1,587 research outputs found
Brans-Dicke theory: Jordan vs Einstein Frame
It is well known that, in contrast to general relativity, there are two
conformally related frames, the Jordan frame and the Einstein frame, in which
the Brans-Dicke theory, a prototype of generic scalar-tensor theory, can be
formulated. There is a long standing debate on the physical equivalence of the
formulations in these two different frames. It is shown here that gravitational
deflection of light to second order accuracy may observationally distinguish
the two versions of the Brans-Dicke theory.Comment: 10 pages, Accepted by Mod. Phys. Letts.
Experimental investigation of the fundamental modes of a collisionless plasma Final report, 10 Mar. 1964 - 31 Oct. 1967
Propagation of electron cyclotron waves and effects of low frequency noise in collisionless plasm
Strong field gravitational lensing in scalar tensor theories
Strong field gravitational lensing in the Brans-Dicke theory has been
studied. The deflection angle for photons passing very close to the photon
sphere is estimated for the static spherically symmetric space-time of the
theory and the position and magnification of the relativistic images are
obtained. Modeling the super massive central object of the galaxy by the
Brans-Dicke space-time, numerical values of different strong lensing observable
are estimated. It is found that against the expectation there is no significant
scalar field effect in the strong field observable lensing parameters. This
observation raises question on the potentiality of the strong field lensing to
discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio
Compatibility of Einstein minimally coupled self interacting scalar field theory with the solar system tests of gravity
We examine the compatibility of the Einstein minimally coupled
self-interacting scalar field theory with the local tests of gravity. We find
that apart from the trivial case of the Schwarzschild-de Sitter solution with
constant scalar field the theory does not admit any other static solution,
which is consistent with the solar system tests of gravity.Comment: 6 pages, a part of the earlier version removed, final version
accepeted by CQ
On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames
Three new classes (II-IV) of solutions of the vacuum low energy effective
string theory in four dimensions are derived. Wormhole solutions are
investigated in those solutions including the class I case both in the Einstein
and in the Jordan (string) frame. It turns out that, of the eight classes of
solutions investigated (four in the Einstein frame and four in the
corresponding string frame), massive Lorentzian traversable wormholes exist in
five classes. Nontrivial massless limit exists only in class I Einstein frame
solution while none at all exists in the string frame. An investigation of test
scalar charge motion in the class I solution in the two frames is carried out
by using the Plebanski-Sawicki theorem. A curious consequence is that the
motion around the extremal zero (Keplerian) mass configuration leads, as a
result of scalar-scalar interaction, to a new hypothetical "mass" that confines
test scalar charges in bound orbits, but does not interact with neutral test
particles.Comment: 18 page
Drosophila Argonaute-1 is critical for transcriptional cosuppression and heterochromatin formation
Argonaute-1 (Ago-1) plays a crucial role in gene regulation and genome stability via biogenesis of small non-coding RNAs. Two “Argonaute” family genes, piwi and Ago-2 in Drosophila are involved in multiple silencing mechanisms in the nucleus, transgene cosuppression, long-distant chromosome interaction, nuclear organization and heterochromatin formation. To investigate whether Ago-1 also plays a similar role, we have generated a series of Ago-1 mutations by excising P element, inserted in the Ago-1 promoter (Ago-1k08121). AGO-1 protein is distributed uniformly in the nucleus and cytosol in early embryos but accumulated predominantly in the cytoplasm during the gastrulation stage. Repeat induced silencing produced by the mini-white (mw) array and transcriptional cosuppression of non-homologous transgenes Adh-w/w-Adh was disrupted by Ago-1 mutation. These effects of Ago-1 are distict from its role in microRNA processing because Dicer-1, a critical enzyme for miRNA biogenesis, has no role on the above silencing. Reduction of AGO-1 protein dislodged the POLYCOMB, EZ (enhancer of zeste) and H3me3K27 binding at the cosuppressed Adh-w transgene insertion sites suggesting its role in Polycomb dependent cosuppression. An overall reduction of methylated histone H3me2K9 and H3me3K27 from the polytene nuclei precisely from the mw promoters was also found that leads to concomitant changes in the chromatin structure. These results suggest a prominent role of Ago-1 in chromatin organization and transgene silencing and demonstrate a critical link between transcriptional transgene cosuppression, heterochromatin formation and chromatin organization. We propose Drosophila Ago-1 as a multifunctional RNAi component that interconnects at least two unrelated events, chromatin organization in the nucleus and microRNA processing in the cytoplasm, which may be extended to the other systems
Tidal Forces in Cold Black Hole Spacetimes
We investigate here the behavior of a few spherically symmetric static
acclaimed black hole solutions in respect of tidal forces in the geodesic
frame. It turns out that the forces diverge on the horizon of cold black holes
(CBH) while for ordinary ones, they do not. It is pointed out that Kruskal-like
extensions do not render the CBH metrics nonsingular. We present a CBH that is
available in the Brans-Dicke theory for which the tidal forces do not diverge
on the horizon and in that sense it is a better one.Comment: 12 pages, no figures. PDF (from original MSWord). Submitted to
International Journal of Modern Physics D, 10 Aug 0
Design and Test of a Forward Neutron Calorimeter for the ZEUS Experiment
A lead scintillator sandwich sampling calorimeter has been installed in the
HERA tunnel 105.6 m from the central ZEUS detector in the proton beam
direction. It is designed to measure the energy and scattering angle of
neutrons produced in charge exchange ep collisions. Before installation the
calorimeter was tested and calibrated in the H6 beam at CERN where 120 GeV
electrons, muons, pions and protons were made incident on the calorimeter. In
addition, the spectrum of fast neutrons from charge exchange proton-lucite
collisions was measured. The design and construction of the calorimeter is
described, and the results of the CERN test reported. Special attention is paid
to the measurement of shower position, shower width, and the separation of
electromagnetic showers from hadronic showers. The overall energy scale as
determined from the energy spectrum of charge exchange neutrons is compared to
that obtained from direct beam hadrons.Comment: 45 pages, 22 Encapsulated Postscript figures, submitted to Nuclear
Instruments and Method
Possible observation sequences of Brans-Dicke wormholes
The purpose of this study is to investigate observational features of
Brans-Dicke wormholes in a case if they exist in our Universe. The energy flux
from accretion onto a Brans-Dicke wormhole and the so-called "maximum impact
parameter" are studied (the last one might allow to observe light sources
through a wormhole throat). The computed values were compared with the
corresponding ones for GR-wormholes and Schwarzschild black holes. We shown
that Brans-Dicke wormholes are quasi-Schwarzschild objects and should differ
from GR wormholes by about one order of magnitude in the accretion energy flux.Comment: 5 pages, 6 figure
Stored Grain Volume MeasurementUsing a Low Density Point Cloud
Citation: Turner, A. P., Jackson, J. J., Koeninger, N. K., McNeill, S. G., Montross, M. D., Casada, M. E., . . . Thompson, S. A. (2017). STORED GRAIN VOLUME MEASUREMENT USING A LOW DENSITY POINT CLOUD. Applied Engineering in Agriculture, 33(1), 105-112. doi:10.13031/aea.11870This technical note presents the development of a new apparatus and data processing method to accurately estimate the volume of stored grain in a bin. Specifically, it was developed to account for the variability in surface topography that can occur in large diameter bins when partially unloaded. This was accomplished using a laser distance meter to create a low density point cloud, from which a surface was interpolated using ArcMap geoprocessing tools. The manually controlled and portable system was designed to hold the laser distance meter and provided a common reference point. The data from the laser distance meter was transmitted to a tablet PC via Bluetooth. Measurement of an empty hopper bottom bin (4.6 m in diameter and 6.5 m tall) demonstrated that the system was able to measure a known volume within 0.02%, and repeated measures of an empty flat bottom bin (1.8 m in diameter, and 5.7 m tall) were within 0.29% of the known volume. Two applications are presented which highlight the system's ability to capture complex surfaces, as well as limitations that result from fill scenarios where the field of view was limited
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