40 research outputs found

    Streamer propagation in humid air

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    We investigate the effect of humidity on the propagation of streamers in air. We present a minimal set of chemical reactions that takes into account the presence of water in a nonthermal air plasma and considers ionization, attachment, detachment, recombination and ion conversion including water cluster formation. We find differences in streamer propagation between dry and humid air that we attribute mostly to an enhanced effective attachment rate in humid air, leading to higher breakdown electric field and threshold field for propagation. This higher effective attachment rate in humid conditions leads to a faster decay of the conductivity in the streamer channel, which hinders the accumulation of charge in the streamer head. In some cases a propagating streamer solution still exists at the expense of a smaller radius and lower velocity. In other cases a high humidity leads to the stagnation of the streamer. We finally discuss how all these statements may affect streamer branching and the dimensions and lifetime of a streamer corona

    On the emergence mechanism of carrot sprites

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    We investigate the launch of negative upward streamers from sprite glows. This phenomenon is readily observed in high‐speed observations of sprites and underlies the classification of sprites into carrot or column types. First, we describe how an attachment instability leads to a sharply defined region in the upper part of the streamer channel. This region has an enhanced electric field, low conductivity and strongly emits in the first positive system of molecular nitrogen. We identify it as the sprite glow. We then show how, in the most common configuration of a carrot sprite, several upward streamers emerge close to the lower boundary of the glow, where negative charge gets trapped and the lateral electric field is high enough. These streamers cut off the current flowing toward the glow and lead to the optical deactivation of the glow above. Finally, we discuss how our results naturally explain angel sprites

    A plasma fatty acid profile associated to type 2 diabetes development: from the CORDIOPREV study

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    Purpose: The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide. For this reason, it is essential to identify biomarkers for the early detection of T2DM risk and/or for a better prognosis of T2DM. We aimed to identify a plasma fatty acid (FA) profile associated with T2DM development. Methods: We included 462 coronary heart disease patients from the CORDIOPREV study without T2DM at baseline. Of these, 107 patients developed T2DM according to the American Diabetes Association (ADA) diagnosis criteria after a median follow-up of 60 months. We performed a random classification of patients in a training set, used to build a FA Score, and a Validation set, in which we tested the FA Score. Results: FA selection with the highest prediction power was performed by random survival forest in the Training set, which yielded 4 out of the 24 FA: myristic, petroselinic, α-linolenic and arachidonic acids. We built a FA Score with the selected FA and observed that patients with a higher score presented a greater risk of T2DM development, with an HR of 3.15 (95% CI 2.04–3.37) in the Training set, and an HR of 2.14 (95% CI 1.50–2.84) in the Validation set, per standard deviation (SD) increase. Moreover, patients with a higher FA Score presented lower insulin sensitivity and higher hepatic insulin resistance (p < 0.05). Conclusión: Our results suggest that a detrimental FA plasma profile precedes the development of T2DM in patients with coronary heart disease, and that this FA profile can, therefore, be used as a predictive biomarker

    Effectiveness of rosuvastatin plus colchicine, emtricitabine/tenofovir and combinations thereof in hospitalized patients with COVID-19 : a pragmatic, open-label randomized trial

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    Q1Q1The use of rosuvastatin plus colchicine and emtricitabine/tenofovir in hospitalized patients with SARS- CoV-2 disease (COVID-19) has not been assessed. The objective of this study was to assess the effectiveness and safety of rosuvastatin plus colchicine, emtricitabine/tenofovir, and their combined use in these patients.Revista Internacional - Indexad

    SPT clusters with des and HST weak lensing. I. Cluster lensing and Bayesian population modeling of multiwavelength cluster datasets

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    We present a Bayesian population modeling method to analyze the abundance of galaxy clusters identified by the South Pole Telescope (SPT) with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). We discuss and validate the modeling choices with a particular focus on a robust, weak-lensing-based mass calibration using DES data. For the DES Year 3 data, we report a systematic uncertainty in weak-lensing mass calibration that increases from 1% at z=0.25 to 10% at z=0.95, to which we add 2% in quadrature to account for uncertainties in the impact of baryonic effects. We implement an analysis pipeline that joins the cluster abundance likelihood with a multiobservable likelihood for the Sunyaev-Zel'dovich effect, optical richness, and weak-lensing measurements for each individual cluster. We validate that our analysis pipeline can recover unbiased cosmological constraints by analyzing mocks that closely resemble the cluster sample extracted from the SPT-SZ, SPTpol ECS, and SPTpol 500d surveys and the DES Year 3 and HST-39 weak-lensing datasets. This work represents a crucial prerequisite for the subsequent cosmological analysis of the real dataset

    SPT Clusters with DES and HST Weak Lensing. I. Cluster Lensing and Bayesian Population Modeling of Multi-Wavelength Cluster Datasets

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    We present a Bayesian population modeling method to analyze the abundance of galaxy clusters identified by the South Pole Telescope (SPT) with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). We discuss and validate the modeling choices with a particular focus on a robust, weak-lensing-based mass calibration using DES data. For the DES Year 3 data, we report a systematic uncertainty in weak-lensing mass calibration that increases from 1\% at z=0.25z=0.25 to 10\% at z=0.95z=0.95, to which we add 2\% in quadrature to account for uncertainties in the impact of baryonic effects. We implement an analysis pipeline that joins the cluster abundance likelihood with a multi-observable likelihood for the SZ, optical richness, and weak-lensing measurements for each individual cluster. We validate that our analysis pipeline can recover unbiased cosmological constraints by analyzing mocks that closely resemble the cluster sample extracted from the SPT-SZ, SPTpol~ECS, and SPTpol~500d surveys and the DES Year~3 and HST-39 weak-lensing datasets. This work represents a crucial prerequisite for the subsequent cosmological analysis of the real dataset.Comment: submitted to PR

    A domain-decomposition method to implement electrostatic free boundary conditions in the radial direction for electric discharges

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    At high pressure electric discharges typically grow as thin, elongated filaments. In a numerical simulation this large aspect ratio should ideally translate into a narrow, cylindrical computational domain that envelops the discharge as closely as possible. However, the development of the discharge is driven by electrostatic interactions and, if the computational domain is not wide enough, the boundary conditions imposed to the electrostatic potential on the external boundary have a strong effect on the discharge. Most numerical codes circumvent this problem by either using a wide computational domain or by calculating the boundary conditions by integrating the Green’s function of an infinite domain. Here we describe an accurate and efficient method to impose free boundary conditions in the radial direction for an elongated electric discharge. To facilitate the use of our method we provide a sample implementation. Finally, we apply the method to solve Poisson’s equation in cylindrical coordinates with free boundary conditions in both radial and longitudinal directions. This case is of particular interest for the initial stages of discharges in long gaps or natural discharges in the atmosphere, where it is not practical to extend the simulation volume to be bounded by two electrodes

    Giant vulvo-abdominal aggressive angiomyxomas, report of two cases

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    Aggressive angiomyxoma is a rare type of soft tissue tumour. It has traditionally been described as a low-grade myxomatous neoplasm of the vulvovaginal, perineal and pelvic regions in women, and has a high rate of recurrence because of its infiltrative potential and locoregional extension. Its pathogenesis and histogenesis are poorly understood, but it is proposed that chromosome 12 alterations and fibroblastic/myofibroblastic tumours are involved in its origin. Around 250 cases have been reported to date in the western literature, some of them with unusual presentations. The biggest reported tumour measures 26 cm × 21 cm × 6 cm. The following article describes two case reports of this neoplasm, which were studied at Mexico's General Hospital “Dr. Eduardo Liceaga” over period of one year. Both case reports state that the tumours are considerably bigger than the ones currently reported (66 cm × 60 cm × 20 cm and 50 cm × 46 cm × 17 cm). We shall focus on histopathology and end with an analysis and discussion. Resumen: El angiomixoma profundo o agresivo es una entidad poco frecuente, agrupada dentro de las neoplasias del estroma genital. Se describe clásicamente como una neoplasia mixomatosa de bajo grado de las regiones vulvovaginal, perineal y pélvica en mujeres, con una tasa de recurrencia alta debido a su potencial de infiltración y extensión locoregional; con patogénesis e histogénesis pobremente entendidas, postulándose alteraciones en el cromosoma 12 y origen fibroblástico/miofibroblástico. La literatura occidental reporta poco más de 250 casos a la fecha, algunos de ellos con presentaciones inusuales, el caso informado de mayor tamaño es de 26 × 21 × 6 cm. A continuación se describen dos casos de dicha neoplasia estudiados en el Hospital General de México “Dr. Eduardo Liceaga”, en el periodo de un año, ambos de tamaños considerablemente mayores a los reportados actualmente (66 × 60 × 20 cm y 50 × 46 × 17 cm) y se hace enfoque en su estudio histopatológico, finalizando con un análisis y discusión sobre el tema. Keywords: Angiomyxoma, Vulvar neoplasms, Palabras clave: Angiomixoma, Neoplasias vulvare

    Sprite streamer at 50 km altitude

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    Reduced electric field and species density produced by a simulated positive sprite streamer 80 micro-s after the onset of the simulation between altitudes 50 km and 49.7 km. The file claw0040.hdf corresponds to the data in each grid-cell. The ZIP files contain text files of the temporal evolution of the data in particular points

    RECUPERACIÓN DE POLI-b-HIDROXIHEXANOATOCO- OCTANOATO SINTETIZADO POR Pseudomonas putida MEDIANTE EL USO DE DISPERSIONES HIPOCLORITO-CLOROFORMO

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    Se estandarizó una técnica de recuperación de poli-3-hidroxihexanoato-co-hidroxioctanoato a partir de P. putida. El método emplea dispersiones de hipoclorito de sodio-cloroformo para la digestión del material celular y solubilización del polímero, respectivamente. Se evaluó el efecto de la concentración de hipoclorito, la temperatura y el tiempo sobre el porcentaje de recuperación, pureza, peso molecular y temperatura de fusión. Las mejores condiciones para recuperar este polímero fueron: hipoclorito al 5.25% (p/v) a 60°C durante 1 hora. Empleando estas condiciones fue posible mantener el peso molecular por encima del 87% con respecto al obtenido mediante extracción con cloroformo. La temperatura de fusión del polímero fue 57.7°C y 56.4°C para dos muestras al azar. La pureza del material recuperado esde 96%
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