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A combined DFT and molecular dynamics study of U(Ⅵ)/calcite interaction in aqueous solution

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Science Bulletin 2017年第15期62卷 1064-1073页

作者： Jian-Hui Lan Zhi-Fang Chai wei-Qun shi Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China School of Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions Soochow University Suzhou 215123 China

Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and solvation effect in U（VI） interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite （104） surface prefers to exist in molecular state rather than dis- sociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U（VI） → Ca（II）. In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U（VI）→ Ca（II）, and the one with UO2（CO3）2（H2O）^2- as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilicability of the （104） surface to different extents, where the UO2（CO3）3Ca2 species contributes to the largest degree of energy changes （ 53 kcal/mol）. Our calcula- tions proved that the （104） surface also has the ability to immobilize U（VI） via either surface complexing or ion exchange mechanisms under different pH values.

关键词： Uranyl Incorporation Adsorption Calcite Density functional theory Molecular dynamics

Effect of Accumulative Strain on Grain Refinement and Strengthening of ZM6 Magnesium Alloy During Continuous Variable Cross-Section Direct Extrusion

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Acta Metallurgica Sinica(English Letters) 2015年第5期28卷 649-655页

作者： Feng Li wei shi Nan Bian Hong-Bin Wu School of Materials Science and Engineering Harbin University of Science and Technology

In order to study the influence of die combination on continuous variable cross-section direct extrusion （CVCDE） in the extrusion process, the accumulative strain formula is derived, and it can be known that the extrusion ratio of various stages directly determines the size of corresponding stage strain by formula. In this paper, as an example of the two interim dies, three die combinations of different angles and extrusion ratio are designed. Aviation magnesium alloy ZM6 is studied, and the results show that dynamic recrystallization is even more complete when continuous shear deformation occurs, so that the refinement and homogenization of microstructure are obtained. By the use of different die combinations, the accumulative strain increases under the conditions of same total extrusion ratio. Thus, the refined crystalline strengthening effect of extrusion deformation can be further analyzed. Due to the dead-zone defects, the actual accumulative strain decreases significantly and the effect of microstructure and performance improvements also decreases with it. Therefore, the optimal design of die combination is the key to the process and product of CVCDE, which provides a scientific basis for the development of severe plastic deformation.

关键词： Continuous variable cross-section direct extrusion (CVCDE) Die combination Accumulative strain Magnesium alloys Severe plastic deformation

Experiment investigation on visualization and operating characteristics of closed loop plate oscillating heat pipe with parallel channels

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Journal of Central South University 2016年第9期23卷 2410-2418页

作者： shi wei-xiu PAN Li-sheng Department of Energy and Power Engineering Beijing University of Civil Engineering and Architecture Beijing 100044 China Beijing Key Lab of Heating Gas Supply Ventilating and Air Conditioning Engineering Beijing 100044 China State Key Laboratory of High-temperature Gas Dynamics （Institute of Mechanics Chinese Academy of Sciences） Beijing 100190 China

Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of *** temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.

关键词： closed loop with parallel channels plate oscillating heat pipe visualization temperature oscillating heat transfer performance filling ratio section scale

High Gain Lateral Semi-Insulating GaAs Photoconductive Switch Triggered by 1064nm Laser Pulses

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Chinese Physics Letters 2002年第3期19卷 351-354页

作者： shi wei Zhang Xian-Bin Li Qi Chen Er-Zhu Zhao wei Department of Applied Physics Xi'an University of Technology Xi'an 710048 State Key Laboratory of Transient Optics and Technology Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi'an 710068

We report on the experimental results of a lateral semi-insulating GaAs photoconductive switch, with a gap of 8mm between two electrodes, triggered by 1064nm laser pulses at a wavelength beyond the GaAs absorption edge. Both the linear and nonlinear modes of the switch were observed when it was triggered by light pulses with an energy of 1.9mJ and a pulse width of 60ns, and operated at high voltages of 3 and 5kV. The results show that when the semi-insulating GaAs photoconductive switch operates under an electrical field of 4.37kV/cm, it will enter into the linear mode first, and then the switch will undergo the nonlinear mode (lock-on) after a delay of about 20-100ns. It is worth noticing that the delay time under high light energy is longer than that in the low optical energy. The non-intrinsic absorption mechanism is discussed. EL2 deep level defects and double-photon absorption in GaAs may play a key part in the absorption process.

关键词： Gallium arsenide

Clinical feature and waveform in infantile nystagmus syndrome in children with FRMD7 gene mutations

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Science China(Life Sciences) 2017年第7期60卷 707-713页

作者： Dayong Bai wei shi Zhan Qi wei Li Aihua wei Yanhui Cui Cheng Li Li Li Department of Ophthalmology Beijing Children's Hospital Capital Medical UniversityNational Center for Children's Health Beijing Pediatric Research Institute Beijing Children's Hospital Capital Medical UniversityNational Center for Children's Health Department of Dermatology Beijing Tongren Hospital Capital Medical University

Infant nystagmus sydrome presents as involuntary eye movement disorder and can affect seriously ocular function. We performed a retrospective study of clinical data and FRMD7 genetic test results in 12 cases of infantile nystagmus syndrome to correlate waveform, stereopsis, and visual acuity. The patients(age 6.40±2.67 years) had FRMD7 mutations as follows: missense in eight cases, shear in two cases, frameshift in one case, and non-frameshift in one case. Horizontal jerk waveform was observed in six cases, versus horizontal pendulum in five cases and dual jerk in one case. The uncorrected visual acuity(24 eyes) was 0.21±0.12,compared with a corrected visual acuity(24 eyes) of 0.32±0.14. All patients had simultaneous perception, versus fusion function in 10 cases(83.33%) and stereoscopic vision in seven cases(58.33%) using the synoptophore. Eleven cases(91.67%) detected the stereo fly, compared with five cases(41.67%) for stereoscopic circles and seven cases(58.33%) for stereoscopic animals by Titmus test. Stereoscopic vision using the synoptophore did not correlate with the frequency, amplitude, or intensity of nystagmus or with corrected binocular visual acuity. The infantile nystagmus syndrome with FRMD7 mutations in our cases was caused primarily de novo and missense mutations. Visual acuity and binocular visual function were significant impaired, and the waveform was generally horizontal jerk. Also, an infrared videonystagmogram can record the frequency, amplitude, and intensity of nystagmus accurately.

关键词： infantile nystagmus FRMD7 gene mutation waveform vision stereopsis

Two-dimensional bimetallic coordination polymers as bifunctional evolved electrocatalysts for enhanced oxygen evolution reaction and urea oxidation reaction

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Journal of Energy Chemistry 2021年第12期30卷 230-238,I0005页

作者： Qiang Li Lele Lu Jingwei Liu wei shi Peng Cheng Key Laboratory of Advanced Energy Materials Chemistry(MOE) College of ChemistryNankai UniversityTianjin 300071China

Two-dimensional coordination polymers(CPs) have aroused tremendous interest as electrocatalysts because the catalytic performance could be fine-tuned by their well-designed coordination layers with highly accessible and active metal ***,it remains great challenge for CP-based catalysts to be utilized for electrocatalytic oxidation reactions due to their inefficient activities and low catalytic ***,we applied a mixed-metal strategy to fabricate two-dimensional Co_xNi_(1-x)-CPs with dual active sites for electrocatalytic water and urea *** metal ratio regulation in the twodimensional layer,an optimized Co_(2/3)Ni_(1/3)-CP exhibits a water oxidation performance with an overpotential of 325 mV at a current density of 10 mA cm^(-2) and a Tafel slope of 86 mV dec^(-1) in alkaline solution for oxygen evolution ***,a lower potential than that of commercial RuO_(2) is observed over20 mA cm^(-2).Co_(2/3)Ni_(1/3)-CP also displays a potential of 1.381 V at 10 mA cm^(-2) for urea oxidation reaction and a Tafel slope of 124 mV dec^(-1).This mixed-metal strategy to maximize synergistic effect of different metal centers may ultimately lead to promising electrocatalysts for small molecule oxidation reaction.

关键词： Coordination Polymers Electrocatalysis Oxygen Evolution Reaction Urea Oxidation Reaction

Weakly supervised action anticipation without object annotations

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Frontiers of Computer Science 2023年第2期17卷 101-110页

作者： Yi ZHONG Jia-Hui PAN Haoxin LI wei-shi ZHENG School of Computer Science and Engineering Sun Yat-sen UniversityGuangzhou 510006China Key Laboratory of Machine Intelligence and Advanced Computing Ministry of EducationGuangzhou 510006China

Anticipating future actions without observing any partial videos of future actions plays an important role in action prediction and is also a challenging *** obtain abundant information for action anticipation,some methods integrate multimodal contexts,including scene object ***,extensively labelling each frame in video datasets requires considerable *** this paper,we develop a weakly supervised method that integrates global motion and local finegrained features from current action videos to predict next action label without the need for specific scene context ***,we extract diverse types of local features with weakly supervised learning,including object appearance and human pose representations without ground ***,we construct a graph convolutional network for exploiting the inherent relationships of humans and objects under present *** evaluate the proposed model on two datasets,the MPII-Cooking dataset and the EPIC-Kitchens dataset,and we demonstrate the generalizability and effectiveness of our approach for action anticipation.

关键词： action anticipation weakly supervised learning relation modelling graph convolutional network

Mechanisms of Salt Tolerance in Transgenic Arabidopsis thaliana Carrying a Peroxisomal Ascorbate Peroxidase Gene from Barley

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Pedosphere 2008年第4期18卷 486-495页

作者： XU wei-Feng shi wei-Ming A. UEDA T. TAKABE State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 （China）. Graduate School of the Chinese Academy of Sciences Beijing 100049 （China） Graduate School of Bioagricultural Sciences Nagoya University Nagoya 464-8601 （Japan

Ascorbate peroxidases （APX）, localized in the cytosol, peroxisome, mitochondria, and chloroplasts of plant cells, catalyze the reduction of H2O2 to water by using ascorbic acid as the specific electron donor. To determine the role of peroxisomal type ascorbate peroxidase （pAPX）, an antioxidant enzyme, in protection against salt-induced oxidative stress, transgenic Arabidopsis thaliana plant carrying a pAPX gene （HvAPX1） from barley （Hordeum vulgate L.） was analyzed. The transgenic line pAPX3 was found to be more tolerant to salt stress than the wild type. Irrespective of salt stress, there were no significant differences in Na^＋, K^＋, Ca^2＋, and Mg^2＋ contents and the ratio of K^＋ to Na^＋ between pAPX3 and the wild type. Clearly, the salt tolerance in pAPX3 was not due to the maintenance and reestablishment of cellular ion homeostasis. However, the degree of H2O2 and lipid peroxidation （measured as the levels of malondialdehyde） accumulation under salt stress was higher in the wild type than in pAPX3. The mechanism of salt tolerance in transgenic pAPX3 can thus be explained by reduction of oxidative stress injury. Under all conditions tested, activities of superoxide, glutathione reductase, and catalase were not significantly different between pAPX3 and the wild type. In contrast, the activity of APX was significantly higher in the transgenic plant than in wild type under salt stress. These results suggested that in higher plants, HvAPX1 played an important role in salt tolerance and was a candidate gene for developing salttolerant crop plants.

关键词： ascorbate peroxidase oxidative stress peroxisome soil salinity transgenic Arabidopsis thaliana

Hydrogen Peroxide in Plants:a Versatile Molecule of the Reactive Oxygen Species Network

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Journal of Integrative Plant Biology 2008年第1期50卷 2-18页

作者： Li-Juan Quan Bo Zhang wei-wei shi Hong-Yu Li MOE Key Laboratory of Arid and Grassland Ecology School of Life Sciences Lanzhou University Lanzhou 730000 China

Plants often face the challenge of severe environmental conditions, which include various biotic and abiotic stresses that exert adverse effects on plant growth and development. During evolution, plants have evolved complex regulatory mechanisms to adapt to various environmental stressors. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species （ROS）, which are subsequently converted to hydrogen peroxide （H2O2）. Even under normal conditions, higher plants produce ROS during metabolic processes. Excess concentrations of ROS result in oxidative damage to or the apoptotic death of cells. Development of an antioxidant defense system in plants protects them against oxidative stress damage. These ROS and, more particularly, H2O2, play versatile roles in normal plant physiological processes and in resistance to stresses. Recently, H2O2 has been regarded as a signaling molecule and regulator of the expression of some genes in cells. This review describes various aspects of H2O2 function, generation and scavenging, gene regulation and cross-links with other physiological molecules during plant growth, development and resistance responses.

关键词： antioxidant system gene regulation hydrogen peroxide (H2O2) reactive oxygen species (ROS) signaling molecule.