1,721,139 research outputs found
Scher-induzierte Phänomene eines kollabierten Polymers
No full textA fundamental understanding of the dynamical behavior of biopolymers under
non-equilibrium conditions is essential to the investigation of biological
systems on the microscopic scale. The blood clotting protein von Willebrand
factor presents a prominent example of current biophysical research on the
relationship between structural and functional properties of multimeric
proteins under flow conditions with the aim to explain and predict complex
biological processes. The present thesis theoretically investigates several
non-equilibrium phenomena associated with collapsed biopolymers in shear flow.
Specifically, we explore shear-induced dynamics, adsorption, unfolding,
activation, and degradation of von Willebrand factor and associated polymeric
systems by means of Brownian hydrodynamics simulations using coarse-grained
models. We first examine the dynamics and adsorption behavior of a single
collapsed homopolymer globule on homogeneous and inhomogeneous surfaces in
shear flow. Dynamic state diagrams as a function cohesion, adhesion, and shear
rate feature distinct dynamical adsorbed states being classified into rolling
and slipping states, globular and coil-like states, as well as isotropic and
prolate states. We observe stick-roll motion for highly corrugated
inhomogeneous surface potentials due to high lateral surface friction. Despite
low drift velocities and reduced hydrodynamic lift forces on such
inhomogeneous surfaces that are entirely based on energy-conserving pair
potentials, a shear-induced adsorption is not found. Second, we study
adsorption of a globule under shear on smooth surfaces with stochastic
surface-monomer bonds whose two-state kinetics is characterized by the bond
formation rate, bond dissociation rate and an effective catch bond parameter
describing how force acting on a bond influences the dissociation rate.
Constructing adsorption state diagrams as a function of shear rate and all
three bond parameters, we find shear-induced adsorption in a small range of
parameters for low dissociation and association rates and only when the bond
is near the transition between slip and catch bond behavior. We argue that
more elaborate potential-based models are necessary to observe catch bond
behavior that allow for shear-induced surface adsorption phenomena. Third, we
show that the internal tension distribution along the contour of a globule in
shear flow is inhomogeneous and above a threshold shear rate exhibits a
double-peak structure. We argue that these tension maxima close to the termini
of the polymer chain reflect the presence of polymeric protrusions and
establish the connection to shear-induced globule unfolding. By means of
heuristic scaling laws and an quasi-equilibrium theory, simulation results of
average protrusion lengths and maximal tensions are analyzed. Our results are
used to explain experimental data for the shear-sensitive enzymatic
degradation of collapsed biopolymers. In particular, we relate the cleavage
rate of von Willebrand factor in blood plasma to the probability of single
cleavage sites to be accessible for the protease.Ein fundamentales Verständnis des dynamischen Verhaltens von Biopolymeren
unter Nicht-Gleichgewichtsbedingungen ist essentiell für die Untersuchung
mikroskopischer biologischer Systeme. Das Blutgerinnungsprotein von-
Willebrand-Faktor ist ein bedeutendes Beispiel für aktuelle biophysikalische
Forschung über die Beziehung zwischen strukturellen und funktionellen
Eigenschaften von multimeren Proteinen unter Flussbedingungen mit dem Ziel
komplexe biologische Prozesse erklären und vorhersagen zu können. Die
vorliegende Arbeit untersucht theoretisch verschiedene Nicht-
Gleichgewichtsphänomene im Zusammenhang mit kollabierten Biopolymeren im
Scherfluss. Insbesondere erforschen wir scher-induzierte Dynamik, Adsorption,
Entfaltung, Aktivierung und Degradation des von-Willebrand-Faktors und
ähnlichen Polymersystemen mittels Brownscher-Hydrodynamik-Simulationen und
grobkörnigen Modellen. Erstens untersuchen wir die Dynamik und das
Adsorptionsverhalten eines kollabierten Homopolymer-Globules an homogenen und
inhomogenen Oberflächen im Scherfluss. Die erfassten dynamischen
Zustandsdiagramme als Funktion von Kohäsion, Adhäsion und Scherrate weisen
unterschiedliche dynamische, adsorbierte Zustände auf, welche in rollende und
gleitenden, globuläre und gewundene sowie isotrope und prolate Zustände
klassifiziert werden. Stark gewellte, inhomogene Oberflächenpotentiale führen
zu einer Anhaft-Roll-Bewegung aufgrund hoher Oberflächenreibung. Obwohl diese
inhomogenen Oberflächen basierend auf konservativen Paarpotentialen zu
geringen Driftgeschwindigkeiten und schwacher hydrodynamischer Liftkraft
führen, wird keine scher-induzierte Adsorption beobachtet. Zweitens studieren
wir die Adsorption eines Globules im Scherfluss an glatten Oberflächen mit
stochastischen Oberflächen-Monomer-Bindungen, deren Kinetik durch zwei
Zustände und entsprechende Raten für Assoziation und Dissoziation von
Bindungen sowie eines effektiven Catch-Bindungsparameters, der den Einfluss
von Kraft auf die Dissoziation bestimmt, charakterisiert ist. Wir konstruieren
Adsorptions-Zustandsdiagramme als Funktion der Scherrate und den drei
Bindungsparametern und entdecken scher-induzierte Adsorption in einem kleinen
Parameterbereich niedriger Assoziations- und Dissoziationsraten und nur für
Bindungen nahe dem Übergang von Slip- zu Catch-Bindungsverhalten. Wir zeigen,
dass kompliziertere potentialbasierte Modelle nötig sind, um Catch-Bindungen
zu erhalten, die scher-induzierte Oberflächenadsorption erlaubt. Drittens
zeigen wir die inhomogene, interne Spannungsverteilung entlang der Kontour
eines Globules im Scherfluss, welche über einer Grenzscherrate eine Doppel-
Peak-Strukture aufweist. Spannungsmaxima nahe der Polymerenden sind auf die
Existenz von Polymer-Protrusionen zurückzuführen, wobei der Zusammenhang mit
scher-induzierter Globule-Entfaltung hergestellt wird. Mittels heuristischer
Skalengesetze und einer Quasigleichgewichtstheorie werden mittlere
Protrusionslängen und maximale Spannungen analysiert. Unsere Ergebnisse werden
genutzt, um experimentelle Daten von scher-sensitiver enzymatischer
Degradation von kollabierten Biopolymeren zu erklären. Insbesondere wird die
Spaltungsrate des von-Willebrand-Faktors in Blutplasma mit der der
Wahrscheinlichkeit zugänglicher Spaltungsstellen für die Protease in
Verbindung gesetzt
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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