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Sample records for computerized ionospheric tomography

  1. Computerized ionospheric tomography based on geosynchronous SAR

    NASA Astrophysics Data System (ADS)

    Hu, Cheng; Tian, Ye; Dong, Xichao; Wang, Rui; Long, Teng

    2017-02-01

    Computerized ionospheric tomography (CIT) based on spaceborne synthetic aperture radar (SAR) is an emerging technique to construct the three-dimensional (3-D) image of ionosphere. The current studies are all based on the Low Earth Orbit synthetic aperture radar (LEO SAR) which is limited by long repeat period and small coverage. In this paper, a novel ionospheric 3-D CIT technique based on geosynchronous SAR (GEO SAR) is put forward. First, several influences of complex atmospheric environment on GEO SAR focusing are detailedly analyzed, including background ionosphere and multiple scattering effects (induced by turbulent ionosphere), tropospheric effects, and random noises. Then the corresponding GEO SAR signal model is constructed with consideration of the temporal-variant background ionosphere within the GEO SAR long integration time (typically 100 s to 1000 s level). Concurrently, an accurate total electron content (TEC) retrieval method based on GEO SAR data is put forward through subband division in range and subaperture division in azimuth, obtaining variant TEC value with respect to the azimuth time. The processing steps of GEO SAR CIT are given and discussed. Owing to the short repeat period and large coverage area, GEO SAR CIT has potentials of covering the specific space continuously and completely and resultantly has excellent real-time performance. Finally, the TEC retrieval and GEO SAR CIT construction are performed by employing a numerical study based on the meteorological data. The feasibility and correctness of the proposed methods are verified.

  2. A combined reconstruction algorithm for computerized ionospheric tomography

    NASA Astrophysics Data System (ADS)

    Wen, D. B.; Ou, J. K.; Yuan, Y. B.

    Ionospheric electron density profiles inverted by tomographic reconstruction of GPS derived total electron content TEC measurements has the potential to become a tool to quantify ionospheric variability and investigate ionospheric dynamics The problem of reconstructing ionospheric electron density from GPS receiver to satellite TEC measurements are formulated as an ill-posed discrete linear inverse problem A combined reconstruction algorithm of computerized ionospheric tomography CIT is proposed in this paper In this algorithm Tikhonov regularization theory TRT is exploited to solve the ill-posed problem and its estimate from GPS observation data is input as the initial guess of simultaneous iterative reconstruction algorithm SIRT The combined algorithm offer a more reasonable method to choose initial guess of SIRT and the use of SIRT algorithm is to improve the quality of the final reconstructed imaging Numerical experiments from the actual GPS observation data are used to validate the reliability of the method the reconstructed results show that the new algorithm works reasonably and effectively with CIT the overall reconstruction error reduces significantly compared to the reconstruction error of SIRT only or TRT only

  3. Comparisons of ionospheric electron density distributions reconstructed by GPS computerized tomography, backscatter ionograms, and vertical ionograms

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Lei, Yong; Li, Bofeng; An, Jiachun; Zhu, Peng; Jiang, Chunhua; Zhao, Zhengyu; Zhang, Yuannong; Ni, Binbin; Wang, Zemin; Zhou, Xuhua

    2015-12-01

    Global Positioning System (GPS) computerized ionosphere tomography (CIT) and ionospheric sky wave ground backscatter radar are both capable of measuring the large-scale, two-dimensional (2-D) distributions of ionospheric electron density (IED). Here we report the spatial and temporal electron density results obtained by GPS CIT and backscatter ionogram (BSI) inversion for three individual experiments. Both the GPS CIT and BSI inversion techniques demonstrate the capability and the consistency of reconstructing large-scale IED distributions. To validate the results, electron density profiles obtained from GPS CIT and BSI inversion are quantitatively compared to the vertical ionosonde data, which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings. Our study can improve current understanding of the capability and insufficiency of these two methods on the large-scale IED reconstruction.

  4. Using computerized tomography to determine ionospheric structures. Part 1, Notivation and basic approaches

    SciTech Connect

    Vittitoe, C.N.

    1993-08-01

    Properties of the ionosphere are reviewed along with its correlations with other geophysical phenomena and with applications of ionospheric studies to communication, navigation, and surveillance systems. Computer tomography is identified as a method to determine the detailed, three-dimensional distribution of electron density within the ionosphere. Several tomography methods are described, with a basic approach illustrated by an example. Limitations are identified.

  5. 4D computerized ionospheric tomography by using GPS measurements and IRI-Plas model

    NASA Astrophysics Data System (ADS)

    Tuna, Hakan; Arikan, Feza; Arikan, Orhan

    2016-07-01

    Ionospheric imaging is an important subject in ionospheric studies. GPS based TEC measurements provide very accurate information about the electron density values in the ionosphere. However, since the measurements are generally very sparse and non-uniformly distributed, computation of 3D electron density estimation from measurements alone is an ill-defined problem. Model based 3D electron density estimations provide physically feasible distributions. However, they are not generally compliant with the TEC measurements obtained from GPS receivers. In this study, GPS based TEC measurements and an ionosphere model known as International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) are employed together in order to obtain a physically accurate 3D electron density distribution which is compliant with the real measurements obtained from a GPS satellite - receiver network. Ionospheric parameters input to the IRI-Plas model are perturbed in the region of interest by using parametric perturbation models such that the synthetic TEC measurements calculated from the resultant 3D electron density distribution fit to the real TEC measurements. The problem is considered as an optimization problem where the optimization parameters are the parameters of the parametric perturbation models. Proposed technique is applied over Turkey, on both calm and storm days of the ionosphere. Results show that the proposed technique produces 3D electron density distributions which are compliant with IRI-Plas model, GPS TEC measurements and ionosonde measurements. The effect of the GPS receiver station number on the performance of the proposed technique is investigated. Results showed that 7 GPS receiver stations in a region as large as Turkey is sufficient for both calm and storm days of the ionosphere. Since the ionization levels in the ionosphere are highly correlated in time, the proposed technique is extended to the time domain by applying Kalman based tracking and smoothing

  6. Computerized tomography calibrator

    NASA Technical Reports Server (NTRS)

    Engel, Herbert P. (Inventor)

    1991-01-01

    A set of interchangeable pieces comprising a computerized tomography calibrator, and a method of use thereof, permits focusing of a computerized tomographic (CT) system. The interchangeable pieces include a plurality of nestable, generally planar mother rings, adapted for the receipt of planar inserts of predetermined sizes, and of predetermined material densities. The inserts further define openings therein for receipt of plural sub-inserts. All pieces are of known sizes and densities, permitting the assembling of different configurations of materials of known sizes and combinations of densities, for calibration (i.e., focusing) of a computerized tomographic system through variation of operating variables thereof. Rather than serving as a phanton, which is intended to be representative of a particular workpiece to be tested, the set of interchangeable pieces permits simple and easy standardized calibration of a CT system. The calibrator and its related method of use further includes use of air or of particular fluids for filling various openings, as part of a selected configuration of the set of pieces.

  7. A new computerized ionosphere tomography model using the mapping function and an application to the study of seismic-ionosphere disturbance

    NASA Astrophysics Data System (ADS)

    Kong, Jian; Yao, Yibin; Liu, Lei; Zhai, Changzhi; Wang, Zemin

    2016-08-01

    A new algorithm for ionosphere tomography using the mapping function is proposed in this paper. First, the new solution splits the integration process into four layers along the observation ray, and then, the single-layer model (SLM) is applied to each integration part using a mapping function. Next, the model parameters are estimated layer by layer with the Kalman filtering method by introducing the scale factor (SF) γ to solve the ill-posed problem. Finally, the inversed images of different layers are combined into the final CIT image. We utilized simulated data from 23 IGS GPS stations around Europe to verify the estimation accuracy of the new algorithm; the results show that the new CIT model has better accuracy than the SLM in dense data areas and the CIT residuals are more closely grouped. The stability of the new algorithm is discussed by analyzing model accuracy under different error levels (the max errors are 5TECU, 10TECU, 15TECU, respectively). In addition, the key preset parameter, SFγ , which is given by the International Reference Ionosphere model (IRI2012). The experiment is designed to test the sensitivity of the new algorithm to SF variations. The results show that the IRI2012 is capable of providing initial SF values. Also in this paper, the seismic-ionosphere disturbance (SID) of the 2011 Japan earthquake is studied using the new CIT algorithm. Combined with the TEC time sequence of Sat.15, we find that the SID occurrence time and reaction area are highly related to the main shock time and epicenter. According to CIT images, there is a clear vertical electron density upward movement (from the 150-km layer to the 450-km layer) during this SID event; however, the peak value areas in the different layers were different, which means that the horizontal movement velocity is not consistent among the layers. The potential physical triggering mechanism is also discussed in this paper. Compared with the SLM, the RMS of the new CIT model is improved by

  8. Using computerized tomography to determine ionospheric structures. Part 2, A method using curved paths to increase vertical resolution

    SciTech Connect

    Vittitoe, C.N.

    1993-08-01

    A method is presented to unfold the two-dimensional vertical structure in electron density by using data on the total electron content for a series of paths through the ionosphere. The method uses a set of orthonormal basis functions to represent the vertical structure and takes advantage of curved paths and the eikonical equation to reduce the number of iterations required for a solution. Curved paths allow a more thorough probing of the ionosphere with a given set of transmitter and receiver positions. The approach can be directly extended to more complex geometries.

  9. Research on ionospheric tomography based on variable pixel height

    NASA Astrophysics Data System (ADS)

    Zheng, Dunyong; Li, Peiqing; He, Jie; Hu, Wusheng; Li, Chaokui

    2016-05-01

    A novel ionospheric tomography technique based on variable pixel height was developed for the tomographic reconstruction of the ionospheric electron density distribution. The method considers the height of each pixel as an unknown variable, which is retrieved during the inversion process together with the electron density values. In contrast to conventional computerized ionospheric tomography (CIT), which parameterizes the model with a fixed pixel height, the variable-pixel-height computerized ionospheric tomography (VHCIT) model applies a disturbance to the height of each pixel. In comparison with conventional CIT models, the VHCIT technique achieved superior results in a numerical simulation. A careful validation of the reliability and superiority of VHCIT was performed. According to the results of the statistical analysis of the average root mean square errors, the proposed model offers an improvement by 15% compared with conventional CIT models.

  10. X-ray computerized tomography

    SciTech Connect

    Wellington, S.L.; Vinegar, H.J.

    1987-08-01

    Computerized tomography (CT) is a new radiological imaging technique that measures density and atomic composition inside opaque objects. A revolutionary advance in medical radiology since 1972, CT has only recently been applied in petrophysics and reservoir engineering. This paper discusses several petrophysical applications, including three-dimensional (3D) measurement of density and porosity; rock mechanics studies; correlation of core logs with well logs; characterization of mud invasion, fractures, and disturbed core; and quantification of complex mineralogies and sand/shale ratios. Reservoir engineering applications presented include fundamental studies of CO/sub 2/ displacement in cores, focussing on viscous fingering, gravity segregation, miscibility, and mobility control.

  11. Computerized tomography in evaluation of hepatic neoplasms

    SciTech Connect

    Luna, R.F.; Resende, C.; Tishler, J.M.A.; Aldrete, J.S.; Shin, M.S.; Rubin, E.; Rahn, N.H.

    1984-08-01

    The authors reviewed their experience with computerized tomography (CT) of the abdomen in 212 patients with histologically documented liver neoplasms seen during a 30-month period. The CT findings in cavernous hemangioma and focal nodular hyperplasia were specific, and permitted accurate diagnosis of this lesion before biopsy. The CT appearance of all other lesions was variable. CT is useful in providing an accurate evaluation of the intrahepatic and extrahepatic extent of the neoplasm.

  12. Beacon satellite receiver for ionospheric tomography

    NASA Astrophysics Data System (ADS)

    Vierinen, J.; Norberg, J.; Lehtinen, M. S.; Amm, O.; Roininen, L.; Väänänen, A.; Erickson, P. J.; McKay-Bukowski, D.

    2014-12-01

    We introduce a new coherent dual-channel beacon satellite receiver intended for ionospheric tomography. The measurement equation includes neutral atmosphere and ionosphere propagation effects, relative errors in satellite and receiver clocks, and residual Doppler shifts caused by errors in the satellite ephemeris. We also investigate the distribution of errors for phase curve measurements and the use of phase curve measurements for limited angle tomography using the framework of statistical linear inverse problems. We describe the design of our beacon satellite receiver software and present one possible hardware configuration. Finally, we present results obtained using a network of four newly developed receivers and compare the results with those of an existing ionospheric tomography network at Sodankylä Geophysical Observatory.

  13. [Computerized tomography and craniocerebral trauma].

    PubMed

    Richter, H P; Braun, V

    1993-11-01

    Computed tomography (CT) is now the standard neuroradiological examination for patients with major head injuries, although conventional X-ray of the skull should not be neglected. Whereas the latter only shows such skull pathology as fractures or intracranial air following a basal fracture, CT clearly visualizes intracranial pathology. It allows differentiation between haematoma and contusion, between localized oedema and generalized brain swelling; CT is therefore indicated in every patient with disturbed consciousness, focal neurological signs, and/or secondary clinical impairment, and also in all drunken patients with head injury. In a patient with impaired consciousness and focal neurological deficit the probability of a pathologic CT is 85%. An extracerebral haematoma is often present, which needs urgent evacuation. A modern, non-expensive communications system using a standard telephone line enables hospitals without a neurosurgical unit to send CT pictures that are difficult to interpret to a neurosurgeon and to discuss them on-line by telephone. This system has now been in operation for over 2 years and has improved the care of patients with head injury in our region. It is highly efficient and reliable and improves cooperation between distant hospitals. It also helps to avoid unnecessary transfers, which are not only expensive but may even harm a critically ill patient.

  14. Mesoscale ionospheric tomography at the Auroral region

    NASA Astrophysics Data System (ADS)

    Luntama, J.; Kokkatil, G. V.

    2008-12-01

    FMI (Finnish Meteorological Institute) has used observations from the dense GNSS network in Finland for high resolution regional ionospheric tomography. The observation system used in this work is the VRS (Virtual Reference Station) network in Finland operated by Geotrim Ltd. This network contains 86 GNSS ground stations providing two frequency GPS and GLONASS observations with the sampling rate of 1 Hz. The network covers the whole Finland and the sampling of the ionosphere is very good for observing mesoscale ionospheric structures at the Auroral region. The ionospheric tomography software used by FMI is the MIDAS (Multi-Instrument Data Analysis System) algorithm developed and implemented by the University of Bath (Mitchell and Spencer, 2003). MIDAS is a 3-D extension of the 2-D tomography algorithm originally presented by Fremouw et al. (1992). The research at FMI is based on ground based GNSS data collected in December 2006. The impacts of the two geomagnetic storms during the month are clearly visible in the retrieved electron density and TEC maps and they can be correlated with the magnetic field disturbances measured by the IMAGE magnetometer network. This is the first time that mesoscale structures in the ionospheric plasma can be detected from ground based GNSS observations at the Auroral region. The continuous high rate observation data from the Geotrim network allows monitoring of the temporal evolution of these structures throughout the storms. Validation of the high resolution electron density and TEC maps is a challenge as independent reference observations with a similar resolution are not available. FMI has compared the 3-D electron density maps against the 2-D electron density plots retrieved from the observations from the Ionospheric Tomography Chain operated by the Sodankylä Geophysical Observatory (SGO). Additional validation has been performed with intercomparisons with observations from the ground based magnetometer and auroral camera network

  15. Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Huba, J. D.; Chaturvedi, P. K.; Fulford, J. A.; Forsyth, P. A.; Anderson, D. N.; Zalesak, S. T.

    1993-01-01

    Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.

  16. Ionospheric tomography using the FORTE satellite

    SciTech Connect

    Murphy, T.C.

    1993-08-01

    The possibility of obtaining ionospheric profile data via tomographic techniques has elicited considerable interest in recent years. The input data for the method is a set of total electron content measurements along intersecting lines of sight which form a grid. This can conveniently be provided by a fast-moving satellite with a VHF beacon which will generate the multiple paths needed for effective tomography. Los Alamos and Sandia National Laboratories will launch and operate the FORTE satellite for the US Department of Energy, with launch scheduled in 1995. FORTE will provide such a beacon. Additionally, wideband VHF receivers aboard the satellite will allow corraborative measurements of ionospheric profile parameters in some cases.

  17. Ionospheric tomography using Faraday rotation of Automatic Dependent Surveillance Broadcast (UHF) signals Ionospheric Measurement From ADS-B Signals

    NASA Astrophysics Data System (ADS)

    Cushley, Alex Clay

    The proposed launch of a CubeSat carrying the first space-borne ADS-B receiver by RMCC will create a unique opportunity to study the modification of radio waves following propagation through the ionosphere as the signals propagate from the transmitting aircraft to the passive satellite receiver(s). Experimental work is described which successfully demonstrated that ADS-B data can be used to reconstruct two-dimensional electron density maps of the ionosphere using techniques from computerized tomography. Ray-tracing techniques are used to determine the characteristics of individual waves, including the wave path and the state of polarization at the satellite receiver. The modelled Faraday rotation is determined and converted to TEC along the ray-paths. The resulting TEC is used as input for CIT using ART. This study concentrated on meso-scale structures 100--1000 km in horizontal extent. The primary scientific interest of this thesis was to show the feasibility of a new method to image the ionosphere and obtain a better understanding of magneto-ionic wave propagation. Keywords: Automatic Dependent Surveillance-Broadcast (ADS-B), Faraday rotation, electromagnetic (EM) waves, radio frequency (RF) propagation, ionosphere (auroral, irregularities, instruments and techniques), electron density profile, total electron content (TEC), computer ionospheric tomography (CIT), algebraic reconstruction technique (ART).

  18. Medium-scale traveling ionospheric disturbances by three-dimensional ionospheric GPS tomography

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Saito, A.; Lin, C. H.; Yamamoto, M.; Suzuki, S.; Seemala, G. K.

    2016-02-01

    In this study, we develop a three-dimensional ionospheric tomography with the ground-based global position system (GPS) total electron content observations. Because of the geometric limitation of GPS observation path, it is difficult to solve the ill-posed inverse problem for the ionospheric electron density. Different from methods given by pervious studies, we consider an algorithm combining the least-square method with a constraint condition, in which the gradient of electron density tends to be smooth in the horizontal direction and steep in the vicinity of the ionospheric F2 peak. This algorithm is designed to be independent of any ionospheric or plasmaspheric electron density models as the initial condition. An observation system simulation experiment method is applied to evaluate the performance of the GPS ionospheric tomography in detecting ionospheric electron density perturbation at the scale size of around 200 km in wavelength, such as the medium-scale traveling ionospheric disturbances.

  19. Computerized tomography using video recorded fluoroscopic images

    NASA Technical Reports Server (NTRS)

    Kak, A. C.; Jakowatz, C. V., Jr.; Baily, N. A.; Keller, R. A.

    1975-01-01

    A computerized tomographic imaging system is examined which employs video-recorded fluoroscopic images as input data. By hooking the video recorder to a digital computer through a suitable interface, such a system permits very rapid construction of tomograms.

  20. Anti-3-[18F]FACBC Positron Emission Tomography-Computerized Tomography and 111In-Capromab Pendetide Single Photon Emission Computerized Tomography-Computerized Tomography for Recurrent Prostate Carcinoma: Results of a Prospective Clinical Trial

    PubMed Central

    Schuster, David M.; Nieh, Peter T.; Jani, Ashesh B.; Amzat, Rianot; Bowman, F. DuBois; Halkar, Raghuveer K.; Master, Viraj A.; Nye, Jonathon A.; Odewole, Oluwaseun A.; Osunkoya, Adeboye O.; Savir-Baruch, Bital; Alaei-Taleghani, Pooneh; Goodman, Mark M.

    2014-01-01

    Purpose We prospectively evaluated the amino acid analogue positron emission tomography radiotracer anti-3-[18F]FACBC compared to ProstaScint® (111In-capromab pendetide) single photon emission computerized tomography-computerized tomography to detect recurrent prostate carcinoma. Materials and Methods A total of 93 patients met study inclusion criteria who underwent anti-3-[18F]FACBC positron emission tomography-computerized tomography plus 111In-capromab pendetide single photon emission computerized tomography-computerized tomography for suspected recurrent prostate carcinoma within 90 days. Reference standards were applied by a multidisciplinary board. We calculated diagnostic performance for detecting disease. Results In the 91 of 93 patients with sufficient data for a consensus on the presence or absence of prostate/bed disease anti-3-[18F]FACBC had 90.2% sensitivity, 40.0% specificity, 73.6% accuracy, 75.3% positive predictive value and 66.7% negative predictive value compared to 111In-capromab pendetide with 67.2%, 56.7%, 63.7%, 75.9% and 45.9%, respectively. In the 70 of 93 patients with a consensus on the presence or absence of extraprostatic disease anti-3-[18F]FACBC had 55.0% sensitivity, 96.7% specificity, 72.9% accuracy, 95.7% positive predictive value and 61.7% negative predictive value compared to 111In-capromabpendetide with10.0%, 86.7%, 42.9%, 50.0% and 41.9%, respectively. Of 77 index lesions used to prove positivity histological proof was obtained in 74 (96.1%). Anti-3-[18F]FACBC identified 14 more positive prostate bed recurrences (55 vs 41) and 18 more patients with extraprostatic involvement (22 vs 4). Anti-3-[18F]FACBC positron emission tomography-computerized tomography correctly up-staged 18 of 70 cases (25.7%) in which there was a consensus on the presence or absence of extraprostatic involvement. Conclusions Better diagnostic performance was noted for anti-3-[18F]FACBC positron emission tomography-computerized tomography than for 111In

  1. Ionospheric Tomography Using Faraday Rotation of Automatic Dependant Surveillance Broadcast UHF Signals

    NASA Astrophysics Data System (ADS)

    Cushley, A. C.

    2013-12-01

    The proposed launch of a satellite carrying the first space-borne ADS-B receiver by the Royal Military College of Canada (RMCC) will create a unique opportunity to study the modification of the 1090 MHz radio waves following propagation through the ionosphere from the transmitting aircraft to the passive satellite receiver(s). Experimental work successfully demonstrated that ADS-B data can be used to reconstruct two dimensional (2D) electron density maps of the ionosphere using computerized tomography (CT). The goal of this work is to evaluate the feasibility of CT reconstruction. The data is modelled using Ray-tracing techniques. This allows us to determine the characteristics of individual waves, including the wave path and the state of polarization at the satellite receiver. The modelled Faraday rotation (FR) is determined and converted to total electron content (TEC) along the ray-paths. The resulting TEC is used as input for computerized ionospheric tomography (CIT) using algebraic reconstruction technique (ART). This study concentrated on meso-scale structures 100-1000 km in horizontal extent. The primary scientific interest of this thesis was to show the feasibility of a new method to image the ionosphere and obtain a better understanding of magneto-ionic wave propagation. Multiple feature input electron density profile to ray-tracing program. Top: reconstructed relative electron density map of ray-trace input (Fig. 1) using TEC measurements and line-of-sight path. Bottom: reconstructed electron density map of ray-trace input using quiet background a priori estimate.

  2. Model-assisted ionospheric tomography: A new algorithm

    SciTech Connect

    Raymund, T.D.; Bresler, Y.; Anderson, D.N.; Daniell, R.E.

    1994-12-01

    Ionospheric tomography uses total electron content (TEC) records collected by longitudinally aligned stations, which receive a beacon satellite orbiting overhead. The electron density distribution is reconstructed for the region bounded by the satellite orbit and the line of ground receivers. A new reconstruction algorithm is describes which satisfies the TEC records, makes use of an ionospheric model, and allows the incorporation of complementary measurements. The new algorithm also accepts relative (rather than absolute) TEC as input data. A comparison of the new algorithm and one used recently shows significant improvement over early techniques, particularly when a scaled ionogram is included in the data.

  3. IONOTOMO: A new approach for ionospheric tomography using OTH radar

    NASA Astrophysics Data System (ADS)

    Roy, Corinna; Occhipinti, Giovanni; Boschi, Lapo; Moliné, Jean-Philippe

    2013-04-01

    Most of the recent methods in ionospheric tomography are based on the inversion of the Total Electron Content (TEC) measured by ground-based GPS receivers [e.g., Garcia et al. 2008]. As a consequence of the high frequency of the GPS, the electron density structure is principally well reconstructed at the F2 region, where the ionosphere reaches the maximum of ionization, neglecting the lower ionosphere. Here, we develop a new 3D ionospheric tomography method based on the full analysis of over-the-horizon (OTH) radar data. Previous studies in ionospheric tomography by OTH radar (Fridman and Fridman, 1994; Ruelle and Landeau, 1994; Landeau et al., 1997; Fridman, 1998) are all based on the inversion of the leading edge echo curve, consequently an important amount of valuable information present in the data is necessarily neglected. To overcome this limit, we set up a new method, based on the ray-tracing tool TDR [Occhipinti, 2006], to invert the propagation time of electromagnetic waves emitted by monostatic OTH radars. The major advance of our methodology is taking into account, numerically and jointly, not only the speed variation of EM wave induced by the electron density variation (solved analytically with a linear inversion) but also the perturbation in the raypath (nonlinear numerical method). As the present problem is an ill posed problem we calculate the matrix inversion numerically, using a regularisation method (Tikhonov, 1963). We determine the best regularisation parameter using the Lcurve method (Hansen, 2000). We present here the originality and the advantage of our method with a full set of synthetic benchmark highlighting the sensitivity of our tomography to the plasma heterogeneities. Some preliminary test on real data will be presented with a full coverage over Europe. Indeed, the ionospheric tomography by OTH radar, jointly with GPS, could open new exciting perspective in the plasma density estimation with a good resolution to the entire ionosphere

  4. Identifying and classifying hyperostosis frontalis interna via computerized tomography.

    PubMed

    May, Hila; Peled, Nathan; Dar, Gali; Hay, Ori; Abbas, Janan; Masharawi, Youssef; Hershkovitz, Israel

    2010-12-01

    The aim of this study was to recognize the radiological characteristics of hyperostosis frontalis interna (HFI) and to establish a valid and reliable method for its identification and classification. A reliability test was carried out on 27 individuals who had undergone a head computerized tomography (CT) scan. Intra-observer reliability was obtained by examining the images three times, by the same researcher, with a 2-week interval between each sample ranking. The inter-observer test was performed by three independent researchers. A validity test was carried out using two methods for identifying and classifying HFI: 46 cadaver skullcaps were ranked twice via computerized tomography scans and then by direct observation. Reliability and validity were calculated using Kappa test (SPSS 15.0). Reliability tests of ranking HFI via CT scans demonstrated good results (K > 0.7). As for validity, a very good consensus was obtained between the CT and direct observation, when moderate and advanced types of HFI were present (K = 0.82). The suggested classification method for HFI, using CT, demonstrated a sensitivity of 84%, specificity of 90.5%, and positive predictive value of 91.3%. In conclusion, volume rendering is a reliable and valid tool for identifying HFI. The suggested three-scale classification is most suitable for radiological diagnosis of the phenomena. Considering the increasing awareness of HFI as an early indicator of a developing malady, this study may assist radiologists in identifying and classifying the phenomena.

  5. Bayesian statistical ionospheric tomography improved by incorporating ionosonde measurements

    NASA Astrophysics Data System (ADS)

    Norberg, Johannes; Virtanen, Ilkka I.; Roininen, Lassi; Vierinen, Juha; Orispää, Mikko; Kauristie, Kirsti; Lehtinen, Markku S.

    2016-04-01

    We validate two-dimensional ionospheric tomography reconstructions against EISCAT incoherent scatter radar measurements. Our tomography method is based on Bayesian statistical inversion with prior distribution given by its mean and covariance. We employ ionosonde measurements for the choice of the prior mean and covariance parameters and use the Gaussian Markov random fields as a sparse matrix approximation for the numerical computations. This results in a computationally efficient tomographic inversion algorithm with clear probabilistic interpretation. We demonstrate how this method works with simultaneous beacon satellite and ionosonde measurements obtained in northern Scandinavia. The performance is compared with results obtained with a zero-mean prior and with the prior mean taken from the International Reference Ionosphere 2007 model. In validating the results, we use EISCAT ultra-high-frequency incoherent scatter radar measurements as the ground truth for the ionization profile shape. We find that in comparison to the alternative prior information sources, ionosonde measurements improve the reconstruction by adding accurate information about the absolute value and the altitude distribution of electron density. With an ionosonde at continuous disposal, the presented method enhances stand-alone near-real-time ionospheric tomography for the given conditions significantly.

  6. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    NASA Astrophysics Data System (ADS)

    Bahcivan, H.; Leveque, K.; Doe, R. A.

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can

  7. Characterization of flow in fractured tuff using computerized tomography

    SciTech Connect

    Felice, C.W.; Sharer, J.C.

    1991-09-01

    The objective of this effort was to demonstrate TerraTek`s capability to use X-ray computerized tomography (CT) to observe fluid flow down a fracture and rock matrix imbibition in a sample of Bandelier tuff. To accomplish the objective, a tuff sample 152.4 mm long and 50.8 mm in diameter was prepared. A portion of the sample was artificially fractured and coupled to a section of matrix material so that the fracture was not exposed. Water was flowed through the sample at five flow rates and CT scanning performed at set intervals during the flow. Cross sectional images and longitudinal reconstructions were built and saturation profiles calculated for the sample at each time interval at each flow rate. The results showed that for the test conditions, the fracture was not a primary pathway of fluid flow down the sample. Fluid flow was governed by the high imbibition capability of the rock matrix material.

  8. Radio Tomography of Ionospheric Structures (probably) due to Underground-Surface-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Nesterov, I.; Andreeva, E.; Rekenthaler, D. A.

    2012-12-01

    Ionospheric radio-tomography (RT) utilizes radio signals transmitted from the global navigational satellite systems (GNSS), including low-orbiting (LO) navigational systems such as Transit, Tsikada, etc., and high-orbiting (HO) navigational systems such as GPS, GLONASS, Galileo, Beidou, etc. The signals that are transmitted from the LO navigational satellites and recorded by ground receiving chains can be inverted for almost instantaneous (5-8 min) 2D snapshots of electron density. The data from the networks of ground receivers that record the signals of the HO satellites are suitable for implementing high-orbital RT (HORT), i.e. reconstructing the 4D distributions of the ionospheric electron density (one 3D image every 20-30 min). In the regions densely covered by the GNSS receivers, it is currently possible to get a time step of 2-4 min. The LORT and HORT approaches have a common methodical basis: in both these techniques, the integrals of electron density along the ray between the satellite and the receiver are measured, and then the tomographic procedures are applied to reconstruct the distributions of electron density. We present several examples of the experiments on the ionospheric RT, which are related to the Underground-Surface-Atmosphere-Ionosphere (USAI) coupling. In particular, we demonstrate examples of RT images of the ionosphere after industrial explosions, rocket launches, and modification of the ionosphere by high-power radio waves. We also show RT cross sections reflecting ionospheric disturbances caused by the earthquakes (EQ) and tsunami waves. In these cases, there is an evident cause-and-effect relationship. The perturbations are transferred between the geospheres predominantly by acoustic gravity waves (AGW), whose amplitudes increase with increasing height. As far as EQ are concerned, the cause of the USAI coupling mechanism is not obvious. It is clear, however, that the regular RT studies can promote the solution of this challenging problem

  9. Digital balanced detection for fast optical computerized tomography

    NASA Astrophysics Data System (ADS)

    Hafiz, Rehan; Ozanyan, Krikor B.

    2006-10-01

    Analogue Balanced Photo-detection has found extensive usage in high- sensitivity small signal applications e.g. coherent heterodyne detection. It is particularly effective for laser intensity noise removal. Nevertheless, the high cost of the commercially available analogue systems makes them unsuitable for multi-channel applications, such as fast tomography. In this paper a flexible, scalable, inexpensive and compact solution for multi channel digital balanced detection is presented. The proposed system has two components: an analogue front-end, comprising a differential photodiode amplifier for minimizing the external interference noise, and a digital balanced noise remover. The latter component initially calculates a balancing factor (BF) from the average power ratio of the signal and reference photocurrents, measured with the object removed from the signal path. Three digital balancing algorithms (DBAx) are considered for subsequent processing. In DBA1, BF is directly used in real-time ratiometric calculations. In DBA2, the BF is adjusted in real time by monitoring the window-averaged power of the received photocurrents. In DBA3, first the baseline is removed using differentiation and then ratiometric detection is performed. Using the digital alternative only one measurement of the reference beam is necessary for single-source, multi-channel detection systems. The data from multiple channels are processed in parallel by pipelined hardware, configured as a state machine. The proposed system leads to a fast optical computerized tomography system using digital balanced detection.

  10. Sodankylä ionospheric tomography data set 2003-2014

    NASA Astrophysics Data System (ADS)

    Norberg, Johannes; Roininen, Lassi; Kero, Antti; Raita, Tero; Ulich, Thomas; Markkanen, Markku; Juusola, Liisa; Kauristie, Kirsti

    2016-07-01

    Sodankylä Geophysical Observatory has been operating a receiver network for ionospheric tomography and collecting the produced data since 2003. The collected data set consists of phase difference curves measured from COSMOS navigation satellites from the Russian Parus network (Wood and Perry, 1980) and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of the tomographic system. During the observation period, 2003-2014, there were three to five operational stations at the Fennoscandia sector. Altogether the analysis consists of around 66 000 overflights, but to ensure the quality of the reconstructions, the examination is limited to cases with descending (north to south) overflights and maximum elevation over 60°. These constraints limit the number of overflights to around 10 000. Based on this data set, one solar cycle of ionospheric VTEC estimates is constructed. The measurements are compared against the International Reference Ionosphere (IRI)-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model results are on average 40 % higher than that of the tomographic results.

  11. Percutaneous nephrolithotomy in pediatric patients: is computerized tomography a must?

    PubMed

    Gedik, Abdullah; Tutus, Ali; Kayan, Devrim; Yılmaz, Yakup; Bircan, Kamuran

    2011-02-01

    The aim of this study was to retrospectively evaluate the results of pediatric percutaneous nephrolithotomy (PNL) cases, and discuss the results and necessity of non-contrast computerized tomography (CT) in these cases. In all, 48 pediatric patients who underwent PNL were retrospectively evaluated. Before PNL, either intravenous urography or CT was performed. In all patients, we evaluated the PNL time, scopy time with stone burden, and complications. During the PNL procedure, we switched to open surgery in two cases: in one because of renal pelvis perforation and in the other because of transcolonic access. In one patient who was scheduled to undergo PNL, we performed open surgery, primarily because we detected a retrorenal colon with CT. The stone burden in 45 patients who underwent PNL was 445 ± 225 mm(2), the PNL time was 51 ± 23 min, and the scopy time was 6.1 ± 2.7 min. We removed nephrostomy tubes 1-4 days after the procedure. In two patients, 24 h after removal of nephrostomy tubes, we inserted double J stents because of prolonged urine extravasation from the tract. In all, 34 of the 45 patients were stone-free, 5 patients had clinically insignificant stone fragments, and 6 patients had residual stones. PNL is a safe and effective method in the treatment of pediatric patients with kidney stones. Clinical experience is the most important factor in obtaining stone-free results. CT should be performed in all pediatric patients in order to prevent colon perforation.

  12. An alternative approach to computerized tomography (CT) in forensic pathology.

    PubMed

    Thomsen, Asser H; Jurik, Anne Grethe; Uhrenholt, Lars; Vesterby, Annie

    2009-01-10

    Computerized Tomography (CT) is used by some forensic pathology departments as a supplement to the forensic autopsy. Departments with a limited number of autopsies may find it relatively expensive to acquire and operate a CT-scanner. Furthermore, it requires a great deal of training and experience to interpret the radiological data. We are currently evaluating CT in order to decide whether the benefits match the efforts. In selected death-investigations the Department of Radiology at Aarhus University Hospital performs CT of the body on behalf of the Institute of Forensic Medicine at Aarhus University and a skilled radiologist interprets the data. We present our radiological findings in the 20 cases where we have used CT and compare them to the autopsy findings. The cases include fatalities from beatings, stabbings, gunshots, fires and traffic accidents. CT is an excellent tool for documenting and illustrating certain lesions, such as gunshot wounds and bone fractures, where we can obtain information that possibly would have been missed at the autopsy. We believe, however, that further research is required before we can recommend CT as a part of a standard forensic autopsy. The cooperation between forensic and radiological departments is a good approach for smaller forensic departments that insures a skilled interpretation without having to divert a lot of resources to equipment and training.

  13. Vertebral sarcoidosis: demonstration of bone involvement by computerized axial tomography

    SciTech Connect

    Dinerstein, S.L.; Kovarsky, J.

    1984-08-01

    A report is given of a rare case of vertebral sarcoidosis with negative conventional spinal x-ray films, yet with typical cystic lesions of the spine found incidentally during abdominal computerized axial tomography (CAT). The patient was a 28-year-old black man, who was admitted for evaluation of a 1 1/2-year history of diffuse myalgias, intermittent fever to 102 F orally, bilateral hilar adenopathy, and leukopenia. A technetium polyphosphate bone scan revealed diffuse areas of increased uptake over the sternum, entire vertebral column, and pelvis. Conventional x-ray films of the cervical, thoracic, and lumbar spine, and an AP view of the pelvis were all normal. Chest x-ray film revealed only bilateral hilar adenopathy. During the course of an extensive negative evaluation for infection, an abdominal CAT scan was done, showing multiple, small, sclerotic-rimmed cysts at multiple levels of the lower thoracic and lumbar spine. Bone marrow biopsy revealed only changes consistent with anemia of chronic disease. Mediastinal lymph node biopsy revealed noncaseating granulomas. A tentative diagnosis of sarcoidosis was made, and treatment with prednisone, isoniazid and rifampin was begun. Within two weeks of initiation of prednisone therapy, the patient was symptom-free. A repeat technetium polyphosphate bone scan revealed only a small residual area of mildly increased uptake over the upper thoracic vertebrae.

  14. Computerized tomography with total variation and with shearlets

    NASA Astrophysics Data System (ADS)

    Garduño, Edgar; Herman, Gabor T.

    2017-04-01

    To reduce the x-ray dose in computerized tomography (CT), many constrained optimization approaches have been proposed aiming at minimizing a regularizing function that measures a lack of consistency with some prior knowledge about the object that is being imaged, subject to a (predetermined) level of consistency with the detected attenuation of x-rays. One commonly investigated regularizing function is total variation (TV), while other publications advocate the use of some type of multiscale geometric transform in the definition of the regularizing function, a particular recent choice for this is the shearlet transform. Proponents of the shearlet transform in the regularizing function claim that the reconstructions so obtained are better than those produced using TV for texture preservation (but may be worse for noise reduction). In this paper we report results related to this claim. In our reported experiments using simulated CT data collection of the head, reconstructions whose shearlet transform has a small ℓ 1-norm are not more efficacious than reconstructions that have a small TV value. Our experiments for making such comparisons use the recently-developed superiorization methodology for both regularizing functions. Superiorization is an automated procedure for turning an iterative algorithm for producing images that satisfy a primary criterion (such as consistency with the observed measurements) into its superiorized version that will produce results that, according to the primary criterion are as good as those produced by the original algorithm, but in addition are superior to them according to a secondary (regularizing) criterion. The method presented for superiorization involving the ℓ 1-norm of the shearlet transform is novel and is quite general: It can be used for any regularizing function that is defined as the ℓ 1-norm of a transform specified by the application of a matrix. Because in the previous literature the split Bregman algorithm is used

  15. Three-dimensional computerized tomography: a quantum leap in diagnostic imaging?

    PubMed

    Morrison, R; McCarty, J; Cushing, F R

    1994-01-01

    Ever since the discovery of radium by Madame Curie, men and women of vision and science have labored to improve radiation technology. Over a period of approximately 85 years, we have gone from this initial discovery to three-dimensional computerized transmission tomography; one of the latest techniques in modern day x-ray imaging. Its uses are vast and unparalleled in many facets of medicine and surgery, outlining pathology as never before seen, and possibly, never before completely understood. Three-dimensional computerized tomography is rapidly gaining popularity in cross-sectional imaging of the foot and ankle. It has proven invaluable in elucidating osseous and soft tissue pathology. Abnormalities of the musculoskeletal system that exhibit complex anatomy are often difficult to interpret using standard radiographic techniques. Overall, three-dimensional computerized tomography has established itself as a means by which clinicians may appreciate the three-dimensional disposition of anatomy and disease.

  16. Why is high resolution computerized tomography scanning used in evaluating the lungs?

    PubMed Central

    Graves, W. A.; Collins, J. D.; Miller, T. Q.

    1989-01-01

    High resolution computerized tomography scans have been used for medical and legal purposes to evaluate patients with a history of exposure to asbestos. Some investigators argue that high resolution scanning provides a better image of the lungs than routine computerized tomography. A review of the literature shows that although high resolution scanning displays the lymphatics in the lung, it offers no new useful diagnostic information. The authors conclude that no real advantage is attained with high resolution scanning of the lung and that pathology of disease can be determined decisively only by histology. Images Figure 1 Figure 2A Figure 2B Figure 3 Figure 4 PMID:2681799

  17. Positron emission tomography / computerized tomography evaluation of primary Hodgkin's disease of liver.

    PubMed

    Gota, V S; Purandare, N C; Gujral, S; Shah, S; Nair, R; Rangarajan, V

    2009-01-01

    Occurrence of primary Hodgkin's lymphoma (PHL) of the liver is extremely rare. We report on a case of a 60-year-old male who presented with liver mass and B-symptomatology. Hepatoma or hepatic metastasis from a gastrointestinal primary was initially suspected. Tumor markers like AFP, CEA, Total PSA, and CA-19.9 were within normal limits. Positron Emission Tomography / Computerized Tomography (PET/CT) revealed a large hepatic lesion and a nodal mass in the porta hepatis. A liver biopsy was consistent with Hodgkin's lymphoma. There was complete regression of the hepatic lesion and evidence of shrinkage of the nodal mass following four cycles of chemotherapy. 18F Fluro -de-oxy Glucose (FDG) PET / CT in this case helped in establishing a primary hepatic lymphoma by demonstrating the absence of pathologically hypermetabolic foci in any other nodes or organs. PET / CT scan is a useful adjunct to conventional imaging and histopathology, not only to establish the initial diagnosis, but also to monitor treatment response in PHL.

  18. Remote sensing of ionosphere and upper atmosphere based on low-orbital and GNSS radio tomography

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Tereshchenko, E.; Andreeva, E.; Khudukon, B.; Kozharin, M.; Nazarenko, M.; Nesterov, I.

    A dozen of currently operating multi-point receiving networks that carry out measurements of transmissions from low-orbiting LO navigational systems exists at present in different regions of the world - in Europe America and Asia Numerous radio tomographic RT experiments based on LO satellite systems revealed a complexity and variety of ionospheric structures observed under disturbed and quiet conditions Various shapes of the ionospheric trough were detected A series of specific features in the structure and dynamics of the equatorial anomaly were studied RT images of traveling ionospheric disturbances provided information about the parameters of perturbations and allowed investigation of atmospheric-ionospheric coupling RT study of strong ionospheric disturbances caused by anthropogenic factors in particular by rocket launching industrial explosions powerful high-frequency radiation and so on is performed By means of statistical radio tomography distributions of the intensity of ionospheric plasma fluctuations were retrieved LO RT method allows also determination of plasma fluxes from a time-sequence of RT images of the ionosphere Manifestations of particle precipitation in electron density distributions were observed repeatedly in LO RT images of the ionosphere With a several receiving chains spaced a few hundred kilometer apart it is possible to study the three-dimensional structure of the ionosphere In spite of its high efficiency LO RT employment is basically limited due to the necessity to arrange multi-point receiving systems Deployment of

  19. Calcification of all four parathyroid glands in a hemodialysis patient with secondary hyperparathyroidism revealed by computerized tomography.

    PubMed

    Peces, R; Rodríguez, M; González, F; Ablanedo, P

    2001-09-01

    This report describes the parathyroid scan, computerized tomography and histologic findings in a young female hemodialysis patient with severe secondary hyperparathyroidism. These findings included hyperplasia and calcification of all four parathyroid glands.

  20. Sensitivity of radionuclide brain imaging and computerized transaxial tomography in detecting subdural hematoma

    SciTech Connect

    Razzak, M.A.; Mudarris, F.; Christie, J.H.

    1980-04-01

    In a series of 23 patients with surgically proven subdural hematoma of durations ranging between two days to seven months, the detection rate of Tc-99m-pertechnetate brain imaging was higher than computerized transaxial tomography (CT). With dynamic perfusion scanning, the detection rate was 71.5%. In contrast, CT demonstrated the hematoma in 52% of the cases. Lastly, the result of CT scanning was dependent on the size of the subdural hematoma as evaluated at the time of operation.

  1. Dental implants in bilateral bifid canal and compromised interocclusal space using cone beam computerized tomography

    PubMed Central

    Ahmed, Nizar; Arunachalam, Lalitha Tanjore; Jacob, Caroline Annette; Kumar, Suresh Anand

    2016-01-01

    Knowledge of various anatomic landmarks is pivotal for important success. Bifid canals pose a challenge and can lead to difficulties while performing implant surgery in the mandible. Bifid canals can be diagnosed with panoramic radiography and more accurately with cone beam computerized tomography (CBCT). This case report details the placement of the implant in a patient with bilateral bifid canal and compromised interocclusal space, which was successfully treated using CBCT. PMID:27433073

  2. Evaluation of Biomaterials Using Micro-Computerized Tomography

    SciTech Connect

    Torris, A. T. Arun; Columbus, K. C. Soumya; Saaj, U. S.; Krishnan, Kalliyana V.; Nair, Manitha B.

    2008-09-26

    Micro-computed tomography or Micro-CT is a high resolution, non-invasive, x-ray scanning technique that allows precise three-dimensional imaging and quantification of micro-architectural and structural parameters of objects. Tomographic reconstruction is based on a cone-beam convolution-back-projection algorithm. Micro-architectural and structural parameters such as porosity, surface area to volume ratio, interconnectivity, pore size, wall thickness, anisotropy and cross-section area of biomaterials and bio-specimens such as trabecular bone, polymer scaffold, bio-ceramics and dental restorative were evaluated through imaging and computer aided manipulation of the object scan data sets.

  3. Evaluation of Biomaterials Using Micro-Computerized Tomography

    NASA Astrophysics Data System (ADS)

    Torris, A. T. Arun; Columbus, K. C. Soumya; Saaj, U. S.; Nair, Manitha B.; Krishnan, Kalliyana V.

    2008-09-01

    Micro-computed tomography or Micro-CT is a high resolution, non-invasive, x-ray scanning technique that allows precise three-dimensional imaging and quantification of micro-architectural and structural parameters of objects. Tomographic reconstruction is based on a cone-beam convolution-back-projection algorithm. Micro-architectural and structural parameters such as porosity, surface area to volume ratio, interconnectivity, pore size, wall thickness, anisotropy and cross-section area of biomaterials and bio-specimens such as trabecular bone, polymer scaffold, bio-ceramics and dental restorative were evaluated through imaging and computer aided manipulation of the object scan data sets.

  4. IONOSPHERIC POWER-SPECTRUM TOMOGRAPHY IN RADIO INTERFEROMETRY

    SciTech Connect

    Koopmans, L. V. E.

    2010-08-01

    A tomographic method is described to quantify the three-dimensional power spectrum of the ionospheric electron-density fluctuations based on radio-interferometric observations by a two-dimensional planar array. The method is valid for the first-order Born approximation and might be applicable in correcting observed visibilities for phase variations due to the imprint of the full three-dimensional ionosphere. It is shown that the ionospheric electron-density distribution is not the primary structure to model in interferometry, but rather its autocorrelation function or equivalently its power spectrum. An exact mathematical expression is derived that provides the three-dimensional power spectrum of the ionospheric electron-density fluctuations directly from a rescaled scattered intensity field and an incident intensity field convolved with a complex unit phasor that depends on the w-term and is defined on the full sky pupil plane. In the limit of a small field of view, the method reduces to the single phase-screen approximation. Tomographic self-calibration can become important in high-dynamic range observations at low radio frequencies with wide-field antenna interferometers because a three-dimensional ionosphere causes a spatially varying convolution of the sky, whereas a single phase screen results in a spatially invariant convolution. A thick ionosphere can therefore not be approximated by a single phase screen without introducing errors in the calibration process. By applying a Radon projection and the Fourier projection-slice theorem, it is shown that the phase-screen approach in three dimensions is identical to the tomographic method. Finally, we suggest that residual speckle can cause a diffuse intensity halo around sources due to uncorrectable ionospheric phase fluctuations in the short integrations, which could pose a fundamental limit on the dynamic range in long-integration images.

  5. A computerized tomography system for transcranial ultrasound imaging.

    PubMed

    Tang, Sai Chun; Clement, Gregory T

    Hardware for tomographic imaging presents both challenge and opportunity for simplification when compared with traditional pulse-echo imaging systems. Specifically, point diffraction tomography does not require simultaneous powering of elements, in theory allowing just a single transmit channel and a single receive channel to be coupled with a switching or multiplexing network. In our ongoing work on transcranial imaging, we have developed a 512-channel system designed to transmit and/or receive a high voltage signal from/to arbitrary elements of an imaging array. The overall design follows a hierarchy of modules including a software interface, microcontroller, pulse generator, pulse amplifier, high-voltage power converter, switching mother board, switching daughter board, receiver amplifier, analog-to-digital converter, peak detector, memory, and USB communication. Two pulse amplifiers are included, each capable of producing up to 400Vpp via power MOSFETS. Switching is based around mechanical relays that allow passage of 200V, while still achieving switching times of under 2ms, with an operating frequency ranging from below 100kHz to 10MHz. The system is demonstrated through ex vivo human skulls using 1MHz transducers. The overall system design is applicable to planned human studies in transcranial image acquisition, and may have additional tomographic applications for other materials necessitating a high signal output.

  6. EISCAT verification in the development of ionospheric tomography

    NASA Astrophysics Data System (ADS)

    Walker, I. K.; Heaton, J. A. T.; Kersley, L.; Mitchell, C. N.; Pryse, S. E.; Williams, M. J.

    1996-12-01

    This paper highlights the important role played by the EISCAT radar for verification in the development of tomographic techniques to produce images of ionospheric electron density. A brief review is given of some of the stages in the application of tomographic reconstruction techniques to the ionosphere. Results are presented to illustrate the effectiveness of the method in imaging ionospheric structures at high latitudes. In addition, the results include the first tomographic image of the ionosphere for a region extending from mid-latitudes over mainland Scandinavia to high latitudes above Svalbard. Acknowledgements. This work has been supported by the UK Particle-Physics and Astronomy Research Council. The assistance of the director and staff of the EISCAT Scientific Association, the staff of the Norsk Polarinstitutt and the director and staff of the Swedish Institute of Space Physics is gratefully acknowledged. In addition the authors would like to thank Professor Evgeny Tereshchenko of the Polar Geophysical Institute in Mumansk, Russia and Dr Tuomo Nygrén of the University of Oulu, Finland for provision of data from EISCAT special program time during the November 1995 campaign. Topical Editor D. Alcaydé thanks E. J. Fremouw and another referee for their help in evaluating this paper.--> Correspondence to: I. K. Walker-->

  7. Investigating the performance of wavelet neural networks in ionospheric tomography using IGS data over Europe

    NASA Astrophysics Data System (ADS)

    Ghaffari Razin, Mir Reza; Voosoghi, Behzad

    2017-04-01

    Ionospheric tomography is a very cost-effective method which is used frequently to modeling of electron density distributions. In this paper, residual minimization training neural network (RMTNN) is used in voxel based ionospheric tomography. Due to the use of wavelet neural network (WNN) with back-propagation (BP) algorithm in RMTNN method, the new method is named modified RMTNN (MRMTNN). To train the WNN with BP algorithm, two cost functions is defined: total and vertical cost functions. Using minimization of cost functions, temporal and spatial ionospheric variations is studied. The GPS measurements of the international GNSS service (IGS) in the central Europe have been used for constructing a 3-D image of the electron density. Three days (2009.04.15, 2011.07.20 and 2013.06.01) with different solar activity index is used for the processing. To validate and better assess reliability of the proposed method, 4 ionosonde and 3 testing stations have been used. Also the results of MRMTNN has been compared to that of the RMTNN method, international reference ionosphere model 2012 (IRI-2012) and spherical cap harmonic (SCH) method as a local ionospheric model. The comparison of MRMTNN results with RMTNN, IRI-2012 and SCH models shows that the root mean square error (RMSE) and standard deviation of the proposed approach are superior to those of the traditional method.

  8. Intracranial Leptomeningeal Carcinomatosis in Three Cases from Breast Cancer Demonstrated on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computerized Tomography.

    PubMed

    Ortapamuk, Hulya; Demir, Mustafa Kemal

    2017-01-01

    Leptomeningeal carcinomatosis (LC) is an uncommon late manifestation of non-central nervous system (CNS) solid tumors. With prolonged survival in solid tumors, an increased frequency of metastases is noted in these tumors too. The detection of tumor cells in the cerebrospinal fluid remains the gold standard. Noninvasively, magnetic resonance imaging is frequently used for the diagnosis of LC. Although its low sensitivity of F-18 fluorodeoxyglucose positron emission tomography/computerized tomography (F-18 FDG PET/CT) on demonstrating CNS lesions, it could be useful in identifying the possibility of LC of breast carcinoma by giving high attention to the meninges. We discuss here three cases all of them having intracranial LC; where (18)F-FDG PET/CT study helped us in the diagnosis of LC. To our knowledge, this is the second report about intracranial LC from breast cancer demonstrating on (18)F-FDG PET/CT.

  9. Intracranial Leptomeningeal Carcinomatosis in Three Cases from Breast Cancer Demonstrated on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computerized Tomography

    PubMed Central

    Ortapamuk, Hulya; Demir, Mustafa Kemal

    2017-01-01

    Leptomeningeal carcinomatosis (LC) is an uncommon late manifestation of non-central nervous system (CNS) solid tumors. With prolonged survival in solid tumors, an increased frequency of metastases is noted in these tumors too. The detection of tumor cells in the cerebrospinal fluid remains the gold standard. Noninvasively, magnetic resonance imaging is frequently used for the diagnosis of LC. Although its low sensitivity of F-18 fluorodeoxyglucose positron emission tomography/computerized tomography (F-18 FDG PET/CT) on demonstrating CNS lesions, it could be useful in identifying the possibility of LC of breast carcinoma by giving high attention to the meninges. We discuss here three cases all of them having intracranial LC; where 18F-FDG PET/CT study helped us in the diagnosis of LC. To our knowledge, this is the second report about intracranial LC from breast cancer demonstrating on 18F-FDG PET/CT. PMID:28242978

  10. Asymptomatic Emphysematous Pyelonephritis - Positron Emission Tomography Computerized Tomography Aided Diagnostic and Therapeutic Elucidation

    PubMed Central

    Pathapati, Deepti; Shinkar, Pawan Gulabrao; kumar, Satya Awadhesh; Jha; Dattatreya, Palanki Satya; Chigurupati, Namrata; Chigurupati, Mohana Vamsy; Rao, Vatturi Venkata Satya Prabhakar

    2017-01-01

    The authors report an interesting coincidental unearthing by 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) of a potentially serious medical condition of emphysematous pyelonephritis in a case of nasopharyngeal carcinoma. The management by conservative ureteric stenting and antibiotics was done with gratifying clinical outcome. PMID:28242985

  11. Non-Conventional Applications of Computerized Tomography: Analysis of Solid Dosage Forms Produced by Pharmaceutical Industry

    NASA Astrophysics Data System (ADS)

    de Oliveira, José Martins; Germano Martins, Antonio César

    2010-05-01

    X-ray computed tomography (CT) refers to the cross-sectional imaging of an object measuring the transmitted radiation at different directions. In this work, we describe a non-conventional application of computerized tomography: visualization and improvements in the understanding of some internal structural features of solid dosage forms. A micro-CT X-ray scanner, with a minimum resolution of 30 μm was used to characterize some pharmaceutical tablets, granules, controlled-release osmotic tablet and liquid-filled soft-gelatin capsules. The analysis presented in this work are essentially qualitative, but quantitative parameters, such as porosity, density distribution, tablets dimensions, etc. could also be obtained using the related CT techniques.

  12. Non-Conventional Applications of Computerized Tomography: Analysis of Solid Dosage Forms Produced by Pharmaceutical Industry

    SciTech Connect

    Martins de Oliveira, Jose Jr.; Germano Martins, Antonio Cesar

    2010-05-21

    X-ray computed tomography (CT) refers to the cross-sectional imaging of an object measuring the transmitted radiation at different directions. In this work, we describe a non-conventional application of computerized tomography: visualization and improvements in the understanding of some internal structural features of solid dosage forms. A micro-CT X-ray scanner, with a minimum resolution of 30 mum was used to characterize some pharmaceutical tablets, granules, controlled-release osmotic tablet and liquid-filled soft-gelatin capsules. The analysis presented in this work are essentially qualitative, but quantitative parameters, such as porosity, density distribution, tablets dimensions, etc. could also be obtained using the related CT techniques.

  13. Regional application of multi-layer artificial neural networks in 3-D ionosphere tomography

    NASA Astrophysics Data System (ADS)

    Ghaffari Razin, Mir Reza; Voosoghi, Behzad

    2016-08-01

    Tomography is a very cost-effective method to study physical properties of the ionosphere. In this paper, residual minimization training neural network (RMTNN) is used in voxel-based tomography to reconstruct of 3-D ionosphere electron density with high spatial resolution. For numerical experiments, observations collected at 37 GPS stations from Iranian permanent GPS network (IPGN) are used. A smoothed TEC approach was used for absolute STEC recovery. To improve the vertical resolution, empirical orthogonal functions (EOFs) obtained from international reference ionosphere 2012 (IRI-2012) used as object function in training neural network. Ionosonde observations is used for validate reliability of the proposed method. Minimum relative error for RMTNN is 1.64% and maximum relative error is 15.61%. Also root mean square error (RMSE) of 0.17 × 1011 (electrons/m3) is computed for RMTNN which is less than RMSE of IRI2012. The results show that RMTNN has higher accuracy and compiles speed than other ionosphere reconstruction methods.

  14. Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method

    NASA Astrophysics Data System (ADS)

    Roy, Corinna; Occhipinti, Giovanni; Boschi, Lapo; Moliné, Jean-Philippe; Wieczorek, Mark

    2014-09-01

    Most recent methods in ionospheric tomography are based on the inversion of the total electron content measured by ground-based GPS receivers. As a consequence of the high frequency of the GPS signal and the absence of horizontal raypaths, the electron density structure is mainly reconstructed in the F2 region (300 km), where the ionosphere reaches the maximum of ionization, and is not sensitive to the lower ionospheric structure. We propose here a new tomographic method of the lower ionosphere, based on the full inversion of over-the-horizon (OTH) radar data. Previous studies using OTH radar for ionospheric tomography inverted only the leading edge echo curve of backscatter ionograms. The major advantage of our methodology is taking into account, numerically and jointly, the effect that the electron density perturbations induce not only in the speed of electromagnetic waves but also on the raypath geometry. This last point is extremely critical for OTH radar inversions as the emitted signal propagates through the ionosphere between a fixed starting point (the radar) and an unknown end point on the Earth surface where the signal is backscattered. We detail our ionospheric tomography method with the aid of benchmark tests. Having proved the necessity to take into account both effects simultaneously, we apply our method to real data. This is the first time that the effect of the raypath deflection has been quantified and that the ionospheric plasma density has been estimated over the entirety of Europe with an OTH radar.

  15. IDA3D: An Ionospheric Data Assimilative Three Dimensional Tomography Processor

    DTIC Science & Technology

    2001-09-30

    region electron densities, it can contribute important spatial and temporal information to the Joule heating at high latitudes. Figure 2: 2D...using the Greenland tomography data with IDA3D to investigate E-region electron densities and the related Joule heating effects. • Alaska...for long term monitoring of the Alaska ionosphere in support of HAARP activities and to do scientific studies of neutral wind coupling to the

  16. [Computerized axial tomography of the skull - diagnostic possibilities and clinical results (author's transl)].

    PubMed

    Kazner, E; Lanksch, W; Steinhoff, H; Wilske, J

    1975-10-01

    Computerized axial tomography is a new method of tissue examination with x-rays whereby a picture can be produced which is a representation of a slice of the skull. This is done by irradiating the skull from 180 or 225 incremental angles and measuring the absorption at each of these angles. Then with the aid of a computer a tomogram is produced which can be displayed on a screen. These tomograms are representations of a cross-section of the skull composed of 160 X 160 points showing the various intracranial structures with great detail. The present study demonstrates the diagnostic possibilities of the high definition matrix with reference to brain disorders in a large sample of patients for the first time. Some tumours are shown as areas of decreased absorption compared with normal brain tissue. Others, however, have been found to have higher absorption values. With glioblastomas very contrasting pictures are produced with coexistng areas of decreased, increased and similar values to brain tissue. The most important finding is the visualization of brain oedema which appears as a low density area. A grading system of brain oedemas is proposed. The brain oedema associated with tumours has been found to propagate mainly in the white matter producing finger-like shapes. Out of 209 intracranial tumours 203 were recognized in the plain scan, a further five after contrast enhancement. In patients who have suffered from a stroke the differentiation between haemorrhage and infarction is made simple due to the contrasting appearance between the two types of lesion. Location, size and propagation direction of a haematoma as well as rupture of a haemorrhage into the ventricular system can be defined exactly. With brain infarction the hypoxically damaged tissue is well delineated and readily attributable to a given vascular area. In head injuries, for the first time it is possible to differentiate brain contusion with oedema from intracerebral haematoma. Coup and contre

  17. Single photon emission computerized tomography (SPECT) in detecting neurodegeneration in Huntington's disease.

    PubMed

    Reynolds, N C; Hellman, R S; Tikofsky, R S; Prost, R W; Mark, L P; Elejalde, B R; Lebel, R; Hamsher, K S; Swanson, S; Benezra, E E

    2002-01-01

    Single photon emission computerized tomography (SPECT) studies were performed on 34 manifest Huntington's disease (HD) patients at various stages of clinical pathology ranging from early chorea to late dystonia with or without signs of dementia and 12 pre-symptomatic patients with abnormal terminal CAG expansions. Thirty HD patients with obvious clinical signs and seven pre-symptomatic patients without signs or symptoms of HD displayed selective caudate hypoperfusion by direct visual inspection. Such qualitative, selective striatal hypoperfusion patterns can be indicative of early and persistent metabolic changes in striatal neuropathology. SPECT studies can be useful in documenting early pre-clinical changes in patients with abnormal terminal CAG expansions and in confirming the presence of caudate pathology in patients with clinical signs of HD.

  18. Square wave cone beam scanning trajectory for data completeness in three-dimensional computerized tomography

    SciTech Connect

    Eberhard, J.W.; Hedengren, K.H.V.

    1991-12-17

    This paper describes a scanning and data acquisition method for three-dimensional computerized tomography (CT) imaging of a field of view containing at least a portion of an object illuminated by a cone beam source. It comprises: defining a source scanning trajectory as a path traversed by the source; employing the cone beam source fixed with reference to a two-dimensional array detector with both source and detector movably positioned relative to the object in order to scan about the object; specifying the source scanning trajectory as a square wave on a cylindrical surface surrounding the field of view such that each plane passing through the field of view intersects the scanning trajectory in at lease one point; and scanning at a plurality of positions along the source scanning trajectory to obtain cone beam projection data.

  19. Computerized axial tomography of the chest for visualization of ''absent'' pulmonary arteries

    SciTech Connect

    Sondheimer, H.M.; Oliphant, M.; Schneider, B.; Kavey, R.E.W.; Blackman, M.S.; Parker, F.B. Jr.

    1982-05-01

    To expand the search for central pulmonary arteries in six patients with absence of cardiac-pulmonary continuity, computerized axial tomography (CAT) of the chest was performed. The CAT scans were compared with previous arteriograms and pulmonary vein wedge angiograms. Three patients with type IV truncus arteriosus were studied, and none had a central, right or left pulmonary artery on CAT scan. However, two patients with tetralogy of Fallot with pulmonary atresia and a patent ductus arteriosus to the right lung demonstrated the presence of a left pulmonary artery. In addition, one child with truncus arteriosus with ''absent'' left pulmonary artery demonstrated a left pulmonary artery on the CAT scan. The CAT scan may therefore enhance our ability to search for disconnected pulmonary arteries in children with complex cyanotic congenital heart disease.

  20. Comparison of ultrasonography, computerized tomography, and radionuclide imaging in the diagnosis of acute and chronic cholecystitis

    SciTech Connect

    Matolo, N.M.; Stadalnik, R.C.; McGahan, J.P.

    1982-12-01

    Seventy-five patients with abdominal pain in the right upper quadrant who were subsequently confirmed operatively and histologically to have acute or chronic cholecystitis underwent radionuclide imaging of the biliary tree, ultrasonography, and/or computerized tomography before operation. fifty-eight of the patients had acute cholecystitis and 17 had chronic cholecystitis and cholelithiasis. Analysis of our data indicates that ultrasonography is an accurate and better screening test than cholescintigraphy in the diagnosis of chronic cholecystitis and cholelithiasis, but it is less accurate in the detection of acute cholecystitis. On the other hand, radionuclide imaging is highly sensitive and specific in the early diagnosis of acute cholecystitis, but it is poor in the diagnosis of chronic cholecystitis and cholelithiasis unless the cystic duct is obstructed. CT scanning is more expensive than ultrasonography but may be extremely helpful in problematic cases such as the diagnosis of the cause in biliary obstruction or in imaging of the pancreas.

  1. Computerized tomography of pelvic osteomyelitis in patients with spinal cord injuries

    SciTech Connect

    Firooznia, H.; Rafii, M.; Golimbu, C.; Sokolow, J.

    1983-12-01

    Computerized tomography (CT) was performed in 19 patients with spinal cord injury (SCI) who had large pressure sores and in whom other complications were suspected. CT detected the depth, extent, and degree of undermining of the edges of the pressure sores in 19 of 27 lesions. Conventional radiography detected four cases of pelvic osteomyelitis. CT detected eight additional cases of pelvic osteomyelitis, as well as eight clinically unsuspected peripelvic and intrapelvic abscesses. Technetium-99m bone scanning was not very helpful because of localization in chronic proliferative changes of bone and widespread foci of myositis ossificans, as well as in osteomyelitis. Gallium-67 scanning detected only one of six abscesses. It was not very helpful because of confusion of abscess and osteomyelitis with intense soft tissue swelling and cellulitis, which are often associated with pressure sores in patients with chronic SCI. CT was found to be, by far, the modality of choice for detection of pelvic osteomyelitis and abscess in patients with SCI.

  2. Oral chloral hydrate vs. intranasal midazolam for sedation during computerized tomography.

    PubMed

    Fallah, Razieh; Nakhaei, Mohammad Hosein Ataee; Behdad, Shekofah; Moghaddam, Reza Nafisi; Shamszadeh, Ali

    2013-02-01

    We conducted this single blind randomized clinical trial to compare the efficacy and safety of oral chloral hydrate and intranasal midazolam for induction of sedation for computerized tomography scan of brain in children. Participants aged 1-10 years (n=60) were randomized to receive 100 mg/kg chloral hydrate orally with intra nasal normal saline OR intranasal midazolam 0.2 mg/kg with oral normal saline. Adequate sedation (Ramsay sedation score of four) was obtained and CT scan completed successfully in 76.7% of chloral hydrate group and in 40% of midazolam group (P=0.004). No significant difference was seen for side effects frequency between the two drugs (10% in chloral hydrate, 3.3% in midazolam group; P=0.34). We conclude that oral chloral hydrate can be considered as a safe and effective drug for sedation in children undergoing CT scan of brain.

  3. The mobile hospital technology industry: focus on the computerized tomography scanner.

    PubMed

    Hartley, D; Moscovice, I

    1996-01-01

    This study of firms offering mobile hospital technology to rural hospitals in eight northwestern states found that several permanently parked computerized tomography (CT) units were found where mobile routes had atrophied due to the purchase of fixed units by former mobile CT hospital clients. Based on a criterion of 140 scans per month per unit as a threshold of profitable production, units owned by larger firms (those that operate five or more units) were more likely to be profitable than units owned by smaller firms (71% versus 20%, P = 0.03). A substantial number of rural hospitals lose money on mobile CT due to low Medicare reimbursement. In some areas, mobile hospital technology is a highly competitive industry. Evidence was found that several firms compete in some geographic areas and that some firms have lost hospital clients to competing vendors.

  4. A New Ionosphere Tomography Algorithm with Two-Grids Virtual Observations Constraints and 3D Velocity Profile

    NASA Astrophysics Data System (ADS)

    Kong, Jian; Yao, Yibin; Shum, Che-Kwan

    2014-05-01

    Due to the sparsity of world's GNSS stations and limitations of projection angles, GNSS-based ionosphere tomography is a typical ill-posed problem. There are two main ways to solve this problem. Firstly the joint inversion method combining multi-source data is one of the effective ways. Secondly using a priori or reference ionosphere models, e.g., IRI or GIM models, as the constraints to improve the state of normal equation is another effective approach. The traditional way for adding constraints with virtual observations can only solve the problem of sparse stations but the virtual observations still lack horizontal grid constraints therefore unable to fundamentally improve the near-singularity characteristic of the normal equation. In this paper, we impose a priori constraints by increasing the virtual observations in n-dimensional space, which can greatly reduce the condition number of the normal equation. Then after the inversion region is gridded, we can form a stable structure among the grids with loose constraints. We then further consider that the ionosphere indeed changes within certain temporal scale, e.g., two hours. In order to establish a more sophisticated and realistic ionosphere model and obtain the real time ionosphere electron density velocity (IEDV) information, we introduce the grid electron density velocity parameters, which can be estimated with electron density parameters simultaneously. The velocity parameters not only can enhance the temporal resolution of the ionosphere model thereby reflecting more elaborate structure (short-term disturbances) under ionosphere disturbances status, but also provide a new way for the real-time detection and prediction of ionosphere 3D changes. We applied the new algorithm to the GNSS data collected in Europe for tomography inversion for ionosphere electron density and velocity at 2-hour resolutions, which are consistent throughout the whole day variation. We then validate the resulting tomography model

  5. Weight-based contrast administration in the computerized tomography evaluation of acute pulmonary embolism

    PubMed Central

    Laurent, Lisa; Zamfirova, Ina; Sulo, Suela; Baral, Pesach

    2017-01-01

    Abstract Compare individualized contrast protocol, or weight-based protocol, to standard methodology in evaluating acute pulmonary embolism. Retrospective chart review was performed on patients undergoing computed tomography angiography with standard contrast protocol (n = 50) or individualized protocol (n = 50). Computerized tomography images were assessed for vascular enhancement and image quality. Demographics were comparable, however, more patients in the individualized group were admitted to intensive care unit (48% vs 16%, P = 0.004). Vascular enhancement and image quality were also comparable, although individualized protocol had significantly fewer contrast and motion artifact limitations (28% vs 48%, P = 0.039). Fifteen percent decrease in intravenous contrast volume was identified in individualized group with no compromise in image quality. Individualized contrast protocol provided comparable vascular enhancement and image quality to the standard, yet with fewer limitations and lower intravenous contrast volume. Catheter-gauge flow rate restrictions resulting in inconsistent technologist exam execution were identified, supporting the need for further investigation of this regimen. PMID:28151887

  6. Compact cold stage for micro-computerized tomography imaging of chilled or frozen samples

    NASA Astrophysics Data System (ADS)

    Hullar, Ted; Paige, David F.; Rowland, Douglas J.; Anastasio, Cort

    2014-04-01

    High resolution X-ray microCT (computerized tomography) can be used to image a variety of objects, including temperature-sensitive materials. In cases where the sample must be chilled or frozen to maintain sample integrity, either the microCT machine itself must be placed in a refrigerated chamber, or a relatively expensive commercial cold stage must be purchased. We describe here the design and construction of a low-cost custom cold stage suitable for use in a microCT imaging system. Our device uses a boron nitride sample holder, two-stage Peltier cooler, fan-cooled heat sink, and electronic controller to maintain sample temperatures as low as -25 °C ± 0.2 °C for the duration of a tomography acquisition. The design does not require modification to the microCT machine, and is easily installed and removed. Our custom cold stage represents a cost-effective solution for refrigerating CT samples for imaging, and is especially useful for shared equipment or machines unsuitable for cold room use.

  7. Compact cold stage for micro-computerized tomography imaging of chilled or frozen samples

    SciTech Connect

    Hullar, Ted; Anastasio, Cort; Paige, David F.; Rowland, Douglas J.

    2014-04-15

    High resolution X-ray microCT (computerized tomography) can be used to image a variety of objects, including temperature-sensitive materials. In cases where the sample must be chilled or frozen to maintain sample integrity, either the microCT machine itself must be placed in a refrigerated chamber, or a relatively expensive commercial cold stage must be purchased. We describe here the design and construction of a low-cost custom cold stage suitable for use in a microCT imaging system. Our device uses a boron nitride sample holder, two-stage Peltier cooler, fan-cooled heat sink, and electronic controller to maintain sample temperatures as low as −25 °C ± 0.2 °C for the duration of a tomography acquisition. The design does not require modification to the microCT machine, and is easily installed and removed. Our custom cold stage represents a cost-effective solution for refrigerating CT samples for imaging, and is especially useful for shared equipment or machines unsuitable for cold room use.

  8. Effect of ray and speed perturbations on Ionospheric Tomography by Over-the-horizon radar: A new method

    NASA Astrophysics Data System (ADS)

    Roy, C.; Occhipinti, G.; Boschi, L.; Molinié, J. P.

    2014-12-01

    Most recent methods in ionospheric tomography are based on the inversion of the Total Electron Content (TEC) measured by ground-based GPS receivers. As a consequence of the high frequency of the GPS signal and the absence of horizontal ray paths, the electron density structure is mainly reconstructed in the F2 region (300 km), where the ionosphere reaches the maximum of ionization, and is not sensitive to the lower ionospheric structure. We propose here a new tomographic method of the lower ionosphere, based on the full inversion of over-the-horizon (OTH) radar data. Previous studies using OTH radar for ionospheric tomography inverted only the leading edge echo curve of backscatter ionograms. The major advantage of our methodology is taking into account, numerically and jointly, the effect that the electron density perturbations induce not only in the speed of electromagnetic waves, but also on the ray-path geometry. This last point is extremely critical for OTH radar inversions as the emitted signal propagates through the ionosphere between a fixed starting-point (the radar) and an unknown end-point on the Earth surface where the signal is backscattered. We detail our ionospheric tomography method with the aid of benchmark tests. Having proved the necessity to take into account both effects simultaneously, we apply our method to real data. This is the first time that the effect of the ray-path deflection has been quantified and that the ionospheric plasma density has been estimated over the entirety of Europe with an OTH radar.

  9. Ionospheric tomography by gradient-enhanced kriging with STEC measurements and ionosonde characteristics

    NASA Astrophysics Data System (ADS)

    Minkwitz, David; van den Boogaart, Karl Gerald; Gerzen, Tatjana; Hoque, Mainul; Hernández-Pajares, Manuel

    2016-11-01

    The estimation of the ionospheric electron density by kriging is based on the optimization of a parametric measurement covariance model. First, the extension of kriging with slant total electron content (STEC) measurements based on a spatial covariance to kriging with a spatial-temporal covariance model, assimilating STEC data of a sliding window, is presented. Secondly, a novel tomography approach by gradient-enhanced kriging (GEK) is developed. Beyond the ingestion of STEC measurements, GEK assimilates ionosonde characteristics, providing peak electron density measurements as well as gradient information. Both approaches deploy the 3-D electron density model NeQuick as a priori information and estimate the covariance parameter vector within a maximum likelihood estimation for the dedicated tomography time stamp. The methods are validated in the European region for two periods covering quiet and active ionospheric conditions. The kriging with spatial and spatial-temporal covariance model is analysed regarding its capability to reproduce STEC, differential STEC and foF2. Therefore, the estimates are compared to the NeQuick model results, the 2-D TEC maps of the International GNSS Service and the DLR's Ionospheric Monitoring and Prediction Center, and in the case of foF2 to two independent ionosonde stations. Moreover, simulated STEC and ionosonde measurements are used to investigate the electron density profiles estimated by the GEK in comparison to a kriging with STEC only. The results indicate a crucial improvement in the initial guess by the developed methods and point out the potential compensation for a bias in the peak height hmF2 by means of GEK.

  10. Computerized tomography technique for reconstruction of obstructed temperature field in infrared thermography

    NASA Astrophysics Data System (ADS)

    Sham, F. C.; Huang, Y. H.; Liu, L.; Chen, Y. S.; Hung, Y. Y.; Lo, T. Y.

    2010-01-01

    Infrared thermography is a rapid, non-invasive and full-field technique for non-destructive testing and evaluation (NDT&E). With all the achievements on IR instrumentation and image processing techniques attained, it has been extended far beyond simple hot-spot detection and becomes one of the most promising NDT&E techniques in the last decades. It has achieved increasing acceptance in different sectors include medical imaging, manufacturing component fault detection and buildings diagnostic. However, one limitation of IR thermography is that the testing results are greatly affected by object surface emissivity. Surface with various emissivities may lead to difficult discrimination between area of defect and area with different emissivity. Therefore, many studies have been carried out on eliminating emissivity, for example, the time derivative approach, lock-in processing and differential contrast measurements. In these methods, sequence of themo-data/images are recorded and being processed in order to eliminate differences of emissivity. Another problem of IR thermography is that any obstruction may limit stimulations and imaging which leads to the observation of unclear defect image. To solve this problem, this paper proposes an algorithm based on the principle of computerized tomography which permits the reconstruction of unavailable/partially available temperature distribution of the affected area using the measured surrounding temperature field. In the process, a set of imaginary rays are projected from many different directions across the area. For each ray, integration of the temperature derivatives along the ray is equals to the temperature difference between the boundary points intercepted by the ray. Therefore, a set of linear equations can be established by considering the multiple rays. Each equation expresses the unknown temperature derivatives in the affected area in terms of the measured boundary temperature data. Solution of the set of simultaneous

  11. Cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial region: a systematic review of the literature.

    PubMed

    De Vos, W; Casselman, J; Swennen, G R J

    2009-06-01

    This study reviewed the literature on cone-beam computerized tomography (CBCT) imaging of the oral and maxillofacial (OMF) region. A PUBMED search (National Library of Medicine, NCBI; revised 1 December 2007) from 1998 to December 2007 was conducted. This search revealed 375 papers, which were screened in detail. 176 papers were clinically relevant and were analyzed in detail. CBCT is used in OMF surgery and orthodontics for numerous clinical applications, particularly for its low cost, easy accessibility and low radiation compared with multi-slice computerized tomography. The results of this systematic review show that there is a lack of evidence-based data on the radiation dose for CBCT imaging. Terminology and technical device properties and settings were not consistent in the literature. An attempt was made to provide a minimal set of CBCT device-related parameters for dedicated OMF scanners as a guideline for future studies.

  12. Kidney Stone Volume Estimation from Computerized Tomography Images Using a Model Based Method of Correcting for the Point Spread Function

    PubMed Central

    Duan, Xinhui; Wang, Jia; Qu, Mingliang; Leng, Shuai; Liu, Yu; Krambeck, Amy; McCollough, Cynthia

    2014-01-01

    Purpose We propose a method to improve the accuracy of volume estimation of kidney stones from computerized tomography images. Materials and Methods The proposed method consisted of 2 steps. A threshold equal to the average of the computerized tomography number of the object and the background was first applied to determine full width at half maximum volume. Correction factors were then applied, which were precalculated based on a model of a sphere and a 3-dimensional Gaussian point spread function. The point spread function was measured in a computerized tomography scanner to represent the response of the scanner to a point-like object. Method accuracy was validated using 6 small cylindrical phantoms with 2 volumes of 21.87 and 99.9 mm3, and 3 attenuations, respectively, and 76 kidney stones with a volume range of 6.3 to 317.4 mm3. Volumes estimated by the proposed method were compared with full width at half maximum volumes. Results The proposed method was significantly more accurate than full width at half maximum volume (p <0.0001). The magnitude of improvement depended on stone volume with smaller stones benefiting more from the method. For kidney stones 10 to 20 mm3 in volume the average improvement in accuracy was the greatest at 19.6%. Conclusions The proposed method achieved significantly improved accuracy compared with threshold methods. This may lead to more accurate stone management. PMID:22819107

  13. Volumetric computerized tomography as a measurement of periprosthetic acetabular osteolysis and its correlation with wear

    PubMed Central

    Looney, R John; Boyd, Allen; Totterman, Saara; Seo, Gwy-Suk; Tamez-Pena, Jose; Campbell, Debbie; Novotny, Leonore; Olcott, Christopher; Martell, John; Hayes, F Ann; O'Keefe, Regis J; Schwarz, Edward M

    2002-01-01

    Osteolysis, which is considered to be a major source of morbidity following total hip joint replacement, has been notoriously difficult to measure accurately, particularly in the acetabular area. In order to study periacetabular osteolysis, specialized software for computerized tomography (CT) scan image analysis has been developed. This software (3D-CT) eliminates metal artifacts, allows three-dimensional segmentation of the CT image, and reconstructs the segmented image to provide an accurate representation and measurement of volume for osteolytic lesions. In the present study, 20 patients underwent periacetabular osteolytic volume determination using 3D-CT, functional assessment (using the Harris Hip Scale, the Western Ontario and McMaster University Osteoarthritis Index, and the short form 36 questionnaire), and two-dimensional analysis of volumetic polyethylene wear using digitalized plain films. Periacetabular osteolysis correlated directly with the polyethylene wear rate (relative risk [RR] = 0.494, P = 0.027). If one patient with an acetabular revision, one patient with recurrent dislocation, and one patient with a Biomet prosthesis are excluded, then the correlation between wear and osteolysis is improved (RR = 0.685, P = 0.002). In summary, the current study demonstrates both the feasibility of CT imaging of periacetabular osteolysis and the correlation between polyethylene wear and osteolytic volume, providing a potential outcome measure for clinical trials that are designed to examine interventions in this complex disease process. PMID:11879538

  14. Numerical Modeling of Jointed Rock Under Compressive Loading Using X-ray Computerized Tomography

    NASA Astrophysics Data System (ADS)

    Yu, Qinglei; Yang, Shengqi; Ranjith, P. G.; Zhu, Wancheng; Yang, Tianhong

    2016-03-01

    As jointed rocks consist of joints embedded within intact rock blocks, the presence and geometrical fabric of joints have a great influence on the mechanical behavior of rock. With consideration of the actual spatial shape of joints, a numerical model is proposed to investigate the fracture evolution mechanism of jointed rocks. In the proposed model, computerized tomography (CT) scanning is first used to capture the microstructure of a jointed sandstone specimen, which is artificially fabricated by loading the intact sample until the residual strength, and then digital image processing (DIP) techniques are applied to characterize the geometrical fabric of joints from the CT images. A simple vectorization method is used to convert the microstructure based on a cross-sectional image into a layer of 3-D vectorized microstructure and the overall 3-D model of the jointed sandstone including the real spatial shape of the joints is established by stacking the layers in a specific sequence. The 3-D model is then integrated into a well-established code [three-dimensional Rock Failure Process Analysis, (RFPA3D)]. Using the proposed model, a uniaxial compression test of the jointed sandstone is simulated. The results show that the presence of joints can produce tensile stress zones surrounding them, which result in the fracture of jointed rocks under a relatively small external load. In addition, the spatial shape of the joints has a great influence on the fracture process of jointed rocks.

  15. Diagnostic Value of Dual-Source Computerized Tomography Combined with Perfusion Imaging for Peripheral Pulmonary Embolism

    PubMed Central

    Mao, Xijin; Wang, Shanshan; Jiang, Xingyue; Zhang, Lin; Xu, Wenjian

    2016-01-01

    Background Pulmonary embolism has become the third most common cardiovascular disease, which can seriously harm human health. Objectives To investigate the diagnostic value of dual-source computerized tomography (CT) and perfusion imaging for peripheral pulmonary embolism. Patients and Methods Thirty-two patients with suspected pulmonary embolism underwent dual-source CT exams. To compare the ability of pulmonary embolism detection software (PED) with CT pulmonary angiography (CTPA) in determining the presence, numbers, and locations of pulmonary emboli, the subsequent images were reviewed by two radiologists using both imaging modalities. Also, the diagnostic consistency between PED and CTPA images and dual-energy pulmonary perfusion imaging (DEPI) for segmental pulmonary embolism was compared. Results CTPA images revealed 50 (7.81%) segmental and 56 (4.38%) sub-segmental pulmonary embolisms, while the PED images showed 68 (10.63%) segmental and 94 (7.34%) sub-segmental pulmonary embolisms. Thus, the detection rate on PED images for peripheral pulmonary embolism was significantly higher than that of the CTPA images (P < 0.05). There was good consistency for diagnosing segmental pulmonary embolism between PED and CTPA and DEPI (kappa = 0.85). The sensitivity and specificity of DEPI images for the diagnosis of pulmonary embolism were 91.7% and 97.5%, respectively. Conclusion PED software of dual-source CT combined with perfusion imaging can significantly improve the detection rate of peripheral pulmonary embolism. PMID:27703656

  16. Diagnostic value of unenhanced computerized tomography urography in the evaluation of acute renal colic.

    PubMed

    Wang, Jia-Hwia; Lin, Wen-Chiung; Wei, Chao-Jung; Chang, Cheng-Yen

    2003-10-01

    This study prospectively evaluated the diagnostic value of unenhanced computerized tomography (CT) urography in patients with acute renal colic. Fifty-nine patients with clinical manifestations of acute renal colic underwent unenhanced helical CT to evaluate urinary tract abnormalities. Reformatted three-dimensional CT urography was performed in all patients. The findings were correlated with ureteroscopy, surgical findings, histopathologic findings, and clinical course. CT urography detected urinary abnormalities in 57 of 59 patients with the clinical manifestation of acute renal colic, including 45 cases of urolithiasis, three urinary malignancies, one congenital abnormality, and eight ureteral strictures (due to chronic inflammation or fibrosis). CT urography showed negative findings in the urinary system in two patients, and after clinical follow-up, urinary abnormality was excluded in these patients. Incidental findings of extrarenal disease were noted in six patients (pulmonary abnormalities, n = 2; gallstones, n = 4). Only one patient with urolithiasis was misdiagnosed as having a renal tumor by CT urography. The sensitivity and specificity of CT urography in diagnosing urolithiasis was 97.8% (44/45) and 100% (14/14), respectively. Three-dimensional CT urography is a newly developed modality to evaluate anomalies of the urinary tract. The highly accurate diagnostic value of CT urography makes it a suitable alternative or substitutive modality in patients with acute flank pain.

  17. Three-dimensional ionospheric tomography reconstruction using the model function approach in Tikhonov regularization

    NASA Astrophysics Data System (ADS)

    Wang, Sicheng; Huang, Sixun; Xiang, Jie; Fang, Hanxian; Feng, Jian; Wang, Yu

    2016-12-01

    Ionospheric tomography is based on the observed slant total electron content (sTEC) along different satellite-receiver rays to reconstruct the three-dimensional electron density distributions. Due to incomplete measurements provided by the satellite-receiver geometry, it is a typical ill-posed problem, and how to overcome the ill-posedness is still a crucial content of research. In this paper, Tikhonov regularization method is used and the model function approach is applied to determine the optimal regularization parameter. This algorithm not only balances the weights between sTEC observations and background electron density field but also converges globally and rapidly. The background error covariance is given by multiplying background model variance and location-dependent spatial correlation, and the correlation model is developed by using sample statistics from an ensemble of the International Reference Ionosphere 2012 (IRI2012) model outputs. The Global Navigation Satellite System (GNSS) observations in China are used to present the reconstruction results, and measurements from two ionosondes are used to make independent validations. Both the test cases using artificial sTEC observations and actual GNSS sTEC measurements show that the regularization method can effectively improve the background model outputs.

  18. Interpretation of ionospheric F-region structures in the vicinity of ionisation troughs observed by satellite radio tomography

    NASA Astrophysics Data System (ADS)

    Aladjev, G. A.; Evstafiev, O. V.; Mingalev, V. S.; Mingaleva, G. I.; Tereshchenko, E. D.; Khudukon, B. Z.

    2001-01-01

    Tomographic images of the spatial distribution of electron density in the ionospheric F-region are presented from the Russian-American Tomography Experiment (RATE) in November 1993 as well as from campaigns carried out in northern Scandinavia in November 1995 and in Russia in April 1990. The reconstructions selected display the ionisation troughs above the tomographic chains of receivers during geomagnetically quiet and disturbed periods. Two mathematical models of the high-latitude ionosphere developed in the Polar Geophysical Institute have been applied for interpretation of the observed tomographic images.

  19. A computerized tomography study of the morphological interrelationship between the temporal bones and the craniofacial complex

    PubMed Central

    Costa, Helder Nunes; Slavicek, Rudolf; Sato, Sadao

    2012-01-01

    The hypothesis that the temporal bones are at the center of the dynamics of the craniofacial complex, directly influencing facial morphology, has been put forward long ago. This study examines the role of the spatial positioning of temporal bones (frontal and sagittal inclination) in terms of influencing overall facial morphology. Several 3D linear, angular and orthogonal measurements obtained through computerized analysis of virtual models of 163 modern human skulls reconstructed from cone-beam computed tomography images were analyzed and correlated. Additionally, the sample was divided into two subgroups based on the median value of temporal bone sagittal inclination [anterior rotation group (n = 82); posterior rotation group (n = 81)], and differences between groups evaluated. Correlation coefficients showed that sagittal inclination of the temporal bone was significantly (P < 0.01) related to midline flexion, transversal width and anterior–posterior length of the basicranium, to the anterior–posterior positioning of the mandible and maxilla, and posterior midfacial height. Frontal inclination of the temporal bone was significantly related (P < 0.01) to basicranium anterior–posterior and transversal dimensions, and to posterior midfacial height. In comparison with the posterior rotation group, the anterior rotation group presented a less flexed and anterior–posteriorly longer cranial base, a narrower skull, porion and the articular eminence located more superiorly and posteriorly, a shorter posterior midfacial height, the palatal plane rotated clockwise, a more retrognathic maxilla and mandible, and the upper posterior occlusal plane more inclined and posteriorly located. The results suggest that differences in craniofacial morphology are highly integrated with differences in the positional relationship of the temporal bones. The sagittal inclination of the temporal bone seems to have a greater impact on the 3D morphology of the craniofacial complex than

  20. Combining ultrasonography and noncontrast helical computerized tomography to evaluate Holmium laser lithotripsy

    PubMed Central

    Mi, Jia; Li, Jie; Zhang, Qinglu; Wang, Xing; Liu, Hongyu; Cao, Yanlu; Liu, Xiaoyan; Sun, Xiao; Shang, Mengmeng; Liu, Qing

    2016-01-01

    Abstract The purpose of the study was to establish a mathematical model for correlating the combination of ultrasonography and noncontrast helical computerized tomography (NCHCT) with the total energy of Holmium laser lithotripsy. In this study, from March 2013 to February 2014, 180 patients with single urinary calculus were examined using ultrasonography and NCHCT before Holmium laser lithotripsy. The calculus location and size, acoustic shadowing (AS) level, twinkling artifact intensity (TAI), and CT value were all documented. The total energy of lithotripsy (TEL) and the calculus composition were also recorded postoperatively. Data were analyzed using Spearman's rank correlation coefficient, with the SPSS 17.0 software package. Multiple linear regression was also used for further statistical analysis. A significant difference in the TEL was observed between renal calculi and ureteral calculi (r = –0.565, P < 0.001), and there was a strong correlation between the calculus size and the TEL (r = 0.675, P < 0.001). The difference in the TEL between the calculi with and without AS was highly significant (r = 0.325, P < 0.001). The CT value of the calculi was significantly correlated with the TEL (r = 0.386, P < 0.001). A correlation between the TAI and TEL was also observed (r = 0.391, P < 0.001). Multiple linear regression analysis revealed that the location, size, and TAI of the calculi were related to the TEL, and the location and size were statistically significant predictors (adjusted r2 = 0.498, P < 0.001). A mathematical model correlating the combination of ultrasonography and NCHCT with TEL was established; this model may provide a foundation to guide the use of energy in Holmium laser lithotripsy. The TEL can be estimated by the location, size, and TAI of the calculus. PMID:27930563

  1. Toward a new insight of calcium oxalate stones in Drosophila by micro-computerized tomography.

    PubMed

    Chen, Wen-Chi; Chen, Huey-Yi; Liao, Po-Chi; Wang, Shih-Jing; Tsai, Ming-Yen; Chen, Yung-Hsiang; Lin, Wei-Yong

    2017-03-04

    We previously developed an animal model of calcium oxalate (CaOx) deposition on the Malphigian tubules of Drosophila melanogaster as a model of urolithiasis. Here, we introduce a new tool for the study of anatomical structure for Drosophila. As a consequence of technical development, the invention of micro-computerized tomography (CT) has been introduced to the small animal, such as rat and mice. We used Drosophila as a model organism and fed the flies 0.5% lithogenic agent ethylene glycol for 3 weeks. Samples were simply prepared for further scanned by micro-CT to scan samples at 800 nm resolution. CT scanning was performed at 40 kVp of voltage, 250 μA of current, and 1750 ms of exposure time and without filter. Reconstruction of sections was carried out with the GPU-based scanner software. Specific region of interests was further analyzed by DataViewer software. Area with high radiologic density level was defined as CaOx deposition for further 3D analysis. Image of whole lithogenic Drosophila was compared with control. High radiologic density level was detected in the region of Malphigian tubules which can be identified as CaOx stones. There was no stone image in the control group. The image was the same as human non-contrast CT for the diagnosis of stone disease. Micro-CT clearly demonstrated the calcium oxalate calcifications in the Malphigian tubules of fruit fly. The image system provides that a new vision on study animal will facilitate further study of stone disease. With the development of new technology on micro-CT, more delicate and advanced image will be presented in the future.

  2. Application of IRI-Plas in Ionospheric Tomography and HF Communication Studies with Assimilation of GPS-TEC

    NASA Astrophysics Data System (ADS)

    Arikan, Feza; Gulyaeva, Tamara; Sezen, Umut; Arikan, Orhan; Toker, Cenk; Hakan Tuna, MR.; Erdem, Esra

    2016-07-01

    International Reference Ionosphere is the most acknowledged climatic model of ionosphere that provides electron density profile and hourly, monthly median values of critical layer parameters of the ionosphere for a desired location, date and time between 60 to 2,000 km altitude. IRI is also accepted as the International Standard Ionosphere model. Recently, the IRI model is extended to the Global Positioning System (GPS) satellite orbital range of 20,000 km. The new version is called IRI-Plas and it can be obtained from http://ftp.izmiran.ru/pub/izmiran /SPIM/. A user-friendly online version is also provided at www.ionolab.org as a space weather service. Total Electron Content (TEC), which is defined as the line integral of electron density on a given ray path, is an observable parameter that can be estimated from earth based GPS receivers in a cost-effective manner as GPS-TEC. One of the most important advantages of IRI-Plas is the possible input of GPS-TEC to update the background deterministic ionospheric model to the current ionospheric state. This option is highly useful in regional and global tomography studies and HF link assessments. IONOLAB group currently implements IRI-Plas as a background model and updates the ionospheric state using GPS-TEC in IONOLAB-CIT and IONOLAB-RAY algorithms. The improved state of ionosphere allows the most reliable 4-D imaging of electron density profiles and HF and satellite communication link simulations.This study is supported by TUBITAK 115E915 and joint TUBITAK 114E092 and AS CR 14/001.

  3. Central representation of phantom limb phenomenon in amputees studied with single photon emission computerized tomography.

    PubMed

    Liaw, M Y; You, D L; Cheng, P T; Kao, P F; Wong, A M

    1998-01-01

    To explore the possible mechanisms of phantom limb discomfort after amputation, three amputees with phantom limb pain were studied. This study examined the change of regional cerebral blood flow using technetium-99m hexamethylpropyleneamine oxime-single photon emission computerized tomography, which was arranged at the time of severe phantom limb discomfort and after the discomfort subsided or was completely relieved. Nine representative transverse slices parallel to the orbitomeatal line were selected for quantification. The cortical ribbon (2-cm thickness) was equally subdivided into 12 symmetrical pairs of sector regions of interest in each slice. The irregularly shaped regions of interest were drawn manually around the right thalamus and basal ganglion and then mirrored to the left thalamus and basal ganglion. The contralateral to ipsilateral ratio of regional cerebral blood flow for each area was calculated. The intensity of phantom limb pain was evaluated on a 0 to 10 visual analog scale. In Cases 1 and 2, the contralateral to ipsilateral regional cerebral blood flow ratios of multiple areas of the frontal, temporal, or parietal lobes were increased at the time of more severe phantom limb pain, and the ratios were normalized or even decreased when the phantom limb pain subsided. In Case 3, increased contralateral to ipsilateral regional cerebral blood flow ratios were also found over the frontal, temporal, and parietal lobe. However, most of the increased regional cerebral blood flow ratios of regions of interest in the first study persisted in the follow-up study. Also, the regional cerebral blood flow ratios of greater number of regions of interest of the same gyrus and new gyrus were increased. There was no significant right-left difference of regional cerebral blood flow over bilateral thalami and basal ganglia in all three cases. The results suggested that phantom limb pain might be associated with cortical activation involving the frontal, temporal, or

  4. Computerized Tomography-Based Morphologic and Morphometric Features of the Coccyx Among Arab Adults.

    PubMed

    Marwan, Yousef Abbas; Al-Saeed, Osama Mhawes; Esmaeel, Ali Abdulla; Ahmad Kombar, Osama Rabie; Bendary, Abdulla Mohammad; Abdul Azeem, Mokhtar Elsayed

    2014-07-09

    Study Design. Cross-sectional, retrospective.Objective. To identify morphologic and morphometric features of the coccyx among adult Arabs.Summary of Background Data. Different sacrococcygeal morphologic features were found to be associated with coccydynia.Methods. Review of 202 computerized tomography scans of adult Arab subjects was done (mean age: 47.98 ± 16.46 years). Sacrococcygeal morphologic features including number of coccygeal segments, type of coccyx, joint fusion, joint subluxation, coccygeal spicule, coccygeal sacralization, ventral angulation of the terminal sacral segment (S5), and lateral deviation of coccygeal tip were recorded. Moreover, morphometric measurements including lengths and angles of the sacrococcygeal region were measured. Analysis of data was carried out using p-value of <0.05 as the cut-off level of significance.Results. Three coccygeal segments were present in 138 (68.3%) of individuals. The majority of the subjects had coccyx type I (96; 47.5%), II (70; 34.7%) or III (31; 15.3%); type I being more common among males (p = 0.004). Bony spicule was present in 109 (54.0%) individuals. Joint fusion, joint subluxation, coccygeal sacralization, ventral angulation of S5 and lateral deviation of coccygeal tip were present in 38.6%, 31.7%, 34.2%, 38.1% and 38.6% of the subjects respectively. Joint subluxation and ventral angulation of S5 were significantly more present among females (p = 0.015, p = 0.014 respectively). The mean straight and curved lengths of the coccyx were 3.3 ± 0.7 cm and 3.7 ± 0.8 cm respectively. The sacrococcygeal structures were longer in men than women. The mean sacrococcygeal joint angle was 149.2° ± 28.1°. Based on the morphometric measurements, the coccyx was more ventrally angulated among females.Conclusions. The coccygeal morphology and morphometry of Arab adults share some similarities and differences with individuals of other ethnic backgrounds. Future studies should investigate the relation between these

  5. The role of renal scintigraphy and unenhanced helical computerized tomography in patients with ureterolithiasis.

    PubMed

    Lorberboym, M; Kapustin, Z; Elias, S; Nikolov, G; Katz, R

    2000-04-01

    Unenhanced helical computerized tomography (UHCT) has recently evolved as an accurate imaging modality for determination of the presence or absence of ureterolithiasis in patients with acute flank pain. Functional renal scintigraphy is considered the gold standard for urinary tract obstruction. The objective of this study was to correlate the secondary signs of urinary obstruction on UHCT with findings of functional renal scintigraphy. UHCT was performed in 30 patients admitted to the emergency room with acute flank pain. All patients had a calcified urinary stone identified on UHCT. The location of each urinary stone was classified as ureteral or in the ureterovesical junction. The presence of secondary CT signs of ureteral obstruction was determined for each patient. After oral or intravenous hydration, a technetium-99m diethylene triamine penta-acetic acid renal scan was performed in all patients within 12 h of the CT scan. Follow-up delayed scintigraphic images were obtained at 2 h and 24 h in patients with evidence of ureteral obstruction. The sensitivity, specificity and predictive values of each possible combination of CT findings were determined by comparison with the scintigraphic results. The distal ureter was the most common location for a calculus on UHCT, followed in frequency by the ureterovesical junction, proximal ureter and mid-ureter. The renograms showed high-grade, unilateral obstruction in 12 patients, indeterminate scans in five patients and normal renograms in 13 patients. The sensitivities and specificities of individual CT findings ranged from 50% to 75% and from 8% to 69%, respectively. Perinephric stranding gave the highest positive predictive value (PPV) for obstruction (69% including indeterminate renograms). None of the individual CT findings showed a statistically significant correlation with scintigraphic findings. A combination of one or two positive CT findings had a PPV of only 25% for obstruction. A combination of three or four

  6. Computerized Tomography-Guided Paracentesis: An Effective Alternative to Bedside Paracentesis?

    PubMed Central

    Gaduputi, Vinaya; Tariq, Hassan; Chandrala, Chaitanya; Sakam, Sailaja; Abbas, Naeem; Chilimuri, Sridhar

    2017-01-01

    Background Ascites remains the most common cause of hospitalization among patients with decompensated cirrhosis. Paracentesis is a relatively safe procedure with low complication rates. Computerized tomography (CT)-guided therapeutic paracentesis could be a safe and effective alternative to unaided or aided (ultrasonogram-guided) bedside paracentesis. In this retrospective study, we aimed to compare the efficacy, safety, and cost-effectiveness of CT-guided paracentesis with bedside paracentesis. Methods The period of study was from 2002 to 2012. All patients with cirrhosis who underwent therapeutic paracentesis were included in the study. These patients were divided into two groups. Group I consisted of patients who underwent CT-guided pigtail catheter insertion with ascitic fluid drainage. Group II consisted of patients who underwent beside therapeutic paracentesis after localization of fluid either by physical examination or sonographic localization. We measured the efficacy of CT-guided paracentesis and bedside paracentesis in terms of volume of fluid removed, length of stay, discharge doses of diuretics (spironolactone and furosemide) and number of days to readmission for symptomatic ascites. We also computed the cost-effectiveness of CT-guided therapeutic paracentesis when compared to a bedside procedure. Fischer exact test was used to analyze the distribution of categorical data and unpaired t-test was used for comparison of means. Results There were a total of 546 unique patients with diagnosed cirrhosis who were admitted to the hospital with symptomatic ascites and underwent therapeutic paracentesis. Two hundred and forty-seven patients underwent CT-guided paracentesis, while 272 patients underwent bedside paracentesis. There was significant inverse correlation between the amount of ascitic fluid removed and total length of stay in the hospital. We found that the volume of fluid removed via a CT-guided pigtail insertion and drainage (2.72 ± 2.02 L) is

  7. AMPS data management requirements study. [user manuals (computer programs)/display devices - computerized simulation/experimentation/ionosphere

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A data simulation is presented for instruments and associated control and display functions required to perform controlled active experiments of the atmosphere. A comprehensive user's guide is given for the data requirements and software developed for the following experiments: (1) electromagnetic wave transmission; (2) passive observation of ambient plasmas; (3) ionospheric measurements with a subsatellite; (4) electron accelerator beam measurements; and (5) measurement of acoustic gravity waves in the sodium layer using lasers. A complete description of each experiment is given.

  8. Comparison of micro-computerized tomography and cone-beam computerized tomography in the detection of accessory canals in primary molars

    PubMed Central

    Kamburoğlu, Kıvanç; Tatar, İlkan; Arıkan, Volkan; Çelik, Hakan Hamdi; Yüksel, Selcen; Özen, Tuncer

    2015-01-01

    Purpose This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Materials and Methods Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. Results The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images. Conclusion Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth. PMID:26730367

  9. AMPS data management requirements study, appendix 1. [user manuals (computer programs)/display devices - computerized simulation/experimentation/ionosphere

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Flow charts and display formats for the simulation of five experiments are given. The experiments are: (1) electromagnetic wave transmission; (2) passive observations of ambient plasma; (3) ionospheric measurements with subsatellite; (4) electron accelerator beam measurements; and (5) measurement of acoustical gravity waves in the sodium layer using lasers. A detailed explanation of the simulation procedure, definition of variables, and an explanation of how the experimenter makes display choices is also presented. A functional description is included on each flow chart and the assumptions and definitions of terms and scope of the flow charts and displays are presented.

  10. Simultaneous multiplicative column-normalized method (SMART) for 3-D ionosphere tomography in comparison to other algebraic methods

    NASA Astrophysics Data System (ADS)

    Gerzen, T.; Minkwitz, D.

    2016-01-01

    The accuracy and availability of satellite-based applications like GNSS positioning and remote sensing crucially depends on the knowledge of the ionospheric electron density distribution. The tomography of the ionosphere is one of the major tools to provide link specific ionospheric corrections as well as to study and monitor physical processes in the ionosphere. In this paper, we introduce a simultaneous multiplicative column-normalized method (SMART) for electron density reconstruction. Further, SMART+ is developed by combining SMART with a successive correction method. In this way, a balancing between the measurements of intersected and not intersected voxels is realised. The methods are compared with the well-known algebraic reconstruction techniques ART and SART. All the four methods are applied to reconstruct the 3-D electron density distribution by ingestion of ground-based GNSS TEC data into the NeQuick model. The comparative case study is implemented over Europe during two periods of the year 2011 covering quiet to disturbed ionospheric conditions. In particular, the performance of the methods is compared in terms of the convergence behaviour and the capability to reproduce sTEC and electron density profiles. For this purpose, independent sTEC data of four IGS stations and electron density profiles of four ionosonde stations are taken as reference. The results indicate that SMART significantly reduces the number of iterations necessary to achieve a predefined accuracy level. Further, SMART+ decreases the median of the absolute sTEC error up to 15, 22, 46 and 67 % compared to SMART, SART, ART and NeQuick respectively.

  11. Magnetic resonance imaging and computerized tomography in relation to the neurobehavioral sequelae of mild and moderate head injuries.

    PubMed

    Levin, H S; Amparo, E; Eisenberg, H M; Williams, D H; High, W M; McArdle, C B; Weiner, R L

    1987-05-01

    Twenty patients admitted for minor or moderate closed-head injury were studied to investigate the relationship between magnetic resonance imaging (MRI) and neurobehavioral sequelae. The MRI scans demonstrated 44 more intracranial lesions than did concurrent computerized tomography (CT) scans in 17 patients (85%); most of these lesions were located in the frontal and temporal regions. Estimates of lesion volume based on MRI were frequently greater than with CT; however, MRI disclosed no additional lesions that required surgical evacuation. Neuropsychological assessment during the initial hospitalization revealed deficits in frontal lobe functioning and memory that were related to the size and localization of the lesions as defined by MRI. Follow-up MRI and neuropsychological testing at 1 month (13 cases) and 3 months (six cases) disclosed marked reduction of lesion size paralleled by improvement in cognition and memory. These findings encourage further investigation of the prognostic utility of MRI for the clinical management and rehabilitation of mild or moderate head injury.

  12. Diagnosis and management decisions in infections of the deep fascial spaces of the head and neck utilizing computerized tomography.

    PubMed

    Endicott, J N; Nelson, R J; Saraceno, C A

    1982-06-01

    Infections of the deep spaces of the head and neck may still result in major consequences despite the advent of antibiotics. Abscesses in these areas merit special consideration by today's head and neck surgeon because of their relative rarity and the life-threatening complications that may follow inadequate treatment. Diagnosis and management decisions are enhanced by use of computerized tomography (CT) as an adjunctive study. The EMI scan may demonstrate either cellulitis of the neck requiring no surgery or a space abscess displacing the adjacent structures thus requiring surgical drainage. Anatomy of the significant fascial planes and spaces of the neck will reviewed employing CT utilizing 3 mm cuts. Specific case presentations feature early diagnosis and management.

  13. [Role of computeric tomography and magnetic resonance imaging in diagnosis of inflammatory diseases of sacro-ileal joint].

    PubMed

    Baĭramov, R B

    2012-05-01

    Sensitivity of computeric tomography (CT) and magnetic resonance imaging (MRI) for sacroileitis diagnosis was studied, optimal for MRI investigation was established. In 31 patients, owing obvious clinical signs of inflammatory sacroileitis (at average more than 5 mo duration of a low back pain) MRI of sacroiliac joint was conducted in a T1, T2 FS, 2D T2 FLASH regimes and after intravenous infusion of a contrast substance (gadolinium) - in a T1 FS regime, using system, owing a 1,5 T magnetic field intensity. The data obtained were compared with results of CT. Sacroileitis signs were revealed in 27 patients - according to CT data, and in 22 - MRI. CT have demonstrated as a more sensitive method of the bone erosion and sclerosis diagnosis, than MRI. MRI is more sensitive while revealing an active inflammatory process in the bone and joint space. While T1 FS application no additional information for sacroileitis diagnosis was obtained.

  14. An evaluation of the condylar position of the temporomandibular joint by computerized tomography in Class III malocclusions: a preliminary study.

    PubMed

    Seren, E; Akan, H; Toller, M O; Akyar, S

    1994-05-01

    The position of the condyle within the glenoid fossa was investigated in 21 adult patients with untreated skeletal Class III relationships and 18 adult patients with normal occlusions as controls. Axial computerized tomography (CT) was used for precise measurements of the bony structures of the temporamandibular joints. In horizontal sections, the mediolateral dimensions of the condyles of the patient group were found to be statistically higher in the fossa. The anteroposterior glenoid fossa dimensions were found to be smaller in Class III malocclusions. The smaller anterior joint space dimensions in the Class III relationships were also found to be statistically significant. The analysis of the measurements suggests that relative condylar protrusion with a relative mediolateral elongation of the condyle within a relatively smaller glenoid fossa are correlated with the anterior mandibular displacement in skeletal Class III malocclusions.

  15. Evaluation of the accuracy of Cone Beam Computerized Tomography (CBCT): medical imaging technology in head and neck reconstruction

    PubMed Central

    2013-01-01

    Background With the introduction, development and commercialization of Cone Beam Computerized Tomography (CBCT) technologies in the field of head and neck reconstruction, clinicians now have increased access to the technology. Given the growth of this new user group, there is an increasing concern regarding proper use, understanding, quality and patient safety. Methods The present study was carried out to evaluate data acquisition of CBCT medical imaging technology and the accuracy of the scanning at three different machine warming times. The study also compared the accuracy of CBCT at 0.2 mm slice thickness and Computerized Tomography (CT) at 1 mm slice thickness. A control model was CT scanned at five random intervals, at 1 mm slice thickness and CBCT scanned at specialized intervals, at 0.2 mm slice thickness. The data was then converted and imported into a software program where a digital registration procedure was used to compare the average deviations of the scanned models to the control. Results The study found that there was no statistically significant difference amongst the three CBCT machine warming times. There was a statistically significant difference between CT scanning with 1 mm slice thickness and CBCT scanning with 0.2 mm slice thickness. Conclusions The accuracy of the i-CAT CBCT scans used in the present study with a parameter at voxel size 0.2, will remain consistent and reliable at any warming stage. Also the difference between the CBCT i-CAT scans and the CT scans was not clinically significant based on suggested requirements of clinicians in head and neck reconstruction. PMID:23672880

  16. Methods of predicting visceral fat in Brazilian adults and older adults: a comparison between anthropometry and computerized tomography.

    PubMed

    Roriz, Anna Karla Carneiro; de Oliveira, Carolina Cunha; Moreira, Pricilla Almeida; Eickemberg, Michaela; Medeiros, Jairza Maria Barreto; Sampaio, Lílian Ramos

    2011-03-01

    Visceral adipose tissue (VAT) is linked with the metabolic consequences of obesity, being necessary the use alternative methods of predicting this type of fat, like anthropometry. The objective of this study was assess the performance of anthropometry in predicting visceral fat measured with computerized tomography in adults and older adults. Study transversal with 197 individuals underwent computerized tomography (CT) and anthropometry. The variables analized were: visceral adipose tissue area by CT, Sagittal Abdominal Diameter (SAD), Waist Circumference (WC) and Waist-Hip Ratio (WHR). A descriptive analysis, Pearson correlation and ROC curve were carried out. We observed Correlations higher than 0.7 (p = 0.000) between the SAD, WC and the VAT area were found in adult men and older men and in adult women. WHR displayed the least correlations. The most sensitive and specific SAD cut-off points were equal for all the men (Adults: 20.2 cm/Older adults: 20.2 cm) but different for the women (Adults: 21.0 cm; sens.: 83.3; spec.: 79.1/Older adults: 19.9 cm; sens.: 81.0; spec.:79.3). The WC cutoff points that identified a VAT area = 130 cm2 were 90.2 cm and 92.2 cm for men (adult men--sens.: 86.7; spec.: 86.1--and older men-sens.: 79.3; spec.: 77.8 -respectively), while for women the recorded values were 92.3 cm (adult women--sens.: 83.3; spec: 81.4) and 88.2 cm (older women--sens.:76.2; spec.: 69.0). This study showed that WC and SAD achieved the best performance in the identification of visceral fat considered at risk for the development of cardiometabolic diseases in adults and older adults.

  17. Positron emission tomography/computerized tomography for tumor response assessment—a review of clinical practices and radiomics studies

    PubMed Central

    Lu, Wei; Chen, Wengen

    2016-01-01

    Even with recent advances in cancer diagnosis and therapy, treatment outcomes for many cancers remain dismal. Patients often show different response to the same therapy regimen, supporting the development of personalized medicine. 18F-FDG PET/CT has been used routinely in the assessment of tumor response, in prediction of outcomes, and in guiding personalized treatment. These assessments are mainly based on physician’s subjective or semi-quantitative evaluation. Recent development in Radiomics provides a promising objective way for tumor response assessment, which uses computerized tools to extract a large number of image features that capture additional information not currently used in clinic that has prognostic value. In this review, we summarized the clinical use of PET/CT and the PET/CT Radiomics studies for tumor response assessment. Finally, we discussed some challenges and future perspectives. PMID:27904837

  18. Positron emission tomography/computerized tomography for tumor response assessment-a review of clinical practices and radiomics studies.

    PubMed

    Lu, Wei; Chen, Wengen

    2016-08-01

    Even with recent advances in cancer diagnosis and therapy, treatment outcomes for many cancers remain dismal. Patients often show different response to the same therapy regimen, supporting the development of personalized medicine. 18F-FDG PET/CT has been used routinely in the assessment of tumor response, in prediction of outcomes, and in guiding personalized treatment. These assessments are mainly based on physician's subjective or semi-quantitative evaluation. Recent development in Radiomics provides a promising objective way for tumor response assessment, which uses computerized tools to extract a large number of image features that capture additional information not currently used in clinic that has prognostic value. In this review, we summarized the clinical use of PET/CT and the PET/CT Radiomics studies for tumor response assessment. Finally, we discussed some challenges and future perspectives.

  19. Tumor volume, luxury perfusion, and regional blood volume changes in man visualized by subtraction computerized tomography.

    PubMed

    Penn, R D; Walser, R; Kurtz, D; Ackerman, L

    1976-04-01

    Computer and photographic methods for producing subtractions of computerized axial tomographic (CAT) scans have been developed. By subtracting point for point a normal scan from one taken after intravenous infusion of contrast material, a picture of the contrast in the cerebral vessels is created. By this method, tumor size and degree of vascularity may be assessed. Furthermore, abnormalities in perfusion and changes in blood volume due to mass effects and edema may be detected. Subtracting scans should add to the diagnostic potential of CAT and provide a noninvasive way to study vascular changes in cerebral disease.

  20. Application of High- and Low-Orbiting Radio Tomography for Exploring the Ionospheric Structures on Different Scales

    NASA Astrophysics Data System (ADS)

    Andreeva, Elena; Padokhin, Artem; Nazarenko, Marina; Nesterov, Ivan; Tumanova, Yulia; Tereshchenko, Evgeniy; Kozharin, Maksim

    2016-07-01

    The methods of ionospheric radio tomography (RT) are actively developing at present. These methods are suitable for reconstructing the spatial distributions of electron density from radio signals transmitted from the navigational satellite systems and recorded by the networks of ground-based receivers. The RT systems based on the low-orbiting (LO) (Parus/Transit) navigational systems have been in operation since the early 1990s. Recently, the RT methods employing the signals from high-orbiting (HO) satellite navigational systems such as GPS/GLONASS have come into play. In our presentation, we discuss the accuracies, advantages, and limitations of LORT and HORT as well as the possibilities of their combined application fro reconstructing the structure of the ionosphere in the same region during the same time interval on the different spatiotemporal scales. The LORT reconstructions provide practically instantaneous (spanning 5-10 min) 2D snapshots of the ionosphere within a spatial interval with a length of up to a few thousand km. The vertical resolution of LORT is 25-30 km and the horizontal resolution, 15-25 km. The HORT methods are capable of reconstructing the 4D structure of the ionosphere (three spatial coordinates and time). The spatial resolution of HORT is generally not better than 100 km with a 60-20 min interval between the successive reconstructions. In the regions of dense receiving networks, the resolution can be improved to 30-50 km and the time step can be reduced to 30-10 min. In California and Japan which are covered by extremely dense receiving networks the resolution can be even higher (10-30 km) and the time interval between the reconstruction even shorter (up to 2 min). In the presentation, we discuss the LORT and HORT reconstructions of the ionosphere during different time periods of the 23rd and 24th solar cycles in the different regions of the world. We analyze the spatiotemporal features and dynamics of the ionosphere depending on the solar

  1. 3D Tomography of Ionospheric Perturbations Produced by Earthquakes Using Global Positioning System

    NASA Astrophysics Data System (ADS)

    Crespon, F.; Garcia, R.; Lognonné, P.; Murakami, M.

    2004-12-01

    The recent development of Global Positioning System led to establish dense regional networks of bistatic GPS receivers providing today a powerful ionospheric observing system. Now the ionosphere can be imaged by tomographic methods using GPS data. Therefore the ionospheric perturbations can be characterized by monitoring Total Electronic Content (TEC). These disturbances have multiple sources located adove and below ionospheric layers. The most known are the Travelling Ionospheric Disturbances (TID) produced by internal gravity waves. But some ionospheric disturbances are also due to infrasonic waves. We focus this study on ionospheric perturbations generated by infrasonic waves exited by seismic waves, resulting from the coupling between Earth and the atmosphere. We present a spectral analysis of TEC GPS data, the 3D tomographic method and its application to post-seismic perturbations. By removing background noise we are able to monitor acoustic post-seismic waves, generated by the rupture process and the seismic surface waves, that reach the ionosphere. Especially, we show the observations for the Denali earthquake of 3rd November 2002 and the Hokkaido earthquake of 25th September 2003 using respectively the Californian networks (SICGN) and the Japan network (GEONET). Both the horizontal and vertical propagation of the waves are vizualized in the 3D tomographic movies. The observed waves arrive with a timing and a propagation velocity coherent with expected waves and we purpose an interpretation in terms of infrasonic waves in the atmosphere, generated both near the epicenter and at further distance, at the level of the Rayleigh waves front. Finally we present the improvement of the 3D tomographic methods with the advent of the Galileo system and possible application in seismology.

  2. A study of 3D structure of nighttime electron density enhancement in the mid-latitude ionosphere by GPS tomography

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.

    2011-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density larger than that in the daytime mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and observed in the northern hemisphere recently by ionosondes and satellites. Previous studies presented the electron density structure of MSNA by using COSMIC occultation data and found that MSNA is clearly seen around 300 km altitude during local summer. However, due to lack of observation, the day-to-day variation of MSNA was not investigated. A GPS tomography method by SPEL of Kyoto University using the total electron content (TEC) data measured by the ground-based GPS receiver network is employed in this study. The wide coverage and continuous observation of GPS receivers are suitable for investigating the spatial and day-to-day variations of ionospheric electron densities. The algorithm of the GPS tomography developed by SPEL of Kyoto University use a constraint condition that the gradient of election density tends to be smooth in the horizontal direction and steep in the vicinity of the F2 peak, instead of inputting the initial conditions. Therefore, the algorithm is independent of any ionospheric and plasmaspheric electron density distribution models. The dense ground-based GPS receiver network around European region is used to study the three dimensional (3D) structure of MSNA with GPS tomography. Results show that the MSNA usually appear around the geomagnetic mid-latitude region during local summer nighttime. The feature of MSNA is most obvious at the ionospheric F2-peak altitudes. The result also shows a day-to-day variation in the formation of MSNA, in terms of the occurrence time, intensity, and spatial extent. The tomographic results are compared with the ionosondes, satellites, and radar measurements. A theoretical model simulation, SAMI2, is also used to further discuss the mechanism of MSNA. The comparison with other

  3. Three-Dimensional Planning in Maxillofacial Fracture Surgery: Computer-Aided Design/Computer-Aided Manufacture Surgical Splints by Integrating Cone Beam Computerized Tomography Images Into Multislice Computerized Tomography Images.

    PubMed

    Ren, Jiayin; Zhou, Zhongwei; Li, Peng; Tang, Wei; Guo, Jixiang; Wang, Hu; Tian, Weidong

    2016-09-01

    This study aimed to evaluate an innovative workflow for maxillofacial fracture surgery planning and surgical splint designing. The maxillofacial multislice computerized tomography (MSCT) data and dental cone beam computerized tomography (CBCT) data both were obtained from 40 normal adults and 58 adults who suffered fractures. The each part of the CBCT dentition image was registered into MSCT image by the use of the iterative closest point algorithm. Volume evaluation of the virtual splints that were designed by the registered MSCT images and MSCT images of the same object was performed. Eighteen patients (group 1) were operated without any splint. Twenty-one (group 2) and 19 patients (group 3) used the splints designed according to the MSCT images and registered MSCT images, respectively. The authors' results showed that the mean errors between the 2 models ranged from 0.53 to 0.92 mm and the RMS errors ranged from 0.38 to 0.69 mm in fracture patients. The mean errors between the 2 models ranged from 0.47 to 0.85 mm and the RMS errors ranged from 0.33 to 0.71 mm in normal adults. 72.22% patients in group 1 recovered occlusion. 85.71% patients in group 2, and 94.73% patients in group 3 reconstructed occlusion. There was a statistically significant difference between the MSCT images based splints' volume and the registered MSCT splints' volume in patients (P <0.05). The MSCT images based splints' volume was statistically significantly distinct from the registered MSCT splints' volume in normal adults (P <0.05). There was a statistically significant difference between the MSCT images based splints' volume and the registered MSCT splints' volume in patients and normal adults (P <0.05). The occlusion recovery rate of group 3 was better than that of group 1 and group 2. The way of integrating CBCT images into MSCT images for splints designing was feasible. The volume of the splints designed by MSCT images tended to be smaller than the splints designed by

  4. Computerized X-ray reconstruction tomography in stereometric analysis of cardiovascular dynamics

    NASA Technical Reports Server (NTRS)

    Robb, R. A.; Harris, L. D.; Ritman, E. L.

    1977-01-01

    A computerized technique is proposed for obtaining cross-sectional images of the dynamic spatial distribution of X-ray attenuation covering the entire anatomic extent of the thorax and its contents in living dogs with a resolution of 1 mm and at time intervals of 1/60 sec. Use is made of an X-ray imaging chain which is a new high-performance video-fluoroscopic system, unique in its design and construction and called SSDSR for single source dynamic spatial reconstructor. This dynamic spatial reconstruction system is shown to provide the temporally and spatially coherent multiple cross sections required to obtain the full three-dimensional anatomic and simultaneous hemodynamic information necessary for detailed quantitative analyses of regional cardiopulmonary and vascular functions in both basic investigations of animals and clinical diagnostic applications to patients. Numerous photographs supplement the text.

  5. [A quantitative evaluation of brain computerized tomography in children using color image analyzer].

    PubMed

    Yamatani, M; Naganuma, Y; Hongoh, K; Murakami, M; Konishi, T; Okada, T

    1989-11-01

    We attempted the quantitative analysis of brain computerized tomographic scans in children using Color Image Analyzer. A consecutive series of 167 computerized tomographic scans were reviewed. Areas of subarachnoid spaces, cavums, ventricles and cerebellums were measured on three slices: A slice is at the level of head of caudate nucleus, anterior horn of lateral ventricle and third ventricle. B slice is at the level of body of lateral ventricle. C slice is at the level of sella turcica and pons. We investigated these values compared with Evans ratio, Cella Media Index, cerebellar atrophy score and visually evaluations. Serial brain CT scans of eight patient with infantile spasms were also evaluated for the assessment of the brain shrinkage after ACTH therapy. 1) The ratios of the subarachnoid space/the intracranial area on A and B slices (SAS A%, SAS B%) were significantly higher in the patients of severe brain atrophy. 2) There were linear relationship between Evans ratio and SAS A% (r = 0.405, p less than 0.001), Cella Media Index and the ratio of the lateral ventricles/the intracranial areas on B slice (r = -0.501, p less than 0.001), and the cerebellar atrophy score by Une and SAS C% (r = 0.369, p less than 0.001). 3) In the normal patients, the values of SAS A% and SAS B% were much greater in less than 1.5 years old children. These results suggest that the trend of CT findings related to age may reflect physiological changes of the space between the skull and the brain with age. 4) Brain shrinkage after ACTH therapy was more pronounced in the subarachnoid space than the ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Computerized tomography versus perfusion lung scanning in canine radiation lung injury

    SciTech Connect

    Ahmed, I.H.; Logus, J.W.; El-Khatib, E.; Battista, J.J.; Ferri, H.; Lentle, B.C.; Man, G.C.; Man, S.F. )

    1990-03-01

    Computerized tomographic (CT) measurements of lung density were obtained before and serially after thoracic irradiation in dogs to detect the alterations caused by radiation therapy. Fourteen mongrel dogs were given either 2000 cGy (Group A, 10 dogs, right lower zone irradiation), 1000 cGy (Group B, 2 dogs, right lower zone irradiation), or 500 cGy (Group C, 2 dogs, right lung irradiation) in one fraction. Once before and bi-weekly after irradiation, the anesthetized dogs had thoracic CT scans. CT numbers for the irradiated area were compared to their preirradiation control values. Macro-aggregated albumin (MAA) perfusion lung scans were also obtained before and at weekly intervals after irradiation and were evaluated visually and quantitatively for abnormalities. When both these tests were abnormal, or at the end of the scheduled study, the dogs were sacrificed to confirm radiation lung injury histologically. Our results showed that CT numbers (as a measure of tissue density) were higher with higher doses of radiation. Among all the techniques used, only the quantitative assessment of macro-aggregated albumin perfusion scan detected abnormalities in all the dogs given 2000 cGy. Their abnormalities correlated well with the presence of radiation lung damage histologically, however, the applicability of these methods in the detection of early injury has to be further evaluated.

  7. Radio Tomography and Imaging of Ionospheric Disturbances Caused by Active Experiments

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Andreeva, Elena; Tereshchenko, Evgeny; Nesterov, Ivan; Vladimir Frolov, S.

    We present the results of the radiotomographic imaging of the artificial ionospheric disturbances obtained in the experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out during last decade at the Sura heating facility. The experiments were conducted using both O- and X- mode radiowaves at frequencies lower than critical frequency of the ionospheric F2 layer both in daytime and nighttime ionosphere. Various schemes of the radiation of the heating wave were used including square wave modulation of the effective radiated power (ERP) at various frequencies and power stepping. Radio transmissions of the low- (Parus/Tsikada) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. We study the variations in TEC caused by HF heating showing that the GNSS TEC spectra often contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. In this work we also present the radiotomographic reconstructions of the spatial structure of the disturbed area of the ionosphere corresponding to the directivity pattern of the heater as well as the spatial structure of the wave-like disturbances, which are possibly AGWs, diverging from the heated area of the ionosphere. We also compare the effects obsereved during artificial heating experiments with those obsereved during rocket launches and powerful industiral explosions. The possibility of generation of electromagnetic waves by moving wave-like structures in ionosphere (like AGWs induced by HF-heating observed in our experiments) is also addressed in this work. The authors acknowledge the support of the Russian Foundation for Basic Research (grants № 13-05-01122, 14-05-31445, 14-05-00855, 14-05-10069), grants

  8. Application of proton magnetic resonance spectroscopy and computerized tomography in the diagnosis and treatment of nonalcoholic fatty liver disease.

    PubMed

    Wang, Nan; Dong, Hui; Wei, Shichao; Lu, Fuer

    2008-06-01

    In order to investigate the application of proton magnetic resonance spectroscopy ((1)H-MRS) and computerized tomography (CT) in the quantitative diagnosis of nonalcoholic fatty liver disease (NAFLD) and evaluation of therapeutic effects, 22 patients with NAFLD were selected according to the Chinese Medical Association's (CMA) standard of the NAFLD in comparison with 20 healthy volunteers (as control group). Blood samples for biochemistry were collected. The severity of hepatosteatosis was evaluated by (1)H-MRS scan and CT scan of liver. The intrahepatic content of lipid (IHCL) and CT value ratio of liver to spleen were calculated. The patients in NAFLD group were treated with Ganzhixiao Capsule for 8 weeks. The changes in IHCL and CT value ratio of liver to spleen were observed before and after treatment. In NAFLD group serum ALT, TG, IHCL calculated by (1)HMRS were increased and CT value ratio of liver to spleen decreased significantly as compared with control group. After treatment for 8 weeks serum ALT, TG, IHCL were decreased significantly, while CT value ratio of liver to spleen increased significantly in NAFLD group. It was suggested that IHCL could be measured precisely by (1)HMRS. NAFLD was treated effectively by Ganzhixiao capsule.

  9. A novel three-dimensional image reconstruction method for near-field coded aperture single photon emission computerized tomography

    PubMed Central

    Mu, Zhiping; Hong, Baoming; Li, Shimin; Liu, Yi-Hwa

    2009-01-01

    Coded aperture imaging for two-dimensional (2D) planar objects has been investigated extensively in the past, whereas little success has been achieved in imaging 3D objects using this technique. In this article, the authors present a novel method of 3D single photon emission computerized tomography (SPECT) reconstruction for near-field coded aperture imaging. Multiangular coded aperture projections are acquired and a stack of 2D images is reconstructed separately from each of the projections. Secondary projections are subsequently generated from the reconstructed image stacks based on the geometry of parallel-hole collimation and the variable magnification of near-field coded aperture imaging. Sinograms of cross-sectional slices of 3D objects are assembled from the secondary projections, and the ordered subset expectation and maximization algorithm is employed to reconstruct the cross-sectional image slices from the sinograms. Experiments were conducted using a customized capillary tube phantom and a micro hot rod phantom. Imaged at approximately 50 cm from the detector, hot rods in the phantom with diameters as small as 2.4 mm could be discerned in the reconstructed SPECT images. These results have demonstrated the feasibility of the authors’ 3D coded aperture image reconstruction algorithm for SPECT, representing an important step in their effort to develop a high sensitivity and high resolution SPECT imaging system. PMID:19544769

  10. Diagnostic value of multislice computerized tomography angiography for aortic dissection: A comparison with DSA

    PubMed Central

    Lu, Dong; Li, Cheng-Li; Lv, Wei-Fu; Ni, Ming; Deng, Ke-Xue; Zhou, Chun-Ze; Xiao, Jing-Kun; Zhang, Zhen-Feng; Zhang, Xing-Ming

    2017-01-01

    The aim of the present study was to compare multislice computed tomography angiography (MSCTA) and digital subtraction angiography (DSA) in the diagnosis of aortic dissection. In total, 49 patients with aortic lesions received enhanced computed tomography scanning, and three-dimensional (3D) images were reconstructed by volume rendering (VR), maximum intensity projection (MIP), multiplanar reformation (MPR) and curved planar reconstruction (CPR). The display rate of the entry tear site, intimal flap, true and false lumen from each reconstruction method was calculated. For 30 patients with DeBakey type III aortic dissection, the entry tear site and size of the first intimal flap, aortic maximum diameter at the orifice of left subclavian artery (LSCA), distance between the first entry tear site and the orifice of LSCA, and maximum diameter of aortic true and false lumens were measured prior to implantation of endovascular covered stent-grafts. Data obtained by MSCTA and DSA were then compared. For the entry tear site, MPR, CPR and VR provided a display rate of 95.92, 95.92 and 18.37%, respectively, and the display rate of the intimal flap was 100% in the three methods. MIP did not directly display the entry tear site and intimal flap. For true and false lumens, MPR, CPR, and VR showed a display rate of 100%, while MIP only provided a display rate of 67.35%. When MSCTA was compared with DSA, there was a significant difference in the display of entry site number and position (P<0.05), whereas no significant difference was shown in the measurement of aortic maximum diameter at the orifice of LSCA and the maximum diameter of true and false lumens (P>0.05). In conclusion, among the 3D post-processing reconstruction methods of MSCTA used, MPR and CPR were optimal, followed by VR, and MIP. MSCTA may be the preferable imaging method to diagnose aortic dissection and evaluate treatment of endovascular-covered stent-grafting, preoperatively. PMID:28352308

  11. [Evidence of otospongiosis obtained by computerized tomography. Does it compromise the post-stapedectomy auditory gain?].

    PubMed

    Montaño Velázquez, B B; Bello Mora, A; Zepeda López, E G; Ramírez Martínez, J; Hernández Goribar, M; Jáuregui-Renaud, K

    2002-01-01

    To study the influence of tomographic otospongiosis/otosclerosis on the audiometric gain after stapedectomy, we evaluated 34 patients (mean age 39.9 years, S.D. 9.8) with otosclerosis and mixed hearing loss. We performed Computed Tomography (CT) with densitometry before stapedectomy and audiometry before and 4 weeks after the surgery. CT results were classified as compatible or not for otospongiosis (< 1000 UH) or for otosclerosis (> 2000 UH). According to the affected turns of the cochlea, the studies were classified in 3 groups. In 43% of the patients the CT showed otospongiosis. After stapedectomy, air conduction thresholds of the low (125-500 Hz), middle (500-2000 Hz) and high frequency bands (2000-8000 Hz) and for the air/bone gap were similar for the ears with or without otospongiosis (p > 0.05, ANOVA). However, patients with otospongiosis in all the cochlea showed the lowest audiometric gain for the high frequency band (p < 0.05 ANOVA). Evidence of otospongiosis evaluated just by CT has a low impact on the audiometric outcome after stapedectomy.

  12. Interfraction Prostate Rotation Determined from In-Room Computerized Tomography Images

    SciTech Connect

    Owen, Rebecca; Kron, Tomas; Foroudi, Farshad; Milner, Alvin; Cox, Jennifer; Duchesne, Gillian

    2011-07-01

    Fiducial markers (FMs) are commonly used as a correction technique for interfraction translations of the prostate. The aim of this investigation was to determine the magnitude of prostate rotations using 2 methods: FM coordinates and the anatomical border of the prostate and rectum. Daily computed tomography (CT) scans (n = 346) of 10 prostate cancer patients with 3 implanted FMs were acquired using the CT on rails. FM coordinates were used to determine rotation in the sagittal, transverse, and coronal planes, and CT contours of the prostate and rectum were used to determine rotation along the sagittal plane. An adaptive technique based on a subset of images (n = 6; planning and first 5 treatment CTs) to reduce systematic rotation errors in the sagittal plane was tested. The standard deviation (SD) of systematic rotation from FM coordinates was 7.6{sup o}, 7.7{sup o}, and 5.0{sup o} in the sagittal, transverse and coronal planes. The corresponding SD of random error was 10.2{sup o}, 15.8{sup o}, and 6.5{sup o}. Errors in the sagittal plane, determined from prostate and rectal contours, were 10.1{sup o} (systematic) and 7.7{sup o} (random). These results did not correlate with rotation computed from FM coordinates (r = -0.017; p = 0.753, n = 337). The systematic error could be reduced by 43% to 5.6{sup o} when the mean prostate position was estimated from 6 CT scans. Prostate rotation is a significant source of error that appears to be more accurately determined using the anatomical border of the prostate and rectum rather than FMs, thus highlighting the utility of CT image guidance.

  13. Tympanic membrane boundary deformations derived from static displacements observed with computerized tomography in human and gerbil.

    PubMed

    Gea, Stefan L R; Decraemer, Willem F; Funnell, W Robert J; Funnell, Robert W J; Dirckx, Joris J J; Maier, Hannes

    2010-03-01

    The middle ear is too complex a system for its function to be fully understood with simple descriptive models. Realistic mathematical models must be used in which structural elements are represented by geometrically correct three-dimensional (3D) models with correct physical parameters and boundary conditions. In the past, the choice of boundary conditions could not be based on experimental evidence as no clear-cut data were available. We have, therefore, studied the deformation of the tympanic membrane (TM) at its boundaries using X-ray microscopic computed tomography in human and gerbil while static pressure was applied to the ear canal. The 3D models of the TM and its bony attachments were carefully made and used to measure the deformation of the TM with focus on the periphery and the manubrium attachment. For the pars flaccida of the gerbil, the boundary condition can, for the most part, be described as simply supported. For the human pars flaccida, the situation is more complicated: superiorly, the membrane contacts the underlying bone more and more when pushed further inward, and it gradually detaches from the wall when sucked outward. In gerbil, the attachment of the TM to the manubrium can be described as simply supported. In human, the manubrium is attached underneath the TM via the plica mallearis and the contact of the TM with the bone is indirect. For both human and gerbil, a simple boundary condition for the peripheral edge of the pars tensa is not appropriate due to the intricate structure at the edge: the TM thickens rapidly before continuing into the annulus fibrosis which finally makes contact with the bone.

  14. [Digital angiography and lipiodol computerized tomography in the anatomopathological framework of hepatocarcinoma].

    PubMed

    Pozzi-Mucelli, R; Pozzi-Mucelli, R; Pagnan, L; Dalla Palma, L

    1994-12-01

    The introduction of therapies other than conventional surgery of hepatocellular carcinoma (HCC) requires an accurate pathologic classification, which is important because it is well known that HCC may have multicentric growth. The Liver Cancer Study Group of Japan has proposed a classification dividing HCCs into three macroscopic forms from the pathologic point of view: nodular, massive and infiltrating HCCs. The nodular type is subdivided into four types: single nodular type, single nodular type with surrounding proliferation, multinodular fused type and multinodular type. Forty-six HCC patients were examined with Lipiodol Computed Tomography (LCT) to investigate the agreement between pathologic and imaging findings. LCT proved to be in close agreement with pathologic findings. Sixteen cases were classified as type I (single nodular type), 8 as type II (single nodular type with limited foci), 1 as type III (multinodular fused type), 18 as type IV (multiple nodular type with diffuse foci) and 3 cases as type V (massive form). No cases of infiltrative forms were observed in our series. Based on LCT findings, the capabilities of digital subtraction angiography (DSA) were studied in the pathologic classification of HCCs. DSA exhibited some limitations in the pathologic classification of HCCs in 5 of 16 patients with type I lesions. In these cases DSA suggested false-positive diagnoses because of regenerative nodules in cirrhotic liver in 3 cases and of daughter nodules (not confirmed at LCT) in 2 cases. In 7 of 8 patients with type II HCCs, DSA failed to show the daughter nodules surrounding the main nodule. In the 18 patients with multiple distant nodules (type IV), DSA was less sensitive in defining nodule number and site. In the massive form, the information obtained with LCT and DSA was comparable. In conclusion, LCT should be considered a basic examination in the study of HCC extent. Based on LCT findings, the most appropriate treatment can be selected, be it

  15. Laparoscopic vs computerized tomography-guided radiofrequency ablation for large hepatic hemangiomas abutting the diaphragm

    PubMed Central

    Gao, Jun; Kong, Jian; Ding, Xue-Mei; Ke, Shan; Niu, Hai-Gang; Xin, Zong-Hai; Ning, Chun-Min; Guo, Shi-Gang; Li, Xiao-Long; Zhang, Long; Dong, Yong-Hong; Sun, Wen-Bing

    2015-01-01

    AIM: To compare safety and therapeutic efficacy of laparoscopic radiofrequency (RF) ablation vs computed tomography (CT)-guided RF ablation for large hepatic hemangiomas abutting the diaphragm. METHODS: We retrospectively reviewed our sequential experience of treating 51 large hepatic hemangiomas abutting the diaphragm in 51 patients by CT-guided or laparoscopic RF ablation due to either the presence of symptoms and/or the enlargement of hemangioma. Altogether, 24 hemangiomas were ablated via a CT-guided percutaneous approach (CT-guided ablation group), and 27 hemangiomas were treated via a laparoscopic approach (laparoscopic ablation group). RESULTS: The mean diameter of the 51 hemangiomas was 9.6 ± 1.8 cm (range, 6.0-12.0 cm). There was no difference in the diameter of hemangiomas between the two groups (P > 0.05). RF ablation was performed successfully in all patients. There was no difference in ablation times between groups (P > 0.05). There were 23 thoracic complications in 17 patients: 15 (62.5%, 15/24) in the CT-guided ablation group and 2 (7.4%, 2/27) in the laparoscopic ablation group (P < 0.05). According to the Dindo-Clavien classification, two complications (pleural effusion and diaphragmatic rupture grade III) were major in two patients. All others were minor (grade I). Both major complications occurred in the CT-guided ablation group. The minor complications were treated successfully with conservative measures, and the two major complications underwent treatment by chest tube drainage and thoracoscopic surgery, respectively. Complete ablation was achieved in 91.7% (22/24) and 96.3% (26/27) in the CT-guided and the laparoscopic ablation groups, respectively (P > 0.05). CONCLUSION: Laparoscopic RF ablation therapy should be used as the first-line treatment option for large hepatic hemangiomas abutting the diaphragm. It avoids thermal injury to the diaphragm and reduces thoracic complications. PMID:26019459

  16. Metal Artifact Reduction and Segmentation of Dental Computerized Tomography Images Using Least Square Support Vector Machine and Mean Shift Algorithm.

    PubMed

    Mortaheb, Parinaz; Rezaeian, Mehdi

    2016-01-01

    Segmentation and three-dimensional (3D) visualization of teeth in dental computerized tomography (CT) images are of dentists' requirements for both abnormalities diagnosis and the treatments such as dental implant and orthodontic planning. On the other hand, dental CT image segmentation is a difficult process because of the specific characteristics of the tooth's structure. This paper presents a method for automatic segmentation of dental CT images. We present a multi-step method, which starts with a preprocessing phase to reduce the metal artifact using the least square support vector machine. Integral intensity profile is then applied to detect each tooth's region candidates. Finally, the mean shift algorithm is used to partition the region of each tooth, and all these segmented slices are then applied for 3D visualization of teeth. Examining the performance of our proposed approach, a set of reliable assessment metrics is utilized. We applied the segmentation method on 14 cone-beam CT datasets. Functionality analysis of the proposed method demonstrated precise segmentation results on different sample slices. Accuracy analysis of the proposed method indicates that we can increase the sensitivity, specificity, precision, and accuracy of the segmentation results by 83.24%, 98.35%, 72.77%, and 97.62% and decrease the error rate by 2.34%. The experimental results show that the proposed approach performs well on different types of CT images and has better performance than all existing approaches. Moreover, segmentation results can be more accurate by using the proposed algorithm of metal artifact reduction in the preprocessing phase.

  17. The lymph drainage pattern of the mammary glands in the cat: a lymphographic and computerized tomography lymphographic study.

    PubMed

    Papadopoulou, P L; Patsikas, M N; Charitanti, A; Kazakos, G M; Papazoglou, L G; Karayannopoulou, M; Chrisogonidis, I; Tziris, N; Dimitriadis, A

    2009-08-01

    Seventy-three clinically normal, lactating cats were used to investigate the lymph drainage of 73 mammary glands. In 50 cats of the first group, the number of lymphatic vessels emerging from the examined mammary gland, their course and the lymph nodes into which they are drained were studied by indirect lymphography (IL) after intramammary injection of an oily contrast medium. In 23 cats of the second group, the lymph drainage of the mammary glands was studied by computerized tomography indirect lymphography (CT-IL) after intramammary injection of a water soluble contrast medium. The following day, the lymph drainage of the mammary gland examined by CT-IL was studied by IL, as it was described in the first group, for comparison purposes. The main conclusions drawn after this study were as follows: lymph drains from the first and second mammary glands with one or rarely two or three lymphatic vessels to the accessory axillary lymph nodes. Lymph drains from the third mammary gland with one or two and rarely three lymphatic vessels usually to the accessory inguinal lymph nodes or to the accessory axillary lymph nodes. In some cases, it drains to both lymph nodes simultaneously or it may rarely drain only to the medial iliac lymph nodes. The fourth mammary gland with one or two and rarely three lymphatic vessels usually drains to the accessory inguinal lymph nodes. It may rarely drain only to the medial iliac lymph nodes. Mammary lymphatic vessels that cross the midline and lymphatic connection between the mammary glands were not demonstrated. No differences in the mammary lymph drainage pattern between IL and CT-IL were found.

  18. Post transplant urinary tract infection in Autosomal dominant polycystic kidney disease a perpetual diagnostic dilema - 18-fluorodeoxyglucose - Positron emission computerized tomography - A valuable tool.

    PubMed

    Sainaresh, Vv; Jain, Sh; Patel, Hv; Shah, Pr; Vanikar, Av; Trivedi, Hl

    2011-04-01

    Urinary tract infection (UTI) is the most common infection contracted by renal allograft recipients. In patients of autosomal dominant polycystic kidney disease (ADPKD), cyst infection presents a complex diagnostic and therapeutic challenge especially in the post transplant period. Accurate diagnosis forms the cornerstone in salvaging the graft from potentially catastrophic outcome. We describe a case of xanthogranulomatous pyelonephritis (XPN) in the native kidney in a patient of post transplant ADPKD which presented as frequently relapsing UTI with graft dysfunction where in accurate diagnosis was made possible with the aid of 18-fluorodeoxyglucose (FDG) - Positron emission computerized tomography (PET/CT).

  19. Investigating the effect of characteristic x-rays in cadmium zinc telluride detectors under breast computerized tomography operating conditions.

    PubMed

    Glick, Stephen J; Didier, Clay

    2013-10-14

    A number of research groups have been investigating the use of dedicated breast computerized tomography (CT). Preliminary results have been encouraging, suggesting an improved visualization of masses on breast CT as compared to conventional mammography. Nonetheless, there are many challenges to overcome before breast CT can become a routine clinical reality. One potential improvement over current breast CT prototypes would be the use of photon counting detectors with cadmium zinc telluride (CZT) (or CdTe) semiconductor material. These detectors can operate at room temperature and provide high detection efficiency and the capability of multi-energy imaging; however, one factor in particular that limits image quality is the emission of characteristic x-rays. In this study, the degradative effects of characteristic x-rays are examined when using a CZT detector under breast CT operating conditions. Monte Carlo simulation software was used to evaluate the effect of characteristic x-rays and the detector element size on spatial and spectral resolution for a CZT detector used under breast CT operating conditions. In particular, lower kVp spectra and thinner CZT thicknesses were studied than that typically used with CZT based conventional CT detectors. In addition, the effect of characteristic x-rays on the accuracy of material decomposition in spectral CT imaging was explored. It was observed that when imaging with 50-60 kVp spectra, the x-ray transmission through CZT was very low for all detector thicknesses studied (0.5-3.0 mm), thus retaining dose efficiency. As expected, characteristic x-ray escape from the detector element of x-ray interaction increased with decreasing detector element size, approaching a 50% escape fraction for a 100 μm size detector element. The detector point spread function was observed to have only minor degradation with detector element size greater than 200 μm and lower kV settings. Characteristic x-rays produced increasing distortion

  20. Quantification of Soil Physical Properties by Using X-Ray Computerized Tomography (CT) and Standard Laboratory (STD) Methods

    SciTech Connect

    Sanchez, Maria Ambert

    2003-12-12

    The implementation of x-ray computerized tomography (CT) on agricultural soils has been used in this research to quantify soil physical properties to be compared with standard laboratory (STD) methods. The overall research objective was to more accurately quantify soil physical properties for long-term management systems. Two field studies were conducted at Iowa State University's Northeast Research and Demonstration Farm near Nashua, IA using two different soil management strategies. The first field study was conducted in 1999 using continuous corn crop rotation for soil under chisel plow with no-till treatments. The second study was conducted in 2001 and on soybean crop rotation for the same soil but under chisel plow and no-till practices with wheel track and no-wheel track compaction treatments induced by a tractor-manure wagon. In addition, saturated hydraulic (K{sub s}) conductivity and the convection-dispersion (CDE) model were also applied using long-term soil management systems only during 2001. The results obtained for the 1999 field study revealed no significant differences between treatments and laboratory methods, but significant differences were found at deeper depths of the soil column for tillage treatments. The results for standard laboratory procedure versus CT method showed significant differences at deeper depths for the chisel plow treatment and at the second lower depth for no-till treatment for both laboratory methods. The macroporosity distribution experiment showed significant differences at the two lower depths between tillage practices. Bulk density and percent porosity had significant differences at the two lower depths of the soil column. The results obtained for the 2001 field study showed no significant differences between tillage practices and compaction practices for both laboratory methods, but significant differences between tillage practices with wheel track and no-wheel compaction treatments were found along the soil profile for

  1. Investigating the effect of characteristic x-rays in cadmium zinc telluride detectors under breast computerized tomography operating conditions

    SciTech Connect

    Glick, Stephen J.; Didier, Clay

    2013-10-14

    A number of research groups have been investigating the use of dedicated breast computerized tomography (CT). Preliminary results have been encouraging, suggesting an improved visualization of masses on breast CT as compared to conventional mammography. Nonetheless, there are many challenges to overcome before breast CT can become a routine clinical reality. One potential improvement over current breast CT prototypes would be the use of photon counting detectors with cadmium zinc telluride (CZT) (or CdTe) semiconductor material. These detectors can operate at room temperature and provide high detection efficiency and the capability of multi-energy imaging; however, one factor in particular that limits image quality is the emission of characteristic x-rays. In this study, the degradative effects of characteristic x-rays are examined when using a CZT detector under breast CT operating conditions. Monte Carlo simulation software was used to evaluate the effect of characteristic x-rays and the detector element size on spatial and spectral resolution for a CZT detector used under breast CT operating conditions. In particular, lower kVp spectra and thinner CZT thicknesses were studied than that typically used with CZT based conventional CT detectors. In addition, the effect of characteristic x-rays on the accuracy of material decomposition in spectral CT imaging was explored. It was observed that when imaging with 50-60 kVp spectra, the x-ray transmission through CZT was very low for all detector thicknesses studied (0.5–3.0 mm), thus retaining dose efficiency. As expected, characteristic x-ray escape from the detector element of x-ray interaction increased with decreasing detector element size, approaching a 50% escape fraction for a 100 μm size detector element. The detector point spread function was observed to have only minor degradation with detector element size greater than 200 μm and lower kV settings. Characteristic x-rays produced increasing distortion in

  2. Investigating the effect of characteristic x-rays in cadmium zinc telluride detectors under breast computerized tomography operating conditions

    NASA Astrophysics Data System (ADS)

    Glick, Stephen J.; Didier, Clay

    2013-10-01

    A number of research groups have been investigating the use of dedicated breast computerized tomography (CT). Preliminary results have been encouraging, suggesting an improved visualization of masses on breast CT as compared to conventional mammography. Nonetheless, there are many challenges to overcome before breast CT can become a routine clinical reality. One potential improvement over current breast CT prototypes would be the use of photon counting detectors with cadmium zinc telluride (CZT) (or CdTe) semiconductor material. These detectors can operate at room temperature and provide high detection efficiency and the capability of multi-energy imaging; however, one factor in particular that limits image quality is the emission of characteristic x-rays. In this study, the degradative effects of characteristic x-rays are examined when using a CZT detector under breast CT operating conditions. Monte Carlo simulation software was used to evaluate the effect of characteristic x-rays and the detector element size on spatial and spectral resolution for a CZT detector used under breast CT operating conditions. In particular, lower kVp spectra and thinner CZT thicknesses were studied than that typically used with CZT based conventional CT detectors. In addition, the effect of characteristic x-rays on the accuracy of material decomposition in spectral CT imaging was explored. It was observed that when imaging with 50-60 kVp spectra, the x-ray transmission through CZT was very low for all detector thicknesses studied (0.5-3.0 mm), thus retaining dose efficiency. As expected, characteristic x-ray escape from the detector element of x-ray interaction increased with decreasing detector element size, approaching a 50% escape fraction for a 100 μm size detector element. The detector point spread function was observed to have only minor degradation with detector element size greater than 200 μm and lower kV settings. Characteristic x-rays produced increasing distortion in the

  3. Validation of Special Sensor Ultraviolet Limb Imager (SSULI) Ionospheric Tomography using ALTAIR Incoherent Scatter Radar Measurements

    NASA Astrophysics Data System (ADS)

    Dymond, K.; Nicholas, A. C.; Budzien, S. A.; Stephan, A. W.; Coker, C.; Hei, M. A.; Groves, K. M.

    2015-12-01

    The Special Sensor Ultraviolet Limb Imager (SSULI) instruments are ultraviolet limb scanning sensors flying on the Defense Meteorological Satellite Program (DMSP) satellites. The SSULIs observe the 80-170 nanometer wavelength range covering emissions at 91 and 136 nm, which are produced by radiative recombination of the ionosphere. We invert these emissions tomographically using newly developed algorithms that include optical depth effects due to pure absorption and resonant scattering. We present the details of our approach including how the optimal altitude and along-track sampling were determined and the newly developed approach we are using for regularizing the SSULI tomographic inversions. Finally, we conclude with validations of the SSULI inversions against ALTAIR incoherent scatter radar measurements and demonstrate excellent agreement between the measurements.

  4. Ionospheric physics

    SciTech Connect

    Sojka, J.J. )

    1991-01-01

    Advances in all areas of ionospheric research are reviewed for the 1987-1990 time period. Consideration is given to the equatorial ionosphere, the midlatitude ionosphere and plasmasphere, the auroral ionosphere, the polar ionosphere and polar wind, ionospheric electrodynamic inputs, plasma waves and irregularities, active experiments, ionospheric forecasting, and coupling the ionosphere with other regions.

  5. A retrospective radiographic evaluation of the anterior loop of the mental nerve: Comparison between panoramic radiography and cone beam computerized tomography

    PubMed Central

    Vujanovic-Eskenazi, Aleksandar; Valero-James, Jesus-Manuel; Sánchez-Garcés, María-Angeles

    2015-01-01

    Objectives: To compare the prevalence and the length of mental loop, measured with panoramic radiography (PR) and cone beam computerized tomography (CBCT). Material and Methods: PG and CBCT images where analyzed by a single calibrated examiner to determine the presence and the position of the mental foramen (MF), its distance to the lower mandible border, the anterior length of the mental loop (ML) and the bone quality in 82 PR and 82 CBCT. Results: ML was identified in 36.6 % of PR and 48.8 % of CBCT. PR showed a magnification of 1.87 when compared to CBCT. The mean of anterior extension of the inferior alveolar nerve and the distance to the inferior border of the mandible was higher for PR (2.8 mm, sd 0.91 mm on the PR , range 1.5 to 4.7 mm and 1.59, sd 0.9 on the CBCT ,range 0.4 to 4.0 mm) Conclusions: There is a magnification in PR images with respect to those of CBCT. The differences between CBCT and PR with regards to the identification and length of the ML are not statistically significant. Identification and accuracy measurements of ML did not depend on the bone quality. Considering that two dimensional imaging provides less accurate and reliable information regarding the anterior loop, a CBCT scan could be recommended when planning implant placement in the anterior region. Key words:Mental loop, mental nerve, mental canal, preoperative implant planning, panoramic tomography, cone beam computerized tomography. PMID:25549693

  6. The Electron Density Features Revealed by the GNSS-Based Radio Tomography in the Different Latitudinal and Longitudinal Sectors of the Ionosphere

    NASA Astrophysics Data System (ADS)

    Andreeva, Elena; Tereshchenko, Evgeniy; Nazarenko, Marina; Nesterov, Ivan; Kozharin, Maksim; Padokhin, Artem; Tumanova, Yulia

    2016-04-01

    The ionospheric radio tomography is an efficient method for electron density imaging in the different geographical regions of the world under different space weather conditions. The input for the satellite-based ionospheric radio tomography is provided by the signals that are transmitted from the navigational satellites and recorded by the chains or networks of ground receivers. The low-orbiting (LO) radio tomography employs the 150/400 MHz radio transmissions from the Earth's orbiters (like the Russian Tsikada/Parus and American Transit) flying at a height of ~1000 km above the Earth in the nearly polar orbits. The phases of the signals from a moving satellite which are recorded by the chains of ground receivers oriented along the satellite path form the families of linear integrals of electron density along the satellite-receiver rays that are used as the input data for LORT. The LO tomographic inversion of these data by phase difference method yields the 2D distributions of the ionospheric plasma in the vertical plane containing the receiving chain and the satellite path. LORT provides vertical resolution of 20-30 km and horizontal resolution of 30-40 km. The high-orbiting (HO) radio tomography employs the radio transmissions from the GPS/GLONASS satellites and enables 4D imaging of the ionosphere (3 spatial coordinates and time). HORT has a much wider spatial coverage (almost worldwide) and provides continuous time series of the reconstructions. However, the spatial resolution of HORT is lower (~100 km horizontally with a time step 60-20 min). In the regions with dense receiving networks (Europe, USA, Alaska, Japan), the resolution can be increased to 30-50 km with a time interval of 30-10 min. To date, the extensive RT data collected from the existing RT chains and networks enable a thorough analysis of both the regular and sporadic ionospheric features which are observed systematically or appear spontaneously, whose origin is fairly well understood or

  7. X-ray computerized tomography analysis and density estimation using a sediment core from the Challenger Mound area in the Porcupine Seabight, off Western Ireland

    NASA Astrophysics Data System (ADS)

    Tanaka, Akiko; Nakano, Tsukasa; Ikehara, Ken

    2011-02-01

    X-ray computerized tomography (CT) analysis was used to image a half-round core sample of 50 cm long recovered from near Challenger Mound in the Porcupine Seabight, off western Ireland during the Integrated Ocean Drilling Program Expedition 307. This allowed three-dimensional examination of complex shapes of pebbles and ice-rafted debris in sedimentary sequences. X-ray CT analysis was also used for the determination of physical properties; a comparison between bulk density by the mass-volume method and estimated density based on linear attenuation coefficients of X-ray CT images provides insight into a spatially detailed and precise map of density variation in samples through the distribution of CT numbers.

  8. Vertical structure of medium-scale traveling ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Ssessanga, Nicholas; Kim, Yong Ha; Kim, Eunsol

    2015-11-01

    We develop an algorithm of computerized ionospheric tomography (CIT) to infer information on the vertical and horizontal structuring of electron density during nighttime medium-scale traveling ionospheric disturbances (MSTIDs). To facilitate digital CIT we have adopted total electron contents (TEC) from a dense Global Positioning System (GPS) receiver network, GEONET, which contains more than 1000 receivers. A multiplicative algebraic reconstruction technique was utilized with a calibrated IRI-2012 model as an initial solution. The reconstructed F2 peak layer varied in altitude with average peak-to-peak amplitude of ~52 km. In addition, the F2 peak layer anticorrelated with TEC variations. This feature supports a theory in which nighttime MSTID is composed of oscillating electric fields due to conductivity variations. Moreover, reconstructed TEC variations over two stations were reasonably close to variations directly derived from the measured TEC data set. Our tomographic analysis may thus help understand three-dimensional structure of MSTIDs in a quantitative way.

  9. Scattering-related contrast signals in neutron computerized tomography and the new V12 instrument at HMI Berlin

    NASA Astrophysics Data System (ADS)

    Strobl, Markus; Treimer, Wolfgang; Hilger, André

    2006-11-01

    Double-crystal diffractometers (DCD) are widely used for structural investigations at the limit between macroscopic and microscopic inner structures of sample materials. Operating in an ultra-small-angle scattering q-range between 10 -4 and 10 -1 nm -1 structures between 50 nm and nearly 100 μm can be resolved. Hence the DCD connects the resolvable ranges of small-angle neutron scattering (SANS) instruments and neutron tomography facilities. However, the DCD does not only link the resolvable size ranges but can also be operated to yield both, q-space information on microscopic structures combined with real space information in the range of macroscopic inner structures. This method was developed in recent years at the V12 DCD at HMI by introducing refraction and ultra-small-angle neutron scattering (USANS) contrast for tomography. The new V12 DCD set-up has now been optimized to exploit all the opportunities of USANS, refraction and USANS contrast tomography and conventional attenuation contrast tomography with an intense monochromatic neutron beam. The new contrast methods will be introduced as well as the final set-up of the V12 instrument. Additionally, several examples and results achieved by the new techniques and instrument will be given.

  10. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data.

    PubMed

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-08-12

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone.

  11. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data

    PubMed Central

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-01-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone. PMID:26266764

  12. Circular gratings' moiré effect for projection measurement in volume optical computerized tomography with two-step phase-shifting method

    NASA Astrophysics Data System (ADS)

    Wang, Jia; Song, Yang; Li, Zhen-hua; He, An-zhi

    2012-11-01

    Volume optical computerized tomography (VOCT), which can realize real 3D measurement rather than traditional 2D OCT, has great superiority in quantitatively measuring the thermo physical parameters of transient flow field. Among the refractive index reconstruction techniques, filtered back-projection (FBP) method performs better than algebraic reconstruction techniques (ARTs) with higher accuracy and computationally efficient. In order to apply FBP to VOCT, the radial second-order derivative of projection wave front passes through the tested phase object should be obtained firstly. In this paper, a projection device with two circular gratings is established. In particular, owing to an inherent phase shift exists between moiré fringes of +1 and -1 diffraction orders, a two-step phase-shifting algorithm is utilized to extract the wave front's radial first-order derivative which is contained in the moiré fringes. The reliability of the two-step phase-shifting algorithm is proved by a computer simulation. Finally, the radial first-order derivative of wave front passing through a propane flame is measured and retrieved by these methods.

  13. A Family with Von Hippel-Lindau Syndrome: The Findings of Indium-111 Somatostatin Receptor Scintigraphy, Iodine-123 Metaiodobenzylguanidine Scintigraphy and Single Photon Emission Computerized Tomography

    PubMed Central

    Arıcan, Pelin; Okudan Tekin, Berna; Naldöken, Seniha; Şefizade, Rıza; Berker, Dilek

    2017-01-01

    Von Hippel-Lindau syndrome (VHLS) is an autosomal dominant hereditary familial disorder characterized by development of malignant and benign neoplasms. Differential diagnosis of the adrenal and pancreatic masses are difficult in patients with VHLS. Iodine-123 metaiodobenzylguanidine (I-123 MIBG) and indium-111 somatostatin receptor scintigraphies (In-111 SRS) have important roles in the differential diagnosis of adrenal and pancreatic masses in those patients. In this case report, we present the findings of I-123 MIBG single-photon emission computerized tomography (SPECT/CT) and In-111 SRS SPECT/CT in three members of a family with VHLS. In case 1, a residual neuroendocrine tumor (NET) was detected in the head of pancreas on In-111 SRS SPECT/CT images. In case 2 and 3, I-123 MIBG SPECT/CT confirmed the adrenal masses as pheochromocytoma, and the extra-adrenal mass as NET, before surgery. We thought that In-111 SRS and I-123 MIBG scan might be helpful in the routine work up of VHLS patients for diagnostic and therapeutic purposes. Hybrid SPECT/CT system may improve diagnostic accuracy of planar images since it assesses morphologic and functional information together. PMID:28291009

  14. Accuracy of cone beam computerized tomography and a three-dimensional stereolithographic model in identifying the anterior loop of the mental nerve: a study on cadavers.

    PubMed

    Santana, Ruben R; Lozada, Jaime; Kleinman, Alejandro; Al-Ardah, Aladdin; Herford, Alan; Chen, Jung-Wei

    2012-12-01

    The objective of this ex vivo cadaver study was to determine the accuracy of cone beam computerized tomography (CBCT) and a 3-dimensional stereolithographic (STL) model in identifying and measuring the anterior loop length (ANLL) of the mental nerve. A total of 12 cadavers (24 mental nerve plexus) were used for this study. Standardized CBCT scans of each mandible were obtained both with and without radiographic contrast tracer injected into the mental nerve plexus, and STL models of the two acquired CBCT images were made. The ANLL were measured using CBCT, STL model, and anatomy. The measurements obtained from the CBCT images and STL models were then analyzed and compared with the direct anatomic measurements. A paired sample t test was used, and P values less than .05 were considered statistically significant. The mean difference between CBCT and anatomic measurement was 0.04 mm and was not statistically significant (P = .332), whereas the mean difference between STL models and anatomic measurement was 0.4 mm and was statistically significant (P = .042). There was also a statistical significant difference between CBCT and the STL model (P = .048) with the mean difference of 0.35 mm. Therefore, CBCT is an accurate and reliable method in determining and measuring the ANLL but the STL model over- or underestimated the ANLL by as much as 1.51 mm and 1.83 mm, respectively.

  15. [Computerized tomography in craniocerebral, maxillofacial, cervical, and spinal gunshot wounds. Part II--Clinical contribution and medico- legal aspects].

    PubMed

    Scialpi, M; Boccuzzi, F; Romeo, F; Ax, G; Scapati, C; Rotondo, A; Angelelli, G

    1996-12-01

    To assess the diagnostic and medicolegal contribution of Computed Tomography (CT) in patients with craniocerebral, maxillofacial, neck and spine gunshot wounds, we submitted to CT 106 patients with gunshot wounds examined over a 7-year period (February, 1988 to December, 1994). Twenty-four of them had craniocerebral injuries (23%), 9 maxillofacial (8%), 8 neck (8%) and 10 vertebral (9%) injuries. Emergency CT demonstrated the mechanism of the injury, the bullet path and site, the site of bone and/or metallic fragments, and damage extent. In all perforating cranioencephalic injuries (n = 7) intracerebral or extrathecal bone fragments were demonstrated adjacent to the bullet entrance and exit holes, respectively. In injury monitoring. CT showed injury evolution, retained fragments and complications, thus enabling damage extent assessment. High Resolution Computed Tomography (HRCT) was useful in locating minute orbitary retrobulbar and intraspinal fragments. Magnetic Resonance (MR) Imaging in postoperative patients proved a valuable tool to assess the extent of spinal cord damage. To conclude, CT is a useful technique to examine the patients with gunshot wounds, which helps plan adequate treatment and solve complex medicolegal problems.

  16. [Validity of modified radiological views to detect screw protrusion at the distal radius. A comparative study with computerized tomography].

    PubMed

    Mora-Pascual, F E; Aguilella-Fernández, L

    2013-01-01

    Volar fixed-angle plates (VFAP) are currently widely used for the treatment of extra-articular distal radius fractures. Using these plates has a high risk of articular and dorsal screw protrusion due to their special configuration. The aim of this study is to assess the validity of the standard X-rays, performed with the help of wedged supports, in order to detect articular and dorsal screw protrusion. A comparison with computed tomography (CT) scan imaging has been made. The outcome of 26 patients with distal radius articular fracture, treated with a VFAP, is reported. Good correlation between modified X-rays and CT scan was observed. A sensitivity of 100% for articular protrusion and 66% for dorsal have been obtained. When detecting screw protrusion at the distal radius, the use of wedged supports to perform special X-rays intraoperatively is an effective tool.

  17. Clinical significance of mesenteric panniculitis-like abnormalities on abdominal computerized tomography in patients with malignant neoplasms

    PubMed Central

    Ehrenpreis, Eli D; Roginsky, Grigory; Gore, Richard M

    2016-01-01

    AIM To clarify the association of malignancy with mesenteric panniculitis-like changes on computed tomography (CT). METHODS All abdominal CT scans performed at NorthShore University HealthSystem showing mesenteric panniculitis from January 2005 to August 2010 were identified in the Radnet (RadNet Corporation, Los Angeles, CA) database. Patients with a new or known diagnosis of a malignancy were included for this analysis. Longitudinal clinical histories were obtained from electronic medical records. RESULTS In total, 147794 abdominal CT scans were performed during the study period. Three hundred and fifty-nine patients had mesenteric panniculitis (MP)-like abnormalities on their abdominal CT. Of these patients, 81 patients (22.6%) had a known history of cancer at the time of their CT scan. Nineteen (5.3%) had a new diagnosis of cancer in concurrence with their CT, but the majority of these (14/19, 74%) were undergoing CT as part of a malignancy evaluation. Lymphomas were the most common cancers associated with MP-like findings on CT (36 cases, 36%), with follicular lymphoma being the most frequent subtype (17/36). A variety of solid tumors, most commonly prostate (7) and renal cell cancers (6) also were seen. CT follow up was obtained in 56 patients. Findings in the mesentery were unchanged in 45 (80%), worsened in 6 (11%), and improved in 5 patients (9%). Positron emission tomography (PET) scans performed in 44 patients only showed a positive uptake in the mesenteric mass in 2 patients (5%). CONCLUSION A new diagnosis of cancer is uncommon in patients with CT findings suggestive of MP. MP-like mesenteric abnormalities on CT generally remain stable in patients with associated malignancies. PET scanning is not recommended in the evaluation of patients with mesenteric panniculitis-like findings on CT. PMID:28082812

  18. Spatio-temporal characteristics of the Equatorial Ionization Anomaly (EIA) in the East African region via ionospheric tomography during the year 2012

    NASA Astrophysics Data System (ADS)

    Kassa, T.; Damtie, B.; Bires, A.; Yizengaw, E.; Cilliers, P.

    2015-01-01

    We present the characteristics of the EIA in the East African sector inferred from ground-based GPS receivers via ionospheric tomography during the year 2012. For the analysis, we developed and used a 2D ionospheric tomography imaging software based on Bayesian inversion approach. To reconstruct ionospheric electron density form slant Total Electron Content (sTEC) measurements, we selected a chain of ten ground-based GPS receivers with stations' codes and geomagnetic coordinates: ARMI (3.03 °S, 109.29 °E), DEBK (4.32 °N, 109.48 °E), ASOS (1.14 °N, 106.16 °E), NEGE (3.60 °S, 111.35 °E), SHIS (3.26 °N, 110.62 °E), ASAB (4.91 °N, 114.34 °E), SHEB (7.36 °N, 110.60 °E), EBBE (9.54 °S, 104.10 °E), DODM (16.03 °S, 109.04 °E) & NAMA (11.49 °N, 113.60 °E). The temporal, spatial and storm-time characteristics of the EIA and the hourly, day-to-day and seasonal variations of the maximum electron density of F2 region (NmF2) at 15.29°S geomagnetic latitude are presented. We found that the magnitude of the peak and the width/thickness of the EIA pronounced during the equinox and weakened during the solstice seasons at 2100 LT. It is also observed that the EIA persisted for longer time in equinox season than the solstice season. The spatial appearance of the northern and southern anomalies are observed starting from 6.12 ° N and 10 ° S respectively along geomagnetic latitude during equinox season. The EIA is localized between 180 km and 450 km along the altitude during December solstice. The analysis on the NmF2 demonstrated a significant dependence on local time, day and season of the year. We also investigated the storm response of the EIA for the magnetic storm of Day Of the Year (DOY) 274-276. It is observed that the disturbance dynamo related composition change (O/N2 ratio) resulted in a well-developed EIA with an increase in the peak and the width of the EIA at 2100 LT on DOY 275 (main phase of the storm) compared to 274 (initial phase of the storm

  19. Computerized Automated Quantification of Subcutaneous and Visceral Adipose Tissue From Computed Tomography Scans: Development and Validation Study

    PubMed Central

    Kim, Young Jae; Park, Ji Won; Kim, Jong Wan; Park, Chan-Soo; Gonzalez, John Paul S; Lee, Seung Hyun

    2016-01-01

    Background Computed tomography (CT) is often viewed as one of the most accurate methods for measuring visceral adipose tissue (VAT). However, measuring VAT and subcutaneous adipose tissue (SAT) from CT is a time-consuming and tedious process. Thus, evaluating patients’ obesity levels during clinical trials using CT scans is both cumbersome and limiting. Objective To describe an image-processing-based and automated method for measuring adipose tissue in the entire abdominal region. Methods The method detects SAT and VAT levels using a separation mask based on muscles of the human body. The separation mask is the region that minimizes the unnecessary space between a closed path and muscle area. In addition, a correction mask, based on bones, corrects the error in VAT. Results To validate the method, the volume of total adipose tissue (TAT), SAT, and VAT were measured for a total of 100 CTs using the automated method, and the results compared with those from manual measurements obtained by 2 experts. Dice’s similarity coefficients (DSCs) between the first manual measurement and the automated result for TAT, SAT, and VAT are 0.99, 0.98, and 0.97, respectively. The DSCs between the second manual measurement and the automated result for TAT, SAT, and VAT are 0.98, 0.98, and 0.97, respectively. Moreover, intraclass correlation coefficients (ICCs) between the automated method and the results of the manual measurements indicate high reliability as the ICCs for the items are all .99 (P<.001). Conclusions The results described in this paper confirm the accuracy and reliability of the proposed method. The method is expected to be both convenient and useful in the clinical evaluation and study of obesity in patients who require SAT and VAT measurements. PMID:26846251

  20. Computerized tomography based “patient specific blocks” improve postoperative mechanical alignment in primary total knee arthroplasty

    PubMed Central

    Vaishya, Raju; Vijay, Vipul; Birla, Vikas P; Agarwal, Amit K

    2016-01-01

    AIM: To compare the postoperative mechanical alignment achieved after total knee arthroplasty (TKA) using computer tomography (CT) based patient specific blocks (PSB) to conventional instruments (CI). METHODS: Total 80 knees were included in the study, with 40 knees in both the groups operated using PSB and CI. All the knees were performed by a single surgeon using the same cruciate sacrificing implants. In our study we used CT based PSB to compare with CI. Postoperative mechanical femoro-tibial angle (MFT angle) was measured on long leg x-rays using picture archiving and communication system (PACS). We compared mechanical alignment achieved using PSB and CI in TKA using statistical analysis. RESULTS: The PSB group (group 1) included 17 females and seven males while in CI group (group 2) there were 15 females and eight males. The mean age of patients in group 1 was 60.5 years and in group 2 it was 60.2 years. The mean postoperative MFT angle measured on long-leg radiographs in group 1 was 178.23° (SD = 2.67°, range: 171.9° to 182.5°) while in group 2, the mean MFT angle was 175.73° (SD = 3.62°, range: 166.0° to 179.8°). There was significant improvement in postoperative mechanical alignment (P value = 0.001), in PSB group compared to CI. Number of outliers were also found to be less in group operated with PSB (7 Knee) compared to those operated with CI (17 Knee). CONCLUSION: PSB improve mechanical alignment after total knee arthroplasty, compared to CI. This may lead to lower rates of revision in the PSB based TKA as compared to the conventional instrumentation. PMID:27458553

  1. [Comparative evaluation of ultrasonography, computerized tomography, angiography and lipiodol CT in defining extent of hepatocarcinoma. A multicenter study].

    PubMed

    Dalla Palma, L; Pozzi Mucelli, R; Sponza, M; Bartolozzi, C; De Santis, M; Gandini, G; Mannella, P; Matricardi, L; Rossi, C; Simonetti, G

    1995-03-01

    The authors report the results of a multicentric trial on hepatocellular carcinoma (HCC) patients, whose lesions were confirmed with biopsy or by high (> 400 ng/ml) alpha-fetoprotein levels. The series consisted of 149 patients examined in 8 different centers and submitted to ultrasonography (US), Computed Tomography (CT) before and after contrast agent administration, angiography and Lipiodol CT. According to lesion size and number, the patients were divided with each imaging modality into three groups: a) group 1: unifocal HCC < 5 cm diameter; b) group 2: multifocal HCC with 2-3 nodules and/or tumor mass < 80 ml; c) multifocal HCC with more than 3 nodules (with total tumor mass not exceeding 40% of liver volume) or with total tumor mass > 80 ml. In 77 patients all the examinations were available for comparison. US and CT diagnosed more patients as belonging to group 1 than angiography and Lipiodol CT, while more patients were classified as groups 2 and 3 with angiography and Lipiodol CT, meaning that US and CT may understage some HCC cases (about 15%) because they show a lower number of nodules. This observation was confirmed by the direct comparison between US and Lipiodol CT (in 114 patients), CT and Lipiodol CT (in 103 patients) and angiography and Lipiodol CT (in 116 patients). US and Lipiodol CT were in disagreement in 18 cases, CT and Lipiodol CT in 16 cases and angiography and Lipiodol CT in 13 cases. In most of these cases, Lipiodol CT showed more lesions than the other techniques. The size of the undetected lesions was small, ranging few mm to 2 cm in nearly all cases. To conclude, the results of this multicentric trial show that Lipiodol CT is a fundamental tool to evaluate HCC extent. In contrast, conventional CT appeared not to add any significant piece of information and can therefore be excluded from the diagnostic protocol of HCC.

  2. Value of Computerized Tomography Enterography in Predicting Crohn’s Disease Activity: Correlation with Crohn’s Disease Activity Index and C-Reactive Protein

    PubMed Central

    Park, Eun Kyung; Han, Na Yeon; Park, Beom Jin; Sung, Deuk Jae; Cho, Sung Beom; Jeen, Yoon Tae; Keum, Bora; Kim, Min Ju

    2016-01-01

    Background The accurate evaluation of Crohn’s disease activity is important for the treatment of the disease and for monitoring the response. Computerized tomography (CT) enterography is a useful imaging modality that reflects enteric inflammation, as well as extramural complications. Objectives The aim of this study was to evaluate the correlation between CT enterographic (CTE) findings of active Crohn’s disease and the Crohn’s disease activity index (CDAI) and C-reactive protein (CRP). Patients and Methods Fifty CT enterographies of 39 patients with Crohn’s disease in the small bowel were used in our study. The CDAI was assessed through clinical and laboratory variables. Multiple CT parameters, including mural hyperenhancement, mural thickness, mural stratification, comb sign, and mesenteric fat attenuation, were evaluated with a four-point scale. The presence or absence of enhanced lymph nodes, fibrofatty proliferation, sinus or fistula, abscess, and stricture were also assessed. Two gastrointestinal radiologists independently reviewed all CT images, and inter-observer agreement was examined. Correlations between CT findings, CRP, and CDAI were assessed using Spearman’s rank correlation and logistic regression analysis. To assess the predictive accuracy of the model, a receiver-operating characteristic curve analysis for the sum of CT enterographic scores was used. Results Mural hyperenhancement, mural thickness, comb sign, mesenteric fat density, and fibrofatty proliferation were significantly correlated with CDAI and CRP (P < 0.05). The binary logistic regression model demonstrated that mesenteric fat density, mural stratification, and the presence of enhanced lymph nodes (P < 0.05) had an influence on CDAI severity. The area under the receiver operating characteristic curve (AUROC) of the CTE index for predicting disease activity was 0.85. Using a cut-off value of 8, the sensitivity and negative predictive values were 95% and 94%, respectively

  3. Dosimetry of Three Cone Beam Computerized Tomography Scanners at Different Fields of View in Terms of Various Head and Neck Organs

    PubMed Central

    Nikneshan, Sima; Aghamiri, Mahmood Reza; Moudi, Ehsan; Bahemmat, Nika; Hadian, Hoora

    2016-01-01

    Background Marketing new radiography devices necessitates documenting their absorbed X-ray doses. Since the current literature lacks studies on new devices, we assessed the doses of two new devices that had not previously been assessed. Objectives The new devices were compared to the Promax three dimensional (3D) scanner at two fields of view (FOV) in nine critical head and neck tissues and organs. Materials and Methods Seventeen thermoluminescence dosimeters positioned in an average-sized male RANDO phantom were used to determine the dosimetry of the three cone beam computerized tomography devices (NewTom VGi, NewTom 5G, and Promax 3D) at two field of views (FOVs), one small and one large. The exposure by each device per FOV was performed five times (30 exposures). The absorbed and effective doses were calculated for the thyroid, parotid, submandibular gland, sublingual gland, calvarium, cervical vertebra, trunk of the mandible, and mandibular ramus. The doses pertaining to the different devices, the FOVs, and the tissues were compared using the Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests. Results The average absorbed doses, respectively, for the large and small FOVs were 17.19 and 28.89 mGy in the Promax 3D, 19.25 and 35.46 mGy in the NewTom VGi, and 18.85 and 30.63 mGy in the NewTom 5G. The absorbed doses related to the FOVs were not significantly different (P value = 0.1930). However, the effective doses were significantly greater at the smaller FOVs / higher resolutions (P = 0.0039). The doses of the three devices were not significantly different (P = 0.8944). The difference among the nine organs/tissues was significant (Kruskal-Wallis P=0.0000). Conclusion The absorbed doses pertaining to the devices and the FOVs were not significantly different, although the organs/tissues absorbed considerably different doses. PMID:27853498

  4. Large-scale traveling ionospheric disturbances using ionospheric imaging at storm time: A case study on 17 march 2013

    NASA Astrophysics Data System (ADS)

    Tang, Jun; Yao, Yibin; Kong, Jian; Zhang, Liang

    2016-07-01

    A moderate geomagnetic storm occurred on March 17, 2013, during which large-scale traveling ionospheric disturbances (LSTIDs) are observed over China by ionosondes and GPS from Crustal Movement Observation Network of China (CMONOC) and the International GNSS Service (IGS). Ionosonde data and computerized ionospheric tomography (CIT) technique are employed to analyze the disturbances in our study. The maximum entropy cross spectral analysis (MECSA) method is used to obtain the propagation parameters of the LSTIDs. Spatio-temporal variations of ionospheric electron density (IED) and total electron content (TEC) during this geomagnetic storm over China are investigated. Disturbance images of IED and TEC are also presented in the paper. The results show two LSTID events at about 12:00 UT and 15:00 UT during the main phase of the storm. Besides, the LSTIDs with a duration of 40 min are detected over China. It is confirmed that the LSTIDs travel from north to south with a horizontal velocity of 400-500 m/s, and moved southwestwards with a horizontal velocity of 250-300 m/s, respectively.

  5. Massive training artificial neural network (MTANN) for reduction of false positives in computerized detection of lung nodules in low-dose computed tomography.

    PubMed

    Suzuki, Kenji; Armato, Samuel G; Li, Feng; Sone, Shusuke; Doi, Kunio

    2003-07-01

    In this study, we investigated a pattern-recognition technique based on an artificial neural network (ANN), which is called a massive training artificial neural network (MTANN), for reduction of false positives in computerized detection of lung nodules in low-dose computed tomography (CT) images. The MTANN consists of a modified multilayer ANN, which is capable of operating on image data directly. The MTANN is trained by use of a large number of subregions extracted from input images together with the teacher images containing the distribution for the "likelihood of being a nodule." The output image is obtained by scanning an input image with the MTANN. The distinction between a nodule and a non-nodule is made by use of a score which is defined from the output image of the trained MTANN. In order to eliminate various types of non-nodules, we extended the capability of a single MTANN, and developed a multiple MTANN (Multi-MTANN). The Multi-MTANN consists of plural MTANNs that are arranged in parallel. Each MTANN is trained by using the same nodules, but with a different type of non-nodule. Each MTANN acts as an expert for a specific type of non-nodule, e.g., five different MTANNs were trained to distinguish nodules from various-sized vessels; four other MTANNs were applied to eliminate some other opacities. The outputs of the MTANNs were combined by using the logical AND operation such that each of the trained MTANNs eliminated none of the nodules, but removed the specific type of non-nodule with which the MTANN was trained, and thus removed various types of non-nodules. The Multi-MTANN consisting of nine MTANNs was trained with 10 typical nodules and 10 non-nodules representing each of nine different non-nodule types (90 training non-nodules overall) in a training set. The trained Multi-MTANN was applied to the reduction of false positives reported by our current computerized scheme for lung nodule detection based on a database of 63 low-dose CT scans (1765

  6. NOTE: Cone beam computerized tomography: the effect of calibration of the Hounsfield unit number to electron density on dose calculation accuracy for adaptive radiation therapy

    NASA Astrophysics Data System (ADS)

    Hatton, Joan; McCurdy, Boyd; Greer, Peter B.

    2009-08-01

    The availability of cone beam computerized tomography (CBCT) images at the time of treatment has opened possibilities for dose calculations representing the delivered dose for adaptive radiation therapy. A significant component in the accuracy of dose calculation is the calibration of the Hounsfield unit (HU) number to electron density (ED). The aim of this work is to assess the impact of HU to ED calibration phantom insert composition and phantom volume on dose calculation accuracy for CBCT. CBCT HU to ED calibration curves for different commercial phantoms were measured and compared. The effect of the scattering volume of the phantom on the HU to ED calibration was examined as a function of phantom length and radial diameter. The resulting calibration curves were used at the treatment planning system to calculate doses for geometrically simple phantoms and a pelvic anatomical phantom to compare against measured doses. Three-dimensional dose distributions for the pelvis phantom were calculated using the HU to ED curves and compared using Chi comparisons. The HU to ED calibration curves for the commercial phantoms diverge at densities greater than that of water, depending on the elemental composition of the phantom insert. The effect of adding scatter material longitudinally, increasing the phantom length from 5 cm to 26 cm, was found to be up to 260 HU numbers for the high-density insert. The change in the HU value, by increasing the diameter of the phantom from 18 to 40 cm, was found to be up to 1200 HU for the high-density insert. The effect of phantom diameter on the HU to ED curve can lead to dose differences for 6 MV and 18 MV x-rays under bone inhomogeneities of up to 20% in extreme cases. These results show significant dosimetric differences when using a calibration phantom with materials which are not tissue equivalent. More importantly, the amount of scattering material used with the HU to ED calibration phantom has a significant effect on the dosimetric

  7. Injections of Intravenous Contrast for Computerized Tomography Scans Precipitate Migraines in Hereditary Hemorrhagic Telangiectasia Subjects at Risk of Paradoxical Emboli: Implications for Right‐to‐Left Shunt Risks

    PubMed Central

    Patel, Trishan; Elphick, Amy; Jackson, James E.

    2016-01-01

    Objective To evaluate if injection of intravenous particles may provoke migraines in subjects with right‐to‐left shunts due to pulmonary arteriovenous malformations (AVMs). Background Migraine headaches commonly affect people with hereditary hemorrhagic telangiectasia (HHT), especially those with pulmonary AVMs that provide right‐to‐left shunts. In our clinical practice, patients occasionally reported acute precipitation of migraine headaches following injection of technetium‐labeled albumin macroaggregates for nuclear medicine scans. Methods Self‐reported migraine features and exacerbations were examined in HHT subjects with and without pulmonary AVMs, for a series of noninvasive and invasive investigations, using an unbiased online survey. Results One hundred and sixty‐six subjects were classified as having both HHT and migraines. HHT subjects with migraines were more likely to have pulmonary AVMs (P < .0001). HHT subjects with pulmonary AVMs were more likely to report photophobia (P = .010), “flashes of light” (P = .011), or transient visual loss (P = .040). Pulse oximetry, x‐rays, ultrasound, and computerized tomography (CT) scans without intravenous contrast medium rarely, if ever, provoked migraines, but unenhanced magnetic resonance imaging (MRI) was reported to exacerbate migraines by 14/124 (11.2%) subjects. One hundred and fourteen subjects had both enhanced and unenhanced CT examinations: studies with contrast media were more commonly reported to start (9/114 [7.8%]), and/or worsen migraines (18/114 [15.7%]), compared to those undertaken without contrast medium (P < .01), or after simple blood tests (P < .05). Additionally, migraine exacerbation was reported by 9/90 (10%) after contrast echocardiography, 2/44 (4.5%) after nuclear medicine scans, and 10/154 (6.5%) after blood tests. Conclusions HHT subjects frequently report migraine exacerbation following blood tests, contrast echocardiograms, MRI imaging, and

  8. Helical computerized tomography and NT-proBNP for screening of right ventricular overload on admission and at long term follow-up of acute pulmonary embolism

    PubMed Central

    2012-01-01

    Background Right ventricular dysfunction (RVD) in acute pulmonary embolism (APE) can be assessed with helical computerized tomography (CT) and transthoracic echocardiography (TTE). Signs of RVD and elevated natriuretic peptides like NT-proBNP and cardiac troponin (TnT) are associated with increased risk of mortality. However, the prognostic role of both initial diagnostic strategy and the use of NT-proBNP and TnT for screening for long-term probability of RVD remains unknown. The aim of the study was to determine the role of helical CT and NT-proBNP in detection of RVD in the acute phase. In addition, the value of NT-proBNP for ruling out RVD at long-term follow-up was assessed. Methods Sixty-three non-high risk APE patients were studied. RVD was assessed at admission in the emergency department by CT and TTE, and both NT-proBNP and TnT samples were taken. These, excepting CT, were repeated seven months later. Results At admission RVD was detected by CT in 37 (59 %) patients. RVD in CT correlated strongly with RVD in TTE (p < 0.0001). NT-proBNP was elevated (≥ 350 ng/l) in 32 (86 %) patients with RVD but in only seven (27 %) patients without RVD (p < 0.0001). All the patients survived until the 7-month follow-up. TTE showed persistent RVD in 6 of 63 (10 %) patients who all had RVD in CT at admission. All of them had elevated NT-proBNP levels in the follow-up compared with 5 (9 %) of patients without RVD (p < 0.0001). Conclusions TTE does not confer further benefit when helical CT is used for screening for RVD in non-high risk APE. All the patients who were found to have RVD in TTE at seven months follow-up had had RVD in the acute phase CT as well. Thus, patients without RVD in diagnostic CT do not seem to require further routine follow-up to screen for RVD later. On the other hand, persistent RVD and thus need for TTE control can be ruled out by assessment of NT-proBNP at follow-up. A follow-up protocol based on these findings is suggested. PMID:22559861

  9. A computerized tomography scan method for calculating the hernia sac and abdominal cavity volume in complex large incisional hernia with loss of domain.

    PubMed

    Tanaka, E Y; Yoo, J H; Rodrigues, A J; Utiyama, E M; Birolini, D; Rasslan, S

    2010-02-01

    Preoperative progressive pneumoperitoneum (PPP) is a safe and effective procedure in the treatment of large incisional hernia (size > 10 cm in width or length) with loss of domain (LIHLD). There is no consensus in the literature on the amount of gas that must be insufflated in a PPP program or even how long it should be maintained. We describe a technique for calculating the hernia sac volume (HSV) and abdominal cavity volume (ACV) based on abdominal computerized tomography (ACT) scanning that eliminates the need for subjective criteria for inclusion in a PPP program and shows the amount of gas that must be insufflated into the abdominal cavity in the PPP program. Our technique is indicated for all patients with large or recurrent incisional hernias evaluated by a senior surgeon with suspected LIHLD. We reviewed our experience from 2001 to 2008 of 23 consecutive hernia surgical procedures of LIHLD undergoing preoperative evaluation with CT scanning and PPP. An ACT was required in all patients with suspected LIHLD in order to determine HSV and ACV. The PPP was performed only if the volume ratio HSV/ACV (VR = HSV/ACV) was >or=25% (VR >or= 25%). We have performed this procedure on 23 patients, with a mean age of 55.6 years (range 31-83). There were 16 women and 7 men with an average age of 55.6 years (range 31-83), and a mean BMI of 38.5 kg/m(2) (range 23-55.2). Almost all patients (21 of 23 patients-91.30%) were overweight; 43.5% (10 patients) were severely obese (obese class III). The mean calculated volumes for ACV and HSV were 9,410 ml (range 6,060-19,230 ml) and 4,500 ml (range 1,850-6,600 ml), respectively. The PPP is performed by permanent catheter placed in a minor surgical procedure. The total amount of CO(2) insufflated ranged from 2,000 to 7,000 ml (mean 4,000 ml). Patients required a mean of 10 PPP sessions (range 4-18) to achieve the desired volume of gas (that is the same volume that was calculated for the hernia sac). Since PPP sessions were performed

  10. High-resolution nuclear magnetic resonance imaging and single photon emission computerized tomography--cerebral blood flow in a case of pure sensory stroke and mild dementia owing to subcortical arteriosclerotic encephalopathy (Binswanger's disease)

    SciTech Connect

    De Chiara, S.; Lassen, N.A.; Andersen, A.R.; Gade, A.; Lester, J.; Thomsen, C.; Henriksen, O.

    1987-01-01

    Pure sensory stroke (PSS) is typically caused by a lacunar infarct located in the ventral-posterior (VP) thalamic nucleus contralateral to the paresthetic symptoms. The lesion is usually so small that it cannot be seen on computerized tomography (CT), as illustrated by our case. In our moderately hypertensive, 72-year-old patient with PSS, CT scanning and conventional nuclear magnetic resonance imaging (NMRI) scanning using a 7-mm-thick slice on a 1.5 Tesla instrument all failed to visualize the thalamic infarct. Using the high-resolution mode with 2-mm slice thickness it was, however, clearly seen. In addition, NMRI unexpectedly showed diffuse periventricular demyelinization as well as three other lacunar infarcts, i.e., findings characteristic of subcortical arteriosclerotic encephalopathy (SAE). This prompted psychometric testing, which revealed signs of mild (subclinical) dementia, in particular involving visiospatial apraxia; this pointed to decreased function of the right parietal cortex, which was structurally intact on CT and NMRI. Single photon emission computerized tomography by Xenon-133 injection and by hexamethyl-propyleneamine-oxim labeled with Technetium-99m showed asymmetric distribution of cerebral blood flow (CBF), with an 18% lower value in the right parietal cortex compared to the left side; this indicated asymmetric disconnection of the cortex by the SAE. Thus, the tomograms of the functional parameter, CBF, correlated better with the deficits revealed by neuropsychological testing than by CT or NMRI.

  11. Ionospheric Sounding Opportunities Using Signal Data From Preexisting Amateur Radio And Other Networks

    NASA Astrophysics Data System (ADS)

    Cushley, A. C.; Noel, J. M. A.

    2015-12-01

    Amateur radio and other transmissions used for dedicated purposes, such as the Automatic Packet Reporting System (APRS) and Automatic Dependent Surveillance Broadcast (ADS-B), are signals that exist for another reason, but can be used for ionospheric sounding. Whether mandated and government funded or voluntarily constructed and operated, these networks provide data that can be used for scientific and operational purposes which rely on space weather data. Given the current state of the global economic environment and fiscal consequences to scientific research funding in Canada, these types of networks offer an innovative solution with preexisting hardware for more real-time and archival space-weather data to supplement current methods, particularly for data assimilation, modelling and forecasting. Furthermore, mobile ground-based transmitters offer more flexibility for deployment than stationary receivers. Numerical modelling has demonstrated that APRS and ADS-B signals are subject to Faraday rotation (FR) as they pass through the ionosphere. Ray tracingtechniques were used to determine the characteristics of individual waves, including the wave path and the state of polarization. The modelled FR was computed and converted to total electron content (TEC) along the raypaths. TEC data can be used as input for computerized ionospheric tomography (CIT) in order to reconstruct electron density maps of the ionosphere.

  12. Comparative ionospheres

    NASA Astrophysics Data System (ADS)

    Cravens, T.

    2003-04-01

    Ionospheres are created as a consequence of the ionization of the neutral atoms and molecules in a planet’s upper atmosphere either by solar radiation or by fast charged particles. Ionospheres have been detected at all the planets except for Mercury and Pluto, either remotely or by in situ instruments. Active comets have ionospheres as do many planetary satellites, including Io, Europa, Ganymede, Titan, and Triton. A comparative review of ionospheres throughout the solar system will be given in this paper. Observations and theoretical models will be included in the review.

  13. Crossed cerebellar diaschisis in ischemic stroke: a study of regional cerebral blood flow by /sup 133/Xe inhalation and single photon emission computerized tomography

    SciTech Connect

    Meneghetti, G.; Vorstrup, S.; Mickey, B.; Lindewald, H.; Lassen, N.A.

    1984-06-01

    Seventy measurements of CBF were performed in 12 stroke patients by /sup 133/Xe inhalation and a rapidly rotating single photon emission computerized tomograph. CBF was measured every other day during the acute phase and at 2- and 6-month follow-up visits. A persistent contralateral cerebellar blood flow depression was evident in five patients with severe hemispheric low flow areas, which correlated with large, hypodense lesions on the computerized tomographic scan. In a sixth patient with a small, deep infarct, a transient crossed cerebellar low flow was observed, while the clinical symptoms persisted. It is concluded from this serial study that crossed cerebellar diaschisis is a common finding in completed stroke. It is probably caused by disconnection of the corticopontine pathways, a disconnection that tends to persist. The phenomenon is in fact less variable than the stroke-related CBF changes in the infarcted hemisphere, in which a period of relative hyperemia is frequently seen.

  14. Emission tomography of the kidney

    SciTech Connect

    Teates, C.D.; Croft, B.Y.; Brenbridge, N.A.; Bray, S.T.; Williamson, B.R.

    1983-12-01

    Single photon emission computerized tomography (SPECT) was done on two patients with suspected renal masses. Nuclear scintigraphy was equivocal on two tumors readily identified by SPECT. Single photon tomography is cost effective and increases the reliability of nuclear scintigraphy.

  15. Ionosphere research

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A report is presented on on-going research projects in ionospheric studies. The topics discussed are planetary atmospheres, E and F region, D region, mass spectrometer measurements, direct measurements and atmospheric reactions.

  16. Ionospheric research

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Data from research on ionospheric D, E, and F, regions are reported. Wave propagation, mass spectrometer measurements, and atmospheric reactions of HO2 with NO and NO2 and NH2 with NO and O2 are summarized.

  17. Noninvasive quantification of the extent of jeopardized myocardium in patients with single-vessel coronary disease by stress thallium-201 single-photon emission computerized rotational tomography

    SciTech Connect

    Prigent, F.; Maddahi, J.; Garcia, E.; Van Train, K.; Friedman, J.; Berman, D.

    1986-03-01

    In 22 patients with single-vessel coronary artery disease and no history of infarction, stress Tl-201 rotational tomography was used to quantify the extent of jeopardized myocardium. The vertical long- and short-axis tomograms were quantified by means of maximum-count circumferential profile analysis. The scintigraphic extent of jeopardized myocardium was expressed as the percentage of profile points falling 2.5 standard deviations below a previously established mean normal profile and was correlated to a quantitatively expressed angiographic extent of jeopardized myocardium. The extent of jeopardized myocardium varied from 1% to 55% by tomography and 8% to 50% by angiography and correlated with an r = 0.79 and a 10% standard error of the estimate. Defect intensity, reflecting the mean depth by which the abnormal points fell below the normal value of greater than or equal to 10%, was 100% specific for a coronary stenosis of greater than or equal to 70%. In conclusion, this study demonstrates that: patients with single-vessel disease have highly variable extents of hypoperfused myocardium defined by Tl-201 tomography and coronary arteriography, there is a fair relationship between angiographic jeopardy score and perfusion defects by Tl-201 tomography during exercise, and Tl-201 tomography may be used to noninvasively determine the extent of hypoperfused myocardium in coronary artery disease.

  18. First results from the ionospheric tomography experiment using beacon TEC data obtained by means of a network along a longitude of 136°E over Japan

    NASA Astrophysics Data System (ADS)

    Thampi, Smitha V.; Yamamoto, Mamoru

    2010-03-01

    A chain of newly designed GNU (GNU is not UNIX) Radio Beacon Receivers (GRBR) has recently been established over Japan, primarily for tomographic imaging of the ionosphere over this region. Receivers installed at Shionomisaki (33.45°N, 135.8°E), Shigaraki (34.8°N, 136.1°E), and Fukui (36°N, 136°E) continuously track low earth orbiting satellites (LEOS), mainly OSCAR, Cosmos, and FORMOSAT-3/COSMIC, to obtain simultaneous total electron content (TEC) data from these three locations, which are then used for the tomographic reconstruction of ionospheric electron densities. This is the first GRBR network established for TEC observations, and the first beacon-based tomographic imaging in Japanese longitudes. The first tomographic images revealed the temporal evolution with all of the major features in the ionospheric electron density distribution over Japan. A comparison of the tomographically reconstructed electron densities with the ƒ o F 2 data from Kokubunji (35°N, 139°E) revealed that there was good agreement between the datasets. These first results show the potential of GRBR and its network for making continuous, unattended ionospheric TEC measurements and for tomographic imaging of the ionosphere.

  19. Ionospheric Analysis and Ionospheric Modeling

    DTIC Science & Technology

    1975-07-01

    ionospheric data by numerical methods, ITU Tellecomm. Jour. 29, 129-149 4. Edwards, W. R., Rush, C. M. and Miller, D. C. (1975) Studies on the...data including 1958 and 1964 vertical incidence ionosonde measurements, and optical and satellite observations. The repre- sentation of the different...2) Jones, W. B,., and Gallet, R. M. (1962) Representation of divinaland geographic. variatioms of ionospheric data by numerical methods, ITU TeUeconrm

  20. The potential for non-invasive study of mummies: validation of the use of computerized tomography by post factum dissection and histological examination of a 17th century female Korean mummy.

    PubMed

    Lim, Do-Seon; Lee, In Sun; Choi, Ki-Ju; Lee, Soong Deok; Oh, Chang Seok; Kim, Yi-Suk; Bok, Gi Dae; Kim, Myeung Ju; Yi, Yang Su; Lee, Eun-Joo; Shin, Dong Hoon

    2008-10-01

    The socio-cultural antipathies of some descendants with regard to invasive examinations of age-old human remains make permission for dissection of Korean mummies of the Joseon Dynasty (1392-1910) difficult to obtain. Overcoming this obstacle necessitated the use of non-invasive techniques, such as multi-detector computerized tomography (MDCT) and endoscopic examination, enabling determination of the preservation status of internal organs of mummies without significantly damaging the mummies themselves. However, MDCT alone cannot clearly differentiate specific mummified organs. Therefore, in much the same way as diagnostic radiologists make their MDCT readings on living patients more reliable by means of comparison with accumulated post-factum data from autopsies or histological studies, examinations of mummies by invasive techniques should not be decried as mere destruction of age-old human remains. Rather, providing that due permission from descendants and/or other relevant authorities can be obtained, dissection and histological examination should be performed whenever opportunities arise. Therefore, in this study, we compared the radiological data acquired from a 17th century mummy with our dissection results for the same subject. As accumulation of this kind of data could be very crucial for correct interpretation of MDCT findings on Korean mummies, we will perform similar trials on other Korean mummies found in forthcoming days if conditions permit.

  1. The potential for non-invasive study of mummies: validation of the use of computerized tomography by post factum dissection and histological examination of a 17th century female Korean mummy

    PubMed Central

    Lim, Do-Seon; Lee, In Sun; Choi, Ki-Ju; Lee, Soong Deok; Oh, Chang Seok; Kim, Yi-Suk; Bok, Gi Dae; Kim, Myeung Ju; Yi, Yang Su; Lee, Eun-Joo; Shin, Dong Hoon

    2008-01-01

    The socio-cultural antipathies of some descendants with regard to invasive examinations of age-old human remains make permission for dissection of Korean mummies of the Joseon Dynasty (1392–1910) difficult to obtain. Overcoming this obstacle necessitated the use of non-invasive techniques, such as multi-detector computerized tomography (MDCT) and endoscopic examination, enabling determination of the preservation status of internal organs of mummies without significantly damaging the mummies themselves. However, MDCT alone cannot clearly differentiate specific mummified organs. Therefore, in much the same way as diagnostic radiologists make their MDCT readings on living patients more reliable by means of comparison with accumulated post-factum data from autopsies or histological studies, examinations of mummies by invasive techniques should not be decried as mere destruction of age-old human remains. Rather, providing that due permission from descendants and/or other relevant authorities can be obtained, dissection and histological examination should be performed whenever opportunities arise. Therefore, in this study, we compared the radiological data acquired from a 17th century mummy with our dissection results for the same subject. As accumulation of this kind of data could be very crucial for correct interpretation of MDCT findings on Korean mummies, we will perform similar trials on other Korean mummies found in forthcoming days if conditions permit. PMID:19014355

  2. Ionospheric Physics.

    DTIC Science & Technology

    1982-10-07

    system design and ionospheric modification and con- ~trol. In this report, the S3-4 satellite data analyses is summarized. D, JAN73 1473 EDITION OF INOV ...wavelength distribution of solar radiation and the time variations of such emissions as well as the resonant scattering of solar radiation by...ratio square (Ie/I1) 2), is more inside the depletions in most of the depletions suggesting more molecular ions inside the depletions. o The power

  3. Technetium-99m dimercaptosuccinic acid scan in evaluation of renal cortical scarring: Is it mandatory to do single photon emission computerized tomography?

    PubMed Central

    Saleh Farghaly, Hussein Rabie; Mohamed Sayed, Mohamed Hosny

    2015-01-01

    Objectives: Renal cortical scintigraphy with technetium-99m (Tc-99m) dimercaptosuccinic acid (DMSA) is the method of choice to detect acute pyelonephritis and cortical scarring. Different acquisition methods have been used: Planar parallel-hole or pinhole collimation and single photon emission tomography (SPECT). This study compared planar parallel-hole cortical scintigraphy and dual-head SPECT for detection of cortical defects. Patients and Methods: We retrospectively reviewed 190 consecutive patients with 380 kidneys and 200 DMSA scans referred to rule out renal cortical scarring. The diagnoses were 52 vesicoureteric reflux, 61 recurrent urinary tract infection, 39 hydronephrosis, 20 renal impairment, and 18 hypertension. All patients were imaged 3 h after injection of Tc-99m DMSA with SPECT and planar imaging (posterior, anterior, left, and right posterior oblique views). For each patient, planar and SPECT images were evaluated at different sittings, in random order. Each kidney was divided into three cortical segments (upper, middle and lower) and was scored as normal or reduced uptake. The linear correlation coefficient for the number of abnormal segments detected between planner and SPECT techniques was calculated. Results: From 200 DMSA scans, 100 scans were positive for scar in SPECT images, from which only 95 scans were positive for scar in planner imaging. Out of the five mismatched scans, three scans were for patients with renal impairment and high background activity and two scans were for very small scars. No significant difference was seen in the average number of abnormal segments detected by planar versus SPECT imaging (P = 0.31). The average correlation coefficient between was high (r = 0.91 – 0.92). Conclusions: Tc-99m DMSA renal cortical scanning using SPECT offers no statistically significant diagnostic advantage over multiple views planar imaging for detection of cortical defect. PMID:25589802

  4. Comparing non contrast computerized tomography criteria versus dual X-ray absorptiometry as predictors of radio-opaque upper urinary tract stone fragmentation after electromagnetic shockwave lithotripsy.

    PubMed

    Hameed, Diaa A; Elgammal, Mohammed A; ElGanainy, Ehab O; Hageb, Adel; Mohammed, Khaled; El-Taher, Ahmed Mohamed; Mostafa, Mostafa Mohamed; Ahmed, Abdelfatah Ibrahim

    2013-11-01

    The objective of this study was to assess the value of dual X-ray absorptiometry (DXA) in comparison to non contrast computed tomography (NCCT) density as possible predictors of upper urinary tract stone disintegration by shock wave lithotripsy (SWL). This study included 100 consecutive patients, with solitary renal stone 0.5-2 cm or upper ureteral stone up to 1 cm. DXA to calculate stone mineral density (SMD) and stone mineral content (SMC) was done. NCCT was performed to measure Hounsfield units (HU). SWL was performed with an electromagnetic lithotripsy, plain X-ray documented disintegration after SWL. Successful treatment was defined as stone free or complete fragmentation after 1 or 2 sessions of SWL. The impact of patients age, sex, body mass index, stone laterality, location, volume, length, mean SMC and SMD, HU and Hounsfield density (HD), skin to stone distance (SSD) and number of shock waves were evaluated by univariate and multivariate analysis. Only 76 patients were available for follow-up. Success of disintegration was observed in 50 out of 76 patients (65.8 %). On multivariate analysis, SMC and number of shock wave were the significant independent factors affecting SWL outcome (p = 0.04 and p = 0.000, respectively). SMC as detected by DXA is a significant predictor of success of stone disintegration by SWL. SMC measured by DXA is more accurate than HU measured by CT. Patients with high stone mineral content (SMC greater than 0.65 g) should be directly offered another treatment option.

  5. Predictive value of excretory urography, ultrasonography, computerized tomography, and liver and bone scan in the staging of bilharzial bladder cancer in Saudi Arabia

    SciTech Connect

    Hanash, K.A.; Bissada, N.K.; Abla, A.; Esmail, D.; Dowling, A.

    1984-07-01

    The role of ultrasonography, computed tomography (CT), and radioisotopic scanning in the staging of bilharzial bladder cancer has not been reported previously. Forty patients with invasive bladder cancer seen at the King Faisal Specialist Hospital and Research Centre between January 1978 and June 1981 underwent complete preoperative workup for staging of their tumors prior to radical cystectomy. The preoperative radiologic investigations included excretory urography (IVP), ultrasonography (US), CT of the pelvis, and liver and bone scans. The results of these investigations were compared with the operative and pathologic staging. Ninety-three percent of the patients with bilharzial cancer had evidence of ureteric obstruction on IVP compared with 22% of the nonbilharzial cancer patients. The presence of ureteric obstruction in these patients did not correlate with the stage of the disease with 83% of the patients with superficial tumors (T1 and T2) having hydroureteronephrosis. Ultrasonography and CT had an 83% accuracy in the staging of superficial tumors. Stage T3 tumors were understaged in 14% of the cases. Ultrasonography did not differentiate Stages T3 and T4 tumors while CT scan differentiated these two stages in 57% of the cases. Bone scan failed to reveal evidence of metastatic disease in any of the bilharzial cancer patients. Liver scan was suspicious for liver metastases in two patients with bilharzial cancers in whom open liver biopsy revealed only hepatic bilharziasis. Of all the radiographic studies, US or preferably CT scan seem to be of some value in the staging of bilharzial tumors localized to the bladder. Bone and liver scans are probably of no cost effective benefit.

  6. Association of Neutrophil-to-Lymphocyte Ratio with the Severity and Morphology of Coronary Atherosclerotic Plaques Detected by Multidetector Computerized Tomography

    PubMed Central

    Ateş, Ahmet Hakan; Aytemir, Kudret; Koçyiğit, Duygu; Yalcin, Muhammed Ulvi; Gürses, Kadri Murat; Yorgun, Hikmet; Canpolat, Uğur; Hazırolan, Tuncay; Özer, Necla

    2016-01-01

    Background Studies have demonstrated a consistent relationship between white blood cell (WBC) counts and coronary artery disease (CAD). The neutrophil/lymphocyte ratio (NLR) has been considered as a potential marker for identifying individuals under risk of CAD and associated events. In this study, we aimed to evaluate whether NLR was associated with the severity and morphology of coronary atherosclerotic plaques shown by multidetector computed tomography (MDCT). Methods Our study population consisted of 684 patients who underwent dual-source 64 slice MDCT for the assessment of CAD. Coronary arteries were evaluated on a 16-segment basis and critical coronary plaque was described as luminal narrowing > 50%, whereas plaque morphology was assessed on a per segment basis. Total WBC, neutrophil and lymphocyte counts were determined using commercially available assay kits. Results WBC count [7700 (6400-8800) vs. 6800 (5700-7900), p < 0.05] and NLR [2.40 (1.98-3.07) vs. 1.86 (1.50-2.38), p < 0.001] were found to be higher in patients with critical stenosis than in those without. In the binary logistic regression analysis, NLR was a predictor of critical stenosis (odds ratio, 1.68; 95% confidence interval, 1.39-2.03, p < 0.001). NLR levels differed among plaque morphology subtypes (p < 0.05) and was significantly higher in non-calcified plaque (NCP) compared to mixed plaque (MP) and calcified plaque (CP) (p < 0.05). In the multinomial logistic regression analysis, NLR was found to be an independent predictor of NCP, MP and CP (p < 0.001). Conclusions These data show that NLR is associated with both the severity and morphology of coronary atherosclerotic disease. PMID:27899854

  7. Use of computerized tomography and chest x-rays in evaluating efficacy of aerosolized recombinant human DNase in cystic fibrosis patients younger than age 5 years: a preliminary study.

    PubMed

    Nasr, S Z; Kuhns, L R; Brown, R W; Hurwitz, M E; Sanders, G M; Strouse, P J

    2001-05-01

    The aim of this study was to evaluate the ability of high-resolution computerized tomography (HRCT) of the chest and chest x-rays (CXR) to determine efficacy of inhaled recombinant human DNase (rhDNase) in cystic fibrosis (CF) patients younger than 5 years of age. A randomized, double-blind, placebo-controlled pilot study of 12 patients with CF younger than 5 years of age, attending the University of Michigan Cystic Fibrosis Center (Ann Arbor, MI) was conducted. The changes in the HRCT and CXR score from baseline to day 100 of therapy were assessed using a previously validated scoring system. The mean changes of HRCT scores between the rhDNase and placebo groups were found to be significant at the 95% level, with mean change +/- SE mean of - 1.00 +/- 0.53 and 0.58 +/- 0.24 for rhDNase and placebo groups, respectively (P = 0.02). The difference in CXR score was not significant between the two groups. An analysis was performed to relate HRCT subscores to CXR score; only thickening of the intra-interlobular septae was significantly correlated with the total CXR score (r = - 0.7, P < 0.01). There was improvement in the parents' assessments of the patients' well-being, with improvement in physical activity, decreased cough, sleep quality, and appetite in those subjects receiving rhDNase. We conclude that the administration of rhDNase was associated with improvement in the HRCT scan in CF patients younger than 5 years of age. Findings indicate that HRCT of the chest is useful and sensitive in studying responses to therapy in patients with CF lung disease. To our knowledge, this is the first report of the use of HRCT to assess the effectiveness of a therapeutic modality in so young a CF patient population.

  8. Imaging-based assessment of the mineral composition of urinary stones: an in vitro study of the combination of hounsfield unit measurement in noncontrast helical computerized tomography and the twinkling artifact in color Doppler ultrasound.

    PubMed

    Hassani, Hakim; Raynal, Gauthier; Spie, Romain; Daudon, Michel; Vallée, Jean-Noël

    2012-05-01

    We evaluated the value of combining noncontrast helical computerized tomography (NCHCT) and color Doppler ultrasound in the assessment of the composition of urinary stones. In vitro, we studied 120 stones of known composition, that separate into the five main types: 18 calcium oxalate monohydrate (COM) stones, 41 calcium oxalate dihydrate (COD) stones, 24 uric acid stones, 25 calcium phosphate stones and 12 cystine calculi. Stones were characterized in terms of their Hounsfield density (HU) in NCHCT and the presence of a twinkling artifact (TA) in color Doppler ultrasound. There were statistically significant HU differences between calcium and non-calcium stones (p < 0.001), calcium oxalate stones and calcium phosphate stones (p < 0.001) and uric acid stones and cystine calculi (p < 0.001) but not between COM and COD stones (p = 0.786). Hence, the HU was a predictive factor of the composition of all types of stones, other than for COM and COD stones within the calcium oxalate class (p > 0.05). We found that the TA does not enable differentiation between calcium and non-calcium stones (p > 0.999), calcium oxalate stones and calcium phosphate stones (p = 0.15), or uric acid stones and cystine calculi (p = 0.079). However, it did reveal a significant difference between COM and COD stones (p = 0.002). The absence of a TA is a predictive factor for the presence of COM stones (p = 0.008). Hence, the association of NCHCT and Doppler enables the accurate classification of the five types of stones in vitro.

  9. The combined evaluation of interim contrast-enhanced computerized tomography (CT) and FDG-PET/CT predicts the clinical outcomes and may impact on the therapeutic plans in patients with aggressive non-Hodgkin's lymphoma.

    PubMed

    Yang, Deok-Hwan; Min, Jung-Joon; Jeong, Yong Yeon; Ahn, Jae-Sook; Kim, Yeo-Kyeoung; Cho, Sang-Hee; Chung, Ik-Joo; Bom, Hee-Seung; Kim, Hyeoung-Joon; Lee, Je-Jung

    2009-05-01

    We investigated the concomitant interim response of patients with aggressive non-Hodgkin's lymphoma (NHL) using multi-detector row computerized tomography (CT) and (18)F-fluoro-2-deoxy-D: -glucose-positron emission tomography (PET)/CT for prediction of clinical outcomes. One hundred six newly diagnosed patients with aggressive NHL were enrolled. Both the CT and PET/CT were serially performed at the time of diagnosis and after three to four cycles of chemotherapy (interim). The patients were categorized into four different responsive groups according to the interim PET/CT and CT: (1) complete metabolic response (CMR)-complete response unconfirmed (CRu), (2) CMR-partial response (PR), (3) partial metabolic response (PMR)-Cru, and (4) PMR-PR. Fifty-five patients with CMR-CRu, 20 patients with CMR-PR, seven patients with PMR-Cru, and 23 patients with PMR-PR were distributed. In addition, one patient experienced a disease progression. There was a significant difference in relapse rates between PET/CT-positive (67.3%) and PET/CT-negative patients (17.3%; P < 0.01). Also, there was a significant difference between patients with PMR-PR (32.0% and 26.1%) and CMR-CRu (89.3% and 80.0%) for 3-year overall survival (OS) and event-free survival (EFS), respectively. A multivariate analysis revealed that high international prognostic index (> or =3) at diagnosis, T-cell phenotype, and PMR-PR in interim PET/CT and CT were independent prognostic significances for OS. Moreover, bulky disease (>10 cm), T-cell phenotype, and PMR-PR showed significant associations for EFS. PMR-PR in interim response was the predictive prognostic determinant for both OS and EFS, with a hazard ratio of 3.93 (1.61-9.60) and 3.60 (1.62-7.98), respectively. The combined evaluation of interim PET/CT and CT was found to be a significant predictor of disease progression, OS, and EFS.

  10. Innovations in Computerized Assessment.

    ERIC Educational Resources Information Center

    Drasgow, Fritz, Ed.; Olson-Buchanan, Julie B., Ed.

    Chapters in this book present the challenges and dilemmas faced by researchers as they created new computerized assessments, focusing on issues addressed in developing, scoring, and administering the assessments. Chapters are: (1) "Beyond Bells and Whistles; An Introduction to Computerized Assessment" (Julie B. Olson-Buchanan and Fritz Drasgow);…

  11. Prognostic Contribution of Exercise Capacity, Heart Rate Recovery, Chronotropic Incompetence, and Myocardial Perfusion Single-Photon Emission Computerized Tomography in the Prediction of Cardiac Death and All-Cause Mortality.

    PubMed

    Arbit, Boris; Azarbal, Babak; Hayes, Sean W; Gransar, Heidi; Germano, Guido; Friedman, John D; Thomson, Louise; Berman, Daniel S

    2015-12-01

    Chronotropic incompetence, measured by the percentage (%) of heart rate (HR) reserve achieved (%HR reserve), abnormal HR recovery, reduced exercise capacity (EC), and myocardial perfusion single-photon emission computerized tomography (SPECT MPS) abnormalities are known predictors of all-cause mortality (ACM) and cardiac death (CD). The aim of this study was to determine if EC, %HR reserve, and HR recovery add incremental value to MPS in the prediction of ACM and CD. A total of 11,218 patients without valvular disease and not on β blockers underwent symptom-limited exercise MPS. %HR reserve was (peak HR - rest HR)/(220 - age - rest HR) × 100, with %HR reserve <80 defined as low. HR recovery was peak HR - recovery HR. An HR recovery <22 beats/min at 2 minutes after peak exercise was considered abnormal. Poor EC was defined as exercise duration ≤6 minutes (7 metabolic equivalents). Summed stress scores (SSSs) were calculated using a 20-segment, 5-point MPS model. Statistical analysis was performed using Cox regression models. There were 445 deaths (148 CD) during a mean follow-up of 3.2 ± 2.5 years. In multivariate analysis, the independent predictors of ACM were age, χ(2) = 154.81; EC, χ(2) = 74.00; SSS, χ(2) = 32.99; %HR reserve, χ(2) = 24.74; abnormal electrocardiogram at rest, χ(2) = 23.13; HR recovery, χ(2) = 18.45; diabetes, χ(2) = 17.75; and previous coronary artery disease, χ(2) = 11.85 (p ≤0.0006). The independent predictors of CD were SSS, χ(2) = 54.25; EC, χ(2) = 49.34; age, χ(2) = 46.45; abnormal electrocardiogram at rest, χ(2) = 30.60; previous coronary artery disease, χ(2) = 20.69; Duke treadmill score, χ(2) = 19.50; %HR reserve, χ(2) = 11.43; diabetes, χ(2) = 10.23 (all p ≤0.0014); and HR recovery, χ(2) = 5.30 (p = 0.0214). The exercise variables showed increases in Harrell's C static and net improvement reclassification, with EC showing the strongest incremental improvement in predicting ACM and CD (respective C-index 76

  12. [Patient dose optimization in pediatric computerized tomography].

    PubMed

    Verdun, F R; Schnyder, P; Gutièrrez, D; Gudinchet, F

    2006-07-12

    The development of CT applications might become a public health problem if no effort is made on the justification and the optimisation of the examinations. This paper presents some hints to assure that the risk-benefit compromise remains in favour of the patient, especially when one deals with the examinations of young patients. In this context a particular attention has to be made on the justification of the examination. When performing the acquisition one needs to optimise the extension of the volume investigated together with the number of acquisition sequences used. Finally, the use of automatic exposure systems, now available on all the units, and the use of the Diagnostic Reference Levels (DRL) should allow help radiologists to control the exposure of their patients.

  13. Computerized Construction Planning

    ERIC Educational Resources Information Center

    Moucka, Jan; Piskova, Vera

    1971-01-01

    Two Czechoslovakian architects describe how they scheduled construction projects on a statewide scale by computerizing the priority for projects, the resource capacity, the time coordination, and the construction schedules. (Author)

  14. Computerized Interactive Harness Engineering

    NASA Technical Reports Server (NTRS)

    Billitti, J. W.

    1985-01-01

    Computerized interactive harness engineering program inexpensive, interactive system for learning and using engineering approach to interconnection systems. Basically data-base system that stores information as files of individual connectors and handles wiring information in circuit groups stored as records.

  15. Photochemistry of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Nagy, Andrew F.

    1987-01-01

    The dominant photochemical reactions taking place in the ionospheres of Venus, Saturn, and Comet P/Halley are presented. It is shown that the differences in the ionospheres of these celestial bodies result from the different chemistry, energetics, and dynamics of the respective atmospheres. The role of photochemistry in the formation of the individual ionospheres is discussed.

  16. Computerized Ultrasound Risk Evaluation (CURE): First Clinical Results

    NASA Astrophysics Data System (ADS)

    Duric, N.; Littrup, P.; Rama, O.; Holsapple, E.

    The Karmanos Cancer Institute has developed an ultrasound (US) tomography system, known as Computerized Ultrasound Risk Evaluation (CURE), for detecting and evaluating breast cancer, with the eventual goal of providing improved differentiation of benign masses from cancer. We report on our first clinical findings with CURE.

  17. IONOSATS - ionospheric satellite cluster

    NASA Astrophysics Data System (ADS)

    Ivchenko, V.; Korepanov, V.; Lizunov, G.; Yampolsky, Yu.

    The IONOSATS project is proposed by National Space Agency of Ukraine for First European Space Program as well as for Space Weather SW Program as a part of GMES As it commonly accepted Space Weather means the changes of the conditions on the Sun in solar wind magnetosphere and ionosphere which may affect the operation and reliability of on-board and ground technological systems and threaten human health In this chain ionosphere is specific and integral part of SW formation Moreover namely in the ionosphere main part of the energy absorption of Sun-activated sporadic corpuscular and radiation fluxes takes places Short-wave part of solar flares radiation ultraviolet and roentgen dissipates mostly at ionospheric regions E and D heights triggering ionospheric storms The corpuscular fluxes energy absorption occurs in the polar parts of the ionosphere as a result in the auroral regions the current system of aurora causes the neutral atmosphere heating at the E and F regions heights In its turn this produces generation of a set of plasma instabilities including equator-spread large-scale ionospheric disturbances and electromagnetic waves emissions In other words the excitation of ionosphere by falling corpuscular and radiation fluxes produces its luminescence in wide frequency band - from radio waves till ultraviolet - and by this ionosphere works as an efficient screen or SW indicator The proposed project goal is long-term spatial-temporal monitoring of main field and plasma parameters of ionosphere with aim to further develop fundamental conceptions

  18. Psychosocial Communication and Computerization.

    ERIC Educational Resources Information Center

    Bradley, Gunilla; And Others

    1993-01-01

    Discusses the effect of computerization of the work environment on psychosocial communication. The RAM program, developed at Stockholm University to explore the effect of computers on the structure of organizations and the psychosocial work environment, is described; theoretical models are explained; and the future use of knowledge-based systems…

  19. The History Computerization Project.

    ERIC Educational Resources Information Center

    Clark, David L.

    1992-01-01

    Description of the History Computerization Project, which is being developed for the exchange of information between researchers, librarians, archivists, museum curators, preservation groups, and historical societies, focuses on workshops that teach the use of computer database management for historical cataloging and research. (LRW)

  20. Computerizing the Library.

    ERIC Educational Resources Information Center

    Chan, Jeanie; Whelan, Errol

    1988-01-01

    Discusses the development of a computerized high school library which uses CD-ROM optical storage systems. Describes hardware and software, setting up the system, preparing the online catalog, teaching information retrieval skills, and project evaluation. Notes prices of CD-ROM disks and equipment purchased. 4 references. (SV)

  1. Seven Myths of Computerism.

    ERIC Educational Resources Information Center

    Yeaman, Andrew R. J.

    1992-01-01

    Discussion of computerism (i.e., blind faith in the inherent good of computers) focuses on seven myths about computer anxiety, including the relationship between computer use and math skills; fear of breaking computers; the need for keyboarding skills; and gender differences. An annotated bibliography of 21 sources of further information is…

  2. Computerized Language Analysis.

    ERIC Educational Resources Information Center

    Ray, Steven

    1985-01-01

    The article describes a computerized language analysis system that produces a detailed description and summary statistics to track language growth within student populations. This microcomputer-based language assessment system simplifies identification of deficits in productive language, enabling the teacher or clinician to spend more time…

  3. Computerized Drug Information Services

    ERIC Educational Resources Information Center

    And Others; Smith, Daniel R.

    1972-01-01

    To compare computerized services in chemistry, pharmacology, toxicology, and clinical medicine of pharmaceutical interest, equivalent profiles were run on magnetic tape files of CA-Condensates," CBAC," Excerpta Medica," MEDLARS" and Ringdoc." The results are tabulated for overlap of services, relative speed of citing references, and unique…

  4. LUNGx Challenge for computerized lung nodule classification.

    PubMed

    Armato, Samuel G; Drukker, Karen; Li, Feng; Hadjiiski, Lubomir; Tourassi, Georgia D; Engelmann, Roger M; Giger, Maryellen L; Redmond, George; Farahani, Keyvan; Kirby, Justin S; Clarke, Laurence P

    2016-10-01

    The purpose of this work is to describe the LUNGx Challenge for the computerized classification of lung nodules on diagnostic computed tomography (CT) scans as benign or malignant and report the performance of participants' computerized methods along with that of six radiologists who participated in an observer study performing the same Challenge task on the same dataset. The Challenge provided sets of calibration and testing scans, established a performance assessment process, and created an infrastructure for case dissemination and result submission. Ten groups applied their own methods to 73 lung nodules (37 benign and 36 malignant) that were selected to achieve approximate size matching between the two cohorts. Area under the receiver operating characteristic curve (AUC) values for these methods ranged from 0.50 to 0.68; only three methods performed statistically better than random guessing. The radiologists' AUC values ranged from 0.70 to 0.85; three radiologists performed statistically better than the best-performing computer method. The LUNGx Challenge compared the performance of computerized methods in the task of differentiating benign from malignant lung nodules on CT scans, placed in the context of the performance of radiologists on the same task. The continued public availability of the Challenge cases will provide a valuable resource for the medical imaging research community.

  5. LUNGx Challenge for computerized lung nodule classification

    SciTech Connect

    Armato, Samuel G.; Drukker, Karen; Li, Feng; Hadjiiski, Lubomir; Tourassi, Georgia D.; Engelmann, Roger M.; Giger, Maryellen L.; Redmond, George; Farahani, Keyvan; Kirby, Justin S.; Clarke, Laurence P.

    2016-12-19

    The purpose of this work is to describe the LUNGx Challenge for the computerized classification of lung nodules on diagnostic computed tomography (CT) scans as benign or malignant and report the performance of participants’ computerized methods along with that of six radiologists who participated in an observer study performing the same Challenge task on the same dataset. The Challenge provided sets of calibration and testing scans, established a performance assessment process, and created an infrastructure for case dissemination and result submission. We present ten groups that applied their own methods to 73 lung nodules (37 benign and 36 malignant) that were selected to achieve approximate size matching between the two cohorts. Area under the receiver operating characteristic curve (AUC) values for these methods ranged from 0.50 to 0.68; only three methods performed statistically better than random guessing. The radiologists’ AUC values ranged from 0.70 to 0.85; three radiologists performed statistically better than the best-performing computer method. The LUNGx Challenge compared the performance of computerized methods in the task of differentiating benign from malignant lung nodules on CT scans, placed in the context of the performance of radiologists on the same task. Lastly, the continued public availability of the Challenge cases will provide a valuable resource for the medical imaging research community.

  6. LUNGx Challenge for computerized lung nodule classification

    DOE PAGES

    Armato, Samuel G.; Drukker, Karen; Li, Feng; ...

    2016-12-19

    The purpose of this work is to describe the LUNGx Challenge for the computerized classification of lung nodules on diagnostic computed tomography (CT) scans as benign or malignant and report the performance of participants’ computerized methods along with that of six radiologists who participated in an observer study performing the same Challenge task on the same dataset. The Challenge provided sets of calibration and testing scans, established a performance assessment process, and created an infrastructure for case dissemination and result submission. We present ten groups that applied their own methods to 73 lung nodules (37 benign and 36 malignant) thatmore » were selected to achieve approximate size matching between the two cohorts. Area under the receiver operating characteristic curve (AUC) values for these methods ranged from 0.50 to 0.68; only three methods performed statistically better than random guessing. The radiologists’ AUC values ranged from 0.70 to 0.85; three radiologists performed statistically better than the best-performing computer method. The LUNGx Challenge compared the performance of computerized methods in the task of differentiating benign from malignant lung nodules on CT scans, placed in the context of the performance of radiologists on the same task. Lastly, the continued public availability of the Challenge cases will provide a valuable resource for the medical imaging research community.« less

  7. Computerized operating procedures

    SciTech Connect

    Ness, E.; Teigen, J.

    1994-12-31

    A number of observed and potential problems in the nuclear industry are related to the quality of operating procedures. Many of the problems identified in operating procedure preparation, implementation, and maintenance have a technical nature, which can be directly addressed by developing computerized procedure handling tools. The Halden Reactor Project (HRP) of the Organization for Economic Cooperation and Development has since 1985 performed research work within this field. A product of this effort is the development of a second version of the computerized operation manuals (COPMA) system. This paper summarizes the most important characteristics of the COPMA-II system and discusses some of the experiences in using a system like COPMA-II.

  8. Saturn ionosphere - Theoretical interpretation

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Waite, J. H.

    1981-08-01

    Voyager 1 high latitude and Pioneer 11 equatorial ionospheric structure indicate a solar EUV-controlled ionosphere with a possible molecular ion in the topside. Vibrationally excited H2 in the high latitudes may be an important loss mechanism. Dynamical effects are expected to be important for determining the peak density and its location.

  9. Magnetosphere-ionosphere interactions

    NASA Technical Reports Server (NTRS)

    Vondrak, R. R.; Chiu, Y. T.; Evans, D. S.; Patterson, V. G.; Romick, G. J.; Stasiewicz, K.

    1979-01-01

    The present understanding of magnetosphere ionosphere interactions is described, and present and future predictive capabilities are assessed. Ionospheric features directly coupled to the magnetosphere to a significant degree are considered, with emphasis given to those phenomena of major interest to forecasters and users.

  10. International reference ionosphere 1990

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Rawer, K.; Bossy, L.; Kutiev, I.; Oyama, K.-I.; Leitinger, R.; Kazimirovsky, E.

    1990-01-01

    The International Reference Ionosphere 1990 (IRI-90) is described. IRI described monthly averages of the electron density, electron temperature, ion temperature, and ion composition in the altitude range from 50 to 1000 km for magnetically quiet conditions in the non-auroral ionosphere. The most important improvements and new developments are summarized.

  11. IONOSAT Ionospheric satellite cluster

    NASA Astrophysics Data System (ADS)

    Korepanov, V.; Lizunov, G.; Fedorov, O.; Yampolsky, Yu.; Ivchenko, V.

    2008-11-01

    The IONOSAT project (from IONOspheric SATellites) is proposed by National Space Agency of Ukraine for First European Space Program as a part of Space Weather (SW) Program. As it is commonly accepted, Space Weather means the changes of the conditions on the Sun, in solar wind, magnetosphere and ionosphere which may affect the operation and reliability of on-board and ground technological systems and threaten human health. In this chain ionosphere is specific and integral part of SW formation. Moreover, namely in the ionosphere main part of the energy absorption of Sun-activated sporadic corpuscular and radiation fluxes takes places. The excitation of ionosphere by falling fluxes produces its "luminescence" in wide frequency band - from ULF waves till ultraviolet - and by this ionosphere works as an efficient "screen" or SW indicator. A goal of the proposed project is long-term spatial-temporal monitoring of main field and plasma parameters of ionosphere with aim to further develop fundamental conceptions of solar-terrestrial connections physics, nowcasting and forecast of SW, and diagnostics of natural and technogenic hazards with the help of scientific payload installed on-board a cluster of 3 low-Earth orbit (LEO) microsatellites (tentative launch date - 2012 year). The state of the project proposal and realization plans are discussed.

  12. Computerized procedures system

    DOEpatents

    Lipner, Melvin H.; Mundy, Roger A.; Franusich, Michael D.

    2010-10-12

    An online data driven computerized procedures system that guides an operator through a complex process facility's operating procedures. The system monitors plant data, processes the data and then, based upon this processing, presents the status of the current procedure step and/or substep to the operator. The system supports multiple users and a single procedure definition supports several interface formats that can be tailored to the individual user. Layered security controls access privileges and revisions are version controlled. The procedures run on a server that is platform independent of the user workstations that the server interfaces with and the user interface supports diverse procedural views.

  13. Computerized Numerical Control Curriculum Guide.

    ERIC Educational Resources Information Center

    Reneau, Fred; And Others

    This guide is intended for use in a course in programming and operating a computerized numerical control system. Addressed in the course are various aspects of programming and planning, setting up, and operating machines with computerized numerical control, including selecting manual or computer-assigned programs and matching them with…

  14. Computed tomography status

    SciTech Connect

    Hansche, B.D.

    1983-01-01

    Computed tomography (CT) is a relatively new radiographic technique which has become widely used in the medical field, where it is better known as computerized axial tomographic (CAT) scanning. This technique is also being adopted by the industrial radiographic community, although the greater range of densities, variation in samples sizes, plus possible requirement for finer resolution make it difficult to duplicate the excellent results that the medical scanners have achieved.

  15. Computed Tomography Status

    DOE R&D Accomplishments Database

    Hansche, B. D.

    1983-01-01

    Computed tomography (CT) is a relatively new radiographic technique which has become widely used in the medical field, where it is better known as computerized axial tomographic (CAT) scanning. This technique is also being adopted by the industrial radiographic community, although the greater range of densities, variation in samples sizes, plus possible requirement for finer resolution make it difficult to duplicate the excellent results that the medical scanners have achieved.

  16. Ionospheric plasma cloud dynamics

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measurements of the thermospheric neutral wind and ionospheric drift made at Eglin AFB, Florida and Kwajalein Atoll are discussed. The neutral wind measurements at Eglin had little variation over a period of four years for moderate magnetic activity (Kp 4); the ionospheric drifts are small. Evidence is presented that indicates that increased magnetic activity has a significant effect on the neutral wind magnitude and direction at this midlatitude station. The neutral wind at dusk near the equator is generally small although in one case out of seven it was significantly larger. It is described how observations of large barium releases can be used to infer the degree of electrodynamic coupling of ion clouds to the background ionosphere. Evidence is presented that indicates that large barium releases are coupled to the conjugate ionosphere at midlatitudes.

  17. Modeling the martian ionosphere

    NASA Astrophysics Data System (ADS)

    Matta, Majd Mayyasi

    The accessibility of the Martian atmosphere to spacecraft provides an opportunity to study an ionosphere that differs from our own. Yet, despite the half century of measurements made at Mars, the current state of the neutral atmosphere and its embedded plasma (ionosphere) remains largely uncharacterized. In situ measurements of the neutral and ionized constituents versus height exist only from the two Viking Landers from the 1970s. Subsequent satellite and remote sensing data offer sparse global coverage of the ionosphere. Thermal characteristics of the plasma environment are not well understood. Patchy crustal magnetic fields interact with the Martian plasma in a way that has not been fully studied. Hence, investigating the coupled compositional, thermal and crustal-field-affected properties of the ionosphere can provide insight into comparative systems at Earth and other planets, as well as to atypical processes such as the solar wind interaction with topside ionospheric plasma and associated pathways to escape. Ionospheric models are fundamental tools that advance our understanding of complex plasma systems. A pre-existing one-dimensional model of the Martian ionosphere has been upgraded to include more comprehensive chemistry and transport physics. This new BU Mars Ionosphere Model has been used to study the composition, thermal structure and dynamics of the Martian ionosphere. Specifically: the sensitivity of the abundance of ions to neutral atmospheric composition has been quantified, diurnal patterns of ion and electron temperatures have been derived self-consistently using supra-thermal electron heating rates, and the behavior of ionospheric plasma in crustal field regions was simulated by constructing a two-dimensional ionospheric model. Results from these studies were compared with measurements and show that (1) ion composition at Mars is highly sensitive to the abundance of neutral molecular and atomic hydrogen, (2) lighter ions heat up more efficiently

  18. High Latitude Ionospheric Structures

    DTIC Science & Technology

    2006-06-01

    CADI are a mixture of ionograms and ‘fixed’ frequency. The fixed frequency is chosen so as to get continuous ionospheric echoes throughout the day...because of the very dynamic ionospheric behaviour at high latitudes. Ionograms (interleaved with the fixed frequency observations) are at less frequent...intervals, typically each minute. In general it is easier to identify structures on the fixed frequency recordings. Ionograms are mainly useful when

  19. Dayside Ionospheric Superfountain

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Verkhoglyadova, Olga P.; Mannucci, Anthony J.

    2010-01-01

    The Dayside Ionospheric Super-fountain modified SAMI2 code predicts the uplift, given storm-time electric fields, of the dayside near-equatorial ionosphere to heights of over 800 kilometers during magnetic storm intervals. This software is a simple 2D code developed over many years at the Naval Research Laboratory, and has importance relating to accuracy of GPS positioning, and for satellite drag.

  20. Tsunami Ionospheric warning and Ionospheric seismology

    NASA Astrophysics Data System (ADS)

    Lognonne, Philippe; Rolland, Lucie; Rakoto, Virgile; Coisson, Pierdavide; Occhipinti, Giovanni; Larmat, Carene; Walwer, Damien; Astafyeva, Elvira; Hebert, Helene; Okal, Emile; Makela, Jonathan

    2014-05-01

    The last decade demonstrated that seismic waves and tsunamis are coupled to the ionosphere. Observations of Total Electron Content (TEC) and airglow perturbations of unique quality and amplitude were made during the Tohoku, 2011 giant Japan quake, and observations of much lower tsunamis down to a few cm in sea uplift are now routinely done, including for the Kuril 2006, Samoa 2009, Chili 2010, Haida Gwai 2012 tsunamis. This new branch of seismology is now mature enough to tackle the new challenge associated to the inversion of these data, with either the goal to provide from these data maps or profile of the earth surface vertical displacement (and therefore crucial information for tsunami warning system) or inversion, with ground and ionospheric data set, of the various parameters (atmospheric sound speed, viscosity, collision frequencies) controlling the coupling between the surface, lower atmosphere and the ionosphere. We first present the state of the art in the modeling of the tsunami-atmospheric coupling, including in terms of slight perturbation in the tsunami phase and group velocity and dependance of the coupling strength with local time, ocean depth and season. We then show the confrontation of modelled signals with observations. For tsunami, this is made with the different type of measurement having proven ionospheric tsunami detection over the last 5 years (ground and space GPS, Airglow), while we focus on GPS and GOCE observation for seismic waves. These observation systems allowed to track the propagation of the signal from the ground (with GPS and seismometers) to the neutral atmosphere (with infrasound sensors and GOCE drag measurement) to the ionosphere (with GPS TEC and airglow among other ionospheric sounding techniques). Modelling with different techniques (normal modes, spectral element methods, finite differences) are used and shown. While the fits of the waveform are generally very good, we analyse the differences and draw direction of future

  1. Computerized training management system

    DOEpatents

    Rice, H.B.; McNair, R.C.; White, K.; Maugeri, T.

    1998-08-04

    A Computerized Training Management System (CTMS) is disclosed for providing a procedurally defined process that is employed to develop accreditable performance based training programs for job classifications that are sensitive to documented regulations and technical information. CTMS is a database that links information needed to maintain a five-phase approach to training-analysis, design, development, implementation, and evaluation independent of training program design. CTMS is designed using R-Base{trademark}, an-SQL compliant software platform. Information is logically entered and linked in CTMS. Each task is linked directly to a performance objective, which, in turn, is linked directly to a learning objective; then, each enabling objective is linked to its respective test items. In addition, tasks, performance objectives, enabling objectives, and test items are linked to their associated reference documents. CTMS keeps all information up to date since it automatically sorts, files and links all data; CTMS includes key word and reference document searches. 18 figs.

  2. Computerized training management system

    DOEpatents

    Rice, Harold B.; McNair, Robert C.; White, Kenneth; Maugeri, Terry

    1998-08-04

    A Computerized Training Management System (CTMS) for providing a procedurally defined process that is employed to develop accreditable performance based training programs for job classifications that are sensitive to documented regulations and technical information. CTMS is a database that links information needed to maintain a five-phase approach to training-analysis, design, development, implementation, and evaluation independent of training program design. CTMS is designed using R-Base.RTM., an-SQL compliant software platform. Information is logically entered and linked in CTMS. Each task is linked directly to a performance objective, which, in turn, is linked directly to a learning objective; then, each enabling objective is linked to its respective test items. In addition, tasks, performance objectives, enabling objectives, and test items are linked to their associated reference documents. CTMS keeps all information up to date since it automatically sorts, files and links all data; CTMS includes key word and reference document searches.

  3. Computerizing natural history collections.

    PubMed

    Sunderland, Mary E

    2013-09-01

    Computers are ubiquitous in the life sciences and are associated with many of the practical and conceptual changes that characterize biology's twentieth-century transformation. Yet comparatively little has been written about how scientists use computers. Despite this relative lack of scholarly attention, the claim that computers revolutionized the life sciences by making the impossible possible is widespread, and relatively unchallenged. How did the introduction of computers into research programs shape scientific practice? The Museum of Vertebrate Zoology (MVZ) at the University of California, Berkeley provides a tractable way into this under-examined question because it is possible to follow the computerization of data in the context of long-term research programs.

  4. Computerized molecular modeling of carbohydrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Computerized molecular modleing continues to increase in capability and applicability to carbohydrates. This chapter covers nomenclature and conformational aspects of carbohydrates, perhaps of greater use to carbohydrate-inexperienced computational chemists. Its comments on various methods and studi...

  5. Computerized international geothermal information systems

    SciTech Connect

    Phillips, S.L.; Lawrence, J.D.; Lepman, S.R.

    1980-03-01

    The computerized international geothermal energy information system is reviewed. The review covers establishment of the Italy - United States linked data centers by the NATO Committee on Challenges of Modern Society, through a bilateral agreement, and up to the present time. The result of the information exchange project is given as the bibliographic and numerical data available from the data centers. Recommendations for the exchange of computerized geothermal information at the international level are discussed.

  6. Report from ionospheric science

    NASA Technical Reports Server (NTRS)

    Raitt, W. J.; Banks, Peter M.; Nagy, A. F.; Chappell, C. R.

    1989-01-01

    The general strategy to advance knowledge of the ionospheric component of the solar terrestrial system should consist of a three pronged attack on the problem. Ionospheric models should be refined by utilization of existing and new data bases. The data generated in the future should emphasize spatial and temporal gradients and their relation to other events in the solar terrestrial system. In parallel with the improvement in modeling, it will be necessary to initiate a program of advanced instrument development. In particular, emphasis should be placed on the area of improved imaging techniques. The third general activity to be supported should be active experiments related to a better understanding of the basic physics of interactions occurring in the ionospheric environment. These strategies are briefly discussed.

  7. International Reference Ionosphere -2010

    NASA Astrophysics Data System (ADS)

    Bilitza, Dieter; Reinisch, Bodo

    The International Reference Ionosphere 2010 includes several important improvements and ad-ditions. This presentation introduces these changes and discusses their benefits. The electron and ion density profiles for the bottomside ionosphere will be significantly improved by using more ionosonde data as well as photochemical considerations. As an additional lower iono-sphere parameter IRI-2010 will include the transition height from molecular to cluster ions. At the F2 peak Neural Net models for the peak density and the propagation factor M3000F2, which is related to the F2 peak height, are introduced as new options. At high latitudes the model will benefit from the introduction of auroral oval boundaries and their variation with magnetic activity. Regarding the electron temperature, IRI-2010 now models variations with solar activity. The homepage for the IRI project is at http://IRI.gsfc.nasa.gov/.

  8. Ionospheric topside sounding.

    PubMed

    Calvert, W

    1966-10-14

    Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and

  9. Characterizing Extreme Ionospheric Storms

    NASA Astrophysics Data System (ADS)

    Sparks, L.; Komjathy, A.; Altshuler, E.

    2011-12-01

    Ionospheric storms consist of disturbances of the upper atmosphere that generate regions of enhanced electron density typically lasting several hours. Depending upon the storm magnitude, gradients in electron density can sometimes become large and highly localized. The existence of such localized, dense irregularities is a major source of positioning error for users of the Global Positioning System (GPS). Consequently, satellite-based augmentation systems have been implemented to improve the accuracy and to ensure the integrity of user position estimates derived from GPS measurements. Large-scale irregularities generally do not pose a serious threat to estimate integrity as they can be readily detected by such systems. Of greater concern, however, are highly localized irregularities that interfere with the propagation of a signal detected by a user measurement but are poorly sampled by the receivers in the system network. The most challenging conditions have been found to arise following disturbances of large magnitude that occur only rarely over the course of a solar cycle. These extremely disturbed conditions exhibit behavior distinct from moderately disturbed conditions and, hence, have been designated "extreme storms". In this paper we examine and compare the behavior of the extreme ionospheric storms of solar cycle 23 (or, more precisely, extreme storms occurring between January 1, 2000, and December 31, 2008), as represented in maps of vertical total electron content. To identify these storms, we present a robust means of quantifying the regional magnitude of an ionospheric storm. Ionospheric storms are observed frequently to occur in conjunction with magnetic storms, i.e., periods of geophysical activity as measured by magnetometers. While various geomagnetic indices, such as the disturbance storm time (Dst) and the planetary Kp index, have long been used to rank the magnitudes of distinct magnetic storms, no comparable, generally recognized index exists for

  10. Optical Ionospheric Mapping.

    DTIC Science & Technology

    1983-12-15

    0325 I OPTICAL IONOSPHERIC MAPPING Robert H. Eather KEO Consultants 00 27 Irving St. Lfl Brookline Massachusetts 02146 I J CI Final Report U July 28...Irving St. Brookline Ma. 02146 464306AL It. CONTROLLING OFFICE NAME AND ADDRESS 12 REPORT DA ,F Air Force Geophysics Laboratory December 15, 1983

  11. Global Ionospheric Processes

    DTIC Science & Technology

    2008-10-29

    the all-sky imager during the September 2008 Kwajalein C/NOFS campaign 5 3. Ionograms and optical images from conjugate hemispheres during...conjugacy of large-scale ionospheric structures. 6 Figure 3. Ionograms and optical images from conjugate hemispheres during the COPEX experiment

  12. RF Heating the Ionosphere,

    DTIC Science & Technology

    1987-08-01

    Kopka, Geophys. Res. Lett. 11, 523 (1984). 4. H.C. Carlson, V.B. Wickwar, and G. P. Mantas, J. Atmos. and Terr. Phys. 44, 1089 (1982) 5. E. Mjolhus and T...Ionosphere," G. J. Morales, presented at the Seventh APS Topical Conference, Kissimmee, Florida, May 4-6, 1987. PPG- 1089 "Self-Consistent Modification

  13. Radiotomographic observations of corpuscular ionization in the ionosphere

    NASA Astrophysics Data System (ADS)

    Andreeva, E. S.; Kunitsyn, V. E.; Tereshchenko, E. D.; Krysanov, B. Yu.; Nazarenko, M. O.

    2012-04-01

    Along with the antisunward cross-polar convection of the ionospheric plasma and the field-aligned electric currents, the corpuscular fluxes play an important role in the magnetosphere-ionosphere coupling. Being more tightly coupled with the magnetosphere, the subauroral and auroral ionosphere noticeably differs from the midlatitude ionosphere. It experiences much stronger and faster variations in space and time. The particle fluxes and the electric fields of magnetospheric origin penetrate into the ionosphere and substantially affect the production, loss and transport of charged particles. The rate of ionization in the midlatitude ionosphere is controlled almost solely by the X-ray and UV/EUV solar radiation, whereas in high latitudes the fluxes of particles precipitating from the magnetosphere are significant sources of ionization. Moreover, they are probably the single source during the polar night. Typically, the contribution of the magnetospheric corpuscular fluxes into the ionization is small compared to the contribution of electromagnetic radiation; however, during the geomagnetic storms, it may prove significant, especially if these fluxes are sufficiently strong and act in the nighttime when the solar electromagnetic radiation is absent. The present work is devoted to radio tomographic imaging of the ionospheric effects of particle precipitation using the data from low-orbital navigational satellite systems. The ionospheric radio tomography is actively developed during the past two decades. It provides images of the 2D distribution of electron density in the vertical plane (latitude-altitude cross-sections) (averaged over an interval of 10-15 minutes) for the spatial sector covering several thousand kilometers. The horizontal and vertical resolution of the RT method is 20-30 km and 30-40 km, respectively. In the present work, the particle precipitation events are identified from the particle flux measurements onboard DMSP satellites. We present and discuss

  14. Chemistry in the Thermosphere and Ionosphere.

    ERIC Educational Resources Information Center

    Roble, Raymond G.

    1986-01-01

    An informative review which summarizes information about chemical reactions in the thermosphere and ionosphere. Topics include thermal structure, ultraviolet radiation, ionospheric photochemistry, thermospheric photochemistry, chemical heating, thermospheric circulation, auroral processes and ionospheric interactions. Provides suggested followup…

  15. Computerized proof techniques for undergraduates

    NASA Astrophysics Data System (ADS)

    Smith, Christopher J.; Tefera, Akalu; Zeleke, Aklilu

    2012-12-01

    The use of computer algebra systems such as Maple and Mathematica is becoming increasingly important and widespread in mathematics learning, teaching and research. In this article, we present computerized proof techniques of Gosper, Wilf-Zeilberger and Zeilberger that can be used for enhancing the teaching and learning of topics in discrete mathematics. We demonstrate by examples how one can use these computerized proof techniques to raise students' interests in the discovery and proof of mathematical identities and enhance their problem-solving skills.

  16. Thermal structure of the ionosphere

    NASA Technical Reports Server (NTRS)

    Brace, L. H.

    1975-01-01

    A brief review is presented of recent progress made toward gaining a more complete understanding of the thermal structure of the ionosphere. Important heat sources for the ionosphere are described, including the solar EUV flux, midlatitude interactions between the magnetosphere and ionosphere, electric-field enhancements at high latitudes, particle precipitation in the auroral oval, and polar-wind heating. Discrepancies between electron-temperature measurements by satellite probes and incoherent-backscatter techniques are noted.

  17. Planetary waves in rotating ionosphere

    SciTech Connect

    Khantadze, A. G.; Jandieri, V. G.; Jandieri, G. V.

    2008-06-15

    The problem of propagation of ultralong planetary waves in the Earth's upper atmosphere is considered. A new exact solution to the MHD equations for the ionosphere is obtained in spherical coordinates with allowance for the geomagnetic field and Earth's rotation. A general dispersion relation is derived for planetary waves in the ionospheric E and F regions, and the characteristic features of their propagation in a weakly ionized ionospheric plasma are discussed.

  18. Ionospheric disturbance dynamo

    SciTech Connect

    Blanc, M.; Richmond, A.D.

    1980-04-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes.

  19. Arkansas' Curriculum Guide. Competency Based Computerized Accounting.

    ERIC Educational Resources Information Center

    Arkansas State Dept. of Education, Little Rock. Div. of Vocational, Technical and Adult Education.

    This guide contains the essential parts of a total curriculum for a one-year secondary-level course in computerized accounting. Addressed in the individual sections of the guide are the following topics: the complete accounting cycle, computer operations for accounting, computerized accounting and general ledgers, computerized accounts payable,…

  20. Computerizing a High School Library.

    ERIC Educational Resources Information Center

    Whelan, Errol A.; Chan, Jeanie

    1988-01-01

    Describes how the Swift-Current Comprehensive High School (Saskatchewan) library computerized to create an online catalog, provide access to remote databases, and acquire CD-ROM reference systems. Objectives, hardware and software selection and costs, implementation, and evaluation are discussed. Seven references are listed, and a directory of…

  1. Computerized Proof Techniques for Undergraduates

    ERIC Educational Resources Information Center

    Smith, Christopher J.; Tefera, Akalu; Zeleke, Aklilu

    2012-01-01

    The use of computer algebra systems such as Maple and Mathematica is becoming increasingly important and widespread in mathematics learning, teaching and research. In this article, we present computerized proof techniques of Gosper, Wilf-Zeilberger and Zeilberger that can be used for enhancing the teaching and learning of topics in discrete…

  2. Student Perceptions of Computerized Tests

    ERIC Educational Resources Information Center

    Pino-Silva, Juan

    2008-01-01

    The challenge to test small groups by means of microcomputers demands appropriate software design and sound test design. To comply with this demand, students' beliefs or perceptions on the advantages and disadvantages of a computerized test were tapped. Overall, self-reported advantages outnumbered disadvantages to a significant degree. This was…

  3. Computerized Adaptive Testing in Reading.

    ERIC Educational Resources Information Center

    Smittle, Pat

    1991-01-01

    Discusses the use of computerized placement testing at Santa Fe Community College to enable students needing only a short review of reading skills to exit early from a College Preparatory Reading Class (CPRC). Describes CPRC placement, structure, curriculum, and exit criteria; the Early Exit Reading Project; and project results. (DMM)

  4. Total Library Computerization for Windows.

    ERIC Educational Resources Information Center

    Combs, Joseph, Jr.

    1999-01-01

    Presents a general review of features of version 2.1 of Total Library Computerization (TLC) for Windows from On Point, Inc. Includes information about pricing, hardware and operating systems, modules/functions available, user interface, security, on-line catalog functions, circulation, cataloging, and documentation and online help. A table…

  5. Electron Density Profiles of the Topside Ionosphere

    NASA Technical Reports Server (NTRS)

    Huang, Xue-Qin; Reinsch, Bodo W.; Bilitza, Dieter; Benson, Robert F.

    2002-01-01

    The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from h,F2 to - 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms but most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis- status.htm1. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The TOPside Ionogram Scaler with True height algorithm TOPIST software developed for this task is successfully scaling - 70% of the ionograms. An <> is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle.

  6. Computed tomography in supratentorial hemangioblastoma.

    PubMed

    Romero, F J; Rovira, M; Ortega, A; Ibarra, B

    1984-01-01

    Supratentorial hemangioblastomas are rare. A 28-yr-old man with a solid tumor in the left temporal region is described. There was neither meningeal connection nor associated polycythemia or Von Hippel-Lindau disease. Contrast enhanced computerized tomography showed a hyperdense, homogeneous lesion and cerebral angiography demonstrated a nodular tumor blush. The microscopic appearance of the lesion is described with a review of previously reported cases.

  7. LOFAR as an ionospheric probe

    NASA Astrophysics Data System (ADS)

    Gaussiran, T. L., II; Bust, G. S.; Garner, T. W.

    2004-12-01

    At the Low-Frequency Array (LOFAR)(Planet. Space Sci. (2004) these proceedings) frequencies (HF/VHF), extraterrestrial radiation experiences substantial propagation delay as it passes through the ionosphere. The adaptive calibration technique to be employed by LOFAR will use signals from many known bright radio sources in the sky to estimate and remove the effects of this delay. This technique will operate along many simultaneous lines of sight for each of the stations. Measurements will be made on time scales of seconds or shorter, and with accuracies corresponding to path length variations of 1 cm or less. Tomographic techniques can be used to invert the thousands of changing and independent total electron content (TEC) measurements produced by LOFAR into three-dimensional electron density specifications above the array. These specifications will measure spatial and time scales significantly smaller and faster than anything currently available. These specifications will be used to investigate small-scale ionospheric irregularities, equatorial plasma structures, and ionospheric waves. In addition, LOFAR will improve the understanding of the solar drivers of the ionosphere by simultaneously measuring the solar radio bursts and the TEC. Finally, LOFAR, which will be situated to observed the galactic plane, will make continuous, high-resolution observations of the low-latitude ionosphere, an important but under-observed region. This paper will look at LOFAR as an ionospheric probe including comparisons to other ionospheric probes as well as possible methods of operation to optimize ionospheric measurements.

  8. A Medium-Scale Traveling Ionospheric Disturbance Observed from the Ground and from Space

    NASA Astrophysics Data System (ADS)

    Watts, C.; Dymond, K. F.; Coker, C.; Budzien, S.; Bernhardt, P.; Kassim, N.; Lazio, J.; Cohen, A.; Weiler, K.; Crane, P.; Clarke, T.; Rickard, L. J.; Taylor, G. B.; Schinzel, F.; Philstrom, Y.; Kuniyoshi, M.; Close, S.; Colestock, P.; Myers, S.; Datta, A.

    2008-12-01

    We report the first optical observations from space of a Medium-scale Traveling Ionospheric Disturbance (MSTID) of the Traveling Wave Packet type. The observations were made during the Combined Radio Interferometry and COSMIC Experiment in Tomography Campaign (CRICKET) held on September 15, 2007 at ~0830 UT. The experiment used a Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC also known as FORMOSAT-3) satellite in conjunction with the Very Large Array (VLA) radio telescope, located near Socorro, NM, to study the ionosphere from the global scale down to the regional scale while the TIDs propagated through it. The COSMIC/FORMOSAT-3 satellite measured the ionosphere both horizontally and with altitude while the VLA measured the directions and speed of the TIDs. Our observations provide new information on this poorly understood class of TID

  9. Computerized PET/CT image analysis in the evaluation of tumour response to therapy

    PubMed Central

    Wang, J; Zhang, H H

    2015-01-01

    Current cancer therapy strategy is mostly population based, however, there are large differences in tumour response among patients. It is therefore important for treating physicians to know individual tumour response. In recent years, many studies proposed the use of computerized positron emission tomography/CT image analysis in the evaluation of tumour response. Results showed that computerized analysis overcame some major limitations of current qualitative and semiquantitative analysis and led to improved accuracy. In this review, we summarize these studies in four steps of the analysis: image registration, tumour segmentation, image feature extraction and response evaluation. Future works are proposed and challenges described. PMID:25723599

  10. Clinical applications of computerized thermography

    NASA Technical Reports Server (NTRS)

    Anbar, Michael

    1988-01-01

    Computerized or digital, thermography is a rapidly growing diagnostic imaging modality. It has superseded contact thermography and analog imaging thermography which do not allow effective quantization. Medical applications of digital thermography can be classified in two groups: static and dynamic imaging. They can also be classified into macro thermography (resolution greater than 1 mm) and micro thermography (resolution less than 100 microns). Both modalities allow a thermal resolution of 0.1 C. The diagnostic power of images produced by any of these modalities can be augmented by the use of digital image enhancement and image recognition procedures. Computerized thermography has been applied in neurology, cardiovascular and plastic surgery, rehabilitation and sports medicine, psychiatry, dermatology and ophthalmology. Examples of these applications are shown and their scope and limitations are discussed.

  11. Dementia screening using computerized tests.

    PubMed

    Gualtieri, C Thomas

    2004-01-01

    The preclinical phase of dementia usually precedes the clinical diagnosis by many years. Early detection of dementing conditions during this preclinical phase may provide opportunities for treatments that may slow or mitigate progression. Conventional assessment tools usually can only detect dementia when the symptoms are overt and the disease is well-established. Computerized neurocognitive screening tools hold promise for diagnosing dementia in its early phase. The use, performance and development of several computerized screening tools to diagnose and monitor patients with pre-dementias and dementia are reviewed. The ability to accurately assess the presence of dementia clearly has direct relevance to insurance risk assessment and risk management. As new treatments appear, their role in clinical management of dementia patients will increase as well. In a future issue, the differential diagnosis of dementias related to the findings on these screening tools will be reviewed.

  12. Computerized accounting methods. Final report

    SciTech Connect

    1994-12-31

    This report summarizes the results of the research performed under the Task Order on computerized accounting methods in a period from 03 August to 31 December 1994. Computerized nuclear material accounting methods are analyzed and evaluated. Selected methods are implemented in a hardware-software complex developed as a prototype of the local network-based CONMIT system. This complex has been put into trial operation for test and evaluation of the selected methods at two selected ``Kurchatov Institute`` Russian Research Center (``KI`` RRC) nuclear facilities. Trial operation is carried out since the beginning of Initial Physical Inventory Taking in these facilities that was performed in November 1994. Operation of CONMIT prototype system was demonstrated in the middle of December 1994. Results of evaluation of CONMIT prototype system features and functioning under real operating conditions are considered. Conclusions are formulated on the ways of further development of computerized nuclear material accounting methods. The most important conclusion is a need to strengthen computer and information security features supported by the operating environment. Security provisions as well as other LANL Client/Server System approaches being developed by Los Alamos National Laboratory are recommended for selection of software and hardware components to be integrated into production version of CONMIT system for KI RRC.

  13. Soviet ionospheric modification research

    SciTech Connect

    Duncan, L.M.; Carlson, H.C.; Djuth, F.T.; Fejer, J.A.; Gerson, N.C.; Hagfors, T.; Newman, D.B. Jr.; Showen, R.L.

    1988-07-01

    Soviet published literature in ionospheric modification research by high-power radio waves is assessed, including an evaluation of its impact on and applications to future remote-sensing and telecommunications systems. This assessment is organized to place equal emphasis on basic research activities, designed to investigate both the natural geophysical environment and fundamental plasma physics; advanced research programs, such as those studying artificial ionization processes and oblique high-power radio propagation and practical system applications and operational limitations addressed by this research. The assessment indicates that the Soviet Union sustains high-quality theoretical and experimental research programs in ionospheric modification, with a breadth and level of effort greatly exceeding comparable Western programs. Soviet theoretical research tends to be analytical and intuitive, as compared to the Western emphasis on numerical simulation techniques. The Soviet experimental approach is less exploratory, designed principally to confirm theoretical predictions. Although limited by inferior diagnostic capabilities, Soviet experimental facilities are more numerous, operate on a more regular basis, and transmit radio wave powers exceeding those os Western facilities. Because of its broad scope of activity, the Soviet Union is better poised to quickly exploit new technologies and system applications as they are developed. This panel has identified several key areas of Soviet research activity and emerging technology that may offer long-term opportunities for remote-sensing and telecommunications advantages. However, we have found no results that suggest imminent breakthrough discoveries in these fields.

  14. Application of computerized tomography techniques to tokamak diagnostics

    NASA Astrophysics Data System (ADS)

    Stalker, K. T.; Kelly, J. G.

    1980-08-01

    A Coded Aperture Imaging System (CAIS) has been developed at Sandia National Laboratories to image the motion of nuclear fuel rods undergoing tests simulating accident conditions within a liquid metal fast breeder reactor. The tests require that the motion of the test fuel be monitored while it is immersed in a liquid sodium coolant precluding the use of normal optical means of imaging. However, using the fission gamma rays emitted by the fuel itself and coded aperture techniques, images with 1.5 mm radial and 5 mm axial resolution have been attained. Using an electro-optical detection system coupled to a high speed motion picture camera a time resolution of one millisecond can be achieved. This paper will discuss the application of coded aperture imaging to the problem, including the design of the one-dimensional Fresnel zone plate apertures used and the special problems arising from the reactor environment and use of high energy gamma ray photons to form the coded image. Also to be discussed will be the reconstruction techniques employed and the effect of various noise sources on system performance. Finally, some experimental results obtained using the system will be presented.

  15. Multiple-energy Techniques in Industrial Computerized Tomography

    DOE R&D Accomplishments Database

    Schneberk, D.; Martz, H.; Azevedo, S.

    1990-08-01

    Considerable effort is being applied to develop multiple-energy industrial CT techniques for materials characterization. Multiple-energy CT can provide reliable estimates of effective Z (Z{sub eff}), weight fraction, and rigorous calculations of absolute density, all at the spatial resolution of the scanner. Currently, a wide variety of techniques exist for CT scanners, but each has certain problems and limitations. Ultimately, the best multi-energy CT technique would combine the qualities of accuracy, reliability, and wide range of application, and would require the smallest number of additional measurements. We have developed techniques for calculating material properties of industrial objects that differ somewhat from currently used methods. In this paper, we present our methods for calculating Z{sub eff}, weight fraction, and density. We begin with the simplest case -- methods for multiple-energy CT using isotopic sources -- and proceed to multiple-energy work with x-ray machine sources. The methods discussed here are illustrated on CT scans of PBX-9502 high explosives, a lexan-aluminum phantom, and a cylinder of glass beads used in a preliminary study to determine if CT can resolve three phases: air, water, and a high-Z oil. In the CT project at LLNL, we have constructed several CT scanners of varying scanning geometries using {gamma}- and x-ray sources. In our research, we employed two of these scanners: pencil-beam CAT for CT data using isotopic sources and video-CAT equipped with an IRT micro-focal x-ray machine source.

  16. Advanced Ionospheric Sensing using GROUP-C and LITES aboard the ISS

    NASA Astrophysics Data System (ADS)

    Budzien, S. A.; Stephan, A. W.; Chakrabarti, S.; Finn, S. C.; Cook, T.; Powell, S. P.; O'Hanlon, B.; Bishop, R. L.

    2015-12-01

    The GPS Radio Occultation and Ultraviolet Photometer Co-located (GROUP-C) and Limb-imaging Ionospheric and Thermospheric Extreme-ultraviolet Spectrograph (LITES) experiments are manifested for flight aboard the International Space Station (ISS) in 2016 as part of the Space Test Program Houston #5 payload. The two experiments provide technical development and risk-reduction for future DoD space weather sensors suitable for ionospheric specification, space situational awareness, and data products for global ionosphere assimilative models. In addition, the combined instrument complement of these two experiments offers a unique opportunity to study structures of the nighttime ionosphere. GROUP-C includes an advanced GPS receiver providing ionospheric electron density profiles and scintillation measurements and a high-sensitivity far-ultraviolet photometer measuring horizontal ionospheric gradients. LITES is an imaging spectrograph that spans 60-140 nm and will obtain high-cadence limb profiles of the ionosphere and thermosphere from 150-350 km altitude. In the nighttime ionosphere, recombination of O+ and electrons produces optically thin emissions at 91.1 and 135.6 nm that can be used to tomographically reconstruct the two-dimensional plasma distribution in the orbital plane below ISS altitudes. Ionospheric irregularities, such as plasma bubbles and blobs, are transient features of the low and middle latitude ionosphere with important implications for operational systems. Irregularity structures have been studied primarily using ground-based systems, though some spaced-based remote and in-situ sensing has been performed. An ionospheric observatory aboard the ISS would provide new capability to study low- and mid-latitude ionospheric structures on a global scale. By combining for the first time high-sensitivity in-track photometry, vertical ionospheric airglow spectrographic imagery, and recent advancements in UV tomography, high-fidelity tomographic reconstruction of

  17. Characterising the Ionosphere (La caracterisation de l’ionosphere)

    DTIC Science & Technology

    2009-01-01

    Conclusions: Space weather storms have induced power cuts in the U.S.A., Europe and South Africa. Such events demand a regional and global risk analysis , a...region in particular. By the same token, the ionospheric plasma can escape to space (polar wind and auroral bulk upflows of ions with energy of a...ionospheric currents to which they connect. While most of the energy dissipated though Joule heating is associated with the large scale slowly varying

  18. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

    Liu Yu; Cao Jinxiang; Wang Jian; Zheng Zhe; Xu Liang; Du Yinchang

    2012-09-15

    A new approach for investigating ionosphere chemical depletion in the laboratory is introduced. Air glow discharge plasma closely resembling the ionosphere in both composition and chemical reactions is used as the artificially created ionosphere. The ionospheric depletion experiment is accomplished by releasing chemicals such as SF{sub 6}, CCl{sub 2}F{sub 2}, and CO{sub 2} into the model discharge. The evolution of the electron density is investigated by varying the plasma pressure and input power. It is found that the negative ion (SF{sub 6}{sup -}, CCl{sub 2}F{sub 2}{sup -}) intermediary species provide larger reduction of the electron density than the positive ion (CO{sub 2}{sup +}) intermediary species. The negative ion intermediary species are also more efficient in producing ionospheric holes because of their fast reaction rates. Airglow enhancement attributed to SF{sub 6} and CO{sub 2} releases agrees well with the published data. Compared to the traditional methods, the new scheme is simpler to use, both in the release of chemicals and in the electron density measurements. It is therefore more efficient for investigating the release of chemicals in the ionosphere.

  19. Sounding rockets explore the ionosphere

    SciTech Connect

    Mendillo, M. )

    1990-08-01

    It is suggested that small, expendable, solid-fuel rockets used to explore ionospheric plasma can offer insight into all the processes and complexities common to space plasma. NASA's sounding rocket program for ionospheric research focuses on the flight of instruments to measure parameters governing the natural state of the ionosphere. Parameters include input functions, such as photons, particles, and composition of the neutral atmosphere; resultant structures, such as electron and ion densities, temperatures and drifts; and emerging signals such as photons and electric and magnetic fields. Systematic study of the aurora is also conducted by these rockets, allowing sampling at relatively high spatial and temporal rates as well as investigation of parameters, such as energetic particle fluxes, not accessible to ground based systems. Recent active experiments in the ionosphere are discussed, and future sounding rocket missions are cited.

  20. Ionospheric chemistry of NO(+)

    NASA Technical Reports Server (NTRS)

    Breig, E. L.; Hanson, W. B.; Hoffman, J. H.

    1984-01-01

    An investigation is described of the behavior of NO(+) in the daytime F region, with basic ion concentration measurements from the Atmosphere Explorer C satellite. The data set was acquired along select orbits at low latitudes and exhibits substantial variations in the NO(+) concentration, both along and between nearby orbits. An excellent consistency is demonstrated between these observations and current chemical equilibrium theory, in contrast to differences that have been reported for the related N2(+) ion. Large variations in the concurrently observed electron temperature permit a relevant comparison between different laboratory determinations of the dissociative recombination rate coefficient. Contributions to the NO(+) production from several secondary sources are also evaluated. Results strengthen the basis for the current theoretical ionospheric chemistry of NO(+) and establish important constraints on resolution of the difficulties with N2(+).

  1. Ionospheric scintillation studies

    NASA Technical Reports Server (NTRS)

    Rino, C. L.; Freemouw, E. J.

    1973-01-01

    The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

  2. Computerized system for corrosion control

    SciTech Connect

    Hall, C. )

    1991-10-01

    This paper reports that computerization of basic corrosion measurements to provide record-keeping and graphical output has been used by pipeline companies over the lst decade. Northwest Pipeline Corp. has embarked on an ambition project to expand well beyond the scope of standard computer record-keeping by integrating data analysis and management with computer-aided advanced corrosion engineering practices. Most maturing pipeline systems require immense capital and maintenance expenditures to maintain regulatory levels of cathodic protection consistent with traditional corrosion control methods. Major pipeline coating rehabilitation programs and the installation of numerous anode-bed systems will continue in the absence of sophisticated computer-aided corrosion control methods.

  3. A computerized hospital maintenance system.

    PubMed

    Kresch, E; Katz, P; Schwartz, H; Hamarman, H

    1985-01-01

    The Biomedical Instrumentation Department at Thomas Jefferson University Hospital maintains most of the clinical equipment owned by the hospital and provides support to six other hospitals, as well. In order to document these services, a computerized support system has been developed. This system maintains the inventory of equipment, documents the occurrence of repair and preventive maintenance procedures, generates lists of items due for maintenance and inspection, and prints reports and summaries of all activities performed by department staff. The system was designed for ease of use and requires a minimum of training for personnel who use it.

  4. Role of ionospheric conductance in magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Tapas

    Magnetosphere-ionosphere (MI) coupling has been studied for a long time. However, not much work has been done on a systematic understanding of the relation between ionospheric Pedersen conductance, its effect on the evolution and modification of field-aligned currents (FACs), and the influence of conductance and FACs on the formation of parallel electric fields which cause particle precipitation. Though the roles of ionospheric conductance gradients for FACs and parallel electric field evolution are directly related, they are poorly understood. This dissertation advances the understanding of these areas and all results of this study are based on numerical simulations that employ a three-dimensional - two-fluid (ions and neutrals) simulation code. The first part of this dissertation presents a systematic study of the magnetospheric and ionospheric influences on the evolution and modification of FACs with focus on the role of ionospheric Pedersen conductance and its gradients. FACs are typically generated in the magnetosphere and are carried into the ionosphere by Alfven waves. During their reflection from the ionosphere these FACs are modified depending on the magnitude and distribution of ionospheric conductance. For conductance gradients along the polarization of the wave, strong Pedersen currents can be generated which in turn enhance the FAC as well. The second part of this dissertation addresses the properties and evolution of parallel electric fields in an attempt to better understand the formation of discrete auroral arcs in response to the evolution of FACs for predetermined ionospheric conductance patterns. Frequently, auroral acceleration is believed to occur through U or V shaped potentials. Therefore, this part examines the properties of localized parallel electric fields in a uniform magnetic field. It is demonstrated that localized parallel electric fields generate magnetic flux in the absence of source of free energy. It is also shown that parallel

  5. The worldwide ionospheric data base

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    1989-01-01

    The worldwide ionospheric data base is scattered over the entire globe. Different data sets are held at different institutions in the U.S., U.S.S.R., Australia, Europe, and Asia. The World Data Centers on the different continents archive and distribute part of the huge data base; the scope and cross section of the individual data holdings depend on the regional and special interest of the center. An attempt is made to pull together all the strings that point toward different ionospheric data holdings. Requesters are provided with the information about what is available and where to get it. An attempt is also made to evaluate the reliability and compatibility of the different data sets based on the consensus in the ionospheric research community. The status and accuracy of the standard ionospheric models are also discussed because they may facilitate first order assessment of ionospheric effects. This is a first step toward an ionospheric data directory within the framework of NSSDC's master directory.

  6. Anatomy of the cranioencephalic structures of the goat (Capra hircus L.) by imaging techniques: a computerized tomographic study.

    PubMed

    Arencibia, A; Vázquez, J M; Ramirez, J A; Sandoval, J A; Ramirez, G; Sosa, C

    1997-09-01

    A topographic study of the cranioencephalic structure was carried out by computerized tomography on Canarian breed adult goats of medium size and weight, with similar cephalic parameters. In this way, transversal, sagittal and horizontal tomographic images were obtained. Identification of the observed anatomic structures represents the basis of this work from which applicable specie data are derived.

  7. Recent Advances in Ionospheric Anomalies detection

    NASA Astrophysics Data System (ADS)

    Titov, Anton; Vyacheslav, Khattatov

    2016-07-01

    The variability of the parameters of the ionosphere and ionospheric anomalies are the subject of intensive research. It is widely known and studied in the literature ionospheric disturbances caused by solar activity, the passage of the terminator, artificial heating of high-latitude ionosphere, as well as seismic events. Each of the above types of anomalies is the subject of study and analysis. Analysis of these anomalies will provide an opportunity to improve our understanding of the mechanisms of ionospheric disturbances. To solve this problem are encouraged to develop a method of modeling the ionosphere, based on the assimilation of large amounts of observational data.

  8. DOE transporation programs - computerized techniques

    SciTech Connect

    Joy, D.S.; Johnson, P.E.; Fore, C.S.; Peterson, B.E.

    1983-01-01

    One of the major thrusts of the transportation programs at the Oak Ridge National Laboratory has been the development of a number of computerized transportation programs and data bases. The U.S. Department of Energy (DOE) is supporting these efforts through the Transportation Technology Center at Sandia National Laboratories and the Tranportation Operations and Traffic Management (TOTM) organization at DOE Headquarters. Initially this project was centered upon research activities. However, since these tools provide traffic managers and key personnel involved in preshipment planning with a unique resource for ensuring that the movement of radioactive materials can be properly accomplished, additional interest and support is coming from the operational side of DOE. The major accomplishments include the development of two routing models (one for rail shipments and the other for highway shipments), an emergency response assistance program, and two data bases containing pertinent legislative and regulatory information. This paper discusses the mose recent advances in, and additions to, these computerized techniques and provides examples of how they are used.

  9. Resources for Improving Computerized Learning Environments.

    ERIC Educational Resources Information Center

    Yeaman, Andrew R. J.

    1989-01-01

    Presents an annotated review of human factors literature that discusses computerized environments. Topics discussed include the application of office automation practices to educational environments; video display terminal (VDT) workstations; health and safety hazards; planning educational facilities; ergonomics in computerized offices; and…

  10. Computerized Diagnostic Testing: Problems and Possibilities.

    ERIC Educational Resources Information Center

    McArthur, David L.

    The use of computers to build diagnostic inferences is explored in two contexts. In computerized monitoring of liquid oxygen systems for the space shuttle, diagnoses are exact because they can be derived within a world which is closed. In computerized classroom testing of reading comprehension, programs deliver a constrained form of adaptive…

  11. A First Life with Computerized Business Simulations

    ERIC Educational Resources Information Center

    Thavikulwat, Precha

    2011-01-01

    The author discusses the theoretical lens, origins, and environment of his work on computerized business simulations. Key ideas that inform his work include the two dimensions (control and interaction) of computerized simulation, the two ways of representing a natural process (phenotypical and genotypical) in a simulation, which he defines as a…

  12. Computerized Sociometric Assessment for Preschool Children

    ERIC Educational Resources Information Center

    Endedijk, Hinke M.; Cillessen, Antonius H. N.

    2015-01-01

    In preschool classes, sociometric peer ratings are used to measure children's peer relationships. The current study examined a computerized version of preschool sociometric ratings. The psychometric properties were compared of computerized sociometric ratings and traditional peer ratings for preschoolers. The distributions, inter-item…

  13. The Evaluation of SISMAKOM (Computerized SDI Project).

    ERIC Educational Resources Information Center

    University of Science, Penang (Malaysia).

    A survey of 88 users of SISMAKOM, a computerized selective dissemination of information (SDI) and document delivery service provided by the Universiti Sains Malaysia and four other Malaysian universities, was conducted in August 1982 in order to collect data about SISMAKOM and to assess the value of a computerized SDI service in a developing…

  14. Cassel Psych Center Computerized Biofeedback Clinic.

    ERIC Educational Resources Information Center

    Cassel, Russell N.

    1982-01-01

    Describes Cassel Psych Center, a computerized biofeedback clinic, where the "well" patient is a major concern, and where biofeedback instruments are used with computers to form a Computerized-Biofeedback Clinical Support System. The Center's activities are designed to parallel the services of the pathologist in a medical setting. (PAS)

  15. Computerized Classification Testing with the Rasch Model

    ERIC Educational Resources Information Center

    Eggen, Theo J. H. M.

    2011-01-01

    If classification in a limited number of categories is the purpose of testing, computerized adaptive tests (CATs) with algorithms based on sequential statistical testing perform better than estimation-based CATs (e.g., Eggen & Straetmans, 2000). In these computerized classification tests (CCTs), the Sequential Probability Ratio Test (SPRT) (Wald,…

  16. Ionospheric Profiling using GPS/MET Data

    NASA Technical Reports Server (NTRS)

    Hajj, George; Romans, Larry

    1996-01-01

    A report on ionospheric profiling using GPS and MET data is presented. A description of the GPS occultation technique, some examples of GPS/MET data products, the data processing system and a preliminary validation of ionospheric profiles is discussed.

  17. Psychometrics behind Computerized Adaptive Testing.

    PubMed

    Chang, Hua-Hua

    2015-03-01

    The paper provides a survey of 18 years' progress that my colleagues, students (both former and current) and I made in a prominent research area in Psychometrics-Computerized Adaptive Testing (CAT). We start with a historical review of the establishment of a large sample foundation for CAT. It is worth noting that the asymptotic results were derived under the framework of Martingale Theory, a very theoretical perspective of Probability Theory, which may seem unrelated to educational and psychological testing. In addition, we address a number of issues that emerged from large scale implementation and show that how theoretical works can be helpful to solve the problems. Finally, we propose that CAT technology can be very useful to support individualized instruction on a mass scale. We show that even paper and pencil based tests can be made adaptive to support classroom teaching.

  18. Computerized atlas for functional stereotaxis

    NASA Astrophysics Data System (ADS)

    Hardy, Tyrone L.; Brynildson, L. R. D.

    1993-09-01

    Our original brain mapping techniques have been expanded so that MR and CT images can be displayed in a three-dimensionally simulated localization environment. Various combinations of MR images as well as CT images (or combinations of both and angiography) can be selectively displayed and viewed in three-dimensional stereotactic space. Data from the Talairach anatomical library, the architectonics of the atlases of Van Buren and Borke, Schaltenbrand and Bailey, Schaltenbrand and Wahren, and Brodmann's cortico-architectonics have been used to develop a detailed anatomical atlas library and brain mapping system based on brain reference structures common to each of these databases. The data in this mapping and imaging environment can be interrogated to create computerized anatomical displays showing any given functional anatomical region in two-dimensional displays or three-dimensional relief. This composite mapping system allows the interrogation and cross referencing of data from virtually any other brain mapping or localization system.

  19. The International Reference Ionosphere - Climatological Standard for the Ionosphere

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    2006-01-01

    The International Reference Ionosphere (IRI) a joint project of URSI and COSPAR is the defacto standard for a climatological specification of ionospheric parameters. IRI is based on a wide range of ground and space data and has been steadily improved since its inception in 1969 with the ever-increasing volume of ionospheric data and with better mathematical descriptions of the observed global and temporal variation patterns. The IRI model has been validated with a large amount of data including data from the most recent ionospheric satellites (KOMPSAT, ROCSAT and TIMED) and data from global network of ionosondes. Several IRI teams are working on specific aspects of the IRI modeling effort including an improved representation of the topside ionosphere with a seamless transition to the plasmasphere, a new effort to represent the global variation of F2 peak parameters using the Neural Network (NN) technique, and the inclusion of several additional parameters in IRI, e.g., spread-F probability and ionospheric variability. Annual IRI workshops are the forum for discussions of these efforts and for all science activities related to IRI as well as applications of the IRI model in engineering and education. In this paper I will present a status report about the IRI effort with special emphasis on the presentations and results from the most recent IRI Workshops (Paris, 2004; Tortosa, 2005) and on the most important ongoing IRI activities. I will discuss the latest version of the IRI model, IRI-2006, highlighting the most recent changes and additions. Finally, the talk will review some of the applications of the IRI model with special emphasis on the use for radiowave propagation studies and communication purposes.

  20. Ionospheric Profiles from Ultraviolet Remote Sensing

    DTIC Science & Technology

    1997-09-30

    The long-term goal of this project is to obtain ionospheric profiles from ultraviolet remote sensing of the ionosphere from orbiting space platforms... Remote sensing of the nighttime ionosphere is a more straightforward process because of the absence of the complications brought about by daytime

  1. Low-latitude ionospheric effects on SBAS

    NASA Astrophysics Data System (ADS)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  2. Chemical releases in the ionosphere

    NASA Technical Reports Server (NTRS)

    Davis, T. N.

    1979-01-01

    The study of the interaction between the atmosphere, ionosphere and magnetosphere is identified as a major task worthy of pursuit. The present review demonstrates the major contributions to this complex problem already made by active experiments involving the injection of chemicals and energetic electron beams into the atmosphere, ionosphere and magnetosphere. Through the use of chemical releases, it has been possible to investigate a number of quantities including high-altitude winds and electric fields, the detailed configurations of the geomagnetic field within the ionosphere and the magnetosphere, as well as the propagation of energetic particle beams and their interaction with natural neutral and ionized constituents of the high atmosphere. So far, virtually all of this effort has been accomplished using rockets. In the future, it is obvious that satellite platforms will play a greater role, both in making injections and in observing their effects.

  3. Radar soundings of the ionosphere of Mars.

    PubMed

    Gurnett, D A; Kirchner, D L; Huff, R L; Morgan, D D; Persoon, A M; Averkamp, T F; Duru, F; Nielsen, E; Safaeinili, A; Plaut, J J; Picardi, G

    2005-12-23

    We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength.

  4. International Reference Ionosphere: Plasma densities - Status 1988

    NASA Technical Reports Server (NTRS)

    Rawer, K.; Bilitza, D.

    1990-01-01

    An account is given of the changes proposed in 1988 for the International Reference Ionosphere electron density profile, as well as the status of their implementation. The fully analytical profile function under development for the entire ionosphere can be achieved with a linear combination of several LAY functions. Although four LAY functions are required to describe the density features of the middle ionosphere, three LAY functions suffice to reproduce electron densities in both the topside ionosphere and lower ionosphere. Attention is given to the way in which the LAY parameters are computationally derivable from characteristic profile points.

  5. A medium-scale traveling ionospheric disturbance observed from the ground and from space

    NASA Astrophysics Data System (ADS)

    Dymond, K. F.; Watts, C.; Coker, C.; Budzien, S. A.; Bernhardt, P. A.; Kassim, N.; Lazio, T. J.; Weiler, K.; Crane, P. C.; Ray, P. S.; Cohen, A.; Clarke, T.; Rickard, L. J.; Taylor, G. B.; Schinzel, F.; Pihlstrom, Y.; Kuniyoshi, M.; Close, S.; Colestock, P.; Myers, S.; Datta, A.

    2011-10-01

    We report ultraviolet optical observations from space of a Medium-Scale Traveling Ionospheric Disturbance (MSTID) made during the Combined Radio Interferometry and COSMIC Experiment in Tomography Campaign (CRICKET) held on September 15, 2007 at ˜8:30 UT. The experiment used a Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC also known as FORMOSAT-3) satellite in conjunction with the Very Large Array (VLA) radio telescope, located near Socorro, NM, to study the ionosphere from the global scale down to the regional scale while the TIDs propagated through it. The COSMIC/FORMOSAT-3 satellite measured the F region electron density both horizontally and with altitude while the VLA measured the directions and speeds of the TIDs. These observations provide new information on this poorly understood class of TID and demonstrate the possibility of studying MSTIDs using space-based optical instruments.

  6. A Review of Ionospheric Scintillation Models.

    PubMed

    Priyadarshi, S

    This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

  7. Automatic ionospheric layers detection: Algorithms analysis

    NASA Astrophysics Data System (ADS)

    Molina, María G.; Zuccheretti, Enrico; Cabrera, Miguel A.; Bianchi, Cesidio; Sciacca, Umberto; Baskaradas, James

    2016-03-01

    Vertical sounding is a widely used technique to obtain ionosphere measurements, such as an estimation of virtual height versus frequency scanning. It is performed by high frequency radar for geophysical applications called ;ionospheric sounder; (or ;ionosonde;). Radar detection depends mainly on targets characteristics. While several targets behavior and correspondent echo detection algorithms have been studied, a survey to address a suitable algorithm for ionospheric sounder has to be carried out. This paper is focused on automatic echo detection algorithms implemented in particular for an ionospheric sounder, target specific characteristics were studied as well. Adaptive threshold detection algorithms are proposed, compared to the current implemented algorithm, and tested using actual data obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory. Different cases of study have been selected according typical ionospheric and detection conditions.

  8. Graphical Models and Computerized Adaptive Testing.

    ERIC Educational Resources Information Center

    Almond, Russell G.; Mislevy, Robert J.

    1999-01-01

    Considers computerized adaptive testing from the perspective of graphical modeling (GM). GM provides methods for making inferences about multifaceted skills and knowledge and for extracting data from complex performances. Provides examples from language-proficiency assessment. (SLD)

  9. Solving Infeasibility Problems in Computerized Test Assembly.

    ERIC Educational Resources Information Center

    Timminga, Ellen

    1998-01-01

    Discusses problems of diagnosing and repairing infeasible linear-programming models in computerized test assembly. Demonstrates that it is possible to localize the causes of infeasibility, although this is not always easy. (SLD)

  10. The Auditing of Computerized Accounting Systems.

    ERIC Educational Resources Information Center

    Skudrna, Vincent J.

    1982-01-01

    Describes an investigation undertaken to indicate the curricular content (knowledge and skills) needed to prepare the accounting student to audit computerized accounting systems. Areas studied included programing languages, data processing, desired course training, and computer audit techniques. (CT)

  11. Computerized Anatomy Atlas Of The Human Brain

    NASA Astrophysics Data System (ADS)

    Adair, Taylor; Bajcsy, Ruzena; Karp, Peter; Stein, Alan

    1981-10-01

    A software for developing, editing and displaying a 3-D computerized anatomic atlas of a human brain is described. The objective of this atlas is to serve as a reference in identifying various structures in CT scans.

  12. HUMAN RELIABILITY ANALYSIS FOR COMPUTERIZED PROCEDURES

    SciTech Connect

    Ronald L. Boring; David I. Gertman; Katya Le Blanc

    2011-09-01

    This paper provides a characterization of human reliability analysis (HRA) issues for computerized procedures in nuclear power plant control rooms. It is beyond the scope of this paper to propose a new HRA approach or to recommend specific methods or refinements to those methods. Rather, this paper provides a review of HRA as applied to traditional paper-based procedures, followed by a discussion of what specific factors should additionally be considered in HRAs for computerized procedures. Performance shaping factors and failure modes unique to computerized procedures are highlighted. Since there is no definitive guide to HRA for paper-based procedures, this paper also serves to clarify the existing guidance on paper-based procedures before delving into the unique aspects of computerized procedures.

  13. Computerizing a house organ: recharting familiar territory

    SciTech Connect

    1982-01-01

    Computerization can offer great advantages. But one publication ideally suited to computerization was slow to take advantage of the new technology. The main reason was reluctance to try an unfamiliar way of doing things. Having now switched to computerization, the publication has reaped many benefits. Among them: production time is faster; costs are lower; errors are fewer. Computerization has not been without minor problems. The most obvious is vulnerability to the rarity of a system failure. Others include the technology's potential reinforcement of overediting and of excessive reliance on extremely rapid response. Such problems, however, do not indicate weaknesses in the technology itself; rather, they reflect an incomplete adaption to it and the need for more realistic expectations. An unwarranted reluctance to innovate can slow advances in communication. Technical communicators must be willing to rechart their own familiar territory.

  14. Modified Head Shake Computerized Dynamic Posturography

    DTIC Science & Technology

    2009-12-01

    form of dizziness (in- cluding complaints of lightheadedness, vertigo , or un- steadiness) lasting longer than 1 hr or recurring for greater than 1...noted limitations. Method: Forty participants ranging in age from 20 to 79 years with no history of dizziness completed Conditions 2 and 5 of the SOT...shake, Sensory Organization Test, computerized dynamic posturography, dizziness Computerized dynamic posturography (CDP) is anassessment of an

  15. Ionospheric redistribution during geomagnetic storms.

    PubMed

    Immel, T J; Mannucci, A J

    2013-12-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<-100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  16. Magnetospheric-ionospheric Poynting flux

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1994-01-01

    Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.

  17. Calibrating for Ionospheric Phase Delays

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1985-01-01

    Technique determines ionospheric phase delay on real-time universally applicable basis in terms of electrons per meter squared by coherently modulating two L-band carrier frequencies received from two Global Positioning System satelites. Two pseudorandom number sequences cross-correlated to derive delay time.

  18. The energetics of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Roboz, A.; Nagy, A. F.

    1994-02-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  19. The energetics of Titan's ionosphere

    NASA Technical Reports Server (NTRS)

    Roboz, A.; Nagy, A. F.

    1994-01-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  20. A new algorithm of ionospheric tomography——two-step solution

    NASA Astrophysics Data System (ADS)

    Wen, Debao

    The inherent non-ideal geometry of ground-based global navigation satellite system (GNSS) observation stations distribution results in limited-angle tomographic inverse problems that are ill-posed. To cope with the above problem, a new tomographic algorithm, which is called two-step solution (TSS), is presented in this paper. In the new method, the electron density can be estimated by using two steps: 1) Phillips smoothing method (PSM) is first used to resolve the ill-posed problem in ionospheric tomography system; 2) The "coarse" solution of PSM is then input as the initial value of multiplicative algebraic reconstruction technique (MART) and improved by iterative mode. Numerical simulation experiment demonstrates that the two-step solution is feasible to GNSS-based ionospheric tomography and superior to PSM or MART alone.

  1. Unexplained heterochromia. Intraocular foreign body demonstrated by computed tomography.

    PubMed

    Barr, C C; Vine, A K; Martonyi, C L

    1984-01-01

    Standard radiographic techniques are often inadequate in demonstrating the presence and location of intraocular foreign bodies. Computerized axial tomography was used to confirm the presence of a metallic foreign body in a patient with heterochromia iridis and suspected ocular siderosis in whom no foreign material was found by conventional examination methods.

  2. A Randomized Experiment to Compare Conventional, Computerized, and Computerized Adaptive Administration of Ordinal Polytomous Attitude Items

    ERIC Educational Resources Information Center

    Hol, A. Michiel; Vorst, Harrie C. M.; Mellenbergh, Gideon J.

    2005-01-01

    A total of 520 high school students were randomly assigned to a paper-and-pencil test (PPT), a computerized standard test (CST), or a computerized adaptive test (CAT) version of the Dutch School Attitude Questionnaire (SAQ), consisting of ordinal polytomous items. The CST administered items in the same order as the PPT. The CAT administered all…

  3. Three Dimensional High-Resolution Reconstruction of the Ionosphere Over the Very Large Array

    DTIC Science & Technology

    2010-12-15

    campaign (Combined Radio Interferometer- COSMIC Experiment in Tomography) of September, 2007 (see previous report). CORS data from this period was...First results are still under interpretation. Farther afield, a collaboration was begun with the ionospheric group at the LOFAR radio telescope ...project in the Netherlands. Dr. Watts visited the LOFAR site in June, 2010 and met with several key players. The two long wavelength telescopes (LWA and

  4. Preface: International Reference Ionosphere - Progress in Ionospheric Modelling

    NASA Technical Reports Server (NTRS)

    Bilitza Dieter; Reinisch, Bodo

    2010-01-01

    The international reference ionosphere (lRI) is the internationally recommended empirical model for the specification of ionospheric parameters supported by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) and recognized by the International Standardization Organization (ISO). IRI is being continually improved by a team of international experts as new data become available and better models are being developed. This issue chronicles the latest phase of model updates as reported during two IRI-related meetings. The first was a special session during the Scientific Assembly of the Committee of Space Research (COSPAR) in Montreal, Canada in July 2008 and the second was an IRI Task Force Activity at the US Air Force Academy in Colorado Springs in May 2009. This work led to several improvements and additions of the model which will be included in the next version, IRI-201O. The issue is divided into three sections focusing on the improvements made in the topside ionosphere, the F-peak, and the lower ionosphere, respectively. This issue would not have been possible without the reviewing efforts of many individuals. Each paper was reviewed by two referees. We thankfully acknowledge the contribution to this issue made by the following reviewers: Jacob Adeniyi, David Altadill, Eduardo Araujo, Feza Arikan, Dieter Bilitza, Jilijana Cander, Bela Fejer, Tamara Gulyaeva, Manuel Hermindez-Pajares, Ivan Kutiev, John MacDougal, Leo McNamara, Bruno Nava, Olivier Obrou, Elijah Oyeyemi, Vadym Paznukhov, Bodo Reinisch, John Retterer, Phil Richards, Gary Sales, J.H. Sastri, Ludger Scherliess, Iwona Stanislavska, Stamir Stankov, Shin-Yi Su, Manlian Zhang, Y ongliang Zhang, and Irina Zakharenkova. We are grateful to Peggy Ann Shea for her final review and guidance as the editor-in-chief for special issues of Advances in Space Research. We thank the authors for their timely submission and their quick response to the reviewer comments and humbly

  5. Remote Sensing of the Ionosphere and Plasmasphere from Space Using Radiowaves

    NASA Technical Reports Server (NTRS)

    Mannucci, Anthony J.

    2008-01-01

    Topics include the scientific context, trans-ionospheric and sounding, small-scale structure, plasmasphere, fast and slow tomography, and pseudo-imaging. Individual slides focus on where geospace science stands today, variability in inner magnetosphere electric fields, Appleton-Hartree formula, phase and range ionospheric observables, examples of leveling, large ionization changes during storms, new mid-latitude phenomena, ionospheric sounding, COSMIC CERTO/Tri-band beacon, LEO-ground radio tomography, irregularity measurements, COSMIC, critical sensor data from COSMIC GPS limb sounding, occultation geometry, comparison of calibrated slant TEC measurements for 26 June 2006, historic examples of Abel electron density profiles, comparison of UCAR and JPL Able profiles of 26 June 2006, validating UCAR and JPL Abel profiles using Arecibo ISR measurements for 26 June 2006, E-region from GPS/MET 1995, Abel versus gradient assisted retrieval, 3000 profiles/day, plasmasphere, JASON TEC above satellite, GPS equatorial plasmasphere measurements, April 2002 geomagnetic storm, and space-based GPS tomography.

  6. The dynamics of the Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Miller, K. L.

    1988-01-01

    Data from the Pioneer-Venus orbiter has demonstrated the importance of understanding ion dynamics in the Venus ionosphere. The analysis of the data has shown that during solar maximum the topside Venus ionosphere in the dark hemisphere is generated almost entirely on the dayside of the planet during solar maximum, and flows with supersonic velocities across the terminator into the nightside. The flow field in the ionosphere is mainly axially-symmetric about the sun-Venus axis, as are most measured ionospheric quantities. The primary data base used consisted of the ion velocity measurements made by the RPA during three years that periapsis of the orbiter was maintained in the Venus ionosphere. Examples of ion velocities were published and modeled. This research examined the planetary flow patterns measured in the Venus ionosphere, and the physical implications of departures from the mean flow.

  7. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude.

  8. Human-eye versus computerized color matching.

    PubMed

    Yap, A U; Sim, C P; Loh, W L; Teo, J H

    1999-01-01

    This project compared the difference in color matching between human-eye assessment and computerized colorimetry. Fifty dental personnel were asked to color match Vita Lumin shade tabs to seven different randomly arranged test tabs from the Z100 shade guide. All evaluators were blinded to the shades of the test tabs and were asked to match only body shade of the Vita Lumin tab to the middle third or body of each test tab. The results obtained were subsequently computed into L*a*b* values and compared with results obtained by computerized colorimetry. Results indicate that the difference in color matching between human-eye assessment and computerized colorimetry is shade dependent. Discrepancy was significant for b* coordinates for shades A1 and B2 and L* and b* coordinates for shade C4. For all shades evaluated, color difference between human-eye and computerized color matching is perceivable under clinical settings, as delta E values are greater than 3. There is a need for correction factors in the formal specification of the color-matching software due to the discrepancy between human-eye and computerized colorimetric color matching.

  9. Ionospheric Change and Solar EUV Irradiance

    NASA Astrophysics Data System (ADS)

    Sojka, J. J.; David, M.; Jensen, J. B.; Schunk, R. W.

    2011-12-01

    The ionosphere has been quantitatively monitored for the past six solar cycles. The past few years of observations are showing trends that differ from the prior cycles! Our good statistical relationships between the solar radio flux index at 10.7 cm, the solar EUV Irradiance, and the ionospheric F-layer peak density are showing indications of divergence! Present day discussion of the Sun-Earth entering a Dalton Minimum would suggest change is occurring in the Sun, as the driver, followed by the Earth, as the receptor. The dayside ionosphere is driven by the solar EUV Irradiance. But different components of this spectrum affect the ionospheric layers differently. For a first time the continuous high cadence EUV spectra from the SDO EVE instrument enable ionospheric scientists the opportunity to evaluate solar EUV variability as a driver of ionospheric variability. A definitive understanding of which spectral components are responsible for the E- and F-layers of the ionosphere will enable assessments of how over 50 years of ionospheric observations, the solar EUV Irradiance has changed. If indeed the evidence suggesting the Sun-Earth system is entering a Dalton Minimum periods is correct, then the comprehensive EVE solar EUV Irradiance data base combined with the ongoing ionospheric data bases will provide a most fortuitous fiduciary reference baseline for Sun-Earth dependencies. Using the EVE EUV Irradiances, a physics based ionospheric model (TDIM), and 50 plus years of ionospheric observation from Wallops Island (Virginia) the above Sun-Earth ionospheric relationship will be reported on.

  10. Periodic Structures in the Equatorial Ionosphere (Postprint)

    DTIC Science & Technology

    2012-05-13

    AFRL-RV-PS- AFRL-RV-PS- TP-2012-0004 TP-2012-0004 PERIODIC STRUCTURES IN THE EQUATORIAL IONOSPHERE (POSTPRINT) Cheryl Y. Huang...in the Equatorial Ionosphere (Postprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) 5d. PROJECT NUMBER 2301...International Reference Ionosphere model to remove variations in density due to changes in spacecraft altitude and latitude along the orbit. In this

  11. Computerized microtomography for new applications

    SciTech Connect

    Ice, G.; Thompson, A.

    1996-09-01

    The advent of high brilliance synchrotron sources has stimulated the development of advanced x-ray microtomography. However, materials research problems challenge existing tomographic techniques. High spatial resolution is required to identify and characterize microstructure in real materials. Good elemental sensitivity is required to study the effects of microalloying. Three-dimensional crystal texture, strain and phase information is required to understand advanced materials. Materials samples can include a wide range of elements, can come in unfavorable geometries, and sometimes require dynamic measurements of their three-dimensional structure. One challenge for x-ray microtomography is the measurement of low concentrations with good spatial resolution and high elemental sensitivity. Another challenge to standard x-ray microtomography is the study of elemental distributions in planar structures where elemental sensitivity is required in one or two dimensions, but the spatial sensitivity in all three dimensions is not required. For a large class of materials, crystalline structure, strain and texture are critical to the materials properties. Recent work has now demonstrated the possibility of extending X-ray microdiffraction to the study of three dimensional crystallographic distributions. Efforts are now underway at the APS, ALS, SSRL and NSLS to further develop x-ray microdiffraction and x-ray microdiffraction tomography. The measurement of strain and texture in three dimensions will have important applications to the study of high J{sub c} high {Tc} superconductors, the study of second phase distributions and texture in composite materials, and the study of crack and void evolution in structural and electronic materials. Another frontier for x-ray tomography is the development of dynamic, real-time measurements.

  12. HAARP-Induced Ionospheric Ducts

    SciTech Connect

    Milikh, Gennady; Vartanyan, Aram

    2011-01-04

    It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

  13. Investigation of traveling ionospheric disturbances

    NASA Technical Reports Server (NTRS)

    Grossi, M.; Estes, R. D.

    1981-01-01

    Maximum entropy power spectra of the ionospheric electron density were constructed to enable PINY to compare them with the power independently obtained by PINY with in situ measurements of ionospheric electron density and neutral species performed with instrumentation carried by the Atmospheric Explorer (AE) satellite. This comparison corroborated evidence on the geophysical reality of the alleged electron density irregularities detected by the ASTP dual frequency Doppler link. Roughly half of the localized wave structures which are confined to dimensions of 1800 km or less (as seen by an orbiting Doppler baseline) were found to be associated with the larger crest of the geomagnetic anomaly in the Southern (winter) Hemisphere in the morning. The observed nighttime structures are also associated with local peaks in the electron density.

  14. Bimodal Solar Wind-Magnetosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Siscoe, G.

    2005-05-01

    Regarding its coupling to the solar wind, the magnetosphere-ionosphere system appears to be schizophrenic. That is, it seems to manifest two modes with contradictory qualities, modes that alternate depending on solar wind conditions. Normal conditions elicit the normal mode (aka the solar wind-dominated mode). But extreme conditions bring out the un-normal mode (aka the ionosphere-dominated mode). This talk emphasizes the un-normal, ionosphere-dominated mode, which makes its presence during great magnetic storms. Then the magnetosphere-confining Chapman-Ferraro current system fades away to be replaced by the region 1 currents system which links the now dominant ionosphere to the whole of geospace out to and including the bow shock. Dst no longer responds to the ram pressure of the solar wind. The electrical potential across the polar cap stops growing as solar wind driving strengthens. Instead, it becomes bound to ionospheric conductance, which as the storm intensifies transforms under local instability. The ionosphere appears to lose its grip on magnetospheric convection, although this is not certain. The plasmasphere is stripped away, most likely to feed (by global circulation) an intensifying ring current. The outer magnetosphere begins a series of slow, macroscale convulsions. Huge parallel potentials possibly develop in the magnetosphere's outer regions, reacting against the ionosphere's domination. Compared to the solar wind-dominated magnetosphere, the ionosphere-dominated magnetosphere is comparatively unknown and, so, provides opportunities for significantly advancing our understanding of the coupled solar wind-magnetosphere-ionosphere system.

  15. Ionospheric limitations to time transfer by satellite

    NASA Technical Reports Server (NTRS)

    Knowles, S. H.

    1983-01-01

    The ionosphere can contribute appreciable group delay and phase change to radio signals traversing it; this can constitute a fundamental limitation to the accuracy of time and frequency measurements using satellites. Because of the dispersive nature of the ionosphere, the amount of delay is strongly frequency-dependent. Ionospheric compensation is necessary for the most precise time transfer and frequency measurements, with a group delay accuracy better than 10 nanoseconds. A priori modeling is not accurate to better than 25%. The dual-frequency compensation method holds promise, but has not been rigorously experimentally tested. Irregularities in the ionosphere must be included in the compensation process.

  16. Ionospheric research for space weather service support

    NASA Astrophysics Data System (ADS)

    Stanislawska, Iwona; Gulyaeva, Tamara; Dziak-Jankowska, Beata

    2016-07-01

    Knowledge of the behavior of the ionosphere is very important for space weather services. A wide variety of ground based and satellite existing and future systems (communications, radar, surveillance, intelligence gathering, satellite operation, etc) is affected by the ionosphere. There are the needs for reliable and efficient support for such systems against natural hazard and minimalization of the risk failure. The joint research Project on the 'Ionospheric Weather' of IZMIRAN and SRC PAS is aimed to provide on-line the ionospheric parameters characterizing the space weather in the ionosphere. It is devoted to science, techniques and to more application oriented areas of ionospheric investigation in order to support space weather services. The studies based on data mining philosophy increasing the knowledge of ionospheric physical properties, modelling capabilities and gain applications of various procedures in ionospheric monitoring and forecasting were concerned. In the framework of the joint Project the novel techniques for data analysis, the original system of the ionospheric disturbance indices and their implementation for the ionosphere and the ionospheric radio wave propagation are developed since 1997. Data of ionosonde measurements and results of their forecasting for the ionospheric observatories network, the regional maps and global ionospheric maps of total electron content from the navigational satellite system (GNSS) observations, the global maps of the F2 layer peak parameters (foF2, hmF2) and W-index of the ionospheric variability are provided at the web pages of SRC PAS and IZMIRAN. The data processing systems include analysis and forecast of geomagnetic indices ap and kp and new eta index applied for the ionosphere forecasting. For the first time in the world the new products of the W-index maps analysis are provided in Catalogues of the ionospheric storms and sub-storms and their association with the global geomagnetic Dst storms is

  17. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<−100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3–6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  18. Heat budget of ionospheric electrons

    NASA Technical Reports Server (NTRS)

    Prasad, S. S.; Schneck, L. J.

    1976-01-01

    Heat input calculations were detached from solar extreme UV data and monatomic oxygen densities were derived from simultaneously measured data sets (ion composition 146-191 km) in a study of the heat budget of ionosphere electrons. Earlier inferences that cooling predominates over heating are supported. A search for additional heat sources or a revision of the cooling rates is recommended, by way of balancing the heat budget. Importance is attached to electron cooling by fine structure excitation of monatomic oxygen.

  19. Ionospheric Research Using Digital Ionosondes.

    DTIC Science & Technology

    1983-07-01

    employed by your organization, please notify AFGL/DAA, Hanscom AFB, MA 01731. This will assist us in maintaining a current mailing list. Do not return...know, that outputs the standard ionospheric param- eters and profiles in real time, even under disturbed condi- tions. This breakthrough will make it...Echo signals arriving from directions other than the programmed beam direction will be wrongly identified in the ionograms, depending upon which antenna

  20. Ionospheric very low frequency transmitter

    SciTech Connect

    Kuo, Spencer P.

    2015-02-15

    The theme of this paper is to establish a reliable ionospheric very low frequency (VLF) transmitter, which is also broad band. Two approaches are studied that generate VLF waves in the ionosphere. The first, classic approach employs a ground-based HF heater to directly modulate the high latitude ionospheric, or auroral electrojet. In the classic approach, the intensity-modulated HF heater induces an alternating current in the electrojet, which serves as a virtual antenna to transmit VLF waves. The spatial and temporal variations of the electrojet impact the reliability of the classic approach. The second, beat-wave approach also employs a ground-based HF heater; however, in this approach, the heater operates in a continuous wave mode at two HF frequencies separated by the desired VLF frequency. Theories for both approaches are formulated, calculations performed with numerical model simulations, and the calculations are compared to experimental results. Theory for the classic approach shows that an HF heater wave, intensity-modulated at VLF, modulates the electron temperature dependent electrical conductivity of the ionospheric electrojet, which, in turn, induces an ac electrojet current. Thus, the electrojet becomes a virtual VLF antenna. The numerical results show that the radiation intensity of the modulated electrojet decreases with an increase in VLF radiation frequency. Theory for the beat wave approach shows that the VLF radiation intensity depends upon the HF heater intensity rather than the electrojet strength, and yet this approach can also modulate the electrojet when present. HF heater experiments were conducted for both the intensity modulated and beat wave approaches. VLF radiations were generated and the experimental results confirm the numerical simulations. Theory and experimental results both show that in the absence of the electrojet, VLF radiation from the F-region is generated via the beat wave approach. Additionally, the beat wave approach

  1. Saturn's ionosphere - Inferred electron densities

    NASA Astrophysics Data System (ADS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1984-04-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densities measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings. Previously announced in STAR as N84-17102

  2. Challenges in Solar System Ionospheres

    NASA Astrophysics Data System (ADS)

    Mendillo, M.

    2001-12-01

    The solar system contains a robust set of ionospheres among its nine planets, many moons and comets. If one sets aside the transient atmospheres/ionospheres of comets, and those of larger bodies with tenuous surface-boundary-exospheres (e.g., Mercury, Moon, Europa, etc.), plus the under-sampled Pluto, then 10 case studies exist for detailed study and comparison (Venus, Earth, Mars, Jupiter & Io, Saturn & Titan, Uranus, and Neptune & Triton). The ionospheres of these bodies define the full range of natural processes that govern plasma environments in our solar system, and indeed for extra-solar-system planets: (a) photo-chemical mechanisms, (b) energetic (auroral) ionization sources, (c) mesospheric/thermospheric tides, winds and waves, (d) electrodynamics, and (e) solar wind impact and/or shielding by a magnetosphere. This brief review will summarize and compare the dominant production, loss and transport mechanisms thought to occur at each site. Major uncertainties are, surprisingly, not due entirely to remoteness of the bodies being studied.

  3. Dynamic Ionosphere Cubesat Experiment (DICE)

    NASA Astrophysics Data System (ADS)

    Crowley, G.; Fish, C. S.; Bust, G. S.; Swenson, C.; Barjatya, A.; Larsen, M. F.

    2009-12-01

    The Dynamic Ionosphere Cubesat Experiment (DICE) mission has been selected for flight under the NSF "CubeSat-based Science Mission for Space Weather and Atmospheric Research" program. The mission has three scientific objectives: (1) Investigate the physical processes responsible for formation of the midlatitude ionospheric Storm Enhanced Density (SED) bulge in the noon to post-noon sector during magnetic storms; (2) Investigate the physical processes responsible for the formation of the SED plume at the base of the SED bulge and the transport of the high density SED plume across the magnetic pole; (3) Investigate the relationship between penetration electric fields and the formation and evolution of SED. The mission consists of two identical Cubesats launched simultaneously. Each satellite carries a fixed-bias DC Langmuir Probe (DCP) to measure in-situ ionospheric plasma densities, and an Electric Field Probe (EFP) to measure DC and AC electric fields. These measurements will permit accurate identification of storm-time features such as the SED bulge and plume, together with simultaneous co-located electric field measurements which have previously been missing. The mission team combines expertise from ASTRA, Utah State University/Space Dynamics Laboratory (USU/SDL), Embry-Riddle Aeronautical University and Clemson University.

  4. Mechanisms of Ionospheric Mass Ejection

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Khazanov, George V.; Hannah, Mei-Ching; Glocer, Alex

    2010-01-01

    Ionospheric outflows are directly responsive to solar wind disturbances, particularly in the dayside auroral cusp or cleft regions. Inputs of both electromagnetic energy (Poynting flux) and kinetic energy (particle precipitation) are closely correlated with these outflows. We assess the importance of processes thought to drive ionospheric outflows. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitation particles. Solar wind energy dissipation is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma and neutral gas. We assess the importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multi-species global simulation codes. We conclude by assessing outstanding obstacles to this objective.

  5. Ionospheric Drivers of ISS Charging

    NASA Astrophysics Data System (ADS)

    Minow, J. I.; Willis, E. M.

    2015-12-01

    Severe spacecraft surface charging in terrestrial environments typically results from exposure to energetic electrons at some 10's of keV within auroral environments at high latitudes in low Earth orbit or hot thermal plasma in geostationary orbit. Predicting surface charging of a vehicle in these environments depends on our ability to specify and forecast auroral acceleration events and geomagnetic storms. Measurements of ISS frame charging to date, in contrast, are dominated by US 160V solar array interactions with the ionospheric plasma environment with little evidence for strong charging during geomagnetic storms. Predicting ISS charging, therefore, requires an ability to specify and forecast components of ionospheric variability of importance to high voltage solar array interactions with the plasma environment. This presentation provides examples of the ionospheric conditions responsible for typical and extreme ISS charging and discusses current capabilities to forecast these events. Specific examples are given for ISS frame charging observed when the vehicle passes through low latitude dawn density depletions, high latitude plasma troughs, and plasma depletions associated with equatorial spread-f conditions.

  6. Saturn's ionosphere: Inferred electron densities

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1983-01-01

    During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densitis measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings.

  7. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2010-01-01

    The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

  8. Spatial Structure of Large-Scale Plasma Density Perturbations HF-Induced in the Ionospheric F 2 Region

    NASA Astrophysics Data System (ADS)

    Frolov, V. L.; Komrakov, G. P.; Glukhov, Ya. V.; Andreeva, E. S.; Kunitsyn, V. E.; Kurbatov, G. A.

    2016-07-01

    We consider the experimental results obtained by studying the large-scale structure of the HF-disturbed ionospheric region. The experiments were performed using the SURA heating facility. The disturbed ionospheric region was sounded by signals radiated by GPS navigation satellite beacons as well as by signals of low-orbit satellites (radio tomography). The results of the experiments show that large-scale plasma density perturbations induced at altitudes higher than the F2 layer maximum can contribute significantly to the measured variations of the total electron density and can, with a certain arrangement of the reception points, be measured by the GPS sounding method.

  9. Illustration of the obstacles in computerized lung segmentation using examples

    PubMed Central

    Meng, Xin; Qiang, Yongqian; Zhu, Shaocheng; Fuhrman, Carl; Siegfried, Jill M.; Pu, Jiantao

    2012-01-01

    Purpose: Automated lung volume segmentation is often a preprocessing step in quantitative lung computed tomography (CT) image analysis. The objective of this study is to identify the obstacles in computerized lung volume segmentation and illustrate those explicitly using real examples. Awareness of these “difficult” cases may be helpful for the development of a robust and consistent lung segmentation algorithm. Methods: We collected a large diverse dataset consisting of 2768 chest CT examinations acquired on 2292 subjects from various sources. These examinations cover a wide range of diseases, including lung cancer, chronic obstructive pulmonary disease, human immunodeficiency virus, pulmonary embolism, pneumonia, asthma, and interstitial lung disease (ILD). The CT acquisition protocols, including dose, scanners, and reconstruction kernels, vary significantly. After the application of a “neutral” thresholding-based approach to the collected CT examinations in a batch manner, the failed cases were subjectively identified and classified into different subgroups. Results: Totally, 121 failed examinations are identified, corresponding to a failure ratio of 4.4%. These failed cases are summarized as 11 different subgroups, which is further classified into 3 broad categories: (1) failure caused by diseases, (2) failure caused by anatomy variability, and (3) failure caused by external factors. The failure percentages in these categories are 62.0%, 32.2%, and 5.8%, respectively. Conclusions: The presence of specific lung diseases (e.g., pulmonary nodules, ILD, and pneumonia) is the primary issue in computerized lung segmentation. The segmentation failures caused by external factors and anatomy variety are relatively low but unavoidable in practice. It is desirable to develop robust schemes to handle these issues in a single pass when a large number of CT examinations need to be analyzed. PMID:22894423

  10. The Construction and Uses of CATIA, a Computerized Mathematics Testbank

    ERIC Educational Resources Information Center

    Burton, Charles R.; Marosz, Wanda A.

    1977-01-01

    Described is the construction of a computerized test bank to generate and score tests in college algebra, trigonometry, and intermediate algebra; including a discussion of uses, advantages and disadvantages of computerized testing. (JLH)

  11. 39 CFR 501.15 - Computerized Meter Resetting System.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 39 Postal Service 1 2014-07-01 2014-07-01 false Computerized Meter Resetting System. 501.15... AND DISTRIBUTE POSTAGE EVIDENCING SYSTEMS § 501.15 Computerized Meter Resetting System. (a) Description. The Computerized Meter Resetting System (CMRS) permits customers to reset their postage meters...

  12. 21 CFR 884.2800 - Computerized Labor Monitoring System.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Computerized Labor Monitoring System. 884.2800... Devices § 884.2800 Computerized Labor Monitoring System. (a) Identification. A computerized labor monitoring system is a system intended to continuously measure cervical dilation and fetal head descent...

  13. 21 CFR 884.2800 - Computerized Labor Monitoring System.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Computerized Labor Monitoring System. 884.2800... Devices § 884.2800 Computerized Labor Monitoring System. (a) Identification. A computerized labor monitoring system is a system intended to continuously measure cervical dilation and fetal head descent...

  14. 21 CFR 884.2800 - Computerized Labor Monitoring System.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Computerized Labor Monitoring System. 884.2800... Devices § 884.2800 Computerized Labor Monitoring System. (a) Identification. A computerized labor monitoring system is a system intended to continuously measure cervical dilation and fetal head descent...

  15. 21 CFR 884.2800 - Computerized Labor Monitoring System.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Computerized Labor Monitoring System. 884.2800... Devices § 884.2800 Computerized Labor Monitoring System. (a) Identification. A computerized labor monitoring system is a system intended to continuously measure cervical dilation and fetal head descent...

  16. 11 CFR 9033.12 - Production of computerized information.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... magnetic media, such as magnetic tapes or magnetic diskettes, containing the computerized information at.... The computerized magnetic media shall be prepared and delivered at the committee's expense and shall... Commission's Computerized Magnetic Media Requirements for title 26 Candidates/Committees Receiving...

  17. 45 CFR 307.5 - Mandatory computerized support enforcement systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... plans to use and how they will interface with the base system; (3) Provide documentation that the... 45 Public Welfare 2 2014-10-01 2012-10-01 true Mandatory computerized support enforcement systems... HEALTH AND HUMAN SERVICES COMPUTERIZED SUPPORT ENFORCEMENT SYSTEMS § 307.5 Mandatory computerized...

  18. 45 CFR 307.5 - Mandatory computerized support enforcement systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... plans to use and how they will interface with the base system; (3) Provide documentation that the... 45 Public Welfare 2 2011-10-01 2011-10-01 false Mandatory computerized support enforcement systems... HEALTH AND HUMAN SERVICES COMPUTERIZED SUPPORT ENFORCEMENT SYSTEMS § 307.5 Mandatory computerized...

  19. 39 CFR 501.15 - Computerized Meter Resetting System.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... AND DISTRIBUTE POSTAGE EVIDENCING SYSTEMS § 501.15 Computerized Meter Resetting System. (a) Description. The Computerized Meter Resetting System (CMRS) permits customers to reset their postage meters at... 39 Postal Service 1 2010-07-01 2010-07-01 false Computerized Meter Resetting System....

  20. Magnetospheric control of the bulk ionospheric plasma

    SciTech Connect

    Sojka, J.J.; Schunk, R.W.

    1987-01-01

    The temperature, composition, and circulation of the high-latitude, ionosphere display a marked variation with altitude, latitude, longitude, universal time, season, solar cycle, and geomagnetic activity. This variation is largely a consequence of the effect that magnetospheric electric fields, particle precipitation, and heat flows have on the ionosphere. At F-region altitudes, the entire ionosphere drifts in response to magnetospheric electric fields, with the horizontal drift generally displaying a two-cell pattern of antisunward flow over the polar cap and return flow at lower latitudes. This ionospheric motion, in combination with downward magnetospheric heat flows and ion production due to energetic-particle precipitation, act to produce interesting ionospheric features such as ion and electron temperature hot spots, plasma blobs, localized ionization troughs, and extended tongue of ionization, and anomalous F-region peak altitudes and densities. The time delay for the ionosphere to respond to changing magnetospheric conditions is a strong function of altitude and can be as long as 3 to 4 hours in the upper F-region. The ionosphere's response to changing magnetospheric conditions are described using a time-dependent high-latitude ionospheric model.

  1. [Computerization of hospital blood banks in France].

    PubMed

    Daurat, G; Py, J-Y

    2012-11-01

    In France, most blood products are delivered by the établissement francais du sang, directly to the recipients, and hospital blood banks deliver a minor part, but are independent from it. However that may be, hospital blood banks are hazardous activities regarding to recipients, blood products, blood supply of the hospital and regional blood supply. Because of the high risk level, a computerized information system is compulsory for all hospital blood banks, except for those only devoted to vital emergency transfusion. On the field, the integration of computerization in the different processes is very heterogeneous. So, it has been decided to publish guidelines for computerizing hospital blood banks information systems and production management. They have been built according to risk assessment and are intended to minimize those risks. The principle is that all acquisition and processing of data about recipients or blood products and tracking, must be fully computerized and that the result of all manual processes must be checked by computer before proceeding to the next step. The guidelines list the different processes and, for each of them, the functions the software must play. All together, they form the basic level all hospital blood banks should reach. Optional functions are listed. Moreover, the guidelines are also aimed to be a common tool for regional health authorities who supervise hospital blood banks.

  2. [Computerization of hospital blood banks in France].

    PubMed

    Daurat, G; Py, J-Y

    2011-04-01

    In France, most blood products are delivered by the Établissement français du sang, directly to the recipients, and hospital blood banks deliver a minor part, but are independent from it. However that may be, hospital blood banks are hazardous activities regarding recipients, blood products, blood supply for the hospital and regional blood supply. Because of the high risk level, a computerized information system is compulsory for all hospital blood banks, except for those only devoted to vital emergency transfusion. On the field, integration of computerization in the different processes is very heterogeneous. So it has been decided to publish guidelines for computerizing hospital blood banks information systems and production management. They have been built according to risk assessment and are intended to minimize those risks. The principle is that all acquisition and processing of data about recipients or blood products and tracking, must be fully computerized and that the result of all manual processes must be checked by computer before proceeding to the next step. The guidelines list the different processes and, for each of them, the functions the software must play. All together, they form the basic level all hospital blood banks should reach. Optional functions are listed. Moreover, the guidelines are also aimed at being a common tool for regional health authorities who supervise hospital blood banks.

  3. Computerized Testing: The Hidden Figures Test.

    ERIC Educational Resources Information Center

    Jacobs, Ronald L.; And Others

    1985-01-01

    This study adapted the Hidden Figures Test for use on PLATO and determined the reliability of the computerized version compared to the paper and pencil version. Results indicate the test was successfully adapted with some modifications, and it was judged reliable although it may be measuring additional constructs. (MBR)

  4. Principles for Creating a Computerized Test Battery.

    ERIC Educational Resources Information Center

    Kyllonen, Patrick C.

    1991-01-01

    The experience of developing a set of comprehensive aptitude batteries for computer administration for the Air Force Human Resources Laboratory's Learning Abilities Measurement Program resulted in the formulation of nine principles for creation of a computerized test battery. These principles are discussed in the context of research on…

  5. Computerized Adaptive Mastery Tests as Expert Systems.

    ERIC Educational Resources Information Center

    Frick, Theodore W.

    1992-01-01

    Discussion of expert systems and computerized adaptive tests describes two versions of EXSPRT, a new approach that combines uncertain inference in expert systems with sequential probability ratio test (SPRT) stopping rules. Results of two studies comparing EXSPRT to adaptive mastery testing based on item response theory and SPRT approaches are…

  6. MU's Early Space-Planning Computerization.

    ERIC Educational Resources Information Center

    Shader, Scott; Vaughn, Anthony

    1998-01-01

    Discusses the development of the University of Missouri-Columbia's Space Planning and Management office (SPAM) and the computerization of the school's space-planning archives. Discusses SPAM's software selection for standardization as well as its manual development, placing the school's buildings and floor plans on the Web, and its space-modeling…

  7. 36 CFR 1120.52 - Computerized records.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Freedom of Information Act is available to the public as follows: (1) When there is an existing printout... page rate stated in § 1120.51(a) for each 81/2 by 11 inch page. (2) When there is not an existing... information from computerized records frequently involves a minimum computer time cost of approximately...

  8. Computerized management information systems and organizational structures

    NASA Technical Reports Server (NTRS)

    Zannetos, Z. S.; Sertel, M. R.

    1970-01-01

    The computerized management of information systems and organizational structures is discussed. The subjects presented are: (1) critical factors favoring centralization and decentralization of organizations, (2) classification of organizations by relative structure, (3) attempts to measure change in organization structure, and (4) impact of information technology developments on organizational structure changes.

  9. Individual Differences in Computerized Adaptive Testing.

    ERIC Educational Resources Information Center

    Kim, JinGyu

    Research on the major computerized adaptive testing (CAT) strategies is reviewed, and some findings are reported that examine effects of examinee demographic and psychological characteristics on CAT strategies. In fixed branching strategies, all examinees respond to a common routing test, the score of which is used to assign examinees to a…

  10. Computerizing Maintenance Management Improves School Processes.

    ERIC Educational Resources Information Center

    Conroy, Pat

    2002-01-01

    Describes how a Computerized Maintenance Management System (CMMS), a centralized maintenance operations database that facilitates work order procedures and staff directives, can help individual school campuses and school districts to manage maintenance. Presents the benefits of CMMS and things to consider in CMMS selection. (EV)

  11. Computerized Collective Training for Teams. Final Report.

    ERIC Educational Resources Information Center

    Thurmond, Paul; Kribs, H. Dewey

    The purpose of this investigation was to empirically demonstrate and evaluate a brassboard for computerized collective training for teams (COLT2). The underlying tasks were to (1) conduct a state of the art assessment of instructional strategies appropriate for COLT2, (2) derive a conceptual framework for COLT2 instructional strategies, (3)…

  12. Implementation of a Computerized Maintenance Management System

    NASA Technical Reports Server (NTRS)

    Shen, Yong-Hong; Askari, Bruce

    1994-01-01

    A primer Computerized Maintenance Management System (CMMS) has been established for NASA Ames pressure component certification program. The CMMS takes full advantage of the latest computer technology and SQL relational database to perform periodic services for vital pressure components. The Ames certification program is briefly described and the aspects of the CMMS implementation are discussed as they are related to the certification objectives.

  13. Computerized Inspection Of Gear-Tooth Surfaces

    NASA Technical Reports Server (NTRS)

    Handschuh, R. F.; Litvin, F. L.; Zhang, Y.; Kuan, C.

    1994-01-01

    Method of manufacturing gears with precisely shaped teeth involves computerized inspection of gear-tooth surfaces followed by adjustments of machine-tool settings to minimize deviations between real and theoretical versions of surfaces. Thus, iterated cycles of cutting gear teeth, inspection, and adjustments help increase and/or maintain precision of subsequently manufactured gears.

  14. Computerizing the Chinese International School Libraries.

    ERIC Educational Resources Information Center

    McMahon, Marilyn

    This paper describes the computerization of the libraries in the Chinese International School in Hong Kong. The Infant, Junior and Secondary libraries, with a staff of three professional librarians, one library assistant, and one audiovisual technician, needed an automated system which could support their bilingual curriculum. Two computer systems…

  15. Computerized Numerical Control Test Item Bank.

    ERIC Educational Resources Information Center

    Reneau, Fred; And Others

    This guide contains 285 test items for use in teaching a course in computerized numerical control. All test items were reviewed, revised, and validated by incumbent workers and subject matter instructors. Items are provided for assessing student achievement in such aspects of programming and planning, setting up, and operating machines with…

  16. Item Selection in Computerized Classification Testing

    ERIC Educational Resources Information Center

    Thompson, Nathan A.

    2009-01-01

    Several alternatives for item selection algorithms based on item response theory in computerized classification testing (CCT) have been suggested, with no conclusive evidence on the substantial superiority of a single method. It is argued that the lack of sizable effect is because some of the methods actually assess items very similarly through…

  17. Termination Criteria for Computerized Classification Testing

    ERIC Educational Resources Information Center

    Thompson, Nathan A.

    2011-01-01

    Computerized classification testing (CCT) is an approach to designing tests with intelligent algorithms, similar to adaptive testing, but specifically designed for the purpose of classifying examinees into categories such as "pass" and "fail." Like adaptive testing for point estimation of ability, the key component is the…

  18. Strategies for Computerized Adaptive Grading Testing.

    ERIC Educational Resources Information Center

    Xiao, Beiling

    1999-01-01

    Evaluated three strategies for assigning examinees to grading categories in computerized adaptive testing. The expected a posteriori-based method had more correct classifications in the middle range of grade levels and more errors for the extremes than the golden section search grading test and the Z-score grading test. (SLD)

  19. Dichotomous Search Strategies for Computerized Adaptive Testing.

    ERIC Educational Resources Information Center

    Xiao, Beiling

    Dichotomous search strategies (DSSs) for computerized adaptive testing are similar to golden section search strategies (GSSSs). Each middle point of successive search regions is a testing point. After each item is administered, the subject's obtained score is compared with the expected score at successive testing points. If the subject's obtained…

  20. Computerized Financial Reporting Based on GAAP.

    ERIC Educational Resources Information Center

    Tikkanen, Stan; Liljeberg, Burt

    1983-01-01

    Describes the statewide computerized system developed in Minnesota following the 1976 enactment of the Uniform Financial Accounting and Reporting Standards (UFARS) law. UFARS includes provisions for an advisory council responsible for recommending accounting and reporting procedures, and seven data processing centers to serve all 560 Minnesota…

  1. An Introduction to the Computerized Adaptive Testing

    ERIC Educational Resources Information Center

    Tian, Jian-quan; Miao, Dan-min; Zhu, Xia; Gong, Jing-jing

    2007-01-01

    Computerized adaptive testing (CAT) has unsurpassable advantages over traditional testing. It has become the mainstream in large scale examinations in modern society. This paper gives a brief introduction to CAT including differences between traditional testing and CAT, the principles of CAT, psychometric theory and computer algorithms of CAT, the…

  2. Evaluating Content Alignment in Computerized Adaptive Testing

    ERIC Educational Resources Information Center

    Wise, Steven L.; Kingsbury, G. Gage; Webb, Norman L.

    2015-01-01

    The alignment between a test and the content domain it measures represents key evidence for the validation of test score inferences. Although procedures have been developed for evaluating the content alignment of linear tests, these procedures are not readily applicable to computerized adaptive tests (CATs), which require large item pools and do…

  3. Plasma interactions in the Martian Nightside Ionosphere

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Fowler, C. M.; Ergun, R.; Weber, T. D.; Andrews, D. J.; Morooka, M. W.; Delory, G. T.; Eriksson, A. I.; Mitchell, D. L.; McFadden, J. P.; Connerney, J. E. P.

    2015-12-01

    Based on measurements from a number of missions at Mars the nightside ionosphere is patchy. The new mission MAVEN dedicated to observe the upper atmosphere and the plasma interactions provides the first comprehensive observations of the low altitude nightside ionosphere. Observations show that at density gradients the plasma is unstable and significant wave power, heated/accelerated electrons, and heated ions are co-located. Below 300 km, thermal electrons (>3 eV) are observed at the gradients to low density regions. The nightside ionosphere below 180 km is thought to be maintained by electron impact ionization and therefore these regions with thermal electrons may be the primary energy source for the low altitude ionosphere. Outside of the low density regions the plasma is cold. These observations suggest that the wave heating might be the primary process in the Matrian nightside ionosphere. The characteristics of these regions associated with density gradients will be presented and discussed in this presentation.

  4. Interactions between the polar ionosphere and thermosphere

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.

    1987-01-01

    The temperature, composition and circulation of the ionosphere and thermosphere in the polar regions are closely coupled and display a marked variation with altitude, latitude, longitude, universal time, season, solar cycle, and geomagnetic activity. To a large degree, this variation is a consequence of the effect that magnetospheric electric fields, particle precipitation, and heat flows have on the ionosphere-thermosphere system. These magnetospheric processes act to produce ionospheric hot spots, plasma blobs, localized ionization troughs, extended tongues of ionization and ion composition changes. These ionospheric features then affect the thermosphere because of ion-neutral momentum and energy coupling. The resulting interactions act to modify the thermospheric circulation, composition, and temperature, and this, in turn, affects the ionosphere. However, there are significant time delays associated with the various interactions. These and other results are reviewed.

  5. Modifying the ionosphere with intense radio waves.

    PubMed

    Utlaut, W F; Cohen, R

    1971-10-15

    The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications.

  6. Approaches to ionospheric modelling, simulation and prediction

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Sojka, J. J.

    1992-08-01

    The ionosphere is a complex, multispecies, anisotropic medium that exhibits a significant variation with time, space, season, solar cycle, and geomagnetic activity. In recent years, a wide range of models have been developed in an effort to describe ionospheric behavior. The modeling efforts include: (1) empirical models based on extensive worldwide data sets; (2) simple analytical models for a restricted number of ionospheric parameters; (3) comprehensive, 3D, time-dependent models that require supercomputers; (4) spherical harmonic models based on fits to output obtained from comprehensive numerical models; and (5) ionospheric models driven by real-time magnetospheric inputs. In an effort to achieve simplicity, some of the models have been restricted to certain altitude or latitude domains, while others have been restricted to certain ionospheric parameters, such as the F-region peak density, the auroral conductivity, and the plasma temperatures. The current status of the modeling efforts is reviewed.

  7. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

    Bernhardt, P.A.; Price, K.M.; da Rosa, A.V.

    1980-06-01

    This report describes experimental and theoretical studies related to ionospheric disturbances produced by rocket exhaust vapors. The purpose of our research was to estimate the ionospheric effects of the rocket launches which will be required to place the Satellite Power System (SPS) in operation. During the past year, we have developed computational tools for numerical simulation of ionospheric changes produced by the injection of rocket exhaust vapors. The theoretical work has dealt with (1) the limitations imposed by condensation phenomena in rocket exhaust; (2) complete modeling of the ionospheric depletion process including neutral gas dynamics, plasma physics, chemistry and thermal processes; and (3) the influence of the modified ionosphere on radio wave propagation. We are also reporting on electron content measurements made during the launch of HEAO-C on Sept. 20, 1979. We conclude by suggesting future experiments and areas for future research.

  8. Charged particles in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Tripathi, Sachchida

    2010-05-01

    Charged particles in Titan's ionosphere Marykutty Michael1, Sachchida Nand Tripathi1,2,3, Pratima Arya1 1Indian Institute of Technology Kanpur 2Oak Ridge Associated Universities 3NASA Goddard Space Flight Center Observations by two instruments onboard the Cassini spacecraft, Ion Neutral Mass Spectrometer (INMS) and CAssini Plasma Spectrometer (CAPS), revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units at altitudes of 950 - 1400 km in the atmosphere of Titan (Waite et al., 2007; Crary et al., 2009). Though these particles were believed to be molecules, they are most likely aerosols formed by the clumping of smaller molecules (Waite et al., 2009). These particles were estimated to have a density of 10-3 kg m-3 and a size of up to 256 nm. The existence of very heavy ions has also been observed by the CAPS components with a mass by charge ratio of up to 10000 (Coates et al., 2007, 2009; Sittler et al., 2009). The goal of this paper is to find out whether the so called heavy ions (or charged particles) are generated by the charge transfer of ions and electrons to the particles. The charging of these particles has been studied by using the charge balance equations that include positive ions, negative ions, electrons, neutral and charged particles. Information on the most abundant ion clusters are obtained from Vuitton et al., (2009) and Wilson and Atreya, (2004). Mass by charge ratio thus calculated will be compared with those observed by Coates et al. (2007). References: Coates AJ, et al., Discovery of heavy negative ions in Titan's ionosphere, Geophys. Res. Lett., 34:L22103, 2007. Coates AJ, et al., Heavy negative ions in titan's ionosphere: altitude and latitude dependence. Planet. Space Sci., doi:10.1016/j.pss.2009.05.009, 2009. Crary F.J., et al., Heavy ions, temperatures and winds in titan's ionosphere: Combined cassini caps and inms observations. Planet. Space Sci., doi:10.1016/j.pss.2009.09.006, 2009

  9. Ionospheric data assimilation and forecasting during storms

    NASA Astrophysics Data System (ADS)

    Chartier, Alex T.; Matsuo, Tomoko; Anderson, Jeffrey L.; Collins, Nancy; Hoar, Timothy J.; Lu, Gang; Mitchell, Cathryn N.; Coster, Anthea J.; Paxton, Larry J.; Bust, Gary S.

    2016-01-01

    Ionospheric storms can have important effects on radio communications and navigation systems. Storm time ionospheric predictions have the potential to form part of effective mitigation strategies to these problems. Ionospheric storms are caused by strong forcing from the solar wind. Electron density enhancements are driven by penetration electric fields, as well as by thermosphere-ionosphere behavior including Traveling Atmospheric Disturbances and Traveling Ionospheric Disturbances and changes to the neutral composition. This study assesses the effect on 1 h predictions of specifying initial ionospheric and thermospheric conditions using total electron content (TEC) observations under a fixed set of solar and high-latitude drivers. Prediction performance is assessed against TEC observations, incoherent scatter radar, and in situ electron density observations. Corotated TEC data provide a benchmark of forecast accuracy. The primary case study is the storm of 10 September 2005, while the anomalous storm of 21 January 2005 provides a secondary comparison. The study uses an ensemble Kalman filter constructed with the Data Assimilation Research Testbed and the Thermosphere Ionosphere Electrodynamics General Circulation Model. Maps of preprocessed, verticalized GPS TEC are assimilated, while high-latitude specifications from the Assimilative Mapping of Ionospheric Electrodynamics and solar flux observations from the Solar Extreme Ultraviolet Experiment are used to drive the model. The filter adjusts ionospheric and thermospheric parameters, making use of time-evolving covariance estimates. The approach is effective in correcting model biases but does not capture all the behavior of the storms. In particular, a ridge-like enhancement over the continental USA is not predicted, indicating the importance of predicting storm time electric field behavior to the problem of ionospheric forecasting.

  10. The Ionospheric Forerunners of Earthquakes.*

    NASA Astrophysics Data System (ADS)

    Oraevsky, V. N.; Depueva, A. Kh.; Ruzhin, Yu. Ya.; Stefan, V.

    1996-11-01

    A comprehensive analysis of various seismoionospheric precursors was carried out. This made it possible to select three main precursor types in ionosphere characterized by location and time of appearance. It is shown that common property of all seismoionospheric precursors is the fact that horizontal dimensions of precursor observations exist within the radius of earthquake epicenter originally defined by Dobrovolsky theory for ground precursor measurement. Our argument is in favor of atmospheric electricity as a possible cause for appearance of seismoionospheric precursors. Supported in part by Tesla Labs, Inc., La Jolla, CA 92038-2946. ^1Permanent address: IZMIRAN, Troitsk, Moscow Region, Russia.

  11. Aerosol growth in Titan's ionosphere.

    PubMed

    Lavvas, Panayotis; Yelle, Roger V; Koskinen, Tommi; Bazin, Axel; Vuitton, Véronique; Vigren, Erik; Galand, Marina; Wellbrock, Anne; Coates, Andrew J; Wahlund, Jan-Erik; Crary, Frank J; Snowden, Darci

    2013-02-19

    Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere.

  12. Saturn: atmosphere, ionosphere, and magnetosphere.

    PubMed

    Gombosi, Tamas I; Ingersoll, Andrew P

    2010-03-19

    The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn's atmosphere and magnetosphere?

  13. New Concepts in Ionospheric Modification

    DTIC Science & Technology

    1987-04-01

    30/8 198 Arl8 15. SUPPLEMENTARY NOTATION . 17 COSATI CODES ~ .SUBJECT TERMS (Continue on revro If necessary antd identify by block number) W. FIELD...reverse it neceuarY and identif,f by block .iu"boet) Thi repor t conlsiders the ionospheric modi fication that can be produced by energetic cr ,cc pa i. I...SECURITY CLASSIFICATION OF T,4lF PAGE So Block 19 Cont’d Sregions inaccessible to a charged particle beam from the same vhce I . ’ .°° .4.o. ° 4.. *1

  14. Determination of travelling ionospheric disturbances

    NASA Technical Reports Server (NTRS)

    Degenhardt, W.; Hartmann, G. H.; Davies, K.

    1978-01-01

    A total of 35 days of Faraday rotation data was obtained from the ATS-6 radio beacon experiment operating with the closely spaced network of Elbert, Table Mountain, and Fort Morgan. The 140-MHz Faraday bandpass data are uncorrelated in the transmission range from 8 to 45 minutes. There are distinct, well correlated, and time-displaced maxima and minima that allow the calculation of the speed and direction of horizontal motions of plane fronts of disturbances in the ionosphere. For some selected events, velocities between 88 and 278 m/sec were obtained.

  15. Ionospheric Challenges for GNSS Based Augmentation Systems

    NASA Astrophysics Data System (ADS)

    Doherty, P.; Valladares, C. E.

    2007-12-01

    The ionosphere is a highly dynamic physical phenomenon that presents a variable source of error for Global Navigation Satellite System (GNSS) signals and GNSS based operational systems. The Federal Aviation Administration's (FAA) Wide-Area Augmentation System (WAAS) was designed to enhance the GNSS standard positioning service by providing additional accuracy, availability and integrity that is sufficient for use in commercial aviation. It is the first of a number of planned regional Satellite Based Augmentation Systems (SBAS). Other systems in development include the European EGNOS system, the MSAS system in Japan and the GAGAN system in India. In addition, the South American countries are investigating the feasibility of operating an SBAS system in this region. Much of the WAAS ionospheric research and development focused on defining and mitigating ionospheric challenges characteristic of the mid-latitude regions, where the ionosphere is well studied and relatively quiescent. The EGNOS and MSAS systems will primarily operate under a similarly quiescent mid-latitude ionosphere. SBAS system development in South America, India and other low-latitude regions, however, will have to contend with much more extreme conditions. These conditions include strong spatial and temporal gradients, plasma depletions and scintillation. All of these conditions have a potential to limit SBAS performance in the low latitude regions. This presentation will review the effects that the ionosphere has on the mid-latitude WAAS system. It will present the techniques that are used to mitigate ionospheric disturbances induced on the system during severe geomagnetic activity and it will quantify the effect that this activity has on system performance. The presentation will then present data from the South American Low-latitude Ionospheric Sensor Network (LISN) that can be used to infer the ionospheric effects on SBAS performance in the most challenging low-latitude ionospheric environment

  16. Online service for monitoring the ionosphere based on data from the global navigation satellite system

    NASA Astrophysics Data System (ADS)

    Aleshin, I. M.; Alpatov, V. V.; Vasil'ev, A. E.; Burguchev, S. S.; Kholodkov, K. I.; Budnikov, P. A.; Molodtsov, D. A.; Koryagin, V. N.; Perederin, F. V.

    2014-07-01

    A service is described that makes possible the effective construction of a three-dimensional ionospheric model based on the data of ground receivers of signals from global navigation satellite positioning systems (GNSS). The obtained image has a high resolution, mainly because data from the IPG GNSS network of the Federal Service for Hydrometeorology and Environmental Monitoring (Rosgidromet) are used. A specially developed format and its implementation in the form of SQL structures are used to collect, transmit, and store data. The method of high-altitude radio tomography is used to construct the three-dimensional model. The operation of all system components (from registration point organization to the procedure for constructing the electron density three-dimensional distribution and publication of the total electron content map on the Internet) has been described in detail. The three-dimensional image of the ionosphere, obtained automatically, is compared with the ionosonde measurements, calculated using the two-dimensional low-altitude tomography method and averaged by the ionospheric model.

  17. Ionospheric Behaviors Over Korea Peninsula During the Super Geomagnetic Storm Using GPS Measurements

    NASA Astrophysics Data System (ADS)

    Chung, Jong-Kyun; Choi, Byung-Kyu; Baek, Jungho; Jee, Geonhwa; Cho, Jungho

    2009-12-01

    The super-geomagnetic storms called 2003 Halloween event globally occurred during the period of 29 through 31 which are the following days when the solar flares of X18 class exploded on 28 October 2003. The S4 index from GPS signal strength and the peak electron density (NmF2) from GPS tomography method are analyzed according to the date. The occurrences of the cycle slip and scintillation in the GPS signals are 1,094 and 1,387 on 28 and 29 October, respectively and these values are higher than 604 and 897 on 30 and 31 October. These mean the ionospheric disturbances are not always generated by the period of geomagnetic storm. Therefore, GPS S4 index is useful to monitor the ionospheric disturbances. Behaviors of ionospheric electron density estimated from GPS tomography method are analyzed with the date. At UT = 18 hr, the maximum NmF2 is shown on 28 October. It agrees with NmF2 variation measured from Anyang ionosonde, and the GPS signal are better condition on 30 and 31 October than 28 October. In conclusion, GPS signal condition is relation with geomagnetic activities, and depend upon the variation of the electron density. We will study the long-term data to examine the relationship between the GPS signal quality and the electron density as the further works.

  18. CT based computerized identification and analysis of human airways: A review

    SciTech Connect

    Pu Jiantao; Gu Suicheng; Liu Shusen; Zhu Shaocheng; Wilson, David; Siegfried, Jill M.; Gur, David

    2012-05-15

    As one of the most prevalent chronic disorders, airway disease is a major cause of morbidity and mortality worldwide. In order to understand its underlying mechanisms and to enable assessment of therapeutic efficacy of a variety of possible interventions, noninvasive investigation of the airways in a large number of subjects is of great research interest. Due to its high resolution in temporal and spatial domains, computed tomography (CT) has been widely used in clinical practices for studying the normal and abnormal manifestations of lung diseases, albeit there is a need to clearly demonstrate the benefits in light of the cost and radiation dose associated with CT examinations performed for the purpose of airway analysis. Whereas a single CT examination consists of a large number of images, manually identifying airway morphological characteristics and computing features to enable thorough investigations of airway and other lung diseases is very time-consuming and susceptible to errors. Hence, automated and semiautomated computerized analysis of human airways is becoming an important research area in medical imaging. A number of computerized techniques have been developed to date for the analysis of lung airways. In this review, we present a summary of the primary methods developed for computerized analysis of human airways, including airway segmentation, airway labeling, and airway morphometry, as well as a number of computer-aided clinical applications, such as virtual bronchoscopy. Both successes and underlying limitations of these approaches are discussed, while highlighting areas that may require additional work.

  19. CT based computerized identification and analysis of human airways: a review.

    PubMed

    Pu, Jiantao; Gu, Suicheng; Liu, Shusen; Zhu, Shaocheng; Wilson, David; Siegfried, Jill M; Gur, David

    2012-05-01

    As one of the most prevalent chronic disorders, airway disease is a major cause of morbidity and mortality worldwide. In order to understand its underlying mechanisms and to enable assessment of therapeutic efficacy of a variety of possible interventions, noninvasive investigation of the airways in a large number of subjects is of great research interest. Due to its high resolution in temporal and spatial domains, computed tomography (CT) has been widely used in clinical practices for studying the normal and abnormal manifestations of lung diseases, albeit there is a need to clearly demonstrate the benefits in light of the cost and radiation dose associated with CT examinations performed for the purpose of airway analysis. Whereas a single CT examination consists of a large number of images, manually identifying airway morphological characteristics and computing features to enable thorough investigations of airway and other lung diseases is very time-consuming and susceptible to errors. Hence, automated and semiautomated computerized analysis of human airways is becoming an important research area in medical imaging. A number of computerized techniques have been developed to date for the analysis of lung airways. In this review, we present a summary of the primary methods developed for computerized analysis of human airways, including airway segmentation, airway labeling, and airway morphometry, as well as a number of computer-aided clinical applications, such as virtual bronchoscopy. Both successes and underlying limitations of these approaches are discussed, while highlighting areas that may require additional work.

  20. Inductive ionospheric solver for magnetospheric MHD simulations

    NASA Astrophysics Data System (ADS)

    Vanhamäki, H.

    2011-01-01

    We present a new scheme for solving the ionospheric boundary conditions required in magnetospheric MHD simulations. In contrast to the electrostatic ionospheric solvers currently in use, the new solver takes ionospheric induction into account by solving Faraday's law simultaneously with Ohm's law and current continuity. From the viewpoint of an MHD simulation, the new inductive solver is similar to the electrostatic solvers, as the same input data is used (field-aligned current [FAC] and ionospheric conductances) and similar output is produced (ionospheric electric field). The inductive solver is tested using realistic, databased models of an omega-band and westward traveling surge. Although the tests were performed with local models and MHD simulations require a global ionospheric solution, we may nevertheless conclude that the new solution scheme is feasible also in practice. In the test cases the difference between static and electrodynamic solutions is up to ~10 V km-1 in certain locations, or up to 20-40% of the total electric field. This is in agreement with previous estimates. It should also be noted that if FAC is replaced by the ground magnetic field (or ionospheric equivalent current) in the input data set, exactly the same formalism can be used to construct an inductive version of the KRM method originally developed by Kamide et al. (1981).

  1. Development of two new ionospheric indices

    NASA Astrophysics Data System (ADS)

    Noguera D., Cesar O.

    The solar terrestrial environment presently is characterized by a suite of indices that represent the system dynamics and indicate the degree of space weather effects. These indices have extended heritage based on measurements that are well calibrated and readily available. Examples of these are the solar radio flux at 10.7 cm (F10.7), magnetospheric currents inferred from ground-based magnetographs (Dst), and auroral electrojet also based on ground-based magnetograms (AE family of indices). At the present time, the ionosphere dynamics and response to space weather are not characterized by a "true" ionosphere index. However, because ionospheric plasma variability is a major adverse effect on makind's space technologies, the creation of such an index may be appropriate. The major adverse effects are associated with radio wave propagation, either communication or navigation, through the ionosphere. Over the past decade, thousands of ground-based dual frequency GPS receivers have been deployed, each of which measures ionospheric total electron content (TEC) continuously in multiple directions. Hence, with the standardized formatting of these measurements and their relatively real-time nature, a unique ionospheric data stream exists from which indices can, in principle, be developed. This study is an initial exploration of how purely an ionospheric index could be derived from these GPS-TEC data. Regional versus global issues are addressed, as well as diurnal issues.

  2. Ionospheric Indices Based on GPS TEC

    NASA Astrophysics Data System (ADS)

    Noguera, C.; Sojka, J. J.; Thompson, D. C.; Schunk, R. W.

    2005-12-01

    The solar terrestrial environment is presently characterized by a suite of indices that represent the system's dynamics and indicate the degree of space weather effects. These indices an have extended heritage based on measurements that are well calibrated and readily available. Examples of these are the solar radio flux at 10.7 cm (F10.7), magnetospheric currents inferred from ground-based magnetographs (Dst), and auroral electrojet also based on ground-based magnetograms (AE family of indices). At the present time, the ionosphere's dynamics and response to space weather are not characterized by a "true" ionosphere index. However, since ionospheric plasma variability has a major adverse effect on human space technologies, the creation of such an index may be appropriate. The major adverse effects are associated with radio wave propagation through the ionosphere either communications or navigation. Over the past decade thousands of ground-based dual frequency GPS receivers have been deployed. Each of these measures ionospheric total electron content (TEC) continuously in multiple directions. Hence, with the standardized formatting of these measurements and their near real-time nature, a unique ionospheric data stream exists from which indices can, in principle, be developed. This study is an initial exploration of how a purely ionospheric index could be derived from these GPS TEC data. Regional versus global issues are addressed, as well as diurnal issues.

  3. Computerized analysis of pelvic incidence from 3D images

    NASA Astrophysics Data System (ADS)

    Vrtovec, Tomaž; Janssen, Michiel M. A.; Pernuš, Franjo; Castelein, René M.; Viergever, Max A.

    2012-02-01

    The sagittal alignment of the pelvis can be evaluated by the angle of pelvic incidence (PI), which is constant for an arbitrary subject position and orientation and can be therefore compared among subjects in standing, sitting or supine position. In this study, PI was measured from three-dimensional (3D) computed tomography (CT) images of normal subjects that were acquired in supine position. A novel computerized method, based on image processing techniques, was developed to automatically determine the anatomical references required to measure PI, i.e. the centers of the femoral heads in 3D, and the center and inclination of the sacral endplate in 3D. Multiplanar image reformation was applied to obtain perfect sagittal views with all anatomical structures completely in line with the hip axis, from which PI was calculated. The resulting PI (mean+/-standard deviation) was equal to 46.6°+/-9.2° for male subjects (N = 189), 47.6°+/-10.7° for female subjects (N = 181), and 47.1°+/-10.0° for all subjects (N = 370). The obtained measurements of PI from 3D images were not biased by acquisition projection or structure orientation, because all anatomical structures were completely in line with the hip axis. The performed measurements in 3D therefore represent PI according to the actual geometrical relationships among anatomical structures of the sacrum, pelvis and hips, as observed from the perfect sagittal views.

  4. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

    This report investigates the potential of using Global Positioning System (GPS) data and a model of the ionosphere to supply a measure of the sub-satellite Total Electron Current (TEC) of the required accuracy (10 TECU rms) for the purpose of calibrating single frequency radar altimeter measurements. Since climatological (monthly mean) models are known to be in error by as much as 50 percent, this work focused on the Parameterized Real-Time Ionospheric Specification Model (PRISM) which has the capability to improve model accuracy by ingesting (adjusting to) in situ ionospheric measurements. A set of globally distributed TEC measurements were generated using GPS data and were used as input to improve the accuracy of the PRISM model. The adjusted PRISM TEC values were compared to TOPEX dual frequency TEC measurements (which are considered truth) for a number of TOPEX sub-satellite tracks. The adjusted PRISM values generally compared to the TOPEX measurements within the 10 TECU accuracy requirements when the sub-satellite track passed within 300 to 400 km of the GPS TEC data or when the track passed through a night time ionosphere. However, when the sub-satellite points were greater than 300 to 400 km away from the GPS TEC data or when a local noon ionosphere was sampled, the adjusted PRISM values generally differed by greater than 10 TECU rms with data excursions from the TOPEX TEC measurements of as much as 40 TECU (an 8 cm path delay error at K band). Therefore, it can be concluded from this analysis that an unrealistically large number of GPS stations would be needed to predict sub-satellite TEC at the 10 TECU level in the day time ionosphere using a model such as PRISM. However, a technique currently being studied at the Jet Propulsion Laboratory (JPL) may provide a means of supplying adequate TEC data to meet the 10 TECU ionospheric correction accuracy when using a realistic number of ionospheric stations. This method involves using global GPS TEC data to

  5. Ionospheric Profiles from Ultraviolet Remote Sensing

    DTIC Science & Technology

    1998-01-01

    remote sensing of the ionosphere from orbiting space platforms. Remote sensing of the nighttime ionosphere is a relatively straightforward process due to the absence of the complications brought about by daytime solar radiation. Further, during the nighttime hours, the O(+)-H(+) transition level in both the mid- and low-latitude ionospheres lies around 750 km, which is within the range of accuracy of the path matrix inversion. The intensity of the O(+)-e(-) recombination radiation as observed from orbiting space platforms can now be used to

  6. The solar wind-magnetosphere-ionosphere system

    PubMed

    Lyon

    2000-06-16

    The solar wind, magnetosphere, and ionosphere form a single system driven by the transfer of energy and momentum from the solar wind to the magnetosphere and ionosphere. Variations in the solar wind can lead to disruptions of space- and ground-based systems caused by enhanced currents flowing into the ionosphere and increased radiation in the near-Earth environment. The coupling between the solar wind and the magnetosphere is mediated and controlled by the magnetic field in the solar wind through the process of magnetic reconnection. Understanding of the global behavior of this system has improved markedly in the recent past from coordinated observations with a constellation of satellite and ground instruments.

  7. Metropolitan Orlando area computerized signal system

    SciTech Connect

    Aleman, F.R. ); Allen, T.M. )

    1990-06-01

    Florida's Orlando metropolitan area, which has a population measuring 1 million, is among the fastest growing areas in the nation. The city's weather and popular attractions draw 9 to 10 million tourists annually, half of them arriving in their own cars. Add to this the 1.1 million automobiles already on the streets, and the traffic problems become a nightmare. The Orlando metropolitan area has approximately 550 operational traffic signals, with an increasing number of new signals added each year to control the city's expanding growth. A central, computerized signal system has been conceived as one of the solutions necessary to cope with this tremendous traffic growth. The system is flexible, expandable, and capable of meeting future technical challenges. This article describes the steps that led to the feasibility study, design, and implementation of the Orlando area computerized signal system.

  8. Ionosphere/thermosphere heating determined from dynamic magnetosphere-ionosphere/thermosphere coupling

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.

    2011-09-01

    Ionosphere/thermosphere heating driven by magnetospheric convection is investigated through a three-fluid inductive (including Faraday's law) approach to describing magnetosphere-ionosphere/thermosphere coupling, for a 1-D stratified ionosphere/thermosphere in this initial study. It is shown that the response of the ionosphere/thermosphere and thus the heating is dynamic and height-dependent. The heating is essentially frictional in nature rather than Joule heating as commonly assumed. The heating rate reaches a quasi-steady state after about 25 Alfvén travel times. During the dynamic period, the heating can be enhanced and displays peaks at multiple times due to wave reflections. The dynamic heating rate can be more than twice greater than the quasi-steady state value. The heating is strongest in the E-layer but the heating rate per unit mass is concentrated around the F-layer peak height. This implies a potential mechanism of driving O+ upflow from O+ rich F-layer. It is shown that the ionosphere/thermosphere heating caused by the magnetosphere-ionosphere coupling can be simply evaluated through the relative velocity between the plasma and neutrals without invoking field-aligned currents, ionospheric conductance, and electric field. The present study provides understanding of the dynamic magnetosphere-ionosphere/thermosphere coupling from the ionospheric/thermospheric view in addition to magnetospheric perspectives.

  9. Errors associated with outpatient computerized prescribing systems

    PubMed Central

    Rothschild, Jeffrey M; Salzberg, Claudia; Keohane, Carol A; Zigmont, Katherine; Devita, Jim; Gandhi, Tejal K; Dalal, Anuj K; Bates, David W; Poon, Eric G

    2011-01-01

    Objective To report the frequency, types, and causes of errors associated with outpatient computer-generated prescriptions, and to develop a framework to classify these errors to determine which strategies have greatest potential for preventing them. Materials and methods This is a retrospective cohort study of 3850 computer-generated prescriptions received by a commercial outpatient pharmacy chain across three states over 4 weeks in 2008. A clinician panel reviewed the prescriptions using a previously described method to identify and classify medication errors. Primary outcomes were the incidence of medication errors; potential adverse drug events, defined as errors with potential for harm; and rate of prescribing errors by error type and by prescribing system. Results Of 3850 prescriptions, 452 (11.7%) contained 466 total errors, of which 163 (35.0%) were considered potential adverse drug events. Error rates varied by computerized prescribing system, from 5.1% to 37.5%. The most common error was omitted information (60.7% of all errors). Discussion About one in 10 computer-generated prescriptions included at least one error, of which a third had potential for harm. This is consistent with the literature on manual handwritten prescription error rates. The number, type, and severity of errors varied by computerized prescribing system, suggesting that some systems may be better at preventing errors than others. Conclusions Implementing a computerized prescribing system without comprehensive functionality and processes in place to ensure meaningful system use does not decrease medication errors. The authors offer targeted recommendations on improving computerized prescribing systems to prevent errors. PMID:21715428

  10. Computerized flow monitors detect small kicks

    SciTech Connect

    McCann, D.; White, D. )

    1992-02-24

    This paper reports on a smart alarm system installed on a number of offshore rigs and one land rig which can detect kicks more quickly than conventional systems. This rapid kick detection improves rig safety because the smaller the detected influx, the easier it is to control the well. The extensive computerized monitoring system helps drilling personnel detect fluid influxes and fluid losses before the changes in flow would normally be apparent.

  11. Objective assessment of clinical computerized thermal images

    NASA Astrophysics Data System (ADS)

    Anbar, Michael

    1991-06-01

    The efficacy of diagnostic thermal imaging, the visualization of abnormal distribution of temperature over the human skin, can be significantly augmented by computerized image processing procedures that overcome the limitations of subjective image assessment. This paper reviews diagnostic thermal imaging and describes common image processing approaches applicable to the analysis of static thermal images and of time series of images that provide diagnostic information about the dynamics of neurological regulation of skin temperature.

  12. The NASA/LRC Computerized Test System

    NASA Technical Reports Server (NTRS)

    Richardson, W. Kirk; Washburn, David A.; Hopkins, William D.; Savage-Rumbaugh, E. Sue; Rumbaugh, Duane M.

    1990-01-01

    A new testing package, including apparatus and tasks for the behavioral study of a number of species in a variety of experiments is presented. The package is described with respect to the kinds of comparative psychological investigations for which it is best suited. The preliminary data generated within this new testing paradigm demonstrate that the NASA/LRC Computerized Test System provides a flexible yet powerful environment for the investigation of behavioral and psychological processes.

  13. Pseudolocal tomography

    DOEpatents

    Katsevich, Alexander J.; Ramm, Alexander G.

    1996-01-01

    Local tomographic data is used to determine the location and value of a discontinuity between a first internal density of an object and a second density of a region within the object. A beam of radiation is directed in a predetermined pattern through the region of the object containing the discontinuity. Relative attenuation data of the beam is determined within the predetermined pattern having a first data component that includes attenuation data through the region. The relative attenuation data is input to a pseudo-local tomography function, where the difference between the internal density and the pseudo-local tomography function is computed across the discontinuity. The pseudo-local tomography function outputs the location of the discontinuity and the difference in density between the first density and the second density.

  14. Computerized implant-dentistry: Advances toward automation

    PubMed Central

    Gulati, Minkle; Anand, Vishal; Salaria, Sanjeev Kumar; Jain, Nikil; Gupta, Shilpi

    2015-01-01

    Advancements in the field of implantology such as three-dimensional imaging, implant-planning software, computer-aided-design/computer-aided-manufacturing (CAD/CAM) technology, computer-guided, and navigated implant surgery have led to the computerization of implant-dentistry. This three-dimensional computer-generated implant-planning and surgery has not only enabled accurate preoperative evaluation of the anatomic limitations but has also facilitated preoperative planning of implant positions along with virtual implant placement and subsequently transferring the virtual treatment plans onto the surgical phase via static (guided) or dynamic (navigated) systems aided by CAD/CAM technology. Computerized-implant-dentistry being highly predictable and minimally invasive in nature has also allowed implant placement in patients with medical comorbidities (e.g. radiation therapy, blood dyscrasias), in patients with complex problems following a significant alteration of the bony anatomy as a result of benign or malignant pathology of the jaws or trauma and in patients with other physical and emotional problems. With significant achievements accomplished in the field of computerized implant-dentistry, attempts are now been made toward complete automation of implant-dentistry. PMID:25810585

  15. Ionospheric Modelling using GPS to Calibrate the MWA. II: Regional Ionospheric Modelling using GPS and GLONASS to Estimate Ionospheric Gradients

    NASA Astrophysics Data System (ADS)

    Arora, B. S.; Morgan, J.; Ord, S. M.; Tingay, S. J.; Bell, M.; Callingham, J. R.; Dwarakanath, K. S.; For, B.-Q.; Hancock, P.; Hindson, L.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

    2016-07-01

    We estimate spatial gradients in the ionosphere using the Global Positioning System and GLONASS (Russian global navigation system) observations, utilising data from multiple Global Positioning System stations in the vicinity of Murchison Radio-astronomy Observatory. In previous work, the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array. Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System stations than is currently available at the Murchison Radio-astronomy Observatory.

  16. The Combined Radio Interferometry and COSMIC Experiment in Tomography (CRICKET) Campaign

    NASA Astrophysics Data System (ADS)

    Dymond, Kenneth; Coker, Clayton; Bernhardt, Paul; Cohen, Aaron; Crane, Patrick; Kassim, Namir; Lazio, Joseph; Weiler, Kurt; Watts, Christopher; Rickard, Lee J.; Taylor, Greg; Schinzel, Frank; Philstrom, Ylva; Close, Sigrid; Colestock, Patrick; Myers, Steve; Datta, Abirhup

    We report on the Combined Radio Interferometry and COSMIC Experiment in Tomography Campaign (CRICKET) held on September 15 and 17, 2007. The experiment used the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC also known as FORMOSAT-3) in conjunction with the Very Large Array radio telescope, located near Socorro, NM, to study the ionosphere from the global scale down to the regional scale. Each COSMIC satellite includes three instruments capable of measuring the ionosphere: the Tiny Ionospheric Photometer (TIP), a UV radiometer; the GPS Occultation experiment (GOX), a dual-frequency GPS occultation receiver; and the Tri-band Beacon (TBB), a three frequency coherently radiating radio beacon. These three instruments have been demonstrated to be a powerful means for characterizing the global-scale ionosphere. The VLA when deployed at its largest extent and while operating at 73.8 MHz is incredibly sensitive to relative total electron content variations of the regional ionosphere over about a 30-100 km diameter area. In this work, we concentrate on the first set of observations on September 15, 2007 at approximately 0830 UT. We have successfully married these heterogeneous data sets, using a tomographic data fusion approach, to produce a consistent ionospheric specification from the global scale down to the regional scale.

  17. Ionospheric Stimulation By High Power Radio Waves

    NASA Astrophysics Data System (ADS)

    Minami, S.; Nishino, M.; Suzuki, Y.; Sato, S.; Tanikawa, T.; Nakamura, Y.; Wong, A. Y.

    1999-01-01

    We have performed an experiment to artificially stimulate the ionosphere using higher power radio waves at the HIPAS (High Power Auroral Stimulation) facility in Alaska. A radio transmission of 2.85 MHz was made at 80 MW (ERP). Diagnostics were made at the other site located 35 km from the transmission site. The results of cross-correlating the excited HF wave and observed with an 8 channel, 30 MHz scanning cosmic radio noise absorption records revealed the excited height of 90 km. Also atmospheric pressure waves observed on the ground show evident propagation of pressure waves which are generated in the ionosphere by the high-power HF wave. The results determine the excitation height of 90 km in the ionosphere and show evidence of the pressure wave coupling between the ionosphere and the lower atmosphere for periods of 10 min

  18. Propagation studies using a theoretical ionosphere model

    NASA Technical Reports Server (NTRS)

    Lee, M.

    1973-01-01

    The mid-latitude ionospheric and neutral atmospheric models are coupled with an advanced three dimensional ray tracing program to see what success would be obtained in predicting the wave propagation conditions and to study to what extent the use of theoretical ionospheric models is practical. The Penn State MK 1 ionospheric model, the Mitra-Rowe D region model, and the Groves' neutral atmospheric model are used throughout this work to represent the real electron densities and collision frequencies. The Faraday rotation and differential Doppler velocities from satellites, the propagation modes for long distance high frequency propagation, the group delays for each mode, the ionospheric absorption, and the spatial loss are all predicted.

  19. Digital Ionospheric Sounding in the Arctic.

    DTIC Science & Technology

    1977-07-01

    frequency-range bin. Goose Bay vertical ionograms were scaled in terms of 23 parameters. The monthly median curves of the most important ionospheric parameters for the period March 1975 to February 1976 are presented in the report.

  20. Magnetic Fluctuations in the Martian Ionosphere

    NASA Technical Reports Server (NTRS)

    Espley, Jared

    2010-01-01

    The Martian ionosphere is influenced by both the solar wind and the regional magnetic fields present in the Martian crust. Both influences ought to cause time variable changes in the magnetic fields present in the ionosphere. I report observations of these magnetic field fluctuations in the Martian ionosphere. I use data from the Mars Global Surveyor magnetometer instrument. By using data from the aerobraking low altitude passes (approx. 200 km) I find that there are numerous fluctuations both near and far from the strong crustal sources. Using data from the 400 km altitude mapping phase (which is near the topside of the primary ionosphere), I look at the comparative strength of the fluctuations relative to the solar wind and temporal variations. I discuss which wave modes and instabilities could be contributing to these fluctuations. I also discuss the implications of these fluctuations for understanding energy transfer in the Martian system and the effects on atmospheric escape.

  1. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail.

  2. On the Ionospheric Holes of Venus

    NASA Astrophysics Data System (ADS)

    Collinson, G.; Fedorov, A.; Futaana, Y.; Masunaga, K.; Hartle, R. E.; Stenberg, G.; Budnik, E.; Grebowsky, J. M.; Holmstrom, M.; andre, N.; Barabash, S. V.; Zhang, T.

    2013-12-01

    One of the most intriguing unsolved mysteries that endures from the Pioneer Venus Orbiter is that of ~1000km wide ``Holes" in the nightside Ionosphere. The phenomena remains unexplained, despite their frequent observation during the first three years of the mission, and more than thirty years having elapsed since their first description in the literature. We present new observations by the ESA Venus Express of Ionospheric Holes at very high altitudes, providing us with the opportunity to study this fascinating phenomena with modern instrumentation. We discuss the insight that these new data give us into the effect of Ionospheric Holes on atmospheric escape, and the evidence that suggests that Ionospheric Holes are due to an internal planetary magnetic field.

  3. The upper atmosphere and ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Brace, Larry H.

    1992-01-01

    The topics discussed include the following: the dynamic atmosphere of Mars; possible similarities with Earth and Venus; the atmosphere and ionosphere of Mars; solar wind interactions; future approved missions; and possible future mission.

  4. Pulsating aurora: The importance of the ionosphere

    SciTech Connect

    Stenbaek-Nielsen, H.C.

    1980-05-01

    A number of different, but mainly optical, observations made in pulsating auroras are presented. These observations indicate that active ionospheric processes are likely to play an important role in causing and/or modifying pulsating aurora.

  5. Thermospheric storms and related ionospheric effects

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Spencer, N. W.

    1976-01-01

    A comparative study of thermospheric storms for equinox and winter conditions is presented based on neutral-composition measurements from the Aeros-A neutral-atmosphere temperature experiment. The main features of the two storms as inferred from changes in N2, Ar, He, and O are described, and their implications for current theories of thermospheric storms are discussed. On the basis of the study of the F-region critical frequency measured from a chain of ground-based ionospheric stations during the two storm periods, the general characteristics of the ionospheric storms and the traveling ionospheric disturbances are described. It is suggested that the positive and negative phases of ionospheric storms are different manifestations of thermospheric storms.

  6. Magnetic Earth Ionosphere Resonant Frequencies

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1994-01-01

    The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

  7. Remote Sensing of Ionosphere by IONOLAB Group

    NASA Astrophysics Data System (ADS)

    Arikan, Feza

    2016-07-01

    Ionosphere is a temporally and spatially varying, dispersive, anisotropic and inhomogeneous medium that is characterized primarily by its electron density distribution. Electron density is a complex function of spatial and temporal variations of solar, geomagnetic, and seismic activities. Ionosphere is the main source of error for navigation and positioning systems and satellite communication. Therefore, characterization and constant monitoring of variability of the ionosphere is of utmost importance for the performance improvement of these systems. Since ionospheric electron density is not a directly measurable quantity, an important derivable parameter is the Total Electron Content (TEC), which is used widely to characterize the ionosphere. TEC is proportional to the total number of electrons on a line crossing the atmosphere. IONOLAB is a research group is formed by Hacettepe University, Bilkent University and Kastamonu University, Turkey gathered to handle the challenges of the ionosphere using state-of-the-art remote sensing and signal processing techniques. IONOLAB group provides unique space weather services of IONOLAB-TEC, International Reference Ionosphere extended to Plasmasphere (IRI-Plas) model based IRI-Plas-MAP, IRI-Plas-STEC and Online IRI-Plas-2015 model at www.ionolab.org. IONOLAB group has been working for imaging and monitoring of ionospheric structure for the last 15 years. TEC is estimated from dual frequency GPS receivers as IONOLAB-TEC using IONOLAB-BIAS. For high spatio-temporal resolution 2-D imaging or mapping, IONOLAB-MAP algorithm is developed that uses automated Universal Kriging or Ordinary Kriging in which the experimental semivariogram is fitted to Matern Function with Particle Swarm Optimization (PSO). For 3-D imaging of ionosphere and 1-D vertical profiles of electron density, state-of-the-art IRI-Plas model based IONOLAB-CIT algorithm is developed for regional reconstruction that employs Kalman Filters for state

  8. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

    Hartkorn, O. A.; Saur, J.; Bloecker, A.; Strobel, D. F.; Simon, S.

    2014-12-01

    We develop a model of the ionosphere of Jupiter's moon Callisto, where we assume a stationary balance between sources and sinks of electrons and electron energy. Hence, effects of electron transport and electron energy transport are neglected. At Callisto, the production of electrons and electron energy is basically driven by photoionization, which is implemented using the EUVAC model for solar activity. Dissociative recombination is the main electron loss process, whereas electron energy loss is further driven by dissociation, electron impact ionization as well as vibrational and rotational excitations of neutral atmospheric particles. All these effects are incorporated within our model by considering the associated cross sections. The neutral atmosphere is assumed to be stationary and consists of molecular oxygen with a column density of 3 to 4 x 1020 m-2 (e.g. Kliore et al. (2002), Liang et al. (2005)). Our results can be compared to radio occultation observations of four Galileo spacecraft flybys reported by Kliore et al. (2002), which shows that this simple model can explain the general pattern of the observational data. Indeed, our results indicate that the detection of enhanced electron densities is very sensitive to the exact position of the tangential point of the radio occultation method. Our model shows that photoionization produces a strong asymmetry of the electron density distribution between day and night-side of the moon. Further, model results for the electron energy allow for an estimation of the day glow of Callisto's atmosphere. This can be compared to HST observations (Strobel et al. (2002)) in order to evaluate the density of the neutral oxygen atmosphere. Future studies imply the modeling of the modification of the ionospheric structure through interaction with upstreaming jovian magnetospheric plasma.

  9. Artificial Aurora and Ionospheric Heating by HAARP

    NASA Astrophysics Data System (ADS)

    Hadavandkhani, S.; Nikouravan, Bijan; Ghazimaghrebi, F.

    2016-08-01

    A recent experiment was achieved at HAARP to study the scaling of the ionospherically generated ELF signal with power transmitted from the high frequency (HF) array. The results were in excellent agreement with computer simulations. The outcomes approving that the ELF power increases with the square of the incident HF power. This paper present a review on the situation of the ionized particles in Ionospheric layer when stimulated by artificial an ELF and VLF external high energy radio waves.

  10. Studies of Ionospheric Irregularities: Origins and Effects

    DTIC Science & Technology

    2007-09-30

    and Ionospheric Scintillations that can be found at: GPS and ionospheric scintillations, P.M. Kintner, B.M. Ledvina , and E.R. de Paula, Space... Ledvina , and P.M. Kintner, Measurements of equatorial scintillations on the WAAS satellite signal, Radio Sci., submitted, 2005. [refereed] 7...Adv. Space Res., 31(3), 741-747, 2003. [refereed] Humphreys, T.E., B.M. Ledvina , M.L. Psiaki, A.P. Cerruti, and P.M. Kintner, Analysis of

  11. Ionospheric true height profiles from oblique ionograms

    SciTech Connect

    Reilly, M.H.

    1985-06-01

    An improved direct technique in which HF oblique ionograms are reduced to ionospheric true height profiles is introduced. The benefits of this method result principally from the use of a more accurate Breit-Tuve relation to curved earth and ionosphere geometries. By comparing the results of calculations on known cases, the extent of improvement with this technique relative to the techniques by Gething and Maliphant (1967), George (1970), and Smith (1970), is demonstrated. 14 references.

  12. Digital processing of ionospheric electron content data

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.

    1979-01-01

    Ionospheric electron content data contain periodicities that are produced by a diversity of sources including hydromagnetic waves, gravity waves, and lunar tides. Often these periodicities are masked by the strong daily variation in the data. Digital filtering can be used to isolate the weaker components. The filtered data can then be further processed to provide estimates of the source properties. In addition, homomorphic filtering may be used to identify nonlinear interactions in the ionosphere.

  13. Tsunamis warning from space :Ionosphere seismology

    SciTech Connect

    Larmat, Carene

    2012-09-04

    Ionosphere is the layer of the atmosphere from about 85 to 600km containing electrons and electrically charged atoms that are produced by solar radiation. Perturbations - layering affected by day and night, X-rays and high-energy protons from the solar flares, geomagnetic storms, lightning, drivers-from-below. Strategic for radio-wave transmission. This project discusses the inversion of ionosphere signals, tsunami wave amplitude and coupling parameters, which improves tsunami warning systems.

  14. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

    Describes how seismic tomography is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)

  15. Ionospheric Response Due to Seismic Activity

    NASA Astrophysics Data System (ADS)

    Sharma, Dinesh Kumar

    2016-07-01

    Signatures of the seismic activity in the ionospheric F2 region have been studied by analyzing the measurement of electron and ion temperatures during the occurrence of earthquake. The ionospheric electron and ion temperatures data recorded by the RPA payload aboard the Indian SROSS-C2 satellite during the period from January 1995 to December 2000 were used for the altitude range 430-630 km over Indian region. The normal day's electron and ion temperatures have been compared to the temperatures recorded during the seismic activity. The details of seismic events were obtained from USGS earthquake data information website. It has been found that the average electron temperature is enhanced during the occurrence of earthquakes by 1.2 to 1.5 times and this enhancement was for ion temperature ranging from 1.1to 1.3 times over the normal day's average temperatures. The above careful quantitative analysis of ionospheric electron and ion temperatures data shows the consistent enhancement in the ionospheric electron and ion temperatures. It is expected that the seismogenic vertical electrical field propagates up to the ionospheric heights and induces Joule heating that may cause the enhancement in ionospheric temperatures.

  16. 3D Imaging with Holographic Tomography

    NASA Astrophysics Data System (ADS)

    Sheppard, Colin J. R.; Kou, Shan Shan

    2010-04-01

    There are two main types of tomography that enable the 3D internal structures of objects to be reconstructed from scattered data. The commonly known computerized tomography (CT) give good results in the x-ray wavelength range where the filtered back-projection theorem and Radon transform can be used. These techniques rely on the Fourier projection-slice theorem where rays are considered to propagate straight through the object. Another type of tomography called `diffraction tomography' applies in applications in optics and acoustics where diffraction and scattering effects must be taken into account. The latter proves to be a more difficult problem, as light no longer travels straight through the sample. Holographic tomography is a popular way of performing diffraction tomography and there has been active experimental research on reconstructing complex refractive index data using this approach recently. However, there are two distinct ways of doing tomography: either by rotation of the object or by rotation of the illumination while fixing the detector. The difference between these two setups is intuitive but needs to be quantified. From Fourier optics and information transformation point of view, we use 3D transfer function analysis to quantitatively describe how spatial frequencies of the object are mapped to the Fourier domain. We first employ a paraxial treatment by calculating the Fourier transform of the defocused OTF. The shape of the calculated 3D CTF for tomography, by scanning the illumination in one direction only, takes on a form that we might call a 'peanut,' compared to the case of object rotation, where a diablo is formed, the peanut exhibiting significant differences and non-isotropy. In particular, there is a line singularity along one transverse direction. Under high numerical aperture conditions, the paraxial treatment is not accurate, and so we make use of 3D analytical geometry to calculate the behaviour in the non-paraxial case. This time, we

  17. Testing Ionospheric Faraday Rotation Corrections in CASA

    NASA Astrophysics Data System (ADS)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

    The Earth’s ionosphere introduces direction- and time-dependent effects over a range of physical and temporal scales and so is a major source for unmodeled phase offsets for low frequency radioastronomical observations. Ionospheric effects are often the limiting factor to making sensitive radioastronomical measurements to probe the solar corona or coronal mass ejections at low frequencies (< 5 GHz). It has become common practice to use global ionospheric models derived from the Global Positioning System (GPS) to provide a means of externally calibrating low frequency data. We have developed a new calibration algorithm in the Common Astronomy Software Applications (CASA) package. CASA, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array (VLA), did not previously have the capability to mitigate ionospheric effects. This algorithm uses GPS-based global ionosphere maps to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). We investigated several data centers as potential sources for global ionospheric models and chose the International Global Navigation Satellite System Service data product because data from other sources are generally too sparse to use without additional interpolation schemes. This implementation of ionospheric corrections in CASA has been tested on several sets of VLA observations and all of them showed a significant reduction of the dispersion delay. In order to rigorously test CASA’s ability to mitigate ionospheric Faraday rotation, we made VLA full-polarization observations of the standard VLA phase calibrators J0359+5057 and J0423+4150 in August 2014, using L band (1 - 2 GHz), S band (2 - 4 GHz), and C band (4 - 6 GHz) frequencies in the D array configuration. The observations were 4 hours in duration, beginning near local sunrise. In this paper, we give a general description of how these corrections are

  18. Heat balance of the ionosphere - Implications for the International Reference Ionosphere

    NASA Technical Reports Server (NTRS)

    Bilitza, D.

    1985-01-01

    Theoretical considerations can be helpful tools in modeling ionospheric parameters in regions and for times where not enough experimental data are available. This study asks whether results of heat balance calculations should be introduced to supplement the data base for the International Reference Ionosphere. The present status of the theoretical understanding is discussed and the influence of the following unresolved or neglected times are examined: (1) electron heating rate, (2) electron cooling by fine structure excitation of atomic oxygen, and (3) height-dependent Coulomb Logarithm. The ambiguity introduced by these terms leads to up to 30 percent uncertainty in the electron temperature of the lower ionosphere. The electron temperature in the upper ionosphere is largely determined by heat conduction from above and depends critically on the conditions assumed at the boundary between ionosphere and plasmasphere.

  19. Computerized certification of digital ultrasonic instrumentation

    NASA Astrophysics Data System (ADS)

    Moyer, M. W.

    1987-09-01

    A computerized inspection system is being set up at the Oak Ridge Y-12 Plant to enable certification of the Krautkramer Branson ultrasonic instrumentation used extensively in Y-12 production operations. The system takes the data required to certify the linearity and frequency response of the receiver and to certify the correct operation of the pulsers, gates, and computer interface. A subset of the program will be able to verify correct instrumentation in the field by using the actual computer and instrumentation being used for production ultrasonic weld inspections. The system can reduce the certification time from approximately one week to less than an hour.

  20. Critical review of tomography in radiology and nuclear medicine.

    PubMed

    Freedman, G S; Putman, C E; Potter, G D

    1975-04-01

    This review covers conventional radiographic tomography, radioisotopic tomography, and a review of computerized transaxial tomography. Simple, reproducible radiographic tomographic methods are increasing in use, and despite their complexity, the diagnostic results are superior to conventional radiographs. There are many different motions of the X-ray tube and the film which can be employed to create a tomogram. The perfect tomographic motion is partly determined by the geometric shape of the object to be imaged and the thickness of the plane of interest. The undirectional tomographic method blurs a point in a linear fashion; the pleuridirectional method blurs a point over a wider surface. Among the most popular directions used are linear, circular, elliptical, and hypocycloidal. The numerous applications of tomography described in this review are an encouraging, broad-based foundation from which the most clinically useful and economically feasible devices will emerge.

  1. Ionospheric Variability and Storms on Mars

    NASA Technical Reports Server (NTRS)

    Mendillo, Michael

    2004-01-01

    The goal of this grant was to conduct the first-ever study of ionospheric variability on Mars. To do so, we used data from the Radio Science (RS) experiment onboard the Mars Global Surveyor (MGS) satellite. Dr. David Hinson of the RS team at Stanford University was a most helpful and valuable colleague throughout the studies we conducted. For the initial RS datasets available from the MGS mission, there were no severe storms caused by solar wind activity, so we concentrated on day-to-day effects. This turned out to be a wise approach since understanding "normal variability" had to be done before any claim could be made about "space weather" effects. Our approach was three-fold: (1) select a good dataset for characterization of ionosphere variability at Mars, one for which excellent terrestrial data were also available. This turned out to be the period 9-27 March 1999; (2) once the variability at Mars was described, develop and use a new photochemical model of the martian ionosphere to find the extent to which solar variability on those days caused or contributed to the observed patterns; (3) use the results from the above, together with additional datasets from the MGS/RS experiment, to describe some practical consequences that the martian ionosphere would have upon NASA s proposed navigation and communications systems for Mars. The results of these studies showed that: (a) solar variability is the dominant source of ionospheric variability at Mars (during periods of quiet solar wind), (b) that current models do a good job in portraying such effects at the height of the ionospheric peak electron density, and (c) that ionospheric structure on Mars can affect attempts at precise position-fixing at Mars should relatively high (GPS-like) frequencies not be used in a Mars communications and navigation system.

  2. Ionospheric Impacts on UHF Space Surveillance

    NASA Astrophysics Data System (ADS)

    Jones, J.; Ceron-Gomez, D.; Richards, G.

    2016-09-01

    Earth's atmosphere contains regions of ionized plasma caused by the interaction of highly energetic solar radiation. This region of ionization is called the ionosphere and varies significantly with altitude, latitude, local solar time, season, and solar cycle. Significant ionization begins at about 100 km (E layer) with a peak in the ionization at about 350 km (F2 layer). Above the F2 layer, the atmosphere is mostly ionized but the ion and electron densities are low due to the unavailability of neutral molecules for ionization so the electron density decreases exponentially with height to well over 1000 km. The gradients of these variations in the ionosphere play a significant role in radio wave propagation. These gradients induce variations in the index of refraction and cause some radio waves to refract. The amount of refraction depends on the magnitude and direction of the electron density gradient and the frequency of the radio wave. The refraction is significant at HF frequencies (3-30 MHz) with decreasing effects toward the UHF (300-3000 MHz) range. UHF is commonly used for tracking of space objects in low Earth orbit (LEO). While ionospheric refraction is small for UHF frequencies, it can cause errors in range, azimuth angle, and elevation angle estimation by ground-based radars tracking space objects. These errors can cause significant uncertainty in precise orbit determinations. For radio waves transiting the ionosphere, it is important to understand and account for these effects. Using a sophisticated radio wave propagation tool suite and an empirical ionospheric model, we calculate the errors induced by the ionosphere in a simulation of a notional space surveillance radar tracking objects in LEO. These errors are analyzed to determine correlations with ionospheric variability. Corrections to surveillance radar measurements can be adapted from our simulation capability.

  3. Correlative Tomography

    PubMed Central

    Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.

    2014-01-01

    Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640

  4. GPS observations of the ionospheric F2-layer behavior during the 20th November 2003 geomagnetic storm over South Korea

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Luo, O. F.; Park, P.

    2008-12-01

    The ionospheric F2-layer peak density (NmF2) and its height (hmF2) are of great influence on the shape of the ionospheric electron density profile Ne (h) and may be indicative of other physical processes within the ionosphere, especially those due to geomagnetic storms. Such parameters are often estimated using models such as the semiempirical international reference ionosphere (IRI) models or are measured using moderately priced to expensive instrumentation, such as ionosondes or incoherent scatter radars. Global positioning system (GPS) observations have become a powerful tool for mapping high-resolution ionospheric structures, which can be used to study the ionospheric response to geomagnetic storms. In this paper, we describe how 3-D ionospheric electron density profiles were produced from data of the dense permanent Korean GPS network using the tomography reconstruction technique. These profiles are verified by independent ionosonde data. The responses of GPS-derived parameters at the ionospheric F2-layer to the 20th November 2003 geomagnetic storm over South Korea are investigated. A fairly large increase in the electron density at the F2-layer peak (the NmF2) (positive storm) has been observed during this storm, which is accompanied by a significant uplift in the height of the F2 layer peak (the hmF2). This is confirmed by independent ionosonde observations. We suggest that the F2-layer peak height uplift and NmF2 increase are mainly associated with a strong eastward electric field, and are not associated with the increase of the O/N2 ratio obtained from the GUVI instruments aboard the TIMED satellite. It is also inferred that the increase in NmF2 is not caused by the changes in neutral composition, but is related to other nonchemical effects, such as dynamical changes of vertical ion motions induced by winds and E × B drifts, tides and waves in the mesosphere/lower thermosphere region, which can be dynamically coupled upward to generate ionospheric

  5. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by

  6. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-01-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of

  7. Computerized training of cryosurgery - a system approach.

    PubMed

    Keelan, R; Yamakawa, S; Shimada, K; Rabin, Y

    2013-01-01

    The objective of the current study is to provide the foundation for a computerized training platform for cryosurgery. Consistent with clinical practice, the training process targets the correlation of the frozen region contour with the target region shape, using medical imaging and accepted criteria for clinical success. The current study focuses on system design considerations, including a bioheat transfer model, simulation techniques, optimal cryoprobe layout strategy, and a simulation core framework. Two fundamentally different approaches were considered for the development of a cryosurgery simulator, based on a finite-elements (FE) commercial code (ANSYS) and a proprietary finite-difference (FD) code. Results of this study demonstrate that the FE simulator is superior in terms of geometric modeling, while the FD simulator is superior in terms of runtime. Benchmarking results further indicate that the FD simulator is superior in terms of usage of memory resources, pre-processing, parallel processing, and post-processing. It is envisioned that future integration of a human-interface module and clinical data into the proposed computer framework will make computerized training of cryosurgery a practical reality.

  8. Computerized Clinical Decision Support: Contributions from 2014

    PubMed Central

    Koutkias, V.

    2015-01-01

    Summary Objective To summarize recent research and propose a selection of best papers published in 2014 in the field of computerized clinical decision support for the Decision Support section of the IMIA yearbook. Method A literature review was performed by searching two bibliographic databases for papers related to clinical decision support systems (CDSSs) and computerized provider order entry systems in order to select a list of candidate best papers to be then peer-reviewed by external reviewers. A consensus meeting between the two section editors and the editorial team was finally organized to conclude on the selection of best papers. Results Among the 1,254 returned papers published in 2014, the full review process selected four best papers. The first one is an experimental contribution to a better understanding of unintended uses of CDSSs. The second paper describes the effective use of previously collected data to tailor and adapt a CDSS. The third paper presents an innovative application that uses pharmacogenomic information to support personalized medicine. The fourth paper reports on the long-term effect of the routine use of a CDSS for antibiotic therapy. Conclusions As health information technologies spread more and more meaningfully, CDSSs are improving to answer users’ needs more accurately. The exploitation of previously collected data and the use of genomic data for decision support has started to materialize. However, more work is still needed to address issues related to the correct usage of such technologies, and to assess their effective impact in the long term. PMID:26293858

  9. Methods for validating chronometry of computerized tests.

    PubMed

    Salmon, Joshua P; Jones, Stephanie A H; Wright, Chris P; Butler, Beverly C; Klein, Raymond M; Eskes, Gail A

    2017-03-01

    Determining the speed at which a task is performed (i.e., reaction time) can be a valuable tool in both research and clinical assessments. However, standard computer hardware employed for measuring reaction times (e.g., computer monitor, keyboard, or mouse) can add nonrepresentative noise to the data, potentially compromising the accuracy of measurements and the conclusions drawn from the data. Therefore, an assessment of the accuracy and precision of measurement should be included along with the development of computerized tests and assessment batteries that rely on reaction times as the dependent variable. This manuscript outlines three methods for assessing the temporal accuracy of reaction time data (one employing external chronometry). Using example data collected from the Dalhousie Computerized Attention Battery (DalCAB) we discuss the detection, measurement, and correction of nonrepresentative noise in reaction time measurement. The details presented in this manuscript should act as a cautionary tale to any researchers or clinicians gathering reaction time data, but who have not yet considered methods for verifying the internal chronometry of the software and or hardware being used.

  10. The Jovian ionospheric E region

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Fox, J. L.

    1991-02-01

    A model of the Jovian ionosphere was constructed, that includes direct photoionization of hydrocarbon molecules. A high-resolution solar spectrum was synthesized from Hinteregger's solar maximum spectrum (F79050N), and high-resolution cross sections for photoabsorption by H2 bands in the range 842 to 1116 A were constructed. Two strong solar lines and about 30 percent of the continuum flux between 912 and 1116 A penetrate below the methane homopause despite strong absorption by CH4 and H2. It is found that hydrocarbons (mainly C2H2 are ionized at a maximum rate of 55/cu cm per sec at 320 km above the ammonia cloud tops. The hydrocarbon ions produced are quickly converted to more complex hydrocarbon ions through reactions with CH4, C2H2, C2H6, and C2H4. It is found that a hydrocarbon ion layer is formed near 320 km that is about 50 km wide with a peak density in excess of 10,000/cu cm.

  11. Electric fields in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar were analyzed in terms of diurnal, seasonal, magnetic activity, and solar cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days and the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component.

  12. Meteoric Ions in Planetary Ionospheres

    NASA Technical Reports Server (NTRS)

    Pesnell, W. D.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

  13. Ionospheric disturbances and gravity waves

    NASA Technical Reports Server (NTRS)

    Eun, H.; Gross, S. H.

    1976-01-01

    The response of ionization to a gravity wave moving through the ionosphere is studied. Hydrodynamic equations are used, and local thermodynamic equilibrium is imposed for simplicity. The treatment involves a perturbation analysis, and the background medium is assumed to be time stationary, horizontally stratified, and known. It is shown that ionization may be locally resonant at each level for certain frequencies and directions, for which condition neutral and ionized particles are considered closely or critically coupled. The phase direction for this critical coupling is always downward in the absence of a magnetic field. A magnetic field results in two resonant directions for the same frequency, and these directions are mostly downward. Observed TID's associated with gravity waves may be indicative of such resonances. It is also noted that strong coupling may occur to neutral acoustic waves at high altitudes. Previous investigations restrict their use of momentum equations to the diffusion equation. The analysis also shows that such restrictions result in the neglect of terms arising from momentum transport due to any background ambipolar diffusion velocity and wave motion. These terms are mostly relevant at higher altitudes.

  14. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

    As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

  15. Fast ionospheric feedback instability and substorm onset

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Grieger, John; Song, Yan

    1992-01-01

    A study suggesting that the Alfven resonator can play an important role in modifying the ionosphere on the time and space scales required to play a significant role in substorm formation is presented. Although the effect of magnetosphere-ionosphere coupling on the onset of substorms has been studied, the effects due to gradients of the Alfven speed along auroral field line were neglected. The large increase of the Alfven speed with altitude above the ionosphere creates an effective resonant cavity, which can lead to fluctuations in the electric and magnetic fields as well as in particle fluxes in the range 0.1 to 1 Hz. Such fluctuations can be observed from the ground as PiB pulsations associated with substorm onset. These fluctuations can be excited by a fast feedback instability, which can grow on time scales much less than the Alfven travel time between the ionosphere and the plasma sheet. The instability enhances the value of both the Pedersen and Hall conductivity, and may play a role in preparing the ionosphere for substorm onset.

  16. Geophysicochemical model of an ionospheric auroral gyroscope

    NASA Astrophysics Data System (ADS)

    Serban, Andreea I.; Geicu, Ovidiu I.; Serban, Florea

    2016-01-01

    This study presents a geophysicochemical model of an ionospheric auroral gyroscope. The gyroscopic effect occurs due to the electromagnetic interaction in Earth's polar regions between two types of vertical cavity auroras: the herpolhodic cone (proton cavity aurora), operating in the cusp polar region, and two polhodic cones (an electronic cone and a protonic cone), operating in the aurora region. The ratio between the angular speeds of the herpolhodic and polhodic cones is established by the angle between Earth's rotational axis and the geomagnetic dipole axis. We have developed a theory of the ionospheric auroral gyroscope as a kinematic part of the terrestrial magnetosphere and ionosphere that enables a unified explanation of important macroscopic phenomena that occur at this level. Accordingly, we have explained the oval shape of the polar auroras, Schumann resonances, geomagnetic micropulsation excitation, and the structuring of Earth's areas of radiation. The terrestrial gravitomagnetic field and dark matter are implicated in the initiation and behavior of the auroral ionospheric gyroscope, both of which provide stability and accuracy. Viewed in a wider context, the ionospheric auroral gyroscope theory could offer a way to experimentally investigate dark matter on Earth. Furthermore, it may have a potential value as a predictive tool, providing information about the large earthquakes and Earth's phenomena.

  17. Ionospheric TEC observations from TOPEX satellite

    SciTech Connect

    Vladimer, J.A.; Ewell, V.R.; Lee, M.C.; Doherty, P.H.; Decker, D.T.; Anderson, D.N.; Klobuchar, J.A.

    1996-12-31

    Variability of Total Electron Content (TEC) in the equatorial anomaly region of the ionosphere can be studied extensively using the results of measurements taken by the NASA/CNES satellite, TOPEX/Poseidon. The NASA radar altimeter (NRA) is the first space-borne dual-frequency altimeter capable of accurately measuring vertical ionospheric TEC below 1,340 km. TOPEX TEC observations have already been used to support results from an ionospheric measurement campaign that was conducted in equatorial anomaly regions of South America by Phillips Laboratory in Spring, 1994. The best agreement in TEC values is seen during intervals of longitudinal proximity of the satellites` paths. The TOPEX over-ocean data can be used as a supplement to land based measurements in applications to ionospheric research at low and middle latitudes. This study focuses on comparisons between TOPEX vertical TEC data and GPS equivalent vertical TEC measurements taken near the East and West coastal regions of South America. Also the Phillips Laboratory Global Parameterized Ionospheric Model (PIM) is utilized in an effort to estimate slant to vertical conversion errors.

  18. Ionospheric Specifications for SAR Interferometry (ISSI)

    NASA Technical Reports Server (NTRS)

    Pi, Xiaoqing; Chapman, Bruce D; Freeman, Anthony; Szeliga, Walter; Buckley, Sean M.; Rosen, Paul A.; Lavalle, Marco

    2013-01-01

    The ISSI software package is designed to image the ionosphere from space by calibrating and processing polarimetric synthetic aperture radar (PolSAR) data collected from low Earth orbit satellites. Signals transmitted and received by a PolSAR are subject to the Faraday rotation effect as they traverse the magnetized ionosphere. The ISSI algorithms combine the horizontally and vertically polarized (with respect to the radar system) SAR signals to estimate Faraday rotation and ionospheric total electron content (TEC) with spatial resolutions of sub-kilometers to kilometers, and to derive radar system calibration parameters. The ISSI software package has been designed and developed to integrate the algorithms, process PolSAR data, and image as well as visualize the ionospheric measurements. A number of tests have been conducted using ISSI with PolSAR data collected from various latitude regions using the phase array-type L-band synthetic aperture radar (PALSAR) onboard Japan Aerospace Exploration Agency's Advanced Land Observing Satellite mission, and also with Global Positioning System data. These tests have demonstrated and validated SAR-derived ionospheric images and data correction algorithms.

  19. Estimating Ionosphere Conductance on Global Spatial Scales

    NASA Astrophysics Data System (ADS)

    Waters, C. L.; Anderson, B. J.; Green, D. L.; Korth, H.

    2014-12-01

    The ionosphere represents the Earthward boundary of space. For large scale processes, the height integrated conductivities (conductances) of the ionosphere are known to modulate the energy transfer between the magnetosphere and ionosphere. Estimating the Pedersen and Hall conductances on a global scale, particularly in the auroral regions, is fundamental to understanding the dynamics of the high latitude ionosphere and thermosphere. Experimental measurements with sufficient spatial coverage and with time scales of order of minutes or less are required. While the spatial coverage of HF radar and spacecraft measurements has recently improved, it turns out that the most challenging aspects for global estimates of ionosphere conductance are directly related to ground-based magnetometer data. The Iridium satellite constellation consists of more than 70 satellites in circular, polar, 780 km altitude orbits which provides a unique opportunity to obtain in-situ measurements of the global distribution of the Birkeland currents and associated magnetic field perturbations. In this paper, examples and challenges for combining the Iridium satellite, HF radar and ground magnetometer data in order to produce estimates of the Pedersen and Hall conductances on global spatial scales will be presented. We discuss limiting factors in the methodology and some possible alternatives.

  20. A Comparative Study of the Ionospheric TEC Measurements Using Global Ionospheric Maps of GPS, TOPEX Radar and the Bent Model

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wilson, B.; Mannucci, A.; Lindqwister, U.; Yuan, D.

    1997-01-01

    Global ionospheric mapping (GIM) is a new, emerging technique for determining global ionospheric TEC (total electron content) based on measurements from a worldwide network of Global Positioning System (GPS) receivers.

  1. Fluctuation of the Martian ionosphere observed by Mars Express ionospheric sounding

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Gurnett, D. A.; Duru, F.; Akalin, F.; Brain, D. A.

    2009-12-01

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), on board the ESA spacecraft Mars Express, in its Active Ionospheric Sounding mode, produces ionograms that enable us to compute electron density profiles of the Martian ionosphere over a wide range of day-side solar zenith angles and planetary longitudes and latitudes at a maximum resolution of 7.543 s. An electron density profile contains the values of the ionospheric peak electron density and its corresponding altitude. In order to analyze the state of motion of the Martian ionosphere, we have computed the standard deviation of these two quantities for four-minute intervals spanning the time between 14 August 2005 and 19 April 2009 corresponding to 473 orbits of Mars Express between orbits 2032 and 6795. Our analysis shows that fluctuation of the Martian ionosphere, as indicated by both the peak electron density and the peak altitude, increases at solar zenith angles greater than 60° and that this increase is strongest in regions of high remanent magnetic field. Use of the MGS solar-wind magnetic-field-draping direction proxy indicates that these fluctuations are strongest when remanent and solar-wind-borne fields are oppositely directed. These measurements open the possibility that near-terminator fluctuation in the Martian ionosphere is related to magnetic reconnection coupled with bulk outflows from the Martian atmosphere.

  2. Computerized physician order entry systems: the right prescription?

    PubMed

    Koppel, Ross

    2005-03-01

    Policymakers increasingly urge the use of information technology to improve the quality and efficiency of health care. In particular, computerized physician order entry (CPOE) is emphasized for its ability to reduce prescribing errors inherent in paper-based systems. This Issue Brief summarizes research that sounds a cautionary note about the potential for computerized systems to facilitate medication errors, as well as reduce them.

  3. Computerized Ability Testing, 1972-1975. Final Report.

    ERIC Educational Resources Information Center

    Weiss, David J.

    Three and one-half years of research on computerized ability testing are summarized. The original objectives of the research were: (1) to develop and implement the stratified computer-based ability test; (2) to compare, on psychometric criteria, the various approaches to computer-based ability testing, including the stratified computerized test,…

  4. Computerized Adaptive Assessment of Cognitive Abilities among Disabled Adults.

    ERIC Educational Resources Information Center

    Engdahl, Brian

    This study examined computerized adaptive testing and cognitive ability testing of adults with cognitive disabilities. Adult subjects (N=250) were given computerized tests on language usage and space relations in one of three administration conditions: paper and pencil, fixed length computer adaptive, and variable length computer adaptive.…

  5. 11 CFR 9033.12 - Production of computerized information.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... authorized committee maintains or uses computerized information containing any of the categories of data... Funding. The data contained in the computerized magnetic media provided to the Commission shall be... materials for processing and analyzing the information requested. Upon request, the committee shall...

  6. Computerized Literature Searching of Education and Education Related Literature.

    ERIC Educational Resources Information Center

    Zaporozhetz, Laurene E.

    Computerized literature searching allows the educator to become familiar with resources that help develop individual teaching styles and methods, enhance awareness of pupil needs, explain educational research and evaluation, and describe curriculum materials. This document introduces the fundamentals of computerized literature searching. The…

  7. Assessment Outcomes: Computerized Instruction in a Human Gross Anatomy Course.

    ERIC Educational Resources Information Center

    Bukowski, Elaine L.

    2002-01-01

    The first of three successive classes of beginning physical therapy students (n=17) completed traditional cadaver anatomy lecture/lab; the next 17 a self-study computerized anatomy lab, and the next 20 both lectures and computer lab. No differences in study times and course or licensure exam performance appeared. Computerized self-study is a…

  8. The Reality, Direction, and Future of Computerized Publications

    ERIC Educational Resources Information Center

    Levenstein, Nicholas

    2012-01-01

    Sharing information in digital form by using a computer is a growing phenomenon. Many universities are making their applications available on computer. More than one hundred and thirty-six universities have developed computerized applications on their own or through a commercial vendor. Universities developed computerized applications in order to…

  9. Investigation of the Accuracy of Ionospheric Models at Mid-Latitudes: Examining Ionospheric Metrics

    NASA Astrophysics Data System (ADS)

    Eccles, V.; Sojka, J. J.; Gonzalez, S.; Fuller-Rowell, T. J.; Howsden, M.

    2004-12-01

    The electron density specification of the ionosphere is the key parameter supporting many operational products. To assess the accuracy of tools based on space weather models of the ionosphere one must know the accuracy of the underlining models. We are developing a software/database package to assess the accuracy of ionospheric models. The package will be placed at the Community Coordinated Modeling Center (CCMC). Initial focus is on the mid-latitude ionosphere as observed by the Arecibo Incoherent Scatter Radar (ISR). This ISR database has extensive ionospheric coverage over variability in solar cycle, season, local time, and geomagnetic activity. The assessments of models need to be based on careful constructed metric definitions to compare the model specifications with the ISR "ground truth." Our goals for the assessment tool are (1) to provide reliable, metric assessment of models for users represented by agencies of the Nation Space Weather Program and, (2) to provide the scientific community with an assessment of conditions when models are adequate and inadequate. The second implementation plan of the NSWP (2000) has established the priority of metrics and has specified these metrics. We begin with the NSWP ionospheric metrics as a reasonable starting place, but examine other strategies to assess ionosphere weather specifications through several new metric definitions for the F region. We present our initial studies on the weaknesses and benefits of several different metric definitions for F region profile accuracy. Three models will be use in the metric assessment (1) the physics-based Ionospheric Forecast Model (IFM), (2) the physics-based and Coupled Thermospheric-Ionospheric-Plasmasphere-electrodynamics Model (CTIPe), and (3) the empirical International Reference Model (IRI). Central to creating reliable metric results is the need to quantify the quality and accuracy of the "ground truth" ISR database. Metric issues associated with ISR operational modes

  10. Excitation of Earth-Ionosphere Waveguide in the ELF and Lower VLF Bands by Modulated Ionospheric Current

    DTIC Science & Technology

    1993-05-21

    orientation, altitude, and dimension and therefore pertain to experiments using the HIPAS or HAARP ionospheric heaters. In the end-fire mode, the...for HAARP there might be marginal value in modulating at altitudes as high as 100 km. 14. SUBJECT TERMS ionospheric modification ionospheric currents...34 ionospheric heating 16. PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF OF REPORT

  11. Shallow Ocean Bottom BRDF Prediction, Modeling, and Inversion via Simulation with Surface/Volume Data Derived from X-ray Tomography

    DTIC Science & Technology

    2008-01-01

    Shallow Ocean Bottom BRDF Prediction, Modeling, and Inversion via Simulation with Surface/Volume Data Derived from X-ray Tomography G. C...Prediction, Modeling, and Inversion via Simulation with Surface/Volume Data Derived from X-ray Tomography 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...focus Xray Computerized Tomography (MXCT) instrument at NRL SSC. The MXCT instrument requires preparation of the sample by embedding it in an epoxy

  12. Enhanced Airglow by High Frequency Electromagnetic Pumping of the Ionosphere at Auroral Latitudes

    NASA Astrophysics Data System (ADS)

    Leyser, T. B.; Gustavsson, B.; Brändström, B. U. E.; Steen, E.; Honary, F.; Rietveld, M. T.; Aso, T.; Ejiri, M.

    2000-10-01

    A powerful high frequency electromagnetic pump wave transmitted into the ionosphere from the ground may enhance the background airglow. The airglow enhancement is due to an increase in the number of electrons having energies which are an order of magnitude higher than the thermal energy in the ionospheric plasma. The energetic electrons collisionally excite, for example, the meta-stable O(1D) state in atomic oxygen, which radiates at 630 nm as the excited oxygen atom relaxes to its ground state. Airglow enhancement is used to study, for example, the dissipation of the pump-driven plasma turbulence by electron energization. We present experimental results of pumping the ionospheric F region with the EISCAT-Heating facility at auroral latitudes in Norway and detection of the airglow with the multi-station Auroral Large Imaging System (ALIS) in northern Sweden. The experimental results also include simultaneous measurements of background plasma parameter values with the EISCAT-UHF incoherent scatter radar. The multi-station imaging technique enables for the first time tomography-like inversion to estimate the spatial extent of the pumped airglow cloud. Further, the airglow enhancement is correlated with large pump-induced electron temperature enhancements of up to 250

  13. An Initial Investigation of Ionospheric Gradients for Detection of Ionospheric Disturbances over Turkey

    NASA Astrophysics Data System (ADS)

    Koroglu, Meltem; Arikan, Feza; Koroglu, Ozan

    2015-04-01

    Ionosphere is an ionized layer of earth's atmosphere which affect the propagation of radio signals due to highly varying electron density structure. Total Electron Content (TEC) and Slant Total Electron Content (STEC) are convenient measures of total electron density along a ray path. STEC model is given by the line integral of the electron density between the receiver and GPS satellite. TEC and STEC can be estimated by observing the difference between the two GPS signal time delays that have different frequencies L1 (1575 MHz) and L2 (1227 MHz). During extreme ionospheric storms ionospheric gradients becomes larger than those of quiet days since time delays of the radio signals becomes anomalous. Ionosphere gradients can be modeled as a linear semi-infinite wave front with constant propagation speed. One way of computing the ionospheric gradients is to compare the STEC values estimated between two neighbouring GPS stations. In this so-called station-pair method, ionospheric gradients are defined by dividing the difference of the time delays of two receivers, that see the same satellite at the same time period. In this study, ionospheric gradients over Turkey are computed using the Turkish National Permanent GPS Network (TNPGN-Active) between May 2009 and September 2012. The GPS receivers are paired in east-west and north-south directions with distances less than 150 km. GPS-STEC for each station are calculated using IONOLAB-TEC and IONOLAB-BIAS softwares (www.ionolab.org). Ionospheric delays are calculated for each paired station for both L1 and L2 frequencies and for each satellite in view with 30 s time resolution. During the investigation period, different types of geomagnetic storms, Travelling Ionospheric Disturbances (TID), Sudden Ionospheric Disturbances (SID) and various earthquakes with magnitudes between 3 to 7.4 have occured. Significant variations in the structure of station-pair gradients have been observed depending on location of station-pairs, the

  14. Ionospheric Cubeswarm Concept Study: using low-resource instrumentation for truly multipoint in situ ionospheric observations

    NASA Astrophysics Data System (ADS)

    Hampton, D.; Lynch, K. A.; Earle, G. D.; Mannucci, A. J.; Clayton, R.; Fisher, L. E.; Fernandes, P. A.; Roberts, M.; Zettergren, M. D.

    2015-12-01

    Magnetosphere-ionosphere coupling currents close in the nightside lower ionosphere. These spatially inhomogeneous and time varying volume currents are difficult to capture with in situ observations. Our understanding of M-I coupling systems is limited by our understanding of the actual structure of ionospheric current closure. A path forward includes assimilation of a variety of data sets into increasingly capable ionospheric models. While each data set provides only a piece of the picture, the assimilation process allows optimal use of each piece.An important development for the necessary in situ observations involves making them truly multi-point, and therefore, low-resource. For thermal particle observations, the high densities of the lower ionosphere allow the use of low-gain (current-sensing rather than particle-counting) particle sensors. One observational goal is the definition of the actual structure of ionospheric closure currents. This can be approached with a number of different measurement techniques, in tandem with an ionospheric model, since the closure currents need to follow the rules of electrodynamics and current continuity. Low resource thermal plasma sensors such as retarding potential analyzers and drift meters can provide valuable measurements of plasma parameters, including density and plasma flow, without the need for high voltages or deployable boom systems. These low-resource measurements, which can be reproduced on arrays of in situ observation platforms, used in tandem with proper plasma physics interpretation of their signatures in the disturbed observing environment, and as part of an assimilated data set into an ionospheric model, can allow us to progress in our understanding of ionospheric structuring and its effects on auroral coupling. Now, with increasingly capable multipoint arrays of spacecraft, and quantitative 2D-with-time context from cameras and imagery, we are moving toward truly multipoint studies of the system

  15. Representation of the Auroral and Polar Ionosphere in the International Reference Ionosphere (IRI)

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Reinisch, Bodo

    2013-01-01

    This issue of Advances in Space Research presents a selection of papers that document the progress in developing and improving the International Reference Ionosphere (IRI), a widely used standard for the parameters that describe the Earths ionosphere. The core set of papers was presented during the 2010 General Assembly of the Committee on Space Research in Bremen, Germany in a session that focused on the representation of the auroral and polar ionosphere in the IRI model. In addition, papers were solicited and submitted from the scientific community in a general call for appropriate papers.

  16. Ionosphere/microwave beam interaction study

    NASA Technical Reports Server (NTRS)

    Gordon, W. E.; Duncan, L. M.

    1978-01-01

    The microwave beam of the Solar Power Satellite (SPS) is predicted to interact with the ionosphere producing thermal runaway up to an altitude of about 100 kilometers at a power density threshold of 12 mW/cm sq (within a factor of two). The operation of the SPS at two frequencies, 2450 and 5800 MHz, is compared. The ionosphere interaction is less at the higher frequency, but the tropospheric problem scattering from heavy rain and hail is worse at the higher frequency. Microwave signals from communication satellites were observed to scintillate, but there is some concern that the uplink pilot signal may be distorted by the SPS heated ionosphere. The microwave scintillations are only observed in the tropics in the early evenings near the equinoxes. Results indicate that large phase errors in the uplink pilot signal can be reduced.

  17. Whistlers. [in earth ionosphere and magnetosphere

    NASA Technical Reports Server (NTRS)

    Park, C. G.

    1982-01-01

    Theoretical models of ionospheric whistler phenomena are reviewed and compared with experimental data. Whistlers were characterized as lightning discharges through a dispersive medium in 1919, with the first observed appearance of whistler noises detected in telephone communications. Magneto-ionic theory is used to characterize whistlers, with the Appleton-Hartree equations applied to the wave fields arising from lightning interactions with ionospheric plasma. Large values of the refractive index or slow propagation speeds give rise to the whistler mode, i.e., propagation of the wave through plasmas of any density. Propagation through the ionosphere is examined with the Snell's law, and account is taken of absorption and the necessity of obtaining full-wave solutions. Finally, theories are under development to explain the occurrence of ducting, i.e., guiding of the whistler wave by field-aligned plasma density irregularities.

  18. Rocket studies of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Bowhill, Sidney A.

    1990-01-01

    The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications.

  19. Ionospheric density enhancement during relativistic electron precipitation

    NASA Technical Reports Server (NTRS)

    Foster, J. C.; Doupnik, J. R.; Stiles, G. S.

    1980-01-01

    The temporal evolution of the ionospheric density enhancement produced by a widespread relativistic electron precipitation (REP) has been observed with the Chatanika Radar. The REP was associated with a substorm particle energization event, and both the ionospheric absorption and density perturbation exhibited an approximately 90 min periodicity associated with the particles' longitudinal drift. A 80-keV characteristic energy for the precipitating electrons is deduced from ground-based and satellite data. At the maximum of the event, electrons deposited approximately 50 ergs/sq cm per sec in the ionosphere, producing a peak density of 500,000/cu cm at 89 km altitude. At that time the radar observed densities greater than 100,000/cu cm between 70 km and 110 km altitude and riometer absorption at 30 MHz was approximately 12 db.

  20. Monitoring of Earthquake Disasters by Satellite Radio Tomography

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Andreeva, E.; Nesterov, I.; Rekenthaler, D. A.

    2011-12-01

    This work addresses lithospheric-ionospheric coupling during strong earthquakes (EQ). Particular interest is placed on the physical phenomena preceding EQs - the precursors. We discuss both the ionospheric implications of EQs, and the ionospheric precursors to EQ. The requisite ionospheric sounding is carried out using satellite navigational system data; the data are analyzed using the methods of satellite radio tomography (RT). Signals from both low-orbiting beacons (Transit, Tsikada, etc.) and high orbiting global navigational satellite systems (GNSS including GPS and GLONASS) are used. The resulting 2D and 3D tomographic images and their time flow (4D RT) make it possible to study the spatiotemporal structure of ionospheric perturbations induced by EQs and EQ precursors, and to distinguish ionospheric responses to processes of EQ preparation against the effects of other factors. Low-orbital RT (LORT) provides almost "instantaneous" (with a time span of 5-8 min) 2-D snapshots of the electron density over the seismically active region of interest. LORT allows 2D imaging of various anomalies, including wave structures such as ionospheric manifestations of acoustic-gravity waves (AGW), wave-like disturbances, and solitary waves with the gaps between images, depending on the number of operating satellites (currently, 30-100 minutes). High-orbital RT (HORT) is capable of imaging 4D distributions of ionospheric plasma (resulting in 3D snapshots every 20-30 minutes). Using this approach, one can reconstruct RT images of ionospheric irregularities, wave structures, and perturbations such as solitary waves. In regions with a sufficient number of GNSS receivers (California, Japan), 4-D RT images can be generated every 2-4 minutes. The spatial resolution of LORT and HORT systems is on the order of 20-40, and 100 km, respectively. The combination of LORT and HORT systems has the potential for exploiting data provided by other experimental techniques, including radio

  1. Travelling ionospheric disturbance over California mid 2000

    NASA Astrophysics Data System (ADS)

    Hawarey, M.

    2006-01-01

    In this paper, the GPS data collected by more than 130 permanent GPS stations that belong to the Southern California Integrated GPS Network (SCIGN) around the launch of a Minuteman-II missile on 8 July 2000 (UTC) is processed to reveal traveling ionospheric disturbance (TID) all over the network on average 15 min after the launch. This TID was initially perceived to be excited by the launch itself, but this conclusion is challenged by the propagation direction. This is because this TID seems to travel towards the air force base from where the launch took place, not far away from it. This challenge is based on the assumption that TID is occurring at one single ionospheric altitude. While the nature of ionosphere supports such horizontally-guided propagation, multi-altitude ionospheric pierce points are hypothesized, which would support the suggestion that detected TID is excited by the missile launch itself, despite the apparent reverse direction of propagation. The overall analysis rules out any extra-terrestrial sources like solar flares, or seismic sources like earthquakes, which confirms the conclusion of TID excitation by the launch. There is apparent coherence of the TID for about 45 min and the propagation speed of TID within the layer of ionosphere is calculated to be approximately equal to 1230 m/s. While the usual assumption for TID is that they occur around an altitude of 350 km, such sound speed can only occur at much higher altitudes. Further research is recommended to accurately pinpoint the ionospheric pierce points and develop an algorithm to locate the source of TID in case it is totally unknown.

  2. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

    D'Angelo, G.; Spogli, L.; Cesaroni, C.; Sgrigna, V.; Alfonsi, L.; Aquino, M. H. O.

    2015-12-01

    In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and random fluctuations of the phase and the amplitude of the received GNSS signals. For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15°, 20° or 30°) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create diffusion, diffraction and reflection. Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to the misidentification of scintillation events at low elevation angles. With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique, termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the exercise show that, in the considered case of a noisy

  3. Derivation of a planetary ionospheric storm index

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Stanislawska, I.

    2008-09-01

    The planetary ionospheric storm index, Wp, is deduced from the numerical global ionospheric GPS-IONEX maps of the vertical total electron content, TEC, for more than half a solar cycle, 1999-2008. The TEC values are extracted from the 600 grid points of the map at latitudes 60° N to 60° S with a step of 5° and longitudes 0° to 345° E with a step of 15° providing the data for 00:00 to 23:00 h of local time. The local effects of the solar radiant energy are filtered out by normalizing of the TEC in terms of the solar zenith angle χ at a particular time and the local noon value χ0. The degree of perturbation, DTEC, is computed as log of TEC relative to quiet reference median for 27 days prior to the day of observation. The W-index map is generated by segmentation of DTEC with the relevant thresholds specified earlier for foF2 so that 1 or -1 stands for the quiet state, 2 or -2 for the moderate disturbance, 3 or -3 for the moderate ionospheric storm, and 4 or -4 for intense ionospheric storm at each grid point of the map. The planetary ionospheric storm Wp index is obtained from the W-index map as a latitudinal average of the distance between maximum positive and minimum negative W-index weighted by the latitude/longitude extent of the extreme values on the map. The threshold Wp exceeding 4.0 index units and the peak value Wpmax≥6.0 specify the duration and the power of the planetary ionosphere-plasmasphere storm. It is shown that the occurrence of the Wp storms is growing with the phase of the solar cycle being twice as much as the number of the magnetospheric storms with Dst≤-100 nT and Ap≥100 nT.

  4. Multi-GNSS for Ionospheric Scintillation Studies

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2015-12-01

    GNSS have been widely used for ionospheric monitoring. We anticipate over 160 GNSS satellites broadcasting 400 signals by 2023, nearly double the number today. With their well-defined signal structures, high spatial density and spectral diversity, GNSS offers low cost and distributed passive sensing of ionosphere effects. There are, however, many challenges to utilize GNSS resources to characterize and forecast ionospheric scintillation. Originally intended for navigation purposes, GNSS receivers are designed to filter out nuisance effects due to ionosphere effects. GNSS measurements are plagued with errors from multipath, oscillator jitters, processing artifacts, and neutral atmosphere effects. Strong scintillation events are often characterized by turbulent structures in ionosphere, causing simultaneous deep amplitude fading and abrupt carrier phase changes. The combined weak signal and high carrier dynamics imposes conflicting requirements for GNSS receiver design. Therefore, GNSS receivers often experience cycle slips and loss of lock of signals during strong scintillation events. High quality, raw GNSS signals bearing space weather signatures and robust receiver algorithms designed to capture these signatures are needed in order for GNSS to be a reliable and useful agent for scintillation monitoring and forecasting. Our event-driven, reconfigurable data collection system is designed to achieve this purpose. To date, our global network has collected ~150TB of raw GNSS data during space weather events. A suite of novel receiver processing algorithms has been developed by exploitating GNSS spatial, frequency, temporal, and constellation diversity to process signals experiencing challenging scintillation impact. The algorithms and data have advanced our understanding of scintillation impact on GNSS, lead to more robust receiver technologies, and enabled high spatial and temporal resolution depiction of ionosphere responses to solar and geomagnetic conditions. This

  5. Radiowave Imaging of Ionospheric Electron Dynamics

    NASA Astrophysics Data System (ADS)

    van Bavel, Gregory Hugh

    1998-12-01

    This dissertation is a study of disturbances in the polar ionosphere. A relative ionospheric opacity meter (riometer) is a radio frequency instrument that enables the remote sensing of ionospheric disturbances by recording variations in the cosmic radio noise power received at a terrestrial antenna. The Imaging Riometer for Ionospheric Studies (IRIS) produces images of relative ionospheric opacity. In the ionosphere, the attenuation of a radio signal's amplitude is proportional to the electron number density n and the effective collision frequency ν. Therefore, a riometer is sensitive to variations of the product n/nu, but their effects are not separated. The theory of HF radiowave attenuation in a cold magetoplasma and electron continuity yield a pair of uni-directional wave equations that couple the dynamics of cosmic radio noise absorption to the vertical mean value of ν. These equations, and some simplifying assumptions, are the basis of a data analysis that transforms IRIS images into physical quantities related to the absorbing ionospheric electrons: mean velocity, mean effective collision frequency, net production rate and column density. A critical test case and coincident auroral observations support the reliability of the general results of the data analysis. Variations in the mean flow velocity indicate that the ionosphere is not in equilibrium. The mean effective collision frequency shows significant structural variations over 100 km and 1 minute intervals. Column density depletions lead enhancements in a geomagnetic poleward drift, while a net production region moves with the column density enhancement and intensifies as the pole-ward motion ceases. Regions of persistent electron production or loss are found where the collision frequency is relatively low, and specific locations can oscillate between net production and loss with periods of about 1 to 2 minutes. It is found that the spatial structure of a riometer image is chiefly determined by the

  6. Electrodynamics and plasma processes in the ionosphere

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1987-01-01

    The paper examines the advances achieved between 1983 and 1986 on understanding ionospheric electrodynamics and associated plasma processes, including an assessment of the roles of the E- and F-region neutral winds in providing the large-scale electric field in the ionosphere, as well as of the influence of electric fields of magnetospheric origin on the motion and distribution of plasma. Studies of the factors affecting the creation and evolution of plasma structure with many different scale sizes are discussed. Consideration is also given to the ground-based and in situ techniques used in these studies.

  7. Lunar Variation of Several Ionospheric Parameters.

    DTIC Science & Technology

    1981-09-30

    ALBERCA , J 0 CARDUS, E GALDON AFOSR-79-0114 UNCLASSIFIED SCIENTIFIC-Z EOARD-TR-212 ML 111a 11m I.8 II1JIL2 111.6__II MICROCOPY RESOLUTION TEST CHART...X4 SCIENTIFIC REPORT No 2 LUNAR VARIATION OF SEVERAL IONOSPHERIC PARAMETERS L. F. Alberca S. I. J. 0. Card6s 5.1. * E. Gald6n S.I1. * LLCTE... Alberca , e.I. J.O. Cardds, s.1. E. Gald6n, 8., OBSERVATORIO DEL EBR0 IONOSPHERIC SECTION ROQUETES (Tarragona) Spain THE RESEARCH REPORTED IN THIS

  8. Model of traveling ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Fedorenko, Yury P.; Tyrnov, Oleg F.; Fedorenko, Vladimir N.; Dorohov, Vasiliy L.

    2013-10-01

    A multiscale semi-empirical model of traveling ionospheric disturbances (TIDs) is developed. The model is based on the following assumptions: (1) TIDs are generated by acoustic-gravity waves (AGWs) and propagate as pressure waves; (2) time intervals between adjacent extrema of atmospheric pressure oscillations in a disturbance source are constant; (3) the pressure extrema propagate from the source up to ~14 000 km at a constant horizontal velocity; (4) the velocity of each extremum is determined only by its number in a TID train. The model was validated using literature data on disturbances generated by about 20 surface and high-altitude nuclear explosions, two volcano explosions, one earthquake and by energetic proton precipitation events in the magnetospheric cusp of the northern hemisphere. Model tests using literature data show that the spatial and temporal TID periods may be predicted with an accuracy of 12%. Adequacy of the model was also confirmed by our observations collected using transionospheric sounding. The following TID parameters: amplitudes, horizontal spatial periods, and a TID front inclination angle in a vertical plane are increasing as the distance between an AGW and the excitation source is increasing. Diurnal and seasonal variability of the TID occurrence, defined as ratio of TID events to the total number of observations for the corresponding period, is not observed. However, the TID occurrence was growing from ~50% in 1987 to ~98% in 2010. The results of other studies asserting that the TID occurrence does not depend on the number of sunspots and magnetic activity are confirmed. The TID occurrence has doubled over the period from 1987 to 2010 indicating increasing solar activity which is not associated with sunspot numbers. The dynamics of spatial horizontal periods was studied in a range of 150-35 000 km.

  9. Studing Solar Flare Effects on Ionosphere Using AWESOME Receiver

    NASA Astrophysics Data System (ADS)

    Mustafa, Famil; Babayev, Elchin; Alekperov, Ilgar

    2015-08-01

    Ground based observations of Extremely Low Frequency (ELF) / Very Low Frequency (VLF) (300 Hz 30 kHz) waves are considered as an important remote sensing tool for the investigation of the ionosphere and the magnetosphere. VLF waves find their origin in various natural and artificial phenomena; the natural sources include thunderstorms, lightning and associated phenomena. Sub-ionospheric VLF transmissions propagating inside the Earth-ionosphere wave-guide is also being widely used for investigating sudden ionospheric perturbations (SIDs) in lower part of the ionosphere.

  10. Absorption of whistler mode waves in the ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Taylor, W. W. L.; Scarf, F. L.; Russell, C. T.; Brace, L. H.

    1979-01-01

    It is shown that whistler mode waves from the ionosheath of Venus are absorbed by Landau damping at the dayside ionosphere boundary. This process heats the ionospheric electrons and it may provide an important energy input into the dayside ionosphere. Cyclotron damping of the waves does not occur in the same region. However, Landau damping of ionosheath waves is apparently not an important energy source in the nightside ionosphere. Impulsive events in the nightside ionosphere seem to fall into two classes: (1) lightning signals (near periapsis) and (2) noise, which may be caused by gradient or current instabilities.

  11. Absorption of whistler mode waves in the ionosphere of venus.

    PubMed

    Taylor, W W; Scarf, F L; Russell, C T; Brace, L H

    1979-07-06

    It is shown that whistler mode waves from the ionosheath of Venus are absorbed by Landau damping at the dayside ionosphere boundary. This process heats the ionospheric electrons and it may provide an important energy input into the dayside ionosphere. Cyclotron damping of the waves does not occur in the same region. However, Landau damping of ionosheath waves is apparently not an important energy source in the nightside ionosphere. Impulsive events in the nightside ionosphere seem to fall into two classes: (i) lightning signals (near periapsis) and (ii) noise, which may be caused by gradient or current instabilities.

  12. Atmosphere-Ionosphere Response to the M9 Tohoku Earthquake Revealed by Joined Satellite and Ground Observations. Preliminary Results

    NASA Technical Reports Server (NTRS)

    Ouzounov, Dimitar; Pulinets, Sergey; Romanov, Alexey; Tsybulya, Konstantin; Davidenko, Dimitri; Kafatos, Menas; Taylor, Patrick

    2011-01-01

    The recent M9 Tohoku Japan earthquake of March 11, 2011 was the largest recorded earthquake ever to hit this nation. We retrospectively analyzed the temporal and spatial variations of four different physical parameters - outgoing long wave radiation (OLR), GPS/TEC, Low-Earth orbit tomography and critical frequency foF2. These changes characterize the state of the atmosphere and ionosphere several days before the onset of this earthquake. Our first results show that on March 8th a rapid increase of emitted infrared radiation was observed from the satellite data and an anomaly developed near the epicenter. The GPS/TEC data indicate an increase and variation in electron density reaching a maximum value on March 8. Starting on this day in the lower ionospheric there was also confirmed an abnormal TEC variation over the epicenter. From March 3-11 a large increase in electron concentration was recorded at all four Japanese ground based ionosondes, which return to normal after the main earthquake. We found a positive correlation between the atmospheric and ionospheric anomalies and the Tohoku earthquake. This study may lead to a better understanding of the response of the atmosphere/ionosphere to the Great Tohoku earthquake.

  13. Satellite Constellations for Space Weather and Ionospheric Studies: Overview of the COSMIC and COSMIC-2 Missions

    NASA Astrophysics Data System (ADS)

    Schreiner, W. S.; Yue, X.; Kuo, B.

    2013-12-01

    Measurements from constellations of low Earth orbiting (LEO) satellites are proving extremely useful for ionospheric science and space weather studies. The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), a joint US/Taiwan mission launched in April 2006, is a six micro-satellite constellation that is flying three scientific payloads on each spacecraft: 1) a Global Positioning System (GPS) radio occultation (RO) receiver, 2) a nadir-viewing Tiny Ionospheric Photometer (TIP), and 3) a Coherent Electromagnetic Radio Tomography (CERTO) tri-band beacon transmitter. COSMIC has collected a large amount of useful data from these scientific payloads and is still currently collecting 1,500 RO measurement events per day on average. The GPS RO dual-frequency L-band phase and amplitude measurements can be used to observe absolute Total Electron Content (TEC) and scintillation on lines of sight between the LEO and GPS satellites, and electron density profiles (EDP) via the radio occultation (RO) method when GPS satellites are occulted by Earth's ionosphere. The large number and complete global and local time coverage of COSMIC data are allowing scientists to observe ionospheric and plasmaspheric phenomena that are difficult to see with other instruments. The success of COSMIC has prompted U.S. agencies to execute a COSMIC follow-on mission (called COSMIC-2) with Taiwan that will put twelve satellites with GNSS (Global Navigation Satellite System) RO payloads into orbit on two launches in the 2016-18 time frame. The first launch will place six satellites is in a near Equatorial orbit, which is ideal for hurricane prediction and space weather forecasting, and the second launch is in a polar orbit, which is good for global coverage and prediction of all storms. COSMIC-2 will also carry twelve space weather payloads that will fly on the first launch into low inclination orbits: six RF Beacon transmitters, and six Ion Velocity Meter instruments. COSMIC

  14. Computerized EEG: predictor of outcome in schizophrenia.

    PubMed

    Itil, T M; Marasa, J; Saletu, B; Davis, S; Mucciardi, A N

    1975-03-01

    Based on a double blind cross-over study, it was determined that schizophrenic patient who have more high frequency fast activity and a lesser degree of alpha and slow waves in computerized EEG before the treatment have a better therapeutic outcome to the major tranquilizer (neuroleptic) treatment. The correlation between pretreatment high frequency computer EEG measurements and better therapeutic outcome reached the level of statistical significance. "Therapy resistant" schizophrenic patients were characterized by a lesser degree of very fast beta activity, more alpha waves and slow waves, higher amplitudes in computer EEG, and a lesser degree of acute (florid) psychotic symptomatology but more "negative" symptoms such as motor retardation and blunted affect. One of the most striking results of the study is the finding that schizophrenic patients with certain psychopathological profiles also have similar computer EEG profiles.

  15. A COMPUTERIZED OPERATOR SUPPORT SYSTEM PROTOTYPE

    SciTech Connect

    Thomas A. Ulrich; Roger Lew; Ronald L. Boring; Ken Thomas

    2015-03-01

    A computerized operator support system (COSS) is proposed for use in nuclear power plants to assist control room operators in addressing time-critical plant upsets. A COSS is a collection of technologies to assist operators in monitoring overall plant performance and making timely, informed decisions on appropriate control actions for the projected plant condition. A prototype COSS was developed in order to demonstrate the concept and provide a test bed for further research. The prototype is based on four underlying elements consisting of a digital alarm system, computer-based procedures, piping and instrumentation diagram system representations, and a recommender module for mitigation actions. The initial version of the prototype is now operational at the Idaho National Laboratory using the Human System Simulation Laboratory.

  16. Computerization of a telescope at secondary education

    NASA Astrophysics Data System (ADS)

    García Santiago, A.; Martos Jumillas, J.

    2017-03-01

    The work we are presenting in this paper is the computerization of a refractor telescope on an EQ3 type equatorial mount through Arduino. The control of the mount is done via three different interfaces: Stellarium, an Android interface for mobile phones and a second interface for PC made with Processing. The aforementioned work was done by the authors with a double purpose: presenting the interest in astronomy in the Mathematics department, and the development of applications within the subject of Technology in 4th ESO. So, it is a collaborative project between both departments. Except for the telescope and the mount, all the resources we have used can be found in any high school: free software (Guadalinex v9), App Inventor and Processing.The project was carried out under the principle of reducing all possible costs given the economic possibilities of the institution.

  17. The Computerized Anatomical Man (CAM) model

    NASA Technical Reports Server (NTRS)

    Billings, M. P.; Yucker, W. R.

    1973-01-01

    A computerized anatomical man (CAM) model, representing the most detailed and anatomically correct geometrical model of the human body yet prepared, has been developed for use in analyzing radiation dose distribution in man. This model of a 50-percentile standing USAF man comprises some 1100 unique geometric surfaces and some 2450 solid regions. Internal body geometry such as organs, voids, bones, and bone marrow are explicitly modeled. A computer program called CAMERA has also been developed for performing analyses with the model. Such analyses include tracing rays through the CAM geometry, placing results on magnetic tape in various forms, collapsing areal density data from ray tracing information to areal density distributions, preparing cross section views, etc. Numerous computer drawn cross sections through the CAM model are presented.

  18. Computerized, telephone-based stress management program.

    PubMed Central

    Schneider, S. J.; Schwartz, M. D.; Fast, J.

    1993-01-01

    A stress management program that used computerized, telephone-based technology was offered to the public via a free, "800" telephone number. The program was intended to reach a very large number of persons, while requiring a minimum of staff time. The program used an interactive telephone system, employing natural sounding, digitized voice, and touch tone recognition of callers' responses. The program was available 24 hours a day. It composed each message to suit the individual needs and expectations of each caller. A controlled evaluation of the program was conducted to determine how the messages could be worded and presented most effectively. The results suggest that subjects were most likely to find the messages in the program helpful, to carry out the stress management instructions, and to continue calling when the messages were personalized and contained homework assignments. PMID:8130497

  19. The horizontal computerized rotational impulse test.

    PubMed

    Furman, Joseph M; Shirey, Ian; Roxberg, Jillyn; Kiderman, Alexander

    2016-01-01

    Whole-body impulsive rotations were used to overcome several limitations associated with manual head impulse testing. A computer-controlled rotational chair delivered brief, whole-body, earth-vertical axis yaw impulsive rotations while eye movements were measured using video-oculography. Results from an unselected group of 20 patients with dizziness and a group of 22 control subjects indicated that the horizontal computerized rotational head impulse test (crHIT) is well-tolerated and provides an estimate of unidirectional vestibulo-ocular reflex gain comparable to results from caloric testing. This study demonstrates that the horizontal crHIT is a new assessment tool that overcomes many of the limitations of manual head impulse testing and provides a reliable laboratory-based measure of unilateral horizontal semicircular canal function.

  20. Economic Evaluation of Computerized Structural Analysis

    NASA Technical Reports Server (NTRS)

    Fortin, P. E.

    1985-01-01

    This completed effort involved a technical and economic study of the capabilities of computer programs in the area of structural analysis. The applicability of the programs to NASA projects and to other users was studied. The applications in other industries was explored including both research and development and applied areas. The costs of several alternative analysis programs were compared. A literature search covered applicable technical literature including journals, trade publications and books. In addition to the literature search, several commercial companies that have developed computerized structural analysis programs were contacted and their technical brochures reviewed. These programs include SDRC I-DEAS, MSC/NASTRAN, SCADA, SUPERSAP, NISA/DISPLAY, STAAD-III, MICAS, GTSTRUDL, and STARS. These programs were briefly reviewed as applicable to NASA projects.

  1. Modifications of the ionosphere prior to large earthquakes: report from the Ionosphere Precursor Study Group

    NASA Astrophysics Data System (ADS)

    Oyama, K.-I.; Devi, M.; Ryu, K.; Chen, C. H.; Liu, J. Y.; Liu, H.; Bankov, L.; Kodama, T.

    2016-12-01

    The current status of ionospheric precursor studies associated with large earthquakes (EQ) is summarized in this report. It is a joint endeavor of the "Ionosphere Precursor Study Task Group," which was formed with the support of the Mitsubishi Foundation in 2014-2015. The group promotes the study of ionosphere precursors (IP) to EQs and aims to prepare for a future EQ dedicated satellite constellation, which is essential to obtain the global morphology of IPs and hence demonstrate whether the ionosphere can be used for short-term EQ predictions. Following a review of the recent IP studies, the problems and specific research areas that emerged from the one-year project are described. Planned or launched satellite missions dedicated (or suitable) for EQ studies are also mentioned.

  2. Studies of ionospheric plasma and electrodynamics and their application to ionosphere-magnetosphere coupling

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1988-01-01

    The contribution of the Dynamics Explorer (DE) program to the study of small-scale structure in the equatorial ionospheric number density and the bulk motion of the plasma in the equatorial ionosphere is considered. DE results have helped elucidate the role of E region and F region winds in decreasing the magnitude of variations in the east-west plasma drift at night, as a function of magnetic flux tube apex height, with increasing height above the altitude of the peak F region concentration. Other results concern the ionospheric convection pattern at high latitudes during periods of southward IMF, the magnetosphere/solar-wind interaction that may be involved in the production of the convection pattern, and the characteristics of the high-latitude ionospheric plasma motion during periods of northward IMF.

  3. The variability, morphology and outflow of Martian ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Lundin, R.; Barabash, S.; Winningham, D.

    2009-04-01

    ASPERA-3 measurements from Mars Express demonstrate that Martian ionospheric plasma escapes in a comet-like fashion. Low-energy (cold) ionospheric plasma is swept from the dayside, expanding into the nightside/tail of Mars. The primary energization processes brings ionospheric plasma to just above escape velocity (5 - 20 km/s). In analogy with the polar wind of the Earth, ionospheric plasma is expected to become energized by waves and electric fields generated by solar wind energy and momentum transfer processes. The rather symmetric and global comet-like escape of low-energy ionospheric plasma, streaming along the external sheath flow, suggest a "viscous-like" coupling between the sheath plasma and the expanding ionospheric plasma. The ionospheric ion outflow is very structured, fan-like and modulated in the ULF frequency range. The ionospheric densities measured vary correspondingly with time, altitude, latitude and local time. A similar variability of solar wind ions is found in the Martian magnetosheath. This implies that magnetosheath wave activity is involved, transferring energy and momentum to ionospheric ions. We demonstrate that the wave activity modulating ions and electrons, reaches down to the MEX pericenter (≈300 km), suggesting that heating/energization of ionospheric plasma extends deep into the ionosphere.

  4. Electron temperature and heat flow in the nightside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Brace, L. H.; Theis, R. F.; Mayr, H. G.

    1980-01-01

    A steady-state two-dimensional heat balance model is used to analyze the night side Venusian ionospheric electron temperatures given by the Pioneer Venus orbiter electron temperature probe. The energy calculation includes the solar EUV heating at the terminator, electron cooling to ions and neutrals, and heat conduction within the ionospheric plasma. An optimum magnetic field is derived by solving for the heat flux directions which force energy conservation while constrained by the observed temperatures within the range of 80-170 deg solar zenith angle and 160-170 km. The heat flux vectors indicate a magnetic field that connects the lower night side ionosphere to the day side ionosphere, and connects the upper ionosphere to the ionosheath. The lower ionosphere is heated through conduction of heat from the dayside, and the upper ionosphere is heated by the solar wind in the ionosheath with heat flowing downward and from the nightside to the day side.

  5. A review of ionospheric effects on Earth-space propagation

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  6. Ionosphere dynamics in the auroral zone during the magnetic storm of March 17-18, 2015

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D. V.; Sergeeva, M. A.

    2016-11-01

    A comprehensive study of the ionospheric processes encountered during the superstorm which started on March 17th 2015 has been carried out using magnetometer, ionosonde, riometer, ionospheric tomography and an all-sky camera installed in the observatory of Sodankylä, Finland. The storm manifested a number of interesting features. From 12:00 on March 17 there was a significant decrease of critical frequencies foF2 and intensive sporadic Es layers were observed. During the disturbance, there was a lack of variation of the X-component of the magnetic field at times, but the absorption level measured by the riometer was high. A comparison of the electron density distributions for the quiet and disturbed days as shown in the tomography data were very different. Where results were available at the same times, the tomographic foF2 values coincided with the "real" foF2 values from the ionosonde. Where the ionosonde data was missing due to absorption, the tomographic foF2 values were used instead. The keograms from the all-sky camera showed that during disturbed days the aurorae manifested themselves as bright discrete forms. It was shown that the peaks of absorption due to particle precipitation seen by the riometer coincided in time with the brightenings of aurorae seen on the keograms.

  7. Ionospheric effects during severe space weather events seen in ionospheric service data products

    NASA Astrophysics Data System (ADS)

    Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

  8. Normalized mean shapes and reference index values for computerized quantitative assessment indices of chest wall deformities

    NASA Astrophysics Data System (ADS)

    Kim, Ho Chul; Park, Man Sik; Lee, Seong Keon; Nam, Ki Chang; Park, Hyung Joo; Kim, Min Gi; Song, Jae-Jun; Choi, Hyuk

    2015-11-01

    We previously proposed a computerized index (eccentricity index [EI]) for chest-wall deformity measurements, such as pectus excavatum. We sought to define mean shapes based on normal chest walls and to propose for computerized index reference values of that are used in the quantitative analysis of the severity of chest-wall deformities. A total of 584 patients were classified into 18 groups, and a database of their chest-wall computed tomography (CT) scan images was constructed. The boundaries of the chest wall were extracted by using a segmentation algorithm, and the mean shapes were subsequently developed. The reference index values were calculated from the developed mean shapes. Reference index values for the EI were compared with a conventional index, the Haller index (HI). A close association has been shown between the two indices in multiple subjects (r = 0.974, P < 0.001). The newly developed mean shapes and reference index values supply both reliability and objectivity to the diagnosis, analysis, and treatment of chest-wall deformities. They promise to be highly useful in clinical settings.

  9. Three-dimensional computerized selection of hip prostheses in patients with congenital dislocated hips.

    PubMed

    Gelalis, L D; Xenakis, T A; Hantes, M; Vartziotis, K; Soucacos, P N

    2001-11-01

    This study assessed the effectiveness of the combined use of computed tomography (CT) and computer-aided design (CAD) in the preoperative evaluation and implant selection in 20 patients (20 hips) with congenital dislocation of the hip who were scheduled to undergo total hip arthroplasty. Computerized selection of the femoral implant with optimum fit and fill was made after a three-dimensional reconstruction of the femoral canal using CT data and CAD. Implantation of all sizes of 5 noncemented and 2 cemented femoral implants was simulated using CATIA software (IBM, Kingstone, NY). When patients underwent surgery, 18 of 20 preselected prostheses agreed by type and size with the prostheses implanted. The remaining 2 preselected implants agreed by type only. In patients with dislocated and dysplastic hips, combined use of CT and CAD allows effective preoperative planning by providing the surgeon with vital information about the proximal femoral canal geometry and the possible femoral implant with optimum fit and fill to be used.

  10. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  11. Importance of Ionospheric Gradients for error Correction

    NASA Astrophysics Data System (ADS)

    Ravula, Ramprasad

    Importance of Ionospheric Gradients for error Correction R. Ram Prasad1, P.Nagasekhar2 1Sai Spurthi Institute of Technology-JNTU Hyderabad,2Sai Spurthi Institute of Technology-JNTU Hyderabad Email ID:rams.ravula@gmail.com In India, Indian Space Research Organization (ISRO) has established with an objective to develop space technology and its application to various national tasks. To cater to the needs of civil aviation applications, GPS Aided Geo Augmented Navigation (GAGAN) system is being jointly implemented along with Airports Authority of India (AAI) over the Indian region. The most predominant parameter affecting the navigation accuracy of GAGAN is ionospheric delay which is a function of total number of electrons present in one square meter cylindrical cross sectional area in the line of site direction between the satellite and the user on the earth i.e. Total Electron Content (TEC).The irregular distribution of electron densities i.e. rate of TEC variation, causes Ionospheric gradients such as spatial gradients (Expressed in TECu/km) and temporal gradients (Expressed in TECu /minute). Among the satellite signals arriving to the earth in multiple directions, the signals which suffer from severe ionospheric gradients can be estimated i.e. Rate of TEC Index (ROTI) and Rate of TEC (ROT). These aspects which contribute to errors can be treated for improving GAGAN positional accuracy.

  12. Catalog of ionospheric and atmospheric data

    NASA Technical Reports Server (NTRS)

    Liles, J. N.

    1975-01-01

    Available data from planetary atmospheres and ionospheric physics (aeronomy) are announced. Most of the data sets identified result from individual experiments carried on board various spacecraft. A spacecraft Automated Internal Management File and a Nonsatellite Data File are utilized to maintain information on these data. Photoreduced reports produced by these information files are presented. A variety of user oriented indexes are included.

  13. Ionospheric TEC Weather Map Over South America

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Wrasse, C. M.; Denardini, C. M.; Pádua, M. B.; Paula, E. R.; Costa, S. M. A.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. Galera; Ivo, A.; Sant'Anna, N.

    2016-11-01

    Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Contínuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total 140 sites, have been used. TECMAPs with a time resolution of 10 min are produced in 12 h time delay. Spatial resolution of the map is rather low, varying between 50 and 500 km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1 TECU = 1016 el m-2 (TECU) <10) to the crest region (TECU > 80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

  14. Global Response to Local Ionospheric Mass Ejection

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Fok, M.-C.; Delcourt, D. C.; Slinker, S. P.; Fedder, J. A.

    2010-01-01

    We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 Sept 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MIlD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description.

  15. Transionospheric VLF Propagation as an Ionospheric Diagnostic

    NASA Astrophysics Data System (ADS)

    Worthington, E. R.; Cohen, M.

    2015-12-01

    Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground-based sources, such as VLF transmitters or lightning strokes, are attenuated as they travel through the D-region of the ionosphere, making measurements taken of the VLF energy that has escaped this region useful in estimating the electron density. It has been also been suggested that F-region irregularities may contribute additional attenuation to the VLF signal. Additionally, energy at these frequencies that escapes the ionosphere altogether strongly impacts the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributes to the formation of the slot region. We present an analysis of measurements captured by the DEMETER satellite over VLF transmitters. During its six-year mission, DEMETER completed hundreds of passes above well-characterized VLF transmitters while recording electric and magnetic field strengths. Statistically significant (daytime and nighttime) seasonal variations were observed in this data set. We compare observations with estimates obtained using a sophisticated full wave model of trans-ionospheric propagation, and discuss the viability of the International Reference Ionosphere in correctly predicting transionospheric VLF energy.

  16. Plasma-beam instabilities in cometary ionospheres

    NASA Technical Reports Server (NTRS)

    Churyumov, Klim I.; Kotsarenko, N. YA.; Lizunov, G. V.; Verkhoglyadova, O. P.

    1992-01-01

    It is shown that the interaction between the solar wind flux and the cometary ionosphere leads to the excitation of ion sound, whistler, electron-cyclotron, low hybrid, and magnetohydrodynamic waves. We investigated the frequency spectrum and found linear-increasing increments and lengths of excited waves.

  17. Low Frequency Rada Sounding Through Martian Ionosphere

    NASA Technical Reports Server (NTRS)

    Safaeinili, A.; Jordan, R.

    2000-01-01

    In remote radar sounding, it is highly desirable to operate at low frequencies to improve depth of penetration. For spaceborne sounders, the lowest operating frequency is limited by the effect of the ionosphere due to significant dispersion of the radar waves at near plasma frequency.

  18. Magnetospheric and Thermospheric Influence on Ionospheric Outflow

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, K.; Moore, T. E.; Mitchell, E. J.; Olson, D. K.

    2013-12-01

    The Fast Auroral SnapshoT (FAST) small explorer has been used extensively to study ionospheric outflow. Past research has used particle and field data to examine the contemporaneous transfer of electromagnetic energy and particle flow downward from the magnetosphere and upward from the ionosphere. Single event studies published by Strangeway et al. [2005] and Brambles et al. [2011, Supporting Online Material] showed that downward electromagnetic energy and particle flow into the ionosphere are correlated with the upward flow of ions out of the ionosphere. It is expected, however, that this correlation will be affected by circumstances that are unique to each specific event, including but not limited to the outflow location (cusp or nightside), preconditioning due to prior geomagnetic activity, and thermospheric neutral densities. Although knowledge of the thermospheric neutral density is usually unavailable, data from the CHAllenging Minisatellite Payload (CHAMP) is able to provide insight into thermospheric populations at altitudes of about 400 km for a few select events. We expand on the previously-mentioned studies by looking at FAST particle and field data for additional events, and we further examine the influence of thermospheric neutral populations, based on CHAMP data.

  19. Ionosphere-thermosphere space weather issues.

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Sojka, J. J.

    1996-10-01

    Weather disturbances in the ionosphere-thermosphere system can have a detrimental effect on both ground-based and space-based systems. Because of this impact and because this field has matured, it is now appropriate to develop specification and forecast models, with the aim of eventually predicting the occurrence, duration, and intensity of weather effects. As part of the new National Space Weather Program, the CEDAR community will focus on science issues concerning space weather, and this tutorial/review is an expanded version of a tutorial presentation given at the recent CEDAR annual meeting. The tutorial/review provides a brief discussion of weather disturbances and features, the causes of weather, and the status of weather modeling. The features and disturbances discussed include plasma patches, boundary and auroral blobs, Sun-aligned polar cap arcs, the effects of traveling convection vortices and SAID events, the lifetime of density structures, sporadic-E and intermediate layers, spread F and equatorial plasma bubbles, geomagnetic storms and substorms, traveling ionospheric disturbances (TIDs), and the effects of tides and gravity waves propagating from the lower atmosphere. The tutorial/review is only intended to provide an overview of some of the important scientific issues concerning ionospheric-thermospheric weather, with the emphasis on the ionosphere. Tutorials on thermospheric and magnetospheric weather issues are given in companion papers.

  20. Phase perturbation measurements through a heated ionosphere

    NASA Technical Reports Server (NTRS)

    Frey, A.; Gordon, W. E.

    1982-01-01

    High frequency radiowaves incident on an overdense (i.e., HF-frequency penetration frequency) ionosphere produce electron density irregularities. The effect of such ionospheric irregularities on the phase of UHF-radiowaves was determined. For that purpose the phase of radiowaves originating from celestial radio sources was observed with two antennas. The radiosources were chosen such that the line of sight to at least one of the antennas (usually both) passed through the modified volume of the ionosphere. Observations at 430 MHz and at 2380 MHz indicate that natural irregularities have a much stronger effect on the UHF phase fluctuations than the HF-induced irregularities for presently achieved HF-power densities of 20-80 uW/sq m. It is not clear whether some of the effects observed are the result of HF-modification of the ionosphere. Upper limits on the phase perturbations produced by HF-modification are 10 deg at 2380 MHz and 80 deg at 430 MHz.

  1. Ionospheric observations in Western-Europe

    SciTech Connect

    Gorman, F.J.; Soicher, H.

    1990-05-03

    Hourly digital ionograms were taken at two Western European locations: Dourbes, Belgium (50.10 N, 4.60 E) and, Roquetas, Tarragona, Spain (40.80 N, 0.30 E) during Winter through Summer of 1988. Ionospheric parameters were tabulated and compared at the two stations, which were separated by 01000 km, using correlative techniques.

  2. Midday reversal of equatorial ionospheric electric field

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1997-10-01

    A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956-1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  3. Correcting ionospheric Faraday rotation for ASKAP

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Shane; Gaensler, Bryan; Landecker, Tom L.; Willis, Tony

    2012-10-01

    Next-generation polarisation surveys, such as the POSSUM survey on ASKAP, aim to measure weak, statistical, cosmological effects associated with weak magnetic fields, and so will require unprecedented accuracy and stability for measuring polarisation vectors and their Faraday rotation measures (RMs). Ionospheric Faraday rotation (IFR) corrupts polarization observations and cannot be ignored at mid to low frequencies. In aperture-synthesis polarimetry IFR rotates individual visibilities and leads to a loss of coherence and accuracy of polarization angle determination. Through the POSSUM survey science team we have been involved in developing detailed ionospheric prediction software (POSSUM memos #10a,b) that will be used to correct the observed visibilities on ASKAP before imaging to obtain sufficiently accurate polarization and RM data. To provide a stringent test of this software, we propose a continuous 24 hr observing block using the 1.1-3.1 GHz band to monitor the variations caused by the time-variable ionosphere in the polarization angle and RM of a strongly polarized calibrator source, PKS B1903-802. We request a total of 96 hrs (4 x 24 hrs) to monitor the changes in the ionosphere every 3 to 6 months until BETA/ASKAP-12 is taking reliable polarization data.

  4. Physicochemical model of the auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Dashkevich, Zh. V.; Ivanov, V. E.; Sergienko, T. I.; Kozelov, B. V.

    2017-03-01

    A physicochemical model of excited polar ionosphere has been presented. The model makes it possible to calculate vertical profiles of concentrations of the following excited and ionized constituents: O2 +, N2 +, O+(4S), O+(2D), O+(2P), O(1D), O(1S), N(4S), N(2D), N(2P), NO, NO+, N+, N2(A3Σu +), N2(B3Пg), N2(W3Δu), and N2(B'3Σu -) and the electron concentration during electron precipitations. The energy spectrum of the electrons at the upper boundary of the ionosphere and concentrations of neutral constituents are the input parameters of the model. A model has been compiled based on available publications and includes 56 physicochemical reactions that influence concentrations of the aforementioned constituents in the polar ionosphere. The method of calculating vertical profiles of the excitation rates of atmospheric gases and proper allowance for the electron-vibrational kinetics in the processes of exciting the triplet states of N2 are specific features of the presented model. The ionospheric model has been approbated using the results of the coordinated rocket-satellite experiment. The agreement between the modeling results and experimental data best for the time being is achieved.

  5. Cassini observations of ionospheric currents at Titan

    NASA Astrophysics Data System (ADS)

    Ågren, Karin; Andrews, David J.; Coates, Andrew; Cowley, Stanley W. H.; Edberg, Niklas J. T.; Modolo, Ronan; Provan, Gabrielle; Rosenqvist, Lisa; Wahlund, Jan-Erik; Wellbrock, Anne

    The dense atmosphere of Titan is ionised by cosmic rays, meteors, energetic ions, solar EUV ra-diation and particle impact ionisation by Saturn's co-rotating magnetosphere. Besides this, ion transport from dayside to nightside plays a role in the formation of the ionosphere. Numerous Cassini flybys of Titan have shown that the structure and dynamics of the moon's ionosphere is affected by external conditions, such as solar illumination and variations in Saturn's magne-tosphere. In this study we continue the work by Rosenqvist et al. (2009), where conductivities at Titan were calculated. Langmuir probe (LP), magnetometer (MAG) and electron spectrom-eter (ELS) measurements by Cassini are used in order to map the cold plasma properties in the deep ionosphere of the moon. By calculating the curl of the magnetic field and adapt the conductivity computations to the results, we infer currents and electric fields with direction and magnitude. In this paper we give a first view on how the currents in the ionosphere of Titan are flowing.

  6. Problems and Solutions of Popularization of Accounting Computerization

    NASA Astrophysics Data System (ADS)

    Lu, Kan; Fu, YingLi; Gu, CaiDong; Zhang, Liang

    With the integration of China's economy and international markets, accounting computerization, which conducts accounting and accounting control by taking advantage of computer, has become a major component sector of accounting modernization and the main content of accounting reform. The popularization of accounting computerization is beyond question. Only this popularization can meet the requirement of knowledge economy for accounting information. It is the need to deepen accounting reform, to further enhance the level of accounting work and to achieve China's modernization of science and technology as well. This paper discusses problems and relevant solutions in the popularization process of accounting computerization so as to carry out this popularization better.

  7. Coherence Bandwidth and Pulse Distortion through Naturally and Artificially Modified Ionospheres

    DTIC Science & Technology

    1982-08-01

    ionosphere. The problems investigated can be broadly classified into three areas : propagation effects through ionospheric bubbles, propagation effects through...ionospheric irregularities and experimental obser- vations of scintillation effects. Four-year work on these areas is summarized in this report. FORM...three areas : pro)pagation effects through ionospheric bubbles, propagation effects thrc~ugh ionospheric rg- larities and experimental observations of

  8. Global ionospheric disturbances during super magnetic storms

    NASA Astrophysics Data System (ADS)

    Huang, C.; Foster, J.; Rideout, W.; Zhang, Y.; Paxton, L.

    2005-12-01

    Magnetic storms represent the largest disturbances in the magnetosphere and ionosphere. We will present the ionospheric observations by the Millstone Hill incoherent scatter radar, global GPS network, and TIMED GUVI instrument during two super storms. The sudden commencement (SSC) of the 15 July 2000 storm occurred at 19 UT, and the minimum Dst reached -301 nT. The dayside midlatitude ionospheric F region electron density showed a sudden decrease at Millstone Hill and Eglin in response to the SSC. The elevation scan measurements of the Millstone HIll radar show that the sudden decrease in the ionospheric electron density was related to an electron density trough which had an equatorward boundary at Eglin (magnetic latitude 41 degree) at 16 MLT. The formation of the trough may be related to equatorward incursion of the disturbance SAPS electric field. The dayside TEC decreased significantly at the equatorial and upper midlatitudes, and an enhanced TEC band occurred between the depleted regions. The SSC of the 29 October 2003 storm occurred at 07 UT, the storm was further enhanced at 18 UT, and the minimum Dst reached -363 nT. The Millstone Hill radar also detected a sudden decrease of the dayside F region electron density immediately after the storm enhancement. The simultaneous TIMED GUVI measurements show a significant decrease in the O/N2 ratio over the Atlantic sector from the auroral zone to anomaly latitudes, and large TEC depletions occurred coincidentally with the O/N2 decrease. In this second case, both the enhanced electric field and decrease of O/N2 ratio contributed to the depletion of the dayside midlatitude F-region electron density and TEC. The multiple measurements during the two storms reveal the distinct properties and mechanisms of the global ionospheric disturbances.

  9. Electrodynamics of ionospheric weather over low latitudes

    NASA Astrophysics Data System (ADS)

    Abdu, Mangalathayil Ali

    2016-12-01

    The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the

  10. Evaluation of COMPASS ionospheric model in GNSS positioning

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoli; Hu, Xiaogong; Wang, Gang; Zhong, Huijuan; Tang, Chengpan

    2013-03-01

    As important products of GNSS navigation message, ionospheric delay model parameters are broadcasted for single-frequency users to improve their positioning accuracy. GPS provides daily Klobuchar ionospheric model parameters based on geomagnetic reference frame, while the regional satellite navigation system of China's COMPASS broadcasts an eight-parameter ionospheric model, COMPASS Ionospheric Model(CIM), which was generated by processing data from continuous monitoring stations, with updating the parameters every 2 h. To evaluate its performance, CIM predictions are compared to ionospheric delay measurements, along with GPS positioning accuracy comparisons. Real observed data analysis indicates that CIM provides higher correction precision in middle-latitude regions, but relatively lower correction precision for low-latitude regions where the ionosphere has much higher variability. CIM errors for some users show a common bias for in-coming COMPASS signals from different satellites, and hence ionospheric model errors are somehow translated into the receivers' clock error estimation. In addition, the CIM from the China regional monitoring network are further evaluated for global ionospheric corrections. Results show that in the Northern Hemisphere areas including Asia, Europe and North America, the three-dimensional positioning accuracy using the CIM for ionospheric delay corrections is improved by 7.8%-35.3% when compared to GPS single-frequency positioning ionospheric delay corrections using the Klobuchar model. However, the positioning accuracy in the Southern Hemisphere is degraded due apparently to the lack of monitoring stations there.

  11. Computerized Point of Sale = Faster Service + Better Accountability.

    ERIC Educational Resources Information Center

    Pannell, Dorothy V.

    1991-01-01

    Describes selecting and installing a computerized point of sale for a district food service program; the equipment needed and preferred; and the training of trainers, managers, and cashiers. Also discusses the direct benefits and side benefits of the system. (MLF)

  12. Computerized mouse pupil size measurement for pupillary light reflex analysis.

    PubMed

    Lu, Wei; Tan, Jinglu; Zhang, Keqing; Lei, Bo

    2008-06-01

    Accurate measurement of pupil size is essential for pupillary light reflex (PLR) analysis in clinical diagnosis and vision research. Low pupil-iris contrast, corneal reflection, artifacts and noises in infrared eye imaging pose challenges for automated pupil detection and measurement. This paper describes a computerized method for pupil detection or identification. After segmentation by a region-growing algorithm, pupils are detected by an iterative randomized Hough transform (IRHT) with an elliptical model. The IRHT iteratively suppresses the effects of extraneous structures and noise, yielding reliable measurements. Experimental results with 72 images showed a mean absolute difference of 3.84% between computerized and manual measurements. The inter-run variation for the computerized method (1.24%) was much smaller than the inter-observer variation for the manual method (7.45%), suggesting a higher level of consistency of the former. The computerized method could facilitate PLR analysis and other non-invasive functional tests that require pupil size measurements.

  13. Geometric Computerized Proofs = Drawing Package + Symbolic Computation Software.

    ERIC Educational Resources Information Center

    Szymanski, Witold A.

    1994-01-01

    This paper advocates the use of symbolic computation packages as another aid in teaching geometry. The need for such packages and their use in computerized proofs are demonstrated by a problem in high school planar geometry. (LZ)

  14. Survey of methods for improving operator acceptance of computerized aids

    SciTech Connect

    Frey, P. R.; Kisner, R. A.

    1982-04-01

    The success of current attempts to improve the operational performance and safety of nuclear power plants by installing computerized operational aids in the control rooms is dependent, in part, on the operator's attitude toward the aid. Utility experience with process computer systems indicates that problems may already exist with operator acceptance of computerized aids. The growth of the role that computers have in nuclear power plants makes user acceptance of computer technology an important issue for the nuclear industry. The purpose of this report is to draw from the literature factors related to user acceptance of computerized equipment that may also be applicable to the acceptance of computerized aids used in the nuclear power plant control room.

  15. Assimilation Ionosphere Model: Development and testing with Combined Ionospheric Campaign Caribbean measurements

    NASA Astrophysics Data System (ADS)

    Sojka, J. J.; Thompson, D. C.; Schunk, R. W.; Bullett, T. W.; Makela, J. J.

    2001-03-01

    Assimilation Ionosphere Model (AIM) is a physics-based, global, ionospheric specification model that is currently under development. It assimilates a diverse set of real-time (or near-real-time) measurements, such as ionograms, GPS slant total electron content (TEC), and in situ plasma measurements. This study focuses on a middle latitude ionosonde assimilation capability in both local and regional forms. The models described are capable of using theƒ0F2 and hmF2 from ionograms to generate either a local or a regional distribution of the induced plasma drift. This induced drift is usually caused by the meridional neutral wind. Results from a local model (AIM1.03L) and a regional model (AIM1.03R) are presented and compared with the international reference ionosphere (IRI) climatological predictions as well as GPS slant TEC measurements. Results from year-long studies during solar maximum show that the accuracy of the AIM1.03L model is about a factor of 2 better than that of IRI. An initial month-long regional study is also presented, and the results are almost as good. A study is also carried out using observations taken during the Combined Ionospheric Campaign (CIC) held in November, 1997, in the Caribbean. The digisonde located at Ramey Solar Observatory is used to drive the AIM1.03L model, and the predicted GPS slant TECs are compared to those observed by a GPS receiver located at St. Croix. This study confirms that this first step in preparing a weather-sensitive ionospheric representation is superior to a climatological representation. This sets the stage for the development of full assimilation of GPS TEC, in situ density measurements, etc., and it is anticipated that the AIM1.03L-R ionospheric representation will provide an accurate ionospheric specification.

  16. Photoacoustic Tomography

    NASA Astrophysics Data System (ADS)

    Wang, Lihong V.

    Photoacoustic tomography (PAT) refers to imaging that is based on the photoacoustic effect. Although the photoacoustic effect as a physical phenomenon was first reported on by Alexander Graham Bell in 1880 [1], PAT as an imaging technology was developed only after the advent of ultrasonic transducers, computers, and lasers [2-31]. A review on biomedical photoacoustics is available [32]. The motivation for PAT is to combine optical-absorption contrast with ultrasonic spatial resolution for deep imaging in the optical quasi-diffusive or diffusive regime. In PAT, the tissue is irradiated by usually a short-pulsed laser beam to achieve a thermal and acoustic impulse response (Fig. 19.1). Locally absorbed light is converted into heat, which is further converted to a pressure rise via thermo-elastic expansion. The initial pressure rise - determined by the local optical absorption coefficient (μ â ), fluence (ψ) and other thermal and mechanical properties - propagates as an ultrasonic wave, which is referred to as a photoacoustic wave.

  17. The CERTO Beacon on CASSIOPE/e-POP and Experiments Using High-Power HF Ionospheric Heaters

    NASA Astrophysics Data System (ADS)

    Siefring, Carl L.; Bernhardt, Paul A.; James, H. Gordon; Parris, Richard Todd

    2015-06-01

    A new Coherent Electromagnetic Radio Tomography (CERTO) beacon is on the CASSIOPE satellite and part of the enhanced-Polar Outflow Probe (e-POP) suite of scientific instruments. CERTO signals can be used to measure ionospheric Total Electron Content (TEC) and radio scintillations along propagation paths between CERTO and receivers. The combination of CERTO and the array of e-POP in-situ diagnostics form a powerful tool for studying ionospheric plasma processes that have not been previously possible. Of note, the combination CERTO and the Radio Receiver Instrument (RRI), a modern digital receiver, which measures between 10 Hz to 18 MHz in selectable bands allows for innovative High Frequency (HF) radio propagation experiments. The use of high-power HF ionospheric heating facilities for such experiments further allows for repeatable studies of a number of important plasma processes. The new CERTO beacon transmits un-modulated, phase-coherent waves at 150, 400, and 1067 MHz with either right-hand-circular or linear polarization and TEC is measured using either differential phase and/or Faraday rotation. With a linear array of CERTO receivers, TEC data can be used for tomographic imaging of the ionosphere yielding two-dimensional maps of the plasma below the satellite orbit. In addition, the three CERTO frequencies cover a wide range for determination of radio scintillation effects caused by diffraction from propagation through ionospheric irregularities. We will describe the CERTO beacon and several potential innovative experiments using HF heating facilities in conjunction with CERTO, the RRI and other e-POP instruments.

  18. Comprehensive computerized medical imaging: interim hypothetical economic evaluation

    NASA Astrophysics Data System (ADS)

    Warburton, Rebecca N.; Fisher, Paul D.; Nosil, Josip

    1990-08-01

    The 422-bed Victoria General Hospital (VGH) and Siemens Electric Limited have since 1983 been piloting the implementation of comprehensive computerized medical imaging, including digital acquisition of diagnostic images, in British Columbia. Although full PACS is not yet in place at VGH, experience to date habeen used to project annual cost figures (including capital replacement) for a fully-computerized department. The resulting economic evaluation has been labelled hypothetical to emphasize that some key cost components were estimated rather than observed; this paper presents updated cost figures based on recent revisions to proposed departmental equipment configuration which raised the cost of conventional imaging equipment by 0.3 million* and lowered the cost of computerized imaging equipment by 0.8 million. Compared with conventional diagnostic imaging, computerized imaging appears to raise overall annual costs at VGH by nearly 0.7 million, or 11.6%; this is more favourable than the previous results, which indicated extra annual costs of 1 million (16.9%). Sensitivity analysis still indicates that all reasonable changes in the underlying assumptions result in higher costs for computerized imaging than for conventional imaging. Computerized imaging offers lower radiation exposure to patients, shorter waiting times, and other potential advantages, but as yet the price of obtaining these benefits remains substantial.

  19. Computerized grading of anatomy laboratory practical examinations.

    PubMed

    Krippendorf, Beth B; Bolender, David L; Kolesari, Gary L

    2008-01-01

    At the Medical College of Wisconsin, a procedure was developed to allow computerized grading and grade reporting of laboratory practical examinations in the Clinical Human Anatomy course. At the start of the course, first year medical students were given four Lists of Structures. On these lists, numbered items were arranged alphabetically; the items were anatomical structures that could be tagged on a given lab practical examination. Each lab exam featured an anatomy laboratory component and a computer laboratory component. For the anatomy lab component, students moved from one question station to another at timed intervals and identified tagged anatomical structures. As students identified a tagged structure, they referred to a copy of the list (provided with their answer sheet) and wrote the number corresponding to the structure on their answer sheet. Immediately after the anatomy lab component, students were escorted to a computer instruction laboratory where they typed their answer numbers into a secured testing component of a learning management system that recorded their answers for automatic grading. After a brief review of examination scores and item analysis by faculty, exam scores were reported to students electronically. Adding this brief computer component to each lab exam greatly reduced faculty grading time, reduced grading errors and provided faster performance feedback for students without changing overall student performance.

  20. Language networks associated with computerized semantic indices.

    PubMed

    Pakhomov, Serguei V S; Jones, David T; Knopman, David S

    2015-01-01

    Tests of generative semantic verbal fluency are widely used to study organization and representation of concepts in the human brain. Previous studies demonstrated that clustering and switching behavior during verbal fluency tasks is supported by multiple brain mechanisms associated with semantic memory and executive control. Previous work relied on manual assessments of semantic relatedness between words and grouping of words into semantic clusters. We investigated a computational linguistic approach to measuring the strength of semantic relatedness between words based on latent semantic analysis of word co-occurrences in a subset of a large online encyclopedia. We computed semantic clustering indices and compared them to brain network connectivity measures obtained with task-free fMRI in a sample consisting of healthy participants and those differentially affected by cognitive impairment. We found that semantic clustering indices were associated with brain network connectivity in distinct areas including fronto-temporal, fronto-parietal and fusiform gyrus regions. This study shows that computerized semantic indices complement traditional assessments of verbal fluency to provide a more complete account of the relationship between brain and verbal behavior involved organization and retrieval of lexical information from memory.