Search results for "Chen"
showing 10 items of 702 documents
Use of lichens in detecting environmental risk and in geochemical prospecting
1995
This paper provides data on variations in the contents of As, Sb, Ni, V, Pb, Cu, Cr, Au, Zn, Sc, and Al, measured in the thalli of a saxicolous lichen species,Xanthoria calcicola Ochsner s.l., collected in northeastern Sicily, near an industrial zone and along a belt crossing areas of known ores containing sulfides of heavy metals. A total of 91 lichen samples were collected on roof tiles (39) and on rocks (52). In the industrial zone, analysis of lichen thalli revealed high contents of nickel and vanadium, decreasing at increasing distances from the source of contamination. The results have also revealed the versatility ofXanthoria calcicola in geochemical prospecting for heavy metals such…
Lichens as bio-monitors of trace-elements in Central and Eastern France
2003
Lichens (105 samples, mainly P. sulcata and X parietina) have been used to monitor As, Cd, Co, Cr, Cu, Mg, Ni, Pb, and Zn in Burgundy and in the East of France. When the industrial environment seemed to justify it, other elements were also looked for, such as Ag, Sn and V. Research was carried out on areas with little or moderate pollution and supplemented by studies on three hot spots with health problems. Record and background concentrations in lichens are presented as well as the ratios between those values. In the case of lead, the concentrations in lichens are compared with the results in blood tests.
Lichens <i>(Xanthoria parietina)</i> - Bio-Indicators for Sulphur and Metallic Elements for Pollution Investigation in Riga City
2021
The aim of the research was to investigate the pollution level of sulphur and metallic elements in Riga city (Freeport of Riga, Kundziņsala, Mežaparks) by using foliose lichens (Xanthoriaparietina) as a bio-indicators. Obtained results show that the Freeport of Riga is the most polluted area comparing with other neatest places in Riga city, Kundziņsala and Mežaparks. Evaluate a washing effect, obtained results shows that lichen thallus contains about 50 % of total amount of sulphur and investigated elements as dust particles on the surface of lichens.
Profesore Marta Rudzīte: bibliogrāfiskais rādītājs
2004
LU Filoloģijas fakultātes Baltu valodu katedras profesores habilitētās filoloģijas doktores Martas Rudzītes bibliogrāfiskajā rādītājā apkopotas valodnieces zinātniskās, populārzinātniskās, mācību un citas publikācijas no 1954. līdz 2004. gadam, literatūra par viņu. Izdevums atspoguļo prof. M. Rudzītes veikumu zinātnē un kultūrā.
Ancient proteins resolve the evolutionary history of Darwin's South American ungulates.
2015
No large group of recently extinct placental mammals remains as evolutionarily cryptic as the approximately 280 genera grouped as 'South American native ungulates'. To Charles Darwin, who first collected their remains, they included perhaps the 'strangest animal[s] ever discovered'. Today, much like 180 years ago, it is no clearer whether they had one origin or several, arose before or after the Cretaceous/Palaeogene transition 66.2 million years ago, or are more likely to belong with the elephants and sirenians of superorder Afrotheria than with the euungulates (cattle, horses, and allies) of superorder Laurasiatheria. Morphology-based analyses have proved unconvincing because convergences…
Background element content in the lichen Pseudevernia furfuracea: a comparative analysis of digestion methods
2019
In bioaccumulation studies, the interpretation of pollutant contents in the target biomonitor has to be performed by assessing a deviation from an unaltered reference condition. A common strategy consists in the comparison with background element content (BEC) values, often built up by uncritically merging methodologically heterogeneous data. In this respect, the acid digestion of samples was identified as a major step affecting BEC data. Here, the analytical outcomes of two acid mixtures were compared on a set of matched paired samples of the lichen Pseudevernia furfuracea, a widely used biomonitor for which BEC values based on partial digestion were previously provided. The standard refer…
Background element content of the lichen Pseudevernia furfuracea: A supra-national state of art implemented by novel field data from Italy
2018
Abstract In biomonitoring, the knowledge of background element content (BEC) values is an essential pre-requisite for the correct assessment of pollution levels. Here, we estimated the BEC values of a highly performing biomonitor, the epiphytic lichen Pseudevernia furfuracea, by means of a careful review of literature data, integrated by an extensive field survey. Methodologically homogeneous element content datasets, reflecting different exposure conditions across European and extra-European countries, were compiled and comparatively analysed. Element content in samples collected in remote areas was compared to that of potentially enriched samples, testing differences between medians for 2…
New Interpretative Scales for Lichen Bioaccumulation Data: The Italian Proposal
2019
The interpretation of lichen bioaccumulation data is of paramount importance in environmental forensics and decision-making processes. By implementing basic ideas underlying previous interpretative scales, new dimensionless, species-independent &ldquo
Probabilistic foundations of contextuality
2017
Contextuality is usually defined as absence of a joint distribution for a set of measurements (random variables) with known joint distributions of some of its subsets. However, if these subsets of measurements are not disjoint, contextuality is mathematically impossible even if one generally allows (as one must) for random variables not to be jointly distributed. To avoid contradictions one has to adopt the Contextuality-by-Default approach: measurements made in different contexts are always distinct and stochastically unrelated to each other. Contextuality is reformulated then in terms of the (im)possibility of imposing on all the measurements in a system a joint distribution of a particul…
Contextuality in canonical systems of random variables
2017
Random variables representing measurements, broadly understood to include any responses to any inputs, form a system in which each of them is uniquely identified by its content (that which it measures) and its context (the conditions under which it is recorded). Two random variables are jointly distributed if and only if they share a context. In a canonical representation of a system, all random variables are binary, and every content-sharing pair of random variables has a unique maximal coupling (the joint distribution imposed on them so that they coincide with maximal possible probability). The system is contextual if these maximal couplings are incompatible with the joint distributions o…