1,720,986 research outputs found
Acquisition and Analysis of MRS Spectra in Animal Models
No full textLa Spettroscopia di Risonanza Magnetica (MRS) al protone permette di ottenere delle informazioni biochimiche in diverse patologie, attraverso lo studio delle concentrazioni dei metaboliti presenti nel tessuto analizzato.
Il dato spettroscopico in vivo è affetto da artefatti del movimento, cattiva omogeneità del segnale, basso rapporto segnale-rumore e il segnale principale, l'acqua, deve essere rimosso in modo da poter osservare altri segnali la cui concentrazione nel tessuto è 1000 volte minore.
Diversi sono i metodi proposti per migliorare il dato acquisito e poterne ottenere delle informazioni quantitative. Ogni metodo possiede vantaggi e svantaggi, a seconda del tipo di spettro che viene analizzato.
Nel presente lavoro viene proposto un confronto tra le tecniche maggiormente utilizzate per la quantificazione del segnale MRS.
Nella prima parte del lavoro, diversi algoritmi vengono applicati per lo studio degli spettri lipidici simulati, in vitro e in vivo. Questi spettri sono caratterizzati da poche componenti che si sovrappongono, ma sono ben distinguibili, il segnale dell'acqua è presente in minima parte e la linea di base è pressoché costante. La quantificazione di questi spettri così semplici permette un facile confronto tra i metodi.
Nella seconda parte del lavoro, lo stesso confronto viene applicato a segnali più complessi, composti da numerosi componenti, da un basso rapporto segnale rumore e da una linea di base non costante e variabile da spettro a spettro. A questo tipo di segnali appartengono quelli del tessuto cerebrale.
Lo scopo è quello di stabilire la migliore procedura sperimentale da applicare per l'analisi dei dati spettroscopici.Proton Magnetic Resonance Spectroscopy (proton MRS) is a technique which allows to obtain biochemical information of several pathologies by studying the metabolite concentrations of the analyzed tissue. The strongest signal contribution is derived from the water, and it has to be removed during the online acquisition and the off-line post processing step. The presence and the removal of this huge signal may affect significantly the metabolites peaks and the baseline. Moreover acquisition of MRS spectra in living subjects can be affected by motion artifacts, bad shimming and low signal to noise ratio.
Different post -processing techniques have been proposed to improve spectra obtained at difficult acquisition conditions, for water signal suppression and for baseline artifact correction. Nevertheless, among all the techniques proposed, it is difficult to identify the best performance and to rely on it, thus MRS quantification is still a challenge in biomedical research and not yet considered as a stable and fast routine diagnostic technique.
In the present work, a comparison among the most used techniques in MRS quantification is proposed in two steps. In the first part of the thesis, different analysis technique have been applied on simple MRS signals, such as lipid spectra obtained from simulation and acquired in vivo and in vitro measurements. These spectra are characterized by a flat baseline and 11 to 12 slightly overlapping peaks, which are acquired without water suppression, so they constitute a simple field for comparison of quantification algorithms.
In the second part of the thesis, these different techniques will be applied in the quantification of MRS of brain tissue. These spectra are much more complicated than lipid spectra in term of baseline and number of signals to discriminate. Under these experimental conditions, we will also compare methodologies in preclinical models of brain pathologies.
Finally, the aim is to establish the best experimental procedures for both acquisition and analysis of in vivo brain spectra, to be applied first in preclinical, and subsequently in clinical research. An overview of the biological findings in both lipid and brain experimental projects will also be presented
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
1 H-MR spectroscopy characterization of the adipose tissue associated with colorectal tumor.
No full textPURPOSE: To investigate colorectal tumor by looking at the lipid tissue around the lesion. Adipose tissue is not only an inert storage system for excess calories, but is involved in several pathological processes linked to tumor development.
MATERIALS AND METHODS: We obtained 24 colorectal specimens after surgical excision from patients affected by colorectal cancer at different tumor stages. 1 H-MR spectoscopy (MRS) spectra were collected from two voxels, in proximity of the lesion and far from it, in each specimen with a preclinical scanner. We differentiated patients by pathological tumor stage, and we compared the chemical composition of adipose tissue between patient groups, both close the tumor and far from it.
RESULTS: Monounsaturated fatty acids (MUFA) close the lesion are increased at higher tumor stages, while MUFA far from the lesion do not follow this trend. This study is really explorative due to the small numbers of subjects and we are cautious on the interpretation of the results. However, the approach of the present work allows a further insight in the tumor characterization.
CONCLUSION: Looking at the lipid tissue around a lesion through 1 H-MRS can return important information regarding its genesis and development
Antonio Stradivari archettaio
No full textIl contributo offre i risultati di un'analisi interdisciplinare mediante la quale è stato possibile attribuire alla bottega di Antonio Stradivari una serie di archetti conservati in diversi musei del mondo, che finora non era stato possibile riconoscere come prodotti di una specifica bottega di liuteria. Decisiva per il risultato si è dimostrata l'indagine paleografica delle annotazioni sui modelli per nasetti del Museo del Violino di Cremona
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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