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Search Results: 1 - 10 of 461885 matches for " A. Ratti "
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Real and imaginary-time $Q\bar{Q}$ correlators in a thermal medium
A. Beraudo,J. -P. Blaizot,C. Ratti
Physics , 2007, DOI: 10.1016/j.nuclphysa.2008.03.001
Abstract: We investigate the behavior of a pair of heavy fermions, denoted by $Q$ and $\bar{Q}$, in a hot/dense medium. Although we have in mind the situation where $Q$ and $\bar{Q}$ denote heavy quarks, our treatment will be limited to simplified models, which bear only some general similarities with QCD. We study in particular the limiting case where the mass of the heavy fermions is infinite. Then a number of results can be derived exactly: a Schr\"odinger equation can be established for the correlator of the heavy quarks; the interaction effects exponentiate, leading to a simple instantaneous effective potential for this Schr\"odinger equation. We consider simple models for the medium in which the $Q\bar Q$ pair propagates. In the case where the medium is a plasma of photons and light charged fermions, an imaginary part develops in this effective potential. We discuss the physical interpretation of this imaginary part in terms of the collisions between the heavy particles and the light fermions of the medium; the same collisions also determine the damping rate of the heavy fermions. Finally we study the connection between the real-time propagator of the heavy fermion pair and its Euclidean counterpart, and show that the real part of the potential entering the Schr\"odinger equation for the real-time propagator is the free energy calculated in the imaginary-time formalism.
Phase diagram and thermodynamics of the PNJL model
Claudia Ratti,Michael A. Thaler,Wolfram Weise
Physics , 2006,
Abstract: QCD-based thermodynamics at zero and finite quark chemical potential is studied using an extended Nambu and Jona-Lasinio approach in which quarks couple simultaneously to the chiral condensate and to a background temporal gauge field representing Polyakov loop dynamics. This so-called PNJL model thus includes features of both deconfinement and chiral symmetry restoration. We discuss the phase diagram as it emerges from this approach in close comparison with results from lattice QCD thermodynamics. The critical point, separating crossover from first order phase transition, is investigated with special focus on its quark mass dependence, starting from the relatively large masses presently accessible by lattice simulations, down to the chiral limit.
Stability of strange quark matter: MIT bag versus Color Dielectric Model
W. M. Alberico,A. Drago,C. Ratti
Physics , 2001, DOI: 10.1016/S0375-9474(02)00680-2
Abstract: We discuss the properties of strange matter, in particular the minimum of the energy per baryon number as a function of the strangeness fraction. We utilize both the MIT bag model and the Color Dielectric Model and compare the energy per baryon with the masses of hyperons having the corresponding strangeness fraction, which are coherently calculated within both models. We also take into account the perturbative exchange of gluons. The results obtained in the two approaches allow to discuss the stability of strangelets. While the MIT bag model and the double minimum version of the Color Dielectric Model allow the existence of strangelets, the single minimum version of the Color Dielectric Model excludes this possibility.
Evaluación del efecto larvicida de tierra de diatomeas sobre C ulex pipiens L. (Diptera , Culicidae)
Fernando Murúa,Cristina Coria,Juan Carlos Acosta,Daniel Ratti
Multequina , 2005,
Abstract: Se evaluó la Tierra de Diatomeas aislada e integrada con Deltametrina en un insecticida formulado comercialmente, contra larvas de Culex pipiens colectadas de criaderos silvestres. La acción larvicida de cada producto se comparó en 3 dosis. El insecticida tiene un efecto larvicida cercano al 100 % para los dos estadios y en todas las dosis evaluadas. La Tierra de Diatomeas aislada mostró una eficiencia comparativamente muy baja, para ambos estadios y en las 3 dosis. El bajo valor de mortalidad obtenido con la Tierra de Diatomeas aplicada sin los componentes químicos adicionales fortalece la interpretación que el efecto larvicida del producto comercial se debe a la acción del piretroide más que a la de la tierra de diatomeas.
SNS Front End Diagnostics
L. Doolittle,T. Goulding,D. Oshatz,A. Ratti,J. Staples
Physics , 2000,
Abstract: The Front End of the Spallation Neutron Source (SNS) extends from the Ion Source (IS), through a 65 keV LEBT, a 402.5 MHz RFQ, a 2.5 MeV MEBT, ending at the entrance to the DTL. The diagnostics suite in this space includes stripline beam position and phase monitors (BPM), toroid beam current monitors (BCM), and an emittance scanner. Provision is included for beam profile measurement, either gas fluorescence, laser-based photodissociation, or a crawling wire. Mechanical and electrical design and prototyping of BPM and BCM subsystems are proceeding. Significant effort has been devoted to packaging the diagnostic devices in minimal space. Close ties are maintained to the rest of the SNS effort, to ensure long term compatibility of interfaces and in fact share some design work and construction. The data acquisition, digital processing, and control system interface needs for the BPM, BCM, and LEBT diagnostic are similar, and we are committed to using an architecture common with the rest of the SNS collaboration.
Lattice QCD-based equations of state at vanishing net-baryon density
M. Bluhm,P. Alba,W. Alberico,A. Beraudo,C. Ratti
Physics , 2013, DOI: 10.1016/j.nuclphysa.2014.06.013
Abstract: We present realistic equations of state for QCD matter at vanishing net-baryon density which embed recent lattice QCD results at high temperatures combined with a hadron resonance gas model in the low-temperature, confined phase. In the latter, we allow an implementation of partial chemical equilibrium, in which particle ratios are fixed at the chemical freeze-out, so that a description closer to the experimental situation is possible. Given the present uncertainty in the determination of the chemical freeze-out temperature from first-principle lattice QCD calculations, we consider different values within the expected range. The corresponding equations of state can be applied in the hydrodynamic modeling of relativistic heavy-ion collisions at the LHC and at the highest RHIC beam energies. Suitable parametrizations of our results as functions of the energy density are also provided.
Der Schauplatz des Seelenjahres. Eine Wortfeldanalyse zu Stefan Georges Jahr der Seele
Fiorenza Ratti
Studi Linguistici e Filologici Online , 2004,
Abstract: The following work is based on the theory of semantic fields and deals with the way Jahr der Seele is completely collocated on a homogeneous semantic level. It investigates how the global significance of the whole meaning can be interpreted as a structural reality of the linguistic manifestation. The technical-artistic as well as the ermeneutic aspects within the research about semantic fields are concerned. Therefore on one hand, the analysis concerns the single semantic fields/sense areas in order to discover the linguistic Weltansicht; on the other hand, the text construction as well as the sense core of poetic sequence are interpreted. From this points of view the text comprehension means comprehension of the way the linguistic process is organized, through which text and poem owe their origin.
Ionic Liquids: Synthesis and Applications in Catalysis
Rajni Ratti
Advances in Chemistry , 2014, DOI: 10.1155/2014/729842
Abstract: Ionic liquids have emerged as an environmentally friendly alternative to the volatile organic solvents. Being designer solvents, they can be modulated to suit the reaction conditions, therefore earning the name “task specific ionic liquids.” Though primarily used as solvents, they are now finding applications in various fields like catalysis, electrochemistry, spectroscopy, and material science to mention a few. The present review is aimed at exploring the applications of ionic liquids in catalysis as acid, base, and organocatalysts and as soluble supports for catalysts. 1. Introduction One of the twelve principles of green chemistry is that the use of auxiliary substances such as solvents and separation agents should be made unnecessary and if used should be innocuous [1]. The toxic and hazardous properties of many solvents particularly chlorinated hydrocarbons pose crucial environmental concerns such as atmospheric emissions and contamination of water effluents. It is recognized that employing the use of nonconventional solvents as alternatives for environmentally unfriendly traditional solvents can reduce waste solvent production and hence reduce the negative impact on environment to a great extent [2]. The most prevalent of these new solvent systems includes, but not exclusively, water, supercritical fluids (like supercritical CO2), ionic liquids, solventless processes, and fluorous techniques [3]. Of all the above mentioned nonconventional solvents of interest, ionic liquids have emerged as a promising alternative [4]. Ionic liquid is defined as a salt with melting point below the boiling point of water [5]. Ionic liquids are known by several different names like neoteric solvents, designer solvents, ionic fluids, and molten salts. Most of the ionic liquids are composed of organic cation and inorganic anions. In order to be liquid at room temperature, the cation should preferably be unsymmetrical; that is, the alkyl groups should be different. Polarity and hydrophilicity/hydrophobicity of ionic liquids can be tuned by suitable combination of cation and anion. It is this property of ionic liquids which has earned them the accolade “designer solvents.” As solvents, ionic liquids have found applications in a number of reactions [6–16]. Dupont et al. extensively reviewed the application of ionic liquids as catalytic phase in various organometallic reactions [17]. Catalytic applications of metal nanoparticles have been explored in ionic liquid media by Migowski and Dupont [18, 19]. Besides the use of ionic liquids as alternate solvents, lately further
Stability of strange quark matter in the MIT bag model and in the Color Dielectric Model
C. Ratti
Physics , 2001,
Abstract: We utilize the MIT bag model and two different versions of the Color Dielectric Model in order to study the properties of strange matter, and to discuss the stability of strangelets. We also investigate the effect of the introduction of perturbative gluons. The MIT bag model and the Double Minimum version of the Color Dielectric Model allow the existence of strangelets, while the Single Minimum version excludes this possibility.
Trypanocide activity of Castela coccinea Griseb. extracts
María L. MARTíNEZ,María NOEL CAMPAGNA,María S. RATTI,Isabel NOCITO
Boletín Latinoamericano y del Caribe de Plantas Medicinales y Aromáticas , 2009,
Abstract: Castela coccinea Griseb es un árbol de peque o porte que pertenece a la familia Simaroubaceae. En el presente trabajo los extractos de esta planta muestran una fuerte actividad in vitro contra epimastigotes de Trypanosoma cruzi. El extracto diclorometánico de madera es el que presenta mayor efecto tripanocida. Una fracción de este extracto, purificada por cromatografía en columna, está enriquecida en cumarinas, ácidos fenólicos y alcaloides. Esta fracción es aún más activa con una CI50 =15 mg/mL. Nuestros resultados sugieren que los alcaloides son los responsables de esta actividad. Más aún, se ha detectado la presencia del grupo 8-amino-6-metoxiquinolina por cromatografía gaseosa acoplada a un espectrómetro de masa, pero todavía la molécula entera no ha sido identificada. Por otro lado, todos los extractos mostraron actividad citotóxica contra la línea celular humana K-562, a altas concentraciones. Sin embargo, el índice de selectividad para el extracto diclorometánico de la madera es de 7.5.
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