Concentration dependence of excluded volume effects

The concentration dependence of the excluded volume effects in polymer solutions is investigated. Through thermodynamic arguments for the interpenetration of polymer segments and the free energy change, we show that the disappearance of the excluded volume effects should occur at medium concentration. The result is in accord with the recent experimental observations.     

The Design,Synthesis, and Evaluation of 1,5,7‐Trisubstituted‐3‐Pyridyl‐Xanthones for Use as Insecticides Starting from Pyripyropene A

A readily accessible template of 1,5,7‐trisubstituted‐3‐pyridyl‐xanthones was designed starting from naturally occurring pyripyropene A for agrichemical development. Our originally developed Ag₂CO₃‐mediated oxidative cyclization enabled ready access to the key scaffold, 1,5,7‐trihydroxy‐3‐chloro‐xanthone. The chemo‐ and regioselective sequential introduction of four substituents to the scaffold rapidly afforded the desired, structurally diverse 1,5,7‐trisubstituted‐3‐pyridyl‐xanthones. An evaluation of insecticidal activity revealed that one of the synthesized compounds retained insecticidal activity against vetch aphid and green peach aphid. The observed insecticidal spectrum was similar to that of pyripyropene A. The developed template could be a valuable aid for future agrichemical development.     

Design of a Photocatalytic [2+2] Cycloaddition Reaction Using Redox-Tag Strategy

The design of photocatalytic processes is important for a sustainable society. Key to these photocatalytic reactions is electron transfer. This article is focused on titanium dioxide photocatalyzed organic synthesis and the design of a new [2+2] cycloaddition reaction based on the electron transfer process. Electron transfer - not only between the substrate and the photocatalyst but also inter- and intramolecularly – is crucial for the reaction design. Radical cations were generated by the photocatalyst and trapped by alkenes. The resultant cyclobutyl radical cations were immediately reduced by the aryl rings via intramolecular electron transfer to obtain cyclobutane rings. The outcome of the reaction was controlled by substitution of the aryl ring and the linker connecting the aryl ring to the enol ether. The carefully designed substrates were highly effective for photocatalytic cycloaddition.     

Inclusion of Two Different Guest Molecules within a Rationally Designed Macrocyclic Boronic Ester in Organic Solvent

The inclusion of two different guest molecules in a macrocyclic boronic ester in organic solvent utilizing only π‐stacking interactions has been successfully realized. For this purpose, a new tetrol which has an appropriate distance between two 1,2‐diol units for the inclusion of two aromatic molecules is designed and synthesized. Simple mixing of the new tetrol with 2,7‐pyrenediboronic acid in the presence of pyrene‐4,5‐quinone efficiently affords the desired macrocyclic boronic ester, which is found by ¹H NMR spectroscopy, ESI‐MS, and isothermal titration calorimetry studies to include one molecule each of a dinitronaphthalimide derivative and pyrene. Furthermore, inclusion of two planar molecules within the macrocyclic boronic ester is revealed by X‐ray analysis.     

Differential Games of inf-sup Type and Isaacs Equations

Motivated by the work of Fleming, we provide a general framework to associate inf-sup type values with the Isaacs equations. We show that upper and lower bounds for the generators of inf-sup type are upper and lower Hamiltonians, respectively. In particular, the lower (resp. upper) bound corresponds to the progressive (resp. strictly progressive) strategy. By the Dynamic Programming Principle and identification of the generator, we can prove that the inf-sup type game is characterized as the unique viscosity solution of the Isaacs equation. We also discuss the Isaacs equation with a Hamiltonian of a convex combination between the lower and upper Hamiltonians.     

Dynamical symmetry breaking due to vacuum misalignment

We show that under a certain assumption systems with second-class constraints can be regarded as gauge-fixed systems with first-class constraints. The massive Yang-Mills theory, a point particle on a sphere and theO(N) symmetric non-linear σ-model are considered as concrete examples.     

Release and transfer of polystyrene dewetting pattern by hydration force

We studied the release and transfer of polystyrene (PS) microdots on mica. The PS dots were released from the mica in water. The release was affected by the density of K(+) ions on the mica surface, which was controlled by pretreatment with K(2)CO(3) solutions. The release of PS dots became dominant at the concentrations above [K(+)]crit = 1 x 10(-4) M in the K(2)CO(3) solution. In this concentration region, repulsive forces appeared as a result of the hydration of K(+) ions on the mica (J. Colloid Interface Sci. 1981, 83, 531). This result suggests that the repulsive hydration force causes the release of the PS dots. Followed by the release process, we successfully demonstrated the transfer of the array of PS dots from the mica to another substrate.     

Effect of surface interaction of silica nanoparticles modified by silane coupling agents on viscosity of methylethylketone suspension

In order to control the viscosity of a dense silica methylethylketone (MEK) suspension, the surfaces of silica nanoparticles were modified by 3-glycidoxypropyltrimethoxysilane (GPS) or hexyltrimethoxysilane (C6S) in MEK with the addition of a small amount of pH-controlled water. First, the effect of water addition on the amount of chemisorbed coupling agent was investigated. pH-controlled water enhanced the reactivity of the coupling agent in MEK. The amount of chemisorbed coupling agent increased slightly with the addition of pH 3 water and increased remarkably with the addition of pH 12 water. Next, the effect of the organic functional groups of the coupling agent, pH of the additive water, and additive amount of coupling agent on surface interaction were determined by colloid probe AFM. The steric repulsive force between the silica nanoparticles increased due to water addition, particularly when the pH was maintained at 3. The viscosity of the silica MEK suspension reduced effectively when this repulsive force appeared; however, the optimum condition for reducing the suspension viscosity was dependent on the coupling agent species. The viscosity of the dense silica MEK suspension can be controlled by the addition of small amounts of pH-controlled water and the functional groups of the coupling agent.