1,720,957 research outputs found
Microscopia a forza atomica per lo studio di zeoliti
No full textIn un tempo in cui si parla molto di nanotecnologie, o studio di materiali me soporosi come le zeoliti permette di riscoprire vecchie teorie ed osservare nuovi fenomeni.Materiali naturali non degradabili e facilmente rigenerabili, come le zeoliti, possono essere impiegati, per la loro efficienza e sostenibilità, in processi di bonifica ambientale, in particolare per quanto concerne il
risanamento delle falde acquifere inquinate da composti altamente tossici come idrocarburi e organoclorurati. Tali materiali sono già ampiamente utilizzati, quali eccellenti scambiatori ionici, per la rimozione dell’ammonio dalle acque reflue. In questo lavoro vengono studiate le modifiche strutturali prodotte dalla perfusione di tensioattivo in una zeolite naturale di provenienza esotica (Cuba) mediante l’utilizzo della microscopia a forza atomica (AFM). Tale tecnica coniuga la semplicità e la versatilità della microscopia ottica, con le prestazioni tipiche di un microscopio elettronico a trasmissione (TEM) potendo raggiungere una risoluzione spaziale pari a una decina di nanometri.
Il presente lavoro è articolato su due problematiche: la messa a punto di un metodo di osservazione delle zeoliti con con l’APM Nanoscopo III della Digital Instruments e lo studio delle modifiche indotte sulle zeoliti da soluzioni di tensioattivo. In futuro è prevista la messa a punto di un metodo statistico di correlazione dei dati per l’interpretazione delle immagini grazie alle figure caratteristiche delle strutture che si presentano a scale nanometriche
Diagnostic accuracy of Parkinson disease by Support Vector Machine (SVM) analysis of 123I-FP-CIT brain SPECT data: implications of putaminal findings and age
No full textAbstract: Brain single-photon-emission-computerized tomography (SPECT) with 123I-ioflupane (123I-FP-CIT) is useful to diagnose Parkinson disease (PD). To investigate the diagnostic performance of 123I-FP-CIT brain SPECT with semiquantitative analysis by Basal Ganglia V2 software (BasGan), we evaluated semiquantitative data of patients with suspect of PD by a support vector machine classifier (SVM), a powerful supervised classification algorithm.
123I-FP-CIT SPECT with BasGan analysis was performed in 90 patients with suspect of PD showing mild symptoms (bradykinesia-rigidity and mild tremor). PD was confirmed in 56 patients, 34 resulted non-PD (essential tremor and drug-induced Parkinsonism). A clinical follow-up of at least 6 months confirmed diagnosis. To investigate BasGan diagnostic performance we trained SVM classification models featuring different descriptors using both a “leave-one-out” and a “five-fold” method. In the first study we used as class descriptors the semiquantitative radiopharmaceutical uptake values in the left (L) and right (R) putamen (P) and in the L and R caudate nucleus (C) for a total of 4 descriptors (CL, CR, PL, PR). In the second study each patient was described only by CL and CR, while in the third by PL and PR descriptors. Age was added as a further descriptor to evaluate its influence in the classification performance.
123I-FP-CIT SPECT with BasGan analysis reached a classification performance higher than 73.9% in all the models. Considering the “Leave-one-out” method, PL and PR were better predictors (accuracy of 91% for all patients) than CL and CR descriptors; using PL, PR, CL, and CR diagnostic accuracy was similar to that of PL and PR descriptors in the different groups. Adding age as a further descriptor accuracy improved in all the models. The best results were obtained by using all the 5 descriptors both in PD and non-PD subjects (CR and CL + PR and PL + age = 96.4% and 94.1%, respectively). Similar results were observed for the “five-fold” method.
123I-FP-CIT SPECT with BasGan analysis using SVM classifier was able to diagnose PD. Putamen was the most discriminative descriptor for PD and the patient age influenced the classification accuracy
Natural radionuclides in Italian diet and their annual intake
No full textThis study was dedicated to the evaluation of the background activity concentration of natural radionuclides as 228Ra and 228Th of 232Th family, 226Ra of 238U family and 40K in the Italian daily diet. These radionuclides were determined by gamma spectrometry. 40K activity concentration, in the samples taken into account in the present paper, ranged between 70.5 (milk) and 181.1 Bqkg-1ww (pasta), 226Ra activity concentration ranged between 1.1 (milk) and 5.7 Bqkg-1ww (pasta), 228Ra and 228Th activity concentration, in the same samples, ranged between 0.7 (milk) and 3.7 Bqkg-1ww (pasta) and between 1.4 (milk) and 6.1 Bqkg-1ww (flours) respectively. The annual intake of every radionuclide from foodstuffs ingestion was also calculated. The 94-95% of the total intake comes from 40K. For adults and children, the highest activity intake of all radioisotopes was from grain products, for infants it was from milk products
Alpha and gamma spectrometry for the radiological characterization of animal feed
No full textConsumption of food is the most common pathway of radionuclides into the human body. Foods of animal origin are important in the European human diet. Therefore, radiation control of animal feeds and animal products will contribute to producing food for human nutrition without, or with low risk, for human health. This paper presents data obtained by alpha and gamma spectrometric analysis for natural radionuclides and 137Cs in animal feed. 40K, 228Ac, 212Pb, 208Tl, 214Pb, 214Bi and 137Cs were determined by gamma spectrometry, 210Po by alpha spectrometry. In all samples examined, 137Cs activity concentration was below the detection limit (0.25 Bqkgfw-1) except for one sample. The mean activity concentration was 2.26 ± 2.27 Bq kgfw-1 for 214Pb; 2.42 ± 2.24 Bq kgfw-1 for 214Bi; 1.76 ± 1.17 Bq kgfw-1 for 212Pb; 1.88 ± 1.42 Bq kgfw-1for 208Tl; 2.29 ± 1.93 Bq kgfw-1 for 228Ac; 3.48 ± 3.48 Bq kgfw-1 for 210Po, and 322.2 ± 115.6 Bq kgfw-1 for 40K. The Principal Components Analysis showed differences in the radioactivity content between samples with dicalcium phosphate and without dicalcium phosphate explaining 76.5 % of the total variance. A significant difference for 210Po and 40K activity concentration was detected between the samples with and without dicalcium phosphate
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
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