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It is thought that the magnitude of residual force enhancement (RFE) is not affected by stretch velocity. However, the range of stretch velocities studied in previous investigations has been limited to slow and moderate velocities. High velocities of muscle stretching are associated with a loss of force and incomplete cross-bridge attachment to actin, thus creating a unique set of eccentric conditions referred to as slippage. The purpose of this study was to extend the relationship between stretch velocity and RFE to high velocities. We hypothesized that slippage at high velocities might affect RFE. We stretched cat soleus muscles for 4 mm to the plateau of the force-length relationship at speeds of 2, 4, 8, 16, 32, 64 mm/s to induce RFE, and slippage for the fastest condition. For each RFE test, a corresponding isometric reference test was conducted. Residual force enhancement was quantified as the relative increase in isometric steady state force between the experimental stretch and the isometric reference tests. Residual force enhancement was similar for all stretch speeds, as expected, with the exception of the fastest speed (64 mm/s), which was associated with slippage and no significant RFE. These results suggest that if stretch speeds are too fast, and are associated with slippage, RFE is abolished. We conclude from these findings that proper cross-bridge engagement is required during eccentric muscle action to produce RFE.

Thermoplastic tapes are commonly processed by the rapid and efficient stamp forming process. During this forming process, the individual unidirectional tapes of the composite stack move relative to each other and relative to the surface of the tool while being in contact with the corresponding counterpart. As a result, the material exhibits a certain resistance against this movement, which is generally dependent on velocity, normal pressure, and temperature. Therefore, this work investigates the ply/tool and ply/ply slippage of unidirectional, carbon fiber reinforced polycarbonate tapes and provides an alternative implementation of the experimentally observed slippage using cohesive zone modeling. The backbone of the modeling approach is an experimental data set obtained from pull-through experiments. In comparison to common slippage or friction theories, the force plateau of thermoplastic UD tapes at elevated temperatures is observed after an initial force peak has been overcome. For both configurations, ply/tool and ply/ply, a reduction of the initial force peak was observed for increasing temperature. Furthermore, the resulting plateau force value is at least 36% higher in the ply/ply configuration compared to the ply/tool configuration at 200 °C. The derived cohesive zone model allows for accurate modeling of the initial force peak and the plateau.

The flow of water in carbon nanochannels has defied understanding thus far 1 , with accumulating experimental evidence for ultra-low friction, exceptionally high water flow rates and curvature-dependent hydrodynamic slippage 2 – 5 . In particular, the mechanism of water–carbon friction remains unknown 6 , with neither current theories 7 nor classical 8 , 9 or ab initio molecular dynamics simulations 10 providing satisfactory rationalization for its singular behaviour. Here we develop a quantum theory of the solid–liquid interface, which reveals a new contribution to friction, due to the coupling of charge fluctuations in the liquid to electronic excitations in the solid. We expect that this quantum friction, which is absent in Born–Oppenheimer molecular dynamics, is the dominant friction mechanism for water on carbon-based materials. As a key result, we demonstrate a marked difference in quantum friction between the water–graphene and water–graphite interface, due to the coupling of water Debye collective modes with a thermally excited plasmon specific to graphite. This suggests an explanation for the radius-dependent slippage of water in carbon nanotubes 4 , in terms of the electronic excitations of the nanotubes. Our findings open the way for quantum engineering of hydrodynamic flows through the electronic properties of the confining wall. The quantum contribution to friction enables the rationalization of the peculiar friction properties of water on carbon surfaces, and in particular the radius dependence of slippage in carbon nanotubes.

Strain engineering is a promising method to manipulate the electronic and optical properties of two-dimensional (2D) materials. However, with weak van der Waals interaction, severe slippage between 2D material and substrate could dominate the bending or stretching processes, leading to inefficiency strain transfer. To overcome this limitation, we report a simple strain engineering method by encapsulating the monolayer 2D material in the flexible PVA substrate through spin-coating approach. The strong interaction force between spin-coated PVA and 2D material ensures the mechanical strain can be effectively transferred with negligible slippage or decoupling. By applying uniaxial strain to monolayer MoS 2 , we observe a higher bandgap modulation up to ~300 meV and a highest modulation rate of ~136 meV/%, which is approximate two times improvement compared to previous results achieved. Moreover, this simple strategy could be well extended to other 2D materials such as WS 2 or WSe 2 , leading to enhanced bandgap modulation. Strain engineering is a promising method to manipulate properties of two-dimensional (2D) materials but slippage between material and substrate makes strain transfer inefficient. Here the authors overcome slipping effects by encapsulating a 2D material in a polymer substrate.

We present the first in-depth empirical characterization of the costs of trading on a decentralized exchange (DEX). Using quoted prices from the Uniswap Labs interface for two pools -- USDC-ETH (5bps) and PEPE-ETH (30bps) -- we evaluate the efficiency of trading on DEXs. Our main tool is slippage -- the difference between the realized execution price of a trade, and its quoted price -- which we breakdown into its benign and adversarial components. We also present an alternative way to quantify and identify slippage due to adversarial reordering of transactions, which we call reordering slippage, that does not require quoted prices or mempool data to calculate. We find that the composition of transaction costs varies tremendously with the trade's characteristics. Specifically, while for small swaps, gas costs dominate costs, for large swaps price-impact and slippage account for the majority of it. Moreover, when trading PEPE, a popular 'memecoin', the probability of adversarial slippage is about 80% higher than when trading a mature asset like USDC. Overall, our results provide preliminary evidence that DEXs offer a compelling trust-less alternative to centralized exchanges for trading digital assets.

Transcriptional slippage (TS) is used by RNA viruses as another strategy to maximize the coding information in their genomes. This phenomenon is based on a peculiar feature of viral replicases: they may produce indels in a small fraction of newly synthesized viral RNAs when transcribing certain motifs and then produce alternative proteins due to a change of the reading frame or truncated products by premature termination. Here, using plant-infecting RNA viruses as models, we discover cases expanding on previously established features of plant virus TS, prompting us to reconsider and redefine this expression strategy. An interesting conclusion from our study is that TS might be more relevant during RNA virus evolution and infection processes than previously assumed.

An optimization framework for upward jumping motion based on quadratic programming (QP) is proposed in this paper, which can simultaneously consider constraints such as the zero moment point (ZMP), limitation of angular accelerations, and anti-slippage. Our approach comprises two parts: the trajectory generation and real-time control. In the trajectory generation for the launch phase, we discretize the continuous trajectories and assume that the accelerations between the two sampling intervals are constant and transcribe the problem into a nonlinear optimization problem. In the real-time control of the stance phase, the over-constrained control objectives such as the tracking of the center of moment (CoM), angle, and angular momentum, and constraints such as the anti-slippage, ZMP, and limitation of joint acceleration are unified within a framework based on QP optimization. Input angles of the actuated joints are thus obtained through a simple iteration. The simulation result reveals that a successful upward jump to a height of 16.4 cm was achieved, which confirms that the controller fully satisfies all constraints and achieves the control objectives.

Superfast water transport discovered in graphitic nanoconduits, including carbon nanotubes and graphene nanochannels, implicates crucial applications in separation processes and energy conversion. Yet lack of complete understanding at the single-conduit level limits development of new carbon nanofluidic structures and devices with desired transport properties for practical applications. Here, we show that the hydraulic resistance and slippage of single graphene nanochannels can be accurately determined using capillary flow and a novel hybrid nanochannel design without estimating the capillary pressure. Our results reveal that the slip length of graphene in the graphene nanochannels is around 16 nm, albeit with a large variation from 0 to 200 nm regardless of the channel height. We corroborate this finding with molecular dynamics simulation results, which indicate that this wide distribution of the slip length is due to the surface charge of graphene as well as the interaction between graphene and its silica substrate.

Gaseous flow regimes through tight porous media are described by rigorous application of a unified Hagen–Poiseuille-type equation. Proper implementation is accomplished based on the realization of the preferential flow paths in porous media as a bundle of tortuous capillary tubes. Improved formulations and methodology presented here are shown to provide accurate and meaningful correlations of data considering the effect of the characteristic parameters of porous media including intrinsic permeability, porosity, and tortuosity on the apparent gas permeability, rarefaction coefficient, and Klinkenberg gas slippage factor.

The limits of dislocation-mediated metal plasticity are studied by using in situ computational microscopy to reduce the enormous amount of data from fully dynamic atomistic simulations into a manageable form. Probing plasticity limits of metals Fully dynamic atomistic simulations of plastic deformation in metals are so computationally demanding that materials physicists have instead developed mesoscale proxies to model dislocation dynamics. In this paper, Vasily Bulatov and colleagues take on the challenge of modelling metal plasticity at the atomic level. Such simulations require models that contain many millions of atoms (the largest simulation in this study contains 268 million atoms), and algorithms are used to process the datasets down to a volume that allows human interpretation. The authors probe ultrahigh-strain-rate deformation in body-centred-cubic tantalum, a model metal, to investigate the limits of metal plasticity. They show that at certain limiting conditions, dislocations can no longer relieve metal loading and twinning takes over. At a strain rate lower than this limit, flow stress and dislocation density achieve a steady state and a sort of metal kneading is observed. The simulations support previous proposals of the maximum dislocation density that can be reached before a metal collapses. Ordinarily, the strength and plasticity properties of a metal are defined by dislocations—line defects in the crystal lattice whose motion results in material slippage along lattice planes 1 . Dislocation dynamics models are usually used as mesoscale proxies for true atomistic dynamics, which are computationally expensive to perform routinely 2 . However, atomistic simulations accurately capture every possible mechanism of material response, resolving every “jiggle and wiggle” 3 of atomic motion, whereas dislocation dynamics models do not. Here we present fully dynamic atomistic simulations of bulk single-crystal plasticity in the body-centred-cubic metal tantalum. Our goal is to quantify the conditions under which the limits of dislocation-mediated plasticity are reached and to understand what happens to the metal beyond any such limit. In our simulations, the metal is compressed at ultrahigh strain rates along its [001] crystal axis under conditions of constant pressure, temperature and strain rate. To address the complexity of crystal plasticity processes on the length scales (85–340 nm) and timescales (1 ns–1μs) that we examine, we use recently developed methods of in situ computational microscopy 4 , 5 to recast the enormous amount of transient trajectory data generated in our simulations into a form that can be analysed by a human. Our simulations predict that, on reaching certain limiting conditions of strain, dislocations alone can no longer relieve mechanical loads; instead, another mechanism, known as deformation twinning (the sudden re-orientation of the crystal lattice 6 ), takes over as the dominant mode of dynamic response. Below this limit, the metal assumes a strain-path-independent steady state of plastic flow in which the flow stress and the dislocation density remain constant as long as the conditions of straining thereafter remain unchanged. In this distinct state, tantalum flows like a viscous fluid while retaining its crystal lattice and remaining a strong and stiff metal.