1,721,072 research outputs found
Exploiting 40K radioactivity to probe the Earth and the environment
No full textIl potassio è l'ottavo elemento più abbondante nella crosta terrestre. Tra i suoi isotopi naturali il potassio ha un radionuclide, il potassio-40 (40K), che ha un'emivita di oltre un miliardo di anni e che ha avuto un ruolo attivo nell'evoluzione del nostro pianeta. Nei suoi decadimenti, 40K produce elettroni, positroni, fotoni, neutrini e antineutrini attraverso catture elettroniche, decadimenti beta e transizioni gamma. Un radionuclide così abbondante con una dinamica di decadimento così varia offre la possibilità di sondare la Terra su diverse scale spaziali. Durante il suo decadimento, 40K genera calore. Insieme all'uranio-238 (238U) e al torio-232 (232Th), si stima che questi radionuclidi producano ancora oggi metà del calore a disposizione dei processi interni del nostro pianeta.
Tra i prodotti del 40K, gli antineutrini sono di particolare interesse per lo studio del nostro pianeta. Queste particelle possono viaggiare indisturbate per migliaia di chilometri, rendendole preziose messaggere nella comprensione della Terra interna. Lo studio di questi “geoneutrini”, prodotti all'interno della Terra nei decadimenti di 40K e nelle catene di decadimento di 238U e 232Th, permette di recuperare informazioni sulla composizione e sul bilancio energetico del nostro pianeta. In questa tesi, combinando i risultati sperimentali di KamLAND e Borexino, ho stimato la produzione di calore radiogenico del mantello terrestre. Il segnale sperimentale da geoneutrini di 238U e 232Th è stato analizzato alla luce degli attuali modelli geochimici per derivare la produzione di calore radiogenico del nostro pianeta e il contributo complementare dovuto al lento raffreddamento terrestre. Sebbene questi risultati pongano già vincoli all’energetica della Terra, le attuali tecniche di rilevamento non consentono l'osservazione di geoneutrini da 40K, limitando le nostre conoscenze a ipotesi fortemente dipendenti da modelli teorici. In questo lavoro ho proposto un nuovo metodo di rivelazione basato sulla doppia coincidenza offerta dall'interazione di antineutrini su nuclei di 63Cu. Ho mostrato come questa tecnica potrebbe essere sfruttata in un rivelatore da 240 kton per rivelare i geoneutrini da 40K con una significatività di 5σ in 10 anni di acquisizione dati, consentendo di indagare questa regione dello spettro dei geoneutrini ancora inesplorata.
Oltre a questi studi, volevo avere un impatto concreto nel presente, concentrandomi sull'applicazione di tecniche di spettroscopia gamma all'agricoltura di precisione. L'agricoltura rappresenta da sola più della metà dei prelievi idrici globali. Un miglioramento delle pratiche agricole è quindi di fondamentale importanza per assicurare una gestione sostenibile dell'acqua. I fotoni emessi nelle transizioni gamma di 40K possono viaggiare per decine di centimetri e metri nel suolo e nell'aria, conservando preziose informazioni sull'ambiente che ci circonda. In questo lavoro l'evoluzione temporale del segnale gamma da 40K misurato da una stazione spettroscopica installata in un campo sperimentale è stata analizzata per recuperare indirettamente il contenuto idrico del suolo. La dipendenza del coefficiente di attenuazione lineare del suolo dalla quantità d’acqua immagazzinata nel terreno è stata sfruttata per stimare in tempo reale l'umidità del suolo con una scala spaziale di 25m. Contemporaneamente, l'analisi della variazione temporale dei conteggi osservati nella finestra energetica del 214Pb, un prodotto del radon che arricchisce l'acqua piovana, si è dimostrata efficace nel discernere gli episodi di pioggia dall'irrigazione. La capacità di misurare il contenuto idrico del suolo su scala di campo unita alla capacità di distinguere l'acqua piovana dall'irrigazione, diventerà sempre più importante nel contesto di un'agricoltura progressivamente più automatizzata, consentendo alla spettroscopia gamma di riempire un divario spaziale ancora aperto tra sensori puntuali e satelliti.Potassium is the 8th most abundant element in Earth’s crust. Among its natural isotopes potassium has a radionuclide, potassium-40 (40K), which has a half-life of more than a billion years, and which had an active role in the development of our planet. During its decays, 40K produces electrons, positrons, photons, neutrinos, and antineutrinos through electron captures, plus and minus beta decays and gamma transitions. A so abundant radionuclide with such a varied decay dynamics offers the possibility to probe the Earth on different spatial scales. While decaying, 40K generates heat. Together with uranium-238 (238U) and thorium-232 (232Th), it is estimated that these radionuclides still produce half of the heat available to the internal processes that regulate the dynamics of our inner planet.
Among 40K decay products, antineutrinos are of particular interest for studying our planet. These particles can travel undisturbed for millions of kilometers, making them valuable messengers in the comprehension of the inner Earth. The study of these “geoneutrinos”, produced inside the Earth in the decays of 40K and in the decay chains of 238U and 232Th, allow us to recover information on the composition and on the energy budget of Earth’s mantle. One of the most relevant results of my thesis was the estimation of Earth’s radiogenic heat production from the combination of KamLAND and Borexino experimental results. The measured geoneutrino signal coming from 238U and 232Th decays was analyzed in view of present geochemical models to estimate the total radiogenic heat production of our planet and in turn to derive the complementary heat loss contribution due to secular cooling, providing a global vision on the heat sources which power our planet. Although already posing constraints on the internal heat production of the Earth, current detection techniques do not permit the observation of 40K geoneutrinos, restricting our knowledge on Earth's energetics to model dependent assumptions. I proposed in this work a novel detection method based on the double coincidence offered by the interaction of antineutrinos on 63Cu nuclei. I showed how this technique could be exploited in a 240 ktons detector to enable the 40K geoneutrino detection at 5σ level in 10 years of data taking, possibly permitting to uncover this yet unexplored region of the geoneutrino spectrum.
Besides these studies, I wanted to have a concrete impact in the present, focusing on the study and application of gamma spectroscopy techniques to precision agriculture. Agriculture accounts by itself for more than half of global water withdrawals. Improvement of farming practices is thus imperative for a meaningful climate action and for ensuring a sustainable management of water. The photons emitted in 40K gamma transitions can travel for tens of centimeters and meters in matter and air, respectively, and retain precious information on the environment which surround us. In this work, the temporal evolution of the 40K gamma signal measured by a dedicated spectroscopic station installed in a test field was analyzed to indirectly recover soil water content. The dependence of soil’s linear attenuation coefficient on the amount of water stored in the ground was exploited to recover real time insights on soil moisture with a ∼25m footprint. Simultaneously, the analysis of transient increases in the spectral energy window of 214Pb, a radon daughter enriching rainwater, was shown to be effective in discerning rain episodes from irrigation. The capability to measure soil water content at field scale coupled to the ability to distinguish rainwater and irrigation will become increasingly important in the context of a progressively more automated smart agriculture, allowing gamma spectroscopy to fill a still unbridged spatial gap between punctual sensors and satellites
Overview on Diabetes’ interspace mortality and hospitalization in Central Italy
Full text linkCronic diseases, diabetes in particular, are a major problem of Public Health for what concern mortality and hospitalization rates. The aim of this study is to evaluate the weight of it comparing death and hospitalization rates for cardiovascular problems between diabetic and non-diabetic populations
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
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