温度变化对钾离子跨膜通道蛋白传输能力的影响

为了研究温度变化对生物膜跨膜传输能力的影响,本文以钾离子跨膜通道蛋白为研究对象,利用Gromacs分子生物学模拟软件包和Gromos96(53a6)分子力场,通过分子动力模拟技术和伞状采样方法详细研究了300K和275K两个温度条件下钾离子跨膜通道蛋白对单个钾离子的传输机理和Potentials of Means Force自由能在整个传输过程中的变化曲线。分析伞状采样的计算结果表明,温度的下降对钾离子跨膜通道蛋白的传输能力具有较大影响,300K时,钾离子在跨膜通道蛋白中的传输过程是热力学自发过程;然而,当温度下降到275K后,跨膜通道蛋白前沿空腔对钾离子的捕捉能力明显下降,选择性位点的能垒和传输通道的自由能普遍上升,导致跨膜通道蛋白出口的自由能高于其入口的自由能,最终使钾离子跨膜通道蛋白对钾离子传输方向发生逆转。同时该结果还可以对冷害发生的机理和防治给予重要的启示:说明温度下降后,果蔬体内物质传输能力的下降和停滞是造成冷害发生的一个主要原因。     

Particle transport in flow through a ratchet-like channel

We present a fluidic device that shows ratchet-like characteristics for particle transport at low Reynolds. The ratchet consists of a two-dimensional saw-tooth channel, within which a laminar flow is generated by imposing a longitudinal pressure gradient. Particle trajectories are calculated by solving the continuity and Navier–Stokes equations for the fluid flow and the equations for particle transport in both flow directions. The ratchet-like effect is connected with a large asymmetry in the mean transit time, with regard to flow direction, due to particle motion within zones of low flow velocity near the asymmetric wall profile. We show how to obtain ratchet of particles with select Stokes under given flow conditions by adjusting the geometry of the ratchet channel.     

M2M通信技术及其在智能电网中的应用

M2M通信是近年来随着物联网的兴起和发展而得到长足发展的下一代无线通信技术。该技术的发展和普及为智能电网功能的扩展和实现奠定了基础。文章介绍了M2M技术的发展历史和技术特色,探索了M2M通信在智能电网,特别是家庭区域网络的应用前景,同时指出了M2M通信技术目前所面临的问题和挑战。     

Molecular modelling of the GABAA ion channel protein

The GABAA ion channel protein is central to the mechanism of action of general anaesthetics and thus to the phenomenon of human consciousness. A molecular model of the alpha1beta2gamma2 gamma-aminobutyric acid type-A (GABAA) ligand-gated ion channel protein has been constructed. The cryo-electron microscopy structure of the nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata and the X-ray crystal structure of the acetylcholine binding protein (AChBP) from Lymnaea stagnalis were used as starting templates for comparative modelling. Features of the modelling approach used in the development of this GABAA model include: (1) multiple sequence alignment of members of the Cys-loop superfamily; (2) the design and implementation of a quasi-ab initio loop modelling algorithm; (3) expansion of the transmembrane domain (TMD) ion pore to model the open-state of the GABAA channel; (4) hydrophobicity analysis of the TMD to refine the structure in regions involved in general anaesthetic binding. The final model of the alpha1beta2gamma2 GABAA protein agrees with available experimental data concerning general anaesthetics.     

Effect of solvent polarization on electroosmotic transport in a nanofluidic channel

In this paper, we develop a theory based on the Langevin–Bikerman approach to study the electroosmotic (EOS) transport in a nanofluidic channel in the presence of finite solvent polarization effect (SPE). At the outset, we conduct an analysis based on practically achievable parameters to highlight the consequence of SPE in the variation in the electric double-layer (EDL) electrostatics. We witness that SPE invariably increases the effective EDL thickness; our numerical results are justified through a scaling analysis. More importantly, we unravel that the EOS transport, most remarkably, shows negligible influence on the qualitative variation in the EDL electrostatic potential; rather, it is dictated by the ratio of the effective to the actual EDL thicknesses. This finding, supported by scaling analysis, ensures that for the chosen set of parameters, SPE invariably enhances the EOS transport. Apart from shedding light on this extremely non-intuitive nanoscopic electroosmotic flow phenomenon, we anticipate that the present study will embolden us to better control the nanofluidic transport for a plethora of biological and industrial applications.     

Kernel ridge regression model for sediment transport in open channel flow

Neural Computing and Applications - Sediment transport modeling is of primary importance for the determination of channel design velocity in lined channels. This study proposes to model sediment...     

M2M的发展状况与未来

作为物联网在现阶段最普遍的应用形式,M2M已经引起了越来越多的关注。对M2M的发展背景、研究现状及其市场前景进行了深入分析和研究,分析了传统的工业领域、汽车领域以及移动终端之间通信的美好前景,指出了M2M的发展思路与对策。最后给出结论:M2M将改变人们身边的机器,从而最终改变人们的生活。     

1090 MHz信道分析软件设计与实现

为分析1090 MHz信道具体占用情况,提出一种1090 MHz信道分析软件设计与实现方法.该软件采用C++语言编程,将接收机接收到的1090 MHz统计数据帧进行解析处理,利用处理后的数据实时监测信道占用情况;创建本地数据库,将数据进行分类存储和统计;使用MFC制作上位机软件界面,调用后台数据库中存储的数据,对全天的...     

M2M技术及其安全性讨论

文章介绍了M2M的概念、架构与应用,并给出了一个具体的M2M应用实例。分析了M2M的安全威胁和对策,简要回顾了当前的M2M安全研究现状,指出了需要研究的M2M安全问题并加以分析。     

M2M communications based on the M-Bus protocol

M2M communications promise unprecedented prospects for communication specialists: the world communication network currently covers less than 0.1% of the total amount of equipment (estimated at 50 billion). Having considered the problem of energy saving, the European Commission in 2009 issued a mandate for the European Telecommunications Standards Institute (ESTI) to create a common open architecture for metering the domestic use of water, gas, electricity, and heat. We consider the choice of the M-Bus protocol as a unified tool for implementing the interfaces of M2M devices. A new approach to open programming interfaces is proposed.     

New efficient M2C and M2M mutual authentication protocols for IoT-based healthcare applications

Peer-to-Peer Networking and Applications - With the rapid advancement of heterogeneous wireless technologies and their proliferation in ambient connected objects, the Internet of Things (IoT) is a...     

Designing and verifying a P2P service security protocol in M2M environment

Multifunctional high-performance electronic systems in M2M(Machine-to-Machine) industry have been evolving substantially in tandem with the advancement of IT. M2M, standing for machine-to-machine communication, replaces people in cases where human intervention is hardly viable or in such fields as weather, environment or disasters where long-term monitoring is required. Yet, due to the nature of M2M devices involving wireless communication, they are exposed to intruders’ attacks. Thus, the overriding concern in M2M communication is mutual authentication and security. In this context, security communication protocols are considered worth exploring. This paper concerns designing a safe communication protocol by applying hash locks, random numbers and session keys. Instead of arguing for the security of the protocol based on mathematical theorem proving as most previous studies did, the present paper demonstrates the proposed protocol is safe against a variety of intruders’ attacks by formally verifying it using Casper/FDR. In short, the proposed protocol is verified in terms of safety, deadlock and livelock.     

M2M功能架构与安全研究

M2M通信被看作是一种不需要人际互动的机器之间的通信形式,通过通信网络传递信息从而实现机器与机器或人与机器的数据交换。M2M作为物联网在现阶段发展的主要存在形式,其功能架构和安全问题值得重视,文中主要围绕M2M功能架构与安全问题展开研究。针对此问题,欧洲电信标准化协会详细说明了M2M系统相关的安全需求,对机密性、完整性、身份认证以及授权批准进行了研究。此外ETSI还对M2M系统的功能架构进行了设计,提出了概要层的架构方案。最后对该功能架构中各部分涉及安全的模块作了进一步分析。     

M2E2算法的研究

研究了关于ME(Modular Exponentiation)的一种新算法,称之为M^2E^2(Multiple Modular Exponentiation Exploitation)算法。这种新算法是基于带符号数的复数运算(类似于二进制数的综合算术)。此算法对基于多重取幂密码协议的快速运作是很有效用的。     

基于M2M平台的J2ME应用程序的研究与设计

1M2M平台综合了电信和信息技术,能够使业务流程自动化,集成公司IT系统的资产,并创造增值服务。这项平台能够在广泛的应用和解决方案环境中运行,如自动读取停车表、安全设施、自动扶梯控制、车队管理、自动售货机和电动设备等都是其大显身手的应用环境。本文从其概念及应用出发,提出了其与J2ME移动应用相结合的实现策略、实际系统开发设计方案与影响其发展与应用的因素。     

无线网络可靠多播反馈算法的优化

无线网络具有高误码率和高丢失率的特点。可靠多播协议NORM使用基于时间片的反馈补偿机制,反馈周期长,不能充分利用带宽,尤其不能适用于无线网络上具有时延敏感特点的流媒体应用的要求。应用反馈轮机制优化NORM协议的反馈算法,以“轮”为单位实现NACK（Negative-Acknowledgment）控制,及时响应接收端的修复请求,将接收端等待修复的时间平均到每一轮中,有效降低了时延,且提高了带宽利用率。实验结果表明,在最大发送速率为2 Mb/s的设定下,协议在无线网络上的有效载荷吞吐量提高了0.5倍,且消除了抖动,具有低延迟的特点,更适合于流媒体传输应用的需要。     

2M高速信令链路MTP2的分析与设计

随着全国电信业务量的不断增加,特别是移动用户数量的剧增,原有的No．7信令网中使用的信令链路的带宽已经不能完全适应网上业务量的需求,无论是电信运营部门还是设备生产厂商都提出了对高速信令链路的需求;另一方面由于芯片技术的发展,微处理器速度的不断提升也为实现高速信令链路在技术上提供了支持。分析了2M高速信令链路与No．7信令链路在协议上的差别以及2M高速信令链路在MTP2层的软件设计以及功能划分,从而为具体实现提供了步骤及方法。     

质子交换膜在SO_2传感器中的应用

SO2是一种主要的大气污染物,对环境造成的危害十分巨大,对其测定具有重要意义。阐述了用质子交换膜做固体电解质的SO2传感器的工作原理及存在的主要问题,介绍了为解决膜在高温下易失水这一问题,各国研究者在改性Nafion膜及反应合成制备质子交换膜两方面的研究进展。指出这类传感器未来发展情况。     

Dejittering in the transport of MPEG-2 and MPEG-4 video

When multimedia information is transported over a packet-switched network, the quality of presentation can be degraded due to network delay variation or jitter. This paper presents a dejittering scheme that can be used in the transport of MPEG-4 and MPEG-2 video to absorb any introduced network jitter, thus preserving the presentation quality of transported media streams. The dejittering scheme is based on the statistical approximation of delay variation in the arrival times of video packets carrying encoded clock reference values and a filtering and re-stamping mechanism. In addition, a brief overview of the MPEG-4 system is presented.