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  • ASTROPHYSICS  (275)
  • Female
  • 1990-1994  (329)
  • 1994  (329)
  • 1
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    Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. 5: Variability of the ultraviolet continuum and emission lines of NGC 3783 (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or 'dips,' the first lasting is less than or approximately 20 days and the second is less than or approximately 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became 'harder' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (delta(t) is less than 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly(alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or 'lag.' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) approximately 0 days for He II + O III), and approximately 4 days for Ly(alpha) and C IV. The data further suggest lags of approximately 4 days for Si IV + O IV) and 8-30 days for Si III + C III). Mg II lagged the 1460 A continuum by approximately 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of is less than or approximately 2 days, and that the character of the continuum variability may change with time.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 425; 2; p. 582-608
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Functional participation of the IL-2 receptor gamma chain in IL-7 receptor complexes (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 1994-03-11
    Beschreibung: The gamma chain of the interleukin-2 (IL-2) receptor is shared with the functional IL-4 receptor and is causatively related to X-linked severe combined immunodeficiency (XSCID), which is ascribed to a profound T cell defect. Studies with monoclonal antibodies specific for the IL-2 receptor gamma chain showed that the gamma chain participates in the functional high-affinity receptor complexes for IL-7 that are involved in the differentiation of T and B cells. Participation of the gamma subunit in more than one receptor may enable the elucidation of the mechanisms of XSCID development and lymphocyte differentiation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kondo, M -- Takeshita, T -- Higuchi, M -- Nakamura, M -- Sudo, T -- Nishikawa, S -- Sugamura, K -- New York, N.Y. -- Science. 1994 Mar 11;263(5152):1453-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, Tohoku University School of Medicine, Sendai, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8128231" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Antibodies, Monoclonal ; B-Lymphocytes/*immunology ; Cell Line ; Cells, Cultured ; Female ; Genetic Linkage ; Interleukin-7/*metabolism/pharmacology ; Mice ; Mice, Inbred C57BL ; Receptors, Interleukin/*metabolism ; Receptors, Interleukin-2/genetics/immunology/*metabolism ; Receptors, Interleukin-7 ; Severe Combined Immunodeficiency/genetics/immunology ; T-Lymphocytes/*immunology ; X Chromosome
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Mutagenesis and mapping of a mouse gene, Clock, essential for circadian behavior (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 1994-04-29
    Beschreibung: In a search for genes that regulate circadian rhythms in mammals, the progeny of mice treated with N-ethyl-N-nitrosourea (ENU) were screened for circadian clock mutations. A semidominant mutation, Clock, that lengthens circadian period and abolishes persistence of rhythmicity was identified. Clock segregated as a single gene that mapped to the midportion of mouse chromosome 5, a region syntenic to human chromosome 4. The power of ENU mutagenesis combined with the ability to clone murine genes by map position provides a generally applicable approach to study complex behavior in mammals.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3839659/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3839659/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vitaterna, M H -- King, D P -- Chang, A M -- Kornhauser, J M -- Lowrey, P L -- McDonald, J D -- Dove, W F -- Pinto, L H -- Turek, F W -- Takahashi, J S -- P30-CA07175/CA/NCI NIH HHS/ -- R01-DK40493/DK/NIDDK NIH HHS/ -- T32 NS071040/NS/NINDS NIH HHS/ -- Howard Hughes Medical Institute/ -- etc. -- New York, N.Y. -- Science. 1994 Apr 29;264(5159):719-25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8171325" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; *Chromosome Mapping ; Chromosomes, Human, Pair 4 ; Circadian Rhythm/*genetics ; Ethylnitrosourea ; Female ; *Genes ; Genotype ; Humans ; Male ; Mice ; Mice, Inbred C57BL ; *Mutagenesis ; Phenotype
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Mutation of a mutL homolog in hereditary colon cancer (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 1994-03-18
    Beschreibung: Some cases of hereditary nonpolyposis colorectal cancer (HNPCC) are due to alterations in a mutS-related mismatch repair gene. A search of a large database of expressed sequence tags derived from random complementary DNA clones revealed three additional human mismatch repair genes, all related to the bacterial mutL gene. One of these genes (hMLH1) resides on chromosome 3p21, within 1 centimorgan of markers previously linked to cancer susceptibility in HNPCC kindreds. Mutations of hMLH1 that would disrupt the gene product were identified in such kindreds, demonstrating that this gene is responsible for the disease. These results suggest that defects in any of several mismatch repair genes can cause HNPCC.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Papadopoulos, N -- Nicolaides, N C -- Wei, Y F -- Ruben, S M -- Carter, K C -- Rosen, C A -- Haseltine, W A -- Fleischmann, R D -- Fraser, C M -- Adams, M D -- CA35494/CA/NCI NIH HHS/ -- CA47527/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Mar 18;263(5153):1625-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Johns Hopkins Oncology Center, Baltimore, MD 21231.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8128251" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Adaptor Proteins, Signal Transducing ; *Adenosine Triphosphatases ; Amino Acid Sequence ; Bacterial Proteins/chemistry/*genetics ; Base Sequence ; Carrier Proteins ; Chromosome Mapping ; *Chromosomes, Human, Pair 3 ; Codon ; Colorectal Neoplasms, Hereditary Nonpolyposis/*genetics ; *DNA Repair ; *DNA-Binding Proteins ; *Escherichia coli Proteins ; Female ; Frameshift Mutation ; *Genes ; Genetic Markers ; Humans ; Male ; Molecular Sequence Data ; MutS Homolog 2 Protein ; Mutation ; Neoplasm Proteins/chemistry/*genetics ; Nuclear Proteins ; Open Reading Frames ; Polymerase Chain Reaction ; Proto-Oncogene Proteins/genetics ; Sequence Deletion ; Tumor Cells, Cultured
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Specific association of human telomerase activity with immortal cells and cancer (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 1994-12-23
    Beschreibung: Synthesis of DNA at chromosome ends by telomerase may be necessary for indefinite proliferation of human cells. A highly sensitive assay for measuring telomerase activity was developed. In cultured cells representing 18 different human tissues, 98 of 100 immortal and none of 22 mortal populations were positive for telomerase. Similarly, 90 of 101 biopsies representing 12 human tumor types and none of 50 normal somatic tissues were positive. Normal ovaries and testes were positive, but benign tumors such as fibroids were negative. Thus, telomerase appears to be stringently repressed in normal human somatic tissues but reactivated in cancer, where immortal cells are likely required to maintain tumor growth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kim, N W -- Piatyszek, M A -- Prowse, K R -- Harley, C B -- West, M D -- Ho, P L -- Coviello, G M -- Wright, W E -- Weinrich, S L -- Shay, J W -- AG07992/AG/NIA NIH HHS/ -- CA50195/CA/NCI NIH HHS/ -- CA65178/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Dec 23;266(5193):2011-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Geron Corporation, Menlo Park, CA 94025.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7605428" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Base Sequence ; Cell Division ; Cell Line ; Cell Line, Transformed/enzymology ; DNA Nucleotidylexotransferase/*metabolism ; Enzyme Activation ; Enzyme Repression ; Female ; Humans ; Male ; Molecular Sequence Data ; Neoplasms/*enzymology ; Ovary/enzymology ; Polymerase Chain Reaction ; Testis/enzymology ; Tumor Cells, Cultured
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    Possible radio wave precursors associated with the comet Shoemaker-Levy 9/Jupiter impacts (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: We suggest that prior to its impact with Jupiter, comet Shoemaker-Levy 9 will behave as an electrical generator in the Jovian magnetosphere, converting planetary rotational energy to electrical energy via a dust/plasma interaction. This electrical energy will then be deposited in the dayside auroral region where it may drive various auroral phenomena including cyclotron radio emission. Such emission could be detected by spacecraft like Ulysses and Galileo many hours prior to the actual comet impact with the upper atmosphere. We apply the theory originally developed to explain the spokes in Saturn's rings. This theory allows us to quantify the driving potential associated with the comet and, consequently, to determine the radio power created in the auroral region. We conclude that if enough fine dust is present in the cometary system, comet-induced auroral radio emissions will reach detectable levels. This emission should be observable in the dayside hemisphere about 12-24 hours prior to each fragment impact.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 21; 11; p. 1067-1070
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 7
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    Multiwavelength observations of RV Tauri stars. 4: SX Centauri (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: We present ultraviolet, optical and infrared observations of the RV Tauri star SX Cen. From a fit of model atmospheres to the data we conclude that Z/Z solar = 0.033, that SX Cen has an extended atmosphere, and that the spectral types implied by the ultraviolet data close to deep minimum are consistent with those implied from optical spectra. Unlike AC Her, there seems to be no silicate component in the circumstellar dust shell, and the star pulsates in purely radial modes. The implication is that, despite their many similarities, SX Cen seems to be at a significantly earlier phase of post-AGB evolution than AC Her. Additional data, particularly in the infrared, are necessary to confirm this conclusion.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 292; 1; p. 102-114
    Format: text
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  • 8
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    ASCA solid state imaging spectrometer observations of O stars (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We report ASCA Solid State Imaging Spectrometer (SIS) X-ray observations of the O stars delta Ori and lambda Ori. The energy resolution of the SIS allows us to resolve features in the O star X-ray spectra which are not apparent in spectra obtained by X-ray spectrometers with lower energy resolution. SIS spectra from both stars show evidence of line emission, suggesting the thermal nature of the X-ray source. However, the observed line strengths are different for the two stars. The observed stellar X-ray spectra are not well described by isothermal models although absorbed thermal emission models with two or more temperatures can provide an adequate fit to the data. For both stars we present evidence of absorbing columns significantly larger than the known Interstellar Medium (ISM) columns, indicative of absorption by a circumstellar medium, presumably the stellar winds. In addition, the lambda Ori spectrum shows the presence of emission at energies greater than 3 keV which is not seen in the delta Ori spectrum.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 436; 1; p. L95-L98
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Steps toward determination of the size and structure of the broad-line region in active nuclei. 7: Variability of the optical spectrum of NGC 5548 over years (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-08-28
    Beschreibung: We report on the results of a continuation of a large monitoring program of optical spectroscopy of the Seyfert 1 galaxy NGC 5548. The new observations presented here were obtained between 1990 December and 1992 October, and extend the existing database to nearly 1400 days, dating back to 1988 December. The continuum variations are generally smooth and well-resolved, except during the third year of this 4 year project, when the variations were apparently more rapid and of lower amplitude than observed at other times. The broad H(beta) emission line is found to vary in response to the continuum variations with a lag of about 18 days, but with some changes from year to year. The H(beta) transfer functions for each of the 4 yr and for the entire 4 yr database are derived by using a maximum entropy method.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 425; 2; p. 622-634
    Format: text
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  • 10
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    Nonthermal processes in flaring X-ray-bright points (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-08-28
    Beschreibung: X-ray-bright point (XBPs) are known to show variability on a number of timescales, including impulsive X-ray brightenings. The relationship between these XBP 'flares' and normal solar flares is poorly known. A fundamental question is whether nonthermal acceleration of particles takes place in XBP flares. We address this issue by searching for nonthermal radio emission at metric wavelengths from flaring XBPs identified in Yohkoh soft x-ray telescope (SXT) data. Unequivocal evidence for type III-like radio bursts, usually attributed to beams of nonthermal electrons on open field lines, is found. This suggests that XBP flares are similar to normal flares and can indeed accelerate nonthermal populations of energetic particles.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 427; 1; p. L59-L62
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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