1,721,023 research outputs found
Enantioselective MEKC analysis of catechins in tea samples of different origin
No full textEnantioselective separation of catechin and gallocatechin was achieved by using micellar electrokinetic chromatography (MEKC) modified by cyclodextrin (HP-beta-CD). The analytical enantioseparation of these two catechins was found to be very useful because, for the first time, the presence of (-)-gallocatechin and (-)-catechin (chiral phytomarkers) in tea samples, was regarded as an index of thermal degradation of the product. More than twenty tea samples of different origin (China, Japan, Ceylon) were analysed; the chiral phytomarkers of degradation was found in some of the products proving the occured thermal degradation
Experimental design in capillary electrophoretic methods and development.
No full textExperimental design, in particular by means of multivariate methods has shown to be very useful in optimization and validation of analytical separations. In the communication, a brief survey of the use of experimental design - based otpimization techniques in capillary electrophoresis is presented
Analysis of catechins in Theobroma cacao beans by cyclodextrin-modified micellar electrokinetic chromatography
No full textAnalysis of catechins and xanthines in chocolate and Theobroma cacao by micellar electrokinetic chromatography after optimized extraction.
No full textDesign and variable optimization in the adsorptive stripping voltammetric determination of rufloxacin in tablets, human plasma and urine
No full textOptimization by Experimental Design of the adsorptive stripping voltammetric parameters in the determination of cinoxacin
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Acclimation to changing light conditions of long-term shade-grown beech (Fagus sylvatica L.) seedlings of different geographic origins
No full textEffects of changing light conditions on the ecophysiological condition behind survival were examined on beech from two different populations. Plants were grown in a greenhouse under simulated understorey and canopy gap light conditions. Upon exposure to high light maximum photosynthesis of shade-acclimated leaves increased followed by a reduction over several days to between high- and low-light control rates. In the reciprocal transfer, the decrease in maximum photosynthesis was rapid during the first 2–3 days and then levelled off to values comparable to low-light controls. Seedlings from Sicily (Madonie) showed generally higher maximum photosynthetic rates than those from Abetone. Leaf conductance varied in the same direction as photosynthesis in high- to low-light seedlings but to a lesser degree. Leaves grown under low light and exposed to high light experienced photoinhibition. The Abetone population was more susceptible to photoinhibitory damage than the seedlings from Sicily. Exposure to high light of shade-acclimated seedlings resulted in intermediate chlorophyll concentrations between levels of the high-light and low-light seedlings. Carotenoid concentration was unaffected by treatments. Seedlings grew more in high light, but had a lower leaf area ratio. Light-limited seedlings showed a shift in carbon allocation to foliage. Leaves formed in the new light regime maintained the same anatomy that had been developed before transfer. Seedlings from Sicily had thicker leaves than those of seedlings from Abetone. Seedlings from Abetone were found to be more susceptible to changing light conditions than seedlings from Sicily. We conclude that small forest gaps may represent a favorable environment for photosynthesis and growth of beech regeneration as a result of the limited ability of seedlings to acclimate to sudden increases in high irradiance and because of the moderate levels of light stress in small gaps
- …
