非线性抛物型偏积分微分方程的H1-Galerkin 混合有限元方法

收稿给出一类非线性抛物型偏积分微分方程的H1-Galerkin混合有限元方法.给出了一维空间的半离散、全离散格式及最优阶误差估计,并将该方法推广到二维和三维空间.     

The191Os/191mIr generator for clinical use

An evaluation of adsorbents for potential use in the¹⁹¹Os/^191mIr medical radionuclide generator was performed. The adsorbents included 39 inorganic materials broadly classified as oxides, antimonates, ferro-ferricyanides, phosphates, sulfides, and miscellaneous including activated carbon and the organic anion-exchanger AGMP-1. The uptake of¹⁹¹Os in oxidation states (VI) [potassium tetrachloroosmate], (IV) [potassium hexachloroosmate] and (III) [potassium hexathiocyanatoosmate] was measured. Adsorbents having a high¹⁹¹Os uptake were evaluated for^191mIr elution yield using three physiologically compatible eluents. Only activated carbon and AGMP-1 adsorbents showed significant^191mIr elution yields under the test conditions (10% and 37%, respectively). The results of these studies suggest that activated carbon may be a promising adsorbent for development of a new¹⁹¹Os/^191mIr medical radionuclide generator. Activated carbon is a good candidate for further development since it is inert to the chemical and radiation effects which may effect an organic based ion exchange material such as AGMP-1.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.     

Estimation of boron isotope ratios using high resolution continuum source atomic absorption spectrometry

In the production of ¹⁰B enriched steels, the production–recycling process needs to be closely monitored for inadvertent mix-up of materials with different B isotope levels. A quick and simple method for the estimation of boron isotope ratios in high alloyed steels using high resolution continuum source flame AAS (HR-CS-FAAS) was developed. On the 208.9 nm B line the wavelength of the peak absorption of ¹⁰B and ¹¹B differs by 2.5 pm. The wavelength of the peak absorption of boron was determined by fitting a Gauss function through spectra simultaneously recorded by HR-CS-FAAS. It was shown that a linear correlation between the wavelength of the peak absorption and the isotope ratio exists and that this correlation is independent of the total boron concentration. Internal spectroscopic standards were used to compensate for monochromator drift and monochromator resolution changes. Accuracy and precision of the analyzed samples were thereby increased by a factor of up to 1.3. Three steel reference materials and one boric acid CRM, each certified for the boron isotope ratio were used to validate the procedure.     

Sterisch gehinderte Stickstoffbasen zur selektiven Extraktion von Silber

Zusammenfassung Lösungen von sterisch gehinderten Pyridinbasen wie 4-Octadecylthio-2,6-dimethylpyridin (= Lut-S-18 = III) und anderen sterisch gehinderten aliphatischen (und cycloaliphatischen) Stickstoffbasen in Heptanon-3 werden für die radiochemisch verfolgte Extraktion von Silber(I)-Ionen aus wäßriger Lösung eingesetzt. In Gegenwart von 0,5 M NaNO₃ extrahiert die Pyridinbase Lut-S-18 im pH-Bereich 5–10 bis zu 88% des Silbers in einem einzelnen Extraktionsschritt. Das Extraktionsmittel Lut-S-18 ist selektiv für Silber in dem Sinne, daß unter den genannten Bedingungen die Aquokationen Co²⁺, Ni²⁺, Cu²⁺ und Zn²⁺ nur in sehr geringem Ausmaß extrahiert werden. Die Rückextraktion des Silbers aus der organischen Phase kann leicht mit verdünnter Ammoniak-Lösung durchgeführt werden. Die Amine 3-Amino-2,4-dimethylpentan und 2,2,6,6-Tetramethylpiperidin sind auch gute Extraktionsmittel für Silber, aber sie wirken weniger selektiv.

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Sterically hindered nitrogen bases for the selective extraction of silver

Summary Heptanone-3 solutions of sterically hindered pyridine bases such as 4-octadecylthio-2,6-dimethylpyridine (= Lut-S-18=III) and of other sterically hindered aliphatic (and cycloaliphatic) nitrogen bases are used for the radiochemically monitored extraction of silver(I) ions from aqueous solution. In the presence of 0.5 M NaNO₃ the pyridine base Lut-S-18 extracts up to 88% of the silver in a single extraction step in the pH range 5–10. The extraction agent Lut-S-18 is selective for silver in the sense that under the conditions described the aquo cations Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ are extracted to a very minor extent only. Back extraction of the silver from the organic phase is easily achieved with dilute ammonia solution. The amines 3-amino-2, 4-dimethylpentane and 2,2,6,6-tetramethylpiperidine are also good extraction agents for silver, but they are less selective.

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Herrn Prof. Dr. K. H. Lieser zum 65. Geburtstag gewidmet

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Die Autoren danken der Deutschen Forschungsgemeinschaft und dem Verband der Chemischen Industrie e.V. für Unterstützung sowie der Firma E. Merck, Darmstadt, für Zusammenarbeit. Die Durchführung der radiochemischen Messungen wurde durch das Entgegenkommen der Arbeitsgruppe von Herrn Prof. Dr. K. H. Lieser wesentlich erleichtert. Einige der aliphatischen Stickstoffbasen wurden freundlicherweise von der Fa. Hüls zur Verfügung gestellt.     

Complete assignment of 1H and 13C NMR data of pravastatin derivatives

The complete ¹H and ¹³C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd.     

Automatic off/on-line preconcentration for ICP-OES: Powerful instrumentation for water analysis

Automated preconcentration techniques for off/on-line determination with ICP-OES have been developed for various metal ions of environmental interest. Preconcentration studies were performed on two different types of chemically bonded chelating ion-exchangers, namely EDTrA-cellulose (iminoacetate groups) and HSO₃ · oxine-cellulose. Enrichment studies were carried out at various preconcentration factors and also at different loadings.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Design and construction of multicrystal analyser detectors using Rowland circles: application to MAD26 at ALBA

A concept is given for describing multicrystal analyser detectors (MADs), as they are in use for synchrotron powder diffraction, on the basis of the Rowland circle construction. The Rowland circle is typically used to describe focusing geometries and can be adapted for the case of MADs working at a single energy as well as in a limited energy range. With this construction it is also possible to quantify and optimize the walk of the beam along non‐central crystals which is inevitable in certain detector designs. The results of this geometrical inspection are correlated with a real detector design that is implemented at the ALBA synchrotron facility in Spain. An error budget is given to estimate the influence and amount of tolerance of the manufacturing process.     

Sparse asymptotic minimum variance based bearing estimation algorithm for a single vector hydrophone

For underwater target detection using a single vector hydrophone, sparse asymptotic minimum variance(SAMV) method is used to estimate the target bearing. The SAMV discretizes the entire scanning space and the target bearing is located at the position of the discrete direction. The SAMV algorithm utilizes the sparsity of the spatial signal to improve the estimation performance of the target bearing. Background noise level(BNL) of the bearing estimation of SAMV algorithm is lower than those of the conventional beam forming(CBF)method and minimum variance distortionless response(MVDR) method for different signal noise ratios(SNRs). When the SNR is higher than 0 d B, the direction-finding error of this algorithm is less than 2°. Moreover, the SAMV algorithm has a better dimensional orientation resolution capability. The experimental results show that the SAMV algorithm gives a bearing and time recording map with a lower BNL, which effectively verifies the effectiveness of SAMV algorithm in terms of underwater target detection.