1,721,040 research outputs found
B cell receptor endocytosis induced by divalent or multivalent ligands differs in human Naïve and Memory B cells
Full text linkAntigen binding to the B cell antigen receptor (BCR) initiates endocytosis, which represents the first step of antigen processing and presentation to helper T cells. The receptor crosslinking model (CLM), in which BCRs freely diffuse on the cell surface and are clustered after multivalent antigen binding, was considered for a long time the only mechanism responsible for lymphocyte activation and BCR- antigen complex endocytosis. Recently, a different model of B cell activation, called dissociation- activation model (DAM), was described. In the DAM model, BCRs are organized in auto-inhibiting oligomers that, subsequently to antigen binding, dissociate and become activated. Here we investigated BCR endocytosis in human B cells by a novel flow cytometric assay making use of monoclonal antibodies (mAbs) for ligating surface Igs. We found that the binding of mAbs, a situation that might perhaps reproduce the DAM model of BCR activation, induced significant BCR endocytosis in naïve, IgM+ memory and switched B cells. Crosslinking of mAb-coated BCRs with F(ab’)2 goat-anti-mouse IgG (GAMIgG), which putatively reproduces the CLM model of activation by multivalent antigens, increased BCR endocytosis in all B cell subsets. Interestingly, when endocytosis was sequentially induced by DAM (addition of Ig-specific mAb and first step at 37°C) and then by CLM (addition of GAMIgG and second step at 37°C), a model defined as “double triggering”, nearly 100% endocytosis was obtained in switched memory but not in the other B cell subsets, suggesting distinctive features of BCR activation and endocytosis in these subsets. Thus, exploiting mAbs rather than the commonly used polyclonal antibodies for ligating surface Igs provides a simple and accurate way for the analysis of BCR endocytosis potentially useful for untangling the interplay of CLM and DAM
Innovative Surface Elements for Space Exploration: a Lunar Tractor and its Family of Trailers
No full textTechno-functional analysis of small recycled flakes from Late Acheulian Revadim (Israel) demonstrates a link between morphology and function
No full textRevadim is a multi-layered Late Acheulian site in the Levant which has yielded rich lithic assemblages comprising dozens of handaxes, as well as many thousands of other items, mostly flakes. The techno-functional study presented here focuses on Layer C3, the densest layer at the site in terms of flint artefacts and animal bones. The lithic assemblage is characterized by an intense production of flakes, including a specific lithic recycling trajectory oriented towards the production of small flakes from existing flakes (Cores-On-Flakes). In this study, two categories of artefacts are sampled: the flakes used as cores for the production of new blanks (termed here COF-FFs) and the small flakes produced from them (termed BPFCs or products of recycling). Use-wear analysis conducted mainly at a low magnification, combined with residue analysis and a typo-technological characterization of the artefacts demonstrated that the small flakes produced from these COF-FFs were the desired end-products of this lithic trajectory, with a rather high percentage of used items while the COFs were rarely used, confirming their role as cores. The characterization of the used edges suggests a correlation between the activities performed and the different types of small flakes produced. Our results demonstrate the existence of a well-defined link between small flakes form and functionality, highlighting the capability of the Revadim Lower Paleolithic hominins to produce artifacts with pre-determined size, morphology, and specific utilizable edge features, suitable for the execution of anticipated targeted tasks
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
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
Validità del Chronic Pain Acceptance Questionnaire per identificare sottogruppi clinicamente significativi di pazienti con endometriosi
No full textIl Chronic Pain Acceptance Questionnaire (CPAQ) misura due dimensioni che contribuiscono alla “flessibilità psicologica”: Activity Engagement (AE) e Pain Willingness (PW). L’obiettivo del presente studio è esplorare la validità di entrambe le dimensioni nell’identificare sottogruppi significativi di donne affette da endometriosi. ¬
298 donne affette da endometriosi hanno compilato il CPAQ e misure indaganti la Qualità di Vita (QdV) e il benessere psicologico (PWB).
Le analisi di cluster effettuate rilevano tre sottogruppi di pazienti sulla base dei punteggi al CPAQ (Alto-AE/Alto-PW, basso-AE/basso-PW, e alto-AE/alto-PW). Le Analisi di Covarianza, controllando per variabili cliniche e sociodemografiche, hanno dimostrato che questi tre gruppi differiscono significativamente in QdV e in PWB.
I risultati del presente studio supportano la validità di entrambe le dimensioni del CPAQ nell’identificare pazienti a rischio di sviluppare un peggior adattamento alla endometriosi
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
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