The effects of space radiation on thin films of YBa2Cu3O(7-x)

This investigation had two objectives: (1) to determine the effects of space radiation on superconductor parameters that are most important in space applications; and (2) to determine whether this effect can be simulated with Co-60 gamma rays, the standard test method for space materials. Thin films of yttrium barium copper oxide (YBCO) were formed by coevaporation of Y, BaF2, and Cu and post-annealing in wet oxygen at 850 C for 3.5 h. The substrate used was (100) silicon with an evaporated zirconia buffer layer. The samples were characterized by four point probe electrical measurements as a function of temperature. The parameters measured were the zero resistance transition temperature T(sub c) and the room temperature resistance. The samples were then exposed to Co-60 gamma-rays in air and in pure nitrogen, and to 780 keV electrons, in air. The parameters were then remeasured. The results are summarized. The results indicate little or no degradation in the parameters measured for samples exposed up to 10 Mrads of gamma-rays in nitrogen. However, complete degradation is preliminarily attributed to the high level of ozone generated in the chamber by the gamma-ray interaction with air. It can be concluded that: (1) the electron component of space radiation does not degrade the critical temperature of the YBCO films described, at least for energies around 800 keV and doses similar to those received by surface materials on spacecraft in typical remote sensing missions; and (2) for qualifying this and other superconducting materials against the space-radiation threat the standard test method used in the aerospace industry, namely, exposure to Co-60 gamma-rays in air, may require some further investigation. As a minimum, the sample must be either in vacuum or in positive nitrogen pressure

El fenómeno de la internacionalización acelerada: empresas tipo Born Global. Hacía un nuevo modelo de internacionalización

Los cambios acelerados en la economía mundial, la cual está haciendo que exista una intensa competencia entre las empresas por permanecer en el mercado ya no solo doméstico sino en los extranjeros, han hecho que en las últimas décadas la internacionalización empresarial esté tomando mayor relevancia entre los investigadores y académicos desde puntos de vista diferentes. Así, un nuevo fenómeno ha aparecido y esto ha dado oportunidad a nuevas investigaciones sobre el proceso de internacionalización en donde las empresas han puesto en marcha un paradigma alternativo al modelo Uppsala para dar entrada al fenómeno de las empresas tipo Born Global, es decir, empresas que se internacionalizan desde su concepción, reduciendo el tiempo del proceso de internacionalización. Este artículo tiene como objetivo realizar un acercamiento analítico acerca del estudio que se ha desarrollado en torno a este fenómeno con el fin de poner en perspectiva la trayectoria que pueden seguir las empresas bajo este nuevo planteamiento teórico, el cual se encuentra en construcción. La conclusión principal a la que se llega es que independientemente de la ruta de internacionalización seguida por la empresa, existen características distintivas de cada modelo, siendo el Born Global un concepto que abre la posibilidad de desarrollar investigaciones en países y/o mercados emergentes que complementen la construcción del conocimiento que hasta este momento se ha desarrollado.ITESO, A.C.Universidad del Valle de Méxic

A Classification of Countable Lower 1-transitive Linear Orders

This paper contains a classification of countable lower 1-transitive linear orders. This is the first step in the classification of countable 1-transitive trees given in Chicot and Truss (2009): the notion of lower 1-transitivity generalises that of 1-transitivity for linear orders, and it is essential for the structure theory of 1-transitive trees. The classification is given in terms of coding trees, which describe how a linear order is fabricated from simpler pieces using concatenations, lexicographic products and other kinds of construction. We define coding trees and show that a coding tree can be constructed from a lower 1-transitive linear order (X,≤) by examining all the invariant partitions on X. Then we show that a lower 1-transitive linear order can be recovered from a coding tree up to isomorphism

Probabilistic Guarded P Systems, A New Formal Modelling Framework

Multienvironment P systems constitute a general, formal framework for modelling the dynamics of population biology, which consists of two main approaches: stochastic and probabilistic. The framework has been successfully used to model biologic systems at both micro (e.g. bacteria colony) and macro (e.g. real ecosystems) levels, respectively. In this paper, we extend the general framework in order to include a new case study related to P. Oleracea species. The extension is made by a new variant within the probabilistic approach, called Probabilistic Guarded P systems (in short, PGP systems). We provide a formal definition, a simulation algorithm to capture the dynamics, and a survey of the associated software.Ministerio de Economía y Competitividad TIN2012- 37434Junta de Andalucía P08-TIC-0420

Deterministic and stochastic P systems for modelling cellular processes

This paper presents two approaches based on metabolic and stochastic P systems, together with their associated analysis methods, for modelling biological sys- tems and illustrates their use through two case studies.Kingdom's Engineering and Physical Sciences Research Council EP/ E017215/1Biotechnology and Biological Sciences Research Council/United Kingdom BB/D019613/1Biotechnology and Biological Sciences Research Council/United Kingdom BB/F01855X/

The Glycerol-Dependent Metabolic Persistence of Pseudomonas putida KT2440 Reflects the Regulatory Logic of the GlpR Repressor

The growth of the soil bacterium Pseudomonas putida KT2440 on glycerol as the sole carbon source is characterized by a prolonged lag phase, not observed with other carbon substrates. We examined the bacterial growth in glycerol cultures while monitoring the metabolic activity of individual cells. Fluorescence microscopy and flow cytometry, as well as the analysis of the temporal start of growth in single-cell cultures, revealed that adoption of a glycerol-metabolizing regime was not the result of a gradual change in the whole population but rather reflected a time-dependent bimodal switch between metabolically inactive (i.e., nongrowing) and fully active (i.e., growing) bacteria. A transcriptional Φ(glpD-gfp) fusion (a proxy of the glycerol-3-phosphate [G3P] dehydrogenase activity) linked the macroscopic phenotype to the expression of the glp genes. Either deleting glpR (encoding the G3P-responsive transcriptional repressor that controls the expression of the glpFKRD gene cluster) or altering G3P formation (by overexpressing glpK, encoding glycerol kinase) abolished the bimodal glpD expression. These manipulations eliminated the stochastic growth start by shortening the otherwise long lag phase. Provision of glpR in trans restored the phenotypes lost in the ΔglpR mutant. The prolonged nongrowth regime of P. putida on glycerol could thus be traced to the regulatory device controlling the transcription of the glp genes. Since the physiological agonist of GlpR is G3P, the arrangement of metabolic and regulatory components at this checkpoint merges a positive feedback loop with a nonlinear transcriptional response, a layout fostering the observed time-dependent shift between two alternative physiological states

Isolation of Sarcocystis neurona from an opossum (Didelphis albiventris) in Argentina

Sarcocystis neurona is an Apicomplexan parasite which affects awide range of animal hosts. This protozoan is the main cause ofequine protozoal myeloecephalitis (EPM) inWestern Hemispherehorses. The parasite reproduces sexually in the intestine ofdefinitive hosts (DH) and asexually in tissues of intermediate andaberrant hosts. The geographical distribution of S. neurona isrelated with the distribution its definitive hosts, the opossumsDidelphis virginiana and D. albiventris. A recent serological studyconducted in Argentinean horses using S. neurona antigenrevealed an overall seroprevalence of 26.1%. However, the parasitehas not been isolated in Argentina. Tissues from an opossum (D.albiventris) hunted by dogs in a farm from the central region ofBuenos Aires province were collected. Horses raised in the farmshowed a 50% (10/20) S. neurona seroprevalence. One seropositivehorse developed neurological signs and evidenced clinicalimprovement after a 2 month treatment with Ponazuril. A completenecropsy of the opossum was conducted and the intestinalmucosal scraping was subjected to a parasitological study withsucrose solution. A high amount of Sarcocystis spp. oocysts/sporocystswere observed (Fig. 1). DNA was extracted from concentratedoocysts with a commercial kit (ZR Fecal DNA, ZymoResearch). The sample was identified as S. neurona by specificPCR-restriction fragment length polymorphism (RFLP) and bysequencing of a fragment of the 18S rRNA gene. Approximately 5 x105 oocysts were subjected to a pepsin-HCl digestion followed bya physical disruption. Released sporozoites were used to infectfresh BM cell cultures, maintained by 3 passages during 2 monthsand further preserved in liquid nitrogen. This study represents thefirst isolation of S. neurona in Argentina. Further studies will beconducted in order to identify antigen expression as well as tocompare genetic characteristics between the isolated strain andreference strains.Fil: Moré, Gastón Andrés. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Rambead, M.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; ArgentinaFil: Braun, F.. No especifíca;Fil: Campero, Lucía María. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Walkosksi, A.. No especifíca;Fil: Venturini, M. C.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Departamento de Epizootiología y Salud Pública. Laboratorio de Inmunoparasitología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina10th International Equine Infectious Diseases ConferenceCiudad Autónoma de Buenos AiresArgentinathe Equine Infectious Disease Conferenc