Complete assignment of bilberry (Vaccinium myrtillus L.) anthocyanins separated by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) mobilities of fifteen anthocyanins in bilberry extract were completely characterized. Four minor anthocyanins in bilberry extract (malvidin 3-O-alpha-L-arabinopyranoside (Mv 3-ara), peonidin 3-O-beta-D-galactopyranoside (Pn 3-gal), peonidin 3-O-alpha-L-arabinopyranoside (Pn 3-ara), and petunidin 3-O-alpha-L-arabinopyranoside (Pt 3-ara)) that remained unidentified in our previous CZE study were isolated from the bilberry extract, and the chemical structures were assigned by NMR and MS. Their CZE mobilities were then precisely examined together with those of other major anthocyanins in the extract. When the CZE mobilities of the fifteen anthocyanins assigned here were plotted against their molecular weight/numbers of free phenolic group, it was found that separation of anthocyanins by CZE is primarily determined by the type of conjugated sugar present, and secondly by the aglycon structure.     

Dynamic NMR study on the trans-fused eight-membered ether ring model representing G ring of brevetoxin A

Conformational analysis of the trans-fused eight-membered ether ring model (2) representing G ring of brevetoxin A (1) was carried out by dynamic NMR study in combination with molecular mechanics calculations.     

Synthesis of the CDE/FG ring models of prymnesins: reassignment of the relative configuration of the E/F ring juncture

[structure: see text] Synthesis of two diastereomeric models (3a and 3b) corresponding to the CDE/FG ring of prymnesins, polycyclic ether toxins isolated from the red tide phytoflagellate Prymnesium parvum, is described. Comparison of the (1)H and (13)C NMR data for each compound with those reported for prymnesins suggests that the earlier stereochemical assignment of the E/F ring juncture needs to be revised.     

Confirmation of the cation radicals of hexamethylethane and hexamethyldisilane by ESR and other spectroscopy

Unambiguous ESR spectra of cation radicals of hexamethylethane and hexamethyldisilane were obtained for γ-irradiated solutions in CCl₃F at 77 and 140 K. INDO calculations, optical measurements, and comparison with photoelectron spectra are consistent with the observed ESR spectra.     

Cross-metathesis of vinyl aromatic heterocycles: comparison of Grubbs catalyst and Schrock catalyst

Metathesis of 2-vinyl aromatic heterocycles such as furan and thiophene has been investigated in the presence of a ruthenium-based Grubbs catalyst from a synthetic standpoint. The self-metathesis of 2-vinyl aromatic heterocycles was not successful. However, the cross-metathesis of these aromatic heterocycles with 1-octene occurred efficiently, but the selectivity of cross-metathesis product was very low, below 50%. The origin of the low selectivity of heterodimer formation was elucidated through metallacyclobutane intermediate mechanism, observations of carbenes by in situ ¹H NMR, and the reaction products. The effect of oxygen on the reaction behavior was also examined. Furthermore, the data obtained on the Grubbs catalyst were compared with those on a molybdenum-based Schrock catalyst.     

Photoacoustic spectroscopic studies on the solid phase cell with a differential type microphone using a diode laser as radiation source

The design and applications of the solid phase photoacoustic cell with a differential type microphone are described. This cell has higher sensitivity and reproducibility relative to a cell without a differential microphone. The method has been applied to the determination of phosphate ion in water samples. The detection limit for phosphate ion concentrated from 22.5 ml of sample solution on a membrane filter as molybdophosphate-n-dodecyltrimethylammonium bromide was 3.0 ng PO(3-)(4)/ml and the coefficient of variation for five measurements at 20 ng PO(3-)(4)/ml of phosphate ion was 3% using a diode laser (30 mW, 826 nm) as radiation source. The calibration graph for phosphate ion was linear over the range 5-50 ng PO(3-)(4)/ml.     

An experimental study of spallation criterion in phenolic-resin based woven roving glass fibre reinforced composite material

An experimental study of spallation in phenolic-resin based woven roving glass fibre reinforced composite material under uniaxial strain condition is reported in this paper. Experiments were carried out with a 101 mm bore single-stage light gas gun. The stress waves induced by plate impact propagate along the normal to glass fibre mats. The experiments show that the threshold of incipient spallation in this material depends strongly on the duration of stress wave and that this incipient spallation appears essentially in one layer. The criterion of spallation in this material given in this paper is in good agreement with experimental results. Besides, the spallation in phenolic-resin based obliquely laminated woven roving glass fibre reinforced composite material is also discussed in this paper.     

盲优化波前校正提高自由空间光通信光纤耦合效率

为了提高自由空间光通信系统的光纤耦合效率,介绍了一种新颖的基于盲优化波前校正的自适应光学系统。该系统不使用波前传感器,而是在信号进入接收端前,将畸变光信号分束后送入光电探测器,进行耦合效率计算;采用耦合效率的估计公式斯特列尔比为目标函数,用随机并行梯度优化算法最大化目标函数,以实时控制变形镜,从而使耦合进入单模光纤的光达到最优。数值结果表明,此系统能使光纤耦合效率从6%提高到约60%。     

ESR and optical studies on the cation-radical of pyridine in Aγ-irradiated rigid matrix at low temperatures

Evidence for the cation-radical of pyridine is obtained by ESR and optical studies of γ-irradiated frozen solutions of pyridine in trichlorofluoromethane at 77 and 4 K. The cation-radical is a σ-type radical, the positive charge residing mostly in the nitrogen lone pair orbital. Consistent spectral data are obtained also for 2-deutero-, 4-deutero-, 2,6-dideutero-, and perdeutero-pyridines.