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.     

Polyadic codes of prime power length

Polyadic codes constitute a special class of cyclic codes and are generalizations of quadratic residue codes, duadic codes, triadic codes, m-adic residue codes and split group codes, which have good error-correcting properties. In this paper, we give necessary and sufficient conditions for the existence of polyadic codes of prime power length. Examples of some good codes arising from the family of polyadic codes of prime power length are also given.     

Solving large-scale semidefinite programs in parallel

We describe an approach to the parallel and distributed solution of large-scale, block structured semidefinite programs using the spectral bundle method. Various elements of this approach (such as data distribution, an implicitly restarted Lanczos method tailored to handle block diagonal structure, a mixed polyhedral-semidefinite subdifferential model, and other aspects related to parallelism) are combined in an implementation called LAMBDA, which delivers faster solution times than previously possible, and acceptable parallel scalability on sufficiently large problems. This work was supported in part by NSF grants DMS-0215373 and DMS-0238008.     

Robust locally testable codes and products of codes

We continue the investigation of locally testable codes, i.e., error‐correcting codes for which membership of a given word in the code can be tested probabilistically by examining it in very few locations. We give two general results on local testability: First, motivated by the recently proposed notion of robust probabilistically checkable proofs, we introduce the notion of robust local testability of codes. We relate this notion to a product of codes introduced by Tanner and show a very simple composition lemma for this notion. Next, we show that codes built by tensor products can be tested robustly and somewhat locally by applying a variant of a test and proof technique introduced by Raz and Safra in the context of testing low‐degree multivariate polynomials (which are a special case of tensor codes). Combining these two results gives us a generic construction of codes of inverse polynomial rate that are testable with poly‐logarithmically many queries. We note that these locally testable tensor codes can be obtained from any linear error correcting code with good distance. Previous results on local testability, albeit much stronger quantitatively, rely heavily on algebraic properties of the underlying codes. © 2006 Wiley Periodicals, Inc. Random Struct. Alg., 2006     

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.     

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.     

Stereospecific approach to α,β-disubstituted nitroalkenes via coupling of α-bromonitroalkenes with boronic acids and terminal acetylenes

(Z)-α-Bromo-β-substituted nitroethylenes undergo facile Suzuki coupling with aryl, heteroaryl, and vinylboronic acids in the presence of Pd(PPh₃)₄ as catalyst to afford (E)-α,β-disubstituted nitroethylenes in high yield (up to 95%) and complete specificity. Similar coupling of α-bromonitroethylenes with terminal acetylenes (Sonogashira coupling) provides a novel route to (E)-nitroenynes. These Pd-catalyzed coupling methods offer a convenient and stereospecific entry into a diverse array of synthetically and biologically useful α,β-disubstituted nitroethylenes.