Mass transfer in polycrystalline ytterbium monosilicate under oxygen potential gradients at high temperatures

Mass transfer in polycrystalline Yb₂SiO₅ wafers with precise composition control was evaluated and analyzed by oxygen permeation experiments at high temperatures using an oxygen tracer. Oxygen permeation proceeded due to mutual grain boundary diffusion of oxide ions and Yb ions without synergistic effects such as acceleration or suppression. The oxygen shielding properties of Yb₂SiO₅ were compared with those of the other line compounds such as Yb₂Si₂O₇ and Al₂O₃ based on the determined mass transfer parameters. It was found that the more preferentially an oxide ion diffuses in the grain boundary compared to the interior of the grain, the greater the effect of suppressing the movement of the oxide ion by applying an oxygen potential gradient becomes.     

Rapid sensing of trace ionic substances with the novel porous monolith type ion exchanger

Biological and chemical sensor with a rapid response in microlevel test is required for health and environmental monitor. A novel sensing due to porous ion exchanger with three-dimensional acceptor has been first attempted to develop a high-performance sensor. This porous monolith type ion exchanger has an open-cellular monolith structure with 5–50-μm diameter pores. The trace amount of inorganic ions dissolved in aqueous solutions can be quantitatively determined with the impedance given by the monolith, which attracts and adsorbs the ions rapidly. We have succeeded in detecting ions with a concentration as low as 10⁻⁷ mol. The porous ion exchanger has a potentiality as a high-performance device for biological and chemical sensing. POLYM. ENG. SCI., 47:1666–1670, 2007. © 2007 Society of Plastics Engineers     

Purification and some properties of cholesterol oxidase stable in detergents from gamma-proteobacterium Y-134

Cholesterol oxidase (CHO) with high stability in detergents was found from an isolated strain, Y-134, belonging to the gamma-subclass of Proteobacteria. CHO production reached its maximum by incubation at 30 degrees C for 12 d. It was purified from cell-free extract prepared by mixing the cells with 0.4% Triton X-100. The absorption spectrum of the purified enzyme exhibited maxima at 274 and 410 nm, and a shoulder at 330 nm. The molecular mass was 115 kDa with two identical subunits of 58 kDa. The enzyme oxidized cholest-5-en-3beta-ol (cholesterol) and 5alpha-cholestan-3beta-ol (dihydrocholesterol) at a high reaction rate, and the K(m) value for cholesterol was 65 microM. The stability of the enzyme was higher than other CHOs in nonionic detergents with high values of hydrophilelipophile balance (HLB) such as Triton X-450 and sodium cholate. NH2-terminal sequence analysis showed a high similarity to CHO from Burkholderia cepacia, but not to CHOs from Streptomyces or Brevibacterium.     

Spatial dynamics of GFP-tagged proteins investigated by local fluorescence enhancement

We describe a method of monitoring the spatial dynamics of proteins in intact cells by locally enhancing the blue excited fluorescence of green fluorescent protein (GFP) using a spatially focused ultraviolet-laser pulse. GFP fusion proteins were efficiently expressed by micro-electroporation of in vitro synthesized mRNA into adherent mammalian cells. We found that the diffusion coefficient of cycle 3 mutant GFP was 43 microns2/sec, compared to 4 microns2/sec for wild-type GFP, suggesting that cycle 3 GFP diffuses freely in mammalian cells and is ideally suited as a fusion tag. The local fluorescence enhancement method was used to study the membrane dissociation rate of GFP-tagged K-ras, a small GTP binding protein that localizes to plasma membranes by a farnesyl lipid group and a polybasic region. Our data suggest that K-ras exists in a dynamic equilibrium and rapidly switches between a plasma membrane bound form and a cytosolic form with a plasma membrane dissociation time constant of 1.5 sec.     

On the development and characterization of a firebrand generator

A unique experimental apparatus has been constructed in order to generate a controlled and repeatable size and mass distribution of glowing firebrands. The present study reports on a series of experiments conducted in order to characterize the performance of this firebrand generator. Firebrand generator characterization experiments were performed at the Fire Research Wind Tunnel Facility (FRWTF) at the Building Research Institute (BRI) in Tsukuba, Japan. The firebrand generator was fed with three different initial firebrand geometries, two different sized cylinders and one size of disks. Cylinders were used to simulate firebrand fluxes from vegetation, such as trees, while disks were used to simulate a firebrand flux from burning structures. Samples of these geometries were constructed from wood dowels, fed into the firebrand generator, ignited, and the glowing firebrands generated were collected using an array of water filled pans. The pans were filled with water in order to quench combustion. The collected firebrands were subsequently dried and the size and mass distribution was measured. These experiments were performed over a range of wind tunnel speeds, with no wind speed present to 9 m/s, to determine the lofting distance of the firebrands generated. Finally, the size and mass distribution produced from the firebrand generator are compared to those produced from burning trees. Results of the study are presented and discussed.     

中、日、欧的被试者对河川景观注视过程的比较研究

在景观认知·评价过程中,如果把眼球运动作为反映大脑所进行的视觉情报处理过程的外部参数,那么眼的运动方式就可能因评价者的生活经验、知识水平甚至价值观和思维方式的不同而产生差异。因此,可以设想被试者的社会文化背景的差异也有可能会从他们对景观的认知方式上得到体现。作为视觉认知中异域文化差异的比较研究之一,运用眼球运动跟踪仪对评价者的景观认知评价过程进行了跟踪测试,并试图通过对认知过程中的注视点分布、注视点数以及注视点的停留时间和注视内容的变化趋势这几个角度的分析比较来探讨社会文化背景的差异如何体现在人类视觉情报信息的收集整理的外部反应中,从而明确在地域特色景观的保留和营造上构成要素的布局方式的意义。     

Rugate filters fabricated by a radio frequency magnetron sputtering system by use of an optical in situ monitoring technique

We propose, for the first time to our knowledge, a new feedback fabrication technique for rugate filters with sinusoidal refractive index distribution. The technique uses an in situ optical monitoring system, in contrast to conventional techniques for rugate filters that are based on time control, which is generally unsuitable for accurate fabrication of a continuous index distribution. We employed a-SiOx:H thin film as the material for the rugate filters because its refractive index can be successively controlled. Using the proposed technique and material, we fabricated near-infrared rugate minus filters having multiple and continuous refractive index distributions. The experimental and calculated spectra were well correlated as a result of applying the proposed feedback fabrication technique.     

Amino acid sensing by impedance of porous monolith-type ion exchanger

A biological and chemical sensor with rapid response at the microlevel is required for health and environmental monitoring. To develop a high-performance sensor, we use a porous monolith-type ion exchanger having three-dimensional acceptors to sense chemical substances. This porous monolith-type ion exchanger has an open-cellular structure with 5-50-μm diameter pores. The concentration of amino acids in the solution can be detected by measuring the impedance of the monolith-type ion exchanger. The novel ion exchanger has a high-exchange rate and high-electrical conductivity compared with that of the conventional ion-exchange resins. It is found that the impedance of the porous ion exchanger varies widely, depending on the amino acids such as glycine, asparatic acid, lysine, and phenylalanine. The impedance of anion exchanger had the highest value for phenylalanine with a benzene ring. OH-ion conduction is suppressed possibly due to the phenylalanine molecules stabilized by the hydrophobic interaction with the anion exchanger. In addition, we succeeded in sensing amino acid ions with concentration as low as 10⁻⁷ mol. The porous ion exchanger has the potential of a high-performance device for biological and chemical sensing.     

Oxygen permeation mechanism in polycrystalline mullite at high temperatures

The oxygen permeability of polycrystalline mullite wafers, serving as a model environmental barrier coating layer on SiC fiber‐reinforced SiC matrix composites, was evaluated at temperatures above 1673 h with an oxygen tracer gas (¹⁸O₂). Oxygen permeation occurred by grain‐boundary (GB) diffusion of oxygen from the high oxygen partial pressure (high‐Po ₂) surface to the low‐Po ₂ surface, with simultaneous GB diffusion of aluminum in the opposite direction. This GB interdiffusion of both oxygen and aluminum proceeded without acceleration or retardation, maintaining the Gibbs‐Duhem relationship. Oxygen permeation related to the GB diffusion of silicon was negligibly small compared to that generated by aluminum GB diffusion, resulting in decomposition of the mullite near the low‐Po ₂ surface. The GB diffusion coefficients for oxygen in the vicinity of the high‐Po ₂ surface were determined directly from the SIMS‐¹⁸O line profiles along individual GBs, as assessed from cross sections of the exposed wafer. The coefficients thus obtained were comparable to those determined in the absence of an oxygen potential gradient and those calculated from an oxygen permeation trial under the assumption of nearly ionic conductivity.