Effect of TiO2 thin film thickness and specific surface area by low-pressure metal–organic chemical vapor deposition on photocatalytic activities

TiO₂ photocatalyst films having an anatase crystal structure with different thickness were prepared by the low-pressure metal–organic chemical vapor deposition (LPMOCVD) to examine the effect of growth conditions on photocatalytic activity. Film thickness was linearly proportional to the deposition time. Structure of the film was strongly dependent on the deposition time. In early stage of deposition, fine particles deposit on the substrate. As increasing the deposition time, crystal orientation is gradually selected following the Kolmogorov model and c-axis oriented columnar crystals become dominant. The photocatalytic activity strongly depends on the film deposition time (or film thickness) in nonlinear way. The optimum thickness of TiO₂ catalyst film grown by LPMOCVD may locate between 3 and 5 μm.     

Efective Object Identification and Association by Varying Coverage Through RFID Power Control简

This paper presents an effective power scheduling strategy for energy efficient multiple objects identification and association. The proposed method can be utilized in many heterogeneous surveillance systems with visual sensors and RFID （radio-frequency identification） readers where energy efficiency as well as association rate are critical Multiple objects positions and trajectory estimates are used to decide the power level of RFID readers. Several key parameters including the time windows and the distance separations are defined in the method in order to minimize the effects of RFID coverage uncertainty. The power cost model is defined and incorporated into the method to minimize energy consumption and to maximize association performance. The proposed method computes the power cost using the range of the outermost position for possible single association and group associations at every sampling time. An RFID reader is activated with the proper coverage range when the power cost for the current time is lower than the power cost for the next time sample. The simplicity of the power cost model relieves the problematic combinatorial comparisons in multiple object cases. The performance comparison simulation with the minimum and maximum energy consumption shows that the proposed method achieves fast single associations with less energy consumption. Finally, the realistic comparison simulation with the fixed range RFID readers demonstrates that the proposed method outperforms the fixed ranges in terms of single association rate and energy consumption.     

Synthesis and biological activity of phthalimide‐based polymers containing 5‐fluorouracil

The attachment of anticancer agents to polymers is a promising approach towards reducing the toxic side‐effects and retaining the potent antitumour activity of these agents. A new tetrahydrophthalimido monomer containing 5‐fluorouracil (ETPFU) and its homopolymer and copolymers with acrylic acid (AA) and with vinyl acetate (VAc) have been synthesized and spectroscopically characterized. The ETPFU contents in poly(ETPFU‐co‐AA) and poly(ETPFU‐co‐VAc) obtained by elemental analysis were 21 mol% and 20 mol%, respectively. The average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n = 8900 g mol^?1, M_w = 13 300 g mol^?1, M_w/M_n = 1.5 for poly(ETPFU); M_n = 13 500 g mol^?1, M_w = 16 600 g mol^?1, M_w/M_n = 1.2 for poly(ETPFU‐co‐AA); M_n = 8300 g mol^?1, M_w = 11 600 g mol^?1, M_w/M_n = 1.4 poly(ETPFU‐co‐VAc). The in vitro cytotoxicity of the compounds against FM3A and U937 cancer cell lines increased in the following order: ETPFU > 5‐FU > poly(ETPFU) > poly(ETPFU‐co‐AA) > poly(ETPFU‐co‐VAc). The in vivo antitumour activities of all the polymers in Balb/C mice bearing the sarcoma 180 tumour cell line were greater than those of 5‐FU and monomer at the highest dose (800 mg kg^?1). © 2002 Society of Chemical Industry     

Catalytic reduction of no over perovskite-type catalysts

In the present work, we have investigated the reduction of NO by propane over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxides. In addition, the reaction conditions, such as temperature, O₂ concentration, and space velocity have been varied to understand their effects on the catalytic performance. In the LaCoO₃ type catalyst, the partial substitution of Ba and Sr into A site enhanced the catalytic activity in the reduction of NO. For the La_0.6Ba (Sr)_o.4 Co_1−x Fe_xO₃ (x=0-1.0) catalyst, the partial substitution of Fe into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. The surface area and catalytic activity of perovskite catalysts prepared by malic acid method showed higher values than those of solid reaction method. The conversion of NO increased with increasing O₂ concentration and contact time. The introduction of water into reactant feed decreased the catalytic activity but the deactivation was shown to be reversible over La_0.6Ba_0.4Co_1−x ,Fe_xO₃ catalyst.     

Improved mechanical properties of shape‐memory polyurethane block copolymers through the control of the soft‐segment arrangement

High‐performance shape‐memory polyurethane block copolymers, prepared with two types of poly(tetramethylene glycol) (PTMG) used as soft segments, were investigated for their mechanical properties. Copolymers with a random or block soft‐segment arrangement had higher stresses at break and elongations at break than those with only one kind of PTMG. Random copolymers with fewer interchain interactions showed higher elongation than block copolymers. All the copolymers had shape‐recovery ratios higher than 80%. In dynamic mechanical testing, the glass‐transition behavior clearly depended on the soft‐segment arrangement: random copolymers had only one glass‐transition peak, whereas block copolymers showed two separate glass‐transition peaks. Overall, the control of the soft‐segment arrangement plays a vital role in the development of high‐performance shape‐memory polyurethane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2410–2415, 2004     

Characteristics of membrane humidifiers for polymer electrolyte membrane fuel cells

Water management plays an important role in obtaining high performance from a polymer electrolyte membrane fuel cell (PEMFC). To reduce the volume and energy consumption of widely-used bubble humidifiers, membrane humidifiers were fabricated by using an ultrafiltration (UF) membrane and Nafion membranes. The performance of the membrane humidifiers was examined as a function of gas flow rate and operating temperature. A single cell was operated using the UF membrane humidifiers exhibiting almost the same performance with that employing bubble humidifiers.     

Effects of estrogen-induced hyperlipidemia on the erythrocyte membrane in chicks

The effects of estrogen-induced hyperlipidemia on plasma lipid peroxidation, fatty acid composition and osmotic fragility of erythrocytes in chickens were studied. Young male chickens implanted with estrogen for three wk developed a marked hyperlipidemia. Plasma levels of triglyceride, cholesterol and phospholipid were elevated 68-, four- and 24-fold, respectively, over controls. There was also a two-fold increase in plasma lipid peroxidation measured by the thiobarbituric acid test. Vitamin E supplement (1,000 IU/kg diet) reduced the plasma lipid peroxidation to the control level, but had no effect on the plasma lipid content. Estrogen-induced hyperlipidemia resulted in changes in the fatty acid composition of membrane lipids of erythrocytes. The major changes were an increase in oleic acid from 10.0% to 14.2% and a decrease in linoleic acid from 31.3% to 26.0%. The erytrocytes with an altered membrane fatty acid composition were found to have an increased osmotic fragility. It was apparent that there was a direct correlation between the oleic acid content and the osmotic fragility of erythrocytes.     

Structure Evolution of Highly Crystallized BaWO4 Film Prepared by an Electrochemical Method at Room Temperature

Highly crystallized BaWO₄ films have been prepared on a tungsten substrate in an alkaline solution containing barium ions by an electrochemical method with a constant direct current density of 1 mA/cm² at room temperature (25°C). The average grain size was about 13 μm, and the thickness about 9 μm after a treatment time of 35 min. The dependence of cell voltage on deposition time was divided into three steps: conduction, anodic oxidation, and breakdown steps. The BaWO₄ film formed during the first step. Electrochemical dissolution of metal tungsten occurred with an accompanying positive change of overpotential in the first step. The crystallization of BaWO4 was characterized by three-dimensional nucleation. In the second step, an amorphous tungsten oxide film formed, thereby increasing the potential. An electrical breakdown occurred in the third step, and the breakdown voltage (about 90 V) was practically the same as those of anodic tungsten oxide films.     

Microwave Dielectric Properties of (1−x)(Na1/2Nd1/2)TiO3−xLa(Mg1/2Ti1/2)O3 via Ordering and Far IR Reflectivity Spectra

Microwave dielectric properties of (1− x )(Na_1/2Nd_1/2)TiO₃(NNT)− x La(Mg_1/2Ti_1/2)O₃(LMT) system have been investigated with focus on structural ordering and far IR reflectivity spectra. A single perovskite phase was found to exist with various superlattice reflections over the entire compositional range. 1:1 ordering observed in the (111) reflection of X-ray diffraction patterns was found to progress significantly in the specimens above x =0.8. The ordering characteristics that presumably related to B-site Mg/Ti ordering were assumed to affect favorably the quality factor at microwave frequencies. The increase of the quality factor also could be explained in terms of the decrease of lattice anharmonicity with LMT by analysis of far IR reflectivity spectra. As expected from the values of pure NNT and LMT, the dielectric constant and the temperature coefficient of frequency tended to gradually decrease with increasing LMT content.     

Electrophoretic deposition of carbon nanotubes

Electrophoretic deposition (EPD) has been gaining increasing interest as an economical and versatile processing technique for the production of novel coatings or films of carbon nanotubes (CNTs) on conductive substrates. The purpose of the paper is to present an up-to-date comprehensive overview of current research progress in the field of EPD of CNTs. The paper specifically reviews the preparation and characterisation of stable CNT suspensions, and the mechanism of the EPD process; it includes discussion of pure CNT coatings and CNT/nanoparticle composite films. A complete discussion of the EPD parameters is presented, including electrode materials, deposition time, electrode separation, deposition voltage and resultant electric field. The paper highlights potential applications of the resulting CNT and CNT/composite structures, in areas such as field emission devices, fuel cells, and supercapacitors.