Net Displacement Research Articles

A prospective comparative study to evaluate the displacement of four commercially available breast biopsy markers

Radiopaque markers are commonly deployed following breast biopsies to indicate the location of the targeted lesion. A frequently encountered complication is the displacement of these markers. This study compared the degree of displacement among four newer generation markers after stereotactic core needle biopsy. 80 consecutive biopsies were performed at three breast centre sites. The markers included: HydroMARK(®) (Mammotome, Cincinnati, OH), MammoMARK™ (Mammotome, Cincinnati, OH), MammoStar™ (Mammotome, Cincinnati, OH) and SecurMark(®) (Hologic, Bedford, MA). Each marker was composed of a radiopaque core with a unique polymeric encasing component. Post-procedure mammograms were obtained and the degree of marker displacement was measured. MammoMARK™ exhibited the greatest mean net displacement, followed by HydroMARK(®), SecurMark(®) and MammoStar™ (13.9, 7.7, 5.8 and 4.7 mm, respectively), although these differences did not reach statistical significance (p = 0.398). 73% of the markers did not displace at all. However, in the 19 of 22 markers in which displacement occurred, the distance from the biopsy cavity was >10 mm. No statistically significant contributing factors to predict displacement were found. Newer generation biopsy markers perform comparably with one another. However, clinically significant and unpredictable marker displacement persists. Compared with multiple similar studies of older generation bare metallic markers, the overall displacement rate of newer generation markers seems to be lower, possibly owing to the use of polymeric embedding agents that self-expand within the biopsy cavity. This article compares the post-procedure displacement of breast biopsy markers, which have not been evaluated or discussed in detail since markers with polymeric embedding agents gained widespread use.

Topographic constraints on magma accumulation below the actively uplifting Uturuncu and Lazufre volcanic centers in the Central Andes

Geodetic surveys of Volcan Uturuncu and the Lazufre volcanic complex in the Central Andes of South America reveal sustained surface uplift from magmatic intrusion at depth. However, the decadal timescales of geodetic surveys are short relative to the timescales of magma chamber growth. Thus, from ­geodesy alone, it is difficult to infer the deformation and hence magma accumulation history of these volcanoes. Here we combine data from InSAR, long-wavelength topography, GPS and high-resolution topographic surveys of lake shorelines and rivers, and lava flow morphology to constrain the spatial and temporal evolution of magmatism at Uturuncu and Lazufre. Near Uturuncu, dated lake shorelines show no evidence of tilting since ca. 16 ka, and we find no evidence of deformation in the long-wavelength topography. A lack of net surface displacement suggests that uplift related to a rising diapir must be less than a century old, or, more likely, magmatic inflation at Uturuncu is transient over millennial timescales and is therefore not recorded in the topog­raphy. At Lazufre, we also find no evidence for sustained uplift recorded in Late Pleistocene lake shorelines. However, the orientations of multiple dated lava flows suggest that the long-wavelength dome at the center of Lazufre’s uplift has persisted since at least 400 ka. Additionally, we find that the radial distribution of volcanic vents at Lazufre, coupled with the presence of an apical graben, is consistent with experimental and theoretical predictions of magmatic doming. The dome’s longevity indicates significant magma storage at depth, and therefore Lazufre is likely a highly evolved pre-caldera magmatic system. These two case studies demonstrate that combining geomorphic and geophysical data sets to extend the geodetic record back in time can help determine the style and magnitude of magma transport in volcanic systems.

Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach

Abstract. The paper presents an application of shoreline monitoring aimed at understanding the response of a beach to single storms and at identifying its typical behaviour, in order to be able to predict shoreline changes and to properly plan the defence of the shore zone. On the study area, in Jesolo beach (northern Adriatic Sea, Italy), a video monitoring station and an acoustic wave and current profiler were installed in spring 2013, recording, respectively, images and hydrodynamic data. The site lacks previous detailed hydrodynamic and morphodynamic data. Variations in the shoreline were quantified in combination with available near-shore wave conditions, making it possible to analyse the relationship between the shoreline displacement and the wave features. Results denote characteristic patterns of beach response to storm events, and highlight the importance of improving beach protection in this zone, notwithstanding the many interventions experimented in the last decades. A total of 31 independent storm events were selected during the period October 2013–October 2014, and for each of them synthetic indexes based on storm duration, energy and maximum wave height were developed and estimated. It was found that the net shoreline displacements during a storm are well correlated with the total wave energy associated to the considered storm by an empirical power law equation. A sub-selection of storms in the presence of an artificial dune protecting the beach (in the winter season) was examined in detail, allowing to conclude that the adoption of this coastal defence strategy in the study area can reduce shoreline retreat during a storm. This type of intervention can sometimes contribute to prolonging overall stability not only in the replenished zone but also in downdrift areas. The implemented methodology, which confirms to be economically attractive if compared to more traditional monitoring systems, proves to be a valuable system to monitor beach erosive processes and provide detailed indications on how to better plan beach-maintenance activities. The presented methodology and the proposed results can therefore be used as a basis for improving the collaboration between coastal scientists and managers to solve beach erosion problems, in locations where data are scattered and sporadic.

Electroosmosis-modulated peristaltic transport in microfluidic channels

We analyze the peristaltic motion of aqueous electrolytes altered by means of applied electric fields. Handling electrolytes in typical peristaltic channel material such as polyvinyl chloride and Teflon leads to the generation of a net surface charge on the channel walls, which attracts counter-ions and repels co-ions from the aqueous solution, thus leading to the formation of an electrical double layer—a region of net charges near the wall. We analyze the spatial distribution of pressure and wall shear stress for a continuous wave train and single pulse peristaltic wave in the presence of an electrical (electroosmotic) body force, which acts on the net charges in the electrical double layer. We then analyze the effect of the electroosmotic body force on the particle reflux as elucidated through the net displacement of neutrally buoyant particles in the flow as the peristaltic waves progress. The impact of combined electroosmosis and peristalsis on trapping of a fluid volume (e.g., bolus) inside the travelling wave is also discussed. The present analysis goes beyond the traditional analysis, which neglects the possibility of coupling the net pumping of fluids due to peristalsis and allows us to derive general expressions for the pressure drop and flow rate in order to set up a general framework for incorporating flow control and actuation by simultaneous peristalsis and application of electric fields to aqueous solutions. It is envisaged that the results presented here may act as a model for the design of lab-on-a-chip devices.

Imine-Functionalized Triazatriangulenium Platforms: Towards an Artificial Ciliated Epithelium.

Triazatriangulenium (TATA) platforms have been used to prepare highly ordered, self-assembled monolayers of free- and vertically standing imines on Au(111) surfaces. Upon irradiation, the imines undergo trans-cis isomerization and a fast thermal reaction (t1/2 =0.58 s at 20 °C) back to the more stable trans form. It is known that the photochemical reaction proceeds through rotation of the C=N bond and the thermochemical reaction through inversion at the N atom. The imine motors, therefore, should be able to induce a net displacement of particles above the surface similar to cilia epithelia in nature.

Stasis domains and slip surfaces in the locomotion of a bio-inspired two-segment crawler

We formulate and solve the locomotion problem for a bio-inspired crawler consisting of two active elastic segments (i.e., capable of changing their rest lengths), resting on three supports providing directional frictional interactions. The problem consists in finding the motion produced by a given, slow actuation history. By focusing on the tensions in the elastic segments, we show that the evolution laws for the system are entirely analogous to the flow rules of elasto-plasticity. In particular, sliding of the supports and hence motion cannot occur when the tensions are in the interior of certain convex regions (stasis domains), while support sliding (and hence motion) can only take place when the tensions are on the boundary of such regions (slip surfaces). We solve the locomotion problem explicitly in a few interesting examples. In particular, we show that, for a suitable range of the friction parameters, specific choices of the actuation strategy can lead to net displacements also in the direction of higher friction.

Vinculin Regulates Directionality and Cell Polarity in 2D, 3D Matrix and 3D Microtrack Migration.

During metastasis, cells can use proteolytic activity to form tube-like "microtracks" within the extracellular matrix (ECM). Using these microtracks, cells can migrate unimpeded through the stroma. To investigate the molecular mechanisms of microtrack migration, we developed an in vitro 3D micromolded collagen platform. When in microtracks, cells tend to migrate unidirectionally. Since focal adhesions are the primary mechanism by which cells interact with the ECM, we examined the roles of several focal adhesion molecules in driving unidirectional motion. Vinculin knockdown results in the repeated reversal of migration direction compared with control cells. Tracking the position of the Golgi centroid relative to the position of the nucleus centroid reveals that vinculin knockdown disrupts cell polarity in microtracks. Vinculin also directs migration on 2D substrates and in 3D uniform collagen matrices, indicated by reduced speed, shorter net displacement and decreased directionality in vinculin-deficient cells. In addition, vinculin is necessary for Focal Adhesion Kinase (FAK) activation in 3D as vinculin knockdown results in reduced FAK activation in both 3D uniform collagen matrices and microtracks, but not on 2D substrates, and accordingly, FAK inhibition halts cell migration in 3D microtracks. Together, these data indicate that vinculin plays a key role in polarization during migration.

Movement in the matrix: substrates and distance‐to‐forest edge affect postmetamorphic movements of a forest amphibian

AbstractPopulation persistence often depends on functional connectivity for animals that transit multiple vegetation types to acquire resources, particularly for dispersers navigating a landscape matrix fragmented by agriculture, forestry, or urbanization. For many pool‐breeding amphibians, population viability depends on the ability of juveniles to locate and reach suitable habitat in the terrestrial matrix. Thus, identifying the scale and orientation of movements is necessary to predict the consequences of landscape configuration for populations. We conducted three experiments to evaluate if different vegetation types alter the behavior of post‐metamorphic wood frogs (Lithobates sylvaticus). We measured the: (1) fine‐scale movement (velocity, latency, path length, net displacement, path tortuosity, and orientation) of individuals (n = 150) released on five substrates (asphalt, corn, forest leaf litter, hay, lawn); (2) directionality of frogs (n = 168) released at different distances from forest in two open‐cover types (lawns, hayfields); and (3) willingness of frogs (n = 240) to enter three land‐cover types (asphalt, lawn, forest) when released within artificial refugia islands at different distances from forest. Using fluorescent powder, we mapped 318 movement paths and performance differed. Frogs demonstrated straighter paths, and greater net movements, path lengths, and velocities through treatments with lower structural complexity (asphalt > lawn > corn > forest leaf litter > hay). Frogs also exhibited forest‐oriented directionality in asphalt, lawn, and corn but random orientation in forest control and hay. The willingness of individuals to leave a refugia island was lowest on asphalt (12% of released frogs), moderate on lawn (40%), and very high in forest (90%). Overall, results indicate that the quality of nonforest matrix may influence the ability of frogs to traverse open cover and orient toward forest from distances of ≥40–55 m. Thus, it is inaccurate to assume movement performance is uniform across all open‐matrix types, an important distinction because many landscape‐population models use expert‐based values that are a one‐size‐fits‐all measure for open cover. Our study provides field‐based, mechanistic approximations of juvenile movement that can be useful for predicting how matrix composition and configuration might be managed to maintain or restore functional connectivity.

Effect of polyelectrolyte–surfactant complexation on Marangoni transport at a liquid–liquid interface

Complexation of surfactants and oppositely charged polyelectrolytes is expected to alter Marangoni transport at a fluid interface compared to either single component system due to altered interfacial tension isotherms and mass transfer rates as well as adsorption irreversibility effects. We investigate Marangoni transport at the oil/water interface by passing mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and cationic polyelectrolyte poly(3-(2-methylpropionamide)propyl) trimethylammonium chloride-acrylamide (poly[AM-MAPTAC]), or rinsing solutions, over an oil/water interface in a radial, stagnation point flow. The displacements of adsorbed tracer particles are recorded through optical microscopy. The net displacement, defined as the sum of the displacements occurring during the adsorption and desorption stages of one application and rinsing cycle, is up to 10 times greater for complexing surfactant/polymer mixtures compared to either single component system. The enhanced net displacement is largely determined by the enhanced transport upon adsorption, while the reverse displacement that would normally occur upon rinsing is partially suppressed by partially irreversible polymer adsorption at the oil/water interface. In addition to effects of complexation on interfacial tension gradient induced flow, complexation effects on the bulk, and possibly interfacial, viscosity also influence the interfacial transport.

Mesoscale Simulation of self-diffusiophoretic microrotor

Artificial micro-scale or nano-scale machines that are capable of converting energy to mechanical work, have long been pursued by science and engineering communities for their potential applications in microfluidics, biology and medicine. From a physics point of view, they are also ideal models to investigate fundamental statistical phenomena in non-equilibrium active matters. Inspired by bio-machines and bio-motors like ATP synthase and flagellum motors, we propose a simple design of rotary motors based on pure self-diffusiophoresis effects. The basic design of the rotor consists of three colloidal beads with different surface properties, which leads to different interactions between the beads and solvent molecules. Chemical reactions are imposed on the surface of one of the beads, which creates a source of one of the two solvent molecules and generates a local concentration gradient. The other two beads connected to the catalytic bead have different affinities to the solvent molecules, which leads to asymmetric diffusiophoretic forces on the two non-catalytic beads. A net torque is thus obtained from difference of the diffusiophoretic forces between the two non-catalytic beads. In our simulation, we employ hybrid molecular dynamics (MD) simulations and multi-particle collision dynamics (MPC) to investigate the motion of microrotors. The binary fluid is composed with A-type and B-type solvent particle whose interactions are described by multi-particle collision dynamics while beads-particle interactions are modeled by molecular dynamics. In MPC, all fluid particles execute alternating streaming and collision steps. During streaming steps, the solvents move ballistically. During collision steps, particles are sorted into square cells and only interact with particles in the same cell under a specific stochastic rotation rule. MPC algorithm locally conserves mass, linear momentum, angular momentum and energy, and properly captures thermal fluctuation, mass diffusion, dissipation and hydrodynamic interactions. In our simulation, standard MPC parameters are employed which correspond to a liquid-like behavior of fluid. In MD, beads-solvent interactions are described by Lennard-Jones(LJ) potential with different parameter combinations and the equations of motion is integrated by velocity-Verlet algorithm. To perform hybrid molecular dynamic simulations with multi-particle collision dynamics, between two MPC collision steps, 50 MD steps are implemented for the solvent particles that are in the interaction range of colloidal beads. We first investigate the solvent concentration distribution around static microrotor, and confirm that the catalytic bead generates a steady-state local concentration gradient. Net angular displacements are obtained when the rotor is allowed to rotate freely. The rotational direction and speed of the micorotor are determined by bead-solvent interactions, the rotor geometry, the solvent viscosity and the catalytic reaction ratio. We also study the scenario in which two rotors are placed in close vicinity to each other. We find that the coupling between the concentration fields around the rotors reduces the rotational speed of both rotors.

遊走能が亢進したがん細胞の選択回収マイクロ流路デバイス

We propose a micro-channel device to collect cancer cells with high migrating capability, which could cause metastasis. In order to collect cells attached on extracellular matrix, focal adhesions between cells and extracellular matrix should be broken. The desmosomes can be mechanically broken by using extension of cell culture surface. For this purpose, the device locally has a balloon under a cell culture surface. The extension rate of the cell culture surface is 40% with 300 μL water. Using the device, we could detach the high-migration cell, which has net displacement of 150 μm and total path of 250 μm, and collect it by the flow of cultural medium.

Entropic transport without external force in confined channel with oscillatory boundary

The dynamics of point-like Brownian particles in a periodic confined channel with oscillating boundaries has been studied. Directional transport (DT) behavior, characterized by net displacement along the horizontal direction, is observed even without external force which is necessary for the conventional DT where the boundaries are static. For typical parameter values, the average velocity Vt of DT reaches a maximum with the variation of the noise intensity D, being alike to the phenomenon of stochastic resonance. Interestingly, we find that Vt shows nontrivial dependences on the particle gravity G depending on the noise level. When the noise is large, Vt increases monotonically with G indicating that heavier particle moves faster, while for small noise, Vt shows a bell-shape dependence on G, suggesting that a particle with an intermediate weight may move the fastest. Such results were not observed for DT in a channel with static boundaries. To understand these findings, we have adopted an effective one-dimensional coarsening description, which facilitates us to introduce an effective entropic force along the horizontal direction. The average force is apparently nonzero due to the oscillatory boundary, hence leading to the net transport, and it shows similar dependences as Vt on the noise intensity D and particle gravity G. The dependences of the DT behavior on other parameters describing the oscillatory channel have also been investigated, showing that DT is more pronounced for larger oscillation amplitude and frequency, and asymmetric geometry within a channel period and phase difference between neighboring periods are both necessary for the occurrence of DT.

Center of Pressure Displacement of Standing Posture during Rapid Movements Is Reorganised Due to Experimental Lower Extremity Muscle Pain.

BackgroundPostural control during rapid movements may be impaired due to musculoskeletal pain. The purpose of this study was to investigate the effect of experimental knee-related muscle pain on the center of pressure (CoP) displacement in a reaction time task condition.MethodsNine healthy males performed two reaction time tasks (dominant side shoulder flexion and bilateral heel lift) before, during, and after experimental pain induced in the dominant side vastus medialis or the tibialis anterior muscles by hypertonic saline injections. The CoP displacement was extracted from the ipsilateral and contralateral side by two force plates and the net CoP displacement was calculated.ResultsCompared with non-painful sessions, tibialis anterior muscle pain during the peak and peak-to-peak displacement for the CoP during anticipatory postural adjustments (APAs) of the shoulder task reduced the peak-to-peak displacement of the net CoP in the medial-lateral direction (P<0.05). Tibialis anterior and vastus medialis muscle pain during shoulder flexion task reduced the anterior-posterior peak-to-peak displacement in the ipsilateral side (P<0.05).ConclusionsThe central nervous system in healthy individuals was sufficiently robust in maintaining the APA characteristics during pain, although the displacement of net and ipsilateral CoP in the medial-lateral and anterior-posterior directions during unilateral fast shoulder movement was altered.

From steps to home range formation: species‐specific movement upscaling among sympatric ungulates

Summary Animals move to interact with the environment in order to find food resources and cover. Intrinsic characteristics affecting feeding and antipredatory strategies likely shape variation in movement patterns and home range formation between individuals, populations and species. Browsing herbivores selectively forage on patchily distributed resources in areas with more canopy cover, whereas mixed feeders and grazers feed on more open grasslands and tend to aggregate as an antipredatory strategy. We therefore predicted that at small temporal scales, browsers will show greater net displacements (i.e. typical of searching patterns) than mixed feeders or grazers; but at larger temporal scales, we expect the opposite pattern, since gregarious species will need to use larger areas to feed the whole herd. We also predicted that the feeding/antipredatory strategy will determine the behavioural responses to other environmental factors. To test this, we compared spatial movement patterns at multiple scales (from 20‐min intervals to annual home ranges) of three sympatric, similar‐sized, alpine ungulates which differ in their feeding/antipredatory strategy: roe deer (solitary browsers), mouflon (gregarious grazers) and chamois (intermediate feeders in smaller groups). We used location data from GPS‐collared females of the three species in the French Alps. As predicted, we found that multi‐scale spatial patterns depended on the feeding/antipredatory strategy. Browsers foraged within smaller range areas, searching back and forth. Mixed feeders and, especially, grazers covered larger areas, presumably to satisfy herd needs. The feeding/antipredatory strategies also determined the interspecific variability in behavioural responses to factors such as maternal status, weather, habitat type or human disturbance, supporting our hypothesis. Exploring interspecific variability, we showed how movement behaviour and home range formation vary substantially, even among species within the same guild. This mechanism might be important to maintain intra‐guild multi‐species associations and increase biodiversity, through contributing to niche segregation and, thus, coexistence.

Dielectrophoretic manipulation of particle mixtures employing asymmetric insulating posts.

A novel scheme for particle separation with insulator-based dielectrophoresis (iDEP) was developed. This technique offers the capability for an inverted order in particle elution, where larger particles leave the system before smaller particles. Asymmetrically shaped insulating posts, coupled with direct current (DC) biased low-frequency alternating current (AC) electric potentials, were used to successfully separate a mixture of 500 nm and 1 μm polystyrene particles (size difference of 0.5 μm in diameter). In this separation, the 1 μm particles were eluted first, demonstrating the discriminatory potential of this methodology. To extend this technique to biological samples, a mixture containing Saccharomyces cerevisiae cells (6.3 μm) and 2 μm polystyrene particles was also separated, with the cells being eluted first. The asymmetric posts featured a shorter sharp half and a longer blunt half; this produced an asymmetry in the forces exerted on the particles. The negative DC offset produced a net displacement of the smaller particles toward the upstream direction, while the post asymmetry produced a net displacement of the larger particles toward the downstream direction. This new iDEP approach provides a setup where larger particles are quickly concentrated at the outlet of the post array and can be released first when in a mixture with smaller particles. This new scheme offers an extra set of parameters (alternating current amplitude, DC offset, post asymmetry, and shape) that can be manipulated to obtain a desired separation. This asymmetric post iDEP technique has potential for separations where it is important to quickly elute and enrich larger and more fragile cells in biological samples.

Nonconservativity and noncommutativity in locomotion

Geometric mechanics techniques based on Lie brackets provide high-level characterizations of the motion capabilities of locomoting systems. In particular, they relate the net displacement they experience over cyclic gaits to area integrals of their constraints; plotting these constraints thus provides a visual “landscape” that intuitively captures all available solutions of the system’s dynamic equations. Recently, we have found that choices of system coordinates heavily influence the effectiveness of these approaches. This property appears at first to run counter to the principle that differential geometric structures should be coordinate-invariant. In this paper, we provide a tutorial overview of the Lie bracket techniques, then examine how the coordinate-independent nonholonomy of these systems has a coordinate-dependent separation into nonconservative and noncommutative components that respectively capture how the system constraints vary over the shape and position components of the configuration space. Nonconservative constraint variations can be integrated geometrically via Stokes’ theorem, but noncommutative effects can only be approximated by similar means; therefore choices of coordinates in which the nonholonomy is primarily nonconservative improve the accuracy of the geometric techniques.

Single file diffusion into a semi-infinite tube

We investigate single file diffusion (SFD) of large particles entering a semi-infinite tube, such as luminal diffusion of proteins into microtubules or flagella. While single-file effects have no impact on the evolution of particle density, we report significant single-file effects for individually tracked tracer particle motion. Both exact and approximate ordering statistics of particles entering semi-infinite tubes agree well with our stochastic simulations. Considering initially empty semi-infinite tubes, with particles entering at one end starting from an initial time t = 0, tracked particles are initially super-diffusive after entering the system, but asymptotically diffusive at later times. For finite time intervals, the ratio of the net displacement of individual single-file particles to the average displacement of untracked particles is reduced at early times and enhanced at later times. When each particle is numbered, from the first to enter (n = 1) to the most recent (n = N), we find good scaling collapse of this distance ratio for all n. Experimental techniques that track individual particles, or local groups of particles, such as photo-activation or photobleaching of fluorescently tagged proteins, should be able to observe these single-file effects. However, biological phenomena that depend on local concentration, such as flagellar extension or luminal enzymatic activity, should not exhibit single-file effects.

The impact of bedform migration on benthic oxygen fluxes

AbstractPermeable sediments are found wide spread in river beds and on continental shelves. The transport of these sediments is forced by bottom water currents and leads to the formation of bedforms such as ripples and dunes. The bottom water flow across the bedforms results in pressure gradients that drive pore water flow within the permeable sediment and enhance the supply of reactive substrates for biogeochemical processes. This transport‐reaction system has been extensively studied for the case of stationary bedforms, whereas bedform migration—the most ubiquitous form of sediment transport—has been often ignored. To study the impact of sediment transport on pore water flow, we incorporated an empirical model of bedform migration into a numerical transport‐reaction model for porous media, using oxygen as reactive solute. The modeled oxygen flux changes significantly as soon as the sediment divides into an upper mobile layer (migrating bedform) and a stationary layer underneath. The bedform is increasingly flushed with oxic bottom water, whereas pressure gradients and pore water flow reverse at increasing rate underneath the bedform. This suppresses net pore water displacement and reduces the oxygen penetration depth up to 90%. In effect, the overall oxygen uptake decreases significantly with bedform migration although bottom water velocities increase. This counterintuitive effect is systematically described for a range of different sediment types, current velocities, and respiration rates and should be considered in future studies.

Strain and flow in the metamorphic core complex of Ios Island (Cyclades, Greece)

We have analysed strain and flow kinematics in the footwall of the South Cyclades Shear Zone (SCSZ), an important tectonic boundary within the Attic-Cycladic Crystalline Complex exposed on Ios Island, Cyclades, Aegean Sea. Coarse-grained augen gneisses in the basement unit flooring the SCSZ and forming a metamorphic core complex are excellently suited to measure finite strain using the Fry method and estimate the vorticity number (Wk) of flow with the “blocked-object” method. The results show that Oligo-Miocene exhumation of the basement unit during extension brought approximately 70 % N–S crustal stretching and up to 40 % subvertical shortening in a plane strain environment (k = 0.99). Linear down-section strain decrease constrains a zone of contact deformation of the SCSZ of about 1.5 km thick. Kinematic vorticity number estimates suggest little deviation from pure shear (Wk = 0.26). Finite strain and Wk are not correlated, indicating that the Ios basement and the overlying cover units were stretched compatibly. While the SCSZ is a localized zone of high strain, net displacement, however, may be restricted to about ten kilometres. This has important repercussions on large-scale tectonic models for extension in the Aegean.

Efficient transport of droplet sandwiched between saw-tooth plates

The transport of droplet sandwiched between smooth and saw-tooth plates was investigated using molecular dynamics method. The repeated opening and closing of the plates result in sequential stretching and squeezing of the droplet, which provide the driving force. The asymmetrical saw tooth obstructs the backward motion of the droplet, and gives rise to a net forward displacement of the droplet in every opening and closing cycle. This unidirectional motion facilitates the efficient droplet transport, which is referred to as the ratchet-like effect in this work. Our simulations also reveal that the influence of the surface wettability on the droplet transport is different for saw-tooth and smooth plates. Droplet transport efficiency exhibits monotonic decrease with the increase of the solid–liquid interactions for saw-tooth plates. While for smooth plates, unidirectional droplet movement was only observed for certain solid–liquid interactions. Taken together these simulation results and theoretical analysis, we demonstrate that hydrophobic saw-tooth plates can improve the transport efficiency significantly. These findings not only enhance our understanding of the droplet transport from atomistic scale, but also are beneficial to practical applications in designing of micro- and nano-fluidic systems.