The diffusion coefficients of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) in Merrifield network polystyrene gels used as a solid-phase reaction field have been determined as a function of the degree of volume swelling (Q) over the temperature range from 30 to 80 °C by means of the 1 H pulsed-field-gradient spin-echo NMR method. From these experimental results, it was found that the D values for DMF in network polystyrene gels linearly increase with an increase of Q in the Q < 3.2 range, and a change of the D value for DMF in the Q > 3.2 range is smaller than that in the Q < 3.2 range. The activation energies of self-diffusion (E) for DMF in network polystyrene gels as determined from the temperature dependence of D are linearly decreased with an increase of Q in the Q < 1.8 range, and change of the E value for DMF in the Q > 1.8 range is very small. From these experimental results, it was found that the Q dependence of the D value for THF in network polystyrene gels is very similar to that of DMF. Further, it was found that the D values for DMF in network polystyrene gels with Q < 1.8 were significantly influenced by the fraction of chloromethylation in the phenyl rings of network polystyrene. Further, from the diffusion coefficient measurements of Boc-Gly(tert-butyloxycarbonylglycine) and Boc-Phe(tert-butyloxycarbonyl-L-phenylalanine) in network polystyrene gels, it was found that Boc-Gly and Boc-Phe in network polystyrene gels have multicomponents in diffusion by intermolecular interactions between amino acids and polymer network and that the diffusional behavior of Boc-Gly in network polystyrene gels is very close to that of Boc-Phe.

We fabricated a one-dimensional photonic crystal structure with a defect layer of a poly(vinyl alcohol) thin film doped with 2-aminopurine (2AP). The defect induced a transmission peak in the photonic band gap at 610 nm, to which ultrashort laser pulses were tuned. We observed enhanced two-photon fluorescence emission from 2AP in the photonic crystal structure with a factor of 120. The enhancement was attributed to the high local field of light generated by a photonic state localized at the defect layer. Furthermore, under the enhanced light intensity, we carried out photobleaching experiments, which gave useful information on the photochemistry of 2AP.

Inhomogeneity of network size of polymer gels such as polystyrene gel and cross-linked ethoxylate acrylate gel with dimethylformamide as solvent has been studied by using time-dependent diffusion NMR. From the experimental results on the diffusion coefficients of the probe amino acid, tert-butyloxylcarbonyl-l-phenylalanine, in the gels, it is found that, in the short diffusion time range, the amino acid in the gels has two components in diffusion as influenced by the distribution of network size, but in the long diffusion time range the amino acid has a single component in diffusion because the diffusion coefficients which come from the distribution of network size are averaged out. Then, inhomogeneity of the gels is elucidated.

characterization of transfer efficiency in charge-coupled devices,"Abstract-A traveling-wave electrooptic phase modulator using a Tiin-diffused LiNb03 optical waveguide was designed and constructed with emphasis placed on broad-band operation. As a microwave waveguide, a coplanar parallel stripline of aluminum with characteristic impedance of 48 was fabricated on the crystal surface. The electrodes are 1.5 pm thick, 1 cm long, and 60 pm apart. The modulator was tested at 0.63 pm over a bandwidth of 75 GHz. For 250-mW drive power, the measured phase-modulation index was 1 rad up to about 3 GHz and reduced to 0.5 rad at 7.5 GHz. S

Inhomogeneities in poly(acrylic acid) (PAA) gels differing in their degree of cross-linking were detected as a function of the degree of swelling, Q, defined as the mass of the swollen gel divided by the mass of the dry polymer, Q ) M swollen/Mdry. Q was in the range 2.8-10.0 for the gels studied. The networks were prepared at 70 °C by simultaneous polymerization and cross-linking of a mixture of acrylic acid (AA), sodium carbonate, cross-linker (1,4-butanediol diacrylate), and the redox couple sodium persulfate/sodium isoascorbate as the initiator. Two types of networks were prepared by using the same monomer concentration (30 wt %) and the same amount of sodium carbonate but different amounts of the cross-linker, 1.1 and 0.5 wt %, respectively, in the monomer mixture. The corresponding notation is GEL1 and GEL2. Detection of heterogeneities was based on measuring the diffusion coefficients of the probe molecule poly(ethylene glycol) (PEG) as a function of the degree of swelling and diffusing time, ∆, by means of field-gradient 1 H NMR spectroscopy. The inhomogeneities emerged as the degree of swelling of the gels was reduced. For the highly swollen gels (Q ) 10.0 and 5.2 for GEL1 and Q ) 10.0 and 5.1 and 4.5 for GEL2) only one diffusion coefficient was detected, independent of the diffusing time, ∆, in the range 30-500 ms. For less swollen gels (Q ) 2.9-4.5 for GEL1 and 2.8-3.9 for GEL2) two diffusion coefficients were detected, D fast and Dslow, with values that depended on ∆; for these less swollen gels the diffusion distances dfast and dslow, and the relative fractions of the fast and slow diffusion components, ffast and fslow, were calculated. We defined a specific degree of swelling, Qs, above which the diffusion of the probe in the two gel systems changed from one to two components. A larger value of Qs in GEL1 was taken as an indicator of a more inhomogeneous gel. Analysis of the effect of ∆ on the diffusion coefficients, diffusion distances, and fractions of slow and fast diffusion components indicated that the gels form a highly cross-linked region in a narrow Q range. In this Q range, the polymer chains interact and form a highly restricted diffusion region. The extent and distribution of the cross-links form different restricted diffusion regions in GEL1 and GEL2 systems.