144 research outputs found
Metabolic Bile Acid Profile Impairments in Dogs Affected by Chronic Inflammatory Enteropathy
Bile acids (BAs), endogenous acidic steroids synthetized from cholesterol in the liver, play a key role in the gut–liver axis physiopathology, including in hepatotoxicity, intestinal inflammatory processes, and cholesterol homeostasis. Faecal Oxo-BAs, relatively stable intermediates of oxidation/epimerization reactions of the BA hydroxyls, could be relevant to investigating the crosstalk in the liver–gut axis and the relationship between diseases and alterations in microbiota composition. A paucity of information currently exists on faecal BA profiles in dogs with and without chronic inflammatory enteropathy (CIE). Comprehensive assessment of 31 molecules among faecal BAs and related microbiota metabolites was conducted with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Odds ratios (ORs) for associations of BAs with CIE were estimated using logistic regression. Principal component analysis was performed to find differences between the control and pathological dogs. Higher levels of primary BAs and muricholic acids, and lower levels of secondary BAs were found in pathological dogs. Higher concentrations in faecal oxo-metabolites were associated with the absence of CIE (OR < 1). This study shows a marked difference in faecal BA profiles between dogs with and without CIE. Further research will be needed to better understand the role of oxo-BAs and muricholic acids in CIE dogs
FIRI - a Far-Infrared Interferometer
Half of the energy ever emitted by stars and accreting objects comes to us in
the FIR waveband and has yet to be properly explored. We propose a powerful
Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging
spectroscopy in the FIR. This key observational capability is essential to
reveal how gas and dust evolve into stars and planets, how the first luminous
objects in the Universe ignited, how galaxies formed, and when super-massive
black holes grew. FIRI will disentangle the cosmic histories of star formation
and accretion onto black holes and will trace the assembly and evolution of
quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will
observe all stages of planetary system formation and recognise Earth-like
planets that may harbour life, via its ability to image the dust structures in
planetary systems. It will thus address directly questions fundamental to our
understanding of how the Universe has developed and evolved - the very
questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA
and Canada and submitted to the European Space Agency as part of "Cosmic
Vision 2015-2025
Herschel observations of deuterated water towards Sgr B2(M)
Observations of HDO are an important complement for studies of water, because
they give strong constraints on the formation processes -- grain surfaces
versus energetic process in the gas phase, e.g. in shocks. The HIFI
observations of multiple transitions of HDO in Sgr~B2(M) presented here allow
the determination of the HDO abundance throughout the envelope, which has not
been possible before with ground-based observations only. The abundance
structure has been modeled with the spherical Monte Carlo radiative transfer
code RATRAN, which also takes radiative pumping by continuum emission from dust
into account. The modeling reveals that the abundance of HDO rises steeply with
temperature from a low abundance () in the outer envelope
at temperatures below 100~K through a medium abundance () in
the inner envelope/outer core, at temperatures between 100 and 200~K, and
finally a high abundance () at temperatures above 200~K in
the hot core.Comment: A&A HIFI special issue, accepte
Systematic Molecular Differentiation in Starless Cores
(Abridged) We present evidence that low-mass starless cores, the simplest
units of star formation, are systematically differentiated in their chemical
composition. Molecules including CO and CS almost vanish near the core centers,
where the abundance decreases by one or two orders of magnitude. At the same
time, N2H+ has a constant abundance, and the fraction of NH3 increases toward
the core center. Our conclusions are based on a study of 5 mostly-round
starless cores (L1498, L1495, L1400K, L1517B, and L1544), which we have
mappedin C18O(1-0), C17O(1-0), CS(2-1), C34S(2-1), N2H+(1-0), NH3(1,1) and
(2,2), and the 1.2 mm continuum. For each core we have built a model that fits
simultaneously the radial profile of all observed emission and the central
spectrum for the molecular lines. The observed abundance drops of CO and CS are
naturally explained by the depletion of these molecules onto dust grains at
densities of 2-6 10^4 cm-3. N2H+ seems unaffected by this process up to
densities of several 10^5, while the NH3 abundance may be enhanced by reactions
triggered by the disappearance of CO from the gas phase. With the help of our
models, we show that chemical differentiation automatically explains the
discrepancy between the sizes of CS and NH3 maps, a problem which has remained
unexplained for more than a decade. Our models, in addition, show that a
combination of radiative transfer effects can give rise to the previously
observed discrepancy in the linewidth of these two tracers. Although this
discrepancy has been traditionally interpreted as resulting from a systematic
increase of the turbulent linewidth with radius, our models show that it can
arise in conditions of constant gas turbulence.Comment: 25 pages, 9 figures, accepted by Ap
Herschel observations of EXtraordinary Sources: Analysis of the full Herschel/HIFI molecular line survey of Sagittarius B2(N)
A sensitive broadband molecular line survey of the Sagittarius B2(N)
star-forming region has been obtained with the HIFI instrument on the Herschel
Space Observatory, offering the first high-spectral resolution look at this
well-studied source in a wavelength region largely inaccessible from the ground
(625-157 um). From the roughly 8,000 spectral features in the survey, a total
of 72 isotopologues arising from 44 different molecules have been identified,
ranging from light hydrides to complex organics, and arising from a variety of
environments from cold and diffuse to hot and dense gas. We present an LTE
model to the spectral signatures of each molecule, constraining the source
sizes for hot core species with complementary SMA interferometric observations,
and assuming that molecules with related functional group composition are
cospatial. For each molecule, a single model is given to fit all of the
emission and absorption features of that species across the entire 480-1910 GHz
spectral range, accounting for multiple temperature and velocity components
when needed to describe the spectrum. As with other HIFI surveys toward massive
star forming regions, methanol is found to contribute more integrated line
intensity to the spectrum than any other species. We discuss the molecular
abundances derived for the hot core, where the local thermodynamic equilibrium
approximation is generally found to describe the spectrum well, in comparison
to abundances derived for the same molecules in the Orion KL region from a
similar HIFI survey.Comment: Accepted to ApJ. 64 pages, 14 figures. Truncated abstrac
Herschel observations of EXtra-Ordinary Sources: The Terahertz spectrum of Orion KL seen at high spectral resolution
We present the first high spectral resolution observations of Orion KL in the
frequency ranges 1573.4 - 1702.8 GHz (band 6b) and 1788.4 - 1906.8 GHz (band
7b) obtained using the HIFI instrument on board the Herschel Space Observatory.
We characterize the main emission lines found in the spectrum, which primarily
arise from a range of components associated with Orion KL including the hot
core, but also see widespread emission from components associated with
molecular outflows traced by H2O, SO2, and OH. We find that the density of
observed emission lines is significantly diminished in these bands compared to
lower frequency Herschel/HIFI bands.Comment: Accepted for publication in the Herschel HIFI special issue of
Astronomy and Astrophysics Letters, 5 pages, 3 figure
Herschel observations of extra-ordinary sources: Detecting spiral arm clouds by CH absorption lines
We have observed CH absorption lines ()
against the continuum source Sgr~B2(M) using the \textit{Herschel}/HIFI
instrument. With the high spectral resolution and wide velocity coverage
provided by HIFI, 31 CH absorption features with different radial velocities
and line widths are detected and identified. The narrower line width and lower
column density clouds show `spiral arm' cloud characteristics, while the
absorption component with the broadest line width and highest column density
corresponds to the gas from the Sgr~B2 envelope. The observations show that
each `spiral arm' harbors multiple velocity components, indicating that the
clouds are not uniform and that they have internal structure. This
line-of-sight through almost the entire Galaxy offers unique possibilities to
study the basic chemistry of simple molecules in diffuse clouds, as a variety
of different cloud classes are sampled simultaneously. We find that the linear
relationship between CH and H column densities found at lower by UV
observations does not continue into the range of higher visual extinction.
There, the curve flattens, which probably means that CH is depleted in the
denser cores of these clouds.Comment: Accepted for publication in A&A, HIFI Special Issu
The chemistry of C3 & Carbon Chain Molecules in DR21(OH)
(Abridged) We have observed velocity resolved spectra of four ro-vibrational
far-infrared transitions of C3 between the vibrational ground state and the
low-energy nu2 bending mode at frequencies between 1654--1897 GHz using HIFI on
board Herschel, in DR21(OH), a high mass star forming region. Several
transitions of CCH and c-C3H2 have also been observed with HIFI and the IRAM
30m telescope. A gas and grain warm-up model was used to identify the primary
C3 forming reactions in DR21(OH). We have detected C3 in absorption in four
far-infrared transitions, P(4), P(10), Q(2) and Q(4). The continuum sources MM1
and MM2 in DR21(OH) though spatially unresolved, are sufficiently separated in
velocity to be identified in the C3 spectra. All C3 transitions are detected
from the embedded source MM2 and the surrounding envelope, whereas only Q(4) &
P(4) are detected toward the hot core MM1. The abundance of C3 in the envelope
and MM2 is \sim6x10^{-10} and \sim3x10^{-9} respectively. For CCH and c-C3H2 we
only detect emission from the envelope and MM1. The observed CCH, C3, and
c-C3H2 abundances are most consistent with a chemical model with
n(H2)\sim5x10^{6} cm^-3 post-warm-up dust temperature, T_max =30 K and a time
of \sim0.7-3 Myr. Post warm-up gas phase chemistry of CH4 released from the
grain at t\sim 0.2 Myr and lasting for 1 Myr can explain the observed C3
abundance in the envelope of DR21(OH) and no mechanism involving
photodestruction of PAH molecules is required. The chemistry in the envelope is
similar to the warm carbon chain chemistry (WCCC) found in lukewarm corinos.
The observed lower C3 abundance in MM1 as compared to MM2 and the envelope
could be indicative of destruction of C3 in the more evolved MM1. The timescale
for the chemistry derived for the envelope is consistent with the dynamical
timescale of 2 Myr derived for DR21(OH) in other studies.Comment: 11 Pages, 6 figures, accepted for publication in A&
ATCA 3mm observations of NGC6334I and I(N): dense cores, outflows and an UCHII region
Aims: Investigation of the dense gas, the outflows and the continuum emission
from the massive twin cores NGC6334I and I(N) at high spatial resolution.
Methods: We imaged the region with the Australia Telescope Compact Array (ATCA)
at 3.4mm wavelength in continuum as well as CH3CN(5_K-4_K) and HCN(1-0)
spectral line emission. Results: While the continuum emission in NGC6334I
mainly traces the UCHII region, toward NGC6334I(N) we detect line emission from
four of the previously identified dust continuum condensations that are of
protostellar or pre-stellar nature. The CH3CN(5_K-4_K) lines are detected in
all K-components up to energies of 128K above ground toward two protostellar
condensations in both regions. We find line-width increasing with increasing K
for all sources, which indicates a higher degree of internal motions closer to
the central protostars. Toward the main mm and CH3CN source in NGC6334I we
identify a velocity gradient approximately perpendicular to the large-scale
molecular outflow. This may be interpreted as a signature of an accretion disk,
although other scenarios, e.g., an unresolved double source, could produce a
similar signature as well. No comparable signature is found toward any of the
other sources. HCN does not trace the dense gas well but it is dominated by the
molecular outflows. While the outflow in NGC6334I exhibits a normal Hubble-law
like velocity structure, the data indicate a precessing outflow close to the
plane of the sky for NGC6334I(N). Furthermore, we observe a wide (~15.4km/s)
HCN absorption line, much broader than the previously observed CH3OH and NH3
absorption lines. Several explanations for the difference are discussed.Comment: 14 pages, 14 figures, accepted for A&
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