Application of the micro-PIXE technique for analyzing arsenic in biomat and lower plants of lichen and mosses around an arsenic mine site, at Gunma, Japan

Microhabitats of bacteria (biomat) and lower plants, such as lichen and mosses, are known to accumulate hazardous elements. Since the concentration of hazardous elements in the environment is quite low, we have applied the in-air μ-PIXE (particle induced X-ray emission) system developed in the TIARA facility of JAERI, which has low concentration detection limit of ppm, to measure As, one of the hazardous elements, distributions in biomat, lichen and mosses observed around an abandoned As mine site in Gunma, Japan to elucidate the applicability of these biomat and lower plants as bio-indicators of As. Spatial distributions of As, Fe, Si and S in all biomat, lichen and moss collected within 3 m from the mine entrance indicate that As is localized, and is associated with silicate and Fe-containing compounds. In addition, the intensity ratio of peak area for As to Fe in μ-PIXE spectrum of the moss collected from the concrete wall at 3 m downstream of the mine water discharge position is different from those of the lower plants on the rock near the closed entrance, but is the same as that of biomat formed at the mine water discharge position. This indicates that As trapped by the moss on the concrete wall probably has the same origin as the biomat. It is concluded that application of μ-PIXE analysis to the measurement of As in the lower plants and biomat gives not only the distribution of the hazardous element of As, but also the information of the origin.     

Dynamic modeling of the environment in a naturally ventilated, fog-cooled greenhouse

A dynamic simulation model for heat and water vapor transfer in a naturally ventilated, fog-cooled greenhouse was developed to predict the temperatures of air, plant, cover and floor surface and the relative humidity in the greenhouse. Transpiration and evaporation were also predicted. An experiment was conducted on a hot summer day (Aug. 9, 2004) in the Tokyo area to measure the environments inside and outside a glass-covered greenhouse with a floor area of 26 m². The greenhouse was cooled intermittently by spraying water fog at a constant rate of 0.01 kg s⁻¹ for different fogging and interval times (0.5 min on followed by 1.5 min off; 1 min on–3 min off and 1.5 min on–4.5 min off). The system of equations of the model was solved numerically by using the predictor–corrector technique for the differential equations and the iteration procedure for the algebraic equation. The input parameters to the model were the meteorological conditions and the thermo-physical properties of the greenhouse cover, plant, air and soil. The predicted results using the present model were compared with the measured values and showed a good agreement at different fogging and interval times.     

Interleukin-2-collagen chimeric protein which liberates interleukin-2 upon collagenolysis

Interleukin-2 (IL-2) is a potent activator of cellular immunityand has been utilized as an immunotherapeutic agent. We stablyimmobilized human IL-2 to collagen by covalently binding itto the N-terminus of human type III collagen (3A1) as IL2-3A1chimeric protein using recombinant technology. The present studywas aimed at liberating IL-2 from the immobilized chimeric proteinby treating the chimera with bacterial collagenase. These IL2-3A1chimeras were synthesized in insect cells which had been infectedwith baculovirus vectors carrying IL2-3A1 cDNA. The IL2-3A1protein produced was shown to be in a pepsin-resistant triplehelical structure and exhibited IL-2 activity to a similar extentas IL-2 itself. IL2-3A1 could be immobilized on the surfaceof plastic dishes by incubating it in the dishes. The IL-2 regionof the immobilized IL2-3A1 was liberated to culture media bycollagenase treatment and this freed IL-2 stimulated the growthof lined T cells. Thus, IL2-3A1 chimeric protein could be utilizedas an IL-2 deliverer whose T cell mitogenic activity can beliberated by a collagenolytic environment.     

Effect of Bacillus subtilis spo0A mutation on cell wall lytic enzymes and extracellular proteases, and prevention of cell lysis

The Bacillus subtilis spo0A mutant is an adequate host for extracellular protein production (e.g., alpha-amylase). However the mutant was prone to cell lysis. SDS-PAGE and zymography of cell wall lytic proteins indicated that the spo0A mutant contained high amounts of two major autolysins (LytC [CwlB] and LytD [CwlG]) and two minor cell wall lytic enzymes (LytE [CwlF] and LytF [CwlE]). On the other hand, the expression of eight extracellular protease genes was very poor or absent in the spo0A mutant. An eight-extracellular-protease-deficient mutant (Dpr8 strain) was constructed and the strain also exhibited cell lysis. The autolysins from the spo0A mutant were degraded by the supernatant of the wild type but not degraded by that of the Dpr8 mutant. These results suggest that the extensive cell lysis of the spo0A mutant was partially caused by the stability of autolysins via the decrease of the extracellular proteases. The introduction of a major autolysin and/or SigD mutations into the spo0A mutant was effective for preventing cell lysis.     

Adsorptive Recovery of Palladium(II) and Platinum(IV) on the Chemically Modified-Microalgal Residue

A biomass waste of microalgae was chemically modified by immobilizing the functional group of polyethyleneimine to prepare a new type of adsorbent. The adsorption test revealed that this adsorbent exhibited remarkably high selectivity for Pd(II) and Pt(IV) over base metal ions in HCl solution. From the adsorption isotherm, its maximum adsorption capacity for Pd(II) and Pt(IV) was evaluated as 2.0 and 0.8 mmol/g, respectively. This adsorbent also exhibited high affinity and selectivity for Pd(II) and Pt(IV) even in the presence of high concentrations of base metals in actual leach liquor.     

Note EXTRACTION EQUILIBRIUM OF MERCURY(II) FROM AQUEOUS AMMONIUM THIOCYANATE SOLUTION WITH TRIISOBUTYLPHOSPINE SULFIDE

The extraction equilibrium of mercury(II) from aqueous ammonium thiocyanate solution with triisobutyl-phosphine sulfide(=TIBPS=S¯) in toluene has been measured at 303 K. It was found that mercury(II) is extracted according to a solvation reaction by TIBPS as a mercurydl) :TIBPS 1:2 complex, Hg(SCN)₂S2, as follows:

The extraction equilibrium constant, K_e, was evaluated as K_e = 1.8 × 10⁶ (dm³/mol)².     

A Superhydrophobic Microvalve for Manipulating Microliquids Containing Biological Molecules

This paper presents a novel microvalve including a superhydrophobic surface that inhibits adsorption of a liquid that contains biological molecules. This microvalve was fabricated by anodizing the Si surface of a microchannel wall and making the channel surface partially superhydrophobic. The superhydrophobicity could be modified by changing the anodization time and current density during the anodization process. Experiments using a cell‐culture medium showed that the fabricated microvalve successfully opened/closed repeatedly by applying a positive/negative pressure from the inlet, and that it could be opened within 0.5 s by an inlet pressure of more than 9 kPa. Also, we could continue switching the microvalve at 1 Hz for about 3 h (10 800 switching) while adjusting the required inlet pressures, which increased with time. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm⁻² of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 °C under a pressurized condition of 0.35 MPa.     

Polymerization of surface-active monomers: 5. Syntheses and polymerizations of anionic surface-active monomers: sodium di(10-undecenyl)sulphosuccinate and sodium n-undecyl 10-undecenylsulphosuccinate

Novel, anionic surface-active monomers, sodium di(10-undecenyl)sulphosuccinate (DUSS) and sodium n-undecyl 10-undecenylsulphosuccinate (MUSS) were prepared. The monomers were soluble in both water and apolar organic solvents on heating. DUSS and MUSS in water exhibited Kraft points at about 39°C and 48°C, respectively. The critical micelle concentrations for aqueous solutions of DUSS and MUSS at 50°C were determined to be 2.4 × 10⁻⁵ and 1.2 × 10⁻⁵ mol l⁻¹, respectively. Polymerization of the monomers in darkness and under u.v. irradiation at 50°C were studied using three different solvents, namely water, n-hexane and dioxane, giving aqueous micelles (or vesicles), reversed micelles and isotropic solution, respectively. Only traces of polymers were formed for the polymerizations in darkness, while the polymerizations under u.v. irradiation gave polymers, except for the polymerization of MUSS in dioxane. The solvents used for the polymerization were observed to exert an effect on the solubility of the polymers of DUSS and only the polymer obtained from the polymerization in water was soluble in solvents such as water and N,N-dimethylformamide. Thus, the monomer aggregation, especially for the aqueous system, was found to affect the structure of the resulting polymers.     

Algorithms for Distributed Constraint Satisfaction: A Review

When multiple agents are in a shared environment, there usually exist constraints among the possible actions of these agents. A distributed constraint satisfaction problem (distributed CSP) is a problem to find a consistent combination of actions that satisfies these inter-agent constraints. Various application problems in multi-agent systems can be formalized as distributed CSPs. This paper gives an overview of the existing research on distributed CSPs. First, we briefly describe the problem formalization and algorithms of normal, centralized CSPs. Then, we show the problem formalization and several MAS application problems of distributed CSPs. Furthermore, we describe a series of algorithms for solving distributed CSPs, i.e., the asynchronous backtracking, the asynchronous weak-commitment search, the distributed breakout, and distributed consistency algorithms. Finally, we show two extensions of the basic problem formalization of distributed CSPs, i.e., handling multiple local variables, and dealing with over-constrained problems.