73 research outputs found
30% external quantum efficiency from surface textured, thin-film light-emitting diodes
There is a significant gap between the internal efficiency of light-emitting diodes (LEDs) and their external efficiency. The reason for this shortfall is the narrow escape cone for light in high refractive index semiconductors. We have found that by separating thin-film LEDs from their substrates (by epitaxial lift-off, for example), it is much easier for light to escape from the LED structure and thereby avoid absorption. Moreover, by nanotexturing the thin-film surface using "natural lithography," the light ray dynamics becomes chaotic, and the optical phase-space distribution becomes "ergodic," allowing even more of the light to find the escape cone. We have demonstrated 30% external efficiency in GaAs LEDs employing these principles
Surface passivation effects of As2S3 glass on selfâaligned AlGaAs/GaAs heterojunction bipolar transistors
A recently developed As2S3 chemical treatment was used to passivate the perimeters of selfâaligned heterojunction bipolar transistors (HBTs). The As2S3chemical treatment significantly lowered the base current resulting in a two order of magnitude reduction in the collector current density at which dc current gain was observed (ÎČ=1). No degradation with time has been observed in the electrical characteristics of the chemically treated HBTs. This absence of degradation is attributed to the impermeability to oxygen of the As2S3 glass which coats the perimeter of the HBT after chemical treatment
30% External Quantum Efficiency From Surface Textured, Thin-film Light-emitting-diode Arrays
[no abstract
30% external quantum efficiency from surface textured, thinâfilm lightâemitting diodes
Cytological and molecular characterization of three gametoclones of Citrus clementina
Abstract
Background
Three gametoclonal plants of Citrus clementina Hort. ex Tan., cv. Nules, designated ESP,
FRA, and ITA (derived from three labs in Spain, France, and Italy, respectively), were
selected for cytological and molecular characterization in order to elucidate genomic
rearrangements provoked by haploidization. The study included comparisons of their ploidy,
homozygosity, genome integrity, and gene dosage, using chromosome counting, flow
cytometry, SSR marker genotyping, and array-Comparative Genomic Hybridization (arrayCGH).
Results
Chromosome counting and flow cytometry revealed that ESP and FRA were haploid, but ITA
was tri-haploid. Homozygous patterns, represented by a single peak (allele), were observed
among the three plants at almost all SSR loci distributed across the entire diploid donor
genome. Those few loci with extra peaks visualized as output from automated sequencing
runs, generally low or ambiguous, might result from amplicons of paralogous members at the
locus, non-specific sites, or unexpected recombinant alleles. No new alleles were found,
suggesting the genomes remained stable and intact during gametogenesis and regeneration.
The integrity of the haploid genome also was supported by array-CGH studies, in which
genomic profiles were comparable to the diploid control.
Conclusions
The presence of few gene hybridization abnormalities, corroborated by gene dosage
measurements, were hypothetically due to the segregation of hemizygous alleles and minor
genomic rearrangements occurring during the haploidization procedure. In conclusion, these
plants that are valuable genetic and breeding materials contain completely homozygous and
essentially intact genomes
Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication
Cultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes-a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes-and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement. (Résumé d'auteur
Comprehensive study of the CuF<inf>2</inf> conversion reaction mechanism in a lithium ion battery
Conversion materials for lithium ion batteries have recently attracted considerable attention due to their exceptional specific capacities. Some metal fluorides, such as CuF2, are promising candidates for cathode materials owing to their high operating potential, which stems from the high electronegativity of fluorine. However, the high ionicity of the metalâfluorine bond leads to a large band gap that renders these materials poor electronic conductors. Nanosizing the active material and embedding it within a conductive matrix such as carbon can greatly improve its electrochemical performance. In contrast to other fluorides, such as FeF2 and NiF2, good capacity retention has not, however, been achieved for CuF2. The reaction mechanisms that occur in the first and subsequent cycles and the reasons for the poor charge performance of CuF2 are studied in this paper via a variety of characterization methods. In situ pair distribution function analysis clearly shows CuF2 conversion in the first discharge. However, few structural changes are seen in the following charge and subsequent cycles. Cyclic voltammetry results, in combination with in situ X-ray absorption near edge structure and ex situ nuclear magnetic resonance spectroscopy, indicate that Cu dissolution is associated with the consumption of the LiF phase, which occurs during the first charge via the formation of a Cu1+ intermediate. The dissolution process consequently prevents Cu and LiF from transforming back to CuF2. Such side reactions result in negligible capacity in subsequent cycles and make this material challenging to use in a rechargeable battery.We acknowledge the funding from the U.S. DOE BES via
funding to the EFRC NECCES, an Energy Frontier Research
Center funded by the U.S. Department of Energy, Office of
Science, Office of Basic Energy Sciences under Award Number
DE-SC0001294 (support for Rosa Robert and Lin-Shu Du)
and EPSRC via the ânanoionicsâ programme grant (support for
Xiao Hua). Use of the National Synchrotron Light Source
(NSLS), Brookhaven National Laboratory (BNL), was
supported by the U.S. Department of Energy, Office of
Science, Office of Basic Energy Sciences, under Contract No.
DE-AC02-98CH10886. Use of the Advanced Photon Source,
an Office of Science User Facility operated for the U.S.
Department of Energy (DOE) Office of Science by Argonne
National Laboratory, was supported by the U.S. DOE under
Contract No. DE-AC02-06CH11357.This is the final published version of the article. It first appeared at http://pubs.acs.org/doi/abs/10.1021/jp503902z and is posted here under the terms of ACS's Editors' Choice scheme (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html)
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