Brane Isotropisation in Extra-Dimensional Tolman-Bondi Universe

We consider the dynamics of a 3-brane embedded in an extra-dimensional Tolman-Bondi Universe where the origin of space plays a special role. The embedding is chosen such that the induced matter distribution on the brane respects the spherical symmetry of matter in the extra dimensional space. The mirage cosmology on the probe brane is studied, resulting in an inhomogeneous and anisotropic four dimensional cosmology where the origin of space is also special. We then focus on the spatial geometry around the origin and show that the induced geometry, which is initially inhomogeneous and anisotropic, converges to an isotropic and homogeneous Friedmann-Lemaitre 4d space-time. For instance, when a 3-brane is embedded in a 5d matter dominated model, the 4d dynamics around the origin converge to a Friedmann-Lemaitre Universe in a radiation dominated epoch. We analyse this isotropisation process and show that it is a late time attractor.Comment: 16 pages, 8 figures, one reference adde

Classification, characterisation and strategies for improvement of cattle and sheep pasture systems in marginal areas of Southern Chile

Pasture-based livestock systems in farms with medium or low size are especially important in less favored areas and are valuable for society. For these systems to survive, it is necessary to obtain an acceptable level of productivity and ensure commercialization of the products. This study was carried out in the district of Rio Ibáñez, General Carrera Province, in the XI (Aysén) Region of Chile. The sample consisted of 28 small-scale livestock farmers with dual-purpose cattle production; 16 of them also produced sheep for meat. The empirical data produced 55 variables which were subjected to multivariate analysis; three main components were obtained which explain 72.1 % of the variance. By cluster analysis it was obtained four groups with characteristics which varied by farm size, age and personal situation of farmers, farm management and farm profitability. The principal problems found are low productivity in the herds and the poor marketing channels of animals produced. In two groups, due to the low size and poor management, the profitability of the farms is very low and this may compromise their future. To improve production systems, the training and advice of farmers should be strengthened, investment should be supported, especially for young people, and the farmer partnership should be promoted. There is also a need to diversify the families' sources of income (sale of other farm products or handicrafts and touristic activities).Ministerio de Economía de Chile Innova-CORFO Project 11 NTEC 1279

Classification, characterisation and strategies for improvement of cattle and sheep pasture systems in marginal areas of Southern Chile

Pasture-based livestock systems in farms with medium or low size are especially important in less favored areas and are valuable for society. For these systems to survive, it is necessary to obtain an acceptable level of productivity and ensure commercialization of the products. This study was carried out in the district of Rio Ibáñez, General Carrera Province, in the XI (Aysén) Region of Chile. The sample consisted of 28 small-scale livestock farmers with dual-purpose cattle production; 16 of them also produced sheep for meat. The empirical data produced 55 variables which were subjected to multivariate analysis; three main components were obtained which explain 72.1 % of the variance. By cluster analysis it was obtained four groups with characteristics which varied by farm size, age and personal situation of farmers, farm management and farm profitability. The principal problems found are low productivity in the herds and the poor marketing channels of animals produced. In two groups, due to the low size and poor management, the profitability of the farms is very low and this may compromise their future. To improve production systems, the training and advice of farmers should be strengthened, investment should be supported, especially for young people, and the farmer partnership should be promoted. There is also a need to diversify the families' sources of income (sale of other farm products or handicrafts and touristic activities).Ministerio de Economía de Chile Innova-CORFO Project 11 NTEC 1279

PowerAqua: fishing the semantic web

The Semantic Web (SW) offers an opportunity to develop novel, sophisticated forms of question answering (QA). Specifically, the availability of distributed semantic markup on a large scale opens the way to QA systems which can make use of such semantic information to provide precise, formally derived answers to questions. At the same time the distributed, heterogeneous, large-scale nature of the semantic information introduces significant challenges. In this paper we describe the design of a QA system, PowerAqua, designed to exploit semantic markup on the web to provide answers to questions posed in natural language. PowerAqua does not assume that the user has any prior information about the semantic resources. The system takes as input a natural language query, translates it into a set of logical queries, which are then answered by consulting and aggregating information derived from multiple heterogeneous semantic sources

Mentalizing in mothers and children with type 1 diabetes

Studies suggest that the relationship between psychosocial well-being and type 1 diabetes (T1D) is bidirectional, with T1D typically having a negative influence on psychological functioning, which in turn negatively affects the course of T1D. Here, we investigate the potential role of the capacity for mentalizing, or reflective functioning, in children and their mothers in diabetes control. We tested differences in mentalizing as assessed by the Reflective Functioning Scale in two groups of mother–son dyads with good (GDC) versus poor (PDC) diabetes control. Fifty-five boys (8–12 years old) and their mothers were recruited from the Juvenile Diabetes Foundation in Santiago, Chile. The mothers were interviewed with the Parental Development Interview and the children with the Child Attachment Interview, and both were scored for reflective functioning by using the Reflective Functioning Scale. Self-report measures of stress and diabetes outcomes were completed by the mothers and children, and levels of glycated hemoglobin (HbA1c) were assessed as an index of diabetes control. The results showed that both maternal and child reflective functioning were higher in the GDC than the PDC group and were negatively correlated with HbA1c in the total sample. Our findings suggest an important role for mentalizing in diabetes outcomes, but further prospective research is needed

An SIS-based sideband-separating heterodyne mixer optimized for the 600 to 720 GHz band

The Atacama Large Millimeter Array (ALMA) is the largest radio astronomical enterprise ever proposed. When completed, each of its 64 constituting radio-telescopes will be able to hold 10 heterodyne receivers covering the spectroscopic windows allowed by the atmospheric transmission at the construction site, the altiplanos of the northern Chilean Andes. In contrast to the sideband-separating (2SB) receivers being developed at low frequencies, double-side-band (DSB) receivers are being developed for the highest two spectroscopic windows (bands 9 and 10). Despite of the well known advantages of 2SB mixers over their DSB counterparts, they have not been implemented at the highest-frequency bands as the involved dimensions for some of the radio frequency components are prohibitory small. However, the current state-of-the-art micromachining technology has proved that the structures necessary for this development are attainable. Here we report the design, modeling, realization, and characterization of a 2SB mixer for band 9 of ALMA (600 to 720 GHz). At the heart of the mixer, two superconductor-insulator-superconductor (SIS) junctions are used as mixing elements. The constructed instrument presents an excellent performance as shown by two important figures of merit: noise temperature of the system and side band ratio, both of them within ALMA specifications

Spherically symmetric perfect fluid in area-radial coordinates

We study the spherically symmetric collapse of a perfect fluid using area-radial coordinates. We show that analytic mass functions describe a static regular centre in these coordinates. In this case, a central singularity can not be realized without an infinite discontinuity in the central density. We construct mass functions involving fluid dynamics at the centre and investigate the relationship between those and the nature of the singularities.Comment: Accepted by CQG. LaTex file, 14 pages, no figure

Measurement of gas phase characteristics using amonofibre optical probe in a three-phase flow

The study of gas–liquid–solid systems structure requires reliable measurement tools. In this paper, preliminary results on the potential use of a monofibre optical probe to investigate such flow are presented. This probe, manufactured at LEGI, allows the simultaneous measurement of the gas phase residence time and gas phase velocity. This specificity makes this probe more interesting than classical single tip probes (which measure only the gas residence time) or double tip probes (which are more intrusive). Although extensively used in two-phase gas–liquid, this probe was never used in gas–liquid–solid systems. First, the probe signal response is studied for three-phase flow conditions in the presence of solids. Results show that for soft solids, the probe tips can be contaminated when the probe pierces the solid. The signal processing procedure was modified accordingly to take into account these events. Second, the probe results are validated by comparing global results (global void fraction, gas flowrate) deduced from profile measurements with measurements performed by independent means. Lastly, void fraction profiles and interfacial area are studied more in detail. Depending on the solid loading, these profiles exhibit different behaviours. These features are associated to characteristics of the flow such as the transition from an homogeneous regime to an heterogenous regime, and are consistent with global observation performed by independent means. This demonstrates the ability of the probe to connect local information to the global behaviour and structure of the flow.Fundação para a Ciência e a Tecnologia (FCT

Ultra-pure digital sideband separation at sub-millimeter wavelengths

Deep spectral-line surveys in the mm and sub-mm range can detect thousands of lines per band uncovering the rich chemistry of molecular clouds, star forming regions and circumstellar envelopes, among others objects. The ability to study the faintest features of spectroscopic observation is, nevertheless, limited by a number of factors. The most important are the source complexity (line density), limited spectral resolution and insufficient sideband (image) rejection (SRR). Dual Sideband (2SB) millimeter receivers separate upper and lower sideband rejecting the unwanted image by about 15 dB, but they are difficult to build and, until now, only feasible up to about 500 GHz (equivalent to ALMA Band 8). For example ALMA Bands 9 (602-720 GHz) and 10 (787-950 GHz) are currently DSB receivers. Aims: This article reports the implementation of an ALMA Band 9 2SB prototype receiver that makes use of a new technique called calibrated digital sideband separation. The new method promises to ease the manufacturing of 2SB receivers, dramatically increase sideband rejection and allow 2SB instruments at the high frequencies currently covered only by Double Sideband (DSB) or bolometric detectors. Methods: We made use of a Field Programmable Gate Array (FPGA) and fast Analog to Digital Converters (ADCs) to measure and calibrate the receiver's front end phase and amplitude imbalances to achieve sideband separation beyond the possibilities of purely analog receivers. The technique could in principle allow the operation of 2SB receivers even when only imbalanced front ends can be built, particularly at very high frequencies. Results: This digital 2SB receiver shows an average sideband rejection of 45.9 dB while small portions of the band drop below 40 dB. The performance is 27 dB (a factor of 500) better than the average performance of the proof-of-concept Band 9 purely-analog 2SB prototype receiver.Comment: 5 page