Horizontal Interface Research Articles

Fluid transport in geological reservoirs with background flow

This paper presents fundamental analysis of the injection and release of fluid into porous media or geological reservoirs saturated by a different fluid undergoing a background flow, and tests the predictions using analogue laboratory experiments. The study reveals new results important for an understanding of the transport of hazardous contaminants through aquifers and the long-term fate of carbon dioxide ($\text{CO}_{2}$) in geological $\text{CO}_{2}$ sequestration. Using numerical and asymptotic analysis, we describe a variety of flow regimes that arise, and demonstrate an almost instantaneous control of injected fluid by the far field conditions in geological reservoirs. For a continuous input, the flow develops a horizontal interface between the injected and ambient fluids. The background flow thereby effectively caps the height of the injected fluid into a shallower region of vertical confinement. For a released parcel of fluid, gravitational spreading is found to become negligible after a short time. A dominant control of the interface by the background pressure gradient arises, and stems from the different velocities at which it drives the injected and ambient fluids individually. Similarity solutions describing these dynamics show that the parcel approaches a slender triangular profile that grows horizontally as $t^{1/2}$, where $t$ is time, a rate faster than relaxation under gravity. Shock layers develop at the front or back of the parcel, depending on whether it is more or less viscous than the ambient fluid. New analytical results describing the long-term effects of residual trapping due to capillary retention are developed, which yield explicit predictions for the time and length scales on which a parcel of $\text{CO}_{2}$ becomes retained. We end by applying our results to geological contexts, concluding that even slight background motion can have considerable implications for long-term transport through the subsurface.

Thermal Conduction across Metal-Dielectric Sidewall Interfaces.

The heat flow at the interfaces of complex nanostructures is three-dimensional in part due to the nonplanarity of interfaces. One example common in nanosystems is the situation when a significant fraction of the interfacial area is composed of sidewalls that are perpendicular to the principal plane, for example, in metallization structures for complementary metal-oxide semiconductor transistors. It is often observed that such sidewall interfaces contain significantly higher levels of microstructural disorder, which impedes energy carrier transport and leads to effective increases in interfacial resistance. The impact of these sidewall interfaces needs to be explored in greater depth for practical device engineering, and a related problem is that appropriate characterization techniques are not available. Here, we develop a novel electrothermal method and an intricate microfabricated structure to extract the thermal resistance of a sidewall interface between aluminum and silicon dioxide using suspended nanograting structures. The thermal resistance of the sidewall interface is measured to be ∼16 ± 5 m2 K GW-1, which is twice as large as the equivalent horizontal planar interface comprising the same materials in the experimental sample. The rough sidewall interfaces are observed using transmission electron micrographs, which may be more extensive than at interfaces in the substrate plan in the same nanostructure. A model based on a two-dimensional sinusoidal surface estimates the impact of the roughness on thermal resistance to be ∼2 m2 K GW-1. The large disparity between the model predictions and the experiments is attributed to the incomplete contact at the Al-SiO2 sidewall interfaces, inferred by observation of underetching of the silicon substrate below the sidewall opening. This study suggests that sidewall interfaces must be considered separately from planar interfaces in thermal analysis for nanostructured systems.

Stability of the fluid interface in a Hele-Shaw cell subjected to horizontal vibrations.

The stability of the horizontal interface of two immiscible viscous fluids in a Hele-Shaw cell subject to gravity and horizontal vibrations is studied. The problem is reduced to the generalized Hill equation, which is solved analytically by the multiple scale method and numerically. The long-wave instability, the resonance (parametric resonance) excitation of waves at finite frequencies of vibrations (for the first three resonances), and the limit of high-frequency vibrations are studied analytically under the assumption of small amplitudes of vibrations and small viscosity. For finite amplitudes of vibrations, finite wave numbers, and finite viscosity, the study is performed numerically. The influence of the specific natural control parameters and physical parameters of the system on its instability threshold is discussed. The results provide extension to other results [J. Bouchgl, S. Aniss, and M. Souhar, Phys. Rev. E 88, 023027 (2013)10.1103/PhysRevE.88.023027], where the authors considered a similar problem but took into account viscosity in the basic state and did not consider it in the equations for perturbations.

Overview and prospect of fracture propagation and conductivity characteristics in deep shale gas wells

There are tremendous shale gas resources in China, however, many of them can’t achieve economical production due to a lower effective stimulated reservoir volume (ESRV). Up to now, very few researches have been conducting on the mechanisms of fracture propagation and conductivity, which are the two main controlling factors of the effective development of shale gas play. As we all know that with the increasing depth of shale gas wells, many parameters such as in-situ stress, stress difference between minimal horizontal stress and maximal one, rock mechanics, etc. are all changed a simultaneously, which results in different fracture propagation and conductivity mechanisms. Therefore, firstly, a comprehensive analysis on fracture propagation and its conductivity characteristics in shallow wells were conducted. The mechanism of single fracture propagation and multiple fractures’ propagation simultaneously in open hole wells were summarized in detail. Besides, the effect of casing completion and fracturing treatment parameters on single fracture initiation and propagation was analyzed, and the corresponding results for multiple fractures may take references to that in open hole wells. Based on above studies, the mechanism of conductivity of single fracture and complex one in the condition of multiple affecting factors were analyzed too. After that, the proppant transport pattern within the complex fracture and its transportation law in divergent fracture were simulated, which may be used to optimize treatment parameters of hydraulically fracturing and achieve the object of expected conductivity and maximal ESRV. Finally, according to the formation geologic characteristics of deep shale gas play, the future research tendency was indicated, such as the mechanism of fracture propagation in the mode of well pad with multiple horizontal wells and multiple clusters, and in the condition of mixed natural fractures pattern with both horizontal interface and high angle fractures, the mechanism of high conductivity of network fracture formed by rock self-supported, which has great significance for developing deep shale gas play economically and effectively.

Numerical Analysis of Three-Dimensional Natural Convection in a Closed Rectangular Cavity Under Conditions of Radiant Heating and Conjugate Heat Exchange

The numerical simulation results of three-dimensional natural convection in a closed cavity were presented under conditions of the bottom horizontal solid-fluid interface radiant heating and conjugate heat exchange. Conservation equations of mass, momentum, and energy were formulated in terms of vorticity vector – vector potential – temperature dimensionless variables and solved by means of the finite difference method. It was found that the heat transfer process under study had a significant unsteady nature. According to the results of conjugate heat exchange integral analysis, it was shown that similar trends of mean Nusselt numbers versus dimensionless time were formed for both two and three dimensional problem formulations.

Tectonic tremor and slow slip along the northwestern section of the Mexico subduction zone

The southwestern coast of Mexico is marked by active subduction of the Rivera and Cocos plates, producing megathrust earthquakes that tend to recur every 50–100 yr. Herein, we use seismic and GPS data from this region to investigate the potential relationship between earthquakes, tectonic (non-volcanic) tremor, and transient slip along the westernmost 200 km of the Mexico subduction zone. Visual examination of seismograms and spectrograms throughout the 18-month-long MARS seismic experiment reveals clear evidence for frequent small episodes of tremor along the Rivera and Cocos subduction zones beneath the states of Jalisco, Colima, and Michoacán. Using a semi-automated process that identifies prominent energy bursts in envelope waveforms of this new data, analyst-refined relative arrival times are inverted for source locations using a 1-D velocity model. The resulting northwest–southeast trending linear band of tremor is located downdip from the rupture zones of the 1995 Mw 8.0 Colima–Jalisco and 2003 Mw 7.2 Tecoman subduction-thrust earthquakes and just below the regions of afterslip triggered by these earthquakes. Despite the close proximity between tremor and megathrust events, there is no evidence that the time since the last great earthquake influences the spatial or temporal pattern of tremor. A well-defined gap in the tremor beneath the western Colima Graben appears to mark a separation along the subducted Rivera–Cocos plate boundary. From the position time series of 19 continuous GPS sites in western Mexico, we present the first evidence that slow slip events occur on the Rivera plate subduction interface. Unlike the widely-recorded, large-amplitude, slow slip events on the nearly horizontal Cocos plate subduction interface below southern Mexico, slow slip events below western Mexico have small amplitudes and are recorded at relatively few, mostly coastal stations. The smaller slow slip beneath western Mexico may be due to the steeper dip, causing a narrower zone where the conditions for slow slip are met. The prominent afterslip following the M=8 1995 Colima–Jalisco and M=7.2 2003 Tacoma megathrust earthquakes may also shrink the area available for episodic slow slip.

Experimental characterization and detailed micro-modeling of multi-perforated clay brick masonry structural response

Aiming towards a better understanding of the structural response presented by multi-perforated clay brick masonry, this paper presents the results of an experimental program focused on characterizing the behavior of its constituent materials and interfaces, and on providing numerical strategies to appropriately reproduce that behavior. Different displacement controlled test set-ups were carried out in the laboratory for this purpose, giving special attention to characterizing the shear response at horizontal unit-mortar interface in order to point out the influence that mortar spikes penetrating into the perforated bricks cavities can exert. According to its detailed consideration of materials and interfaces, the detailed micro-modeling numerical approach was selected for this study. The numerical strategies proposed have led to a satisfactory reproduction of the shear triplet tests and diagonal compression tests that were performed, showing that the complex structural response of multi-perforated clay brick masonry can be appropriately reproduced from experimental evidence.

Aspect Ratio Dependence of Isotropic-Nematic Phase Separation of Nanoplates in Gravity

Abstract We studied isotropic-nematic (I-N) phase separation via gravity sedimentation in suspensions of plate-like colloidal particles of identical thickness but different lateral sizes (diameters). It is well-known that I-N phase transition occurs at a higher concentration for particles with larger aspect ratio (thickness/diameter) than for particles with smaller aspect ratio. Here we report that for the larger aspect ratios of nanoplates, gravity-driven I-N phase separation is faster. In a homogenously mixed I-N biphasic suspension of nanoplates, nematic tactoids nucleate, grow, and then undergo sedimentation in gravity, leading to the formation of a clear horizontal interface between the I and N phase. For I-N coexistent suspension of nanoplates with different aspect ratios but the same amount of nematic fractions, the larger the aspect ratio, the faster the formation of nematic tactoids and interface between isotropic liquid and nematic liquid crystal phase. The tactoid formation rate is governed by the rotational and translational diffusion rates, which are faster at larger aspect ratios. The time required for I-N separation (t*, seconds) varies inversely with the mean aspect ratio (< ξ >) of nanoplates and follows the relation, t * = α < ξ > n , where α = 0.97 ± 1.30 s and n = −2.1 ± 0.2. The phase separation kinetics studied in our experiments offers guidance for the selection of aspect ratio of nanoplates for samples to be studied at the International Space Station (ISS).

Non-equilibrium Thermodynamics of Rayleigh–Taylor Instability

Here, the fundamental problem of Rayleigh–Taylor instability (RTI) is studied by direct numerical simulation (DNS), where the two air masses at different temperatures, kept apart initially by a non-conducting horizontal interface in a 2D box, are allowed to mix. Upon removal of the partition, mixing is controlled by RTI, apart from mutual mass, momentum, and energy transfer. To accentuate the instability, the top chamber is filled with the heavier (lower temperature) air, which rests atop the chamber containing lighter air. The partition is positioned initially at mid-height of the box. As the fluid dynamical system considered is completely isolated from outside, the DNS results obtained without using Boussinesq approximation will enable one to study non-equilibrium thermodynamics of a finite reservoir undergoing strong irreversible processes. The barrier is removed impulsively, triggering baroclinic instability by non-alignment of density, and pressure gradient by ambient disturbances via the sharp discontinuity at the interface. Adopted DNS method has dispersion relation preservation properties with neutral stability and does not require any external initial perturbations. The complete inhomogeneous problem with non-periodic, no-slip boundary conditions is studied by solving compressible Navier–Stokes equation, without the Boussinesq approximation. This is important as the temperature difference between the two air masses considered is high enough ( $$\Delta T = 70$$ K) to invalidate Boussinesq approximation. We discuss non-equilibrium thermodynamical aspects of RTI with the help of numerical results for density, vorticity, entropy, energy, and enstrophy.

Zonal PANS: evaluation of different treatments of the RANS–LES interface

ABSTRACTThe partially Reynolds-averaged Navier–Stokes (PANS) model can be used to simulate turbulent flows either as RANS, large eddy simulation (LES) or DNS. Its main parameter is fk whose physical meaning is the ratio of the modelled to the total turbulent kinetic energy. In RANS fk = 1, in DNS fk = 0 and in LES fk takes values between 0 and 1. Three different ways of prescribing fk are evaluated for decaying grid turbulence and fully developed channel flow: fk = 0.4, fk = k3/2tot/ϵ and, from its definition, fk = k/ktot where ktot is the sum of the modelled, k, and resolved, kres, turbulent kinetic energy. It is found that the fk = 0.4 gives the best results. In Girimaji and Wallin, a method was proposed to include the effect of the gradient of fk. This approach is used at RANS– LES interface in the present study. Four different interface models are evaluated in fully developed channel flow and embedded LES of channel flow: in both cases, PANS is used as a zonal model with fk = 1 in the unsteady RANS (URANS) region and fk = 0.4 in the LES region. In fully developed channel flow, the RANS– LES interface is parallel to the wall (horizontal) and in embedded LES, it is parallel to the inlet (vertical). The importance of the location of the horizontal interface in fully developed channel flow is also investigated. It is found that the location – and the choice of the treatment at the interface – may be critical at low Reynolds number or if the interface is placed too close to the wall. The reason is that the modelled turbulent shear stress at the interface is large and hence the relative strength of the resolved turbulence is small. In RANS, the turbulent viscosity – and consequently also the modelled Reynolds shear stress – is only weakly dependent on Reynolds number. It is found in the present work that it also applies in the URANS region.

Dynamics response of complex defects near bimaterials interface by incident out-plane waves

Dynamics response of an elliptical cavity and a crack (on different sides) near bimaterials interface under incident out-plane waves is studied by applying the methods of complex variables and Green’s function. Firstly, based on “conjunction,” the analytical model is divided along the horizontal interface into an elastic half-plane possessing an elliptical cavity and a full elastic half-plane containing a crack. Using complex variables, the scattering displacement field of the half-plane containing an elliptical cavity under incident out-plane waves is then derived. According to the method of Green’s function, the corresponding Green’s functions of two half-planes impacted by an out-plane source load are further deduced. Combined with “crack division,” a crack at the full elastic the half-plane is created, and thus, expressions of displacement and stress are derived while the cavity coexists with the crack. Undetermined antiplane forces are loaded on the horizontal surfaces for conjunction of two sections and then solved by a series of Fredholm integral equations on account of continuity conditions of the interface. Finally, this paper focuses on the discussion of the influence law of different parameters on the dynamics response of complex defects near bimaterials interface by comprehensive numerical results.

Molten Corium–Concrete Interaction: Investigation of convective heat transfer in a pool with gas sparging

During a severe accident in a Pressurized Water Reactor, corium may fall in the reactor pit and interact with concrete. The CLARA facility, financed by EDF, IRSN, GDF-Suez and CEA, has been designed to understand the heat transfer phenomena involved in the Molten Concrete–Corium Interaction (MCCI). The facility is composed of a pool of simulant liquids, percolated by air and internally heated by direct electrical current. It is in contact with several heat exchangers in order to maintain walls at a constant temperature and to measure local heat losses. The experiments performed aimed at studying the influence on heat transfer of liquid viscosity (varying from 1 to 10,000mPa.s by dissolution of hydroxyethyl cellulose in the water), air injection superficial velocities (ranging from 0 to 10cm/s) on both horizontal and vertical walls, and pool length.After a literature review on the existing heat transfer experiments and correlations for two-phase (liquid–gas) flow, the CLARA experiments are described. Then, the results obtained are presented: influence of superficial gas velocity and liquid properties (especially viscosity) on heat transfer, evaluation of ratio between heat transfer on vertical and horizontal interface, influence of the pool dimensions. Finally, the analysis and interpretation of CLARA experiments are given: comparison to the literature data, development of correlations concerning the heat transfer along the vertical and horizontal plate, comparison to results obtained with real materials. The results show that the presence of bubbles enhances heat exchange while an increasing viscosity lowers the heat transfer. The MCCI isotropic trends are different from those observed with prototypical materials suggesting that phenomena occurring at the corium–concrete interface are more complex than the ones present in CLARA experiments.

Thermal Convection Induced by an Infinitesimally Thin and Unstably Stratified Layer

AbstractWe examine the linear stability analysis of the equations governing Rayleigh–Bénard convection flows when the basic temperature profile is unstably stratified solely over a thin horizontal slice of the fluid region. We conduct both asymptotic and numerical analyses on three distinct shapes of the basic temperature: (i) a hyperbolic tangent profile, (ii) a piecewise linear profile and (iii) a step-function profile. In the first two cases, the thin unstably stratified layer is centrally located. The presence of stably stratified regions below and above the central layer diminishes the effect of the velocity and thermal boundary layers that form at the plates. This in turn allows for the analysis of the convection process without the constraints of the horizontal boundaries to be simulated in a finite domain. We obtain expressions for the threshold parameters for convection onset as well as flow features as function of the thickness of the unstably stratified layer. In the limit of a vanishingly small thickness, the hyperbolic tangent profile tends to a step-function profile with a heavy top layer overlying a lighter bottom layer. These two layers are separated by an interface where a jump in density occurs. This situation resembles the Rayleigh–Taylor instability of a horizontal interface except that neither is the interface free nor is the buoyancy diffusion absent. The exploration of this case uncovers new instability threshold values and flow patterns. Finally, we discuss some relevant applications.

A Markov Random Field orientation prior for electronic cleansing in CT Colonography.

Tagging of the bowel content with an oral contrast facilitates CT Colonography with limited bowel preparation. Electronic colon cleansing (ECC) reconstructs the colon lumen, devoid of feces from a CT scan acquired with fecal fluid tagging. A popular method to estimate the stool composition in an image (with the purpose of removing it) is the well-established Expectation Maximization (EM) method. The tagged fluid residue appears as a contrast enhanced region with a largely horizontal interface with air above it. One of the issues is the partial volume (PV) effect that creates voxels with attenuations similar to that of the colon wall at the boundary of air and tagged fluid. We present here, a novel orientation prior formulated as a Markov Random Field that is included as part of the EM tissue segmentation framework to mitigate this PV effect at the air and tagged fluid layer. We show quantitative results on a simple synthetic dataset and qualitative results on patient data that highlight improvements due to the inclusion of the orientation prior.

Dynamic dip-slip fault rupture in a layered geological medium: Broken symmetry of seismic motion

As recorded recently on 22 November 2014 during the Nagano-ken Hokubu (Kamishiro Fault), Japan, earthquake, one important observation in dynamic rupture (fracture) related to a shallow dip-slip earthquake (usually assumed as mode-II shear crack propagation from depth towards a free surface) is the broken symmetry of seismic motion in the vicinity of the fracturing fault plane. Generally, the strong motion (particle motion) on the hanging wall is much larger than that on the footwall, but the physical mechanisms causing this asymmetry have not been fully clarified yet. Here, utilising the techniques of finite difference calculations and dynamic photoelasticity in conjunction with high speed cinematography, we investigate the fracture dynamics of a dip-slip fault plane situated near a free surface and try to explain the mechanics behind the asymmetry, numerically as well as experimentally. In our two-dimensional crack-like rupture models, we prepare a flat fault plane, which dips either vertically or at an angle, in a monolithic (scenario (1)) or layered (scenario (2)) linear elastic medium (representing rocks). In the basic scenario (1), when the primary fault rupture initiated at some depth approaches the free surface, four Rayleigh-type waves may be induced: two of them propagate along the free surface as Rayleigh surface waves into the opposite directions to the far field, and the other two travel back downwards along the fractured fault plane as interface waves into depth. If the fault plane is inclined, in the hanging wall, the interface and Rayleigh waves may interact with each other and a shear wave carrying concentrated energy (corner wave) can be produced to cause stronger disturbances. The corner waves, generated by primary fault rupture, may exist only when the fault plane is inclined, i.e. only when the geometry considered is asymmetric. In the scenario (2), however, we indicate that (anti-)symmetry of mode-II seismic motion can be easily broken even in geometrically symmetric models if the secondary fracture is allowed at an interface between layers. If primary vertical dip-slip fault rupture in an (anti-)symmetric model moves from depth and interacts with a horizontal interface that follows, for example, a tensile fracture criterion, basically only the interface segments where the primary rupture induces dynamic tension (in the relatively subsiding footwall) may be fractured and the segments in compression (in the rising hanging wall) may remain unbroken. In this case, in the hanging wall, the dynamic stresses in the upper layer above the interface become relatively large because the compressive parts of the primary rupture-induced wave (rupture front wave) can propagate from the lower layer across the still bonded interface into the upper layer, with less reflection back to the lower one. On the contrary, in the footwall, much of the energy carried by the rupture front wave in the lower layer is reflected at the broken interface and dynamic disturbances in the upper layer tend to become smaller. Thus, the strong motion on the hanging wall is expected to become larger than that on the footwall not only in geometrically asymmetric cases but also in symmetric ones.

Research on Twice-Prestressed Composite Beam and Its Application in Highway Bridges

The concept, basic principle, and characteristics of twice-prestressed composite beam are introduced, and the mechanical performance, deformation performance, and creep stress redistribution of the horizontal interface of twice-prestressed beam are discussed. In addition, previous studies regarding the application of twice-prestressed composite beams in highway bridges are summarized and analyzed. It is concluded that the twice-prestressed composite beam can decrease the creep camber of a prestressed concrete beam by more than 50%; thus, the contradiction of reducing creep camber and improving the safety of section crack resistance can be effectively resolved. Moreover, twice-prestressed composite beam can save approximately 10% of prestressed tendons and has comprehensive technical and economical advantages in highway ultrathin beam bridges and urban overpass bridges. Future research of twice-prestressed composite beam will focus on the design method, connection model, structure, and shear performance of horizontal interface in addition to the construction technology.

Buoyancy-driven exchange flow between two adjacent building zones connected with top and bottom vents

We examine the buoyancy driven flow between two adjacent building zones separated by top and bottom vents with and without a source of buoyancy. In the absence of a source, by opening the vents, the pressure difference between the two zones drives the exchange flow. When there is an isolated source of buoyancy, two distinct flow regimes are defined: a ventilation-dominated regime in which the flow that is generated by the initial temperature difference, and a source-dominated regime in which the flow is principally governed by the source. Here, we restrict attention to the former case. Thus in each zone our analytical model assumes a horizontal interface that separates the upper layer, which is comprised of fluid having the initial density of the light zone, from the lower layer, comprised of fluid whose density is larger than that of the light zone. The transient evolution of such interfaces along with the stratification and buoyancy in each zone are predicted. Attention is focused on the influence of the effective area, source buoyancy flux and the time during which the source is switched on. Because the interface elevations change significantly at early times, a non-monotonic behavior is predicted for the evolution of stratification in the light zone. We also find that the terminal stratification and buoyancy in both zones are not impacted by the number of connecting vents; however, this number has a strong influence on how quickly steady state is achieved. Similitude laboratory experiments help to corroborate key predictions.

An exact analytical solution for steady seepage from a perched Aquifer to a low‐permeable sublayer: Kirkham‐Brock's legacy revisited

AbstractAn analytical solution is obtained for steady 2‐D potential seepage flow from a nonclogged and nonlined soil channel into a highly permeable porous layer, with phreatic surfaces tapering toward a horizontal interface with a subjacent low‐permeable formation. Along this boundary, a vertical component of the Darcian velocity vector equals the formation saturated hydraulic conductivity. The image of the physical flow domain in the hodograph plane is a circular polygon, a triangle or digon in a limiting case of a “phreatic jet” impinging on the low‐permeable substratum. The polygon is mapped onto an auxiliary half plane, where the complex physical coordinate and complex potential are reconstructed by the Polubarinova‐Kochina method, i.e., by solution of a Riemann BVP. The seepage flow rate from the channel, free surfaces, and a saturated (water‐logged) area are found for different thicknesses of the top layer, channel widths, and conductivity ratios of the two strata. In particular, the earlier results of Brock, Kirkham, and Youngs, which are based on a numerical solution, Dupuit‐Forchheimer (DF) approximation, and approximate potential model, are confirmed in the full 2‐D models. Sufficiently far from the channel, the phreatic surface and interface make a wedge. For a sufficiently deep substratum, three zones are analytically distinguished: an almost vertical 1‐D descending flow, an almost wedge‐configured 1‐D flow, and an essentially 2‐D zone in between, where neither a standard infiltration theory nor DF analysis are valid.

Development of concentration-capillary convection on an interfacial surface

The onset of Marangoni convection initiated by introducing a surfactant solution drop onto a horizontal liquid interface is studied experimentally and theoretically. It is revealed that the film of admixtures adsorbed by this surface from the bulk of the contacting liquids begins to move only as a certain shear stress is reached, that is, the capillary flow development is of threshold nature. If compared with Marangoni convection development on the free liquid surface, the threshold shear stress may turn out to be either lower or higher, depending on the surfactant admixture concentration in both liquids and the pattern of changes in the surface tension with approaching the interfacial surface. In order to describe the threshold development of concentration convection, a nonlinear dependence of the shear stress at the liquid surface on the liquid velocity is proposed. In a numerical experiment, the convective flow pattern on the interface is determined and the time dependence of the flow intensity is obtained.

Super-resolution imaging of the natural killer cell immunological synapse on a glass-supported planar lipid bilayer.

The glass-supported planar lipid bilayer system has been utilized in a variety of disciplines. One of the most useful applications of this technique has been in the study of immunological synapse formation, due to the ability of the glass-supported planar lipid bilayers to mimic the surface of a target cell while forming a horizontal interface. The recent advances in super-resolution imaging have further allowed scientists to better view the fine details of synapse structure. In this study, one of these advanced techniques, stimulated emission depletion (STED), is utilized to study the structure of natural killer (NK) cell synapses on the supported lipid bilayer. Provided herein is an easy-to-follow protocol detailing: how to prepare raw synthetic phospholipids for use in synthesizing glass-supported bilayers; how to determine how densely protein of a given concentration occupies the bilayer's attachment sites; how to construct a supported lipid bilayer containing antibodies against NK cell activating receptor CD16; and finally, how to image human NK cells on this bilayer using STED super-resolution microscopy, with a focus on distribution of perforin positive lytic granules and filamentous actin at NK synapses. Thus, combining the glass-supported planar lipid bilayer system with STED technique, we demonstrate the feasibility and application of this combined technique, as well as intracellular structures at NK immunological synapse with super-resolution.