301 research outputs found
The calibration of the first Large-Sized Telescope of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) represents the next generation of very
high-energy gamma-ray observatory, which will provide broad coverage of gamma
rays from 20 GeV to 300 TeV with unprecedented sensitivity. CTA will employ
three different sizes of telescopes, and the Large-Sized Telescopes (LSTs) of
23-m diameter dish will provide the sensitivity in the lowest energies down to
20 GeV. The first LST prototype has been inaugurated in October 2018 at La
Palma (Canary Islands, Spain) and has entered the commissioning phase. The
camera of the LST consists of 265 PMT modules. Each module is equipped with
seven high-quantum-efficiency Photomultiplier Tubes (PMTs), a slow control
board, and a readout board. Ensuring high uniformity and precise
characterization of the camera is the key aspects leading to the best
performance and low systematic uncertainty of the LST cameras. Therefore, prior
to the installation on site, we performed a quality check of all PMT modules.
Moreover, the absolute calibration of light throughput is essential to
reconstruct the amount of light received by the telescope. The amount of light
is affected by the atmosphere, by the telescope optical system and camera, and
can be calibrated using the ring-shaped images produced by cosmic-ray muons. In
this contribution, we will show the results of off-site quality control of PMT
modules and on-site calibration using muon rings. We will also highlight the
status of the development of Silicon Photomultiplier modules that could be
considered as a replacement of PMT modules for further improvement of the
camera
Electrocatalytic CO2 conversion to C2 products: Catalysts design, market perspectives and techno-economic aspects
The energy crisis caused by the incessant growth in global energy demand joint to its associated greenhouse emissions motivates the urgent need to control and mitigate atmospheric CO2 levels. Leveraging CO2 as carbon pool to produce value-added products represents a cornerstone of the circular economy. Among the CO2 utilization strategies, electrochemical reduction of CO2 conversion to produce fuels and chemicals is booming due to its versatility and end-product flexibility. Herein most of the studies focused on C1 products although C2 and C2+ compounds are chemically and economically more appealing targets requiring advanced catalytic materials. Still, despite the complex pathways for C2+ products formation, their multiple and assorted applications have motivated the search of suitable electrocatalysts. In this review, we gather and analyse in a comprehensive manner the progress made regarding C2+ products considering not only the catalyst design and the electrochemistry features but also techno-economic aspects in order to envisage the most profitable scenarios. This state-of-the-art analysis showcases that electrochemical reduction of CO2 to C2 products will play a key role in the decarbonisation of the chemical industry paving the way towards a low-carbon future
Optimizing Jastrow factors for the transcorrelated method
We investigate the optimization of flexible tailored real-space Jastrow factors for use in the transcorrelated (TC) method in combination with highly accurate quantum chemistry methods, such as initiator full configuration interaction quantum Monte Carlo (FCIQMC). Jastrow factors obtained by minimizing the variance of the TC reference energy are found to yield better, more consistent results than those obtained by minimizing the variational energy. We compute all-electron atomization energies for the challenging first-row molecules C2, CN, N2, and O2 and find that the TC method yields chemically accurate results using only the cc-pVTZ basis set, roughly matching the accuracy of non-TC calculations with the much larger cc-pV5Z basis set. We also investigate an approximation in which pure three-body excitations are neglected from the TC-FCIQMC dynamics, saving storage and computational costs, and show that it affects relative energies negligibly. Our results demonstrate that the combination of tailored real-space Jastrow factors with the multi-configurational TC-FCIQMC method provides a route to obtaining chemical accuracy using modest basis sets, obviating the need for basis-set extrapolation and composite techniques
Experiencias de manejo adaptativo derivadas de la retroalimentaci\uf3n investigaci\uf3n-gesti\uf3n en los Pinsapares andaluces
Changes in Muscle Metabolism are Associated with Phenotypic Variability in Golden Retriever Muscular Dystrophy
Duchenne muscular dystrophy (DMD) is an X-chromosome-linked disorder and the most common monogenic disease in people. Affected boys are diagnosed at a young age, become non-ambulatory by their early teens, and succumb to cardiorespiratory failure by their thirties. Despite being a monogenic condition resulting from mutations in the DMD gene, affected boys have noteworthy phenotypic variability. Efforts have identified genetic modifiers that could modify disease progression and be pharmacologic targets. Dogs affected with golden retriever muscular dystrophy (GRMD) have absent dystrophin and demonstrate phenotypic variability at the functional, histopathological, and molecular level. Our laboratory is particularly interested in muscle metabolism changes in dystrophin-deficient muscle. We identified several metabolic alterations, including myofiber type switching from fast (type II) to slow (type I), reduced glycolytic enzyme expression, reduced and morphologically abnormal mitochondria, and differential AMP-kinase phosphorylation (activation) between hypertrophied and wasted muscle. We hypothesize that muscle metabolism changes are, in part, responsible for phenotypic variability in GRMD. Pharmacological therapies aimed at modulating muscle metabolism can be tested in GRMD dogs for efficacy
Scientific Opinion on the safety and efficacy of Urea for ruminants
Urea supplementation to feed for ruminants provides non-protein nitrogen for microbial protein synthesis in the rumen and thus in part replaces other dietary protein sources. Urea supplementation of feed for ruminants at doses up to 1 % of complete feed DM (corresponding to 0.3 g/kg bw/day) is considered safe when given to animals with a well adapted ruminal microbiota and fed diets rich in easily digestible carbohydrates. Based on the metabolic fate of urea in ruminants, the use of urea in ruminant nutrition does not raise any concern for consumers\u2019 safety. Urea is considered to be non irritant to skin and eyes and its topical use suggests that it is not a dermal sensitiser. The risk of exposure by inhalation would be low. The substitution of protein by urea in well balanced feed for ruminants would not result in an increased environmental nitrogen load. Urea is an effective source of non-protein nitrogen substituting for dietary protein in ruminants
VALES VI: ISM enrichment in star-forming galaxies up to z0.2 using CO(1-0), CO(1-0) and CO(1-0) line luminosity ratios
We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations
towards 27 low-redshift () star-forming galaxies taken from the
Valpara\'iso ALMA/APEX Line Emission Survey (VALES). We perform stacking
analyses of the CO(), CO() and CO()
emission lines to explore the (CO())/(CO()))
(hereafter (CO)/(CO)) and
(CO())/(CO()) (hereafter
(CO)/(CO) line luminosity ratio dependence as a function
of different global galaxy parameters related to the star formation activity.
The sample has far-IR luminosities L and stellar
masses of M corresponding to typical star-forming and
starburst galaxies at these redshifts. On average we find a
(CO)/(CO) line luminosity ratio value of 16.12.5.
Galaxies with evidences of possible merging activity tend to show higher
(CO)/(CO) ratios by a factor of two, while variations of
this order are also found in galaxy samples with higher star formation rates or
star formation efficiencies. We also find an average
(CO)/(CO) line luminosity ratio of 2.50.6, which is
in good agreement with those previously reported for starburst galaxies. We
find that galaxy samples with high , SFR and SFE show low
(CO)/(CO) line luminosity ratios with high
(CO)/(CO) line luminosity ratios, suggesting that these
trends are produced by selective enrichment of massive stars in young
starbursts.Comment: 16 pages, 10 figures to be published in MNRA
ALMA Lensing Cluster Survey: A strongly lensed multiply imaged dusty system at z ≥ 6
We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift z = 6.07 viewed through the cluster MACSJ0600.1–2008 (z = 0.46). A ≃ 4σ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large programme, and the redshift is secured via [C II] 158 μm emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy’s spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification μ ≳ 30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionization. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of 2.9-2.3+115
7 109 and 4.8-3.4+45
7 106 M☉, respectively, a star formation rate of 9.7-6.6+220 M☉ yr−1, an intrinsic size of 0.54-0.14+026 kpc, and a luminosity-weighted age of 200 \ub1 100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation
The Gas and Stellar Content of a Metal-poor Galaxy at z = 8.496 as Revealed by JWST and ALMA
We present a joint analysis of the galaxy S04590 at z = 8.496 based on NIRSpec, NIRCam, and NIRISS observations obtained as part of the Early Release Observations program of the James Webb Space Telescope (JWST) and the far-infrared [C ii] 158 μm emission line detected by dedicated Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the physical properties of S04590 from modeling of the spectral energy distribution (SED) and through the redshifted optical nebular emission lines detected with JWST/NIRSpec. The best-fit SED model reveals a low-mass (M ⋆ = 107.2-108 M ⊙) galaxy with a low oxygen abundance of 12 + log ( O / H ) = 7.16 − 0.12 + 0.10 derived from the strong nebular and auroral emission lines. Assuming that [C ii] effectively traces the interstellar medium, we estimate the total gas mass of the galaxy to be M gas = (8.0 \ub1 4.0)
7 108 M ⊙ based on the luminosity and spatial extent of [C ii]. This yields an exceptionally high gas fraction, f gas = M gas/(M gas + M ⋆) ≳ 90%, though one still consistent with the range expected for low metallicity. We further derive the metal mass of the galaxy based on the gas mass and gas-phase metallicity, which we find to be consistent with the expected metal production from Type II supernovae. Finally, we make the first constraints on the dust-to-gas (DTG) and dust-to-metal (DTM) ratios of galaxies in the epoch of reionization at z ≳ 6, showing overall low mass ratios of logDTG < −3.8 and logDTM < −0.5, though they are consistent with established scaling relations and in particular with those of the local metal-poor galaxy I Zwicky 18. Our analysis highlights the synergy between ALMA and JWST in characterizing the gas, metal, and stellar content of the first generation of galaxies
A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
A key legacy of the recently launched TESS mission will be to provide the
astronomical community with many of the best transiting exoplanet targets for
atmospheric characterization. However, time is of the essence to take full
advantage of this opportunity. JWST, although delayed, will still complete its
nominal five year mission on a timeline that motivates rapid identification,
confirmation, and mass measurement of the top atmospheric characterization
targets from TESS. Beyond JWST, future dedicated missions for atmospheric
studies such as ARIEL require the discovery and confirmation of several hundred
additional sub-Jovian size planets (R_p < 10 R_Earth) orbiting bright stars,
beyond those known today, to ensure a successful statistical census of
exoplanet atmospheres. Ground-based ELTs will also contribute to surveying the
atmospheres of the transiting planets discovered by TESS. Here we present a set
of two straightforward analytic metrics, quantifying the expected
signal-to-noise in transmission and thermal emission spectroscopy for a given
planet, that will allow the top atmospheric characterization targets to be
readily identified among the TESS planet candidates. Targets that meet our
proposed threshold values for these metrics would be encouraged for rapid
follow-up and confirmation via radial velocity mass measurements. Based on the
catalog of simulated TESS detections by Sullivan et al. (2015), we determine
appropriate cutoff values of the metrics, such that the TESS mission will
ultimately yield a sample of high-quality atmospheric
characterization targets across a range of planet size bins, extending down to
Earth-size, potentially habitable worlds.Comment: accepted to PAS
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