Ni(2+) and H(2)PO(4)(-) uptake properties of compounds in the CaTiO(3)-CaFeO(2.5) system

A batch method was used to investigate the uptake of heavy metal cations and anions by the compounds in the CaTiO(3)-CaFeO(2.5) system, in which a series of oxygen vacancies was systematically introduced into a perovskite structure as the x-value of Ca(Fe(x)Ti(1-x))O(3-x/2) was increased. Samples of CaTiO(3), CaFe(0.1)Ti(0.9)O(2.95), CaFe(0.5)Ti(0.5)O(2.75), CaFe(0.67)Ti(0.33)O(2.67) and CaFeO(2.5) were prepared by solid mixing (SM), co-precipitation (CP) and gel evaporation (GE) methods. The resulting samples were calcined at temperatures between 400 and 1000 °C. The target crystalline phases differed according to the preparation method, but in most cases were formed at 700-800 °C. The Ni(2+) sorption isotherms of all the samples were fitted better by the Langmuir model than by the Freundlich model, while in the case of H(2)PO(4)(-) sorption isotherms, these were better fitted by the latter model. The uptake ability increased with increasing x value of the samples. The maximum values for the saturated sorption of Ni(2+) (Q(0)(Ni(2+)) = 2.83 mmol/g) and H(2)PO(4)(-) (K(F)(H(2)PO(4)(-)) = 2.95 mmol/g) were achieved for x = 1 (i.e. CaFeO(2.5)) sample.     

Wet chemical synthesis and self-assembly of SnS2 nanoparticles on TiO2 for quantum dot-sensitized solar cells

SnS2 nanoparticles were synthesized through a simple wet chemical process at room temperature. The SnS2 nanoparticles were approximately spherical in shape and had diameter about 3-4 nm. SnS2-sensitized TiO2 electrodes were fabricated by the immersion of chemically modified TiO2 to well-dispersed SnS2 solution for 72 h (i.e., self-assembly method.) SnS2-sensitized TiO2 electrodes were applied in quantum dot-sensitized solar cells (QDSSCs). Under AM1.5 irradiation with 100 mW/cm2 light intensity (at 1 sun), the short-circuit current density (J(sc)), the open-circuit voltage (V(oc)), the fill factor (FF), and the energy conversion efficiency (eta) were 0.47 mA/cm2, 0.29 V, 0.58 and 0.081%, respectively.     

In-situ study of the carbon nanotube yarn drawing process

Recognizing the main factors affecting the spinning of carbon nanotube (CNT) yarns from vertically aligned brush-like CNTs (BCNTs) persists as a difficult challenge. Here, using in-situ drawing of as few as 20 CNTs from as-grown BCNT and measuring the force required for their separation from BCNT, we demonstrate that samples with different spinnability levels exhibit different separation force behaviors. Moreover, the average separation force per CNT differs among samples. Results show that the separation force in spinnable samples depends on the drawing location: it can be as high as 15 nN/CNT at the top of a sample and as low as 3 nN/CNT in the middle of a sample. In contrast, this force is around 10 nN/CNT for un-spinnable samples and is nearly constant throughout such samples. Detailed drawing site observations can pave the way to elucidation of the mechanisms of dry drawing processes of BCNT, which are vital for enhancing the strength of carbon nanotube yarns.     

Effects of cholesterol feeding to maternal rats on metabolism of cholesterol and bile acids in the dams and their offspring

The influence of feeding cholesterol to rats during pregnancy and postpartum (from the 11th day of gestation to the third day after delivery) on the serum and hepatic cholesterol levels and on the bile acid composition in the pool and in the liver in relationship to the dams and their pups was examined. The hepatic content of cholesterol in both dam and offspring increased during cholesterol feeding without any changes in serum cholesterol level. In the dams, mainly the esterified cholesterol was increased; in the pups, mainly the free cholesterol was increased. Cholesterol feeding led to a pronounced increase in the pool of β-muricholic acid and a relative decrease in the lithocholic acid concentration in pregnant rats. In fetal rats, the chenodeoxycholic acid pool was increased by cholesterol intake. The lithocholic acid pool was larger in the postpartum rats fed cholesterol than in the controls, while the concentration of α- and β-muricholic acids was decreased. The neonates of cholesterol-fed dams had a larger pool of chenodeoxycholic acid but a smaller pool of β-muricholic acid. These results suggest that the metabolism of cholesterol and of bile acids in dams and their offspring respond differently to cholesterol intake.     

Basic study on filtering using the frequency characteristics of reflected waves from underground radar

The waves reflected from objects were extracted and basic studies were conducted on the frequency characteristics of these reflected waves with aim of improving the signal/noise ratio of underground radar images. Aerial tests conducted on steel pipes and steel plates showed that the respective hyperbolic curve signals have different characteristics. Using this principle to filter the signals from buried pipes made it possible to extract only the buried pipe signals.The efficiency to distinguish individual object in underground radar images can be improving by using this filter effectively.     

Capillary rise properties of porous mullite ceramics prepared by an extrusion method using organic fibers as the pore former

Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method to investigate their capillary rise properties. Rayon fibers 16.5 μm in diameter and 800 μm long were used as the pore formers by kneading with alumina powder, kaolin clay, China earthen clay and binder with varying Fe₂O₃ contents of 0, 5 and 7 mass%. The resulting pastes were extruded into cylindrical tubes (outer diameter (OD) 30–50 mm and inner diameter (ID) 20–30 mm), dried at room temperature and fired at 1500 °C for 4 h. The bulk densities of the resulting porous ceramics ranged from 1.31 to 1.67 g/cm³, with apparent porosities of 43.2–59.3%. The pore size distributions measured by Hg porosimetry showed a sharp peak at 10.0 μm in the sample without Fe₂O₃ and at 15.6 μm in the samples containing Fe₂O₃; these pores, which arose from the burnt-out rayon fibers, corresponded to total pore volumes ranging from 0.24 to 0.34 ml/g. SEM showed a microstructure consisting of unidirectionally oriented pores in a porous mullite matrix. Prismatic mullite crystals were well developed on the surfaces of the pore walls owing to the liquid phase formed by the Fe₂O₃ component added to color the samples. The bending strengths of the tubular samples ranged from 15.6 to 26.3 MPa. The height of capillary rise, measured under controlled relative humidities (RH) of 50, 65 and 85%, was greater in the ceramics containing Fe₂O₃ than in those without Fe₂O₃, especially in the thinner samples. The maximum capillary rise reached about 1300 mm, much higher than previously reported. This excellent capillary rise ability is thought to be due to the controlled pore size, pore distribution and pore orientation in these porous mullite ceramics.     

Low temperature preparation and machinability of porous ceramics from talc and foamed glass particles

Porous ceramics were prepared by firing mixtures of talc (Mg₃Si₄O₁₀(OH)₂) and foamed glass particles (ceramic balloons, CB) with and without LiCl as a sintering acid. The mixing ratios of the starting materials were talc:CB = 7:3, 8:2, 9:1 and 10:0, with additions of LiCl of 0, 2 and 5 mass%. The mixtures were formed into pellets and fired at 600–1000 °C. The pellets without LiCl showed very poor strength even when fired at 1000 °C but those containing LiCl were much stronger, even when fired at only 600 °C. The crystalline phases in these samples changed to enstatite (MgSiO₃) at ≥ 700 °C by decomposition of the talc under the fluxing action of the LiCl. The resulting samples were machinable and easily cut and drilled. The cutting rate decreased with increasing bending strength, for example, from 105 mm²/s and 6.3 MPa to 50 mm²/s and 16.3 MPa, respectively. The drilling rate of the present sample was found to be only slightly less than Teflon (polytetrafluoroethylene, PTFE) but much faster than graphite, glass ceramics, etc.     

Optimal electric power-plant planning under uncertainty of demand by means of the scenario aggregation algorithm

Recently, electric power systems have faced increasing uncertainties in demand, energy price and environmental constraints in the future. In such a situation, a plan for expansion of the system capacity must be made robust against the aforementioned uncertainties. Large-scale power plants require a long time for construction so that the decision of construction must be made under much uncertainty in the future. On the other hand, small-scale plants require less time for construction, i.e., the decision can be made under less uncertainty in spite of their relatively higher costs. This paper is concerned with an optimal combination of the large-scale and the small-scale plants having the aforementioned characteristics under uncertainty of future demand. First, the demand growth in the future is described by scenarios of demand growth branching like a tree. Then the optimization problem of the system expansion is formulated into a stochastic linear-programming problem. An optimal solution of the problem is obtained by using the scenario-aggregation algorithm proposed by Rockafellar and Wets. The simulation results, yielded by using a parallel computation on transputers, show that there is a possibility of constructing small-scale power plants to cope with the uncertainty even if they are more expensive than the large-scale plants.     

Change of nitrogen functionality of N-enriched condensation products during pyrolysis

Changes in the nitrogen functionality of ¹⁵N-enriched condensation products prepared from glucose and ¹⁵N-glycine were investigated during pyrolysis at 600–1000 °C. The structural changes in the condensation products were studied by means of solid-state ¹³C and ¹⁵N NMR spectroscopies. During pyrolysis, the aliphatic moieties of the condensation products decomposed and evolved as gas and tar. At pyrolysis temperatures above 600 °C, almost all the carbon in the chars were converted to aromatic carbon. After pyrolysis, large amounts of nitrogen remained in the chars as char nitrogen (char-N), and about 30% of the nitrogen was eliminated from the chars as HCN and NH₃. With increasing temperature, the production of HCN and NH₃ increased and the amount of char-N decreased. By combining X-ray photoelectron spectroscopy and NMR results, detailed results for nitrogen fractions in chars were obtained. During pyrolysis, the fraction of unsubstituted pyrrole-N decreased and the fraction of quaternary-N increased. The fraction of pyridine-N remained almost constant at temperatures below 800 °C, but at 900 °C and above, the fraction of pyridine-N decreased. The fraction of substituted pyrrole-N showed minimum at 800 °C. On the basis of these results, structural changes of nitrogen functional groups during pyrolysis are discussed.     

Simultaneous uptake of ammonium and phosphate ions by composites of γ-alumina/potassium aluminosilicate gel

The simultaneous uptake of ammonium and phosphate ions from solution by composites of γ-alumina/potassium aluminosilicate (KAS) gel has been investigated. The composites were prepared by selective leaching of calcined kaolinite (Al₂Si₂O₅(OH)₄) using KOH solution, followed by neutralization of the leachate at pH 5.5 with nitric acid. The composites were reacted with solutions containing various concentrations of (NH₄)₂HPO₄ at pH 5, 7 and 10 at room temperature for 24 h to examine their uptake of ammonium and phosphate ions. Simultaneous uptake of ammonium and phosphate ions was found, the uptake of ammonium ions being greater than for phosphate ions, especially at pH=7. This observation is considered to result mainly from the porous properties of the composites, which should therefore be controlled to enhance the simultaneous uptake of both ions, especially phosphate ion.