Well‐Defined Functional Linear Aliphatic Diblock Copolyethers: A Versatile Linear Aliphatic Polyether Platform for Selective Functionalizations and Various Nanostructures

Low‐temperature anionic ring‐opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal‐free catalyst system, 3‐phenyl‐1‐propanol (PPA) (an initiator) and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris‐(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄) (a promoter) in order to obtain well‐defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring‐opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well‐defined linear AGE‐homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE‐homopolymer in a unimodal narrow molecular‐weight distribution. In this case, however, a side reaction (i.e., chain‐transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well‐defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post‐modification products are examined. Overall, this study demonstrates that a low‐temperature metal‐free anionic ROP using the PPA/t‐Bu‐P₄ catalyst system is suitable for the production of well‐defined linear AGE‐homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post‐modifications, nanostructures, and their applications.     

Evaluation of fluorescence emitting characteristics of a microparticle by illumination angle scanning utilizing a resin-based monolithic TAS chip

Microsystem Technologies - An optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a...     

Cation-Exchange Characteristics of Sintered Hydroxyapatite in the Strongly Acidic Region

The ion-exchange behavior of hydroxyapatite (Ca₁₀(PO₄)₆-OH)₂) (HAp), fired at high temperatures, has been investigated in the strongly acidic region (pH 2 and 3). According to the present study, HAp fired above 1000°C can exchange ions from Ca²⁺ to Pb²⁺, even at pH 2, without dissolution. The molar ratios of Pb²⁺/Ca²⁺ after ion exchange are approximately unity in all cases. Ion exchange occurs in a thin layer near the surface of HAp particles fired at 1300°C. After ion exchange, Pb-Cl-apatite crystals are created in the strongly acidic region (pH 2).     

Effects of substrate surface finish and substrate material on durability of thermally sprayed WC cermet coating in rolling with sliding contact

In this study, using a two-roller testing machine, the authors examined the surface durability of thermally sprayed WC-Cr-Ni cermet coating in lubricated rolling with sliding contact conditions. The coating was formed onto the axially ground, blasted and circumferentially ground roller specimens made of a thermally refined carbon steel or an induction hardened carbon steel by means of the high energy type flame spraying (Hi-HVOF) method. The WC cermet coated roller finished to a mirror-like condition was mated with the carburized steel roller without coating having a surface roughness of Ry=3.05.0 μm. In the experiments, a maximum Hertzian stress of P_H=0.6 or 0.8 GPa was applied for the thermally refined carbon steel roller and P_H=1.4 GPa was applied for the induction hardened carbon steel roller in line contact condition. As a result, it was found that in the case of induction hardened steel substrate, the coated roller generally exhibits a long life without any serious damage and the surface durability is hardly affected by the substrate surface finish, while in the case of thermally refined steel substrate, the durability of coated roller is lowered and the life to flaking is very short particularly when the substrate surface is circumferentially ground and the mating surface is rough. The surface durability of coated roller was also compared with the durability of steel roller without coating. Finally, in order to discuss the durability of coated roller, the elastic-plastic behavior of the subsurface layer under repeated rolling with sliding contact was analyzed using a finite element method (FEM).     

Metallurgical aspects on the formation of self-organized anodic oxide nanotube layers

The present work reports how metallurgical factors such as grain size and chemical composition of substrate affect the current behavior during anodization and the morphology of resulting formed oxide layers. The grain size of pure Ti sheet is controlled by the accumulative roll-bonding (ARB) process. Tubular oxide layers are formed on the ARB-processed Ti sheets with different grain sizes, but grain size does not affect the length, diameter of tubes and the degree of tube arrangement. The effect of chemical composition is examined using Ti-Zr alloys (Ti-20Zr, Ti-50Zr, Ti-80Zr) that can consist of a single phase, meaning that homogeneous tube formation can be achieved. With increasing Zr content in the alloys, tube diameter decreases while tube length increases. For the Ti-50Zr and Ti-80Zr, self-organization is achieved on two size scales, that is, nanotube arrays with two distinct diameters are observed. TEM observation revealed that anodic oxide layers are in crystalline state only in the case of pure Zr.     

Determination of levulinic acid in soy sauce by liquid chromatography with mass spectrometric detection

A novel method using liquid chromatography coupled with mass spectrometry (LC–MS) was developed for the determination of levulinic acid (LV) in soy sauces to identify the addition of acid hydrolyzed vegetable protein (acid-HVP). One hundred percentage naturally brewed soy sauce (NBS) and enzymatic hydrolyzed vegetable protein (enzymatic HVP) did not contain LV (<0.01 mg/mL). There was apparent detection of LV in acid-HVP and blended soy sauce with acid-HVP (2.98–21.66 mg/mL). Gas chromatography (GC) and high performance liquid chromatography (HPLC) at 430 nm methods were also investigated. The results by GC gave similar data to those by LC–MS. In enzymatic HVP, LV was detected by HPLC at 430 nm, but it was confirmed that the detected component was not in fact LV by mass spectrometric identification of the isolated peak compound. We found that LV is under the detection limit in enzymatic HVP. This study showed that LV is below the detection limit in NBS and enzymatic HVP and is apparently detected in acid-HVP and blended soy sauces with acid-HVP. These results indicate that LV is a practical index of blend with acid-HVP and also corresponds with the JAS (Japanese Agricultural Standard) or CNS (Chinese National Standard) criteria in which the presence of LV in soy sauces indicates adulteration with acid-HVP. The LC–MS method is analytically optimal for the precise determination of LV, because peak misidentification may be practically eliminated.     

Flow characteristics of gas–liquid two phase plunging jet absorber–gas holdup and bubble penetration depth

A gas-liquid two phase plunging jet is formed through a gas sucking type multi-jet ejector nozzle. In this study, the effects of various conditions in the multi-jet ejector nozzle, the column diameter, and the liquid jet length on penetration depth of air bubblesl _B and gas holdup h_G in a gas-liquid two phase plunging jet absorber were studied experimentally. Consequently, empirical equations concerningl _B and h_G were obtained, respectively. These equations agree with the experimental data with an accuracy of ±20% forl _B and ±25% for h_G.     

Illumination and scattered light detection using a light source consisting of sub-micrometer defect arrays formed on a extremely flat light waveguide core

We have previously argued that an optical sensor combined total analysis system (TAS) is one of the indispensable functional components needed to realize a “ubiquitous human healthcare” system. To achieve this goal, we have proposed a fundamental structure for illuminating a minute cell or particle running along a microfluidic channel using a flat waveguide construction. It is desirable that the TAS light source should be arranged as close to the specimen flow as possible in order to acquire the necessary optical properties; hence, artificial defects formed on the surface of a flat light waveguide are considered to be a promising candidate for realizing the arbitrary-shaped light source for a highly functional optical TAS structure. Based on this idea, we fabricated a structure, constructing a flat and square light source consisting of rectangular solids, sub-micrometer in size, with a 1-μm thick and a 12-μm wide light waveguide core. We successfully trial-manufactured an optical TAS chip with a fluidic channel containing a 14 × 10-μm cross section, and an extremely flat light waveguide core. We repeatedly confirmed that the defect array could function as an approximately square light source when a 650-nm wavelength laser power was carefully introduced. Furthermore, we developed a hybrid numerical calculation method base on the finite-difference, time-domain method together with the beam propagation method. Utilizing this hybrid method, we evaluated the optical response when a particle runs across the light source while changing the aperture length of a shading mask to obtain signals with both higher intensity and shorter full width at half maximum. The numerical results were compared with experimental results obtained using an image acquisition system, and demonstrated good qualitative accord.     

Reconnaissance report on geotechnical damage caused by a localized torrential downpour with emergency warning level in Kyushu,Japan

Kumamoto and Kogoshima prefectures are located in the southern Kyushu district of western Japan. In July 2020, a warm, humid air front triggered the delayed rains of the rainy season, resulting in torrential rains in many parts of Japan, especially in Kyushu. In particular, heavy downpours occurred in the southern Kyushu district on July 4th, causing severe damage to much of the infrastructure. Details could not be analyzed as usual because some branch office of local government were also damaged by floods. The spatial distribution of precipitation in the Kuma River basin, in the southern part of Kumamoto, was characterized by the uniformity of 400–500 mm on July 3rd and 4th. Finally, emergency warnings of torrential rain were issued for the southern Kumamoto and the northern Kagoshima Prefectures by Japan Meteorological Agency (JMA) at 4:50 a.m., July 4th, 2020. Then, the active rain front gradually shifted towards northern Kyushu. Again, torrential rain fell on northern Kyushu in the afternoon due to a stagnant rainy season front, and the JMA issued an emergency warning for a localized torrential downpour for parts of Fukuoka, Saga and Nagasaki prefectures at 4:30 pm. Gradually, the damage status involving geodisasters such as several types of slope failures, road subsidence, damage of the river levee was reported by local governments in each area where there had been emergency warnings.Based on the brief report of the pre-investigation team from the Kyushu branch of the Japan Geotechnical Society (JGS) in the first week after the disaster on July 4th, the geo-research teams investigated the following: 1) landslides; 2) damaged roads; 3) damaged river levees, and 4) any geotechnical infrastructures which were partially damaged and may be even more severely damaged by the next torrential rain. This reconnaissance report introduces the geological features in Kyushu, the analysis of precipitation distribution and geotechnical damages on the slope failures, road failures and river embankments based on reports obtained from July 4th to August 31st, 2020.