Variation of the X-ray non-thermal emission in the Arches cloud

The origin of the iron fluorescent line at 6.4 keV from an extended region surrounding the Arches cluster is debated and the non-variability of this emission up to 2009 has favored the low-energy cosmic-ray origin over a possible irradiation by hard X-rays. By probing the variability of the Arches cloud non-thermal emission in the most recent years, including a deep observation in 2012, we intend to discriminate between the two competing scenarios. We perform a spectral fit of XMM-Newton observations collected from 2000 to 2013 in order to build the Arches cloud lightcurve corresponding to both the neutral Fe Kalpha line and the X-ray continuum emissions. We reveal a 30% flux drop in 2012, detected with more than 4 sigma significance for both components. This implies that a large fraction of the studied non-thermal emission is due to the reflection of an X-ray transient source.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter

A Lithocodium and Bacinella signature of a late Hauterivian, local microbial event: the Urgonian limestone in South-East France

Sediment binding crusts of Lithocodium aggregatum and associated Bacinella irregularis abound in a shallow water limestone layer, in South–East France. The sudden appearance of these crusts denotes a local, conspicuous change in an otherwise balanced, open marine depositional environment. Based on regional correlation, the layer belongs to the Lower Hauterivian, Ligatus Zone, directly dated by an assemblage of orbitolinid foraminifera, and indirectly by a specimen of ammonite. It is older than the Faraoni oceanic anoxic event (OAE), (latest Hauterivian, Angulicostata auct. Zone), and presumably not linked with a global climate change. Two facies are recognized: (1) Lithocodium bindstone, with Bacinella, other microencrusters, and fluorescent automicrite of microbial origin; (2) fl oatstones containing numerous fragments of Lithocodium and accompanying biota. Coarse rhombohedral dolomite is locally present. Two modern analogues of microbial mediation are put forward to explain the Lithocodium event: (a) Lagoa Vermelha, in Brazil, along with anoxic, marginal marine conditions; (b) Highborne Cay, in the Bahamas, along with oxic, open marine conditions. A stack of four Upper Hauterivian parasequences is described: Parasequence 1 ends with oolitic deposits; the somewhat deeper water Parasequence 2 occurs only in the south-eastern part of the study area, towards the Subalpine depocenter; Parasequence 3 matches the layer with Lithocodium and Bacinella, of variable thickness (0.8 m – 11 m), resulting from syn-sedimentary tectonic activity in the area of the Vuache fault system which is a major feature; Parasequence 4 corresponds with the resumption of the normal, Urgonian carbonate factory

Echoes of multiple outbursts of Sagittarius A* revealed by Chandra

The relatively rapid spatial and temporal variability of the X-ray radiation from some molecular clouds near the Galactic center shows that this emission component is due to the reflection of X-rays generated by a source that was luminous in the past, most likely the central supermassive black hole, Sagittarius A*. Studying the evolution of the molecular cloud reflection features is therefore a key element to reconstruct Sgr A*'s past activity. The aim of the present work is to study this emission on small angular scales in order to characterize the source outburst on short time scales. We use Chandra high-resolution data collected from 1999 to 2011 to study the most rapid variations detected so far, those of clouds between 5' and 20' from Sgr A* towards positive longitudes. Our systematic spectral-imaging analysis of the reflection emission, notably of the Fe Kalpha line at 6.4 keV and its associated 4-8 keV continuum, allows us to characterize the variations down to 15" angular scale and 1-year time scale. We reveal for the first time abrupt variations of few years only and in particular a short peaked emission, with a factor of 10 increase followed by a comparable decrease, that propagates along the dense filaments of the Bridge cloud. This 2-year peaked feature contrasts with the slower 10-year linear variations we reveal in all the other molecular structures of the region. Based on column density constraints, we argue that these two different behaviors are unlikely to be due to the same illuminating event. The variations are likely due to a highly variable active phase of Sgr A* sometime within the past few hundred years, characterized by at least two luminous outbursts of a few-year time scale and during which the Sgr A* luminosity went up to at least 10^39 erg/s.Comment: 17 pages, 16 figures, Accepted for publication in Astronomy & Astrophysic

Las deformidades vertebrales a través de las artes plásticas

Si la medicina constituye el primero y más poderoso medio de intervención del hombre con respecto a su vulnerable naturaleza, el arte es también el primero y más poderoso instrumento que el hombre ha podido encontrar para expresar su propia condición. Con los años el hombre ha evolucionado, y con él la medicina y el arte. El arte trabaja sobre el mismo motivo que la medicina: el hombre. De ahí el extraordinario valor, desde el punto de vista ontológico, de muchas obras de arte, que jamás habrían sido realizadas si la enfermedad y el ejercicio del arte médico no les hubiera creado el tema; ya no tiene sentido la separación entre ciencias del espíritu y ciencias de la naturaleza para el mejor entendimiento del ser humano, porque lo correcto es considerar que los conocimientos médico-científicos y artístico-plásticos se unen en el hombre

The evolution of GX 339-4 in the low-hard state as seen by NuSTAR and Swift

We analyze eleven NuSTAR and Swift observations of the black hole X-ray binary GX 339-4 in the hard state, six of which were taken during the end of the 2015 outburst, five during a failed outburst in 2013. These observations cover luminosities from 0.5%-5% of the Eddington luminosity. Implementing the most recent version of the reflection model relxillCp, we perform simultaneous spectral fits on both datasets to track the evolution of the properties in the accretion disk including the inner edge radius, the ionization, and temperature of the thermal emission. We also constrain the photon index and electron temperature of the primary source (the "corona"). We find the disk becomes more truncated when the luminosity decreases, and observe a maximum truncation radius of $37R_g$. We also explore a self-consistent model under the framework of coronal Comptonization, and find consistent results regarding the disk truncation in the 2015 data, providing a more physical preferred fit for the 2013 observations.Comment: 15 pages, 8 figures, 6 tables, accepted for publication in The Astrophysical Journa

Effects of legume cover crop and sub-soiling on soil properties and Maize (Zea mays L) growth in semi arid area of Machakos district, Kenya = Efecto del cultivo de cobertua y el subsolado sobre las propiedades del suelo y crecimiento de maiz (Zea mays L.) en la region semi arida de Machakos, Kenia

Low crop yields in the semi arid areas of Kenya have been attributed to, among other factors, low soil fertility, low farm inputs, labour constraints and inappropriate tillage practices that lead to pulverized soils. The aim of this study was to determine the effects of legume cover crops (LCC) on soil properties and maize growth in the semi arid area of Machakos District, Kenya. The study was undertaken in farmers’ fields. The field experiments were carried out in a RCBD with four treatments each replicated four times during the 2008 long (LR) and short rain (SR) seasons. The treatments were T1 = maize + dolichos (Lablab purpureus) + subsoiling; T2 = maize + dolichos + no subsoiling; T3 = maize alone + no subsoiling; T4 = maize alone with subsoiling). Results from the field experiments showed that rainfall amount and its distribution affected the growth and yield of dolichos and maize. There were significant differences in ground cover between the treatments at P = 0.05 in all the different weeks after planting when measurements were taken. The penetration resistance in all the plots ranged from 3.83 - 4.18 kg cm-2 with treatment T4 having the highest and treatment T1 lowest penetration resistance. There were also siginificant changes in soil N in plots which were under dolichos compared to plots without dolichos. The results obtained in this study also indicated that subsoiling in combination with dolichos had the greatest potential of improving soil properties and crop yields in semi arid environments of Kenya

Towards the specification and verification of modal properties for structured systems

System specification formalisms should come with suitable property specification languages and effective verification tools. We sketch a framework for the verification of quantified temporal properties of systems with dynamically evolving structure. We consider visual specification formalisms like graph transformation systems (GTS) where program states are modelled as graphs, and the program behavior is specified by graph transformation rules. The state space of a GTS can be represented as a graph transition system (GTrS), i.e. a transition system with states and transitions labelled, respectively, with a graph, and with a partial morphism representing the evolution of state components. Unfortunately, GTrSs are prohibitively large or infinite even for simple systems, making verification intractable and hence calling for appropriate abstraction techniques

Relación entre la orientación del cotilo y los cambios radiológicos evolutivos tras prótesis total de cadera tipo Charnley-Müller

Los autores realizan un estudio retrospectivo de 87 cotilos cementados, para averiguar si la posición del implante determina alteraciones radiológicas alrededor de este cotilo en la evolución de la prótesis total de cadera. Se valoraron una serie de parámetros radiológicos: protusión acetabular del cotilo, osteoporosis regional periacetabular, presencia de imágenes quísticas alrededor del acetábulo, presencia de esclerosis subcondral, calcificaciones yuxtacotiloideas y migración vertical del cotilo. Estos parámetros se relacionaron con los ángulos de inclinación y anteversión del cotilo. En los resultados obtenidos, destaca la relación estadísticamente significativa entre la posición del cotilo con la presencia de protusión acetabular, imágenes quísticas y osteoporosis regional y esclerosis subcondral periacetabulares. La posición «idónea» para este cotilo cementado parece ser de 35° a 45° el ángulo de inclinación y de 15° el ángulo de anteversiónEighty-seven cemented total hip prothesis were retrospectively reviewed in order to ascertain whether the position of the acetabular implant induces radiographic changes around the cup during follow-up. Several radiographic parameters were evaluated: acetabular protrusión of the cup, periacetabular local osteoporosis, cystic images, subchondral sclerosis, presence of calcifications around the cup and vertical displacement of the cup. These findings were correlated with the inclination and anteversion angles of the cup. A statistically significant correlation was found between the position of the cup the following parameters: degree of acetabular protrusion, presence of cystic images, local osteoporosis and periacetabular subchondral sclerosis. The ideal position of the cemented cup results to be of 35-45° inclination angle and 15° anteversion angle