Synthesis and Thermal Characterization of Novel Fluorene-Based Polysiloxane Derivatives

Three novel poly(tetramethylsilfluorenylenesiloxane) derivatives having different substituent at 9-position of fluorenylene moiety, i.e. dimethyl (P1), spirocyclohexyl (P2), and spirofluorenyl (P3) substituents, were obtained by polycondensation of novel three disilanol monomers, i.e. 2,7-bis(dimethylhydroxysilyl)-9,9-dimethyl- fluorene (M1), 2’,7’-bis(dimethylhydroxysilyl)-spiro(cyclohexane-1,9’-fluorene) (M2), 2,7-bis(dimethylhydroxysilyl)-9,9’-spirobifluorene (M3), respectively. P1–P3 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. It was suggested from the differential scanning calorimetry (DSC) and the X-ray diffraction analysis that P1 exhibited the crystallinity whereas P2 and P3 were amorphous polymers. The glass transition temperature (T _g) determined by DSC and the temperature at 5% weight loss (T _d5) determined by thermogravimetry (TG) were dependent on the substituent at 9-position on fluorene; both orders of T _g and T _d5 were P3 > P2 > P1, indicating the bulkiness of substituent at 9-position of fluorene resulted in the good thermal stability. It is noteworthy that amorphous P3 exhibiting very high T _g of 156 °C and T _d5 of 535 °C is a new heat-resistant polysiloxane derivative as well as a promising candidate for blue-light-emitting materials.     

Effect of static magnetic field on cell migration

The effect of a magnetic field on cells has long been investigated, but there are few quantitative investigations of the migration of cells. Cell migration is important as one of the fundamental activities of the cell. This study proposes a method to evaluate quantitatively the cell diffusion constant and the effect of a static magnetic field on cell migration. The cell lines are neuroblastoma (NG108‐15), fibroblastoma (NIH/3T3), and osteoblastoma (MC3T3‐E1). The static magnetic field of 30 or 120 mT is impressed by a permanent magnet in a vertical or horizontal direction to the dish. It is shown that the cell diffusion constant can represent the cell migration as the cell activity. It is found that the cell migration is enhanced by exposure to the magnetic field, depending on the kind of cell. It is conjectured that the static magnetic field affects cell migration, which is downstream of the information transmission. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 46– 52, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20203     

Effects of rainfall on the occurrence of human adenoviruses, total coliforms, and Escherichia coli in seawater.

A two-month survey was conducted in order to evaluate the effects of rainfall on the fate of microorganisms in seawater in the Tokyo Bay, Japan. The seawater sample (1,000 mL) was applied to a method to concentrate virus, followed by a quantification of human adenoviruses using the real-time PCR. Total coliforms and E. coli, which were determined by the colony forming method, were detected in all 47 seawater samples, while human adenoviruses were detected in 38 (81%) of the samples. The concentration of tested microorganisms showed 1-2 log units increase after rainfall events, followed by the gradual decrease to the level before the rainfall within a few days.     

Microgravity experiments on flame spread along fuel-droplet arrays at high temperatures

Microgravity experiments on droplet-array combustion were conducted under high-ambient-temperature conditions. n-Decane droplet arrays suspended on SiC fibers were inserted into a high-temperature combustion chamber and were ignited at one end to initiate the flame spread in high-temperature air. Flame-spread modes, burning behavior after the flame spread, and flame-spread rate were examined at different ambient temperatures. Experimental results showed that the appearance of flame-spread modes and the flame-spread rate were affected by the ambient temperature. The flame-spread rate increased with the ambient temperature. These facts are discussed based on the temperature effects on the droplet heating and the development of a flammable-mixture layer around the next droplet. A simple model was introduced to analyze these effects. The effects of the ambient temperature on the appearance of group combustion of the array after the flame spread and the scale effect in the flame spread are also discussed.     

The activity of calcium in calcium-metal-fluoride fluxes

The standard Gibbs energy of reaction Ca (1) +O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: ΔG° = -64,300(±700) + 19.8(±3.5)T J/mol (1373 to 1623 K) The activities of calcium in the CaO_satd-Ca-MF₂ (M: Ca, Ba, Mg) and CaO_satd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF₂, BaF₂, and MgF₂ at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed. Formerly Graduate Student, Department of Metallurgy, The University of Tokyo.     

A Numerical Simulation of Time-Dependent Interface Failure Under Shear and Compressive Loads in Single-Fiber Composites

We performed a numerical simulation of a time-dependent interfacial failure accompanied by a fiber failure, and examined their evolution under shear and compressive loads in single-fiber composites. The compressive load on the interface consists of Poisson’s contraction for matrix resin subjected to longitudinal tensile load. As time progresses, compressive stress at the interface in the fiber radial direction relaxes under the constant longitudinal tensile strain condition for the specimen, directly causing the relaxation of the interface frictional stress. This relaxation facilitates the failure of the interface. In this analysis, a specific criterion for interface failure is applied; apparent interfacial shear strength is enhanced by compressive stress, which is referred as quasi-parabolic criterion in the present study. The results of the stress recovery profile around the fiber failure and the interfacial debonding length as a function of time simulated by the finite element analysis employing the criterion are very similar to experimental results obtained using micro-Raman spectroscopy.     

Engineering study of continuous supercritical hydrothermal method using a T-shaped mixer: Experimental synthesis of NiO nanoparticles and CFD simulation

In the synthesis of metal oxide fine particles by continuous supercritical hydrothermal method, rapid mixing of starting solution with supercritical water is a key factor for producing nanoparticles that have a narrow size distribution. In this paper, continuous hydrothermal synthesis of NiO nanoparticles from Ni(NO₃)₂ aqueous solution at 400 °C and 30 MPa was carried out with T-shaped mixers and the effect of inner diameter, flow rate, and mixing directions on the particle size was examined. The computational fluid dynamics (CFD) simulation of the mixers was performed to evaluate the heating rate of the starting solution. When the inner diameter of the T-shaped mixer was decreased from 2.3 to 0.3 mm and the flow rate was increased from 30 to 60 g/min, the produced NiO particle size decreased remarkably from 54.3 to 20.1 nm. This trend of the decrease in particle size could be described as a function of the heating rate. The experimental and CFD results showed the detail regions of local heating that correlated with the NiO nanoparticle size.     

Color influences on human beings evaluated by nasal skin temperature

Since colors affect human beings both physiologically and mentally, various studies have been conducted about the infl uences of color. Most of the studies have been focused on the psychological aspects. In this study, we investigated the infl uences of color physiologically by the use of infrared thermography. With this technique, the subjects wear no devices, and objective values are expected to be obtained to evaluate the infl uences of color. Nasal skin temperatures were measured by infrared thermography under yellow, red, and blue illuminations. A significant temperature change was observed under red illumination.     

Cosmic-ray muon radiography of UO2 fuel assembly

A technical demonstration of cosmic-ray muon radiography of a UO₂ fuel assembly was performed at Toshiba Nuclear Critical Assembly (NCA). The fuel assembly in the NCA was imaged through obstacles such as steel and concrete. The result suggested that the method can be applicable to assess the damage to the reactors at the Fukushima Daiichi nuclear power plant. Here, both scattering and displacement methods are presented, and the results are shown to agree with Monte Carlo simulations. In addition, detailed Monte Carlo simulations of the Fukushima Daiichi reactor were performed, which showed capability of muon radiography to locate the fuel in the damaged reactors.