A bioreactor with an internal contactor for primary recovery of bovine serum albumin from yeast suspension

In this paper the internal contactor is a newly developed device for the primary recovery of protein from crude feedstock. Ion exchanges (DEAE-Streamline) are confined inside the internal contactor in a stirred tank. Interactions between the ion exchange in the internal contactor and protein (BSA) in yeast suspension have been studied. For better performance, two strategies are considered: to determine the ion conductivity of a simulated yeast suspension, and to select the optimum process time for adsorption. In this system, advantages of both batch adsorption and expanded bed adsorption were obtained. Furthermore, in denser cell concentration (50 g/L) where EBA cannot be operated, the primary recovery was carried out in 1–2 hr. The efficiency of yield is higher than 80% in this condition.     

Oxidation and reduction effects of propane–oxygen on Pd–chlorine/alumina catalysts

Pd–chloride precursor salt was used to prepare Pd/Al₂O₃ catalysts. TPSR measurements showed three distinct reactions for the oxidation of propane on palladium surface under excess of hydrocarbon: complete oxidation, steam reforming and propane hydrogenolysis. Propane oxidation on palladium catalysts was related to the Pd²⁺ sites observed on Pd/Al₂O₃ through infrared of adsorbed carbon monoxide. In fresh catalysts reduced by H₂, the IR spectra showed the linear and bridge adsorbed CO species on the Pd⁰ surface. After propane reaction, a new band at 2130 cm^-1 related to CO adsorption on Pd²⁺ species was noted. Carbon monoxide species adsorbed on Pd⁰ were also observed in all samples after reaction. Our results suggest surface ratios of Pd⁰/PdO during the propane oxidation. On the other hand, time on stream conversions of the complete oxidation of propane were affected by either the water generated during the reaction or added as a reactant at 10 vol%. The water generated by the reaction helped to eliminate chlorine residues in the form of oxychloride species leading to an increasing of the activity. However, the presence of water into the reaction mixture caused a strong decreasing of the activity. The inhibition mechanism of propane oxidation in the presence of water consisted in the dissociative adsorption of water on palladium sites with the possible formation of palladium hydroxide (Pd–OH) at the surface, diminishing the number of active surface sites. Dynamic fluctuations into the reaction conditions supported the idea that a pseudo‐equilibrium adsorption–desorption of water was reached. After water removal or increasing in the reaction temperature the equilibrium was shifted to the direction of OH–Pd decomposition. This behavior suggests that the inhibitory effect of water is a reversible phenomenon, being a function of the amount of water and the reaction temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

SET/CMOS hybrid process and multiband filtering circuits

We have developed an integration technology for the single electron transistor (SET)/CMOS hybrid systems. SET and CMOS transistors can be optimized without any possible degradation due to mixing dissimilar devices by adopting just one extra mask step for the separate gate oxidation (SGOX). We have confirmed that discrete devices show ideal characteristics required for the SET/CMOS hybrid systems. An SET shows obvious Coulomb oscillations with a 200-mV period and CMOS transistors show high voltage gain. Based on the hybrid process, new hybrid circuits, called periodic multiband filters, are proposed and successfully implemented. The new filter is designed to perform a filtering operation according to the periodic multiple blocking bands of which a period is originated from the SET. Such a novel function was implemented efficiently with a few transistors by making full use of the periodic nature of SET characteristics.     

Damping estimation using free decays and ambient vibration tests

This paper studies the quality of modal damping ratios estimates based on ambient and free vibration tests using both numerical simulations and data collected on large Civil Engineering structures where both tests were performed. The simulated data allowed to study the influence of factors like non-proportional damping or proximity of natural frequencies on the quality of the estimates and also to illustrate the influence of the identification algorithms parameters on the accuracy of the results. The analysis of data collected on a cable-stayed bridge, on the suspended roof of a stadium and on a footbridge permitted to compare the results of both testing approaches in real applications where some factors that cannot be realistically included in the numerical simulations can play an important role. The processing of ambient vibration responses is performed with two output-only identification approaches: frequency domain decomposition and stochastic subspace identification methods. The numerically simulated and the measured free decays were analyzed with a simple method based on filters and fitting of exponential decays and also with the use of subspace models.     

Gas-phase Photocatalytic Oxidation of Acrylonitrile on Sulphated TiO<Subscript>2</Subscript>: Continuous Flow and Transient Study

Abstract  

The gaseous products of photocatalytic oxidation (PCO) of acrylonitrile on sulphated P25 in concentrations from 10 to 100 ppm at 60 to 130 °C were CO₂, HCN and HNCO. This photocatalyst showed disproportionally improved performance at higher temperature and longer retention times. The temperature-programmed oxidation (TPO) after PCO disclosed possible reaction routes.     

Synthesis and characterization of mesoporous TiO2 nanostructured films prepared by a modified sol-gel method for application in dye solar cells

Anatase TiO₂ colloidal dispersions were obtained by hydrothermal synthesis at 200 °C from titanium isopropoxide gels modified with acetic acid in the presence of a non-ionic surfactant. Absolute ethanol, anhydrous terpineol and ethyl cellulose were added to this anatase dispersion resulting in a 23 wt% TiO₂ paste. Mesoporous films for application as working electrodes in dye-sensitized solar cells were prepared by the screen-printing method, yielding reproducible films with thicknesses about 10 μm and desired porosity levels in a single printing operation. An average energy conversion efficiency of 5.2%, and a fill factor of 0.66 were achieved with anatase particle sizes ranging between 15 and 20 nm. The reproducibility of the results was confirmed by electrochemical impedance spectroscopy analysis.     

Analysis of the HVAC system’s sound quality using the design of experiments

Human hearing is very sensitive to sound, so a subjective index of sound quality is required. Each situation of sound evaluation is composed of Sound Quality (SQ) metrics. When substituting the level of one frequency band, we could not see the tendency of substitution at the whole frequency band during SQ evaluation. In this study, the Design of Experiments (DOE) is used to analyze noise from an automotive Heating, Ventilating, and Air Conditioning (HVAC) system. The frequency domain is divided into 12 equal parts, and each level of the domain is given an increase or decrease due to the change in frequency band based on the “loud” and “sharp” sound of the SQ analyzed. By using DOE, the number of tests is effectively reduced by the number of experiments, and the main result is a solution at each band. SQ in terms of the “loud” and “sharp” sound at each band, the change in band (increase or decrease in sound pressure) or no change in band will have the most effect on the identifiable characteristics of SQ. This will enable us to select the objective frequency band. Through the results obtained, the physical level changes in arbitrary frequency domain sensitivity can be determined.     

Unconstrained springback behavior of Al-Mg-Si sheets for different sitting times

In this work, the springback behavior of the commercial 6022 aluminum alloy in temper aging (T4) is investigated taking into account that the sheets, prior to deformation process, are initially pre-strained and then submitted to various sitting times at room temperature. The unconstrained cylindrical bending test based on the NUMISHEET2002 proceedings as presented by Yoon et al. [Yoon JW, Pourboghrat F, Chung K, Yang DY. Springback prediction for sheet metal forming process using a 3D hybrid membrane/shell method. International Journal of Mechanical Sciences 2002;44:2133-53] is selected as validation benchmark. For finite element simulations, the geometry is modeled by solid-shell finite elements using the formulation of Alves de Sousa et al. [Alves de Sousa RJ, Yoon JW, Cardoso RPR, Fontes Valente RA, Grácio JJ. On the use of a reduced enhanced solid-shell (RESS) element for sheet forming simulations. International Journal of Plasticity 2007;23:490-515; Alves de Sousa RJ, Cardoso RPR, Fontes Valente RA, Yoon J-W, Natal Jorge RM, Grácio JJ. A new one-point quadrature enhanced assumed strain (EAS) solid-shell element with multiple integration points along thickness: Part I—Geometrically linear applications. International Journal for Numerical Methods in Engineering 2005;62:952-77; Alves de Sousa RJ, Cardoso RPR, Fontes Valente RA, Yoon JW, Grácio JJ, Natal Jorge RM. A new one-point quadrature enhanced assumed strain (EAS) solid-shell element with multiple integration points along thickness: Part II—Nonlinear applications. International Journal for Numerical Methods in Engineering 2006;67:160-88]. The material behavior is described based on the work of Correia et al. [Correia JPM, Simões F, Gracio JJ, Barlat F, Ahzi S. A simple hardening rule accounting for time-dependent behavior in Al-Mg-Si alloys. Materials Science Engineering A 2007;456:170-9]. The results of conducted experiments and numerical simulations are compared. It can be concluded about the good agreement between experiments and simulations attesting the effectiveness of the material model utilized to describe the time-dependent hardening behavior.     

Monolithically integrated grating cavity tunable lasers

A novel grating cavity tunable laser is proposed and experimentally demonstrated. It is realized by monolithically integrating a semiconductor optical amplifier, a dispersive element, a phase-control section, and an etched diffraction grating in a single chip. Tuning operation is based on electrically controlled beam deflection provided by dispersive element and phase matching by phase-control section. With the electrical control, the wavelength tuning of 8.5 nm with a sidemode suppression ratio of about 35 dB has been successfully achieved.