The qualitative and quantitative compositions of the carbohydrates of the leaf vegetables Lactuca sativa L., Spinacea oleracea L., and Rumex acetosa L. have been studied.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 349–351, May–June, 1993. 相似文献
We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity. 相似文献
A new and simple LC-MS method for analysis of flavonoids from Sambucus ebulus berry extracts was developed and validated. Successfully were quantitated seven polyphenols: epicatechin, epigallocatechin gallate, rutin, resveratrol, myricetin, quercetin, and kaempferol.
Two detectors, working in parallel, were used: photodiode-array and single quadrupole mass-detector. The mass detection was used for identification and quantification of the analytes, while the diode-array detector was as confirmation tool. The following m/z were tracked: 457.15 (epigallocatechin gallate); 289.06 (epicatechin); 609.13 (rutin); 227.05 (resveratrol); 317.0 (myricetin); 301.02 (quercetin); 285.02 (kaempferol). For optimization the chromatographic separation three wavelengths 205?nm, 305?nm, 272?nm were monitored. The method was capable to detect in one run compounds with no UV or fluorescence chromophore and with very similar structures, such as plant polyphenols. The linearity was from 0.05?mg/L to 50?mg/L (R2 0.9962–0.9987). The recoveries for all tested analytes were between 81.6% and 104.7%.
The method was applied for analysis of crude extract of Sambucus ebulus ripe fruits. Three major polyphenols – epicatechin (0.84?mg/100gFW), quercetin (0.15?mg/100gFW) and kaempferol (0.05?mg/100gFW) were identified and quantified.
The proposed method could be successfully used for routine analysis of epigallocatechin gallate, epicatechin, rutin, resveratrol, myricetin, quercetin, and kaempferol in Sambucus ebulus extracts. 相似文献
Herein, the ligand‐based concept of shortening quintuple bonds and some of its limitations are reported. In dichromium–diguanidinato complexes, the length of the quintuple bond can be influenced by the substituent at the central carbon atom of the used ligand. The guanidinato ligand with a 2,6‐dimethylpiperidine backbone was found to be the optimal ligand. The reduction of its chromium(II) chloride–ate complex gave a quintuply bonded bimetallic complex with a Cr? Cr distance of 1.7056 (12) Å. Its metal–metal distance, the shortest observed in any stable compound yet, is of essentially the same length as that of the longest alkane C? C bond (1.704 (4) Å). Both molecules, the alkane and the Cr complex, are of remarkable stability. Furthermore, an unsupported CrI dimer with an effective bond order (EBO) of 1.25 between the two metal atoms, indicated by CASSCF/CASPT2 calculations, was isolated as a by‐product. The formation of this by‐product indicates that with a certain bulk of the guanidinato ligand, other coordination isomers become relevant. Over‐reduction takes place, and a chromium–arene sandwich complex structurally related to the classic dibenzene chromium complex was observed, even when bulkier substituents are introduced at the central carbon atom of the used guanidinato ligand. 相似文献
The present article demonstrates a simple, eco-friendly route for the fabrication of carbon nanotubes (CNTs) with different morphologies, including the fascinating bamboo-like structures without complex catalyst/support preparation procedures. A thermal chemical vapor deposition (CVD) technique that utilized natural pozzolan supports and a solid carbon source, that is, a mixture of camphor and ferrocene in a weight ratio of 20:1, was carried out at different temperatures where the ferrocene played also the role of catalyst. The pozzolan chemical composition and mineral identification were determined by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The morphology of the fabricated CNTs was studied via scanning and transmission electron microscopies (SEM and TEM). It was revealed that both conventional tubular and bamboo-like nanotubes grow at 750 °C while the bamboo-like morphology prevails at 850 °C. The better nanostructure uniformity at higher deposition temperature was accompanied by an improved nanotube graphitization degree that was verified by Raman spectroscopy. Yet, the reduction of the CNTs production yield was recorded by thermogravimetric analysis (TGA). The experimental data are interpreted and discussed as an interplay between the CNTs processing temperature, morphology and growth mechanism. Thus, the growth of either tubular or bamboo-like nanostructures is suggested to be ruled by the competitive surface and bulk diffusions of carbon onto and into the catalyst surface. The growth depends on the size of catalyst nanoparticles sintered at different temperatures. The favorable role of the pozzolan supporting materials in the formation of bamboo-like tubes is emphasized. 相似文献
The emission spectra of the solids [n-Bu(4)N](2)Tc(2)X(8) (X = Cl, Br) have been investigated at room temperature and 77 K. In each case, the emission originates in the (1)δ-δ* excited state, as with the rhenium homologues, but has a shorter lifetime. 相似文献
The qualitative and quantitative compositions of the carbohydrates of the leaf vegetables Lactuca sativa L., Spinacea oleracea L., and Rumex acetosa L. have been studied. 相似文献
1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can … 相似文献
Li2RhO3 was synthesized by solid state reaction and its crystal structure was refined from X‐ray powder data by the Rietveld‐method. The compound was obtained as a black powder and crystallizes in the monoclinic space group C2/m, with unit cell parameters a = 5.1198(1), b = 8.8497(1), c = 5.1030(1) Å, β = 109.61(2) °, V = 217.80(1), and Z = 4. The structure determination shows that the oxygen atoms in Li2RhO3 form an approximate cubic close packing, where all octahedral voids are occupied by Rh4+ and Li+ cations. The structure is closely related to the α‐NaFeO2 and Li2MnO3 layered structure types (layered variants of the NaCl‐type), but in Li2RhO3 the lithium and rhodium atoms are partially disordered. Li2RhO3 behaves as a semiconductor with rather small activation energy of 7.68 kJ · mol–1 and is thermally stable up to 1273 K in argon atmosphere. According to measurements of the magnetic susceptibility in the temperature range from 2 to 330 K, Li2RhO3 is paramagnetic, obeys the Curie–Weiss law at temperatures above 150 K, and has an effective magnetic moment of 1.97 μB at 300 K. 相似文献