2,319 research outputs found
New Constraints on the Yukawa-Type Hypothetical Interaction From The Recent Casimir Force Measurement
We calculate the constraints on the constants of hypothetical long-range
interactions which follow from the recent measurement of the Casimir force. A
comparison with previous constraints is given. The new constraints are up to a
factor of 3000 stronger in some parameter regions .Comment: 10 pages, Latex, 2 figures, to appear in Phys. Rev.
Dual-doped thermographic phosphor particles as surrogates for green fluorescent protein-labeled cells in tests of cytometric neurocatheters
We investigated the laser-induced fluorescence of particles of a compound thermographic phosphorLa2O2S:Eu(1%) and Gd2O2S:Eu(1%) to see if they can serve as a surrogate for cells transfected with the green fluorescent protein, in tests of neurocatheters used for intraparenchymal celldelivery. At an excitation wavelength of 337 nm and a concentration of ≈2×106 particles ml−1, the resulting slurries produced fluorescence intensities at 625 nm that were within a factor of 2 of those produced by similar number densities of relevant cells, thus suggesting the utility of this approach
Universality in the Gravitational Stretching of Clocks, Waves and Quantum States
There are discernible and fundamental differences between clocks, waves and
physical states in classical physics. These fundamental concepts find a common
expression in the context of quantum physics in gravitational fields; matter
and light waves, quantum states and oscillator clocks become quantum synonymous
through the Planck-Einstein-de Broglie relations and the equivalence principle.
With this insight, gravitational effects on quantum systems can be simply and
accurately analyzed. Apart from providing a transparent framework for
conceptual and quantitative thinking on matter waves and quantum states in a
gravitational field, we address and resolve with clarity the recent
controversial discussions on the important issue of the relation and the
crucial difference between gravimetery using atom interferometers and the
measurement of gravitational time dilation.Comment: Gravity Research Foundation honorable mention, 201
Observation of opto-mechanical multistability in a high Q torsion balance oscillator
We observe the opto-mechanical multistability of a macroscopic torsion
balance oscillator. The torsion oscillator forms the moving mirror of a
hemi-spherical laser light cavity. When a laser beam is coupled into this
cavity, the radiation pressure force of the intra-cavity beam adds to the
torsion wire's restoring force, forming an opto-mechanical potential. In the
absence of optical damping, up to 23 stable trapping regions were observed due
to local light potential minima over a range of 4 micrometer oscillator
displacement. Each of these trapping positions exhibits optical spring
properties. Hysteresis behavior between neighboring trapping positions is also
observed. We discuss the prospect of observing opto-mechanical stochastic
resonance, aiming at enhancing the signal-to-noise ratio (SNR) in gravity
experiments.Comment: 4 pages, 5 figure
Standard and derived Planck quantities: selected analysis and derivations
We provide an overview of the fundamental units of physical quantities
determined naturally by the values of fundamental constants of nature. We
discuss a comparison between the 'Planck units', now widely used in theoretical
physics and the pre-quantum 'Stoney units' in which, instead of the Planck
constant, the charge of the electron is used with very similar quantitative
results. We discuss some of the physical motivation for these special units,
attributed much after they were introduced, and also put forth a summary of the
arguments supporting various cases for making specific physical interpretations
of the meanings of some of these units. The new aspects we discuss are a
possible physical basis for the Stoney units, their link to the Planck units,
and also the importance of Planck units for thermodynamical quantities in the
context of quantum gravity.Comment: 22 pages, 1 tabl
Changes in Creep Behaviour and Microstructure of Model Mozzarella Cheese During Working
The effect of shear work input on the microstructure, fat particle size and creep behavior of model Mozzarella type cheeses was studied. Cheese samples were prepared in a twin screw cooker at 70 °C by mixing protein and fat phases together with different amounts of shear work input. Major changes in cheese structure were observed while working at 150 rpm and 250 rpm screw speeds. Confocal microstructures plus macroscopic observations showed systematic changes in structure with increased shear work inputs with unmixed buttery liquid observed at kg−1, typical Mozzarella type microstructures (elongated fat-serum channels) at 6–15 kJ kg−1 and homogeneously distributed, small size fat droplets at \u3e58 kJ kg−1. At very high shear work inputs, \u3e 75 kJ kg−1, striations or anisotropy in the microstructures had disappeared and small micro-cracks were evident. A 4-element Burger\u27s model was found adequate for fitting the creep data of model cheese at 70 °C but a 6-element model was required at 20 °C. As shear work input increased retarded compliance decreased and zero shear viscosity increased indicating the more elastic behavior of the cheeses with higher shear work input. Changes in the protein matrix appear to be the main reason for increased elastic behavior
Precise Measurement of Gravity Variations During a Total Solar Eclipse
The variations of gravity were measured with a high precision LaCoste-Romberg
D gravimeter during a total solar eclipse to investigate the effect of solar
eclipse on the gravitational field. The observed anomaly m/s during the eclipse implies that there may be a shielding
property of gravitation
Quintessence, the Gravitational Constant, and Gravity
Dynamical vacuum energy or quintessence, a slowly varying and spatially
inhomogeneous component of the energy density with negative pressure, is
currently consistent with the observational data. One potential difficulty with
the idea of quintessence is that couplings to ordinary matter should be
strongly suppressed so as not to lead to observable time variations of the
constants of nature. We further explore the possibility of an explicit coupling
between the quintessence field and the curvature. Since such a scalar field
gives rise to another gravity force of long range (\simg H^{-1}_0), the solar
system experiments put a constraint on the non-minimal coupling: |\xi| \siml
10^{-2}.Comment: 9 pages, a version to be published in Phys.Rev.
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