分类： 医学、药学 >> 预防医学与公共卫生学 提交时间： 2023-03-29
摘要：Emerging in December 2019, coronavirus disease 2019 (COVID-19) eventually became a pandemic and posed a tremendous threat to global public health. However, the origins of SARS-CoV-2, the causative agent of COVID-19, remain to be determined. It has been reported that a certain number of the early case clusters had a contact history with the Huanan Seafood Market. Therefore, surveillance of SARS-CoV-2 within the market is of vital importance. Herein, we presented the SARS-CoV-2 detection results of 1380 samples collected from the environment since 1st Jan and animals since 18th Jan within the market in early 2020. By SARS-CoV-2-specific RT-qPCR, 73 environmental samples tested positive for SARS-CoV-2 and three live viruses were successfully isolated. The viruses from the market shared nucleotide identity of 99.99% to 100% with the human isolate HCoV-19/Wuhan/IVDC-HB-01/2019. The A lineage (8782T and 28144C), as the likely ancestral SARS-CoV-2 lineage, was found in an environmental sample. No virus was detected in the animal swabs covering 18 species of animals in the market. The RNA-seq analysis of SARS-CoV-2 positive/negative environmental samples showed the abundance of different vertebrata genera. In summary, this study provided convincing evidence of the prevalence of SARS-CoV-2 in the Huanan Seafood Market during the early stage of COVID-19 outbreak.
分类： 材料科学 >> 材料科学（综合） 提交时间： 2020-08-12
摘要： Graphene has well demonstrated its unique properties and advantageous performances in lots of fields during the last 16 years. However, its industrial applications are still impeded by inefficient mass fabrication of high-quality graphene because of the great challenge in deep yet non-destructive graphite exfoliation. Herein, we demonstrated a delocalized electrochemical exfoliation (DEE) technique to efficiently fabricate high-quality graphene. Importantly, chemically transmitting the electric potentials was firstly proposed to spatially extend the exfoliation capability of electric potentials and electrochemically exfoliate every graphite particle dispersed in the electrolyte. The resulting graphene possesses ultralow defect density (ID/IG~0.07) and extremely high carbon-to-oxygen ratio (~28). Remarkably, high yields (~98.4%, 1-10 layers) and record high production rates (~72.7 g h?1) are realized in up-scaled batch of DEE. Further mechanism investigation revealed that the exfoliation capability of the electric potentials was transmitted to the whole electrolyte system by a dynamically favorable pathway. This pathway includes electrochemical oxidation, intercalation and interlayer bubble generation reactions, which makes deep and non-destructive exfoliation possible for every dispersed graphite particle in a scalable and reproducible manner. This way of using electric potentials differs from existing electrochemical methods and guarantees high throughput as well as high quality. The strategy of delocalized electrochemical exfoliation and the underlying concept of chemically transmitting the electric potentials would accelerate the commercialization of graphene and inspire more efficient fabrication of two-dimensional materials.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要：The High Energy cosmic Radiation Detection (HERD) facility is a space mission designed for detecting cosmic ray (CR) electrons, γ-rays up to tens of TeV and CR nuclei from proton to iron up to several PeV. The main instrument of HERD is a 3-D imaging calorimeter (CALO) composed of nearly ten thousand cubic LYSO crystals. A large dynamic range of single HERD CALO Cell (HCC) is necessary to achieve HERD’s PeV observation objectives, which means that the response of HCC should maintain a good linearity from minimum ionizing particle (MIP) calibration to PeV shower maximum. In order to study the linearity of HCC over such a large energy range, a beam test has been implemented at the E2 and E3 beam lines of BEPC. High intensity pulsed electron beam provided by E2 line are used for producing high energy density within HCC; π+/proton provided by E3 line are used for HCC calibration. The results show that no saturation eﬀect occurs and the linearity of HCC is better than 10% from 30 MeV (1 MIP) to 1.1×103 TeV (energy density is 93 TeV/cm3), which can meet the requirement mentioned above.
分类： 地球科学 >> 空间物理学 提交时间： 2017-03-10
摘要：For the spaceborne scanning pencil-beam scatterometer, the azimuth resolution is low that could not meet the demands. Based on the motion of platform and the scanning rules of the spaceborne scatterometer, this paper takes an unfocused SAR approach to improve the Azimuth Resolution.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要：In this article, we present the scalar-diquark-scalar-diquark-antiquark type and scalar-diquark-axialvector-diquark-antiquark type pentaquark configurations in the diquark model, and study the masses and pole residues of the JP=12± hidden-charmed pentaquark states in details with the QCD sum rules by extending our previous work on the JP=32− and 52+ hidden-charmed pentaquark states. We calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion by constructing both the scalar-diquark-scalar-diquark-antiquark type and scalar-diquark-axialvector-diquark-antiquark type interpolating currents. The present predictions of the masses can be confronted to the LHCb experimental data in the future.
分类： 物理学 >> 核物理学 提交时间： 2016-08-30
摘要：In this letter, we explore the nature of the electroweak phase transition (EWPT) with both particle colliders and gravitational wave (GW) detection. With the observed Higgs mass, the shape of the Higgs potential is fully determined within the standard model (SM) of particle physics. However, it could be changed if there exists new physics beyond the SM. Working with the effective field theory, we show that a modified Higgs potential with a sextic term included can keep the observed 125 GeV Higgs mass but behave different when compared with the SM case. Furthermore, this potential can produce a strong first order phase transition (SFOPT) for the electroweak baryogenesis and interestingly predict new phenomena in the Higgs sector, which can be tested at colliders such as the Large Hadron Collider (LHC) and the planning Circular Electron Positron Collider (CEPC). We point out this SFOPT can lead to detectable signals for the GW interferometers , such as eLISA, DECIGO and BBO. Our present study on the EWPT bridges the particle physics at colliders with the astrophysics and cosmology in the early universe.
分类： 生物学 >> 植物学 >> 植物生理学 提交时间： 2016-05-03
In plants, Vacuole H+-PPases (VPPs) are important proton pumps and encoded by multiple genes. In addition to full-length VPPs, several truncated forms are expressed, but their biological functions are unknown. In this study, we functionally characterized maize vacuole H+-PPase 5 (ZmVPP5), a truncated VPP in the maize genome. Although ZmVPP5 shares high sequence similarity with ZmVPP1, ZmVPP5 lacks the complete structure of the conserved proton transport and the inorganic pyrophosphatase-related domain. Phylogenetic analysis suggests that ZmVPP5 might be derived from an incomplete gene duplication event. ZmVPP5 is expressed in multiple tissues, and ZmVPP5 was detected in the plasma membrane, vacuole membrane and nuclei of maize cells. The overexpression of ZmVPP5 in yeast cells caused a hypersensitivity to salt stress. Transgenic maize lines with overexpressed ZmVPP5 also exhibited the salt hypersensitivity phenotype. A yeast two-hybrid analysis identified the ZmBag6-like protein as a putative ZmVPP5-interacting protein. The results of bimolecular luminescence complementation (BiLC) assay suggest an interaction between ZmBag6-like protein and ZmVPP5 in vivo. Overall, this study suggests that ZmVPP5 might act as a VPP antagonist and participate in the cellular response to salt stress. Our study of ZmVPP5 has expanded the understanding of the origin and functions of truncated forms of plant VPPs.