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An existence and uniqueness theory is developed for general nonlinear and nonautonomous differential-algebraic equations (DAEs) by exploiting their underlying differential-geometric structure. A DAE is called regular if there is a unique nonautonomous vector field such that the solutions of the DAE and the solutions of the vector field are in one-to-one correspondence. Sufficient conditions for regularity of a DAE are derived in terms of constrained manifolds. Based on this differential-geometric characterization, existence and uniqueness results are stated for regular DAEs. Furthermore, our not ons are compared with techniques frequently used in the literature such as index and solvability. The results are illustrated in detail by means of a simple circuit example.
Inhalt: - Zum Wissenschaftsbegriff der älteren Pädagogik - Religiöse und ständische Elemente des überlieferten Praxisanspruchs - Ist praktisches Engagement rationalisierbar? - Zur pädagogischen Kritik der „positiven Wissenschaft" - Zum praktischen Wert von Forschung - Zum Gegenstand der Erziehungswissenschaft
Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and without spacers are true surfactants, all the polymers are water-insoluble, but form monomolecular layers at the air-water interface. In analogy to the monomer behavior, the incorporation of the spacer groups increases the area occupied per repeat unit at the air-water interface substantially, but hardly affects the surface activity.
Recent research related to the concept of interest is reviewed. It is argued that current constructs of motivation fail to include crucial aspects of the meaning of interest emphasized by classical American and German educational theorists. In contrast with many contemporary concepts (e.g., intrinsic learning orientation), interest is defined as a content-specific motivational characteristic composed of intrinsic feeling-related and value-related valences. Results from a number of studies are presented that indicate the importance of interest for the depth of text comprehension, the use of learning strategies, and the quality of the emotional experience while learning. The implications of these results and possible directions for future research are discussed.
Die Untersuchung beschäftigte sich mit dem Einfluß des thematischen Interesses auf die Ausprägung der nach dem Textverarbeitungsmodell von van Dijk & Kintsch (1983) unterschiedenen Komponenten der Textrepräsentation. Darüber hinaus sollte der Einfluß von Interesse auf motivationale und kognitive Variablen des Leseprozesses (z.B. Elaboration) überprüft werden. Zusätzlich wurde eine Reihe relevanter Einflußgrößen (z.B. Vorwissen) im Sinne von Kontrollvariablen erhoben. 43 Studenten wurden auf der Basis eines Fragebogens in hoch und niedrig thematisch interessierte eingeteilt. Die Vpn bekamen einen Text zum Thema «Kommunikation» zu lesen. Anschließend wurde retrospektiv eine Reihe von Prozeßvariablen erhoben. Es folgte ein Rekognitionstest, der die Ermittlung der unterschiedlichen Stärke der wörtlichen, propositionalen und situativen Textrepräsentation erlaubt. Die Ergebnisse zeigen, daß die wörtliche Textrepräsentation bei den niedrig Interessierten signifikant stärker ausgeprägt ist, während die hoch Interessierten eine stärker ausgeprägte propositionale Abbildung des Textes erkennen lassen. Keine erkennbaren Unterschiede zwischen den beiden Versuchsgruppen zeigten sich hinsichtlich der situativen Repräsentation. Die Berücksichtigung der einbezogenen Kontrollvariablen hatte keine Minderung des Interesseneffekts zur Folge. Interesse hängt darüber hinaus eng mit dem Ausmaß von Aktivierung, Flow-Erleben, elaborativen Prozessen und der Häufigkeit von Notizen zusammen. Es ergaben sich Anhaltspunkte, daß diese Variablen auch eine wichtige Rolle bei der Vermittlung des beobachteten Interesseneffekts spielen.
The study investigates police officers' definitions of different rape situations. On the basis of the concept of 'cognitive prototypes' a methodology is developed which elicits consensual feature lists describing six rape situations: the typical, i.e. most common rape, the credible, dubious, and false rape complaints as weil as the rape experiences that are particularly hard vs. relatively easy for the victim to cope with. Qualitative analysis of the data allows the identification of the characteristic features defining the prototype of each rape situation, as weil as comparisons between the situations in terms of their common and distinctive features. It is shown that police officers, while sharing some of the widely held stereotypes about rape, generally perceive rape as a serious crime with long-term negative consequences for the victim. The quantitative analysis of prototype similarity between the six situations corroborates this conclusion by demonstrating a high similarity between the prototypes of the typical and the credible rape situation: In addition, subjects' general attitude towards rape victims is measured to compare the prototypes provided by respondents holding a positive vs. negative attitude towards rape victims. Findings for the two groups, however, reveal more similarities than differences in their descriptions of rape prototypes. The paper concludes with a discussion of the feasibility of the prototype approach presented in this study as a strategy for investigating implicit or common-sense theories of rape.
The chapter presents a social psychological approach to the study of rape and sexual assault. Two issues are at the core of this approach: identifying the critical variables that affect attributions of responsibility to victims of rape. and exploring people's subjective definitions of rape, which may differ markedly from legal definitions. Following a review of the American evidence, a series of studies conductcd in two European countries is presented to address these issues.