New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom‐transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well‐controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well‐controlled polymerization and block copolymerization even with lower catalyst concentrations.     

Role of boric acid for a poly (vinyl alcohol) film as a cross-linking agent: Melting behaviors of the films with boric acid

We have investigated the role of boric acid as a cross-linking agent for a poly (vinyl alcohol) (PVA) film when the film is immersed in boric acid aqueous solution. DSC results show that the films with boric acid exhibit the higher glass transition temperatures than that of the PVA film without boric acid, when the films are dried after immersing in boric acid aqueous solutions with various boric acid concentrations, implying that boric acid penetrating into the films slows down the PVA molecular motion. Furthermore, simultaneous small-angle X-ray scattering and wide-angle X-ray diffraction measurements were performed on the melting processes of the PVA films with boric acid. We found that the crystallite size increase originated from melting and recrystallization do not occur for the PVA films with boric acid, whereas in the case of the PVA without boric acid the crystallite size is enlarged in both directions parallel and perpendicular to the chain axis via melting and recrystallization on melting. These indicate that chemical reactions of boric acid to the PVA molecular chains in amorphous regions resulted in cross-linking points take place in boric acid aqueous solutions, inhibiting recrystallization on melting, because the cross-links slow down the PVA molecular motion and must not be included in the crystalline domains.     

AFM observation of OMVPE grown ErP on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates

ErP has been grown on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates by low-pressure organometallic vapor-phase epitaxy. The morphological change with growth temperature has been explored by atomic force microscope. On all the substrates, ErP is grown in island structure. Height and area size of the ErP islands on (1 1 1)A substrate exhibit an obvious dependence on growth temperature. ErP islands grown at 540°C, that is the suitable temperature for ErP formation, gather to step edges to make wires.     

NO/CH4 reaction over nanodispersed Pt particles

The catalytic behavior of the cubic (≈70%) Pt nanoparticles supported on alumina, with an average diameter of 132 nm, was investigated for NO/CH₄ reaction. It was observed that the formation of reaction products (N₂O, CO and NH₃) is related to the size as well to the shape (facet) of the Pt nanoparticles.

     

Energy-dispersive XAFS study on the decarbonylation process of Mo(CO)6 in NaY zeolite

The temperature-programmed decarbonylation process of Mo(CO)₆ in NaY zeolite was studied by means of a time-resolved energy-dispersive XAFS method. The XANES analysis demonstrated that the decarbonylation proceeded by two successive steps via a stable intermediate which existed between 440 and 490 K. The curve fitting analysis of the EXAFS data revealed that the intermediate was a molybdenum monomer subcarbonyl species Mo(CO)₃(O_L)₃ coordinated by three CO ligands and three oxygen atoms of zeolite framework (O_L). Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that the DXAFS technique is a powerful method to study the dynamic behavior of the Mo carbonyl species during decarbonylation process.     

Ultra-lean combustion through the backflow of burned gas in rotating counterflow twin premixed flames

Rotating counterflow twin premixed flames of methane–air were numerically simulated with detailed chemistry based on a similarity solution to explore the leanest extinction limit without preheating and to elucidate the mechanism of “ultra-lean” combustion. We focused on high rotation rate cases in which unrealistic backflow from infinity is allowed to occur since ultra-lean combustion was found to be realized in such a situation. It was found that the reaction zone is in the backflow zone, where the flame’s apparent burning velocity is negative, and that the flame zone width is much smaller than that of a 1-D planar premixed flame due to an inversion of the convexity directions of the profiles of temperature and main species concentrations. The decrease of the flame width seems to make the flame less extinguishable. The equivalence ratio of the leanest flame obtained neglecting radiative heat loss is 0.32, while that obtained with an optically thin radiation model is 0.42, which is still much leaner than the ratio of 0.49 for a 1-D planar premixed flame generated using the same radiation model.     

Electroviscoelastic effect of polymeric composites consisting of polyelectrolyte particles and polymer gel

The dynamic viscoelasticity of polymeric composites consisting of silicone gel and polymethacrylic acid cobalt(II) salt (PMACo) particles was studied in d.c. electric fields. It was measured by applying sinusoidally varying shear strain or compressive strain to the composites. It was found that the electric fields enhanced the storage and loss moduli of the composites, and changed the loss tangent (electroviscoelastic effect). The amount of the electroviscoelastic effect was influenced by the content of absorbed water in the PMACo particle, the fraction of PMACo particles, and the intensity of the electric field. It also depended on the amplitude and frequency of the applied strain. The increments of the compressive moduli due to the electroviscoelastic effect were much larger than those of the shear moduli.     

Construction of an in vitro model system for the anatomical reentry phenomenon of cardiac tissues by using microfabrication techniques

Anatomical reentry has been identified as a major cause of clinical cardiac arrhythmia. The probability for anatomical reentry is strongly dependent on the structures and cell characteristics of the causal cardiac regions. In this paper, we propose a simple in vitro model system for analyzing and simulating the anatomical reentry phenomenon in cardiac tissues. Rat ventricular myocytes were cultured and aligned in predesigned structures by using a microcontact printing method. Excitation propagation in the cultures was visualized and evaluated by applying electrical stimulation and the calcium imaging technique. We confirmed that differences between passage times along the two excitation pathways were modulated by changing the structures of cultured myocytes. This simple in vitro model system will be useful for studying the anatomical reentry phenomenon. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Magnetroviscoelastic behavior of composite gels

Dynamic viscoelasticity of silicone gels having many lines of dispersed iron particles under the influence of external magnetic fields was studied. The particulate composite enhanced its elastic modulus by action of magnetic fields. The magnetroviscoelastic behavior was caused by the cohesive forces between magnetically polarized particles and was analyzed using a simple model of induced dipole-induced dipole interactions. The presented results provide insight into the relationship between macroscopic viscoelastic behavior of the composite gels and the microscopic bondings between dispersed particles. © 1995 John Wiley & Sons, Inc.