Tat-specific cytotoxic T lymphocytes select for SIV escape variants during resolution of primary viraemia

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by early peaks of viraemia that decline as strong cellular immune responses develop. Although it has been shown that virus-specific CD8-positive cytotoxic T lymphocytes (CTLs) exert selective pressure during HIV and SIV infection, the data have been controversial. Here we show that Tat-specific CD8-positive T-lymphocyte responses select for new viral escape variants during the acute phase of infection. We sequenced the entire virus immediately after the acute phase, and found that amino-acid replacements accumulated primarily in Tat CTL epitopes. This implies that Tat-specific CTLs may be significantly involved in controlling wild-type virus replication, and suggests that responses against viral proteins that are expressed early during the viral life cycle might be attractive targets for HIV vaccine development.     

Fringe is a glycosyltransferase that modifies Notch

Notch receptors function in highly conserved intercellular signalling pathways that direct cell-fate decisions, proliferation and apoptosis in metazoans. Fringe proteins can positively and negatively modulate the ability of Notch ligands to activate the Notch receptor. Here we establish the biochemical mechanism of Fringe action. Drosophila and mammalian Fringe proteins possess a fucose-specific beta1,3 N-acetylglucosaminyltransferase activity that initiates elongation of O-linked fucose residues attached to epidermal growth factor-like sequence repeats of Notch. We obtained biological evidence that Fringe-dependent elongation of O-linked fucose on Notch modulates Notch signalling by using co-culture assays in mammalian cells and by expression of an enzymatically inactive Fringe mutant in Drosophila. The post-translational modification of Notch by Fringe represents a striking example of modulation of a signalling event by differential receptor glycosylation and identifies a mechanism that is likely to be relevant to other signalling pathways.     

基于双尺度连续小波变换的二相编码信号识别

针对信号和噪声小波变换的模极大值在不同尺度上表现出截然不同的性质,提出一种利用粗细定位相结合的思想对二相编码信号奇异点实现精确定位的方法。该方法采用大尺度上的模极值点进行粗略定位奇异点出现的范围,并据此去除小尺度上的伪极值点,用小尺度上的模极值点精确定位奇异点出现的时刻。实验仿真比较了几种不同小波基函数下的算法性能,结果表明,该方法在采用db3小波基下对二相编码信号突变点的识别具有很好的效果。     

MIPv6切换延迟的优化方案

移动节点从一个接入路由器移到另一个接入路由器时会发生切换.由于链路交换延迟和IP层的相关操作使得移动节点在这个过程中不能够发送和接收数据.为减少移动IPv6切换延迟和满足时实需求,分析了快速移动IPv6和阶层移动IPv6切换协议特点,采用预先注册的方法给出了一种快速和阶层移动IPv6切换的融合方案,并详细的描述了该方案在宏观移动和微观移动情景下的原理架构结构和数据包的流程图.切换延迟分析结果,证明了方案的优越性.     

阵列天线通道不一致性校正的辅加阵元法

MUSIC算法是一种基于特征值分解的超分辨DOA估计算法,在理想阵列条件下,其估计性能良好,但当信号模型与实际信号环境不匹配,即存在系统误差时,MUSIC算法的估计性能会严重下降,甚至失效。针对模型中普遍存在的通道不一致性误差,本文首先分析了此类误差对测向性能的影响,并提出了一种通道误差校正的简易算法,该方法通过对来自辅加阵元信号的数据信息进行处理,获取通道不一致性误差的估计,通过误差补偿有效地抑制了通道不一致性的影响,提高了DOA估计的性能。给出了应用该方法的具体步骤,计算机仿真结果证明了该算法的有效性。     

空空导弹红外成像导引头建模与仿真

红外成像导引头仿真平台是分析导引头性能的重要手段,通过分析红外成像导引头仿真系统的设计要求,建立了仿真系统的总体结构,主要包括红外图像合成系统、成像探测系统、图像处理系统和平台伺服控制系统,并描述了各子系统的功能、组成、模型原理和工作过程。它们模拟了导引头接收目标红外辐射、从背景和干扰中检测识别目标并进行跟踪的过程。给出了系统的实现途径和攻击仿真实例,验证了系统的有效性,表明系统可用于改进导引头的性能设计。