Showing papers on "TEC published in 1985"

Ionospheric electron content depletion associated with amplitude scintillation at the equatorial anomaly crest region

Abstract: The diurnal and seasonal behaviors of the ionospheric total electron content (TEC) depletion associated with VHF amplitude scintillation observed at Lunping, Taiwan (25.00 deg N, 121.17 deg E geographic), during the period March 1977 to February 1980 were presented. Diurnally, the maximum occurrence of TEC depletion appears during the late evening hours for all seasons except winter. Seasonally, the maximum occurrence of TEC depletion is not fixed at a certain season but varies with sunspot number because of the different sunspot number dependence of the occurrence of TEC depletion in different seasons. The most probable maximum TEC depletion ranges from 0.8 to 3.6 x 10 to the 16th el/sq m, and the duration ranges from 10 to 33 min. No correlation was found between the maximum TEC depletion and the duration or between the maximum TEC depletion and the associated ionospheric scintillation index. The association between TEC depletion and range spread F is much better than that between TEC depletion and frequency spread F. 32 references.

Seasonal and day-to-day variability of total electron content at mid-latitudes near solar maximum

Abstract: Faraday rotation observations were conducted at Fort Monmouth, New Jersey (40.15°N, 74.01°W), utilizing beacon transmissions from a geostationary satellite during the period just following the maximum phase of solar cycle 21. Seasonal and day-to-day variabilities are observed. Unique representation of the data has permitted the study of the day-to-day variability of derived total electron content (TEC) values. For example, winter data indicate uniformity of day-to-day TEC values during the buildup and decay phases of the diurnal variation, and summer data indicate uniformity during the predawn and sunrise phases, whereas equinox data indicate wide variability during all phases. In addition, winter and summer data indicate that during non-magnetically-disturbed periods, TEC values at the diurnal peak, which exceed monthly mean values, tend to occur on consecutive days. During the equinoxes the peak values may occur randomly. The response of TEC to magnetic activity is also discussed. Since day-to-day variability is a most difficult quantity to predict, the results have implications for prediction improvement.

Deep depletions of total electron content associated with severe mid‐latitude gigahertz scintillations during geomagnetic storms

Abstract: Using 136-MHz Faraday rotation data obtained at three closely spaced stations, we present evidence that severe nighttime gigahertz scintillations, which appear rarely at mid-latitudes around Japan only during geomagnetic storm conditions, are closely associated with deep depletions of total electron content (TEC). The TEC depletions amount to 2–8×1016 el/m² (10–30% of the background TEC), and their durations range from 10 min to 1 hour. These depletions move northeastward or eastward with velocities between 60 and 260 m/s. The depletions are probably not counterparts of the equatorial bubbles but seem to be formed in localized regions around Japan under complicated and peculiar ionospheric conditions. There is an indication that the oscillation of the F region caused by large-scale TID's propagating from north to south (∼600 m/s) may initiate the generation of the depletion.

Compositional dependence of thermal expansion coefficient of metallic glasses

Abstract: The thermal expansion behavior of various NiSiB, (Fe x Ni 1− x ) 78 Si 8 B 14 and Co 75 Si x B 25− x metallic glasses (as-quenched, relaxed and crystallized samples) has been investigated. It was found that the thermal expansion coefficient (TEC) of Ni 75 Si x B 25− x and Co 75 Si x B 25− x metallic glasses depends upon the Si/B ratio. The TEC of NiSiB metallic glasses decreases with increasing Si and B contents and by addition of Ta, Nb and Mo atoms. A small decrease (within 10%) in the TEC was observed in the relaxed and crystallized samples of NiSiB metallic glasses. It was found that the TEC of (Fe x Ni 1− x ) 78 Si 8 B 14 metallic glasses decreases monotonically with increasing Fe content and the TEC of metallic glasses with a large Fe content involves a contribution of magnetic energy.

Semi-empirical low-latitude ionospheric model. Environmental research papers

Abstract: Since current empirical models specifying low-latitude electron density profiles severely underestimate the daytime plasma density scale-height and total electron content (TEC), a Semi-empirical, Low-latitude, Ionospheric Model (SLIM) was developed that is not only more realistic but is also computationally fast. Electron-density profiles (180 to 1800 km) are theoretically calculated as a function of latitude (every 2/sup 0/ between 24 N and 24 S dip latitude) and local time (every half-hour over 24 hours LT) by solving the time-dependent plasma-continuity equation. Assuming a Chapman-like profile, sets coefficients are then generated that reproduce these individual profiles. The coefficients themselves are easily stored, quickly retrieved, and form the basis for a fast, portable, semi-empirical computer code. This report describes briefly the input parameters used to theoretically calculate profiles and the procedures used to generate the coefficients. The SLIM profiles are compared with the Chiu and Bent empirical models for Equinox, solar-maximum conditions. Finally, electron densities, the coefficients, TEC and 6300 A airglow intensities are listed in tabular form for three seasons (Equinox, June solstice, and December solstice) and two solar-cycle periods (solar maximum and solar minimum).

Measurements of irregularities in the mid-latitude ionosphere with a radio interferometer

Abstract: Radio astronomy interferometers have potential use for systematic monitoring of medium-scale irregularities in the ionosphere. In this article, precepts for their use are derived, and preliminary analysis of data samples from interferometers at Green Bank, West Virginia, and Magdalena, New Mexico, is presented. A typical differential electron content of about 1015/m2 over a 35-km baseline is observed. A day-night correlation with TEC values is observed; we found the nighttime ionosphere to be more disturbed during high geomagnetic activity. Ionospheric irregularities are observed to persist over periods of an hour or longer.

The variability of the ionospheric total electron content and its effect on satellite microwave communications

Abstract: Rotation of linearly polarized waves (Faraday rotation) passing through the ionosphere causes depolarization in frequency reuse satellite communication systems As the ionospheric total electron content (TEC) is not constant, dynamic compensation for this effect may be required This paper investigates the magnitude of the TEC variations, the time scales of the variability and the predictability of the excursions Analysis of long-term TEC measurements shows that the variations are statistical with yearly and seasonal trends strongly coupled to long term solar and geophysical effects Short-term variations are difficult to predict Data indicate that reliable Faraday rotation estimates can be made for 99·9 per cent of the time, provided that long-term solar, seasonal and geographical factors are considered Occasional bursts of solar activity limit the accuracy of long-term predictions

Is Ia antigen expression by thymic epithelial cells constitutive

Abstract: The thymus plays a special role as a principal site of T cell differentiation and maturation (Cantor and Weissman, 1976). The framework of the thymus is formed principally by thymic epithelial cells (TEC), with which thymocytes are in intimate contact (Rouse and Weissman, 1981). A distinctive feature of TEC is expression of la (class n major histocompatibility complex) antigens, antigens which are generally observed on other epithelia only after stimulation (Barclay and Mason, 1982; Scheynius and Tjerlung, 1984; Cerf-Bensussan et al, 1984). In a few situations this apparently distinctive feature of TEC is not observed. These exceptions may shed light upon the role of TEC la antigen expression in thymocyte differentiation.

Filling Cyprane Tec 4 vaporizers

Abstract: adult Respiratory Distress Syndrome. He produced large volumes of infected fluid from his lungs, which overwhelmed both limbs of the breathing system during unsuccessful resuscitation for cardiac arrest. The breathing system was later sent for washing and autoclaving, but lung aspirate had also dried onto the humidifier heating element (which does not require to be sterilized because of its high operating temperature.) On testing the ventilator and humidifier before use on another patient, there was immediate production of a thin blue acrid smoke from the burning proteinaceous accumulation on the hot element. After this, the breathing system required repeated washing to clear it of the smell. On a second occasion, a middle-aged woman, whose lungs were being ventilated for the same condition, began to produce over one litre per hour of a thin fluid aspirated from the tracheal tube. A nurse lifted the coaxial tubing to ‘milk’ it, and, simultaneously, a wave of grey lung fluid was seen to flow backwards along the inspiratory tube and submerge the hot element. The patient was instantly disconnected from the breathing system, before the next ventilator cycle ejected a blast of thin blue smoke. These two incidents highlight the need for constant vigilance by all staff in charge of ventilators. The heating element in the system must be isolated from extraneous sources of fluid. If the small fluid trap on the outer limb were available on the inner limb, it could still be overwhelmed by rush of fluid from the patient end. The hot element should be more easily removable for cleaning of debris if still used in the present location, where it can be fouled. One also notes that this Penlon co-axial tubing is opaque at each end, and internal disconnexions may be quite invisible.

Group-Path Delays in the Trans-Ionospheric Radio Wave Propagation Derived from TEC

Abstract: The total electron content measurements made at Waltair (17.7°N, 83.3°E) by measuring the Faraday Rotation of the 136.1123 MHz Radio Beacon from the ETS-II geostationary satellite have been used to derive the range errors introduced by the ionosphere due to the group path delays of radio waves in trans-ionospheric communication systems. Corrections for oblique incidence propagation were also outlined. The mathematical relations used in the present study have been derived and the experiment is described. Diurnal and seasonal variations of the group-path delays are studied.