Electrical properties and Schottky diodes using N-N′diphenyl-1-4phenylenediamine

Thin films of, N-N′diphenyl 1-4phenylene-diamineane are prepared using vacuum sublimation technique. The electrical conductivity from room temperature down to 127 K is studied. It is found that the conduction of charge carriers obeys T^−1/2 dependence on temperature. The average hopping distance, hopping energy, density of states and their variation due to post-deposition heat treatment are studied. Schottky diodes are fabricated with gold as ohmic contact and aluminium as Schottky contact. From the observed current voltage characteristics the saturation current density, diode ideality factor and the barrier height are determined. Their variation with air annealing is also investigated.     

Multibody dynamics of aircraft occupants seated behind interior walls

To improve aircraft crash safety, conditions critical to occupants survival during a crash must be known. In view of the importance of this problem, studies of post-crash dynamic behavior of victims are necessary in order to reduce severe injuries. In this study, crash dynamics program SOM-LA/TA, incorporating a dynamic model of the human body with a finite element model of the seat structure was used. Modifications were performed in the program for reconstruction of an occupant's head impact with the interior walls or bulkhead. A viscoelastic-type contact force model was used to represent the compliance characteristics of the bulkhead. Correlated studies of analytical simulations with impact sled test results were accomplished. A parametric study of the coefficients in the contact force model was then performed in order to obtain the correlations between the coefficients and the Head Injury Criteria. A measure of optimal values for the bulkhead compliance and displacement requirements was thus achieved in order to keep the possibility of a head injury as little as possible. This information could in turn be used in the selection of suitable materials for the bulkhead, instrument panel, or interior walls of an aircraft.     

Imaging in turbid media with intensity-modulated lasers

We describe the formation of a narrow beam for intensity-modulated electromagnetic radiation propagating through highly scattering materials. We propose to use this beam to reconstruct images, similar to X-ray back-projection techniques. For sufficiently high modulation frequency, the photon density wave is primarily carried by photons that suffer small or no large-angle scattering, which gives rise to the beam’s narrow divergence. The beam-narrowing concept is supported by large-scale numerical simulations to examine the quality of the imaging.     

Operational characteristics and power scaling of a transverse flow transversely excited CW CO<Subscript>2</Subscript> laser

Transverse flow transversely excited (TFTE) CO₂ lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow and discharge volume. It was observed in a TFTE CW CO₂ laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant. The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity. This necessitated revision of the scaling laws for designing this type of high power CO₂ laser. Experimental results of laser performance for different electrode separations are discussed and the modifications in the scaling laws are presented.     

Thermodynamic metal-ligand stability constants of rare earths with N-p-chlorophenyl-m-substituted benzohydroxamic acids

The thermodynamic metal ligand stability constants of rare earths, La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Bu³⁺, Gd³⁺ and Tb³⁺, with N-p-chlorophenyl-m-substituted benzohydroxamic acids in dioxan-water (60–70%) media at 25° C, have been determined by the potentiometric method. The effect of basicity of the ligand, central metal ion and the order of stability constants are discussed. The order of stability constants of rare earths with the hydroxamic acids is La<Pr<Nd<Sm<Eu<Gd>Tb.     

Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography

A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min^–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL^–1 for pioglitazone and 0.10–10.00 g mL^–1 for glimepiride.     

Photocondensation polymers: Polybenzopinacols. II. Photolytic coupling of aromatic diketones

Photolytic condensations of p,p′-dibenzoyldiphenyl sulfide, p,p′-dibenzoyldiphenyl ether, p,p′-dibenzoyldiphenylmethane, and p,p′-dibenzoyldiphenylethane with a 100-W long-wavelength ultraviolet lamp gave polypinacols having inherent viscosities ranging from 0.12 to 0.45. Treatment of the same monomers under similar conditions with a 450-W ultraviolet lamp produced polypinacols having inherent viscosities ranging from 0.04 to 0.37.     

PHOTOSENSITIZATION OF MELANINS: A COMPARATIVE STUDY

Abstract— Measurements of photosensitized free-radical production and oxygen consumption have been made in several melanin systems. The melanins studied were cysteinyldopa melanin (a model for pheomelanin), natural pheomelanins extracted from red hair and from red chicken feathers, and eumelanin extracted from bovine eyes. Rose Bengal was used as photosensitizer. A significant enhancement in the rates of free radical production and oxygen consumption was found in all systems when sensitizer was present. The largest effects were found with cysteinyldopa melanin and effects on pheomelanins were shown to be greater (by factors of4–6) than on eumelanins.