Total oxidation of propane over Cu-Mn mixed oxide catalysts prepared by co-precipitation method

The catalytic activity of Cu-Mn mixed oxides with varying Cu/Mn ratios prepared by co-precipitation method was examined for the total oxidation of propane. The nature and phase of the metal oxide species formed were characterized by various methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (TPR) as well as BET surface area measurement. The co-precipitation method provides highly interdispersed copper and manganese metallic elements forming Cu-Mn mixed oxide of spinel structure (Cu_1.5 Mn_1.5O₄). Besides the spinel-type Cu-Mn mixed oxide, CuO or Mn₂O₃ phases could be formed depending on the Cu/Mn molar ratio of their precursors. The catalytic activity of Cu-Mn mixed oxide catalyst for propane oxidation was much higher than those of single metal oxides of CuO and Mn₂O₃. The higher catalytic activity likely originates from a synergic effect of spinel-type Cu-Mn mixed oxide and CuO. The easier reducibility and BET surface area seems to be partially responsible for the high activity of Cu-Mn mixed oxide for total oxidation of propane.     

Isolation of the polysaccharidase-producing bacteria from the gut of sea snail, <Emphasis Type="Italic">Batillus cornutus</Emphasis>

This study was conducted to isolate microorganisms from the gut of the marine turban shell, Batillus cornutus, which inhabits the mainland of South Korea and primarily feeds on brown algae. We were interested in isolating such gut bacteria by considering their potential to produce the polysaccharidases required for digestion of brown seaweeds and isolated three different bacteria from the gut of Batillus cornutus. The isolated bacteria were identified as Bacillus sp. JMP-A, Bacillus sp. JMP-B and Staphylococcus sp. JMP-C. The organisms were evaluated for their ability to produce polysaccharidases such as cellulase, alginate lyase, laminarinase and kelp-lyase. Bacillus sp. JMP-A and Bacillus sp. JMP-B showed a clear zone of CMC hydrolysis with a radius 1.10 (±0.057) and 3.88 cm (±0.088), respectively, whereas Staphylococcus sp. JMP-C showed no zone of CMC hydrolysis. SEM analysis confirmed that the ability of the bacterial isolates to degrade kelp differs and is correlated with kelp-lyase production. The cell free extract of the Bacillus sp. JMP-A isolate showed the highest activities of CM-cellulase, α-cellulase, laminarinase and kelp-lyase, which were 22.76, 27.10, 66.59 and 64.36 U/mg, respectively. Meanwhile, the amount of sugars released was higher during the saccharification of kelp by dialyzed intracellular enzymes of the bacterial isolates than when dialyzed extracellular enzyme was used. Experimental results of dialyzed enzymatic saccharification of the kelp demonstrated that use of partially purified enzymes was effective for glucose production.     

Air gap membrane distillation on the different types of membrane

Seawater desalination through the air gap membrane distillation (AGMD) process shows merit for its ambient operational conditions and low energy consumption. In this paper nine types of commercially available membranes were characterized to understand the membranes more comprehensively. The density, porosity, mean pore radius, liquid entry pressure (LEP), and contact angle (CA) of the membranes were determined. AGMD experiments were performed for the membranes to investigate the membrane difference on permeation flux and salt rejection. The effects of operating parameters such as temperature, flow rate, and NaCl concentration were studied. The 0.22 μm pore size PTFE membrane showed excellent performance for its higher permeability and higher hydrophobicity than other membranes. The mass transfer coefficients for three types of PTFE membranes were calculated from the results of the experiments.     

Metal catalyst residues in carbon nanotubes decrease the thermal stability of carbon nanotube/silicone composites

An anomalous decrease in the thermal stability of silicone was observed when carbon nanotubes (CNTs) were added as fillers. The decreased thermal stability is found to result from the residues of cobalt nanoparticles in CNTs, whereas CNTs synthesized with other metal catalysts do not show such a phenomenon. The analysis of thermal degradation products indicates that CNT fillers do not change the mechanism of the thermal degradation of silicone but cobalt nanoparticles within CNTs may accelerate the degradation through free radical generation. Radical scavengers such as hindered amines and impurity-free CNTs, or removal of cobalt nanoparticles by acid treatment, can mitigate the accelerated thermal degradation.     

Chemical vapor deposition of highly dispersed Pt nanoparticles on multi-walled carbon nanotubes for use as fuel-cell electrodes

Fuel-cell electrode catalysts with improved electrochemical properties have been prepared by dispersing Pt nanoparticles onto carbon nanotubes (CNT) using a chemical vapor deposition (CVD) method. (Trimethyl)methylcyclopentadienyl platinum (MeCpPtMe₃) has been used as a Pt precursor in the CVD process and the CVD conditions have been optimized to disperse small Pt particles onto the CNT. Pt particles synthesized by CVD have a relatively uniform size of approximately 1 nm, which is substantially smaller than in the case of a commercial Pt/carbon black catalyst (?4.5 nm) prepared by wet impregnation. The dispersion of Pt, estimated by CO chemisorption, is also more than 14% greater than the commercial catalyst with these smaller particles. The electrochemically active surface area (ESA), measured by cyclic voltammetry (CV), and the long-time durability of the surface area of Pt/CNT prepared by CVD are higher than those of the commercial catalyst. Consequently, the single cell performance of the former catalyst is superior to that of the latter one.     

Photochemical loading of metal nanoparticles on reduced graphene oxide sheets using phosphotungstate

Well-dispersed reduced graphene oxide (r-GO) sheets loaded with metal nanoparticles were produced in dimethylformamide (DMF). The r-GO suspension was prepared through the photocatalytic reduction of graphene oxide (GO) using a phosphotungstate as a homogeneous photocatalyst under UV irradiation. Immediately after UV lamp was turned off, the injection of precursors of Ag, Au, and Pd caused the rapid nucleation because photoreduced phosphotungstates as well as electrons stored in r-GO directly reduced metal ions. Furthermore, the r-GO sheets not only provided the nucleation sites but also prohibited the metal nanoparticles from agglomeration. As a result, relatively uniform-sized metal nanoparticles were formed on the r-GO sheets. With phosphotungstates and UV light irradiation, both GO and metal ions can be reduced to form the hybrids of Ag, Au, and Pd/r-GO as a suspension in DMF or an isolated paper sheet without using any toxic reagents.     

Bulk modulus of basic sodalite, Na8[AlSiO4]6(OH)2·2H2O, a possible zeolitic precursor in coal-fly-ash-based geopolymers

Synthetic basic sodalite, Na₈[AlSiO₄]₆(OH)₂·2H₂O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample was subjected to a process similar to geopolymerization, using high concentrations of a NaOH solution at 90 °C for 24 hours. Basic sodalite was chosen as a representative analogue of the zeolite precursor existing in Na-based Class F fly ash geopolymers. To determine its bulk modulus, high-pressure synchrotron X-ray powder diffraction was applied using a diamond anvil cell (DAC) up to a pressure of 4.5 GPa. A curve-fit with a truncated third-order Birch–Murnaghan equation of state with a fixed K'_o = 4 to pressure-normalized volume data yielded the isothermal bulk modulus, K_o = 43 ± 4 GPa, indicating that basic sodalite is more compressible than sodalite, possibly due to a difference in interactions between the framework host and the guest molecules.     

Temporary Increase of PPAR-γ and Transient Expression of UCP-1 in Stromal Vascular Fraction Isolated Human Adipocyte Derived Stem Cells During Adipogenesis

In this study, cells from the stromal vascular fraction of human subcutaneous tissues were induced to differentiate toward adipose cells in vitro for 2 weeks. During adipogenic differentiation, we followed the chronological changes in their morphology with Coherent anti-Stokes Raman scattering (CARS) microscopy and checked the PPAR-γ and UCP-1 expression with RT-PCR. On day 4 after inducing adipogenic differentiation, CARS imaging showed multiple small lipid droplets (LD) distributed peripherally along the cellular membrane. PPAR-γ began to express at this time and increased until day 14 at a steady rate. On day 7, the cells appeared as brown adipocytes with numerous small LD throughout the cytoplasm, and the mRNA level of UCP-1 rose abruptly by 6- to 7-fold. After an additional 7 days, CARS imaging showed the development of a large LD, which is characteristic of white adipocytes, and the mRNA level of UCP-1 slumped significantly. These results demonstrate the possibility that ADSC pass through a brown adipocyte-like stage while differentiating into white adipocytes.     

Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition

Carbon nanotube (CNT) is an attractive material for needle-like conducting electrodes because it has high electrical conductivity and mechanical strength. However, CNTs cannot provide the desired properties in certain applications. To obtain micro- and nanoneedles having the desired properties, it is necessary to fabricate functional needles using various other materials. In this study, functional micro- and nanoneedle electrodes were fabricated using a tungsten tip and an atomic force microscope probe with a CNT needle template and electrodeposition. To prepare the conductive needle templates, a single-wall nanotube nanoneedle was attached onto the conductive tip using dielectrophoresis and surface tension. Through electrodeposition, Au, Ni, and polypyrrole were each coated successfully onto CNT nanoneedle electrodes to obtain the desired properties.     

Synthesis and biological activity of phthalimide‐based polymers containing 5‐fluorouracil

The attachment of anticancer agents to polymers is a promising approach towards reducing the toxic side‐effects and retaining the potent antitumour activity of these agents. A new tetrahydrophthalimido monomer containing 5‐fluorouracil (ETPFU) and its homopolymer and copolymers with acrylic acid (AA) and with vinyl acetate (VAc) have been synthesized and spectroscopically characterized. The ETPFU contents in poly(ETPFU‐co‐AA) and poly(ETPFU‐co‐VAc) obtained by elemental analysis were 21 mol% and 20 mol%, respectively. The average molecular weights of the polymers determined by gel permeation chromatography were as follows: M_n = 8900 g mol^?1, M_w = 13 300 g mol^?1, M_w/M_n = 1.5 for poly(ETPFU); M_n = 13 500 g mol^?1, M_w = 16 600 g mol^?1, M_w/M_n = 1.2 for poly(ETPFU‐co‐AA); M_n = 8300 g mol^?1, M_w = 11 600 g mol^?1, M_w/M_n = 1.4 poly(ETPFU‐co‐VAc). The in vitro cytotoxicity of the compounds against FM3A and U937 cancer cell lines increased in the following order: ETPFU > 5‐FU > poly(ETPFU) > poly(ETPFU‐co‐AA) > poly(ETPFU‐co‐VAc). The in vivo antitumour activities of all the polymers in Balb/C mice bearing the sarcoma 180 tumour cell line were greater than those of 5‐FU and monomer at the highest dose (800 mg kg^?1). © 2002 Society of Chemical Industry