1,055 research outputs found

    Renormalization Group Theory for a Perturbed KdV Equation

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    We show that renormalization group(RG) theory can be used to give an analytic description of the evolution of a perturbed KdV equation. The equations describing the deformation of its shape as the effect of perturbation are RG equations. The RG approach may be simpler than inverse scattering theory(IST) and another approaches, because it dose not rely on any knowledge of IST and it is very concise and easy to understand. To the best of our knowledge, this is the first time that RG has been used in this way for the perturbed soliton dynamics.Comment: 4 pages, no figure, revte

    Computational models for inferring biochemical networks

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    Biochemical networks are of great practical importance. The interaction of biological compounds in cells has been enforced to a proper understanding by the numerous bioinformatics projects, which contributed to a vast amount of biological information. The construction of biochemical systems (systems of chemical reactions), which include both topology and kinetic constants of the chemical reactions, is NP-hard and is a well-studied system biology problem. In this paper, we propose a hybrid architecture, which combines genetic programming and simulated annealing in order to generate and optimize both the topology (the network) and the reaction rates of a biochemical system. Simulations and analysis of an artificial model and three real models (two models and the noisy version of one of them) show promising results for the proposed method.The Romanian National Authority for Scientific Research, CNDI–UEFISCDI, Project No. PN-II-PT-PCCA-2011-3.2-0917

    Aberrant Splicing of the Senataxin Gene in a Patient with Ataxia with Oculomotor Apraxia Type 2

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    Ataxia with oculomotor apraxia type 2 (AOA2) is caused by a diversity of mutations within the coding region of the senataxin gene. Recently, rare noncoding senataxin mutations affecting RNA processing have been identified in AOA2. Here, we report the case of an 18-year-old woman, with classic clinical features of AOA2, who was found to harbor a mutation within senataxin intron 16. This mutation disrupts the local 5′ splice site architecture via a novel intronic frameshift mechanism, causing skipping of exon 16 with predicted disruption of the conserved DNA/RNA helicase domain. RNA processing mutations expand the growing complexity of pathogenic senataxin mutations

    On the influence of spatial information for hyper-spectral satellite imaging characterization

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    Land-use classification for hyper-spectral satellite images requires a previous step of pixel characterization. In the easiest case, each pixel is characterized by its spectral curve. The improvementof the spectral and spatial resolution in hyper-spectral sensors has led to very large data sets. Some researches have focused on better classifiers that can handle big amounts of data. Others have faced the problem of band selection to reduce the dimensionality of the feature space. However, thanks to the improvement in the spatial resolution of the sensors, spatial information may also provide new featuresfor hyper-spectral satellite data. Here, an study on the influence of spectral-spatial features combined with an unsupervised band selection method is presented. The results show that it is possible to reduce very significantly the number of spectral bands required while having an adequate description of the spectral-spatial characteristics of the image for pixel classification tasksThis work has been partly supported by grant FPI PREDOC/2007/20 from FundaciĂł Caixa CastellĂł-Bancaixa and projects CSD2007-00018 (Consolider Ingenio 2010) and AYA2008-05965-C04-04 from the Spanish Ministry of Science and Innovatio

    NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region

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    We describe results from a new ground-based monitoring campaign on NGC 5548, the best studied reverberation-mapped AGN. We find that it was in the lowest luminosity state yet recorded during a monitoring program, namely L(5100) = 4.7 x 10^42 ergs s^-1. We determine a rest-frame time lag between flux variations in the continuum and the Hbeta line of 6.3 (+2.6/-2.3) days. Combining our measurements with those of previous campaigns, we determine a weighted black hole mass of M_BH = 6.54 (+0.26/-0.25) x 10^7 M_sun based on all broad emission lines with suitable variability data. We confirm the previously-discovered virial relationship between the time lag of emission lines relative to the continuum and the width of the emission lines in NGC 5548, which is the expected signature of a gravity-dominated broad-line region. Using this lowest luminosity state, we extend the range of the relationship between the luminosity and the time lag in NGC 5548 and measure a slope that is consistent with alpha = 0.5, the naive expectation for the broad line region for an assumed form of r ~ L^alpha. This value is also consistent with the slope recently determined by Bentz et al. for the population of reverberation-mapped AGNs as a whole.Comment: 24 pages, 3 tables, 7 figures, accepted for publication in Ap

    The Mass of the Black Hole in the Seyfert 1 Galaxy NGC 4593 from Reverberation Mapping

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    We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the H_beta emission-line light curve with the optical continuum light curve reveals an emission-line time delay of 3.73 (+-0.75) days. By combining this time delay with the H_beta line width, we derive a central black hole mass of M_BH = 9.8(+-2.1)x10^6 M_sun, an improvement in precision of a factor of several over past results.Comment: 22 pages, 3 tables, 5 figures, accepted for publication in Ap

    Dynamics of Flux Creep in Underdoped Single Crystals of Y_1-xPr_xBa_2Cu_3O_7-d

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    Transport as well as magnetic relaxation properties of the mixed state were studied on strongly underdoped Y_1-xPr_xBa_2Cu_3O_7-d crystals. We observed two correlated phenomena - a coupling transition and a transition to quantum creep. The distribution of transport current below the coupling transition is highly nonuniform, which facilitates quantum creep. We speculate that in the mixed state below the coupling transition, where dissipation is nonohmic, the current distribution may be unstable with respect to self-channeling resulting in the formation of very thin current-carrying layers.Comment: 11 pages, 9 figures, Submitted to Phys. Rev.

    The Disconnect Between the Guidelines, the Appropriate Use Criteria, and Reimbursement Coverage Decisions The Ultimate Dilemma

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    Recently, the American College of Cardiology Foundation in collaboration with the Heart Rhythm Society published appropriate use criteria (AUC) for implantable cardioverter-defibrillators and cardiac resynchronization therapy. These criteria were developed to critically review clinical situations that may warrant implantation of an implantable cardioverter-defibrillator or cardiac resynchronization therapy device, and were based on a synthesis of practice guidelines and practical experience from a diverse group of clinicians. When the AUC was drafted, the writing committee recognized that some of the scenarios that were deemed “appropriate” or “may be appropriate” were discordant with the clinical requirements of many payers, including the Medicare National Coverage Determination (NCD). To charge Medicare for a procedure that is not covered by the NCD may be construed as fraud. Discordance between the guidelines, the AUC, and the NCD places clinicians in the difficult dilemma of trying to do the “right thing” for their patients, while recognizing that the “right thing” may not be covered by the payer or insurer. This commentary addresses these issues. Options for reconciling this disconnect are discussed, and recommendations to help clinicians provide the best care for their patients are offered

    Absence of a Zero Temperature Vortex Solid Phase in Strongly Disordered Superconducting Bi Films

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    We present low temperature measurements of the resistance in magnetic field of superconducting ultrathin amorphous Bi films with normal state sheet resistances, RNR_N, near the resistance quantum, RQ=â„Źe2R_Q={\hbar\over {e^2}}. For RN<RQR_N<R_Q, the tails of the resistive transitions show the thermally activated flux flow signature characteristic of defect motion in a vortex solid with a finite correlation length. When RNR_N exceeds RQR_Q, the tails become non-activated. We conclude that in films where RN>RQR_N>R_Q there is no vortex solid and, hence, no zero resistance state in magnetic field. We describe how disorder induced quantum and/or mesoscopic fluctuations can eliminate the vortex solid and also discuss implications for the magnetic-field-tuned superconductor-insulator transition.Comment: REVTEX, 4 pages, 3 figure
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