Dispersion polymerization of vinyl acetate in a mixture of ethanol and water

Dispersion polymerization of vinyl acetate (VAc) was studied in a mixed solvent of ethanol and water using poly(vinyl alcohol) (PVA) with a low degree of hydrolysis as a steric stabilizer. Six compositions were chosen from a homogeneous phase before the polymerization. In a composition with the highest solubility parameter, 450 nm particles with a size distribution close to monodispersity were obtained. With decreasing solubility parameters of the compositions, the particles became polydisperse. In the compositions with solubility parameter lower than 17.1, particles were not formed even at 100 % conversion. Degrees of polymerization obtained in this homogeneous phase were less than 100 and close to calculated values. With increasing solubility parameters of the system, degrees of polymerization increased but were still less than 200. Grafting of VAc onto PVA and grafted PVA were very small, indicating the presence of a competing reaction to the grafting. Copyright © 2004 Society of Chemical Industry     

Experimental and mathematical evaluation of trichloroethylene removal from saturated soil using acetic acid with saturated ozone

The present study is an experimental and numerical analysis of trichloroethylene (TCE) removal from soil by ozone oxidation combined with acetic acid flushing. A one-dimensional advective–dispersive flow model is proposed to mathematically describe the TCE dissolution and oxidation from the porous medium using acetic acid and ozone, respectively. The model could reasonably well predict the experimental data in the effluent for dissolution, oxidation, and total removal of TCE. Sensitivity analyses evaluated the effects of different parameters, such as ozone and acetic acid concentration, flow rate, and initial TCE concentration, on the dissolution and oxidation processes. Remediation time was reduced by more than 29% by applying acetic acid solutions saturated with ozone. Increasing the ozone concentration was the best method for reducing remediation time, followed by increasing acetic acid concentration and increasing flow rate.     

Temperature Dependence of Electrical and Thermal Conductivities of an Epoxy-Based Isotropic Conductive Adhesive

The temperature dependence of the transport properties, including electrical and thermal conductivities, of a practical isotropic conductive adhesive (ICA) including an epoxy-based binder was investigated in order to comprehensively evaluate the physical changes induced during exposure to elevated temperatures. The ICA specimens were cured and post-annealed under various conditions in order to clarify the effect of curing state of the adhesive binder on the electrical resistivity. The electrical resistivity at ambient temperature tends to decrease with increasing curing temperature, even if the samples exhibit full conversion. In addition, an annealing effect, resulting in a deviation from a linear relationship in the temperature dependence of resistivity, can be induced during the heating process experienced during resistivity measurements. However, the ICA specimens exhibited similar values for the temperature coefficient of resistivity (TCR), regardless of the curing and post-annealing conditions in the temperature range where the annealing effect is rarely induced, although the thermal history of the specimens significantly influences the absolute values of electrical resistivity. The temperature dependence of the thermal conductivity is almost accounted for by the decrease in the contribution of conducting electrons in the temperature range below the glass-transition temperature, T _g.     

Transient charge accumulation in pentacene field effect transistor with silver electrode

Time-resolved microscopic optical second harmonic generation (TRM-SHG) imaging was employed to study a transient charge accumulation in top-contact pentacene field effect transistor (FET) with Ag electrodes. It was demonstrated that the SHG signal at the edge of the Ag electrode decayed but remained in a steady state depending on biasing condition. An electric field formed in pentacene layer below Ag electrode activates the SHG, indicating the insufficient accumulation of injected carriers in the FET channel. By using the TRM-SHG technique transient change of the carrier density in the OFET is obtained.     

Ozone decomposition of hazardous chemical substance in organic solvents

Performance on the ozonation of hazardous chemicals in non-aqueous solutions, i.e. organic solvents, was studied in comparison with those in water. The specific conclusions obtained from this study are as follows: the rate of decomposition and the specific amount of decomposition per ozone consumption for orange II were higher in organic solvents like acetic acid, acetone, ter-butyl alcohol than in distilled water. The rates of trichloroethylene decomposition in organic solvents like acetic acid, acetone, and ethyl acetate were also higher than those in distilled water.     

Optical frequency-domain reflectometry with a rapid wavelength-scanning superstructure-grating distributed Bragg reflector laser

Superstructure-grating distributed Bragg reflector lasers are particularly suited for optical frequency-domain reflectometry optical-coherence tomography with wide wavelength tunability and frequency agility. We report theoretical estimates of and experimental results for the data acquisition speed, the observable depth range, the resolution, and the dynamic range of an optical frequency-domain reflectometry system that uses a superstructure-grating distributed Bragg reflector laser whose wavelength can be tuned from 1533 to 1574 nm with a tuning speed of 10 micros/0.1-nm step.     

Simulation of water-bloom in a eutrophic lake—II. Reassessment of buoyancy,gas vacuole and Turgor pressure of Microcystis aeruginosa

The rate of vertical migration (rising or sinking) of Microcystis aeruginosa colonies in water was represented by Stokes' law. The density, p_p of the colony, estimated conversely from observations on vertical migration rate by using Stokes' law, was shown as a function of gas vacuoles' fraction, V_f in algal cells.Referring to the experimental studies by previous workers on factors that the affect the value of V_f, gas vacuoles in the cells were assumed to collapse instantly, V_f decreasing to V_feq once V_f values exceed those of V_feq. The latter values of V_feq were defined from a cumulative and normal distribution of gas vacuoles that withstand the turgor pressure. P, Incidentally, the regeneration rate of gas vacuoles in the cells that were subjected to sonication, yielding V_f = 0 (non-vacuolate) was constant regardless of the post-sonication environment of light and/or dark.Taking for granted that there exist upper and lower limits of turgor pressures for a given algal cell, an equation on the rate of change in turgor presure of the cell was derived. Presentation of these rate equations is a prerequisite for modeling and simulating emergence and/or disappearance of the waterbloom in still waters of eutrophic lakes and/or ponds.     

Fiber-strengthening of a Cu−Fe−Cr duplex alloy by cold drawing

Copper wire containing strong chromium ferrite needles has been produced by aligning the chromium ferrite phase of a two-phase Cu?Fe?Cr alloy into needles by cold drawing and subsequently annealing the wire at 480°C. At this temperature the chromium ferrite needles exhibit marked age-hardening. The volume fraction of the chromium ferrite needles in the alloy investigated was nearly 25 pct. Strength up to 50 kg per sq mm with nearly 8 pct elongation has been achieved in 3 mm-wire annealed at 480°C. The annealed wire can be drawn again to give a further increase in strength up to 73 kg per sq mm.