312 research outputs found
Home composting as an alternative treatment option for organic household waste in Denmark: An environmental assessment using life cycle assessment-modelling
Impact of intensified testing for urogenital Chlamydia trachomatis infections: a randomised study with 9-year follow-up
An Effective-Medium Tight-Binding Model for Silicon
A new method for calculating the total energy of Si systems is presented. The
method is based on the effective-medium theory concept of a reference system.
Instead of calculating the energy of an atom in the system of interest a
reference system is introduced where the local surroundings are similar. The
energy of the reference system can be calculated selfconsistently once and for
all while the energy difference to the reference system can be obtained
approximately. We propose to calculate it using the tight-binding LMTO scheme
with the Atomic-Sphere Approximation(ASA) for the potential, and by using the
ASA with charge-conserving spheres we are able to treat open system without
introducing empty spheres. All steps in the calculational method is {\em ab
initio} in the sense that all quantities entering are calculated from first
principles without any fitting to experiment. A complete and detailed
description of the method is given together with test calculations of the
energies of phonons, elastic constants, different structures, surfaces and
surface reconstructions. We compare the results to calculations using an
empirical tight-binding scheme.Comment: 26 pages (11 uuencoded Postscript figures appended), LaTeX,
CAMP-090594-
A radium assay technique using hydrous titanium oxide adsorbent for the Sudbury Neutrino Observatory
As photodisintegration of deuterons mimics the disintegration of deuterons by
neutrinos, the accurate measurement of the radioactivity from thorium and
uranium decay chains in the heavy water in the Sudbury Neutrino Observatory
(SNO) is essential for the determination of the total solar neutrino flux. A
radium assay technique of the required sensitivity is described that uses
hydrous titanium oxide adsorbent on a filtration membrane together with a
beta-alpha delayed coincidence counting system. For a 200 tonne assay the
detection limit for 232Th is a concentration of 3 x 10^(-16) g Th/g water and
for 238U of 3 x 10^(-16) g U/g water. Results of assays of both the heavy and
light water carried out during the first two years of data collection of SNO
are presented.Comment: 12 pages, 4 figure
First principles electronic structure of spinel LiCr2O4: A possible half-metal?
We have employed first-principles electronic structure calculations to
examine the hypothetical (but plausible) oxide spinel, LiCr2O4 with the d^{2.5}
electronic configuration. The cell (cubic) and internal (oxygen position)
structural parameters have been obtained for this compound through structural
relaxation in the first-principles framework. Within the one-electron band
picture, we find that LiCr2O4 is magnetic, and a candidate half-metal. The
electronic structure is substantially different from the closely related and
well known rutile half-metal CrO2. In particular, we find a smaller conduction
band width in the spinel compound, perhaps as a result of the distinct topology
of the spinel crystal structure, and the reduced oxidation state. The magnetism
and half-metallicity of LiCr2O4 has been mapped in the parameter space of its
cubic crystal structure. Comparisons with superconducting LiTi2O4 (d^{0.5}),
heavy-fermion LiV2O4 (d^{1.5}) and charge-ordering LiMn2O4 (d^{3.5}) suggest
the effectiveness of a nearly-rigid band picture involving simple shifts of the
position of E_F in these very different materials. Comparisons are also made
with the electronic structure of ZnV2O4 (d^{2}), a correlated insulator that
undergoes a structural and antiferromagnetic phase transition.Comment: 9 pages, 7 Figures, version as published in PR
Optical symmetries and anisotropic transport in high-Tc superconductors
A simple symmetry analysis of in-plane and out-of-plane transport in a family
of high temperature superconductors is presented. It is shown that generalized
scaling relations exist between the low frequency electronic Raman response and
the low frequency in-plane and out-of-plane conductivities in both the normal
and superconducting states of the cuprates. Specifically, for both the normal
and superconducting state, the temperature dependence of the low frequency
Raman slope scales with the axis conductivity, while the
Raman slope scales with the in-plane conductivity. Comparison with experiments
in the normal state of Bi-2212 and Y-123 imply that the nodal transport is
largely doping independent and metallic, while transport near the BZ axes is
governed by a quantum critical point near doping holes per
CuO plaquette. Important differences for La-214 are discussed. It is also
shown that the axis conductivity rise for is a consequence of
partial conservation of in-plane momentum for out-of-plane transport.Comment: 16 pages, 8 Figures (3 pages added, new discussion on pseudogap and
charge ordering in La214
Inverse magnetic catalysis in field theory and gauge-gravity duality
We investigate the surface of the chiral phase transition in the
three-dimensional parameter space of temperature, baryon chemical potential and
magnetic field in two different approaches, the field-theoretical
Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model. The
latter is a top-down approach to a gravity dual of QCD with an asymptotically
large number of colors and becomes, in a certain limit, dual to an NJL-like
model. Our main observation is that, at nonzero chemical potential, a magnetic
field can restore chiral symmetry, in apparent contrast to the phenomenon of
magnetic catalysis. This "inverse magnetic catalysis" occurs in the
Sakai-Sugimoto model and, for sufficiently large coupling, in the NJL model and
is related to the physics of the lowest Landau level. While in most parts our
discussion is a pedagogical review of previously published results, we include
new analytical results for the NJL approach and a thorough comparison of
inverse magnetic catalysis in the two approaches.Comment: 37 pages, 11 figures, to appear in Lect. Notes Phys. "Strongly
interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K.
Landsteiner, A. Schmitt, H.-U. Ye
Lattice QCD Simulations in External Background Fields
We discuss recent results and future prospects regarding the investigation,
by lattice simulations, of the non-perturbative properties of QCD and of its
phase diagram in presence of magnetic or chromomagnetic background fields.
After a brief introduction to the formulation of lattice QCD in presence of
external fields, we focus on studies regarding the effects of external fields
on chiral symmetry breaking, on its restoration at finite temperature and on
deconfinement. We conclude with a few comments regarding the effects of
electromagnetic background fields on gluodynamics.Comment: 31 pages, 10 figures, minor changes and references added. To appear
in Lect. Notes Phys. "Strongly interacting matter in magnetic fields"
(Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye
Mechanisms of international influence on domestic elite sport policy
In the analysis of sport policy the permeability of domestic policy processes and the significance of non-domestic policy influences is increasingly acknowledged. There is also a growing awareness of the role of domestic institutional arrangements in mediating influences external to the domestic policy system. Taking the interaction between non-domestic influences and domestic policy processes as its starting point the article evaluates, in relation to elite sport, the variety of mechanisms that have been identified as linking the domestic and non-domestic policy spheres. It is argued that the mechanisms vary in relation to the locus of initiative, the basis of engagement, the key relationships and the nature of power relationships. It is also argued that in many countries in relation to elite sport policy there is a dual process in operation of domestically initiated policy learning and non-domestically initiated policy harmonisation through policy regimes
- âŠ