Formation and Persistence of Brine on Mars: Experimental Simulations throughout the Diurnal Cycle at the Phoenix Landing Site

In the last few years, water ice and salts capable of melting this ice and producing liquid saline water (brine) have been detected on Mars. Moreover, indirect evidence for brine has been found in multiple areas of the planet. Here, we simulate full diurnal cycles of temperature and atmospheric water vapor content at the Phoenix landing site for the first time and show experimentally that, in spite of the low Mars-like chamber temperature, brine forms minutes after the ground temperature exceeds the eutectic temperature of salts in contact with water ice. Moreover, we show that the brine stays liquid for most of the diurnal cycle when enough water ice is available to compensate for evaporation. This is predicted to occur seasonally in areas of the polar region where the temperature exceeds the eutectic value and frost or snow is deposited on saline soils, or where water ice and salts coexist in the shallow subsurface. This is important because the existence of liquid water is a key requirement for habitability. Key Words: Mars?Ice?Perchlorates?Brine?Water?Raman spectroscopy. Astrobiology 16, 937?948.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140311/1/ast.2016.1525.pd

Continuous Transmission of Spatially Coupled LDPC Code Chains

We propose a novel encoding/transmission scheme called continuous chain (CC) transmission that is able to improve the finite-length performance of a system using spatially coupled low-density parity-check (SC-LDPC) codes. In CC transmission, instead of transmitting a sequence of independent code words from a terminated SC-LDPC code chain, we connect multiple chains in a layered format, where encoding, transmission, and decoding are performed in a continuous fashion. The connections between chains are created at specific points, chosen to improve the finite-length performance of the code structure under iterative decoding. We describe the design of CC schemes for different SC-LDPC code ensembles constructed from protographs: a (J,K) -regular SC-LDPC code chain, a spatially coupled repeat-accumulate (SC-RA) code, and a spatially coupled accumulate-repeat-jagged-accumulate (SC-ARJA) code. In all cases, significant performance improvements are reported and it is shown that using CC transmission only requires a small increase in decoding complexity and decoding delay with respect to a system employing a single SC-LDPC code chain for transmission.This material is based upon work supported in part by the National Science Foundation under Grant Nos. CCF-1161754 and CCSS-1710920, in part by NSERC Canada, and in part by the Spanish Ministry of Economy and Competitiveness and the Spanish National Research Agency under grants TEC2016-78434-C3-3-R (AEI/FEDER, EU) and Juan de la Cierva Fellowship IJCI-2014-19150

Epidemiología de los nematodes gastrointestinales en caprinos lecheros en los valles templados del NOA, Argentina

Con el fin de estudiar la epidemiología y los efectos de los nematodes gastrointestinales (NGI) sobre cabras en ordeño en predios bajo riego en el Valle de Lerma (Salta), se monitoreó la infestación parasitaria en 41 cabras naturalmente infestadas por NGI, desde el 4 de octubre de 2010 hasta el 26 de mayo de 2011. Se evaluaron dos grupos de cabras en ordeño: PJ (n=17) paridas en junio y PS (n=24) paridas en septiembre. Sólo se desparasitaron de urgencia aquellos animales que superaran los 3000 de hpg o y que presentaran signos de parasitosis

Spatially coupled generalized LDPC codes: asymptotic analysis and finite length scaling

Generalized low-density parity-check (GLDPC) codes are a class of LDPC codes in which the standard single parity check (SPC) constraints are replaced by constraints defined by a linear block code. These stronger constraints typically result in improved error floor performance, due to better minimum distance and trapping set properties, at a cost of some increased decoding complexity. In this paper, we study spatially coupled generalized low-density parity-check (SC-GLDPC) codes and present a comprehensive analysis of these codes, including: (1) an iterative decoding threshold analysis of SC-GLDPC code ensembles demonstrating capacity approaching thresholds via the threshold saturation effect; (2) an asymptotic analysis of the minimum distance and free distance properties of SC-GLDPC code ensembles, demonstrating that the ensembles are asymptotically good; and (3) an analysis of the finite-length scaling behavior of both GLDPC block codes and SC-GLDPC codes based on a peeling decoder (PD) operating on a binary erasure channel (BEC). Results are compared to GLDPC block codes, and the advantages and disadvantages of SC-GLDPC codes are discussed.This work was supported in part by the National Science Foundation under Grant ECCS-1710920, Grant OIA-1757207, and Grant HRD-1914635; in part by the European Research Council (ERC) through the European Union's Horizon 2020 research and innovation program under Grant 714161; and in part by the Spanish Ministry of Science, Innovation and University under Grant TEC2016-78434-C3-3-R (AEI/FEDER, EU)

A generalization of the Heine--Stieltjes theorem

We extend the Heine-Stieltjes Theorem to concern all (non-degenerate) differential operators preserving the property of having only real zeros. This solves a conjecture of B. Shapiro. The new methods developed are used to describe intricate interlacing relations between the zeros of different pairs of solutions. This extends recent results of Bourget, McMillen and Vargas for the Heun equation and answers their question on how to generalize their results to higher degrees. Many of the results are new even for the classical case.Comment: 12 pages, typos corrected and refined the interlacing theorem

Impacto de la atención ambulatoria del primer nivel de atención en la hospitalización de población asegurada con diabetes mellitus tipo 2

ObjetivoDeterminar el impacto de atención ambulatoria del primer nivel de atención en la hospitalización del diabético tipo 2 en una población con condiciones iguales de aseguramiento.DiseñoEstudio de casos y controles. Los casos son pacientes diabéticos hospitalizados por enfermedad relacionada con el padecimiento, y los controles son pacientes diabéticos sin antecedente de hospitalización en el último año.EmplazamientoCentros de atención primaria urbanos.ParticipantesLos casos fueron seleccionados consecutivamente en 4 de 5 hospitales generales urbanos (n=123). Los controles fueron elegidos al azar en la unidad de atención primaria de donde provenía el caso (n=135). Se excluyó a las mujeres con diabetes gestacional y a todos los que no contaban con expediente localizable (aproximadamente un 15%).MedicionesSe construyó un índice de atención primaria según las recomendaciones de la Asociación de Médicos Norteamericanos, la Comisión Conjunta de Acreditación de Organizaciones de Salud, el Comité Nacional de Aseguramiento para la Calidad, la Asociación Norteamericana de Diabetes y la Norma Oficial Mexicana. Se consideró que un cumplimiento menor al 60% correspondía a una atención subóptima.ResultadosLos factores de riesgo para la hospitalización fueron los siguientes: menos de 2 vistas al médico de familia en el último año (OR ajustada, 16,2; IC del 95%, 1,5–174,2), valor de glucosa (OR ajustada, 1,006; IC del 95%, 1,002–1,010) y nivel de conocimientos sobre la enfermedad (OR ajustada, 0,98; IC del 95%, 0,96–0,99), además de la práctica de ejercicio y el tiempo de diagnóstico. La atención primaria subóptima se registró en el 65,3% de los casos y el 49,1% de los controles (p=0,03) e incrementó 2,5 veces el riesgo de hospitalización (IC del 95%, 1,2–5,0; seudo R2=0,279; p < 0,001).ConclusionesLa evidencia disponible indica que la atención primaria puede ser un factor potencial para reducir la tasa de hospitalización por diabetes mellitus tipo 2. Los programas de manejo efectivos contribuirían a evitar hospitalizaciones innecesarias.ObjectiveTo determine the impact of primary care on hospitalization of type 2 diabetics with equal conditions of health insurance.DesignA case-control study. Case=diabetic hospitalized by a disease related condition. Control=diabetic without hospitalization during the last 12 months.SettingUrban primary care centers.ParticipantsCases were consecutively selected from four out of five urban hospitals (n=123). Controls were chosen at random from primary care units matched by primary care source (n=135).Women with gestational diabetes were excluded as well as individuals with missing medical charts (approximately 15%).MeasurementsA primary care index was constructed with process and outcome indicators recommended by the American Medical Association, the Joint Commission on Accreditation of Healthcare Organizations, the National Committee for Quality Assurance, the American Diabetes Association and the Official Mexican Standards. Compliance to less than 60% of recommendations was considered unsatisfactory primary care.ResultsThe following were hospitalization risk factors: less than 2 visits to family physician during the last year (OR adjusted, 16,2; 95% CI, 1,5–174,2), glucose level (OR adjusted, 1,006; 95% CI, 1,002–1,010) and cognitive level (OR adjusted, 0,98; 95% CI, 0,96–0,99), in addition to exercising and year of diagnosis. Sixty-five percent of cases observed unsatisfactory primary care compared with 49,1% of controls (P=0,03). Unsatisfactory primary care increased 2,5 times the risk of hospitalization (95% CI, 1,2–5,0) (pseudo R2=0,279; P<0,001).ConclusionsPrimary care is a potential factor for reducing hospitalization of type 2 diabetics. Effective primary care programs would contribute to a better disease control and less unnecessary hospitalizations

FCNC Top Quark Decays in Extra Dimensions

The flavor changing neutral top quark decay t -> c X is computed, where X is a neutral standard model particle, in a extended model with a single extra dimension. The cases for the photon, X= \gamma$, and a Standard Model Higgs boson, X = H, are analyzed in detail in a non-linear$R_\xi gauge. We find that the branching ratios can be enhanced by the dynamics originated in the extra dimension. In the limit where 1/R >> ->, we have found Br(t -> c \gamma) \simeq 10^{-10} for 1/R = 0.5 TeV. For the decay t -> c H, we have found Br(t -> cH) \simeq 10^{-10} for a low Higgs mass value. The branching ratios go to zero when 1/R -> \infty.Comment: Accepted to be published in the Europ. Phys. Jour. C; 16 pages, 2 figure

The role of ν\nu-induced reactions on lead and iron in neutrino detectors

We have calculated cross sections and branching ratios for neutrino induced reactions on ^{208}Pb and ^{56}Fe for various supernova and accelerator-relevant neutrino spectra. This was motivated by the facts that lead and iron will be used on one hand as target materials in future neutrino detectors, on the other hand have been and are still used as shielding materials in accelerator-based experiments. In particular we study the inclusive ^{56}$Fe(\nu_e,e^-)$^{56}Co and ^{208}$Pb(\nu_e,e^-)$^{208}Bi cross sections and calculate the neutron energy spectra following the decay of the daughter nuclei. These reactions give a potential background signal in the KARMEN and LSND experiment and are discussed as a detection scheme for supernova neutrinos in the proposed OMNIS and LAND detectors. We also study the neutron-emission following the neutrino-induced neutral-current excitation of ^{56}Fe and ^{208}Pb.Comment: 23 pages (including 7 figures

Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes

A chromosphere is a universal attribute of stars of spectral type later than ~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This chapter provides a review of the observational requirements and theoretical approaches for modeling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma heating and wind acceleration, and discusses the challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript; accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake (Berlin: Springer