Difference In Surface Tension Research Articles

Development of prednisolone-containing eye drop formulations by cyclodextrin complexation and antimicrobial, mucoadhesive biopolymer.

PurposeThe formulation of topical ophthalmic products with appropriate therapeutic effect and patient compliance is a major challenge. To increase the efficiency of the ocular delivery of the drug, the enhancement of water solubility and the contact time of the drug on the surface of the cornea are necessary. In this work, prednisolone (PR)-containing eye drops were formulated with antimicrobial, mucoadhesive biopolymer and PR–cyclodextrin inclusion complex. This approach can be used for the development of innovative ophthalmic formulations.Materials and methodsAfter adjusting the optimal physiological parameters, the amount of the required cyclodextrin for the highest penetration of PR was determined by dialysis membrane diffusion study. The viscosity, surface tension and mucoadhesion of the eye drops were measured. The microbiological effectiveness of zinc-hyaluronate (ZnHA) was investigated by a standard method of the European Pharmacopoeia.ResultsIn this case, no significant difference of surface tension was measured in products with different amounts of cyclodextrin. According to the results of the tensile test, ZnHA as a mucoadhesive biopolymer improves the mucoadhesion of ophthalmic products. The antimicrobial stability of formulations preserved by ZnHA meets requirement B of the European Pharmacopoeia.ConclusionIt can be stated that the innovative PR-containing compositions are suitable for producing mucoadhesive, properly preserved aqueous ophthalmic solutions with increased bioavailability attributes.

Delayed coalescence of surfactant containing sessile droplets

The coalescence of surfactant solutions on a substrate is studied. By varying both the contact angle of the droplets and their difference in surface tension, various regimes with distinct timescales of noncoalescence are identified.

Development of a Rapid and Simple Method for Preparing Tea-Leaf Saponins and Investigation on Their Surface Tension Differences Compared with Tea-Seed Saponins.

The relative overcapacity in China's tea-leaf production and the potential application of tea-leaf saponins in soil remediation encouraged in-depth developments and comprehensive utilizations of tea-leaf resources. Through variables optimizations using Box–Behnken designs for ultrasonic power, temperature as well as ultrasonic treatment time in ultrasonic-assisted water extraction and single-variable experiments for acetone-extraction solution ratio in acetone precipitation, a rapid and simple method was developed for preparing tea-leaf saponins. Tea-leaf saponins with the concentration of 3.832 ± 0.055 mg/mL and the purity of 76.5% ± 1.13% were acquired under the optimal values of 78 w, 60 °C, 20 min and 0.1 ratio of acetone-extraction solution. Both Fourier transform-infrared (FT-IR) spectra and ultraviolet (UV) spectra revealed slight composition differences between tea-leaf saponins and tea-seed saponins, while these differences were not reflected in the critical micelle concentration (CMC) and the surface tension of tea-leaf saponins and tea-seed saponins, indicating there was no need to distinguish them at the CMC. Further research attention on where tea-leaf saponins were in low concentrations is deserved to discover whether they had differences in comparison with tea-seed saponins, which was beneficial to apply them in the phytoremediation of contaminated soils.

Does Marine Surface Tension Have Global Biogeography? Addition for the OCEANFILMS Package

We apply principles of Gibbs phase plane chemistry across the entire ocean-atmosphere interface to investigate aerosol generation and geophysical transfer issues. Marine surface tension differences comprise a tangential pressure field controlling trace gas fluxes, primary organic inputs, and sea spray salt injections, in addition to heat and momentum fluxes. Mapping follows from the organic microlayer composition, now represented in ocean system models. Organic functional variations drive the microforcing, leading to (1) reduced turbulence and (by extension) laminar gas-energy diffusion; plus (2) altered bubble film mass emission into the boundary layer. Interfacial chemical behaviors are, therefore, closely reviewed as the background. We focus on phase transitions among two dimensional “solid, liquid, and gaseous” states serving as elasticity indicators. From the pool of dissolved organic carbon (DOC) only proteins and lipids appear to occupy significant atmospheric interfacial areas. The literature suggests albumin and stearic acid as the best proxies, and we distribute them through ecodynamic simulation. Consensus bulk distributions are obtained to control their adsorptive equilibria. We devise parameterizations for both the planar free energy and equation of state, relating excess coverage to the surface pressure and its modulus. Constant settings for the molecular surrogates are drawn from laboratory study and successfully reproduce surfactant solid-to-gas occurrence in compression experiments. Since DOC functionality measurements are rare, we group them into super-ecological province tables to verify aqueous concentration estimates. Outputs are then fed into a coverage, tension, elasticity code. The resulting two dimensional pressure contours cross a critical range for the regulation of precursor piston velocity, bubble breakage, and primary aerosol sources plus ripple damping. Concepts extend the water-air adsorption theory currently embodied in our OCEANFILMS aerosol emissions package, and the two approaches could be inserted into Earth System Models together. Uncertainties in the logic include kinetic and thermochemical factors operating at multiple scales.

Evaporation-Triggered Segregation of Sessile Binary Droplets.

Droplet evaporation of multicomponent droplets is essential for various physiochemical applications, e.g., in inkjet printing, spray cooling, and microfabrication. In this work, we observe and study the phase segregation of an evaporating sessile binary droplet, consisting of a miscible mixture of water and a surfactantlike liquid (1,2-hexanediol). The phase segregation (i.e., demixing) leads to a reduced water evaporation rate of the droplet, and eventually the evaporation process ceases due to shielding of the water by the nonvolatile 1,2-hexanediol. Visualizations of the flow field by particle image velocimetry and numerical simulations reveal that the timescale of water evaporation at the droplet rim is faster than that of the Marangoni flow, which originates from the surface tension difference between water and 1,2-hexanediol, eventually leading to segregation.

A novel combination of sandwich and co‐continuous structure based on polypropylene and styrene‐butadiene‐styrene block copolymer formed with wide range of polypropylene content

ABSTRACTThe styrene–butadiene–styrene block copolymer (SBS)/polypropylene (PP) blends with a unique sandwich layered co‐continuous structure were prepared by melt compounding. Differing from single conventional co‐continuous and sandwich structure, this structure was formed, where pure PP and co‐continuous SBS/PP phase acting as the face sheets and core. Even though the volume content was 20 or 10 vol %, PP always amazingly formed a continuous phase in SBS/PP blends, whereas the morphology of SBS phase relatively changed from dispersed particles to continuous network as its content increased to 50 vol %. For immiscible SBS/PP blends, due to the huge difference of complex viscosity and surface tension between SBS and PP, a pure PP layer existed on the surface of blends which can be ascribed to the PP enrichment. Herein, the structure of blends with more than 50 vol % SBS was presented as sandwich layered co‐continuous structure by combining the pure PP layer and co‐continuous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46580.

Prediction of surface tension of highly nonideal aqueous-organic mixtures as a function of composition by a partitioning model between surface and bulk phases and use of partial molar surface areas

The composition dependence of the surface tension of highly nonideal aqueous-organic nonelectrolyte solutions is described in detail. The Wilson, NRTL, UNIFAC and ideal solution models are used for activity coefficients of surface and bulk phases and compared with one another and with experimental data. Paquette and Rasmussen molar surface areas are employed for prediction of the surface tension of the mixtures and results compared. A new procedure consisting of a partitioning model between surface and bulk phases combined with determination of partial molar surface areas is evolved and tested with experimental data taken on the surface tension of aqueous-organic systems. Comparisons of the calculated surface tensions with experimental data yield mean absolute errors of only 2.8% for the systems studied, all of which exhibit highly nonideal behavior, with excess surface tensions as high as 35 mN m−1. The surface tension predictions are found to be extremely sensitive to the values of the molar surface areas used in the computation. Use of the partitioning model with partial molar surface areas improves surface tension predictions of highly nonideal aqueous-organic mixtures by 30% over use of pure component molar surface areas. Moreover, this improvement in predictions is found to occur for every value of composition without exception for each aqueous-organic system studied. Analysis of the data suggests the attractive hypothesis that the extent of nonideality of aqueous-organic mixtures is characterized by and is directly proportional not only to the difference in pure component surface tension of the binary constituents but also to the ratio of pure component molar (or partial molar) surface areas of the organic to that of water. It is proposed that this physical area parameter is correlated to the value of the partition constant between the surface and the bulk. It therefore constitutes an important determinant of the surface chemical properties of the organic species in the aqueous-organic mixture, in addition to the intrinsic chemical nature of the organic compound, although further research is needed to find out the exact relationship between them and to arrive at a quantitative theory.

Vapor phase nucleation of the short-chain n-alkanes (n-pentane, n-hexane and n-heptane): Experiments and Monte Carlo simulations.

We measured the nucleation rates of n-pentane through n-heptane in a supersonic nozzle at temperatures ranging from ca. 109 K to 168 K. For n-pentane and n-hexane, these are the first nucleation rate measurements that have been made, and the trends in the current data agree well with those in the earlier work of Ghosh et al. [J. Chem. Phys. 132, 024307 (2010)] for longer chain alkanes. Complementary Monte Carlo simulations, using the transferable potentials for phase equilibria-united atom potentials, suggest that despite the high degree of supercooling, the critical clusters remain liquid like under experimental conditions for n-pentane through n-heptane, but adopt more ordered structures for n-octane and n-nonane. For all three alkanes, the experimental and simulated nucleation rates are offset by ∼3 orders of magnitude when plotted as a function of ln S/(Tc/T - 1)1.5. Explicitly accounting for the surface tension difference between the real and model substances, or alternatively using the Hale [Phys. Rev. A 33, 4156 (1986); Metall. Mater. Trans. A 23, 1863 (1992)] scaling parameter, Ω, consistent with the model potential, increases the offset to ∼6 orders of magnitude.

Evolution of Self-Propelled Objects: From the Viewpoint of Nonlinear Science.

A variety of moving objects driven by chemical energy have been reported. In this Minireview, we focus on self-propelled objects driven by interfacial tension and explain three types of basic mechanisms for such self-propelled motion, that is, driven by a) surface tension difference, b) contact angle difference, and c) axisymmetric swirling flow in a droplet. Simple behavior induced from the basic mechanisms is then extended by coupling to a chemical reaction or increasing the number of moving objects. Even though the chemicals used here are still simple, the extended systems could show characteristic nonlinear behavior, such as reciprocating motion, oscillatory motion, and spatiotemporal pattern formation. Combining the dynamical information about these characteristic motions with the knowledge of molecular structures will lead to the development of more advanced self-propelled objects. We believe this Minireview can help chemists in investigating self-propelled objects displaying various functional motions observed in a biological system.

Size-Dependent Thermodynamics and Kinetics of Adsorption on Nanoparticles: A Theoretical and Experimental Study.

Owing to their excellent adsorption properties compared with those of the corresponding bulk materials, nanoparticles have been widely applied in many fields. Their properties depend on the thermodynamics and kinetics of adsorption, which depend on the particle size. In this paper, we present universal theories of the thermodynamics and kinetics for nanoadsorption that have been developed over the past few years. Theoretically, we have derived relationships between the adsorption thermodynamic properties and the particle size, as well as those between the adsorption kinetic parameters and the particle size. Moreover, we discuss the regularities and mechanisms of influence of the particle size on the thermodynamics and kinetics of adsorption. Experimentally, taking the adsorption of methyl orange on nano-CeO2 in aqueous solution as a system, we have studied the size-dependent thermodynamics and kinetics of the system, and the size dependences were confirmed to be consistent with the theoretical relationships. The results indicate that particle size has a significant effect on the thermodynamic properties and kinetic parameters of adsorption: with decreasing particle size of nano-CeO2, the adsorption equilibrium constant K⊖ and the adsorption rate constant k increase, while the molar Gibbs free energy of adsorption Δads Gm⊖, the molar adsorption entropy Δads Sm⊖, the molar adsorption enthalpy Δads Hm⊖, the adsorption activation energy Ea, and the adsorption pre-exponential factor A all decrease. Indeed, ln K⊖, Δads Gm⊖, Δads Sm⊖, Δads Hm⊖, ln k, Ea, and ln A are each linearly related to the reciprocal of particle size. Furthermore, thermodynamically, Δads Gm⊖ and ln K⊖ are influenced by the molar surface area and the difference in surface tensions, Δads Sm⊖ is influenced by the molar surface area and the difference in temperature coefficients of surface tension, and Δads Hm⊖ is influenced by the molar surface area, the difference in surface tensions, and the difference in temperature coefficients of surface tension. Kinetically, Ea is influenced by the partial molar surface enthalpy of the nanoadsorbent, ln A is influenced by the partial molar surface entropy, and ln k is influenced by the partial molar surface Gibbs energy. The theories can quantitatively describe adsorption behavior on nanoparticles, explain the regularities and mechanisms of influence of particle size, and provide guidance for the research and application of nanoadsorption.

The impact of dissolved fluorine on bubble nucleation in hydrous rhyolite melts

Surface tension of hydrous rhyolitic melt is high enough that large degrees of supersaturation are needed to homogeneously nucleate H2O bubbles during eruptive magma ascent. This study examines whether dissolved fluorine lowers surface tension of hydrous rhyolite, and thus lowers the supersaturation required for bubble nucleation. Fluorine was targeted because it, like H2O, changes melt properties and is highly soluble, unlike all other common magmatic volatiles. Rhyolite melts were saturated at Ps = 245 MPa with H2O fluid that contained F, generating rhyolite with 6.7 ± 0.4 wt.% H2O and 1.1–1.3 wt.% F. When these melts were decompressed rapidly to Pf = 149–202 MPa and quenched after 60 s, bubbles nucleated at supersaturations of ΔP = Ps − Pf ≥52 MPa, and reached bubble number densities of NB = 1012–13 m−3 at ΔP = 78–101 MPa. In comparison, rhyolite saturated with 6.34 ± 0.09 wt.% H2O, but only 0.25 wt.% F, did not nucleate bubbles until ΔP ≥ 100–116 MPa, and even then, at significantly lower NB (<1010 m−3). Numerical modeling of bubble nucleation and growth was used to estimate the values of surface tension required to generate the observed values of NB. Slight differences in melt compositions (i.e., alkalinity and H2O content), H2O diffusivity, or melt viscosity cannot explain the observed differences in NB. Instead, surface tension of F–rich rhyolite must be lower by approximately 4% than that of F–poor rhyolite. This difference in surface tension is significant and, for example, exceeds that found between hydrous basaltic andesite and hydrous rhyolite. These results suggest that is likely that surface tension for F–rich magmas, such as topaz rhyolite, is significantly lower than for F–poor magmas.

Effect of viscosity and surface tension on dynamic percolation in liquid media

ABSTRACTPercolation of carbon nanotubes in liquid media has been studied as a function of their surface tension and intrinsic viscosity. Carbon nanotubes were dispersed in different liquids by means of ultrasound, and the suspensions were gradually further diluted to obtain a large number of well‐defined filler contents. Percolation was probed with a remarkable accuracy thanks to a specific test procedure combining dilutions and electrical testing. Percolation threshold values were found to be lower (close to 0.01 vol %) than the ones obtained in molten polymers, due to the ease of particles aggregating in liquid media. The aggregation over time of carbon nanotubes from a dispersed and distributed state into particle networks was also monitored. Best known as dynamic percolation, this resulted in a percolation threshold eventually reduced by a factor of two. We then show that decreasing the matrix viscosity increases the dynamic component of the percolation process, yielding decreased critical filler fraction and percolation time (0.002 vol %). Finally, the effect of the difference in surface tension between the filler and matrix was also quantified. Large differences favor the aggregation mechanisms and thereby reduce the percolation threshold. An analytical model is finally proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46313.

Development of a simulation method for evaluating Marangoni convection with free surface for tungsten divertor

A tungsten (W) divertor has been developed for tokamak-type nuclear fusion reactors, such as ITER. Because the divertor will be repetitively subjected to high heat flux when plasma disruption or edge localized mode occurs, W at the surface of the divertor will be melted and solidified during reactor operation. The surface shape of the W divertor after or during such a heat load strongly influences its lifetime. Thus, evaluating the behavior of W in such conditions is important. An important driving force in molten metal is Marangoni convection due to a difference in surface tension resulting from a temperature gradient at the surface. To clarify the mechanism of Marangoni convection in molten W, a simulation method that can simultaneously treat surface deformation and convection in molten W, including Marangoni convection, is required. We have been developing such a simulation code based on the constrained interpolation profile combined unified procedure method. In this paper, we simulated molten W under a given temperature gradient or heat load and validated the model by simulating the flow in a molten W pool with a temperature gradient. The development process of Marangoni convection in molten W with a free surface was evaluated.

Sex differences in the gastrointestinal tract of rats and the implications for oral drug delivery

Pre-clinical research often uses rodents as animal models to guide the selection of appropriate oral drug and dose selection in humans. However, traditionally, such research fails to consider the gastrointestinal differences between the sexes of rats and the impact on oral drug delivery. This study aimed to identify and characterise the potential sex-related differences in the gastrointestinal environment of sacrificed male and female Wistar rats. Their gastrointestinal tracts were excised and segmented into the stomach, duodenum, jejunum, ileum, caecum and colon. The respective contents and tissue sections were collected and analysed for pH, buffer capacity, surface tension, osmolality and relative P-glycoprotein (P-gp) expression. The pH in the stomach of females was found to be lower than in males. Female rats also exhibited a higher buffer capacity in the caecum and colon when compared with their male counterparts. Males were found to have a higher osmolality than females in the duodenum, ileum and colon. Significant sex differences (p < 0.05) in surface tension were observed in the ileum, where females exhibited a higher surface tension. Interestingly, female rats displayed significantly higher relative P-gp expression levels (p < 0.05) when compared with male rats in the duodenum (1.24 ± 0.85 vs. 0.36 ± 0.26), jejunum (1.45 ± 0.88 vs. 0.38 ± 0.26) and ileum (0.92 ± 0.43 vs. 0.40 ± 0.18) but not in the colon (0.5 ± 0.32 vs. 0.33 ± 0.16) segments. The work reported has demonstrated the stark physiological differences between male and female rats at a physiological level, indicating how the ‘sex of the gut’ could influence oral drug delivery. These findings, therefore, are of critical importance in pre-clinical research and drug development.

Influence of difference in surface tension on indirect fire suppression on fire extinguishing ability

Influence of difference in surface tension on indirect fire suppression on fire extinguishing ability

Surface tension driven aggregation of organic nanowires via lab in a droplet.

Directing the architecture of complex organic nanostructures is desirable and still remains a challenge in areas of materials science due to their structure-dependent collective optoelectronic properties. Herein, we demonstrate a simple and versatile solution strategy that allows surface tension to drive low-dimensional nanostructures to aggregate into complex structures via a lab in a droplet technique. By selecting a suitable combination of a solvent and an anti-solvent with controllable surface tension difference, the droplets can be automatically cracked into micro-droplets, which provides an aggregation force directed toward the centre of the droplet to drive the low-dimensional building blocks to form the special aggregations during the self-assembly process. This synthetic strategy has been shown to be universal for organic materials, which is beneficial for further optimizing the optoelectronic properties. These results contribute to gaining an insightful understanding on the detailed growth mechanism of complex organic nanostructures and greatly promoting the development of organic nanophotonics.

Sandwiched droplet actuated by Marangoni force in a Hele-Shaw cell

We present a novel method of actuating a microliter droplet held within a Hele-Shaw cell by means of the surface tension gradient or Marangoni effect. A food color droplet is first injected within the gap formed by the parallel plates to produce a cylindrical droplet, followed by a lateral injection of a lower surface tension droplet. Our results show the actuation of the food color droplet, for various droplet volumes and viscosities. Analytical studies on the effect of contact angle on distance traveled are presented. Numerical values of the Marangoni force show good agreement with analytical values. Mathematical analysis shows the surface tension difference required for actuation, and how the surface tension changes as a function of angular position on the droplet.

Production of Biosurfactants by &lt;i&gt;Actinomycetes&lt;/i&gt; Isolated from Hydrocarbon Contaminated Soils and Ikpoba River Sediments in Benin-City, Nigeria

The production of biosurfactants by Actinomycetes isolated from hydrocarbon contaminated soils and Ikpoba river sediments were evaluated. Soil samples were collected from mechanic workshops located in various parts of Benin City and Ikpoba river sediments. Physico-chemical analyses were performed. Isolation of Actnomycetes was done using starch casein agar incorporation with antibiotics incubated for 7 – 10 days at 30 o C. Growth on mineral salt medium initiated the production of biosurfactants which was extracted by centrifugation and filtration followed by liquid extraction using chloroform: methanol (2:1v/v). Characterization and stability studies were conducted. The pH of the contaminated soil was 4.92 +/- 0.049 while that of Ikpoba river sediments was 6.62+/-0.056. The hydrocarbon contaminated soils had a higher concentration of surphur, nitrogen, potassium, sodium, magnesium and manganese compared to Ikpoba River, but only chlorine concentration was higher in Ikpoba River. Aerobic Gram positive rods with extensive branching were observed confirming growth of Streptomyces sp. The result showed stability across different temperature ranges with no significant difference observed in the two sites in emulsification activity (P>0.05). There was significant difference observed in the mean surface tension of the biosurfactants produced from the two sites across different temperature ranges with hydrocarbon contaminated soil having higher values (P>0.05). There was also significant surface tension difference between pH2 and pH8 (P<0.05) suggesting higher activity within those ranges. The result also show stability across different salt concentrations and had foaming characteristics. Actinomycetes have complex enzymatic mechanism that aids hydrocarbon mineralization and thus increases the potential for biosurfactant production. These biosurfactants are stable across temperature ranges and are not majorly affected by salt concentration; this property aids its potential usage in decontamination of oil contaminated areas in the Niger Delta region of Nigeria and other countries. Keywords : Biosurfactants, Actinomycetes , hydrocarbon contaminated soils and Ikpoba river sediments

Surface deformation during an action potential in pearled cells.

Electric pulses in biological cells (action potentials) have been reported to be accompanied by a propagating cell-surface deformation with a nanoscale amplitude. Typically, this cell surface is covered by external layers of polymer material (extracellular matrix, cell wall material, etc.). It was recently demonstrated in excitable plant cells (Chara braunii) that the rigid external layer (cell wall) hinders the underlying deformation. When the cell membrane was separated from the cell wall by osmosis, a mechanical deformation, in the micrometer range, was observed upon excitation of the cell. The underlying mechanism of this mechanical pulse has, to date, remained elusive. Herein we report that Chara cells can undergo a pearling instability, and when the pearled fragments were excited even larger and more regular cell shape changes were observed (∼10-100μm in amplitude). These transient cellular deformations were captured by a curvature model that is based on three parameters: surface tension, bending rigidity, and pressure difference across the surface. In this paper these parameters are extracted by curve-fitting to the experimental cellular shapes at rest and during excitation. This is a necessary step to identify the mechanical parameters that change during an action potential.

Marangoni flow traveling with reaction fronts: Eikonal approximation.

Chemical reaction fronts traveling in liquids generate gradients of surface tension leading to fluid motion. This surface tension driven flow, known as Marangoni flow, modifies the shape and the speed of the reaction front. We model the front propagation using the Eikonal relation between curvature and normal speed of the front, resulting in a front evolution equation that couples to the fluid velocity. The sharp discontinuity between the reactants and products leads to a surface tension gradient proportional to a delta function. The Stokes equations with the surface tension gradient as part of the boundary conditions provide the corresponding fluid velocity field. Considering stress free boundaries at the bottom of the liquid layer, we find an analytical solution for the fluid vorticity leading to the velocity field. Solving numerically the appropriate no-slip boundary condition, we gain insights into the role of the boundary condition at the bottom layer. We compare our results with results from two other models for front propagation: the deterministic Kardar-Parisi-Zhang equation and a reaction-diffusion equation with cubic autocatalysis, finding good agreement for small differences in surface tension.