248 research outputs found
The role of natural clays in the sustainability of landfill liners
Engineered synthetic liners on their own cannot protect the environment and human health against landfill leachate pollution. Despite their initial impermeability, they are susceptible to failure during and after installation and have no attenuation properties. Conversely, natural clay liners can attenuate leachate pollutants by sorption, redox transformations, biodegradation, precipitation, and filtration, decreasing the pollutant flux. Depending on the clay, significant differences exist in their shrinkage potential, sorption capacity, erosion resistance and permeability to fluids, which affects the suitability and performance of the potential clay liner. Here, the physico-chemical, mineralogical and geotechnical characteristics of four natural clayey substrata were compared to discuss their feasibility as landfill liners. To study their chemical compatibility with leachate and rainwater, hydraulic conductivities were measured every ≈2 days spread over 7 weeks of centrifugation at 25 gravities. At field-scale, this is equivalent to every 3.4 yrs spread over 80 yrs. All the clayey substrata had favourable properties for the attenuation of leachate pollutants, although different management options should be applied for each one. London Clay (smectite-rich) is the best material based on the sorption capacity, hydraulic conductivity and low erodibility, but has the greatest susceptibility to excessive shrinkage and alterable clay minerals that partially collapse to illitic structures. Oxford Clay (illite rich) is the best material for buffering acid leachates and supporting degradation of organic compounds. The Coal Measures Clays (kaoline-rich) have the lowest sorption capacity, but also the lowest plasticity and have the most resistant clay minerals to alteration by leachate exposure
High Attenuation Recycled Materials as landfill liners (the HARM project) – a new concept for improved landfill liner design
A new approach in landfill liner design which combines hydraulic containment of leachate with contaminant attenuation to improve the performance of these environmental control systems at landfills is described. The idea is to re-use readily available industrial waste residues (construction and biomass waste) as additives for natural clay liners, wherein the additives have specific properties which enhance the attenuation of contaminants by the mixture. The aim is to (1) evaluate the contaminant attenuation capacity of these mixtures, (2) develop design guidelines to construct liners for waste containment systems and similar applications, and (3) interpret their performance using numerical modelling. This is evaluated in permeation studies using a geotechnical centrifuge, which enables the performance of liner compositions to be tested for representive time-scales (100 years), pressures and temperatures at realistic experimental time-scales of days-weeks in the laboratory. The permeation experiments include liner compositions flushed with leachate to deduce contaminant transport and attenuation mechanisms, followed by rainwater to assess the potential for release of attenuated contaminants. This experimental methodology is illustrated with depth profiles from permeation studies conducted on different clay-additive compositions. The concept will be applicable for liner design at other waste disposal facilities and is a timely improvement which addresses the problem of managing large quantities of industrial residues. Instead of disposal these can be recycled as an additive in host clay to construct these liners, thus conserving natural resources (clay) and reducing construction costs. It also provides an effective and more environmentally sustainable basis to reduce risks from leachate leakage
Multimode mean-field model for the quantum phase transition of a Bose-Einstein condensate in an optical resonator
We develop a mean-field model describing the Hamiltonian interaction of
ultracold atoms and the optical field in a cavity. The Bose-Einstein condensate
is properly defined by means of a grand-canonical approach. The model is
efficient because only the relevant excitation modes are taken into account.
However, the model goes beyond the two-mode subspace necessary to describe the
self-organization quantum phase transition observed recently. We calculate all
the second-order correlations of the coupled atom field and radiation field
hybrid bosonic system, including the entanglement between the two types of
fields.Comment: 10 page
Analysis of LIGO data for gravitational waves from binary neutron stars
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers. We
establish an observational upper limit of 1.7 \times 10^{2}M_\odot$.Comment: 17 pages, 9 figure
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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