Novel abrasive-free planarization of 4H-SiC (0001) using catalyst

A new abrasive-free planarization method for silicon carbide (SiC) wafers was proposed using the catalytic nature of platinum (Pt). We named it catalyst-referred etching (CARE). The setup equipped with a polishing pad made of Pt is almost the same as the lapping setup. However, CARE chemically removes SiC with an etching agent activated by a catalyst in contrast to mechanical removal by the lapping process. Hydrofluoric acid which is well known as an etchant of silicon dioxide (SiO₂) that cannot etch SiC, was used as the source of the etching agent to SiC. The processed surfaces were observed by Nomarski differential interference contrast (NDIC) microscopy, atomic force microscopy (AFM), and optical interferometry. Those observations presented a marked reduction in surface roughness. Moreover, low-energy electron diffraction (LEED) images showed that a crystallographically well-ordered surface was realized.     

Comparative analysis of co-authorship networks considering authors' roles in collaboration: Differences between the theoretical and application areas

Summary Many studies have analyzed “direct” partnerships in co-authorship networks. On the other hand, the global network structure, including “indirect” links between researchers, has not yet been sufficiently studied. This study analyzes researchers' activities from the viewpoints considering their roles in the global structures of co-authorship networks, and compares the co-authorship networks between the theoretical and application areas in computer science. The modified HITS algorithm is used to calculate the two types of importance of researchers in co-authorship networks, i.e., the importance as the leader and that as the follower.     

Separation and Determination of Functional Complex Lipids from Chicken Skin

Complex lipids including sphingolipid and plasmalogens were expected to be used as functional supplement, although their physiological activities have not been fully demonstrated. Although these complex lipids exist voluminously in brain and nervous tissues, hardly any animal resources of these lipids have been used since the outbreak of bovine spongiform encephalopathy. Thus, the chemical composition and concentration method of complex lipids from the skin of mature laying hens, a huge amount of which is wasted every year, has been investigated. Total lipid yield (32 g/100 g) prepared from chicken skin contained 2% complex lipids. Total lipids predominantly consisted of triacylglycerol (TAG), with phosphatidylcholine, sphingomyelin (SM) and phosphatidylethanolamine (PE) generally predominant as complex lipids. PE was primarily plasmalogens (62 mol%), of which arachidonic acid (47.6 mol%) and docosahexaenoic acid (11.2 mol%) were the predominant fatty acids. The component sphingoid base of sphingomyelin was almost totally 4-trans sphingenine (sphingosine). The complex lipids were able to be separated from an ethanol extract of minced skin in good yield by solvent fractionation with a hexane/ethanol system. Moreover, highly purified SM (>95 wt%) was prepared by a combination of solvent fractionation and alkaline/acidic hydrolysis from the ethanol extract. Thus, it was shown that culled chicken skin could be a potential resource of the antioxidant phospholipid plasmalogens and human-type sphingolipid.     

LiBH4 as solid electrolyte for Li-ion batteries with Bi2Te3 nanostructured anode

The present study highlights the first-ever application of fastest lithium (Li) ion conducting complex hydride containing cluster anions, namely lithium borohydride (LiBH₄) into an all-solid-state Li-ion battery having Bi₂Te₃ as anode material. Bi₂Te₃ nanostructures were prepared by the simple wet chemical method and characterized by their crystal structure, morphology and electronic structure using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). SEM and TEM experiments revealed the dimensions as 20–60 nm for nanoparticles and 30–90 nm for nanosheets. The formation of Bi₂Te₃ nanostructures along with Bi₂O₃ as the residual phase is confirmed by XRD analysis. The crystallite size of nanoparticles and nanosheets are calculated as 19 nm and 39 nm respectively from XRD profile. The XPS study also confirms the formation of nanostructured Bi₂Te₃ along with Bi₂O₃. Finally, the electrochemical performance of these nanostructures is observed using the galvanostatic charge-discharge curve at 0.1C and 0.5C.     

Distinct roles of two anaplerotic pathways in glutamate production induced by biotin limitation in Corynebacterium glutamicum

Corynebacterium glutamicum is a biotin auxotrophic bacterium in which glutamate production is induced under biotin-limited conditions. During glutamate production, anaplerotic reactions catalyzed by phosphoenolpyruvate carboxylase (PEPC) and a biotin-containing enzyme pyruvate carboxylase (PC) are believed to play an important role in supplying oxaloacetate in the tricarboxylic acid cycle. To understand the distinct roles of PEPC and PC on glutamate production by C. glutamicum, we observed glutamate production induced under biotin-limited conditions in the disruptants of the genes encoding PEPC (ppc) and PC (pyc), respectively. The pyc disruptant retained the ability to produce high amounts of glutamate, and lactate was simultaneously produced probably due to the increased intracellular pyruvate levels. On the other hand, the ppc knockout mutant could not produce glutamate. Additionally, glutamate production in the pyc disruptant was enhanced by overexpression of ppc rather than disruption of the lactate dehydrogenase gene (ldh), which is involved in lactate production. Metabolic flux analysis based on the 13C-labeling experiment and measurement of 13C-enrichment in glutamate using nuclear magnetic resonance spectroscopy revealed that the flux for anaplerotic reactions in the pyc disruptant was lower than that in the wild type, concomitantly increasing the flux for lactate formation. Moreover, overexpression of ppc increased this flux in both the pyc disruptant and the wild type. Our results suggest that the PEPC-catalyzed anaplerotic reaction is necessary for glutamate production induced under biotin-limited conditions, because PC is not active during glutamate production, and overexpression of ppc effectively enhances glutamate production under biotin-limited conditions.     

Swelling pressure and leaching behaviors of synthetic bituminized waste products with various salt contents under a constant-volume condition

We investigated the swelling pressure of synthetic bituminized waste products (BWPs) and the amount of Na⁺ in the leachate from them under a constant-volume condition when the BWPs were in contact with water to understand influences of salt content on the surrounding environments after disposal of radioactive BWPs in a geological repository. The observation of the cross section of the synthetic BWP specimens revealed that micropores, which were formed after soluble salts leached out from the specimens, shrank and deformed near the surface of the specimens. The salt content in the synthetic BWP specimens depended on the amount of water taken up, indicating that an increase in the amount of water led to increases in the swelling pressure and the cumulative amount of Na⁺ in the leachate. It was found that the shrinkage and deformation of the micropores near the surface of the synthetic BWP specimens that arose under the constant-volume condition significantly influenced increases in the swelling pressure and cumulative amount of Na⁺ in the leachate.     

Photocatalytic reduction of CO2 with H2O on Ti-MCM-41 and Ti-MCM-48 mesoporous zeolite catalysts

Titanium oxide species included within the framework of mesoporous zeolites (Ti-MCM-41 and Ti-MCM-48) prepared by a hydrothermal synthesis exhibited high and unique photocatalytic reactivity for the reduction of CO₂ with H₂O at 328 K to produce CH₄ and CH₃OH in the gas phase. In situ photoluminescence, diffuse reflectance absorption, ESR and XAFS investigations indicated that the titanium oxide species are highly dispersed within the zeolite framework and exist in tetrahedral coordination. The charge transfer excited state of the highly dispersed titanium oxide species played a significant role in the reduction of CO₂ with H₂O exhibiting a high selectivity for the formation of CH₃OH.     

Oxidation‐Resistant and Elastic Mesoporous Carbon with Single‐Layer Graphene Walls

An oxidation‐resistant and elastic mesoporous carbon, graphene mesosponge (GMS), is prepared. GMS has a sponge‐like mesoporous framework (mean pore size is 5.8 nm) consisting mostly of single‐layer graphene walls, which realizes a high electric conductivity and a large surface area (1940 m² g^?1). Moreover, the graphene‐based framework includes only a very small amount of edge sites, thereby achieving much higher stability against oxidation than conventional porous carbons such as carbon blacks and activated carbons. Thus, GMS can simultaneously possess seemingly incompatible properties; the advantages of graphitized carbon materials (high conductivity and high oxidation resistance) and porous carbons (large surface area). These unique features allow GMS to exhibit a sufficient capacitance (125 F g^?1), wide potential window (4 V), and good rate capability as an electrode material for electric double‐layer capacitors utilizing an organic electrolyte. Hence, GMS achieves a high energy density of 59.3 Wh kg^?1 (material mass base), which is more than twice that of commercial materials. Moreover, the continuous graphene framework makes GMS mechanically tough and extremely elastic, and its mean pore size (5.8 nm) can be reversibly compressed down to 0.7 nm by simply applying mechanical force. The sponge‐like elastic property enables an advanced force‐induced adsorption control.     

简易拉伸装置的设计及其在含氮奥氏体钢中子散射中的应用

结合原位中子小角度散射的实际要求,设计了一种整体结构简单、试样安装方便的U型悬臂式拉伸变形装置.该装置通过导向滑孔与移动滑杆间的耦合来确保实现单向拉伸变形;分别贴于试样平直部位与夹头圆柱部位的应变片组用于获取试样的应力-应变响应.分步拉伸试验表明,塑性变形过程中试样的应力松弛在停止加载后的前200 s最为显著,过后松弛较为缓慢.中子小角散射初步结果表明该装置能满足原位拉伸变形的要求,并在含氮奥氏体钢中纳米偏聚团对材料形变强化过程的影响机制研究中发挥着重要作用.