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401.
Synthesis and properties of a novel high temperature pyridine‐containing phthalonitrile polymer 下载免费PDF全文
Zhenjie Xi Xinggang Chen Xiaoyan Yu Yuanhui Ma Puguang Ji Kimiyoshi Naito Huili Ding Xiongwei Qu Qingxin Zhang 《Journal of polymer science. Part A, Polymer chemistry》2016,54(24):3819-3825
A novel pyridine‐containing aromatic phthalonitrile monomer, 2,6‐bis[4‐(3,4‐dicyanophenoxy)benzoyl]pyridine (BCBP) was synthesized from the nitro displacement of 4‐nitrophthalonitrile by the phenoxide of 2,6‐bis (4‐hydroxybenzoyl)pyridine (BHBP). 4‐(Aminophenoxy) phthalonitrile (APPH) was selected to promote the curing reaction, and the curing behavior has been investigated by differential scanning calorimetric (DSC), suggesting a wide processing window about 64 °C. Different curing additive concentrations resulted in polymers with different crosslinking degrees and subsequently influenced the performance of resins. The resulting BCBP polymer exhibited high glass transition temperatures exceeding 400 °C, outstanding thermo‐oxidative stability with weight retention of 95% at 530 °C, indicating a significant improvement in thermal properties endowed by pyridine units. Additionally, it also showed a lower overall water absorption after submersion in boiling water for 50 hours. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3819–3825 相似文献
402.
Naoto Yoshinaga Eol Cho Kyoko Koji Yuki Mochida Mitsuru Naito Kensuke Osada Kazunori Kataoka Horacio Cabral Satoshi Uchida 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11482-11485
Ribonuclease (RNase)‐mediated degradation of messenger RNA (mRNA) poses a huge obstruction to in vivo mRNA delivery. Herein, we propose a novel strategy to protect mRNA by structuring mRNA to prevent RNase attack through steric hinderance. Bundling of mRNA strands through hybridization of RNA oligonucleotide linkers allowed the preparation of mRNA nano‐assemblies (R‐NAs) comprised of 7.7 mRNA strands on average, mostly below 100 nm in diameter. R‐NA formation boosted RNase stability by around 100‐fold compared to naïve mRNA and preserved translational activity, allowing protein production. A mechanistic analysis suggests that an endogenous mRNA unwinding mechanism triggered by 5′‐cap‐dependent translation may induce selective R‐NA dissociation intracellularly, leading to smooth translation. R‐NAs showed efficient mRNA transfection in mouse brain, demonstrating the feasibility for in vivo administration. 相似文献
403.
Ryo Inoue Dr. Masaya Naito Prof. Dr. Masahiro Ehara Prof. Dr. Takeshi Naota 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(14):3650-3661
The heat-resistant properties towards thermal emission quenching of trans-bis[(β-iminomethyl)aryloxy]platinum(II) complexes bearing 3-iminomethyl-2-naphtholato- ( 1 ), 1-iminomethyl-2-naphtholato- ( 2 ), 2-iminomethyl-1-naphtholato- ( 3 ), and 2-iminomethyl-1-phenolato ( 4 ) moieties, and a mechanistic rationale of these properties, are described in this report. Complex 1 a , with N,N′-dipentyl groups, exhibits intense red emission in 2-methyl-2,3,4,5-tetrahydrofuran (2-MeTHF) at 298 K, whereas the analogues 2 a – 4 a are less or non-emissive under the same measurement conditions. All four complexes are highly emissive at 77 K. The heat-resistant properties toward thermal emission quenching (Φ298 K/Φ77 K) increase in the order 1 a (0.52)> 2 a (0.09)> 3 a (0.02)>> 4 a (0.00). We investigated the emission decay and thermal-deactivation processes using density functional theory (DFT), time-dependent (TD) DFT, and double-hybrid density functional theory (DHDF) calculations of N,N′-diethyl forms 1 b – 4 b , and discuss the results with a focus on the energy levels, molecular structures, and electronic configurations in the triplet excited states. The energy differences between the triplet metal–ligand charge transfer (3MLCT) state and minimum-energy crossing point between the lowest triplet state and singlet ground state (MECP) increase in the order 1 a > 2 a , 3 a > 4 a , consistent with the experimental results for the heat-resistant properties of these complexes. The origin of the present structure dependence of the 3MLCT–MECP energy gap is ascribed to the ease or difficulty of the high-lying dσ* orbital participating in the MECP upon thermal structural distortion. The structure dependence in energy gaps between the π* and dσ* orbitals, which is key for facilitating the thermal deactivation process, is rationally correlated with the extent of aromaticity on the coordination platforms ( 1 b >( 2 b , 3 b )> 4 b ). 相似文献
404.
Dr. Yuichi Kitagawa Ayu Naito Kota Aikawa Kaori Shima Dr. Sunao Shoji Dr. Koji Fushimi Prof. Yasuchika Hasegawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(16):e202104401
A spin-selective tribo-chemical reaction using a dinuclear lanthanide complex is demonstrated for the first time. The dinuclear complex is composed of two EuIII ions, hexafluoroacetylacetonato ligands, and anthracene-based phosphine oxide bridges. Single-crystal analysis revealed a face-to-face-type anthracene dimer structure in the dinuclear EuIII complex. Mechanical stimulus on the dinuclear EuIII complex induced selective formation of oxidized anthracene. The tribo-chemical reaction is based on a characteristic energy-transfer pathway for the selective formation of an excited triplet state. 相似文献
405.
ABSTRACTThe dynamics of the radical pairs generated from the electron transfer reaction from indole derivatives to flavin derivatives are studied by three techniques, time resolved magnetic field effect (TR-MARY) and pulse absorption detected magnetic resonance (ADMR), and absorption detected switching of external magnetic field techniques (AD-SEMF). The three techniques complementarily work for the precise analysis of the radical pair kinetics. The results by all three techniques reflect the difference of the hydrophobic nature of the radicals in the lifetime of RP in a micelle. Overcoming the difficulty of the determination of the short RP lifetime under the nearly quasi steady state due to slow and inhomogeneous decay kinetics of the precursor triplet excited state, AD-SEMF analysis enabled us to determine the kinetic parameters, which is consistent with the qualitatively observed by the other techniques. 相似文献
406.
Sato Masatoshi Yasui Yukio Kobayashi Yoshiaki Sato Kenji Naito Yutaka Tarui Yasuko Kawamura Yuji 《Solid State Sciences》2010,12(5):670-675
Results of experimental studies carried out by various methods on systems with CuO2 ribbon chains are presented. For LiVCuO4, which was found to have helimagnetic and ferroelectric simultaneous transitions (multiferroic transitions), the relationship between the magnetic structure and the ferroelectricity is described in detail by showing their magnetic field dependences. For Li2ZrCuO4, NMR studies have revealed that the system has ac-helical magnetic structure. However, we have not observed the ferroelectricity in this ordered phase. This result suggests that there may exist the antiferro-type ordering, for example, of the helical axis vectors, of the CuO2 chains. Several new findings are also shown on the magnetic and dielectric properties of other ribbon chain systems, LiVCuO4, Li2ZrCuO4, LiCu2O2 and NaCu2O2 and a related system Na2Cu3(GeO3)4. 相似文献
407.
O. Matsumoto A. Tsukada H. Yamamoto T. Manabe M. Naito 《Physica C: Superconductivity and its Applications》2010,470(20):1029-1032
Recently we have achieved superconductivity in T′-RE2CuO4 (RE = Pr, Nd, Sm, Eu, and Gd), films by metal organic decomposition (MOD). In this article, we first report the cation off-stoichiometry effect, which aims at screening out the possibility of hole doping by cation deficiencies. We also investigated the structure and microstructure of superconducting T′-Nd2CuO4 films synthesized by MOD. This investigation aims at elucidating why MOD-grown Nd2CuO4 films become superconducting whereas our previous Nd2CuO4 films grown by molecular beam epitaxy were not superconducting. 相似文献
408.
R. Bevilacqua S. Pomp V.D. Simutkin U. Tippawan P. Andersson J. Blomgren M. ?sterlund M. Hayashi S. Hirayama Y. Naito Y. Watanabe M. Tesinsky F.-R. LeColley N. Marie A. Hjalmarsson A.V. Prokofiev A. Kolozhvari 《Radiation measurements》2010,45(10):1145-1150
We have measured light-ion (p, d, t, 3He and α) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20° to 160°, in steps of 20°). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons. 相似文献
409.
Tomohito Naito Kohei Asai Tomoyuki Amano Masanobu Taniguchi 《Statistical Inference for Stochastic Processes》2010,13(3):163-174
In this paper, we propose a local Whittle likelihood estimator for spectral densities of non-Gaussian processes and a local
Whittle likelihood ratio test statistic for the problem of testing whether the spectral density of a non-Gaussian stationary
process belongs to a parametric family or not. Introducing a local Whittle likelihood of a spectral density f
θ
(λ) around λ, we propose a local estimator [^(q)] = [^(q)] (l){\hat{\theta } = \hat{\theta } (\lambda ) } of θ which maximizes the local Whittle likelihood around λ, and use f[^(q)] (l) (l){f_{\hat{\theta } (\lambda )} (\lambda )} as an estimator of the true spectral density. For the testing problem, we use a local Whittle likelihood ratio test statistic
based on the local Whittle likelihood estimator. The asymptotics of these statistics are elucidated. It is shown that their
asymptotic distributions do not depend on non-Gaussianity of the processes. Because our models include nonlinear stationary
time series models, we can apply the results to stationary GARCH processes. Advantage of the proposed estimator is demonstrated
by a few simulated numerical examples. 相似文献
410.
D. Kaneko K. Yamagishi A. Tsukada T. Manabe M. Naito 《Physica C: Superconductivity and its Applications》2009,469(15-20):936-939
We report the synthesis of infinite-layer LaNiO2 thin films by metal organic decomposition. Our work is aimed to synthesize perovskite-like oxides with 3d9 electronic configuration, which high-Tc copper oxides commonly take. The 3d9 configuration is very rare in oxides other than cuprates. Ni1+ oxides, even though Ni1+ is an unusual oxidation state, may be one of very few candidates. One example is infinite-layer LaNiO2. The bulk synthesis of LaNiO2 is difficult, but we demonstrate in this article that the thin-film synthesis of LaNiO2 by metal organic decomposition is rather easy. This is due to the advantage of thin films with a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Although superconductivity has not been observed yet, resistivity measurements indicate that LaNiO2 is conductive. 相似文献