Clinical electron beams contain an admixture of bremsstrahlung produced in structures in the accelerator head, in field-defining cerrobend or lead cutouts, and in the irradiated patient or water phantom. Accurate knowledge of these components is important for dose calculations and treatment planning. In the first article, “Comparing the Measurement Value of Photon Contamination Absorbed Dose in Electron Beam Field for Varian Clinical Accelerator”, the authors, M Mahdavi, S R M Mahdavi, H Alijanzadeh and M Zabihzadeh, used MCNP-4C code of Monte Carlo for simulating the linear accelerator head. Percentage, depth dose of the electron beam and photon contamination from 6, 9 and 12 MeV electron beam energies were calculated.

In the second article, “A Simple Model to Evaluate Force Constants of Para-Disubstituted Benzenes”, the authors, N Jigeesh and M Rangacharyulu, have evaluated the force constants in para-disubstituted benzenes of the four sulpha drug molecules using a simple force field method. The derived values of stretching force constants were well in agreement with the reported values.

The objective of the third article, “An Approach to the Understanding of Structure and Stability of Atom”, by Seikh Hannan Mandal, is to show that the experimental discoveries in atomic physics are logically connected and how it led to a consistent theoretical explanation of the structure and stability of the atom. As a generalization to Bohr’s quantum condition, the Wilson-Sommerfeld quantization condition for multiperiodic systems is presented with a derivation.

Cosmic rays are high energy charged particles originating in outer space that travel nearly at the speed of light, and strike the earth from all directions. Scientists analyze cosmic rays as ionized radiations because they have the tendency to impact molecules with such force that they knock the electrons off their constituent atoms, creating destructive ions. How to repel them is one of the greatest challenges for human space colonization.

In the fourth article, “Analysis of Cosmic Rays and Their Composition with Reference to Energy Spectrum”, the authors, Dhirendra Kumar Tiwari and Richa Dixit, explained the interactions and particle production of the cosmic ray air showers. The paper also analyzes the energy spectrum which relates to the source of cosmic rays and their propagation to earth over many orders of magnitude in energy. The authors discussed the correlation and interpretation of different observatories.

Novel materials suitable for the development of new photonic devices for high density optical storage, optoelectronics or medical diagnostics that exploit green light sources via frequency up-conversion are currently widely investigated. In the fifth article, “Optical Properties of Rare-Earth Doped Magnesium Borax Glasses”, the authors, Sujeet Jain and Ragini Singh, investigated the optical and spectroscopic properties of magnesium borax glasses doped with rare earths. From the recorded optical absorption spectra, different radiative and optical properties have been evaluated.

In the sixth article, “Theoretical Investigation of the Optical Properties of (Ge0.17Se0.83)100–xInx Glass System”, the authors, Saurabh Tiwari, Ashish Kumar Saxena and Dinesh Saxena, reported the compositional effect of Indium (In) on the optical and physical properties of Germanium (Ge)-Selenium (Se)-Indium (In) system. Optical gap has been determined from heat of atomization data by Balkanski procedure and the energetic distribution of the gap and it has been observed that the optical gap, average heat of atomization and mean bond energy decrease with increasing In content.

In the propagation of radio waves through the atmosphere, the radio refractivity of air is an important parameter to be considered because its space-time distribution results in scattering, sub-refraction, super-refraction, ducting and absorption phenomena. In the seventh article, “Radio Refractive Index Variation with Related Weather Parameters at Surface Level in Ilorin, North Central Nigeria”, the authors, K C Igwe, I A Adimula, O A Falaiye and O D Oyedum, obtained the results which reveal that surface radio refractivity over IIorin, North Central Nigeria, is more variable in the dry season than the wet season, thereby resulting in variation of field strength in the very high frequency band in this region. Also, the relationship between diurnal profile of surface refractivity and related atmospheric variables of temperature, humidity and pressure show that refractivity and temperature are out-of-phase with each other while refractivity and humidity are in phase with each other.

-- BVVSN Prabhakara Rao
Consulting Editor