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11.
Summary Two methods of instrumental neutron activation analysis for the determination of selenium in steels, based on respectively77mSe (t
1/2
= 17.5 s) and75Se (t
1/2 = 120 d) are presented. Good agreement is obtained by application of both methods on a series of steels containing selenium at the 0.1% level. Interferences and advantages associated with either method are discussed.
Bestimmung von Selen in Stahl durch Neutronenaktivierung und Ge(Li)--Spektrometrie
Zusammenfassung Zwei Methoden werden beschrieben, die auf der Messung von77mSe (t 1/2 = 17,5 s) bzw.75Se (t 1/2 = 120 d) beruhen. Bei der Anwendung auf Stähle mit Selengehalten in der Größenordnung von 0,1 % wurden gut übereinstimmende Werte erhalten. Störungen und Vorteile der Methoden werden diskutiert.相似文献
12.
Helge Johansen 《International journal of quantum chemistry》1975,9(3):459-471
Ab initio SCF-LCAO-MO calculations have been performed for TCNQ and its positive and negative ions in various electronic states. A basis set consisting of 412 primitive Gaussian type orbitals contracted to 180 was used in the investigation. The electron density distribution in TCNQ and the negative ions, and the redistribution upon ionization has been illustrated by plotting difference density contour maps. The quinone structure of the neutral TCNQ system undergoes a transformation to a benzenoid structure when electrons are added. Electronic transitions, ionization potentials and electron affinities have also been calculated. 相似文献
13.
Vogensen SB Greenwood JR Varming AR Brehm L Pickering DS Nielsen B Liljefors T Clausen RP Johansen TN Krogsgaard-Larsen P 《Organic & biomolecular chemistry》2004,2(2):206-213
(RS)-3-Hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid (5-HPCA)(), which is a conformationally constrained cyclised analogue of AMPA has previously been described as causing glutamate receptor mediated excitations of spontaneously firing cat spinal interneurons in a similar fashion to AMPA. We have now prepared the enantiomers of through chiral chromatographic resolution of (RS)-3-(carboxymethoxy)-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid () followed by a stereoconservative hydrolysis resulting in the enantiomers of with high enantiomeric excess (% ee [greater-than-or-equal] 99). The absolute configurations indicated by an X-ray analysis of (-)- monohydrate were confirmed by comparing observed and ab initio calculated electronic circular dichroism spectra and by stereoconservative synthesis of (S)- from (S)-AMPA, the pharmacologically active form of AMPA. The pharmacological effects at native and cloned (GluR1-4) AMPA receptors were shown to reside exclusively with (R)-(+)-, in striking contrast to the usual stereoselectivity trend among AMPA receptor agonists. The reasons for this anomalous behaviour became clear upon docking both enantiomers of to the agonist binding site of GluR2. 相似文献
14.
15.
Lars Carlsena Klaus Bechgaardb Claus S. Jacobsen Ib Johansen 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Tetrathiafulvalene S-oxide (TTF-ox) was first detected by mass spectrometry in samples of Tetrathiafulvalene (TTF) which had been exposed to oxygen. Pure TTF-ox was prepared by peracid oxidation of TTF and isolated as a relativly stable solid. Physical data will be presented. 相似文献
16.
Son Tung Dang Ernst Arne Meese John Christian Morud Stein Tore Johansen 《国际流体数值方法杂志》2019,91(9):419-447
In this paper, we introduce numerical methods that can simulate complex multiphase flows. The finite volume method, applying Cartesian cut-cell is used in the computational domain, containing fluid and solid, to conserve mass and momentum. With this method, flows in and around any geometry can be simulated without complex and time consuming meshing. For the fluid region, which involves liquid and gas, the ghost fluid method is employed to handle the stiffness of the interface discontinuity problem. The interaction between each phase is treated simply by wall function models or jump conditions of pressure, velocity and shear stress at the interface. The sharp interface method “coupled level set (LS) and volume of fluid (VOF)” is used to represent the interface between the two fluid phases. This approach will combine some advantages of both interface tracking/capturing methods, such as the excellent mass conservation from the VOF method and good accuracy of interface normal computation from the LS function. The first coupled LS and VOF will be generated to reconstruct the interface between solid and the other materials. The second will represent the interface between liquid and gas. 相似文献
17.
(111) oriented n-type silicon wafers which were implanted with 2 × 1015 B+/cm2 at 77 K and at an energy of 60 keV are laser annealed (Nd:YAG pulse laser) in air for mean laser powers between P = 1.8 W and P = 4.0 W. The comparative application of scanning electron microscopy (SE, EBIC) and high voltage transmission electron microscopy (HVTEM, 1000 keV) allows an estimation of the annealing quality in separated lines without overlapping. Values specifically ascertained by SEM in the SE contrast mode for the annealing threshold power P th, the power range for optimal annealing ΔP 0 and for the geometric width of the monocrystalline resolidification perpendicular to the direction of the specimen movement (and related to the spot diameter) at different laser pulse powers P agree completely with the results found in EBIC. At an optimal laser pulse power of P 0 = 3.2 W HVTEM enables monocrystalline epitaxially resolidified areas free of defects to be identified in the same geometric width as that ascertained by SE and EBIC. 相似文献
18.
19.
We propose a theoretical model for the recently reported anomalously long decay of a space-charge field that was resonantly excited in a photorefractive sillenite crystal [Phys. Rev. Lett. 79, 67 (1997)]. The model is based on the conventional concept of charge transfer and does not require excessively large values of the quality factor for space-charge waves. The effect in question is qualified as a critical slowing of the relaxation process as the threshold of optical oscillation is approached. 相似文献
20.
M. R. Koblischka S. L. Huang K. Fossheim T. H. Johansen H. Bratsberg 《Physica C: Superconductivity and its Applications》1998,300(3-4):207-211
Flux distributions of partial-melting processed Bi2Sr2CaCu2O8+δ ceramics are obtained using magneto-optic imaging. In remanent states (μ0Ha=0 T), large amounts of trapped flux are observed along (Sr,Ca)2CuOy particles embedded in the Bi2Sr2CaCu2O8+δ matrix. Despite the relatively large size of these particles (up to 30 μm), the pinning effect is similar to that of Y2BaCuO5 particles in melt-processed YBa2Cu3O7−δ. Furthermore, we discuss how the pinning capability of non-superconducting particles of different sizes and densities will show up in magneto-optic images. 相似文献