35,777 research outputs found
Flux limitation in ultrafiltration: Osmotic pressure model and gel layer model
The characteristic permeate flux behaviour in ultrafiltration, i.e., the existence of a limiting flux which is independent of applied pressure and membrane resistance and a linear plot of the limiting flux versus the logarithm of the feed concentration, is explained by the osmotic pressure model. In the mathematical description presented here, a quantity ΔΠn/(Rmk) is introduced which is the ratio of the resistance caused by the osmotic pressure and the resistance of the membrane itself. For high values of this quantity (19) the flux is practically limited by the osmotic pressure. p]Factors leading to high values of the quantityΔΠnn/(Rmk) are discussed and it is concluded that in the ultrafiltration of medium molecular weight solutes (10,000 to 100,000 daltons) osmotic pressure limitation is more likely than gel layer limitatio
The osmotic pressure of 3He-4He mixtures along the phase separation curve
The osmotic pressure of 3He-4He mixtures was measured along the phase separation curve at temperatures up to 500 mK by balancing it with the fountain pressure of pure 4He. The usefullness of the secondary osmotic pressure thermometer was reinvestigated
Observations on the physiological development of trout eggs [Translation from: Roux. Arch. f. Entwicklungsmechanik der Organismen, 114. 771, 1929]
The osmotic pressure of the perivitelline fluid and the yolk of trout (Salmo trutta) eggs were measured separately by the Drucker-Schrein method. The permeability of the egg membrane and the variations in the osmotic pressure of the eggs when placed in salt solutions were also investigated
Unbinding Transition Induced by Osmotic Pressure in Relation to Unilamellar Vesicle Formation
Small-angle X-ray scattering and phase-contrast microscopy experiments were
performed to investigate the effect of the osmotic pressure on vesicle
formation in a dioleoylphosphatidylcholine (DOPC)/water/NaI system.
Multi-lamellar vesicles were formed when a pure lipid film was hydrated with an
aqueous solution of NaI. On the other hand, uni-lamellar vesicles (ULVs) were
formed when a lipid film mixed with an enough amount of NaI was hydrated. To
confirm the effect of the osmotic pressure due to NaI, a free-energy
calculation was performed. This result showed that the osmotic pressure induced
an unbinding transition on the hydration process, which resulted in ULV
formation
Theoretical Framework for Microscopic Osmotic Phenomena
The basic ingredients of osmotic pressure are a solvent fluid with a soluble
molecular species which is restricted to a chamber by a boundary which is
permeable to the solvent fluid but impermeable to the solute molecules. For
macroscopic systems at equilibrium, the osmotic pressure is given by the
classical van't Hoff Law, which states that the pressure is proportional to the
product of the temperature and the difference of the solute concentrations
inside and outside the chamber. For microscopic systems the diameter of the
chamber may be comparable to the length-scale associated with the solute-wall
interactions or solute molecular interactions. In each of these cases, the
assumptions underlying the classical van't Hoff Law may no longer hold. In this
paper we develop a general theoretical framework which captures corrections to
the classical theory for the osmotic pressure under more general relationships
between the size of the chamber and the interaction length scales. We also show
that notions of osmotic pressure based on the hydrostatic pressure of the fluid
and the mechanical pressure on the bounding walls of the chamber must be
distinguished for microscopic systems. To demonstrate how the theoretical
framework can be applied, numerical results are presented for the osmotic
pressure associated with a polymer of N monomers confined in a spherical
chamber as the bond strength is varied
New Osmosis Law and Theory: the New Formula that Replaces van't Hoff Osmotic Pressure Equation
This article derived a new abstract concept from the osmotic process and
concluded it via "osmotic force" with a new law -- "osmotic law". The "osmotic
law" describes that, in an osmotic system, osmolyte moves osmotically from the
side with higher "osmotic force" to the side with lower "osmotic force". In
addition, it was proved mathematically that the osmotic process could be
explained perfectly via "osmotic force" and "osmotic laws", which can prevent
the difficulties in using current "osmotic pressure" concept to explain the
osmotic process and phenomenon. A theory and equation to describe the curve of
osmotic pressure vs. different ideal solution concentrations are also derived,
which can overcome the limitedness and incompleteness of van't Hoff osmotic
pressure formula (a linear equation) which is applicable to ideal dilute
solution only
Ultrafiltration of protein solutions; the role of protein association in rejection and osmotic pressure
The monomer-dimer equilibrium of the protein β-lactoglobulin under neutral conditions appears to influence the rejection and the osmotic pressure build-up, both phenomena closely related to ultrafiltration. Rejection measurements indicate different rejections for the β-lactoglobulin monomers and dimers: the membrane rejects the dimer almost completely and the monomer only partially. The osmotic pressure turns out to be highly dependent on the protein concentration. A good agreement, up to high concentrations, is found between experimental data and theoretical osmotic pressures, calculated by taking into account the state of association, the excluded volume and the Donnan effects. The effect of changes in pH on the osmotic pressure has been measured: a minimum was found around pH = 4.5, where according to the literature, maximum protein-protein interaction occurs
Exact Solution of the Discrete (1+1)-dimensional RSOS Model in a Slit with Field and Wall Interactions
We present the solution of a linear Restricted Solid--on--Solid (RSOS) model
confined to a slit. We include a field-like energy, which equivalently weights
the area under the interface, and also include independent interaction terms
with both walls. This model can also be mapped to a lattice polymer model of
Motzkin paths in a slit interacting with both walls and including an osmotic
pressure. This work generalises previous work on the RSOS model in the
half-plane which has a solution that was shown recently to exhibit a novel
mathematical structure involving basic hypergeometric functions .
Because of the mathematical relationship between half-plane and slit this work
hence effectively explores the underlying -orthogonal polynomial structure
to that solution. It also generalises two other recent works: one on Dyck paths
weighted with an osmotic pressure in a slit and another concerning Motzkin
paths without an osmotic pressure term in a slit
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