1,721,258 research outputs found
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
Aplicacion del analisis mutivariante en las ciencias sensoriales: bases teoricas y supuestos practicos
No full textVariations 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
MICROBIAL FOOD FERMENTATIONS: INNOVATIVE APPROACH USING INFRARED SPECTROSCOPY
Full text linkInterest in food quality and production has increased in recent decades, mainly due to changes in consumer habits and behaviour, and the development and increase in the industrialisation of food chains. The growing demand for quality and safety in food production obviously calls for high standards for quality and process control, which in turn requires appropriate analytical tools for the analysis of food.
In particular, many unit operations in industrial food processes are related to microbial fermentation, namely milk coagulation in dairy, dough in bakery, as well as must fermentation in wine and beer productions.
Fermentation is one of the earliest methods adopted to obtain value-added food products with an extended shelf life. Humans applied fermentation to make products such as wine, mead, cheese and beer long before the biochemical process behind was understood. Even now the biochemistry of fermentations commonly applied in food processes has many aspects which have not been fully investigated yet.
Briefly, fermentation is any metabolic process in which an organism converts a carbohydrate, such as starch or sugar, into an alcohol and/or organic acids entailing modifications in the final product.
The transition to industrial productions entailed a standardisation of the fermentation processes and the obtained products. Currently, the main objective is to develop instruments able to be implemented in the process in order to closely monitor the products of interest and to detect in real time the smallest changes bringing to a more effective process control and management.
In this contest, spectroscopy revealed to be an interesting analytical method to monitor food fermentations processes. Spectroscopy is a secondary analytical method which consists in recording the absorption changes due to the interaction of electromagnetic radiation with the matter. The basic principle is that every chemical compound absorbs, transmits or reflects light (electromagnetic radiation) over a certain range of wavelengths. The information recorded can, thus, be used to measure the amount of a known chemical substance if correlated to a reference analysis. Spectroscopy reveals to be one of the most useful methods for quantitative analysis in various fields such as chemistry, physics, biochemistry, material and chemical engineering and clinical applications. Indeed, any application that deals with chemical substances or materials can use this technique. Moreover, the improved instrumentation for performing in-line and on-line analyses at industrial level has rose in the last decades giving the opportunity to obtained real-time information about the progression of any process and allowed its implementation as strategy to monitor complex systems as food production.
The food monitoring with spectroscopic devices has become possible thanks to Chemometrics (i.e. multivariate data analysis). Chemometrics has widely demonstrated to be the perfect partner to spectroscopy to deal with the complex chemical/physical systems that food matrix conforms. Chemometrics is able to extract relevant information from redundant and noisy spectra. In the last years the combination of spectroscopic analysis and Chemometrics was applied crosswise in food processes for qualitative and quantitative modelling in industrial applications. In particular, for the determination of compositional parameters affecting quality and safety of fermented food products such as wine, beer, yoghurt, vinegar and bakery products. Nevertheless, concerning complex biotransformations spectroscopy and Chemometrics are emerging techniques in food fermentation monitoring.
The purpose of this PhD Thesis is the demonstration of the feasibility in the combination of spectroscopy and Chemometrics as an innovative working procedure for real time monitoring of food fermentation processes.
The thesis consists of five main chapters
Chapter 1 Chapters 2 and 3 present an introduction to the main fermentations and their control from an historical prospective, the employed analytical techniques (Near infrared and Mid Infrared spectroscopy) and to Chemometrics, respectively. Chapter 4 presents the experiments carried out on various fermentation food processes. In this section seven studies represent examples of applications of different spectroscopic methods in strong combination with Chemometrics to food fermentation processes as yogurt fermentation (Paper I, II and Paper III), wine malolactic transformation (Paper IV and V) and beer (Paper VI and VII). In addition to the mentioned contributions a brief state of the art and some preliminary results are reported regarding sourdough leaving process monitoring.
The two basic Chemometrics tools, principal component analysis (PCA) and partial least squares (PLS) regression were mainly applied to the spectroscopic data collected from the fermentation processes in order to evaluate the results and focus on the relevant information and to correlate the spectral features with different relevant physical and/or chemical parameters such as the concentration of the main chemical species involved in the biotransformation. In particular, the principal components (PCs) scores obtained by monitoring wine and yoghurt fermentations were modelled as function of time to find out kinetic parameters, as maximum acceleration and deceleration of the transformation, important for the process control (PAPER I and V). The spectroscopic data obtained during yoghurt and beer fermentation monitoring were also investigated with multivariate curve resolution- alternating least squares (MCR-ALS), proving to be able to resolve multi-component mixtures into a simpler model (PAPER II and VII).
The main conclusive remarks on the presented studies are given in Chapter 5 (CONCLUSIONS), including a discussion of challenges and future perspectives for further application of spectral monitoring and chemometrics in fermented food processes
IDENTIFICATION OF THE ANTIGEN RECOGNIZED BY RHIGM22, A REMYELINATION-PROMOTING HUMAN MONOCLONAL ANTIBODY
Full text linkOligodendrocytes (OLs) are the myelin-forming cells of the central nervous system (CNS). They synthesize large amounts of plasma membrane and extends multiple processes that individually wrap around axons generating a multilayered stack of membranes tightly attached at their cytosolic and external surfaces, i.e. myelin. The myelin membrane provides electric insulation of axons and dictates the clustering of the sodium channels at the nodes of Ranvier and the organization of the node itself, allowing saltatory nerve conduction. A number of neurological diseases of the CNS are characterized by destruction of oligodendrocytes with consequent damage or loss of the myelin sheath. In most experimental models, the normal response to this is remyelination, a process mediated by oligodendrocyte precursor cells (OPC) that ultimately leads to functional recovery. However in human diseases, and in specific in multiple sclerosis (MS), this process is inefficient and fails to successfully counteract the accumulation of lasting axonal damage and increasing brain atrophy, thus resulting in motor and neurological deficits. The development of strategies aimed to increase the efficiency of the remyelination process is therefore an important therapeutic goal. One of these strategies involves the use of CNS reactive antibodies to promote remyelination. One of these antibodies, rHIgM22, is able to bind to oligodendrocytes and myelin in vitro. Moreover, rHIgM22 is able to enter the CNS, accumulate at lesion site and promote remyelination in mouse models of chronical demyelination. As a matter of fact, this antibody has recently passed a phase I clinical trial for treatment of MS.
rHIgM22 binds to CNS tissues with a pattern very similar to that of the anti-sulfatide antibody O4, and binding of rHIgM22 is abolished in CNS tissue slices from CST (-/-) mice, suggesting that rHIgM22 binding to myelin requires the presence of a product of cerebroside sulfotransferase, possibly sulfatide. However the exact identity of the antigen recognized by this antibody remains to be elucidated. The binding of rHIgM22 to purified lipids and to lipid extracts from various sources, including wild type, ASM (-/-), CST (+/-) and CST (-/-) mice brains, mouse mixed glial cells (MGC), mouse astrocytes, rat rHIgM22+ oligodendrocytes (OL), rat microglia, and mouse myelin, has been tested using TLC immunostaining assays and SPR experiments with lipid monolayers with different composition.
The results obtained show that rHIgM22 binds to sulfatide, and, to a lesser extent, to lysosulfatide in vitro, while it does not bind to other myelin sphingolipids, including galactosylceramide and sphingomyelin, suggesting that sulfatide at the oligodendrocyte surface might be important for the binding of rHIgM22 to the surface of these cells and to myelin. The binding affinity for both sulfatide and its deacylated derivate is low, even if the binding is specific. On the other hand, our data shows that the binding affinity of rHIgM22 for sulfatide can be modulated by the presence of other lipids suggesting a possible role of the membrane microenvironment in the recognition of the antigen by rHIgM22. In addition, rHIgM22 also reacts with phosphatidic acid, and with an unknown molecule present in lipid extracts from various sources, including CST knock-out mice brains, MGC, and isolated astrocytes and microglia. The exact identity of this antigen has yet to be confirmed but preliminary data suggests it might be a form of phosphatidylethanolamine with a free amino group and multiple hydroxylation in the fatty acid residues. Remarkably, this antigen is also present in the extracts from mixed glial cultures, which do not contain mature O4-positive oligodendrocytes, and also in isolated astrocytes and microglia suggesting that other glial cells in addition to oligodendrocytes might be important in the response to rHIgM22. All this suggests that not only sulfatide, but also other membrane lipids might play a role in the binding of rHIgM22 to oligodendrocytes and other cell types. Moreover, binding of rHIgM22 to intact cells might require a complex molecular arrangement, and, in particular, sulfatide might be part of the functional rHIgM22 antigen localized at the cell surface
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