Review and test of chilldown methods for space-based cryogenic tanks

The literature for tank chilldown methods applicable to cryogenic tankage in the zero gravity environment of earth orbit is reviewed. One method is selected for demonstration in a ground based test. The method selected for investigation was the charge-hold-vent method which uses repeated injection of liquid slugs, followed by a hold to allow complete vaporization of the liquid and a vent of the tank to space vacuum to cool tankage to the desired temperature. The test was conducted on a 175 cubic foot, 2219 aluminum walled tank weighing 329 pounds, which was previously outfitted with spray systems to test nonvented fill technologies. To minimize hardware changes, a simple control-by-pressure scheme was implemented to control injected liquid quantities. The tank cooled from 440 R sufficiently in six charge-hold-vent cycles to allow a complete nonvented fill of the test tank. Liquid hydrogen consumed in the process is estimated at 32 pounds

Θ-modifications on weak spaces

In this article, we want to study and investigate if it is possible to use the notions of weak structures to develop a new theory of - modi cations in weak spaces and study their properties, nally we study some forms of weak continuity using this modi cations

Weakly (I, J)-continuous multifunctions and contra (I, J)-continuous multifunctions

The purpose of the present paper is to introduce, study and characterize upper and lower weakly (I, J)-continuous multifunctions and contra (I, J)-continuous multifunctions. Also, we investigate its relation with another class of continuous multifunctions. AMS Subject Classification: 54C10, 54C08, 54C05, 54C6

El problema ético de la limitación del acceso a beneficios en salud : el caso de los medicamentos innovadores

Un problema que enfrentan los sistemas de salud alrededor del mundo es el del envejecimiento de las poblaciones, junto con el cambio en los patrones de enfermedad, hacia una mayor prevalencia de las enfermedades crónicas que requieren de costosas intervenciones en salud para su cubrimiento. Si bien todas las economías se enfrentan a la limitación de recursos para asegurar el disfrute del derecho a la salud y a la atención en salud, hoy en día la búsqueda de una salud perfecta se ha convertido en un objetivo inadecuado e ilusorio que podría ir en detrimento de otros aspectos de la sociedad. Así pues, hoy más que nunca, es imperativo establecer límites en acceso a innovación en salud. En este texto, desde la perspectiva de cuatro grupos de autores (Callahan; Daniels; Powers y Faden; y Callon, Lascoumes y Barthe), se discute cómo el derecho a la salud implica una conexión con otros determinantes y cómo las decisiones que se tomen sobre el establecimiento de límites en salud solo pueden alcanzar una plena legitimidad si los tomadores de decisión son responsables de las razones que les asistieron, y si los directamente afectados por las decisiones, y en general los actores involucrados, proveen criterios para evaluar su aceptabilidad ética. En un contexto así, la metodología de controversias socio-técnicas implementadas en foros híbridos puede ser una herramienta para asegurar la democratización de las decisiones en la búsqueda de procesos justos e imparciales, en los que se privilegie la centralidad del ser humano que sufre.A problem faced by health systems around the world is that of aging populations, together with the change in disease patterns, towards a higher prevalence of chronic diseases that require expensive health interventions to cover them. While all economies face limited resources to ensure the enjoyment of the right to health and health care, today the search for perfect health has become an inappropriate and illusory goal that could be detrimental for other aspects of society. Thus, today more than ever, it is imperative to set limits on access to innovation in health. In this text, from the perspective of four groups of authors (Callahan; Daniels; Powers and Faden; and Callon, Lascoumes and Barthe), it is discussed how the right to health implies a connection with other determinants and how decisions are made on the establishment of limits in health. These decisions can only achieve full legitimacy if the decision makers are responsible for the reasons that assisted them, and if those directly affected by the decisions, and in general the actors involved, provide criteria to assess their ethical acceptability . In such a context, the methodology of socio-technical controversies implemented in hybrid forums can be a tool to ensure the democratization of decisions in the search for fair and impartial processes, in which the centrality of the suffering human being is privileged.Magíster en BioéticaMaestrí

On the hereditary character of certain spectral properties and some applications

In this paper we study the behavior of certain spectral properties of an operator T on a proper closed and T-invariant subspace W ⊆ X such that T n(X) ⊆ W, for some n ≥ 1, where T ∈ L(X) and X is an infinite-dimensional complex Banach space. We prove that for these subspaces a large number of spectral properties are transmitted from T to its restriction on W and vice-versa. As consequence of our results, we give conditions for which semi-Fredholm spectral properties, as well as Weyl type theorems, are equivalent for two given operators. Additionally, we give conditions under which an operator acting on a subspace can be extended on the entire space preserving the Weyl type theorems. In particular, we give some applications of these results for integral operators acting on certain functions spaces

Sport participation and vigilance in children: Influence of different sport expertise

PURPOSE: The present study aimed to investigate the relationship between different types of sport expertise (externally-paced vs. self-paced sports) and vigilance performance in children by evaluating the cardiovascular fitness level of the participants. METHODS: Three groups of children (11.0 ± 0.2 years) differentiated in terms of their regular sport participation (football players, n = 20; track and field athletes, n = 20; non-athletic controls, n = 20) took part in the study. In one session, participants performed the Leger Multi-stage fitness test to estimate their aerobic fitness level. In another session, participants completed the Psychomotor Vigilance Task (PVT) to evaluate their vigilance performance under 2 conditions of velocity demands (normal vs. speed). RESULTS: The results revealed that both groups of sport practitioners had higher cardiovascular fitness than non-athlete controls. In contrast, no significant differences in the performance PVT were found between track and field athletes and controls. Crucially, football players showed better performance in the PVT than track and field athletes and controls. These between-group differences were not modulated by the speed demands of the task. CONCLUSION: The major novel finding of this research points to a positive relationship between sport participation and vigilance performance during childhood. We discuss our results in terms of the different hypotheses put forward in the literature to explain the relationship between regular exercise and cognitive functioning: the "cardiovascular fitness" and the "cognitive component skills" hypotheses.Spanish Ministerio de Educación y Cultura (FPU13-05605)Junta de Andalucia Proyecto de Excelencia (SEJ-6414)Ministerio de Economía y Competitividad (PSI2013-46385)Ministerio de Economía y Competitividad (PSI2013-46385)Ciencias de la Actividad Física y del Deport