Absorption and Direct Processes in Chaotic Wave Scattering

Recent results on the scattering of waves by chaotic systems with losses and direct processes are discussed. We start by showing the results without direct processes nor absorption. We then discuss systems with direct processes and lossy systems separately. Finally the discussion of systems with both direct processes and loses is given. We will see how the regimes of strong and weak absorption are modified by the presence of the direct processes.Comment: 8 pages, 4 figures, Condensed Matter Physics (IV Mexican Meeting on Mathematical and Experimental Physics), Edited by M. Martinez-Mares and J. A. Moreno-Raz

Electromagnetic prompt response in an elastic wave cavity

A rapid, or prompt response, of an electromagnetic nature, is found in an elastic wave scattering experiment. The experiment is performed with torsional elastic waves in a quasi-one-dimensional cavity with one port, formed by a notch grooved at a certain distance from the free end of a beam. The stationary patterns are diminished using a passive vibration isolation system at the other end of the beam. The measurement of the resonances is performed with non-contact electromagnetic-acoustic transducers outside the cavity. In the Argand plane, each resonance describes a circle over a base impedance curve which comes from the electromagnetic components of the equipment. A model, based on a variation of Poisson's kernel is developed. Excellent agreement between theory and experiment is obtained.Comment: 4 pages, 5 figure

Scattering of Elastic Waves in a Quasi-one-dimensional Cavity: Theory and Experiment

We study the scattering of torsional waves through a quasi-one-dimensional cavity both, from the experimental and theoretical points of view. The experiment consists of an elastic rod with square cross section. In order to form a cavity, a notch at a certain distance of one end of the rod was grooved. To absorb the waves, at the other side of the rod, a wedge, covered by an absorbing foam, was machined. In the theoretical description, the scattering matrix S of the torsional waves was obtained. The distribution of S is given by Poisson's kernel. The theoretical predictions show an excellent agreement with the experimental results. This experiment corresponds, in quantum mechanics, to the scattering by a delta potential, in one dimension, located at a certain distance from an impenetrable wall

The High-Frequency QPOs in GRS 1915+105

We analyzed two 1996 observations of the Galactic Microquasar GRS 1915+105 taken with the Proportional Counter Array on board the Rossi X-ray Timing Explorer. We focus on the properties of the high-frequency QPO as a function of the `dip' oscillations, a factor of 1000 slower. In one observation, 1996 May 5th, we find that the energy spectrum of the QPO at ~65 Hz changes drastically between the high-intervals and the dips, hardening during the dips to the point that the QPO peak is no longer detected at low energies. In the second observation, 1996 May 14th, although it has similar overall characteristics, the 65 Hz QPO is not seen, but another broader QPO peak appears at 27 Hz, only during the dips. This peak is too weak to obtain reliable information about its spectrum. Our results indicate that the presence/absence of high-frequency features in this enigmatic source are intimately linked to the slower oscillations and variations that happen on longer time scales

Attitudes of students of a health sciences university towards the extension of smoke-free policies at the university campuses of Barcelona

OBJECTIVE: To assess attitudes towards the extension of outdoor smoke-free areas on university campuses. METHODS: Cross-sectional study (n=384) conducted using a questionnaire administered to medical and nursing students in Barcelona in 2014. Information was obtained pertaining to support for indoor and outdoor smoking bans on university campuses, and the importance of acting as role models. Logistic regression analyses were performed to examine agreement. RESULTS: Most of the students agreed on the importance of health professionals and students as role models (74.9% and 64.1%, respectively) although there were statistically significant differences by smoking status and age. 90% of students reported exposure to smoke on campus. Students expressed strong support for indoor smoke-free policies (97.9%). However, only 39.3% of participants supported regulation of outdoor smoking for university campuses. Non-smokers (OR=12.315; 95% CI: 5.377-28.204) and students ≥22 years old (OR=3.001; 95% CI: 1.439-6.257) were the strongest supporters. CONCLUSIONS: The students supported indoor smoke-free policies for universities. However, support for extending smoke-free regulations to outdoor areas of university campuses was limited. It is necessary to educate students about tobacco control and emphasise their importance as role models before extending outdoor smoke-free legislation at university campuses

Nuevos medios, nuevos perfiles y conectividad emocional con la audiencia: los periodistas en la praxis profesional

This paper aims to shed light on a Journalism that does not remain exempt from the innovations that Web 2.0 brings inside. The media try to adapt to the needs of two hot topics: digital convergence and social means, and the journalists have to confront the new professional challenges as consequence of the technological, media and social revolution. It is determined the existence of the new professional profiles upon labor demand and in the professional exercise, the use of the social platforms by the journalists and the emotional connectivity that is established by the readership in these environments. We employ the poll as quantitative and qualitative methodological technology to analyze at local level the opinion of the journalists of two newspapers edited in Seville: Abc and Diario de Sevilla.Este artículo pretende dar a conocer la existencia de un periodismo que no queda exento de las innovaciones que trae consigo la Web 2.0. Los medios están intentando adaptarse a las exigencia de la convergencia digital y de los medios sociales y los periodistas tienen que afrontar los nuevos retos profesionales como consecuencia de la revolución tecnológica, mediática y social. Se determina la existencia de los nuevos perfiles profesionales bajo demanda laboral y en el ejercicio de la profesión, el uso de las plataformas sociales por parte de los periodistas y la conectividad emocional que se establece con la audiencia en estos entornos. Utilizamos la encuesta como técnica metodológica cuantitativa y cualitativa para analizar a nivel local la opinión de los periodistas de dos diarios editados en Sevilla: Abc y Diario de Sevilla.Cet article réflechit sur les changements que la Web 2.0 implique pour le journalisme. Les mèdia essaient de s’adapter aux nouveaux défis professionnaux que la revolution technologique et sociale produisent. Des nouveaux profils proféssionels sont demandés pour le secteur, et la connectivité emotionnelle est un trait necéssaire pour communiquer avec les lecteurs. Dans la pièce s’utilisent des études quantitatifs et qualitatifs pour analiser l’opinion des journalists de deux journals en Seville, Abc et Diario de Sevill

Experimental determination of the absorption strength in absorbing chaotic cavities

Due to the experimental necessity we present a formula to determine the absorption strength by power losses inside a chaotic system (cavities, graphs, acoustic resonators, etc) when the antenna coupling, always present in experimental measurements, is taken into account. This is done by calculating the average of the absorption coefficient as a function of the absorption strength and the coupling of the antenna to the system, in the one channel case.Comment: 6 pages, 3 figures, Submitted to Phys. Rev.