Approximating J -holomorphic curves by holomorphic ones

Abstract.: Given an almost complex structure J in a cylinder of $\mathbb{R}^{2p}$ (p > 1) together with a compatible symplectic form $\omega$ and given an arbitrary J-holomorphic curve $\Sigma$ without boundary in that cylinder, we construct an holomorphic perturbation of $\Sigma$ , for the canonical complex structure J 0 of $\mathbb{R}^{2p}$ , such that the distance between these two curves in W 1,2 and $L^\infty$ norms, in a sub-cylinder, are controled by quantities depending on J, $\omega$ and by the area of $\Sigma$ only. These estimates depend neither on the topology nor on the conformal class of $\Sigma$ . They are key tools in the recent proof of the regularity of 1-1 integral currents in [RT

Antarctic Ozone Depletion and Trends in Tropopause Rossby Wave Breaking

Trends in summer tropopause Rossby wave breaking (RWB) are examined using meteorological reanalyses and model integrations. The reanalyses for the last 30 years show large increases in RWB on the equatorward side of the tropospheric jet and weak decreases on the poleward side. Comparable changes in RWB are found in general circulation model integrations whose stratospheric ozone differs between 1960 and 2000 levels, but not in integrations that differ only in their greenhouse gas concentrations and sea-surface temperatures. These results indicate that the formation of the ozone hole has led to changes in RWB frequency during southern summer

Desenganchados de la educación: procesos, experiencias, motivaciones y estrategias del abandono y del fracaso escolar

En este artículo, se presenta una parte de los resultados de una investigación sobre el fracaso y el abandono escolares llevada a cabo desde el Departamento de Sociología de la Universidad de Salamanca. La idea de partida, ya presentada en otras investigaciones, es que el abandono escolar prematuro es el resultado de un proceso progresivo de desvinculación de la escuela por parte de aquéllos que acaban abandonando antes de la obtención de un título post-obligatorio. Los diversos aspectos del proceso de fracaso deben observarse, desde este punto de vista, como síntomas de ese desenganche progresivo y previo por parte del alumno con respecto a la institución. El objetivo de este artículo es presentar los pasos y los elementos de este proceso a partir de la información con la que contamos. Para realizar este análisis, se ha recopilado una base de datos de expedientes (académicos, disciplinarios y de orientación) de alumnos entre 16 y más de 25 años que ya habían abandonado el sistema en el curso 2007-08, y se han realizado entrevistas con alumnos que han abandonado recientemente. A partir de esta información, se ha generado una serie de perfiles de comportamiento académico de los alumnos, se sientan las bases para realizar una crítica de la eficacia de las medidas de diversificación, y se corrobora la escasa importancia de los problemas disciplinarios en el proceso de abandono. Desde el punto de vista del alumnado, aparecen como elementos clave para el abandono: (1) la atracción relativa de la incorporación al empleo, (2) la desmotivación progresiva con la oferta vital de la escuela, (3) los cambios de centro, (4) el peso de los “malos profesores” y (5) la consideración del abandono como un éxito personal – como una victoria táctica–. Todos estos aspectos aparecen en los discursos de los alumnos como elementos clave en el proceso

First-principles modelling of molecular single-electron transistors

We present a first-principles method for calculating the charging energy of a molecular single-electron transistor operating in the Coulomb blockade regime. The properties of the molecule are modeled using density-functional theory, the environment is described by a continuum model, and the interaction between the molecule and the environment are included through the Poisson equation. The model is used to calculate the charge stability diagrams of a benzene and C$_{60}$ molecular single-electron transistor

Health economic evaluation of Human Papillomavirus vaccines in women from Venezuela by a lifetime Markov cohort model

Abstract Background Cervical cancer (CC) and genital warts (GW) are a significant public health issue in Venezuela. Our objective was to assess the cost-effectiveness of the two available vaccines, bivalent and quadrivalent, against Human Papillomavirus (HPV) in Venezuelan girls in order to inform decision-makers. Methods A previously published Markov cohort model, informed by the best available evidence, was adapted to the Venezuelan context to evaluate the effects of vaccination on health and healthcare costs from the perspective of the healthcare payer in an 11-year-old girls cohort of 264,489. Costs and quality-adjusted life years (QALYs) were discounted at 5%. Eight scenarios were analyzed to depict the cost-effectiveness under alternative vaccine prices, exchange rates and dosing schemes. Deterministic and probabilistic sensitivity analyses were performed. Results Compared to screening only, the bivalent and quadrivalent vaccines were cost-saving in all scenarios, avoiding 2,310 and 2,143 deaths, 4,781 and 4,431 CCs up to 18,459 GW for the quadrivalent vaccine and gaining 4,486 and 4,395 discounted QALYs respectively. For both vaccines, the main determinants of variations in the incremental costs-effectiveness ratio after running deterministic and probabilistic sensitivity analyses were transition probabilities, vaccine and cancer-treatment costs and HPV 16 and 18 distribution in CC cases. When comparing vaccines, none of them was consistently more cost-effective than the other. In sensitivity analyses, for these comparisons, the main determinants were GW incidence, the level of cross-protection and, for some scenarios, vaccines costs. Conclusions Immunization with the bivalent or quadrivalent HPV vaccines showed to be cost-saving or cost-effective in Venezuela, falling below the threshold of one Gross Domestic Product (GDP) per capita (104,404 VEF) per QALY gained. Deterministic and probabilistic sensitivity analyses confirmed the robustness of these results

Photoprocessing of H2S on dust grains: building S chains in translucent clouds and comets

Stars and planetary system

Ensemble Dynamics and Bred Vectors

We introduce the new concept of an EBV to assess the sensitivity of model outputs to changes in initial conditions for weather forecasting. The new algorithm, which we call the "Ensemble Bred Vector" or EBV, is based on collective dynamics in essential ways. By construction, the EBV algorithm produces one or more dominant vectors. We investigate the performance of EBV, comparing it to the BV algorithm as well as the finite-time Lyapunov Vectors. We give a theoretical justification to the observed fact that the vectors produced by BV, EBV, and the finite-time Lyapunov vectors are similar for small amplitudes. Numerical comparisons of BV and EBV for the 3-equation Lorenz model and for a forced, dissipative partial differential equation of Cahn-Hilliard type that arises in modeling the thermohaline circulation, demonstrate that the EBV yields a size-ordered description of the perturbation field, and is more robust than the BV in the higher nonlinear regime. The EBV yields insight into the fractal structure of the Lorenz attractor, and of the inertial manifold for the Cahn-Hilliard-type partial differential equation.Comment: Submitted to Monthly Weather Revie

An integrated approach of multiple correspondences analysis (MCA) and fuzzy AHP method for occupational health and safety performance evaluation in the land cargo transportation

Land cargo transportation is one of the components of the logistics chain with high impact on economic and social development worldwide. However, problems such as top logistics costs, deficiencies in transportation infrastructure and the failure to adopt good operating practices in aspects such as quality, environment, and occupational safety and health affect the ability of companies to comply with the agreements, requirements, and regulations of the clients and other interested parties. One of the most relevant problems for the sector is associated with the high accident rates that make this medium less advantageous compared to other means of transport with impact on operational costs, on logistics indicators, on compliance with legal regulations and customer satisfaction. However, although there are legal standards and management standards in occupational safety and health, evaluating performance can become a difficult and subjective process, due to the complexity of the land cargo transportation and the different interest groups involved. Besides, there is little information in the literature that provides solutions for the industry. Therefore, this document presents an integrated approach between multi-criterion decision making models (MCDM) and the Multiple Correspondences Analysis (MCA) to facilitate the evaluation and improvement of occupational health and safety performance, with a logical process, objective, robust and using both qualitative and quantitative techniques, with real application in the land cargo transportation sector. First, the multivariate method of Multiple Correspondences Analysis (MCA) was used for the evaluation of a sample of companies in the industry, considering the factors and sub-factors identified in the first stage and performing correlational analyzes among the variables. Subsequently, a multicriteria decision-making model was designed to determine the factors and sub-factors that affect occupational health and safety performance through the technique of the Fuzzy Analytic Hierarchy Process (FAHP). Finally, improvement strategies are proposed based on the approaches suggested in this document

Linking the dust and chemical evolution: Taurus and Perseus -- New collisional rates for HCN, HNC, and their C, N, and H isotopologues

HCN, HNC, and their isotopologues are ubiquitous molecules that can serve as chemical thermometers and evolutionary tracers to characterize star-forming regions. Despite their importance in carrying information that is vital to studies of the chemistry and evolution of star-forming regions, the collision rates of some of these molecules have not been available for rigorous studies in the past. We perform an up-to-date gas and dust chemical characterization of two different star-forming regions, TMC 1-C and NGC 1333-C7, using new collisional rates of HCN, HNC, and their isotopologues. We investigated the possible effects of the environment and stellar feedback in their chemistry and their evolution. With millimeter observations, we derived their column densities, the C and N isotopic fractions, the isomeric ratios, and the deuterium fractionation. The continuum data at 3 mm and 850 $\mu$m allowed us to compute the emissivity spectral index and look for grain growth as an evolutionary tracer. The H$^{13}$CN/HN$^{13}$C ratio is anticorrelated with the deuterium fraction of HCN, thus it can readily serve as a proxy for the temperature. The spectral index $(\beta\sim 1.34-2.09)$ shows a tentative anticorrelation with the H$^{13}$CN/HN$^{13}$C ratio, suggesting grain growth in the evolved, hotter, and less deuterated sources. Unlike TMC 1-C, the south-to-north gradient in dust temperature and spectral index observed in NGC 1333-C7 suggests feedback from the main NGC 1333 cloud. With this up-to-date characterization of two star-forming regions, we found that the chemistry and the physical properties are tightly related. The dust temperature, deuterium fraction, and the spectral index are complementary evolutionary tracers. The large-scale environmental factors may dominate the chemistry and evolution in clustered star-forming regions.Comment: 25 pages, 20 figure