Perfluoroalkylporphyrin complexes as active catalysts for the reaction of isobutane with oxygen and the decomposition of tert-butyl hydroperoxide

A new family of metalloporphyrin complexes having perfluoroalkyl groups in the meso-positions of the ring are active catalysts for the oxidation of isobutane to tert-butyl alcohol, TBA, and for the decomposition of tert-butyl hydroperoxide to TBA. This discovery extends the limited number of meso-substituents that can be used to enhance catalytic activity and fits the postulate that groups that withdraw electrons from the porphyrin periphery give rise to active catalysts for alkane oxidation. The perfluoroalkyl groups also confer oxidative stability, hydrophobicity and lower cost to the catalyst.     

A study of seeds of musk melon (Cucumis melo L.): A lesser known source of edible oil

The oil content and oil characteristics of seeds of 91 accessions of musk melon (Cucumis melo), including two allied species collected from different parts of the world, have been studied to assess their variability. Oil content (on a whole seed basis) ranged from 12.5 to 39.1% and iodine values from 106.0 to 124.1. Gas liquid chromatographic analysis showed that only linoleic, oleic, palmitic and stearic acids were present. Unsaturated fatty acids constituted 64.6–88.2% of the total fatty acids present. The proportion of kernel in the seeds of different accessions, varied from 25.0 to 74.1% and contributed significantly to the total oil content of the whole seed. A similar relationship existed in the case of the 100-seed weight.     

Electromechanical properties of knitted fabric integrated with laser engraved carbon-loaded fiber

In this article, the electromechanical properties of laser-engraved carbon-loaded fiber integrated with knitted fabric are investigated theoretically and experimentally. The fabric can be used as flexible strain sensor due to the change of resistance caused by change of the fabric configuration. In order to improve the sensitivity, linearity, repeatability of the knitted fabric strain sensor, laser treatment and integration with knitted structure are proposed. It can be seen from the results that the sensitivity of the fiber can be improved by laser engraving due to the change of the rigidity of fiber and conductive contacts created by laser corrosion on the surface of fiber. The repeatability of the integrated fabrics is improved due to the “push” effect created by fabric structures. Meanwhile, the linearity of fabric sensor with laser-treated fiber is higher than that without laser treatment due to the fiber pretension applied by fabric structure and the decrease of rigidity of fiber.     

Overpotential decay behavior—I. Complex electrode reactions involving adsorption

Evaluation of the open-circuit overpotential decay behaviour of a previously polarized electrode provides a useful way of examining the kinetics of the electrode reaction and the electrochemical adsorption behaviour of reaction intermediates involved in the electrode process. Limiting cases have previously been considered. Analytical and numerical solutions of equations for the open-circuit decay of potential of a polarized electrode are now given for a complete range of coverages of the electrode by electro-active intermediates arising in a complex sequence and obeying a Frumkin-type isotherm. The behavior for various values of the interaction/heterogeneity factor g in the adsorption isotherm is derived. The course of the potential-log (time) relations for various g values are compared with the experimental behavior observed in chlorine evolution on C and Ir. The overpotential decay and the Tafel slopes are closely related to the adsorption pseudo-capacitance behaviour of the electrode interface bearing electroactive chemisorbed intermediates.     

Studies on the nutritional quality of some cucurbit kernel proteins

The nutritional quality of proteins of four cultivated cucurbit species was measured by nitrogen balance. The biological value of muskmelon, watermelon and pumpkin proteins were 59, 64, and 67 respectively. A value of 70 for bittergourd kernels was calculated from chemical score. Lysine was the first limiting essential amino acid in all the proteins. The leucine:isoleucine and leucine:lysine ratios did not show imbalance.     

Electrostatic microactuators for precise positioning of neural microelectrodes

Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 microm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation, packaging and interconnect issues will be necessary before this technology can be validated in long-term experiments.     

Overpotential decay behavior—II. Generalized treatment for reaction pathways involving discharge,recombination and electrochemical desorption of adsorbed intermediates

Theoretical equations are developed to represent the overpotential decay behavior of a polarized electrode following current interruption in the course of a faradaic reaction. Three mechanistic schemes are considered: (a) Fast discharge—slow recombination and/or slow electrochemical desorption; (b) Slow discharge—fast recombination of fast electrochemical desorption; (c) Coupled discharge—electrochemical desorption or recombination. Analytical solutions are presented for the above cases under conditions of negligible backward reaction rate and interaction parameter g. Some experimental and theoretical difficulties specific to further generalization of the theory of overpotential buildup and decay processes are outlined, and the manner in which the coverage variation with overpotential could influence the measured stoichiometric number is briefly discussed.     

Electron-Scattering Mechanisms in Heavily Doped Silicon Carbide MOSFET Inversion Layers

Hall-effect measurements of n-channel MOS devices were used to determine the main scattering mechanisms limiting mobility in SiC MOSFETs. MOS-gated Hall characterization, which was performed as a function of gate bias and body bias, indicates that surface-roughness scattering and Coulomb scattering are the main scattering mechanisms limiting electron mobility in SiC MOSFETs at room temperature. A charge-sheet model, including incomplete ionization and Fermi-Dirac statistics, is used to calculate the surface electric fields in order to develop an expression for surface-roughness scattering. In the samples used for this paper, at electron sheet densities less than 1.8times10¹² cm^-2, Coulomb scattering dominates, while surface roughness is dominant at higher sheet densities.