The spatial damping of magnetohydrodynamic waves in a flowing partially ionised prominence plasma

Solar prominences are partially ionised plasmas displaying flows and oscillations. These oscillations show time and spatial damping and, commonly, have been explained in terms of magnetohydrodynamic (MHD) waves. We study the spatial damping of linear non-adiabatic MHD waves in a flowing partially ionised plasma, having prominence-like physical properties. We consider single fluid equations for a partially ionised hydrogen plasma including in the energy equation optically thin radiation, thermal conduction by electrons and neutrals, and heating. Keeping the frequency real and fixed, we have solved the obtained dispersion relations for the complex wavenumber, k, and have analysed the behaviour of the damping length, wavelength and the ratio of the damping length to the wavelength, versus period, for Alfven, fast, slow and thermal waves.Comment: 28 pages, 9 figure

Magnetohydrodynamic waves in solar partially ionized plasmas: two-fluid approach

We derive the dynamics of magnetohydrodynamic waves in two-fluid partially ionized plasmas and to compare the results with those obtained under single-fluid description. Two-fluid magnetohydrodynamic equations are used, where ion-electron plasma and neutral particles are considered as separate fluids. Dispersion relations of linear magnetohydrodynamic waves are derived for simplest case of homogeneous medium. Frequencies and damping rates of waves are obtained for different parameters of background plasma. We found that two- and single-fluid descriptions give similar results for low frequency waves. However, the dynamics of MHD waves in two-fluid approach is significantly changed when the wave frequency becomes comparable or higher than ion-neutral collision frequency. Alfven and fast magneto-acoustic waves attain their maximum damping rate at particular frequencies (for example, the peak frequency equals 2.5 ion-neutral collision frequency for 50 % of neutral Hydrogen) in wave spectrum. The damping rates are reduced for higher frequency waves. The new mode of slow magneto-acoustic wave appears for higher frequency branch, which is connected to neutral hydrogen fluid. The single-fluid approach perfectly deals with slow processes in partially ionized plasmas, but fails for time-scales smaller than ion-neutral collision time. Therefore, two-fluid approximation should be used for the description of relatively fast processes. Some results of single-fluid description, for example the damping of high-frequency Alfven waves in the solar chromosphere due to ion-neutral collisions, should be revised in future.Comment: 8 pages, 7 figures, accepted in A&

New objects in old structures: The Iron Age hoard of the Palacio III megalithic funerary complex (Almadén de la Plata, Seville, Spain)

Cultural contact, exchange and interaction feature high in the list of challenging topics of current research on European Prehistory. Not far off is the issue of the changing role of monuments in the making and maintaining of key cultural devices such as memory and identity. Addressing both these highly-debated issues from a science-based perspective, in this paper we look at an unusual case study set in southern Iberia and illustrate how these archaeological questions can benefit from robust materials-science approaches.We present the contextual, morphological and analytical study of an exceptional Early Iron Age hoard composed of a number of different (and mostly exotic) materials such as amber, quartz, silver and ceramic. This hoard, found under the fallen orthostat of a megalithic structure built at least 2000 years earlier, throws new light on long-distance exchange networks and the effect they could have had on the cultural identities and social relations of local Iberian Early Iron Age communities. Moreover, the archaeometric study reveals how diverse and distant the sources of these item are (Northern Europe to Eastern and Western Mediterranean raw materials, as well as local and eastern technologies), therefore raising questions concerning the social mechanisms used to establish change and resistance in contexts of colonial encounter

Interaction of dexamethasone and montmorillonite

3 pages, 1 figure, 7 references.-- Congreso celebrado del 7-10 septiembre 1987 en Sevilla, España.-- EUROCLAY'87.Clay-drug interactions have been widely studied during the last decade. However, the reaction mechanisms responsible of these interactions only have been elucidated in sorne cases (1,2), most of them when cationic drugs are ínvolved. Neutral molecules are known to interact with clays by physical adsorption (3), and/or by hydrogen bonding (4). Dioxin is adsorbed onto montmorillonite by a reversible adsorption mechanism (5) and degrades by acid-catalyzed hydrolisis. The mechanism of ad sorption and degradation of the neutral steroid hydrocortisone by palygorskite and sepio1ite has be en recently studied (6,7). Two types of ferric iron present in these clays may be responsible for the different degradation rates of hydrocortisone.Peer reviewe

Language and cultural awareness of a non-native ESP teacher

Introduction. The relation between culture and language is a central issue in foreign language teaching and research where the need to give cultural content the same value as language content and language skills has been stressed. However, conceptualization of teacher language awareness, by focusing largely on formal aspects of language, largely neglects culture as a component of teacher cognition. This paper expands the category of ESP-teacher language awareness suggesting the inclusion of cultural awareness as a separate component of teacher cognition. This concept extension actualizes ESP teaching in the situation shaped by unprecedented mobility and intercultural contacts. Materials and Methods. The historic-logical method was used to determine shortcomings of pedagogical experience and the need to teach culture in ESP. Grounded theory, as an inductive methodology, was utilized to generate conceptual expansion theoretically tied with research in medical and business communication as well as with data on population movement and international scientific cooperation. Results. We defined ESP-cultural knowledge as a system comprising the permanent (know-that) and temporary (know-of) cultural manifestations in a society as well as how they are manifested through language (know-how). That system practical representation is exemplified in medicine and business English discourse. The study expands the structure of ESP-TLA, claiming the focus on cultural awareness as part of ESP discourse which fosters cultural-response education. Discussion and Conclusion. Such claim is pertinent to practitioners involved in the tourism industry, health care, economics, and academic activities such as research and development. This paper is relevant for teachers of English for Specific purposes in the fields mentioned above as well as for researchers engaged in analyzing the problems and methods of teaching a foreign language. However, because of the multiple manifestations and complexity of student motivation to get ESP course, the paper acknowledges the difficulties in addressing cultural content salient to all students in class, an aspect meriting further research. © 2019 National Research Ogarev Mordovia State University. All rights reserved.This research was financially supported by the Russian Foundation for Basic Research (Grant No. 17-29-09136/18 «Multilingualism in the era of post-literacy: Philosophical and cultural studies and methodological and pedagogical development of a multilingual education model»).Российский Фонд Фундаментальных Исследований (РФФИ): 17-29-09136/1

Problemas psicológicos y socio-laborales de las personas que sufren epilepsia, .

En primer lugar se exponen unas generalidades sobre el concepto actual de epilepsia, analizándose después, de forma panorámica, la problemática psicológica y socio-laboral de los epilépticos. La tercera parte de éstos presenta alteraciones psicológicas diversas, y sólo la mitad alcanza el mercado laboral competitivo. El estigma social que conlleva la epilepsia, limita, junto a los déficits individuales, la inserción social de estas personas. Se analiza el origen de la animadversión social hacia los epilépticos, que tiene una raíz psicosociológica, estudiándose los grupos sociales que contribuyen a su mantenimiento. Se concluye afirmando que es necesario un esfuerzo de los profesionales de la salud para propiciar la plena incorporación de estos sujetos en la sociedad

Problemas psicológicos y socio-laborales de las personas que sufren epilepsia, .

En primer lugar se exponen unas generalidades sobre el concepto actual de epilepsia, analizándose después, de forma panorámica, la problemática psicológica y socio-laboral de los epilépticos. La tercera parte de éstos presenta alteraciones psicológicas diversas, y sólo la mitad alcanza el mercado laboral competitivo. El estigma social que conlleva la epilepsia, limita, junto a los déficits individuales, la inserción social de estas personas. Se analiza el origen de la animadversión social hacia los epilépticos, que tiene una raíz psicosociológica, estudiándose los grupos sociales que contribuyen a su mantenimiento. Se concluye afirmando que es necesario un esfuerzo de los profesionales de la salud para propiciar la plena incorporación de estos sujetos en la sociedad

Dating young open clusters using delta Scuti stars. Results for Trumpler 10 and Praesepe

Aims. The main goal of this work is to date young open clusters using $\delta$ Sct stars. Seismic indices such as the large separation and the frequency at maximum power can help to constrain the models to better characterise the stars. We propose a reliable method to identify some radial modes, which gives us greater confidence in the constrained models. Methods. We extract the frequency content of a sample of $\delta$ Sct stars belonging to the same open cluster. We estimate the low-order large separation by means of different techniques and the frequency at maximum power for each member of the sample. We use a grid of models built with the typical parameters of $\delta$ Sct stars, including mass, metallicity and rotation as independent variables, and determine the oscillation modes. We select the observed frequencies whose ratios match those of the models. Once we find a range of radial modes matching the observed frequencies, mainly the fundamental mode, we add it to the other seismic parameters to derive the stellar age. Assuming star groups have similar chemistry and age, we estimate their mean age by computing a weighted probability density function fit to the age distribution of the seismically constrained models. Results. We estimate the age of Trumpler 10 to be $30_{-20}{+30}$ Myr, and that of Praesepe to be $580 \pm 230$ Myr. In this latter case, we find two apparent populations of $\delta$ Sct stars in the same cluster, one at $510 \pm 140$ Myr and another at $890 \pm 140$ Myr. This may be due to two different formation events, different rotational velocities of the members in our sample of stars (as rapid rotation may modify the observed large separation), or to membership of unresolved binary systems.Comment: 20 pages, 25 figure, uses the open-source code MultiModes (see https://github.com/davidpamos/MultiModes). It will be published in A&