1,720,990 research outputs found
Cyclo-(His,Leu): A new microbial diketopiperazine from a terrestrial Bacillus subtilis strain B38
No full textIn continuation of our search for bioactive secondary metabolites from terrestrial Bacillus spp., a new microbial diketopiperazine, cis-cyclo-(His,Leu) (1) was isolated from the ethyl acetate extract of a strain B. subtilis B38, together with cis-cyclo-(Phe,Phe) (2), tryptophane (3), cis-cyclo-(Leu,Tyr) (4), cis-cyclo-(Trp,Tyr) (5) and macrolactin A (6). The chemical structures of the isolated compounds were identified by comparison of their 1D, 2D NMR and HRESIMS data with authentic spectra and literatures. To the best of our knowledge, this is the first time that cyclo-(His,Leu) has been isolated from natural products
Isolation and identification of an antibacterial compound from Diplotaxis harra (Forssk.) Boiss
No full textThe emergence of the antibiotic resistance is an ongoing problem in public health, and therefore the search for new natural molecules represents an alternative to synthetic drugs. The aim of this study was to test the antibacterial activity of ten Mediterranean plants (Diplotaxis harra, Ecballium elaterium, Pergularia tomentosa, Myrtus communis, Solanum villosum, Solanum sodomaeum, Peganum harmala, Lepidium sativum, Pistacia lentiscus, and Calendula arvensis) against seven pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Klebsiella sp., Salmonella enteritidis, and Bacillus cereus) using the disk diffusion method, in order to isolate and identify the active compound(s). Dichloromethane extract of D. harra flower showed the best activity against S. aureus and L. monocytogenes (MIQ = 30 μg/disk and 15 μg/disk, respectively). This extract was submitted to a bio-guided purification using Thin Layer Chromatography (TLC)-bioautography, and an antibacterial fraction (MIQ = 2 μg/disk) was isolated. The active fraction was characterized by RP-HPLC-DAD-ESI-MSn and GC–MS. Sulforaphane, an isothiocyanate known for its anti-cancer, antioxidant, and anti-inflammatory properties, was identified as antibacterial agent in D. harra for the first time. Due to its high antibacterial activity, sulforaphane could be considered a good candidate for the selection of new natural antibacterial molecules
Identification of an antiviral compound isolated from Pistacia lentiscus
No full textThis study screened mastic gum (Pistacia lentiscus L.) for antiviral activity against herpes simplex virus type 2 (HSV-2), coxsackievirus type B3, and adenovirus type 5. The organs of this plant (leaves, stem, and seed) were macerated sequentially using solvents of increasing polarity (hexane, dichloromethane, ethyl acetate, and methanol). Only the methanol extract of stem exhibited significant activity against HSV-2. This extract showed anti-HSV-2 activity with a selectivity index of 51 (50% cytotoxic concentration = 186 μg/mL; 50% inhibitory concentration = 3.63 μg/mL), and demonstrated direct inhibition against this virus with a virucidal selectivity index of 620 (50% virucidal concentration = 0.30 μg/mL). A bio-guided assay involving thin-layer chromatography led to the isolation of two active compounds, which have been identified as dammaradienone and dammaradienol using high-performance liquid chromatography-diode array detection coupled with electrospray ionization mass spectrometry. P. lentiscus has been widely studied for other biological activities. However, to our knowledge, this is the first report of P. lentiscus L. exhibiting antiviral activity
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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