1,063 research outputs found
The census of complex organic molecules in the solar type protostar IRAS16293-2422
Complex Organic Molecules (COMs) are considered crucial molecules, since they
are connected with organic chemistry, at the basis of the terrestrial life.
More pragmatically, they are molecules in principle difficult to synthetize in
the harsh interstellar environments and, therefore, a crucial test for
astrochemical models. Current models assume that several COMs are synthesised
on the lukewarm grain surfaces (30-40 K), and released in the gas
phase at dust temperatures 100 K. However, recent detections of COMs
in 20 K gas demonstrate that we still need important pieces to
complete the puzzle of the COMs formation. We present here a complete census of
the oxygen and nitrogen bearing COMs, previously detected in different ISM
regions, towards the solar type protostar IRAS16293-2422. The census was
obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS.
Six COMs, out of the 29 searched for, were detected: methyl cyanide, ketene,
acetaldehyde, formamide, dimethyl ether, and methyl formate. The multifrequency
analysis of the last five COMs provides clear evidence that they are present in
the cold (30 K) envelope of IRAS16293-2422, with abundances 0.03-2
. Our data do not allow to support the hypothesis that the
COMs abundance increases with increasing dust temperature in the cold envelope,
as expected if COMs were predominately formed on the lukewarm grain surfaces.
Finally, when considering also other ISM sources, we find a strong correlation
over five orders of magnitude, between the methyl formate and dimethyl ether
and methyl formate and formamide abundances, which may point to a link between
these two couples of species, in cold and warm gas
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ISO Detection of CO<sup>+</sup> toward the protostar IRAS 16293-2422
In this letter we report the detection of eight high-N rotational transitions of CO+ towards a low mass protostar, IRAS 16293-2422. The source was observed with the Long Wavelength Spectrometer on board the Infrared Space Observatory. This is the first time that CO+ has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed CO+ emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at ~ 500 AU from the star is the origin of the CO+ emission. This model predicts CO+ column densities in rough agreement with the observations if the magnetic field is ~ 1 mG and the shock velocity is 100 km s-1
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Shocks and PDRs in an intermediate mass star forming globule: the case of IC1396N
The dark globule IC1396N is a typical example of a star formation process induced by radiation driven implosion due to the strong UV field from a nearby O6 star. The IRAS source embedded in the globule and its associated molecular outflow have been observed with the Long Wavelength Spectrometer (LWS) on ISO revealing an extremely rich spectrum including: CO rotational lines from J=14-13 up to J=28-27, rotational lines from ortho-H2O, OH lines involving the first four rotational levels of both ladders, atomic (OI 63μm, OI 145μm) and ionic (CII 157μm, OIII 52μm, OIII 88μm) lines. A complex picture arises, where an externally illuminated PDR coexists with strong C-shocks within IC1396N and whose origin is not clear
CD73 expression and clinical significance in human metastatic melanoma.
CD73 is an ectoenzyme involved in the production of adenosine. It exerts immunosuppressive and protumoral roles and has emerged as a potential immuno-oncology target.
CD73 expression was detected in TC in 54% of melanoma metastases, involving < 50% TC in the majority of the cases, with variable intensity. CD73 expression was significantly associated with a lower Breslow's depth of the primary lesion and was more frequent in patients having received prior non-surgical therapies. In an adjusted analysis, CD73 expression in TC (H-score > 37.5 or intensity > 1) significantly correlated to decreased overall survival (OS) from biopsy. Of the samples containing TIMC, 35% presented CD73+ TIMC. Highly infiltrated tumors were more likely to contain CD73+ TIMC. CD73 expression in TIMC (percentage ≥1%) significantly correlated with improved OS from biopsy.
Immunohistochemistry detected CD73 expression in more than half of metastatic melanomas. While CD73 expression in TC significantly correlated with decreased OS, CD73 expression in TIMC significantly associated with improved OS. These results encourage the study of anti-CD73 therapies for metastatic melanoma patients.
CD73 expression was assessed by immunohistochemistry in metastatic melanomas from 114 patients. Immunostainings were evaluated in tumor cells (TC) (percentage, intensity (1-3) and H-score) and in tumor-infiltrating mononuclear cells (TIMC) (percentage)
Exact Multifractality for Disordered N-Flavour Dirac Fermions in Two Dimensions
We present a nonperturbative calculation of all multifractal scaling
exponents at strong disorder for critical wavefunctions of Dirac fermions
interacting with a non-Abelian random vector potential in two dimensions. The
results, valid for an arbitrary number of fermionic flavours, are obtained by
deriving from Conformal Field Theory an effective Gaussian model for the
wavefunction amplitudes and mapping to the thermodynamics of a single particle
in a random potential. Our spectrum confirms that the wavefunctions remain
delocalized in the presence of strong disorder.Comment: 4 pages, no figue
Multispinon continua at zero and finite temperature in a near-ideal Heisenberg chain
The space- and time-dependent response of many-body quantum systems is the
most informative aspect of their emergent behaviour. The dynamical structure
factor, experimentally measurable using neutron scattering, can map this
response in wavevector and energy with great detail, allowing theories to be
quantitatively tested to high accuracy. Here, we present a comparison between
neutron scattering measurements on the one-dimensional spin-1/2 Heisenberg
antiferromagnet KCuF3, and recent state-of-the-art theoretical methods based on
integrability and density matrix renormalization group simulations. The
unprecedented quantitative agreement shows that precise descriptions of
strongly correlated states at all distance, time and temperature scales are now
possible, and highlights the need to apply these novel techniques to other
problems in low-dimensional magnetism
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