1,721,041 research outputs found
Larvicidal activity of essential oils of five Apiaceae taxa and some of their main constituents against Culex quinquefasciatus
No full textApiaceae are aromatic herbs producing essential oils which are used on an industrial scale for various purposes.Notably, Apiaceae essential oils may replace synthetic insecticides keeping most of their efficacy and avoidingenvironmental pollution and human poisoning. In the present work, we explored the insecticidal potential of theessential oils from five Apiaceae taxa, namely Sison amomum, Echinophora spinosa, Heracleum sph ondylium subsp.sphondylium, Heracleum sphondylium sub sp. ternatum, and Trachyspemum ammi, as well as their major constituents(sabinene, p-cymene, terpinolene, myristicin, and thymol), against the filariasis vector Culex quinquefasciatus. For thepurpose, the essential oils were obtained by hydrodistillation and their composition was achieved by gaschromatography/mass spectrometry (GC/MS). Their acute toxicity on third instar larvae of C. quinquefasciatus wasdetermined. The two most active ess ential oils were those from T. ammi fruits and E. spinosa roots, showing LC50below 20 ll/l and LD90below 50 ll/l. These oils were dominated by the monoterpene phenol thymol and thephenylpropanoid myristicin, respectively, which showed the strongest larvicidal activity (LC50of 15.1 and 16.3 ll/l,respectively) among the pure compounds tested. These results showed that Apiaceae may be useful as source oflarvicidal compounds to be used for the development of cheap, effective and eco-fr iendly insecticidal formulations
Commentary: Making Green Pesticides Greener? The Potential of Plant Products for Nanosynthesis and Pest Control
No full textThe resurgence of interest on natural substances and their progressive affirmation in the market open doors for novel marketed products, with intrinsic original approaches. Evident examples are in the food supplements sector as well as in mix of synthetic drugs and natural substances, as novel drugs. A decisive key role will be played by technology and the capacity of throw novel opportunities out of the normal landscape. As in other fields, most of the future technology developments rely on nanotechnology. In this Commentary, after the discussion focused on
the novel roles of natural products, we report the recent results in the application of nanotechnology in one of the most relevant challenge for mankind, consisting in the resurgence of important vector-borne diseases and emergence of new epidemic alerts. In particular, the green synthesis of nanopesticides is cheap and environmental friendly, since it does not require the employment of highly toxic chemicals or elevate energy inputs. In the conclusions, a brief agenda summarizing the challenges for nano-based pest control is outlined
Identification of Onosma visianii Roots Extract and Purified Shikonin Derivatives as Potential Acaricidal Agents against Tetranychus urticae
Full text linkThere is an increasing need for the discovery of reliable and eco-friendly pesticides and natural plant-derived products may play a crucial role as source of new active compounds. In this research, a lipophilic extract of Onosma visianii roots extract containing 12% of shikonin derivatives demonstrated significant toxicity and inhibition of oviposition against Tetranychus urticae mites. Extensive chromatographic separation allowed the isolation of 11 naphthoquinone derivatives that were identified by spectral techniques and were tested against Tetranychus urticae. All the isolated compounds presented effects against the considered mite and isobutylshikonin (1) and isovalerylshikonin (2) were the most active, being valuable model compounds for the study of new anti-mite agents
Clausena anisata and Dysphania ambrosioides essential oils: from ethno-medicine to modern uses as effective insecticides
No full textDysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) and Clausena anisata (Willd.) Hook. f. ex Benth. (Rutaceae) are two aromatic species traditionally used in Cameroon to repel and kill insects. The present work was carried out to substantiate this traditional use and to evaluate the possible incorporation in commercial botanical insecticides of their essential oils (EOs). The EOs were distilled from leaves of C. anisata and aerial parts of D. ambrosioides and analyzed by gas chromatography-mass spectrometry (GC-MS). The insecticidal activity of both EOs was investigated against the filariasis vector, Culex quinquefasciatus and the housefly, Musca domestica. As possible mode of action, the inhibition of acetylcholinesterase (AChE) by the two EOs was investigated as well. The D. ambrosioides EO was characterized by the monoterpene peroxide ascaridole (61.4%) and the aromatic p-cymene (29.0%), whereas the C. anisata EO was dominated by the phenylpropanoids (E)-anethole (64.6%) and (E)-methyl isoeugenol (16.1%). The C. anisata EO proved to be very toxic to 3rd instar larvae of C. quinquefasciatus showing LC50 of 29.3 l/l, whereas D. ambrosioides EO was more toxic to adults of M. domestica showing a LD50 of 51.7g/adult. The mixture of both EOs showed a significant synergistic effect against mosquito larvae with LC50 estimated as 19.3 l/l, whereas this phenomenon was not observed upon application to M. domestica adults (LD50 = 75.9g/adult). Of the two EOs, the D. ambrosioides one provided a good inhibition of AChE (IC50 = 77 g/ml), whereas C. anisata oil was not effective. These findings provide new evidences supporting the ethnobotanical use of these two Cameroonian plants, and their possible application even in synergistic binary blends, to develop new eco-friendly, safe and effective herbal insecticides
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
- …
