Showing papers on "Surface tension published in 1983"
TL;DR: The number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species.
Abstract: The adhesion of five strains of bacteria, i.e., Staphylococcus aureus (strain 049), Staphylococcus epidermidis (strain 047), Escherichia coli (strains 055 and 2627), and Listeria monocytogenes, to various polymeric surfaces was studied. The design of the experimental protocol was dictated by thermodynamic considerations. From the thermodynamic model for the adhesion of small particles from a suspension onto a solid substratum, it follows that the extent of adhesion is determined by the surface properties of all three phases involved, i.e., the surface tensions of the adhering particles, of the substrate, and of the suspending liquid medium. In essence, adhesion is more extensive to hydrophilic substrata (i.e., substrata of relatively high surface tension) than to hydrophobic substrata, when the surface tension of the bacteria is larger than that of the suspending medium. When the surface tension of the suspending liquid is larger than that of the bacteria, the opposite pattern of behavior prevails. Suspensions of bacteria at a concentration of 10(8) microorganisms per ml were brought into contact with several polymeric surfaces (Teflon, polyethylene, polystyrene, and acetal and sulfonated polystyrene) for 30 min at 20 degrees C. After rinsing, the number of bacteria adhering per unit surface area was determined by image analysis. The surface tension of the suspending medium. Hanks balanced salt solution, was modified through the addition of various amounts of dimethyl sulfoxide. It was found that the number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species. The surface tensions of the bacteria obtained in this fashion are in excellent agreement with those obtained by other methods.
721 citations
TL;DR: It was shown that, for the former three amino acids, known to have a positive surface tension increment, their perturbation of the surface free energy of water is consistent with their preferential exclusion from the protein surface.
327 citations
TL;DR: In this paper, a planar surface of a liquid of molecules with truncated Lennard-Jones potentials has been simulated at two temperatures, and the normal component of the pressure tensor, p N(z), is shown to be a constant, independent of the height z.
Abstract: The planar surface of a liquid of molecules with truncated Lennard-Jones potentials has been simulated at two temperatures. The normal component of the pressure tensor, p N(z), is shown to be a constant, independent of the height z. There are many possible definitions of the transverse component, p T(z); two of these are computed and are shown to differ by small but significant amounts. All definitions of p T(z) give the same value of the surface tension, but they lead to different values for the apparent height of the surface of tension, that is, the height at which the tension is supposed to act. The difference is about 0·3-0·5 d, where d is the molecular collision diameter, for the two choices of p T(z) considered here.
276 citations
TL;DR: In this paper, the surface free energy and surface tension of solid metals reported in the literature are compared and preferred values for preferred values are suggested, the basic criteria which determine the value of obtained results are shown.
Abstract: Measurements of surface free energy and surface tension of solid metals reported in the literature are collected and compared and preferred values are suggested. The basic criteria which determine the value of obtained results are shown.
271 citations
TL;DR: In this paper, the authors considered time-dependent potential flows of a liquid with a free surface, with surface tension the force that drives them, and the velocities were found to be proportional to the time from the start of the motion.
Abstract: Time-dependent potential flows of a liquid with a free surface are considered, with surface tension the force that drives them. Two types of configuration are analyzed, in each of which the flow and the free surface are self-similar at all times. One is a model of a breaking sheet of liquid. The other is a model of the flow near the intersection of the free surface of a liquid with a solid boundary. In both flows, the velocities are found to be proportional to $( \sigma /\rho t )^{1/3} $, where $\sigma $ is the surface tension, $\rho $ is the liquid density and t is the time from the start of the motion. Each free surface is determined by converting the problem to an integrodifferential system of equations for the free surface and the potential on it. This system is discretized and solved numerically. On the resulting surfaces there are waves, which are also calculated analytically.
255 citations
TL;DR: In this article, the free energy of crystallization is derived from regular solution models for the liquid and solid and is used, together with model-based estimates of the interfacial tension, to calculate the nucleation frequency from the classical theory.
248 citations
TL;DR: In this paper, it is argued that such slow equilibration is more likely to be caused by structure formation in the surface, in particular by the slow formation of structures resembling lamellar liquid crystals.
196 citations
01 Oct 1983
TL;DR: In this article, the effect of the capillary number on two-phase (oil-water) relative permeability curves was investigated using a series of steady-state relative measurements.
Abstract: The goal of this study is to determine the effect of the capillary number on two-phase (oil-water) relative permeability curves Specifically, a series of steady-state relative permeability measurements were carried out to determine if the capillary number causes changes in the two-phase permeabilities or if any one of its constituents, such as flow velocity, fluid viscosity, or interfacial tension, are the controlling variables For the core tests, run in fired Berea sandstone, a Soltrol 170 oil-calcium chloride brine-isopropyl alcohol-glycerin system was utilized Alcohol was the interfacial tension reducer and glycerin was the wetting phase viscosifier The non-wetting phase (oil) relative permeability showed little correlation with the capillary number As the interfacial tension decreased below 20 dynes/cm, the oil permeability increased dramatically However, as the wetting phase viscosity increased, the non-wetting phase demonstrated less ability to flow For the wetting phase (water) relative permeability, the opposite capillary number effect was shown For both the tension decrease and the viscosity increase, ie, a capillary number rise, the water permeability increased, but not as much as with the oil curves No velocity effects were noted for the range studied A relative permeability model was then developed from the experimental data, based on fluidmore » saturations, interfacial tension, fluid viscosities, and the residual saturations, using regression analysis The applicability of these regression models were then tested with the aid of a two-phase reservoir simulator« less
177 citations
TL;DR: In this paper, a general model of adsorption of surfactants at a gas-liquid surface has been developed, which accounts for both the diffusion in the bulk and the barrier to adaption.
133 citations
TL;DR: In this paper, the thermodynamic surface excess of water at several organic solvents-aqueous solution interfaces has been determined for different salt solutions and the coordinates of pendant drops were measured with a video image digitising technique and the interfacial tension was calculated using a simple computational approach.
109 citations
TL;DR: In this article, approximate partition functions are constructed from approximate quantum mechanical models of near-rigid, solid-like and nonrigid liquid-like clusters, and the Helmholtz free energies are evaluated for these clusters as functions of temperature T and cluster size N.
Abstract: Approximate partition functions are constructed from approximate quantum mechanical models of near‐rigid, solidlike and nonrigid, liquidlike clusters. The Helmholtz free energies are evaluated for these clusters as functions of temperature T and cluster size N. The thermodynamic temperatures of melting, at which the free energies of the two forms are equal, match well with the melting temperatures determined from classical simulations of Ar clusters. Moreover, the effective coexistence ranges of temperature for solid‐ and liquidlike forms are approximately the same as the range of ‘‘supercooling’’ and ‘‘superheating’’ found in molecular dynamics computations of Ar. The surface tension is determined from an expansion of the free energy in powers of N−1/3. The concept of melting in small clusters, as a transition from a near‐rigid, small‐amplitude vibrator to a nonrigid molecule capable of frequent passage from one local equilibrium geometry to another, is related to the recent proposal by Stillinger and We...
TL;DR: In this paper, the results of calculations of the density profiles, relative adsorption and surface tension of the liquid-vapour interface of a binary mixture of Lennard-Jones fluids on a path of constant temperature and varying composition which passes through the consolute point for liquid-liquid separation but lies entirely in the two phase region.
Abstract: We present the results of calculations of the density profiles, relative adsorption and surface tension of the liquid-vapour interface of a binary mixture of Lennard-Jones fluids on a path of constant temperature and varying composition which passes through the consolute point for liquid-liquid separation but lies entirely in the two phase region. Our calculations are based on a square gradient approximation to the free energy functional of the inhomogeneous fluid. For bulk liquid concentrations x 1≲0·5 the density profile of species 1, the more volatile component, exhibits a maximum in the interface indicating pronounced surface segregation. The relative adsorption Г1,2 is positive for x 1≲0·66 and negative for larger x 1, i.e. the system exhibits an aneotrope. Our analysis suggests that it may be more useful to focus attention on the ratio Г1,2/x 1 than Г1,2 itself. We comment on recent attempts to measure Г1,2 for such interfaces. Our results for the surface tension in the vicinity of the critical end ...
TL;DR: In this paper, surface tension of sedimentary fulvic acid (FA) and humic acid (HA) with molecular weight from 300,000 was measured at 5°C and 25°C, over a wide range of concentrations (0.114-107.4 g/l).
TL;DR: In this article, the surface tension is determined by the curvature dependence of the density in the region of the wall and the potential distribution theory is used to obtain the exact relationship between the statistical mechanical surface tension expression and the grand potential.
Abstract: Statistical mechanical theories of spherical fluid interfaces are discussed in the context of fluids in contact with structureless walls. The thermodynamic route to the surface tension leads to a formula involving gradients of the external field, which is especially suited to the study of fluid-wall systems. The surface tension is found to be determined by the curvature dependence of the density in the region of the wall. For hard walls, potential distribution theory is used to obtain the exact relationship between the statistical mechanical surface tension expression and the grand potential. The accuracy of simple scaled particle theory calculations of the surface tension is estimated from predictions for the equation of state of pair potential fluids with hard core plus attractive tail interactions. Problems with the mechanical route to the curvature dependence of the surface tension are discussed. The planar wall and results for lower dimensionality are included in appendices.
TL;DR: In this article, the results of surface tension measurements of liquid iron and iron-oxygen alloys by the oscillating droplet method using the levitation technique were compared to those obtained by the sessile drop method, the technique most frequently employed for surface tension measurement of liquid metals.
TL;DR: In this paper, the axial dispersion characteristics of liquid phase in two (gas-liquid, liquid-solid) and three (gas liquid, solid) phase fluidized beds were studied in a 14.5 cm-I.D. column.
Abstract: The axial dispersion characteristics of liquid phase in two (gas-liquid, liquid-solid) and three (gas-liquid-solid) phase fluidized beds were studied in a 14.5 cm-I.D. column. The effects of liquid velocity (2-13 cm/s), gas velocity (0-12 cm/s), liquid viscosity (1-27 cP), surface tension (38.5-76 dyn/cm) and particle size (1.7-6.0 mm) on axial dispersion of liquid phase were examined. Liquid-phase axial dispersion in terms of Peclet numbers were correlated empirically by equations involving the ratio of fluid velocities and the ratio of particle-to-column diameters. The dispersion coefficients increased with gas flow rate, liquid surface tension and viscosity. However, liquid viscosity generally reduced the coefficient in beds of smaller particles at higher gas rates.
TL;DR: In this paper, the air-water interfacial tension has been determined by the capillary rise and Wilhelmy plate methods at 25°C, and the drop-volume method, using the Harkins-Brown corrections, gives good values for glass tips if appropriate precautions are taken.
01 Oct 1983
TL;DR: In this article, the authors present a numerical solution for the equation of motion describing the coalescence of two particles using an integral equation representation for the surface velocities, and show a similar behavior for all particles to fluid viscosity ratios λ.
Abstract: Coalescence of particles in a continuous fluid occurs quite commonly, e.g., in engineering, physics, and biology. The motion is induced by the tendency of the interface to reduce its area in order to minimize the interfacial energy. In this communication we present a numerical solution for the equation of motion describing the coalescence of two particles using an integral equation representation for the surface velocities. The results show a similar behavior for all particles to fluid viscosity ratios λ. Processes such as polymer sintering (λ→∞), biological particles fusion (λ→1) and bubble coalescence (λ→0) share a similar dynamics when simulated by surface tension driven flows. It is shown that Frenkel's constant power law for the evolution of the neck radius and its velocity of growth does not generally hold during the bulk of the coalescence process. The simulation predicts well the available experimental data describing the isothermal sintering of polymer particles.
TL;DR: In this article, the inter-facial tension has been measured as a function of pressure for the interfaces of four members of the homologous series of alkane (hexane, octane, decane, and dodecane), the substances of symmetrical ring structure (cyclohexane and benzene) against water.
TL;DR: In this paper, the authors generalize the linear stability analysis of Pearson for Marangoni instability to the case where surface tension depends on both temperature and solute concentration, and find that the onset of instability has the form of stationary convection and oscillatory convection.
Abstract: This paper generalizes the linear stability analysis of Pearson for Marangoni instability to the case where surface tension depends on both temperature and solute concentration. The results are expressed in terms of a thermal Marangoni number BT and a solutal Marangoni number BS. It is found when BS > 0 the onset of instability has the form of stationary convection, while when BS < 0 there are circumstances in which the onset of instability is in the form of oscillatory convection.
TL;DR: In this paper, the authors used a fast expansion chamber to measure the homogeneous nucleation rate of toluene as a function of temperature and supersaturation, and compared it with the classical nucleation theory and with the RKC theory.
Abstract: The authors have used a fast expansion chamber to measure the homogeneous nucleation rate of toluene as a function of temperature and supersaturation. The measured nucleation rate ranges from 102 to 105 drops/cm3 s over a temperature range of 215–267 K. The measurements are compared with the ‘‘classical’’ nucleation theory and with the RKC theory. The inclusion of the RKC replacement factor brings the data into good agreement with theory using physically realistic values of the surface tension and the sticking coefficient. An empirical curve fit to the data is presented as well as a full listing of the thermodynamic constants used for the calculations.
TL;DR: Surface tension measurements and friction experiments support the theory that lubrication by nonwetting drops occurs in joints and may be responsible for the exceptional friction characteristics of the joints.
Abstract: Measurements of the surface tension of articular cartilage and friction experiments were carried out to provide further evidence in support of a new theory regarding the mechanism of friction in joints. To determine the surface tension of cartilage, contact angle measurements were used in conjunction with the equation of state for interfacial tensions. The advancing contact angle between saline drops and articular cartilage was found to be 100°±5°, indicating a highly hydrophobic surface. The corresponding surface tension value was calculated to be 22.5 ergs/cm2. Friction of cartilage against hydrophobic surfaces is shown to be lower than the friction of cartilage against hydrophilic surfaces. All these results further support the theory that lubrication by nonwetting drops occurs in joints and may be responsible for the exceptional friction characteristics of the joints.
TL;DR: In this article, the authors proposed a recommended methodology for the measurement of contact angles from wetting force measurements without the need for independent determinations of specimen perimeter or liquid surface tension, including corrections for buoyancy and limitations on the magnitude of the contact angle.
TL;DR: In this article, the dynamic drop weight technique originally proposed by Brady and Brown was investigated for the determination of the dynamic surface tension of both aqueous and nonaqueous surfactant solutions.
TL;DR: In this paper, a test of doubly-diffuse space charge theory for describing the potential profile across the interface and subsequent evaluation of the chi-potential (dipole potential) differnece was provided.
TL;DR: The surface energy, the surface free energy and the surface entropy of liquid water are calculated from the decrease in the number of hydrogen bonds in the surface layer, estimated on the bash of a simplified aater structure scheme as mentioned in this paper.
TL;DR: In this article, the mean droplet diameter in the spray resulting from transverse injection of liquid jets into supersonic airstream was investigated by the use of diffractively scattered light method.
Abstract: The mean droplet diameter in the spray resulting from transverse injection of liquid jets into supersonic airstream was investigated in detail by the use of the diffractively scattered light method. The effects of viscosity, surface tension, jet/freestream dynamic pressure ratio, injector diameter, and location in the plume on the mean droplet diameter were determined. AH tests were performed at A/^ =3.0, with P0 4.2 atm and T0 = 300 K. The injectants used were water, various solutions of glycerine and ethanol in water, and Fluorinert to produce wide variations in viscosity and surface tension. The important results can be summarized as follows: 1) the droplet size has an inverse relation with respect to jet/freestream dynamic pressure ratio, 2) the droplet diameter decreases as the measurement station moves downstream, 3) the smallest droplets are formed at the outer edge of the spray plume, 4) droplet size has a direct relation with respect to surface tension and viscosity of the injectant, and 5) at very high viscosities the jet does not break up into nominally spherical particles. For a certain range of viscosity and dynamic pressure ratio, the breakup of the jet is into ligaments rather than droplets.
TL;DR: Department o f Mechanical Engineering Institute of Biomedical Engineering f Institute of Medical Sciences University of Toronto Toronto, Canada, M5S IA4 lJ Research Institute Hospital for Sick Children Toronto,Canada, and M5G 1x8 Department o f Microbiology.
Abstract: Department o f Mechanical Engineering Institute of Biomedical Engineering f Institute of Medical Sciences University of Toronto Toronto, Canada, M5S IA4 lJ Research Institute Hospital for Sick Children Toronto, Canada, M5G 1x8 Department o f Microbiology Department of Chemical Engineering State University of New York at Buffalo Buffalo, New York 14214 Separation Processes Branch NASAIGeorge C. Marshall Space Flight Center Huntsville, Alabama 35812
01 Apr 1983
TL;DR: The surface tension of the n-alcohols from methanol through n-octanol have been measured between about −40°C and + 40°C as mentioned in this paper, and the surface tension data can be represented within ± 0.5% by linear functions of temperature over the considered temperature range.
Abstract: The surface tensions of the n-alcohols from methanol through n-octanol have been measured between about −40°C and + 40°C. The surface tension data can be represented within ± 0.5% by linear functions of temperature over the considered temperature range. The increase of surface tension with increasing chain length of the alcohol is in accord with the theorem of corresponding states.