1,720,989 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
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
Studies in Molecular Mechanisms of Skeletal Muscle Contraction: Applications to Transgenic Mice with Inherited Cardiomyopathies
No full textMuscular contraction impacts virtually every physiological function in a human body. Nearly 50% of the body weight is contributed by muscle. Skeletal muscle contraction is responsible for performing every day general functions such as moving, grabbing things and lifting weights. Cardiac muscle contraction is responsible for blood circulation in the body and smooth muscle contraction is involved in the contraction of hollow organs such as lungs, stomach and kidneys. It also maintains body temperature. Central to these events is the transformation of energy derived by hydrolysis of ATP to mechanical force. The force generating steps of muscle contraction is thought to result from the interaction of actin and myosin proteins. Although much of the general knowledge of the mechanism of contraction has been known for over 50 years, emerging advanced techniques have identified some of the key intermediate steps and regulating parameters. My doctoral research involves utilizing one such high resolution technique – single molecule fluorescence spectroscopy. I have used it to discern the motion and conformation of myosin cross-bridges in ex-vivo muscle. When studying the dynamic behavior of actin and myosin it is essential to reduce the number of molecules under observation because 1. The local concentration of actin and myosin is dense and the information obtained by averaging trillions of molecules doesn’t reflect the true character of the process. 2. The trajectory of an enzyme catalyzed reaction cannot be followed and the associated kinetics of actomyosin interaction is lost. 3. The situation becomes worse when studying mutations in sarcomeric proteins with low expression. 4. Heterogeneity between neighboring sarcomeres can be reduced. An important goal of muscle research is to measure the rate of the power stroke. Therefore, part of my thesis is focused on characterizing the pre- and post- power stroke states of muscle contraction. While the extent of force generated during muscle contraction is proportional to the extent of Ca2+ released into the muscle, some of the recent studies have shown that the phosphorylation of the regulatory light chain (RLC) of myosin also modulates contraction. Considering the importance of the phosphorylation of RLC, I investigated the distribution of orientation and kinetics of myosin cross-bridges in phosphorylated and de-phosphorylated muscle. Lastly, I have applied our fluorescence polarization technique with single molecule sensitivity to unravel the deranged contractile properties of muscle in people afflicted with Familial Hypertrophic Cardiomyopathy (FHC) disease.
Some of the significant conclusions drawn from my project include evidence for the existence of distinct pre- and post- power stroke states of myosin cross-bridges during contraction in Ex Vivo muscle, Regulatory Light Chain phosphorylation disturbs cross-bridge organization and enhances the power stroke state of contraction and FHC induced by mutations in Troponin-T protein impairs myosin cross-bridge interaction with actin and alters cross-bridge kinetics. Clinically, drugs can be developed to modulate power stroke and enhance muscle performance in myopathies. Site targeted small molecules (peptides) can now be screened to correct for hypo-contractile or hyper-contractile properties associated with FHC. Our technique may also serve as a diagnosis tool for early identification of FHC disease. Finally increasing the basal ATPase activity of resting muscle by RLC phosphorylation is of therapeutic importance in treating individuals with Obesity, Type II Diabetes and Metabolic syndrome
POWER STROKE OF SKELETAL MUSCLE CROSS-BRIDGES CONTAINING PHOSPHORYLATED AND DE-PHOSPHORYLATED MYOSIN REGULATORY LIGHT CHAIN
No full textPurpose: Muscle contracts by cyclic, ATP-driven, reorientations of myosin cross-bridges while they are interacting with actin. It is widely recognized that during force generating step of this interaction, referred to as a power-stroke, myosin head forms a firm attachment to actin, while the torque is provided by the rotation of myosin neck (a cross-bridge consists of a head plus a neck). During contraction, the Regulatory Light Chain of myosin (RLC), which resides on the neck, gets phosphorylated. An important goal of muscle research is to elucidate the role of phosphorylation during active contraction. We set out to measure how the rate of power stroke is affected by phosphorylation in muscle ex vivo. Methods: The rate can only be established when small number of molecules is investigated. This is accomplished by Confocal Fluorescence Correlation Spectroscopy (CFCS). Results: Phosphorylation of RLC speeds up power stroke from ~0.64/s when RLC is de-phosphorylated to ~1.5/s when it is phosphorylated. Conclusions: Using this technique, we show that the state of phosphorylation of the Regulatory Light Chain (RLC) of myosin has a profound effect on kinetics of ex vivo rabbit psoas cross-bridges during contraction
BIOPHYSICAL STUDIES OF MEMBRANE TOPOLOGY OF HUMAN PRESENELIN-1
No full textPurpose: Alzheimer's disease (AD) afflicts ~5 million Americans. Amyloid (Abeta) plaques accumulate in the brain of patients during AD leading to neurodegeneration. Presenelin-1 (PS1), a trans-membrane protein, acts as the catalytic subunit of gamma-secretase enzyme to cleave amyloid precursor protein (APP) and produce Abeta peptides. Mutations in the PS1 gene have been linked to the pathogenesis of early onset of familial AD (FAD). Recently, it has been reported that PS1 also acts as Ca2+ leak channel on the membrane of endoplasmic reticulum (ER). Currently there are divergent views in the literature on the subunit association and the correct membrane topology of PS1 protein. Considering the several physiological functions and the critical role of PS1 in the pathogenesis of AD, we sought to investigate the membrane topology of PS1 protein through various biophysical studies. Methods: Neuroblastoma (SK-N-SH) cells expressing PS1 protein with NH2-terminal tagged yellow fluorescent protein (YFP-PS1) and COOH-terminal tagged cyano fluorescent protein (PS1-CFP) were used as a model in our studies. Membrane localization and subunit association of PS1 were determined by biophysical assays. Expression and colocalization of YFP-PS1 and PS1-CFP proteins were assessed by confocal imaging. Localization of the N-terminal and C-terminal of PS1 was assessed by fluorescence correlation spectroscopy (FCS). Finally subunit aggregation of PS1 protein was determined by Forster Resonance Energy Transfer (FRET) assay. Results: When cells expressing both PS1-CFP and YFP-PS1 proteins were independently excited and imaged, their respective fluorescence overlapped suggesting co-expression and co-localization of the PS1 subunits. The diffusion coefficient of the PS1 protein in the transmembrane was the same (~0.15µm2/s) when FCS was measured in cells with and without 80% glycerol in 1XPBS indicating that the NH2 and COOH termini are facing the cytosolic side of the plasma-membrane. The quench in the fluorescence lifetime of CFP (donor) in the presence of YFP (acceptor) in FRET assay demonstrates the protein-protein interaction between PS1-CFP and YFP-PS1. Conclusions: Both YFP-PS1 and PS1-CFP chimeric proteins are expressed on the plasma membrane and intracellular membranes with NH2-terminal and COOH-terminal oriented towards the cytosolic side of the membrane. PS1 is a dynamic transmembrane protein which associates as dimer or multimer to form ERCa2+ channel and thus regulates intracellular calcium signaling
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
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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