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Sugar Uptake and Transport in Rice Embryo. Expression of Companion Cell-Specific Sucrose Transporter (OsSUT1) Induced by Sugar and Light
No full textFrictional, transport properties, and microstructures of simulated basalt faults
Get PDFI terremoti indotti dalle attività antropiche costituiscono una discriminante per il successo delle attività industriali quali l’iniezione di acque reflue, l’estrazione di petrolio e gas naturale, lo sfruttamento di energia geotermica e lo stoccaggio geologico di anidride carbonica. Negli ultimi anni, i basalti hanno catturato l’attenzione dell’industria del settore energetico e della comunità scientifica, a causa della loro vasta diffusione nella litosfera oceanica e della loro capacità di mineralizzare la CO2 “trasformandola in roccia” (New York Times 9/2/2015). Tale proprietà, consente di fatto di sottrarre a lungo termine l’anidride carbonica presente in atmosfera, contribuendo pertanto alla riduzione locale delle emissioni di CO2 di origine antropogenica. Comprendere le proprietà di attrito, meccaniche e idrologiche di faglie e fratture in basalto ha assunto pertanto un'importanza fondamentale, per le dirette implicazioni riguardanti l'enucleazione dei terremoti, la loro propagazione e l'arresto in ambienti geologici dominati dai basalti.
Per meglio comprendere le proprietà meccaniche di faglie e fratture in basalto, e in particolare la fase di enucleazione dei terremoti, esperimenti di attrito sono stati realizzati mediante l’apparato biassiale BRAVA e l’apparato di tipo rotativo SHIVA, entrambi installati presso l’Istituto Nazionale di Geofisica e Vulcanologia (INGV, Roma). Invece, per caratterizzare le proprietà di trasporto delle carote di basalto e delle faglie sperimentali, la trasmissività idraulica è stata misurata mediante il permeametro, prima e dopo gli esperimenti di attrito su SHIVA.
Sono stati trattati tre principali argomenti seguendo un approccio sperimentale per caratterizzare: 1) le proprietà di resistenza di attrito, stabilità e di healing delle faglie sperimentali in basalto (ovvero, faglie polverizzate e superfici di faglia) in condizioni di umidità atmosferica e in condizioni bagnate, integrando i dati meccanici con quelli microstrutturali (Capitolo 2); 2) le instabilità dell’attrito ed i processi di carbonatazione delle superfici di faglia sperimentali aventi diversi gradi di alterazione, cagionati dall’iniezione di fluidi ricchi in H2O, CO2, misture H2O-CO2, e Argon (Capitolo 3); 3) le variazioni delle proprietà idromeccaniche delle superfici di faglia sperimentali e la loro influenza sul loro comportamento durante l’iniezione di acqua in pressione (Capitolo 4). Per quanto concerne i cilindri cavi descritti nel capitolo 4, l’analisi accurata dello stato di sforzo negli esperimenti di tipo rotativo, ha richiesto lo sviluppo di un modello basato sui dati sperimentali che tenesse conto della geometria cilindrica dei campioni montati su SHIVA, la quale modifica il modo in cui la pressione di fluido influisce sullo sforzo normale efficace agente sulla faglia (Appendice 1). Tutti i test sono stati realizzati a temperatura ambiente, che può emulare le condizioni di temperatura di un sito energetico a bassa entalpia.
In questa tesi, complessivamente si osservano valori del coefficiente di attrito statico intorno a μ ~ 0.6 – 0.8, a diverse condizioni che spaziano dall’umidità atmosferica a quelle sovra-idrostatiche, indipendentemente dello stato di alterazione dei basalti e della composizione chimica del fluido iniettato durante gli esperimenti a breve termine (< 60 min). Pertanto, le faglie in basalto sono considerate “forti”, e gli elevati tassi di healing testimoniano la loro abilità di riguadagnare la resistenza al taglio durante il periodo intersismico. Secondariamente, metto in evidenza come la struttura delle faglie controlli le proprietà di rate and state e la stabilità delle stesse: mentre le polveri sono più propense ad enucleare terremoti (ovvero possiedono un comportamento di indebolimento con l’aumento di velocità: velocity weakening) quando, a seguito di processi cataclastici con riduzione della granulometria, la deformazione diventa localizzata lungo zone di deformazione ben sviluppate, al contrario, le superfici di faglia passano a un comportamento di incremento dell’attrito con l’aumentare della velocità (velocity strengthening), a seguito di processi di dilatanza che accompagnano la produzione di detrito durante lo scivolamento. Infine, si è osservato che i cambiamenti nelle proprietà idromeccaniche durante la pressurizzazione di fluido possono diventare dominanti rispetto agli effetti prodotti dai cambiamenti di attrito di secondo ordine predetti dalle leggi
di rate. A tale riguardo, ho rilevato un più pronunciato indebolimento idromeccanico, laddove la trasmissività idraulica della faglia è minore. Questa osservazione fornisce un efficace meccanismo per l’indebolimento delle faglie e in ultima istanza, portare all’enucleazione di terremoti anche nelle porzioni faglie in basalto caratterizzate da un comportamento “velocity strengthening”.Earthquakes induced by anthropic activities are a major concern for the success of the industrial operations associated with in-situ underground wastewater injection, oil and gas withdrawals,
geothermal energy exploitation, and geological carbon sequestration. Over the last few decades, basalt rocks have drawn heightened attention from the geo-energy industry and the scientific
community because of their widespread occurrence in the oceanic lithosphere and their efficiency to act as carbon sinks, thus contributing to locally reduce the CO2 anthropogenic emissions. Given the
direct implications for earthquake nucleation, propagation, and arrest in basaltic-dominated environments, understanding the frictional, mechanical, and transport properties of basalts-bearing
faults and fractures has become of paramount importance. To gain better insights on the mechanical behavior of basalt-hosted faults, notably the earthquake nucleation phase, friction experiments were performed using the biaxial deformation machine BRAVA and the rotary-shear apparatus SHIVA, both installed at the National Institute of Geophysics and Volcanology (INGV, Rome), Italy.
Whereas, to characterize the transport properties of basalt cores and simulated faults, hydraulic transmissivity was measured on the permeameter and before and after friction tests on SHIVA.
Three main scientific topics were addressed using an experimental approach: 1) the frictional strength, stability, and healing properties of basalt-built experimental faults (i.e., simulated gouge and
bare rock surfaces) under room-dry and wet conditions, by integrating the mechanical data with fault microstructures (Chapter 2); 2) the frictional instabilities and carbonation processes of
simulated initially bare rock surfaces with different degree of alteration, triggered by injection of pressurized H2O, pure CO2 , CO2 - rich water, and Argon (Chapter 3); 3) the hydromechanical
properties changes of simulated initially bare rock surfaces and their influence on the fault slip behavior during water pressurization (Chapter 4). The accurate stress paths analysis from rotary-shear
tests involving hollow bare rock surfaces in Ch.4 required the development of an experimentally derived model accounting for the cylindrical geometry of SHIVA samples, that modifies the fluid
pressure contribution on the effective normal stress acting on the laboratory fault, (Appendix 1). All the tests were performed at ambient temperature, which may mimic the temperature conditions in low
enthalpy geo-energy sites in basalts.
In this dissertation, overall, I demonstrate that the static friction coefficient of basalts is in the range of μ ~ 0.6 – 0.8, at conditions ranging from room-dry to supra-hydrostatic, regardless of the alteration state of basalts and the fluid chemistry during short-term laboratory experiments (< 60 min). Therefore, basalts are inherently frictionally strong and the high healing rates testify their ability to regain shear strength during the interseismic period. Secondly, I show that fault microstructure controls their frictional stability: while simulated gouge are more prone to host earthquake nucleation (i.e., velocity weakening behavior) when deformation becomes localized along well-developed shear zones formed in response to cataclasis and grain size reduction, bare rock surfaces show the opposite behavior, transitioning to velocity strengthening behavior promoted by dilatancy processes coupled with gouge production during shearing. Finally, I illustrate that changes in coupled hydromechanical properties during fluid pressurization can dominate over the effects of second-order frictional changes predicted by the rate-and state-friction laws. In this regard, I observed that hydromechanical weakening effects become more pronounced the lower the fault transmissivity. This evidence provides an effective mechanism for inducing fault weakening and ultimately, to bring about earthquake slip also in velocity-strengthening basalt fault patches
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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