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31.
A total of 87 market fish samples representing five types of fish were evaluated for the presence of Aeromonas spp. Of the samples examined, 69%, 55%, 11.5% and 2.3% harbored Aeromonas spp., A. veronii biovar sobria, A. hydrophila and A. caviae, respectively. The 60 isolated Aeromonas spp. strains were further examined for hemolytic activity, resistance to antimicrobial agents and presence of plasmids. Hemolytic activity varied widely among the isolated strains. Though all the isolates demonstrated resistance to three or more of the antibiotics tested, all were susceptible to ceptazidime. Thirty-four (56.7%) of the sixty isolates harbored plasmids, with sizes ranging from 2.3 to 15.7 kb. These results indicate that hemolytic, multiple antibiotic resistant and genetically diverse aeromonads are easily recovered from fish in this region.  相似文献   
32.
Multiple quantum spin counting is shown to yield an upper limit ofn = 6 for strongly bound, rigid intermediates C m H n in the reaction of ethylene over Ru/SiO2. The results eliminate the possibility of major components of such intermediates being polymer-like coke precursers. A precurser to 2-butene is one possible intermediate.  相似文献   
33.
Incorporation of urea into puddled rice soils is known to reduce ammoniacal-N buildup in floodwater and the subsequent loss of N as ammonia. Little is known, however, about seasonal and temperature effects on the effectiveness of basal urea incorporation in puddled soils. A field experiment was conducted in northern Vietnam on an Aquic Ustifluvent in the spring season (February to June) and summer season (July to November) to determine the effect of the presence of floodwater and method of fertilizer incorporation on floodwater ammoniacal-N, floodwater urea-N, andpNH3 following urea application. During the 4 d following basal urea application, floodwater temperature at 1400 h was 7 to 15°C higher in summer (July) than that in spring (February), and floodwater pH at 1400 h was 0.5 to 1.0 higher in summer than that in spring. ThepNH3 was much higher in summer than that in spring, suggesting a high potential for ammonia volatilization in summer. The movement of transplanters through the field did not reducepNH3, irrespective of floodwater depth (0 or 5 cm) and season. Harrowing and subsequent transplanter movement partially reducedpNH3 in the summer;pNH3 reduction, however, was greater when floodwater depth was 0 rather than 5 cm during harrowing and transplanting. This partial reduction ofpNH3 in summer did not result in a corresponding increase in rice yield, presumably because N losses were only slightly reduced and because yield was constrained by additional factors, such as the adverse climate. In spring, the removal of floodwater before urea application and incorporation increased grain yield by 0.2 Mg ha–1, even thoughpNH3 was consistently low and was not reduced by urea incorporation. This result suggests that water management and tillage during basal urea application may influence rice growth and yield in ways other than reduced N loss.  相似文献   
34.
    
Geopolymer ceramics undergo a series of thermal phase transitions, progressing from an amorphous geopolymer gel to a crystalline phase, and eventually to an amorphous glass phase as the temperature increases. However, there is a lack of mechanism understanding regarding to the crystallization process and the subsequent thermal degradation. Here, we fundamentally investigated the kinetics of nepheline formation in Na-based geopolymer systems and its thermal stability up to 1400°C. Nepheline crystallization is controlled by bulk nucleation and three-dimensional crystal growth based on the Avrami factor of 4.64, where the activation energy of nepheline formation is 350.59 kJ/mol. High thermal stability of geopolymer ceramics is achieved due to the appearance of nepheline up to 1400°C with the Si/Al ratio ranging from 1.40 to 1.94, while melting and amorphous structure are formed above a higher Si/Al ratio of 2.22. The nature of sintering for geopolymer ceramics consists of shrinkage, expansion and shrinkage corresponding to dehydroxylation, crystallization, and densification, leading to a thermal shrinkage of 21% at 1400°C.  相似文献   
35.
The use of laser Raman spectroscopy in the investigation of interactions in α–bromoacrylamide reactive dye–wool fibre systems has been established. The spectra obtained (in particular using C. I. Reactive Red 84) provide some evidence to support the proposal that the dye reacts via addition at the double bond of the reactive group, followed by ring closure through nucleophilic substitution. Furthermore, preliminary studies of the effect of the commercial levelling assistant Albegal B on the aqueous dye environment have been made using C. I. Reactive Yellow 39. The results show that, whilst the primary interaction between the dye and auxiliary may be via the water–solubilising sulphonate groups of the dye, hydrophobic interactions are also important.  相似文献   
36.
The feasibility of employing a NiO-yttria stabilized zirconia (YSZ) nano-powder slurry spin coating (NSC) to fabricate a thin film (≤ 1 μm) electrolyte solid oxide fuel cell (TF-SOFC) on a relatively rough surface of the support is investigated in this study. The NiO-YSZ nano-powder with ~ 200 nm particle size was synthesized by a single-step glycine nitrate process and super-apex milling. Through varying the NiO-YSZ nano-powder slurry condition by changing polymeric additives, a leveled surface of the spin coated layer which enabled to overcome the surface roughness of the bulk ceramic processed anode substrate was obtained. On the NSC layer, TF-SOFC components with flat profiles could be fabricated using pulsed laser deposition. A stable open circuit voltage of 1.04 V was obtained with these thin film components on an anode support with a rough surface.  相似文献   
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39.
The novel Fe/Nb co-doped SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) perovskite oxides were synthesized by the solid-state method. Structural and chemical stability of the SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) oxides were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffraction (XRD). The results demonstrated that the structural and chemical stability of the Fe/Nb co-doped SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) is improved significantly. The oxygen sorption properties of the SrCo1 ? 2x(Fe,Nb)xO3 ? δ (x = 0.05, 0.10) oxides were investigated between 300–900 °C in air, and the high oxygen sorption capacity of 11.5 and 10.3 mL O2 (STP)/g oxide, respectively, are obtained.  相似文献   
40.
The effect of injection molding conditions and reactive compatibilization on the morphology of maleic anhydryde‐modified poly(phenylene oxide)/polyamide‐6 blends was investigated. The injection flow rate primarily influenced the position of the subskin layer, and the injection temperature affected the aspect ratio of the dispersed phase. A reduction of the sue of the dispersed phase occured during the converging flow in the barrel‐to‐sprue zone. The reactive compatibilization reduced the flow induced deformation, the coalescence and the breakup of particles and improved the dispersion of the minor phase.  相似文献   
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