553 research outputs found

    Evaluation of knowledge level of adolescents and adults with congenital heart disease: Effectiveness of a structured CHD education program in adolescents

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    BackgroundAdolescents with congenital heart disease (CHD) constitute a growing population of individuals for whom a well-planned and well-executed “transition process” is essential. Transition program should include education about medical conditions and promote skills in decision-making and self-care. To improve their level of health related knowledge, a structured education program was implemented in a transition CHD program. This study aimed 1/to evaluate level of knowledge of adolescents who received structured CHD education as compared to adults who did not, 2/to evaluate whether patients who received structured education improve their knowledge.Methods and results42 adolescents (16±2years old, 21 girls) were included in a structured CHD education program and were compared to 22 adults (33±7, 6 women) with CHD who have never followed education program. Knowledge in adolescents was assessed before and after the educational program using questionnaire exploring specific issues related to CHD. A same questionnaire was used in non-educated adult patients. The mean total knowledge score in the educated adolescent group was significantly higher as compared to the non-educated adult with CHD (score=15.6/20±3.6 vs. 12.5±4.5, P<0.01). Provision of structured CHD education and female sex were determinant of higher levels of knowledge. A significant improvement of knowledge was observed in adolescents group after CHD education program (range of increase was 23 to 44%). This result was not influenced by age, sex, education level, socio-economic status of parents and disease complexity, and persists at 10months mean follow-up.ConclusionA structured education program was associated with a higher level of knowledge, above all in male CHD patients. Education at transition period has a significant impact on the adolescent knowledge. Structured education program should improve adult CHD understanding of their heart condition, and could prevent potential complications

    Testing Comptonizing coronae on a long BeppoSAX observation of the Seyfert 1 galaxy NGC 5548

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    We test accurate models of Comptonization spectra over the high quality data of the BeppoSAX long look at NGC 5548, allowing for different geometries of the scattering region, different temperatures of the input soft photon field and different viewing angles. We find that the BeppoSAX data are well represented by a plane parallel or hemispherical corona viewed at an inclination angle of 30∘^{\circ}. For both geometries the best fit temperature of the soft photons is close to 15−9+3^{+3}_{-9} eV. The corresponding best fit values of the hot plasma temperature and optical depth are kTe≃kT_{\rm e}\simeq 250--260 keV and τ≃\tau\simeq 0.16--0.37 for the slab and hemisphere respectively. These values are substantially different from those derived fitting the data with a power-law + cut off approximation to the Comptonization component (kT_{\rm e}\lta 60 keV, τ≃\tau\simeq 2.4). This is due to the fact that accurate Comptonization spectra in anisotropic geometries show "intrinsic" curvature which reduces the necessity of a high energy cut-off. The Comptonization parameter derived for the slab model {is} larger than predicted for a two phase plane parallel corona in energy balance, suggesting that a more ``photon-starved'' geometry is necessary. The spectral softening detected during a flare which occurred in the central part of the observation corresponds to a decrease of the Comptonization parameter, probably associated with an increase of the soft photon luminosity, the {hard} photon luminosity remaining constant.Comment: 36 pages, 9 figures, accepted by Ap

    Mid-Infrared Emission Features in the ISM: Feature-to-Feature Flux Ratios

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    Using a limited, but representative sample of sources in the ISM of our Galaxy with published spectra from the Infrared Space Observatory, we analyze flux ratios between the major mid-IR emission features (EFs) centered around 6.2, 7.7, 8.6 and 11.3 microns, respectively. In a flux ratio-to-flux ratio plot of EF(6.2)/EF(7.7) as a function of EF(11.3)/EF(7.7), the sample sources form roughly a Λ\Lambda-shaped locus which appear to trace, on an overall basis, the hardness of a local heating radiation field. But some driving parameters other than the radiation field may also be required for a full interpretation of this trend. On the other hand, the flux ratio of EF(8.6)/EF(7.7) shows little variation over the sample sources, except for two HII regions which have much higher values for this ratio due to an ``EF(8.6\um) anomaly,'' a phenomenon clearly associated with environments of an intense far-UV radiation field. If further confirmed on a larger database, these trends should provide crucial information on how the EF carriers collectively respond to a changing environment.Comment: 16 pages, 1 figure, 1 table; accepted for publication in ApJ Letter

    Incidence and survival of remnant disks around main-sequence stars

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    We present photometric ISO 60 and 170um measurements, complemented by some IRAS data at 60um, of a sample of 84 nearby main-sequence stars of spectral class A, F, G and K in order to determine the incidence of dust disks around such main-sequence stars. Of the stars younger than 400 Myr one in two has a disk; for the older stars this is true for only one in ten. We conclude that most stars arrive on the main sequence surrounded by a disk; this disk then decays in about 400 Myr. Because (i) the dust particles disappear and must be replenished on a much shorter time scale and (ii) the collision of planetesimals is a good source of new dust, we suggest that the rapid decay of the disks is caused by the destruction and escape of planetesimals. We suggest that the dissipation of the disk is related to the heavy bombardment phase in our Solar System. Whether all stars arrive on the main sequence surrounded by a disk cannot be established: some very young stars do not have a disk. And not all stars destroy their disk in a similar way: some stars as old as the Sun still have significant disks.Comment: 16 pages, 9 figures, Astron & Astrophys. in pres

    Debris disks around Sun-like stars

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    We have observed nearly 200 FGK stars at 24 and 70 microns with the Spitzer Space Telescope. We identify excess infrared emission, including a number of cases where the observed flux is more than 10 times brighter than the predicted photospheric flux, and interpret these signatures as evidence of debris disks in those systems. We combine this sample of FGK stars with similar published results to produce a sample of more than 350 main sequence AFGKM stars. The incidence of debris disks is 4.2% (+2.0/-1.1) at 24 microns for a sample of 213 Sun-like (FG) stars and 16.4% (+2.8/-2.9) at 70 microns for 225 Sun-like (FG) stars. We find that the excess rates for A, F, G, and K stars are statistically indistinguishable, but with a suggestion of decreasing excess rate toward the later spectral types; this may be an age effect. The lack of strong trend among FGK stars of comparable ages is surprising, given the factor of 50 change in stellar luminosity across this spectral range. We also find that the incidence of debris disks declines very slowly beyond ages of 1 billion years.Comment: ApJ, in pres

    Multiple Scale Reorganization of Electrostatic Complexes of PolyStyrene Sulfonate and Lysozyme

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    We report on a SANS investigation into the potential for these structural reorganization of complexes composed of lysozyme and small PSS chains of opposite charge if the physicochemical conditions of the solutions are changed after their formation. Mixtures of solutions of lysozyme and PSS with high matter content and with an introduced charge ratio [-]/[+]intro close to the electrostatic stoichiometry, lead to suspensions that are macroscopically stable. They are composed at local scale of dense globular primary complexes of radius ~ 100 {\AA}; at a higher scale they are organized fractally with a dimension 2.1. We first show that the dilution of the solution of complexes, all other physicochemical parameters remaining constant, induces a macroscopic destabilization of the solutions but does not modify the structure of the complexes at submicronic scales. This suggests that the colloidal stability of the complexes can be explained by the interlocking of the fractal aggregates in a network at high concentration: dilution does not break the local aggregate structure but it does destroy the network. We show, secondly, that the addition of salt does not change the almost frozen inner structure of the cores of the primary complexes, although it does encourage growth of the complexes; these coalesce into larger complexes as salt has partially screened the electrostatic repulsions between two primary complexes. These larger primary complexes remain aggregated with a fractal dimension of 2.1. Thirdly, we show that the addition of PSS chains up to [-]/[+]intro ~ 20, after the formation of the primary complex with a [-]/[+]intro close to 1, only slightly changes the inner structure of the primary complexes. Moreover, in contrast to the synthesis achieved in the one-step mixing procedure where the proteins are unfolded for a range of [-]/[+]intro, the native conformation of the proteins is preserved inside the frozen core

    The European Photon Imaging Camera on XMM-Newton: The MOS Cameras

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    The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs to record the images and spectra of celestial X-ray sources focused by the three X-ray mirrors. There is one camera at the focus of each mirror; two of the cameras contain seven MOS CCDs, while the third uses twelve PN CCDs, defining a circular field of view of 30 arcmin diameter in each case. The CCDs were specially developed for EPIC, and combine high quality imaging with spectral resolution close to the Fano limit. A filter wheel carrying three kinds of X-ray transparent light blocking filter, a fully closed, and a fully open position, is fitted to each EPIC instrument. The CCDs are cooled passively and are under full closed loop thermal control. A radio-active source is fitted for internal calibration. Data are processed on-board to save telemetry by removing cosmic ray tracks, and generating X-ray event files; a variety of different instrument modes are available to increase the dynamic range of the instrument and to enable fast timing. The instruments were calibrated using laboratory X-ray beams, and synchrotron generated monochromatic X-ray beams before launch; in-orbit calibration makes use of a variety of celestial X-ray targets. The current calibration is better than 10% over the entire energy range of 0.2 to 10 keV. All three instruments survived launch and are performing nominally in orbit. In particular full field-of-view coverage is available, all electronic modes work, and the energy resolution is close to pre-launch values. Radiation damage is well within pre-launch predictions and does not yet impact on the energy resolution. The scientific results from EPIC amply fulfil pre-launch expectations.Comment: 9 pages, 11 figures, accepted for publication in the A&A Special Issue on XMM-Newto

    SPI/INTEGRAL observation of the Cygnus region

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    We present the analysis of the first observations of the Cygnus region by the SPI spectrometer onboard the Integral Gamma Ray Observatory, encompassing ∌{\sim} 600 ks of data. Three sources namely Cyg X-1, Cyg X-3 and EXO 2030+375 were clearly detected. Our data illustrate the temporal variability of Cyg X-1 in the energy range from 20 keV to 300 keV. The spectral analysis shows a remarkable stability of the Cyg X-1 spectra when averaged over one day timescale. The other goal of these observations is SPI inflight calibration and performance verification. The latest objective has been achieved as demonstrated by the results presented in this paper.Comment: 6 pages, 10 figures, accepted for publication in A&A (special INTEGRAL volume

    Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm

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    The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to <100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews and as hard cover in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher
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