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177 results on '"Parga G"'

1. Electronic plasma diffusion with radiation reaction force and time-dependent electric field

Author

García-Camacho, J. F., Contreras-Vergara, O., Sánchez-Salas, N., de Parga, G. Ares, and Jiménez-Aquino, J. I.

Subjects
Condensed Matter - Statistical Mechanics, 60J70
Abstract

In this work the explicit solution of the electronic plasma diffusion with radiation reaction force, under the action of an exponential decay external electric field is given. The electron dynamics is described by a classical generalized Langevin equation characterized by an Ornstein-Uhlenbeck-type friction memory kernel, with an effective memory time which accounts for the effective thermal interaction between the electron and its surroundings (thermal collisions between electrons + radiation reaction force). The incident electric field exerts an electric force on the electron, which in turn can induce an additional damping to the braking radiation force, allowing a delay in the electron characteristic time. This fact allows that the effective memory time be finite and positive, and as a consequence, obtaining physically admissible solutions of the stochastic Abraham-Lorentz-like equation. It is shown that the diffusion process is quasi-Markovian which includes the radiation effects., Comment: 16 pages, 8 figures

Published
2023

2. Influence of the magnetic field topology in the evolution of small-scale two-fluid jets in the solar atmosphere

Author

Díaz-Figueroa, E. E., de Parga, G. Ares, and González-Avilés, J. J.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We perform a series of numerical simulations to recreate small-scale two-fluid jets using the JOANNA code, considering the magnetohydrodynamics of two fluids (ions + electrons and neutral particles). We first excite the jets in a uniform magnetic field by using velocity pulse perturbations located at $y_{0}=$1.3, 1.5, and 1.8 Mm, considering the base of the photosphere at $y=0$ Mm. Then, we repeat the excitation of the jets in a magnetic field that mimics a flux tube. Mainly, the jets excited at the upper chromosphere ($y\sim1.8$ Mm) reach lower heights than those excited at the lower chromosphere ($y\sim1.3$ Mm); this is due to the higher initial vertical location because of the lesser amount of plasma dragging. In both scenarios, the dynamics of the neutral particles and ions show similar behavior; however, we can still identify some differences in the velocity drift, which in our simulations is of the order of $10^{-3}$ km s$^{-1}$ at the tips of the jets once they reached their maximum heights. Also, we estimate the heat generation due to the friction between ions and neutrals ($Q^{in}_{i,n}$), which is of the order of $0.002-0.06$ W m$^{-3}$; however it is small to contribute to the heating of the surroundings of the solar corona. The jets in the two magnetic environments do not show substantial differences other than a slight variation in the maximum heights reached, particularly in the uniform magnetic field scenario. Finally, the maximum heights reached by the three different jets are in the range of some morphological parameters corresponding to macrospicules, Type I spicules, and Type II spicules., Comment: 15 pages, 6 figures. Accepted for publication in Physics

Published
2023
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16. A further analysis of the blackbody radiation

Author

de Parga, G. Ares and Gutierez-Mejia, F.

Subjects
Radiation -- Laws, regulations and rules -- Analysis -- Observations, Astronomy, Physics
Abstract

A review of the classical deduction of the Rayleigh-Jeans formula is done. By using the same procedure but substituting the Abraham-Lorentz equation by the Eliezer-Ford equation, we derive another expression for the frequency energy density of a blackbody. In the new formulation the new frequency energy density does not diverge, even though the ultraviolet catastrophe still appears because the integral over the frequency is infinite. Thus, the consequences of the new formulation are discussed and its uselfulness is analyzed. Keywords: Blackbody, steady state, reaction force., Introduction Classical thermodynamics was developed in the middle of the 19th century. One of the most important creator or contributor of the theory was Kirchhoff. During this time, the engineering [...]

Published
2010

17. The largest multicentre data collection on prepectoral breast reconstruction : The iBAG study

Author

Masià, J, Salgarello, M, Cattelani, L, Parodi, P, Ribuffo, D, Onesti, M, Berna, G, Cawthorn, S, Bozza, F, Duodeci, S, Harries, S, Governa, M, Barmasse, R, Vidya, R, Sircar, T, Deol, H, Guzzetti, T, Meggiolaro, F, Schiavon, M, Parmeshwar, R, Ferguson, D, Mortimer, C, Manca, G, Thekkinkattil, D, Rathinaezhil, R, Bhaskar, P, Roche, N, Rivarossa, A, De Castro Parga, G, Massarut, S, Polotto, S, Di Bartolomeo, M, Rampino Cordaro, E, Mura, S, Adesi, L, Marruzzo, G, Dell'Antonia, F, Maritan, M, Saibene, T, Michieletto, S, Cecconi, C, Maino, M, Clarke, D, Mirandola, S, Morelli, L, Biral, M, Baraziol, R, Zanin, C, and Gregorelli, C

Subjects
medicine.medical_specialty, medicine.medical_treatment, Breast Implants, Mammaplasty, Breast Neoplasms, acellular dermal matrix, Audit, Pectoralis Muscles, Prepectoral, 03 medical and health sciences, 0302 clinical medicine, Milestone (project management), medicine, Humans, breast reconstruction, Breast reconstruction, Mastectomy, Research Articles, radiotherapy, Acellular dermal matrix, Retrospective Studies, braxon, prepectoral, Radiotherapy, business.industry, Braxon, General surgery, Data Collection, Postoperative complication, General Medicine, Capsular contracture, Middle Aged, Prophylactic Surgery, United Kingdom, Radiation therapy, Oncology, Italy, Spain, 030220 oncology & carcinogenesis, 030211 gastroenterology & hepatology, Surgery, Female, Implant, business, Research Article
Abstract

Background and Objectives In the last years, prepectoral breast reconstruction has increased its popularity, becoming a standard reconstructive technique by preserving pectoralis major anatomy and functionality. Nevertheless, the lack of solid and extensive data negatively impacts on surgeons’ correct information about postoperative complication rates and proper patient selection. This study aims to collect the largest evidence on this procedure. Methods A multicentre retrospective audit, promoted by the Barcelona Hospital, collected the experience of 30 centers on prepectoral breast reconstruction with Braxon ADM. The study had the scientific support of INPECS and IIB societies which provided the online database Clinapsis. Results A total of 1450 procedures were retrospectively collected in a 6‐year period. Mean age 52.4 years, BMI 23.9, follow‐up 22.7 months. Reconstruction was carried out after a tumor in 77.1% of the cases, 20.1% had prophylactic surgery, 2.8% had revisions. Diabetes, smoke, and immunosuppression had an influence on complications occurrence, as well as implant weight. Capsular contracture was associated with postoperative radiotherapy, but the overall rate was low (2.1%). Complications led to implant loss in 6.5% of the cases. Conclusions The international Braxon Audit Group multicentre data collection represents a milestone in the field of breast reconstruction, extensively improving the knowledge on this procedure.

Published
2020

33. Comment on 'Convective heat transfer law for an endoreversible engine' [J. Appl. Phys. 100, 014911 (2006)]

Author

Arias-Hernandez, L.A., de Parga, G. Ares, and Angulo-Brown, F.

Subjects
Heat-engines -- Thermal properties, Heat -- Convection, Heat -- Research, Physics
Abstract

The article examines the article 'Convective heat transfer law for an endoreversible engine' and proves the reliability of the derived exponent of the convective heat transfer, as it is found to be working well for other optimization criteria also. The author reveals that the proposal discussed in the paper is quite reliable and hence can be used widely, even for the power plants where internal irreversibilities are included in the engines.

Published
2007

36. Method for solving the diffusion equation for a model of seismic dilatant zone

Author

Dominguez-Hernandez, S., Ares Parga, G., and F Angulo-Brown

Subjects
diffusion equation, Física, Astronomía y Matemáticas, Seismic precursors, Physics::Geophysics, dilatant zone
Abstract

"In this paper we find the solution of the pressure diffusion equation [PDE] for a three-dimensional model of a seismic dilatant zone. We made a quantitative analysis of to the PDE solutions in order to see their applicability to explain the electric self-potential anomalies observed prior to earthquakes in different seismic regions around the world. The results here reported lead in a first approximation to reasonable comparisons with field measurements of electrotelluric activity in active seismic regions."

Published
2013

44. What nature knows about solving equations of motion

Author

Ares-de-Parga, G. and Rosales, M.A.

Subjects
Particles -- Tests, problems and exercises, Differential equations -- Tests, problems and exercises, Motion -- Tests, problems and exercises, Physics
Abstract

The problem of representing an equation of motion by means of an integro-differential equation and a series is analyzed and the results are used to clarify a recent controversy on the equation of motion for classical charged particles.

Published
1989

45. The Curzon-Ahlborn efficiency for three different energy converters

Author

Angulo Brown, F., Sánchez Salas, N., Ares de Parga, G., Angulo Brown, F., Sánchez Salas, N., and Ares de Parga, G.

Abstract

In this work we present three energy converters which have the same efficiency under certain optimum conditions of performance. The first one is the well-known Curzon-Ahlborn finite-time heat engine. The second one is an infinitetime cycle operating between two thermal bodies with finite heat capacities. The last case is a water mixer working as engine, which is designed with two stationary fluxes of water at different temperatures, T1 and T2, with only one exit, at temperature T, the specific heat capacity, c, is considered as a constant., En este trabajo se presentan tres diferentes convertidores de energia que tienen la misma eficiencia bajo ciertas condiciones optimas de operacion. El primero se trata de la ampliamente conocida maquina de Curzon-Ahlborn operando a tiempo finito. El segundo se trata de una sucesion de ciclos de Carnot operando entre dos cuerpos termicos con capacidad calorifica finita. El ultimo caso es una mezcladora de agua trabajando como maquina, la cual esta disenada con la entrada de dos flujos estacionarios de agua a diferentes temperaturas, T1 y T2, con una sola salida, a temperatura T, con calor especifico, c, que se toma como constante.

Published
2010

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