The program realization of the severance system method and the linear algebra procedure in the MATLAB environment

Запропоновано новий підхід до розв’язання методу відсічених систем. Показано тестування кліткових алгоритмів розв’язання числових систем лінійних алгебраїчних рівнянь. Наведено спосіб тестування розв’язання деяких типів розріджених СЛАР. Охарактеризовано систему лінійних алгебраїчних рівнянь з числовими елементами. Проведено порівняльну характеристику СЛАР з числовими елементами та описано тестування процедур лінійної алгебри в середовищі MatLab.New approach to the severance system method solution is suggested in the work. The cellular algorythm of the numerical system of linear algebraic equation solution testing is shown. The way of some rarefied SLAR types solution testing is shown. The system of linear algebraic equation with numerical elements is characterized. Comparative characteristic of SLAR with numerical elements is conducted and the linear algebraic testing procedure in the MatLab environment is described

Сalculative stableness of algorithms solution analysis of the linear algebraic equations with matrix

Запропоновано новий підхід до обчислювальної стійкості алгоритмів розв’язання систем лінійних алгебричних рівнянь з матрицями. Розглянуто деякі результати з теорії похибок для розв’язання систем лінійних алгебричних рівнянь з матрицями. Проведено аналіз обчислювальної стійкості засобами зворотного аналізу похибок. Показано реалізацію методу розрізання для систем лінійних алгебричних рівнянь з матрицями. Проаналізовано похибки схеми розрізання для розв’язання систем з матрицями.The linear algebraic equations solution is one of the calculative mathematics actual tasks. Investigating certain processes with the mathematics methods and Electronic Calculative Machine usage firstly the mathematical model of the investigated object was built. Then the built mathematical model is transformed into such appearance that the solution is being found as a numerical result with the help of arithmetical and logical operations. Such transformation is carried out by the numerical methods usage. Naturally at the given stage a number of problems dealing with their calculative stableness arise. That is why the new approach to the calculative stableness system of linear algebraic equations with matrix algorithm solution is proposed in the article. During the linear algebraic equations solution there arise the errors caused by the initial data unpreciseness or the error approximation. Besides, during calculation the errors almost always occur within the task itself (because of the arithmetical operations inaccurate completion). The mistakes of this type (so-called calculative) in many cases being aggregated equal the exact solution of the same task, but with the changed initial data. Even provided that the previous measurements and calculations were carried out with a high preciseness and a stable calculative method was chosen for the solution of the task, the initial data error, though very small would occur. These errors influence, to some extent, the solution of the system solution. Some results from the error theory for the linear algebraic equations with matrix are analysed in the article. Some results from the theory of error for the linear algebraic equations with matrix system solution are studied. The calculative stableness is analyzed by means of the error inverse analysis. Realization of the incision method for the system of the linear algebraic equations with matrix is revealed. The incision scheme errors for the system with matrix solution are analyzed. Theoretical and methodological bases of the investigation are composed by the methods of optimization and mathematical modeling

Comparison of Yarrowia lipolytica and Pichia pastoris cellular response to different agents of oxidative stress

Yeast cells exposed to adverse conditions employ a number of defense mechanisms in order to respond effectively to the stress effects of reactive oxygen species. In this work, the cellular response of Yarrowia lipolytica and Pichia pastoris to the exposure to the ROSinducing agents’ paraquat, hydrogen peroxide, and increased air pressure was analyzed. Yeast cells at exponential phase were exposed for 3 h to 1 mM paraquat, to 50 mM H2O2, or to increased air pressure of 3 or 5 bar. For both strains, the cellular viability loss and lipid peroxidation was lower for the cells exposed to increased air pressure than for those exposed to chemical oxidants. The glutathione induction occurred only in Y. lipolytica strain and reached the highest level as a response to PQ exposure. In general, antioxidant enzymes were more expressed in Y. lipolytica than in P. pastoris. The enzyme superoxide dismutase was induced in both strains under all the oxidant conditions but was dependent on the cellular growth phase, being undetectable in non-growing cells, whereas glutathione reductase was more induced in those conditions. Hydrogen peroxide was the most efficient inducer of catalase. Both yeast cultures underwent no cellular growth inhibition with increased air pressure, indicating that these yeast species were able to adapt to the oxidative stressful environment.The authors acknowledge the financial support provided by "Fundacao para a Ciencia e Tecnologia" (Grant SFRH/BD/47371/2008)

Bacterial Toxicity of Potassium Tellurite: Unveiling an Ancient Enigma

Biochemical, genetic, enzymatic and molecular approaches were used to demonstrate, for the first time, that tellurite (TeO(3) (2−)) toxicity in E. coli involves superoxide formation. This radical is derived, at least in part, from enzymatic TeO(3) (2−) reduction. This conclusion is supported by the following observations made in K(2)TeO(3)-treated E. coli BW25113: i) induction of the ibpA gene encoding for the small heat shock protein IbpA, which has been associated with resistance to superoxide, ii) increase of cytoplasmic reactive oxygen species (ROS) as determined with ROS-specific probe 2′7′-dichlorodihydrofluorescein diacetate (H(2)DCFDA), iii) increase of carbonyl content in cellular proteins, iv) increase in the generation of thiobarbituric acid-reactive substances (TBARs), v) inactivation of oxidative stress-sensitive [Fe-S] enzymes such as aconitase, vi) increase of superoxide dismutase (SOD) activity, vii) increase of sodA, sodB and soxS mRNA transcription, and viii) generation of superoxide radical during in vitro enzymatic reduction of potassium tellurite

Glucose-6-Phosphate Dehydrogenase Protects Escherichia coli from Tellurite-Mediated Oxidative Stress

The tellurium oxyanion tellurite induces oxidative stress in most microorganisms. In Escherichia coli, tellurite exposure results in high levels of oxidized proteins and membrane lipid peroxides, inactivation of oxidation-sensitive enzymes and reduced glutathione content. In this work, we show that tellurite-exposed E. coli exhibits transcriptional activation of the zwf gene, encoding glucose 6-phosphate dehydrogenase (G6PDH), which in turn results in augmented synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Increased zwf transcription under tellurite stress results mainly from reactive oxygen species (ROS) generation and not from a depletion of cellular glutathione. In addition, the observed increase of G6PDH activity was paralleled by accumulation of glucose-6-phosphate (G6P), suggesting a metabolic flux shift toward the pentose phosphate shunt. Upon zwf overexpression, bacterial cells also show increased levels of antioxidant molecules (NADPH, GSH), better-protected oxidation-sensitive enzymes and decreased amounts of oxidized proteins and membrane lipids. These results suggest that by increasing NADPH content, G6PDH plays an important role in E. coli survival under tellurite stress