Cationic surfactants for demulsification of produced water from alkaline-surfactant-polymer flooding

In this research, demulsification of produced water (which is an oil-in-water emulsion) from alkaline–surfactant–polymer flooding, containing sodium alkyl sulfate, was evaluated using five different surfactants from the classes of nonionic, amphoteric, and cationic. It was observed that only single-tail cationic surfactants, namely, dodecyltriemthylammonium chloride (DTAC) and alkyltrimethylammonium bromide (ATAB), with a concentration of 1000 ppm, were capable of attaining transparent separated water phases following 3 h separation at room temperature with relative separation efficiencies, determined using fluorescence spectroscopy, of 89.4 and 59%, respectively. However, the cationic surfactant dimethyldioctadecylammonium chloride (DDOAC) could achieve a relative separation efficiency of only 28.4% after 13 days, in contrast to nonionic and amphoteric surfactants that did not reveal any progress in demulsification. Similarly, given the demulsifier concentration of 1000 ppm, only DTAC and ATAB reduced the negative surface charge of oil droplets in the produced water after 3 h separation, and large droplets were formed owing to their coalescence after the addition of the respective demulsifiers as viewed by optical microscopy. The dominant emulsification mechanism is believed to be electrostatic stabilization. Consequently, the proposed demulsification mechanism is the formation/adsorption of cationic–anionic pairs at the oil–water interface. When comparing the demulsification performances of various demulsifying surfactants, although high interfacial activity (low interfacial tension (IFT)) is an essential feature for a demulsifier to be considered effective, it was concluded that lower equilibrium IFT does not necessarily result in superior separation efficiency, and other parameters such as type, tail branch number (i.e., single-tail or double-tail), and purity of surfactant may have profound effects on both separation efficiency and demulsification speed of the emulsion. From the dynamic IFT data, it was realized that DTAC and ATAB caused faster demulsification than DDOAC. The undesirable demulsification performance of DDOAC might have been due to its double-tail structure, which confined its interfacial adsorption. The operational variables, including salinity, pH, and temperature, in the demulsification process by DTAC were optimized with respect to the changes of IFT, and the optimum values were found to be 2 wt %, 7.0, and 35 °C, respectively

Towards sustainable polymeric nano-carriers and surfactants: facile low temperature enzymatic synthesis of bio-based amphiphilic copolymers in scCO2

We demonstrate that useful bio-based amphiphilic polymers can be produced enzymatically at a mild temperature, in a solvent-free system and using renewably sourced monomers, by exploiting the unique properties of supercritical CO2 (scCO2). We present the use of a novel near-ambient temperature approach to prepare renewable amphiphilic ABA copolymers in scCO2. Bio-based commercially available monomers have been polymerised to prepare chains with targeted molecular weight. The amphiphilic materials were prepared by end-capping the synthesised polymers with methoxy poly(ethylene glycol) (MPEG) chains in a one-pot high pressure reaction utilising Candida Antarctica Lipase B (CaLB) as a catalyst at a temperature as low as 35 °C. The block copolymers are characterised by 1H-NMR, GPC and DSC in order to carefully assess their structural and thermal properties. These polymers form self-assembled aggregates in aqueous environment and these nanostructures are studied through DLS, TEM and UV-Vis. Highly hydrophobic Coumarin-6 was used as a model to prove dispersion in water of lipophilic molecules. Maximum bubble pressure tests demonstrate the reduction in surface tension of these polymers and comparisons are made directly to commercial polymeric non-ionic surfactants

The Major Surface-Associated Saccharides of Klebsiella pneumoniae Contribute to Host Cell Association

Analysing the pathogenic mechanisms of a bacterium requires an understanding of the composition of the bacterial cell surface. The bacterial surface provides the first barrier against innate immune mechanisms as well as mediating attachment to cells/surfaces to resist clearance. We utilised a series of Klebsiella pneumoniae mutants in which the two major polysaccharide layers, capsule and lipopolysaccharide (LPS), were absent or truncated, to investigate the ability of these layers to protect against innate immune mechanisms and to associate with eukaryotic cells. The capsule alone was found to be essential for resistance to complement mediated killing while both capsule and LPS were involved in cell-association, albeit through different mechanisms. The capsule impeded cell-association while the LPS saccharides increased cell-association in a non-specific manner. The electrohydrodynamic characteristics of the strains suggested the differing interaction of each bacterial strain with eukaryotic cells could be partly explained by the charge density displayed by the outermost polysaccharide layer. This highlights the importance of considering not only specific adhesin:ligand interactions commonly studied in adherence assays but also the initial non-specific interactions governed largely by the electrostatic interaction forces

Suddenly Pressurized Elastomagnetohydrodynamic Channel Flow

The channel flow of a suddenly pressurized visco‐elastic and electrically conducting fluid under the influence of a constant and transversal magnetic field is given analytic treatment. Flow oscillations resulting from the elasticity of the fluid and damping effect of the magnetic field on these oscillations are shown in terms of three parameters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69906/2/PFLDAS-9-10-1970-1.pd

Suddenly Pressurized Elastomagnetohydrodynamic Channel Flow

The channel flow of a suddenly pressurized visco‐elastic and electrically conducting fluid under the influence of a constant and transversal magnetic field is given analytic treatment. Flow oscillations resulting from the elasticity of the fluid and damping effect of the magnetic field on these oscillations are shown in terms of three parameters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69906/2/PFLDAS-9-10-1970-1.pd

Osteoporosi e Attivit\ue0 motoria

These are the results of a study regarding 30 women affected by osteoporosis with an age between 60 and 85 years. These patients attended a physical re-education course that lasted three month. Thanks to the collaboration of an ISEF coacher these patients improved meaningfully both from a densitometric and from a physical and phycological point of view, and it was possible to obtain economic saving, useful both for sanitary stucture and for single subject. Therefore the physical re-education can be consider an effective means of prevention

TestTube: A System for Selective Regression Testing

This paper describes a system called TestTube that combines static and dynamic analysis to perform selective retesting of software systems written in C. TestTube first identifies which functions, types, variables and macros are covered by each test unit in a test suite. Each time the system under test is modified, TestTube identifies which entities were changed to create the new version. Using the coverage and change information, TestTube selects only those test units that cover the changed entities for testing the new version. We have applied TestTube to selective retesting of two software systems, an I/O library and a source code analyzer. Additionally, we are adapting TestTube for selective retesting of nondeterministic systems, where the main drawback is the unsuitability of dynamic analysis for identification of covered entities. Our experience with TestTube has been quite encouraging, with an observed reduction of 50% or more in the number of test cases needed to test typical ..