Effect of chemical additives on biomass deposition onto beaded adsorbents

Common limitations encountered during the direct recovery of bioproducts from an unclarified feedstock are related to the presence of biomass in such processing systems. Biomass-related effects can be described as biomass-to-support deposition and cell-to-cell aggregation. In this work, a number of chemical additives were screened for their ability to inhibit either biomass deposition, cell aggregation, or a combination of both effects. Several interacting pairs were screened. These were composed of (i) a commercial chromatographic matrix harbouring a variety of ligand types and (ii) intact yeast cells — as a model biomass type. Studies were performed based on partitioning tests, colloid deposition experiments, and sorption performance studies in expanded beds. Results indicated that the coating of anion-exchanger beads with the synthetic polymer PVP 360 alleviated biomass deposition and consequently restored EBA process performance. This behaviour correlated well with calculations performed according to the XDLVO approach: the secondary (interaction) free energy pockets decreased from − 230 kT to − 100 kT in the absence and in the presence of PVP 360, respectively. Experiments performed in parallel demonstrated that total binding capacity for the model protein (BSA) – under dynamic conditions – remained almost constant (≈ 55.7 kg m^− 3). Other combinations of additives and adsorbents were tested. However, no solution chemistry was able to inhibit biomass deposition onto strong (composite) ion exchangers. Moreover, yeast cell deposition was only marginally decreased when hydrophobic interaction and pseudo-affinity supports were explored. The utilization of non-toxic polymers could help to avoid detrimental biomass deposition during expanded bed adsorption of bioproducts and other direct contact sequestration methods.     

High dimension dynamic programming model for water resources expansion projects

An optimization model for High Dimension Dynamic Programming (HDDP) was developed to determine the optimal size of water resources projects within a planning period. The model uses Objective Space Dynamic Programming (OSDP) technique to determine the size of the projects and a Mixed Integer Programming (MIP) formulation to overcome the ‘inner’ and ‘outer’ problems of OSDP and to check for the global optimality of the solution. The model is applied to determine the optimal capacity of proposed desalination plants needed to satisfy a number of demand points from different cities, during a planning period of 20 years in Egypt. The model’s speed towards the optimal solution depends on the objective space bounds and search method for these bounds. The integration of OSDP and MIP is shown to be an efficient approach for solving optimization problems. Results show that the model is well suited for solving large-scale water resources expansion problems.     

Microfluidic spatial growth of vertically aligned ZnO nanostructures by soft lithography for antireflective patterning

Hierarchical assemblies of nanostructured building blocks on conducting substrates are significant for construction of functional devices. Microfluidics is powerful but less exploited tool for spatial organization or growth of functionally sophisticated nanostructures with precise control. In this paper, we introduce a simple but unique strategy for the hydrothermal synthesis and patterned assembly of ZnO nanostructures within microchannels by soft lithography technique. Optical/antireflection properties of such hierarchically structured nanostructures are studied.     

Synthesis and characterization of photocatalytic polyurethane and poly(methyl methacrylate) microcapsules for the controlled release of methotrexate

Abstract

The aim of this work is to prepare ultraviolet (UV) triggered controlled release of compounds from microcapsule systems (MCs). Polyurethane (PU) and poly(methyl methacrylate) (PMMA) microcapsules were studied with/without chemical functionalization using photocatalytic TiO₂ nanoparticles (NPs) on their surface. Once TiO₂ nanoparticles are illuminated with UV light (λ?=?370?nm), they initiate the rupture of the polymeric bonds of the microcapsule and subsequently initiate the encapsulated compound release, methotrexate (MTX) or rhodamine (Rh), in the present work. The size, polydispersity, charge, and yield of all MCs were measured, being the methotrexate drug release for all systems determined and compared with and without functionalization with TiO₂ NPs, under dark, visible light and UV illumination in vitro. Finally, the Rh release was characterized using fluorescence microscopy. The TiO₂ NPs size is around 10?nm, as determined by X-ray diffraction experiments. The PU MCs average size is around 60?µm, its electric charge +3.11?mV and yield around 85%. As for the PMMA MCs, the average size is around 280?µm, its electric charge ?7.2?mV and yield around 25% and 30% for both MTX and Rh, respectively. In general, adding TiO₂ NPs or the encapsulated products to the MCs does not affect the size but functionalization with TiO₂ NPs lowers the electric charge. Microcapsules functionalized with TiO₂ nanoparticles and irradiated with UV light presented the highest release of MTX and Rh. All other samples showed lower drug release levels when studied under the same conditions.     

Interface fracture toughness of a multi-directional woven composite

The aim of this investigation is to measure the interface fracture toughness of a woven composite. For this purpose, double cantilever beam (DCB) specimens are tested to measure the load as the delamination grows. The specimen is composed of 15 layers of a carbon–epoxy, balanced weave with alternate layers containing fibers in the $0^{\circ }\!/90^{\circ }$ 0 ° / 90 ° directions and the $+45^{\circ }\!/\!\!-\!45^{\circ }$ + 45 ° / - 45 ° directions. A thin piece of Teflon is placed between two layers of differing directions. The specimens are analyzed by means of the finite element method and an interaction energy or $M$ M -integral to determine the stress intensity factors, interface energy release rate and phase angles. The first term of the asymptotic solution for the stress and displacement fields obtained by means of the Stroh and Lekhnitskii formalisms is used to define auxiliary solutions for the $M$ M -integral. The critical interface energy release rate is found and exhibits a slowly increasing resistance curve. Comparisons are made to a simple expression from the literature.     

Precipitation of proteins from potato juice with bentonite

The recovery of proteins from potato juice by treatment with bentonite has been investigated. All proteins can be precipitated from potato juice by acidification and addition of bentonite. The acid-coagulatable protein fraction is adsorbed less by bentonite than the acid-soluble protein fraction. Maximum adsorption of the acid-soluble fraction occurs at pH 5.0. The working conditions recommended for obtaining a protein-free potato juice are acidification to pH 4.5 and addition of bentonite to obtain a weight ratio of soluble protein: bentonite of 0.9. At the natural pH of potato juice (pH 5.8-6.0), adsorption of potato proteins on bentonite is irreversible. About 62% of the adsorbed protein can be recovered by alkali treatment at pH 13.     

On the Interplay of Parallelization, Program Performance, and Energy Consumption

This paper derives simple, yet fundamental formulas to describe the interplay between parallelism of an application, program performance, and energy consumption. Given the ratio of serial and parallel portions in an application and the number of processors, we derive optimal frequencies allocated to the serial and parallel regions in an application to either minimize the total energy consumption or minimize the energy-delay product. The impact of static power is revealed by considering the ratio between static and dynamic power and quantifying the advantages of adding to the architecture capability to turn off individual processors and save static energy. We further determine the conditions under which one can obtain both energy and speed improvement, as well as the amount of improvement. While the formulas we obtain use simplifying assumptions, they provide valuable theoretical insights into energy-aware processor resource management. Our results form a basis for several interesting research directions in the area of energy-aware multicore processor architectures.     

Degradation analysis and modeling of reinforced catalyst coated membranes operated under OCV conditions

This paper studies the degradation of Gore™ PRIMEA^® series 5510 catalyst coated membranes with an ePTFE reinforcement layer under open circuit voltage conditions at 90 °C, 75% RH, and no backpressure. Scanning electron microscopy (SEM) imaging of cross-sections revealed extensive cathode-side ionomer degradation and the presence of a platinum band. Cumulative fluoride release measurements show more fluoride exiting with the cathode effluent. Furthermore, both anode and cathode cumulative fluoride release plateau after long degradation times. Open circuit voltage was also monitored and the degradation rate was found to decrease after a long duration. It is proposed that all fluoride species are generated from the cathode-side ionomer degradation process and that the fluoride then diffuses to the anode and cathode channels. Further, once the cathode-side ionomer is consumed the degradation reaction slows as the “degradation front” passes through the inert reinforcement layer. This process was modeled using a semi-empirical transient model and compared to experimental results.     

Acute diarrhea associated with heat-stable enteroxin producing strains of Vibrio cholerae non-O1: first report from Cuba

We examined polysomnography (PSG) and body temperature in a patient with delayed sleep phase syndrome who responded to phototherapy. The patient was a 31-year-old woman whose condition had slightly improved by a vitamin B12 administration. Phototherapy was administered to her in combination with the vitamin B12 medication, and this combined treatment successfully advanced her delayed sleep phase. On PSG, the regimen showed shortened sleep latency, decreased total sleep time and stages 1 and 2 sleep, and increased slow wave sleep. Phototherapy also improved temporal distribution of delta half-waves (0.5-2.0 Hz, > or = 31 microV) as well as phase relationship between sleep and body temperature.