Synthesis of cyclic poly(methyl methacrylate) by the intramolecular cyclization of α-amino, ω-carboxyl heterodifunctional poly(methyl methacrylate)

Summary α-Amino, ω-carboxyl heterodifunctional poly(methyl methacrylate) was prepared by a living anionic polymerization of methyl methacrylate using N,N'-diphenylethylenediamine monolithium amide and succinic anhydride as an initiator and terminator, respectively. Its intramolecular cyclization was carried out to obtain a well-defined cyclic poly(methyl methacrylate). Received: 27 June 2001/Accepted: 16 July 2001     

Poly(N‐isopropylacrylamide) gel‐based macroporous monolith for continuous‐flow recovery of palladium(II) ions

Macroporous monoliths, composed of thermoresponsive, tertiary‐aminated, and crosslinking monomers, were prepared for continuous‐flow separation of palladium(II) ions. N ‐Isopropylacrylamide was required to form the porous structure in the monoliths, indicating that the mechanism of porous structure formation involved polymerization‐induced phase separation of the poly(N ‐isopropylacrylamide) gel. Tertiary‐aminated monoliths showed adsorption selectivity for palladium(II) ions in hydrochloric media, compared with copper(II) ions. The maximum capacities of the monoliths with tertiary amine contents of 10, 20, 30, and 70 mol % for palladium(II) ions were 0.6, 1.1, 1.3, and 2.3 mmol/g, respectively. Darcy's permeabilities of water through the macroporous monolith were 10^?14 to 10^?13 m², and those were comparable to that through a commercially available membrane filter with a pore size of several micrometers. In the continuous‐flow process, the macroporous monolith with tertiary amine selectively adsorbed palladium(II) ions in the coexistence of copper(II) ions with 10 times higher concentration than the palladium(II) ions. The palladium(II) ions were eluted from the macroporous monolith, and the concentration of palladium(II) ions in the eluate was up to 45 times of that in the feed solution. The average enrichment factor and total recovery percentage of palladium(II) ions were 8.7 times and 95%, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44385.     

Metastatic Voyage of Ovarian Cancer Cells in Ascites with the Assistance of Various Cellular Components

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy and has a unique metastatic route using ascites, known as the transcoelomic root. However, studies on ascites and contained cellular components have not yet been sufficiently clarified. In this review, we focus on the significance of accumulating ascites, contained EOC cells in the form of spheroids, and interaction with non-malignant host cells. To become resistant against anoikis, EOC cells form spheroids in ascites, where epithelial-to-mesenchymal transition stimulated by transforming growth factor-β can be a key pathway. As spheroids form, EOC cells are also gaining the ability to attach and invade the peritoneum to induce intraperitoneal metastasis, as well as resistance to conventional chemotherapy. Recently, accumulating evidence suggests that EOC spheroids in ascites are composed of not only cancer cells, but also non-malignant cells existing with higher abundance than EOC cells in ascites, including macrophages, mesothelial cells, and lymphocytes. Moreover, hetero-cellular spheroids are demonstrated to form more aggregated spheroids and have higher adhesion ability for the mesothelial layer. To improve the poor prognosis, we need to elucidate the mechanisms of spheroid formation and interactions with non-malignant cells in ascites that are a unique tumor microenvironment for EOC.     

Superplastic behaviour of Ti-48at.%Al two-phase titanium aluminide compacts made from mechanically alloyed powder

An HIP compact of MA-processed powder having a nominal composition of Ti-48at.% Al was produced. The compact consisted of a large amount of TiAl(λ) and a small amount of Ti₃Al (₂), in a completely ultra-fine equiaxed grain structure. This two-phase compact showed typical superplastic deformation behaviour. A maximum elongation of 550% was obtained. A strain exponent, n = 2, and grain size exponent, p = 2, were determined from the results of a strain-rate-change test and a creep test at constant initial stress using samples having various grain sizes, respectively. The activation energy for creep, Q_c at constant stress was calculated to be 350 kJ/mole. It is concluded that the superplastic deformation mechanism of the material under study is grain boundary sliding controlled by lattice diffusion in the TiAl phase.     

Random mutagenesis improves the low-temperature activity of the tetrameric 3-isopropylmalate dehydrogenase from the hyperthermophile Sulfolobus tokodaii

In general, the enzymes of thermophilic organisms are more resistant to thermal denaturation than are those of mesophilic or psychrophilic organisms. Further, as is true for their mesophilic and psychrophilic counterparts, the activities of thermophilic enzymes are smaller at temperatures that are less than the optimal temperature. In an effort to characterize the properties that would improve its activity at temperatures less than the optimal, we subjected the thermostable Sulfolobus tokodaii (S. tokodaii) 3-isopropylmalate dehydrogenase to two rounds of random mutagenesis and selected for improved low-temperature activity using an in vivo recombinant Escherichia coli system. Five dehydrogenase mutants were purified and their catalytic properties and thermostabilities characterized. The mutations favorably affect the K(m) values for NAD (nicotinamide adenine dinucleotide) and/or the k(cat) values. The results of thermal stability measurements show that, although the mutations somewhat decrease the stability of the enzyme, the mutants are still very resistant to heat. The locations and properties of the mutations found for the S. tokodaii enzyme are compared with those found for the previously isolated low-temperature adapted mutants of the homologous Thermus thermophilus enzyme. However, there are few, if any, common properties that enhance the low-temperature activities of both enzymes; therefore, there may be many ways to improve the low-temperature catalytic activity of a thermostable enzyme.     

Thermal and electrical properties of perovskite-type strontium molybdate

Polycrystalline samples of perovskite-type strontium molybdate, SrMoO₃, have been prepared and the thermal and electrical properties have been measured from room temperature to about 1000 K. The electrical resistivity is of an order of magnitude of 10⁻⁵ to 10⁻⁶ (Ω m) in the whole temperature range. The Seebeck coefficient is around 4–9 μV K⁻¹. At room temperature, the thermal conductivity is about 30 W m⁻¹ K⁻¹, and it decreases with increasing temperature.     

Characterization of a Novel Thermostable Dye-Linked l-Lactate Dehydrogenase Complex and Its Application in Electrochemical Detection

Flavoenzyme dye-linked l-lactate dehydrogenase (Dye-LDH) is primarily involved in energy generation through electron transfer and exhibits potential utility in electrochemical devices. In this study, a gene encoding a Dye-LDH homolog was identified in a hyperthermophilic archaeon, Sulfurisphaera tokodaii. This gene was part of an operon that consisted of four genes that were tandemly arranged in the Sf. tokodaii genome in the following order: stk_16540, stk_16550 (dye-ldh homolog), stk_16560, and stk_16570. This gene cluster was expressed in an archaeal host, Sulfolobus acidocaldarius, and the produced enzyme was purified to homogeneity and characterized. The purified recombinant enzyme exhibited Dye-LDH activity and consisted of two different subunits (products of stk_16540 (α) and stk_16550 (β)), forming a heterohexameric structure (α3β3) with a molecular mass of approximately 253 kDa. Dye-LDH also exhibited excellent stability, retaining full activity upon incubation at 70 °C for 10 min and up to 80% activity after 30 min at 50 °C and pH 6.5–8.0. A quasi-direct electron transfer (DET)-type Dye-LDH was successfully developed by modification of the recombinant enzyme with an artificial redox mediator, phenazine ethosulfate, through amine groups on the enzyme’s surface. This study is the first report describing the development of a quasi-DET-type enzyme by using thermostable Dye-LDH.     

Reflection and absorption characteristics of electromagnetic waves for PV modules

In this paper, the authors investigated the reflection and absorption characteristics of a general photovoltaic (PV) module. As a result, the electromagnetic waves could be attenuated only 6 dB in typical PV module. However, if the PV module is installed in the outer wall of buildings, electromagnetic interference is caused by the surroundings. To reduce this electromagnetic interference, the authors suggested a method to absorb electromagnetic wave using multiple PV modules that have deference impedance, and simulation was performed. As a result, it was confirmed that using a typical PV module and the PV module including electronic device, the reflection waves of those PV modules could be attenuated up to 12 dB.     

Determination of internal state variables and constitutive modeling for Type 316 stainless steel

The purpose of this study is to develop an approach for unified constitutive modeling based on experimentally determined back stress and overstress. Back stress and overstress were experimentally determined for Type 316 stainless steel at 600°C, by analyzing the unloading curve for the stress-strain response of cyclic strain tests. The result has indicated that the cyclic strain hardening behavior is mainly caused by hardening in the back stress. A phenomenological unified constitutive model in which the back stress and drag stress are taken as the internal state variables is proposed, and has been shown that this model is able to simulate the cyclic inelastic behavior.     

Acoustic phonon modulation and electron�Cphonon interaction in?semiconductor slabs and nanowires

The acoustic phonon modulation (confinement) in semiconductor nanostructures and their interaction with electrons are reviewed. Special emphasis will be placed on free-standing and layered slabs, as well as nanowires. Analysis includes acoustic phonon dispersion relations, displacement wave functions, amplitudes, form factor, electron-phonon scattering rate, and electron mobility.