2,593 research outputs found
Low prevalence of atrial fibrillation in asymptomatic adults in Geneva, Switzerland
Rapport de synthèse
« Faible prévalence de la fibrillation auriculaire chez des adultes asymptomatiques à Genève, Suisse »
But : l'augmentation de la prévalence de la fibrillation auriculaire (FA) est dans les pays développés un problème de santé publique. L'ampleur de cette augmentation demeure cependant peu claire. L'objectif de ce travail est de déterminer la prévalence de la FA au sein d'un échantillon représentatif d'adultes asymptomatiques de plus de 50 ans.
Méthode : entre janvier 2005 et décembre 2007, des individus résidants du canton de Genève et ayant déjà participé précédemment à une étude randomisée ont été invités pour un examen de contrôle. Le diagnostic de FA a été posé à l'aide d'un tracé électrocardiographique 6 pistes. Tous les tracés ont étés revus par un cardiologue. Les prévalences de FA ont ensuite été standardisées pour la distribution d'âge dans la population genevoise. Une prise de sang veineuse a été réalisée chez tous les participants après 8 heures de jeûne et la glycémie, la triglyceridémie, le cholestérol sérique total ainsi que le cholestérol HDL sérique ont été déterminés.
Résultats : la participation a été de 72.8%. 29 cas de FA (22 hommes) ont été diagnostiqués parmi 3285 sujets (1696 hommes). La prévalence de la FA (95% Cl) était de 0.88% (0.86, 0.90). La prévalence standardisée pour l'âge était légèrement plus élevée [0.94% (0.91, 0.97), hommes: 1.23% (1.19, 1.27), femmes; 0.54% (0.47, 0.61)]. Les sujets avec une FA étaient plus âgés (72.1 vs. 63.1 ans, ρ < 0.0001), plus souvent de sexe masculin (75.9% vs. 50.4%, ρ = 0.0087), avaient un indice de masse corporelle plus élevé (27.9 vs. 25,9 kg/m2, ρ = 0.011), un périmètre abdominal plus important (98.8 vs. 90.2 cm, ρ = 0.0034), une tension artérielle diastolique plus élevée (80.9 vs. 75.7mmhg, ρ = 0.0093), un cholestérol sérique total plus bas (5.16 vs. 5.75mmol/L, ρ = 0.0019) et un HDL cholestérol sérique plus bas (1.31 vs. 1.48 mmol/L, ρ = 0.02). A l'anamnèse un antécédent « d'embolie artérielle » (cérébrale ou membres inférieurs) était significativement plus fréquent chez les sujets avec une FA (10.3 vs. 3.3%, ρ = 0.03).
Conclusion : cette étude basée sur une population suisse asymptomatique montre une prévalence de la FA inférieure à 1%. Ces résultats sont moins alarmants que ceux obtenus lors de précédentes études
NLTE model calculations for the solar atmosphere with an iterative treatment of opacity distribution functions
Modeling the variability of the solar spectral irradiance is a key factor for
understanding the solar influence on the climate of the Earth. As a first step
to calculating the solar spectral irradiance variations we reproduce the solar
spectrum for the quiet Sun over a broad wavelength range with an emphasis on
the UV. We introduce the radiative transfer code COSI which calculates solar
synthetic spectra under conditions of non-local thermodynamic equilibrium
(NLTE). A self-consistent simultaneous solution of the radiative transfer and
the statistical equation for the level populations guarantees that the correct
physics is considered for wavelength regions where the assumption of local
thermodynamic equilibrium (LTE) breaks down. The new concept of iterated
opacity distribution functions (NLTE-ODFs), through which all line opacities
are included in the NLTE radiative transfer calculation, is presented. We show
that it is essential to include the line opacities in the radiative transfer to
reproduce the solar spectrum in the UV. Through the implemented scheme of
NLTE-ODFs the COSI code is successful in reproducing the spectral energy
distribution of the quiet Sun.Comment: 13 pages, 9 figures. accepted for publication in Astronomy and
Astrophysic
Imaging electric fields in the vicinity of cryogenic surfaces using Rydberg atoms
The ability to characterize static and time-dependent electric fields in situ
is an important prerequisite for quantum-optics experiments with atoms close to
surfaces. Especially in experiments which aim at coupling Rydberg atoms to the
near field of superconducting circuits, the identification and subsequent
elimination of sources of stray fields is crucial. We present a technique that
allows the determination of stray-electric-field distributions
at distances of less than from (cryogenic) surfaces using
coherent Rydberg-Stark spectroscopy in a pulsed supersonic beam of metastable
helium atoms. We demonstrate the
capabilities of this technique by characterizing the electric stray field
emanating from a structured superconducting surface. Exploiting coherent
population transfer with microwave radiation from a coplanar waveguide, the
same technique allows the characterization of the microwave-field distribution
above the surface.Comment: 6 pages, 4 figure
Vacuum-ultraviolet frequency-modulation spectroscopy
Frequency-modulation (FM) spectroscopy has been extended to the
vacuum-ultraviolet (VUV) range of the electromagnetic spectrum. Coherent VUV
laser radiation is produced by resonance-enhanced sum-frequency mixing
() in Kr and Xe using two
near-Fourier-transform-limited laser pulses of frequencies
and . Sidebands generated in the output of the second laser ()
using an electro-optical modulator operating at the frequency
are directly transfered to the VUV and used to record FM
spectra. Demodulation is demonstrated both at and
. The main advantages of the method are that its
sensitivity is not reduced by pulse-to-pulse fluctuations of the VUV laser
intensity, compared to VUV absorption spectroscopy is its background-free
nature, the fact that its implementation using table-top laser equipment is
straightforward and that it can be used to record VUV absorption spectra of
cold samples in skimmed supersonic beams simultaneously with
laser-induced-fluorescence and photoionization spectra. To illustrate these
advantages we present VUV FM spectra of Ar, Kr, and N in selected regions
between 105000cm and 122000cm.Comment: 23 pages, 10 figure
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High Density Genetic Maps of Seashore Paspalum Using Genotyping-By-Sequencing and Their Relationship to The Sorghum Bicolor Genome.
As a step towards trait mapping in the halophyte seashore paspalum (Paspalum vaginatum Sw.), we developed an F1 mapping population from a cross between two genetically diverse and heterozygous accessions, 509022 and HI33. Progeny were genotyped using a genotyping-by-sequencing (GBS) approach and sequence reads were analyzed for single nucleotide polymorphisms (SNPs) using the UGbS-Flex pipeline. More markers were identified that segregated in the maternal parent (HA maps) compared to the paternal parent (AH maps), suggesting that 509022 had overall higher levels of heterozygosity than HI33. We also generated maps that consisted of markers that were heterozygous in both parents (HH maps). The AH, HA and HH maps each comprised more than 1000 markers. Markers formed 10 linkage groups, corresponding to the ten seashore paspalum chromosomes. Comparative analyses showed that each seashore paspalum chromosome was syntenic to and highly colinear with a single sorghum chromosome. Four inversions were identified, two of which were sorghum-specific while the other two were likely specific to seashore paspalum. These high-density maps are the first available genetic maps for seashore paspalum. The maps will provide a valuable tool for plant breeders and others in the Paspalum community to identify traits of interest, including salt tolerance
A One-dimensional Ensemble Forecast and Assimilation System for Fog Prediction
A probabilistic fog forecast system was designed based on two high resolution numerical 1-D models called COBEL and PAFOG. The 1-D models are coupled to several 3-D numerical weather prediction models and thus are able to consider the effects of advection. To deal with the large uncertainty inherent to fog forecasts, a whole ensemble of 1-D runs is computed using the two different numerical models and a set of different initial conditions in combination with distinct boundary conditions. Initial conditions are obtained from variational data assimilation, which optimally combines observations with a first guess taken from operational 3-D models. The design of the ensemble scheme computes members that should fairly well represent the uncertainty of the current meteorological regime. Verification for an entire fog season reveals the importance of advection in complex terrain. The skill of 1-D fog forecasts is significantly improved if advection is considered. Thus the probabilistic forecast system has the potential to support the forecaster and therefore to provide more accurate fog forecast
Measuring the dispersive frequency shift of a rectangular microwave cavity induced by an ensemble of Rydberg atoms
In recent years the interest in studying interactions of Rydberg atoms or
ensembles thereof with optical and microwave frequency fields has steadily
increased, both in the context of basic research and for potential applications
in quantum information processing. We present measurements of the dispersive
interaction between an ensemble of helium atoms in the 37s Rydberg state and a
single resonator mode by extracting the amplitude and phase change of a weak
microwave probe tone transmitted through the cavity. The results are in
quantitative agreement with predictions made on the basis of the dispersive
Tavis-Cummings Hamiltonian. We study this system with the goal of realizing a
hybrid between superconducting circuits and Rydberg atoms. We measure maximal
collective coupling strengths of 1 MHz, corresponding to 3*10^3 Rydberg atoms
coupled to the cavity. As expected, the dispersive shift is found to be
inversely proportional to the atom-cavity detuning and proportional to the
number of Rydberg atoms. This possibility of measuring the number of Rydberg
atoms in a nondestructive manner is relevant for quantitatively evaluating
scattering cross sections in experiments with Rydberg atoms
Analysis of Radiation Discretization for Modelling a Spark Gap for Surge Currents
In this paper we address a method for spectrally resolved radiation modelling in thermal plasmas encountered in surge protective devices based on spark gaps. Compared to most switching applications, power input and plasma pressure are much higher which leads to an optically thick plasma with line broadening and enhanced wall ablation. In this situation it is possible to capture the full effect of spectrally resolved radiation on plasma dynamics by performing line-by-line calculations with downsampled absorption spectra. We show that it is possible to achieve radiation convergence with 1000 lines. Approaches for a further reduction of calculation times using band-averaged models and -group models are discussed. The κ-group model is based upon a grouping of the absorption coefficients into subgroups with different ranges of κ before averaging. The spectral calculation results are compared to the approximative methods and significant differences for Rosseland means are observed
Hyperbaric oxygen therapy (HBO) for the treatment of an epidural abscess in the posterior fossa in an 8-month-old infant
Epidural abscesses in children are extremely rare, especially in the posterior fossa. In some cases antibiotic therapy and surgical drainage are insufficient for complete healing. We present the case of an 8-month-old boy who developed an epidural abscess in the posterior fossa after repeated surgical procedures for retrocerebellar arachnoid cysts and hydrocephalus. We decided to use adjuvant hyperbaric oxygen therapy (HBO) to avoid removal of the bone and the existing ventriculoperitoneal shunt. In this way osteomyelitis, potentially leading to bone removal and shunt infection, could be prevented. HBO is a relatively safe, noninvasive and cost-effective therapy to improve healing of chronic and deep-seated wound infections. To our knowledge HBO has never been used before in such a young child in neurosurgery. Multidisciplinary management is recommended to optimize treatment
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