Direct Monitoring of Ultrafast Redox Commutation at the Nanosecond and Nanometer Scales by Ultrafast Voltammetry: From Molecular Wires to Cation Releasing Systems

This review documents that, contrary to the general impression that molecular electrochemistry is mostly devoted to the analysis of reaction mechanisms induced by electron transfer into homogeneous solutions of molecules, its concepts and methods are perfectly suited to the investigation of extremely fast molecular events occurring within nano- and sub-nanometric distances from a working electrode surface. Ultrafast cyclic voltammetry (i.e., up to the range of a few megavolts per second) coupled to online electronic compensation of ohmic drop is thus shown to provide direct measurements of extremely fast electron transfer between redox centers tethered to electrodes, by conducting molecular bridges, or of dendrimers adsorbed onto the electrode surface. This allows discussing in particular the role of counterions in the process of electronic commutation of self-assembled monolayers.     

Development of a Novel Parenteral Formulation for Tetrazepam Using a Lipid Emulsion

A novel parenteral formulation for tetrazepam (10 mg/ml) was developed using lipid emulsions. This formulation utilized a new lipid emulsion formulation, which was developed by changing the polarity of the oil phase. It was found that increasing the polarity of the oil phase resulted in enhanced solubility of tetrazepam. Tetrazepam showed higher solubility in a mixture of castor oil and middle-chain triglycerides (MCTs) (1:1) than in any other oil investigated. This mixture resulted in low interfacial tension and moderate viscosity, which seemed to be the optimum oil phase. In addition, to increase the concentration of tetrazepam, an emulsion formulation containing 30% oil phase was produced and optimized. The drug-free emulsion formulation showed fine particle sizes with an imperceptible change in physicochemical properties after more than 2 years on the shelf. As a result, it was possible to produce a parenteral emulsion formulation containing 10 mg/ml tetrazepam. No change in the physicochemical properties of the emulsion was observed after the addition of tetrazepam. The tetrazepam emulsion showed stable behavior during the autoclaving process and good shelf stability for at least 10 months as well. Tetrazepam itself also displayed good stability during the autoclaving process and also showed good shelf stability in this emulsion formulation.     

Influence of sulfate solution concentration on the formation of gypsum in sulfate resistance test specimen

The sulfate concentration, which is required to form gypsum from portlandite, was derived from thermodynamical calculations and experimental measurements. The obtained results were compared to the sulfate concentrations in laboratory solutions that are commonly used to test the performance of concrete exposed to sulfate attack and also to sulfate concentrations that can be expected under field conditions. It was derived that the formation of gypsum can strongly affect the performance of binders in the tests, but has a less marked impact under most field conditions. An SEM investigation of mortar bars that were exposed to different sulfate concentrations supports the suggestion made.     

Efficiency enhancement of a dielectric barrier plasma discharge by dielectric barrier optimization

The characteristic feature of a dielectric barrier discharge (DBD) is the dielectric barrier placed between the electrodes. In the present work, the influence of the dielectric barrier to the properties of a DBD in air was investigated. Spectroscopic characterization of the DBD and electrical measurements were carried out. It was shown that the efficiency of a DBD can be considerably improved by optimizing the dielectric barrier. The dielectric material should possess an appropriate relative permittivity and thickness. For thin dielectric barriers, a high secondary emission coefficient becomes important. Additionally, the use of only one dielectric barrier is advantageous.     

In‐line analysis of the influence of monomeric and oligomeric hindered amine on the hydrolysis of polycarbonate in a PC/ABS blend

The polycarbonate/polyacrylonitrile butadiene styrene (PC/ABS) blends lose mechanical properties when exposed to outdoor conditions. This is due to the ultraviolet (UV) induced photo‐oxidation of the PC phase and the polybutadiene portion of the ABS. It is known that ABS can be stabilised against terrestrial light by the use of hindered amine in combination with a UV absorber. However, such hindered amine cannot be used when PC is present in a multi component polymer blend. The hydrolysis of PC is accelerated when a small amount of hindered amine light stabilisers (HALS) is incorporated in the resin and is exposed to elevated temperature. In this article the effect of monomeric and oligomeric hindered amine on the hydrolysis of PC during the compounding of PC/ABS blend in a twin screw extruder at 240°C is observed by means of in‐line UV‐vis spectroscopy. Tinuvin 765 was used as monomeric hindered amine and Tinuvin 622 as oligomeric hindered amine. The molecular weight of the compounded sample was determined by gel permeation chromatography (GPC) and the rheological properties were observed using an online viscometer. It was found that the extent of hydrolysis induced by the oligomeric hindered amine is less compared to monomeric amine. It was also observed that polymeric hindered amine imparts better dispersion of the ABS phase into the polymer blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010