1,720,959 research outputs found
Detoxification of natural and synthetic phenolic mixtures by Trametes versicolor laccase.
No full textShort-term effects of olive mill waste water (OMW) on chemical and biochemical properties of a semiarid Mediterranean soil
No full textOlive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g-1 soil of OMW (corresponding to a field rate of 0, 40 and 80 m3 ha-1, respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, b-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m3 ha-1 OMW. After 42 days’ incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m3 ha-1 OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms
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
Transformation of phenolic pollutants by fungal laccases purified or expressed in tobacco plants
No full textIntense pollution of the environment by xenobiotic chemicals continuously released into the biosphere has been one of the biggest concerns for science in the second part of the twentieth century.
Several types of industrial and agricultural wastes contain phenols. Many of these compounds and their derivatives are extremely harmful because they are highly toxic towards living organisms and represent a serious environmental problem. Conventional methods of remediation of phenol-polluted systems (e.g. solvent extraction, chemical oxidation, adsorption on activated supports, etc.) have some disadvantages due to high cost, time-consuming procedures and formation of toxic residues. Conversely, the use of enzymatic oxidative catalysts is a promising alternative technology to address the clean up of such a waste. Oxideductases catalyze several biochemical transformations. Among them, laccases have received a great attention because of their possible role in the detoxification of polluted
environments, and as catalysts in several applications. They are classified as polyphenoloxidases, i.e. enzymes capable to oxidize a reduced substrate and to start a polymerization process.
Laccases, mainly from fungal origins, are capable to degrade and/or to transform various pollutants into safer products. The potential of these enzymes as decontaminating agents of polluted environments has been verified in studies performed with a large range of xenobiotic substances, representative of pollutants from different origins. Several compounds (substituted phenols, anilines, non phenolic substances) have been partly or totally transformed in polymeric aggregates of different nature and size. Furthermore, it has been demonstrated that the catalytic efficiency of the enzymes towards less-reactive compounds can be greatly improved by additives, which behave as enhancing co-substrates. By contrast, other compounds, eventually present along with the target pollutants, may exhibit not negligible inhibitory effects. Moreover, experiments direct at evaluating the residual activity of the involved enzymes have indicated that some enzyme molecules may be entrapped or adsorbed into the polymeric products, loosing to some extent their activity. The use of whole plants and/or their root exudates as sources of laccases have been also proposed as an effective tool to deal with the detoxification of phenolic polluted wastes. The ability
of these detoxifying agents can be greatly magnified by their expression in a greater extend by metabolic engineering applications. However, plant laccases are much less effective than laccases produced by bacteria and fungi in their oxidative activity on phenols.
The efficiency of various laccases, purified from fungal sources, in the detoxification of either simulated or natural phenolic-polluted waters as well as their possible practical applications in polluted soil will be addresses. Furthermore, attempts to express a fungal phenoloxidase (POXC) in tobacco plants were successful, after gene transfer mediated by Agrobacterium tumefaciens. The poxC gene expression was ascertained by Western blot and its activity was checked by appropriate chemical reactions using ABTS as substrate. It has been also shown that the heterologous laccase is released by root exudates into the culture medium, thus giving rise to a new tobacco genotype useful for soil remediation
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
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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