Organic crystals growth for optical channel waveguides

Optical channel waveguides of meta-nitroaniline (m-NA) crystal, which has potential applications to nonlinear optical devices, have been fabricated on glass substrates having fine grooves. The crystal growth was performed by zone-melting, scanning a CO₂ laser beam along the grooves filled with the polycrystal m-NA. Optical and X-ray observations showed that zone-melting changed the polycrystalline state to a single crystalline state with the 〈001〉 direction along the groove. The scattering loss for a 5 mm-long m-NA crystal waveguide (100 μm both in width and in depth) was found to decrease from 50 dB to 2.5 dB with this process.     

Enantioselective synthesis of β-hydroxyisobutyric acid: a useful synthon in the synthesis of polypropionate-type natural products

The aldol reaction of formaldehyde with the dicyclopentylborinyl enolate derived from $\text{S}$-(or $\text{R}$-) 1-tert-butyldimethylsilyloxy-l-cyclohexylbutan-2-one, followed by desilylation and sodium meta-periodate oxidation, provides $\text{R}$-(or $\text{S}$-) β-hydroxyisobutyric acid.     

Compound-forming effect for the electrical resistivity of liquid IVB-Te alloys

The resistivity isotherm of liquid IVb(Sn,Pb)-Te alloys has a remarkable maximum and temperature coefficient of resistivity has large negative value around the equiatomic composition, suggesting that a kind of compound formation exists at this composition. The excess resistivities are interpreted in terms of resonance scattering by the compound of MTe(M=Sn, Pb) with a finite life time.     

Scale-up of wet kneading in a novel vertical high shear kneader

A novel multi-functional vertical high shear kneader has been developed and its performance in wet kneading has previously been reported [Watano et al., Chem. Pharm. Bull., 50(3), 341-345 (2002)]. In this study, scale-up of wet kneading in the novel vertical high shear kneader was conducted. Pharmaceutical excipients composed of lactose, cornstarch and micro-crystalline cellulose were used as powder samples. Kneading operations were conducted under various operating conditions and three different vessel scales. The dried pellets were then prepared by extruding the wet kneaded masses through a dome-type extruder and their drying by a fluidized bed. The physical properties such as strength and disintegration time of the dried pellets were evaluated. It was found that the properties of the dried pellets and their scale-up characteristics were well expressed by an agitation power per unit vessel volume and dimensionless Froude number.     

Nonadiabatic photodissociation process using an optical near field

We demonstrated the deposition of nanometric Zn dots using photodissociation with gas-phase diethylzinc and an optical near field under nonresonant conditions. To explain the experimental results, we proposed an exciton-phonon polariton model, and discuss the quantitative experimental dependence of the deposition rate on the optical power and photon energy based on photodissociation involving multiple-step excitation via molecular vibration modes. The physical basis of this process, which seems to violate the Franck-Condon principle, is the optically nonadiabatic excitation of the molecular vibration mode due to the steep spatial gradient of the optical near-field energy.     

Electrical resistivities of the uranium carbides

Electrical resistivities of arc-melted uranium carbides, UC, UC₂, U₂C₃ and UC + UC₂, were measured over the temperature range between 4 and 1900 K. The monocarbide, dicarbide and the mixture of carbides showed metallic character in their resistivity dependence on temperature above 30 K, while below this the resistivities were constant. U₂C₃ showed a knee in the resistivity curve at 54.0 K corresponding to a magnetic transition. Above 1100 K, the resistivity of U₂C₃ did not vary with temperature. The resistivity of the mixture (UC + UC₂ with U₂C₃ precipitates) showed an arrest between 800 and 950 K.     

Coenzym-Modelle. 5. Mitt. Additionsreaktion des Cyanidions an monomere und polymere Nicotinamide Beziehung zwischen den Gleichgewichts-und Reaktionsgeschwindigkeiten

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