514 research outputs found
General Approach To Compute Phosphorescent OLED Efficiency
Phosphorescent organic light-emitting diodes (PhOLEDs) are widely used in the
display industry. In PhOLEDs, cyclometalated Ir(III) complexes are the most
widespread triplet emitter dopants to attain red, e.g., Ir(piq)3 (piq =
1-phenylisoquinoline), and green, e.g., Ir(ppy)3 (ppy = 2-phenylpyridine),
emissions, whereas obtaining operative deep-blue emitters is still one of the
major challenges. When designing new emitters, two main characteristics besides
colors should be targeted: high photostability and large photoluminescence
efficiencies. To date, these are very often optimized experimentally in a
trial-and-error manner. Instead, accurate predictive tools would be highly
desirable. In this contribution, we present a general approach for computing
the photoluminescence lifetimes and efficiencies of Ir(III) complexes by
considering all possible competing excited-state deactivation processes and
importantly explicitly including the strongly temperature-dependent ones. This
approach is based on the combination of state-of-the-art quantum chemical
calculations and excited-state decay rate formalism with kinetic modeling,
which is shown to be an efficient and reliable approach for a broad palette of
Ir(III) complexes, i.e., from yellow/orange to deep-blue emitters
Theory of conserved spin current and its application to two dimensional hole gas
We present a detailed microscopic theory of the conserved spin current which
is introduced by us [Phys. Rev. Lett. \textbf{96}, 196602 (2006)] and satisfies
the spin continuity equation even for spin-orbit coupled systems. The spin
transport coefficients as a response to the electric
field are shown to consist of two parts, i.e., the conventional part
and the spin torque dipole correction . As one key result, an Onsager relation between and other kinds of transport coefficients are shown. The expression for
in terms of single-particle Bloch states are derived, by
use of which we study the conserved spin Hall conductivity in the two
dimensional hole gas modeled by a combined Luttinger and SIA Rashba spin-orbit
coupling. It is shown that the two components in spin Hall conductivity usually
have the opposite contributions. While in the absence of Rashba spin splitting,
the spin Hall transport is dominated by the conventional contribution, the
presence of Rashba spin splitting stirs up a large enhancement of the spin
torque dipole correction, leading to an overall sign change for the total spin
Hall conductivity. Furthermore, an approximate two-band calculation and the
subsequent comparison with the exact four-band results are given, which reveals
that the coupling between the heavy hole and light hole bands should be taken
into account for strong Rashba spin splitting.Comment: 10 pages, 4 figure
Methods and compositions for transgenic plants with enhanced cold tolerance, ability to flower without vernalization requirement and impacted fertility
The present invention provides transgenic plants having increased tolerance to cold and altered flowering characteristics. Also provided are methods and compositions for producing said transgenic plants
Methods and compositions for transgenic plants with enhanced resistance to biotic and abiotic stress
The present invention provides methods and compositions for producing transgenic plants having increased resistance to biotic and/or abiotic stress and comprising an exogenous nucleotide sequence encoding a cysteine protease inhibitor
Heterologous expression of a rice miR395 gene in Nicotiana tabacum impairs sulfate homeostasis
Sulfur participates in many important mechanisms and pathways of plant development. The most common source of sulfur in soil –SO42−– is absorbed into root tissue and distributed into aerial part through vasculature system, where it is reduced into sulfite and finally sulfide within the subcellular organs such as chloroplasts and mitochondria and used for cysteine and methionine biosynthesis. MicroRNAs are involved in many regulation pathways by repressing the expression of their target genes. MiR395 family in Arabidopsis thaliana has been reported to be an important regulator involved in sulfate transport and assimilation, and a high-affinity sulphate transporter and three ATP sulfurylases (ATPS) were the target genes of AthmiR395 (Arabidopsis thaliana miR395). We have cloned a miR395 gene from rice (Oryza sativa) and studied its function in plant nutritional response. Our results indicated that in rice, transcript level of OsamiR395 (Oryza sativa miR395) increased under sulfate deficiency conditions, and the two predicted target genes of miR395 were down-regulated under the same conditions. Overexpression of OsamiR395h in tobacco impaired its sulfate homeostasis, and sulfate distribution was also slightly impacted among leaves of different ages. One sulfate transporter (SULTR) gene NtaSULTR2 was identified to be the target of miR395 in Nicotiana tobacum, which belongs to low affinity sulfate transporter group. Both miR395 and NtaSULTR2 respond to sulfate starvation in tobacco
Multi-objective time-cost optimization using Cobb-Douglas production function and hybrid genetic algorithm
 Existing research on construction time-cost tradeoff issues rarely explore the origin of the crashing cost. Crashing cost function was either assumed without much justification, or came from historical data of some real proÂjects. As a result the conclusions of the papers can hardly be used to guide allocations of labor and equipment resources respectively. The authors believe Cobb-Douglas function provides a much-needed piece to modeling the cost functions in the construction time-cost tradeoff problem during the crashing process. We believe this new perspective fills a gap of existing time-cost tradeoff research by considering project duration, labor and equipment cost as parameters of the Cobb- Douglas production function. A case study was presented to show how the proposed framework works. Our conclusion is that introducing Cobb-Douglas function into time-cost tradeoff problem provides us extra capacity to further identify the optimal allocations of labor and equipment resources during crashing
Trace elements accumulation in the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) - A threat to the endangered freshwater cetacean
As a freshwater cetacean with a population of only approximately 1000 individuals, the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is threatened by water pollution. However, studies of contaminants accumulated in the Yangtze finless porpoise remain limited. In this study, concentrations of 11 trace elements in different tissues sampled from 38 Yangtze finless porpoise individuals were determined. The elements V, Ni, Zn, and Pb were mostly accumulated in the epidermis, Cr, Mn, Cu, Se, and Hg were mostly accumulated in the liver, while As and Cd were mostly accumulated in the blubber and kidney, respectively. The results show that trace elements concentrations in the epidermis do not reliably indicate concentrations in internal tissues of the Yangtze finless porpoises. Positive correlations between different trace elements concentrations in tissues with the highest concentrations suggested the similar mechanism of metabolism or uptake pathway of those elements. Concentrations of As, Se, Cd, Hg, and Pb in the tissues with the highest concentrations were significantly positively correlated with the body length. Furthermore, significantly higher trace elements concentrations were measured in the reproductive organs of females (ovaries) than males (testis). However, no significant difference of trace elements concentrations between habitats was found. In consideration of higher Hg and Cd level in Yangtze finless porpoises compared to other small cetaceans, the potential risk of Hg (in particular) and Cd toxicity to Yangtze finless porpoises needs further attention. (C) 2019 Elsevier B.V. All rights reserved.</p
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