Tensorial perturbations in the bulk of inflating brane worlds

In this paper we consider the stability of some inflating brane-world models in quantum cosmology. It is shown that whereas the singular model based on the construction of inflating branes from Euclidean five-dimensional anti-de Sitter space is unstable to tensorial cosmological perturbations in the bulk, the nonsingular model which uses a five-dimensional asymptotically anti-de Sitter wormhole to construct the inflating branes is stable to these perturbations.Comment: 4 pages, RevTex, to appear in Phys. Rev.

Food portion sizes, obesity, and related metabolic complications in children and adolescents [Tamaño de las porciones de alimentos, obesidad y complicaciones metabólicas asociadas en niños y adolescentes]

The purpose of this narrative review is to provide evidence for the impact of food portion sizes on the development of obesity in children and adolescents. Strategies are needed on portion size estimation and on the relationship of portion size with certain health problems such as obesity, insulin resistance, and emotional eating in all age groups, in order to provide information for parents, teachers, and health professionals aiming to promote healthy eating. A wide range of controlled laboratory studies have found that portion size (PS) had the strongest effect on the amount of food consumed. The effect of PS on total energy intake has been already observed with different types of foods and beverages, especially with energy-dense foods. The influence of large PS was persistent and happened regardless of demographic characteristics such as age, gender, income level, or body mass index. Although a direct causal link between PS and obesity remains controversial, some health and dietetics organi-zations recommend to moderate PS, especially for energy-dense foods. Research studies in both laboratory and free-living contexts are needed to determine the causal link between increased PS, obesity, and related metabolic complications in children and adolescents

Tuning alginate microparticle size via atomization of non-newtonian fluids

A new approach based on the atomization of non-Newtonian fluids has been proposed to produce microparticles for a potential inhalation route. In particular, different solutions of algi-nate were atomized on baths of different crosslinkers, piperazine and barium chloride, obtaining microparticles around 5 and 40 microns, respectively. These results were explained as a consequence of the different viscoelastic properties, since oscillatory analysis indicated that the formed hydrogel beads with barium chloride had a higher storage modulus (1000 Pa) than the piperazine ones (20 Pa). Pressure ratio (polymer solution-air) was identified as a key factor, and it should be from 0.85 to 1.00 to ensure a successful atomization, obtaining the smallest particle size at intermediate pressures. Finally, a numerical study based on dimensionless numbers was performed to predict particle size depending on the conditions. These results highlight that it is possible to control the microparticles size by modifying either the viscoelasticity of the hydrogel or the experimental conditions of atom-ization. Some experimental conditions (using piperazine) reduce the particle size up to 5 microns and therefore allow their use by aerosol inhalation. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

POLYBIUS2020, a cost-effective underwater autonomous video system to record fishing gear selectivity performance catching fish and marine litter

Underwater video cameras are a highly versatile survey solution for marine fisheries research. The POLYBIUS2020 is a system specially designed to be used as a tool for video recording inside towed fishing gears. Its design allows for rapid installation onboard commercial fishing vessels as well as for quick reconfiguration and battery replacement. The system is based on simple commercial components to ensure low costs and the opportunity of future studies using house technology. The field experiments carried out have shown the flexibility and ability of the system to obtain key information about fishing selectivity, flora and fauna characterization and marine litter presence

Magnetotunneling Between Two-dimensional Electron Gases in InAs-AlSb-GaSb Heterostructures

We have observed that the tunneling magnetoconductance between two-dimensional (2D) electron gases formed at nominally identical InAs-AlSb interfaces most often exhibits two sets of Shubnikov-de Haas oscillations with almost the same frequency. This result is explained quantitatively with a model of the conductance in which the 2D gases have different densities and can tunnel between Landau levels with different quantum indices. When the epitaxial growth conditions of the interfaces are optimized, the zero-bias magnetoconductance shows a single set of oscillations, thus proving that the asymmetry between the two electron gases can be eliminated.Comment: RevTeX format including 4 figures; submit for publicatio

Mediterranean diet, diet quality, and bone mineral content in adolescents: the HELENA study

Summary: Dietary scores, rather than individual nutrients, allow exploring associations between overall diet and bone health. The aim of the present study was to assess the associations between the Mediterranean Diet Score for Adolescents (MDS-A) and the Diet Quality Index for Adolescents (DQI-A) and bone mineral content (BMC) among Spanish adolescents. Our results do not support an association between dietary scores or indices and BMC in adolescents. Introduction: To assess the associations between the MDS-A and a DQI-A with the BMC measured with dual-energy X-ray absorptiometry. Methods: The MDS-A and the DQI-A were calculated in 179 Spanish adolescents, based on two 24-h dietary recalls from the HELENA cross-sectional study. The associations between the diet scores and the BMC outcomes [total body less head (TBLH), femoral neck (FN), lumbar spine (LS), and hip] were analyzed using logistic regression models adjusting for several confounders. Results: Four hundred ninety-two models were included and only fruits and nuts and cereal and roots were found to provide significant ORs with regard to BMC. The risk of having low BMC reduced by 32% (OR 0.684; CI 0.473–0.988) for FN when following the ideal MDS-A, but this association lost significance when adjusting for lean mass and physical activity. For every 1-point increase in the cereal and root and the fruit and nut components, the risk of having low FN diminished by 56% (OR 0.442; CI 0.216–0.901) and by 67% (OR 0.332; CI 0.146–0.755), respectively. Conclusion: An overall dietary score or index is not associated with BMC in our adolescent Spanish sample

Review and comparison of effective delayed neutron fraction calculation methods with Monte Carlo codes

The calculation of the effective delayed neutron fraction, beff , with Monte Carlo codes is a complex task due to the requirement of properly considering the adjoint weighting of delayed neutrons. Nevertheless, several techniques have been proposed to circumvent this difficulty and obtain accurate Monte Carlo results for beff without the need of explicitly determining the adjoint flux. In this paper, we make a review of some of these techniques; namely we have analyzed two variants of what we call the k-eigenvalue technique and other techniques based on different interpretations of the physical meaning of the adjoint weighting. To test the validity of all these techniques we have implemented them with the MCNPX code and we have benchmarked them against a range of critical and subcritical systems for which either experimental or deterministic values of beff are available. Furthermore, several nuclear data libraries have been used in order to assess the impact of the uncertainty in nuclear data in the calculated value of beff

Nuclear data requirements for the ADS conceptual design EFIT: Uncertainty and sensitivity study

In this paper, we assess the impact of activation cross-section uncertainties on relevant fuel cycle parameters for a conceptual design of a modular European Facility for Industrial Transmutation (EFIT) with a “double strata” fuel cycle. Next, the nuclear data requirements are evaluated so that the parameters can meet the assigned design target accuracies. Different discharge burn-up levels are considered: a low burn-up, corresponding to the equilibrium cycle, and a high burn-up level, simulating the effects on the fuel of the multi-recycling scenario. In order to perform this study, we propose a methodology in two steps. Firstly, we compute the uncertainties on the system parameters by using a Monte Carlo simulation, as it is considered the most reliable approach to address this problem. Secondly, the analysis of the results is performed by a sensitivity technique, in order to identify the relevant reaction channels and prioritize the data improvement needs. Cross-section uncertainties are taken from the EAF-2007/UN library since it includes data for all the actinides potentially present in the irradiated fuel. Relevant uncertainties in some of the fuel cycle parameters have been obtained, and we conclude with recommendations for future nuclear data measurement programs, beyond the specific results obtained with the present nuclear data files and the limited available covariance information. A comparison with the uncertainty and accuracy analysis recently published by the WPEC-Subgroup26 of the OECD using BOLNA covariance matrices is performed. Despite the differences in the transmuter reactor used for the analysis, some conclusions obtained by Subgroup26 are qualitatively corroborated, and improvements for additional cross sections are suggested

Procesadores de bajo coste y su aplicación en la docencia de Ingeniería de Computadores

La Informática evoluciona a gran velocidad y es necesario actualizar con frecuencia los recursos de aprendizaje para mantener el interés de los estudiantes. En la actualidad, hay una gran diversidad de plataformas de cómputo de bajo coste que son utilizadas como recursos en los estudios de Informática. Raspberry Pi y algunos modelos de Arduino (como Arduino Due), ambas basadas en procesadores ARM, son ejemplos representativos de este tipo de plataformas. Las arquitecturas ARM son ejemplos de procesadores RISC que actualmente gozan de gran popularidad por su buena relación entre potencia computacional, consumo y coste. De hecho, constituyen el núcleo de muchos de los teléfonos móviles y sistemas empotrados actuales. Al estar tan cerca de los estudiantes, el uso de este tipo de recursos en el aula representa una oportunidad para: (1) motivar a los alumnos de Bachillerato y Educación Secundaria para estudiar el Grado de Informática y (2) potenciar el interés de los alumnos de Grado de Informática por la Ingeniería de Computadores. Existe una serie de eventos consolidados que tienen una gran difusión social. En ellos, se muestran vistosos ejemplos de aplicación y funcionamiento de este tipo de plataformas. En este trabajo se describen el conjunto de sistemas interactivos y basados en plataformas computacionales de bajo coste que se han desarrollado para ser utilizadas en este tipo de eventos. De acuerdo con nuestra experiencia de participación, creemos que están sirviendo para despertar el interés del alumno de secundaria por la Informática en general, y más específicamente por la Ingeniería de Computadores. Por otra parte, un porcentaje de los alumnos que cursan el Grado de Ingeniería Informática no está interesado en el análisis de los componentes hardware y de su organización para construir un computador moderno. Piensan que la asignatura de Arquitectura de Computadores del Grado en Ingeniería Informática está lejos de su futura actividad profesional. En este contexto, nos planteamos seleccionar ARM como arquitectura de referencia para desarrollar los contenidos de la asignatura de Arquitectura de Computadores. Creemos que esta decisión mejora el interés del alumno por dos motivos: (1) el objeto de estudio se usa en multitud de plataformas muy cotidianas para el alumno y (2) es posible diseñar las actividades prácticas de las asignaturas basadas en elementos reales y no únicamente virtuales. Este trabajo muestra las distintas actividades tanto a nivel teórico como práctico que se plantean al alumno en el marco de la asignatura Arquitectura de Computadores.Computer Science is advancing rapidly and it is necessary to keep the educational resources up to date in order to keep the interest of students. Nowadays, there is a wide variety of low-cost computing platforms that are used as educational resources in the Computer Science degree. Raspberry Pi and some models of Arduino (such as Arduino Due), which are both based on ARM processors, are representative examples of this kind of platforms. ARM architectures are instances of RISC processors which nowadays have reached an important popularity due to their good relation between performance, consumption and cost. In fact, they constitute the core of numerous current mobile phones and embedded systems. Considering their proximity to the students, the use of this kind of resources in the classroom is an opportunity to: (1) encourage the high schools pupils to study the Computer Science degree and (2) to increase the interest of the students for the Computer Engineering. There are several consolidated informational events of great social outreach in which different examples of application of this kind of platforms are shown. In this work, the set of interactive systems designed to be used in this kind of events is described. According to our experience, we think that they arouse the interest of high schools pupils for the Computer Science in general, and, more specifically, for the Computer Engineering. Furthermore, a percentage of the students of the Computer Science degree is not interested in the analysis of hardware components and the architecture of modern computers. They think that the subject of Computer Architecture of the Computer Science Degree is far from his/her future career. In this context, we will select ARM as a reference architecture where the contents of the subject Computer Architecture will be developed on. We think this might improve the motivation of the students mainly for two reasons: (1) the object of study is being used in a lot of modern platforms; and (2) it is possible to design the practical activities of the subjects using real platforms and not only virtual ones. This work shows the activities proposed to the students in the context of the subject Computer Architecture, considering both practical and theoretical approaches