Selective incorporation of functional dicarboxylates into zinc metal-organic frameworks

Zinc(II) nitrate reacts with different ratios of 1,4-benzenedicarboxylic acid (H(2)bdc) and 2-halo-1,4-benzenedicarboxylic acid (H(2)bdc-X, X = Br or I) to give [Zn(4)O(bdc)(3-x)(bdc-X)(x)], in which preferential incorporation of bdc is observed. The selective incorporation is related to crystal growth rates, and the proportion of incorporated bdc-X rises with increasing reaction time.     

Intermolecular potential energy functions from gaseous viscosity data. Choice of the well depth

Dilute gas viscosity data may be inverted directly to give the intermolecular potential energy function if the well depth is known. The consequences of using different values of the well depth are studied, and it is concluded that the correct value may be distinguished by using second virial coefficient data.     

Scaled particle equation of state for hard non-spherical molecules

Applications of the method of anti-symmetrized product of strongly orthogonal geminals (APSG) to the boron hydrides B₂H₆, B₄H₄, B₄H₁₀, B₅H₉, B₅H₁₁ and B₆H₁₀ are described. Minimal basis sets of Slater-type orbitals are employed throughout. The APSG method is found to act as a localization process, with the B-H (terminal) and B-H (bridge)-B geminals well localized and transferable. Generation of several valence structures for B₅H₉, B₅H₁₁ and B₆H₁₀ suggests that the framework geminals of the preferred structure are of the closed three-centre type, although structures involving open BBB framework geminals are less stable by only a few kcal mol^-1. The principal natural orbital of each geminal is similar to the corresponding orbital produced by various localization criteria, while the weakly occupied natural orbitals are also localized and involve anti-bonding interactions between the component atoms of the bond.     

Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film

La_0.67Ba_0.33MnO₃ (LBMO) thin film is deposited on a 36.7°C SrTiO₃ bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance with the increase in temperature is due to enhanced spin-flip scattering process.     

Perspective Graves triads and triads of perspective inscribed triangles

Any Pappus configuration can be regarded (in six ways) as a triad of triangles, each inscribed in the previous one; such a triad of triangles is called aGraves triad. Graves triads in which each pair of triangles is in perspective may be calledperspective Graves triads; such triads occur in connection with various results in both projective and metrical geometry. In this paper we give a synthetic proof of the existence of perspective Graves triads; the proof is of interest because it holds in allharmonic planes and requires neither the axiom of Pappus nor the full axiom of Desargues. The paper also includes synthetic proofs of other related results.(Results involving perspective Graves triads can be found in [l, p.149] and [2]. This paper is the result of recent correspondence with Guinand concerning [2] and [3].)     

Molar extinction coefficients of some carbohydrates in aqueous solutions

Molar extinction coefficients of some carbohydrates viz. l-arabinose (C₅H₁₀O₅), d-glucose (C₆H₁₂O₆), d-mannose (C₆H₁₂O₆), d-galactose (C₆H₁₂O₆), d(-) fructose (C₆H₁₂O₆) and maltose (C₁₂H₂₄O₁₂) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well.     

Removal of methoxyethoxymethyl ethers with trimethylsilyl chloride-sodium iodide

Trimethylsilyl chloride-sodium iodide has been used for the mild removal of methoxyethoxymethyl ethers.     

Pappus lines and Leisenring lines

The three Leisenring points of a Pappus hexagon are collinear on the Leisenring line of the hexagon. The six Leisenring lines associated with two triplets of collinear points are concurrent in threes.     

Equation of state for systems of hard non-spherical molecules

The equation of state for systems of hard prolate spherocylinders has been obtained using a Monte Carlo simulation method. The result in the fluid region are compared with the predictions of scaled particle theory, and are found to agree quite well. The equation of state is significantly different from that for hard sphere molecules, and it is concluded that the effects of non-spherical shape must be explicitly dealt with.