Blood-brain barrier transport of amino acids in healthy controls and in patients with phenylketonuria

Blood-brain barrier permeability to phenylalanine and leucine in four patients with phenylketonuria and in four volunteers was measured five times by the double-indicator method at increasing plasma concentrations of phenylalanine. Based on the permeability-surface area product (PS) from blood to brain (PS1) and on plasma phenylalanine levels, Vmax and the apparent Km for phenylalanine were determined. Statistically significant relationships between plasma phenylalanine and PS1 were established in three out of four volunteers, the average Vmax value being 46.7 nmol/g per min and the apparent Km 0.328 mmol/L. Owing to saturation of the carrier, such a relationship could not be established in the patients. In phenylketonuria, PS1 for phenylalanine and leucine decreased significantly by 55% and 46%, respectively. Transport from brain back to blood, PS2, decreased significantly and cerebral large neutral amino acid net uptake was generally decreased in patients with phenylketonuria. In conclusion, the transport of L-phenylalanine across the human blood-brain barrier follows Michaelis-Menten kinetics. In phenylketonuria, brain permeability to large neutral amino acids is reduced by about 50% and net uptake appears decreased.     

能耗的不等时距灰色模型及其应用

文章提出了能耗的不等时距灰色模型。该模型在浏阳磷矿的能耗预测中得以利用,结果证明该方法既简单,又可靠。     

Effect of hypoxia on the proliferation of retinal microvessel endothelial cells in culture

BACKGROUND: To determine if hypoxia stimulates the proliferation of retinal microvessel endothelial cells in culture. METHODS: Bovine retinal microvessel endothelial cells were cultured in normoxic (95% air, 5% CO2) and hypoxic (2% O2, 5% CO2, 93% N2) conditions. Endothelial cells were identified by acetylated LDL and Factor VIII-related antigen immunocytochemical staining. Cells from passages three to eight were used in these experiments. Proliferation assays included cell counts by hemocytometer and autoradiographic analysis of incorporated 3H-thymidine (3H-TdR). RESULTS: At day 4, cell counts of endothelial cells in hypoxia showed a 133% increase over those grown in normoxic conditions (N = 25, P < 0.01). Cell counts per day for 5 days were 121-181% greater in hypoxia. Autoradiography of endothelial cells exposed to 3H-TdR and counted every 12 hours for 60 hours exhibited labeling indices 112-118% higher in hypoxic conditions (P < 0.0001). Endothelial cells cultured under hypoxic conditions were smaller and spindle-shaped, whereas those grown under normoxic conditions were larger and more polygonal. CONCLUSIONS: Hypoxia increases DNA synthesis and stimulates proliferation of retinal microvessel endothelial cells in vitro and induces alterations in morphology. These results may be relevant to microvessel angiogenesis, which occurs in vivo under ischemic conditions.     

高压IGBT的研制

介绍高压绝缘栅双极晶体管（ＩＧＢＴ）的终端和单元的设计与制造技术；实验验证了两种用于１０００～１２００ＶＩＧＢＴ的高压终端，研制的芯片获得了７．５Ａ，耐压１１５０Ｖ的实验结果。     

Cu—Ni—Be高导电耐磨合金时效析出的TEM研究

本文用TEM确定了Cu—Ni—Be合金时效时G·P区和γ’析出相(NiBe)是合金硬度、电导率变化的重要原因,同时确立了NiBe与母相之间的相位关系:(110)_P//(100)_M,[001]_P//[001]_M;惯析面为[001]。     

First SIR-C ScanSAR results

During the two space shuttle missions in 1994, the Space-borne Imaging Radar-C (SIR-C) acquired several experimental datatakes: using the ScanSAR mode. Same of these ScanSAR data have been processed into images of swath wider than 200 km. Example images are shown. These early results demonstrate that ScanSAR operation is not only feasible, but also represents a potentially useful tool for regional and global scale imaging by the future SAR missions     

结构型铁砂基复合电波吸收体研究

由天然尖晶石铁氧体（铁砂）为基制备的复合电波吸收材料，在７～１２ＧＨｚ，吸收率Ａ为１２～２７ｄＢ，匹配厚度ｄ为１．４ｍｍ。将几种铁砂基复合吸收材料制成双层结构电波吸收体，Ａ最大达４０ｄＢ，匹配厚度ｄ为１ｍｍ，频带增宽。这是一种廉价的吸收材料，其造价仅为一般铁氧体吸收材料的１／１０，有较大实用价值。     

A robust and energy-efficient data dissemination framework for wireless sensor networks

Wireless sensor networks (WSNs) are appealing in obtaining fine-granular observations about the physical world. Due to the fact that WSNs are composed of a large number of low-cost and energy-constrained sensor nodes, along with the notorious time-varying and error-prone nature of wireless links, scalable, robust and energy-efficient data dissemination techniques are needed for the emerging WSN applications such as environment monitoring and surveillance. In this paper, we examine this emerging field from the point of view of supply chain management and propose a hybrid data dissemination framework for WSNs. In particular, for each sensing task, the whole sensor field is conceptually partitioned into several functional regions based on the supply chain management methodology. Different routing schemes are applied to different regions in order to provide better performance in terms of reliability and energy consumption. For this purpose, we also propose a novel zone flooding scheme, essentially a combination of conventional geometric routing and flooding techniques. Our hybrid data dissemination framework features low overhead, high reliability, good scalability and flexibility, and preferable energy efficiency. Detailed simulation studies are carried out to validate the effectiveness and efficiency of our scheme.