Showing papers on "TEC published in 1978"

Effect of toxigenic Escherichia coli on myoelectric activity of small intestine.

Abstract: When exposed to cholera toxin (CT), distal ileal loops of the rabbit small intestine showed an alteration in myoelectric activity. This alteration was defined as the migrating action potential complex (MAPC). The purpose of this study was to determine, using myoelectric recording techniques, the effects of live toxigenic Escherichia coli (TEC) on motility. Live TEC, live nontoxigenic E. coli (NTEC), and culture filtrates of these organisms were studied. Live TEC and its filtrate induced MAPC activity similar to that of CT. Live TEC induced a mean of 3.8 MAPCs/h, significantly greater than induced by live NTEC. TEC filtrate induced a mean of 14.2 MAPCs/h, significantly greater than NTEC filtrate. Heating the TEC filtrate to 100 degrees C before use resulted in a significant decrease of MAPC activity. This experiment demonstrated that live TEC and its culture filtrate altered ileal myoelectric activity. The effect may have been mediated by a heat-labile enterotoxin. This study suggests that alterations in small intestinal motility may be important in the pathogenesis of TEC diarrhea.

Spatial correlation of transionospheric signal time delays

Abstract: Excess time delays of transionospheric radio signals introduce ranging errors in satellite-navigation and radar systems, which are directly proportional to the total electron content (TEC) along the propagation path. Correlation between TEC at Fort Monmouth, NJ ( 40.18\deg N, 74.06\deg W) and Richmond, FL ( 25.60\deg N, 80.40\deg W) was determined. The correlation analysis was performed at monthly and daily intervals for the equinoctial and winter periods during the quiet phase of the solar cycle. Positive maxima of monthly correlation coefficients were \gsim 0.9 for data comparisons at identical or nearly identical times, and decreased when the data sets were shifted in time with respect to each other. Positive maxima of daily correlation coefficients were, in general, \gsim 0.9 . Seasonal variations were noticeable.

Behavior of the ionospheric F-region during geomagnetic storms

Abstract: : The behavior of the ionospheric F-region during geomagnetic storms is addressed by examining many years of total electron content (TEC) data obtained from a semi-global network of TEC observing sites. An analysis procedure is described which leads to the derivation of average disturbance patterns which capture the characteristic features seen during individual storms. These average storm patterns give percentage deviations from monthly median behavior on a local time basis over a 4-day storm period. Primary emphasis is given to disturbance patterns seen over a latitude network spanning the geomagnetic L-shell range L approx. = 1 1/2 to 5. A clear and recurrent pattern of coupled positive and negative excursions over this latitude range are describes on a season by season basis. At lower mid-latitudes (L approx. = 1 1/2 - 2), where the largest net changes in ionospheric plasma contents occur, a longitudinal network is used to confirm and contrast the effects observed in the context of the latitudinal patterns.

Total electron content at low latitudes

Abstract: Radio beacon from ATS-6 at 140 MHz was used to measure the changes in the polarization angle (Faraday rotation) at Bombay, Rajkot, Ahmedabad, Udaipur and Patiala during October 1975 to July 1976. In this paper, results of diurnal, seasonal and latitudinal variations in total electron content (TEC) derived from these measurements are reported. The amplitude of diurnal peak is found to be higher at Rajkot, Ahmedabad and Udaipur as compared to that at Patiala or Bombay, indicating that the peak of Appleton anomaly in the latitudinal variation of TEC was close to the latitude of Ahmedabad. The diurnal maximum of TEC occurs around the same time during summer and winter months. The peak electron content shows a semiannual variation at all the stations with large values in equinoxes as compared to winter and summer. The TEC at Bombay shows a seasonal anamoly with high values in winter as compared to summer. The paper describes the development of latitudinal anomaly with the time of the day for different seasons. This anomaly is maximum during 1000 to 1800 LT and is located between 12° and 14° N (dip latitude) in summer and equinoxes and at about 10°N in winter.

The Nasathermionic-Conversion (TEC-Art) Program a Proposed Paper for Presentation at the May 1977 IEEE International Conference on Plasma Science at Rensselaer Polytechnic Institute

Abstract: The NASA program for applied research and technology (ART) in thermionic energy conversion (TEC) comprises in-house, university-grant, and industrial-contract studies. In a few years this TEC-ART program has produced important results. Although many of these accomplishments are incremental, their integration has yielded performance gains and the knowledge necessary to direct future work. The current emphasis on out-of-core thermionics allows materials and designs previously prohibited by in-core nucleonics and geometrics. The additional degrees of freedom offer new potentialities. But as always high-temperature material effects will determine the level and lifetime of TEC performance: New electrodes must not only raise power outputs but also maintain them regardless of emitter-vapor deposition on collectors. In addition effective electrodes must serve compatibly with hot-shell alloys. Then, of course, space TEC must withstand external and internal high-temperature vaporization problems. And terrestrial TEC must tolerate hot corrosive atmospheres outside and near-vacuum inside. Finally reduction of losses between converter electrodes is essential even though rather demanding geometrics appear to be required for some modes of enhanced operation. In these and other areas from basic material characterizations to possible system definitions, significant progress is being made in the NASA TEC-ART Program.

A numerical model for low-latitude ionospheric TEC

Abstract: A numerical model of total electron content (TEC) at low latitudes has been constructed from the Faraday rotation data recorded at a number of locations in India during the period Oct. 1975-July 1976 when the geostationary satellite ATS-6 was located at 35 deg E. In all, 36 coefficients for each season are required to represent the model. The model can be used for satellite tracking systems in estimating quickly the range, range rate and angular refraction errors. The present model is an improvement over the previously constructed model based on orbiting satellite data.

Electron reflection from one-dimensional potential barriers

Abstract: This report summarizes the relevant experimental evidence for electron reflectivity effects in TEC and describes the analytical effort to better understand electron reflectivity as a function of the potential configuration of the surface layer The analyses consider rectangular and triangular barrier models with, and without, image potentials The calculated results are presented and discussed Details of the solutions are given in Appendices A, B, and C The computer programs to obtain these results are listed in Appendix D These analyses demonstrate that cesium-oxygen composites with potential discontinuities around one volt and 20 A thick can be expected to be highly reflective to thermal electrons Consequently, such composites would be expected to have significant effects on TEC performance

Comparison of Storm-Time Changes of Ionospheric Total Electron Content at Nearby Locations in Mid-Latitudes

Abstract: The changes in the total electron content (TEC) at some mid-latitude locations in the American zone are compared during nine geomagnetc storms which are comparatively clean (clear-cut single main phase). It is found that TEC changes are sometimes related to sudden storm commencement (SSC) and sometimes to main phase onset (MPO) and the changes are sometimes positive and sometimes negative with no obvious relationship either with season or with any particular phase of the geomagnetic storm. It is concluded that there is no direct cause-effect relationship between ionospheric changes and changes of geomagnetic field as such and the only thing common between these is their common source viz, impact of interplanetary plasma blobs while subsequent evolutions are independent and unrelated.

Forwards with TEC

Abstract: (1978). Forwards with TEC. Journal of Further and Higher Education: Vol. 2, No. 2, pp. 29-35.