Asian Journal of Physical and Chemical Sciences

This Research of electron impact excitation of autoionizing states of rubidium have calculated the  integral cross section using  Distorted Wave Method in the range of incident energy of 15.8 -1000 eV. Numerical calculations have been done using a modified dwba1 fortran computer program which was originally made for hydrogen atom. The results are compared with Borovik work which showed a systematic agreement  with inclusion of absorption potential, it also clear that incomparision with Pangantiwar  and Srivastava there is a good qualitative agreement  though the quantitave is attributed to the Multi Zeta Hartree fork wave functions applied.

The study of natural convective boundary layer flow of heat and mass transfer of incompressible viscous dissipative fluid over a porous stretching vertical surface in the presence of thermal radiation with heat absorption in a porous medium is considered. A similarity variables is used to reduce the governing system of PDEs to a set of nonlinear ordinary differential equations which are solved numerically using shooting technique coupled with fourth order Runge-Kutta method. The numerical computations are presented in graphically and tabular for various fluid parameters controlling the fluid flow of heat and mass transfer. It is observed that an increase in radiation produced a rise in the velocity, temperature and concentration profiles. Skin friction and Nusselt number increased with an increase in the radiation.

Chromium substituted Co-ferrite nanoparticles with general formula Cr_xCoFe_2−xO₄ (0≤ x ≤0.5) have been synthesized by using sol-gel technique. The samples were sintered at 900°C for 3hours. The effect of chromium substitution on dielectric properties of Co-ferrites is reported in this paper. The X-ray diffraction patterns indicate the formation of single phase spinel structure for all the samples. The particle size of all samples was calculated using Debye- Scherer's formula and it is in the range of 56-75 nm. The investigation on dielectric constant (ε'), dissipation  factor(D) and AC conductivity(σ_ac) was carried out at a fixed frequency 1kHz and in the frequency range of 100Hz to 1MHz at room temperature using LCR meter. The frequency dependence of the dielectric constant (ε') and AC conductivity (σ_ac) show a normal dielectric behaviour. The frequency dependence of dissipation factor (D) of the chromium substituted cobalt ferrite samples displays a relaxation peak at certain frequency. This peak suggests the presence of relaxing dipoles in the Cr-Co nano ferrite samples. It is also observed that the broadening of the relaxation peak with chromium-content(x) in dissipation factor versus frequency curve is due to the strengthening of dipole-dipole interactions. The dielectric behaviour of the Cr-doped cobalt nano ferrites is explained based on Koop’s two layer model and Maxwell- Wagner interfacial polarization theory and Debye-relaxation theory.

Computational chemistry is used as computer programming to solve real problems in chemical, pharmaceutical, biotechnological and material science. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids. For the calculation using molecular mechanics by Gaussian 09, two basis set such as Molecular mechanics (Mm+) and Parameterized Model number 3 (PM3) and quantum mechanics such as Density functional theory (DFT) with (WB97XD) and Hybrid functional (HF) are used to make the profile on the physical properties such as total energy, binding energy, hydration energy, dipole moment, heat of formation and energies for Highest occupied molecular orbital (HOMO) and Lowest unoccupied molecular orbital ((LUMO). Nitrobenzene and aniline were tested in two basis set of DFT and HF to make the profile on the physical properties. These physical properties are the theoretical agreement of physical properties to safe the time and chemical in laboratory.

This work presents an experimental study of the drying process of tomato in thin layer thanks to an indirect solar dryer operating in natural convection called "solar tower dryer". This experiment was performed under varying conditions of solar radiation. The objective of this study is to present the drying kinetics of the tomato and determine its physicochemical parameters such as diffusion coefficient and activation energy. The results show that the diffusion coefficient of the tomato is 6.2687 ×10^-9 m²s^-1 with an activation energy estimated at 20.091 kJ.mol^-1.