Short-time activation analysis with and without A6LiD converter

Neutron activation analysis (NAA) at various irradiation and measurement systems of the Institute's TRIGA mark II reactor provides a choice of sample oriented analyzing systems. This is demonstrated on the analysis of waste products, on an analysis of the phase content of a high-T_c superconductor and on a fluorine analysis in a standard reference material.     

Gas transport in heterogeneous polymer blends : II. Blends of polydimethylsiloxane and poly(ethylene-copropylene) elastomers

The solution and transport of propane in blends of polydimethyl siloxane and poly(ethylene-co-propylene) elastomers has been studied in the range 25–50°C. The dependence of the blend permeability on composition was determined and compared with the Maxwell and other expressions for transport in heterogeneous media.     

Polynomials orthogonal with respect to discrete convolution

The concept of “Discrete Convolution Orthogonality” is introduced and investigated. This leads to new orthogonality relations for the Charlier and Meixner polynomials. This in turn leads to bilinear representations for them. We also show that the zeros of a family of convolution orthogonal polynomials are real and simple. This proves that the zeros of the Rice polynomials are real and simple.     

Extremal measures for a system of orthogonal polynomials

We characterize the extremal measures of an indeterminate moment problem associated with a system of orthogonal polynomials defined by a three-term recurrence relation.     

New convenient one-step synthesis of 4-arylphthalaz-1 -ones

4-Arylphthalaz-1-ones (2a–e) are prepared by the hitherto unknown reaction of N-aminophthalimide (1) with aromatic hydrocarbons under Friedel-Crafts conditions. The reaction of N-aminophthalimide with Grignard reagents presents another convenient method for the synthesis of 4-alkyl or 4-arylphthalaz-1-ones.     

Intersubband transitions and refractive index changes in coupled double quantum well with different well shapes

In this study, both the linear intersubband transitions and the refractive index changes in coupled double quantum well (DQW) with different well shapes for different electric fields are theoretically calculated within framework of the effective mass approximation. Results obtained show that intersubband transitions and the energy levels in coupled DQW can importantly be modified and controlled by the electric field strength and direction. By considering the variation of the energy differences, it should point out that by varying electric field we can obtain a blue or red shift in the intersubband optical transitions. The modulation of the absorption coefficients and the refractive index changes which can be suitable for good performance optical modulators and various infrared optical device applications can be easy obtained by tuning applied electric field strength and direction.     

Water-mediated binding of agents that target the DNA minor groove

Small molecule complexes with DNA that incorporate linking water molecules are rare, and the DB921-DNA complex has provided a unique and well-defined system for analysis of water-mediated binding in the context of a DNA complex. DB921 has a benzimidazole-biphenyl system with terminal amidines that results in a linear conformation that does not possess the appropriate radius of curvature to match the minor groove shape and represents a new paradigm that does not fit the classical model of minor groove interactions. To better understand the role of the bound water molecule observed in the X-ray crystal structure of the DB921 complex, synthetic modifications have been made in the DB921 structure, and the interactions of the new compounds with DNA AT sites have been evaluated with an array of methods, including DNase I footprinting, biosensor-surface plasmon resonance, isothermal titration microcalorimetry, and circular dichroism. The interaction of a key compound, which has the amidine at the phenyl shifted from the para position in DB921 to the meta position, has also been examined by X-ray crystallography. The detailed structural, thermodynamic, and kinetic results provide valuable new information for incorporation of water molecules in the design of new lead scaffolds for targeting DNA in chemical biology and therapeutic applications.