95 research outputs found

    Viscosity bound for anisotropic superfluids in higher derivative gravity

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    In the present paper, based on the principles of gauge/gravity duality we analytically compute the shear viscosity to entropy ratio corresponding to the superfluid phase in Einstein Gauss-Bonnet gravity. From our analysis we note that the ratio indeed receives a finite temperature correction below certain critical temperature. This proves the non universality of shear viscosity to entropy ratio in higher derivative theories of gravity. We also compute the upper bound for the Gauss-Bonnet coupling corresponding to the symmetry broken phase and note that the upper bound on the coupling does not seem to change as long as we are close to the critical point of the phase diagram. However the corresponding lower bound of the shear viscosity to entropy ratio seems to get modified due to the finite temperature effects.Comment: 27 pages; v2: Details added, typos fixed, references updated; version to appear in JHE

    Fast spinning strings on η \eta deformed AdS5×S5 AdS_5 \times S^{5}

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    In this paper, considering the correspondence between spin chains and string sigma models, we explore the rotating string solutions over η \eta deformed AdS5×S5 AdS_5 \times S^{5} in the so called fast spinning limit. In our analysis, we focus only on the bosonic part of the full superstring action and compute the relevant limits on both (R×S3)η(R \times S^{3})_{\eta} and (R×S5)η(R \times S^{5})_{\eta} models. The resulting system reveals that in the fast spinning limit, the sigma model on η \eta deformed S5S^5 could be approximately\textit{approximately} thought of as the continuum limit of anisotropic SU(3) SU(3) Heisenberg spin chain model. We compute the energy for a certain class of spinning strings in deformed S5S^5 and we show that this energy can be mapped to that of a similar spinning string in the purely imaginary β\beta deformed background.Comment: 30 pages; references updated; version to appear in JHE

    Method of Destroying Hazardous Organic Compounds

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    The present invention relates to a method of destroying hazardous vapor phase or aqueous phase organic compound(s) by providing a polymeric siloxane based solvent in a vessel and adding the hazardous organic compound(s) and ozone to the solvent. The solvent may also comprise a mixture of polymeric siloxane based solvent and fluorinated hydrocarbon solvent

    Water Purification Device and a Method of Decontaminating a Water Supply

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    A water purification device is provided in the form of a hydrogel matrix containing immobilized nanoparticles that are directly synthesized in-situ in the hydrogel matrix. The hydrogel matrix is temperature sensitive, such that swelling draws in pollutants that are captured by the nanoparticles, while deswelling releases purified water. A related method of decontaminating the water supply contaminated with a target pollutant is also disclosed

    Low Pressure Membrane Separation Process to Remove Heavy Metal Complexes

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    The overall objective of this investigation is to establish the rejection behavior of heavy metals in the presence of complexing agents, utilizing negatively charged ultrafiltration membranes. An extensive experimental investigation is conducted with Zn2+, Cd2+, Cu2+, and Cu1+ in the presence of cyanide, ethylenediamine tetraacetic acid, and oxalates, under insignificant concentration polarization condition. The rejection dependence of the heavy metals is found to be a function of feed metal concentration, metal types, complexing agent to metal feed molar ratio, pH and ionic strength. The dependence of rejection behavior of heavy metals and complexing agents on pH and concentration is explained in terms of metal complex species distribution and Donnan Exclusion model. For EDTA and oxalate systems, the rejections of metal are independent of initial metal concentration; whereas for the cyanide system the rejections of both metal and cyanide decrease with concentration. At transmembrane pressure of 5.6 x 105 N/m2, metal rejections range between 77% to 96%. For all cases, the rejection of metal is highly dependent on the size and charge of the complex metal species. For example, the rejections of Zn(CN)2-4 \u3e Zn(CN)31-, and Cu(EDTA)2- \u3e Cu(CN)32- \u3e Cu(C2O4)2- are observed

    Charged Membrane, Low Pressure Ultrafiltration to Treat Acid Mine Drainage Waters

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    Low-pressure ultrafiltration with negatively-charged, non-cellulosic membranes is shown to be a feasible process in terms of achieving the simultaneous separation of dissolved metals (and sulfate) and of suspended solids from acid mine drainage water. The process is evaluated in terms of the simultaneous achievement of good water flux without membrane fouling and of adequate ultrafiltrate quality at high water recovery for water reuse operation. At a transmembrane pressure of 5.6 x 105 N/m2, water fluxes in the range of 5.8 x 10-4 cm/sec to 12.5 x 10-4 cm/sec could be obtained at 97% water recovery. The results of the ultrafiltration investigations are compared with the reported results from lime precipitation-settling and reverse osmosis treatment field studies in terms of treated water quality, reusability, concentrate (sludge) production rates, water recovery and membrane flux behavior. With a lime precipitation-settling process the treated water would be saturated with calcium sulfate

    Chemical Processing Cell with Nanostructured Membranes

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    A chemical processing cell includes an upstream membrane and a downstream membrane. The upstream membrane generates a first reaction product. The downstream membrane converts the first reaction product to a second reaction product

    Composite membrane fabrication with nanoporous metallic films

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    Magnetron sputtering is a physical vapor deposition method widely used for deposition of thin films of different materials on a variety of substrate materials. Sputtering allows fine control of the film thickness and composition through co-sputtering from multiple target materials. As part of this study thin films have been sputtered on top of membrane substrates. Microfiltration, ultrafiltration, and nanofiltration membranes have been investigated as substrates for thin film deposition. The resulting composite membranes have remained permeable under testing with deionized water. The base nanofiltration membrane showed permeability of 9.75 LMH/bar, while the membrane-film composite had a permeability of 2.76 LMH/bar. Thin films of metallic alloys deposited in this way can be made nanoporous through a process called dealloying. The process involves the removal of the less noble component of an alloy by an etchant creating an open nanoporous structure. The pores created by this method commonly vary from a few nanometers to a few hundred nanometers. This research focuses on using magnetron sputtering to deposit precursor metallic alloy films from 100 to 250nm thick on top of porous membrane substrates. These dense precursor films are then dealloyed to produce pore/ligament structures of approximately 10nm characteristic size. In these studies iron and palladium were chosen as a precursor alloy. A portion of the iron is etched away with sulfuric acid to generate an open nanoporous structure. Fe/Pd nanoparticles have been used with success to dechlorinate various chlorinated organic compounds (COCs) for wastewater treatment purposes. Nanoporous Fe/Pd films have shown similar activity in batch testing towards PCB degradation as nanoparticles. Taken together this means the composite membrane produced by fabricating a high surface area, porous Fe/Pd film on top of a membrane substrate shows promise both as a catalyst and as a platform for separations. This project is funded by NIH-NIEHS-SRC and by NSF KY EPSCOR at the University of Kentucky

    A Membrane-Organic Phase Oxidation Process for the Destruction of Toxic Organics in Hazardous Wastewaters

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    The examination of the extraction/oxidation of organic solutes in a two phase oxidation process was undertaken to discern the important parameters and the process mechanism of this system. Several parameter were adjusted to measure their effect on the disappearance rate of each organic from the water phase. The water to PFD volume ratio proved to be the most sensitive parameter affecting the disappearance rate, although temperature was also significant. Comparison with one phase oxidation systems demonstrated that the water/PFD system improved on the reduction of organics from the water phase. B-napthol oxidation increased over 50% in a 2/6 water/PFD volume ratio compared with the water phase oxidation. Phenol, which had the smallest distribution coefficient of the three organics tested, showed a significant reduction rate in the two phase system which was greater than a water phase oxidation system operating at higher pressures. Napthalene and H-coal wastewater also showed more oxidation in the two phase system than in a single water phase system. These results show that two-phase oxidation is a viable process and testing of the total membrane-oxidation system is in order. The feasibility of membrane concentration step is also demonstrated with model organics and actual wastewaters