Efficient wet etching of GaN (0001) substrate with subsurface damage layer

Photoenhanced chemical (PEC) etching is applicable for processing an n-GaN (0001) surface rapidly. In this process, the surface oxidation is enhanced by photo-generated holes and the resulting oxide can dissolve into solutions. In current work, we conduct bias-assisted PEC etching in a KOH solution with a positively biased wafer, to remove the crystallographically highly damaged layer. The employed substrate was mechanically polished with diamond slurry of sub-micrometer particle size. Without the positive bias, the rate of PEC etching was quite low because the photogenerated holes were quickly depleted by the recombination process at the crystallographic defects and they could not contribute to the oxidation. On the other hand, in the case where the bias was applied, the photogenerated holes and electrons are separated forcibly in the band-bended surface, which effectively contributed to surface oxidation. As a result, a high removal rate was realized even on the damaged surface.     

Exceptional plasticity of silicon nanobridges

The plasticity of covalently bonded materials is a subject at the forefront of materials science, bearing on a wide range of technological and fundamental aspects. However, covalent materials fracture in a brittle manner when the deformation exceeds just a few per cent. It is predicted that a macroscopically brittle material like silicon can show nanoscale plasticity. Here we report the exceptional plasticity observed in silicon nanocontacts ('nanobridges') at room temperature using a special experimental setup combining a transmission electron microscope and a microelectromechanical system. When accounting for surface diffusion, we succeeded in elongating the nanocontact into a wire-like structure, with a fivefold increase in volume, up to more than twenty times the original length. Such a large plasticity was caused by the stress-assisted diffusion and the sliding of the intergranular, amorphous-like material among the nanocrystals.     

Averaging effect on stochastic response prediction in FastADR aggregation for building air‐conditioning facilities

This letter reports on the averaging effect on prediction errors of the fast automated demand response (FastADR) power limitation amount calculated by our autoregressive and neural net models for a large number of multi‐type building air‐conditioning facilities. The standard deviation of prediction error variation decreases with the number of FastADR trials according to the rule. This result will be useful for estimating the averaging effect in the prediction of FastADR for a large number of target facilities. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

绍兴市地下管线普查管理特色与经验

许多城市开展了地下管线普查,但普查管理方法却不尽相同。本文基于笔者从项目调研到项目竣工验收全过程参与绍兴市地下管线普查建设与管理的经验,从不同的角度介绍了绍兴市管线普查管理与项目运作过程,重点阐述了管线普查的质量管理及项目管理的特色,希望对其他城市地下管线普查有所借鉴。     

Chemical States of Implanted Aluminum Ions in Silica and Silicon Ions in Alumina

Aluminum and silicon ions have been implanted in silica glass and α-alumina single crystal, respectively, to doses ranging from 1 × 10¹⁵ to 1 × 10¹⁷ ions·cm^-2. The chemical states of these implanted ions have been studied by X-ray fluorescence spectroscopy. It is found that the implanted aluminum atoms are coordinated only by oxygen atoms, irrespective of implantation dose. On the other hand, the implanted silicon atoms are coordinated only by oxygen atoms at low doses and by both oxygen and silicon atoms at high doses. Although the chemical state of the aluminum atoms is unchanged by heat treatment, that of the silicon atoms is changed toward a less positively charged state. It is inferred that the chemical states of the implanted atoms are controlled by the transport process, although these tend to obey the thermodynamic stability.     

Effects of La substitution for Nd in (Nd2−xLax)BaZnO5 solid solutions on microwave dielectric properties and crystal structure

The synthesis and microwave dielectric characterization of (Nd_2−xLa_x)BaZnO₅ solid solutions were studied. The samples obtained were single phase over the whole composition range and the lattice parameters of solid solutions were linearly increased with increasing the composition. Moreover, the expansion of the volume in the RO₈ (R=Nd and La) and BaO₁₀ polyhedra and ZnO₄ tetrahedron were recognized when Nd ions were substituted by La. These variations in the lattice parameters and volumes of the polyhedra are basically attributed to the differences in ionic radii between Nd³⁺ and La³⁺ ions. From the evaluation of microwave dielectric properties, it was shown that the appropriate τ_f values ranging from 4.6 to −5.0 ppm/°C are obtained by La substitution for Nd ion, and the highest Q · f value was 17,832 GHz at x=2.     

Wave-induced liquefaction and instability of offshore monopile in a drum centrifuge

This paper discusses the instability of an offshore monopile in association with wave-induced liquefaction of sand beds. Centrifuge wave tests in a drum channel were performed with viscous scaling introduced such that the time-scaling laws for fluid wave propagation and consolidation of the soil were matched. The relationships between liquefaction and the start and development of monopile instability in a sand bed under wave loading were investigated. The monopile started significant structural rocking when liquefaction occurred and progressed to one-third of the monopile embedment depth. The residual displacement of the pile increased markedly with the downward progress of the liquefied zone, eventually leading to the collapse of the pile. The characteristics of the onset of liquefaction around the monopile were also investigated. It was found that liquefaction first took place at the sides of the monopile rather than at the front or rear presented to the direction of the travelling waves, which highlights the importance of the rotation of the principal stress axes induced in the sand bed under the passage of progressive waves. The experimental results further demonstrated the effect of embedment of the pile in a dense layer. It was found that embedding the pile in the dense layer with thickness equal to or more than half of the pile embedment depth was effective in preventing the significant inclination and collapse of the pile. The present study also clarified the effects of scour protection around the monopile on wave-induced liquefaction and pile instability. It was found that the scour protection increased the liquefaction resistance depending on the diameter ratios of the scour protection and the pile, however, it could not prevent the collapse of the monopile once liquefaction occurred. These results show the importance of soil stratification on the wave-seabed-structure interaction in light of wave-induced liquefaction.     

Role of Glycated High Mobility Group Box-1 in Gastric Cancer

Advanced glycation end products (AGEs) are produced in response to a high-glucose environment and oxidative stress and exacerbate various diseases. N^ε-(Carboxymethyl)lysine (CML) is an AGE that is produced by the glycation of lysine residues of proteins. There are a few reports on alterations in protein function due to CML modification; however, its association with cancer is not clear. We investigated the significance of CML modification in high mobility group box protein-1 (HMGB1), a cytokine that is significantly associated with cancer progression. Treatment of the gastric cancer cell lines TMK1 and MKN74 with glyoxal or glucose resulted in increased CML modification compared to untreated cells. CML-HMGB1 was modified via oxidation and more pronouncedly activated the receptor for AGE and downstream AKT and NF-κB compared to naïve HMGB1 and oxidized HMGB1. CML-HMGB1 bound with reduced affinity to DNA and histone H3, resulting in enhanced extranuclear translocation and extracellular secretion. Treatment of gastric cancer cells with CML-HMGB1 enhanced cell proliferation and invasion, sphere formation, and protection from thapsigargin-induced apoptosis, and decreased 5-FU sensitivity in comparison to HMGB1. Further, CML-HMGB1 was detected at various levels in all the 10 gastric cancer tumor specimens. HMGB1 levels correlated with primary tumor progression and distant metastasis, whereas CML-HMGB1 levels were associated with primary tumor progression, lymph node metastasis, distant metastasis, and stage. In addition, CML-HMGB1 levels correlated with oxidative stress in cancer tissues and resistance to neoadjuvant therapy. Therefore, CML modification of HMGB1 enhanced the cancer-promoting effect of HMGB1. In this study, CML-HMGB1 has been highlighted as a new therapeutic target, and analysis of the molecular structure of CML-HMGB1 is desired in the future.