320 research outputs found
Mantle formation, coagulation and the origin of cloud/core-shine: II. Comparison with observations
Many dense interstellar clouds are observable in emission in the near-IR,
commonly referred to as "Cloudshine", and in the mid-IR, the so-called
"Coreshine". These C-shine observations have usually been explained with grain
growth but no model has yet been able to self-consistently explain the dust
spectral energy distribution from the near-IR to the submm. We want to
demonstrate the ability of our new core/mantle evolutionary dust model THEMIS
(The Heterogeneous dust Evolution Model at the IaS), which has been shown to be
valid in the far-IR and submm, to reproduce the C-shine observations. Our
starting point is a physically motivated core/mantle dust model. It consists of
3 dust populations: small aromatic-rich carbon grains; bigger core/mantle
grains with mantles of aromatic-rich carbon and cores either made of amorphous
aliphatic-rich carbon or amorphous silicate. We assume an evolutionary path
where these grains, when entering denser regions, may first form a second
aliphatic-rich carbon mantle (coagulation of small grains, accretion of carbon
from the gas phase), second coagulate together to form large aggregates, and
third accrete gas phase molecules coating them with an ice mantle. To compute
the corresponding dust emission and scattering, we use a 3D Monte-Carlo
radiative transfer code. We show that our global evolutionary dust modelling
approach THEMIS allows us to reproduce C-shine observations towards dense
starless clouds. Dust scattering and emission is most sensitive to the cloud
central density and to the steepness of the cloud density profile. Varying
these two parameters leads to changes, which are stronger in the near-IR, in
both the C-shine intensity and profile. With a combination of aliphatic-rich
mantle formation and low-level coagulation into aggregates, we can
self-consistently explain the observed C-shine and far-IR/submm emission
towards dense starless clouds.Comment: Paper accepted for publication in A&A with companion paper "Mantle
formation, coagulation and the origin of cloud/core-shine: I. Dust scattering
and absorption in the IR", A.P Jones, M. Koehler, N. Ysard, E. Dartois, M.
Godard, L. Gavila
Uncertainties in gas kinematics arising from stellar continuum modelling in integral field spectroscopy data: the case of NGC2906 observed with MUSE/VLT
We study how the use of several stellar subtraction methods and line fitting
approaches can affect the derivation of the main kinematic parameters (velocity
and velocity dispersion fields) of the ionized gas component. The target of
this work is the nearby galaxy NGC 2906, observed with the MUSE instrument at
Very Large Telescope. A sample of twelve spectra is selected from the inner
(nucleus) and outer (spiral arms) regions, characterized by different
ionization mechanisms. We compare three different methods to subtract the
stellar continuum (FIT3D, STARLIGHT and pPXF), combined with one of the
following stellar libraries: MILES, STELIB and GRANADA+MILES. The choice of the
stellar subtraction method is the most important ingredient affecting the
derivation of the gas kinematics, followed by the choice of the stellar library
and by the line fitting approach. In our data, typical uncertainties in the
observed wavelength and width of the H\alpha and [NII] lines are of the order
of _rms \sim 0.1\AA\ and _rms \sim 0.2\AA\ (\sim 5
and 10km/s, respectively). The results obtained from the [NII] line seem to be
slightly more robust, as it is less affected by stellar absorption than
H\alpha. All methods considered yield statistically consistent measurements
once a mean systemic contribution
\Delta\bar\lambda=\Delta\bar\sigma=0.2xDelta_{MUSE} is added in quadrature to
the line fitting errors, where \Delta_{MUSE} = 1.1\AA\ \sim 50 km/s denotes the
instrumental resolution of the MUSE spectra. Although the subtraction of the
stellar continuum is critical in order to recover line fluxes, any method
(including none) can be used in order to measure the gas kinematics, as long as
an additional component of 0.2 x Delta_MUSE is added to the error budget.Comment: 20 pages, 14 figure
Genetic Basis of Tetracycline Resistance in Bifidobacterium animalis subsp lactis
All strains of Bifidobacterium animalis subsp. lactis described to date show medium level resistance to tetracycline. Screening of 26 strains from a variety of sources revealed the presence of tet(W) in all isolates. A transposase gene upstream of tet(W) was found in all strains, and both genes were cotranscribed in strain IPLAIC4. Mutants with increased tetracycline resistance as well as tetracycline-sensitive mutants of IPLAIC4 were isolated and genetically characterized. The native tet(W) gene was able to restore the resistance phenotype to a mutant with an alteration in tet(W) by functional complementation, indicating that tet(W) is necessary and sufficient for the tetracycline resistance seen in B. animalis subsp. lactis
Water, Sanitation, and Hygiene: Linkages with Stunting in Rural Ethiopia
Stunting is a global burden affecting nearly 160 million children younger than five years of age. Whilst the linkages between nutrition and stunting are well recognized, there is a need to explore environmental factors such as water and sanitation, which may influence feeding practices and result in potential infection pathways. This paper explores the linkages between stunting and water, sanitation and hygiene (WASH) factors in Ethiopia, which is a relatively understudied context. The research draws upon baseline data for children under the age of five from 3200 households across four regions in Ethiopia as part of a wider study and integrated program led by the United Nations Children’s Fund (UNICEF). Using World Health Organization (WHO) z-scoring, the average stunting rate in the sample is 47.5%. This paper also takes into account demographic and social behavioural factors such as the age, gender of children, and gender of the primary caregiver, in addition to handwashing behaviour and drinking water facilities. The evidence recommends efforts to improve handwashing behaviour for mothers and children with a focus on access to clean water. Higher stunting rates with an increase in the age of children highlight the need for continued interventions, as efforts to improve nutrition and WASH behaviours are most effective early on in promoting long-term health outcomes for children
Mantle formation, coagulation and the origin of cloud/core shine: I. Modelling dust scattering and absorption in the infra-red
Context. The observed cloudshine and coreshine (C-shine) have been explained
in terms of grain growth leading to enhanced scatter- ing from clouds in the J,
H and K photometric bands and the Spitzer IRAC 3.6 and 4.5 {\mu}m bands. Aims.
Using our global dust modelling approach THEMIS (The Heterogeneous dust
Evolution Model at the IaS) we explore the effects of dust evolution in dense
clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain
coagulation. Methods. We model the effects of wide band gap a-C:H mantle
formation and the low-level aggregation of diffuse interstellar medium dust in
the moderately-extinguished outer regions of molecular clouds. Results. The
formation of wide band gap a-C:H mantles on amorphous silicate and amorphous
carbon (a-C) grains leads to a decrease in their absorption cross-sections but
no change in their scattering cross-sections at near-IR wavelengths, resulting
in higher albedos. Conclusions. The evolution of dust, with increasing density
and extinction in the diffuse to dense molecular cloud transition, through
mantle formation and grain aggregation, appears to be a likely explanation for
the observed C-shine.Comment: 12 pages, 15 figures, accepted for publication in A&A along with the
companion paper entitled, Mantle formation, coagulation and the origin of
cloud/core shine: II Comparison with observations, by Ysard et al. (also
accepted for publication in A&A
Disconnecting the Golgi ribbon from the centrosome prevents directional cell migration and ciliogenesis
AKAP450 is a critical determinant of Golgi ribbon integrity, positioning, and function
Whole genome analysis of extensively drug resistant Mycobacterium tuberculosis strains in Peru
Peru has the highest burden of multidrug-resistant tuberculosis in the Americas region. Since 1999, the annual number of extensively drug-resistant tuberculosis (XDR-TB) Peruvian cases has been increasing, becoming a public health challenge. The objective of this study was to perform genomic characterization of Mycobacterium tuberculosis strains obtained from Peruvian patients with XDR-TB diagnosed from 2011 to 2015 in Peru. Whole genome sequencing (WGS) was performed on 68 XDR-TB strains from different regions of Peru. 58 (85.3%) strains came from the most populated districts of Lima and Callao. Concerning the lineages, 62 (91.2%) strains belonged to the Euro-American Lineage, while the remaining 6 (8.8%) strains belonged to the East-Asian Lineage. Most strains (90%) had high-confidence resistance mutations according to pre-established WHO-confident grading system. Discordant results between microbiological and molecular methodologies were caused by mutations outside the hotspot regions analysed by commercial molecular assays (rpoB I491F and inhA S94A). Cluster analysis using a cut-off ≤ 10 SNPs revealed that only 23 (34%) strains evidenced recent transmission links. This study highlights the relevance and utility of WGS as a high-resolution approach to predict drug resistance, analyse transmission of strains between groups, and determine evolutionary patterns of circulating XDR-TB strains in the country.Revisión por pare
Constitutive regulation of mitochondrial morphology by Aurora A kinase depends on a predicted cryptic targeting sequence at the N-terminus.
Aurora A kinase (AURKA) is a major regulator of mitosis and an important driver of cancer progression. The roles of AURKA outside of mitosis, and how these might contribute to cancer progression, are not well understood. Here, we show that a fraction of cytoplasmic AURKA is associated with mitochondria, co-fractionating in cell extracts and interacting with mitochondrial proteins by reciprocal co-immunoprecipitation. We have also found that the dynamics of the mitochondrial network are sensitive to AURKA inhibition, depletion or overexpression. This can account for the different mitochondrial morphologies observed in RPE-1 and U2OS cell lines, which show very different levels of expression of AURKA. We identify the mitochondrial fraction of AURKA as influencing mitochondrial morphology, because an N-terminally truncated version of the kinase that does not localize to mitochondria does not affect the mitochondrial network. We identify a cryptic mitochondrial targeting sequence in the AURKA N-terminus and discuss how alternative conformations of the protein may influence its cytoplasmic fate.MRC
CRU
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