1,721,015 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
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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Synaptic transmission and signal processing in the leech central nervous system: Studies including conduction block and laser axotomy
No full textSynaptic transmission and dynamic aspects of signal processing were studied in the leech central nervous system (CNS). Specific questions addressed were: (1) how are synapses distributed between touch sensory cells, (2) can conduction block in presynaptic pressure sensory neurons affect synaptic transmission to different postsynaptic targets, and (3) how are sensory synaptic signals integrated in motoneurons?Chapter I shows that functional electrical synapses between touch (T) sensory neurons are distributed in the ganglion. During conduction block, selective activation of branches of the anterior axon of the presynaptic T cell, for example, produced a synaptic potential 37% of control amplitude, which was consistent with counts of 40% of contacts made by these branches, a distribution also confirmed by laser axotomy. Conduction block can thus modulate electrical synapses within the ganglion by silencing particular contacts between cells.Chapter II shows that naturally occurring conduction block in another sensory neuron, the medial pressure (mP) cell, differentially affects synaptic transmission to three different postsynaptic neurons: the anterior pagoda (AP) cell, the longitudinal (L) motoneuron and the annulus erector (AE) motoneuron. The mP cell was found to have one major receptive field, innervated by a large axon, with contiguous anterior and posterior minor receptive fields, each innervated by a fine axon, all on ipsilateral dorsolateral skin. Exciting only the anterior part of the mP cell during conduction block at the anterior axon's central branch point reduced transmission to the AE cell much more than to the AP or L cells, while exciting only the posterior part of the mP cell during conduction block at the posterior axon's central branch point had the reverse effect. Laser microsurgery and dye-marking of cell pairs confirmed that the anterior branches synapse with the AP and L cells while the posterior branches synapse with the AE cell. Thus, conduction block can act as a switch, so that the mP cell may transmit to only one group of neurons or another, depending upon how it is stimulated.The monosynaptic connection between the mP cell and AE motoneuron mediates reflexive erection of annuli when the leech's dorsal skin is pressed. Chapter III describes, based on laser microsurgery and combined dye staining, how functional synaptic inputs to the AE from each mP sensory neuron are distributed bilaterally. Synaptic potentials sum at the primary axon fork, as confirmed by measurements of impulse timing. The results explain the concerted action of the AE cells to erect complete annuli.</p
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Enhancement of electrical signalling by neuronal morphology: New presynaptic and postsynaptic mechanisms
No full textEffects of neuronal morphology on synaptic transmission and action potential initiation were demonstrated in the nervous system of the leech, where it is possible to record at separate locations from neurons with known morphologies and defined behavioral roles. Specific questions addressed were (1) How do a neuron's morphological and electrical properties influence whether action potentials reverse their direction of propagation, known as reflection? (2) What is the effect of reflection on synaptic transmission? (3) How do reflection and action potential failure influence transmission from a spatially distributed synapse? (4) How does the morphology of a postsynaptic neuron influence firing rate by producing multiple impulse initiation sites?Chapter I describes how action potentials reflect at central axon branch points of pressure mechanosensory neurons (P cells). Reflection operates as a new mechanism to enhance synaptic transmission from a subset of a neuron's branches. Reflection can change with electrical activity, making this enhancement of transmission reversible. Impulses from the periphery activated a synapse, then reflected from a central branch point, and then quickly activated the synapse a second time, greatly increasing transmission by producing facilitation. A compartmental model based on experimental data indicates that reflection can occur for a greater range of membrane morphology than previously thought.Chapter II describes how reflection and action potential failure, or conduction block, at P cell central branch points affect synaptic transmission to the S cell, a neuron essential for a type of nonassociative learning. Reflection at P cell central branch points increased transmission, and conduction block at the same branch points decreased it.Chapter III describes a new mechanism to increase the firing rate of a neuron, initiation of impulses at multiple sites. In the S cell chain, a linear group of strongly electrically coupled neurons, a single skin stimulus evoked synaptic input that initiated impulses at multiple locations. Impulses that arose at different sites initiated at different times, and therefore did not collide, but propagated throughout the chain.Neuronal structure, therefore, can affect signalling by influencing activity in separate sets of presynaptic terminals within a single neuron, and by creating multiple initiation sites that can increase postsynaptic activity.</p
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Neuronal competition for action potential initiation sites in a circuit controlling simple learning
No full textThe spatial and temporal patterns of action potential initiations were studied in a behaving leech preparation to determine the basis of increased firing that accompanies sensitization, a form of non-associative learning requiring the S-interneurons. Little is known at the network level about mechanisms of behavioral sensitization. The S-interneurons, one in each ganglion and linked by electrical synapses with both neighbors to form a chain, are interposed between sensory and motor neurons. In sensitized preparations the strength of shortening is related to S-cell firing, which itself is the result of impulses initiating in several S-cells. Because the S-cells, as independent initiation sites, all contribute to activity in the chain, it was hypothesized that during sensitization, increased multi-site activity increased the chain's firing rate. However, it was found that during sensitization, the single site with the largest initiation rate, the S-cell in the stimulated segment, suppressed initiations in adjacent ganglia. Experiments showed this was both because (1) it received the earliest, greatest input and (2) the delayed synaptic input to the adjacent S-cells coincided with the action potential refractory period. A compartmental model of the S-cell and its inputs showed that a simple, intrinsic mechanism of inexcitability after each action potential may account for suppression of impulse initiations. Thus, a non-synaptic competition between neurons alters synaptic integration in the chain. In one mode, inputs to different sites sum independently, whereas in another, synaptic input to a single site precisely specifies the overall pattern of activity.</p
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