Multidimensional perfect fluid cosmology with stable compactified internal dimensions

Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is achieved for a special class of perfect fluids. The external space behaves in accordance with the standard Friedmann model. Necessary restrictions on the parameters of the models are found to ensure dynamical behavior of the external (our) universe in agreement with observations.Comment: 11 pages, Latex2e, uses IOP packages, submitted to Class.Quant.Gra

Quantum Tests of the Foundations of General Relativity

The role of the equivalence principle in the context of non-relativistic quantum mechanics and matter wave interferometry, especially atom beam interferometry, will be discussed. A generalised form of the weak equivalence principle which is capable of covering quantum phenomena too, will be proposed. It is shown that this generalised equivalence principle is valid for matter wave interferometry and for the dynamics of expectation values. In addition, the use of this equivalence principle makes it possible to determine the structure of the interaction of quantum systems with gravitational and inertial fields. It is also shown that the path of the mean value of the position operator in the case of gravitational interaction does fulfill this generalised equivalence principle.Comment: Classical and Quantum Gravity 15, 13 (1998

Potentiale zur Integration von Elektrofahrzeugen in innerstädtischen Verkehrsstrukturen : Schlußbericht zum Forschungs- und Entwicklungsvorhaben FE-Nr. 70386/92 des Bundesministers für Verkehr, Bonn

Die vorliegende Studie untersucht, aufgrund umfangreicher Erfahrungen aus Praxistests, welche Energie in kWh/km bisher gebaute Elektrofahrzeuge mit unterschiedlichen Batterien bei unterschiedlichen Tagesfahrleistungen verbrauchen. Die für die Ladung der Traktionsbatterien notwendigen "Stromtankstellen", unterteilt in Haupt- und Nachladestellen, können auf der Basis der vorhandenen Technik installiert werden, wobei Normungen durchgeführt und Genehmigungsverfahren vereinfacht werden sollten. Hauptladestellen werden hauptsächlich Steckdosen in Garagen und privaten Parkanlagen sein, die mit geringen Kosten installierbar sind. Durch den Ersatz von Fahrzeugen mit konventionellem Otto- und Dieselantrieb durch Elektrofahrzeuge läßt sich der verkehrsbedingte CO2-Ausstoß mindern, wenn die CO2-Emissionen bei der Bereitstellung des elektrischen Stroms geringer sind als die mit der Nutzung fossiler Treibstoffe verbundenen Emissionen. Eine Minderung der CO2-Emissionen bei der Stromemerzeugung kann insbesondere durch die Nutzung von CO2-freien Energieträgern erreicht werden. Das Forschungsvorhaben zeigt, daß Elektrofahrzeuge kaufbar sind, die Infrastruktur für ihre Energieversorgung mit der heutigen Technik geschaffen und die Energie für 2 Mio. Elektrofahrzeuge von dem heutigen Kraftwerkspark - vor allem während der Nacht - zur Verfügung gestellt werden kann

Bedeutung von CI-Nutzungsverhalten und CI-Anpassung für sprachproduktive Leistungen sehr früh cochleaimplantierter Kinder

Background!#!Children's age at implantation is an important factor for their outcome in auditory and language skills with a cochlear implant (CI). CI use and frequency of CI fitting may also influence speech performance. Purpose of this study was to evaluate CI use and CI fitting of very early implanted infants and its potential influence on age-related speech production performance.!##!Methods!#!Data of 34 bilaterally cochlea-implanted infants (age at CI in months: M = 8,8; SD = 1,7) were included. During the third year of life speech production performance was evaluated and related to datalogging-based CI use and number of CI fitting sessions.!##!Results!#!About half of the cohort achieved speech production level within the normal range of hearing peers. Daily time of CI use was approximately 8 h. Analysis of listening environment showed that infants were exposed most of the time to quiet environment and least amount of time to speech in noise. Daily time of CI use seems to be a significant predictor of speech production, speech-exposition particularly predicts word production. Number of daily disconnection between CI-processor and implant as well as the monthly number of CI fitting sessions were not correlated with speech production.!##!Conclusion!#!Very early cochlear implanted infants may achieve age-appropriate speech production performance in the third year of life. Time of daily CI use in the study cohort is comparable to results of other studies. Time of daily CI use and exposure to speech seem to be important factors for early speech production. These findings should be integrated in pre- and postoperative parent counselling