Measurements and Simulation Studies of Piezoceramics for Acoustic Particle Detection

Calibration sources are an indispensable tool for all detectors. In acoustic particle detection the goal of a calibration source is to mimic neutrino signatures as expected from hadronic cascades. A simple and promising method for the emulation of neutrino signals are piezo ceramics. We will present results of measruements and simulations on these piezo ceramics.Comment: 5 pages, 5 figure

pi-/pi+ ratio in heavy ions collisions: Coulomb effect or chemical equilibration?

We calculate the pi-/pi+ ratio for Pb+Pb at CERN/SPS energies and for Au+Au at BNL/AGS energies using a (3+1) dimensional hydrodynamical model. Without consideration of Coulomb effect an enhancement of this ratio at low mt is found compatible with that observed in these experiments. Our calculations are based on previous (3+1) dimensional hydrodynamical simulations (HYLANDER), which described many other aspects of experimental data. In this model the observed enhancement is a consequence of baryon and strangeness conservation and of chemical equilibration of the system and is caused by the decay of produced hyperons, which leads to a difference in the total number of positive and negative pions as well. Based on the same approach, we also present results for the pi-/pi+ ratio for S+S (CERN/SPS) collisions, where we find a similar effect. The absence of the enhancement of the pi-/pi+ ratio in the S+S data presented by the NA44 Collaboration, if confirmed, could indicate that chemical equilibration has not yet been estabilished in this reaction.Comment: 8 pages and 2 figures, submmited to Phys. Lett. B. This reviewed version (Nov.29,1996) contains more details about the model simulated efficiency considering the experimental detection conditions. Other small modifications were mad

Bernoulli, Daniel (29.1.1700 - 17.3.1782)

Der Mathematiker und Physiker Daniel Bernoulli (1700-1782) aus der bekannten Schweizer Gelehrtenfamilie studierte 1718 in Heidelberg Medizin. Die Materialsammlung enthält: 1. Lexikonartikel, 2. Biographische Informationen, 3. Bestandsnachweise zum Werk (gedruckt / digital) und 4. Hinweise zu Bibliographien

Cauchy's almost forgotten Lagrangian formulation of the Euler equation for 3D incompressible flow

Two prized papers, one by Augustin Cauchy in 1815, presented to the French Academy and the other by Hermann Hankel in 1861, presented to G\"ottingen University, contain major discoveries on vorticity dynamics whose impact is now quickly increasing. Cauchy found a Lagrangian formulation of 3D ideal incompressible flow in terms of three invariants that generalize to three dimensions the now well-known law of conservation of vorticity along fluid particle trajectories for two-dimensional flow. This has very recently been used to prove analyticity in time of fluid particle trajectories for 3D incompressible Euler flow and can be extended to compressible flow, in particular to cosmological dark matter. Hankel showed that Cauchy's formulation gives a very simple Lagrangian derivation of the Helmholtz vorticity-flux invariants and, in the middle of the proof, derived an intermediate result which is the conservation of the circulation of the velocity around a closed contour moving with the fluid. This circulation theorem was to be rediscovered independently by William Thomson (Kelvin) in 1869. Cauchy's invariants were only occasionally cited in the 19th century --- besides Hankel, foremost by George Stokes and Maurice L\'evy --- and even less so in the 20th until they were rediscovered via Emmy Noether's theorem in the late 1960, but reattributed to Cauchy only at the end of the 20th century by Russian scientists.Comment: 23 pages, 6 figures, EPJ H (history), in pres

Zur Magneto-Hydrodynamik kompressibler Medien

In einer konsequenten Theorie des kompressiblen Plasmas muß die Ladungstrennung berücksichtigt werden, besonders dann, wenn makroskopische Geschwindigkeiten auftreten, die mit der Schallgeschwindigkeit vergleichbar oder größer als diese sind. Es wird der Einbau der Ladungstrennung für ein zweikomponentiges Plasma durchgeführt und das System der magneto-hydrodynamischen Gleichungen so umgeformt, daß es nur noch 2 Größen enthält: das Vektorpotential und die Plasmageschwindigkeit. © 1955, Walter de Gruyter. Alle Rechte vorbehalten

Three-Sphere Low Reynolds Number Swimmer with a Cargo Container

A recently introduced model for an autonomous swimmer at low Reynolds number that is comprised of three spheres connected by two arms is considered when one of the spheres has a large radius. The Stokes hydrodynamic flow associated with the swimming strokes and net motion of this system can be studied analytically using the Stokes Green's function of a point force in front of a sphere of arbitrary radius $R$ provided by Oseen. The swimming velocity is calculated, and shown to scale as $1/R^3$ with the radius of the sphere.Comment: 4 pages, 1 figur

The Euler Equations on Thin Domains

For the Euler equations in a thin domain Q_ε = Ω×(0, ε), Ω a rectangle in R^2, with initial data in (W^(2,q)(Qε))^3, q > 3, bounded uniformly in ε, the classical solution is shown to exist on a time interval (0, T(ε)), where T(є) → +∞ as є → 0. We compare this solution with that of a system of limiting equations on Ω