1,744 research outputs found
Effects of season and waterbody on transparency tube estimates of suspended sediment in large rivers
This paper reports the measurement (N>132) of the effect of river and season on transparency in cm and Total Suspended Solids in mg/L in a navigational pool of the Ohio River and one of its tributaries, the Muskingum River. Both river of origin and season affected water transparency. The transparency-TSS relationship was stronger in spring (R2 = 0.894) than autumn (R2 =0.710), with an overall correlation of R2=0.86 for N=93 observations in both water bodies and seasons. Regression equations for the transparency-TSS relationships for the two rivers under low (autumn) and high (spring) flow conditions were developed. Our study demonstrates that properly trained volunteers can assist with rapid assessment of water turbidity from suspended solids in large rivers, reservoirs and lakes, but seasonal calibration of these measures will improve accuracy of sediment monitoring and management.Keywords: Transparency tube, turbidity, monitoring, sediment transport, citizen science, water qualit
Energy Distribution associated with Static Axisymmetric Solutions
This paper has been addressed to a very old but burning problem of energy in
General Relativity. We evaluate energy and momentum densities for the static
and axisymmetric solutions. This specializes to two metrics, i.e., Erez-Rosen
and the gamma metrics, belonging to the Weyl class. We apply four well-known
prescriptions of Einstein, Landau-Lifshitz, Papaterou and Mller to
compute energy-momentum density components. We obtain that these prescriptions
do not provide similar energy density, however momentum becomes constant in
each case. The results can be matched under particular boundary conditions.Comment: 18 pages, accepted for publication in Astrophysics and SpaceScienc
Energy and Momentum densities of cosmological models, with equation of state , in general relativity and teleparallel gravity
We calculated the energy and momentum densities of stiff fluid solutions,
using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes,
in both general relativity and teleparallel gravity. In our analysis we get
different results comparing the aforementioned complexes with each other when
calculated in the same gravitational theory, either this is in general
relativity and teleparallel gravity. However, interestingly enough, each
complex's value is the same either in general relativity or teleparallel
gravity. Our results sustain that (i) general relativity or teleparallel
gravity are equivalent theories (ii) different energy-momentum complexes do not
provide the same energy and momentum densities neither in general relativity
nor in teleparallel gravity. In the context of the theory of teleparallel
gravity, the vector and axial-vector parts of the torsion are obtained. We show
that the axial-vector torsion vanishes for the space-time under study.Comment: 15 pages, no figures, Minor typos corrected; version to appear in
International Journal of Theoretical Physic
Energy-Momentum Localization for a Space-Time Geometry Exterior to a Black Hole in the Brane World
In general relativity one of the most fundamental issues consists in defining
a generally acceptable definition for the energy-momentum density. As a
consequence, many coordinate-dependent definitions have been presented, whereby
some of them utilize appropriate energy-momentum complexes. We investigate the
energy-momentum distribution for a metric exterior to a spherically symmetric
black hole in the brane world by applying the Landau-Lifshitz and Weinberg
prescriptions. In both the aforesaid prescriptions, the energy thus obtained
depends on the radial coordinate, the mass of the black hole and a parameter
, while all the momenta are found to be zero. It is shown that for
a special value of the parameter , the Schwarzschild space-time
geometry is recovered. Some particular and limiting cases are also discussed.Comment: 10 pages, sections 1 and 3 slightly modified, references modified and
adde
Beautiful Mirrors and Precision Electroweak Data
The Standard Model (SM) with a light Higgs boson provides a very good
description of the precision electroweak observable data coming from the LEP,
SLD and Tevatron experiments. Most of the observables, with the notable
exception of the forward-backward asymmetry of the bottom quark, point towards
a Higgs mass far below its current experimental bound. The disagreement, within
the SM, between the values for the weak mixing angle as obtained from the
measurement of the leptonic and hadronic asymmetries at lepton colliders, may
be taken to indicate new physics contributions to the precision electroweak
observables. In this article we investigate the possibility that the inclusion
of additional bottom-like quarks could help resolve this discrepancy. Two
inequivalent assignments for these new quarks are analysed. The resultant fits
to the electroweak data show a significant improvement when compared to that
obtained in the SM. While in one of the examples analyzed, the exotic quarks
are predicted to be light, with masses below 300 GeV, and the Higgs tends to be
heavy, in the second one the Higgs is predicted to be light, with a mass below
250 GeV, while the quarks tend to be heavy, with masses of about 800 GeV. The
collider signatures associated with the new exotic quarks, as well as the
question of unification of couplings within these models and a possible
cosmological implication of the new physical degrees of freedom at the weak
scale are also discussed.Comment: 21 pages, 4 embedded postscript figures, LaTeX. Two minor corrections
performe
UNDERSTANDING THE DETERMINANTS OF BLOCKCHAIN ADOPTION IN SUPPLY CHAINS: AN EMPIRICAL STUDY IN CHINA
This study adopts affordance approach to understand how supply chain managers interpret the possible benefits that can be performed within blockchain-enabled supply chain applications. With a focus on governance efficiency improvement, the impacts of traceability and transparency affordance on uncertainty reduction were examined from the perspective of transaction cost theory in supply chain industry. Partial least squares – structural equation modelling (PLS-SEM) was used to analyze the data collected from 364 experienced supply chain managers in China. The results revealed that traceability affordance exerted significant impacts on environmental and trading partner uncertainty rather than transparency affordance, which in turn affected the adoption intention. This study contributes to the extant literature by embedding transaction cost in blockchain affordances. The findings are useful in guiding practitioners to improve blockchain system design for reducing uncertainties in supply chain environment, leading to a higher adoption rate of blockchain technology
Energy Distribution in f(R) Gravity
The well-known energy problem is discussed in f(R) theory of gravity. We use
the generalized Landau-Lifshitz energy-momentum complex in the framework of
metric f(R) gravity to evaluate the energy density of plane symmetric solutions
for some general f(R) models. In particular, this quantity is found for some
popular choices of f(R) models. The constant scalar curvature condition and the
stability condition for these models are also discussed. Further, we
investigate the energy distribution of cosmic string spacetime.Comment: 15 pages, accepted for publication in Gen. Relativ. & Gra
Lepton Flavor Violation and the Origin of the Seesaw Mechanism
The right--handed neutrino mass matrix that is central to the understanding
of small neutrino masses via the seesaw mechanism can arise either (i) from
renormalizable operators or (ii) from nonrenormalizable or super-renormalizable
operators, depending on the symmetries and the Higgs content of the theory
beyond the Standard Model. In this paper, we study lepton flavor violating
(LFV) effects in the first class of seesaw models wherein the \nu_R Majorana
masses arise from renormalizable Yukawa couplings involving a B-L = 2 Higgs
field. We present detailed predictions for \tau -> \mu + \gamma and \mu -> e +
\gamma branching ratios in these models taking the current neutrino oscillation
data into account. Focusing on minimal supergravity models, we find that for a
large range of MSSM parameters suggested by the relic abundance of neutralino
dark matter and that is consistent with Higgs boson mass and other constraints,
these radiative decays are in the range accessible to planned experiments. We
compare these predictions with lepton flavor violation in the second class of
models arising entirely from the Dirac Yukawa couplings. We study the
dependence of the ratio r \equiv B(\mu -> e+\gamma)/B(\tau ->\mu +\gamma) on
the MSSM parameters and show that measurement of r can provide crucial insight
into the origin of the seesaw mechanism.Comment: 20 pages, Revtex, 7 figure
Can the Zee Model Explain the Observed Neutrino Data?
The eigenvalues and mixing angles in the Zee model are investigated
parameter-independently. When we require |\Delta m^2_{12}/\Delta m^2_{23}| \ll
1 in order to understand the solar and atmospheric data simultaneously, the
only solution is one which gives bi-maximal mixing. It is pointed out that the
observed values \sin^2 2\theta_{solar} \simeq 0.66 in the MSW LMA solution
cannot be explained within the framework of the Zee model, because we derive a
severe constraint on the value of \sin^2 2 \theta_{solar}, \sin^2 2
\theta_{solar} \geq 1 -(1/16)(\Delta m^2_{solar}/\Delta m^2_{atm})^2.Comment: Latex file, 10 pages, 1 figure, explanations and references added,
typos corrected, to be published in Phys.Rev.
Distribution of Energy-Momentum in a Schwarzschild-Quintessence Space-time Geometry
An analysis of the energy-momentum localization for a four-dimensional\break
Schwarzschild black hole surrounded by quintessence is presented in order to
provide expressions for the distributions of energy and momentum. The
calculations are performed by using the Landau-Lifshitz and Weinberg
energy-momentum complexes. It is shown that all the momenta vanish, while the
expression for the energy depends on the mass of the black hole, the state
parameter and the normalization factor . The special case of
is also studied, and two limiting cases are examined.Comment: 9 page
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