Characterization of ozone decomposition in a soil slurry: kinetics and mechanism.

A series of soil slurry experiments were performed in a carefully conceived reactor set-up to investigate the characteristics of the catalytic decomposition of ozone on a sand and iron surface. Real time on-line monitoring of ozone in the reaction module was possible using flow injection analysis coupled with a computer-controlled UV detector and data acquisition system. The effects of the soil media and size, ozone dosage, pH and p-CBA as a probe compound were examined at the given experimental conditions. Two apparent phases existed, and ozone instantaneously decomposed within one second in the first phase. These were defined as the instantaneous ozone demand (ID) phase, and the relatively slow decay stage. The interactions of ozone with the soil organic matter (SOM) and metal oxides were attributed mostly to the instantaneous decomposition of ozone. From the probe (p-CBA) experiments, 60-68% of total p-CBA removal occurred during the ID phase. The generation of hydroxyl radicals (OH.) was demonstrated and was closely related with metal oxides as well as SOM. Metal oxides in soil surface were considered to have relatively faster reaction rate with ozone and provide more favorable reactive sites to generate higher amount of OH. than SOM. Even at one-tenth concentration of the sands, a goethite-induced catalytic reaction outfitted the removal rate ofp-CBA among all the soils tested. More than 40% of total p-CBA removal occurred on the soil surface. It was inferred that the radical reaction with the probe compound seemed to take place not only on the soil surface but also in the solid-liquid interface. Ozone decomposition and the reaction between OH. and p-CBA appeared to be independent of any change in pH.     

Monitoring thiocyanate-degrading microbial community in relation to changes in process performance in mixed culture systems near washout

Changes in microbial community structure, associated with changes in process performance, were investigated with respect to the sludge retention time (SRT) in bioreactors treating thiocyanate. Among the seven reactors operated at 0.8-3.0 d SRTs, respectively, the reactor at 2.0 d SRT displayed the maximal thiocyanate removal rate of 240.2mg/L/d. However, the thiocyanate removal efficiency suddenly decreased from 96.1% to 43.1% when the SRT was reduced from 2.0 to 1.8d, corresponding to a 50.1% drop in the removal rate. Microbial communities in the reactors operated at short SRTs, near washout, were analyzed by denaturing gradient gel electrophoresis (DGGE) based on bacterial 16S rRNA genes. All band sequences recovered were assigned to two phyla, Proteobacteria and Bacteriodetes. A Thiobacillus-like microorganism was commonly detected in all the reactors and is suggested to be the main organism responsible for thiocyanate decomposition. Several DGGE band sequences were closely related to the environmental clones detected in environments rich in sulfur and/or nitrogen compounds. Statistical analysis of the DGGE profiles demonstrated that the structure of thiocyanate-degrading communities, as well as the process performance, changed with change in SRT. The microbial community profiles were not always more closely related to those at similar SRT than those at less similar SRT on the non-metric multidimensional scaling (NMDS) map. This was also supported by clustering analysis. These results were contrary to the general notion that the community structures in continuous systems will be controlled by the washout of microbial populations. Our experimental results suggest that the structure of a microbial thiocyanate-degrading community at a given SRT would not be determined only by the washout effect.     

Field performance measurements of a heat pump desiccant unit in dehumidification mode

The variable refrigerant volume (VRV) air conditioning system needs to be operated in conjunction with a ventilation system, because the VRV system cannot provide any fresh air. The common ventilation unit used with the VRV system is the heat recovery ventilation (HRV) unit. In this study, a new ventilation unit, a self-regenerating heat pump desiccant (HPD) unit, was introduced and the characteristics of the HPD unit was experimentally investigated over a wide range of operating conditions in a field performance test. In addition, the energy saving contribution of the HPD and HRV units to the VRV system was compared. It was found that the HPD unit maintained the target indoor humidity ratio of 10 g/kg throughout the cooling season resulting in a better indoor thermal comfort than the HRV unit. Besides, it was found that the outdoor unit of the VRV system consumed 26.3% less energy for the operation in conjunction with the HPD unit as compared to the operation in conjunction with the HRV unit.     

Characteristics of wood–polymer composite for journal bearing materials

Wood is widely used as a construction material, automotive parts, and equipment for leisure-time amusement; however, its application on the journal bearing was restricted, because of its low strength and poor tribological characteristics.In this work, paulownia wood which has low density and high porosity was impregnated with polyethylene glycol (PEG), lubricant oil (SAE 30), release agent and epoxy to improve the mechanical properties and tribological characteristics. The ultrasonic vibration was given to the wood immersed in the acetone tub to remove debris generated during the cutting process of wood and to dissolve the membrane of lignin in the wood. From the test results, it was found that the PEG was the promising material to improve the physical properties of wood for journal bearings.     

Oxidation of 17alpha-ethinylestradiol with Mn(III) and product identification

With increasing concern about the contamination of aquatic environments by estrogenic pollutants, removal of synthetic estrogens such as 17alpha-ethinylestradiol (EE2) has been widely studied, especially with respect to the treatment methods. However, the degradation products have rarely been identified. The purpose of this study was to identify structurally the oxidation products of EE2. Mn(III) was used as an oxidizing agent. To obtain sufficient oxidation products for HPLC, LC-MS and NMR spectroscopy, a highly concentrated solution of EE2 (1mM) was prepared in a mixture of water and a water-miscible organic solvent. From HPLC of the reaction products, a single compound (I) was found to be predominant. From LC-MS, its molecular mass was found to be 294, and two hydrogens were believed to have been removed from EE2 (M.W. 296) to form a C=C . The structure of compound I (position of the double bond) was determined using 1H NMR, 13C NMR, H-H COSY, HSQC and HMBC. As minor products, isomeric dimers (M.W. 590) of EE2, as well as the products (M.W. 588) in which EE2 was coupled to compound I were also formed during the Mn(III)-mediated oxidation of EE2.     

Memory characteristics of a self-assembled monolayer of Pt nanoparticles as a charge trapping layer

A self-assembled monolayer of Pt nanoparticles (NPs) was studied as a charge trapping layer for non-volatile memory (NVM) applications. Pt NPs with a narrow size distribution (diameter ～4?nm) were synthesized via an alcohol reduction method. The monolayer of these Pt NPs was immobilized on a SiO(2) substrate using poly(4-vinylpyridine) (P4VP) as a surface modifier. A metal-oxide-semiconductor (MOS) type memory device with Pt NPs exhibits a relatively large memory window of 5.8?V under ± 7?V for program/erase voltage. These results indicate that the self-assembled Pt NPs can be utilized for NVM devices.