Archives-September 2012

The purpose of present study was to explore and to compare public and private biology teachers’ views about use of audio visual aid in teaching of Biology at secondary school level. The data for the study was collected from secondary schools teachers of biology. The results of present study show that there is a positive relationship between facility of audio-visual aids and the teacher’s attitude. The findings report that secondary schools teachers of biology do realize the importance using audio visual aids in teaching of biology. However, finings reported that teachers of public sectors were more familiar about the importance of use of audio visual aids for teaching of biology than private sector teachers. It was concluded that in public sector school all teachers were trained as only trained teachers were appointed at public sector schools at secondary level. Finding further reported that there were no proper facilities of audio visual aids for biology teaching. Results further inferred that utilization of audio-visual aids in teaching of biology was very effective as it increases the level of interest and enhances motivation for learning in students and the only visual aid available at maximum secondary school was black board.

This study examines a survey and analysis of the wrong use of the past perfect tenses by students in essay writing. The survey became necessary because of the in-depth deficiency students exhibited in essay writing in West African Senior Certificate Examination (WASSCE) and National Examination Council (NECO). The respondents of the study consisted of final year senior secondary student for the WASSCE and NECO classes and respondents from High Impact Capacity Teacher Building Workshop. They were required to write an essay or composition titled ‘My Best Teacher’ on page I of High Impact Capacity Teacher Building Workshop. It was discovered that there were some similarities in the type of errors, especially in the area of past perfect tenses in the second composition: ‘My First Day in the School (page 48-50). (Taken from Countdown for WASSCE/SSCE, NECO, JME English Language (Ogunsanwo et al 2005).

Cu₂Se particles have been synthesized by the hydrothermal method at a temperature of 200° C. The synthesized nanoparticles were characterized by a variety of techniques like XRD, UV, FTIR, SEM and EDAX. Experimental data reveals that the final product almost consists of hexagonal flakes in the [111] plane. The estimated optical band gap for the particles was found to be within the reported range.

In this paper, we present the concept demonstrating some of the possibilities of nanotechnologies might enable in the future communication devices. Nanotechnology aloows control of physical problem of nanostructures and devices with single molecule precision. The device is build by numerous nano-transistors. This device is used for sensing toxicity of the materials. The devices constructed by nanotechnology can be stretched and folded to desired length since it has the strength of spider silk. As the transistors are temperature dependent, the devices are auto-chargeable when exposed to sunlight (solar energy). Nanoscale electronics are invisible to human eye, the devices are transparent.

We deposited CdS and ZnS chalcogenides thin films on different substrates by Chemical Bath Deposition Technique. Structural, Surface Morphology and Optical properties of as deposited CdS and ZnS films were investigated by XRD, SEM, FTIR and UV-VIS Spectrophotometer. It is found that, the average grain size of CdS and ZnS in the films is 08 to 130nm and 08 to 113nm. The band gap is also calculated from the equation relating absorption co-efficient to wavelength. The band gap indicates the film is transmitting within the visible range and the band gaps changes because of the grain size of the CdS and ZnS in the films. We also observed that, the change in preparative parameters affects the deposition rate of thin films. From the observation, it is clear that the growth rate increases as the deposition temperature, deposition time, molarities of the solution increases. It is also clear that the growth rate increases as the film thickness and grain sizes increases while band gap decreases.

Well-ordered SAMs using adipic acid were formed on the oxide of iron carbon steel surface by immersion method. This leads to ordered, robust monolayers bound to the surface in a tetradentate manner. Monolayer formation takes place when carbon steel is immersed in an aqueous solution containing 60ppm of Cl– and 100ppm of adipic acid for 5 minutes, and rinsing the physisorbed molecules in distilled water and heating in a hot air oven. The adipic acid monolayers on iron oxide steel carbon can withstand rinsing with water, concentrated acid and base exposure. Additionally, these monolayers are stable over the course of at least one week. The formations of monolayers were confirmed by AFM study and FTIR spectra. The SAMs were tested by polarization and EIS electrochemical analysis. The results of this study show that adipic acid monolayers adsorbed on metal surface can reduce electrochemical activity on the surface, often the first step in corrosion.

A study on the DC performance of Nano Quantum Dot Transistor under illumination is presented. A device structure consist of Quantum Dots(QD) in the GaAs layer is considered for illumination. The photoconductive effect in the GaAs and QD layer which increases the 2DEG Channel electron concentration is considered. The I-V Characteristics of Quantum Dot Transistor, under dark and illumination condition have been calculated, plotted and discussed.

Exciton binding energy is obtained in a Zn_xCd_1-xTe/ZnTe strained quantum dot taking into account the phonon confinement effect. The effect of mismatch between the dielectric constants of the dot and the barrier (dielectric mismatch effect) is taken into account in our calculation. The calculations include the effect of exciton and the LO phonon interaction is derived by the effective potential (V_PB) between the electron and hole along with the self energy term (E_self). It is observed that  the potential taking into account the effects of phonon makes the  exciton binding energies more than  the obtained results using a Coulomb potential screened by a static dielectric constant and the optical properties of exciton  in a quantum dot are strongly affected by the confining potential and the quantum size.

The effect of Mn content on donor binding energy of a hydrogenic donor as a function of dot radius in a GaAs diluted magnetic semiconductor quantum dot is investigated. The Mn based GaAs material is the most thoroughly studied ferromagnetic dilute magnetic semiconductor which brings out the relationship between magnetic and semiconducting properties. All the calculations include the exchange interaction of Mn alloy content with an itinerant carrier. The worked out computation are performed within a single band effective mass approximation using variational technique. The binding energy is calculated by varying its dot radius, for various Mn incorporation in Mn based GaAs inner quantum dot surrounded by the GaAlAs outer barrier material.

The effects of magnetic field on the exciton binding energy and the Phosphorous alloy content in a cylindrical Phosphorous doped GaAs quantum dot are investigated with the geometrical confinement. The various Phosphorous alloy concentration in the (xin = <0.3) quantum dot has been taken into account. All the computations to get the electronic states are performed using variational procedure within the single band effective mass approximation by the magnetic field strength. The effect of strain due to the spontaneous and piezoelectric polarizations is included.