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  • 1990-1994  (9)
  • 1991  (9)
Datenquelle
Materialart
Erscheinungszeitraum
  • 1990-1994  (9)
Jahr
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  • 1
    Digitale Medien
    Digitale Medien
    Study of the influence of the phosphorus pressure on the preparation of nominally undoped semi-insulating InP wafers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3860-3864 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The conditions for the preparation of nominally undoped semi-insulating (SI) InP wafers by annealing under controlled phosphorus pressure are described. It is demonstrated by the results of electrical profile measurements (differential Hall effect) and by photoluminescence that diffusion effects in a thin peripheral layer (≈20 μm) can be correlated to a phosphorus in- and indium out-diffusion. But diffusion of these species is correlated to a donor behavior and relatively slow. It can, therefore, not be used to explain the SI bulk property which seems not to depend on the phosphorus overpressure during annealing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348442
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  • 2
    Digitale Medien
    Digitale Medien
    Humoral immunity in children with proven bronchiectasis, bronchial deformations and chronic bronchitis (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Pediatric allergy and immunology 2 (1991), S. 0 
    Details
    ISSN: 1399-3038
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: In 70 children with defined chronic chest disease, immunoglobulins, IgG subclass levels and antibody concentrations specific for Haemophilus influenzae b (Hib), and pneumococcal antigen, were related to disease severity. Bronchological examinations revealed 30 children with chronic bronchitis, 21 with bronchial deformations and 19 with bronchiectasis. Of the 70 children 12 (17.1%) showed an underlying immunodeficiency. The commonest finding was an IgG subclass deficiency, 7 were IgG2 and 1 IgG3 deficient, followed by IgA deficiency in 3 patients. All patients had normal IgG and IgM levels except one who had immunodeficiency with elevated IgM. Pneumococcal antibody levels were found to increase between patient groups in the order healthy children 〈 chronic bronchitis 〈 bronchiectasis 〈 bronchial deformations (p 〈 0.01), but this was not the case for Hib antibodies. We found no selective deficiency of pneumococcal and Hib antibodies in our patients. Pathogens were detected in bronchial cultures from 10% of patients with chronic bronchitis, 33% of those with bronchial deformations and in 63% with bronchiectasis. This increase (p 〈 0.01) reflects a more severe inflammation of the respiratory tract in such patients. However, immunodeficiencies were equally distributed between patient groups. We conclude that only a subgroup of children with chronic chest disease have an underlying immunodefiency, but most patients (83%) do synthesize normal or even high antibodies in the presence of a bacterial load.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3038.1991.tb00193.x
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  • 3
    Digitale Medien
    Digitale Medien
    MRI in tracheal stenosis by innominate artery in children (1991)
    Springer
    Pediatric radiology 21 (1991), S. 89-93 
    Details
    ISSN: 1432-1998
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Pediatric airway obstruction due to anomalies of the course of the innominate artery may produce respiratory distress. MR imaging of the trachea was performed after bronchoscopy on forty-one children with congenital tracheal stenosis. Bronchoscopy only allows the evaluation of the lumen of the trachea, and the degree and location of collapse, and it may be difficult to determine the etiology of the tracheal narrowing. In eighteen out of the forty-one patients MR imaging showed a compression of the trachea by the innominate artery. The MR imaging diagnoses were subsequently compared for accuracy with the diagnoses determined by direct surgical observations. MR imaging of the trachea, the surrounding tissue and vessels allows the evaluation of the cause of tracheal compression and the degree and location of collapse. For evaluation of the cause of airway obstruction, MRI is an ideal method depicting detailed anatomic structure without employing ionizing radiation or intravenous contrast medium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02015611
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  • 4
    Digitale Medien
    Digitale Medien
    Decrease of summer tropospheric ozone concentrations in Antarctica (1991)
    [s.l.] : Nature Publishing Group
    Nature 351 (1991), S. 726-729 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] According to current theory of the tropospheric ozone budget, photochemical production and stratospheric flux are principal sources of ozone, which are balanced by photochemical destruc-tion and surface deposition2"5. The photochemical production of ozone is mainly limited by the availability of ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/351726a0
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  • 5
    Digitale Medien
    Digitale Medien
    Aircraft sulphur emissions (1991)
    [s.l.] : Nature Publishing Group
    Nature 349 (1991), S. 659-659 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SIR-The background level of non-volcanic stratospheric sulphate aerosol may be increasing at a rate of about 5 per cent per year1. This increase is believed to be due to an increase in sulphuric acid in the stratosphere, possibly derived from sulphurous gases emitted naturally and ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/349659a0
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  • 6
    Digitale Medien
    Digitale Medien
    Evidence from balloon measurements for chemical depletion of stratospheric ozone in the Arctic winter of 1989–90 (1991)
    [s.l.] : Nature Publishing Group
    Nature 349 (1991), S. 300-305 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Measurements of the vertical ozone profile with balloon-borne sensors in the Arctic during January and February 1990 indicate repeated minima in the 22-km region. A general negative correlation of the 22-km ozone mixing ratio with time spent by the air parcel in regions cold enough for the ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/349300a0
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  • 7
    Digitale Medien
    Digitale Medien
    ppb-PIXE analysis of the trace-element content in precipitation (1991)
    Springer
    Journal of atmospheric chemistry 12 (1991), S. 391-400 
    Details
    ISSN: 1573-0662
    Schlagwort(e): PIXE ; preconcentration ; freeze-drying ; rainwater ; fogwater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract PIXE is a well established and valuable method for quantitative and qualitative aerosol elemental analysis. Using this method, we have developed a technique to simultaneously analyse the trace-element content in precipitation for elements with Z〉 12. Freeze-drying and leaching was used as a nonselective preconcentration technique. A special backing foil to take up the sample liquid to be dried was developed for these experiments. By careful adjustment of the experimental parameters, we reached a detection limit lower than 1 ppb for most detected elements. Thus, it will be possible to analyze precipitation at low concentrations of trace elements which are important for air chemistry and environmental studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00114776
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  • 8
    Digitale Medien
    Digitale Medien
    Bud formation in the scyphozoan Cassiopea andromeda: epithelial dynamics and fate map (1991)
    Springer
    Hydrobiologia 216-217 (1991), S. 53-59 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Cnidaria ; Cassiopea ; reproduction ; budding ; cell recruitment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cassiopea andromeda scyphistomae reproduce asexually by forming spindle shaped buds which, after detachment, metamorphose into polyps. Parent polyps appear to contribute to the buds' ecto- and endodermal epithelial cells, septal muscle cells, nematocytes and some zooxanthellae. Herein we describe bud morphogenesis, define 5 bud stages, and investigate the recruitment of bud ectoderm. India ink vital marking experiments reveal permanent apicobasal displacement of ectoderm. Labelled polyp cells are displaced towards and incorporated into the emerging bud. Ectoderm is recruited from all angular positions and cells labelled at increasing distances from the bud center are traced at increasingly more proximal positions on the buds. Unlike in Hydra attenuata, the recruitment area appears to be asymmetric since the zone contributing ectoderm from below is smaller than the zones above and lateral to the buds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00026443
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  • 9
    Digitale Medien
    Digitale Medien
    Crystallinity and lateral crystallite size of different UHMW PE materials (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 863-866 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70-75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15-25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1991.070420332
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