Potential-dependent competitive processes on platinum in acid solution in the presence of propargyl alcohol

The electroadsorption interactions between dilute propargyl alcohol and smooth platinum in 0.5 M H2SO4 at 25° C have been investigated at different potentials. When the platinum electrode is covered by H atoms the hydrogenation of propargyl alcohol takes place. Otherwise, when the platinum electrode is held at a potential located in the double-layer region, the electroadsorption of propargyl alcohol involves a disruptive electro-oxidation yielding strongly bound adsorbed residues. The latter can be electrodesorbed presumably as carbon dioxide and protons. This process occurs within the O-electroadsorption potential range. The complete residue electrodesorption requires several voltammetric cycles. Competition between the hydrogenation reaction and the disruptive electroadsorption process can be observed at potentials where the platinum surface is partially covered by H atoms.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Potential-dependent competitive processes on platinum in acid solution in the presence of propargyl alcohol

The electroadsorption interactions between dilute propargyl alcohol and smooth platinum in 0.5 M H2SO4 at 25° C have been investigated at different potentials. When the platinum electrode is covered by H atoms the hydrogenation of propargyl alcohol takes place. Otherwise, when the platinum electrode is held at a potential located in the double-layer region, the electroadsorption of propargyl alcohol involves a disruptive electro-oxidation yielding strongly bound adsorbed residues. The latter can be electrodesorbed presumably as carbon dioxide and protons. This process occurs within the O-electroadsorption potential range. The complete residue electrodesorption requires several voltammetric cycles. Competition between the hydrogenation reaction and the disruptive electroadsorption process can be observed at potentials where the platinum surface is partially covered by H atoms.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Planeación y gestión estratégica de la empresa Erie en el simulador de negocios Capstone

En este documento se presenta un análisis de la toma de decisiones, la estrategia de negocios aplicada y los resultados en la empresa Erie dentro del simulador de negocios Capstone

Fire response of the endangered Pinus culminicola stands after 18 years in Cerro El Potosí, northeast Mexico

Abstract Aim of the study: To analyze the impact of the 1998 wildfire on dwarf pine (Pinus culminicola) population stands 18 years after the fire. Area of study: Cerro el Potosí, Nuevo León (México). Material and methods: We measured regeneration, biovolume of individuals, diversity and species composition in unburned and burned plots randomly selected in the area. Main results: Recovery was very slow, with limited dense natural regeneration and very slow growth. Significant differences between control and burned plots were found with respect to regeneration, species composition, evenness and soil nutrients, suggesting that fire could promote natural regeneration and biodiversity in these communities. Research highlights: Management efforts are necessary to maintain a natural fire regime and ensure grazing exclusion in order to favor the conservation of the community dominated by this rare species P. culminicola. Additional keywords: fire ecology; DCA; Permanova; richness. Abbreviations used: CIC (Cationic Interchange Complex); DCA (Detrended Correspondence Analysis); EC (Exchangeable Cation); OM (Organic Matter). Authors´ contributions: Conceived, designed and performed the experiments: JRA, EE and HGR. Analyzed the data: JRA, JAV, JRE and YM. Contributed reagents/materials/analysis tools: JAV, JRE, YM, IC and JU. Wrote the paper: JRA, JAE and EE. All authors read and approved the final manuscript. Citation: Arévalo, J. R.; Estrada, E.; Encina, J. A.; Villarreal, J. A.; Escobedo, J. R.; Morales, Y.; Cantú, I.; González-Rodríguez, H.; Uvalle, J. (2017). Fire response of the endangered Pinus culminicola stands after 18 years in Cerro El Potosí, northeast Mexico. Forest Systems, Volume 26, Issue 3, e015. https://doi.org/10.5424/fs/2017263-11566 Received: 20 Apr 2017. Accepted: 21 Nov 2017. Copyright © 2017 INIA. This is an open access article distributed under the terms of the Creative Commons Attribution (CC-by) Spain 3.0 License. Funding: Program of cooperation Universidad de La Laguna-Universidad Autónoma de Nuevo León, included in the official frame agreement of these institutions; Facultad de Ciencias Forestales of the Universidad Autónoma de Nuevo León; University of La Laguna (Research Program) covered the travel expenses of JRA. Competing interests: The authors have declared that no competing interests exist. Correspondence should be addressed to José R. Arévalo: [email protected]

Constraining X-ray reflection in the low-luminosity AGN NGC 3718 using NuSTAR and XMM--Newton

One distinctive feature of low-luminosity active galactic nuclei (LLAGN) is the relatively weak reflection features they may display in the X-ray spectrum, which can result from the disappearance of the torus with decreasing accretion rates. Some material, however, must surround the active nucleus, i.e., the accretion flow itself and, possibly, a flattened-out or thinned torus. In this work, we study whether reflection is indeed absent or undetectable due to its intrinsically weak features together with the low statistics inherent to LLAGN. Here we focus on NGC 3718 ($L/L_{\rm Edd}\sim10^{-5}$) combining observations from XMM--Newton and the deepest to date NuSTAR (0.5--79 keV) spectrum of a LLAGN, to constrain potential reflectors, and analyze how the fitted coronal parameters depend on the reflection model. We test models representing both an accretion disc (Relxill) and a torus-like (MYTorus and Borus) neutral reflector. From a statistical point of view, reflection is not required, but its inclusion allows to place strong constraints on the geometry and physical features of the surroundings: both neutral reflectors (torus) tested should be Compton thin ($N_H<10^{23.2}$cm$^{-2}$) and preferentially cover a large fraction of the sky. If the reflected light instead arises from an ionized reflector, a highly ionized case is preferred. These models produce an intrinsic power-law spectral index in the range [1.81--1.87], where the torus models result in steeper slopes. The cut-off energy of the power-law emission also changes with the inclusion of reflection models, resulting in constrained values for the disc reflectors and unconstrained values for torus reflectors.Comment: 15 pages and 16 Figure

La papilomatosis faríngea bovina en Colombia

Se discute sobre la enfermedad conocida como papilomatosis faríngea bovina o tusa. Se describen los resultados de la investigación de la enfermedad bajo los aspectos epidemiológico, morfológico, clínico y microbiológico y su posible implicación en salud pública. El estudio epidemiológico basado en una población de 5445 bovinos en el norte de Antioquia, demostró que la enfermedad no afecta a machos de ninguna edad y sí en forma severa a las vacas adultas mayores de tres años. No se obtuvo reportes de machos enfermos, por lo cual se puede afirmar que es un factor ligado al sexo. La raza más afectada es la Holstein seguida por la Ayrshire. La enfermedad se presenta en áreas montañosas de suelos áridos con temperatura media de 15 grados centígrados. Predominan en estos suelos las malezas y existen algunas fincas en la región con pastos mejorados y praderas en las cuales el problema ha decrecido o desaparecido totalmente. El estudio morfológico demostró la presencia de varios tipos de lesiones en la cavidad bucal que van desde papilomas a carcinomas escamosos con invasión de tejidos adyacentes y metástasis a los ganglios linfáticos regionales. Estudios ultraestructurales son indicativos de un proceso citopático de naturaleza viral. Las muestras obtenidas de animales enfermos han sido estudiadas en líneas celulares y cultivos primarios, en ambos casos se ha observado un efecto citopático celular. Sobre la membrana cariolantoidea de huevos embrionados, la suspensión de la muestra ha formado lesiones similares a placas Además se llevó a cabo la reproducción experimental de la enfermedad en tres terneros jóvenes y se recomienda un estudio inmunológico para complementar las investigaciones futurasGanado de leche-Ganadería lech

Constraining the X-ray reflection in low accretion rate AGN using XMM-Newton, NuSTAR and Swift

An interesting feature in active galactic nuclei (AGN) accreting at low rate is the weakness of the reflection features in their X-ray spectra, which can result from the gradual disappearance of the torus with decreasing accretion rates. It has been suggested that low luminosity AGN (LLAGN) would have a different reflector configuration compared with high luminosity AGN, either covering a smaller fraction of the sky or simply having less material. Additionally, we note that the determination of the spectral index ($\Gamma$) and the cut-off energy of the primary power-law emission is affected by the inclusion of reflection models, showing the importance of using them to study the accretion mechanism, especially in the case of the LLAGN that have previously shown a high dispersion on the relation between $\Gamma$ and the accretion rate. Our purpose is to constrain the geometry and column density of the reflector in a sample of LLAGN covering a broad X-ray range of energy combining data from XMM-Newton + NuSTAR + Swift of a hard X-ray-flux limited sample of 17 LLAGN from BASS/DR2 with accretion rates $\lambda_{Edd}$=L$_{\rm Bol}$/L$_{\rm Edd}$<10$^{-3}$. We fit all spectra using the reflection model for torus (borus02) and accretion disk (Xillver) reflectors. We found a tentative correlation between the torus column density and the accretion rate, LLAGN shows a lower column density compared with the high-luminosity objects. We also confirm the relation between $\Gamma$ and $\lambda_{Edd}$, with a smaller scatter than previously reported, thanks to the inclusion of high-energy data and the reflection models. Our results are consistent with a break at $\lambda_{Edd}\sim10^{-3}$, suggestive of a different accretion mechanism compared with higher accretion AGN.Comment: Accepted for publication in Astronomy & Astrophysic

Discovery of a relation between black hole mass and soft X-ray time lags in active galactic nuclei

We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM-Newton. The analysis of X-ray lags (up to the highest/shortest frequencies/time-scales), is performed in the Fourier-frequency domain, between energy bands where the soft excess (soft band) and the primary power law (hard band) dominate the emission. We report a total of 15 out of 32 sources displaying a high frequency soft lag in their light curves. All 15 are at a significance level exceeding 97 per cent and 11 are at a level exceeding 99 per cent. Of these soft lags, 7 have not been previously reported in the literature, thus this work significantly increases the number of known sources with a soft/negative lag. The characteristic time-scales of the soft/negative lag are relatively short (with typical frequencies and amplitudes of \nu\sim 0.07-4 \times 10^{-3} Hz and \tau\sim 10-600 s, respectively), and show a highly significant (\gsim 4\sigma) correlation with the black hole mass. The measured correlations indicate that soft lags are systematically shifted to lower frequencies and higher absolute amplitudes as the mass of the source increases. To first approximation, all the sources in the sample are consistent with having similar mass-scaled lag properties. These results strongly suggest the existence of a mass-scaling law for the soft/negative lag, that holds for AGN spanning a large range of masses (about 2.5 orders of magnitude), thus supporting the idea that soft lags originate in the innermost regions of AGN and are powerful tools for testing their physics and geometry.Comment: 12 pages, 6 figures. Revised version, accepted for publication in MNRA

Las termas y el Suburbium marítimo de Baelo Claudia. Avance de un reciente descubrimiento

Entre los años 2010 y 2012, la Universidad de Cádiz y la Junta de Andalucía han desarrollado investigaciones arqueológicas en la zona extramuros de la ciudad hispanorromana, en el marco del Proyecto General de Investigación “La economía marítima y las actividades haliéuticas en Baelo Claudia”. Se presentan en esta sede los primeros resultados, que han permitido identificar la existencia de un suburbium occidental en la ciudad, entre el cauce del arroyo de las Villas, la playa y la necrópolis oeste, cuya existencia se ha podido confirmar por datos geofísicos y arqueológicos. En él han podido ser excavadas parcialmente unas estructuras que se han identificado con unas termas suburbanas, activas entre el s. II y el V d.C., habiéndose excavado una piscina del frigidarium y algunas estancias calefactadas, con hallazgos muy significativos como parte de la decoración marmórea y escultórica del complejo, que en época tardorromana fue amortizado intencionalmente por motivos posiblemente religiosos. Estos hallazgos son de gran interés, pues además de verificar la existencia de un segundo complejo balneario público en la ciudad plantean la importancia del poblamiento periurbano, una línea de investigación totalmente inédita hasta la fechaBetween the year 2010 and 2012, the University of Cadiz and the Regional Government (Junta de Andalucía) have developed archaeological activities in the zone outside the hispano-roman city, in the frame of the General Project of Research titled “The maritime economy and the halieutic activities in Baelo Claudia”. We are presenting in this paper the first results, which have allowed to identify the existence of a western suburbium outside the city, between the riverbed of the so called “arroyo de las Villas”, the beach and the western necropolis, whose remains have been confirmed by geophysical and archaeological techniques. Inside this area a few structures have been excavated, identified as a Roman baths complex, active from the 2nd up to the 5th century a.D. A big pool, part of the frigidarium and some heated rooms have been unearthed, with very significant findings as part of the marmoreal and sculptural decoration of the complex, which in late roman times was intentionally broken into pieces possibly by religious motives. These findings are of great interest, since beside confirming the existence of the second public thermae of the city they raise the importance of the peri-urban buildings, a new line of research up to dat