Photoconductivity of n-type semiconductor nanoparticle-doped poly(N-vinylcarbazole) films

TiO₂, CdS and ZnS nanoparticles that disperse stably in organic solvents are synthesized. Poly(N-vinylcarbazole) films doped with the n-type semiconductor nanoparticles are prepared with a cast method. The films exhibit a transient photocurrent when irradiated by a light pulse and act such as a diode when AC voltage is applied under continuous illumination. The transient photocurrent response and diode-like properties are significantly different depending on the kind of the nanoparticles and their amounts. The films doped with TiO₂ and CdS nanoparticles increase the transient photocurrent at lower doped amounts, which is remarkable for TiO₂-doped films. Time of flight analysis of the transient photocurrent shows that mobility of hole in PVK increases with increase in the amount of CdS and TiO₂. From the studies on the diode-like properties, the current increase at lower dopant concentration is concluded to be due to increase in the amount of holes by an electron transfer from PVK to the photo-excited nanoparticles. At higher doping with CdS nanoparticles, main charge carrier of the films is found to change from holes to electrons.     

Microscopic phase-dependent residual stresses in the machined surface layer of two-phase alloy

Residual stresses in the machined surface layer, which affect fatigue crack nucleation and stress corrosion cracking especially in aerospace engines and gas turbines for power generation, depend on microstructures in case of machining a multiple-phase alloy. Hence, the microscopic phase-dependent residual stresses should be known when a machined part is used under critical stress conditions and circumstances. In the present paper, finite element modeling of machining two-phase alloys has been developed for obtaining the residual stresses in the machined surface layer. Iron and steels, which consist of different volume fractions of ferrite and eutectoid pearlite, were selected as work materials to be machined. First, it was confirmed that the calculated results agree well in chip formation and cutting forces with experimental ones. Then, residual stresses in the machined surface layer were obtained for different carbon contents and regular/random arrangements of microstructure. As a result, it is found that the microstructure of the workpiece has a great influence on the residual stress distribution on the machined surface and that tensile surface residual stress on pearlite is much larger than that on ferrite. Finite element machining of the work material with stripe arrangement of ferrite and pearlite revealed that the peak of residual stress would be reduced by decreasing the width of stripes of ferrite and pearlite.     

Production of L-sorbitol from L-fructose by Aureobasidium pullulans LP23 isolated from soy sauce mash

A strain LP23 that can convert L-fructose to L-sorbitol was isolated from soy sauce mash and identified as Aureobasidium pullulans. The cells grown on L-arabinose were found to have relatively high L-fructose to L-sorbitol conversion potential. Addition of erythritol to the reaction mixture considerably accelerated the conversion rate of L-fructose to L-sorbitol. During the conversion reaction, erythritol was added to the reaction mixture at 8-h intervals to maintain the concentration of erythritol at 1.0%. The final conversion ratios were 82.8%, 95.3%, 92.4%, and 42.6% using washed cells when the concentrations of L-fructose were 1.0%, 2.0%, 5.0% and 10.0%, respectively. The product from L-fructose was identified as L-sorbitol by HPLC analysis, infrared spectroscopy, optical rotation and melting point measurements.     

Effect of thrombolytic therapy on pulmonary-capillary blood volume in patients with pulmonary embolism

To compare the effects of heparin thrombolytic agents in pulmonary thromboembolic disease, we randomly assigned 40 patients with pulmonary emboli but without other clinical cardiopulmonary disease either to heparin followed by oral anticoagulants (21 patients) or to urokinse or streptokinase followed by heparin and then by oral anticoagulants (19 patients). The effects on pulmonary-capillary blood volume and diffusing capacity were compared at two weeks and at one year. The pulmonary-capillary blood volume (in milliliters per square meter of body-surface area) was abnormally low (30 +/- 2.4) [+/- S.E.]; normal, 47 +/- 1.5) in the heparin-treated group at two weeks and remained unchanged at one year. In contrast, it was normal (45 +/- 2.5) in the group receiving thrombolytic agents, both at two weeks and at one year (P < 0.001). The pulmonary diffusing capacity was reduced to 69% of the predicted value in the heparin group at two weeks and 72% at one year, whereas it was 85% of the predicted value in the thrombolytic group at two weeks and 93% at one year (P < 0.001). These results indicate that thrombolytic agents allow more complete resolution of thromboemboli than do heparin and anticoagulants and that they improve capillary perfusion and diffusion.     

Photocatalytic decomposition of 2-propanol in air by mechanical mixtures of TiO2 crystalline particles and silicalite adsorbent: The complete conversion of organic molecules strongly adsorbed within zeolitic channels

Fundamental photocatalytic behaviors were investigated for mechanical mixtures of TiO₂ crystalline particles (P25) and MFI type zeolite (silicalite) in the decomposition reaction of 2-propanol vapor in air for the first time. Mechanical mixing enables reliable comparisons to be made between photocatalysts because the contents of TiO₂ and the adsorbent can be widely varied (51 times in this study) while keeping the particle size and crystallinity of TiO₂ unchanged. That is, the use of mechanical mixture highlights the behavior of molecules adsorbed in the microporous crystals, keeping the TiO₂ unchanged. In the case of the mixed photocatalysts, the initial 2-propanol concentration in the gas phase was significantly reduced because of adsorption into the zeolite. After photo-irradiation started, 2-propanol was decomposed to CO₂ with no (or trace amount of) acetone detected in the gas phase. The analysis of final amount of CO₂ formed by the decomposition demonstrated that just by the mechanical mixing of TiO₂ and zeolite, the TiO₂ photocatalyst decomposed completely the reactant and intermediate molecules strongly adsorbed into the zeolite. On the other hand, in reference experiments in which TiO₂ and zeolite were not mixed and were separately placed in a photoreactor, the organic compounds strongly adsorbed in the zeolite could not be decomposed to CO₂ by the photocatalyst. It is notable that the CO₂ formation rates for the mixed photocatalysts were mostly constant for those comprising 40 wt% or larger amounts of zeolite, while being slower than for pure TiO₂. The rate-determining step was discussed based on these data. The present study showed that the mixed photocatalyst could remove organic vapors by adsorption in the dark and decompose completely to CO₂ at moderate reaction rates under photo-irradiation with minimized evolution of intermediate molecules into the gas phase.     

Effects of Light‐Induced Regularity on the Physical Properties of Multiphase Polymers

A method that combines UV irradiation and pausing was developed to manipulate the regularity and the length scales of the morphology generated by phase separation in full‐interpenetrating polymer networks of polystyrene and poly(methyl methacrylate). Upon increasing the pause time of photopolymerization and photo‐crosslink processes, the morphology gradually changes from hexagonal‐like packing to random structures. The width of the loss tan δ obtained for these phase‐separated materials changes with the morphological regularity, suggesting a potential technique for fabrication of mechanical bandgap materials.