The Role of the Frank–Starling Law in the Transduction of Cellular Work to Whole Organ Pump Function: A Computational Modeling Analysis

We have developed a multi-scale biophysical electromechanics model of the rat left ventricle at room temperature. This model has been applied to investigate the relative roles of cellular scale length dependent regulators of tension generation on the transduction of work from the cell to whole organ pump function. Specifically, the role of the length dependent Ca2+ sensitivity of tension (Ca50), filament overlap tension dependence, velocity dependence of tension, and tension dependent binding of Ca2+ to Troponin C on metrics of efficient transduction of work and stress and strain homogeneity were predicted by performing simulations in the absence of each of these feedback mechanisms. The length dependent Ca50 and the filament overlap, which make up the Frank-Starling Law, were found to be the two dominant regulators of the efficient transduction of work. Analyzing the fiber velocity field in the absence of the Frank-Starling mechanisms showed that the decreased efficiency in the transduction of work in the absence of filament overlap effects was caused by increased post systolic shortening, whereas the decreased efficiency in the absence of length dependent Ca50 was caused by an inversion in the regional distribution of strain

Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes

Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed

Modelling of methane and n-butane sorption, diffusion and permeation in polydimethylsiloxane using PC-SAFT

Published sorption, diffusion and permeation data for methane and n-butane in polydimethylsiloxane (PDMS) from −20 to 50 °C was simulated using a perturbed chain statistical association theory (PC-SAFT) based model. The use of a temperature-dependent interaction parameter within the PC-SAFT model allowed the pure gas sorption data to be very well represented. The mixed gas sorption results were fully predictable from these pure gas parameters, without the introduction of any additional parameters, and agreed well with the experimental data. The model was also able to model the dilation behavior of PDMS under various gas compositions, making it possible to analyse gas sorption properties using pure gas sorption data only. A diffusion model coupled with the PC-SAFT model was capable of fitting both pure and mixed gas permeation data well by applying an exponential expression to account for such dilation in the diffusivity term. Only two parameters (i.e. infinite dilution mobility coefficient L0 and plasticization factor β) were used and no coupling effect between the two penetrants was needed. The activation energies of L0 were 11.7 and 13.4 kJ mol−1 for methane and n-butane. Moreover, the model was also able to calculate the concentration profiles of the penetrants across the membrane thickness. For n-butane, the mass concentration profile changed from linear to non-linear when the feed pressure increased from 4 to 11 atm for 8 mol% n-butane at 25 °C. Conversely, methane showed a linear concentration profile under both conditions

Separation Technologies for Salty Wastewater Reduction in the Dairy Industry

The wastewater discharged by cheese manufacturing processes is highly saline. This waste is generated from whey demineralization, chromatography and clean-in-place processes. Salty effluent can be diluted with other effluents and discharged as trade waste but the high salinity can trigger penalties imposed by local water authorities. Alternatively, such waste can be sent to evaporation ponds, but in some areas in Australia, environmental impacts regarding land degradation, odor and dust have prevented further pond construction. Similar concentrate and brine management issues are emerging in the seawater desalination and mining industries. This paper reviews a range of commercial and emerging separation technologies that may be suitable to both reduce the costs of salty wastewater treatment and to improve the recoveries of dairy and salt-based products. These technologies have been commercialized or applied at a laboratory scale to the fields of desalination and brine concentration. Each technology is discussed in terms of its principle of operation and suitability for treating high-salinity dairy wastewater. The potential energy requirement and processing cost of each technology is identified with respect to feed water salinity, to provide additional insights into the energy and cost efficiencies of these technologies

The effects of medium salinity on the delivery of carbon dioxide to microalgae from capture solvents using a polymeric membrane system

Efficient provision of carbon dioxide to microalgae is one of the major challenges to cost-effective large-scale cultivation. Previously, we have demonstrated the effectiveness of a novel membrane system in delivering CO2 to a marine strain of Chlorella sp. from CO2-loaded solvents. In this approach, the solvent is pumped through a non-porous hollow fibre membrane immersed in a microalgae medium, allowing passive transfer of CO2 that is utilised by the microalgae to enhance their growth, while simultaneously regenerating the solvent. In this article, we compare the growth of both fresh water and marine strains of algae using this membrane delivery system. While the fresh water medium has less pH buffering capacity and can dissolve less CO2, it proves similarly effective in delivering CO2 to the growing algae. Both the freshwater and marine species of Chlorella have slightly higher growth rates than the other species tested—Dunaliella tertiolecta and Haematococcus pluvialis. However, due to the lower osmotic pressure of the fresh water medium, more water is drawn through the membrane into the solvent than when the salt water medium is used. In conclusion, while CO2 delivery through the membrane system is effective for both salt and fresh water media, better performance is obtained for the salt water medium

Small scale production of cream cheese: A comparison of batch centrifugation and cloth bag methods

Accepted version has the title: A small scale laboratory process for cream cheese production and characterisation.Cream cheese production is well established at large scale but an effective small scale process could facilitate higher throughput and lower the cost of experimental studies. Whey was separated using centrifugation or the cloth bag method and the effect of heating prior to separation examined. Heat treatment and centrifugation resulted in cream cheese with a microstructure, composition and rheological properties comparable with that of a commercial scale cream cheese. Heating was necessary to achieve effective separation, the desired product microstructure and an adequate firmness and viscosity, with the heat induced denaturation of some whey proteins contributing to these properties. Whilst both whey separation methods resulted in a similar microstructure, centrifugation led to less fat loss and an optimal product. These data provide new insights into the development of cream cheese microstructure and provide a route to further understand and optimise this process

Isolation of lactoferrin and immunoglobulins from dairy whey by an electrodialysis with filtration membrane process

Isolation of high value minor proteins such as lactoferrin and immunoglobulins from crude dairy streams is a major challenge for the dairy industry. Here we investigate an electrodialysis with filtration membrane (EDFM) approach to separate lactoferrin (LF) and immunoglobulins (Ig) from other dairy proteins. A polyvinyl alcohol (PVA) membrane is prepared using phase inversion in a coagulation bath with 80% ethanol to serve as the filtration membrane. A range of treatment times and two electric field strengths (38.5 and 77 V/cm) were then investigated within the electrical cell. The results show that the filtration membrane prepared in-house can offer strong rejection for LF and Ig while allowing a high flux of other proteins. The separation of LF and Ig from a simulated whey solution can be achieved. The use of a partially demineralised whey reduces protein loss, but there is a tradeoff between the energy consumption and the protein removal rate as the extent of this demineralisation is increased

The effect of surface-active solutes on bubble coalescence in the presence of ultrasound

The sonication of an aqueous solution generates cavitation bubbles, which may coalesce and produce larger bubbles. This paper examines the effect of surface-active solutes on such bubble coalescence in an ultrasonic field. A novel capillary system has been designed to measure the change in the total volume resulting from the sonication of aqueous solutions with 515 kHz ultrasound pulses. This volume change reflects the total volume of larger gas bubbles generated by the coalescence of cavitation bubbles during the sonication process. The total volume of bubbles generated is reduced when surface-active solutes are present. We have proposed that this decrease in the total bubble volume results from the inhibition of bubble coalescence brought about by the surface-active solutes. The observed results revealed similarities with bubble coalescence data reported in the literature in the absence of ultrasound. It was found that for uncharged and zwitterionic surface-active solutes, the extent of bubble coalescence is affected by the surface activity of the solutes. The addition of 0.1 M NaCl to such solutes had no effect on the extent of bubble coalescence. Conversely, for charged surface-active solutes, the extent of bubble coalescence appears to be dominated by electrostatic effects. The addition of 0.1 M NaCl to charged surfactant solutions was observed to increase the total bubble volume close to that of the zwitterionic surfactant. This suggests the involvement of electrostatic interactions between cavitation bubbles in the presence of charged surfactants in the solution