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61.
A series of new tetraazaspiro[5,5]-undec-4-ene-2,7,9,11-tetraones have been obtained by reaction of 5-(2-arylethylidene-2-oxo)-1,3-dimethylpyrimidine-2,4,6-triones with ureas. A three-component one-pot procedure to the spiranes synthesis was also developed. One-pot reaction of arylglyoxals, 1,3-dimethylbarbituric acid, and dimethylurea led to imidazolyl-1,3-dimethylbarbituric acids. Mechanisms of studied reactions were discussed. 相似文献
62.
Lu JJ Yu LM Cheung WW Goldthorpe IA Zuo YY Policova Z Cox PN Neumann AW 《Colloids and surfaces. B, Biointerfaces》2005,41(2-3):145-151
Shortage or malfunction of pulmonary surfactant in alveolar space leads to a critical condition termed respiratory distress syndrome (RDS). Surfactant replacement therapy, the major method to treat RDS, is an expensive treatment. In this paper, the effect of poly(ethylene glycol) (PEG) to improve dynamic surface activity of a bovine lipid extract surfactant (BLES) was studied by axisymmetric drop shape analysis (ADSA) and a captive bubble method. The activity of BLES+PEG mixtures was compared to that of a natural surfactant containing surfactant proteins A and D. When PEG was added into BLES mixtures, the surface tension hysteresis of BLES films was minimized when the films were compressed by more than 50%. PEG also helps to quickly restore surfactant films after film collapse. Thus, as far as surface tension effects go, the findings suggest that PEG might be used as a substitute for surfactant-associated protein SP-A in therapeutic surfactant products, and might also be used to reduce the amount of BLES required in clinical applications. 相似文献
63.
Miroslav Holub Miloš Buděšínský Zdenka Smítalová David Šaman Urszula Rychlewska 《Tetrahedron letters》1982,23(46):4853-4856
A new stereochemical group of eudesmanolides - 5βH,6αH,7αH,10αCH3-eudesman-6,12-olides - was identified mainly on the basis of proton NMR spectroscopy and checked by X-ray analysis 相似文献
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Dr. Oldrich Vrana Dr. Vojtech Novohradsky Dr. Zdenka Medrikova Ing. Jana Burdikova Ing. Olga Stuchlikova Prof. Jana Kasparkova Prof. Dr. Viktor Brabec 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2728-2735
Anticancer therapy by platinum complexes, based on nanocarrier‐based delivery, may offer a new approach to improve the efficacy and tolerability of the platinum family of anticancer drugs. The original rules for the design of new anticancer platinum drugs were affected by the fact that, although cisplatin (cis‐[PtCl2(NH3)2) was an anticancer drug, its isomer transplatin was not cytotoxic. For the first time, it is demonstrated that simple encapsulation of an inactive platinum compound in phospholipid bilayers transforms it into an efficient cytotoxic agent. Notably, the encapsulation of transplatin makes it possible to overcome the resistance mechanisms operating in cancer cells treated with cisplatin and prevents inactivation of transplatin in the extracellular environment. It is also shown that transplatin delivered to the cells in nanocapsules, in contrast to free (nonencapsulated) complex, forms cytotoxic cross‐links on DNA. 相似文献
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J. T. van Elteren Zdenka Šlejkovec Marta Svetina Andrej Glinšek 《Analytical and bioanalytical chemistry》2001,370(4):408-412
Because stabilization of arsenite in water samples during transit and storage is troublesome, this work deals with a method to prevent this by on-site selective coprecipitation of arsenite with dibenzyldithiocarbamate and recovery of the coprecipitate by filtration through a 0.45-μm membrane filter. In the laboratory arsenic on the filter is quantitatively released by oxidation of arsenite to arsenate with H2O2 (6%) in alkaline medium (8 mmol L–1 NaOH) at elevated temperature (85?°C) for 30 min followed by ultratrace determination by routine HGAFS and ICP–MS. It is shown that arsenate contamination of the coprecipitate is so low that arsenate concentrations three orders of magnitude higher than the arsenite concentration do not interfere; this is essential, because arsenate is usually the dominant arsenic species in water. Because significant preconcentration can be achieved in the solution obtained from the leached filter (normally a factor 20 but easily increased to 100) very low detection limits can be obtained (only limited by the purity of the materials and the cleanliness of working); a realistic limit of determination is 0.01 μg L–1 arsenite. The procedure was used for the determination of arsenite in two ground waters from an ash depository site in the ?alek valley (Slovenia). The matrix contained some elements at very high levels but this did not impair the efficiency of arsenite coprecipitation. The results obtained by use of HGAFS and ICP–MS were not significantly different at the 5% level for sub-μg L–1 arsenite concentrations. 相似文献
70.
Lalić M. V. Mestnik-Filho J. Carbonari A. W. Saxena R. N. Haas H. 《Hyperfine Interactions》2001,136(3-8):743-747
Electronic band structure calculations for the CeIn3 compound utilizing the full potential linearized augmented plane waves method were performed with the aim to compute the
hyperfine fields acting on Ce and In atoms. The latter are found to be in reasonable agreement with the values measured at
low temperatures. The 4f orbital contribution dominates the magnetic hyperfine field at Ce ions while the contact field is
negligible due to an almost complete cancellation of valence and core contributions. A non-zero magnetic hyperfine field appears
at In sites due to the spin-polarization of the 5p sub-shells through the hybridization with the extended 6s, 6p and 5d Ce
states which, in turn, are spin-polarized by the Ce 4f states. No net magnetic moment at In is observed since the sum of its
5p sub-shell spins is zero. The 5p shell of In is responsible for the presence of an electric field gradient at In nuclei.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献