Multi-biclustering solutions for classification and prediction problems

2009 - 20101The search for similarities in large data sets has a relevant role in many scientific fields. It permits to classify several types of data without an explicit information about them. Unfortunately, the experimental data contains noise and errors, and therefore the main task of mathematicians is to find algorithms that permit to analyze this data with maximal precision. In many cases researchers use methodologies such as clustering to classify data with respect to the patterns or conditions. But in the last few years new analysis tool such as biclustering was proposed and applied to many specific problems. My choice of biclustering methods is motivated by the accuracy obtained in the results and the possibility to find not only rows or columns that provide a dataset partition but also rows and columns together. In this work, two new biclustering algorithms, the Combinatorial Biclustering Algorithm (CBA) and an improvement of the Possibilistic Biclustering Algorithm, called Biclustering by resampling, are presented. The first algorithm (that I call Combinatorial) is based on the direct definition of bicluster, that makes it clear and very easy to understand. My algorithm permits to control the error of biclusters in each step, specifying the accepted value of the error and defining the dimensions of the desired biclusters from the beginning. The comparison with other known biclustering algorithms is shown. The second algorithm is an improvement of the Possibilistic Biclustering Algorithm (PBC). The PBC algorithm, proposed by M. Filippone et al., is based on the Possibilistic Clustering paradigm, and finds one bicluster at a time, assigning a membership to the bicluster for each gene and for each condition. PBC uses an objective function that maximizes a bicluster cardinality and minimizes a residual error. The biclustering problem is faced as the optimization of a proper functional. This algorithm obtains a fast convergence and good quality of the solutions. Unfortunately, PBC finds only one bicluster at a time. I propose an improved PBC algorithm based on data resampling, specifically Bootstrap aggregation, and Genetics algorithms. In such a way I can find all the possible biclusters together and include overlapped solutions. I apply the algorithm to a synthetic data and to the Yeast dataset and compare it with the original PBC method. [edited by the author]IX n.s

Corrosion of Iron and Iron Alloys in Seawater

The article is a review of the latest European research on the problems of iron corrosion in seawater. Such damages are typical for objects of marine archaeology, in particular shipwrecks. For a long time, the study of such corrosion processes was complicated by the fact that samples taken in seawater quickly oxidized in the air and their composition changed significantly. In the early 1980s, after the development of sampling techniques, the study of underwater artifacts corrosion began to develop faster and more efficiently. First of all, the basic processes of iron corrosion and the factors that stimulate them are discussed in the article. These include sea­water salinity, oxygen concentration, microbiological activity, pH, temperature, and water circulation patterns, which, in turn, influence the prevalence of other parameters. Next, the iron corrosion products characteristic of the marine environment are described in detail. Finally, the role of microorganisms in the corrosion process and their influence on the preservation of the monument are highlighted

Multi-cycle rolled aluminum alloy 3103 sandwiches: mechanical properties and stamp ability

Constructional part producing by sheet stamping of multilayer composites requires the stamping ability data. The aim of a work is to estimate mechanical properties, stamping ratio and anisotropy indexes of 2, 4, 8 and 12 layer sandwiches produced from aluminium alloy AA3103. The pieces were received by the cold rolling. Interoperation annealing was at 500°C for 1 hour. Charts of tensile strength, yield stress, elongation depending on layer thickness were composed. It was found that cold strain hardening does not disappear after annealing if the foil’s thickness become 0.4 mm and less. Microstructure analysis has shown a good contact between layers for all samples and thicker outer layers

Regular MDMA Use is Associated with Decreased Risk of Drug Injection Among Street-Involved Youth Who Use Illicit Drugs.

OBJECTIVES: Childhood trauma is common among street-involved youth and is associated with injection drug use. Illicit 3,4-Methylenedioxymethamphetamine (MDMA) use is also common among street-involved youth, and data suggest this substance has clinical utility in management of post-traumatic stress disorder (PTSD) and associated harms. Despite this, little is known about co-occurring patterns of MDMA use and injection drug use. METHODS: Data were derived from a prospective cohort of street-involved youth using illicit drugs in Vancouver, Canada. Using multivariable generalized estimating equation logistic regression, we examined the association between MDMA use and the use of injection drugs, adjusting for confounders such as polysubstance use and sociodemographic factors. RESULTS: 4941 surveys from 1208 participants between September 2005 and May 2015 were included. Of these, 829 (68.6%) were male, 815 (67.5%) reported white ethnicity, and median age was 21.7 years. Overall, 599 (49.6%) participants reported MDMA use, 544 (45.0%) reported injection drug use, and 244 (20.2%) reported concurrent MDMA and injection drug use at least once during the study period. In multivariable analyses, regular MDMA use was significantly negatively associated with injection drug use (Adjusted Odds Ratio [AOR] = 0.57, 95% CI: 0.46-0.69). DISCUSSION: After accounting for socio-demographic factors and polysubstance use, periods of reported regular MDMA use were negatively associated with reported injection drug use among this cohort. These findings suggest that, unlike the use of most other non-injection drugs, illicit MDMA use does not appear to promote injection drug use but rather is associated with a reduced likelihood of injection drug use