Preparation and characteristics of ultrafine metal particles immobilized on fine polymer particles

Ultrafine metal particles immobilized on fine copolymer particles were produced by reduction of copolymer particles–metal ion complexes. Submicrometer-size copolymer particles containing nitrogen, prepared by emulsifier-free emulsion polymerization, were applied. Transmission electron microscopy (TEM) observation and X-ray diffraction analysis indicated that ultrafine noble metal particles with diameter below 10 nm were formed and uniformly immobilized on the surface of copolymer particles. © 1995 John Wiley & Sons, Inc.     

METASTABLE R-PHASE IN Fe-Cr-Mo AND Fe-Cr-W ALLOYS

The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.     

Preparation of ultrafine metal particles supported on alumina by pyrolysis of polymer complex/alumina composites

Ultrafine metal particles supported on alumina were prepared by pyrolysis of poly(vinylferrocene) (Poly(VFc))/alumina or sodium polyacrylate-Pd(II) (Poly(AANa)-Pd(II))/alumina precursors at 800 ～ 1200°C. α-Fe particles produced on k-Al₂O₃ was obtained by pyrolysis of the mixture of Poly(VFc)/alumina(5/5) at 1000°C. Crystalline Pd supported on alumina was also obtained from Poly(AANa)-Pd(II)/alumina precursor. The size of metal particles formed increased with increasing mixing ratio of polymer complex with alumina. © 1994 John Wiley & Sons, Inc.     

Load Tests of Piled Raft Models with Different Pile Head Connection Conditions and Their Analyses

A series of experimental and analytical studies on the behaviours of model pile groups and model piled rafts in dry sand subjected to static vertical loading and static cyclic horizontal loading were carried out in order to investigate the influence of various pile head connection conditions between the raft and the piles on the behaviours of the foundations models and to examine the applicability of an simplified analytical method to simulate the load tests. In the load tests, the behaviours of the model foundations were investigated in detail, with particular focus on cyclic horizontal loading, and behaviour such as horizontal stiffness and the rotation of the foundation, the load proportions between the raft and the piles, and the bending moments and shear forces generated in the piles. A simplified three-dimensional deformation analysis method was used to simulate the experiments.     

The Role of Momilactones in Rice Allelopathy

Large field screening programs and laboratory experiments in many countries have indicated that rice is allelopathic and releases allelochemical(s) into its environment. A number of compounds, such as phenolic acids, fatty acids, phenylalkanoic acids, hydroxamic acids, terpenes, and indoles, have been identified as potential rice allelochemicals. However, the studies reviewed here demonstrate that the labdane-related diterpenoid momilactones are the most important, with momilactone B playing a particularly critical role. Rice plants secrete momilactone B from their roots into the neighboring environments over their entire life cycle at phytotoxic levels, and momilactone B seems to account for the majority of the observed rice allelopathy. In addition, genetic studies have shown that selective removal of the momilactones only from the complex mixture found in rice root exudates significantly reduces allelopathy, demonstrating that these serve as allelochemicals, the importance of which is reflected in the presence of a dedicated momilactone biosynthetic gene cluster in the rice genome.     

Oviposition stimulants for the tropical swallowtail butterfly,Papilio polytes,feeding on a rutaceous plant,Toddalia asiatica

In nature, Papilio polytes utilizes a limited range of rutaceous plants as hosts. We isolated and identified oviposition stimulants for the butterfly from the foliage of its primary host plant Toddalia asiatica. Females readily deposited eggs in response to a methanolic extract of the plant. Partition of the extract with organic solvents revealed that chemicals responsible for eliciting egg-laying resided in a water-soluble fraction. Further bioassay-guided fractionation of the active fraction by column chromatography, preparative TLC, and HPLC led to the isolation of two oviposition stimulants. One was isolated from an amphoteric fraction and identified as trans-4-hydroxy-N-methyl-L-proline [(–)-(2S,4R)-4-hydroxy-1-methyl pyrrolidine-2-carboxylic acid; HMP]. The other, isolated from an acidic fraction, was identified as 2-C-methyl-D-erythronic acid [(–)-(2R,3R)-2-methyl-2,3,4-trihydroxybutanoic acid; MEA]. HMP alone evoked significant oviposition-stimulatory activity, although this was much lower than that of the original water-soluble fraction. MEA, on the other hand, alone did not elicit positive responses from females. However, HMP, when assayed in combination with MEA, markedly enhanced the female response, and the mixture was as active in stimulating oviposition as were the original water-soluble fraction and the plant foliage. We conclude that HMP is a substance crucial for host recognition by females, while MEA is a synergistic stimulant involved in host recognition and/or preference.     

Simple preparation of TiO2 particles dispersed activated carbons and their photo-sterilization activity

We report a simple preparation method for TiO₂ particles dispersed activated carbons and their photo-sterilization activity for E. coli and B. subtilis. The TiO₂ particles dispersed activated carbons were readily prepared by steam activation of pitch containing titanium isopropoxide Ti(OiPr)₄ or titanium acetylacetonate TiO(acac)₃. The resulting activated carbons have high BET surface area and fine TiO₂ particles are uniformly dispersed. The photo-sterilization activities for E. coli and B. subtilis were estimated by the sterilization activity for bacteria spores by irradiation of black light to the solutions containing activated carbons. The obtained activated carbons exhibited high photo-sterilization activity for E. coli and B. subtilis with short irradiation time of 15 min.     

Phase transformation and precipitation hardening behavior of Cr and Fe in BS40CrFeSn alloy

Phase transformation and precipitation hardening behavior of the water atomized copper alloy powder was studied by aging treatment, to develop high strength Cu–40Zn–X (X: Cr, Fe, Sn) alloys by powder metallurgy process. Super-saturated solid solution elements of Cr and Fe are formed in the brass matrix, and single β phase was retained in the raw powder after water atomization. Solid solubility of Cr and Fe decreased with increase of aging temperature, and phase transformation evolved from single β phase to α + β duplex phase structure after aged at the elevated temperature of 773 K and over. It was clarified that Cr showed higher precipitation potential than Fe in the brass matrix. The hardness depended strongly upon solid solubility of Cr and Fe, and upon phase transformation.     

Training effect on damping capacity in Fe–20 mass% Mn binary alloy

Two-dimensional finite element analysis together with stream function and neural network models are employed to determine thermo-mechanical behavior during hot strip rolling of AA5083. An appropriate velocity field and stream function is first determined using the rule of volume constancy and upper bound theorem and then temperature field within the metal is predicted by means of a two-dimensional conduction–convection model. In order to consider the effect of flow stress and its dependence on temperature, strain and strain rate, a neural network model is also employed in the analysis. Based on the performed tensile tests, two different neural network models are constructed one for smooth yielding and the other one for the serrated flow. Then, the ANN models are coupled with the thermo-mechanical analysis. In the next step, by combination of the predicted temperature, strain and strain rates fields and the experimental data achieved from the tensile tests, the occurence of dynamic strain ageing during hot rolling is predicted. The model predictions are then compared with the experimental data and good agreement is observed between the two sets of results that shows the validity of the proposed model.