Neural mechanism for a cognitive timer

To examine a possible biological mechanism for a cognitive timer, the stochastic dynamics of a network of neurons possessing two stable states ("on" and "off" states) is studied. The fraction of on neurons existing at t = 0 remains large for an extended interval, and then abruptly falls. The distribution of the lengths of the interval is scale invariant in the following sense: The ratio (k root of (mu(k))/m, with m and mu(k) being the mean and the kth central moment, respectively, is invariant under scale transformations of m and mu(k). In the special case k = 2, this gives Weber's law, a hallmark of cognitive timing.     

Confirmation of the structures of kuwanons G and H (albanins F and G) by partial synthesis

Conclusive evidence is presented supporting structures $\text{1}$ and $\text{2}$ for two natural Diels-Alder adducts isolated from mulberry and designated as kuwanon G (albanin F, moracenin B) and Kuwanon H (albanin G, Moracenin A).     

Hypothesis on the foundation of stochastic interpretations of quantum mechanics

The hypothesis that a particle exists in a cavity space in thermal equilibrium with photons and executes a Brownian motion is due to collisions with the photons leads to a realistic stochastic interpretation of quantum mechanics.     

An improved radiochemical procedure for low-level measurements of americium in environmental matrices

The chemical yield and accuracy of measurements of (241)Am at low levels in marine environmental matrices have been substantially improved by applying the extraction procedure with DDCP (dibutyl-N,N-diethylcarbamylphosphonate). The improved procedure is described, and its advantages over the conventional procedure are discussed.     

Nucleoside analogs. I. A synthesis of 1,3-dihydroxy-2-(6-substituted-9-purinyl)cyclohexane

Biologically active 1,3-dihydroxy-2-(6-substituted-9-purinyl)cyclohexanes (VI-X) were prepared by a reaction between trans-2-amino-1,3-cyclohexanediol (I) and 4,6-dichloro-5-amino-pyrimidine (II), followed by cyclization and nucleophilic substitution. Compounds VI and VII showed a weak inhibitory effect against Xanthomonas oryzae, a pathogenic bacteria of leaf blight of rice plant.     

On-line determination of trace sulfur dioxide in air by integrated microchip coupled with fluorescence detection

A microchip-based method was developed for on-line determination of trace sulfur dioxide (SO₂) in air. Gaseous SO₂, which diffused through the porous glass materials on the microchip, was absorbed into an absorption solution of triethanolamine (TEA) as sulfite ions and reacted with N-(9-acridinyl)maleimide (NAM), which was used as a fluorescent reagent. The fluorescence of NAM-sulfite in micro-fluidic channel was detected. The calibration curve of sulfite ions in the range of 1.5-30 μmol/L (SO₂ 3-60 ppbv) showed a linear relation R² = 0.995, and the relative standard deviation (R.S.D.) was 1.9% for 10 μmol/L sulfite ions in five measurements. The entire measurement procedure was achieved by the integrated microchip, and the consumption of reagents was drastically reduced. It was satisfactory to apply this method to determine on-line the SO₂ level in the air.     

General method of obtaining deuterium-labeled heterocyclic compounds using neutral D2O with heterogeneous Pd/C

A protocol of a versatile H-D exchange reaction of heterocyclic compounds catalyzed by heterogeneous Pd/C in D₂O is described. The reaction of various nitrogen-containing heterocycles with 10% Pd/C (10 wt % of the substrate) under hydrogen atmosphere in D₂O as a deuterium source at 110-180 °C for 24 h afforded the corresponding deuterated compounds with satisfactory efficiency of deuteration in moderate to excellent isolated yields. Furthermore, the Pd/C-H₂-D₂O system can be extended to the direct deuteration of biologically active compounds such as sulfamethazine, which is used as a synthetic antibacterial drug for fat stocks and would be applied as a general method for the preparation of the standard materials for the analysis of residual chemicals in foods and so on.