345 research outputs found
Mid- and high-J CO observations towards UCHIIs
A study of 12 ultracompact HII regions was conducted to probe the physical
conditions and kinematics in the inner envelopes of the molecular clumps
harboring them. The APEX telescope was used to observe the sources in the CO
(4-3) and 13CO (8-7) lines. Line intensities were modeled with the RATRAN
radiative transfer code using power laws for the density and temperature to
describe the physical structure of the clumps. All sources were detected in
both lines. The optically thick CO (4-3) line shows predominantly blue skewed
profiles reminiscent of infall. Line intensities can be reproduced well using
the physical structure of the clumps taken from the literature. The optically
thick line profiles show that CO is a sensitive tracer of ongoing infall in the
outer envelopes of clumps harboring ultracompact HII regions and hot molecular
cores.Comment: APEX A&A special issue, accepte
ADSORPTION ESSAYS OF PALLADIUM IN MODIFIED SILICA GEL WITH THIOURONIUM GROUPS: EXPERIMENTAL AND THEORICAL STUDIES
Indexación: Web of Science; ScieloThe silylant 3-cloropropyltriethoxysilyl was anchored over silica gel in anhydrous conditions in order to react with thiourea to obtain modified silica gel with thiouronium. The aim to obtain an inorganic support that is able to hijack metals from the VIII group such as palladium. The product was characterized by Sbet and FTIR infrared spectroscopy. For the determination of the structure in the modified silica gel NMR spectra of silicon and carbon were preformed in solid state. The coordination form of the modified silica gel to the metal was studied computationally in the context of the DFT theory, using the ADF code. This was a collaborative work with "Fundación Chile" for the recuperation of precious metals from the mining industry.http://ref.scielo.org/gk7rm
Reply to the comment by D. Kreimer and E. Mielke
We respond to the comment by Kreimer et. al. about the torsional contribution
to the chiral anomaly in curved spacetimes. We discuss their claims and refute
its main conclusion.Comment: 9 pages, revte
AMBER on the VLTI: data processing and calibration issues
We present here the current performances of the AMBER / VLTI instrument for
standard use and compare these with the offered modes of the instrument. We
show that the instrument is able to reach its specified precision only for
medium and high spectral resolution modes, differential observables and bright
objects. For absolute observables, the current achievable accuracy is strongly
limited by the vibrations of the Unit Telescopes, and also by the observing
procedure which does not take into account the night-long transfer function
monitoring. For low-resolution mode, the current limitation is more in the data
reduction side, since several effects negligible at medium spectral resolution
are not taken into account in the current pipeline. Finally, for faint objects
(SNR around 1 per spectral channel), electromagnetic interferences in the VLTI
interferometric laboratory with the detector electronics prevents currently to
get unbiased measurements. Ideas are under study to correct in the data
processing side this effect, but a hardware fix should be investigated
seriously since it limits seriously the effective limiting magnitude of the
instrument.Comment: 10 page
The Circumstellar Environment of High Mass Protostellar Objects. III Evidence of Infall?
The results are presented of a molecular line survey to search for the
spectral signature of infall towards 77 850 micron continuum sources believed
to be candidate high mass protostellar objects. Up to six different
transitions, HCO+ 1-0, 3-2 and 4-3, H2CO 2_12-1_11, N2H+ and H13CO+ 3-2, were
observed towards each source. Towards the peak of the 850 micron emission, N2H+
was typically strong, with a peak antenna temperature of ~1.5K, with a typical
linewidth of ~2km/s. The good agreement between the velocity and velocity width
of the N2H+ and H13CO+ emission suggests that both species are tracing similar
material in the sources. With respect to the velocity of the N2H+, there is a
statistically significant excess of blue asymmetric line profiles in both the
HCO+ 1-0 and H2CO transitions. This excess reaches levels similar to that seen
towards samples of low mass protostars, and suggests that the material around
these high mass sources is infalling. We identify 22 promising candidate infall
sources which show at least one blue asymmetric line profile and no red
asymmetric profiles. The infall velocity is estimated to be in the range of 0.1
km/s to 1 km/s with an implied mass accretion rate of between 2x10^{-4} Msol/yr
and 10^{-3}Msol/yr.Comment: Accepted for publication in Astronomy and Astrophysics. Higher
resolution versions of Figures 1 and 2 are available from
http://www.jb.man.ac.uk/~gaf/Papers.htm
Does Infall End Before the Class I Stage?
We have observed HCO+ J=3-2 toward 16 Class I sources and 18 Class 0 sources,
many of which were selected from Mardones et al. (1997). Eight sources have
profiles significantly skewed to the blue relative to optically thin lines. We
suggest six sources as new infall candidates. We find an equal "blue excess"
among Class 0 and Class I sources after combining this sample with that of
Gregersen et al. (1997). We used a Monte Carlo code to simulate the temporal
evolution of line profiles of optically thick lines of HCO+, CS and H2CO in a
collapsing cloud and found that HCO+ had the strongest asymmetry at late times.
If a blue-peaked line profile implies infall, then the dividing line between
the two classes does not trace the end of the infall stage.Comment: 21 pages, 8 figures, accepted by ApJ for April 20, 2000, added
acknowledgmen
Phytochemicals as Potential Epidrugs in Type 2 Diabetes Mellitus
Type 2 diabetes Mellitus (T2DM) prevalence has significantly increased worldwide in recent years due to population age, obesity, and modern sedentary lifestyles. The projections estimate that 439 million people will be diabetic in 2030. T2DM is characterized by an impaired ß-pancreatic cell function and insulin secretion, hyperglycemia and insulin resistance, and recently the epigenetic regulation of ß-pancreatic cells differentiation has been underlined as being involved. It is currently known that several bioactive molecules, widely abundant in plants used as food or infusions, have a key role in histone modification and DNA methylation, and constituted potential epidrugs candidates against T2DM. In this sense, in this review the epigenetic mechanisms involved in T2DM and protein targets are reviewed, with special focus in studies addressing the potential use of phytochemicals as epidrugs that prevent and/or control T2DM in vivo and in vitro. As main findings, and although some controversial results have been found, bioactive molecules with epigenetic regulatory function, appear to be a potential replacement/complementary therapy of pharmacological hypoglycemic drugs, with minimal side effects. Indeed, natural epidrugs have shown to prevent or delay the T2DM development and the morbidity associated to dysfunction of blood vessels, eyes and kidneys due to sustained hyperglycemia in T2DM patients.This work was supported by CONICYT PIA/APOYO CCTE AFB170007.
NC-M acknowledges the Portuguese Foundation for Science and Technology under the Horizon 2020 Program (PTDC/PSI-GER/ 28076/2017)
Topological Invariants, Instantons and Chiral Anomaly on Spaces with Torsion
In a spacetime with nonvanishing torsion there can occur topologically stable
configurations associated with the frame bundle which are independent of the
curvature. The relevant topological invariants are integrals of local scalar
densities first discussed by Nieh and Yan (N-Y). In four dimensions, the N-Y
form is the only closed
4-form invariant under local Lorentz rotations associated with the torsion of
the manifold. The integral of over a compact D-dimensional (Euclidean)
manifold is shown to be a topological invariant related to the Pontryagin
classes of SO(D+1) and SO(D). An explicit example of a topologically nontrivial
configuration carrying nonvanishing instanton number proportional to
is costructed. The chiral anomaly in a four-dimensional spacetime with torsion
is also shown to contain a contribution proportional to , besides the usual
Pontryagin density related to the spacetime curvature. The violation of chiral
symmetry can thus depend on the instanton number of the tangent frame bundle of
the manifold. Similar invariants can be constructed in D>4 dimensions and the
existence of the corresponding nontrivial excitations is also discussed.Comment: 6 pages, RevTeX, no figures, two column
New Gauge Supergravity in Seven and Eleven Dimensions
Locally supersymmetric systems in odd dimensions whose Lagrangians are
Chern-Simons forms for supersymmetric extensions of anti-de Sitter gravity are
discussed. The construction is illustrated for D=7 and 11. In seven dimensions
the theory is an N=2 supergravity whose fields are the vielbein
(), the spin connection (), two gravitini
() and an gauge connection (). These
fields form a connection for . In eleven dimensions the theory is an
N=1 supergravity containing, apart from and ,
one gravitino , and a totally antisymmetric fifth rank Lorentz
tensor one-form, . These fields form a connection for
. The actions are by construction invariant under local
supersymmetry and the algebra closes off shell without requiring auxiliary
fields. The -theory can be shown to have nonnegative energy around
an AdS background, which is a classical solution that saturates the Bogomolnyi
bound obtained from the superalgebra.Comment: 5pages, RevTeX, no figures, two columns, minor typos correcte
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