Heat of formation of solid solution of alkali halides

Based on a semicontinuum model, the electrostatic, the polarisation, and the repulsive energy change of a lattice is calculated numerically, as a function of the relaxation of the nearest neighbouring ions of a substitutional impurity in an alkali halide crystal. It is found that for a particular displacement, the total energy change of the lattice is a minimum. Thus the heat of formation of a dilute solid solution is obtained. Here, we report calculations on the heat of formation of the following systems-Na⁺ in LiCl, Li⁺ in NaCl, K⁺ in NaCl, Na⁺ in KCl, Rb⁺ in NaCl, Na⁺ in RbCl, F^? in NaCl, Cl^? in NaF. Br^? in NaCl and Cl^? in NaBr.     

Novel intramolecular rearrangement leading to the synthesis of biheterocyclic indole-benzoimidazole derivatives on solid phase

[reaction: see text] A novel intramolecular SNAr rearrangement observed during the S-alkylation of benzoimidazole-2-thione with alpha-haloacetophenone is reported. The rearrangement led to the formation of a new benzoimidazole-based intermediate, which is further utilized for the generation of a new biheterocyclic indole-benzimidazole derivatives with a two-point diversity.     

Kinetics of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticle evolution from an organic precursor

-Fe₂O₃ particles with an average size of 10 nm were prepared by heating the precipitates obtained from a homogeneous solution of stearic acid and hydrated iron (III) nitrate. The compositional and thermal characteristics of the precipitates were studied with the aid of Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Presence of -Fe₂O₃ nanoparticles in the heat treated product was established by X-ray diffraction (XRD) investigations. The average particle size was estimated from the XRD patterns by single line profile analysis and directly from transmission electron microscopic (TEM) images. Kinetic analysis of the calorimetric data revealed that nucleation and growth type kinetic law remain operative during the process and the activation energy of the process is 115 kJ/mol.     

An atomic mutation cycle for exploring RNA's 2'-hydroxyl group

The 2'-hydroxyl group fulfills numerous structural and functional roles in RNA, including those of hydrogen bond donor and acceptor. While loss of function upon 2'-deoxynucleotide substitution establishes the importance of specific 2'-hydroxyl groups within RNA, this approach provides no information about how these hydroxyl groups impart their functional contribution. We use an atomic mutation cycle to evaluate the functional importance of the 2'-hydroxyl group's hydrogen atom. Using the Tetrahymena ribozyme reaction, we challenge the cycle to expose the catalytic contribution of the cleavage site 2'-hydroxyl group and its associated hydrogen bond network. The results establish the viability of this cycle as an approach to reveal 2'-hydroxyl groups that donate functionally significant hydrogen bonds.     

Analytical properties of the amidoxime group. XII

Journal of Thermal Analysis and Calorimetry - The acid-base equilibria of succinediamidoxime (SIDA) were studied by means of potentiometric and thermometric techniques. RefinedpK values (pK...     

Modified electronic charge densities of alkali bromide crystals

The free ion wavefunctions of the outermost electrons of the alkali bromides have been modified by considering the effect of the crystal lattice. The nearest neighbours of an ion are considered as extended charges while the rest of the ions are approximated as point charges. A Hartree-Fock-Slater Scheme has been utilised to determine the wavefunction through a numerical procedure. The corresponding modified spherical electronic charge densities of the ions indicate the extension of the positive ion radii and contraction of the negative ion radii in the crystal.     

CNDO/2 calculations on the structure and properties of chlorine difluoride

According to the open-shell CNDO/2 calculations on ClF₂, performed by using the computer programme developed by Pople, Beveridge and Dobosh, the molecule is linear and stable, with equilibrium bond length 1.507Å and binding energy ?173.7 kcal/mole. The molecule has a tendency to dimerise and to disproportionate into ClF₃ and ClF. The netd-orbital population in the monomer is 0.88. Bonding characteristics and other molecular properties are also discussed.     

Binariness and rational choice

The concept of numerical representability of preferences together with maximality is at the heart of the concept of rationality embodied in classical optimization models. The difficulty of representing social preferences arises from inherent intransitivities thrown up by democratic voting procedures and by non-binary choice rules which need to be adopted to cope with these intransitivities. An alternative (weaker) concept of representability is developed and it is shown that this concept can partially accommodate intransitivity and non-binariness. ‘Weak transitivity’ and ‘weak binaries’ conditions are provided and it is shown that these conditions are necessary and sufficient for ‘weak representability’. While the weak transitivity condition would be violated by social aggregation procedures, the non-binary functions used by social choice theorists do indeed satisfy the condition of ‘weak binariness’.     

Analysis of stone column-supported geosynthetic-reinforced embankments

In the present paper, the behavior of stone column-supported geosynthetic-reinforced embankments has been studied. The soil arching effect is incorporated in the study to determine the stresses acting on stone columns as well as soft soil. The effect of stiffness of the stone column is also incorporated in the present study. Based on the stress action in the improved ground, stress concentration ratio, axial strain of geosynthetic reinforcement, tension developed in it and settlement of the improved soft ground are determined by using the developed methodology. Present analytical method is also verified with several current design methods. It is observed from parametric studies that modular ratio or stiffness of the stone columns, spacing to diameter ratio, height of the embankment, depth of the soft soil, stiffness of the geosynthetic reinforcement significantly affect the behavior of geosynthetic-reinforced stone column-supported embankments resting on soft soil.