79 research outputs found
Qualitative study in Loop Quantum Cosmology
This work contains a detailed qualitative analysis, in General Relativity and
in Loop Quantum Cosmology, of the dynamics in the associated phase space of a
scalar field minimally coupled with gravity, whose potential mimics the
dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with
the orbits (solutions) of the system, we will see that there are analytic ones,
which lead to the same dynamics as the perfect fluid, and our goal is to check
their stability, depending on the value of the EoS parameter, i.e., to show
whether the other orbits converge or diverge to these analytic solutions at
early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ
The weak-line T Tauri star V410Tau I. A multi-wavelength study of variability
We present the results of an intensive coordinated monitoring campaign in the
optical and X-ray wavelength ranges of the low-mass, pre-main sequence star
V410Tau carried out with the aim to study the relation between various
indicators for magnetic activity that probe emission from different atmospheric
layers: optical photometric star spot (rotation) cycle, chromospheric Halpha
emission, and coronal X-rays. Two X-ray pointings were carried out with the
Chandra satellite simultaneously with the optical observations, and centered
near the maximum and minimum levels of the optical lightcurve. A relation of
their different count levels to the rotation period of the dominating spot is
not confirmed by a third Chandra observation carried out some months later,
during another minimum of the 1.87d cycle. Similarly we find no indications for
a correlation of the Halpha emission with the spots' rotational phase. The
extraordinary stability of the largest spot is confirmed by long-term
photometric and radial velocity measurements. Joining our optical photometry
with previous data we provide a new estimate for the dominant periodicity of
V410Tau. This updated value removes systematic offsets of the time of minimum
observed in data taken over the last decade. Furthermore, the combination of
the new data with published measurements taken during the last decade allows us
to examine long-term changes in the mean light level of the photometry of
V410Tau. A variation on the timescale of 5.4yr is suggested. Assuming that this
behavior is truely cyclic V410Tau is the first pre-main sequence star on which
an activity cycle is detected.Comment: 16 pages, accepted for publication in A&
Patterns of care and dropout rates from outpatient mental healthcare in low-, middle- and high-income countries from the World Health Organization’s World Mental Health Survey Initiative
Background:There is a substantial proportion of patients who drop out of treatment beforethey receive minimally adequate care. They tend to have worse health outcomes than thosewho complete treatment. Our main goal is to describe the frequency and determinants ofdropout from treatment for mental disorders in low-, middle-, and high-income countries.Methods: Respondents from 13 low- or middle-income countries (N= 60 224) and 15 in high-income countries (N= 77 303) were screened for mental and substance use disorders. Cross-tabulations were used to examine the distribution of treatment and dropout rates for thosewho screened positive. The timing of dropout was examined using Kaplan–Meier curves. Predictors of dropout were examined with survival analysis using a logistic link function. Results: Dropout rates are high, both in high-income (30%) and low/middle-income (45%)countries. Dropout mostly occurs during the first two visits. It is higher in general medicalrather than in specialist settings (nearly 60%v.20% in lower income settings). It is also higherfor mild and moderate than for severe presentations. The lack of financial protection for men-tal health services is associated with overall increased dropout from care.Conclusions:Extending financial protection and coverage for mental disorders may reducedropout. Efficiency can be improved by managing the milder clinical presentations at theentry point to the mental health system, providing adequate training, support and specialistsupervision for non-specialists, and streamlining referral to psychiatrists for more severe casesPeer ReviewedPostprint (author's final draft
The CARMENES search for exoplanets around M dwarfs
Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets.
Aims: We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey.
Methods: The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained.
Results: We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online.
Conclusions: CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres
Spectroscopic confirmation of CEERS NIRCam-selected galaxies at
We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from
the Cosmic Evolution Early Release Science Survey (CEERS) NIRCam imaging with
photometric redshifts z_phot>8. We measure emission line redshifts of z=7.65
and 8.64 for two galaxies, and z=9.77(+0.37,-0.29) and 10.01(+0.14,-0.19) for
two others via the detection of continuum breaks consistent with Lyman-alpha
opacity from a mostly neutral intergalactic medium. The presence (absense) of
strong breaks (strong emission lines) give high confidence that these two
galaxies are at z>9.6, but the break-derived redshifts have large uncertainties
given the low spectral resolution and relatively low signal-to-noise of the
CEERS NIRSpec prism data. The two z~10 sources are relatively luminous
(M_UV<-20), with blue continua (-2.3<beta<-1.9) and low dust attenuation
(A_V=0.15(+0.3,-0.1)); and at least one of them has high stellar mass for a
galaxy at that redshift (log(M_*/M_sol)=9.3(+0.2,-0.3)). Considered together
with spectroscopic observations of other CEERS NIRCam-selected high-z galaxy
candidates in the literature, we find a high rate of redshift confirmation and
low rate of confirmed interlopers (8.3%). Ten out of 34 z>8 candidates with
CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of
emission lines in their spectra is consistent with redshifts z>9.6. We find
that z>8 photometric redshifts are generally in agreement (within
uncertainties) with the spectroscopic values. However, the photometric
redshifts tend to be slightly overestimated (average Delta(z)=0.50+/-0.12),
suggesting that current templates do not fully describe the spectra of very
high-z sources. Overall, our results solidifies photometric evidence for a high
space density of bright galaxies at z>8 compared to theoretical model
predictions, and further disfavors an accelerated decline in the integrated UV
luminosity density at z>8.Comment: Submitted to ApJL. 24 pages, 9 figures, 7 tables. File with Table 6
included in source .tar fil
Skipper-CCD Sensors for the Oscura Experiment: Requirements and Preliminary Tests
Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark
matter (DM) direct detection search that will reach unprecedented sensitivity
to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is
planning to operate at SNOLAB with 2070 m overburden, and aims to reach a
background goal of less than one event in each electron bin in the 2-10
electron ionization-signal region for the full 30 kg-year exposure, with a
radiation background rate of 0.01 dru. In order to achieve this goal, Oscura
must address each potential source of background events, including instrumental
backgrounds. In this work, we discuss the main instrumental background sources
and the strategy to control them, establishing a set of constraints on the
sensors' performance parameters. We present results from the tests of the first
fabricated Oscura prototype sensors, evaluate their performance in the context
of the established constraints and estimate the Oscura instrumental background
based on these results
Activation of PKR Causes Amyloid ß-Peptide Accumulation via De-Repression of BACE1 Expression
BACE1 is a key enzyme involved in the production of amyloid ß-peptide (Aß) in Alzheimer's disease (AD) brains. Normally, its expression is constitutively inhibited due to the presence of the 5′untranslated region (5′UTR) in the BACE1 promoter. BACE1 expression is activated by phosphorylation of the eukaryotic initiation factor (eIF)2-alpha, which reverses the inhibitory effect exerted by BACE1 5′UTR. There are four kinases associated with different types of stress that could phosphorylate eIF2-alpha. Here we focus on the double-stranded (ds) RNA-activated protein kinase (PKR). PKR is activated during viral infection, including that of herpes simplex virus type 1 (HSV1), a virus suggested to be implicated in the development of AD, acting when present in brains of carriers of the type 4 allele of the apolipoprotein E gene. HSV1 is a dsDNA virus but it has genes on both strands of the genome, and from these genes complementary RNA molecules are transcribed. These could activate BACE1 expression by the PKR pathway. Here we demonstrate in HSV1-infected neuroblastoma cells, and in peripheral nervous tissue from HSV1-infected mice, that HSV1 activates PKR. Cloning BACE1 5′UTR upstream of a luciferase (luc) gene confirmed its inhibitory effect, which can be prevented by salubrinal, an inhibitor of the eIF2-alpha phosphatase PP1c. Treatment with the dsRNA analog poly (I∶C) mimicked the stimulatory effect exerted by salubrinal over BACE1 translation in the 5′UTR-luc construct and increased Aß production in HEK-APPsw cells. Summarizing, our data suggest that PKR activated in brain by HSV1 could play an important role in the development of AD
CIBERER : Spanish national network for research on rare diseases: A highly productive collaborative initiative
Altres ajuts: Instituto de Salud Carlos III (ISCIII); Ministerio de Ciencia e Innovación.CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research
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