Osmotic Pressure Of Solution Research Articles

Drosophila glia use a conserved cotransporter mechanism to regulate extracellular volume

The nervous system is protected by blood barriers that use multiple systems to control extracellular solute composition, osmotic pressure, and fluid volume. In the human nervous system, misregulation of the extracellular volume poses serious health threats. Here, we show that the glial cells that form the Drosophila blood-nerve barrier have a conserved molecular mechanism that regulates extracellular volume: the Serine/Threonine kinase Fray, which we previously showed is an ortholog of mammalian PASK/SPAK; and the Na-K-Cl cotransporter Ncc69, which we show is an ortholog of human NKCC1. In mammals, PASK/SPAK binds to NKCC1 and regulates its activity. In Drosophila, larvae mutant for Ncc69 develop a peripheral neuropathy, where fluid accumulates between glia and axons. The accumulation of fluid has no detectable impact on action potential conduction, suggesting that the role of Ncc69 is to maintain volume or osmotic homeostasis. Drosophila Ncc69 has kinetics similar to human NKCC1, and NKCC1 can rescue Ncc69, suggesting that they function in a conserved physiological mechanism. We show that fray and Ncc69 are coexpressed in nerve glia, interact in a yeast-two-hybrid assay, and have an essentially identical bulging nerve phenotype. We propose that normally functioning nerves generate extracellular solutes that are removed by Ncc69 under the control of Fray. This mechanism may perform a similar role in humans, given that NKCC1 is expressed at the blood-brain barrier.

Osmotic stress regulates the strength and kinetics of sugar binding to the maltoporinchannel

We study the effect of osmotic stress, exerted by salts, on carbohydrate binding to thesugar-specific bacterial channel maltoporin. When the channel is reconstituted intoplanar lipid bilayers, single events of its occlusion by sugar are seen as transientinterruptions in the flow of small ions. We find that, for most salts, changes inthe free energy of maltoporin–sugar binding vary linearly with solution osmoticpressure. Such a change in binding with solution osmolarity indicates that foreach salt a constant number of salt-excluding water molecules is released uponsugar–maltoporin association at all salt concentrations. We find that largernumbers of water molecules are released upon binding of the cyclic carbohydrateβ-cyclodextrin (CD) than upon binding of the corresponding linear homologuemaltoheptaose (m7). Remarkably, the extent to which salts affect the binding constantsand rates depends sensitively on the type of salt; dehydration in solutions of differentanions corresponds to the Hofmeister series. In sodium sulfate solutions, CD and m7respectively release about 120 and 35 salt-excluding water molecules; in sodium chloridesolutions, 35 and 15 waters. No water release is observed with sodium bromide. Finally, byadding adamantane, known to form an inclusion complex with CD, we can infer that CDnot only dehydrates but also undergoes a conformational change upon binding to thechannel. As a practical outcome, our results also demonstrate how osmotic stress canimprove single-molecule detection of different solutes using protein-based nanopores.

Cellulose acetate nanofiltration hollow fiber membranes for forward osmosis processes

Abstract Cellulose acetate (CA) nanofiltration (NF) hollow fiber membranes have been fabricated and tested in the forward osmosis (FO) process. A two-step heat-treatment, i.e., 60 min at 60 °C and 20 min at 95 °C, effectively shrinks the membrane mean pore radius from 0.63 to 0.30 nm. The molecular weight cut off (MWCO) of the resultant CA NF membrane is 186 Da. In the NF experiments under 1 bar transmembrane pressure, the newly developed CA NF membrane shows a pure water permeability (PWP) of 0.47 L m −2 bar −1 h −1 and rejection levels of 90.17% to NaCl and 96.67% to MgCl 2 . The water flux and the salt leakage of the CA NF hollow fiber are measured in the FO process using NaCl or MgCl 2 draw solutions. With increasing the draw solution concentration, the water flux increases. However, the increase is almost linear when the draw solution flows in the shell side and is nonlinear when the draw solution flows in the lumen side. With 2.0 M MgCl 2 draw solution (osmotic pressure ≈ 258.3 bar) flowing in the shell side, the water flux and the salt leakage are 7.3 L m −2 h −1 (LMH) and 0.53 g m −2 h −1 (gMH), respectively. When using saline water as the feed solution, the efficiency of the osmotic pressure decreases with increasing feed concentration due to the more severe internal concentrative concentration polarization. These preliminary results indicate that CA NF membrane is a promising candidate for FO processes.

Steady state modeling for membrane separation of pretreated liming effluent under cross-flow mode

A steady state model is formulated for a two step membrane separation processes (ultrafiltration followed by nanofiltration) for treatment of the liming effluent collected from a tannery. The extent of polarization on the membrane surface is quantified. The model parameters are determined by fitting of the calculated results of permeate flux and permeate concentration with the corresponding experimental data. Solution diffusion and osmotic pressure model are combined for continuous, cross-flow membrane processes. Three flow regimes, namely, laminar, laminar with promoter and turbulent are investigated. The effective osmotic coefficient, solute diffusivity, solute permeability through the membrane have been estimated for liming effluent of a tannery. For both ultrafiltration and nanofiltration, the extent of polarization increases with transmembrane pressure and decreases with cross-flow rate.

Particle Pressure in a Sheared Suspension: A Bridge from Osmosis to Granular Dilatancy

The normal stress exerted by particles in a sheared suspension is measured by analogy with a method used to measure osmotic pressure in solutions. Particles in a liquid are confined by a fine screen to a gap between two vertical concentric cylinders, the inner of which rotates. Pressure in the liquid is sensed either by a manometer or by a pressure transducer across the screen. The particles are large enough so that Brownian motion and equilibrium osmotic pressure are vanishingly small. The measured pressure yields the shear-induced particle pressure Pi, the nonequilibrium continuation of equilibrium osmotic pressure. For volume fractions 0.3< or =varphi< or =0.5, Pi is strongly dependent on varphi, and linear in shear rate. Comparisons of the measured particle pressure with modeling and simulation show good agreement.

Effects of feed water temperature on inorganic fouling of brackish water RO membranes

A bench scale RO process simulator was operated in a batch concentration mode to determine the effects of product water recovery and feed water temperature on flux, rejection, and inorganic fouling by gypsum scale formation for simulated brackish water. As feed water temperature increased, salt rejection and concentration polarization decreased (reducing scale formation potential at a given recovery). However, gypsum crystal nucleation and growth rates increased with temperature. Specifically, at 15 and 25°C gypsum scale formation resulted in slow, steady flux decline at recoveries as low as 10–20%. At these temperatures, many small crystals formed over the entire membrane surface. In contrast, at 35°C flux decline was due to the increasing feed solution osmotic pressure — up to a recovery of about 70%. At this recovery, we observed a sudden, rapid loss of flux and a concomitant spike in feed water turbidity. Relatively few (in number), large crystals formed on the membrane towards the brine outlet of the RO simulator, but the entire membrane surface was covered with “needle-like” crystal fragments. The crystal fragments broke off from growing gypsum rosettes and re-deposited uniformly across the membrane forming a “cake layer” that caused the massive flux decline. These results suggest that high temperature operation of brackish water RO processes could enable higher recovery and lower energy consumption, but operating near the limiting recovery (at elevated temperature) creates an increased risk of a catastrophic fouling event.

Steady‐state modeling for membrane separation of pretreated soaking effluent under cross flow mode

AbstractA two‐step membrane separation process, namely, nanofiltration (NF), followed by reverse osmosis (RO), is proposed to treat the soaking effluent collected from a tannery. Solution diffusion and osmotic pressure model are combined to predict the steady‐state permeate flux and permeate concentration for continuous, cross flow membrane separation operations. Three flow regimes, namely, laminar, laminar with promoters, and turbulent flow are considered. The extent of polarization on the membrane surface is quantified. For both NF and RO, the extent of polarization increases with increasing transmembrane pressure and decreases with cross flow rate. The model parameters are optimized by comparing the calculated results with the experimental data. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Counterion Localization in Solutions of Starlike Polyelectrolytes and Colloidal Polyelectrolyte Brushes: A Self-Consistent Field Theory

A quantitative analysis of the distribution of counterions in salt-free solutions of colloidal polyelectrolyte brushes and starlike polyelectrolytes is performed on the level of the Poisson-Boltzmann approximation. Exact numerical solutions are obtained for starlike polyelectrolyte molecules composed of f = 20, . . ., 50 arms with a fixed fractional charge alpha per segment by applying the self-consistent field method of Scheutjens and Fleer (SF-SCF). The Wigner-Seitz cell dimension defines the concentration of polyelectrolyte stars in the system. The numerical results are compared to predictions of an analytical mean field theory and related to experimental observations on the osmotic pressure in solutions of starlike polyelectrolytes and colloidal polyelectrolyte brushes.

Fast Membrane Osmometer as Alternative to Freezing Point and Vapor Pressure Osmometry

Osmometry is an essential technique for solution analysis and the investigation of chemical and biological phenomena. Commercially available osmometers rely on the measurements of freezing point, vapor pressure, and osmotic pressure of solutions. Although vapor pressure osmometry (VPO) and freezing point osmometry (FPO) can perform rapid and inexpensive measurements, they are indirect techniques, which rely on thermodynamic assumptions, which limit their applicability. While membrane osmometry (MO) provides a potentially unlimited direct measurement of osmotic pressure and solution osmolality, the conventional technique is often time-consuming and difficult to operate. In the present work, a novel membrane osmometer is presented. The instrument significantly reduces the conventional MO measurement time and is not subject to the limitations of VPO and FPO. For this paper, the osmotic pressure of aqueous sucrose solutions was collected in a molality range 0-5.5, by way of demonstration of the new instrument. When compared with data found in the literature, the experimental data were generally in good agreement. However, differences among results from the three techniques were observed.

Swelling pressure and elastic behavior of polymacromonomer networks with different functionalities of junctions

Networks with different junction functionalities as obtained by polymerization of a macromonomer (composed of 20 units) at identical concentrations were studied by computer simulation. The functionality determined by the length of chains produced from the end units of the macromonomer was varied over a wide range by varying the kinetic parameters of polymerization. From the number of collisions of units with the lattice walls at different swelling stages, the network swelling pressure and the osmotic pressure of solution of its fragments obtained by cutting in half interjunction chains were determined. From these data, the osmotic and elastic components of swelling pressure were found, the former was defined as the pressure of solution and the latter was defined as the difference of the network and solution pressures. The osmotic component is a power function of the polymer concentration with the power index increasing from 2.7 to 3.9 with an increase in functionality from 4.8 to 55 in accordance with a change in network topology. The elastic pressure depends on the swelling ratio Q in different manners at a low and a high functionality of junctions. Its absolute value decreases with a growth in Q in the former case, in agreement with the theory of elasticity of phantom networks (∼Q−1/3), but increases in the latter case. This behavior is consistent with the effect of functionality on the elastic behavior of real polymacromonomer networks and confirms that differences in the character of change in the modulus of such networks during swelling are due to a difference in the functionality of their junctions. Possible mechanisms of the influence of multifunctional junctions on the elasticity of polymer networks are discussed.

Model for Calculating the Viscosity of Non-Newtonian Aqueous Solutions of Poly(ethylene glycol) 6000 at 313.15 K and 0.1 MPa

In this work, a model for calculating the dynamic viscosity of polymer solutions was developed. The model is based on the Eyring absolute rate theory and on the solution theory of McMillan−Mayer. An equation of state is used for the calculation of the solution osmotic pressure and, thus, the excess molar McMillan−Mayer free energy. The final expression shows an explicit dependence between the viscosity of the polymer solution and the applied shear stress. The proposed model contains three terms. The first term describes the viscosity of an ideal polymer solution. The second term takes into account non-Newtonian behavior of the polymer solution. Finally, the third term represents the deviation from the thermodynamic ideal behavior. The whole model presented five adjustable parameters, with two of them also considered as being a function of the applied shear stress. To test the proposed model, we have measured experimental rheological data for poly(ethylene glycol) aqueous solutions (nominal molecular weight 6000 g/mol) for nine different polymer concentrations, at different shear rates, at 313.15 K and 0.1 MPa. The proposed model has been used for correlating the experimental viscosity data of these polymer solutions at different values of the applied shear stress and polymer concentration. It has been found that the agreement between the experimental and calculated values is within the experimental error.

Solutes Probe Hydration in Specific Association of Cyclodextrin and Adamantane

Using microcalorimetry, we follow changes in the association free energy of beta-cyclodextrin (CD) with the hydrophobic part of adamantane carboxylate (AD) due to added salt or polar (net-neutral) solutes that are excluded from the molecular interacting surfaces. Changes in binding constants with solution osmotic pressure (water activity) translate into changes in the preferential hydration upon complex formation. We find that these changes correspond to a release of 15-25 solute-excluding waters upon CD/AD association. Reflecting the preferential interaction of solute with reactants versus products, we find that changes in hydration depend on the type of solute used. All solutes used here result in a large change in the enthalpy of the CD-AD binding reaction. In one class of solutes, the corresponding entropy change is much smaller, while in the other class, the entropy change almost fully compensates the solute-specific enthalpy. For many of the solutes, the number of waters released correlates well with their effect on air-water surface tensions. We corroborate these results using vapor pressure osmometry to probe individually the hydration of reactants and products of association, and we discuss the possible interactions and forces between cosolute and hydrophobic surfaces responsible for different kinds of solute exclusion.

Current Fertilizer Salt Index Tables are Misleading

In the 1940s, fertilizer materials that were available at that time were evaluated for changes that occurred in the soil solution osmotic pressure upon application. The term “salt index” was then used to compare the increase in osmotic pressure for 45 fertilizer materials against the same weight of sodium nitrate. During the 1950s a simplified laboratory method was developed where salt index was measured by electrical conductance rather than by osmotic pressure. Current salt-index tables in fertilizer references have combined the values from the two methods. The objective of this study was to evaluate five potassium (K) sources by the electrical-conductance method. Sources included potassium chloride, potassium sulfate, potassium nitrate, sulfate of potash magnesia, and potassium thiosulfate. Salt-index values obtained from the laboratory method are significantly higher than values reported in the original soil study. These differences range from 28.6% for potassium chloride to 141.2% for potassium sulfate. These limited results with potassium fertilizer materials indicate that a new system for evaluation should be developed or that current fertilizer materials should be evaluated under the same set of experimental conditions.

Current Fertilizer Salt Index Tables are Misleading

Abstract In the 1940s, fertilizer materials that were available at that time were evaluated for changes that occurred in the soil solution osmotic pressure upon application. The term “salt index” was then used to compare the increase in osmotic pressure for 45 fertilizer materials against the same weight of sodium nitrate. During the 1950s a simplified laboratory method was developed where salt index was measured by electrical conductance rather than by osmotic pressure. Current salt-index tables in fertilizer references have combined the values from the two methods. The objective of this study was to evaluate five potassium (K) sources by the electrical-conductance method. Sources included potassium chloride, potassium sulfate, potassium nitrate, sulfate of potash magnesia, and potassium thiosulfate. Salt-index values obtained from the laboratory method are significantly higher than values reported in the original soil study. These differences range from 28.6% for potassium chloride to 141.2% for potassium sulfate. These limited results with potassium fertilizer materials indicate that a new system for evaluation should be developed or that current fertilizer materials should be evaluated under the same set of experimental conditions.

Electroporation-mediated ex vivo gene transfer into graft not requiring injection pressure in orthotopic liver transplantation.

We investigated optimum conditions for ex vivo gene transfer into liver grafts by plasmid injection via the portal vein combined with electroporation in rat liver transplantation. Anesthetized 9-week-old male Shionogi-Wistar rats were used as donors and recipients. After harvest of the liver graft from the donor rat, a tapered 3Fr. catheter was inserted into the portal vein of the liver graft ex vivo. After clamping the afferent vessels around the right and caudal liver lobes, pCAGGS-luciferase, which was diluted with one of several osmotic pressure solutions, or pCAGGS-green fluorescence protein (GFP) plasmid was injected into these lobes to keep the efferent vessels patent. Electrical pulses were applied to the liver graft during cold preservation in lactated Ringer's solution, University of Wisconsin solution, and histidine-tryptophan-ketoglutarate solution. Transfection efficacy was estimated by measurement of luciferase activity. Luciferase activity in the liver was dependent on both the voltage and electric current of the electrical pulse, and also on the type of preservation solution and plasmid osmotic pressure. Luciferase activity was noted only in plasmid-injected lobes of the liver graft. GFP-transfected cells were identified by GFP fluorescence. GFP was observed predominantly in perivascular cells, including hepatocytes. We have demonstrated successful ex vivo gene transfection into liver grafts without injection pressure by using a non-viral method.

Monte Carlo analysis of the osmotic pressure of athermal polymer solutions in dilute and semi-dilute regimes

The enrichment Monte Carlo algorithm is applied here, for the first time, to calculate the osmotic pressure of an athermal solution of linear chains on a lattice, in dilute and semi-dilute regimes. Complementarily to the Widom's test particle insertion method, the algorithm enables one to estimate directly the free energy and the osmotic pressure of the solution. The result shows that there is a large deviation in the free energy from the Flory–Huggins theory which may be attributed to the chain internal entropy. Moreover, the osmotic pressure shows des Cloizeaux's c9/4 behavior clearly when the concentration, c, is greater than the estimated overlap concentration. We estimate also the second and third virial coefficients that are compared with experimental values.

Density calculation of electrolyte solutions with the solution osmotic pressure

A new generalized model was developed for the density calculation of single and mixed electrolyte solutions in the temperature range of 273.15–373.15 K by using the principle of corresponding states and the main idea of the TTG model for electrolyte aqueous solutions. The molar volume of electrolyte solutions consists of both intrinsic ionic volume and apparent water molar volume; the former was evaluated from the expression given by Conway (1981, Studies in physical and theoretical chemistry 12. Amsterdam: Elsevier) expression and the latter from the generalized relationship between apparent water molar volume and osmotic pressure. The validity of the proposed model was extensively tested for 151 single and 30 binary electrolyte solutions at 298.15 K, and 11 single electrolyte solutions in the temperature range of 273.15–373.15 K. With the optimized ionic radii which is temperature and concentration independent, the AADs were found to be within 1% for single and binary-electrolyte solutions.

Transport and fate of volatile organic chemicals in unsaturated, nonisothermal, salty porous media:: 1. Theoretical development

A wide variety of volatile organic chemicals (VOC) have been applied to agricultural land or buried in chemical waste sites. The fate of these chemicals depends upon several mechanisms such as sorption, degradation, and transport in liquid and gaseous phases. Understanding the transport mechanisms affecting the volatile chemicals can lead to better management strategies. A theory describing inorganic solute transport, water and heat transfer, and the fate and transport of VOC in porous media has been developed. This theory includes matric water pressure head, solution osmotic pressure head, gravity pressure head, temperature, inorganic solute concentration, and VOC concentration gradients as driving forces for heat and mass transfer. The effect of surface tension, as a function of VOC concentration and temperature, on the matric water pressure head is included. The VOC can be associated with gas, liquid, and solid phases of the porous media. The gas and liquid phases are mobile, but the solid phase is immobile. The transfer of VOC across the gas/liquid, liquid/solid, and gas/solid interfaces is included using sorption–equilibrium assumptions at the interfaces. The VOC can degrade. This degradation is described by a first-order decay rate. The theory can be used to predict spatial and temporal variations of water content, temperature, inorganic concentration and the total concentration of VOC within a porous medium. The concentration of VOC in each phase can be predicted also.

Micellization in Model Surfactant Systems

Formation of micelles in model lattice surfactant systems was studied by a novel methodology based on grand-canonical Monte Carlo simulations. The methodology involves combining free-energy information from a series of simulations in small systems by histogram reweighting. The solution osmotic pressure as a function of overall volume fraction of surfactant shows a sharp break at the critical micelle concentration (cmc) at sufficiently low temperatures. Studies in larger systems at appropriate values of the surfactant chemical potential are used to investigate the size distribution of micellar aggregates. The methodology allows for a clear distiction between micellization and macroscopic phase separation. Two symmetric diblock surfactants have been considered in the present work. The cmc was found to increase with increasing temperature. The enthalpy change on micellization was determined to be proportional to the chain length of the surfactant. The mean micelle aggregation numbers were found to decrease a...

Concentration Polarization of Interacting Solute Particles in Cross-Flow Membrane Filtration

A theoretical approach for predicting the influence of interparticle interactions on concentration polarization and the ensuing permeate flux decline during cross-flow membrane filtration of charged solute particles is presented. The Ornstein–Zernike integral equation is solved using appropriate closures corresponding to hard-spherical and long-range solute–solute interactions to predict the radial distribution function of the solute particles in a concentrated solution (dispersion). Two properties of the solution, namely the osmotic pressure and the diffusion coefficient, are determined on the basis of the radial distribution function at different solute concentrations. Incorporation of the concentration dependence of these two properties in the concentration polarization model comprising the convective-diffusion equation and the osmotic-pressure governed permeate flux equation leads to the coupled prediction of the solute concentration profile and the local permeate flux. The approach leads to a direct quantitative incorporation of solute–solute interactions in the framework of a standard theory of concentration polarization. The developed model is used to study the effects of ionic strength and electrostatic potential on the variations of solute diffusivity and osmotic pressure. Finally, the combined influence of these two properties on the permeate flux decline behavior during cross-flow membrane filtration of charged solute particles is predicted.