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This study describes epidemiological trends for acute rotavirus gastroenteritis (RVGE) in Belgium in children aged ⩽5 years during the period June 2007 to May 2014 after the introduction of routine rotavirus (RV) vaccination. This period encompassed the switch from lyophilized to the liquid formulation of Rotarix™ (GlaxoSmithKline, Belgium) in August 2011. Uptake of RV vaccine remained consistently high throughout the study period with Rotarix the brand most often used. RV was present in 9% (1139/12 511) of hospitalized cases with acute gastroenteritis included in the study. Epidemiological trends for hospital admissions for RVGE remained consistent throughout the study period, with no evidence of any change associated with the switch from lyophilized to liquid formulation of Rotarix. This suggests both formulations perform similarly, with the liquid formulation not inferior regarding ability to reduce hospital admissions for acute RVGE in children aged ⩽5 years. A strong seasonal effect was observed with most RVGE occurring in the winter months but with some variability in intensity, with highest incidence found in those aged 6–24 months. The main observation was the decreased number of hospital admissions for RVGE in Belgium that occurred during winter 2013/2014.
Photospheric parameters and abundances of 13 chemical species are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Our results indicate that the X-ray active binaries studied are not as metal poor as previously claimed, but are at most mildly iron-depleted relative to the Sun (—0.41 ≲ [Fe/H] ≲ +0.11). A significant overabundance of several elements (e.g., Na, Mg, Al, Ca) is observed. The temperatures derived from the (V — R) and (V — I) colours are found to be significantly affected by activity processes.
We present preliminary results of a long-term spectroscopic monitoring of a magnitude-limited (V < 7.5) sample of OB-supergiants (07.5-B9) aimed at establishing the incidence of co-rotating, large-scale wind structures. In the optical, this can be achieved by detecting rotationally modulated variability in Hα. Dramatic line-profile variations operating on a daily (and in some cases on a hourly) timescale are observed. Firm conclusions regarding the origin of the variability must, however, await a detailed period analysis. There is no clear evidence for a causal link between photospheric and wind activities.
Studying exoplanets with their parent stars is crucial to understand their population, formation and history. We review some of the key questions regarding their evolution with particular emphasis on giant gaseous exoplanets orbiting close to solar-type stars. For masses above that of Saturn, transiting exoplanets have large radii indicative of the presence of a massive hydrogen-helium envelope. Theoretical models show that this envelope progressively cools and contracts with a rate of energy loss inversely proportional to the planetary age. The combined measurement of planetary mass, radius and a constraint on the (stellar) age enables a global determination of the amount of heavy elements present in the planet interior. The comparison with stellar metallicity shows a correlation between the two, indicating that accretion played a crucial role in the formation of planets. The dynamical evolution of exoplanets also depends on the properties of the central star. We show that the lack of massive giant planets and brown dwarfs in close orbit around G-dwarfs and their presence around F-dwarfs are probably tied to the different properties of dissipation in the stellar interiors. Both the evolution and the composition of stars and planets are intimately linked.
The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.
We present the results of an abundance analysis of two magnetic B-type stars in the Orion Nebula Cluster that support the lack of a direct relationship between the existence of a magnetic field and a nitrogen excess in the photosphere.
Time-resolved photoluminescence experiments at varying temperature are performed on a series of InxGa1−xN/GaN quantum well and quantum box samples of similar compositions (0.15 < x < 0.20). The results are analyzed by using envelope-function calculations of transition energies and oscillator strengths, accounting for internal electric fields. The respective influences of localization and electric fields on radiative and nonradiative lifetimes and on the Stokes shift are deduced. The results indicate that the spatial extension of localization centers is much smaller than the size of the quantum boxes (∼10 × 3 nm, typically). The room-temperature radiative efficiency of both quantum well and quantum box samples is enhanced by replacing the topmost GaN barrier by an AlGaN one.
During the five years of the mission, the Gaia spectrograph, the Radial Velocity
Spectrometer (RVS) will repeatedly survey the celestial sphere down to magnitude
V ~ 17–18. This talk presents: (i) the system which is currently developed within
the Gaia Data Processing and Analysis Consortium (DPAC) to reduce and calibrate the
spectra and to derive the radial and rotational velocities, (ii) the RVS expected
performances and (iii) scientific returns.
We employed in situ ellipsometry in the monitoring of surface damage to monocrystalline silicon (Si) substrates under hydrogen plasma conditions. These measurements were complemented with spectroscopic ellipsometry and Raman spectroscopy, in order to characterize the surface conditions. It was found that heating the Si substrate to 700°C in the presence of molecular hydrogen produces etching of the native oxide layer, which is typically 10 Å thick. When the already hot and bare silicon surface is submitted to hydrogen plasma, it deteriorates very fast, becoming rough and full of voids. Modeling of the spectroscopic ellipsometry data was used to obtain a quantitative physical picture of the surface damage, in terms of roughness layer t ickness and void fraction. The results indicate that by the time a thin film starts to grow on these silicon surfaces, like in the chemical vapor deposition of diamond, the roughness produced by the hydrogen plasma has already determined to a large extent the rough nature of the film to be grown.
We studied the effects of low-energy electron bombardment during diamond growth over the film crystalline quality and morphology. The film growth was monitored via the effective extinction coefficient (k) at 1.96 eV with in situ ellipsometry, in order to determine the developmental stage of the film in real time. Taking advantage of this in situ monitoring, we triggered the electron bombardment over the growing surface at different growth stages and studied the corresponding induced changes in film morphology and crystalline quality. Ex situ Raman spectroscopy and scanning electron microscopy (SEM) were also employed to evaluate the crystalline quality and the morphology of the grown films, respectively. We found that electron bombardment can be used to control the surface morphology of the films (triangular, pyramidal, square, amorphous). The results also indicate that applying the electron bombardment over the diamond film during the whole time of growth is detrimental to its crystalline quality and favors the formation of non-sp3 carbon. However, when the electron bombardment is triggered just after high quality scattered diamond crystallites have formed, the resulting film is of similar quality as those grown without bombardment. Therefore, properly chosen and triggered electron bombardment during diamond growth by chemical vapor deposition (CVD) can be used to control the film morphology while maintaining the film crystalline quality.
Electron field emission measurements have been performed on thin film cold cathode materials grown, on molybdenum, by a modified MPACVD diamond process. Specifically the modification is due to the addition of nitrogen and oxygen, in varying ratios, during the diamond growth phase. Characterization using Raman spectroscopy shows features at 1190, 1330 and 1550 cm−1. A simple triode device was fabricated for electron emission characterization. KAPTON® film is used as the insulating layer and a Mo mesh is used as the extraction gate electrode. The collector is an indium tin oxide (ITO) coated glass plate which is positively biased with respect to the gate electrode. Field emission characteristics have shown current measurements of greater than I microamp for fields of 40 V/micron. Gate currents are typically 1000 times greater than the emitted current. Issues currently being addressed include improvement in the total emitted current, current stability and device failure. We also present field emission measurements on diamond films grown by HFCVD.
Within Silicon Carbide Junction Field Effect Transistor (SiC-JFET) model,
body diode is not extensively studied and almost under-researched. Body
diode remains a complex device to study particularly during switching
transients. In this paper, the JFET body diode is experimentally
demonstrated to be a power PiN diode. Finite element method model based on
the device geometry and SiC material is used to accurately simulate this
diode. Accurate simulations are necessary for analysis and verification
purposes. Simulation relies on component models and associated parameters.
The paper focuses on a step-by-step extraction procedure for design
parameters of the SiC-JFET body diode. A comparative study between
experimental data and simulation results is given to validate the device
model and associate parameters.
This paper focuses on the modelling of a SiC-JFET. The novelty aspect is the
dependence on temperature. An accurate model has been used in a previous
work and an identification procedure for the main model parameters has been
demonstrated. Readers have asked for a more advanced SiC JFET
temperature-dependent model. A limitation of the current model versus
temperature is verified and explained in order to introduce the necessity of
a new temperature dependence model. A more advanced model is then considered
and a comparative study between experiment and simulation of the device is
established. The characteristics of three SiC JFETs devices are considered
from experimental and simulation point-of-view. Simulations results clearly
replicate the experimental data at different temperatures and a new validity
approach, namely validity maps, is proposed. Validity domains are discussed.
We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in january 2009. This object is known as the archetype of colliding wind binaries and has a relatively large period (≃8 years) and eccentricity (≃0.89). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates.
We present preliminary results of a 4-month campaign carried out in the framework of the Mons project, where time-resolved Hα observations are used to study the wind and circumstellar properties of a number of OB stars.
The present study investigated the effects of maternal plasma iodine concentration on twin- and triplet-born lamb plasma thyroid hormone concentrations, rectal temperature and maximal heat production. On pregnancy day 68 (P68), 16 twin- and 14 triplet-bearing ewes were randomly chosen from ewes that were injected intramuscularly with 1·5 ml of iodized peanut oil and ewes that were not. Selected ewes were grazed on ad libitum pasture from P68 until parturition. After parturition, lamb blood samples were collected within 5 min of birth and at 3, 12 and 24–36 h after birth. Lamb rectal temperatures were measured within 5 min of birth and at 1, 3 and 12 h after birth. Lamb body weight, crown–rump length and thoracic-girth circumference were recorded at 3 h of age, and the capability of the lamb to produce heat at 24–36 h of age was measured using indirect open-circuit calorimetry. Maternal iodine supplementation successfully increased plasma iodine concentrations of twin- and triplet-bearing ewes throughout pregnancy, but had no effect on the rectal temperature, thyroid hormone concentration and maximal heat production of twin- or triplet-born lambs. Compared with twin-born lambs, triplet-born lambs had lower birth weights, rectal temperatures and plasma T4 and T3 concentrations within 5 min of birth. Overall, under the conditions of the present study, maternal iodine supplementation offered no benefit in improving lamb heat production.
Silicon carbide junction field effect transistor
(SiC-JFETs) is a mature power switch newly applied in several industrial
applications. SiC-JFETs are often simulated by Spice model in order to
predict their electrical behaviour. Although such a model provides
sufficient accuracy for some applications, this paper shows that it presents
serious shortcomings in terms of the neglect of the body diode model, among
many others in circuit model topology. Simulation correction is then
mandatory and a new model should be proposed. Moreover, this paper gives an
enhanced model based on experimental dc and ac data. New devices are added
to the conventional circuit model giving accurate static and dynamic
behaviour, an effect not accounted in the Spice model. The improved model is
implemented into VHDL-AMS language and steady-state dynamic and transient
responses are simulated for many SiC-VJFETs samples. Very simple and
reliable optimization algorithm based on the optimization of a cost function
is proposed to extract the JFET model parameters. The obtained parameters
are verified by comparing errors between simulations results and