8,571 research outputs found
Measurement of Gravitomagnetic and Acceleration Fields Around Rotating Superconductors
It is well known that a rotating superconductor produces a magnetic field
proportional to its angular velocity. The authors conjectured earlier, that in
addition to this so-called London moment, also a large gravitomagnetic field
should appear to explain an apparent mass increase of Niobium Cooper-pairs. A
similar field is predicted from Einstein's general relativity theory and the
presently observed amount of dark energy in the universe. An experimental
facility was designed and built to measure small acceleration fields as well as
gravitomagnetic fields in the vicinity of a fast rotating and accelerating
superconductor in order to detect this so-called gravitomagnetic London moment.
This paper summarizes the efforts and results that have been obtained so far.
Measurements with Niobium superconductors indeed show first signs which appear
to be within a factor of 2 of our theoretical prediction. Possible error
sources as well as the experimental difficulties are reviewed and discussed. If
the gravitomagnetic London moment indeed exists, acceleration fields could be
produced in a laboratory environment.Comment: To appear in the proceedings of the STAIF-2007 conference published
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Laser power stabilization for second-generation gravitational wave detectors
We present results on the power stabilization of a Nd:YAG laser in the frequency band from 1 Hz to 100 kHz. High-power, low-noise photodetectors are used in a dc-coupled control loop to achieve relative power fluctuations down to 5Ă10â9 Hzâ1/2 at 10 Hz and 3.5Ă10â9 Hzâ1/2 up to several kHz, which is very close to the shot-noise limit for 80 mA of detected photocurrent on each detector. We investigated and eliminated several noise sources such as ground loops and beam pointing. The achieved stability level is close to the requirements for the Advanced LIGO gravitational wave detector
Gravity-Induced Shape Transformations of Vesicles
We theoretically study the behavior of vesicles filled with a liquid of
higher density than the surrounding medium, a technique frequently used in
experiments. In the presence of gravity, these vesicles sink to the bottom of
the container, and eventually adhere even on non - attractive substrates. The
strong size-dependence of the gravitational energy makes large parts of the
phase diagram accessible to experiments even for small density differences. For
relatively large volume, non-axisymmetric bound shapes are explicitly
calculated and shown to be stable. Osmotic deflation of such a vesicle leads
back to axisymmetric shapes, and, finally, to a collapsed state of the vesicle.Comment: 11 pages, RevTeX, 3 Postscript figures uuencode
Electronic transport properties through thiophenes on switchable domains
The electronic transport of electrons and holes through stacks of
,\ome ga-dicyano-,'-dibutyl- quaterthiophene (DCNDBQT)
as part of a nov el organic ferroic field-effect transistor (OFFET) is
investigated. The novel ap plication of a ferroelectric instead of a dielectric
substrate provides the poss ibility to switch bit-wise the ferroelectric
domains and to employ the polarizat ion of these domains as a gate field in an
organic semiconductor. A device conta ining very thin DCNDBQT films of around
20 nm thickness is intended to be suitab le for logical as well as optical
applications. We investigate the device proper ties with the help of a
phenomenological model called multilayer organic light-e mitting diodes
(MOLED), which was extended to transverse fields. The results sho wed, that
space charge and image charge effects play a crucial role in these org anic
devices
Can the Tajmar effect be explained using a modification of inertia?
The Tajmar effect is an unexplained acceleration observed by accelerometers
and laser gyroscopes close to rotating supercooled rings. The observed ratio
between the gyroscope and ring accelerations was 3+/-1.2x10^-8. Here, a new
model for inertia which has been tested quite successfully on the Pioneer and
flyby anomalies is applied to this problem. The model assumes that the inertia
of the gyroscope is caused by Unruh radiation that appears as the ring and the
fixed stars accelerate relative to it, and that this radiation is subject to a
Hubble-scale Casimir effect. The model predicts that the sudden acceleration of
the nearby ring causes a slight increase in the inertial mass of the gyroscope,
and, to conserve momentum in the reference frame of the spinning Earth, the
gyroscope rotates clockwise with an acceleration ratio of 1.8+/-0.25x10^-8 in
agreement with the observed ratio. However, this model does not explain the
parity violation seen in some of the gyroscope data. To test these ideas the
Tajmar experiment (setup B) could be exactly reproduced in the southern
hemisphere, since the model predicts that the anomalous acceleration should
then be anticlockwise.Comment: 9 pages, 1 figure. Accepted by EPL on the 4th December, 200
Complex Line Bundles over Simplicial Complexes and their Applications
Discrete vector bundles are important in Physics and recently found
remarkable applications in Computer Graphics. This article approaches discrete
bundles from the viewpoint of Discrete Differential Geometry, including a
complete classification of discrete vector bundles over finite simplicial
complexes. In particular, we obtain a discrete analogue of a theorem of Andr\'e
Weil on the classification of hermitian line bundles. Moreover, we associate to
each discrete hermitian line bundle with curvature a unique piecewise-smooth
hermitian line bundle of piecewise constant curvature. This is then used to
define a discrete Dirichlet energy which generalizes the well-known cotangent
Laplace operator to discrete hermitian line bundles over Euclidean simplicial
manifolds of arbitrary dimension
Noninvasive Measurement of Dissipation in Colloidal Systems
According to Harada and Sasa [Phys. Rev. Lett. 95, 130602 (2005)], heat
production generated in a non-equilibrium steady state can be inferred from
measuring response and correlation functions. In many colloidal systems,
however, it is a nontrivial task to determine response functions, whereas
details about spatial steady state trajectories are easily accessible. Using a
simple conditional averaging procedure, we show how this fact can be exploited
to reliably evaluate average heat production. We test this method using
Brownian dynamics simulations, and apply it to experimental data of an
interacting driven colloidal system
Single Sex Mathematics Classes: A Critical Analysis of the Impact at aSecondary School
Single sex classes have recently been emphasized as an effective way to promote mathematics learning. Despite their popularity, the research on the effectiveness of such programs is mixed underscoring the need for additional research and discussion. This research is set in one of the twenty-five largest public school systems in the United States, where schools have recently been allowed to begin instructional initiatives with same sex classes in mathematics.
Preliminary data on the effectiveness of one program will be highlighted. Achievement data, compared to traditional classes, will be considered to demonstrate the academic effectiveness of the project. Qualitative data analysis will provide a rich description of the affective issues relative to this innovation. The current project will be framed in critical analysis of the research literature and will discuss the potential benefits and disadvantages both from this current project and from the related literature
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