Streak Preventive Image Reconstruction with ART and Adaptive Filtering

Streaks arise in computed tomograms for a variety of reasons, such as presence of high-contrast edges and objects, aliasing errors, patient movement, and use of very few views. The problem appears to be an inherent difficulty with all reconstruction methods, including backprojection (with convolution) and the algebraic reconstruction technique (ART). This paper presents the derivation and results of an ART-like algorithm (SPARTAF) oriented towards prevention of streaks via optimization of a cost function based on features of streaks, subject to the constraints of the given projection data. The object-dependent method employs pattern recognition of streaks and adaptive filtering during iterative reconstruction by ART. Results of experiments with a test pattern and of application of the method to reconstructive tomography from radiographic films are presented and the convergence properties demonstrated.     

Discovery of context-specific ranking functions for effective information retrieval using genetic programming

The Internet and corporate intranets have brought a lot of information. People usually resort to search engines to find required information. However, these systems tend to use only one fixed ranking strategy regardless of the contexts. This poses serious performance problems when characteristics of different users, queries, and text collections are taken into account. We argue that the ranking strategy should be context specific and we propose a , new systematic method that can automatically generate ranking strategies for different contexts based on genetic programming (GP). The new method was tested on TREC data and the results are very promising.     

A short course in antivirus software testing: seven simple rules for evaluating tests

Antivirus software tests are important when selecting antivirus software. However, there are many different tests, and interpreting the results can be challenging. Additionally, the needs of the corporate customer and home user differ, and it is important to understand these differences in order to evaluate antivirus software tests critically.     

Environmentally friendly methods of water disinfection: The chemistry of alternative disinfectants

The risk of disease from microbiological organisms far surpasses any chemical risk associated with water treatment by chemical oxidation. Giardia lamblia and Cryptosporidium parvum, common microbiological contaminants, sometimes have fatal consequences to individuals with weak immune systems. Because effective environmentally friendly oxidants are available and accessible for treating drinking water, utilities throughout the industrialized world are investigasting alternative disinfection/oxidation practices. Chlorine dioxide and ozone are frequently used to remove taste and odor problems, color and to inactive problem microbiological species. To understand the unique value of ozone and chlorine dioxide in water treatment, one must start with the chemistry.     

The HIV-1 Gag Protein Displays Extensive Functional and Structural Roles in Virus Replication and Infectivity

Once merely thought of as the protein responsible for the overall physical nature of the human immunodeficiency virus type 1 (HIV-1), the Gag polyprotein has since been elucidated to have several roles in viral replication and functionality. Over the years, extensive research into the polyproteins’ structure has revealed that Gag can mediate its own trafficking to the plasma membrane, it can interact with several host factors and can even aid in viral genome packaging. Not surprisingly, Gag has also been associated with HIV-1 drug resistance and even treatment failure. Therefore, this review provides an extensive overview of the structural and functional roles of the HIV-1 Gag domains in virion integrity, functionality and infectivity.