ISS and TPD study of the adsorption and interaction of CO and H2 on polycrystalline Pt

The adsorption and interaction of CO and H2 on polycrystalline Pt has been studied using ion scattering spectroscopy (ISS) and temperature programmed desorption (TPD). The ISS results indicate that the initial CO adsorption on Pt takes place very rapidly and saturates the Pt surface with coverage close to a monolayer. ISS also shows that the CO molecules adsorb at an angular orientation from the surface normal and perhaps parallel to the surface. A TPD spectrum obtained after coadsorbing C-12 O-16 and C-13 O-18 on Pt shows no isotopic mixing, which is indicative of molecular CO adsorption. TPD spectra obtained after coadsorbing H2 and CO on polycrystalline Pt provides evidence for the formation of a CO-H surface species

La categoría ambiental en el paradigma del desarrollo sustentable, la visión de la ciencia económica

Tlatemoani, Revista Académica de Investigación. Año 7. Número 21. Abril 2016. Pp. 124-139. ISSN. 19899300. http://www.eumed.net/rev/tlatemoani/21/index.htmCon el proceso de expansión social, se asumió que el ambiente ofrecía todos los recursos necesarios, y que el ser humano debía controlarla y manipularla, provocando un rompimiento en el paradigma vigente, marcando así el paso del mundo mítico al universo racional y al mundo clásico, surgiendo y consolidando el racional empirista. A partir de ello, se desarrollaron diferentes concepciones y múltiples interpretaciones sobre la importancia y papel del ambiente en la sociedad y en la propia economía, imponiéndose una visión utilitarista, quedando atrás los miedos ante el entorno, convirtiéndolo en una canasta de recursos que pueden ser extraídos y utilizados. Desde esta perspectiva, los componentes del medio fueron considerados como recursos con valor nominal directo e indirecto que influyen en el bienestar social y económico de los territorios. La conceptualización del desarrollo en esta transición paradigmática ha sido correlato de la modernidad, pues los supuestos epistemológicos dominantes impedían aprehender la realidad social en su complejidad, por lo que el desarrollo devino en sinónimo de crecimiento económico al cual podía accederse de manera lineal desde la sociedad tradicional agrícola a la sociedad industrial, subestimando los factores sociales, políticos, culturales e históricos involucrados estructuralmente en dicho desarrollo. Todo ello asociado a un particular modo de interacción del hombre con la naturaleza y consigo mismo, emanado del comentado discurrir de la civilización occidental que abrió los horizontes del capitalismo, la ciencia, la técnica y la conducta humana individual y social. La incorporación del ambiente a la concepción del desarrollo es visto no sólo como un proceso histórico, de carácter continuo e integral, sino como un entorno de igualdad de oportunidades y justicia que permite una plena valorización de la dignidad humana, esto es, un proceso de cambio dirigido al logro de los objetivos específicos cuya dirección y velocidad constituyen puntos de controversia en los planos económico, político, social, ambiental, tecnológico y territorial, asociado a procesos y cuestiones de crecimiento de la producción, el progreso técnico, la distribución del poder, del ingreso, de oportunidades individuales y colectivas; la preservación de los recursos y del medio ambiente en general, así como de la organización territorial de la sociedad, donde está implícito la imagen del futuro deseado, en el que generalmente predomina la visión de bienestar y justicia social. El punto de partida de lo que ahora se concibe como desarrollo sustentable fue el medio humano, donde se integraron los aspectos económicos y sociales con la dimensión ambiental, ya que es una forma de explicar el funcionamiento de los mercados, el crecimiento económico y el desarrollo de la sociedad. Con esta relación tripartida, se empezó a teorizar al ambiente, explicando su importancia e influencia en los niveles de progreso económico. El desarrollo sustentable, busca minimizar los efectos y externalidades negativas hacia los recursos de los cuales se nutre, interesándose al contrario en proteger su entorno ecológico, económico y social, ya que la sustentabilidad no es simplemente un asunto del ambiente, de justicia y de desarrollo, sino más bien de la gente y de sobrevivencia como individuos y culturas, por ello debe verse no sólo como un paradigma contemporáneo sino un objetivo alcanzable en el tiempo en las diferentes escalas territoriales. En esta contribución se enfatiza la concepción e importancia que algunas doctrinas económicas le atribuyeron al ambiente, no sólo como factor determinante de los ritmos de crecimiento y desarrollo humano, sino como generador de recientes paradigmas teóricos como el desarrollo sustentable. La gran diversidad de las posturas teóricas, a pesar de mostrar algunas discrepancias interpretativas, hay coincidencias en la importancia del ambiente para determinar el desenvolvimiento del entorno

Feasibility Study of Slotted, Natural-Laminar-Flow Airfoils for High-Lift Applications

A computational fluid dynamics approach to evaluate the feasibility of a slotted, natural-laminar-flow airfoil designed for transonic applications, to perform as a high-lift system was developed. Reynolds-Averaged Navier-Stokes equations with a laminar-turbulent transition model for subsonic flow at representative flight conditions were used for this analysis. Baseline high-lift simulations were performed to understand the stall characteristics of the slotted, natural-laminar-flow airfoil. Maximum aerodynamic efficiency was observed with a constant slot-width. In addition, the effectiveness of the aft-element as a high-lift device was explored. Results indicate that a micro-flap is a viable option as a lift effector. These are most effective when combined with a Fowler-like motion. However, the maximum lift coefficient was limited, in part, by an early leading-edge stall largely due to the small nose radius required for supporting laminar flow. As a result, a drooped leading edge was added to the S207, the latest evolution of slotted, natural-laminar-flow airfoil technology. Morphing technology was also applied to mitigate abrupt wing-stall characteristics and further increase maximum lift. The use of morphing technology was observed to produce superior high-lift performance over hinged leading edge flap motions. However, off-body separation and narrow stall region in lift curves were observed for the S207\u27s high-lift system due to the aft-element position. The aft-element position was based on a previous study for the S204, a placeholder airfoil. Hence, an S207 aft-element optimized for high-lift was identified as the natural next step. A low-fidelity, slot-width sensitivity study was performed with the S207\u27s aft element in the form of a 9-point study. The focus of this study was to identify sensitivities of the slotted, natural-laminar-flow high-lift system to aft-element position variability. Three positioning boundaries were selected in reference to the stowed aft element and the gap between elements. Results show that the S207\u27s flap schedule should be dependent on the flap deflection angle and exit slot-width gap. Finally, a delayed-detached-eddy simulation was performed to improve confidence in the developed methodology. Strong agreement between RANS and DDES results was observed. These findings contribute novel knowledge to the state-of-the-art understanding of the revolutionary slotted, natural-laminar-flow airfoil technology

Studies on the Radical Enzymes Glutamate Mutase and Viperin.

Adenosylcobalamin (coenzyme B12) serves as a source of organic radicals that are generated by homolytic scission of the cobalt-carbon bond to form cob(II)alamin and a highly reactive 5'-deoxyadenosyl radical, which then catalyzes a variety of unusual rearrangement reactions. The mechanism by which adenosylcobalamin-dependent enzymes accelerate cobalt-carbon bond homolysis by approximately one trillion-fold remains unclear. To gain molecular-level insight into this process for glutamate mutase, detailed kinetic analysis was combined with molecular dynamics simulations to examine a series of active site point mutations. These mutations cause a progressive increase in the mean distance between the 5'-carbon of the adenosyl radical and the substrate's abstractable hydrogen. This distance (determined computationally) was found to inversely correlate with the logk of tritium exchange between the coenzyme and the substrate (determined experimentally). The enzymatic homolysis of adenosylcobalamin may also be susceptible to external magnetic fields. A magnetic field can modulate the rate at which the initially formed singlet radical pair (which can recombine to reform the Co-C bond) converts to the triplet state (which cannot recombine). Magnetic field effect studies on glutamate mutase suggest that the 5'-deoxyadenosyl radical produced by homolysis is rapidly siphoned off by reaction with the substrate. This is consistent with the idea that the coupling of Co-C homolysis to hydrogen abstraction contributes to the acceleration of Co-C bond homolysis observed in adenosylcobalamin-dependent enzymes. Similar to adenosylcobalamin enzymes, radical SAM enzymes use an enzyme-bound [4Fe-4S] cluster to reductively cleave S-adenosyl-L-methionine (SAM) and generate a 5'-deoxyadenosyl radical that is then used to catalyze chemically-difficult transformations. Viperin, a newly identified radical SAM enzyme, is an interferon-stimulated gene that directs antiviral activity against a number of pathogens that infect eukaryotic cells. To gain insight into the mechanism by which viperin regulates viral replication, its interaction with farnesyl pyrophosphate synthase (the best-established target of viperin) was studied to elucidate the novel role radical SAM chemistry plays in the innate immune response. This study provides preliminary data that suggests viperin reduces cellular levels of farnesyl pyrophosphate synthase by approximately 50 percent.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111388/1/gdroman_1.pd

Search for New Physics in Rare Top Decays: ttˉt \bar t Spin Correlations and Other Observables

In this paper we study new-physics contributions to the top-quark decay $t \to b \bar b c$. We search for ways of detecting such new physics via measurements at the LHC. As top quarks are mainly produced at the LHC in $t \bar t$ production via gluon fusion, we analyze the process $gg \to t \bar t \to (b \bar b c) (\bar b \ell \bar \nu)$. We find six observables that can be used to reveal the presence of new physics in $t \to b \bar b c$. Three are invariant mass-squared distributions involving two of the final-state particles in the top decay, and three are angular correlations between the final-state quarks coming from the $t$ decay and the $\ell^-$ coming from the $\bar t$ decay. The angular correlations are related to the $t \bar t$ spin correlation.Comment: Published versio

Decreased Specific Star Formation Rates in AGN Host Galaxies

We investigate the location of an ultra-hard X-ray selected sample of AGN from the Swift Burst Alert Telescope (BAT) catalog with respect to the main sequence (MS) of star-forming galaxies using Herschel-based measurements of the star formation rate (SFR) and stellar mass (\mstar) from Sloan Digital Sky Survey (SDSS) photometry where the AGN contribution has been carefully removed. We construct the MS with galaxies from the Herschel Reference Survey and Herschel Stripe 82 Survey using the exact same methods to measure the SFR and \mstar{} as the Swift/BAT AGN. We find a large fraction of the Swift/BAT AGN lie below the MS indicating decreased specific SFR (sSFR) compared to non-AGN galaxies. The Swift/BAT AGN are then compared to a high-mass galaxy sample (COLD GASS), where we find a similarity between the AGN in COLD GASS and the Swift/BAT AGN. Both samples of AGN lie firmly between star-forming galaxies on the MS and quiescent galaxies far below the MS. However, we find no relationship between the X-ray luminosity and distance from the MS. While the morphological distribution of the BAT AGN is more similar to star-forming galaxies, the sSFR of each morphology is more similar to the COLD GASS AGN. The merger fraction in the BAT AGN is much higher than the COLD GASS AGN and star-forming galaxies and is related to distance from the MS. These results support a model in which bright AGN tend to be in high mass star-forming galaxies in the process of quenching which eventually starves the supermassive black hole itself.Comment: 23 pages, 14 figures, Accepted for publication in MNRAS 2015 June 23. In original form 2015 January 2

Measuring CP-Violating Observables in Rare Top Decays at the LHC

In this paper we consider CP-violating new-physics contributions to the decay $t \to b \bar b c$. We examine the prospects for detecting such new physics at the LHC, which requires studying the process $gg \to t (\to b \bar b c) \bar t (\to \bar b \ell \bar \nu)$. We find two observables that can be used to reveal the presence of CP-violating new physics in $t \to b \bar b c$. They are (i) the partial-rate asymmetry and (ii) the triple-product correlations involving the momenta of various particles associated with the interaction. A Monte Carlo analysis is performed to determine how well these observables can be used to detect the presence of new physics, and to measure its parameters. We find that there is little difficulty in extracting the value of the relevant new-physics parameter from the partial-rate asymmetry. For the triple-product correlations, we test multiple strategies that can be used for the extraction of the corresponding combination of new-physics parameters.Comment: Published versio

Cold Stowage Flight Systems

The International Space Station (ISS) provides a test bed for researchers to perform science experiments in a variety of fields, including human research, life sciences, and space medicine. Many of the experiments being conducted today require science samples to be stored and transported in a temperature controlled environment. NASA provides several systems which aid researchers in preserving their science. On orbit systems provided by NASA include the Minus Eighty Laboratory freezer for ISS (MELFI), Microgravity Experiment Research Locker Incubator (MERLIN), and Glacier. These freezers use different technologies to provide rapid cooling and cold stowage at different temperature levels on board ISS. Systems available to researchers during transportation to and from ISS are MERLIN, Glacier, and Coldbag. Coldbag is a passive cold stowage system that uses phase change materials to maintain temperature. Details of these current technologies are provided along with operational experience gained to date. This paper discusses the capability of the current cold stowage hardware and how it may continue to support NASA s mission on ISS and in future exploration missions

Percepções e crenças dos alunos de ILE sobre a avaliação em sala de aula em uma universidade colombian

The higher education institution, where the present study is conducted, proposes in its school handbook that a formative and democratic learning assessment approach should prevail in all academic activities. In the English as a Foreign Language TeacherEducation Program at this university, eighty percent of students’ grades come from summative testing, and the teachers are the ones who regularly make the decisions regarding any assessment criteria. That is, the formative and democratic componentsare not present in the process. To delve deeper into these aspects, we have inquired students on their perceptions and beliefs concerning classroom assessment and suggestions to improve the process. A small-scale qualitative research study wasconducted with 49 participants. The data collected through questionnaires, focus-group interviews, and narratives allowed us to organize the findings according to three emerging categories: students’ perceptions of assessment as Assessment of Learning (aol), Assessment for Learning (afl), and suggestions for improving the overall language evaluation process. The different concepts provided by the participants go from believing that classroom evaluation constitutes a procedure to elicit rote reproduction to that of perceiving it as an opportunity to enhance students’ formation. Actions for improving assessment go from particular procedural aspects to those related to a more general approach.  Las Instituciones de Educación Superior, objeto del presente artículo de investigación, propone que en todas las actividades académicas prevalece un enfoque de evaluación formativo y democrático, tal como se estipula en el manual de convivencia. En el caso del Programa de Licenciatura en Lengua Extranjera de esta universidad, el ochenta por ciento de las notas de los estudiantes proviene de evaluaciones sumativas y los docentes son quienes normalmente toman las decisiones relacionadas con procesos evaluativos; es decir, los componentes formativos y democráticos no parecen estar presentes en el proceso. Para revisar un poco más en profundidad estos aspectos, decidimos preguntarles a los estudiantes sobre sus percepciones y creencias acerca de la evaluación implementada, donde nos ofrecieron sugerencias que permitan cualificar el proceso. De esta forma, se desarrolló un estudio cualitativo a pequeña escala con 49 estudiantes, donde los datos fueron recopilados a través de cuestionarios, entrevistas focales y narrativas, herramientas que permitieron organizar los resultados en tres categorías emergentes: percepciones de los estudiantes sobre evaluación del aprendizaje (AOL, por sus siglas en inglés), sobre evaluación para el aprendizaje (afl, por sus siglas en inglés) y sugerencias para mejorar el proceso de evaluación. Los diferentes conceptos proporcionados por los participantes van desde la concepción de evaluación como un procedimiento que suscita la reproducción memorística hasta la percepción de este proceso como una oportunidad para fortalecer la formación de los estudiantes. Finalmente, las acciones para mejorar el proceso evaluativo van desde aspectos procedimentales particulares hasta aquellos relacionados con un enfoque de evaluación más general.  A instituição de ensino superior, na qual o presente estudo é desenvolvido, propõe em seu manual escolar que a abordagem formativa e democrática de avaliação da aprendizagem deve prevalecer em todas as atividades acadêmicas. No Programade Formação de Professores de Inglês como Língua Estrangeira desta universidade, oitenta por cento das notas dos alunos vêm de testes somativos e os professores são os que regularmente tomam as decisões sobre os critérios de avaliação. Ou seja, os componentes formativo e democrático não estão aparentemente presentes no processo. Para aprofundar esses aspectos, questionamos os alunos sobre suas percepções e crenças em relação à avaliação em sala de aula e sugestões para melhorar o processo. Uma pesquisa qualitativa de pequena escala foi conduzida com 49 participantes. Os dados coletados por meio de questionários, entrevistas de grupos focais e narrativas nos permitiram organizar os resultados segundo três categorias emergentes: as percepções dos alunos sobre a avaliação como Avaliação da aprendizagem, Avaliação para aaprendizagem e sugestões para melhorar processo geral de avaliação da linguagem. Os diferentes conceitos fornecidos pelos participantes vão desde acreditar que a avaliação em sala de aula constitui um procedimento para eliciar a reprodução mecânica até percebê-la como uma oportunidade para potencializar a formação dos alunos. As ações para melhorar a avaliação vão desde aspectos processuais particulares até aqueles relacionados a uma abordagem mais geral

Elliptical Galaxy in the Making: The Dual Active Galactic Nuclei and Metal-enriched Halo of Mrk 273

A systematic analysis of the X-ray emission from the nearby ultraluminous infrared galaxy Mrk 273 was carried out by combining new 200 ksec Chandra data with archived 44 ksec data. The active galactic nucleus (AGN) associated with the Southwest nucleus is confirmed by the new data, and a secondary hard X-ray (4-8 keV) point source is detected, coincident with the Northeast nucleus at a projected distance of 0.75 kpc from the Southwest nucleus. The hard X-ray spectrum of the Northeast nucleus is consistent with a heavily absorbed AGN, making Mrk 273 another example of a dual AGN in a nearby galaxy merger. Significant 1-3 keV emission is found along the ionization cones and outflowing gas detected in a previous study. The data also map the giant X-ray nebula south of the host galaxy with unprecedented detail. This nebula extends on a scale of $\sim$ 40 kpc $\times$ 40 kpc, and is not closely related to the well-known tidal tail seen in the optical. The X-ray emission of the nebula is best described by a single-temperature gas model, with a temperature of $\sim$ 7 million K and a super-solar $\alpha$/Fe ratio. Further analysis suggests that the southern nebula has most likely been heated and enriched by multiple galactic outflows generated by the AGN and/or circumnuclear starburst in the past, on a time scale of $\lesssim$0.1 Gyr, similar to the merger event itself.Comment: 25 pages, 22 figures, 4 tables, accepted for publication in the Astrophysical Journa