983 resultados para 397


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本文简略地回顾了重离子治疗的历史,更多的兴趣集中在重离子治癌的进展上。为了利用重离子的优越特性(例如:剂量局域性和高的生物效率),已经开发了几种技术。在临床试验中获得了令人鼓舞的治疗效果,广泛地提出了物理和辐射生物方面的临床结果和治疗技术,概要地分析了重离子治癌的前景。

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The collisions of the isocharged sequence ions of q=6 (C6+, N6+, O6+, F6+, Ne6+, Ar6+, and Ca6+), q=7 (F7+, Ne7+, S7+, Ar7+, and Ca7+), q=8 (F8+, Ne8+, Ar8+, and Ca8+), q=9 (F9+, Ne9+, Si9+, S9+, Ar9+, and Ca9+) and q=11 (Si11+, Ar11+, and Ca11+) with helium at the same velocities were investigated. The cross-section ratios of the double-electron transfer (DET) to the single-electron capture (SEC) sigma(DET)/sigma(SEC) and the true double-electron capture (TDC) to the double-electron transfer sigma(TDC)/sigma(DET) were measured. It shows that for different ions in an isocharged sequence, the experimental cross-section ratio sigma(DET)/sigma(SEC) varies by a factor of 3. The results confirm that the projectile core is another dominant factor besides the charge state and the collision velocity in slow (0.35-0.49v(0); v(0) denotes the Bohr velocity) highly charged ions (HCIs) with helium collisions. The experimental cross-section ratio sigma(DET)/sigma(SEC) is compared with the extended classical over-barrier model (ECBM) [A. Barany , Nucl. Instrum. Methods Phys. Res. B 9, 397 (1985)], the molecular Coulombic barrier model (MCBM) [A. Niehaus, J. Phys. B 19, 2925 (1986)], and the semiempirical scaling laws (SSL) [N. Selberg , Phys. Rev. A 54, 4127 (1996)]. It also shows that the projectile core properties affect the initial capture probabilities as well as the subsequent relaxation of the projectiles. The experimental cross-section ratio sigma(TDC)/sigma(DET) for those lower isocharged sequences is dramatically affected by the projectile core structure, while for those sufficiently highly isocharged sequences, the autoionization always dominates, hence the cross-section ratio sigma(TDC)/sigma(DET) is always small.

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本论文的实验工作,是在兰州重离子加速器国家实验室完成的。实验中,使用ORTEC公司生产HPGe探测器测量了84MeV的12C4+重离子轰击系列金属箔生成的特征X射线。本论文研究了金属薄靶Ag、Cd、In和Sn产生的特征KX射线的能移现象。实验发现Ag、Cd、In和Sn的Kα1和Kα2X射线没有明显的能移现象,而Kβ1X、Kβ2X射线的能移却有100~200eV。对此,应用经典电磁理论详细地解释了该问题。在多组态Dirac-Fock(MCDF)程序计算的单空穴能移的基础上,分别根据实验中测量的特征KX射线的能移值和“几何”模型研究了重离子轰击下Ag、Cd、In和Sn的L、M壳层的多重电离。另外,在相同的条件下,实验测量的厚靶Au的特征LX射线能移不明显,而薄靶Au的特征LX射线却有1.5keV以上的能移。本文定性解释了该实验现象

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束流储存寿命对于储存环的建造和内靶实验都是一个很重要的参数。由于重离子冷却储存环工程的优化,HIRFL-CSR主环将能提供2.SGev的质子束流,这为强子物理研究提供了一个很好的平台。设计并建立一套针对强子物理的内靶系统己经列入到计划当中,与内靶相关的束流储存寿命研究也随之展开。本论文首先分析了在内靶实验中束流储存寿命的影响因素,即真空管道中的残余气体分子、冷却电子束和内靶,以及束内散射和集体效应等,并用理论解析和数值计算的方法,对各种因素的影响程度进行估算。研究表明,内靶散射影响下的束流储存寿命比其他因素导致的短2~3个数量级,内靶是影响束流寿命的决定性因素。其次,对CSRm将来实验中主要用到的Pelle七内靶和碳薄膜靶做了简要介绍,并计算了它们的有效靶厚大约为lx10、切ms/cmZ和5火1017atoms/CmZ。再者,用理论推导方法,对内靶的多次库仑散射和束流能量损失扰动对束流的影响进行了研究,推导了束流的横向和纵向发射度增长与束流每次打靶产生的小库仑散射角均方值气s和相对动量分散气了:之间的关系,并通过数值计算的方法给出了CSRm内靶实验条件的发射度增长曲线。最后,建立了内靶散射的MOnte-Carlo模拟程序,在模拟数据的基础上,总结研究束流的发射度增长规律,以及束流存储寿命与内靶厚度和束流能量的关系。计算表明,当存在Pellet靶(1、1016atoms/cm2)和c膜(5*1017 atoms/cmZ)时,2800Mev质子束的束流储存寿命分别为397秒和0.7秒,将来的内靶实验亮度大约为2 x 1033cm-2·s-1。

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2001~2003年在长白山自然保护区内3个垂直植被带的典型群落红松阔叶林、云冷杉林和岳桦林内,利用网袋埋藏法对群落内的6个主要优势乔木树种凋落物进行埋藏分解试验,研究凋落物分解速率及其变化动态;同时利用分解模型,模拟预测凋落物的分解进展,为深入研究这6个树种的营养策略、群落养分循环等奠定基础,也为森林生态系统管理提供理论依据。研究结果表明,所研究的6个树种凋落物都表现出随时间进程失重率增大的现象,但失重率并不与时间呈线性相关。在分解的638d(1.75a)后,6种叶凋落物的分解速率明显升高。到分解实验结止时(699d),叶凋落物干重剩余率从小至大依次为白桦(24.56%)、紫椴(24.81%)、红松(38.48%)、鱼鳞云杉(41.15%)、岳桦(41.53%)和臭冷杉(42.62%)。枝凋落物分解速率明显低于叶,枝干重剩余率从小至大依次为紫椴(44.98%)、臭冷杉(64.62%)、红松(72.07%)、鱼鳞云杉(73.51%)、白桦(77.37%)和岳桦(80.35%)。在同一海拔高度,阔叶树种叶凋落物分解速率大于针叶树种。并且随着海拔的升高,叶凋落物分解速率逐渐减慢。模型分析预测结果表明,长白山北坡各垂直植被带的优势树种叶凋落物分解95%需4.5~8.0a;年分解系数为紫椴(0.686)>白桦(0.624)>红松(0.441)>鱼鳞云杉(0.406)>臭冷杉(0.397)>岳桦(0.385);枝凋落物分解95%需7.8~29.3a,不同树种间的差异明显。枝年分解系数为紫椴(0.391)>臭冷杉(0.204)>红松(0.176)>鱼鳞云杉(0.157)>白桦(0.148)>岳桦(0.102)。

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由辽宁南部菜田土中分离出GK,BK2林硅酸盐细菌,在纯培养条件下,用钾长石为底物解钾量可达397%、32.3%;施入土壤中,无作物的情况下,在草甸棕壤上中速效钾可提高110.6%,山地棕壤上中速效钾可提高335.1%;在栽种西红柿条件下,植物总钾与土壤中速钾量高于对照,同时土壤中途钾量比对照降低,并有刺激植物生长和吸收钾的作用。

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C-6-carboxylated chitosan obtained by oxidation of chitosan was selectively modified in order to obtain derivatives similar to bacterial antigens. Selective O-acetylation of 6-carboxyl chitosan afforded a modified polysaccharide with the 2-amino group available for further modifications to create carbonyl groups. A deaminative degradation reaction allowed the formation of oligosaccharides with terminal aldehyde groups. Reductive alkylation with lactose introduced lactityl branches which were oxidized with galactose oxidase to give aldehyde groups in its -galactose residues.

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细辛是一种重要的中草药,活性物质主要是挥发油。研究采用生长速率法和孢子萌发法测定了细辛精油对引起苹果病害的6种病原菌(灰斑病菌、褐斑病菌、斑点落叶病病菌、炭疽病菌、苹果轮纹病菌和干腐病菌)的菌丝生长和4种病原菌(灰斑病菌、褐斑病菌、斑点落叶病病菌、炭疽病菌)的孢子萌发的影响。结果表明,细辛精油对两者均有一定的抑制作用:对褐斑病菌菌丝生长的抑制效果最好,EC90仅为397.37mg/L;对炭疽病菌孢子萌发的抑制效果最好,EC90仅为276.77mg/L。对于同一种病原菌来说,细辛精油对其孢子萌发的抑制效果好于对其菌丝生长的抑制效果。

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针对陆地生态系统碳汇/源的时空格局、碳循环过程的驱动机制及未来情景等前沿科学问题,提出陆地碳循环研究的地球信息科学方法,采用陆地生态系统碳通量/储量与碳循环过程的综合网络观测、生物过程的适应性实验研究以及河流碳输运过程研究为支撑系统的自下而上途径、与以土地利用/土地覆被变化和对地观测数据生态参量反演为基础的自上而下研究途径、经相互验证和尺度转换模型实现有机结合的研究方法,开展综合观测、调查、比对分析、模拟和评价研究,把握陆地生态系统碳循环的格局与过程规律,辨析自然和人为因素对陆地生态系统碳循环过程的影响,探讨全球气候变化条件下陆地生态系统碳循环过程的演变趋势。

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Rapid urbanization and industrialization in southern Jiangsu Province have consumed a huge amount of arable land. Through comparative analysis of land cover maps derived from TM images in 1990, 2000 and 2006, we identified the trend of arable land loss. It is found that most arable land is lost to urbanization and rural settlements development. Urban settlements, rural settlements, and industrial park-mine-transport land increased, respectively, by 87 997 ha (174.65%), 81 041 ha (104.52%), and 12 692 ha (397.99%) from 1990 to 2006. Most of the source (e.g., change from) land covers are rice paddy fields and dryland. These two covers contributed to newly urbanized areas by 37.12% and 73.52% during 1990-2000, and 46.39% and 38.86% during 2000-2006. However, the loss of arable land is weakly correlated with ecological service value, per capita net income of farmers, but positively with grain yield for some counties. Most areas in the study site have a low arable land depletion rate and a high potential for sustainable development. More attention should be directed at those counties that have a high depletion rate but a low potential for sustainable development. Rural settlements should be controlled and rationalized through legislative measures to achieve harmonious development between urban and rural areas, and sustainable development for rural areas with a minimal impact on the ecoenvironment. (C) 2009 Elsevier Ltd. All rights reserved.

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beta-NaYF4 hexagonal microprisms and microrods with different aspect ratios have been prepared via a simple hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. The influences of reaction temperature and the molar ratio of NaF to y(3+) on the crystal phases and shapes of final products have been studied in detail. The aspect ratios of products increase gradually with the increase of reaction temperature and NaF/Y3+ molar ratio. The growth mechanisms of crystals prepared under the different conditions are presented systematically. More importantly, the systematical investigation on the luminescence properties of beta-NaYF4:xEu(3+) (x = 0.5, 1, 2, 3, 5, and 10 mol %) with hexagonally microprismatic morphology shows the characteristic emissions of Eu3+ (D-5(J)-F-7(J'), J, J' = 0, 1, 2, 3). Under the excitation of single wavelength light of 397 nm, the luminescence colors of the corresponding products can be tuned feasibly from bluish white to yellow to red by changing the doping concentration of Eu3+.

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CaIn2O4:xEu(3+) (x=0.5%,1.0%,1.5%) phosphors were prepared by the Pechini sol-gel process [U.S. Patent No. 3,330,697 (1967)] and characterized by x-ray diffraction and photoluminescence and cathodoluminescence spectra as well as lifetimes. Under the excitation of 397 nm ultraviolet light and low voltage electron beams, these phosphors show the emission lines of Eu3+ corresponding to D-5(0,1,2,3)-F-7(J) (J=0,1,2,3,4) transitions from 400 to 700 nm (whole visible spectral region) with comparable intensity, resulting in a white light emission with a quantum efficiency near 10%. The luminescence mechanism for Eu3+ in CaIn2O4 has been elucidated.

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beta-NaYF4:Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu(3+) (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to D-5(0-3) -> F-7(J) (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively.

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Effective enhancement of electrochermluminescence (ECL) of peroxydisulfate on a C-60/didodecyldimethyl ammonium bromide (C-60/DDAB) film coated glassy carbon electrode (GCE) surface is reported in this paper. The C60/DDAB film gave lower cathodic current in the presence of peroxydisulfate than that from a bare GCE. To our surprise, electrochemiluminescent intensity from peroxydisulfate reduction was effectively enhanced on the C60/DDAB film, which was 50 times and 250 times higher than those from a DDAB film coated and bare GCE, respectively. Moreover, the ECL onset potential on the C60/DDAB film was about -0.9 V, which positively shifted 200 mV compared with that from the bare GCE. Dissolved oxygen and the applied potential also affected the electrochemiluminescent intensity. The presence of oxygen decreased the intensity, and the intensity reached maximum at the applied potential of -1.7 V. The unique property will greatly enrich ECL studies and applications based on fullerenes.