1,845 research outputs found
Type II supernovae from the Carnegie Supernova Project-I. II. Physical parameter distributions from hydrodynamical modelling
Linking supernovae to their progenitors is a powerful method for furthering
our understanding of the physical origin of their observed differences, while
at the same time testing stellar evolution theory. In this second study of a
series of three papers where we characterise SNe II to understand their
diversity, we derive progenitor properties (initial and ejecta masses, and
radius), explosion energy, Ni mass, and its degree of mixing within the
ejecta for a large sample of SNe II. This dataset was obtained by the Carnegie
Supernova Project-I and is characterised by a high cadence of their optical and
NIR light curves and optical spectra that were homogeneously observed and
processed. A large grid of hydrodynamical models and a fitting procedure based
on MCMC methods were used to fit the bolometric light curve and the evolution
of the photospheric velocity of 53 SNe II. We infer ejecta masses between 7.9
and 14.8 , explosion energies between 0.15 and 1.40 foe, and
Ni masses between 0.006 and 0.069 . We define a subset of
24~SNe (the `gold sample') with well-sampled bolometric light curves and
expansion velocities for which we consider the results more robust. Most SNe~II
in the gold sample (88%) are found with ejecta masses in the range of
8-10 , coming from low zero-age main-sequence masses (9-12
). The modelling of the initial-mass distribution of the gold sample
gives an upper mass limit of 21.3 and a much
steeper distribution than that for a Salpeter massive-star IMF. This IMF
incompatibility is due to the large number of low-mass progenitors found --
when assuming standard stellar evolution. This may imply that high-mass
progenitors lose more mass during their lives than predicted. However, a deeper
analysis of all stellar evolution assumptions is required to test this
hypothesis.Comment: Accepted for publication in Astronomy & Astrophysic
Type II supernovae from the Carnegie Supernova Project-I. I. Bolometric light curves of 74 SNe II using uBgVriYJH photometry
The present study is the first of a series of three papers where we
characterise the type II supernovae (SNe~II) from the Carnegie Supernova
Project-I to understand their diversity in terms of progenitor and explosion
properties. In this first paper, we present bolometric light curves of 74
SNe~II. We outline our methodology to calculate the bolometric luminosity,
which consists of the integration of the observed fluxes in numerous
photometric bands () and black-body (BB) extrapolations to account
for the unobserved flux at shorter and longer wavelengths. BB fits were
performed using all available broadband data except when line blanketing
effects appeared. Photometric bands bluer than that are affected by line
blanketing were removed from the fit, which makes near-infrared (NIR)
observations highly important to estimate reliable BB extrapolations to the
infrared. BB fits without NIR data produce notably different bolometric light
curves, and therefore different estimates of SN~II progenitor and explosion
properties when data are modelled. We present two methods to address the
absence of NIR observations: (a) colour-colour relationships from which NIR
magnitudes can be estimated using optical colours, and (b) new prescriptions
for bolometric corrections as a function of observed SN~II colours. Using our
74 SN~II bolometric light curves, we provide a full characterisation of their
properties based on several observed parameters. We measured magnitudes at
different epochs, as well as durations and decline rates of different phases of
the evolution. An analysis of the light-curve parameter distributions was
performed, finding a wide range and a continuous sequence of observed
parameters which is consistent with previous analyses using optical light
curves.Comment: Accepted for publication in A&
Type II supernovae from the Carnegie Supernova Project-I: I. Bolometric light curves of 74 SNe II using uBgVriYJH photometry
The present study is the first of a series of three papers where we characterise the type II supernovae (SNe II) from the Carnegie Supernova Project-I to understand their diversity in terms of progenitor and explosion properties. In this first paper, we present bolometric light curves of 74 SNe II. We outline our methodology to calculate the bolometric luminosity, which consists of the integration of the observed fluxes in numerous photometric bands (uBgVriYJH) and black-body (BB) extrapolations to account for the unobserved flux at shorter and longer wavelengths. BB fits were performed using all available broadband data except when line blanketing effects appeared. Photometric bands bluer than r that are affected by line blanketing were removed from the fit, which makes near-infrared (NIR) observations highly important to estimate reliable BB extrapolations to the infrared. BB fits without NIR data produce notably different bolometric light curves, and therefore different estimates of SN II progenitor and explosion properties when data are modelled. We present two methods to address the absence of NIR observations: (a) colour-colour relationships from which NIR magnitudes can be estimated using optical colours, and (b) new prescriptions for bolometric corrections as a function of observed SN II colours. Using our 74 SN II bolometric light curves, we provide a full characterisation of their properties based on several observed parameters. We measured magnitudes at different epochs, as well as durations and decline rates of different phases of the evolution. An analysis of the light-curve parameter distributions was performed, finding a wide range and a continuous sequence of observed parameters which is consistent with previous analyses using optical light curves.The work of the Carnegie Supernova Project was supported by the National Science Foundation under grants AST-0306969, AST-0607438, AST-1008343, AST-1613426, AST-1613472, and AST-1613455. L. M. acknowledges support from a CONICET fellowship. L. M. and M. O. acknowledge support from UNRN PI2018 40B885 grant. M. H. acknowledges support from the Hagler Institute of Advanced Study at Texas A&M University. S. G. G. acknowledges support by FCT under Project CRISP PTDC/FIS-AST-31546/2017 and Project No. UIDB/00099/2020. M. S. is supported by grants from the VILLUM FONDEN (grant number 28021) and the Independent Research Fund Denmark (IRFD; 8021-00170B). F. F. acknowledges support from the National Agency for Research and Development (ANID) grants: BASAL Center of Mathematical Modelling AFB-170001, Ministry of Economy, Development, and Tourismâs Millennium Science Initiative through grant IC12009, awarded to the Millennium Institute of Astrophysics, and FONDECYT Regular #1200710. L. G. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 RamĂłn y Cajal program RYC2019-027683 and from the Spanish MICIU project PID2020-115253GA-I00. P.H. acknowledges the support by National Science Foundation (NSF) grant AST-1715133
Innovative downhole geophysical methods for high frequency seawater intrusion dynamics monitoring
The detailed characterization of salt water intrusion is a key to understand both submarine groundwater discharge and
manage often intensively exploited groundwater resources in coastal areas. With the objective to study the response of
a coastal aquifer to a series of boundary conditions, a new experimental site has been developed through a clastic aquifer
located north of Barcelona (Spain). This hectometer scale site is located 50 m from the seashore and equipped with
17 nearby shallow holes, with depths ranging from 15 to 28 m.
In order to study not only the sedimentary structure but also the response of the aquifer to a set of natural boundary
conditions, downhole geophysical measurements have been deployed over the past 3 years in an innovative manner,
either in a time-lapse or stationary manner. The downhole measurements are complicated by the unconsolidated nature
of the sediment, obliging to perform all measurements through PVC. Also, the granitic nature of the sediment prevents
clays identification from a direct use of gamma ray profiles. For this, constituting minerals (quartz, albite, feldspar,
microcline, illite) were identified from X-ray diffraction on cores, and spectral gamma logs used to determine the illite
fractions from Th/K ratios.
In time lapse, high frequency electrical resistivity induction measurements show that preferential flow paths through the
aquifer can be identified in a fast and reliable manner. Also, changes in depth of the fresh to salt water interface (FSWI)
are precisely described, either in response to marine tides, or to a short but intense mediterranean rain event. Changes
on the order of than 1.70 m are obtain in less than a day of heavy rain. Overnight as well as seasonal changes such as
months of dryness are also illustrated due to the variability of pore fluid salinity and temperature, even over short
periods of time such as tens of minutes.
In stationary mode, the spectral natural gamma sensor located in front of the FSWI fluctuation zones records changes
in front of all radioactive peaks (from K, Tl, Bi, but also Ra with Rn) during intense rain events such as that of October
18-19, 2017. This places constraints on Ra and Rn production rate during such an event, leading to trace fresh water
outpour into the sea.Peer reviewe
Hydrodynamics and hydrogeochemical changes in the mixing zone of a coastal aquifer during a heavy rain event
The coastal aquifers are the place where meet fresh water and seawater. This confluence
between both of them is called mixing zone which is in equilibrium due to the different
density of the two masses and where various biogeochemical reactions takes place. We
know that this equilibrium can be canceled during an important recharge event. Within the
aquifer, such events displace the mixing zone over a short time period.
This study is aims at the identification and description at high frequency of spatial and
temporal response of the mixing zone and its impact on geochemical processes during one
such fast water inflow event.
We choose the experimental site of Argentona as the place of this study. Located in the
northeast of Spain this site is subjected to a Mediterranean climate characterized by heavy
rainfall amount recorded during Fall and early Spring period, concentrated during a few
hours. Furthermore, this site is located on an alluvial aquifer, equipped with 16 shallow
boreholes over a 100 m scale (Fig.1). The geological cross section presented in Fig.2 shows
that the aquifer is multilayered and we suspect an effect of a clay/silt layer located at
around 12 m.This work was funded by the projects CGL2013-48869-C2-1 y
CGL2013-48869-C2-2-R of the Spanish Government.
We would like to thank SIMMAR (Serveis Integrals de
Manteniment del Maresme) and the Consell
Comarcal del Maresme in the construction of the research site.Peer reviewe
SARS-CoV-2 infection induces DNA damage, through CHK1 degradation and impaired 53BP1 recruitment, and cellular senescence
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the RNA virus responsible for the coronavirus disease 2019 (COVID-19) pandemic. Although SARS-CoV-2 was reported to alter several cellular pathways, its impact on DNA integrity and the mechanisms involved remain unknown. Here we show that SARS-CoV-2 causes DNA damage and elicits an altered DNA damage response. Mechanistically, SARS-CoV-2 proteins ORF6 and NSP13 cause degradation of the DNA damage response kinase CHK1 through proteasome and autophagy, respectively. CHK1 loss leads to deoxynucleoside triphosphate (dNTP) shortage, causing impaired S-phase progression, DNA damage, pro-inflammatory pathways activation and cellular senescence. Supplementation of deoxynucleosides reduces that. Furthermore, SARS-CoV-2 N-protein impairs 53BP1 focal recruitment by interfering with damage-induced long non-coding RNAs, thus reducing DNA repair. Key observations are recapitulated in SARS-CoV-2-infected mice and patients with COVID-19. We propose that SARS-CoV-2, by boosting ribonucleoside triphosphate levels to promote its replication at the expense of dNTPs and by hijacking damage-induced long non-coding RNAsâ biology, threatens genome integrity and causes altered DNA damage response activation, induction of inflammation and cellular senescence
BMC Geriatr
BACKGROUND: With the global population aging and life expectancy increasing, dementia has turned a priority in the health care system. In Chile, dementia is one of the most important causes of disability in the elderly and the most rapidly growing cause of death in the last 20 years. Cognitive complaint is considered a predictor for cognitive and functional decline, incident mild cognitive impairment, and incident dementia. The GERO cohort is the Chilean core clinical project of the Geroscience Center for Brain Health and Metabolism (GERO). The objective of the GERO cohort is to analyze the rate of functional decline and progression to clinical dementia and their associated risk factors in a community-dwelling elderly with subjective cognitive complaint, through a population-based study. We also aim to undertake clinical research on brain ageing and dementia disorders, to create data and biobanks with the appropriate infrastructure to conduct other studies and facilitate to the national and international scientific community access to the data and samples for research. METHODS: The GERO cohort aims the recruitment of 300 elderly subjects (> 70 years) from Santiago (Chile), following them up for at least 3 years. Eligible people are adults not diagnosed with dementia with subjective cognitive complaint, which are reported either by the participant, a proxy or both. Participants are identified through a household census. The protocol for evaluation is based on a multidimensional approach including socio-demographic, biomedical, psychosocial, neuropsychological, neuropsychiatric and motor assessments. Neuroimaging, blood and stool samples are also obtained. This multidimensional evaluation is carried out in a baseline and 2 follow-ups assessments, at 18 and 36 months. In addition, in months 6, 12, 24, and 30, a telephone interview is performed in order to keep contact with the participants and to assess general well-being. DISCUSSION: Our work will allow us to determine multidimensional risks factors associated with functional decline and conversion to dementia in elderly with subjective cognitive complain. The aim of our GERO group is to establish the capacity to foster cutting edge and multidisciplinary research on aging in Chile including basic and clinical research. TRIAL REGISTRATION: NCT04265482 in ClinicalTrials.gov. Registration Date: February 11, 2020. Retrospectively Registered
Standalone vertex ïŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H âÎł Îł, H â Z Zâ â4l and H âW Wâ âlÎœlÎœ. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of âs = 7 TeV and âs = 8 TeV, corresponding to an integrated luminosity of about 25 fbâ1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined ïŹts probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson
Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV
A measurement of the production cross-section for top quark pairs(\ttbar)
in collisions at \sqrt{s}=7 \TeV is presented using data recorded with
the ATLAS detector at the Large Hadron Collider. Events are selected in two
different topologies: single lepton (electron or muon ) with large
missing transverse energy and at least four jets, and dilepton (,
or ) with large missing transverse energy and at least two jets. In a
data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton
topology and 9 events in the dilepton topology. The corresponding expected
backgrounds from non-\ttbar Standard Model processes are estimated using
data-driven methods and determined to be events and events, respectively. The kinematic properties of the selected events are
consistent with SM \ttbar production. The inclusive top quark pair production
cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where
the first uncertainty is statistical and the second systematic. The measurement
agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables,
CERN-PH number and final journal adde
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