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21.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
22.
Summary We study the integration theory for general integral metrics when restricted to upper integrals q, finding improvements in the relation between the classes of the q-integrable and the ql-integrable functions. We give new results and notions which lead to the desirable characterizations of q-integrable functions as ql-integrable f with q(|f|) < ∞, and of ql-integrable functions via the integrability of their upper truncations, under natural conditions which are fulfilled in most
finitely additive integration theories. 相似文献
23.
24.
J. J. EGOZCUE J. L. DIAZ-BARRERO V. PAWLOWSKY-GLAHN 《数学学报(英文版)》2006,22(4):1175-1182
The set of probability functions is a convex subset of L1 and it does not have a linear space structure when using ordinary sum and multiplication by real constants. Moreover, difficulties arise when dealing with distances between densities. The crucial point is that usual distances are not invariant under relevant transformations of densities. To overcome these limitations, Aitchison's ideas on compositional data analysis are used, generalizing perturbation and power transformation, as well as the Aitchison inner product, to operations on probability density functions with support on a finite interval. With these operations at hand, it is shown that the set of bounded probability density functions on finite intervals is a pre-Hilbert space. A Hilbert space of densities, whose logarithm is square-integrable, is obtained as the natural completion of the pre-Hilbert space. 相似文献
25.
Generally, in homotopy theory a cylinder object (or, its dual, a path object) is used to define homotopy between morphisms,
and a cone object is used to build exact sequences of homotopy groups. Here, an axiomatic theory based on a cone functor is
given. Suspension objects are associated to based objects and cofibrations, obtaining homotopy groups referred to an object
and relative to a cofibration, respectively. Exact sequences of these groups are built. Algebraic and particular examples
are given. We point out that the main results of this paper were already stated in [3], and the purpose of this article is
to give full details of the foregoing. 相似文献
26.
The big trip is a cosmological process thought to occur in the future by which the entire universe would be engulfed inside a gigantic wormhole and might travel through it along space and time. In this Letter we discuss different arguments that have been raised against the viability of that process, reaching the conclusions that the process can actually occur by accretion of phantom energy onto the wormholes and that it is stable and might occur in the global context of a multiverse model. We finally argue that the big trip does not contradict any holographic bounds on entropy and information. 相似文献
27.
E. Liénard G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière F. Mauger A. Méry O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《Hyperfine Interactions》2006,172(1-3):29-33
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller
decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The
6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to
deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this
experiment. Up to 105 coincidences were recorded during a second run in 2006. 相似文献
28.
Summary The gas chromatographic behaviour of crosslinked macroporous 2-hydroxyethyl methacrylate grafted with 2-methyloxazoline was
investigated and the range of applicability of the copolymer was assessed. Retention index values were measured on this copolymer
and compared with those obtained on the terpolymer 2-hydroxyethyl methacrylate-ethylene dimethacrylate-acrylonitrile. Rohrschneider
constants and efficiency data for selected sorbates are given. The use of this type of polymer in the separation of various
types of compounds is documented by various examples. 相似文献
29.
30.
Pedro Ontaneda 《Geometriae Dedicata》2004,104(1):25-35
We study the following question: does a compact nonpositively curved space have a totally geodesic core? 相似文献