What is moving in silica at 1 K? A computer study of the low-temperature anomalies

Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in many physical observables, knowledge about their properties is very rare. For silica which is one of the prototype glass-forming systems we elucidate the properties of the TLS via computer simulations by applying a systematic search algorithm. We get specific information in the configuration space, i.e. about relevant energy scales, the absolute number of TLS and electric dipole moments. Furthermore important insight about the real-space realization of the TLS can be obtained. Comparison with experimental observations is included

Testing two alternatives theories to dark matter with the Milky Way dynamics

Two alternative theories to dark matter are investigated by testing their ability to describe consistently the dynamics of the Milky Way. The first one refers to a modified gravity theory having a running gravitational constant and the second assumes that dark matter halos are constituted by a Bose-Einstein condensation. The parameters of each model as well as those characterizing the stellar subsystems of the Galaxy were estimated by fitting the rotation curve of the Milky Way. Then, using these parameters, the vertical acceleration profile at the solar position was computed and compared with observations. The modified gravity theory overestimates the vertical acceleration derived from stellar kinematics while predictions of the Bose-Einstein condensation halo model are barely consistent with observations. However, a dark matter halo based on a collisionless fluid satisfies our consistency test, being the best model able to describe equally well the rotation curve and the vertical acceleration of the Galaxy.Comment: 16 pages, 4 figures, Accepted in Gen. Rel. Gra

Metastability of persistent currents in trapped gases of atoms

We examine the conditions that give rise to metastable, persistent currents in a trapped Bose-Einstein condensate. A necessary condition for the stability of persistent currents is that the trapping potential is not a monotonically increasing function of the distance from the trap center. Persistent currents also require that the interatomic interactions are sufficiently strong and repulsive. Finally, any off-center vortex state is shown to be unstable, while a driven gas shows hysteresis.Comment: 7 pages, RevTex, 5 figure

Ehrenfest theorem, Galilean invariance and nonlinear Schr\"odinger equations

Galilean invariant Schr\"odinger equations possessing nonlinear terms coupling the amplitude and the phase of the wave function can violate the Ehrenfest theorem. An example of this kind is provided. The example leads to the proof of the theorem: A Galilean invariant Schr\"odinger equation derived from a lagrangian density obeys the Ehrenfest theorem. The theorem holds for any linear or nonlinear lagrangian.Comment: Latex format, no figures, submitted to journal of physics

Automated collection and dissemination of ionospheric data from the digisonde network

The growing demand for fast access to accurate ionospheric electron density profiles and ionospheric characteristics calls for efficient dissemination of data from the many ionosondes operating around the globe. The global digisonde network with over 70 stations takes advantage of the Internet to make many of these sounders remotely accessible for data transfer and control. Key elements of the digisonde system data management are the visualization and editing tool SAO Explorer, the digital ionogram database DIDBase, holding raw and derived digisonde data under an industrial-strength database management system, and the automated data request execution system ADRES

Nonlinear interference in a mean-field quantum model

Using similar nonlinear stationary mean-field models for Bose-Einstein Condensation of cold atoms and interacting electrons in a Quantum Dot, we propose to describe the original many-particle ground state as a one-particle statistical mixed state of the nonlinear eigenstates whose weights are provided by the eigenstate non-orthogonality. We search for physical grounds in the interpretation of our two main results, namely, quantum-classical nonlinear transition and interference between nonlinear eigenstates.Comment: RevTeX (pdfLaTeX), 7 pages with 5 png-figures include

Einkaufsmotivatoren industrieller Kunden: Ergebnisse einer empirischen Untersuchung im österreichischen Technologieumfeld

Die herausragende Bedeutung eines nicht 'nur' effizienten sondern auch effektiven Kundenbeziehungs-managements wurde in der Praxis von vielen Industrieunternehmen in Technologiebranchen als 'die' Voraussetzung für nachhaltigen Geschäftserfolg erkannt. Empirische Untersuchungen bestätigen dies und zeigen u.a. auf, dass für das Unternehmensergebnis der Kundenbeziehungsmanagementprozess der mit Abstand wichtigste Geschäftsprozess der Gegenwart und der Zukunft ist. Paradoxerweise ist aber der Kenntnisstand von Beweggründen i.S.v. Motiven, die Einkäufer in der Praxis dazu veranlassen mit Verkäufern in eine Beziehung einzutreten, bestenfalls als 'sehr entwicklungsfähig' zu bezeichnen. Und genau an diesem Punkt setzt die vorliegende BWL Schriftenreihe Nummer 15 an: Ziel ist es, einen empirischen Forschungskurzbericht über Beziehungsmotive zu geben, die industrielle Kunden resp. Einkäufer in österreichischen Technologieunternehmen motivieren, bei ihren industriellen Anbietern von Technologien zu kaufen

Ein neuer, der ISO/FDIS 14242-1 entsprechender Hüftsimulator: E-SIM

The continuing development of new, highly sophisticated materials for the articulating surfaces of total hip endoprostheses involves the need for testing, not only of biocompatibility and dynamic loadability, but also of tribological properties (friction, wear, lubrication). For decades, the wear resistance of these materials has been tested in wear simulators. In consequence of the currently often widely differing test methods, the technical committee (TC 150) of the ISO (International Organization for Standardization) has been concerned to develop an International Standard (ISO/FDIS 14242 1 and 2: Implants for Surgery - wear of total hip joint prostheses - on the basis of kinetic and kinematic data from gait analysis. This new standard will be the basis for ensuring the comparability of scientific data obtained from tribological. testing of total hip endoprotheses. The new hip simulator, E-SIM, presented in this paper, complies with the currently published FDIS (Final Draft International Standard), and enables testing in accordance with these specifications