Polymerization of macromers

Summary The possibility of group transfer polymerization of methyl methacrylate-terminated polystyrene macromer (MA-PSt) was explored by using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene and tris(dimethylamino)sulfonium difluorotrimethylsilicate as initiator and catalyst, respectively. The results obtained at the polymerization temperature of 0°C were undesirable. However, the oligomerization at -78°C gave almost quantitatively oligo(MA-PSt) of which the degree of polymerization was in good agreement with the mole ratio of macromer to initiator. The GPC curve of oligo(MA-PSt) was sharp and symmetrical. In addition, it was shown by the copolymerization with methyl methacrylate that the polymerizability of the macromer was markedly enhanced in the presence of methyl methacrylate comonomer.     

Oxygen evolution anodes composed of anodically deposited Mn-Mo-Fe oxides for seawater electrolysis

Preparation of anodes for oxygen evolution in seawater electrolysis was carried out. Manganese-molybdenum double oxides, Mn_1−xMo_xO_2+x, prepared by anodic deposition from MnSO₄-Na₂MoO₄ solutions showed the 100% oxygen evolution efficiency at a current density of 1000 A m⁻² in 0.5 M NaCl at 30 °C and pH 12, but an increase in solution temperature resulted in dissolution of the oxides as molybdate and permanganate ions. In order to increase the stability of the electrodes at higher temperatures the addition of iron to the manganese-molybdenum oxides was performed by anodic deposition in MnSO₄-Na₂MoO₄-FeNH₄(SO₄)₂ solutions. The electrodes thus prepared showed the 100% oxygen evolution efficiency at 1000 A m⁻² in 0.5 M NaCl at 30-90 °C, when proper amounts of molybdenum and iron were contained. The iron addition also enhanced the oxygen evolution efficiency. The electrodes were not composed of oxide mixtures but triple oxides, Mn_1−x−yMo_xFe_yO_2+x−0.5y, consisting of Mn⁴⁺, Mo⁶⁺ and Fe³⁺. The formation of the triple oxides seemed responsible for enhancement of both oxygen evolution efficiency and stability.     

Thermal decomposition of uranium peroxide hydrates

The thermal decomposition of uranium peroxide hydrates, UO₄·4H₂O and UO₄·2H₂O, has been investigated by thermal analyses, X-ray diffraction study and infrared spectroscopy. As a result, it is concluded that the thermal decomposition of uranium peroxide hydrates proceeds in the following sequence: where 3 ≤ x ≤ 3.5.     

Immobilization of multicopper oxidase from Pyrobaculum aerophilum onto an electrospun-aligned single-walled carbon nanotube surface via a carbon-nanotube-binding peptide for biocathode

Biofuel cells (BFCs) that produce electrical energy from organic resources through enzymatic reactions have been attracting significant attention. Owing to the high electrical conductivity of carbon nanotubes (CNTs), their modification on the electrode surface of a BFC is expected to increase the current, and their high specific surface area may be useful in increasing the power output. Previously, we constructed a biocathode by immobilizing multicopper oxidase from Pyrobaculum aerophilum (McoP) with a carbon nanotube binding peptide (CBP) sequence on the CNTs. This resulted in higher current densities than when using enzymes without CBP sequences. However, owing to the randomly stacked CNTs on the surface of the electrodes, their conductive properties were impaired and performance as biocathodes was poor. Herein, we constructed a biocathode in which single-walled CNTs (SWCNTs) were oriented one-dimensionally and McoP is immobilized on the surface of an SWNCT via CBP. The current density was successfully increased by two-fold by orienting the CNTs and orienting and immobilizing McoP on their surfaces. This technology provides insights into the development of biodevices with controlled orientation of both the SWCNTs and enzymes immobilized on their surfaces.     

基于固态LTD的大容量脉冲功率电源

固态直线变压器驱动源(LTD)是新型的脉冲功率电路方法之一.其工作原理基于大量功率半导体器件的同步控制,因此它在电路结构和工作特性方面与传统的脉冲功率电源有很大不同.在此通过实验,首先验证了LTD的基本工作原理,进而试制了一台采用650个功率MOSFET的LTD系统.实验结果分别给出了超过20 kV的最高输出电压和超过3.2 kA的最高输出电流,上升时间(10％～90％)小于20 ns.在此基础上还采用少量的模块验证了双极性LTD的可行性.实验结果同时也显示了开关的导通电阻对LTD输出参数的影响和由此带来的技术问题.     

Materials for global carbon dioxide recycling

CO₂ emissions, which induce global warming, increase with the development of economic activity. It is impossible to decrease the CO₂ emissions by suppression of the economic activity. Global CO₂ recycling can solve this problem. The global CO₂ recycling consists of three district: The electricity is generated by solar cells on deserts. At desert coasts, the electricity is used for H₂ production by seawater electrolysis and H₂ is used for CH₄ production by the reaction with CO₂. CH₄ which is the main component of liquefied natural gas is liquefied and transported to energy consuming districts where CO₂ is recovered, liquefied and transported to the desert coasts. A CO₂ recycling plant for substantiation of our idea has been built on the roof of the Institute for Materials Research in 1996. Key materials necessary for the global CO₂ recycling are the anode and cathode for seawater electrolysis and the catalyst for CO₂ conversion. All of them have been tailored by us. They have very high activity and selectivity for necessary reactions in addition to excellent durability. A pilot plant consisting of minimum units in an industrial scale is going to be built in three years.     

Generalized multiplicative stochastic processes arising from one-dimensional maps with noise

Artificial Life and Robotics - We propose a class of generalized multiplicative stochastic processes obtained by introducing an endo-perspective into one-dimensional maps with additive noise. We...     

A two-step surface-based 3D deep learning pipeline for segmentation of intracranial aneurysms

Computational Visual Media - The exact shape of intracranial aneurysms is critical in medical diagnosis and surgical planning. While voxel-based deep learning frameworks have been proposed for this...     

Morphological characteristics of flood refugia of cobble-bed vegetation

Periodic flooding alters riverine vegetation community composition; moderate flood disturbance maintains communities at an early seral stage, whereas severe floods may remove entire communities. After disturbance, plants may recolonize riverbeds from refugia.Here, we investigated the morphological characteristics of refugia where riverine plants survived large floods. At three sites, plant communities growing on cobble-bars were surveyed, and the hydraulic characteristics of each site were analyzed. The populations of an indicator plant, Anaphalis margaritacea sub-species yedoensis (Franch. et Savat.) were assessed after major floods in 2004 and 2009. At each survey, the particle size and bed composition were measured, and the critical shear-stress required to move particles at each site was calculated. A one-dimensional flow and the average and local shear-stress at ten different discharges, including that of the largest flood were calculated. The results demonstrate that the A. margaritacea community is maintained at locations where the local shear-stress at peak discharge in large-floods does not exceed a critical value. These conditions were achieved in locations with particular morphological characteristics, where the river is not constrained by levees and is restricted by a downstream narrow-pass; in this reach river width increases with discharge thus limiting the increase in water depth with increasing discharge and allowing the establishment of refugia where plant species may survive large floods.Flooding and reestablishment from refugia maintain a characteristic riverbed community in equilibrium.     

Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature

Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO₂ under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO₂, above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials.