Building maps of local apparent conductivity of the epicardium with a 2-D electrophysiological model of the heart

In this paper, we address the problem of estimating the parameters of an electrophysiological model of the heart from a set of electrical recordings. The chosen model is the reaction-diffusion model on the transmembrane potential proposed by Aliev and Panfilov. For this model of the transmembrane, we estimate a local apparent two-dimensional conductivity from a measured depolarization time distribution. First, we perform an initial adjustment including the choice of initial conditions and of a set of global parameters. We then propose a local estimation by minimizing the quadratic error between the depolarization time computed by the model and the measures. As a first step we address the problem on the epicardial surface in the case of an isotropic version of the Aliev and Panfilov model. The minimization is performed using Brent method without computing the derivative of the error. The feasibility of the approach is demonstrated on synthetic electrophysiological measurements. A proof of concept is obtained on real electrophysiological measures of normal and infarcted canine hearts.     

硫化铜矿抑制剂的结构—活性关系

抑制硫化铜矿然后浮选 MoS_2是 Cu-Mo 分离最常应用的工艺。虽然过去已经研究了不少有机抑制剂,但目前使用的铜抑制剂多数还是无机化合物(如 NaHS,诺克斯抑制剂等)。有机抑制剂超过无机化合物的一个独特的优点,是适应多种需要而进行有机分子设计时有较大的多功能性。本工作着手系统研究大量有机络合剂的结构—活性关系,与常用的也常常是无效、危险的无机抑制剂进行比较。用得到的实际溶液氧化还原电位与抑制剂活性间的关系这一看法,讨论了本研究获得的结果。研究确定了为使一种药剂达到工业应用的一系列必要条件,诸如在有机分子中存在一个-SH 活性基及-OH,-COOH 亲水基等。也讨论了关于非黄药捕收剂体系捕收剂在硫化矿表面覆盖层的解吸性(或破坏)的一些初步结果。     

雷达信号处理中的课题 第一部分:概述和相关处理技术(续)

杂波抑制抑制杂波是许多雷达系统中主要考虑的问题。利用动目标显示(MTI)或脉冲多卜勒(PD)原理就可以实现杂波对消。MTI或PD的设计取决于雷达的特殊性能和所确定的杂波形式。特别重要的是:是否只抑制固定的(零多卜勒)杂波或者还须抑制运动的杂波(云雨、金属箔条)。为了抑制固定的地杂波,有人曾     

采用介质谐振器的砷化镓MESFET振荡器的温度稳定性

本文提出了采用介质谐振器的场效应晶体管振荡器的简单的温度稳定性模型,并根据振荡条件,用该模型推出了振荡功率和振荡频率与温度的关系。具有适当的线性谐振频率/温度特性的叠式谐振器已试制成功,并被用来稳定采用介质谐振器的振荡器(DRO),在频率为11.5GHz、温度为-20℃到80℃时,获得了±120kHz的频率稳定度((?)±0.1ppm/K)。     

关于雷达自动检测和跟踪的综述

引言自雷达早期使用以来,雷达操纵员都是利用平面位置显示器和 A 型显示器的可见输入信息来检测和跟踪目标的.当操纵员精确地完成这项任务时,他们的大脑很容易饱和,而且很快就疲劳。为了改变这一状态,目前正在把自动检测和跟踪系统附加到许多雷达上。毫无疑问,由于数字处理速度提高,且硬件成本降低,体积减小,除了一些最简单的雷达之外,自动     

改进窄带语言传输的谐差线性预测声码器

本文介绍一种称之为谐差(Harmonic Deviations)声码器(HDV)的窄带语言编码器的发展、究究和试验结果。HDV编码器以LPC声码器为基础,除了LPC声码器所传输的数据外,它还传输谱差形式的附加信息,该谱差系指在选定频率组上语言谱和LPC全极点模型谱之间的差。在收端,则用这些谱差产生全极点综合滤波器的激励信号。本文描述并比较了以语言信号提取谱差并对谱差编码的若干种方法。为了将HDV编码器的比特率限制在2·4 kb/s,文中还讨论了包括正交变换和对数面积比的最小均方误差标量量化、两级矢量——标量量化以及可变帧率传输等。此外,文中还介绍了2·4kb/s HDV编码器的语言质量最佳化结果,研究了低噪声和噪声信道应用。指出所获得的HDV编码器在语言质量上比LPC声码器有了明显的提高。     

Atomic layer deposition of aluminum oxide films for carbon nanotube network transistor passivation

Ultra-thin (2-5 nm thick) aluminum oxide layers were grown on non-functionalized individual single walled carbon nanotubes (SWCNT) and their bundles by atomic layer deposition (ALD) technique in order to investigate the mechanism of the coating process. Transmission electron microscopy (TEM) was used to examine the uniformity and conformality of the coatings grown at different temperatures (80 degrees C or 220 degrees C) and with different precursors for oxidation (water and ozone). We found that bundles of SWCNTs were coated continuously, but at the same time, bare individual nanotubes remained uncoated. The successful coating of bundles was explained by the formation of interstitial pores between the individual SWCNTs constituting the bundle, where the precursor molecules can adhere, initiating the layer growth. Thicker alumina layers (20-35 nm thick) were used for the coating of bottom-gated SWCNT-network based field effect transistors (FETs). ALD layers, grown at different conditions, were found to influence the performance of the SWCNT-network FETs: low temperature ALD layers caused the ambipolarity of the channel and pronounced n-type conduction, whereas high temperature ALD processes resulted in hysteresis suppression in the transfer characteristics of the SWCNT transistors and preserved p-type conduction. Fixed charges in the ALD layer have been considered as the main factor influencing the conduction change of the SWCNT network based transistors.     

The new EC technical recommendations for monitoring individuals occupationally exposed to external radiation

The purpose of the European Commission technical recommendations (TR) for monitoring individuals occupationally exposed to external radiation is to provide guidance on those aspects of the implementation of the European Union Parliament and Council Directives directly related to individual monitoring of external radiation, and to encourage harmonisation thereof. They are mainly aimed at the management and staff of IM services but also at manufacturers, laboratories supplying type-testing services, national authorities trying to harmonise approval procedures, and government bodies to harmonise regulations and guidance. The TR main topics are: objectives and aims of IM for external radiation; dosimetry concepts; accuracy requirements; calibration, type testing and performance testing; approval procedures; quality assurance and quality control; and dose record keeping. Attention is paid to particular aspects, such as wide energy ranges for the use of personal dosemeters, pulsed fields and non-charged particle equilibrium; and use of active personal dosemeters. The TR give proposals towards achieving harmonisation in IM and the eventual mutual recognition of services and of dose results.     

A Poly(amphiphilic pyrrole)-Flavin Reductase Electrode for Amperometric Determination of Flavins

The electropolymerization of a flavin reductase-amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provides the efficient entrapment of the enzyme in a functionalized polypyrrole film. The enzyme film was characterized and applied to the detection of several flavins and pyridine nucleotides. The response of the bioelectrode was based on the amperometric oxidation, at -0.1 V vs SCE, of the enzymically generated dihydroflavins in the presence of reduced pyridine nucleotides. The highest sensitivities and detection limits were 668 mA M(-1) cm(-2) and 4 nM for riboflavin, 179 mA M(-1) cm(-2) and 20 nM for flavin mononucleotide, and 107 mA M(-1) cm(-2) and 40 nM for flavin adenine dinucleotide. Direct electrochemical measurements at -0.65 V and electroenzymatic measurements at -0.1 V of riboflavin, carried out with these bioelectrodes, show that an amplification phenomenon occurs, due to an electrochemical recycling reaction of enzyme substrate. A nonamplified response to reduced pyridine nucleotides was also obtained in the presence of 0.1 mM riboflavin. The sensitivity and detection limit of the bioelectrode are 19.6 mA M(-1) cm(-2) and 0.2 μM for NADH and 11.2 mA M(-1) cm(-2) and 0.5 μM for NADPH.     

Particulate material analysis by a laser ionization fast conductivity method. Water content effects

Combined laser multiphoton ionization and fast-conductivity methods have been applied to probe organic contamination on wet particulate samples. This is a first attempt of testing such a technique for this purpose. A special emphasis has been made on establishing correlation between sample water content and detection of pyrene, which has been used as a probe contaminant in this study. Environmental (soil) and artificial samples (silica gel) have been studied. The experimental setup includes a pulsed N(2) laser and a fast-conductivity detection system, operated in an opened chamber under ambient conditions. The correlation between the observed photoionization signals and water content has been investigated in a slow-drying mode, where water has been gradually evaporated. Surface contamination of wet samples has been more efficient than moist ones. This was evident, in the case of soil samples, from the earlier appearance (at lower pyrene concentrations) of saturation-type features of the detected photoionization signals. Assumptions of a contamination model has enabled certain compensation for sample and matrix effects.