Simultaneous enhancement of out-coupling efficiency, internal quantum efficiency, and color purity in thermally activated delayed fluorescence (TADF) emitters is highly desired for the practical ...application of these materials. We designed and synthesized two isomeric TADF emitters, 2DPyM-mDTC and 3DPyM-pDTC, based on di(pyridinyl)methanone (DPyM) cores as the new electron-accepting units and di(tert-butyl)carbazole (DTC) as the electron-donating units. 3DPyM-pDTC, which is structurally nearly planar with a very small ΔE ST, shows higher color purity, horizontal ratio, and quantum yield than 2DPyM-mDTC, which has a more flexible structure. An electroluminescence device based on 3DPyM-pDTC as the dopant emitter can reach an extremely high external quantum efficiency of 31.9% with a pure blue emission. This work also demonstrates a way to design materials with a high portion of horizontal molecular orientation to realize a highly efficient pure-blue device based on TADF emitters.
The grain refinement process of Ti-6Al-4V alloy under LSP: (a) LDD in original grains; (b) Dislocations in β phase; (c) DTIs in α phase; (d) DTs transform into DCs; (e) DWs develop into sub-GBs; (f) ...GR accomplishes.
•LSP could repair the surface defects and reduce the surface roughness.•Microstructure evolution of α phase in Ti-6Al-4V alloy processed by LSP is distinct from β phase.•Multidirectional twin intersections and subgrain boundaries are the main mechanism of grain refinement of Ti-6Al-4V alloy.•Grain refinement process of the Ti-6Al-4V alloy was illustrated.
Microstructure evolution and grain refinement of Ti-6Al-4V alloy after laser shock processing (LSP) are systematically investigated in this paper. Laser shock waves were induced by a Q-switched Nd:YAG laser system operated with a wave-length of 1064nm and 10ns pulse width. The microstructures of LSP samples were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Present results indicate that the surface hardness of samples subjected to LSP impacts has significantly improved. Multidirectional twin intersections and dislocation movements lead to grain subdivision in α phase with ultra-high plastic deformation. High-density dislocations are found in β phase. Multidirectional twin intersections and division of sub-grain boundaries play an important role in the grain refinement of Ti-6Al-4V alloy under LSP loading conditions.
Sorbitol dehydrogenase (SDH) catalyses the reversible oxidation of sorbitol, xylitol and ribitol to their corresponding ketoses. In this study, we investigated the expression and role of Arabidopsis ...SDH in salt and osmotic stress tolerance, and abscisic acid (ABA) response. The expression patterns of SDH were investigated using transgenic Arabidopsis plants expressing beta-glucuronidase (GUS) under control of the promoter with the first intron of SDH. qRT-PCR and histochemical assay of GUS activity were used to study SDH expression regulation by ABA, salt and osmotic stress. SDH-overexpression lines of Arabidopsis were used to investigate the role of SDH in salt and osmotic stress, and ABA response. Arabidopsis SDH was predominantly expressed in source organs such as green cotyledons, fully expanded leaves and sepals, especially in vascular tissues of theses organs. SDH expression was inhibited by NaCl and mannitol treatments. Seed germination and post-germination growth of SDH-overexpressing lines exhibited decreased sensitivity to salt and osmotic stress compared to WT plants. The transcript of SDH was induced by ABA. Overexpression of SDH decreased sensitivity to ABA during seed germination and post-germination growth. Expression of AAO3 increased but ABI5 and MYB2 decreased in SDH-overexpressing lines after ABA treatment. This study demonstrates that expression of SDH is regulated by ABA, salt and osmotic stress. SDH functions in plant tolerance to salt and osmotic stress, and ABA response via specific regulating gene expression of ABA synthesis and signalling in Arabidopsis.
A Li-ion capacitor (LIC), typically composed of a pre-lithiated negative electrode and an activated-carbon positive electrode, can provide high energy and power density. In this work, we compare the ...electrochemical performances of pre-lithiated graphene nanosheets and conventional graphite as negative electrode materials for LICs. The LICs employing pre-lithiated graphene nanosheets show a specific capacitance of 168.5 F g−1 with 74% capacitance retention at 400 mA g−1 after 300 cycles. Moreover, the capacitors deliver a maximum power density of 222.2 W kg−1 at an energy density of 61.7 Wh kg−1, operated in the voltage range of 2.0–4.0 V. Therefore, pre-lithiated graphene nanosheets are promising negative electrode materials for high power LICs.
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•Pre-lithiated graphene nanosheets are explored for Li-ion capacitors.•The Li-ion capacitors exhibit high energy and power density at high voltages.•Pre-lithiated graphene nanosheets are promising for high power Li-ion capacitors.
Background
While the majority of studies report that a raised serum α‐fetoprotein (AFP) level before operation is associated with a high risk of recurrence and death in patients who undergo ...hepatectomy for hepatocellular carcinoma (HCC), results are conflicting. The aim of this study was to assess the prognostic value of AFP.
Methods
Serum AFP levels were measured in patients with hepatitis‐associated HCC who underwent hepatectomy between 1995 and 2012. Kaplan–Meier and multivariable analyses were performed to identify risk factors for overall and disease‐free survival. Univariable and multivariable Cox proportional hazards regression was used to evaluate the predictive value of AFP. Receiver operating characteristic (ROC) curves were generated to identify the AFP level that had the highest accuracy in discriminating between survivors and non‐survivors.
Results
Some 376 patients with hepatitis B virus (HBV)‐associated HCC were included in the study. The overall survival rate was 58·8 per cent in patients with an AFP level of 400 ng/ml or less compared with 40·4 per cent for those with a level exceeding 400 ng/ml (P = 0·001). AFP concentration above 400 ng/ml was an independent risk factor for shorter disease‐free and overall survival after surgery. ROC analysis indicated that the optimal cut‐off values for AFP varied for different subtypes of HCC. The sensitivity and specificity were lower with areas under the ROC curve of less than 0·600. An AFP level greater than 400 ng/ml was not sensitive enough to predict the prognosis in patients with an HCC diameter smaller than 3 cm.
Conclusion
A serum AFP level above 400 ng/ml predicts poor overall and recurrence‐free survival after hepatectomy in patients with HBV‐associated HCC. AFP is not a strong prognostic marker given its poor discriminatory power, with low sensitivity and specificity.
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Free-standing aligned carbon nanotubes have previously been grown above 700°C on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square ...centimeters were grown on nickel-coated glass below 666°C by plasma-enhanced hot filament chemical vapor deposition. Acetylene gas was used as the carbon source and ammonia gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0.1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.
The outbreak of Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2), has thus far killed over 3,000 people and infected over 80,000 in ...China and elsewhere in the world, resulting in catastrophe for humans. Similar to its homologous virus, SARS-CoV, which caused SARS in thousands of people in 2003, SARS-CoV-2 might also be transmitted from the bats and causes similar symptoms through a similar mechanism. However, COVID-19 has lower severity and mortality than SARS but is much more transmissive and affects more elderly individuals than youth and more men than women. In response to the rapidly increasing number of publications on the emerging disease, this article attempts to provide a timely and comprehensive review of the swiftly developing research subject. We will cover the basics about the epidemiology, etiology, virology, diagnosis, treatment, prognosis, and prevention of the disease. Although many questions still require answers, we hope that this review helps in the understanding and eradication of the threatening disease.
Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena found both in bulk samples containing nanoscale constituents and in nanoscale samples ...themselves. Prior theoretical and experimental proof‐of‐principle studies on quantum‐well superlattice and quantum‐wire samples have now evolved into studies on bulk samples containing nanostructured constituents prepared by chemical or physical approaches. In this Review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications, thus bringing together low‐dimensional and bulk materials for thermoelectric applications. Particular emphasis is given in this Review to the ability to achieve 1) a simultaneous increase in the power factor and a decrease in the thermal conductivity in the same nanocomposite sample and for transport in the same direction and 2) lower values of the thermal conductivity in these nanocomposites as compared to alloy samples of the same chemical composition. The outlook for future research directions for nanocomposite thermoelectric materials is also discussed.
Nanostructural composites (shown schematically in the figure) are shown to exhibit nanostructures and promising properties for thermoelectric applications, thus bringing together low‐dimensional and bulk materials. The ability to achieve a simultaneous increase in the power factor and a decrease in the thermal conductivity in the same nanocomposite, and lower values of thermal conductivity compared to alloy samples of the same chemical composition is discussed.
WUDAPT Ching, J.; Mills, G.; Bechtel, B. ...
Bulletin of the American Meteorological Society,
09/2018, Letnik:
99, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The World Urban Database and Access Portal Tools (WUDAPT) is an international community-based initiative to acquire and disseminate climate relevant data on the physical geographies of cities for ...modeling and analysis purposes. The current lacuna of globally consistent information on cities is a major impediment to urban climate science toward informing and developing climate mitigation and adaptation strategies at urban scales. WUDAPT consists of a database and a portal system; its database is structured into a hierarchy representing different levels of detail, and the data are acquired using innovative protocols that utilize crowdsourcing approaches, Geowiki tools, freely accessible data, and building typology archetypes. The base level of information (L0) consists of local climate zone (LCZ) maps of cities; each LCZ category is associated with a range of values for model-relevant surface descriptors (roughness, impervious surface cover, roof area, building heights, etc.). Levels 1 (L1) and 2 (L2) will provide specific intra-urban values for other relevant descriptors at greater precision, such as data morphological forms, material composition data, and energy usage. This article describes the status of the WUDAPT project and demonstrates its potential value using observations and models. As a community-based project, other researchers are encouraged to participate to help create a global urban database of value to urban climate scientists.
ABSTRACT
We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from ...Gaia Data Release 2 (DR2) and in almost all cases, had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stellar remnants in the sample are relatively cool (〈Teff〉 = 6200 K), showing either hydrogen Balmer lines or a featureless spectrum, corresponding to 89 DA and 76 DC white dwarfs, respectively. We also recover two DBA white dwarfs and 9–10 magnetic remnants. We find two carbon-bearing DQ stars and 14 new metal-rich white dwarfs. This includes the possible detection of the first ultra-cool white dwarf with metal lines. We describe three DZ stars for which we find at least four different metal species, including one that is strongly Fe- and Ni-rich, indicative of the accretion of a planetesimal with core-Earth composition. We find one extremely massive (1.31 ± 0.01 M⊙) DA white dwarf showing weak Balmer lines, possibly indicating stellar magnetism. Another white dwarf shows strong Balmer line emission but no infrared excess, suggesting a low-mass sub-stellar companion. A high spectroscopic completeness (>99 per cent) has now been reached for Gaia DR2 sources within 40-pc sample, in the Northern hemisphere (δ > 0°) and located on the white dwarf cooling track in the Hertzsprung–Russell diagram. A statistical study of the full northern sample is presented in a companion paper.
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