A uniqueness theorem of radially symmetric positive stationary solutions for a competition–diffusion system

In this paper, as a first step to study the global structure of solution, we treat a class of reaction–diffusion systems with competitive interaction, and discuss a uniqueness theorem of radially symmetric solutions for the system. To do this, the comparison principle and the shooting method are employed, and the spatial profile is investigated.     

Efficient transformation of 7,14-dihydroxy-ent-kaurenes to novel ent-abietanes having cis-fused α-methylene γ-lactones under Mitsunobu reaction conditions and their cytotoxicities

Transformation of plant-origin 7,14-dihydroxy-ent-kaurenes to ent-abietanes having a cis-fused α-methylene γ-lactones was accomplished efficiently under the Mitsunobu reaction conditions. The yields of the desired products were apparently influenced by the steric hindrance at C-1. The cytotoxic activity on P388 murine leukemia cells of the ent-abietanes having cis-fused α-methylene γ-lactones produced were assayed.     

Garcinielliptone G from Garcinia subelliptica Induces Apoptosis in Acute Leukemia Cells

Cytotoxicity and apoptosis-inducing properties of compounds isolated from Garcinia subelliptica leaves were investigated. The hexane-soluble portion of MeOH extracts of G. subelliptica leaves that showed cytotoxic activity was separated to yield seven compounds 1–7. Chemical structure analysis using NMR spectroscopy and mass spectrometry confirmed that compound 1 was canophyllol, and compounds 2–7 were garcinielliptones N, O, J, G, F, and garcinielliptin oxide, respectively. Among them, garcinielliptone G (5) showed growth inhibition by causing apoptosis in THP-1 and Jurkat cells derived from human acute monocytic leukemia and T lymphocyte cells, respectively. Apoptosis induced by garcinielliptone G (5) was demonstrated by the detection of early apoptotic cells with fluorescein-labeled Annexin V and increases in cleaved caspase-3 and cleaved PARP protein levels. However, the addition of caspase inhibitor Z-VAD-FMK did not affect growth arrest or apoptosis induction. These results suggest that garcinielliptone G (5) can induce both caspase-3 activation and caspase-independent apoptosis. Therefore, garcinielliptone G (5) may be a potential candidate for acute leukemia treatment.     

Study of the thermal degradability of poly(α-methylstyrene) with modified end groups

To induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-(p-tolyl)allyl bromide, and α-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the ω-2-phenylallyl-PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, ω-3,3-difluoro-2-phenylallyl- and ω-2-(4-toly)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω-hydrogen- > ω-3,3-difluoro-2-phenylallyl- > ω-2-phenylallyl- > ω-2-(p-tolyl)allyl-PMS. Actually, the onset temperature of ω-2-(p-tolyl)allyl-PMS derivatives was 50°C lower than that of ω-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.     

A hydrogel with rubber elasticity transition

Reaction between dimethyldivinylsilane and 3,6-diazaoctane in the presence of 3-lithio-3,6-diazaoctane yields a new telechelic oligomer, poly(silamine), which consists of alternating 3,3-dimethyl-3-silapentane and N,N′-diethylethylenediamine units in the main chain. Poly(silamine) shows unique phase transition properties in response to the degree of protonation of amino groups in the polymer. Poly(silamine) also shows a strong interaction with several anions. Due to the interaction between poly(silamine) and anions along with the protonation of amino groups in the poly(silamine), the rubber elasticity of poly(silamine) is drastically changed. A discrete volume change can be observed when the environmental pH of the poly(silamine) gels is varied. This can be explained not only by a change in ionic osmotic pressure but also by a change in the rubber elasticity of the networks in the gel.     

Changes of electrochemical responses of the bulk solution species by thermotropic permeability of liquid crystalline membranes coated on electrodes

Liquid crystalline/polymer composite membrane-coated electrodes were prepared by casting a 1,2-dichloroethane solution of N-(4-ethoxybenzylidene)-4′-n-butylaniline (EBBA) and polycarbonate (PC) on an electrode surface. The temperature-dependence of the permeability of the EBBA/PC composite membrane on electrodes to Fe(CN)^3?₆ ion as a solution-phase redox ion was investigated by means of hydrodynamic voltammetry at a rotating disk electrode. The permeability changed with temperature over the range of the crystalline-nematic-phase transition temperature of EBBA. It is demonstrated that the observed temperature-dependence of the permeability reflects the thermotropic properties of EBBA in the EBBA/PC composite membrane. Furthermore, the dependence of the limiting current of the steady-state current-potential curves for the reduction of Fe(CN)^—₆ at the EBBA/PC composite membrane-coated electrode upon the membrane thickness, the blend ratio of EBBA and PC and the concentration of Fe(CN)^3?₆ in a bulk solution was examined in order to understand the transport process of Fe(CN)^?3₆ through the EBBA/PC composite membrane from the membrane/solution interface to the electrode/membrane interface. The transport process of Fe(CN)^3?₆ within the membrane was found to obey Fick's Law.     

Simultaneous determination of silicate and phosphate in environmental waters using pre-column derivatization ion-pair liquid chromatography

A highly sensitive HPLC method for the simultaneous determination of soluble silicate and phosphate in environmental waters was developed, using ion-pair liquid chromatography preceded by the formation of their yellow α-heteropolymolybdates. The moderate-pH mobile phase enabled to use a highly efficient reversed-phase silica column. The pre-column coloring reactions at moderate-pH were reproducible for both silicate and phosphate in all quantification ranges with R.S.D.s less than 2% and 5%, respectively. The linear calibration lines between concentrations (mg-SiO₂/L and mg-PO₄/L) and peak area intensities were obtained for silicate and phosphate both with acceptable determination coefficients (r²) of 0.9999. The limits of determination for both analytes were 0.007 mg-SiO₂/L and 0.003 mg-PO₄/L, which were calculated theoretically using 10σ/slope. The four-digit dynamic ranges were obtained for 0.007-10 mg-SiO₂/L and 0.003-20 mg-PO₄/L. The developed method was applied for the analysis of tap water, river water, coastal seawater, well water, hot-spring water, commercial mineral water, and laboratory water. The results were very reasonable and acceptable from the environmental viewpoints, which were well correlated with those confirmed by the molybdenum-blue spectrophotometry.     

Sonochemically enhanced adsorption and degradation of methyl orange with activated aluminas

Removal of Methyl orange (MO), as a model contaminants, in aqueous solution by the simultaneous application of ultrasound with the addition of porous adsorbent powders is reported. Activated alumina powders in acidic form were used as an adsorbent. Results showed that MO could be degraded by ultrasonic irradiation at 130 kHz with the first order rate constant of 8x10(-4) and 5x10(-4) sec(-1), in acidic and basic conditions, respectively, without adsorbents. Adsorption rates of MO by activated alumina mainly depended on the acidity of alumina, the pH of solution and the stirring speed. At pH=4.2 with mechanical stirring without ultrasonic radiation, acidic activated alumina (0.1 g/100 ml) removed MO at about two times more rapidly than ultrasonic irradiation. In the case of simultaneous application of ultrasound irradiation and activated alumina, MO was almost removed from the solution within 10 min, which corresponded to as a rate constant of 5x10(-3) sec(-1). This kind of synergistic enhancement of removal rate with ultrasound and adsorbents should be practically useful for the elimination of contaminants in the water treatment processes. In addition, the effects of pH and coexisting chemicals in the solution were examined for the processes. Although the adsorption process was effective in some selected conditions, ultrasonic degradation was more robust in wider range of pH and coexisting chemicals. Simultaneous application of the two processes can perform complementary.     

Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.