Effect Of Drop Size Research Articles

SIZE EFFECT ON SURFACE TENSION AND CONTACT ANGLE BETWEEN PROTEIN SOLUTION AND SILICON COMPOUND, PC, AND PMMA SUBSTRATES

Detailed contact angle measurements are performed for protein drops on phenylcarbamide (PC), polymethyl methacrylate (PMMA), silicon nitride, and glass substrates by goniometer-sessile drop technique. Drop sizes are ranged from 0.1 to 6 w l with radius of curvature less than 1 mm. The bovine serum albumin (BSA) protein concentrations are 0.0, 0.1, 1.0, and 10 mg/ml. The results show weak dependence of the drop size for deionized water drops on all substrates and increased dependence of the drop size for protein drops with different protein concentrations. The significance of drop size effect varies from substrate to substrate; the effect is strongest for PC substrate, which is a nearly hydrophobic surface. The drop size dependence can be partly explained by the modified Young's equation.

Viscosity of surfactant stabilized emulsions

A new scaling parameter for the viscosity of surfactant stabilized emulsions is proposed. We suggest that the attractive force between emulsion droplets is caused by the small surfactant micelles in the continuous phase of an emulsion. The new scaling parameter will be referred to as the depletion flow number, Fld=4πηsa2am/kTϕm, and is defined as the ratio between the viscous energy needed to separate the droplets and the depletion energy that opposes this separation. Here ηs, a, am, and ϕm are the solvent viscosity, dispersed phase droplet radius, micelle radius, and micelle volume fraction, respectively. Fld is of the order of unity at the onset of shear thinning and is capable of explaining all previously observed effects of drop size, solvent viscosity, and surfactant concentration. With master curves which are obtained by using Fld as the running parameter, a relatively simple empirical model is constructed which can reproduce the viscosity curves of many previously reported in the literature.

A simple modification of the Q-plate for parallel screening and combinatorial crystallization

In many cases it can be advantageous to screen crystallization conditions in parallel. Tasks, such as the setting up a standard screen for several proteins simultaneously or analyzing the effect of drop size and different precipitant-protein drop ratios can be done more efficiently when drops are set up in parallel using a common reservoir. However, a real need for parallel screening becomes apparent when analyzing a large number of different complexes of the same protein, or when using methods such as stoichiometry variation screening and other combinatorial crystallization methods. Because of its large size, the Q-plate is easily adapted to the screening of a variable number of sitting drops in parallel. The drops are set up on a single glass slide placed over the same reservoir solution. The modification is simple and does not require a robot although it is well suited for automation. A record of each drop in multi-drop setup is kept as an HTML-file which allows for rapid navigation between experiments. Flexibility in the number drops makes the method effective for most combinatorial and non-combinatorial applications.

IMPACTS OF PACKING SECTION ON MASS TRANSFER TO DROP SWARMS

Terminal velocity and mass transfer coefficient data for drop swarms were measured in a 0.1 m diameter glass column filled with SMR (Super Mini Ring) packing, using a computerized video imaging system; 30% TBP-Kerosene/acetic acid/water and 50% TBP-Kerosene/acetic acid/water were used as the working systems. A number of techniques for the prediction of the observed mass transfer data were considered, and a new model to predict the mass transfer film coefficient, which accounts for the effects of surface contaminants on the mobility of the interface, is presented and shown to fit the experimental data. The effects of drop size and the presence of packing on overall dispersed phase mass transfer coefficient are presented. It is shown that overall dispersed phase mass transfer coefficient increases with increasing drop diameter, and decreases in the presence of SMR packing.

Effect of Drop Size on the Print Quality in Continuous Ink Jet Printing

Very little attention has been paid in the literature to the impact of the drop size on the dynamics of spreading and on the final dot quality with different paper grades. In this study, the development of the image properties was observed on a time scale of a few milliseconds and upwards, by using a special high speed imaging environment and continuous ink jet (CIJ) printers, with different nozzle sizes but similar water based ink compositions. The results clearly show that there is a strong paper dependent affiliation between the size of the ink jet drop and the high-speed dynamic phenomenon of dot spreading and drying. With coated paper grades, the interrelation between the drop size and the magnitude of the surface structure was found important, compared with the final shape of the dot. With uncoated papers, the growth of the dot is dependent on the size of the drop. The final intensity of the print was found to be the outcome of the characteristics of the ink and the absorption properties of the paper.

Determination of the Receding Contact Angle of Sessile Drops on Polymer Surfaces by Evaporation

The receding contact angles of water drops on PMMA and PET surfaces were determined by using video microscopy to follow the time-dependent evaporation of sessile drops. Depending on the initial drop size, receding angles of θr = 54−64° for PMMA and θr = 64−66° for PET were found with an average hysteresis of 23.5 ± 1.5 and 19.5 ± 1.5°, respectively. Advancing and receding angles, θa and θr, were also determined by the needle-syringe and the inclined plane methods for comparison. The discrepancies from the mean of the maximum and minimum contact angle results of both the needle-syringe and the inclined plane methods were larger than expected for all the polymer surfaces. A general trend was seen with samples giving a larger hysteresis also producing a larger discrepancy for all the samples. The major cause of this discrepancy is the variation of the rate of liquid introduction and withdrawal with the syringe in the needle-syringe method and the drop size effect in the inclined plane method. In this respect...

Van der Waals attraction forces and line tension

The effect of drop size on the contact angle between a van der Waals liquid drop and a thin liquid film can be presented as a line tension effect. The line tension κ is positive and of the order of σd, where σ = surface tension and d = molecular length, The dependence of κ on r, the radius of the circular contact line, is obtained.

Density functional theory for spherical drops

We have applied Sullivan's model to study the interfacial properties of a spherical drop embedded in a one-component fluid using the mean field approximation. We have examined the effect of drop size (expressed by the equimolar radius Re) on the density profile, pressure tensor, pressure difference Delta p across the interface, surface tension, Tolman's length, and density, pressure, and normal component of pressure tensor at the centre of the drop. Delta p is found to be an ill defined quantity in the sense that it can be defined in various ways, whose results coincide for large drops. The surface tension is a non-monotonic function of Re; it increases slowly from its flat interface value as Re decreases until a maximum value is attained, then it decreases rapidly. For small supersaturations, the drops are under tension and compression while at large supersaturations they are only under tension. The results of this theory are compared qualitatively with previous molecular dynamics simulations and theoretical calculations for drops.

The Effect of Drop Size on Contact Angle over a Wide Range of Drop Volumes

Contact angle measurements for the air/water/polyethylene and for the oil/water/quartz systems have been carried out over a wide range of drop (bubble) sizes, from 60 μm to 2 mm. Two distinctly different experimental techniques were used: placement of the drop (bubble) with a microsyringe, the static technique, and collision of the drop (bubble) with the surface due to the buoyant force, the dynamic technique. A nonlinear relationship between the cosine of the contact angle measured through the aqueous phase (cos θ) and the reciprocal radius of the drop base (1/ r) was obtained. The lack of linearity for this range of drop sizes cannot be attributed to a variation in line tension which should be constant. Nevertheless, a pseudo line tension can be calculated and it was found that negative pseudo line tensions on the order of -1 × 10 -8 N(-1.2 × 10 -8 -6.6 × 10 -8 N) were obtained for small drops or bubbles (drop volume less than 0.1 μl, drop base diameter less than 0.3 to 0.4 mm). The pseudo line tensions increased when the drop (bubble) volume increased above 0.1 μl, reaching a maximum of about -1 × 10 -6 N (-0.6 × 10 -6 to -1.4 × 10 -6 N). Thus, it was found that the contact angle for small drops (bubbles) changes significantly from that measured for large drops (bubbles) which may be an important fundamental aspect in certain phase separation phenomena.

EFFECTS OF INTERFACIAL POLYUREA FILM ON THE STABILITY OF OIL IN WATER EMULSIONS

ABSTRACT The stability of oil in water emulsions containing a triisocyanate soluble in the oil phase was investigated. The oil component was either di-n-butyl phthalate (DBP) or a mixture of DBP with liquid paraffin. The time required for the average size parameter to reach a constant value was studied. It was found that the polyurea film produced by an interfacial polymerization reaction between water and a triisocyanate contributed to make the stable emulsions. The effects of drop size, temperature, polarity of oil phase, triisocyanate concentration, and mechanical stirring on the stability of the emulsions were established in this study. The film thickness at the point where the average size parameter reached a constant value was found to be of the order of 0. 002 ∼ 0. 004μ.

Embryo density and medium volume effects on early murine embryo development.

One-cell mouse embryos were used to determine the effects of drop size and number of embryos per drop for optimum development in vitro. Embryos were collected from immature C57BL6 female mice superovulated with pregnant mare serum gonadotropin and human chorionic gonadotropin and mated by CD1 males. Groups of 1, 5, 10, or 20 embryos were cultured in 5-, 10-, 20-, or 40-microliters drops of CZB under silicon oil at 37.5 degrees C in a humidified atmosphere of 5% CO2 and 95% air. Development score for embryos cultured in 10 microliters was higher than that of embryos cultured in 20 or 40 microliters. Embryos cultured in groups of 5, 10, or 20 had higher development scores than embryos cultured singly. The highest development score was obtained by the combination of 5 embryos per 10-microliters drop. The percentage of live embryos in 20 or 40 microliters was lower than that of embryos cultured in 10 microliters. Additionally, the percentage of live embryos cultured singly was lower than that of embryos cultured in groups. Our results suggest that a stimulatory interaction occurs among embryos possibly exerted through the secretion of growth factors. This effect can be diluted if the embryos are cultured in large drops or singly.

The effects of drop size and formulation upon the spread of pesticide droplets impacting on water-sensitive papers

Abstract The effects of drop size and formulation upon the spread of pesticide droplets impacting on water‐sensitive papers (WSPs) was investigated. Droplets of diameter 70–350 μm, of four permethrin formulations, were produced using a monosize droplet generator. The droplets were collected on WSPs and in Dow Corning fluid and their diameters measured using a binocular microscope. Spread factors, upon the WSPs, for each dropsize/formulation combination were then calculated. Spread factors varied with both formulation and droplet size and for droplets of 200 and 300 μm diameter spread was significantly correlated with the dynamic surface tension of the formulation. The results suggest that proper calibration of WSPs is necessary for effective droplet sizing.

The influence of spray droplet characteristics on the efficacy of permethrin against the diamondback moth Plutella xylostella: The effect of drop size and concentration on the potency of ulv‐ and ec‐based residual deposits

AbstractThe effect of droplet diameter (36‐274 μm) and concentration (10‐400 g litre−1) of permethrin on the knockdown and mortality of 2nd‐instar Plutella xylostella larvae was investigated. Larvae were placed on brussels sprout leaf discs treated with residual deposits of permethrin applied as ULV or emulsion formulations. The LD50 of permethrin decreased with droplet size at all concentrations tested. This effect could not be accounted for solely by increased drop numbers per unit area of leaf, suggesting that for both formulations transfer of permethrin to larvae is more efficient for deposits composed of small drops. The concentration of permethrin in the ULV formulation could be reduced to approach a minimum quantity of toxicant per unit area to maintain 50 per cent mortality. The approach to the minimum dose varied with drop size and drop number per unit leaf area. The ULV formulation was approximately 2.7 times more effective at killing larvae than the emulsion, presumably as a result of greater availability of toxicant and transfer to larvae.

Drop coalescence in pipe flows tropfenkoagulation in rohrströmungen

The object of the work was to demonstrate clearly the turbulence-dependent coalescence of water droplets in a relatively short pipe section using a modern, high-resolution, non-intrusive light-scattering measuring method. The investigation was carried out excluding condensation processes. The polydisperse droplets were produced by mixing two air streams of different temperature and saturated with water vapor. The effect of drop size and the shape of the drop size distribution on the coalescence was investigated. The deposition of particles which occurred at the pipe inner wall was measured. The measured values were compared with the results of various model calculations, the conservation equations for a drop system being solved numerically. The theoretical simulation of the turbulence-dependent drop coalescence also made allowances for the effects of turbulent cross-mixing and wall deposition of the drops in the pipe.

Equipment for Studying Effects of Spray Drop Size, Distribution, and Dosage on Pest Control1

A system for generating and distributing uniform-size drops was assembled to study effects of drop size, distribution, and dosage on pest control. Uniform-size drops within a range of 50–500 μm were produced with a drop generator. Number of drops per unit area of target was varied by adjusting amount of electrical charge placed on the drops and speed of the conveyor carrying the target. Water-sensitive paper disks were used to show uniformity of drops and their distributions when drops were electrostatically charged. A horizontally mounted microscope and stroboscope arrangement allowed drops to be viewed and photographed.

Effect of drop size and physical properties on dispersion height in the separating section of a liquid/liquid extraction column

AbstractThe height of the dispersion formed in the separating section of an extraction column is given byH = K/g (σ/Δρg)1/2 I/ϕo (Qd/A)2Since calm conditions prevail the height of the sedimentation zone can be neglected and the dispersion is essentially dense‐packed. The effect of physical properties was investigated in a spray column using nine different liquid/liquid systems. A distributor divided into seven equal sectors enabled the effect of drop size and dispersed phase flow rate to be independently investigated.

Assessment of the wettability of powders by use of compressed powder discs

The value of contact angle measurements on compressed discs of powder has been critically examined as a method of assessing the wettability of five barbiturate powders. The contact angle was found to reduce with increased compression force, until a constant value was achieved. This was demonstrated, by use of scanning electron micrographs, to be due to plastic deformation of the powder surface. The values of θ obtained did not alter after electrostatic forces were discharged with an antistatic gun, and are thus not responsible for the hydrophobic nature of the loosely compressed beds. The effect of drop size, in the range 10 to 50 μl, and surface roughness were not large enough to be detected amongst the scatter of results. Small drops of water on the plane faces of large crystals formed a contact angle in close agreement with the plastic skin on the compacts. It is postulated that the crystal defects and heterogeneities are responsible for raising the value of θ in the uncompacted powders.

Drying of a drop of polymer solution of PAN (polyacrylonitrile)-DMF (dimethylformamide) system.

The drying behaviour of a drop of polymer solution of the polyacrylonitrile-dimethylformamide system was investigated in a wide range of drying air temperature (323-423 K), initial drop volume (2-8 μl), and initial concentration of solvent in a drop (5-18 kg DMF/kg PAN). The theoretical calculation of the drying history of a drop, based on the diffusion equation and the differential heat balance equation, using the experimental values of activity and apparent mutual diffusion coefficient, represented the experimental values satisfactorily. The changes of solvent content and temperature of a drop during drying were well correlated by the ratio (drying time)/(initial radius of a drop)2, eliminating the effect of drop size. The shift in controlling step of the drying rate from surface evaporation resistance controlling to internal diffusion resistance controlling is shown by means of changes in the concentrations at the center and the surface of a drop.

Movement of solids in air and water by raindrop impact. effects of drop-size and water-depth variations

Transportation of 200 pm sand grains by impacting raindrops in both air and water was experimentally investigated through the water depth range 0-75 mm, employing four drop sizes. Airsplash movement, greatest for large drops impacting bare sand, fell rapidly with decreasing dropsize and increasing water depth. Shallow surface water inhibited airsplash strongly, yields falling by large factors through the depth range 0-2 mm. Hence, airsplashing of solids, even if randomly directed from any one point, must produce net migration from bare to water-covered surfaces. Drops over about 1.5 mm in diameter disrupt on impacting water at terminal velocity, generating disturbances which can, if water is shallow, suspend soil particles. Smaller drops evidently penetrate water surfaces without disruption, disturbing soil particles more directly and efficiently. If target water flows, even very slowly on low slopes, net downstream particle migration (rain-flow transportation) results. Rain-flow transportation rates rose from zero at zero depth to near-maximum values at 2 mm. Actual maxima were reached at depths of 2-3 drop diameters, transport rates declining rapidly with further depth increases. The combination of airsplash and rain-flow transportation extends transportation to areas where overland flow is either absent or too weak, acting alone, to move solids significantly.

Laboratory studies on the effect of drop size on splash erosion

Splash erosion of 210–250 μm sand subjected to a drainage suction in splash cups was studied in relation to three variations in the size of drops (2·7, 3·8 and 5·1 mm) impacting at close to their terminal velocity. Splash loss per drop varied with the square of the drop mass. This result indicates that drops of different sizes travelling at terminal velocity may vary more in their ability to cause splash erosion than was previously supposed.