scispace - formally typeset
Search or ask a question
Topic

TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: The results indicate that a number of mouse TEC subsets can be distinguished by cytokeratin expression and can be applied to analyze TEC sensitivity to drugs and might also be useful to further understanding of differential TEC function regarding intrathymic T-cell differentiation.
Abstract: A major component of the thymic microenvironment is a network of thymic epithelial cells (TEC) which are able to express class II major histocompatibility complex products and to secrete thymic hormones. In the present investigation, we used a panel of anti-cytokeratin (CK) antibodies to establish distinct cytokeratin-defined TEC subsets. Four subpopulations were identified. One, in the cortex, is defined by anti-CK8 and anti-CK18 monoclonal antibodies (MAb). The other three subsets are medullary, two minor ones respectively reactive with anti-CK19 and KL1 monoclonal antibodies (the latter being specific for CK3 and 10), and a major one characterized by negative reaction with the above-mentioned MAb but strongly positive after labeling with a polyclonal (and polyspecific) anti-keratin immunoserum. Ontogenetic studies revealed that the CK8+/18+ TEC subset is the first to be detected in fetal life. Moreover, the numbers of CK3/10+ cells and CK19+ cells decrease in aging normal mice, a phenomenon that seems to occur early in autoimmune mice. We also observed that these two medullary TEC subsets are sensitive to high-dose in vivo treatment with hydrocortisone, which stimulates a dramatic increase in CK3/10+ cells and a certain decrease in CK19+ cells. Our results indicate that a number of mouse TEC subsets can be distinguished by cytokeratin expression. Such a strategy can be applied to analyze TEC sensitivity to drugs and might also be useful to further understanding of differential TEC function regarding intrathymic T-cell differentiation.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a methodology to estimate the total electron content (TEC) of the low-latitude ionosphere based on GPS measurements and compare with results from other geophysical instruments, such as all-sky imagers and ionosondes.
Abstract: The ionosphere over the Brazilian region has particular characteristics due to the large geomagnetic declination angle over most of the territory. Furthermore, the equatorial ionization anomaly southern crest is located over the Brazilian territory. In this region, plasma irregularities may arise in the post-sunset hours. These ionospheric irregularities develop in the form of magnetic field-aligned plasma depletions, known as equatorial plasma bubbles, which may seriously affect radio signals that propagate through them. These irregularity structures can cause amplitude and phase scintillation of the propagating signals, thereby compromising the availability, performance, and integrity of satellite-based communication and navigation systems. Additionally, the total electron content (TEC) introduces propagation delays that can contribute to range measurement errors for global positioning system (GPS) users. The ionospheric characteristics change significantly according to the time of day, season, as well as the solar and geomagnetic activities, among other factors. Indeed, the ionosphere is one of the most significant sources of errors in the positioning and navigation systems based on the GPS satellites. Due to these features, there is a strong interest by the scientific community in better understanding and characterizing the ionospheric behavior. In this context, the TEC analysis has wide applicability for space plasma studies and is a well-established tool for investigating the ionospheric behavior and its potential impact on space-based navigation systems. One of the goals of these studies is the generation of TEC maps for a geographic region based on GPS observations. In the present work, some electrodynamic processes of the low-latitude ionosphere are reviewed and the TEC estimation based on GPS measurements is revisited in detail. A methodology aimed at creating the TEC maps is presented and validated by comparison with results from other geophysical instruments, such as all-sky imagers and ionosondes. Finally, examples of the ionospheric behavior displayed by TEC maps during equatorial plasma bubble events and a geomagnetic storm are fully described and discussed.

31 citations

Book ChapterDOI
01 Jan 2013
TL;DR: In this article, the authors provide an overview of ionospheric effects on microwave signals, including the group and phase velocities along with the refractive index in the ionosphere.
Abstract: The ionosphere is a dispersive medium for space geodetic techniques operating in the microwave band. Thus, signals traveling through this medium are—to the first approximation—affected proportionally to the inverse of the square of their frequencies. This effect, on the other hand, can reveal information about the parameters of the ionosphere in terms of Total Electron Content (TEC) of the electron density. This part of the book provides an overview of ionospheric effects on microwave signals. First, the group and phase velocities are defined along with the refractive index in the ionosphere and the ionospheric delay. Then, we focus mainly on the mitigation and elimination of ionospheric delays in the analysis of space geodetic observations, specifically for Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) observations. In particular, we summarize existing models as well as strategies based on observations at two or more frequencies to eliminate first and higher order delays. Finally, we review various space geodetic techniques (including satellite altimetry and radio occultation data) for estimating values and maps of TEC.

31 citations

Journal ArticleDOI
TL;DR: In this article, a new model of the thermionic energy converter (TEC) configured with the graphene-based cathode is proposed, which includes the thermal radiation between the cathode and the anode electrodes and the heat losses from the anodes to the environment.
Abstract: A new model of the thermionic energy converter (TEC) configured with the graphene-based cathode is proposed, which includes the thermal radiation between the cathode and the anode electrodes and the heat losses from the anode to the environment. Analytic expressions for the power output density and efficiency of the TEC are derived. The performance characteristics of the TEC are analyzed by numerical calculations. It is found that the maximum efficiency and power density can, respectively, reach 30% and $\textsf {0.575}\,\,\textsf {Wcm}^{-\textsf {2}}$ when the TEC is operated between the two heat reservoirs at temperatures 1500 and 300 K. In addition, the optimum regions of the efficiency, power density, voltage output, electric current, and anode temperature are determined. The maximum efficiency and power density of the graphene-based TEC operated at different temperatures are calculated and compared with those of the metal-based TEC. It shows that the graphene-based TEC operated at 1200–1800 K displays the better performance than the metal-based TEC. The results obtained here may provide guidance for the appropriate selection of electrode materials and optimum design of practical TEC devices.

31 citations

Journal ArticleDOI
TL;DR: In this paper, a neural network based regional ionospheric model is developed using GPS-TEC data from 1 January 2012 to 31 December 2015, which can capture most of the spatio-temporal variations of the regional TEC.

31 citations


Network Information
Related Topics (5)
Global Positioning System
53.7K papers, 697.1K citations
79% related
Solar wind
26.1K papers, 780.2K citations
75% related
Radar
91.6K papers, 1M citations
75% related
Atmosphere
30.8K papers, 737.8K citations
72% related
Frequency domain
53.8K papers, 701.3K citations
69% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022578
2021284
2020321
2019293
2018272