12,929 research outputs found
Nonclassical photon pairs generated from a room-temperature atomic ensemble
We report experimental generation of non-classically correlated photon pairs
from collective emission in a room-temperature atomic vapor cell. The
nonclassical feature of the emission is demonstrated by observing a violation
of the Cauchy-Schwarz inequality. Each pair of correlated photons are separated
by a controllable time delay up to 2 microseconds. This experiment demonstrates
an important step towards the realization of the Duan-Lukin-Cirac-Zoller scheme
for scalable long-distance quantum communication.Comment: 4 pages, 2 figure
Multi-scale anisotropy in NE China: Evidence for localized mantle upwelling
It is commonly proposed that the subduction of the Pacific plate has been responsible for widespread Holocene intraplate volcanism across NE China and the Korean Peninsula. Yet, how this process drives volcanism and even if it plays a critical role remains a topic of vigorous debate. In this study, using seismic data from four networks across NE China and northern Democratic People's Republic of Korea (DPRK), we analyze shear wave splitting in converted P to S-waves at the Moho (Pms), S-waves from the subducted slab interface (local S), and SKS phases. The Pms phases show a relatively weak crustal anisotropy (<0.25 s), with fast polarization directions aligned sub-parallel to major tectonic features. For the local S and SKS phases, fast polarization directions show significant lateral variations. We further perform a quantitative inversion to show that the depth of the anisotropy is âŒ150 km, thus driven by flow within the asthenosphere associated with Pacific subduction. However, the presence of many null SKS splitting phases, together with scattered local S anisotropy across a wide range of incidence angles suggests a localized region of vertical flow directly beneath Changbaishan volcano. Such patterns correspond well to regional upper-mantle seismic velocity structure, and suggest that a localized upwelling with a relatively deep origin drives volcanism in the Changbaishan region. Furthermore, we infer that this mantle upwelling is deflected to the SW beneath Changbaishan and spreads asymmetrically at the base of the lithosphere, possibly because of the long history of volcanism in the region
Divergent behaviour of soil nutrients imprinted by different land management practices in the Three Gorges Reservoir Area, China
Soil nutrients are essentially regulated by land management practices via modulating biotic element input and metabolism. The Three Gorges Reservoir Area in China was dominated by a farming landscape, but land management has become diversified over recent decades. How these restorative management practices may have affected soil nutrients is not completely understood. In this study, a space-time substitution approach was applied to evaluate soil nutrients and their stoichiometric changes in response to post-farming land management practices. Soil samples(0â10 cm, 10â20 cm, and 20â40 cm) were collected from present-day croplands, cypress plantations, eucalyptus plantations, abandoned croplands, and citrus plantations. Soil organic matter, soil organic carbon, total nitrogen, alkaline hydrolyzed nitrogen, total phosphorus, and available phosphorus were determined. The results showed that soil organic matter and total nitrogen in abandoned croplands, cypress plantations, eucalyptus
plantations and citrus plantations were increased by 186% and 190%, 184% and 107%, 45% and 33%, and 45% and 54%, respectively, in comparison with present-day croplands. Soil nutrients except for total phosphorus decreased more with soil depth by exclusion of tillage mixing. The analysis of the comprehensive soil nutrient index showed that abandoned croplands (0.90) and cypress plantations(0.72) exhibited better nutrient recovery capacity. Soil C:P and N:P ratios increase in abandoned croplands, cypress plantations, and eucalyptus plantations. Phosphorus may become a limiting factor for plant growth with prolonged recovery in abandoned croplands, cypress plantations, and eucalyptus plantations, while soil organic matter and total nitrogen deficiencies are exacerbated in citrus plantations and present-day croplands. Therefore, cropland abandonment and reforestation (particularly cypress trees plantation) are recommended practices for restoring soil nutrients in the
Three Gorges Reservoir Area
The SVOM gamma-ray burst mission
We briefly present the science capabilities, the instruments, the operations,
and the expected performance of the SVOM mission. SVOM (Space-based multiband
astronomical Variable Objects Monitor) is a Chinese-French space mission
dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade. The SVOM
mission encompasses a satellite carrying four instruments to detect and
localize the prompt GRB emission and measure the evolution of the afterglow in
the visible band and in X-rays, a VHF communication system enabling the fast
transmission of SVOM alerts to the ground, and a ground segment including a
wide angle camera and two follow-up telescopes. The pointing strategy of the
satellite has been optimized to favor the detection of GRBs located in the
night hemisphere. This strategy enables the study of the optical emission in
the first minutes after the GRB with robotic observatories and the early
spectroscopy of the optical afterglow with large telescopes to measure the
redshifts. The study of GRBs in the next decade will benefit from a number of
large facilities in all wavelengths that will contribute to increase the
scientific return of the mission. Finally, SVOM will operate in the era of the
next generation of gravitational wave detectors, greatly contributing to
searches for the electromagnetic counterparts of gravitational wave triggers at
Xray and gamma-ray energies.Comment: 13 pages, 5 figures, published by PoS, proceedings of the conference
Swift: 10 Years of Discovery, 2-5 December 2014, La Sapienza University,
Rome, Ital
Allometric scaling of skin thickness, elasticity, viscoelasticity to mass for micro-medical device translation:From mice, rats, rabbits, pigs to humans
Abstract Emerging micro-scale medical devices are showing promise, whether in delivering drugs or extracting diagnostic biomarkers from skin. In progressing these devices through animal models towards clinical products, understanding the mechanical properties and skin tissue structure with which they interact will be important. Here, through measurement and analytical modelling, we advanced knowledge of these properties for commonly used laboratory animals and humans (~30âg to ~150âkg). We hypothesised that skinâs stiffness is a function of the thickness of its layers through allometric scaling, which could be estimated from knowing a speciesâ body mass. Results suggest that skin layer thicknesses are proportional to body mass with similar composition ratios, inter- and intra-species. Experimental trends showed elastic moduli increased with body mass, except for human skin. To interpret the relationship between species, we developed a simple analytical model for the bulk elastic moduli of skin, which correlated well with experimental data. Our model suggest that layer thicknesses may be a key driver of structural stiffness, as the skin layer constituents are physically and therefore mechanically similar between species. Our findings help advance the knowledge of mammalian skin mechanical properties, providing a route towards streamlined micro-device research and development onto clinical use
Direct Imaging of Graphene Edges: Atomic Structure and Electronic Scattering
We report an atomically-resolved scanning tunneling microscopy (STM)
investigation of the edges of graphene grains synthesized on Cu foils by
chemical vapor deposition (CVD). Most of the edges are macroscopically parallel
to the zigzag directions of graphene lattice. These edges have microscopic
roughness that is found to also follow zigzag directions at atomic scale,
displaying many ~120 degree turns. A prominent standing wave pattern with
periodicity ~3a/4 (a being the graphene lattice constant) is observed near a
rare-occurring armchair-oriented edge. Observed features of this wave pattern
are consistent with the electronic intervalley backscattering predicted to
occur at armchair edges but not at zigzag edges
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