2,344 research outputs found
A note on the magnetic spatial forcing of a ferrofluid layer
We report on the response of a thin layer of ferrofluid to a spatially
modulated magnetic field. This field is generated by means of a constant
current in a special arrangement of aluminum wires. The full surface profile of
the liquid layer is recorded by means of the absorption of X-rays. The outcome
is analyzed particularly with regard to the magnetic self focusing effect under
a deformable fluid layer
Spectral properties of Bunimovich mushroom billiards
Properties of a quantum mushroom billiard in the form of a superconducting
microwave resonator have been investigated. They reveal unexpected nonuniversal
features such as, e.g., a supershell effect in the level density and a dip in
the nearest-neighbor spacing distribution. Theoretical predictions for the
quantum properties of mixed systems rely on the sharp separability of phase
space - an unusual property met by mushroom billiards. We however find
deviations which are ascribed to the presence of dynamic tunneling.Comment: 4 pages, 7 .eps-figure
Magnetic traveling-stripe-forcing: enhanced transport in the advent of the Rosensweig instability
A new kind of contactless pumping mechanism is realized in a layer of
ferrofluid via a spatio-temporally modulated magnetic field. The resulting
pressure gradient leads to a liquid ramp, which is measured by means of X-rays.
The transport mechanism works best if a resonance of the surface waves with the
driving is achieved. The behavior can be understood semi-quantitatively by
considering the magnetically influenced dispersion relation of the fluid.Comment: 6 Pages, 8 Figure
Induced Time-Reversal Symmetry Breaking Observed in Microwave Billiards
Using reciprocity, we investigate the breaking of time-reversal (T) symmetry
due to a ferrite embedded in a flat microwave billiard. Transmission spectra of
isolated single resonances are not sensitive to T-violation whereas those of
pairs of nearly degenerate resonances do depend on the direction of time. For
their theoretical description a scattering matrix model from nuclear physics is
used. The T-violating matrix elements of the effective Hamiltonian for the
microwave billiard with the embedded ferrite are determined experimentally as
functions of the magnetization of the ferrite.Comment: 4 pages, 4 figure
Theoretical investigation into the possibility of very large moments in Fe16N2
We examine the mystery of the disputed high-magnetization \alpha"-Fe16N2
phase, employing the Heyd-Scuseria-Ernzerhof screened hybrid functional method,
perturbative many-body corrections through the GW approximation, and onsite
Coulomb correlations through the GGA+U method. We present a first-principles
computation of the effective on-site Coulomb interaction (Hubbard U) between
localized 3d electrons employing the constrained random-phase approximation
(cRPA), finding only somewhat stronger on-site correlations than in bcc Fe. We
find that the hybrid functional method, the GW approximation, and the GGA+U
method (using parameters computed from cRPA) yield an average spin moment of
2.9, 2.6 - 2.7, and 2.7 \mu_B per Fe, respectively.Comment: 8 pages, 3 figure
Prevalence of marginally unstable periodic orbits in chaotic billiards
The dynamics of chaotic billiards is significantly influenced by coexisting
regions of regular motion. Here we investigate the prevalence of a different
fundamental structure, which is formed by marginally unstable periodic orbits
and stands apart from the regular regions. We show that these structures both
{\it exist} and {\it strongly influence} the dynamics of locally perturbed
billiards, which include a large class of widely studied systems. We
demonstrate the impact of these structures in the quantum regime using
microwave experiments in annular billiards.Comment: 6 pages, 5 figure
First Experimental Observation of Superscars in a Pseudointegrable Barrier Billiard
With a perturbation body technique intensity distributions of the electric
field strength in a flat microwave billiard with a barrier inside up to mode
numbers as large as about 700 were measured. A method for the reconstruction of
the amplitudes and phases of the electric field strength from those intensity
distributions has been developed. Recently predicted superscars have been
identified experimentally and - using the well known analogy between the
electric field strength and the quantum mechanical wave function in a
two-dimensional microwave billiard - their properties determined.Comment: 4 pages, 5 .eps figure
Die Entwickelung der Dermatologie in Berlin
DIE ENTWICKELUNG DER DERMATOLOGIE IN BERLIN
Die Entwickelung der Dermatologie in Berlin / Richter, Paul Friedrich (Public Domain) ( - )
Bibliothek des Hauptgesundheitsamtes der Stadtgemeinde Berlin ( - )
Title page ( - )
Preface ( - )
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Imprint ( - )
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