1,766 research outputs found
Transmission spectroscopy of the inflated exo-Saturn HAT-P-19b
We observed the Saturn-mass and Jupiter-sized exoplanet HAT-P-19b to refine
its transit parameters and ephemeris as well as to shed first light on its
transmission spectrum. We monitored the host star over one year to quantify its
flux variability and to correct the transmission spectrum for a slope caused by
starspots. A transit of HAT-P-19b was observed spectroscopically with OSIRIS at
the Gran Telescopio Canarias in January 2012. The spectra of the target and the
comparison star covered the wavelength range from 5600 to 7600 AA. One
high-precision differential light curve was created by integrating the entire
spectral flux. This white-light curve was used to derive absolute transit
parameters. Furthermore, a set of light curves over wavelength was formed by a
flux integration in 41 wavelength channels of 50 AA width. We analyzed these
spectral light curves for chromatic variations of transit depth. The transit
fit of the combined white-light curve yields a refined value of the
planet-to-star radius ratio of 0.1390 pm 0.0012 and an inclination of 88.89 pm
0.32 degrees. After a re-analysis of published data, we refine the orbital
period to 4.0087844 pm 0.0000015 days. We obtain a flat transmission spectrum
without significant additional absorption at any wavelength or any slope.
However, our accuracy is not sufficient to significantly rule out the presence
of a pressure-broadened sodium feature. Our photometric monitoring campaign
allowed for an estimate of the stellar rotation period of 35.5 pm 2.5 days and
an improved age estimate of 5.5^+1.8_-1.3 Gyr by gyrochronology.Comment: 14 pages, 9 figures, Accepted for publication in A&
First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b
We present the characterization of two engineered diffusers mounted on the
2.5 meter Nordic Optical Telescope, located at Roque de Los Muchachos, Spain.
To assess the reliability and the efficiency of the diffusers, we carried out
several test observations of two photometric standard stars, along with
observations of one primary transit observation of TrES-3b in the red (R-band),
one of CoRoT-1b in the blue (B-band), and three secondary eclipses of WASP-12b
in V-band. The achieved photometric precision is in all cases within the
sub-millimagnitude level for exposures between 25 and 180 seconds. Along a
detailed analysis of the functionality of the diffusers, we add a new transit
depth measurement in the blue (B-band) to the already observed transmission
spectrum of CoRoT-1b, disfavouring a Rayleigh slope. We also report variability
of the eclipse depth of WASP-12b in the V-band. For the WASP-12b secondary
eclipses, we observe a secondary-depth deviation of about 5-sigma, and a
difference of 6-sigma and 2.5-sigma when compared to the values reported by
other authors in similar wavelength range determined from Hubble Space
Telescope data. We further speculate about the potential physical processes or
causes responsible for this observed variabilityComment: 11 pages, 9 figure
Broad-band spectrophotometry of the hot Jupiter HAT-P-12b from the near-UV to the near-IR
The detection of trends or gradients in the transmission spectrum of
extrasolar planets is possible with observations at very low spectral
resolution. Transit measurements of sufficient accuracy using selected
broad-band filters allow for an initial characterization of the atmosphere of
the planet. We obtained time series photometry of 20 transit events and
analyzed them homogeneously, along with eight light curves obtained from the
literature. In total, the light curves span a range from 0.35 to 1.25 microns.
During two observing seasons over four months each, we monitored the host star
to constrain the potential influence of starspots on the derived transit
parameters. We rule out the presence of a Rayleigh slope extending over the
entire optical wavelength range, a flat spectrum is favored for HAT-P-12b with
respect to a cloud-free atmosphere model spectrum. A potential cause of such
gray absorption is the presence of a cloud layer at the probed latitudes.
Furthermore, in this work we refine the transit parameters, the ephemeris and
perform a TTV analysis in which we found no indication for an unseen companion.
The host star showed a mild non-periodic variability of up to 1%. However, no
stellar rotation period could be detected to high confidence.Comment: 13 pages, 6 figures, Accepted for publication in A&
Generalized Robba rings
We prove that any projective coadmissible module over the locally analytic
distribution algebra of a compact -adic Lie group is finitely generated. In
particular, the category of coadmissible modules does not have enough
projectives. In the Appendix a "generalized Robba ring" for uniform pro-
groups is constructed which naturally contains the locally analytic
distribution algebra as a subring. The construction uses the theory of
generalized microlocalization of quasi-abelian normed algebras that is also
developed there. We equip this generalized Robba ring with a self-dual locally
convex topology extending the topology on the distribution algebra. This is
used to show some results on coadmissible modules.Comment: with an appendix by Peter Schneider; revised; new titl
Fean wetter buorkje II : Samenvattende rapportage praktijkproeven hoger zomerpeil Fries Veenweidegebied 2007-2008
De provincie FryslĂąn en Wetterskip FryslĂąn zoeken naar een vorm van peilbeheer die de bodemdaling in het Friese veenweidegebied vertraagt, maar een sterke landbouw niet in de weg staat. De oplossing wordt gezocht in hoger zomerpeil. Daarbij is âs zomers, wanneer vanwege de lagere grondwaterstanden en de hogere temperaturen 90% van de bodemdaling plaatsvindt, de drooglegging 60-70 cm, terwijl die âs winters 90 cm blijft
Persistent high burden and mortality associated with advanced HIV disease in rural Tanzania despite uptake of World Health Organization "test and treat" guidelines
BACKGROUND: Information about burden, characteristics, predictors, and outcomes of advanced human immunodeficiency virus disease (AHD) is scarce in rural settings of sub-Saharan Africa. Human immunodeficiency virus (HIV) infections and associated deaths remain high despite specific guidelines issued by the World Health Organization (WHO). METHODS: Burden of AHD and 6-month death/loss to follow-up (LTFU) were described among 2498 antiretroviral therapy (ART)-naive nonpregnant people with HIV (PWH) aged >15 years enrolled in the Kilombero Ulanga Antiretroviral Cohort in rural Tanzania between 2013 and 2019. Baseline characteristics associated with AHD and predictors of death/LTFU among those with AHD were analyzed using multivariate logistic and Cox regression, respectively. RESULTS: Of the PWH, 62.2% had AHD at diagnosis (66.8% before vs 55.7% after national uptake of WHO "test and treat" guidelines in 2016). At baseline, older age, male sex, lower body mass index, elevated aminotransferase aspartate levels, severe anemia, tachycardia, decreased glomerular filtration rate, clinical complaints, impaired functional status, and enrollment into care before 2018 were independently associated with AHD. Among people with AHD, incidence of mortality, and LTFU were 16 and 34 per 100 person-years, respectively. WHO clinical stage 3 or 4, CD4 counts <100 cells/microL, severe anemia, tachypnea, and liver disease were associated with death/LTFU. CONCLUSIONS: More than 50% of PWH enrolled in our cohort after test and treat implementation still had AHD at diagnosis. Increasing HIV testing and uptake and implementation of the WHO-specific guidelines on AHD for prevention, diagnosis, treatment of opportunistic infections, and reducing the risks of LTFU are urgently needed to reduce morbidity and mortality
Dutch patients, retail chicken meat and poultry share the same ESBL genes, plasmids and strains
Intestinal carriage of extended-spectrum beta-lactamase (ESBL) -producing bacteria in food-producing animals and contamination of retail meat may contribute to increased incidences of infections with ESBL-producing bacteria in humans. Therefore, distribution of ESBL genes, plasmids and strain genotypes in Escherichia coli obtained from poultry and retail chicken meat in the Netherlands was determined and defined as âpoultry-associatedâ (PA). Subsequently, the proportion of E. coli isolates with PA ESBL genes, plasmids and strains was quantified in a representative sample of clinical isolates. The E. coli were derived from 98 retail chicken meat samples, a prevalence survey among poultry, and 516 human clinical samples from 31 laboratories collected during a 3-month period in 2009. Isolates were analysed using an ESBL-specific microarray, sequencing of ESBL genes, PCR-based replicon typing of plasmids, plasmid multi-locus sequence typing (pMLST) and strain genotyping (MLST). Six ESBL genes were defined as PA (blaCTX-M-1, blaCTX-M-2, blaSHV-2, blaSHV-12, blaTEM-20, blaTEM-52): 35% of the human isolates contained PA ESBL genes and 19% contained PA ESBL genes located on IncI1 plasmids that were genetically indistinguishable from those obtained from poultry (meat). Of these ESBL genes, 86% were blaCTX-M-1 and blaTEM-52 genes, which were also the predominant genes in poultry (78%) and retail chicken meat (75%). Of the retail meat samples, 94% contained ESBL-producing isolates of which 39% belonged to E. coli genotypes also present in human samples. These findings are suggestive for transmission of ESBL genes, plasmids and E. coli isolates from poultry to humans, most likely through the food chain
GJ1214: Rotation period, starspots, and uncertainty on the optical slope of the transmission spectrum
Brightness inhomogeneities in the stellar photosphere (dark spots or bright
regions) affect the measurements of the planetary transmission spectrum. To
investigate the star spots of the M dwarf GJ 1214, we conducted a multicolor
photometric monitoring from 2012 to 2016. The measured variability shows a
periodicity of 125 +- 5 days, which we interpret as the signature of the
stellar rotation period. This value overrules previous suggestions of a
significantly shorter stellar rotation period. A light curve inversion of the
monitoring data yields an estimation of the flux dimming of a permanent spot
filling factor not contributing to the photometric variability, a temperature
contrast of the spots of about 370 K and persistent active longitudes. The
derived surface maps over all five seasons were used to estimate the influence
of the star spots on the transmission spectrum of the planet from 400 nm to
2000 nm. The monitoring data presented here do not support a recent
interpretation of a measured transmission spectrum of GJ 1214b as to be caused
by bright regions in the stellar photosphere. Instead, we list arguments as to
why the effect of dark spots likely dominated over bright regions in the period
of our monitoring. Furthermore, our photometry proves an increase in
variability over at least four years, indicative for a cyclic activity
behavior. The age of GJ 1214 is likely between 6 and 10 Gyr. The long-term
photometry allows for a correction of unocculted spots. For an active star such
as GJ 1214, there remains a degeneracy between occulted spots and the transit
parameters used to build the transmission spectrum. This degeneracy can only be
broken by high-precision transit photometry resolving the spot crossing
signature in the transit light curve.Comment: 11 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen
While measurements of the hyperfine structure of hydrogen-like atoms are
traditionally regarded as test of bound-state QED, we assume that theoretical
QED predictions are accurate and discuss the information about the
electromagnetic structure of protons that could be extracted from the
experimental values of the ground state hyperfine splitting in hydrogen and
muonic hydrogen. Using recent theoretical results on the proton polarizability
effects and the experimental hydrogen hyperfine splitting we obtain for the
Zemach radius of the proton the value 1.040(16) fm. We compare it to the
various theoretical estimates the uncertainty of which is shown to be larger
that 0.016 fm. This point of view gives quite convincing arguments in support
of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.
Threat of an influenza pandemic: family physicians in the front line
<p>Abstract</p> <p>Background</p> <p>The chance of an influenza pandemic is real and clinicians should keep themselves informed about the rationale and science behind preventive and therapeutic principles relating to an (impending) influenza pandemic.</p> <p>Discussion</p> <p>Vaccination is considered the best prevention in case of a pandemic threat and first choice to contain the impact of a pandemic. Pending the availability of an effective pandemic vaccine, antivirals are likely the only effective agents for prevention and treatment. When an influenza pandemic is impending, all interventions aim to prevent people becoming infected and to suppress replication and transmission of the virus as much as possible. Antivirals will be prescribed to patients with laboratory confirmed pre-pandemic influenza as well as to their contacts (post-exposure prophylaxis) which may delay development of or even prevent a pandemic. During a manifest influenza pandemic, however, there is large-scale spreading of the influenza virus. Therefore, preventive use of antivirals is less efficient to prevent transmission. Delaying the pandemic is then important in order to prevent exhausting public health resources and disruption of society. Thus, during a manifest pandemic everyone with influenza symptoms should receive antivirals as quickly as possible, regardless of virological confirmation. To ensure optimal effectiveness of antivirals and to minimize development of drug resistant viral strains, the use of antivirals for annual influenza should be restrictive. The crucial position of family physicians during an (impending) influenza pandemic necessitates the development of primary health care guidelines on this topic for all countries.</p> <p>Summary</p> <p>Family physicians will play a key role in assessing and treating victims of a new influenza virus, and in reassuring the worried well. We outline various possible interventions in the event of an impending and a manifest influenza pandemic, such as non-medial measures, prescription of antivirals, and vaccination, and emphasize the need for pandemic influenza preparedness.</p
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