Refine
Has Fulltext
- yes (77) (remove)
Year of publication
- 1994 (77) (remove)
Document Type
- Postprint (46)
- Article (17)
- Monograph/Edited Volume (8)
- Preprint (6)
Language
- German (52)
- English (23)
- Multiple languages (1)
- Slovak (1)
Keywords
- Anatomy (1)
- Animal (1)
- Biochemical analysis (1)
- Confluence (1)
- Experimental study (1)
- Exploration (1)
- Glucagon (1)
- Hepatic artery (1)
- Hepatocyte (rat) (1)
- Inflammation (1)
Institute
- Department Erziehungswissenschaft (21)
- Extern (17)
- Institut für Physik und Astronomie (8)
- Wirtschaftswissenschaften (8)
- Department Psychologie (6)
- Interdisziplinäres Zentrum für Dynamik komplexer Systeme (6)
- Institut für Ernährungswissenschaft (4)
- Institut für Germanistik (4)
- Institut für Mathematik (4)
- Institut für Umweltwissenschaften und Geographie (4)
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 Schrödinger 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.
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.
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.
After a review of previous work on the prosody of emotional involvement, data extracts from natural conversations are analyzed in order to argue for the constitution of an 'emphatic (speech) style', which linguistic devices are used to signal heightened emotive involvement. Participants use prosodic cues, in co-occurrence with syntactic and lexical cues, to contextualize turn-constructional units as 'emphatic'. Only realizations of prosodic categories that are marked in relation to surrounding uses of these categories have the power to contextualize units as displaying 'more-than-normal involvement'. In the appropriate context, and in cooccurrence with syntactic and lexical cues and sequential position, the context-sensitive interpretation of this involvement is 'emphasis'. Prosodic marking is used in addition to various unmarked cues that signal and constitute different activity types in conversation. Emphatic style highlights and reinforms particular conversational activities, and makes certain types of recipient responses locally relevant. In particular, switches from non-emphatic to emphatic style are used to contextualize 'peaks of involvement' or 'climaxes' in story-telling. These are shown in the paper to be 'staged' by speakers and treated by recipients as marked activities calling for displays of alignment with respect to the matter at hand. Signals of emphasis are deployable as techniques for locally organizing demonstrations of shared understanding and participant reciprocity in conversational interaction.
Inhalt: 1. Kritische Erläuterung der Bilder und Texte jeder Folge - 1. Folge: Funde der Bronzezeit (Ein Film von Uschi Demitter) - 2. Folge: Germanische Stämme (Ein Film von Uschi Demitter) - 3. Folge: Siedlung der Slawen (Ein Film von Kurt Barthel - 4. Folge: Das verschwundene Heiligtum (Ein Film von Kurt Barthel) - 5. Folge: Von der Kaiserpfalz zur Stadt (Ein Film von Uschi Demitter und Richard Krause) 2. Einordnung der historischen Details der Folgen in den Geschichtsprozeß - 1. Folge: Funde der Bronzezeit - 2. Folge: Germanische Stämme - 3. Folge: Siedlung der Slawen - 4. Folge: Das verschwundene Heiligtum - 5. Folge: Von der Kaiserpfalz zur Stadt 3. Didaktisch-methodische Empfehlungen zum Einsatz der Sendereihe 3.1 Zuordnung der Sendefolgen zu den Rahmenplänen 3.2 Hinweise für die Unterrichtsarbeit des Lehrers 4. Ergänzende Medien zu den Themenbereichen in der Sammlung des MPZ
Die ehemalige Brandenburg auf der Brandenburger Dominsel, der alte Fürstensitz der slawischen Heveller, gab der Mark Brandenburg ihren Namen. 1150 konnte der Markgraf der sächsischen Nordmark, Albrecht der Bär aus dem Geschlecht der am Ostharz begüterten Askanier, die Havelfeste nach dem Tod des letzten Hevellerherrschers besetzen. Zu den bis heute ungeklärten Problemen im Zusammenhang mit der Entstehung der Mark Brandenburg gehört die Frage, wann Albrecht die Burg wieder verlor, so daß er gezwungen war, sie durch eine Belagerung zum zweiten Male in seine Gewalt zu bringen, was am 11. Juni 1157 geschah. In der folgenden Untersuchung soll erneut der Frage nachgegangen werden, zu welchem Zeitpunkt dem Markgrafen die Brandenburg noch einmal entrissen worden war.
A paradigm for the determination of time-accuracy functions (TAFs) for individual participants is introduced for two pairs of tasks differing in cognitive complexity, that is, word scanning vs cued recognition and figural scanning vs figural reasoning. TAFs can be used to test dissociations of cognitive processes beyond scale-related ambiguities of ordinal interactions. The approach is applied to examine the cognitive-aging hypothesis that a single slowing factor can account for interactions between adult age and cognitive task complexity. Twenty young and 20 old adults participated in 17 sessions. Presentation times required for 75, 87.5, and 100% accuracies were determined for each task with a variant of the psychophysical method of limits. Accuracy was fit by negatively accelerated functions of presentation time. State-trace analyses showed that different slowing factors are required for high- and low-complexity tasks. Relations to speed-accuracy and performance-resource functions are discussed.