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991.
Mass transfer coefficients between particles and liquids in a slurry bubble column and a three-phase fluidized bed containing small size particles were obtained with two mass transfer systems: (1) K+ –Na+ ion-exchange in cation-exchange resin bead beds, including anion-exchange resin beads as inert particles; (2) zinc dissolution by HCl in zinc-plated glass bead beds, and in beds of non-plated glass beads. Operating parameters were gas velocity, liquid velocity, particle diameter, and particle concentration. The dependence of mass transfer coefficients on these parameters is discussed from the viewpoint of the energy supplied into the systems. Correlations of the experimental data using dimensionless groups are compared to previous correlations. 相似文献
992.
The setup and deposition conditions of electrode arrangement and pressure have been studied to synthesize diamond films at high growth rate on wide area efficiently by arc discharge plasma jet chemical vapor deposition. An apparatus has been used in which four plasma torches, one is used for cathode and the others for divided anodes, are arranged and the positions of these torches are changeable. Growth rate, deposition area and thickness of diamond films have increased with changing the electrode arrangements without improvement of thickness variation. Maximum growth rate of our apparatus has occurred at the pressure of 6.7 kPa and diamond films that have less variations of quality and surface roughness have been synthesized at lower pressure during deposition. Moreover, a high conversion rate, which is the ratio of carbon atoms that form diamond in supplied methane gas, of 16% has been obtained at the pressure of 6.7 kPa and methane concentration of 2%. 相似文献
993.
Miscibility between acrylic copolymers and tackifier resins are investigated in terms of phase diagrams, and the probe tack of the blends are measured as a function of both temperature and rate of separation in order to obtain the master curves. It is found that the probe tack of the pressure sensitive adhesives are closely related to the miscibility between the components. The master curves of the miscible blends shift along the X(rate)-axis according to the change of Tg of the bulk materials with a gradual variation of the peak heights. However, those of the immiscible blends will not shift along the X(rate)-axis, but the magnitude will decrease with increase of a dispersed phase. 相似文献
994.
l-3,4-Dihydroxyphenylalanine (l-dopa) is one of the few allelochemicals in which the phytotoxic action mechanism has been studied. Excess exogenous l-dopa suppresses root elongation in some plant species, and the inhibitory action is species-selective. The main factor of
phytotoxicity of l-dopa is considered to be oxidative damage by reactive oxygen species (ROS) and/or free radical species (FRS). This study
was performed to elucidate the mechanism of species-selective phytotoxicity. The involvement of ROS/FRS and polyphenol oxidase
(PPO) in species-selective phytotoxicity was examined with barnyardgrass (Echinochloa crus-galli L.) and lettuce (Lactuca sativa L.), tolerant and susceptible species, respectively. Lipid peroxidation and melanin accumulation correlated with growth inhibition
by L-dopa. Antioxidants, ascorbic acid and α-tocopherol, decreased lipid peroxidation and melanin accumulation and rescued
lettuce root from growth inhibition. The oxidation of L-dopa by PPO was much greater in lettuce than in barnyardgrass. From
these results, the phytotoxicity of L-dopa is considered due to the oxidative damage caused by ROS/FRS generated from the
melanin synthesis pathway. PPO activity might be involved in the mechanism of species-selective phytotoxicity between barnyardgrass
and lettuce. 相似文献
995.
996.
We have evaluated the optical properties of close‐packed and non close‐packed colloidal crystalline arrays made of hollow polystyrene spheres. Close‐packed colloidal crystalline arrays were fabricated by simple evaporation of dispersions, whereas nonclose‐packed colloidal crystalline arrays were fabricated by exploiting electrostatic interactions between the spheres in aqueous dispersion. Optical properties of the arrays were estimated from angle‐resolved reflection spectra. The Bragg diffraction peak of the colloidal crystalline array made of hollow spheres was of shorter wavelength than in the case of solid spheres, not only for the close‐packed array but also for the nonclose‐packed array. These shifts were caused by a decrease in the effective refractive index neff with decreasing particle refractive index. We have found that this relationship could be explained by the simple equation neff = nparticle?+ nsolvent (1 ? ?), where ? is the volume fraction of the particles, for both close‐packed and non close‐packed arrays. The current work suggests new possibilities for the creation of advanced colloidal crystals. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2364–2368, 2007 相似文献
997.
An investigation was undertaken on the application of dilute chitosan solutions gelled by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semidilute chitosan solutions. The viscosity of the chitosan solutions increased highly by the tyrosinase‐catalyzed reaction and the subsequent reactions between o‐quinone compounds and chitosan. These highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and held them in water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. The increase in the amino group concentration of the chitosan solutions and the molecular mass of the chitosan used effectively led to the increase in adhesive strength of the glass slides. In addition, in the case where the chitosan solution was gelled by the enzymatic reaction with dopamine in the presence of poly(ethylene glycol), adhesive strength sharply increased at shorter reaction times concomitantly with the increase in the viscosity of the chitosan solutions because the tyrosinase activity effectively was retained by poly(ethylene glycol). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1818–1827, 2007 相似文献
998.
Kasashima Y Nishida T Fujimoto H Mino T Sakamoto M Fujita T 《Journal of oleo science》2007,56(4):189-193
Intramolecular cyclization of 3-hydroxy acids was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in the heterogeneous system. Lactones were obtained by intramolecular cyclization of 3-hydroxy acids. Propella lactone (11-oxatricyclo[4.4.3.0(1,6)]tridecan-12-one) was conveniently synthesized from 3-hydroxy acid ((6-hydroxyspiro[4.5]dec-6-yl)acetic acid) in 88% yield with carbon skeleton rearrangement. Spiro lactones and bicyclic lactones were also obtained from the corresponding 3-hydroxy acids in yields of over 75%. The most suitable reaction conditions were a temperature of 80 degrees C, a molar ratio of 3-hydroxy acid:iodine = 1:0.1, and a time period of 6 h. In addition, terpenic lactones were efficiently synthesized from the corresponding 3-hydroxy acids, derived from (+)-camphor, (-)-fencone, and (-)-pulegone, with skeleton rearrangement. The yield of the solvent-free reaction was as high as that of the corresponding reaction in solution. 相似文献
999.
Fluoroalkyl end-capped acrylic acid oligomers/fullerenes nanocomposites reacted smoothly with tetraethoxysilane (TEOS) and silica nanoparticles under alkaline conditions to give fluoroalkyl end-capped oligomers/silica composites-encapsulated fullerenes. Interestingly, these isolated fluorinated composites were found to afford nanometer size-controlled colloidal particles with a good dispersibility in a variety of organic solvents including water. More interestingly, these fluorinated silica nanocomposites-encapsulated fullerenes were applied to a new type of surface modification agent, and these nanocomposites were able to disperse well above the poly(methyl methacrylate) films to exhibit not only surface active property imparted by fluorine but also a unique characteristic related to fullerenes in the nanocomposites on the surface, effectively. 相似文献
1000.
Chengzhou Li Yusuke Imai Yoshio Adachi Hiroshi Yamada Keiko Nishikubo Chao-Nan Xu 《Journal of the American Ceramic Society》2007,90(7):2273-2275
An organic aqueous solution of metal acetylacetonate precursors was subjected to spray pyrolysis in order to fabricate SrAl2 O4 :Eu (SAO) nanoparticles. Non-agglomerated luminescent SAO nanoparticles, having a spherical shape with a size of 10–30 nm, were achieved in a single step, while only submicrometer-sized SAO particles were obtained from the conventional ultrasonic pyrolysis of the metal nitrates. Without any post-annealing process, the as-prepared SAO nanoparticles were observed to exhibit a strong photoluminescence, which is comparable with that of the submicrometer-sized SAO particles. A mechanism for the formation of the nanoparticles is also discussed. 相似文献