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The problem considered is that of determining the shape of aplane acoustically sound-soft obstacle from the knowledge ofthe far-field pattern for one time-harmonic incident field.An iterative procedure is proposed based on two boundary integralsrepresenting the incident field and the far-field pattern, respectively.Numerical examples are included which show that the proceduregives accurate numerical approximations in relatively few iterations. 相似文献
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Bo Olsson György Marko-Varga Lo Gorton Roger Appelqvist Gillis Johansson 《Analytica chimica acta》1988
A selective and sensitive flow-injection system for the determination of myo-inositol (hexahydroxycyclohexane) is described. Inositol dehydrogenase, IDH, lactate dehydrogenase, LDH, and lactate oxidase, LOD, are co-immobilized on porous glass and used in a packed-bed enzyme reactor. myo-Inositol reacts to produce an equivalent amount of hydrogen peroxide, which oxidizes hexacyanoferrate(II) to hexacyanoferrate(III) in a second reactor containing immobilized peroxidase. The hexacyanoferrate(III) is then detected amperometrically at 0 mV vs. SCE in a flow-through detector. The system responds linearly to injected samples of myo-inositol (25 μl) in the concentration range 1–300 μM. The maximum throughput was 90 samples per hour. The IDH/LDH/LOD reactor was stable for at least 5 weeks. 相似文献
5.
Fluorogenic probes dual-labeled with reporter and quencher dyes use a change in fluorescence to monitor biochemical events (e.g., substrate binding or enzyme digestion). Such events change the reporter-quencher distance, which affects fluorescence. Recently, it is has been shown that static quenching through intramolecular dimers is an important mechanism that can sometimes be more efficient than F?rster resonance energy transfer (FRET). 相似文献
6.
Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques 总被引:1,自引:0,他引:1
S Andersson-Engels J Johansson U Stenram K Svanberg S Svanberg 《Journal of photochemistry and photobiology. B, Biology》1990,4(4):363-369
We report on the enhanced demarcation between human atherosclerotic plaques and normal vessel wall obtained using time-resolved detection of laser-induced fluorescence rather than the customary time-integrated monitoring technique. A frequency-doubled mode-locked and cavity-dumped continuous wave dye laser was used for picosecond pulse generation at 320 nm, and photon-counting techniques were employed for the time-resolved signal monitoring from human aorta samples in vitro. Implications for imaging fluorescence angioscopy and spectroscopic guidance in laser ablation of plaque are indicated. 相似文献
7.
Johansson A Håkansson M Jagner S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(18):5311-5318
Stereochemically labile copper and zinc complexes with the N,N'-dimethylethylenediamine ligand (dmeda) have been shown to be promising precursors for the total spontaneous resolution of chiral covalent networks. (N,N')-[Cu(NO3)2(dmeda)]infinity crystallises as a conglomerate and yields either enantiopure (R,R)-1 or enantiopure (S,S)-1. A mixed-valence copper(I/II) complex, [{Cu(II)Br2(dmeda)}3(Cu(I)Br)2]infinity (2), which crystallises as a pair of interpenetrating chiral (10,3)-a nets, is formed from CuBr, CuBr2 and dmeda. One net contains ligands with solely (R,R) configuration and exhibits helices with (P) configuration while the other has solely (S,S)-dmeda ligands and gives rise to a net in which the helices have (M) configuration. The whole crystalline arrangement is racemic, because the interpenetrating chiral nets are of opposite handedness. With zinc chloride (R,S)-[ZnCl(dmeda)2]2[ZnCl4] (3) is obtained, which is a network structure, although not chiral. Total spontaneous resolution of stereochemically labile metal complexes formed from achiral or racemic building blocks is suggested as a viable route for the preparation of covalent chiral networks. Once the absolute structure of the compound has been determined by X-ray crystallography, a quantitative determination of the enantiomeric excess of the bulk product can be undertaken by means of solid-state CD spectroscopy. 相似文献
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B Johansson 《Journal of chromatography. A》1986,381(1):107-113
A method for on-line high-performance liquid immunoaffinity chromatographic analysis of 5,5-diphenylhydantoin (phenytoin) in human plasma is described. The technique is simple and does not require sample preparation or addition of an internal standard, and the phenytoin is eluted from the columns in 12 min. A phenytoin-specific polyclonal immunoglobulin was attached to an organic silane derivative on silica. The immunosorbent was packed into a short liquid chromatography column and installed in a modified high-performance liquid chromatography system for on-line sample pre-purification. Standard curve linearity of plasma phenytoin was obtained at concentrations up to 160 mumol/l. When compared to conventional high-performance liquid chromatography, plasma phenytoin levels gave a correlation coefficient of 0.993. The phenytoin is highly bound to plasma proteins (ca. 87%). When plasma is injected onto the pre-column, a dissociation and partition of phenytoin from plasma proteins to a complete association with on-column insolubilized antibodies results. 相似文献
9.
A temperature-controlled graphite furnace for atomic-absorption analysis has been built and tested. The temperature of the graphite tube was monitored with an infrared-sensitive detector. Samples were introduced directly or via a separately heated graphite cup. Micro-samples of solid biological tissue were analysed directly for Zn, Mn and Co and the sensitivities for 1% absorption were 0.05,2 and 10 pg respectively. The salt content of the tissue limits the sample sizes, owing to non-specific absorption. The ashing conditions were investigated and found to be especially critical for Zn. 相似文献
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