Study of the mechanical interaction between an electromagnetic field and a nanoscopic thin film near electronic resonance

The mechanical interaction between an electromagnetic field and a nanoscopic thin film near electronic resonance is theoretically studied by calculation of Maxwell's stress tensor. As a result of numerical demonstrations for both propagating and evanescent incident waves, the following effects that are specific to this condition have been clarified: (1) The force exerted on a nanoscopic thin film is greatly enhanced near the resonance frequency to the same order of magnitude as for a film with macroscopic thickness. (2) The peak position of the gradient force in its spectrum is highly sensitive to the change in nanoscopic thickness that is due to the polaritonic effect. (3) In a total-reflection region a large enhancement of the repulsive force between the two thin films occurs when the films act as an optical cavity.     

Oxidative decarboxylation of α-keto carboxylic acids by carbonyl oxides

Photosensitized oxygenation of α-keto carboxylic acids in the presence of diazo compounds afforded the corresponding carboxylic acids and carbon dioxide in high yields; oxidative decarboxylation by carbonyl oxides occurred.     

Mode-selective dynamic light scattering spectroscopy: application to the isotropic phase of liquid crystals

We have developed a new method of "mode-selective" dynamic light scattering spectroscopy. This method allows us to study dynamic modes usually hidden behind large fluctuations of a critical mode. Here we apply this method to measurements of three dynamic modes of the isotropic phase of liquid crystals near the isotropic-nematic transition. In conventional methods detecting thermally excited modes, the thermal diffusion and sound modes are usually overwhelmed by the orientational relaxation mode since the intensity of the last mode diverges toward the isotropic-nematic critical point. Thanks to the phase-coherent detection ability of our method, we have successfully observed the thermal diffusion and sound modes without the interference of incoherent critical orientational fluctuations.     

Diastereoselective protonation on radical anions of electron-deficient alkenes via photoinduced electron transfer

Diastereoselective protonations in the photoinduced electron transfer (PET) reactions of 1,1-dicyanoethene derivatives (1a-e) by use of organosilicon compounds such as allyltrimethylsilane (2) and benzyltrimethylsilane (5) are described. Irradiation of an acetonitrile-acetic acid solution containing 4-tert-butylcyclohexylidenepropanedinitrile (1a) and an excess of 2 in the presence of phenanthrene (Phen) as a sensitizer afforded reduction and allylated products (3a, 4a) in 63:37 and 57:43 ratios in a less regioselective manner. Photoreactions of 3,3,5-trimethylcyclohexylidenepropanedinitrile (1b), 2-methylcyclohexylidenepropanedinitrile (1c), bicyclo[2.2.1]-2-heptylidenepropanedinitrile (1d), and 1,7,7-trimethylbicyclo[2.2.1]-2-heptylidenepropanedinitrile (1e) with 2 showed higher diastereoselectivity via the PET process. Similar diastereoselectivities were obtained in the Phen-sensitized photoreaction of 1a-e with 5. When 2,4,6-trimethylpyridinium tosylate (7) was used as a proton source in place of acetic acid, the product ratios were substantially changed in several cases. From these results, steric and torsional effects have been postulated as important factors for the control of the diastereoselectivity in these PET reactions.     

Synthesis and antifungal activity of novel 14-membered benzomacrolides, as galbonolide analogues

Asymmetric total synthesis of benzene analogues of galbonolide, a 14-membered antifungal macrolide, possessing a benzene ring instead of a conjugated diene structure, was achieved starting from chiral 1-aryl-1-propanol obtained by enzyme-catalyzed kinetic resolution with high enantioselectivity. Representatively, a method for the introduction of a methylthio and chloride function at the vinyl position was also established. The resulting analogues unfortunately exhibited very little antifungal potency in comparison with galbonolide A.     

Spectroscopy of Ar-SH and Ar-SD. I. Observation of rotation-vibration transitions of a van der Waals mode by double-resonance spectroscopy

Rotation-vibration transitions of a van der Waals bending vibration, P = 1/2 <-- 3/2, of the Ar-SHSD (X 2pi) complexes in the electronic ground state have been observed by applying newly developed microwave-millimeter-wave double-resonance spectroscopy. The rotational energy-level structure for the two isotopomers, with hyperfine structure due to the hydrogen or deuterium nuclei and parity doublings in the P = 1/2 state, has now been clarified. Detailed explanation of the double-resonance technique is also given.     

Control of the fragility of a glass-forming liquid using the liquid-liquid phase transition

When a liquid approaches its glass-transition temperatures T(g), the structural relaxation time tau dramatically increases. This basic feature is ubiquitous, but this increase of tau can be classified between strong and fragile extremes using T(g) as a scaling parameter. Liquids, whose tau obeys the Arrhenius law, are called "strong," while "fragile" liquids have the super-Arrhenius behavior. Here we report the first continuous control of the fragility of liquid of the same material over a wide range of fragility, using a continuous liquid-liquid transition. Our study clearly demonstrates that the fragility is not a material-specific quantity, but is controlled by the order parameter governing the liquid-liquid transition, which may be the fraction of locally favored structures in the liquid.     

Viscoelastic phase separation of protein solutions

In addition to the known behavior of normal phase separation and gelation, we report novel phase-separation behavior of protein solutions as their intermediate case. A network structure of the protein-rich phase may be formed even if it is the minority phase, contrary to the conventional wisdom. This behavior is characteristic of viscoelastic phase separation found in polymer solutions. This kinetic pathway may play crucial roles in the complex phase ordering of protein solutions, in particular, protein network formation in biological systems and foods.