La cause principale est leur état de cristallisation imparfaite. En effet, après avoir subi un échauffement à 150° C pendant plusieurs heures, le coefficient de température négatif change de signe (le minimum disparaît) et la loi d'Ohm est respectée.
Research-fellow of the Belgian «Fonds National de la Recherche Scientifique» 相似文献
Research-fellow of the Belgian «Fonds National de la Recherche Scientifique» 相似文献
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NATREX AND DETERMINATION OF REAL EXCHANGE RATE OF RMB 总被引:1,自引:0,他引:1
Holger van Eden 《系统科学与复杂性》2001,(4)
1 IntroductionIn the past decades, a lot of 1iteratures appeared in the determination of excfiange rate, boththeoretic and empirical. One preValing paradigm is that the puxchasing power parity (PPP)holds in the long run either in weak--fOrm or in strongform. Under this hyPothesis, fluctuationsin real exchange rates are often regaJrded as temporary deviations from the long--run equllibriumexchange rate. However, these ekisting models fail to eXPlain the 1arge fluctuations in the realexchang… 相似文献
118.
Renée van de Vall 《Foundations of Science》2013,18(1):169-172
My review of Ike Kamphof’s “Webcams to Save Nature: Online Space as Affective and Ethical Space” focuses on the question how the engagement of the spectator of the described websites is temporally structured and how the discrepancy between the instantaneity of affective response and the duration of moral engagement is solved. I propose to draw on Alexander Nehamas’ philosophy of beauty as an in-between, bringing affect and ethics closer together. 相似文献
119.
Enhancement of LFA-1-mediated cell adhesion by triggering through CD2 or CD3 on T lymphocytes 总被引:61,自引:0,他引:61
Y van Kooyk P van de Wiel-van Kemenade P Weder T W Kuijpers C G Figdor 《Nature》1989,342(6251):811-813
The lymphocyte function-associated molecule LFA-1 (CD11a/CD18) plays a key part in lymphocyte adhesion. Lymphocytes do not adhere spontaneously; activation of protein kinase C (PKC) by phorbol esters, however, gives rise to strong LFA-1-dependent adhesion, indicating that activation of LFA-1 is required to induce cell adhesion. We have now investigated whether the functionally important CD2 and CD3 surface structures on T lymphocytes are involved in the activation of LFA-1. The stimulation of these molecules, which causes activation of PKC, strongly promoted LFA-1-dependent adhesion. Furthermore, we demonstrate by using cells from an LFA-1-deficient patient that this enhanced lymphocyte adhesion is caused by activation of the LFA-1 molecule and not by activation of its ligands. LFA-1 was persistently activated by triggering through CD2 but only transiently by triggering through CD3. We postulate that CD2 and CD3 can differentially regulate the affinity of LFA-1 for its ligands by modulating its molecular conformation through PKC-dependent mechanisms. 相似文献
120.
Isolation and characterization of a cDNA clone encoding the murine homologue of the human 20K T3/T-cell receptor glycoprotein 总被引:1,自引:0,他引:1
The antigen receptor on the surface of human T lymphocytes, which consists of a heterodimer of relative molecular mass (Mr) 90,000 (90K) (alpha- and beta-chains), is associated with the T3 antigen (gamma = 25K, delta = 20K and epsilon = 20K). A working model for the mode of action of the T3/T-cell receptor complex is that the clonotypic alpha- and beta-chains are involved in the recognition and binding of antigen in the context of polymorphic major histocompatibility complex (MHC) gene products on the surface of target cells. Antigen binding by the clonotypic receptor probably results in conformational changes in this structure which are recognized by and subsequently trigger the associated T3 complex to transmit signals into the cell, resulting in a proliferative response. The similarity in structure between murine and human clonotypic antigen receptors suggests that such a mechanism of recognition and activation also exists in mouse T lymphocytes, but so far there has been no evidence for the existence of a murine T3 complex. Here we demonstrate the existence of a T3 delta-chain mRNA in murine T lymphocytes. Our sequence data strongly suggest that this mouse mRNA codes for a complete T3 delta polypeptide chain and reveal some interesting properties of the protein. 相似文献