Electrocatalytic activity of sol-gel-prepared RuO2/Ti anode in chlorine and oxygen evolution reactions

Electrocatalytic properties of RuO₂/Ti anode with different coating masses, which are prepared by the alkoxide sol-gel procedure, are investigated in chlorine and oxygen evolution reactions by polarization measurements and electrochemical impedance spectroscopy in H₂SO₄ and NaCl electrolytes. According to polarization measurements, the activity of anodes at overpotentials below 100 mV is independent of coating mass. However, impedance measurements above 100 mV reveal changes in the activity of anodes in chlorine evolution reaction for different coating masses. The diffusion limitations related to the evolved chlorine are registered in low-frequency domain at 1.10 V (SCE), diminishing with the increase in potential to the 1.15 V (SCE). The observed impedance behavior is discussed with respect to the activity model for activated titanium anodes in chlorine evolution reaction involving formation of gas channels within porous coating structure. Gas channels enhance the mass transfer rate similarly to the forced convection, which also increases the activity of anode. This is more pronounced for the anode of greater coating mass due to its more compact surface structure. The more compact structure appears to be beneficial for gas channels formation. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 10, pp. 1173–1179. The text was submitted by the authors in English.     

The evolution of comprehensive two-dimensional gas chromatography (GC x GC)

For a technology little over a decade old, comprehensive two-dimensional gas chromatography (GC x GC) has quickly reached the status of one of the most powerful analytical tools for volatile organic compounds. At the heart of any GC x GC system is an interface, which physically connects the primary and the secondary columns and acts to preserve the separation obtained in the first dimension (first column) while allowing additional separation in the second dimension. The paper presents a review of the technology, including fundamental principles of the technique, data processing and interpretation and a timeline of inventive contributions to interface design. In addition, applications of the technique are presented, with a more detailed discussion of selected examples.     

Sodium bromide catalysed one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component cyclocondensation under microwave irradiation and solvent free conditions

Sodium bromide catalysed three-component cyclocondensation of aryl aldehydes, alkyl nitriles and dimedone proceeds under microwave irradiation in solvent free conditions to give highly functionalised tetrahydrobenzo[b]pyrans in excellent yields.     

An integrated process for purification of lysozyme, ovalbumin, and ovomucoid from hen egg white

This article describes an integrated process for simultaneous purification of lysozyme, ovalbumin, and ovomucoid from hen egg white. The crude egg white extract was passed through a cation exchanger Streamline trade mark SP and the bound lysozyme was eluted with 5% ammonium carbonate, pH 9.0, containing 1 M NaCl after elution of avidin. This partially purified lysozyme was further purified 639-fold on dye-linked cellulose beads. Ovalbumin and ovomucoid did not bind to Streamline SP. Ovalbumin could be precipitated from this unbound fraction by 5% trichloroacetic acid, and ovomucoid was removed from the supernatant by precipitation with ethanol. The yields of lysozyme, ovomucoid, and ovalbumin were 77, 94, and 98%, respectively. All the purified proteins showed single bands on sodium dodecyl sulfate polyacrylamide gel electrophoresis. All the steps are easily scalable, and the process described here can be used for large-scale simultaneous purification of these proteins in the pure form.     

Purification and characterization of a solvent stable protease from Pseudomonas aeruginosa PseA

A solvent tolerant Pseudomonas aeruginosa PseA strain was isolated from soil. It secreted a novel alkaline protease, which was stable and active in the presence of range of organic solvents, thus potentially useful for catalysis in non-aqueous media. The protease was purified 11.6-fold with 60% recovery by combination of ion exchange and hydrophobic interaction chromatography using Q-Sepharose and Phenyl Sepharose 6 Fast Flow matrix, respectively. The apparent molecular mass based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was estimated to be 35,000 Da. The enzyme was stable in the pH range of 6.0-9.0, the optimum being 8.0. The Km and Vmax towards caseinolytic activity were found to be 2.7 mg/ml and 3 micromol/min, respectively. The protease was most active at 60 degrees C and characterized as a metalloprotease because of its sensitivity to EDTA and 1,10-phenanthroline. It was tested positive for elastase activity towards elastin-orcein, thus appears to be an elastase, which is known as pseudolysin in other strains of P. aeruginosa. The protease withstands range of detergents, surfactants and solvents. It is stable and active in all the solvents having log P above 3.2, at least up to 72 h. These two properties make it an ideal choice for applications in detergent formulations and enzymatic peptide synthesis.     

Small and large signal analysis using circuit model of InGaAs/InP based uni-travel carrier photodiode

An equivalent circuit model of uni-traveling carrier photodiode (UTC-PD) is developed from integral carrier density rate equation and few important properties of the device such as the electrical and optical characteristics are evaluated by employing advanced device physics. Circuit model incorporates chip and package parasitic of the device quite simply to provide practical behaviour of UTC-PD. We have developed small signal ac circuit model which is useful for the analysis of low power modulation characteristics of the device and dc circuit model which is advantageous to find wavelength dependent responsivity fairly accurately. At high optical input power the device bandwidth is found to be increased through enhancement of self-induced field in the absorption region and high output power can be derived from the device when absorption width is large. Such condition calls for large signal analysis. We have developed large signal circuit model by combining few mathematical transformations with small signal circuit model with different circuit element values. Our large signal model is unique that the same circuit can be used for both small and large signal analysis. With large signal model the optical power induced bandwidth improvement and output photocurrent saturation are explained. Large signal model is validated through linearity and IP3 analysis which found close agreement with the measured results.