Statistics of polymer capture by a nanopore: A Brownian dynamics simulation study

We investigate the statistics of polymer capture by a nanopore using Brownian dynamics simulations. It is found that when the velocity flux is greater than a critical velocity flux, the capture picture is a random selection process, otherwise it tends to a statistical process governed by energetic considerations. In addition, the chain ends capture probability decreases as the chain length increases and satisfies a power-law scaling of P0(N)~N-0.8.     

HIRFL–CSR加速器中束流与真空中剩余气体的碰撞损失

研究了重离子加速器中束流与真空中剩余气体的碰撞损失过程和碰撞截面,在依据大量实验数据的基础上,提出了一组计算离子一原子的电荷交换截面的经验公式.以兰州重离子加速器HDRFL及冷却储存环CSR为例,给出了依据碰撞截面的公式计算束流在加速器真空中的传输效率的方法,并计算了在不同真空度下HIRFL的ECR源轴向注入束运线、注入器SFC、前束运线、主加速器SSC和后束运线等不同加速阶段及CSR的传输效率,并提出合理的真空度要求.HIRFL的真空分布测量和束流的损失测量证明了该计算方法的可靠性.     

重新初始化的LS方法跟踪二维可压缩多介质流界面运动

 用非耦合求解方法计算Level Set函数方程与流体力学方程组，应用重新初始化的Level Set函数确保距离函数性质，流体力学方程组采用二阶精度多介质流波传播差分格式计算，重新初始化方程采用五阶WENO格式计算。并给出了二维可压缩多介质流界面运动的计算结果。     

用紧耦合方法研究C4+和O6+与He原子碰撞

用双中心原子轨道紧耦合方法计算了C4+-He以及O6+-He碰撞的单俘获总截面,入射离子的能量范围为10～100keV/amu,所得计算结果在实验误差范围内与实验值很好符合.对满壳层入射离子,研究了单俘获截面随入射离子电荷态的变化,并讨论了原子轨道展开波函数数目对计算结果的影响.p     

高俘获效率电子辐照加速器的设计研究

加速管是一台加速器的核心部分. 一般电子辐照加速器的俘获效率在50%左右, 一半的电子都损失在加速管内. 丢失的电子打在加速管内壁, 产生轫致辐射、腔体发热量增加、真空变坏等许多负面影响. 采用一段等梯度加速结构, 相速沿加速管呈线形增加,调整相速变化规律及加速管腔体的尺寸参数, 设计出的加速管最终的俘获效率提高到90%以上, 同时平均加速梯度没有因此降低, 加速管总长度没有增加.     

Modulation of Particle Concentrations in the Interference Laser Radiation Field

Spatial redistribution of microparticles in a suspension on exposure to the interference laser field depending on the parameters of the particles and the field characteristics has been analyzed theoretically. Results of experimental investigations are presented that illustrate the capture of an ensemble of polymeric small spheres and also of the lymphocytes of human blood and other microparticles in a liquid in the interference radiation bands of the He–Ne laser.     

Determination of iphosphamide and seven metabolites in blood plasma,as stable trifluoroacetyl derivatives,by electron capture chemical ionization GC-MS

A method is described for the determination of the antitumor agent iphosphamide and seven of its metabolites in the plasma of cancer patients by multiple ion monitoring (MIM) GC-MS, mainly using the electron capture chemical ionization mode, of stable methyl and/or trifluoroacetyl derivatives. The metabolites determined were 2- and 3-dechloroethyliphosphamide, 4-ketoiphosphamide, carboxyiphosphamide, iphosphamide mustard, and two previously undetected metabolites, chloroethylamine and 1,3-oxazolidine-2-one. The isolation of the acidic and neutral metabolites was performed by solid phase extraction on to C₁₈ adsorbent at pH 4. The weakly acidic iphosphamide mustard, isolated under these conditions with a yield of ca 50%, was measured as a stable methyltrifluoroacetyl derivative, in contrast to the corresponding phosphoramide mustard of the isomer cyclophosphamide which decomposes during derivatization. Chloroethylamine and 1,3-oxazolidine-2-one were isolated with high yield by liquid extraction with ethyl acetate at pH 10. Selective measurement of several metabolite derivatives with similar retention times was performed by multiple ion monitoring MS of specific ion masses, using a methyl phenyl siloxane capillary column previously employed in the study of cyclophosphamide metabolites. Quantitation of metabolites in patient plasma samples could be performed in the concentration range 3 ng to 20 μg per ml of original plasma.     

硼中子俘获治疗的蒙特卡罗方法模拟

用通用蒙特卡罗程序MCNP模拟了粒子在人脑中的输运过程. 吸收剂量率主要来自以下四个反应:¹⁰B(n,α)⁷Li,¹⁴N(n,p)¹⁴C,¹H(n,γ)²D,快中子弹性散射反应.对肿瘤区的贡献主要来自硼中子吸收反应.结果表明,超热中子比热中子适合于深肿瘤的治疗,而热中子对浅肿瘤的治疗有优越性,比如皮肤癌.同确定论方法的结果相比,蒙特卡罗方法不失为一种模拟中子俘获治疗的好工具.     

BNCT蒙特卡洛剂量计算的混合网格算法研究

在硼中子俘获治疗(BNCT)的蒙特卡洛(MC)剂量计算中,通常使用单一的网格模式,如16mm,8mm,4mm.使用细网格计算资源太大,使用粗网格,计算精度不够,为此,根据粒子穿透深度和计数量的变化梯度,采用混合网格模拟计算,达到了细网格的精度,时间仅为细网格的37%.     

四种溴代甲苯异构体的质谱区分

本工作用四种较新的质谱技术(碰撞诱导解离(CID),电荷剥离(CS),电荷分离(CSe),电子捕获诱导解离(ECID)谱研究了邻、间、对溴甲苯和溴化苄四种异构体。四种技术在一定程度上都可区分这些异构体。其中比较四种异构体ECID谱中ECID峰的相对强度可得到满意的区分效果。