Satellite observations have shown that the Asian Summer Monsoon strongly influences the upper troposphere and lower stratosphere (UTLS) aerosol morphology through its role in the formation of the ...Asian Tropopause Aerosol Layer (ATAL). Stratospheric Aerosol and Gas Experiment II solar occultation and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations show that summertime UTLS Aerosol Optical Depth (AOD) between 13 and 18 km over Asia has increased by three times since the late 1990s. Here we present the first in situ balloon measurements of aerosol backscatter in the UTLS from Western China, which confirm high aerosol levels observed by CALIPSO since 2006. Aircraft in situ measurements suggest that aerosols at lower altitudes of the ATAL are largely composed of carbonaceous and sulfate materials (carbon/sulfur elemental ratio ranging from 2 to 10). Back trajectory analysis from Cloud‐Aerosol Lidar with Orthogonal Polarization observations indicates that deep convection over the Indian subcontinent supplies the ATAL through the transport of pollution into the UTLS. Time series of deep convection occurrence, carbon monoxide, aerosol, temperature, and relative humidity suggest that secondary aerosol formation and growth in a cold, moist convective environment could play an important role in the formation of ATAL. Finally, radiative calculations show that the ATAL layer has exerted a short‐term regional forcing at the top of the atmosphere of −0.1 W/m2 in the past 18 years.
Key Points
Increase of summertime upper tropospheric aerosol levels over Asia since the 1990s
Upper tropospheric enhancement also observed by in situ backscatter measurements
Significant regional radiative forcing of −0.1 W/m2
Here, in an analysis of a 2.92 fb–1 data sample taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be B(D0 → K–e+νe) = ...(3.505 ± 0.014 ± 0.033)% and B(D0 → π–e+νe) = (0.295 ± 0.004 ± 0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f$ $^{K}_{+}$(0)|Vcs| = 0.7172 ± 0.0025 ± 0.0035 and $f$ $^{π}_{+}$(0)|Vcd| = 0.1435 ± 0.0018 ± 0.0009.
In this work, we perform first-principles calculations, coupled with synchrotron small-angle x-ray scattering (SAXS) to investigate electronic origins of the chemical short-range ordering (CSRO) and ...to reveal the relationship between CSROs and mechanical properties in a typical bcc (body-centered-cubic) TiZrHfNb high-entropy alloys (HEAs). It was found that existence of an appropriate degree of CSROs not only stabilizes the HEA lattice structure, but also enhances the hardness, elastic modulus, and ideal strength. Comprehensive electronic structure analyses uncover that the reduction of d electrons at the Fermi level due to the development of (Ti, Zr)-based CSROs stabilizes the bcc HEA, and the CSRO-induced strengthening is attributed to the local lattice distortion and the d-electron transfer from high-energy to low-energy states under applied strains. This finding not only gives insight into understanding the nature of CSRO strengthening in bcc HEAs, but also provides a paradigm for achieving desired mechanical properties via tailoring CSROs in HEAs.
Metallic nanoparticles are usually polyhedrons instead of perfect spheres, which presents a challenge to characterize their elastic response. In the present paper, the elastic compression of ...truncated octahedral nanoparticles is investigated through finite element calculations and atomic simulations. An analytical expression of load is obtained for octahedral particles, which is linearly proportional to indent depth, instead of the 3/2 power law relation predicted by Hertzian model for elastic sphere. Comparisons with molecular dynamics simulations demonstrate that the obtained relation can predict the elastic response of polyhedral nanoparticles. This study is helpful to measure the elastic properties of polyhedral nanoparticles, and characterize their elastic response.
Even inherently brittle hollow silicon nanoparticles (NPs) can withstand larger strain to failure than solid NPs. However, the influence of wall thickness on the mechanical behavior of hollow Si NPs ...is not fully understood. Using molecular dynamics simulations, we investigate the compressive behavior of hollow Si NPs. Three distinct failure mechanisms of hollow NPs are uncovered, and their strength and deformability are analyzed quantitatively. For extra-thick-walled NPs, dislocations will nucleate below the contact area and cut through the particles till failure. For mid-thick-walled NPs, however, dislocations will emit from the inner surface and slip towards the outer surface. For thin-walled NPs, elastic buckling is the cause of failure. Compared to solid NPs, hollow NPs with wall thickness being around half of its outer radius can achieve significant improvement in both strength and deformability.
Recently, the nested genes G72 and G30 on chromosome 13q32-q33 have been implicated in the etiology of schizophrenia. We genotyped six single-nucleotide polymorphisms (SNPs: rs3916965, rs3916967, ...rs2391191, rs778294, rs779293 and rs3918342), which span approximately 82.5 kb in the region encompassing the G72/G30 genes in 1176 Han Chinese subjects (588 cases and 588 controls) and 365 Scottish subjects (183 cases and 182 controls). Significant association between an allele of marker rs778293 and schizophrenia was found in our Chinese samples (P = 0.0013), and was replicated in the Scottish samples (P = 0.022). LD analysis revealed that four SNPs between rs3916965 and rs778294 were in LD, called block I, and the two distal SNPs (rs778293 and rs3918342) constituted a block II in both the Chinese and Scottish samples. We selected one SNP from each block (rs778294 from block I and rs778293 from block II), and then analyzed the haplotypes. A significant difference was observed for the common haplotype GC in the Chinese sample (P = 0.0145), and was replicated in the Scottish sample (P = 0.003). On meta-analysis, we separately analyzed the studies in Asian and European populations because of significant heterogeneity in the homogeneity test. We found a statistically significant association between rs778293 and schizophrenia in Asian populations, but no difference was found between cases and controls in the European populations. Overall, our data give further support to the existing evidence that G72/G30 genes are involved in conferring susceptibility to schizophrenia.
The reductive dechlorination and behavior of
p,
p′-dichlorodiphenyltrichloroethane (
p,
p′-DDT) was investigated in a paddy soil. Treatment with 5% (w/w) metallic iron (Fe
0) resulted in sharp ...decrease of
p,
p′-DDT, whereas there was no extra effect when 2% (w/w) aluminum sulfate (Al
2(SO
4)
3) was added to the Fe
0 treatment. These results suggest that Fe
0 could effectively promote the reductive dechlorination of
p,
p′-DDT and its metabolites while Al
2(SO
4)
3 did not show any effect on those processes. Furthermore,
p,
p′-DDT and its daughter compounds inhibited holistic soil respiration greatly at first but could be metabolized by certain species of indigenous microorganisms after a period of adaptation time in the soil. When treated with Fe
0, the polluted soil produced much less CO
2 while the addition of Al
2(SO
4)
3 counteracted its negative effect to much extent.
In this paper, an experimental investigation was conducted to explore the relationship between explosive spalling occurrence and residual mechanical properties of fiber-toughened high-performance ...concrete exposed to high temperatures. The residual mechanical properties measured include compressive strength, tensile splitting strength, and fracture energy. A series of concretes were prepared using OPC (ordinary Portland cement) and crushed limestone. Steel fiber, polypropylene fiber, and hybrid fiber (polypropylene fiber and steel fiber) were added to enhance fracture energy of the concretes. After exposure to high temperatures ranged from 200 to 800 °C, the residual mechanical properties of fiber-toughened high-performance concrete were investigated. For fiber concrete, although residual strength was decreased by exposure to high temperatures over 400 °C, residual fracture energy was significantly higher than that before heating. Incorporating hybrid fiber seems to be a promising way to enhance resistance of concrete to explosive spalling.
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