Dealing with software viruses: A biological paradigm

We introduce a probability model for populations of cells and viruses that interact in the presence of an anti-viral agent. Cells can be infected by viruses, and their longevity and ability to avoid infection are modified if they survive successive attacks by viruses. Viruses that survive the effect of the anti-viral agent may find that their ability to survive a future encounter with molecules of the anti-viral agent is modified, as is their ability to infect a healthy cell. Additionally, we assume that the anti-viral agents can be a cocktail with different proportions of agents that target different strains of the virus. In this paper, we give the state equations for the model and derive its analytical solution in steady state. The solution then provides insight into the appropriate mix or “cocktail” of anti-viral agents that can be designed to deal with the virus' ability to mutate. In particular, the analysis shows that the concentration of anti-viral agent by itself does not suffice to ultimately control the infection, and that it is important to dose a mix of anti-viral agents so as to target each strain of virus in a specific manner, taking into account the ability of each virus strain to survive in the presence of the anti-viral agents. Models of this kind may eventually lead to the computer aided design of therapeutic protocols or drug design.     

高校多媒体网络教室的病毒防治

本文针对高校多媒体网络教室面临的计算机病毒、网络攻击等安全问题,首先分析了病毒的传播途径,然后探讨了计算机病毒防治的方法,从技术上和管理等方面有的放矢地采取安全防治对策,为师生创造安全的实验教学环境。     

磁碟机病毒破坏机制与防治策略研究

磁碟机病毒及其变种是近几年来病毒技术含量最高、破坏性最强的病毒,已感染数十万台计算机,造成的损失远远超过"熊猫烧香"。为了能有效地防御和查杀该病毒,该文特地对磁碟机病毒进行了深入的研究,分析了磁碟机的破坏机制,指出了磁碟机的种种危害,提出了防治磁碟机的几种技术方法,这对当前防御和清除磁碟机病毒具有一定的现实意义。     

手机病毒的危害与防治研究

随着信息技术迅猛发展,互联网已越来越深入到了当今社会的各行各业以及人们的生活当中,尤其是当3G网络以及智能手机的投入使用,正式宣告着全民手机上网时代的来临,人们可以随时随地通过手机网络进行各种活动,因此受到广大用户的欢迎。然而网络在带来方便的同时,也不可避免地带来了种种危害,而其中最为危险的便是那些潜伏在网络中的黑客,通过编译病毒和木马攻击广大网络用户,盗取用户的信息账号,造成了巨大的损失。而因为现在的手机在软硬件条件上还不够成熟,对于新出现的那些专门针对手机的病毒木马缺乏有效的防治手段,因此也已经日益成为了黑客病毒攻击的重点目标。如何保护手机的信息安全,防范来自网络黑客的攻击,便是讨论的重点。     

双歧杆菌微囊肠溶胶囊的制备

目的:制备全封闭的双歧杆菌活菌微囊胶囊。方法:采用胶囊肠溶包衣新技术和微囊化技术,将不同的高分子材料用于制备全封闭的双歧杆菌活菌微囊胶囊。结果:微囊和微囊胶囊在模拟人工胃液(pH1.5～2.0)中处理4h,活菌数分别保持在27.6%和84.4%以上,而在人工肠液中处理30min,微囊全部溶出释放出活性菌,释放率达90%以上。微囊胶囊在37℃下保存3个月(相当于常温下1年以上),其中的活菌数仍大于109个·g-1。结论:制备的微囊对活性菌有保护作用,有效地提高了活性菌体的耐酸性能,微囊中的菌体仍保持较高的活性且能在微囊中继续增殖。     

Atomic force microscopy analysis of enveloped and non-enveloped viral entry into, and egress from, cultured cells

Since its invention, the atomic force microscope has been used to image a wide variety of biological samples, including viruses. Viral entry into, and egress from, cultured cells has been extensively studied using numerous scientific techniques and to a limited extent using atomic force microscopy. One of the main structural differences that can exist between viruses is the absence, or presence, of an envelope and this factor has consequences for the mode of viral entry and egress. In this study, the entry into, and egress from, cultured cells of enveloped and non-enveloped viruses were investigated using atomic force microscopy. No significant cell surface changes were observed following infection with enveloped or non-enveloped viruses. Although roughness analysis of viral entry revealed cell smoothing post-infection, no differences between the roughness values of enveloped and non-enveloped viral entry were observed. Line analysis of viral entry revealed minor differences between cells infected with an enveloped rather than a non-enveloped virus. These differences may represent a distinction between the uptake processes of enveloped and non-enveloped viruses. Studies of viral egress revealed that infected cells were undergoing cytopathic changes. Whilst topographic, height and roughness differences clearly occurred between virally- and mock-infected cells, no significant differences were elucidated between enveloped and non-enveloped viral egress.     

Effects of pH, ionic strength, dissolved organic matter, and flow rate on the co-transport of MS2 bacteriophages with kaolinite in gravel aquifer media

Viruses are often associated with colloids in wastewater and could be transported with colloids into groundwater from land disposal of human and animal effluent and sludge, causing contamination of groundwater. To investigate the role of colloids in the transport of viruses in groundwater, experiments were conducted using a 2 m long column packed with heterogeneous gravel aquifer media. Bacteriophage MS2 was used as the model virus and kaolinite as the model colloid. Experimental data were analyzed using Temporal Moment Analysis and Filtration Theory. In the absence of kaolinite colloid, MS2 phage traveled slightly faster than the conservative tracer bromide (Br), with little differences observed between unfiltered and filtered MS2 phage (0.22 μm as the operational cut-off for colloid-free virus). In the presence of kaolinite colloids, MS2 phage breakthrough occurred concurrently with that of the colloidal particles and the time taken to reach the peak virus concentration was reduced, suggesting a colloid-facilitated virus transport in terms of peak-concentration time and velocity. Meanwhile mass recovery and magnitude of concentrations of the phages were significantly reduced, indicating colloid-assisted virus attenuation in terms of concentrations and mass. Decreasing the pH or increasing the ionic strength increased the level of virus attachment to the aquifer media and colloids, and virus transport became more retarded, resulting in lower peak-concentration, lower mass recovery, longer peak-concentration time, and greater apparent collision efficiency. Increasing the concentration of dissolved organic matter (DOM) or flow rate resulted in faster virus transport velocity, higher peak-concentrations and mass recoveries, and lower apparent collision efficiencies. The dual-role of colloids in transport viruses has important implications for risk analysis and remediation of virus-contaminated sites.     

Variation of composition of an enteric formulation based on Kollicoat MAE 30 D

Using a formulation described previously with Kollicoat MAE 30 D as the film-forming agent, the effect of variations in plasticizer type and quantity and talc concentration on the preparation and processing of spray-coating suspensions and the properties of isolated films and film-coated caffeine tablets prepared using them was investigated. In the preparation and processing of spray-coating suspensions, the plasticizers polyethylene glycol (PEG) 400, PEG1500, and TEC (triethyl citrate) tended to coagulate at all concentrations investigated, while Cremophor RH 40 coagulated above 10% (expressed as a percentage of the mass of the film-forming agent used). Analogous preparations using propylene glycol (PG), PEG6000, and Lutrol F 68, on the other hand, were found to be stable at all concentrations. The instability was not caused by the Kollicoat MAE 30 D polymer dispersion as such, but by interactions between the finely dispersed pigments and other formulation ingredients. Equivalent nonpigmented preparations are stable and do not coagulate. With all the plasticizers investigated, the minimum film-forming temperature (MFT) fell, albeit to differing degrees, as the amount of plasticizer increased. Similarly, the tensile strength of isolated films declined as plasticizer concentration increased, while the reverse was true as regards their elongation at break. Whereas neither the subsequent disintegration time nor the rate of release of active ingredient at pH 6.8 was significantly affected by the various plasticizer additives, the different film-coated tablet formulations with a core containing a powerful disintegrant exhibited varying degrees of permeability to simulated gastric fluid. With PEG6000, permeability increased as the plasticizer concentration increased, while Lutrol F 68 provided an optimum barrier at 20%, and PG provided a good barrier between 10% and 30%. No gastroresistance was obtained with TEC at 10%. Only the best plasticizer formulations were used in the trials with different talc concentrations, namely, those formulations with 20% PEG6000, 20% Lutrol F 68, 20% PG, and 10% PG. When talc was added, the MFT rose, reaching its maximum at 13% talc (as a proportion of the film-forming agent). In the test for gastroresistance, film-coated caffeine tablets without talc absorbed distinctly more acid than those containing talc. Above 27% talc, the acid resistance improved only insignificantly. On the other hand, during this test, only a maximum of 3% of the active ingredient was released into the gastric juice. Of the variants investigated, the formulation with 20% PG and 27% talc performed best.     

Faecal contamination of greywater and associated microbial risks

The faecal contamination of greywater in a local treatment system at Viby?sen, north of Stockholm, Sweden was quantified using faecal indicator bacteria and chemical biomarkers. Bacterial indicator densities overestimated the faecal load by 100-1000-fold when compared to chemical biomarkers. Based on measured levels of coprostanol, the faecal load was estimated to be 0.04 g person(-1) day(-1). Prevalence of pathogens in the population and the faecal load were used to form the basis of a screening-level quantitative microbial risk assessment (QMRA) that was undertaken for rotavirus, Salmonella typhimurium, Campylobacter jejuni, Giardia lamblia and Cryptosporidium parvum. The different exposure scenarios simulated--direct contact, irrigation of sport fields and groundwater recharge--gave unacceptably high rotavirus risks (0.04 < Pinf < 0.60) despite a low faecal load. The poor reduction of somatic coliphages, which were used as a virus model, in the treatment was one main reason and additional treatment of the greywater is suggested. Somatic coliphages can under extreme circumstances replicate in the wastewater treatment system and thereby underestimate the virus reduction. An alternative QMRA method based on faecal enterococci densities estimated similar risks as for rotavirus. Growth conditions for Salmonella in greywater sediments were also investigated and risk modelling based on replication in the system increased the probability of infection from Salmonella 1000-fold, but it was still lower than the risk of a rotavirus infection.