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  • Digitale Medien  (34)
  • 1990-1994  (30)
  • 1965-1969  (3)
  • 1925-1929  (1)
Materialart
  • Digitale Medien  (34)
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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1055-1058 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new excitation/detection scheme for Fourier-transform–ion-cyclotron-resonance (FT-ICR) studies is described. The ions are created in the center of a hyperbolic Penning trap and excited to a large magnetron radius. Parametric-mode excitation is used to drive the cyclotron motion. The ions are detected in the conventional dipole-mode detection scheme by use of a segmented ring electrode. Since the resonance frequencies of excitation (ν+−ν−) and detection (ν+, the reduced cyclotron frequency) differ by the magnetron frequency (ν−), this method allows the simultaneous excitation and detection of the ion motion.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The design of a novel electrode structure for electric-field ionization of Rydberg atoms in a fast atomic beam is described. It allows the resolution of the ion signal from Rydberg atoms with adjacent effective principal quantum numbers n* in the range of 14≤n*≤40 and minimizes the volume where field ionization takes place. These features drastically reduce the number of background events arising from collisions of fast atoms with residual gas molecules and thus are essential for trace analysis applications of the technique of resonance ionization spectroscopy in collinear geometry.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Laser resonance ionization has been applied to ionize radioactive atoms released from thick ISOLDE/CERN targets. Laser light from pulsed dye lasers with a high repetition rate (10 kHz) was used for stepwise excitation and ionization. By this method, efficiency as well as the selectivity of the target/ion source system could be improved. In a series of off-line and on-line studies, the resonance ionization of elements with different ionization potentials, such as Yb (Ei=6.2 eV), Tm (Ei=5.8 eV) and Sn (Ei=7.3 eV), was investigated. For Yb, photoionization efficiencies of up to 15% have been measured. An efficiency of 0.2% was obtained for Sn at the on-line separator ISOLDE-3. However, this value can be improved by about two orders of magnitude using a transition to an autoionizing state at 59 375.9 cm−1.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 350 (1994), S. 207-214 
    ISSN: 1434-601X
    Schlagwort(e): 27.80.+w
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Excited states in198,199Po have been studied by in-beamγ-ray spectroscopy. These nuclei were produced in the 4n and 5n reaction channels for 115 MeV20Ne on183W-targets. Multipolarities and mixing ratios ofγ-transitions were determined from DCO-ratios, leading to spin/parity assignments. In198Po,γ-cascades have been observed above several excited levels that are similar to the vibration-like structure built on the ground state. In199Po, the coupling of the oddi13/2 neutron seems to favor the spherical shape of the even core; no levels resembling the intruder states of the even nuclei are found. A semi-quantitative evaluation of the cross-sections for nuclei produced in fission and multi-particle transfer is presented.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 340 (1991), S. 109-110 
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The very neutron deficient nucleus 104Sn has been identified in in-beam spectroscopy using the reaction50Cr(58Ni, 2p2n) and neutron and charged particle multiplicity filter detectors. Excited states up to I ≈ 10 and Ex=4 MeV were observed and the level scheme is discussed in the frame work of the spherical shell model.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-0649
    Schlagwort(e): 32.30.—r ; 32.80.Rm ; 32.80.Dz ; 35.10.Hn
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Resonance ionization mass spectroscopic (RIMS) measurements for trace analysis and spectroscopy of 237Np, the ecologically most important isotope of neptunium, are described. The chemical procedure for the separation of neptunium from aqueous samples as well as the preparation of filaments for RIMS are outlined. Several two- and three-step excitation schemes have been investigated in order to find suitable conditions for the sensitive detection of 237Np. Using a three-step, three-color excitation and ionization scheme an overall detection efficiency of 3×10−8 was obtained, resulting in a detection limit of 4×108 atoms (160 fg) of 237Np. The hyperfine structure splittings of the levels under investigation, which influence the detection limit, were measured. A new method to determine the first ionization potential (IP) was applied to neptunium yielding a value of IP=6.2655(2) eV.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0649
    Schlagwort(e): 07.77 ; 07.80 ; 32.80 F ; 14.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report here on the development of a high-temperature laser ion source useful for trace analysis and other applications. It consists of a high temperature ionization chamber, three tunable dye lasers pumped by copper vapor lasers for stepwise resonant ionization and a Mattauch-Herzog mass spectrometer for the analysis of photo-ions. The principle of the laser ion source and its theoretical efficiency are discussed, where the efficiency of a laser ion source is the ratio of photo-ions extracted out to the number of atoms introduced into the cavity. Experimentally, an efficiency of 2×10−3 has been achieved for technetium. The scheme of gated detection is described which is used for suppressing isobaric background of molybdenum. The possible improvements are briefly mentioned for achieving isotopic analysis of 108 atoms of 97,98Tc in the presence of 1015 atoms of molybdenum, as separated chemically from molybdenum ore. Such an analysis of technetium isotopes produced in molybdenite ore by a (v,e −) reaction, is expected to yield information about the solar neutrino flux.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0649
    Schlagwort(e): 89.60.+x ; 07.75.+h ; 28.70.+y
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new, fast technique for trace analysis of the radioactive isotopes89Sr and90Sr in environmental samples has been developed. Conventional mass separation is combined with resonance ionization spectroscopy in collinear geometry, which provides high selectivity and sensitivity. In addition, a chemical separation procedure for sample preparation has been developed. The described technique was used to determine the90Sr content in ≈ 870 m3 air samples collected near Munich during and shortly after the Chernobyl reactor accident in April 1986. The content of90Sr was measured to be 1.4 mBq per m3, corresponding to 1.6 × 109 atoms of90Sr per sample. This value is in good agreement with the results of radiochemical measurements.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 47 (1969), S. 1268-1269 
    ISSN: 1432-1440
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary In cerebrospinal fluids (CSF) of patients with acute inflammatory cerebral diseases, brain atrophies and tumours of the CNS we observed a higher activity of adenosine deaminase than in normal persons. Activities in CSF of patients with epilepsies, vascular, degenerative and chronical inflammatory cerebral diseases did not differ from normal values. The range of activities found in normal CSF was 0–0,26 IU. The results were discussed. The estimation of adenosine deaminase activity in CSF was commended as an additional diagnostical method in unclear neurological diseases.
    Notizen: Zusammenfassung Im Liquor läßt sich zu hohen Prozentsätzen bei akut entzündlichen cerebralen Erkrankungen, Hirnatrophien und Tumoren im Bereich des ZNS eine erhöhte spezifische Aktivität der Adenosindesaminase nachweisen. Die übrigen untersuchten Krankheitsbilder, wie Epilepsien, gefäßbedingte, degenerative und chronisch entzündliche Erkrankungen des ZNS zeigten keine Unterschiede zur Normalaktivität, die in einem Bereich von 0–0,26 IE festgelegt wurde. Die Befunde werden diskutiert und die Bestimmung der Adenosindesaminase in Liquores als ergänzende Untersuchung bei neurologisch unklaren Erkrankungen empfohlen.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 188 (1966), S. 300-307 
    ISSN: 1432-1459
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wurden nahezu zellfreie Liquores von 60 Patienten mit verschiedenen Erkrankungen des ZNS und 5 Kontrollpersonen auf den Gehalt an folgenden, meist zellstrukturgebundenen Oxydoreduktasen untersucht: NADH2- und NADPH2-Oxydasen mit O2 als Elektronenacceptor, endogene NADH2- (NADPH2)-Oxydationsraten, NADH2- und NADPH2-Oxydoreduktasen mit Ferricyanid und 2,6-Dichlorphenolindophenol als Elektronenacceptoren, Vitamin K3-Reduktase, NADH2- und NADPH2-Cytochrom c-Reduktasen und Glutathionreduktase. NADH2- und NADPH2-Oxydasen mit O2, Ferricyanid und 2,6-Dichlorphenolindophenol als Elektronenacceptoren, Vitamin K3-Reduktase und NADPH2-Cytochrom c-Reduktase waren in keinem Fall nachweisbar. Nur in zwei von 20 untersuchten Liquores von Patienten mit gefäßbedingten Blutungen konnte das Vorkommen von NADH2-Cytochrom c-Reduktase gesichert werden. Ein Liquor von getesteten Tumorpatienten enthielt deutlich Glutathionreduktaseaktivität. Ansonsten fanden sich beide letztgenannten Fermente in keinem weiteren Liquor. Die endogene NADH2-Oxydationsrate betrug bei Tumoren im pH-Optimum (6–6,5) 7, bei allen übrigen Fällen etwa 3 μ M/min und 1000 ml Liquor. Eine endogene NADPH2-Oxydation wurde in keinem Fall beobachtet. Die Frage nach dem Austritt strukturgebundener Oxydoreduktasen (Elektronentransportfermente) in den Liquor bei verschiedenen Erkrankungen des ZNS muß am Beispiel der getesteten Enzyme vorerst verneint werden.
    Notizen: Summary The following oxidoreductases were measured in nearly cell-free specimens of cerebrospinal fluid from 60 patients with various diseases of the CNS and from 5 normal controls: NADH2 (NADPH2)-oxidases with molecular oxygen, ferricyanide or 2,6-dichlorophenolindophenol as electron acceptors; the rates of endogenous NADH2 (NADPH2)-oxidation and activities of vitamine K3 reductase, NADH2 (NADPH2)-cytochrome c reductases and glutathione reductase. There were no oxidase activities at all when molecular oxygen, ferricyanide and dichlorophenolindophenol served as electron acceptors nor vitamine K3 reductase or NADPH2-cytochrome c reductase activities. Only 2 out of 20 specimens of cerebrospinal fluid from patients with cerebrovascular hemorrhages exhibited NADH2-cytochrome c reductase activity. One of the tumor patients clearly showed glutathione reductase activity. No activities of these two enzymes were found in the other specimens. The rate of endogenous NADH2-oxidation at the optimal pH of 6–6.5 amounted to 7 μM per minute and 1000 ml cerebrospinal fluid in tumor patients and to 3 μM in all other cases. An endogenous NADPH2-oxidation was never demonstrable. Most of the enzymes investigated in this study are bound to cellular structures. They do not appear to be released into the cerebrospinal fluid in the disease entities which were subject of this investigation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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