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Metodologie per la quantificazione dell'azotofissazione simbiotica delle leguminose
No full textIl lavoro si inserisce nell'ambito delle attività relative al progetto di rilevante interesse nazionale (PRIN) "Fisiologia della
produzione e azotofissazione di leguminose foraggere in sistemi agricoli ecocompatibili" e ha come obiettivo quello di fare il
punto sulle le principali metodologie impiegabili per la quantificazione in campo dell' azotofissazione simbiotica delle leguminose.
Sono stati illustrati gli assunti, le procedure, i vantaggi e i limiti di applicazione dei seguenti metodi: bilancio dell' azoto
(NB), riduzione dell'acetilene (ARA), riduzione di 15N2 (lR), diluizione isotopica (ID), abbondanza naturale (NA) e metodo
dell'ureide. Sono state inoltre descritte alcune applicazioni relative alla quantificazione dell'azoto ipogeo delle leguminose
e del trasferimento dell'azoto fissato alla coltura in successione.
Lo sviluppo delle metodologie basate sulla discriminazione isotopica dell'azoto, in particolare il metodo ID e NA, hanno
permesso di superare molti dei limiti di applicazione dei metodi più tradizionali (es. ARA e NB), ma il loro impiego non è scevro
da errate interpretazioni se non vengono rispettati gli assunti fondamentali, tra i quali il principale è quello della irregolare
distribuzione spazio-temporale dell'arricchimento isotopico (metodo ID) e della scelta della specie di riferimento. I modelli
di simulazione possono contribuire ad attenuare questi problemi. Per la quantificazione dell' azoto ipogeo delle leguminose
derivante da azotofissazione, che rappresenta un elemento di grande rilevanza da un punto di vista agronomico, non è stata
messa a punto una procedura standard, in quanto occorre adattare la metodologia alla specie e al sito sperimentale. Occorre
quindi investire, in particolare a livello nazionale, sullo sviluppo di metodologie per la quantificazione dell'azoto delle parti
ipogee e della quota di azoto fissato che, attraverso i residui colturali, entra nel ciclo dell'azoto, tenendo conto anche dell'esigenza
di valorizzare i risultati attraverso metodi che facilitino il coinvolgimento dei principali attori delle filiere produttive
basate sulle leguminose.nitrogen fixation of forage legumes in eco-compatible farming systems", with the aim of analysing the state of the art on the
main methods to estimate symbiotic nitrogen fixation of legumes in the field. Assumptions, procedures, advantages and limits
of the following methods are illustrated: nitrogen balance (NB), acetylene reduction assay (ARA), 15N2 isotope reduction OR),
15N isotopic dilution (ID), 15N natural abundance (NA) and xylem sap analysis. Some applications on the estimate of belowground
nitrogen of legumes and the implications on rotations and mixtures are also described.
The developrnent of methods based on the nitrogen isotopic discrimination, particularly ID and NA methods, have substantially
contributed to overcome the limitations of old methods such as ARA and NB. However, new methods can be misused
if fundamental assumptions are not satisfied, such as the time-space uniformity of soil 15N enrichment and the similar N uptake dynamics of the fixing and reference species. Modelling approaches can help to mitigate the assumptio~ violations:
It is not available a standard methodology to assess the below-ground fixed mtrogen of any.legume specles, as speclfic
procedures should be developed for each species and experimental site. As this is a relevant pomt from .an. agrono~lc perspective,
further research is needed to assess below-ground nitrogen of legumes and the amount of symblOtIc fixed mtroge!1
which enters the nitrogen cycle. Particular attention should also be deserved to the developme~t of adequate methods to explOIt
the results of the field experiments involving main stakeholders of the legume-based productIon systems
Metodologie per la quantificazione in campo dell'azotofissazione simbiotica delle leguminose
Full text linkThis paper has been written in the context of the Italian national research project (PRIN) "Physiology of production and
nitrogen fixation of forage legumes in eco-compatible farming systems", with the aim of analysing the state of the art on the
main methods to estimate symbiotic nitrogen fixation of legumes in the field. Assumptions, procedures, advantages and limits
of the following methods are illustrated: nitrogen balance (NB), acetylene reduction assay (ARA),15N2isotope reduction (IR),15N isotopic dilution (ID),15N natural abundance (NA) and xylem sap analysis. Some applications on the estimate of below-ground nitrogen of legumes and the implications on rotations and mixtures are also described.The developrnent of methods based on the nitrogen isotopic discrimination, particularly ID and NA methods, have substantially
contributed to overcome the limitations of old methods such as ARA and NB. However, new methods can be misused
if fundamental assumptions are not satisfied, such as the time-space uniformity of soil15N enrichment and the similar N
uptake dynamics of the fixing and reference species. Modelling approaches can help to mitigate the assumption violations.It is not available a standard methodology to assess the below-ground fixed mtrogen of any legume species, as specific
procedures should be developed for each species and experimental site. As this is a relevant point from an agronomic perspective,
further research is needed to assess below-ground nitrogen of legumes and the amount of symbiotic fixed nitrogen
which enters the nitrogen cycle. Particular attention should also be deserved to the development of adequate methods to exploit
the results of the field experiments involving main stakeholders of the legume-based production systems
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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