113 research outputs found
Статистичнi властивостi рiвнiв енергiї в квантовiй теорiї аксиального каналювання
No full textThe energy of transversal motion of relativistic charged particles in the uniform potential of atomic strings of a crystal could be quantized. The energy levels of electrons axially channeled in the system of parallel [110] atomic strings of silicon crystal are obtained. The distribution of distances between neighbor energy levels in the quasi-classical region, where the levels density is high, is agreed with quantum chaos theory predictions.При каналировании быстрых заряженных частиц в кристалле может иметь место квантование энергии поперечного движения частицы в непрерывных потенциалах атомных цепочек. В предлагаемой работе найдены уровни энергии электронов, движущихся в режиме аксиального каналирования в системе параллельных атомных цепочек (на примере цепочек [110] кристалла кремния). Показано, что распределение межуровневых расстояний в квазиклассической области, где плотность уровней велика, согласуется с предсказаниями теории квантового хаоса.При каналюваннi швидких заряджених частинок у кристалi може бути наявним квантування енергiї поперечного руху в неперервних потенцiалах атомних ланцюжкiв. У запропонованiй роботi знайденi рiвнi енергiї електронiв, якi рухаються у режимi аксиального каналювання у системi паралельних атомних ланцюжкiв (на прикладi ланцюжкiв [110] кристала кремнiя). Показано, що розподiл мiжрiвневих вiдстанiв у квазикласичнiй областi, де щiльнiсть рiвнiв є великою, узгоджується з передбаченнями теорiї квантового хаосу.The work was supported by the Ministry of Education
and Science of the Russian Federation (the State
assignment N 3.500.2014/K)
Статистичнi властивостi рiвнiв енергiї в квантовiй теорiї аксиального каналювання
No full textThe energy of transversal motion of relativistic charged particles in the uniform potential of atomic strings of a crystal could be quantized. The energy levels of electrons axially channeled in the system of parallel [110] atomic strings of silicon crystal are obtained. The distribution of distances between neighbor energy levels in the quasi-classical region, where the levels density is high, is agreed with quantum chaos theory predictions.При каналировании быстрых заряженных частиц в кристалле может иметь место квантование энергии поперечного движения частицы в непрерывных потенциалах атомных цепочек. В предлагаемой работе найдены уровни энергии электронов, движущихся в режиме аксиального каналирования в системе параллельных атомных цепочек (на примере цепочек [110] кристалла кремния). Показано, что распределение межуровневых расстояний в квазиклассической области, где плотность уровней велика, согласуется с предсказаниями теории квантового хаоса.При каналюваннi швидких заряджених частинок у кристалi може бути наявним квантування енергiї поперечного руху в неперервних потенцiалах атомних ланцюжкiв. У запропонованiй роботi знайденi рiвнi енергiї електронiв, якi рухаються у режимi аксиального каналювання у системi паралельних атомних ланцюжкiв (на прикладi ланцюжкiв [110] кристала кремнiя). Показано, що розподiл мiжрiвневих вiдстанiв у квазикласичнiй областi, де щiльнiсть рiвнiв є великою, узгоджується з передбаченнями теорiї квантового хаосу.The work was supported by the Ministry of Education
and Science of the Russian Federation (the State
assignment N 3.500.2014/K)
Simulation of NAPL vertical infiltration in a heterogeneous soil
No full textThe research deals with simulation of contaminant infiltration and spreading in soils. The problem has substantial ecological sense to predict possible contamination of the soil air and the groundwater. As contaminants, for example, mineral fuels, solvents and detergents (in other words Non-Aqueous Phase Liquids - NAPLs) can be considered. These liquids are immiscible with gas and water therefore one has to treat multiphase flows. The governing model takes into account capillary and gravity forces and includes some capillary pressure - saturation relation [1, 2]. There are Light and Dense NAPLs depending on the relation of their density to the water density. A number of test problems were solved. Tests concerning the DNAPL (tetrachloroethylene) infiltration into a fully saturated reservoir and the LNAPL (oil) infiltration into an unsaturated reservoir require the two-phase problem statement. Numerical implementations are based on the finite differences with consequent solution by the IMPES method. All the problems are treated in the 2D vertical section. It is assumed that porous media are heterogeneous, i.e. they consist of layers with different porosities and permeabilities or contain low permeability lenses. The special transition conditions are used at the interface of heterogeneity to ensure physically correct solutions. The applied problem that will be further under consideration is connected with the petrol infiltration from the earth surface into the relatively dry ground until reaching the water table. Realistic data obtaining by measuring in the locality will be used. Investigation of the oil-products propagation is of great practical importance due to the potential danger of drinking water contamination. In this case the three-phase flow has to be considered. Software tools developed and tested up to the present time will be implemented for solving such kind of ecological problems. Another aim for the future is to develop an efficient fully implicit algorithm to avoid strong time-step restrictions
The binding of haem and zinc in the 1.9 A X-ray structure of Escherichia coli bacterioferritin.
No full textaddresses: School of Biosciences, Henry Wellcome Building for Biocatalysis, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK.types: Journal Article; Research Support, Non-U.S. Gov'tThis a post-print, author-produced version of an article accepted for publication in Journal of Biological Inorganic Chemistry . Copyright © 2008 Springer Verlag / SBIC . The definitive version is available at http://link.springer.com/article/10.1007%2Fs00775-008-0438-8The crystal structure of Escherichia coli bacterioferritin has been solved to 1.9 A, and shows the symmetrical binding of a haem molecule on the local twofold axis between subunits and a pair of metal atoms bound to each subunit at the ferroxidase centre. These metals have been identified as zinc by the analysis of the structure and X-ray data and confirmed by microfocused proton-induced X-ray emission experiments. For the first time the haem has been shown to be linked to both the internal and the external environments via a cluster of waters positioned above the haem molecule
Positrons vs electrons channeling in silicon crystal: energy levels, wave functions and quantum chaos manifestations
No full textThe motion of fast electrons through the crystal during axial channeling could be regular and chaotic. The dynamical chaos in quantum systems manifests itself in both statistical properties of energy spectra and morphology of wave functions of the individual stationary states. In this report, we investigate the axial channeling of high and low energy electrons and positrons near direction of a silicon crysta
Biochemical and structural studies of a L-haloacid dehalogenase from the thermophilic archaeon Sulfolobus tokodaii
No full textaddresses: Henry Wellcome Building for Biocatalysis, School of Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.types: Journal Article; Research Support, Non-U.S. Gov'tThis a post-print, author-produced version of an article accepted for publication in Extremophiles. Copyright © 2009 Springer Verlag. The definitive version is available at http://link.springer.com/article/10.1007%2Fs00792-008-0208-0Haloacid dehalogenases have potential applications in the pharmaceutical and fine chemical industry as well as in the remediation of contaminated land. The L: -2-haloacid dehalogenase from the thermophilic archaeon Sulfolobus tokodaii has been cloned and over-expressed in Escherichia coli and successfully purified to homogeneity. Here we report the structure of the recombinant dehalogenase solved by molecular replacement in two different crystal forms. The enzyme is a homodimer with each monomer being composed of a core-domain of a beta-sheet bundle surrounded by alpha-helices and an alpha-helical sub-domain. This fold is similar to previously solved mesophilic L: -haloacid dehalogenase structures. The monoclinic crystal form contains a putative inhibitor L: -lactate in the active site. The enzyme displays haloacid dehalogenase activity towards carboxylic acids with the halide attached at the C2 position with the highest activity towards chloropropionic acid. The enzyme is thermostable with maximum activity at 60 degrees C and a half-life of over 1 h at 70 degrees C. The enzyme is relatively stable to solvents with 25% activity lost when incubated for 1 h in 20% v/v DMSO
Barthes, Bakhtin, Structuralism: A Reassessment
No full textPhDThe thesis is a comparative analysis of the shared ideas and concerns in the works of
Mikhail Bakhtin and Roland Barthes from the point of view of differences between
French and Slavic literary structuralisms. Its background argument is that the
structuralism developed in the later works of the Russian Formalists and by Prague
Structuralists and Soviet Semioticians is more historically and socially oriented than its
French version, defining the structure of a literary work as a system of all of its
elements and effects (even those that take us outside of the text, like literary tradition
and historical and political circumstances). In this sense, Bakhtin can be seen as a part
of the Slavic structuralist tradition (and not opposed to it as is often claimed), and
Barthes (seen throughout his career) is on the whole perhaps closer to the Slavic
structuralism than he is to the French.
The particular problems discussed are those of the relationship between
literature and ideology, the notions of intertextuality, heteroglossia, dialogism and
polyphony and the differences between them, and the role of the author.
Barthes and Bakhtin shared a lifelong interest in the role of ideology in literature
and the influence of authoritarian language or myth on culture in general and the literary
text in particular. They looked for ways in which the deadening effect of the
mythological (epic, monological) thought and word can be counteracted through
literature, and different versions of what Kristeva termed 'intertextuality' played an
important part in their treatment of the subject. They also both discussed the role of the
author and their voice in the literary text, and the question of their power over the text,
its characters (Bakhtin) and the reader (Barthes).
The main thread of Barthes and Bakhtin's thought focuses on the problem of
counteracting authoritarian language through literature, and the solutions they proposed
can fruitfully be seen in the light of Slavic structuralism's notions of literary structure
The crystal structure and conformations of an unbranched mixed tri-ubiquitin chain containing K48 and K63 linkages.
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The ability of ubiquitin to function in a wide range of cellular processes is ascribed to its capacity to cause a diverse spectrum of modifications. While a target protein can be modified with monoubiquitin, it can also be modified with ubiquitin chains. The latter include seven types of homotypic chains as well as mixed ubiquitin chains. In a mixed chain, not all the isopeptide bonds are restricted to a specific lysine of ubiquitin, resulting in a chain possessing more than one type of linkage. While structural characterization of homotypic chains has been well elucidated, less is known about mixed chains. Here we present the crystal structure of a mixed tri-ubiquitin chain at 3.1-Å resolution. In the structure, the proximal ubiquitin is connected to the middle ubiquitin via K48 and these two ubiquitins adopt a compact structure as observed in K48 di-ubiquitin. The middle ubiquitin links to the distal ubiquitin via its K63 and these ubiquitins adopt two conformations, suggesting a flexible structure. Using small-angle X-ray scattering, we unexpectedly found differences between the conformational ensembles of the above tri-ubiquitin chains and chains possessing the same linkages but in the reverse order. In addition, cleavage of the K48 linkage by DUB is faster if this linkage is at the distal end. Taken together, our results suggest that in mixed chains, not only the type of the linkages but also their sequence determine the structural and functional properties of the chain.The work was supported by a Marie Curie Career Integration grant (PCIG13-GA-2013-630755) to R.W
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