7,677 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
by AI
Effects of seasonability and variability of streamflow on nearshore coastal areas: final report
General nature and scope of the study:
This study examines the variability of streamflow in all
gaged Alaskan rivers and streams which terminate in the ocean.
Forty-one such streams have been gaged for varying periods of
time by the U. S. Geological Survey, Water Resources Division.
Attempts have been made to characterize streamflow statistically
using standard hydrological methods. The analysis scheme
which was employed is shown in the flow chart which follows.
In addition to the statistical characterization, the following
will be described for each stream when possible:
1. average period of break-up initiation (10-day period)
2. average period of freeze-up (10-day period)
3. miscellaneous break-up and freeze-up data.
4. relative hypsometric curve for each basin
5. observations on past ice-jam flooding
6. verbal description of annual flow variation
7. original indices developed in this study to relate streamflow
variability to basin characteristics and regional
climate.This study was supported under contract 03-5-022-56, Task Order
#4, Research Unit #111, between the University of Alaska and NOAA,
Department of Commerce to which funds were provided by the Bureau of
Land Management through an interagency agreement
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 5×10−9 Hz−1/2 at 10 Hz and 3.5×10−9 Hz−1/2 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
Dynamic model and stationary shapes of fluid vesicles
A phase-field model that takes into account the bending energy of fluid
vesicles is presented. The Canham-Helfrich model is derived in the
sharp-interface limit. A dynamic equation for the phase-field has been solved
numerically to find stationary shapes of vesicles with different topologies and
the dynamic evolution towards them. The results are in agreement with those
found by minimization of the Canham-Helfrich free energy. This fact shows that
our phase-field model could be applied to more complex problems of
instabilities.Comment: Accepted for publication in EPJE. 9 pages, 7 figure
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
Operational applications of NOAA-VHRR imagery in Alaska
Near-real time operational applications of NOAA satellite enhanced thermal infrared imagery to snow monitoring for river flood forecasts, and a photographic overlay technique of imagery to enhance snowcover are presented. Ground truth comparisons show a thermal accuracy of approximately + or - 1 C for detection of surface radiative temperatures. The application of NOAA imagery to flood mapping is also presented
Bilayer Membrane in Confined Geometry: Interlayer Slide and Steric Repulsion
We derived free energy functional of a bilayer lipid membrane from the first
principles of elasticity theory. The model explicitly includes
position-dependent mutual slide of monolayers and bending deformation. Our free
energy functional of liquid-crystalline membrane allows for incompressibility
of the membrane and vanishing of the in-plane shear modulus and obeys
reflectional and rotational symmetries of the flat bilayer. Interlayer slide at
the mid-plane of the membrane results in local difference of surface densities
of the monolayers. The slide amplitude directly enters free energy via the
strain tensor. For small bending deformations the ratio between bending modulus
and area compression coefficient, Kb/KA, is proportional to the square of
monolayer thickness, h. Using the functional we performed self-consistent
calculation of steric potential acting on bilayer between parallel confining
walls separated by distance 2d. We found that temperature-dependent curvature
at the minimum of confining potential is enhanced four times for a bilayer with
slide as compared with a unit bilayer. We also calculate viscous modes of
bilayer membrane between confining walls. Pure bending of the membrane is
investigated, which is decoupled from area dilation at small amplitudes. Three
sources of viscous dissipation are considered: water and membrane viscosities
and interlayer drag. Dispersion has two branches. Confinement between the walls
modifies the bending mode with respect to membrane in bulk solution.
Simultaneously, inter-layer slipping mode, damped by viscous drag, remains
unchanged by confinement.Comment: 23 pages,3 figures, pd
Evaluation of selected chemical processes for production of low-cost silicon, phase 3
A Process Development Unit (PDU), which consisted of the four major units of the process, was designed, installed, and experimentally operated. The PDU was sized to 50MT/Yr. The deposition took place in a fluidized bed reactor. As a consequences of the experiments, improvements in the design an operation of these units were undertaken and their experimental limitations were partially established. A parallel program of experimental work demonstrated that Zinc can be vaporized for introduction into the fluidized bed reactor, by direct induction-coupled r.f. energy. Residual zinc in the product can be removed by heat treatment below the melting point of silicon. Current efficiencies of 94 percent and above, and power efficiencies around 40 percent are achievable in the laboratory-scale electrolysis of ZnCl2
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