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  • Author: Erzsébet Tóth x
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There is a growing need for practical solutions to provide flexible access to digital documents in a structured form on the Web. The existing library classification schemes serve as good bases for achieving this goal. This paper presents a brief review of the various methods applied in automatic classification. It focuses on the main activities fulfilled within various research projects to make possible the effective automatic indexing and classification of Web sources. It describes the approaches taken in the Nordic WAIS/WWW; DESIRE II – Engineering Electronic Library System (EELS); GERHARD; and SCORPION projects. Artificial neural networks and artificial intelligence show great potential.

in Libri

This paper presents a test that examined the linguistic capabilities of English and Hungarian search engines. Three English-language search engines were tested: Google, AltaVista and AlltheWeb. For comparison, five significant Hungarian search engines were considered: Heuréka, Origo-Vizsla, Kurzor, Góliát and Altavizsla. The analysis was based on the following aspects: stemming, handling of stopwords and diacritics, truncation and searching for synonyms. The results indicate that while the Hungarian search engines are motivated to take into consideration the specific characteristics of the Hungarian language, on the whole the English-language search engines ignore the special characteristics of the Hungarian language. In the cases examined none of the general search engines handled diacritics well; that caused their resulting weaknesses in finding information relevant for Hungarian users.

in Libri

Abstract

In this research, a diffuse coplanar surface barrier discharge (DCSBD) type plasma reactor was used for the surface modification of raw linen fabric. Changes in physical properties and chemical composition of the fiber surface as well as color of the fabric were measured as a function of time of the atmospheric air plasma treatment. Furthermore, ageing of the effects created on the fiber surface by plasma treatment was also characterized in a period of 0-14 days elapsed after the plasma treatment. Significant differences were found between the properties of the raw and plasma treated linen fabrics, including increase of wettability, wickability, surface energy and O/C ratio, and decrease of water contact angle and deterioration of the waxy outer layer of the fibers. Most of the parameters depended on the time of plasma treatment (0–180 s). O/C ratio increased steadily with the increase of duration of the plasma treatment, which was explained by destruction of the waxy surface layer, creation of polar groups and exposure of cellulosic components. Most of the properties tested were found to be stable during two weeks of storage after the plasma treatment, indicating that the surface ‘topography’ created by plasma remained almost unaltered and the recovery of the etched waxy coverage of the fiber did not occur.

Abstract

Objective: The aim of the study was to determine the content of polyphenols and flavonoids from sixteen selected medicinal plants from the spontaneous Romanian flora and fifteen tinctures obtained with propylene glycol.

Methods: The polyphenols were determined by the Folin-Ciocalteu method while the flavonoids by using a colorimetric method from the 10th edition of the Romanian Pharmacopoeia. The antioxidant activities of the most common nine medicinal plants and fifteen tinctures were determined by DPPH and ABTS methods.

Results: The results highlighted that the phenolic compounds and flavonoids have contributed to their antioxidant activities and the medicinal plants and tinctures included in the study are rich sources of natural antioxidants.

Conclusions: There are a wide variety of extraction methods for the determination of phenolics and flavonoids. The study confirms a correlation between phenolic and flavonoid contents obtained by using the DPPH and ABTS tests.

Abstract

The aim of this study was to reveal the spatial and temporal variation in biomass, density, and size structure of the invasive clam, Corbicula fluminea in the Danube River catchment and to explore the environmental factors determining these patterns. Samples were taken seasonally during the years 2007 and 2008 at 15 sites located along a river continuum from a second order stream to the Danube River. C. fluminea was the most abundant species in the main arm of the Danube; however, it was found in great density in the side arms, too. In the Ipoly River it only occured close to the conjuction, and it was not present at all in the second and third order streams. Regression models were developed to predict dry mass (DW, g) from linear body dimension [shell length (L), mm]. For the description of length-dry mass relationship, the power function (DW = a * Lb) was applied. The highest density, biomass, and mean shell length were 178 ind. m−2, 24.9697 g DW m−2, and 21.99 mm, respectively. ANOVA detected significant spatial variation in biomass; however, significant temporal variation was not recorded between the years, only among the seasons. Multiple linear regressions were used to find the relationship between the biomass and the environmental parameters. The coarse and very fine sediment fractions and the high water temperature provided suitable habitat for C. fluminea. Although statistically significant correlation was not detected between the chlorophyll-a content of water and the biomass, the highest biomass values were recorded at sites with high chlorophyll-a value.

Abstract

Cadmium (Cd), a highly toxic heavy metal affects growth and metabolic pathways in plants, including photosynthesis. Though Cd is a transition metal with no redox capacity, it generates reactive oxygen species (ROS) indirectly and causes oxidative stress. Nevertheless, the mechanisms involved in long-term Cd tolerance of poplar, candidate for Cd phytoremediation, are not well known. Hydroponically cultured poplar (Populus jacquemontiana var. glauca cv. ‘Kopeczkii’) plants were treated with 10 μM Cd for 4 weeks. Following a period of functional decline, the plants performed acclimation to the Cd induced oxidative stress as indicated by the decreased leaf malondialdehyde (MDA) content and the recovery of most photosynthetic parameters. The increased activity of peroxidases (PODs) could have a great impact on the elimination of hydrogen peroxide, and thus the recovery of photosynthesis, while the function of superoxide dismutase (SOD) isoforms seemed to be less important. Re-distribution of the iron content of leaf mesophyll cells into the chloroplasts contributed to the biosynthesis of the photosynthetic apparatus and some antioxidative enzymes. The delayed increase in photosynthetic activity in relation to the decline in the level of lipid peroxidation indicates that elimination of oxidative stress damage by acclimation mechanisms is required for the restoration of the photosynthetic apparatus during long-term Cd treatment.