Taiwan/TriG Radio Occultation Process System (TROPS): A Brief Introduction of Atmospheric Productions

NASA Astrophysics Data System (ADS)

Huang, Cheng-Yung; Yeh, Wen-Hao; Tseng, Tzu-Pang; Chen, Linton J.

2017-04-01

Global Positioning System (GPS) Radio Occultation (RO) technique has been used to investigate the Earth's atmosphere since 1990s. In 2006, Taiwan has launched six low Earth orbit (LEO) satellites as a RO constellation mission, named FORMOSAT-3 /COSMIC (F-3/C). F-3/C mission can release 1500-2500 data sets per day for both neutral atmosphere and ionosphere. With the advent of Global Navigation Satellite System (GNSS) in ten years and FORMOSAT-7/COSMIC-2 (F-7/C-2) mission, 12 LEO satellites are planned to be launched and deployed in two clusters of 6-satellites into the designated low and high inclination orbits in 2017 and 2020(TBD), respectively. The amount of RO data set will increase to about 8000 set per day with the using of GNSS TriG (GPS, Glonass, Galileo) receivers. The first phase of FS-7 mission is designed to low inclination (24 deg) orbit to improve the ability of server weather forecasting, like typhoon and monsoon rainfall around tropical region. The second is high inclination (72 deg) for global distribution. In order to observe better water vapor profiles, the 4x3 antennas arrays will be on board to receive weak signals which pass through low troposphere around earth surface. This report will introduce the status of F-7/C-2 mission and atmospheric part of occultation data process software TROPS.

Global climatology of planetary boundary layer top obtained from multi-satellite GPS RO observations

NASA Astrophysics Data System (ADS)

Basha, Ghouse; Kishore, P.; Ratnam, M. Venkat; Ravindra Babu, S.; Velicogna, Isabella; Jiang, Jonathan H.; Ao, Chi O.

2018-05-01

Accurate estimation of the planetary boundary layer (PBL) top is essential for air quality prediction, weather forecast, and assessment of regional and global climate models. In this article, the long-term climatology of seasonal, global distribution of PBL is presented by using global positioning system radio occultation (GPSRO) based payloads such as Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), Communication/Navigation Outage Forecast System (C/NOFS), TerraSAR-X, and The Gravity Recovery and Climate Experiment (GRACE) from the year 2006-2015. We used Wavelet Covariance Transform (WCT) technique for precise PBL top identification. The derived PBL top from GPSRO data is rigorously evaluated with GPS radiosonde data over Gadanki. Significant seasonal variation is noticed in both radiosonde and GPSRO observations. Further, we compared the PBL obtained GPS RO with global radiosonde network and observed very good correlation. The number of occultations reaching down to 500 m and retrieval rate of PBL top from WCT method is very high in mid-latitudes compared to tropical latitudes. The global distribution of PBL top shows significant seasonal variation with higher during summer followed by spring, fall, and minimum in winter. In the vicinity of Inter Tropical Convergence Zone (ITCZ), the PBL top is high over eastern Pacific compared to other regions. The ERA-Interim reanalysis data underestimate the PBL top compared to GPS RO observations due to different measurement techniques. The seasonal variation of global averaged PBL top over land and ocean shows contrasting features at different latitude bands.

Space Weather Observations by GNSS Radio Occultation: From FORMOSAT-3/COSMIC to FORMOSAT-7/COSMIC-2

PubMed Central

Yue, Xinan; Schreiner, William S; Pedatella, Nicholas; Anthes, Richard A; Mannucci, Anthony J; Straus, Paul R; Liu, Jann-Yenq

2014-01-01

The joint Taiwan-United States FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission, hereafter called COSMIC, is the first satellite constellation dedicated to remotely sense Earth's atmosphere and ionosphere using a technique called Global Positioning System (GPS) radio occultation (RO). The occultations yield abundant information about neutral atmospheric temperature and moisture as well as space weather estimates of slant total electron content, electron density profiles, and an amplitude scintillation index, S4. With the success of COSMIC, the United States and Taiwan are moving forward with a follow-on RO mission named FORMOSAT-7/COSMIC-2 (COSMIC-2), which will ultimately place 12 satellites in orbit with two launches in 2016 and 2019. COSMIC-2 satellites will carry an advanced Global Navigation Satellite System (GNSS) RO receiver that will track both GPS and Russian Global Navigation Satellite System signals, with capability for eventually tracking other GNSS signals from the Chinese BeiDou and European Galileo system, as well as secondary space weather payloads to measure low-latitude plasma drifts and scintillation at multiple frequencies. COSMIC-2 will provide 4–6 times (10–15X in the low latitudes) the number of atmospheric and ionospheric observations that were tracked with COSMIC and will also improve the quality of the observations. In this article we focus on COSMIC/COSMIC-2 measurements of key ionospheric parameters. PMID:26213514

Space Weather Observations by GNSS Radio Occultation: From FORMOSAT-3/COSMIC to FORMOSAT-7/COSMIC-2.

PubMed

Yue, Xinan; Schreiner, William S; Pedatella, Nicholas; Anthes, Richard A; Mannucci, Anthony J; Straus, Paul R; Liu, Jann-Yenq

2014-11-01

The joint Taiwan-United States FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) mission, hereafter called COSMIC, is the first satellite constellation dedicated to remotely sense Earth's atmosphere and ionosphere using a technique called Global Positioning System (GPS) radio occultation (RO). The occultations yield abundant information about neutral atmospheric temperature and moisture as well as space weather estimates of slant total electron content, electron density profiles, and an amplitude scintillation index, S4. With the success of COSMIC, the United States and Taiwan are moving forward with a follow-on RO mission named FORMOSAT-7/COSMIC-2 (COSMIC-2), which will ultimately place 12 satellites in orbit with two launches in 2016 and 2019. COSMIC-2 satellites will carry an advanced Global Navigation Satellite System (GNSS) RO receiver that will track both GPS and Russian Global Navigation Satellite System signals, with capability for eventually tracking other GNSS signals from the Chinese BeiDou and European Galileo system, as well as secondary space weather payloads to measure low-latitude plasma drifts and scintillation at multiple frequencies. COSMIC-2 will provide 4-6 times (10-15X in the low latitudes) the number of atmospheric and ionospheric observations that were tracked with COSMIC and will also improve the quality of the observations. In this article we focus on COSMIC/COSMIC-2 measurements of key ionospheric parameters.

Case study on complex sporadic E layers observed by GPS radio occultations

NASA Astrophysics Data System (ADS)

Yue, X.; Schreiner, W. S.; Zeng, Z.; Kuo, Y.-H.; Xue, X.

2015-01-01

The occurrence of sporadic E (Es) layers has been a hot scientific topic for a long time. The GNSS (global navigation satellite system)-based radio occultation (RO) has proven to be a powerful technique for detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC (University Corporation for Atmospheric Research (UCAR) the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center (CDAAC)). We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between colocated simultaneous RO events and between RO and lidar observations, it could be concluded that some of these do manifest the multiple Es layer structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by independent ionosondes observations. It is possible to explain these complex Es structures using the popular wind shear theory. We could map the global Es occurrence routinely in the near future, given that more RO data will be available. Further statistical studies will enhance our understanding of the Es mechanism. The understanding of Es should benefit both Es-based long-distance communication and accurate neutral RO retrievals.

Towards SI-traceable radio occultation excess phase processing with integrated uncertainty estimation for climate applications

NASA Astrophysics Data System (ADS)

Innerkofler, Josef; Pock, Christian; Kirchengast, Gottfried; Schwaerz, Marc; Jaeggi, Adrian; Schwarz, Jakob

2016-04-01

The GNSS Radio Occultation (RO) measurement technique is highly valuable for climate monitoring of the atmosphere as it provides accurate and precise measurements in the troposphere and stratosphere regions with global coverage, long-term stability, and virtually all-weather capability. The novel Reference Occultation Processing System (rOPS), currently under development at the WEGC at University of Graz aims to process raw RO measurements into essential climate variables, such as temperature, pressure, and tropospheric water vapor, in a way which is SI-traceable to the universal time standard and which includes rigorous uncertainty propagation. As part of this rOPS climate-quality processing system, accurate atmospheric excess phase profiles with new approaches integrating uncertainty propagation are derived from the raw occultation tracking data and orbit data. Regarding the latter, highly accurate orbit positions and velocities of the GNSS transmitter satellites and the RO receiver satellites in low Earth orbit (LEO) need to be determined, in order to enable high accuracy of the excess phase profiles. Using several representative test days of GPS orbit data from the CODE and IGS archives, which are available at accuracies of about 3 cm (position) / 0.03 mm/s (velocity), and employing Bernese 5.2 and Napeos 3.3.1 software packages for the LEO orbit determination of the CHAMP, GRACE, and MetOp RO satellites, we achieved robust SI-traced LEO orbit uncertainty estimates of about 5 cm (position) / 0.05 mm/s (velocity) for the daily orbits, including estimates of systematic uncertainty bounds and of propagated random uncertainties. For COSMIC RO satellites, we found decreased accuracy estimates near 10-15 cm (position) / 0.1-0.15 mm/s (velocity), since the characteristics of the small COSMIC satellite platforms and antennas provide somewhat less favorable orbit determination conditions. We present the setup of how we (I) used the Bernese and Napeos package in mutual

A model-assisted radio occultation data inversion method based on data ingestion into NeQuick

NASA Astrophysics Data System (ADS)

Shaikh, M. M.; Nava, B.; Kashcheyev, A.

2017-01-01

Inverse Abel transform is the most common method to invert radio occultation (RO) data in the ionosphere and it is based on the assumption of the spherical symmetry for the electron density distribution in the vicinity of an occultation event. It is understood that this 'spherical symmetry hypothesis' could fail, above all, in the presence of strong horizontal electron density gradients. As a consequence, in some cases wrong electron density profiles could be obtained. In this work, in order to incorporate the knowledge of horizontal gradients, we have suggested an inversion technique based on the adaption of the empirical ionospheric model, NeQuick2, to RO-derived TEC. The method relies on the minimization of a cost function involving experimental and model-derived TEC data to determine NeQuick2 input parameters (effective local ionization parameters) at specific locations and times. These parameters are then used to obtain the electron density profile along the tangent point (TP) positions associated with the relevant RO event using NeQuick2. The main focus of our research has been laid on the mitigation of spherical symmetry effects from RO data inversion without using external data such as data from global ionospheric maps (GIM). By using RO data from Constellation Observing System for Meteorology Ionosphere and Climate (FORMOSAT-3/COSMIC) mission and manually scaled peak density data from a network of ionosondes along Asian and American longitudinal sectors, we have obtained a global improvement of 5% with 7% in Asian longitudinal sector (considering the data used in this work), in the retrieval of peak electron density (NmF2) with model-assisted inversion as compared to the Abel inversion. Mean errors of NmF2 in Asian longitudinal sector are calculated to be much higher compared to American sector.

An upper limit on Pluto's ionosphere from radio occultation measurements with New Horizons

NASA Astrophysics Data System (ADS)

Hinson, D. P.; Linscott, I. R.; Strobel, D. F.; Tyler, G. L.; Bird, M. K.; Pätzold, M.; Summers, M. E.; Stern, S. A.; Ennico, K.; Gladstone, G. R.; Olkin, C. B.; Weaver, H. A.; Woods, W. W.; Young, L. A.; New Horizons Science Team

2018-06-01

On 14 July 2015 New Horizons performed a radio occultation (RO) that sounded Pluto's neutral atmosphere and ionosphere. The solar zenith angle was 90.2° (sunset) at entry and 89.8° (sunrise) at exit. We examined the data for evidence of an ionosphere, using the same method of analysis as in a previous investigation of the neutral atmosphere (Hinson et al., 2017). No ionosphere was detected. The measurements are more accurate at occultation exit, where the 1-sigma sensitivity in integrated electron content (IEC) is 2.3 × 1011 cm-2. The corresponding upper bound on the peak electron density at the terminator is about 1000 cm-3. We constructed a model for the ionosphere and used it to guide the analysis and interpretation of the RO data. Owing to the large abundance of CH4 at ionospheric heights, the dominant ions are molecular and the electron densities are relatively small. The model predicts a peak IEC of 1.8 × 1011 cm-2 for an occultation at the terminator, slightly smaller than the threshold of detection by New Horizons.

Ionospheric Signatures in Radio Occultation Data

NASA Technical Reports Server (NTRS)

Mannucci, Anthony J.; Ao, Chi; Iijima, Byron A.; Kursinkski, E. Robert

2012-01-01

We can extend robustly the radio occultation data record by 6 years (+60%) by developing a singlefrequency processing method for GPS/MET data. We will produce a calibrated data set with profile-byprofile data characterization to determine robust upper bounds on ionospheric bias. Part of an effort to produce a calibrated RO data set addressing other key error sources such as upper boundary initialization. Planned: AIRS-GPS water vapor cross validation (water vapor climatology and trends).

Validation of COSMIC radio occultation electron density profiles by incoherent scatter radar data

NASA Astrophysics Data System (ADS)

Cherniak, Iurii; Zakharenkova, Irina

The COSMIC/FORMOSAT-3 is a joint US/Taiwan radio occultation mission consisting of six identical micro-satellites. Each microsatellite has a GPS Occultation Experiment payload to operate the ionospheric RO measurements. FS3/COSMIC data can make a positive impact on global ionosphere study providing essential information about height electron density distribu-tion. For correct using of the RO electron density profiles for geophysical analysis, modeling and other applications it is necessary to make validation of these data with electron density distributions obtained by another measurement techniques such as proven ground based facili-ties -ionosondes and IS radars. In fact as the ionosondes provide no direct information on the profile above the maximum electron density and the topside ionosonde profile is obtained by fitting a model to the peak electron density value, the COSMIC RO measurements can make an important contribution to the investigation of the topside part of the ionosphere. IS radars provide information about the whole electron density profile, so we can estimate the agreement of topside parts between two independent measurements. To validate the reliability of COS-MIC data we have used the ionospheric electron density profiles derived from IS radar located near Kharkiv, Ukraine (geographic coordinates: 49.6N, 36.3E, geomagnetic coordinates: 45.7N, 117.8E). The Kharkiv radar is a sole incoherent scatter facility on the middle latitudes of Eu-ropean region. The radar operates with 100-m zenith parabolic antenna at 158 MHz with peak transmitted power 2.0 MW. The Kharkiv IS radar is able to determine the heights-temporal distribution of ionosphere parameters in height range of 70-1500 km. At the ionosphere in-vestigation by incoherent scatter method there are directly measured the power spectrum (or autocorrelation function) of scattered signal. With using of rather complex procedure of the received signal processing it is possible to estimate the

Method of Modeling and Simulation of Shaped External Occulters

NASA Technical Reports Server (NTRS)

Lyon, Richard G. (Inventor); Clampin, Mark (Inventor); Petrone, Peter, III (Inventor)

2016-01-01

The present invention relates to modeling an external occulter including: providing at least one processor executing program code to implement a simulation system, the program code including: providing an external occulter having a plurality of petals, the occulter being coupled to a telescope; and propagating light from the occulter to a telescope aperture of the telescope by scalar Fresnel propagation, by: obtaining an incident field strength at a predetermined wavelength at an occulter surface; obtaining a field propagation from the occulter to the telescope aperture using a Fresnel integral; modeling a celestial object at differing field angles by shifting a location of a shadow cast by the occulter on the telescope aperture; calculating an intensity of the occulter shadow on the telescope aperture; and applying a telescope aperture mask to a field of the occulter shadow, and propagating the light to a focal plane of the telescope via FFT techniques.

Exploring earth's atmosphere with radio occultation: contributions to weather, climate and space weather

NASA Astrophysics Data System (ADS)

Anthes, R. A.

2011-01-01

The launch of the proof-of-concept mission GPS/MET in 1995 began a revolution in profiling earth's atmosphere through radio occultation (RO). GPS/MET; subsequent single-satellite missions CHAMP, SAC-C, GRACE, METOP-A, and TerraSAR-X; and the six-satellite constellation, FORMOSAT-3/COSMIC, have proven the theoretical capabilities of RO to provide accurate and precise profiles of electron density in the ionosphere and refractivity, containing information on temperature and water vapor, in the stratosphere and troposphere. This paper summarizes results from these RO missions and the applications of RO observations to atmospheric research and operational weather analysis and prediction.

Precipitation information from GNSS Polarimetric Radio Occultation observations

NASA Astrophysics Data System (ADS)

Padulles, R.; Cardellach, E.; Turk, J.; Tomás, S.; Ao, C. O.; de la Torre-Juárez, M.

2017-12-01

There is currently a gap in satellite observations of the moisture structure during heavy precipitation conditions, since infrared and microwave sounders cannot sense water vapor structure near the surface in the presence of intense precipitation. Conversely, Global Navigation Satellite System (GNSS) Radio Occultations (RO) can profile the moisture structure with high precision and vertical resolution, but cannot directly indicate the presence of precipitation. Polarimetric RO (PRO) measurements have been proposed as a method to characterize heavy rain in GNSS RO, by measuring the polarimetric differential phase delay induced by large size hydrometeors. The PRO concept will be tested from space for the first time on board the Spanish PAZ satellite, planned for launch by the end of 2017. Therefore, for the first time ever, GNSS RO measurements will be taken at two polarizations, to exploit the potential capabilities of polarimetric RO for detecting and quantifying heavy precipitation events. If the concept is proved, PAZ will mean a new application of the GNSS Radio-Occultation observations, by providing coincident thermodynamic and precipitation information with high vertical resolution within regions with thick clouds. Before the launch, a series of studies have been performed in order to assess the retrieval of precipitation information from the polarimetric observations. These studies have been based on coincident observations from the COSMIC / FORMOSAT-3 RO satellite constellation, and TRMM and GPM missions. This massive collocation exercise allowed us to build a series of Look Up Tables that relate probabilistically the precipitation intensity to the polarimetric observables. Such studies needed a previous characterization of the polarimetric observable, since it contains contributions from the ionosphere and the emitting and receiving systems. For this purpose, complete end-to-end simulations have been performed, where information from the ionospheric state

Study of sporadic E layers based on GPS radio occultation measurements and digisonde data over the Brazilian region

NASA Astrophysics Data System (ADS)

Resende, Laysa C. A.; Arras, Christina; Batista, Inez S.; Denardini, Clezio M.; Bertollotto, Thainá O.; Moro, Juliano

2018-04-01

This work presents new results about sporadic E-layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data. The RO profiles are used to study the Es layer occurrence as well as its intensity of the signal-to-noise ratio (SNR) of the 50 Hz GPS L1 signal. The methodology was applied to identify the Es layer on RO measurements over Cachoeira Paulista, a low-latitude station in the Brazilian region, in which the Es layer development is not driven tidal winds only as it is at middle latitudes. The coincident events were analyzed using the RO technique and ionosonde observations during the year 2014 to 2016. We used the electron density obtained using the blanketing frequency parameter (fbEs) and the Es layer height (h'Es) acquired from the ionograms to validate the satellite measurements. The comparative results show that the Es layer characteristics extracted from the RO measurements are in good agreement with the Es layer parameters from the digisonde.

GNSS Radio Occultation Excess Phase Processing with Integrated Uncertainty Estimation for Thermodynamic Cal/Val of Passive Atmospheric Sounders and Climate Science

NASA Astrophysics Data System (ADS)

Innerkofler, J.; Pock, C.; Kirchengast, G.; Schwaerz, M.; Jaeggi, A.; Andres, Y.; Marquardt, C.; Hunt, D.; Schreiner, W. S.; Schwarz, J.

2017-12-01

Global Navigation Satellite System (GNSS) radio occultation (RO) is a highly valuable satellite remote sensing technique for atmospheric and climate sciences, including calibration and validation (cal/val) of passive sounding instruments such as radiometers. It is providing accurate and precise measurements in the troposphere and stratosphere regions with global coverage, long-term stability, and virtually all-weather capability since 2001. For fully exploiting the potential of RO data as a cal/val reference and climate data record, uncertainties attributed to the data need to be assessed. Here we focus on the atmospheric excess phase data, based on the raw occultation tracking and orbit data, and its integrated uncertainty estimation within the new Reference Occultation Processing System (rOPS) developed at the WEGC. These excess phases correspond to integrated refractivity, proportional to pressure/temperature and water vapor, and are therefore highly valuable reference data for thermodynamic cal/val of passive (radiometric) sounder data. In order to enable high accuracy of the excess phase profiles, accurate orbit positions and velocities as well as clock estimates of the GNSS transmitter satellites and RO receiver satellites are determined using the Bernese and Napeos orbit determination software packages. We find orbit uncertainty estimates of about 5 cm (position) / 0.05 mm/s (velocity) for daily orbits for the MetOp, GRACE, and CHAMP RO missions, and decreased uncertainty estimates near 20 cm (position) / 0.2 mm/s (velocity) for the COSMIC RO mission. The strict evaluation and quality control of the position, velocity, and clock accuracies of the daily LEO and GNSS orbits assure smallest achievable uncertainties in the excess phase data. We compared the excess phase profiles from WEGC against profiles from EUMETSAT and UCAR. Results show good agreement in line with the estimated uncertainties, with millimetric differences in the upper stratosphere and

Improved planetary boundary layer retrievals using a combination of direct and reflected bending angles from radio occultations

NASA Astrophysics Data System (ADS)

Wang, K. N.; Ao, C. O.; de la Torre Juarez, M.

2017-12-01

As a remote sensing technique, Global Positioning System (GPS) radio occultation (RO) is a suitable method to observe lower troposphere due to its high vertical resolution and cloud-penetrating capability. However, super-refraction (SR), or ducting, caused by large refractivity gradients usually associated with the top of the planetary boundary layer, can violate the uniqueness condition necessary for the traditional inverse Abel transform. Consequently, the retrieved refractivity, which is the minimum profile among an infinite number of potential solutions corresponding to the same bending angle profile, will be negatively biased under ducting layers. Previous research has shown that optimal estimation techniques that combine low altitude RO retrievals and the collocated precipitable water (PW) estimates can effectively reduce the negative RO bias and enhance the data quality under the ducting layer (Wang et al, 2017). Here we propose an improvement that uses the reflected RO bending angle observation information as a source for refractivity constraints. The RO signal reflected from the Earth surface profile can be reconstructed by solely using GPS-RO data without requiring external information such as PW. The radio holographic (RH) method is adapted here to calculate the reflected RO bending angle, and the forward model simulation is implemented to validate this preliminary concept. Our results suggest that this new approach can distinguish between different refractivity profiles when ducting occurs and theoretically this should reduce the negative bias. In addition, It also improves the RO observation in lower troposphere by capturing the sharpness and height of the critical layer separating the free troposphere from the boundary layer.

Application of GPS radio occultation to the assessment of temperature profile retrievals from microwave and infrared sounders

NASA Astrophysics Data System (ADS)

Feltz, M.; Knuteson, R.; Ackerman, S.; Revercomb, H.

2014-05-01

Comparisons of satellite temperature profile products from GPS radio occultation (RO) and hyperspectral infrared (IR)/microwave (MW) sounders are made using a previously developed matchup technique. The profile matchup technique matches GPS RO and IR/MW sounder profiles temporally, within 1 h, and spatially, taking into account the unique RO profile geometry and theoretical spatial resolution by calculating a ray-path averaged sounder profile. The comparisons use the GPS RO dry temperature product. Sounder minus GPS RO differences are computed and used to calculate bias and RMS profile statistics, which are created for global and 30° latitude zones for selected time periods. These statistics are created from various combinations of temperature profile data from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) network, Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) instrument, and the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU), Infrared Atmospheric Sounding Interferometer (IASI)/AMSU, and Crosstrack Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) sounding systems. By overlaying combinations of these matchup statistics for similar time and space domains, comparisons of different sounders' products, sounder product versions, and GPS RO products can be made. The COSMIC GPS RO network has the spatial coverage, time continuity, and stability to provide a common reference for comparison of the sounder profile products. The results of this study demonstrate that GPS RO has potential to act as a common temperature reference and can help facilitate inter-comparison of sounding retrieval methods and also highlight differences among sensor product versions.

Application of GPS radio occultation to the assessment of temperature profile retrievals from microwave and infrared sounders

NASA Astrophysics Data System (ADS)

Feltz, M.; Knuteson, R.; Ackerman, S.; Revercomb, H.

2014-11-01

Comparisons of satellite temperature profile products from GPS radio occultation (RO) and hyperspectral infrared (IR)/microwave (MW) sounders are made using a previously developed matchup technique. The profile matchup technique matches GPS RO and IR/MW sounder profiles temporally, within 1 h, and spatially, taking into account the unique RO profile geometry and theoretical spatial resolution by calculating a ray-path averaged sounder profile. The comparisons use the GPS RO dry temperature product. Sounder minus GPS RO differences are computed and used to calculate bias and rms profile statistics, which are created for global and 30° latitude zones for selected time periods. These statistics are created from various combinations of temperature profile data from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) network, Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) instrument, and the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU), Infrared Atmospheric Sounding Interferometer (IASI)/AMSU, and Crosstrack Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) sounding systems. By overlaying combinations of these matchup statistics for similar time and space domains, comparisons of different sounders' products, sounder product versions, and GPS RO products can be made. The COSMIC GPS RO network has the spatial coverage, time continuity, and stability to provide a common reference for comparison of the sounder profile products. The results of this study demonstrate that GPS RO has potential to act as a common temperature reference and can help facilitate inter-comparison of sounding retrieval methods and also highlight differences among sensor product versions.

First results from stellar occultations in the "GAIA era"

NASA Astrophysics Data System (ADS)

Benedetti-Rossi, G.; Vieira-Martins, R.; Sicardy, B.

2017-09-01

Stellar occultation is a powerful technique to study distant solar system bodies. It allows high angular resolution of the occulting body from the analysis of a light curve acquired with high temporal resolution with uncertainties comparable as probes. In the "GAIA era", stellar occultations is now able to obtain even more impressive results such as the presence of atmosphere, rings and topographic features.

Observing atmospheric blocking with GPS radio occultation - one decade of measurements

NASA Astrophysics Data System (ADS)

Brunner, Lukas; Steiner, Andrea

2017-04-01

Atmospheric blocking has received a lot of attention in recent years due to its impact on mid-latitude circulation and subsequently on weather extremes such as cold and warm spells. So far blocking studies have been based mainly on re-analysis data or model output. However, it has been shown that blocking frequency exhibits considerable inter-model spread in current climate models. Here we use one decade (2006 to 2016) of satellite-based observations from GPS radio occultation (RO) to analyze blocking in RO data building on work by Brunner et al. (2016). Daily fields on a 2.5°×2.5° longitude-latitude grid are calculated by applying an adequate gridding strategy to the RO measurements. For blocking detection we use a standard blocking detection algorithm based on 500 hPa geopotential height (GPH) gradients. We investigate vertically resolved atmospheric variables such as GPH, temperature, and water vapor before, during, and after blocking events to increase process understanding. Moreover, utilizing the coverage of the RO data set, we investigate global blocking frequencies. The main blocking regions in the northern and southern hemisphere are identified and the (vertical) atmospheric structure linked to blocking events is compared. Finally, an inter-comparison of results from RO data to different re-analyses, such as ERA-Interim, MERRA 2, and JRA-55, is presented. Brunner, L., A. K. Steiner, B. Scherllin-Pirscher, and M. W. Jury (2016): Exploring atmospheric blocking with GPS radio occultation observations. Atmos. Chem. Phys., 16, 4593-4604, doi:10.5194/acp-16-4593-2016.

Feasibility of blocking detection in observations from radio occultation

NASA Astrophysics Data System (ADS)

Brunner, Lukas; Steiner, Andrea Karin; Scherllin-Pirscher, Barbara; Jury, Martin

2015-04-01

Blocking describes an atmospheric situation in which the climatological westerly flow at mid latitudes is weakened or reversed. This is caused by a persistent high pressure system which can be stationary for several days to weeks. In the Northern Hemisphere blocking preferably occurs over the Atlantic/European and the Pacific regions. In recent years blocking has been under close scientific investigation due to its effect on weather extremes, triggering heat waves in summer and cold spells in winter. So far, scientific literature mainly focused on the investigation of blocking in reanalysis and global climate model data sets. However, blocking is underestimated in most climate models due to small-scale processes involved in its evolution. For a detection of blocking, most commonly applied methods are based on the computation of meridional geopotential height gradients at the 500 hPa level. Therefore measurements with adequate vertical, horizontal, and temporal resolution and coverage are required. We use an observational data set based on Global Positioning System (GPS) Radio Occultation (RO) measurements fulfilling these requirements. RO is a relatively new, satellite based remote sensing technique, delivering profiles of atmospheric parameters such as geopotential height, pressure, and temperature. It is characterized by favorable properties like long-term stability, global coverage, and high vertical resolution. Our data set is based on the most recent WEGC RO retrieval. Here we report on a feasibility study for blocking detection and analysis in RO data for two exemplary blocking events: the blocking over Russia in summer 2010 and the blocking over Greenland in late winter 2013. For these two events about 700 RO measurements per day are available in the Northern Hemisphere. We will show that the measurement density and quality of RO observations are favorable for blocking analysis and can therefore contribute to blocking research.

Radio Occultation Experiments with Venus Express and Mars Express using the Planetary Radio Interferometry and Doppler Experiment (PRIDE) Technique

NASA Astrophysics Data System (ADS)

Bocanegra Bahamon, T.; Gurvits, L.; Molera Calves, G.; Cimo, G.; Duev, D.; Pogrebenko, S.; Dirkx, D.; Rosenblatt, P.

2017-12-01

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can be used to enhance multiple radio science experiments of planetary missions. By 'eavesdropping' on the spacecraft signal using radio telescopes from different VLBI networks around the world, the PRIDE technique provides precise open-loop Doppler and VLBI observables to able to reconstruct the spacecraft's orbit. The application of this technique for atmospheric studies has been assessed by observing ESA's Venus Express (VEX) and Mars Express (MEX) during multiple Venus and Mars occultation events between 2012 and 2014. From these observing sessions density, temperature and pressure profiles of Venus and Mars neutral atmosphere and ionosphere have been retrieved. We present an error propagation analysis where the uncertainties of the atmospheric properties measured with this technique have been derived. These activities serve as demonstration of the applicability of the PRIDE technique for radio occultation studies, and provides a benchmark against the traditional Doppler tracking provided by the NASA's DSN and ESA's Estrack networks for these same purposes, in the framework of the upcoming ESA JUICE mission to the Jovian system.

Earth Occultation Monitoring with the Fermi Gamma Ray Burst Monitor

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.

2014-01-01

Using the Gamma Ray Burst Monitor (GBM) on-board Fermi, we are monitoring the hard X-ray/soft gamma ray sky using the Earth occultation technique (EOT). Each time a source in our catalog is occulted by (or exits occultation by) the Earth, we measure its flux using the change in count rates due to the occultation. Currently we are using CTIME data with 8 energy channels spanning 8 keV to 1 MeV for the GBM NaI detectors for daily monitoring. Light curves, updated daily, are available on our website http://heastro.phys.lsu.edu/gbm. Our software is also capable of performing the Earth occultation monitoring using up to 128 energy bands, or any combination of those bands, using our 128-channel, 4-s CSPEC data. The GBM BGO detectors, sensitive from about 200 keV to 40 keV, can also be used with this technique. In our standard application of the EOT, we use a catalog of sources to drive the measurements. To ensure that our catalog is complete, our team has developed an Earth occultation imaging method. In this talk, I will describe both techniques and the current data products available. I will highlight recent and important results from the GBM EOT, including the current status of our observations of hard X-ray variations in the Crab Nebula.

A technique for routinely updating the ITU-R database using radio occultation electron density profiles

NASA Astrophysics Data System (ADS)

Brunini, Claudio; Azpilicueta, Francisco; Nava, Bruno

2013-09-01

Well credited and widely used ionospheric models, such as the International Reference Ionosphere or NeQuick, describe the variation of the electron density with height by means of a piecewise profile tied to the F2-peak parameters: the electron density,, and the height, . Accurate values of these parameters are crucial for retrieving reliable electron density estimations from those models. When direct measurements of these parameters are not available, the models compute the parameters using the so-called ITU-R database, which was established in the early 1960s. This paper presents a technique aimed at routinely updating the ITU-R database using radio occultation electron density profiles derived from GPS measurements gathered from low Earth orbit satellites. Before being used, these radio occultation profiles are validated by fitting to them an electron density model. A re-weighted Least Squares algorithm is used for down-weighting unreliable measurements (occasionally, entire profiles) and to retrieve and values—together with their error estimates—from the profiles. These values are used to monthly update the database, which consists of two sets of ITU-R-like coefficients that could easily be implemented in the IRI or NeQuick models. The technique was tested with radio occultation electron density profiles that are delivered to the community by the COSMIC/FORMOSAT-3 mission team. Tests were performed for solstices and equinoxes seasons in high and low-solar activity conditions. The global mean error of the resulting maps—estimated by the Least Squares technique—is between and elec/m for the F2-peak electron density (which is equivalent to 7 % of the value of the estimated parameter) and from 2.0 to 5.6 km for the height (2 %).

A Climate Benchmark of Upper Air Temperature Observations from GNSS Radio Occultation

NASA Astrophysics Data System (ADS)

Ao, C. O.; Mannucci, A. J.; Leroy, S. S.; Verkhoglyadova, O. P.

2017-12-01

GPS (Global Positioning System), or more generally Global Navigation Satellite System (GNSS), radio occultation (RO) is a remote sensing technique that produces highly accurate temperature in the upper troposphere and lower stratosphere across the globe with fine vertical resolution. Its fundamental measurement is the time delay of the microwave signal as it travels from a GNSS satellite to the receiver in low Earth orbit. With a relatively simple physical retrieval, the uncertainty in the derived temperature can be traced rigorously through the retrieval chain back to the raw measurements. The high absolute accuracy of RO allows these observations to be assimilated without bias correction in numerical weather prediction models and provides an anchor for assimilating other types of observations. The high accuracy, coupled with long-term stability, makes RO valuable in detecting decadal temperature trends. In this presentation, we will summarize the current state of RO observations and show temperature trends derived from 15 years of RO data in the upper troposphere and lower stratosphere. We will discuss our recent efforts in developing retrieval algorithms that are more tailored towards climate applications. Despite the relatively robust "self-calibrating" nature of RO observations, disparity in receiver hardware and software may introduce subtle differences that need to be carefully addressed. While the historic RO data record came from relatively homogeneous hardware based largely on NASA/JPL design (e.g., CHAMP and COSMIC), the future data will likely be comprised of a diverse set of observations from Europe, China, and various commercial data providers. In addition, the use of non-GPS navigation systems will become more prevalent. We will discuss the challenges involved in establishing a long-term RO climate data record from a suite of research and operational weather satellites with changes in instrumentation and coverage.

Occult spondyloarthritis in inflammatory bowel disease.

PubMed

Bandinelli, Francesca; Manetti, Mirko; Ibba-Manneschi, Lidia

2016-02-01

Spondyloarthritis (SpA) is a frequent extra-intestinal manifestation in patients with inflammatory bowel disease (IBD), although its real diffusion is commonly considered underestimated. Abnormalities in the microbioma and genetic predisposition have been implicated in the link between bowel and joint inflammation. Otherwise, up to date, pathogenetic mechanisms are still largely unknown and the exact influence of the bowel activity on rheumatic manifestations is not clearly explained. Due to evidence-based results of clinical studies, the interest on clinically asymptomatic SpA in IBD patients increased in the last few years. Actually, occult enthesitis and sacroiliitis are discovered in high percentages of IBD patients by different imaging techniques, mainly enthesis ultrasound (US) and sacroiliac joint X-ray examinations. Several diagnostic approaches and biomarkers have been proposed in an attempt to correctly classify and diagnose clinically occult joint manifestations and to define clusters of risk for patient screening, although definitive results are still lacking. The correct recognition of occult SpA in IBD requires an integrated multidisciplinary approach in order to identify common diagnostic and therapeutic strategies. The use of inexpensive and rapid imaging techniques, such as US and X-ray, should be routinely included in daily clinical practice and trials to correctly evaluate occult SpA, thus preventing future disability and worsening of quality of life in IBD patients.

Wave optics-based LEO-LEO radio occultation retrieval

NASA Astrophysics Data System (ADS)

Benzon, Hans-Henrik; Høeg, Per

2016-06-01

This paper describes the theory for performing retrieval of radio occultations that use probing frequencies in the XK and KM band. Normally, radio occultations use frequencies in the L band, and GPS satellites are used as the transmitting source, and the occultation signals are received by a GPS receiver on board a Low Earth Orbit (LEO) satellite. The technique is based on the Doppler shift imposed, by the atmosphere, on the signal emitted from the GPS satellite. Two LEO satellites are assumed in the occultations discussed in this paper, and the retrieval is also dependent on the decrease in the signal amplitude caused by atmospheric absorption. The radio wave transmitter is placed on one of these satellites, while the receiver is placed on the other LEO satellite. One of the drawbacks of normal GPS-based radio occultations is that external information is needed to calculate some of the atmospheric products such as the correct water vapor content in the atmosphere. These limitations can be overcome when a proper selected range of high-frequency waves are used to probe the atmosphere. Probing frequencies close to the absorption line of water vapor have been included, thus allowing the retrieval of the water vapor content. Selecting the correct probing frequencies would make it possible to retrieve other information such as the content of ozone. The retrieval is performed through a number of processing steps which are based on the Full Spectrum Inversion (FSI) technique. The retrieval chain is therefore a wave optics-based retrieval chain, and it is therefore possible to process measurements that include multipath. In this paper simulated LEO to LEO radio occultations based on five different frequencies are used. The five frequencies are placed in the XK or KM frequency band. This new wave optics-based retrieval chain is used on a number of examples, and the retrieved atmospheric parameters are compared to the parameters from a global European Centre for Medium

Evaluating the lower-tropospheric COSMIC GPS radio occultation sounding quality over the Arctic

NASA Astrophysics Data System (ADS)

Yu, Xiao; Xie, Feiqin; Ao, Chi O.

2018-04-01

Lower-tropospheric moisture and temperature measurements are crucial for understanding weather prediction and climate change. Global Positioning System radio occultation (GPS RO) has been demonstrated as a high-quality observation technique with high vertical resolution and sub-kelvin temperature precision from the upper troposphere to the stratosphere. In the tropical lower troposphere, particularly the lowest 2 km, the quality of RO retrievals is known to be degraded and is a topic of active research. However, it is not clear whether similar problems exist at high latitudes, particularly over the Arctic, which is characterized by smooth ocean surface and often negligible moisture in the atmosphere. In this study, 3-year (2008-2010) GPS RO soundings from COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) over the Arctic (65-90° N) show uniform spatial sampling with average penetration depth within 300 m above the ocean surface. Over 70 % of RO soundings penetrate deep into the lowest 300 m of the troposphere in all non-summer seasons. However, the fraction of such deeply penetrating profiles reduces to only about 50-60 % in summer, when near-surface moisture and its variation increase. Both structural and parametric uncertainties of GPS RO soundings were also analyzed. The structural uncertainty (due to different data processing approaches) is estimated to be within ˜ 0.07 % in refractivity, ˜ 0.72 K in temperature, and ˜ 0.05 g kg-1 in specific humidity below 10 km, which is derived by comparing RO retrievals from two independent data processing centers. The parametric uncertainty (internal uncertainty of RO sounding) is quantified by comparing GPS RO with near-coincident radiosonde and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim profiles. A systematic negative bias up to ˜ 1 % in refractivity below 2 km is only seen in the summer, which confirms the moisture impact on GPS RO quality.

Radio occultation measurements of Pluto's neutral atmosphere with New Horizons

NASA Astrophysics Data System (ADS)

Hinson, D. P.; Linscott, I. R.; Young, L. A.; Tyler, G. L.; Stern, S. A.; Beyer, R. A.; Bird, M. K.; Ennico, K.; Gladstone, G. R.; Olkin, C. B.; Pätzold, M.; Schenk, P. M.; Strobel, D. F.; Summers, M. E.; Weaver, H. A.; Woods, W. W.

2017-07-01

On 14 July 2015 New Horizons performed a radio occultation (RO) that sounded Pluto's atmosphere down to the surface. The sensitivity of the measurements was enhanced by a unique configuration of ground equipment and spacecraft instrumentation. Signals were transmitted simultaneously by four antennas of the NASA Deep Space Network, each radiating 20 kW at a wavelength of 4.2 cm. The polarization was right circular for one pair of signals and left circular for the other pair. New Horizons received the four signals and separated them by polarization for processing by two independent receivers, each referenced to a different ultra-stable oscillator. The two data streams were digitized, filtered, and stored on the spacecraft for later transmission to Earth. The results reported here are the first to utilize the complete set of observations. We calibrated each signal to remove effects not associated with Pluto's atmosphere, including the limb diffraction pattern. We then applied a specialized method of analysis to retrieve profiles of number density, pressure, and temperature from the combined phase measurements. Occultation entry sounded the atmosphere at sunset at 193.5°E, 17.0°S - on the southeast margin of an ice-filled basin known informally as Sputnik Planitia (SP); occultation exit occurred at sunrise at 15.7°E, 15.1°N - near the center of the Charon-facing hemisphere. Above 1215 km radius (∼25 km altitude) there is no discernible difference between the measurements at entry and exit, and the RO profiles are consistent with results derived from ground-based stellar occultation measurements. At lower altitudes the RO measurements reveal horizontal variations in atmospheric structure that had not been observed previously, and they are the first to reach the ground. The entry profile has a strong temperature inversion that ends 3.5 km above the surface, and the temperature in the cold boundary layer beneath the inversion is nearly constant, 38.9 ± 2.1 K, and

Comparison of COSMIC RO Data with European Digisondes and GPS TEC measurements

NASA Astrophysics Data System (ADS)

Zakharenkova, Irina; Krypiak-Gregorczyk, Anna; Shagimuratov, Irk; Krankowski, Andrzej; Lagovsky, Anatoly

FormoSat-3/COSMIC now provides unprecedented global coverage of GPS occultations mea-surements, each of which yields the ionosphere electron density information with high vertical resolution. However systematic validation work is still needed before using the powerful RO technique for sounding the ionosphere on a routine basis. In the given study electron density profiles retrieved from the Formosat-3/COSMIC RO measurements were compared with differ-ent kinds of ground-based observations. We used the ionospheric data recorded by European digisondes of DIAS network (Rome, Ebro, Arenosillo, Athens, Chilton, Pruhonice and Julius-ruh) for temporal interval of 2007-2009 and compare these ground measured data with the GPS COSMIC RO ionospheric profiles. It was revealed that in general the form of COSMIC profile in the bottom side is in a good agreement with ionosonde profiles, the heights of the peak density value are also good comparable. Special attention was focused to the question of the topside part of electron density profile. Practically for all analyzed cases there are observed the understated values of electron density in the topside part of the ionosonde profiles in compare with RO profiles. As the topside ionosonde profile is obtained by fitting a model to the peak electron density value, the COSMIC radio occultation measurements can make an important contribution to the investigation of the topside part of the ionosphere. In order to assess the ac-curacy of the COSMIC ionospheric electron density retrievals, coincidences of ionosonde data with COSMIC NmF2 values have been examined. NmF2 was calculated from the observed critical plasma frequency foF2 of the F2 layer. Values of foF2 have been scaled manually from ionograms for all considered time-location cases to avoid the evident risks related with using of the autoscaled data. The created scatter plots show a high degree of correlation between two independent estimates of NmF2. Also it was analyzed the

Testing for Occult Heartworm Infection

PubMed Central

Stogdale, L.

1984-01-01

Heartworm infection in dogs is endemic in southern Ontario but occurs only sporadically throughout the remainder of Canada. The disease may either be associated with microfilariae in the patient's blood, a patent infection, or it may be occult. This paper describes a case of occult dirofilariasis in a dog, with emphasis on the diagnosis. A patent infection could be missed if the clinician tests an insufficient amount of blood. He should perform multiple concentration tests using either the modified Knott's technique or a filtration method. Occult infections occur in prepatent or unisexual infections, when the worms become sterile following therapy, or when the host produces antibodies that result in the destruction of the microfilariae. The recent release of a kit which detects the presence of antibodies to the adult heartworms now enables veterinarians to make an accurate diagnosis in the vast majority of dogs. PMID:17422386

A Comprehensive Assessment of Radio Occultation Ionospheric Measurements at Mid-Latitudes

NASA Astrophysics Data System (ADS)

Keele, C.; Brum, C. G. M.; Rodrigues, F. S.; Aponte, N.; Sulzer, M. P.

2015-12-01

The GPS radio occultation (RO) has become a widely used technique for global measurements of the ionospheric electron density (Ne). To advance our understanding of the accuracy of the RO profiles at mid latitudes, we performed a comprehensive comparison of RO measurements made by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations of Ne profiles made by the Arecibo Observatory incoherent scatter radar (ISR). COSMIC is formed by six satellites in circular, 800 km altitude low-Earth orbit (LEO) at 72° inclination. The satellites orbit in their own plane, approximately 24° apart in ascending node. The satellites are equipped with dual-frequency GPS receivers capable of making measurements of the total electron content (TEC) along the signal path and, therefore, RO observations. The Arecibo ISR, located at(18.35°N, 66.75°W; ˜28.25°N dip latitude), operates at a frequency of 430 MHz with a maximum bandwidth of about 1 MHz. The large collecting area provided by the 300 m dish antenna combined with high peak power transmitters (2.0-2.5 MW) allows the radar to make accurate Ne measurements throughout the entire ionospheric F-region and topside heights. We analyzed 74 and 89 days of line feed and Gregorian data, respectively, collected between 2006 and 2014. There were 638 RO profiles measured within 10° of latitude and 20° of longitude from Arecibo Observatory and within ±10 minutes of the radar measurements. Preliminary analyses of the observations show patterns in the relationship between densities measured by the Arecibo ISR and densities estimated from the COSMIC ROs. We will present and discuss the behavior of the patterns. We will also present results of a numerical model representing the patterns and discuss the possibility of using this model to improve RO estimates of density profiles.

Observing Climate with GNSS Radio Occultation: Characterization and Mitigation of Systematic Errors

NASA Astrophysics Data System (ADS)

Foelsche, U.; Scherllin-Pirscher, B.; Danzer, J.; Ladstädter, F.; Schwarz, J.; Steiner, A. K.; Kirchengast, G.

2013-05-01

GNSS Radio Occultation (RO) data a very well suited for climate applications, since they do not require external calibration and only short-term measurement stability over the occultation event duration (1 - 2 min), which is provided by the atomic clocks onboard the GPS satellites. With this "self-calibration", it is possible to combine data from different sensors and different missions without need for inter-calibration and overlap (which is extremely hard to achieve for conventional satellite data). Using the same retrieval for all datasets we obtained monthly refractivity and temperature climate records from multiple radio occultation satellites, which are consistent within 0.05 % and 0.05 K in almost any case (taking global averages over the altitude range 10 km to 30 km). Longer-term average deviations are even smaller. Even though the RO record is still short, its high quality already allows to see statistically significant temperature trends in the lower stratosphere. The value of RO data for climate monitoring is therefore increasingly recognized by the scientific community, but there is also concern about potential residual systematic errors in RO climatologies, which might be common to data from all satellites. We started to look at different error sources, like the influence of the quality control and the high altitude initialization. We will focus on recent results regarding (apparent) constants used in the retrieval and systematic ionospheric errors. (1) All current RO retrievals use a "classic" set of (measured) constants, relating atmospheric microwave refractivity with atmospheric parameters. With the increasing quality of RO climatologies, errors in these constants are not negligible anymore. We show how these parameters can be related to more fundamental physical quantities (fundamental constants, the molecular/atomic polarizabilities of the constituents of air, and the dipole moment of water vapor). This approach also allows computing

Assimilation of GNSS radio occultation observations in GRAPES

NASA Astrophysics Data System (ADS)

Liu, Y.; Xue, J.

2014-07-01

This paper reviews the development of the global navigation satellite system (GNSS) radio occultation (RO) observations assimilation in the Global/Regional Assimilation and PrEdiction System (GRAPES) of China Meteorological Administration, including the choice of data to assimilate, the data quality control, the observation operator, the tuning of observation error, and the results of the observation impact experiments. The results indicate that RO data have a significantly positive effect on analysis and forecast at all ranges in GRAPES not only in the Southern Hemisphere where conventional observations are lacking but also in the Northern Hemisphere where data are rich. It is noted that a relatively simple assimilation and forecast system in which only the conventional and RO observation are assimilated still has analysis and forecast skill even after nine months integration, and the analysis difference between both hemispheres is gradually reduced with height when compared with NCEP (National Centers for Enviromental Prediction) analysis. Finally, as a result of the new onboard payload of the Chinese FengYun-3 (FY-3) satellites, the research status of the RO of FY-3 satellites is also presented.

All-Sky Earth Occultation Observations with the Fermi Gamma-Ray Burst Monitor

NASA Technical Reports Server (NTRS)

Wilson-Hodge, C. A.; Beklen, E.; Bhat, P. N.; Briggs, M.; Camero-Arranz, A.; Case, G.; Jenke, P.; Chaplin, V.; Cherry, M.; Connaughton, V.;

Assimilation of Radio Occultation Data From the Chinese Fengyun Meterological Satellite at GRAPES

NASA Astrophysics Data System (ADS)

LIU, Y.

2016-12-01

GNOS (GNSS Occultation Sounder) is a new radio occultation payload onboard the Chinese FY-3 series satellites, which probes the Earth's neutral atmosphere and the ionosphere. GNOS is capable of tracking the signals of both the Beidou (the Chinese navigation satellite system) and the GPS navigation satellite systems. The first FY-3C satellite with GNOS launch on 23 September 2013 successfully, and has more than 500 RO events daily, including approximately 400 GPS and 100 Beidou RO events. In this paper the data quality from FY3C GNOS, including GPS and Beidou radio accultation data, will be presented. The impact experiments of assimilating GNOS radio accultation refractivity profiles in GRAPES (Global and Regional Assimilation Prediction System) a new generation numerical model system of China Meteorological Administration, are also presented. Results show that the lowest probing height of 90% GNOS profile can reach 4KM away from the surface. The bias of GNOS refractivity profiles compared to reanalysis and radiosonde data is greater than those of COSMIC and GRAS, but after data quality control the standard deviation of GNOS refractivity is approximately 2%. The results of the GNOS assimilation experiments show that GNOS data can improve the analysis in the upper troposphere and lower stratosphere, particularly in the southern hemisphere and the ocean, which produce the neutral and positive impacts in GRAPES assimilation system. The combined impact of assimilating both GPS and Beidou GNOS radio occultation is greater than assimilating either instrument individually.

Polarimetric mountain based radio-occultation for rain detection: The ROHP-PAZ ground campaign

NASA Astrophysics Data System (ADS)

Padulles, Ramon; Cardellach, Estel; Tomas, Sergio; de la Torre, Manuel; Turk, Joe

2014-05-01

The Radio Occultation and Heavy Precipitation experiment aboard the PAZ Low Earth Orbiter (ROHP-PAZ) is a mission of opportunity: The Spanish Ministry of Science and Innovation (MICINN) approved in 2009 a proposal to include a polarimetric Global Navigation Satellite System (GNSS) Radio-Occultation (RO) payload on board of the Spanish Earth Observation satellite PAZ. This will be a new technique that has never been tested before, that aims to improve the knowledge of precipitation through simultaneous thermodynamic and vertical rain profiles. Prior to the launch of the satellite, expected for 2014, a ground experimental campaign is being conducted with the goal of starting the process of identifying and understanding all the factors that might affect the polarimetric RO observables. The campaign is being carried out at the top of Puig Sesolles, a 1667m peak in the Natural Park of Montseny (41º46'24 N, 2º26'17 E), 50 km N-NE from Barcelona, with clear views over the horizon to the South (East to West) direction, an area in which intense precipitation events tend to occur a few times per year. The campaign uses a ICE-CSIC/IEEC's GOLD-RTR open-loop receiver initially designed for collecting GNSS signals reflected off the sea surface. The receiver has been adjusted to track occulting GNSS radio-links. A double polarization (H and V) GNSS antenna has been designed and manufactured by the Polytechnic University of Barcelona (UPC) team for this particular ground-based experiment. The antenna is a phase-array made of 7 elements, each of them being a square patch built using a Rogers 4003 substrate, and symmetrically fed by four probes. It provides a pattern of 12.9 dB peak gain, 45 degrees half-power beam-width, and <-35 dB cross-polar isolation at the peak (better than -30 dB in the main lobe). The preliminary results show that not only precipitation, but also other factors are affecting the GNSS signal, wich means that the polarimetric signal is richer than expected

Electron density extrapolation above F2 peak by the linear Vary-Chap model supporting new Global Navigation Satellite Systems-LEO occultation missions

NASA Astrophysics Data System (ADS)

Hernández-Pajares, Manuel; Garcia-Fernández, Miquel; Rius, Antonio; Notarpietro, Riccardo; von Engeln, Axel; Olivares-Pulido, Germán.; Aragón-Àngel, Àngela; García-Rigo, Alberto

2017-08-01

The new radio-occultation (RO) instrument on board the future EUMETSAT Polar System-Second Generation (EPS-SG) satellites, flying at a height of 820 km, is primarily focusing on neutral atmospheric profiling. It will also provide an opportunity for RO ionospheric sounding, but only below impact heights of 500 km, in order to guarantee a full data gathering of the neutral part. This will leave a gap of 320 km, which impedes the application of the direct inversion techniques to retrieve the electron density profile. To overcome this challenge, we have looked for new ways (accurate and simple) of extrapolating the electron density (also applicable to other low-Earth orbiting, LEO, missions like CHAMP): a new Vary-Chap Extrapolation Technique (VCET). VCET is based on the scale height behavior, linearly dependent on the altitude above hmF2. This allows extrapolating the electron density profile for impact heights above its peak height (this is the case for EPS-SG), up to the satellite orbital height. VCET has been assessed with more than 3700 complete electron density profiles obtained in four representative scenarios of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) in the United States and the Formosa Satellite Mission 3 (FORMOSAT-3) in Taiwan, in solar maximum and minimum conditions, and geomagnetically disturbed conditions, by applying an updated Improved Abel Transform Inversion technique to dual-frequency GPS measurements. It is shown that VCET performs much better than other classical Chapman models, with 60% of occultations showing relative extrapolation errors below 20%, in contrast with conventional Chapman model extrapolation approaches with 10% or less of the profiles with relative error below 20%.

Layered Structures and Internal Waves in the Ionosphere and Atmosphere as Seen from GPS Occultation Data

NASA Astrophysics Data System (ADS)

Pavelyev, Alexander; Pavelyev, Alexander; Gubenko, Vladimir; Wickert, Jens; Liou, Yuei An

High-precision signals emitted by GPS satellites create favourable conditions both for monitoring of the atmosphere and ionosphere and for investigation of the radio wave propagation effects. Comparative theoretical and experimental analysis of the phase and amplitude variations of the GPS radio-holograms discovered a relationship which relates the refraction attenuation, the phase path excess acceleration and Doppler frequency via a classical dynamics equationtype. The advantages of the introduced relationship consist in: (1) a possibility to separate the layered structure and turbulence contributions to RO signal; (2) a possibility to estimate the absorption in the atmosphere by dividing the refraction attenuations found from amplitude and phase data; (3) a possibility to locate the tangent point in the atmosphere with accuracy in the distance from the standard position of of about ±100 km. The suggested method has a general importance because it may be applied for analysis in the trans-ionospheric satellite-to-Earth links. We showed also that the amplitude variations of GPS occultation signals are very sensitive sensors to the internal waves in the atmosphere. The sensitivity of the amplitude method is inversely proportional to the square of the vertical period of the internal wave, indicating high sensitivity of the amplitude data to the wave structures with small vertical periods in the 0.8-4 km interval. Combined analysis of the amplitude and phase of radio occultation signal allows one to determine with high level of reliability the main characteristics of the atmospheric and ionospheric layeres including the vertical distribution of the refractivity, electron density and their gradients. A possibility exists to measure important parameters of the internal waves: the intrinsic phase speed, the horizontal wind perturbations and, under some assumptions, the intrinsic frequency as functions of height in the atmosphere. A new technique has been applied to

Predicted occultation of Regulus

NASA Astrophysics Data System (ADS)

Waagen, Elizabeth O.

2014-03-01

The predicted occultation of Regulus (alpha Leo) by the magnitude-12.4 V asteroid (163) Erigone on 2014 March 20 at approximately 02:06 a.m. EDT (06:06 UT) is discussed. The occultation track includes Bermuda and northwest along a corridor stretching from the mid-Atlantic USA through Ontario, Canada. Unusual things about this occultation include the facts that the track includes major metropolitan areas such as New York City, and the star being occulted is one of the brightest in the Northern sky and is in a constellation pattern that makes it easy to find. The International Occultation Timing Association (IOTA) website (http://occultations.org/Regulus2014/) has comprehensive information about this predicted occultation and observing and reporting instructions, as well as links to other resources. In addition to witnessing a very rare event (Regulus is the brightest star ever to be predicted to be occulted from the USA), the possibilities for science include these three:! determining the shape of Erigone, detecting a possible companion of Erigone, and detecting the suspected white dwarf companion of Regulus. See the Alert Notice for details.

All-Sky Earth Occultation Observations with the Fermi Gamma Ray Burst Monitor

NASA Technical Reports Server (NTRS)

Wilson-Hodge, C. A.; Beklen, E.; Bhat, P. N.; Briggs, M.; Camero-Arranz, A.; Case, G.; Chaplin, V.; Cherry, M.; Connaughton, V.; Finger, M.;

Using GPS radio occultations to infer the water vapor feedback

NASA Astrophysics Data System (ADS)

Vergados, Panagiotis; Mannucci, Anthony J.; Ao, Chi O.; Fetzer, Eric J.

2016-11-01

The air refractive index at L-band frequencies depends on the air's water vapor content and density. Exploiting this relationship, we derive for the first time a theoretical model to infer the specific humidity response to surface temperature variations, dq/dTs, given knowledge of how the air refractive index and temperature vary with surface temperature. We validate this model by using 1.2-1.6 GHz Global Positioning System Radio Occultation (GPS RO) observations from 2007 to 2010 at 250 hPa, where the water vapor feedback on surface warming is strongest. The dq/dTs estimation from GPS RO observations shows excellent agreement with previously published results and the responses estimated by using the Atmospheric Infrared Sounder and the NASA's Modern-Era Retrospective Analysis for Research and Applications data sets. Because of their high sensitivity to fractional changes in water vapor, current and future GPS RO observations show great promise in monitoring climate feedback and their trends.

Deep shadow occulter

NASA Technical Reports Server (NTRS)

Cash, Webster (Inventor)

2010-01-01

Methods and apparatus are disclosed for occulting light. The occulter shape suppresses diffraction at any given size or angle and is practical to build because it can be made binary to avoid scatter. Binary structures may be fully opaque or fully transmitting at specific points. The diffraction suppression is spectrally broad so that it may be used with incoherent white light. An occulter may also include substantially opaque inner portion and an at least partially transparent outer portion. Such occulters may be used on the ground to create a deep shadow in a short distance, or may be used in space to suppress starlight and reveal exoplanets.

Possible occultation by Pluto from US East Coast

NASA Astrophysics Data System (ADS)

Waagen, Elizabeth O.

2012-06-01

We have been asked to help disseminate the news of a possible occultation by Pluto visible to observers on the US East coast. Although the AAVSO does not ordinarily issue announcements of upcoming occultations, in this case the object is Pluto and the NASA New Horizons mission (http://www.nasa.gov/mission_pages/newhorizons/main/index.html) will be visiting Pluto in 2015. The information below has been supplied by Dr. Leslie Young (Southwest Research Institute), who is coordinating this observing campaign on Pluto. Dr. Young is also Deputy Project Scientist for the New Horizons mission. ALERT: Possible Pluto occultation Wednesday night (2012/06/14 03:28 UT) from US East coast. CONTACT: Leslie Young (layoung@boulder.swri.edu; work: 303-546-6057; skype: drpluto). Also see our planning pages in progress at http://wiki.boulder.swri.edu/mediawiki/index.php/2012-06-14_Pluto_occultation. Pluto's thin, nitrogen atmosphere is in vapor-pressure equilibrium with the surface ice, and changes seasonally. We've seen it double since 1988, and now we measure its pressure once or twice a year. The technique we use is stellar occultation, when a star passes behind Pluto's atmosphere. The atmosphere defocuses the starlight. By the timing of the fading of the star, we measure the pressure and temperature in Pluto's atmosphere at ~10 km resolution. MORE INFORMATION: See http://wiki.boulder.swri.edu/mediawiki/index.php/2012-06-14_Pluto_occultation.

PAPR reduction and receiver sensitivity improvement in 16QAM-OFDM RoF system using DMT modulation and BTN-PS technique

NASA Astrophysics Data System (ADS)

Shao, Yufeng

2016-03-01

In this letter, we present the generation, the peak-to average power ratio (PAPR) reduction, the heterodyne detection, the self-mixing reception, and the transmission performance evaluation of 16QAM-OFDM signals in 60 GHz radio over fiber (RoF) system using Discrete multitone (DMT) modulation and Better Than Nyquist pulse shaping (BTN-PS) technique. DMT modulation is introduced in the RoF system, in-phase and quadrature (IQ) will not be required using BTN-PS method, and the computation complexity is much lower than other published techniques for reduced PAPR in the RoF system. In the experiment, 5 Gb/s 16QAM-OFDM downlink signals are transmitted over 42 km SMF-28 and a 0.4 m wireless channel. The experimental results show that the receiver sensitivity is effectively enhanced using this method. Therefore, the introduced BTN-PS technique and its application is a competitive scheme for reducing PAPR, and enhancing the receiver sensitivity in future RoF system.

Uranus occults SAO158687. [stellar occultation and planetary parametric observation

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Veverka, J.; Millis, R. L.

1977-01-01

Experience gained in obtaining atmospheric parameters, oblatenesses, and diameters of Jupiter and Mars from recent stellar occultations by these planets is used to predict what can be learned from the March 1977 occultation of the star SAO158687 by Uranus. The spectra of this star and Uranus are compared to indicate the relative instrument intensities of the two objects, the four passbands where the relative intensities are most nearly equal are listed, and expected photon fluxes from the star are computed on the assumption that it has UBVRI colors appropriate for a K5 main-sequence object. It is shown that low photon noise errors can be achieved by choosing appropriate passbands for observation, and the rms error expected for the Uranus temperature profiles obtained from the occultation light curves is calculated. It is suggested that observers of this occultation should record their data digitally for optimum time resolution.

The Occult Today: Why?

ERIC Educational Resources Information Center

Kessler, Gary E.

1975-01-01

Author offered some reflections on the "why" of the contemporary interest in the occult. He attempted to convince the reader that, if he or she has been surprised by the recent rise of occultism, sober reflection will dispell some fears and, perhaps, even convince him or her that occultism is not merely superstition. (Author/RK)

GNSS Polarimetric Radio Occultations: Thermodynamical Structure of pecipitating clouds

NASA Astrophysics Data System (ADS)

De La Torre Juarez, M.; Padulles, R.; Cardellach, E.; Turk, F. J.; Tomás, S.; Ao, C. O.

2016-12-01

Recent analysis of changes in the hydrological sensitivity during a recent weakening of transient warming show that the representation of the processes linking the condensation of water vapor and the growth and invigoration of convective precipitation produce the greatest disparities between cloud resolving models and current observations of convective cloud systems. The temperature and moisture structure of a cloud environment is the main control on the thermodynamical processes leading to the development of precipitation. The surrounding environmental state acts as the broader sink and source for moisture exchange between clouds and their surroundings. As precipitation develops, water vapor condensation leads to an evolving 3D temperature and moisture structure in and near clouds different from the larger scale structure or the clear-sky environment. Yet there is a gap in existing space-based observations since conventional IR and microwave sounding data are degraded in the presence of clouds and precipitation. GNSS radio occultations (RO) are a low-cost approach to sounding the global atmosphere with high precision, accuracy and vertical resolution inside clouds and across land-ocean boundaries. GNSS provides reliable, sustained signal sources. While current RO provide no direct information on the associated precipitation state, a recently studied concept of Polarimetric RO (PRO) can characterize the moist thermodynamics within precipitating systems. Since precipitation-sized hydrometeors are non-spherically shaped, precipitation induces a cross-polarized component during propagation through clouds, recorded by a dual-channel RO receiver as a differential phase shift. Theoretical analysis performed using coincident TRMM Precipitation Radar and COSMIC observations shows that the polarimetric phase shift is sensitive to the path-integrated rain rate. Based on the expected signal-to-noise ratio (SNR) of simulated PRO measurements, the precision of the differential

Estimation and evaluation of COSMIC radio occultation excess phase using undifferenced measurements

NASA Astrophysics Data System (ADS)

Xia, Pengfei; Ye, Shirong; Jiang, Kecai; Chen, Dezhong

2017-05-01

In the GPS radio occultation technique, the atmospheric excess phase (AEP) can be used to derive the refractivity, which is an important quantity in numerical weather prediction. The AEP is conventionally estimated based on GPS double-difference or single-difference techniques. These two techniques, however, rely on the reference data in the data processing, increasing the complexity of computation. In this study, an undifferenced (ND) processing strategy is proposed to estimate the AEP. To begin with, we use PANDA (Positioning and Navigation Data Analyst) software to perform the precise orbit determination (POD) for the purpose of acquiring the position and velocity of the mass centre of the COSMIC (The Constellation Observing System for Meteorology, Ionosphere and Climate) satellites and the corresponding receiver clock offset. The bending angles, refractivity and dry temperature profiles are derived from the estimated AEP using Radio Occultation Processing Package (ROPP) software. The ND method is validated by the COSMIC products in typical rising and setting occultation events. Results indicate that rms (root mean square) errors of relative refractivity differences between undifferenced and atmospheric profiles (atmPrf) provided by UCAR/CDAAC (University Corporation for Atmospheric Research/COSMIC Data Analysis and Archive Centre) are better than 4 and 3 % in rising and setting occultation events respectively. In addition, we also compare the relative refractivity bias between ND-derived methods and atmPrf profiles of globally distributed 200 COSMIC occultation events on 12 December 2013. The statistical results indicate that the average rms relative refractivity deviation between ND-derived and COSMIC profiles is better than 2 % in the rising occultation event and better than 1.7 % in the setting occultation event. Moreover, the observed COSMIC refractivity profiles from ND processing strategy are further validated using European Centre for Medium

Using the EXIST Active Shields for Earth Occultation Observations of X-Ray Sources

NASA Technical Reports Server (NTRS)

Wilson, Colleen A.; Fishman, Gerald; Hong, Jae-Sub; Gridlay, Jonathan; Krawczynski, Henric

2005-01-01

The EXIST active shields, now being planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors; and they will have a good geometry on the spacecraft for viewing both the leading and training Earth's limb for occultation observations. These occultation observations will complement the imaging observations of EXIST and can extend them to higher energies. Earth occultatio observations of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for this method. With BATSE, a catalog of 179 X-ray sources was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5-sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (galactic and extragalactic). This poster will describe the Earth occultation technique, summarize the BATSE occultation observations, and compare the basic observational parameters of the occultation detector elements of BATSE and EXIST.

Occultation studies of the Solar System

NASA Technical Reports Server (NTRS)

Millis, Robert L.

1987-01-01

The planetary occultation program began at Lowell Observatory in 1973 with a worldwide campaign to observe mutual occultations and eclipses of the Galilean Satellites. Then the temperature profile of the Martian atmosphere was measured from data taken during the occultation of epsilon Geminorum, the Rings of Uranus were discovered as they occulted SAO 158687, and the dimensions of Pallas were measured when that minor planet occulted SAO 85009. In 1979 the present grant was initiated, providing funds for portable photometric instrumentation used to observe occultations by asteroids as well as by Uranus and Neptune. Software for predicting occultations of catalog stars by asteroids, planets, and comets was written in 1983. Lowell currently provides most of the available predictions for asteroid occultations. Realizing in 1983 that the lack of a high-quality astrometric telescope dedicated to occultation work was limiting progress, an 18-inch, F/8 lens was acquired and adapted to an existing mounting at Lowell. Although acquisition of the lens and implementation of the new telescope has been accomplished primarily with non-grant funds, the instrument makes a major contribution to occultation research.

New Occultation Systems and the 2005 July 11 Charon Occultation

NASA Astrophysics Data System (ADS)

Young, L. A.; French, R. G.; Gregory, B.; Olkin, C. B.; Ruhland, C.; Shoemaker, K.; Young, E. F.

2005-08-01

Charon's density is an important input to models of its formation and internal structure. Estimates range from 1.59 to 1.83 g/cm3 (Olkin et al. 2003. Icarus 164, 254), with Charon's radius as the main source of uncertainty. Reported values of Charon's radius from mutual events range from 593±13 (Buie et al. 1992, Icarus 97, 211) to 621±21 km (Young & Binzel 1994, Icarus 108), while an occultation observed from a single site gives a lower limit on the radius of 601.5 km (Walker 1980 MNRAS 192, 47; Elliot & Young 1991, Icarus 89, 244). On 2005 July 11 UT (following this abstract submission date), Charon is predicted to occult the star C313.2. If successful, this event will be the first Charon occultation observed since 1980, and the first giving multiple chords across Charon's disk. This event is expected to measure Charon's radius to 1 km. Our team is observing from three telescopes in Chile, the 4.0-m Blanco and the 0.9-m telescopes at Cerro Tololo and the 4.2-m SOAR telescope at Cerro Pachon. At SOAR, we will be using the camera from our new PHOT systems (Portable High-speed Occultation Telescopes). The PHOT camera is a Princeton Instrument MicroMAX:512BFT from Roper Scientific, a 512×512 frame-transfer CCD with a readnoise of only 3 electrons at the 100 kHz digitization rate. The camera's exposures are triggered by a custom built, compact, stand-alone GPS-based pulse-train generator. A PHOT camera and pulse-train generator were used to observe the occultation of 2MASS 1275723153 by Pluto on 2005 June 15 UT from Sommers-Bausch Observatory in Boulder Colorado; preliminary analysis shows this was at best a grazing occultation from this site and a successful engineering run for the July 11 Charon occultation. The work was supported, in part, by NSF AST-0321338 (EFY) and NASA NNG-05GF05G (LAY).

Evaluating tropospheric humidity from GPS radio occultation, radiosonde, and AIRS from high-resolution time series

NASA Astrophysics Data System (ADS)

Rieckh, Therese; Anthes, Richard; Randel, William; Ho, Shu-Peng; Foelsche, Ulrich

2018-05-01

While water vapor is the most important tropospheric greenhouse gas, it is also highly variable in both space and time, and water vapor concentrations range over 3 orders of magnitude in the troposphere. These properties challenge all observing systems to accurately measure and resolve the vertical structure and variability of tropospheric humidity. In this study we characterize the humidity measurements of various observing techniques, including four separate Global Positioning System (GPS) radio occultation (RO) humidity retrievals (University Corporation for Atmospheric Research (UCAR) direct, UCAR one-dimensional variational retrieval (1D-Var), Wegener Center for Climate and Global Change (WEGC) 1D-Var, Jet Propulsion Laboratory (JPL) direct), radiosonde, and Atmospheric Infrared Sounder (AIRS) data. Furthermore, we evaluate how well the ERA-Interim reanalysis and NCEP Global Forecast System (GFS) model perform in analyzing water vapor at different levels. To investigate detailed vertical structure, we analyzed time-height cross sections over four radiosonde stations in the tropical and subtropical western Pacific for the year 2007. We found that the accuracy of RO humidity is comparable to or better than both radiosonde and AIRS humidity over 800 to 400 hPa, as well as below 800 hPa if super-refraction is absent. The various RO retrievals of specific humidity agree within 20 % in the 1000-400 hPa layer, and differences are most pronounced above 600 hPa.

The Pinhole/Occulter Facility

NASA Technical Reports Server (NTRS)

Tandberg-Hanssen, E. A. (Editor); Hudson, H. S. (Editor); Dabbs, J. R. (Editor); Baity, W. A. (Editor)

1983-01-01

Scientific objectives and requirements are discussed for solar X-ray observations, coronagraph observations, studies of coronal particle acceleration, and cosmic X-ray observations. Improved sensitivity and resolution can be provided for these studies using the pinhole/occulter facility which consists of a self-deployed boom of 50 m length separating an occulter plane from a detector plane. The X-ray detectors and coronagraphic optics mounted on the detector plane are analogous to the focal plane instrumentation of an ordinary telescope except that they use the occulter only for providing a shadow pattern. The occulter plane is passive and has no electrical interface with the rest of the facility.

Measurement of stellar occultations

NASA Astrophysics Data System (ADS)

Eberle, Andreas

2008-09-01

Whenever an asteroid occults a star, we have the opportunity to study that asteroid in great detail. As frequently shown in the past, amateur astronomers1 have the necessary equipment to measure such events successfully2. Combined with the dense net of amateur observatories and online coordination tools3 for movable stations, they can create fine grids to detect even small bodies. The analysis of these events gives us the possibility to receive high precision astrometry data, to determine the asteroids size and shape (and therefore its albedo), and even to collect information on the star itself.4 While usually a set of several light curves is required to do so, a single recording5 of (10734) Wieck's occultation of HIP 22157 on 2008 Feb 08 was sufficient to retrieve the necessary data6. 1 Observation campaigns are organized by the International Occultation Timing Association (IOTA), http://www.iota-es.de/ 2 for results see e.g. euraster.net by E. Frappa, http://www.euraster.net/ 3 Occult Watcher by H. Pavlov, http://www.hristopavlov.net/OccultWatcher/OccultWatcher.html 4 see K. Miyashita's analysis of the observation of the occultation of TYC 1886-01206-1 by Kalliope and Linus, http://www005.upp.so-net.ne.jp/k miyash/occ02/kalliope/doublestar en.html 5 recording obtained by H. Michels, MPC Station Code 240 6 using Limovie by K. Miyashita

Stellar Occultation Studies of Pluto, Triton, Charon, and Chiron

NASA Technical Reports Server (NTRS)

Elliot, James L.

2002-01-01

Bodies inhabiting the outer solar system are of interest because, due to the colder conditions, they exhibit unique physical processes. Also, some of the lessons learned from them can be applied to understanding what occurred in the outer solar system during its formation and early evolution. The thin atmospheres of Pluto and Triton have structure that is not yet understood, and they have been predicted to undergo cataclysmic seasonal changes. Charon may have an atmosphere - we don't know. Chiron exhibits cometary activity so far from the sun (much further than most comets), so that H2O sublimation cannot be the driving mechanism. Probing these bodies from Earth with a spatial resolution of a few kilometers can be accomplished only with the stellar occultation technique. In this program we find and predict stellar occultation events by small outer-solar system bodies and then attempt observations of the ones that can potentially answer interesting questions. We also develop new methods of data analysis for occultations and secure other observations that are necessary for interpretation of the occultation data.

Orbit dynamics and geographical coverage capabilities of satellite-based solar occultation experiments for global monitoring of stratospheric constituents

NASA Technical Reports Server (NTRS)

Brooks, D. R.

1980-01-01

Orbit dynamics of the solar occultation technique for satellite measurements of the Earth's atmosphere are described. A one-year mission is simulated and the orbit and mission design implications are discussed in detail. Geographical coverage capabilities are examined parametrically for a range of orbit conditions. The hypothetical mission is used to produce a simulated one-year data base of solar occultation measurements; each occultation event is assumed to produce a single number, or 'measurement' and some statistical properties of the data set are examined. A simple model is fitted to the data to demonstrate a procedure for examining global distributions of atmospheric constitutents with the solar occultation technique.

Integrating uncertainty propagation in GNSS radio occultation retrieval: from excess phase to atmospheric bending angle profiles

NASA Astrophysics Data System (ADS)

Schwarz, Jakob; Kirchengast, Gottfried; Schwaerz, Marc

2018-05-01

Global Navigation Satellite System (GNSS) radio occultation (RO) observations are highly accurate, long-term stable data sets and are globally available as a continuous record from 2001. Essential climate variables for the thermodynamic state of the free atmosphere - such as pressure, temperature, and tropospheric water vapor profiles (involving background information) - can be derived from these records, which therefore have the potential to serve as climate benchmark data. However, to exploit this potential, atmospheric profile retrievals need to be very accurate and the remaining uncertainties quantified and traced throughout the retrieval chain from raw observations to essential climate variables. The new Reference Occultation Processing System (rOPS) at the Wegener Center aims to deliver such an accurate RO retrieval chain with integrated uncertainty propagation. Here we introduce and demonstrate the algorithms implemented in the rOPS for uncertainty propagation from excess phase to atmospheric bending angle profiles, for estimated systematic and random uncertainties, including vertical error correlations and resolution estimates. We estimated systematic uncertainty profiles with the same operators as used for the basic state profiles retrieval. The random uncertainty is traced through covariance propagation and validated using Monte Carlo ensemble methods. The algorithm performance is demonstrated using test day ensembles of simulated data as well as real RO event data from the satellite missions CHAllenging Minisatellite Payload (CHAMP); Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and Meteorological Operational Satellite A (MetOp). The results of the Monte Carlo validation show that our covariance propagation delivers correct uncertainty quantification from excess phase to bending angle profiles. The results from the real RO event ensembles demonstrate that the new uncertainty estimation chain performs robustly. Together

Global morphology of ionospheric F-layer scintillations using FS3/COSMIC GPS radio occultation data

NASA Astrophysics Data System (ADS)

Tsai, Lung-Chih; Su, Shin-Yi

2016-07-01

The FormoSat-3/ Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) has been proven a successful mission on profiling and modeling of ionospheric electron density by the radio occultation (RO) technique. In this study we report FS3/COSMIC limb-viewing observations of the GPS L-band scintillation since mid 2006 and propose to study F-layer irregularity morphology. Generally the FS3/COSMIC has performed >1000 ionospheric RO observations per day. Most of these observations can provide limb-viewing profiles of S4 scintillation index at dual L-band frequencies. There are a few percentage of FS3/COSMIC RO observations having >0.08 S4 values on average. However, seven identified areas at Central Pacific Area (-20∘~ 20∘dip latitude, 160∘E~130∘W), South American Area (-20∘~ 20∘dip latitude, 100∘W~30∘W), African Area (-20∘~ 20∘dip latitude, 30∘W~50∘E), European Area (30∘~55∘N, 0∘~55∘E), Japan See Area (35∘~55∘N, 120∘~150∘E), Arctic Area (> 65∘dip latitude), and Antarctic Area (< -65∘dip latitude) have been designated to have much higher percentage of strong L-band RO scintillation. During these years in most of the last sunspot cycle from mid 2006 to end 2014 the climatology of scintillations, namely, its variations with each identified area, season, local time, magnetic activity and solar activity have been documented.

Spherical Occulter Coronagraph Cubesat

NASA Technical Reports Server (NTRS)

Davila, Joseph M. (Inventor); Rabin, Douglas M. (Inventor); Reginald, Nelson (Inventor); Gong, Qian (Inventor); Shah, Neerav (Inventor); Chamberlin, Phillip C. (Inventor)

2018-01-01

The present invention relates to a space-based instrument which provides continuous coronal electron temperature and velocity images, for a predetermined period of time, thereby improving the understanding of coronal evolution and how the solar wind and Coronal Mass Ejection transients evolve from the low solar atmosphere through the heliosphere for an entire solar rotation. Specifically, the present invention relates to using a 6U spherical occulter coronagraph CubeSat, and a relative navigational system (RNS) that controls the position of the spacecraft relative to the occulting sphere. The present invention innovatively deploys a free-flying spherical occulter, and after deployment, the actively controlled CubeSat will provide an inertial formation flying with the spherical occulter and Sun.

Diagnostic accuracy of oblique chest radiograph for occult pneumothorax: comparison with ultrasonography.

PubMed

Matsumoto, Shokei; Sekine, Kazuhiko; Funabiki, Tomohiro; Orita, Tomohiko; Shimizu, Masayuki; Hayashida, Kei; Kazamaki, Taku; Suzuki, Tatsuya; Kishikawa, Masanobu; Yamazaki, Motoyasu; Kitano, Mitsuhide

2016-01-01

An occult pneumothorax is a pneumothorax that is not seen on a supine chest X-ray but is detected by computed tomography scanning. However, critical patients are difficult to transport to the computed tomography suite. We previously reported a method to detect occult pneumothorax using oblique chest radiography (OXR). Several authors have also reported that ultrasonography is an effective technique for detecting occult pneumothorax. The aim of this study was to evaluate the usefulness of OXR in the diagnosis of the occult pneumothorax and to compare OXR with ultrasonography. All consecutive blunt chest trauma patients with clinically suspected pneumothorax on arrival at the emergency department were prospectively included at our tertiary-care center. The patients underwent OXR and ultrasonography, and underwent computed tomography scans as the gold standard. Occult pneumothorax size on computed tomography was classified as minuscule, anterior, or anterolateral. One hundred and fifty-nine patients were enrolled. Of the 70 occult pneumothoraces found in the 318 thoraces, 19 were minuscule, 32 were anterior, and 19 were anterolateral. The sensitivity and specificity of OXR for detecting occult pneumothorax was 61.4 % and 99.2 %, respectively. The sensitivity and specificity of lung ultrasonography was 62.9 % and 98.8 %, respectively. Among 27 occult pneumothoraces that could not be detected by OXR, 16 were minuscule and 21 could be conservatively managed without thoracostomy. OXR appears to be as good method as lung ultrasonography in the detection of large occult pneumothorax. In trauma patients who are difficult to transfer to computed tomography scan, OXR may be effective at detecting occult pneumothorax with a risk of progression.

Sampling the Vertical Moisture Structure of an Atmospheric River Event Using Airborne GPS Radio Occultation Profiling

NASA Astrophysics Data System (ADS)

Haase, J. S.; Malloy, K.; Murphy, B.; Sussman, J.; Zhang, W.

2015-12-01

Atmospheric rivers (ARs) are of high concern in California, bringing significant rain to the region over extended time periods of up to 5 days, potentially causing floods, and more importantly, contributing to the Sierra snowpack that provides much of the regional water resources. The CalWater project focuses on predicting the variability of the West Coast water supply, including improving AR forecasting. Unfortunately, data collection over the ocean remains a challenge and impacts forecasting accuracy. One novel technique to address this issue includes airborne GPS radio occultation (ARO), using broadcast GPS signals from space to measure the signal ray path bending angle and refractivity to retrieve vertical water vapor profiles. The Global Navigation Satellite System Instrument System for Multistatic and Occultation Sensing (GISMOS) system was developed for this purpose for recording and processing high-sample rate (10MHz) signals in the lower troposphere. Previous studies (Murphy et al, 2014) have shown promising results in acquiring airborne GPS RO data, comparing it to dropsondes and numerical weather models. CalWater launched a field campaign in the beginning of 2015 which included testing GISMOS ARO on the NOAA GIV aircraft for AR data acquisition, flying into the February 6th AR event that brought up to 35 cm of rain to central California. This case study will compare airborne GPS RO refractivity profiles to the NCEP-NCAR final reanalysis model and dropsonde profiles. We will show the data distribution and explain the sampling characteristics, providing high resolution vertical information to the sides of the aircraft in a manner complementary to dropsondes beneath the flight track. We will show how this method can provide additional reliable data during the development of AR storms.

Technical Note: A Time-Dependent I(sub 0) Correction for Solar Occultation Instruments

NASA Technical Reports Server (NTRS)

Burton, Sharon P.; Thomason, Larry W.; Zawodny, Joseph M.

2009-01-01

Solar occultation has proven to be a reliable technique for the measurement of atmospheric constituents in the stratosphere. NASA's Stratospheric Aerosol and Gas Experiments (SAGE, SAGE II, and SAGE III) together have provided over 25 years of quality solar occultation data, a data record which has been an important resource for the scientific exploration of atmospheric composition and climate change. Herein, we describe an improvement to the processing of SAGE data that corrects for a previously uncorrected short-term timedependence in the calibration function. The variability relates to the apparent rotation of the scanning track with respect to the face of the sun due to the motion of the satellite. Correcting for this effect results in a decrease in the measurement noise in the Level 1 line-of-sight optical depth measurements of approximately 40% in the middle and upper stratospheric SAGE II and III where it has been applied. The technique is potentially useful for any scanning solar occultation instrument, and suggests further improvement for future occultation measurements if a full disk imaging system can be included.

[Clinical assessment of occult infections in children].

PubMed

Sporisević, L; Bajraktarević, A; Begić, Z

2000-01-01

Children's occult infections are characterised presenting pathogenic bacteries in blood of children in age 3 to 36 months, but they are good general aspect and orderly immunologic status and they don't have signs of focal infection. Manifestation of occult infections determined: age of child, increasing bodies temperature, testsphysical observance and clinical-biochemistry tests. Prevalence of manifestation occult infections is 3-8%, but they manifest ni a form occult bacteremia, occult pneumonia nad occult urinary infection. Methodic, systematic admission and adequate clinical-biochemical monitoring, we minimise sequeles of occult infections. Risk of serious sequeles at occult infections is importantly decreasing by epidemiological changes that it rises by using vaccination against Haemophilus influenzae and Streptococcus pneumoniae is leading ethiological source. Many contraversal opinions are presented in glance of therapeutic strategy at children's occult infection. Future of solutions at many hesitations ni context diagnosis and therapy of occult infections is established in using recent detectional tests /pneumococcus PCR, plasmas tumor reaction, interleukin lâ/ and preventive intervetions activities /conjugated pneumococcus vaccination/.

21 CFR 864.6550 - Occult blood test.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Occult blood test. 864.6550 Section 864.6550 Food... DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6550 Occult blood test. (a) Identification. An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is...

21 CFR 864.6550 - Occult blood test.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Occult blood test. 864.6550 Section 864.6550 Food... DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6550 Occult blood test. (a) Identification. An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is...

21 CFR 864.6550 - Occult blood test.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Occult blood test. 864.6550 Section 864.6550 Food... DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6550 Occult blood test. (a) Identification. An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is...

21 CFR 864.6550 - Occult blood test.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Occult blood test. 864.6550 Section 864.6550 Food... DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6550 Occult blood test. (a) Identification. An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is...

21 CFR 864.6550 - Occult blood test.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Occult blood test. 864.6550 Section 864.6550 Food... DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6550 Occult blood test. (a) Identification. An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is...

[Stellar Occultation Studies of Small Bodies in the Outer Solar System: Accomplishments, Status, and Plans

NASA Technical Reports Server (NTRS)

Elliott, James

2005-01-01

Bodies residing in the outer solar system exhibit unique physical processes, and some of the lessons learned from them can be applied to understanding what occurred in the outer solar system during its formation and early evolution. Pluto, the largest known Kuiper Belt object (KBO), and its near twin Triton--an ex-KBO that has been captured by Neptune--have nitrogen atmospheres that are in vapor-pressure equilibrium with surface ice. These atmospheres are most sensitively probed from Earth by the technique of Stellar occultations, which can provide the temperature and pressure profiles of these atmospheres at a spatial resolution of a few kilometers. Recent results from occultations show that the surface pressure of Triton's atmosphere has been increasing and that the shape of the atmosphere deviates from its expected spherical figure. With the occultation technique we can also learn the sizes of smaller bodies that have formed in the outer solar system: Charon, the Centaurs, and KBOs. Our proposed program involves identifying occultation candidates, predicting occultations, observing occultations, analysis of the data, and synthesis of the occultation results with other data. The main goals for our proposed work are to (i) further observe occultations by Triton with the objectives of understanding its pressure changes, distortion, and enigmatic thermal structure (ii) determine whether the abrupt drop in Pluto's stellar occultation light curve is caused by a sharp thermal gradient near its surface or by atmospheric haze, (iii) further observations to characterize the potential collapse of Pluto's atmosphere as it recedes from the sun (information that should be of interest to the Pluto-Kuiper Express), ( iv ) determine Charon's radius more accurately than can be done with the mutual events to derive a better estimate of Charon's density, and ( v ) directly determine the size (and albedo) of Centaurs with the goal of more accurately estimating the sizes of KBOS.

DSP-based CSO cancellation technique for RoF transmission system implemented by using directly modulated laser.

PubMed

Kim, Byung Gon; Bae, Sung Hyun; Kim, Hoon; Chung, Yun C

2017-05-29

We propose and demonstrate a simple composite second-order (CSO) cancellation technique based on the digital signal processing (DSP) for the radio-over-fiber (RoF) transmission system implemented by using directly modulated lasers (DMLs). When the RoF transmission system is implemented by using DMLs, its performance could be limited by the CSO distortions caused by the interplay between the DML's chirp and fiber's chromatic dispersion. We present the theoretical analysis of these nonlinear distortions and show that they can be suppressed at the receiver by using a simple DSP. To verify the effectiveness of the proposed technique, we demonstrate the transmission of twenty-four 100-MHz filtered orthogonal frequency-division multiplexing (f-OFDM) signals in 64 quadrature amplitude modulation (QAM) format over 20 km of the standard single-mode fiber (SSMF). The results show that, by using the proposed technique, we can suppress the CSO distortion components by >10 dB and achieve the error-vector magnitude performance better than 6% even after the 20-km long SSMF transmission.

James Webb Space Telescope Observations of Stellar Occultations by Solar System Bodies and Rings

NASA Technical Reports Server (NTRS)

Santos-Sanz, P.; French, R. G.; Pinilla-Alonso, N.; Stansberry, J.; Lin, Z-Y.; Zhang, Z-W.; Vilenius, E.; Mueller, Th.; Ortiz, J. L.; Braga-Ribas, F.;

Prediction of stellar occultations by distant solar system bodies in the Gaia era

NASA Astrophysics Data System (ADS)

Desmars, Josselin; Camargo, Julio; Sicardy, Bruno; Braga-Ribas, Felipe; Vieira-Martins, Roberto; Assafin, Marcelo; Bérard, Diane; Benedetti-Rossi, Gustavo

2018-04-01

Stellar occultations are a unique technique to access physical characteristics of distant solar system objects from the ground. They allow the measure of the size and the shape at kilometric level, the detection of tenuous atmospheres (few nanobars), and the investigation of close vicinity (satellites, rings) of Transneptunian objects and Centaurs. This technique is made successful thanks to accurate predictions of occultations. Accuracy of the predictions depends on the uncertainty in the position of the occulted star and the object's orbit. The Gaia stellar catalogue (Gaia Collaboration (2017)) now allows to get accurate astrometric stellar positions (to the mas level). The main uncertainty remains on the orbit. In this context, we now take advantage of the NIMA method (Desmars et al.(2015)) for the orbit determination and of the Gaia DR1 catalogue for the astrometry. In this document, we show how the orbit determination is improved by reducing current and some past observations with Gaia DR1. Moreover, we also use more than 45 past positive occultations observed in the 2009-2017 period to derive very accurate astrometric positions only depending on the position of the occulted stars (about few mas with Gaia DR1). We use the case of (10199) Chariklo as an illustration. The main limitation lies in the imprecision of the proper motions which is going to be solved by the Gaia DR2 release.

On the reduction of occultation light curves. [stellar occultations by planets

NASA Technical Reports Server (NTRS)

Wasserman, L.; Veverka, J.

1973-01-01

The two basic methods of reducing occultation light curves - curve fitting and inversion - are reviewed and compared. It is shown that the curve fitting methods have severe problems of nonuniqueness. In addition, in the case of occultation curves dominated by spikes, it is not clear that such solutions are meaningful. The inversion method does not suffer from these drawbacks. Methods of deriving temperature profiles from refractivity profiles are then examined. It is shown that, although the temperature profiles are sensitive to small errors in the refractivity profile, accurate temperatures can be obtained, particularly at the deeper levels of the atmosphere. The ambiguities that arise when the occultation curve straddles the turbopause are briefly discussed.

Preliminary evaluation of the diffraction behind the PROBA 3/ASPIICS optimized occulter

NASA Astrophysics Data System (ADS)

Baccani, Cristian; Landini, Federico; Romoli, Marco; Taccola, Matteo; Schweitzer, Hagen; Fineschi, Silvano; Bemporad, Alessandro; Loreggia, Davide; Capobianco, Gerardo; Pancrazzi, Maurizio; Focardi, Mauro; Noce, Vladimiro; Thizy, Cédric; Servaye, Jean-Sébastien; Renotte, Etienne

2016-07-01

PROBA-3 is a technological mission of the European Space Agency (ESA), devoted to the in-orbit demon- stration of formation flying (FF) techniques and technologies. ASPIICS is an externally occulted coronagraph approved by ESA as payload in the framework of the PROBA-3 mission and is currently in its C/D phase. FF offers a solution to investigate the solar corona close the solar limb using a two-component space system: the external occulter on one spacecraft and the optical instrument on the other, separated by a large distance and kept in strict alignment. ASPIICS is characterized by an inter-satellite distance of ˜144 m and an external occulter diameter of 1.42 m. The stray light due to the diffraction by the external occulter edge is always the most critical offender to a coronagraph performance: the designer work is focused on reducing the stray light and carefully evaluating the residuals. In order to match this goal, external occulters are usually characterized by an optimized shape along the optical axis. Part of the stray light evaluation process is based on the diffraction calculation with the optimized occulter and with the whole solar disk as a source. We used the field tracing software VirtualLabTM Fusion by Wyrowski Photonics [1] to simulate the diffraction. As a first approach and in order to evaluate the software, we simulated linear occulters, through as portions of the flight occulter, in order to make a direct comparison with the Phase-A measurements [2].

Characteristics of tropical cyclones and overshooting from GPS radio occultation data

NASA Astrophysics Data System (ADS)

Biondi, Riccardo; Rieckh, Therese; Steiner, Andrea; Kirchengast, Gottfried

2014-05-01

Tropical cyclones (TCs) are extreme weather events causing every year huge damages and several deaths. In some countries they are the natural catastrophes accounting for the major economic damages. The thermal structure of TCs gives important information on the cloud top height allowing for a better understanding of the troposphere-stratosphere transport, which is still poorly understood. The measurement of atmospheric parameters (such as temperature, pressure and humidity) with high vertical resolution and accuracy in the upper troposphere and lower stratosphere (UTLS) is difficult especially during severe weather events (e.g TCs). Satellite remote sensing has improved the TC forecast and monitoring accuracy. In the last decade the Global Positioning Systems (GPS) Radio Occultation (RO) technique contributed to improve our knowledge especially at high troposphere altitudes and in remote regions of the globe thanks to the high vertical resolution, avoiding temperature smoothing issues (given by microwave and infrared instruments) in the UTLS and improving the poor temporal resolution and global coverage given by lidars and radars. We selected more than twenty-thousand GPS RO profiles co-located with TC best tracks for the period 2001 to 2012 and computed temperature anomaly profiles relative to a RO background climatology in order to detect TC cloud tops. We characterized the thermal structure for different ocean basins and for different TC intensities, distinguishing between tropical and extra-tropical cases. The analysis shows that all investigated storms have a common feature: they warm the troposphere and cool the UTLS near the cloud top. This behavior is amplified in the extra-tropical areas. Results reveal that the storms' cloud tops in the southern hemisphere basins reach higher altitudes and lower temperatures than in the northern hemisphere basins. We furthermore compared the cloud top height of each profile with the mean tropopause altitude (from the RO

Using GPS radio occultation data in the study of tropical cyclogenesis

NASA Astrophysics Data System (ADS)

Didlake, A. C., Jr.; Kuo, Y. B.; Metcalfe, T.

2005-12-01

Numerous studies have examined atmospheric conditions and patterns in tropical cyclogenesis. Although much has been accomplished, a complete understanding of tropical cyclogenesis is hindered by the lack of data in the regions where formation occurs. The GPS (Global Positioning System) radio occultation technique can provide valuable data in key areas. In GPS radio occultation, GPS satellites emit radio signals through the atmosphere that are received by another satellite in a low Earth orbit. Various atmospheric properties are calculated based on the alteration of the signal. This study assessed the value of GPS radio occultation data in the study of tropical cyclogenesis by examining storms of the 2002 Western North Pacific typhoon season. The signature of precursor disturbances to tropical cyclogenesis was determined by analyzing composites of data from the NCEP Aviation (AVN) analysis over four days. Similar composites of GPS radio occultation data were produced. The AVN analysis showed strong signals of precursor disturbances in the low-level wind fields and atmospheric refractivity. The GPS radio occultation data detected similarly increased refractivity values in corresponding regions, but had sizeable measurement differences with the AVN analysis. These differences were attributed to AVN analysis error due to the lack of input observational data and the high accuracy of GPS radio occultation measurements. Further comparisons showed that with the limited quantity of data currently available, GPS radio occultation by itself was not sufficient to detect precursor disturbances. It can best be used in data assimilation to improve the analysis and forecasts of tropical storms.

Detection of occult abscesses with /sup 111/In-labeled leukocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, W.R.; Gurevich, N.; Goris, M.L.

1979-07-01

Clinicians are frequently faced with the problem of a patient in whom they suspect an occult abscess. In such a situation, there may be no clinical signs to localize the site of the abscess and often extensive investigations do not provide additional useful information. This report illustrates the efficacy of autologous leukocytes labeled with /sup 111/In oxine in detecting the site and extent of occult abscesses in two patients. The technique of in vitro lebeling of leukocytes is simple and has been mastered by all of our nuclear medicine technologists.

Triton stellar occultation candidates - 1992-1994

NASA Technical Reports Server (NTRS)

Mcdonald, S. W.; Elliot, J. T.

1992-01-01

A search for Triton stellar occultation candidates for the period 1992-1994 has been completed with CCD strip-scanning observations. The search reached an R magnitude of about 17.4 and found 129 candidates within 1.5 arcsec of Triton's ephemeris during this period. Of these events, around 30 occultations are expected to be visible from the earth, indicating that a number of Triton occultation events should be visible from major observatories. Even the faintest of the present candidate events could produce useful occultation data if observed with a large enough telescope. The present astrometric accuracy is inadequate to identify which of these appulse events will produce occultations on the earth; further astrometry is needed to refine the predictions for positive occultation identification. To aid in selecting candidates for additional astrometric and photometric studies, finder charts and earth-based visibility charts for each event are included.

Predictions of stellar occultations by TNOs/Centaurs using Gaia

NASA Astrophysics Data System (ADS)

Desmars, Josselin; Camargo, Julio; Berard, Diane; Sicardy, Bruno; Leiva, Rodrigo; Vieira-Martins, Roberto; Braga-Ribas, Felipe; Assafin, Marcelo; Rossi, Gustavo; Chariklo occultations Team, Rio Group, Lucky Star Occultation Team, Granada Occultation Team

2017-10-01

Stellar occultations are the unique technique from the ground to access physical parameters of the distant solar system objects, such as the measure of the size and the shape at kilometric level, the detection of tenuous atmospheres (few nanobars), and the investigation of close vicinity (satellites, rings, jets).Predictions of stellar occultations require accurate positions of the star and the object.The Gaia DR1 catalog now allows to get stellar position to the milliarcsecond (mas) level. The main uncertainty in the prediction remains in the position of the object (tens to hundreds of mas).Now, we take advantage of the NIMA method for the orbit determination that uses the most recent observations reduced by the Gaia DR1 catalog and the astrometric positions derived from previous positive occultations.Up to now, we have detected nearly 50 positive occultations for about 20 objects that provide astrometric positions of the object at the time of the occultation. The uncertainty of these positions only depends on the uncertainty on the position of the occulted stars, which is a few mas with the Gaia DR1 catalog. The main limitation is now on the proper motion of the star which is only given for bright stars in the Tycho-Gaia Astrometric Solution. This limitation will be solved with the publicationof the Gaia DR2 expected on April 2018 giving proper motions and parallaxes for the Gaia stars. Until this date, we use hybrid stellar catalogs (UCAC5, HSOY) that provide proper motions derived from Gaia DR1 and another stellar catalog.Recently, the Gaia team presented a release of three preliminary Gaia DR2 stellar positions involved in the occultations by Chariklo (22 June and 23 July 2017) and by Triton (5 October 2017).Taking the case of Chariklo as an illustration, we will present a comparison between the proper motions of DR2 and the other catalogs and we will show how the Gaia DR2 will lead to a mas level precision in the orbit and in the prediction of stellar

Progress on the occulter experiment at Princeton

NASA Astrophysics Data System (ADS)

Cady, Eric; Balasubramanian, Kunjithapatham; Carr, Michael; Dickie, Matthew; Echternach, Pierre; Groff, Tyler; Kasdin, Jeremy; Laftchiev, Christian; McElwain, Michael; Sirbu, Dan; Vanderbei, Robert; White, Victor

2009-08-01

An occulter is used in conjunction with a separate telescope to suppress the light of a distant star. To demonstrate the performance of this system, we are building an occulter experiment in the laboratory at Princeton. This experiment will use an etched silicon mask as the occulter, with some modifications to try to improve the performance. The occulter is illuminated by a diverging laser beam to reduce the aberrations from the optics before the occulter. We present the progress of this experiment and expectations for future work.

Several Well-observed Asteroidal Occultations in 2010

NASA Astrophysics Data System (ADS)

Timerson, Brad; Durech, J.; Abramson, H.; Brooks, J.; Caton, D.; Clark, D.; Conard, S.; Cooke, B.; Dunham, D. W.; Dunham, J.; Edberg, S.; Ellington, C.; Faircloth, J.; Herchak, S.; Iverson, E.; Jones, R.; Lucas, G.; Lyzenga, G.; Maley, P.; Martinez, L.; Menke, J.; Mroz, G.; Nolan, P.; Peterson, R.; Preston, S.; Rattley, G.; Ray, J.; Scheck, A.; Stamm, J.; Stanton, R.; Suggs, R.; Tatum, R.; Thomas, W.

2011-10-01

During 2010 IOTA observers in North America reported about 190 positive observations for 106 asteroid occultation events. For several asteroids, this included observations with multiple chords. For two events, an inversion model was available. An occultation by 16 Psyche on 2010 August 21 yielded a best-fit ellipse of 235.4 x 230.4 km. On 2010 December 24, an occultation by 93 Minerva produced a best-fit ellipse of 179.4 x 133.4 km. An occultation by 96 Aegle on 2010 October 29 yielded a best-fit ellipse of 124.9 x 88.0 km. An occultation by 105 Artemis on 2010 June 24 showed a best-fit ellipse of 125.0 x 92.0 km. An occultation by 375 Ursula on 2010 December 4 produced a best-fit ellipse of 125.0 km x 135.0 km. Of note are two events not summarized in this article. On 2010 August 31, an occultation by 695 Bella yielded a new double star. That event will be summarized in the JDSO. Finally, on 2010 April 6, an occultation of zeta Ophiuchi by 824 Anastasia was observed by 65 observers at 69 locations. Unfortunately a large shift in the path yielded only 4 chords. Results of that event, and all the events mentioned here, can be found on the North American Asteroidal Occultation Results web page.

Stellar Occultation Studies of the Solar System

NASA Technical Reports Server (NTRS)

Elliot, James L.

1998-01-01

Earth-based observations of stellar occultations provide extremely high spatial resolution for bodies in the outer solar system, about 10,000 times better than that of traditional imaging observations. Stellar occultation data can be used to establish the structure of atmospheres and rings of solar system bodies at high spatial resolution. Airborne occultation observations are particularly effective, since the controlled mobility of the observing platform allows the observer to fly within the optimum part of the occultation shadow for most events that are visible from Earth. Airborne observations are carried out above any clouds and are nearly free of scintillation noise from the Earth's atmosphere. KAO occultation observations resulted in the first detection of gravity waves in the Martian atmosphere, discovery of the Uranian rings, the first detection of Pluto's atmosphere, the first Earth-based investigations of Triton's atmosphere, and the discovery of narrow jets from Chiron's nucleus. The first SOFIA occultation opportunity will be an investigation of Pluto's atmospheric structure in November, 2002, and will resolve a problem that has lingered since the KAO discovery observation fourteen years earlier. We plan to continue our successful airborne occultation program with the greatly enhanced capability provided by SOFIA. We propose here to replace our KAO occultation photometer with one having twice the throughput, half the noise, a somewhat wider wavelength range, four times the field of view, and ten times the frame rate to optimize its performance and to capitalize on the larger collecting area offered by SOFIA. It will also allow for simultaneous visible and IR occultation observations, greatly enriching the results that we can obtain from occultations. We call this new imaging occultation photometer HOPI (High-speed Occultation Photometer and Imager). HOPI will provide a signal-to-noise ratio two to four times that of our present photometer for a given

Intermediate-scale plasma irregularities in the polar ionosphere inferred from GPS radio occultation

NASA Astrophysics Data System (ADS)

Shume, E. B.; Komjathy, A.; Langley, R. B.; Verkhoglyadova, O.; Butala, M. D.; Mannucci, A. J.

2015-02-01

We report intermediate-scale plasma irregularities in the polar ionosphere inferred from high-resolution radio occultation (RO) measurements using GPS (Global Positioning System) to CASSIOPE (CAScade Smallsat and IOnospheric Polar Explorer) satellite radio links. The high inclination of CASSIOPE and the high rate of signal reception by the GPS Attitude, Positioning, and Profiling RO receiver on CASSIOPE enable a high-resolution investigation of the dynamics of the polar ionosphere with unprecedented detail. Intermediate-scale, scintillation-producing irregularities, which correspond to 1 to 40 km scales, were inferred by applying multiscale spectral analysis on the RO phase measurements. Using our multiscale spectral analysis approach and satellite data (Polar Operational Environmental Satellites and Defense Meteorological Satellite Program), we discovered that the irregularity scales and phase scintillations have distinct features in the auroral oval and polar cap. We found that large length scales and more intense phase scintillations are prevalent in the auroral oval compared to the polar cap implying that the irregularity scales and phase scintillation characteristics are a function of the solar wind and magnetospheric forcings.

Predicted occultations by Uranus - 1981-1984

NASA Technical Reports Server (NTRS)

Klemola, A. R.; Mink, D. J.; Elliot, J. L.

1981-01-01

Predictions are presented for 11 occultations by and appulses to Uranus and its ring system for ten stars from 1981 through 1984. The brightest stars are occulted on April 26, 1981 (BD - 19 deg 4222) and on April 22, 1982 (Hyd - 20 deg 51699). The ring system occults the same star twice during March 1983 (Hyd - 21 deg 64352).

Monitoring the Low-Energy Gamma-Ray Sky Using Earth Occultation with GLAST GBM

NASA Technical Reports Server (NTRS)

Case, G.; Wilson-Hodge, C.; Cherry, M.; Kippen, M.; Ling, J.; Radocinski, R.; Wheaton, W.

2007-01-01

Long term all-sky monitoring of the 20 keV - 2 MeV gamma-ray sky using the Earth occultation technique was demonstrated by the BATSE instrument on the Compton Gamma Ray Observatory. The principles and techniques used for the development of an end-to-end earth occultation data analysis system for BATSE can be extended to the GLAST Gamma-ray Burst Monitor (GBM), resulting in multiband light curves and time-resolved spectra in the energy range 8 keV to above 1 MeV for known gamma-ray sources and transient outbursts, as well as the discovery of new sources of gamma-ray emission. In this paper we describe the application of the technique to the GBM. We also present the expected sensitivity for the GBM.

Radio occultation experiments with INAF-IRA radiotelescopes.

NASA Astrophysics Data System (ADS)

Pluchino, S.; Schillirò, F.; Salerno, E.; Pupillo, G.

The Radio Occultation research program performed at the Medicina and Noto Radioastronomical Stations of the Istituto Nazionale di Astrofisica (INAF) - Istituto di Radioastronomia (IRA) includes observations of spacecraft by satellite and satellite by satellite events. The Lunar Radio Occultation (LRO) part of the program consists in collecting data of the lunar Total Electron Content (TEC), at different limb longitudes and at different time, in order to study long term variation of the Moon's ionosphere. The LRO program started at Medicina in September 2006 with the observation of the European probe SMART-1 during its impact on the lunar soil. It proceeded in 2007 with the observation of the lunar occultations of Saturn and Venus, and with the observation of Mars in 2008. On this occasion the probes Cassini, Venus Express, Mars Express, Mars Reconaissance Orbiter and Mars Odissey were respectively occulted by the moon. On Dec 1st 2008 a Venus lunar occultation occurred. On that occasion we performed the first Italian-VLBI (I-VLBI) tracking experiment by detecting the carrier signals coming from the Venus Express (VEX) spacecraft with both the IRA radiotelescopes together with the Matera antenna of the Italian Space Agency. The second part of the radio occultation program includes the observation of satellite by satellite occultation events, as well as mutual occultations of Jupiter satellites. These events are referred to as mutual phenomena (PHEMU). These observations are aimed to measure the radio flux variation during the occultation and to derive surface spatial characteristics such as Io's hot spots. In this work preliminary results of the Radio Occultation program will be presented.

Radiologically occult medulloblastoma with hydrocephalus: case report.

PubMed

Honma, Hirokuni; Ogiwara, Hideki

2017-09-01

There have been no reports of occult medulloblastoma nor noncommunicating hydrocephalus due to radiologically occult brain tumors. Herein, we report radiologically occult medulloblastoma with noncommunicating hydrocephalus. A 3-year-old boy presented with macrocephaly, visual field constriction, and papilledema. Neuroimagings showed enlargement of the ventricles without any mass lesions. The CT cisternography did not show influx of the contrast into the ventricles, which suggested local cerebrospinal fluid (CSF) circulatory disturbance at the outlet of the fourth ventricle. Due to possible obstructive nature of hydrocephalus, endoscopic third ventriculostomy (ETV) was performed. Three months after the ETV, he presented with repeated vomiting. Neuroimagings showed a 3-cm fourth ventricular mass with progressive hydrocephalus. Surgical resection was performed, which revealed the pathology was medulloblastoma. We report the case of radiologically occult medulloblastoma which was demonstrated radiologically in the follow-up period of ETV for noncommunicating hydrocephalus of uncertain etiology. This is the first description of a radiologically occult medulloblastoma and also the first description of an occult brain tumor with noncommunicating hydrocephalus. The occult brain tumor may be included in the etiology of hydrocephalus.

Overview of SPICAV occultation results for the UV channel

NASA Astrophysics Data System (ADS)

Montmessin, Franck; Bertaux, Jean-Loup; Belyaev, Denis; Marcq, Emmanuel; Korablev, Oleg; Vandaele, Ann-Carine; Fedorova, Anna

The SPICAV instrument onboard the Venus Express spacecraft is a multi-channel suite cov-ering the far ultraviolet to the mid-infrared. In this presentation, we will focus on the results obtained by the UV channel during stellar occultations observations. Stellar occultation tech-nique possesses well-known advantages: self-calibration, low sensitivity to instrument aging, simple laws of radiative transfer. In addition, occultation with stars permit to cover a broad range of latitudes at any given season and they provide optimal geometrical registration. Since Venus Express orbit insertion, several hundreds of occultations have been performed by SPI-CAV, yielding profiles of atmospheric constituents between 80 and 140 km. In the SPICAV UV range, CO2 possesses a broad signature shortward of 200 nm which allows one to retrieve CO2 concentration and subsequently to deduce atmospheric pressure and temperature profiles in the upper mesosphere and in the thermosphere. The Venusian thermosphere shows excessive variability, with the equivalent of more than three scale heights change in density in less than a few days. No other spectral signature besides that of CO2 and haze particles was expected to appear in SPICAV ultraviolet spectra at this altitude range but a consistent search was undertaken, revealing the presence of aan ozone at 100 km (¡108 cm-3) and of sulfur dioxide above 90 km at a concentration of 0.1 to 1 ppm.

[Progress in research of occult hepatitis B virus infection].

PubMed

Huang, X Y; Shi, Q F; Huang, T

2017-05-10

Occult hepatitis B virus infection is a worldwide public health problem, which seriously affects the clinical diagnosis of hepatitis B and threatens the safety of blood transfusion. The concept of occult hepatitis B virus infection, the pathogenesis of occult hepatitis B virus infection, the prevalence of occult hepatitis B virus infection in different groups, including healthy population and different patients, and the possibility of transmission were summarized. The prevalence of occult hepatitis B virus infection was found in healthy population and different patients, and there is possibility of occult hepatitis B virus infection to be transmitted through blood transfusion. The paper provides a comprehensive introduction of the pathogenesis and prevalence of occult hepatitis B virus infection. More attention should be paid to occult hepatitis B virus infection.

New perspectives in occult hepatitis C virus infection

PubMed Central

Carreño, Vicente; Bartolomé, Javier; Castillo, Inmaculada; Quiroga, Juan Antonio

2012-01-01

Occult hepatitis C virus (HCV) infection, defined as the presence of HCV RNA in liver and in peripheral blood mononuclear cells (PBMCs) in the absence of detectable viral RNA in serum by standard assays, can be found in anti-HCV positive patients with normal serum levels of liver enzymes and in anti-HCV negative patients with persistently elevated liver enzymes of unknown etiology. Occult HCV infection is distributed worldwide and all HCV genotypes seem to be involved in this infection. Occult hepatitis C has been found not only in anti-HCV positive subjects with normal values of liver enzymes or in chronic hepatitis of unknown origin but also in several groups at risk for HCV infection such as hemodialysis patients or family members of patients with occult HCV. This occult infection has been reported also in healthy populations without evidence of liver disease. Occult HCV infection seems to be less aggressive than chronic hepatitis C although patients affected by occult HCV may develop liver cirrhosis and even hepatocellular carcinoma. Thus, anti-HCV negative patients with occult HCV may benefit from antiviral therapy with pegylated-interferon plus ribavirin. The persistence of very low levels of HCV RNA in serum and in PBMCs, along with the maintenance of specific T-cell responses against HCV-antigens observed during a long-term follow-up of patients with occult hepatitis C, indicate that occult HCV is a persistent infection that is not spontaneously eradicated. This is an updated report on diagnosis, epidemiology and clinical implications of occult HCV with special emphasis on anti-HCV negative cases. PMID:22736911

Sporadic-E Studies by Ionospheric Scintillation Using Ground-Based GPS and Radio Occultation Measurements

NASA Astrophysics Data System (ADS)

Seif, A.; Liu, T. J. Y.; Mannucci, A. J.; Carter, B. A.; Norman, R.

2016-12-01

The Global Navigation Satellite System (GNSS) based radio occultation (RO) technique provides an ideal limb-viewing geometry from space for studying the occurrence of sporadic E (Es). This study focuses on the detection and analysis of Es from RO measurements, to conclusively show the presence of Es's relationship with daytime scintillation. We bring two data sets to bear, using GNSS signal transmissions received on the ground and from space, which provide a unique opportunity to retrieve information about Es. RO signatures of Es and in GHz scintillation are not the same as ground-based signatures of Es. The viewing geometries are approximately orthogonal, which means the irregularity sources are not the same. That is, irregularities responsible for RO scintillations are essentially in a vertical plane, whereas those responsible for ground-based scintillations are essentially in a horizontal plane. Hence, complementary information is available regarding plasma structure in an Es patch. An analysis of combined data sets should prove to be a profitable avenue for research. In this study, we present the occurrence of scintillation using GPS Ionospheric Scintillation and Total Electron Content Monitor (GISTM) systems from two equatorial stations UKM (2.55°N, 101.46°E), and Langkawi (6.19°N, 99.51°E) in Malaysia. To better understand scale size irregularities as well as identify the occurrence of Es, we use COSMIC RO data. Two key findings coming out from our study are 1) According to the characteristics of daytime scintillation analyzed at, UKM and Langkawi stations, scintillation shows no significant TEC depletions and ROTI enhancements. The finding that ROTI does not exceed 0.5 TECU/min during daytime implies that large scale ionospheric irregularities with a scale length of a few kilometers do not exist at these stations. This is a piece of evidence which positively supports that daytime scintillation shows irregularities consistent with thin layer Es and

Stellar occultation studies of the solar system

NASA Technical Reports Server (NTRS)

Elliot, J. L.

1979-01-01

The paper covers the principles, observational procedures, and results relating to occultations of stars by solar system bodies other than the moon. Physical processes involved in occultations are presented including (1) extinction by ring material, (2) differential refraction by a planetary atmosphere, (3) extinction by a planetary atmosphere, and (4) Fresnel diffraction by sharp edges. It is noted that from a sufficient number of immersion and emersion timings of a stellar occultation, the radius and ellipticity of the occulting body can be accurately determined. From an occultation by a planet having an atmosphere, temperature, pressure, and number density profiles can be obtained along with information about the composition of the atmosphere and the extinction.

Occult Participation: Its Impact on Adolescent Development.

ERIC Educational Resources Information Center

Tennant-Clark, Cynthia M.; And Others

1989-01-01

Investigated relationship between occult participation, substance abuse, and level of self-esteem among 25 clinical (alcohol or drug treatment) and 25 nonclinical adolescents. Results indicated that adolescent substance abuse and occult participation were significantly related. Found significant differences between high versus low occult groups…

The Northrop Grumman External Occulter Testbed: Preliminary Results

NASA Astrophysics Data System (ADS)

Lo, Amy; Glassman, T.; Lillie, C.

2007-05-01

We have built a subscale testbed to demonstrate and validate the performance of the New Worlds Observer (NWO), a terrestrial planet finder external-occulter mission concept. The external occulter concept allows observations of nearby exo-Earths using two spacecraft: one carrying an occulter that is tens of meters in diameter and the other carrying a generic space telescope. The occulter is completely opaque, resembling a flower, with petals having a hypergaussian profile that enable 10-10 intensity suppression of stars that potentially harbor terrestrial planets. The baseline flight NWO system has a 30 meter occulter flying 30,000 km in front of a 4 meter class telescope. Testing the flight configuration on the ground is not feasible, so we have matched the Fresnel number of the flight configuration ( 10) using a subscale occulter. Our testbed consists of an 80 meter length evacuated tube, with a high precision occulter in the center of the tube. The occulter is 4 cm in diameter, manufactured with ¼ micron metrological accuracy and less than 2 micron tip truncation. This mimics a 30 meter occulter with millimeter figure accuracy and less than centimeter tip truncation. Our testbed is an evolving experiment, and we report here the first, preliminary, results using a single wavelength laser (532 nm) as the source.

Probing Pluto's Atmosphere Using Ground-Based Stellar Occultations

NASA Astrophysics Data System (ADS)

Sicardy, Bruno; Rio de Janeiro Occultation Team, Granada Team, International Occultation and Timing Association, Royal Astronomical Society New Zealand Occultation Section, Lucky Star associated Teams

2016-10-01

Over the last three decades, some twenty stellar occultations by Pluto have been monitored from Earth. They occur when the dwarf planet blocks the light from a star for a few minutes as it moves on the sky. Such events led to the hint of a Pluto's atmosphere in 1985, that was fully confirmed during another occultation in 1988, but it was only in 2002 that a new occultation could be recorded. From then on, the dwarf planet started to move in front of the galactic center, which amplified by a large factor the number of events observable per year.Pluto occultations are essentially refractive events during which the stellar rays are bent by the tenuous atmosphere, causing a gradual dimming of the star. This provides the density, pressure and temperature profiles of the atmosphere from a few kilometers above the surface up to about 250 km altitude, corresponding respectively to pressure levels of about 10 and 0.1 μbar. Moreover, the extremely fine spatial resolution (a few km) obtained through this technique allows the detection of atmospheric gravity waves, and permits in principle the detection of hazes, if present.Several aspects make Pluto stellar occultations quite special: first, they are the only way to probe Pluto's atmosphere in detail, as the dwarf planet is far too small on the sky and the atmosphere is far too tenuous to be directly imaged from Earth. Second, they are an excellent example of participative science, as many amateurs have been able to record those events worldwide with valuable scientific returns, in collaboration with professional astronomers. Third, they reveal Pluto's climatic changes on decade-scales and constrain the various seasonal models currently explored.Finally, those observations are fully complementary to space exploration, in particular with the New Horizons (NH) mission. I will show how ground-based occultations helped to better calibrate some NH profiles, and conversely, how NH results provide some key boundary conditions

Triton stellar occultation candidates: 1995-1999

NASA Technical Reports Server (NTRS)

Mcdonald, S. W.; Elliot, J. L.

1995-01-01

We have completed a search for candidates for stellar occultations by Triton over the years 1995-1999. CCd strip scan images provided star positions in the relevant sky area to a depth of about 17.5 R magnitude. Over this time period, we find that Triton passes within 1.0 arcsec of 75 stars. Appulses with geocentric minimum separations of less than 0.35 arcsec will result in stellar occultations, but further astrometry and photometry is necessary to refine individual predictions for identification of actual occultations. Finder charts are included to aid in further studies and prediction refinement. The two most promising potential occultations, Tr176 and Tr180, occur in 1997.

Variability of Kelvin wave momentum flux from high-resolution radiosonde and radio occultation data

NASA Astrophysics Data System (ADS)

Sjoberg, J. P.; Zeng, Z.; Ho, S. P.; Birner, T.; Anthes, R. A.; Johnson, R. H.

2017-12-01

Direct measurement of momentum flux from Kelvin waves in the stratosphere remains challenging. Constraining this flux from observations is an important step towards constraining the flux from models. Here we present results from analyses using linear theory to estimate the Kelvin wave amplitudes and momentum fluxes from both high-resolution radiosondes and from radio occultation (RO) data. These radiosonde data are from a contiguous 11-year span of soundings performed at two Department of Energy Atmospheric Radiation Measurement sites, while the RO data span 14 years from multiple satellite missions. Daily time series of the flux from both sources are found to be in quantitative agreement with previous studies. Climatological analyses of these data reveal the expected seasonal cycle and variability associated with the quasi-biennial oscillation. Though both data sets provide measurements on distinct spatial and temporal scales, the estimated flux from each provides insight into separate but complimentary aspects of how the Kelvin waves affect the stratosphere. Namely, flux derived from radiosonde sites provide details on the regional Kelvin wave variability, while the flux from RO data are zonal mean estimates.

Exploring the Solar System with Stellar Occultations

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Dunham, E. W.

1984-01-01

By recording the light intensity as a function of time when a planet occults a relatively bright star, the thermal structure of the upper atmosphere of the planet can be probed. The main feature of stellar occultation observations is their high spatial resolution, typically several thousand times better than the resolution achievable with ground-based imaging. Five stellar occultations have been observed. The main results of these observations are summarized. Stellar occultations have been observed on Uranus, Mars, Pallas, Neptune and the Jovian Ring.

Intermediate scale plasma density irregularities in the polar ionosphere inferred from radio occultation

NASA Astrophysics Data System (ADS)

Shume, E. B.; Komjathy, A.; Langley, R. B.; Verkhoglyadova, O. P.; Butala, M.; Mannucci, A. J.

2014-12-01

In this research, we report intermediate scale plasma density irregularities in the high-latitude ionosphere inferred from high-resolution radio occultation (RO) measurements in the CASSIOPE (CAScade Smallsat and IOnospheric Polar Explorer) - GPS (Global Positioning System) satellites radio link. The high inclination of the CASSIOPE satellite and high rate of signal receptionby the occultation antenna of the GPS Attitude, Positioning and Profiling (GAP) instrument on the Enhanced Polar Outflow Probe platform on CASSIOPE enable a high temporal and spatial resolution investigation of the dynamics of the polar ionosphere, magnetosphere-ionospherecoupling, solar wind effects, etc. with unprecedented details compared to that possible in the past. We have carried out high spatial resolution analysis in altitude and geomagnetic latitude of scintillation-producing plasma density irregularities in the polar ionosphere. Intermediate scale, scintillation-producing plasma density irregularities, which corresponds to 2 to 40 km spatial scales were inferred by applying multi-scale spectral analysis on the RO phase delay measurements. Using our multi-scale spectral analysis approach and Polar Operational Environmental Satellites (POES) and Defense Meteorological Satellite Program (DMSP) observations, we infer that the irregularity scales and phase scintillations have distinct features in the auroral oval and polar cap regions. In specific terms, we found that large length scales and and more intense phase scintillations are prevalent in the auroral oval compared to the polar cap region. Hence, the irregularity scales and phase scintillation characteristics are a function of the solar wind and the magnetospheric forcing. Multi-scale analysis may become a powerful diagnostic tool for characterizing how the ionosphere is dynamically driven by these factors.

Occult hemorrhage in children with severe ITP.

PubMed

Flores, Adolfo; Buchanan, George R

2016-03-01

Little is known about the frequency and significance of clinically unapparent or occult hemorrhage in ITP. Therefore, we prospectively explored the sites and frequency of occult bleeding in children with severe ITP at diagnosis or upon symptomatic relapse in a prospective, single-institution cohort study of patients ≤ 18 years of age and a platelet count ≤ 10,000/mm(3) . Data collected included bleeding severity assessment, urinalysis, fecal occult blood testing, and non-contrast brain MRI. Stool and urine samples were tested within 7 days of diagnosis or symptomatic relapse. Three months after diagnosis or relapse a noncontrast brain MRI evaluated hemosiderin deposits resulting from prior localized hemorrhage. Fifty-two ITP patients were enrolled with a mean platelet count of 4,000/mm(3) . A significant occurrence of occult hemorrhage was identified in the urine (27%) compared with clinically overt hematuria (0.91%, P < 0.0005). CNS microbleeding in the superficial cortex of the left frontal lobe was identified in one child with occult bleeding in the urinary tract. There was no relationship between occult hemorrhage and bleeding manifestations on physical examination. Occult hemorrhage was not a harbinger of subsequent bleeding. Our findings suggest that occult hemorrhage occurs with greater frequency than overt bleeding in children with severe ITP. CNS microbleeding is a potential risk in this patient population. Assessment of brain microbleeds and microscopic hematuria in this patient population require additional study. © 2015 Wiley Periodicals, Inc.

Radiologically occult pulmonary lymphangitic carcinomatosis detected by /sup 67/Ga-citrate scintiscan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Band, P.R.; Lentle, B.C.; Amy, R.

1976-10-01

The use of gallium-67-citrate scintiscanning in the diagnosis of radiologically occult lung metastases is illustrated. The technique was used to demonstrate pulmonary lymphangitic carcinomatosis metastatic from breast cancer. (ERB)

Observational Constraints on the Water Vapor Feedback Using GPS Radio Occultations

NASA Astrophysics Data System (ADS)

Vergados, P.; Mannucci, A. J.; Ao, C. O.; Fetzer, E. J.

2016-12-01

The air refractive index at L-band frequencies depends on the air's density and water vapor content. Exploiting these relationships, we derive a theoretical model to infer the specific humidity response to surface temperature variations, dq/dTs, given knowledge of how the air refractive index and temperature vary with surface temperature. We validate this model using 1.2-1.6 GHz Global Positioning System Radio Occultation (GPS RO) observations from 2007 to 2010 at 250 hPa, where the water vapor feedback on surface warming is strongest. Current research indicates that GPS RO data sets can capture the amount of water vapor in very dry and very moist air more efficiently than other observing platforms, possibly suggesting larger water vapor feedback than previously known. Inter-comparing the dq/dTs among different data sets will provide us with additional constraints on the water vapor feedback. The dq/dTs estimation from GPS RO observations shows excellent agreement with previously published results and the responses estimated using Atmospheric Infrared Sounder (AIRS) and NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) data sets. In particular, the GPS RO-derived dq/dTs is larger by 6% than that estimated using the AIRS data set. This agrees with past evidence that AIRS may be dry-biased in the upper troposphere. Compared to the MERRA estimations, the GPS RO-derived dq/dTs is 10% smaller, also agreeing with previous results that show that MERRA may have a wet bias in the upper troposphere. Because of their high sensitivity to fractional changes in water vapor, and their inherent long-term accuracy, current and future GPS RO observations show great promise in monitoring climate feedbacks and their trends.

Occultation Predictions Using CCD Strip-Scanning Astrometry

NASA Technical Reports Server (NTRS)

Dunham, Edward W.; Ford, C. H.; Stone, R. P. S.; McDonald, S. W.; Olkin, C. B.; Elliot, J. L.; Witteborn, Fred C. (Technical Monitor)

1994-01-01

We are developing the method of CCD strip-scanning astrometry for the purpose of deriving reliable advance predictions for occultations involving small objects in the outer solar system. We are using a camera system based on a Ford/Loral 2Kx2K CCD with the Crossley telescope at Lick Observatory for this work. The columns of die CCD are aligned East-West, the telescope drive is stopped, and the CCD is clocked at the same rate that the stars drift across it. In this way we obtain arbitrary length strip images 20 arcmin wide with 0.58" pixels. Since planets move mainly in RA, it is possible to obtain images of the planet and star to be occulted on the same strip well before the occultation occurs. The strip-to-strip precision (i.e. reproducibility) of positions is limited by atmospheric image motion to about 0.1" rms per strip. However, for objects that are nearby in R.A., the image motion is highly correlated and their relative positions are good to 0.02" rms per strip. We will show that the effects of atmospheric image motion on a given strip can be removed if a sufficient number of strips of a given area have been obtained. Thus, it is possible to reach an rms precision of 0.02" per strip, corresponding to about 0.3 of Pluto or Triton's angular radius. The ultimate accuracy of a prediction based on strip-scanning astrometry is currently limited by the accuracy of the positions of the stars in the astrometric network used and by systematic errors most likely due to the optical system. We will show the results of . the prediction of some recent occultations as examples of the current capabilities and limitations of this technique.

Optical performance of the New Worlds Occulter

NASA Astrophysics Data System (ADS)

Arenberg, Jonathan W.; Lo, Amy S.; Glassman, Tiffany M.; Cash, Webster

2007-04-01

The New Worlds Observer (NWO) is a multiple spacecraft mission that is capable of detecting and characterizing extra-solar planets and planetary systems. NWO consists of an external occulter and a generic space telescope, flying in tandem. The external occulter has specific requirements on its shape and size, while the telescope needs no special modification beyond that required to do high-quality astrophysical observations. The occulter is a petal-shaped, opaque screen that creates a high-suppression shadow large enough to accommodate the telescope. This article reports on the optical performance of the novel New Worlds occulter design. It also introduces two new aspects of its optical performance which enhance the detectability of extra-solar planets. We also include a brief discussion of the buildability and the tolerances of the occulter. It is also shown that an occulter design can be found for any set of science requirements. We show that NWO is a viable mission concept for the study of extra-solar planets. To cite this article: J.W. Arenberg et al., C. R. Physique 8 (2007).

Density Waves in Saturn's Rings from Cassini Radio Occultations

NASA Astrophysics Data System (ADS)

French, R. G.; Rappaport, N. J.; Marouf, E. A.; McGhee, C. A.

2005-12-01

The Cassini Radio Science Team conducted a set of optimized diametric occultations by Saturn and its rings from May to September 2005, providing 11 separate probes of Saturn's ionosphere and atmosphere, and 12 optical depth profiles of the complete ring system. Each event was observed by the stations of the Deep Space Net (DSN) at three radio frequencies (S, X, Ka bands, with corresponding wavelengths of ? = 13, 3.6, and 0.9 cm). Very accurate pointing by the spacecraft and ground antennas resulted in stable baseline signal levels, and the relatively large ring opening angle (B=19-25°) permitted us to probe even quite dense ring regions with excellent SNR. The RSS occultation technique enables us to recover very fine detailed radial structure by correcting for diffraction effects. Multiple occultation chords, covering a variety of ring longitudes and ring opening angles, reveal the structure of the rings in remarkable detail, including density and bending waves, satellite wakes, and subtle variations at the 100-m radius scale. Janus and Epimetheus are responsible for a particularly rich set of density waves, and their coorbital interactions result in a complex interplay of time-variable ring structure over the 8-year libration period of the two satellites. We compare the first-order 2:1, 4:3, 5:4, and 6:5 coorbital density waves from multiple occultation chords to linear density wave models based on a dynamical model of the orbital exchange between the moons. From the observed dispersion relation of the wave crests, we infer the surface mass density and eccentricity gradient of particle streamlines, and match the detailed shapes of the wave crests using a non-linear analysis. Second-order coorbital features are also evident, and there are even hints of third-order density waves in the high SNR radio occultation data.

Pioneer 10 and 11 radio occultations by Jupiter. [atmospheric temperature structure

NASA Technical Reports Server (NTRS)

Kliore, A. J.; Woiceshyn, P. M.; Hubbard, W. B.

1977-01-01

Results on the temperature structure of the Jovian atmosphere are reviewed which were obtained by applying an integral inversion technique combined with a model for the planet's shape based on gravity data to Pioneer 10 and 11 radio-occultation data. The technique applied to obtain temperature profiles from the Pioneer data consisted of defining a center of refraction based on a computation of the radius of curvature in the plane of refraction and the normal direction to the equipotential surface at the closest approach point of a ray. Observations performed during the Pioneer 10 entry and exit and the Pioneer 11 exit are analyzed, sources of uncertainty are identified, and representative pressure-temperature profiles are presented which clearly show a temperature inversion between 10 and 100 mb. Effects of zonal winds on the reliability of radio-occultation temperature profiles are briefly discussed.

Experiment D005: Star occultation navigation

NASA Technical Reports Server (NTRS)

Silva, R. M.; Jorris, T. R.; Vallerie, E. M., III

1971-01-01

The usefulness of star occultation measurements for space navigation and the determination of a horizon density profile which could be used to update atmospheric models for horizon-based measurement systems were studied. The time of occultation of a known star by a celestial body, as seen by an orbiting observer, determines a cylinder of position, the axis of which is the line through the star and the body center, and the radius of which is equal to the occulting-body radius. The dimming percentage, with respect to the altitude of this grazing ray from the star to the observer, is a percentage altitude for occultation. That is, the star can be assumed to be occulted when it reaches a predetermined percentage of its unattenuated value. The procedure used was to measure this attenuation with respect to time to determine the usefulness of the measurements for autonomous space navigation. In this experiment, the crewmembers had to accomplish star acquisition, identification, calibration, and tracking. Instrumentation was required only for measurement of the relative intensity of the star as it set into the atmosphere.

Management of occult adrenocorticotropin-secreting bronchial carcinoids: limits of endocrine testing and imaging techniques.

PubMed

Loli, P; Vignati, F; Grossrubatscher, E; Dalino, P; Possa, M; Zurleni, F; Lomuscio, G; Rossetti, O; Ravini, M; Vanzulli, A; Bacchetta, C; Galli, C; Valente, D

2003-03-01

The differential diagnosis and the identification of the source of ACTH in occult ectopic Cushing's syndrome due to a bronchial carcinoid still represents a challenge for the endocrinologist. We report our experience in six patients with occult bronchial carcinoid in whom extensive hormonal, imaging, and scintigraphic evaluation was performed. All patients presented with hypercortisolism associated with high plasma ACTH values. The CRH test and high dose dexamethasone suppression test suggested an ectopic source of ACTH in three of six patients. During bilateral inferior petrosal sinus sampling, none of the patients showed a central to peripheral ACTH gradient. At the time of diagnosis, none of the patients had radiological evidence of the ectopic source of ACTH, whereas pentetreotide scintigraphy identified the lesion in two of four patients. Finally, a chest computed tomography scan revealed the presence of a bronchial lesion in all patients, and pentetreotide scintigraphy identified four of six lesions. In all patients a bronchial carcinoid was found and removed. In one patient with scintigraphic evidence of residual disease after two operations, radioguided surgery, using a hand-held gamma probe after iv administration of radiolabeled pentetreotide, was performed; this allowed detection and removal of residual multiple mediastinal lymph node metastases. In conclusion, our data show that there is not a single endocrine test or imaging procedure accurate enough to diagnose and localize occult ectopic ACTH-secreting bronchial carcinoids. Radioguided surgery appears to be promising in the presence of multiple tumor foci and previous incomplete removal of the tumor.

Evaluation for Occult Fractures in Injured Children

PubMed Central

French, Benjamin; Song, Lihai; Feudtner, Chris

2015-01-01

OBJECTIVES: To examine variation across US hospitals in evaluation for occult fractures in (1) children <2 years old diagnosed with physical abuse and (2) infants <1 year old with injuries associated with a high likelihood of abuse and to identify factors associated with such variation. METHODS: We performed a retrospective study in children <2 years old with a diagnosis of physical abuse and in infants <1 year old with non-motor vehicle crash–related traumatic brain injury or femur fractures discharged from 366 hospitals in the Premier database from 2009 to 2013. We examined across-hospital variation and identified child- and hospital-level factors associated with evaluation for occult fractures. RESULTS: Evaluations for occult fractures were performed in 48% of the 2502 children with an abuse diagnosis, in 51% of the 1574 infants with traumatic brain injury, and in 53% of the 859 infants with femur fractures. Hospitals varied substantially with regard to their rates of evaluation for occult fractures in all 3 groups. Occult fracture evaluations were more likely to be performed at teaching hospitals than at nonteaching hospitals (all P < .001). The hospital-level annual volume of young, injured children was associated with the probability of occult fracture evaluation, such that hospitals treating more young, injured patients were more likely to evaluate for occult fractures (all P < .001). CONCLUSIONS: Substantial variation in evaluation for occult fractures among young children with a diagnosis of abuse or injuries associated with a high likelihood of abuse highlights opportunities for quality improvement in this vulnerable population. PMID:26169425

Evaluation for Occult Fractures in Injured Children.

PubMed

Wood, Joanne N; French, Benjamin; Song, Lihai; Feudtner, Chris

2015-08-01

To examine variation across US hospitals in evaluation for occult fractures in (1) children <2 years old diagnosed with physical abuse and (2) infants <1 year old with injuries associated with a high likelihood of abuse and to identify factors associated with such variation. We performed a retrospective study in children <2 years old with a diagnosis of physical abuse and in infants <1 year old with non-motor vehicle crash-related traumatic brain injury or femur fractures discharged from 366 hospitals in the Premier database from 2009 to 2013. We examined across-hospital variation and identified child- and hospital-level factors associated with evaluation for occult fractures. Evaluations for occult fractures were performed in 48% of the 2502 children with an abuse diagnosis, in 51% of the 1574 infants with traumatic brain injury, and in 53% of the 859 infants with femur fractures. Hospitals varied substantially with regard to their rates of evaluation for occult fractures in all 3 groups. Occult fracture evaluations were more likely to be performed at teaching hospitals than at nonteaching hospitals (all P < .001). The hospital-level annual volume of young, injured children was associated with the probability of occult fracture evaluation, such that hospitals treating more young, injured patients were more likely to evaluate for occult fractures (all P < .001). Substantial variation in evaluation for occult fractures among young children with a diagnosis of abuse or injuries associated with a high likelihood of abuse highlights opportunities for quality improvement in this vulnerable population. Copyright © 2015 by the American Academy of Pediatrics.

Molecular Mechanisms Underlying Occult Hepatitis B Virus Infection

PubMed Central

Samal, Jasmine; Kandpal, Manish

2012-01-01

Summary: Chronic hepatitis B virus (HBV) infection is a complex clinical entity frequently associated with cirrhosis and hepatocellular carcinoma (HCC). The persistence of HBV genomes in the absence of detectable surface antigenemia is termed occult HBV infection. Mutations in the surface gene rendering HBsAg undetectable by commercial assays and inhibition of HBV by suppression of viral replication and viral proteins represent two fundamentally different mechanisms that lead to occult HBV infections. The molecular mechanisms underlying occult HBV infections, including recently identified mechanisms associated with the suppression of HBV replication and inhibition of HBV proteins, are reviewed in detail. The availability of highly sensitive molecular methods has led to increased detection of occult HBV infections in various clinical settings. The clinical relevance of occult HBV infection and the utility of appropriate diagnostic methods to detect occult HBV infection are discussed. The need for specific guidelines on the diagnosis and management of occult HBV infection is being increasingly recognized; the aspects of mechanistic studies that warrant further investigation are discussed in the final section. PMID:22232374

Avoiding the use of a femoral bridging catheter using a two-stage Hemodialysis Reliable Outflow (HeRO) graft implantation technique.

PubMed

Yoon, William J; Lorelli, David R

2015-01-01

To evaluate a two-stage Hemodialysis Reliable Outflow (HeRO) implantation technique that avoids the use of a femoral bridging catheter versus the conventional one-stage technique requiring a bridging catheter in selected patients. A retrospective review was performed on 20 end-stage renal disease patients with an internal jugular vein (IJV) catheter selected for two-stage HeRO implantation at our institution between January 2010 and March 2013. The arterial graft component (AGC) was implanted without anastomosing it to the target artery (first stage). After AGC incorporation, the venous outflow component was inserted (second stage). The preexisting IJV catheter was maintained for hemodialysis access during the interstage period. Patient characteristics, patency using Kaplan-Meier method and infection rates were analyzed. A total of 17 patients with a mean age of 59 years (70.6% women) completed the two-stage procedure. During the interstage period (mean 12 weeks, range 4-22 weeks), no graft- or surgery-related infection occurred. The need of a femoral bridging catheter was avoided by utilizing the preexisting IJV dialysis catheter. The accumulated HeRO days were 3,916 days with a mean follow-up of 7.7 months (range 1-22.6 months). The HeRO-related infection rate was 0.3/1,000 days. The primary assisted and secondary patency rates at 6 months were 69% and 82%, respectively, which were similar to those of arteriovenous grafts. Staging conferred immediate vascular accessibility. Avoiding the use of a femoral bridging catheter using the two-stage technique may lower infection rate, with comparable primary assisted and secondary patency to arteriovenous grafts and added benefit of immediate cannulatability in this subset of patients.

ASTEROID SIZING BY RADIOGALAXY OCCULTATION AT 5 GHZ

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehtinen, K.; Muinonen, K.; Poutanen, M.

Stellar occultations by asteroids observed at visual wavelengths have been an important tool for studying the size and shape of asteroids and for revising the orbital parameters of asteroids. At radio frequencies, a shadow of an asteroid on the Earth is dominated by diffraction effects. Here, we show, for the first time, that a single observation of an occultation of a compact radio source at a frequency of 5 GHz can be used to derive the effective size of the occulting object and to derive the distance between the observer and the center of the occultation path on the Earth.more » The derived diameter of the occulting object, asteroid (115) Thyra, is 75 ± 6 km. The observed occultation profile shows features that cannot be explained by diffraction of a single asteroid.« less

The power of vertical geolocation of atmospheric profiles from GNSS radio occultation.

PubMed

Scherllin-Pirscher, Barbara; Steiner, Andrea K; Kirchengast, Gottfried; Schwärz, Marc; Leroy, Stephen S

2017-02-16

High-resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic atmospheric variables. Here we introduce and demonstrate the utility of this independent information from RO and discuss the computation, uncertainty, and use of RO atmospheric profiles on isohypsic coordinates-mean sea level altitude and geopotential height-as well as on thermodynamic coordinates (pressure and potential temperature). Using geopotential height as vertical grid, we give information on errors of RO-derived temperature, pressure, and potential temperature profiles and provide an empirical error model which accounts for seasonal and latitudinal variations. The observational uncertainty of individual temperature/pressure/potential temperature profiles is about 0.7 K/0.15%/1.4 K in the tropopause region. It gradually increases into the stratosphere and decreases toward the lower troposphere. This decrease is due to the increasing influence of background information. The total climatological error of mean atmospheric fields is, in general, dominated by the systematic error component. We use sampling error-corrected climatological fields to demonstrate the power of having different and accurate vertical coordinates available. As examples we analyze characteristics of the location of the tropopause for geopotential height, pressure, and potential temperature coordinates as well as seasonal variations of the midlatitude jet stream core. This highlights the broad applicability of RO and the utility of its versatile vertical geolocation for investigating the vertical structure of the troposphere and stratosphere.

Image Analysis of the 2012 Pluto (Near) Occultation

DTIC Science & Technology

2013-09-01

Image Analysis of the 2012 Pluto (Near) Occultation Keith T. Knox Air Force Research Laboratory ABSTRACT Imagery was gathered at the AMOS...observatory on the 3.6-meter telescope for the expected occultation of a star by the dwarf planet, Pluto , on 29 June 2012. The imagery was taken at...5 Hz for 40 minutes before and after the expected time of occultation. The initial analysis of the photometry indicated that Pluto did not occult

Occult pneumomediastinum in blunt chest trauma: clinical significance.

PubMed

Rezende-Neto, J B; Hoffmann, J; Al Mahroos, M; Tien, H; Hsee, L C; Spencer Netto, F; Speers, V; Rizoli, S B

2010-01-01

Thoracic injuries are potentially responsible for 25% of all trauma deaths. Chest X-ray is commonly used to screen patients with chest injury. However, the use of computed tomography (CT) scan for primary screening is increasing, particularly for blunt trauma. CT scans are more sensitive than chest X-ray in detecting intra-thoracic abnormalities such as pneumothoraces and pneumomediastinums. Pneumomediastinum detected by chest X-ray or "overt pneumomediastinum", raises the concern of possible aerodigestive tract injuries. In contrast, there is scarce information on the clinical significance of pneumomediastinum diagnosed by CT scan only or "occult pneumomediastinum". Therefore we investigated the clinical consequences of occult pneumomediastinum in our blunt trauma population. A 2-year retrospective chart review of all blunt chest trauma patients with initial chest CT scan admitted to a level I trauma centre. Data extracted from the medical records include; demographics, occult, overt, or no pneumomediastinum, the presence of intra-thoracic aerodigestive tract injuries (trachea, bronchus, and/or esophagus), mechanism and severity of injury, endotracheal intubation, chest thoracostomy, operations and radiological reports by an attending radiologist. All patients with intra-thoracic aerodigestive tract injuries from 1994 to 2004 were also investigated. Of 897 patients who met the inclusion criteria 839 (93.5%) had no pneumomediastinum. Five patients (0.6%) had overt pneumomediastinum and 53 patients (5.9%) had occult pneumomediastinum. Patients with occult pneumomediastinum had significantly higher ISS and AIS chest (p<0.0001) than patients with no pneumomediastinum. A chest thoracostomy tube was more common (p<0.0001) in patients with occult pneumomediastinum (47.2%) than patients with no pneumomediastinum (10.4%), as well as occult pneumothorax. None of the patients with occult pneumomediastinum had aerodigestive tract injuries (95%CI 0-0.06). Follow up CT scan of

Stellar occultation of polarized light from circumstellar electrons. I - Flat envelopes viewed edge on

NASA Technical Reports Server (NTRS)

Brown, John C.; Fox, Geoffrey K.

1989-01-01

The depolarizing and occultation effects of a finite spherical light source on the polarization of light Thomson-scattered from a flat circumstellar envelope seen edge-on are analyzed. The analysis shows that neglect of the finite size of the light source leads to a gross overestimate of the polarization for a given disk geometry. By including occultation and depolarization, it is found that B-star envelopes are necessarily highly flattened disk-type structures. For a disk viewed edge-on, the effect of occultation reduces the polarization more than the inclusion of the depolarization factor alone. Analysis of a one-dimensional plume leads to a powerful technique that permits the electron density distribution to be explicitly obtained from the polarimetric data.

Dynamic statistical optimization of GNSS radio occultation bending angles: advanced algorithm and performance analysis

NASA Astrophysics Data System (ADS)

Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.

2015-08-01

We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS)-based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAllenging Minisatellite Payload (CHAMP) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction of random errors (standard deviations) of optimized bending angles down to about half of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; and (4) realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well-characterized and high-quality atmospheric profiles over the entire stratosphere.

Magnetic field orientations in Saturn's upper ionosphere inferred from Voyager radio occultations

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1984-01-01

The radio scintillations observed during occultations of Voyagers 1 and 2 by Saturn are analyzed to determine the morphology of plasma irregularities and hence the magnetic field orientation in Saturn's upper atmosphere. The measurement techniques, the weak scattering theory, and the method used to relate the observed radio scintillations to physical properties of the ionospheric irregularities are briefly described. Results on the spatial characteristics of the irregularities are presented, and the magnetic field orientation in Saturn's ionosphere is inferred. Although the occultation measurements generally confirm the accuracy of the Saturnian magnetic field model of Connerney et al. (1982), it is found that a small adjustment of the coefficients in that model's zonal harmonic expansion would remove the discrepancy between the model predictions and the measurements. A strategy for obtaining improved measurements of Saturn's magnetic field from radio occultation observations of scintillations and Faraday rotation using an orbiting spacecraft is briefly discussed.

Implementation of a GPS-RO data processing system for the KIAPS-LETKF data assimilation system

NASA Astrophysics Data System (ADS)

Kwon, H.; Kang, J.-S.; Jo, Y.; Kang, J. H.

2014-11-01

The Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing a new global numerical weather prediction model and an advanced data assimilation system. As part of the KIAPS Package for Observation Processing (KPOP) system for data assimilation, preprocessing and quality control modules for bending angle measurements of global positioning system radio occultation (GPS-RO) data have been implemented and examined. GPS-RO data processing system is composed of several steps for checking observation locations, missing values, physical values for Earth radius of curvature, and geoid undulation. An observation-minus-background check is implemented by use of a one-dimensional observational bending angle operator and tangent point drift is also considered in the quality control process. We have tested GPS-RO observations utilized by the Korean Meteorological Administration (KMA) within KPOP, based on both the KMA global model and the National Center for Atmospheric Research (NCAR) Community Atmosphere Model-Spectral Element (CAM-SE) as a model background. Background fields from the CAM-SE model are incorporated for the preparation of assimilation experiments with the KIAPS-LETKF data assimilation system, which has been successfully implemented to a cubed-sphere model with fully unstructured quadrilateral meshes. As a result of data processing, the bending angle departure statistics between observation and background shows significant improvement. Also, the first experiment in assimilating GPS-RO bending angle resulting from KPOP within KIAPS-LETKF shows encouraging results.

Occult urolithiasis in asymptomatic primary hyperparathyroidism.

PubMed

Tay, Yu-Kwang Donovan; Liu, Minghao; Bandeira, Leonardo; Bucovsky, Mariana; Lee, James A; Silverberg, Shonni J; Walker, Marcella D

2018-05-01

Recent international guidelines suggest renal imaging to detect occult urolithiasis in all patients with asymptomatic primary hyperparathyroidism (PHPT), but data regarding their prevalence and associated risk factors are limited. We evaluated the prevalence and risk factors for occult urolithiasis. Cross-sectional analysis of 96 asymptomatic PHPT patients from a university hospital in the United States with and without occult nephrolithiasis. Occult urolithiasis was identified in 21% of patients. Stone formers had 47% higher 24-hour urinary calcium excretion (p = 0.002). Although available in only a subset of patients (n = 28), activated vitamin D [1,25(OH) 2 D] was 29% higher (p = 0.02) in stone formers. There was no difference in demographics, BMI, calcium or vitamin D intake, other biochemistries, renal function, BMD, or fractures. Receiver operating characteristic curves indicated that urinary calcium excretion and 1,25(OH) 2 D had an area under the curve of 0.724 (p = 0.003) and 0.750 (p = 0.04), respectively. A urinary calcium threshold of >211mg/day provided a sensitivity of 84.2% and a specificity of 55.3% while a 1,25(OH) 2 D threshold of >91pg/mL provided a sensitivity and specificity of 62.5% and 90.0% respectively for the presence of stones. Occult urolithiasis is present in about one-fifth of patients with asymptomatic PHPT and is associated with higher urinary calcium and 1,25(OH) 2 D. Given that most patients will not have occult urolithiasis, targeted imaging in those most likely to have occult stones rather than screening all asymptomatic PHPT patients may be useful. The higher sensitivity of urinary calcium versus 1,25(OH) 2 D suggests screening those with higher urinary calcium may be an appropriate approach.

Progress on an external occulter testbed at flight Fresnel numbers

NASA Astrophysics Data System (ADS)

Kim, Yunjong; Sirbu, Dan; Galvin, Michael; Kasdin, N. Jeremy; Vanderbei, Robert J.

2016-01-01

An external occulter is a spacecraft flown along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. Laboratory verification of occulter designs is necessary to validate the optical models used to design and predict occulter performance. At Princeton, we have designed and built a testbed that allows verification of scaled occulter designs whose suppressed shadow is mathematically identical to that of space occulters. The occulter testbed uses 78 m optical propagation distance to realize the flight Fresnel numbers. We will use an etched silicon mask as the occulter. The occulter is illuminated by a diverging laser beam to reduce the aberrations from the optics before the occulter. Here, we present first light result of a sample design operating at a flight Fresnel number and the mechanical design of the testbed. We compare the experimental results with simulations that predict the ultimate contrast performance.

Earth rotation derived from occultation records

NASA Astrophysics Data System (ADS)

Sôma, Mitsuru; Tanikawa, Kiyotaka

2016-04-01

We determined the values of the Earth's rotation parameter, ΔT = T T - UT, around AD 500 after confirming that the value of the tidal acceleration, dot{n}, of the lunar motion remained unchanged during the period between ancient times and the present. For determining of ΔT, we used contemporaneous occultations of planets by the Moon. In general, occultation records are not useful. However, there are some records that give us a stringent condition for the range of ΔT. Records of the lunar occultations in AD 503 and AD 513 are such examples. In order to assure the usefulness of this occultation data, we used contemporaneous annular and total solar eclipses, which have not been used in the preceding work. This is the first work in which the lunar occultation data have been used as primary data to determine the value of ΔT together with auxiliary contemporaneous annular and total solar eclipses. Our ΔT value is less than a smoothed value (Stephenson 1997) by at least 450 s. The result is consistent with our earlier results obtained from solar eclipses.

Association of preS/S Mutations with Occult Hepatitis B Virus (HBV) Infection in South Korea: Transmission Potential of Distinct Occult HBV Variants

PubMed Central

Kim, Hong; Kim, Bum-Joon

2015-01-01

Occult hepatitis B virus infection (HBV) is characterized by HBV DNA positivity but HBV surface antigen (HBsAg) negativity. Occult HBV infection is associated with a risk of HBV transmission through blood transfusion, hemodialysis, and liver transplantation. Furthermore, occult HBV infection contributes to the development of cirrhosis and hepatocellular carcinoma. We recently reported the characteristic molecular features of mutations in the preS/S regions among Korean individuals with occult infections caused by HBV genotype C2; the variants of preS and S related to severe liver diseases among chronically infected patients were also responsible for the majority of HBV occult infections. We also reported that HBsAg variants from occult-infected Korean individuals exhibit lower HBsAg secretion capacity but not reduced HBV DNA levels. In addition, these variants exhibit increased ROS-inducing capacity compared with the wild-type strain, linking HBV occult infections to liver cell damage. Taken together, our previous reports suggest the transmission potential of distinct HBV occult infection-related variants in South Korea. PMID:26084041

Association of preS/S Mutations with Occult Hepatitis B Virus (HBV) Infection in South Korea: Transmission Potential of Distinct Occult HBV Variants.

PubMed

Kim, Hong; Kim, Bum-Joon

2015-06-15

Occult hepatitis B virus infection (HBV) is characterized by HBV DNA positivity but HBV surface antigen (HBsAg) negativity. Occult HBV infection is associated with a risk of HBV transmission through blood transfusion, hemodialysis, and liver transplantation. Furthermore, occult HBV infection contributes to the development of cirrhosis and hepatocellular carcinoma. We recently reported the characteristic molecular features of mutations in the preS/S regions among Korean individuals with occult infections caused by HBV genotype C2; the variants of preS and S related to severe liver diseases among chronically infected patients were also responsible for the majority of HBV occult infections. We also reported that HBsAg variants from occult-infected Korean individuals exhibit lower HBsAg secretion capacity but not reduced HBV DNA levels. In addition, these variants exhibit increased ROS-inducing capacity compared with the wild-type strain, linking HBV occult infections to liver cell damage. Taken together, our previous reports suggest the transmission potential of distinct HBV occult infection-related variants in South Korea.

Advanced Electrocardiography Can Identify Occult Cardiomyopathy in Doberman Pinschers

NASA Technical Reports Server (NTRS)

Spiljak, M.; Petric, A. Domanjko; Wilberg, M.; Olsen, L. H.; Stepancic, A.; Schlegel, T. T.; Starc, V.

2011-01-01

Recently, multiple advanced resting electrocardiographic (A-ECG) techniques have improved the diagnostic value of short-duration ECG in detection of dilated cardiomyopathy (DCM) in humans. This study investigated whether 12-lead A-ECG recordings could accurately identify the occult phase of DCM in dogs. Short-duration (3-5 min) high-fidelity 12-lead ECG recordings were obtained from 31 privately-owned, clinically healthy Doberman Pinschers (5.4 +/- 1.7 years, 11/20 males/females). Dogs were divided into 2 groups: 1) 19 healthy dogs with normal echocardiographic M-mode measurements: left ventricular internal diameter in diastole (LVIDd . 47mm) and in systole (LVIDs . 38mm) and normal 24-hour ECG recordings (<50 ventricular premature complexes, VPCs); and 2) 12 dogs with occult DCM: 11/12 dogs had increased M-mode measurements (LVIDd . 49mm and/or LVIDs . 40mm) and 5/11 dogs had also >100 VPCs/24h; 1/12 dogs had only abnormal 24-hour ECG recordings (>100 VPCs/24h). ECG recordings were evaluated via custom software programs to calculate multiple parameters of high-frequency (HF) QRS ECG, heart rate variability, QT variability, waveform complexity and 3-D ECG. Student's t-tests determined 19 ECG parameters that were significantly different (P < 0.05) between groups. Principal component factor analysis identified a 5-factor model with 81.4% explained variance. QRS dipolar and non-dipolar voltages, Cornell voltage criteria and QRS waveform residuum were increased significantly (P < 0.05), whereas mean HF QRS amplitude was decreased significantly (P < 0.05) in dogs with occult DCM. For the 5 selected parameters the prediction of occult DCM was performed using a binary logistic regression model with Chi-square tested significance (P < 0.01). ROC analyses showed that the five selected ECG parameters could identify occult ECG with sensitivity 89% and specificity 83%. Results suggest that 12-lead A-ECG might improve diagnostic value of short-duration ECG in earlier detection

An overview of occult hepatitis B virus infection

PubMed Central

Said, Zeinab Nabil Ahmed

2011-01-01

Occult hepatitis B virus (HBV) infection (OBI), alternatively defined as occult hepatitis B (OHB), is a challenging clinical entity. It is recognized by two main characteristics: absence of HBsAg, and low viral replication. The previous two decades have witnessed a remarkable progress in our understanding of OBI and its clinical implications. Appropriate diagnostic techniques must be adopted. Sensitive HBV DNA amplification assay is the gold standard assay for detection of OBI. Viral as well as host factors are implicated in the pathogenesis of OBI. However, published data reporting the infectivity of OBI by transfusion are limited. Several aspects including OBI transmission, infectivity and its relation to the development of chronic liver diseases and hepatocellular carcinoma have to be resolved. The aim of the present review is to highlight recent data on OBI with a focus on its virological diagnosis and clinical outcome. PMID:21528070

Reducing representativeness and sampling errors in radio occultation-radiosonde comparisons

NASA Astrophysics Data System (ADS)

Gilpin, Shay; Rieckh, Therese; Anthes, Richard

2018-05-01

Radio occultation (RO) and radiosonde (RS) comparisons provide a means of analyzing errors associated with both observational systems. Since RO and RS observations are not taken at the exact same time or location, temporal and spatial sampling errors resulting from atmospheric variability can be significant and inhibit error analysis of the observational systems. In addition, the vertical resolutions of RO and RS profiles vary and vertical representativeness errors may also affect the comparison. In RO-RS comparisons, RO observations are co-located with RS profiles within a fixed time window and distance, i.e. within 3-6 h and circles of radii ranging between 100 and 500 km. In this study, we first show that vertical filtering of RO and RS profiles to a common vertical resolution reduces representativeness errors. We then test two methods of reducing horizontal sampling errors during RO-RS comparisons: restricting co-location pairs to within ellipses oriented along the direction of wind flow rather than circles and applying a spatial-temporal sampling correction based on model data. Using data from 2011 to 2014, we compare RO and RS differences at four GCOS Reference Upper-Air Network (GRUAN) RS stations in different climatic locations, in which co-location pairs were constrained to a large circle ( ˜ 666 km radius), small circle ( ˜ 300 km radius), and ellipse parallel to the wind direction ( ˜ 666 km semi-major axis, ˜ 133 km semi-minor axis). We also apply a spatial-temporal sampling correction using European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) gridded data. Restricting co-locations to within the ellipse reduces root mean square (RMS) refractivity, temperature, and water vapor pressure differences relative to RMS differences within the large circle and produces differences that are comparable to or less than the RMS differences within circles of similar area. Applying the sampling correction shows the most significant

Probing Titan's atmosphere with a stellar occultation

NASA Technical Reports Server (NTRS)

Hubbard, W. B.

1991-01-01

The 3 July, 1989 occultation of 28 Sgr by Titan is discussed. The star was readily detectable throughout the occultation, reaching a minimum normalized flux of about 0.05. The occultation probed Titan's atmosphere in a region not studied by the Voyager spacecraft. The region is important for the aerobraking of Titan entry probes, and direct information about its properties is important for the Cassini mission. Occultation data (normalized stellar flux vs universal time) is shown in chart form for NASA supported stations, along with data from a collaborating group at the Wise observatory in Israel. Strong scintillation data of the star is noticeable in the data records, and provides information on waves/turbulence in Titan's high atmosphere.

Estimation of the marine boundary layer height over the central North Pacific using GPS radio occultation

NASA Astrophysics Data System (ADS)

Winning, Thomas E.; Chen, Yi-Leng; Xie, Feiqin

2017-01-01

Global positioning system radio occultation (GPS RO) refractivity data obtained from the first Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) for the years 2007 to 2012 were used to estimate an overall climatology for the height of the marine boundary layer (MBL) over the central North Pacific Ocean including the Hawaiian Island region (10°N-45°N; 125°W-175°W). The trade wind days are identified based on the six-year National Centers for Environmental Prediction (NCEP) global analysis for the same period. About 87% of the RO soundings in summer (June-July-August, JJA) and 47% in winter (December-January-February, DJF) are under trade wind conditions. The MBL height climatology under trade wind conditions is derived and compared to the overall climatology. In general, MBL heights are lowest adjacent to the southern coast of California and gradually increase to the south and west. During the summer (JJA) when the northeasterly trade winds are the dominant surface flow, the median MBL height decreases from 2.0 km over Kauai to 1.9 km over the Big Island with an approximate 2 km maximum that progresses from southwest to northeast throughout the year. If the surface flow is restricted to trade winds only, the maximum MBL heights are located over the same areas, but they increase to a median height of 1.8 km during DJF and 2.1 km during JJA. For the first time, the GPS RO technique allows the depiction of the spatial variations of the MBL height climatology over the central North Pacific.

The diameter of Pallas from its occultation of SAO 85009

NASA Technical Reports Server (NTRS)

Wasserman, L. H.; Millis, R. L.; Franz, O. G.; Bowell, E.; Giclas, H. L.; Martin, L. J.; Elliot, J. L.; Dunham, E.; Mink, D.; White, N. M.

1979-01-01

The May 29, 1978, occultation of SAO 85009 by Pallas was observed photoelectrically at seven widely spaced sites. The observations are well represented by an elliptical apparent limb profile having semimajor and semiminor axes of 279.5 + or - 2.9 and 262.7 + or - 4.5 km, respectively. Combining these results with published information on the light curve and rotational pole position, Pallas's mean diameter is found to be 538 + or - 12 km, which yields a mean density for Pallas of 2.8 + or - 0.5 g/cu cm and a visual geometric albedo of 0.103 + or - 0.005. The diameter of Pallas as determined from this occultation is significantly smaller than the values derived by radiometric, polarimetric, and double-image techniques.

Reflected ray retrieval from radio occultation data using radio holographic filtering of wave fields in ray space

NASA Astrophysics Data System (ADS)

Gorbunov, Michael E.; Cardellach, Estel; Lauritsen, Kent B.

2018-03-01

Linear and non-linear representations of wave fields constitute the basis of modern algorithms for analysis of radio occultation (RO) data. Linear representations are implemented by Fourier Integral Operators, which allow for high-resolution retrieval of bending angles. Non-linear representations include Wigner Distribution Function (WDF), which equals the pseudo-density of energy in the ray space. Representations allow for filtering wave fields by suppressing some areas of the ray space and mapping the field back from the transformed space to the initial one. We apply this technique to the retrieval of reflected rays from RO observations. The use of reflected rays may increase the accuracy of the retrieval of the atmospheric refractivity. Reflected rays can be identified by the visual inspection of WDF or spectrogram plots. Numerous examples from COSMIC data indicate that reflections are mostly observed over oceans or snow, in particular over Antarctica. We introduce the reflection index that characterizes the relative intensity of the reflected ray with respect to the direct ray. The index allows for the automatic identification of events with reflections. We use the radio holographic estimate of the errors of the retrieved bending angle profiles of reflected rays. A comparison of indices evaluated for a large base of events including the visual identification of reflections indicated a good agreement with our definition of reflection index.

Io hot spots - Infrared photometry of satellite occultations

NASA Technical Reports Server (NTRS)

Goguen, J. D.; Matson, D. L.; Sinton, W. M.; Howell, R. R.; Dyck, H. M.

1988-01-01

Io's active hot spots, which are presently mapped on the basis of IR photometry of this moon's occultation by other Gallilean satellites, are obtained with greatest spatial resolution near the sub-earth point. A model is developed for the occultation lightcurves, and its fitting to the data defines the apparent path of the occulting satellite relative to Io; the mean error in apparent relative position of occulting satellites is of the order of 178 km. A heretofore unknown, 20-km diameter hot spot is noted on Io's leading hemisphere.

Strong scintillations during atmospheric occultations Theoretical intensity spectra. [radio scattering during spacecraft occultations by planetary atmospheres

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1986-01-01

Each of the two Voyager spacecraft launched in 1977 has completed a reconnaissance of the Jovian and Saturnian systems. In connection with occultation experiments, strong scintillations were observed. Further theoretical work is required before these scintillations can be interpreted. The present study is, therefore, concerned with the derivation of a theory for strong scattering during atmospheric occultation experiments, taking into account as fundamental quantity of interest the spatial spectrum (or spectral density) of intensity fluctuations. Attention is given to a theory for intensity spectra, and numerical calculations. The new formula derived for Phi-i accounts for strong scattering of electromagnetic waves during atmospheric occultations.

Sensing Water Vapon via Spacecraft Radio Occultation Observations

NASA Technical Reports Server (NTRS)

Kursinski, E. Robert; Hajj, George A.

2000-01-01

The radio occultation technique has been used to characterize planetary atmospheres since the 1960's spanning atmospheric pressures from 16 microbars to several bars. In 1988, the use of GPS signals to make occultation observations of Earth's atmosphere was realized by Tom Yunck and Gunnar Lindal at JPL. In the GPS to low-Earth-orbiter limb- viewing occultation geometry, Fresnel diffraction yield a unique combination of high vertical resolution of 100 m to 1 km at long wavelengths (approx. 20 cm) insensitive to particulate scattering which allows routine limb sounding from the lower mesosphere through the troposphere. A single orbiting GPS/GLONASS receiver can observe - 1000 to 1400 daily occultations providing as many daily, high vertical resolution soundings as the present global radiosonde network, but with far more evenly distributed, global coverage. The occultations yield profiles of refractivity as a function of height. In the cold, dry conditions of the upper troposphere and above (T less than 240 K), profiles of density, pressure (geopotential), and temperature can be derived. Given additional temperature information, water vapor can be derived in the midddle and lower troposphere with a unique combination of vertical resolution, global distribution and insensitivity to clouds and precipitation to an accuracy of approx. 0.2 g/kg. At low latitudes, moisture profiles will be accurate to 1-5% within the convective boundary layer and better than 20% below 6 to 7 km. Accuracies of climatological averages should be approx. 0. 1 g/kg limited by the biases in the temperature estimates. To use refractivity to constrain water vapor, knowledge of temperature is required. The simplest approach is to use the temperature field from an analysis such as the 6 hour ECMWF global analysis interpolated to the locations of each occultation. A better approach is to combine the temperature and moisture fields from such an analysis with the occultation refractivity in a weighting

OCCULT-ORSER complete conversational user-language translator

NASA Technical Reports Server (NTRS)

Ramapriyan, H. K.; Young, K.

1981-01-01

Translator program (OCCULT) assists non-computer-oriented users in setting up and submitting jobs for complex ORSER system. ORSER is collection of image processing programs for analyzing remotely sensed data. OCCULT is designed for those who would like to use ORSER but cannot justify acquiring and maintaining necessary proficiency in Remote Job Entry Language, Job Control Language, and control-card formats. OCCULT is written in FORTRAN IV and OS Assembler for interactive execution.

A new retrieval algorithm for tropospheric temperature, humidity and pressure profiling based on GNSS radio occultation data

NASA Astrophysics Data System (ADS)

Kirchengast, Gottfried; Li, Ying; Scherllin-Pirscher, Barbara; Schwärz, Marc; Schwarz, Jakob; Nielsen, Johannes K.

2017-04-01

The GNSS radio occultation (RO) technique is an important remote sensing technique for obtaining thermodynamic profiles of temperature, humidity, and pressure in the Earth's troposphere. However, due to refraction effects of both dry ambient air and water vapor in the troposphere, retrieval of accurate thermodynamic profiles at these lower altitudes is challenging and requires suitable background information in addition to the RO refractivity information. Here we introduce a new moist air retrieval algorithm aiming to improve the quality and robustness of retrieving temperature, humidity and pressure profiles in moist air tropospheric conditions. The new algorithm consists of four steps: (1) use of prescribed specific humidity and its uncertainty to retrieve temperature and its associated uncertainty; (2) use of prescribed temperature and its uncertainty to retrieve specific humidity and its associated uncertainty; (3) use of the previous results to estimate final temperature and specific humidity profiles through optimal estimation; (4) determination of air pressure and density profiles from the results obtained before. The new algorithm does not require elaborated matrix inversions which are otherwise widely used in 1D-Var retrieval algorithms, and it allows a transparent uncertainty propagation, whereby the uncertainties of prescribed variables are dynamically estimated accounting for their spatial and temporal variations. Estimated random uncertainties are calculated by constructing error covariance matrices from co-located ECMWF short-range forecast and corresponding analysis profiles. Systematic uncertainties are estimated by empirical modeling. The influence of regarding or disregarding vertical error correlations is quantified. The new scheme is implemented with static input uncertainty profiles in WEGC's current OPSv5.6 processing system and with full scope in WEGC's next-generation system, the Reference Occultation Processing System (rOPS). Results from

Sizes, Shapes, and Satellites of Asteroids from Occultations

NASA Astrophysics Data System (ADS)

Waring Dunham, David; Herald, David Russell; Preston, Steve; Timerson, Bradley; Maley, Paul; Frappa, Eric; Hayamizu, Tsutomu; Talbot, John; Poro, Atila

2015-08-01

For 40 years, the sizes and shapes of dozens of asteroids have been determined from observations of asteroidal occultations. Some of the first evidence for satellites of asteroids was obtained from the early efforts; now, the orbits and sizes of some satellites discovered by other means have been refined from occultation observations. Also, several close binary stars have been discovered, and the angular diameters of some stars have been measured from analysis of these observations. The International Occultation Timing Association (IOTA) coordinates this activity worldwide, from predicting and publicizing the events, to accurately timing the occultations from as many stations as possible, and publishing and archiving the observations.The release of the Hipparcos and Tycho catalogs in 1997, from ESA’s Hipparcos space mission, revolutionized asteroidal occultation work, increasing the routine accuracy of the predictions and the annual number of observations by an order of magnitude. IOTA developed an efficient procedure for predicting the occultations using a combination of new star catalogs, based on Hipparcos and new star catalogs, generated mainly at the U. S. Naval Observatory (USNO), and new observations of asteroids relative to the improved astrometric nets mainly from USNO’s Flagstaff Astrometric Scanning Transit Telescope and JPL’s Table Mountain Observatory. In addition, many IOTA observers now use inexpensive low-light-level video cameras and specially built GPS video time inserters to accurately time the events. This automation has also allowed some observers to deploy multiple remote video stations across occultation paths. Then, one observer can record several “chords” across the asteroid. The cameras are sensitive enough that easily-hidden telescopes, many of which can be packed in standard air travel suitcases, can be used for many of the predicted occultations. IOTA’s network of regional coordinators collect and reduce the observations

Impact assessment of GPS radio occultation data on Antarctic analysis and forecast using WRF 3DVAR

NASA Astrophysics Data System (ADS)

Zhang, H.; Wee, T. K.; Liu, Z.; Lin, H. C.; Kuo, Y. H.

2016-12-01

This study assesses the impact of Global Positioning System (GPS) Radio Occultation (RO) refractivity data on the analysis and forecast in the Antarctic region. The RO data are continuously assimilated into the Weather Research and Forecasting (WRF) Model using the WRF 3DVAR along with other observations that were operationally available to the National Center for Environmental Prediction (NCEP) during a month period, October 2010, including the Advance Microwave Sounding Unit (AMSU) radiance data. For the month-long data assimilation experiments, three RO datasets are used: 1) The actual operational dataset, which was produced by the near real-time RO processing at that time and provided to weather forecasting centers; 2) a post-processed dataset with posterior clock and orbit estimates, and with improved RO processing algorithms; and, 3) another post-processed dataset, produced with a variational RO processing. The data impact is evaluated with comparing the forecasts and analyses to independent driftsonde observations that are made available through the Concordiasi field campaign, in addition to utilizing other traditional means of verification. A denial of RO data (while keeping all other observations) resulted in a remarkable quality degradation of analysis and forecast, indicating the high value of RO data over the Antarctic area. The post-processed RO data showed a significantly larger positive impact compared to the near real-time data, due to extra RO data from the TerraSAR-X satellite (unavailable at the time of the near real-time processing) as well as the supposedly improved data quality as a result of the post-processing. This strongly suggests that the future polar constellation of COSMIC-2 is vital. The variational RO processing further reduced the systematic and random errors in both analysis and forecasts, for instance, leading to a smaller background departure of AMSU radiance. This indicates that the variational RO processing provides an improved

The occult submucous cleft palate.

PubMed

Kaplan, E N

1975-10-01

We have studied 41 patients with classic submucous cleft and 32 cases with occult submucous cleft. Both groups have the same anatomic abnormality that leads to velar dysfunction-the insertion of the palate muscles onto the hard palate rather than onto the midline soft palate raphe. However, the occult submucous cleft palate does not have the classic triad of bifid uvula, hard palate bony notch, and furrow in the midline of the soft palate. Characteristic facial features, cephalmetric x-rays, and cine voice studies can help make a presumptive diagnosis of occult submucous cleft palate. Surgical management includes a diagnostic palate exploration to identify muscle configuration followed by levator muscle sling reconstruction, palate pushback, and pharyngeal flap. Excellent speech results are obtained except with patients having palate paresis.

Quality aspects of the Wegener Center multi-satellite GPS radio occultation record OPSv5.6

NASA Astrophysics Data System (ADS)

Angerer, Barbara; Ladstädter, Florian; Scherllin-Pirscher, Barbara; Schwärz, Marc; Steiner, Andrea K.; Foelsche, Ulrich; Kirchengast, Gottfried

2017-12-01

The demand for high-quality atmospheric data records, which are applicable in climate studies, is undisputed. Using such records requires knowledge of the quality and the specific characteristics of all contained data sources. The latest version of the Wegener Center (WEGC) multi-satellite Global Positioning System (GPS) radio occultation (RO) record, OPSv5.6, provides globally distributed upper-air satellite data of high quality, usable for climate and other high-accuracy applications. The GPS RO technique has been deployed in several satellite missions since 2001. Consistency among data from these missions is essential to create a homogeneous long-term multi-satellite climate record. In order to enable a qualified usage of the WEGC OPSv5.6 data set we performed a detailed analysis of satellite-dependent quality aspects from 2001 to 2017. We present the impact of the OPSv5.6 quality control on the processed data and reveal time-dependent and satellite-specific quality characteristics. The highest quality data are found for MetOp (Meteorological Operational satellite) and GRACE (Gravity Recovery and Climate Experiment). Data from FORMOSAT-3/COSMIC (Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate) are also of high quality. However, comparatively large day-to-day variations and satellite-dependent irregularities need to be taken into account when using these data. We validate the consistency among the various satellite missions by calculating monthly mean temperature deviations from the multi-satellite mean, including a correction for the different sampling characteristics. The results are highly consistent in the altitude range from 8 to 25 km, with mean temperature deviations less than 0.1 K. At higher altitudes the OPSv5.6 RO temperature record is increasingly influenced by the characteristics of the bending angle initialization, with the amount of impact depending on the receiver quality.

Implementation of a GPS-RO data processing system for the KIAPS-LETKF data assimilation system

NASA Astrophysics Data System (ADS)

Kwon, H.; Kang, J.-S.; Jo, Y.; Kang, J. H.

2015-03-01

The Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing a new global numerical weather prediction model and an advanced data assimilation system. As part of the KIAPS package for observation processing (KPOP) system for data assimilation, preprocessing, and quality control modules for bending-angle measurements of global positioning system radio occultation (GPS-RO) data have been implemented and examined. The GPS-RO data processing system is composed of several steps for checking observation locations, missing values, physical values for Earth radius of curvature, and geoid undulation. An observation-minus-background check is implemented by use of a one-dimensional observational bending-angle operator, and tangent point drift is also considered in the quality control process. We have tested GPS-RO observations utilized by the Korean Meteorological Administration (KMA) within KPOP, based on both the KMA global model and the National Center for Atmospheric Research Community Atmosphere Model with Spectral Element dynamical core (CAM-SE) as a model background. Background fields from the CAM-SE model are incorporated for the preparation of assimilation experiments with the KIAPS local ensemble transform Kalman filter (LETKF) data assimilation system, which has been successfully implemented to a cubed-sphere model with unstructured quadrilateral meshes. As a result of data processing, the bending-angle departure statistics between observation and background show significant improvement. Also, the first experiment in assimilating GPS-RO bending angle from KPOP within KIAPS-LETKF shows encouraging results.

A variational regularization of Abel transform for GPS radio occultation

NASA Astrophysics Data System (ADS)

Wee, Tae-Kwon

2018-04-01

In the Global Positioning System (GPS) radio occultation (RO) technique, the inverse Abel transform of measured bending angle (Abel inversion, hereafter AI) is the standard means of deriving the refractivity. While concise and straightforward to apply, the AI accumulates and propagates the measurement error downward. The measurement error propagation is detrimental to the refractivity in lower altitudes. In particular, it builds up negative refractivity bias in the tropical lower troposphere. An alternative to AI is the numerical inversion of the forward Abel transform, which does not incur the integration of error-possessing measurement and thus precludes the error propagation. The variational regularization (VR) proposed in this study approximates the inversion of the forward Abel transform by an optimization problem in which the regularized solution describes the measurement as closely as possible within the measurement's considered accuracy. The optimization problem is then solved iteratively by means of the adjoint technique. VR is formulated with error covariance matrices, which permit a rigorous incorporation of prior information on measurement error characteristics and the solution's desired behavior into the regularization. VR holds the control variable in the measurement space to take advantage of the posterior height determination and to negate the measurement error due to the mismodeling of the refractional radius. The advantages of having the solution and the measurement in the same space are elaborated using a purposely corrupted synthetic sounding with a known true solution. The competency of VR relative to AI is validated with a large number of actual RO soundings. The comparison to nearby radiosonde observations shows that VR attains considerably smaller random and systematic errors compared to AI. A noteworthy finding is that in the heights and areas that the measurement bias is supposedly small, VR follows AI very closely in the mean refractivity

Atmospheric diurnal and semi-diurnal variations observed with GPS radio occultation soundings

NASA Astrophysics Data System (ADS)

Xie, F.; Wu, D. L.; Ao, C. O.; Mannucci, A. J.

2009-11-01

Diurnal and semi-diurnal variations, driven by solar forcing, are two fundamental modes in the Earth's weather and climate system. Radio occultation (RO) measurements from the six COSMIC satellites (Constellation Observing System for Meteorology Ionosphere and Climate) provide rather uniform global coverage with high vertical resolution, all-weather and diurnal sampling capability. This paper analyzes the diurnal and semi-diurnal variations of both temperature and refractivity from two-year (2007-2008) COSMIC RO measurements in the troposphere and stratosphere. The RO observations reveal both propagating and trapped vertical structures of diurnal and semi-diurnal variations, including transition regions near the tropopause where data with high vertical resolution are critical. In the tropics the diurnal amplitude in refractivity decreases with altitude from a local maximum in the planetary boundary layer and reaches the minimum around 14 km and then further increase amplitude in the stratosphere. The upward propagating component of the migrating diurnal tides in the tropics is clearly captured by the GPS RO measurements, which show a downward progression in phase from upper troposphere to the stratopause with a vertical wavelength of about 25 km. Below 500 hPa (~5.5 km), seasonal variations of the peak diurnal amplitude in the tropics follow the solor forcing change in latitude, while at 30 km the seasonal pattern reverses with the diurnal amplitude peaking at the opposite side of the equator relative to the solar forcing. Polar regions shows large diurnal variations in the stratosphere with strong seasonal variations and the cause(s) of these variations require further investigations.

SU-E-T-218: The IHE-RO Helper Tool: Demonstrating the Connectivity Issues Solved by IHE-RO.

PubMed

Kapoor, Rishabh; Yeung, Daniel; Kumar, Sabari Ajay; Alex, Daley; Kapur, Priyanka; Palta, Jatinder

2012-06-01

To develop a Web-based application (IHE-RO Helper) to allow comprehensive review of the interconnectivity and interoperability of various radiotherapy devices established through testing sanctioned by the Integrating Healthcare Enterprise-Radiation Oncology (IHE-RO). IHE-RO is an initiative sponsored by ASTRO to improve the way computer based systems in radiation oncology share information using well-defined data exchange standards (DICOM / HL7). At the IHE-RO Connectathon events over the last 4 years, 11 vendors with 14 different products have successfully tested and identified solutions to connectivity problems in treatment planning, simulation and delivery. Because the test results are highly technical, the interconnectivity issues amongst the RT devices may get overlooked by the end users. The IHE-RO helper tool is designed to operate in simple clinical terms with queries and presentations organized based on treatment techniques and clinical features that are familiar to the practitioners. For example, if you are planning to purchase a treatment planning system capable of generating plans (e.g. Stereotactic treatments) and are concerned whether the TPS can successfully transfer such data to your treatment management system (TMS) and subsequently to your treatment delivery system (TDS), the IHE-RO Helper can identify the connectivity requirements and list vendors that have successfully passed an IHE-RO Connectathon and validated their solution to the specific requirements. The IHE-RO helper tool provides a graphical and textual user interface to effectively demonstrate the solved interconnectivity problems between TPS, TMS and TDS. A report is also provided that explains the interconnectivity problems and its solutions. The IHE-RO helper is an effective tool to clearly identify vendor products that are IHE-RO compliant, thereby encourages vendor participation in testing and validation. Such a tool will be invaluable in procurement of new equipment to ensure a

Fecal Occult Blood Test (FOBT): MedlinePlus Lab Test Information

MedlinePlus

... medlineplus.gov/labtests/fecaloccultbloodtestfobt.html Fecal Occult Blood Test (FOBT) To use the sharing features on this ... enable JavaScript. What is a Fecal Occult Blood Test? A fecal occult blood test (FOBT) looks at ...

A Digital Video System for Observing and Recording Occultations

NASA Astrophysics Data System (ADS)

Barry, M. A. Tony; Gault, Dave; Pavlov, Hristo; Hanna, William; McEwan, Alistair; Filipović, Miroslav D.

2015-09-01

Stellar occultations by asteroids and outer solar system bodies can offer ground based observers with modest telescopes and camera equipment the opportunity to probe the shape, size, atmosphere, and attendant moons or rings of these distant objects. The essential requirements of the camera and recording equipment are: good quantum efficiency and low noise; minimal dead time between images; good horological faithfulness of the image timestamps; robustness of the recording to unexpected failure; and low cost. We describe an occultation observing and recording system which attempts to fulfil these requirements and compare the system with other reported camera and recorder systems. Five systems have been built, deployed, and tested over the past three years, and we report on three representative occultation observations: one being a 9 ± 1.5 s occultation of the trans-Neptunian object 28978 Ixion (m v =15.2) at 3 seconds per frame; one being a 1.51 ± 0.017 s occultation of Deimos, the 12 km diameter satellite of Mars, at 30 frames per second; and one being a 11.04 ± 0.4 s occultation, recorded at 7.5 frames per second, of the main belt asteroid 361 Havnia, representing a low magnitude drop (Δm v = ~0.4) occultation.

A New Method for Detecting and Monitoring Atmospheric Natural Hazards with GPS RO

NASA Astrophysics Data System (ADS)

Biondi, R.; Steiner, A. K.; Rieckh, T. M.; Kirchengast, G.

2014-12-01

Global Positioning System (GPS) Radio Occultation (RO) allows measurements in any meteorological condition, with global coverage, high vertical resolution, and high accuracy. With more than 13 years of data availability, RO also became a fundamental tool for studying climate change. We present here the application of RO for detecting and monitoring tropical cyclones (TCs), deep convective systems (CSs) and volcanic ash clouds (ACs).Deep CSs and TCs play a fundamental role in atmospheric circulation producing vertical transport, redistributing water vapor and trace gases, changing the thermal structure of the Upper Troposphere and Lower Stratosphere (UTLS) and affecting climate through overshooting into the stratosphere. Explosive volcanic eruptions produce large ACs dangerous for the aviation and they can impact climate when the ash is injected into the UTLS.The detection of cloud top height, the determination of cloud extent, the discrimination of ACs from CSs clouds and the detection of overshooting are main challenges for atmospheric natural hazards study. We created a reference atmosphere with a resolution of 5° in latitude and longitude, sampled on a 1° x 1° grid, and a vertical sampling of 100 m. We then compared RO profiles acquired during TCs, CSs and ACs to the reference atmosphere and computed anomaly profiles.CSs, TCs and the ACs leave a clear signature in the atmosphere which can be detected by RO. Using RO temperature and bending angle profiles we gain insight into the vertical thermal structure and developed a new method for detecting the cloud top altitude with high accuracy.We have characterized the TCs by ocean basins and intensities, showing that they have a different thermal structure and reach to different altitudes according to the basin. We provide statistics on overshooting frequency, achieving results consistent with patterns found in the literature and demonstrating that RO is well suited for this kind of study. We have analyzed the

Ultrasound for diagnosing radiographically occult scaphoid fracture.

PubMed

Kwee, Robert M; Kwee, Thomas C

2018-04-04

To systematically review the literature on the performance of ultrasound in diagnosing radiographically occult scaphoid fracture. A systematic search was performed in the MEDLINE and Embase databases. Original studies investigating the performance of ultrasound in diagnosing radiographically occult scaphoid fracture in more than 10 patients were eligible for inclusion. Studies that included both radiographically apparent and occult scaphoid fractures (at initial radiography) were only included if independent data on radiographically occult fractures were reported. Methodological quality of the studies included was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Accuracy data were extracted. Sensitivity and specificity were pooled with a bivariate random-effects model. The inclusion criteria were met by 7 studies; total sample size comprised 314 patients. All studies, except 1, included cortical disruption of the scaphoid in their diagnostic criteria. The sensitivity and specificity of ultrasound in diagnosing radiographically occult scaphoid fracture ranged from 77.8% to 100% and from 71.4% to 100% respectively, with pooled estimates of 85.6% (95% CI: 73.9%, 92.6%) and 83.3% % (95% CI: 72.0%, 90.6%) respectively. Exclusion of two studies with a high risk of bias in any QUADAS-2 domain did not affect the pooled results. Ultrasound can diagnose radiographically occult scaphoid fracture with a fairly high degree of accuracy. Because of its relatively low costs and fairly high sensitivity, ultrasound seems more cost-effective than empiric cast immobilization and may be used when CT and MRI are not readily available.

Chiron stellar occultation candidates: 1993-1996

NASA Technical Reports Server (NTRS)

Bus, S. J.; Wasserman, L. H.; Elliot, J. L.

1994-01-01

A photographic search was conducted for stars that may be occulted by the unusual solar system object (2060) Chiron during the period from fall 1993 through summer 1996. 44 candidates were identified to a limiting V magnitude of 16, and for which the minimum appulse separation with Chiron is predicted to be less than 2.5 arcsec. The successful observation of a stellar occultation by Chiron would give a direct measure of its diameter (currently estimated to be between 60 and 300 km), and would help considerably in constraining Chiron's surface properties and volatile makeup. If at the time of the occultation, Chiron exhibits a significant coma, there is also the potential for measuring the optical-depth profile of the dust in its inner coma.

Case study of inclined sporadic E layers in the Earth's ionosphere observed by CHAMP/GPS radio occultations: Coupling between the tilted plasma layers and internal waves

NASA Astrophysics Data System (ADS)

Gubenko, Vladimir N.; Pavelyev, A. G.; Kirillovich, I. A.; Liou, Y.-A.

2018-04-01

We have used the radio occultation (RO) satellite data CHAMP/GPS (Challenging Minisatellite Payload/Global Positioning System) for studying the ionosphere of the Earth. A method for deriving the parameters of ionospheric structures is based upon an analysis of the RO signal variations in the phase path and intensity. This method allows one to estimate the spatial displacement of a plasma layer with respect to the ray perigee, and to determine the layer inclination and height correction values. In this paper, we focus on the case study of inclined sporadic E (Es) layers in the high-latitude ionosphere based on available CHAMP RO data. Assuming that the internal gravity waves (IGWs) with the phase-fronts parallel to the ionization layer surfaces are responsible for the tilt angles of sporadic plasma layers, we have developed a new technique for determining the parameters of IGWs linked with the inclined Es structures. A small-scale internal wave may be modulating initially horizontal Es layer in height and causing a direction of the plasma density gradient to be rotated and aligned with that of the wave propagation vector k. The results of determination of the intrinsic wave frequency and period, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase speeds, and other characteristics of IGWs under study are presented and discussed.

Nondimensional Representations for Occulter Design and Performance Evaluation

NASA Technical Reports Server (NTRS)

Cady, Eric

2011-01-01

An occulter is a spacecraft with a precisely-shaped optical edges which ies in formation with a telescope, blocking light from a star while leaving light from nearby planets una ected. Using linear optimization, occulters can be designed for use with telescopes over a wide range of telescope aperture sizes, science bands, and starlight suppression levels. It can be shown that this optimization depends primarily on a small number of independent nondimensional parameters, which correspond to Fresnel numbers and physical scales and enter the optimization only as constraints. We show how these can be used to span the parameter space of possible optimized occulters; this data set can then be mined to determine occulter sizes for various mission scenarios and sets of engineering constraints.

Sizes, Shapes, and Satellites of Asteroids from Occultations

NASA Astrophysics Data System (ADS)

Dunham, David W.; Herald, David; Preston, Steve; Timerson, Brad; Maley, Paul; Frappa, Eric; Hayamizu, Tsutomu; Talbot, John; Poro, Atila

2016-01-01

For 40 years, the sizes and shapes of many dozens of asteroids have been determined from observations of asteroidal occultations, and over a thousand high-precision positions of the asteroids relative to stars have been measured. Some of the first evidence for satellites of asteroids was obtained from the early efforts; now, the orbits and sizes of some satellites discovered by other means have been refined from occultation observations. Also, several close binary stars have been discovered, and the angular diameters of some stars have been measured from analysis of these observations. The International Occultation Timing Association (IOTA) coordinates this activity worldwide, from predicting and publicizing the events, to accurately timing the occultations from as many stations as possible, and publishing and archiving the observations.

Retrieval Algorithms for the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)

Thompson, Robert E.; Gordley, Larry L.

2009-01-01

The Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) provided high quality measurements of key middle atmosphere constituents, aerosol characteristics, and temperature for 14 years (1991-2005). This report is an outline of the Level 2 retrieval algorithms, and it also describes the great care that was taken in characterizing the instrument prior to launch and throughout its mission life. It represents an historical record of the techniques used to analyze the data and of the steps that must be considered for the development of a similar experiment for future satellite missions.

Mutations Associated With Occult Hepatitis B in HIV-Positive South Africans

PubMed Central

Powell, Eleanor A.; Gededzha, Maemu P.; Rentz, Michael; Rakgole, Nare J.; Selabe, Selokela G.; Seleise, Tebogo A.; Mphahlele, M. Jeffrey; Blackard, Jason T.

2015-01-01

Occult hepatitis B is characterized by the absence of hepatitis B surface antigen (HBsAg) but the presence of HBV DNA. Because diagnosis of hepatitis B virus (HBV) typically includes HBsAg detection, occult HBV remains largely undiagnosed. Occult HBV is associated with increased risk of hepatocellular carcinoma, reactivation to chronic HBV during immune suppression, and transmission during blood transfusion and liver transplant. The mechanisms leading to occult HBV infection are unclear, although viral mutations are likely a significant factor. In this study, sera from 394 HIV-positive South Africans were tested for HBV DNA and HBsAg. For patients with detectable HBV DNA, the overlapping surface and polymerase open reading frames (ORFs) were sequenced. Occult-associated mutations—those mutations found exclusively in individuals with occult HBV infection but not in individuals with chronic HBV infection from the same cohort or GenBank references—were identified. Ninety patients (22.8%) had detectable HBV DNA. Of these, 37 had detectable HBsAg, while 53 lacked detectable surface antigen. The surface and polymerase ORFs were cloned successfully for 19 patients with chronic HBV and 30 patients with occult HBV. In total, 235 occult-associated mutations were identified. Ten occult-associated mutations were identified in more than one patient. Additionally, 15 amino acid positions had two distinct occult-associated mutations at the same residue. Occult-associated mutations were common and present in all regions of the surface and polymerase ORFs. Further study is underway to determine the effects of these mutations on viral replication and surface antigen expression in vitro. PMID:25164924

Mutations associated with occult hepatitis B in HIV-positive South Africans.

PubMed

Powell, Eleanor A; Gededzha, Maemu P; Rentz, Michael; Rakgole, Nare J; Selabe, Selokela G; Seleise, Tebogo A; Mphahlele, M Jeffrey; Blackard, Jason T

2015-03-01

Occult hepatitis B is characterized by the absence of hepatitis B surface antigen (HBsAg) but the presence of HBV DNA. Because diagnosis of hepatitis B virus (HBV) typically includes HBsAg detection, occult HBV remains largely undiagnosed. Occult HBV is associated with increased risk of hepatocellular carcinoma, reactivation to chronic HBV during immune suppression, and transmission during blood transfusion and liver transplant. The mechanisms leading to occult HBV infection are unclear, although viral mutations are likely a significant factor. In this study, sera from 394 HIV-positive South Africans were tested for HBV DNA and HBsAg. For patients with detectable HBV DNA, the overlapping surface and polymerase open reading frames (ORFs) were sequenced. Occult-associated mutations-those mutations found exclusively in individuals with occult HBV infection but not in individuals with chronic HBV infection from the same cohort or GenBank references-were identified. Ninety patients (22.8%) had detectable HBV DNA. Of these, 37 had detectable HBsAg, while 53 lacked detectable surface antigen. The surface and polymerase ORFs were cloned successfully for 19 patients with chronic HBV and 30 patients with occult HBV. In total, 235 occult-associated mutations were identified. Ten occult-associated mutations were identified in more than one patient. Additionally, 15 amino acid positions had two distinct occult-associated mutations at the same residue. Occult-associated mutations were common and present in all regions of the surface and polymerase ORFs. Further study is underway to determine the effects of these mutations on viral replication and surface antigen expression in vitro. © 2014 Wiley Periodicals, Inc.

Design of an occulter testbed at flight Fresnel numbers

NASA Astrophysics Data System (ADS)

Sirbu, Dan; Kasdin, N. Jeremy; Kim, Yunjong; Vanderbei, Robert J.

2015-01-01

An external occulter is a spacecraft flown along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. Laboratory verification of occulter designs is necessary to validate the optical models used to design and predict occulter performance. At Princeton, we are designing and building a testbed that allows verification of scaled occulter designs whose suppressed shadow is mathematically identical to that of space occulters. Here, we present a sample design operating at a flight Fresnel number and is thus representative of a realistic space mission. We present calculations of experimental limits arising from the finite size and propagation distance available in the testbed, limitations due to manufacturing feature size, and non-ideal input beam. We demonstrate how the testbed is designed to be feature-size limited, and provide an estimation of the expected performance.

Application Side Casing on Open Deck RoRo to Improve Ship Stability

NASA Astrophysics Data System (ADS)

Hasanudin; K. A. P Utama, I.; Chen, Jeng-Horng

2018-03-01

RoRo is a vessel that can transport passengers, cargo, container and cars. Open Car Deck is favourite RoRo Vessel in developing countries due to its small GT, small tax and spacious car deck, but it has poor survival of stability. Many accident involve Open Car Deck RoRo which cause fatalities and victim. In order to ensure the safety of the ship, IMO had applied intact stability criteria IS Code 2008 which adapted from Rahola’s Research, but since 2008 IMO improved criteria become probabilistic damage stability SOLAS 2009. The RoRo type Open Car Deck has wide Breadth (B), small Draft (D) and small freeboard. It has difficulties to satisfy the ship’s stability criteria. Side Casings which has been applied in some RoRo have be known reduce freeboard or improve ship’s safety. In this paper investigated the effect side casings to survival of intact dan damage ship’s stability. Calculation has been conducted for four ships without, existing and full side casings. The investigation results shows that defect stability of Open Deck RoRo can be reduce with fitting side casing.

Diagnostic strategy for occult hepatitis B virus infection

PubMed Central

Ocana, Sara; Casas, Maria Luisa; Buhigas, Ingrid; Lledo, Jose Luis

2011-01-01

In 2008, the European Association for the study of the liver (EASL) defined occult hepatitis B virus infection (OBI) as the “presence of hepatitis B virus (HBV) DNA in the liver (with detectable or undetectable HBV DNA in the serum) of individuals testing hepatitis B surface antigen (HBsAg) negative by currently available assays”. Several aspects of occult HBV infection are still poorly understood, including the definition itself and a standardized approach for laboratory-based detection, which is the purpose of this review. The clinical significance of OBI has not yet been established; however, in terms of public health, the clinical importance arises from the risk of HBV transmission. Consequently, it is important to detect high-risk groups for occult HBV infection to prevent transmission. The main issue is, perhaps, to identify the target population for screening OBI. Viremia is very low or undetectable in occult HBV infection, even when the most sensitive methods are used, and the detection of the viral DNA reservoir in hepatocytes would provide the best evaluation of occult HBV prevalence in a defined set of patients. However, this diagnostic approach is obviously unsuitable: blood detection of occult hepatitis B requires assays of the highest sensitivity and specificity with a lower limit of detection < 10 IU/mL for HBV DNA and < 0.1 ng/mL for HBsAg. PMID:21472120

Portable high speed photometry systems for observing occultations

NASA Astrophysics Data System (ADS)

Elliot, J. L.; Dunham, E. W.

1986-09-01

Ring orbit studies for Uranus have been particularly fruitful because of the ability, through occultations, to obtain data of high spatial resolution at the rate of 1 to 2 times per year. The occultation program at M.I.T. involves: (1) identifying the scientific questions that can be answered by occultation events, (2) predicting the zone of visibility for the useful events, (3) maintaining and improving a set of portable high-speed photometric systems, (4) obtaining the observations, and (5) reducing the data and interpreting the results. Two stellar occultations by Uranus occurred in May 1985, and were observed with a network of large telescopes that encompassed the Northern and Southern Hemispheres. Portable quartz-oscillator time standards were used at all observatories, and were calibrated before and after each event. Observations obtained form Cerro Tololo and McDonald Observatories of the 4 May and 24 May 1985 occultations by the Uranian rings clearly show a companion to the delta ring on both the immersion and emersion traces. The occultation by Ceres that occurred on 12 November 1984 was observed. Preliminary results give a mean diameter of 933 + or - 10 km, which implies a geometric albedo, Pv = 0.07 + or - 0.01 and a density 2.7 + or - 0.3 gm cu/cm. Hence Ceres is likely composed of silicate material throughout.

Solar Occultation Retrieval Algorithm Development

NASA Technical Reports Server (NTRS)

Lumpe, Jerry D.

2004-01-01

This effort addresses the comparison and validation of currently operational solar occultation retrieval algorithms, and the development of generalized algorithms for future application to multiple platforms. initial development of generalized forward model algorithms capable of simulating transmission data from of the POAM II/III and SAGE II/III instruments. Work in the 2" quarter will focus on: completion of forward model algorithms, including accurate spectral characteristics for all instruments, and comparison of simulated transmission data with actual level 1 instrument data for specific occultation events.

Occult Intertrochanteric Fracture Mimicking the Fracture of Greater Trochanter.

PubMed

Chung, Phil Hyun; Kang, Suk; Kim, Jong Pil; Kim, Young Sung; Lee, Ho Min; Back, In Hwa; Eom, Kyeong Soo

2016-06-01

Occult intertrochanteric fractures are misdiagnosed as isolated greater trochanteric fractures in some cases. We investigated the utility of three-dimensional computed tomography (3D-CT) and magnetic resonance imaging (MRI) in the diagnosis and outcome management of occult intertrochanteric fractures. This study involved 23 cases of greater trochanteric fractures as diagnosed using plain radiographs from January 2004 to July 2013. Until January 2008, 9 cases were examined with 3D-CT only, while 14 cases were screened with both 3D-CT and MRI scans. We analyzed diagnostic accuracy and treatment results following 3D-CT and MRI scanning. Nine cases that underwent 3D-CT only were diagnosed with isolated greater trochanteric fractures without occult intertrochanteric fractures. Of these, a patient with displacement received surgical treatment. Of the 14 patients screened using both CT and MRI, 13 were diagnosed with occult intertrochanteric fractures. Of these, 11 were treated with surgical intervention and 2 with conservative management. Three-dimensional CT has very low diagnostic accuracy in diagnosing occult intertrochanteric fractures. For this reason, MRI is recommended to confirm a suspected occult intertrochanteric fracture and to determine the most appropriate mode of treatment.

Advances and Limitations of Atmospheric Boundary Layer Observations with GPS Occultation over Southeast Pacific Ocean

NASA Technical Reports Server (NTRS)

Xie, F.; Wu, D. L.; Ao, C. O.; Mannucci, A. J.; Kursinski, E. R.

2012-01-01

The typical atmospheric boundary layer (ABL) over the southeast (SE) Pacific Ocean is featured with a strong temperature inversion and a sharp moisture gradient across the ABL top. The strong moisture and temperature gradients result in a sharp refractivity gradient that can be precisely detected by the Global Positioning System (GPS) radio occultation (RO) measurements. In this paper, the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) GPS RO soundings, radiosondes and the high-resolution ECMWF analysis over the SE Pacific are analyzed. COSMIC RO is able to detect a wide range of ABL height variations (1-2 kilometer) as observed from the radiosondes. However, the ECMWF analysis systematically underestimates the ABL heights. The sharp refractivity gradient at the ABL top frequently exceeds the critical refraction (e.g., -157 N-unit per kilometer) and becomes the so-called ducting condition, which results in a systematic RO refractivity bias (or called N-bias) inside the ABL. Simulation study based on radiosonde profiles reveals the magnitudes of the N-biases are vertical resolution dependent. The N-bias is also the primary cause of the systematically smaller refractivity gradient (rarely exceeding -110 N-unit per kilometer) at the ABL top from RO measurement. However, the N-bias seems not affect the ABL height detection. Instead, the very large RO bending angle and the sharp refractivity gradient due to ducting allow reliable detection of the ABL height from GPS RO. The seasonal mean climatology of ABL heights derived from a nine-month composite of COSMIC RO soundings over the SE Pacific reveals significant differences from the ECMWF analysis. Both show an increase of ABL height from the shallow stratocumulus near the coast to a much higher trade wind inversion further off the coast. However, COSMIC RO shows an overall deeper ABL and reveals different locations of the minimum and maximum ABL heights as compared to the ECMWF analysis

Temperature trend estimates in the troposphere over Antarctica by use of analysis of the GPS radio occultation data

NASA Astrophysics Data System (ADS)

Zhang, Kefei; Fu, Erjiang; Wang, Chuan-Sheng; Liou, Yuei-An; Pavelyev, Alexander; Kuleshov, Yuriy

2010-05-01

Analyses of the Antarctic climate change during recent decades have demonstrated a positive continent-wide average near-surface temperature trend. Strong warming of the Antarctic Peninsula in contrast to slight cooling of the Antarctic continental interior in the last five decades has been emphasised [Turner et al. 2005]. Recently, it has been reported that significant warming of the Antarctic ice-sheet surface extends well beyond the Antarctic Peninsular to cover most of West Antarctica with a warming rate exceeding 0.1°C per decade over the past 50 years, and is strongest in winter and spring [Steig et al. 2009]. Assessments of atmospheric temperature trends have also found significant warming of the Antarctic winter troposphere. Analysing data from nine Antarctic radiosonde stations, it has been shown that regional midtropospheric temperatures have increased at a statistically significant rate of 0.5 to 0.7°C per decade over the past three decades - a major warming of the Antarctic winter troposphere that is larger than any previously identified regional tropospheric warming on Earth [Turner et al. 2006]. Analysis of climate change over the Polar Regions is particularly challenging due to the scarcity of observations from a small number of sparsely located weather stations. Obviously, data obtained by various satellite remote sensing techniques are invaluable in order to obtain spatially-complete distributions of near-surface and atmospheric temperature trends in high latitudes. For example, using the climate quality records of satellite Microwave Sounding Unit (MSU) observations, it has been shown that significant tropospheric warming prevails during Antarctic winters and springs, with the largest winter tropospheric warming of about 0.6°C per decade for 1979-2005 between 120°W and 180°W [Johanson and Fu 2007]. Recently, a new atmospheric observation technique, GPS radio occultation (RO), has been developed for acquiring the Earth's atmospheric

Assessment of COSMIC radio occultation and AIRS hyperspectral IR sounder temperature products in the stratosphere using observed radiances

NASA Astrophysics Data System (ADS)

Feltz, M. L.; Knuteson, R. O.; Revercomb, H. E.

2017-08-01

Upper air temperature is defined as an essential climate variable by the World Meteorological Organization. Two remote sensing technologies being promoted for monitoring stratospheric temperatures are GPS radio occultation (RO) and spectrally resolved IR radiances. This study assesses RO and hyperspectral IR sounder derived temperature products within the stratosphere by comparing IR spectra calculated from GPS RO and IR sounder products to coincident IR observed radiances, which are used as a reference standard. RO dry temperatures from the University Corporation for Atmospheric Research (UCAR) Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission are compared to NASA Atmospheric Infrared Sounder (AIRS) retrievals using a previously developed profile-to-profile collocation method and vertical temperature averaging kernels. Brightness temperatures (BTs) are calculated for both COSMIC and AIRS temperature products and are then compared to coincident AIRS measurements. The COSMIC calculated minus AIRS measured BTs exceed the estimated 0.5 K measurement uncertainty for the winter time extratropics around 35 hPa. These differences are attributed to seasonal UCAR COSMIC biases. Unphysical vertical oscillations are seen in the AIRS L2 temperature product in austral winter Antarctic regions, and results imply a small AIRS tropical warm bias around 35 hPa in the middle stratosphere.

First light of an external occulter testbed at flight Fresnel numbers

NASA Astrophysics Data System (ADS)

Kim, Yunjong; Sirbu, Dan; Hu, Mia; Kasdin, Jeremy; Vanderbei, Robert J.; Harness, Anthony; Shaklan, Stuart

2017-01-01

Many approaches have been suggested over the last couple of decades for imaging Earth-like planets. One of the main candidates for creating high-contrast for future Earth-like planets detection is an external occulter. The external occulter is a spacecraft flown along the line-of-sight of a space telescope to suppress starlight and enable high-contrast direct imaging of exoplanets. The occulter is typically tens of meters in diameter and the separation from the telescope is of the order of tens of thousands of kilometers. Optical testing of a full-scale external occulter on the ground is impossible because of the long separations. Therefore, laboratory verification of occulter designs is necessary to validate the optical models used to design and predict occulter performance. At Princeton, we have designed and built a testbed that allows verification of scaled occulter designs whose suppressed shadow is mathematically identical to that of space occulters. The goal of this experiment is to demonstrate a pupil plane suppression of better than 1e-9 with a corresponding image plane contrast of better than 1e-11. The occulter testbed uses a 77.2 m optical propagation distance to realize the flight Fresnel number of 14.5. The scaled mask is placed at 27.2 m from the artificial source and the camera is located 50.0 m from the scaled mask. We will use an etched silicon mask, manufactured by the Microdevices Lab(MDL) of the Jet Propulsion Laboratory(JPL), as the occulter. Based on conversations with MDL, we expect that 0.5 μm feature size is an achievable resolution in the mask manufacturing process and is therefore likely the indicator of the best possible performance. The occulter is illuminated by a diverging laser beam to reduce the aberrations from the optics before the occulter. Here, we present first light result of a sample design operating at a flight Fresnel number and the experimental setup of the testbed. We compare the experimental results with simulations

Histopathological Parameters predicting Occult Nodal Metastases in Tongue Carcinoma Cases: An Indian Perspective.

PubMed

Jacob, Tina Elizabeth; Malathi, N; Rajan, Sharada T; Augustine, Dominic; Manish, N; Patil, Shankargouda

2016-01-01

extensive histopathological screening, which holds the key for establishing occult metastases. Pathological upgrading of tumors is possible following histopathological studies similar to the present one. Presence of occult metastases justify neck dissection in these clinically N0 cases. In an Indian setting, histopathological evaluation assumes a bigger role than other expensive and advanced techniques.

Occultation Lightcurves for Selected Pluto Volatile Transport Models

NASA Astrophysics Data System (ADS)

Young, L. A.

2004-11-01

The stellar occultations by Pluto in 1988 and 2002 are demonstrably sensitive to changes in Pluto's atmosphere near one microbar (Elliot and Young 1992, AJ 103, 991; Elliot et al. 2003, Nature 424, 165; Sicardy 2003, Nature 424, 168). However, Pluto volatile-transport models focus on the changes in the atmospheric pressure at the surface (e.g., Hansen and Paige 1996, Icarus 20, 247; Stansberry and Yelle 1999, Icarus 141, 299). What's lacking is a connection between predictions about the surface properties and either temperature and pressure profiles measurable from stellar occultations, or the occultation light curve morphology itself. Radiative-conductive models can illuminate this connection. I will illustrate how Pluto's changing surface pressure, temperature, and heliocentric distance may affect occultation light curves for a selection of existing volatile transport models. Changes in the light curve include the presence or absence of an observable ``kink'' (or departure from an isothermal light curve), the appearance of non-zero minimum flux levels, and the detectability of the solid surface. These light curves can serve as examples of what we may anticipate during the upcoming Pluto occultation season, as Pluto crosses the galactic plane.

Prevalence of occult hepatitis B virus infection in hemodialysis patients in Isfahan, Iran.

PubMed

Kalantari, Hamid; Ferdowsi, Faezeh; Yaran, Majid

2016-01-01

The absence of a detectable hepatitis B surface antigen (HBsAg) with or without hepatitis B core antibody (anti-HBc) or hepatitis B surface antibody (anti-HBs) in the presence of hepatitis B virus-DNA (HBV-DNA) is defined as occult HBV infection. This study was aimed to evaluate the prevalence of occult HBV infection in patients receiving hemodialysis (HD) in Isfahan, Iran. This cross sectional study was done on 400 patients without acute or chronic HBV infection with end-stage renal disease undergoing regular HD. Blood samples were collected prior to the HD session, and serological markers of viral hepatitis B included HBsAg, anti-HBs and anti-HBc were measured using standard third generation commercially available enzyme immunoassays kit, then samples of positive anti-HBc and negative anti-HBs were tested for HBV DNA using quantitative real-time polymerase chain reaction techniques. Data were analyzed by SPSS using t -test and Chi-square test. The mean age of patients was 51.6 ± 11.2 years. Anti-HBc positive was observed in 32 (8%) of 400 studied patients with negative HBsAg. Of 32 patients with anti-HBc positive, 15 were males and 17 were females with mean age of 49.7 ± 12.6 years. Among 32 patients with anti-HBc positive, 10 patients were negative for anti-HBs. All of 10 patients were negative for HBV DNA. The prevalence of occult HBV infection was 0%. The prevalence of occult HBV infection in HBsAg negative patients undergoing HD was 0% and look to be among the lowest worldwide. So, occult HBV infection is not a significant health problem in HD patients in this region.

New global electron density observations from GPS-RO in the D- and E-Region ionosphere

NASA Astrophysics Data System (ADS)

Wu, Dong L.

2018-06-01

A novel retrieval technique is developed for electron density (Ne) in the D- and E-region (80-120 km) using the high-quality 50-Hz GPS radio occultation (GPS-RO) phase measurements. The new algorithm assumes a slow, linear variation in the F-region background when the GPS-RO passes through the D- and E-region, and extracts the Ne profiles at 80-130 km from the phase advance signal caused by Ne. Unlike the conventional Abel function, the new approach produces a sharp Ne weighting function in the lower ionosphere, and the Ne retrievals are in good agreement with the IRI (International Reference Ionosphere) model in terms of monthly maps, zonal means and diurnal variations. The daytime GPS-RO Ne profiles can be well characterized by the α-Chapman function of three parameters (NmE, hmE and H), showing that the bottom of E-region is deepening and sharpening towards the summer pole. At high latitudes the monthly GPS-RO Ne maps at 80-120 km reveal clear enhancement in the auroral zones, more prominent at night, as a result of energetic electron precipitation (EEP) from the outer radiation belt. The D-/E-region auroral Ne is strongly correlated with Kp on a daily basis. The new Ne data allow further comprehensive analyses of the sporadic E (Es) phenomena in connection with the background Ne in the E-region. The layered (2-10 km) and fluctuated (<2 km) Es components, namely Ne_Layer than Ne_Pert, are extracted with respect to the background Ne_Region on a profile-by-profile basis. The Ne_Layer component has a strong but highly-refined peak at ∼105 km, with an amplitude smaller than Ne_Region approximately by an order of magnitude. The Ne_Pert component, which was studied extensively in the past, is ∼2 orders of magnitude weaker than Ne_Layer. Both Ne_Layer and Ne_Pert are subject to significant diurnal and semidiurnal variations, showing downward progression with local time in amplitude. The 11-year solar cycle dominates the Ne interannual variations, showing larger Ne

Structure of scintillations in Neptune's occultation shadow

NASA Technical Reports Server (NTRS)

Hubbard, W. B.; Lellouch, Emmanuel; Sicardy, Bruno; Brahic, Andre; Vilas, Faith

1988-01-01

An exceptionally high-quality data set from a Neptune occultation is used here to derive a number of new results about the statistical properties of the fluctuations of the intensity distribution in various parts of Neptune's occultation shadow. An approximate numerical ray-tracing model which successfully accounts for many of the qualitative aspects of the observed intensity fluctuation distribution is introduced. Strong refractive scintillation is simulated by including the effects of 'turbulence' with projected atmospheric properties allowed to vary in both the direction perpendicular and parallel to the limb, and an explicit two-dimensional picture of a typical intensity distribution throughout an occulting planet's shadow is presented. The results confirm the existence of highly anisotropic turbulence.

Revisiting the 1988 Pluto Occultation

NASA Astrophysics Data System (ADS)

Bosh, Amanda S.; Dunham, Edward W.; Young, Leslie A.; Slivan, Steve; Barba née Cordella, Linda L.; Millis, Robert L.; Wasserman, Lawrence H.; Nye, Ralph

2015-11-01

In 1988, Pluto's atmosphere was surmised to exist because of the surface ices that had been detected through spectroscopy, but it had not yet been directly detected in a definitive manner. The key to making such a detection was the stellar occultation method, used so successfully for the discovery of the Uranian rings in 1977 (Elliot et al. 1989; Millis et al. 1993) and before that for studies of the atmospheres of other planets.On 9 June 1988, Pluto occulted a star, with its shadow falling over the South Pacific Ocean region. One team of observers recorded this event from the Kuiper Airborne Observatory, while other teams captured the event from various locations in Australia and New Zealand. Preceding this event, extensive astrometric observations of Pluto and the star were collected in order to refine the prediction.We will recount the investigations that led up to this important Pluto occultation, discuss the unexpected atmospheric results, and compare the 1988 event to the recent 2015 event whose shadow followed a similar track through New Zealand and Australia.

Occult Intertrochanteric Fracture Mimicking the Fracture of Greater Trochanter

PubMed Central

Chung, Phil Hyun; Kang, Suk; Kim, Jong Pil; Kim, Young Sung; Back, In Hwa; Eom, Kyeong Soo

2016-01-01

Purpose Occult intertrochanteric fractures are misdiagnosed as isolated greater trochanteric fractures in some cases. We investigated the utility of three-dimensional computed tomography (3D-CT) and magnetic resonance imaging (MRI) in the diagnosis and outcome management of occult intertrochanteric fractures. Materials and Methods This study involved 23 cases of greater trochanteric fractures as diagnosed using plain radiographs from January 2004 to July 2013. Until January 2008, 9 cases were examined with 3D-CT only, while 14 cases were screened with both 3D-CT and MRI scans. We analyzed diagnostic accuracy and treatment results following 3D-CT and MRI scanning. Results Nine cases that underwent 3D-CT only were diagnosed with isolated greater trochanteric fractures without occult intertrochanteric fractures. Of these, a patient with displacement received surgical treatment. Of the 14 patients screened using both CT and MRI, 13 were diagnosed with occult intertrochanteric fractures. Of these, 11 were treated with surgical intervention and 2 with conservative management. Conclusion Three-dimensional CT has very low diagnostic accuracy in diagnosing occult intertrochanteric fractures. For this reason, MRI is recommended to confirm a suspected occult intertrochanteric fracture and to determine the most appropriate mode of treatment. PMID:27536653

The Treatment of the Occult in General Encyclopedias.

ERIC Educational Resources Information Center

Sonnenfeld, Gary F.

This paper is a content analysis of three general encyclopedias, "Encyclopedia Americana" (EA), "Encyclopaedia Brittanica" (EB), and "World Book Encyclopedia" (WBC), which quantifies the treatment of the occult. Entries are selected from each by starting with the article "Occultism" and tracing all…

Stellar Occultation Probe of Triton's Atmosphere

NASA Technical Reports Server (NTRS)

Elliot, James L.

1998-01-01

The goals of this research were (i) to better characterize Triton's atmospheric structure by probing a region not well investigated by Voyager and (ii) to begin acquiring baseline data for an investigation of the time evolution of the atmosphere which will set limits on the thermal conductivity of the surface and the total mass of N2 in the atmosphere. Our approach was to use observations (with the Kuiper Airborne Observatory) of a stellar occultation by Triton that was predicted to occur on 1993 July 10. As described in the attached reprint, we achieved these objectives through observation of this occultation and a subsequent one with the KAO in 1995. We found new results about Triton's atmospheric structure from the analysis of the two occultations observed with the KAO and ground-based data. These stellar occultation observations made both in the visible and infrared, have good spatial coverage of Triton including the first Triton central-flash observations, and are the first data to probe the 20-100 km altitude level on Triton. The small-planet light curve model of Elliot and Young (AJ 103, 991-1015) was generalized to include stellar flux refracted by the far limb, and then fitted to the data. Values of the pressure, derived from separate immersion and emersion chords, show no significant trends with latitude indicating that Triton's atmosphere is spherically symmetric at approximately 50 km altitude to within the error of the measurements. However, asymmetry observed in the central flash indicates the atmosphere is not homogeneous at the lowest levels probed (approximately 20 km altitude). From the average of the 1995 occultation data, the equivalent-isothermal temperature of the atmosphere is 47 +/- 1 K and the atmospheric pressure at 1400 km radius (approximately 50 km altitude) is 1.4 +/- 0.1 microbar. Both of these are not consistent with a model based on Voyager UVS and RSS observations in 1989 (Strobel et al, Icarus 120, 266-289). The atmospheric

All about Occultation.

ERIC Educational Resources Information Center

Riddle, Bob

2001-01-01

Describes occultation events involving the moon, when the moon blocks the view of planets or stars. Describes other events such as a partial solar eclipse, a penumbral lunar eclipse, meteor showers, and moon phases. Provides a list of internet resources related to these events. (DLH)

Occult Carbon Monoxide Poisoning

PubMed Central

Kirkpatrick, John N.

1987-01-01

A syndrome of headache, fatigue, dizziness, paresthesias, chest pain, palpitations and visual disturbances was associated with chronic occult carbon monoxide exposure in 26 patients in a primary care setting. A causal association was supported by finding a source of carbon monoxide in a patient's home, workplace or vehicle; results of screening tests that ruled out other illnesses; an abnormally high carboxyhemoglobin level in 11 of 14 patients tested, and abatement or resolution of symptoms when the source of carbon monoxide was removed. Exposed household pets provided an important clue to the diagnosis in some cases. Recurrent occult carbon monoxide poisoning may be a frequently overlooked cause of persistent or recurrent headache, fatigue, dizziness, paresthesias, abdominal pain, diarrhea and unusual spells. PMID:3825110

Occult carbon monoxide poisoning.

PubMed

Kirkpatrick, J N

1987-01-01

A syndrome of headache, fatigue, dizziness, paresthesias, chest pain, palpitations and visual disturbances was associated with chronic occult carbon monoxide exposure in 26 patients in a primary care setting. A causal association was supported by finding a source of carbon monoxide in a patient's home, workplace or vehicle; results of screening tests that ruled out other illnesses; an abnormally high carboxyhemoglobin level in 11 of 14 patients tested, and abatement or resolution of symptoms when the source of carbon monoxide was removed. Exposed household pets provided an important clue to the diagnosis in some cases. Recurrent occult carbon monoxide poisoning may be a frequently overlooked cause of persistent or recurrent headache, fatigue, dizziness, paresthesias, abdominal pain, diarrhea and unusual spells.

The clinical significance of occult gynecologic primary tumours in metastatic cancer.

PubMed

Hannouf, M B; Winquist, E; Mahmud, S M; Brackstone, M; Sarma, S; Rodrigues, G; Rogan, P K; Hoch, J S; Zaric, G S

2017-10-01

We estimated the frequency of occult gynecologic primary tumours (gpts) in patients with metastatic cancer from an uncertain primary and evaluated the effect on disease management and overall survival (os). We used Manitoba administrative health databases to identify all patients initially diagnosed with metastatic cancer during 2002-2011. We defined patients as having an "occult" primary tumour if the primary was classified at least 6 months after the initial diagnosis. Otherwise, we considered patients to have "obvious" primaries. We then compared clinicopathologic and treatment characteristics and 2-year os for women with occult and with obvious gpts. We used Cox regression adjustment and propensity score methods to assess the effect on os of having an occult gpt. Among the 5953 patients diagnosed with metastatic cancer, occult primary tumours were more common in women ( n = 285 of 2552, 11.2%) than in men ( n = 244 of 3401, 7.2%). In women, gpts were the most frequent occult primary tumours ( n = 55 of 285, 19.3%). Compared with their counterparts having obvious gpts, women with occult gpts ( n = 55) presented with similar histologic and metastatic patterns but received fewer gynecologic diagnostic examinations during diagnostic work-up. Women with occult gpts were less likely to undergo surgery, waited longer for radiotherapy, and received a lesser variety of chemotherapeutic agents. Having an occult compared with an obvious gpt was associated with decreased os (hazard ratio: 1.62; 95% confidence interval: 1.2 to 2.35). Similar results were observed in adjusted analyses. In women with metastatic cancer from an uncertain primary, gpts constitute the largest clinical entity. Accurate diagnosis of occult gpts early in the course of metastatic cancer might lead to more effective treatment decisions and improved survival outcomes.

Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO2 Radicals and Their Reactions with NO, NO2, SO2, and Other RO2 Radicals.

PubMed

Berndt, Torsten; Richters, Stefanie; Kaethner, Ralf; Voigtländer, Jens; Stratmann, Frank; Sipilä, Mikko; Kulmala, Markku; Herrmann, Hartmut

2015-10-15

The gas-phase reaction of ozone with C5-C8 cycloalkenes has been investigated in a free-jet flow system at atmospheric pressure and a temperature of 297 ± 1 K. Highly oxidized RO2 radicals bearing at least 5 O atoms in the molecule and their subsequent reaction products were detected in most cases by means of nitrate-CI-APi-TOF mass spectrometry. Starting from a Criegee intermediate after splitting-off an OH-radical, the formation of these RO2 radicals can be explained via an autoxidation mechanism, meaning RO2 isomerization (ROO → QOOH) and subsequently O2 addition (QOOH + O2 → R'OO). Time-dependent RO2 radical measurements concerning the ozonolysis of cyclohexene indicate rate coefficients of the intramolecular H-shifts, ROO → QOOH, higher than 1 s(-1). The total molar yield of highly oxidized products (predominantly RO2 radicals) from C5-C8 cycloalkenes in air is 4.8-6.0% affected with a calibration uncertainty by a factor of about two. For the most abundant RO2 radical from cyclohexene ozonolysis, O,O-C6H7(OOH)2O2 ("O,O" stands for two O atoms arising from the ozone attack), the determination of the rate coefficients of the reaction with NO2, NO, and SO2 yielded (1.6 ± 0.5) × 10(-12), (3.4 ± 0.9) × 10(-11), and <10(-14) cm(3) molecule(-1) s(-1), respectively. The reaction of highly oxidized RO2 radicals with other peroxy radicals (R'O2) leads to detectable accretion products, RO2 + R'O2 → ROOR' + O2, which allows to acquire information on peroxy radicals not directly measurable with the nitrate ionization technique applied here. Additional experiments using acetate as the charger ion confirm conclusively the existence of highly oxidized RO2 radicals and closed-shell products. Other reaction products, detectable with this ionization technique, give a deeper insight in the reaction mechanism of cyclohexene ozonolysis.

The Research and Education Collaborative Occultation Network: A System for Coordinated TNO Occultation Observations

NASA Astrophysics Data System (ADS)

Buie, Marc W.; Keller, John M.

2016-03-01

We describe a new system and method for collecting coordinated occultation observations of trans-Neptunian objects (TNOs). Occultations by objects in the outer solar system are more difficult to predict due to their large distance and limited span of the astrometric data used to determine their orbits and positions. This project brings together the research and educational community into a unique citizen-science partnership to overcome the difficulties of observing these distant objects. The goal of the project is to get sizes and shapes for TNOs with diameters larger than 100 km. As a result of the system design it will also serve as a probe for binary systems with spatial separations as small as contact systems. Traditional occultation efforts strive to get a prediction sufficiently good to place mobile ground stations in the shadow track. Our system takes a new approach of setting up a large number of fixed observing stations and letting the shadows come to the network. The nominal spacing of the stations is 50 km so that we ensure two chords at our limiting size. The spread of the network is roughly 2000 km along a roughly north-south line in the western United States. The network contains 56 stations that are committed to the project and we get additional ad hoc support from International Occultation Timing Association members. At our minimum size, two stations will record an event while the other stations will be probing the inner regions for secondary events. Larger objects will get more chords and will allow determination of shape profiles. The stations are almost exclusively sited and associated with schools, usually at the 9-12 grade level. We present a full description of the system we have developed for the continued exploration of the Kuiper Belt.

The stellar occultation by the dwarf planet Haumea

NASA Astrophysics Data System (ADS)

Santos-Sanz, Pablo; Ortiz, Jose Luis; Sicardy, Bruno; Rossi, Gustavo; Berard, Diane; Morales, Nicolas; Duffard, Rene; Braga-Ribas, Felipe; Hopp, Ulrich; Ries, Christoph; Nascimbeni, Valerio; Marzari, Francesco; Granata, Valentina; Pál, András; Kiss, Csaba; Pribulla, Theodor; Milan Komzík, Richard; Hornoch, Kamil; Pravec, Petr; Bacci, Paolo; Maestripieri, Martina; Nerli, Luca; Mazzei, Leonardo; Bachini, Mauro; Martinelli, Fabio; Succi, Giacomo; Ciabattari, Fabrizio; Mikuz, Herman; Carbognani, Albino; Gaehrken, Bernd; Mottola, Stefano; Hellmich, Stephan; Rommel, Flavia; Fernández-Valenzuela, Estela; Campo Bagatin, Adriano; Haumea occultation international Collaboration: https://cloud.iaa.csic.es/public.php?service=files&t=d9276f8ab1a316cef13bee28bef75add

2017-10-01

The dwarf planet Haumea is a very peculiar Trans-Neptunian Object (TNO) with unique and exotic characteristics. It is currently classified as one of the five dwarf planets of the solar system, and it is the only one for which size, shape, albedo, density and other basic properties were not accurately known. To solve that we predicted an occultation of the star GaiaDR1 1233009038221203584 by Haumea and organized observations within the expected shadow path. Medium/large telescopes were needed to record the occultation with enough signal to noise ratio because the occulted star is of similar brightness as Haumea (R~17.7 mag). We will report results derived from this successful stellar occultation by Haumea on 2017 January 21st. The occultation was positive from 12 telescopes at 10 observing stations in Europe: the Asiago Observatory 1.8m telescope (Italy), the Mount Agliale Observatory 0.5m telescope (Italy), the Lajatico Astronomical Centre 0.5m telescope (Italy), the S.Marcello Pistoiese Observatory 0.6m telescope (Italy), the Crni Vrh Observatory 0.6m telescope (Slovenia), the Ondrejov Observatory 0.65m telescope (Czech Republic), the Bavarian Public Observatory 0.81m telescope (Germany), the Konkoly Observatory 1m and 0.6m telescopes (Hungary), the Skalnate Pleso Observatory 1.3m telescope (Slovakia), and the Wendelstein Observatory 2m and 0.4m telescopes (Germany). This is the occultation by a TNO with the largest number of chords ever recorded.Part of this work has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 687378.

Occult diaphragmatic injuries caused by stab wounds.

PubMed

Leppäniemi, Ari; Haapiainen, Reijo

2003-10-01

Missed diaphragmatic perforation caused by penetrating trauma can lead to subsequent strangulation of a hollow viscus, which has prompted the use of invasive diagnostic procedures to exclude occult diaphragmatic injuries in asymptomatic, high-risk patients. The objective of this study was to determine the incidence of occult diaphragmatic injuries caused by stab wounds of the lower chest and upper abdomen, and to examine the natural history and consequences of missed diaphragmatic injuries. On the basis of patient data from two previous randomized studies from our institution, a retrospective analysis was performed on 97 patients treated for anterior stab wounds located between the nipple line, the umbilical level, and the posterior axillary lines not having indications for immediate surgical exploration. The patients were divided into two groups on the basis of their initial randomized management (open or laparoscopic exploration vs. expectant observation). In the exploration group (n = 47), four diaphragmatic injuries (9%) were detected (three left-sided and one right-sided). Excluding patients with associated injuries requiring surgical repair, the incidence of occult diaphragmatic injuries was 3 of 43 (7%). In the observation group (n = 50), there were two patients (4%) with delayed presentation of missed left-sided diaphragmatic injury 2 and 23 months later, respectively. Both injuries resulted from stab wounds of the left flank and presented with herniation of the stomach or small bowel and colon. The overall incidence of occult diaphragmatic injuries in left-sided thoracoabdominal stab wounds was 4 of 24 (17%), and was much lower after stab wounds of left epigastrium (0%), right lower chest (0%), and right epigastrium (4%). In asymptomatic patients with anterior or flank stab wounds of the lower chest or upper abdominal area, the risk of an occult diaphragmatic injury is approximately 7% which, if undetected, is associated with a high risk of subsequent

Occult Cushing's syndrome in type-2 diabetes.

PubMed

Catargi, Bogdan; Rigalleau, Vincent; Poussin, Agathe; Ronci-Chaix, Nathalie; Bex, Veronique; Vergnot, Vincent; Gin, Henri; Roger, Patrick; Tabarin, Antoine

2003-12-01

Subclinical Cushing's syndrome (SCS) caused by adrenal incidentalomas is frequently associated with overweight and insulin resistance. Metabolic syndrome X may therefore be a clue to the presence of CS. However, the incidence of CS in this situation remains unknown. We have conducted a prospective study to evaluate the prevalence of occult CS in overweight, type-2 diabetic patients devoided of specific clinical symptoms of CS. Two hundred overweight, type-2 diabetic patients, consecutively referred for poor metabolic control (HbA(1C) > 8%), were studied as inpatients. A first screening step was performed with the 1-mg overnight dexamethasone suppression test (DST) using a revised criterion for cortisol suppression (60 nmol/liter) to maximize the sensitivity of the procedure. A second confirmatory step of biochemical investigations (midnight plasma cortisol concentration, plasma cortisol circadian rhythm, morning plasma ACTH concentration, 24-h urinary free cortisol, and 4-mg i.v. DST) was performed in patients with impaired 1-mg DST. A third step of imaging studies was performed according to the results of second-step investigations. Fifty-two patients had impaired 1-mg DST. Among these, 47 were further evaluated. Thirty were considered as false positives of the 1-mg DST, whereas 17 displayed at least one additional biological abnormality of the hypothalamic-pituitary-adrenal axis. Definitive occult CS was identified in four patients (2% of the whole series) with Cushing's disease (n = 3) and surgically proven adrenal adenoma (n = 1). Definitive diagnosis remains to be established in seven additional patients (3.5%) with mild occult CS associated with unsuppressed plasma ACTH concentrations and a unilateral adrenal tumor of 10-29 mm in size showing prevalent uptake at radiocholesterol scintigraphy. In conclusion, a relatively high prevalence of occult CS was found in our study. Further studies are needed to evaluate the impact of the cure of occult CS on obesity

Cassini First Diametric Radio Occultation of Saturn's Rings

NASA Astrophysics Data System (ADS)

Marouf, E.; French, R.; Rappaport, N.; Kliore, A.; Flasar, M.; Nagy, A.; Ambrosini, R.; McGhee, C.; Schinder, P.; Anabtawi, A.; Barbinis, E.; Goltz, G.; Thomson, F.; Wong, K.

2005-05-01

We present preliminary results expected from the first planned Cassini radio occultation observation of Saturn's rings, to be conducted on May 3rd, 2005. The path of Cassini as seen from Earth (the occultation track) has been designed to cross the rings from the west to the east ansa almost diametrically, allowing for occultation of all major ring features at two widely separated longitudes (about 180 deg apart). The duration of the geometric occultation is about 1.5 hours on each side. During the occultation, Cassini transmits through the rings three coherent monochromatic radio signals of wavelength 0.94, 3.6, and 13 cm (Ka-, X-, and S-band respectively), a capability unique to Cassini. The perturbed signals received at the Earth are recorded at the NASA DSN complexes at Goldstone and Canberra. Both direct and forward-scattered components of the signal may be identified in spectrograms of the received signals. The time history of the extinction of the direct signal is expected to yield high-spatial-resolution optical depth and phase shift profiles of ring structure. The timing of the occultation was optimized to allow probing the rings when the ring-opening-angle B (the angle between the line-of-sight and the ring plane) is relatively large (B = 23 deg), hence maximizing chances of measuring for the first time the structure of the relatively optically thick Ring B. In a similar experiment by Voyager in 1980, excessive signal attenuation along the long path within the nearly closed rings (B = 5.9 deg) limited the utility of the observations in relatively thick ring regions, in particular the main Ring B. For the Cassini optimized occultation geometry, a large B, slow radial velocity along the occultation track, and much improved phase stability of the reference ultrastable oscillator (USO) on board Cassini combine to promise achievable radial resolution approaching 100 m over a good fraction of the rings. Measurement of the amplitude and phase of the diffracted

Close Double Stars from Occultation Video Recordings

NASA Astrophysics Data System (ADS)

Waring Dunham, David; George, Anthony; Loader, Brian; Herald, David Russell

2015-08-01

Astronomers around the world, both amateur and professional, have been recording lunar and asteroidal occultations of close double stars during the past several years using inexpensive but quite sensitive video cameras that are now available. Several new double stars have been discovered, and the parameters of many close systems have been determined. Besides rather good measurements of the relative magnitudes of the components, the actual separations and position angles can be measured if observations of the same event are made from two or more separate stations. These observations collected by the International Occultation Timing Association (IOTA) are published in the Journal of Double Star Observations. Recently, IOTA has encouraged the observation of occultations of stars in the Kepler 2 program, which is interested in data about close duplicity that affects their analyses for exoplanet transits.

Radio Occultation Measurements of Pluto's Atmosphere with New Horizons

NASA Astrophysics Data System (ADS)

Hinson, D. P.; Linscott, I.; Tyler, G. L.; Bird, M. K.; Paetzold, M.; Strobel, D. F.; Summers, M. E.; Woods, W. W.; Stern, A.; Weaver, H. A., Jr.; Olkin, C.; Young, L. A.; Ennico Smith, K.; Gladstone, R.; Greathouse, T.; Kammer, J.; Parker, A. H.; Parker, J. W.; Retherford, K. D.; Schindhelm, E.; Singer, K. N.; Steffl, A.; Tsang, C.; Versteeg, M.

2015-12-01

The reconnaissance of the Pluto System by New Horizons included radio occultations at both Pluto and Charon. This talk will present the latest results from the Pluto occultation. The REX instrument onboard New Horizons received and recorded uplink signals from two 70-m antennas and two 34-m antennas of the NASA Deep Space Network - each transmitting 20 kW at 4.2-cm wavelength - during a diametric occultation by Pluto. At the time this was written only a short segment of data at occultation entry (193°E, 17°S) was available for analysis. The REX measurements extend unequivocally to the surface, providing the first direct measure of the surface pressure and the temperature structure in Pluto's lower atmosphere. Preliminary analysis yields a surface pressure of about 10 microbars, smaller than expected. Data from occultation exit (16°E, 15°N) are scheduled to arrive on the ground in late August 2015. Those observations will yield an improved estimate of the surface pressure, a second temperature profile, and a measure of the diameter of Pluto with a precision of a few hundred meters.

Atmospheric QBO and ENSO indices with high vertical resolution from GNSS radio occultation temperature measurements

NASA Astrophysics Data System (ADS)

Wilhelmsen, Hallgeir; Ladstädter, Florian; Scherllin-Pirscher, Barbara; Steiner, Andrea K.

2018-03-01

We provide atmospheric temperature variability indices for the tropical troposphere and stratosphere based on global navigation satellite system (GNSS) radio occultation (RO) temperature measurements. By exploiting the high vertical resolution and the uniform distribution of the GNSS RO temperature soundings we introduce two approaches, both based on an empirical orthogonal function (EOF) analysis. The first method utilizes the whole vertical and horizontal RO temperature field from 30° S to 30° N and from 2 to 35 km altitude. The resulting indices, the leading principal components, resemble the well-known patterns of the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) in the tropics. They provide some information on the vertical structure; however, they are not vertically resolved. The second method applies the EOF analysis on each altitude level separately and the resulting indices contain information on the horizontal variability at each densely available altitude level. They capture more variability than the indices from the first method and present a mixture of all variability modes contributing at the respective altitude level, including the QBO and ENSO. Compared to commonly used variability indices from QBO winds or ENSO sea surface temperature, these new indices cover the vertical details of the atmospheric variability. Using them as proxies for temperature variability is also of advantage because there is no further need to account for response time lags. Atmospheric variability indices as novel products from RO are expected to be of great benefit for studies on atmospheric dynamics and variability, for climate trend analysis, as well as for climate model evaluation.

29 CFR 1918.86 - Roll-on roll-off (Ro-Ro) operations (see also § 1918.2, Ro-Ro operations, and § 1918.25).

Code of Federal Regulations, 2011 CFR

2011-07-01

... simultaneous use of the ramp by vehicles and pedestrians. (d) Ramp maintenance. Ramps shall be properly... ramp inclines safely. (j) Safe speeds. Power driven vehicles used in Ro-Ro operations shall be operated at speeds that are safe for prevailing conditions. (k) Ventilation. Internal combustion engine-driven...

The clinical significance of occult gynecologic primary tumours in metastatic cancer

PubMed Central

Hannouf, M.B.; Winquist, E.; Mahmud, S.M.; Brackstone, M.; Sarma, S.; Rodrigues, G.; Rogan, P.K.; Hoch, J.S.; Zaric, G.S.

2017-01-01

Objective We estimated the frequency of occult gynecologic primary tumours (gpts) in patients with metastatic cancer from an uncertain primary and evaluated the effect on disease management and overall survival (os). Methods We used Manitoba administrative health databases to identify all patients initially diagnosed with metastatic cancer during 2002–2011. We defined patients as having an “occult” primary tumour if the primary was classified at least 6 months after the initial diagnosis. Otherwise, we considered patients to have “obvious” primaries. We then compared clinicopathologic and treatment characteristics and 2-year os for women with occult and with obvious gpts. We used Cox regression adjustment and propensity score methods to assess the effect on os of having an occult gpt. Results Among the 5953 patients diagnosed with metastatic cancer, occult primary tumours were more common in women (n = 285 of 2552, 11.2%) than in men (n = 244 of 3401, 7.2%). In women, gpts were the most frequent occult primary tumours (n = 55 of 285, 19.3%). Compared with their counterparts having obvious gpts, women with occult gpts (n = 55) presented with similar histologic and metastatic patterns but received fewer gynecologic diagnostic examinations during diagnostic work-up. Women with occult gpts were less likely to undergo surgery, waited longer for radiotherapy, and received a lesser variety of chemotherapeutic agents. Having an occult compared with an obvious gpt was associated with decreased os (hazard ratio: 1.62; 95% confidence interval: 1.2 to 2.35). Similar results were observed in adjusted analyses. Conclusions In women with metastatic cancer from an uncertain primary, gpts constitute the largest clinical entity. Accurate diagnosis of occult gpts early in the course of metastatic cancer might lead to more effective treatment decisions and improved survival outcomes. PMID:29089807

29 CFR 1918.86 - Roll-on roll-off (Ro-Ro) operations (see also § 1918.2, Ro-Ro operations, and § 1918.25).

Code of Federal Regulations, 2010 CFR

2010-07-01

..., Ro-Ro operations, and § 1918.25). 9 [Reserved] (a) Traffic control system. An organized system of... simultaneous use of the ramp by vehicles and pedestrians. (d) Ramp maintenance. Ramps shall be properly...: (1) Sufficient power to ascend ramp inclines safely; and (2) Sufficient braking capacity to descend...

Pluto-Charon Stellar Occultation Candidates: 1990-1995

NASA Technical Reports Server (NTRS)

Dunham, E. W.; McDonald, S. W.; Elliot, J. L.

1991-01-01

We have carried out a search to identify stars that might be occulted by Pluto or Charon during the period 1990-1995 and part of 1996. This search was made with an unfiltered CCD camera operated in the strip scanning mode, and it reaches an R magnitude of approximately 17.5-about 1.5 mag fainter than previous searches. Circumstances for each of the 162 potential occultations are given, including an approximate R magnitude of the star, which allows estimation of the signal-to-noise ratio (S/N) for observation of each occultation. The faintest stars in our list would yield an S/N of about 20 for a 1 S integration when observed with a CCD detector on an 8 m telescope under a dark sky. Our astrometric precision (+/- 0.2 arcsec, with larger systematic errors possible for individual cases) is insufficient to serve as a final prediction for these potential occultations, but is sufficient to identify stars deserving of further, more accurate, astrometric observations. Statistically, we expect about 32 of these events to be observable somewhere on Earth. The number of events actually observed will be substantially smaller because of clouds and the sparse distribution of large telescopes. Finder charts for each of the 91 stars involved are presented.

Pluto-Charon stellar occultation candidates - 1990-1995

NASA Technical Reports Server (NTRS)

Dunham, E. W.; Mcdonald, S. W.; Elliot, J. L.

1991-01-01

A search to identify stars that might be occulted by Pluto or Charon during the period 1990-1995 and part of 1996 is studied. This search was made with an unfiltered CCD camera operated in the strip scanning mode, and it reaches an R magnitude of approximately 17.5 - about 1.5 mag fainter than previous searches. Circumstances for each of the 162 potential occultations are given, including an approximate R magnitude of the star, which allows estimation of the signal-to-noise ratio (S/N) for observation of each occultation. The faintest stars in the list would yield an S/N of about 20 for a 1 s integration when observed with a CCD detector on an 8 m telescope under a dark sky. The astrometric precision (+/- 0.2 arcsec, with larger systematic errors possible for individual cases) is insufficient to serve as a final prediction for these potential occultations, but is sufficient to identify stars deserving of further, more accurate, astrometric observations. Statistically, about 32 of these events to be observable somewhere on earth are expected. The number of events actually observed will be substantially smaller because of clouds and the sparse distribution of large telescopes. Finder charts for each of the 91 stars involved are presented.

CT detection of occult pneumothorax in head trauma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tocino, I.M.; Miller, M.H.; Frederick, P.R.

1984-11-01

A prospective evaluation for occult pneumothorax was performed in 25 consecutive patients with serious head trauma by combining a limited chest CT examination with the emergency head CT examination. Of 21 pneuomothoraces present in 15 patients, 11 (52%) were found only by chest CT and were not identified clinically or by supine chest radiograph. Because of pending therapeutic measures, chest tubes were placed in nine of the 11 occult pneumothoraces, regardless of the volume. Chest CT proved itself as the most sensitive method for detection of occult pneumothorax, permitting early chest tube placement to prevent transition to a tension pneumothoraxmore » during subsequent mechanical ventilation or emergency surgery under general anesthesia.« less

Bone scanning in the detection of occult fractures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batillas, J.; Vasilas, A.; Pizzi, W.F.

1981-07-01

The potential role of bone scanning in the early detection of occult fractures following acute trauma was investigated. Technetium 99m pyrophosphate bone scans were obtained in patients with major clinical findings and negative or equivocal roentgenograms following trauma. Bone scanning facilitated the prompt diagnosis of occult fractures in the hip, knee, wrist, ribs and costochondral junctions, sternum, vertebrae, sacrum, and coccyx. Several illustrative cases are presented. Roentgenographic confirmation occurred following a delay of days to weeks and, in some instances, the roentgenographic findings were subtle and could be easily overlooked. This study demonstrates bone scanning to be invaluable and definitivemore » in the prompt detection of occult fractures.« less

Exploring the Solar System using stellar occultations

NASA Astrophysics Data System (ADS)

Sicardy, Bruno

2018-04-01

Stellar occultations by solar system objects allow kilometric accuracy, permit the detection of tenuous atmospheres (at nbar level), and the discovery of rings. The main limitation was the prediction accuracy, typically 40 mas, corresponding to about 1,000 km projected at the body. This lead to large time dedicated to astrometry, tedious logistical issues, and more often than not, mere miss of the event. The Gaia catalog, with sub-mas accuracy, hugely improves both the star positions, resulting in achievable accuracies of about 1 mas for the shadow track on Earth. This permits much more carefully planned campaigns, with success rate approaching 100%, weather permitting. Scientific perspectives are presented, e.g. central flashes caused by Plutos atmosphere revealing hazes and winds near its surface, grazing occultations showing topographic features, occultations by Chariklos rings unveiling dynamical features such as proper mode ``breathing''.

Review: Occult hepatitis C virus infection: still remains a controversy.

PubMed

Vidimliski, Pavlina Dzekova; Nikolov, Igor; Geshkovska, Nadica Matevska; Dimovski, Aleksandar; Rostaing, Lionel; Sikole, Aleksandar

2014-09-01

Occult hepatitis C virus (HCV) infection is characterized by the presence of HCV RNA in the liver cells or peripheral blood mononuclear cells of the patients whose serum samples test negative for HCV RNA, with or without presence of HCV antibodies. The present study reviews the existing literature on the persistence of occult hepatitis C virus infection, with description of the clinical characteristics and methods for identification of occult hepatitis C. Occult hepatitis C virus infection was detected in patients with abnormal results of liver function tests of unknown origin, with HCV antibodies and HCV RNA negativity in serum, and also in patients with spontaneous or treatment-induced recovery from hepatitis C. The viral replication in the liver cells and/or peripheral blood mononuclear cells was present in all clinical presentations of occult hepatitis C. The peripheral blood mononuclear cells represent an extra-hepatic site of HCV replication. The reason why HCV RNA was not detectable in the serum of patients with occult hepatitis C, could be the low number of circulating viral particles not detectable by the diagnostic tests with low sensitivity. It is uncertain whether occult hepatitis C is a different clinical entity or just a form of chronic hepatitis C virus infection. Data accumulated over the last decade demonstrated that an effective approach to the diagnosis of HCV infection would be the implementation of more sensitive HCV RNA diagnostic assays, and also, examination of the presence of viral particles in the cells of the immune system. © 2014 Wiley Periodicals, Inc.

Cassini Radio Occultation by Enceladus Plume

NASA Astrophysics Data System (ADS)

Kliore, A.; Armstrong, J.; Flasar, F.; French, R.; Marouf, E.; Nagy, A.; Rappaport, N.; McGhee, C.; Schinder, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Aguilar, R.; Rochblatt, D.

2006-12-01

A fortuitous Cassini radio occultation by Enceladus plume occurs on September 15, 2006. The occultation track (the spacecraft trajectory in the plane of the sky as viewed from the Earth) has been designed to pass behind the plume (to pass above the south polar region of Enceladus) in a roughly symmetrical geometry centered on a minimum altitude above the surface of about 20 km. The minimum altitude was selected primarily to ensure probing much of the plume with good confidence given the uncertainty in the spacecraft trajectory. Three nearly-pure sinusoidal signals of 0.94, 3.6, and 13 cm-wavelength (Ka-, X-, and S-band, respectively) are simultaneously transmitted from Cassini and are monitored at two 34-m Earth receiving stations of the Deep Space Network (DSN) in Madrid, Spain (DSS-55 and DSS-65). The occultation of the visible plume is extremely fast, lasting less than about two minutes. The actual observation time extends over a much longer time interval, however, to provide a good reference baseline for potential detection of signal perturbations introduced by the tenuous neutral and ionized plume environment. Given the likely very small fraction of optical depth due to neutral particles of sizes larger than about 1 mm, detectable changes in signal intensity is perhaps unlikely. Detection of plume plasma along the radio path as perturbations in the signals frequency/phase is more likely and the magnitude will depend on the electron columnar density probed. The occultation time occurs not far from solar conjunction time (Sun-Earth-probe angle of about 33 degrees), causing phase scintillations due to the solar wind to be the primary limiting noise source. We estimate a delectability limit of about 1 to 3E16 electrons per square meter columnar density assuming about 100 seconds integration time. Potential measurement of the profile of electron columnar density along the occultation track is an exciting prospect at this time.

29 CFR 1918.86 - Roll-on roll-off (Ro-Ro) operations (see also § 1918.2, Ro-Ro operations, and § 1918.25).

Code of Federal Regulations, 2014 CFR

2014-07-01

..., Ro-Ro operations, and § 1918.25). 9 [Reserved] (a) Traffic control system. An organized system of vehicular and pedestrian traffic control shall be established and maintained at each entrance/exit ramp and on ramps within the vessel as traffic flow warrants. (b) Ramp load limit. Each ramp shall be plainly...

29 CFR 1918.86 - Roll-on roll-off (Ro-Ro) operations (see also § 1918.2, Ro-Ro operations, and § 1918.25).

Code of Federal Regulations, 2012 CFR

2012-07-01

..., Ro-Ro operations, and § 1918.25). 9 [Reserved] (a) Traffic control system. An organized system of vehicular and pedestrian traffic control shall be established and maintained at each entrance/exit ramp and on ramps within the vessel as traffic flow warrants. (b) Ramp load limit. Each ramp shall be plainly...

29 CFR 1918.86 - Roll-on roll-off (Ro-Ro) operations (see also § 1918.2, Ro-Ro operations, and § 1918.25).

Code of Federal Regulations, 2013 CFR

2013-07-01

..., Ro-Ro operations, and § 1918.25). 9 [Reserved] (a) Traffic control system. An organized system of vehicular and pedestrian traffic control shall be established and maintained at each entrance/exit ramp and on ramps within the vessel as traffic flow warrants. (b) Ramp load limit. Each ramp shall be plainly...

Prognostic Value of Occult Isolated Tumour Cells within Regional Lymph Nodes of Dogs with Malignant Mammary Tumours.

PubMed

Coleto, A F; Wilson, T M; Soares, N P; Gundim, L F; Castro, I P; Guimarães, E C; Bandarra, M B; Medeiros-Ronchi, A A

2018-01-01

Canine mammary tumours (CMTs) are the most common type of neoplasm in bitches. As in women, the presence of metastasis in regional lymph nodes is an important prognostic factor in bitches with mammary carcinomas, but the clinical significance of occult isolated tumour cells (ITCs) within lymph nodes is still undefined in this species. The effectiveness of immunohistochemistry (IHC) in identifying occult ITCs and micrometastasis (MIC) was compared with that of the conventional haematoxylin and eosin staining technique. The relationship between tumour size, histological type, histological grade and the presence of metastasis was evaluated. The overall survival (OS) of female dogs with occult mammary carcinomas and ITCs within lymph nodes was analysed. Fragments of mammary carcinoma and regional lymph nodes of 59 female dogs were also evaluated. Histological sections of mammary carcinoma and lymph node samples were studied for tumour diagnosis and lymph node samples were tested by IHC using a pan-cytokeratin antibody. It was found that 35.2% of occult ITCs and 2.8% of hidden MIC were detected when IHC was used. There was a good correlation between the size of the tumour and metastasis to the lymph nodes (P = 0.77). ITCs were observed more frequently in the medullary region (60.7%) and metastases in the cortical region (44.4%). There was no significant difference in the OS between female dogs with occult ITCs and lymph nodes without ITCs. IHC can detect occult tumour cells in lymph nodes that are negative by histopathological examination. Female dogs with nodal ITCs do not have lower survival. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detection of Occult Invasion in Melanoma In Situ.

PubMed

Bax, Michael J; Johnson, Timothy M; Harms, Paul W; Schwartz, Jennifer L; Zhao, Lili; Fullen, Douglas R; Chan, May P

2016-11-01

It is unclear why some patients with in situ melanoma develop metastases. Few reports demonstrate occult invasion with immunohistochemistry staining, which were discordant with reports interpreting such staining as false-positive. To investigate the occurrence of occult invasive disease within in situ melanoma by using methods to circumvent potential limitations in prior study designs. Unequivocal in situ melanoma without associated nevi or regression was identified using a consecutive sample of 33 cases plus 1 index case in an academic medical center. After cutting deeper into the most representative tissue block, 3 sequential slides were stained with hematoxylin-eosin (H-E), melanoma antigen (melan-A), and again with H-E. Melan-A-stained slides showing definitive invasion were double-stained with Sry-related HMg-Box gene 10 (SOX10) to confirm the melanocytic nature of the cells of interest. The study evaluated the possibilities of occult invasion detected by immunohistochemistry, sectioning deeper into the tissue block, or both. Slides were independently scored by 3 dermatopathologists with interrater reliability assessed. The study was conducted from January 1, 2012, to July 31, 2014. Assessment of the occurrence of occult invasion, diagnosis of invasion by immunohistochemistry alone vs cutting deeper into the tissue block, and occurrence of false-positive results using immunohistochemistry alone. Occult invasive melanoma was detected in 11 of 33 consecutive cases (33%) of previously diagnosed unequivocal in situ melanoma. Six of 11 melanomas (55%) were diagnosable only by immunohistochemistry. The remaining 5 tumors (45%) were diagnosable by both melan-A and H-E staining, likely as a result of simply cutting deeper into the tissue block. Four cases (12%) showed a few melan-A-positive cells in the dermis, which was insufficient for a diagnosis of invasive melanoma and most consistent on a cytomorphologic basis with occult nevi. Although rare, in situ melanoma

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Technical Reports Server (NTRS)

Mink, Douglas J.

1991-01-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Astrophysics Data System (ADS)

Mink, Douglas J.

1991-03-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO

NASA Astrophysics Data System (ADS)

Hindley, N. P.; Wright, C. J.; Smith, N. D.; Mitchell, N. J.

2015-07-01

Nearly all general circulation models significantly fail to reproduce the observed behaviour of the southern wintertime polar vortex. It has been suggested that these biases result from an underestimation of gravity wave drag on the atmosphere at latitudes near 60° S, especially around the "hot spot" of intense gravity wave fluxes above the mountainous Southern Andes and Antarctic peninsula. Here, we use Global Positioning System radio occultation (GPS-RO) data from the COSMIC satellite constellation to determine the properties of gravity waves in the hot spot and beyond. We show considerable southward propagation to latitudes near 60° S of waves apparently generated over the southern Andes. We propose that this propagation may account for much of the wave drag missing from the models. Furthermore, there is a long leeward region of increased gravity wave energy that sweeps eastwards from the mountains over the Southern Ocean. Despite its striking nature, the source of this region has historically proved difficult to determine. Our observations suggest that this region includes both waves generated locally and orographic waves advected downwind from the hot spot. We describe and use a new wavelet-based analysis technique for the quantitative identification of individual waves from COSMIC temperature profiles. This analysis reveals different geographical regimes of wave amplitude and short-timescale variability in the wave field over the Southern Ocean. Finally, we use the increased numbers of closely spaced pairs of profiles from the deployment phase of the COSMIC constellation in 2006 to make estimates of gravity wave horizontal wavelengths. We show that, given sufficient observations, GPS-RO can produce physically reasonable estimates of stratospheric gravity wave momentum flux in the hot spot that are consistent with measurements made by other techniques. We discuss our results in the context of previous satellite and modelling studies and explain how they

Exploring small bodies in the outer solar system with stellar occultations

NASA Technical Reports Server (NTRS)

Elliot, Jim L.; Dunham, Edward W.; Olkin, C. B.

1995-01-01

Stellar occultation observations probe the atmospheric structure and extinction of outer solar system bodies with a spatial resolution of a few kilometers, and an airborne platform allows the observation of occultations by small bodies that are not visible from fixed telescopes. Results from occultations by Triton, Pluto, and Chiron observed with KAO are discussed, and future directions for this program are presented.

Diffraction-based analysis of tunnel size for a scaled external occulter testbed

NASA Astrophysics Data System (ADS)

Sirbu, Dan; Kasdin, N. Jeremy; Vanderbei, Robert J.

2016-07-01

For performance verification of an external occulter mask (also called a starshade), scaled testbeds have been developed to measure the suppression of the occulter shadow in the pupil plane and contrast in the image plane. For occulter experiments the scaling is typically performed by maintaining an equivalent Fresnel number. The original Princeton occulter testbed was oversized with respect to both input beam and shadow propagation to limit any diffraction effects due to finite testbed enclosure edges; however, to operate at realistic space-mission equivalent Fresnel numbers an extended testbed is currently under construction. With the longer propagation distances involved, diffraction effects due to the edge of the tunnel must now be considered in the experiment design. Here, we present a diffraction-based model of two separate tunnel effects. First, we consider the effect of tunnel-edge induced diffraction ringing upstream from the occulter mask. Second, we consider the diffraction effect due to clipping of the output shadow by the tunnel downstream from the occulter mask. These calculations are performed for a representative point design relevant to the new Princeton occulter experiment, but we also present an analytical relation that can be used for other propagation distances.

A multi-year comparison of lower stratospheric temperatures from CHAMP radio occultation data with MSU/AMSU records

NASA Astrophysics Data System (ADS)

Steiner, A. K.; Kirchengast, G.; Borsche, M.; Foelsche, U.; Schoengassner, T.

2007-11-01

Long-term upper air temperature records have been established by different groups with considerable effort from radiosonde data and from satellite based (Advanced) Microwave Sounding Unit (MSU/AMSU) measurements, the latter providing information on layer-average stratospheric and tropospheric brightness temperatures. Comparisons of the temperature series show discrepancies not only with respect to radiosonde data but also between MSU data sets stemming from different retrievals. In this context the Global Navigation Satellite System radio occultation (RO) technique offers new possibilities by providing high quality observations of the atmosphere in an active limb sounding mode. RO temperature climatologies have been constructed at the WegCenter/UniGraz based on RO observations of the CHAllenging Minisatellite Payload for geoscientific research (CHAMP) satellite since September 2001, and based on a few months of RO data from other satellite missions (SAC-C, GRACE, COSMIC). Focusing on the MSU lower stratosphere channel (TLS), synthetic TLS temperatures were calculated by applying global weighting functions to zonal-mean monthly mean RO temperature climatology profiles for September 2001-December 2006. These synthetic CHAMP TLS temperatures were compared to recent MSU TLS records from the University of Alabama in Huntsville (UAH, USA) and from Remote Sensing Systems (RSS, USA), as well as to synthetic TLS temperatures from HadAT2 radiosonde data (Hadley Centre/MetOffice, UK) and ECMWF (European Centre for Medium-Range Weather Forecasts) analyses. In terms of TLS temperature anomalies, overall very good agreement of CHAMP temperature anomalies with UAH, RSS, and ECMWF anomalies was found for intra-annual variability (RMS difference of de-trended data <0.1 K globally, 0.1 K in the tropics, <0.25 K in the extratropics), while HadAT2 anomalies show larger differences (factor of two globally and more in the extratropics). Regarding 2001-2006 trends, UAH and RSS exhibit a

The occultation of Kappa Geminorum by Eros. [stellar occultation observed for asteroid size and shape

NASA Technical Reports Server (NTRS)

Oleary, B.; Marsden, B. G.; Dragon, R.; Hauser, E.; Mcgrath, M.; Backus, P.; Robkoff, H.

1976-01-01

The paper discusses predictions and observations of the occultation of Kappa Gem by (433) Eros on January 24, 1975. Several positive and negative observations made in western New England are described. Local circumstances for the occultation are reconstructed, and the size and shape of Eros are determined analytically as well as graphically. The calculations yield two extremes for the cross section: a circle 23 km in diameter or a somewhat irregular figure 20 km by 6 or 7 km. Arguments based on the expected albedo of the asteroid suggest that the circle should be warped into an ellipse 21 by 13 km or that the irregular figure might be one component of a dumbbell-like profile.

High Resolution Asteroid Profile by Multi Chord Occultation Observations

NASA Astrophysics Data System (ADS)

Degenhardt, Scott

2009-05-01

For millennia man has observed celestial objects occulting other bodies and distant stars. We have used these celestial synchronicities to measure the properties of objects. On January 1, 1801 Italian astronomer Giusappe Piazzi discovered the first asteroid that would soon be named Ceres. To date 190,000 of these objects have been catalogued, but only a fraction of these have accurate measurements of their true size and shape. The International Occultation Timing Association (IOTA) currently facilitates the prediction and reduction of asteroidal occultations. By measuring the shadow cast on the earth by an asteroid during a stellar occultation one can directly measure the physical size, shape, and position in space of this body to accuracies orders of magnitudes better than the best ground based adaptive optics telescope and can provide verification to 3D inverted reflective lightcurve prediction models. Recent novel methods developed by IOTA involving an individual making multiple observations through unattended remote observing stations have made way for numerous chords of occultation measurement through a single body yielding high resolution profiles of asteroid bodies. Methodology of how observing stations are deployed will be demonstrated, results of some of these observations are presented as comparisons to their inverted lightcurve are shown.

Analysis of a Triple Star System Occulted By Saturn’s Rings

NASA Astrophysics Data System (ADS)

Bratcher, Allison; Colwell, J. E.; Bolin, B.

2012-10-01

On January 4, 2012, the Ultraviolet Imaging Spectrograph aboard the Cassini Spacecraft observed Saturn’s rings as they occulted the triple star system, Iota Orionis. Remarkably, the brightest star was occulted by the moon Prometheus, and we provide the timing information of first and last contact for navigation purposes and a chord across the moon. The large separation of the individual stars projected in the ring plane makes it possible to measure the profiles of narrow features in the rings as they were occulted by each of the three stars. This occultation thus provides a unique opportunity to measure short-scale longitudinal variations in narrow ringlets with stellar occultation data that usually provide only a single longitudinal sample. Iota Orionis has a low elevation angle (B=1.4 degrees) above the plane of the rings, enhancing the sensitivity of the occultation (by a factor of 1/sin(B)=41) to the optically thin regions of the rings such as the C Ring and the Cassini Division as well as faint ringlets in the Encke gap. We distinguished the three signals by creating a model triple star signal using data from another occultation. We were able to identify several faint, narrow ringlets, including two in the Encke gap, occulted by two of the three stars and more prominent ringlets, such as the Huygens ringlet, in all three stellar light curves. We present the equivalent widths of these ringlets in the data from this triple star system and limits on ring variability over the azimuthal separation of the stars that ranges from 6000 km at the inner C ring to 200 km at the outer A ring.

Observation and Interpretation of Lunar Occultations. Ph.D. Thesis; [Uranus and beta Capricorni

NASA Technical Reports Server (NTRS)

Radick, R. R.

1978-01-01

The importance of timings and high resolution astrometry in occultation observations is discussed as well as the occultation process itself. The design and operation of the telescope, photodetector, and data acquisition systems are described. Methods are presented for data analysis and model fitting. Observations of beta Capricorni and Uranus occultations are examined. General conclusions concerning occultation observations are explored and future activities at Prairie Observatory are discussed.

On the occurrence of F region irregularities over Haikou retrieved from COSMIC GPS radio occultation and ground-based ionospheric scintillation monitor observations

NASA Astrophysics Data System (ADS)

Yu, Xiao; Yue, Xinan; Zhen, Weimin; Xu, Jisheng; Liu, Dun; Guo, Shan

2017-01-01

In this paper, the amplitude scintillation index (s4) derived from COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) radio occultation (RO) technique and ground-based Ionospheric Scintillation Monitor (ISM) at Haikou station (geographic latitude: 20.0°N, geographic longitude: 110.3°E, and geomagnetic latitude: 10.02°N) is used to investigate the morphology of F region irregularities in the low latitudes of China. The RO events of tangent point within the range of 10-30°N latitude, 70-160°E longitude, and 150-500 km altitude are adopted to analyze the ionospheric scintillation characteristics. The percentage of ionospheric scintillation occurrence is computed to obtain its diurnal variations, seasonal trends, and the dependence on solar and geomagnetic activities. Based on a statistical analysis of a long-term period data set (years 2007 to 2013), we found that the ionospheric scintillation occurrence from both techniques show similar variations. After sunset (18 LT), the scintillation occurrence increases rapidly and reaches the maximum 3 h later. Then it decreases rapidly till 04 LT and remains low level during the daytime. The ionospheric scintillation tends to occur more frequently during vernal and autumnal equinoxes, especially in March-April and September-October. The equinoctial asymmetry could be seen clearly from the ground-based ISM observations. The peak ionospheric scintillation occurrence time varies with seasons. It is reached latest in summer, while in spring it is very close to that in autumn. The nighttime ionospheric scintillation occurrence tends to increase with increasing solar activities. The increasing tendency is more prominent in vernal and autumnal equinoxes than that in summer and winter. In general, the control of geomagnetic activities is apt to inhibit ionospheric scintillation at equinox nighttime. In summer and winter, the geomagnetic activities could either trigger or inhibit the generation of

The Atmosphere of Titan from Cassini Radio Occultations

NASA Astrophysics Data System (ADS)

Schinder, Paul J.; Flasar, F. M.; Marouf, E. A.; French, R. G.; McGhee, C. A.; Kliore, A. J.; Rappaport, N.; Nagy, A. F.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D. U.; Goltz, G. L.

2006-09-01

The first two radio occultations of Cassini by Titan occurred on March 19 and May 20, 2006. On March 19, the ingress occultation occurred at a latitude of 31 S, and egress at 53 S. On May 20, ingress was at 33 S, and egress at 34 S. We present the temperature-pressure profiles for the atmosphere of Titan for these 4 locations.

Occult chemical deposition to a Maritime forest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vong, R.J.; Kowalski, A.S.

1996-12-31

Studies of chemical fluxes from the atmosphere to vegetated surfaces have suggested that, along with conventional wet and dry processes, an additional chemical input occurs when wind-blown cloud droplets are directly intercepted by vegetation. This cloud water deposition process has been sometimes termed {open_quote}occult deposition{close_quote} because the water fluxes cannot ordinarily be observed using rain gauges. Such occult deposition of cloud water has rarely been measured directly, in part because of the complexity of the governing turbulent transfer process. However, reviews by the National Acidic Precipitation Assessment Program (NAPAP SoS/T-2,6) have suggested that the chemical flux to be forest declinemore » in the eastern USA. This paper presents direct field measurements occult chemical fluxes to a silver fir forest located in complex terrain on the Olympic Peninsula near the coast of Washington State, USA.« less

Altimetry Using GPS-Reflection/Occultation Interferometry

NASA Technical Reports Server (NTRS)

Cardellach, Estel; DeLaTorre, Manuel; Hajj, George A.; Ao, Chi

2008-01-01

A Global Positioning System (GPS)- reflection/occultation interferometry was examined as a means of altimetry of water and ice surfaces in polar regions. In GPS-reflection/occultation interferometry, a GPS receiver aboard a satellite in a low orbit around the Earth is used to determine the temporally varying carrier- phase delay between (1) one component of a signal from a GPS transmitter propagating directly through the atmosphere just as the GPS transmitter falls below the horizon and (2) another component of the same signal, propagating along a slightly different path, reflected at glancing incidence upon the water or ice surface.

Partially Transparent Petaled Mask/Occulter for Visible-Range Spectrum

NASA Technical Reports Server (NTRS)

Shiri, Ron Shahram; Wasylkiwskyj, Wasyl

2013-01-01

The presence of the Poisson Spot, also known as the spot of Arago, has been known since the 18th century. This spot is the consequence of constructive interference of light diffracted by the edge of the obstacle where the central position can be determined by symmetry of the object. More recently, many NASA missions require the suppression of this spot in the visible range. For instance, the exoplanetary missions involving space telescopes require telescopes to image the planetary bodies orbiting central stars. For this purpose, the starlight needs to be suppressed by several orders of magnitude in order to image the reflected light from the orbiting planet. For the Earth-like planets, this suppression needs to be at least ten orders of magnitude. One of the common methods of suppression involves sharp binary petaled occulters envisioned to be placed many thousands of miles away from the telescope blocking the starlight. The suppression of the Poisson Spot by binary sharp petal tips can be problematic when the thickness of the tips becomes smaller than the wavelength of the incident beam. First they are difficult to manufacture and also it invalidates the laws of physical optics. The proposed partially transparent petaled masks/occulters compensate for this sharpness with transparency along the surface of the petals. Depending on the geometry of the problem, this transparency can be customized such that only a small region of the petal is transparent and the remaining of the surface is opaque. This feature allows easy fabrication of this type of occultation device either as a mask or occulter. A partially transparent petaled mask/ occulter has been designed for the visible spectrum range. The mask/occulter can suppress the intensity along the optical axis up to ten orders of magnitude. The design process can tailor the mask shape, number of petals, and transparency level to the near-field and farfield diffraction region. The mask/occulter can be used in space

General Information about Metastatic Squamous Neck Cancer with Occult Primary

MedlinePlus

... Occult Primary Treatment (Adult) (PDQ®)–Patient Version General Information About Metastatic Squamous Neck Cancer with Occult Primary ... the PDQ Adult Treatment Editorial Board . Clinical Trial Information A clinical trial is a study to answer ...

Critical Analysis of Different Methods to Retrieve Atmosphere Humidity Profiles from GNSS Radio Occultation Observations

NASA Astrophysics Data System (ADS)

Vespe, Francesco; Benedetto, Catia

2013-04-01

The huge amount of GPS Radio Occultation (RO) observations currently available thanks to space mission like COSMIC, CHAMP, GRACE, TERRASAR-X etc., have greatly encouraged the research of new algorithms suitable to extract humidity, temperature and pressure profiles of the atmosphere in a more and more precise way. For what concern the humidity profiles in these last years two different approaches have been widely proved and applied: the "Simple" and the 1DVAR methods. The Simple methods essentially determine dry refractivity profiles from temperature analysis profiles and hydrostatic equation. Then the dry refractivity is subtracted from RO refractivity to achieve the wet component. Finally from the wet refractivity is achieved humidity. The 1DVAR approach combines RO observations with profiles given by the background models with both the terms weighted with the inverse of covariance matrix. The advantage of "Simple" methods is that they are not affected by bias due to the background models. We have proposed in the past the BPV approach to retrieve humidity. Our approach can be classified among the "Simple" methods. The BPV approach works with dry atmospheric CIRA-Q models which depend on latitude, DoY and height. The dry CIRA-Q refractivity profile is selected estimating the involved parameters in a non linear least square fashion achieved by fitting RO observed bending angles through the stratosphere. The BPV as well as all the other "Simple" methods, has as drawback the unphysical occurrence of negative "humidity". Thus we propose to apply a modulated weighting of the fit residuals just to minimize the effects of this inconvenient. After a proper tuning of the approach, we plan to present the results of the validation.

Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

NASA Astrophysics Data System (ADS)

Wu, Kang-Hung; Su, Ching-Lun; Chu, Yen-Hsyang

2015-03-01

In this article, we use the International Reference Ionosphere (IRI) model to simulate temporal and spatial distributions of global E region electron densities retrieved by the FORMOSAT-3/COSMIC satellites by means of GPS radio occultation (RO) technique. Despite regional discrepancies in the magnitudes of the E region electron density, the IRI model simulations can, on the whole, describe the COSMIC measurements in quality and quantity. On the basis of global ionosonde network and the IRI model, the retrieval errors of the global COSMIC-measured E region peak electron density (NmE) from July 2006 to July 2011 are examined and simulated. The COSMIC measurement and the IRI model simulation both reveal that the magnitudes of the percentage error (PE) and root mean-square-error (RMSE) of the relative RO retrieval errors of the NmE values are dependent on local time (LT) and geomagnetic latitude, with minimum in the early morning and at high latitudes and maximum in the afternoon and at middle latitudes. In addition, the seasonal variation of PE and RMSE values seems to be latitude dependent. After removing the IRI model-simulated GPS RO retrieval errors from the original COSMIC measurements, the average values of the annual and monthly mean percentage errors of the RO retrieval errors of the COSMIC-measured E region electron density are, respectively, substantially reduced by a factor of about 2.95 and 3.35, and the corresponding root-mean-square errors show averaged decreases of 15.6% and 15.4%, respectively. It is found that, with this process, the largest reduction in the PE and RMSE of the COSMIC-measured NmE occurs at the equatorial anomaly latitudes 10°N-30°N in the afternoon from 14 to 18 LT, with a factor of 25 and 2, respectively. Statistics show that the residual errors that remained in the corrected COSMIC-measured NmE vary in a range of -20% to 38%, which are comparable to or larger than the percentage errors of the IRI-predicted NmE fluctuating in a

Radio Occultation Measurements of Pluto’s Atmosphere with New Horizons

NASA Astrophysics Data System (ADS)

Hinson, David P.; Linscott, Ivan; Tyler, Len; Bird, Mike; Paetzold, Martin; Strobel, Darrell; Summers, Mike; Woods, Will; Stern, Alan; Weaver, Hal; Olkin, Cathy; Young, Leslie; Ennico, Kimberly; Gladstone, Randy; Greathouse, Tommy; Kammer, Josh; Parker, Alex; Parker, Joel; Retherford, Kurt; Schindhelm, Eric; Singer, Kelsi; Steffl, Andrew; Tsang, Con; Versteeg, Maarten

2015-11-01

The reconnaissance of the Pluto System by New Horizons included radio occultations at both Pluto and Charon. This talk will present the latest results from the Pluto occultation. The REX instrument onboard New Horizons received and recorded uplink signals from two 70-m antennas and two 34-m antennas of the NASA Deep Space Network - each transmitting 20 kW at 4.2-cm wavelength - during a diametric occultation by Pluto. At the time this was written only a short segment of data at occultation entry (193°E, 17°S) was available for analysis. The REX measurements extend unequivocally to the surface, providing the first direct measure of the surface pressure and the temperature structure in Pluto’s lower atmosphere. Data from occultation exit (16°E, 15°N) are scheduled to arrive on the ground in late August 2015. Those observations will yield an improved estimate of the surface pressure, a second temperature profile, and a measure of the diameter of Pluto with a precision of a few hundred meters. This work is supported by the NASA New Horizons Mission.

Recent progress on external occulter technology for imaging exosolar planets

NASA Astrophysics Data System (ADS)

Kasdin, N. J.; Vanderbei, R. J.; Sirbu, D.; Samuels, J.; Shaklan, S.; Lisman, D.; Thomson, M.; Cady, E.; Martin, S.

Imaging planets orbiting nearby stars requires a system for suppressing the host starlight by at least ten orders of magnitude. One such approach uses an external occulter, a satellite flying far from the telescope and employing a large screen, or starshade, to suppress the incoming starlight. This trades the added complexity of building the precisely shaped starshade and flying it in formation against simplifications in the telescope since extremely precise wavefront control is no longer necessary. Much progress has been made recently in designing, testing and manufacturing starshade technology. In this paper we describe the design of starshades and report on recent accomplishments in manufacturing and measuring a prototype occulter petal as part of NASA's first Technology Development for Exoplanet Missions (TDEM) program. We demonstrate that the as-built petal is consistent with a full-size occulter achieving better than 10-10 contrast. We also discuss laboratory testing at the Princeton Occulter Testbed. These experiments use sub-scale, long-distance beam propagation to verify the diffraction analysis associated with occulter starlight suppression. We demonstrate roughly 10-10 suppression in the laboratory and discuss the important challenges and limitations.

Stellar occultation spikes as probes of atmospheric structure and composition. [for Jupiter

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Veverka, J.

1976-01-01

The characteristics of spikes observed in occultation light curves of Beta Scorpii by Jupiter are discussed in terms of the gravity-gradient model. The occultation of Beta Sco by Jupiter on May 13, 1971, is reviewed, and the gravity-gradient model is defined as an isothermal atmosphere of constant composition in which the refractivity is a function only of the radial coordinate from the center of refraction, which is assumed to lie parallel to the local gravity gradient. The derivation of the occultation light curve in terms of the atmosphere, the angular diameter of the occulted star, and the occultation geometry is outlined. It is shown that analysis of the light-curve spikes can yield the He/H2 concentration ratio in a well-mixed atmosphere, information on fine-scale atmospheric structure, high-resolution images of the occulted star, and information on ray crossing. Observational limits are placed on the magnitude of horizontal refractivity gradients, and it is concluded that the spikes are the result of local atmospheric density variations: atmospheric layers, density waves, or turbulence.

Improvements to GPS Airborne Radio Occultation in the Lower Troposphere Through Implementation of the Phase Matching Method

NASA Astrophysics Data System (ADS)

Wang, K.-N.; Garrison, J. L.; Haase, J. S.; Murphy, B. J.

2017-10-01

Airborne radio occultation (ARO) is a remote sensing technique for atmospheric sounding using Global Positioning System signals received by an airborne instrument. The atmospheric refractivity profile, which depends on pressure, temperature, and water vapor, can be retrieved by measuring the signal delay due to the refractive medium through which the signal traverses. The ARO system was developed to make repeated observations within an individual meteorological event such as a tropical storm, regardless of the presence of clouds and precipitation, and complements existing observation techniques such as dropsondes and satellite remote sensing. RO systems can suffer multipath ray propagation in the lower troposphere if there are strong refractivity gradients, for example, due to a highly variable moisture distribution or a sharp boundary layer, interfering with continuous carrier phase tracking as well as complicating retrievals. The phase matching method has now been adapted for ARO and is shown to reduce negative biases in the refractivity retrieval by providing robust retrievals of bending angle in the presence of multipath. The retrieval results are presented for a flight campaign in September 2010 for Hurricane Karl in the Caribbean Sea. The accuracy is assessed through comparison with the European Centre for Medium Range Weather Forecasts Interim Reanalysis. The fractional difference in refractivity can be maintained at a standard deviation of 2% from flight level down to a height of 2 km. The phase matching method decreases the negative refractivity bias by as much as 4% over the classical geometrical optics retrieval method.

Satellite radio occultation investigations of internal gravity waves in the planetary atmospheres

NASA Astrophysics Data System (ADS)

Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander

Internal gravity waves (IGWs) modulate the structure and circulation of the Earth’s atmosphere, producing quasi-periodic variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. In this context, an original method for the determination of IGW parameters from a vertical temperature profile measurement in a planetary atmosphere has been developed [Gubenko et al., 2008, 2011, 2012]. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, the analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitudes of the wave field and on the linear IGW saturation theory in which these amplitudes are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability threshold, energy is assumed to be dissipated in such a way that the IGW amplitude is maintained at the instability threshold level as the wave propagates upwards. We have extended the developed technique [Gubenko et al., 2008] in order to reconstruct the complete set of wave characteristics including such important parameters as the wave kinetic and potential energy per unit mass and IGW fluxes of the energy and horizontal momentum [Gubenko et al., 2011]. We propose also an alternative method to estimate the relative amplitudes and to extract IGW parameters from an analysis of perturbations of the Brunt-Vaislala frequency squared [Gubenko et al., 2011]. An application of the developed method to the radio occultation (RO) temperature data has given the possibility to identify the IGWs in the Earth's, Martian and Venusian atmospheres and

The Assessment of the Ultimate Hull Girder Strength of RO-RO Ship after Damages

NASA Astrophysics Data System (ADS)

Zubair Muis Alie, Muhammad; Sitepu, Ganding; Izaak Latumahin, Samuel

2018-03-01

Many accidents of Ro-Ro ships happen in Indonesia such as collision and grounding. When the collision or grounding takes place on the Ro-Ro ship, the ultimate strength of hull structure after damage becomes decrease. Car and passenger decks are critical location since collision and/or grounding occur. In the present study, the assessment of the ultimate hull girder strength is conducted. The cross section of Ro-Ro ship is taken to be analyzed. The collision and grounding damages are assumed to be palced on the side and bottom area, respectively. The damages are created by removing the element from the side shell and bottom part. Finally, the result obtained is compared with one another.

Constraints on Pluto's Hazes from 2-Color Occultation Lightcurves

NASA Astrophysics Data System (ADS)

Hartig, Kara; Barry, T.; Carriazo, C. Y.; Cole, A.; Gault, D.; Giles, B.; Giles, D.; Hill, K. M.; Howell, R. R.; Hudson, G.; Loader, B.; Mackie, J. A.; Olkin, C. B.; Rannou, P.; Regester, J.; Resnick, A.; Rodgers, T.; Sicardy, B.; Skrutskie, M. F.; Verbiscer, A. J.; Wasserman, L. H.; Watson, C. R.; Young, E. F.; Young, L. A.; Buie, M. W.; Nelson, M.

2015-11-01

The controversial question of aerosols in Pluto's atmosphere first arose in 1988, when features in a Pluto occultation lightcurve were alternately attributed to haze opacity (Elliot et al. 1989) or a thermal inversion (Eshleman 1989). A stellar occultation by Pluto in 2002 was observed from several telescopes on Mauna Kea in wavelengths ranging from R- to K-bands (Elliot et al. 2003). This event provided compelling evidence for haze on Pluto, since the mid-event baseline levels were systematically higher at longer wavelengths (as expected if there were an opacity source that scattered more effectively at shorter wavelengths). However, subsequent occultations in 2007 and 2011 showed no significant differences between visible and IR lightcurves (Young et al. 2011).The question of haze on Pluto was definitively answered by direct imaging of forward-scattering aerosols by the New Horizons spacecraft on 14-JUL-2015. We report on results of a bright stellar occultation which we observed on 29-JUN-2015 in B- and H-bands from both grazing and central sites. As in 2007 and 2011, we see no evidence for wavelength-dependent extinction. We will present an analysis of haze parameters (particle sizes, number density profiles, and fractal aggregations), constraining models of haze distribution to those consistent with and to those ruled out by the occultation lightcurves and the New Horizons imaging.References:Elliot, J.L., et al., "Pluto's Atmosphere." Icarus 77, 148-170 (1989)Eshleman, V.R., "Pluto's Atmosphere: Models based on refraction, inversion, and vapor pressure equilibrium." Icarus 80 439-443 (1989)Elliot, J.L., et al., "The recent expansion of Pluto's atmosphere." Nature 424 165-168 (2003)Young, E.F., et al., "Search for Pluto's aerosols: simultaneous IR and visible stellar occultation observations." EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France (2011)

Characterizing Daytime GHZ Scintillation at Equatorial Regions Using Gnss Radio Occultation Measurements

NASA Astrophysics Data System (ADS)

Seif, A.; Zhang, K.; Tsunoda, R. T.; Abdullah, M.; Carter, B. A.; Norman, R.; Wu, S.

2015-12-01

Ionospheric scintillation of radio waves can behave differently at different locations with a strong diurnal dependence; particularly in the equatorial regions. Ionospheric scintillations at gigahertz (GHz) frequencies have been observed during both daytime and nighttime. It is believed that daytime scintillation is associated with blanketing sporadic E (Esb), whereas nighttime scintillation is attributed to F layer irregularities. Scintillation events associated with Esbduring daytime are of our primary interest. Recent studies show that in the ionosphere, electron density profiles from Global Navigation Satellite System (GNSS) Radio Occultation (RO) provide valuable information to help better understand the physics of the ionosphere. In particular, GNSS RO observations of GHz scintillation in the proximity of the E-layer have been interpreted as being caused by sporadic E. In this paper the characteristics of daytime scintillations at 1.5 GHz recorded simultaneously from two stations (i) Universiti Kebangsaan Malaysia (UKM) (2.55°N, 101.461°E; dip latitude 5.78°S), and (ii) Langkawi (6.19°N, 99.51°E; dip latitude 1.90°S) during November and December 2010 are analyzed. The characteristics of daytime GHz scintillation and its relationship with E region irregularities at equatorial regions are investigated. Ground-based scintillation and Total Electron Content (TEC) data recorded by the GSV4004 receivers were utilized in combination with the amplitude scintillation measurements in terms of GPS C/A code SNR fluctuations during a ground-based GPS and space-borne GNSS RO experiment at the two equatorial stations. Scintillation activity was found to be more prominent at UKM. Moreover, strong scintillation with the S4 index exceeding 0.6 has only been observed at UKM, while at Langkawi the scintillation intensity (S4 index) did not exceed 0.3. Signal-to-noise measurements obtained from GNSS RO indicate that daytime scintillations are very likely caused by Esb. Our

Correcting negatively biased refractivity below ducts in GNSS radio occultation: an optimal estimation approach towards improving planetary boundary layer (PBL) characterization

NASA Astrophysics Data System (ADS)

Wang, Kuo-Nung; de la Torre Juárez, Manuel; Ao, Chi O.; Xie, Feiqin

2017-12-01

Global Navigation Satellite System (GNSS) radio occultation (RO) measurements are promising in sensing the vertical structure of the Earth's planetary boundary layer (PBL). However, large refractivity changes near the top of PBL can cause ducting and lead to a negative bias in the retrieved refractivity within the PBL (below ˜ 2 km). To remove the bias, a reconstruction method with assumption of linear structure inside the ducting layer models has been proposed by Xie et al. (2006). While the negative bias can be reduced drastically as demonstrated in the simulation, the lack of high-quality surface refractivity constraint makes its application to real RO data difficult. In this paper, we use the widely available precipitable water (PW) satellite observation as the external constraint for the bias correction. A new framework is proposed to incorporate optimization into the RO reconstruction retrievals in the presence of ducting conditions. The new method uses optimal estimation to select the best refractivity solution whose PW and PBL height best match the externally retrieved PW and the known a priori states, respectively. The near-coincident PW retrievals from AMSR-E microwave radiometer instruments are used as an external observational constraint. This new reconstruction method is tested on both the simulated GNSS-RO profiles and the actual GNSS-RO data. Our results show that the proposed method can greatly reduce the negative refractivity bias when compared to the traditional Abel inversion.

[A retrospective analysis on occult neck lymphatic metastasis in early tongue cancer].

PubMed

Gong, Q L; Bian, C; Liu, H

2016-10-07

Objective: To investigate the number and level of occult neck lymphatic metastasis for squamous cell carcinoma of tongue in clinical stage Ⅰ/Ⅱ, and the relationship between cell differentiation and occult neck lymphatic metastasis. Methods: A total of 101 cases diagnosed preoperatively as having squamous cell carcinoma of tongue in clinical stage Ⅰ/Ⅱ (cT1/T2N0M0) between January 2005 and April 2015 were analysed retrospectively. Whether presence of occult neck lymphatic metastasis in these cases was studied. Results: Occult neck lymphatic metastases were found in 22 (21.78%) of 101 cases, 10 men and 12 women, with an age range of 22 to 83 years. There was not statistically significant association between tumor size or cell differentiation and occult neck lymphatic metastasis ( P >0.05). The metastasis occurred most commonly in level Ⅱ, followed by levelsⅠ, Ⅲ and Ⅳ. There was no lymph node metastasis in Level Ⅴ. There were total 20 cases with occult neck lymphatic metastasis in at least one of levelⅠ, Ⅱ, Ⅲ(90.9%), One of these case was skipping metastasis in level Ⅲ(4.6%). Conclusion: The early tongue cancer has a high rate of occult lymph metastasis, which occurs commonly in levels Ⅱ, Ⅰ and Ⅲ, but there is not significant association between the metastasis and tumor size or cell differentiation.

Wave optics of the central spot in planetary occultations

NASA Technical Reports Server (NTRS)

Hubbard, W. B.

1977-01-01

The detection of a bright central spot during the occultation of epsilon Geminorum by Mars demonstrates that an exponentially-stratified planetary atmosphere can act as a lens providing very high resolution of distant objects (e.g., quasars, white dwarfs, and pulsars). The diffraction nature of the central occultation spot is investigated, with special reference to Mars and Venus. In practice, however, central occultations by these planets are seldom observable from the earth's surface, and spacecraft would have to be used to obtain a suitable orientation for observers. Further difficulties may be encountered in image deconvolution needed for extended objects, in location of the image of a true point source, and in compensation for peculiarities of planets and their atmospheres.

An occultation satellite system for determining pressure levels in the atmosphere

NASA Technical Reports Server (NTRS)

Ungar, S. G.; Lusignan, B. B.

1972-01-01

An operational two-satellite microwave occultation system will establish a pressure reference level to be used in fixing the temperature-pressure profile generated by the SIRS infrared sensor as a function of altitude. In the final error analysis, simulated data for the SIRS sensor were used to test the performance of the occultation system. The results of this analysis indicate that the occultation system is capable of measuring the altitude of the 300-mb level to within 24 mrms, given a maximum error of 2 K in the input temperature profile. The effects of water vapor can be corrected by suitable climatological profiles, and improvements in the accuracy of the SIRS instrument should yield additional improvements in the performance of the occultation system.

The Occult: Diabolica to Alchemists

ERIC Educational Resources Information Center

Delaney, Oliver J.

1971-01-01

The 91 items in this bibliography deal with works of occult science. The material is subdivided into biographies, dictionaries, encyclopedias, handbooks, noteworthy histories, indices, annuals, and a few miscellany works with treatises. (95 references) (Author)

Decreased sensitivity of early imaging with In-111 oxine-labeled leukocytes in detection of occult infection: concise communication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datz, F.L.; Jacobs, J.; Baker, W.

1984-03-01

Imaging with leukocytes labeled with indium-111 oxine is a sensitive technique for detecting sites of occult infection. Traditionally, imaging is performed 24 hr after injection. The authors undertook a prospective study of 35 patients (40 studies) with possible occult infection to see whether a 24-hr delay in imaging is really necessary. Patients were imaged at 1-4 hr and again at 24 hr after injection. The early images had a sensitivity of only 33%, compared with 95% for the 24-hr images. Of the seven studies that were positive on both early and delayed images, 71% had more intense uptake at 24more » hr. There were no false-positive early images. It was concluded that imaging 1-4 hr after injection with In-111 oxine-labeled leukocytes has a low sensitivity for detecting occult infection. However, a positive early image is specific for a site of infection.« less

Results of Observations of Occultations of Stars by Main-Belt and Trojan Asteroids, and the Promise of Gaia

NASA Astrophysics Data System (ADS)

Dunham, David W.; Herald, David Russell; Preston, Steven; Loader, Brian; Bixby Dunham, Joan

2016-10-01

For 40 years, the sizes and shapes of scores of asteroids have been determined from observations of asteroidal occultations, and many hundreds of high-precision positions of the asteroids relative to stars have been measured. Earlier this year, the 3000th observation of an asteroidal occultation was documented. Some of the first evidence for satellites of asteroids was obtained from the early efforts; now, the orbits and sizes of some satellites discovered by other means have been refined from occultation observations. Also, several close binary stars have been discovered, and the angular diameters of some stars have been measured from analysis of these observations. The International Occultation Timing Association (IOTA) coordinates this activity worldwide, from predicting and publicizing the events, to accurately timing the occultations from as many stations as possible, and publishing and archiving the observations. The first observations were timed visually, but now nearly all observations are either video-recorded, or recorded with CCD drift scans, allowing small magnitude-drop events to be recorded, and resulting in more consistent results. Techniques have been developed allowing one or two observers to set up multiple stations with small telescopes, video cameras, and timers, thereby recording many chords, even across a whole asteroid; some examples will be shown.Later this year, the first release of Gaia data will allow us to greatly improve the vast star catalog that we use for both predicting and analyzing these events. Although the first asteroidal data will wait until the 4th Gaia release, before that, we can greatly improve the orbits of asteroids that have occulted 3 or more stars in the past so that we can start computing the paths of future occultations by them to few km accuracy. In a couple of years, we'll be able to realistically predict one to two orders of magnitude more events than we can now, allowing efforts to be concentrated on smaller

Preview of the BATSE Earth Occultation Catalog of Low Energy Gamma Ray Sources

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Wilson, C. A.; Fishman, G. J.; McCollough, M. L.; Robinson, C. R.; Sahi, M.; Paciesas, W. S.; Zhang, S. N.

1999-01-01

The Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma Ray Observatory (CGRO) has been detecting and monitoring point sources in the high energy sky since 1991. Although BATSE is best known for gamma ray bursts, it also monitors the sky for longer-lived sources of radiation. Using the Earth occultation technique to extract flux information, a catalog is being prepared of about 150 sources potential emission in the large area detectors (20-1000 keV). The catalog will contain light curves, representative spectra, and parametric data for black hole and neutron star binaries, active galaxies, and super-nova remnants. In this preview, we present light curves for persistent and transient sources, and also show examples of what type of information can be obtained from the BATSE Earth occultation database. Options for making the data easily accessible as an "on line" WWW document are being explored.

Seroprevalence of occult hepatitis B among Egyptian paediatric hepatitis C cancer patients.

PubMed

Raouf, H E; Yassin, A S; Megahed, S A; Ashour, M S; Mansour, T M

2015-02-01

Occult hepatitis B infection is characterized by the presence of hepatitis B virus (HBV) DNA in the serum in the absence of hepatitis B surface antigen (HBsAg). Prevalence of hepatitis C virus (HCV) infections in Egypt is among the highest in the world. In this study, we aim at analysing the rates of occult HBV infections among HCV paediatric cancer patients in Egypt. The prevalence of occult HBV was assessed in two groups of paediatric cancer patients (HCV positive and HCV negative), in addition to a third group of paediatric noncancer patients, which was used as a general control. All groups were negative for HBsAg and positive for HCV antibody. HBV DNA was detected by nested PCR and real-time PCR. HCV was detected by real-time PCR. Sequencing was carried out in order to determine HBV genotypes to all HBV patients as well as to detect any mutation that might be responsible for the occult phenotype. Occult hepatitis B infection was observed in neither the non-HCV paediatric cancer patients nor the paediatric noncancer patients but was found in 31% of the HCV-positive paediatric cancer patients. All the detected HBV patients belonged to HBV genotype D, and mutations were found in the surface genome of HBV leading to occult HBV. Occult HBV infection seems to be relatively frequent in HCV-positive paediatric cancer patients, indicating that HBsAg negativity is not sufficient to completely exclude HBV infection. These findings emphasize the importance of considering occult HBV infection in HCV-positive paediatric cancer patients especially in endemic areas as Egypt. © 2014 John Wiley & Sons Ltd.

Occult Hepatitis B Virus Infection in a Previously Vaccinated Injection Drug User.

PubMed

Powell, Eleanor A; Razeghi, Sanam; Zucker, Stephen; Blackard, Jason T

2016-02-01

Occult hepatitis B virus (HBV) is defined by the presence of HBV DNA in patient sera in the absence of HBsAg. Occult HBV has been associated with hepatocellular carcinoma, reactivation during immune suppression, and transmission to others. While the hepatitis B vaccine is very effective at preventing chronic HBV infection, recent studies indicate it is less effective at preventing occult HBV following infant vaccination. No studies, however, have examined the efficacy of adult HBV vaccination at preventing occult HBV. Here, we present the first report of occult HBV following adult vaccination. A 21-year old Caucasian female presented with tricuspid valve endocarditis secondary to methicillin-susceptible Staphylococcus aureus with non-ischemic cardiomyopathy. She reported active use of intravenous drugs. Her liver enzymes were elevated (ALT = 1873 IU/mL; AST = 4518 IU/mL), and she was found to have HCV and occult HBV. HBV viral loads ranged from 4608 - 8364 copies IU/mL during hospitalization. The patient's HBV was sequenced and found to be genotype D3 without any known diagnostic escape mutations. Immune complexes that may have prevented HBsAg detection were not observed. HBV vaccination in infancy is effective at preventing chronic HBV infection but is less effective at preventing occult HBV infection. Similar studies examining the efficacy of adult HBV vaccination in preventing occult HBV have not been performed. This case highlights the importance of carefully determining the HBV status of high-risk individuals, as vaccination history and the presence of anti-HBs may not be adequate to rule out HBV infection, even in the absence of HBsAg.

Periprosthetic Occult Fractures of the Acetabulum Occur Frequently During Primary THA.

PubMed

Hasegawa, Kazuhiro; Kabata, Tamon; Kajino, Yoshitomo; Inoue, Daisuke; Tsuchiya, Hiroyuki

2017-02-01

Periprosthetic fractures of the acetabulum occurring during primary THA are rare. Periprosthetic occult fractures are defined as those not identified by the surgeon during the procedure which might be missed on a routine postoperative radiograph. However, it is unclear how frequently these fractures occur and whether their presence affects functional recovery. In this study, using routine CT scans that were obtained as part of another primary hip arthroplasty study protocol, we retrospectively assessed (1) the prevalence of occult fractures of the acetabulum occurring during primary THA, (2) the location of occult fractures of the acetabulum during THA, and (3) risk factors contributing to such occult fractures. Between 2004 and 2013, our institute performed 585 primary THAs (cementless or hybrid) in 494 patients with DICOM pre- and postoperative CT; during the period in question, all patients undergoing THA underwent CT before and after surgery. Preoperative CT images were taken as part of a CT-based three-dimensional templating software and navigation system. Postoperative CT images were taken an average of 1 week after surgery as part of a different protocol to evaluate cup position, restoration of leg length and offset, volume of postoperative hematoma to assess anticoagulation effects after THA, and fractures that were not found on routine postoperative radiographs (which we defined as occult fractures). Patients with a history of prior pelvic osteotomy, trauma, and infection were excluded (88 patients/99 hips); 406 patients (102 males and 304 females; 486 hips) form the basis of this report. The mean age of the patients was 60 ± 11 years, with a mean BMI of 23 ± 4 kg/m 2 . The mean followup of the patients with periprosthetic fracture of the acetabulum was 58 ± 28 months (range, 12-131 months). Potential risk factors for occult acetabular fracture including age, sex, BMI, preoperative diagnosis, additional dome screw fixation, composition and size of each

Occult cancer detection in patients with hemostatic disorder and venous thromboembolism.

PubMed

Husseinzadeh, Holleh; Carrier, Marc

2018-03-01

There are physiologic ties between Von Willebrand Factor (VWF) and circulating tumor cells. VWF appears to play a role in tumor biology, but it is unclear whether cancer behavior differs in Von Willebrand Disease. In patients presenting with venous thromboembolism (VTE), occult cancer is frequently considered as an underlying cause. The prevalence of occult cancer after provoked VTE is low (3%); therefore, cancer screening in these patients is not routinely recommended. In those with unprovoked VTE, occult cancer is more prevalent, estimated between 4 and 10%. Due to this elevated risk, occult cancer screening is recommended in this population. Multiple studies have investigated whether a "limited" approach (including history and physical exam, basic labs, and chest X-ray) versus "extensive" approach (addition of advanced imaging, such as computer tomography) is more effective. Current data fails to demonstrate extensive screening strategies diagnose more occult cancer, miss fewer cancers during follow up, or improve cancer-related mortality. Furthermore, many patients may be needlessly exposed to unnecessary diagnostic procedures with their associated complications and costs, as well as significant anxiety. Therefore, the decision to perform additional testing should be made on a case-by-case basis. Additional studies are needed to identify subgroups of patients with unprovoked VTE at highest risk for occult cancer. Copyright © 2017 Elsevier Ltd. All rights reserved.

Astrometry of Single-Chord Occultations: Application to the 1993 Triton Event

NASA Technical Reports Server (NTRS)

Olkin, Catherine B.; Elliot, J. L.; Bus, Schelte J.; McDonald, Stephen W.; Dahn, Conrad C.

1996-01-01

This paper outlines a method for reducing astrometric data to derive the closest approach time and distance to the center of an occultation shadow for a single observer. The method applies to CCD frames, strip scans or photographic plates and uses a set of field stars of unknown positions to define a common coordinate system for all frames. The motion of the occulting body is used to establish the transformation between this common coordinate system and the celestial coordinate system of the body's ephemeris. This method is demonstrated by application to the Tr6O occultation by Triton on 1993 July 10 UT. Over an interval of four nights that included the occultation time, 80 frames of Triton and Tr6O were taken near the meridian with the U.S. Naval Observatory (USNO) 61-inch astrometric reflector. Application of the method presented here to these data yields a closest approach distance of 359 +/- 133 km (corresponding to 0.017 +/- 0.006 arcsec) for the occultation chord obtained with the Kuiper Airborne Observatory (KAO). Comparison of the astrometric closest approach time with the KAO light-curve midtime shows a difference of 2.2 +/- 4.1 s. Relative photometry of Triton and Tr6O, needed for photometric calibration of the occultation light curve, is also presented.

[Occultism, parapsychology and the esoteric from the perspective of psychopathology].

PubMed

Scharfetter, C

1998-10-01

The concepts and main themes of occultism, parapsychology and esoterics are set in comparison to religion, spirituality, mysticism. The cultural relativity of these concepts is emphasised. Occultism means dealing with phenomena, processes, and/or powers which are not accessible to "normal perception". The manipulation of such powers is effected via (white, black, grey) magic. Parapsychology, in its popular sense, deals with occult phenomena, whereas scientific parapsychology investigates them empirically. Esoterics is a complex of beliefs within a hermetic tradition about occult processes and about desting after death. Transpersonal psychology deals with these issues while calling them "spiritual". Effects of paranormal experiences and actions on the side of the actor as well as the adept are discussed: personality types, interpersonal effects, crises and psychoses (mediumistic psychoses). The concept of dissociation of subpersonalities (subselves) appears to be a viable perspective to explain these phenomena. In mediumistic psychoses, the splitting of non-ego parts of the psyche leads to a manifestation of schizophrenic symptoms. Dangers for mental health are an ego inflation by self-attribution of "superhuman" power. A personality disposition for parapsychological perception and/or action may be seen in schizotypia and similar near-psychotic "personalities up the border". Adepts of occultism may present with a "false self" in the sense of Winnicott.

Evaluation of atmospheric profiles derived from single- and zero-difference excess phase processing of BeiDou radio occultation data from the FY-3C GNOS mission

NASA Astrophysics Data System (ADS)

Bai, Weihua; Liu, Congliang; Meng, Xiangguang; Sun, Yueqiang; Kirchengast, Gottfried; Du, Qifei; Wang, Xianyi; Yang, Guanglin; Liao, Mi; Yang, Zhongdong; Zhao, Danyang; Xia, Junming; Cai, Yuerong; Liu, Lijun; Wang, Dongwei

2018-02-01

The Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) is one of the new-generation payloads onboard the Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth's neutral atmosphere and ionosphere. The GNOS was designed for acquiring setting and rising radio occultation (RO) data by using GNSS signals from both the Chinese BeiDou System (BDS) and the US Global Positioning System (GPS). An ultra-stable oscillator with 1 s stability (Allan deviation) at the level of 10-12 was installed on the FY-3C GNOS, and thus both zero-difference and single-difference excess phase processing methods should be feasible for FY-3C GNOS observations. In this study we focus on evaluating zero-difference processing of BDS RO data vs. single-difference processing, in order to investigate the zero-difference feasibility for this new instrument, which after its launch in September 2013 started to use BDS signals from five geostationary orbit (GEO) satellites, five inclined geosynchronous orbit (IGSO) satellites and four medium Earth orbit (MEO) satellites. We used a 3-month set of GNOS BDS RO data (October to December 2013) for the evaluation and compared atmospheric bending angle and refractivity profiles, derived from single- and zero-difference excess phase data, against co-located profiles from European Centre for Medium-Range Weather Forecasts (ECMWF) analyses. We also compared against co-located refractivity profiles from radiosondes. The statistical evaluation against these reference data shows that the results from single- and zero-difference processing are reasonably consistent in both bias and standard deviation, clearly demonstrating the feasibility of zero differencing for GNOS BDS RO observations. The average bias (and standard deviation) of the bending angle and refractivity profiles were found to be about 0.05 to 0.2 % (and 0.7 to 1.6 %) over the upper troposphere and lower stratosphere. Zero differencing was found

McDonald's and the Occult.

ERIC Educational Resources Information Center

Singer, Barry

1979-01-01

Discusses "occult" and "paranormal" literature which is often mistaken for nonfiction. Suggests that most publishers are unwilling to publish scientific perspectives on the paranormal because such writings would be unmarketable. Journal availability: see SO 507 190. (KC)

Changes in Pluto's Atmosphere Revealed by Occultations

NASA Astrophysics Data System (ADS)

Sicardy, Bruno; Widemann, Thomas; Lellouch, Emmanuel; Veillet, Christian; Colas, Francois; Roques, Francoise; Beisker, Wolfgang; Kretlow, Mike; Cuillandre, Jean-Charles; Hainaut, Olivier

After the discovery and study of Pluto's tenuous atmosphere in 1985 and 1988 with stellar occultations 14 years were necessary before two other occultations by the planet could be observed on 20 July 2002 and 21 August 2002 from Northern Chile with a portable telescope and from CFHT in Hawaii respectively. These occultations reveal drastric changes in Pluto's nitrogen atmosphere whose pressure increased by a factor two or more since 1988. In spite of an increasing distance to the Sun (and a correlated decrease of solar energy input at Pluto) this increase can be explained by the fact that Pluto's south pole went from permanent darkness to permanent illumination between 1988 and 2002. This might cause the sublimation of the south polar cap and the increase of pressure which could go on till 2015 according to current nitrogen cycle models. Furthermore we detect temperature contrasts between the polar and the equatorial regions probed on Pluto possibly caused by different diurnally averaged insolations at those locations. Finally spikes observed in the light curves reveal a dynamical activity in Pluto's atmosphere.

High spatial resolution multi-color observations of Neptune during occultation by the moon

NASA Technical Reports Server (NTRS)

Veverka, J.

1976-01-01

Preparations for the observation of Mars occultation using the 36 inch telescope on a C-141 airborne observatory were described, including technical improvements made to existing equipment. The abstracts of the following four publications supported by the grant were presented: (1) atmosphere composition from refractivity measurements made during occultations, (2) how big is lapetus?, (3) the diameter of Titan, (4) design and operating characteristics of voltage to frequency converters suited for occultation work. The planned observation of the April 8, 1976 occultation of the epsilon Gem star from the C-141 airborne observatory was described.

Prevalence of occult inflammatory bowel disease in ankylosing spondylitis.

PubMed Central

Costello, P B; Alea, J A; Kennedy, A C; McCluskey, R T; Green, F A

1980-01-01

Fifty-five patients with ankylosing spondylitis and 16 control patients matched for sex and age were examined for evidence of occult inflammatory bowel disease. In all patients evaluation included history and physical examination, barium enema, sigmoidoscopy, and rectal biopsy. The results of this study suggest that there is no increased prevalence of occult inflammatory bowel disease in patients with ankylosing spondylitis. PMID:7436576

Prevalence of occult inflammatory bowel disease in ankylosing spondylitis.

PubMed

Costello, P B; Alea, J A; Kennedy, A C; McCluskey, R T; Green, F A

1980-10-01

Fifty-five patients with ankylosing spondylitis and 16 control patients matched for sex and age were examined for evidence of occult inflammatory bowel disease. In all patients evaluation included history and physical examination, barium enema, sigmoidoscopy, and rectal biopsy. The results of this study suggest that there is no increased prevalence of occult inflammatory bowel disease in patients with ankylosing spondylitis.

Tropospheric dry layers in the tropical western Pacific: comparisons of GPS radio occultation with multiple data sets

NASA Astrophysics Data System (ADS)

Rieckh, Therese; Anthes, Richard; Randel, William; Ho, Shu-Peng; Foelsche, Ulrich

2017-03-01

We use GPS radio occultation (RO) data to investigate the structure and temporal behavior of extremely dry, high-ozone tropospheric air in the tropical western Pacific during the 6-week period of the CONTRAST (CONvective TRansport of Active Species in the Tropics) experiment (January and February 2014). Our analyses are aimed at testing whether the RO method is capable of detecting these extremely dry layers and evaluating comparisons with in situ measurements, satellite observations, and model analyses. We use multiple data sources as comparisons, including CONTRAST research aircraft profiles, radiosonde profiles, AIRS (Atmospheric Infrared Sounder) satellite retrievals, and profiles extracted from the ERA (ERA-Interim reanalysis) and the GFS (US National Weather Service Global Forecast System) analyses, as well as MTSAT-2 satellite images. The independent and complementary radiosonde, aircraft, and RO data provide high vertical resolution observations of the dry layers. However, they all have limitations. The coverage of the radiosonde data is limited by having only a single station in this oceanic region; the aircraft data are limited in their temporal and spatial coverage; and the RO data are limited in their number and horizontal resolution over this period. However, nearby observations from the three types of data are highly consistent with each other and with the lower-vertical-resolution AIRS profiles. They are also consistent with the ERA and GFS data. We show that the RO data, used here for the first time to study this phenomenon, contribute significant information on the water vapor content and are capable of detecting layers in the tropics and subtropics with extremely low humidity (less than 10 %), independent of the retrieval used to extract moisture information. Our results also verify the quality of the ERA and GFS data sets, giving confidence to the reanalyses and their use in diagnosing the full four

Comparison of Water Vapor Measurements from Ground-based and Space-based GPS Atmospheric Remote Sensing Techniques

NASA Astrophysics Data System (ADS)

Colon-Pagan, Ian; Kuo, Ying-Hwa

2008-10-01

In this study, we compare precipitable water vapor (PWV) values from ground-based GPS water vapor sensing and COSMIC radio occultation (RO) measurements over the Caribbean Sea, Gulf of Mexico, and United States regions as well as global analyses from NCEP and ECMWF models. The results show good overall agreement; however, the PWV values estimated by ground-based GPS receivers tend to have a slight dry bias for low PWV values and a slight wet bias for higher PWV values, when compared with GPS RO measurements and global analyses. An application of a student T-test indicates that there is a significant difference between both ground- and space-based GPS measured datasets. The dry bias associated with space-based GPS is attributed to the missing low altitude data, where the concentration of water vapor is large. The close agreements between space-based and global analyses are due to the fact that these global analyses assimilate space-based GPS RO data from COSMIC, and the retrieval of water vapor profiles from space-based technique requires the use of global analyses as the first guess. This work is supported by UCAR SOARS and a grant from the National Oceanic and Atmospheric Administration, Educational Partnership Program under the cooperative agreement NA06OAR4810187.

The future of stellar occultations by distant solar system bodies: Perspectives from the Gaia astrometry and the deep sky surveys

NASA Astrophysics Data System (ADS)

Camargo, J. I. B.; Desmars, J.; Braga-Ribas, F.; Vieira-Martins, R.; Assafin, M.; Sicardy, B.; Bérard, D.; Benedetti-Rossi, G.

2018-05-01

Distant objects in the solar system are crucial to better understand the history and evolution of its outskirts. The stellar occultation technique allows the determination of their sizes and shapes with kilometric accuracy, a detailed investigation of their immediate vicinities, as well as the detection of tenuous atmospheres. The prediction of such events is a key point in this study, and yet accurate enough predictions are available to a handful of objects only. In this work, we briefly discuss the dramatic impact that both the astrometry from the Gaia space mission and the deep sky surveys - the Large Synoptic Survey Telescope in particular - will have on the prediction of stellar occultations and how they may influence the future of the study of distant small solar system bodies through this technique.

Lunar occultation of Saturn. IV - Astrometric results from observations of the satellites

NASA Technical Reports Server (NTRS)

Dunham, D. W.; Elliot, J. L.

1978-01-01

The method of determining local lunar limb slopes, and the consequent time scale needed for diameter studies, from accurate occultation timings at two nearby telescopes is described. Results for photoelectric observations made at Mauna Kea Observatory during the occultation of Saturn's satellites on March 30, 1974, are discussed. Analysis of all observations of occultations of Saturn's satellites during 1974 indicates possible errors in the ephemerides of Saturn and its satellites.

Comparisons of COSMIC and C/NOFS GPS Occultation Ionospheric Scintillation Measurements with Ground-based Radar and VHF Measurements

NASA Astrophysics Data System (ADS)

Ruggiero, F. H.; Groves, K. M.; Straus, P. R.; Caton, R. G.; Starks, M. J.; Tanyi, K. L.; Verlinden, M.

2009-12-01

Ionospheric irregularities are known to cause scintillation of trans-ionospheric radio signals and can affect space-based UHF/VHF communications, causing outages, and degrading GPS accuracy and precision. Current capability for characterizing and predicting ionospheric scintillation utilizes a network of ground-based receivers to detect scintillation and then extrapolate for short-term forecasts. Practical limits on deploying the ground receivers limits the accuracy and spatial coverage one can achieve with this approach. A more global approach is to use a set of space-based satellites equipped with GPS receivers, such as the COSMIC satellite constellation, to measure scintillations observed during so-called occultations with GPS satellites. In this paper the signal-to-noise values of GPS L1 signals received on the COSMIC and C/NOFS satellites for the portions of the occultations that are not affected by the terrestrial atmosphere are examined to help identify areas of ionospheric scintillation. Three years of S4 scintillation index values from COSMIC occultations are compared with near-zenith ground-based VHF S4 scintillation measurements from the AFRL SCIntillation Network Decision Aid (SCINDA) network stations. The data are correlated to ascertain the viability of using space-based scintillation measurements to characterize and predict scintillation to ground-based receivers. Several days of COSMIC and C/NOFS data are compared with each other and the ALTAIR radar located on Kwajalein Atoll, Marshall Islands to examine how occultation geometry affects observed scintillation and also to verify techniques that provide an upper bound on the spatial location of the ionospheric irregularities contributing to scintillations observed in the occultations.

Local time dependence of the thermal structure in the Venusian equatorial region revealed by Akatsuki radio occultation measurements

NASA Astrophysics Data System (ADS)

Ando, H.; Fukuhara, T.; Takagi, M.; Imamura, T.; Sugimoto, N.; Sagawa, H.

2017-12-01

The radio occultation technique is one of the most useful methods to retrieve vertical temperature profiles in planetary atmospheres. Ultra-Stable Oscillator (USO) onboard Venus Climate Orbiter, Akatsuki, enables us to investigate the thermal structure of the Venus atmosphere between about 40-90 km levels. It is expected that 35 temperature profiles will be obtained by the radio occultation measurements of Akatsuki until August 2017. Static stability derived from the temperature profiles shows its local time dependence above the cloud top level at low-latitudes equatorward of 25˚. The vertical profiles of the static stability in the dawn and dusk regions have maxima at 77 km and 82 km levels, respectively. A general circulation model (GCM) for the Venus atmosphere (AFES-Venus) reproduced the thermal structures above the cloud top qualitatively consistent with the radio occultation measurements; the maxima of the static stability are seen both in the dawn and dusk regions, and the local maximum of the static stability in the dusk region is located at a highler level than in the dawn region. Comparing the thermal structures between the radio occultation measurements and the GCM results, it is suggested that the distribution of the static stability above the cloud top could be strongly affected by the diurnal tide. The thermal tide influences on the thermal structure as well as atmospheric motions above the cloud level. In addition, it is shown that zonally averaged zonal wind at about 80 km altitude could be roughly estimated from the radio occultation measurements using the dispersion relation of the internal gravity wave.

Pluto's Atmospheric Figure from the P131.1 Stellar Occultation

NASA Astrophysics Data System (ADS)

Person, M. J.; Elliot, J. L.; Clancy, K. B.; Kern, S. D.; Salyk, C. V.; Tholen, D. J.; Pasachoff, J. M.; Babcock, B. A.; Souza, S. P.; Ticehurst, D. R.; Hall, D.; Roberts, L. C., Jr.; Bosh, A. S.; Buie, M. W.; Dunham, E. W.; Olkin, C. B.; Taylor, B.; Levine, S. E.; Eikenberry, S. S.; Moon, D.-S.; Osip, D. J.

2003-05-01

The stellar occultation by Pluto of the 15th magnitude star designated P131.1 (McDonald and Elliot, AJ, 119, 1999) on 2002 August 21 (UT) provided the first significant chance to compare Pluto's atmospheric structure to that determined from the 1988 occultation of P8 (Millis, et al., Icarus, 105, 282). The P131.1 occultation was observed from several stations in Hawaii and the western United States (Elliot et al., Nature, in press, 2003). Numerous occultation chords were obtained enabling us to examine Pluto's atmospheric figure. The light curves from the observations were analyzed together in the occultation coordinate system of Elliot et al., (AJ, 106, 2544). The Mauna Kea and Lick datasets straddle the center of Pluto's figure, providing strong constraints on model fits to cross sections of the atmospheric shape. In 1988, Millis (et al., Icarus, 105, 282) did not report any deviation from sphericity in Pluto's atmospheric figure. From the 2002 data, Pluto;s isobars at the radii probed by the occultation ( 1250 km) appear to be distorted from a circular cross-section. Least-squares fits to this cross-section by elliptical models reveal ellipticities in the range 0.05-0.08 although the shape may be more complex than ellipsoidal. The orientation of the distortion appears uncorrelated with Pluto;s rotational axis. Taken at face value, this ellipticity could imply wind speeds of up to twice the sonic speed ( 200 m/s), which would be difficult to explain. Similar distortions have been reported for Triton's atmosphere (Elliot, J. L., et al., Icarus 148, 347). This work has been supported in part by Research Corporation, the Air Force Research Laboratory, NSF, and NASA.

Detection of occult endocervical glandular dysplasia in cervical conization specimens for squamous lesions.

PubMed

Sopracordevole, F; Clemente, N; Alessandrini, L; Di Giuseppe, J; Cigolot, F; Buttignol, M; Ciavattini, A; Canzonieri, V

2017-03-01

The aim of this work was to evaluate the incidence of occult cervical glandular intraepithelial neoplasia (CGIN) and adenocarcinoma of the cervix (AC) in women treated with CO2-laser conization for cervical intraepithelial neoplasia (CIN) or squamocellular cervical cancer (SCC). The medical records of all women with a histological diagnosis of squamous lesions of the uterine cervix (persistent CIN1, CIN2, CIN3 and SCC) who were subsequently treated with CO2-laser conization at our institution, during the period from January 1991 to December 2014, were analyzed in a retrospective case series. Among the 1004 women fulfilling the study inclusion/exclusion criteria, 77 cases (7.7%) of occult glandular lesions (CGIN and AC) were detected on the final cone specimen (48 cases of occult low-grade cervical glandular intraepithelial neoplasia (LCGIN), 25 cases of occult high-grade cervical glandular intraepithelial neoplasia (HCGIN), and four cases of occult "usual-type" AC). No difference in the mean age between women diagnosed with occult glandular lesions and women without occult glandular lesions on the final specimen emerged (39.1±9.3 vs 38.4±9.4, p=0.5). In women with occult LCGIN on cone specimen, mean follow-up of 48 months was reported (range 7-206 months) and no cases of progression to HCGIN or AC were observed. In conclusion, a relatively high rate of occult glandular lesions was found in women treated for squamous lesions. The natural history of CGIN is still uncertain and, in particular, there are some controversies as to whether LCGIN is a precursor lesion of HCGIN or AC. In this context the role of pathologists become very important since the appropriate diagnosis of these lesions could have potential implications in the clinical management of these patients. Copyright © 2017 Elsevier GmbH. All rights reserved.

New Radiosonde Temperature Bias Adjustments for Potential NWP Applications Based on GPS RO Data

NASA Astrophysics Data System (ADS)

Sun, B.; Reale, A.; Ballish, B.; Seidel, D. J.

2014-12-01

Conventional radiosonde observations (RAOBs), along with satellite and other in situ data, are assimilated in numerical weather prediction (NWP) models to generate a forecast. Radiosonde temperature observations, however, have solar and thermal radiation induced biases (typically a warm daytime bias from sunlight heating the sensor and a cold bias at night as the sensor emits longwave radiation). Radiation corrections made at stations based on algorithms provided by radiosonde manufacturers or national meteorological agencies may not be adequate, so biases remain. To adjust these biases, NWP centers may make additional adjustments to radiosonde data. However, the radiation correction (RADCOR) schemes used in the NOAA NCEP data assimilation and forecasting system is outdated and does not cover several widely-used contemporary radiosonde types. This study focuses on work whose objective is to improve these corrections and test their impacts on the NWP forecasting and analysis. GPS Radio Occultation (RO) dry temperature (Tdry) is considered to be highly accurate in the upper troposphere and low stratosphere where atmospheric water vapor is negligible. This study uses GPS RO Tdry from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) as the reference to quantify the radiation induced RAOB temperature errors by analyzing ~ 3-yr collocated RAOB and COSMIC GPS RO data compile by the NOAA Products Validation System (NPROVS). The new radiation adjustments are developed for different solar angle categories and for all common sonde types flown in the WMO global operational upper air network. Results for global and several commonly used sondes are presented in the context of NCEP Global Forecast System observation-minus-background analysis, indicating projected impacts in reducing forecast error. Dedicated NWP impact studies to quantify the impact of the new RADCOR schemes on the NCEP analyses and forecast are under consideration.

The diameter of Juno from its occultation of AG + 0 deg 1022

NASA Technical Reports Server (NTRS)

Millis, R. L.; Wasserman, L. H.; Bowell, E.; Franz, O. G.; White, N. M.; Lockwood, G. W.; Nye, R.; Bertram, R.; Klemola, A.; Dunham, E.;

Ground Support Network for Operational Radio Occultation Missions

NASA Astrophysics Data System (ADS)

Zandbergen, R.; Enderle, W.; Marquardt, C.; Wollenweber, F.

2012-04-01

The EUMETSAT/ESA Metop/EPS GRAS radio occultation mission stands out for its operational nature. From the beginning, EUMETSAT has decided to rely on an operational system for provision of the auxiliary GPS products that are needed in the occultation processing. This system is the GRAS Ground Support Network (GSN), operated in the Navigation Facility of ESOC in Darmstadt, which was first presented at EGU in 2008. The GRAS GSN is driven primarily by timeliness, availability and accuracy requirements. The performance of the GSN, measured on a monthly basis, has not only consistently met these requirements since the start of its operations, but has also been improved through several system enhancements. Currently, an additional service is being delivered on an experimental basis, consisting of a near-real time Navigation Bit Stream product, which will allow the processing of open-loop data, further increasing the scientific return of the GRAS instrument, or any other radio occultation mission using this data. This paper will present the GRAS GSN in its current configuration, and demonstrate its excellent performance in terms of accuracy, availability and timeliness. The application of the bit stream data will be shown. Some future evolution perspectives of the GRAS GSN will also be addressed. It will be demonstrated that the GRAS GSN has the potential of serving also other present and future radio occultation missions.

Impact of fecal occult blood on obscure gastrointestinal bleeding: Observational study

PubMed Central

Kobayashi, Yuka; Watabe, Hirotsugu; Yamada, Atsuo; Suzuki, Hirobumi; Hirata, Yoshihiro; Yamaji, Yutaka; Yoshida, Haruhiko; Koike, Kazuhiko

2015-01-01

AIM: To elucidate the association between small bowel diseases (SBDs) and positive fecal occult blood test (FOBT) in patients with obscure gastrointestinal bleeding (OGIB). METHODS: Between February 2008 and August 2013, 202 patients with OGIB who performed both capsule endoscopy (CE) and FOBT were enrolled (mean age; 63.6 ± 14.0 years, 118 males, 96 previous overt bleeding, 106 with occult bleeding). All patients underwent immunochemical FOBTs twice prior to CE. Three experienced endoscopists independently reviewed CE videos. All reviews and consensus meeting were conducted without any information on FOBT results. The prevalence of SBDs was compared between patients with positive and negative FOBT. RESULTS: CE revealed SBDs in 72 patients (36%). FOBT was positive in 100 patients (50%) and negative in 102 (50%). The prevalence of SBDs was significantly higher in patients with positive FOBT than those with negative FOBT (46% vs 25%, P = 0.002). In particular, among patients with occult OGIB, the prevalence of SBDs was higher in positive FOBT group than negative FOBT group (45% vs 18%, P = 0.002). On the other hand, among patients with previous overt OGIB, there was no significant difference in the prevalence of SBDs between positive and negative FOBT group (47% vs 33%, P = 0.18). In disease specific analysis among patients with occult OGIB, the prevalence of ulcer and tumor were higher in positive FOBT group than negative FOBT group. In multivariate analysis, only positive FOBT was a predictive factors of SBDs in patients with OGIB (OR = 2.5, 95%CI: 1.4-4.6, P = 0.003). Furthermore, the trend was evident among patients with occult OGIB who underwent FOBT on the same day or a day before CE. The prevalence of SBDs in positive vs negative FOBT group were 54% vs 13% in patients with occult OGIB who underwent FOBT on the same day or the day before CE (P = 0.001), while there was no significant difference between positive and negative FOBT group in those who underwent

Impact of fecal occult blood on obscure gastrointestinal bleeding: observational study.

PubMed

Kobayashi, Yuka; Watabe, Hirotsugu; Yamada, Atsuo; Suzuki, Hirobumi; Hirata, Yoshihiro; Yamaji, Yutaka; Yoshida, Haruhiko; Koike, Kazuhiko

2015-01-07

To elucidate the association between small bowel diseases (SBDs) and positive fecal occult blood test (FOBT) in patients with obscure gastrointestinal bleeding (OGIB). Between February 2008 and August 2013, 202 patients with OGIB who performed both capsule endoscopy (CE) and FOBT were enrolled (mean age; 63.6 ± 14.0 years, 118 males, 96 previous overt bleeding, 106 with occult bleeding). All patients underwent immunochemical FOBTs twice prior to CE. Three experienced endoscopists independently reviewed CE videos. All reviews and consensus meeting were conducted without any information on FOBT results. The prevalence of SBDs was compared between patients with positive and negative FOBT. CE revealed SBDs in 72 patients (36%). FOBT was positive in 100 patients (50%) and negative in 102 (50%). The prevalence of SBDs was significantly higher in patients with positive FOBT than those with negative FOBT (46% vs 25%, P = 0.002). In particular, among patients with occult OGIB, the prevalence of SBDs was higher in positive FOBT group than negative FOBT group (45% vs 18%, P = 0.002). On the other hand, among patients with previous overt OGIB, there was no significant difference in the prevalence of SBDs between positive and negative FOBT group (47% vs 33%, P = 0.18). In disease specific analysis among patients with occult OGIB, the prevalence of ulcer and tumor were higher in positive FOBT group than negative FOBT group. In multivariate analysis, only positive FOBT was a predictive factors of SBDs in patients with OGIB (OR = 2.5, 95%CI: 1.4-4.6, P = 0.003). Furthermore, the trend was evident among patients with occult OGIB who underwent FOBT on the same day or a day before CE. The prevalence of SBDs in positive vs negative FOBT group were 54% vs 13% in patients with occult OGIB who underwent FOBT on the same day or the day before CE (P = 0.001), while there was no significant difference between positive and negative FOBT group in those who underwent FOBT two or more days

Scaled model guidelines for solar coronagraphs' external occulters with an optimized shape.

PubMed

Landini, Federico; Baccani, Cristian; Schweitzer, Hagen; Asoubar, Daniel; Romoli, Marco; Taccola, Matteo; Focardi, Mauro; Pancrazzi, Maurizio; Fineschi, Silvano

2017-12-01

One of the major challenges faced by externally occulted solar coronagraphs is the suppression of the light diffracted by the occulter edge. It is a contribution to the stray light that overwhelms the coronal signal on the focal plane and must be reduced by modifying the geometrical shape of the occulter. There is a rich literature, mostly experimental, on the appropriate choice of the most suitable shape. The problem arises when huge coronagraphs, such as those in formation flight, shall be tested in a laboratory. A recent contribution [Opt. Lett.41, 757 (2016)OPLEDP0146-959210.1364/OL.41.000757] provides the guidelines for scaling the geometry and replicate in the laboratory the flight diffraction pattern as produced by the whole solar disk and a flight occulter but leaves the conclusion on the occulter scale law somehow unjustified. This paper provides the numerical support for validating that conclusion and presents the first-ever simulation of the diffraction behind an occulter with an optimized shape along the optical axis with the solar disk as a source. This paper, together with Opt. Lett.41, 757 (2016)OPLEDP0146-959210.1364/OL.41.000757, aims at constituting a complete guide for scaling the coronagraphs' geometry.

Characterization of the occult nature of injury for frequently occurring motor vehicle crash injuries.

PubMed

Schoell, Samantha L; Doud, Andrea N; Weaver, Ashley A; Talton, Jennifer W; Barnard, Ryan T; Winslow, James E; Stitzel, Joel D

2017-01-01

Occult injuries are not easily detected and can be potentially life-threatening. The purpose of this study was to quantify the perceived occultness of the most frequent motor vehicle crash injuries according to emergency medical services (EMS) professionals. An electronic survey was distributed to 1,125 EMS professionals who were asked to quantify the likelihood that first responders would miss symptoms related to a particular injury on a 5-point Likert scale. The Occult Score for each injury was computed from the average of all the survey responses and normalized to be a continuous metric ranging from 0 to 1 where 0 is a non-occult (highly apparent on initial presentation) injury and 1 is an occult (unapparent on initial presentation) injury. Overall, 110,671 survey responses were collected. The Occult Score ranged from 0 to 1 with a mean, median, and standard deviation of 0.443, 0.450, and 0.233, respectively. When comparing the Occult Score of an injury to its corresponding AIS severity, there was no relationship between the metrics. When stratifying by body region, injury type, and AIS severity, it was evident that AIS 2-4 abdominal injuries with lacerations, hemorrhage, or contusions were perceived as the most occult injuries. Timely triage is key to reduce the morbidity and mortality associated with occult injuries. The Occult Score developed in this study to describe the predictability of an injury in a motor vehicle crash will be used as part of a larger effort, including incorporation into an advanced automatic crash notification (AACN) algorithm to detect crash conditions associated with a patient's need for prompt treatment at a trauma center. Copyright © 2016 Elsevier Ltd. All rights reserved.

Radio scintillations observed during atmospheric occultations of Voyager: Internal gravity waves at Titan and magnetic field orientations at Jupiter and Saturn. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1983-01-01

The refractive index of planetary atmospheres at microwave frequencies is discussed. Physical models proposed for the refractive irregularities in the ionosphere and neutral atmosphere serve to characterize the atmospheric scattering structures, and are used subsequently to compute theoretical scintillation spectra for comparison with the Voyager occultation measurements. A technique for systematically analyzing and interpreting the signal fluctuations observed during planetary occultations is presented and applied to process the dual-wavelength data from the Voyager radio occultations by Jupiter, Saturn, and Titan. Results concerning the plasma irregularities in the upper ionospheres of Jupiter and Saturn are reported. The measured orientation of the irregularities is used to infer the magnetic field direction at several locations in the ionospheres of these two planets; the occultation measurements conflict with the predictions of Jovian magnetic field models, but generally confirm current models of Saturn's field. Wave parameters, including the vertical fluxes of energy and momentum, are estimated, and the source of the internal gravity waves discovered in Titan's upper atmosphere is considered.

Enabling Narrow(est) IWA Coronagraphy with STIS BAR5 and BAR10 Occulters

NASA Astrophysics Data System (ADS)

Schneider, Glenn; Gaspar, Andras; Debes, John; Gull, Theodore; Hines, Dean; Apai, Daniel; Rieke, George

2017-09-01

The Space Telescope Imaging Spectrograph's (STIS) BAR5 coronagraphic occulter was designed to provide high-contrast, visible-light, imaging in close (> 0.15") angular proximity to bright point-sources. We explored and verified the functionality and utility of the BAR5 occulter. We also investigated, and herein report on, the use of the BAR10 rounded corners as narrow-angle occulters and compare IWA vs. contrast performance for the BAR5, BAR10, and Wedge occulters. With that, we provide recommendations for the most efficacious BAR5 and BAR10 use on-orbit in support of GO science.

Occult Klebsiella pneumoniae bacteremia at emergency department: A single center experience.

PubMed

Chang, Eileen Kevyn; Kao, Kai-Liang; Tsai, Mao-Song; Yang, Chia-Jui; Huang, Yu-Tsung; Liu, Chia-Ying; Liao, Chun-Hsing

2015-12-01

Patients with undetected bacteremia when discharged from a hospital are considered to have occult bacteremia. Klebsiella pneumoniae bacteremia (KPB) is endemic to Taiwan. Our purpose was to study the impact of occult KPB. We retrospectively reviewed the records of patients who were discharged from our emergency department (ED) and subsequently diagnosed with KPB (occult bacteremia), from January 2008 to March 2014. All patients are followed for at least 3 months after the index ED visit. The study group was compared to KPB patients who were directly hospitalized (DH) from ED in 2008. Thirty-day mortality was the primary endpoint. A total of 913 patients were admitted to our ED with KPB, and 88 of these patients (9.6%) had occult KPB. Among them, 43 had second ED visit and 41 were admitted. The overall 30-day mortality was 2.3%. Relative to patients with occult KPB, DH patients had more respiratory tract infections (p < 0.001) but fewer other intra-abdominal infections (p = 0.015). Liver abscess was the major diagnosis for the second ED visit (37.2%). DH patients had significantly greater 30-day mortality than that of overall patients with KPB (19.2% vs.2.3%, p < 0.001). Most patients with occult KPB had favorable outcomes, but about half of them required a second ED visit. Clinicians should aggressively follow patients with occult KPB and should seek to identify the focus of infection in this endemic area. Copyright © 2015. Published by Elsevier B.V.

Occult HBV infection in HIV-infected adults and evaluation of pooled NAT for HBV.

PubMed

Dinesha, T R; Boobalan, J; Sivamalar, S; Subashini, D; Solomon, S S; Murugavel, K G; Balakrishnan, P; Smith, D M; Saravanan, S

2018-06-01

The study aimed to determine the prevalence of occult hepatitis B virus infection among HIV-infected persons and to evaluate the use of a pooling strategy to detect occult HBV infection in the setting of HIV infection. Five hundred and two HIV-positive individuals were tested for HBV, occult HBV and hepatitis C and D with serologic and nucleic acid testing (NAT). We also evaluated a pooled NAT strategy for screening occult HBV infection among the HIV-positive individuals. The prevalence of HBV infection among HIV-positive individuals was 32 (6.4%), and occult HBV prevalence was 10%. The pooling HBV NAT had a sensitivity of 66.7% and specificity of 100%, compared to HBV DNA NAT of individual samples. In conclusion, this study found a high prevalence of occult HBV infection among our HIV-infected population. We also demonstrated that pooled HBV NAT is highly specific, moderately sensitive and cost-effective. As conventional HBV viral load assays are expensive in resource-limited settings such as India, pooled HBV DNA NAT might be a good way for detecting occult HBV infection and will reduce HBV-associated complications. © 2018 John Wiley & Sons Ltd.

David Levy's Guide to Eclipses, Transits, and Occultations

NASA Astrophysics Data System (ADS)

Levy, David H.

2010-08-01

Introduction; Part I. The Magic and History of Eclipses: 1. Shakespeare, King Lear, and the Great Eclipse of 1605; 2. Three centuries later: Einstein, relativity, and the solar eclipse of 1919; 3. What causes solar and lunar eclipses; Part II. Observing Solar Eclipses: 4. Safety considerations; 5. What to expect during a partial eclipse; 6. Annular eclipses and what to see in them; 7. Total eclipse of the Sun: introduction to the magic; 8. The onset: temperature drop, Baily's Beads, Diamond Ring; 9. Totality: Corona, Prominences, Chromosphere, and surrounding area; 10. Photographing and imaging a solar eclipse; Part III. Observing Lunar Eclipses: 11. Don't forget the penumbral eclipses!; 12. Partial lunar eclipses; 13. Total lunar eclipses; 14. Photographing and imaging lunar eclipses; Part IV. Occultations: 15. When the Moon occults a star; Part V. Transits: 16. When planets cross the Sun; Part VI. My Favorite Eclipses: 17. A personal canon of eclipses, occultations, and transits I have seen; Appendices; Index.

Occult traumatic hemothorax: when can sleeping dogs lie?

PubMed

Bilello, John F; Davis, James W; Lemaster, Deborah M

2005-12-01

Size of traumatic occult hemothorax on admission requiring drainage has not been defined. Computed axial tomography (CAT) may guide drainage criteria. A retrospective review of patients with hemothoraces on CAT was performed. Extrapolating previously described methods of pleural fluid measurement, hemothoraces were quantified using the fluid stripe in the dependent pleural "gutter." Data included patient age, injury severity, and intervention (thoracentesis or tube thoracostomy). Seventy-eight patients with 99 occult hemothoraces met the criteria for study inclusion: 52 hemothoraces qualified as "minimal" and 47 as "moderate/large." Eight patients (15%) in the minimal group and 31 patients (66%) in the moderate/large group underwent intervention (P < .001). There was no difference in patient age, injury severity, ventilator requirement, or presence of pulmonary contusion. CAT in stable blunt-trauma patients can predict which patients with occult hemothorax are likely to undergo intervention. Patients with hemothorax > or = 1.5 cm on CAT were 4 times more likely to undergo drainage intervention compared with those having hemothorax < 1.5 cm.

Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations

NASA Astrophysics Data System (ADS)

Liu, Congliang; Kirchengast, Gottfried; Sun, Yueqiang; Zhang, Kefei; Norman, Robert; Schwaerz, Marc; Bai, Weihua; Du, Qifei; Li, Ying

2018-04-01

The Global Navigation Satellite System (GNSS) radio occultation (RO) technique is widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source to RO at upper stratospheric altitudes, and a linear dual-frequency bending angle correction is commonly used to remove the first-order ionospheric effect. However, the higher-order residual ionospheric error (RIE) can still be significant, so it needs to be further mitigated for high-accuracy applications, especially from 35 km altitude upward, where the RIE is most relevant compared to the decreasing magnitude of the atmospheric bending angle. In a previous study we quantified RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on investigating the causes of the high RIE of these exceptional events, employing detailed along-ray-path analyses of atmospheric and ionospheric refractivities, impact parameter changes, and bending angles and RIEs under asymmetric and symmetric ionospheric structures. We found that the main causes of the high RIEs are a combination of physics-based effects - where asymmetric ionospheric conditions play the primary role, more than the ionization level driven by solar activity - and technical ray tracer effects due to occasions of imperfect smoothness in ionospheric refractivity model derivatives. We also found that along-ray impact parameter variations of more than 10 to 20 m are possible due to ionospheric asymmetries and, depending on prevailing horizontal refractivity gradients, are positive or negative relative to the initial impact parameter at the GNSS transmitter. Furthermore, mesospheric RIEs are found generally higher than upper-stratospheric ones, likely due to

Occult Nodal Disease Prevalence and Distribution in Recurrent Laryngeal Cancer Requiring Salvage Laryngectomy.

PubMed

Birkeland, Andrew C; Rosko, Andrew J; Issa, Mohamad R; Shuman, Andrew G; Prince, Mark E; Wolf, Gregory T; Bradford, Carol R; McHugh, Jonathan B; Brenner, J Chad; Spector, Matthew E

2016-03-01

The indications for neck dissection concurrent with salvage laryngectomy in the clinically N0 setting remain unclear. Our goals were to determine the prevalence of occult nodal disease, analyze nodal disease distribution patterns, and identify predictors of occult nodal disease in a salvage laryngectomy cohort. Case series with planned data collection. Tertiary academic center. Patients with persistent or recurrent laryngeal squamous cell carcinoma (LSCC) after radiation/chemoradiation failure undergoing salvage laryngectomy with neck dissection. We analyzed a single-institution retrospective case series of patients between 1997 and 2014 and identified those who had clinically N0 (cN0) necks (n = 203). Clinical and pathologic data, including nodal prevalence and distribution, were collected and statistical analyses performed. Overall, cN0 necks had histologically positive occult nodes in 17% (n = 35) of cases. Univariate predictors of occult nodal positivity included recurrent T4 stage (34% T4 vs 12% non-T4; P = .0003) and supraglottic subsite (28% supraglottic vs 10% nonsupraglottic; P = .0006). Histologically positive nodes associated with supraglottic primaries were most frequently positive in ipsilateral levels II and III (17% and 16%). Positive nodes for glottic LSCC were most frequently positive in the ipsilateral and contralateral paratracheal nodes (11% and 9%). Histologically positive occult nodes are identified in 17% of cN0 patients undergoing salvage laryngectomy with neck dissection. Occult nodal disease varies in frequency and distribution based on tumor subsite. Predictors of high (>20%) occult nodal positivity include T4 tumors and supraglottic subsite. In glottic LSCC, the most frequent sites of occult nodal disease are the paratracheal nodal basins. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016.

Radio Occultation Investigation of the Rings of Saturn and Uranus

NASA Technical Reports Server (NTRS)

Marouf, Essam A.

1997-01-01

The proposed work addresses two main objectives: (1) to pursue the development of the random diffraction screen model for analytical/computational characterization of the extinction and near-forward scattering by ring models that include particle crowding, uniform clustering, and clustering along preferred orientations (anisotropy). The characterization is crucial for proper interpretation of past (Voyager) and future (Cassini) ring, occultation observations in terms of physical ring properties, and is needed to address outstanding puzzles in the interpretation of the Voyager radio occultation data sets; (2) to continue the development of spectral analysis techniques to identify and characterize the power scattered by all features of Saturn's rings that can be resolved in the Voyager radio occultation observations, and to use the results to constrain the maximum particle size and its abundance. Characterization of the variability of surface mass density among the main ring, features and within individual features is important for constraining the ring mass and is relevant to investigations of ring dynamics and origin. We completed the developed of the stochastic geometry (random screen) model for the interaction of electromagnetic waves with of planetary ring models; used the model to relate the oblique optical depth and the angular spectrum of the near forward scattered signal to statistical averages of the stochastic geometry of the randomly blocked area. WE developed analytical results based on the assumption of Poisson statistics for particle positions, and investigated the dependence of the oblique optical depth and angular spectrum on the fractional area blocked, vertical ring profile, and incidence angle when the volume fraction is small. Demonstrated agreement with the classical radiative transfer predictions for oblique incidence. Also developed simulation procedures to generate statistical realizations of random screens corresponding to uniformly packed

ACCURATE: Influence of Cloud Layers and Aerosol on Infrared Laser Occultation Signals for Sensing of Greenhouse Gases

NASA Astrophysics Data System (ADS)

Proschek, V.; Schweitzer, S.; Emde, C.; Ladstädter, F.; Fritzer, J.; Kirchengast, G.

2009-04-01

ACCURATE (Atmospheric Climate and Chemistry in the UTLS Region And climate Trends Explorer), a new climate satellite concept, enables simultaneous measurement of profiles of greenhouse gases, isotopes, wind and thermodynamic variables from Low Earth Orbit (LEO) satellites. The measurement principle applied is a combination of the novel LEO-LEO infrared laser occultation (LIO) technique and the well-studied but not yet flown LEO-LEO microwave occultation (LMO) technique. As intrinsic to the space-borne occultation technique, the measurements are evenly distributed around the world, have high vertical resolution and high accuracy and are stable over long time periods. The LIO uses near-monochromatic signals in the short-wave infrared range (~2-2.5 m in the case of ACCURATE) which are absorbed by various trace species in the Earth's atmosphere. From signal transmission measurements, profiles of the concentration of the absorbing species can be derived given that temperature and pressure are accurately known from LMO. The current ACCURATE mission design is arranged for the measurement of six greenhouse gases (H2O, CO2, CH4, N2O, O3, CO) and four isotopes (13CO2, C18OO, HDO, H218O) with focus on the upper troposphere/lower stratosphere region (UTLS, 5-35 km). Wind speed in line-of-sight can be derived from a line-symmetric transmission difference which is caused by wind-induced Doppler shift. By-products are information on cloud layering, aerosol extinction and scintillation strength. This contribution presents an overview on the ACCURATE mission design and the expected accuracy of retrieved atmospheric variables and further focuses on the influence of clouds and aerosols on propagating LIO signals. Special emphasis will be given to sub-visible cirrus clouds which are semi-transparent to infrared signals. A simple frequency dependent cloud extinction parametrization was included into the occultation propagation software EGOPS and evaluated against results of the

Subxiphoid pericardial window to exclude occult cardiac injury after penetrating thoracoabdominal trauma.

PubMed

Hommes, M; Nicol, A J; van der Stok, J; Kodde, I; Navsaria, P H

2013-10-01

An occult cardiac injury may be present in patients with an acute abdomen after penetrating thoracoabdominal trauma. This study assessed the use of a subxiphoid pericardial window (SPW) as a diagnostic manoeuvre in this setting. This was a retrospective review of a trauma database (2001-2009). Patients presenting with a penetrating thoracoabdominal injury with an acute abdomen, and in whom there was concern about a potential cardiac injury from the site or tract of the injury, were included. Fifty patients with an indication for emergency laparotomy underwent a SPW for a possible cardiac injury. An occult haemopericardium was present at SPW in 14 patients (28 per cent) mandating, median sternotomy. Nine cardiac injuries (18 per cent) were identified including five tangential injuries and four perforations. The specific complication rate relating to the SPW was 2 per cent. The SPW is a useful technique at laparotomy to identify cardiac injuries in patients with penetrating thoracoabdominal injuries. © 2013 British Journal of Surgery Society Ltd. Published by John Wiley & Sons Ltd.

Biopsy of CT-Occult Bone Lesions Using Anatomic Landmarks for CT Guidance.

PubMed

Hillen, Travis J; Talbert, Robert J; Friedman, Michael V; Long, Jeremiah R; Jennings, Jack W; Wessell, Daniel E; Baker, Jonathan C

2017-07-01

The purpose of this study is to evaluate the histopathologic diagnostic yield, sample size, procedural time, and dose-length product (DLP) for the biopsy of CT-occult lesions found at MRI or PET or both. A retrospective review of our radiology information system for biopsies of CT-occult lesions using CT guidance from January 1, 2010, through December 31, 2014, was performed and compared with a selection of CT-guided biopsies of CT-evident bone lesions during the same period. The data were then evaluated for diagnostic yield of histopathologic diagnosis, procedural time, use of sedation medication, DLP, and size of specimens obtained. A total of 30 CT-occult biopsies met the inclusion criteria. Twenty-seven of those biopsies had results that were concordant with the patient's primary histopathologic diagnosis, imaging findings, and clinical course. In the CT-evident lesion group, concordant histopathologic abnormalities were identified in 27 of 30 patients. There was a statistically significant increase in number of samples obtained for the CT-evident lesions compared with CT-occult lesions. There was no statistically significant difference in total specimen length, DLP, number of CT scans, procedural time, or use of sedation medication between the CT-occult and CT-evident biopsy groups. Biopsy of CT-occult lesions using anatomic landmarks achieves diagnostic yields similar to those for CT-guided biopsy of CT-evident lesions.

Laboratory Verification of Occulter Contrast Performance and Formation Flight

NASA Astrophysics Data System (ADS)

Sirbu, Dan

2014-01-01

Direct imaging of an exo-Earth is a difficult technical challenge. First, the intensity ratio between the parent star and its dim, rocky planetary companion is expected to be ten billion times. Additionally, for a planetary companion in the habitable zone the angular separation to the star is very small, such that only nearby stars are feasible targets. An external occulter is a spacecraft that is flown in formation with the observing space telescope and blocks starlight prior to the entrance pupil. Its shape must be specially designed to control for diffraction and be tolerant of errors such as misalignment, manufacturing, and deformations. In this dissertation, we present laboratory results pertaining to the optical verification of the contrast performance of a scaled occulter and implementation of an algorithm for the alignment of the telescope in the shadow of the occulter. The experimental testbed is scaled from space dimensions to the laboratory by maintaining constant Fresnel numbers while preserving an identical diffraction integral. We present monochromatic results in the image plane showing contrast better than 10 orders of magnitude, consistent with the level required for imaging an Exo-earth, and obtained using an optimized occulter shape. We compare these results to a baseline case using a circular occulter and to the theoretical predictions. Additionally, we address the principal technical challenge in the formation flight problem through demonstration of an alignment algorithm that is based on out-of-band leaked light. Such leaked light can be used a map to estimate the location of the telescope in the shadow and perform fine alignment during science observations.

Occurrence of occult CSF leaks during standard FESS procedures.

PubMed

Bucher, S; Kugler, A; Probst, E; Epprecht, L; Stadler, R S; Holzmann, D; Soyka, M B

2018-03-18

To determine the incidence of occult cerebrospinal fluid leaks (CSF) after functional endoscopic sinus surgery (FESS) and to evaluate the diagnostic performance of beta2-transferrin in blood-contaminated conditions. Prospective cohort study. An analysis of 57 intraoperative samples using hydrogel 6 beta2-transferrin assay after FESS was undertaken. In case of CSF positive samples and continuing rhinorrhea, reanalysis after more than 1 year was conducted. In-vivo analysis of a primary spontaneous CSF leak sample took place to verify difficulties in detecting beta2-transferrin in blood-contaminated settings. Own titrations were performed to evaluate detection limits of CSF by beta2-transferrin and beta-trace protein assays in these settings. An incidence of 13% for occult CSF leaks after FESS was found. In blood-contaminated conditions, routine beta2-transferrin assays showed low sensitivity. In over 1 year follow-up, all samples were negative for CSF and none of them developed clinical relevant CSF leaks or meningitis. Occult and clinically irrelevant CSF leaks do occur in a significant proportion of patients during and shortly after FESS. Intra- and postoperatively, routine beta2-transferrin assays show low sensitivity. They should not be used in these settings. The clinical course of patients with occult CSF leaks indicated possibility of an uneventful follow-up.

Calculated occultation profiles of Io and the hot spots

NASA Technical Reports Server (NTRS)

Mcewen, A. S.; Soderblom, L. A.; Matson, D. L.; Johnson, T. V.; Lunine, J. I.

1986-01-01

Occultations of Io by other Galilean satellites in 1985 provide a means to locate volcanic hot spots and to model their temperatures. The expected time variations in the integral reflected and emitted radiation of the occultations are computed as a function of wavelength (visual to 8.7 microns). The best current ephemerides were used to calculate the geometry of each event as viewed from earth. Visual reflectances were modeled from global mosaics of Io. Thermal emission from the hot spots was calculated from Voyager 1 IRIS observations and, for regions unobserved by IRIS, from a model based on the distribution of low-albedo features. The occultations may help determine (1) the location and temperature distribution of Loki; (2) the source(s) of excess emission in the region from long 50 deg to 200 deg and (3) the distribution of small, high-temperature sources.

Optimization of the occulter for the Solar Orbiter/METIS coronagraph

NASA Astrophysics Data System (ADS)

Landini, Federico; Vivès, Sébastien; Romoli, Marco; Guillon, Christophe; Pancrazzi, Maurizio; Escolle, Clement; Focardi, Mauro; Antonucci, Ester; Fineschi, Silvano; Naletto, Giampiero; Nicolini, Gianalfredo; Nicolosi, Piergiorgio; Spadaro, Daniele

2012-09-01

METIS (Multi Element Telescope for Imaging and Spectroscopy investigation), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived to perform imaging (in visible, UV and EUV) and spectroscopy (in EUV) of the solar corona, by means of an integrated instrument suite located on a single optical bench and sharing the same aperture on the satellite heat shield. As every coronagraph, METIS is highly demanding in terms of stray light suppression. Coronagraphs history teaches that a particular attention must be dedicated to the occulter optimization. The METIS occulting system is of particular interest due to its innovative concept. In order to meet the strict thermal requirements of Solar Orbiter, METIS optical design has been optimized by moving the entrance pupil at the level of the external occulter on the S/C thermal shield, thus reducing the size of the external aperture. The scheme is based on an inverted external-occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield. A spherical mirror rejects back the disk-light through the IEO. A breadboard of the occulting assembly (BOA) has been manufactured in order to perform stray light tests in front of two solar simulators (in Marseille, France and in Torino, Italy). A first measurement campaign has been carried on at the Laboratoire d'Astrophysique de Marseille. In this paper we describe the BOA design, the laboratory set-up and the preliminary results.

Forthcoming Occultations of Astrometric Radio Sources by Planets

NASA Technical Reports Server (NTRS)

L'vov, Victor; Malkin, Zinovy; Tsekmeister, Svetlana

2010-01-01

Astrometric observations of radio source occultations by solar system bodies may be of large interest for testing gravity theories, dynamical astronomy, and planetary physics. In this paper, we present an updated list of the occultations of astrometric radio sources by planets expected in the coming years. Such events, like solar eclipses, generally speaking can only be observed in a limited region. A map of the shadow path is provided for the events that will occurr in regions with several VLBI stations and hence will be the most interesting for radio astronomy experiments.

Radioimmune localization of occult carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duda, R.B.; Zimmer, A.M.; Rosen, S.T.

1990-07-01

Patients with a rising serum carcinoembryonic antigen level and no clinical or roentgenographic evidence of recurrent or metastatic cancer present a treatment dilemma. Eleven such patients, 10 with a previously treated colorectal carcinoma and 1 with a previously treated breast carcinoma, received an injection of the anticarcinoembryonic antigen monoclonal antibody ZCE-025 labeled with the radioisotope indium 111. Nuclear scintigraphy was performed on days 3 and 5 through 7 to detect potential sites of tumor recurrence. The monoclonal antibody scan accurately predicted the presence or absence of occult malignancy in 7 (64%) patients. Second-look laparotomy confirmed the monoclonal antibody scan resultsmore » in the patients with colorectal cancer, and magnetic resonance imaging confirmed metastatic breast cancer. This study demonstrates that In-ZCE-025 can localize occult carcinoma and may assist the surgeon in facilitating the operative exploration. In-ZCE-025 assisted in the initiation of adjuvant therapy for the patient with breast cancer.« less

Assessment of NOAA NUCAPS upper air temperature profiles using COSMIC GPS radio occultation and ARM radiosondes

NASA Astrophysics Data System (ADS)

Feltz, M. L.; Borg, L.; Knuteson, R. O.; Tobin, D.; Revercomb, H.; Gambacorta, A.

2017-09-01

The U.S. National Oceanic and Atmospheric Administration (NOAA) recently began operational processing to derive vertical temperature profiles from two new sensors, Cross-Track Infrared Sounder and Advanced Technology Microwave Sounder, which were developed for the next generation of U.S. weather satellites. The NOAA-Unique Combined Atmospheric Processing System (NUCAPS) has been developed by NOAA to routinely process data from future Joint Polar Satellite System operational satellites and the preparatory Suomi-NPP satellite. This paper assesses the NUCAPS vertical temperature profile product from the upper troposphere into the middle stratosphere using radiosonde and GPS radio occultation (RO) data. Radiosonde data from the Department of Energy Atmospheric Radiation Measurement (ARM) program are=] compared to both the NUCAPS and GPS RO temperature products to evaluate bias and RMS errors. At all three fixed ARM sites for time periods investigated the NUCAPS temperature in the 100-40 hPa range is found to have an average bias to the radiosondes of less than 0.45 K and an RMS error of less than 1 K when temperature averaging kernels are applied. At a 95% confidence level, the radiosondes and RO were found to agree within 0.4 K at the North Slope of Alaska site and within 0.83 K at Southern Great Plains and Tropical Western Pacific. The GPS RO-derived dry temperatures, obtained from the University Corporation for Atmospheric Research Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission, are used as a common reference for the intercomparison of NUCAPS temperature products to similar products produced by NASA from Atmospheric Infrared Sounder (AIRS) and by European Organisation for the Exploitation of Meteorological Satellites from MetOp-B Infrared Atmospheric Sounding Interferometer (IASI). For seasonal and zonal scales, the NUCAPS agreement with AIRS and IASI is less than 0.5 K after application of averaging kernels.

Stray light rejection in giant externally-occulted solar coronagraphs: experimental developments

NASA Astrophysics Data System (ADS)

Venet, M.; Bazin, C.; Koutchmy, S.; Lamy, P.

2017-11-01

The advent of giant, formation-flight, externally-occulted solar coronagraphs such as ASPIICS (Association de Satellites Pour l'Imagerie et l'Interférométrie de la Couronne Solaire [1,2,3,4]) selected by the European Space Agency (ESA) for its third PROBA (Project for On-Board Autonomy) mission of formation flying demonstration (presently in phase B) and Hi-RISE proposed in the framework of ESA Cosmic Vision program, presents formidable challenges for the study and calibration of instrumental stray light. With distances between the external occulter (EO) and the optical pupil (OP) exceeding hundred meters and occulter sizes larger than a meter, it becomes impossible to perform tests at the real scale. The requirement to limit the over-occultation to less than 1.05 Rsun, orders of magnitude to what has been achieved so far in past coronagraphs, further adds to the challenge. We are approaching the problem experimentally using reduced scale simulators and present below a progress report of our work.

Characterization of the occult nature of frequently occurring pediatric motor vehicle crash injuries.

PubMed

Doud, Andrea N; Schoell, Samantha L; Talton, Jennifer W; Barnard, Ryan T; Petty, John K; Stitzel, Joel D; Weaver, Ashley A

2018-04-01

Occult injuries are those likely to be missed on initial assessment by first responders and, though initially asymptomatic, they may present suddenly and lead to rapid patient decompensation. No scoring systems to quantify the occultness of pediatric injuries have been established. Such a scoring system will be useful in the creation of an Advanced Automotive Crash Notification (AACN) system that assists first responders in making triage decisions following a motor vehicle crash (MVC). The most frequent MVC injuries were determined for 0-4, 5-9, 10-14 and 15-18 year olds. For each age-specific injury, experts with pediatric trauma expertise were asked to rate the likelihood that the injury may be missed by first responders. An occult score (ranging from 0-1) was calculated by averaging and normalizing the responses of the experts polled. Evaluation of all injuries across all age groups demonstrated greater occult scores for the younger age groups compared to older age groups (mean occult score 0-4yo: 0.61 ± 0.23, 5-9yo: 0.53 ± 0.25, 10-14yo: 0.48 ± 0.23, and 15-18yo: 0.42 ± 0.22, p < 0.01). Body-region specific occult scores revealed that experts judged abdominal, spine and thoracic injuries to be more occult than injuries to other body regions. The occult scores suggested that injuries are more difficult to detect in younger age groups, likely given their inability to express symptoms. An AACN algorithm that can predict the presence of clinically undetectable injuries at the scene can improve triage of children with these injuries to higher levels of care. Copyright © 2018 Elsevier Ltd. All rights reserved.

[Occult hepatitis B virus infection in normal population, Xiamen].

PubMed

He, Shuizhen; Su, Chenghao; Shen, Litong; Niu, Jianjun

2015-02-01

To investigate the prevalence of occult HBV infection in the normal population in Xiamen. 4 437 registered permanent residents, aged 1-59 years old, were selected in Xiamen using stratified random sampling method from September to October in 2006. Serum samples were obtained, the basic characteristics, inoculation of HBV vaccine, and liver disease were surveyed. The serum samples were tested five HBV seroimmunological markers. The HBsAg-negative specimens were subjected to HBV-DNA detection by nested PCR targeting for multiple gene segments. The amplified products were sequenced and the sequence was used for determination of HBV genotype and mutation analysis of amino acids located in HBsAg "a" epitope. Subjects with serum detectable HBV-DNA and negative result of HBsAg were considered as occult HBV infection. Among the 4 437 subjects, 482 individuals were observed HBsAg positive and 3 944 were observed negative. Of the 3 955 HBsAg- negative specimens, 27 occult HBV infections were determined with the positive rate of 0.68% (27/3 955). There were 16 samples with genotype B and 11 with genotype C. 3 types of amino acid (AA) mutation (M133T, T140I, G145R) that influence "a" epitope conformation were observed in 9 subjects with occult HBV infection. S region was successfully sequenced in 312 of the 482 HBsAg positive samples. In subjects with occult HBV infection, the infection rate of genotype C HBV (40.74%, 11/27), inoculation rate of HBV vaccine (62.96%, 17/27), positive rate of HBsAb (51.85%, 14/27), and mutation rate of critical amino acid of "a" epitope (33.33%, 9/27) were higher than HBsAg positive individuals (22.76% (71/312), 13.78% (43/312),0.32% (1/312),0.99% (31/312), respectively), and all the difference were significant (χ(2) = 4.29, 41.26, 156.00, 13.07, respectively, and P value = 0.038, <0.001, <0.001, <0.001, respectively). While the average age in subjects with occult HBV infection (18.3 ± 16.2) were lower than that in HBsAg positive infection (34

The solar occultation technique for remote sensing of particulates in the earth's atmosphere. I - The inversion of horizon radiances from space

NASA Technical Reports Server (NTRS)

Schuerman, D. W.; Giovane, F.; Greenberg, J. M.

1976-01-01

The aerosol scattering coefficient as a function of height can be recovered from a direct inversion of the single-scattering horizon radiance provided the sun is above the horizon and an independent measurement of extinction as a function of height is made. Aerosol detection is effected by means of spacecraft measurements of the horizon radiance made during periods of spacecraft twilight. A solar occultation technique which allows the twilight measurements to be made when the sun is still above the horizon greatly reduces the complexity of the inversion problem. The second part of the paper reports on the use of a coronograph aboard Skylab to photograph the horizon just before spacecraft twilight in order to monitor the aerosol component above the tropopause. The coronograph picture, centered on 26.5 degrees E longitude and 63.0 degrees S latitude, shows that the aerosol layer peaks at a height of 48 plus or minus 1 km.

Stellar occultation candidates from the guide star catalog. I - Saturn, 1991-1999

NASA Technical Reports Server (NTRS)

Bosh, A. S.; Mcdonald, S. W.

1992-01-01

A list of 203 potential occultations by Saturn and its ring of stars from the HST Guide Star Catalog (GSC) during the years 1991-1999 is presented. This list features many fainter candidates than do current occultation candidate lists for Saturn; these fainter stars can also provide a high signal-to-noise ratio if observed with a large telescope or in the IR where Saturn and its rings have absorption bands. The occultation circumstances are listed, as well as star information found in the GSC.

Risk factors of occult malignancy in patients with unprovoked venous thromboembolism.

PubMed

Robin, Philippe; Le Roux, Pierre-Yves; Tromeur, Cécile; Planquette, Benjamin; Prévot-Bitot, Nathalie; Lavigne, Christian; Pastre, Jean; Merah, Adel; Couturaud, Francis; Le Gal, Grégoire; Salaun, Pierre-Yves

2017-11-01

Venous thromboembolism (VTE) can occur as the first manifestation of an underlying occult malignancy. It remains unclear whether or not a better selection of high risk patients might lead to more efficient occult cancer screening strategies. Our aim was to assess the predictors of occult malignancy diagnosis in patients with unprovoked VTE. Univariate analyses were performed to assess the effect of candidate predictors on occult cancer detection in patients enrolled in a prospective, multicenter, randomized, controlled study (MVTEP study) whose primary aim was to compare a limited screening strategy with a strategy combining limited screening and FDG PET/CT in patients with unprovoked VTE. This trial is completed and registered with ClinicalTrials.gov, number NCT00964275. Between March 3, 2009, and August 18, 2012, 399 patients were included. Five patients withdrew consent and refused the use of their data, and no VTE was confirmed in 2 patients who were excluded from this analysis. A total of 25 (6.4%) out of the 392 analysed patients received a new diagnosis of malignancyduring the 2-years follow-up. Age≥50years (p=0.01), male gender (p=0.04), leukocytes count (p=0.01), and platelets count (p=0.03) were associated with occult cancer detection. Patients with leukocytosis or thrombocytosis had a risk of cancer way above 10%. Previous VTE and smoker status (combining previous and current smokers) were not associated with occult cancer diagnosis (p>0.05). Demographic characteristics (age and sex), and laboratory tests (high platelets and leukocytes counts) may be associated with cancer detection in patients withunprovoked VTE. Copyright © 2017 Elsevier Ltd. All rights reserved.

Magnitudes of selected stellar occultation candidates for Pluto and other planets, with new predictions for Mars and Jupiter

NASA Technical Reports Server (NTRS)

Sybert, C. B.; Bosh, A. S.; Sauter, L. M.; Elliot, J. L.; Wasserman, L. H.

1992-01-01

Occultation predictions for the planets Mars and Jupiter are presented along with BVRI magnitudes of 45 occultation candidates for Mars, Jupiter, Saturn, Uranus, and Pluto. Observers can use these magnitudes to plan observations of occultation events. The optical depth of the Jovian ring can be probed by a nearly central occultation on 1992 July 8. Mars occults an unusually red star in early 1993, and the occultations for Pluto involving the brightest candidates would possibly occur in the spring of 1992 and the fall of 1993.

Evaluation and Improved Use of Fecal Occult Blood Test in the Constipated Child.

PubMed

Kilway, Denise M

2016-01-01

This quality improvement project examined the use of fecal occult blood test in the constipated child in a pediatric gastroenterology outpatient clinic. A retrospective chart review was completed on 100 children seen for an initial visit with the gastroenterology provider. The number of fecal occult blood tests performed and the child's coinciding symptoms were tallied and compared with the North American Society of Pediatric Gastroenterology, Hepatology, and Nutrition recommendations. An educational intervention was held with the pediatric gastroenterology providers consisting of a PowerPoint presentation summarizing aims of the quality improvement project and reviewing recommendations for use of fecal occult blood test in the constipated child. Pre- and post-intervention chart review data sets were compared. Results showed a 19.6% decrease in the use of fecal occult blood tests performed during the post-intervention timeframe. However, when used in conjunction with North American Society of Pediatric Gastroenterology, Hepatology, and Nutrition recommendations, the appropriateness of fecal occult blood test use increased by 71.4% in the post-intervention patients. Reviewing the recommendations with gastroenterology providers assisted in optimizing the meaningful use of fecal occult blood test, improving quality and safety of care for children seen in the pediatric gastroenterology outpatient clinic.

Turbulence in planetary occultations. IV - Power spectra of phase and intensity fluctuations

NASA Technical Reports Server (NTRS)

Haugstad, B. S.

1979-01-01

Power spectra of phase and intensity scintillations during occultation by turbulent planetary atmospheres are significantly affected by the inhomogeneous background upon which the turbulence is superimposed. Such coupling is particularly pronounced in the intensity, where there is also a marked difference in spectral shape between a central and grazing occultation. While the former has its structural features smoothed by coupling to the inhomogeneous background, such features are enhanced in the latter. Indeed, the latter power spectrum peaks around the characteristic frequency that is determined by the size of the free-space Fresnel zone and the ray velocity in the atmosphere; at higher frequencies strong fringes develop in the power spectrum. A confrontation between the theoretical scintillation spectra computed here and those calculated from the Mariner 5 Venus mission by Woo et al. (1974) is inconclusive, mainly because of insufficient statistical resolution. Phase and/or intensity power spectra computed from occultation data may be used to deduce characteristics of the turbulence and to distinguish turbulence from other perturbations in the refractive index. Such determinations are facilitated if observations are made at two or more frequencies (radio occultation) or in two or more colors (stellar occultation).

On Combining Thermal-Infrared and Radio-Occultation Data of Saturn's Atmosphere

NASA Technical Reports Server (NTRS)

Flasar, F. M.; Schinder, P. J.; Conrath, B. J.

2008-01-01

Radio-occultation and thermal-infrared measurements are complementary investigations for sounding planetary atmospheres. The vertical resolution afforded by radio occultations is typically approximately 1 km or better, whereas that from infrared sounding is often comparable to a scale height. On the other hand, an instrument like CIRS can easily generate global maps of temperature and composition, whereas occultation soundings are usually distributed more sparsely. The starting point for radio-occultation inversions is determining the residual Doppler-shifted frequency, that is the shift in frequency from what it would be in the absence of the atmosphere. Hence the positions and relative velocities of the spacecraft, target atmosphere, and DSN receiving station must be known to high accuracy. It is not surprising that the inversions can be susceptible to sources of systematic errors. Stratospheric temperature profiles on Titan retrieved from Cassini radio occultations were found to be very susceptible to errors in the reconstructed spacecraft velocities (approximately equal to 1 mm/s). Here the ability to adjust the spacecraft ephemeris so that the profiles matched those retrieved from CIRS limb sounding proved to be critical in mitigating this error. A similar procedure can be used for Saturn, although the sensitivity of its retrieved profiles to this type of error seems to be smaller. One issue that has appeared in inverting the Cassini occultations by Saturn is the uncertainty in its equatorial bulge, that is, the shape in its iso-density surfaces at low latitudes. Typically one approximates that surface as a geopotential surface by assuming a barotropic atmosphere. However, the recent controversy in the equatorial winds, i.e., whether they changed between the Voyager (1981) era and later (after 1996) epochs of Cassini and some Hubble observations, has made it difficult to know the exact shape of the surface, and it leads to uncertainties in the retrieved

Occult cancer-related first venous thromboembolism is associated with an increased risk of recurrent venous thromboembolism.

PubMed

Gran, O V; Braekkan, S K; Paulsen, B; Skille, H; Rosendaal, F R; Hansen, J-B

2017-07-01

Essentials Recurrence risk after an occult cancer-related incident venous thromboembolism (VTE) is unknown. We compared the risk of VTE recurrence in occult-, overt- and non-cancer related first VTE. Patients with occult-cancer related first VTE had the highest risk of VTE recurrence. The high recurrence risk in occult cancer is likely due to the advanced cancers. Background Although venous thromboembolism (VTE) is associated with a high recurrence rate, the absolute recurrence rates for cancer-related VTE, particularly occult cancer, are not well known. Objectives To investigate the risk of VTE recurrence in patients with occult and overt cancer-related VTE. Methods Incident VTE events among participants of the first to sixth Tromsø surveys occurring in the period 1994-2012 were included. Occult cancer was defined as cancer diagnosed within a year following a VTE, and overt cancer was defined as cancer diagnosed within the 2 years before a VTE. Results Among 733 patients with incident VTE, 110 had overt cancer and 40 had occult cancer. There were 95 recurrent VTE events during a median of 3.2 years of follow-up. The 1-year cumulative incidence of VTE recurrence was 38.6% in subjects with occult cancer, 15.5% in subjects with overt cancer, and 3.8% in non-cancer subjects. The 1-year risk of recurrence was 12-fold (hazard ratio [HR] 12.4, 95% confidence interval [CI] 5.9-26.3) higher in subjects with occult cancer and four-fold (HR 4.3, 95% CI 2.0-9.2) higher in subjects with overt cancer than in non-cancer subjects. The occult cancers associated with VTE recurrence were typically located at prothrombotic sites (i.e. lung and gastrointestinal) and presented at advanced stages. The majority (69%) of recurrences in subjects with occult cancer occurred before or shortly after cancer diagnosis, and were therefore not treatment-related. Conclusion Our findings suggest that the increased risk of recurrence in patients with occult cancer is mainly attributable to the

Unsuccesfull occultation observation of stars by asteroids

NASA Astrophysics Data System (ADS)

Gaina, Alex; Maley, Paul D.

2010-12-01

A report is given about an attempt to observe occultations of stars HIP 7268 and TYC1868-02234-01 by asteroids Tisiphone and Thisbe on 3 november 2010 in Chisinau, The Republic of Moldova, which was placed very close to the central line of the occultations in spite of. The main cause of the insucces was weather. Few days before a cyclon developed above the Black Sea, while above the Western Europe, including Greece the sky was covered during many days. Some critics are made concerning the preparation of astronomical facilities in the Republic of Moldova for succesfull observations. The meteo conditions in Lozova-Ciuciuleni were better, but bad, than in other parts of the Republic of Moldova.

Recurring sets of recurring starspot occultations on exoplanet host Qatar-2

NASA Astrophysics Data System (ADS)

Močnik, T.; Southworth, J.; Hellier, C.

2017-10-01

We announce the detection of recurring sets of recurring starspot occultation events in the short-cadence K2 light curve of Qatar-2, a K dwarf star transited every 1.34 d by a hot Jupiter. In total, we detect 34 individual starspot occultation events, caused by five different starspots, occulted in up to five consecutive transits or after a full stellar rotation. The longest recurring set of recurring starspot occultations spans over three stellar rotations, setting a lower limit for the longest starspot lifetime of 58 d. Starspot analysis provided a robust stellar rotational period measurement of 18.0 ± 0.2 d and indicates that the system is aligned, having a sky-projected obliquity of 0° ± 8°. A pronounced rotational modulation in the light curve has a period of 18.2 ± 1.6 d, in agreement with the rotational period derived from the starspot occultations. We tentatively detect an ellipsoidal modulation in the phase curve, with a semi-amplitude of 18 ppm, but cannot exclude the possibility that this is the result of red noise or imperfect removal of the rotational modulation. We detect no transit-timing and transit-duration variations with upper limits of 15 s and 1 min, respectively. We also reject any additional transiting planets with transit depths above 280 ppm in the orbital period region 0.5-30 d.

Feasibility of Juno radio occultations of the Io plasma torus

NASA Astrophysics Data System (ADS)

Phipps, P. H.; Withers, P.

2016-12-01

Jupiter's magnetosphere is driven by internally produced plasma. The innermost Galilean satellite, Io, isthe dominant source of this plasma. Volcanoes on Io's surface create an atmosphere of sulfur and oxygenwhich escapes into Jupiter's magnetosphere and becomes ionized. This ionized material is trapped byJupiter's magnetic field and creates a torus of plasma centered at Io's orbital radius, called the Io plasmatorus. This torus is divided into three regions distinct in both density and composition. Densities in thistorus can be probed by spacecraft via radio occultations. A radio occultation occurs when plasma comesbetween a spacecraft and a receiver during a time when the spacecraft is sending a radio signal. The Junospacecraft, which arrived in orbit around Jupiter in July 2016, is in an orbit which will be ideal forperforming radio occultations of the Io plasma torus. We test the feasibility of using thetelecommunications system on the Juno spacecraft to perform a radio occultation. Io plasma torusdensities derived from Voyager 1 data are used in creating a model torus. Using the Ka and X-band radiofrequencies we derive vertical profiles for the total electron content of the modeled Io plasma torus. AMarkov Chain Monte Carlo fit is performed on the derived profiles to extract, for each of the torusregions, the scale height and peak total electron content. The scale height can be used to derive atemperature for the torus while the peak total electron content can be used to derive the peak electrondensity. We show that Juno radio occultation measurements of the Io plasma torus are feasible andscientifically valuable.

A method to detect occult pneumothorax with chest radiography.

PubMed

Matsumoto, Shokei; Kishikawa, Masanobu; Hayakawa, Koichi; Narumi, Atsushi; Matsunami, Katsutoshi; Kitano, Mitsuhide

2011-04-01

Small pneumothoraces are often not visible on supine screening chest radiographs because they develop anteriorly to the lung. These pneumothoraces are termed occult. Occult pneumothoraces account for an astonishingly high 52% to 63% of all traumatic pneumothoraces. A 19-year-old obese woman was involved in a head-on car accident. The admission anteroposterior chest radiographs were unremarkable. Because of the presence of right chest tenderness and an abrasion, we suspected the presence of a pneumothorax. Thus, we decided to take a supine oblique chest radiograph of the right side of the thorax, which clearly revealed a visceral pleural line, consistent with a diagnosis of traumatic pneumothorax. A pneumothorax may be present when a supine chest radiograph reveals either an apparent deepening of the costophrenic angle (the "deep sulcus sign") or the presence of 2 diaphragm-lung interfaces (the "double diaphragm sign"). However, in practice, supine chest radiographs have poor sensitivity for occult pneumothoraces. Oblique chest radiograph is a useful and fast screening tool that should be considered for cases of blunt chest trauma, especially when transport of critically ill patients to the computed tomographic suite is dangerous or when imminent transfer to another hospital is being arranged and early diagnosis of an occult pneumothorax is essential. Copyright © 2010 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.

Developing an Optical Lunar Occultation Measurement Reduction System for Observations at Kaau Observatory

NASA Astrophysics Data System (ADS)

Malawi, Abdulrahman A.

2013-06-01

We present here a detailed explanation of the reduction method that we use to determine the angular diameters of the stars occulted by the dark limb of the moon. This is a main part of the lunar occultation observation program running at King Abdul Aziz University observatory since late 1993. The process is based on the least square model fitting method of analyzing occultation data, first introduced by Nather et al. (Astron. J. 75:963, 1970).

Occult purulent pericarditis detected by indium-111 leukocyte imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenberg, M.L.; Niebulski, H.I.; Uretsky, B.F.

1984-05-01

Leukocyte imaging with indium-111 is a relatively new technique which, to this point in time, has been discussed almost exclusively in the radiologic literature. Although this procedure has been used mainly to detect intra-abdominal infection, the thorax is routinely imaged along with the abdomen, and therefore detection of cardiac disease may be feasible. This case report is of a young woman after liver transplantation who developed occult purulent pericarditis initially detected by a leukocyte scan with indium-111. This case demonstrates that striking pericardial uptake on a whole-body indium-111 leukocyte scan can occur with purulent pericarditis, and it reemphasizes how insidiouslymore » purulent pericarditis may present in an immunosuppressed patient.« less

Occult hepatitis B virus infection in hematopoietic stem cell donors in a hepatitis B virus endemic area.

PubMed

Hui, Chee-kin; Sun, Jian; Au, Wing-yan; Lie, Albert K W; Yueng, Yui-hung; Zhang, Hai-ying; Lee, Nikki P; Hou, Jin-ling; Liang, Raymond; Lau, George K K

2005-06-01

The acquisition of hepatitis B virus (HBV) infection following organ transplantation from donors with occult HBV infection is an important cause of morbidity and mortality. The aim of this study is to determine the prevalence of occult HBV in allogeneic hematopoietic stem cell (HSC) transplantation donors. We performed a retrospective study on 124 consecutive hepatitis B surface antigen negative HSC donors. Their serum samples were analyzed by PCR for the pre-S/S, pre-core/core and X regions of the virus. Samples reactive by at least two PCR assays were considered HBV-DNA positive. Nineteen of the 124 HSC donors (15.3%) had occult HBV infection. Sixteen of these 19 donors with occult HBV infection (84.2%) tested positive for hepatitis B core antibody while 78 of 105 subjects (74.3%) without occult HBV infection were also positive (P=0.56). Fourteen of the 19 donors (73.7%) with occult HBV infection tested positive for hepatitis B surface antibody while 67 of the 105 subjects without occult HBV infection were also positive (P=0.45). The prevalence of occult HBV infection among HSC donors in Hong Kong is high. Anti-HBc and anti-HBs status had no significant correlation with the presence of occult HBV infection.

Validation of ionospheric electron density profiles inferred from GPS occultation observations of the GPS/MET experiment

NASA Astrophysics Data System (ADS)

Kawakami, Todd Mori

In April of 1995, the launch of the GPS Meteorology Experiment (GPS/MET) onboard the Orbview-1 satellite, formerly known as Microlab-1, provided the first technology demonstration of active limb sounding of the Earth's atmosphere with a low Earth orbiting spacecraft utilizing the signals transmitted by the satellites of the Global Positioning System (GPS). Though the experiment's primary mission was to probe the troposphere and stratosphere, GPS/MET was also capable of making radio occultation observations of the ionosphere. The application of the GPS occultation technique to the upper atmosphere created a unique opportunity to conduct ionospheric research with an unprecedented global distribution of observations. For operational support requirements, the Abel transform could be employed to invert the horizontal TEC profiles computed from the L1 and L2 phase measurements observed by GPS/MET into electron density profiles versus altitude in near real time. The usefulness of the method depends on how effectively the TEC limb profiles can be transformed into vertical electron density profiles. An assessment of GPS/MET's ability to determine electron density profiles needs to be examined to validate the significance of the GPS occultation method as a new and complementary ionospheric research tool to enhance the observational databases and improve space weather modeling and forecasting. To that end, simulations of the occultation observations and their inversions have been conducted to test the Abel transform algorithm and to provide qualitative information about the type and range of errors that might be experienced during the processing of real data. Comparisons of the electron density profiles inferred from real GPS/MET observations are then compared with coincident in situ measurements from the satellites of Defense Meteorological Satellite Program (DMSP) and ground-based remote sensing from digisonde and incoherent scatter radar facilities. The principal focus of

Screening for colon cancer: A test for occult blood.

PubMed

Khakimov, N; Khasanova, G; Ershova, K; Gibadullina, L; Vetkina, T; Lobisheva, G; Chumakova, A

2015-01-01

The relevance of the problem of colorectal cancer (CRC) is evident because of extremely high morbidity and mortality rates, associated with this disease. CRC is mostly diagnosed only at very advanced stages. The reduction of mortality can be achieved by the popularization of screening-methods for early identification of CRC and adenomatous polyps of the colon, which are proved to be precancerous condition. Fecal occult blood test is a well-known method of screening for CRC. The advantages of this method when compared, for example, with colonoscopy are its simplicity and cost-effectiveness.Two techniques are usually used for detection of occult blood in the stool: Hemoccult (Guaiac) test and immunochemical test for hemoglobin. There is no consensus among researchers regarding the validity of these tests for the diagnosis of colorectal cancer. For example, J.S. Mandel (1996) notes 60% sensitivity of Guaiac-test for the detection of the early forms of colorectal cancer, while O.I. Kit (2014) suggets that it is not higher than 30%. There are also various opinions about specificity of these two tests. To review the literature on the validity of the fecal occult blood tests for the diagnosis of CRC. We looked for articles (electronic versions) available for free in the full-text versions, published from June 1, 1990 to December 31, 2014 in Russian or English. The following databases were used for search: E-LIBRARY; Cochrane; MEDLINE; EMBASE; Google search. Only original research papers were analyzed. Literature reviews or systematic reviews were not taken for analyses. 1) use of Guaiac and/or immunochemical fecal occult blood test as screening-tests for the detection of colorectal cancer and/or colon polyps (1 cm or more in diameter) in people older than 45 years; 2) comparing of results with the results of colonoscopy (colonoscopy is counted by majority of the authors as a "gold standard" for the diagnosis of CRC and adenomatous polyps). Initial keyword search returned

The optimization of the inverted occulter of the solar orbiter/METIS coronagraph/spectrometer

NASA Astrophysics Data System (ADS)

Landini, F.; Vives, S.; Romoli, M.; Guillon, C.; Pancrazzi, M.; Escolle, C.; Focardi, M.; Fineschi, S.; Antonucci, E.; Nicolini, G.; Naletto, G.; Nicolosi, P.; Spadaro, D.

2017-11-01

The coronagraph/spectrometer METIS (Multi Element Telescope for Imaging and Spectroscopy), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived to perform imaging (in visible, UV and EUV) and spectroscopy (in EUV) of the solar corona. It is an integrated instrument suite located on a single optical bench and sharing a unique aperture on the satellite heat shield. As every coronagraph, METIS is highly demanding in terms of stray light suppression. In order to meet the strict thermal requirements of Solar Orbiter, METIS optical design has been optimized by moving the entrance pupil at the level of the external occulter on the S/C thermal shield, thus reducing the size of the external aperture. The scheme is based on an inverted external-occulter (IEO). The IEO consists of a circular aperture on the Solar Orbiter thermal shield. A spherical mirror rejects back the disk-light through the IEO. The experience built on all the previous space coronagraphs forces designers to dedicate a particular attention to the occulter optimization. Two breadboards were manufactured to perform occulter optimization measurements: BOA (Breadboard of the Occulting Assembly) and ANACONDA (AN Alternative COnfiguration for the Occulting Native Design Assembly). A preliminary measurement campaign has been carried on at the Laboratoire d'Astrophysique de Marseille. In this paper we describe BOA and ANACONDA designs, the laboratory set-up and the preliminary results.

Effect of Occult Metastases on Survival in Node-Negative Breast Cancer

PubMed Central

Weaver, Donald L.; Ashikaga, Takamaru; Krag, David N.; Skelly, Joan M.; Anderson, Stewart J.; Harlow, Seth P.; Julian, Thomas B.; Mamounas, Eleftherios P.; Wolmark, Norman

2011-01-01

BACKGROUND Retrospective and observational analyses suggest that occult lymph-node metastases are an important prognostic factor for disease recurrence or survival among patients with breast cancer. Prospective data on clinical outcomes from randomized trials according to sentinel-node involvement have been lacking. METHODS We randomly assigned women with breast cancer to sentinel-lymph-node biopsy plus axillary dissection or sentinel-lymph-node biopsy alone. Paraffin-embedded tissue blocks of sentinel lymph nodes obtained from patients with pathologically negative sentinel lymph nodes were centrally evaluated for occult metastases deeper in the blocks. Both routine staining and immunohistochemical staining for cytokeratin were used at two widely spaced additional tissue levels. Treating physicians were unaware of the findings, which were not used for clinical treatment decisions. The initial evaluation at participating sites was designed to detect all macrometastases larger than 2 mm in the greatest dimension. RESULTS Occult metastases were detected in 15.9% (95% confidence interval [CI], 14.7 to 17.1) of 3887 patients. Log-rank tests indicated a significant difference between patients in whom occult metastases were detected and those in whom no occult metastases were detected with respect to overall survival (P = 0.03), disease-free survival (P = 0.02), and distant-disease–free interval (P = 0.04). The corresponding adjusted hazard ratios for death, any outcome event, and distant disease were 1.40 (95% CI, 1.05 to 1.86), 1.31 (95% CI, 1.07 to 1.60), and 1.30 (95% CI, 1.02 to 1.66), respectively. Five-year Kaplan-Meier estimates of overall survival among patients in whom occult metastases were detected and those without detectable metastases were 94.6% and 95.8%, respectively. CONCLUSIONS Occult metastases were an independent prognostic variable in patients with sentinel nodes that were negative on initial examination; however, the magnitude of the difference in

[Surgical Diagnosis and Treatment of Primary Hyperthyroidism Complicated with Occult Thyroid Carcinoma].

PubMed

Wu, Xin; Yu, Jian-chun; Kang, Wei-ming; Ma, Zhi-qiang; Ye, Xin

2015-08-01

To evaluate the surgical diagnosis and treatment of primary hyperthyroidism complicated with occult thyroid carcinoma. Data of 51 cases of primary hyperthyroidism complicated with occult thyroid carcinoma admitted during January 2004 to November 2014 were analyzed retrospectively. The incidence of occult thyroid carcinoma was 5.03% in hyperthyroidism,and 47 cases (92.16%) were female. The preoperative diagnosis of all these 51 cases was primary hyperthyroidism and 11 cases were diagnosed thyroid carcinoma at the same time;25 cases were diagnosed thyroid carcinoma by frozen section and the remaining 26 cases were diagnosed by postoperative pathology. Finally,26 cases underwent subtotal thyroidectomy,4 cases underwent total thyroidectomy, and 21 cases underwent total thyroidectomy with lymphadenectomy. The tumor size ranged from 0.1 to 1.0 cm [mean:(0.63 ± 0.35) cm]. The lesions were less than or equal to 0.5 cm in 28 cases (54.9%). The follow-up lasted from 1 to 121 months [mean:(28.6 ± 22.7)months] in 43 patients,and all of them survived. Primary hyperthyroidism complicated with occult thyroid carcinoma is commonly found in female patients. Preoperative diagnosis is difficult. Ultrasound is the major examining method. Frozen section can increase the detection rate. The postoperative prognosis of hyperthyroidism complicated with occult thyroid carcinoma is satisfactory.

Occult fractures of the knee: tomographic evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apple, J.S.; Martinez, S.; Allen, N.B.

1983-08-01

Seven adults with painful effusions of the knee were examined for occult fractures using pluridirectional tomograph in the coronal and lateral planes. Six patients (ages 50 to 82 years) were osteopenic and gave histories ranging from none to mild trauma; one 26-year-old man was not osteopenic and had severe trauma. In all cases, routine radiographs were interpreted as negative, but tomography demonstrated a fracture. Five fractures were subchondral. Bone scans in 2 patients were positive. The authors conclude that osteopenic patients with a painful effusion of the knee should be considered to have an occult fracture. While bone scans maymore » be helpful, tomography is recommended as the procedure of choice to define the location and extent of the fracture.« less

Occult Metastases in Pelvic Lymphadenectomy Specimens From Patients With Urothelial Carcinoma of the Bladder.

PubMed

Gordetsky, Jennifer; Gibson, Briana; Stevens, Todd M; Ellenburg, J Luke; Grizzle, William; Rais-Bahrami, Soroush

2016-08-01

To identify occult metastases within lymph nodes (LNs) reported as negative by routine histologic evaluation. In patients with high-grade, muscle-invasive urothelial carcinoma (UC) of the bladder, pelvic lymphadenectomy during radical cystectomy demonstrates a survival advantage, increasing with the number of LNs removed, even if negative for metastatic disease. This finding may potentially be explained by the presence of occult metastases. Radical cystectomy specimens with high-grade UC invading the perivesical tissue and negative LNs (pT3N0) between 2000 and 2014 were reviewed. Five levels were cut for each LN block. Two sections were cut per level: 1 stained for hematoxylin and eosin and 1 for AE1/AE3. Micrometastases were defined as tumor deposits >0.2 mm but <2 mm. Isolated tumor cells were defined as ≤0.2 mm. Medical records and survival data were reviewed. We identified 21 cases, consisting of 370 lymph nodes. Six of 21 patients (29%) had occult metastases, including 5 occult metastatic UC and 1 occult metastatic prostate adenocarcinoma. There were 10 positive LNs; 2 macrometastases, 2 micrometastases, and 6 with ITCs. Two of 6 patients (33%) had lymphovascular invasion identified in the primary tumor. Kaplan-Meier analysis showed no significant difference in overall survival between the group of patients who remained N0 versus those upstaged due to discovery of occult metastases (P-value = .42). In patients with pT3 UC undergoing cystectomy, we demonstrated the presence of occult metastases in 29% of patients. The high percentage of occult metastases present in these cases possibly explains the proven survival advantage of removing "negative" LNs. This finding might also have implications in the histologic evaluation of LNs. Copyright © 2016 Elsevier Inc. All rights reserved.

Predictive Power of Distal Radial Metaphyseal Tenderness for Diagnosing Occult Fracture.

PubMed

Glickel, Steven Z; Hinojosa, Lauren; Eden, Claire M; Balutis, Elaine; Barron, O Alton; Catalano, Louis W

2017-10-01

To correlate the physical examination finding of distal radial metaphyseal tenderness with plain radiographic and magnetic resonance imaging after acute wrist injury to diagnose occult distal radius fractures. We hypothesized that persistent distal radial metaphyseal tenderness 2 weeks after acute injuries is predictive of an occult fracture. Twenty-nine adult patients presented, after acute trauma, with distal radial metaphyseal tenderness and initial plain radiographs and/or fluoroscopic images that did not show a distal radius fracture. Patients were reevaluated clinically and radiographically at approximately 2 weeks after initial presentation. Patients with persistent distal radial tenderness and negative radiographs underwent magnetic resonance imaging to definitively diagnose an occult distal radius fracture. We calculated the sensitivity and positive predictive value for persistent distal radial metaphyseal tenderness using a 95% confidence interval and standard formulas. Both radiographs and magnetic resonance imaging were used as our endpoint diagnosis for a distal radius fracture. We diagnosed 28 occult distal radius fractures, 8 by follow-up radiograph and 20 by magnetic resonance imaging. The positive predictive value for patients who completed the protocol was 96%. One patient who did not have an occult distal radius fracture had a fracture of the ulnar styloid. Tenderness of the distal radial metaphysis after wrist injury is strongly suggestive of a distal radius fracture despite both normal plain radiographs and fluoroscopic images. Diagnostic III. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Occult HCV Infection: The Current State of Knowledge

PubMed Central

Rezaee-Zavareh, Mohammad Saeid; Hadi, Reza; Karimi-Sari, Hamidreza; Hossein Khosravi, Mohammad; Ajudani, Reza; Dolatimehr, Fardin; Ramezani-Binabaj, Mahdi; Miri, Seyyed Mohammad; Alavian, Seyed Moayed

2015-01-01

Context Occult HCV infection (OCI) is defined as the presence of HCV-RNA in hepatocytes and the absence of HCV in the serum according to usual tests. We aimed to define OCI and provide information about the currently available diagnostic methods. Then we focus on specific groups that are at high risk of OCI and finally investigate immune responses to OCI and the available treatment approaches. Evidence Acquisition PubMed, Scopus and Google Scholar were comprehensively searched with combination of following keywords: “occult”, “hepatitis C virus” and “occult HCV infection”. The definition of OCI, diagnostic methods, specific groups that are at high risk and available treatment approaches were extract from literature. An analysis of available articles on OCI also was done based on Scopus search results. Results OCI has been reported in several high-risk groups, especially in hemodialysis patients and subjects with cryptogenic liver disease. Furthermore, some studies have proposed a specific immune response for OCI in comparison with chronic hepatitis C (CHC). Conclusions With a clinical history of approximately 11 years, occult HCV infection can be considered an occult type of CHC. Evidences suggest that considering OCI in these high-risk groups seems to be necessary. We suggest that alternative diagnostic tests should be applied and that there is a need for the participation of all countries to determine the epidemiology of this type of HCV infection. Additionally, evaluating OCI in blood transfusion centers and in patients who receive large amounts of blood and clotting factors, such as patients with hemophilia, should be performed in future projects. PMID:26734487

Dusty Dwarfs Galaxies Occulting A Bright Background Spiral

NASA Astrophysics Data System (ADS)

Holwerda, Benne

2017-08-01

The role of dust in shaping the spectral energy distributions of low mass disk galaxies remains poorly understood. Recent results from the Herschel Space Observatory imply that dwarf galaxies contain large amounts of cool (T 20K) dust, coupled with very modest optical extinctions. These seemingly contradictory conclusions may be resolved if dwarfs harbor a variety of dust geometries, e.g., dust at larger galactocentric radii or in quiescent dark clumps. We propose HST observations of six truly occulting dwarf galaxies drawn from the Galaxy Zoo catalog of silhouetted galaxy pairs. Confirmed, true occulting dwarfs are rare as most low-mass disks in overlap are either close satellites or do not have a confirmed redshift. Dwarf occulters are the key to determining the spatial extent of dust, the small scale structure introduced by turbulence, and the prevailing dust attenuation law. The recent spectroscopic confirmation of bona-fide low mass occulting dwarfs offers an opportunity to map dust in these with HST. What is the role of dust in the SED of these dwarf disk galaxies? With shorter feedback scales, how does star-formation affect their morphology and dust composition, as revealed from their attenuation curve? The resolution of HST allows us to map the dust disks down to the fine scale structure of molecular clouds and multi-wavelength imaging maps the attenuation curve and hence dust composition in these disks. We therefore ask for 2 orbits on each of 6 dwarf galaxies in F275W, F475W, F606W, F814W and F125W to map dust from UV to NIR to constrain the attenuation curve.

Overt Skeletal Metastases in a Patient of Occult (Microscopic) Follicular Thyroid Carcinoma: a Rare Case.

PubMed

Jha, Chandan Kumar; Agrawal, Vinita; Mishra, Anjali; Pradhan, P K

2018-03-01

Occult follicular thyroid carcinoma (FTC) presenting as distant metastases is a rare occurrence. However, despite being occult in majority of these cases, primary tumor can be detected on thyroid imaging or during surgery. Here, we present an extremely rare case of an occult FTC with overt skeletal metastases in which primary tumor was discernible only on microscopic examination.

Wave-optics uncertainty propagation and regression-based bias model in GNSS radio occultation bending angle retrievals

NASA Astrophysics Data System (ADS)

Gorbunov, Michael E.; Kirchengast, Gottfried

2018-01-01

A new reference occultation processing system (rOPS) will include a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval chain with integrated uncertainty propagation. In this paper, we focus on wave-optics bending angle (BA) retrieval in the lower troposphere and introduce (1) an empirically estimated boundary layer bias (BLB) model then employed to reduce the systematic uncertainty of excess phases and bending angles in about the lowest 2 km of the troposphere and (2) the estimation of (residual) systematic uncertainties and their propagation together with random uncertainties from excess phase to bending angle profiles. Our BLB model describes the estimated bias of the excess phase transferred from the estimated bias of the bending angle, for which the model is built, informed by analyzing refractivity fluctuation statistics shown to induce such biases. The model is derived from regression analysis using a large ensemble of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO observations and concurrent European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields. It is formulated in terms of predictors and adaptive functions (powers and cross products of predictors), where we use six main predictors derived from observations: impact altitude, latitude, bending angle and its standard deviation, canonical transform (CT) amplitude, and its fluctuation index. Based on an ensemble of test days, independent of the days of data used for the regression analysis to establish the BLB model, we find the model very effective for bias reduction and capable of reducing bending angle and corresponding refractivity biases by about a factor of 5. The estimated residual systematic uncertainty, after the BLB profile subtraction, is lower bounded by the uncertainty from the (indirect) use of ECMWF analysis fields but is significantly lower than the systematic uncertainty without BLB correction. The systematic and

Orbital Metastasis: Rare Initial Presentation of an Occult Gall Bladder Carcinoma.

PubMed

Jain, Tarun Kumar; Parihar, Ashwin Singh; Sood, Ashwani; Basher, Rajender Kumar; Bollampally, Neeraja; Shekhawat, Amit Singh; Mittal, Bhagwant Rai

2018-03-01

Orbital metastases are known to arise from primary breast carcinoma followed by prostate, malignant melanoma, and lung carcinoma. We report a case of orbital metastasis as the initial presentation of an occult primary gall bladder carcinoma. The FDG PET/CT helped in localizing the occult distant primary site, which previously escaped detection, and also enabled the evaluation of orbital metastasis.

Prevalence of occult hepatitis C infection in chronic hemodialysis and kidney transplant patients.

PubMed

Baid-Agrawal, Seema; Schindler, Ralf; Reinke, Petra; Staedtler, Adrienne; Rimpler, Sunda; Malik, Barbara; Frei, Ulrich; Berg, Thomas

2014-05-01

Detection of hepatitis C virus (HCV) RNA in peripheral blood mononuclear cells (PBMC) and/or hepatocytes in absence of HCV RNA in serum, designated as 'occult HCV infection', has been a matter of controversy in recent years. We investigated for the first time the prevalence of occult HCV infection in large cohorts of chronic hemodialysis (CHD) and kidney transplant (KTx) patients. We enrolled 417 CHD patients, 417 KTx recipients and 2 control groups - 25 anti-HCV (antibody against HCV)-positive and HCV RNA-positive patients with chronic hepatitis C, and 40 anti-HCV-, HCV RNA-, and HBsAg-negative healthy subjects. HCV RNA was tested in serum and PBMC using a sensitive commercial assay. In CHD patients, the prevalence of anti-HCV was 3.6% (15/417) and of positive serum HCV RNA 2.4% (10/417). HCV RNA was detected in PBMC in 1/407 (0.25%) HCV serum RNA-negative patients ("occult HCV infection"). In KTx recipients, prevalence of anti-HCV was 4.8% (20/417) and of positive serum HCV RNA 4.6% (19/417). Occult HCV infection was found in 2/398 (0.5%) serum HCV RNA-negative patients. On a mean longitudinal follow-up of 30months of the 3 patients with occult HCV infection, there was no clinical or virological evidence of HCV infection. The prevalence of occult HCV infection was very low in our CHD and KTx patients, and it did not appear to be clinically relevant. Further studies in geographic populations with high HCV endemicity are required to clarify the significance of occult HCV infection in these patient groups. Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

A prospective evaluation of occult disorders in obstructed defecation using the 'iceberg diagram'.

PubMed

Pescatori, M; Spyrou, M; Pulvirenti d'Urso, A

2006-11-01

Surgical treatment of constipation and obstructed defecation (OD) carries frequent recurrences, as OD is an 'iceberg syndrome' characterized by 'underwater rocks' or occult diseases which may affect the outcome of surgery. The aim of this study was to evaluate occult disorders in order to alert the clinician of these and minimize failures. One hundred consecutive constipated patients with OD symptoms, 81 female patients, median age 52 years, underwent perineal examination, proctoscopy, anorectal manometry, and anal/vaginal ultrasound. Anorectal physiology and imaging tests were also carried out when indicated, as well as psychological and urogynaecological consultation. Symptoms were graded using a modified 1-20 constipation score. Both evident (e.g. rectocele) and occult (e.g. anismus) diseases were prospectively evaluated using a novel 'iceberg diagram'. The type of treatment, whether conservative or surgical, was also recorded. Fifty-four (54%) patients had both mucosal prolapse and rectocele. All patients had at least two occult OD-related diseases, 66 patients had at least three: anxiety-depression, anismus and rectal hyposensation were the most frequent (66%, 44% and 33% respectively). The median constipation score was 11 (range 2-20), the median number of 'occult disorders' was 5 (range 2-8). Conservative treatment was carried out in most patients. Surgery was carried out in 14 (14%) patients. The novel 'iceberg diagram' allowed the adequate evaluation of OD-related occult diseases and better selection of patients for treatment. Most were managed conservatively, and only a minority were treated by surgery.

A prospective evaluation of occult disorders in obstructed defecation using the 'iceberg diagram'.

PubMed

Pescatori, M; Spyrou, M; Pulvirenti d'Urso, A

2007-06-01

Surgical treatment of constipation and obstructed defecation (OD) carries frequent recurrences, as OD is an 'iceberg syndrome' characterized by 'underwater rocks' or occult diseases which may affect the outcome of surgery. The aim of this study was to evaluate occult disorders, in order to alert the clinician of these and minimize failures. One hundred consecutive constipated patients with OD symptoms, 81 women, median age 52 years, underwent perineal examination, proctoscopy, anorectal manometry and anal/vaginal ultrasound (US). Anorectal physiology and imaging tests were also carried out when indicated, as well as psychological and urogynaecological consultations. Symptoms were graded using a modified 1-20 constipation score. Both evident (e.g. rectocele) and occult (e.g. anismus) diseases were prospectively evaluated using a novel 'iceberg diagram'. The type of treatment, whether conservative or surgical, was also recorded. Fifty-four (54%) patients had both mucosal prolapse and rectocele. All patients had at least two occult OD-related diseases, 66 patients had at least three of them: anxiety-depression, anismus and rectal hyposensation were the most frequent (66%, 44% and 33%, respectively). The median constipation score was 11 (range 2-20), the median number of 'occult disorders' was 5 (range 2-8). Conservative treatment was carried out in most cases. Surgery was carried out in 14 (14%) patients. The novel 'iceberg diagram' allowed the adequate evaluation of OD-related occult diseases and better selection of patients for treatment. Most were managed conservatively, and only a minority were treated by surgery.

Occult head injury is common in children with concern for physical abuse.

PubMed

Boehnke, Mitchell; Mirsky, David; Stence, Nicholas; Stanley, Rachel M; Lindberg, Daniel M

2018-04-13

Studies evaluating small patient cohorts have found a high, but variable, rate of occult head injury in children <2 years old with concern for physical abuse. The American College of Radiology (ACR) recommends clinicians have a low threshold to obtain neuroimaging in these patients. Our aim was to determine the prevalence of occult head injury in a large patient cohort with suspected physical abuse using similar selection criteria from previous studies. Additionally, we evaluated proposed risk factors for associations with occult head injury. This was a retrospective, secondary analysis of data collected by an observational study of 20 U.S. child abuse teams that evaluated children who underwent subspecialty evaluation for concern of abuse. We evaluated children <2 years old and excluded those with abnormal mental status, bulging fontanelle, seizure, respiratory arrest, underlying neurological condition, focal neurological deficit or scalp injury. One thousand one hundred forty-three subjects met inclusion criteria and 62.5% (714) underwent neuroimaging with either head computed tomography or magnetic resonance imaging. We found an occult head injury prevalence of 19.7% (141). Subjects with emesis (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.8-6.8), macrocephaly (OR 8.5, 95% CI 3.7-20.2), and loss of consciousness (OR 5.1, 95% CI 1.2-22.9) had higher odds of occult head injury. Our results show a high prevalence of occult head injury in patients <2 years old with suspected physical abuse. Our data support the ACR recommendation that clinicians should have a low threshold to perform neuroimaging in patients <2 years of age.

New Global Electron Density Observations from GPS-RO in the D- and E-Region Ionosphere

NASA Technical Reports Server (NTRS)

Wu, Dong L.

2017-01-01

A novel retrieval technique is developed for electron density (N(sub e)) in the D- and E-region (80-120 km) using the high-quality 50-Hz GPS radio occultation (GPS-RO) phase measurements. The new algorithm assumes a slow, linear variation in the F-region background when the GPS-RO passes through the D- and E-region, and extracts the N(sub e) profiles at 80-130 km from the phase advance signal caused by N(sub e). Unlike the conventional Abel function, the new approach produces a sharp N(sub e) weighting function in the lower ionosphere, and the N(sub e) retrievals are in good agreement with the IRI (International Reference Ionosphere) model in terms of monthly maps, zonal means and diurnal variations. The daytime GPS-RO N(sub e) profiles can be well characterized by the alpha-Chapman function of three parameters (N(sub mE), h(sub mE) and H), showing that the bottom of E-region is deepening and sharpening towards the summer pole. At high latitudes the monthly GPS-RO N(sub e) maps at 80-120 km reveal clear enhancement in the auroral zones, more prominent at night, as a result of energetic electron precipitation (EEP) from the outer radiation belt. The D-/E-region auroral N(sub e) is strongly correlated with K(sub p) on a daily basis. The new N(sub e) data allow further comprehensive analyses of the sporadic E (E(sub s)) phenomena in connection with the background N(sub e) in the E-region. The layered (2-10 km) and fluctuated (less than 2 km) E(sub s) components, namely N(sub e_Layer) than N(sub e_Pert), are extracted with respect to the background N( sub e_Region) on a profile-by-profile basis. The N(sub e_Layer) component has a strong but highly-refined peak at approximately 105 km, with an amplitude smaller than N(sub e_Region) approximately by an order of magnitude. The N(sub e_Pert) component, which was studied extensively in the past, is approximately 2 orders of magnitude weaker than N(sub e_Layer). Both N(sub e_Layer) and N(sub e_Pert) are subject to

Probing the Martian Atmosphere with MAVEN/IUVS Stellar Occultations

NASA Astrophysics Data System (ADS)

Gröller, H.; Yelle, R. V.; Koskinen, T.; Montmessin, F.; Lacombe, G.; Schneider, N. M.; Deighan, J.; Stewart, I. F.; Jain, S.; Chaffin, M.; Crismani, M. M. J.; Stiepen, A.; Lefèvre, F.; McClintock, B.; Clarke, J. T.; Holsclaw, G.; Mahaffy, P. R.; Bougher, S. W.; Jakosky, B. M.

2015-12-01

We present the first results of FUV and MUV stellar occultations taken with the Imaging UltraViolet Spectrometer (IUVS) onboard MAVEN. The FUV and MUV channels of the IUVS together cover the spectral range from 115 to 330 nm. The first two campaigns were executed during March 24 and March 26, 2015, and during May 17 and May 18, 2015, respectively. So far 13 occultations could be used to retrieve CO2 and O2 number densities in the altitude range between 100 and 150 km from the first occultation campaign. From the second occultation campaign number densities for CO2, O3, and aerosols were obtained between 20 and 100 km altitude. Temperature profiles for the same altitude ranges were calculated by applying the constraint of hydrostatic equilibrium to the CO2 densities. With a cadence of 2.6 s, including a 2.0 s integration time, the altitude resolution of the density and temperature profiles is between 1.5 and 4.5 km, depending on the geometry of the particular occultation. The retrieved density profiles of CO2 and O2 agree with previous measurements obtained by the Mars Express SPICAM instrument and by Viking 1 and 2. The corresponding O2 mixing ratios range from 1 to 5 x 10-3, also in agreement with previous observations. The temperatures that we retrieved agree with the models in the Mars Climate Database (MCD) between 10-2 and 10-4 Pa. At lower pressures, however, the measured temperatures are on average 70 K to 100 K cooler than the temperatures predicted by the MCD. This is because the model temperatures increase steadily with altitude above the mesopause whereas the observed temperatures decrease at pressures less than 3.5 x 10-5 Pa, reaching a minimum near 7 x 10-6 Pa. The large differences between the MCD and our results indicate that global models of thermal structure around the mesopause need to be revised.

Influence of misalignments on the performance of externally occulted solar coronagraphs. Application to PROBA-3/ASPIICS

NASA Astrophysics Data System (ADS)

Shestov, S. V.; Zhukov, A. N.

2018-05-01

Context. The ASPIICS instrument is a novel externally occulted coronagraph that will be launched on board the PROBA-3 mission of the European Space Agency. The external occulter will be placed on one satellite 150 m ahead of the second satellite that will carry an optical instrument. During 6 h out of 19.38 h of orbit, the satellites will fly in a precise (accuracy around a few millimeters) formation, constituting a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights 1.1R⊙. Aims: We intend to analyze influence of shifts of the satellites and misalignments of optical elements on the ASPIICS performance in terms of diffracted light. Based on the quantitative influence of misalignments on diffracted light, we provide a recipe for choosing the size of the internal occulter (IO) to achieve a trade-off between the minimal height of observations and sustainability to possible misalignments. Methods: We considered different types of misalignments and analyzed their influence from optical and computational points of view. We implemented a numerical model of the diffracted light and its propagation through the optical system and computed intensities of diffracted light throughout the instrument. Our numerical approach is based on a model from the literature that considered the axisymmetrical case. Here we extend the model to include nonsymmetrical cases and possible misalignments. Results: The numerical computations fully confirm the main properties of the diffracted light that we obtained from semi-analytical consideration. We obtain that relative influences of various misalignments are significantly different. We show that the internal occulter with RIO = 1.694 mm = 1.1R⊙ is large enough to compensate possible misalignments expected to occur in PROBA-3/ASPIICS. Besides that we show that apodizing the edge of the

Parapsychology on the couch: the psychology of occult belief in Germany, c. 1870-1939.

PubMed

Wolffram, Heather

2006-01-01

This article considers the attempts of academic psychologists and critical occultists in Germany during the late nineteenth and early twentieth centuries to construct a psychology of occult belief. While they claimed that the purpose of this new subdiscipline was to help evaluate the work of occult researchers, the emergence of a psychology of occult belief in Germany served primarily to pathologize parapsychology and its practitioners. Not to be outdone, however, parapsychologists argued that their adversaries suffered from a morbid inability to accept the reality of the paranormal. Unable to resolve through experimental means the dispute over who should be allowed to mold the public's understanding of the occult, both sides resorted to defaming their opponent. (c) 2006 Wiley Periodicals, Inc.

Comparing different Ultraviolet Imaging Spectrograph (UVIS) occultation observations using modeling of water vapor jets

NASA Astrophysics Data System (ADS)

Portyankina, Ganna; Esposito, Larry W.; Hansen, Candice; Aye, Klaus-Michael

2016-10-01

Motivation: On March 11, 2016 the Cassini UVIS observed its 6th star occultation by Enceladus' plume. This observation was aimed to determine variability in the total gas flux from the Enceladus' southern polar region. The analysis of the received data suggests that the total gas flux is moderately increased comparing to the average gas flux observed by UVIS from 2005 to 2011 [1]. However, UVIS detected variability in individual jets. In particular, Baghdad 1 is more collimated in 2016 than in 2005, meaning its gas escapes at higher velocity.Model and fits: We use 3D DSMC model for water vapor jets to compare different UVIS occultation observations from 2005 to 2016. The model traces test articles from jets' sources [2] into space and results in coordinates and velocities for a set of test particles. We convert particle positions into the particle number density and integrate along UVIS line of sight (LoS) for each time step of the UVIS observation using precise observational geometry derived from SPICE [3]. We integrate all jets that are crossed by the LoS and perform constrained least-squares fit of resulting modeled opacities to the observed data to solved for relative strengths of jets. The geometry of each occultation is specific, for example, during solar occultation in 2010 UVIS LoS was almost parallel to tiger stripes, which made it possible to distinguish jets venting from different tiger stripes. In 2011 Eps Orionis occultation LoS was perpendicular to tiger stripes and thus many of the jets were geometrically overlapping. Solar occultation provided us with the largest inventory of active jets - our model fit detects at least 43 non-zero jet contributions. Stellar occultations generally have lower temporal resolution and observe only a sub-set of these jets: 2011 Eps Orionis needs minimum 25 non-zero jets to fit UVIS data. We will discuss different occultations and models fits, including the most recent Epsilon Orionis occultation of 2016.[1] Hansen et al

VizieR Online Data Catalog: Outer satellites occultation predictions (Gomes-Junior+, 2016)

NASA Astrophysics Data System (ADS)

Gomes-Junior, A. R.; Assafin, M.; Beauvalet, L.; Desmars, J.; Vieira-Martins, R.; Camargo, J. I. B.; Morgado, B. E.; Braga-Ribas, F.

2016-07-01

Tables contain the day of the year and UTC central instant of the prediction; right ascension and declination of the occulted star - at the central instant of the occultation (corrected by proper motions); C/A: apparent geocentric distance between the satellite and the star (a.k.a. the distance between the shadow and the center of the Earth) at the moment of the geocentric closest approach, in arcseconds; P/A: the satellite position angle with respect to the occulted star at C/A, in degrees (zero at north of the star, increasing clockwise); v: relative velocity of event in km/s: positive = prograde, negative = retrograde; D: Geocentric distance to the occulting object in AU; R*: normalized UCAC4 magnitude in the R-band to a common shadow of 20km/s by the relationship R*=RUCAC4+2.5xlog(velocity/(20km/s)), the value 20km/s is typical of events around the opposition; long: east longitude of subplanet point in degrees, positive towards east, at the instant of the geocentric closest approach; LST: UT + long: local solar time at subplanet point, hh:mm; pmra and pmdec: proper motions in right ascension and declination, respectively (mas/year). For more detailed information about the definition and use of these stellar occultation geometric elements see Assafin et al. (2010, Cat. J/A+A/515/A32). (2 data files).

Defining occult injuries of the distal forearm and wrist in children.

PubMed

Elvey, Michael; Patel, S; Avisar, Erez; White, W J; Sorene, E

2016-06-01

The nonspecific terms "wrist sprain" and "suspected occult bony injury" are frequently documented as diagnoses in occult paediatric wrist injuries. To date, however, no one has accurately defined their true underlying pathology. The primary objective of this study was to identify the true pathoanatomy of occult acute paediatric wrist injuries. Our secondary objective was to compare our findings with existing adult data in order to determine any population differences that might be clinically relevant. We performed a single-centre retrospective case series evaluating MRI findings in acute paediatric wrist injuries presenting to the hand injury unit between 2011 and 2014. All patients underwent standardised radiographs of the wrist and, where clinically indicated, of the scaphoid. Where no bony anomaly was identified, MRI scanning was offered. Cohen's kappa coefficient was used to calculate the agreement between clinical and MRI diagnosis. 57 patients met the final inclusion criteria. Occult fractures and bony contusions comprised the majority of the pathologies, at 36.5 and 35.0 %, respectively. There were no cases of isolated soft-tissue injury. MRI effected management change in 35.1 % of cases. Paediatric wrists demonstrated differences in injury pattern and distribution when compared to an adult population. This study defines for the first time the true pathology of occult paediatric wrist injuries. The current definition of a wrist sprain was not applicable to a single case and therefore appears to be inappropriate for use in the paediatric population. A precise knowledge of the likely pathology facilitates accurate information delivery whilst reducing parental uncertainty and treatment variation.

Shape and Size of Patroclus and Menoetius from a Stellar Occultation

NASA Astrophysics Data System (ADS)

Buie, Marc W.; Olkin, Catherine B.; Merline, William J.; Timerson, Brad; Herald, Dave; Owen, William M.; Abramson, Harry B.; Abramson, Katherine J.; Breit, Derek C.; Caton, D. B.; Conard, Steve J.; Croom, Mark A.; Dunford, R. W.; Dunford, J. A.; Dunham, David W.; Ellington, Chad K.; Liu, Yanzhe; Maley, Paul D.; Olsen, Aart M.; Royer, Ronald; Scheck, Andrew E.; Sherrod, Clay; Sherrod, Lowell; Swift, Theodore J.; Taylor, Lawrence W.; Venable, Roger

2014-11-01

We will present results of a stellar occultation by the Jupiter Trojan asteroid, Patroclus and its nearly equal size moon, Menoetius. The occultation was observed widely across the United States on 2013 Oct 21 UT. Eleven sites out of 36 successfully recorded an occultation. Seven chords across Patroclus yielded a elliptical limb fit of 124.6 km by 98.2 km. There were six chords across Menoetius that yielded an elliptical limb fit of 117.2 km by 93.0 km. There were three sites that got chords on both objects. At the time of the occultation we measured a separation of 0.247 arcsec and a position angle for Menoetius of 265.7 deg measured eastward from J2000 North. More surprisingly, there were two sites that should have seen an occultation by Menoetius but instead never saw the star disappear. These two non-detections indicate the presence of a large void on the southern limb of the satellite. The observations are consistent with a large impact basin centered on the rotation pole. The depth of the projected crater profile is roughly 15 km, measured from the elliptical limb profile. The inferred diameter of the crater would be about 85 km. Combining this occultation data with previous lightcurve data, the axial ratios (ignoring the mass void) of both objects is 1.26:1.19:1 indicative of a mostly oblate ellipsoid with a slight asymmetry in its equatorial projection. These results are consistent with a fully tidally evolved system with the mass void or putative crater in a position consistent with principal axis rotation that is itself consistent with the largely oblate shape. Note: the location for IOTA listed in the affiliations is not correct (but was required to be entered) as there is no location for this global virtual organization. This research is funded, in part, by NSF AST-1212159.

Risk of Ischemic and Hemorrhagic Strokes in Occult and Manifest Cancers.

PubMed

Andersen, Klaus Kaae; Olsen, Tom Skyhøj

2018-06-04

Manifest cancer is associated with increased risk of stroke. The risk of stroke in people with occult cancer in comparison to the risk in the background population without cancer has not been investigated. Smoking is a risk factor for both cancer and stroke, but the role of smoking for the risk of stroke in cancer has not been investigated. We identified all incident cases of cancer in Denmark 2003 to 2012 (n=264.376) from the Danish Cancer Registry. Each person with cancer was matched by age, sex, and income with 10 randomly selected persons without cancer at index date (n=2.571.260). Linking data to the Danish Stroke Registry, we studied risk of ischemic/hemorrhagic stroke the year before (occult cancer) and after cancer diagnosis was established in the Danish Stroke Registry (manifest cancer) and stratified into the 15 most common cancer types related (lung, colon, bladder, rectum, pancreas, kidney, stomach, and head and neck cancer) and unrelated (non-Hodgkin lymphoma, breast, prostate, melanoma, central nervous system, ovary and endometrial) to smoking. Risk of ischemic/hemorrhagic stroke was increased for both occult (relative risk, 1.75/2.00) and manifest cancers (relative risk, 1.30/1.41). For occult cancer, risk of ischemic stroke was increased for all of the smoking-related cancers, but among cancers unrelated to smoking, only lymphoma, central nervous system, and endometrial cancer were associated with increased risk of stroke; breast, prostate, melanoma, and ovarian cancers were not. For occult cancer, risk of hemorrhagic stroke was generally increased for smoking-related cancers while not for cancers unrelated to smoking. For manifest cancer, risk of ischemic and hemorrhagic stroke was generally increased for cancers related to smoking while not for cancers unrelated to smoking. Cancer, occult and manifest, is associated with increased risks for stroke. The increased risk is linked mainly to cancers related to smoking. © 2018 American Heart

Electron densities in the ionosphere of Mars: A comparison of MARSIS and radio occultation measurements

NASA Astrophysics Data System (ADS)

Vogt, Marissa F.; Withers, Paul; Fallows, Kathryn; Flynn, Casey L.; Andrews, David J.; Duru, Firdevs; Morgan, David D.

2016-10-01

Radio occultation electron densities measurements from the Mariner 9 and Viking spacecraft, which orbited Mars in the 1970s, have recently become available in a digital format. These data are highly complementary to the radio occultation electron density profiles from Mars Global Surveyor, which were restricted in solar zenith angle and altitude. We have compiled data from the Mariner 9, Viking, and Mars Global Surveyor radio occultation experiments for comparison to electron density measurements made by Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), the topside radar sounder on Mars Express, and MARSIS-based empirical density models. We find that the electron densities measured by radio occultation are in generally good agreement with the MARSIS data and model, especially near the altitude of the peak electron density but that the MARSIS data and model display a larger plasma scale height than the radio occultation profiles at altitudes between the peak density and 200 km. Consequently, the MARSIS-measured and model electron densities are consistently larger than radio occultation densities at altitudes 200-300 km. Finally, we have analyzed transitions in the topside ionosphere, at the boundary between the photochemically controlled and transport-controlled regions, and identified the average transition altitude, or altitude at which a change in scale height occurs. The average transition altitude is 200 km in the Mariner 9 and Viking radio occultation profiles and in profiles of the median MARSIS radar sounding electron densities.

Naturally Occurring Mutations in Large Surface Genes Related to Occult Infection of Hepatitis B Virus Genotype C

PubMed Central

Kim, Hong; Lee, Seoung-Ae; Kim, Dong-Won; Lee, Sueng-Hyun; Kim, Bum-Joon

2013-01-01

Molecular mechanisms related to occult hepatitis B virus (HBV) infection, particularly those based on genotype C infection, have rarely been determined thus far in the ongoing efforts to determine infection mechanisms. Therefore, we aim to elucidate the mutation patterns in the surface open reading frame (S ORF) underlying occult infections of HBV genotype C in the present study. Nested PCRs were applied to 624 HBV surface antigen (HBsAg) negative Korean subjects. Cloning and sequencing of the S ORF gene was applied to 41 occult cases and 40 control chronic carriers. Forty-one (6.6%) of the 624 Korean adults with HBsAg-negative serostatus were found to be positive for DNA according to nested PCR tests. Mutation frequencies in the three regions labeled here as preS1, preS2, and S were significantly higher in the occult subjects compared to the carriers in all cases. A total of two types of deletions, preS1 deletions in the start codon and preS2 deletions as well as nine types of point mutations were significantly implicated in the occult infection cases. Mutations within the “a” determinant region in HBsAg were found more frequently in the occult subjects than in the carriers. Mutations leading to premature termination of S ORF were found in 16 occult subjects (39.0%) but only in one subject from among the carriers (2.5%). In conclusion, our data suggest that preS deletions, the premature termination of S ORF, and “a” determinant mutations are associated with occult infections of HBV genotype C among a HBsAg-negative population. The novel mutation patterns related to occult infection introduced in the present study can help to broaden our understanding of HBV occult infections. PMID:23349904

Circulating Tumor Cells Predict Occult Metastatic Disease and Prognosis in Pancreatic Cancer.

PubMed

Court, Colin M; Ankeny, Jacob S; Sho, Shonan; Winograd, Paul; Hou, Shuang; Song, Min; Wainberg, Zev A; Girgis, Mark D; Graeber, Thomas G; Agopian, Vatche G; Tseng, Hsian-Rong; Tomlinson, James S

2018-04-01

Occult metastatic tumors, below imaging thresholds, are a limitation of staging systems that rely on cross-sectional imaging alone and are a cause of the routine understaging of pancreatic ductal adenocarcinomas (PDACs). We investigated circulating tumor cells (CTCs) as a preoperative predictor of occult metastatic disease and as a prognostic biomarker for PDAC patients. A total of 126 patients (100 with cancer, 26 with benign disease) were enrolled in our study and CTCs were identified and enumerated from 4 mL of venous blood using the microfluidic NanoVelcro assay. CTC enumeration was correlated with clinicopathologic variables and outcomes following both surgical and systemic therapies. CTCs were identified in 78% of PDAC patients and CTC counts correlated with increasing stage (ρ = 0.42, p < 0.001). Of the 53 patients taken for potentially curative surgery, 13 (24.5%) had occult metastatic disease intraoperatively. Patients with occult disease had significantly more CTCs than patients with local disease only (median 7 vs. 1 CTC, p < 0.0001). At a cut-off of three or more CTCs/4 mL, CTCs correctly identified patients with occult metastatic disease preoperatively (area under the receiver operating characteristic curve 0.82, 95% confidence interval (CI) 0.76-0.98, p < 0.0001). CTCs were a univariate predictor of recurrence-free survival following surgery [hazard ratio (HR) 2.36, 95% CI 1.17-4.78, p = 0.017], as well as an independent predictor of overall survival on multivariate analysis (HR 1.38, 95% CI 1.01-1.88, p = 0.040). CTCs show promise as a prognostic biomarker for PDAC patients at all stages of disease being treated both medically and surgically. Furthermore, CTCs demonstrate potential as a preoperative biomarker for identifying patients at high risk of occult metastatic disease.

First lunar occultation results from the 2.4 m Thai national telescope equipped with ULTRASPEC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richichi, A.; Irawati, P.; Soonthornthum, B.

2014-11-01

The recently inaugurated 2.4 m Thai National Telescope (TNT) is equipped with, among other instruments, the ULTRASPEC low-noise, frame-transfer EMCCD camera. At the end of its first official observing season, we report on the use of this facility to record high time resolution imaging using small detector subarrays with a sampling as fast as several 10{sup 2} Hz. In particular, we have recorded lunar occultations of several stars that represent the first contribution to this area of research made from Southeast Asia with a telescope of this class. Among the results, we discuss an accurate measurement of α Cnc, whichmore » has been reported previously as a suspected close binary. Attempts by several authors to resolve this star have so far met with a lack of unambiguous confirmation. With our observation we are able to place stringent limits on the projected angular separation (<0.''003) and brightness (Δm > 5) of a putative companion. We also present a measurement of the binary HR 7072, which extends considerably the time coverage available for its yet undetermined orbit. We discuss our precise determination of the flux ratio and projected separation in the context of other available data. We conclude by providing an estimate of the performance of ULTRASPEC at TNT for lunar occultation work. This facility can help to extend the lunar occultation technique in a geographical area where no comparable resources were available until now.« less

Harmonic analysis of the ionospheric electron densities retrieved from FORMOSAT-3/COSMIC radio occultation measurements

NASA Astrophysics Data System (ADS)

Masoumi, S.; Safari, A.; Sharifi, M.; Sam Khaniani, A.

2011-12-01

In order to investigate regular variations of the ionosphere, the least-squares harmonic estimation is applied to the time series of ionospheric electron densities in the region of Iran derived from about five years of Global Positioning System Radio Occultation (GPS RO) observations by FORMOSAT-3/COSMIC satellites. Although the obtained results are slightly different from the expected ones due to the low horizontal resolution of RO measurements, high vertical resolution of the observations enables us to detect not only the Total Electron Content (TEC) variations, but also periodic patterns of electron densities in different altitudes of the ionosphere. Dominant diurnal and annual signals, together with their Fourier series decompositions, and also periods close to 27 days are obtained, which is consistent with the previous analyses on TEC. In the equatorial anomaly band, the annual component is weaker than its Fourier decomposition periods. In particular, the semiannual period dominates the annual component, which is probably due to the effect of geomagnetic field. By the investigation of the frequencies at different local times, the semiannual signal is more significant than the annual one in the daytime, while the annual frequency is dominant at night. By the detection of the phases of the components, it is revealed that the annual signal has its maximum in summer at high altitudes, and in winter at lower altitudes. This suggests the effect of neutral compositions in the lower atmosphere. Further, the semiannual component peaks around equinox during the day, while its maximum mostly occurs in solstice at night. Since RO measurements can be used to derive TEC along the signal path between a GPS satellite and a receiver, study on the potentiality of using these observations for the prediction of electron densities and its application to the ionospheric correction of the single frequency receivers is suggested.

Heparin as a pharmacologic intervention to induce positive scintiscan in occult gastrointestinal bleeding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhuri, T.K.; Brantly, M.

1984-04-01

The value of using heparin as a pharmacologic intervention to induce a positive scintiscan was studied in a patient with chronic occult gastrointestinal bleeding. When all standard diagnostic tests (upper and lower gastrointestinal series, upper and lower endoscopy, and conventional noninterventional Tc-99m RBC imaging) fail to detect and localize gastrointestinal bleeding in a patient who has definite clinical evidence (guaiac positive stool and dropping hemoglobin, hematocrit) of chronic occult gastrointestinal oozing, heparin may be used (with proper precaution) as a last resort to aid in the scintigraphic detection and localization of chronic occult gastrointestinal bleeding.

Asteroid astrometry with Gaia: stellar occultations and beyond

NASA Astrophysics Data System (ADS)

Tanga, Paolo; Spoto, Federica; Hestroffer, Daniel; Altmann, Martin; Bouquillon, Sebastien; Desmars, Josselin

2017-10-01

The first data release of star astrometry by Gaia (Sept. 2016) has given an anticipation of the mission capabilities. By providing positions with uncertainties at the level of few milli-arcsec (mas) a new frame to calibrate ground-based observations has immediately become available, thus disclosing a new possibility of exploitation for archive data. We will discuss, in particular, the new role of stellar occulations.Successful observations of occultations have been used in the past to provide accurate shape and size of the targets and to calibrate other size determination methods. Now, a new possibility of exploitation exists, as occultation astrometry provides the possibility of measuring precise asteroid position, at the level of Gaia accuracy. This approach will have an increasing impact, also thanks to the much improved prediction accuracy that Gaia is going to provide, for smaller asteroids and fainter target stars.The scientific goals of improving asteroid astrometry are multiple. For instance, reaching sensitivity to Yarkovsky drift in the Main Belt might become possible, by occultation astrometry performed on smaller asteroids, thanks to future Gaia predictions.The second data release (April 2018) will also contain astrometry of asteroids observed directly by Gaia. The properties of this new data set, that will permit direct orbit improvement, will be illustrated.

Titan's Upper Atmosphere from Cassini/UVIS Solar Occultations

NASA Astrophysics Data System (ADS)

Capalbo, Fernando J.; Bénilan, Yves; Yelle, Roger V.; Koskinen, Tommi T.

2015-12-01

Titan’s atmosphere is composed mainly of molecular nitrogen, methane being the principal trace gas. From the analysis of 8 solar occultations measured by the Extreme Ultraviolet channel of the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini, we derived vertical profiles of N2 in the range 1100-1600 km and vertical profiles of CH4 in the range 850-1300 km. The correction of instrument effects and observational effects applied to the data are described. We present CH4 mole fractions, and average temperatures for the upper atmosphere obtained from the N2 profiles. The occultations correspond to different times and locations, and an analysis of variability of density and temperature is presented. The temperatures were analyzed as a function of geographical and temporal variables, without finding a clear correlation with any of them, although a trend of decreasing temperature toward the north pole was observed. The globally averaged temperature obtained is (150 ± 1) K. We compared our results from solar occultations with those derived from other UVIS observations, as well as studies performed with other instruments. The observational data we present confirm the atmospheric variability previously observed, add new information to the global picture of Titan’s upper atmosphere composition, variability, and dynamics, and provide new constraints to photochemical models.

Altered regional and circuit resting-state activity in patients with occult spastic diplegic cerebral palsy.

PubMed

Mu, Xuetao; Wang, Zhiqun; Nie, Binbin; Duan, Shaofeng; Ma, Qiaozhi; Dai, Guanghui; Wu, Chunnan; Dong, Yuru; Shan, Baoci; Ma, Lin

2017-10-07

Very few studies have been made to investigate functional activity changes in occult spastic diplegic cerebral palsy (SDCP). The purpose of this study was to analyze whole-brain resting state regional brain activity and functional connectivity (FC) changes in patients with SDCP. We examined 12 occult SDCP and 14 healthy control subjects using resting-state functional magnetic resonance imaging. The data were analyzed using Resting-State fMRI Data Analysis Toolkit (REST) software. The regional homogeneity (ReHo), amplitude of low-frequency fluctuations (ALFF), and whole brain FC of the motor cortex and thalamus were analyzed and compared between the occult SDCP and control groups. Compared with the control group, the occult SDCP group showed decreased ReHo regions, including the bilateral frontal, parietal, and temporal lobes, the cerebellum, right cingulate gyrus, and right lenticular nucleus, whereas an increased ReHo value was observed in the left precuneus, calcarine, fusiform gyrus, and right precuneus. Compared with the control group, no significant differences in ALFF were noted in the occult SDCP group. With the motor cortex as the region of interest, the occult SDCP group showed decreased connectivity regions in the bilateral fusiform and lingual gyrus, but increased connectivity regions in the contralateral precentral and postcentral gyrus, supplementary motor area, and the ipsilateral postcentral gyrus. With the thalamus being regarded as the region of interest, the occult SDCP group showed decreased connectivity regions in the bilateral basal ganglia, cingulate, and prefrontal cortex, but increased connectivity regions in the bilateral precentral gyrus, the contralateral cerebellum, and inferior temporal gyrus. Resting-state regional brain activities and FC changes in the patients with occult SDCP exhibited a special distribution pattern, which is consistent with the pathology of the disease. Copyright © 2017. Published by Elsevier B.V.

Prevalence of occult hepatitis B virus infection in haemodialysis patients from central Greece

PubMed Central

Mina, Paraskevi; Georgiadou, Sarah P; Rizos, Christos; Dalekos, George N; Rigopoulou, Eirini I

2010-01-01

AIM: To assess the hepatitis B virus (HBV)-DNA and the prevalence of occult HBV infection in end-stage renal failure (ESRF) patients from Central Greece. METHODS: Sera from 366 ESRF patients attending five out of six dialysis units from Central Greece were investigated for HBV-DNA by real-time polymerase chain reaction. Only serum samples with repeatedly detectable HBV-DNA were considered positive. IgG antibodies to hepatitis C virus (anti-HCV) were tested by a third generation enzyme linked immunosorbent assay (ELISA), while IgG antibodies to hepatitis E virus (anti-HEV) were tested by two commercially available ELISAs. RESULTS: HBV-DNA was detected in 15/366 patients (4.1%) and HBsAg in 20/366 (5.5%). The prevalence of occult HBV infection was 0.9% (3/346 HBsAg-negative patients). Occult HBV was not associated with a specific marker of HBV infection or anti-HCV or anti-HEV reactivity. There was no significant difference in HBV-DNA titres, demographic and biochemical features, between patients with occult HBV infection and those with HBsAg-positive chronic HBV infection. CONCLUSION: In central Greece, 4% of ESRF patients had detectable HBV-DNA, though in this setting, the prevalence of occult HBV seems to be very low (0.9%). PMID:20066742

Prevalence of occult hepatitis B virus infection in haemodialysis patients from central Greece.

PubMed

Mina, Paraskevi; Georgiadou, Sarah P; Rizos, Christos; Dalekos, George N; Rigopoulou, Eirini I

2010-01-14

To assess the hepatitis B virus (HBV)-DNA and the prevalence of occult HBV infection in end-stage renal failure (ESRF) patients from Central Greece. Sera from 366 ESRF patients attending five out of six dialysis units from Central Greece were investigated for HBV-DNA by real-time polymerase chain reaction. Only serum samples with repeatedly detectable HBV-DNA were considered positive. IgG antibodies to hepatitis C virus (anti-HCV) were tested by a third generation enzyme linked immunosorbent assay (ELISA), while IgG antibodies to hepatitis E virus (anti-HEV) were tested by two commercially available ELISAs. HBV-DNA was detected in 15/366 patients (4.1%) and HBsAg in 20/366 (5.5%). The prevalence of occult HBV infection was 0.9% (3/346 HBsAg-negative patients). Occult HBV was not associated with a specific marker of HBV infection or anti-HCV or anti-HEV reactivity. There was no significant difference in HBV-DNA titres, demographic and biochemical features, between patients with occult HBV infection and those with HBsAg-positive chronic HBV infection. In central Greece, 4% of ESRF patients had detectable HBV-DNA, though in this setting, the prevalence of occult HBV seems to be very low (0.9%).

The Clinical Significance of Occult Gastrointestinal Primary Tumours in Metastatic Cancer: A Population Retrospective Cohort Study.

PubMed

Hannouf, Malek B; Winquist, Eric; Mahmud, Salaheddin M; Brackstone, Muriel; Sarma, Sisira; Rodrigues, George; Rogan, Peter K; Hoch, Jeffrey S; Zaric, Gregory S

2018-01-01

The purpose of this study was to estimate the incidence of occult gastrointestinal (GI) primary tumours in patients with metastatic cancer of uncertain primary origin and evaluate their influence on treatments and overall survival (OS). We used population heath data from Manitoba, Canada to identify all patients initially diagnosed with metastatic cancer between 2002 and 2011. We defined patients to have "occult" primary tumour if the primary was found at least 6 months after initial diagnosis. Otherwise, we considered primary tumours as "obvious." We used propensity-score methods to match each patient with occult GI tumour to four patients with obvious GI tumour on all known clinicopathologic features. We compared treatments and 2-year survival data between the two patient groups and assessed treatment effect on OS using Cox regression adjustment. Eighty-three patients had occult GI primary tumours, accounting for 17.6% of men and 14% of women with metastatic cancer of uncertain primary. A 1:4 matching created a matched group of 332 patients with obvious GI primary tumour. Occult cases compared to the matched group were less likely to receive surgical interventions and targeted biological therapy, and more likely to receive cytotoxic empiric chemotherapeutic agents. Having an occult GI tumour was associated with reduced OS and appeared to be a nonsignificant independent predictor of OS when adjusting for treatment differences. GI tumours are the most common occult primary tumours in men and the second most common in women. Patients with occult GI primary tumours are potentially being undertreated with available GI site-specific and targeted therapies.

Do X-ray-occult fractures play a role in chronic pain following a whiplash injury?

PubMed

Hertzum-Larsen, Rasmus; Petersen, Henrik; Kasch, Helge; Bendix, Tom

2014-08-01

Whiplash trauma in motor vehicle accidents (MVA) may involve various painful soft tissue damages, but weeks/months later a minority of victims still suffers from various long-lasting and disabling symptoms, whiplash-associated disorders (WAD). The etiology is currently unknown, but X-ray-occult fractures may be one cause in some cases. The purpose of this prospective study was to examine the association between occult fractures, as seen on bone single photon emission computed tomography (SPECT), with neck-, head- and arm pain. An inception cohort of 107 patients presenting with acute whiplash symptoms following an MVA was invited to have a cervical SPECT shortly post injury and again 6 months later. Associations between occult fractures and pain levels at baseline, 6 and 12 months of follow-up were analyzed. Eighty-eight patients had baseline SPECT performed at median 15 days (range 3-28) post injury, but only 49 patients accepted to have the follow-up SPECT at 6 months. Abnormal SPECT, defined as minimum one area of focal uptake, was seen in 32 patients at baseline, reflecting an occult fracture. Occult fractures were not associated with pain levels, neither at baseline nor at follow-up. Occult fractures do not seem to play a role for development of chronic pain after whiplash.

Occult infection related hepatitis B surface antigen variants showing lowered secretion capacity

PubMed Central

Kim, Hong; Lee, Seoung-Ae; Won, You-Sub; Lee, HyunJoo; Kim, Bum-Joon

2015-01-01

AIM: To elucidate the molecular mechanisms underlying hepatitis B virus (HBV) occult infection of genotype C. METHODS: A total of 10 types of hepatitis B surface antigen (HBsAg) variants from a Korean occult cohort were used. After a complete HBV genome plasmid mutated such that it does not express HBsAg and plasmid encoding, each HBsAg variant was transiently co-transfected into HuH-7 cells. The secretion capacity and intracellular expression of the HBV virions and HBsAgs in their respective variants were analyzed using real-time quantitative polymerase chain reaction assays and commercial HBsAg enzyme-linked immunosorbent assays, respectively. RESULTS: All variants exhibited lower levels of HBsAg secretion into the medium compared with the wild type. In particular, in eight of the ten variants, very low levels of HBsAg secretion that were similar to the negative control were detected. In contrast, most variants (9/10) exhibited normal virion secretion capacities comparable with, or even higher than, the wild type. This provided new insight into the intrinsic nature of occult HBV infection, which leads to HBsAg sero-negativeness but has horizontal infectivity. Furthermore, most variants generated higher reactive oxidative species production than the wild type. This finding provides potential links between occult HBV infection and liver disease progression. CONCLUSION: The presently obtained data indicate that deficiency in the secretion capacity of HBsAg variants may have a pivotal function in the occult infections of HBV genotype C. PMID:25684944

ASPIICS/PROBA-3 formation flying solar coronagraph: Stray light analysis and optimization of the occulter

NASA Astrophysics Data System (ADS)

Landini, F.; Mazzoli, A.; Venet, M.; Vivès, S.; Romoli, M.; Lamy, P.; Massone, G.

2017-11-01

The "Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire", ASPIICS, selected by ESA for the PROBA-3 mission, heralds the next generation of coronagraph for solar research, exploiting formation flying to gain access to the inner corona under eclipse-like conditions for long periods of time. A detailed description of the ASPIICS instrument and of its scientific objectives can be found in [1]. ASPIICS is distributed on the two PROBA 3 spacecrafts (S/C) separated by 150 m. The coronagraph optical assembly is hosted by the "coronagraph S/C" protected from direct solar disk light by the occulting disk on the "occulter S/C". The most critical issue in the design of a solar coronagraph is the reduction of the stray light due to the diffraction and scattering of the solar disk light by the occulter, the aperture and the optics. In the present article, we deal with two of these issues: - The analysis of the stray light inside the telescope. - The optimization of the external occulter edge, in order to eliminate the Poisson spot behind the occulter and to lower the stray light level going through the entrance pupil of the telescope. This work was performed in the framework of the ESA STARTIGER program which took place at the Laboratoire d'Astrophysique de Marseille (LAM) during a 6-month period from September 2009 to March 2010. In general, it is a very complicated task to combine the above two stray light issues together in the simulation and design phase as it requires to consider the propagation inside the telescope of the light diffracted by the external occulter. Actually, the present literature only reports diffraction calculations performed for simple occulting systems (i.e., two disks and serrated disk). A more pragmatic approach, also driven by the tight schedule of the STARTIGER program, is to separate the two contributions, and perform two different stray light analyses. This paper is dedicated to the description of both analyses

First Ionospheric Results From the MAVEN Radio Occultation Science Experiment (ROSE)

NASA Astrophysics Data System (ADS)

Withers, Paul; Felici, M.; Mendillo, M.; Moore, L.; Narvaez, C.; Vogt, M. F.; Jakosky, B. M.

2018-05-01

Radio occultation observations of the ionosphere of Mars can span the full vertical extent of the ionosphere, in contrast to in situ measurements that rarely sample the main region of the ionosphere. However, most existing radio occultation electron density profiles from Mars were acquired without clear context for the solar forcing or magnetospheric conditions, which presents challenges for the interpretation of these profiles. Here we present 48 ionospheric electron density profiles acquired by the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) Radio Occultation Science Experiment (ROSE) from 5 July 2016 to 27 June 2017 at solar zenith angles of 54° to 101°. Latitude coverage is excellent, and comprehensive context for the interpretation of these profiles is provided by other MAVEN instruments. The profiles show a 9-km increase in ionospheric peak altitude in January 2017 that is associated with a lower atmospheric dust storm, variations in electron densities in the M1 layer that cannot be explained by variations in the solar soft X-ray flux, and topside electron densities that are larger in strongly magnetized regions than in weakly magnetized regions. MAVEN Radio Occultation Science Experiment electron density profiles are publicly available on the NASA Planetary Data System.

Repeated faecal occult blood testing is associated with decreased advanced colorectal cancer risk: A population-based study.

PubMed

James, Paul D; Rabeneck, Linda; Yun, Lingsong; Paszat, Lawrence; Baxter, Nancy N; Govindarajan, Anand; Antonova, Lilia; Tinmouth, Jill M

2017-01-01

Objective To evaluate the association between repeated faecal occult blood testing and advanced colorectal cancer risk at population level in Canada. Methods A retrospective cohort study of all Ontario residents aged 56-74 diagnosed with colorectal cancer from 1 April 2007 to 31 March 2010, identified using health administrative data. The primary outcome was stage IV colorectal cancer, and primary exposure was faecal occult blood testing use within five years prior to colorectal cancer diagnosis. Patients were categorized into four mutually exclusive groups based on their exposure to faecal occult blood testing in the five years prior to colorectal cancer diagnosis: none, pre-diagnostic, repeated, and sporadic. Logistic regression was utilized to adjust for confounders. Results Of 7753 patients (median age 66, interquartile range 61-70, 62% male) identified, 1694 (22%) presented with stage I, 2056 (27%) with stage II, 2428 (31%) with stage III, and 1575 (20%) with stage IV colorectal cancer. There were 4092 (53%) with no record of prior faecal occult blood testing, 1485 (19%) classified as pre-diagnostic, 1693 (22%) as sporadic, and 483 (6%) as repeated faecal occult blood testing. After adjusting for confounders, patients who had repeated faecal occult blood testing were significantly less likely to present with stage IV colorectal cancer at diagnosis (Odds ratio 0.46, 95% Confidence Interval 0.34-0.62) than those with no prior faecal occult blood testing. Conclusions Repeated faecal occult blood testing is associated with a decreased risk of advanced colorectal cancer. Our findings support the use of organized screening programmes that employ repeated faecal occult blood testing to improve colorectal cancer outcomes at population level.

Incidence of occult athlete's foot in swimmers.

PubMed

Attye, A; Auger, P; Joly, J

1990-09-01

Athlete's foot is a dermatophytic infection frequently found in adults. This disease is, in some cases, asymptomatic. In order to evaluate the incidence of subclinical infection, we obtained 300 toe-web samples from the fourth interdigital space of 150 regular swimmers. More over, 66 specimens from the pool area were analysed. The method used was the carpet technique described by Mariat et al. (10). The fungal isolates were identified according to standard methods. A list of epidemiological data was completed for every swimmer. In our results, 22 swimmers had positive cultures (15%), 8 of these cases had no lesions (36%). They included 7 infections with Trichophyton mentagrophytes (87.5%) and one with T. rubrum (12.5%). We observed one case with a dual infection. Only one sample from the inanimate environment was positive. This study showed a significant incidence of occult athlete's foot in swimmers. To control this endemic problem, adequate preventive measures must be taken.

What can the occult do for you?

NASA Astrophysics Data System (ADS)

Holwerda, B. W.; Keel, W. C.

2017-03-01

Interstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.

Identification of occult tumors by whole-specimen mapping in solitary papillary thyroid carcinoma.

PubMed

Park, Seog Yun; Jung, Yuh-S; Ryu, Chang Hwan; Lee, Chang Yoon; Lee, You Jin; Lee, Eun Kyung; Kim, Seok-Ki; Kim, Tae Sung; Kim, Tae Hyun; Jang, Jeyun; Park, Daeyoon; Dong, Seung Myung; Kang, Jae-Goo; Lee, Jin Soo; Ryu, Junsun

2015-08-01

We undertook this study to estimate an accurate incidence and spread patterns of occult papillary thyroid carcinoma (PTC) in patients with a preoperative diagnosis of solitary PTC by using whole-specimen mapping of all specimens after a total thyroidectomy. Enrolled prospectively in this whole-thyroid mapping study are 82 consecutive patients who underwent a total thyroidectomy under a preoperative diagnosis of solitary PTC. All thyroidectomy specimens were serially sectioned in 2 mm thickness and whole-thyroid mapping was carried out for additional foci of occult PTC. The frequencies of occult lesions detected in the whole and contralateral lobe were determined, and clinicopathologic factors associated with multifocality were assessed. Whole-thyroid mapping revealed 66 occult PTC lesions missed by preoperative ultrasound in 37 (45.1%) of the 82 patients. The great majority (92.5%) of the occult PTC was smaller than 3 mm in size and 25 patients (30.5%) had contralateral lesions. We found that the male sex was an independent predictor of multifocality (odds ratio (OR), 3.00; 95% CI, 1.11-8.14), adjusting for preoperative findings. Analysis with pathologic parameters showed that the male sex (OR, 5.03; 95% CI, 1.68-15.08) and extrathyroidal extensions (OR, 3.03; 95% CI, 1.03-8.95) were associated with multifocal PTC. However, none of the clinicopathologic factors evaluated predicted contralateral PTC. Our study demonstrates the diagnostic limitations of ultrasound for the detection of multifocal PTC and the need to consider the possibility of occult lesions in the management of solitary PTC, especially in male patients. © 2015 Society for Endocrinology.

The Regulus occultation light curve and the real atmosphere of Venus

NASA Technical Reports Server (NTRS)

Veverka, J.; Wasserman, L.

1974-01-01

An inversion of the light curve observed during the July 7, 1959, occultation of Regulus by Venus leads to the conclusion that the light curve cannot be reconciled with models of the Venus atmosphere based on spacecraft observations. The event occurred in daylight and, under the subsequently difficult observation conditions, it seems likely that the Regulus occultation light curve is marred by a systematic errors in spite of the competence of the observers involved.

Winds and the occultation experiment. [for Venus and Mars atmospheric parameters

NASA Technical Reports Server (NTRS)

Gross, S. H.

1974-01-01

A spacecraft orbiting about another planet, such as Mars or Venus, may be used to obtain data about the pressure, density, and temperature fields over the planet from multiple occultations if the orbit precesses or retrogresses. Under certain conditions successive occultations will provide mean dynamic information such as wind speeds over the time and spacing intervals. It is shown that data concerning winds may be found by comparing refractivity information rather than pressure or temperature.

External occulter laboratory demonstrator for the forthcoming formation flying coronagraphs.

PubMed

Landini, Federico; Vives, Sébastien; Venet, Mélanie; Romoli, Marco; Guillon, Christophe; Fineschi, Silvano

2011-12-20

The design and optimization of the external occulter geometry is one of the most discussed topics among solar coronagraph designers. To improve the performance of future coronagraphs and to stretch their inner fields of view toward the solar limb, the new concept of coronagraphs in formation flight has been introduced in the scientific debate. Solar coronagraphs in formation flight require several mechanical and technological constraints to be met, mainly due to the large dimension of the occulter and to the spacecraft's reciprocal alignment. The occulter edge requires special attention to minimize diffraction while being compatible with the handling and integrating of large delicate space components. Moreover, it is practically impossible to set up a full-scale model for laboratory tests. This article describes the design and laboratory tests on a demonstrator for a coronagraph to be operated in formation flight. The demonstrator is based on the principle of the linear edge, thus the presented results cannot be directly extrapolated to the case of the flying circular occulter. Nevertheless, we are able to confirm the results of other authors investigating on smaller coronagraphs and provide further information on the geometry and tolerances of the optimization system. The described work is one of the results of the ESA STARTIGER program on formation flying coronagraphs ["The STARTIGER's demonstrators: toward a new generation of formation flying solar coronagraphs," in 2010 International Conference on Space Optics (ICSO) (2010), paper 39].

Calibration and Validation of Aqua AIRS and AMSU Measurements using COSMIC Global Positioning System Radio Occultation Observations

NASA Astrophysics Data System (ADS)

Ho, S. P.; Peng, L.

2015-12-01

On board NASA Aqua satellite, the hyper-spectral infrared sounding from Atmospheric Infrared Sounder (AIRS) is the first of a new generation of operational remote sensors for upwelling atmospheric emission that provide excellent temperature and water vapor retrievals at middle atmosphere, which has significant impacts on short-term numerical weather forecasts. Also on board NASA Aqua satellite, Advanced Microwave Sounding Unit (AMSU) measurements provide the all weather temperature and water vapor profiles which are used as the first guess for AIRS inversion algorithm. However, due to lack of absolute on orbit calibration, both AIRS and AMSU also exhibit biases in retrieving atmospheric temperatures and moistures when compared with in situ measurements. These retrieval biases have diverse and complex dependencies on the temperature/moisture being measured, the season and geographical location, surface conditions, and sensor temperature, which is difficult to quantify. The purpose of this study is to demonstrate the usefulness of Global Positioning System (GPS) Radio Occultation (RO) data to serve as a climate calibration observatory in orbit to calibrate and validate AIRS and AMSU measurements. In this study, we use COSMIC RO data to simulate AMSU and AIRS brightness temperatures for the lower stratosphere (TLS) and compare them to AMSU TLS and those of AIRS brightness temperatures at the same height. Our analysis shows that because RO data do not contain mission-dependent biases and orbit drift errors, and are not affected by on-orbit heating and cooling of the satellite component, they are very useful to identify the AMSU time/location dependent biases for different NOAA missions and possible long term drift of the AIRS retrieved temperatures.

Layer structure of the Venus daytime ionosphere from Venera-15,-16 radio occultation

NASA Astrophysics Data System (ADS)

Gavrik, Anatoly

Up to now more than five hundred radio occultation experiments had been carried out by different missions to research physical properties of the Venus ionosphere. The purpose of this report is to show new properties of the Venus daytime ionosphere reanalyzing Venera-15,-16 dual-frequency occultation data. The high coherence and stability of radio signals of Venera- 15,-16 at wave lengths 32 cm and 8 cm, along with the fact, that the refractive amplification at 32 cm in the ionosphere exceeds by factor 6 the refractive amplification at 13 cm used by others researches, have allowed to perform analysis of radiophysical parameters in the Venus ionosphere more accurate. Progress in the radiovision theory and up-to-date digital processing techniques have provided an opportunity to discover unknown layered structure of the Venus daytime ionosphere. We offer the new technique of the data analysis that allows us to separate influence of noise, ionosphere and atmosphere on the radio occultation results. We point out that significant gradient variations in the vertical distribution of the electron density are observed in the region of maximum electron density of the daytime ionosphere at altitudes of 150-175 km. That testifies layered structure of this part of the Venus ionosphere. The results of data analysis reveal the regular existence of the ionospheric layers in the bottom daytime ionosphere at altitudes from 80 up to 115 km. The bottom border of the ionosphere part can vary in the range of 80-100 km, and gradients of the electron density show strong variability. We detect the wave structure in the top atmosphere and in the bottom ionosphere at altitudes from 60 up to 115 km as well. It is difficult to obtain correct electron density in the region, where we have detected the new ionospheric layers. Relative errors of the electron density are greater than 100% at altitudes between 80 and 120 km. The bottom part of the ionosphere is more variable, than overlying area of

Simple, Accurate, Low-cost RO Science with the Iridium-NEXT Satellite Constellation

NASA Astrophysics Data System (ADS)

Meehan, T.; Mannucci, A. J.

2011-12-01

Over the last decade, a disparate collection of GNSS-RO instruments have been measuring the refractivity of the Earth's ionosphere and atmosphere. These measurements have proven to be robust and precise data sets for operational weather, climate and geospace sciences. Future GNSS-RO weather and science will most benefit from a large number of profiles (10000+/day), with lower latency and greater accuracy in the lowest 5 km altitude. For weather, latencies below 90 minutes are required, 30 minutes desired. Space weather latency requirements are more stringent, with 15 minutes being a long sought goal. Climate studies benefit from averaging measurements uniformly distributed over the Earth, acquired over decades, with local time sampling errors minimized by dense coverage or well designed orbits. There's much more of course, because space GNSS science is still nascent but with gathering momentum among the international community. Although individual GNSS-RO instruments are relatively cheap as space hardware goes, growing the measurement density can be costly when a dozen or more are required for a single program. In this presentation, we propose a novel technique for greatly reducing the cost of a constellation of GNSS-RO instruments and discuss the science trade-offs of this approach versus the more traditional GNSS-RO designs.

Occult pneumothorax in trauma patients: should this be sought in the focused assessment with sonography for trauma examination?

PubMed

Tam, Michael M K

2005-01-01

At present, CT scan is the gold standard for detecting occult traumatic pneumothorax not apparent on supine chest X-ray radiograph. Recently there were suggestions to expand focused assessment with sonography for trauma (FAST) to include thoracic ultrasound for detecting pneumothorax. The aim of the present study is to determine the incidence of occult pneumothorax (as shown by CT) in the subgroup of trauma patients undergoing FAST. Review of all trauma patients with FAST done from 1 June 2001 to 31 October 2002. Incidence of occult pneumothorax as diagnosed by CT was determined. Patients were not counted as having true occult pneumothorax if they had chest drains inserted before arrival or imaging studies. Selected clinical findings were tested for association with occult pneumothorax. In total, 143 patients underwent FAST, of whom 137 (95.8%) had chest X-ray examination performed. Of the 137 patients 59 required CT abdomen and/or thorax. Occult pneumothorax was found in three patients (2.1%). A history of thorax and/or abdominal injury plus one or more of: (i) mechanisms potentially causing major trauma; (ii) abnormal chest examination; and (iii) chest X-ray radiograph abnormality in the absence of pneumothorax, was significantly associated with the presence of occult pneumothorax (P = 0.03, Fisher's exact test; sensitivity: 100%; specificity: 71%; likelihood ratio: 3.42). The incidence of occult pneumothorax in the subgroup of trauma patients undergoing FAST is low. It implies that routine screening for its presence by adding thoracic ultrasound to FAST is unnecessary. Identifying those at risk of occult pneumothorax for further investigation appeared feasible.

Amplification and protein overexpression of cyclin D1: Predictor of occult nodal metastasis in early oral cancer.

PubMed

Noorlag, Rob; Boeve, Koos; Witjes, Max J H; Koole, Ronald; Peeters, Ton L M; Schuuring, Ed; Willems, Stefan M; van Es, Robert J J

2017-02-01

Accurate nodal staging is pivotal for treatment planning in early (stage I-II) oral cancer. Unfortunately, current imaging modalities lack sensitivity to detect occult nodal metastases. Chromosomal region 11q13, including genes CCND1, Fas-associated death domain (FADD), and CTTN, is often amplified in oral cancer with nodal metastases. However, evidence in predicting occult nodal metastases is limited. In 158 patients with early tongue and floor of mouth (FOM) squamous cell carcinomas, both CCND1 amplification and cyclin D1, FADD, and cortactin protein expression were correlated with occult nodal metastases. CCND1 amplification and cyclin D1 expression correlated with occult nodal metastases. Cyclin D1 expression was validated in an independent multicenter cohort, confirming the correlation with occult nodal metastases in early FOM cancers. Cyclin D1 is a predictive biomarker for occult nodal metastases in early FOM cancers. Prospective research on biopsy material should confirm these results before implementing its use in routine clinical practice. © 2016 Wiley Periodicals, Inc. Head Neck 39: 326-333, 2017. © 2016 Wiley Periodicals, Inc.

Early infection risk with primary versus staged Hemodialysis Reliable Outflow (HeRO) graft implantation.

PubMed

Griffin, Andrew S; Gage, Shawn M; Lawson, Jeffrey H; Kim, Charles Y

2017-01-01

This study evaluated whether the use of a staged Hemodialysis Reliable Outflow (HeRO; Merit Medical, South Jordan, Utah) implantation strategy incurs increased early infection risk compared with conventional primary HeRO implantation. A retrospective review was performed of 192 hemodialysis patients who underwent HeRO graft implantation: 105 patients underwent primary HeRO implantation in the operating room, and 87 underwent a staged implantation where a previously inserted tunneled central venous catheter was used for guidewire access for the venous outflow component. Within the staged implantation group, 32 were performed via an existing tunneled hemodialysis catheter (incidentally staged), and 55 were performed via a tunneled catheter inserted across a central venous occlusion in an interventional radiology suite specifically for HeRO implantation (intentionally staged). Early infection was defined as episodes of bacteremia or HeRO infection requiring resection ≤30 days of HeRO implantation. For staged HeRO implantations, the median interval between tunneled catheter insertion and conversion to a HeRO graft was 42 days. The overall HeRO-related infection rate ≤30 days of implantation was 8.6% for primary HeRO implantation and 2.3% for staged implantations (P = .12). The rates of early bacteremia and HeRO resection requiring surgical resection were not significantly different between groups (P = .19 and P = .065, respectively), nor were age, gender, laterality, anastomosis to an existing arteriovenous access, human immunodeficiency virus status, diabetes, steroids, chemotherapy, body mass index, or graft location. None of the patient variables, techniques, or graft-related variables correlated significantly with the early infection rate. The staged HeRO implantation strategy did not result in an increased early infection risk compared with conventional primary implantation and is thus a reasonable strategy for HeRO insertion in hemodialysis patients

Results from the 2010 Feb 14 and July 4 Pluto Occultations

NASA Astrophysics Data System (ADS)

Young, Leslie; Sicardy, B.; Widemann, T.; Brucker, M. J.; Buie, M. W.; Fraser, B.; Van Heerden, H.; Howell, R. R.; Lonergan, K.; Olkin, C. B.; Reitsema, H. J.; Richter, A.; Sepersky, T.; Wasserman, L. H.; Young, E. F.

2010-10-01

The Portable High-speed Occultation Telescope (PHOT) group observed two occultations by Pluto in 2010. The first, of a I=9.3 magnitudue star on 2010 Feb 14, was organized by the Meudon occultation group, with the PHOT group as collaborators. For this bright but low-elevation event, we deployed to three sites in Europe: Obs. Haute Provence, France (0.8-m; L. Young, H. Reitsema), Leopold Figl, Austria (1.5-m; E. Young), and Apline Astrovillage, Lu, Switzerland (0.36-m; C. Olkin, L. Wasserman). We obtained a lightcurve at Lu under clear conditions, which will be combined with two other lightcurves from the Meudon group, from Sisteron and Pic du Midi, France. We observed the second Pluto occultation, of a I=13.2 star on 2010 July 4 UT, from four sites in South Africa: with our portable telescope near Upington (0.36-m; M. Buie, L. Wasserman), the Boyden telescope in Bloemfontein (1.5-m; L. Young, M. Brucker), the Innes telescope in Johannesburg (0.67-m; T. Sepersky, B. Fraser), and the telescope at Aloe Ridge north of Johannesburg (0.62-m; R. Howell, K. Lonergan, A. Richter). Upington was cloudy, Boyden had heavy scattered clouds, and Innes suffered from haze and telescope mechanical problems. A lightcurve was obtained from Aloe Ridge under clear conditions. Data was also obtained by Karl-Ludwig Bath & Thomas Sauer at Hakos, Namibia and by Berto Monard of ASSA near Pretoria, South Africa. The length of the Aloe Ridge chord suggests it is nearly central. These observations give us four contiguous years in which we observed one or more Pluto occultations, providing constraints on the seasonal evolution of Pluto's atmosphere. Thanks are due to Marcelo Assafin and Jim Elliot for sharing predictions prior to the July event. This work was supported, in part, by NASA PAST NNX08A062G.

Association of maximum standardized uptake value with occult mediastinal lymph node metastases in cN0 non-small cell lung cancer.

PubMed

Lin, Jun-Tao; Yang, Xue-Ning; Zhong, Wen-Zhao; Liao, Ri-Qiang; Dong, Song; Nie, Qiang; Weng, Si-Xian; Fang, Xiao-Jing; Zheng, Jun-Yi; Wu, Yi-Long

2016-11-01

The management of non-small cell lung cancer (NSCLC) relies on the tumour-node-metastasis (TNM) stage, and the treatment regimen differs based on the N status. Positron emission tomography-computed tomography (PET-CT) has emerged as a powerful imaging tool for the detection of various cancers with a relatively low false-negative rate. We explored predictors to identify false-negative N2 disease in PET-CT. A total of 284 consecutive cN0 patients with peripheral NSCLC who underwent PET-CT scans followed by curative intent resections were enrolled as a training set to identify predictors of occult N2 metastases by multivariable analysis. The accuracy and cut-off values for the predictors were calculated using a receiver operating characteristic curve. Clinical and pathological data were analysed retrospectively. An additional 151 patients were collected as a test set to validate the results, including the occult N2 rate and accuracy. In total, 8.5% (24/284) PET-CT-diagnosed N0 NSCLC cases had pathologically diagnosed N2 metastases. The SUV max of the primary tumour was a unique independent risk factor for occult N2 NSCLC [P = 0.003, 95% confidence interval = 0.81-0.96, odds ratio (OR) = 0.88]. Occult N2 metastases occurred more frequently in the subcarinal (16/24) and right lower paratracheal lymph nodes (12/24). Accordingly, we divided the patients into two groups by SUV max : the occult N2 rates in the SUV max of <2.6 and SUV max of ≥2.6 groups were 1.0% (1/100) and 12.5% (23/184), respectively (P = 0.001). In the test set, the occult N2 incidence rate was 9.3% (14/151), with the highest rates occurring in the subcarinal (9/14) and right lower paratracheal lymph nodes (6/14). In the two groups defined by SUV max , the occult N2 rates were 4% (2/50) and 11.9% (12/101), respectively. The SUV max of the primary tumour was an independent risk factor for occult N2 metastases in NSCLC patients diagnosed as clinical N0 by PET-CT. SUV max of ≥2.6 of the primary tumour

Ultrasonography in diagnosing clinically occult groin hernia: systematic review and meta-analysis.

PubMed

Kwee, Robert M; Kwee, Thomas C

2018-05-14

To provide an updated systematic review on the performance of ultrasonography (US) in diagnosing clinically occult groin hernia. A systematic search was performed in MEDLINE and Embase. Methodological quality of included studies was assessed. Accuracy data of US in detecting clinically occult groin hernia were extracted. Positive predictive value (PPV) was pooled with a random effects model. For studies investigating the performance of US in hernia type classification (inguinal vs femoral), correctly classified proportion was assessed. Sixteen studies were included. In the two studies without verification bias, sensitivities were 29.4% [95% confidence interval (CI), 15.1-47.5%] and 90.9% (95% CI, 70.8-98.9%); specificities were 90.0% (95% CI, 80.5-95.9%) and 90.6% (95% CI, 83.0-95.6%). Verification bias or a variation of it (i.e. study limited to only subjects with definitive proof of disease status) was present in all other studies. Sensitivity, specificity, and negative predictive value (NPV) were not pooled. PPV ranged from 58.8 to 100%. Pooled PPV, based on data from ten studies with low risk of bias and no applicability concerns with respect to patient selection, was 85.6% (95% CI, 76.5-92.7%). Proportion of correctly classified hernias, based on data from four studies, ranged between 94.4% and 99.1%. Sensitivity, specificity and NPV of US in detecting clinically occult groin hernia cannot reliably be determined based on current evidence. Further studies are necessary. Accuracy may strongly depend on the examiner's skills. PPV is high. Inguinal and femoral hernias can reliably be differentiated by US. • Sensitivity, specificity and NPV of ultrasound in detecting clinically occult groin hernia cannot reliably be determined based on current evidence. • Accuracy may strongly depend on the examiner's skills. • PPV of US in detection of clinically occult groin hernia is high [pooled PPV of 85.6% (95% confidence interval, 76.5-92.7%)]. • US has very high

Occult Pelvic Lymph Node Involvement in Bladder Cancer: Implications for Definitive Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldsmith, Benjamin; Baumann, Brian C.; He, Jiwei

2014-03-01

Purpose: To inform radiation treatment planning for clinically staged, node-negative bladder cancer patients by identifying clinical factors associated with the presence and location of occult pathologic pelvic lymph nodes. Methods and Materials: The records of patients with clinically staged T1-T4N0 urothelial carcinoma of the bladder undergoing radical cystectomy and pelvic lymphadenectomy at a single institution were reviewed. Logistic regression was used to evaluate associations between preoperative clinical variables and occult pathologic pelvic or common iliac lymph nodes. Percentages of patient with involved lymph node regions entirely encompassed within whole bladder (perivesicular nodal region), small pelvic (perivesicular, obturator, internal iliac, andmore » external iliac nodal regions), and extended pelvic clinical target volume (CTV) (small pelvic CTV plus common iliac regions) were calculated. Results: Among 315 eligible patients, 81 (26%) were found to have involved pelvic lymph nodes at the time of surgery, with 38 (12%) having involved common iliac lymph nodes. Risk of occult pathologically involved lymph nodes did not vary with clinical T stage. On multivariate analysis, the presence of lymphovascular invasion (LVI) on preoperative biopsy was significantly associated with occult pelvic nodal involvement (odds ratio 3.740, 95% confidence interval 1.865-7.499, P<.001) and marginally associated with occult common iliac nodal involvement (odds ratio 2.307, 95% confidence interval 0.978-5.441, P=.056). The percentages of patients with involved lymph node regions entirely encompassed by whole bladder, small pelvic, and extended pelvic CTVs varied with clinical risk factors, ranging from 85.4%, 95.1%, and 100% in non-muscle-invasive patients to 44.7%, 71.1%, and 94.8% in patients with muscle-invasive disease and biopsy LVI. Conclusions: Occult pelvic lymph node rates are substantial for all clinical subgroups, especially patients with LVI on biopsy

Precise predictions of stellar occultations by Pluto, Charon, Nix, and Hydra for 2008-2015

NASA Astrophysics Data System (ADS)

Assafin, M.; Camargo, J. I. B.; Vieira Martins, R.; Andrei, A. H.; Sicardy, B.; Young, L.; da Silva Neto, D. N.; Braga-Ribas, F.

2010-06-01

Context. We investigate transneptunian objects, including Pluto and its satellites, by stellar occultations. Aims: Our aim is to derive precise, astrometric predictions for stellar occultations by Pluto and its satellites Charon, Hydra and Nix for 2008-2015. We construct an astrometric star catalog in the UCAC2 system covering Plutoarcmins sky path. Methods: We carried out in 2007 an observational program at the ESO2p2/WFI instrument covering the sky path of Pluto from 2008 to 2015. We made the astrometry of 110 GB of images with the Platform for Reduction of Astronomical Images Automatically (PRAIA). By relatively simple astrometric techniques, we treated the overlapping observations and derived a field distortion pattern for the WFI mosaic of CCDs to within 50 mas precision. Results: Positions were obtained in the UCAC2 frame with errors of 50 mas for stars up to magnitude R = 19, and 25 mas up to R = 17. New stellar proper motions were also determined with 2MASS and the USNO B1.0 catalog positions as first epoch. We generated 2252 predictions of stellar occultations by Pluto, Charon, Hydra and Nix for 2008-2015. An astrometric catalog with proper motions was produced, containing 2.24 million stars covering Plutoarcmins sky path with 30arcmin width. Its magnitude completeness is about R = 18-19 with a limit about R = 21. Based on the past 2005-2008 occultations successfully predicted, recorded and fitted, a linear drift with time in declination with regard to DE418/plu017 ephemerides was determined for Pluto and used in the current predictions. For offset (mas) = A * (t (yr) - 2005.0) + B, we find A = +30.5 ± 4.3 mas yr-1 and B = -31.5 ± 11.3 mas, with standard deviation of 14.4 mas for the offsets. For these past occultations, predictions and follow-up observations were made with the 0.6 m and 1.6 m telescopes at the Laboratório Nacional de Astrofísica/Brazil. Conclusions: Recurrent issues in stellar occultation predictions were addressed and properly

Finding Terrestrial Planets Using External Occulters

NASA Technical Reports Server (NTRS)

Heap, Sara

2007-01-01

In order to identify a detected exoplanet as an Earth-like (habitable) planet, we must obtain its spectrum to verify that its atmosphere shows evidence of water vapor. We argue that a regular, optical telescope combined with a large occulter to block light from the star offers the most promising, cost-effective way to detect and characterize exoplanets.

Software and hardware complex for observation of star occultations by asteroids

NASA Astrophysics Data System (ADS)

Karbovsky, V.; Kleshchonok, V.; Buromsky, M.

2017-12-01

The preparation to the program for observation of star occultations by asteroids on the AZT-2 telescope was started in 2016. A new method for registration of occultation with a CCD camera in the synchronous transfer mode was proposed and developed. The special program was written to control the CCD camera and record images during such observations. The speed of image transfer can vary within wide limits, which makes it possible to carry out observations in a wide range of stellar magnitudes. The telescope AZT-2 is used, which has the largest mirror diameter in Kiev (D = 0.7 m. F = 10.5 m). A 3-fold optical reducer was produced, which providing a field of view with a CCD camera Apogee Alta U47 10 arcminutes and the equivalent focal length of the telescope 3.2 meters. The results of test observations are presented. The program is implemented jointly by the Main Astronomical Observatory of the National Academy of Sciences of Ukraine and the Astronomical Observatory of the Taras Shevchenko National University of Kyiv. Regular observations of star occultation by asteroids are planned with the help of this complex. % Z https://occultations.org Kleshchonok,V.V.,Buromsky,M. I. 2005, Kinematics and Physics of Celestial Bodies, 21, 5, 405 Kleshchonok, V.V., Buromskii, N. I., Khat’ko,I.V.2008, Kinematics and Physics of Celestial Bodies, 24, 2, 114

Occult Hepatitis B Virus Among the Patients With Abnormal Alanine Transaminase

PubMed Central

Makvandi, Manoochehr; Neisi, Niloofar; Khalafkhany, Davod; Makvandi, Kamyar; Hajiani, Eskandar; Shayesteh, Ali Akbar; Masjedi Zadeh, Abdolrahim; Sina, Amir Hosein; Hamidifard, Mojtaba; Rasti, Mojtaba; Aryan, Ehsan; Ahmadi, Kambiz; Yad Yad, Mohammad Jafar

2014-01-01

Background: The occult hepatitis B infection (OBI) is defined as the presence of hepatitis B virus (HBV) DNA in the sera or in the liver biopsy and the absence of hepatitis B surface antigen (HBsAg) by serological test. Objectives: The current study aimed to evaluate the occult HBV infection by polymerase chain reaction (PCR) and determine HBV genotyping among the patients with abnormal alanine transaminase (ALT) in Ahvaz city, Iran. Patients and Methods: The sera of 120 patients, 54 (45%) females and 66 (55%) males, with abnormal ALT 40-152 IU were collected. All the patients were negative for HBsAg for more than one year. The patients` sera were tested by PCR using primers specified for the S region of HBV. Then the positive PCR products were sequenced to determine HBV genotyping and phylogenic tree. Results: Of these 120 subjects, 12 (10%) patients including 6 (5%) males and 6 (5%) females were found positive for HBV DNA by PCR, which indicated the presence of occult HBV infection among these patients. The sequencing results revealed that genotype D was predominant with sub-genotyping D1 among OBI patients. Conclusions: Occult hepatitis B infection is remarkably prevalent in Ahvaz, Iran, and should be considered as a potential risk factor for the transmission of Hepatitis B Virus throughout the community by the carriers. PMID:25485052

Outcome of Concurrent Occult Hemothorax and Pneumothorax in Trauma Patients Who Required Assisted Ventilation

PubMed Central

Mahmood, Ismail; Tawfeek, Zainab; El-Menyar, Ayman; Zarour, Ahmad; Afifi, Ibrahim; Kumar, Suresh; Latifi, Rifat; Al-Thani, Hassan

2015-01-01

Background. The management and outcomes of occult hemopneumothorax in blunt trauma patients who required mechanical ventilation are not well studied. We aimed to study patients with occult hemopneumothorax on mechanical ventilation who could be carefully managed without tube thoracostomy. Methods. Chest trauma patients with occult hemopneumothorax who were on mechanical ventilation were prospectively evaluated. The presence of hemopneumothorax was confirmed by CT scanning. Hospital length of stay, complications, and outcome were recorded. Results. A total of 56 chest trauma patients with occult hemopneumothorax who were on ventilatory support were included with a mean age of 36 ± 13 years. Hemopneumothorax was managed conservatively in 72% cases and 28% underwent tube thoracostomy as indicated. 29% of patients developed pneumonia, 16% had Acute Respiratory Distress Syndrome (ARDS), and 7% died. Thickness of hemothorax, duration of mechanical ventilation, and development of ARDS were significantly associated with tube thoracostomy in comparison to no-chest tube group. Conclusions. The majority of occult hemopneumothorax can be carefully managed without tube thoracostomy in patients who required positive pressure ventilation. Tube thoracotomy could be restricted to those who had evidence of increase in the size of the hemothorax or pneumothorax on follow-up chest radiographs or developed respiratory compromise. PMID:25785199

The Structure of Titan's Atmosphere from Cassini Radio Occultations

NASA Technical Reports Server (NTRS)

Schinder, Paul J.; Flasar, F. Michael; Marouf, Essam A.; French, Richard G.; McGhee, Colleen A.; Kliore, Arvydas J.; Rappaport, Nicole J.; Barbinis, Elias; Fleischman, Don; Anabtawi, Aseel

2011-01-01

We present results from the two radio occultations of the Cassini spacecraft by Titan in 2006, which probed mid-southern latitudes. Three of the ingress and egress soundings occurred within a narrow latitude range, 31.34 deg S near the surface, and the fourth at 52.8 deg S. Temperature - altitude profiles for all four occultation soundings are presented, and compared with the results of the Voyager 1 radio occultation (Lindal et al., 1983), the HASI instrument on the Huygens descent probe (Fulchignoni et al., 2005), and Cassini CIRS results (Flasar et al., 2005; Achterberg et al., 2008b). Sources of error in the retrieved temperature - altitude profiles are also discussed, and a major contribution is from spacecraft velocity errors in the reconstructed ephemeris. These can be reduced by using CIRS data at 300 km to make along-track adjustments of the spacecraft timing. The occultation soundings indicate that the temperatures just above the surface at 31-34 deg S are about 93 K, while that at 53 deg S is about 1 K colder. At the tropopause, the temperatures at the lower latitudes are all about 70 K, while the 53 deg S profile is again 1 K colder. The temperature lapse rate in the lowest 2 km for the two ingress (dawn) profiles at 31 and 33 deg S lie along a dry adiabat except within approximately 200m of the surface, where a small stable inversion occurs. This could be explained by turbulent mixing with low viscosity near the surface. The egress profile near 34 deg S shows a more complex structure in the lowest 2 km, while the egress profile at 53 deg S is more stable.

The complete set of Cassini's UVIS occultation observations of Enceladus plume: model fits

NASA Astrophysics Data System (ADS)

Portyankina, G.; Esposito, L. W.; Hansen, C. J.

2017-12-01

Since the discovery in 2005, plume of Enceladus was observed by most of the instruments onboard Cassini spacecraft. Ultraviolet Imaging Spectrograph (UVIS) have observed Enceladus plume and collimated jets embedded in it in occultational geometry on 6 different occasions. We have constructed a 3D direct simulation Monte Carlo (DSMC) model for Enceladus jets and apply it to the analysis of the full set of UVIS occultation observations conducted during Cassini's mission from 2005 to 2017. The Monte Carlo model tracks test particles from their source at the surface into space. The initial positions of all test particles for a single jet are fixed to one of 100 jets sources identified by Porco et al. (2014). The initial three-dimensional velocity of each particle contains two components: a velocity Vz which is perpendicular to the surface, and a thermal velocity which is isotropic in the upward hemisphere. The direction and speed of the thermal velocity of each particle is chosen randomly but the ensemble moves isotropically at a speed which satisfies a Boltzmann distribution for a given temperature Tth. A range for reasonable Vz is then determined by requiring that modeled jet widths match the observed ones. Each model run results in a set of coordinates and velocities of a given set of test particles. These are converted to the test particle number densities and then integrated along LoS for each time step of the occultation observation. The geometry of the observation is calculated using SPICE. The overarching result of the simulation run is a test particle number density along LoS for each time point during the occultation observation for each of the jets separately. To fit the model to the data, we integrate all jets that are crossed by the LoS at each point during an observation. The relative strength of the jets must be determined to fit the observed UVIS curves. The results of the fits are sets of active jets for each occultation. Each UVIS occultation

Rapid-Adiabatic Control of Ro-Vibrational Populations in Polyatomic Molecules

NASA Astrophysics Data System (ADS)

Zak, Emil J.; Yachmenev, Andrey

2017-06-01

We present a simple method for control of ro-vibrational populations in polyatomic molecules in the presence of inhomogeneous electric fields [1]. Cooling and trapping of heavy polar polyatomic molecules has become one of the frontier goals in high-resolution molecular spectroscopy, especially in the context of parity violation measurement in chiral compounds [2]. A key step toward reaching this goal would be development of a robust and efficient protocol for control of populations of ro-vibrational states in polyatomic, often floppy molecules. Here we demonstrate a modification of the stark-chirped rapid-adiabatic-passage technique (SCRAP) [3], designed for achieving high levels of control of ro-vibrational populations over a selected region in space. The new method employs inhomogeneous electric fields to generate space- and time- controlled Stark-shifts of energy levels in molecules. Adiabatic passage between ro-vibrational states is enabled by the pump pulse, which raises the value of the Rabi frequency. This Stark-chirped population transfer can be used in manipulation of population differences between high-field-seeking and low-field-seeking states of molecules in the Stark decelerator [4]. Appropriate timing of voltages on electric rods located along the decelerator combined with a single pump laser renders our method as potentially more efficient than traditional Stark decelerator techniques. Simulations for NH_3 show significant improvement in effectiveness of cooling, with respect to the standard 'moving-potential' method [5]. At the same time a high phase-space acceptance of the molecular packet is maintained. E. J. Zak, A. Yachmenev (submitted). C. Medcraft, R. Wolf, M. Schnell, Angew. Chem. Int. Ed., 53, 43, 11656-11659 (2014) M. Oberst, H. Munch, T. Halfman, PRL 99, 173001 (2007). K. Wohlfart, F. Grätz, F. Filsinger, H. Haak, G. Meijer, J. Küpper, Phys. Rev. A 77, 031404(R) (2008). H. L. Bethlem, F. M. H. Crompvoets, R. T. Jongma, S. Y. T. van de

Results of two multichord stellar occultations by dwarf planet (1) Ceres

NASA Astrophysics Data System (ADS)

Gomes-Júnior, A. R.; Giacchini, B. L.; Braga-Ribas, F.; Assafin, M.; Vieira-Martins, R.; Camargo, J. I. B.; Sicardy, B.; Timerson, B.; George, T.; Broughton, J.; Blank, T.; Benedetti-Rossi, G.; Brooks, J.; Dantowitz, R. F.; Dunham, D. W.; Dunham, J. B.; Ellington, C. K.; Emilio, M.; Herpich, F. R.; Jacques, C.; Maley, P. D.; Mehret, L.; Mello, A. J. T.; Milone, A. C.; Pimentel, E.; Schoenell, W.; Weber, N. S.

2015-08-01

We report the results of two multichord stellar occultations by the dwarf planet (1) Ceres that were observed from Brazil on 2010 August 17, and from the USA on 2013 October 25. Four positive detections were obtained for the 2010 occultation, and nine for the 2013 occultation. Elliptical models were adjusted to the observed chords to obtain Ceres' size and shape. Two limb-fitting solutions were studied for each event. The first one is a nominal solution with an indeterminate polar aspect angle. The second one was constrained by the pole coordinates as given by Drummond et al. Assuming a Maclaurin spheroid, we determine an equatorial diameter of 972 ± 6 km and an apparent oblateness of 0.08 ± 0.03 as our best solution. These results are compared to all available size and shape determinations for Ceres made so far, and shall be confirmed by the NASA's Dawn space mission.

Clinical management of occult hemothorax: a prospective study of 81 patients.

PubMed

Mahmood, Ismail; Abdelrahman, Husham; Al-Hassani, Ammar; Nabir, Syed; Sebastian, Mark; Maull, Kimball

2011-06-01

Intrapleural blood detected by computed tomography scan, but not evident on plain chest radiograph, defines occult hemothorax. This study determined the role for tube thoracostomy. Hemothorax was quantified on computed tomography by measuring the deepest lamellar fluid stripe at the most dependent portion. Data were collected prospectively on demographics, injury mechanism/severity, chest injuries, mechanical ventilation, hospital length of stay, complications, and outcome. Indications for tube thoracostomy were recorded. Tube thoracostomy was avoided in 67 patients (83%). Indications for chest tube placement included progression of hemothorax (8), desaturation (4), and delayed hemothorax (2). Patients with intrapleural fluid thickness greater than 1.5 cm were 4 times more likely to require tube thoracostomy. Occult hemothorax can be managed successfully without tube thoracostomy in most cases. Mechanical ventilation is not an indication for chest tube placement. Accompanying occult pneumothorax may be expected in 50% of cases, but did not affect clinical management. Copyright © 2011 Elsevier Inc. All rights reserved.

IRTF observations of the occultation of 28 Sgr by Saturn

NASA Technical Reports Server (NTRS)

Harrington, Joseph; Cooke, Maren L.; Forrest, William J.; Pipher, Judith L.; Dunham, Edward W.; Elliot, J. L.

1993-01-01

NASA's Mauna Kea IR Telescope Facility obtained an IR-imaging time series for the July 3, 1989 occultation of 28 Sgr by Saturn and its rings; the stellar signal is present in these images throughout the ring occultation event. These data are noted to vary systematically with respect to the Voyager data over large radius scales, perhaps due to stellar signal diffraction through the rings. The stellar diameter, which is projected to be about 20 km, placed most bending- and density-wave trains below measurable resolution. Masses and mean optical depths are presented for individual ring sections.

Boundary Layer Remote Sensing with Combined Active and Passive Techniques: GPS Radio Occultation and High-Resolution Stereo Imaging (WindCam) Small Satellite Concept

NASA Technical Reports Server (NTRS)

Mannucci, A.J.; Wu, D.L.; Teixeira, J.; Ao, C.O.; Xie, F.; Diner, D.J.; Wood, R.; Turk, Joe

2012-01-01

Objective: significant progress in understanding low-cloud boundary layer processes. This is the Single largest uncertainty in climate projections. Radio occultation has unique features suited to boundary layer remote sensing (1) Cloud penetrating (2) Very high vertical resolution (approximately 50m-100m) (3) Sensitivity to thermodynamic variables

Cassini UVIS solar occultations by Saturn's F ring and the detection of collision-produced micron-sized dust

NASA Astrophysics Data System (ADS)

Becker, Tracy M.; Colwell, Joshua E.; Esposito, Larry W.; Attree, Nicholas O.; Murray, Carl D.

2018-05-01

We present an analysis of eleven solar occultations by Saturn's F ring observed by the Ultraviolet Imaging Spectrograph (UVIS) on the Cassini spacecraft. In four of the solar occultations we detect an unambiguous signal from diffracted sunlight that adds to the direct solar signal just before or after the occultations occur. The strongest detection was a 10% increase over the direct signal that was enabled by the accidental misalignment of the instrument's pointing. We compare the UVIS data with images of the F ring obtained by the Cassini Imaging Science Subsystem (ISS) and find that in each instance of an unambiguous diffraction signature in the UVIS data, the ISS data shows that there was a recent disturbance in that region of the F ring. Similarly, the ISS images show a quiescent region of the F ring for all solar occultations in which no diffraction signature was detected. We therefore conclude that collisions in the F ring produce a population of small ring particles that can produce a detectable diffraction signal immediately interior or exterior to the F ring. The clearest example of this connection comes from the strong detection of diffracted light in the 2007 solar occultation, when the portion of the F ring that occulted the Sun had suffered a large collisional event, likely with S/2004 S 6, several months prior. This collision was observed in a series of ISS images (Murray et al., 2008). Our spectral analysis of the data shows no significant spectral features in the F ring, indicating that the particles must be at least 0.2 μm in radius. We apply a forward model of the solar occultations, accounting for the effects of diffracted light and the attenuated direct solar signal, to model the observed solar occultation light curves. These models constrain the optical depth, radial width, and particle size distribution of the F ring. We find that when the diffraction signature is present, we can best reproduce the occultation data using a particle population

Comparisons of the tropospheric specific humidity from GPS radio occultations with ERA-Interim, NASA MERRA, and AIRS data

NASA Astrophysics Data System (ADS)

Vergados, Panagiotis; Mannucci, Anthony J.; Ao, Chi O.; Verkhoglyadova, Olga; Iijima, Byron

2018-03-01

We construct a 9-year data record (2007-2015) of the tropospheric specific humidity using Global Positioning System radio occultation (GPS RO) observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission. This record covers the ±40° latitude belt and includes estimates of the zonally averaged monthly mean specific humidity from 700 up to 400 hPa. It includes three major climate zones: (a) the deep tropics (±15°), (b) the trade winds belts (±15-30°), and (c) the subtropics (±30-40°). We find that the RO observations agree very well with the European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim), the Modern-Era Retrospective Analysis for Research and Applications (MERRA), and the Atmospheric Infrared Sounder (AIRS) by capturing similar magnitudes and patterns of variability in the monthly zonal mean specific humidity and interannual anomaly over annual and interannual timescales. The JPL and UCAR specific humidity climatologies differ by less than 15 % (depending on location and pressure level), primarily due to differences in the retrieved refractivity. In the middle-to-upper troposphere, in all climate zones, JPL is the wettest of all data sets, AIRS is the driest of all data sets, and UCAR, ERA-Interim, and MERRA are in very good agreement, lying between the JPL and AIRS climatologies. In the lower-to-middle troposphere, we present a complex behavior of discrepancies, and we speculate that this might be due to convection and entrainment. Conclusively, the RO observations could potentially be used as a climate variable, but more thorough analysis is required to assess the structural uncertainty between centers and its origin.

Application of the Langley plot for calibration of sun sensors for the Halogen Occultation Experiment (HALOE)

NASA Technical Reports Server (NTRS)

Moore, Alvah S., Jr.; Mauldin, L. ED, III; Stump, Charles W.; Reagan, John A.; Fabert, Milton G.

1989-01-01

The calibration of the Halogen Occultation Experiment (HALOE) sun sensor is described. This system consists of two energy-balancing silicon detectors which provide coarse azimuth and elevation control signals and a silicon photodiode array which provides top and bottom solar edge data for fine elevation control. All three detectors were calibrated on a mountaintop near Tucson, Ariz., using the Langley plot technique. The conventional Langley plot technique was modified to allow calibration of the two coarse detectors, which operate wideband. A brief description of the test setup is given. The HALOE instrument is a gas correlation radiometer that is now being developed for the Upper Atmospheric Research Satellite.

[Prevalence of occult hepatitis B virus infection and its phylogenetic features among mother-teenager pairs].

PubMed

Dong, Xiao-lian; Yao, Qing-qing; Wang, Xue-cai; Xu, Hai-tao; Wang, Xiao-li; Chen, Sheng-yu; Tang, Zhi-feng; Zheng, Ying-Jie

2013-03-01

Prevalence of occult hepatitis B virus (HBV) infection (OBI) was investigated in a paired mother-teenager population and HBV S gene variation including overt and occult HBV, was determined. A follow-up study based on an initial survey of 135 mother-teenager pairs was carried out through collection of questionnaires and blood samples HBsAg were detected by ELISA method, viral load by PCR amplification and HBV S gene by phylogenetic analysis. 102 pairs of subjects were followed-up. Blood samples from 94 mothers and 101 children were collected. OBI prevalence in mothers was 10.0% (6/60), significantly higher than 2.0% (2/101) in teenagers. Medians of viral load were 399.9 IU/ml and 247.6 IU/ml in overt and occult HBV strains, but without significant difference. 1 occult HBV strain belonged to genotype B with serotype adw while the other 7 were genotype C with serotype adr. 15 of the overt HBV strains belonged to genotype B with serotype adw and the other 8 were genotype C with serotype adr. Proportions of genotype-C strains were significantly higher in occult HBV strains than in overt HBV strains. OBI was seen in teenage-mother population.

Ground-based photometric support for the CoRoT mission by the CoRoT-Hungarian Asteroseismology Group

NASA Astrophysics Data System (ADS)

Bognár, Zs.; Paparó, M.

2012-12-01

The CoRoT-Hungarian Asteroseismology Group was established in 2005 and joined the preparatory work of the CoRoT Mission via an ESA PECS project. After the successful launch of the telescope, we have continued our work of ground-based multi-colour photometric observations and contributed to the analyses of CoRoT data. Our observations were focused on δ Scuti, γ Doradus, and RR Lyrae stars. The follow-up of some selected targets' pulsations in different wavelengths has provided valuable information for mode identification. We provided additional support by the confirmation of relatively faint variables' spectral types. We proved that our ground-based observations can help in the interpretation of a target with a contaminated CoRoT light curve. In this paper, we summarize our most important results of the photometric support for the CoRoT Mission. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

[Results of conservative treatment in patients with occult pneumothorax].

PubMed

Llaquet Bayo, Heura; Montmany Vioque, Sandra; Rebasa, Pere; Navarro Soto, Salvador

2016-04-01

An occult pneumothorax is found in 2-15% trauma patients. Observation (without tube thoracostomy) in these patients presents still some controversies in the clinical practice. The objective of the study is to evaluate the efficacy and the adverse effects when observation is performed. A retrospective observational study was undertaken in our center (university hospital level II). Data was obtained from a database with prospective registration. A total of 1087 trauma patients admitted in the intensive care unit from 2006 to 2013 were included. In this period, 126 patients with occult pneumothorax were identified, 73 patients (58%) underwent immediate tube thoracostomy and 53 patients (42%) were observed. Nine patients (12%) failed observation and required tube thoracostomy for pneumothorax progression or hemothorax. No patient developed a tension pneumothorax or experienced another adverse event related to the absence of tube thoracostomy. Of the observed patients 16 were under positive pressure ventilation, in this group 3 patients (19%) failed observation. There were no differences in mortality, hospital length of stay or intensive care length of stay between the observed and non-observed group. Observation is a safe treatment in occult pneumothorax, even in pressure positive ventilated patients. Copyright © 2014 AEC. Publicado por Elsevier España, S.L.U. All rights reserved.

Regional 3-D ionospheric electron density specification on the basis of data assimilation of ground-based GNSS and radio occultation data

NASA Astrophysics Data System (ADS)

Aa, Ercha; Liu, Siqing; Huang, Wengeng; Shi, Liqin; Gong, Jiancun; Chen, Yanhong; Shen, Hua; Li, Jianyong

2016-06-01

In this paper, a regional 3-D ionospheric electron density specification over China and adjacent areas (70°E-140°E in longitude, 15°N-55°N in latitude, and 100-900 km in altitude) is developed on the basis of data assimilation technique. The International Reference Ionosphere (IRI) is used as a background model, and a three-dimensional variational technique is used to assimilate both the ground-based Global Navigation Satellite System (GNSS) observations from the Crustal Movement Observation Network of China (CMONOC) and International GNSS Service (IGS) and the ionospheric radio occultation (RO) data from FORMOSAT-3/COSMIC (F3/C) satellites. The regional 3-D gridded ionospheric electron densities can be generated with temporal resolution of 5 min in universal time, horizontal resolution of 2° × 2° in latitude and longitude, and vertical resolution of 20 km between 100 and 500 km and 50 km between 500 and 900 km. The data assimilation results are validated through extensive comparison with several sources of electron density information, including (1) ionospheric total electron content (TEC); (2) Abel-retrieved F3/C electron density profiles (EDPs); (3) ionosonde foF2 and bottomside EDPs; and (4) the Utah State University Global Assimilation of Ionospheric Measurements (USU-GAIM) under both geomagnetic quiet and disturbed conditions. The validation results show that the data assimilation procedure pushes the climatological IRI model toward the observation, and a general accuracy improvement of 15-30% can be expected. Thecomparisons also indicate that the data assimilation results are more close to the Center for Orbit Determination of Europe (CODE) TEC and Madrigal TEC products than USU-GAIM. These initial results might demonstrate the effectiveness of the data assimilation technique in improving specification of local ionospheric morphology.

A 2017 stellar occultation by Orcus/Vanth

NASA Astrophysics Data System (ADS)

Sickafoose, Amanda A.; Bosh, Amanda S.; Levine, Stephen; Zuluaga, Carlos A.; Genade, Anja; Schindler, Karsten; Lister, Tim; Person, Michael J.

2017-10-01

(90482) Orcus is a large trans-Neptunian object (TNO) of diameter ~900 km, located in the 3:2 orbital resonance with Neptune. This plutino has a satellite, Vanth, approximately 280 km in diameter. Vanth orbits roughly 9000 km from Orcus in a ~9.5-day period. This system is particularly interesting, as Orcus falls between the small, spectrally-bland TNOs and the large TNOs having spectra rich in volatile features, while Vanth might have resulted from either collision or capture.A stellar occultation by Orcus was predicted to occur on 07 March 2017. Observations were made from five sites: the 0.6-m Astronomical Telescope of the University of Stuttgart (ATUS) at Sierra Remote Observatories (SRO), California; Las Cumbres Observatory’s 1-m telescope (ELP) at McDonald Observatory, Fort Davis, Texas; NASA’s 3-m InfraRed Telescope Facility (IRTF) on Mauna Kea, Hawaii; the 4.1-m Southern Astrophysical Research telescope (SOAR) on Cerro Pachón, Chile; and the 0.6-m Southeastern Association for Research in Astronomy telescope (SARA-CT) at Cerro Tololo, Chile. High-speed, visible-wavelength images were taken at all sites, in addition to simultaneous K-band images at the IRTF. A solid-body occultation was observed at both ELP and the IRTF. Offset midtimes and incompatible light ratios suggest that two different stars were occulted by two different bodies, likely Orcus and Vanth. See Bosh et al. this conference for details of the astrometry for the event. Here, we present results from the observations, including light curves, size and albedo estimates, and upper limits on a possible atmosphere.

[Prediction of occult carcinoma in contralateral nodules based on the ultrasonic features of unilateral papillary thyroid carcinoma].

PubMed

Yang, L M; Li, Q; Zhao, B W; Lyu, J G; Xu, H S; Xu, L L; Li, S Y; Gao, L; Zhu, J

2017-04-07

Objective: To investigate the occurrence of occult carcinoma in contralateral lobes based on the ultrasonic features of unilateral papillary thyroid carcinoma. Methods: The study included 202 consecutives cases of unilateral papillary thyroid carcinoma with benign nodules in the contralateral lobe identified by preoperative ultrasound or fine-needle aspiration from June 2014 to December 2015. All patients received total thyroidectomies, and with postoperative pathological examination they were divided into two groups, one including 60 cases with positive occult cancer and another one consisting of 142 cases with negative occult cancer. Univariate and multivariate analyses were performed to analyze the sonographic features of unilateral papillary thyroid carcinoma relevant to the occurrence of occult carcinoma in the contralateral nodules. Results: Univariate analysis indicated occult carcinoma in the contralateral lobes was associated with Hashimoto's thyroiditis(χ(2)=3.955, P =0.047), unclear border (χ(2)=4.375, P =0.036)and multifocality in the ipsilateral(χ(2)=7.375, P =0.007), but not with tumors maximum size, location, A/T, shape, internal structure, internal echo, acoustic halo, calcification, capsular invasion and blood flow signal in the lobe with carcinoma on another side. Multivariate analysis showed unclear border ( OR =2.727, P =0.010) and multifocality in the ipsilateral( OR =2.807, P =0.005)of carcinoma were independent predictive factor for contralateral occult PTC. Conclusions: Unclear border and multifocality of PTC in the ipsilateral were closely relevant to the occurrence of occult carcinoma in the contralateral nodules.

Prediction of occult hepatitis B virus infection in liver transplant donors through hepatitis B virus blood markers.

PubMed

Tandoi, Francesco; Caviglia, Gian Paolo; Pittaluga, Fabrizia; Abate, Maria Lorena; Smedile, Antonina; Romagnoli, Renato; Salizzoni, Mauro

2014-11-01

Occult hepatitis B virus infection is defined as detectable HBV-DNA in liver of HBsAg-negative individuals, with or without detectable serum HBV-DNA. In deceased liver donors, results of tissue analysis cannot be obtained prior to allocation for liver transplantation. we investigated prevalence and predictability of occult hepatitis B using blood markers of viral exposure/infection in deceased liver donors. In 50 consecutive HBsAg-negative/anti-HBc-positive and 20 age-matched HBsAg-negative/anti-HBc-negative donors, a nested-PCR assay was employed in liver biopsies for diagnosis of occult hepatitis B according to Taormina criteria. All donors were characterized for plasma HBV-DNA and serum anti-HBs/anti-HBe. In liver tissue, occult hepatitis B was present in 30/50 anti-HBc-positive (60%) and in 0/20 anti-HBc-negative donors (p<0.0001). All anti-HBc-positive donors with detectable HBV-DNA in plasma (n=5) or anti-HBs>1,000 mIU/mL (n=5) eventually showed occult infection, i.e, 10/30 occult hepatitis B-positive donors which could have been identified prior to transplantation. In the remaining 40 anti-HBc-positive donors, probability of occult infection was 62% for anti-HBe-positive and/or anti-HBs ≥ 58 mIU/mL; 29% for anti-HBe-negative and anti-HBs<58 mIU/mL. In deceased donors, combining anti-HBc with other blood markers of hepatitis B exposure/infection allows to predict occult hepatitis B with certainty and speed in one third of cases. These findings might help refine the allocation of livers from anti-HBc-positive donors. Copyright © 2014 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

IgV peptide mapping of native Ro60 autoantibody proteomes in primary Sjögren's syndrome reveals molecular markers of Ro/La diversification.

PubMed

Wang, Jing J; Al Kindi, Mahmood A; Colella, Alex D; Dykes, Lukah; Jackson, Michael W; Chataway, Tim K; Reed, Joanne H; Gordon, Tom P

2016-12-01

We have used high-resolution mass spectrometry to sequence precipitating anti-Ro60 proteomes from sera of patients with primary Sjögren's syndrome and compare immunoglobulin variable-region (IgV) peptide signatures in Ro/La autoantibody subsets. Anti-Ro60 were purified by elution from native Ro60-coated ELISA plates and subjected to combined de novo amino acid sequencing and database matching. Monospecific anti-Ro60 Igs comprised dominant public and minor private sets of IgG1 kappa and lambda restricted heavy and light chains. Specific IgV amino acid substitutions stratified anti-Ro60 from anti-Ro60/La responses, providing a molecular fingerprint of Ro60/La determinant spreading and suggesting that different forms of Ro60 antigen drive these responses. Sequencing of linked anti-Ro52 proteomes from individual patients and comparison with their anti-Ro60 partners revealed sharing of a dominant IGHV3-23/IGKV3-20 paired clonotype but with divergent IgV mutational signatures. In summary, anti-Ro60 IgV peptide mapping provides insights into Ro/La autoantibody diversification and reveals serum-based molecular markers of humoral Ro60 autoimmunity. Copyright © 2016 Elsevier Inc. All rights reserved.

Functional analysis of 'a' determinant mutations associated with occult HBV in HIV-positive South Africans.

PubMed

Powell, Eleanor A; Boyce, Ceejay L; Gededzha, Maemu P; Selabe, Selokela G; Mphahlele, M Jeffrey; Blackard, Jason T

2016-07-01

Occult hepatitis B is defined by the presence of hepatitis B virus (HBV) DNA in the absence of hepatitis B surface antigen (HBsAg). Occult HBV is associated with the development of hepatocellular carcinoma, reactivation during immune suppression, and virus transmission. Viral mutations contribute significantly to the occult HBV phenotype. Mutations in the 'a' determinant of HBsAg are of particular interest, as these mutations are associated with immune escape, vaccine escape and diagnostic failure. We examined the effects of selected occult HBV-associated mutations identified in a population of HIV-positive South Africans on HBsAg production in vitro. Mutations were inserted into two different chronic HBV backbones and transfected into a hepatocyte-derived cell line. HBsAg levels were quantified by enzyme-linked immunosorbent assay (ELISA), while the detectability of mutant HBsAg was determined using an HA-tagged HBsAg expression system. Of the seven mutations analysed, four (S132P, C138Y, N146D and C147Y) resulted in decreased HBsAg expression in one viral background but not in the second viral background. One mutation (N146D) led to a decrease in HBsAg detected as compared to HA-tag, indicating that this mutation compromises the ability of the ELISA to detect HBsAg. The contribution of occult-associated mutations to the HBsAg-negative phenotype of occult HBV cannot be determined adequately by testing the effect of the mutation in a single viral background, and rigorous analysis of these mutations is required.

Occult hepatitis B virus infection of hemodialysis patients: a cross-sectional study in a hepatitis B virus-endemic region.

PubMed

Kim, So Mi; Kim, Hyun Woo; Lee, Ji Eun; Lee, Eun Kyoung; Shin, Hyun Deok; Song, Il Han

2015-01-01

Occult hepatitis B virus (HBV) infection is defined as the presence of HBV DNA in the liver tissue and/or serum of subjects seronegative for hepatitis B surface antigen (HBsAg). Occult HBV infection of hemodialysis (HD) patients is informative in terms of virus transmission, reactivation after kidney transplantation, and the progression of liver disease. However, there is little detailed information about occult HBV infection in the context of virus endemicity. We tried to investigate the seroprevalence and clinical features of occult HBV infection in HD patients in HBV-endemic regions. We enrolled a total of 159 HD patients and 121 apparently healthy subjects at Dankook University Hospital and Jeju National University Hospital in Korea. HBsAg, anti-HBs, anti-HBc, and anti-hepatitis C virus (HCV) antibody levels were measured by radioimmunoassay. Serum levels of HBV DNA were measured by real-time polymerase chain reaction. The seroprevalence of occult HBV infection was 1.3% in HD patients and 2.5% in the healthy controls. This difference was not significant. The HBV load in all subjects with occult infection was <116 copies/mL, and all were positive for IgG anti-HBc, regardless of the presence of anti-HBs. None of the occult HBV-infected subjects were co-infected with HCV. One of the 2 HD patients with occult HBV infection had no history of blood transfusion. In this HBV-endemic region, the seroprevalence of occult HBV infection in HD patients with a very low viral load was not significantly different from that in apparently healthy subjects. © 2014 International Society for Hemodialysis.

Occultation and Triangulation Camera (OcTriCam) Cubesat

NASA Astrophysics Data System (ADS)

Batchelor, D. A.

2018-02-01

A camera at Earth-Moon L2 would provide a 240,000 km triangulation baseline to augment near-Earth object observations with Earth-based telescopes such as Pan-STARRS, and planetary occultation research to refine ephemerides and probe ring systems.

Treatment for occult hepatocellular carcinoma: does it offer survival advantages over symptom-driven treatment?

PubMed

Kim, Kwang Min; Kim, Jiyu; Sinn, Dong Hyun; Kim, Hye Seung; Kim, Kyunga; Kang, Wonseok; Gwak, Geum-Youn; Paik, Yong-Han; Choi, Moon Seok; Lee, Joon Hyeok; Koh, Kwang Cheol; Paik, Seung Woon

2018-04-03

In order to claim a benefit of screen-based diagnosis for asymptomatic individuals, treatment of occult disease needs to offer survival advantages compared to the treatment of symptomatic disease, yet information on this issue is scarce with regard to hepatocellular carcinoma (HCC) screening. A total of 3353 treatment-naïve, consecutive, newly diagnosed HCC patients [age: 57.9 ± 10.3, male: 2,689 (80.2%), hepatitis B virus: 2555 (76.2%)], diagnosed between 2010 and 2013 were analyzed. Data on the mode of detection was prospectively collected at the time of HCC diagnosis and was used to group patients into occult or symptomatic cases. Overall, 643 (19.2%) patients were symptomatic cases. The proportion of patients undergoing resection, radiofrequency ablation or transplantation were lower in symptomatic cases than occult cases (20.8 vs. 56.2%, p < .001). Survival was better in occult cases than symptomatic cases (71.2 vs. 30.4% at three-years, p < .001), with a multivariable-adjusted hazard ratio of 1.40 (95% confidence interval (CI), 1.24-1.58). When stratified by tumor stage, a survival benefit was not observed for patients diagnosed at modified International Union Against Cancer (mUICC) stage I, but presenting symptoms were diverse and nonspecific. In a statistical model adjusting for potential lead-time bias, the association between overall survival and the mode of detection was markedly attenuated and was no longer significant when the treatment modality was included in the model (hazard ratio, 0.94; 95% CI, 0.82-1.07). Treatment of occult disease offered a survival benefit to patients over symptomatic cases. These data support screening practices for asymptomatic individuals to diagnose occult HCC.

The Thermal Structure of Triton's Atmosphere: Results from the 1993 and 1995 Occultations

NASA Astrophysics Data System (ADS)

Olkin, C. B.; Elliot, J. L.; Hammel, H. B.; Cooray, A. R.; McDonald, S. W.; Foust, J. A.; Bosh, A. S.; Buie, M. W.; Millis, R. L.; Wasserman, L. H.; Dunham, E. W.; Young, L. A.; Howell, R. R.; Hubbard, W. B.; Hill, R.; Marcialis, R. L.; McDonald, J. S.; Rank, D. M.; Holbrook, J. C.; Reitsema, H. J.

1997-09-01

This paper presents new results about Triton's atmospheric structure from the analysis of all ground-based stellar occultation data recorded to date, including one single-chord occultation recorded on 1993 July 10 and nine occultation lightcurves from the double-star event on 1995 August 14. These stellar occultation observations made both in the visible and in the infrared have good spatial coverage of Triton, including the first Triton central-flash observations, and are the first data to probe the altitude level 20-100 km on Triton. The small-planet lightcurve model of J. L. Elliot and L. A. Young (1992,Astron. J.103,991-1015) was generalized to include stellar flux refracted by the far limb, and then fitted to the data. Values of the pressure, derived from separate immersion and emersion chords, show no significant trends with latitude, indicating that Triton's atmosphere is spherically symmetric at ∼50-km altitude to within the error of the measurements; however, asymmetry observed in the central flash indicates the atmosphere is not homogeneous at the lowest levels probed (∼20-km altitude). From the average of the 1995 occultation data, the equivalent-isothermal temperature of the atmosphere is 47 ± 1 K and the atmospheric pressure at 1400-km radius (∼50-km altitude) is 1.4 ± 0.1 μbar. Both of these are not consistent with a model based on Voyager UVS and RSS observations in 1989 (D. F. Strobel, X. Zhu, M. E. Summers, and M. H. Stevens, 1996,Icarus120,266-289). The atmospheric temperature from the occultation is 5 K colder than that predicted by the model and the observed pressure is a factor of 1.8 greater than the model. In our opinion, the disagreement in temperature and pressure is probably due to modeling problems at the microbar level, since measurements at this level have not previously been made. Alternatively, the difference could be due to seasonal change in Triton's atmospheric structure.

Theoretical performance of serrated external occulters for solar coronagraphy. Application to ASPIICS

NASA Astrophysics Data System (ADS)

Rougeot, R.; Aime, C.

2018-04-01

Context. This study is made in the context of the future solar coronagraph ASPIICS of the ESA formation-flying mission Proba-3. Aims: In the context of solar coronagraphy, we provide a comparative study of the theoretical performance of serrated (or toothed) external occulters by varying the number and size of the teeth, which we compare to the sharp-edged and apodized disks. The tooth height is small (a few centimeters), to avoid hindering the observation of the solar corona near the limb. We first analyze the diffraction pattern produced by such occulters. In a second step, we compute the umbra profile by integration over the Sun. Methods: We explored a few methods to compute the diffraction pattern. Two of them were implemented. The first is based on 2D fast Fourier transformation (FFT) routines and a multiplication by the Fresnel filter of the form exp(-iπλzu2). Simple rules were derived and discussed to set the sampling conditions. The Maggi-Rubinowicz representation is then proposed as an alternative method, and is proven to be very efficient for this study. Results: Serrated occulters tend to create a two-level intensity pattern, the inner being the darker, which perfectly matches a previously reported geometrical prediction. The diffraction in this central region is lower by two to four orders of magnitude when compared to the sharp-edged disk. The achieved umbra level at the center ranges from 10-4 to below 10-7, depending on the geometry of the teeth. Conclusions: Our study shows that serrated occulters can achieve a high rejection and can almost reach the performance of the apodized disk when very many teeth are used. We prove that shaped occulters must be preferred to simple disks in solar and stellar coronagraphy.

Lunar Occultations as a Simple Tool for High Angular Resolution Astronomy

NASA Astrophysics Data System (ADS)

Richichi, Andrea

1999-08-01

At the turn of the millennium, modern astronomy is seeing the creation of several new impressive facilities. Among them, large telescopes and long baseline interferometers are beginning to break the limitations imposed by seeing and to push our angular resolution limits at the level of the millisecond of arc. In this race for the state-of-the-art in angular resolution, one should not forget the considerable aid which has been provided for some decades by the more humble technique of lunar occultations. Although burdened with obvious limitations in the choice of the sources, this latter method has two main features that can make it attractive for the modern amateur astronomer: it is simple, and can be implemented also at realtively small telescopes.

An Occultation by Saturn's Rings on 1991 October 2-3 October 2-3 Observed with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Bosh, A. S.; Cooke, M. L.; Bless, R. C.; Nelson, M. J.; Percival, J. W.; Taylor, M. J.; Dolan, J. F.; Robinson, E. L.; Van Citters, G. W.

1993-01-01

An occultation of the star GSC 6323-01396 (V = 11.9) by Saturn's rings was observed with the High-Speed Photometer on the Hubble Space Telescope (HST) on 1991 October 2-3. This occultation occurred when Saturn was near a stationary point, so the apparent motion of Saturn relative to the star was dominated by the HST orbital motion (8 km/s). Data were recorded simultaneously at effective wavelengths of 3200 and 7500 A, with an integration time of 0.15 s. Fifteen segments of occultation data, totaling 6.8 h, were recorded in 13 successive orbits during the 20.0 h interval from UTC 1991 October 2, 19:35 until UTC 1991 October 3, 15:35. Occultations by 43 different features throughout the classical rings were unambiguously identified in the light curve, with a second occultation by 24 of them occurring due to spacecraft orbital parallax during this extremely slow event. Occultation times for features currently presumed circular were measured and employed in a geometrical model for the rings. This model, relating the observed occultation times to feature radii and longitudes, is presented here and is used in a least-squares fit for the pole direction and radius scale of Saturn's ring system.

[Relationship between salivary occult blood and level of volatile sulphur compounds in oral cavity].

PubMed

An, Yue-bang; He, Lu; Meng, Huan-xin; Liu, Ting-ting; Liu, Jian

2010-07-01

To observe the change of the salivary occult blood after periodontal mechanical therapy, and to assess the correlations between salivary occult blood and the level of volatile sulphur compounds (VSC) in oral cavity, periodontal clinical parameters, respectively. Fifty patients with gingivititis, mild or moderate periodontitis were included. The level of VSC were measured by Halimeter(®) and salivary occult blood was tested by Perioscreen(®) before periodontal examination. Then full mouth plaque index (PLI), probing depth (PD), bleeding index (BI) were charted. Attachment loss (AL) of the Ramfjörd teeth were recorded lastly. Intensive periodontal mechanical therapy was conducted including oral hygiene instruction, scaling and root planing (SRP). Four weeks after SRP, the same examinations were repeated. Salivary occult blood was significantly correlated with BI (r = 0.294) and PLI (r = 0.308) before periodontal therapy (P < 0.01), and also significantly correlated with VSC level (r = 0.386), PLI (r = 0.456), BI (r = 0.352), AL (r = 0.325) after therapy (P < 0.05). The improvement of VSC level [211.0 (111.0 - 389.5) × 10⁻⁹ vs 100.0 (46.3 - 165.3) × 10⁻⁹], the clinical periodontal parameters including PLI [(1.3 ± 1.0) vs (0.4 ± 0.6)], PD [(3.7 ± 1.5) mm vs (2.7 ± 0.9) mm], BI [(1.8 ± 1.2) vs (0.4 ± 0.7)] and AL [(1.0 ± 1.1) mm vs (0.1 ± 0.5) mm after the treatment was statistically significant (P < 0.001). However, standing on the viewpoint of salivary occult blood changes from positive before therapy to negative after therapy, only 80% (40/50) individuals were totally cured. VSC level in oral cavity and periodontal clinical parameters significantly decreased (P < 0.001) following the trends from strong positive, weak positive, to negative results of salivary occult blood test. Salivary occult blood was correlated with VSC level in oral cavity of periodontal treated patients. It may be an objective parameter to evaluate the gingival inflammation

Impact of D-Dimer for Prediction of Incident Occult Cancer in Patients with Unprovoked Venous Thromboembolism.

PubMed

Han, Donghee; ó Hartaigh, Bríain; Lee, Ji Hyun; Cho, In-Jeong; Shim, Chi Young; Chang, Hyuk-Jae; Hong, Geu-Ru; Ha, Jong-Won; Chung, Namsik

2016-01-01

Unprovoked venous thromboembolism (VTE) is related to a higher incidence of occult cancer. D-dimer is clinically used for screening VTE, and has often been shown to be present in patients with malignancy. We explored the predictive value of D-dimer for detecting occult cancer in patients with unprovoked VTE. We retrospectively examined data from 824 patients diagnosed with deep vein thrombosis or pulmonary thromboembolism. Of these, 169 (20.5%) patients diagnosed with unprovoked VTE were selected to participate in this study. D-dimer was categorized into three groups as: <2,000, 2,000-4,000, and >4,000 ng/ml. Cox regression analysis was employed to estimate the odds of occult cancer and metastatic state of cancer according to D-dimer categories. During a median 5.3 (interquartile range: 3.4-6.7) years of follow-up, 24 (14%) patients with unprovoked VTE were diagnosed with cancer. Of these patients, 16 (67%) were identified as having been diagnosed with metastatic cancer. Log transformed D-dimer levels were significantly higher in those with occult cancer as compared with patients without diagnosis of occult cancer (3.5±0.5 vs. 3.2±0.5, P-value = 0.009, respectively). D-dimer levels >4,000 ng/ml was independently associated with occult cancer (HR: 4.12, 95% CI: 1.54-11.04, P-value = 0.005) when compared with D-dimer levels <2,000 ng/ml, even after adjusting for age, gender, and type of VTE (e.g., deep vein thrombosis or pulmonary thromboembolism). D-dimer levels >4000 ng/ml were also associated with a higher likelihood of metastatic cancer (HR: 9.55, 95% CI: 2.46-37.17, P-value <0.001). Elevated D-dimer concentrations >4000 ng/ml are independently associated with the likelihood of occult cancer among patients with unprovoked VTE.

TITAN’S UPPER ATMOSPHERE FROM CASSINI/UVIS SOLAR OCCULTATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capalbo, Fernando J.; Bénilan, Yves; Yelle, Roger V.

2015-12-01

Titan’s atmosphere is composed mainly of molecular nitrogen, methane being the principal trace gas. From the analysis of 8 solar occultations measured by the Extreme Ultraviolet channel of the Ultraviolet Imaging Spectrograph (UVIS) on board Cassini, we derived vertical profiles of N{sub 2} in the range 1100–1600 km and vertical profiles of CH{sub 4} in the range 850–1300 km. The correction of instrument effects and observational effects applied to the data are described. We present CH{sub 4} mole fractions, and average temperatures for the upper atmosphere obtained from the N{sub 2} profiles. The occultations correspond to different times and locations,more » and an analysis of variability of density and temperature is presented. The temperatures were analyzed as a function of geographical and temporal variables, without finding a clear correlation with any of them, although a trend of decreasing temperature toward the north pole was observed. The globally averaged temperature obtained is (150 ± 1) K. We compared our results from solar occultations with those derived from other UVIS observations, as well as studies performed with other instruments. The observational data we present confirm the atmospheric variability previously observed, add new information to the global picture of Titan’s upper atmosphere composition, variability, and dynamics, and provide new constraints to photochemical models.« less

Patient factors associated with non-attendance at colonoscopy after a positive screening faecal occult blood test.

PubMed

Plumb, Andrew A; Ghanouni, Alex; Rainbow, Sandra; Djedovic, Natasha; Marshall, Sarah; Stein, Judith; Taylor, Stuart A; Halligan, Steve; Lyratzopoulos, Georgios; von Wagner, Christian

2017-03-01

Background Screening participants with abnormal faecal occult blood test results who do not attend further testing are at high risk of colorectal cancer, yet little is known about their reasons for non-attendance. Methods We conducted a medical record review of 170 patients from two English Bowel Cancer Screening Programme centres who had abnormal guaiac faecal occult blood test screening tests between November 2011 and April 2013 but did not undergo colonoscopy. Using information from patient records, we coded and categorized reasons for non-attendance. Results Of the 170 patients, 82 were eligible for review, of whom 66 had at least one recorded reason for lack of colonoscopy follow-up. Reasons fell into seven main categories: (i) other commitments, (ii) unwillingness to have the test, (iii) a feeling that the faecal occult blood test result was a false positive, (iv) another health issue taking priority, (v) failing to complete bowel preparation, (vi) practical barriers (e.g. lack of transport), and (vii) having had or planning colonoscopy elsewhere. The most common single reasons were unwillingness to have a colonoscopy and being away. Conclusions We identify a range of apparent reasons for colonoscopy non-attendance after a positive faecal occult blood test screening. Education regarding the interpretation of guaiac faecal occult blood test findings, offer of alternative confirmatory test options, and flexibility in the timing or location of subsequent testing might decrease non-attendance of diagnostic testing following positive faecal occult blood test.

Observational studies of roAp stars

NASA Astrophysics Data System (ADS)

Sachkov, M.

2014-11-01

Rapidly oscillating Ap (roAp) stars are high-overtone, low-degree p-mode pulsators that are also chemically peculiar magnetic A stars. Until recently the classical asteroseismic analysis i.e. frequency analysis, of these stars was based on ground and space photometric observations. Significant progress was achieved through access to uninterrupted, ultra-high-precision data from MOST, COROT and Kepler satellites. Over the last ten years the study of roAp stars has been altered drastically from an observational point of view through studies of time-resolved, high-resolution spectra. Their unusual pulsational characteristics, caused by an interplay between the short vertical lengths of the pulsation waves and strong stratification of chemical elements, allow us to examine the upper roAp atmosphere in more detail than is possible for any star except the Sun. In this paper I review the results of recent studies of the pulsations of roAp stars.

The impact of the number of occult metastatic lymph nodes on postoperative relapse of resectable esophageal cancer.

PubMed

Morimoto, J; Tanaka, H; Ohira, M; Kubo, N; Muguruma, K; Sakurai, K; Yamashita, Y; Maeda, K; Sawada, T; Hirakawa, K

2014-01-01

Clinical stage II/III esophageal cancer (EC), as defined by the Japanese Classification, relapses at a moderately high rate even after curative resection. The number of lymph node metastases is known to be associated with tumor relapse. Recently, the prognostic significance of occult metastatic lymph nodes (MLNs), as well as that of overt MLNs, has been reported. The aim of this study was to investigate the impact of the total number of MLNs including occult MLNs on postoperative relapse in clinical stage II/III EC. One hundred and five patients with clinical stage II/III EC who underwent esophagectomy accompanied by radical lymphadenectomy at the Department of Surgical Oncology in Osaka City University Hospital between January 2000 and October 2008 were included in this study. Occult MLNs, metastases not detected by hematoxylin-eosin staining, were identified by immunohistochemistry (IHC) using antipancytokeratin antibody AE1/AE3. The clinicopathological features of occult MLNs were compared between the relapse and no relapse groups. A total of 6558 lymph nodes (1357 from two-field dissection and 5201 from three-field dissection) were examined by IHC staining; 362 overt MLNs and 143 occult MLNs were detected. The number of occult MLNs increased in proportion to the International Union Against Cancer pathological (p)N-status and pStage. When the number of occult MLNs was added to the number of pNs, the number of total MLNs was associated with postoperative relapse. With respect to tumor, node, metastasis stage, 6 of 22 patients (27%) who were pathological node-negative converted to node-positive by considering total MLNs. The number of N3 patients with relapse increased markedly with restaging by total MLNs. The number of total MLNs, but not overt MLNs, was an independent prognostic factor on multivariate analysis. These results suggest that occult MLNs were often found, and they were associated with postoperative relapse of resectable esophageal cancer. The total

Halogen Occultation Experiment (HALOE) optical filter characterization

NASA Technical Reports Server (NTRS)

Harvey, Gale A.

1989-01-01

The Halogen Occultation Experiment (HALOE) is a solar occultation experiment that will fly on the Upper Atmosphere Research Satellite to measure mixing ratio profiles of O3, H2O, NO2, NO, CH4, HCl, and HF. The inversion of the HALOE data will be critically dependent on a detailed knowledge of eight optical filters. A filter characterization program was undertaken to measure in-band transmissions, out-of-band transmissions, in-band transmission shifts with temperature, reflectivities, and age stability. Fourier Transform Infrared Spectrometers were used to perform measurements over the spectral interval 400/cm to 6300/cm (25 micrometers to 1.6 micrometers). Very high precision (0.1 percent T) in-band measurements and very high resolution (0.0001 percent T) out-of-band measurements have been made. The measurements revealed several conventional leaks at 0.01 percent transmission and greatly enhanced (1,000) leaks to the 2-element filters when placed in a Fabry-Perot cavity. Filter throughput changes by 5 percent for a 25 C change in filter temperature.

An integration time adaptive control method for atmospheric composition detection of occultation

NASA Astrophysics Data System (ADS)

Ding, Lin; Hou, Shuai; Yu, Fei; Liu, Cheng; Li, Chao; Zhe, Lin

2018-01-01

When sun is used as the light source for atmospheric composition detection, it is necessary to image sun for accurate identification and stable tracking. In the course of 180 second of the occultation, the magnitude of sun light intensity through the atmosphere changes greatly. It is nearly 1100 times illumination change between the maximum atmospheric and the minimum atmospheric. And the process of light change is so severe that 2.9 times per second of light change can be reached. Therefore, it is difficult to control the integration time of sun image camera. In this paper, a novel adaptive integration time control method for occultation is presented. In this method, with the distribution of gray value in the image as the reference variable, and the concepts of speed integral PID control, the integration time adaptive control problem of high frequency imaging. The large dynamic range integration time automatic control in the occultation can be achieved.

Stellar Occultations by TNOs and Centaurs: first results in the “Gaia era”

NASA Astrophysics Data System (ADS)

Rossi, Gustavo; Vieira-Martins, Roberto; Sicardy, Bruno; Ortiz, Jose Luis; Rio Group, Lucky Star Occultation Team, Granada Occultation Team

2017-10-01

After the first release of the GAIA catalog (in September/2016), stellar positions are now known with unprecedented accuracy, reaching values of the order of milliarcseconds. This improvement reflected into a stunning accuracy on the astrometry of moving objects, such as TNOs. Unfortunately, Gaia stars proper motions will be only available on the second data release (DR2) next year, so there is still a need to use hybrid stellar catalogs for occultation predictions until then. Despite that, stellar occultations predictions are now much more accurate, and the biggest uncertainties comes mainly from the object ephemerides. This issue will be overcome by large surveys such as the LSST, which will provide positions for the known TNOs and it is expected to increase the number of known TNOs by nearly 40,000, with an unprecedent amount of acquired information.This huge amount of data also poses a new era in stellar occultations: predictions will be very accurate and the participation of professional astronomers, laboratories, and the amateur community will be crucial to observe the predicted events; observation campaigns will need to be selected according to a specific scientific purpose such as the probability to detect rings or archs around a body, the presence of atmosphere or even the detection of topographic features; the development of softwares capable of reducing the data more efficiently and an easier method to coordinate observation campaigns are needed.Here we present some impressive results obtained from predictions and observed occultations in 2017 (among them we have Pluto, Chariklo and Haumea), the problems we are starting to face in the beginning of the “Gaia era” and the future challenges of stellar occultation.

The influence of NO and ClO variations at twilight on the interpretation of solar occultation measurements

NASA Technical Reports Server (NTRS)

Boughner, R.; Larsen, J. C.; Natarajan, M.

1980-01-01

The influence of short lived photochemically produced species on solar occultation measurements of ClO and NO was examined. Time varying altitude profiles of ClO and NO were calculated with a time dependent photochemical model to simulate the distribution of these species during a solar occultation measurement. These distributions were subsequently used to calculate simulated radiances for various tangent paths from which mixing ratios were inferred with a conventional technique that assumes spherical symmetry. These results show that neglecting the variation of ClO in the retrieval process produces less than a 10 percent error between the true and inverted profile for both sunrise and sunset above 18 km. For NO, errors are less than 10 percent for tangent altitudes above about 35 km for sunrise and sunset; at lower altitudes, the error increases, approaching 100 percent at altitudes near 25 km. the results also show that average inhomogeneity factors, which measure the concentration variation along the tangent path and which can be calculated from a photochemical model, can indicate which species require more careful data analysis.

Spire's 3U CubeSat GNSS-RO Constellation for Meteorological and Space Weather Applications

NASA Astrophysics Data System (ADS)

Nguyen, V.; Duly, T.; Ector, D.; Irisov, V.; Nogues-Correig, O.; Tan, L.; Yuasa, T.

2017-12-01

Spire Global, Inc., is a leading player in the nanosatellite sector and the first commercial company to provide GNSS radio occultation measurements to support meteorological and space weather forecasting. Each Spire satellite is equipped with a state-of-the-art, in-house designed software receiver, which is capable of open-loop tracking of occulted GNSS signals. By utilizing this receiver on a low-earth orbiting, 3U satellite constellation platform, Spire is able to provide high-quality profile measurements of the lower atmosphere as well as ionospheric total electron content and scintillation data at unprecedented low cost, coverage, and latency. In this talk, we provide an overview of the current capabilities of Spire's satellite constellation and radio occultation processing system. Recent results describing the state of the lower atmosphere and ionosphere will be presented and briefly discussed. Finally, we focus on Spire's future capabilities, and the potential impacts on both the meteorological and space weather scientific communities.

An atmosphere on Ganymede from its occultation of SAO 186800 on 7 June 1972.

NASA Technical Reports Server (NTRS)

Carlson, R. W.; Bhattacharyya, J. C.; Smith, B. A.; Johnson, T. V.; Hidayat, B.; Smith, S. A.; Taylor, G. E.; O'Leary, B.; Brinkmann, R. T.

1973-01-01

The observational data obtained during the occultation are of sufficient quality to determine the occultation radius and to support the inference that Ganymede does possess at least a modest atmosphere. Assuming a circular cross section, the diameter of Ganymede was found to be 5271 km. Effects of the atmosphere on the accuracy of the value obtained for the Ganymede diameter are discussed.

First results from the ionospheric radio occultations of Saturn by the Cassini spacecraft

NASA Astrophysics Data System (ADS)

Nagy, Andrew F.; Kliore, Arvydas J.; Marouf, Essam; French, Richard; Flasar, Michael; Rappaport, Nicole J.; Anabtawi, Aseel; Asmar, Sami W.; Johnston, Douglas; Barbinis, Elias; Goltz, Gene; Fleischman, Don

2006-06-01

The first set of near-equatorial occultations of the Saturn ionosphere was obtained by the Cassini spacecraft between May and September of 2005. The occultations occurred at near-equatorial latitudes, between 10°N and 10°S, at solar zenith angles from about 84° to 96°. The entry observations correspond to dusk conditions and the exit ones to dawn. An initial look at the data indicates that the average peak densities are lower and the peak altitude higher at dawn than at dusk, possibly the result of ionospheric decay during the night hours. There are also significant differences between individual dawn and dusk occultations; the initial thought is that this variation must be connected to changes in the water inflow into the upper atmosphere and/or variations in the particle impact ionization rates.

Helios-1 Faraday rotation experiment - Results and interpretations of the solar occultations in 1975

NASA Technical Reports Server (NTRS)

Volland, H.; Bird, M. K.; Levy, G. S.; Stelzried, C. T.; Seidel, B. L.

1977-01-01

The first of two solar occultations of the satellite Helios-1 in 1975 occurred in April when the satellite's ray path approached the west limb of the sun to a minimum distance of 1.63 solar radii. The second occultation took place in late August/early September when Helios-1 was totally eclipsed by the photosphere. Measurements of the polarization angle of the linearly polarized telemetry signal were performed with automatic tracking polarimeters at the 64 m Goldstone Tracking Station in California and also at the 100 m radio telescope in Effelsberg, West Germany. The coronal Faraday rotation as a function of the solar offset for both occultations is shown in graphs. The theoretical significance of the observations is investigated.

Relationship between occult hepatitis B virus infection and chronic kidney disease in a Chinese population-based cohort.

PubMed

Kong, Xiang-Lei; Ma, Xiao-Jing; Su, Hong; Xu, Dong-Mei

2016-03-01

Previous studies have revealed inconsistent results regarding the association between occult hepatitis B virus (HBV) infection and chronic kidney disease (CKD). Therefore, we conducted a prospective cohort study to evaluate the association between occult HBV infection and CKD. A total of 4329 adults, aged 46.2 ± 13.7 years, without CKD at baseline were enrolled while undergoing physical examinations. Occult HBV infection was defined as seropositivity for antibody to HBV core antigen. CKD was defined as decreased estimated glomerular filtration rate (eGFR < 60 ml·min -1 ·1.73 m -2 ) or presence of proteinuria ≥1+, assessed using a repeated dipstick method. eGFR was computed using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. The prevalence of occult HBV infection was 8.1% (352/4329). During 5 years of follow-up, 165 patients (3.8%) developed CKD. Univariate Logistic regression analysis showed that occult HBV infection was positively associated with decreased eGFR, with an odds ratio ( OR ) of 2.15 (95% confidence interval ( CI ): 1.05-4.11). In contrast, occult HBV infection was not associated with either proteinuria or CKD ( P  > 0.05). After adjustment for potential confounders in the multivariate Logistic regression analysis, age, hypertension, diabetes, and the highest quartile of uric acid were associated with CKD, with OR s of 1.04 (95% CI : 1.02-1.05), 2.1 (95% CI : 1.46-3.01), 2.02 (95% CI : 1.36-2.99), and 1.86 (95% CI : 1.17-2.95), respectively. However, occult HBV infection was not associated with CKD, with an OR of 1.12 (95% CI : 0.65-1.95). This study did not find an association between occult HBV infection and CKD. However, high-risk patients infected with HBV should still be targeted for monitoring for the development of CKD.

Toward a Next Generation Solar Coronagraph: Diffracted Light Simulation and Test Results for a Cone Occulter with Tapered Surface

NASA Astrophysics Data System (ADS)

Yang, Heesu; Bong, Su-Chan; Cho, Kyung-Suk; Choi, Seonghwan; Park, Jongyeob; Kim, Jihun; Baek, Ji-Hye; Nah, Jakyoung; Sun, Mingzhe; Gong, Qian

2018-04-01

In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun Because the intensity of the solar outer corona is 10-6 to 10-10 times of that of the solar disk (\\ir), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of 7.6×10-10 \\ir when the cone angle θc was about 0.39°. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of 6×10-9 \\ir at θc=0.40°. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be 0.05°, the lateral alignment tolerance was 45 \\um, and the angular alignment tolerance was 0.043°. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.

JPL/USC GAIM: Using COSMIC Occultations in a Real-Time Global Ionospheric Data Assimilation Model

NASA Astrophysics Data System (ADS)

Mandrake, L.; Komjathy, A.; Wilson, B. D.; Pi, X.; Hajj, G.; Iijima, B.; Wang, C.

2006-12-01

We are in the midst of a revolution in ionospheric remote sensing driven by the illuminating powers of ground and space-based GPS receivers, new UV remote sensing satellites, and the advent of data assimilation techniques for space weather. In particular, the COSMIC 6-satellite constellation launched in April 2006. COSMIC will provide unprecedented global coverage of GPS occultations (~5000 per day), each of which yields electron density information with unprecedented ~1 km vertical resolution. Calibrated measurements of ionospheric delay (total electron content or TEC) suitable for input into assimilation models will be available in near real-time (NRT) from the COSMIC project with a latency of 30 to 120 minutes. Similarly, NRT TEC data are available from two worldwide NRT networks of ground GPS receivers (~75 5-minute sites and ~125 more hourly sites, operated by JPL and others). The combined NRT ground and space-based GPS datasets provide a new opportunity to more accurately specify the 3-dimensional ionospheric density with a time lag of only 15 to 120 minutes. With the addition of the vertically-resolved NRT occultation data, the retrieved profile shapes will model the hour-to-hour ionospheric "weather" much more accurately. The University of Southern California (USC) and the Jet Propulsion Laboratory (JPL) have jointly developed a real-time Global Assimilative Ionospheric Model (GAIM) to monitor space weather, study storm effects, and provide ionospheric calibration for DoD customers and NASA flight projects. JPL/USC GAIM is a physics- based 3D data assimilation model that uses both 4DVAR and Kalman filter techniques to solve for the ion & electron density state and key drivers such as equatorial electrodynamics, neutral winds, and production terms. Daily (delayed) GAIM runs can accept as input ground GPS TEC data from 1000+ sites, occultation links from CHAMP, SAC-C, and the COSMIC constellation, UV limb and nadir scans from the TIMED and DMSP satellites

Occult tinea pedis in an Israeli population and predisposing factors for the acquisition of the disease.

PubMed

Sakka, Nicole; Shemer, Avner; Barzilai, Aviv; Farhi, Renata; Daniel, Ralph

2015-02-01

Tinea pedis is a commonly encountered dermatophytic infection with a clinical prevalence of 15-25%. Limited studies have evaluated the prevalence of occult tinea pedis. The aims of this study were to evaluate the prevalence of occult tinea pedis in asymptomatic subjects with feet that appeared healthy and to identify possible related risk factors. A prospective study of 221 asymptomatic subjects with apparently normal feet was conducted. All subjects completed a questionnaire covering anamnestic details (personal and family histories of tinea pedis, preferred footwear) and were examined for foot odor and the clinical presence of tinea pedis and onychomycosis. Samples were taken from the foot for direct microscopic examination and culture. Among the 221 patients, 31 (14.0%) were positive for occult tinea pedis. Positive cultures from both the anterior and posterior aspects of the foot were obtained in 22 patients. The most common pathogen isolated was Trichophyton rubrum. Strong correlations emerged between occult tinea pedis and characteristics such as male gender, foot odor, previous personal and family histories of tinea pedis, and clinical and mycological evidence of onychomycosis. No significant associations were found between occult tinea pedis and age or preferred footwear. The prevalence of occult tinea pedis is similar to that of clinical tinea pedis. This may imply that patients with subclinical infection carry a risk for transmitting disease similar to that of clinical carriers. This is of great importance in the prevention and management of the disease as high-risk asymptomatic carriers can be identified. © 2014 The International Society of Dermatology.

Functional analysis of ‘a’ determinant mutations associated with occult HBV in HIV-positive South Africans

PubMed Central

Powell, Eleanor A.; Boyce, Ceejay L.; Gededzha, Maemu P.; Selabe, Selokela G.; Mphahlele, M. Jeffrey

2016-01-01

Occult hepatitis B is defined by the presence of hepatitis B virus (HBV) DNA in the absence of hepatitis B surface antigen (HBsAg). Occult HBV is associated with the development of hepatocellular carcinoma, reactivation during immune suppression, and virus transmission. Viral mutations contribute significantly to the occult HBV phenotype. Mutations in the ‘a’ determinant of HBsAg are of particular interest, as these mutations are associated with immune escape, vaccine escape and diagnostic failure. We examined the effects of selected occult HBV-associated mutations identified in a population of HIV-positive South Africans on HBsAg production in vitro. Mutations were inserted into two different chronic HBV backbones and transfected into a hepatocyte-derived cell line. HBsAg levels were quantified by enzyme-linked immunosorbent assay (ELISA), while the detectability of mutant HBsAg was determined using an HA-tagged HBsAg expression system. Of the seven mutations analysed, four (S132P, C138Y, N146D and C147Y) resulted in decreased HBsAg expression in one viral background but not in the second viral background. One mutation (N146D) led to a decrease in HBsAg detected as compared to HA-tag, indicating that this mutation compromises the ability of the ELISA to detect HBsAg. The contribution of occult-associated mutations to the HBsAg-negative phenotype of occult HBV cannot be determined adequately by testing the effect of the mutation in a single viral background, and rigorous analysis of these mutations is required. PMID:27031988

Facial paralysis due to an occult parotid abscess.

PubMed

Orhan, Kadir Serkan; Demirel, Tayfun; Kocasoy-Orhan, Elif; Yenigül, Kubilay

2008-01-01

Facial paralysis associated with benign diseases of the parotid gland is very rare. It has been reported in approximately 16 cases of acute suppurative parotitis or parotid abscess. We presented a 45-year-old woman who developed facial paralysis secondary to an occult parotid abscess. Initially, there was no facial paralysis and the signs and symptoms were suggestive of acute parotitis, for which medical treatment was initiated. Three days later, left-sided facial palsy of HB (House-Brackmann) grade 5 developed. Ultrasonography revealed a pretragal, hypoechoic mass, 10x8 mm in size, causing inflammation in the surrounding tissue. Fine needle aspiration biopsy obtained from the mass revealed polymorphonuclear leukocytes and lymphocytes. No malignant cells were observed. The lesion was diagnosed as an occult parotid abscess. After a week, the mass disappeared and facial paralysis improved to HB grade 4. At the end of the first month, facial paralysis improved to HB grade 1. At three months, facial nerve function was nearly normal.

Prevalence of occult HBV among hemodialysis patients in two districts in the northern part of the West Bank, Palestine.

PubMed

Dumaidi, Kamal; Al-Jawabreh, Amer

2014-10-01

Occult hepatitis B infection is the case with undetectable HBsAg, but positive for HBV DNA in liver tissue and/or serum. Occult hepatitis B infection among hemodialysis patients in Palestine has been understudied. In this study, 148 hemodialysis patients from 2 northern districts in Palestine, Jenin (89) and Tulkarem (59), were investigated for occult hepatitis B, HBV, HCV infections with related risk factors. ELISA and PCR were used for the detection of anti-HBc and viral DNA, respectively. The overall prevalence of occult hepatitis B infection among the study group was 12.5% (16/128). Occult hepatitis B infection is more prevalent among males with most cases (15/16) from Jenin District. About one-third (42/132) of the hemodialysis patients were anti-HBc positive. Approximately 27% of the hemodialysis patients were infected with HCV. Around 20% (28/140) were positive for HBV DNA, but only 8.2% (12/146) of the hemodialysis patients were positive for HBsAg. The comparison between hemodialysis patients with occult hepatitis B infection and those without occult hepatitis B infection for selected risk factors and parameters as liver Enzyme, age, sex, HCV infection, blood transfusion, kidney transplant, anti-HBc, and vaccination showed no statistical significance between both categories. Duration of hemodialysis significantly affected the rate of HCV infection. HCV is significantly higher in hemodialysis patients with both Diabetes mellitus and hypertension. The prevalence of occult hepatitis B infection among hemodialysis patients is high; requiring stringent control policies. HBsAg assay is insufficient test for accurate diagnosis of HBV infection among hemodialysis patients. © 2014 Wiley Periodicals, Inc.

Preliminary Global Topographic Model of Mars Based on MOLA Altimetry, Earth-Based Radar, and Viking, Mariner and MGS Occultations

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.

1999-01-01

The recent altimetry data acquired by MOLA over the northern hemisphere of Mars have been combined with the Earth-based radar data obtained between 1971 and 1982, and occultation measurements of the Viking 1 and 2 Orbiters, Mariner 9, and MGS to derive a global model of the shape and topography of Mars. This preliminary model has a horizontal resolution of about 300 km. Vertical accuracy is on average a few hundred meters in the region of the data. Datasets: The altimetry and radar datasets were individually binned in 1.25 degree grids and merged with the occultation data. The Viking and Mariner occultation data in the northern hemisphere were excluded from the combined dataset where MOLA altimetry were available. The laser altimetry provided extensive and almost complete coverage of the northern hemisphere north of latitude 30 while the radar provided longitudinal coverage at several latitude bands between 23N and 23S. South of this region the only data were occultations. The majority of the occultations were obtained from Mariner 9, and the rest from Viking 1 & 2, and MGS. Earlier studies had shown that the Viking and Mariner occultations were on average only accurate to 500 meters. The recent MGS occultations are accurate to a few tens of meters. However, the highest southern latitude reached by the MGS occultations is only about 64S and data near the target region for the Mars 98 lander is limited to a few Viking and Mariner observations of relatively poor quality. In addition to the above datasets the locations of the Viking 1, Viking 2, and Pathfinder landers, obtained from the radio tracking of their signals, were included.

Recurring Occultations of RW Aurigae by Coagulated Dust in the Tidally Disrupted Circumstellar Disk

NASA Astrophysics Data System (ADS)

Rodriguez, Joseph E.; Reed, Phillip A.; Siverd, Robert J.; Pepper, Joshua; Stassun, Keivan G.; Gaudi, B. Scott; Weintraub, David A.; Beatty, Thomas G.; Lund, Michael B.; Stevens, Daniel J.

2016-02-01

We present photometric observations of RW Aurigae, a Classical T Tauri system, that reveal two remarkable dimming events. These events are similar to that which we observed in 2010-2011, which was the first such deep dimming observed in RW Aur in a century’s worth of photometric monitoring. We suggested the 2010-2011 dimming was the result of an occultation of the star by its tidally disrupted circumstellar disk. In 2012-2013, the RW Aur system dimmed by ˜0.7 mag for ˜40 days and in 2014/2015 the system dimmed by ˜2 mag for >250 days. The ingress/egress duration measurements of the more recent events agree well with those from the 2010-2011 event, providing strong evidence that the new dimmings are kinematically associated with the same occulting source as the 2010-2011 event. Therefore, we suggest that both the 2012-2013 and 2014-2015 dimming events, measured using data from the Kilodegree Extremely Little Telescope and the Kutztown University Observatory, are also occultations of RW Aur A by the tidally disrupted circumstellar material. Recent hydrodynamical simulations of the eccentric fly-by of RW Aur B suggest the occulting body to be a bridge of material connecting RW Aur A and B. These simulations also suggest the possibility of additional occultations which are supported by the observations presented in this work. The color evolution of the dimmings suggest that the tidally stripped disk material includes dust grains ranging in size from small grains at the leading edge, typical of star-forming regions, to large grains, ices or pebbles producing gray or nearly gray extinction deeper within the occulting material. It is not known whether this material represents arrested planet building prior to the tidal disruption event, or perhaps accelerated planet building as a result of the disruption event, but in any case the evidence suggests the presence of advanced planet building material in the space between the two stars of the RW Aur system.

A 2016 Ganymede stellar occultation event

NASA Astrophysics Data System (ADS)

D'Aversa, Emiliano; Oliva, Fabrizio; Sindoni, Giuseppe; Hinse, Tobias Cornelius; Plainaki, Christina; Aoki, Shohei; Person, Michael J.; Carlson, Robert W.; Orton, Glenn S.

2017-04-01

On 2016 April,13th the Jovian satellite Ganymede occulted a 7th magnitude star. The predicted occultation track crossed the Northern Pacific Ocean, Japan, and South Korea. Hence, it was a very favorable event due to the star brightness and to the visibility from the large aperture telescopes at Hawaii. While no other similar event is expected for the next 10 years, only two occultation events are reported in literature in the past, from Earth in 1972 [1] and from Voyager [2], in large disagreement in respect to the atmosphere detection. However, evidence of an exosphere around Ganymede was inferred by [3], through H Lyman alpha emission detected by Galileo UVS, and by [4], through HST/GHRS detection of far-UV atomic O airglow emissions, signature of dissociated molecular oxygen ([5],[6]). Later, the HST/STIS observations by [7] provided further evidence for exospheric neutral hydrogen. Since Ganymede is known to have an intrinsic magnetic field ([8]) reconnecting with the Jovian magnetic field and (partially) shielding the surface equatorial latitudes from the electron impact, the UV emissions have been so far attributed to auroral processes ([6]). Nevertheless, the physical mechanisms governing these processes are not known with certainty (e.g. whether the emissions morphology is determined by the spatial distribution of magnetospheric electrons or by an uneven O2 exosphere or both, see e.g.[9]). We took advantage of this event in order to search for a signature of Ganymede's exosphere in the occultation light curve, by using facilities on Mauna Kea at Hawaii (NASA-IRTF observatory) and at Sobaeksan Optical Astronomy Observatory (SOAO) in South Korea. At IRTF, both MORIS [10] and SpeX [11] instruments have been used, fed by the same optical entrance through a dichroic beam splitter at 0.95 micron. MORIS acquired a high-rate sequence of images about 0.25 sec apart in the visible range, while SpeX acquired a sequence of spectra at a bit lower rate, covering the 0

The prevalence of occult endometrial cancer in women undergoing hysterectomy for benign indications.

PubMed

Parsons, Lavanya H Palavalli; Pedersen, Rebecca; Richardson, Debra L; Kho, Kimberly A

2018-04-01

To estimate the frequency of occult endometrial cancer in women undergoing hysterectomy for benign indications. We performed a retrospective review of all patients undergoing hysterectomies for benign indications at our institution from 2006 to 2014. A departmental database was used to identify all hysterectomies performed, and institutional tumor registry was used to identify cases of endometrial carcinoma. Occult carcinomas were defined as cases with no suspicion preoperatively and histopathologic diagnosis of endometrial cancer postoperatively. A total of 6981 hysterectomies were performed for benign indications. Among these, thirteen patients (0.19%) were found to have occult endometrial cancer, with an overall rate of 1 in 537 patients (95% confidence interval 1:314-1:1008). Twelve patients had stage IA and one had stage IB disease. Median age of women found to have endometrial cancer was 50 years (range 35-72 years). The median BMI was 29.8 kg/m 2 (range 21.3-50.4 kg/m 2 ). The most common indications for hysterectomy were abnormal bleeding (47%), postmenopausal bleeding (15%), adnexal mass (15%), prolapse (15%), and endometrial hyperplasia without atypia (8%). Of the postmenopausal women that had bleeding, all patients underwent evaluation of the endometrium, however 75% of samples did not have adequate amount of endometrium to be evaluated and 25% were found to have hyperplasia. This is one of the largest single institution cohorts to examine occult malignancy. Unexpected endometrial carcinomas were found to occur in 0.19% or 1:537 (95% confidence interval 1:314-1:1008) hysterectomies for benign indications in our population. PRéCIS: Occult endometrial carcinomas are found to occur in 1:537 (0.19%) hysterectomies for benign indications. Copyright © 2018 Elsevier B.V. All rights reserved.

Occult hepatitis B virus coinfection in HIV-positive African migrants to the UK: a point prevalence study.

PubMed

Chadwick, D; Doyle, T; Ellis, S; Price, D; Abbas, I; Valappil, M; Geretti, A M

2014-03-01

Occult (surface antigen-negative/DNA-positive) hepatitis B virus (HBV) infection is common in areas of the world where HBV is endemic. The main objectives of this study were to determine the prevalence of occult HBV infection in HIV-infected African migrants to the UK and to determine factors associated with occult coinfection. This anonymized point-prevalence study identified Africans attending three HIV clinics, focussing on patients naïve to antiretroviral therapy (ART). Stored blood samples were tested for HBV DNA. Prevalence was calculated in the entire cohort, as well as in subpopulations. Risk factors for occult HBV coinfection were identified using logistic regression analysis. Among 335 HIV-positive African migrants, the prevalence of occult HBV coinfection was 4.5% [95% confidence interval (CI) 2.8-7.4%] overall, and 6.5% (95% CI 3.9-10.6%) and 0.8% (95% CI 0.2-4.6%) in ART-naïve and ART-experienced patients, respectively. Among ART-naïve anti-HBV core (anti-HBc)-positive patients, the prevalence was 16.4% (95% CI 8.3-25.6%). The strongest predictor of occult coinfection was anti-HBc positivity [odds ratio (OR) 7.4; 95% CI 2.0-27.6]. Median HBV DNA and ALT levels were 54 IU/mL [interquartile range (IQR) 33-513 IU/mL] and 22 U/L (IQR 13-27 U/L), respectively. Occult HBV coinfection remains under-diagnosed in African HIV-infected patients in the UK. Given the range of HBV DNA levels observed, further studies are warranted to determine its clinical significance and to guide screening strategies and ART selection in these patients. © 2013 British HIV Association.

Serendipitous occultations by kilometer size Kuiper Belt with MIOSOTYS

NASA Astrophysics Data System (ADS)

Doressoundiram, A.; Liu, C.-Y.; Maquet, L.; Roques, F.

2017-09-01

MIOSOTYS (Multi-object Instrument for Occultations in the SOlar system and TransitorY Systems) is a multi-fiber positioner coupled with a fast photometry camera. This is a visitor instrument mounted on the 193 cm telescope at the Observatoire de Haute-Provence, France and on the 123 cm telescope at the Calar Alto Observatory, Spain. Our immediate goal is to characterize the spatial distribution and extension of the Kuiper Belt, and the physical size distribution of TNOs. We present the observation campaigns during 2010-2013, objectives and observing strategy. We report the detection of potential candidates for occultation events of TNOs. We will discuss more specifically the method used to process the data and the modelling of diffraction patterns. We, finally present the results obtained concerning the distribution of sub-kilometer TNOs in the Kuiper Belt.

Astrometry of the Orcus/Vanth occultation on UT 7 March 2017

NASA Astrophysics Data System (ADS)

Bosh, Amanda S.; Zuluaga, Carlos; Levine, Stephen; Sickafoose, Amanda A.; Genade, Anja; Schindler, Karsten; Lister, Tim; Person, Michael J.

2017-10-01

On UT 7 March 2017, Orcus was predicted to occult a star with m=14.3. Observations were made at five observatories: the 0.6-m Astronomical Telescope of the University of Stuttgart (ATUS) at Sierra Remote Observatories (SRO), California; Las Cumbres Observatory’s 1-m telescope (ELP) at McDonald Observatory, Fort Davis, Texas; NASA’s 3-m InfraRed Telescope Facility (IRTF) on Mauna Kea, Hawaii; the 4.1-m Southern Astrophysical Research telescope (SOAR) on Cerro Pachón, Chile; and the 0.6-m Southeastern Association for Research in Astronomy telescope (SARA-CT) at Cerro Tololo, Chile. While observations at all sites were successful, only two—ELP and IRTF—observed solid-body occultation signatures. We will discuss the various predictions for this event and the reasons for the differences among them, including an offset of 130 mas for the star position from the position in the Gaia catalog. The sum of the positive and negative detections place constraints on the geometry of the Orcus/Vanth system, and we present our astrometric results for the geometric solution for this occultation. The implications of the light curve analyses are presented by Sickafoose et al., this conference.

Structure of the Atmosphere of Saturn at Low Latitudes: Results from the First Six Cassini Radio Occultation Experiments

NASA Astrophysics Data System (ADS)

Schinder, P. J.; Flasar, F. M.; Kliore, A. J.; Rappaport, N. J.; Asmar, S.; Anabtawi, A.; Barbinis, E.; Fleischman, D. U.; Goltz, G. L.; Johnston, D. V.; Rochblatt, D.; French, R. G.; McGhee, C. A.; Marouf, E. A.

2005-08-01

On May 3, 2005 occurred the first of a series of seven occultations of Cassini by Saturn which have taken or will take place during the spring and summer of 2005. These near diametric occultations cover a latitude range of between 8 N and 10 S planetocentric latitude, and will give us a detailed look at the structure of the low latitude neutral atmosphere of Saturn down to ˜ 1.6 \\ bar. These occultations are the first to be done at three wavelengths (S, X, and Ka bands) simultaneously. Preliminary results of the occultations that have occurred to date show abundant small scale structure in the temperature-pressure profiles, and a recurring temperature inversion starting at about 100 mbar and extending to roughly 200 mbar.

Impact of D-Dimer for Prediction of Incident Occult Cancer in Patients with Unprovoked Venous Thromboembolism

PubMed Central

Han, Donghee; ó Hartaigh, Bríain; Lee, Ji Hyun; Cho, In-Jeong; Shim, Chi Young; Chang, Hyuk-Jae; Hong, Geu-Ru; Ha, Jong-Won; Chung, Namsik

2016-01-01

Background Unprovoked venous thromboembolism (VTE) is related to a higher incidence of occult cancer. D-dimer is clinically used for screening VTE, and has often been shown to be present in patients with malignancy. We explored the predictive value of D-dimer for detecting occult cancer in patients with unprovoked VTE. Methods We retrospectively examined data from 824 patients diagnosed with deep vein thrombosis or pulmonary thromboembolism. Of these, 169 (20.5%) patients diagnosed with unprovoked VTE were selected to participate in this study. D-dimer was categorized into three groups as: <2,000, 2,000–4,000, and >4,000 ng/ml. Cox regression analysis was employed to estimate the odds of occult cancer and metastatic state of cancer according to D-dimer categories. Results During a median 5.3 (interquartile range: 3.4–6.7) years of follow-up, 24 (14%) patients with unprovoked VTE were diagnosed with cancer. Of these patients, 16 (67%) were identified as having been diagnosed with metastatic cancer. Log transformed D-dimer levels were significantly higher in those with occult cancer as compared with patients without diagnosis of occult cancer (3.5±0.5 vs. 3.2±0.5, P-value = 0.009, respectively). D-dimer levels >4,000 ng/ml was independently associated with occult cancer (HR: 4.12, 95% CI: 1.54–11.04, P-value = 0.005) when compared with D-dimer levels <2,000 ng/ml, even after adjusting for age, gender, and type of VTE (e.g., deep vein thrombosis or pulmonary thromboembolism). D-dimer levels >4000 ng/ml were also associated with a higher likelihood of metastatic cancer (HR: 9.55, 95% CI: 2.46–37.17, P-value <0.001). Conclusion Elevated D-dimer concentrations >4000 ng/ml are independently associated with the likelihood of occult cancer among patients with unprovoked VTE. PMID:27073982

Plasma D-dimer levels and ischaemic lesions in multiple vascular regions can predict occult cancer in patients with cryptogenic stroke.

PubMed

Gon, Y; Sakaguchi, M; Takasugi, J; Kawano, T; Kanki, H; Watanabe, A; Oyama, N; Terasaki, Y; Sasaki, T; Mochizuki, H

2017-03-01

Cancer patients with cryptogenic stroke often have high plasma D-dimer levels and lesions in multiple vascular regions. Hence, if patients with cryptogenic stroke display such characteristics, occult cancer could be predicted. This study aimed to investigate the clinical characteristics of cryptogenic stroke as the first manifestation of occult cancer and to determine whether plasma D-dimer levels and lesions in multiple vascular regions can predict occult cancer in patients with cryptogenic stroke. Between January 2006 and October 2015, data on 1225 patients with acute ischaemic stroke were extracted from the stroke database of Osaka University Hospital. Among them, 184 patients were classified as having cryptogenic stroke, and 120 patients without a diagnosis of cancer at stroke onset were identified. Clinical variables were analyzed between cryptogenic stroke patients with and without occult cancer. Among 120 cryptogenic stroke patients without a diagnosis of cancer, 12 patients had occult cancer. The body mass index, hemoglobin levels and albumin levels were lower; plasma D-dimer and high-sensitivity C-reactive protein levels were higher; and lesions in multiple vascular regions were more common in patients with than in those without occult cancer. Multiple logistic regression analysis revealed that plasma D-dimer levels (odds ratio, 3.48; 95% confidence interval, 1.68-8.33; P = 0.002) and lesions in multiple vascular regions (odds ratio, 7.40; 95% confidence interval, 1.70-39.45; P = 0.01) independently predicted occult cancer. High plasma D-dimer levels and lesions in multiple vascular regions can be used to predict occult cancer in patients with cryptogenic stroke. © 2016 EAN.

Data inversion algorithm development for the hologen occultation experiment

NASA Technical Reports Server (NTRS)

Gordley, Larry L.; Mlynczak, Martin G.

1986-01-01

The successful retrieval of atmospheric parameters from radiometric measurement requires not only the ability to do ideal radiometric calculations, but also a detailed understanding of instrument characteristics. Therefore a considerable amount of time was spent in instrument characterization in the form of test data analysis and mathematical formulation. Analyses of solar-to-reference interference (electrical cross-talk), detector nonuniformity, instrument balance error, electronic filter time-constants and noise character were conducted. A second area of effort was the development of techniques for the ideal radiometric calculations required for the Halogen Occultation Experiment (HALOE) data reduction. The computer code for these calculations must be extremely complex and fast. A scheme for meeting these requirements was defined and the algorithms needed form implementation are currently under development. A third area of work included consulting on the implementation of the Emissivity Growth Approximation (EGA) method of absorption calculation into a HALOE broadband radiometer channel retrieval algorithm.

Low-Latitude Ionospheric Density Irregularities and Associated Scintillations Investigated by Combining COSMIC RO and Ground-Based Global Positioning System Observations Over a Solar Active Period

NASA Astrophysics Data System (ADS)

Yang, Zhe; Liu, Zhizhao

2018-05-01

This study for the first time presents a locally integrated analysis of occurrences of ionospheric E and F region irregularities/scintillations in southeast China, by employing radio occultation (RO) profile data retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations from a ground-based Global Navigation Satellite System receiver over a solar active period from 2014 to 2015. Their occurrences in both nighttime and daytime were examined by using both amplitude scintillation index (S4) and the rate of change of total electron content index. It is found that (1) F region irregularities occurred predominantly during 20-03 local time (LT) and exhibited maximum (minimum) during equinoxes (solstices) and equinoctial (solstice) asymmetry. Their geographic mapping reveals the maximum occurrence in the westward tilted structure of equatorial plasma bubbles. In addition, the altitude-time variations indicate that their occurrences at higher altitudes were prevailing at 20-22 LT. (2) The E region irregularities were found prominently during 15-00 LT at altitudes of 90-110 km with an even geographic distribution. Their occurrences with maximum in summer (May-August) were distinctly detected by RO observations but insignificantly by ground-based observations. (3) By examining simultaneous observations of E and F region irregularities, it is found that they appeared absent during 21-00 LT and predominant after midnight. This could be related to the weakening/disruption of sporadic E (Es) layers during the development of equatorial plasma bubbles. A sign of coupling of E and F regions during nighttime is likely revealed from RO profile data.

The impact of nonuniform sampling on stratospheric ozone trends derived from occultation instruments

NASA Astrophysics Data System (ADS)

Damadeo, Robert P.; Zawodny, Joseph M.; Remsberg, Ellis E.; Walker, Kaley A.

2018-01-01

This paper applies a recently developed technique for deriving long-term trends in ozone from sparsely sampled data sets to multiple occultation instruments simultaneously without the need for homogenization. The technique can compensate for the nonuniform temporal, spatial, and diurnal sampling of the different instruments and can also be used to account for biases and drifts between instruments. These problems have been noted in recent international assessments as being a primary source of uncertainty that clouds the significance of derived trends. Results show potential recovery trends of ˜ 2-3 % decade-1 in the upper stratosphere at midlatitudes, which are similar to other studies, and also how sampling biases present in these data sets can create differences in derived recovery trends of up to ˜ 1 % decade-1 if not properly accounted for. Limitations inherent to all techniques (e.g., relative instrument drifts) and their impacts (e.g., trend differences up to ˜ 2 % decade-1) are also described and a potential path forward towards resolution is presented.

The BRAFT1799A mutation is not associated with occult contralateral carcinoma in patients with unilateral papillary thyroid microcarcinoma.

PubMed

Wan, Han-Feng; Zhang, Bin; Yan, Dan-Gui; Xu, Zhen-Gang

2015-01-01

The phenomenon of occult carcinoma maybe observed in patients with clinically unilateral papillary thyroid microcarcinoma (PTMC). Although many studies have reported that the BRAFT1799A mutation is associated with aggressive PTMC, the relationship between BRAFT1799A mutation and occult carcinoma is unclear. The aim of this study was to investigate the risk factors, including BRAFT1799A mutation, for occult contralateral carcinoma in clinically unilateral PTMC accompanied by benign nodules in the contralateral lobe. From January 2011 to December 2013,we prospectively enrolled 89 consecutive PTMC patients with clinically unilateral carcinoma accompanied by benign nodules in the contralateral lobe who received a total thyroidectomy and cervical lymph node dissection. BRAFT1799A mutation was tested by pyrosequencing on postoperative paraffin specimens. The frequency and predictive factors for occult contralateral carcinoma were analyzed with respect to the following variables: age, gender, family history, tumor size, presence of Hashimoto thyroiditis, extrathyroidal extension, central lymph node metastasis, multifocality of primary tumor, or BRAFT1799A mutation. A total of 36 patients (40.4%) had occult PTMC in the contralateral lobe. The median diameter of the occult tumors was 0.33±0.21 cm. The BRAFT1799A mutation was found in 38 cases (42.7%). According to the univariate analysis, there were no significant differences between the presence of occult contralateral carcinoma and age, gender, family history, tumor size, presence of Hashimoto thyroiditis, extrathyroidal extension, central lymph node metastasis, multifocality of primary tumor, or BRAFT1799A mutation. Using current methods, it is difficult to preoperatively identify patients with PTMC, and further research is needed to determine predictive factors for the presence of occult contralateral carcinoma in patients with unilateral PTMC.

Thematic trip: "Save Roşia MontanÄă"

NASA Astrophysics Data System (ADS)

Eugenia, Marcu

2015-04-01

The name Roşia Montană, situated in Transylvania, became well known after a Romanian-Canadian company, Roşia Montană Gold Company (RMGC), obtained the concession license on exploitation for gold and silver minerals in the Roşia Montană area. The project consists of opening the largest surface gold mines in Europe using cyanide, which will include four open pits and a processing plant for gold and silver in The Roşia Valley and a tailings facility with an area of 367 hectares in the Corna Valley. One of the main fears is related to a possible ecological accident like the one in Baia Mare in 2000, when a tailing facility dam break led to cyanide pollution of Tisa and Danube rivers that resulted in the death of 1,200 tons of fish and contamination of water resources for 2 million people. This thematic trip is important for the scientific preparation of students and an opportunity to educate them in the spirit of environmental protection. The training and education of students will require assimilation and understanding, actively and consciously, using the knowledge acquired during the compulsory curriculum and training skills. REASON: The continuous degradation of the environment is a major crisis due to human intervention in nature, and the proposed Roşia Montană mining project will continue this trend. The company proposes to extract gold from mines by using the gold separation technique using cyanide, a process that involves destroying a total area of 16 km² which includes 5 mountains, 7 churches, 11 cemeteries and the ruins of Alburnus Maior Citadel, as well as creating pollution that would last for hundreds of years. The extraction of gold from low-grade ores using cyanide processes was estimated to result in a worldwide emission of 45,300 tons of hydrogen cyanide. Environmental education for a healthy life has children as target group, because they are the trustees and beneficiaries of tomorrow's natural resources and can influence the attitudes of

Lunar Occultations, Setting the Stage for VLTI: The Case Study of CW-Leo (aka IRC+10216)

NASA Astrophysics Data System (ADS)

Käufl, Hans Ulrich; Stecklum, Bringfried; Richter, Steffen; Richichi, Andrea

Lunar occultation allows for a sneak preview of what the VLTI will observe, both with comparable angular resolution and sensitivity. In the thermal infrared ( λ ≈ 10μ m, angular resolution ≤ 0.03^' ') the technique has been pioneered with TIMMI on La Silla. Using this technique several dust shells around Asymptotic Giant Branch stars have been resolved. For the Carbon star CW-Leo (IRC+10 216) high S/N scans will allow for `11/2-dimensional' imaging of the source. At the present state of data reduction the light curves already provide for a very convincing proof of theories on the milli-arcsec scale. In combination with VLTI the technique allows for checks of the visibility calibration and related issues. Moreover, in the (u,v)-plane both techniques are extremely complementary, so that a merging of the data sets appear highly desirable. At La Silla and Paranal ESO a suite of instruments which can be (ab)used for this project is under construction.

Alice Solar Occultation

NASA Image and Video Library

2015-07-17

This figure shows how the Alice instrument count rate changed over time during the sunset and sunrise observations. The count rate is largest when the line of sight to the sun is outside of the atmosphere at the start and end times. Molecular nitrogen (N2) starts absorbing sunlight in the upper reaches of Pluto's atmosphere, decreasing as the spacecraft approaches the planet's shadow. As the occultation progresses, atmospheric methane and hydrocarbons can also absorb the sunlight and further decrease the count rate. When the spacecraft is totally in Pluto's shadow the count rate goes to zero. As the spacecraft emerges from Pluto's shadow into sunrise, the process is reversed. By plotting the observed count rate in the reverse time direction, it is seen that the atmospheres on opposite sides of Pluto are nearly identical. http://photojournal.jpl.nasa.gov/catalog/PIA19716

[Identification of occult disseminated tumor cells by recombinant herpes simplex virus expressing GFP (HSV(GFP))].

PubMed

Han, Xiang-ping; Shi, Gui-lan; Wang, Cheng-feng; Li, Jie; Zhang, Jian-wei; Zhang, Yu; Zhang, Shu-ren; Liu, Bin-lei

2012-12-01

To develop a novel rapid protocol for the detection of occult disseminated tumor cells by a recombinant herpes simplex virus expressing GFP (HSV(GFP)). Tumor cells of seven cell lines were exposed to HSV(GFP) and then examined for GFP expression by fluorescence microscopy. Various numbers of tumor cells (10, 100, 1000, 10 000) were mixed into 2 ml human whole blood, separated with lymphocytes separation medium, exposed to HSV(GFP), incubated at 37°C for 6 - 24 h and then counted for the number of green cells under the fluorescence microscope. Some clinical samples including peripheral blood, pleural effusion, ascites, spinal fluid from tumor-bearing patients were screened using this protocol in parallel with routine cytological examination. HSV(GFP) was able to infect all 7 tumor cell lines indicating that the HSV(GFP) can be used to detect different types of tumor cells. The detection sensitivity was 10 cancer cells in 2 ml whole blood. In the clinical samples, there were 4/15 positive by routine cytological examination but 11/15 positive by HSV(GFP), indicating a higher sensitivity of this new protocol. Recombinant herpes simplex virus-mediated green fluorescence is a simple and sensitive technique for the identification of occult disseminated cancer cells including circulating tumor cells (CTCs).

A stellar occultation by (486958) 2014 MU69: results from the 2017 July 17 portable telescope campaign

NASA Astrophysics Data System (ADS)

Zangari, Amanda Marie; Buie, Marc W.; Stern, S. Alan; Terrell, Dirk; Porter, Simon Bernard; Verbiscer, Anne J.; Soto, Alejandro; Tamblyn, Peter; Benecchi, Susan; Parker, Alex; Wasserman, Lawrence H.; Young, Eliot F.; Skrutskie, Michael F.; New Horizons MU69 Occultation Observing Team

2017-10-01

On 2017 July 17, (486958) 2014 MU69 passed in front of a star as seen from the area north of Comodoro Rivadavia, in Chubut Province, Argentina. Despite challenging wind conditions, twenty two portable telescopes recorded data of the g'= 12.60 mag star in a 45-minute block centered on the predicted midtime of roughly 03:50 UT. Each telescope was spaced approximately 4 km apart in a “picket fence” pattern to target an object as small as 10 km. The picket fence spanned roughly 100 km. Five telescopes observed a solid body occultation.Occultation data provide a unique one-dimensional probe of the 2014 MU69 system that is impossible to achieve from direct imaging. These data will allow for fits of the size and shape of 2014 MU69, and from its derived size, the albedo . The occultation data will also aid in navigation of NASA’s New Horizons spacecraft toward its January 1, 2019 encounter with 2014 MU69.We will detail the July 17 occultation campaign and present analyses of the light curves from each portable station, including occultation timing and constraints on dust and and other objects in the system derived from the occultation baseline data.This work would not have been possible without the financial support of the New Horizons mission and NASA, astrometric support of the Gaia mission and HST, and logistical support from Argentina, CONAE and specifically Comodoro Rivadavia as well as assistance from the US Embassy in Buenos Aires.

Digital solar edge tracker for the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)