Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides

To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.     

Measurement and numerical simulation of three‐dimensional fiber orientation states in injection‐molded short‐fiber‐reinforced plastics

To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003     

A study of CaCO3 fouling with a microscopic imaging technique

The present study introduces a new experimental method to visualize the fouling process of CaCO₃. A mini-channel heat exchanger system with a microscopic imaging technique was developed for real-time visualization of the fouling process. The present study discussed how scale started initially, how scale formed thick layers, and how a small crystal grew into a large one, touching the adjacent one. Detail microscopic images of scale crystals and corresponding fouling resistances were obtained over the entire fouling process. The microscopic observation indicated that the fouling process could be divided into three stages: an induction period, a period of uniform generation of nuclei, and a period of uniform growth of scale. Sudden appearance of numerous small nuclei indicated the end of the induction period, a key event before the rapid increase in the fouling resistance. The present experimental method using microscopic images of the wet fouling process provides a valuable insight on the fouling mechanism.     

A simple mathematical analysis on the effect of sand in Cr(VI) reduction using zero valent iron

A simple mathematical model was proposed to analyze the enhancement of Cr(VI) reduction when sand materials are added to the zero valent iron (ZVI). Natural decay of Cr(VI) in a control experiment was analyzed by using a zero-order decay reaction. Adsorption kinetics of Cr(VI) to sand was modeled as a first-order reversible process, and the reduction rate by ZVI was treated as a first-order reaction. Natural decay of Cr(VI) was also included in other experiments, i.e., the adsorption to sand, the reduction by ZVI, and both adsorption and reduction when sand and ZVI are present together. The model parameters were estimated by fitting the solution of each model to the corresponding experimental data. To observe the effect of sand addition to ZVI, both adsorption and reduction rate models were considered simultaneously including the natural decay. The solution of the combined model was fitted to the experimental data to determine the first-order adsorption and reduction rate constants when sand as well as ZVI is present. The first-order reduction rate constant in the presence of sand was about 35 times higher than that with ZVI only.     

Onset of buoyancy-driven convection in melting from below

When a horizontal homogeneous solid is melted from below, convection can be induced in a thermally unstable melt layer. In this study the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed disturbance equations. The critical Rayleigh numbers based on the melt-layer thickness are found numerically for various conditions. For small superheats, the present predictions approach the well known results of classical Rayleigh-Bénard problems, that is, critical Rayleigh numbers are located between 1,296 and 1,708, regardless of the Prandtl number. However, for high superheats the critical Rayleigh number increases with an increase in phase change rate but with decrease in Prandtl number.     

Reduction of optical beat interference using gain-saturated RSOA in upstream WDM/SCM optical links

A new scheme for reducing optical beat interference (OBI) noise in optical network units is proposed for subcarrier multiplexing-based access network applications. The optical spectrum of the transmit lasers is broadened by using a radio frequency (RF) clipping tone with a modulation depth greater than one. This reduces the impact of the OBI noise. The distortions caused by an RF clipping tone are also suppressed by introducing a gain-saturated reflective optical amplifier, which shows the characteristics of high-pass filter. The proposed scheme has been verified by measuring the error vector magnitude of 16QAM signal with 20 Mbps. Error-free transmission has been achieved even when the light of OBI-noise-causing lasers is stronger than that of the signal laser by 7 dB     

Isothermal interphase diffusion with consecutive reactions

For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction rate at steady state. From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients. Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the concentrations to the effectiveness factors were examined with graphical presentations. Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds number and diffusivity to the extent of the mass-transfer resistance were presented.     

New queueing strategies employing service interval-based priority for real-time communications in atm networks

In this paper, we propose queueing strategies employing the service interval-based priority (sip) which can provide delay-bounded, and loss-free services, while maximizing bandwidth utilization in the atm network. We also describe a variation of the sip, the residual service interval-based priority (rsip) which can achieve almost full utilization by assigning priorities dynamically on the basis of the residual service interval. We store the realtime cells belonging to different connections in logically separated queues, and for each queue, we set a parameter called service interval, during which only one cell is allowed to be transmitted. The sip server takes and transmits the head-of-line (hol) cell of the queue which has the smallest service interval, while the rsip server selects the queue with the smallest residual service interval. When there is no eligible real-time cell, it transmits non-real-time cell, thus enabling a maximized bandwidth utilization. Employing the above queueing strategies, we analyze the delay characteristics deterministically with the leaky bucket bounded input traffic and then dimension the optimal service interval. In dimensioning the service interval and buffer space of each real-time service queue, we consider burstiness of traffic in conjunction with delay constraints, so that bandwidth utilization can get maximized. In addition, we consider the issues of protection from malicious users, average bandwidth utilization, and coupling between the delay bound and the bandwidth allocation granularity.     

Analysis of culture fluorescence by a fiber-optic sensor inNicotiana tabacum plant cell culture

The on-line sensing of viable cell weight in plant cell culture process is applied to analysis and control of process. The fiber-optic fluorescence sensor was constructed to measure the NADH-dependent fluorescence inNicotiana tabacum plant cell culture and the analysis of fluorescence signal was done to be correlated with the viable cell weight. The structured kinetic model for cell growth was proposed to estimate the theoretical viable cell weight. The dimensional analysis was proposed for the interpretation of fluorescence signal, in which the path length, the inner filter effect and the hydrodynamic conditions were considered as the key factors on fluorescence signal. The dimensional analysis and empirical correlation of fluorescence signal to viable cell weight was applied to the interpretation of the detected fluorescence signal during cultivation. The proposed interpretation of fluorescence signal using dimensional analysis was well correlated with the viable cell weight estimated by the structured kinetic model as well as by empirical correlation.     

A QoS management framework for distributed multimedia systems

This paper proposes a high‐performance connection management architecture to design a common QoS framework applied to an ATM network based on the Open Distributed Processing (ODP) concept. We design the QoS framework in accordance from the RM‐ODP information and computational viewpoints. Copyright © 2003 John Wiley & Sons, Ltd.