Synthesis of semiaromatic polyimides from aromatic diamines containing adamantyl units and alicyclic dianhydrides

We prepared new semiaromatic polyimides from alicyclic dianhydrides and aromatic diamines containing adamantyl and biadamantyl units. Polycondensations were performed in 1‐methyl‐2‐pyrrolidinone at room temperature for 7 h and then 80 °C for 23 h, giving poly(amic acid)s with inherent viscosities up to 0.58 dL/g. Poly(amic acid)s were converted to corresponding poly(imide)s by thermal treatment. Poly(imide)s showed relatively high thermal stability (5% weight loss around 450 °C) and low dielectric constants (2.69–2.79). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 144–150, 2004     

ENHANCEMENT OF PHOTOREPAIR OF ULTRAVIOLET-INDUCED PYRIMIDINE DIMERS BY PREILLUMINATION WITH FLUORESCENT LIGHT IN THE GOLDFISH CELL LINE. THE RELATIONSHIP BETWEEN SURVIVAL AND YIELD OF PYRIMIDINE DIMERS

The enhancement of photorepair of UV-induced pyrimidine dimers by preillumination with fluorescent light, previously reported with RBCF-1 cells derived from caudal fin of a goldfish, was studied in terms of clonogenic ability and yields of dimers. In the logarithmic growth phase, the ability of photorepair increased with the time after preillumination, reached a maximum at 8 h, and gradually declined. At 8 h, the dose decrement with the photorepair-treatment for 20 min at 7.5 J/m2 UV increased by preillumination for 1 h from 1.6 to 3.1 J/m2 in terms of restoration of survival and from 1.2 to 4.3 J/m2 in terms of the disappearance of dimers. Incubation of the preilluminated cells in the medium containing cycloheximide (0.5 microgram/mL) after preillumination until UV-irradiation diminished their enhancement of photorepair. In the density-inhibited state, the ability of photorepair was higher than in the log phase, and it was hardly enhanced by preillumination.     

Characteristics of whispering-gallery-mode dye lasers utilizing dye-doped solid microspheres by UV N2-laser pumping

The characteristics of a whispering-gallery-mode (WGM) dye laser using a variety of dye-doped solid microspheres, pumped by a UV N₂-laser, are presented. Experimental results for the WGM dye laser are presented with the spatial distribution and spectral and temporal responses of lasing. The spectral response of a new variety of WGM dye laser is in the blue-green or red spectral regions, and over a wide spectral range.     

Technique to Estimate the Reflectance of a High-Reflectance Dielectric Multilayer Coating Mirror Using Incident Beam Angular Dependence of Its Transmittance

The reflectance of a high-reflectance dielectric multilayer coating mirror tuned to a monochromatic laser wavelength was estimated from its transmittance which was measured with 0.4 ppm accuracy. The transmittance was calculated from its theoretical formula including three parameters (refractive indexes of low and high refractive films (n_L, n_H) and a number of layer units composed of a pair of one low and one high refractive film (N)) which were estimated from the incident beam angular dependence curve of the transmittance. This calculated transmittance agreed with that measured as a ratio of the laser beam power before and after the mirror with 6 ppm difference.     

Reduction of Oxygen Bound with Hemoglobin by Electrolytic Method Using Hydrogen Gas in Phosphate-buff ered Solution

Hemoglobin( Hb) is widely used as an artificial red cell[1 ] to realize the function ofoxygen-delivery,one Hb molecule can bind up with four oxygen molecules through theFe2 +in Hb molecule to form oxygenated Hb( oxy Hb) .Heat treatment at60℃ is animportant step in the purification of Hb for the removal of stroma or unnecessaryproteins and the inactivation of viruses[2 ] .However,oxy Hb is quickly oxidized tomethemoglobin( met Hb,a status that Fe2 +is oxidized to Fe3+) ,and even furtheroxi…     

Propagation characteristics of cold lower hybrid waves in linear tokamak plasmas

Propagation of the cold lower hybrid waves in a cylindrical and a cylindrical tokamak plasmas is studied theoretically. The energy flow trajectory in spiral in the poloidal direction and extends along the toroidal direction, as well. The latter distance to the resonance layer is equal to √M/ma, in order (a: radius of plasma column).     

SiO production from Si(100) and (111) surfaces by reaction with O2 beams

Desorption kinetics of SiO in the reaction of O₂ with Si(100) and (111) surfaces were investigated at surface temperatures between 1000 and 1300 K by using a pulsed molecular beam technique. The gaseous SiO product was detected by a mass spectrometer above 1000 K. At temperatures lower than 1050 K, the SiO signal appeared with an induction time after the O₂ beam irradiation onto the surface, which means that the desorption occurs via sequential steps. The rate constants for two steps were obtained by a computer simulation of the relaxation waveforms of the SiO signal. The values obtained are in the same range as those of D'Evelyn et al. However, they are one order of magnitude larger than those of Yu and Eldridge. The activation energies for the two steps are 2.8 and 2.4 eV for both Si(100) and (111) surfaces. No significant difference between the two kinds of surfaces was found from these values. However, many etch pits were observed on the Si(100) surface after the reaction, while no such etch pits were formed on the Si(111) surface. The planes of the etch pits formed on the (100) surfaces consisted mostly of the {111} facets.     

Total syntheses of both enantiomers of sarcophytols A and T based on stereospecific [2,3]Wittig rearrangement

Both enantiomers of sarcophytols A (1) and T (2), cembranolide diterpenes isolated from a soft coral, were synthesized from a common chiral intermediate, obtained by baker's yeast reduction, using a stereospecific [2,3]Wittig rearrangement as the key step.     

A novel synthesis of 2-(disubstituted amino)-5(4)phenylimidazoles

The reaction of 1-phenyl-1,2-propanedione with 1,1-disubstituted guanidines in methanol yielded 2-(disubstituted amino)-4-hydroxy-4-methyl-4H-imidazoles (III). Compound III produced 5(4)methylimidazoles by catalytic hydrogenation and 5(4)chloromethylimidazoles (IV) by concentrated hydrochloric acid treatment. Solvolysis of IV in water and alcohols gave 5(4)hydroxymethyl- and 5(4)alkoxymethylimidazoles, respectively.