Living cationic polymerization of 2‐adamantyl vinyl ether

Living cationic polymerization of 2‐adamantyl vinyl ether (2‐vinyloxytricyclo[3.3.1.1]^3,7decane; 2‐AdVE) was achieved with the CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride/ethyl acetate [CH₃CH(OiBu)OCOCH₃/Et_1.5AlCl_1.5/CH₃COOEt] initiating system in toluene at 0 °C. The number‐average molecular weights (M_n's) of the obtained poly(2‐AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (M_w/M_n = ～1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the M_n's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2‐AdVE with n‐butyl vinyl ether (CH₂?CH? O? CH₂ CH₂CH₂CH₃; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (T_g) and thermal decomposition temperature (T_d) of the poly(2‐AdVE) (e.g., M_n = 22,000, M_w/M_n = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629–1637, 2008     

Pulsed laser deposition of pure fluoroapatite film without OH groups

The relation between O₂ pressure and composition in the pulsed‐laser deposition of fluoroapatite was investigated using both on‐axis and off‐axis methods to determine the optimal conditions for obtaining a pure fluoroapatite film without OH groups. Through this, it was found that an O₂ pressure of 10 Pa, combined with an off‐axis method, results in P/Ca and F/Ca values (0.6 and 0.2, respectively) that match closely with a stoichiometric composition of Ca₁₀(PO₄)₆F₂. Fourier transform infrared spectroscopy analysis confirmed that this optimized film was almost pure fluoroapatite, with no evidence of any OH groups originating from hydroxyapatite. X‐ray diffraction also revealed that this fluoroapatite film crystallizes with a c‐axis orientation perpendicular to its surface.     

Residual Stress Determination Using Hole Drilling and 3D Image Correlation

In recent years, the hole drilling method for determining residual stresses has been implemented with optical methods such as holographic interferometry and ESPI to overcome certain limitations of the strain rosette version of hole drilling. Although offering advantages, the interferometric methods require vibration isolation, a significant drawback to their use outside of the laboratory. In this study, a 3D image correlation approach was used to measure micron-sized surface displacements caused by the localized stress relief associated with hole drilling. Residual stresses were then found from the displacements using non-dimensional relations previously derived by finite element analysis. A major advantage of image correlation is that it does not require interferometric vibration isolation. Experiments were performed to check the ability of this new approach for uniaxial and equi-biaxial states of stress. Stresses determined by the approach were in good agreement with computed values and those determined by hole drilling using holographic interferometry.     

The microenvironment of DNA switches the activity of singlet oxygen generation photosensitized by berberine and palmatine

The effect of the interaction between DNA and the photosensitizer on photosensitized singlet oxygen (1O2) generation was investigated using DNA-binding alkaloids, berberine and palmatine. These photosensitizers were bound to DNA by electrostatic force. Near-infrared luminescence measurement demonstrated that the photoexcited alkaloids can generate 1O2 only when the photosensitizers are bound to DNA. A fluorescence decay study showed significant enhancement of the lifetime of their photoexcited state with the DNA binding. A calculation study suggested that the electrostatic interaction with DNA inhibits the quenching of the photoexcited state of these alkaloids via intramolecular electron transfer, leading to the prolongation of the lifetime of their excited state. This effect should enhance their intersystem crossing and the yield of energy transfer to molecular oxygen. The results show that the electrostatic interaction with DNA significantly affects the 1O2 generation activity of a photosensitizer. In addition, this interaction may be applied to the control and the design of photosensitizers for medical applications such as photodynamic therapy.     

Exciton transfer between localized states in ZnO quantum well structures

The dynamics of photocreated excitons in a CdZnO/MgZnO quantum well (QW) was studied by comparing the experimental photoluminescence (PL) data with the results of Monte Carlo simulations of the exciton hopping. The temperature-dependent PL linewidth was found to be in reasonable agreement with the model of exciton hopping, with an additional inhomogeneous broadening (Γ) accounted for. The simulation analysis revealed fluctuations of the band potential to be 20 meV with an additional inhomogeneous broadening of , and a crossover from a non-thermalized to thermalized exciton energy distribution at about 100 K. In addition, a Bose–Einstein distribution like temperature dependence of the exciton energy in the wells was extracted using the data on the PL peak position.     

Analysis of natural convection melting inside isothermally heated horizontal rectangular capsule

Melting characteristics of phase change material by natural convection heat transfer inside horizontal rectangular capsules are examined experimentally. The capsules are heated isothermally and three kinds of aspect ratios (qH/W=3, 1 and 1/3) are provided. Octadecane and ice are used, respectively, as the phase change material. A method of analysis applying the empirical correlations for natural convection heat transfer in a vertical or horizontal enclosure to the melting in the rectangular capsules is presented. The predicted results show good agreement with the experimental data. For the melting of octadecane and ice, it is found that the effect of aspect ratio on the melting process is not significant for the range ofB=1/3 to 3.     

Imaging and quantitative analysis of water evaporation process using spectral-domain optical coherence tomography under illumination with two near-infrared wavelengths

Optical Review - Dynamics of water content in a biological tissue is an important information of a biological activity. However, although the conventional measurement method measures the total...     

Anthranilamide-protected vinylboronic acid: rational monomer design for improved polymerization/transformation ability providing access to conventionally inaccessible copolymers

We have studied several protecting groups for vinylboronic-acid derivatives as monomers in radical polymerizations with the objective to improve the polymerization ability and C–B bond-cleaving post-transformation performance. Anthranilamide (aam)-protected vinylboronic acid (VBaam) exhibited experimentally a relatively high polymerization activity, which was theoretically corroborated by density functional theory (DFT) calculations that revealed a peculiar effect of the interaction between the aam groups on the polymerization behavior. The VBaam units in the copolymers can subsequently be transformed into vinyl alcohols or into ethylene units through C–B-bond-cleaving side-chain replacement, which affords valuable copolymers such as poly(vinyl alcohol-co-styrene), poly(ethylene-co-styrene), and poly(ethylene-co-acrylate).

We designed a vinyl-boronic-acid protected by anthranilamide as a “transformable” monomer in radical polymerization to synthesize conventionally inaccessible copolymers, such as poly(vinyl alcohol-co-styrene) and poly(ethylene-co-acrylate).     

Bremsstrahlung in proton-α scattering

Proton-α bremsstrahlung cross sections have been measured at 45 MeV for θ_p = 91°, θ_α = 30° and θ_p = 70°, θ_α = 39°; at 40 MeV for θ_p = 92°, θ_α = 29°; and at 22 MeV for θ_p = 70°, θ_α = 30°. Calculations for these cross sections have been made using the Feshbach-Yennie model following the methods of Green and Prodon including p-α partial waves up to L = 4. These potential-independent calculations have only the proton-α elastic-scattering phase shifts as input. Good agreement with the experimental cross sectios has been obtained.