Impervious Barriers Research Articles

A model for saturated–unsaturated flow with fractures acting as capillary barriers

AbstractHigh‐resolution modeling of the flow dynamics in fractured soils is highly complex and computationally demanding as it requires precise geometrical description of the fractures in addition to resolving a multiphase free‐flow problem inside the fractures. In this paper, we present an idealized model for saturated–unsaturated flow in fractured soils that preserves the core aspects of fractured flow dynamics using an explicit representation of the fractures. The model is based on Richards’ equation in the matrix and hydrostatic equilibrium in the fractures. While the first modeling choice is standard, the latter is motivated by the difference in flow regimes between matrix and fractures, that is, the water velocity inside the fractures is considerably larger than in the soil even under saturated conditions. On matrix/fracture interfaces, the model permits water exchange between matrix and fractures only when the capillary barrier offered by the presence of air inside the fractures is overcome. Thus, depending on the wetting conditions, fractures can either act as impervious barriers or as paths for rapid water flow. Since in numerical simulations each fracture face in the computational grid is a potential seepage face, solving the resulting system of nonlinear equations is a nontrivial task. Here, we propose a general framework based on a discrete‐fracture matrix approach, a finite volume discretization of the equations, and a practical iterative technique to solve the conditional flow at the interfaces. Numerical examples support the mathematical validity and the physical applicability of the model.

Terrestrial solute fingering flow behind subsurface physical barriers during seawater intrusion

Blocking seawater intrusion in coastal aquifers through impervious subsurface physical barriers is a commonly used method, which creates a relatively closed hydrodynamic environment behind the barrier for the transport of land-sourced contaminants. This study investigated the phenomenon of terrestrial solute fingering flow behind subsurface physical barriers for the first time under field-scale hydrological and hydrogeological conditions. A prediction model for the onset of flow instability and the size of subsequent solute fingers was proposed based on the identified effects of these conditions. Once a modified Rayleigh number exceeded 4000, solute fingering flow behind subsurface physical barriers would occur, and the size of individual fingers followed a sigmoidal function growth with increasing Rayleigh number. Solute fingering flow resulted in a series of morphological changes in individual fingers from finger-like to foot-like with decreased salinity. The movement of solute fingers altered the trajectory and residence time of tracer particles, which led to an early particle arrival for those initially located behind. Compared to a no-finger situation, solute fingering flow accelerated the movement of tracer particles out of the suspended barriers with a reduced residence time by 45%. Shortened residence times and changed transport patterns as a result of solute fingering flow may have significant implications for the fate of terrestrial contaminants. Thus, caution should be exercised in the interpretation of field measurements on groundwater contamination in coastal aquifers if solute fingering flow behind subsurface physical barriers is expected, e.g., from the present prediction model.

Improvement of the Work Technology in the Construction of Impervious Barriers Using the Diaphragm Wall Method

Improvement of the Work Technology in the Construction of Impervious Barriers Using the Diaphragm Wall Method

Well hydraulics in wedge-shaped aquifer: Unsteady Darcian flow model revisited by lagging theory

Pumping events are often conducted in the alluvial fan due to its considerable amount of water; If pumping events occur in the nearby vicinity of the streams, it will inevitably influence the complex microbial ecosystems in both the river and the aquifer, induce the issue of water rights permits, and affect the development of the water resource management. Therefore, it becomes necessary to accurately predict groundwater flow as a result of pumping in the wedge-shaped aquifer. In this paper, we propose an analytical solution to describe the drawdown distribution and the stream depletion rate (SDR) due to pumping in a wedge-shaped aquifer, which represents the shape of the alluvial fan bounded by two streams. Moreover, we adopt the lagging theory into the model by introducing two lagging parameters in Darcy’s law to allow the water flow and the hydraulic gradient to occur at different times. This measure facilitates the reflection of the inertial force because of a higher pumping rate and the microstructural interaction resulting from the water transfer between the primary pores and secondary pores (e.g., dead-end pores and very-small pores). It leads to the predicted result being closer to reality when these effects are profound. We found that the drawdown and SDR curves will behave like waves when the flux lagging dominates. The SDR value can be over unit due to the additional recharge driven by inertial force; the drawdown and SDR acts more like an unconfined or dual-porosity flow if storage lagging governs the system. Moreover, lagging parameters have the largest effect on drawdown and SDR when the times are close to the corresponding values of lagging parameters. The case of wedge-shaped domain bounded by two impervious barriers is considered to further explore the boundary effects on aquifer response to pumping.

Integral equation technique for water wave interaction by an array of vertical flexible porous wave barriers

AbstractScattering of obliquely incident surface gravity waves by an array of partial flexible vertical porous wave barriers of varied configurations is studied in finite water depth and deep water cases. For the mathematical modeling purpose, linearized water wave theory is considered. Firstly, the problem associated with double vertical barriers is handled for a solution. To solve the problem, the associated BVP (boundary value problem) is transformed into a system of Fredholm integral equations of the second kind. By using suitable quadrature formulae, these integral equations are converted to a system of linear algebraic equations. These are solved to compute various important physical quantities associated with wave scattering. The energy identities for both finite water depth and deep water cases are derived. These derived energy identities are used to check the computational accuracy and to quantify the loss of wave energy by the barrier system. Subsequently, the study is extended to deal with wave scattering by multiple non‐identical unequally spaced barriers using wide‐spacing approximation and results for equally spaced identical barriers are obtained as a special case. The methodology is further generalized to deal with Bloch problem to incorporate a periodic array of infinite barriers. Occurrences of Bragg resonance in case of multiple barriers are analyzed. From the results associated with the linearized water wave theory, the second‐order mean wave forces are computed and compared with the first‐order wave forces. The phenomena of cloaking for wave scattering by multiple impervious barriers are discussed for a wide variety of wave and structural parameters. The methodology used in this present study can easily be generalized to solve similar problems that arise in mathematical physics.

Muco-adhesive clarithromycin-loaded nanostructured lipid carriers for ocular delivery: Formulation, characterization, cytotoxicity and stability

Topical ophthalmic formulations are the preferred approach to treat the anterior segment of the eye as it is a non-invasive therapeutic approach. The ocular bioavailability of drugs is generally limited, due to the presence of impervious anatomical barriers and low residence time and contact with the target tissue. Optimization of clarithromycin-loaded nanostructured lipid carriers using Design of Experiments was undertaken. Manufacture of nanostructured lipid carriers was achieved using hot emulsification ultrasonication. Formulation and process parameters were successfully identified following screening and subsequently optimized using Tween® 20, as a stabilizer. Muco-adhesive properties that could potentially increase ocular residence time, in vitro clarithromycin release and cytotoxicity against HeLa cells were evaluated. Short term stability studies of the optimized lipidic formulations was assessed at 4 °C and 22 °C. The optimized formulation exhibited muco-adhesive properties under stationary conditions assessed using Laser Doppler Anemometry, sustained release of API over 24 h under in vitro conditions. In vitro cytotoxicity studies revealed that the NLC were less cytotoxic to HeLa cells in comparison to pure API. The results suggest that the optimized carriers may have the potential to enhance precorneal retention, increase ocular availability and permit dose reduction or permit use of a longer dosing frequency.

Effect of water on the triaxial behavior under dynamic loading of asphalt concrete used in impervious barriers

Abstract Dams with an asphalt concrete core are a viable alternative in the construction of rockfill dams; therefore, characterization of the materials used in their construction is required. Part of this characterization requires obtaining the response parameters upon applying cyclic loads under different stress and temperature conditions. The objective of this research is to determine the effect of water on the dynamic properties of asphalt concrete after prolonged contact. To this end, an extensive program of laboratory tests was carried out in which specimens of this material were prepared, saturated and exposed to water. After the saturation process, the results of the tests indicated that the asphalt concrete presented a decrease in the shear modulus of 6.5% and an increase in the damping ratio of 16.1%, on average, with respect to the values obtained for the dry material. No significant change in the mechanical response was observed as a result of exposure to water for a period of up to 12 months.

Hydraulic, Volumetric, and Mechanical Approach in Asphalt Mixture Design for Impervious Barriers

AbstractAsphalt concrete has been used as an appropriate impervious barrier for water retention. The performance of asphalt concrete in dam cores, reservoir coatings, and canals is comparable with ...

Laboratory Investigation of Shear Behavior of High-Density Polyethylene Geomembrane Interfaces.

As a product of polymeric materials, geomembranes (GMs) are widely used in engineered systems as impervious barriers due to their low permeability. In this study, a large-scale composite shear test apparatus was developed to investigate the shear behaviors of various GM interfaces. A series of direct shear tests were conducted on GM–soil, GM–geotextile, and GM–concrete interfaces. Two types of high-density polyethylene (HDPE) GMs, a smooth GM and a textured GM, were used to evaluate the effect of GM-texturing on the shear properties of these interfaces. Based on the experimental data, the friction angles and adhesions of GM interfaces were calculated using the Mohr–Coulomb criterion. Test results describing the behavior of GM–soil and GM–geotextile interfaces from the current study were then compared with results from previous studies. The test results are shown to verify the reliability of the new large-scale composite shear apparatus. In addition, this paper presents preliminary experimental results of the GM–concrete interface shear tests.

Effect of water on the triaxial response under monotonic loading of asphalt concrete used in dams

Embankment dams with asphalt concrete cores have been constructed on practically all continents with satisfactory results. Nowadays many advantages, such as the mechanical strength, are known that makes asphalt concrete a competitive alternative for the construction of the impervious elements of dams. However, the current available information does not describe the effect of prolonged contact between asphalt concrete and water on the structure of an embankment dam. In this research cylindrical asphalt concrete specimens with a void content similar to that used in impervious barriers of dams were fabricated and submerged in water for a prolonged period to simulate the conditions experienced by asphalt concrete placed inside an embankment dam as its core material. Subsequently, triaxial compression tests were conducted on the specimens. The results indicated that the asphalt concrete exhibited a reduction in strength because of the saturation process to which the material was subjected. However, no changes were observed in the mechanical response to prolonged contact with water for periods of up to 12 months.

Interpretation of high pressure pack tests for design of impervious barriers under high-head conditions

High pressure packer test (HPPT) is an enhanced constant head packer test widely applied for characterizing the permeability or coupled hydromechanical properties of fractured rocks under high water pressure condition, but it remains an issue about how to choose a representative quantity from the test data for the design of impervious barriers in high-head geotechnical projects. In this study, the typical type curves of HPPTs are summarized and related to the intactness of rocks, flow condition in fractures and the possible hydraulic fracturing phenomenon in the tested rocks. Based on an interpretative model recently developed for HPPTs, a criterion is proposed to determine a proper permeability rate from the HPPT data for design of grout curtains by taking into account the type curves and the transition of flow conditions, and is applied to illustrate the implication of the proposed criterion for the design of impervious barrier in a high arch dam foundation. The proposed criterion could be of significance in the design of impervious barriers for reducing the risk of leakage in rocks under high water pressure condition.

Sensitivity of groundwater flow with respect to the drain–aquifer leakage coefficient

Abstract Mitigation measures may be used to prevent soil and water pollution from waste disposal, landfill sites, septic or chemical storage tanks. Among them, drains and impervious barriers may be set up. The efficiency of this technique can be evaluated by means of groundwater modeling tools. The groundwater flow and the leakage drain–aquifer interactions are implemented in a conforming finite element method (FEM) and a mixed hybrid FEM (MHFEM) in a horizontal two-dimensional domain modeling regional aquifer below chemical storage tanks. Considering the influence of uncertainties in the drain–aquifer exchange rate parameter and using an automatic differentiation (AD) tool, the aim of this paper is to carry out a sensitivity analysis with respect to the leakage coefficient for the piezometric head, velocity field, and streamlines to provide a new insight into groundwater waterbody exchanges. Computations are performed with both an ideal homogeneous hydraulic conductivity and a realistic heterogeneous one. The tangent linear codes are validated using Taylor tests performed on the head and the velocity field. The streamlines computed using AD are well approximated in comparison with the nondifferentiated codes. Piezometric head computed by the MHFEM is the more sensitive, particularly near to the drain, than the FEM one.

Advancement of sweep zones in waterflooding: conceptual insight based on flow visualizations of oil-withdrawal contours and waterflood time-of-flight contours using complex potentials

Sweep zones are traced in synthetic reservoir models of waterflood advancement based on potential functions. Time-of-flight contours, oil-withdrawal contours and streamlines corresponding to fluid withdrawal paths are visualized. The effects of differential well rates on waterflood sweep regions for a range of well architectures are systematically investigated using reservoirs that are continuous isotropic with and without impervious fault barriers. Complex potentials are capable of solving the drainage path for any constellation of producer and injection wells, accounting for any discontinuities that affect the flow path and productivity of the wells. Flood patterns are visualized for a series of doublets and 7-spot well patterns. Loss of planned drainage symmetry occurs when an undiscovered fault barrier obstructs and diverts the waterflood. Our method is assumed effective in illustrating the value of analytical streamline simulations for first-order assessment of sweep patterns in hydrocarbon field produced with waterflooding. The critical impact of injection rates and fault barriers on the shape of the waterflooding patterns is visualized in detail. The analytical streamline simulator allows tracing of the respective flow paths of displacing oil and water in the reservoir and visualizes both oil-withdrawal contours and waterflood time-of-flight contours. Generic rules are formulated to aid sweep maximization both prior to drilling and during the surveillance of producing wells.

Evaluation of gas permeability and mechanical behaviour of soil barriers of landfill cap covers through laboratory tests

The soil barrier is one of the commonly used impervious barriers which are required to sustain deformation and prevent the migration of biogas to the atmosphere. In the present study, a simple custom designed gas permeability–bending test setup was developed and used to evaluate the deformation behaviour of the soil barrier material in-relation with gas permeability measurements. A series of conventional beam bending tests, unconfined compression tests and gas permeability–bending tests was performed to evaluate the influence of loading pattern, compaction characteristics and fibre reinforcement on the deformation behaviour of the soil barrier material. The experimental results reveal that loading pattern was not found to have any significant influence on the flexural tensile strength of the soil; however, a considerable influence on the displacement corresponding to gas breakthrough was noticed mainly due to the variation in the cracking pattern. An increase in the moulding moisture content of the soil leads to a significant delay in crack initiation and gas breakthrough with a slight reduction in the flexural tensile strength. The percentage increase in the flexural tensile strength of the soil beam compacted with 2% and 4% wet of optimum, upon inclusion of fibres was found to be 33% and 92% respectively. Similarly, the percentage increase in the limiting displacement of the soil moist-compacted at 2% and 4% wet of optimum, upon inclusion of fibres was found to be 30% and 25% respectively, which implies that soil reinforced with fibres can sustain its integrity in-terms of gas intactness up to relatively larger distortion than an un-reinforced soil barrier material. The performance of the deformation behaviour of the soil barrier material has significantly improved in-terms of flexural tensile strength and gas intactness upon inclusion of discrete fibre inclusions within the soil.

Vapor Intrusion of VOCs and Indoor Exposure Risk: A Field Study in an Urban Neighborhood

Background: Characterizing vapor intrusion (VI) exposure risk often involves the collection of indoor air samples from affected buildings. Interpretation of field data and the assessment of health risks are widely recognized as challenging. Aims: To conduct field measurements at a well characterized site with the goal of improving VI models of transport mechanisms and risk characterization. Methods: Owners of three different properties (each with different foundation-types) were recruited to participate in our assessment in a Boston area neighborhood (USA) where VI of chlorinated solvents (VOCs) was known to be occurring and regulatory action underway. Ten (10) exterior soil gas sampling locations (nested at multiple depths) and three subslab sampling locations were installed. We conducted five quarterly sampling events. At each event, soil gas, indoor air, and groundwater samples were collected. Soil moisture content was also monitored and the soil geology was qualitatively described and evaluated. We communicated results with property owners and regulatory agencies. Results: Saturated soil zones appear to act as impervious barriers to vapor transport. Geologic features may also affect vapor transport. In several locations geologic stratigraphy correlated with soil gas concentrations. We identified the infiltration of sewer gas at one property resulting in PCE concentrations in indoor air that were nearly two-orders of magnitude higher compared to when infiltration of sewer gas was not known to be occurring. We are identifying implications of how our research can inform and improve VI characterization methods. Conclusion: Site models for VI should consider sewer lines as potential sources of volatile organic chemicals to indoor air, as well as geologic features that may restrict vapor transport. The integration of modeling results and field data, can be used to better understand site conditions and the potential for vapor intrusion exposure and health risk.

Heavy metal pollution in the Quaternary Garza basin: A multidisciplinary study of the environmental risks posed by mining (Linares, southern Spain)

Abstract In the metallogenic district of Linares (Jaen, Spain), intense deep mining associated with vein-type deposits of Pb and Cu has been conducted for centuries and has generated large mine waste accumulations. The objective of this study was to elucidate the influence of these mine wastes on the quality of the soil, the surface water and the groundwater. For this purpose, a sedimentary endorheic basin in the mining district was selected as the study location: the Quaternary Garza basin. The characterisation of the basin geometry and the tailings dams in the area was conducted by electrical resistivity imaging (ERI), which was supported with data provided by mechanical probing. The ERI data indicated that the basin is bounded by fractures that cause sudden changes in the thickness of the sedimentary cover and the wedging of the layers toward the edges of the basin. Furthermore, the resistivity profiles allowed the morphological identification of the deposits associated with the tailings dams. In addition, zones of weakness, preferential groundwater flow paths and the contact between the slimes deposits and the substratum were identified. These results confirmed the absence of impervious barriers at the tailings sites, which is a situation that poses a high pollution risk for soils and waters. A geochemical characterisation of the tailings dams and the surrounding soils indicated the presence of a high concentration of metals and metalloids. Of the 19 elements analysed at the dams, it is important to highlight the following values expressed in mg kg− 1: 19 913 for Pb, 418 for Cu, 4149 for Mn, 43 for As, 190 for Zn and 26 200 for Fe. Furthermore, the hydrochemical data showed the mobilisation through the aqueous media of certain heavy elements (Fe, Mn and Pb) that originate from lixiviation at these ancient tailings impoundments and from the adits that drain mine waters.

Watertightness, cracking resistance, and self-healing of asphalt concrete used as a water barrier in dams

The coefficient of permeability of hydraulic asphalt concrete is in the range 10−8–10−10cm/s. Laboratory test results show that triaxial specimens in axial compression can undergo axial strains up to 18% without any significant increase in permeability until approaching the compressive strength. For temperatures between 5 and 20 °C and strain rates between 2 × 10−3%/s and 5 × 10−3%/s, conventional hydraulic asphalt concrete can tolerate 1%–3% tensile strains before cracking in direct tension tests and strains up to 3%–4% in bending. At 20 °C the tensile and bending strains at cracking are 2–4 times higher than those at 0 °C, and at −20 °C they are approximately 0.2% and 0.8%, respectively. Asphalt concrete possesses pronounced crack self-healing properties. In the experiments, the crack leakage rate dropped 1–4 orders of magnitude within a few hours and the cracked specimens regained 55% of the intact tensile strength after only 1 day of self-healing. In summary, the comprehensive series of laboratory tests documents that asphalt concrete has characteristics that make the material extremely well suited for use in impervious barriers in dams, and the test results reported herein can be of great use in barrier design.

New record of the invasive Asian House Gecko (Hemidactylus frenatus) in Canberra

Until recently, biotic distributions were largely dictated by the interactions of dispersal, evolution, and plate tectonics (Huggett 2004; Cox and Moore 2005). Now, merchandise and people are transported at unprecedented rates in an embrace of globalisation, thereby providing pathways for flora and fauna to breach previously impervious geographic barriers (Lowe et al. 2000; Stachowicz et al. 2002). Despite Australia's geographic isolation, it has not escaped this phenomenon as there are an estimated 80 invasive, non-indigenous vertebrate species, an order of magnitude more for invertebrates, and approximately 2700 species of non-indigenous plant that have established populations in Australia (Low 1999; Bomford and Hart 2002; Pimentel 2002).

Soft Lithographic Functionalization and Patterning Oxide-free Silicon and Germanium

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a stable interface that permits efficient electron transport and protects underlying substrates from oxidative degradation. Group IV semiconductors can be effectively protected with highly-ordered self-assembled monolayers (SAMs) composed of simple alkyl chains that act as impervious barriers to both organic and aqueous solutions. Simple alkyl SAMs, however, are inert and not amenable to traditional patterning techniques. The motivation for immobilizing organic molecular systems on semiconductors is to impart new functionality to the surface that can provide optical, electronic, and mechanical function, as well as chemical and biological activity. Microcontact printing (μCP) is a soft-lithographic technique for patterning SAMs on myriad surfaces.1-9 Despite its simplicity and versatility, the approach has been largely limited to noble metal surfaces and has not been well developed for pattern transfer to technologically important substrates such as oxide-free silicon and germanium. Furthermore, because this technique relies on the ink diffusion to transfer pattern from the elastomer to substrate, the resolution of such traditional printing is essentially limited to near 1 μm.10-16 In contrast to traditional printing, inkless μCP patterning relies on a specific reaction between a surface-immobilized substrate and a stamp-bound catalyst. Because the technique does not rely on diffusive SAM formation, it significantly expands the diversity of patternable surfaces. In addition, the inkless technique obviates the feature size limitations imposed by molecular diffusion, facilitating replication of very small (<200 nm) features.17-23 However, up till now, inkless μCP has been mainly used for patterning relatively disordered molecular systems, which do not protect underlying surfaces from degradation. Here, we report a simple, reliable high-throughput method for patterning passivated silicon and germanium with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The technique utilizes a preformed NHS-reactive bilayered system on oxide-free silicon and germanium. The NHS moiety is hydrolyzed in a pattern-specific manner with a sulfonic acid-modified acrylate stamp to produce chemically distinct patterns of NHS-activated and free carboxylic acids. A significant limitation to the resolution of many μCP techniques is the use of PDMS material which lacks the mechanical rigidity necessary for high fidelity transfer. To alleviate this limitation we utilized a polyurethane acrylate polymer, a relatively rigid material that can be easily functionalized with different organic moieties. Our patterning approach completely protects both silicon and germanium from chemical oxidation, provides precise control over the shape and size of the patterned features, and gives ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. The approach is general and applicable to other technologically-relevant surfaces.

Soft lithographic functionalization and patterning oxide-free silicon and germanium.

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a stable interface that permits efficient electron transport and protects underlying substrates from oxidative degradation. Group IV semiconductors can be effectively protected with highly-ordered self-assembled monolayers (SAMs) composed of simple alkyl chains that act as impervious barriers to both organic and aqueous solutions. Simple alkyl SAMs, however, are inert and not amenable to traditional patterning techniques. The motivation for immobilizing organic molecular systems on semiconductors is to impart new functionality to the surface that can provide optical, electronic, and mechanical function, as well as chemical and biological activity. Microcontact printing (μCP) is a soft-lithographic technique for patterning SAMs on myriad surfaces.1-9 Despite its simplicity and versatility, the approach has been largely limited to noble metal surfaces and has not been well developed for pattern transfer to technologically important substrates such as oxide-free silicon and germanium. Furthermore, because this technique relies on the ink diffusion to transfer pattern from the elastomer to substrate, the resolution of such traditional printing is essentially limited to near 1 μm.10-16In contrast to traditional printing, inkless μCP patterning relies on a specific reaction between a surface-immobilized substrate and a stamp-bound catalyst. Because the technique does not rely on diffusive SAM formation, it significantly expands the diversity of patternable surfaces. In addition, the inkless technique obviates the feature size limitations imposed by molecular diffusion, facilitating replication of very small (<200 nm) features.17-23 However, up till now, inkless μCP has been mainly used for patterning relatively disordered molecular systems, which do not protect underlying surfaces from degradation.Here, we report a simple, reliable high-throughput method for patterning passivated silicon and germanium with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The technique utilizes a preformed NHS-reactive bilayered system on oxide-free silicon and germanium. The NHS moiety is hydrolyzed in a pattern-specific manner with a sulfonic acid-modified acrylate stamp to produce chemically distinct patterns of NHS-activated and free carboxylic acids. A significant limitation to the resolution of many μCP techniques is the use of PDMS material which lacks the mechanical rigidity necessary for high fidelity transfer. To alleviate this limitation we utilized a polyurethane acrylate polymer, a relatively rigid material that can be easily functionalized with different organic moieties. Our patterning approach completely protects both silicon and germanium from chemical oxidation, provides precise control over the shape and size of the patterned features, and gives ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. The approach is general and applicable to other technologically-relevant surfaces.