Mechanisms of orientational and photoelastic birefringence generation of methacrylates for the design of zero–zero‐birefringence polymers

The intrinsic birefringence Δn⁰ and photoelastic coefficient C of poly(methyl methacrylate), poly(2,2,2‐trifluroethyl methacrylate), poly(phenyl methacrylate), and poly(2,2,3,3,3‐pentafluorophenyl methacrylate) were determined. We categorized these methacrylate polymers into four birefringence‐types, even though their molecular structures differed only by the substituents on the side chains. Based on the results of Δn⁰ and C, novel polymers that exhibit neither orientational nor photoelastic birefringence, i.e., zero–zero‐birefringence polymers, were designed and synthesized by quaternary copolymerization system. Furthermore, we confirmed that the mechanisms of orientational birefringence and photoelastic birefringence generation were different in these methacrylate polymers. The conformation of the repeat unit of the polymers was nearly constant during the generation of orientational birefringence. In contrast, the conformation of the repeat unit of the polymers changed during the generation of photoelastic birefringence in the glassy state. These findings demonstrated the reasonability of evaluating orientational and photoelastic birefringence separately, as well as the adequacy of the classification of polymers into four birefringence‐types. Given these results and the fact that zero–zero‐birefringence polymers could be prepared successfully by four‐birefringence type monomers, we demonstrated the reasonability of the method for designing the zero–zero‐birefringence polymers. POLYM. ENG. SCI., 55:1330–1338, 2015. © 2015 Society of Plastics Engineers     

Chaos control and noise suppression in external-cavitysemiconductor lasers

Feedback-induced chaos and intensity noise enhancement in a laser diode with external optical feedback are studied by computer simulations. The enhancement of relative intensity noise (RIN) that is often observed in experiments is considered as a result of the feedback-induced deterministic chaos and the intensity noise suppression is treated from the viewpoint of chaos control. Especially, the conventional noise suppressing technique known as a high-frequency injection modulation is turned into a problem of stabilizing chaos through parameter modulations. We developed an analytical method which allows to optimize the modulation frequency from the linear stability analysis of the dynamical model that describes the laser diode with external feedback. The robustness of the modulation with respect to the modulation frequency and depth is verified and the results suggest the feasibility of applying our method to actual noise suppression. The RIN in the low-frequency region (up to 100 MHz) is shown to be reduced to the solitary laser level when the feedback-induced chaos is effectively controlled with the optimized modulation frequency     

Pulmonary vascular disease and operative indications in complete atrioventricular canal defect in early infancy

Pulmonary vascular disease was morphometrically analyzed in 67 patients (mean age, 19 months) with isolated complete atrioventricular canal defect. Complete obstruction of the small pulmonary arterial lumen resulting from acute fibrous proliferation and atrophy of the peripheral arterial media, which were considered absolute operative contraindications, were characteristic in six patients with Down's syndrome. Morphometric analysis of medial thickness revealed that thinning of the media of the small pulmonary arteries is generally observed at around 6 months of age in patients with complete atrioventricular canal defect and that the media in patients who have complete atrioventricular canal defect and Down's syndrome was thinner than that in such patients without Down's syndrome. These results suggest that thinning of the media as a result of two factors--Down's syndrome and aging--facilitates the rapid occurrence of fibrous intimal proliferation. Therefore intracardiac repair is desirable within 6 months of life, before medial thinning, in patients with complete atrioventricular canal defect and Down's syndrome. Excluding patients with absolute operative contraindications, the scores of the index of pulmonary vascular disease in operative survivors were below 2.0 and death occurred when scores were more than 2.2. The pulmonary vascular resistances measured in room air and by the oxygen inhalation and tolazoline tests in patients with operative contraindications were more than 7.3, 3.8, and 6.6 units.m2, respectively. We thus conclude that lung biopsy should be undertaken for patients in whom pulmonary vascular resistance is beyond these values to determine the appropriateness of surgical intervention.     

Graphite formation on Ni film by chemical vapor deposition

Thin film formation of graphite by chemical vapor deposition using 2-methyl-1,2′-naphthyl ketone as a starting material was carried out on Ni film substrates. On Ni films directly deposited on quartz glass, the graphite films were obtained when the Ni film thickness was above 1 000 Å and above 5 000 Å at 700 °C and 1 000 °C, respectively. Depositions on thinner Ni film substrates comprise amorphous carbon (a-C) or graphite tubes which was owing to the thermal coagulation of the Ni film into droplets. On the other hand, graphite film was obtained on the Ni film with thickness 10 Å when a-C was inserted between the Ni film and the quartz glass. The coagulation of the Ni film is considered to be avoided by inserting a-C layer.     

Prediction of spectral reflectance factor distribution of automotive paint finishes

It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125     

New approach to environmentally benign epoxidation: the solid-phase-system using urea–H2O2 and recyclable dodecatungstate on apatite

On the basis of new concept using a solid disperse phase we have developed an efficient catalytic solid-phase-system for epoxidations of alkenes using urea–hydrogen peroxide (urea–H₂O₂) complex and cetylpyridinium dodecatungstate ((CetylPy)₁₀[H₂W₁₂O₄₂]) catalyst on fluorapatite (FAp). The recovered solid catalyst phase was reused to keep the catalytic activity after several times. In the conceptual idea it is a key point that in situ solid-phase-activation of the catalyst with urea–H₂O₂ proceeds to form microcrystals of the active species dispersed on the solid phase. The dispersion of the catalyst on FAp in the case of tungstic acid (H₂WO₄) was suggested by EPMA analysis. We proposed the peroxo type of species keeping the parent polyoxometalate framework as novel active species from FT-IR spectroscopic studies. FAp phase plays important roles of dispersing the active species on its surface to have high catalytic activity and of stabilizing the active species to lead to high reusability.     

Fibre Bragg grating compression-tuned over 110 nm

A fibre Bragg grating with a tuning range covering beyond the C- and L-bands has been realised, which represents the broadest tuning range reported of any Bragg grating. The device exhibits constant spectral response and polarisation mode dispersion within these bands.     

Phenol novolac/poly(4- hydroxyphenylmaleimide) blend hardeners for DGEBA-type epoxy resin

Phenol novolac/poly (4-hydroxyphenylmaleimide) (PHPMI) blends were used as an epoxy resin hardener. The curing behavior of the above system and the thermal and mechanical properties of the cured epoxy resin were studied. It was not necessary to use a curing accelerator for this system, because PHPMI caused acceleration of the curing reaction. The curing mechanism of this system was investigated by using model compounds. Test pieces from the neat resins and the glass fiber reinforced resins were evaluated in terms of thermal and mechanical properties, respectively. It was found that heat resistance and mechanical properties were improved by increasing the amount of PHPMI in the hardener.