142 research outputs found
Protonated CO2 in massive star-forming clumps
Interstellar CO2 is an important reservoir of carbon and oxygen, and one of
the major constituents of the icy mantles of dust grains, but it is not
observable directly in the cold gas because has no permanent dipole moment. Its
protonated form, HOCO+, is believed to be a good proxy for gaseous CO2.
However, it has been detected in only a few star-forming regions so far, so
that its interstellar chemistry is not well understood. We present new
detections of HOCO+ lines in 11 high-mass star-forming clumps. Our observations
increase by more than three times the number of detections in star-forming
regions so far. We have derived beam-averaged abundances relative to H2 in
between 0.3 and 3.8 x 10^{-11}. We have compared these values with the
abundances of H13CO+, a possible gas-phase precursor of HOCO+, and CH3OH, a
product of surface chemistry. We have found a positive correlation with H13CO+,
while with CH3OH there is no correlation. We suggest that the gas-phase
formation route starting from HCO+ plays an important role in the formation of
HOCO+, perhaps more relevant than protonation of CO2 (upon evaporation of this
latter from icy dust mantles).Comment: 5 pages, 4 figures, 1 table, accepted for publication in MNRA
First interferometric study of enhanced N-fractionation in NH: the high-mass star-forming region IRAS 05358+3543
Nitrogen (N) fractionation is used as a tool to search for a link between the
chemical history of the Solar System and star-forming regions. A large
variation of N/N is observed towards different astrophysical
sources, and current chemical models cannot reproduce it. With the advent of
high angular resolution radiotelescopes it is now possible to search for
N-fractionation at core scales. We present IRAM NOEMA observations of the J=1-0
transition of NH, NNH and NNNH towards
the high-mass protocluster IRAS 05358+3543. We find N/N ratios
that span from 100 up to 220 and these values are lower or equal
than those observed with single-dish observations towards the same source.
Since N-fractionation changes across the studied region, this means that it is
regulated by local environmental effects. We find also the possibility, for one
of the four cores defined in the protocluster, to have a more abundant
NNH with respect to NNNH. This is another indication
that current chemical models may be missing chemical reactions or may not take
into account other mechanisms, like photodissociation or grain surface
chemistry, that could be important.Comment: 19 pages, 8 figures, 6 tables, 3 appendices Accepted in Monthly
Notices of the Royal Astronomical Society Letter
An integrated analysis of functional and genetic diversity in depicting the adaptive strategies of plants. The case study of Silene paradoxa.
Combined model for , , and spin-state chemistry in molecular clouds
We present a new gas-grain chemical model for the combined isotopic
fractionation of carbon and nitrogen in molecular clouds, in which the isotope
chemistry of carbon and nitrogen is coupled with a time-dependent description
of spin-state chemistry. We updated the rate coefficients of some isotopic
exchange reactions considered in the literature, and present here a set of new
exchange reactions involving molecules substituted in and simultaneously. We apply the model to a series of zero-dimensional
simulations representing a set of physical conditions across a prototypical
prestellar core, exploring the deviations of the isotopic abundance ratios in
the various molecules from the elemental isotopic ratios as a function of
physical conditions and time. We find that the ratio can
deviate from the elemental ratio by up to a factor of several depending on the
molecule, and that there are highly time-dependent variations in the ratios.
The ratio, for example, can obtain values of less than 10
depending on the simulation time. The ratios tend to remain
close to the assumed elemental ratio within ten per cent, with no clear
trends as a function of the physical conditions. Abundance ratios between -containing molecules and +-containing molecules
show somewhat increased levels of fractionation due to the newly included
exchange reactions, though still remaining within a few tens of per cent of the
elemental ratio. Our results imply the existence of
gradients in isotopic abundance ratios across prestellar cores, suggesting that
detailed simulations are required to interpret observations of isotopically
substituted molecules correctly, especially given that the various isotopic
forms of a given molecule do not necessarily trace the same gas layers.Comment: Accepted to A\&A; abstract abridged to meet arXiv requirement
DCN observations towards high-mass star-forming regions
We present the study of deuteration of cyanoacetylene (HCN) towards a
sample of 28 high-mass star-forming cores divided into different evolutionary
stages, from starless to evolved protostellar cores. We report for the first
time the detection of DCN towards 15 high-mass cores. The abundance ratios
of DCN with respect HCN range in the interval 0.0030.022, lower than
those found in low-mas protostars and dark clouds. No significant trend with
the evolutionary stage, or with the kinetic temperature of the region, has been
found. We compare the level of deuteration of HCN with those of other
molecules towards the same sample, finding weak correlation with species formed
only or predominantly in gas phase (NH and HNC, respectively), and no
correlation with species formed only or predominantly on dust grains (CHOH
and NH, respectively). We also present a single-dish map of DCN towards
the protocluster IRAS 05358+3543, which shows that DCN traces an extended
envelope (0.37 pc) and peaks towards two cold condensations separated
from the positions of the protostars and the dust continuum. The observations
presented in this work suggest that deuteration of HCN is produced in the
gas of the cold outer parts of massive star-forming clumps, giving us an
estimate of the deuteration factor prior to the formation of denser gas.Comment: Accepted in Monthly Notices of the Royal Astronomical Society -- 11
pages, 7 Figures, 2 Tables. Version with some typos correcte
Intraspecific trait variability and genetic diversity in the adaptive strategies of serpentine and non-serpentine populations of Silene paradoxa L
CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy III. Nitrogen isotopic ratios in the outer Galaxy
Nitrogen isotopic ratios are a key tool for tracing Galactic stellar
nucleosynthesis. We present the first study of the N/N abundance
ratio in the outer regions of the Milky Way (namely, for galactocentric
distances, , from 12 kpc up to 19 kpc), with the aim to study the
stellar nucleosynthesis effects in the global Galactic trend. We analysed IRAM
30m observations towards a sample of 35 sources in the context of the CHEMical
complexity in star-forming regions of the OUTer Galaxy (CHEMOUT) project. We
derived the N/N ratios from HCN and HNC for 14 and 3 sources,
respectively, using the = 1-0 rotational transition of HNC,
HNC, HCN, and HCN. The results found in the outer Galaxy
have been combined with previous measurements obtained in the inner Galaxy. We
find an overall linear decreasing HCN/HCN ratio with increasing
. This translates to a parabolic N/N ratio with a
peak at 11 kpc. Updated Galactic chemical evolution models have been taken into
account and compared with the observations. The parabolic trend of the
N/N ratio with can be naturally explained (i) by a
model that assumes novae as the main N producers on long timescales
(1 Gyr) and (ii) by updated stellar yields for low- and intermediate-mass
stars.Comment: 19 pages, 8 figures, 6 tables, 4 appendix - Accepted for publication
in A&
Identification of Histopathological Criteria for the Diagnosis of Canine Cutaneous Progressive Angiomatosis
The term angiomatosis is used to denote a group of well-known to poorly characterized
proliferative vascular entities. In animals, cutaneous progressive angiomatosis (CPA) is a disorder
with variable prognosis related to the extension and depth of infiltration of the surrounding tissues
by vessels. CPA may share some microscopical features with other vascular proliferations such as
low-grade well-differentiated capillaritic hemangiosarcoma (HS), making the diagnosis not always
straightforward, especially in small biopsies. The aim of this study is to retrospectively assess the most
common diagnostic microscopical features of CPA in dogs. In this work, 11 histopathological criteria
were analyzed on 31 CPA and 11 primary cutaneous HS in dogs. Features significantly associated with
CPA included: lobular growth, interposition of connective tissue and adnexa between the vascular
proliferation, presence of nerve fibers, and a mixed vascular proliferative component. Absence of
plump/prominent endothelial cells, lack of atypia, and lack of mitoses were also significant factors
differentiating CPA from HS. Additional distinctive findings in CPA, although with no statistical
association to CPA diagnosis, were vascular shunting, absence of necrosis, and endothelial cell piling
up. In conclusion, the combined use of different microscopical clues allowed for the distinction of
CPA from HS and was considered useful for the diagnosis of CPA
Effects of Wood Distillate (Pyroligneous Acid) on the Yield Parameters and Mineral Composition of Three Leguminous Crops
The excessive use of chemical fertilizers and pesticides in agriculture is increasing the demand for novel products to improve the quality of crops in a more sustainable way. Wood distillate (WD, pyroligneous acid) is a by-product obtained during the pyrolysis of plant biomass that can be successfully applied in agriculture due to its ability to enhance the growth, size, and weight of edible plant parts. However, there is little information concerning its plant yield-promoting effects on leguminous crops. The present work investigated the effects of WD on the yield, protein content and mineral composition of chickpea (Cicer arietinum L.), lentil (Lens culinaris L.) and bean (Phaseolus vulgaris L.) plants grown in field conditions. The application of WD showed remarkable yield-promoting effects mostly in lentil plants, which significantly increased plant and shoot biomass, the number and weight of both pods and seeds, as well as the total seed protein content. Furthermore, seeds from WD-treated plants differentially increased the concentration of elements with high nutritional value for human health, including Fe, Ca, Mg and K. These results suggest that the effects of WD among the legumes tested are species-specific and that WD could be an optimal candidate to grow high-yielding legumes with improved seed nutritional quality
Cucurbita pepo L. extracts as a versatile hydrotropic source for the synthesis of gold nanoparticles with different shapes
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