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Search Results: 1 - 10 of 550295 matches for " Tamás János Katona "
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Modelling of Fatigue-Type Seismic Damage for Nuclear Power Plants  [PDF]
Tamás János Katona
Open Journal of Safety Science and Technology (OJSST) , 2012, DOI: 10.4236/ojsst.2012.22006
Abstract: Assessment of seismic safety of the nuclear power plants requires knowledge of plant fragilities. In the paper, preliminary analysis is made on use of the cumulative absolute velocity in modelling of fatiguetype seismic damage. The dependence of the cumulative absolute velocity on the strong motion parameters is analysed. It is demonstrated that the cumulative absolute velocity is an appropriate damage indicator for fatigue failure mode. Failure criteria are defined in terms of cumulative absolute velocity using various fatigue failure theories.
Switch of Voltage-Gated K+ Channel Expression in the Plasma Membrane of Chondrogenic Cells Affects Cytosolic Ca2+-Oscillations and Cartilage Formation
Zoltan Varga, Tamás Juhász, Csaba Matta, János Fodor, éva Katona, Adam Bartok, Tamás Oláh, Attila Sebe, László Csernoch, Gyorgy Panyi, Róza Zákány
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0027957
Abstract: Background Understanding the key elements of signaling of chondroprogenitor cells at the earliest steps of differentiation may substantially improve our opportunities for the application of mesenchymal stem cells in cartilage tissue engineering, which is a promising approach of regenerative therapy of joint diseases. Ion channels, membrane potential and Ca2+-signaling are important regulators of cell proliferation and differentiation. Our aim was to identify such plasma membrane ion channels involved in signaling during chondrogenesis, which may serve as specific molecular targets for influencing chondrogenic differentiation and ultimately cartilage formation. Methodology/Principal Findings Using patch-clamp, RT-PCR and Western-blot experiments, we found that chondrogenic cells in primary micromass cell cultures obtained from embryonic chicken limb buds expressed voltage-gated NaV1.4, KV1.1, KV1.3 and KV4.1 channels, although KV1.3 was not detectable in the plasma membrane. Tetrodotoxin (TTX), the inhibitor of NaV1.4 channels, had no effect on cartilage formation. In contrast, presence of 20 mM of the K+ channel blocker tetraethyl-ammonium (TEA) during the time-window of the final commitment of chondrogenic cells reduced KV currents (to 27±3% of control), cell proliferation (thymidine incorporation: to 39±4.4% of control), expression of cartilage-specific genes and consequently, cartilage formation (metachromasia: to 18.0±6.4% of control) and also depolarized the membrane potential (by 9.3±2.1 mV). High-frequency Ca2+-oscillations were also suppressed by 10 mM TEA (confocal microscopy: frequency to 8.5±2.6% of the control). Peak expression of TEA-sensitive KV1.1 in the plasma membrane overlapped with this period. Application of TEA to differentiated chondrocytes, mainly expressing the TEA-insensitive KV4.1 did not affect cartilage formation. Conclusions/Significance These data demonstrate that the differentiation and proliferation of chondrogenic cells depend on rapid Ca2+-oscillations, which are modulated by KV-driven membrane potential changes. KV1.1 function seems especially critical during the final commitment period. We show the critical role of voltage-gated cation channels in the differentiation of non-excitable cells with potential therapeutic use.
Experiences and Conclusions of the Hungarian Emergency Sepsis Register  [PDF]
Péter Kanizsai, Tamás Berényi, Miklós Pálv?lgyi, János Gál, Zoltán Pet?
Open Journal of Epidemiology (OJEpi) , 2017, DOI: 10.4236/ojepi.2017.71005
Abstract: Objective: Early recognition is a key step in decreasing morbidity and mortality in sepsis. Like in other European countries an ever growing number of septic patients enter hospitals via emergency departments. Our goal was to assess the number and severity of patients with sepsis, severe sepsis and septic shock attending the Hungarian emergency departments. Methods: Two-hundred and ninety-nine patients were entered into the Hungarian Emergency Sepsis Register, focusing on age, disease severity, monitoring and oxygenation. Application and time of administration of antibiotics, use of biomarkers, i.e. lactate and procalcitonin, disposition of patients were assessed using a web-based electronic questionnaire. Results: Data arriving from twenty emergency departments revealed that with severity of the disease oxygen administration and level of monitoring increased, along with antibiotic administration and use of biomarkers. Time spent in the ED did not differ between septic, severely septic and septic shock patients; however higher level of care was provided for the sickest patients. Conclusion: Our register data indicate that sepsis presents a substantial challenge to Hungarian emergency departments. The set standards for timely, adequate treatment are not yet met. The results are however also influenced by characteristics of the Hungarian health care system, most notably the lack of hospice systems. Further studies are needed to separate the subset of patients who would require and of life care.
Improvement of PSO algorithm by memory based gradient search - application in inventory management
Tamás Varga,András Király,János Abonyi
Computer Science , 2014,
Abstract: Advanced inventory management in complex supply chains requires effective and robust nonlinear optimization due to the stochastic nature of supply and demand variations. Application of estimated gradients can boost up the convergence of Particle Swarm Optimization (PSO) algorithm but classical gradient calculation cannot be applied to stochastic and uncertain systems. In these situations Monte-Carlo (MC) simulation can be applied to determine the gradient. We developed a memory based algorithm where instead of generating and evaluating new simulated samples the stored and shared former function evaluations of the particles are sampled to estimate the gradients by local weighted least squares regression. The performance of the resulted regional gradient-based PSO is verified by several benchmark problems and in a complex application example where optimal reorder points of a supply chain are determined.
Modelling of the Annual Mean Urban Heat Island Pattern for Planning of Representative Urban Climate Station Network
János Unger,Stevan Savi ,Tamás Gál
Advances in Meteorology , 2011, DOI: 10.1155/2011/398613
Abstract: The spatial distribution of the annual mean urban heat island (UHI) intensity pattern was analysed for the medium-sized city Novi Sad, Serbia, located on the low and flat Great Hungarian Plain. The UHI pattern was determined by an empirical modelling method developed by (Balázs et al. 2009). This method was based on datasets from urban areas of Szeged and Debrecen (Hungary). The urban study area in Novi Sad (60 km2) was established as a grid network of 240 cells (0.5 km ×0.5 km). A Landsat satellite image (from June 2006) was used in order to evaluate normalized difference vegetation index and built-up ratio by cells. The pattern of the obtained UHI intensity values show concentric-like shapes when drawn as isotherms, mostly increase from the suburbs towards the inner urban areas. Results of this thermal pattern and determination of one of the local climate classification systems were used for recommending 10 locations for representative stations of an urban climate network in Novi Sad.
Evolutionary Strategy for Feeding Trajectory Optimization of Fed-batch Reactors
Tamás Varga,Ferenc Szeifert,János Abonyi
Acta Polytechnica Hungarica , 2007,
Abstract: Safe and optimal operation of complex production processes is one of the mostimportant research and development problems in process engineering. This problem is themost relevant at the design of the optimal feeding profile of fed-batch chemical reactorsdue to the nonlinear and unstable dynamical behavior of the processes. This paper showsthat how the optimal feeding policy can be determined in fed-batch reactors by sequentialquadratic programming, classical evolutionary strategy (ES) and the advanced version ofES that is based on covariance matrix adaptation. A multi-objective function was createdand the search space was constrained in case of all of the three applied algorithms. Theswitching times between states in the feeding trajectory and the feed rates in each statewere manipulated to find the global minima of the objective function. To obtain the optimalfeeding policy the first-principle model of a pilot fed-batch reactor was implemented inMATLAB and applied as a dynamic simulator of the process. Off-line optimization processwas carried out in case of different dosing time distribution. As the results show asignificant improvement can be achieved in process performance applying advanced ESbased optimization algorithms to generate feeding trajectories.
Modelling of the Annual Mean Urban Heat Island Pattern for Planning of Representative Urban Climate Station Network
János Unger,Stevan Savi?,Tamás Gál
Advances in Meteorology , 2011, DOI: 10.1155/2011/398613
Abstract: The spatial distribution of the annual mean urban heat island (UHI) intensity pattern was analysed for the medium-sized city Novi Sad, Serbia, located on the low and flat Great Hungarian Plain. The UHI pattern was determined by an empirical modelling method developed by (Balázs et al. 2009). This method was based on datasets from urban areas of Szeged and Debrecen (Hungary). The urban study area in Novi Sad (60 km2) was established as a grid network of 240 cells (0.5?km?×0.5?km). A Landsat satellite image (from June 2006) was used in order to evaluate normalized difference vegetation index and built-up ratio by cells. The pattern of the obtained UHI intensity values show concentric-like shapes when drawn as isotherms, mostly increase from the suburbs towards the inner urban areas. Results of this thermal pattern and determination of one of the local climate classification systems were used for recommending 10 locations for representative stations of an urban climate network in Novi Sad. 1. Introduction In the second part of the 20th century, urbanization accelerated and reached enormous magnitude. The growth rate of the Earth’s urban population is greater than that of the total population; therefore, more and more people live in urbanized regions. Nowadays, about half of the human population is affected by the burdens of urban environments: environmental pollution, noise, stress of the accelerated life-style, and last but not least the modified parameters of the urban atmosphere compared to the natural environment. This makes studies dealing with the urban impact on climate particularly important. Not only the large cities but also the smaller ones modify materials, structure, and energy balance of the surface and almost all properties of the urban atmospheric environment compared to the natural surroundings. Thus, owing to the artificial factors, a local climate (urban climate) develops which means a modification to the preurban situation. This climate is a result of the construction of buildings as well as by the emission of heat, moisture, and pollution related to human activities. According to Oke [1], two layers can be distinguished in the urban atmosphere. The first one is the urban canopy layer (UCL) containing air between the urban roughness elements (mainly buildings). It is a microscale concept, and its climate is dominated geographical factors and modified by the nature of the immediate surroundings. The upper boundary of the UCL is at about roof level. The second layer is the urban boundary layer (UBL) which is situated directly above the
Extended Breadth-First Search Algorithm
Tamás Kádek,János Pánovics
Computer Science , 2014,
Abstract: The task of artificial intelligence is to provide representation techniques for describing problems, as well as search algorithms that can be used to answer our questions. A widespread and elaborated model is state-space representation, which, however, has some shortcomings. Classical search algorithms are not applicable in practice when the state space contains even only a few tens of thousands of states. We can give remedy to this problem by defining some kind of heuristic knowledge. In case of classical state-space representation, heuristic must be defined so that it qualifies an arbitrary state based on its "goodness," which is obviously not trivial. In our paper, we introduce an algorithm that gives us the ability to handle huge state spaces and to use a heuristic concept which is easier to embed into search algorithms.
Using Robust PCA to estimate regional characteristics of language use from geo-tagged Twitter messages
Dániel Kondor,István Csabai,László Dobos,János Szüle,Norbert Barankai,Tamás Hanyecz,Tamás Seb?k,Zsófia Kallus,Gábor Vattay
Computer Science , 2013,
Abstract: Principal component analysis (PCA) and related techniques have been successfully employed in natural language processing. Text mining applications in the age of the online social media (OSM) face new challenges due to properties specific to these use cases (e.g. spelling issues specific to texts posted by users, the presence of spammers and bots, service announcements, etc.). In this paper, we employ a Robust PCA technique to separate typical outliers and highly localized topics from the low-dimensional structure present in language use in online social networks. Our focus is on identifying geospatial features among the messages posted by the users of the Twitter microblogging service. Using a dataset which consists of over 200 million geolocated tweets collected over the course of a year, we investigate whether the information present in word usage frequencies can be used to identify regional features of language use and topics of interest. Using the PCA pursuit method, we are able to identify important low-dimensional features, which constitute smoothly varying functions of the geographic location.
Efficacy of 6-mercaptopurine treatment after azathioprine hypersensitivity in inflammatory bowel disease
Ferenc Nagy, Tamás Molnár, Zoltán Szepes, Klaudia Farkas, Tibor Nyári, János Lonovics
World Journal of Gastroenterology , 2008,
Abstract: AIM:To investigate the efficacy of 6-mercaptopurine (6-MP) in cases of azathioprine (AZA) hypersensitivity in patients with inflammatory bowel disease.METHODS: Twenty nine previously confirmed Crohn’s disease (CD) (n = 14) and ulcerative colitis (UC) (n = 15) patients with a known previous (AZA) hypersensitivity reaction were studied prospectively. The 6-MP doses were gradually increased from 0.5 up to 1.0-1.5 mg/kg per day. Clinical activity indices (CDAI/CAI), laboratory variables and daily doses of oral 5-ASA, corticosteroids, and 6-MP were assessed before and in the first, sixth and twelfth months of treatment.RESULTS: In 9 patients, 6-MP was withdrawn in the first 2 wk due to an early hypersensitivity reaction. Medication was ineffective within 6 mo in 6 CD patients, and myelotoxic reaction was observed in two. Data were evaluated at the end of the sixth month in 12 (8 UC, 4 CD) patients, and after the first year in 9 (6 UC, 3 CD) patients. CDAI decreased transiently at the end of the sixth month, but no significant changes were observed in the CDAI or the CAI values at the end of the year. Leukocyte counts (P = 0.01), CRP (P = 0.02), and serum iron (P = 0.05) values indicated decreased inflammatory reactions, especially in the UC patients at the end of the year, making the possibility to taper oral steroid doses.CONCLUSION: About one-third of the previously AZA-intolerant patients showed adverse effects on taking 6MP. In our series, 20 patients tolerated 6MP, but it was ineffective in 8 CD cases, and valuable mainly in ulcerative colitis patients.
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