Discurso, conocimiento social e identidad en un grupo de iguales gitano

This article examines the way in which a group of Gypsy children talks in their spontaneous interactions about different sets of residents of their neighborhood. The data is part of a linguistic ethnography of peer interactions of a group of Gypsy children from a mid-sized Spanish city and this article focuses on a ‘night stroll’ the children took in which they moved away from their habitual play areas and walked through different parts of their district. The neighborhood is relatively heterogeneous in socio-economic and ethnic terms as a result of several social and urban transformations. Two discursive mechanisms, membership categorization and stylization, are examined to show the role talk plays in children’s understanding of this social heterogeneity in relation to their own ethnic and social identity. Finally, the article points out some of the potentials of ethnographic microanalysis of social interaction to study children’s social knowledge in action

A Survey for Spectroscopic Binaries Among Very Low-Mass Stars

We report on the results of a survey for radial velocity variability in a heterogeneous sample of very low-mass stars and brown dwarfs. One distinguishing characteristic of the survey is its timespan, which allows an overlap between spectroscopic binaries and those which can be found by high angular-resolution imaging. We are able to place a new constraint on the total binary fraction in these objects, which suggests that they are more likely the result of extending the same processes at work at higher masses into this mass range, rather than a distinct mode of formation. Our basic result is that there are $6 \pm 2$ out of 53, or $11^{+0.07}_{-0.04}$% spectroscopic binaries in the separation range 0-6 AU, nearly as many as resolved binaries. This leads to an estimate of an upper limit of $26 \pm 10$% for the binary fraction of VLM objects (it is an upper limit because of the possible overlap between the spectroscopic and resolved populations). A reasonable estimate for the very low-mass binary fraction is $20 - 25$%. We consider several possible separation and frequency distributions, including the same one as found for GK stars, a compressed version of that, a version of the compressed distribution truncated at 15 AU, and a theoretical distribution which considers the evaporation of small-N clusters. We conclude that the latter two bracket the observations, which may mean that these systems form with intrinsically smaller separations due to their smaller mass, and then are truncated due to their smaller binding energy. We do not find support for the ``ejection hypothesis'' as their dominant mode of formation, particularly in view of the similarity in the total binary fraction compared with slightly more massive stars, and the difficulty this mechanism has in producing numerous binary systems.Comment: 36 pages, accepted for publication in AJ, abstract shortened for arXiv.or

The Becklin-Neugebauer Object as a Runaway B Star, Ejected 4000 years ago from the theta^1C system

We attempt to explain the properties of the Becklin-Neugebauer (BN) object as a runaway B star, as originally proposed by Plambeck et al. (1995). This is one of the best-studied bright infrared sources, located in the Orion Nebula Cluster -- an important testing ground for massive star formation theories. From radio observations of BN's proper motion, we trace its trajectory back to Trapezium star theta^1C, the most massive (45 Msun) in the cluster and a relatively tight (17 AU) visual binary with a B star secondary. This origin would be the most recent known runaway B star ejection event, occurring only \~4000 yr ago and providing a unique test of models of ejection from multiple systems of massive stars. Although highly obscured, we can constrain BN's mass (~7 Msun) from both its bolometric luminosity and the recoil of theta^1C. Interaction of a runaway B star with dense ambient gas should produce a compact wind bow shock. We suggest that X-ray emission from this shocked gas may have been seen by Chandra: the offset from the radio position is ~300 AU in the direction of BN's motion. Given this model, we constrain the ambient density, wind mass-loss rate and wind velocity. BN made closest approach to the massive protostar, source ``I'', 500 yr ago. This may have triggered enhanced accretion and thus outflow, consistent with previous interpretations of the outflow being a recent (~10^3 yr) "explosive" event.Comment: 6 pages, accepted to ApJ Letter

Hot-Moments of Soil CO2 Efflux in a Water-Limited Grassland

The metabolic activity of water-limited ecosystems is strongly linked to the timing and magnitude of precipitation pulses that can trigger disproportionately high (i.e., hot-moments) ecosystem CO2 fluxes. We analyzed over 2-years of continuous measurements of soil CO2 efflux (Fs) under vegetation (Fsveg) and at bare soil (Fsbare) in a water-limited grassland. The continuous wavelet transform was used to: (a) describe the temporal variability of Fs; (b) test the performance of empirical models ranging in complexity; and (c) identify hot-moments of Fs. We used partial wavelet coherence (PWC) analysis to test the temporal correlation between Fs with temperature and soil moisture. The PWC analysis provided evidence that soil moisture overshadows the influence of soil temperature for Fs in this water limited ecosystem. Precipitation pulses triggered hot-moments that increased Fsveg (up to 9000%) and Fsbare (up to 17,000%) with respect to pre-pulse rates. Highly parameterized empirical models (using support vector machine (SVM) or an 8-day moving window) are good approaches for representing the daily temporal variability of Fs, but SVM is a promising approach to represent high temporal variability of Fs (i.e., hourly estimates). Our results have implications for the representation of hot-moments of ecosystem CO2 fluxes in these globally distributed ecosystems

Dynamical decay of a massive multiple system in Orion KL?

We present absolute astrometry of 35 radio sources in the Orion Trapezium and Becklin-Neugebauer/Kleinman-Low regions, obtained from Very Large Array archival observations collected over a period of 15 years. By averaging the results for all the sources, we estimate the mean absolute proper motion of Orion to be --in Galactic coordinates-- $\mu_\ell \cos b$ = +2.1 $\pm$ 0.2 mas yr$^{-1}$; $\mu_b$ = $-$0.1 $\pm$ 0.2 mas yr$^{-1}$. These values agree remarkably well with those expected from the differential rotation of the Milky Way. Subtraction of this mean motion from the individual measurements allows us to register all proper motions to the rest frame of the Orion nebula, and identify radio sources with large residual velocities. In the KL region, we find three sources in this situation: the BN object, the radio source I, and the radio counterpart of the infrared source n. All three objects appear to be moving away from a common point where they must all have been located about 500 years ago. This suggests that all three sources were originally part of a multiple massive stellar system that recently disintegrated as a result of a close dynamicalComment: Accepted for publication in the Ap

Pedagogical Practice – Index of Readiness of Future Physics Teacher to Professional Activity

У статті проаналізовано організаційно-методичні засади педагогічної практики у вищому навчальному закладі на даний час, розкрито її значення в системі професійного становлення майбутнього вчителя фізики. Зазначено, що ефективне проведення педпрактики залежить від належного рівня організації і управління діяльністю студентів. Обґрунтовано, що результати педагогічної практики виступають показником готовності студента до майбутньої професійної діяльності та одночасно вказують на недоліки і прогалини у знаннях студентів, на які необхідно звернути особливу увагу під час фахової підготовки. Описано основні розділи «Програми педагогічної практики» для студентів-майбутніх вчителів фізики (4-й курс), розробленої авторами статті у співавторстві з колективом досвідчених викладачів кафедри. Окреслено перспективи педагогічної практики студентів у зв’язку з реформуванням вищої освіти в Україні. Висвітлено деякі особливості організації педагогічної практики у вищих навчальних закладах різних країн світу.The article analyzes organizational-methodical bases of pedagogical practice in higher education at the present time, revealed its importance in the system of professional formation of future teachers of physics. Noted that effective implementation of the internship depends on the appropriate level of the organization and management of students. It is proved that the results of the pedagogical practices act as an indicator of students 'readiness for future professional activity and at the same time indicate shortcomings and gaps in students' knowledge that need special attention in training. Describes the main sections of "teaching practice Program" for students-future physics teachers (4th year) developed by the authors in collaboration with a team of experienced teachers of the Department. Perspectives of pedagogical practice of students in connection with the reform of higher education in Ukraine. Highlight some features of the organization of pedagogical practice in higher education institutions around the world

A systematic review of the Trypanosoma cruzi genetic heterogeneity, host immune response and genetic factors as plausible drivers of chronic chagasic cardiomyopathy

Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30-40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are responsible of this clinical pattern. To date, no conclusive data support the reason why a few percentages of the infected individuals will develop CCC. Therefore, we decided to conduct a systematic review analysing the host genetic factors, immune response, cytokine production, virulence factors and the plausible association of the parasite DTUs and CCC. The epidemiological and clinical implications are herein discussed. © Cambridge University Press 2018