Effect of Coulomb interactions on the optical properties of doped graphene

Recent optical conductivity experiments of doped graphene in the infrared regime reveal a strong background in the energy region between the intra and interband transitions difficult to explain within conventional pictures. We propose a phenomenological model taking into account the marginal Fermi liquid nature of the quasiparticles in graphene near the neutrality point that can explain qualitatively the observed features. We also study the electronic Raman signal and suggest that it will also be anomalous.Comment: 4 pages, 2 figure

Polymer/trimer/metal complex mixtures as precursors of gold nanoparticles: tuning the morphology in the solid-state

The pyrolysis of several physical mixtures of AuCl(PPh3) with polymeric [NP(O2C12H8)]n or cyclic N3P3(O2C12H8)3 phosphazenes, formed as solid powders or films with different molar ratios, have been studied under air and at 800 °C. The characterization of the products has shown that the particle size and morphology are strongly dependent on the nature of the phosphazene, the phosphazene/AuCl(PPh3) molar ratio and on the preparation methodology. Gold nanoparticles (NPs) with mean sizes as small as 3.5 nm were obtained from a [NP(O2C12H8)]n/AuCl(PPh3) 1:1 film. The particle morphology was also strongly dependent on the experimentally conditions of the pyrolysis. Powdered materials exhibit a 3-D irregular morphology in the mixture [NP(O2C12H8)]n/AuCl(PPh3) 3:1 film, and gold foams in the 1:1 ratio, both from the [NP(O2C12H8)]n/AuCl(PPh3) as well as N3P3(O2C12H8)3/AuCl(PPh3) mixtures. These results show for the first time the possibility of controlling morphology and size of gold particles obtained by solid-state reactions

Topological Fermi liquids from Coulomb interactions in the doped Honeycomb lattice

We get an anomalous Hall metallic state in the Honeycomb lattice with nearest neighbors only arising as a spontaneously broken symmetry state from a local nearest neighbor Coulomb interaction V . The key ingredient is to enlarge the unit cell to host six atoms that permits Kekul\'e distortions and supports self-consistent currents creating non trivial magnetic configurations with total zero flux. We find within a variational mean field approach a metallic phase with broken time reversal symmetry (T) very close in parameter space to a Pomeranchuk instability. Within the T broken region the predominant configuration is an anomalous Hall phase with non zero Hall conductivity, a realization of a topological Fermi liquid. A T broken phase with zero Hall conductivity is stable in a small region of the parameter space for lower values of V

Una propuesta metodológica para la identificación de categorías de paisajes culturales patrimoniales en la región noroeste de Corrientes

En el trabajo se propone delinear un proceso metodológico para el abordaje del estudio de los paisajes culturales de la región noroeste de Corrientes, de ocupación colonial española que por sus características es una de las más antiguas de la provincia. Esta región presenta ciertas particularidades naturales que, a través del tiempo, han condicionado fuertemente la historia de los asentamientos humanos establecidos en ella. Los paisajes culturales resultantes de su evolución son similares y, por tanto, comparables. Se pretende, a través de la metodología propuesta, arribar a la definición de categorías de paisaje que pudieran ser claramente identificables y comparables en la región, así como destacar su valor como bien patrimonial

El poblado histórico de Caá Catí : la dimensión de lo público y lo privado del paisaje cultural

El trabajo está centrado en el estudio de los paisajes culturales de Caá Catí donde se conjugan lo público y privado en la configuración del espacio como respuesta a las características climáticas que propiciaron la vida al aire libre y del paisaje natural definido por extensas áreas anegables, estrechos y alargadas lomadas arenosas, factores que condicionaron fuertemente el desarrollo urbano y económico-productivo, y forjaron un entramado social con fuertes rasgos identitarios expresados a través de manifestaciones culturales que hallan en el espacio público, creado en etapas tempranas y recreado en varias versiones hasta en la época actual, el lugar propicio para llevarlas a cabo. Por tanto, el estudio indaga sobre las características del soporte físico natural y en la conformación del tejido urbano en respuesta a las condiciones físicas, así como, en el tejido sociocultural que se fue conformando en respuesta a las dos primeras dimensiones a través de algunas de su expresiones culturales y religiosas más antiguas y emblemáticas, enlazando así, a modo de hilo conductor, el trinomio Paisaje-CulturaSociedad

Metallophosphazene precursor routes to the solid-state deposition of metallic and dielectric microstructures and nanostructures on Si and SiO2

We present a method for the preparation and deposition of metallic microstructures and nanostructures deposited on silicon and silica surfaces by pyrolysis in air at 800 °C of the corresponding metallophosphazene (cyclic or polymer). Atomic force microscopy studies reveal that the morphology is dependent on the polymeric or oligomeric nature of the phosphazene precursor, on the preparation method used, and on the silicon substrate surface (crystalline or amorphous) and its prior inductively couple plasma etching treatment. Microscale and nanoscale structures and high-surface-area thin films of gold, palladium, silver, and tin were successfully deposited from their respective newly synthesized precursors. The characteristic morphology of the deposited nanostructures resulted in varied roughness and increased surface area and was observed to be dependent on the precursor and the metal center. In contrast to island formation from noble metal precursors, we also report a coral of SnP2O7 growth on Si and SiO2 surfaces from the respective Sn polymer precursor, leaving a self-affine fractal structure with a well-defined roughness exponent that appears to be independent (within experimental error) of the average size of the islands. The nature of the precursor will be shown to influence the degree of surface features, and the mechanism of their formation is presented. The method reported here constitutes a new route to the deposition of single-crystal metallic, oxidic, and phosphate nanostructures and thin films on technologically relevant substrates

Aerosol properties over the western Mediterranean basin: temporal and spatial variability

This study focuses on the analysis of Aerosol Robotic Network (AERONET) aerosol data obtained over Alborán Island (35.90° N, 3.03° W, 15 m a.s.l.) in the western Mediterranean from July 2011 to January 2012. Additional aerosol data from the three nearest AERONET stations (Málaga, Oujda and Palma de Mallorca) and the Maritime Aerosol Network (MAN) were also analyzed in order to investigate the temporal and spatial variations of aerosol over this scarcely explored region. High aerosol loads over Alborán were mainly associated with desert dust transport from North Africa and occasional advection of anthropogenic fine particles from central European urban-industrial areas. The fine particle load observed over Alborán was surprisingly similar to that obtained over the other three nearest AERONET stations, suggesting homogeneous spatial distribution of fine particle loads over the four studied sites in spite of the large differences in local sources. The results from MAN acquired over the Mediterranean Sea, Black Sea and Atlantic Ocean from July to November 2011 revealed a pronounced predominance of fine particles during the cruise period.This work was supported by the Andalusia Regional Government through projects P12-RNM-2409 and P10-RNM-6299, by the Spanish Ministry of Science and Technology through projects CGL2010-18782, and CGL2013-45410-R; and by the EU through ACTRIS project (EU INFRA-2010-1.1.16-262254). CIMEL Calibration was performed at the AERONET-EUROPE calibration center, supported by ACTRIS (European Union Seventh Framework Program (FP7/2007-2013) under grant agreement no. 262254

Pro-oxidant status and matrix metalloproteinases in apical lesions and gingival crevicular fluid as potential biomarkers for asymptomatic apical periodontitis and endodontic treatment response

<p>Abstract</p> <p>Background</p> <p>Oxidative stress and matrix metalloproteinases -9 and -2 are involved in periodontal breakdown, whereas gingival crevicular fluid has been reported to reflect apical status. The aim of this study was to characterize oxidant balance and activity levels of MMP -2 and -9 in apical lesions and healthy periodontal ligament; and second, to determine whether potential changes in oxidant balance were reflected in gingival crevicular fluid from asymptomatic apical periodontitis (AAP)-affected teeth at baseline and after endodontic treatment.</p> <p>Methods</p> <p>Patients with clinical diagnosis of AAP and healthy volunteers having indication of tooth extraction were recruited. Apical lesions and healthy periodontal ligaments, respectively, were homogenized or processed to obtain histological tissue sections. Matrix metalloproteinase -9 and -2 levels and/or activity were analyzed by Immunowestern blot, zymography and consecutive densitometric analysis, and their tissue localization was confirmed by immunohistochemistry. A second group of patients with AAP and indication of endodontic treatment was recruited. Gingival crevicular fluid was extracted from AAP-affected teeth at baseline, after endodontic treatment and healthy contralateral teeth. Total oxidant and antioxidant status were determined in homogenized tissue and GCF samples. Statistical analysis was performed using STATA v10 software with unpaired t test, Mann-Whitney test and Spearman's correlation.</p> <p>Results</p> <p>Activity of MMP-2 and MMP-9 along with oxidant status were higher in apical lesions (p < 0.05). Total oxidant status correlated positively with matrix metalloproteinase-2 and lesion size (p < 0.05). Gingival crevicular fluid showed significantly lower levels of total antioxidant status in diseased teeth at baseline compared to controls and endodontically-treated groups.</p> <p>Conclusions</p> <p>Apical lesions display an oxidant imbalance along with increased activity of matrix metalloproteinase-2 and -9 and might contribute to AAP progression. Oxidant imbalance can also be reflected in GCF from AAP-affected teeth and was restored to normal levels after conservative endodontic treatment. These mediators might be useful as potential biomarkers for chair-side complementary diagnostic of apical status in GCF.</p

Should we use meshes or solid tube shelters when planting in Mediterranean semiarid environments?

Tree shelters in Mediterranean environments have a two-sided effect. They not only protect seedlings from browsing but also ameliorate microclimatic conditions, improving post-planting survival and growth. However, the ecophysiological basis of these effects are poorly understood. A factorial experiment combining light transmissivity and shelter type (solid tube vs. mesh wall) was carried out to assess the impact of contrasting microclimatic characteristics on seedling performance and physiological stress levels of shelters in two Mediterranean shrubland species (Quercus coccifera and Rhamnus lycioides) planted in a semiarid site. Even though seedlings in solid tube shelters experienced higher temperature and were slightly more photoinhibited, they had higher predawn water potential and, in general, better survival and growth than in mesh wall shelters. However, these effects were species-specific, with Rh. lycioides more favoured by solid wall shelters than Q. coccifera. However, root growth cannot explain these interactions between species and shelter type on seedling survival. Since light transmission had a marginal effect compared with wall type, we proposed that the observed effects and interaction with species are not dependent on light intensity or temperature but on other microclimatic differences like air velocity or light quality and distribution. Further studies should assess the importance of these factors on post-planting growth and physiological stress levels, which can be critical for matching the correct tree shelters type for each species in plantations in semiarid environments

Instancia comparativa de los paisajes culturales de la región noroeste de la provincia de Corrientes como herramienta para la planificación y gestión territorial

The northwest region of the province of Corrientes is made up of cultural landscapes originating in the times of colonial occupation and early republican years, whose evolution was conditioned by the natural geography that made its development difficult. This condition made possible, however, the conservation of colonial landscapes, although in a precarious state due to the lack of coordinated and collaborative public policies in the regional context. This condition made possible, however, the conservation of colonial landscapes, although in a precarious state due to the lack of coordinated and collaborative public policies in the regional context. To facilitate planning at a regional scale, a comparative analysis of cultural landscapes of five urban centers has been implemented, through a matrix that includes both the urban dimension, through the settlement processes that determined layers of the landscape, and the architectural and spatial dimension, through patterns.La región noroeste de la provincia de Corrientes está conformada por paisajes culturales originados en los tiempos de ocupación colonial y primeros años republicanos, cuya evolución fue condicionada por la geografía natural que dificultó su desarrollo. Esta condición posibilitó, sin embargo, la conservación de paisajes coloniales, aunque en estado precario debido a la falta de políticas públicas coordinadas y colaborativas en el contexto regional. Para facilitar la planificación a escala regional se ha implementado el análisis comparativo de paisajes culturales de cinco núcleos urbanos, a través de una matriz que incluye tanto la dimensión urbana, a través de los procesos de poblamiento que determinaron capas del paisaje, como la dimensión arquitectónica y espacial, a través de patrones