@phdthesis{Regenstein1972, author = {Regenstein, Wolfgang}, title = {Absorptionsspektroskopische Untersuchungen zum Einfluß des Mediums und des Aggregatzustandes auf die Gestalt und Lage der Charge-Transfer-Bande}, doi = {10.25932/publishup-49670}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-496702}, school = {Universit{\"a}t Potsdam}, pages = {56}, year = {1972}, abstract = {An einigen CT-Modellkomplexen in verschiedenen L{\"o}sungsmitteln und bei Temperaturen von 113-300 K sollte der Einfluß der Umgebung auf die Form und Lage der Absorption von CT-Komplexen unterschiedlicher Bindungsfestigkeit untersucht werden. Dazu wurden bekannte Bandenprofilfunktionen auf ihre Anwendbar-keit gepr{\"u}ft. Da eine optimale Anpassung nicht m{\"o}glich war, wurde eine neue Profilfunktion entwickelt, die eine bessere Beschreibung ergab. Nach der Bestimmung der Gleichgewichtskonstante und des Extink-tionskoeffizienten konnte mit der Profilfl{\"a}che das {\"U}bergangsmoment berechnet werden. Die L{\"o}sungsmittelabh{\"a}ngigkeit wurde bei verschiedenen Brechzahlen und Dielektrizit{\"a}tskonstanten untersucht. F{\"u}r feste Komplexe wurde eine spezielle Pr{\"a}parationstechnik gew{\"a}hlt. Die beobachteten Feinstrukturen und der auftretende Streuuntergrund werden diskutiert.}, language = {de} } @phdthesis{Regenstein1989, author = {Regenstein, Wolfgang}, title = {Fluoreszenzl{\"o}schung durch Elektronen- und Resonanzenergietransfer in L{\"o}sungen}, doi = {10.25932/publishup-49137}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-491377}, school = {Universit{\"a}t Potsdam}, pages = {86, 17}, year = {1989}, abstract = {Intermolekulare Desaktivierung zwischen einem angeregten Fluorophor und einem L{\"o}scher durch Elektronen{\"u}bertragung kann mit dynamischer und statischer L{\"o}schung beschrieben werden. Es wird vorgeschlagen den dynamischen L{\"o}schprozess in Transport- und Wechselwirkungsphase einzuteilen. Ergebnisse der L{\"o}schung der N-Heteroarene durch Naphthalen bei hohen L{\"o}scherkonzentrationen werden mit der statischen L{\"o}schung beschrieben. Außerdem werden CT-Systeme untersucht. Nach einem {\"U}berblick {\"u}ber statische Modelle zum Resonanzenergietransfer wird ein aus der Treffertheorie abgeleitetes Modell vorgestellt und an Beispielen getestet. Die Experimente sind computergesteuert.}, language = {de} } @unpublished{FeudelSeehafer1994, author = {Feudel, Fred and Seehafer, Norbert}, title = {On the bifurcation phenomena in truncations of the 2D Navier-Stokes equations}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13390}, year = {1994}, abstract = {We have studied bifurcation phenomena for the incompressable Navier-Stokes equations in two space dimensions with periodic boundary conditions. Fourier representations of velocity and pressure have been used to transform the original partial differential equations into systems of ordinary differential equations (ODE), to which then numerical methods for the qualitative analysis of systems of ODE have been applied, supplemented by the simulative calculation of solutions for selected initial conditions. Invariant sets, notably steady states, have been traced for varying Reynolds number or strength of the imposed forcing, respectively. A complete bifurcation sequence leading to chaos is described in detail, including the calculation of the Lyapunov exponents that characterize the resulting chaotic branch in the bifurcation diagram.}, language = {en} } @unpublished{Schwarz1994, author = {Schwarz, Udo}, title = {Einf{\"u}hrung in die nichtlineare Dynamik}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13525}, year = {1994}, abstract = {Aus dem Inhalt: 1. Einf{\"u}hrung 2. Motivation f{\"u}r die nichtlineare Dynamik 3. Logistische Abbildung (Parabel-Abbildung) 4. Lorenz-Gleichungen 5. Fraktale Selbst{\"a}hnlichkeit 6. Die Brownsche Bewegung 7. St{\"o}ße \& Billards 8. K{\"o}rper mit gravitativer Wechselwirkung 9. Glossar 10. Turbo-Pascal-Texte 11. IDL-Texte 12. Reduce-Texte}, language = {de} } @misc{HenkelSteaneKaiseretal.1994, author = {Henkel, Carsten and Steane, Andrew M. and Kaiser, Robin and Dalibard, Jean}, title = {A modulated mirror for atomic interferometry}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42279}, year = {1994}, abstract = {A novel atomic beam splitter, using reflection of atoms off an evanescent light wave, is investigated theoretically. The intensity or frequency of the light is modulated in order to create sidebands on the reflected de Broglie wave. The weights and phases of the various sidevands are calculated using three different approaches: the Born approximation, a semiclassical path integral approach, and a numerical solution of the time-dependent Schrdinger equation. We show how this modulated mirror could be used to build practical atomic interferometers.}, language = {en} } @misc{HenkelCourtoisAspect1994, author = {Henkel, Carsten and Courtois, Jean-Yves and Aspect, Alain}, title = {Atomic diffraction by a thin phase grating}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42269}, year = {1994}, abstract = {We present a semiclassical perturbation method for the description of atomic diffraction by a weakly modulated potential. It proceeds in a way similar to the treatment of light diffraction by a thin phase grating, and consists in calculating the atomic wavefunction by means of action integrals along the classical trajectories of the atoms in the absence of the modulated part of the potential. The capabilities and the validity condition of the method are illustrated on the well-known case of atomic diffraction by a Gaussian standing wave. We prove that in this situation the perturbation method is equivalent to the Raman-Nath approximation, and we point out that the usually-considered Raman-Nath validity condition can lead to inaccuracies in the evaluation of the phases of the diffraction amplitudes. The method is also applied to the case of an evanescent wave reflection grating, and an analytical expression for the diffraction pattern at any incidence angle is obtained for the first time. Finally, the application of the method to other situations is briefly discussed.}, language = {en} } @misc{HenkelCourtoisKaiseretal.1994, author = {Henkel, Carsten and Courtois, Jean-Yves and Kaiser, Robin and Westbrook, C. and Aspect, Alain}, title = {Phase shifts of atomic de Broglie waves at an evanescent wave mirror}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42289}, year = {1994}, abstract = {A detailed theoretical investigation of the reflection of an atomic de Broglie wave at an evanescent wave mirror is presented. The classical and the semiclassical descriptions of the reflection process are reviewed, and a full wave-mechanical approach based on the analytical soution of the corresponding Schr{\"o}dinger equation is presented. The phase shift at reflection is calculated exactly and interpreted in terms of instantaneous reflection of the atom at an effective mirror. Besides the semiclassical regime of reflection describable by the WKB method, a pure quantum regime of reflection is identified in the limit where the incident de Broglie wavelength is large compared to the evanescent wave decay length.}, language = {en} } @unpublished{PikovskijFeudel1994, author = {Pikovskij, Arkadij and Feudel, Ulrike}, title = {Characterizing strange nonchaotic attractors}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13405}, year = {1994}, abstract = {Strange nonchaotic attractors typically appear in quasiperiodically driven nonlinear systems. Two methods of their characterization are proposed. The first one is based on the bifurcation analysis of the systems, resulting from periodic approximations of the quasiperiodic forcing. Secondly, we propose th characterize their strangeness by calculating a phase sensitivity exponent, that measures the sensitivity with respect to changes of the phase of the external force. It is shown, that phase sensitivity appears if there is a non-zero probability for positive local Lyapunov exponents to occur.}, language = {en} } @unpublished{WittKurthsKrauseetal.1994, author = {Witt, Annette and Kurths, J{\"u}rgen and Krause, F. and Fischer, K.}, title = {On the validity of a model for the reversals of the Earth's magnetic field}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13460}, year = {1994}, abstract = {We have used techniques of nonlinear dynamics to compare a special model for the reversals of the Earth's magnetic field with the observational data. Although this model is rather simple, there is no essential difference to the data by means of well-known characteristics, such as correlation function and probability distribution. Applying methods of symbolic dynamics we have found that the considered model is not able to describe the dynamical properties of the observed process. These significant differences are expressed by algorithmic complexity and Renyi information.}, language = {en} } @unpublished{KurthsVossWittetal.1994, author = {Kurths, J{\"u}rgen and Voss, A. and Witt, Annette and Saparin, P. and Kleiner, H. J. and Wessel, Niels}, title = {Quantitative analysis of heart rate variability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13470}, year = {1994}, abstract = {In the modern industrialized countries every year several hundred thousands of people die due to the sudden cardiac death. The individual risk for this sudden cardiac death cannot be defined precisely by common available, non-invasive diagnostic tools like Holter-monitoring, highly amplified ECG and traditional linear analysis of heart rate variability (HRV). Therefore, we apply some rather unconventional methods of nonlinear dynamics to analyse the HRV. Especially, some complexity measures that are basing on symbolic dynamics as well as a new measure, the renormalized entropy, detect some abnormalities in the HRV of several patients who have been classified in the low risk group by traditional methods. A combination of these complexity measures with the parameters in the frequency domain seems to be a promising way to get a more precise definition of the individual risk. These findings have to be validated by a representative number of patients.}, language = {en} }