1,721,075 research outputs found
Advanced modeling for studying antineutrinos and gamma rays coming from the Earth
No full textIn questa tesi sono presentate le sfide scientifiche e i risultati dell'attività ricerca svolta durante il corso di dottorato a supporto della modellazione avanzata per l'analisi spaziale di dati di spettroscopia gamma e per la stima dei segnali di geoneutrini. Questi due argomenti, apparentemente distanti, sono in realtà strettamente connessi: in entrambi i casa la radioattività naturale rappresenta uno strumento per lo studio delle proprietà della superficie e dell'interno della Terra. In particolare ho trattato gli aspetti problematici relativi alla modellazione numerica e cartografica a differenti scale e ho proposto soluzioni operative riguardanti lo studio delle distribuzioni statistiche, il trattamento delle incertezze di input e output e la combinazione di informazioni multivariate. Questi studi mi hanno dato l'opportunità di prender parte al dibattito scientifico che cerca di rispondere alle domande ancora aperte sulla formazione e la composizione del nostro pianeta. I contenuti di questa tesi sono inclusi in 6 studi pubblicati, la cui realizzazione ha visto il coinvolgimento di circa 30 coautori, tra geologi e fisici, provenienti da diverse istituzioni di ricerca di rilevanza internazionale. In ogni capitolo uno specifico caso di studio è presentato e trattato da un particolare punto di vista in modo da mettere in luce il mio contributo. Lo studio degli elementi radiogenici e le previsioni sulla loro distribuzione sono elementi chiave per la comprensione dei processi geologici locali che interessano la crosta così come per lo studio della radioattività ambientale. La mappa della radioattività naturale terrestre della regione Veneto è stata ottenuta sulla base di un dataset integrato di spettroscopia gamma costituito da misure in laboratorio su campioni di roccia e misure airborne. In particolare ho integrato questi due differenti tipi di dati in un unico prodotto cartografico, usando algoritmi geostatistici adatti alle caratteristiche geologiche e morfologiche pecualiari delle aree investigate. I differenti contributi delle incertezze sono stati ampiamente discussi nel caso di studio nel Nord-Est della Sardegna. In questo lavoro la mappa di distribuzione dell'uranio è stata ottenuta sulla base di un dettagliato studio radiometrico realizzato con due differenti tecniche di spettroscopia gamma, caratterizzati da differenti errori di misura. Affrontando questa sfida, ho applicato un particolare metodo geostatistico che ha permesso di analizzare le incertezze di input e di output. Nel caso del rilievo gamma airborne dell'isola d'Elba, è stata usata un'interpolazione spaziale multivariata per ottenere le mappe radiometriche adottando la carta geologica come informazione a priori. In quest'ambito ho trattato gli aspetti complessi della correlazione di dati quantitativi (misure gamma) con le informazioni qualitative geologiche. La forte correlazione tra informazioni geologiche e contenuto di radioattività è stata enfatizzata nell'indagine approfondita condotta in una delle regioni più produttive di petrolio in Albania (Vlora-Elbasan) per la valutazione dei NORM (Naturally Occurring Radioactive Materials). Ho partecipato all'analisi delle misure di concentrazione di attività basata su argomentazioni geologiche e geochimiche. La caratterizzazione litologica delle aree petrolifere risulterà di importanza strategica per la pianificazione di future valutazioni radiologiche della regione. La combinazione dei risultati sperimentali dei segnali di geoneutrini da esperimenti in corso e futuri, può porre vincoli stringenti sul segnale atteso dal mantello e di conseguenza sulla sua composizione. In questa prospettiva una profonda conoscenza della crosta continentale, ed in particolare della regione immediatamente vicina al detector, è imprescindibile. In questo contesto, un dettagliato modello 3D derivante da informazioni geologiche, geofisiche e geochimiche è stato realizzato per stimare il flusso dei geoneutrini atteso al detector SNO+ (Canada). In particolare ho sviluppato un modello 3D strutturale della regione, trattando gli aspetti relativi alla complessità della modellazione del flusso di geoneutrini. Inoltre ho partecipato allo studio che ha portato alla prima stima del segnale dei geoneutrini atteso a JUNO, un rivelatore a scintillatore liquido attualmente in costruzione in Cina, insieme alla stima del segnale atteso degli antineutrini da reattore. La posizione dell'esperimento, molto vicina a due centrali nucleari progettate, riflette il principale goal scientifico di JUNO, ovvero lo studio della gerarchia di massa sulla base delle misure di antineutrini da reattore. In quest'ambito ho prodotto gli spettri dei geoneutrini e le relative incertezze fornendo un risultato che sarà un punto di riferimento e una guida per gli studi futuri. Questi studi riflettono l'interazione di tre discipline scientifiche fondamentali: la Fisica delle particelle, le Scienze della Terra e la Statistica. La loro interconnessione rivela un grande potenziale per il superamento delle frontiere della conoscenza. Ho trattato in prima persona i problemi specifici che nascono necessariamente quando differenti, ma non distanti, campi scientifici sono chiamati ad interagire.This thesis presents the scientific challenges and the goals of my research activity supporting the advanced modeling for the spatial analysis of gamma-ray data and for the predictions of geoneutrinos signal. These two topics, based on different measurements techniques and fields of view, are apparently distant but both make the natural radioactivity a probe for the study of the properties of Earth's surface and interior. I dealt the problematic aspects related to the numerical and cartographic modeling at different scales and I proposed operative solutions regarding mainly the study of statistical distributions, the treatment of the input and output uncertainties and the combination of multivariate information. These studies gave me the opportunity to take part in the scientific debate that tries to answer to the still open questions about the formation and composition of our planet. The contents of this thesis are included in 6 published works realized with the involvement of about 30 coauthors, geologists and physicists, from different istitutions in the world. In each chapter a specific case study is presented from a particular point of view shedding light on my contribution. The study of heat producing elements and the previsions of their distribution are key-points for the understanding of local geological processes affecting the crust as well as for the investigation of environmental radioactivity. The map of terrestrial natural radioactivity of the Veneto region (Italy) was obtained on the basis of an integrated gamma-ray dataset composed by laboratory measurements performed on rock samples and airborne measurements. I integrated these two different types of data in a unique cartographic product, using suitable geostatistical algorithms based on the distinctive geological and morphological features of the investigated areas. The different contributions of the uncertainties were widely faced in case study in the Northeastern Sardinia in which the uranium distribution map comes from a very refined radiometric investigation realized with two different γ-ray spectroscopy measurements methods, characterized by heterogeneous measurement errors. Taking on this challenge, I applied a particular geostatistical method that permitted to analyze the input and the output uncertainties. In the case of airborne gamma ray survey of Elba Island, a multivariate spatial interpolation was used for obtaining the radiometric maps using the geological map as a constraint. I dealt with the complex aspects of correlating quantitative data (γ-ray measurements) with the qualitative information of the geological map. The strong correlation between geological information and radioactivity content was emphasized in the extensive survey in one of the most important oil productive regions (Vlora-Elbasan) in Albania for the assessment of Naturally Occurring Radioactive Materials. I participated to the analysis of the activity concentrations measurements based on geological and geochemical arguments. The discrimination of the lithologic features of the oil fields and the test of geodynamic models can result strategic issues for the planning of the future radiological assessment of the region. Combining experimental results of geoneutrino signals at operating and future experiments, can place better constraints on the mantle signal and in turn on its composition. In this perspective a deep understanding of the continental crust, in particular the region immediately surrounding the detector, is mandatory. In this framework a detailed 3D model compiled from geological, geophysical, and geochemical information provided the estimation of the geoneutrino flux expected at the SNO+ detector (Canada). I developed the geophysical construction of a 3D structural model of the region, dealing with the related aspects to the complexity of the modeling the prediction of the geoneutrino flux. Moreover I performed the first estimation of the geoneutrino signal expected at JUNO, a liquid scintillation detector that will be built in China, together with a prediction of the expected reactor antineutrino signal. The experiment will be located very close to two planned nuclear plants in order to study the neutrino mass hierarchy, which is the last missing ingredient in the neutrino puzzle. I produced the geoneutrino spectra and the relative uncertainties providing a result that will be a reference point and a guide for future refinements. These studies reflect the melting of three fundamental scientific disciplines: Particle physics, Earth science and Statistics. Their interconnection reveals a great potential for advancing the frontiers of knowledge. I had to deal with specific problems that necessarily emerge when different, but not distant, fields of science are called to interact
Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux
No full textThe SNO1 detector that is currently under construction in Ontario, Canada, will be a new kilotonscale
liquid scintillation detector with the capability of recording geoneutrino events that can be used to constrain
the strength of the Earth’s radiogenic power, and in turn, to test compositional models of the bulk silicate
Earth (BSE). We constructed a detailed 3-D model of the regional crust centered at SNO1 from compiled
geological, geophysical, and geochemical information. Crustal cross sections obtained from refraction and
reflection seismic surveys were used to characterize the crust and assign uncertainties to its structure. The average
Moho depth in the study area is 42.362.6 km. The upper crust was divided into seven dominant lithologic
units on the basis of regional geology. The abundances of U and Th and their uncertainties in each upper
crustal lithologic unit were determined from analyses of representative outcrop samples. The average chemical
compositions of the middle and lower crust beneath the SNO1 region were determined by coupling local seismic
velocity profiles with a global compilation of the chemical compositions of amphibolite and granulite
facies rocks. Monte Carlo simulations were used to predict the geoneutrino signal originating from the regional
crust at SNO1 and to track asymmetrical uncertainties of U and Th abundances. The total regional crust contribution
of the geoneutrino signal at SNO1 is predicted to be 15:615:3
23:4 TNU (a Terrestrial Neutrino Unit is one
geoneutrino event per 1032 target protons per year), with the Huronian Supergroup near SNO1 dominantly
contributing 7:315:0
23:0 TNU to this total. Future systematically sampling of this regional unit and denser seismic
surveys will better model its composition and structure, and thus reduce the uncertainty on geoneutrino signal
at SNO1. The bulk crustal geoneutrino signal at SNO1 is estimated to be 30:716:0
24:2 TNU, which is lower than
that predicted in a global-scale reference model that uses an average composition of the global upper continental
crust, due to the fact that Archean to Proterozoic Canadian Shield has lower U and Th concentrations.
Finally, without accounting for uncertainties on the signal from continental lithospheric mantle and convecting
mantle, the total geoneutrino signal at SNO1 is predicted to be 4016
24 TNU
Towards a refined regional geological model for predicting geoneutrinos flux at Sudbury Neutrino Observatory (SNO+).
No full textReference worldwide model for antineutrinos from reactors
No full textAntineutrinos produced at nuclear reactors constitute a severe source of background for the detection of geoneutrinos, which bring to the Earth’s surface information about natural radioactivity in the whole planet. In this framework, we provide a reference worldwide model for antineutrinos from reactors, in view of reactors operational records yearly published by the International Atomic Energy Agency. We evaluate the expected signal from commercial reactors for ongoing (KamLAND and Borexino), planned (SNO+), and proposed (Juno, RENO-50, LENA, and Hanohano) experimental sites. Uncertainties related to reactor antineutrino production, propagation, and detection processes are estimated using a Monte Carlo-based approach, which provides an overall site-dependent uncertainty on the signal in the geoneutrino energy window on the order of 3%. We also implement the off-equilibrium correction to the reference reactor spectra associated with the long-lived isotopes, and we estimate a 2.4% increase of the unoscillated event rate in the geoneutrino energy window due to the storage of spent nuclear fuels in the cooling pools. We predict that the research reactors contribute to less than 0.2% to the commercial reactor signal in the investigated 14 sites. We perform a multitemporal analysis of the expected reactor signal over a time lapse of ten years using reactor operational records collected in a comprehensive database published at www.fe.infn.it/antineutrino
Geoneutrinos and reactor antineutrinos at SNO+
No full textIn the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector is foreseen to observe almost in equal proportion electron antineutrinos produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the first long baseline experiment to measure a reactor signal dominated by CANDU cores (~55% of the total reactor signal), which generally burn natural uranium. Approximately 18% of the total geoneutrino signal is generated by the U and Th present in the rocks of the Huronian Supergroup-Sudbury Basin: the 60% uncertainty on the signal produced by this lithologic unit plays a crucial role on the discrimination power on the mantle signal as well as on the geoneutrino spectral shape reconstruction, which can in principle provide a direct measurement of the Th/U ratio in the Earth
Biomass water content effect on soil moisture assessment via proximal gamma-ray spectroscopy
No full textProximal gamma-ray spectroscopy supported by adequate calibration and correction for growing biomass is an effective field scale technique for a continuous monitoring of top soil water content dynamics to be potentially employed as a decision support tool for automatic irrigation scheduling. This study demonstrates that this approach has the potential to be one of the best space–time trade-off methods, representing a joining link between punctual and satellite fields of view. The inverse proportionality between soil moisture and gamma signal is theoretically derived taking into account a non-constant correction due to the presence of growing vegetation beneath the detector position. The gamma signal attenuation due to biomass is modelled with a Monte Carlo-based approach in terms of an equivalent water layer which thickness varies in time as the crop evolves during its life-cycle. The reliability and effectiveness of this approach is proved through a 7 months continuous acquisition of terrestrial gamma radiation in a 0.4 ha tomato (Solanum lycopersicum) test field. We demonstrate that a permanent gamma station installed at an agricultural field can reliably probe the water content of the top soil only if systematic effects due to the biomass shielding are properly accounted for. Biomass corrected experimental values of soil water content inferred from radiometric measurements are compared with gravimetric data acquired under different soil moisture levels, resulting in an average percentage relative discrepancy of about 3% in bare soil condition and of 4% during the vegetated period. The temporal evolution of corrected soil water content values exhibits a dynamic range coherent with the soil hydraulic properties in terms of wilting point, field capacity and saturation
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
A century of oil and gas exploration in Albania: Assessment of Naturally Occurring Radioactive Materials (NORMs)
No full textThe Naturally Occurring Radioactive Materials (NORMs) that are potentially generated from oil and gas
extractions in Albania have been disposed of without regulations for many decades, and therefore, an
extensive survey in one of the most productive regions (Vlora-Elbasan) was performed. A total of 52
gamma ray spectrometry measurements of soil, oil-sand, sludge, produced water and crude oil samples
were performed. We discovered that relatively low activity concentrations of 226Ra, 228Ra, 228Th and 40K,
with concentrations of 23 ± 2 Bq/kg, 23 ± 2 Bq/kg, 24 ± 3 Bq/kg and 549 ± 12 Bq/kg, respectively, came
from the oil-sands produced by the hydrocarbon extraction of the molasses formations. The mineralogical
characterizations and the 228Ra/40K and 226Ra/40K ratios of these Neogene deposits confirmed the predictions
of the geological and geodynamic models of a dismantling of the Mesozoic source rocks. The
average activity concentrations (±standard deviations) of the radium isotopes (226Ra and 228Ra) and of
the 228Th and 40K radionuclides in soil samples were 20 ± 5 Bq/kg, 25 ± 10 Bq/kg, 25 ± 9 Bq/kg and
326 ± 83 Bq/kg, respectively. Based on the measurements in this study, the future radiological assessments
of other fields in the region should be strategically planned to focus on the oil-sands from the
molasses sediments. Disequilibrium in the 228Ra decay segment was not observed in the soil, sludge or
oil-sand samples within the standard uncertainties. After a detailed radiological characterization of the
four primary oil fields, we concluded that the outdoor absorbed dose rate never exceeded the worldwide
population weighted average absorbed dose rate in outdoor air from terrestrial gamma radiation
- …
