1,105 research outputs found
Risks of Perfluoroalkyl and Polyfluoroalkyl substances (PFAS) for sustainable water recycling via aquifers
The prediction of the fate of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in water recycling with urban stormwater and treated wastewater is important since PFAS are widely used, persistent, and have potential impacts on human health and the environment. These alternative water sources have been utilized for water recycling via aquifers or managed aquifer recharge (MAR). However, the fate of these chemicals in MAR schemes and the potential impact in terms of regulation have not been studied. PFAS can potentially be transported long distances in the subsurface during MAR. This article reviews the potential risks to MAR systems using recycled water and urban stormwater. To date, there are insufficient data to determine if PFAS can be degraded by natural processes or retained in the aquifer and become suitable pre-treatment or post-treatment technologies that will need to be employed depending upon the end use of the recovered water. The use of engineered pre-treatment or post-treatment methods needs to be based on a âfit for purposeâ principle and carefully integrated with the proposed water end use to ensure that human and environmental health risks are appropriately managed
Quantum Ferromagnetism and Phase Transitions in Double-Layer Quantum Hall Systems
Double layer quantum Hall systems have interesting properties associated with
interlayer correlations. At where is an odd integer they exhibit
spontaneous symmetry breaking equivalent to that of spin easy-plane
ferromagnets, with the layer degree of freedom playing the role of spin. We
explore the rich variety of quantum and finite temperature phase transitions in
these systems. In particular, we show that a magnetic field oriented parallel
to the layers induces a highly collective commensurate-incommensurate phase
transition in the magnetic order.Comment: 4 pages, REVTEX 3.0, IUCM93-013, 1 FIGURE, hardcopy available from:
[email protected]
A Novel Approach to the Common Due-Date Problem on Single and Parallel Machines
This paper presents a novel idea for the general case of the Common Due-Date
(CDD) scheduling problem. The problem is about scheduling a certain number of
jobs on a single or parallel machines where all the jobs possess different
processing times but a common due-date. The objective of the problem is to
minimize the total penalty incurred due to earliness or tardiness of the job
completions. This work presents exact polynomial algorithms for optimizing a
given job sequence for single and identical parallel machines with the run-time
complexities of for both cases, where is the number of jobs.
Besides, we show that our approach for the parallel machine case is also
suitable for non-identical parallel machines. We prove the optimality for the
single machine case and the runtime complexities of both. Henceforth, we extend
our approach to one particular dynamic case of the CDD and conclude the chapter
with our results for the benchmark instances provided in the OR-library.Comment: Book Chapter 22 page
D*-->Dpi and D*-->Dgamma decays: Axial coupling and Magnetic moment of D* meson
The axial coupling and the magnetic moment of D*-meson or, more specifically,
the couplings g(D*Dpi) and g(D*Dgamma), encode the non-perturbative QCD effects
describing the decays D*-->Dpi and D*-->Dgamma. We compute these quantities by
means of lattice QCD with Nf=2 dynamical quarks, by employing the Wilson
("clover") action. On our finer lattice (a=0.065 fm) we obtain: g(D*Dpi)=20 +/-
2, and g(D0*D0gamma)=[2.0 +/- 0.6]/GeV. This is the first determination of
g(D0*D0gamma) on the lattice. We also provide a short phenomenological
discussion and the comparison of our result with experiment and with the
results quoted in the literature.Comment: 22 pages, 3 figure
Large-scale magnetic fields from inflation in dilaton electromagnetism
The generation of large-scale magnetic fields is studied in dilaton
electromagnetism in inflationary cosmology, taking into account the dilaton's
evolution throughout inflation and reheating until it is stabilized with
possible entropy production. It is shown that large-scale magnetic fields with
observationally interesting strength at the present time could be generated if
the conformal invariance of the Maxwell theory is broken through the coupling
between the dilaton and electromagnetic fields in such a way that the resultant
quantum fluctuations in the magnetic field has a nearly scale-invariant
spectrum. If this condition is met, the amplitude of the generated magnetic
field could be sufficiently large even in the case huge amount of entropy is
produced with the dilution factor as the dilaton decays.Comment: 28 pages, 5 figures, the version accepted for publication in Phys.
Rev. D; some references are adde
Universal features of the order-parameter fluctuations : reversible and irreversible aggregation
We discuss the universal scaling laws of order parameter fluctuations in any
system in which the second-order critical behaviour can be identified. These
scaling laws can be derived rigorously for equilibrium systems when combined
with the finite-size scaling analysis. The relation between order parameter,
criticality and scaling law of fluctuations has been established and the
connexion between the scaling function and the critical exponents has been
found. We give examples in out-of-equilibrium aggregation models such as the
Smoluchowski kinetic equations, or of at-equilibrium Ising and percolation
models.Comment: 19 pages, 10 figure
Phase Diagram of the Heisenberg Spin Ladder with Ring Exchange
We investigate the phase diagram of a generalized spin-1/2 quantum
antiferromagnet on a ladder with rung, leg, diagonal, and ring-exchange
interactions. We consider the exactly soluble models associated with the
problem, obtain the exact ground states which exist for certain parameter
regimes, and apply a variety of perturbative techniques in the regime of strong
ring-exchange coupling. By combining these approaches with considerations
related to the discrete Z_4 symmetry of the model, we present the complete
phase diagram.Comment: 17 pages, 10 figure
SuperWIMP Dark Matter Signals from the Early Universe
Cold dark matter may be made of superweakly-interacting massive particles,
superWIMPs, that naturally inherit the desired relic density from late decays
of metastable WIMPs. Well-motivated examples are weak-scale gravitinos in
supergravity and Kaluza-Klein gravitons from extra dimensions. These particles
are impossible to detect in all dark matter experiments. We find, however, that
superWIMP dark matter may be discovered through cosmological signatures from
the early universe. In particular, superWIMP dark matter has observable
consequences for Big Bang nucleosynthesis and the cosmic microwave background
(CMB), and may explain the observed underabundance of 7Li without upsetting the
concordance between deuterium and CMB baryometers. We discuss implications for
future probes of CMB black body distortions and collider searches for new
particles. In the course of this study, we also present a model-independent
analysis of entropy production from late-decaying particles in light of WMAP
data.Comment: 19 pages, 5 figures, typos correcte
The modulation effect for supersymmetric dark matter detection with asymmetric velocity dispersion
The detection of the theoretically expected dark matter is central to
particle physics cosmology. Current fashionable supersymmetric models provide a
natural dark matter candidate which is the lightest supersymmetric particle
(LSP). Such models combined with fairly well understood physics like the quark
substructure of the nucleon and the nuclear form factor and the spin response
function of the nucleus, permit the evaluation of the event rate for
LSP-nucleus elastic scattering. The thus obtained event rates are, however,
very low or even undetectable. So it is imperative to exploit the modulation
effect, i.e. the dependence of the event rate on the earth's annual motion. In
this review we study such a modulation effect in directional and undirectional
experiments. We calculate both the differential and the total rates using
symmetric as well as asymmetric velocity distributions. We find that in the
symmetric case the modulation amplitude is small, less than 0.07. There exist,
however, regions of the phase space and experimental conditions such that the
effect can become larger. The inclusion of asymmetry, with a realistic enhanced
velocity dispersion in the galactocentric direction, yields the bonus of an
enhanced modulation effect, with an amplitude which for certain parameters can
become as large as 0.46.Comment: 35 LATEX pages, 7 Tables, 8 PostScript Figures include
Multiband tight-binding theory of disordered ABC semiconductor quantum dots: Application to the optical properties of alloyed CdZnSe nanocrystals
Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a
broad range of applications, as their spectrum and thus their excitation gap
can be tailored by variation of their size. Additionally, nanocrystals of the
type ABC can be realized by alloying of two pure compound semiconductor
materials AC and BC, which allows for a continuous tuning of their absorption
and emission spectrum with the concentration x. We use the single-particle
energies and wave functions calculated from a multiband sp^3 empirical
tight-binding model in combination with the configuration interaction scheme to
calculate the optical properties of CdZnSe nanocrystals with a spherical shape.
In contrast to common mean-field approaches like the virtual crystal
approximation (VCA), we treat the disorder on a microscopic level by taking
into account a finite number of realizations for each size and concentration.
We then compare the results for the optical properties with recent experimental
data and calculate the optical bowing coefficient for further sizes
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