1,720,953 research outputs found
Renal modulation: arginine vasopressin and atrial natriuretic peptide
No full textTotal body water (TBW) is distributed in compartments divided by semi-permeable membranes. In postnatal life, approximately two thirds of TBW is located in the intracellular space and one third is located in the extracellular space. The latter is further divided with a 3:1 ratio in the interstitial and plasma compartments.
Passive equilibration of solutes between body compartments is driven by electrochemical gradients and is mediated by a complex system of transport mechanisms that includes pumps, channels, facilitated carriers and selective paracellular pathways. With few exceptions, water diffuses rapidly across epithelia and cell membranes, following osmotic gradients. High transcellular water transport cannot occur through pure lipid bilayers, as these have low osmotic water permeability (∼0.002 cm/s). Water diffusion through cell membranes is therefore mediated by specific water channels, termed aquaporins (AQPs), which enhance osmotic water permeability by 10–1000 fold. Because solutes diffuse less rapidly than their solvent, the relative water content of body compartments is primarily regulated by their solute distribution. This allows the organism to adjust its TBW distribution by regulating the activity of solute transporters located in biological membranes that separate body compartments.
During early fetal life, TBW represents approximately 90% of body mass. As pregnancy progresses, TBW decreases progressively, to reach 75–80% of body mass at the end of gestation. These changes are primarily due to a decline in extracellular water, while intracellular water increases. In the first 24–48 h after birth, the extracellular compartment further decreases, as a result of a negative fluid balance in the immediate postnatal period.
The fetus constantly regulates its TBW by salt and water exchanges through the placenta membrane. After birth, uptake of water and solutes is limited to gastro-intestinal intakes, while insensible fluid losses increase dramatically. The newborn needs therefore to activate mechanisms that are aimed at controlling water and salt losses. Most of these mechanisms involve the secretion of hormones, which act directly on the kidney. To be efficient, these mechanisms require that sensors, hormone secretion pathways and target organs have reached an appropriate level of maturity.
Water excretion or retention is primarily modulated through the regulation of arginine vasopressin (AVP) secretion. Stimulation of thirst has only limited value in newborns, because of their restricted access to free water and immaturity of the central nervous system.
Salt retention by the kidney is predominantly achieved by activation of the renin-angiotensin-aldosterone system, which is potentiated by endothelins and adrenergic renal nerve activity. Conversely renal salt losses are stimulated by natriuretic peptides (NPs), prostaglandins, kinins, nitric oxide (NO) and adrenomedullin.
In this review, the roles of AVP and NPs in the regulation of body fluid composition during the prenatal and perinatal periods are briefly reviewed. It is important to notice however, that their action is part of a complex network in which all of the above mentioned pathways are synergistically activated or inhibited to maintain body homeostasis
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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