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

The envelope of the power spectra of over a thousand \delta Scuti stars. The Tˉeff\bar{T}_{eff}-νmax\nu_{max} scaling relation

CoRoT and Kepler high-precision photometric data allowed the detection and characterization of the oscillation parameters in stars other than the Sun. Moreover, thanks to the scaling relations, it is possible to estimate masses and radii for thousands of solar-type oscillating stars. Recently, a \Delta\nu - \rho relation has been found for \delta Scuti stars. Now, analyzing several hundreds of this kind of stars observed with CoRoT and Kepler, we present an empiric relation between their frequency at maximum power of their oscillation spectra and their effective temperature. Such a relation can be explained with the help of the \kappa-mechanism and the observed dispersion of the residuals is compatible with they being caused by the gravity-darkening effect

Evidence of amplitude modulation due to Resonant Mode Coupling in the delta Scuti star KIC5892969

A study of the star KIC5892969 observed by the Kepler satellite is presented. Its three highest amplitude modes present a strong amplitude modulation. The aim of this work is to investigate amplitude variations in this star and their possible cause. Using the 4 years-long observations available, we obtained the frequency content of the full light curve. Then, we studied the amplitude and phase variations with time using shorter time stamps. The results obtained are compared with the predicted ones for resonant mode coupling of an unstable mode with lower frequency stable modes. Our conclusion is that resonant mode coupling is consistent as an amplitude limitation mechanism in several modes of KIC5892969 and we discuss to which extent it might play an important role for other delta Scuti stars

Evidence of chaotic modes in the analysis of four delta Scuti stars

Since CoRoT observations unveiled the very low amplitude modes that form a flat plateau in the power spectrum structure of delta Scuti stars, the nature of this phenomenon, including the possibility of spurious signals due to the light curve analysis, has been a matter of long-standing scientific debate. We contribute to this debate by finding the structural parameters of a sample of four delta Scuti stars, CID 546, CID 3619, CID 8669, and KIC 5892969, and looking for a possible relation between these stars' structural parameters and their power spectrum structure. For the purposes of characterization, we developed a method of studying and analysing the power spectrum with high precision and have applied it to both CoRoT and Kepler light curves. We obtain the best estimates to date of these stars' structural parameters. Moreover, we observe that the power spectrum structure depends on the inclination, oblateness, and convective efficiency of each star. Our results suggest that the power spectrum structure is real and is possibly formed by 2-period island modes and chaotic modes

Вопрос грамматики в понимании академического чтения

Изменение экономических условий и приоритетов в настоящее время влечет за собой и более научно-ориентированное высшее образование в России. Даже социальные и гуманитарные науки должны изучать больше научной литературы, написанной на английском языке, который является сегодня языком научной коммуникации. Основываясь на примерах, взятых из современных научных журналов и учебников, в статье фокусируется внимание на необходимости выделения того, как термины и грамматика, переплетаясь, могут естественно выражать сложные мысли и отвечать требованиям академических жанров на уровне текста. Выбранные примеры демонстрируют, как такое смешивание нередко приводит к проблемам в понимании существенного первоочередного условия для производства языка, что должны учитывать преподаватели в процессе обучения.The present changing economic conditions and priorities are very likely to pose a more science-oriented higher education in Russia. Even the social sciences and humanities will have to consume more scientific literature written in English, the language of scholarly communication today. Based on examples taken from journals and textbooks, the article focuses on the need to highlight how terms and grammar mingle naturally to express complex thought and meet the requirements of academic genres at text level. The instances of language chosen demonstrate how such mingling quite often leads to problems in comprehension as an essential requirement prior to language production, an issue teachers should consider in the teaching learning process

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

The effect of the solar corona on the attenuation of small-amplitude prominence oscillations. I. Longitudinal magnetic field

Context. One of the typical features shown by observations of solar prominence oscillations is that they are damped in time and that the values of the damping times are usually between one and three times the corresponding oscillatory period. However, the mechanism responsible for the attenuation is still not well-known. Aims. Thermal conduction, optically thin or thick radiation and heating are taken into account in the energy equation, and their role on the attenuation of prominence oscillations is evaluated. Methods. The dispersion relation for linear non-adiabatic magnetoacoustic waves is derived considering an equilibrium made of a prominence plasma slab embedded in an unbounded corona. The magnetic field is orientated along the direction parallel to the slab axis and has the same strength in all regions. By solving the dispersion relation for a fixed wavenumber, a complex oscillatory frequency is obtained, and the period and the damping time are computed. Results. The effect of conduction and radiation losses is different for each magnetoacoustic mode and depends on the wavenumber. In the observed range of wavelengths the internal slow mode is attenuated by radiation from the prominence plasma, the fast mode by the combination of prominence radiation and coronal conduction and the external slow mode by coronal conduction. The consideration of the external corona is of paramount importance in the case of the fast and external slow modes, whereas it does not affect the internal slow modes at all. Conclusions. Non-adiabatic effects are efficient damping mechanisms for magnetoacoustic modes, and the values of the obtained damping times are compatible with those observed.Comment: Accepted in A&

V12 248. Reemplazo de raíz de aorta según técnica de david y de arco aórtico con injerto trifurcado, en un paciente diagnosticado de síndrome de loeys-dietz

IntroducciónSe describe la técnica quirúrgica de un paciente de 24 años de edad con síndrome de Loeys-Dietz. Se trata de una enfermedad hereditaria del tejido conectivo producida por la mutación del gen del receptor del factor de crecimiento transformante (TGF)-β;. Su característica principal y condicionante del pronóstico es la dilatación del sistema vascular, principalmente la aorta.MétodoEl paciente presentaba dilatación aneurismática de la raíz y del arco aórtico, con un diámetro máximo de 50 mm. Tenía además historia familiar de muerte súbita de origen cardíaco en tres familiares de primer grado a edades tempranas. Ante la indicación de tratamiento quirúrgico se procedió a realizar sustitución de los segmentos aneurismáticos. En la raíz aórtica se realizó técnica de preservación valvular (técnica de David, modificación de Miller). La sustitución del arco aórtico se llevó a cabo mediante interposición de injerto trifurcado, en hipotermia moderada y con perfusión cerebral anterógrada.Resultado y conclusionesNo hubo complicaciones postoperatorias. El tratamiento quirúrgico precoz en los pacientes afectos de síndrome de Loeys-Dietz es imprescindible. La experiencia acumulada hasta el momento revela la agresividad de esta enfermedad. Por ello, es necesario un abordaje completo cuando existe afectación a distintos niveles. El empleo de técnicas de preservación valvular permite además disminuir la morbimortalidad asociada a las prótesis valvulares

CO72 357. Reconstrucción del cuerpo fibroso mitroaórtico: Resultados perioperatorios y supervivencia a largo plazo

ObjetivosDescribir las características clínicas, resultados perioperatorios y supervivencia a largo plazo de pacientes sometidos a sustitución valvular mitral y aórtica con reconstrucción de la fbrosa mitroaórtica según técnica de David.MétodosRevisión retrospectiva de pacientes sometidos a sustitución valvular y reconstrucción de la fibrosa mitroaórtica intervenidos en los últimos 14 años. Se incluyen 27 pacientes, 63% varones, edad 55,3±16,1 años, EuroSCORE 34,4±25,9. El 70,4% de los pacientes presentaban al menos una cirugía previa. La indicación para el procedimiento fue endocarditis infecciosa complicada con absceso de la unión mitroaórtica en el 74,1%; en el restante 25,9% la principal indicación fue la necesidad de ampliación del anillo aórtico en el seno de una valvulopatía mitroaórtica.ResultadosLa supervivencia perioperatoria (30 días) fue del 85,2%. No se observó mortalidad entre los pacientes sin endocarditis. Estancia media: 42,8±42,8 días. Complicaciones perioperatorias: accidente cerebrovascular agudo (ACVA) 3,1% (1), balón de contrapulsación intraaórtica (BCIA) 11,1% (3), insuficiencia renal aguda (IRA) 7,4% (2), infarto agudo de miocardio (IAM) 3,7% (1), reintervención por sangrado 14,8% (4), ventilación mecánica prolongada 11,1% (3), necesidad de marcapasos (MP) definitivo 22,2%. La supervivencia acumulada para los supervivientes a 1, 3 y 5 años fue de 85,9±7,6%, 75,8 ± 9,5% y 45,5 ± 11,1%, respectivamente. No se observó diferencia significativa al comparar la super-vivencia a 1, 3 y 5 años entre los grupos intervenidos por endocarditis y los no endocarditis (log rank 0,146).ConclusionesLa reconstrucción de la fibrosa mitroaórtica mediante técnica de David representa una alternativa terapéutica para el manejo de patología compleja que involucra esta estructura. Hemos observado buenos resultados perioperatorios y a largo plazo teniendo en cuenta el perfil de alto riesgo de los pacientes que requieren este tipo de intervención