Spectroscopic and spectroelectrochemical characterization of acceptor--sigma spacer--donor monolayers

A novel self-assembled monolayer based on benzoquinone--sigma spacer--ferrocene assembly has been prepared on the surface of gold. The preceding paper gives the reaction conditions for the synthesis of the monolayer and a detailed electrochemical characterization of the assembly. In the present paper, the monolayer structure and the orientation of the redox moieties are followed by a detailed spectroscopic analysis. The monolayer has been characterized by reflectance absorbance IR spectroscopy, FT-Raman spectroscopy, and X-ray photoelectron spectroscopy at every step of modification. Additionally, spectroelectrochemical studies have been carried out by coupling Raman spectroscopy with cyclic voltammetry to elucidate the structural variations associated with the monolayer as a function of applied dc bias.     

Reaction of allenylmagnesium and allenylindium bromides with nitrile oxides: synthesis of novel 5-butynyl- and 5-methylisoxazoles

5-Butynylisoxazoles were obtained in high yields through a domino addition, C-O heterocyclization involving allenylmagnesium bromide and benzonitrile oxide in dry THF, in which the corresponding 5-methylisoxazoles were isolated in trace amounts. However, when the reactions were attempted in aqueous media using allenylindium bromide, 5-methylisoxazoles were formed as the sole products in high yields.     

Antioxidants and a new germacrane sesquiteroene from Carissa spinarum

A new germacrane derivative, care none (1) was isolated from the stems of a well-known medicinal plant, Carissa spinarum L. together with a new ester, 3'-(4'-methoxyphenyl)-3-oxo-ropionyl hexadecanoate (2). Their structures were established using 1D, 2D NMR spectroscopic and synthetic methods. The chloroform extract of the plant displayed strong antioxidant (DPPH) activity. Several other known compounds were also isolated for the first time from this active extract. The antioxidant activity of major lignans was studied.     

Influence of backbone conformation on protein aggregation

Effect(s) of organic solvents on an all beta-sheet protein are investigated to understand the influence of backbone conformation on protein aggregation. Results obtained in the present study reveal that protein aggregation is accompanied by the formation of non-native beta-sheet conformation. In contrast, induction of non-native helical segments in the protein is found to inhibit aggregation. The differential effects of the secondary structures on protein aggregation are proposed to stem from the disparity in the nature of the hydrogen bonds and packing of the side chains of hydrophobic residues in the beta-sheet and alpha-helix conformation. In our opinion, the results of the present study provide useful hints to develop methods to alleviate the problems of both in vitro and in vivo protein aggregation.     

Electrical conductivity and dielectric constant measurements of liquid crystal-gold nanoparticle composites

The behaviour of the anisotropic electrical conductivity of liquid crystal-gold nanoparticle (LC-GNP) composites consisting of a commercially available room temperature nematic compound doped with alkylthiol-capped GNPs has been investigated. The nematic-isotropic transition of the composite decreases nearly linearly with increasing X, the concentration of GNP (in weight %) at a rate of about 1°C /weight %. The inclusion of GNPs increases the electrical conductivity of the system with the value increasing by more than two orders of magnitude for X = 5%. However, the anisotropy in conductivity, defined as the ratio of the conductivity along (σ_∥) and orthogonal (σ_⊥) to the director shows a much smaller but definite decrease as X increases.     

Measurement of velocity and kinetic energy of turbulence in swirling flows and their numerical prediction

Swirling flows are often employed in gas turbine combustion systems and high intensity industrial furnaces. A detailed analysis of the turbulence in the flow is necessary to achieve optimum combustion conditions. In this paper a method has been described to measure the turbulence levels in three directions using a hot wire anemometer. So far there is no established method available for measurement of turbulence in swirling and recirculating flows. The present method, it is hoped, will bridge the gap. The merit of the present method is the use of a single-wire probe rather than the X-probe. The method has been used for the measurement of turbulence levels in swirling recirculating flows generated by vane swirlers. From the measured turbulence levels, the kinetic energy of turbulence has been calculated and the results are compared with a well-established numerical prediction method. Mean velocity measurements have also been made using a 3-hole Pitot probe. The agreement between the measured and predicted values is quite satisfactory.     

Intermediate-range order in permanently densified GeO2 glass

Information about the partial structure factors of densified GeO2 glass has been obtained from neutron and x-ray diffraction measurements. Densification causes a reduction in the length scale of the intermediate range order (IRO). The difference structure factors obtained by combining the x-ray and neutron data so as to eliminate one partial structure factor at a time shows the greatest effects when the Ge-Ge correlations are eliminated and least when O-O correlations are eliminated. This implies that the reduced length scale results from a decrease in the next-nearest neighbor Ge-O and O-O distance caused by a rotation about the Ge-O-Ge bonds and a distortion of the GeO4 tetrahedra.     

An improved method of triggering oscilloscopes for dynamic-strain measurements

In dynamic-strain measurements of wave-propagation phenomena using an oscilloscope, a trigger signal is necessary to initiate the single-sweep operation. This technical note describes the use of an analog differentiator to produce reliable trigger signals by differentiating the output of a trigger strain gage. It is shown that the differentiator produces a strong trigger signal with a delay of less than 5-μs duration.