271 research outputs found
An evaluation of enhanced geotextile layer in permeable pavement to improve stormwater infiltration and attenuation
This paper reports on an evaluation of the properties of a novel structure known as OASISÂź which was designed at Coventry University as an enhancement of the commercially available geotextiles when incorporated in the permeable pavement system (PPS). The impact on the hydraulic behaviour of a PPS was analysed through the study of infiltration rate, throughout the PPS and time required to reach the steady-state stage behaviour of the water within the PPS, under extreme rainfall intensities of 100 mm/hr, 200 mm/hr and 400 mm/hr, corresponding to a 100-year return period rainfall over a duration of 15 min in different parts of the world. The result indicated that the novel structure provides an extra benefit when incorporated in PPSs, delaying peak flow of a rainfall event by retaining and storing great volumes of water within its structure. These additional benefits are especially important under extreme rainfall events
Volume contraction at the Jahn-Teller transition of LaMnO
We have studied the volume collapse of LaMnO at the Jahn- Teller (JT)
transition temperature T=750 K which has recently been found in high
temperature powder x- ray and neutron diffraction experiments. We construct a
model Hamiltonian involving the pseudospin of Mn e states, the
staggered JT distortion and the volume strain coordinate. We show that the
anharmonic coupling between these primary and secondary order parameters leads
to the first order JT phase transition associated with a comparatively large
reduction of the unit cell volume of V/V 10. We explain
the temperature dependence of JT distortions and volume strain and discuss the
volume change as function of the anharmonic coupling constant. A continuous
change to a second order transition as function of model parameters is
obtained. This behaviour is also observed under Ba doping.Comment: 5 pages, 4 figure
Ferromagnetic Polarons in La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3
Unrestricted Hartree-Fock calculations on La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3
in the full magnetic unit cell show that the magnetic ground states of these
compounds consist of 'ferromagnetic molecules' or polarons ordered in
herring-bone patterns. Each polaron consists of either three or five Mn ions
separated by O- ions with a magnetic moment opposed to those of the Mn ions.
Ferromagnetic coupling within the polarons is strong while coupling between
them is relatively weak. Magnetic moments on the Mn ions range between 3.8 and
3.9 Bohr magnetons in La0.5Ca0.5MnO3 and moments on the O- ions are -0.7 Bohr
magnetons. Each polaron has a net magnetic moment of 7.0 Bohr magnetons, in
good agreement with recently reported magnetisation measurements from electron
microscopy. The polaronic nature of the electronic structure reported here is
obviously related to the Zener polaron model recently proposed for
Pr0.6Ca0.4MnO3 on the basis of neutron scattering data.Comment: 4 pages 5 figure
Charged lepton electric dipole moments with the localized leptons and the new Higgs doublet in the two Higgs doublet model
We study the lepton electric dipole moments in the split fermion scenario, in
the two Higgs doublet model, where the new Higgs scalars are localized around
the origin in the extra dimension, with the help of the localizer field. We
observe that the numerical value of the electron (muon, tau) electric dipole
moment is at the order of the magnitude of 10^{-31} (10^{-24}, 10^{-22}) (e-cm)
and this quantity is sensitive the new Higgs localization in the extra
dimension.Comment: 20 pages, 7 figure
Orbital Ordering in Paramagnetic LaMnO3 and KCuF3
{\it Ab-initio} studies of the stability of orbital ordering, its coupling to
magnetic structure and its possible origins (electron-phonon and/or
electron-electron interactions) are reported for two perovskite systems,
LaMnO and KCuF. We present a new Average Spin State (ASS) calculational
scheme that allowed us to treat a paramagnetic state. Using this scheme, we
succesfully described the experimental magnetic/orbital phase diagram of both
LaMnO and KCuF in crystal structures when the Jahn-Teller distortions
are neglected. Hence, we conclude that the orbital ordering in both compounds
is purely electronic in origin.Comment: 10 pages, 5 figure
Field-induced segregation of ferromagnetic nano-domains in PrSrMnO, detected by Mn NMR
The antiferromagnetic manganite PrSrMnO was investigated
at low temperature by means of magnetometry and Mn NMR. A field-induced
transition to a ferromagnetic state is detected by magnetization measurements
at a threshold field of a few tesla. NMR shows that the ferromagnetic phase
develops from zero field by the nucleation of microscopic ferromagnetic
domains, consisting of an inhomogeneous mixture of tilted and fully aligned
parts. At the threshold the NMR spectrum changes discontinuously into that of a
homogeneous, fully aligned, ferromagnetic state, suggesting a percolative
origin for the ferromagnetic transition.Comment: Latex 2.09 language. 4 pages, 3 figures, 23 references. Submitted to
physical Review
Exchange coupling in CaMnO and LaMnO: configuration interaction and the coupling mechanism
The equilibrium structure and exchange constants of CaMnO and LaMnO
have been investigated using total energy unrestricted Hartree-Fock (UHF) and
localised orbital configuration interaction (CI) calculations on the bulk
compounds and MnO and MnO clusters. The
predicted structure and exchange constants for CaMnO are in reasonable
agreement with estimates based on its N\'eel temperature. A series of
calculations on LaMnO in the cubic perovskite structure shows that a
Hamiltonian with independent orbital ordering and exchange terms accounts for
the total energies of cubic LaMnO with various spin and orbital orderings.
Computed exchange constants depend on orbital ordering. UHF calculations tend
to underestimate exchange constants in LaMnO, but have the correct sign
when compared with values obtained by neutron scattering; exchange constants
obtained from CI calculations are in good agreement with neutron scattering
data provided the Madelung potential of the cluster is appropriate. Cluster CI
calculations reveal a strong dependence of exchange constants on Mn d e
orbital populations in both compounds. CI wave functions are analysed in order
to determine which exchange processes are important in exchange coupling in
CaMnO and LaMnO.Comment: 25 pages and 9 postscript figure
Loop Corrections to Cosmological Perturbations in Multi-field Inflationary Models
We investigate one-loop quantum corrections to the power spectrum of
adiabatic perturbation from entropy modes/adiabatic mode cross-interactions in
multiple DBI inflationary models. We find that due to the non-canonical kinetic
term in DBI models, the loop corrections are enhanced by slow-varying parameter
and small sound speed . Thus, in general the loop-corrections
in multi-DBI models can be large. Moreover, we find that the loop-corrections
from adiabatic/entropy cross-interaction vertices are IR finite.Comment: 21 pages, 7 figures; v2, typos corrected, ref added; v3 typos
corrected, version for publishing in jca
Colonialism, postcolonialism and the liberal welfare state
This article addresses the colonial and racial origins of the welfare state with a particular emphasis on the liberal welfare state of the USA and UK. Both are understood in terms of the centrality of the commodified status of labour power expressing a logic of market relations. In contrast, we argue that with a proper understanding of the relations of capitalism and colonialism, the sale of labour power as a commodity already represents a movement away from the commodified form of labour represented by enslavement. European colonialism is integral to the development of welfare states and their forms of inclusion and exclusion which remain racialised through into the twenty-first century
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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