Relaxed States in Relativistic Multi-Fluid Plasmas

The evolution equations for a plasma comprising multiple species of charged fluids with relativistic bulk and thermal motion are derived. It is shown that a minimal fluid coupling model allows a natural casting of the evolution equations in terms of generalized vorticity which treats the fluid motion and electromagnetic fields equally. Equilibria can be found using a variational principle based on minimizing the total enstrophy subject to energy and helicity constraints. A subset of these equilibria correspond to minimum energy. The equations for these states are presented with example solutions showing the structure of the relaxed states.Comment: 8 pages, 2 figure

The use of genre analysis in the design of electronic meeting systems

WOS:000237136400002 (Nº de Acesso Web of Science)Introduction. Genre analysis is an approach to study communication patterns and thus it can be applied to the specific context of meetings. This research investigates the use of genre analysis in the design of electronic meeting systems. Background. The primary goal of genre analysis is to understand how virtual communities use digital communication to collaborate. This knowledge is fundamental for informing the design of information systems, particularly in areas where communication and informality are paramount. However, the research literature does not report any experiments where genre analysis has been used to inform the design of electronic meeting systems. Problems. The paper tackles the following common problems found in current electronic meeting systems: (1) reduced organizational integration, neglecting many contextual cues and explaining factors necessary to make meeting outcomes usable within the organization; (2) lack of support to specific communities of users, stressing the dependency on a facilitator to configure and manage the technology; and (3) lack of support to meeting occurrences that span long time periods. Conclusions. The paper describes how genre analysis was used to develop electronic meeting systems for several organizations and meeting genres. It covers the complete design process, from genre elicitation to validation. The obtained results demonstrate that the genre approach produces electronic meeting systems focused on organizational integration, pre-configured to communities of users, supporting long-term usage and added organizational value

Evidence for a Very Large-Scale Fractal Structure in the Universe from Cobe Measurements

In this work, we analyse the temperature fluctuations of the cosmic microwave background radiation observed by COBE and show that the distribution can be fitted by a fractal distribution with a fractal dimension $D= 1.43 \pm 0.07$. This value is in close agreement with the fractal dimension obtained by Coleman and Pietronero (1992) and Luo and Schramm (1992) from galaxy-galaxy and cluster-cluster correlations up to $\sim 100 h^{-1} Mpc$. The fact that the observed temperature fluctuations correspond to scales much larger than $100 h^{-1} Mpc$ and are signatures of the primordial density fluctuations at the recombination layer suggests that the structure of the matter at the early universe was already fractal and thus non-homogeneous on those scales. This result may have important consequences for the theoretical framework that describes the universe.Comment: 11 pages, postscript file, 2 figures available upon request. To appear in ApJ Letter

Experiences in teaching Hydrogen Technologies in the framework of the International Campus of Excellence Andalucia TECH

The increasing importance of hydrogen technologies is demanding prepared professionals in the numerous topics related to this energy vector. Apart from some basic and advanced courses given by actual experts in these topics, universities must play an important role in the general formation of future professionals. In this way, the International Campus of Excellence (ICE) Andalucía TECH has created several degrees taught jointly by its participating universities of Seville (US) and Málaga (UMA). Among those degrees, Energy Engineering is the best suited to the field of this conference because this degree provide future engineers with specialized training in energy generation, transformation and management. In relation to hydrogen technologies this degree includes a cross sectional optional unit named Hydrogen Based Systems (4.5 ECTS/112.5 h), which is placed in the last term of the fourth year and sharing space with work placement and mobility courses. This paper will present some author’s experiences as teachers of that unit during its short history of only three years. In spite of being a joint degree, which is coordinated between both universities (US and UMA) trying to give similar contents, it is interesting to highlight the differential experiences coming from the teachers of both universities in relation to the teaching methodologies and academic results.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The Ljapunov-Schmidt reduction for some critical problems

This is a survey about the application of the Ljapunov-Schmidt reduction for some critical problems

Psychometric Properties of the Barrier Autoinform for the Practice of the Physical Exercise (ABPEF)

El estudio consistió en examinar las propiedades psicométricas del cuestionario de autoinforme de barreras para la práctica del ejercicio físico (ABPEF) y comprobar el efecto del género sobre dichas barreras. Se han estudiado sus propiedades psicométricas con una muestra de 342 adolescentes (media de edad: 15.02±1.86). Se realizaron análisis de confiabilidad, análisis factorial exploratorio, correlación ítem con puntaje total y análisis factorial confirmatorio. Se encuentra una buena confiabilidad interna (α = .86), adecuada correlación ítem con puntaje total, y la presencia de cuatro factores en el análisis factorial exploratorio con correlaciones significativas entre las mismas. El análisis factorial confirmatorio mostró adecuado ajuste a los datos de un modelo tetrafactorial del cuestionario (χ2 /gl = 3.696; GFI=.89; AGFI=.86; RMSEA=.061). El género femenino presenta mayores barreras para la práctica del ejercicio físico. Este cuestionario es un instrumento fiable y válido y se sugiere su uso en futuras investigacionesThe objective of this study was to examine the psychometric properties of the self-report questionnaire for physical exercise (ABPEF). And to chek the effect of gender on those barriers. Their psychometric properties were studied with a sample of 342 adolescents (mean age: 15.02 ± 1.86). We performed reliability analysis, exploratory factor analysis, item correlation with total score and confirmatory factor analysis. We found a good internal reliability (α = .86), an adequate item correlation with total score, and the presence of four factors in the exploratory factor analysis with significant correlations between them. The confirmatory factor analysis showed adequate adjustment to the data of a tetrafactorial model of the questionnaire (χ2 / gl = 3.696; GFI = .89; AGFI = .86; RMSEA = .061). The female gender presents greater barriers to the practice of physical exercise. This questionnaire is a reliable and valid instrument for the population under study, and its use in future research is suggeste

Turbulence and the formation of filaments, loops and shock fronts in NGC 1275 in the Perseus Galaxy Cluster

NGC1275, the central galaxy in the Perseus cluster, is the host of gigantic hot bipolar bubbles inflated by AGN jets observed in the radio as Perseus A. It presents a spectacular $H{\alpha}$-emitting nebulosity surrounding NGC1275, with loops and filaments of gas extending to over 50 kpc. The origin of the filaments is still unknown, but probably correlates with the mechanism responsible for the giant buoyant bubbles. We present 2.5 and 3-dimensional MHD simulations of the central region of the cluster in which turbulent energy, possibly triggered by star formation and supernovae (SNe) explosions is introduced. The simulations reveal that the turbulence injected by massive stars could be responsible for the nearly isotropic distribution of filaments and loops that drag magnetic fields upward as indicated by recent observations. Weak shell-like shock fronts propagating into the ICM with velocities of 100-500 km/s are found, also resembling the observations. The isotropic outflow momentum of the turbulence slows the infall of the intracluster medium, thus limiting further starburst activity in NGC1275. As the turbulence is subsonic over most of the simulated volume, the turbulent kinetic energy is not efficiently converted into heat and additional heating is required to suppress the cooling flow at the core of the cluster. Simulations combining the MHD turbulence with the AGN outflow can reproduce the temperature radial profile observed around NGC1275. While the AGN mechanism is the main heating source, the supernovae are crucial to isotropize the energy distribution.Comment: accepted by ApJ Letter