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101.
A new C19 hydroxylated enyne 15, as potential A-ring building block of vitamin D analogues, was synthesized in enantiomerically pure form in nine steps from (−)-(S)-limonene. This short synthesis involved ozonolyzis of 1,2-limonene oxide followed by a Criegee rearrangement, epoxide trans diaxial ring opening by lithium acetylide, elimination, epoxidation and syn β-elimination of the resulting homopropargylic oxirane. 相似文献
102.
H. A. Ergül S. Topcuo?lu E. Ölmez Ç. K?rbaşo?lu 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(1):133-136
Summary Radionuclide (137Cs, 238U, 232Th and 40K) concentrations were determined in a sediment trap and bottom sediment samples collected from a station at the eastern Turkish
coast of the Black Sea. The specific activity of the 137Cs radionuclide in the settling particles ranged from 0.04±0.01 to 0.10±0.02 Bq. g-1dry weight. The calculated flux rate of the 137Cs was between 0.37 and 2.59 Bq. m-2. d-1in the sampling periods of 2002 and 2003. The 137Cs concentration in the bottom sediment profile were between 0.039±0.013-9.083±0.017 Bq. g-1dry weight in the same station. The vertical profile of the radionuclides suggests that they have little mobility during the
17 years after the Chernobyl accident. 相似文献
103.
The reaction of 1-(hydrazidomethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 3 with aromatic aldehydes yield hydrazones 4a,b or pyrimido[6,1-a]isoquinolines 5a-c depending upon the proportions of the reagents. With ketones, 3 gives only hydrazones 4a-d and 7 , which can be transformed to pyrimidoisoquinolines 10a-e and 11 with aldehydes. The ring closures are stereospecific; the relative configurations were determined by DNOE measurements. 相似文献
104.
A way of using gravity flow to induce a linear convection within a microfluidic system is presented. It is shown and mathematically supported that tilting a 1 cm long covered microchannel is enough to generate flow rates up to 1000 nL.min(-1), which represents a linear velocity of 2.4 mm.s(-1). This paper also presents a method to monitor the microfluidic events occurring in a covered microchannel when a difference of pressure is applied to force a solution to flow in said covered microchannel, thanks to electrodes inserted in the microfluidic device. Gravity-induced flow monitored electrochemically is applied to the performance of a parallel-microchannel enzyme-linked immunosorbent assay (ELISA) of the thyroid-stimulating hormone (TSH) with electrochemical detection. A simple method for generating and monitoring fluid flows is described, which can, for instance, be used for controlling parallel assays in microsystems. 相似文献
105.
106.
A new Li-containing quaternary nitride, Li4Sr3Ge2N6, was obtained as single crystals from constituent elements in molten Na. It crystallizes in space group C2/m (No. 12) with a=6.1398(7) Å, b=10.021(1) Å, c=6.3130(7) Å, β=91.279(2)°, and Z=2. It contains the first example of isolated nitridogermanate anions of Ge2N610−, which is also the first example of edge-sharing tetrahedral [GeN4]. 相似文献
107.
Sándor Balogh Ede Kolos Gaszton Gáll und Pál Kolonits 《Fresenius' Journal of Analytical Chemistry》1975,276(3):201-204
Zusammenfassung Es wurden die Möglichkeiten für die titrimetrische Bestimmung von dimerem Glykolaldehyd (Fp: 94–96° C) und dl-Glycerinaldehyd (Fp: 138–141° C) untersucht. Die systematischen Fehler der auf Grund verschiedener funktioneller Gruppen durchführbaren Messungen sind von der Stabilität ihrer cyclischen Halbacetale sowie von den ihrer Depolymerisation folgenden weiteren Gleichgewichten bestimmt. Das aus dem dl-Glycerinaldehyd gebildete Halbacetal besitzt höhere Stabilität als dasjenige aus dem Glykolaldehyd.Mit der Hydrogensulfit-Methode werden 95–96%, mit der Hydroxylamin-Methode dagegen 98–99% vom wahren Wert gefunden.In Wasser gelöst zersetzt sich der Glykolaldehyd verhältnismäßig rasch, und das Gleichgewicht kann durch beide Aldehydreaktionen quantitativ gegen die Monomerenform verschoben werden.Unsere Untersuchungen ergaben, daß die Hydroxylamin-Methode zur Bestimmung der in Form cyclischer Halbacetale kristallisierenden, dimeren Hydroxyaldehyde Vorteile gegenüber der Hydrogensulfit-Methode bietet.Frau Dipl.-Ing. Eva Varsányi-Kiss danken wir für die derivatographischen Aufnahmen und deren Auswertung. 相似文献
108.
New transesterification reaction between acetylated wood and tetramethoxysilane: A feasibility study 总被引:1,自引:0,他引:1
Novel transesterification of acetylated maritime pine sapwood (Pinus pinaster Soland) reaction was performed with tetramethoxysilane (TMOS) in presence of dibutyltin oxide as a catalyst. Transesterification was confirmed by weight percent gain calculations (WPG), infrared spectroscopy (FTIR) as well as 13C and 29Si NMR CP-MAS analysis. The results showed that transesterification indeed occurs via exchange of acetate groups from acetylated wood and methoxysilane groups from TMOS. The effect of temperatures and reaction time upon transesterification efficiency was also investigated. 相似文献
109.
Allylsilanes show in certain cases a behaviour towards electrophiles which is opposite to that of its carbon homologues. Theoretical calculations using Dewar's MINDO/3 method performed on 3-methyl 3-butenyl trimethylsilane and 2-methyl 2-butene show that geometrical optimization leads to a silicon-allylic carbon bond nearly parallel to the double bond π cloud, and both net atomic charges and HOMO coefficients indicate an inversion between these two substrates. 相似文献
110.
The present paper deals with the experimental and theoretical determination of energies of conjugation of organic molecules.A computation process has been applied, first to simple molecules comprising an hydrocarbon (styrene), an oxygen function (benzaldehyde) and a nitrogen function (aniline). The results are compared with those obtained from the literature.The application of this computation process to naphthoic acids permits the determination of energies of conjugation and isomerization of these molecules. 相似文献