8,383 research outputs found
The silicate absorption profile in the ISM towards the heavily obscured nucleus of NGC 4418
The 9.7-micron silicate absorption profile in the interstellar medium
provides important information on the physical and chemical composition of
interstellar dust grains. Measurements in the Milky Way have shown that the
profile in the diffuse interstellar medium is very similar to the amorphous
silicate profiles found in circumstellar dust shells around late M stars, and
narrower than the silicate profile in denser star-forming regions. Here, we
investigate the silicate absorption profile towards the very heavily obscured
nucleus of NGC 4418, the galaxy with the deepest known silicate absorption
feature, and compare it to the profiles seen in the Milky Way. Comparison
between the 8-13 micron spectrum obtained with TReCS on Gemini and the larger
aperture spectrum obtained from the Spitzer archive indicates that the former
isolates the nuclear emission, while Spitzer detects low surface brightness
circumnuclear diffuse emission in addition. The silicate absorption profile
towards the nucleus is very similar to that in the diffuse ISM in the Milky Way
with no evidence of spectral structure from crystalline silicates or silicon
carbide grains.Comment: 7 Pages, 3 figures. MNRAS in pres
Reinforcing the link between the double red clump and the X-shaped bulge of the Milky Way
The finding of a double red clump in the luminosity function of the Milky Way bulge has been interpreted as evidence for an X-shaped structure. Recently, an alternative explanation has been suggested, where the double red clump is an effect of multiple stellar populations in a classical spheroid. In this Letter we provide an observational assessment of this scenario and show that it is not consistent with the behaviour of the red clump across different lines of sight, particularly at high distances from the Galactic plane. Instead, we confirm that the shape of the red clump magnitude distribution closely follows the distance distribution expected for an X-shaped bulge at critical Galactic latitudes. We also emphasize some key observational properties of the bulge red clump that should not be neglected in the search for alternative scenarios
On the semiclassical mass of -kinks
One-loop mass shifts to the classical masses of stable kinks arising in a
massive non-linear -sigma model are computed. Ultraviolet
divergences are controlled using the heat kernel/zeta function regularization
method. A comparison between the results achieved from exact and
high-temperature asymptotic heat traces is analyzed in depth.Comment: RevTex file, 15 pages, 2 figures. Version to appear in Journal of
Physics
Why Optically--Faint AGN Are Faint: The Spitzer Perspective
Optically--faint X-ray sources (those with f_X/f_R > 10) constitute about 20%
of X-ray sources in deep surveys, and are potentially highly obscured and/or at
high redshift. Their faint optical fluxes are generally beyond the reach of
spectroscopy. For a sample of 20 optically--faint sources in CDFS, we compile
0.4--24 um photometry, relying heavily on Spitzer. We estimate photometric
redshifts for 17 of these 20 sources. We find that these AGN are
optically--faint both because they lie at significantly higher redshifts
(median z ~ 1.6) than most X-ray--selected AGN, and because their spectra are
much redder than standard AGN. They have 2--8 keV X-ray luminosities in the
Seyfert range, unlike the QSO--luminosities of optically--faint AGN found in
shallow, wide--field surveys. Their contribution to the X-ray Seyfert
luminosity function is comparable to that of z>1 optically--bright AGN.Comment: Accepted for publication in the Astrophysical Journa
Hypoalbuminaemia predicts outcome in adult patients with congenital heart disease
Background In patients with acquired heart failure, hypoalbuminaemia is associated with increased risk of death. The prevalence of hypoproteinaemia and hypoalbuminaemia and their relation to outcome in adult patients with congenital heart disease (ACHD) remains, however, unknown. Methods Data on patients with ACHD who underwent blood testing in our centre within the last 14â
years were collected. The relation between laboratory, clinical or demographic parameters at baseline and mortality was assessed using Cox proportional hazards regression analysis. Results A total of 2886 patients with ACHD were included. Mean age was 33.3â
years (23.6â44.7) and 50.1% patients were men. Median plasma albumin concentration was 41.0â
g/L (38.0â44.0), whereas hypoalbuminaemia (<35â
g/L) was present in 13.9% of patients. The prevalence of hypoalbuminaemia was significantly higher in patients with great complexity ACHD (18.2%) compared with patients with moderate (11.3%) or simple ACHD lesions (12.1%, p<0.001). During a median follow-up of 5.7â
years (3.3â9.6), 327 (11.3%) patients died. On univariable Cox regression analysis, hypoalbuminaemia was a strong predictor of outcome (HR 3.37, 95% CI 2.67 to 4.25, p<0.0001). On multivariable Cox regression, after adjusting for age, sodium and creatinine concentration, liver dysfunction, functional class and disease complexity, hypoalbuminaemia remained a significant predictor of death. Conclusions Hypoalbuminaemia is common in patients with ACHD and is associated with a threefold increased risk of risk of death. Hypoalbuminaemia, therefore, should be included in risk-stratification algorithms as it may assist management decisions and timing of interventions in the growing ACHD population
Optimization of the appearance quality in CO2 processed ready-to-eat carrots through image analysis
A high-pressure CO2 process applied to ready-to-eat food products guarantees an increase of both their microbial safety and shelf-life. However, the treatment often produces unwanted changes in the visual appearance of products depending on the adopted process conditions. Accordingly, the alteration of the visual appearance influences consumersâ perception and acceptability. This study aims at identifying the optimal treatment conditions in terms of visual appearance by using an artificial vision system. The developed methodology was applied to fresh-cut carrots (Daucus carota) as the test product. The results showed that carrots packaged in 100% CO2 and subsequently treated at 6 MPa and 40âŠC for 15 min maintained an appearance similar to the fresh product for up to 7 days of storage at 4âŠC. Mild appearance changes were identified at 7 and 14 days of storage in the processed products. Microbiological analysis performed on the optimal treatment condition showed the microbiological stability of the samples up to 14 days of storage at 4âŠC. The artificial vision system, successfully applied to the CO2 pasteurization process, can easily be applied to any food process involving changes in the appearance of any food product
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