Continuous hydrolysis of olive oil by lipase in microporous hydrophobic membrane bioreactor

Continuous hydrolysis of olive oil byCandida cylindracea’s lipase was studied in a microporous hydrophobic membrane bioreactor. Olive oil and buffer solution, fed continuously through two compartments partitioned by membrane, caused reaction at the interface of lipase-adsorbed membrane and buffer solution. Fatty acid was obtained in a single phase without being mixed with components of other phases. At all mean residence times, countercurrent flow mode was superior to cocurrent one. The lipase was adsorbed onto the membrane, and its adsorption was suggested to be partially specific from the experiments with enzymes having various levels of purity. The percent hydrolysis depended hyperbolically on the interfacial enzyme concentration. The hydrolysis seemed to be limited by diffusion of fat or fatty acid through the micropores of the membrane at higher interfacial enzyme concentrations. The lipase was stabilized significantly by glycerol added to the buffer solution. Satisfactory performance of the membrane bioreactor was obtained in a longterm continuous operation which lasted for 24 days by feeding buffer-glycerol (18.0%) solution over the adsorbed lipase. The operational half-life of the adsorbed enzyme was 15 days at 40 C.     

Establishment time of liquid flow in a bath agitated by bottom gas injection

The establishment time of gas-liquid two-phase flows in a cylindrical bath agitated by bottom gas injection through a central single-hole bottom nozzle was investigated. Because the turbulence intensity in the bath was comparable to or larger than the unity, the conventional definition of the flow establishment time based on the history of mean velocity was not suitable for the present case. In fact, it was difficult to determine the flow establishment time based on the well-known 90 or 99 pct criterion for the mean velocity. Accordingly, two methods of determining the flow establishment time by focusing on the turbulence components instead of the mean velocity components were proposed. Velocity measurements were made with a two-channel laser Doppler velocimeter. The flow establishment time was correlated as a function of gas flow rate. Close agreement was obtained by the two methods.     

Changes in Aging Behavior and Defect Structure of Yttria-Fully-Stabilized ZrO2 with Sc2O3 Doping

Methods of suppressing decreased conductivity in 8 mol% Y₂O₃-stabilized–92 mol% ZrO₂ (8YSZ) with aging were investigated. Different amounts of Sc₂O₃ were doped into 8YSZ. The electrochemical properties of Sc₂O₃-doped 8YSZ were measured, and the microstructural and local structural changes were characterized. The present results indicate that an appropriate amount of Sc₂O₃ doping, 3 or 4 mol%, effectively suppresses decreased conductivity with aging in 8YSZ.     

Dielectric properties above the glass transition for a series of epoxide prepolymers

Dielectric properties above the glass transition have been investigated for a series of bisphenol-A type epoxide prepolymers (388 ≤ M?_w ≤ 2640). Dielectric measurements were performed over a frequency range of 50 Hz–1 MHz using a vertical parallel plate cell which was constructed in the laboratory. The dielectric α-relaxation for each prepolymer fits the empirical model of the Havriliak–Negami equation. The temperature dependence of the dielectric relaxation time τ is described by the Williams–Landel–Ferry (WLF) equation as well as that of the direct current conductivity σ, which can be measured using the same cell. The relationship between τ and σ, σ^· τ^m = const, is derived from experimental results. The exponent m, which depends on the molecular weight of the prepolymer, is considered to correspond to the ratio of the segmental mobility to ionic mobility. The dielectric loss ε″ can be used as an indicator of the direct current conduction in the temperatures where the ionic component in ε″ becomes much larger than the dipole one.     

Determination of glass transition temperature from dielectric analysis for a series of epoxide oligomers

Dielectric properties have been investigated for a bisphenol-A type epoxide oligomer, whose weight average molecular weight (M?_w) was 9454. The dielectric α-relaxation of the oligomer was found to be governed by the Havriliak–Negami equation as well as the same series of oligomers with smaller M?_ws (388≦M?_w ≦ 3903). The dielectric relaxation times (τ)s for the oligomers with different M?_ws (1396 ≦ M?_w ≦ 9454) can be expressed by the Williams–Landel–Ferry (WLF) equation as a function of the glass transition temperature (T_g) at fixed temperatures from 70 to 100°C. The finding indicates that the T_g of the epoxide oligomer is calculated from the τ through the WLF equation, providing the relation between T_g and τ. The same type of WLF equation was also successfully applied to describe the T_g, dependence of the practical dielectric relaxation time (τ_p), which was obtained from the peak of the dielectric loss vs. frequency curve. The τ_p can be calculated more easily than the τ, based on the Havriliak–Negami equation, not only in the measurement of epoxide oligomer, but also in that of the reactive epoxy resin systems during curing. The T_g of an epoxy–aromatic amine system, which was determined from the τ_p nondestructively detected in the dielectric cure monitoring, was consistent with the T_g experimentally measured by differential scanning calorimetry (DSC).     

Molecular motions of non-crystalline poly(aryl ether-ether-ketone) PEEK and influence of elecron beam irradiation

The dynamic mechanical relaxation of non-crystalline poly(aryl ether-ether-ketone) PEEK and the one irradiated with electron beam were studied. The three distinct γ, β, α′ relaxation maxima were observed in unirradiated PEEK from low to high temperature. It was revealed from the study on the irradiation effects that three different molecular processes are overlapped in γ relaxation peak, i.e., molecular motion of water bound to main chain (peak temperature; at ?100°C), local motion of main chain (at ?80°C), and local mode of the aligned and/or oriented moiety (at ?40°C). The β relaxation connected with the glass transition occurred at 150°C and it shifted to higher temperature by irradiation. The α′ relaxation which can be attributed to rearrangement of molecular chain due to crystallization was observed in unirradiated PEEK ～ 180°C and its magnitude decreased with the increase in irradiation dose. This effect indicates the formation of structures inhibiting crystallization such as crosslinking and/or short branching during irradiation. A new relaxation, β′, appeared in the temperature range of 40° to 100°C by irradiation and its magnitude increased with dose. This relaxation was attributed to rearrangement of molecular chain from loosened packing around chain ends, which were introduced into the non-crystalline region by chain scission under irradiation, to more rigid molecular packing, From these observations, we proposed that deterioration in mechanical properties of non-crystalline PEEK by high energy electron beam was brought about not only by chain scission but structural changes such as crosslinking and/or branching in the main chain.     

2-Hydroxyhexadecanoic and 8,9,13-trihydroxydocosanoic acid accumulation by yeasts treated with fumonisin B1

Fumonisin B₁ is a sphingolipid-like compound that enhances the accumulation of yeast sphingolipids and 2-hydroxy fatty acids. These lipids occur both as freely extractable and cell bound components in yeast fermentations. Both free and bound 2-hydroxy fatty acids produced byPichia sydowiorum NRRL Y-7130 were increased when fumonisin B₁ (50 mg/L) was added to the usual growth medium containing yeast extract/malt extract/peptone/glucose. Fumonisin-treated cultures contained 38 mg/L more 2-hydroxyhexadecanoic and 15 mg/L more 2-hydroxyoctadecanoic acids than did untreated cultures. By contrast, fumonisin inhibited the accumulation of free 8,9,13-trihydroxydocosanoic acid inRhodotorula sp. YB-2501 cultures, leading to 240 mg/L lower trihydroxy acid production than by untreated cultures.     

Adsorption of synthetic polyelectrolytes on colloidal spheres

Summary The adsorption of synthetic polyelectrolytes on the surfaces of monodisperse polystyrene spheres and colloidal silica spheres is studied by electrophoretic mobility measurements. Electrolytes used are NaCl, CaCl₂, LaCl₃, Na₂SO₄, sodium poly(ethylenesulfonate) (NaPES), sodium poly(styrenesulfonate) (NaPSS), polybrene^? (PB), poly-4-vinyl-N-ethylpyridinium bromide (C2PVP), poly-4-vinyl-N-benzylpyridinium chloride (BzPVP), and copolymer of 4-vinyl-N-benzylpyridinium chloride (95%) and 4-vinyl-N-n-hexadecylpyridinium bromide (5%) (C16BzPVP). Electrophoretic velocity (u) and the effective charge number (α) of a colloidal sphere increase in the presence of PB, C2PVP, BzPVP, and C16BzPVP, and turn to the positive from the negative values in their absence. Addition of NaPES and NaPSS further decreases u and α values. Adsorption of the polymers on the colloidal spheres are explained by the hydrophobic and/or dipoledipole interactions in addition to the electrostatic forces. Weak adsorption of simple electrolytes on the colloidal spheres is deduced from the electrophoretic measurements.     

Topology optimization for fluid–thermal interaction problems under constant input power

This paper deals with density-based topology optimization considering fluid and thermal interactions, in which the Navier–Stokes and heat transport equations are coupled. We particularly focus on designing heat exchangers. In the engineering context, heat exchangers are designed while considering a certain amount of input power. Therefore it is important to maximize the performance of a heat exchanger under a constant input power. In this paper we propose a way to control the input power by introducing an extra integral equation. To be more precise, in the fluid analysis, the inlet pressure is determined by solving the extra integral equation together with the Navier–Stokes equation. By doing this we can keep the inlet power constant even when the flow channels are changed in the optimization process. Consequently, the system of equations of the fluid field takes an integrodifferential form. On the other hand, in the heat transport analysis, a single governing equation is defined for simultaneously modeling both the solid and fluid parts. The design variable is a fluid fraction whose distribution represents the topology of the solid and fluid domains. When designing heat exchangers, two different heat conditions are considered in the formulation of the optimization problems, namely temperature-dependent and temperature-independent heat sources. Through the numerical examples for designing flow channels in a heat exchanger, it is shown that distinct topologies can be obtained according to the input power and the heat source conditions.     

High‐pixel‐rate grating‐light‐valve laser projector

Abstract— A high‐pixel‐rate, high‐contrast (30,000:1) wide‐color‐gamut grating‐light‐valve laser projector is reported. A new optical engine enabling high‐frame‐rate (240 Hz) scan projection is employed. Panoramic wide‐angle‐scan projection with a 64:9 aspect ratio was also developed. Speckle noise is eliminated using a simple but highly efficient technique. The optical throughput efficiency of the grating‐light‐valve laser projector is reviewed.