121,953 research outputs found
Asymmetric Nature of MscL Opening Revealed by Molecular Dynamics Simulations
Full text linkThe bacterial mechanosensitive channel, MscL, opens in response to elevated membrane tension during osmotic shock. Some mutations, like L17A and V21A, can reduce the activation tension threshold, thus offering an approach to study the mechanism of MscL gating. We employed all-atom molecular dynamics to simulate the L17A, V21A double mutant of MscL under a tension of 30 mN/m. Under these conditions, the closed state initially adopts a funnel-like conformation. Subsequently, five chains of MscL undergo sequential transitions into asymmetric states (S1, S2, etc.). Within its “open” fragment, the S1 state is similar to the expanded state of Methanosarcina acetivorans MscL and has a conductance 10 times lower than the open state. We applied committor analysis and a nonlinear regression model to construct a reaction coordinate for the transition between the closed and the S1 state as a linear combination of interatomic distances and contacts. The main contributions to the reaction coordinate are (1) the disruption of the “cytoplasmic” contact sites between the considered chain and two adjacent chains, (2) the delipidation of the lipid-binding pocket, formed by the I82, V86, and V22 residues, and (3) pulling the two neighboring chains apart via the tension sensors. The free energy profile along the reaction coordinate was calculated using the umbrella sampling approach. The S1 state is approximately 5 kJ/mol more favorable than the closed state under tension. The height of the free energy barrier for the transition toward the S1 state is approximately 10 kJ/mol, which is in reasonable agreement with the corresponding average transition time, estimated to be 133 ± 13 ns. The results and approach can be employed to elucidate the wild-type protein gating mechanism
Electromechanical Analysis of an Asymmetric Piezoelectric/Elastic Laminated Structure: Theory and Experiment
No full textMetamaterials: demonstrating toroidal moment in the frame of classical electrodynamics
No full textWe present electromagnetic metamaterials the resonant response of which cannot be attributed to the excitation of conventional magnetic or charge multipoles and can only be explained by the existence of the induced toroidal dipole
Dual Hierarchy for Gravitational n-body
No full textThe n-body problem is the simulation of pair-wise interactions between n objects. This problem appears in many forms, with the classic example being the modeling of gravitational forces between point masses, necessary for cosmological simulations. Many approximation approaches have been devised to reduce the complexity of this problem.t-SNE is a data visualization method that requires repeatedly solving a variant of the n-body problem. A recent paper (An Efficient Dual-Hierarchy t-SNE Minimization, van de Ruit et. al.) proposes a novel algorithm that outperforms other t-SNE minimization methods on medium-scale datasets. The report proves the viability of a dual-traversal method that uses an embedding tree to emit forces and an independent field tree to collect forces. Because the embedding tree is a Linear-BVH and the field tree is an orthtree built to a fixed depth, the overall algorithm has linear complexity.This thesis demonstrates how the dual-tree approach can be adapted for gravitational n-body simulations. Following this, it measures the performance against similar implementations of other algorithms and shows that while the adapted Dual Hierarchy approach is faster than Barnes-Hut, it is outperformed by the Fast Multipole Method on realistic large-scale cosmological datasets.https://github.com/JacksonCampolattaro/n-body Git repository containing an implementation of the adapted Dual Hierarchy algorithm for Gravitational n-body, as well as implementations of several other common algorithms compared against during benchmarking.Computer Engineerin
A note on mapping class group actions on derived categories
Full text linkLet Xnbe a cycle of n projective lines and Tn a symplectic torus with n punctures. Using the theory of spherical twists introduced by Seidel and Thomas, the author will define an action of the pure mapping class group of Tn on Db(Coh(Xn)). The motivation comes from homological mirror symmetry for degenerate elliptic curves, which was studied by the author with Treumann and Zaslow
Reactions of n,n-dibromobenzenesulfonamide with alcohols and mercaptans, 1971
Full text linkN,N-Dibromobenzenesulfonamide reacts with primary alcohols in a 1:2 molar ratio to yield the esters of the alcohols. The reaction is believed to proceed via a free radical mechanism to generate the reac-tive acylbromide species which then reacts with another mole of the alcohol to yield the ester as the final product. Benzyl alcohol and short chain primary alcohols give the corresponding aldehydes as side reactions. NNDBS reacts with secondary alcohols to give ketones and alpha bromoketones. No reaction takes place with tertiary alcohols. N,N-Dibromobenzenesulfonamide reacts with primary, secondary and tertiary mercaptans to yield the disulfide of the mercaptans in each case. When molecular bromine was used as the brominating agent, the alcohols did not react but the corresponding disulfide was obtained from each mercaptan
Experimental investigation into the effect of substrate clamping on the piezoelectric behaviour of thick-film PZT elements
No full textThis paper details an experimental investigation of the clamping effect associated with thick-film piezoelectric elements printed on a substrate. The clamping effect reduces the measured piezoelectric coefficient, d33, of the film. This reduction is due to the influence of the d31 component in the film when a deformation of the structure occurs, by either the direct or indirect piezoelectric effect. Theoretical analysis shows a reduction in the measured d33 of 62%, i.e. a standard bulk lead zirconate titanate (PZT)-5H sample with a manufacturer specified d33 of 593pC/N would fall to 227.8pC/N. To confirm this effect, the d33 coefficients of five thin bulk PZT-5H samples of 220µm thickness were measured before and after their attachment to a metallized 96% alumina substrate. The experimental results show a reduction in d33 of 74% from 529pC/N to 139pC/N. The theoretical analysis was then applied to existing University of Southampton thick-film devices. It is estimated that the measured d33 value of 131pC/N of the thick-film devices is the equivalent of an unconstrained d33 of 345pC/N
Olfactory space in poetry of N. A. Nekrasov
No full textПоэтика обонятельного пространства рассматривается в связи со спецификой субъектной организации лирики Н.А. Некрасова и особенностями его стиля.The poetics of olfactory space is studied in connection with the specifics of individual organization of N.A. Nekrasov's lyrical text and features of his poetic style. The analysis of a remarkable corpus of his texts helps to single out features of transition of poetic system from realist to symbolist type
On ternary monoid of hypersubstitutions of type ? = (n)
No full textA ternary monoid of hypersubstitutions of type ? = (n) is the set Hyp(n) of all hypersubstitutions of type ? = (n) with a ternary operation which satis es the associative law, and has the identity element ?id . For n = 2 , the idempotent and regular elements, the ideals of submonoids and some algebraic-properties of this monoid were studied by author. In this present paper, we study the algebraic-structural properties of Hyp(n), n > 2 and characterize the idempotent and regular elements. In particular, we describe the relationships between some submonoids of this monoid under the ideal of this submonoids
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