| 1. |
- Qian, Li-Bing, et al.
(författare)
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Transmission of electrons through the conical glass capillary with the grounded conducting outer surface
- 2017
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 66:12
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Tidskriftsartikel (refereegranskat)abstract
- The transmission of 1.5 keV-electrons through a conical glass capillary is reported. This study aims to understand the so-called guiding effect for the negatively charged particles (e.g. electrons). The guiding mechanism is understood quite well with positively charged particles in particular highly charged ions, but not clear with electrons, i. e., even the basic scheme mediated by the existence of negative charge patches to guide the electrons is still somewhat controversial.. The study of the charging-up dynamics causing the electrons transport inside the capillary will shed light on this issue. In order to perform this, a data acquisition system has been setup to follow the time evolution of the two-dimensional angular distribution of the transmitted electrons. The electrons are detected by the multi-channel plate (MCP) detector with a phosphor screen. The image from the phosphor screen is recorded by a charge-coupled device camera. The timing signals for the detected events are extracted from the back stack of the MCP detector and recorded by the data acquisition system, synchronized with the acquired images. The electron beam has a size of 0.5 mm x 0.5 mm and a divergence of less than 0.35.. The inner diameter of the straight part of the capillary is 1.2 mm and the exit diameter is 225 mu m. A small conducting aperture of 0.3 mm in diameter is placed at the entrance of the capillary. Two-dimensional angular distribution of the transmitted electrons through conical glass capillary and its time evolution are measured. The results show that the transmission rate decreases and reaches to a constant value for the completely discharged glass capillary with time going by. The centroid of the angular distribution moves to an asymptotic value while the width remains unchanged. These transmission characteristics are different from those indicated in our previous work (2016 Acta Phys: Si n: 65 204103). The difference originates from the different manipulations of the capillary outer surface. A conducting layer is coated on the outer surface of the capillary and grounded in this work. This isolates various discharge/charge channels and forms a new stable discharge channel. The transmission rate as a function of the tilt angle shows that the allowed transmission occurs at the tilt angle limited by the geometrical factors, i. e., the geometrical opening angle given by the aspect ratio as well as the beam divergence. The transmission characteristics suggest that most likely there are formed no negative patches to facilitate the electron transmission through the glass capillary at this selected beam energy. It is different from that of highly charged ions, where the formation of the charge patches prohibits the close collisions between the following ions and guides them out of the capillary.
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| 2. |
- Wan, Cheng-Liang, et al.
(författare)
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Dynamics of slow electrons transmitting through straight glass capillary and tapered glass capillary
- 2016
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 65:20
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Tidskriftsartikel (refereegranskat)abstract
- It has been found that the transmission rate of the electrons through insulating capillaries as a function of time/incident charge is not the same as that of the ions. The question arises that by using the electrons, if the negative charge patches can be formed to facilitate the transmission of the following electrons, thereby substantiating that the so-called guiding effect works also for electrons. This study aims to observe the time evolutions of the transmission of electrons through a straight glass tube and a tapered glass capillary. This will reveal the details of how and (or) if the negative charge patches can be formed when the electrons transport through them. In this work, a set of MCP/phosphor two-dimensional detection system based on Labview platform is developed to obtain the time evolution of the angular distribution of the transmitted electrons. The pulsed electron beams are obtained to test our detection system. The time evolution of the angular profile of 1.5 keV electrons transmitting through the glass tube/capillary is observed. The transmitted electrons are observed on the detector for a very short time and disappear for a time and then appear again for both the glass tube and tapered glass capillary, leading to an oscillation. The positive charge patches are formed in the insulating glass tube and tapered glass capillary since the secondary electron emission coefficient for the incident energy is larger than 1. It is due to the fact that fast discharge of the deposited charge leads to the increase of the transmission rate, while the fast blocking of the incident electrons due to the deposited positive charge leads to the decrease of the transmission rate. The geometrical configuration of the taper glass capillary tends to make the secondary electrons deposited at the exit part to form the negative patches that facilitate the transmission of electrons. This suggests that if the stable transmission needs to be reached for producing the electron micro-beam by using tapered glass capillaries, the steps must be taken to have the proper grounding and shielding of the glass capillaries and tubes. Our results show a difference in transmission through the insulating capillary between electrons and highly charged ions.
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| 3. |
- Wan, Cheng-Liang, et al.
(författare)
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基于玻璃毛细管的大气环境MeV质子微束的产生与测量 : [Production and measurement of MeV proton microbeams in atmospheric environment based on glass capillary]
- 2024
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Ingår i: Wuli xuebao. - 1000-3290. ; 73:10
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Tidskriftsartikel (refereegranskat)abstract
- 本文采用玻璃毛细管产生了大气环境中工作的2.5 MeV质子外束微束, 并对束斑直径及能量分布随玻璃毛细管与束流方向之间角度(倾角)变化进行测量. 测量结果表明, 在玻璃毛细管轴向与束流方向一致时(倾角为0°), 产生的微束中存在保持初始入射能量的直接穿透部分以及散射部分, 其中直接穿透的质子占比最大, 束斑直径也最大. 随着玻璃毛细管倾角的增大, 当其大于几何张角时, 束斑直径变小, 产生的微束全部为能量减小的散射部分, 直接穿透质子消失. 我们对质子在玻璃毛细管内传输时的内壁散射过程进行了模拟计算及离子轨迹分析, 发现大角度的散射部分决定了形成的外束微束斑外围轮廓, 而束斑中心区域由不与毛细管内壁产生任何作用的直接穿透离子构成, 其大小由玻璃毛细管出口直径以及几何容许张角决定. 采用玻璃毛细管产生的外束微束具有产生简单廉价, 微束区域定位简单的特点, 有望在辐射生物学、医学、材料等领域得到广泛应用.
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| 4. |
- Shi, Fangzhong, et al.
(författare)
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Seasonal compensation implied no weakening of the land carbon sink in the Northern Hemisphere under the 2015/2016 El Niño
- 2024
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Ingår i: Science China Earth Sciences. - 1674-7313 .- 1869-1897. ; 67:1, s. 294-308
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Tidskriftsartikel (refereegranskat)abstract
- The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere (NH). However, we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH (mainly in the extra-tropics), based on multiple evidences from remote sensing observations, global ecosystem model simulations and atmospheric CO2 inversions. We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015 (average increases of 23.34% and 0.63% in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event, respectively) and spring of 2016 (6.82%), especially in the extra-tropics of the NH, where the water supply during the pre-growing-season (November of the previous year to March of the current year) had a positive anomaly. This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase. The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months. Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events.
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| 5. |
- Shi, F., et al.
(författare)
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Synthesis and properties of a new donor model compound for PSII
- 2004
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Ingår i: Gaodeng xuéxiào huàxué xuébào. - 0251-0790. ; 25:9, s. 1666-1672
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Tidskriftsartikel (refereegranskat)abstract
- As a model compound for redox components on the donor side of photosystem II (PS II) in green plants, a supramolecular complex 2 was synthesized and characterized. In this complex, two {[(2-hydroxy-3-(morpholin-4-ylmethyl)-5-tert-butyl-benzyl)(pyridyl-2-methyl)amino]methyl} arms are linked to the ortho-positions of a phenol which is expected covalently to be linked to Ru(II) tris-bipyridine through an amide bond. The arms on the substituted-phenol can coordinate two Mn(III) ions. The structure of complex 2 was confirmed by electrospray ionization mass spectrometry (ESI-MS) and 2D-NMR (gCOSY, HSQC and HMBC). Its photochemical and electrochemical properties were studied. The results showed that the MLCT band of the compound was red-shifted compared to that of [Ru(byp)(3)](2+) and the luminescence quantum yield was enhanced. In addition, the oxidation potential of ruthenium was higher than the phenol(+)/phenol and Mn(III, IV)/Mn(III) which was consisted with the electron transfer sequence of the donor side of PS II in nature. All these showed that this compound was a good model to mimic the donor side of PS II.
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| 6. |
- Shi, F., et al.
(författare)
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Synthesis and spectral properties of a new ruthenium(II) tris-bipyridine with four ester groups and substituted phenol
- 2004
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Ingår i: Huaxue xuebao. - 0567-7351. ; 62:7, s. 713-719
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Tidskriftsartikel (refereegranskat)abstract
- A new ruthenium(II) complex (1) with four ester groups have been designed and synthesized, in which a phenol substituted by {[(2-hydroxy-3-(morpholin-4-ylmethyl)-5-tent-butylbenzyl) (pyridyl-2-methyl) amino]methyl} groups was covalently linked to ruthenium (II) tris-bipyridine. The structure of complex 1 was characterized by electrospray ionization mass spectrometer (ESI-MS) and 1D-NMR, 2D-NMR (gCOSY, HSQC and HMBC) spectra. The electrochemical and spectral properties were also studied. Introduction of the four carboxyl acid groups and the donor ligand tuned the spectra and the redox properties of compound 1. The MLCT transition was turned from 451 to 474 nm and the complex had long lifetime of the (MLCT)-M-3 state emission. Moreover, the oxidation potential of Ru3+/Ru2 + of compound 1 was similar to 360 mV higher than that of [Ru(bpy)(3)](2+) which would enhance the driving-force of electron transfer. These results showed that the compound 1 had proper redox potentials and was suitable for being used as photosensitizer of solar cell.
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| 7. |
- Sun, S. G., et al.
(författare)
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Electrospray ionization mass spectrometry of rhenium(I) bipyridyl complexes
- 2003
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Ingår i: Youji huaxue. - 0253-2786. ; 23:10, s. 1135-1138
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Tidskriftsartikel (refereegranskat)abstract
- The electrospray ionization mass spectrometry (ESI-MS) of a series of rhenium(I) bipyridyl complexes [(4,4'-(COOEt)(2)-bPY)Re(CO)(3)RPF6], where bpy is 2,2'-bipyridine and R is pyridine, 4-methylpyridine, 4-hydroxypyridine, 4-aminopyridine or 10-(4-picolyl)phenothiazine (py-PTZ) was studied. The dissociation of the ligands (R) forms the fragment of [(4, 4'-( COOEt)(2)-bpy) Re (CO)3](+) at different voltages of in-source collision induced dissociation (CID). The dissociation tendency is in an order: pyridine > 4-methylpyridine > 4-hydroxypyridine > 4-aminopyridine > py-PTZ. It might be used to deduce the stability of these complexes when they are used as photosensitizers in solar cells.
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| 8. |
- Wang, Yan, et al.
(författare)
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Disaster effects of climate change and the associated scientific challenges
- 2024
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Ingår i: Chinese Science Bulletin. - 1001-6538. ; 69:2, s. 286-300
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Forskningsöversikt (refereegranskat)abstract
- Climate change can be observed in various spheres of the Earth's system, including atmosphere, lithosphere, hydrosphere, biosphere and cryosphere. The interactions among these spheres collectively impact the changes of the climate system. Natural disasters represent the most intense manifestation of the interactions among the Earth's spheres, and they have profound impacts on human society. In this study, we discuss the impact of climate change on natural disasters by examining the characteristics of climate change-induced hazards and the activity patterns of natural disasters. Furthermore, the response mechanisms of natural disasters to climate change are elaborated by exploring the formation and evolution of different types of natural disasters. Additionally, the future trends of disaster-pregnant environment under climate change are estimated, and the future trends of disaster risk are revealed by jointly considering the exposure and vulnerability. The main driving forces and formation conditions of natural disasters vary greatly among different geomorphic units, but they can generally be classified into three categories: Thermally driven disasters, gravitationally driven disasters, and hydrologically driven disasters. For example, heatwaves, tropical cyclones, tornadoes, and wildfires are common examples of thermally driven disasters which are forced by high temperatures or great thermal gradients. In addition, gravitationally driven disasters mainly occur in mountainous areas with significant differences in elevation, such as landslides, snow-ice avalanches and debris flows. The tsunamis caused by seabed movement are also gravity disasters. Furthermore, the disasters such as droughts, regional floods and sea-level rise are primarily driven by the changes in hydraulic conditions, and thus are classified as hydrologically driven disasters. In the context of enhanced climate change, the interactions among multiple spheres of the Earth's system are strengthened, causing the disaster-pregnant environment to evolve towards a more vulnerable state. Thus, the natural disasters present some new characteristics and trends, and the disaster risk shows a sharp increase. The interactions among different types of natural disasters have also become stronger, resulting in a significant rise in the risk of compound and cascading disaster. The differences in driving forces lead to significant variations in the disaster feedback to climate change among the varied geomorphic units. For example, the strengthened interaction between ocean and atmosphere leads to enhanced compound risk and destructive power of marine disasters. Besides, the intensification of water cycle contributes to increased spatial heterogeneity in drought and flood disasters, whose durations, intensities, and magnitudes show significant increasing trends. In addition, the high mountainous areas with altitude-dependent warming and the urban areas with significant heat island effects have obvious amplification effects in the responses to climate warming. This study advocates the goal of improving the accuracy and effectiveness of natural disaster prediction and early warning, and reducing the risk of climate change-related disasters. Five major scientific challenges of climate change-related disaster risk are proposed: (1) The mechanisms of climate change-driven interactions among Earth's spheres and the coupling of internal and external forces; (2) the spatio-temporal patterns of disaster development across different scales; (3) the perception of extreme event information and the data-driven risk identification; (4) the dynamics of disasters and the evolution of risk; (5) the disaster risk management and the resilient social development. By addressing the key issues in these five challenges through comprehensive and diversified approaches, we can deepen our scientific understanding on the Earth's system, adapt to global changes, and reduce disaster risks.
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| 9. |
- Zhang, Fei-yan, et al.
(författare)
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Single-step purification of sIgA from bovine colostrums by anion-exchange chromatography
- 2011
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Ingår i: Science and Technology of Food Industry. - 1002-0306.
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Tidskriftsartikel (refereegranskat)abstract
- A fraction containing sIgA(sIgA-rich fraction)was prepared from bovine colostrum by anion exchange chromatography using alkali resin. The effect of changing buffer properties(pH and ionic strength)on purity of sIgA was studied. The best result was sIgA purity increasing from 16.31% in bovine colostrum solution to 91.24% in the eluting fraction with a recovery of 47% at the condition of pH 7.0,0.03mol/L sodium phosphate. These results suggested that the anion exchange chromatography using alkali resin was a potential process for sIgA purification from bovine colostrum.
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