Factorization Index for Completely Positive Graphs

In this paper, we prove that the set of all factorization indices of a completely positive graph has no gaps. In other words, we give an affirmative answer to a question raised by N. Kogan and A. Berman [8] in the case of completely positive graphs. Received December 9, 1997, Accepted May 16, 2002     

城乡结合部小学高年级学生学习适应性的调查研究

通过对孝感城郊一小学高年级学生学习适应性的调查，运用科学的量表反映了城乡结合部小学高年级学生学习适应性不良的现状．由此分析了城乡结合部小学高年级学生学习适应性不良的几个显著原因，并提出了改善这种状况的四条建议。     

Modulation of low-frequency oscillations in GaAs MESFETs’ channel current by sidegating bias

Low-frequency oscillations in channel current are usually observed when measuring the GaAs MESFET‘s output characteristics. This paper studies the oscillations by testing the MESFET‘s output characteristics under different sidegate bias conditions. It is shown that the low-frequency oscillations of channel current are directly related to the sidegate bias. In other words, the sidegate bias can modulate the oscillations. Whether the sidegate bias varies positively or negatively, there will inevitably be a threshold voltage after which the low-frequency oscillations disappear. The observation is strongly dependent upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL2 under high field. This conclusion is of particular pertinence to the design of low-noise GaAs IC‘s.     

十二相整流器二极管功耗和结壳温升仿真计算

为了在十二相整流器设计中,实现仿真计算二极管功耗和结壳温升,保证其在高温的环境中可靠地工作,对非常规小型散热器,选用大容量二极管在中小电流条件下工作,以降低功耗和热阻,充分保证整流器有较高的过载能力,实现高可靠性的设计,提出了特殊要求的整流器体积可以做得更小,为解决目前十二相整流器设计中功耗和结壳温升问题提出了新的思路.     

间隙连接在鸡胚水晶体发育中的作用

初步报道已揭示，单克隆抗体ＮＤ６可影响鸡胚水晶体的发育，使之明显增大．ＮＤ６是一种被认为专一于膜蛋白ＭＰ２６细胞外侧段的单抗．ＭＰ２６已被认为是水晶体纤维细胞间隙连接的成份．因此，ＮＤ６很可能可阻断水晶体纤维细胞间隙连接的形成．本人试图用定量显微镜技术证实ＮＤ６对水晶体发育的影响与间隙连接数量减少之间的相关性。注射ＮＤ６于２０期鸡胚的右眼；同胚未注射的左眼作为对照．培养２４ｈ后周定，然后作下列三种处理：（１）测量整体水晶体的大小；（２）制备水晶体超薄切片，并统计间隙连接数量；（３）制备鸡胚头部的连续石蜡切片，并统计水晶体纤维细胞的数量．实验结果指出，在ＮＤ６处理２４ｈ，水晶体大小及纤维细胞数量均比对照组明显增大（表１，Ｐ＜０．０１或０．００１）；而间隙连接数量则比对照组明显减少（表２），Ｐ＜０．００１）．这表明，水晶体的增大及纤维细胞的增多是由间隙连接的减少所引起．这些结果证实，间隙连接在鸡胚水晶体的发育中起重要作用．     

Tunneling magnetoresistance of the double spin-filter junctions at nonzero bias

A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respectively) could have very high tunneling magnetoresistance (TMR) at zero bias. To meet the requirement in research and application of the magnetoresistance devices, we have calculated the dependences of tunneling magnetoresistance of DSFJ on the bias (voltage), the thicknesses of ferromagnetic insulators (semiconductors) and the average barrier height. Our results show that except its very high value, the TMR of DSFJ does not decrease monotonously and rapidly with rising bias, but increase slowly at first and decrease then after having reached a maximum value. This feature is in distinct contrast to the ordinary magnetic tunnel junction FM/NI/FM (FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator (semiconductor) spacer, respectively), and is of benefit to the use of DSFJ as a magnetoresistance device.     

Pseudoreceptor model for ryanodine derivatives at calcium release channels

This paper describes the generation of a pseudoreceptor model for ryanodine receptor (RyR) modulating ryanoids in rabbit skeletal muscle. For this purpose, the molecular modelling software PrGen was applied to correlate experimentally determined and calculated free energies of binding for a set of 15 ryanodine derivatives. The final model indicates a narrow cleft with hydrogen bond donor and acceptor capacities (represented by an Asn) as most crucial for binding the pyrrole carboxylate substituent at C3 of ryanodine. In addition, hydrophobic residues flank the aromatic pyrrole ring (Tyr, Phe, and Ile). Two of those residues (Tyr and Ile) interact with the 2-isopropyl moiety, which seems to contribute to binding. Opposite to the pyrrole locus, a second hydrophobic region (represented by a Leu) restricts ryanodine derivatives in their longitudinal axis and leads to the discrimination of equatorial and axial positioned methyl groups and of polar substituents at C9. Finally, a charged glutamate residue generates strong hydrogen bonding and electrostatic interactions with the hydroxyl groups at C10 and C15. For this binding-site model – composed of six amino acid residues – a correlation for the training set ligands of R = 0.99 (Q² = 0.975) and a root mean square (rms) deviation of 0.568 kcal/mol for the prediction of the binding energies of four test set ligands was obtained. Based on this pseudoreceptor model the putative topology of the real binding site of ryanoids will be discussed.     

螺旋CT三维重建及多平面成像对胸腰段脊柱爆裂骨折的诊断价值探讨

目的：探讨螺旋CT三维重建（CT3D）及多平面重建（MPR）对胸腰段脊柱爆裂骨折诊断的优缺点及临床应用价值。方法分析53例胸腰段脊柱爆裂骨折病例。分别行X线平片，CT及螺旋CT三维重建、多平面重建检查及技术处理。结果：CT对椎体中后柱骨折的显示有明显优越性，而三维重建及多平面重建不仅能具体、直观、形象显示骨折情况，而且对脊髓、神经根损伤的显示价值清楚。结论平片诊断爆裂骨折需与单纯压缩骨折鉴别，明确诊断需CT证实，螺旋CT3D和MPR对诊断及了解椎管内损伤有很好的应用价值。