346 research outputs found
Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073
The physical processes occurring within the inner few astronomical units of
proto-planetary disks surrounding Herbig Ae stars are crucial to setting the
environment in which the outer planet-forming disk evolves and put critical
constraints on the processes of accretion and planet migration. We present the
most complete published sample of high angular resolution H- and K-band
observations of the stars HD 163296 and HD 190073, including 30 previously
unpublished nights of observations of the former and 45 nights of the latter
with the CHARA long-baseline interferometer, in addition to archival VLTI data.
We confirm previous observations suggesting significant near-infrared emission
originates within the putative dust evaporation front of HD 163296 and show
this is the case for HD 190073 as well. The H- and K-band sizes are the same
within for HD 163296 and within for HD 190073. The
radial surface brightness profiles for both disks are remarkably Gaussian-like
with little or no sign of the sharp edge expected for a dust evaporation front.
Coupled with spectral energy distribution analysis, our direct measurements of
the stellar flux component at H and K bands suggest that HD 190073 is much
younger (<400 kyr) and more massive (~5.6 M) than previously thought,
mainly as a consequence of the new Gaia distance (891 pc).Comment: 19 pages, 6 figure
Modelling LAI at a regional scale with ISBA-A-gs: comparison with satellite-derived LAI over southwestern France
International audienceA CO2-responsive land surface model (the ISBAA- gs model of MÂŽetÂŽeo-France) is used to simulate photosynthesis and Leaf Area Index (LAI) in southwestern France for a 3-year period (2001â2003). A domain of about 170 000 km2 is covered at a spatial resolution of 8 km. The capability of ISBA-A-gs to reproduce the seasonal and the interannual variability of LAI at a regional scale, is assessed with satellite-derived LAI products. One originates from the CYCLOPES programme using SPOT/VEGETATION data, and two products are based on MODIS data. The comparison reveals discrepancies between the satellite LAI estimates and between satellite and simulated LAI values, both in their intensity and in the timing of the leaf onset. The model simulates higher LAI values for the C3 crops than the satellite observations, which may be due to a saturation effect within the satellite signal or to uncertainties in model parameters. The simulated leaf onset presents a significant delay for C3 crops and mountainous grasslands. In-situ observations at a mid-altitude grassland site show that the generic temperature response of photosynthesis used in the model is not appropriate for plants adapted to the cold climatic conditions of the mountainous areas. This study demonstrates the potential of LAI remote sensing products for identifying and locating models' shortcomings at a regional scale
Goodness-of-Fit tests with Dependent Observations
We revisit the Kolmogorov-Smirnov and Cram\'er-von Mises goodness-of-fit
(GoF) tests and propose a generalisation to identically distributed, but
dependent univariate random variables. We show that the dependence leads to a
reduction of the "effective" number of independent observations. The
generalised GoF tests are not distribution-free but rather depend on all the
lagged bivariate copulas. These objects, that we call "self-copulas", encode
all the non-linear temporal dependences. We introduce a specific, log-normal
model for these self-copulas, for which a number of analytical results are
derived. An application to financial time series is provided. As is well known,
the dependence is to be long-ranged in this case, a finding that we confirm
using self-copulas. As a consequence, the acceptance rates for GoF tests are
substantially higher than if the returns were iid random variables.Comment: 26 page
Monitoring of water and carbon fluxes using a land data assimilation system: a case study for southwestern France
International audienceA Land Data Assimilation System (LDAS) able to ingest surface soil moisture (SSM) and Leaf Area Index (LAI) observations is tested at local scale to increase prediction accuracy for water and carbon fluxes. The ISBAA-gs Land Surface Model (LSM) is used together with LAI and the soil water content observations of a grassland at the SMOSREX experimental site in southwestern France for a seven-year period (2001-2007). Three configurations corresponding to contrasted model errors are considered: (1) best case (BC) simulation with locally observed atmospheric variables and model parameters, and locally observed SSM and LAI used in the assimilation, (2) same as (1) but with the precipitation forcing set to zero, (3) real case (RC)simulation with atmospheric variables and model parameters derived from regional atmospheric analyses and from climatological soil and vegetation properties, respectively. In configuration (3) two SSM time series are considered: the observed SSM using Thetaprobes, and SSM derived from the LEWIS L-band radiometer located 15m above the ground. Performance of the LDAS is examined in the three configurations described above with either one variable (either SSM or LAI) or two variables (both SSM and LAI) assimilated. The joint assimilation of SSM and LAI has a positive impact on the carbon, water, and heat fluxes. It represents a greater impact than assimilating one variable (either LAI or SSM). Moreover, the LDAS is able to counterbalance large errors in the precipitation forcing given as input to the model
Prediction Models for Clinical Outcome After a Carotid Revascularization Procedure.
Background and Purpose- Prediction models may help physicians to stratify patients with high and low risk for periprocedural complications or long-term stroke risk after carotid artery stenting or carotid endarterectomy. We aimed to evaluate external performance of previously published prediction models for short- and long-term outcome after carotid revascularization in patients with symptomatic carotid artery stenosis. Methods- From a literature review, we selected all prediction models that used only readily available patient characteristics known before procedure initiation. Follow-up data from 2184 carotid artery stenting and 2261 carotid endarterectomy patients from 4 randomized trials (EVA-3S [Endarterectomy Versus Angioplasty in Patients With Symptomatic Severe Carotid Stenosis], SPACE [Stent-Protected Angioplasty Versus Carotid Endarterectomy], ICSS [International Carotid Stenting Study], and CREST [Carotid Revascularization Endarterectomy Versus Stenting Trial]) were used to validate 23 short-term outcome models to estimate stroke or death risk â€30 days after the procedure and the original outcome measure for which the model was developed. Additionally, we validated 7 long-term outcome models for the original outcome measure. Predictive performance of the models was assessed with C statistics and calibration plots. Results- Stroke or death â€30 days after the procedure occurred in 158 (7.2%) patients after carotid artery stenting and in 84 (3.7%) patients after carotid endarterectomy. Most models for short-term outcome after carotid artery stenting (n=4) or carotid endarterectomy (n=19) had poor discriminative performance (C statistics ranging from 0.49-0.64) and poor calibration with small absolute risk differences between the lowest and highest risk groups and overestimation of risk in the highest risk groups. Long-term outcome models (n=7) had a slightly better performance with C statistics ranging from 0.59 to 0.67 and reasonable calibration. Conclusions- Current models did not reliably predict outcome after carotid revascularization in a trial population of patients with symptomatic carotid stenosis. In particular, prediction of short-term outcome seemed to be difficult. Further external validation of existing prediction models or development of new prediction models is needed before such models can be used to support treatment decisions in individual patients
The brazilian Amaryllidaceae as a source of acetylcholinesterase inhibitory alkaloids
Nine Brazilian Amaryllidaceae species were studied for their alkaloid composition and acetylcholinesterase (AChE) inhibitory activity via GC-MS and a modified Ellman assay, respectively. A total of thirty-six alkaloids were identified in these plants, of which Hippeastrum papilio and H. glau-cescens exhibited the highest galanthamine content and the best IC50 values against AChE. Furthermore, Hippeastrum vittatum and Rhodophiala bifida also showed notable AChE inhibitory effects. X-ray crys-tallographic data for four galanthamine-type com-pounds revealed significant differences in the orientation of theN-methyl group, which are shown to be related to AChE inhibition
The nowcasting SAF products and services: recent improvements in the new SW packages PPS v2018 and GEO v2018 and future plans
PresentaciĂłn realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073
The physical processes occurring within the inner few astronomical units of protoplanetary disks surrounding Herbig Ae stars are crucial to setting the environment in which the outer planet-forming disk evolves and put critical constraints on the processes of accretion and planet migration. We present the most complete published sample of high angular resolution H- and K-band observations of the stars HD 163296 and HD 190073, including 30 previously unpublished nights of observations of the former and 45 nights of the latter with the CHARA long-baseline interferometer, in addition to archival VLTI data. We confirm previous observations suggesting that significant near-infrared emission originates within the putative dust evaporation front of HD 163296 and show that this is the case for HD 190073 as well. The H- and K-band sizes are the same within (3 ± 3)% for HD 163296 and within (6 ± 10)% for HD 190073. The radial surface brightness profiles for both disks are remarkably Gaussian-like with little or no sign of the sharp edge expected for a dust evaporation front. Coupled with spectral energy distribution analysis, our direct measurements of the stellar flux component at the H and K bands suggest that HD 190073 is much younger (<400 kyr) and more massive (~5.6 M â) than previously thought, mainly as a consequence of the new Gaia distance (891 pc)
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