Etvs Lornd University

Budapest, Hungary

Etvs Lornd University

Budapest, Hungary
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Kereszturi A.,Institute for Advanced Study | Kereszturi A.,C Laborc Street | Kereszturi A.,Etvs Lornd University
Planetary and Space Science | Year: 2010

Six tributaries of Shalbatana outflow channel were analyzed based on visible imagery by THEMIS, MOC, HRSC, and HiRISE, as well as on topographic data by MOLA. Two different sections could be identified on the tributaries: the upper and the lower reaches. The upper reaches are shallow, showing U-shaped cross-sectional profiles. Their bottom level is filled with sediments, forming a plain. They have nearly horizontal longitudinal profiles, suggesting either the formation under long term fluvial erosion, or their bottom level represents a strong subsurface layer, until which the valley could cut itself downward into the rocks. Lower reaches show wider and deeper cross-sectional V-shaped profiles, with a narrow, infilled central bottom level. They show steep and at some occasion convex longitudinal profiles, indicating other erosional processes than the upper reaches, and/or that the erosion did not have time to form an equilibrium-like profile. They were formed after the Shalbatana outflow channel, probably by a process different from the formation of the upper reaches that may not involve fluvial erosion, or under different environmental conditions. Two possible scenarios are proposed to explain the formation of these two classes of reaches: (1) They may have formed under different climatic conditions on Mars, and show examples for surface forming forces that changed during the planetary evolution. Such different valley sections may point to differences both in lithology and differences in the Martian surface conditions if they formed at different periods. (2) The other possibility is that they formed roughly during the same period, and the two different sections represent differences only in lithology and erodibility. The incut of the upper reach happened in a harder rock unit, forming a nearly horizontal longitudinal profile, and was not deep enough to reach the deeper, more erodible rock level. At the lower reach a different type of erosion took place because of different lithology, and formed the deeper, steeper lower reaches there. © 2010 Elsevier Ltd. All rights reserved.

Ladanyi A.,University of Bedfordshire | Lopez-Perez D.,King's College London | Juttner A.,Etvs Lornd University | Chu X.,King's College London | Zhang J.,University of Bedfordshire
2011 IEEE GLOBECOM Workshops, GC Wkshps 2011 | Year: 2011

This paper proposes a decentralized model for the allocation of modulation and coding schemes, subchannels and transmit power to users in OFDMA femtocell deployments. The proposed model does not rely on any exchanged information between cells, which is especially useful for femtocell networks. Coordination between femtocells is achieved through the intrinsic properties of minimising transmit power independently at each cell, which leads the network to self-organize into an efficient frequency reuse pattern. This paper also provides a two-level decomposition approach for solving this intricate resource assignment problem that is able to find optimal solutions at cell level in reduced periods of time. System-level simulations show a significant performance improvement in terms of user outages and network capacity when using the proposed distributed resource allocation in comparison with scheduling techniques based on uniform power distributions among subcarriers. © 2011 IEEE.

Farag I.,Etvs Lornd University | Havasi G.,Etvs Lornd University | Zlatev Z.,University of Aarhus
Computers and Mathematics with Applications | Year: 2010

Richardson Extrapolation is a powerful computational tool which can successfully be used in the efforts to improve the accuracy of the approximate solutions of systems of ordinary differential equations (ODEs) obtained by different numerical methods (including here combined numerical methods consisting of appropriately chosen splitting procedures and classical numerical methods). Some stability results related to two implementations of the Richardson Extrapolation (Active Richardson Extrapolation and Passive Richardson Extrapolation) are formulated and proved in this paper. An advanced atmospheric chemistry scheme, which is commonly used in many well-known operational environmental models, is applied in a long sequence of experiments in order to demonstrate the fact that it is indeed possible to improve the accuracy of the numerical results when the Richardson Extrapolation is used (also when very difficult, badly scaled and stiff non-linear systems of ODEs are to be treated),the computations can become unstable when the combination of the Trapezoidal Rule and the Active Richardson Extrapolation is used,the application of the Active Richardson Extrapolation with the Backward Euler Formula is leading to a stable computational process,experiments with different algorithms for solving linear systems of algebraic equations are very useful in the efforts to select the most suitable approach for the particular problems solved andthe computational cost of the Richardson Extrapolation is much less than that of the underlying numerical method when a prescribed accuracy has to be achieved. © 2010 Elsevier Ltd. All rights reserved.

Ivanov I.,Ecole Polytechnique Federale de Lausanne | Vajda P.,VU University Amsterdam | Vajda P.,Etvs Lornd University | Lee J.-S.,KAIST
IEEE Signal Processing Magazine | Year: 2012

Tagging in online social networks is very popular these days, as it facilitates search and retrieval of multimedia content. However, noisy and spam annotations often make it difficult to perform an efficient search. Users may make mistakes in tagging and irrelevant tags and content may be maliciously added for advertisement or self-promotion. This article surveys recent advances in techniques for combatting such noise and spam in social tagging. We classify the state-of-the-art approaches into a few categories and study representative examples in each. We also qualitatively compare and contrast them and outline open issues for future research. © 2012 IEEE.

Spisak S.,Dana-Farber Cancer Institute | Spisak S.,Cedars Sinai Medical Center | Lawrenson K.,University of Southern California | Lawrenson K.,Cedars Sinai Medical Center | And 27 more authors.
Nature Medicine | Year: 2015

The vast majority of disease-associated single-nucleotide polymorphisms (SNPs) mapped by genome-wide association studies (GWASs) are located in the non-protein-coding genome, but establishing the functional and mechanistic roles of these sequence variants has proven challenging. Here we describe a general pipeline in which candidate functional SNPs are first evaluated by fine mapping, epigenomic profiling, and epigenome editing, and then interrogated for causal function by using genome editing to create isogenic cell lines followed by phenotypic characterization. To validate this approach, we analyzed the 6q22.1 prostate cancer risk locus and identified rs339331 as the top-scoring SNP. Epigenome editing confirmed that the rs339331 region possessed regulatory potential. By using transcription activator-like effector nuclease (TALEN)-mediated genome editing, we created a panel of isogenic 22Rv1 prostate cancer cell lines representing all three genotypes (TT, TC, CC) at rs339331. Introduction of the 'T' risk allele increased transcription of the regulatory factor 6 (RFX6) gene, increased homeobox B13 (HOXB13) binding at the rs339331 region, and increased deposition of the enhancer-associated H3K4me2 histone mark at the rs339331 region compared to lines homozygous for the 'C' protective allele. The cell lines also differed in cellular morphology and adhesion, and pathway analysis of differentially expressed genes suggested an influence of androgens. In summary, we have developed and validated a widely accessible approach that can be used to establish functional causality for noncoding sequence variants identified by GWASs. © 2015 Macmillan Publishers Limited. All rights reserved.

Karsai I.,East Tennessee State University | Kampis G.,Etvs Lornd University
BioScience | Year: 2010

Biology is changing and becoming more quantitative. Research is creating new challenges that need to be addressed in education as well. New educational initiatives focus on combining laboratory procedures with mathematical skills, yet it seems that most curricula center on a single relationship between scientific knowledge and scientific method: that of the validity of knowledge claims, judged in terms of their consistency with data. Collecting data and obtaining results (however quantitative) are commonly part of science, but are not science itself. We envision that the operative use of the complete scientific method will play a critical role in providing the necessary underpinning for the integration of math and biology at various professional levels. © 2010 by American Institute of Biological Sciences. All rights reserved.

Soumelidis A.,Computer and Automation Research Institute | Fazekas Z.,Computer and Automation Research Institute | Pap M.,University of Pécs | Schipp F.,Etvs Lornd University
MeMeA 2011 - 2011 IEEE International Symposium on Medical Measurements and Applications, Proceedings | Year: 2011

Meshes of points over the unit disk were found some years ago that ensure the discrete orthogonality of the Zernike functions. These meshes are referred in the paper as generic Zernike meshes. Presently, however, the corneal surface points are measured, e.g., with reflection-based corneal topographers, and computed, with their respective built-in surface(-point) reconstruction programs, at other, that is, non-generic Zernike meshes. In the present paper, the corneal surface points measured over conventional non-generic Zernike meshes are converted - via cubic spline-interpolation and appropriate re-sampling - to surface points over generic Zernike meshes. With these spatial points as input points, discrete Zernike transformation is carried out. The resulting Zernike coefficients are then used to geometrically reconstruct the optically smooth corneal surface. In the work reported herein, generic Zernike meshes of different cardinalities were used and the resulting surface representations were evaluated. Then, the error-surfaces were compared to the ones resulting from the Zernike-based reconstructions of a cornea-like mathematical surface that had been properly fitted to the input data. © 2011 IEEE.

Tatrai A.,Etvs Lornd University
Journal of Parallel and Distributed Computing | Year: 2011

In this paper the author make a comprehensive comparison of different parallelizations of a sequential number theoretic algorithm having large memory requirements. Brunotte's algorithm is one of the currently known best methods for the decision of the canonical number system (or more generally shift radix system) property. Still, it can be very space-consuming in some cases. Pushing the algorithm to its limits may hopefully shed light on mathematical patterns that would otherwise not be discernible. The algorithm contains many n-dimensional vector operations and set operations like insert, find, clear, etc. The parallel algorithms encounter two difference kinds of concurrency problems. First, they need computationally intensive arithmetic vector operations, second, the set implementations require a huge amount of memory and general purpose processors. The algorithms described in this article are basically designed for two platforms. The first platform is a generic symmetric multiprocessing (SMP) architecture without any vector processor extension, the second is the Cell Broadband Engine. The SMP platforms have several general purpose processors in contrast with the Cell Broadband Engine where the processors have Synergistic vector processors. © 2010 Elsevier Inc. All rights reserved.

Felfoldi T.,Etvs Lornd University | Somogyi B.,Balaton Limnological Research Institute | Marialigeti K.,Etvs Lornd University | Voros L.,Balaton Limnological Research Institute
Journal of Plankton Research | Year: 2011

Comparative phylogenetic analysis of non-marine planktonic picocyanobacterial isolates (based on the 16S ribosomal RNA gene and the phycocyanin operon) revealed that the geographic restriction of several clades is the outcome of under-sampling or database search bias. This result supports the high dispersive potential of planktonic picocyanobacteria and emphasizes that endemic genotypes do not seem as widespread as suggested by the latest publications. © 2011 The Author.

Varga L.K.,Hungarian Academy of Sciences | Kovacs G.,Etvs Lornd University
IEEE Transactions on Magnetics | Year: 2012

In this work, we have investigated the effect of a transversal applied DC magnetic field on the longitudinally measured magnetic properties of nanocrystalline Finemet cores. The core was prepared by stacking up toroidal sheets ( Dext}=17.5\ mm , Dint}=8.5\ mm) cut from 20 mm wide Finemet ribbon of 22 μmm thickness. The resulting height of the toroid was 5 mm. The stack was heat treated in hydrogen at 550 °C for 1 h. Quantitative measurements were conducted by using a Helmholtz coil for generating the transversal field along the ring axis so that the magnetization of the toroidal core is forced to turn out of the sheet, transversal to the measuring magnetic field applied along the toroid. Flattening of the quasi-static loop as a function of transversal field is accompanied by a diminution of the remanence and coercive field. The relative permeability could be diminished by more than two orders of magnitude (from 60 000 to 700). Correspondingly, the eddy current frequency limit (where the imaginary part of the permeability is maximal) was shifted from 60 kHz to 1 MHz. Tayloring the hysteresis loop will be discussed in terms of rotational magnetization which dominates over the domain wall displacement mechanism when the magnetization is forced to turn out of the sheet plane. © 2006 IEEE.

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