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

Constructed wetland design for produced water treatment on a colombian petroleum field

En el presente artículo se plantea una alternativa de solución al gran problema que enfrentan los campos de petróleo de Colombia, con respecto al manejo y disposición del agua de producción. En su mayoría, estos&nbsp; campos de petróleo asumen grandes costos para el tratamiento, manejo y disposición de la misma. El artículo describe el diseño de un humedal construido a escala real, propuesto como tratamiento secundario para una posible implementación de tratamiento del agua de producción. Para el diseño se tuvieron en cuenta las características fisicoquímicas del agua afluente del campo petrolero colombiano como concentraciones de materia orgánica (DBO5) y sólidos suspendidos totales (SST), acorde con los principales criterios de diseño de la tecnología, como tipo y concentración de contaminantes, tipología de humedal, caudal de entrada y área total requerida. una vez seleccionado el tipo de humedal, el diseño contempló las variables que afectan principalmente su desempeño, incluyendo procedimientos de operación y manejo para su implementación. El diseño consistió en un Humedal Construido de&nbsp; flujo Sub-Superficial Horizontal (HC fSSH) de 120.000 m2 de superficie y una profundidad de 2 ft para tratar un caudal de 678.607 Bbl/d. El HC de fSSH consistió en 60 celdas de 109,35 ft por 196,85 ft dispuestas en paralelo (12) y en serie (5), plantadas con macrófitas acuáticas nativas para potencializar los procesos de depuración. Este diseño con una gran cantidad de área superficia, se considera compensado por los bajos costos de operación y mantenimiento, calculados para un período de 10 años; Mientras que un sistema convencional de tratamiento de agua de producción en un campo petrolero, invierte 4.380.338,1 uS$por año, un HC de fSSH opera con 23.681,78 uS$ para el mismo período de tiempo. La implementación de esta tecnología para el tratamiento de aguas residuales de la industria petrolera, se considera una alternativa viable, siempre y cuando se tengan los terrenos disponibles para su funcionamiento. &nbsp;The development of this paper permits to find and set a new and alternative solution to the big problem that Colombian petroleum fields are facing: Management and Disposal of produced water. Due to the conventional treatment facilities, petroleum companies are spending great amounts of money to treat and dispose petroleum wastewaters. The present project describes a full-scale constructed wetland design proposed as a secondary treatment for a Colombian field produced water. The design takes into account the physicochemical characteristics of a Colombian field water affluent, represented as organic matter (BOD) and Total Suspended Solids (TSS) oncentrations, according to the main design criteria for the technology, like type and ollutants concentrations, type of wetland, entrance water rate and total area required. Once the type of wetland is selected, the design realizes the principal constraints that affect wetland performance, including operational and maintenance procedures for a future implementation. The design consists in a Horizontal Subsurface flow Constructed Wetland (HSSf CW) with 12 ha of superficial area and 2 ft depth, to treat an average water rate of 678.607 Bbl/day. The HSSf CW consisted on 60 cells of 109,35 x 196,85 ft each, organized in parallel (12) and in series (5). Each cell will be planted with native aquatic macrophytes to enhance purification processes. This grand superficial area design is considered compensated by the low operational and maintenance costs, calculated for a 10-year period. While a conventional treatment system for produced water needs an inversion of US$4.380.338,1 per year, a HSSF CW works with US$23.681,78 for the same time period

Electrochemical reduction of CO2 in water-acetonitrile mixtures on nanostructured Cu electrode

This communication studies the CO2 reduction reaction in H2O/CH3CN mixtures on nanostructured copper. It was found that the nanostructured copper electrode presents a well-defined voltammogram in acetonitrile, where it can be seen three signals related to adsorbed or surface attached (thin films) species. Also, it was found that the current density of CO2 reduction in mixtures H2O/CH3CN on nanostructured copper electrodes with a mole fraction around 0.25 is higher than those observed with mole fractions lower than 0.15 or higher than 0.35. Finally, nanostructured Cu electrodes show higher catalytic activity towards the CO2 reduction than copper electrode.APSR acknowledges the scholarship “Estudiantes sobresalientes de posgrado” at the “Universidad Nacional de Colombia (UNAL)” and COLCIENCIAS National Doctoral Scholarship (567). MFS acknowledges the support of UNAL (Research Project 19030)

Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.Comment: Submitted to J. Stat. Mech. for the proceedings of UPON 2008 (Lyon), topic: crackling nois

Sentinel network for monitoring in vitro susceptibility of Plasmodium falciparum to antimalarial drugs in Colombia: a proof of concept

Drug resistance is one of the principal obstacles blocking worldwide malaria control. In Colombia, malaria remains a major public health concern and drug-resistant parasites have been reported. In vitro drug susceptibility assays are a useful tool for monitoring the emergence and spread of drug-resistant Plasmodium falciparum. The present study was conducted as a proof of concept for an antimalarial drug resistance surveillance network based on in vitro susceptibility testing in Colombia. Sentinel laboratories were set up in three malaria endemic areas. The enzyme linked immunosorbent assay-histidine rich protein 2 and schizont maturation methods were used to assess the susceptibility of fresh P. falciparum isolates to six antimalarial drugs. This study demonstrates that an antimalarial drug resistance surveillance network based on in vitro methods is feasible in the field with the participation of a research institute, local health institutions and universities. It could also serve as a model for a regional surveillance network. Preliminary susceptibility results showed widespread chloroquine resistance, which was consistent with previous reports for the Pacific region. However, high susceptibility to dihydroartemisinin and lumefantrine compounds, currently used for treatment in the country, was also reported. The implementation process identified critical points and opportunities for the improvement of network sustainability strategies.PAHO [057-1-3144141]; COLCIENCIAS [ID 2229-405-20319]info:eu-repo/semantics/publishedVersio

Geology of La Reforma caldera complex, Baja California, Mexico

A new geological map at 1:50,000 scale of La Reforma Caldera Complex has been produced applying modern survey methodologies to volcanic areas. This map aims to represent a reliable and objective tool to understand the geological evolution of the region. La Reforma Caldera Complex is a Pleistocene nested caldera located in the central part of the Baja California peninsula, Mexico. The twelve formations defined within the Quaternary volcanic record were grouped into three phases (pre-caldera, caldera, and post-caldera). The pre-caldera phase (>1.35 Ma) is characterized by scattered eruptions, mostly occurred in submarine environment. The caldera phase (1.35–0.96 Ma) groups several distinct explosive and effusive eruptions that formed the present-day caldera depression. The post caldera phase includes scattered effusive eruptions (ended at 0.28 Ma) and resurgence, characterized by several hundred meters of uplift of the central block within the caldera depression

México y Jalisco en la coyuntura : segundo semestre de 1998

Análisis de coyuntura sobre los principales sucesos del segundo semestre de 1998 en Jalisco y México. El caso del FOBAPROA, la seguridad pública, los derechos humanos, las elecciones efectuadas en el período y las estrategias de los partidos políticos en Jalisco son analizados por autores diversos. Se estudia también el caso de la industria electrónica en Guadalajara y la relación de los grupos de la sociedad civil con el gobierno.ITESO, A.C

Transiciones, conflictos y democracia : estudios de coyuntura

México ha vivido un largo proceso de transición que ha desencadenado dinamismos económicos, culturales y políticos. En la actual coyuntura, estos dinamismos muestran toda su complejidad, su inevitable articulación y la tensión entre las fuerzas que intentan sostener un viejo modelo de gobernar y decidir el rumbo del país, y aquellas que buscan abrirse a un espectro mucho más amplio y diversificado de actores. En ellos se conjuntan las aspiraciones más legítimas de los mexicanos por avanzar en el reconocimiento y respeto de la pluralidad étnica, de género y entre generaciones, y por impulsar una dinámica en la que —en medio de los procesos de mundialización— los distintos grupos e intereses de los mexicanos puedan ser incluidos. La transición mexicana tiende a centrarse en la dimensión política. La intensidad que cobran los procesos políticos y el énfasis que importantes analistas ponen en dichos procesos, contribuyen a que esta asociación vaya cobrandoíuerza. En este sentido, es necesario advertir que en las transiciones la tendencia privatizadora, la reducción del gasto social, así como la necesidad de pactos sociales que sean respetados, la participación creciente de la sociedad civil, etc. son factores importantes que, en medio de contradicciones, van generando nuevos esquemas de relación entre gobierno y sociedad.ITESO, A.C