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Search Results: 1 - 10 of 28052 matches for " Cristina Rodriguez-Lopez "
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Pairwise Summation Approximation of Casimir energy from first principles
Pablo Rodriguez-Lopez
Physics , 2009, DOI: 10.1103/PhysRevE.80.061128
Abstract: We obtain the Pairwise Summation Approximation (PSA) of the Casimir energy from first principles in the soft dielectric and soft diamagnetic limit, so we find that the PSA is an asymptotic approximation of the Casimir energy valid for large distances between the objects. We also obtain the PSA for the electromagnetic coupling part of the Casimir energy, so we are able to complete the PSA limit at a first time for the complete electromagnetic field.
Casimir repulsion between Topological Insulators in the diluted regime
Pablo Rodriguez-Lopez
Physics , 2011, DOI: 10.1103/PhysRevB.84.165409
Abstract: The Pairwise Summation Approximation (PSA) of Casimir energy is applied to a system of two dielectrics with magnetoelectric coupling. In particular, the case of Topological Insulators (TI) is studied in detail. Depending on the the optical response of the TI, we obtain a stable equilibrium distance, atraction for all distances, or repulsion for all distances at zero temperature. This equilibrium distance disappears in the high temperature limit. These results are independent on the geometry of the TI, but are only valid in the diluted approximation.
Casimir Energy and Entropy in the Sphere--Sphere Geometry
Pablo Rodriguez-Lopez
Physics , 2011, DOI: 10.1103/PhysRevB.84.075431
Abstract: We calculate the Casimir energy and entropy for two spheres described by the perfect metal model, plasma model, and Drude model in the large separation limit. We obtain nonmonotonic behavior of the Helmholtz free energy with separation and temperature for the perfect metal and plasma models, leading to parameter ranges with negative entropy, and also nonmonotonic behavior of the entropy with temperature and the separation between the spheres. This nonmonotonic behavior has not been found for Drude model. The appearance of this anomalous behavior of the entropy is discussed as well as its thermodynamic consequences.
Casimir Energy and Entropy between perfect metal Spheres
Pablo Rodriguez-Lopez
Physics , 2012, DOI: 10.1142/S201019451200760X
Abstract: We calculate the Casimir energy and entropy for two perfect metal spheres in the large and short separation limit. We obtain nonmonotonic behavior of the Helmholtz free energy with separation and temperature, leading to parameter ranges with negative entropy, and also nonmonotonic behavior of the entropy with temperature and with the separation between the spheres. The appearance of this anomalous behavior of the entropy is discussed as well as its thermodynamic consequences.
Casimir Effect in systems in and out of Equilibrium
Pablo Rodriguez-Lopez
Physics , 2012,
Abstract: This thesis consists on two separate parts. In the first part, we discuss about the nature of the Casimir effect as the response of a fluctuant medium to the breakdown of the translation symmetry because the presence of intrusions in that medium. To do so, we present a dynamical approximation of Casimir effect, which generalizes Casimir effect studies to out of equilibrium steady states. The equilibrium known case is recovered as a particular case, including the case of electromagnetic (EM) Casimir effect generated because of quantum fluctuations. This formalism also allows us to define (and calculate) the variance of Casimir forces. In the second part of this thesis, by the use of a Multiscattering formalism, we study the nature of the multibody Casimir effect. We demonstrate that the Casimir force and energy between two spheres in presence of a plate (perfect metal objects all of them) is non-monotonous with the distance between spheres and between sphere and plate. We derive the Pairwise Summation Approximation (PSA) of the EM field from this multiscattering formalism for generalized dielectrics, including magnetic responses and Topological Insulators as an example of magnetoelectric couplings. We also study the nonmonotonous behavior of the entropy with the temperature for a system of two perfect metal spheres and describes the Casimir energy between non-parallel cylinders, a geometry not studied until now to our knownledge.
Importance of CO2 Emissions in Construction Phase. Two Case Studies: New Construction and Renovated Building  [PDF]
Gonzalo Fernandez-Sanchez, Fernando Rodriguez-Lopez
Low Carbon Economy (LCE) , 2012, DOI: 10.4236/lce.2012.31002
Abstract: With the new Technical Code for Construction and Energy Certification (application of the EPBD in Spain) energy consumption and carbon dioxide emissions are now taken into consideration during building’s operating phase. There is no doubt that this is a step forward. However, economic cost and emissions involved in extracting materials, manufacture, transport and installing on site (embodied energy in the materials used in construction) can be considerable and even more when promotor seeks to improve the building’s energy rating with the corresponding increases in insulation, improvements in cladding and so on. Two case studies are used (new construction and renovation) in order to analyze both economic cost and CO2 emissions in construction and operating stage (using LIDER and CALENER softwares) of two actual cases.
Repulsive Casimir Effect with Chern insulators
Pablo Rodriguez-Lopez,Adolfo G. Grushin
Physics , 2013, DOI: 10.1103/PhysRevLett.112.056804
Abstract: We theoretically predict that the Casimir force in vacuum between two Chern insulator plates can be repulsive (attractive) at long distances whenever the sign of the Chern numbers characterizing the two plates are opposite (equal). A unique feature of this system is that the sign of the force can be tuned simply by turning over one of the plates or alternatively by electrostatic doping. We calculate and take into account the full optical response of the plates and argue that such repulsion is a general phenomena for these systems as it relies on the quantized zero frequency Hall conductivity. We show that achieving repulsion is possible with thin films of Cr-doped (Bi,Sb)$_2$Te$_3$, that were recently discovered to be Chern insulators with quantized Hall conductivity.
Casimir interaction between inclined metallic cylinders
P. Rodriguez-Lopez,T. Emig
Physics , 2012, DOI: 10.1103/PhysRevA.85.032510
Abstract: The Casimir interaction between one-dimensional metallic objects (cylinders, wires) displays unconventional features. Here we study the orientation dependence of this interaction by computing the Casimir energy between two inclined cylinders over a wide range of separations. We consider Dirichlet, Neumann and perfect metal boundary conditions, both at zero temperature and in the classical high temperature limit. For all types of boundary conditions, we find that at large distances the interaction decays slowly with distance, similarly to the case of parallel cylinders, and at small distances scales as the interaction of two spheres (but with different numerical coefficients). Our numerical results at intermediate distances agree with our analytic predictions at small and large separations. Experimental implications are discussed.
Global boundedness of multilinear Fourier integral operators
Salvador Rodriguez-Lopez,Wolfgang Staubach
Mathematics , 2011,
Abstract: We study the global boundedness of bilinear and multilinear Fourier integral operators on Banach and quasi-Banach $L^p$ spaces, where the amplitudes of the operators are smooth or rough in the spatial variables. The results are obtained by proving suitable global boundedness of rough linear Fourier integral operators with amplitudes that behave as $L^{p}$ functions in the spatial variables. The bilinear and multilinear boundedness estimates are proven by using either an iteration procedure or decomposition of the amplitudes, and thereafter applying our global results for linear Fourier integral operators with rough amplitudes.
Pectinmethylesterase extraction from orange solid wastes: Optimization and comparison between conventional and ultrasound-assisted treatments  [PDF]
Antonio D. Rodriguez-Lopez, Luis Mayor, María M. Galfarsoro, Jorge Martinez-Otalo, Esperanza M. Garcia-Castello
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.49B008

During orange juice production, a half of fresh oranges weight is considered as production waste (peels, pulp, seeds, orange leaves and damaged orange fruits). An alternative for the management of these wastes is their treatment by addition of lime and a latter pressing, obtaining a press cake and a press liquor rich in sugars (10° Brix) and citric acid, protein, pectin and ethanol. For non-thermal concentration of press liquor to obtain citruss molasses (65°-70° Brix), the removal of pectin is necessary. Traditionally, depectinization of juices has been done by using pectinmethylesterase (PME) enzymes from external sources. In this work it performed the extraction of PME enzymes from orange peels to obtain the optimum extraction conditions. Two different methods of solventextraction were compared (conventional andultrasound-assisted methods). For the conventional extraction experiments, a central composite design with three variables ([NaCl], pH and time) and five replicates of the center point was used. For ultrasound-assisted extraction, experiments were done at pH = 5.5 and [NaCl] = 1.25M), varying extraction time (1-30 min). Response variables were PME activity, protein content and a ratio between them, named PME effectiveness (ηPME). At the same experimental conditions (pH =5.5, [NaCl] = 1.25 M, t = 15 min) it was found that conventional extractions led to slightly better results in terms of ηPME than ultrasound-assisted extraction method.

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