Preparation of pyrochlores. A1−xHxTaO3·nH2O (A=Na,K)

Pyrochlores of A_1?xH_xTaO₃·nH₂O (A=Na,K) were prepared under the hydrothermal conditions. The values of x for these compounds were increased from 0.3 to 0.5 for A=Na and from 0.2 to 0.5 for A=K by treatment with the distilled water. The compounds with x<0.5 were decomposed to a mixture of NaTaO₃ and Na₂Ta₄O₁₁ for A=Na, or to a mixture of KTaO₃ and a tetragonal tungsten bronze phase, and those with x=0.5 to a single phase of A₂Ta₄O₁₁ at elevated temperatures. Below the decomposition temperatures, defect pyrochlores with oxygen vacancies, $\text{A}{}_{\mathrm{<mtext>1?</mtext><mtext>x</mtext>}}\text{TaO}{}_{\mathrm{<mtext>3?</mtext><mtext>x</mtext><mtext>2</mtext>}}$, were produced. They were hygroscopic, and in the case of A=K and x=0.5 the original phase was recovered by leaving in air for several hours.     

Cooperative behavior of various agents in dynamic environment

The multi-agent model is a model in which agents with limited ability cooperate each other to accomplish a goal. In this paper, we introduce a multi-agent model in which agents are created to imitate real ants. There are two different type of agents, each type of which has a particular task. We designed agents to communicate each other by using pheromone considering noise. On this model, we observed cooperative behavior of agents and evaluated conditions to make an order of behavior in the model.     

Paraneoplastic neurologic syndromes. 2. Lambert-Eaton myasthenic syndrome. 1) The molecular structure of calcium channel and immunology

The effect of divalent cations on the inactivation of Escherichia coli by high hydrostatic pressure was investigated. The presence of 0.5 mmol l-1 of CaCl2, MgCl2, MnCl2 and FeCl2 reduced pressure inactivation of E. coli MG1655, while 0.5 mmol l-1 of ZnCl2, NiCl2, CuCl2 and CoCl2 increased inactivation. Baroprotection by Ca2+ was found to be dose-dependent up to at least 80 mmol l-1 and was studied in more detail in terms of inactivation kinetics. Logarithmic survivor plots against time deviated from first order kinetics, suggesting that MG1655 cultures were heterogeneous with regard to pressure resistance. All cultures were shown to contain a small proportion of cells that were only slowly inactivated. Addition of Ca2+ increased the proportion of these tolerant cells in the cultures up to 1000-fold at 80 mmol l-1, but did not affect their inactivation rate. The addition of EDTA resulted in the opposite effect, lowering the proportion of pressure-tolerant cells in the cultures. Three pressure-resistant mutants of E. coli MG1655 were found to be more resistant to EDTA under pressure compared with MG1655, and were unaffected by Ca2+ under pressure. In addition, these mutants had a 30-40% lower Ca2+ content than MG1655. Based on these results, it is postulated that pressure killing of E. coli MG1655 is mediated primarily by the destabilization of Ca(2+)-binding components, and that the mutations underlying pressure resistance have resulted in pressure-stable targets with reduced Ca(2+)-binding affinity.     

Ion exchange of intercalation compounds from WOP2O7 and intercalation ofn-alkylamines

Ion exchange of Na _x WOP₂O₇ ·nH₂O (x 1.4) prepared from WOP₂O₇ was attempted, using alkaline and alkaline earth ions. The degree of exchange was observed to be >50% at 90° C except for Mg²⁺. The basal spacing of ion-exchanged materials for the hydrated phase were dependent on the number of water molecules in the interlayer spaces, while those for the dehydrated phase increased with the size of ions in the interlayer spaces. The network of water molecules linked by the hydrogen bond in the interlayer spaces seems to determine the basal spacing. By the ion-exchange reaction,n-alkylammonium ions were intercalated into the interlayer spaces of Na _x WOP₂O₇ ·nH₂O (x 1.4) and Sn _x H _y WOP₂O₇ ·nH₂O (2x +y 0.5). In spite of the difference in the charge density of the host layer, a similar arrangement of alkyl chains in the interlayer spaces resulted, and neutral amines were considered to be intercalated as well as ammonium ions. Direct reaction ofn-alkylamine with WOP₂O₇ produced an intercalation compound without reduction of tungsten. The arrangement of the amines in the interlayer spaces is similar to that supposed to the ion-exchanged derivatives when heated at 140° Cin vacuo.     

New catalytic functions of Pd–Zn, Pd–Ga, Pd–In, Pt–Zn, Pt–Ga and Pt–In alloys in the conversions of methanol

Pd and Pt supported on ZnO, Ga₂O₃ and In₂O₃ exhibit high catalytic performance for the steam reforming of methanol, CH₃OH+H₂OCO₂+3HH₂, and the dehydrogenation of methanol to HCOOCH₃, 2CH₃OHHCOOCH₃+2HH₂. Combined results with temperature-programmed reduction (TPR) and XRD method revealed that Pd–Zn, Pd–Ga, Pd–In, Pt–Zn, Pt–Ga and Pt–In alloys were produced upon reduction. Over the catalysts having the alloy phase, the reactions proceeded selectively, whereas the catalysts having metallic phase exhibited poor selectivities.     

Abnormal metabolism of polyunsaturated fatty acids and phospholipids in diabetic glomeruli

Studies were done on changes in phospholipid content and fatty acid composition of phospholipids and on the role of the acylation pathway in synthesis of phospholipids in the development of abnormal fatty acid composition in the glomeruli of rats 2 and 10 mo after induction of diabetes with streptozotocin. The proportions of individual phospholipids in the glomeruli of rats were not changed 2 mo after induction of diabetes, but the proportion of phosphatidylethanolamine (PE) decreased and that of sphingomyelin increased 10 mo after induction of diabetes. In contrast, in liver the proportion of PE was increased and that of phosphatidylcholine was decreased. These results showed that changes of individual phospholipids in glomeruli were time-dependent and tissue-specific. Two mo after induction of diabetes, the main change in the phospholipid fatty acid composition of diabetic glomeruli was a decrease in arachidonic acid (AA); the main change in serum free fatty acids (FFA) was an increase in linoleic acid (LA) and a decrease in AA. Ten mo after induction of diabetes, the main changes in the phospholipid fatty acid composition of glomeruli were an increase in LA and a decrease in AA; the main change of the serum FFA composition was a decrease in AA. Thus, the fatty acid composition of glomerular phospholipids was not directly correlated to that of the serum in diabetic rats. Acyl-CoA synthetase and acyltransferase activities increased in diabetic glomeruli with either AA or LA as substrate, but activity toward LA increased more at 2 mo after induction of diabetes. Acyl-CoA synthetase activity increased in diabetic glomeruli with LA as substrate, but that did not change with AA as substrate at 10 mo after induction of diabetes. Furthermore, acyltransferase activity decreased in diabetic glomeruli with AA as substrate, although that did not change with LA as substrate at 10 mo after induction of diabetes.     

Upper and lower critical solution temperatures in poly (ethylene glycol) solutions

Upper and lower critical solution temperatures have been determined for solutions of poly(ethylene glycol) in t-butyl acetate and water over the molecular weight range of M_η = 2.18 × 10³ to ～1020 × 10³. The phase diagram for solutions of poly(ethylene glycol) (M_η = 719 × 10³) in t-butyl acetate was expressed as the ‘hour glass’ type, while the phase diagram for solution of poly(ethylene glycol) (M_η = 2.18 × 10³ to ～2.29 × 10³) in water was expressed as the ‘closed loop’ type. The value of the pressure dependence of the lower critical solution temperature $\text{(}\text{d}\text{T}\text{d}\text{P}\text{)}{}_{\mathrm{c}}$ in the poly(ethylene glycol) (M_η = 1020 × 10³)/water system over the pressure range of 0 to ～50 atm was negligibly small and positive.     

Dispersion of SiC in Aqueous Media with Al2O3 and Y2O3 as Sintering Additives

It has been well accepted that polyethylene imine (PEI) is an effective dispersant for silicon carbide (SiC) in aqueous media. However, after the addition of sintering additives (Al₂O₃ and Y₂O₃), this dispersing effect is reduced significantly. In this work, a second dispersant, citric acid, was used to resolve this problem. It was found that citric acid could decrease the slurry viscosity (without sintering additives) and enhance the PEI adsorption on SiC particle surface. The optimal amount of citric acid required to achieve a minimum viscosity for 55 vol% SiC suspensions was equal to ∼0.87 wt% (at pH ∼6.8). With the aid of citric acid, well-stabilized SiC suspensions (containing sintering additives) were realized, which exhibited slight shear thinning rheologies. After tape casting and SPS sintering, dense SiC samples were obtained with a homogeneous fine-crystalline microstructure. Results showed that citric acid was an effective dispersant for improving the dispersion of SiC particles containing sintering additives.