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Search Results: 1 - 10 of 337240 matches for " András Temesvári "
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Preventing complicated transseptal puncture with intracardiac echocardiography: case report
Tchavdar Shalganov, Dora Paprika, Sarolta Borbás, András Temesvári, Tamás Szili-T?r?k
Cardiovascular Ultrasound , 2005, DOI: 10.1186/1476-7120-3-5
Abstract: A case of a patient with paroxysmal atrial fibrillation and atrial flutter, and distorted intracardiac anatomy is presented. Intracardiac echocardiography showed a small oval fossa abouting to an enlarged aorta anteriorly. A very small distance from the interatrial septum to the left atrial free wall was seen. The latter two conditions were predisposing to a complicated transseptal puncture. According to fluoroscopy the transseptal needle had a correct position, but the intracardiac echo image showed that it was actually pointing towards the aortic root and most importantly, that it was virtually impossible to stabilize it in the fossa itself. Based on intracardiac echo findings a decision was made to limit the procedure only to ablation of the cavotricuspid isthmus and not to proceed further so as to avoid complications.This case report illustrates the usefulness of the intracardiac echocardiography in preventing serious or even fatal complications in transseptal procedures when the cardiac anatomy is unusual or distorted. It also helps to understand the possible mechanisms of mechanical complications in cases where fluoroscopic images are apparently normal.Since the advent of ICE in the electrophysiology practice it proved its value in guiding transseptal procedures with providing an extra safety margin for the patients. The possibility to visualize the oval fossa, the LA free wall and the aortic root helps in preventing mechanical complications. ICE can visualize also intracardiac thrombus and spontaneous echocontrast, which is helpful in avoiding thromboembolic complications. Although the value of ICE is well known, it is rather hard to admit that it is a universal tool for achieving uncomplicated access to the left atrium. The aim of this case presentation is to show that ICE can lead to interruption of a transseptal procedure due to the presence of risk factors for mechanical complications when the fluoroscopic image is seemingly satisfying.A seventy-year-old
Almeida-Thouless transition below six dimensions
Tamás Temesvári
Physics , 2008, DOI: 10.1103/PhysRevB.78.220401
Abstract: The existence of an Almeida-Thouless (AT) instability surface below the upper critical dimension 6 is demonstrated in the generic replica symmetric field theory. Renormalization flows from around the zero-field fixed point are investigated. By introducing the temperature and magnetic field dependence of the bare parameters, the fate of the AT line can be followed from mean field (infinite dimensions) down to d<6.
The perturbative structure of spin glass field theory
Tamás Temesvári
Physics , 2013, DOI: 10.1016/j.nuclphysb.2014.01.020
Abstract: Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the epsilon-expansion around the critical fixed point (d=6-epsilon). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.
Could successful cryoballoon ablation of paroxysmal atrial fibrillation prevent progressive left atrial remodeling?
Tamás Erdei, Mónika Dénes, Attila Kardos, Attila Mihálcz, Csaba F?ldesi, András Temesvári, Mária Lengyel
Cardiovascular Ultrasound , 2012, DOI: 10.1186/1476-7120-10-11
Abstract: 36 patients selected for their first CCA because of nonvalvular paroxysmal AF had echocardiography before and 3, 6 and 12 months after CCA. LA diameters, volumes (LAV) and LA volume index (LAVI) were evaluated. LA function was assessed by: early diastolic velocities of the mitral annulus (Aasept, Aalat), LA filling fraction (LAFF), LA emptying fraction (LAEF) and the systolic fraction of pulmonary venous flow (PVSF). Detailed left ventricular diastolic function assessment was also performed.Excluding recurrences in the first 3-month blanking period, the clinical success rate was 64%. During one-year of follow-up, recurrent atrial arrhythmia was found in 21 patients (58%). In the recurrent group at 12 months after ablation, minimal LAV (38 ± 19 to 44 ± 20 ml; p < 0.05), maximal LAV (73 ± 23 to 81 ± 24 ml; p < 0.05), LAVI (35 ± 10 to 39 ± 11 ml/m2; p = 0.01) and the maximal LA longitudinal diameter (55 ± 5 to 59 ± 6 mm; p < 0.01) had all increased. PVSF (58 ± 9 to 50 ± 10%; p = 0.01) and LAFF (36 ± 7 to 33 ± 8%; p = 0.03) had decreased. In contrast, after successful cryoballoon ablation LA size had not increased and LA function had not declined. In the recurrent group LAEF was significantly lower at baseline and at follow-up visits.In patients whose paroxysmal atrial fibrillation recurred within one year after cryoballoon catheter ablation left atrial size had increased and left atrial function had declined. In contrast, successful cryoballoon catheter ablation prevented progressive left atrial remodeling.The relationship between left atrial (LA) dilatation and atrial fibrillation (AF) has been widely accepted for a long time [1]. Electrophysiological, structural and functional atrial remodeling have been observed in patients with AF, and it has been shown that normal myocardial tissue is often replaced with fibrosis [2]. Dilated left atrium predict later cardiovascular events [3]. Catheter ablation of atrial fibrillation has been established as a therapeutic option f
Non-trivial two-armed partial-monitoring games are bandits
András Antos,Gábor Bartók,Csaba Szepesvári
Computer Science , 2011,
Abstract: We consider online learning in partial-monitoring games against an oblivious adversary. We show that when the number of actions available to the learner is two and the game is nontrivial then it is reducible to a bandit-like game and thus the minimax regret is $\Theta(\sqrt{T})$.
Online Learning with Gaussian Payoffs and Side Observations
Yifan Wu,András Gy?rgy,Csaba Szepesvári
Computer Science , 2015,
Abstract: We consider a sequential learning problem with Gaussian payoffs and side information: after selecting an action $i$, the learner receives information about the payoff of every action $j$ in the form of Gaussian observations whose mean is the same as the mean payoff, but the variance depends on the pair $(i,j)$ (and may be infinite). The setup allows a more refined information transfer from one action to another than previous partial monitoring setups, including the recently introduced graph-structured feedback case. For the first time in the literature, we provide non-asymptotic problem-dependent lower bounds on the regret of any algorithm, which recover existing asymptotic problem-dependent lower bounds and finite-time minimax lower bounds available in the literature. We also provide algorithms that achieve the problem-dependent lower bound (up to some universal constant factor) or the minimax lower bounds (up to logarithmic factors).
Online Learning under Delayed Feedback
Pooria Joulani,András Gy?rgy,Csaba Szepesvári
Computer Science , 2013,
Abstract: Online learning with delayed feedback has received increasing attention recently due to its several applications in distributed, web-based learning problems. In this paper we provide a systematic study of the topic, and analyze the effect of delay on the regret of online learning algorithms. Somewhat surprisingly, it turns out that delay increases the regret in a multiplicative way in adversarial problems, and in an additive way in stochastic problems. We give meta-algorithms that transform, in a black-box fashion, algorithms developed for the non-delayed case into ones that can handle the presence of delays in the feedback loop. Modifications of the well-known UCB algorithm are also developed for the bandit problem with delayed feedback, with the advantage over the meta-algorithms that they can be implemented with lower complexity.
Fast Cross-Validation for Incremental Learning
Pooria Joulani,András Gy?rgy,Csaba Szepesvári
Computer Science , 2015,
Abstract: Cross-validation (CV) is one of the main tools for performance estimation and parameter tuning in machine learning. The general recipe for computing CV estimate is to run a learning algorithm separately for each CV fold, a computationally expensive process. In this paper, we propose a new approach to reduce the computational burden of CV-based performance estimation. As opposed to all previous attempts, which are specific to a particular learning model or problem domain, we propose a general method applicable to a large class of incremental learning algorithms, which are uniquely fitted to big data problems. In particular, our method applies to a wide range of supervised and unsupervised learning tasks with different performance criteria, as long as the base learning algorithm is incremental. We show that the running time of the algorithm scales logarithmically, rather than linearly, in the number of CV folds. Furthermore, the algorithm has favorable properties for parallel and distributed implementation. Experiments with state-of-the-art incremental learning algorithms confirm the practicality of the proposed method.
In Vivo Examination of Fat Deposition in Growing Rabbits Selected for High and Low Body Fat Content
Gábor Milisits,András Lévai,Gabriella Andrássy-Baka,Róbert Romvári
Agriculturae Conspectus Scientificus (ACS) , 2003,
Abstract: Pannon White rabbits of average ± 1 S.D. live weight at 10 weeks and of average± 1 S.D. daily weight gain between 6 and 10 weeks of age were chosen from the experimental stock of our university, and their fat content was determined with an EM-SCAN SA-3152 type small animal body composition analyser (by means of TOBEC method) at 10 weeks of age. Based on the fat content determined, the best and worst 16% of the does and the best and worst 8% of the bucks were chosen and mated with each other (fatty doe with fatty buck and lean doe with lean buck). Their offspring were examined by computer tomography (CT) weekly between 6 and 11 weeks of age. Cross-sectional images (scans) were taken from the scapular arch to the end of the femur on each animal. From this scans the amount of fat was determined and its ratio to the total amount of body was calculated in the scapular, perirenal and pelvic region. In the most cases it was established that the total body fat content and also fat content in the scapular, perirenal and pelvic regions are significantly higher in the offspring of fatty rabbits as in the offspring of non-fatty ones. In the group of non-fatty rabbits the scapular fat increased intensively from the age of 7 weeks. The perirenal fat content began to grow rapidly at 8 weeks in fatty group and at 10 weeks of age in the non-fatty rabbits. Based on the results of this experiment TOBEC method seems to be a useful thing for selecting rabbits based on their body fat content.
On $3$-uniform hypergraphs without linear cycles
András Gyárfás,Ervin Gy?ri,Miklós Simonovits
Mathematics , 2014,
Abstract: We explore properties of $3$-uniform hypergraphs $H$ without linear cycles. Our main results are that these hypergraphs must contain a vertex of strong degree at most two and must have independent sets of size at least ${2|V(H)|\over 5}$.
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