SDS-PAGE for identification of species belonging to the Mycobacterium fortuitum complex

We performed a study to determine the usefulness of SDS-PAGE of whole cell proteins for the characterization of species of rapidly growing mycobacteria belonging to the Mycobacterium fortuitum complex. Strains included 37 M. fortuitum, 32 M. chelonae, 10 M. peregrinum, 5 M. abscessus, and 3 M. mucogenicum. Eight collection strains (including type strains of the five species) were also included in the study. All strains yielded between 44 and 58 bands in the electrophoretograms. Intraspecies similarity showed Dice coefficients higher than 95%, with only one strain of M. fortuitum having a six-band difference (Dice coefficient 87.75%). However, interspecies similarity was always below 75%, the similarity being higher between M. fortuitum and M. peregrinum (75.51%) and between M. chelonae and M. abscessus (54.9%). Visual examination of the electrophoretograms was sufficient for species characterization. SDS-PAGE of whole cell proteins is a useful technique for identification of isolates of the M. fortuitum complex, and is easy to perform without the need for complex or expensive equipment

A high efficiency 10W MMIC PA for K-b and satellite communications

This paper discusses the design steps and experimental characterization of a monolithic microwave integrated circuit (MMIC) power amplifier developed for the next generation of K-band 17.3–20.2 GHz very high throughput satellites. The technology used is a commercially available 100-nm gate length gallium nitride on silicon process. The chip was developed taking into account the demanding constraints of the spacecraft and, in particular, carefully considering the thermal constraints of such technology, in order to keep the junction temperature in all devices below 160°C in the worst-case condition (i.e., maximum environmental temperature of 85°C). The realized MMIC, based on a three-stage architecture, was first characterized on-wafer in pulsed regime and, subsequently, mounted in a test-jig and characterized under continuous wave operating conditions. In 17.3–20.2 GHz operating bandwidth, the built amplifier provides an output power >40 dBm with a power added efficiency close to 30% (peak >40%) and 22 dB of power gain

Interaction of Hydrogen with Graphitic Surfaces, Clean and Doped with Metal Clusters

Producción CientíficaHydrogen is viewed as a possible alternative to the fossil fuels in transportation. The technology of fuel-cell engines is fully developed, and the outstanding remaining problem is the storage of hydrogen in the vehicle. Porous materials, in which hydrogen is adsorbed on the pore walls, and in particular nanoporous carbons, have been investigated as potential onboard containers. Furthermore, metallic nanoparticles embedded in porous carbons catalyze the dissociation of hydrogen in the anode of the fuel cells. For these reasons the interaction of hydrogen with the surfaces of carbon materials is a topic of high technological interest. Computational modeling and the density functional formalism (DFT) are helping in the task of discovering the basic mechanisms of the interaction of hydrogen with clean and doped carbon surfaces. Planar and curved graphene provide good models for the walls of porous carbons. We first review work on the interaction of molecular and atomic hydrogen with graphene and graphene nanoribbons, and next we address the effects due to the presence of metal clusters on the surface because of the evidence of their role in enhancing hydrogen storage.Ministerio de Economía, Industria y Competitividad (Grant MAT2014-54378-R

Effects of landscape metrics and land-use variables on macroinvertebrate communities and habitat characteristics

ABSTRACT: The growing number of studies establishing links between stream biota, environmental factors and river classification has contributed to a better understanding of fluvial ecosystem function. Environmental factors influencing river systems are distributed over hierarchically organised spatial scales. We used a nested hierarchical sampling design across four catchments to assess how benthic macroinvertebrate community composition and lower spatial scale habitat descriptors were shaped by landscape and land-use patterns. We found that benthic macroinvertebrate community structure and composition varied significantly from catchment to habitat level. We assessed and identified fractal metrics of landscape descriptors capable of explaining compositional and functional change in the benthic faunal indicators and compared them with the traditional variables describing land use and reach level habitat descriptors within a 1 km radius of each sampling site. We found that fractal landscape metrics were the best predictor variables for benthic macroinvertebrate community composition, function, instream habitat and river corridor characteristics

Effects of landscape metrics and land-use variables on macroinvertebrate communities and habitat characteristics

The growing number of studies establishing links between stream biota, environmental factors and river classification has contributed to a better understanding of fluvial ecosystem function. Environmental factors influencing river systems are distributed over hierarchically organised spatial scales. We used a nested hierarchical sampling design across four catchments to assess how benthic macroinvertebrate community composition and lower spatial scale habitat descriptors were shaped by landscape and land-use patterns. We found that benthic macroinvertebrate community structure and composition varied significantly from catchment to habitat level. We assessed and identified fractal metrics of landscape descriptors capable of explaining compositional and functional change in the benthic faunal indicators and compared them with the traditional variables describing land use and reach level habitat descriptors within a 1 km radius of each sampling site. We found that fractal landscape metrics were the best predictor variables for benthic macroinvertebrate community composition, function, instream habitat and river corridor characteristics.El creciente número de estudios que relacionan la biota fluvial, los factores ambientales y la clasificación de los ríos, ha contribuido a comprender el funcionamiento de los ecosistemas fluviales. La organización de los factores ambientales fluviales es entendida, en la actualidad, como una jerarquía de factores con varias escalas espaciales. Para evaluar cómo la composición de los macroinvertebrados bentónicos y las características del hábitat a escala local son afectadas por el uso del paisaje y del suelo, se siguió un diseño de muestreo jerárquico en cuatro cuencas. Hemos verificado que la estructura y composición de las comunidades de macroinvertebrados bentónicos varió significativamente desde la escala de cuenca hasta la del hábitat. Fueron evaluadas e identificadas métricas fractales del paisaje que podrían explicar los cambios en la composición y funcionalidad de la fauna bentónica y se ha comparado también con la influencia de las tradicionales variables de usos del suelo y descriptores del hábitat al nivel del tramo, en un círculo de 1 km de radio alrededor de cada tramo. Encontramos que las métricas fractales del paisaje fueron las mejores variables predictoras de la composición y funcionalidad de las comunidades de macroinvertebrados y de las características del hábitat en el cauce y del corredor fluvial

From graphene oxide to pristine graphene: revealing the inner workings of the full structural restoration

Producción CientíficaHigh temperature annealing is the only method known to date that allows the complete repair of a defective lattice of graphenes derived from graphite oxide, but most of the relevant aspects of such restoration processes are poorly understood. Here, we investigate both experimentally (scanning probe microscopy) and theoretically (molecular dynamics simulations) the thermal evolution of individual graphene oxide sheets, which is rationalized on the basis of the generation and the dynamics of atomic vacancies in the carbon lattice. For unreduced and mildly reduced graphene oxide sheets, the amount of generated vacancies was so large that they disintegrated at 1773–2073 K. By contrast, highly reduced sheets survived annealing and their structure could be completely restored at 2073 K. For the latter, a minor atomic-sized defect with six-fold symmetry was observed and ascribed to a stable cluster of nitrogen dopants. The thermal behavior of the sheets was significantly altered when they were supported on a vacancy-decorated graphite substrate, as well as for the overlapped/stacked sheets. In these cases, a net transfer of carbon atoms between neighboring sheets via atomic vacancies takes place, affording an additional healing process. Direct evidence of sheet coalescence with the step edge of the graphite substrate was also gathered from experiments and theory.Ministerio de Economía, Industria y Competitividad (Project AT2011-26399 and MAT2011-22781)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA158A11-2

Optical absorption in boron clusters B6_{6} and B6+_{6}^{+} : A first principles configuration interaction approach

The linear optical absorption spectra in neutral boron cluster B$_{6}$ and cationic B$_{6}^{+}$ are calculated using a first principles correlated electron approach. The geometries of several low-lying isomers of these clusters were optimized at the coupled-cluster singles doubles (CCSD) level of theory. With these optimized ground-state geometries, excited states of different isomers were computed using the singles configuration-interaction (SCI) approach. The many body wavefunctions of various excited states have been analysed and the nature of optical excitation involved are found to be of collective, plasmonic type.Comment: 22 pages, 38 figures. An invited article submitted to European Physical Journal D. This work was presented in the International Symposium on Small Particles and Inorganic Clusters - XVI, held in Leuven, Belgiu

Fully relativistic calculation of magnetic properties of Fe, Co and Ni adclusters on Ag(100)

We present first principles calculations of the magnetic moments and magnetic anisotropy energies of small Fe, Co and Ni clusters on top of a Ag(100) surface as well as the exchange-coupling energy between two single adatoms of Fe or Co on Ag(100). The calculations are performed fully relativistically using the embedding technique within the Korringa-Kohn-Rostoker method. The magnetic anisotropy and the exchange-coupling energies are calculated by means of the force theorem. In the case of adatoms and dimers of iron and cobalt we obtain enhanced spin moments and, especially, unusually large orbital moments, while for nickel our calculations predict a complete absence of magnetism. For larger clusters, the magnitudes of the local moments of the atoms in the center of the cluster are very close to those calculated for the corresponding monolayers. Similar to the orbital moments, the contributions of the individual atoms to the magnetic anisotropy energy strongly depend on the position, hence, on the local environment of a particular atom within a given cluster. We find strong ferromagnetic coupling between two neighboring Fe or Co atoms and a rapid, oscillatory decay of the exchange-coupling energy with increasing distance between these two adatoms.Comment: 8 pages, ReVTeX + 4 figures (Encapsulated Postscript), submitted to PR

Mapping the temporary and perennial character of whole river networks

Knowledge of the spatial distribution of temporary and perennial river channels in a whole catchment is important for effective integrated basin management and river biodiversity conservation. However, this information is usually not available or is incomplete. In this study, we present a statistically based methodology to classify river segments from a whole river network (Deva-Cares catchment, Northern Spain) as temporary or perennial. This method is based on an a priori classification of a subset of river segments as temporary or perennial, using field surveys and aerial images, and then running Random Forest models to predict classification membership for the rest of the river network. The independent variables and the river network were derived following a computer-based geospatial simulation of riverine landscapes. The model results show high values of overall accuracy, sensitivity, and specificity for the evaluation of the fitted model to the training and testing data set (?0.9). The most important independent variables were catchment area, area occupied by broadleaf forest, minimum monthly precipitation in August, and average catchment elevation. The final map shows 7525 temporary river segments (1012.5 km) and 3731 perennial river segments (662.5 km). A subsequent validation of the mapping results using River Habitat Survey data and expert knowledge supported the validity of the proposed maps. We conclude that the proposed methodology is a valid method for mapping the limits of flow permanence that could substantially increase our understanding of the spatial links between terrestrial and aquatic interfaces, improving the research, management, and conservation of river biodiversity and functioning.We would like to thank the Journal Editor and the three referees for their comments and suggestions, which have greatly improved the manuscript. This study was partly funded by the Spanish Ministry of Economy and Competitiveness as part of the RIVERLANDS (Ref: BIA-2012–33572) and HYDRA (Ref: BIA-2015–71197) projects. Alexia María González-Ferreras is supported by a predoctoral research grant (Ref: BES-2013–065770) from the Spanish Ministry of Economy and Competitiveness, and José Barquín was supported by a Ramon y Cajal grant (Ref: RYC-2011–08313) from the Spanish Ministry of Economy and Competitiveness. We would like to thank the Government of Cantabria, the Principado de Asturias and the forest guards of the study areas for providing useful information. We would also like to acknowledge the Interautonomic Consortium of the Picos de Europa National Park and the Biodiversity Foundation from the Ministry of Agriculture, Food and Environment, for their advice and project support. Finally, we would also like to thank all the people involved in the field data collection, and those who read an early draft of the manuscript and suggested several improvements. The data and the data sources used in this study are cited and explained in the text. Readers can obtain further information about the data supporting the analysis and conclusions by contacting the corresponding author

Mycobacterium lentiflavum in Drinking Water Supplies, Australia

Humans may acquire infection from potable water