Resonant states in GaAs/Ga1-xAlxAs Multi-Quantum-Wells

The effect of buffer layers on resonant states in a Multi-Quantum-Well (MQW) sandwiched between two substrates is investigated here theoretically. These resonances appear as well-defined peaks in the density of states (DOS). The local and total densities of states are obtained from an analytical determination of the Green functions. Due to the substrate/buffer layer/ MQW /substrate interaction, different kinds of resonant states are found and their properties are investigated. We show in particular that an incident electron in the left-hand side substrate is transmitted in the right hand side substrate of the structure with large time delays in the phase time. The peaks in the phase time associated with the transmission coefficient are found to be similar to those corresponding to the DOS. The intensity of these peaks associated with extended states in MQW’s and Tamm like states lying at the MQW/buffer layer interface, strongly depends on the width of the buffer layer.The effect of buffer layers on resonant states in a Multi-Quantum-Well (MQW) sandwiched between two substrates is investigated here theoretically. These resonances appear as well-defined peaks in the density of states (DOS). The local and total densities of states are obtained from an analytical determination of the Green functions. Due to the substrate/buffer layer/ MQW /substrate interaction, different kinds of resonant states are found and their properties are investigated. We show in particular that an incident electron in the left-hand side substrate is transmitted in the right hand side substrate of the structure with large time delays in the phase time. The peaks in the phase time associated with the transmission coefficient are found to be similar to those corresponding to the DOS. The intensity of these peaks associated with extended states in MQW’s and Tamm like states lying at the MQW/buffer layer interface, strongly depends on the width of the buffer layer

Electronic properties in heterostructures

Using the interface response, the effect of internal surface of Single Quantum Well (SQW) and of Superlattice (SL) (Substrate / Single Quantum Well and of Substrate / Superlattice interfaces) are studied in term of changing the heterostructures parameters and keeping constant the parameters of substrate. Surface and interface considered as well as planar defects are associated with the states which are localised in mini gaps (MG). Electronic properties are touched in this way and their investigation is made by band structures and variational density of states (DOS).Using the interface response, the effect of internal surface of Single Quantum Well (SQW) and of Superlattice (SL) (Substrate / Single Quantum Well and of Substrate / Superlattice interfaces) are studied in term of changing the heterostructures parameters and keeping constant the parameters of substrate. Surface and interface considered as well as planar defects are associated with the states which are localised in mini gaps (MG). Electronic properties are touched in this way and their investigation is made by band structures and variational density of states (DOS)

Vibrational Properties in heterostructures

This is a comprehensive path about theoretical approaches to the vibrational properties in periodic and multilayered structures. The phonons modes taking a large part of our work are detailed beyond the limit offered by the area targeted by this sort of paper. In fact, in many cases of this type of materials, metallic, semiconductor or insulator, these modes are investigated. Although, the electronic properties are devoted, generally, to the semiconductor ones as well as the optical properties will be derived in the second paper of this volume. Another topic can be touched which concerns the coupling effect between phonons and electrons or photons and electrons giving rise to interesting results; but it is not addressed here. Throughout this paper, we bring forth the theoretical model currently used by us, and the results obtained in consequence. This model is called the response function based on the Green function and its properties are stressed as well as the results obtained.This is a comprehensive path about theoretical approaches to the vibrational properties in periodic and multilayered structures. The phonons modes taking a large part of our work are detailed beyond the limit offered by the area targeted by this sort of paper. In fact, in many cases of this type of materials, metallic, semiconductor or insulator, these modes are investigated. Although, the electronic properties are devoted, generally, to the semiconductor ones as well as the optical properties will be derived in the second paper of this volume. Another topic can be touched which concerns the coupling effect between phonons and electrons or photons and electrons giving rise to interesting results; but it is not addressed here. Throughout this paper, we bring forth the theoretical model currently used by us, and the results obtained in consequence. This model is called the response function based on the Green function and its properties are stressed as well as the results obtained

Pathology of peste des petits ruminants virus infection in small ruminants and concurrent infections

Peste des petits ruminant (PPR) is a systemic viral disease of goats and sheep characterized by gastrointestinal and respiratory system lesions with high rate of mortality. Rhinitis, conjunctivitis, serous-mucopurulent naso-ocular discharge, pneumonia, coughing, dispnea, erosive-ulcerative oral lesions, and diarrhea are the most prominent clinicopathological features of the disease. Histopathologically, pseudomembraneous stomatitis, necrotic tonsillitis, fibrinohemorrhagic enteritis, and proliferative interstitial pneoumonia are seen. Syncytial cells and cytoplasmic and/or nuclear eosinophilic inclusion bodies are considered as pathognomonic. Like the other morbilli viruses, PPR virus can also cause lesions in the kidney, brain, and abomasum. The PPRV tropism can be explained by the mechanism in which PPRV binds to receptors on the cell surface. The PPR in small ruminants often shows coassociation with secondary viral, bacterial, and parasitary infections