Isolation and structure elucidation of genuine oat phytoalexin,avenalumin I

The major phytoalexin from oat leaves has been identified as 2-[2-(4-hydroxyphenyDethenyl] -6-hydroxy-4H-3,1-benzoxazin-4-one ($\text{A}$).     

Reaktionsgeschwindigkeit der Bildung von Pfropf-Copolymerem durch die Kopplungsreaktion des Polystyryl-Anions mit chlormethyliertem Polysterol

Ohne Zusammenfassung     

Regeneration of small eddies by data assimilation in turbulence

The effect of data assimilation of large-scale eddies on small-scale eddies in turbulence is studied by direct numerical simulations (DNSs) of Navier-Stokes turbulence with Taylor microscale Reynolds numbers up to 179. The DNSs show that even if the data of small-scale eddies are lost at some initial instant, they can be regenerated from the data of large-scale eddies under the condition that Fourier modes with wave number less than a critical wave number k(*) are continuously assimilated, where k(*) approximately 0.2eta(-1) with eta identical with(nu(3)/epsilon)(1/4), epsilon the mean energy dissipation rate, and nu the viscosity.     

Oscillating fluorescence in an unstable colloidal dispersion of CdSe/ZnS core/shell quantum dots

Fluorescence oscillation is observed in an ensemble of colloidal CdSe/ZnS core/shell quantum dots (QDs) dispersed in nonpolar solvent under continuous irradiation. The QDs dispersed in toluene gradually aggregate and change their fluorescence intensity, even in the dark. During the aggregation, the QD/toluene suspension is unstable, that is, overdispersed. The fluorescence oscillation is found only in this unstable state before the system reaches steady state. In addition, the aggregation rate is promoted by irradiation and strongly correlates with the oscillation amplitude. Our experimental results indicate that the dispersion instability plays an important role in both linear and nonlinear dynamics of the fluorescence. It is inferred from the experimental results and previous studies that the complex time evolution of fluorescence in the QD/toluene dispersion is possibly due to adsorption and desorption of surface ligand molecules over the course of QD aggregation.     

Analysis of cigarette smoke by an online thermal desorption system and multidimensional GC-MS

Single puffs of cigarette smoke with a wide continuous range of volatility are directly analyzed using a new system. The system consists of a smoking machine, an online thermal desorption system (TDS), and a multidimensional gas chromatograph-mass spectrometer (MDGC-MS) system. The online TDS with the smoking machine collects the single-puff cigarette smoke with glass beads as the cryogenic adsorbent. The MDGC is composed of three capillary columns, Poraplot Q, and DB-WAX for separation and a deactivated capillary column for pressure balance, which enables simultaneous separation of the two different phases. The smoke desorbed from the TDS is divided into vapor and semivolatile phases and analyzed individually with each column by the MDGC. Thus, the system enables the overall analysis of the two phases simultaneously, including acetaldehyde and 1,4-benzenediol. This system also provides more appropriate analysis for compounds crossing the two phases such as toluene and pyridine. For the approach of introducing internal standards, a gas mixture of toluene-d(8) and o-xylene-d(10) is applied and the compounds are detected in the vapor and semivolatile phases, respectively.     

Formation of formal compounds in reaction of dimethyl phenols with formaldehyde

Formaldehyde was reacted with both 2,4-dimethylphenol(2,4-xyenol) and 2,6-dimethylphenol(2,6-xylenol), which are model compounds of monofunctional phenols, and the reaction products were subjected to HLC analysis to elucidate details of the formation process and bonding manner of a formal group, which can greatly affect the performance of phenol–formaldehyde resins. As a result, formal compounds of dimethylphenols were successfully separated by HLC. It was further found, as a result of tracing the reactions by HLC, that the formation of a formal group occurs at either position of the ortho and para positions, and that methylol compounds were formed following formation of the formal compounds. Furthermore, as a result of NMR analysis as well as consideration of solvation on the basis of the relative elution volumes of the nonacetylated and acetylated reaction products it was found that the formal group was added to the phenol nuclei.     

Layer structure estimation of three‐dimensional crystal and two‐dimensional molecular film for fluorinated comb copolymers

Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008