372 research outputs found
Notules sur Emptiness: A Double Comic Strip de Bharath Murthy
No full textÀ travers ces 12 notules je cherche à montrer comment l’auteur Bharath Murthy a su développer une BD « scientifique » ici plus concrètement philosophique sur le la présence-absence d’une essence appelée « âme » (ou « moi », « soi », « dieu », etc.) dans la tradition occidentale et réaffirmée jusque dans l’IA par certains, et déconstruite par l’« emptiness » aporétique bouddhique en utilisant les techniques spécifiques de la bande dessinée procurées par le texte et l’image (du bleed à la graphiation).Through these 12 “footnotes” I try to show how the author Bharath Murthy has been able to develop a "scientific" comic strip, here more concretely a philosophical one, on the presence-absence of an essence called "soul" (or "self", "self", "god", etc.) in the Western tradition and reaffirmed in AI by some, and deconstructed by the Buddhist aporetic "emptiness", using the specific techniques of comics provided by the text and the image (from bleed to graphiation)
A fast method of comparing protein structures
No full textAbstractComparative studies on protein structures form an integral part of protein crystallography. Here, a fast method of comparing protein structures is presented. Protein structures are represented as a set of secondary structural elements. The method also provides information regarding preferred packing arrangements and evolutionary dynamics of secondary structural elements. This information is not easily obtained from previous methods. In contrast to those methods, the present one can be used only for proteins with some secondary structure. The method is illustrated with globin folds, cytochromes and dehydrogenases as examples
Dynamic rheology of capsule suspension: the role of unsteady capsule dynamics and multiparticle interaction
No full textThree-dimensional numerical simulations using immersed-boundary methods are performed to study the rheology of capsule suspensions. Two well-known dynamics of the capsules are the tank-treading and tumbling motions. The motivation of the thesis is twofold: first, to study the micro-macro link between the individual cell dynamics and the rheology of the cell suspension under a dilute condition, and, second, to extend the analysis to a dense suspension in which the multi-body interaction also contributes to the suspension rheology. A recent theoretical study in the limit of small deformation, supported by experimental work, suggested that the effective viscosity of a vesicle suspension in dilute limit exhibits a singularity in the form of a viscosity minimum at the threshold of the transition between the tank-treading and the tumbling motion. In the first part of the thesis, we extend this study to the dilute suspension of capsules undergoing large deformation. The objective here is to relate the time- dependent rheology with the time-dependent capsule dynamics, and study the role of the tank-treading-to- tumbling transition. We find that the time-averaged rheology obtained for the non-spherical capsules undergoing the unsteady motion is qualitatively similar to that obtained for the spherical capsules undergoing the steady tank-treading motion, and that the tank-treading-to-tumbling transition has only a marginal effect. The time-averaged rheology exhibits a shear viscosity minimum when the capsules are in a swinging motion at high shear rates but not at low shear rates unlike that of a vesicle suspension which exhibits a shear viscosity minimum at the point of transition. In the second part, we extend our study to dense suspension of initially spherical capsules. We find that the shear viscosity minimum gradually diminishes with increasing capsule volume fraction. We explain this result by decomposing the particle shear stress into elastic and viscous components. The elastic component is observed to increase but the viscous component remains constant with respect to increasing volume fraction. It is also shown that the elastic contribution is shear-thinning, but the viscous contribution is shear-thickening. The deformation and orientation dynamics of the capsules in dense suspension are also presented. Non-trivial results for the normal stress differences and particle pressure are also analysed.Ph. D.Includes bibliographical referencesIncludes vitaby Ram Chandra Murthy Kallur
Dynamics and rheology of a dilute suspension of elastic capsules
No full textThree-dimensional numerical simulations using front-tracking method are considered to study the dynamics and rheology of a suspension of elastic capsules in linear shear flow over a broad range of viscosity contrast (ratio of internalto- external fluid viscosity), shear rate (or, capillary number), and aspect ratio. First, we focus on the coupling between the shape deformation and orientation dynamics of capsules, and show how this coupling influences the transition from the tank-treading to tumbling motion. At low capillary numbers, three distinct modes of motion are identified: a swinging or oscillatory (OS) mode at a low viscosity contrast in which the inclination angle θ(t) oscillates but always remains positive; a vacillating-breathing (VB) mode at a moderate viscosity contrast in which θ(t) periodically becomes positive and negative, but a full tumbling does not occur; and a pure tumbling mode (TU) at a higher viscosity contrast. At higher capillary numbers, three types of transient motions occur, in addition to the OS and TU modes, during which the capsule switches from one mode to the other as (i) VB to OS, (ii) TU to VB to OS, and (iii) TU to VB. It is shown that the coupling between the shape deformation and orientation is the strongest in the VB mode. The numerical results are compared with the theories of Keller and Skalak, and Skotheim and Secomb. Significant departures from the two theories are discussed and related to the strong coupling between the shape deformation, inclination, and transition dynamics. We then address the rheology of a dilute suspension of liquid-filled elastic capsules. We consider capsules of spherical resting shape for which only a steady tank-treading motion is observed. It is shown that the suspension exhibits a shear viscosity minimum at moderate values of the viscosity ratio, and high capillary numbers. The normal stress differences are shown to decrease with increasing capillary number at high viscosity ratios. Such non-trivial results can neither be predicted by the small-deformation theory, nor can be explained by the capsule geometry alone. Physical mechanisms underlying these novel results are studied by decomposing the particle stress tensor into a contribution due to the elastic stresses in the capsule membrane, and a contribution due to the viscosity differences between the internal and suspending fluids. It is shown that the elastic contribution is shear-thinning, but the viscous contribution is shear-thickening. The coupling between the capsule geometry, and the elastic and viscous contributions is analysed to explain the observed trends in the bulk rheology.M.S.Includes bibliographical referencesby Ram Chandra Murthy Kallur
Aktivitet: Co-author of Chapter 19 of the book "Maintenance of Complex Systems"
No full textCo-author of Chapter 19 of the book "Maintenance of Complex Systems" Edited by Prof DNP Murthy and Khairy Kobbacy, by Springers</p
Molecular dynamics studies on the domain swapped <i>Salmonella typhimurium</i> survival protein SurE: insights on the possible reasons for catalytic cooperativity
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