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  • 1
    Electronic Resource
    Electronic Resource
    Modeling of microwave-excited gas discharges (1994)
    Springer
    Electrical engineering 78 (1994), S. 63-68 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht Der Artikel behandelt die Berechnung der Feldstärke-Leistungsdichte-Kennlinie mikrowellenangeregter Gasentladungen am Beispiel von Entladungen in typischen CO2-Lasergasgemischen. Das Berechnungsverfahren beruht auf einem einfachen, auf die meisten Anregungsstrukturen anwendbaren elektrischen Ersatzschaltbild und der Tatsache einer vom Plasma erzwungenen stationären Brennfeldstärke. Letztere wird über eine Elektronenbilanz unter Berücksichtigung der nicht Maxwell'schen Elektronen-Energieverteilung ermittelt. Es zeigt sich, daß bei einer CW-Anregung mit Mikrowellen hohe Mindestleistungsdichten im Plasma auftreten, wodurch beispielsweise im Fall des CO2-Lasers kein Laserbetrieb ohne sehr effektive Maßnahmen zur Gaskühlung möglich ist. Neben einer Diskussion der Plasmakennlinie werden Vergleichsmessungen an einer konkreten Anregungsstruktur vorgestellt.
    Notes: Content This paper is dealing with the power density versus electric field characteristic of microwave-excited discharges on the example of typical CO2 laser gas discharges. The fundamentals of the method are a simple electric equivalent circuit for the excitation structure and the assumption of a fixed reduced electric field intensity within the plasma. This operating field is enforced by the plasma under stationary conditions and can be calculated using an electron balance under consideration of the non-Maxwellian electron energy distribution function. The calculations turn out that c.w. excitation with microwaves is involved with considerable plasma power densities. In the case of the CO2 laser this requires special discharge channel designs for effective gas cooling. Besides a discussion of the plasma characteristic, measurements taken from a microwave applicator are presented and compared to the calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01233220
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  • 2
    Electronic Resource
    Electronic Resource
    Mikrowellen-geschaltete Gasentladungen und ihre Anwendung beim CO2-Laser (1996)
    Springer
    Electrical engineering 79 (1996), S. 71-75 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents This paper is dealing with a new method of controlling gas discharges by the means of microwave energy. The technique calledmicrowave/d.c. hybrid excitation combines the simple energy storage in the case of d.c. excitation with the wide tracking range of r.f. excited discharges especially with respect to pulse frequency and power density. Shifting the energy storage to a high voltage circuit allows the use of very inexpensive microwave sources such as magnetrons for microwave cooking, while no power switch is necessary at the high voltage side. The feasibility of microwave/d.c excited CO2 lasers is demonstrated with several examples. It is shown that these lasers can be continuously operated between a cw mode and a pulsed mode with high peak power exaltation, in which the operating mode can be dynamicaly changed within a few milliseconds.
    Notes: Übersicht Der Artikel beschreibt ein neuartiges Verfahren zur Steuerung von Gasentladungen mittels Mikrowellen-Energie. Das vorgestellte Verfahren derMikrowellen/DC-Hybridanregung kombiniert die Stärken der Gleichspannungsanregung mit der einfachen Steuerbarkeit und der schnellen Pulsbarkeit HF-angeregter Entladungen. Anders als bei einer reinen HF-Anregung können durch die Verlagerung der Energiespeicherung auf die Gleichspannungsseite sehr kostengünstige Hochfrequenzquellen wie beispielsweise Küchenherd-Magnetrons eingesetzt werden; hochspannungsseitig besteht der Vorteil im Wegfall jeglicher Schalter im Entladungsstromkreis. Am Beispiel des CO2-Lasers wird gezeigt, wie mikrowellen/DC-hybridangeregte Laser realisiert werden können. Diese Laser lassen sich-gesteuert durch die Mikrowellenquelle-kontinuierlich zwischen einem Dauerstrichbetrieb und einem Pulsbetrieb mit hohen Pulsleistungsüberhöhungen betreiben, wobei ein dynamischer Wechsel zwischen den Betriebsarten innerhalb von Millisekunden möglich ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01840711
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  • 3
    Electronic Resource
    Electronic Resource
    Evolutionary analysis of the plastid-encoded gene for the α subunit of the DNA-dependent RNA polymerase of Pyrenomonas salina (cryptophyceae) (1992)
    Springer
    Current genetics 22 (1992), S. 479-482 
    Details
    ISSN: 1432-0983
    Keywords: Pyrenomonas salina (Cryptophyceae) ; Plastid ; DNA-dependent RNA polymerase α subunit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence of the gene coding for the plastid-encoded α subunit of DNA-dependent RNA polymerase from the cryptomonad alga Pyrenomonas salina was determined. The deduced amino-acid sequence, corresponding to a 35.2 kDa polypeptide, was compared to homologues from other organisms. Evolutionary relationships were analyzed in detail by the parsimony method together with bootstrap analysis. The deduced phylogenetic tree shows that the cryptomonad gene is the most ancient type of known plastid-encoded RNA polymerase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326413
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  • 4
    Electronic Resource
    Electronic Resource
    EPR and ENDOR of Defects in Silicon Carbide (1996)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 239-241 (Nov. 1996), p. 149-154 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/02/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.239-241.149.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Electron Paramagnetic Resonance of the Scandium Acceptor in 4H and 6H Silicon Carbide (2000)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 338-342 (May 2000), p. 809-812 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/04/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.338-342.809.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    A fiber-optic sensor for microwave field measurements (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4031-4033 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fiber-optic sensor for weak interaction measuring of the electric field intensity in microwave fields is presented. The most remarkable features of the sensor are a low isotropy error, a good selectivity between the electric and magnetic field component, a high sensitivity, low field distortions, and inexpensive fabrication. A tiny microwave absorber mounted at the end of an optical fiber changes its temperature according to the electric field intensity. The absorber temperature is measured by making use of the optical transmittivity variation of a semiconductor element. A simple evaluation of the optical attenuation leads to a readout which is proportional to the square of the electric field strength. In order to overcome the problems due to fiber bend losses a mode acceptance filter is described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145412
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  • 7
    Electronic Resource
    Electronic Resource
    A power-stable CO2 laser with ceramic resonator frame (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3735-3737 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A CO2 laser with a resonator frame made of low expansion ceramics has been developed to provide superior passive stability properties. High stiffness, low specific weight, and very good electric insulation properties recommend ceramic as an attractive material for many laser applications. The long-term power stability of a first prototype was better than ±0.44% measured over 15 min, the short-term stability was better than ±0.24%. Both values were achieved without any active stabilization technique, without damping of external vibrations, and with a non-temperature-controlled coolant. With a new switch mode power supply without ballast resistor a wall-plug efficiency of about 14% has been achieved under quasi-sealed-off conditions. The specific laser output power was about 20 W/m at a gas pressure of 18.5 mbar and a gas mixture He:N2:CO2=75:15:10+5.5% Xe. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145430
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  • 8
    Electronic Resource
    Electronic Resource
    A versatile microwave plasma source and its application for a CO2 laser (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2980-2983 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A single ridged waveguide with nonconstant ridge height, operated with a traveling wave has been proven to be a versatile microwave plasma applicator. Easy dimensioning, inexpensive production, and compatibility to standard rectangular waveguide components are the main advantages compared to other designs. The described plasma source is especially suitable for any applications where an exceptionally uniform plasma is required. Design equations are given for easy adaption of the applicator to individual requirements. The applicator has been investigated for microwave excitation of a diffusion-cooled CO2 laser. With a nonoptimized system, laser output power of 9 W could be achieved in a quasi-cw mode. A traveling discharge operating mode is described which is useful for plasma diagnostics and for pulsed laser applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144588
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular Cloning. A Laboratory Manual. 2. Auflage. Hrsg. von J. Sambrook, E. F. Fritsch, T. Maniatis, Cold Spring Harbor Laboratory Press, Cold Spring Harbour 1989, $ 115. ISBN 0-87969-309-6 (1990)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 20 (1990), S. 285-285 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19900200607
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