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Search Results: 1 - 10 of 391720 matches for " Péter V. Tóth "
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Boundary conditions for many-electron systems
Péter V. Tóth
Physics , 2010,
Abstract: It is shown that natural boundary conditions for non-relativistic wave functions are of periodic or of homogeneous Robin type. Using asymptotic central symmetry of Hamiltonian and theory of singular differential equations the many-electron wave function is expanded in series both in the vicinity of Coulomb singularities and at infinity. Hydrogenic angular dependence of three leading terms of expansion about Coulomb singularities is found. Exact first- and second-order cusp conditions are obtained demonstrating redundancy of spherical average in Kato's cusp condition. Our first-order cusp condition exhibits CP symmetry. Homogeneous Robin boundary conditions are obtained for aperiodic many-electron systems from the expansions. Use of our explicit boundary conditions improves both speed and accuracy of numerical calculations. A confluent hypergeometric series defining arbitrarily high order cusp conditions for the spherically averaged Hamiltonian is presented.
Multilocus dataset reveals demographic histories of two peat mosses in Europe
Péter Sz?vényi, Zsófia Hock, Jakob J Schneller, Zoltán Tóth
BMC Evolutionary Biology , 2007, DOI: 10.1186/1471-2148-7-144
Abstract: All three nuclear regions supported the presence of an Atlantic and Non-Atlantic clade of S. fimbriatum suggesting glacial survival of the species along the Atlantic coast of Europe. Contrarily, S. squarrosum haplotypes showed three clades but no geographic structure at all. Maximum likelihood, mismatch and Bayesian analyses supported a severe historical bottleneck and a relatively recent demographic expansion of the Non-Atlantic clade of S. fimbriatum, whereas size of S. squarrosum populations has probably decreased in the past. Species wide molecular diversity of the two species was nearly the same with an excess of replacement mutations in S. fimbriatum. Similar levels of molecular diversity, contrasting phylogeographic patterns and excess of replacement mutations in S. fimbriatum compared to S. squarrosum mirror unexpected differences in the demography and population history of the species.This study represents the first detailed European wide phylodemographic investigation on bryophytes and shows how pattern of nucleotide polymorphism can reveal unexpected differences in the population history of haploid plants with seemingly similar characteristics.Geographic distribution of species is continuously shaped by several extrinsic factors causing repeated historical range and demographic expansions/contractions [1,2]. Using historical observations, short-term range expansions and contractions, together with associated demographic changes, have been documented in several, mostly invasive species in Europe and also world-wide [3-6]. From a conservation biological point of view, it is of high importance to reconstruct the historical demography of populations, which can help to work out conservation strategies. In addition, correlations between demographic changes and climatic oscillations may be useful to predict species responses to the accelerated climate change [7]. If a series of temporarily spaced data is available, demographic changes over several decades are re
Utilisation of 2nd generation web technologies in master level vocational teacher training
Péter Tóth
Acta Didactica Napocensia , 2009,
Abstract: The Masters level Opportunities and Technological Innovation in Vocational Teacher Education project (project site: http://motivate.tmpk.bmf.hu/) aims to develop the use and management of virtual learning environments in the area of vocational teacher training, drawing on a well established international partnership of institutions providing both technical and educational expertise. This paper gives an overall picture of the first results and products of the collaboration. We touch upon the goals, the assessments and the learning process of using “Multimedia and e-Learning: e-learning methods and tools” module in details. The main cooperative and collaborative devices are presented in virtual learning environment. The communication during collaborative learning, the structured debate on forum and the benefits of collaborative learning in VLE are interpreted at the end of this paper.
Characterization of Virulence Properties in the C. parapsilosis Sensu Lato Species
Tibor Németh, Adél Tóth, Judit Szenzenstein, Péter Horváth, Joshua D. Nosanchuk, Zsuzsanna Grózer, Renáta Tóth, Csaba Papp, Zsuzsanna Hamari, Csaba Vágv?lgyi, Attila Gácser
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068704
Abstract: The C. parapsilosis sensu lato group involves three closely related species, C. parapsilosis sensu stricto, C. orthopsilosis and C. metapsilosis. Although their overall clinical importance is dramatically increasing, there are few studies regarding the virulence properties of the species of the psilosis complex. In this study, we tested 63 C. parapsilosis sensu stricto, 12 C. metapsilosis and 18 C. orthopsilosis isolates for the ability to produce extracellular proteases, secrete lipases and form pseudohyphae. Significant differences were noted between species, with the C. metapsilosis strains failing to secrete lipase or to produce pseudohyphae. Nine different clinical isolates each of C. parapsilosis sensu stricto, C. orthopsilosis and C. metapsilosis were co-cultured with immortalized murine or primary human macrophages. C. parapsilosis sensu stricto isolates showed a significantly higher resistance to killing by primary human macrophages compared to C. orthopsilosis and C. metapsilosis isolates. In contrast, the killing of isolates by J774.2 mouse macrophages did not differ significantly between species. However, C. parapsilosis sensu stricto isolates induced the most damage to murine and human macrophages, and C. metapsilosis strains were the least toxic. Furthermore, strains that produced lipase or pseudohyphae were most resistant to macrophage-mediated killing and produced the most cellular damage. Finally, we used 9 isolates of each of the C. parapsilosis sensus lato species to examine their impact on the survival of Galleria mellonella larvae. The mortality rate of G. mellonella larvae infected with C. metapsilosis isolates was significantly lower than those infected with C. parapsilosis sensu stricto or C. orthopsilosis strains. Taken together, our findings demonstrate that C. metapsilosis is indeed the least virulent member of the psilosis group, and also highlight the importance of pseudohyphae and secreted lipases during fungal-host interactions.
Applying Web-Mining Methods for Analysis of Student Behaviour in VLE Courses
Lajos Izsó,Péter Tóth
Acta Polytechnica Hungarica , 2008,
Abstract: In Hungary, a lot of electronic-based syllabuses have been developed during thelast 8-10 years at a most considerable cost. However, not much has been heard of theirsuccess or efficiency, as would be supported by scientific testing. First, the present study isto provide a survey of our project, which aimed at creating an integrated electroniclearning environment. The processing of an education technology syllabus integrated in theMoodle virtual learning environment system took place in the passing academic year. Theanalysis of student behaviour in the learning environment is based on log files created onthe server during the course of interaction between learners and the electronic syllabus.We analysed the learning activity of the students in the learning environment in exactnumeric terms by using methods of web-mining. The second part of the study presents someof our first empirical results in this field.
Entropy and Hausdorff Dimension in Random Growing Trees
Anna Rudas,Imre Péter Tóth
Mathematics , 2010, DOI: 10.1142/S0219493712500104
Abstract: We investigate the limiting behavior of random tree growth in preferential attachment models. The tree stems from a root, and we add vertices to the system one-by-one at random, according to a rule which depends on the degree distribution of the already existing tree. The so-called weight function, in terms of which the rule of attachment is formulated, is such that each vertex in the tree can have at most K children. We define the concept of a certain random measure mu on the leaves of the limiting tree, which captures a global property of the tree growth in a natural way. We prove that the Hausdorff and the packing dimension of this limiting measure is equal and constant with probability one. Moreover, the local dimension of mu equals the Hausdorff dimension at mu-almost every point. We give an explicit formula for the dimension, given the rule of attachment.
Heat Stress Causes Spatially-Distinct Membrane Re-Modelling in K562 Leukemia Cells
Gábor Balogh,Giuseppe Maulucci,Imre Gombos,Ibolya Horváth,Zsolt T?r?k,Mária Péter,Elfrieda Fodor,Tibor Páli,Sándor Benk?,Tiziana Parasassi,Marco De Spirito,John L. Harwood,László Vígh
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021182
Abstract: Cellular membranes respond rapidly to various environmental perturbations. Previously we showed that modulations in membrane fluidity achieved by heat stress (HS) resulted in pronounced membrane organization alterations which could be intimately linked to the expression and cellular distribution of heat shock proteins. Here we examine heat-induced membrane changes using several visualisation methods. With Laurdan two-photon microscopy we demonstrate that, in contrast to the enhanced formation of ordered domains in surface membranes, the molecular disorder is significantly elevated within the internal membranes of cells preexposed to mild HS. These results were compared with those obtained by anisotropy, fluorescence lifetime and electron paramagnetic resonance measurements. All probes detected membrane changes upon HS. However, the structurally different probes revealed substantially distinct alterations in membrane heterogeneity. These data call attention to the careful interpretation of results obtained with only a single label. Subtle changes in membrane microstructure in the decision-making of thermal cell killing could have potential application in cancer therapy.
Membrane-Lipid Therapy in Operation: The HSP Co-Inducer BGP-15 Activates Stress Signal Transduction Pathways by Remodeling Plasma Membrane Rafts
Imre Gombos, Tim Crul, Stefano Piotto, Burcin Güng?r, Zsolt T?r?k, Gábor Balogh, Mária Péter, J. Peter Slotte, Federica Campana, Ana-Maria Pilbat, ákos Hunya, Noémi Tóth, Zsuzsanna Literati-Nagy, László Vígh, Attila Glatz, Mario Brameshuber, Gerhard J. Schütz, Andrea Hevener, Mark A. Febbraio, Ibolya Horváth, László Vígh
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028818
Abstract: Aging and pathophysiological conditions are linked to membrane changes which modulate membrane-controlled molecular switches, causing dysregulated heat shock protein (HSP) expression. HSP co-inducer hydroxylamines such as BGP-15 provide advanced therapeutic candidates for many diseases since they preferentially affect stressed cells and are unlikely have major side effects. In the present study in vitro molecular dynamic simulation, experiments with lipid monolayers and in vivo ultrasensitive fluorescence microscopy showed that BGP-15 alters the organization of cholesterol-rich membrane domains. Imaging of nanoscopic long-lived platforms using the raft marker glycosylphosphatidylinositol-anchored monomeric green fluorescent protein diffusing in the live Chinese hamster ovary (CHO) cell plasma membrane demonstrated that BGP-15 prevents the transient structural disintegration of rafts induced by fever-type heat stress. Moreover, BGP-15 was able to remodel cholesterol-enriched lipid platforms reminiscent of those observed earlier following non-lethal heat priming or membrane stress, and were shown to be obligate for the generation and transmission of stress signals. BGP-15 activation of HSP expression in B16-F10 mouse melanoma cells involves the Rac1 signaling cascade in accordance with the previous observation that cholesterol affects the targeting of Rac1 to membranes. Finally, in a human embryonic kidney cell line we demonstrate that BGP-15 is able to inhibit the rapid heat shock factor 1 (HSF1) acetylation monitored during the early phase of heat stress, thereby promoting a prolonged duration of HSF1 binding to heat shock elements. Taken together, our results indicate that BGP-15 has the potential to become a new class of pharmaceuticals for use in ‘membrane-lipid therapy’ to combat many various protein-misfolding diseases associated with aging.
An expansion estimate for dispersing planar billiards with corner points
Jacopo De Simoi,Imre Péter Tóth
Mathematics , 2012,
Abstract: It is known that the dynamics of planar billiards satisfies strong mixing properties (e.g. exponential decay of correlations) provided that some expansion condition on unstable curves is satisfied. This condition has been shown to always hold for smooth dispersing planar billiards, but it needed to be assumed separately in the case of dispersing planar billiards with corner points. We prove that this expansion condition holds for any dispersing planar billiard with corner points, no cusps and bounded horizon.
On the limiting Markov process of energy exchanges in a rarely interacting ball-piston gas
Péter Bálint,Thomas Gilbert,Péter Nándori,Domokos Szász,Imre Péter Tóth
Mathematics , 2015,
Abstract: We analyse the process of energy exchanges generated by the elastic collisions between a point-particle, confined to a two-dimensional cell with convex boundaries, and a `piston', i.e. a line-segment, which moves back and forth along a one-dimensional interval partially intersecting the cell. This model can be considered as the elementary building block of a spatially extended high-dimensional billiard modeling heat transport in a class of hybrid materials exhibiting the kinetics of gases and spatial structure of solids. Using heuristic arguments and numerical analysis, we argue that, in a regime of rare interactions, the billiard process converges to a Markov jump process for the energy exchanges and obtain the expression of its generator.
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