Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm^-3 FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm^-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe²⁺]² and po₂, exhibiting an activation energy of 51.6 . kJ mol^-1. In another path the reaction rate was proportional to [Fe²⁺]², [SO_4-], and po₂ with an activation energy of 144.6 kJ . mol^-1. A reaction mechanism in which the SO_4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol . dm^-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² and Po₂, and was also affected by [H⁺] and [SO_2- ⁴]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).     

Pulsed KrF excimer laser annealing of silicon solar cell

The pulsed KrF excimer laser annealing of silicon films for solar cell with EBEP-CVD and LP-CVD was studied theoretically and experimentally. Three-dimensional thermal diffusion equation for microcrystalline and amorphous silicon was solved by using the finite difference methods. The results of our heat-flow simulation of laser re-crystallization in a laser irradiation with 50 ns pulse duration almost agree with the experimental results in re-crystallization depth of 0.7 μm for microcrystalline silicon (EBEP-CVD) and 0.4 μm for amorphous silicon (LP-CVD) in a single pulse excimer laser annealing.     

A load dispatch method using fractional programming and semidefinite programming

This paper describes a load dispatch method which minimizes power cost—[fuel cost]/[electric output]—for a power system with thermal plants and energy storage facilities. The proposed method employs fractional programming to convert a minimization problem with fractional objective function to a series of quadratic minimization problems, and semidefinite programming to solve converted problems. The method provides the optimum time‐dependent power output/input and storage level of energy storage facilities as well as time‐dependent power output of thermal plants. The method has been applied to a power system with five thermal plants, two energy storage facilities of various performances, and five load demands. The optimum load scheme of four time mesh points is obtained for the thermal plants and energy storage facilities. The fractional programming successfully converges the optimal scheme through a few iterations. The semidefinite programming deals with a variable matrix of 164 dimensions, and 185 inequality constraints. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 49–58, 2002     

Change of characteristics of desulfurization and denitrification by combustion flue gas composition and electrode configuration under pulsed corona discharge

Laboratory-scale and parametric experiments of SO₂ and NO_x removal from the simulated combustion gas by pulsed corona discharge have been performed by changing the combustion gas composition and temperature, the electrode configuration of plasma reactor, and the polarity of high-voltage electrode. The following results are obtained: 1) the higher the concentration of H₂O and O₂, the higher the efficiency of desulfurization and denitrification at the same specific input; 2) the pulsed corona discharge with a voltage pulsewidth as short as 200 ns of negative polarity shows the possibility to attain almost 90 percent deSO_x and deNO_x efficiency at the specific discharge input of 20 J/g, which is almost the same as the specific input in the electron-beam process; 3) the deNO_x characteristics show a little temperature dependence in the range of 70 to 130°C, but the deSO_x efficiency increases rapidly in the temperature region below 100°C suggesting the thermochemical dependence of deSO_x reaction; 4) when desulfurization and denitrification proceed, the white dendritic powder deposits on the plasma reactor whose composition is identified to be 49 mol% (NH₄)₂SO₄ and 47 mol% of 2NH₄NO₃ · (NH₄)₂SO₄, and the ratio of SO₂, NO and NH₃ of the deposit is almost equal to that of supplied gas.     

Characterization of calcium-independent cytosolic phospholipase A2 activity in the submucosal regions of rat stomach and small intestine

This study was undertaken to compare the calcium-independent phospholipase A₂ (PLA₂) activities in the cytosols of twelve rat tissues and to determine whether their activities were distinct. 1-O-Alk-1′-enyl-2-[¹⁴C]-oleoyl-sn-glycero-3-phosphocho-line (PlsC) and 1-O-Alk-1′-enyl-2-[¹⁴C]oleoyl-sn-glycero-3-phosphethanolamine (PlsE) were synthesized and used as substrates, instead of phosphatidyl compounds, to exclude hydrolysis by cytosolic PLA₁ activity that could be present in some of the cytosolic preparations. For each tissue, we examined substrate specificity, pH optimum, and effect of adenosine triphosphate (ATP) and ATP analogues. PLA₂ activity was detected in eleven out of the twelve issues examined. Based on substrate specificity and pH optimum, cytosolic calcium-independent PLA₂ were classified in three groups. The first group, which included PLA₂ from small intestine, stomach and spleen, had the highest specific activity with PlsC as substrate (1253, 309 and 75 nmol/mg protein/hour, respectively) and an optimal pH at 6.5. Activity with PlsE as substrate was much lower (20–37%) than with PlsC. The second group of PLA₂ activities included the cytosolic activities from thymus, lung, liver and pancreas that showed lower specific activities for both substrates (14–23 nmol/mg protein/hour with PlsC) and had a broader optimal pH range of 6.1 to 7.5. The cytosols from brain, kidney, heart and muscle comprised the third PLA₂ group that was found to have a higher specific activity with PlsE (5–20 nmol/mg protein/hour) than PlsC and an optimal pH range from 7.4 to 7.9. Since the highest specific activity was found in the cytosol from small intestine, this PLA₂ was examined further. PLA₂ activity was found to be equally distributed in the cytosol of the submucosal portion of duodenum, jejunum and ileum with an optimal pH of 6.1 and a 5-fold higher activity with PlsC than PlsE as substrate. Moreover, this PLA₂ activity was inhibited by treatment with detergents. These results indicate the presence in the submucosal portion of the intestine of a calcium-independent cytosolic PLA₂ with a high specific activity toward PlsC and properties distinct from those described for the PLA₂ found in the intestinal brush-border.     

Synthesis and optical properties of the [2.2]paracyclophane-containing π-conjugated polymer with a diacetylene unit

Summary Novel through-spaceπ-conjugated polymer based on poly(p-henyleneethynylene)/poly(p-phenylenebutadiynylene) hybrids containing a [2.2]paracyclophane unit in the main chain was synthesized by copper-catalyzed alkyne coupling reaction. The structure of the polymer was supported by ¹H NMR and IR spectra. The obtained polymer was soluble in common organic solvents such as THF, CH₂C1₂, CHC1₃ and toluene. The number-average of molecular weight of the polymer was estimated to be 63000 by GPC. The polymer emitted a bluish green light in solution and in the solid state. Received:24 September 2002/Revised version: 19 November 2002/Accepted: 19 November 2002 Correspondence to Yoshiki Chujo     

Carrying capacity and vulnerability of four Asian lakes: A comparative study

To present axes for evaluating the water resources, lake environment and water use in a lake and its watershed, a comparative study was done for four East Asian lakes; lake Kasumigaura (Japan), Lake Laguna (Philippines), Lake Songkhla (Thailand) and Lake Dianchi (China). Two axes were then determined from the relationship between: (1) water use and water supply rate, and (2) water use and water quality. To clarify the meanings ‘carrying capacity’ and ‘vulnerability’, the maximum population density in the lake basin and total nitrogen concentration in the lake water were calculated and discussed to decide the direction of environmentally sound management of the drainage basin.     

Antitumor activity of 1 M tegafur-0.4 M 5-chloro-2,4-dihydroxypyridine-1 M potassium oxonate (S-1) against human colon carcinoma orthotopically implanted into nude rats

The purpose of this study was to establish a nude rat orthotopic (organ-specific) human colorectal cancer model as an in vivo secondary screen for general evaluation of new anticancer agents against colorectal cancer and to evaluate practically the antitumor activity of 1 M tegafur-0.4 M 5-chloro-2,4-dihydroxypyridine-1 M potassium oxonate (S-1), a new p.o. fluoropyrimidine, in comparison to 1 M tegafur-4 M uracil [(UFT) effective on colorectal tumor in clinical]. After implantation of KM12C, a human colorectal cancer cell line, into the subserosal layer of the colon as a single-cell suspension, extensive local tumor growth and invasion to both the mucosal and the serosal sides were observed in all rats. Metastatic foci were also formed in both lymph nodes and lungs following local tumor growth in all of them. Using this method, an equitoxic dose of S-1 (15 mg/kg/day) and UFT (30 mg/kg/day) was administered p.o. for 14 consecutive days from 7 days after tumor cell implantation. S-1 showed a higher tumor growth inhibition than UFT did [S-1, 57% (significantly different from the tumor weight of the untreated group at P < 0.05) and UFT, 18% (P > 0.05)]. When both drugs were administered to nude rats bearing KM12C injected into the cecal wall for 28 consecutive days at equitoxic doses, the mean survival in the S-1 group was 16 days longer than that in the untreated group (P < 0.01) but that in the UFT group was only 8 days longer (P > 0.05). After the administration of an equitoxic dose of both drugs, S-1 gave the higher levels than UFT in various pharmacokinetic parameters as follows: area under the curve 0-24 h of 5-fluorouracil in plasma (3.5-fold), area under the curve 0-24 h of 5-fluorouracil incorporated into RNA in the tumor (1.3-fold), and thymidylate synthase inhibition rate (percentage) in the tumor (about 20%). Collectively, these findings suggested that this orthotopic human colorectal tumor model in nude rats is useful to evaluate the clinical therapeutic efficacy of drugs or therapies for colorectal cancer, and that S-1 had a higher therapeutic effect on human colorectal tumor than UFT did.