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1.
UCINSKI DARIUSZ; JAI ABDELHAQ EL 《IMA Journal of Mathematical Control and Information》1997,14(2):153-174
In this paper, the concept of weak spreadability is introduced.It constitutes an extension of the idea developed by El Jai& Kassara. In the case of linear distributed systems weconsider quadratic control techniques with a conveniently penalizedcriterion which makes the system weakly spreadable. The approachis outlined for a convectiondiffusion system, and theresults of a numerical study are also included to illustratethe main features of the considered problem. 相似文献
2.
Lancaster G.P.T. Häffner H. Wilson M.A. Becher C. Eschner J. Schmidt-Kaler F. Blatt R. 《Applied physics. B, Lasers and optics》2003,76(8):805-808
We present a scheme for employing a violet extended-cavity diode laser in experiments with single, trapped ions. For this the grating-stabilised laser is spatially and spectrally filtered and referenced to a Fabry–Pérot cavity. We measure an upper limit to the line width by observing a 305-kHz FWHM beat note with the second harmonic of a titanium sapphire laser. The laser is subsequently used to optically cool a single 40Ca+ ion close to the Doppler limit. PACS 03.67.Lx; 32.80.Pj; 42.55.Px 相似文献
3.
Axel Ingendoh Jan Becher Helen Clausen Helle Chris Nielsen 《Tetrahedron letters》1985,26(9):1249-1252
The high reactivity of the -1-acyloxy-1,3-pentadiene-5-ols as dienes in intramolecular Diels-Alder reactions with maleic anhydride and fumaric acid ethylester monochloride is discussed. 相似文献
4.
M. Tinggaard P. Hansen P. K. Mogensen O. Simonsen J. Becher 《Journal of heterocyclic chemistry》1989,26(2):439-444
2-Acyl-3-methylthiofurans 3 are obtained in fair yields from 3-methylthio-2-pentene-1,5-dione enolates 1 by reaction with iodine. In a similar reaction 1-phenyl-3-methylthio-4-nitro-2-buten-1-one gave 3-methylthio-2-nitro-5-phenylfuran 11. In the crystalline state the 2-benzoyl-3-methylthio-5-phenylfuran 3b showed a non-bonded sulfur-oxygen interaction as inferred from an X-ray diffraction determination, with a S····O distance of 2.871(5)Å. 相似文献
5.
Le Derf F Mazari M Mercier N Levillain E Trippé G Riou A Richomme P Becher J Garín J Orduna J Gallego-Planas N Gorgues A Sallé M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(2):447-455
A series of redox-responsive ligands that associate the electroactive tetrathiafulvalene core with polyether subunits of various lengths has been synthesized. X-ray structures are provided for each of the free ligands. The requisite structural criteria for reaching switchable ligands are satisfied for the largest macrocycles, that is, planarity of the 1,1',3,3'-tetrathiafulvalene (TTF) pi system and correctly oriented coordinating atoms. The ability of these ligands to recognize various metal cations as a function of the cavity size has been investigated by various techniques (LSIMS, 1H NMR, and UV/Vis spectroscopy, cyclic voltammetry). These systems exhibit an unprecedented high coordination ability among TTF crown ethers. Their switchable ligating properties have been confirmed by cyclic voltammetry, and metal-cation complexation has been illustrated by X-ray structures of three of the corresponding metal complexes (Pb2+, Sr2+, and Ba2+). Solid-state structures of these complexes display original packing modes with channel-like arrangements. 相似文献
6.
7.
Hege Rebecka Johansen Christian Thorstensen Tyge Greibrokk Georg Becher 《Journal of separation science》1993,16(3):148-152
On-line coupled supercritical fluid extraction and gas chromatography (SFE-GC) has been utilized for the determination of PCBs and other organochlorine compounds in human milk and blood serum. The procedure involved preconcentration of the sample on C18-silica sorbent in an extraction cell: after precipitation of the proteins up to 20 ml of human milk was concentrated on 0.5 g of sorbent. Serum (up to 5 ml) was applied to the C18 material without pretreatment. Basic alumina was utilized as a selective adsorbent for lipids in the on-line SFE-GC system. The method was used to analyze milk and serum spiked with 0.5 and 10 ng of Aroclor 1260 and the results compared with those obtained by liquid–liquid extraction of serum. 相似文献
8.
Jan Becher Klaus Brsndum Poul Hansen Jens Peter Jan Jacobsen 《Journal of heterocyclic chemistry》1988,25(3):795-798
The anions of 1,4-diaryl-3-buten-2-ones 1 reacts with arylisothiocyanates, yielding intermediates 4 which can ring close to 5,6-dihydro-4H-thiopyran-4-ones 5 . Under similar reaction conditions ethyl 3-oxo-4-pentenoates 7 gives the 6-spiropyrans 9 . Methylation of 3 gives the S-methylated open form 6 . 相似文献
9.
The solid–liquid equilibria of the ternary system H2O–Fe(NO3)3–Co(NO3)2 were studied by using a synthetic method based on conductivity measurements.
Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO3)3·9H2O), the iron nitrate hexahydrate (Fe(NO3)3·6H2O), the cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and the cobalt nitrate trihydrate (Co(NO3)2·3H2O). 相似文献
10.
A number of nucleophilic ring openings of 3-substituted pyridinium salts have been reinvestigated and summarized. The structure of the resulting stable glutaconaldehyde derivatives was investigated in detail by 1H NMR. It has been concluded that in general nucleophilic pyridinium ring openings are highly regiospecific. In each case investigated to date a single product was isolated, as a result of attack by the nucleophile at only one of the pyridine α-positions. With the OH ion as the only nucleophile, attack occurs at the pyridine C-2, while larger nucleophiles such as amines and carbanions attack at the pyridine C-6. This was found to be the case for a variety of 3-substituted pyridines such as 3-methyl, 3-methoxy-, 3-cyano-, 3 chloro-pyridine. 相似文献