Degradation in tensile properties of aromatic polymers by electron beam irradiation

Electron beam irradiation effects of ten kinds of polymers containing various aromatic rings linked by functional groups in the main chain (aromatic polymer) were studied with reference to change in tensile properties. The polymers studied were polyimides ‘Kapton H’, and ‘UPILEX’, polyetherimide ‘ULTEM’, polyamides ‘A-Film’, and ‘APH-50 (nomex type paper)’, poly-ether-ether-ketone ‘PEEK’, polyarylate ‘U-Polymer’, polysulphones ‘Udel-Polysulphone’, and ‘PES’, and modified poly(phenylene oxide) ‘NORYL’. Irradiation was carried out by use of electron beam at a dose rate of 5 × 10³ Gy s^?1 at room temperature. The elongation at break was the most severely influenced by the irradiation and it decreased with increasing dose. The order of radiation resistivity which was evaluated from the dose required for the elongation to become 50% and 20% of the initial value was as follows:Polyimide>PEEK>polyamide>polyetherimide>polyarylate>polysulphone, poly(phenylene oxide)Based on the above experimental results, the following order was proposed as for the radiation stability of the aromatic repeating units composing the main chain:

     

High performance polymer actuator based on carbon nanotube-ionic liquid gel: Effect of ionic liquid

In this study, we investigated a dependence of anionic species of ionic liquids (ILs) (IL: perfluoroalkyltrifluoroborate anions ([C_nF_2n+1BF₃]⁻ (n = 0, 1, 2) and bis(perfluoroalkylsulfonyl)imide anions ([(C_mF_2m+1SO₂)(C_nF_2n+1SO₂)N]⁻ (m, n = 0, 1, 2)) on electrochemical and electromechanical properties. 1-Ethyl-3-methylimidazolium (EMI⁺) was selected as a cation for ILs. 1-Ethyl-3-methylimidazolium trifluoromethyltrifluoroborate (EMI[CF₃BF₃]), 1-ethyl-3-methylimidazolium pentafluoroethyltrifluoroborate (EMI[CF₃CF₂BF₃]), 1-ethyl-3-methylimidazolium fluorosulfonyl(trifluoromethylsulfonyl)imide (EMI[FTA]) and 1-ethyl-3-methylimidazolium pentafluoroethylsulfonyl(trifluoromethylsulfonyl)imide (EMI[C₁C₂]) were synthesized according to the literatures. The generated strains of the bucky-gel electrodes of the actuators containing EMI[CF₃BF₃] (in the high frequency range: 10-0.5 Hz) and EMI[CF₃CF₂BF₃] (in the high frequency range of 1-0.5 Hz) are larger than that containing EMI[BF₄] (that is to say the quick response). For low frequencies (0.1-0.005 Hz), the generated strain containing EMI[CF₃CF₂BF₃] was larger than those containing other ILs (EMI[C_nF_2n+1BF₃] (n = 0, 1) and EMI[(C_mF_2m+1SO₂)(C_nF_2n+1SO₂)N] (m, n = 0, 1, 2)). The Young's modulus of actuators containing EMI[CF₃BF₃] and EMI[CF₃CF₂BF₃] were 145 and 110 MPa, respectively. The melting points of EMI[CF₃BF₃] and EMI[CF₃CF₂BF₃] are lower than that of EMI[BF₄].Therefore, trifluoromethyltrifluoroborate ([CF₃BF₃]⁻) and pentafluoroethyltrifluoroborate ([CF₃CF₂BF₃]⁻) anions performed much better as the actuator using the polymer-supported bucky-gel electrode containing the IL. These results are considered to be the actuator enough to apply actual applications (e.g. tactile display).     

Quantitative method for specific nucleic acid sequences using competitive polymerase chain reaction with an alternately binding probe

We have developed a simple, cost-effective, and accurate method for the quantification of specific nucleic acid sequences by the combined use of competitive PCR and a sequence-specific fluorescent probe that binds to either the gene of interest (target) or internal standard (competitor), referred to as alternately binding probe (ABProbe). In this method, the target and competitor were coamplified with the ABProbe, and then the fluorescence intensity was measured. The ratio of the target to the competitor can be calculated from the fluorescence intensity of the ABProbe using fluorescence quenching and fluorescence resonance energy transfer, that is, the starting quantity of the target is successfully calculated by end-point fluorescence measurement. Therefore, this method eliminates the complex post-PCR steps and expensive devices for real-time fluorescence measurement. We called this method alternately binding probe competitive PCR (ABC-PCR). We quantified amoA as a model target by ABC-PCR and real-time PCR. By comparison, the sensitivity, accuracy, and precision of ABC-PCR were similar to those of real-time PCR. Moreover, ABC-PCR was able to correctly quantify DNA even when PCR was inhibited by humic acid; therefore, this method will enable accurate DNA quantification for biological samples that contain PCR inhibitors.     

Ultrasonic tissue characterization of atherosclerosis by a speed-of-sound microscanning system

We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featuring quantitative measurement of ultrasonic parameters of soft tissues. In the present study, we propose a new concept sound speed microscopy that can measure the thickness and speed of sound in the tissue using fast Fourier transform of a single pulsed wave instead of burst waves used in conventional SAM systems. Two coronary arteries were frozen and sectioned approximately 10 microm in thickness. They were mounted on glass slides without cover slips. The scanning time of a frame with 300 x 300 pixels was 90 s and two-dimensional distribution of speed of sound was obtained. The speed of sound was 1680 +/- 30 m/s in the thickened intima with collagen fiber, 1520 +/- 8 m/s in the lipid deposition underlying the fibrous cap, and 1810 +/- 25 m/s in a calcified lesion in the intima. These basic measurements will help in the understanding of echo intensity and pattern in intravascular ultrasound images.