148 research outputs found
Coronal Mass Ejections - Propagation Time and Associated Internal Energy
In this paper, we analyze 91 coronal mass ejection (CME) events studied by
Manoharan et al. (2004) and Gopalswamy and Xie (2008). These earth-directed
CMEs are large (width 160) and cover a wide range of speeds
(120--2400 {\kmps}) in the LASCO field of view. This set of events also
includes interacting CMEs and some of them take longer time to reach 1 AU than
the travel time inferred from their speeds at 1 AU. We study the link between
the travel time of the CME to 1 AU (combined with its final speed at the Earth)
and the effective acceleration in the Sun-Earth distance. Results indicate that
(1) for almost all the events (85 out of 91 events), the speed of the CME at 1
AU is always less than or equal to its initial speed measured at the near-Sun
region, (2) the distributions of initial speeds, CME-driven shock and CME
speeds at 1 AU clearly show the effects of aero-dynamical drag between the CME
and the solar wind and in consequence, the speed of the CME tends to equalize
to that of the background solar wind, (3) for a large fraction of CMEs (for
50% of the events), the inferred effective acceleration along the
Sun-Earth line dominates the above drag force. The net acceleration suggests an
average dissipation of energy 10 ergs, which is likely provided
by the Lorentz force associated with the internal magnetic energy carried by
the CME.Comment: 18 pages, 6 figure
Gangrena de Fournier en paciente obeso con COVID-19: reporte de caso
La Gangrena de Fournier (GF) es una fascitis necrotizante que afecta los planos superficiales. Se presenta frecuentemente en hombres entre 50 y 79 años con una elevada tasa de mortalidad, la cual aumenta con la presencia de factores de riesgo destacándose entre ellos la diabetes y obesidad. Se reporta el caso de un paciente obeso diagnosticado con COVID-19 antes del ingreso y tratado con corticoides, que acude por aparente celulitis escrotal que evoluciona a GF, la cual fue diagnosticada 2 días luego de la hospitalización. Se le realiza intervención quirúrgica inmediata, previa cobertura antibiótica. La COVID-19 no tuvo relevancia clínica en la evolución y pronóstico de la GF; sin embargo, fueron las terapias desmesuradas las que influyeron negativamente. A pesar de ello, el paciente evolucionó favorablemente hasta su recuperación total.
Palabras clave: Gangrena de Fournier, obesidad, COVID-19 (MeSH)
DOI: http://dx.doi.org/10.17268/rmt.2020.v16i01.1
Detection of Bartonella bovis DNA in blood samples from a veterinarian in Mexico
The genus Bartonella encompasses 38 validated species of Gram-negative, facultative intracellular bacteria that colonize the endothelial cells and erythrocytes of a wide spectrum of mammals. To date, 12 Bartonella species have been recorded infecting humans, causing diseases of long historical characterization, such as cat scratch fever and trench fever, and emerging bartonellosis that mainly affect animal health professionals. For this reason, this study aimed to report a documented case of Bartonella bovis infecting a veterinarian from Mexico by the amplification, sequencing and phylogenetic reconstruction of the citrate synthase (gltA) and the RNA polymerase beta-subunit (rpoB) genes, and to report the natural course of this infection. To our knowledge, this work is the first to report the transmission of B. bovis via needlestick transmission to animal health workers in Latin America
First observations of oblique ionospheric sounding chirp signal in Mexico
The results of the first experiment of oblique ionospheric sounding (OIS) chirp signal reception in Mexico are
reported. Maximal and Lowest Observed Frequencies variations were studied under the quiet Space Weather
conditions. The diurnal ionospheric variations by OIS signal confirm the results based on GNSS data in the
Mexican region. The best HF radio propagation conditions along the considered path are during morning and
daytime hours. The multi-hop propagation is frequent. The interlayer propagation modes are present at nighttime
First joint observations of space weather events over Mexico
Abstract. The Mexican Space Weather Service (SCiESMEX in Spanish) and National Space Weather Laboratory (LANCE in Spanish) were organized in 2014 and in 2016, respectively, to provide space weather monitoring and alerts, as well as scientific research in Mexico. In this work, we presenttheresultsofthefirstjointobservationsoftwoevents (22 June and 29 September 2015) with our local network of instruments and their related products. This network includes the MEXART radio telescope (solar flare and radio burst), the Compact Astronomical Low-frequency, Low-cost Instrument for Spectroscopy in Transportable Observatories (CALLISTO)attheMEXARTstation(solarradioburst),the Mexico City Cosmic Ray Observatory (cosmic ray fluxes), GPS receiver networks (ionospheric disturbances), and the Teoloyucan Geomagnetic Observatory (geomagnetic field). The observations show that we detected significant space weather effects over the Mexican territory: geomagnetic and ionospheric disturbances (22 June 2015), variations in cosmicrayfluxes,andalsoradiocommunications’interferences (29September2015).Theeffectsoftheseperturbationswere registered,forthefirsttime,usingspaceweatherproductsby SCiESMEX:totalelectroncontent(TEC)maps,regionalgeomagneticindexKmex,radiospectrographsoflowfrequency, and cosmic ray fluxes. These results prove the importance of
monitoring space weather phenomena in the region and the need to strengthening the instrumentation network
Abrasive Wear Behavior of Al–4Cu–1.5Mg–WC Composites Synthesized through Powder Metallurgy
Different Al–4Cu–1.5Mg/WC composites were synthesized through powder metallurgy to establish the effect of WC particle addition on the abrasive wear behavior of an Al–4Cu–1.5Mg (wt. %) alloy. The wear tests were performed using a pin-on-disc tribometer at room temperature in dry conditions using SiC abrasive sandpaper as a counterbody and tribometer of linear configuration. The results showed that WC additions increase the hardness of the Al–4Cu–1.5Mg alloy due to the strengthening effect of particle dispersion in the aluminum matrix, which generates an improvement in the wear resistance of the composites by preventing direct contact of the sample with the counterbody, in turn delaying the plastic deformation phenomena responsible for the degradation sequence. In addition, the dominant wear mechanism was abrasive wear, and the increased friction coefficient did not bring a rapid wear rate, which was related to the enhanced deformation resistance due to the high hardness
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