Robust Entanglement in Atomic Systems via Lambda-Type Processes

It is shown that the system of two three-level atoms in $\Lambda$ configuration in a cavity can evolve to a long-lived maximum entangled state if the Stokes photons vanish from the cavity by means of either leakage or damping. The difference in evolution picture corresponding to the general model and effective model with two-photon process in two-level system is discussed.Comment: 10 pages, 3 figure

Radiative Decay B→lνγ B \to l \nu \gamma in the Light Cone QCD Approach

We calculate to the leading twist 2 accuracy the rate for the decay $B_{u} \rightarrow l \nu \gamma$ using the light cone QCD sume rules. We find $Br( B_{u} \rightarrow l \nu \gamma) \simeq 2 \cdot 10^{-6}$. The results are used to test the applicability of the constituent quark model approximation to the same process.The latter estimate is proportional to $1/m_{u}^{2}$, where $m_{u} \simeq \bar{\Lambda}_{u}$ is the "constituent quark mass", indicating that the process is of long distance type. We find that the two approaches yield similar results for the rate with the choice $m_{u} \simeq 430-480 \;MeV$. This indicates that the constituent quark model may be used for estimates of the radiative "annihilation" contribution to this and other radiative decays. We point out that this decay may be useful for the measurement of $|V_{ub}|$.Comment: latex, 14 pages, one figure is available upon reques

Bianchi Type I Cosmology in Generalized Saez-Ballester Theory via Noether Gauge Symmetry

In this paper, we investigate the generalized Saez-Ballester scalar-tensor theory of gravity via Noether gauge symmetry (NGS) in the background of Bianchi type I cosmological spacetime. We start with the Lagrangian of our model and calculate its gauge symmetries and corresponding invariant quantities. We obtain the potential function for the scalar field in the exponential form. For all the symmetries obtained, we determine the gauge functions corresponding to each gauge symmmetry which include constant and dynamic gauge. We discuss cosmological implications of our model and show that it is compatible with the observational data.Comment: 13 pages, 2 figures, accepted for publication in 'European Physical Journal C

Leveraging antibacterial efficacy of silver loaded chitosan nanoparticles on layer-by-layer self-assembled coated cotton fabric

The present study relates to forma self-assembled coating on cotton fabric using layer-by-layer (L-B-L) technique to impart antimicrobial property. Poly(styrenesulfonate) (PSS) and synthesised silver loaded chitosan (CS-Ag) nanoparticles were used as anionic and cationic agents, respectively, for the L-B-L electrostatic assembly of polyelectrolytes. The alternate L B-L deposition of PSS and CS-Ag nanoparticles on fabric was done up to 15 bi-layers, which was confirmed by measuring the change in depth of colour of fabric after each single layer deposition. Scanning electron micrographs showed the successful deposition of CS-Ag nanoparticles as the topmost surface layer of coated fabric, which was further reaffirmed by X ray photoelectron spectroscopy analysis. Results of both qualitative and quantitative analysis showed enhancement in the antibacterial activity of fabric coated L-B-L with CS-Ag nanoparticles (using minimal loading of silver) with respect to that of fabric coated L-B-L with chitosan (CS) nanoparticles. This was further substantiated by sustained release of Ag+ from fabric coated L-B-L with CS-Ag nanoparticles, as observed by atomic absorption spectroscopy. Besides, no adverse effect on the physical and mechanical properties of the fabric, such as air-permeability, tensile strength and bending (flexural) rigidity, was observed after L-B-L coating of nanoparticles

Two-loop HTL Thermodynamics with Quarks

We calculate the quark contribution to the free energy of a hot quark-gluon plasma to two-loop order using hard-thermal-loop (HTL) perturbation theory. All ultraviolet divergences can be absorbed into renormalizations of the vacuum energy and the HTL quark and gluon mass parameters. The quark and gluon HTL mass parameters are determined self-consistently by a variational prescription. Combining the quark contribution with the two-loop HTL perturbation theory free energy for pure-glue we obtain the total two-loop QCD free energy. Comparisons are made with lattice estimates of the free energy for N_f=2 and with exact numerical results obtained in the large-N_f limit.Comment: 33 pages, 6 figure

Partially Annealed Disorder and Collapse of Like-Charged Macroions

Charged systems with partially annealed charge disorder are investigated using field-theoretic and replica methods. Charge disorder is assumed to be confined to macroion surfaces surrounded by a cloud of mobile neutralizing counterions in an aqueous solvent. A general formalism is developed by assuming that the disorder is partially annealed (with purely annealed and purely quenched disorder included as special cases), i.e., we assume in general that the disorder undergoes a slow dynamics relative to fast-relaxing counterions making it possible thus to study the stationary-state properties of the system using methods similar to those available in equilibrium statistical mechanics. By focusing on the specific case of two planar surfaces of equal mean surface charge and disorder variance, it is shown that partial annealing of the quenched disorder leads to renormalization of the mean surface charge density and thus a reduction of the inter-plate repulsion on the mean-field or weak-coupling level. In the strong-coupling limit, charge disorder induces a long-range attraction resulting in a continuous disorder-driven collapse transition for the two surfaces as the disorder variance exceeds a threshold value. Disorder annealing further enhances the attraction and, in the limit of low screening, leads to a global attractive instability in the system.Comment: 21 pages, 2 figure

Persistent Spin Currents in Helimagnets

We demonstrate that weak external magnetic fields generate dissipationless spin currents in the ground state of systems with spiral magnetic order. Our conclusions are based on phenomenological considerations and on microscopic mean-field theory calculations for an illustrative toy model. We speculate on possible applications of this effect in spintronic devices.Comment: 9 pages, 6 figures, updated version as published, Journal referenc

Fabrication of CdS/CdTe-based thin film solar cells using an electrochemical technique

Thin film solar cells based on cadmium telluride (CdTe) are complex devices which have great potential for achieving high conversion efficiencies. Lack of understanding in materials issues and device physics slows down the rapid progress of these devices. This paper combines relevant results from the literature with new results from a research programme based on electro-plated CdS and CdTe. A wide range of analytical techniques was used to investigate the materials and device structures. It has been experimentally found that n-, i- and p-type CdTe can be grown easily by electroplating. These material layers consist of nano- and micro-rod type or columnar type grains, growing normal to the substrate. Stoichiometric materials exhibit the highest crystallinity and resistivity, and layers grown closer to these conditions show n - p or p - n conversion upon heat treatment. The general trend of CdCl2 treatment is to gradually change the CdTe material’s n-type electrical property towards i-type or p-type conduction. This work also identifies a rapid structural transition of CdTe layer at 385 ± 5 °C and a slow structural transition at higher temperatures when annealed or grown at high temperature. The second transition occurs after 430 °C and requires more work to understand this gradual transition. This work also identifies the existence of two different solar cell configurations for CdS/CdTe which creates a complex situation. Finally, the paper presents the way forward with next generation CdTe-based solar cells utilising low-cost materials in their columnar nature in graded bandgap structures. These devices could absorb UV, visible and IR radiation from the solar spectrum and combine impact ionisation and impurity photovoltaic (PV) effect as well as making use of IR photons from the surroundings when fully optimised

How can we explain the differences between the OARSI and ESCEO Guidelines for the management of knee osteoarthritis?

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