1,721,055 research outputs found
Botanica generale e diversità vegetale II edizione
No full textIl testo descrive le peculiarità della cellula vegetale, i diversi livelli di organizzazione, la struttura morfologica ed anatomica delle piante, i meccanismi di sviluppo e riproduttivi, mettendo in evidenza le relazioni fra aspetti citologici, istologici e morfologici. Illustra le principali linee evolutive, le metodiche più diffuse di studio della variabilità e le modalità di identificazione dei taxa; approfondimenti ed esempi sono relativi soprattutto alla realtà italiana ed europea
Botanica generale e diversità vegetale
No full textIl testo descrive le peculiarità della cellula vegetale, i diversi livelli di organizzazione, la struttura morfologica ed anatomica delle piante, i meccanismi di sviluppo e riproduttivi, mettendo in evidenza le relazioni fra aspetti citologici, istologici e morfologici. Illustra le principali linee evolutive, le metodiche più diffuse di studio della variabilità e le modalità di identificazione dei taxa; approfondimenti ed esempi sono relativi soprattutto alla realtà italiana ed europea
Duckweed: A Tool for Ecotoxicology and a Candidate for Phytoremediation
No full textAbstract: Background: Duckweed is the common name for Lemnaceae, a plant family consisting of
five major genera: Lemna, Spirodela, Wolffia, Wolffiella and Landoltia. They are the world's smallest
and simplest flowering plants with a high growth rate under appropriate environmental conditions.
Duckweed can be used as a feed source for livestock and poultry, as well as biomass for production of
biofuel and recombinant proteins. Over the last 40 years a great deal of research has been published on
the use of duckweed to treat wastewater. These plants can recover nutrients, such as nitrogen and phosphorus, and they can also remove or accumulate metals, radionuclides, and other pollutants in their tissues.
Methods: A summary of some of the published works done on duckweed species to remediate natural, domestic, industrial and agricultural wastewaters is presented. The potential of these species for phytoremediation is considered and discussed.
Results: Certain duckweed species have the ability to grow on wastewaters, making their biomass production an environmentally friendly process. Duckweed has been extensively studied in pilot-studies and in tertiary treatment of municipal and industrial wastewaters, as well as nutrient recovery from swine wastewater. A relevant number of studies concerns the behaviour of duckweed species towards heavy metals and other elements, such as selenium and arsenic.
More recently the attention has been also focused on metals, named Rare Earth Elements (REE) and on emerging pollutants (i.e. pharmaceuticals, personal care products, pesticides and surfactants). The phytoremediation ability of duckweed depends on the growth conditions of the species, the type of pollutants and their concentrations.
Conclusion: Progress has been made on use of duckweed in phytoremediation. Current knowledge on the removal efficiencies of several pollutants is limited to laboratory experiments and batch systems, rarely on microcosm- or mesocosm-scale. The removal mechanisms involved, the toxicity to plants caused by contaminants, and the influences of certain important environmental parameters are not fully elucidated. Further studies in this area are still needed in order to provide more and better convincing evidence of the remediation performance of larger laboratory-scale, pilot-scale or fullscale of duckweed
Use of Biostimulants as a New Approach for the Improvement of Phytoremediation Performance—A Review
No full textEnvironmental pollution is one of the most pressing global issues, and it requires priority attention. Environmental remediation techniques have been developed over the years and can be applied to polluted sites, but they can have limited effectiveness and high energy consumption and costs. Bioremediation techniques, on the other hand, represent a promising alternative. Among them, phytoremediation is attracting particular attention, a green methodology that relies on the use of plant species to remediate contaminated sites or prevent the dispersion of xenobiotics into the environment. In this review, after a brief introduction focused on pollution and phytoremediation, the use of plant biostimulants (PBs) in the improvement of the remediation effectiveness is proposed. PBs are substances widely used in agriculture to raise crop production and resistance to various types of stress. Recent studies have also documented their ability to counteract the deleterious effects of pollutants on plants, thus increasing the phytoremediation efficiency of some species. The works published to date, reviewed and discussed in the present work, reveal promising prospects in the remediation of polluted environments, especially for heavy metals, when PBs derived from humic substances, protein and amino acid hydrolysate, inorganic salts, microbes, seaweed, plant extracts, and fungi are employed
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
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