251 research outputs found
Ionization fraction and the enhanced sulfur chemistry in Barnard 1
Barnard B1b has revealed as one of the most interesting globules from the
chemical and dynamical point of view. It presents a rich molecular chemistry
characterized by large abundances of deuterated and complex molecules.
Furthermore, it hosts an extremely young Class 0 object and one candidate to
First Hydrostatic Core (FHSC). Our aim was to determine the cosmic ray
ionization rate and the depletion factors in this extremely young star forming
region. We carried out a spectral survey towards Barnard 1b as part of the IRAM
Large program ASAI using the IRAM 30-m telescope at Pico Veleta (Spain). This
provided a very complete inventory of neutral and ionic C-, N- and S- bearing
species with, up to our knowledge, the first secure detections of the
deuterated ions DCS+ and DOCO+. We used a state-of-the-art
pseudo-time-dependent gas-phase chemical model to determine the value of the
cosmic ray ionization rate and the depletion factors. The observational data
were well fitted with between 3E-17 s and 1E-16 s.
Elemental depletions were estimated to be ~10 for C and O, ~1 for N and ~25 for
S. Barnard B1b presents similar depletions of C and O than those measured in
pre-stellar cores. The depletion of sulfur is higher than that of C and O but
not as extreme as in cold cores. In fact, it is similar to the values found in
some bipolar outflows, hot cores and photon-dominated regions. Several
scenarios are discussed to account for these peculiar abundances. We propose
that it is the consequence of the initial conditions (important outflows and
enhanced UV fields in the surroundings) and a rapid collapse (~0.1 Myr) that
permits to maintain most S- and N-bearing species in gas phase to great optical
depths. The interaction of the compact outflow associated with B1b-S with the
surrounding material could enhance the abundances of S-bearing molecules, as
well.Comment: Paper accepted in Astronomy and Astrophysics; 28 pags, 21 figure
The chemistry of H2NC in the interstellar medium and the role of the C + NH3 reaction
We carried out an observational search for the recently discovered molecule
H2NC, and its more stable isomer H2CN, toward eight cold dense clouds (L1544,
L134N, TMC-2, Lupus-1A, L1489, TMC-1 NH3, L1498, and L1641N) and two diffuse
clouds (B0415+379 and B0355+508) in an attempt to constrain its abundance in
different types of interstellar regions and shed light on its formation
mechanism. We detected H2NC in most of the cold dense clouds targeted, 7 out of
8, while H2CN was only detected in 5 out of 8 clouds. The column densities
derived for both H2NC and H2CN are in the range 1e11-1e12 cm-2 and the
abundance ratio H2NC/H2CN varies between 0.51 and >2.7. The metastable isomer
H2NC is therefore widespread in cold dense clouds where it is present with an
abundance similar to that of H2CN. We did not detect either H2NC or H2CN in any
of the two diffuse clouds targeted, which does not allow to shed light on how
the chemistry of H2NC and H2CN varies between dense and diffuse clouds. We
found that the column density of H2NC is correlated with that of NH3, which
strongly suggests that these two molecules are chemically linked, most likely
ammonia being a precursor of H2NC through the C + NH3 reaction. We performed
electronic structure and statistical calculations which show that both H2CN and
H2NC can be formed in the C + NH3 reaction through two different channels
involving two different transition states which lie very close in energy. The
predicted product branching ratio H2NC/H2CN is very method dependent but values
between 0.5 and 0.8 are the most likely ones. Therefore, both the astronomical
observations and the theoretical calculations support that the reaction C + NH3
is the main source of H2NC in interstellar clouds.Comment: Accepted for publication in A&
OH+ in astrophysical media: state-to-state formation rates, Einstein coefficients and inelastic collision rates with He
The rate constants required to model the OH observations in different
regions of the interstellar medium have been determined using state of the art
quantum methods.
First, state-to-state rate constants for the H+ O()
H + OH reaction have been obtained using
a quantum wave packet method. The calculations have been compared with
time-independent results to asses the accuracy of reaction probabilities at
collision energies of about 1 meV. The good agreement between the simulations
and the existing experimental cross sections in the 1 eV energy range
shows the quality of the results.
The calculated state-to-state rate constants have been fitted to an
analytical form. Second, the Einstein coefficients of OH have been obtained
for all astronomically significant ro-vibrational bands involving the
and/or electronic states.
For this purpose the potential energy curves and electric dipole transition
moments for seven electronic states of OH are calculated with {\it ab
initio} methods at the highest level and including spin-orbit terms, and the
rovibrational levels have been calculated including the empirical spin-rotation
and spin-spin terms. Third, the state-to-state rate constants for inelastic
collisions between He and OH have been calculated using a
time-independent close coupling method on a new potential energy surface. All
these rates have been implemented in detailed chemical and radiative transfer
models. Applications of these models to various astronomical sources show that
inelastic collisions dominate the excitation of the rotational levels of
OH. In the models considered the excitation resulting from the chemical
formation of OH increases the line fluxes by about 10 % or less depending
on the density of the gas
The magnesium paradigm in IRC+10216: Discovery of MgCH, MgCN, MgCH, and MgCN
We found four series of harmonically related lines in IRC\,+10216 with the
Yebes\,40m and IRAM\,30m telescopes. The first series corresponds to a molecule
with a rotational constant, , of 1448.59940.0013 MHz and a distortion
constant, , of 63.451.15 Hz and covers upper quantum numbers from
=11 up to 33 (B1449). The second series is fitted with
=1446.93800.0098 MHz and =9123 Hz and covers upper quantum
numbers from =11 up to 17 (B1447). The third series is fitted with
=598.74950.0011 MHz and D=6.130.43 Hz and covers quantum numbers
from =26 up to 41 (B599). Finally, the frequencies of the last series of
lines can be reproduced with =594.31760.0026 MHz and =4.921.16
Hz (B594). The large values of point toward four metal-bearing carriers.
After exploring all plausible candidates containing Na, Al, Mg, and other
metals, our ab initio calculations indicate that the cations MgCH,
MgCN, MgCH, and MgCN must be the carriers of B1449,
B1447, B599, and B594, respectively. These cations could be formed by the
radiative association of Mg with CH, CN, CH, and CN,
respectively. We calculated the radiative association rate coefficient of
Mg with CH, CN, CH, and CN and incorporated them in our
chemical model. The results confirm that the Mg-bearing cations can be formed
through these radiative association reactions in the outer layers of
IRC\,+10216. This is the first time that cationic metal-bearing species have
been found in space. These results provide a new paradigm on the reactivity of
ionized metals with abundant radicals and open the door for further
characterization of similar species in metal-rich astrophysical environments
The PKC, HOG and Ca2+ signalling pathways co-ordinately regulate chitin synthesis in Candida albicans
Open Access via PMC2649417Peer reviewedPublisher PD
Psychiatric care in university population
[EN] It is well-known that university students experience high levels of mental health problems. University life presents changes and challenges that can be stressful and may affect the mental health of its community. More than 20 years ago, the Social Affairs Service (SAS) of the University of Salamanca started a program that ensured the mental health care in their community. The Psychiatric Care Unit is part of this program and its objectives are: 1) to detect serious mental disorders; 2) treat mild mental disorders; 3) give information to prevent illness and promote mental health; 4) serve as support in patients with previous follow-up that has been discontinued due to the beginning of their studies; 5) liaise with referral psychiatrists
Transcriptomic and genetic studies identify NFAT5 as a candidate gene for cocaine dependence
Cocaine reward and reinforcing effects are mediated mainly by dopaminergic neurotransmission. In this study, we aimed at evaluating gene expression changes induced by acute cocaine exposure on SH-SY5Y-differentiated cells, which have been widely used as a dopaminergic neuronal model. Expression changes and a concomitant increase in neuronal activity were observed after a 5 μM cocaine exposure, whereas no changes in gene expression or in neuronal activity took place at 1 μM cocaine. Changes in gene expression were identified in a total of 756 genes, mainly related to regulation of transcription and gene expression, cell cycle, adhesion and cell projection, as well as mitogen-activeated protein kinase (MAPK), CREB, neurotrophin and neuregulin signaling pathways. Some genes displaying altered expression were subsequently targeted with predicted functional single-nucleotide polymorphisms (SNPs) in a case-control association study in a sample of 806 cocaine-dependent patients and 817 controls. This study highlighted associations between cocaine dependence and five SNPs predicted to alter microRNA binding at the 3′-untranslated region of the NFAT5 gene. The association of SNP rs1437134 with cocaine dependence survived the Bonferroni correction for multiple testing. A functional effect was confirmed for this variant by a luciferase reporter assay, with lower expression observed for the rs1437134G allele, which was more pronounced in the presence of hsa-miR-509. However, brain volumes in regions of relevance to addiction, as assessed with magnetic resonance imaging, did not correlate with NFAT5 variation. These results suggest that the NFAT5 gene, which is upregulated a few hours after cocaine exposure, may be involved in the genetic predisposition to cocaine dependence
The MRN complex is transcriptionally regulated by MYCN during neural cell proliferation to control replication stress
The MRE11/RAD50/NBS1 (MRN) complex is a major sensor of DNA double strand breaks, whose role in controlling faithful DNA replication and preventing replication stress is also emerging. Inactivation of the MRN complex invariably leads to developmental and/or degenerative neuronal defects, the pathogenesis of which still remains poorly understood. In particular, NBS1 gene mutations are associated with microcephaly and strongly impaired cerebellar development, both in humans and in the mouse model. These phenotypes strikingly overlap those induced by inactivation of MYCN, an essential promoter of the expansion of neuronal stem and progenitor cells, suggesting that MYCN and the MRN complex might be connected on a unique pathway essential for the safe expansion of neuronal cells. Here, we show that MYCN transcriptionally controls the expression of each component of the MRN complex. By genetic and pharmacological inhibition of the MRN complex in a MYCN overexpression model and in the more physiological context of the Hedgehog-dependent expansion of primary cerebellar granule progenitor cells, we also show that the MRN complex is required for MYCN-dependent proliferation. Indeed, its inhibition resulted in DNA damage, activation of a DNA damage response, and cell death in a MYCN- and replication-dependent manner. Our data indicate the MRN complex is essential to restrain MYCN-induced replication stress during neural cell proliferation and support the hypothesis that replication-born DNA damage is responsible for the neuronal defects associated with MRN dysfunctions.Cell Death and Differentiation advance online publication, 12 June 2015; doi:10.1038/cdd.2015.81
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Real world safety of methoxyflurane analgesia in the emergency setting: a comparative hybrid prospective-retrospective post-authorisation safety study.
BACKGROUND: Low-dose analgesic methoxyflurane (Penthrox®) was approved in Europe for emergency relief of moderate to severe pain in conscious adults with trauma in 2015. A comparative post-authorisation safety study (PASS) was conducted to assess the risk of hepatotoxicity and nephrotoxicity with methoxyflurane during routine clinical practice. METHODS: This was a comparative hybrid prospective-retrospective cohort study. The comparative cohorts consisted of adults who were given methoxyflurane (methoxyflurane cohort) or another analgesic (concurrent cohort) routinely used for moderate to severe trauma and associated pain in the emergency setting (ambulance and Emergency Department) in the UK between December 2016 and November 2018. Hepatic and renal events were captured in the ensuing 12 weeks. A blinded clinical adjudication committee assessed events. A historical comparator cohort (non-concurrent cohort) was identified from patients with fractures in the English Hospital Episode Statistics (HES) accident and emergency database from November 2013 and November 2015 (before commercial launch of methoxyflurane). Hepatic and renal events were captured in the ensuing 12 weeks via linkage with the Clinical Practice Research Datalink (CPRD) and HES hospital admissions databases. RESULTS: Overall, 1,236, 1,101 and 45,112 patients were analysed in the methoxyflurane, concurrent and non-concurrent comparator cohorts respectively. There was no significant difference in hepatic events between the methoxyflurane and concurrent cohorts (1.9% vs. 3.0%, P = 0.079) or between the methoxyflurane and non-concurrent cohorts (1.9% vs. 2.5%, P = 0.192). Renal events were significantly less common in the methoxyflurane cohort than in the concurrent cohort (2.3% vs. 5.6%, P < 0.001). For methoxyflurane versus non-concurrent cohort the lower occurrence of renal events (2.3% vs. 3.2%, P = 0.070) was not statistically significant. Multivariable adjustment did not change these associations. CONCLUSIONS: Methoxyflurane administration was not associated with an increased risk of hepatotoxicity or nephrotoxicity compared with other routinely administered analgesics and was associated with a reduced risk of nephrotoxicity compared with other routinely administered analgesics. TRIAL REGISTRATION: Study registered in the EU PAS Register (ENCEPP/SDPP/13040)
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