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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
STRATEGIES TO INCREASE WATER PRODUCTIVITY IN IRRIGATED RICE SYSTEMS: IS REDUCING WATER INPUTS THE KEY?
Full text linkLa crescita della domanda mondiale di cibo e l’aumentata incidenza di situazioni di carenza idrica ha notevolmente accentuato l’attenzione sulla risicoltura, data la sua importanza per la nutrizione umana e il suo contributo ai prelievi idrici per fini irrigui. Più del 75% della produzione mondiale di riso ha infatti luogo in risaie irrigate che utilizzano circa il 40% dell’acqua destinata al settore agricolo.
Alla luce di questo contesto (descritto nel Capitolo 1), la Tesi si pone l’obiettivo di valutare diverse tecniche di gestione dell’acqua in risaia come risposta alle crescenti pressioni sugli agricoltori che sono chiamati a massimizzare le produzioni, riducendo al contempo i volumi irrigui apportati. Il lavoro è articolato su tre principali aree di indagine tra loro interconnesse: (i) ruolo delle tecniche di monitoraggio nel favorire l’analisi dei fattori che determinano l’efficienza d’uso dell’acqua; (ii) valutazione di diverse strategie irrigue alla scala di risaia; (iii) studio delle variazioni dei fabbisogni irrigui distrettuali laddove la sommersione tradizionale fosse sostituita da tecniche di risparmio idrico su larga scala.
Per quanto concerne il primo punto, l’attività di Tesi ha contribuito allo sviluppo del prototipo di un innovativo sistema per il monitoraggio delle dinamiche dell’acqua in camere di risaia soggette a diverse tecniche irrigue. Svariati sensori sono stati utilizzati in maniera integrata permettendo la misura di diversi processi con alta risoluzione temporale (Capitolo 2). In aggiunta alle tecniche di monitoraggio a terra, è stata valutata la possibilità di impiego di dati da satellite per la valutazione dello sviluppo della vegetazione nel tempo e nello spazio, informazione necessaria per lo studio di processi legati allo sviluppo vegetativo (Capitolo 3).
Alla scala di campo sono stati valutati i bilanci idrici e gli indici di uso dell’acqua di tre diverse tecniche di gestione: semina in acqua e sommersione continua (pratica tradizionale), e due tecniche alternative che consistono nella semina interrata e sommersione ritardata e semina interrata e irrigazione intermittente. Se, da un alto, la sommersione ritardata ha determinato riduzioni del raccolto del 3% a fronte di risparmi idrici del 20%, l’irrigazione intermittente ha visto riduzioni del raccolto pari a circa il 30% come contraltare a risparmi idrici dell’ordine del 65%. I valori più alti per quanto riguarda l’indice di produttività dell’acqua sono stati ottenuti con riso irrigato ad intermittenza, tuttavia la sua sostenibilità economica sarebbe da valutare attentamente, date le significative perdite di raccolto osservate. Inoltre, è stata riscontrata una significativa variabilità nei fabbisogni irrigui dei trattamenti in sommersione, i quali hanno subito variazioni comprese tra il 40% e il 50% da un anno al successivo (variazione concentrate soprattutto all’inizio della stagione). Prendendo come riferimento la sommersione tradizionale, si è riscontrato un dimezzamento dei volumi irrigui necessari che sono passati da circa 3000 mm a 1500 mm. Tali variazioni sono state avvalorate da un’analisi statistica e sono state attribuite alla combinazione di diversi fattori quali la profondità di falda all’inizio della stagione e modificazioni a livello delle proprietà e della struttura del suolo.
Successivamente, il potenziale risparmio idrico conseguente ad un abbandono della tecnica di sommersione è stato valutato alla scala di distretto irriguo (Capitolo 5). I fabbisogni irrigui delle diverse colture del distretto (riso sommerso, mais irriguo e pioppo irriguo) sono stati stimati lungo un periodo di 4 anni grazie all’applicazione, in maniera distribuita, del modello idrologico SWAP e all’uso di equazioni di bilancio di massa. Successivamente, è stata individuata una relazione empirica che lega la soggiacenza alla ricarica di falda (data dall’acqua di percolazione dei campi irrigati). Per lo scenario di conversione a riso irrigato, si è prestata particolare attenzione al meccanismo di feedback che lega il livello di falda ai volumi irrigui necessari. L’importanza di questo legame è stata messa in luce attraverso lo sviluppo di due casi di studio. Nel primo caso, il feedback è stato trascurato e la stima dei fabbisogni irrigui è fatta sulla base degli attuali livelli di falda. Nel secondo caso invece, la stima devi volumi irrigui necessari è fatta in funzione dall’equilibrio soggiacenza-ricarica che verrebbe ad instaurarsi a seguito di una consistente variazione delle pratiche irrigue. Nello scenario senza feedback sono state stimate riduzioni dei fabbisogni irrigui dopo una conversione delle tecniche irrigue pari al 65%. Tali riduzioni sono state invece del 45% quando il meccanismo di feedback è stato considerato nell’analisi. Tuttavia il mantenimento di un turno irriguo per il mais di 15 giorni si è rivelato non sufficiente per il soddisfacimento dei fabbisogni idrici della coltura a causa dell’aumentata soggiacenza. Accorciare il turno irriguo del mais a 10 giorni ha determinato un’ulteriore riduzione dei risparmi ottenibili con una completa conversione a riso irrigato ad intermittenza (riduzione dei fabbisogni irrigui distrettuali pari al 40%).
Oltre ad aspetti strettamente legati ai volumi idrici, sono state inoltre investigate le dinamiche del carbonio organico disciolto in funzione delle diverse tecniche di gestione dell’acqua (Capitolo 6). Lo studio ha evidenziato un legame molto forte tra il ciclo del carbonio organico disciolto e le condizioni riducenti indotte dalla continua saturazione del suolo.
Infine è stato sviluppato un caso di studio per quantificare il ruolo della falda nella riduzione dei fabbisogni irrigui di colture irrigate ad intermittenza come il mais. I risultati hanno evidenziato un contributo della risalita capillare pari a circa il 50% del volume evapotraspirato dalla coltura in aree con bassa soggicanza di falda (Capitolo 7).
In conclusione, nonostante la tendenza a voler proporre soluzioni di carattere generale al problema dell’efficienza d’uso dell’acqua in agricoltura, le attività di ricerca proposte nella seguente Tesi hanno messo in luce come sia difficile stabilire se il risparmio idrico sia effettivamente un obiettivo da perseguire in qualsiasi contesto produttivo (Capitolo 8).In a context of increasing food demand and increasing risk of water scarcity, irrigated rice systems are receiving a specific attention because of the role of rice in food nutrition and because of the relevant share of water withdrawals required by rice farming. More than 75% of the global rice supply is in fact produced in lowland irrigated areas, which in turn require around 40% of the global water used for irrigation.
Given this background (Chapter 1), the Thesis investigates the role of water management in irrigated rice system, in response to the compelling pressures on farmers to maximise crop production while reducing the amount of water used for irrigation purposes. Three interlinked focus areas have been evaluated: (i) the role of monitoring techniques in improving knowledge on processes driving water use in rice systems, (ii) field-scale evaluation of the performance of different water regimes, (iii) effects induced by a large adoption of water saving technologies on the irrigation requirements at the district scale.
First, a prototype of an innovative integrated multi-sensor system was developed in order to monitor water dynamics in paddy fields under different water regimes. Several monitoring devices were effectively used in an combined way, enabling to measure different processes with a high temporal resolution (Chapter 2). In addition to on-ground devices, the opportunity offered by the use of remote sensed data to capture the spatio-temporal evolution of crop growth and study crop-related processes was investigated (Chapter 3).
Focussing on the field scale (Chapter 4), water balances and water use indices of three rice water managements were compared: water seeding-continuous flooding (“traditional” practice) and two alternative regimes being dry seeding-delayed flooding and dry seeding-intermittent irrigation. If delayed flooding determined average yield reductions by 3% against a decrease of water applications by 20%, the 65% reduction of water applications in intermittent irrigated rice was counterbalanced by yield losses close to 30%. Therefore, in spite of intermittent irrigation achieving the highest water productivity, the economic practicality of the method could be questioned. Moreover, the irrigation requirements of the flooded treatments were found to vary significantly between years, with variations by 40% to 50% (mostly occurred in the first part of the season). Taking as a reference the traditional flooding regime, irrigation requirements halved from 3,000 mm in the first season to 1,500 mm in the subsequent one. Variations were statically validated and they were attributed to a combination of abiotic and biotic factors including groundwater levels at the beginning of the season and soil-related aspects.
Then, the extent of reductions in irrigation requirements when replacing traditional flooding with intermittent irrigation was investigated at the scale of an irrigation district (Chapter 5). Water requirements of the different crops (flooded rice, irrigated maize and irrigated poplars) were investigated over a 4-year period by the application of a distributed modelling approach (use of the SWAP model) and water balance equations. An empirical relationship between groundwater recharge (provided by percolation from irrigated fields) and the groundwater levels was thus identified. For the scenario of intermittent irrigated rice, a particular attention was paid to the role of the feedback between groundwater levels and irrigation applications. The importance of feedback effects was highlighted by developing a case study where groundwater is assumed invariant from the present state (no feedback) and a case study where the estimated irrigation requirements are congruent with the “new” equilibrium state between groundwater levels and groundwater recharge. According to the estimates of the scenarios, irrigation withdrawals of the district decreased by around 65% when the feedback mechanism was neglected, while a reduction by 45% was observed when the feedback was accounted for. However, maintaining a 15-days turn for maize irrigation, like in the present state, was found to be inadequate for the full satisfaction of maize water requirements due to the decrease in the groundwater levels. Shortening the irrigation turn of maize to 10 days instead of 15 further decreased the estimate of the savings achievable with flush irrigated rice (reduction of irrigation requirements equal to 40%).
In addition to implications on water balance terms, a specific attention was paid on the dynamics of dissolved organic carbon in relation to the water regime. Results of the study highlighted a strong link between the cycling of dissolved organic carbon and the reducing soil conditions resulting from field flooding (Chapter 6).
Finally, the role of shallow groundwater table on the reduction of the irrigation requirements of lowland crops under intermittent irrigation was quantified via modelling simulations. Results showed a contribution of capillary rise up to 50% of the amount of water evapotranspirated by the crop (Chapter 7).
In spite of the tendency to seek for general and global solutions, the research activities presented in the Thesis highlighted the difficulty to provide a univocal response to the question as to whether reductions of water consumptions in rice paddies should really represent the target to be reached regardless the specific context (Chapter 8)
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
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