4,327 research outputs found

    Hybrid Neural Networks for Frequency Estimation of Unevenly Sampled Data

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    In this paper we present a hybrid system composed by a neural network based estimator system and genetic algorithms. It uses an unsupervised Hebbian nonlinear neural algorithm to extract the principal components which, in turn, are used by the MUSIC frequency estimator algorithm to extract the frequencies. We generalize this method to avoid an interpolation preprocessing step and to improve the performance by using a new stop criterion to avoid overfitting. Furthermore, genetic algorithms are used to optimize the neural net weight initialization. The experimental results are obtained comparing our methodology with the others known in literature on a Cepheid star light curve.Comment: 5 pages, to appear in the proceedings of IJCNN 99, IEEE Press, 199

    IIR Adaptive Filters for Detection of Gravitational Waves from Coalescing Binaries

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    In this paper we propose a new strategy for gravitational waves detection from coalescing binaries, using IIR Adaptive Line Enhancer (ALE) filters. This strategy is a classical hierarchical strategy in which the ALE filters have the role of triggers, used to select data chunks which may contain gravitational events, to be further analyzed with more refined optimal techniques, like the the classical Matched Filter Technique. After a direct comparison of the performances of ALE filters with the Wiener-Komolgoroff optimum filters (matched filters), necessary to discuss their performance and to evaluate the statistical limitation in their use as triggers, we performed a series of tests, demonstrating that these filters are quite promising both for the relatively small computational power needed and for the robustness of the algorithms used. The performed tests have shown a weak point of ALE filters, that we fixed by introducing a further strategy, based on a dynamic bank of ALE filters, running simultaneously, but started after fixed delay times. The results of this global trigger strategy seems to be very promising, and can be already used in the present interferometers, since it has the great advantage of requiring a quite small computational power and can easily run in real-time, in parallel with other data analysis algorithms.Comment: Accepted at SPIE: "Astronomical Telescopes and Instrumentation". 9 pages, 3 figure

    The ubiquitin–proteasome system as a molecular target in solid tumors: an update on bortezomib

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    The ubiquitin–proteasome system has become a promising molecular target in cancer therapy due to its critical role in cellular protein degradation, interaction with cell cycle and apoptosis regulation, and unique mechanism of action. Bortezomib (PS-341) is a potent and specific reversible proteasome inhibitor, which has shown strong in vitro antitumor activity as single agent and in combination with other cytotoxic drugs in a broad spectrum of hematological and solid malignancies. In preclinical studies, bortezomib induced apoptosis of malignant cells through the inhibition of NF-|B and stabilization of pro-apoptotic proteins. Bortezomib also promotes chemo- and radiosensitization of malignant cells in vitro and inhibits tumor growth in murine xenograft models. The proteasome has been established as a relevant target in hematologic malignancies and bortezomib has been approved for the treatment of multiple myeloma. This review summarizes recent data from clinical trials in solid tumors

    Determination of Gd concentration profile in UO2-Gd2O3 fuel pellets

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    A transversal mapping of the Gd concentration was measured in UO2-Gd2O3 nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The quantification was made from the comparison with a Gd2O3 reference sample. The nominal concentration in the pellets is UO2: 7.5 % Gd2O3. A concentration gradient was found, which indicates that the Gd2O3 amount diminishes towards the edges of the pellets. The concentration varies from (9.3 +/- 0.5)% in the center to (5.8 +/- 0.3)% in one of the edges. The method was found to be particularly suitable for the precise mapping of the distribution of Gd3+ ions in the UO2 matrix.Comment: 10 pages, 5 figures, 2 tables. Submitted to Journal of Nuclear Material

    Teaching the old dog new tricks: Supervised learning with constraints

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    Methods for taking into account external knowledge in Machine Learning models have the potential to address outstanding issues in data-driven AI methods, such as improving safety and fairness, and can simplify training in the presence of scarce data. We propose a simple, but effective, method for injecting constraints at training time in supervised learning, based on decomposition and bi-level optimization: a master step is in charge of enforcing the constraints, while a learner step takes care of training the model. The process leads to approximate constraint satisfaction. The method is applicable to any ML approach for which the concept of label (or target) is well defined (most regression and classification scenarios), and allows to reuse existing training algorithms with no modifications. We require no assumption on the constraints, although their properties affect the shape and complexity of the master problem. Convergence guarantees are hard to provide, but we found that the approach performs well on ML tasks with fairness constraints and on classical datasets with synthetic constraints

    Exploiting the photoactivity of bacterial reaction center to investigate liposome dynamics

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    Charge recombination kinetics of bacterial photosynthetic protein Reaction Center displays an exquisite sensitivity to the actual occupancy of ubiquinone-10 in its QB-binding site. Here, we have exploited such phenomenon for assessing the growth and the aggregation/fusion of phosphocholine vesicles embedding RC in their membrane, when treated with sodium oleate

    Late Winter Dietary Overlap among Greater Rheas and Domestic Herbivores on the Argentinean Flooding Pampa

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    This study evaluates the dietary overlap among greater rheas (Rhea americana L.) sheep and cattle in the Flooding Pampa, Buenos Aires, Argentina during late winter, when is observed the lowest forage availability. The work was carried out with the following forage classes (FC): warm and cool season grasses and forbs (legumes and no-legumes). Diet botanical composition was estimated by microanalysis of faeces. Principal Component Analysis and Kulcyznsky´s index of similarity were used for data analysis. Rhea populations selected diets with higher forb percentages. On the contrary, vegetation structure and their own morpho-physiology conditioned cattle to diets almost exclusively gramineous. Although forbs were more consumed by sheep than by cattle, they do not represent a major portion of sheep diets. In the Flooding Pampa grasslands, the probability of competition for forage between greater rheas and sheep is intermediate, and that between rheas and cattle is low

    Thermodynamic conditions during growth determine the magnetic anisotropy in epitaxial thin-films of La0.7_{0.7}Sr0.3_{0.3}MnO3_{3}

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    The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet La0.7_{0.7}Sr0.3_{0.3}MnO3_{3} (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of X-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (001) SrTiO3_{3} by Pulsed Laser Deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow Chemical Solution Deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show a in-plane cubic anisotropy with an overimposed uniaxial term. A large anisotropy constant perpendicular to the film plane was also observed in these films. However, the uniaxial anisotropy is completely suppressed in the CSD films. The out of plane anisotropy is also reduced, resulting in a much stronger in plane cubic anisotropy in the chemically synthesized films. This change is due to a different rotation pattern of MnO6_{6} octahedra to accomodate epitaxial strain, which depends not only on the amount of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition.Comment: 6 pages, 8 Figure
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