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31.
Hwan Myung Kim Pil Rye Yang Young-Gyu Ko Young Dae Chung Seung-Joon Jeon 《Tetrahedron letters》2007,48(15):2791-2795
2H-Benzo[h]chromene-2-one derivatives showing appreciable water solubility, significant two-photon cross sections, high photostability, cell permeability, low toxicity, and ability to be converted to a protein TP probe have been developed by incorporating all of the needed functions within a small molecule. 相似文献
32.
Fullerenols revisited as stable radical anions 总被引:2,自引:0,他引:2
Husebo LO Sitharaman B Furukawa K Kato T Wilson LJ 《Journal of the American Chemical Society》2004,126(38):12055-12064
The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene. 相似文献
33.
K. H. Kim J. H. Lee M. Y. Ko K. S. Shin J. S. Kang W. C. Mar J. R. Youm 《Chromatographia》2002,55(1-2):81-85
Summary A method for the assay of R-(+)- and S-(−)- metoprolol in human urine has been developed using gas chromatography-mass spectrometry.
The method involved purification by liquid-liquid extraction and derivatization with N-methyl-N-(trimethylsilyl)trifluoroacetamide
to form an O-silyl ether, followed by subsequent chiral derivatization with (−)-α-methoxy-α-(trifluoromethyl)phenylacetyl
chloride to form diastereomeric amide. The reaction was rapid and the diastereomeric derivatives were well resolved. Quantitation
was performed by selected-ion monitoring of fragment ions of the diastereomers in electron impact ionization mode. No racemization
was found during the reaction. The detection limit was 0.5 ng·mL−1. The intra-day variation ranged between 0.38 and 7.86% in relation to the measured concentration and inter-day variation
was 2.26–8.06%. The method has been applied to the determination of R-(+)-and S-(−)- metoprolol in human urine from healthy
volunteers dosed with racemic metoprolol tartrate. 相似文献
34.
Zusammenfassung Es wird eine neue polarographische Methode zur direkten Bestimmung des Pyridoxols in Injektionspräparaten und Tabletten beschrieben. Die ausgearbeitete Methode beruht auf der polarographischen Reduktion des Pyridoxolmoleküls im Milieu von Ammoniak-Ammoniumchlorid-Puffern und weiter auf der Bildung einer katalytischen Stufe des Pyridoxols in Veronalpuffern. Die polarographische Methode ist rascher und in manchen Fällen genauer und empfindlicher als die bisher in Gebrauch stehenden Methoden. Die Anwesenheit der in den Präparaten laufend vorkommenden Begleitstoffe des Pyridoxols stört nicht die polarographische Bestimmung. Die Methode kann auch zur Bestimmung des 3-Hydroxy-4-methoxymethyl-5-oxymethyl-2-methylpyridins benutzt werden, das ein Zwischenprodukt bei der Pyridoxolerzeugung ist.
Herrn Dr.P. Zuman danken wit für Ratsehläge bei der Abfassung dieser Arbeit. 相似文献
Summary A new polarographic method is described for the direct determination of pyridoxol in injection preparations and tablets. This method is based on the polarographic reduction of the pyridoxol in ammonia-ammonium chloride buffer medium and also on the formation of a catalytic stage of the pyridoxol in veronal buffers. The polarographic method is faster and in many cases more accurate and more sensitive than the methods now in use. The presence of the materials which always accompany the pyridoxol in the preparations does not interfere with the polarographic determination. The method can likewise be used for determining 3-hydroxy-4-methoxymethyl-5-oxymethyl-2-methylpyridine, which is an intermediate product in the manufacture of pyridoxol.
Résumé On décrit une nouvelle méthode polarographique pour le dosage direct du pyridoxol dans les préparations pour injections et dans les comprimés. La méthode élaborée repose sur la réduction polarographique de la molécule de pyridoxol dans le milieu tampon ammoniaque-chlorure d'ammonium, et, en outre, sur la formation d'une phase catalytique du pyridoxol dans les tampons au véronal. La méthode polarographique est plus rapide et dans de nombreux cas plus exacte et plus sensible que les méthodes utilisées jusqu'ici. La présence d'impuretés existant couramment dans les préparations à côté du pyridoxol ne gêne pas le dosage polarographique. On peut aussi utiliser la méthode pour le dosage de l'hydroxy-3 méthoxyméthyl-4 oxyméthyl-5 méthyl-2 pyridine, substance intermédiaire dans la préparation du pyridoxol.
Herrn Dr.P. Zuman danken wit für Ratsehläge bei der Abfassung dieser Arbeit. 相似文献
35.
36.
Let u(x, y) be defined in B
1×B
2 where B
1
m
and B
2
n
, and assume that u(x, ·) harmonic for every fixed x and u(·, y) is subharmonic for every fixed y. We show that if u(·, y) is, in addition, C
2 for each y then u is subharmonic in B
1×B
2 in both variables jointly. 相似文献
37.
An analytical scheme is proposed which combines three speciation techniques for determination of particular Al species in soil extracts and percolating waters. A cation-exchange fast protein liquid chromatography — inductively coupled plasma atomic emission spectrometry (FPLC-ICP-AES) procedure, a microcolumn chelating ion-exchange chromatography- atomic absorption spectrometry (MCC-ETAAS) technique and the 8-hydroxyquinoline spectrophotometric method (8HQ-spectrophotometry) were employed. The FPLC-ICP-AES procedure offers determination of Al3+ (retention time 4.5 min) and Al(OH)2+ species (retention time 4.0 min) which are separated from Al(OH)+
2 (retention time 1.5min). AlF2+ coelutes with Al(OH)2+ species, while Al(SO4)+, AlF+
2 and negatively charged Al organic complexes coelute with Al(OH)+
2 species. The MCC-ETAAS technique enables determination of the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphate- and fluoro-Al complexes. Employing the 8HQ-spectrophotometry the sum of positively charged monomeric aqua- and hydroxy-Al species plus sulphato- and most of the labile organic Al species are determined. The sensitivities of these selected techniques were adequate for speciation of Al in the samples analyzed. On the basis of the specific selectivity of a particular technique various groups of Al species may be determined. Thus, the comparison of analytical data from complementary procedures provides more comprehensive information on Al species present in soil extracts and percolating waters. 相似文献
38.
39.
40.
Jakub Kołacz Henry G. Gotjen Robel Y. Bekele Jason D. Myers Jesse A. Frantz Michael Ziemkiewicz 《Liquid crystals》2020,47(4):531-539
ABSTRACTIn a planar dielectric waveguide, weak confinement of a propagating mode in a high index core leads to a measurable evanescent interaction with the cladding. In this work, we study the effect of a reorientable anisotropic cladding on the behaviour of Transverse Electric (TE) and Transverse Magnetic (TM) mode polarisations using a liquid crystal (LC)-clad waveguide architecture. The polarised evanescent field of a guided mode interacts with a voltage-tunable birefringent LC cladding to deflect an out-coupled beam. Experimental measurements are coupled with a theoretical framework and show good consistency with simulation results. We isolate the effect of mode confinement by changing the thickness of the high index core. Interactions between the LC index ellipsoid and the mode polarisation are probed by changing the initial alignment of the LC. Finally, we examine the difference in deflection between TE and TM modes, which incorporates both a change in mode confinement and a difference in LC index components. 相似文献