1,721,054 research outputs found
New insights on the Xylaria species (Ascomycota, Xylariales) with bright-coloured exudates: Xylaria aurantiorubroguttata sp. nov. and revision of X. haemorrhoidalis and X. anisopleura type collections
Full text linkA new species of Xylaria is described based on morphological characters of both sexual and asexual morphs, and molecular data based on nuclear rDNA internal transcribed spacer, α-actin, β-tubulin and RNA polymerase subunit II sequences. Xylaria aurantiorubroguttata is characterized by the presence of both upright, cylindrical, long-stipitate and globose to subglobose, short-stipitate stromata, immature stromatal stages producing at first orange and then red drops, and ascospores with a slightly oblique, straight half spore-length germ slit. We provide also new morphological descriptions for X. haemorrhoidalis (holotype) and X. anisopleura (isosyntype), two Xylaria species belonging to X. polymorpha complex together with X. aurantiorubroguttata
Lithobiontic recolonization following cleaning and preservative treatments on the rock engravings of Valle Camonica, Italy: A 54-months monitoring
Full text link: Both the indirect control of microclimate conditions and the direct application of preservative products to contrast stone bioreceptivity may contribute to limit lithobiontic recolonization of cultural heritage surfaces after cleaning interventions. However, the priority deserved by these different preventive approaches has still been poorly evaluated, particularly in outdoor environments. This work dealt with the engraved sandstone surfaces of the National Park of Rock Engravings of Naquane (Italy, UNESCO WHS), widely colonized by lichens, mosses and a dark cyanobacterial biofilm, and thus requiring frequent cleaning interventions to preserve their legibility for visitors and scholars. In particular, post-cleaning recolonization by the different lithobionts was seasonally monitored along 54 months in different zones of an engraved outcrop, primarily differing in levels of shading, on parcels exposed to nine different conservative treatments. These included (or not) a pre-cleaning devitalization of lithobionts and the post-cleaning application of biocidal (benzalkonium chloride, plant essential oils, usnic acid) and other restoration products (nanocrystalline anatase, polysiloxane-based water repellent, ethyl-silicate-based consolidant). The combination of surface image analyses, fluorimetric and colorimetric measurements showed that mosses and the cyanobacterial biofilm rapidly recolonized all the parcels in the more shaded zone, irrespective of conservative treatments. In the other areas, recolonization significantly differed depending on the treatment. The post-cleaning application of biocides determined the best results through two vegetative seasons, but only nanocrystalline anatase and the polysiloxane-based water repellent maintained the surfaces lighter than uncleaned controls along the whole monitoring period. Recolonization primarily proceeded by the uncleaned surfaces surrounding the parcels and, at least in the examined case of lichens, did not show substantial shifts in community composition, although some nitrophytic species increased their frequency. In conclusion, the effectiveness of preservative treatments to prevent a rapid recolonization of heritage stone surfaces appeared subordinate to the presence of microenvironmental conditions less favourable to lithobionts
Next generation sequencing of ancient fungal specimens: The case of the Saccardo mycological herbarium
Full text linkDespite their essential role in the environment, the number of known fungal species is still
low compared to the recent estimates of the fungal biodiversity (from 2.2 to 3.8 million
species), principally because of their often cryptic or ambiguous morphological traits.
Recent studies have reported that only about approx. 35,000 correctly identified fungal
species are represented by DNA sequences in public databases. This corresponds to
a mere 1% of the estimated total number of species. Thus, the linkage of curated DNA
sequence data to properly identified voucher specimens is of fundamental importance
to fill the present gap between the different sizes of described and sequenced
fungal diversity. For this purpose, mycological herbarium collections are considered
an important source for fungal DNA-barcoding, and collection-based sequencing is
a relevant priority for the coming decades. Unfortunately, ancient herbarium samples
have both time and conservation related DNA damages, besides exogenous DNA
contamination, that make nucleic acid extraction and amplification challenging. Here, we
present the results of DNA extraction, ITS2 amplification and Illumina MiSeq sequencing
of 36 specimens from the Saccardo Mycological Herbarium that were collected in the
late XIX century and assigned to the genus Peziza. High-throughput sequencing was
chosen as an alternative to the conventional Sanger- and cloning-based methods to
overcome the high fragmentation of the ancient DNA and the massive occurrence of
non-target DNA from fungal contaminants. Our approach has permitted the assignment
of ITS2 sequences to 23 out of the 36 specimens studied in this work, thus providing
a univocal DNA sequence for those one century old samples. Furthermore, the ITS2
sequence analysis has permitted a taxonomic study of the samples that has resulted in
a re-evaluation of five samples at the species level and 18 samples at genus or higher
level. Our results highlight the possibility to apply the technique presented in this work
also to the old and more precious type specimens in order to relate a DNA sequence
to these important samples, coupling the traditional morphological description of the
species with a DNA sequence
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
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
- …
