Measurement of enantiomeric excess using molecularly imprinted polymers

[reaction: see text] A new method is presented for the measurement of enantiomeric excess (ee) utilizing molecularly imprinted polymers (MIPs). The method is demonstrated to be accurate and rapid, as the ee values can be calculated from straightforward concentration measurements. The MIP-based assay can also be adapted to measure the ee of samples of differing initial concentrations.     

Memory effect on the glass transition in vulcanized rubber

The memory effect upon glassification is studied in the glass-to-rubber transition of vulcanized rubber with the strain as a controlling parameter. A phenomenological model is proposed, taking the history of the temperature and the strain into account, by which the experimental results are interpreted. The data and the model demonstrate that the glassy state memorizes the time course of strain upon glassification, not as a single parameter but as the history itself. The data also show that the effect of irreversible deformation in the glassy state is beyond the scope of the present model.     

Probing acoustic nonlinearity on lengths scales comparable to material grain dimensions

The focus of this presentation is to describe our efforts at laser generation of high frequency surface acoustic waves and detection of the nonlinear contribution in the acoustic near-field of the source. Narrow band acoustic generation is accomplished by interfering two pulsed laser beams at the surface of the sample. A Michelson interferometer, that incorporates a high power microscope objective, is used to detect the acoustic disturbance. Detection near the source combined with high frequency generation (approximately 0.1 GHz) facilitates investigation of fundamental processes of harmonic generation on length scales comparable to grain size dimensions.     

Interferometric two-photon photoemission correlation technique and femtosecond wet-electron dynamics at the TiO2(110) surface

The femtosecond time-resolved two-photon photoemission (TR-2PP) and the ultra high vacuum (UHV) surface science techniques are integrated to investigate the electronic structures and the interfacial electron transfer dynamics at the atomically ordered adsorbate overlayers on TiO₂ singlecrystalline surfaces. Our research into the CH₃OH/TiO₂ system exhibits complex dynamics, providing abundant information with regard to electron transport and solvation processes in the interfacial solvent structures. These represent the fundamentally physical, photochemical, and photocatalytic reactions of protic chemicals covered with metal-oxides.     

Reinvestigation of the thermoelectric properties of Ag8GeTe6

High‐density polycrystalline samples (above 98% of the theoretical density) of Ag₈GeTe₆ were prepared by solid‐state reactions of Ag₂Te, GeTe, and Te, followed by hot‐pressing. The thermoelectric properties were measured at temperatures ranging from room temperature to around 700 K. The thermal conductivity values were extremely low (0.25 Wm^–1 K^–1 at room temperature), and consequently Ag₈GeTe₆ exhibited a relatively high thermoelectric figure of merit, ZT = 0.48 at 703 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Indivisibility of Class Numbers of Real Quadratic Fields

Let D denote the fundamental discriminant of a real quadratic field, and let h(D) denote its associated class number. If p is prime, then the Cohen and Lenstra Heuristics give a probability that ph(D). If pgt;3 is prime, then subject to a mild condition, we show that

Geometrical limitations in the intramolecular addition of unsymmetrical allylsilanes to enones

The geometrical constraints of the fluoride-initiated and Lewis acid-catalyzed intramolecular addition of allylsilanes to enone systems were shown to be governed by kinetic-ring-size preferences. Molecules containing adjacent quaternary carbon atoms can be prepared using this method.     

Functional organic gels. Enantioselective elution using chiral gels from amino acid-derived lipids

The L-glutamic acid-derived lipids form organic gels in benzene, which show enantioselective elution of N-dansyl L-phenylalanine from organic gels to aqueous phases. Differential scanning calorimetry and circular dichroism measurements demonstrate that this enantioselectivity occurred through highly-oriented structures of aggregated lipids like those of aqueous lipid membrane systems.     

Reply to the note on the flow behaviour of combustion gas in the boundary layer of an MHD generator

The temperature profile in Fig. 3 of Ref. 1 is better approximated by a relation for a turbulent boundary layer than a laminar boundary layer. The critical Reynolds number is expected to be lowered in the flow train of MHD combustion gas because of large turbulence in the combustor and by roughness along the duct.     

Effects of buffer gases on the infrared multiphoton dissociation of C2H4DCl: A chemical clock to explore highly excited molecules

Observations are reported of the effect of the buffer gases He, Ne, and CF₄, in the pressure range of 0–30 torr, on the branching ratio [HCl]/[DCl] of the unimolecular decomposition The ratio R = k_H/k_D has been measured in high-pressure thermal decomposition (670–1100 K) and was shown to give a unique measure of the internal energy of the decomposing molecules and hence, with RRKM theory and pressure fall-off data, a time scale for their decomposition. Applying the thermal data to the photolysis leads to the conclusion that excitation and decomposition are produced by the laser spike (high intensity, 70 ns FWHM) and also at a slower rate by the larger, less intense tail (1.6 μs). Added buffer gases quench the latter, leaving the former which, from measurements of R, is shown to correspond to excitations of 115 ± 15 kcal/mol and lifetimes of ～30 ps. No bond breaking is seen despite the high energies, in accord with theoretical expectations. The results require an enhanced rate of photon absorption by the highly excited molecules, which are about hundredfold greater than that observed for 300 K molecules. Data are also reported for C₂H₂F₂ and the secondary multiphoton photolysis of the ethylenes produced. Effects of beam geometry and wavelength are explored.