A new method for the synthesis of some 9-β-D-arabinofuranosylpurines by a combination of chemical and enzymatic reactions

An enzymatic transarabinosylation between 2-chlorohypoxanthine and 1-β-$\text{D}$-arabinofuranosyluracil gave 9-β-$\text{D}$-arabinofuranosyl-2-chlorohypoxanthine which was chemically converted to 9-β-$\text{D}$-arabinofuranosylguanine and its derivatives.     

Fluorination of 2-alkyl-substituted oxanes. The synthesis and purification of perfluoro(2-alkyl-substituted oxane)s

Five kinds of 2-alkyl-substituted oxanes like 2-ethyloxane, 2-n-propyloxane, 2-iso-propyloxane, 2-n-butyloxane and 2-n-amyloxane were fluorinated electrochemically to give the corresponding perfluoro(2-alkyloxane)s. The perfluoro(2-alkyloxane)s were obtained in good yields from these starting materials together with isomeric perfluoro(2-alkyloxolane)s, perfluoro(2-alkyl-5-methyloxolane)s and perfluoro(dialkyl ether)s. The purification of the perfluoro(2-alkyloxane)s which contained small amounts of isomeric perfluoro(2-alkyloxolane)s was successfully achieved by recovering the former unreacted after treating these mixture with anhydrous aluminum chloride at 150 /sR 160 °C during /sR 48 hrs in order to convert the latter into the easy-separable perfluoro(2,5,5- trichloro-2-alkyloxolane)s. Small quantities of new perfluoro(5,5-dichloroalkanoyl chloride)s were also among the chlorination products. The spectroscopic data as well as the physical properties of these new fluorination products, and perfluoro(2,5,5-trichloro-2-alkyloxolane)s and perfluoro(5,5-dichloroalkanoyl chloride)s are presented.     

Investigation of Molecular Diffusion at Block Copolymer Thin Films Using Maximum Entropy Method-Based Fluorescence Correlation Spectroscopy and Single Molecule Tracking

Fluorescence correlation spectroscopy (FCS) has been widely used to investigate molecular diffusion behavior in various samples. The use of the maximum entropy method (MEM) for FCS data analysis provides a unique means to determine multiple distinct diffusion coefficients without a priori assumption of their number. Comparison of the MEM-based FCS method (MEM-FCS) with another method will reveal its utility and advantage as an analytical tool to investigate diffusion dynamics. Herein, we measured diffusion of fluorescent probes doped into nanostructured thin films using MEM-FCS, and validated the results with single molecule tracking (SMT) data. The efficacy of the MEM code employed was first demonstrated by analyzing simulated FCS data for systems incorporating one and two diffusion modes with broadly distributed diffusion coefficients. The MEM analysis accurately afforded the number of distinct diffusion modes and their mean diffusion coefficients. These results contrasted with those obtained by fitting the simulated data to conventional two-component and anomalous diffusion models, which yielded inaccurate estimates of the diffusion coefficients. Subsequently, the MEM analysis was applied to FCS data acquired from hydrophilic dye molecules incorporated into microphase-separated polystyrene-block-poly(ethylene oxide) (PS-b-PEO) thin films characterized under a water-saturated N₂ atmosphere. The MEM analysis revealed distinct fast and slow diffusion components attributable to molecules diffusing on the film surface and inside the film, respectively. SMT studies of the same materials yielded trajectories for mobile molecules that appear to follow the curved PEO microdomains. Diffusion coefficients obtained from the SMT data were consistent with those obtained for the slow diffusion component detected by MEM-FCS. These results highlight the utility of MEM-FCS and SMT for gaining complementary information on molecular diffusion processes in heterogeneous material systems.

Graphical Abstract

     

A modified layered-step interior-point algorithm for linear programming

The layered-step interior-point algorithm was introduced by Vavasis and Ye. The algorithm accelerates the path following interior-point algorithm and its arithmetic complexity depends only on the coefficient matrixA. The main drawback of the algorithm is the use of an unknown big constant in computing the search direction and to initiate the algorithm. We propose a modified layered-step interior-point algorithm which does not use the big constant in computing the search direction. The constant is required only for initialization when a well-centered feasible solution is not available, and it is not required if an upper bound on the norm of a primal—dual optimal solution is known in advance. The complexity of the simplified algorithm is the same as that of Vavasis and Ye. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Research supported in part by ONR contract N00014-94-C-0007 and the Grant-in-Aid for Scientific Research (C) 08680478 and the Grant-in-Aid for Encouragement of Young Scientists (A) 08780227 of the Ministry of Science, Education and Culture of Japan. This research was partially done while S. Mizuno and T. Tsuchiya were visiting IBM Almaden Research Center in the summer of 1995.     

Polycrystalline silicon carbide film deposition using monomethylsilane and hydrogen chloride gases

A polycrystalline silicon carbide film is formed on a silicon surface by chemical vapor deposition using monomethylsilane gas along with hydrogen chloride gas in ambient hydrogen at atmospheric pressure. The film deposition is performed near 1000 K, at which temperature the monomethylsilane maintains a chemical bond between the silicon and carbon present in the molecular structure. The excess amount of silicon on the film surface is reduced using the hydrogen chloride gas. Although the film deposition stops within 1 min after beginning the supply of the monomethylsilane gas and hydrogen chloride gas, annealing at 1273 K in ambient hydrogen after the film deposition allows further deposition so that a thick silicon carbide film can be obtained.     

Ag precipitation and optical behavior in Na2O---B2O3 glasses

Ag particles of different sizes in the nanometer range were produced in Na₂O---B₂O₃ glasses containing Ag₂O by the melt-quenching and heat-treatment method. The quenching rate was 10³ K s⁻¹ and the heat treatment was at 738 K for 2–300 h. The precipitation was dependent on diffusion limited growth. The optical absorption of Ag particles in the glasses was measured and correlated to the distribution of particle radii. The peak energy of the surface plasmon resonance was blue shifted and the width decreased with increasing average particle radius. These results are compared with previous data on similar systems.     

Synthesis of a porphyrin-fullerene pinwheel

We disclose the synthesis of a porphyrin-fullerene pinwheel that was subsequently observed by scanning tunneling microscopy. The molecule was designed to further our understanding of fullerene-surface interactions, directional control, and surface-rolling versus pivoting capabilities of this class of nanomachines. The inner porphyrin provides the square planar configuration that might lead to realization of the pinwheel spiraling motion on surfaces.     

Correlated equilibrium and concave games

This paper shows that if a game satisfies the sufficient condition for the existence and uniqueness of a pure-strategy Nash equilibrium provided by Rosen (Econometrica 33:520, 1965), then the game has a unique correlated equilibrium, which places probability one on the unique pure-strategy Nash equilibrium. In addition, it shows that a weaker condition suffices for the uniqueness of a correlated equilibrium. The condition generalizes the sufficient condition for the uniqueness of a correlated equilibrium provided by Neyman (Int J Game Theory 26:223, 1997) for a potential game with a strictly concave potential function. I thank the editor, an associate editor, and an anonymous referee for detailed comments and suggestions, which have substantially improved this paper. Special thanks are due to the referee for pointing out Lemmas 4 and 5. I acknowledge financial support by The Japan Economic Research Foundation and by MEXT, Grant-in-Aid for Scientific Research. All remaining errors are mine.     

Electrochemical activity of nanocrystalline Fe3O4 in aprotic Li and Na salt electrolytes

Fe₃O₄ powders, whose average particle sizes were 400 nm, 100 nm, and 10 nm in diameter, were prepared in order to investigate the effect of particle size on their electrochemical activity. X-ray diffraction and electron microscopy measurements confirmed that all the prepared samples were identified as inverse-spinel type Fe₃O₄, whose crystallite/particle sizes were between 400 nm and 10 nm. We found that the electrochemical activity of Fe₃O₄ in a lithium salt electrolyte was enhanced with a decrease in the particle size from 400 nm to 10 nm. The 10 nm nanocrystalline Fe₃O₄ powder demonstrated the high discharge capacities of about 130 and 160 mAh g⁻¹ with a satisfactory capacity retention as the active cathode material of Li and Na batteries, respectively.