1,721,127 research outputs found
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
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Investigating protein condensation in ligand mediated cell signaling
No full textT cells discriminate between foreign agonist- and self-antigen peptides presented on Major Histocompatibility Complexes (MHC) proteins that bind to T-cell Receptors (TCRs). Mimicking this process is difficult in vivo due to the monoclonal activity of pMHC. To overcome this, antibodies are commonly used to activate T-cells via conserved regions of the TCR. However, antibodies bind TCRs strongly and activate T-cells via a different mechanism than pMHC binding. We previously reported the binding capabilities of a Fab’-DNA ligand that mimics strong TCR agonists and only activates T-cells when tethered to a supported lipid bilayer. To mimic native pMHC, we created a panel of a human antiCD3 -fab’ (OKT3-Fab’) that more closely mimic native pMHC binding kinetics, but in a polyclonal manner. Single molecule characterization via total internal reflection fluorescence (TIRF) is used to determine dwell times and measure diffusion characteristics. Potential uses for these ligands include measuring the activation of human primary T-cells. Following activation, adapter proteins including growth factor receptor bound protein 2 (Grb2) and son of sevenless (SOS) are recruited to the lipid bilayer. Two-dimensional protein condensation phase transitions on the membrane driven by tyrosine phosphorylation have been identified in several receptor signaling systems, including T cell receptor via the Linker for the Activation of T-cells (LAT) that contains a tyrosine sites and Epidermal Growth Factor Receptor (EGFR) that contains tyrosine sites on the cytoplasmic tail. In the cases of both LAT and EGFR, we have found that the receptor scaffold and Grb2 are sufficient to form a membrane surface condensate in reconstituted systems using supported bilayer membranes. Furthermore, phosphorylation at the Y160 residue on Grb2 is sufficient to block this condensation. To follow up on these reconstitution results in live cells, we investigated Grb2 mediated phase condensation in epithelial cells. CHO cells, a type of epithelial cell with a low expression of Grb2 and no endogenous EGFR, were transfected with various Grb2 mutants and EGFR-eGFP. Clustering of EGFR was observed with all Grb2 dimer mutants, suggesting EGFR clustering is not mediated solely through the Grb2:Grb2 dimer interaction. However, EGFR clustering was prevented with a mutant that blocks the Grb2:SOS interaction. EGFR clustering was recovered with larger amounts of this mutant, suggesting that the Grb2:Grb2 dimer plays a role in EGFR clustering under certain conditions
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Mapping Input-Response Function of Early T Activation
Get PDFCells integrate signals from environmental inputs to regulate cellular programming, such as protein production, differentiation, and proliferation. This cellular decision making process occurs across multiple time and length scales, during which a cascade of biochemical reactions transduces signal from inputs to a functional outcome. T cells are a prototypical example of cells that make activation decisions based on discriminating a low level of agonist ligands, which is a peptide fragment presented on Major Histocompatibility Complex (pMHC). In recent years it has become evident that only a handful of ligands are sufficient to activate T cells to secrete cytokines or cytotoxic granules. In this low density pMHC regime, the sequence of T cell receptor (TCR) binding events that a T cell collects is highly stochastic, and the physical mechanism of input integration that overcomes the noise and accurately translates the signal remains unknown.This work investigates the molecular processes underlying how T cell input integration results in a cellular activation outcome. First, an imaging assay based on a live cell-supported membrane platform is introduced to directly observe the sequence of single molecule pMHC:TCR bindings (inputs) and the presence of ligand:receptor:kinase complexes. Titrations of pMHC densities are performed to study the effect of initial binding events on subsequent binding events. Similar measurements were extended to auto-reactive human T cells to compare their binding affinities to normal human T cells. We further map the sequence of pMHC:TCR binding events to early T cell activation, as read out by the translocation of the transcription factor NFAT. Results from the input-outcome assay indicates that T cells may coordinate input accumulation. We then investigate protein assemblies as a potential mechanism of coordinated input accumulation. This work highlights the common feature of spatiotemporally coordinated input accumulation as a general design principle in cellular decision making
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
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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Molecular stochaticity in mammalian cell signaling: Lipid membrane organization and CaMKII kinetics
Get PDFMolecular processes viewed at the single molecule level are stochastic and living cells are full of stochastic processes. Cellular processes frequently occur with a discrete number of molecules and understanding the stochastic behavior of them is of fundamental importance. Here, I studied physical chemistry of two important molecular species in cells: the lipid and the protein. On the subject of lipids, I studied miscibility phase structure of the live cell membrane. Observations of liquid-liquid miscibility phase transition in ternary mixture membranes with hypothetical existence of heterogeneous membrane domains in mammalian cells caused hypothesis of immiscible domains in live cell membranes. Discussion on the subject is often misleading when the discussion is only focused on the qualitative picture of domain existence, but does not consider the physical principles behind it. The question is where in the phase diagram the living cell membrane is poised. To address this question directly I observed physical parameters of the live cell membrane as a function of temperature and I conclude that the live cell membrane is poised reasonably far from the transition temperature. I also discuss the lack of direct evidence for miscibility phase structures playing an important role in actual signaling and the implication of criticality in membrane reactions.On the subject of protein, I studied kinetics of CaMKII, a major protein involved in hippocampal synaptic plasticity. CaMKII holoenzyme has a complex structure comprising of twelve subunits and as a molecular component in a neuronal signaling network, this complex structure allows the enzyme to carry out complicated functions. Using a recently solved x-ray crystallographic structure of the CaMKII holoenzyme, I have modeled the relationship between docked-extended states equilibrium and the calcium frequency response of CaMKII. Stochastic kinetics simulations show that CaMKII frequency response can be fine-tuned by adjusting the equilibrium constant. I also show for the first time, activation dependent subunit exchange of CaMKII dodecamer using single molecule TIRF microscopy. This strongly supports the hypothesis that the CaMKII dodecamer, with its continuous turnover of subunits, can serve as a form of molecular memory
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