Molecular motion of isolated polybutadiene chains tethered on the fresh surface of polytetrafluoroethylene

The polybutadiene (PBD) chains tethered on the fresh surface of a polytetrafluoroethylene (PTFE) were produced by a block copolymerization of PTFE with 1,3-butadiene in vacuum at 77 K. The extremely low segmental density of the tethered chains was estimated by a spin labelling technique. The tethered chains can be regarded as ‘isolated polymer chains’. The PBD tethered chain has an unpaired electron at the chain end. We studied the molecular mobility of the PBD tethered chains by electron spin resonance (e.s.r.) spectroscopy, using the PBD chain end radical as a probe. The site exchange motion between two conformations at the chain end was observed in the temperature range 77–173 K and the rate of the exchange motion was determined by spectral simulations. The tethered chains are mobile even below 218 K which is a glass transition temperature of 1,4-PBD in the bulk. The high mobility of the PBD chains tethered on the PTFE surface is attributed to: the PBD chains have a very large space around the chains because of an extremely low segmental density on the PTFE surface. © 1997 Elsevier Science Ltd.     

Sequence‐Specific DNA Photosplitting of Crosslinked DNAs Containing the 3‐Cyanovinylcarbazole Nucleoside by Using DNA Strand Displacement

An oligodeoxynucleotide (ODN) containing the ultrafast reversible 3‐cyanovinylcarbazole (^CNVK) photo‐crosslinker was photo‐crosslinked to a complementary strand upon exposure to 366 nm irradiation and photosplit by use of 312 nm irradiation. In this paper we report that the photoreaction of ^CNVK on irradiation at 366 nm involves a photostationary state and that its reaction can be controlled by temperature. Guided by this new insight, we proposed and have now demonstrated previously unknown photosplitting of ^CNVK aided by DNA strand displacement as an alternative to heating. The photo‐crosslinked double‐stranded DNA (dsDNA) underwent >80 % photosplitting aided by DNA strand displacement on irradiation at 366 nm without heating. In this photosplitting based on DNA strand displacement, the relative thermal stability of the invader strand with respect to the template strands plays an important role, and an invader strand/template strand system that is more stable than the passenger strand/template strand system induces photosplitting without heating. This new strand‐displacement‐aided photosplitting occurred in a sequence‐specific manner through irradiation at 366 nm in the presence of an invader strand.     

Development of Strategic Establishment of Technology Bases for a Fusion DEMO Reactor in Japan

The strategic establishment of technology bases required for the development of a fusion demonstration reactor (DEMO) has been discussed by joint endeavors throughout the Japanese fusion community. The mission of Fusion DEMO is to demonstrate the technological and economic feasibility of fusion energy. The basic concept of Fusion DEMO has been identified and the structure of technological issues to ensure the feasibility of this DEMO concept has been examined. The Joint-Core Team consisting of experts from the Japanese fusion community including industry has pointed out that DEMO should be aimed at steady power generation beyond several hundred thousand kilowatts, availability which must be extensible to commercialization, and overall tritium breeding sufficient to achieve fuel-cycle self-sufficiency. The necessary technological issues and activities have been sorted out along with 11 identified elements of DEMO, such as superconducting coils, blanket, divertor, and others. These will be arranged within a time line to lead to the Japanese fusion roadmap.     

Switched current circuit using fixed gate‐potential transistor and automatic tuning circuit

Clock feedthrough (CFT) error is one of the most important problems for switched current (SI) circuits. This paper proposes a SI circuit which can reduce CFT error drastically. The proposed circuit will theoretically reduce both signal‐dependent and independent errors by using CMOS switches under a fixed and appropriate bias. Although conventional circuits based on a similar idea need operational amplifiers or additional capacitors, our proposed circuit requires only MOSFETs. The proposed circuit can reduce CFT current with less power consumption and chip area compared to those of conventional circuits. An automatic tuning circuit, which controls the gate potential appropriately, is also proposed. Simulation results demonstrate the effectiveness of the proposed circuits. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 21–29, 1999     

Photochemical RNA Editing of C to U by Using Ultrafast Reversible RNA Photo-crosslinking in DNA/RNA Duplexes

RNA editing, which is used to edit nucleobases in RNA strands; is more feasible for use in medical applications than DNA editing. We previously reported the photochemical conversion of cytosine to uracil, which required photo-crosslinking, deamination, and photo-splitting. Here, we evaluated the influence of the bases surrounding the target cytosine on the conversion of cytosine to uracil in the RNA strand. The photo-crosslinker 3-carboxyvinylcarbazole(^OHVK), which is more hydrophilic than 3-cyanovinylcarbazole(^CNVK), 3-carboxyamidevinylcarbazole(^NH2VK), and 3-methoxy carbonylvinylcarbazole(^OMeVK), induced faster deamination of cytosine. Furthermore, inosine, which forms two hydrogen bonds with cytosine, was the most efficiently paired base for accelerating photochemical RNA editing. Upon evaluation of the conversion from cytosine to uracil in RNA, the use of oligodeoxynucleotides containing ^OHVK and inosine and the polarity of the bases surrounding the target cytosine were found to be crucial.     

Magnetically actuated micromirror and measurement system for motioncharacteristics using specular reflection

Micromachined magnetically actuated torsional micromirrors have been fabricated. The micromirrors based on silicon were actuated by moving magnet system using hard magnetic (Co-Pt) or soft magnetic (Fe-Ni) thin films. And a system to measure motion characteristics of the micromirrors was assembled with an optical table, optical mounts, and optics. The system is based on a specular reflection of He-Ne laser from the micromirrors. We measured static and resonance characteristics of the micromirrors with Co-Pt film or Fe-Ni film. Then we measured Q factors of the micromirrors; with Co-Pt film in vacuum. Using our system for measurements, we obtained motion characteristics of micromirrors at large angular deflections. Measured resonance characteristics of all micromirrors are in good agreement with the equation of forced vibration with viscous damping. Micromirrors with Co-Pt films have better reproducibility of torsional motions than ones with Fe-Ni films in both dc magnetic field and ac magnetic field. And micromirrors with Fe-Ni films have torsional motion with subpeak at resonance characteristics. The Co-Pt film is more useful as a magnetic film for the micromirror than the Fe-Ni film at static and resonance characteristics     

Integrated polarisation beam splitter using waveguide birefringencedependence on waveguide core width

A novel integrated polarisation beam splitter on a silica-based planar lightwave circuit that utilises the waveguide birefringence dependence on waveguide core width is proposed. It was successfully confirmed that the fabricated splitter has a polarisation extinction ratio of >21 dB over a wide wavelength range of 1530 to 1620 nm     

Uniform electron emission from a nitrogen-doped diamond-basedelectron emitter fabricated by the sintering technique

A nitrogen (N)-doped diamond-based electron emitter has been fabricated by the sintering technique prior to the chemical vapor deposition process in order to improve the uniformity. There are no spatial differences in reflective electron energy loss spectra (REELS) from the diamond-based electron emitter, suggesting that uniform surface conditions are obtained. The uniform electron emission from the obtained electron emitter is confirmed through emission current vs anode voltage characteristics measurements. It seems that the uniformity of the emitter surface results in uniform electron emission from the diamond electron emitter     

Experimental and Numerical Study of Twin Underexpanded Impinging Jets

In this paper, the dual underexpanded impinging jets are experimentally and numerically studied. The experiments were performed by measuring the unsteady and averaged wall static pressures and by visualizing density fields using schlieren method. Numerical calculations were also conducted by solving unsteady three dimensional compressible Navier-Stokes equations with Baldwin-Lomax turbulence model. The main parameters for the dual jets are the non-dimensional distance between the two nozzle centers HID covering 1.5, 2.0, the nozzle to plate separation LID 2.0, 3.0,4.0 and 5.0 and the pressure ratio defined by po/pb 1.0~6.0, where D is the diameter of each nozzle exit, p0 the stagnation pressure and pb the back pressure. It is found that the agreement between the experiments and the calculations is good. The fountain flow at the middle of the two jets is observed both in the experiments and the calculation. According to FFT analysis of the experiments for the twin jets, relatively low frequency (up to 5