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  • 2000-2004  (2)
  • 1965-1969  (1)
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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft fuer Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser–gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Serial examinations of rabbit eyes at different times following intravenous injections of a blastospore suspension of Candida albicans were performed. All histological findings in PAS stained slides demonstrate that the microorganisms reach the eye via the ciliary arteries and infection starts primarily in the choroid. Here the outpoured leukocytes are soon replaced by histocytic cell formations. The fungi break into the retina through Bruch's membrane followed by these inflammatory cells. In contrast to this there is a conspicuous absence of blastospores in and around the retinal vessels. The retina's lack of primary involvement is of great advantage to the function of the eye as the uvea has all defense mechanisms available to combat the invaders. Our results show that there are apparently particular ways of blood supply to the retinal circulation.
    Notes: Zusammenfassung An Hand von histologischen Befunden, die bei Serienuntersuchungen von Kaninchenaugen nach intravenöser Injektion von Candida albicans-Suspensionen zur Beobachtung kamen, konnte gezeigt werden, daß die Einschleusung der Keime über die Ciliararterien erfolgt und die Infektion primär in der Aderhaut beginnt. Hier bilden sich nach einer vorübergehenden Ausschüttung von polymorphkernigen Leukocyten histiocytäre Granulome. Die Pilze wandern, gefolgt von den Entzündungszellen, durch die Bruchsche Membran in die Retina ein. In den Netzhautgefäßen finden sich hingegen praktisch nie Blastosporen. Für den Bestand des Auges ist dieser Weg, der die Netzhaut offensichtlich weitgehend verschont, von entscheidendem Vorteil, da in der Chorioidea alle Defensivkräfte mobilisiert werden können, die letzten Endes die Zerstörung der eingedrungenen Erreger bewirken.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4242-4250 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nanocapsule dispersions are investigated by 1H–13C cross polarization experiments. The capsule walls, made up from polybutylcyanoacrylate, are detectable merely as a solid state signal, whereas the triglyceride forming the liquid core and the surfactant on the outside of the capsules give rise to narrow resonance lines in the cp-spectrum indicating their mobility. In order to clarify the mechanism of cross polarization for the mobile components, the time-resolved polarization of the corresponding 13C-signals is investigated. Further, the spin-lattice relaxation times for the proton magnetization in the rotating frame are studied under direct excitation as well as under cross polarization conditions. Based on the results, we propose a special mechanism of cross polarization which is initiated by a temporary adsorption of mobile molecules to the more rigid capsule surface. During this short period of immobilization, the polarization is transferred from 1H to 13C nuclei. After desorption, the freshly generated 13C-signal is essentially conserved, now being motionally averaged by a high molecular mobility and detectable as a narrow line in the corresponding spectrum. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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