3,385 research outputs found

    Luminescent Cyclometalated Gold(III) Alkyl Complexes: Photophysical and Photochemical Properties

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    Quenching and reactivation of electroluminescence by charge trapping and detrapping in Si-implanted silicon nitride thin film

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    In this brief, quenching of electroluminescence (EL) from Si-implanted silicon nitride (SNR) thin film under a forward bias has been observed. The quenching phenomenon is shown to be due to charge trapping in the defect states involved in the radiative recombination. The composite EL bands have different quenching rates, causing a change in the EL spectrum shape by the EL quenching. Release of the trapped charges by a low-temperature annealing at 120 °C or an application of a reverse gate bias can partially recover the quenched EL both in the intensity and spectrum shape. The quenching phenomenon poses a serious challenge to the application of Si-implanted SNR thin films in light-emitting devices. © 2009 IEEE.published_or_final_versio

    Evolution of electroluminescence from multiple Si-implanted silicon nitride films with thermal annealing

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    Influence of thermal annealing on electroluminescence (EL) from multiple-Si-implanted silicon nitride films has been investigated. A reduced injection current and an enhanced EL intensity have been obtained simultaneously by increasing the annealing temperature, which results in a higher EL quantum efficiency. In addition, four emission bands are identified, and their peak energies, intensities, and full widths at half maxima are found to change with annealing temperature. A model is proposed to illustrate the carrier transport, the mechanisms of the four emission bands, and the evolution of the EL bands with annealing as well. The two major bands and the minor ultraviolet band are explained in terms of the recombination of the injected electrons in either the silicon dangling-bond (≡ Si 0) states or the nitride conduction band with the injected holes in either the band tail states above the nitride valence band or the valence band itself, while the minor near infrared band is attributed to the Si nanocrystals formed in the thin film. © 2009 American Institute of Physics.published_or_final_versio

    Intensive expression of Bmi-1 is a new independent predictor of poor outcome in patients with ovarian carcinoma

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    Background: It has been suggested that the B-cell specific moloney leukemia virus insertion site 1 (Bmi-1) gene plays an oncogenic role in several types of human cancer, but the status of Bmi-1 amplification and expression in ovarian cancer and its clinical/prognostic significance are unclear.Methods: The methods of immunohistochemistry and fluorescence in situ hybridization were utilized to examine protein expression and amplification of Bmi-1 in 30 normal ovaries, 30 ovarian cystadenomas, 40 borderline ovarian tumors and 179 ovarian carcinomas.Results: Intensive expression of Bmi-1 was detected in none of the normal ovaries, 3% cystadenomas, 10% borderline tumors, and 37% ovarian carcinomas, respectively. Amplification of Bmi-1 was detected in 8% of ovarian carcinomas. In ovarian carcinomas, significant positive associations were found between intensive expression of Bmi-1 and the tumors ascending histological grade, later pT/pN/pM and FIGO stages (P < 0.05). In univariate survival analysis of the ovarian carcinoma cohorts, a significant association of intensive expression of Bmi-1 with shortened patient survival (mean 49.3 months versus 100.3 months, p < 0.001) was demonstrated. Importantly, Bmi-1 expression provided significant independent prognostic parameters in multivariate analysis (p = 0.005).Conclusions: These findings provide evidence that intensive expression of Bmi-1 might be important in the acquisition of an invasive and/or aggressive phenotype of ovarian carcinoma, and serve as a independent biomarker for shortened survival time of patients. © 2010 Yang et al; licensee BioMed Central Ltd.published_or_final_versio

    Three geographically separate domestications of Asian rice

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    Domesticated rice (Oryza sativa L.) accompanied the dawn of Asian civilization(1) and has become one of world's staple crops. From archaeological and genetic evidence various contradictory scenarios for the origin of different varieties of cultivated rice have been proposed, the most recent based on a single domestication(2,3). By examining the footprints of selection in the genomes of different cultivated rice types, we show that there were three independent domestications in different parts of Asia. We identify wild populations in southern China and the Yangtze valley as the source of the japonica gene pool, and populations in Indochina and the Brahmaputra valley as the source of the indica gene pool. We reveal a hitherto unrecognized origin for the aus variety in central India or Bangladesh. We also conclude that aromatic rice is a result of a hybridization between japonica and aus, and that the tropical and temperate versions of japonica are later adaptations of one crop. Our conclusions are in accord with archaeological evidence that suggests widespread origins of rice cultivation(1,4). We therefore anticipate that our results will stimulate a more productive collaboration between genetic and archaeological studies of rice domestication, and guide utilization of genetic resources in breeding programmes aimed at crop improvement.European Research Council [339941]info:eu-repo/semantics/publishedVersio
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