1,085 research outputs found
The nematic phase in stripe forming systems within the self consistent screening approximation
We show that in order to describe the isotropic-nematic transition in stripe
forming systems with isotropic competing interactions of the Brazovskii class
it is necessary to consider the next to leading order in a 1/N approximation
for the effective Hamiltonian. This can be conveniently accomplished within the
self-consistent screening approximation. We solve the relevant equations and
show that the self-energy in this approximation is able to generate the
essential wave vector dependence to account for the anisotropic character of
two-point correlation function characteristic of a nematic phase.Comment: 8 pages, 4 figure
Coherent Population Trapping with a controlled dissipation: applications in optical metrology
We analyze the properties of a pulsed Coherent Population Trapping protocol
that uses a controlled decay from the excited state in a -level
scheme. We study this problem analytically and numerically and find regimes
where narrow transmission, absorption, or fluorescence spectral lines occur. We
then look for optimal frequency measurements using these spectral features by
computing the Allan deviation in the presence of ground state decoherence and
show that the protocol is on a par with Ramsey-CPT. We discuss possible
implementations with ensembles of alkali atoms and single ions and demonstrate
that typical pulsed-CPT experiments that are realized on femto-second
time-scales can be implemented on micro-seconds time-scales using this scheme.Comment: 9 pages, 7 figure
Different strategies for recovering metals from CARON process residue
http://dx.doi.org/10.1016/j.jhazmat.2011.03.048The capacity of Acidithiobacillus thiooxidans DMS 11478 to recover the heavy metals contained in
the residue obtained from the CARON process has been evaluated. Different bioreactor configurations
were studied: a two-stage batch system and two semi-continuous systems (stirred-tank reactor
leaching and column leaching). In the two-stage system, 46.8% Co, 36.0% Mg, 26.3% Mn and 22.3% Ni
were solubilised after 6 h of contact between the residue and the bacteria-free bioacid. The results
obtained with the stirred-tank reactor and the column were similar: 50% of the Mg and Co and
40% of the Mn and Ni were solubilised after thirty one days. The operation in the column reactor
allowed the solid–liquid ratio to be increased and the pH to be kept at low values (<1.0). Recirculation
of the leachate in the column had a positive effect on metal removal; at sixty five days
(optimum time) the solubilisation levels were as follows: 86% Co, 83% Mg, 72% Mn and Ni, 62% Fe and
23% Cr. The results corroborate the feasibility of the systems studied for the leaching of metals from
CARON process residue and these methodologies can be considered viable for the recovery of valuable
metals
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