Hardware Design Improvements to the Major Constituent Analyzer

The Major Constituent Analyzer (MCA) onboard the International Space Station (ISS) is designed to monitor the major constituents of the ISS's internal atmosphere. This mass spectrometer based system is an integral part of the Environmental Control and Life Support System (ECLSS) and is a primary tool for the management of ISS atmosphere composition. As a part of NASA Change Request CR10773A, several alterations to the hardware have been made to accommodate improved MCA logistics. First, the ORU 08 verification gas assembly has been modified to allow the verification gas cylinder to be installed on orbit. The verification gas is an essential MCA consumable that requires periodic replenishment. Designing the cylinder for subassembly transport reduces the size and weight of the maintained item for launch. The redesign of the ORU 08 assembly includes a redesigned housing, cylinder mounting apparatus, and pneumatic connection. The second hardware change is a redesigned wiring harness for the ORU 02 analyzer. The ORU 02 electrical connector interface was damaged in a previous on-orbit installation, and this necessitated the development of a temporary fix while a more permanent solution was developed. The new wiring harness design includes flexible cable as well as indexing fasteners and guide-pins, and provides better accessibility during the on-orbit maintenance operation. This presentation will describe the hardware improvements being implemented for MCA as well as the expected improvement to logistics and maintenance

Aeromonas IN CHILDREN LESS THAN 5 YEAR-OLD WITH ACUTE DIARRHEA

OBJETIVO: Determinar la importancia de Aeromonas como agente diarreogénico en niños meno- res de 5 años, así como comparar su frecuencia con la de otros enteropatógenos. MATERIAL Y MÉTODOS: Entre 1998 y 1999, se tomó 285 muestras de heces de niños con diarrea aguda, en 5 Centros Hospitalarios, las que fueron enviadas al Instituto de Medicina Tropical Daniel A. Carrión en el medio de transporte Cary Blair, para su procesamiento e identificación de Aeromonas por el método Aerokey II. RESULTADOS: Aeromonas fue la bacteria más aislada entre los enteropatógenos, sobre todo en niños menores de 2 años y en verano, y la Aeromonas caviae fue la especie más frecuente. Aeromonas fue aislada en la mayoría de los casos del agar TCBS, por lo que empleamos discos de O/129 para diferenciarla de Vibrio cholerae. Todas las Aeromonas fueron sensibles in vitro a furazolidona y neomicina. CONCLUSIONES: Aeromonas fue el prin- cipal agente etiológico de la diarrea aguda acuosa, en niños menores de 5 años.OBJECTIVE: To determine Aeromonas importance as diarrhea agent in children less than 5 year- old and compare its frequency with other enteropathogens. MATERIAL AND METHODS: Between 1998 and 1999 285 fecal samples were taken from children with acute diarrhea in 5 hospitals, which were then sent to Daniel A. Carrión Institute of Tropical Medicine in Cary Blairs transportation medium for processing by Aerokey II method. RESULTS: Aeromonas was the most frequent bacteria isolated among enteropathogens, mainly in children less than 2-year old and in summer, and Aeromonas caviae was the most frequent species. Aeromonas was mainly isolated in agar TCBS, employing O/129 disks to differentiate it from Vibrio cholerae. All Aeromonas were sensitive in vitro to furazolidone and neomycin. CONCLUSIONS: Aeromonas was the main etiological agent of aquous acute diarrhea in children less than 5 year-old

Transiciones, conflictos y democracia : estudios de coyuntura

México ha vivido un largo proceso de transición que ha desencadenado dinamismos económicos, culturales y políticos. En la actual coyuntura, estos dinamismos muestran toda su complejidad, su inevitable articulación y la tensión entre las fuerzas que intentan sostener un viejo modelo de gobernar y decidir el rumbo del país, y aquellas que buscan abrirse a un espectro mucho más amplio y diversificado de actores. En ellos se conjuntan las aspiraciones más legítimas de los mexicanos por avanzar en el reconocimiento y respeto de la pluralidad étnica, de género y entre generaciones, y por impulsar una dinámica en la que —en medio de los procesos de mundialización— los distintos grupos e intereses de los mexicanos puedan ser incluidos. La transición mexicana tiende a centrarse en la dimensión política. La intensidad que cobran los procesos políticos y el énfasis que importantes analistas ponen en dichos procesos, contribuyen a que esta asociación vaya cobrandoíuerza. En este sentido, es necesario advertir que en las transiciones la tendencia privatizadora, la reducción del gasto social, así como la necesidad de pactos sociales que sean respetados, la participación creciente de la sociedad civil, etc. son factores importantes que, en medio de contradicciones, van generando nuevos esquemas de relación entre gobierno y sociedad.ITESO, A.C

Structure of NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 glasses and glass-ceramics

The crystallization of iron-containing sodium silicate phases holds particular importance, both in the management high-level nuclear wastes and in geosciences. Here, we study three asquenched glasses and their heat-treated chemical analogues, NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 (with nominal stoichiometries from feldspathoid, pyroxene, and feldspar mineral groups – i.e., Si/Fe = 1, 2, and 3 respectively) – using a variety of techniques. Phase analyses revealed that as-quenched NaFeSiO4 cannot accommodate all Fe in the glass phase (some Fe crystallizes as Fe3O4), whereas as-quenched NaFeSi2O6 and NaFeSi3O8 form amorphous glasses upon quenching. NaFeSi2O6 glass is the only composition that crystallizes into its respective isochemical crystalline polymorph, i.e. aegirine, upon isothermal heat-treatment. As revealed by Mössbauer spectroscopy, iron is predominantly present as 4-coordinated Fe3+ in all glasses, though it is present as 6-coordinated Fe3+ in the aegirine crystals (NaFeSi2O6), as expected from crystallography. Thus, Fe can form the crystalline phases in which it is octahedrally coordinated, even though it is mostly tetrahedrally coordinated in the parent glasses. Thermal behavior, magnetic properties, iron redox state (including Fe K-edge X-ray absorption), and vibrational properties (Raman spectra) of the above compositions are discussed

Laccase Production from <i>Agrocybe pediades</i>: Purification and Functional Characterization of a Consistent Laccase Isoenzyme in Liquid Culture

Laccases are valuable enzymes as an excellent ecological alternative for bioremediation issues because they can oxidize persistent xenobiotic compounds. The production and characterization of extracellular laccases from saprotrophic fungi from disturbed environments have been scarcely explored, even though this could diversify their functional characteristics and expand the conditions in which they carry out their catalysis. Agrocybe pediades, isolated from a disturbed forest, produces an extracellular laccase in liquid culture. The enzyme was purified, identified and characterized. Copper and hexachlorobenzene do not function as inducers for the laccase produced. Partial amino acid sequences were obtained by LC-MS/MS that share similarity with laccases from other fungi. Purified laccase is a monomer with a molecular mass between 55–60 kDa and had an optimum activity at pH 5.0 and the optimum temperature at 45 °C using 2,6-dimethoxyphenol (2,6-DMP) as substrate. The Km and Vmax also determined with 2,6-DMP were 100 μM and 285 μmol∙min−1∙mg−1, respectively, showing that the laccase of A. pediades has a higher affinity for this substrate than that of other Agaricales. These features could provide a potential catalyst for different toxic substrates and in the future laccase could be used in environmental recovery processes