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Deep convection possesses markedly distinct properties at different spatiotemporal scales. We present an original high-resolution (4?km, hourly) unified data product of mesoscale convective systems (MCSs) and isolated deep convect...
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Deep convection possesses markedly distinct properties at different spatiotemporal scales. We present an original high-resolution (4?km, hourly) unified data product of mesoscale convective systems (MCSs) and isolated deep convection (IDC) in the United States east of the Rocky Mountains and examine their climatological characteristics from 2004 to 2017. The data product is produced by applying an updated Flexible Object Tracker algorithm to hourly satellite brightness temperature, radar reflectivity, and precipitation datasets. Analysis of the data product shows that MCSs are much larger and longer-lasting than IDC, but IDC occurs about 100 times more frequently than MCSs, with a mean convective intensity comparable to that of MCSs. Hence both MCS and IDC are essential contributors to precipitation east of the Rocky Mountains, although their precipitation shows significantly different spatiotemporal characteristics. IDC precipitation concentrates in summer in the Southeast with a peak in the late afternoon, while MCS precipitation is significant in all seasons, especially for spring and summer in the Great Plains. The spatial distribution of MCS precipitation amounts varies by season, while diurnally, MCS precipitation generally peaks during nighttime except in the Southeast. Potential uncertainties and limitations of the data product are also discussed. The data product is useful for investigating the atmospheric environments and physical processes associated with different types of convective systems; quantifying the impacts of convection on hydrology, atmospheric chemistry, and severe weather events; and evaluating and improving the representation of convective processes in weather and climate models. The data product is available at https://doi.org/10.25584/1632005 (Li et al., 2020).
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Nitrogen oxides ( NO x ? = ? NO ? + ? NO 2 ) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial va...
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Nitrogen oxides ( NO x ? = ? NO ? + ? NO 2 ) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial variations in NO 2 are functions of emissions, advection, deposition, vertical mixing, and chemistry. Their observations, therefore, provide useful constraints in our understanding of these factors. We employ a Regional chEmical and trAnsport model (REAM) to analyze the observed temporal (diurnal cycles) and spatial distributions of NO 2 concentrations and tropospheric vertical column densities (TVCDs) using aircraft in situ measurements and surface EPA Air Quality System (AQS) observations as well as the measurements of TVCDs by satellite instruments (OMI: the Ozone Monitoring Instrument; GOME-2A: Global Ozone Monitoring Experiment?– 2A), ground-based Pandora, and the Airborne Compact Atmospheric Mapper (ACAM) instrument in July 2011 during the DISCOVER-AQ campaign over the Baltimore–Washington region. The model simulations at 36 and 4? km resolutions are in reasonably good agreement with the regional mean temporospatial NO 2 observations in the daytime. However, we find significant overestimations (underestimations) of model-simulated NO 2 ( O 3 ) surface concentrations during nighttime, which can be mitigated by enhancing nocturnal vertical mixing in the model. Another discrepancy is that Pandora-measured NO 2 TVCDs show much less variation in the late afternoon than simulated in the model. The higher-resolution 4? km simulations tend to show larger biases compared to the observations due largely to the larger spatial variations in NO x emissions in the model when the model spatial resolution is increased from 36 to 4? km . OMI, GOME-2A, and the high-resolution aircraft ACAM observations show a more dispersed distribution of NO 2 vertical column densities (VCDs) and lower VCDs in urban regions than corresponding 36 and 4? km model simulations, likely reflecting the spatial distribution bias of NO x emissions in the National Emissions Inventory (NEI) 2011.
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摘要 :
Nitrogen oxides ( NO x ? = ? NO ? + ? NO 2 ) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial va...
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Nitrogen oxides ( NO x ? = ? NO ? + ? NO 2 ) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial variations in NO 2 are functions of emissions, advection, deposition, vertical mixing, and chemistry. Their observations, therefore, provide useful constraints in our understanding of these factors. We employ a Regional chEmical and trAnsport model (REAM) to analyze the observed temporal (diurnal cycles) and spatial distributions of NO 2 concentrations and tropospheric vertical column densities (TVCDs) using aircraft in situ measurements and surface EPA Air Quality System (AQS) observations as well as the measurements of TVCDs by satellite instruments (OMI: the Ozone Monitoring Instrument; GOME-2A: Global Ozone Monitoring Experiment?– 2A), ground-based Pandora, and the Airborne Compact Atmospheric Mapper (ACAM) instrument in July 2011 during the DISCOVER-AQ campaign over the Baltimore–Washington region. The model simulations at 36 and 4? km resolutions are in reasonably good agreement with the regional mean temporospatial NO 2 observations in the daytime. However, we find significant overestimations (underestimations) of model-simulated NO 2 ( O 3 ) surface concentrations during nighttime, which can be mitigated by enhancing nocturnal vertical mixing in the model. Another discrepancy is that Pandora-measured NO 2 TVCDs show much less variation in the late afternoon than simulated in the model. The higher-resolution 4? km simulations tend to show larger biases compared to the observations due largely to the larger spatial variations in NO x emissions in the model when the model spatial resolution is increased from 36 to 4? km . OMI, GOME-2A, and the high-resolution aircraft ACAM observations show a more dispersed distribution of NO 2 vertical column densities (VCDs) and lower VCDs in urban regions than corresponding 36 and 4? km model simulations, likely reflecting the spatial distribution bias of NO x emissions in the National Emissions Inventory (NEI) 2011.
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The synthesis of poly(ADP-ribose) (PAR) reconfigures the local chromatin environment and recruits DNA-repair complexes to damaged chromatin. PAR degradation by poly(ADP-ribose) glycohydrolase (PARG) is essential for progression an...
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The synthesis of poly(ADP-ribose) (PAR) reconfigures the local chromatin environment and recruits DNA-repair complexes to damaged chromatin. PAR degradation by poly(ADP-ribose) glycohydrolase (PARG) is essential for progression and completion of DNA repair. Here, we show that inhibition of PARG disrupts homology-directed repair (HDR) mechanisms that underpin alternative lengthening of telomeres (ALT). Proteomic analyses uncover a new role for poly(ADP-ribosyl)ation (PARylation) in regulating the chromatin-assembly factor HIRA in ALT cancer cells. We show that HIRA is enriched at telomeres during the G2 phase and is required for histone H3.3 deposition and telomere DNA synthesis. Depletion of HIRA elicits systemic death of ALT cancer cells that is mitigated by re-expression of ATRX, a protein that is frequently inactivated in ALT tumors. We propose that PARylation enables HIRA to fulfill its essential role in the adaptive response to ATRX deficiency that pervades ALT cancers.
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Indosinian W-Sn metallogeny associated with granites in South China has been reported in recent years by many researchers. However, the refined genetic relations between these deposits and the related granites remain unclear in mo...
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Indosinian W-Sn metallogeny associated with granites in South China has been reported in recent years by many researchers. However, the refined genetic relations between these deposits and the related granites remain unclear in most areas, and the tectonic setting of Indosinian magmatism and W-Sn mineralization are still widely contro-versial. The Banjiaoyuan tin deposit is located in the east vicinity of Yangmingshan pluton in the middle Nanling Range, South China. The granitic stocks in this deposit comprise two intrusive episodes, i.e., the first episode of medium-coarse-grained porphyritic tourmaline-biotite monzogranite (G1), and the second episode of micron-fine-grained tourmaline-muscovite monzogranite (G2). LA-ICP-MS zircon U-Pb dating gives weighted ages of 226.9 +/- 1.6 Ma to 223.8 +/- 1.9 Ma for G1, and 224.3 +/- 2.0 Ma for G2, respectively. LA-MC-ICP-MS cassiterite U-Pb dating yields Tera-Wasserburg concordia age of 216.7 +/- 2.4 Ma for tin mineralization. These ages indicate that both the granitic magmatism and related mineralization were initiated in the late Indosinian period. All the granites have high SiO2, Al2O3, P2O5 contents, and low TFeO, CaO, MgO, TiO2 contents, indicating that the granites are highly differentiated S-type granites, and furthermore, the high DI and Rb, K, U, Hf, Sm, low SI and Ba, Sr, Ti, TREE further show that the granites have undergone high extent of differentiation and evolution. High Rb/Nb and K/Nb ratios, low Nb/Ta and Zr/Hf ratios, widely varying CaO/Na2O ratios, low and uniform epsilon Nd(t) values, and dominantly negative and relatively dispersed epsilon Hf(t) values jointly indicate that the granites were derived from a heterogeneous mixture of calcium-poor mudstone and calcium-rich psammite (or metamorphic igneous rocks) in the crust. The known Indosinian W-Sn deposits in South China are more closely related to S-type granites than to I-type granites, suggesting that their ore-forming materials are mainly derived from the crust. In addition, individual positive epsilon Hf(t) values indicate that a small amount of newborn crustal components were involved in the formation of granitic magma. Compared with G1, G2 differs distinctly in petrological, chemical and isotopic characteristics, especially it is more richer in F content and contains magmatic cassiterite and wolframite crystals, suggesting that G2 have undergone higher extent of differentiation and evolution, and are much more closely related to the Sn-W miner-alization than G1. The late Indosinian granites in this deposit were formed in post-collisional extensional tectonic environment, while the early Indosinian granites intruded in the Yangmingshan area were formed in syn-collision compression environment. Based on the statistics, the metallogenic ages of Indosinian W-Sn deposits in South China are between 212 and 230 Ma, and the petrogenetic ages of related granites are between 211 and 230 Ma, both age groups belong to the late Indosinian period, representing a regional large-scale granitic magma intrusion and mineralization event that initiated in post-collisional extensional tectonic environment.
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Foot and ankle deformity remains a common presenting complaint in orthopedic surgery. External fixator is a key medical device to assist gradual correction. Its configuration selection has a significant influence on correction res...
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Foot and ankle deformity remains a common presenting complaint in orthopedic surgery. External fixator is a key medical device to assist gradual correction. Its configuration selection has a significant influence on correction results. Among two external fixators currently used in clinic, conventional Ilizarov external fixator (IEF) has high use difficulty and low accuracy, whereas the single configuration of later hexapod external fixator (HEF) leads to inadequate adaptation to diverse deformity types in foot and ankle. To solve the above problems, this paper presents a novel parallel distraction apparatus (PDA). First, corrective degree-of-freedom (c-DOF) is defined to determine expected posture transformation of external fixator required by corrective manipulation. By summarizing and classifying c-DOF, predominant foot and ankle deformities with fewer correction requirements are divided into six types. Subsequently, six lower-mobility parallel mechanisms are introduced as the configurations of external fixators via the c-DOF based configuration synthesis approach. After performing reconfigurable structural design, PDA can respectively form six types of parallel external fixators for six deformity types. Finally, clinical case simulations are provided to verify the application potential and advantages of PDA.
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Until now, driving mechanisms behind recurring droughts and hydroclimate variations that controls the Nile River Basin (NRB) remains poorly understood. Our results show significant hydroclimatic changes that contributed to recent ...
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Until now, driving mechanisms behind recurring droughts and hydroclimate variations that controls the Nile River Basin (NRB) remains poorly understood. Our results show significant hydroclimatic changes that contributed to recent increasing aridity of NRB since the 1970s. Besides climate warming, the influence of stronger ENSO and Indian Ocean dipole (IOD) in NRB has increased after 1980s, which have significantly contributed to NRB’s drought severity at inter-annual to inter-decadal timescales. Our results demonstrate that warming, El Ni?o and IOD have played a crucial role on NRB’s inter-decadal hydroclimate variability, but IOD has played a more important role in modulating NRB’s hydroclimate at higher timescales than El Ni?o. Results also indicate that the impacts of positive phases of ENSO and IOD events are larger than the negative phases in the NRB hydroclimate. Further, the southward (westward) shift in stream functions and meridional (zonal) winds caused an enhancement in the blocking pattern, with strong anticyclonic waves of dry air that keeps moving into NRB, has resulted in drier NRB, given stream function, geopotential height and U-wind anomalies associated with El Ni?o shows that changes in regional atmospheric circulations during more persistent and stronger El Ni?o has resulted in drier NRB. After 1970s, El Ni?o, IOD, and drought indices shows significant anti-phase relationships, which again demonstrates that more frequent and severe El Ni?o and IOD in recent years has led to more severe droughts in NRB. Our results also demonstrate that IOD and and the western pole of the Indian Ocean Dipole (WIO) are better predictors of the Nile flow than El Ni?o, where its flow has decreased by 13.7 (upstream) and by 114.1?m3/s/decade (downstream) after 1964. In summary, under the combined impact of warming and stronger IOD and El Ni?o, future droughts of the NRB will worsen.
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Upper limb rehabilitation exoskeletons are critical equipments for stroke patients with motor function disorders. According to the floating characteristic of human gleno-humeral (GH) joint center, the configuration synthesis for t...
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Upper limb rehabilitation exoskeletons are critical equipments for stroke patients with motor function disorders. According to the floating characteristic of human gleno-humeral (GH) joint center, the configuration synthesis for the four-degrees of freedom (4-DOFs) self-aligning exoskeleton mechanisms (SAEMs) is addressed. Based on the configuration priorities of SAEMs, a novel 4-DOFs SAEM is proposed. While the exoskeleton is connected to the upper limb, a human-exoskeleton closed chain with two loops is formed. Subsequently, the kinematic equations of the human-exoskeleton closed chain are established and a position solution method is presented. To evaluate the kinematic performance of the SAEM, the movements of the upper limb in activities of daily living (ADL) are quantified experimentally, on which the joint angle trajectories are generated. Finally, kinematic characteristics of the SAEM in ADL are investigated. Results of the study indicate that the SAEM is suitable for the upper limb rehabilitation and can be used as primary design parameters for the proposed SAEM. (C) 2019 Elsevier Ltd. All rights reserved.
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The performances of low-velocity impact (LVI) and compression after impact (CAI) of honeycomb sandwich composite panels are investigated experimentally and numerically. Honeycomb sandwich panels with different facesheet thicknesse...
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The performances of low-velocity impact (LVI) and compression after impact (CAI) of honeycomb sandwich composite panels are investigated experimentally and numerically. Honeycomb sandwich panels with different facesheet thicknesses are impacted by drop-weight machine under gradually increasing impact energies. The visible surface damage is recorded and ultrasonic C-scan technology is used to inspect the internal damage of sandwich plates. Numerical simulation is conducted using finite element method, taking into account both facesheet damage and honeycomb damage. The facesheet damage model is based on the continuum damage mechanics and cohesive zone model to simulate intralaminar and interlaminar damage respectively. The honeycomb damage model, which takes into account of both compressive damage and shear damage, is addressed and verified by three-point bending experimental tests. The numerical results show good agreements on LVI and CAI with the experiments, thus verifying the validity of the presented numerical model. Then we use the numerical model to simulate the LVI properties of sandwich plates under compressive and tensile preloading. We conclude that the interlaminar delamination damage of facesheet easily evolves under compressive preloading while intralaminar fiber fracture damage could expand under tensile preloading. The conclusion in our article could be useful to the design and analysis of composite sandwich structures.
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Partial differential equations (PDEs) are the most ubiquitous tools for modeling natural science problems and have long received attention. Physics-informed neural networks (PINNs) are emerging approaches to approximately solve PD...
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Partial differential equations (PDEs) are the most ubiquitous tools for modeling natural science problems and have long received attention. Physics-informed neural networks (PINNs) are emerging approaches to approximately solve PDEs. PINNs use automatic differentiation technology to construct the residual of PDEs in the loss function to encode physics conservation laws. We call this process the Single-Net strategy. Due to the dependency of automatic differentiation among different orders of derivatives, the efficiency of PINNs under the Single-Net strategy is limited. To address this issue, we propose the Multi-Net strategy to decouple the dependency. Compared with the Single-Net strategy, the Multi-Net strategy reduces the training time of PINNs, and meanwhile, keeps the prediction accuracy. The effectiveness of the proposed strategy is demonstrated through time complexity analysis and a collection of experiments on Burgers equation, advection-dispersion equation, Kdv equation, and Allen-Cahn equation.
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