1,184 research outputs found

    Electron and trap dynamics in As-ion-implanted and annealed GaAs

    Get PDF
    The ultrafast dynamics of As-ion-implanted and annealed GaAs is investigated using transmission pump–probe measurements.Carrier recombination time was found to increase from 4 to 40 ps with increasing annealing temperature. At lower annealing temperatures, the transmitted optical signal is dominated by induced absorption and at higher annealing temperatures this effect is replaced by induced transparency.This work was supported in part by the EC INCOCOPERNICUS project ‘‘DUO—devices for ultrafast optoelectronics’’ and the Lithuanian Science and Study Foundation

    Diagnostic approach to a functional adrenal tumour in a Shih-Tzu Poodle mix

    Get PDF
    Hyperadrenocorticism is the excessive production of cortisol by the adrenal cortex. 15-20% of hyperadrenocorticism in dogs may be due to functional adrenal tumour. Here we present a case of functional adrenal tumour in a 10 years old Shih-Tzu Poodle mixed-breed dog that was presented to University Veterinary Hospital, Universiti Putra Malaysia. Physical examination findings include multiple cutaneous myiasis, a pendulous abdomen with comedones on the ventral thoracic region and thinning of the skin. Clinical signs shown were polyuria, polydipsia and polyphagia. Serum biochemistry result showed elevated alkaline phosphatase enzyme of 5 folds. Urinary specific gravity was minimally concentrated (1.015). Radiography showed generalised hepatomegaly. Meanwhile, ultrasonography showed unilateral enlargement of the right adrenal gland with mineralisation. Invasion of the right adrenal gland into the caudal vena cava was observed. A differentiation test (high-dose dexamethasone suppression test) was performed and a lack of suppression of the cortisol level was observed. Based on the appropriate clinical signs and physical examination findings, elevated alkaline phosphatase enzyme, minimally concentrated urinary specific gravity, generalised hepatomegaly, unilateral adrenal gland enlargement, and high-dose dexamethasone suppression test, a diagnosis of functional adrenal tumour was made

    Suppression of thermal atomic interdiffusion in C-doped InGaAs∕AlGaAs quantum well laser structures using TiO₂ dielectric layers

    No full text
    The effects of thermal annealing on C-doped InGaAs∕AlGaAs quantum well laser structures capped with titanium dioxide (TiO₂) layers were investigated. The atomic interdiffusion was greatly suppressed by the presence of a TiO₂ capping layer during annealing, inhibiting even the thermal intermixing observed in the uncapped sample. An increase in the amount of lattice contraction associated with the presence of substitutional carbonCAs after annealing without a capping layer was observed, but not after annealing with a TiO₂ capping layer. Capacitance–voltage measurements confirmed the electrical activation of carbon after annealing without a dielectric layer and show a negligible change after annealing using a TiO₂ capping layer. The possible mechanisms involving both the atomic intermixing on the group III sublattice and carbon activation on the group V sublattice and the implications for optoelectronic device integration using impurity-free intermixing are discussed.P.L.G. acknowledges the scholarship funded by the Australian Agency for International Development (AusAID). Australian Research Council is gratefully acknowledged for the financial support

    Cellular Programming of Plant Gene Imprinting

    Get PDF
    Gene imprinting, the differential expression of maternal and paternal alleles, independently evolved in mammals and in flowering plants. A unique feature of flowering plants is a double-fertilization event in which the sperm fertilize not only the egg, which forms the embryo, but also the central cell, which develops into the endosperm (an embryo-supporting tissue). The distinctive mechanisms of gene imprinting in the endosperm, which involve DNA demethylation and histone methylation, begin in the central cell and sperm prior to fertilization. Flowering plants might have coevolved double fertilization and imprinting to prevent parthenogenetic development of the endosperm

    A study of quantum well solar cell structures with bound-to-continuum transitions for reduced carrier recombination

    No full text
    A bound-to-continuum quantum well solar cell structure is proposed, and the band structure and absorption spectra are analyzed by the use of an eight band k⋅p model. The structure is based on quantum wells that only support bound states for the valence band. The absence of bound conduction band states has a number of potential advantages, including a reduction of electron trapping and, therefore, a reduction of quantum well induced photocarrier recombination due to reduced spatial overlap of the electron and hole wavefunctions.Thanks are due to the Australian Research Council for the financial support of this research
    corecore