1,721,000 research outputs found
Lichens as bioindicators of temporal variations in air quality around Thessaloniki, northern Greece
No full textThe epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia, northern Greece)
surveyed in 1987 was sampled again in 1997 to monitor any changes in lichen communities and
consequently in air quality. A general impoverishment in lichen communities was recorded in the
10-year period, presumably chiefly due to changes in the air pollution status. A small increase in
lichen species diversity was recorded in some stations, probably as a result of the buffering capac-
ity of airborne dust
DNA metabarcoding of air samples for the taxonomic identification of airborne pollen
No full textMetabarcoding is a promising DNA-based method for identifying airborne pollen from environmental samples, with potential advantages over microscopic methods. This method includes several steps and its successful outcome depends on a good DNA quality and quantity, which will be used as a starting material. Currently, there is no clear protocol for the sample preparation and the DNA extraction, especially for gravitational pollen samplers. Here, we present a methodology to analyze environmental samples collected by both volumetric (Burkard spore trap) and gravitational samplers (Tauber trap). For this, we compared different protocols (e.g. DNA extraction kits) on pure pollen (single species) and the best combination, in terms of DNA yield, was applied to environmental samples (pollen mixtures of different taxa). For the environmental samples, a short fragment (about 150 base pairs) of chloroplast DNA (cpDNA) was amplified by universal primers for plants (trnL), 30 amplicons were Sanger-sequenced and the taxonomic assignment was accomplished through a comparison to a reference custom-made database, including important widespread anemophilous taxa from the study area (Eastern Italian Alps). Having as reference the microscope results, we proved that metabarcoding is efficient in identifying taxa even at the species level, having established improved protocols and a good reference database. We plan to apply a semi-quantitative analysis by Next Generation Sequencing to assess the pollen spectra of different Natura 2000 habitats in the Alps
Vertical distribution patterns of trace elements in an urban environment as reflected by their accumulation in lichen transplants
No full textThe results of an investigation about the vertical distribution patterns of selected trace elements in an urban environment, as reflected by their accumulation in lichen transplants, are reported. Thalli of the lichen Pseudevernia furfuracea were transplanted in 2 sites in the urban area of Thessaloniki (N Greece), subjected to very different traffic loads: 1) Tsimiski, downtown of Thessaloniki, at one of the busiest streets of the city, a street canyon 2) Toumba, far from the city centre, at the edge of the city, at an open street. In each site, thalli were suspended along a vertical transect at 3, 6, 9 and 12 m, and retrieved after one year. The results showed that while at Toumba the elemental composition of lichen samples was essentially influenced by natural occurrence, mainly airborne soil dust, at Tsimiski also anthropogenic input of pollutants determined by vehicle traffic was involved for some elements such as Cd, Cu, Ni, Pb and Zn. The vertical distribution patterns of heavy metals accumulated in lichens showed that in general elevation has no statistically significant influence on the concentration of most metals, but this was not true for Pb, whose concentrations increased with increasing elevation from ground. Residents may thus be more exposed to high concentrations of Pb than pedestrians
A DNA-based methodology for airborne pollen identification in complex environmental samples
Full text linkMetabarcoding is a promising DNA-based method for identifying airborne pollen from environmental samples, with potential advantages over microscopic methods. This method requires several preparatory steps of the samples, with the extraction protocol being of fundamental importance to obtain optimal DNA yield. Currently, there is no clear consensus in sample preparation and DNA extraction, especially for gravitational pollen samplers. Here, we present a DNA-based method to analyse environmental samples collected by both volumetric (Burkard spore trap) and gravitational samplers (Tauber trap). Results obtained are compared to those from microscopic analysis. DNA extraction was tested for three variables (extraction kit, bead beating, lysis) on pure pollen (single species) and the best combination was applied to environmental samples (pollen mixtures of different taxa). For the environmental samples, an improved protocol for the preparation of pollen pellets was established: DNA was extracted from the pollen and a short fragment of chloroplast DNA (cpDNA) was amplified by universal primers for plants (trnL). After PCR amplification, 30 amplicons were Sanger-sequenced and taxonomic assignment was accomplished through comparison to a reference custom-made database, including important widespread anemophilous taxa from the study area (Eastern Italian Alps). Results of metabarcoding with the trnL primers were consistently similar to those with microscopic analyses. For the environmental samples collected by volumetric trap, 75% of the taxa identified with the microscope were also identified by molecular analysis, which proved more efficient in identifying taxa even at the species level. We plan to apply a semi-quantitative analysis by Next Generation Sequencing in order to assess the pollen spectra of different Natura 2000 habitats in the Alps
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
DNA metabarcoding of airborne pollen: new protocols for improved taxonomic identification of environmental samples
No full textMetabarcoding is a promising DNA-based method for identifying airborne pollen from environmental samples with advantages over microscopic methods. Sample preparation and DNA extraction are of fundamental importance for obtaining an optimal DNA yield. Currently, there is no standard procedure for these steps, especially for gravimetric pollen samplers. Therefore, the aim of this study was to develop protocols for processing environmental samples for pollen DNA extraction and for metabarcoding analysis and to assess the efficacy of these protocols for the taxonomic assignment of airborne pollen collected by gravimetric (Tauber trap) and volumetric (Hirst-type trap) samplers. Protocols were tested across an increasing complexity of samples, from pure single-species pollen to environmental multi-species samples. A short fragment (about 150 base pairs) of the chloroplast trnL gene was amplified using universal primers for plants. After PCR amplification, amplicons were Sanger-sequenced and taxonomic assignment was accomplished by comparison with a custom-made reference database including chloroplast DNA sequences from most of the anemophilous taxa occurring in the study area (Trentino, northern Italy), representing 46 plant families. Using the classical morphological pollen analysis as a benchmark, we show that DNA metabarcoding is efficient and applicable even in complex samples, provided that protocols for sample preparation, DNA extraction, and metabarcoding analysis are carefully optimize
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
