3,248 research outputs found
Removal of Radium from Synthetic Shale Gas Brines by Ion Exchange Resin
Rapid development of hydraulic fracturing for natural gas production from shale reservoirs presents a significant challenge related to the management of the high-salinity wastewaters that return to the surface. In addition to high total dissolved solids (TDS), shale gas-produced brines typically contain elevated concentrations of radium (Ra), which must be treated properly to prevent contamination of surface waters and allow for safe disposal or reuse of produced water. Treatment strategies that isolate radium in the lowest volume waste streams would be desirable to reduce disposal cost and generate useful treatment by-products. The present study evaluates the potential of a commercial strong acid cation exchange resin for removing Ra2+ from high-TDS brines using fixed-bed column reactors. Column reactors were operated with varying brine chemistries and salinities in an effort to find optimal conditions for Ra2+ removal through ion exchange. To overcome competing divalent cations present in the brine for exchange sites, the chelating agent, EDTA, was used to form stable complexes predominantly with the higher concentration Ca2+, Mg2+, and Sr2+ divalent cations, while isolating the much lower concentration Ra2+ species. Results showed that Ra2+ removal by the resin strongly depended on the TDS concentration and could be improved with careful selection of EDTA concentration. This strategy of metal chelation coupled with ion exchange resins may be effective in enhancing Ra2+ removal and reducing the generation and disposal cost if volume reduction of low-level radioactive solid waste can be achieved.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140367/1/ees.2016.0002.pd
Seesaw and Lepton Flavour Violation in SUSY SO(10)
That and are sensitive probes of
SUSY models with a see-saw mechanism is a well accepted fact. Here we propose a
`top-down' approach in a general SUSY SO(10) scheme. In this framework, we show
that at least one of the neutrino Yukawa couplings is as large as the top
Yukawa coupling. This leads to a strong enhancement of these leptonic flavour
changing decay rates. We examine two `extreme' cases, where the lepton mixing
angles in the neutrino Yukawa couplings are either small (CKM-like) or large
(PMNS-like). In these two cases, we quantify the sensitivity of leptonic
radiative decays to the SUSY mass spectrum. In the PMNS case, we find that the
ongoing experiments at the B-factories can completely probe the spectrum up to
gaugino masses of 500 GeV (any tan ). Even in the case of CKM-like
mixings, large regions of the parameter space will be probed in the near
future, making these two processes leading candidates for indirect SUSY
searches.Comment: 22 pages with 2 figures. Figures for \tau -> \mu \gamma decay
corrected after typo found in the program. Decay \mu -> e gamma completely
unchanged and conclusions basicaly unchange
Ly Leaks and Reionization
Ly absorption spectra of QSOs at redshifts show complete
Gunn-Peterson absorption troughs (dark gaps) separated by tiny leaks. The dark
gaps are from the intergalactic medium (IGM) where the density of neutral
hydrogen are high enough to produce almost saturated absorptions, however,
where the transmitted leaks come from is still unclear so far. We demonstrate
that leaking can originate from the lowest density voids in the IGM as well as
the ionized patches around ionizing sources using semi-analytical simulations.
If leaks were produced in lowest density voids, the IGM might already be highly
ionized, and the ionizing background should be almost uniform; in contrast, if
leaks come from ionized patches, the neutral fraction of IGM would be still
high, and the ionizing background is significantly inhomogeneous. Therefore,
the origin of leaking is crucial to determining the epoch of
inhomogeneous-to-uniform transition of the the ionizing photon background. We
show that the origin could be studied with the statistical features of leaks.
Actually, Ly leaks can be well defined and described by the equivalent
width and the full width of half area , both of which are less
contaminated by instrumental resolution and noise. It is found that the
distribution of and of Ly leaks are sensitive to the
modeling of the ionizing background. We consider four representative
reionization models. It is concluded that the leak statistics provides an
effective tool to probe the evolutionary history of reionization at
. Similar statistics would also be applicable to the reionization
of He II at (Abridged)Comment: 11 pages including 10 figures, accepted for publication in MNRA
Anomalous U(1) symmetry and lepton flavor violation
We show that in a large class of models based on anomalous U(1) symmetry
which addresses the fermion mass hierarchy problem, leptonic flavor changing
processes are induced that are in the experimentally interesting range. The
flavor violation occurs through the renormalization group evolution of the soft
SUSY breaking parameters between the string scale and the U(1)_A breaking
scale. We derive general expressions for the evolution of these parameters in
the presence of higher dimensional operators. Several sources for the flavor
violation are identified: flavor-dependent contributions to the soft masses
from the U(1)_A gaugino, scalar mass corrections proportional to the trace of
U(1)_A charge, non-proportional A-terms from vertex corrections, and the U(1)_A
D-term. Quantitative estimates for the decays \mu -> e \gamma and \tau -> \mu
\gamma are presented in supergravity models which accommodate the relic
abundance of neutralino dark matter.Comment: References added, typos corrected, 28 pages LaTeX, includes 14 eps
figure
Background Dependent Lorentz Violation: Natural Solutions to the Theoretical Challenges of the OPERA Experiment
To explain both the OPERA experiment and all the known phenomenological
constraints/observations on Lorentz violation, the Background Dependent Lorentz
Violation (BDLV) has been proposed. We study the BDLV in a model independent
way, and conjecture that there may exist a "Dream Special Relativity Theory",
where all the Standard Model (SM) particles can be subluminal due to the
background effects. Assuming that the Lorentz violation on the Earth is much
larger than those on the interstellar scale, we automatically escape all the
astrophysical constraints on Lorentz violation. For the BDLV from the effective
field theory, we present a simple model and discuss the possible solutions to
the theoretical challenges of the OPERA experiment such as the Bremsstrahlung
effects for muon neutrinos and the pion decays. Also, we address the Lorentz
violation constraints from the LEP and KamLAMD experiments. For the BDLV from
the Type IIB string theory with D3-branes and D7-branes, we point out that the
D3-branes are flavour blind, and all the SM particles are the conventional
particles as in the traditional SM when they do not interact with the
D3-branes. Thus, we not only can naturally avoid all the known phenomenological
constraints on Lorentz violation, but also can naturally explain all the
theoretical challenges. Interestingly, the energy dependent photon velocities
may be tested at the experiments.Comment: RevTex4, 14 pages, minor corrections, references adde
Lepton Flavor Violation within a realistic SO(10)/G(224) Framework
Lepton flavor violation (LFV) is studied within a realistic unified
framework, based on supersymmetric SO(10) or an effective G(224) =
SU(2)_L\times SU(2)_R\times SU(4)^c symmetry, that successfully describes (i)
fermion masses and mixings, (ii) neutrino oscillations, as well as (iii) CP
violation. LFV emerges as an important prediction of this framework, bringing
no new parameters, barring the few SUSY parameters, which are assumed to be
flavor-universal at M^*>= M_{GUT}. We study LFV (i.e. \mu -> e\gamma, \tau ->
\mu\gamma, \tau -> e\gamma and \mu N -> e N) within this framework by including
contributions both from the presence of the right handed neutrinos as well as
those arising from renormalization group running in the post-GUT regime (M^* to
M_{GUT}). Typically the latter, though commonly omitted in the literature, is
found to dominate. Our predicted rates for \mu -> e\gamma show that while some
choices of (m_o, m_{1/2}) are clearly excluded by the current empirical limit,
this decay should be seen with an improvement of the current sensitivity by a
factor of 10--100, even if sleptons are moderately heavy (<= 800 GeV, say). For
the same reason, \mu-e conversion (\mu N -> e N) should show in the planned
MECO experiment. Implications of WMAP and (g-2)_{\mu}-measurements are noted,
as also the significance of the measurement of parity-odd asymmetry in the
decay of polarized \mu^+ into e^+ \gamma.Comment: 17 pages, 1 figur
Experimental Studies of Phase Change Materials in a Bubbling Fluidized Bed
Proceedings of: 14th International Conference on Fluidization: From Fundamentals to Products. Noordwijkerhout, Netherlands, 26-31 may 2013.The aim of this work is to experimentally study the behaviour of three microencapsulated PCM in a bubbling fluidized bed for thermal energy storage. Different experiments, heating and cooling the granular PCM with fluidizing air, are carried out with different superficial gas velocities. When achieving their phase change temperature two of the three materials present agglomeration. For this reason, the material flowability and wear resistance are studied by measuring the angle of repose and attrition, respectively. Nevertheless, the angle of repose does not seem to be influenced by the temperature of the material and the particle size distributions after the attrition tests indicate that the bed particles are just slightly smaller than the original ones.This work was partially founded by the Spanish Government (Project ENE2010-15403), the regional Government of Castilla-La Mancha (Project PPIC10-0055-4054) and Castilla-La Mancha University (Project GE20101662).Publicad
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
Geodesic motion in the Kundt spacetimes and the character of envelope singularity
We investigate geodesics in specific Kundt type N (or conformally flat)
solutions to Einstein's equations. Components of the curvature tensor in
parallelly transported tetrads are then explicitly evaluated and analyzed. This
elucidates some interesting global properties of the spacetimes, such as an
inherent rotation of the wave-propagation direction, or the character of
singularities. In particular, we demonstrate that the characteristic envelope
singularity of the rotated wave-fronts is a (non-scalar) curvature singularity,
although all scalar invariants of the Riemann tensor vanish there.Comment: 21 pages, 3 figures. To appear in Class. Quantum Gra
Relic abundance of mass-varying cold dark matter particles
In models of coupled dark energy and dark matter the mass of the dark matter
particle depends on the cosmological evolution of the dark energy field. In
this note we exemplify in a simple model the effects of this mass variation on
the relic abundance of cold dark matter.Comment: 5 pages, no figures. Version published in PL
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