| 1. |
- Ruilope, LM, et al.
(author)
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Design and Baseline Characteristics of the Finerenone in Reducing Cardiovascular Mortality and Morbidity in Diabetic Kidney Disease Trial
- 2019
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In: American journal of nephrology. - : S. Karger AG. - 1421-9670 .- 0250-8095. ; 50:5, s. 345-356
-
Journal article (peer-reviewed)abstract
- <b><i>Background:</i></b> Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. <b><i>Patients and</i></b> <b><i>Methods:</i></b> The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate ≥25 mL/min/1.73 m<sup>2</sup> and albuminuria (urinary albumin-to-creatinine ratio ≥30 to ≤5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level α = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. <b><i>Conclusions:</i></b> FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049.
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| 2. |
- Kanoni, Stavroula, et al.
(author)
-
Implicating genes, pleiotropy, and sexual dimorphism at blood lipid loci through multi-ancestry meta-analysis.
- 2022
-
In: Genome biology. - : Springer Science and Business Media LLC. - 1474-760X .- 1465-6906 .- 1474-7596. ; 23:1
-
Journal article (peer-reviewed)abstract
- Genetic variants within nearly 1000 loci are known to contribute to modulation of blood lipid levels. However, the biological pathways underlying these associations are frequently unknown, limiting understanding of these findings and hindering downstream translational efforts such as drug target discovery.To expand our understanding of the underlying biological pathways and mechanisms controlling blood lipid levels, we leverage a large multi-ancestry meta-analysis (N=1,654,960) of blood lipids to prioritize putative causal genes for 2286 lipid associations using six gene prediction approaches. Using phenome-wide association (PheWAS) scans, we identify relationships of genetically predicted lipid levels to other diseases and conditions. We confirm known pleiotropic associations with cardiovascular phenotypes and determine novel associations, notably with cholelithiasis risk. We perform sex-stratified GWAS meta-analysis of lipid levels and show that 3-5% of autosomal lipid-associated loci demonstrate sex-biased effects. Finally, we report 21 novel lipid loci identified on the X chromosome. Many of the sex-biased autosomal and X chromosome lipid loci show pleiotropic associations with sex hormones, emphasizing the role of hormone regulation in lipid metabolism.Taken together, our findings provide insights into the biological mechanisms through which associated variants lead to altered lipid levels and potentially cardiovascular disease risk.
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| 3. |
- Callaway, EM, et al.
(author)
-
A multimodal cell census and atlas of the mammalian primary motor cortex
- 2021
-
In: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 598:7879, s. 86-102
-
Journal article (peer-reviewed)abstract
- Here we report the generation of a multimodal cell census and atlas of the mammalian primary motor cortex as the initial product of the BRAIN Initiative Cell Census Network (BICCN). This was achieved by coordinated large-scale analyses of single-cell transcriptomes, chromatin accessibility, DNA methylomes, spatially resolved single-cell transcriptomes, morphological and electrophysiological properties and cellular resolution input–output mapping, integrated through cross-modal computational analysis. Our results advance the collective knowledge and understanding of brain cell-type organization1–5. First, our study reveals a unified molecular genetic landscape of cortical cell types that integrates their transcriptome, open chromatin and DNA methylation maps. Second, cross-species analysis achieves a consensus taxonomy of transcriptomic types and their hierarchical organization that is conserved from mouse to marmoset and human. Third, in situ single-cell transcriptomics provides a spatially resolved cell-type atlas of the motor cortex. Fourth, cross-modal analysis provides compelling evidence for the transcriptomic, epigenomic and gene regulatory basis of neuronal phenotypes such as their physiological and anatomical properties, demonstrating the biological validity and genomic underpinning of neuron types. We further present an extensive genetic toolset for targeting glutamatergic neuron types towards linking their molecular and developmental identity to their circuit function. Together, our results establish a unifying and mechanistic framework of neuronal cell-type organization that integrates multi-layered molecular genetic and spatial information with multi-faceted phenotypic properties.
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| 4. |
- Creely, A. J., et al.
(author)
-
Overview of the SPARC tokamak
- 2020
-
In: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 86:5
-
Journal article (peer-reviewed)abstract
- The SPARC tokamak is a critical next step towards commercial fusion energy. SPARC is designed as a high-field (B-0 = 12.2 T), compact (R-0 = 1.85 m, a = 0.57 m), superconducting, D-T tokamak with the goal of producing fusion gain Q > 2 from a magnetically confined fusion plasma for the first time. Currently under design, SPARC will continue the high-field path of the Alcator series of tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in a compact device. The goal of Q > 2 is achievable with conservative physics assumptions (H-98,H- y2 = 0.7) and, with the nominal assumption of H-98,H- y2 = 1, SPARC is projected to attain Q approximate to 11 and P-fusion approximate to 140 MW. SPARC will therefore constitute a unique platform for burning plasma physics research with high density (< n(e)> approximate to 3 x 10(20) m(-3)), high temperature (< Te > approximate to 7 keV) and high power density (P-fusion/V-plasma approximate to 7 MWm(-3)) relevant to fusion power plants. SPARC's place in the path to commercial fusion energy, its parameters and the current status of SPARC design work are presented. This work also describes the basis for global performance projections and summarizes some of the physics analysis that is presented in greater detail in the companion articles of this collection.
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| 5. |
- Mahajan, Anubha, et al.
(author)
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Multi-ancestry genetic study of type 2 diabetes highlights the power of diverse populations for discovery and translation
- 2022
-
In: Nature Genetics. - : Springer Nature. - 1061-4036 .- 1546-1718. ; 54:5, s. 560-572
-
Journal article (peer-reviewed)abstract
- We assembled an ancestrally diverse collection of genome-wide association studies (GWAS) of type 2 diabetes (T2D) in 180,834 affected individuals and 1,159,055 controls (48.9% non-European descent) through the Diabetes Meta-Analysis of Trans-Ethnic association studies (DIAMANTE) Consortium. Multi-ancestry GWAS meta-analysis identified 237 loci attaining stringent genome-wide significance (P < 5 x 10(-9)), which were delineated to 338 distinct association signals. Fine-mapping of these signals was enhanced by the increased sample size and expanded population diversity of the multi-ancestry meta-analysis, which localized 54.4% of T2D associations to a single variant with >50% posterior probability. This improved fine-mapping enabled systematic assessment of candidate causal genes and molecular mechanisms through which T2D associations are mediated, laying the foundations for functional investigations. Multi-ancestry genetic risk scores enhanced transferability of T2D prediction across diverse populations. Our study provides a step toward more effective clinical translation of T2D GWAS to improve global health for all, irrespective of genetic background. Genome-wide association and fine-mapping analyses in ancestrally diverse populations implicate candidate causal genes and mechanisms underlying type 2 diabetes. Trans-ancestry genetic risk scores enhance transferability across populations.
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| 6. |
- Zhou, Wei, et al.
(author)
-
Global Biobank Meta-analysis Initiative : Powering genetic discovery across human disease
- 2022
-
In: Cell Genomics. - : Elsevier. - 2666-979X. ; 2:10
-
Journal article (peer-reviewed)abstract
- Biobanks facilitate genome-wide association studies (GWASs), which have mapped genomic loci across a range of human diseases and traits. However, most biobanks are primarily composed of individuals of European ancestry. We introduce the Global Biobank Meta-analysis Initiative (GBMI)-a collaborative network of 23 biobanks from 4 continents representing more than 2.2 million consented individuals with genetic data linked to electronic health records. GBMI meta-analyzes summary statistics from GWASs generated using harmonized genotypes and phenotypes from member biobanks for 14 exemplar diseases and endpoints. This strategy validates that GWASs conducted in diverse biobanks can be integrated despite heterogeneity in case definitions, recruitment strategies, and baseline characteristics. This collaborative effort improves GWAS power for diseases, benefits understudied diseases, and improves risk prediction while also enabling the nomination of disease genes and drug candidates by incorporating gene and protein expression data and providing insight into the underlying biology of human diseases and traits.
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| 7. |
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| 8. |
- Wang, H. Y., et al.
(author)
-
Cellular Analysis and Comparative Transcriptomics Reveal the Tolerance Mechanisms of Candida tropicalis Toward Phenol
- 2020
-
In: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 11
-
Journal article (peer-reviewed)abstract
- Phenol is a ubiquitous pollutant and can contaminate natural water resources. Hence, the removal of phenol from wastewater is of significant importance. A series of biological methods were used to remove phenol based on the natural ability of microorganisms to degrade phenol, but the tolerance mechanism of phenol-degraded strains to phenol are not very clear. Morphological observation on Candida tropicalis showed that phenol caused the reactive oxygen species (ROS) accumulation, damaging the mitochondrial and the endoplasmic reticulum. On the basis of transcriptome data and cell wall susceptibility analysis, it was found that C. tropicalis prevented phenol-caused cell damage through improvement of cell wall resistance, maintenance of high-fidelity DNA replication, intracellular protein homeostasis, organelle integrity, and kept the intracellular phenol concentration at a low level through cell-wall remodeling and removal of excess phenol via MDR/MXR transporters. The knowledge obtained will promote the genetic modification of yeast strains in general to tolerate the high concentrations of phenol and improve their efficiency of phenol degradation.
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| 9. |
- Badelek, B, et al.
(author)
-
The photon collider at TESLA
- 2004
-
In: International Journal of Modern Physics A. - 0217-751X. ; 19:30, s. 5097-5186
-
Research review (peer-reviewed)abstract
- High energy photon colliders (gammagamma,gammae) are based on e(-)e(-) linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.(1) Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.
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| 10. |
- Kuang, H. Y., et al.
(author)
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Acupuncture and Clomiphene Citrate for Live Birth in Polycystic Ovary Syndrome: Study Design of a Randomized Controlled Trial
- 2013
-
In: Evidence-Based Complementary and Alternative Medicine. - : Hindawi Limited. - 1741-427X .- 1741-4288.
-
Journal article (peer-reviewed)abstract
- Acupuncture is an alternative therapy to induce ovulation in women with polycystic ovary syndrome (PCOS), but there is no study reporting the live birth rate following ovulation induction by acupuncture or its potential as an adjuvant treatment to clomiphene citrate (CC). We assess the efficacy of acupuncture with or without CC in achieving live births among 1000 PCOS women in Mainland China. This paper reports the methodology of an ongoing multicenter randomized controlled trial. The randomization scheme is coordinated through the central mechanism and stratified by the participating sites. Participants will be randomized into one of the four treatment arms: (A) true acupuncture and CC, (B) control acupuncture and CC, (C) true acupuncture and placebo CC, and (D) control acupuncture and placebo CC. To ensure the quality and integrity of the trial we have developed a unique multinational team of investigators and Data and Safety Monitoring Board. Up to the end of April 2013, 326 subjects were recruited. In conclusion, the success of this trial will allow us to evaluate the additional benefit of acupuncture beyond the first line medicine for fertility treatment in PCOS women in an unbiased manner.
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| 11. |
- Qi, W., et al.
(author)
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Divergent and Changing Importance of Glaciers and Snow as Natural Water Reservoirs in the Eastern and Southern Tibetan Plateau
- 2022
-
In: Journal of Geophysical Research-Atmospheres. - : American Geophysical Union (AGU). - 2169-897X .- 2169-8996. ; 127:7
-
Journal article (peer-reviewed)abstract
- Glaciers and snow are natural water reservoirs in the Tibetan Plateau (TP), affecting ecosystems, water and food security, and more than one billion downstream people. Meltwater volumes are traditionally estimated using the degree-day concept considering only air temperature, which cannot consider the influence from downward solar and longwave radiation, humidity, wind and resultant turbulent heat fluxes. Here, we used a physically based energy budget approach considering the full energy balance in seven large river basins in the eastern and southern TP. For 1982-2011, the estimated average glacier melt was 0.32 +/- 0.007 m water equivalent/yr with large spatial variability. Air temperature, downward longwave radiation, humidity, and wind speed influenced the overall glacier melt trend, and glacier melt accelerated with a rate of 0.42 mm/yr. Yet, downward shortwave radiation played an additional role in influencing the glacier melt rate fluctuation. On average, snow and glacier melt contributed 17.6% of annual river discharge during 1982-2011, including 10.0% from snow and 7.6% from glaciers. The highest and lowest relative melt contributions were in the Yarlung Tsangpo and Yalong Rivers, respectively. Mainly due to decreasing snow melt, glacier and snow melt contributions to discharge would decrease to 11.9% during 2021-2050 under the extreme climate scenario (RCP8.5), and the greatest change in the relative contributions would occur in the Upper Nu River (-9.2%). These findings indicate the divergent and changing importance of glaciers and snow as natural water reservoirs, potentially affecting socioeconomic development and adaptation to climate change in South, Southeast, and East Asia.
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| 12. |
- Zhang, X., et al.
(author)
-
Revisiting Lightning Activity and Parameterization Using Geostationary Satellite Observations
- 2021
-
In: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:19
-
Journal article (peer-reviewed)abstract
- The Geostationary Lightning Mapper (GLM) on the Geostationary Operational Environmental Satellite 16 (GOES-16) detects total lightning continuously, with a high spatial resolution and detection efficiency. Coincident data from the GLM and the Advanced Baseline Imager (ABI) are used to explore the correlation between the cloud top properties and flash activity across the continental United States (CONUS) sector from May to September 2020. A large number of collocated infrared (IR) brightness temperature (TBB), cloud top height (CTH) and lightning data provides robust statistics. Overall, the likelihood of lightning occurrence and high flash density is higher if the TBB is colder than 225 K. The higher CTH is observed to be correlated with a larger flash rate, a smaller flash size, stronger updraft, and larger optical energy. Furthermore, the cloud top updraft velocity (w) is estimated based on the decreasing rate of TBB, but it is smaller than the updraft velocity of the convective core. As a result, the relationship between CTH and lightning flash rate is investigated independently of w over the continental, oceanic and coastal regimes in the tropics and mid-latitudes. When the CTH is higher than 12 km, the flash rates of oceanic lightning are 38% smaller than those of both coastal and continental lightning. In addition, it should be noted that more studies are necessary to examine why the oceanic lightning with low clouds (CTH < 8 km) has higher flash rates than lightning over land and coast. Finally, the exponents of derived power relationship between CTH and lightning flash rate are smaller than four, which is underestimated due to the GLM detection efficiency and the difference between IR CTH and 20 dBZ CTH. The results from combining the ABI and GLM products suggest that merging multiple satellite datasets could benefit both lightning activity and parameterization studies, although the parallax corrections should be considered.
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| 13. |
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| 14. |
- Liu, Y., et al.
(author)
-
Increases in China's wind energy production from the recovery of wind speed since 2012
- 2022
-
In: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 17:11
-
Journal article (peer-reviewed)abstract
- China has realized a 56-fold increase in installed wind capacity, from 5.9 GW in 2007 to 328 GW in 2021. In addition to increasing installed capacity, plans to substantially increase wind energy production for climate change mitigation also depend on future wind speeds, which strongly influences the efficiencies of installed turbines within individual wind farms. A reversal in globally decreasing wind speeds over several decades has been reported previously. However, subsequent studies using other data sources reported only a slight increase or no reversal in China. These uncertainties regarding China's wind energy production hamper estimates of wind energy production potential. Here, our analysis of quality-controlled wind speed measurements from in-situ stations shows that the wind speed decline in China reversed significantly since 2012 (P < 0.001), but with substantial spatio-temporal variability. We further estimated the capacity factor (CF) growth and the wind power gain solely associated with the changes in wind speed ranges from 31.6 to 56.5 TWh yr(-1) based on the 2019 installed capacity. This estimate explains 22.0%-39.3% of the rapid increase in wind generation CF in China during 2012-2019. The result implies that the site selection of wind farms should consider both current wind situation and future wind speed trends. Further studies are needed to understand the driving factor of wind speed recovery in support of the wind energy industry.
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| 15. |
- Liu, Y., et al.
(author)
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Inorganic carbon and alkalinity biogeochemistry and fluxes in an intertidal beach aquifer: Implications for ocean acidification
- 2021
-
In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 595
-
Journal article (peer-reviewed)abstract
- While submarine groundwater discharge (SGD) is well known to release large amounts of dissolved nutrients and organic carbon into the ocean, the contribution of SGD to the marine inorganic carbon cycle is poorly understood. Here, the biogeochemistry of inorganic carbon in an intertidal aquifer and related SGD-derived fluxes into Tolo Harbor, Hong Kong was investigated over tidal and seasonal time scales. The results revealed the production of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) in the intertidal aquifer over the entire salinity range. The locally produced TAlk and DIC in the intertidal aquifer contributed to >50% of the TAlk and DIC discharged with SGD to the ocean. The distributions of TAlk and DIC in the transition (mangrove) and high salinity (bare beach) zones were different due to the distinct hydrogeological and geochemical conditions. In the organic-rich mangrove zone, TAlk and DIC productions were driven by biotic processes such as aerobic respiration, denitrification, and sulfate reduction. In the organic-poor bare beach zone, TAlk and DIC productions were likely driven by abiotic processes such as precipitation/dissolution of carbonate minerals. Temperature, pH, physical mixing, and iron cycling in the intertidal aquifer also considerably influenced the carbonate biogeochemistry. TAlk inventory in the intertidal aquifer was seasonally stable but TAlk discharged with SGD was similar to 60% greater in the wet season than in the dry season (73.3 vs. 45.6 mol d(-1) per m coastline). The DIC inventory in the intertidal aquifer and DIC discharged with SGD were similar to 24% and 95% higher, respectively, in the wet season than dry season. Overall, through analyzing TAlk:DIC ratios and related fluxes, SGD was thought to reduce the CO2 buffering capacity of the receiving ocean, and act as a local driver of ocean acidification.
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| 16. |
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| 17. |
- Chen, C., et al.
(author)
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Structure-property-function relationships of natural and engineered wood
- 2020
-
In: Nature Reviews Materials. - : Nature Research. - 2058-8437. ; 5:9, s. 642-666
-
Journal article (peer-reviewed)abstract
- The porous hierarchical structure and anisotropy of wood make it a strong candidate for the design of materials with various functions, including load bearing, multiscale mass transport, and optical and thermal management. In this Review, the composition, structure, characterization methods, modification strategies, properties and applications of natural and modified wood are discussed.The complex structure of wood, one of the most abundant biomaterials on Earth, has been optimized over 270 million years of tree evolution. This optimization has led to the highly efficient water and nutrient transport, mechanical stability and durability of wood. The unique material structure and pronounced anisotropy of wood endows it with an array of remarkable properties, yielding opportunities for the design of functional materials. In this Review, we provide a materials and structural perspective on how wood can be redesigned via structural engineering, chemical and/or thermal modification to alter its mechanical, fluidic, ionic, optical and thermal properties. These modifications enable a diverse range of applications, including the development of high-performance structural materials, energy storage and conversion, environmental remediation, nanoionics, nanofluidics, and light and thermal management. We also highlight advanced characterization and computational-simulation approaches for understanding the structure-property-function relationships of natural and modified wood, as well as informing bio-inspired synthetic designs. In addition, we provide our perspective on the future directions of wood research and the challenges and opportunities for industrialization.
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| 18. |
- Ciers, Joachim, 1991, et al.
(author)
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Polariton relaxation and polariton nonlinearities in nonresonantly cw-pumped III-nitride slab waveguides
- 2020
-
In: PHYSICAL REVIEW B. - 2469-9950 .- 2469-9969. ; 102:15
-
Journal article (peer-reviewed)abstract
- Polariton lasers are mostly based on planar cavities. Here we focus on an alternative configuration with slab waveguide modes strongly coupled to excitons confined in GaN/AlGaN quantum wells. We study experimentally and theoretically polariton relaxation at temperatures ranging from 4 to 200 K. We observe a good robustness of the lower polariton population peak energy position against temperature changes due to a balance between the shift of the exciton energy and the change in the normal mode splitting, a promising feature for future applications such as lasers and amplifiers where a small temperature drift in the emission wavelength is a desired asset. Finally, at T = 4 K we observe the signature of polariton nonlinearities occurring in the continuous wave regime that are assigned to an optical parametric oscillation process.
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| 19. |
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| 20. |
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| 21. |
- Dobrovolsky, Alexandr, et al.
(author)
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Energy Upconversion in GaP/GaNP Core/Shell Nanowires for Enhanced Near-Infrared Light Harvesting
- 2014
-
In: Small. - : Wiley-VCH Verlagsgesellschaft. - 1613-6810 .- 1613-6829. ; 10:21, s. 4403-4408
-
Journal article (peer-reviewed)abstract
- Semiconductor nanowires (NWs) have recently gained increasing interest due to their great potential for photovoltaics. A novel material system based on GaNP NWs is considered to be highly suitable for applications in efficient multi-junction and intermediate band solar cells. This work shows that though the bandgap energies of GaNx P1-x alloys lie within the visible spectral range (i.e., within 540-650 nm for the currently achievable x < 3%), coaxial GaNP NWs grown on Si substrates can also harvest infrared light utilizing energy upconversion. This energy upconversion can be monitored via anti-Stokes near-band-edge photoluminescence (PL) from GaNP, visible even from a single NW. The dominant process responsible for this effect is identified as being due to two-step two-photon absorption (TS-TPA) via a deep level lying at about 1.28 eV above the valence band, based on the measured dependences of the anti-Stokes PL on excitation power and wavelength. The formation of the defect participating in the TS-TPA process is concluded to be promoted by nitrogen incorporation. The revealed defect-mediated TS-TPA process can boost efficiency of harvesting solar energy in GaNP NWs, beneficial for applications of this novel material system in third-generation photovoltaic devices.
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| 22. |
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| 23. |
- Dobrovolsky, Alexandr, et al.
(author)
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Mechanism for radiative recombination and defect properties of GaP/GaNP core/shell nanowires
- 2012
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 101:16, s. 163106-1-163106-4
-
Journal article (peer-reviewed)abstract
- Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on a Si substrate by molecular beam epitaxy are examined using a variety of optical characterization techniques, including cw- and time-resolved photoluminescence and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated based on the observation of intense emission from a single NW at room temperature. This emission is shown to originate from radiative transitions within N-related localized states. From ODMR, growth of GaP/GaNP NWs is also found to facilitate formation of complex defects containing a P atom at its core that act as centers of competing non-radiative recombination.
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| 24. |
- Dobrovolsky, Alexander, et al.
(author)
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Optical properties of GaP/GaNP core/shell nanowires : a temperature-dependent study
- 2013
-
In: Nanoscale Research Letters. - : Springer. - 1931-7573 .- 1556-276X. ; 8:1, s. 239-
-
Journal article (peer-reviewed)abstract
- Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on Si are studied by employing temperature-dependent continuous wave and time-resolved photoluminescence (PL) spectroscopies. The NWs exhibit bright PL emissions due to radiative carrier recombination in the GaNP shell. Though the radiative efficiency of the NWs is found to decrease with increasing temperature, the PL emission remains intense even at room temperature. Two thermal quenching processes of the PL emission are found to be responsible for the degradation of the PL intensity at elevated temperatures: (a) thermal activation of the localized excitons from the N-related localized states and (b) activation of a competing non-radiative recombination (NRR) process. The activation energy of the latter process is determined as being around 180 meV. NRR is also found to cause a significant decrease of carrier lifetime.
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| 25. |
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| 26. |
- Dobrovolsky, A., et al.
(author)
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Raman spectroscopy of GaP/GaNP core/shell nanowires
- 2014
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 105:19, s. 193102-
-
Journal article (peer-reviewed)abstract
- Raman spectroscopy is employed to characterize structural and phonon properties of GaP/GaNP core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates. According to polarization-dependent measurements performed on single NWs, the dominant Raman modes associated with zone-center optical phonons obey selection rules in a zinc-blende lattice, confirming high crystalline quality of the NWs. Two additional modes at 360 and 397 cm(-1) that are specific to the NW architecture are also detected in resonant Raman spectra and are attributed to defect-activated scattering involving zone-edge transverse optical phonons and surface optical phonons, respectively. It is concluded that the formation of the involved defect states are mainly promoted during the NW growth with a high V/III ratio.
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| 27. |
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| 28. |
- Dobrovolsky, Alexandr, et al.
(author)
-
Signatures of N incorporation in Raman and optical properties of GaP/GaNP core/shell nanowires
- 2013
-
In: 2013 MRS Fall Meeting.
-
Conference paper (peer-reviewed)abstract
- GaP/GaNP core shell NWs is a novel material system that has been most recently suggested for applications in solar cells. Adding nitrogen not only allow to tune the bandgap energy of GaNP alloy but also causes splitting of conduction band (CB) states, promising for intermediate band solar cells with improved efficiency. The purpose of this work is to investigate effects of N incorporation on band structure of such GaP/GaNxP1-x core/shell NWs using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Structural quality of the wires will be also evaluated from Raman measurements.The GaP/GaN0.009P0.991core/shell NWs studied in this work were grown on Si (111) substrates by gas-source molecular beam epitaxy (MBE). The GaP NW cores were grown under the vapor liquid-solid (VLS) mechanism, whereas the GaNP shell was formed via the step-mediated growth. The resulted core/shell NWs were found to have an axial length of about 2.5 μm, a total diameter of about 220 nm, and a typical diameter of the GaP core of ~110 nm. According to performed TEM measurements, the NWs predominantly have zincblende structure with some inclusions of the wurtzite crystal phase. Excellent structural quality of the wires was concluded based on the performed Raman measurements. The Raman scattering spectra were found to contain several first-order Raman modes including intense and sharp peaks at 366 and 403 cm-1 and weaker modes at 387, 397 and 499 cm-1. The first two modes are typical for zinc-blende GaP and are related to transverse-optic (TO) and longitudinal-optical (LO) phonons, respectively. The spectral positions of these modes were unaffected by the N incorporation indicating that the formed GaNP shell is unstrained. The Raman mode at 499 cm-1 peak is related to the Ga-N bond vibrations, confirming the formation of the GaNP alloy. The 397 cm-1 peak can be identify as a surface optical (SO) phonon mode due to its sensitivity to the dielectric constant of an external medium.It is also found that incorporation of N causes a dramatic increase of the PL intensity, which can be easily detected at room temperature even from a single wire. This is accompanied by a shortening of the PL decay time revealed from the performed transient PL measurements. We attribute these changes to the N-induced transformation of the band gap from the indirect one in GaP to a direct band gap in the GaNP alloy. Secondly, N incorporation causes a red shift of the fundament absorption edge revealed via the PLE measurements due to the bowing effect. The red shift of the conduction band (CB) edge is accompanied by a strong blue shift of the Γ CB state. This is ascribed to the splitting of the host CB states that are strongly perturbed by N. The revealed changes in the band structure are potentially beneficial for the applications of GaNP/GaP NWs in novel intermediate band solar cell structures with high efficiency.
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| 29. |
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| 30. |
- Stehr, Jan Eric, et al.
(author)
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Defects in GaNP Nanowires
- 2014
-
In: Abstract Book of the 56th Electronic Materials Conference. ; , s. 114-
-
Conference paper (peer-reviewed)
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Sukrittanon, S., et al.
(author)
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Growth and characterization of dilute nitride GaNxP1−x nanowires and GaNxP1−x/GaNyP1−y core/shell nanowires on Si (111) by gas source molecular beam epitaxy
- 2014
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 105:7, s. 072107-
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Journal article (peer-reviewed)abstract
- We have demonstrated self-catalyzed GaN xP1−x and GaN xP1−x/GaNyP1−y core/shell nanowire growth by gas-source molecular beam epitaxy. The growth window for GaN xP1−x nanowires was observed to be comparable to that of GaP nanowires (∼585 °C to ∼615 °C). Transmission electron microscopy showed a mixture of cubic zincblende phase and hexagonal wurtzite phase along the [111] growth direction in GaN xP1−x nanowires. A temperature-dependent photoluminescence (PL) study performed on GaN xP1−x/GaNyP1−y core/shell nanowires exhibited an S-shape dependence of the PL peaks. This suggests that at low temperature, the emission stems from N-related localized states below the conduction band edge in the shell, while at high temperature, the emission stems from band-to-band transition in the shell as well as recombination in the GaN xP1−x core.
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