Studies of Sodium Dodecylbenzenesulfonate-Water-Electrolyte Interactions

A surfactant selective electrode using a PVC membrane was constructed. A surfactant (sodium dodecylbenzene-sulfonate)-H2O system was studied at 15°, 19°, 25°, and 40°C with the PVC electrodes, a Na+ selective electrode, and a conductivity bridge. Pre-micelle regions at the above temparatures were observed. The critical micelle concentrations (CMCb) obtained by the PVC electrodes in salt-free systems are: 1.63x10-3 M at 15°C, 1.48x10-3 M at 19.1°C, 1.52x10-3 M at 25°C, and 1.73x10-3 M at 41.6°C. The CMC\u27c obtained by the Na+ electrode are: 1.62x10-3 M at 15°C, 1.37x10-3 M at 19.3°C, 1.47x10-3 M at 25°C, and 1.98x10-3 M at 40.5°c. The CMC obtained by the conductivity measurement is: 1.62x10-3 M at 25°C. The counterion binding was calculated and it was found that it is not constant. An equation, log[DBS-] = constant - rlog[Na+], was obtained. The r value was calculated mathematically and it was found that it is related only to the slopes of the plots of EMF vs log [NaDBS] obtained by the PVC electrode and the Na+ electrode. Hence the equality of r and the counterion binding proposed by the charged phase separation model is questionable. A decrease of the CMC by the addition of salts (NaNO3 and NaCl) was observed with the PVC electrodes. The surfactant system with Cu2+ and Na+ present was also investigated by the PVC electrodes and by a Cu2+ electrode. Complexation between Cu2+ and the micelles was observed and the solubility product of Cu(DBS)2 was calculated to be about 5x10-10

A tilted spacetime positive mass theorem

We show a spacetime positive mass theorem for asymptotically flat initial data sets with a noncompact boundary. We develop a mass type invariant and a boundary dominant energy condition. Our proof is based on spinors.Comment: 18 pages, 1 figure, comments welcom

Evaluation of nano-antimicrobial coated biomaterials in advanced in vitro co-culture models

Biomaterial-associated infections (BAI) are the major cause of implant failure and can develop many years after implantation, which threatens the device functionality and longevity. Therefore, novel antimicrobial biomaterials and coatings to make surfaces less prone to BAI are essential to develop and evaluate in suitable in vitro models