221 research outputs found
Neutron Energy Spectrum Measurements with a Compact Liquid Scintillation Detector on EAST
A neutron detector based on EJ301 liquid scintillator has been employed at
EAST to measure the neutron energy spectrum for D-D fusion plasma. The detector
was carefully characterized in different quasi-monoenergetic neutron fields
generated by a 4.5 MV Van de Graaff accelerator. In recent experimental
campaigns, due to the low neutron yield at EAST, a new shielding device was
designed and located as close as possible to the tokamak to enhance the count
rate of the spectrometer. The fluence of neutrons and gamma-rays was measured
with the liquid neutron spectrometer and was consistent with 3He proportional
counter and NaI (Tl) gamma-ray spectrometer measurements. Plasma ion
temperature values were deduced from the neutron spectrum in discharges with
lower hybrid wave injection and ion cyclotron resonance heating. Scattered
neutron spectra were simulated by the Monte Carlo transport Code, and they were
well verified by the pulse height measurements at low energies.Comment: 19 pages,10 figures, 1 tabl
A combined methodology for reconstructing source-to-sink basin evolution, exemplified by the Triassic SongpanâGanzi basin, central China
Source-to-sink evolution of a basin is a key to understand sedimentary processes, especially in a complex regional orogenic setting. Detrital zircon populations can be traced from their primary sources to their depositional settings. The resulting interpretations are enhanced by calculation of the adjacent orogen's paleoaltimetry, which provides additional insights into paleogeography. In this study, we present a combined methodology which aims to reconstruct source-to-sink evolution by the analysis of detrital zircon age distribution in sandstones, together with the calculation of paleo-elevation of surrounding orogens based on the chemical compositions of coeval magmatic rocks. We test the method using detrital zircon UâPb geochronological data sets from the Triassic SongpanâGanzi basin in central China, combined with whole-rock geochemical data from intermediate-composition magmatic rocks in adjacent crustal blocks. Application of the combined methodology supports a syn-collisional basin model for the formation of the Triassic Songpan-Ganzi basin in preference to a continental back-arc basin. The clastic sediments, mainly deep-marine turbidites, accumulated in a remnant Paleotethyan Ocean that was surrounded by the converging North China Block, South China Block, East Kunlun Orogenic Belt and the Qiangtang Block. The North China Block and the North Qaidam Block were major proto-sources of detrital zircons to the basin, contributing on average 12âŻ% and 15âŻ%, respectively. Triassic magmatic rocks in the East Kunlun and Qiangtang regions were major sources of igneous zircons, up to 68âŻ% for the former and up to 56âŻ% for the latter. Despite being located at a calculated elevation of ca. 4000âŻm, the Qinling Orogenic Belt contributed only ca. <10âŻ% of the zircons, mostly restricted to the eastern depocenter of the basin. In contrast, supply from the North Qiangtang Block, despite its calculated lower elevation (1000â3000âŻm), accounts for 2â10âŻ% of the detrital zircons in the basin, suggesting high erosion rates of this block. The minimal supply of zircons from the South China Block, restricted to 3â6âŻ% in the central and western depocenters, is inconsistent with the zircon abundances predicted in the alternative back-arc basin model of the SongpanâGanzi basin
Doping and temperature dependence of electron spectrum and quasiparticle dispersion in doped bilayer cuprates
Within the t-t'-J model, the electron spectrum and quasiparticle dispersion
in doped bilayer cuprates in the normal state are discussed by considering the
bilayer interaction. It is shown that the bilayer interaction splits the
electron spectrum of doped bilayer cuprates into the bonding and antibonding
components around the point. The differentiation between the bonding
and antibonding components is essential, which leads to two main flat bands
around the point below the Fermi energy. In analogy to the doped
single layer cuprates, the lowest energy states in doped bilayer cuprates are
located at the point. Our results also show that the striking
behavior of the electronic structure in doped bilayer cuprates is intriguingly
related to the bilayer interaction together with strong coupling between the
electron quasiparticles and collective magnetic excitations.Comment: 9 pages, 4 figures, updated references, added figures and
discussions, accepted for publication in Phys. Rev.
Virulence of H5N1 virus in mice attenuates after in vitro serial passages
The virulence of A/Vietnam/1194/2004 (VN1194) in mice attenuated after serial passages in MDCK cells and chicken embryos, because the enriched large-plaque variants of the virus had significantly reduced virulence. In contrast, the small-plaque variants of the virus and the variants isolated from the brain of mice that were infected with the parental virus VN1194 had much higher virulence in mice. The virulence attenuation of serially propagated virus may be caused by the reduced neurotropism in mice. Our whole genome sequence analysis revealed substitutions of a total of two amino acids in PB1, three in PB2, two in PA common for virulence attenuated variants, all or part of which may be correlated with the virulence attenuation and reduced neurotropism of the serially propagated VN1194 in mice. Our study indicates that serial passages of VN1194 in vitro lead to adaptation and selection of variants that have markedly decreased virulence and neurotropism, which emphasizes the importance of direct analysis of original or less propagated virus samples
Revisiting Image Aesthetic Assessment via Self-Supervised Feature Learning
Visual aesthetic assessment has been an active research field for decades.
Although latest methods have achieved promising performance on benchmark
datasets, they typically rely on a large number of manual annotations including
both aesthetic labels and related image attributes. In this paper, we revisit
the problem of image aesthetic assessment from the self-supervised feature
learning perspective. Our motivation is that a suitable feature representation
for image aesthetic assessment should be able to distinguish different
expert-designed image manipulations, which have close relationships with
negative aesthetic effects. To this end, we design two novel pretext tasks to
identify the types and parameters of editing operations applied to synthetic
instances. The features from our pretext tasks are then adapted for a one-layer
linear classifier to evaluate the performance in terms of binary aesthetic
classification. We conduct extensive quantitative experiments on three
benchmark datasets and demonstrate that our approach can faithfully extract
aesthetics-aware features and outperform alternative pretext schemes. Moreover,
we achieve comparable results to state-of-the-art supervised methods that use
10 million labels from ImageNet.Comment: AAAI Conference on Artificial Intelligence, 2020, accepte
Experimental Study on Unconfined Compressive Strength of Basalt Fiber Reinforced Clay Soil
In order to study the mechanism and effect of basalt fiber reinforced clay soil, a series of unconfined compressive strength tests conducted on clay soil reinforced with basalt fiber have been performed under the condition of optimum water content and maximum dry density. Both the content and length of basalt fiber are considered in this paper. When the effect of content is studied, the 12âmm long fibers are dispersed into clay soil at different contents of 0.05%, 0.1%, 0.15%, 0.20%, 0.25%, 0.30%, and 0.35%. When the effect of length is researched, different lengths of basalt fibers with 4âmm, 8âmm, 12âmm, and 15âmm are put into soil at the same content of 0.05%. Experimental results show that basalt fiber can effectively improve the UCS of clay soil. And the best content and length are 0.25% and 12âmm, respectively. The results also show that the basalt fiber reinforced clay soil has the âpoststrongâ characteristic. About the reinforcement mechanism, the fiber and soil column-net model is proposed in this paper. Based on this model and SEM images, the effect of fiber content and length is related to the change of fiber-soil column and formation of effective fiber-soil net
Development of an ELISA-array for simultaneous detection of five encephalitis viruses
Japanese encephalitis virus(JEV), tick-borne encephalitis virus(TBEV), and eastern equine encephalitis virus (EEEV) can cause symptoms of encephalitis. Establishment of accurate and easy methods by which to detect these viruses is essential for the prevention and treatment of associated infectious diseases. Currently, there are still no multiple antigen detection methods available clinically. An ELISA-array, which detects multiple antigens, is easy to handle, and inexpensive, has enormous potential in pathogen detection. An ELISA-array method for the simultaneous detection of five encephalitis viruses was developed in this study. Seven monoclonal antibodies against five encephalitis-associated viruses were prepared and used for development of the ELISA-array. The ELISA-array assay is based on a "sandwich" ELISA format and consists of viral antibodies printed directly on 96-well microtiter plates, allowing for direct detection of 5 viruses. The developed ELISA-array proved to have similar specificity and higher sensitivity compared with the conventional ELISAs. This method was validated by different viral cultures and three chicken eggs inoculated with infected patient serum. The results demonstrated that the developed ELISA-array is sensitive and easy to use, which would have potential for clinical use
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