1,720,962 research outputs found
Antibacterial and antioxidant constituents of Acaplypha wilkesiana.
No full textThis study was aimed at characterising the secondary metabolites responsible for antibacterial and antioxidant activities of Acalypha wilkesiana. Purification of the defatted methanol leaves extract was guided by the DPPH free radical scavenging assay as well as by evaluation of the antibacterial activity against four bacterial strains. As a result, geraniin, corilagin, quadrangularic acid M and shikimic acid were purified and isolated. Shikimic acid, reported for the first time from this plant, proved to be the major metabolite of the extract. All the four isolated compounds showed bactericidal activity against extended spectrum beta-lactamase-producing Klebsiella pneumoniae (700603), while corilagin was the single compound to exhibit antioxidant activity (IC50 53 μg/mL)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Ptaquiloside, the major carcinogen of bracken fern, in the pooled raw milk of healthy sheep and goats: an underestimated, global concern of food safety
No full textBracken fern (Pteridium aquilinum) is a worldwide plant containing toxic substances, which represent an important chemical hazard for animals, including humans. Ptaquiloside, 1, a norsesquiterpenoid glucoside, is the major carcinogen of bracken detected in the food chain, particularly in the milk from farm animals. To date, ptaquiloside has been shown in the milk of cows feeding on a diet containing bracken fern. This is the first study that shows the systematic detection of ptaquiloside, 1, and reports its direct quantitation in pooled raw milk of healthy sheep and goats grazing on bracken. Ptaquiloside, 1, was detected by a sensitive method based on the chemical conversion of ptaquiloside, 1, into bromopterosine, 4, following gas chromatography–mass spectrometry (GC–MS) analysis. The presence of ptaquiloside, 1, possibly carcinogenic to humans, in the milk of healthy animals is an unknown potential health risk, thus representing a harmful and potential global concern of food safety
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Il ruolo della Cassa Depositi e Prestiti nella prospettiva degli investimenti strategici di lungo periodo.
No full textIl lavoro ha l’obiettivo di illustrare il compito della Cassa Depositi e Prestiti nel finanziare gli investimenti strategici in un’ottica di lungo periodo.
All’interno del primo capitolo si ripercorre l’evoluzione storica della Cassa negli ultimi 160 anni ed il rapporto con le Fondazioni bancarie. Nel secondo capitolo, invece, dopo una breve definizione di infrastruttura, sono stati analizzati i vari strumenti che la Cassa adopera per i finanziamenti infrastrutturali, suddividendoli tra capitale di debito, fondi di private equity e partecipazioni strategiche. Grande importanza è stata data al ruolo della Cassa a livello europeo, sottolineato anche dalla partecipazione al Piano Juncker ideato con l’intento di rilanciare la crescita economica e produrre investimenti senza incrementare il debito pubblico. Infine, nel terzo capitolo si è analizzata l’infrastruttura portuale e logistica italiana, evidenziando punti di forza, di debolezza e i contatti con la Cassa Depositi e Prestiti
Isolation and structural elucidation of bioactive secondary metabolites from marine and terrestrial organisms
No full textNatural products have historically been a rich source of "lead compounds" in drug discovery. The investigation of terrestrial plants and marine organisms aimed at searching new biologically active compounds is a central issue of this kind of studies, through structure elucidation combined with biological evaluation. My research work, described in this PhD thesis, falls within this research field and was addressed at three different topics: - i) isolation and structural elucidation of cytotoxic macrolides and depsipeptides and sterols active on PXR receptors from sponge Theonella swinhoei; ii) isolation and structural elucidation of metabolites modulating kinase activity from sponge Iotrochota purpurea; iii) isolation and analysis of correlation between reactivity and bioactivity for antimalarial and antinflammatory metabolites from the African plant Vernonia amygdalina. The structure elucidation of new molecules was performed using advanced spectroscopic techniques (2D-NMR and MS) and advanced methods of stereochemical determination (Murata's method and Marfey's method).
The chemical investigation of spongal metabolites carried out during my PhD was financed by the European project "Bluegenics". Several structurally interesting bioactive molecules have been isolated from Theonella sp., namely swinholides (cyclic 44-member macrolides) and theonellapeptolides (cyclic tridecadepsipeptides with a large amount of non-ribosomial amino acids), both featuring in vitro antiproliferative activity and providing important information regarding structure-activity relationship. The class of 4-methylensterols, typical of Theonella sponges, showed activity on nuclear receptor PXR, shedding light on structure-activity relationships useful for synthesis of lead compunds to be used for therapy of metabolic diseases.
Regarding the second topic, the isolation of haloindole derivatives, by bioguided approach, allowed their evaluation for antikinase activity, which could have an important impact on the manipulation of cell proliferation, diabetes, and neurodegenerative disorders.
Finally, a bioguided analysis of Vernonia amygdalina, a plant from Africa used as foodstuff and as drugs in the folk medicine, allowed the characterization of plant extracts for stage specific effects on gametocytes and sporogonic stages of Plasmodium and identification of compounds responsible for antimalarial activity. In particular, leaves of V. amygdalina contain sesquiterpenes lactones vernolide and vernodalol featuring this kind of activity; thus, they have a potential for drug discovery and for the development of standardized V. amygdalina based phytomedicines. The second aim of the investigation on V. amygdalina was the isolation and structural elucidation of a series of sesquiterpenes compounds with Michael related bioactivity, capable of shedding light on the molecular mechanisms underlying the anti-inflammatory and anticancer activities detected for the extract. On these series, cysteamine assay proved to be a tool to build a sort of Michael-oma profile of this class of metabolites, identifying the most reactive site in polyfunctional compounds and ranking them in terms of reactivity. Considering the correlation between thia-Michael acceptor reactivity and modulation of important biological target, sesquiterpene lactones were evaluated on transcription factors NF-κB, STAT3 and Nrf2 involved in cancer initiation and progression, concluding that vernolide is the major anti-inflammatory constituent of extracts and elucidating the anticancer activity reported
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