| 1. |
- Liu, Shaohui, et al.
(författare)
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Data-Driven Controlled Synthesis of Oriented Quasi-Spherical CsPbBr3 Perovskite Materials
- 2024
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 63:14
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Tidskriftsartikel (refereegranskat)abstract
- Controlled synthesis of lead-halide perovskite crystals is challenging yet attractive because of the pivotal role played by the crystal structure and growth conditions in regulating their properties. This study introduces data-driven strategies for the controlled synthesis of oriented quasi-spherical CsPbBr3, alongside an investigation into the synthesis mechanism. High-throughput rapid characterization of absorption spectra and color under ultraviolet illumination was conducted using 23 possible ligands for the synthesis of CsPbBr3 crystals. The links between the absorption spectra slope (difference in the absorbance at 400 nm and 450 nm divided by a wavelength interval of 50 nm) and crystal size were determined through statistical analysis of more than 100 related publications. Big data analysis and machine learning were employed to investigate a total of 688 absorption spectra and 652 color values, revealing correlations between synthesis parameters and properties. Ex situ characterization confirmed successful synthesis of oriented quasi-spherical CsPbBr3 perovskites using polyvinylpyrrolidone and Acacia. Density functional theory calculations highlighted strong adsorption of Acacia on the (110) facet of CsPbBr3. Optical properties of the oriented quasi-spherical perovskites prepared with these data-driven strategies were significantly improved. This study demonstrates that data-driven controlled synthesis facilitates morphology-controlled perovskites with excellent optical properties.
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| 2. |
- Zhou, Jing, et al.
(författare)
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Dense Gas and Star Formation in Nearby Infrared-bright Galaxies: APEX Survey of HCN and HCO+ J=2 -> 1
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 936:1
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Tidskriftsartikel (refereegranskat)abstract
- Both Galactic and extragalactic studies of star formation suggest that stars form directly from dense molecular gas. To trace such high volume density gas, HCN and HCO+ J = 1 -> 0 have been widely used for their high dipole moments, relatively high abundances, and often being the strongest lines after CO. However, HCN and HCO+ J = 1 -> 0 emission could arguably be dominated by the gas components at low volume densities. The HCN J = 2 -> 1 and HCO+ J = 2 -> 1 transitions, with more suitable critical densities (1.6 x 10(6) and 2.8 x 10(5) cm(-3)) and excitation requirements, would trace typical dense gas closely related to star formation. Here we report new observations of HCN J = 2 -> 1 and HCO+ J = 2 -> 1 toward 17 nearby infrared-bright galaxies with the APEX 12 m telescope. The correlation slopes between the luminosities of HCN J = 2 -> 1 and HCO+ J = 2 -> 1 and total infrared emission are 1.03 +/- 0.05 and 1.00 +/- 0.05, respectively. The correlations of their surface densities, normalized with the area of radio/submillimeter continuum, show even tighter relations (slopes: 0.99 +/- 0.03 and 1.02 +/- 0.03). The eight active galactic nucleus (AGN)-dominated galaxies show no significant difference from the 11 star-formation-dominated galaxies in the above relations. The average HCN/HCO+ ratios are 1.15 +/- 0.26 and 0.98 +/- 0.42 for AGN- and star-formation-dominated galaxies, respectively, without obvious dependencies on infrared luminosity, dust temperature, or infrared pumping. The Magellanic Clouds roughly follow the same correlations, expanding to 8 orders of magnitude. On the other hand, ultraluminous infrared galaxies with AGNs systematically lie above the correlations, indicating potential biases introduced by AGNs.
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| 3. |
- Chen, Qiang, et al.
(författare)
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Transient Relativistic Plasma Grating to Tailor High-Power Laser Fields, Wakefield Plasma Waves, and Electron Injection
- 2022
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 128:16
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Tidskriftsartikel (refereegranskat)abstract
- We show the first experiment of a transverse laser interference for electron injection into the laser plasma accelerators. Simulations show such an injection is different from previous methods, as electrons are trapped into later acceleration buckets other than the leading ones. With optimal plasma tapering, the dephasing limit of such unprecedented electron beams could be potentially increased by an order of magnitude. In simulations, the interference drives a relativistic plasma grating, which triggers the splitting of relativistic-intensity laser pulses and wakefield. Consequently, spatially dual electron beams are accelerated, as also confirmed by the experiment.
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| 4. |
- Golovin, Grigory, et al.
(författare)
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Generation of ultrafast electron bunch trains via trapping into multiple periods of plasma wakefields
- 2020
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 27:3
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a novel approach to the generation of femtosecond electron bunch trains via laser-driven wakefield acceleration. We use two independent high-intensity laser pulses, a drive, and an injector, each creating their own plasma wakes. The interaction of the laser pulses and their wakes results in a periodic injection of free electrons in the drive plasma wake via several mechanisms, including ponderomotive drift, wake-wake interference, and pre-acceleration of electrons directly by strong laser fields. Electron trains were generated with up to four quasi-monoenergetic bunches, each separated in time by a plasma period. The time profile of the generated trains is deduced from an analysis of beam loading and confirmed using 2D particle-in-cell simulations.
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| 5. |
- Li, Shanghuo, et al.
(författare)
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The ALMA Survey of 70 mu m Dark High-mass Clumps in Early Stages (ASHES). II. Molecular Outflows in the Extreme Early Stages of Protocluster Formation
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 903:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA Survey of 70 mu m dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6-70 mu m dark prestellar clump candidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-three outflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rate of 14%. We discover six episodic molecular outflows associated with low- to high-mass cores, indicating that episodic outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range of core masses. The time span between consecutive ejection events is much smaller than those found in more evolved stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer accretion timescales than less massive cores. The lower accretion rates in these 70 mu m dark objects compared to the more evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller than the turbulent energy dissipation rate, which suggests that outflow-induced turbulence cannot sustain the internal clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 mu m dark clumps that is unrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars, or other motions.
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| 6. |
- Li, Shanghuo, et al.
(författare)
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The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VII. Chemistry of Embedded Dense Cores
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 939:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the chemistry toward 294 dense cores in 12 molecular clumps, using data obtained from the ALMA Survey of 70 μm dark High-mass clumps in Early Stages. We identified 97 protostellar cores and 197 prestellar core candidates, based on the detection of outflows and molecular transitions of high upper-energy levels (E u /k > 45 K). The detection rate of the N2D+ emission toward the protostellar cores is 38%, which is higher than 9% for the prestellar cores, indicating that N2D+ does not exclusively trace prestellar cores. The detection rates of the DCO+ emission are 35% for the prestellar cores and 49% for the protostellar cores, which are higher than those for N2D+, implying that DCO+ appears more frequently than N2D+ in both prestellar and protostellar cores. Both the N2D+ and DCO+ abundances appear to decrease from the prestellar to the protostellar stage. The DCN, C2D, and 13CS emission lines are rarely seen in the dense cores of early evolutionary phases. The detection rate of the H2CO emission toward dense cores is 52%, three times higher than that for CH3OH (17%). In addition, the H2CO detection rate, abundance, line intensities, and line widths increase with the core evolutionary status, suggesting that the H2CO line emission is sensitive to protostellar activity.
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| 7. |
- Sakamoto, K., et al.
(författare)
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P Cygni Profiles of Molecular Lines Toward Arp 220 Nuclei
- 2009
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Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 700:2, s. L104-L108
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Tidskriftsartikel (refereegranskat)abstract
- We report ~100 pc (0farcs3) resolution observations of (sub)millimeter HCO+ and CO lines in the ultraluminous infrared galaxy Arp 220. The lines peak at two merger nuclei, with HCO+ being more spatially concentrated than CO. Asymmetric line profiles with blueshifted absorption and redshifted emission are discovered in HCO+(3-2) and (4-3) toward the two nuclei and in CO(3-2) toward one nucleus. We suggest that these P Cygni profiles are due to ~100 km s–1 outward motion of molecular gas from the nuclei. This gas is most likely outflowing from the inner regions of the two nuclear disks rotating around individual nuclei, clearing the shroud around the luminosity sources there.
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| 8. |
- Shah, Suraj, et al.
(författare)
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Evaluating the added value of multi-variable calibration of SWAT with remotely sensed evapotranspiration data for improving hydrological modeling
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 603
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Tidskriftsartikel (refereegranskat)abstract
- Hydrological processes in a watershed consist of multiple sub-processes (such as plant growth, evapotranspiration, water yield, and soil–water balance) that have complex interactions. The common practice of calibrating hydrological models against only a single variable (e.g., streamflow) can lead to parameter uncertainty (also known as equifinality), resulting in significant uncertainties in the representation and simulation of sub-processes. As multi-variable calibration can be a potential solution to this issue, we tested the integration of spatially and temporally gridded remotely sensed evapotranspiration (RS-ET) data with the Soil and Water Assessment Tool (SWAT) hydrological model. This approach was intended to reduce equifinality by enhancing related hydrological sub-processes in both space and time rather than improving the evaluation metrics at the streamflow outlet. We further introduced the principle of repeated measure design in the calibration process, where the SWAT was calibrated under two different schemes: Scheme1 (using only streamflow data) and Scheme2 (using both RS-ET and streamflow data). The model's performance was evaluated using the concept of stability at multiple spatial scales (basin outlet, sub-basins, and hydrological response units) and aspects (different model outputs and most sensitive calibrated parameters). The significance of the difference between the stabilities produced by the two schemes was estimated using the Mann–Whitney U test. Testing this approach in Meichuan Basin (China) showed that Scheme2 substantially reduced equifinality for calibrated parameters and model outputs compared to Scheme1. In addition, the model solutions and outputs for Scheme2 were significantly different from Scheme1. Our results demonstrate the added value of using increasingly available open-access RS-ET data for improving hydrological model calibration.
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| 9. |
- Zhang, Lei, et al.
(författare)
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Discovery of a radio jet in the Cloverleaf quasar at z = 2.56
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 524:3, s. 3671-3682
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Tidskriftsartikel (refereegranskat)abstract
- The fast growth of supermassive black holes and their feedback to the host galaxies play an important role in regulating the evolution of galaxies, especially in the early Universe. However, due to cosmological dimming and the limited angular resolution of most observations, it is difficult to resolve the feedback from the active galactic nuclei (AGNs) to their host galaxies. Gravitational lensing, for its magnification, provides a powerful tool to spatially differentiate emission originating from AGN and host galaxy at high-redshifts. Here, we report a discovery of a jet-like radio structure in a strongly lensed starburst quasar, H1413+117 or Cloverleaf at redshift z = 2.56, based on observational data at optical, submillimetre, and radio wavelengths. With both parametric and non-parametric lens models and with reconstructed images in the source plane, we find a well-separated, kpc-scaled, single-sided radio jet located at projected to the north-west of the host galaxy in the source plane. This could indicate the co-existence of feedback from the AGN by both wind and jet in the Cloverleaf quasar.
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