Hydrothermal syntheses, structures and magnetic properties of coordination frameworks of divalent transition metals

The hydrothermal syntheses, single-crystal X-ray structures and magnetic properties of [Co(C₄O₄)(H₂O)₂] (1), [Co₃(OH)₂(C₄O₄)₂] · 3H₂O (2) and [Fe(OH)₂(C₄O₄)] (3) are described. Pale yellow cubes of 1 and brown red crystals of 2 were obtained from the reaction of Co(OH)₂ and squaric acid at 200 °C. Brown needle of 3 were obtained similarly from Fe(SO₄) · 7H₂O, squaric acid and NaOH. 1 consists of a cubic sodalite arrangement with empty cavities where the Co atoms are connected by μ₄-squarate and two trans-water molecules each, while 2 and 3 contain metal-hydroxide double-chains of edge-sharing octahedral, brucite-type for 2 and goethite for 3, connected by μ₆-squarate. 2 contains water molecules in the channels which can be removed and re-inserted repeatedly without loss of crystallinity. All three compounds possess 3D frameworks made up of coordination and hydrogen bonds. 1 behaves as a paramagnet while 2 and 3 are antiferromagnets and 2 transforms to a ferromagnet reversibly upon dehydration and rehydration. The structures of two one-dimensional polymers employing 2,5-pyridinedicarboxylate, [Co₂(H₂O)₆(2,5-pydc)₂] · 2H₂O (4) and Cu(2,5-pydc)₂ (5), are also reported.     

A Link between Spin Fluctuation and Fermi Surface in the High T c Cuprates — A Description within the Single-band Hubbard Model

A link between the spin structure and the shape of the Fermi surface is sys-tematically explored for the single-band repulsive Hubbard model with the fluctuation exchange (FLEX) approximation. We show that (i) the ex-perimentally observed band filling dependence of the peak position of the spin structure in the high T _C cuprates can be understood for both the hole-doped (YBCO, Bi2212) and electron-doped (NCCO) regimes. (ii) For La _2?xSr_xCuO₄, the spin-structure incommensurability and the ARPES re-sult for the Fermi surface can be understood simultaneously if the second nearest neighbor hopping decreases with the hole doping.     

Graft copolymerization of styrene onto poly(p-nitrophenyl acrylate) by chain transfer reaction

Styrene (St) was polymerized in the presence of poly(p-nitrophenyl acrylate) (PNPA) with azobisisobutyronitrile as an initiator to prepare graft copolymers through the chain transfer reaction of growing polystyrene (PSt) radicals to the aromatic nitro groups on PNPA. The maximum number of branches attained was 16.4 (P _n of PNPA was 1780), which corresponds to 108 monomer units per PSt branch. This is far less than the value of 43, previously obtained for poly(vinyl p-nitrobenzoate) as a trunk polymer. Therefore, several model compounds for trunk polymers were prepared, and the chain transfer constants of PSt radicals to these model compounds were determined. As a result of the Hammett plot, it is concluded that higher electron attracting property of the substituents increases the reactivity of nitro groups to the growing PSt radicals, resulting in more highly branched graft copolymers.     

Determination of newly installed feeder route considering use of existing feeder

In planning a distribution system for an urban area, when a feeder is newly installed, the route of the feeder must be determined among many candidates, considering investment cost and constraints. However, it is difficult for planners to find the optimal route of the newly installed feeder, because too many candidate routes exist which can be constructed along roads in the service area of the power company, and it must be considered whether the end part of an existing feeder can be used as a part of a newly installed feeder within specified loaded value. In this paper, in order to support planners' decision making in selecting an optimal route for newly installed feeders, the authors have formulated the problem mathematically, and propose a new solution algorithm to find the optimal route by the Dijkstra method. Through numerical examples, the authors demonstrate the validity of the proposed method. © 1999 Scripta Technica, Electr Eng Jpn, 129(3): 40–50, 1999     

Economical load dispatching method considering power plant dynamics

To reduce boiler fuel cost, a new ELD (economic load dispatching) method based on a dynamic fuel cost model, which is more accurate than the conventional quadratic model, is proposed. First, an ARMA (autoregressive moving average) model, which is constant‐coefficient linear digital filter, is applied in order to supplement the quadratic model. We call this the supplemented model ARMA‐model‐supplemented quadratic model. By using this model, the model deviations from actual data have been reduced. Second, based on the ARMA‐model‐supplemented quadratic model, we formulated the ELD problem as a quadratic programming problem, where the objective function is the summation of all units' fuel costs over multiple time points and the constraints are the supply–demand balances, the upper and lower generation limits, and the ramp rate limits. This problem can be solved by the standard quadratic programming technique. We call this new ELD method BEST (boiler‐dynamics‐based economical load dispatching) method. Then, in order to make the problem size smaller, we propose a scheme to ignore all time points except for those corresponding to the peak, the bottom, and the steepest point on the forecasted load curve. We call this scheme the sample scheme. Finally, the BEST method with the sample scheme is evaluated by numerical simulations on the Kansai Electric Power Co. system and it is shown that the proposed method can reduce the calculation time without compromising the fuel cost. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 39–46, 1999     

Improving fire retardancy of fast growing wood by coating with fire retardant and surface densification

Fire retardant fast-growing wood product was developed by coating with fire retardant and densifying the surface of wood. Trimethylol melamineformaldehyde resin mixed with phosphoric acid was coated on the wood surface, preheated and followed by hot pressing. Effects of the amount of coating, preheating temperature, and densifying ratio on the fire retardancy of sugi (Cryptomeria japonica D. Don) wood, and pressing temperature and pressing time on that of albizia (Paraserianthes falcataria Becker) wood were discussed. Bending strength, creep performance under fire and fire retardancy were evaluated. The results showed that the treatments improved the fire retardancy of woods without reduction in the bending strength. © 1998 John Wiley & Sons, Ltd.     

Quasi‐static and chaotic characteristics of the natural convection field in a vertical slot

In this paper, the time‐dependent characteristics of natural convection in a vertical slot with hot and cold side walls were experimentally examined. In the experiment, the test liquid was a glycerine–water mixture (80 wt%) and the Prandtl number in the center of the slot was held constant at 295. On the other hand, the Grashof number was varied in the range between 370 and 3.06 × 10³. As a result, it was revealed that low‐pass filtering for the time evolution data of temperature made it possible to compute the largest Lyapunov exponents precisely. Secondary flow cells are observed in both chaotic and nonchaotic regions. Moreover, the secondary flow cells appeared in regions where the power spectrum of temperature fluctuation was regarded as significant and where the autocorrelation function decreased rapidly with time. © 2000 Scripta Technica, Heat Trans Asian Res, 30(1): 40–53, 2001     

Suppression of Problematic Compound Oligomerization by Cosolubilization of Nondetergent Sulfobetaines

Numerous small organic compounds exist in equilibrium among monomers, soluble oligomers, and insoluble aggregates in aqueous solution. Compound aggregation is a major reason for false positives in drug screening, and even soluble oligomers can interfere with structural and biochemical analyses. However, an efficient way to manage the equilibrium of aggregation‐prone compounds, especially those involved with soluble oligomers, has not been established. In this study, solution NMR spectroscopy was used as a suitable technique to detect compound oligomers in equilibrium, and it was demonstrated that cosolubilization of nondetergent sulfobetaines (NDSBs) can largely suppress compound oligomerization and aggregation by shifting the equilibrium toward the monomers. The rotational correlation time was obtained from the ratio of the selective and nonselective longitudinal NMR relaxation times, which directly and quantitatively reflected the apparent sizes of the compounds in the equilibrium. The rotational correlation time of the aggregation‐prone compound SKF86002 (1 mM ) was substantially reduced from 0.31 to 0.23 ns by cosolubilization of 100 mM NDSB195. NDSB cosolubilization allowed us to perform successful structural and biochemical experiments with substantially fewer artifacts, which represents a strategy to directly resolve the problematic oligomerization and aggregation of compounds.     

Simultaneous quantitation of ceramides and 1,2-diacylglycerol in tissues by latroscan thin-layer chromatography-flame-ionization detection

Ceramides and 1,2-diacylglycerol have been demonstrated in intracellular signaling pathways. A method of simultaneous mass determination of ceramides and 1,2-diacylglycerol in tissues was developed using the latroscan which combines thin layer chromatography and flame ionization detection (TLC/FID) techniques. Because of relatively low amounts of these components in tissues, the fraction of nonpolar lipids, which included ceramides and glycerides, was eluted with chloroform/acetone mixture (3∶1, vol/vol) through a silicic acid column to eliminate the polar phospholipids. Development of Chromarods was carried out using three solvent systems in a four-step development technique. The relationship of the peak area ratio to weight ratio compared with cholesteryl acetate added as an internal standard was linear. The amount of ceramides increased with incubation of rat heart homogenate and human erythrocyte membranes in the presence of sphingomyelinase (E.C. 3.1.4.12). The latroscan TLC/FID system provided a quick and reliable assessment of ceramides and 1,2-diacylglycerol.