Effect of heating process on the formation of nanoparticles of elastin model polypeptide, (GVGVP)251, by gamma-ray crosslinking

Nanoparticles were prepared by the thermosensitive aggregation of the elastin model polypeptide, (GVGVP)₂₅₁, and gamma-ray crosslinking. Three different heating processes, “slow heating,” “fast heating,” and “heat shock,” were used for the aggregation of the peptide, followed by gamma-ray crosslinking. Only the “heat shock” process successfully yielded stable nanoparticles with diameters of less than ca. 150 nm and a narrow size distribution. Circular dichroism (CD) spectrometry showed that this polypeptide formed a type-II β-turn structure when the temperature was increased to above the cloudy point in the case of the “heat shock” process; suggesting that this structure might contribute to stable nanoparticle formation by gamma-rays. CD spectrometry also suggested that this structure would be affected during the formation of stable crosslinked particles.     

Optical and acoustical investigation for plastic deformation of isotactic polypropylene/ethylene-1-hexene copolymer blends

The effects of morphology on mechanism of plastic deformation are investigated for binary blends of isotactic polypropylene and rubbery ethylene-1-hexene copolymers. In this work, plastic deformation developed during elongation is investigated by measuring light transmittance, electron microscopy, and ultrasonic propagation in the temperature region between 298 K and 353 K. It is found that the compatible blends hardly show stress-whitening at any temperature, whereas the incompatible blends show distinct stress-whitening below 333 K. Furthermore, microscopic defects such as microvoids and crystalline defects are found to be precursors for crazing which are origin of the stress-whitening.     

Hot Isostatic Pressing of Reactive SnO2 Powder

Tin(IV) oxide (SnO₂) crystallizes at room temperature by adding hydrazine monohydrate ((NH₂)₂· H₂O) to a hydrochloric acid solution of tin, followed by washing and drying. Well-densified SnO₂ ceramics (99.8% of theoretical) with an average grain size of 0.9 μm have been fabricated by hot isostatic pressing for 2 h at 900°C and 196 MPa. Their Vickers hardness and bending strength are 14.4 GPa and 200 MPa, respectively. They exhibit an electrical conductivity of 2 × 10⁻³−9 × 10⁻³ S·cm⁻¹ at room temperature.     

各种引气剂以及抑泡剂对混凝土经时变化状态等的影响

众所周知,采用粉煤灰制备混凝土,因粉煤灰成分中含有未燃炭等微粒子,容易造成阴离子型引气剂吸附在这些微粒子上,导致含气量经时损失.同时在混凝土的制备、运输过程中,因受采用的材料、拌和状态等物理因素影响,还会发生含气量经时增加的现象.所以在制备、管理混凝土时,如何保证出机初期一定的含气量、缓解含气量的经时损失或经时增加,是一项极其关键的技术.本文将就采用能改善上述状态的引气剂、抑泡剂拌和混凝土,对混凝土的经时变化以及抗冻融性等特征产生的影响进行论述.     

Characterization of microstructural damage due to low-cycle fatigue by EBSD observation

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the damage due to cyclic or uniform strain. Samples of Type 316 stainless steel after fatigue and tensile tests were prepared for EBSD observation and the misorientation angle between neighboring points (local misorientation) was evaluated. It was shown that the local misorientation developed due to the cyclic and uniform strain and that its spatial distribution was not uniform. In fatigue samples, the area of large local misorientation tended to form clusters, whereas it localized to the grain boundaries in the tensile samples, and the magnitude of local misorientation and the degree of the localization increased with the strain amplitude. The degree of localization was quantified via statistical processing of the measured data. It was also shown that the source of damage (cyclic or uniform strain) and the loading direction could be deduced from the EBSD observations of the damaged sample.     

Preliminary spectrum shifter design for intermediate energy nuclear data benchmark experiments with DT neutrons

Integral benchmark experiments with DT neutrons are not always sufficient for nuclear data benchmarking in the MeV region, below 10 MeV. A neutron spectrum shifter, which will be placed between a sample and a DT neutron source, is effective to moderate DT neutrons incident to the sample. In order to estimate effects of the spectrum shifter, the ratio of the contribution of 14 MeV neutrons in the leakage neutron and gamma-ray spectra was calculated with MCNP-4C for an experimental configuration at FNS of JAEA, Japan. The calculations were carried out for a Li₂TiO₃ sample with a Be, D₂O, or ⁷LiD spectrum shifter. It was found out that the Be shifter was superior to others and the Be shifter was effective to decrease the contribution of 14 MeV neutrons especially for secondary gamma-ray spectrum measurements.     

A novel ferromagnetic thermo-stent for plaque stabilization that self-regulates the temperature

The purpose of this study is to investigate the vascular wall with a thermally self-regulating, cylindrical stent made of a low Curie temperature ferromagnetic alloy. Physiologic saline was circulated in the silicone model vessel implanted with the stent. The stent-temperature remained nearly constant for variable saline flows, saline temperatures, and magnetic flux densities. Stent implants of this type in human blood vessels could potentially enable thermotherapy and temperature determination without catheterization.     

A carbon dioxide gas sensor by combination of multivalent cation and anion conductors with a water-insoluble oxycarbonate-based auxiliary electrode

A compact and inexpensive carbon dioxide gas sensor was successfully realized by the combination of a divalent magnesium ionic conductor of Mg0.7(Zr0.85Nb0.15)4P6O24 and a divalent oxide anion conducting ZrO2-Y2O3 solid electrolyte with the water-insoluble Li- and Ba-codoped Nd2O2CO3 solid solution as the auxiliary electrode. The sensor response was continuous and reproducible, and the present sensor also demonstrated a theoretical Nernst response in the atmosphere where water vapor, nitrogen oxides, ammonia, etc., coexist. The exposure of the present sensor to water dew and variation in oxygen concentration does not interfere with the sensor response, which will be a great advantage in applying the in situ practical CO2 detection in combustion exhaust gas atmospheres.     

Space charge behavior in polymer film based on increment of capacitance under AC high field

Polymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1 . AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement. We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10018     

Tan δ of ethylene-propylene rubber in cryogenic temperature region–effects of additives and sample thickness

The authors have been developing extruded polymer insulated superconducting power cables. Dielectric loss in electrical insulation cannot be ignored in superconducting cables since conductor loss in the cables is minimal. Studies so far show that ethylene-propylene rubber (EPR) is suitable as an electrical insulating material in the extruded polymer insulated superconducting cable design because it demonstrates excellent mechanical and relatively good electrical qualities at a cryogenic temperature. Widely used EPR includes some kinds of additives; however, their effect on tan δ of EPR at cryogenic temperature remains unknown. The effect of additives such as crosslinking agent and fillers on tan δ of EPR was examined at temperatures of between 4.2 K and 300 K. Thickness dependence of tan δ was also measured using EPR films of different thickness and an extruded EPR insulated cable sample. The results show that additives increase tan δ of relatively thin films of EPR even in the cryogenic temperature region; however, they do not have an intolerable dielectric loss in comparison with conductor loss and heat inflow of the superconducting cable. The remedy to tan δ increase due to the polymer contraction relative to shielding wires has been established.