The non-crossing rule in molecular quantum mechanics

Previous mathematical proofs of the non-crossing rule concerning the potential energy curves of a diatomic molecule are examined and criticised. A new treatment is presented which is simple and mathematically rigorous.     

Expeditious implementation of two new methods for analysing the pigment composition of photosynthetic specimens

Two new methods for analysing the pigment composition of photosynthetic samples have been developed during the last few years. One, called the spectral reconstruction method, uses linear least-squares fitting, while the other, named the Gauss-peak spectra method, entails non-linear optimisation; each has some advantages over the other, but both use a large number of data points and surpass the traditional method which uses absorbance at a few wavelengths. In order to make the new methods transparent to experimentalists who are not well versed in statistical analysis, curve fitting and interpolation, simple procedures are described for implementing the methods with the aid of a spreadsheet. The problem of analysing a sample containing chlorophyll c, which is difficult to isolate in a form sufficiently pure to serve as an analytical standard, is also briefly addressed.     

Synthetic strategies toward the synthesis of polyphenolic natural products: Pauciflorol F and isopaucifloral F: A review

Pauciflorol F and isopaucifloral F are very important polyphenolic natural products and exhibit a variety of biological activities such as antibiotic, anticancer, anti-HIV, antioxidant, antifungal, and anti-inflammatory activities. These important molecules have gained significant attraction of medicinal chemists and several new strategies have been developed toward the synthesis of pauciflorol F and isopaucifloral F. This review article summarizes the major synthetic approaches adopted for the synthesis of these two indanone-based compounds.     

Kinetics of phase transition and thermal stability in Se80?x Te20Zn x (x?=?2, 4, 6, 8, and 10) glasses

Se_80?x Te₂₀Zn _x (x?=?2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E _t), activation energy of crystallization (E _c), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K _o) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se₇₀Te₂₀Zn₁₀ glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T _g, onset crystallization temperature T _c, and peak crystallization temperature T _p. In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples.     

Scattering from a coated nihility circular cylinder placed in chiral metamaterial

The scattering of electromagnetic plane wave from a coated nihility circular cylinder placed in chiral metamaterial is investigated. The nihility cylinder is coated with chiral or chiral-nihility metamaterial and the medium hosting the coated cylinder is also considered as chiral or chiral-nihility metamaterial. The vector wave equation is used to find out the solution for the fields scattered from the concentric chiral ciruclar cylinders immersed in chiral metamaterial. Inner chiral cylinder is reduced to nihility cylinder taking permittivity and permeability approaching to zero with chirality parameter equal to zero. Coated perfect electric conductor (PEC)/perfect magnetic conductor (PMC) are obtained by taking very large value of permittivity/permeability of the inner cylinder. Numerical results for fields reflected from coated nihility cylinder are compared with those obtained for coated PEC/PMC cylinder. Our results for the special case of dielectric coated nihility/PEC cylinders in free space are shown to be in agreement with already published results thus validating the scheme of analysis.