Nucleoside-diphosphate kinase-mediated signal transduction via histidyl-aspartyl phosphorelay systems in Escherichia coli

Nucleoside-diphosphate kinase (NDP kinase), a key enzyme in nucleotide metabolism, is also known to be involved in growth and developmental control and tumor metastasis suppression. Interestingly, we find that coexpression of NDP kinase with Taz1, a Tar/EnvZ chimera, in the absence of its native signal, can activate a porin gene ompC-lacZ expression in Escherichia coli. Further studies show that NDP kinase can act as a protein kinase to phosphorylate histidine protein kinases such as EnvZ and CheA which are members of the His-Asp phosphorelay signal transduction systems in E. coli. Instead of ATP, the exclusive phosphodonor for histidine kinases, GTP can be utilized in vitro in the presence of NDP kinase to phosphorylate EnvZ and CheA, which then transfer the phosphoryl group to OmpR and CheY, the respective response regulators. The direct involvement of GTP for the phosphorylation of EnvZ through NDP kinase was further demonstrated by the use of a mutant EnvZ, which lost ability to be autophosphorylated with ATP. Phospho-OmpR thus formed can bind specifically to an ompF promoter sequence. These results suggest that NDP kinase may play a physiological role in signal transduction.     

Long-term progression in chronic manganism: ten years of follow-up

We studied the long-term clinical course of five patients with chronic manganese intoxication. The mean scores of the King's College Hospital Rating Scale for Parkinson's disease increased from 15.0 +/- 4.2 in 1987 to 28.3 +/- 6.70 in 1991 and then to 38.1 +/- 12.9 in 1995. The deterioration was most prominent in gait, rigidity, speed of foot tapping, and writing. Tissue concentrations of manganese in blood, urine, scalp hair, and pubic hair returned to normal. Follow-up MRIs did not show paramagnetic high-signal intensity on T1-weighted images. The data indicate that clinical progression in patients with manganese parkinsonism continues even 10 years after cessation of exposure.     

基于公共存储器进行数据交换的高速数字图象处理系统

本文介绍了一种基于公共存储器进行数据交换的高速数字图象处理系统．给出了公共存储器的设计，描述了处理器对公共存储器的进程同步控制．     

稀土萃取信息系统

应稀土化学发展的需要,我们组建了稀土萃取信息系统。其中包括:数据的来源和数据类型;数据的组织;检索功能;数据间的关联;最优化设计以及萃取剂结构与其物理性质和结构与萃取性能的相关分析研究。     

一种弧焊机器人实时激光扫描视觉系统

研制了一种小型高精度弧焊机器人实时激光扫描视觉系统，对其各项性能进行了测试，并进行了抗电弧光干扰试验，结果表明，此系统精度高，抗干扰能力强，检测范围宽，能广泛地应秀于机器人和自动化焊接中。     

Perceptual learning reflects external noise filtering and internal noise reduction through channel reweighting

To investigate the nature of plasticity in the adult visual system, perceptual learning was measured in a peripheral orientation discrimination task with systematically varying amounts of external (environmental) noise. The signal contrasts required to achieve threshold were reduced by a factor or two or more after training at all levels of external noise. The strong quantitative regularities revealed by this novel paradigm ruled out changes in multiplicative internal noise, changes in transducer nonlinearites, and simple attentional tradeoffs. Instead, the regularities specify the mechanisms of perceptual learning at the behavioral level as a combination of external noise exclusion and stimulus enhancement via additive internal noise reduction. The findings also constrain the neural architecture of perceptual learning. Plasticity in the weights between basic visual channels and decision is sufficient to account for perceptual learning without requiring the retuning of visual mechanisms.     

Closed-form physical model for VLSI bipolar devices consideringenergy transport

A closed-form physical model is reported for VLSI bipolar devices considering energy transport. Based on the model, for a base width of 810 Å, the bipolar device, biased at V_cb=2 V, has a peak electron temperature of over 700 K, which results in a 5% reduction in the collector current     

添加煤沥青提高焦炭强度的研究

本文进行了煤和煤沥青共炭化试验,将煤沥青添加到20kg焦炉内进行炼焦试验。结果表明,煤沥青对武钢用煤有一定的改质作用,添加煤沥青可提高焦炭强度。     

SiC颗粒尺寸及含量对SiCp／2024Al复合材料性能的影响

本文对粉末冶金法制备的SiCp/2024Al复合材料的性能进行了研究。随SiC颗粒尺寸的增大,复合材料的强度降低,而塑性和磨损抗力则增加。SiC颗粒尺寸对复合材料的物理性能没有什么影响。增加SiC颗粒含量,复合材料的强度、模量均增大,磨损抗力亦明显增加,而塑性和热膨胀系数则降低。     

Optimal Hybrid Control for Structures

A new method for integrated design of passive and active elements is presented. Rather than the existing qualitative selection of parameters for passive elements, a quantitative approach is proposed that finds optimal active and passive parameters with respect to an H₂/H_∞ performance requirement. This new approach automatically yields passive designs when the given performance limits are high enough and active (hybrid) designs when the given performance constraints are stringent. Furthermore, our algorithm finds the special performance requirement (the peak of the frequency response) that cannot be satisfied by any passive design. Hence this article shows how to determine when control is required rather than assuming a priori that it is or is not required. A simple design method given herein yields either passive, active, or hybrid designs depending only on the level of the performance constraints that are specified in the statement of the problem.