TELLUS: A combined surface temperature, soil moisture and evaporation mapping approach

There are no author-identified significant results in this report

Role of bound pairs in the optical properties of highly excited semiconductors: a self consistent ladder approximation approach

Presence of bound pairs (excitons) in a low-temperature electron-hole plasma is accounted for by including correlation between fermions at the ladder level. Using a simplified one-dimensional model with on-site Coulomb interaction, we calculate the one-particle self-energies, chemical potential, and optical response. The results are compared to those obtained in the Born approximation, which does not account for bound pairs. In the self-consistent ladder approximation the self-energy and spectral function show a characteristic correlation peak at the exciton energy for low temperature and density. In this regime the Born approximation overestimates the chemical potential. Provided the appropriate vertex correction in the interaction with the photon is included, both ladder and Born approximations reproduce the excitonic and free pair optical absorption at low density, and the disappearance of the exciton absorption peak at larger density. However, lineshapes and energy shifts with density of the absorption and photoluminescence peaks are drastically different. In particular, the photoluminescence emission peak is much more stable in the ladder approximation. At low temperature and density a sizeable optical gain is produced in both approximations just below the excitonic peak, however this gain shows unphysical features in the Born approximation. We conclude that at low density and temperature it is fundamental to take into account the existence of bound pairs in the electron-hole plasma for the calculation of its optical and thermodynamic properties. Other approximations that fail to do so are intrinsically unphysical in this regime, and for example are not suitable to address the problem of excitonic lasing.Comment: 14 pages, 12 figure

Gravity map of the isla Grande de Tierra de Fuego, and morphology of Lago Fagnano

A complete Bouguer gravity map of the central-eastern part of the Isla Grande de Tierra del Fuego, and a general bathymetric chart of the Lago Fagnano have been realized, on the basis of a series of field geophysical surveys carried out on the Island since 1998. The regional gravity anomaly trend onshore shows a progressive negative gradient from N to S. Distinct, broadly E-W-trending gravity minima are superimposed on this regional negative gradient. They follow the main trace of the Magallanes-Fagnano fault system, which represents the western segment of the left-lateral South America-Scotia transform plate boundary. The gravity minima reflect the presence in the subsurface of restricted and elongated basins developed within the principal displacement zone of the fault system. A relative positive gravity maximum is located just at the SE corner of the Lago Fagnano, and represents the response of a partially exposed crystalline body, occupying an area 3 x 3 km wide. A 2D vertical crustal model has been constructed, combining gravity data inversion and geological information available for the central-eastern region of Lago Fagnano. The bathymetric map of the Lago Fagnano delineates the main morphological features of this 110-km-long, 7-km-wide lake, the largest of Isla Grande. The floor is divided into distinct parts, which suggests that the basin is composed of different sub-basins. In most areas, the basin floor is highly asymmetric in shape, with flat depocentral areas. The most pronounced asymmetry of the basin is seen in the eastern end of the lake, where there is also the deepest depression. The steeper slope of the basin, along the northern shore of the Lago Fagnano, also coincides with the most pronounced regional topographic gradient. The general gravimetric and morphological features of the investigated region are here discussed

Requerimientos de energía de cincel y subsolador en suelos de la Región Semiárida Pampeana

Los suelos agrícolas de la Región Semiárida Pampeana presentan, por lo general, capas subsuperficiales endurecidas, con distintos grados de densificación, produciendo efectos negativos en el rendimiento de los cultivos. El control de estas capas con labranza vertical profunda, tiene efectos diferentes sobre el suelo y distintos requerimientos de energía del tractor, según el diseño de herramienta que se utilice. En el presente trabajo se estudiaron un arado de cinceles y un subsolador a dos velocidades de trabajo, en Haplustoles énticos de la Facultad de Agronomía de la Universidad Nacional de La Pampa. Se realizaron determinaciones de esfuerzos de tracción, patinamiento, humedad del suelo, velocidad de trabajo y consumo de combustible. Los datos obtenidos fueron analizados por medio del test de Tukey con una significancia del 5%. Entre los dos diseños utilizados no se encontraron diferencias significativas en la roturación del suelo, excepto entre los 20-25 cm de profundidad, donde se observó mejores efectos con el subsolador. No hubo diferencias significativas en el esfuerzo de tracción al aumentar la velocidad de trabajo de ambos diseños. Se registraron esfuerzos de tracción y requerimientos de potencia, significativamente mayores para el cincel que para el sub solador.Director: lng. Agr. Ulises R. Hernández. Cátedra de Maquinaria Agrícola.

Ultrasound-guided oblique approach for peripheral venous access in a phantom model

BACKGROUND: Ultrasound (US) vascular guidance is traditionally performed in transverse (T) and longitudinal (L) axes, each with drawbacks. We hypothesized that the introduction of a novel oblique (O) approach would improve the success of US-guided peripheral venous access. We examined emergency physician (EP) performance using the O approach in a gel US phantom. METHODS: In a prospective, case control study, EPs were enrolled from four levels of physician experience including postgraduate years one to three (PGY1, PGY2, PGY3) and attending physicians. After a brief training session, each participant attempted vessel aspiration using a linear probe in T, L, and O axes on a gel US phantom. Time to aspiration and number of attempts to aspiration were recorded. The approach order was randomized, and descriptive statistics were used. RESULTS: Twenty-four physicians participated. The first-attempt success rate was lower for O, 45.83%, versus 70.83% for T (p = 0.03) and 83.33% for L (p = 0.01). The average time to aspiration was 12.5 s (O) compared with 9.47 s (T) and 9.74 s (L), respectively. There were no significant differences between all four groups in regard to total amount of time and number of aspiration attempts; however, a trend appeared revealing that PGY3 and attending physicians tended to aspirate in less time and by fewer attempts in all three orientations when compared with the PGY2 and PGY1 physicians. CONCLUSION: In this pilot study, US-guided simulated peripheral venous access using a phantom gel model in a mixed user group showed that the novel oblique approach was not initially more successful versus T and L techniques

Electron-hole correlation effects in the emission of light from quantum wires

We present a self-consistent treatment of the electron-hole correlations in optically excited quantum wires within the ladder approximation, and using a contact potential interaction. The limitations of the ladder approximation to the excitonic low-density region are largely overcome by the introduction of higher order correlations through self consistency. We show relevance of these correlations in the low-temperature emission, even for high density relevant in lasing, when large gain replaces excitonic absorption.Comment: 4 paes 3 figure

Immune Camouflage: Relevance to Vaccine Design and Human Immunology

High strain sequence variability, interference with innate immune mechanisms, and epitope deletion are all examples of strategies that pathogens have evolved to subvert host defenses. To this list we would add another strategy: immune camouflage. Pathogens whose epitope sequences are cross-conserved with multiple human proteins at the TCR-facing residues may be exploiting ignorance and tolerance, which are mechanisms by which mature T cells avoid immune responses to self-antigens. By adopting amino acid configurations that may be recognized by autologous regulatory T cells, pathogens may be actively suppressing protective immunity. Using the new JanusMatrix TCR-homology-mapping tool, we have identified several such \u27camouflaged\u27 tolerizing epitopes that are present in the viral genomes of pathogens such as emerging H7N9 influenza. Thus in addition to the overall low number of T helper epitopes that is present in H7 hemaglutinin (as described previously, see http://dx.doi.org/10.4161/hv.24939), the presence of such tolerizing epitopes in H7N9 could explain why, in recent vaccine trials, whole H7N9-HA was poorly immunogenic and associated with low seroconversion rates (see http://dx.doi.org/10.4161/hv.28135). In this commentary, we provide an overview of the immunoinformatics process leading to the discovery of tolerizing epitopes in pathogen genomic sequences, provide a brief summary of laboratory data that validates the discovery, and point the way forward. Removal of viral, bacterial and parasite tolerizing epitopes may permit researchers to develop more effective vaccines and immunotherapeutics in the future

Profile alterations of a symmetrical light pulse coming through a quantum well

The theory of a response of a two-energy-level system, irradiated by symmetrical light pulses, has been developed.(Suchlike electronic system approximates under the definite conditions a single ideal quantum well (QW) in a strong magnetic field {\bf H}, directed perpendicularly to the QW's plane, or in magnetic field absence.) The general formulae for the time-dependence of non-dimensional reflection {\cal R}(t), absorption {\cal A}(t) and transmission {\cal T}(t) of a symmetrical light pulse have been obtained. It has been shown that the singularities of three types exist on the dependencies {\cal R}(t), {\cal A}(t), {\cal T}(t). The oscillating time dependence of {\cal R}(t), {\cal A}(t), {\cal T}(t) on the detuning frequency \Delta\omega=\omega_l-\omega_0 takes place. The oscillations are more easily observable when \Delta\omega\simeq\gamma_l. The positions of the total absorption, reflection and transparency singularities are examined when the frequency \omega_l is detuned.Comment: 9 pages, 13 figures with caption

iVax: An integrated toolkit for the selection and optimization of antigens and the design of epitope-driven vaccines

Computational vaccine design, also known as computational vaccinology, encompasses epitope mapping, antigen selection and immunogen design using computational tools. The iVAX toolkit is an integrated set of tools that has been in development since 1998 by De Groot and Martin. It comprises a suite of immunoinformatics algorithms for triaging candidate antigens, selecting immunogenic and conserved T cell epitopes, eliminating regulatory T cell epitopes, and optimizing antigens for immunogenicity and protection against disease. iVAX has been applied to vaccine development programs for emerging infectious diseases, cancer antigens and biodefense targets. Several iVAX vaccine design projects have had success in pre-clinical studies in animal models and are progressing toward clinical studies. The toolkit now incorporates a range of immunoinformatics tools for infectious disease and cancer immunotherapy vaccine design. This article will provide a guide to the iVAX approach to computational vaccinology

Spontaneous formation and stability of small GaP fullerenes

We report the spontaneous formation of a GaP fullerene cage in ab-initio Molecular Dynamics simulations starting from a bulk fragment. A systematic study of the geometric and electronic properties of neutral and ionized GaP clusters suggests the stability of hetero-fullerenes formed by a compound with zincblend bulk structure. We find that GaP fullerenes up to 28 atoms have high symmetry, closed electronic shells, large HOMO-LUMO energy gaps and do not dissociate when ionized. We compare our results for GaP with those obtained by other groups for the corresponding BN clusters.Comment: To appear on PRL, 4 pages, 1 figure, Late