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911.
C.H.陈 《国外科技新书评介》2006,(12):11-12
本书的第一、二、三版分别于1993、1999和2005年出版。书中全面提供了过去20年中在模式识别与计算机视觉领域中的进展和成就,作者都是这个领域的第一流专家,其中的两位Thomas Huang和Jake Aggarwal是权威的K.S.Fu奖金获得者,该项奖金是由国际模式识别协会(IAPR)授予。 相似文献
912.
本书全面论述了传输、管理和控制位面的技术,介绍了一些有用的、现行的和下一代电讯网络技术的参考信息。四位作者均在电信学研究、产品开发等方面具有20年以上的经验。 相似文献
913.
党刚 《国外科技新书评介》2006,(2):20-21
这是一本关于哲学如何给物理带来灵感,而物理又如何去影响哲学的书。哲学给科学带来基本观念和预设,但通过科学发现,这些观念又常常受到怀疑和修正,而伟大的科学家常常知道这种影响的脉络所在。本书通过清晰的论述和精美的插图,以科学哲人为中心讲述了他们的伟大发现,以及什么力量又促使他们重新考虑那些过去科学描述自然世界的惯常观念。书中还阐述了:因为电磁学、热力学和原子结构上的发现,使我们对科学和自然的理解经历了基本概念上的改变。 相似文献
914.
D. DiFrancesco F. Porciatti I. S. Cohen 《Cellular and molecular life sciences : CMLS》1991,47(5):449-452
Summary The isolation of ionic fluxes contributing to electric currents through cell membranes often requires block of other undesired components which can be achieved, among others, by divalent cations. Mn2+ and Ba2+ are often used, for example, to block Ca and K currents. Here we have investigated the effects of these two cations on the properties of the hyperpolarization-activated pacemaker current if, in rabbit sino-atrial node myocytes, as obtained by voltage clamp analysis. We find that 2 mM Mn2+ shifts the if activation curve by 3.2±0.3 mV towards more positive values. However, when 1 mM Ba2+ is also added, the positive shift is more than halved (1.3±0.2 mV). We find, too, that in the absence of blocking cations the ACh-induced if inhibition is slightly higher than in their presence. These results indicate that the alteration of if kinetic properties by Ba2+ plus Mn2+-containing solutions is minimal. 相似文献
915.
1 .INTRODUCTIONTheabilityofpositioningmobileobjects (MOs) ,in cludingvehiclesandtravelersholdingmobiletermi nals,isafundamentalfunctionforsomeITSsubsys tems,suchasemergencyrescue,securitysystem ,au tomaticnavigationsystem ,andtrafficinducementsystem[1 ] .Atpresent,therearethreedominatingtypes[2 ]ofwirelesspositioningtechnologies,i.e.positioningbasedonsatellites,positioningbasedondedicatedcommunicationsystemsandpositioningbasedonpub liclandwirelesstelecommunicationsystems (PLMTS) ,respe… 相似文献
916.
S. Benvenuti A. Gagliardo T. Guilford P. Luschi 《Cellular and molecular life sciences : CMLS》1996,52(6):608-612
In order to investigate the pigeon's compass mechanism, a series of overcast tests with clock-shifted birds were run at two familiar release sites. While controls were able to assume a correct homeward direction, the experimental birds' initial orientation cannot be explained either on the basis of a time-compensated sun compass or of a time-independent magnetic compass. Speculative explanations of our paradoxical results are attempted. 相似文献
917.
Sequence-directed curvature of DNA 总被引:42,自引:0,他引:42
P J Hagerman 《Nature》1986,321(6068):449-450
DNAs from both prokaryotic and eukaryotic organisms have yielded restriction fragments which manifest markedly anomalous electrophoretic behaviour (reduced mobility) when run on polyacrylamide gels. We have shown previously that the abnormal electrophoretic behaviour of one such fragment is a consequence of stable curvature of the helix axis in solution. The molecules involved tend to contain oligo(dA)-oligo(dT) runs which are approximately in-phase with the helix repeat; however, the precise structural elements responsible for DNA curvature have not been identified. One popular model for curvature invokes a non-coplanar 'wedge-like' conformation of ApA/TpT dinucleotide pairs. Despite a lack of direct evidence in support of this model, it has been used to provide quantitative estimates of curvature. To critically evaluate the ApA wedge model, we have performed an electrophoretic analysis of a series of closely related DNA polymers in which oligo(dA)-oligo(dT) runs of different polarity were compared. We conclude that ApA dinucleotide wedges cannot account for DNA curvature. Therefore, quantitative estimates for ApA wedge deformations, based solely on apparent curvature, cannot be correct. 相似文献
918.
919.
920.
High frequency of unequal recombination in pseudoautosomal region shown by proviral insertion in transgenic mouse 总被引:16,自引:0,他引:16
The mammalian X and Y chromosomes, in contrast to the autosomes, pair during male meiosis only near the telomeres. Alleles localized in this region can undergo reciprocal exchange during meiosis. Because such sequences do not show strict sex-linked inheritance, they have been termed pseudoautosomal. In man, several DNA sequences have been described which show pseudoautosomal transmission and which are localized in the pairing region at the ends of the short arms of both the X and Y chromosomes (refs 6-9, and D. Page, unpublished results). We now show that the transgenic mouse strain, Mov-15, contains a single Moloney murine leukaemia virus (M-MuLV) genome in its germline, and genetic evidence indicates that the provirus is integrated into the pseudoautosomal region of the sex chromosome. Proviral copies are lost or gained in 7% of male meioses in this strain, and mouse sequences flanking the provirus are tandemly repeated and highly variable. We conclude that unequal recombination events occur with high frequency in the pairing region, possibly because of the presence of repeated sequences. 相似文献