Determination of biologically active substances in roasted coffees using a diode-array HPLC system.

We studied the simultaneous quantitative analysis of biologically active substances, such as nicotinic acid, trigonelline, caffeine, qunolinic acid and tannic acid and pyrogallic acid, in several roasted coffees by an HPLC/diode-array system with a home-made sol-gel and ODS-2 columns. A simple method for simultaneous quantitative analysis of biologically active substances in the coffee brew became feasible by an HPLC/diode-array system with a sol-gel column at a single wavelength of 210 nm. The most efficient condition of the Rs value was above 1.05 when two sol-gel columns were connected. In addition, the elution behavior of nicotinic acid in brew extracted from commercially available coffee beans suggests the thermal decomposition process during roasting, and indicated the maximum value for full city roasted coffee.     

Surfaces which contain helical geodesics

LetM be a complete smooth surface of constant mean curvature in the Euclidean 3-space. If there exists two helical geodesics onM through each point ofM, thenM is either a plane, a sphere, or a circular cylinder.     

Electronic surface states on Pd(110): Theory and comparison with experiment

A relativistic Green function formalism has been applied to calculate layer-projected densities of states on Pd(110). In particular, we obtained unoccupied surface states and their dispersion relations along two directions in the surface Brillouin zone. Good agreement with recent inverse photoemission data is reached by using an energy-dependent dynamical surface potential barrier, which is based on a simple electron-plasmon interaction model, instead of a static surface barrier.     

Electron spin resonance studies on radiation graft copolymerization in polyethylene. II. Grafting initiated by allyl radicals trapped in irradiated polyethylene

The regions trapping allyl radicals in irradiated polyethylene and the reactivity of the radicals with various monomers have been studied by electron spin resonance. Most of the allyl radicals are trapped in defects or surfaces of the crystallite, and only 10% of the radicals are trapped inside the crystallites. Since the reactivity of the allyl radicals depends on whether they come in contact with reactive monomers, the rate of reaction is related to the concentration of the monomers. When grafting reactions are initiated by allyl radicals, the rate of initiation is rapid and the rate of termination at the initial stage is also very fast. Consequently the yield of grafting increases at the initial stage but soon levels off, which is in contrast to the grafting behavior with alkyl radicals.     

Vibrational frequencies and infrared absorption intensities of 1,2-dibromoethane

Infrared and Raman spectra of 1,2-dibromoethane CH₂BrCH₂Br and CD₂BrCD₂Br were observed in the liquid state, and the fundamental frequencies were determined by comparison with those of related molecules. Infrared absorption intensities of fundament bands were measured in the liquid state, and the intensity data were interpreted on the basis of the valence-optical theory. From the converged value of a population ratio, the energy difference between the trans and gauche isomers was determined, which was in good agreement with the value obtained from the temperature effect of the IR spectrum.