1,720,975 research outputs found
Elektrische stimulatie van de wand van de abnormale hersenactiviteit om de geassocieerde symptonen te verlichten. Een generische aanpak toegepast bij centrale pijn na een beroerte.
No full textMillions of people worldwide suffer from neurological symptoms that are associated with an abnormal brain cavity (aBC). This aBC is the anatomical result of neuronal loss, mostly after stroke, brain trauma, surgery or infection. The symptomatology is dependent on the location and extent of the aBC.
We hypothesised that electrical stimulation of the aBC wall can alleviate aBC-associated symptoms. This is reasonable, as there is both experimental and clinical evidence that the aBC wall contains viable tissue and that this tissue can be modulated by electrical stimulation.
Our goal was to test this generic hypothesis in a rat model for central post-stroke pain (CPSP), which is a neuropathic pain syndrome that can develop after stroke, typically but not exclusively affecting the sensory thalamus (ST), then named thalamic syndrome. We chose this disorder because it (1) is associated with an aBC; (2) is poorly understood and this work might lend more insight into its mechanisms; (3) currently lacks effective treatment options; and (4) is probably associated with thalamic hyperactivity, which could be treated more effectively by electrical stimulation ES than hypoactivity.
In the presented work, we first reviewed the 5 published rat models and 4 published mouse models for CPSP, and critically appraised the face (symptom similarity), construct (underlying mechanism similarity) and predictive (similarity in effective and non-effective treatments) validity, as well as the robustness and reproducibility. These models mainly rely on sensory changes in response to thermal (heat and cold) and mechanical stimuli, which are presumed to be similar to those observed in CPSP patients. Although every author claims his model to be valid, much room for improvement exists.
Next, we have attempted to replicate and refine 3 of the published CPSP rat models, all lesioning the ST.
In the haemorrhagic model, in which collagenase (a blood-vessel degrading enzyme) is injected in the ST, we found an optimal protocol in terms of injected dose and volume and target coordinates, that evoked contralesional hypersensitivity for cold and heat and decreased motor performance, but did not yield mechanical hypersensitivity (vs. baseline, sham-operated control rats and ipsilesional limb results). However, we could not replicate the thermal hypersensitivity in a larger group with longer follow-up.
In the excitotoxic model, kainate (a potent excitatory amino acid causing neuronal overactivation and eventually cell death) is injected in the ST. When injected directly, we observed very high early mortality due to status epilepticus, anorexia and adipsia. When injected via a previously implanted cannula, mortality was reduced but only motor impairment and no sensory changes were observed (vs. baseline, sham-operated control rats and ipsilesional limb results). Importantly, the presence of seizures unblinded the observer from day 1 until 2 weeks post-injection.
In the electrolytic CPSP rat model, an ST lesion was made electrolytically (by temporarily inserting electrodes and applying a lesioning current). We found a long-lasting motor deficit but no consistent changes in mechanical and thermal sensibility (vs. baseline, sham-operated control rats and ipsilesional limb results)
As this motor deficit was a consistent, long-lasting and easily measurable aBC-associated symptom, we tested our generic hypothesis focused on this symptom.
First, we implanted 3 linear twisted-bipolar electrodes targeting the ventral aBC wall and electrically stimulated electrolytically lesioned rats during motor tests. In a group analysis, we found no improvement of the motor impairment with electrical stimulation ON vs. OFF.
Next, we implanted a custom-made flexible electrode with 7 electrode contacts that opens flower-wise when pushed through a cannula that connects the brain surface with the electrolytic aBC. Electrical stimulation via this electrode resulted in a significant improvement of the motor performance in 2/8 rats (in 2/6 rats that showed a significant motor deficit vs. pre-lesioning) vs. OFF, as assessed with the rotarod test. No motor improvement was observed with electrical stimulation ON vs. OFF when using the ladder rung walking test.
Next, positron emission tomography after injecting a radioactively labelled glucose analogue in rats with electrolytic ST lesions resulted in decreased tracer uptake in the vicinity of the aBC, extending to the ipsilateral primary and secondary sensorimotor cortices and in increased tracer uptake in the central pontine grey and its direct environment vs. sham-operated rats. Moreover, we have measured electrical signals (local field potentials; LFPs) from the aBC wall. LFPs recorded from the aBC wall appear similar to those recorded from intact brain tissue at the same anatomical location, and display a correlation with paw-specific movement.
Further, we have developed and validated new techniques for electrode tip localisation and electrode implantation, based on computed tomography (CT) imaging. They resulted in similar localisation accuracy but higher cost- and time-efficiency, but not in increased implantation accuracy, compared to conventional techniques, respectively. We have also defined the optimal protocol for iodine immersion to increase the internal brain contrast in ex vivo rat brain CT imaging.
Lastly, we have conducted a prospective clinical study in patients with deep brain stimulation (DBS) for obsessive-compulsive disorder. The use of rechargeable stimulators in this very specific population appeared to be effective, applicable and safe and diminished the need for stimulator replacements. We have also conducted histopathological examinations on a brain donated by a 66-year old female with 11 years of DBS in the subthalamic nucleus for Parkinson’s disease, providing the longest histopathological follow-up of DBS in this target, for this indication and of a patient in whom microelectrode recording (MER) was applied. Interestingly, although we confirmed the histopathological changes around the DBS electrodes as observed prior in studies with shorter follow-up, we did not detect significant changes induced by MER electrode passing.
Taken together, our work has laid an interesting and solid foundation for the hypothesis of aBC wall electrical stimulation, which, once optimised in terms of stimulation parameters, stimulation area and electrodes, has the potential of becoming a therapeutic neurosurgical option in patients suffering from aBC-associated symptoms.status: Publishe
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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