1,720,958 research outputs found
Surface-embedded mechanical and chemical cues modulate neuronal mechanoadaptation in primary hippocampal networks
Get PDFThe possibility of external modulation of neuronal electrical behavior is becoming increasingly valuable and captivating for modern (neuro)medical research. Indeed, exogenous neuromodulation could open to the development of innovative technological tools that, in the field of neuro-engineering, concretize in advanced implantable devices (e.g., active and passive neurostimulators), neuro-prosthesis (e.g., neuro-regenerative scaffolds or synthetic ganglia) or neural interfaces (e.g., brain-machine interfaces). In this framework, there is a rising expectation about the critical role that mechano-chemical artificial cues could play in triggering or temper neuronal activity. This belief is mainly supported by the natural role recognized to extracellular matrix (ECM) physicochemical properties (e.g., stiffness, micro- nano-topography and/or chemical composition) in governing different cellular processes as well as inducing physiological or pathological evolution in tissues. In reason of that, a deeper investigation of the impact of external mechanical and chemical stimuli in regulating neuronal behavior represents a critical necessity in the attempt to govern neuronal behavior in a controlled way.
Therefore, in this study, I exploited functional substrates that aim to recapitulate in a in vitro model the complexity of ECM-mediated mechanochemical cues. Indeed, I studied the effect they have on primary murine neuronal cultures through a multidisciplinary approach.
In the first study, I evaluated the impact of substrate stiffness on primary hippocampal cultures. Specifically, nerve cells were let to develop for 9-10 days-in-vitro interfaced with polyacrylamide (PAA) hydrogels characterized by different “physiological” stiffnesses (Young’s elastic modulus E in the range 1–50 kPa). I investigated the impact of PAA-coupling on neuronal network development and morphology via immunofluorescence experiments, and on its functional aspects exploiting electrophysiological techniques. I focused, in particular, on how the synaptic activity of neuronal cells changes in relation to environmental stiffness. Surprisingly, a drastic reduction in spontaneous network activity was detected when cells were cultured on soft substrates. By treating hippocampal cultures with specific compounds, we hypothesized that this electro-mechanical adaptation is ultimately associated with an altered homeostasis of plasma-membrane cholesterol in interfaced cells.
In a second investigation, I mimicked the contribution of external chemical cues making use of substrates endowing chemical functionalities. For the purpose of the study, I let rat hippocampal neuronal networks develop above glass control, single-layer graphene, and carboxyl-modified graphene substrates. In this case, the morphological and functional network adaptation was also evaluated through immunofluorescence and electrophysiology experiments, respectively. Furthermore, the study has taken advantage of advanced nano-microscopy techniques (i.e., Atomic Force Microscopy, and Total Internal Reflection Microscopy) to investigate the different surface chemistry’s impact on focal adhesions organization and neuronal cell stiffness. My results demonstrated that, compared to glass controls, pristine graphene and functionalized graphene substrates induce an opposite effect on the spontaneous electrical activity of interfaced cells: an enhancement in the first case, a reduction in the latter.
Finally, in the attempt to evaluate the synergic contribution of ECM mechanical and chemical cues, primary hippocampal neurons were grown on three-dimensional carbon nanotubes (CNTs) foams where specific chemical functionalizations were introduced with the intent to modify substrate stiffness and introduce neuronal-specific responses in the interfaced network. In these preliminary experiments, I evaluated the neuronal network morphology uncovering a significantly different adaptation induced by pristine and functionalized CNTs foams in the form of cell distribution, elongation and orientation. Furthermore, from a functional point of view, I monitored neuronal functionality in terms of spontaneous calcium oscillations. I highlighted an increased calcium activity in cells developed above the stiffer functionalized CNTs compared to the pristine ones
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
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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