Large-Eddy Simulation closures of passive scalar turbulence: a systematic approach

The issue of the parameterization of small scale (``subgrid'') turbulence is addressed in the context of passive scalar transport. We focus on the Kraichnan advection model which lends itself to the analytical investigation of the closure problem. We derive systematically the dynamical equations which rule the evolution of the coarse-grained scalar field. At the lowest-order approximation in $l/r$, $l$ being the characteristic scale of the filter defining the coarse-grained scalar field and $r$ the inertial range separation, we recover the classical eddy-diffusivity parameterization of small scales. At the next-leading order a dynamical closure is obtained. The latter outperforms the classical model and is therefore a natural candidate for subgrid modelling of scalar transport in generic turbulent flows.Comment: 10 LaTex pages, 1 PS figure. Changes: comments added below previous (3.10); Previous (3.16) has been corrected; Minor changes in the conclusion

The Phoenix Deep Survey: The 1.4 GHz microJansky catalogue

The initial Phoenix Deep Survey (PDS) observations with the Australia Telescope Compact Array have been supplemented by additional 1.4 GHz observations over the past few years. Here we present details of the construction of a new mosaic image covering an area of 4.56 square degrees, an investigation of the reliability of the source measurements, and the 1.4 GHz source counts for the compiled radio catalogue. The mosaic achieves a 1-sigma rms noise of 12 microJy at its most sensitive, and a homogeneous radio-selected catalogue of over 2000 sources reaching flux densities as faint as 60 microJy has been compiled. The source parameter measurements are found to be consistent with the expected uncertainties from the image noise levels and the Gaussian source fitting procedure. A radio-selected sample avoids the complications of obscuration associated with optically-selected samples, and by utilising complementary PDS observations including multicolour optical, near-infrared and spectroscopic data, this radio catalogue will be used in a detailed investigation of the evolution in star-formation spanning the redshift range 0 < z < 1. The homogeneity of the catalogue ensures a consistent picture of galaxy evolution can be developed over the full cosmologically significant redshift range of interest. The 1.4 GHz mosaic image and the source catalogue are available on the web at http://www.atnf.csiro.au/~ahopkins/phoenix/ or from the authors by request.Comment: 16 pages, 11 figures, 4 tables. Accepted for publication by A

CHARACTERIZATION OF EQUILIBRIUM CONDITIONS OF ADSORBED SILICAGEL/WATER BED ACCORDING TO DUBININASTAKHOV AND FREUNDLICH

Systems of adsorption have been studied as an alternative for the cooling systems for saving electrical energy. The main advantage is the heat as the driving sources, for example, hot water or waste heat, widely used in the industries, and solar energy. The pair adsorbent/ adsorbate determines the behavior of these systems. Therefore, the knowledge of the equilibrium conditions between the adsorbent and the adsorbate is very important. The pair silica gel/water has the advantage of exploiting low-temperature heat sources. In this paper, the equilibrium conditions of the pair silica gel/water were investigated and the data were used to identify the coefficients of Dubinin-Astakhov equation and Freundlich equation. The experiments consisted of measuring temperature and pressure for different adsorbed mass of water in the adsorbent (silica gel). The amount of adsorbed mass (kg) per adsorbent mass (kg) used were: 0.007, 0.013, 0.024, 0.047, 0.092, 0.162 and 0.209. Both equations showed good agreement with experimental data, the coefficients of regression (R2) were 0.991 on the Dubinin-Astakhov equation and 0.993 for the Freundlich equation

Economic efficiency of public secondary education expenditure: how different are developed and developing countries?

Este estudio mide la eficiencia del gasto público en educación secundaria en 35 países desarrollados y en desarrollo mediante el uso de una metodología semiparamétrica DEA (análisis envolvente de datos) en dos pasos. En primer lugar, implementamos dos modelos de frontera transfronteriza para el período 2009-2012: uno que utiliza un aporte físico (es decir, relación maestro-alumno) y otro que utiliza un aporte monetario (es decir, gasto gubernamental por estudiante secundario). Estos resultados se corrigen por los efectos del PIB per cápita y el logro educativo de los adultos como insumos no discrecionales. Obtenemos cuatro resultados importantes: (i) los países desarrollados y en desarrollo tienen los mismos procesos de producción educativa cuando se comparan utilizando insumos físicos, pero no cuando se los compara con insumos monetarios; (ii) los países en desarrollo podrían aumentar sus tasas de matrícula y puntajes PISA en aproximadamente un 9% y un 5%, respectivamente, al mantener las mismas proporciones maestro-alumno y los niveles de gasto público que los países desarrollados; (iii) Irlanda, Japón y Corea son países eficientes en los dos modelos de frontera (Colombia también se incluye en esta categoría cuando se utiliza la relación maestro-alumno como insumo); y (iv) la sólida evidencia empírica indica que tanto el ingreso como el logro educativo de los padres afectan positivamente la eficiencia de la educación pública en ambos modelos.This study measures the efficiency of public secondary education expenditure in 35 developing and developed countries using a two-step semi-parametric DEA (data envelopment analysis) methodology. First, we implement two cross-country frontier models for the 2009-2012 period: one using a physical input (i.e., teacher-pupil ratio) and one using a monetary input (i.e., government expenditure per secondary student). These results are corrected by the effects of GDP per capita and adult educational attainment as non-discretionary inputs. We obtain four important results: (i) developed and developing countries have the same education production processes when they are compared using physical inputs but not when compared using monetary inputs; (ii) developing countries could increase their enrollment rates and PISA scores by approximately 9% and 5%, respectively, by maintaining the same teacher-pupil ratios and public spending levels as developed countries; (iii) Ireland, Japan and Korea are efficient countries in the two frontier models (Colombia is also included in this category when the teacher-pupil ratio is used as input); and (iv) robust empirical evidence indicates that both income and parental educational attainment positively affect the efficiency of public education in both models

Competition controls the rate of transition between the peripheral pools of CD4+CD25− and CD4+CD25+ T cells

Recent reports have hinted that it is possible to regenerate CD4+CD25+ regulatory T cells (Treg) from CD4+CD25− cells, a phenomenon termed conversion. We evaluated the relative contribution of this process to the Treg pool by transferring purified populations of CD4+ T cells into T cell-deficient mice. We report that conversion of CD25− cells into the CD4+CD25+Treg pool is minor if other bona fide CD25+ Tregs are present. Moreover, in the same hosts, the loss of CD25 expression by a population of Tregs also decreases in the presence of co-injected CD4+CD25− cells. Thus, the rate of exchange between CD25− and CD25+ T-cell populations is determined by the presence or absence of T-cell competitors. Our results attest for the role of competition in the contribution of different T-cell subsets for the regeneration of the peripheral CD4+ T-cell pool during lymphopeni

Coarse-grained description of a passive scalar

The issue of the parameterization of small-scale dynamics is addressed in the context of passive-scalar turbulence. The basic idea of our strategy is to identify dynamical equations for the coarse-grained scalar dynamics starting from closed equations for two-point statistical indicators. With the aim of performing a fully-analytical study, the Kraichnan advection model is considered. The white-in-time character of the latter model indeed leads to closed equations for the equal-time scalar correlation functions. The classical closure problem however still arises if a standard filtering procedure is applied to those equations in the spirit of the large-eddy-simulation strategy. We show both how to perform exact closures and how to identify the corresponding coarse-grained scalar evolution.Comment: 22 pages; submitted to Journal of Turbulenc

Análise da qualidade das águas superficiais de Ponte de Lima

No âmbito do tema recursos hídricos e o conceito de sustentabilidade, foi desenvolvido um estudo de caracterização do estado das águas superficiais, de uma área geográfica específica do Alto Minho. O desenvolvimento do estudo assentou numa base temporal e espacial de análise de parâmetros organolépticos, físico-químicos e microbiológicos. Fez-se uma previsão espacial e temporal de parâmetros de qualidade ao longo do rio, de montante para jusante, exclusivamente até aos pontos de amostragem (estações) referentes à área em estudo. Caracterizou-se alguns aspectos hidrográficos da bacia hidrográfica onde está inserida a região em estudo e também deu-se alguma relevância a aspectos sanitários da Estação de Tratamento de Águas Residuais da região. Foram também definidas algumas tendências em termos de indicadores fulcrais de sustentabilidade

A hot Jupiter transiting a mid-K dwarf found in the pre-OmegaCam Transit Survey

We describe the pre-OmegaTranS project, a deep survey for transiting extra-solar planets in the Carina region of the Galactic Disk. In 2006-2008 we observed a single dense stellar field with a very high cadence of ~2min using the ESO Wide Field Imager at the La Silla Observatory. Using the Astronomical Wide-field System for Europe and the Munich Difference Imaging Analysis pipeline, a module that has been developed for this project, we created the light curves of 16000 stars with more than 4000 data points which we searched for periodic transit signals using a box-fitting least-squares detection algorithm. All light curves are publicly available. In the course of the pre-OmegaTranS project we identified two planet candidates - POTS-1b and POTS-C2b - which we present in this work. With extensive follow-up observations we were able to confirm one of them, POTS-1b, a hot Jupiter transiting a mid-K dwarf. The planet has a mass of 2.31+-0.77M_Jup and a radius of 0.94+-0.04R_Jup and a period of P=3.16d. The host star POTS-1 has a radius of 0.59+-0.02R_Sun and a mass of 0.70+-0.05M_Sun. Due to its low apparent brightness of I=16.1mag the follow-up and confirmation of POTS-1b was particularly challenging and costly.Comment: 18 pages, 23 figures, accepted for publication in MNRA

An intra-vehicular wireless sensor network based on Android mobile devices and bluetooth low energy

This chapter presents the development and test of an intra-vehicular wireless sensor network (IVWSN), based on Bluetooth Low Energy (BLE), designed to present to the driver, in real-time, information collected from multiple sensors distributed inside of the car, using a human-machine interface (HMI) implemented on an Android smartphone. The architecture of the implemented BLE network is composed by the smartphone, which has the role of central station, and two BLE modules (peripheral stations) based on the CC2540 system-on-chip (SoC), which collect relevant sensor information from the battery system and the traction system of a plug-in electric car. Results based on an experimental performance evaluation of the wireless network show that the network is able to satisfy the application requirements, as long as the network parameters are properly configured taking into account the peculiarities of the BLE data transfer modes and the observed limitations of the BLE platform used in the implementation of the IVWSN.This work is supported by FCT with the reference project UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01-0145-FEDER-006941

Microjansky radio sources in DC0107-46 (Abell 2877)

The cluster DC0107-46 (Abell 2877) lies within the Phoenix Deep Survey, made at 1.4 GHz with the Australia Telescope Compact Array. Of 89 known optical cluster members, 70 lie within the radio survey area. Of these 70 galaxies, 15 (21%) are detected, with luminosities as faint as 10^20 W/Hz. Spectroscopic observations are available for 14/15 of the radio-detected cluster galaxies. Six galaxies show only absorption features and are typical low-luminosity AGN radio sources. One galaxy hosts a Seyfert 2 nucleus, two are star-forming galaxies, and the remaining five may be star-forming galaxies, AGNs, or both.Comment: 14 pages, 3 figures, Accepted by ApJS (v128n2p JUN 2000 issue