Heterotic-type IIA duality with fluxes

In this paper we study a possible non-perturbative dual of the heterotic string compactified on K3 x T^2 in the presence of background fluxes. We show that type IIA string theory compactified on manifolds with SU(3) structure can account for a subset of the possible heterotic fluxes. This extends our previous analysis to a case of a non-perturbative duality with fluxes.Comment: 26 pages, minor corrections; version to appear in JHE

Evaluation of inorganic arsenic species in drinking water of the southeastern of the Buenos Aires province, Argentina

Arsenic in natural water is a worldwide concern due to chronic health effects in people exposed through the drinking water. The aim was to evaluate the distribution of As(III) and As(V), through ASV, in an Argentine area with low or absent information about these contaminant. The species of inorganic arsenic were quantified in groundwater, surface and drinking water, by Anodic Stripping Voltammetry (ASV) using a gold disc electrode. Total As was analyzed after the reduction step, calculated As(V) by difference. In some sites, total As values exceed the maximum limit for human consumption (10 µg/l), but the As(III)/As(V) ratio was significantly low. The lowest levels of total As were found in those sites related to possible anthropogenic activities, indicating that the content of it in the studied water is coming from natural environment. This study constitutes the first report of inorganic As speciation for the southeastern of Buenos Aires province.Fil: Robles, A. D. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras. Departamento de Ciencias Marinas. Toxicología Ambiental; Argentina.Fil: Robles, A. D. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Cohen, M. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras. Departamento de Ciencias Marinas. Toxicología Ambiental; Argentina.Fil: Romero, M. B. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras. Departamento de Ciencias Marinas. Toxicología Ambiental; Argentina.Fil: Romero, M. B. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Garay, F. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Físico Química; Argentina.Fil: Garay, F. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Bioquímica de Córdoba; Argentina.Fil: Gerpe, M. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras. Departamento de Ciencias Marinas. Toxicología Ambiental; Argentina.Fil: Gerpe, M. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Química Analític

High accuracy 234U(n,f) cross section in the resonance energy region

New results are presented of the 234U neutron-induced fission cross section, obtained with high accuracy in the resonance region by means of two methods using the 235U(n,f) as reference. The recent evaluation of the 235U(n,f) obtained with SAMMY by L. C. Leal et al. (these Proceedings), based on previous n-TOF data [1], has been used to calculate the 234U(n,f) cross section through the 234U/235U ratio, being here compared with the results obtained by using the n-TOF neutron flux

Characterization of the n-TOF EAR-2 neutron beam

The experimental area 2 (EAR-2) at CERNs neutron time-of-flight facility (n-TOF), which is operational since 2014, is designed and built as a short-distance complement to the experimental area 1 (EAR-1). The Parallel Plate Avalanche Counter (PPAC) monitor experiment was performed to characterize the beam prole and the shape of the neutron 'ux at EAR-2. The prompt γ-flash which is used for calibrating the time-of-flight at EAR-1 is not seen by PPAC at EAR-2, shedding light on the physical origin of this γ-flash

Measurement of the 240Pu(n,f) cross-section at the CERN n-TOF facility : First results from experimental area II (EAR-2)

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle is essential for the design of advanced nuclear systems, such as Generation-IV nuclear reactors. Such experimental data can also provide the necessary feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n-TOF facility relative to the well-known 235U(n,f) cross section, over a wide range of neutron energies, from meV to almost MeV, using the time-of-flight technique and a set-up based on Micromegas detectors. This measurement was the first experiment to be performed at n-TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the already existing experimental area (EAR-1). Preliminary results as well as the experimental procedure, including a description of the facility and the data handling and analysis, are presented

High-accuracy determination of the neutron flux in the new experimental area n_TOF-EAR2 at CERN

A new high flux experimental area has recently become operational at the n_TOF facility at CERN. This new measuring station, n_TOF-EAR2, is placed at the end of a vertical beam line at a distance of approximately 20m from the spallation target. The characterization of the neutron beam, in terms of flux, spatial profile and resolution function, is of crucial importance for the feasibility study and data analysis of all measurements to be performed in the new area. In this paper, the measurement of the neutron flux, performed with different solid-state and gaseous detection systems, and using three neutron-converting reactions considered standard in different energy regions is reported. The results of the various measurements have been combined, yielding an evaluated neutron energy distribution in a wide energy range, from 2meV to 100MeV, with an accuracy ranging from 2%, at low energy, to 6% in the high-energy region. In addition, an absolute normalization of the n_TOF-EAR2 neutron flux has been obtained by means of an activation measurement performed with 197Au foils in the beam.Peer reviewe

Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1¿, 9¿-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric, H 2 NMR, and calorimetric study

The nature of the nematic-nematic phase transition in the liquid crystal dimer 1¿, 9¿-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and H2 NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and H2 magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. H2 NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director

CREENCIAS, CONOCIMIENTOS Y PRÁCTICAS DE CONDUCTAS DE SALUD EN JOVENES UNIVERSITARIOS: EVOLUCIÓN EN UNA DÉCADA

El presente trabajo forma parte de un Estudio Europeo sobre Conducta y Salud realizado en 1990 y, de nuevo, en el 2000. Se estudian las diferencias entre hom-bres y mujeres en un amplio rango de conductas relacionadas con la salud, así como el nivel de conocimientos y las creencias sobre la importancia de tales con-ductas. La Encuesta Europea fue aplicada a 483 estudiantes. Las variables analiza-das son: tabaquismo, alcohol, conductas de conducción, y prácticas y cuidados preventivos. Los resultados, en general, comparados con el primer estudio, son desalentadores: Las mujeres fuman más, los hombres beben más habitualmente y, una prevalencia alta, conducen después de beber y, por último, continua muy baja la frecuencia de cuidados preventivos, especialmente en los hombres. De nuevo, encontramos una alta relación entre creencias y conductas, pero no entre éstas y conocimientos. Se enfatiza la necesidad de incrementar las actitudes positivas hacia estilos de vida saludables. Palabras clave: creencias, conocimientos, tabaquismo, alcohol, conducción, prevención

Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

Peer reviewe

D-instantons and twistors

Finding the exact, quantum corrected metric on the hypermultiplet moduli space in Type II string compactifications on Calabi-Yau threefolds is an outstanding open problem. We address this issue by relating the quaternionic-Kahler metric on the hypermultiplet moduli space to the complex contact geometry on its twistor space. In this framework, Euclidean D-brane instantons are captured by contact transformations between different patches. We derive those by recasting the previously known A-type D2-instanton corrections in the language of contact geometry, covariantizing the result under electro-magnetic duality, and using mirror symmetry. As a result, we are able to express the effects of all D-instantons in Type II compactifications concisely as a sum of dilogarithm functions. We conclude with some comments on the relation to microscopic degeneracies of four-dimensional BPS black holes and to the wall-crossing formula of Kontsevich and Soibelman, and on the form of the yet unknown NS5-brane instanton contributions.Comment: 47 pages, 1 figure, uses JHEP3.cl