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  • Electric fields and currents  (1)
  • Electromagnetic (Transient and time domain) Geomagnetism and paleomagnetism (geomagnetic induction) Ionosphere (equatorial ionosphere)  (1)
  • Genetics  (1)
  • Infant  (1)
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  • 1
    ISSN: 0992-7689
    Keywords: Equatorial electrojet ; Magnetosphere-ionosphere interactions ; Electric fields and currents ; Auroral ionosphere ; Ionospheric disturbances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400–0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800–0950 UT. Subsequent to the change in h’F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ΔH variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0992-7689
    Keywords: Electromagnetic (Transient and time domain) Geomagnetism and paleomagnetism (geomagnetic induction) Ionosphere (equatorial ionosphere)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the SRE source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the SR*E source) was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at dip equator latitudes with the electromagnetic diurnal variation is consequently impossible to perform. In the case of irregular variations, the source effect related to the equatorial electrojet is also discussed. A Gaussian model of equatorial electrojet was considered, and apparent resistivities were computed for two models of stratified Earth corresponding to the average resistive structure of the two tectonic provinces crossed by the profile: a sedimentary basin and a cratonic shield. The apparent resistivity curves were found to depend significantly on both the model used and the distance to the center of the electrojet. These numerical results confirm the existence of a daytime source effect related to the equatorial electrojet. Furthermore, we show that the results account for the observed differences between daytime and night-time apparent resistivity curves. In particular, it was shown that electromagnetic probing of the Earth using the classical Cagniard-Tikhonov magnetotelluric method is impossible with daytime recordings made at dip latitude stations.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; chromosome IV ; POL3 (CDC2) ; KIN28 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The nucleotide sequence of a 5 kb EcoRI-NcoI fragment of chromosome IV, contiguous to gene POL3 (CDC2), has been determined. It contains three open reading frames: QRI1, QRI2 and QRI7. Two of them are essential genes. QRI7 is homologous to the Escherichia coli orfx gene. Accession number to EMBL/Genbank Data Library is X79380.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0942-0940
    Keywords: Infant ; brain tumours ; irradiation ; sequelae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Between 1975 and 1989, 98 children with brain tumours under the age of three at time of diagnosis were entered into a retrospective study. Twenty of them are alive and free of tumour more than five years after treatment and were evaluated in this study. Thirteen tumour localizations were infratentorial and 7 were supratentorial. A histological examination was performed in 15 patients: 5 ependymomas, 6 medulloblastomas and 4 astrocytomas were identified. Fifteen patients underwent surgical removal of tumour, all but one received radiotherapy and 8 were given chemotherapy. Only two children have not late effects. Analysis of long-term sequelae in survivors showed central endocrinopathies in 14 (70%), a neurological handicap in 13 (65%) and impaired cognitive functions in 17 (85%). Irradiation was clearly responsible for mental sequelae in 7 patients and endocrinopathies in 6 patients. The other possible causes are tumour injury, hydrocephalus or surgery. The risks incurred with radiotherapy and advances in infant brain tumour therapy are discussed.
    Type of Medium: Electronic Resource
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