131,703 research outputs found
Charm suppression in Pb-Pb collisions at the LHC measured using D0 K-Ï + reconstruction with the ALICE experiment
No full textThe thesis is focused on the measurement of the nuclear modification of charm quark production, in lead-lead collisions at the Large Hadron Collider. This observable is sensitive to the interaction of this quark with the high-density strongly interacting medium formed in ultra-relativistic heavy-ion collisions and, thus, to the properties of the state of matter. The partons traversing the medium lose energy via gluon radiation or elastic collisions with other partons already present in the medium. The charm quark allows to study the mass and colour charge dependences of the energy loss, since heavy quarks are expected to behave differently from light partons.
The measurement presented in this thesis is performed for the first time in nucleus-nucleus collisions, with the full reconstruction of D mesons via their hadronic decay. The strategy to reconstruct D0 mesons in the two-prong decay D0->K-ÃÂÃÂ+, with the ALICE experiment, will be described. Results obtained in Pb-Pb collisions at the energy of 2.76 TeV in the centre of mass of the collision for nucleons pair will be shown. In particular, the selection cut optimization was studied to compute the raw signal of D mesons with an invariant mass analysis. Selection and reconstruction efficiencies were considered with the detector acceptance, to correct for experimental effects. The corresponding data systematic uncertainties were evaluated in detail.
The comparison with the production cross section obtained in proton-proton collisions at the same energy allows then to compute the nuclear modification of D0 meson, the first direct evidence of the charm quark energy loss.
The measurement was compared with other open heavy flavour results and with light-charged hadrons suppression, measured at the LHC, to test the mass and colour charge dependences of the interaction with the medium. Results have been also compared with models that compute the charm quark energy loss using different theoretical approaches.
These results were recently approved by the ALICE Collaboration and a publication has been proposed and is being review by the Collaboration.La tesi descrive la misura della modifica della produzione di quark charm, in collisioni tra ioni piombo al Large Hadron Collider. Questa misura permette di studiare l'interazione del quark charm con il mezzo ad alta densitÃÂàe fortemente interagente, formato in collisioni di ioni pesanti ad energie ultra-relativistiche e le proprietÃÂàdi questo stato della materia. I partoni che attraversano il mezzo perdono energia per emissione di gluoni (gluonnstrahlung) e collisioni elastiche con gli altri partoni del mezzo. Il quark charm permette di studiare come variano le proprietÃÂàdell'interazione in funzione della massa e della carica di colore del quark, poichÃÂé i modelli teorici prevedono un comportamento diverso dei quark pesanti nel mezzo, rispetto a quelli leggeri.
La misura presentata in questa tesi ÃÂÃÂ ̈ la prima fatta in collisioni tra nuclei pesanti, attraverso la ricostruzione esclusiva dei mesoni D nel loro decadimento adronico. In particolare, verrÃÂÃÂ presentata la strategia di ricostruzione del mesone D0 nel suo decadimento in due corpi D0->K-ÃÂÃÂ+, fatta con l'esperimento ALICE. Verranno, quindi, illustrati i risultati ottenuti con i dati di collisioni Pb-Pb ad un energia nel centro di massa per coppia di nucleoni di 2.76 TeV. In particolare, ÃÂÃÂ ̈ stata studiata l'ottimizzazione dei tagli di selezione per misurare il segnale, estratto con un'analisi di massa invariante. Le efficienze di selezione e ricostruzione delle particelle e gli effetti di accettanza del rivelatore, sono stati considerati con uno studio Monte Carlo, per considerare gli effetti sperimentali. Nella tesi viene anche descritto in dettaglio lo studio sulle incertezze sistematiche.
Il confronto delle sezioni d'urto di produzione ottenute in collisioni Pb-Pb e protone-protone, alla stessa energia, permette di misurare il fattore di modifica nucleare del mesone D0, prima evidenza diretta di perdita energia del quark charm nel mezzo.
La misura ÃÂÃÂ ̈ stata confrontata con altri risultati ottenuti nel settore dei quark pesanti alla stessa energia, e con la soppressione degli adroni carichi, per valutare le dipendenze dalla massa e dalla carica di colore del quark, nella sua interazione con il mezzo. I risultati sono stati confrontati con modelli teorici che descrivono la perdita di energia del quark charm, utilizzando diversi metodi di calcolo.
I risultati sono stati recentemente approvati dalla collaborazione ALICE, una pubblicazione ÃÂÃÂ ̈ stata proposta ed ÃÂÃÂ ̈ in fase di review nella collaborazione
L’educazione infermieristica perioperatoria e la soddisfazione dell’utente: uno studio osservazionale
No full textRiconoscere la centralità del ruolo dell’utente all’interno del percorso assistenziale è sicuramente uno dei maggiori traguardi, in ambito sanitario, dell’epoca in cui viviamo.Tale centralità vede il suo fulcro nella realizzazione di un percorso di cura che si basa soprattutto su un progetto educativo da instaurarsi tra paziente ed operatore sanitario. Questo rapporto permette al professionista di aiutare il malato ad acquisire la consapevolezza del proprio stato di salute, ed al paziente di apprendere le nozioni fondamentali per comprendere e partecipare al proprio percorso di cura.La ricerca da noi condotta si è posta come obiettivo quello di valutare come l’educazione svolta dagli infermieri prima della dimissione ospedaliera da una degenza chirurgica, risulti rilevante nell’acquisizione di autonomia del paziente a domicilio e nella percezione di “soddisfazione” dello stesso per le informazioni ricevute. Sono stati intervistati 80 pazienti provenienti da diversi reparti chirurgici dell’Arcispedale Santa Maria Nuova di Reggio Emilia prevalentemente al momento della prima visita di controllo post dimissione; per indagare le diverse aree è stato utilizzato un questionario composto da domande aperte e chiuse, con lo scopo di valutare meglio l’aspetto qualitativo delle risposte. I risultati hanno evidenziato come i pazienti si ritengano complessivamente soddisfatti dell’educazione sanitaria ricevuta nel corso della degenza, nello specifico in merito al trattamento del dolore post operatorio, prevenzione delle infezioni, gestione della terapia, mobilizzazione e graduale ripresa di alimentazione ed idratazione.Restano tuttavia ancora due aspetti da migliorare: il primo è quello relativo al desiderio dei pazienti di ricevere un contatto telefonico da parte del personale ospedaliero, una volta dimessi; il secondo riguarda, invece, la necessità di una maggiore integrazione tra ospedale e territorio
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
The major antenna complex of photosystem II (LHCII) has a xanthophyll binding site not involved in light harvesting
No full textWe have characterized a xanthophyll binding site, called V1, in the major light harvesting complex of photosystem II, distinct from the three tightly binding sites previously described as L1, L2, and N1. Xanthophyll binding to the V1 site can be preserved upon solubilization of the chloroplast membranes with the mild detergent dodecyl-alpha -D-maltoside, while an IEF purification step completely removes the ligand. Surprisingly, spectroscopic analysis showed that when bound in this site, xanthophylls are unable to transfer absorbed light energy to chlorophyll a. Pigments bound to sites L1, L2, and N1, in contrast, readily transfer energy to chlorophyll a. This result suggests that this binding site is not directly involved in light harvesting function. When violaxanthin, which in normal conditions is the main carotenoid in this site, is depleted by the de-epoxidation in strong light, the site binds other xanthophyll species, including newly synthesized zeaxanthin, which does not induce detectable changes in the properties of the complex. It is proposed that this xanthophyll binding site represents a reservoir of readily available violaxanthin for the operation of the xanthophyll cycle in excess light condition
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