2,097 research outputs found

    Positive solutions of Schr\"odinger equations and fine regularity of boundary points

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    Given a Lipschitz domain Ω\Omega in RN{\mathbb R} ^N and a nonnegative potential VV in Ω\Omega such that V(x) d(x,∂Ω)2V(x)\, d(x,\partial \Omega)^2 is bounded in Ω\Omega we study the fine regularity of boundary points with respect to the Schr\"odinger operator LV:=Δ−VL_V:= \Delta -V in Ω\Omega . Using potential theoretic methods, several conditions equivalent to the fine regularity of z∈∂Ωz \in \partial \Omega are established. The main result is a simple (explicit if Ω\Omega is smooth) necessary and sufficient condition involving the size of VV for zz to be finely regular. An essential intermediate result consists in a majorization of ∫A∣ud(.,∂Ω)∣2 dx\int_A | {\frac {u} {d(.,\partial \Omega)}} | ^2\, dx for uu positive harmonic in Ω\Omega and A⊂ΩA \subset \Omega . Conditions for almost everywhere regularity in a subset AA of ∂Ω \partial \Omega are also given as well as an extension of the main results to a notion of fine L1∣L0{\mathcal L}_1 | {\mathcal L}_0-regularity, if Lj=L−Vj{\mathcal L}_j={\mathcal L}-V_j, V0, V1V_0,\, V_1 being two potentials, with V0≤V1V_0 \leq V_1 and L{\mathcal L} a second order elliptic operator.Comment: version 1. 23 pages version 3. 28 pages. Mainly a typo in Theorem 1.1 is correcte

    Coinductive subtyping for abstract compilation of object-oriented languages into Horn formulas

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    In recent work we have shown how it is possible to define very precise type systems for object-oriented languages by abstractly compiling a program into a Horn formula f. Then type inference amounts to resolving a certain goal w.r.t. the coinductive (that is, the greatest) Herbrand model of f. Type systems defined in this way are idealized, since in the most interesting instantiations both the terms of the coinductive Herbrand universe and goal derivations cannot be finitely represented. However, sound and quite expressive approximations can be implemented by considering only regular terms and derivations. In doing so, it is essential to introduce a proper subtyping relation formalizing the notion of approximation between types. In this paper we study a subtyping relation on coinductive terms built on union and object type constructors. We define an interpretation of types as set of values induced by a quite intuitive relation of membership of values to types, and prove that the definition of subtyping is sound w.r.t. subset inclusion between type interpretations. The proof of soundness has allowed us to simplify the notion of contractive derivation and to discover that the previously given definition of subtyping did not cover all possible representations of the empty type

    Quantum and Classical Glass Transitions in LiHoxY1−xF4Li Ho_x Y_{1-x} F_4

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    When performed in the proper low field, low frequency limits, measurements of the dynamics and the nonlinear susceptibility in the model Ising magnet in transverse field, LiHoxY1−xF4\text{LiHo}_x\text{Y}_{1-x}\text{F}_4, prove the existence of a spin glass transition for xx = 0.167 and 0.198. The classical behavior tracks for the two concentrations, but the behavior in the quantum regime at large transverse fields differs because of the competing effects of quantum entanglement and random fields.Comment: 5 pages, 5 figures. Updated figure 3 with corrected calibration information for thermometr

    Some Results on the Boundary Control of Systems of Conservation Laws

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    This note is concerned with the study of the initial boundary value problem for systems of conservation laws from the point of view of control theory, where the initial data is fixed and the boundary data are regarded as control functions. We first consider the problem of controllability at a fixed time for genuinely nonlinear Temple class systems, and present a description of the set of attainable configurations of the corresponding solutions in terms of suitable Oleinik-type estimates. We next present a result concerning the asymptotic stabilization near a constant state for general n×nn\times n systems. Finally we show with an example that in general one cannot achieve exact controllability to a constant state in finite time.Comment: 10 pages, 4 figures, conferenc

    Leave-one-out prediction error of systolic arterial pressure time series under paced breathing

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    In this paper we show that different physiological states and pathological conditions may be characterized in terms of predictability of time series signals from the underlying biological system. In particular we consider systolic arterial pressure time series from healthy subjects and Chronic Heart Failure patients, undergoing paced respiration. We model time series by the regularized least squares approach and quantify predictability by the leave-one-out error. We find that the entrainment mechanism connected to paced breath, that renders the arterial blood pressure signal more regular, thus more predictable, is less effective in patients, and this effect correlates with the seriousness of the heart failure. The leave-one-out error separates controls from patients and, when all orders of nonlinearity are taken into account, alive patients from patients for which cardiac death occurred

    A comparative study of Gaussian Graphical Model approaches for genomic data

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    The inference of networks of dependencies by Gaussian Graphical models on high-throughput data is an open issue in modern molecular biology. In this paper we provide a comparative study of three methods to obtain small sample and high dimension estimates of partial correlation coefficients: the Moore-Penrose pseudoinverse (PINV), residual correlation (RCM) and covariance-regularized method (â„“2C)(\ell_{2C}). We first compare them on simulated datasets and we find that PINV is less stable in terms of AUC performance when the number of variables changes. The two regularized methods have comparable performances but â„“2C\ell_{2C} is much faster than RCM. Finally, we present the results of an application of â„“2C\ell_{2C} for the inference of a gene network for isoprenoid biosynthesis pathways in Arabidopsis thaliana.Comment: 7 pages, 1 figure, RevTex4, version to appear in the proceedings of 1st International Workshop on Pattern Recognition, Proteomics, Structural Biology and Bioinformatics: PR PS BB 2011, Ravenna, Italy, 13 September 201

    Micropropagation supports reintroduction of an apulian artichoke landrace in sustainable cropping systems

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    Artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori) is a perennial plant of the Aster-aceae’s family native to the Mediterranean basin. Italy has rich artichoke biodiversity, but many landraces are subjected to genetic erosion caused by increasing use of commercial varieties that are more homogenous in production. An Apulian landrace ‘Troianella’ was established in vitro to valorize and provide high-quality material for propagation in nurseries and, subsequently, for cultivation in production fields. The shoot proliferation was tested on four different growth media, adding cytokinin (-6-benzylamminopurine (BAP-0.05 mg L−1 ). Among these, the best results were achieved on MS519-A and BM media in which MS macronutrients were supplemented with additional doses of CaCl2 and MgSO4 (plus 120 mg L−1 and 190 mg L−1, respectively). In vitro root induction was obtained with 10 mg L−1 of Indole-3-acetic acid (IAA) and 30 g L−1 of sucrose. Plants derived from tissue culture were acclimatized in greenhouse using mycorrhizal symbiosis to increase survival during the acclimatization phase and to improve their performance after transplanting in field. Three arbuscular mycorrhizal (AM) fungi (Septoglomus viscosum, Funelliformis mosseae, and Symbivit, a commercial mix) were added to a sterile substrate and compared to a sterile control without any AM fungal inocula. After 3 months, the best growth and plant appearance were on substrates with S. viscosum fungus or the commercial mycorrhizal fungi mix. The results supported a development of an efficient micropropagation protocol and a production of high quality plant material for sustainable farming of the endangered ’Troianella’ landrace

    Performance Increase of a Small-scale Liquefied Natural Gas Production Process by Means of Turbo-expander☆

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    Abstract In the last years, the growing demand of the energy market has led to the increasing penetration of renewable energy sources in order to achieve the primary energy supply. However, in the next years fossil fuels are expected to remain the dominant energy source, due to the forecasted increase of global energy consumption. In particular, the natural gas is predicted to still play a key role in the energy market, on account of its lower environmental impact than other fossil fuels. Natural gas is currently employed mainly as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas (LNG) is currently produced in large plants directly located at the extraction sites. The aim of the study is the definition of an optimal small-scale production process for LNG, to be realized – in opposition to the current habit – directly at filling stations. With this purpose, two different LNG production layouts have been proposed and investigated within a thermodynamic analysis: starting from a Joule-Thompson LNG expansion process, a new layout with a turbo-expander has been proposed for the natural gas liquefaction. The carried-out simulations show that the new proposed solution allow to optimize the LNG production process and to minimize the process' energy consumption

    First record of Ozognathus cornutus (LeConte, 1859) (Coleoptera Ptinidae) from Sardinia, Italy.

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    Ozognathus cornutus (LeConte, 1859) is recorded on the invasive alien tree Robinia pseudocacia L. (Fabaceae) in an urban area in Italy. The species has already been reported in two other Italian regions, but this is the first record for the Sardinian fauna. Due to the great adaptability of this alien species and the increasingly cosmopolitan trend, we suggest monitoring it with caution for early detection and to plan an appropriate rapid management response

    Complex energy networks: Energy-ecological efficiency based evaluations towards the sustainability in energy sector

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    In the last years, international programs in diverse sectors and national frameworks have been driven by the need of a sustainable growth, in a green economy perspective. In order to reduce the energy losses/dissipations, as well as the fossil fuels employment and related pollutant emissions, indeed, the spread of combined heat and power units and/or renewable sources generators is promoted into both the electrical grids and the thermal networks but are often in conflict with the economic aspects. In this context, the optimal management of complex energy networks - including, in particular, smart district heating - may lead to the achievement of important goals from the environmental and sustainability viewpoints. The aim of this paper is to develop a preliminary methodology for the complete evaluation of complex energy networks, considering energy, economic and environmental aspects. With this purpose, a case study consisting in a network for the fulfillment of electrical and thermal needs of the connected users will be analyzed, considering different scenarios in terms of energy generation mix and operation and applying different optimization software. In addition, the carried out evaluations will allow to set the basis for the discussion about the future of energy policies and possible incentives towards the sustainable development of the energy sector
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