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Search Results: 1 - 10 of 1596 matches for " Gy?rgy Nagy "
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Randomized algorithm for the k-server problem on decomposable spaces
Judit Nagy-Gyrgy
Computer Science , 2007,
Abstract: We study the randomized k-server problem on metric spaces consisting of widely separated subspaces. We give a method which extends existing algorithms to larger spaces with the growth rate of the competitive quotients being at most O(log k). This method yields o(k)-competitive algorithms solving the randomized k-server problem, for some special underlying metric spaces, e.g. HSTs of "small" height (but unbounded degree). HSTs are important tools for probabilistic approximation of metric spaces.
Rheumatoid arthritis and smoking: putting the pieces together
Zsuzsanna Baka, Edit Buzás, Gyrgy Nagy
Arthritis Research & Therapy , 2009, DOI: 10.1186/ar2751
Abstract: It has long been known that there is a connection between seropositive rheumatoid arthritis (RA) and smoking. The exact underlying mechanism, however, has only been speculated.Cigarette smoking is one of the major environmental factors suggested to play a crucial role in the development of several diseases. Disorders affecting the great portion of the population, such as atherosclerosis, lung cancer or cardiovascular diseases, are highly associated with tobacco consumption. More recently, it has been reported that smoking is involved in the pathogenesis of certain autoimmune diseases such as RA, systemic lupus erythematosus, systemic sclerosis, multiple sclerosis and Crohn's disease.Firstly, Vessey and colleagues described an association between hospitalization due to RA and cigarette smoking, which was an unexpected finding of their gynecological study [1]. Since then several population-wide case–control and cohort studies have been carried out [2]. For example, a population-based case–control study in Norfolk, England showed that ever smoking was associated with a higher risk of developing RA [3]. Only an early Dutch study from 1990 involving female RA patients (control patients with soft-tissue rheumatism and osteoarthritis) reported that smoking had a protective effect in RA, albeit they only investigated recent smoking and their controls were not from the general population [4]. Investigations have elucidated that many aspects of RA (rheumatoid factor (RF) positivity, severity, and so forth) can be linked to smoking. Recent data suggest that cigarette smoking establishes a higher risk for anti-citrulli-nated protein antibody (ACPA)-positive RA. In the present paper we attempt to give a thorough review of this field, concerning the main facts and hypotheses in the development of RA in connection with smoking.Smoking is considered to have a crucial role in the pathogenesis of many diseases and, as a significant part of the population smokes, it is one of the most
Experimental Tests Concerning the Behaviour of the Steel-Concrete Composite Joints
Daniel Dan,Valeriu Stoian,Tamás Nagy-Gyrgy
Bulletin of the Polytechnic Institute of Jassy, Constructions, Architechture Section , 2006,
Abstract: The design of the building structures situated in a seismic area deals with some spe cial provisions in order to satisfy the design concept for earthquake loads. Thus, some inelastic deformations must be concentrated in predefined zones for seismic energy dissi pation. Therefore, it is important to evaluate correctly the load bearing capacity of each basic structural element, such as beams, columns and joints too. At the "Politehnica" University of Timisoara, it was developed an experimental test program for a specific steel and composite (steel-concrete) joint. Two load hypotheses were considered in order to simulate the permanent loads and the horizontal (seismic) loads, respectively, acting on the structure and the corresponding joints. Two series of joints were tested in laboratory for monotonous and cyclic behavior. Both the steel and the steel-concrete joints were studied. A comparative study between the steel and the steel-concrete composite joints is presented.
Maps on classes of Hilbert space operators preserving measure of commutativity
Gyrgy Pál Gehér,Gerg? Nagy
Mathematics , 2014, DOI: 10.1016/j.laa.2014.08.026
Abstract: In this paper first we give a partial answer to a question of L. Moln\'ar and W. Timmermann. Namely, we will describe those linear (not necessarily bijective) transformations on the set of self-adjoint matrices which preserve a unitarily invariant norm of the commutator. After that we will characterize those (not necessarily linear or bijective) maps on the set of self-adjoint rank-one projections acting on a two-dimensional complex Hilbert space which leave the latter quantity invariant. Finally, this result will be applied in order to obtain a description of such bijective preservers on the unitary group and on the set of density operators.
Visual Pathways Serving Motion Detection in the Mammalian Brain
Alice Rokszin,Zita Márkus,Gábor Braunitzer,Antal Berényi,Gyrgy Benedek,Attila Nagy
Sensors , 2010, DOI: 10.3390/s100403218
Abstract: Motion perception is the process through which one gathers information on the dynamic visual world, in terms of the speed and movement direction of its elements. Motion sensation takes place from the retinal light sensitive elements, through the visual thalamus, the primary and higher visual cortices. In the present review we aim to focus on the extrageniculo-extrastriate cortical and subcortical visual structures of the feline and macaque brain and discuss their functional role in visual motion perception. Special attention is paid to the ascending tectofugal system that may serve for detection of the visual environment during self-motion.
Gábor Nagy,Jen? Hancsók,Zoltán Varga,Gyrgy P?lczmann
Petroleum and Coal , 2007,
Abstract: Beside the reduction of sulphur content in diesel fuels, aromatics reduction is also relevant, because it contributes to the increase of cetane number and to be abatement of exhaust gas emissions, mainly hydrocarbons (HC) and particulate matter (PM). The aim of present study was to identify and quantify the key process parameters for hydrodearomatization of prehydrogenated gas oil fractions on Pt-Pd/USY zeolite catalysts. The effect of key process parameters (temperature, pressure, LHSV, H2-to-hydrocarbon ratio) on the yield and quality of products was investigated. Additionally, the effect of the reduction of aromatic content on the main properties of gas oils (density, refractive index, cetane number etc.) was also studied.
Thrombophilic screening in retinal artery occlusion patients
Valeria Nagy,Lili Takacs,Zita Steiber,György Pfliegler
Clinical Ophthalmology , 2008,
Abstract: Valeria Nagy1, Lili Takacs1, Zita Steiber1, Gy rgy Pfliegler2, Andras Berta11Department of Ophthalmology, 2Division of Rare Diseases, University of Debrecen Medical and Health Science Center, Debrecen, HungaryBackground: Retinal artery occlusion (RAO) is an ischemic vascular damage of the retina, which frequently leads to sudden, mostly irreversible loss of vision. In this study, blood thrombophilic factors as well as cardiovascular risk factors were investigated for their relevance to this pathology. Thrombophilic risk factors so far not evaluated were included in the study.Patients and methods: 28 RAO patients and 81 matched control subjects were examined. From blood samples, protein C, protein S, antithrombinopathy, and factor V (Leiden) mutation (FV), factor II gene polymorphism, factor VIII C level, plasminogen activity, lipoprotein(a) and fibrinogen levels, hyperhomocysteinemia and presence of anticardiolipin – antiphospholipid antibodies were investigated. Possibly relevant pathologies such as diabetes mellitus, hypertension, and ischemic heart disease were also registered. Statistical analysis by logistic regression was performed with 95% confidence intervals.Results: In the group of patients with RAO only the incidence of hypertension (OR: 3.33, 95% CI: 1.30–9.70, p = 0.014) as an average risk factor showed significant difference, but thrombophilic factors such as hyperfibrinogenemia (OR: 2.9, 95% CI: 1.29–6.57, p = 0.010) and the presence of FV (Leiden mutation) (OR: 3.9, 95% CI: 1.43–10.96, p = 0.008) increased the chances of developing this disease.Conclusions: Our results support the assumption that thrombophilia may contribute to the development of RAO besides vascular damage due to the presence of cardiovascular risk factors. Further studies are needed, however, to justify the possible use of secondary prophylaxis in form of anticoagulant/antiplatelet therapy.Keywords: retinal arterial occlusion, risk factors, thrombophilia
In Plan Shear Retrofit of Masonry Walls with Fibre Reinforced Polymer Composites Experimental Investigations
Tamás Nagy-Gyrgy,Valeriu Stoian,Daniel Dan,Dan Diaconu
Bulletin of the Polytechnic Institute of Jassy, Constructions, Architechture Section , 2006,
Abstract: The paper presents the results from tests on clay brick masonry walls strengthened using fiber reinforced polymer (FRP) composites. Five 1.50x1.50 m wall specimens have been subjected to pure in plan shear loads up to failure and then retrofitted on one side, with different types, percentages and lay-ups of the fiber sheets. Based on the experi mental results, it was proven the effectiveness of using externally bonded composites for retrofitting brick masonry walls, with less disruption during strengthening, and in this way with reduced costs compared with other conventional repairing and strengthening tech niques. Performances of the different strengthening configurations were compared in terms of ultimate load, strain in composite and failure mechanism.
Biclique coverings, rectifier networks and the cost of $\varepsilon$-removal
Szabolcs Iván,ádám Dániel Lelkes,Judit Nagy-Gyrgy,Balázs Sz?rényi,Gyrgy Turán
Computer Science , 2014,
Abstract: We relate two complexity notions of bipartite graphs: the minimal weight biclique covering number $\mathrm{Cov}(G)$ and the minimal rectifier network size $\mathrm{Rect}(G)$ of a bipartite graph $G$. We show that there exist graphs with $\mathrm{Cov}(G)\geq \mathrm{Rect}(G)^{3/2-\epsilon}$. As a corollary, we establish that there exist nondeterministic finite automata (NFAs) with $\varepsilon$-transitions, having $n$ transitions total such that the smallest equivalent $\varepsilon$-free NFA has $\Omega(n^{3/2-\epsilon})$ transitions. We also formulate a version of previous bounds for the weighted set cover problem and discuss its connections to giving upper bounds for the possible blow-up.
Central role of nitric oxide in the pathogenesis of rheumatoid arthritis and sysemic lupus erythematosus
Gyrgy Nagy, Agnes Koncz, Tiffany Telarico, David Fernandez, Barbara érsek, Edit Buzás, András Perl
Arthritis Research & Therapy , 2010, DOI: 10.1186/ar3045
Abstract: Nitric oxide (NO) is a short-lived signaling molecule that plays an important role in a variety of physiologic functions, including the regulation of blood vessel tone, inflammation, mitochondrial functions and apoptosis [1,2]. NO was originally identified as endothelium-derived relaxant factor based on the observations of Furchgott and Zawadzki [3]. They observed that acethylcholine-induced blood vessel relaxation occurred only if the endothelium was intact. Some years later, the endothelium-derived relax ant factor was identified as NO [4]. NO is synthesized from L-arginine by NO synthetases (NOSs): neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) [5]. NO also serves as a potent immuno regulatory factor, and influences the cytoplasmic redox balance through the generation of peroxynitrite (ONOO-) following its reaction with superoxide (O2-) [6]. In addition, NO regulates signal transduction by regulating Ca2+ signaling, by regulating the structure of the immuno logical synapse, or through the modification of intra cellular proteins, such as by inter actions with heme groups (Figure 1). Here we summarize the effects of NO on T lymphocyte functions in both systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).NO regulates mitochondrial membrane potential in human T cells [7], and may both stimulate and inhibit apoptosis [8]. It was shown to inhibit cytochrome c oxidase, leading to cell death through ATP depletion (Figure 1). In addition, NO was shown to regulate mitochondrial biogenesis in U937 and HeLa cells and adipocytes through the cGMP-dependent peroxisome proliferator-activating receptor λ coactivator 1α [9]. According to our earlier work, NO regulates mitochondrial biogenesis in human lymphocytes as well [10]. Nitrosylation of sulfhydryl groups represents an important cGMP-independent, NO-dependent post-translational modification. Several important signal transduction proteins are potential targets of S-nitrosylation, such as ca
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