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PubMed2003

Variations in acaricidal effect of wettable sulfur on Tetranychus urticae (Acari:Tetranychidae): effect of temperature, humidity and life stage.

Under laboratory conditions, the acaricidal effect of wettable sulfur is influenced by climatic conditions and the stage of development of Tetranychus urticae. Its ovicidal effect results from the combined action of temperature and relative humidity (RH). Wettable sulfur becomes effective at 27.5 degrees C and 75% RH. Beyond this threshold, the acaricidal effect increases with rising temperature or humidity, to become complete at a temperature of 35 degrees C and 90% RH. Within the range of temperatures and humidities 20 degrees C/30% RH and 35 degrees C/90% RH the mortality of immatures (from protonymphs to teleiochrysalis) was total. Under similar experimental conditions, females usually died before the end of the experiment. Temperature and relative humidity increased the adulticidal potential of wettable sulfur. The fecundity of the sulfur-treated females and the viability of their progeny was found to depend on temperature and RH. According to the same climatic conditions, eggs were less susceptible than females, which were in turn less susceptible than juvenile stages.

Aging↗

PubMed1996

Germination of Phyllosticta ampelicidaPycnidiospores: Prerequisite of Adhesion to the Substratum and the Relationship of Substratum Wettability

Pycnidiospores of Phyllosticta ampelicida, the causal agent of black rot of grape, were found to germinate only on substrata on which they were firmly attached. Such surfaces were poorly wettable and had advancing contact angles (straight thetaa) formed by a water drop of >80°, e.g., grape leaf, polystyrene, Teflon, polycarbonate, collodion, and glass treated with the silanes n-octadecyltrichlorosilane, dimethyldichlorosilane, or diphenyldichlorosilane. When pycnidiospores were deposited on more wettable surfaces they did not attach firmly and did not germinate. Such highly wettable surfaces had straight thetaa </= 40° and were represented by heat-treated glass, cellophane, nutrient- and water-agars, polystyrene treated with UV-irradiation or sulfuric acid, and glass silanized with n-2-aminoethyl-3-aminopropyltrimethoxysilane, n-(trimethoxysilylpropyl)ethylenediamine triacetic acid trisodium, or 3-aminopropyltriethoxysilane. Adhesion of pycnidiospores was assessed with and without a hydraulic shearing force. Pycnidiospore adhesion occurred over several minutes in distilled deionized water, unless it was first acidified, which decreased attachment time to <0.03 s. Attachment of pycnidiospores treated with sodium azide, formaldehyde, or boiled in water for 10 min was similar to nontreated conidia. Possible mechanisms of adhesion of the conidia to surfaces include hydrophobic and ionic interactions.

Journal Article↗

PubMed2000

The Effect of Fluid Shear Stress on Endothelial Cell Adhesiveness to Polymer Surfaces with Wettability Gradient.

In this study, the adhesive strength of endothelial cells (ECs) attached on polymer surfaces with different hydrophilicity was investigated using wettability gradient polyethylene (PE) surfaces prepared by corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The EC-attached wettability gradient surfaces were mounted on parallel-plate flow chambers in a flow system prepared for cell adhesiveness test. Three different shear stresses (150, 200, and 250 dyne/cm(2)) were applied to the flow chambers and each shear stress was maintained for 120 min to investigate the effect of shear stress and surface hydrophilicity on the EC adhesion strength. It was observed that the ECs were adhered more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion of the cells appeared at around water contact angles of 55 degrees. The EC adhesion strength was higher on the hydrophilic positions than on the hydrophobic ones. However, the maximum adhesion strength of the cells also appeared at around water contact angles of 55 degrees. More than 90% of the adhered cells remained on that position after applying the shear stress, 250 dyne/cm(2) for 2 h, whereas the cells were completely detached on the hydrophobic position (water contact angle, about 86 degrees ) within 10 min after applying the same shear stress. It seems that surface hydrophilicity plays a very important role for cell adhesion strength. Copyright 2000 Academic Press.

Journal Article↗

PubMed1989

Wettability of a hydrophilic addition silicone impression material.

Silicone impression materials, long noted for their poor wettability, have typically demonstrated contact angles with water greater than 90 degrees. This study compared the wettability of a new hydrophilic addition silicone with that of other impression materials. Specimens from various viscosities of polyether, polysulfide, hydrophobic addition silicone, and hydrophilic addition silicone were formed against a smooth surface. The advancing contact angle of a saturated aqueous solution of CaSO4 on the impression materials was measured after 1 minute. Mean contact angles were calculated and results were analyzed by ANOVA and a multiple comparison of means procedure. Differences between pairs of contact angle means were found to be statistically significant except for the polyether-hydrophilic addition silicone pair. The wettability of the hydrophilic addition silicone impression material was found to be not significantly different from that of a polyether impression material.

Calcium Sulfate↗

PubMed1985

Interaction of cultured human endothelial cells with polymeric surfaces of different wettabilities.

The in vitro interaction of human endothelial cells (HEC) and polymers with different wettabilities in culture medium containing serum was investigated. Optimal adhesion of HEC generally occurred onto moderately wettable polymers. Within a series of cellulose type of polymers the cell adhesion increased with increasing contact angle of the polymer surfaces. Proliferation of HEC occurred when adhesion was followed by progressive flattening of the cells. Our results suggest that moderately wettable polymers exhibit a serum and/or cellular protein adsorption pattern that is favourable for growth of HEC.

Cell Adhesion↗

PubMed2004

The effect of wettability on drop attachment to glass rods.

The coalescence of droplets in fibrous filters depends on many parameters such as wettability, filter depth, flow velocity, and filter materials. The objective of this work is to determine the effect of the wettability on the coalescence mechanism. Experimental results from tests on coated glass rods are presented. Three different silanes are deposited on the glass rod surfaces to change the surface wettability. Flow of water-in-oil emulsion past the glass rods is observed. When the rod surface is wetting the dispersed phase coats the rod. When the surface is nonwetting the drops do not stick easily to the surface and do not coat it but slide around to the downstream side, where they are dragged off the rod. Such behavior is important in understanding the performance of coalescing filter media.

Journal Article↗

PubMed2005

Wettability of Freon hydrates in crude oil/brine emulsions.

The surface energy of petroleum hydrates is believed to be a key parameter with regard to hydrate morphology and plugging tendency in petroleum production. As of today, the surface energy of natural gas hydrates is unknown, but will depend on the fluids in which they grow. In this work, the wettability of Freon hydrates is evaluated from their behavior in crude oil emulsions. For emulsions stabilized by colloidal particles, the particle wettability is a governing parameter for the emulsion behavior. The transition between continuous and dispersed phases as a function of brine volume in crude oil-brine emulsions containing Freon hydrates has been determined for 12 crude oils. Silica particles are used for comparison. The results show that phase inversion is highly dependent on crude oil properties. Based on the measured points of phase inversion, the wettability of the Freon hydrates generated in each system is evaluated as being oil-wet, intermediate-wet, or water-wet. Generation of oil-wet hydrates correlates with low hydrate plugging tendency. The formation of oil-wet hydrates will prevent agglomeration into large hydrate aggregates and plugs. Hence, it is believed that the method is applicable for differentiating oils with regard to hydrate morphology.

Journal Article↗

PubMed2006

Wettability of nano-epoxies to UHMWPE fibers.

Ultra high molecular weight polyethylene (UHMWPE) fibers have a unique combination of outstanding mechanical, physical, and chemical properties. However, as reinforcements for manufacturing high performance composite materials, UHMWPE fibers have poor wettability with most polymers. As a result, the interfacial bonding strength between the fibers and polymer matrices is very low. Recently, developing so-called nano-matrices containing reactive graphitic nanofibers (r-GNFs) has been proposed to promote the wetting of such matrices to certain types of fiber reinforcements. In this work, the wettability of UHMWPE fibers with different epoxy matrices including a nano-epoxy, and a pure epoxy was investigated. Systematic experimental work was conducted to determine the viscosity of the epoxies, the contact angle between the epoxies and the fibers. Also obtained are the surface energy of the fibers and the epoxies. The experimental results show that the wettability of the UHMWPE fibers with the nano-epoxy is much better than that of the UHMWPE fibers with the pure epoxy.

Journal Article↗

PubMed2004

Infiltration of PCE in a system containing spatial wettability variations.

A two-dimensional infiltration experiment was conducted to investigate and quantify the effect of spatial wettability variations on DNAPL migration and entrapment in saturated sands. Experimental observations of tetrachloroethylene (PCE) infiltration showed that organic-wet sand lenses acted as very effective capillary barriers, retaining PCE and inhibiting its downward migration. A multiphase numerical simulator was used to model this sand box experiment. The simulator incorporates wettability-modified van Genuchten and Brooks-Corey capillary pressure/saturation relationships as well as Burdine and Mualem relative permeability relationships. PCE mass distributions, estimated by image analysis of digital photographs taken during the infiltration event, were compared to simulation results. Although both relative permeability models were qualitatively able to predict the PCE retention in the organic-wet layers, simulations with the Mualem model failed to capture the observed rate of PCE migration. A traditional multiphase simulator, incorporating water-wet capillary retention relations, failed to predict both PCE pathways and retention behavior. This study illustrates the potential influence of subsurface wettability variations on DNAPL migration and entrapment and supports the use of modified capillary relations in conjunction with the Burdine model in multiphase flow simulators.

Environmental Pollutants↗

PubMed2003

Cell adhesion and cytotoxicity studies over polyanionic collagen surfaces with variable negative charge and wettability.

This work describes the cytotoxicity, and the cell adhesion behavior of K562 cell line from human erythroleukemia transfected with the DNA for the alpha(2)beta(1) integrin over type-I collagen matrices with variable degree of carboxyl group and wettability. The results showed that type-I collagen materials with variable degree of carboxyl group prepared by selective hydrolysis of carboxyamide side chains of Asn and Gln residues present in the protein, independently from the extent of side chain hydrolysis, was characterized by preserved triple helix structure for materials with a carboxyl group content up to 87 +/- 17. Imbibition and wettability increased linearly with increasing carboxyl group content from 46 +/- 12 to 87 +/- 17, and no signs of cytotoxicity were detected. Nevertheless, in comparison to native collagen, K562 cell adhesion to PACMs was significantly improved by factors ranging from 1.60 to 1.47x, with the reduction in cell adhesion observed with increasing carboxyl content attributed to a balance between the inhibition of increasing negative charge and the stimulation by increased wettability. On the other hand, the overall improvement of K562 cell adhesion to polyanionic collagen was attributed to the introduction of new distinct motifs described as the minimal active recognition sequence for alpha(2)beta(1) integrins binding with type-I collagen produced as a result of Asn-Gly Glu-Ala alpha2(I)294-297, and Gly Gln-Arg-Gly Val-Val carboxyamide side chains hydrolysis.

Animals↗

PubMed2000

Wettability studies of morphine sulfate powders.

A capillary penetration technique was used to determine the wettability of morphine sulfate powders by a range of wetting and partially wetting liquids. Wetting rates were found to be dependent on both the properties of the wetting liquid and the morphine sulfate batch. A number of liquids were established as perfectly wetting, and the critical surface tension for morphine sulfate wetting was estimated to be approximately 40 mN m(-1). Effective capillary radii for packed beds of morphine sulfate powders were determined in the range 0.3-0.6 microm; these are compared with particle size, shape and surface area data. From the Washburn approach, the advancing water-particle contact angles for the different morphine sulfate samples were determined to be in the range 57-79 degrees, with errors less than +/-3 degrees. Sessile drop measurements on the same samples were unable to determine reproducible equilibrium contact angles and could not differentiate between the batches. The role of surface chemistry, crystal morphology and crystal structure in controlling morphine sulfate powder wettability was explored by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction. Contact angles were shown to correlate with both the aspect ratio of the morphine sulfate crystals and the nitrogen-to-oxygen surface atomic concentration ratio, determined by SEM and XPS, respectively. The relative exposure of different crystal faces is considered to play an important role in controlling the wettability of morphine sulfate powders.

Crystallization↗

PubMedDate not supplied

Quantitative evaluation of porous media wettability using NMR relaxometry.

We propose a new method to determine wettability indices from NMR relaxometry. The new method uses the sensitivity of low field NMR relaxometry to the fluid distribution in oil-water saturated porous media. The model is based on the existence of a surface relaxivity for both oil and water, allowing the determination of the amount of surface wetted either by oil or by water. The proposed NMR wettability index requires the measurement of relaxation time distribution at four different saturation states. At the irreducible water saturation, we determine the dominant relaxation time of oil in the presence of a small amount of water, and at the oil residual saturation, we determine the dominant relaxation time of water in the presence of a small amount of oil. At 100% water and 100% oil saturation, we determine the surface relaxivity ratio. The interaction of oil with the surface is also evidenced by the comparison of the spin-lattice (T1) and spin-locking (T1rho) relaxation times. The new NMR index agrees with standard wettability measurements based on drainage-imbibition capillary pressure curves (USBM test) in the range [-0.3-1].

Geologic Sediments↗

PubMed2004

Effect of layer integrity of spin self-assembled multilayer films on surface wettability.

We investigated the correlation between surface wettability and internal structure of polyelectrolyte (PE)/PE and PE/inorganic multilayer films prepared by the spin self-assembly (SA) method. Spin self-assembled poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) multilayer films deposited from PE solutions of 10 mM show the distinct oscillation in contact angles with variation of the outermost PE layer, representing the saturated values in contact angles of individual PAH and PSS layers. These contact angles are also well consistent with the angles measured from respective PE layers (i.e., PAH and PSS) of the spin SA (PAH/CdS-COO-) and (CdS-NH3+/PSS) films carrying the flat interface between PE and inorganic CdS nanoparticle layers as confirmed by X-ray reflectivity. Furthermore, based on the contact angle of CdS-NH3+ layer in the ordered (CdS-NH3+/PSS) films, the change in surface wettability of CdS-NH3+ layers of two different spin SA (CdS-NH3+/poly(methacrylic acid) (PMAA)) multilayer films with ordered and disordered internal structure is also investigated. The films with ordered and disordered internal structure were fabricated by the pH adjustment of PMAA. The CdS-NH3+ layer in both CdS-NH3+/PSS and CdS-NH3+/PMAA multilayer films with the ordered internal structure has the contact angle of about 25 +/- 2 degrees irrespective of the PSS or PMAA sublayer. As a result, the same surface wettability of PE or inorganic layers, despite different sublayers, strongly indicates that the spin SA method in optimum condition allows the top surface to be completely covered with a low level ofinterdigitation with a sublayer at each deposition step, and this leads to the conclusion that physical and chemical characteristics of the sublayers have no significant influence on those of the outermost layer.

Journal Article↗

PubMed2006

Experiments on the motion of drops on a horizontal solid surface due to a wettability gradient.

Results from experiments performed on the motion of drops of tetraethylene glycol in a wettability gradient present on a silicon surface are reported and compared with predictions from a recently developed theoretical model. The gradient in wettability was formed by exposing strips cut from a silicon wafer to dodecyltrichlorosilane vapors. Video images of the drops captured during the experiments were subsequently analyzed for drop size and velocity as functions of position along the gradient. In separate experiments on the same strips, the static contact angle formed by small drops was measured and used to obtain the local wettability gradient to which a drop is subjected. The velocity of the drops was found to be a strong function of position along the gradient. A quasi-steady theoretical model that balances the local hydrodynamic resistance with the local driving force generally describes the observations; possible reasons for the remaining discrepancies are discussed. It is shown that a model in which the driving force is reduced to accommodate the hysteresis effect inferred from the data is able to remove most of the discrepancy between the observed and predicted velocities.

Models, Theoretical↗

PubMed2001

Influence of temperature, filter wettability, and timing of filtration on the removal of WBCs from RBC concentrates.

BACKGROUND: The efficacy of the removal of WBCs from buffy coat-reduced RBC concentrates by filtration is determined by many variables. The aim of this study was to investigate the influence of the filtration temperature, the wettability of the filter material, and the timing of the filtration after collection. STUDY DESIGN AND METHODS: The investigation used commercially available filters: 3 dry "online" filters (Cellselect FR, Fresenius Hemocare; BioR-01-max, Fresenius; Leucoflex LCG1, MacoPharma) and one wet "inline" filter (Leucoflex LCR4, MacoPharma) that contained saline-adenine-glucose-mannitol additive solution for RBCs and differed from the online version only in wettability. After buffy coat removal and suspension in saline-adenine-glucose-mannitol, filtrations were performed immediately at room temperature (RT) and after 2 hours' storage of the RBC concentrates at 4 degrees C, while the Leucoflex LCR4 was also tested after 24 hours' storage of the RBC concentrates at 4 degrees C. Sets of 12 pooled experiments were performed to prevent donor-dependent differences. RESULTS: The Cellselect FR gave significantly better WBC removal from RBC concentrates at 4 degrees C than at RT, with residual WBCs of 1.44 +/- 0.58 x 10(6) and 2.78 +/- 1.23 x 10(6), respectively (p<0.001). The BioR-01-max gave no significant difference: 0.62 +/- 0.27 x 10(6) WBCs (at 4 degrees C) versus 0.61 +/- 0.25 x 10(6) WBCs (at RT). Filtration with the Leucoflex LCG1 resulted in 0.06 +/- 0.03 x 10(6) and 0.07 +/- 0.07 x 10(6) WBCs at 4 degrees C and RT, respectively, which is not a significant difference. The Leucoflex LCR4, however, gave 2.08 +/- 0.84 x 10(6) WBCs at RT, 0.52 +/- 0.44 x 10(6) WBCs at 4 degrees C after 2 hours' cooling, and 0.05 +/- 0.10 x 10(6) WBCs at 4 degrees C after 24 hours' cooling (all p<0.001). CONCLUSION: Temperature, filter wettability, and timing of filtration after collection influence the efficacy of a filter for RBC concentrates. These variables need to be established, validated, and controlled before a filter can be selected for routine use.

Blood Component Removal↗

PubMed2006

Homogeneous nucleation at high supersaturation and heterogeneous nucleation on microscopic wettable particles: A hybrid thermodynamic/density-functional theory.

Homogeneous nucleation at high supersaturation of vapor and heterogeneous nucleation on microscopic wettable particles are studied on the basis of Lennard-Jones model system. A hybrid classical thermodynamics and density-functional theory (DFT) approach is undertaken to treat the nucleation problems. Local-density approximation and weighted-density approximation are employed within the framework of DFT. Special attention is given to the disjoining pressure of small liquid droplets, which is dependent on the thickness of wetting film and radius of the wettable particle. Different contributions to the disjoining pressure are examined using both analytical estimations and numerical DFT calculation. It is shown that van der Waals interaction results in negative contribution to the disjoining pressure. The presence of wettable particles results in positive contribution to the disjoining pressure, which plays the key role in the heterogeneous nucleation. Several definitions of the surface tension of liquid droplets are discussed. Curvature dependence of the surface tension of small liquid droplets is computed. The important characteristics of nucleation, including the formation free energy of the droplet and nucleation barrier height, are obtained.

Journal Article↗

PubMed2006

Mussel (Mytilus edulis) byssus deposition in response to variations in surface wettability.

Mussels (Mytilus edulis) are economically important in their role as an aquaculture species and also with regard to marine biofouling. They attach tenaciously to a wide variety of submerged surfaces by virtue of collagenous attachment threads termed 'byssi'. The aim of this study was to characterize the spreading of the byssal attachment plaque, which mediates attachment to the surface, on a range of surfaces in response to changes in wettability. To achieve this, well characterized self-assembled monolayers of omega-terminated alkanethiolates on gold were used, allowing correlation of byssal plaque spreading with a single surface characteristic--wettability. The present results were inconsistent with those from previous studies, in that there was a positive correlation between plaque size and surface wettability; a trend which is not explained by conventional wetting theory for a three-phase system. A recent extension to wetting theory with regard to hydrophilic proteins is discussed and the results of settlement assays are used to attempt reconciliation of these results with those of similar previous studies and, also, with recent data presented for the spreading of Ulva linza spore adhesive.

Adhesiveness↗

PubMed1990

Measurement of wettability of the corneal epithelium. II. Contact angle method.

Adult rabbit corneas were saline-rinsed, mucolytic-rinsed, or wiped to remove mucus. The corneas were allowed to dry in air; sessile droplets of saline were placed on the surface at various drying times, and their equilibrium contact angle theta measured. Several stages of drying can be distinguished: 1) an initial period when excess water is present, with either complete spreading of droplets or very low value of theta; 2) a 'plateau' region lasting about 20-25 min in which theta is low and changes slowly with time, and reflects the intrinsic wettability of the surface; 3) a region when more severe drying takes place and theta rises sharply. Computed tables are used with known values of theta and the surface tension of the saline drops, to give the surface tension of the corneal surface and the interfacial tension between cornea and saline. Acetylcysteine-washed corneas showed a plateau value of about 16 degrees and corneal surface tension of 69.3 mN/m. Rinsed corneas remained fully wettable (theta = 0 degrees) for longer than 90 min; hence the plateau value must also be near zero and corneal surface tension about 72 mN/m. Mechanically-wiped corneas dried more rapidly and theta rose continuously with no marked plateau value, indicating much lower wettability due to cellular damage (about 40 mN/m).

Acetylcysteine↗