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1.
Alberto Plaza Sonia Piacente Angela Perrone Arafa Hamed Cosimo Pizza Giuseppe Bifulco 《Tetrahedron》2004,60(52):12201-12209
Stemmosides C and D, two novel pregnane glycosides characterized by an unusual C-17 side chain were isolated from the pericarps of Solenostemma argel. In addition, stemmoside D displays an uncommon 14β proton configuration, apparently being the first pregnane isolated from plants known to have a 15 keto, cis CD ring junction. Their structures have been established by ESIMS and NMR experiments. The relative configuration of the molecules was determined using a strategy based on the simulation of 1H, 13C, and J coupling NMR parameters. DFT calculations of 1H and 13C chemical shifts, and of the 1H homonuclear spin–spin coupling constants were performed with the mPW1PW91 functional using the 6-31G(d,p) basis set on the fully optimized geometries of all the possible stereoisomers. 相似文献
2.
The separation of fluoride by extraction with toluene solution of triphenyltin chloride has been studied. Quantitative isolation of fluoride from solutions with a wide acidity range (pH 4.0–11.5) has been established. It is suggested that interferences by Ca, Mg, Fe, and Al can be avoided by masking these elements using sulfate and hydroxyde ions. Interference by phosphate ions can be overcome in a similar fashion. The halogenated species can be masked by mercury nitrate. Detection limit for fluorine determination is about 3 g for a neutron generator flux of 2·1111 n·cm–1·s–1. A method for fluorine assay in water using a neutron generator with a detection limit of 1 ppm has been developed. 相似文献
3.
Alberto Plaza Ciro Balestrieri Giuseppe Bifulco Arafa Hamed Sonia Piacente 《Tetrahedron》2005,61(31):7470-7480
Eight new 14,15-secopregnane glycosides, namely argelosides C-J, possessing two ketal functions involved in three five-membered rings, have been isolated from the hairy seeds of Solenostemma argel. Their structures have been established by MS and NMR experiments, combined with quantum mechanical calculations of the 13C chemical shifts for the interpretation of the experimental data. On the basis of the obtained results, the structures of argelosides A and B have been revised. Additionally, the effect of these compounds on the VEGF-induced in Kaposi's sarcoma cell proliferation was evaluated. Results indicated that all the compounds reduced the cell proliferation in a dose-dependent manner. 相似文献
4.
5.
ElShazali Ahmed Mohamed Nahid Abdelraheem Ali Salma Hashim Ahmed Isam A. Mohamed Ahmed Elfadil E. Babiker 《Radiation Physics and Chemistry》2010,79(7):791-796
Whole and dehulled flours of millet cultivars Ashana and Dembi were stored for 30 and 60 days before and after radiation and/or cooking. Phytic acid and polyphenols contents were assayed for all treatments. The results revealed that the storage period was found to have no effect on phytate and polyphenols contents. Moreover, dehulling of the grains reduced more than 50% of phytate and polyphenols of both cultivars. Cooking of the raw whole and dehulled flour significantly (P≤0.05) reduced phytate and polyphenols contents for both cultivars. Radiation process alone had no effect on phytate and polyphenols contents but when followed by cooking significantly (P≤0.05) reduced the level of such antinutrients for the whole and dehulled flour of both cultivars. Dehulling alone significantly (P≤0.05) decreased Ca and P content but slightly decreased Fe content. Radiation alone or in combination with cooking was found to have slight effect on minerals content of the whole and dehulled raw flour for both cultivars. Cooking alone or in combination with radiation of whole or dehulled raw flour significantly (P≤0.05) improved the extractable Ca but had no significant (P≤0.05) effect on extractable P and Fe for both cultivars. 相似文献
6.
Four different silica-based urea-formaldehyde (UF/SiO2) composite materials were prepared by various sol-gel synthetic procedures to yield an interpenetrating (IPN-UF/SiO2), a micro-size UF resin encapsulated inside silica shell (Encap-UF/SiO2), a micro-size silica encapsulated inside UF shell (Encap-SiO2/UF), and a blend mixture (Blend-UF/SiO2) hybrid systems. The thermal properties of the obtained organic-inorganic hybrid composite materials were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The structure and morphology of the obtained systems were investigated by infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Their surface porosity and acidity were evaluated from the nitrogen adsorption isotherm and the pH of the corresponding 10% aqueous suspension, respectively. All the results provided evidence for the formation of different hybrid systems with different surface, structural and morphological characteristics. 相似文献
7.
8.
Ang WH Khalaila I Allardyce CS Juillerat-Jeanneret L Dyson PJ 《Journal of the American Chemical Society》2005,127(5):1382-1383
A rationally designed Pt(IV) anticancer compound is described, employing the novel concept of tethering an inhibitor of glutathione-S-transferase, an enzyme associated with Pt-based drug-resistance, to cisplatin. Its enzyme inhibition activity, investigated using spectrophotometric and mass spectrometry-based techniques, and cytotoxic profile in resistant cancer cells are described. 相似文献
9.
Ali Ali Arafa Ibrahim Sayed Shafie Fathi Sultan Ahmed Sultan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1956,7(3):256-264
The thermoelectric power of natural specimens of lead sulphide crystals has been measured between room temperature and 700° K. Specimens which are of then-type remain as such throughout the temperature range. Thep-type specimens, however, show an initial small rise followed by a gradual decrease and a subsequent change of sign ata temperature which, in some specimens, is well defined. Further increase of temperature results in a negative extremum. From this stage onwards there seems to develop a common behaviour for both types of specimens. Some crystals which were initially of thep-type changed over to then-type and remained as such throughout subsequent investigation. Among the crystals one showed a metallic conduction and an extraordinary large thermoelectric power. 相似文献
10.
In this paper, numerical solutions of a reaction-diffusion chemotactic model of fractional orders for bacterial growth will
be present. A new solution is constructed in power series. The fractional derivatives are described in the Caputo sense. We
compare the experimental result obtained with those obtained by simulation of the chemotactic model without fractional derivatives.
The results show that the solution continuously depends on the time-fractional derivative. The resulting solutions spread
faster than the classical solutions and may exhibit asymmetry, depending on the fractional derivative used. We present results
of numerical simulations to illustrate the method, and investigate properties of numerical solutions. The Adomian’s decomposition
method (ADM) is used to find the approximate solution of fractional ‘reaction-diffusion chemotactic model. Numerical results
show that the approach is easy to implement and accurate when applied to partial differential equations of fractional order. 相似文献