New Thermal Energy Converters Based on Polyelectrolyte Hydrogels

The theory of thermal energy converters based on polyelectrolyte hydrogels has been developed. The possibility of providing the circulation of a fluid in the contour by controlled variations of the local value of concentrations of the mobile ions that cause an osmotic pressure gradient was shown. On the basis of the solution of motion equations of the mobile ions the numerical estimates of parameters of proposed type of circulation contour are given.

Influence of Organic Matters on Forward Osmosis Membrane Performance

Forward osmosis is an emerging membrane technology with potential applications in desalination and wastewater reclamation, osmotic pressure gradient cross the FO membrane is used to generate water flux. In contrast with conventional pressure-driving membrane process, the advantage of FO is significant: energy saving, high solute rejection and low fouling propensity. In this study, alginic acid (AA), boving serum albumin (BSA), humic acid (HA) and tannic acid (TA) were used to investigate the influence of organic fouling. The flux changed obviously, the rejection was approving and the absorption of organics was observed in the study. Ultrasonic oscillation was employed to wipe the organics off the fouling membranes, which was intend to study the quality of absorption of organic matters.

Distributions During Cryoprotective Agent Loading in a Microchannel

Cryopreservation of cells and tissues is critical to long term storage and off the shelf availability of biomaterials for a variety of disciplines[1]. Typical cryopreservation protocols aim to remove intracellular water by exposing the sample to a cryoprotective agent (CPA) to create an osmotic pressure gradient[2]. While CPAs are useful in preventing cell damage due to intracellular ice formation, the dehydration process can induce harmful osmotic shock[3].

Osmosis and Solute Size: A Molecular Dynamics Study

Osmosis plays an essential role in a wide range of phenomena, and therefore it is useful to understand how to manipulate the rate at which osmosis occurs. In the present study we conduct molecular dynamics simulations to consider the influence of solute size on the osmotic pressure gradient which drives the flow. Our results show how selective choice of the size of the solute can enhance, or hinder, the establishment of a strong osmotic gradient.

The Variability in Ultrafiltration Achieved with Icodextrin, Possibly Explained

Background A recent study by Jeloka et al. (Perit Dial Int 2006; 26:336–40) highlighted the high variability in maximum ultrafiltered volume (UFmax) and the corresponding dwell time (tmax) obtained using 7.5% icodextrin solution. We aimed to pinpoint the possible sources of this phenomenon by simulating the icodextrin ultrafiltration (UF) profiles according to the three-pore model of peritoneal transport. Method The individual UF time courses observed in the study by Jeloka et al. ( n = 29) were first characterized by linear and quadratic regression. We were then able to identify four main patterns. These were then adapted to UF profiles generated by the three-pore model by systematically altering the values of some model parameters, namely, the mass transfer area coefficient (MTAC or PS) for icodextrin/glucose, the peritoneal UF coefficient (LpS), the plasma colloid osmotic pressure gradient (ΔΠ), and the macromolecular clearance out of the peritoneal cavity (ClLF). Results Modifications in the PS values caused only marginal variations in UFmax and tmax, while more significant changes were produced by altering LpS and ClLF. However, far more evident was the importance of changes in ΔΠ In fact, lowering ΔΠ to 14 mmHg caused a steady increase in UF with 10 – 14 hour dwells. On the contrary, the UF profiles became nearly “flat” when ΔΠ was increased to 30 mmHg. The parallel shifts induced by altering icodextrin metabolite concentrations did not markedly influence UFmax or tmax. Conclusion The UF pattern in icodextrin dwells seem to be mainly determined by the plasma colloid osmotic pressure, while only moderate changes can be seen with alterations in LpS and ClLF. The result is not completely unexpected considering that icodextrin acts by inducing a strong colloid osmotic gradient. A number of clinical studies would be needed, however, in order to prove this hypothesis.

Practical Kedem-Katchalsky equations and their modification

The research problem presented in this work concerns modification of the Kedem-Katchalsky (K-K) equation for volume flow (J v) through system (h|M|l), consisting of a membrane M and boundary layers h and l. Such boundary layers appear in the vicinity of the membrane on both sides due to the lack of mixing of solutions. This paper also includes the derivation of the equation for volume flow (J vr) dissipated on concentration boundary layers h and l. The derivation of these equations concerns the case in which the substance transport through the membrane is generated by the osmotic pressure gradient $$\Delta \dot \prod $$ . On the basis of the equations for the volume flows (J v) and (J vr), some calculations for a nephrophane membrane, used in medicine, and for aqueous glucose solutions have been carried out. In order to test the equations for (J v) and (J vr), we have also carried out calculations for the volume flow (J′ v) that is transferred through the membrane in the case of mixed solutions on both sides of the membrane. This volume flux has been calculated on the basis of the original (K-K) equation. The results are presented in Fig. 2.

Interstitial albumin concentration measured during growth of perivascular cuffs in liquid-filled rabbit lung

The growth rate and albumin concentration of interstitial fluid cuffs were measured in isolated rabbit lungs inflated with albumin solution (3 g/dl) to constant airway (Paw) and vascular pressures for up to 10 h. Cuff size was measured from images of frozen lung sections, and cuff albumin concentration (Cc) was measured from the fluorescence of Evans blue labeled albumin that entered the cuffs from the alveolar space. At 5-cmH2O Paw, cuff size peaked at 1 h and then decreased by 75% in 2 h. The decreased cuff size was consistent with an osmotic absorption into the albumin solution that filled the vascular and alveolar spaces. At 15-cmH2O Paw, cuff size peaked at 0.25 h and then remained constant. Cc rose continuously at both pressures, but was greater at the higher pressure. The increasing Cc with a constant cuff size was modeled as diffusion through epithelial pores. Initial Cc-to-airway albumin concentration ratio was 0.1 at 5-cmH2O Paw and increased to 0.3 at 15 cmH2O, a behavior that indicated an increased permeability with lung inflation. Estimated epithelial reflection coefficient was 0.9 and 0.7, and equivalent epithelial pore radii were 4.5 and 6.1 nm at 5- and 15-cmH2O Paw, respectively. The initial cuff growth occurred against an albumin colloid osmotic pressure gradient because a high interstitial resistance reduced the overall epithelial-interstitial reflection coefficient to the low value of the interstitium.