M Spectra of the Rare Earth Elements Measured with an Ultra-Thin Window Si(Li) Detector

The oxides of the rare earth elements 57Z71 were excited by electrons with an energy between 3 and 15keV. X-rays were detected by an energy dispersive Si(Li) spectrometer, with an ultra-thin polymer entrance window. Due to the limited resolution of this type of spectrometer, the M spectra of the rare earths appear to consist of only four peaks: M, M,, M, and M₂N₄. The net height of these peaks relative to that of M, was used as a measure of the relative intensity. For 3keV electrons, a continuous decrease of the relative intensity of M with increasing Z was observed, ranging from approximately 90% for 57 La to less than 10% for 71 Lu. This behaviour is in agreement with a model involving a gradual filling up of the levels N6 and N7 with increasing Z. The relative intensity of M is lower than that of M by about a factor of 5, whereas M₂N₄ is approximately half as intense as M.     

Selective ultratrace analysis of 41Ca by laser resonance ionization

A compact resonance ionization mass spectrometer is presented. It is presently applied for sensitive and highly selective ultratrace determination of the long-lived radioisotope ⁴¹Ca for environmental, biological, and fundamental investigations. The development of coherent multistep resonance ionization enables the realization of experimental detection limits as low as10⁶ atoms per sample and very high isotopic selectivity above 10¹². This revised version was published online in August 2006 with corrections to the Cover Date.     

青藏铁路多年冻土区工程复杂性分析

青藏铁路穿越550km多年冻土区,多年冻土地温、冻土类型以及沿线生态环境等存在较大的差异,使多年冻土区工程较为复杂。因此本文提出了冻土工程复杂性概念,建立冻土工程复杂性评价模型,并利用GIS平台对青藏铁路沿线唐古拉山越岭地段工程复杂性进行了分析和研究。研究结果表明,青藏铁路穿越的唐古拉山越岭地段工程复杂性相对较小,而青藏公路的工程复杂性相对较大。这表明了青藏公路沿线冻土工程比青藏铁路沿线更为复杂,在各种因素的影响下,青藏公路路基稳定性变化比青藏铁路更加复杂。     

Multivariate multifractal analysis

We show how a joint multifractal analysis of a collection of signals unravels correlations between the locations of their pointwise singularities. The multivariate multifractal formalism, reformulated in the general setting supplied by multiresolution quantities, provides a framework which allows to estimate joint multifractal spectra. General results on joint multifractal spectra are derived, and illustrated by the theoretical derivation and practical estimation of the joint multifractal spectra of simple mathematical models, including correlated binomial cascades.     

Nuclear moments of strongly deformed strontium isotopes

Nuclear spins, moments and mean square charge radii of^78–100Sr have been obtained by fast ion-beam collinear laserspectroscopy. The experiments performed at ISOLDE have been extended to include⁹⁹Sr, measured by a non-optical detection scheme with a two-step optical pumping sequence. The results for the strongly deformed isotopes are discussed in the frame of the particle-plus-deformed core model.     

Development Towards a Laser Ion Source Trap for the Production of Exotic Species

A new type of resonance ionization laser ion source (RILIS) is presently being developed and tested at the off-line mass separator at Mainz University for future use at on-line exotic rare isotopes production facilities. For highest isobaric selectivity, this RILIS approach decouples the evaporation and ionization process. A further advantage is the generation of full temporal control of the resulting high quality ion beam. These facts are realized by a combination of atomizer – ion repeller – ion cooler and trap, which is operated together with a state-of-the-art, all solid state laser system. The principle and performance of this laser ion source trap (LIST) system are discussed applying simulation studies for the repeller-trap combination and first measurements for characterization.     

Coercive singular perturbations II: Reduction and convergence

An algebra of pseudodifferential singular perturbations is introduced. It provides a constructive machinery in order to reduce an elliptic singularly perturbed operator (in $\text{R}$ⁿ or on a smooth manifold without border) to a regular perturbation. The technique developed is applied to some singularly perturbed boundary value problems as well. Special attention is given to a singular perturbation appearing in the linear theory of thin elastic plates. A Wiener-Hopf-type operator containing the small parameter reduces this singular perturbation to a regular one. It also gives rise to a natural recurrence process for the construction of high-order asymptotic formulae for the solution of the perturbed problem. The method presented can be extended to the general coercive singular perturbations.     

Esca investigations of some NiO/SiO2 and NiO—Al2 O3 /SiO2 catalysts

The ESCA spectra of a series of NiO/SiO₂ and NiO—Al₂ O₃/SiO₂ catalysts are reported, together with those of some reference compounds. The positions and shapes of the lines, in conjunction with a quantitative surface analysis from relative intensities, allow the identification of different surface phases, e.g. an NiO-like phase in the impregnated catalysts with very low catalytic activity and an Ni talc-like phase in the precipitated catalysts which have higher activity. The addition of Al₂O₃ has a great influence on the surface structure (formation of alumosilicate).     

Modeling of the submicron particles formation and initial layer ash deposition during high temperature oxy-coal combustion

The future use of coal as a fuel for power generation in the US depends on the availability of financially viable technologies for capture and storage of CO₂ emissions from power plants. Key second-generation candidates for CO₂ capture include high temperature and pressurized oxy-firing of coal, which has the potential to increase efficiency, lower capital costs, avoid air ingress and reduce oxygen requirements. However, unquantified challenges, such as flame behavior, heat transfer, ash transformation, ash deposition and char oxidation, still exist for those technologies. This study specifically focuses on the formation of submicron particles and initial layer ash deposition during high temperature oxy-coal combustion. Previous work has shown that the initial layer deposits are mainly formed of submicron size ash aerosols transported by thermophoresis. Unfortunately, the importance of submicron particle deposition has not received much attention, probably due to the insignificant deposit mass and difficulty in prediction of the submicron particles formation. In this work, models including mineral matter vaporization model, scavenging model and deposition model are developed and applied into a three-dimensional CFD framework to predict the submicron particles formation and subsequent initial layer deposits formation. The model results are comparable to experimental data. The merits of this work are that it has led to the development of a novel approach to predict both submicron particle formation and initial layer ash deposition during oxy-coal combustion.     

Expansion of Germanato‐Polyoxovanadate Cluster Cores: Solvothermal Syntheses and Selected Properties of (trenH2)2[{M(tren)}4V15Ge6O48(H2O)] (M = Co and Zn)

Two germanato‐polyoxovanadates with the {V₁₅Ge₆O₄₈} cluster core are extended by covalent bonds to four transition metal amine complexes [M(tren)]²⁺ (M = Co and Zn, tren = tris(2‐aminoethyl)amine). The complexes have bonds to terminal atoms of the Ge₂O₇ units and such expansion of a germanato‐polyxovanadate was never observed before. The characterization of these compounds revealed the presence of two protonated tren molecules charge balancing the negative charges of the [{M(tren)}₄V₁₅Ge₆O₄₈(H₂O)]^4– anion.