43 research outputs found
Theoretical investigation of InAs/GaSb type-II pin superlattice infrared detector in the mid wavelength infrared range
In this study, we present the theoretical investigation of type-II InAs/GaSb superlattice p-i-n detector. Kronig-Penney and envelope function approximation is used to calculate band gap energy and superlattice minibands. Variational method is also used to calculate exciton binding energies. Our results show that carriers overlap increases at GaSb/InAs interface on the higher energy side while it decreases at InAs/GaSb interface on the lower energy side with increasing reverse bias due to shifting the hole wavefunction toward to the GaSb/InAs interface decisively. Binding energies increase with increasing electric field due to overall overlap of electron and hole wave functions at the both interfaces in contrast with type I superlattices. This predicts that optical absorption is enhanced with increasing electric field. © 2013 American Institute of Physics
Annual and perennial Medicago show signatures of parallel adaptation to climate and soil in highly conserved genes
Human induced environmental change may require rapid adaptation of plant populations and crops, but the genomic basis of environmental adaptation remain poorly understood. We analysed polymorphic loci from the perennial crop Medicago sativa (alfalfa or lucerne) and the annual legume model species M. truncatula to search for a common set of candidate genes that might contribute to adaptation to abiotic stress in both annual and perennial Medicago species. We identified a set of candidate genes of adaptation associated with environmental gradients along the distribution of the two Medicago species. Candidate genes for each species were detected in homologous genomic linkage blocks using genome-environment (GEA) and genome-phenotype association analyses. Hundreds of GEA candidate genes were species-specific, of these, 13.4% (M. sativa) and 24% (M. truncatula) were also significantly associated with phenotypic traits. A set of 168 GEA candidates were shared by both species, which was 25.4% more than expected by chance. When combined, they explained a high proportion of variance for certain phenotypic traits associated with adaptation. Genes with highly conserved functions dominated among the shared candidates and were enriched in gene ontology terms that have shown to play a central role in drought avoidance and tolerance mechanisms by means of cellular shape modifications and other functions associated with cell homeostasis. Our results point to the existence of a molecular basis of adaptation to abiotic stress in Medicago determined by highly conserved genes and gene functions. We discuss these results in light of the recently proposed omnigenic model of complex traits
Patterns of linkage disequilibrium and association mapping in diploid alfalfa (M. sativa L.)
Cardiac abnormalities 15 years and more after adriamycin therapy in 229 childhood survivors of a solid tumour at the Institut Gustave Roussy
Electron transport in electrically biased inverse parabolic double-barrier structure
A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed by using the non-equilibrium Green's function approach based on the finite difference method. It is found that the resonant peak of the transmission coefficient, being unity for a symmetrical case, reduces under the applied electric field and depends strongly on the variation of the structure parameters
Electron transport in electrically biased inverse parabolic double-barrier structure
BATI, Mehmet/0000-0001-7154-2198; BATI, Mehmet/0000-0003-2304-4869WOS: 000375681800053A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed by using the non-equilibrium Green's function approach based on the finite difference method. It is found that the resonant peak of the transmission coefficient, being unity for a symmetrical case, reduces under the applied electric field and depends strongly on the variation of the structure parameters
The effects of the variable mass on the electronic and nonlinear optical properties of octic anharmonic oscillators
Impurity-related linear and nonlinear optical response in quantum-well wires with triangular cross section
ABSTRACT: The 1s-like and 2p-like donor impurity energy states are studied in a semiconductor quantum wire of
equilateral triangular cross section as functions of the impurity position and the geometrical size of the
structure. Linear and nonlinear coefficients for the optical absorption and relative refractive index change
associated with 1s-2p transitions are calculated for both the x-polarization and y-polarization of the
incident light. The results show a mixed effect of redshift and blueshift depending on the location of the
donor atom. Also, strong nonlinear contributions to the optical absorption coefficient are obtained for
both polarizations in the on-center impurity case
The effects of the magnetic field and dielectric screening on the diamagnetic susceptibility of a donor in a quantum well with anisotropic effective mass
The diamagnetic susceptibility and the binding energy of a hydrogenic donor in a quantum well with different mass anisotropy parameters gamma=m(perpendicular to)/m(parallel to) are investigated in the presence of a magnetic field using a trial wave function with two parameters in the framework of the effective mass approximation. It is observed that the effects of magnetic field on diamagnetic susceptibility of the donor in two-dimensional semiconductors with various effective mass anisotropy parameters are quite different. Also it has been found that for Si there is an obvious increase in the binding energy for spatially dependent screening compared with that for constant screening in the range of considered well widths, whereas the spatially dependent screening effect is small for Ge and GaAs materials. (C) 2010 Elsevier B.V. All rights reserved