Open Access Original Research Article

Structural and Solvent Dependence of the Electronic Properties and Corrosion Inhibitive Potentials of 1,3,4-thiadiazole and Its Substituted Derivatives- A Theoretical Investigation

O. E. Oyeneyin

Physical Science International Journal, Page 1-8
DOI: 10.9734/PSIJ/2017/36555

The frontier molecular orbitals (FMOs) are very important for describing chemical reactivity and understanding the static molecular reactivity. The HOMO and LUMO energies of 1,3,4-thiadiazole and its substituted derivatives were calculated using the hybrid B3LYP method with a large polar 6-31G* basis set in vacuum, acetone, ethanol and tetrahydrofuran (THF). It was revealed that substitution at position -2 with -NO2, -CH3, -NH2, -CN and -CH=C(CN)COOH  results in enhanced reactivities due to reduction of the energy band gap, Eg. It also altered some important molecular properties like η, S, ΔN, μ, α and β. Substituted -NO2, -CN and -CH=C(CN)COOH may possess better inhibitive potentials and better reactivities than other derivatives on the basis of studied parameters. It was observed that solvent media affect molecular properties.

 

Open Access Original Research Article

Fundamental Acoustic Wave Generation in Crystalline Organic Conductors with Two Conducting Channels

Danica Krstovska

Physical Science International Journal, Page 1-13
DOI: 10.9734/PSIJ/2017/36390

A linear thermoelectric generation of a fundamental acoustic wave in organic conductors with two conducting channels, quasi-one dimensional (q1D) and quasi-two dimensional (q2D), is analyzed theoretically. Specifically, the case when an acoustic wave with a fundamental frequency w is generated along the most conducting axis of the multi-band organic conductor a-(BEDT-TTF)2KHg(SCN)4 is considered. The magnetic field and angular dependences of the wave amplitude for two boundary conditions, isothermal and adiabatic are obtained. Findings show that the wave amplitude for the isothermal boundary is much larger than the one for the adiabatic boundary although there is a heat flux through the conductor's surface in the former. This is completely different compared to the case of a wave generated along the least conducting axis and the possible reasons behind this behavior are discussed. The angular oscillations of the fundamental wave amplitude are associated with the charge carriers motion on both the cylindrical part and quasi-planar sheets of the Fermi surface in a tilted magnetic field. The changes in the wave amplitude with the field orientation are correlated with the corresponding angular changes in the in-plane thermoelectric coefficient and thermal conductivity. Following the magnetic field behavior of both the in-plane electromagnetic and thermal skin depth we find that the wave generation and propagation in the plane of the layers are determined mainly by the thermal wave as its skin depth is thousand times larger than the one of the electromagnetic wave. It is shown that both the q1D and q2D charge carriers contribute to the observation of the effect but the group of charge carriers with a q1D energy spectrum is significantly dominant in the generation of the fundamental acoustic wave in the plane of the layers.

 

Open Access Original Research Article

Natural Radioactivity in Vegetables from Selected Areas of Manyoni District in Central Tanzania

Pendo B. Nyanda, Leonid L. Nkuba

Physical Science International Journal, Page 1-10
DOI: 10.9734/PSIJ/2017/34746

The study determined the mean concentrations of natural radionuclides, the annual intake of radionuclides and annual effective dose due to the ingestion of Vegetables from selected areas of Manyoni in Tanzania. Thirty (30) bunches of leafy vegetable samples grouped into five categories were collected randomly from different locations of the study area. The activity concentration levels of U-238, Th-232, and K-40 were measured by direct γ‐ray spectrometry using HPGe detector by Compton suppression method. The radioactivity in vegetables ranged from 2.2 Bq/kg – 36.8 Bq/kg for U-238, 4.1 Bq/kg – 30.1 Bq/kg for Th-232 and 700.0 Bq/kg – 2520.0 Bq/kg for K-40, respectively. Except for K-40, the activity levels reported into this study were lower than the activity levels of vegetables reported from various parts of Tanzania. However, the concentrations of radionuclides in the vegetables samples found in this study were higher than the world average values suggested by the UNSCEAR. The annual effective dose due to intake of vegetables was 2.73 mSv/year. This dose value was found 9.4 times higher than total exposure per person resulting from the ingestion of terrestrial radionuclides as proposed by UNSCEAR. Also the dose was higher than the annual dose limit of 1 mSv/year recommended by the ICRP for the general public. The annual intakes of U-238 and Th-232 in vegetables were much higher than the world reference value in diets. Hence a conclusion could be made that vegetables cultivated in Manyoni might expose the population to high radiation dose which might be detrimental to their health.

 

Open Access Original Research Article

Elemental Characterization and Source Identification of Fine Particulate Matter (PM2.5) in an Industrial Area of Lagos State, Nigeria

J. M. Okuo, I. E. Chiedu, B. Anegbe, F. O. Oyibo, W. Ojo

Physical Science International Journal, Page 1-11
DOI: 10.9734/PSIJ/2017/36683

Fine particles (PM2.5) are mainly generated by combustion processes including emissions from motor vehicles, combustion of fossil fuel for power generation and large industrial processes such as ore and metal smelting. They may also include natural emissions such as fine windblown soils, sea spray and smoke from biomass burning. Based on the field study conducted, the concentrations of PM2.5 at the different locations vary with respect to anthropogenic activities. The PM2.5 levels obtained ranged from 14.00 to 32.67 µg/m3 during wet season and 18.67 to 34.67 µg/m3 during dry season. Trace elements especially heavy metals are significant components of PM2.5 in industrial environments. The heavy metals are of particular concern due to their persistence in the environmental media and their human toxicity. The particulate matter concentration was obtained using Casella cel-712 microdust pro-real time dust monitor and flame atomic absorption spectrophotometer was used to determine the elemental content. The Enrichment Factor (EF) analysis showed very high enrichment for the elements; Pb, Cd, Cr, Cu, Ni, Na, K, Mg, and Ca in the fine fraction (PM2.5). The Principal Component Analysis explained three common contributing sources of fine particulates (PM2.5) such as entrained soil, sea salt and combustion. Spatial variation was performed and mean concentration of some of the elements in the various locations showed significant difference at P<0.05. Correlation matrix was also determined and some of the elements were strongly correlated while some were not. Seasonal variation for the elemental concentration also revealed that the mean values for some of the elements were statistically significant at P<0.05 for both seasons.

 

Open Access Original Research Article

Synthesis of Polar Dielectric Barium Magnesium Niobate at Low Sintering Temperature: Dielectric Relaxation and AC Conductivity Study

K. N. Singh, P. K. Bajpai

Physical Science International Journal, Page 1-13
DOI: 10.9734/PSIJ/2017/37111

Ba(Mg1/3Nb2/3)O3 is an important microwave polar dielectric material. However, the large leakage current and losses due to defects incorporated during high temperature processing restricts its use in microwave devices. We have synthesized phase pure perovskite Ba(Mg1/3Nb2/3)O3 by controlling the cooling rates during calcination and sintering, using two stage columbite method at relatively low sintering of 1150°C. X-ray diffraction has been used to determine the structural details. Ceramics stabilizes in hexagonal perovskite structure with lattice constant a=5.7803A˚, c=7.0780A˚. Sintered ceramics with density > 93% exhibit surface morphology having homogeneous grain distribution with average grain size is ≈1.0-2.0 mm. Temperature and frequency dependent dielectric response has been analyzed to understand the dielectric dispersion. Dielectric response is temperature independent up to ≈180°C. Beyond this temperature dielectric dispersion is observed which is more pronounced at lower frequencies and associated with significant electrical conductivity. Impedance spectroscopic formalism has been used to separate out the contributions from gains and grain boundary using equivalent circuit approach, whereas, electrical modulus approach has revealed the role of conductivity relaxation. The frequency/ temperature dependent ac conductivity suggests conduction being thermally activated process. AC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.