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International audience; When simply put on a solid, a liquid drop usually adopts the shape of a spherical cap or a puddle depending on its volume and on the wetting conditions. However, when the drop is subjected to a periodic field, a parametric excitation can induce a transition of shape and can break the drop’s initial axial symmetry, provided that the pinning forces at the contact-line are weak enough. Therefore, a standing wave appears at the drop interface and induces a periodic motion, with a frequency that equals half the excitation frequency. In the first part, we review the different situations where star drops can be generated from various types of periodic excitations. In the second part, we show that similar star drops can occur in a much less intuitive fashion when the drop is put on an air cushion, where no periodic motion is imposed a priori. Preliminary experiments as well as theoretical clues for a hydrodynamic interpretation, suggest that the periodic vibration is due to an inertial instability in the air layer below the drop.

There is a paucity of data on the relative transfer rates of deposited biological substances which could assist evaluation of the probability of given crime scene scenarios, especially for those relating to objects originally touched by hand. This investigation examines factors that may influence the secondary transfer of DNA from this source, including the freshness of the deposit, the nature of the primary and secondary substrate and the manner of contact between the surfaces. The transfer rates showed that both the primary and secondary type of substrate and the manner of contact are important factors influencing transfer of skin cells, but, unlike other biological fluids, such as blood and saliva, the freshness of the deposit in most instances is not. Skin cells deposited on a non-porous primary substrate transferred more readily to subsequent substrates than those deposited on a porous substrate. Porous secondary substrates, however, facilitated transfer more readily than non-porous secondary substrates, from both porous and non-porous surfaces. Friction as the manner of contact significantly increased the rate of transfer. The findings of this study improve our general understanding of the transfer of DNA material contained in fingerprints that is left on a surface, and assist in the evaluation of the probability of secondary and further DNA transfer under specific conditions.

Non-linear waves on the surface of a falling film of power-law fluid on a vertical porous plane are investigated. The waves are described by evolution equations generalising equations previously derived in the case of solid plane. It is shown that the slip condition on the interface between pure liquid and the porous substrate drastically changes structure of the steady waves travelling in the film. � 2009 Elsevier Ltd. All rights reserved.

Wicking is the spontaneous flow of a liquid in a porous substrate, driven by capillary force. This flow in aporous medium, caused by capillary action, is governed by the properties of the liquid such as surface tension, viscosity and density as well as the surface-wetting forces and geometric configuration of the pore structure such as yarn construction, number of fibres in the cross section, the randomness of the internal structure, twist and the fabric structure. In this study of wickability, the most widely used structures such as single jersey, single pique, double pique and honeycomb with two structural-cell stitch lengths have been considered. Wickability increases with structural-cell stitch length. Among the different structures of fabrics, single jersey with higher structural-cell stitch length shows better performance of wickability and absorption of water when drop is placed on the fabric. The wickability of knitted fabrics was also evaluated in different directions such as wale, course, and bi...

This manuscript introduces a new technique for depositing materials at controlled depths within porous substrates. This technique uses the passivating effect produced by one ALD precursor to prevent the adsorption of a second ALD precursor. For example, a surface exposed to trimethyl aluminum is not reactive towards diethyl zinc. This effect, combined with Knudsen diffusion through the nanopores in which the reactant exposure times dictate the depth of penetration of the ALD layer, enables spatially controlled "stripe coating" within porous supports such as anodic aluminum oxide (AAO) membranes. We have used this method to deposit stripes of ZnO, TiO2, V2O5, and Nb2O5 at specified depths in AAO membranes. The stripes were visualized by cross-sectional elemental mapping of the coated AAO membranes. The factors controlling the stripe locations and widths were identified by comparing the experimental results with the results of Monte Carlo simulations. This new technique opens up potential applications in sensors, separation devices, and multi-step catalysts.

Inspired by the wound healing property of certain trees, we report a novel microbes based additive process for producing three dimensional patterns, which has a potential of engineering applications in a variety of fields. Imposing a two dimensional pattern of microbes on a gel media and allowing them to grow in the third dimension is known from its use in biological studies. Instead, we have introduced an intermediate porous substrate between the gel media and the microbial growth, which enables three dimensional patterns in specific forms that can be lifted off and used in engineering applications. In order to demonstrate the applicability of this idea in a diverse set of areas, two applications are selected. In one, using this method of microbial growth, we have fabricated microlenses for enhanced light extraction in organic light emitting diodes, where densely packed microlenses of the diameters of hundreds of microns lead to luminance increase by a factor of 1.24X. In another entirely different type of application, braille text patterns are prepared on a normal office paper where the grown microbial colonies serve as braille tactile dots. Braille dot patterns thus prepared meet the standard specifications (size and spacing) for braille books.

Na2Ti7O15 nanotubes on a Ti net substrate were fabricated for the first time and used directly as a binder-free anode for Na-ion batteries. This material exhibited high reversible capacity and excellent stability which might be due to its unique characteristics including the porous substrate, nanoscale large surface area, nanotube structure and so on.

A model for drainage/imbibition of a foam placed on the top of a porous substrate is presented. The equation of liquid imbibition into the porous substrate is coupled with a foam drainage equation at the foam/porous substrate interface. The deduced dimensionless equations are solved using a finite element method. It was found that the kinetics of foam drainage/imbibition depends on three dimensionless numbers and the initial liquid volume fraction. The result shows that there are three different regimes of the process. Each regime starts after initial rapid decrease of a liquid volume fraction at the foam/porous substrate interface: (i) rapid imbibition: the liquid volume fraction inside the foam at the foam/porous substrate interface remains constant close to a final liquid volume fraction; (ii) intermediate imbibition: the liquid volume fraction at the interface with the porous substrate experiences a peak point and imbibition into the porous substrate is slower as compared with the drainage; (iii) slow imbibition: the liquid volume fraction at the foam/porous substrate interface increases to a maximum limiting value and a free liquid layer is formed between the foam and the porous substrate. However, the free liquid layer disappears after some time. The transition points between these three different drainage/imbibition regimes were delineated by introducing two dimensionless numbers.

One-year-old Pinus sylvestris donor plants were top-pruned in early May, allowing cuttings of three types to develop: shoots from adventitious buds near the top of the plant (T), weaker shoots from adventitious buds emerging further down the stem (M) and shoots from normal buds on branches (B). Cuttings from 46 half-sib families were collected at the beginning of August, treated with indole-butyric acid, immediately inserted in containers with porous substrate and put in a greenhouse, where soil was heated and high air humidity was maintained. The rooting frequency, estimated by counting living plants 10 months after insertion, was 54%. The family variance component for rooting was small and non-significant, while the clone-within-family component was strongly significant and accounted for 21% of the total random variance. Type M and type B cuttings showed significantly better rooting ability than type T cuttings. Including only plants with at least four acceptable shoots in the propagation exper...

For hybrid media, involving both a porous substrate and an unobstructed flow region, difficulties arise due to the proper mathematical treatment given at the macroscopic interface. The literature proposes a jump condition in which shear stresses on both sides of the interface are not of the same value. This paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a porous layer through which an incompressible fluid flows in turbulent regime. Here, diffusion fluxes of both momentum and turbulent kinetic energy across the interface present a discontinuity in their values, which is based on a certain jump coefficient. Effects of such parameter on mean and turbulence fields around the interface region are numerically investigated. Results indicate that depending on the value of the stress jump parameter, a substantially different structure for the turbulent field is obtained.

A SiC layer was grown by vacuum sublimation epitaxy on porous silicon carbide. A porous SiC layer about 10 µm thick was fabricated by electrochemical etching of an off-axis 6H-SiC substrate. The epitaxial layer was ∼ 10 µm thick. Structural and optical properties of the initial substrate and the porous and epitaxial layers were investigated by X-ray, IR-reflection and photoluminescence methods. An epitaxial SiC layer grown on porous SiC exhibits improved characteristics when compared to a SiC layer on a conventional substrate.

This study aimed to evaluate under photoautotrophic conditions the effect of CO2-enriched atmosphere (360 or 1,000 μmol CO2 mol−1 air) combined with two substrate types (agar or Florialite®) in vitro on plants of Pfaffia glomerata, an endangered medicinal species with promising applications in phytotherapy and phytomedicine. The effects of the treatments on the growth, stomatal density, Rubisco activity, carbon isotopic discrimination, metabolite accumulation, photosynthetic pigments and ultrastructural characteristics were investigated. After a 35-day cultivation period, the in vitro-growth of P. glomerata nodal segments under the different treatments resulted in plants with substantial differences in relation to their growth, photosynthetic pigments, stomatal density and leaf ultrastructural characteristics. The enrichment with CO2 coupled with a porous substrate increased the growth of P. glomerata. The stomatal density in the abaxial epidermis more than doubled in response to the high CO2 supply in both supporting types, whereas the Rubisco activity and activation state were both unresponsive to the treatments. Regardless of the CO2 supply, the plants grown in agar displayed higher carbon isotope discrimination than their counterparts grown in Florialite®. We propose that the long-term photosynthetic performance was improved using Florialite® as a growth support in combination with a high CO2 supply. No apparent signs of photosynthetic down-regulation could be found under elevated CO2 conditions. The enrichment of in vitro atmospheres with CO2 coupled with a porous substrate offers new possibilities for improving the growth and production on a commercial scale of high morphological and physiological quality Pfaffia plants.

Changes in film composition and characteristics that occur during and/or immediately after the application of latex paints on porous inorganic substrates were investigated. Gas chromatography (GC) and thermal analysis were among the techniques used for this purpose. The changes in coalescing agent and binder content were determined by GC and thermogravimetric-analysis, respectively, and the changes in glass transition temperature by differential scanning calo rimetry. It was found that the type of porous substrate could significantly affect the paint composition (pigment volume concentration, coalescent level) during the film formation process.

High-density, large-scale culture of hepatocytes is a key requirement in the development of a bioartificial liver that can replace liver functions in patients with severe liver insufficiency. We have applied a porous polymer, polyvinyl formal (PVF) resin, as a cell-supporting material for hepatocyte culture. We evaluated the performance of the culture system using PVF resin under three different culture conditions: a shake culture on conventional dishes, perfusion culture with sheet-shaped PVF, and a packed-bed-type module. Among them, the packed-bed reactor using PVF resin enabled high-density culture of hepatocytes (2×107 cells/cm3-PVF). The hepatocytes immobilized in the PVF resin maintained satisfactory metabolic functions (ammonium metabolism and albumin secretion) comparable to those of the monolayer dish cultures. Furthermore, by maintaining dissolved oxygen concentration at a relatively high level (260–460μM), the metabolic functions of the hepatocytes were improved. It was concluded that the packed-bed reactor using PVF resin is a promising system for developing a bioartificial liver using hepatocytes.

In this work, the thermal performance of a conventional tubeless collector is improved by inserting porous substrates at the inner side of the collector absorber plate. The porous substrates improve the convective heat transfer coefficient between the absorber plate and the fluid. This improvement is investigated numerically and its effects on the efficiency and the useful gain of the collector are evaluated. It is found that inserting the porous substrate may raise the collector efficiency by 3–32% especially at high values of the overall heat loss coefficient.

Simulation of gelation occurring during ceramic membrane formation by sol-gel process is reported. The main cause for gelation in this case is the suction of liquid from the sol by a porous substrate. When aggregation takes place by random collisions only and there is no liquid removal, the gelation takes place uniformly in the liquid. However, when gelation results from the removal of liquid from the surface, a clear gradient in concentration from the interface to the bulk is seen. The structure formed shows maximum compactness at the interface and it progressively becomes more open as the distance from the interface increases. As the liquid removal rate increases, the structure as a whole becomes more compact and as the pH increases the structure becomes more open. The shapes of the pores in the structure of gels formed exhibit directionality, i.e. the pores tend to be perpendicular to the surface of the liquid removal which may be advantageous for a system like the ceramic membrane.

In this paper, the transmission and leakage loss of post-wall waveguide depending on the thickness of porous substrate was evaluated. The transmission loss for various thickness of the porous waveguide was simulated in millimeter-wave band by using EM simulator. The valid substrate thickness for improving transmission loss by air-holes was studied. The leakage of the waveguide was also evaluated as a function of substrate thickness, and the relationship between transmission loss and leakage was discussed.

A physical model for VOC emission from a coating film applied on porous substrates was proposed. In the model, the mass transfer at the air–film interface, at the film–substrate interface, and in the substrate is mathematically described and the mass change of the film because of the evaporation into indoor air and penetration into the substrate was quantified. Therefore, a whole process from “wet” state to “dry” state for the coating film can be characterized. Compared with the experimental data in the literature, the model is validated. Through a case study, it is found that VOC emissions prolong for a longer time after a sharp VOC release, and that the liquid VOC may exists in the substrate, though the film becomes “dry.” After the liquid VOC evaporates completely, the gas-phase VOC in the porous substrate keeps in a relative high concentration level for a longer time.

For the correct interpretation of results of tangential electrokinetic measurements with porous materials, in particular, composite/asymmetric membranes on porous supports, it is necessary to have the data available for various channel heights. In some kinds of equipment, the variation of channel height is technically possible only for a range of relatively large heights. This communication shows that under these conditions, the fluid flow can become undeveloped and the conventional approaches to the interpretation of electrokinetic measurements should be modified accordingly. In particular, the dependence of streaming-current coefficient on the channel height becomes sub-linear. If the experimental data are available only for larger channel heights, this can be mistakenly taken for the manifestation of contribution of porous sub-structure to the streaming current. In this communication, we investigate electrokinetic phenomena in undeveloped flows both numerically and experimentally. We confirm that the aforementioned sub-linearity occurs for nonporous as well as porous substrates. We also demonstrate that the channel heights estimated from the volume flow rate by using numerical simulations of undeveloped flows are in very good agreement with the reference values obtained from the electrical conductance (in contrast to the values estimated by using the conventional approach of Hagen–Poiseuille equation). The numerical fitting of channel-height dependences of streaming-current coefficient enables us to separate the contributions of external surface and porous sub-structure (in case of porous substrates) and obtain quite reasonable values of (effective) zeta-potentials in both cases. Nonetheless, the accuracy of experimental data deteriorates with increasing channel height, so it is generally advisable to vary the heights within a range below 100–150 μm.

International audience; Fluid confinement is ubiquitous in nature and industry, and is the most widely used technique to characterize porous materials. The main characterization tool consists in measuring the so-called adsorption/desorption isotherms, i.e. the amount of gas adsorbed by the poroussubstrate as a function of the fluid chemical potential (or relative pressure). The models used to analyse the data are generally quite simple, leading to inaccurate characterization of the porous materials. In particular, ignoring the interdependence between the elemental pores or domains leads to inappropriate conclusions. Our approach proposes to cure this problem in the molecular simulation approaches

The sound field within a layered porous granular medium may be explored by means of suitably protected probe microphones. The field within a system consisting of a granular surface layer above a thick porous substrate with considerably higher flow resistivity is modelled by assuming the granular media to be characterized by uniform slit-pores within a rigid solid matrix and by applying boundary conditions at each interface. The predicted relative amplitude spectrum within the surface layer is influenced by interferences between the first few wave components of the internally reflected field. Predictions are in qualitative agreement with data obtained in washed sand and gravel.

The present investigation deals with the application of a continuous wave-high power diode laser to modify the surface of porous substrates made from spherical particles in sintered bronze. In particular, the influence of laser power and interaction time on the capability of the laser processing to restructure the substrate morphology was investigated. Scanning Electron Microscope (SEM) and contact-gage surface profiler were used to analyze the evolution of the substrate morphology after laser treatments, whilst their mechanical properties were evaluated by micro-hardness and scratch tests. The experimental findings showed a decrease in the surface roughness of the porous substrates after laser treatments of ∼70%. In addition, an improvement in micro-hardness, scratch and wear resistance could also be achieved. Indeed, large laser power combined with high scan speed took to the most attractive results, thus favoring the onset of a promising morphological structure and the establishment of improved hardness and scratch resistance. © 2012 Elsevier Ltd. All rights reserved.

На основе интегральных законов сохранения массы и энергии построена математическая численно-аналитическая модель деформации сплошной жидкометаллической капли после ее соударения с плоской пористой поверхностью. Модель учитывает капиллярные и адгезионные свойства расплава. Проведены численные расчеты для модельного случая соударения сплошной жидкой капли из диоксида циркония с пористой подложкой., A numerical analytical model of deformation of a liquid metal droplet impacted on a flat porous surface was developed from the integral laws of conservation of mass and energy. The model takes into account capillary and adhesive properties of the melt. Numerical model calculations were performed for impact of a molten zirconium dioxide droplet on a porous substrate.

Torsional joints have been made using stainless steel cylinders bonded together with a polyurethane ‘adhesive’. Fully dense steel and sintered substrates have been employed. Whilst the fully dense steel adherends gave rise to maximum shear stresses at failure of the order of 3.5 MPa, joints made with sintered steel were found to be far stronger. Apparent energies of adhesion were typically five to six times greater. Separation bully dense metal substrates and the polymer is apparently interfacial whilst sintered adherends give rise to mechanical interlocking of the polymer within the pores. The extra energy required to provoke failure is related to that needed to extend and break polymer fibrils embedded in the porous substrate structure and still attached to the bulk polymer.

The binding of polyelectrolyte to a temperature- and pH-responsive microgel based on poly-N-isopropylacrylamide (PNiPAM) copolymerized with methacrylic acid (MAA) as a soft and porous substrate was investigated as a function of time and temperature in order to probe rearrangements in such complexes. Oppositely charged polyelectrolytes bind to the charged microgels, and the composition of the resulting complexes stays constant with time. The number of titrable COOH groups, the size, and the electrophoretic mobility of the complexes, however, change with time due to rearrangements of polyelectrolyte chains inside of the microgel. Polyelectrolytes can be used to modify the properties of microgels. The volume phase transition temperature (VPTT) of PNiPAM-co-MAA microgels depends on the pH value, while microgel polyelectrolyte complexes collapse above the VPTT of 32 °C independently of the pH value. The experiments reveal that polyelectrolytes can be partially released from microgel-polyelectrolyte complexes at TVPTT. In addition, rearrangements are induced by the collapse. Rebinding of the polyelectrolyte occurs upon reswelling of the complex when the temperature is reduced below the VPTT. Such temperature cycles affect the size and electrophoretic mobility of complexes. The rearrangements can be used to increase the amount of polyelectrolyte that is bound to the microgel and are thus important for applications that rely on loading microgels with polymers. Interestingly, the colloidal stability of the complexes at TVPTT depends on the preparation temperature; complexes prepared at TVPTT remain colloidally stable when heated to TVPTT; on the other hand, complexes prepared at TVPTT display poor colloidal stability.

International audience; The temporal stability of a Carreau fluid flowing down an inclined porous substrate is considered. A reduced model is derived under the assumption of small permeability which decouples the flow in the liquid layer from the filtration flow in the porous medium and incorporates the effect of the porous medium by means of an effective slip condition at the liquid-solid interface. The slip coefficient in the effective slip condition is a function of the structure, permeability of the porous medium and the rheology of the fluid saturating the porous medium. The effects of shear-thinning rheology and permeability of the substrate on the stability of the film flow system are investigated. This problem gives rise to a generalized eigenvalue formulation which is solved through two approaches. The problem is solved analytically for long waves in the limiting cases of weakly and strongly non-Newtonian behaviors (power-law limit). A numerical investigation is carried out in the general case. The results are shown to agree well for the weakly non-Newtonian limit. Further, the power-law model and the Carreau model agree on a wide range of shear-thinning parameter values for a thin film over a rigid substrate. However, when considering a porous medium, this trend is not observed. The Carreau model gives valid results for the entire range of shear-thinning parameter values for a film over a rigid/porous substrate. The novelty of the present investigation lies in the inclusion of both the effects of bottom permeability and shear-thinning rheology. Both permeability and shear-thinning rheology have a destabilizing effect on the film flow system. The numerical results indicate the correlation between the effects due to shear-thinning properties and permeability. An energy balance analysis performed on the perturbation fields shows that destabilization induced by both shear-thinning and permeability is linked to the viscous shear work rate on the free surface.

Electrochemical transfer junctions (ETJs) were synthesized via a physical or chemical covering method onto a porous ceramic substrate (mullite and alumina). The Mo6S8 layer thickness ranged from 10 to 100 μm. The ETJ composites placed between two tanks lead to a cobalt transfer by applying a current density between electrodes placed in both tanks. The thickness decrease compared to a hot pressed junction allows imposing current densities equal to 7 or 9 mA cm−2 inducing 4–6 fold faster Co2+ fluxes (1.3.10−4 and 1.7.10−4 mol h−1 cm−2 for physical and chemical covering respectively, versus 2.9.10−5 mol h−1 cm−2 for hot pressed junctions). Keywords: Mo6S8, Chevrel phase, Electrochemical cation transfer, Porous substrate, Metal recovery

Potential utilization of calcium alkoxides as stone consolidants was considered. Reaction of Ca(OCH3)2, Ca(OCH2CH3)2(CH3CH2OH)4 and Ca[OCH(CH3)2]2 with the atmosphere in different experimental conditions was studied. The reaction produced CaCO3 and two different pathways seem to be involved, the first taking place through CO2 insertion into the Ca–O bond of Ca(OR)2 species with formation of an alkylcarbonate derivative, subsequently transformed into CaCO3 through ROH elimination; the second takes place through hydrolysis of Ca(OR)2 to Ca(OH)2, which is then carbonated to CaCO3. The vaterite/calcite ratios found in the final CaCO3 vary considerably with the experimental conditions adopted. Investigations demonstrated the potentiality of Ca(OCH3)2 to act as a stone consolidant. In fact, impregnation of a porous substrate, simulating the deteriorated stone, with a methanol solution of Ca(OCH3)2, produced a crystalline vaterite film, which gradually filled all the pores and cavities of substrate and seems to fulfil the necessary requirements for a consolidant. Copyright © 2008 John Wiley & Sons, Ltd.

A new methodology has been developed to measure the maximum pressure that can be withstood by a bilayer lipid membrane (BLM) formed over porous substrates. A custom test fixture was fabricated to pressurize BLMs in very fine increasing increments until they fail. This experiment was performed on 1-Stearoyl-2-Oleoyl-sn-Glycero-3-Phosphatidylocholine (SOPC) BLMs formed over polycarbonate substrates with a single pore ranging from 5 to 20 microns in diameter. Failure pressure was found to be inversely proportional to pore diameter. The same set of experiments was repeated for BLMs that were formed from a mixture of SOPC and 50 mol% cholesterol (CHOL). The presence of cholesterol was found to increase the failure pressure of the BLMs by 56% on average. A model of the characteristic pressure curve from this experiment was developed based on the pressurization and flow of fluid through a porous substrate. The model was found to accurately fit the experimental pressure curves.

A dynamic filtration technology, called rotating and vibrating filtration (RVF technology), has been investigated for the clarification of rough beer. The module was divided into two parallel cells including flat disc membranes fixed onto porous substrate which drained the permeate, and impeller-shaped rotating bodies attached to a central shaft. Experiments were carried out at pilot scale and under industrial operating conditions (temperature regulation: 0-4 degrees C, CO2 pressure: 1000-1500 mbar) with two different rough beers (lager beer type, 11 degrees and 15 degrees Plato) and a model beer (yeast suspension). In a first step, the radial additional pressure and the core velocity coefficient were determined. In a second step, the technology was evaluated with regards to qualitative (pH, haze, dry matter, yeast concentration, colour, bitterness, carbohydrates, proteins, polyphenols) and quantitative (flux, retention rate) criteria versus mean pore diameter. Finally, the performances versus the volume reduction factor were specifically scrutinised with real and model beers. RVF technology demonstrates high performances in terms of flux as well as producing a clarified beer of good quality (EBC norm). Overall results were compared to recent scientific literature and industrial practice.

Eu 3+ - and Ce 3+ -doped yttrium silicate, as well as Eu 2+ -doped zinc silicate nanoparticles, were grown in a porous SiO 2 matrix using an impregnation method. For Y 2 Si 2 O 7 :Eu 3+ , particles of about 50 nm size were obtained that exhibited several photoluminescence (PL) peaks in red. Different peaks showed slightly different decay times; however, their excitation mechanism was found the same. Increasing the Eu concentration increased the PL intensity while reducing the decay time. Y 2 Si 2 O 7 :Ce 3+ nanoparticles in the porous matrix showed bright blue emission, consisting of two peaks at 358 nm and 378 nm. Re-impregnation process was found effective in changing the relative intensity of the two peaks. Zn 2 SiO 4 :Eu 2+ nanoparticles in porous glass consisted of amorphous particles of about 20 nm size inside the porous matrix. The luminescence was a broad peak centered at 418 nm. These phosphor systems, together with our previously reported Zn 2 SiO 4 :Mn 2+ in porous SiO 2 structure, comprise a red–green–blue system that can be used in display applications.