Non-Invasive Detection of Coronary Artery Disease in Patients With Left Bundle Branch Block Using 64-Slice Computed Tomography

ObjectivesThe goal of this study was to evaluate the diagnostic accuracy of 64-slice computed tomography (CT) to identify coronary artery disease (CAD) in patients with complete left bundle branch block (LBBB).BackgroundLeft bundle branch block increases risk of cardiac mortality, and prognosis is primarily determined by the underlying coronary disease. Non-invasive stress tests have limited performance, and conventional coronary angiography (CCA) is usually required.MethodsSixty-six consecutive patients with complete LBBB and sinus rhythm admitted for CCA were enrolled. Computed tomography was performed 3 ± 3.9 days before CCA. The accuracy of 64-slice CT to detect significant stenosis (>50% lumen narrowing) was compared with quantitative coronary angiography. All segments were analyzed regardless of image quality from coronary calcification or motion artifacts. Results were analyzed by patient and by coronary segment (990) using the American Heart Association 15-segment model.ResultsLower heart rates were associated with improved image quality. Computed tomography correctly identified 35 of 37 (95%) patients without significant stenosis and 28 of 29 (97%) patients with significant stenosis on CCA. Computed tomography correctly assessed 68 of 94 (72%) significant stenosis. Overall, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 64-slice CT for identifying CAD by patient was 95%, 97%, 95%, 93%, and 97%, respectively, and by segment was 97%, 72%, 99%, 91%, and 97%, respectively.ConclusionsIn a routine clinical practice, 64-slice CT detects with excellent accuracy a significant CAD in patients with complete LBBB. A normal CT in this clinical setting is a robust tool to act as a filter and avoid invasive diagnostic procedures

Observing Mars from Areostationary Orbit: Benefits and Applications

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Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions

We put model-independent, dynamical constraints on the net electric charge Q of some astronomical and astrophysical objects by assuming that their exterior spacetimes are described by the Reissner-Nordstroem metric, which induces an additional potential U_RN \propto Q^2 r^-2. Our results extend to other hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version matching the one at press in General Relativity and Gravitation (GRG). arXiv admin note: substantial text overlap with arXiv:1112.351

Handbook of satellite orbits: from Kepler to GPS

Fifty years after Sputnik, artificial satellites have become indispensable monitors in many areas, such as economics, meteorology, telecommunications, navigation and remote sensing. The specific orbits are important for the proper functioning of the satellites. This book discusses the great variety of satellite orbits, both in shape (circular to highly elliptical) and properties (geostationary, Sun-synchronous, etc.). This volume starts with an introduction into geodesy. This is followed by a presentation of the fundamental equations of mechanics to explain and demonstrate the properties for all types of orbits. Numerous examples are included, obtained through IXION software developed by the author. The book also includes an exposition of the historical background that is necessary to help the reader understand the main stages of scientific thought from Kepler to GPS. This book is intended for researchers, teachers and students working in the field of satellite technology. Engineers, geographers and all those involved in space exploration will find this information valuable. Michel Capderou’s book is an essential treatise in orbital mechanics for all students, lecturers and practitioners in this field, as well as other aerospace systems engineers. —Charles Elachi, Director, NASA Jet Propulsion Laborator

Les orbites des satellites météorologiques

Les satellites météorologiques sont étudiés ici du point de vue de leur orbite. On présente en détail les deux principaux types d'orbite utilisés : l'orbite géostationnaire (GEO), qui fournit au satellite un point de vue fixe de la Terre sur l'équateur terrestre mais très éloigné ; l'orbite plus basse (LEO), qui permet d'observer, grâce à la propriété d'héliosynchronisme, avec de bonnes conditions d'éclairement solaire. Nous terminons par d'autres types d'orbites utilisées plus récemment.Meteorological satellites are studied in this article from the point of view of their orbit. The two most common orbit types are explained: the geostationary orbit (GEO), which provides the satellite with a fixed point of view of the Earth on the terrestrial equator, but is very remote; the lower orbit (LEO), which makes it possible to observe Earth scenes with good conditions of solar illumination, thanks to the property of Sunsynchronism. We end with other types of orbit more recently used

Optimal orbits for Mars atmosphere remote sensing

International audienceMost of the spacecrafts currently around Mars (or planned to reach Mars in the near future) use Sun-synchronous or near-polar orbits. Such orbits offer a very poor sampling of the diurnal cycle. Yet, sampling the diurnal cycle is of key importance to study Mars meteorology and climate. A comprehensive remote sensing data set should have been obtained by the end of the MRO mission, launched in 2005. For later windows, time-varying phenomena should be given the highest priority for remote sensing investigations. We present possible orbits for such missions which provide a rich spatial and temporal sampling with a relatively short repeat cycle (50 sols). After computation and determination of these orbits, said "optimal orbits", we illustrate our results by tables of sampling and comparison with other orbits

Megha-Tropiques : un satellite hydrométéorologique franco-indien

Une forte variabilité caractérise les systèmes météorologiques qui conditionnent les échanges d'énergie et d'eau dans les tropiques. L'objectif de Megha-Tropiques est de mesurer avec une bonne répétitivité des observables liés aux flux radiatifs, à la vapeur d'eau, aux précipitations. L'orbite du satellite a une inclinaison de 20 degrés sur l'équateur, et la charge utile comporte trois instruments : un imageur hyperfréquences pour les nuages et la pluie (Madras), un sondeur hyperfréquences de vapeur d'eau (Saphir) et un instrument à bandes larges destiné à la mesure des flux radiatifs (Scarab). Les caractéristiques de ces instruments et de l'échantillonnage sont présentées, ainsi que les grandes lignes du traitement et de l'utilisation envisagé des données. Le lancement de ce satellite est prévu à la fin de l'année 2009.Tropical systems driving water and energy exchanges present a large space-time variability. Megha-Tropiques aims to measure with a high repetitivity radiances linked to radiative fluxes, water vapour and precipitation. The satellite orbit has an inclination of 20 degrees and the payload is composed by three instruments: a microwave imager for clouds and rain (Madras), a microwave sounder for water vapour (Saphir) and a wide band instrument for radiative fluxes (Scarab). These instruments and the sampling are presented, as well as the leading principles of the data processing and use. The launch is foreseen in the end of 2009

Using Kinematic GNSS Data to Assess the Accuracy and Precision of the TanDEM-X DEM Resampled at 1-m Resolution Over the Western Corinth Gulf, Greece

International audienceWe assess the accuracy and the precision of the TanDEM-X digital elevation model (DEM) of the western Gulf of Corinth, Greece. We use a dense set of accurate ground coordinates obtained by kinematic Global Navigation Satellite Systems (GNSS) observations. Between 2001 and 2019, 148 surveys were made, at a 1 s sampling rate, along highways, roads, and tracks, with a total traveled distance of ∼25 000 km. The data are processed with the online Canadian Spatial Reference System precise point positioning software. From the output files, we select 885 252 coordinates from epochs with theoretical uncertainty below 0.1 m in horizontal and 0.2 m in vertical. Using specific calibration surveys, we estimate the mean vertical accuracy of the GNSS coordinates at 0.2 m. Resampling the DEM by a factor of 10 allows one to compare it with the GNSS in pixels of metric size, smaller than the width of the roads, even the small trails. The best fit is obtained by shifting the DEM by 0.47 ± 0.03 m upward, 0.10 ± 0.1 m westward, and 0.36 ± 0.1 m southward. Those values are 20 times below the nominal resolution of the DEM. Once the shift is corrected, the root mean square deviation between TanDEM-X DEM and GNSS elevations is 1.125 m. In forest and urban areas, the shift between the DEM and the GNSS increases by ∼0.5 m. The metric accuracy of the TanDEM-X DEM paves the way for new applications for long-term deformation monitoring of this area

GRGS simulations for a GRASP-like satellite

International audienceGRASP (Geodetic Reference Antenna in SPace) is a spacecraft system designed to provide the needed data for an enduring and stable TRF (Terrestrial Reference Frame) for accurately measuring and understanding changes in global and regional sea levels, ice sheets and other elements of the dynamic Earth system. To reach the goals for the TRF realization of 1 mm accuracy and 0.1 mm/yr stability (GGOS, Meeting the Requirements of a Global Society on a Changing Planet in 2020, Plag and Pearlman, eds., 2009), GRASP would carry very precise sensor systems for all the key geodetic techniques used to define and monitor the TRF (DORIS, GNSS, SLR, and VLBI). In this study, we present the results obtained regarding the simulations carried out by the French GRGS (Groupe de Recherche de Géodésie Spatiale) for a GRASP-like satellite. First, we searched for the optimal orbit for such a geodetic mission with Genetic Algorithms (stochastic optimization). Then, with the best found orbit, we simulated the measurements of the four geodetic techniques (DORIS and SLR measurements to GRASP, VLBI PPP or interferometric measurements to GRASP, and GNSS measurements received from ground stations and from GRASP) over three years, and we evaluated the expected accuracy and stability of the TRF obtained with the processing of these measurements. Finally, we also investigated the expected impact of the on-board instrument calibration on the quality of the TRF

GRGS simulations for a GRASP-like satellite

International audienceGRASP (Geodetic Reference Antenna in SPace) is a spacecraft system designed to provide the needed data for an enduring and stable TRF (Terrestrial Reference Frame) for accurately measuring and understanding changes in global and regional sea levels, ice sheets and other elements of the dynamic Earth system. To reach the goals for the TRF realization of 1 mm accuracy and 0.1 mm/yr stability (GGOS, Meeting the Requirements of a Global Society on a Changing Planet in 2020, Plag and Pearlman, eds., 2009), GRASP would carry very precise sensor systems for all the key geodetic techniques used to define and monitor the TRF (DORIS, GNSS, SLR, and VLBI). In this study, we present the results obtained regarding the simulations carried out by the French GRGS (Groupe de Recherche de Géodésie Spatiale) for a GRASP-like satellite. First, we searched for the optimal orbit for such a geodetic mission with Genetic Algorithms (stochastic optimization). Then, with the best found orbit, we simulated the measurements of the four geodetic techniques (DORIS and SLR measurements to GRASP, VLBI PPP or interferometric measurements to GRASP, and GNSS measurements received from ground stations and from GRASP) over three years, and we evaluated the expected accuracy and stability of the TRF obtained with the processing of these measurements. Finally, we also investigated the expected impact of the on-board instrument calibration on the quality of the TRF