Highly controlled side-chain chromophore orientation in poly[N-1-(1-pyrenyl)ethyl-l-glutamines]

Poly[N⁵-(R and S)-1-(1-pyrenyl)ethyl-l-glutamines] (1 and 2) were prepared by condensation of poly(l-glutamic acid) with optically resolved amines. In solution, these polymers, 2 in particular, gave large circular dichroism (CD) indicative of exciton coupling among the side-chain pyrene chromophores. When compared with the corresponding polymer with achiral side groups, i.e. poly(1-pyrenylmethyl-l-glutamine) (3), 1 and 2 not only gave much stronger CD, but also gave much reduced excimer emission with a significant hypsochromic shift of emission maximum. The highly controlled orientation of the side-chain chromophores is apparently brought about by the specific steric interactions among the bulky chiral side chains along the helical main chain.     

Fundamental study of the development of a transformer with low‐viscosity silicone liquid

Silicone liquid is less flammable and produces less environmental pollution compared with mineral oil. Applicability of 20‐cSt silicone liquid to transformers was investigated from the viewpoints of insulation, cooling performance, and the less‐flammability evaluation. The results showed that the basic characteristics of 20‐cSt silicone liquid were verified in application to a less‐flammable transformer. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 21–28, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20483     

Degradation of trichloroethylene and related compounds by <Emphasis Type="Italic">Mycobacterium</Emphasis> spp. isolated from soil

 Mycobacterium spp. strains TA5 and TA27 (ethane-utilizing bacteria), which can degrade trichloroethylene (TCE) and 1,1,1-trichloroethane (1,1,1-TCA), were isolated from soil. Both bacteria could cometabolically degrade dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-TCA, 1,1,2-TCA, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, and TCE with ethane as a carbon source. They could not degrade carbon tetrachloride, freon 113, or tetrachloroethylene. The TCE degradation characteristics of strain TA27 were determined. Under a head-space gas containing 3% ethane, strain TA27 degraded more than 95% of TCE at an initial concentration of 1 mg l^–1 within 3 days. We observed good growth and TCE degradation between 25 and 35  °C. At an initial TCE concentration of 30 mg l^–1, it degraded 30% of TCE within 7 days. Although growth was inhibited for more than 50 mg l^–1 TCE at 3% ethane concentration, good growth and 50% degradation of TCE were observed at 12% ethane concentration within 14 days. High ethane concentration may mitigate the toxicity of TCE. Received: 24 January 2000 / Accepted: 10 March 2000     

Growth arrest and chromosome instability in aneuploid yeast

Aneuploid generation and stability are biologically important. In the present study, we investigated fission yeast aneuploids, focusing on the process through which aneuploidy is resolved into stable euploidy. The viability and growth patterns of aneuploid spores were greatly influenced by culture conditions, including nutrition and temperature. Germ tube formation and DNA synthesis in a major portion of aneuploids were greatly delayed or arrested. Observation of individual spores and their growth profiles revealed that a certain type(s) of aneuploid resolved its aneuploidy into normal euploids through anomalous cell divisions, which in many cases produced dead cells. Another type of aneuploid, disomy of chromosome 3, the only maintainable aneuploid between n and 2n, showed a peculiar cell division arrest phenotype under a certain growth condition. Microcolonies that formed from this type of aneuploid often contained a population of cells that became incompetent for cell division. This cell division arrest was not due to a nutritional limitation. During this peculiar process of colony formation, stable haploids or diploids were frequently produced. All other types of aneuploids are usually inviable, at least under our experimental conditions. To examine the aneuploid issue more systematically, we constructed a system to select for disomy of chromosome 1 or 2 using intragenic complementation of ade6-M210 and -M216 alleles. This genetic selection system revealed that fission yeast aneuploids can be stabilized through structural chromosome changes, including partial duplication and circular mini-chromosomes.     

Fast scanning method for one-dimensional surface profile measurement by detecting angular deflection of a laser beam

A fast scanning method for one-dimensional surface profile measurement is proposed. The profile is measured by integration of a slope distribution of the surface obtained from angular deflection of a scanning laser beam. A scanning optical system that consists principally of a spherical concave mirror and a rotating scanner mirror has reasonably low cost and is insensitive to mechanical vibration because of its high-speed scanning, of the order of milliseconds. A surface profile of a polygonal mirror along a 5-mm width was measured with the scanning method and with an interferometer. The root-mean-square difference between the two measured results is 0.98 nm.     

Disturbance-free distributed Bragg reflector laser-diode interferometer with a double sinusoidal phase-modulating technique for measurement of absolute distance

A new range-finding technique that uses both double sinusoidal phase modulation and quasi-two-wavelength interferometry is described. Two independent interference signals are generated with respect to two different wavelengths on a time-sharing basis. We clarify that external disturbances of these interference signals are eliminated by both feedback control and differential detection and that the feedback control does not affect the distance measurement. A single distributed Bragg reflector laser diode allows us to simplify the optical setup and to improve the measurement accuracy. After discussing a measurement range, we estimate a measurement error by making several measurements.     

Fracture mechanism of unidirectional carbon-fibre reinforced epoxy resin composite

The object of this study was to investigate the fracture mechanism of unidirectional carbon-fibre reinforced epoxy resin composite. For this purpose, the failure process of the composite under load was observedin situ by scanning electron microscopy and the matrix deformation around the broken fibre tip was examined by polarized transmission optical microscopy using a thin section of the composite. The failure process was shown to proceed through the following four stages: (1) fibre breakage began to occur at a load of about 60% of the failure load; (2) as the applied load was increased, plastic deformation occurred first from the broken fibre tip along the fibre sides, followed by final matrix cracking in the plastic region; (3) just before failure, partial delamination occurred, originating from fibre breakage and matrix cracking; (4) finally, a catastrophic crack propagation occurred from the delamination, leading to composite failure. Acoustic emission monitoring was also carried out for non-destructive evaluation, which indicated that internal failure began to occur at a load of 60% of the failure load and propagated remarkably before composite failure. A close correspondence between the acoustic signal and crack formation was obtained. The acoustic signal at lower amplitude, occurring over whole load range, corresponded to fibre breakage and matrix cracking while that at higher amplitude, occurring only just before failure, corresponded to partial delamination. From these experimental studies, the fracture mechanism of the composite has been clarified.     

Mechanism of fracture of short glass fibre-reinforced polyamide thermoplastic

The mechanism of fracture of short glass fibre-reinforced polyamide 6.6 thermoplastic was studied by means of optical and electron microscopy and acoustic emission methods. It was found that there were three stages in the failure, i.e. initiation of the interfacial cracks at fibre ends, propagation of the interfacial cracks along fibre sides, and propagation of the crack into the matrix leading to the failure of the composite. On the fracture surface, fibres were almost pulled-out from the matrix, not broken. The close correspondence between the crack initiation and propagation and the amplitude of AE signals was observed. The AE signals of lower amplitude occurring under a relatively low stress were considered to be made in association with the initiation and propagation of the interfacial cracks. The AE signals of higher amplitude observed prior to the failure of the composite were considered to be made in association with the occurrence of the matrix cracks. Furthermore, in order to analyse the effect of the stress state in the composite on crack occurrence and propagation, the stress levels in matrix, fibre and interface were estimated for the composite stressed to the failure stress. The calculation was based on the equivalent inclusion method proposed by Eshelby and on an assumption of a perfect bond between the matrix and the fibres. The result was found to be consistent with the mechanism of the fracture, the occurrence of the interfacial cracking in the initial stage and the matrix cracking in the final one.     

An experimental study of the acousto-elastic effect in a rolled plate of steel

The acousto-elastic effect in rolled steel is studied experimentally by transmitting ultrasonic transverse waves and measuring amplitudes of reflected echoes. A Y-cut quartz transducer with a frequency 4.8 MH_z and ultrasonic flaw detection equipment are used for generation and detection of waves, and three tensile specimens with different orientations are prepared from a rolled plate so as to ascertain an important role of its slight orthotropy. At first the variation of amplitude with the transducer direction is examined in the unstressed state, and the slight orthotropy of each specimen is determined quantitatively. Then the variation of amplitude with the tensile stress is examined in the elastic range. The results depend clearly on the orientation of each specimen, and rotation of polarization direction is affirmed in the specimen with an inclination 45° against the rolling direction. Quantitative discussions about the whole experimental results give the conclusion that the acousto elastic effect in this rolled plate obeys the relations which were proposed theoretically by one of the authors.