396 research outputs found

    A simple analytical description of the non-stationary dynamics in Ising spin systems

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    The analytical description of the dynamics in models with discrete variables (e.g. Isingspins) is a notoriously difficult problem, that can be tackled only undersome approximation.Recently a novel variational approach to solve the stationary dynamical regime has beenintroduced by Pelizzola [Eur. Phys. J. B, 86 (2013) 120], where simpleclosed equations arederived under mean-field approximations based on the cluster variational method. Here wepropose to use the same approximation based on the cluster variational method also for thenon-stationary regime, which has not been considered up to now within this framework. Wecheck the validity of this approximation in describing the non-stationary dynamical regime ofseveral Ising models defined on Erdos-R ŐĀenyi random graphs: westudy ferromagnetic modelswith symmetric and partially asymmetric couplings, models with randomfields and also spinglass models. A comparison with the actual Glauber dynamics, solvednumerically, showsthat one of the two studied approximations (the so-called ‚Äėdiamond‚Äôapproximation) providesvery accurate results in all the systems studied. Only for the spin glass models we find somesmall discrepancies in the very low temperature phase, probably due to the existence of alarge number of metastable states. Given the simplicity of the equations to be solved, webelieve the diamond approximation should be considered as the ‚Äėminimalstandard‚Äô in thedescription of the non-stationary regime of Ising-like models: any new method pretending toprovide a better approximate description to the dynamics of Ising-like models should performat least as good as the diamond approximation

    Identifying the factors that determine ecosystem services provision in Pampean agroecosystems (Argentina) using a data-mining approach

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    Ecosystem services (ES) have become a key concept in the assessment of natural resources, as a way to connect human well-being and ecosystems degradation. However, ES quantification is considered a basic problem because provision varies considerably as a result of land use change and site-specific characteristics (i.e. climate, soil, topography, and time). Thus, more detailed studies are needed to assess whether these changes affect ecological variables. We explored the use of environmental and crop management variables in predicting the provision of four ES (soil C balance, soil N balance, N2O emission control and groundwater contamination control) in three agroecosystems located in the Pampa region (Argentina). Data-mining, represented by k-means cluster and classification trees, was used to identify the dependence of ES provision on the variation of both environmental and crop management factors. We used plot level crop management and environmental field information stored in a large database during a 10-year period. The k-means method selected five different clusters. The final configuration showed two contrasting clusters: one with the lowest ES provision, and another one with the highest ES provision. The five clusters were represented in the terminal nodes of the final classification tree. Regarding the predictive power of the variables, crop and year were the most important predictors. Then, differences observed in ES provision resulted from changes in land use (variable ‚Äúcrop‚ÄĚ) and crop season (variable ‚Äúyear‚ÄĚ). These results are meant to enlighten stakeholders in terms of how to manage Pampean agroecosystems in order to positively influence ES provision.Fil: Rositano, Florencia. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Oficina de Coordinaci√≥n Administrativa Parque Centenario. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronom√≠a. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronom√≠a. Departamento de Producci√≥n Vegetal. C√°tedra de Cerealicultura; ArgentinaFil: Bert, Federico Esteban. Universidad de Buenos Aires. Facultad de Agronom√≠a. Departamento de Producci√≥n Vegetal. C√°tedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas; ArgentinaFil: Pi√Īeiro, Gervasio. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Oficina de Coordinaci√≥n Administrativa Parque Centenario. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronom√≠a. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronom√≠a. Departamento de Recursos Naturales y Ambiente. C√°tedra de Ecolog√≠a; ArgentinaFil: Ferraro, Diego Omar. Universidad de Buenos Aires. Facultad de Agronom√≠a. Departamento de Producci√≥n Vegetal. C√°tedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Oficina de Coordinaci√≥n Administrativa Parque Centenario. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronom√≠a. Instituto de Investigaciones Fisiol√≥gicas y Ecol√≥gicas Vinculadas a la Agricultura; Argentin

    Improving the entanglement transfer from continuous variable systems to localized qubits using non Gaussian states

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    We investigate the entanglement transfer from a bipartite continuous-variable (CV) system to a pair of localized qubits assuming that each CV mode couples to one qubit via the off-resonance Jaynes-Cummings interaction with different interaction times for the two subsystems. First, we consider the case of the CV system prepared in a Bell-like superposition and investigate the conditions for maximum entanglement transfer. Then we analyze the general case of two-mode CV states that can be represented by a Schmidt decomposition in the Fock number basis. This class includes both Gaussian and non Gaussian CV states, as for example twin-beam (TWB) and pair-coherent (TMC, also known as two-mode-coher ent) states respectively. Under resonance conditions, equal interaction times for both qubits and different initial preparations, we find that the entanglement transfer is more efficient for TMC than for TWB states. In the perspective of applications such as in cavity QED or with superconducting qubits, we analyze in details the effects of off-resonance interactions (detuning) and different interaction times for the two qubits, and discuss conditions to preserve the entanglement transfer.Comment: revised version, 11 pages, 7 figures (few of them low-res

    Hands on GINGER: Seismic Wave measurement

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    GINGER (Gyroscopes IN GEneral Relativity) will be a 3-D array of mutually orthogonal ring lasers able to measure the general relativistic effects due to the rotation of the Earth (LenseThirring effect). The development of highly sensitive ring laser gyroscopes gives as well the possibility to accurately monitor the rotational ground motions on Earth. The GP2 ring laser, a prototype developed to study how to keep constant at the level of 1 part in 1010 the scale factor of the ring lasers in the GINGER array, has been recently designed and realized and some of its data have been analyzed for geophysical studies. The signal has been extracted from the interferogram raw data and the seismic wave contribution has been obtained by subtracting the contribution due to the Earth rotation

    Theoretical estimates of the anapole magnetizabilities of C4H4X2 cyclic molecules for X=O, S, Se, and Te

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    Calculations have been carried out for C4H4X2 cyclic molecules, with X=O, S, Se, and Te, characterized by the presence of magnetic-field induced toroidal electron currents and associated orbital anapole moments. The orbital anapole induced by a static nonuniform magnetic field B, with uniform curl C =‚ąá√ó B, is rationalized via a second-rank anapole magnetizability tensor aőĪő≤ , defined as minus the second derivative of the second-order interaction energy with respect to the components CőĪ and Bő≤. The average anapole magnetizability a equals ‚ąíŌá, the pseudoscalar obtained by spatial averaging of the dipole-quadrupole magnetizability ŌáőĪ,ő≤ő≥ . It has different sign for D and L enantiomeric systems and can therefore be used for chiral discrimination. Therefore, in an isotropic chiral medium, a homogeneous magnetic field induces an electronic anapole AőĪ, having the same magnitude, but opposite sign, for two enantiomorphs.Fil: Pagola, Gabriel Ignacio. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Oficina de Coordinaci√≥n Administrativa Ciudad Universitaria. Instituto de F√≠sica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de F√≠sica de Buenos Aires; ArgentinaFil: Ferraro, Marta Beatriz. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Oficina de Coordinaci√≥n Administrativa Ciudad Universitaria. Instituto de F√≠sica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de F√≠sica de Buenos Aires; ArgentinaFil: Provasi, Patricio Federico. Consejo Nacional de Investigaciones Cient√≠ficas y T√©cnicas. Centro Cient√≠fico Tecnol√≥gico Conicet - Nordeste. Instituto de Modelado e Innovaci√≥n Tecnol√≥gica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovaci√≥n Tecnologica; ArgentinaFil: Pelloni, Stefano. Universidad de Modena y Reggio Emilia. Departamento de Qu√≠mica; ItaliaFil: Lazzeretti, Paolo. Universidad de Modena y Reggio Emilia. Departamento de Qu√≠mica; Italia; Itali

    Bayesian Modeling for Differential Cryptanalysis of Block Ciphers: a DES instance

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    Encryption algorithms based on block ciphers are among the most widely adopted solutions for providing information security. Over the years, a variety of methods have been proposed to evaluate the robustness of these algorithms to different types of security attacks. One of the most effective analysis techniques is differential cryptanalysis, whose aim is to study how variations in the input propagate on the output. In this work we address the modeling of differential attacks to block cipher algorithms by defining a Bayesian framework that allows a probabilistic estimation of the secret key. In order to prove the validity of the proposed approach, we present as case study a differential attack to the Data Encryption Standard (DES) which, despite being one of the methods that has been most thoroughly analyzed, is still of great interest to the scientific community since its vulnerabilities may have implications on other ciphers

    Strengths of the resonances at 436, 479, 639, 661, and 1279 keV in the 22^{22}Ne(p,ő≥\gamma)23^{23}Na reaction

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    The 22^{22}Ne(p,ő≥\gamma)23^{23}Na reaction is included in the neon-sodium cycle of hydrogen burning. A number of narrow resonances in the Gamow window dominates the thermonuclear reaction rate. Several resonance strengths are only poorly known. As a result, the 22^{22}Ne(p,ő≥\gamma)23^{23}Na thermonuclear reaction rate is the most uncertain rate of the cycle. Here, a new experimental study of the strengths of the resonances at 436, 479, 639, 661, and 1279 keV proton beam energy is reported. The data have been obtained using a tantalum target implanted with 22^{22}Ne. The strengths ŌČő≥\omega\gamma of the resonances at 436, 639, and 661 keV have been determined with a relative approach, using the 479 and 1279 keV resonances for normalization. Subsequently, the ratio of resonance strengths of the 479 and 1279 keV resonances was determined, improving the precision of these two standards. The new data are consistent with, but more precise than, the literature with the exception of the resonance at 661 keV, which is found to be less intense by one order of magnitude. In addition, improved branching ratios have been determined for the gamma decay of the resonances at 436, 479, and 639 keV.Comment: Final version, now using the Kelly et al. (2015) data [15] for normalization; 10 pages, 7 figures, 3 table

    Effects of Microencapsulated Ferulic Acid or Its Prodrug Methyl Ferulate on Neuroinflammation Induced by Muramyl Dipeptide

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    Ferulic acid (Fer) is known for its antioxidant and anti-inflammatory activities, which are possibly useful against neurodegenerative diseases. Despite the ability of Fer to permeate the brain, its fast elimination from the body does not allow its therapeutic use to be optimized. The present study proposes the preparation and characterization of tristearin- or stearic acid-based solid lipid microparticles (SLMs) as sustained delivery and targeting systems for Fer. The microparticles were produced by conventional hot emulsion techniques. The synthesis of the methyl ester of Fer (Fer-Me) allowed its encapsulation in the SLMs to increase. Fer-Me was hydrolyzed to Fer in rat whole blood and liver homogenate, evidencing its prodrug behavior. Furthermore, Fer-Me displayed antioxidant and anti-inflammatory properties. The amount of encapsulated Fer-Me was 0.719 +/- 0.005% or 1.507 +/- 0.014% in tristearin or stearic acid SLMs, respectively. The tristearin SLMs were able to control the prodrug release, while the stearic acid SLMs induced a significant increase of its dissolution rate in water. Jointly, the present results suggest that the tristearin SLMs loaded with Fer-Me could be a potential formulation against peripheral neuropathic pain; conversely, the stearic acid SLMs could be useful for Fer-Me uptake in the brain after nasal administration of the formulation
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