A Review of Semiconductor Quantum Well Devices

Quantum well devices feature very thin epitaxial layers of heterostructure III-V and II-VI semiconductor materials that are grown using Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapour Deposition (MOCVD) growth techniques. These devices are monolithically integrated with various optoelectronic devices to provide photonic integrated circuit with increased functionality .The quantum well structure can be realized with GaAs as wells and AlGaAs as barriers for wavelength about 0.8 μm and InGaAsP/InP offering longer wavelengths (0.9-1.6 μm). Quantum well devices find their applications in quantum well lasers or improved lasers, photodetectors, modulators and switches. These devices operate much faster, more economically and have led to a million increases in speed, a point of enormous importance to the telecommunication and computer industry. Keywords: Quantum well, Semiconductor, Heterostructures, Lasers, Detectors, Modulators

Evaluation of Aeromagnetic Data Over Some Parts of Lower Benue Trough, Nigeria Using Spectral Analysis

We obtained, processed, and interpreted spectral analyses of aeromagnetic data across a portion of the Lower Benue Trough with the goal of estimating the depth to magnetic basement, modeling a conspicuous magnetic anomaly, identifying the basement topography, and evaluating basin configurations. Qualitative interpretation based on visual examination of the total magnetic intensive anomalies map, residual contour map, and first vertical derivative map reveals major faults trending east-west (E-W) and minor faults trending northeast-southwest (NE-SW), which is consistent with the structure of the lower Benue Trough. The western portion of the research region indicates structural change near the towns of Afikpo and Ishiagu, indicating areas of documented intrusive igneous body activity. According to the quantitative interpretation of the aeromagmatic data, the average sedimentary thickness is between (2.3 and 3.2 kilometers) and Quantitative interpretation utilizing spectral analysis identifies two distinct depth sources in the region: shallower sources ranging from 1.09 to 1.6 kilometers in the southern portion of the research area, and deeper sources ranging from 1.61 to 4.90 kilometers in the northern section. Additionally, the research reveals that the depths to the centroid and magnetic bodies (sedimentary thicknesses) vary between 5.02 and 10.65 kilometers and 0.23 and 3.5 kilometers, respectively. It was recommended that a ground magnetic survey be used in conjunction with this work to provide a more conclusive result

SIR modeling of a disease spread with a detectable and undetectable infectious syndrome

This paper proposes a model for the analysis of an infectious disease spread using a renewed deterministic model of Susceptible-Infected-Recovered (SIR). The SIR is based on compartments or partitions. In this case, the contaminated (infected) class is divided into two sub-compartments: detectable and undetectable. Numerical simulations are carried out to test the obtained theoretical results, and presentations follow graphicall

Oxo-Functionalization and Reduction of the Uranyl Ion through Lanthanide-Element Bond Homolysis:Synthetic, Structural, and Bonding Analysis of a Series of Singly Reduced Uranyl-Rare Earth 5f¹-4f^<em>n</em> Complexes

The heterobimetallic complexes [{UO2Ln-(py)2(L)}2], combining a singly reduced uranyl cation and a rare-earth trication in a binucleating polypyrrole Schiff-base macrocycle (Pacman) and bridged through a uranyl oxo-group, have been prepared for Ln = Sc, Y, Ce, Sm, Eu, Gd, Dy, Er, Yb, and Lu. These compounds are formed by the single-electron reduction of the Pacman uranyl complex [UO2(py)(H2L)] by the rare-earth complexes LnIII(A)3 (A = N(SiMe3)2, OC6H3But 2-2,6) via homolysis of a Ln−A bond. The complexes are dimeric through mutual uranyl exo-oxo coordination but can be cleaved to form the trimetallic, monouranyl “ate” complexes [(py)3LiOUO(μ-X)Ln(py)(L)] by the addition of lithium halides. X-ray crystallographic structural characterization of many examples reveals very similar features for monomeric and dimeric series, the dimers containing an asymmetric U2O2 diamond core with shorter uranyl U=O distances than in the monomeric complexes. The synthesis by LnIII−A homolysis allows [5f1-4fn]2 and Li[5f1-4fn] complexes with oxobridged metal cations to be made for all possible 4fn configurations. Variable-temperature SQUID magnetometry and IR, NIR, and EPR spectroscopies on the complexes are utilized to provide a basis for the better understanding of the electronic structure of f-block complexes and their f-electron exchange interactions. Furthermore, the structures, calculated by restricted-core or allelectron methods, are compared along with the proposed mechanism of formation of the complexes. A strong antiferromagnetic coupling between the metal centers, mediated by the oxo groups, exists in the UVSmIII monomer, whereas the dimeric UVDyIII complex was found to show magnetic bistability at 3 K, a property required for the development of single-molecule magnets.JRC.E.6-Actinide researc

Strongly coupled binuclear uranium-oxo complexes from uranyl oxo rearrangement and reductive silylation

The most common motif in uranium chemistry is the d0f0 uranyl ion [UO2]21 in which the oxo groups are rigorously linear and inert. Alternative geometries, such as the cis-uranyl, have been identified theoretically and implicated in oxo-atom transfer reactions that are relevant to environmental speciation and nuclear waste remediation. Single electron reduction is now known to impart greater oxo-group reactivity, but with retention of the linear OUO motif, and reactions of the oxo groups to form new covalent bonds remain rare. Here, we describe the synthesis, structure, reactivity and magnetic properties of a binuclear uranium–oxo complex. Formed through a combination of reduction and oxo-silylation and migration from a trans to a cis position, the new butterfly-shaped Si–OUO2UO–Si molecule shows remarkably strong UV–UV coupling and chemical inertness, suggesting that this rearranged uranium oxo motif might exist for other actinide species in the environment, and have relevance to the aggregation of actinide oxide clusters.JRC.E.6-Actinides researc

Evaluation of Aeromagnetic Data Over Some Parts of Lower Benue Trough, Nigeria Using Spectral Analysis

We obtained, processed, and interpreted spectral analyses of aeromagnetic data across a portion of the Lower Benue Trough with the goal of estimating the depth to magnetic basement, modeling a conspicuous magnetic anomaly, identifying the basement topography, and evaluating basin configurations. Qualitative interpretation based on visual examination of the total magnetic intensive anomalies map, residual contour map, and first vertical derivative map reveals major faults trending east-west (E-W) and minor faults trending northeast-southwest (NE-SW), which is consistent with the structure of the lower Benue Trough. The western portion of the research region indicates structural change near the towns of Afikpo and Ishiagu, indicating areas of documented intrusive igneous body activity. According to the quantitative interpretation of the aeromagmatic data, the average sedimentary thickness is between (2.3 and 3.2 kilometers) and Quantitative interpretation utilizing spectral analysis identifies two distinct depth sources in the region: shallower sources ranging from 1.09 to 1.6 kilometers in the southern portion of the research area, and deeper sources ranging from 1.61 to 4.90 kilometers in the northern section. Additionally, the research reveals that the depths to the centroid and magnetic bodies (sedimentary thicknesses) vary between 5.02 and 10.65 kilometers and 0.23 and 3.5 kilometers, respectively. It was recommended that a ground magnetic survey be used in conjunction with this work to provide a more conclusive result

What Is the Preferred Conformation of Phosphatidylserine–Copper(II) Complexes? A Combined Theoretical and Experimental Investigation

Phosphatidylserine (PS) has previously been found to bind Cu²⁺ in a ratio of 1 Cu²⁺ ion per 2 PS lipids to form a complex with an apparent dissociation constant that can be as low as picomolar. While the affinity of Cu²⁺ for lipid membranes containing PS lipids has been well characterized, the structural details of the Cu–PS₂ complex have not yet been reported. Coordinating to one amine and one carboxylate moiety on two separate PS lipids, the Cu–PS₂ complex is unique among ion–lipid complexes in its ability to adopt both <i>cis</i> and <i>trans</i> conformations. Herein, we determine which stereoisomer of the Cu–PS₂ complex is favored in lipid bilayers using density functional theory calculations and electron paramagnetic resonance experiments. It was determined that a conformation in which the nitrogen centers are <i>cis</i> to each other is the preferred binding geometry. This is in contrast to the complex formed when two glycine molecules bind to Cu²⁺ in bulk solution, where the <i>cis</i> and <i>trans</i> isomers exist in equilibrium, indicating that the lipid environment has a significant steric effect on the Cu²⁺ binding conformation. These findings are relevant for understanding lipid oxidation caused by Cu²⁺ binding to lipid membrane surfaces and will help us understand how ion binding to lipid membranes can affect their physical properties

Instrumental Neutron Activation Analysis (INAA) As-sessment of REE of Soil from Mining Site Umuahia, Abia State, South East, Nigeria

In this work, the main goal was to examine the REE concentration and distribution pattern in soil from Umuahia, Abia State, Southeast, Nigeria, in a clay mining site compared with a non-contaminated site approximately 3 km away. The REE were determined by Instrumental Neutron Activation Analysis (INAA) at IPEN, Brazil. The main mineralogy of the samples was determined by XRD. The following REE were determined: Ce, Eu, La, Lu, Nd, Sm, Tb and Yb. Soil samples from the mining area present quartz and kaolinite as their main constituents, with REE concentrations comparable with that of the Upper Continental Crust and the North American Shale Composite. The calculated Geoaccumulation index (IGeo) indicate that REE have natural origin and ∑LREEN/∑HREEN ratio show an enrichment of the light over heavy REE, in samples of the clay mining area