| 1. |
- Zhang, Tiankai, et al.
(author)
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Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells
- 2022
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In: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 377:6605, s. 495-501
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Journal article (peer-reviewed)abstract
- Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.
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| 2. |
- Lu, Junjing, et al.
(author)
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An improved sectional model to simulate multi-component aerosol dynamics in a containment of pressurized water reactor
- 2021
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In: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 157
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Journal article (peer-reviewed)abstract
- Simulating an evolving aerosol population in a reactor containment is essential for estimating the radioactivity that is possible to leak to the environment. In this study, a sectional model is developed to simulate multi-component aerosol dynamics in the containment during severe ac-cidents of a pressurized water reactor by improving the widely used MAEROS (Multicomponent AEROSol) model. An important advantage of the improved model is its simplified calculation method by introducing a series of correction factors to the equation coefficients when the thermal boundary conditions and the aerosol particle density in the containment change continuously. In addition, the restriction of the maximum section number in the MAEROS model is removed. The reliability of the model is validated against four analytical solutions and three sets of test data. Moreover, the improvements in the model are also proven to be necessary to effectively capture the influences of thermal boundary conditions and aerosol particle density on aerosol dynamics.
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| 3. |
- Yao, Su, et al.
(author)
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Detection of a parsec-scale jet in a radio-quiet narrow-line Seyfert 1 galaxy with highly accreting supermassive black hole
- 2021
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 508:1, s. 1305-1313
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Journal article (peer-reviewed)abstract
- The jet in active galactic nuclei (AGN) is a key ingredient in understanding the co-evolution of galaxies and their central supermassive black holes (SMBHs). Unfortunately, the mechanism of jet launching and collimation is still elusive. The observational evidence of decreasing radio loudness with increasing Eddington ratio implies that the jet should be coupled with the accretion process. To further explore the relationship between the jet and accretion, it is necessary to extend our knowledge of the jet to an extreme end of the Eddington ratio distribution of AGN. Using Very Long Baseline Array (VLBA), we report the detection of the parsec-scale radio structure in Mrk 335, a radio-quiet narrow-line Seyfert 1 galaxy with an Eddington ratio close to/above unity. The VLBA image at 1.5 GHz reveals an elongated structure extending ∼20 pc in north-south direction with a peak flux density of 1.98 ± 0.05 mJy beam-1 and radio brightness temperatures as high as 6 × 107 K. This feature provides a strong evidence of a parsec-scale (bipolar) jet launched from a highly accreting SMBH. We discuss the result by comparing Mrk 335 with other highly accreting systems, e.g. Galactic black holes and tidal disruption events, and recall the discovery of collimated corona in the vicinity of SMBH in Mrk 335 by previous X-ray observations, whose relation to the parsec-scale radio jet should be explored by future simultaneous X-ray spectroscopy and high resolution radio observations.
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| 4. |
- Dever, Thomas E, et al.
(author)
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Modulation of tRNA(iMet), eIF-2, and eIF-2B expression shows that GCN4 translation is inversely coupled to the level of eIF-2.GTP.Met-tRNA(iMet) ternary complexes
- 1995
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In: Molecular and Cellular Biology. - : American Society for Microbiology. - 0270-7306 .- 1098-5549. ; 15:11, s. 6351-6363
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Journal article (peer-reviewed)abstract
- To understand how phosphorylation of eukaryotic translation initiation factor (eIF)-2 alpha in Saccharomyces cerevisiae stimulates GCN4 mRNA translation while at the same time inhibiting general translation initiation, we examined the effects of altering the gene dosage of initiator tRNA(Met), eIF-2, and the guanine nucleotide exchange factor for eIF-2, eIF-2B. Overexpression of all three subunits of eIF-2 or all five subunits of eIF-2B suppressed the effects of eIF-2 alpha hyperphosphorylation on both GCN4-specific and general translation initiation. Consistent with eIF-2 functioning in translation as part of a ternary complex composed of eIF-2, GTP, and Met-tRNA(iMet), reduced gene dosage of initiator tRNA(Met) mimicked phosphorylation of eIF-2 alpha and stimulated GCN4 translation. In addition, overexpression of a combination of eIF-2 and tRNA(iMet) suppressed the growth-inhibitory effects of eIF-2 hyperphosphorylation more effectively than an increase in the level of either component of the ternary complex alone. These results provide in vivo evidence that phosphorylation of eIF-2 alpha reduces the activities of both eIF-2 and eIF-2B and that the eIF-2.GTP. Met-tRNA(iMet) ternary complex is the principal component limiting translation in cells when eIF-2 alpha is phosphorylated on serine 51. Analysis of eIF-2 alpha phosphorylation in the eIF-2-overexpressing strain also provides in vivo evidence that phosphorylated eIF-2 acts as a competitive inhibitor of eIF-2B rather than forming an excessively stable inactive complex. Finally, our results demonstrate that the concentration of eIF-2-GTP. Met-tRNA(iMet) ternary complexes is the cardinal parameter determining the site of reinitiation on GCN4 mRNA and support the idea that reinitiation at GCN4 is inversely related to the concentration of ternary complexes in the cell.
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| 5. |
- He, Wei, et al.
(author)
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China's Terrestrial Carbon Sink Over 2010–2015 Constrained by Satellite Observations of Atmospheric CO2 and Land Surface Variables
- 2022
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In: Journal of Geophysical Research: Biogeosciences. - 2169-8953. ; 127:2
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Journal article (peer-reviewed)abstract
- The magnitude and distribution of China's terrestrial carbon sink remain uncertain due to insufficient constraints at large scales, whereby satellite data offer great potential for reducing the uncertainty. Here, we present two carbon sink estimates for China constrained either by satellite CO2 column concentrations (XCO2) within the Global Carbon Assimilation System or by remotely sensed soil moisture and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) in addition to in situ CO2 observations within the Carbon Cycle Data Assimilation System. They point to a moderate size of carbon sinks of 0.34 ± 0.14 (mean ± unc.) and 0.43 ± 0.09 PgC/yr during 2010–2015, which are supported by an inventory-based estimate for forest and soil carbon sink (0.26 PgC/yr) and fall in the range of contemporary ensemble atmospheric inversions (0.25–0.48 PgC/yr). They also agree reasonably well on interannual variations, which reflect the carbon sink anomalies induced by regional droughts in southwest China. Furthermore, their spatial distributions are broadly consistent that of the forest inventory-based estimate, indicating that the largest carbon sinks locate in central and eastern China. Their estimates for forest carbon sink coincide fairly well with the inventory-based estimate across different regions, especially when aggregated to the north and south of China. Although enhanced recently by afforestation, China's carbon sink was also significantly weakened by regional droughts, which were often not fully represented in previous in situ CO2-based inversions due to insufficient observations. Our results suggest that satellite-based atmospheric CO2 and land surface observations are vital in characterizing terrestrial net carbon fluxes at regional scales.
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| 6. |
- Hu, Kejia, et al.
(author)
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Risk of Psychiatric Disorders Among Spouses of Patients With Cancer in Denmark and Sweden
- 2023
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In: JAMA Network Open. - : American Medical Association. - 2574-3805. ; 6:1
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Journal article (peer-reviewed)abstract
- IMPORTANCE: There is emerging evidence that spouses of patients with cancer may have a higher prevalence of mental illness, but these studies have been limited by pre-post designs, focus on a single mental illness, and short follow-up periods. OBJECTIVES: To assess the overall burden of psychiatric disorders among spouses of patients with cancer vs spouses of individuals without cancer and to describe possible changes in this burden over time.DESIGN, SETTING, AND PARTICIPANTS: This population based cohort study included spouses of patients with cancer (diagnosed 1986-2016 in Denmark and 1973-2014 in Sweden; exposed group) and spouses of individuals without cancer (unexposed group). Members of the unexposed group were individually matched to individuals in the exposed group on the year of birth, sex, and country. Spouses with and without preexisting psychiatric morbidity were analyzed separately. Data analysis was performed between May 2021 and January 2022. EXPOSURES: Being spouse to a patient with cancer.MAIN OUTCOMES AND MEASURES: The main outcome was a clinical diagnosis of psychiatric disorders through hospital-based inpatient or outpatient care. Flexible parametric models and Cox models were fitted to estimate hazard ratios (HRs) with 95% CIs, adjusted for sex, age and year at cohort entry, country, household income, and cancer history.RESULTS: Among 546 321 spouses in the exposed group and 2 731 574 in the unexposed group who had no preexisting psychiatry morbidity, 46.0% were male participants, with a median (IQR) age at cohort entry of 60 (51-68) years. During follow-up (median, 8.4 vs 7.6 years), the incidence rate of first-onset psychiatric disorders was 6.8 and 5.9 per 1000 person-years for the exposed and unexposed groups, respectively (37 830 spouses of patients with cancer [6.9%]; 153 607 of spouses of individuals without cancer [5.6%]). Risk of first-onset psychiatric disorders increased by 30% (adjusted HR, 1.30; 95% CI, 1.25-1.34) during the first year after cancer diagnosis, especially for depression (adjusted HR, 1.38; 95% CI, 1.30-1.47) and stress-related disorders (adjusted HR, 2.04; 95% CI, 1.88-2.22). Risk of first-onset psychiatric disorders increased by 14% (adjusted HR, 1.14; 95% CI, 1.13-1.16) during the entire follow-up, which was similar for substance abuse, depression, and stress-related disorders. The risk increase was more prominent among spouses of patients diagnosed with a cancer with poor prognosis (eg, pancreatic cancer: adjusted HR, 1.41; 95% CI, 1.32-1.51) or at an advanced stage (adjusted HR, 1.31; 95% CI, 1.26-1.36) and when the patient died during follow-up (adjusted HR, 1.29; 95% CI, 1.27-1.31). Among spouses with preexisting psychiatric morbidity, the risk of psychiatric disorders (first-onset or recurrent) increased by 23% during the entire follow-up (adjusted HR, 1.23; 95% CI, 1.20-1.25).CONCLUSIONS AND RELEVANCE: In this cohort study of 2 populations in Denmark and Sweden, spouses of patients with cancer experienced increased risk of several psychiatric disorders that required hospital-based specialist care. Our results support the need for clinical awareness to prevent potential mental illness among the spouses of patients with cancer.
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| 7. |
- Huang, Yuqing, et al.
(author)
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Effect of a Phonon Bottleneck on Exciton and Spin Generation in Self-Assembled In1-xGaxAs Quantum Dots
- 2018
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In: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 9:4
-
Journal article (peer-reviewed)abstract
- We provide direct experimental evidence for the effect of a phonon bottleneck on exciton and spin generation in self-assembled In0.5Ga0.5As quantum dots (QDs). With the aid of tunable laser spectroscopy, we resolve and identify efficient exciton generation channels in the QDs mediated by longitudinal-optical (LO) phonons from an otherwise inhomogeneously broadened QD emission background that suffers from the phonon bottleneck effect in exciton generation. Spin-generation efficiency is found to be enhanced under the LO-assisted excitation condition due to suppressed spin relaxation accompanying accelerated exciton generation. These findings underline the importance of fine-tuning QD energy levels that will benefit potential spin-optoelectronic applications of QDs by reducing spin loss due to the phonon bottleneck.
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| 8. |
- Huang, Yuqing, et al.
(author)
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Size dependence of electron spin dephasing in InGaAs quantum dots
- 2015
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 106:9, s. 093109-
-
Journal article (peer-reviewed)abstract
- We investigate ensemble electron spin dephasing in self-assembled InGaAs/GaAs quantum dots (QDs) of different lateral sizes by employing optical Hanle measurements. Using low excitation power, we are able to obtain a spin dephasing time T-2* (in the order of ns) of the resident electron after recombination of negative trions in the QDs. We show that T-2* is determined by the hyperfine field arising from the frozen fluctuation of nuclear spins, which scales with the size of QDs following the Merkulov-Efros-Rosen model. This scaling no longer holds in large QDs, most likely due to a breakdown in the lateral electron confinement. (C) 2015 AIP Publishing LLC.
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| 9. |
- Li, X., et al.
(author)
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Flow Pattern Identification of Porous Media Based on Signal Feature Extraction and SVM
- 2022
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In: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - : Science Press. - 0253-231X. ; 43:11, s. 2957-2965
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Journal article (peer-reviewed)abstract
- In this paper, the visualization experiment of gas-liquid two-phase flow in porous media is carried out. The typical flow patterns of bubbly flow, slug flow and annular flow are photographed by high-speed camera, and the corresponding differential pressure fluctuation signals are measured and recorded, Using probability density function (PDF) and power spectral density (PSD) curves, the time-domain and frequency-domain characteristics of differential pressure signals corresponding to each flow pattern are analyzed, and the quantitative characteristic parameters are introduced to construct the characteristic vector reflecting the time-frequency characteristics of differential pressure signals. A two-phase flow pattern identification method in porous media based on support vector machine (SVM) is proposed. The results show that the overall recognition rate of the three flow patterns measured by the method is 98.18%, which can provide a new technical support for the on-line recognition of gas-liquid two-phase flow patterns in porous media.
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| 10. |
- Li, Xiangyu, et al.
(author)
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Identification of two-phase flow pattern in porous media based on signal feature extraction
- 2022
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In: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 83
-
Journal article (peer-reviewed)abstract
- The statistical analysis methods based on differential pressure signals of two-phase flow are employed in the present study to identify the flow patterns in packed porous bed. The typical flow pattern images of two-phase flow in the packed porous beds are recognized and the corresponding differential pressure signals are recorded based on the visualization experiments. Then the statistical analysis methods, including probability density function (PDF), power spectral density (PSD), and wavelet energy spectrum (WES), are employed to extract the features of differential pressure signals in the time domain, frequency domain, and time-frequency domain respectively. The dimensionless parameters are proposed as the evaluation index to quantify the differences among flow patterns. The results show that the PDF, PSD, and WES methods can effectively characterize different flow patterns in the time, frequency, and time-frequency domain, respectively. The comprehensive recognition efficiency is about 88.5% using the introduced dimensionless parameters.
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