180 research outputs found
ELM divertor peak energy fluence scaling to ITER with data from JET, MAST and ASDEX upgrade
A newly established scaling of the ELM energy fluence using dedicated data sets from JET operation with CFC & ILW plasma facing components (PFCs), ASDEX Upgrade (AUG) operation with both CFC and full-W PFCs and MAST with CFC walls has been generated. The scaling reveals an approximately linear depen- dence of the peak ELM energy with the pedestal top electron pressure and with the minor radius; a square root dependence is seen on the relative ELM loss energy. The result of this scaling gives a range in parallel peak ELM energy fluence of 10â30 MJm â2 for ITER Q = 10 operation and 2.5â7.5 MJm â2 for in- termediate ITER operation at 7.5 MA and 2.65 T. These latter numbers are calculated using a numerical regression ( Δ II = 0 . 28 MJ m 2 n 0 . 75 e T 1 e E 0 . 5 ELM R 1 geo ). A simple model for ELM induced thermal load is introduced, resulting in an expression for the ELM energy fluence of Δ II âŒ= 6 Ïp e R geo q edge . The relative ELM loss energy in the data is between 2â10% and the ELM energy fluence varies within a range of 10 0.5 âŒ3 con- sistently for each individual device. The so far analysed power load database for ELM mitigation experi- ments from JET-EFCC and Kicks, MAST-RMP and AUG-RMP operation are found to be consistent with both the scaling and the introduced model, ie not showing a further reduction with respect to their pedestal pressure. The extrapolated ELM energy fluencies are compared to material limits in ITER and found to be of concern.RCUK Energy Programme P012450/1EURATOM 63305
The Perils of Clumpfind: The Mass Spectrum of Sub-structures in Molecular Clouds
We study the mass spectrum of sub-structures in the Perseus Molecular Cloud
Complex traced by 13CO (1-0), finding that for the
standard Clumpfind parameters. This result does not agree with the classical
. To understand this discrepancy we study the robustness
of the mass spectrum derived using the Clumpfind algorithm. Both 2D and 3D
Clumpfind versions are tested, using 850 m dust emission and 13CO
spectral-line observations of Perseus, respectively. The effect of varying
threshold is not important, but varying stepsize produces a different effect
for 2D and 3D cases. In the 2D case, where emission is relatively isolated
(associated with only the densest peaks in the cloud), the mass spectrum
variability is negligible compared to the mass function fit uncertainties. In
the 3D case, however, where the 13CO emission traces the bulk of the molecular
cloud, the number of clumps and the derived mass spectrum are highly correlated
with the stepsize used. The distinction between "2D" and "3D" here is more
importantly also a distinction between "sparse" and "crowded" emission. In any
"crowded" case, Clumpfind should not be used blindly to derive mass functions.
Clumpfind's output in the "crowded" case can still offer a statistical
description of emission useful in inter-comparisons, but the clump-list should
not be treated as a robust region decomposition suitable to generate a
physically-meaningful mass function. We conclude that the 13CO mass spectrum
depends on the observations resolution, due to the hierarchical structure of
MC.Comment: 5 pages, 3 figures. Accepted for publication in ApJ Letter
Fragmentation in the Massive Star-Forming Region IRAS 19410+2336
The Core Mass Functions (CMFs) of low-mass star-forming regions are found to
resemble the shape of the Initial Mass Function (IMF). A similar result is
observed for the dust clumps in high-mass star forming regions, although at
spatial scales of clusters that do not resolve the substructure found in them.
The region IRAS 19410+2336 is one exception, having been observed at spatial
scales on the order of ~2500AU, resolving the clump substructure into
individual cores.
We mapped that region with the PdBI in the 1.4mm and 3mm continuum and
several transitions of H2CO and CH3CN. The H2CO transitions were also observed
with the IRAM 30m Telescope. We detected 26 continuum sources at 1.4mm with a
spatial resolution down to ~2200 AU, distributed in two protoclusters. With the
lines emission we derived the temperature structure of the region, ranging from
35 to 90K. With them we calculated the core masses of the detected sources,
ranging from ~0.7 to ~8 M_sun. These masses were strongly (~90%) affected by
the interferometer spatial filtering. Considering only the detected dense cores
we derived a CMF with a power-law index b=-2.3+-0.2. We resolve the Jeans
length of the protoclusters by one order of magnitude, and only find little
velocity dispersion between the different subsources.
Since we cannot unambiguously differentiate protostellar and prestellar
cores, the derived CMF is not prestellar. Also, because of the large missing
flux, we cannot establish a firm link between the CMF and the IMF. This implies
that future high-mass CMF studies will need to complement the interferometer
continuum data with the short spacing data, a task suitable for ALMA. We note
that the method of extracting temperatures using H2CO lines becomes less
applicable when reaching the dense core scales of the interferometric
observations because most of the H2CO appears to originate in the envelope
structure.Comment: 17 pages, 12 figures, accepted by A&
Vanadium oxide supported on porous clay heterostructure for the partial oxidation of hydrogen sulphide to sulfur
Vanadium oxide supported on porous clay heterostructures (PCH) catalysts have been synthesized, characterized and evaluated in the selective oxidation of H2S to elemental sulfur. The catalysts were characterized by XRD, adsorption-desorption of N-2 at -196 degrees C, diffuse reflectance UV-vis, H-2-TPR, Raman spectroscopy and XPS. The catalysts with higher vanadium content are more active and selective, exhibiting a H2S conversion close to 70% after 360h on stream with a high selectivity toward elemental sulfur and a low formation of undesired SO2. The catalysts with V2O5 crystallites have shown a higher activity and resistance to the deactivation. The analysis of the spent catalyst has revealed the formation of V4O9 crystals during the catalytic test, which has been reported as the active phase in the selective oxidation of the H2S. (C) 2015 Elsevier B.V. All rights reserved.The authors would like to thank the DGICYT in Spain (Projects CTQ2012-37925-C03-01, CTQ2012-37925-C03-03 and FEDER funds, and MAT2010-19837-C06-05) and project of Excellence of Junta de Andalucia (project P12-RNM-1565) for financial support. A. Natoli thanks to SECAT (Spain) for a grant.Soriano RodrĂguez, MD.; Cecilia, JA.; Natoli, A.; Jimenez-Jimenez, J.; LĂłpez Nieto, JM.; Rodriguez Castellon, E. (2015). Vanadium oxide supported on porous clay heterostructure for the partial oxidation of hydrogen sulphide to sulfur. Catalysis Today. 254:36-42. https://doi.org/10.1016/j.cattod.2014.12.022S364225
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Gas phase Elemental abundances in Molecular cloudS (GEMS) : IV. Observational results and statistical trends
Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30 m Large Program designed to provide estimates of the S, C, N, and O depletions and gas ionization degree, X(e(-)), in a selected set of star-forming filaments of Taurus, Perseus, and Orion. Our immediate goal is to build up a complete and large database of molecular abundances that can serve as an observational basis for estimating X(e(-)) and the C, O, N, and S depletions through chemical modeling. We observed and derived the abundances of 14 species ((CO)-C-13, (CO)-O-18, HCO+, (HCO+)-C-13, (HCO+)-O-18, HCN, (HCN)-C-13, HNC, HCS+, CS, SO, (SO)-S-34, H2S, and OCS) in 244 positions, covering the A(V) similar to 3 to similar to 100 mag, n(H-2) similar to a few 10(3) to 10(6) cm(-3), and T-k similar to 10 to similar to 30 K ranges in these clouds, and avoiding protostars, HII regions, and bipolar outflows. A statistical analysis is carried out in order to identify general trends between different species and with physical parameters. Relations between molecules reveal strong linear correlations which define three different families of species: (1) (CO)-C-13 and (CO)-O-18 isotopologs; (2) (HCO+)-C-13, (HCO+)-O-18, H-13 CN, and HNC; and (3) the S-bearing molecules. The abundances of the CO isotopologs increase with the gas kinetic temperature until T-K similar to 15 K. For higher temperatures, the abundance remains constant with a scatter of a factor of similar to 3. The abundances of H-13 CO+, HC18 O+, H-13 CN, and HNC are well correlated with each other, and all of them decrease with molecular hydrogen density, following the law proportional to n(H-2)(-0.8 +/- 0.2). The abundances of S-bearing species also decrease with molecular hydrogen density at a rate of (S-bearing/H)(gas) proportional to n(H-2)(-0.6 +/- 0.1). The abundances of molecules belonging to groups 2 and 3 do not present any clear trend with gas temperature. At scales of molecular clouds, the (CO)-O-18 abundance is the quantity that better correlates with the cloud mass. We discuss the utility of the (CO)-C-13/(CO)-O-18, HCO+/(HCO+)-C-13, and H-13 CO+/(HCN)-C-13 abundance ratios as chemical diagnostics of star formation in external galaxies.Peer reviewe
Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-Correlation Techniques to JWST NIRSpec G395H Data
Carbon monoxide was recently reported in the atmosphere of the hot Jupiter
WASP-39b using the NIRSpec PRISM transit observation of this planet, collected
as part of the JWST Transiting Exoplanet Community Early Release Science (JTEC
ERS) Program. This detection, however, could not be confidently confirmed in
the initial analysis of the higher resolution observations with NIRSpec G395H
disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b
using the NIRSpec G395H data and cross-correlation techniques. We do this by
searching for the CO signal in the unbinned transmission spectrum of the planet
between 4.6 and 5.0 m, where the contribution of CO is expected to be
higher than that of other anticipated molecules in the planet's atmosphere. Our
search results in a detection of CO with a cross-correlation function (CCF)
significance of when using a template with only lines. The CCF significance of the CO signal increases to when including in the template lines from additional CO isotopologues,
with the largest contribution being from . Our results
highlight how cross-correlation techniques can be a powerful tool for unveiling
the chemical composition of exoplanetary atmospheres from medium-resolution
transmission spectra, including the detection of isotopologues.Comment: Accepted for publication in The Astrophysical Journal Letter
The Incidence of AIDS-Defining Illnesses at a Current CD4 Count â„200 Cells/”L in the Post-Combination Antiretroviral Therapy Era
The incidence of AIDS was higher in patients with a current CD4 count of 500-749 cells/”L compared to 750-999 cells/”L, but did not decrease further at higher CD4 levels. Results were similar in those virologically suppressed on combination antiretroviral therapy, suggesting immune reconstitution is incomplete until CD4 >750/”
Evaluating expert-based habitat suitability information of terrestrial mammals with GPS-tracking data
Aim Macroecological studies that require habitat suitability data for many species often derive this information from expert opinion. However, expert-based information is inherently subjective and thus prone to errors. The increasing availability of GPS tracking data offers opportunities to evaluate and supplement expert-based information with detailed empirical evidence. Here, we compared expert-based habitat suitability information from the International Union for Conservation of Nature (IUCN) with habitat suitability information derived from GPS-tracking data of 1,498 individuals from 49 mammal species. Location Worldwide. Time period 1998-2021. Major taxa studied Forty-nine terrestrial mammal species. Methods Using GPS data, we estimated two measures of habitat suitability for each individual animal: proportional habitat use (proportion of GPS locations within a habitat type), and selection ratio (habitat use relative to its availability). For each individual we then evaluated whether the GPS-based habitat suitability measures were in agreement with the IUCN data. To that end, we calculated the probability that the ranking of empirical habitat suitability measures was in agreement with IUCN's classification into suitable, marginal and unsuitable habitat types. Results IUCN habitat suitability data were in accordance with the GPS data (> 95% probability of agreement) for 33 out of 49 species based on proportional habitat use estimates and for 25 out of 49 species based on selection ratios. In addition, 37 and 34 species had a > 50% probability of agreement based on proportional habitat use and selection ratios, respectively. Main conclusions We show how GPS-tracking data can be used to evaluate IUCN habitat suitability data. Our findings indicate that for the majority of species included in this study, it is appropriate to use IUCN habitat suitability data in macroecological studies. Furthermore, we show that GPS-tracking data can be used to identify and prioritize species and habitat types for re-evaluation of IUCN habitat suitability data
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