Global ETD Search

1	Dynamics of the B-A Transition of DNA Double Helices / Dynamik der B-A Umwaldung von DNA Doppelhelices Jose, Davis 26 April 2005 (has links) No description available. 540 Chemie Mathematics and Computer Science B-A Umwaldung von DNA doppelhelices elektrischen Feldimpulsmethode Magische Winkel Methode feldinduzierte Reakionseffekte. B-A transition of DNA double helices Electric field jump technique Magic angle measurements Field induced reaction effects. 35.10 SD
2	Spatial Dynamics of Wave Packets in Semiconductor Heterostructures / Räumliche Wellenpaketdynamik in Halbleiterheterostrukturen Meinhold, Dirk 11 June 2005 (has links) (PDF) This thesis presents the first study of the damping of a Bloch oscillating wave packet by Zener tunneling to above-barrier states [1]. We investigate the time evolution of an below-barrier subband Wannier-Stark wave packet in a strongly coupled GaAs/AlGaAs superlattice (SL) with shallow quantum well barriers by optical interband spectroscopy. We use a sub-100 fs homodyne pump-probe technique which is sensitive to the intraband polarization. The presented experimental data unambiguously show an electric field-dependent continuous decrease of the intraband coherence time. Besides the continuous field-induced damping of the intraband polarization, we observe the signature of resonant Zener tunneling of a Bloch oscillating wave packet between discrete states belonging to below and above-barrier bands. This coupling manifests itself as a revival of the intraband polarization [2]. The experiment is modelled in two aspects. First, in a 1D single-particle calculation the wave functions the BO wave packet is composed of are derived. Here, the inter-subband dynamics are found to be given by the energetic splitting between nearly-degenerate below and above-barrier states. The wave packet tunnels from the below-barrier band to the above-barrier band while remaining coherently oscillating. At this time, it is spatially spread over more than 100 nm... Bloch Oszillationen Feldinduzierte Delokalisierung Pump-Probe Spektroskopie Resonanter Zener-Durchbruch Wellenfunktionstomographie Wellenpaketdynamik Zener-Durchbruch Übergitter Bloch oscillation Pump probe spectroscopy Zener breakdown field-induced delocalisation field-induced delocalization graded superlattice resonant Zener breakdown superlattice wave function tomography wave packet dynamics ddc:530 rvk:UF 5000 Delokalisierung Dynamik Optische Spektroskopie Schwingung Tomographie Wellenfunktion Wellenpaket Zener-Effekt Übergitter
3	Spatial Dynamics of Wave Packets in Semiconductor Heterostructures Meinhold, Dirk 13 May 2005 (has links) This thesis presents the first study of the damping of a Bloch oscillating wave packet by Zener tunneling to above-barrier states [1]. We investigate the time evolution of an below-barrier subband Wannier-Stark wave packet in a strongly coupled GaAs/AlGaAs superlattice (SL) with shallow quantum well barriers by optical interband spectroscopy. We use a sub-100 fs homodyne pump-probe technique which is sensitive to the intraband polarization. The presented experimental data unambiguously show an electric field-dependent continuous decrease of the intraband coherence time. Besides the continuous field-induced damping of the intraband polarization, we observe the signature of resonant Zener tunneling of a Bloch oscillating wave packet between discrete states belonging to below and above-barrier bands. This coupling manifests itself as a revival of the intraband polarization [2]. The experiment is modelled in two aspects. First, in a 1D single-particle calculation the wave functions the BO wave packet is composed of are derived. Here, the inter-subband dynamics are found to be given by the energetic splitting between nearly-degenerate below and above-barrier states. The wave packet tunnels from the below-barrier band to the above-barrier band while remaining coherently oscillating. At this time, it is spatially spread over more than 100 nm... info:eu-repo/classification/ddc/530 ddc:530
4	Pyroelektrische Materialien: elektrisch induzierte Phasenumwandlungen, thermisch stimulierte Radikalerzeugung Mehner, Erik 17 October 2018 (has links) Zur Messung pyrelektrischer Koeffzienten wurde ein Messplatz nach einem erweiterten SHARP-GARN-Verfahren entwickelt und zur Untersuchung von Phasenumwandlungen in Pyroelektrika eingesetzt. Einerseits konnten pyroelektrische Messungen im elektrischen Feld die Pyroelektrizität einer neuen durch elektrisch angetriebene Defektmigration erzeugten Phase in Strontiumtitanat nachweisen. Andererseits gelang es, Ferroelektrizität in der Hochtemperaturphase von Poly(Vinylidenfluorid-Trifluorethylen), mittels phasenreiner Präparation der Hochtemperaturphase unterhalb der CURIEtemperatur und anschließender Polarisierung, nachzuweisen. Ferner ließen sich mittels thermisch angeregter Pyroelektrika Redoxprozesse antreiben, was durch Desinfektion von Escherichia coli Bakterien in wässriger Lösung mittels Lithiumniobat und -tantalat gezeigt wurde. Die Hypothese der Desinfektion durch reaktive Sauerstoffspezies konnte durch spektroskopisch nachgewiesene OH-Radikale - erzeugt mittels thermisch angeregter Bariumtitanatnanopartikel - belegt werden. info:eu-repo/classification/ddc/540 ddc:540 Pyroelektrizität Phasenumwandlung elektrisches Feld Radikal <Chemie> Messtechnik

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