BCS and BEC p-wave pairing in Bose-Fermi gases

The pairing of fermionic atoms in a mixture of atomic fermion and boson gases at zero temperature is investigated. The attractive interaction between fermions, that can be induced by density fluctuations of the bosonic background, can give rise to a superfluid phase in the Fermi component of the mixture. The atoms of both species are assumed to be in only one internal state, so that the pairing of fermions is effective only in odd-l channels. No assumption about the value of the ratio between the Fermi velocity and the sound velocity in the Bose gas is made in the derivation of the energy gap equation. The gap equation is solved without any particular "ansatz" for the pairing field or the effective interaction. The p-wave superfluidity is studied in detail. By increasing the strength and/or decreasing the range of the effective interaction a transition of the fermion pairing regime, from the Bardeen-Cooper-Schrieffer state to a system of tightly bound couples can be realized. These composite bosons behave as a weakly-interacting Bose-Einstein condensate.Comment: 14 pages, 6 eps-figures. To be published in European Physical Journal

Solitary waves in the Nonlinear Dirac Equation

In the present work, we consider the existence, stability, and dynamics of solitary waves in the nonlinear Dirac equation. We start by introducing the Soler model of self-interacting spinors, and discuss its localized waveforms in one, two, and three spatial dimensions and the equations they satisfy. We present the associated explicit solutions in one dimension and numerically obtain their analogues in higher dimensions. The stability is subsequently discussed from a theoretical perspective and then complemented with numerical computations. Finally, the dynamics of the solutions is explored and compared to its non-relativistic analogue, which is the nonlinear Schr{\"o}dinger equation. A few special topics are also explored, including the discrete variant of the nonlinear Dirac equation and its solitary wave properties, as well as the PT-symmetric variant of the model

Characterization of transport across polyamide hydrazide ultrafiltration membranes

79-84<span style="font-size:11.0pt;line-height: 115%;font-family:Calibri;mso-fareast-font-family:" times="" new="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">The transport characterization of aromatic polyamide hydrazide (APAH) ultrafiltration membranes has been discussed. The average pore radius of these membranes is evaluated using modified poiseulle's flow and gaseous permeation methods. Separation of polyethylene glycols (PEG) of varying molecular weights and complexed polyvalent ionic species across these membranes are reported as a function of applied pressure. The molecular weight cut off (MWCO) of these membranes are predicted using Sourirajan's preferential sorption and capillary flow mechanism and are compared with experimental values in order to test the applicability of the mechanism for such membranes. The chemical and radiation stability aspects of these membranes are also discussed.</span

Casting and characterization of cellulose acetate butyrate based UF membranes

This paper describes the development of ultrafiltration (UF) membranes from cellulose acetate butyrate polymer (CAB). The casting conditions are studied with reference to changes in composition of the casting solution, total thickness, solvent evaporation period and gelation bath temperature (GBT). The membranes are characterized in terms of product permeation rates and solute separation using poly (ethylene) glycols (PEG) of different average molecular weights, molecular weight cut-off (MWCO), pore size distribution profiles and scanning electron micrographs (SEM) of either surface of the membrane samples. The separation behaviour of CAB membranes prepared for turbidity, colouring matter, hardness and uranyl ion from aqueous streams indicate the feasibility of their use in water and effluent treatment applications

Studies on fouling and gel polarisation aspects of polyvinyl butyral blended cellulose acetate ultrafiltration membrane by resistance model approach

55-60Ultrafiltration (UF) process is gaining increasing attention for process in g a variety of chemical effluent streams. A large number of polymeric candidates have been identified as potentially useful UF membrane candidates. A series of UF membranes from polyvinyl butyral blended cellulose acetate were synthesized and their fouling characteristics were investigated with respect to changing polarity of the polymer candidate. The results are analysed using resistance model approach using polyethylene glycol and polyethyleneimine solutes. Membrane fouling and gel polarisation aspects are studied from the observed changes in water permeation rates when polar and nonpolar macromolecular solutes are employed. The effect of operating pressure, time and concentration were studied and the various resistances are quantified. Attempts were made to predict gel polarisation resistance using a simplified model

Studies on ultrafiltration Membrane systems based on cellulosic and polysulfone polymers

376-378Ultrafiltration (UF) membranes have been prepared from aromatic polysulfone and cellulose acetate polymers using the appropriate polymer, solvent and additive composition, The membranes have been characterized in terms of pure water permeability (PWP), membrane constant (A), solute transport parameter (DAM/Kδ)NaCl and average pore size on the skin surface. The UF performance has been evaluated in terms of water permeation velocity and solute separation using polyethylene glycol solute (PEG-6000). Characterization data and UF performance data have also been discussed

Preparation, characterization and performance of polyethersulfone ultrafiltration membranes

Asymmetric ultrafiltration (UF) membranes were prepared from locally made wholly aromatic polyethersulfone (PES) polymer, similar to Vitrex type, using aprotic solvents and organic additives by phase inversion method. The effect of nature of additive, solvent, ambient humidity during membrane casting and gelling medium on membrane performance were studied. The membranes were characterized in terms of separation behaviour far polyethylene glycol-5000 solute, molecular weight cut off (MWCO) profile and direct electron microscopic observations. The performance of UF membranes for sodium sulfate, rhodamine-B dye and oligomers of starch hydrolyzate are reported as a function of pressure

Synthesis and characterization of low molecular weight cut off ultrafiltration membranes from cellulose propionate polymer

This pager describes the synthesis and characterization of low molecular weight cut-off ultrafiltration (UF) membranes from cellulose propionate (CP) polymer using dimethyl acetamide solvent. The casting conditions are studied with reference to changes in the nature of additive and additive to solvent ratio. The membranes are characterized in terms of product permeation rate, solute retention for different electrolytes, as a function of feed concentration and pressure. The retention of different dyes are also included. Molecular weight cut off profiles using polyethylene glycol solutes of different molecular weights are presented. The separation behaviour of oil-water and milk protein systems are presented in order to highlight the fouling resistance of CP membranes