Topological Mechanism of Nucleation of Cyclic Polyethylene(Knots and soft-matter physics: Topology of polymers and related topics in physics, mathematics and biology)

この論文は国立情報学研究所の電子図書館事業により電子化されました。In order to clarify the effects of entanglement species on nucleation of polymers, we studied the nucleation rate I of cyclic and linear polyethylenes (C-PE and L-PE) from the melt as a function of degree of supercooling ΔT by means of polarizing optical microscope. We prepared several C-PEs with different weight average molecular weights M_w=4600-114800. I of all the sample were obeyed the equation, I=I_0exp(-C/ΔT^2). I_0s of C-PE with M_w=114800 and L-PE with M_w=35400 were almost the same. This indicates that C-PE is easier to nucleate than L-PE due to lack of knot entanglements. On the other hand, Cs for C-PE significantly increased with increasing M_w. This tendency is quite different with L-PE previously reported. The increase of C indicates that folding regularity of end surface of nucleus increases. Since topological constraint of C-PE arose from the lack of chain ends is relatively decreased with increasing M_w, it was implied that the nucleation behavior of C-PE approaches that of L-PE

Robust control of multi-jointed arm with a decentralized autonomous control mechanism

A decentralized autonomous control mechanism applied to the control of three dimensional manipulators and its robustness to partial damage was assessed by computer simulation. Decentralized control structures are believed to be quite robust to time delay between the operator and the target system. A 10-jointed manipulator based on our control mechanism was able to continue its positioning task in three-dimensional space without revision of the control program, even after some of its joints were damaged. These results suggest that this control mechanism can be effectively applied to space telerobots, which are associated with serious time delay between the operator and the target system, and which cannot be easily repaired after being partially damaged

Efficient Chain Extension Reaction of Poly (butylene terephthalate) by using Crystallization

Plastics are quite important materials for not only industrial usages but also our daily life. Many plastics are difficult to reuse because they are susceptible to UV, hydrolysis and so on leading to the reduction of molecular weight. Among them, poly (butylenes terephthalate) (PBT) is a valuable materials prepared by polycondensation reaction, and PBT has the same limitation to reuse. Hence, efficient chain extension reaction for recovered PBT has been needed to improve the properties damaged by chain scission. In this study, new chain extension reaction had been examined by using crystallization as pre-treatment. Isothermal crystallization at 161℃ concentrated the chain end-groups on the surface of the crystals, and chain extension reaction at 210℃, which was lower than the melting temperature of PBT, enhanced the molecular weight significantly compared with the reaction over the melting temperature. It concluded that the pre-treatment of crystallization was favorable for the efficient chain extension reaction and this result provided the new technology for the effective reuse of the plastics

Mutations other than 103N in human immunodeficiency virus type 1 reverse transcriptase (RT) emerge from K103R polymorphism under non-nucleoside RT inhibitor pressure

AbstractK103N mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) confers high-level resistance against non-nucleoside RT inhibitors (NNRTIs) and it easily occurs partly because it arises by a single nucleotide substitution from wild-type K103. There are polymorphisms at codon 103 of HIV-1 RT. We found K103R polymorphic mutation in 3.3% of treatment-naive HIV-1-infected patients. R103N does not seem to occur as easily as K103N because R103N requires two nucleotide substitutions. To induce NNRTI resistance-associated mutations, HIV-1K103R was propagated in the presence of increasing concentrations of efavirez (EFV) or nevirapine (NVP). V179D emerged in all three EFV cultures and in two of four NVP cultures. R103G emerged by a single nucleotide substitution in one of three EFV cultures. R103N did not emerge in any of 7 NNRTI cultures. Analysis of recombinant HIV-1s showed that HIV-1K103R/V179D was significantly resistant and HIV-1K103G was moderately resistant against EFV and NVP

A Temperature Responsive Polysaccharide Derivative in Aqueous Solution : Amylose Ethyl Carbamates

Shunji Kimura, Ryotaro Kochi, Shinichi Kitamura, and Ken Terao. A Temperature Responsive Polysaccharide Derivative in Aqueous Solution: Amylose Ethyl Carbamates. ACS Applied Polymer Materials, 2(6), 2426-2433, 2020. Copyright © 2020, American Chemical Society. https://doi.org/10.1021/acsapm.0c00366

Effect of the blend ratio of cyclic and linear polyethylene blends on isothermal crystallization in the quiescent state

The role of entanglements that form between cyclic and linear polymers in crystallization is of particular interest, but it is not fully understood. We investigated the crystallization behaviors of blends of cyclic polyethylene (C-PE) and linear polyethylene (L-PE) in a quiescent state to elucidate the role of this novel entanglement in crystallization. The samples were prepared by mixing the prepared C-PE and L-PE specimens at L-PE weight fraction (ΦL-PE) values of 0–100 wt%, with the weight average molecular weights of C-PE and L-PE being 175 × 103 and 154 × 103, respectively. The isothermal crystallization behaviors were analyzed through polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The morphology observed through POM was similar to that of ΦL-PE. From the time evolution of the heat flow measured via DSC, we obtained the half-crystallization time (t1/2) values as functions of ΦL-PE at different degrees of supercooling (ΔT). The 1/t1/2 values of the C-PE and L-PE homopolymers were approximately the same at ΔT = 25.5 and 26.5 K. At a larger ΔT value, the 1/t1/2 value of C-PE was significantly larger than that of L-PE. In contrast, 1/t1/2 reached a minimum value at ΦL-PE = 30–40 wt%, irrespective of ΔT. As the entanglement density increased with increasing ΦL-PE, the crystallization rate was expected to decrease monotonically. By considering the experimental relationship between 1/t1/2 and ΦL-PE, we speculated that the suppression of crystallization in the blended system was caused by a novel entanglement formed by the penetration of the L-PE chain into the C-PE chain

Does local chain conformation affect the chiral recognition ability of an amylose derivative? Comparison between linear and cyclic amylose tris(3,5-dimethylphenylcarbamate)

The full-text file will be made open to the public on 16 August 2021 in accordance with the publisher's policy.Akiyuki Ryoki, Yuto Kimura, Shinichi Kitamura, Katsuhiro Maeda, Ken Terao. Does local chain conformation affect the chiral recognition ability of an amylose derivative? Comparison between linear and cyclic amylose tris(3,5-dimethylphenylcarbamate). Journal of Chromatography A, 1599, 2019, pp. 144-151. https://doi.org/10.1016/j.chroma.2019.04.019

Antenna-assembling mechanism test on ETS-7

The Communications Research Laboratory plans to test an antenna-assembling mechanism on the Engineering Test Satellite 7. The test is one of the application missions for the space robotics experiments that will be conducted mainly by the National Space Development Agency of Japan (NASDA). The purpose of the test is to verify the ability of the antenna assembling mechanism to function in space and to experiment on the teleoperation of a space robot to develop antenna-assembling technology. We present the test experiment plans and the outline of the onboard assembling mechanism