一种抗阻断攻击的认证组密钥协商协议

一个非认证的组密钥协商协议不能对通信参与者和消息进行认证,它必须依赖认证的网络信道或其它的认证方法.分析了Burmester等人在认证广播信道下提出的著名组密钥协商协议,指出它不能抵抗内部恶意节点发起的密钥协商阻断攻击,该攻击导致组内其它诚实节点不能正确计算出一致的组密钥.提出了一种改进的认证的组密钥协商协议,在原协议中加入了消息正确性的认证方法,能够对组内恶意节点进行检测,并在随机预言模型下证明了改进的协议能够抵抗密钥协商阻断攻击.     

Ad Hoc网络的数据安全传输方案研究

由于Ad Hoc网络结构的特点,使其更容易遭到攻击,安全的路由和安全数据传输已成为Ad HOC网络研究的热点.对于网络的外部攻击,在不同的假设条件下,已经提出了一些有效的抵制方案.但对于内部攻击,还没有一种快速、准确、可行的对恶意行为进行预防和检测的方法,一般采用信誉机制加以解决,但存在较多缺点.本文基于Reed-Solomon编码的纠错技术,提出了一种在存在Byzantine攻击节点的网络环境下的安全数据传输协议(Secure Data Transmission Protocol,SDTP).该协议不仅能实现数据的安全传输,而且能准确判定恶意攻击的发生和攻击节点的位置,为在Ad Hoc网络中检测内部攻击节点提供了一种更准确、具体且实际可行的算法,该算法也可被用于安全路由协议中.     

Ad Hoc网络中一种基于环状分层结构的组密钥协商协议

移动ad hoc网络是一种新型的移动多跳无线网络.其自身的特征,如网络规模庞大、动态的拓扑结构、有限的计算、通信和存储能力等,使得传统的密钥分配和管理机制无法直接应用于该网络.提出了一种新的适用于移动 ad hoc网络的组密钥协商协议.该协议在环状分层结构上基于多线性映射进行组密钥的协商和分配,使得节点在密钥协商过程中具有低计算开销与低通信开销的优势,较好地解决了在移动ad hoc网络中进行组密钥协商时所遇到的节点能量受限问题,适用于移动ad hoc网络.     

基于攻击因子的Ad hoc网络多路径安全路由机制

作为Ad hoc网络大规模应用的先决条件,安全问题必须得到解决.为了加强对中间节点的安全评估以及对多路径路由的保护,本文提出一种基于攻击因子AF(Attacking Factor)的多路径安全路由机制,引入能够衡量节点当前及未来遭受攻击的可能性的攻击因子以评估多路径集的安全性,并在此基础上实现了链路安全预警,降低了恶意攻击带来的损失.仿真结果表明,在不安全的网络环境下,本文机制有效保护了路由控制消息,提高了多路径路由建立的效率.     

一种基于链路状态组合度量的无线网状网路由协议

在分析Ad hoc网络中的经典路由协议AODV的基础上,结合无线网状网的特点,提出了基于链路加权的无线网状网路由协议MODVWLS.协议通过节点的可用带宽、缓冲队列和吞吐性能等计算每一跳的代价(即权重),选择从信源到信宿累计权重最小的路径作为路由.对链路权重计算、报文格式、路由发现和维护过程进行了详细阐述,并利用NS2对MODVWLS协议进行了仿真实现.结果表明,MODVWLS协议能合理利用空闲节点和链路资源,较好地均衡网络负载,在数据包转发率、端到端延迟和标准化路由负载等性能上均优于AODV协议.     

一种基于双线性配对的移动自组网密钥协商协议

移动自组网是一种无固定网络基础设施、能量和计算资源有限的分布式动态网络,由于其无线传输链路的开放性,使得它非常需要一种计算和通信开销较小的密钥协商方案.本文基于椭圆曲线上双线性配对的概念,提出了一种适用于移动自组网的可认证密钥协商方案,既实现了邻居节点组成员身份认证的匿名性,也实现了需建立会话的节点之间的可认证密钥协商.分析表明,我们所提出的方案计算和通信开销比较小,安全性较好,非常适合于资源有限的移动自组网.     

密钥协商协议进展

密钥协商协议允许两个或多个用户在公开网络中建立一个共享密钥,是最基本的密码原型和公钥密码学的基础.本文综述密钥协商协议的研究进展,包括密钥协商的安全模型、传统离散对数环境下的密钥协商协议、最近发展起来的基于双线性对的密钥协商协议以及基于口令的密钥协商协议,指出了密钥协商协议中的公开问题和未来可能的发展方向.     

Ad Hoc网络中QoS路由协议算法的研究

Ad Hoc网络是一种由移动节点组成、拓扑结构动态变化的自组织网络,在Ad Hoc网络中实现带有QoS约束的路由是当今研究的重要问题.QoS路由协议算法中最主要的三个方面是:QoS参数的选取,对单向链路的支持和路由协议的多播功能.本文首先介绍了应用较广的几类QoS路由协议的算法,接着选取了以上三个方面中几个典型的QoS路由协议,详细介绍了它们的特点以及算法思想,并对协议的性能进行了具体分析,分析结果对研究QoS路由协议有一定的指导意义.     

非否认协议中认证保密性的设计与形式化分析

探讨了非否认协议的保密性认证目标,用攻击的方法验证了A(0)协议在认证保密性方面的不足;对其消息格式和会话密钥建立后确认方式做了修改,提出了NA(0)协议;进一步运用SVO逻辑对NA(0)协议进行了形式化的分析,验证了NA(0)协议满足主体身份的认证性和会话密钥的保密性.     

PGA:一种基于最优路径的Ad Hoc网络地理路由算法

本文提出了一种基于最优路径的Ad Hoc网络的地理路由算法PGA及其改进算法H-PGA,该算法在路径的构造、路由、路由恢复各个方面都应用了最优路径路由的概念,较好地解决了地理路由算法中的凹节点问题.在网络节点数n较大的情况下,依然保持很高的报文投递率(n=400、网络度为4时,报文投递率为96%),且实际路径很接近最短路径路径.同时H-PGA路由表的大小与平方根√n成线性关系,单个节点的协议带宽消耗也为O(平方根n),这使得H-PGA可以适用于较大的应用范围.     

Efficacy of gut lavage,hemodialysis, and hemoperfusion in the therapy of paraquat or diquat intoxication

Clinical and in vitro investigations were carried out to test the efficacy of gut lavage, hemodialysis, and hemoperfusion in the treatment of poisoning with paraquat or diquat. In a patient suffering from diquat intoxication 130 times more diquat was removed by gut lavage 30 h after ingestion than was removed by complete aspiration of the gastric contents.Determination of in vitro clearances for paraquat and diquat by hemodialysis showed that, at serum concentrations of 1–2 ppm, such as are frequently encountered in poisoning in man, toxicologically relevant quantities of herbicide cannot be removed from the body. At a concentration of 20 ppm, on the other hand, hemodialysis proved to be effective, the clearance being 70 ml/min at a blood flow rate of 100 ml/min. The efficacy of hemoperfusion with coated activated charcoal was on the whole better. Especially at concentrations around 1–2 ppm, the clearance values for hemoperfusion were some 5–7 times higher than those for hemodialysis.In a patient suffering from paraquat poisoning, both hemodialysis as well as hemoperfusion were carried out. The in vitro results could be confirmed: At serum concentrations of paraquat less than 1 ppm no clearance could be obtained by hemodialysis while by hemoperfusion with activated charcoal quite high clearance values were measured and the serum level dropped down to zero.

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Zusammenfassung Klinische Untersuchungen und Laboratoriumsversuche wurden durchgeführt, um die Wirksamkeit von Darmspülung, Hämodialyse und Hämoperfusion bei Paraquat- und Deiquat-Vergiftungen zu prüfen.Bei einem Patienten wurde 30 Std nach Deiquat-Aufnahme durch Darmspülung 130mal mehr Deiquat entfernt als durch vollständige Aspiration des Mageninhaltes. In vitro-Versuche ergaben, daß bei Blutserumkonzentrationen von 1–2 ppm, die bei Vergiftungen oft gemessen werden, durch Hämodialyse keine toxikologisch relevanten Paraquat- oder Deiquat-Mengen entfernt werden können. Dagegen erwies sich die Hämodialyse bei 20 ppm und einer Blutumlaufgeschwindigkeit von 100 ml/min mit einer Clearance von 70 ml/min als wirksam. Die Hämoperfusion mit beschicheter Aktivkohle war in diesen Versuchen aber eindeutig überlegen, denn insbesondere bei Konzentrationen um 1–2 ppm waren die Clearance-Werte 5–7mal höher als bei der Hämodialyse.Die in vitro-Ergebnisse wurden bei einem Patienten mit einer Paraquat-Vergiftung bestätigt: Bei Konzentrationen unter 1 ppm war die Hämodialyse wirkungslos, während durch Hämoperfusion relativ hohe Clearance-Werte erreicht wurden, so daß der Serumspiegel rasch unter die Nachweisgrenze abfiel.

     

In vitro studies on sterically stabilized liposomes (SL) as enzyme carriers in organophosphorus (OP) antagonism

This study describes a new approach for organophosphorous (OP) antidotal treatment by encapsulating an OP hydrolyzing enzyme, OPA anhydrolase (OPAA), within sterically stabilized liposomes. The recombinant OPAA enzyme was derived from Alteromonas strain JD6. It has broad substrate specificity to a wide range of OP compounds: DFP and the nerve agents, soman and sarin. Liposomes encapsulating OPAA (SL)* were made by mechanical dispersion method. Hydrolysis of DFP by (SL)* was measured by following an increase of fluoride ion concentration using a fluoride ion selective electrode. OPAA entrapped in the carrier liposomes rapidly hydrolyze DFP, with the rate of DFP hydrolysis directly proportional to the amount of (SL)* added to the solution. Liposomal carriers containing no enzyme did not hydrolyze DFP. The reaction was linear and the rate of hydrolysis was first order in the substrate. This enzyme carrier system serves as a biodegradable protective environment for the recombinant OP-metabolizing enzyme, OPAA, resulting in prolongation of enzymatic concentration in the body. These studies suggest that the protection of OP intoxication can be strikingly enhanced by adding OPAA encapsulated within (SL)* to pralidoxime and atropine.     

Aquatic Insects and Trace Metals: Bioavailability,Bioaccumulation, and Toxicity

Abstract

The uptake of metals from food and water sources by insects is thought to be additive. For a given metal, the proportions taken up from water and food will depend both on the bioavailable concentration of the metal associated with each source and the mechanism and rate by which the metal enters the insect. Attempts to correlate insect trace metal concentrations with the trophic level of insects should be made with a knowledge of the feeding relationships of the individual taxa concerned. Pathways for the uptake of essential metals, such as copper and zinc, exist at the cellular level, and other nonessential metals, such as cadmium, also appear to enter via these routes. Within cells, trace metals can be bound to proteins or stored in granules. The internal distribution of metals among body tissues is very heterogeneous, and distribution patterns tend to be both metal and taxon specific. Trace metals associated with insects can be both bound on the surface of their chitinous exoskeleton and incorporated into body tissues. The quantities of trace meals accumulated by an individual reflect the net balance between the rate of metal influx from both dissolved and particulate sources and the rate of metal efflux from the organism. The toxicity of metals has been demonstrated at all levels of biological organization: cell, tissue, individual, population, and community. Much of the literature pertaining to the toxic effects of metals on aquatic insects is based on laboratory observations and, as such, it is difficult to extrapolate the data to insects in nature. The few experimental studies in nature suggest that trace metal contaminants can affect both the distribution and the abundance of aquatic insects. Insects have a largely unexploited potential as biomonitors of metal contamination in nature. A better understanding of the physico-chemical and biological mechanisms mediating trace metal bioavailability and exchange will facilitate the development of general predictive models relating trace metal concentrations in insects to those in their environment. Such models will facilitate the use of insects as contaminant biomonitors.     

Pharmacological treatment of COVID-19: an opinion paper

The precocity and efficacy of the vaccines developed so far against COVID-19 has been the most significant and saving advance against the pandemic. The development of vaccines has not prevented, during the whole period of the pandemic, the constant search for therapeutic medicines, both among existing drugs with different indications and in the development of new drugs. The Scientific Committee of the COVID-19 of the Illustrious College of Physicians of Madrid wanted to offer an early, simplified and critical approach to these new drugs, to new developments in immunotherapy and to what has been learned from the immune response modulators already known and which have proven effective against the virus, in order to help understand the current situation.     

Alzheimer’s disease – current trends in basic and clinical research. Highlights from the 16th ECNP

Advances in the molecular biological knowledge of neuronal nicotinic acetylcholine receptors (nAChRs) have led to a growing interest by the pharmaceutical industry in the development of novel compounds that selectively modulate nAChR function. The ability of (-)-nicotine, an activator of nAChRs, to enhance attentional aspects of cognition in animals and humans, to exert neuroprotective and anxiolytic-like effects, and presumably to mediate the negative correlation between smoking and Alzheimer's (and Parkinson's) Disease, has focused interest on the potential therapeutic utility of modulators of nAChR function for treatment of some of the deficits associated with these progressive, neurodegenerative conditions. Numerous compounds are known which activate nAChRs and which might serve as lead compounds toward the development of such agents. The pharmacologic diversity of neuronal nAChR subtypes suggests the possibility of developing selective compounds which would have more favourable side-effect profiles than existing agents. This broader class of agents, collectively called cholinergic channel modulators (ChCMs), is anticipated to encompass compounds which would have more favourable side-effect profiles than existing agents, which generally exhibit low selectivity. This selectivity may be achieved by preferentially activating some subtypes of nAChRs (i.e., Cholinergic Channel Activators, ChCAs) or inhibiting the function of other subtypes (Cholinergic Channel Inhibitors, ChCIs). An overview of the biology of nAChRs and the rationale for the use of ChCMs for the treatment of dementia related to neurodegenerative diseases are presented, followed by a discussion of lead compounds and compounds under consideration for clinical evaluation.     

Steroidal sapogenin contents in some domestic plants

In order to find out the values of the steroid resources for the future use. the compositions and contents of steroidal sapogenins from 13 domestic plants have been investigated. As a result,Dioscorea nipponica, D. quinqueloba andSmilax china were found to have large amount of diosgenin. And pennogenin inTrillium kamtschaticum andParis verticillata, yuccagenin inAllium fistulosum, hecogenin inAgave americana and neochlorogenin inSolanum nigum were appeared to be major steroidal sapogenins.