Search

Research was carried out on the isolation of betulin and suberin from the debarking waste of the Arkhangelsk Pulp and Paper Mill pulpwood, ground on an abrasive crusher. Betulin was extracted from various fractions of technical bark with 86% ethanol under exposure to microwave electromagnetic field (EMF) (microwave extraction). Suberin was isolated from the extracted bark by hydrolysis with an aqueous KOH solution under microwave heating conditions as well. The maximum yields of betulin and suberin were achieved when using coarse bark fractions (3–4.5 mm), which were essentially crushed birch bark. The resulting products were identified by IR and NMR spectroscopy and by gas chromatography combined with mass spectrometry (GC/MS). The contents of the components in the bark extracts were determined by HPLC analysis. The extractives were dominated by triterpenoid betulinol (70–72%), with betulinic acid, lupeol, and erythrodiol being present less abundantly. Fatty, dibasic carboxylic acids, and hydroxy acids, dominated by 2-hydroxydecanedioic (2-hydroxysebacic) acid, were identified among the suberin monomers. The content of ferulic acid, a natural antioxidant, was determined in the product from different fractions of the bark (from 2.65 to 11.27 g/kg). The suberin obtained from fine bark fractions differs in the composition from that obtained from coarse fractions. Ribofuranose and xylose were detected in the product obtained from the 1–2 mm bark fraction but were absent in that from the 2–3 mm fraction; lanosterol was present in the suberin from fine fraction of the bark, and cycloartenol, in that from coarse fraction. [ABSTRACT FROM AUTHOR]

The process of isolation of the extractives and betulin from birch bark exposed to a microwave field was investigated. It was shown that under the use of microwave treatment in a microwave field the duration of the extraction process was reduced 10-15 times, as compared with the extraction by infusion. The influence of the main parameters on the process of microwave extraction of extractives from birch bark was studied. Using high performance liquid chromatography we established quantitatively the content of betulin in the birch bark extracts. [ABSTRACT FROM AUTHOR]

Results of VRI photometry of two components of the gravitationally lensed quasar UM 673 in 2003–2005 are presented. The observational data were obtained on the 1.5-m telescope of the Maidanak observatory. During the monitoring of the system, considerable brightness variations in components A and B with amplitudes of about 0.2 m were recorded, demonstrating variability of the quasar. The increase in the brightness of the components was accompanied by reddening of their V-R color indices. Analysis of the brightness and color variations of the components shows no variations related to microlensing. [ABSTRACT FROM AUTHOR]

A two-stage algorithm for reconstructing images made up of point sources is proposed and applied to images of the gravitational lens QSO 2237+0305 obtained with the 1.5-m telescope of the Maıdanak Observatory. In the first stage, a modified Tikhonov regularization algorithm is used to split an image with a high signal-to-noise ratio into two parts, corresponding to numerical galaxy and quasar components. In the second stage, the astrometric and photometric characteristics of the individual images of the gravitational-lens system are determined using information about the brightness distribution in the galaxy and a least-squares fit. The two-stage algorithm substantially reduces the time required for the image analysis. A comparison of our method with CLEAN is presented.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]