The measurement of the electronic g-factor in hydrogen-like ions --A promising tool for determining fundamental and nuclear constants

We describe a double-Penning-trap experiment suitable for testing QED in strong fields by determining the electronic g-factor of a single hydrogen-like ion in its ground state. Our measurements on ¹²C^{5 +} reach a relative accuracy of 2×10^-9, where the largest uncertainty results from the mass of the electron. Together with equally precise theoretical predictions therefore, it is possible to evaluate a new value for the electron's mass. The possibilities to obtain other fundamental constants and nuclear parameters are lined out. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: t.beier@gsi.de     

Capillary electrophoresis of DNA damage after irradiation: apoptosis and necrosis

Apoptosis is a type of cellular death but also directly regulates tumorigenesis through different gene expression. This phenomenon is often used as end-point in studies of radio- and chemosensitivity of cancer cells. Restriction DNA fragments have been separated quickly, efficiently and successfully by capillary gel electrophoresis (CGE). In this study CGE has been applied to distinguish between the discrete pattern of degraded DNA produced by apoptosis and randomized DNA breaks produced by ionizing radiation. The influence of different variables has been discussed and an example of fast separation by CGE of the apoptotic fragments produced by UV light treatment is shown.     

稀土对水泥熟料烧成的矿化作用机理

利用SEM—EDS分析了稀土氧化物在熟料中的分布并结合熟料的岩相分析初步探讨了稀土对水泥熟料烧成的矿化作用机理。研究结果表明,稀土元素La和Y在熟料煅烧过程中更多地分布在硅酸盐相中,同时增加了溶剂型氧化物（Al2O3、Fe2O3）在A矿中的固溶量;稀土离子的掺杂引起微观介质应力场发生畸变,增加结构中的空位缺陷,降低扩散活化能,从而提高质点的扩散速度,促进了C3S矿物的形成。     

Ferromagnetic resonance in Ni–Zn ferrite nanoparticles in different aggregation states

Ferrite nanoparticles of composition Zn_0.5Ni_0.5Fe₂O₄ were synthesized by forced hydrolysis in polyol from the corresponding zinc, nickel and iron acetates. By varying the preparation conditions, different aggregation states were obtained, ranging from isolated nanoparticles with average diameter of 5 nm, to clusters of some 20 nm, formed as well by nanoparticles with average diameter in the 5 nm range, as confirmed by X-ray diffraction and high resolution transmission electron microscopy. Ferromagnetic resonance measurements exhibited a ferrimagnetic behavior for both aggregation states at 77 K; at 300 K, however, isolated nanoparticles showed a superparamagnetic behavior while clustered ones remained ferrimagnetic with a broad linewidth. These results are interpreted on the basis of interactions between nanoparticles.     

Conductivity anisotropy in the antiferromagnetic state of iron pnictides

Recent experiments on iron pnictides have uncovered a large in-plane resistivity anisotropy with a surprising result: The system conducts better in the antiferromagnetic x direction than in the ferromagnetic y direction. We address this problem by calculating the ratio of the Drude weight along the x and y directions, D(x)/D(y), for the mean-field Q=(π,0) magnetic phase diagram of a five-band model for the undoped pnictides. We find that D(x)/D(y) ranges between 0.2相似文献   

Gas Adsorption Equilibria

Gas adsorption is a process for purification or separation of gas mixtures. Distillation is usually the first choice for bulk separations when liquefaction can be accomplished conveniently and when the relative volatilities of the materials to be separated do not approach or equal unity (azeotropy). If these conditions are not met, adsorption may offer an advantage, either by avoiding high or low temperatures or by providing higher separation factors and lower energy costs. Therefore the first step in the consideration of adsorption for a particular separation is the identification of a suitable adsorbent.     

Topological minors in bipartite graphs

For a bipartite graph G on m and n vertices, respectively, in its vertices classes, and for integers s and t such that 2 ≤ s ≤ t, 0 ≤ m − s ≤ n − t, and m + n ≤ 2s + t − 1, we prove that if G has at least mn − (2(m − s) + n − t) edges then it contains a subdivision of the complete bipartite K _(s,t) with s vertices in the m-class and t vertices in the n-class. Furthermore, we characterize the corresponding extremal bipartite graphs with mn − (2(m − s) + n − t + 1) edges for this topological Turan type problem.     

Temperature Dependence Kinetic Studies of the Reaction of O(3P) with CHI3 and C2H5I and the 298 K Reaction of OH(X2Π) with CHI3

A flash photolysis–resonance fluorescence technique was used to investigate the kinetics of the OH(X²Π) radical and O(³P) atom‐initiated reactions with CHI₃ and the kinetics of the O(³P) atom‐initiated reaction with C₂H₅I. The reactions of the O(³P) atom with CHI₃ and C₂H₅I were studied over the temperature range of 296 to 373 K in 14 Torr of helium, and the reaction of the OH (X²Π) radical with CHI₃ was studied at T = 298 K in 186 Torr of helium. The experiments involved time‐resolved resonance fluorescence detection of OH (A²Σ⁺ → X²Π transition at λ = 308 nm) and of O(³P) (λ = 130.2, 130.5, and 130.6 nm) following flash photolysis of the H₂O/He, H₂O/CHI₃/He, O₃/He, and O₃/C₂H₅I/He mixtures. A xenon vacuum UV (VUV) flash lamp (λ > 120 nm) served as a photolysis light source. The OH radicals were produced by the VUV flash photolysis of water, and the O(³P) atoms were produced by the VUV flash photolysis of ozone. Decays of OH radicals and O(³P) atoms in the presence of CHI₃ and C₂H₅I were observed to be exponential, and the decay rates were found to be linearly dependent on the CHI₃ and C₂H₅I concentrations. Measured rate coefficients for the reaction of O(³P) atoms with CHI₃ and C₂H₅I are described by the following Arrhenius expressions (units are cm³ s^?1): k_O+C2H5I(T) = (17.2 ± 7.4) × 10^?12 exp[?(190 ± 140)K/T] and k_O+CHI3(T) = (1.80 ± 2.70) × 10^?12 exp[?(440 ± 500)K/T]; the 298 K rate coefficient for the reaction of the OH radical with CHI₃ is k_OH+CHI3(298 K) = (1.65 ± 0.06) × 10^?11 cm³ s^?1. The listed uncertainty values of the Arrhenius parameters are 2σ‐standard errors of the calculated slopes by linear regression.