The anthocyanins of sunflower

The extraction process of red pigments from the husks of a cultivar of sunflower has been studied. It has been shown that a fraction containing circa 80% of the starting pigments could be obtained by grinding. Best extractions were obtained with distilled water-organic solvent mixtures of intermediate polarity values. The extraction yields are strongly influenced by the pH and the solvent/powder ratio and reach the maximum after about 2 hr.
The experimental data showed that the greater part of the pigments, readily precipitable by acidification to pH 2.0, are bonded to a macromolecule, probably of protein nature, as confirmed by electrophoresis.     

水泵水轮机泵工况下近设计点驼峰现象的流动机理研究*

中高比转速水泵水轮机泵工况下近设计点驼峰严重制约了其稳定运行范围,是制约抽水蓄能电站安全与经济运行的关键问题之一。作为流动问题的宏观表现,驼峰现象必然与水泵水轮机内部的非定常流动存在密切关系。为此,基于试验和数值模拟,对水泵水轮机泵工况下可调导叶流道内的非定常流动进行研究,探究模型机泵工况下的压力脉动特性、非定流动机理及与性能曲线稳定性之间的关系。结果表明：在设计和小于设计工况下,可调导叶流道内均存在两种显著的周期性压力脉动。模型机泵工况下的流量扬程曲线在0.45~0.75倍设计流量区间内出现驼峰,频域分析清晰地揭示了以上两种压力脉动是对该驼峰存在重要影响的流动参量。     

Anthocyanins of Sunflower (Helianthus annuus)

The presence of anthocyanins in the achenes of some varieties of sunflower was ascertained for the first time. The two major pigments were identified as Pn-3-divanillylsambubioside and Cy-3-vanillylsambubioside. For two other pigments present in smaller quantities, a tentative identification awaiting confirmation was made and the constituents were identified. Traces were found of five other pigments for which chromatographic data are presented.     

Characterization of the Porous CaO Particles Formed by Decomposition of CaCO3 and Ca(OH)2 in Vacuum

The solid products of decomposing CaCO₃ powder in vacuum at 510°C (sr-CaO) and of decomposing Ca(OH)₂ powder at 320°C in vacuum (h-CaO) are particles which have approximately the same exterior dimensions as the parent CaCO₃ or Ca(OH)₂ particles. N₂ adsorption and desorption isotherms show that sr-and h-CaO have high internal surface areas which for sr-CaO have cylindrical symmetry, with the most common diameters being ∼ 10 nm, and for h-CaO are slit-shaped, with the most common slit width being ∼ 2.7 nm. The conclusions reached in earlier investigations, i.e that these decomposition reactions in vacuum initially yield a form of CaO which has the same unit cell dimensions as the parent solid, were in error, probably because water vapor converts much of the CaO to poorly crystalline Ca(OH)₂ before XRD measurements can be completed in air. From the volume of N₂ adsorbed by the porous powders, the porosity of h-CaO is calculated to be 36±5% and of sr-CaO 41.5±5%. These porosities imply that the linear dimensions of the 1 to 20 μm particles of h-CaO and sr-CaO are ∼5% smaller than those of the parent particles. XRD measurements made as a function of time show that particle shrinkage must occur by cooperative, diffusionless movement of crystallites of sr-CaO or h-CaO as they form.     

Linear and nonlinear optical properties of plasma-enhanced chemical-vapour deposition grown silicon nanocrystals

We provide a systematic study on the linear and nonlinear optical properties of silicon nanocrystals (Si-nc) grown by plasma-enhanced chemical vapour deposition (PECVD). Linear optical properties, namely absorption, emission and refractive indices are reported. The sign and magnitude of both real and imaginary parts of third-order nonlinear susceptibility X(³) of Si-nc are measured by the Z-scan method. Closed aperture Z-scan reveals a positive nonlinearity for all the samples. From the open aperture measurements, nonlinear absorption coefficients are evaluated and attributed to two-photon absorption. Absolute values of X(³) are in the order of 10^-9 esu and show systematic correlation with the Si-nc size, due to quantum confinement related effects. A correlation has been made between X(³), nanocrystalline size, linear refractive index and optical band gap.