Novel concept for the mass spectrometric determination of absolute isotopic abundances with improved measurement uncertainty: Part 2 – Development of an experimental procedure for the determination of the molar mass of silicon using MC-ICP-MS

The isotopic abundances and thus molar mass M(Si) of a silicon crystal material with natural isotopic abundances have been measured for the first time using multicollector-ICP-mass spectrometry (MC-ICP-MS) in combination with a novel concept of a modified isotope dilution mass spectrometry (IDMS)-method. This experimental work is the further development of part 1 of this series of papers. While part 1 describes the theoretical background and the mathematical derivation of the novel concept in detail, the measurements presented here serve to validate the novel concept and give experimental proof of its capability. Moreover, the also new method for the analytical calculation of calibration factors needed in the determination of absolute isotope amount ratios has been tested successfully. Silicon isotopic abundances have been measured directly from an aqueous alkaline matrix following a new sample preparation protocol developed within the framework of this study. A molar mass of M(Si) = 28.08548(13) g/mol with an associated relative uncertainty of u_rel = 4.6 × 10^?6 (k = 1) has been measured. This is in excellent agreement with the current IUPAC value for the molar mass of natural silicon M(Si_nat) = 28.08550(15) g/mol with u_rel = 5.3 × 10^?6 (k = 1). An uncertainty budget according to the Guide to the Expression of Uncertainty in Measurement (GUM) was calculated to assess the presented results and to validate the novel concept with the help of experimental data. The development of a new experimental procedure is presented in detail and the contributions to the uncertainty are discussed in comparison to part 1 of this work.     

Electronic state selectivity in dication-molecule single electron transfer reactions: NO(2+) + NO

The single-electron transfer reaction between NO(2+) and NO, which initially forms a pair of NO(+) ions, has been studied using a position-sensitive coincidence technique. The reactivity in this class of collision system, which involves the interaction of a dication with its neutral precursor, provides a sensitive test of recent ideas concerning electronic state selectivity in dicationic single-electron transfer reactions. In stark contrast to the recently observed single-electron transfer reactivity in the analogous CO(2)(2+)/CO(2) and O(2)(2+)/O(2) collision systems, electron transfer between NO(2+) and NO generates two product NO(+) ions which behave in an identical manner, whether the ions are formed from NO(2+) or NO. This observed behaviour is in excellent accord with the recently proposed rationalization of the state selectivity in dication-molecule SET reactions using simple propensity rules involving one-electron transitions.     

Uniform Estimates for the Fourier Transform of Surface Carried Measures in ?3 and an Application to Fourier Restriction

Let S be a hypersurface in \BbbR³{\Bbb{R}}^{3} which is the graph of a smooth, finite type function φ, and let μ=ρ  dσ be a surface carried measure on S, where dσ denotes the surface element on S and ρ a smooth density with sufficiently small support. We derive uniform estimates for the Fourier transform [^(m)]\hat{\mu} of μ, which are sharp except for the case where the principal face of the Newton polyhedron of φ, when expressed in adapted coordinates, is unbounded. As an application, we prove a sharp L ^p -L ² Fourier restriction theorem for S in the case where the original coordinates are adapted to φ. This improves on earlier joint work with M. Kempe.     

Topological Factors Derived from Bohmian Mechanics

We derive for Bohmian mechanics topological factors for quantum systems with a multiply-connected configuration space $$ \mathcal{Q}. $$ These include nonabelian factors corresponding to what we call holonomy-twisted representations of the fundamental group of $$ \mathcal{Q}. $$ We employ wave functions on the universal covering space of $$ \mathcal{Q}. $$ As a byproduct of our analysis, we obtain an explanation, within the framework of Bohmian mechanics, of the fact that the wave function of a system of identical particles is either symmetric or anti-symmetric. Communicated by Yosi Avron Submitted: 21/06/2005 Revised: 10/01/2006 Accepted: 27/01/2006     

Selective nucleophilic replacement of the benzylsulfanyl group in 2,4‐disulfanyl‐substituted thieno[2,3‐d]pyrimidin‐6‐carboxylic acid derivatives by secondary amines

Thieno[2,3‐d]pyrimidines with benzylsulfanyl and allylsulfanyl group in the presence of other alkylsul‐fanyl substituents react selectively under mild conditions with secondary amines under replacement of the benzyl or allyl residue whereas the other substituents remain intact. This enables the synthesis of different basic substituted derivatives with potentially biologically activity.     

A global equilibrium as the foundation of quantum randomness

We analyze the origin of quantum randomness within the framework of a completely deterministic theory of particle motion—Bohmian mechanics. We show that a universe governed by this mechanics evolves in such a way as to give rise to the appearance of randomness, with empirical distributions in agreement with the predictions of the quantum formalism. Crucial ingredients in our analysis are the concept of the effective wave function of a subsystem and that of a random system. The latter is a notion of interest in its own right and is relevant to any discussion of the role of probability in a deterministic universe.Research supported in part by NSF Grant DMS-9105661.     

Über vollständige Normtopologien in linearen Räumen

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