Magnetocaloric effect of (ErxR1−x)Co2 (R = Ho, Dy) for magnetic refrigeration between 20 and 80 K

Two series of RCo₂ compounds, (Er_xHo_1−x)Co₂ and (Er_yDy_1−y)Co₂, were investigated as magnetic refrigerants for hydrogen liquefaction. A large magnetocaloric effect (MCE) was observed just above the Curie temperature (T_c) of these compounds which both undergo a first-order magnetic transition. The isothermal entropy change ΔS and the adiabatic temperature change ΔT_ad of these compounds were larger than those of other Laves-phase materials such as RAl₂ and RNi₂. However, the temperature range of the large MCE for these compounds was limited. It has been shown that T_c increases almost linearly against the de Gennes factor, and can be controlled by changing the concentration of the rare earth elements while maintaining a first-order transition. By measuring the magnetization and heat capacity, we obtained temperature entropy (T–S) diagrams, which are essential for analyzing the magnetic refrigeration cycle. Both series of compounds showed high potential for use in a regenerative thermal cycle, especially as a combination of several compositions to cover a wide temperature range.     

Highly flame retardant coating consisting of starch and amorphous sodium polyborate

Mixture of starch and amorphous sodium polyborate (SPB) is found to show high flame retardancy, when its aqueous solution is deposited and dried on organic polymer materials such as polyethylene terephthalate (PET) nonwoven, rigid polyurethane (RPU) foam, and polypropylene (PP) nonwoven. The PET nonwoven (10 mm thickness) and the RPU foam (10 mm thickness) coated with the mixture endure the premixed flame of butane gas burner with length of 100 mm for more than 12 min. The PP nonwoven (0.7 mm thickness) endures the nonpremixed flame with length of 65 mm in the 45 degrees Meckel burner test for more than 2 min. The backside temperatures in the both tests remain below 130 °C. The thermal analyses and the SEM observation indicate the mechanism that the SPB foam promotes the carbonization of starch and that the carbonized layer together with the SPB foam insulate inside from oxygen and heat.     

Al-laminated film packaged organic radical battery for high-power applications

A 100-mAh class of aluminum-laminated film packaged organic radical battery with a poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) composite cathode and a graphite anode has been fabricated. Its total weight was 22 g and the thickness was 4.3 mm. Because PTMA comprised only 6.2% of the total cell weight, the energy density was considerably less than that of a lithium ion battery. However, the power density per active material weight was found to be better than that of lithium ion battery. The applications which require high-power capability rather than high-energy density, such as the sub-battery in electronic devices and motor drive assistance in electric vehicles, would be appropriate for organic radical batteries in the future.     

Continuous Band‐Filling Control and One‐Dimensional Transport in Metallic and Semiconducting Carbon Nanotube Tangled Films

Field‐effect transistors that employ an electrolyte in place of a gate dielectric layer can accumulate ultrahigh‐density carriers not only on a well‐defined channel (e.g., a two‐dimensional surface) but also on any irregularly shaped channel material. Here, on thin films of 95% pure metallic and semiconducting single‐walled carbon nanotubes (SWNTs), the Fermi level is continuously tuned over a very wide range, while their electronic transport and absorption spectra are simultaneously monitored. It is found that the conductivity of not only the semiconducting but also the metallic SWNT thin films steeply changes when the Fermi level reaches the edges of one‐dimensional subbands and that the conductivity is almost proportional to the number of subbands crossing the Fermi level, thereby exhibiting a one‐dimensional nature of transport even in a tangled network structure and at room temperature.     

Precipitation sequence in friction stir weld of 6063 aluminum during aging

The precipitation sequence in friction stir weld of 6063 aluminum during postweld aging, associated with Vickers hardness profiles, has been examined by transmission electron microscopy. Friction stir welding produces a softened region in the weld, which is characterized by dissolution and growth of the precipitates. The precipitate-dissolved region contains a minimum hardness region in the aswelded condition. In the precipitate-dissolved region, postweld aging markedly increases the density of strengthening precipitates and leads to a large increase in hardness. On the other hand, aging forms few new precipitates in the precipitate-coarsened region, which shows a slight increase in hardness. The postweld aging at 443 K for 43.2 ks (12 hours) gives greater hardness in the overall weld than in the as-received base material and shifts the minimum hardness from the as-welded minimum hardness region to the precipitate-coarsened region. These hardness changes are consistent with the subsequent precipitation behavior during postweld aging. The postweld solution heat treatment (SHT) and aging achieve a high density of strengthening precipitates and bring a high hardness homogeneously in the overall weld.     

Design and In Vitro Evaluation of Splice-Switching Oligonucleotides Bearing Locked Nucleic Acids,Amido-Bridged Nucleic Acids,and Guanidine-Bridged Nucleic Acids

Our group previously developed a series of bridged nucleic acids (BNAs), including locked nucleic acids (LNAs), amido-bridged nucleic acids (AmNAs), and guanidine-bridged nucleic acids (GuNAs), to impart specific characteristics to oligonucleotides such as high-affinity binding and enhanced enzymatic resistance. In this study, we designed a series of LNA-, AmNA-, and GuNA-modified splice-switching oligonucleotides (SSOs) with different lengths and content modifications. We measured the melting temperature (T_m) of each designed SSO to investigate its binding affinity for RNA strands. We also investigated whether the single-stranded SSOs formed secondary structures using UV melting analysis without complementary RNA. As a result, the AmNA-modified SSOs showed almost the same T_m values as the LNA-modified SSOs, with decreased secondary structure formation in the former. In contrast, the GuNA-modified SSOs showed slightly lower T_m values than the LNA-modified SSOs, with no inhibition of secondary structures. We also evaluated the exon skipping activities of the BNAs in vitro at both the mRNA and protein expression levels. We found that both AmNA-modified SSOs and GuNA-modified SSOs showed higher exon skipping activities than LNA-modified SSOs but each class must be appropriately designed in terms of length and modification content.     

Characterization and properties of polypropylene‐block‐poly(ethylene‐co‐propylene) synthesized by short‐period polymerization

The morphology and mechanical properties of novel block copolymers consisting of isotactic polypropylene (PP) and ethylene–propylene rubber (EPR) synthesized by a short‐period polymerization method were examined using differential scanning calorimetry, atomic force microscopy, dynamic mechanical analysis, and a rheooptical technique. It was found that the novel block copolymers show a single glass transition and EPR segments are trapped into the amorphous region of PP. Furthermore, the rheooptical analysis demonstrates that a drawing process of the EPR‐rich block copolymer induces orientation of the PP lamellae in the EPR matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 958–964, 1999     

Highly Efficient Multi-Step Oxidation Bioanode Using Microfluidic Channels

With the rapid decline of fossil fuels, various types of biofuel cells (BFCs) are being developed as an alternative energy source. BFCs based on multi-enzyme cascade reactions are utilized to extract more electrons from substrates. Thus, more power density is obtained from a single molucule of substrate. In the present study, a bioanode that could extract six electrons from a single molecule of L-proline via a three-enzyme cascade reaction was developed and investigated for its possible use in BFCs. These enzymes were immobilized on the electrode to ensure highly efficient electron transfer. Then, oriented immobilization of enzymes was achieved using two types of self-assembled monolayers (SAMs). In addition, a microfluidic system was incorporated to achieve efficient electron transfer. The microfluidic system, in which the electrodes were arranged in a tooth-shaped comb, allowed for substrates to be supplied continuously to the cascade, which resulted in smooth electron transfer. Finally, we developed a high-performance bioanode which resulted in the accumulation of higher current density compared to that of a gold disc electrode (205.8 μA cm⁻²: approximately 187 times higher). This presents an opportunity for using the bioanode to develop high-performance BFCs in the future.