2,961 research outputs found

    Conceptual design of the EU-DEMO dual coolant lithium lead equatorial module

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    © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Within the framework of EUROfusion Program, the Dual Coolant Lithium Lead (DCLL) is one of the four EU breeder blanket concepts that are being investigated as candidates for DEMO. DCLL uses PbLi as the main coolant, tritium breeder, tritium carrier, and neutron multiplier. The main structures, including the first wall, are cooled with helium. The EU program proposed for the next years will consider a DCLL version limited to 550 °C in order to allow the use of conventional materials and technologies. During the first year of EUROfusion activities, a draft design of the DCLL has been proposed. The main blanket performances were adapted to the new specifications and the CAD model of DEMO. The breeder zone has been toroidally divided into four parallel PbLi circuits, separated through stiffening grid radial walls. The PbLi flow routing has been designed to maximize the amount of thermal power extracted by flowing PbLi and to avoid the occurrence of reverse flows due to volumetric heating. Thermal hydraulics, magnetohydrodynamic and neutronics calculations have been performed for the first draft design. The new DCLL design employs Eurofer-alumina-Eurofer sandwich as flow channel insert (FCI).Postprint (published version

    Effectiveness of a Multifactorial Intervention in the First 1000 Days of Life to Prevent Obesity and Overweight in Childhood: Study Protoco

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    (1) Background: Obesity is a global health problem, and its prevention must be a priority goal of public health, especially considering the seriousness of the problem among children. It is known that fetal and early postnatal environments may favor the appearance of obesity in later life. In recent years, the impact of the programs to prevent obesity in childhood has been scarce. The aim of this research is to evaluate the effectiveness of an intervention based on the concept of early programming. (2) Methods: Non-randomized controlled trial design. Inclusion criteria are: two-year-old infants whose gestational period begins in the 14 months following the start of the intervention, and whose mothers have made the complete follow-up of their pregnancy in the same clinical unit of the study. The intervention will be developed over all the known factors that affect early programming, during pregnancy up to 2 years of life. Data will be collected through a data collection sheet by the paediatricians. A unibivariate and multivariate analysis of the data will be carried out. (3) Ethics and dissemination: The trial does not involve any risk to participants and their offspring. Signed informed consent is obtained from all participants. Ethical approval has been obtained. (4) Results: It is expected that this study will provide evidence on the importance of the prevention of obesity from the critical period of the first 1000 days of life, being able to establish this as a standard intervention in primary care

    The impact of dopaminergic treatment over cognitive networks in Parkinson's disease : Stemming the tide?

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    Altres ajuts: Fundació la Marató de TV3/20142910Dopamine-replacing therapies are an effective treatment for the motor aspects of Parkinson's disease. However, its precise effect over the cognitive resting-state networks is not clear; whether dopaminergic treatment normalizes their functional connectivity-as in other networks- and the links with cognitive decline are presently unknown. We recruited 35 nondemented PD patients and 16 age-matched controls. Clinical and neuropsychological assessments were performed at baseline, and conversion to dementia was assessed in a 10 year follow-up. Structural and functional brain imaging were acquired in both the ON and practical OFF conditions. We assessed functional connectivity in both medication states compared to healthy controls, connectivity differences within participants related to the ON/OFF condition, and baseline connectivity of PD participants that converted to dementia compared to those who did not convert. PD participants showed and increased frontoparietal connectivity compared to controls: a pattern of higher connectivity between salience (SN) and default-mode (DMN) networks both in the ON and OFF states. Within PD patients, this higher SN-DMN connectivity characterized the participants in the ON state, while within-DMN connectivity prevailed in the OFF state. Interestingly, participants who converted to dementia also showed higher SN-DMN connectivity in their baseline ON scans compared to nonconverters. To conclude, PD patients showed higher frontoparietal connectivity in cognitive networks compared to healthy controls, irrespective of medication status, but dopaminergic treatment specifically promoted SN-DM hyperconnectivity

    The impact of dopaminergic treatment over cognitive networks in Parkinson's disease: Stemming the tide?

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    Dopamine-replacing therapies are an effective treatment for the motor aspects of Parkinson's disease. However, its precise effect over the cognitive resting-state networks is not clear; whether dopaminergic treatment normalizes their functional connectivity-as in other networks- and the links with cognitive decline are presently unknown. We recruited 35 nondemented PD patients and 16 age-matched controls. Clinical and neuropsychological assessments were performed at baseline, and conversion to dementia was assessed in a 10 year follow-up. Structural and functional brain imaging were acquired in both the ON and practical OFF conditions. We assessed functional connectivity in both medication states compared to healthy controls, connectivity differences within participants related to the ON/OFF condition, and baseline connectivity of PD participants that converted to dementia compared to those who did not convert. PD participants showed and increased frontoparietal connectivity compared to controls: a pattern of higher connectivity between salience (SN) and default-mode (DMN) networks both in the ON and OFF states. Within PD patients, this higher SN-DMN connectivity characterized the participants in the ON state, while within-DMN connectivity prevailed in the OFF state. Interestingly, participants who converted to dementia also showed higher SN-DMN connectivity in their baseline ON scans compared to nonconverters. To conclude, PD patients showed higher frontoparietal connectivity in cognitive networks compared to healthy controls, irrespective of medication status, but dopaminergic treatment specifically promoted SN-DM hyperconnectivity

    Detection of an optical transient following the 13 March 2000 short/hard gamma-ray burst

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    We imaged the error box of a gamma-ray burst of the short (0.5 s), hard type (GRB 000313), with the BOOTES-1 experiment in southern Spain, starting 4 min after the gamma-ray event, in the I-band. A bright optical transient (OT 000313) with I = 9.4 +/- 0.1 was found in the BOOTES-1 image, close to the error box (3-sigma) provided by BATSE. Late time VRIK'-band deep observations failed to reveal an underlying host galaxy. If the OT 000313 is related to the short, hard GRB 000313, this would be the first optical counterpart ever found for this kind of events (all counterparts to date have been found for bursts of the long, soft type). The fact that only prompt optical emission has been detected (but no afterglow emission at all, as supported by theoretical models) might explain why no optical counterparts have ever been found for short, hard GRBs.This fact suggests that most short bursts might occur in a low-density medium and favours the models that relate them to binary mergers in very low-density enviroments.Comment: Revised version. Accepted for publication in Astronomy and Astrophysics Letters, 5 pages, 3 figure

    Extinction law variations and dust excitation in the spiral galaxy NGC 300

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    We investigate the origin of the strong radial gradient in the ultraviolet-to-infrared ratio in the spiral galaxy NGC 300, and emphasize the importance of local variations in the interstellar medium geometry, concluding that they cannot be neglected with respect to metallicity effects. This analysis is based upon a combination of maps from GALEX and Spitzer, and from the ground (UBVRI, Halpha and Hbeta). We select ionizing stellar clusters associated with HII regions of widely varying morphologies, and derive their fundamental parameters from population synthesis fitting of their spectral energy distributions, measured to eliminate local backgrounds accurately. From these fits, we conclude that the stellar extinction law is highly variable in the line of sight of young clusters of similar ages. In the particular model geometry that we consider most appropriate to the sampled regions, we checked that our findings are not significantly altered by the correct treatment of radiative transfer effects. The variations are systematic in nature: extinction laws of the Milky Way or LMC type are associated with compact HII regions (the compacity being quantified in two different ways), while clusters surrounded by diffuse HII regions follow extinction laws of the 30 Doradus or SMC type. The Calzetti starburst attenuation law, although most often degenerate with the 30 Doradus extinction law, overpredicts ionizing photon fluxes by large amounts. We also find that the extinction law variations are correlated with the column density of dust species emitting in the near- and mid-infrared. Finally, we briefly discuss the nebular to stellar extinction ratios, and the excitation of aromatic band carriers, invalidating their claimed association with cold dust.Comment: accepted for publication in ApJ -- figure 6 abridged her

    Search for blue compact dwarf galaxies during quiescence II: metallicities of gas and stars, ages, and star-formation rates

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    We examine the metallicity and age of a large set of SDSS/DR6 galaxies that may be Blue Compact Dwarf (BCD) galaxies during quiescence (QBCDs).The individual spectra are first classified and then averaged to reduce noise. The metallicity inferred from emission lines (tracing ionized gas) exceeds by ~0.35 dex the metallicity inferred from absorption lines (tracing stars). Such a small difference is significant according to our error budget estimate. The same procedure was applied to a reference sample of BCDs, and in this case the two metallicities agree, being also consistent with the stellar metallicity in QBCDs. Chemical evolution models indicate that the gas metallicity of QBCDs is too high to be representative of the galaxy as a whole, but it can represent a small fraction of the galactic gas, self enriched by previous starbursts. The luminosity weighted stellar age of QBCDs spans the whole range between 1 and 10 Gyr, whereas it is always smaller than 1 Gyr for BCDs. Our stellar ages and metallicities rely on a single stellar population spectrum fitting procedure, which we have specifically developed for this work using the stellar library MILES.Comment: Accepted for publication in ApJ. 20 pages. 16 figures (corrected typos

    Influence of time dependent flows on the threshold of the kinematic dynamo action

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    A numerical study of the influence of slowly evolving velocity fields in the threshold of the dynamo action is presented. Using experimental time averaged velocity fields, harmonic variations are introduced in a kinematic code in order to characterize the response of the magnetic field to a broad range of frequencies. A critical frequency is found around ωc = 200 where a transition is obtained. For large values of the frequency (i.e. smaller periods) the magnetic field can not see the velocity fluctuations and the response of the system corresponds to that of the mean flow. For smaller frequencies, the magnetic field sees the slow evolution of the velocity field, and reduces significatively its growth rates when compared to the mean value. This loss of efficiency is due to the dissipation that appears during the transition between the magnetic eigenvectors corresponding to each one of the velocity fields
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