569 research outputs found
O impacto da emigração recente no número de nados-vivos em Portugal
A recente crise económica observada em Portugal não foi exclusiva do país e registou repercussões massivas a
nível internacional. Desde 2008, em Portugal, registaram-se os mais variados cortes no investimento e
despesa pública, resultando num grande aumento da taxa de desemprego. Realizaram-se algumas tentativas
de minoração dos efeitos da crise económica com a institucionalização de medidas de austeridade como o
Programa de Estabilidade e Crescimento (PEC), mas estas não evitaram a intervenção do Fundo Monetário
Internacional (FMI), trazendo a Troika a Portugal (Alves, 2015; Ribeiro et al., 2015). Durante o seu período em
Portugal (2011 – 2014), o país não conseguiu manter a capacidade para atrair novos residentes ou até de fazer
regressar aqueles que tinham há muito saído em busca de melhores condições de vida, voltando a ser um
país com forte emigração à semelhança do já observado no passado. Apesar desta emigração se dividir entre
temporária e permanente, a verdade é que, muito provavelmente, alguns daqueles que pensaram sair do país
apenas temporariamente, poderão passar a emigrantes permanentes
Admittance spectroscopy of Cu2ZnSnS4 based thin film solar cells
In this report, we propose an AC response equivalent circuit model to describe the admittance
measurements of Cu2ZnSnS4 thin film solar cell grown by sulphurization of stacked metallic
precursors. This circuit describes the contact resistances, the back contact, and the heterojunction
with two trap levels. The study of the back contact resistance allowed the estimation of a back
contact barrier of 246 meV. The analysis of the trap series with varying temperature revealed
defect activation energies of 45 meV and 113 meV. The solar cell’s electrical parameters were
obtained from the J-V curve: conversion efficiency, 1.21%; fill factor, 50%; open circuit voltage,
360 mV; and short circuit current density, 6.8 mA/cm2
Left Ventricular Diastolic Function in Type 2 Diabetes Mellitus and the Association With Coronary Artery Calcium Score: A Cardiac MRI Study
OBJECTIVE:
The purpose of this study was to compare cardiac MRI-derived parameters of left ventricular (LV) diastolic function between uncomplicated type 2 diabetes mellitus (DM2) and normoglycemic control subjects and to evaluate whether these parameters of LV diastolic function are related to coronary atherosclerosis.
SUBJECTS AND METHODS:
We prospectively studied 41 subjects with DM2 and 21 normoglycemic control subjects (30 women and 32 men; mean age, 57.2 ± 7.1 [SD] years) with no evidence of overt cardiovascular disease. We used cardiac MRI to measure LV volumes, LV peak filling rate (PFR), and transmitral flow and CT to determine coronary artery calcium scores.
RESULTS:
Absolute values of the peak filling rate (PFR) were significantly lower in DM2 patients than in control subjects (mean ± SD, 293.2 ± 51.7 vs 375.7 ± 102.8 mL/s, respectively; p < 0.001). Mitral peak E velocities (mean ± SD, 42.8 ± 10.7 vs 48.8 ± 10.4 cm/s; p = 0.040) and peak E velocity-to-peak A velocity ratios (0.88 ± 0.3 vs 1.1 ± 0.3; p = 0.002) were also lower in DM2 patients compared with control subjects. DM2 patients with coronary artery calcification showed a lower PFR normalized to stroke volume (SV) (mean ± SD, 4.4 ± 1.0 vs 5.3 ± 1.4, respectively; p = 0.038) and lower mitral peak E velocities (40.1 ± 11.3 vs 48.0 ± 7.3 cm/s; p = 0.024) than DM2 patients without coronary calcification. PFR normalized to SV was independently associated with the presence of coronary artery calcification (β = -1.5, p = 0.005).
CONCLUSION:
DM2 decreases cardiovascular MRI-derived parameters of LV diastolic function. Patients with DM2 and coronary atherosclerosis show a more impaired LV diastolic function than patients without coronary atherosclerosis
Effect of annealing temperature on structural, morphology and dielectric properties of La0.75Ba0.25FeO3 perovskite
The effect of annealing temperature on the structure, morphology and dielectric properties of La0.75Ba0.25FeO3 compound prepared by the sol-gel method was investigated. The increase of the annealing temperature from 900 to 1100 °C, promotes an increase of the average grain size value. Two dielectric relaxations are detected using the dielectric modulus formalism, attributed to grain and grain boundary relaxations. This behavior was confirmed by both Nyquist and Argand's plots of dielectric impedance and Modulus results at different measuring temperatures. The ac conductivity could be described by Jonscher's power law revealing the presence of both overlapping large polaron tunneling and non-overlapping small polaron tunneling mechanisms.publishe
Polarimetric Responses and Scattering Mechanisms of Tropical Forests in the Brazilian Amazon
This chapter discusses the polarimetric responses of PALSAR (L-band) data and scattering mechanisms of some tropical forest typologies based on target decomposition. The fundamentals of polarimetric theory related to both SAR topics under development are summarized. For representation of polarimetric signatures, the cross-section of the forest target (σ) was plotted on a bi-dimensional graphic as a function of the orientation angle, ellipticity angle and the intensity of co-polar components of the radar signal. The analysis of scattering mechanisms was done by the association of entropy and mean alpha angle values of each sample, plotted in a bi-dimensional classification space. This study improves the understanding of the interaction mechanisms between L-band PALSAR signals and structural parameters, supporting the forest inventory in the Brazilian Amazon region
I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g.
with unfavourable ion
B
∇
direction. It is characterised by the development of a temperature
pedestal while the density remains roughly as in the L-mode. This leads to a confinement
improvement above the L-mode level which can sometimes reach H-mode values. This
regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has
been studied again since 2009 taking advantage of the development of new diagnostics
and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different
heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold,
pedestal characteristics and confinement, are independent of the heating method. The power
required at the L-I transition exhibits an offset linear density dependence but, in contrast
to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be
mainly determined by the edge pressure gradient and the comparison between ECRH and
NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often
evolves gradually over a few confinement times until the transition to H-mode which offers
a very interesting situation to study the transport reduction and its link with the pedestal
formation. Exploratory discharges in which
n
=
2 magnetic perturbations have been applied
indicate that these can lead to an increase of the I-mode power threshold by flattening the edge
pressure at fixed heating input power: more heating power is necessary to restore the required
edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in
detail.European Commission (EUROfusion 633053
Influence of bacterial dynamics upon the final characteristics
The microbiological profile in raw milk cheeses is typically characterized by a multitude of microbial
groups, with interactions among them throughout ripening that are not fully understood to date. Incidence
of undesired microorganisms in raw cheesemaking milk, as is the case of either spoilage or even
pathogenic ones, is a common trait in Portuguese traditional cheeses. Hence, they will likely contribute
to the physicochemical changes occurring therein and, consequently, to the characteristics of the final
product. In order to gain insight into their role, model cheese systems, manufactured as far as possible
according to artisanal practices (except that the initial microbial load and biodiversity were controlled),
were experimentally tested. Single contaminants, or a consortium thereof, were inoculated at two levels
in sterilized raw ewe's milk, and duly combined with inocula containing one or two lactic acid bacteria
normally found in those traditional cheeses. The physicochemical composition, organic acid profile, and
evolution of both protein breakdown and rheology were monitored throughout a 60 d-ripening period.
Modifications brought about within the cheese matrix as a result of microbial metabolism, especially
those arising from the interaction between lactic acid bacteria and unwanted microorganisms, included
the enhanced release of peptides and free amino acids, which in turn led to higher viscoelastic moduli.
The final model cheeses could be well discriminated, based on the impact of the various inocula
considered upon the levels of organic acids. Conversely, proteolysis and viscoelastic properties appeared
to be essentially independent of the initial microflora.info:eu-repo/semantics/publishedVersio
Electrical, morphology and structural properties of biodegradable nanocomposite polyvinyl-acetate/ cellulose nanocrystals
In this work, the dielectric properties and the electrical conductivity of polyvinyl acetate (PVAc) polymer doped with cellulose nanocrystals (CNC), extracted from the date palm rachis, are reported. We investigate the filler effect on the molecular mobility of the PVAc polymer chains and the charge transport properties of this material. PVAc/CNC films structure was characterized by powder X-Ray diffraction (XRD), showing the crystalline behavior of the cellulose filler. The dielectric properties were investigated using impedance spectroscopy, in the frequency range of 102–106 Hz and temperatures from 200 to 350 K. A β relaxation, assigned to the motions of the -OCOCH3 side groups, and α relaxation, associated with the glass transition of the PVAc matrix, can be detected.publishe
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