1,720,978 research outputs found
The role of filament flexibility in the response of a bundle of actin filaments to load in supercritical conditions.
No full textConstant pressure-constant temperature molecular dynamics for rigid and partially rigid molecular systems
No full textThe method of molecular dynamics at fixed pressure and/or temperature is adapted to rigid or partly rigid molecular systems with geometrical constraints using the cartesian coordinate approach. Both isotropic and anisotropic volume fluctuations, allowing for shape variation, are considered. The simulation of a benzene crystal at zero pressure and various temperatures is given as an illustration. © 1985 Taylor and Francis Group, LLC.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Molecular dynamics of rigid systems in cartesian coordinates: A general formulation
No full textinfo:eu-repo/semantics/publishe
The structure of liquid benzene
No full textMolecular dynamics simulation of liquid benzene is exploited to test the degree of sensitivity of the local structure to the intermolecular potential. Three effective potential models (based on a six Lennard-Jones centres potential) are investigated. The usually admitted picture of a liquid with quasi-crystalline short range molecular arrangement is shown to be very doubtful. Analysis of the crystalline structure predicted by the different interaction potentials indicates a manifest superiority of the only model including a point quadrupole at the centre of the benzene ring. © 1983 Taylor & Francis Group, LLC.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
A semi-flexible model prediction for the polymerization force exerted by a living F-actin filament on a fixed wall
No full textWe consider a single living semi-flexible filament with persistence length ℓp in chemical equilibrium with a solution of free monomers at fixed monomer chemical potential μ1 and fixed temperature T. While one end of the filament is chemically active with single monomer (de)polymerization steps, the other end is grafted normally to a rigid wall to mimic a rigid network from which the filament under consideration emerges. A second rigid wall, parallel to the grafting wall, is fixed at distance L < < ℓp from the filament seed. In supercritical conditions where monomer density ρ1 is higher than the critical density ρ1c, the filament tends to polymerize and impinges onto the second surface which, in suitable conditions (non-escaping filament regime), stops the filament growth. We first establish the grand-potential Ω(μ1, T, L) of this system treated as an ideal reactive mixture, and derive some general properties, in particular the filament size distribution and the force exerted by the living filament on the obstacle wall. We apply this formalism to the semi-flexible, living, discrete Wormlike chain model with step size d and persistence length ℓp, hitting a hard wall. Explicit properties require the computation of the mean force f i (L) exerted by the wall at L and associated potential f i (L) = - d W i (L) / d L on a filament of fixed size i. By original Monte-Carlo calculations for few filament lengths in a wide range of compression, we justify the use of the weak bending universal expressions of Gholami et al. [Phys. Rev. E 74, 041803 (2006)] over the whole non-escaping filament regime. For a filament of size i with contour length Lc = (i - 1) d, this universal form is rapidly growing from zero (non-compression state) to the buckling value f b (L c, ℓ p) = π 2 k B T ℓ p 4 L c 2 over a compression range much narrower than the size d of a monomer. Employing this universal form for living filaments, we find that the average force exerted by a living filament on a wall at distance L is in practice L independent and very close to the value of the stalling force F s H = (k B T / d) ln (ρ 1) predicted by Hill, this expression being strictly valid in the rigid filament limit. The average filament force results from the product of the cumulative size fraction x = x (L, ℓ p, ρ 1), where the filament is in contact with the wall, times the buckling force on a filament of size Lc ≈ L, namely, F s H = x f b (L; ℓ p). The observed L independence of F s H implies that x ∝ L-2 for given (ℓ p, ρ 1) and x ∝ ln ρ 1 for given (ℓp, L). At fixed (L, ρ 1), one also has x ∝ ℓ p - 1 which indicates that the rigid filament limit ℓp → ∞ is a singular limit in which an infinite force has zero weight. Finally, we derive the physically relevant threshold for filament escaping in the case of actin filaments.SCOPUS: ar.jinfo:eu-repo/semantics/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
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