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排序方式: 共有244条查询结果,搜索用时 93 毫秒
1.
Summary Epitaxial films of YBa2Cu3O7−x
were depositedin situ on LaAlO3 substrates using single-target 90° off-axis sputtering. The films were characterized by magnetization measurements (M vs. T, H), applying the field parallel toc-axis. The observed differences in theT
c andJ
c values are attributed to the different oxygen content in the superconducting films.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
2.
This paper presents the preliminary results obtained using an Electron Paramagnetic Resonance imaging apparatus operating at 280 MHz. The acquisition technique and the procedure used to obtain the spin density spatial localization are presented and specimen images of extended samples are given. The accuracy of the images and the spatial resolution are also discussed. 相似文献
3.
The application of a new technique to the separation of some actinide elements by means of a single reducing and extracting column is described. Tri-n-octylphosphine oxide (TOPO) was used as the extractant. The following reducing agents were supported on microporous polyethylene together with TOPO: tetrachlorohydroquinone, 2,3-dichloro-1,4-naphthahydroquinone, 2,5-di-tert-butylhydroquinone and 2,5-di-tert-pentylhydroquinone. The last compound was chosen for the separation experiments; it allowed quantitative reduction of plutonium to Pu(III) and of neptunium to Np(IV). The separations Pu(III)-Np(IV), Pu(III)-U(VI) and Am(III)-Np(IV) in 6 M hydrochloric acid were obtained. 相似文献
4.
5.
Yvan Giroud Pierre-Alain Carrupt Alessandra Pagliara Bernard Testa Ronald G. Dickinson 《Helvetica chimica acta》1998,81(2):330-341
In this study, we compared the lipophilicity of O-glucuronides and their aglycones. Distribution coefficients (log D) and P values of neutral species (log P) were determined by centrifugal partition chromatography (CPC) in octanol/buffer systems. Two-phase potentiometry was also used to measure the log P value of some lipophilic solutes. The experimentally determined global influence of glucuronidation on lipophilicity, obtained as the difference (decrement) log P(glucuronide) ? log P(aglycone), was found to be ?1.30 ± 0.16 (n = 4) for glucuronides of alcohols (methyl, menthyl, neomenthyl, and chloramphenicol O-glucuronide). The mean decrement was ?2.06 ± 0.31 (n = 9) for glucuronides of phenols (phenyl, p-nitrophenyl, 1-naphthyl, 6-bromo-2-naphthyl, 4-methylumbelliferyl, 3-coumarinyl, phenolphthalein, 4′-benzophenonyl O-glucuronide, and diflunisal phenolic glucuronide). For the acylglucuronide of diflunisal and its rearrangement isomers, the mean decrement was ?1.80 ± 0.08 (n = 4; range ?1.7 to ?1.9). Differences in through-bond proximity effects as parametrized in the CLOGP algorithm seem to account for much of this difference. Conformational factors may also play a role, although it appears modest and unassessable for the glucuronides investigated here. The results imply that in vivo glucuronidation should have a stronger influence on the excretion of phenols than on that of alcohols. 相似文献
6.
Stella C Galland A Liu X Testa B Rudaz S Veuthey JL Carrupt PA 《Journal of separation science》2005,28(17):2350-2362
An RPLC was developed to rapidly determine lipophilicity of neutral and basic compounds using three base deactivated RPLC stationary phases particularly designed for the analysis of basic compounds, namely, Supelcosil ABZ(+)Plus, Discovery RP Amide C16, and Zorbax Extend C18. The work consisted of three sets of experiments. In the first log kw values of neutral compounds were extrapolated using hydroorganic mobile phases at different compositions. Good correlation between log kw and log Poct indicated that the method was appropriate for these supports, without adding a silanol masking agent. In the second set of experiments, isocratic log k values of neutral and basic compounds were measured with three different mobile phases. The best estimation of lipophilicity was obtained for neutral and basic compounds when the secondary interactions were strongly reduced (i. e., when basic compounds were under their neutral form). In the third set of experiments, isocratic retention factors of basic compounds (in their neutral form) were measured with a high-pH mobile phase, on a chemically stable support (Zorbax Extend C18). Under these chromatographic conditions, correlation between the isocratic retention factors and log Poct (log D10.5) for basic compounds was similar to that for neutral compounds. 相似文献
7.
Gancitano P Ciriminna R Testa ML Fidalgo A Ilharco LM Pagliaro M 《Organic & biomolecular chemistry》2005,3(13):2389-2392
Valuable organic compounds such as alpha-hydroxy acids are easily synthesised with relevant selectivity enhancement using a sol-gel hydrophobized nanostructured silica matrix doped with the organocatalyst TEMPO: A materials science based synthetic route which cannot be achieved via classical homogeneous synthesis. 相似文献
8.
Domenico Armenise Nicolino De Laurentis Antonia Reho Antonio Rosato Flaviano Morlacchi 《Journal of heterocyclic chemistry》2004,41(5):771-775
A series of 6‐fluoro‐4‐(5 or 7)‐chloro‐2‐(difluorobenzoyl)aminobenzothiazoles 3a‐r were prepared to investigate their potential biological activity. In this work, the results of their in vitro antifungal activity against some strains of Candida albicans are reported. It was found that some derivatives displayed antifungal activity higher than that for 3k [1a] compound already described in literature. 相似文献
9.
10.
C. Testa D. Desideri M. A. Meli C. Roselli A. Bassignani P. B. Finazzi 《Journal of Radioanalytical and Nuclear Chemistry》1993,170(1):117-124
Low specific activity scales consisting of alkaline earth metal carbonates and sulfates are often present in some gaseous and liquid hydrocarbon plants; these scales contain a certain concentration of radium, uranium and thorium, which can cause a risk of -irradiation and of internal radiocontamination when they must be mechanically removed. That being stated,238U,232Th and226Ra were determined in scales, sludges and waters coming from different plants.238U and232Th concentrations were found very low; the isotopes238U and234U resulted in radioactive equilibrium, whilst232Th and228Th were not always in equilibrium.226Ra concentration was higher in scales and sludges than in waters. 相似文献