1,720,962 research outputs found
Fast Determination of Histamine in Cheese by Nuclear Magnetic Resonance (NMR)
No full textA rapid and quantitative 1H nuclear magnetic resonance (NMR) method was developed to analyze histamine in cheeses. The procedure is simple because the acid extract is analyzed directly, without any need for further filtration, derivatization, or other manipulation. This NMR method was demonstrated to be specific by 2D total correlation spectroscopy (TOCSY) and heteronuclear multiple-quantum coherence (HMQC) experiments and reliable in terms of linearity, accuracy, recovery, repeatability, and limits of detection (LOD). Good precision, with relative standard deviation (RSD) < 4%, recovery of 100%, and a range of 0.6−1 mg/kg for the LOD were obtained. The NMR method was successfully applied to different types of cheese, ranging from soft to hard. No interference from free amino acids, proteins, and other natural components was detected. The NMR method could be transferred to other kinds of food
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
NMR sugar-profile in genuine grape must
No full textThe wine market has always faced the problem of fraud, including the addition of exogenous sugar solutions to grape musts to increase the final alcohol content. Since in some countries the practice of chaptalization is prohibited (except by adding concentrated must) it is necessary to broaden the analytical techniques that allow the identification of this type of fraud. The aim of this study was to define an NMR-based sugar profile of genuine grape must to set concentration limits for each sugar as parameters of authenticity. Glucose, fructose, together with eleven minor sugars were quantified in 82 genuine Italian grape musts, developing an analytical procedure based on highly selective chemical shift filters followed by TOCSY. Alongside the characteristic myo- and scylloinositol, significant contents of mannose, galactose, and trehalose were also found. Otherwise, maltose, rhamnose, arabinose, sucrose and lactose are present in lower concentrations and show great concentration variability
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
Distribution analysis of myo and scyllo-inositol in natural grape must
No full textAs it is well known, myo and scyllo-inositol are two characteristic sugars of grape must and, for this reason, their quantification has been proposed to control the authenticity of the concentrated and rectificated grape must. Indeed, these polyalcohols, which originate in the grape berries and are not retained by the resins used for the concentration process, are not naturally present in other commercial sugars from different botanical origins [1]. However, up to now, no study has exhaustively investigated the concentration variability of myo and scyllo-inositol in natural grape musts and for this reason in the definition of rectified concentrated grape must the only presence of meso-inositol is prescribed without reporting any minimum limit [2]. In this work, 200 authentic Italian grape musts were collected and the concentration of the two polyalcohols was determined. The sampling was done during 2019 and 2020 harvest in 17 different Italian Regions (Abruzzo, Basilicata, Calabria, Campania, Emilia Romagna, Friuli Venezia Giulia, Lazio, Lombardy, Marche, Piedmont, Puglia, Sardinia, Sicily, Tuscany, Trentino-Alto Adige, Umbria, and Veneto). A total of 85 different grape varieties were considered to describe the natural variability. Quantification of myo and scyllo-inositol was performed by gas chromatography after silylation. The method used was obtained by modifying the official method RESOLUTION OIV-OENO 419C-2015 concerning the quantification of myo and scyllo -inositol in rectified concentrated grape musts [3]. The aim of our work was to create an extensive data bank and to investigate the impact of the geographical origin, grape variety and the different year of harvest on the concentration of myo and scyllo-inositol. Furthermore, it has been verified the influence of the process to obtain the concentrated grape must starting from the natural one on the content of the two polyalcohol
Caratterizzazione fisiologica e molecolare dei trasportatori ad alta affinità del nitrato in radici di mais
No full textL’uso dei fertilizzanti in agricoltura sta diventando sempre più oneroso non solo dal punto di vista economico, ma soprattutto per l’impatto ambientale che esso ha. In questo conteso un obiettivo di ricerca importante è quello di migliorare l’efficienza di assorbimento da parte delle piante, in quanto è ormai assodato che gli apparati radicali recuperano quote piuttosto ridotte dei fertilizzanti applicati. Questi aspetti sono stati molto spesso affrontati empiricamente con un approccio dose-effetto invece che attraverso un attento studio dei meccanismi biochimici e molecolari che ne stanno alla base.
Gli ioni nitrato e ammonio presenti nel suolo sono le due principali fonti di azoto per le piante coltivate alle nostre latitudini. Per l’assorbimento del nitrato, le piante hanno sviluppato due distinti sistemi di trasporto, uno ad alta affinità (HATS, high-affinity transport system) e uno a bassa affinità (LATS, low-affinity transport system); entrambi sono caratterizzati dalla presenza di una componente costitutiva e una inducibile dalla presenza dell’anione.
Il presente lavoro è stato focalizzato sulla caratterizzazione biochimica e molecolare dei
trasportatori ad alta affinità del nitrato in Zea mays (Pioneer, hybrid PR33T56) con
riferimento anche ai meccanismi regolatori che ne sottendono l’attività. Attraverso l’uso di
15
N sono state studiate le variazioni della velocità di assorbimento dello ione da parte di radici di piante eziolate di 4 giorni, cresciute in coltura idroponica e successivamente messe a contatto con una soluzione nutritiva contenente nitrato 500 μM. Per il sistema HATS, la più alta velocità di assorbimento è stata riscontrata dopo 8 ore di contatto fra radici e nitrato. Usando il database Maizesequence Browser, sono stati identificati 4 putativi geni codificanti trasportatori ad alta affinità (NRT2) e due putativi geni NAR2; quest’ultimi codificano per una proteina che si è rivelata necessaria per conferire funzionalità ai trasportatori NRT2 di Arabidopsis thaliana e Hordeum vulgare.
Ai diversi tempi di trattamento, sulla base delle informazioni di sequenza ottenute dal genoma, sono state effettuate, sia nelle radici che nel germoglio, analisi di espressione dei geni (real time RT-PCR) codificanti i trasportatori NRT2 e le proteine NAR2. In radice, il gene ZmNRT2.2 ha mostrato di avere la più alta induzione, seguendo il comportamento fisiologico precedentemente studiato. Riguardo i geni NAR2, solamente il trascritto del putativo gene ZmNAR2.1 risultava indotto e con un andamento di espressione simile a quello del gene ZmNRT2.2 suggerendo un suo possibile coinvolgimento nel fenomeno. Lo sviluppo di un anticorpo specifico per i trasportatori NRT2 ha dato la possibilità di studiare, attraverso analisi Western-blot, le variazioni a livello proteico dei geni identificati. L’andamento di questi correlava solo parzialmente con l’attività di trasporto Tale risultato suggerisce che modificazioni post-traduzionali possano regolare l’attività dei trasportatori stessi Un possibile, anche se non esclusivo, candidato per questo tipo di regolazione, potrebbe essere una proteina della famiglia NAR2 la cui associazione fisica con i trasportatori del nitrato è stata vista essere, in Arabidopsis e Orzo, condizione necessaria per conferire loro proprietà di trasporto. Per chiarire questo aspetto sono in corso indagini mediante elettroforesi nativa delle proteine di membrana
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
- …
