299 research outputs found
Estimating magnetic filling factors from simultaneous spectroscopy and photometry : disentangling spots, plage, and network
A.C.C. acknowledges support from the Science and Technology Facilities Council (STFC) consolidated grant number ST/R000824/1.State-of-the-art radial velocity (RV) exoplanet searches are limited by the effects of stellar magnetic activity. Magnetically active spots, plage, and network regions each have different impacts on the observed spectral lines and therefore on the apparent stellar RV. Differentiating the relative coverage, or filling factors, of these active regions is thus necessary to differentiate between activity-driven RV signatures and Doppler shifts due to planetary orbits. In this work, we develop a technique to estimate feature-specific magnetic filling factors on stellar targets using only spectroscopic and photometric observations. We demonstrate linear and neural network implementations of our technique using observations from the solar telescope at HARPS-N, the HK Project at the Mt. Wilson Observatory, and the Total Irradiance Monitor onboard SORCE. We then compare the results of each technique to direct observations by the Solar Dynamics Observatory. Both implementations yield filling factor estimates that are highly correlated with the observed values. Modeling the solar RVs using these filling factors reproduces the expected contributions of the suppression of convective blueshift and rotational imbalance due to brightness inhomogeneities. Both implementations of this technique reduce the overall activity-driven rms RVs from 1.64 to 1.02 m s(-1), corresponding to a 1.28 m s(-1) reduction in the rms variation. The technique provides an additional 0.41 m s(-1) reduction in the rms variation compared to traditional activity indicators.PostprintPeer reviewe
An 11 Earth-mass, Long-period Sub-Neptune Orbiting a Sun-like Star
Although several thousands of exoplanets have now been detected and
characterized, observational biases have led to a paucity of long-period,
low-mass exoplanets with measured masses and a corresponding lag in our
understanding of such planets. In this paper we report the mass estimation and
characterization of the long-period exoplanet Kepler-538b. This planet orbits a
Sun-like star (V = 11.27) with M_* = 0.892 +/- (0.051, 0.035) M_sun and R_* =
0.8717 +/- (0.0064, 0.0061) R_sun. Kepler-538b is a 2.215 +/- (0.040, 0.034)
R_earth sub-Neptune with a period of P = 81.73778 +/- 0.00013 d. It is the only
known planet in the system. We collected radial velocity (RV) observations with
HIRES on Keck I and HARPS-N on the TNG. We characterized stellar activity by a
Gaussian process with a quasi-periodic kernel applied to our RV and cross
correlation function full width at half maximum (FWHM) observations. By
simultaneously modeling Kepler photometry, RV, and FWHM observations, we found
a semi-amplitude of K = 1.68 +/- (0.39, 0.38) m s^-1 and a planet mass of M_p =
10.6 +/- (2.5, 2.4) M_earth. Kepler-538b is the smallest planet beyond P = 50 d
with an RV mass measurement. The planet likely consists of a significant
fraction of ices (dominated by water ice), in addition to rocks/metals, and a
small amount of gas. Sophisticated modeling techniques such as those used in
this paper, combined with future spectrographs with ultra high-precision and
stability will be vital for yielding more mass measurements in this poorly
understood exoplanet regime. This in turn will improve our understanding of the
relationship between planet composition and insolation flux and how the rocky
to gaseous transition depends on planetary equilibrium temperature
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Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar Radial Velocities
Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone around Sun-like stars are limited by the effects of stellar variability on the host star. In particular, suppression of convective blueshift and brightness inhomogeneities due to photospheric faculae/plage and starspots are the dominant contribution to the variability of such stellar RVs. Gaussian process (GP) regression is a powerful tool for statistically modeling these quasi-periodic variations. We investigate the limits of this technique using 800 days of RVs from the solar telescope on the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph. These data provide a well-sampled time series of stellar RV variations. Into this data set, we inject Keplerian signals with periods between 100 and 500 days and amplitudes between 0.6 and 2.4 ms−1. We use GP regression to fit the resulting RVs and determine the statistical significance of recovered periods and amplitudes. We then generate synthetic RVs with the same covariance properties as the solar data to determine a lower bound on the observational baseline necessary to detect low-mass planets in Venus-like orbits around a Sun-like star. Our simulations show that discovering planets with a larger mass (∼0.5 ms−1) using current-generation spectrographs and GP regression will require more than 12 yr of densely sampled RV observations. Furthermore, even with a perfect model of stellar variability, discovering a true exo-Venus (∼0.1 m s −1 ) with current instruments would take over 15 yr. Therefore, next-generation spectrographs and better models of stellar variability are required for detection of such planets
Essential oils as antibacterial agents against food-borne pathogens: are they really as useful as they are claimed to be ?
Original articleMost studies evaluating the use of essential oils
(EO) as antibacterial agents focus mainly on minimal
inhibitory concentrations (MIC) rather than minimal bactericidal
concentrations (MBC). In this work, we compared
MICs and MBCs of EO from condiment plants commonly
used in Mediterranean Europe, namely Origanum vulgare,
Salvia lavandulaefolia, Salvia officinalis, Salvia sclarea
and Rosmarinus officinalis, aiming to evaluate their
application as disinfecting agents in minimally processed
produce. Outbreaks-related pathogens such as Listeria
monocytogenes, Pseudomonas aeruginosa and Yarrowia
lipolytica were used. Results showed that all EO were able
to reduce bacterial growth in all bacterial strains tested,
particularly O. vulgare. However, fewer EO exhibited
bactericidal activities, and were only effective against one
or two bacterial strains, hence eliminating the possibility to
use them as broad range disinfectants. Furthermore, the
necessary concentrations were too high for food application.
Hence, our work suggests the need to evaluate MBC
rather than MIC and questions EO usefulness in controlling
undesired microorganisms. Overall, and despite the large volume of data published on EO, results obtained were not
very encouraging for a realistic application on produce and
question the viability of EOs as disinfecting agents in foodinfo:eu-repo/semantics/publishedVersio
Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar Radial Velocities
Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone
around Sun-like stars are limited by the effects of stellar variability on the
host star. In particular, suppression of convective blueshift and brightness
inhomogeneities due to photospheric faculae/plage and starspots are the
dominant contribution to the variability of such stellar RVs. Gaussian process
(GP) regression is a powerful tool for statistically modeling these
quasi-periodic variations. We investigate the limits of this technique using
800 days of RVs from the solar telescope on the High Accuracy Radial velocity
Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph. These data
provide a well-sampled time series of stellar RV variations. Into this data
set, we inject Keplerian signals with periods between 100 and 500 days and
amplitudes between 0.6 and 2.4 m s. We use GP regression to fit the
resulting RVs and determine the statistical significance of recovered periods
and amplitudes. We then generate synthetic RVs with the same covariance
properties as the solar data to determine a lower bound on the observational
baseline necessary to detect low-mass planets in Venus-like orbits around a
Sun-like star. Our simulations show that discovering planets with a larger mass
( 0.5 m s) using current-generation spectrographs and GP
regression will require more than 12 yr of densely sampled RV observations.
Furthermore, even with a perfect model of stellar variability, discovering a
true exo-Venus ( 0.1 m s) with current instruments would take over
15 yr. Therefore, next-generation spectrographs and better models of stellar
variability are required for detection of such planets
Genome of the Avirulent Human-Infective Trypanosome—Trypanosoma rangeli
Background: Trypanosoma rangeli is a hemoflagellate protozoan parasite infecting humans and other wild and domestic mammals across Central and South America. It does not cause human disease, but it can be mistaken for the etiologic agent of Chagas disease, Trypanosoma cruzi. We have sequenced the T. rangeli genome to provide new tools for elucidating the distinct and intriguing biology of this species and the key pathways related to interaction with its arthropod and mammalian hosts. Methodology/Principal Findings: The T. rangeli haploid genome is ,24 Mb in length, and is the smallest and least repetitive trypanosomatid genome sequenced thus far. This parasite genome has shorter subtelomeric sequences compared to those of T. cruzi and T. brucei; displays intraspecific karyotype variability and lacks minichromosomes. Of the predicted 7,613 protein coding sequences, functional annotations could be determined for 2,415, while 5,043 are hypothetical proteins, some with evidence of protein expression. 7,101 genes (93%) are shared with other trypanosomatids that infect humans. An ortholog of the dcl2 gene involved in the T. brucei RNAi pathway was found in T. rangeli, but the RNAi machinery is non-functional since the other genes in this pathway are pseudogenized. T. rangeli is highly susceptible to oxidative stress, a phenotype that may be explained by a smaller number of anti-oxidant defense enzymes and heatshock proteins. Conclusions/Significance: Phylogenetic comparison of nuclear and mitochondrial genes indicates that T. rangeli and T. cruzi are equidistant from T. brucei. In addition to revealing new aspects of trypanosome co-evolution within the vertebrate and invertebrate hosts, comparative genomic analysis with pathogenic trypanosomatids provides valuable new information that can be further explored with the aim of developing better diagnostic tools and/or therapeutic targets
Educational intervention to improve physician reporting of adverse drug reactions (ADRs) in a primary care setting in complementary and alternative medicine
<p>Abstract</p> <p>Background</p> <p>Recent studies have shown that adverse drug reactions (ADRs) are underreported. This may be particularly true of ADRs associated with complementary and alternative medicine (CAM). Data on CAM-related ADRs, however, are sparse.</p> <p>Objective was to evaluate the impact of an educational intervention and monitoring programme designed to improve physician reporting of ADRs in a primary care setting.</p> <p>Methods</p> <p>A prospective multicentre study with 38 primary care practitioners specialized in CAM was conducted from January 2004 through June 2007. After 21 month all physicians received an educational intervention in terms of face-to-face training to assist them in classifying and reporting ADRs. The study centre monitored the quantity and quality of ADR reports and analysed the results.</p> <p>To measure changes in the ADR reporting rate, the median number of ADR reports and interquartile range (IQR) were calculated before and after the educational intervention. The pre-intervention and post-intervention quality of the reports was assessed in terms of changes in the completeness of data provided for obligatory items. Interrater reliability between the physicians and the study centre was calculated using Cohen's kappa with a 95% confidence interval (CI). We used Mann Whitney U-test for testing continuous data and chi-square test was used for categorical data. The level of statistical significance was set at <it>P </it>< 0.05.</p> <p>Results</p> <p>A total of 404 ADRs were reported during the complete study period. An initial 148% increase (<it>P </it>= 0.001) in the number of ADR reports was observed after the educational intervention. Compared to baseline the postinterventional number of ADR reportings was statistically significant higher (P < 0.005) through the first 16 months after the intervention but not significant in the last 4-month period (median: 8.00 (IQR [2.75; 8.75]; P = 0.605). The completeness of the ADR reports increased from 80.3% before to 90.7% after the intervention. The completeness of the item for classifying ADRs as serious or non-serious increased significantly (<it>P </it>< 0.001) after the educational intervention. The quality of ADR reports increased from kappa 0.15 (95% CI: 0.08; 0.29) before to 0.43 (95% CI: 0.23; 0.63) after the intervention.</p> <p>Conclusion</p> <p>The results of the present study demonstrate that an educational intervention can increase physician awareness of ADRs. Participating physicians were able to incorporate the knowledge they had gained from face-to-face training into their daily clinical practice. However, the effects of the intervention were temporary.</p
The effect of systematic pediatric care on neonatal mortality and hospitalizations of infants born with oral clefts
<p>Abstract</p> <p>Background</p> <p>Cleft lip and/or palate (CL/P) increase mortality and morbidity risks for affected infants especially in less developed countries. This study aimed at assessing the effects of systematic pediatric care on neonatal mortality and hospitalizations of infants with cleft lip and/or palate (CL/P) in South America.</p> <p>Methods</p> <p>The intervention group included live-born infants with isolated or associated CL/P in 47 hospitals between 2003 and 2005. The control group included live-born infants with CL/P between 2001 and 2002 in the same hospitals. The intervention group received systematic pediatric care between the 7<sup>th </sup>and 28<sup>th </sup>day of life. The primary outcomes were mortality between the 7<sup>th </sup>and 28<sup>th </sup>day of life and hospitalization days in this period among survivors adjusted for relevant baseline covariates.</p> <p>Results</p> <p>There were no significant mortality differences between the intervention and control groups. However, surviving infants with associated CL/P in the intervention group had fewer hospitalization days by about six days compared to the associated control group.</p> <p>Conclusions</p> <p>Early systematic pediatric care may significantly reduce neonatal hospitalizations of infants with CL/P and additional birth defects in South America. Given the large healthcare and financial burden of CL/P on affected families and the relatively low cost of systematic pediatric care, improving access to such care may be a cost-effective public policy intervention.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00097149">NCT00097149</a></p
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
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