互相关优化改进矩阵束算法及其在次同步振荡模态参数辨识的应用

针对传统的矩阵束算法在低信噪比时存在计算数值不稳定、极点提取精确度不高的缺点,提出了一种基于互相关(cross-correlation,CC)优化的改进矩阵束(improved matrix pencil algorithm,IMP)算法,应用于电力系统次同步振荡模态辨识,并结合算例与传统的矩阵束算法和改进Prony算法辨识结果进行了比较。结果表明:该方法能快速准确地辨识系统的次同步振荡模态,具有拟合度高、抗噪声能力强的特点,有助于大系统及强噪声背景下次同步振荡模态分析及阻尼控制器的设计研究。     

脑显像剂IMP的放射性碘标记及动物实验

文章报道了对本校合成的RS-N-Isopropyl-P-Iodoamphetamine进行~(125)I标记和动物实验的初步结果。我们采用水热法进行同位素交换反应,在Cu(II)和过量还原剂存在的条件下,可以方便地获得高标记率的~(125)I-IMP。经萃取纯化后,放化纯度>98%;游离~(125)I<1%。测定了在大鼠体内静脉注射~(125)I-IMP的分布,结果表明,~(125)I-IMP具有脑摄取率高、脑与血的比值大、在脑贮留时间长等优点,是一种有用的新型脑显象剂。     

静电注入对55 nm MV/HV GGNMOS ESD性能的影响

静电防护问题是提升集成电路可靠性面临的主要挑战之一.基于55 nm HV CMOS工艺,研究了静电注入对中压(MV)和高压(HV) GGNMOS(Gate-Grounded NMOS)器件静电防护性能的影响.研究结果表明,对MV GGNMOS器件来说,静电注入能够在有效降低开启电压(Vt)、保持电压(Vh)的同时,减小...     

Mitochondrial Processing Peptidases—Structure,Function and the Role in Human Diseases

Mitochondrial proteins are encoded by both nuclear and mitochondrial DNA. While some of the essential subunits of the oxidative phosphorylation (OXPHOS) complexes responsible for cellular ATP production are synthesized directly in the mitochondria, most mitochondrial proteins are first translated in the cytosol and then imported into the organelle using a sophisticated transport system. These proteins are directed mainly by targeting presequences at their N-termini. These presequences need to be cleaved to allow the proper folding and assembly of the pre-proteins into functional protein complexes. In the mitochondria, the presequences are removed by several processing peptidases, including the mitochondrial processing peptidase (MPP), the inner membrane processing peptidase (IMP), the inter-membrane processing peptidase (MIP), and the mitochondrial rhomboid protease (Pcp1/PARL). Their proper functioning is essential for mitochondrial homeostasis as the disruption of any of them is lethal in yeast and severely impacts the lifespan and survival in humans. In this review, we focus on characterizing the structure, function, and substrate specificities of mitochondrial processing peptidases, as well as the connection of their malfunctions to severe human diseases.     

基于谐波插入的提高混频器线性度方法的研究

提出了将谐波插入用于提高混频器线性度的方法。该方法是将输出信号的二次谐波及二次互调产物反馈(插入)到输入端,通过非线性系统后产生的信号可抵消由原信号引入的交调产物,从而减少输出端交调失真的一种反馈技术。与前馈法相比,二次谐波插入法具有电路简单、性能稳定、成本低廉等优点,而且便于实现。谐波插入方法对中频三阶交调产物抑制作用明显。给出了该方法的理论分析并做了仿真实验。     

Ascorbate enhances iron uptake into intestinal cells through formation of a FeCl3–ascorbate complex

It has been well documented that ascorbate enhances iron uptake, with a proposed mechanism based on reduction to the more absorbable ferrous form. We have performed a study on the effects of ascorbate on ferric iron uptake in the human epithelial Caco-2 cell-line. Ascorbate increased uptake in a concentration-dependent manner with a significant difference between iron uptake and reduction. Uptake kinetics are characteristic of a non-essential activator and the formation of an Fe³⁺–ascorbate complex. This investigation provides evidence that ascorbate enhances the apical uptake of ferric iron into Caco-2 cells through the formation of a Fe³⁺–ascorbate complex.     

肌苷酸的研究现状及展望

从发展历史、特性、检测技术以及在食品科学和动物科学中应用等方面对目前肌苷酸的研究现状进行概述,并简要介绍了影响肌苷酸降解和生成的酶系和工业中生产肌苷酸的方法原理。针对目前的研究进展,并从检测技术、遗传育种、食品加工和评价新鲜度方面提出需要进一步解决的问题和研究发展方向。     

Interfacial Reaction Between Cu Substrates and Zn-Al Base High-Temperature Pb-Free Solders

Chemical reactions between Cu substrates and Zn-Al high-temperature solder alloys, Zn-4Al and Zn-4Al-1Cu (mass%), at temperatures ranging from 420°C to 530°C were experimentally investigated by a scanning electron microscope using backscattered electrons (SEM-BSE) and an electron probe microanalyzer (EPMA). Intermediate phases (IMPs), β(A2) or β′(B2), γ(D8₂), and ε(A3) phases formed and grew during the soldering and aging treatments. The consumption rate of the IMP for Cu substrates is described by the square root of t in both the alloys, while the additional Cu in the molten Zn-Al alloy slightly suppresses the consumption of Cu substrates. The growth of IMPs during soldering treatment is controlled by the volume diffusion of constituent elements, and its activation energy increases in the order of Q _ε < Q _γ < Q _β. In view of the aging process, the growth of IMPs is considered to be controlled by the volume diffusion. In particular, the layer thickness of γ rapidly grows over 200°C, although the thickness of the β layer grows very slowly.     

Molecular cloning and sequence analysis of the Schizosaccharomyces pombe ade10+ gene

We have cloned and sequenced the Schizosaccharomyces pombe ade10 gene encoding 5-phosphoribosyl-4-carboxamide 5-aminoimidazole transformylase inosine monophosphate cyclohydrolase. The sequence has an uninterrupted open reading frame of 1755 nucleotides corresponding to 585 amino acid residues. The deduced amino acid sequence shows a high degree of similarity to the purH gene product of many species, including Saccharomyces cerevisiae, human, chicken and Escherichia coli. Moreover our data indicate that intrachromosomal recombination in Schiz. pombe is enhanced if the ade10 gene product is defective. The sequence has been submitted to the EMBL data library under Accession Number Y16419. © 1998 John Wiley & Sons, Ltd.