分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要：Hefei Light Source (HLS)-II is a vacuum ultraviole (VUV) synchrotron light source. A major upgrade of the light source was finished at the end of 2014. The timing system was rebuilt using compact peripheral component interconnect (cPCI) event-driven hardware to meet synchronization requirements of the machine. In the new system, the cPCI event-driven products manufactured by the micro-research finland (MRF) Oy are employed to achieve about 100 output signals with different interfaces. Device supports and drivers developed for common Experimental Physics and Industrial Control System (EPICS) records are used to access the registers on the timing modules. Five cPCI-bus input/output controllers (IOCs) distributed in different areas of the light source host timing modules for various subsystems. The delay resolution of this system is 9.8 ns for most channels and 9 ps for the channels used for triggering the electron gun and the injection kickers. The measured rms jitter of the output signal is less than 27 ps. Using the bucket chooser, this system enables the HLS-II to fill the storage ring with any designated bunch pattern. Benefitting from this upgrade, brightness and performance of the light source are significantly improved.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要：For a high-energy electron facility, estimates of induced radioactivity in materials are of considerable importance to ensure that the exposure of personnel and the environment remains as low as reasonably achievable. In addition, accurate predictions of induced radioactivity are essential to the design, operation, and decommissioning of a high-energy electron linear accelerator. In the case of the 200-MeV electron linac of the National Synchrotron Radiation Laboratory (NSRL), the electrons are accelerated by five acceleration tubes and collimated by copper scrapers. The scrapers, which play a vital role in protecting the acceleration cavity, are bombarded by many electrons over a long-term operation, which causes a significant amount of induced radioactivity. Recently, the NSRL Linac is the first high-energy electron linear accelerator in China to be out of commission. Its decommissioning is highly significant for obtaining decommissioning experience. This paper focuses on the measurement of induced radioactivity on the fourth scraper, where the electron energy was 158 MeV. The radionuclides were classified according to their half-lives. Such a classification provides a reliable basis for the formulation of radiation protection and facility decommissioning. To determine the high-radioactivity area and to facilitate the decommissioning process, the slicing method was applied in this study. The specific activity of 60Co in each slice was measured at a cooling time of ten months, and the results were compared with the predictions generated by Monte Carlo program FLUKA. The trend of the measured results is in good agreement with the normalized simulation results. The slicing simulation using Monte Carlo method is useful for the determination of high-radiation areas and proper material handling protocols and, therefore, lays a foundation for the accumulation of decommissioning experience.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
ZHANG Xiao-Ding
LI Yi-Ding
YANG Guo-Jun
WEI Tao
HE Xiao-Zhong
LONG Ji-Dong
JIANG Xiao-Guo
MA Chao-Fan
ZHAO Liang-Chao
YANG Xing-Lin
ZHANG Zhuo
WANG Yuan
LI Wei-Feng
SHI Jin-Shui
摘要：Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron. The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve ∼100 μm.
分类： 生物学 >> 生态学 提交时间： 2023-06-01
Fu, Hui
Ge, Yili
Cai, Guojun
Deng, Jianming
Liu, Huanyao
Wu, Aiping
Li, Youzhi
Li, Wei
Yuan, Guixiang
Erik Jeppesen
摘要：Understanding how phytoplankton interacts with local and regional drivers as well as their feedbacks is a great challenge, and quantitative analyses of the regulating role of human activities and climate changes on these feedback loops are also limited. By using monthly monitoring dataset (2000-2017) from Lake Taihu and empirical dynamic modelling to construct causal networks, we quantified the strengths of causal feedbacks among phytoplankton, local environments, zooplankton, meteorology as well as global climate oscillation. Prevalent bidirectional causal linkages between phytoplankton and the tested drivers were found, providing holistic and quantitative evidence of the ubiquitous feedback loops. Phytoplankton exhibited the highest feedbacks with total inorganic nitrogen and ammonia and the lowest with nitrate. The feedbacks between phytoplankton and environmental factors from 2000 to 2017 could be classified by two groups: the local environments (e.g., nutrients, pH, transparency, zooplankton)-driven enhancement loops promoting the response of the phytoplankton, and the climate (e.g., wind speed)-driven regulatory loops suppressing it. The two counterbalance groups modified the emergent macroecological patterns. Our findings revealed that the causal feedback networks loosened significantly after 2007 following nutrient loading reduction and unsuccessful biomanipulation restoration attempts by stocking carp. The strength of enhancement loops underwent marked decreases leading to reduced phytoplankton responses to the tested drivers, while the climate (decreasing wind speed, warming winter)-driven regulatory loops increased– like a tug-of-war. To counteract the self-amplifying feedback loops, the present eutrophication mitigation efforts, especially nutrient reduction, should be continued, and introduction of alternative measures to indirectly regulate the critical components (e.g., pH, Secchi depth, zooplankton biomass) of the loops would be beneficial.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Stella Yimiao Zhang
Gaspard Duchêne
Robert J. De Rosa
Megan Ansdell
Quinn Konopacky
Thomas Esposito
Eugene Chiang
Malena Rice
Brenda Matthews
Paul Kalas
Bruce Macintosh
Franck Marchis
Stan Metchev
Jenny Patience
Julien Rameau
Kimberly Ward-Duong
Schuyler Wolff
Michael P. Fitzgerald
Vanessa P. Bailey
Travis S. Barman
摘要：The HR 2562 system is a rare case where a brown dwarf companion resides in a cleared inner hole of a debris disk, offering invaluable opportunities to study the dynamical interaction between a substellar companion and a dusty disk. We present the first ALMA observation of the system as well as the continued GPI monitoring of the companion's orbit with 6 new epochs from 2016 to 2018. We update the orbital fit and, in combination with absolute astrometry from GAIA, place a 3$\sigma$ upper limit of 18.5 $M_J$ on the companion's mass. To interpret the ALMA observations, we used radiative transfer modeling to determine the disk properties. We find that the disk is well resolved and nearly edge on. While the misalignment angle between the disk and the orbit is weakly constrained due to the short orbital arc available, the data strongly support a (near) coplanar geometry for the system. Furthermore, we find that the models that describe the ALMA data best have an inner radius that is close to the companion's semi-major axis. Including a posteriori knowledge of the system's SED further narrows the constraints on the disk's inner radius and place it at a location that is in reasonable agreement with, possibly interior to, predictions from existing dynamical models of disk truncation by an interior substellar companion. HR\,2562 has the potential over the next few years to become a new testbed for dynamical interaction between a debris disk and a substellar companion.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：Ultraviolet (UV) electro-optic modulation system based on graphene-plasmonic metamaterials nanomechanical system (NEMS) with superlubricity is investigated. Due to the strong optical absorption intensity of graphene in the UV region and the combination of metamaterial structure based on surface plasmons, the modulation depth of the UV NEMS electro-optic modulator approaches as high as 8.5 times compared to the counterpart modulator in visible light region. Meanwhile, the superlubricity significantly reduces the power consumption of the UV electro-optic modulation system due to its extremely low friction coefficient. It also significantly improves the response speed of the modulator, which can reach the order of a nanosecond. The modulation voltage can be lower than 200 mV. The proposed electro-optic modulation system has a simple structure and high sensitivity, which is supposed to have important applications in UV optoelectronic devices and systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：Photonic states encoded in spatial modes of paraxial light fields provide a promising platform for high-dimensional quantum information protocols and related studies, where several pioneering theoretical and experimental demonstrations have paved the path for future technologies. Crucially, critical issues encountered in free-space propagation still represent a major challenge. This is the case of asynchronous diffraction between spatial modes with different modal orders, which experience variations in their transverse structure upon free-space propagation. Here we address this issue by proposing an encoding method based on the use of Laguerre-Gaussian (LG) modes of the same modal order N to define a N + 1 dimensional space. Noteworthy, such modes endowed with orbital angular momentum (OAM) experience the same propagation aberrations featuring an identical Gouy phase and wavefront curvature. We demonstrate our proposal experimentally by using time-correlated-single-photon imaging combined with a digital propagation technique. Importantly, our technique allows to eliminate, without the use of imaging systems, all issues related to asynchronous diffraction, providing an accessible way to generate propagation-invariant OAM qudits for quantum optical protocols.
分类： 计算机科学 >> 计算机软件 提交时间： 2022-02-24
摘要：
This paper focus on the researches of Maximal Independent Set (MIS). Based on reading and analysis of several recent papers, we divide the MIS problems into several classifications. The first is the classification based on the research objects, including the solution and maintenance of MIS; the second is the classification based on research methods, including serial, parallel, deterministic and randomized algorithms; the third is experimental analysis, including worst time complexity and expected time complexity.
分类： 机械工程 >> 机械制造自动化 提交时间： 2018-03-16
摘要：A machine-vision-based method of locating crops is described in this research. This method was used to provide real-time positional information of crop plants for a mechanical intra-row weeding robot. Within the normalized red, green, and blue chromatic coordinates (rgb), a modified excess green feature (g-r>T & g-b>T) was used to segment plant material from back ground in color images. The threshold T was automatically selected by the maximum variance (OTSU) algorithm to cope with variable natural light. Taking into account the geometry of the camera arrangement and the crop row spacing, the target regions covering the crop rows were defined based on a pinhole camera model. According to the statistical variation in the pixel histogram in each target region, locations of the crop plants were initially estimated. To obtain the accurate locations of crops, median filtering was conducted locally in the bounding boxes of the crops close to the bottom of the images. For the lateral guidance of the robot, a novel method of calculating lateral offset was proposed based on a simplified match between a template and the detected crops. Field experiments were conducted under three different illumination conditions. The results showed that the accurate identification rates on lettuce, cauliflower and maize were all above 95%. The positional error as within ±15 mm, and the average processing time for a 640×480 image was 31 ms. The method was adequate to meet the technical requirement of the weeding robot, and laid a foundation for robotic weeding in commercial production system.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要：A new lanthanide formate oxalate framework [Eu(C2O4)(HCOO)]n (1) has been synthesized via hydrothermal method and characterized by single-crystal X-ray diffraction (SC-XRD). The framework crystallizes in the orthorhombic Pnma space group, with a = 7.0984(4), b = 6.6442(3), c = 10.6793(6) Å, V = 503.68(4) Å3, Z = 3, C3HO6Eu, Mr = 285.00 g/mol, Dc = 3.7581 g/cm3, F(000) = 520.3796, μ = 12.413 mm-1, the final R = 0.0264 and wR = 0.0628 for 797 observed reflections with I > 2σ(I). The photoluminescence (PL) measurements reveal the significant red emission of the framework is dominated by the (5D0 → 7F2) electronic transition at 614 nm. Further variable-temperature powder X-ray diffraction (VT-PXRD) indicates that framework 1 shows slight negative thermal expansion (NTE) along the a-axis, and positive thermal expansion (PTE) along the b and c axes.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-05
摘要：In a recent paper (arXiv: 0801.4566) it was shown that all global energy eigenstates of asymptotically AdS3 chiral gravity have non-negative energy at the linearized level. This result was questioned (arXiv: 0803.3998) by Carlip, Deser, Waldron and Wise (CDWW), who work on the Poincare patch. They exhibit a linearized solution of chiral gravity and claim that it has negative energy and is smooth at the boundary. We show that the solution of CDWW is smooth only on that part of the boundary of AdS3 included in the Poincare patch. Extended to global AdS3, it is divergent at the boundary point not included in the Poincare patch. Hence it is consistent with the results of (arXiv: 0801.4566).
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2017-08-05
摘要：Three dimensional Einstein gravity with negative cosmological constant -1/\ell^2 deformed by a gravitational Chern-Simons action with coefficient 1/\mu is studied in an asymptotically AdS_3 spacetime. It is argued to violate unitary or positivity for generic \mu due to negative-energy massive gravitons. However at the critical value \mu\ell=1, the massive gravitons disappear and BTZ black holes all have mass and angular momentum related by \ell M=J. The corresponding chiral quantum theory of gravity is conjectured to exist and be dual to a purely right-moving boundary CFT with central charges (c_L,c_R)=(0,3\ell /G).
提交时间： 2017-05-02
Liu, L [Liu, Lei][ 1,2 ]
Liu, Z [Liu, Zhuang][ 1,2 ]
Chen, RJ [Chen, Renjie][ 1,2 ]
Liu, XM [Liu, Xingmin][ 1,2 ]
Yan, A [Yan, Aru][ 1,2 ]
Lee, D [Lee, Don][ 1,2,3 ]
Li, W [Li, Wei][ 1,2 ]
摘要：The 2:17 type Sm-Co sintered magnets were made with strips and ingots, separately. The phase structure and microstructure of the cast alloys and their effects on magnetic properties of the magnets have been comparatively studied. X-ray diffraction analysi
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
GUO Yue
WANG Liang-Liang
JU Xu-Dong
WU Ling-Hui
XIU Qing-Lei
WANG Hai-Xia
DONG Ming-Yi
HU Jing-Ran
LI Wei-Dong
LI Wei-Guo
LIU Huai-Min
OU-YANG Qun
SHEN Xiao-Yan
YUAN Ye
ZHANG Yao
摘要：Considering the aging effects of existing Inner Drift Chamber (IDC) of BES\uppercase\expandafter{\romannumeral3}, a GEM based inner tracker is proposed to be designed and constructed as an upgrade candidate for IDC. This paper introduces a full simulation package of CGEM-IT with a simplified digitization model, describes the development of the softwares for cluster reconstruction and track fitting algorithm based on Kalman filter method for CGEM-IT. Preliminary results from the reconstruction algorithms are obtained using a Monte Carlo sample of single muon events in CGEM-IT.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
WANG Wen-Wen
QIAN Sen
QI Minga XIA Jing-Kai
CHENG Ya-Ping
NING Zhe
LUO Feng-Jiao
HENG Yue-Kun
LIU Shu-Lin
SI Shu-Guang
Sun Jian-Ning
LI Dong
WANG Xing-Chao
HUANG Guo-Rui
TIAN Jing-Shou
WEI Yong-Lin
LIU Hu-Lin
LI Wei-Hua
WANG Xing
XIN Li-Wei
摘要：Aging experiments of a novel type of large area MCP-PMT made by JUNO collaboration were conducted.In these aging experiments, the multi-photoelectron spectrum and single photoelectron spectrum were measured daily,as well as the MCP resistance of the second PMT before and after the experiment. Two PMTs were aged successivelyfor cross check. The first PMT was aged for 52 days, while the other one was aged for 84 days. In order to study the mechanism of the aging process, the high voltage on the second PMT was increased to accelerate its aging process when the cumulative output of charge from its anode was about 4 C. From our study, it can be known that large area MCP-PMT aging had a strong relationship with the related MCPs. In accordance with the PMT aging curve,a PMT aging model was setup and a general aging formula was given.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Men, Dong
Zhou, Juan
Zhang, Zhi-Ping
Cui, Zong-Qiang
Deng, Jiao-Yu
Wang, Dian-Bing
Zhang, Xian-En
Men, Dong
Zhang, Ting-Ting
Hou, Li-Wei
Shi, Yuan-Yuan
Zhang, Jin-Li
摘要：The self-assembly of nanoparticles into larger superstructures is a powerful strategy to develop novel functional nanomaterials, as these superstructures display collective properties that are different to those displayed by individual nanoparticles or bulk samples. However, there are increasing bottlenecks in terms of size control and multifunctionalization of nanoparticle assemblies. In this study, we developed a self-assembly strategy for construction of multifunctional nanoparticle assemblies of tunable size, through rational regulation of the number of self-assembling interaction sites on each nanoparticle. As proof-of-principle, a size-controlled enzyme nanocomposite (ENC) was constructed by self-assembly of streptavidin-labeled horseradish peroxidase (SA-HRP) and autobiotinylated ferritin nanoparticles (bFNP). Our ENC integrates a large number of enzyme molecules, together with a streptavidin-coated surface, allowing for a drastic increase in enzymatic signal when the SA is bound to a biotinylated target molecule. As result, a 10000-fold increase in sensitivity over conventional enzyme-linked immunosorbent assays (ELISA) methods was achieved in a cardiac troponin immunoassay. Our method presented here should provide a feasible approach for constructing elaborate multifunctional superstructures of tunable size useful for a broad range of biomedical applications.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
Hao, Zhenhua
Feng, Yaqin
Ma, Jing
Li, Wei
Hao, Zhenhua
Wei, Lisi
Chen, Xiaowei
Zhou, Zhuan
Chen, Liangyi
Wei, Lisi
Chen, Xiaowei
Zhou, Zhuan
Chen, Liangyi
Feng, Yaqin
Du, Wen
Li, Wei
摘要：The large dense-core vesicle (LDCV), a type of lysosome-related organelle, is involved in the secretion of hormones and neuropeptides in specialized secretory cells. The granin family is a driving force in LDCV biogenesis, but the machinery for granin sorting to this biogenesis pathway is largely unknown. The mu mutant mouse, which carries a spontaneous null mutation on the Muted gene (also known as Bloc1s5), which encodes a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), is a mouse model of Hermansky-Pudlak syndrome. Here, we found that LDCVs were enlarged in mu adrenal chromaffin cells. Chromogranin A (CgA, also known as CHGA) was increased in mu adrenals and muted-knockdown cells. The increased CgA in mu mice was likely due a failure to export this molecule out of immature LDCVs, which impairs LDCV maturation and docking. In mu chromaffin cells, the size of readily releasable pool and the vesicle release frequency were reduced. Our studies suggest that the muted protein is involved in the selective export of CgA during the biogenesis of LDCVs.
分类： 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间： 2016-05-12
Zhang, Xiao-Li
Zhang, Xian-En
Zhang, Xiao-Li
Li, De-Feng
Fleming, Joy
Wang, Li-Wei
Zhou, Ying
Wang, Da-Cheng
Zhang, Xian-En
Bi, Li-Jun
Zhang, Xiao-Li
Li, De-Feng
Fleming, Joy
Wang, Li-Wei
Zhou, Ying
Wang, Da-Cheng
Zhang, Xian-En
Bi, Li-Jun
Zhang, Xiao-Li
摘要：Pathogenic mycobacteria transport virulence factors across their complex cell wall via a type VII secretion system (T7SS)/early secreted antigenic target-6 of kDa secretion system (ESX). ESX conserved component (Ecc) B, a core component of the T7SS architecture, is predicted to be a membrane bound protein, but little is known about its structure and function. Here, we characterize EccB1, showing that it is an ATPase with no sequence or structural homology to other ATPases located in the cell envelope of Mycobacterium tuberculosis H37Rv. We obtained the crystal structure of an EccB1-DN72 truncated transmembrane helix and performed modeling and ATP docking studies, showing that EccB1 likely exists as a hexamer. Sequence alignment and ATPase activity determination of EccB1 homologues indicated the presence of 3 conserved motifs in the N- and C-terminals of EccB1-DN72 that assemble together between 2 membrane proximal domains of the EccB1-DN72 monomer. Models of the EccB1 hexamer show that 2 of the conserved motifs are involved in ATPase activity and form an ATP binding pocket located on the surface of 2 adjacent molecules. Our results suggest that EccB may act as the energy provider in the transport of T7SS virulence factors and may be involved in the formation of a channel across the mycomembrane.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-12
Xie, Qing
Li, Xiangrui
Xie, Qing
Parlet, Corey
Borcherding, Nicholas
Kolb, Ryan
Li, Wei
Tygrett, Lorraine
Waldschmidt, Thomas
Olivier, Alicia
Zhang, Weizhou
Klesney-Tait, Julia
Keck, Kathy
Chen, Songhai
Liu, Guang-Hui
Liu, Guang-Hui
摘要：Neutrophils play an essential role in the innate immune response to infection. Neutrophils migrate from the vasculature into the tissue in response to infection. Recently, a neutrophil cell surface receptor, CD177, was shown to help mediate neutrophil migration across the endothelium through interactions with PECAM1. We examined a publicly available gene array dataset of CD177 expression from human neutrophils following pulmonary endotoxin instillation. Among all 22,214 genes examined, CD177 mRNA was the most upregulated following endotoxin exposure. The high level of CD177 expression is also maintained in airspace neutrophils, suggesting a potential involvement of CD177 in neutrophil infiltration under infectious diseases. To determine the role of CD177 in neutrophils in vivo, we constructed a CD177-genetic knockout mouse model. The mice with homozygous deletion of CD177 have no discernible phenotype and no significant change in immune cells, other than decreased neutrophil counts in peripheral blood. We examined the role of CD177 in neutrophil accumulation using a skin infection model with Staphylococcus aureus. CD177 deletion reduced neutrophil counts in inflammatory skin caused by S. aureus. Mechanistically we found that CD177 deletion in mouse neutrophils has no significant impact in CXCL1/KC- or fMLP-induced migration, but led to significant cell death. Herein we established a novel genetic mouse model to study the role of CD177 and found that CD177 plays an important role in neutrophils.
分类： 生物学 >> 生物物理学 >> 影像医学与生物医学工程 提交时间： 2016-05-12
Chen, Minghai
Li, Wei
Zhang, Zhiping
Liu, Sanying
Zhang, Xiaowei
Zhang, Xian-En
Cui, Zongqiang
Zhang, Xian-En
Chen, Minghai
Liu, Sanying
摘要：Monitoring protein protein interactions (PPIs) in live subjects is critical for understanding these fundamental biological processes. Bimolecular fluorescence complementation (BiFC) provides a good technique for imaging PPIs; however, a BiFC system with a long wavelength remains to be pursued for in vivo imaging. Here, we conducted systematic screening of split reporters from a bacterial phytochrome-based, near-infrared fluorescent protein (iRFP). Several new near-infrared phytochrome BiFC systems were built based on selected split sites including the amino acids residues 97/98, 99/100,122/123, and 123/124. These new near-infrared BiFC systems from a bacterial phytochrome were verified as powerful tools for imaging PPIs under physiological conditions in live cells and in live mice. The interaction between HIV-1 integrase (IN) and cellular cofactor protein Lens epithelium-derived growth factor (LEDGF/p75) was visualized in live cells using the newly constructed iRFP BiFC system because of its important roles in HIV-1 integration and replication. Because the HIV IN-LEDGF/p75 interaction is an attractive anti-HIV target, drug evaluation assays to inhibit the HIV IN-LEDGF/p75 interaction were also performed using the newly constructed BiFC system. The results showed that compound 6 and carbidopa inhibit the HIV IN-LEDGF/p75 interaction in a dose-dependent manner under physiological conditions in the BiFC assays. This study provides novel near-infrared BiFC systems for imaging protein interactions under physiological conditions and provides guidance for splitting other bacterial phytochrome-like proteins to construct BiFC systems. The study also provides a new method for drug evaluation in live cells based on iRFP BiFC systems and supplies some new information regarding candidate drugs for anti-HIV therapies. (C) 2015 Elsevier Ltd. All rights reserved.
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