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91.
Tetramethylammonium hydroxide (TMAH) thermochemolysis of 2-arylcoumaran lignin model compounds 总被引:1,自引:0,他引:1
Ken-ichi Kuroda Akiko Nakagawa-izumi Tatsuya Ashitani Koki Fujita 《Journal of Analytical and Applied Pyrolysis》2009,86(1):185-191
Phenolic 2-arylcoumarans 1–6 were used to examine the behaviors of β-5 subunits in lignin during tetramethylammonium hydroxide (TMAH) thermochemolysis. Products were monitored by gas chromatography/mass spectrometry. The process predominantly provided dimeric products with the opened hydrofuran ring. Substituent changes at the γ-position of ring A and at the 5-position of ring B had a large effect on the product compositions. 2-Arylcoumarans 1 and 6 with the γ-CH2OH substituent predominantly gave 2,3,3′,4′-tetramethoxystilbenes involving the elimination of the γ-CH2OH substituent, while 2–5 with the γ-CH3 substituent gave a mixture of 2,3,3′,4′-tetramethoxy-α-methylstilbenes and α-methoxy-α-(3′,4′-dimethoxyphenyl)-β-(2,3-dimethoxyphenyl)propanes. Substituent –CHCHCH3 on ring B remained unaffected. Substituents –CHCHCH2OH and –COOH on ring B produced the corresponding methyl ether and ester, respectively, by methylation. The –CHCHCHO substituent on ring B was converted to the –CHO substituent. 相似文献
92.
Masanobu Nakayama Kenta Kanamori Koki Nakano Randy Jalem Ichiro Takeuchi Hisatsugu Yamasaki 《Chemical record (New York, N.Y.)》2019,19(4):771-778
Interest in all‐solid‐state Li‐ion batteries (LIBs) using non‐flammable Li‐conducting ceramics as solid electrolytes has increased, as safe and robust batteries are urgently desired as power sources for (hybrid) electric vehicles. However, the low Li‐ion conductivities of ceramics have hindered all‐solid‐state LIB commercialization; many researchers have attempted to develop fast Li‐ion conductors. We introduce two efficient high‐throughput computational approaches for materials exploration: (i) exhaustive search and (ii) informatics‐aided prediction. For demonstration, ~400 Li‐ and Zn‐containing oxide (Li?Zn?X?O) compounds of varied crystal structures are extracted from Materials Project datasets. We calculate the migration energies for Li‐ion conduction and the phase stabilities (decomposition energies) of these materials by simulation and apply Bayesian optimization to determine the material with the highest ionic conductivity. The results show much greater efficiency than a random search algorithm. 相似文献
93.
The catalytic enantioselective difluoromethylation of arylidene Meldrum's acids with (difluoromethyl)zinc reagent, easily prepared through zinc/iodide exchange reaction of difluoroiodomethane and diethylzinc with co-solvent such as pyridines, by a chiral phosphoramidite-Cu catalyst is shown to provide highly enantioselective sp [3]-difluoromethyl Michael addition product in good yields and high levels of enantioselectivity. 相似文献
94.
95.
Wataru Sakai Koki Chiga Naoto Tsutsumi 《Journal of Polymer Science.Polymer Physics》2001,39(2):247-255
This article presents the molecular orientation and second‐order optical nonlinearity of newly prepared polyureas and copolyurea with dipole moments aligned transverse to the main backbone. Nonlinear optical (NLO) polyureas, TPU and TPU2, were prepared from 2,4‐diamino‐4′‐nitroazobenzene (2R‐DIAMINE) with 4,4′‐diphenylmethane diisocyanate (DMDI) and tolylene 2,4‐diisocyanate, respectively. NLO copolyurea was prepared from DMDI with 2R‐DIAMINE and m‐phenylene diamine. TPU and TPU2 gave d33 values of 12.5 and 9.8 pm/V, respectively, under optimum poling conditions. A time‐dependent decay curve of second‐order nonlinear susceptibility was fitted well with a Kohlrausch–Williams–Watts stretched exponential function. The relaxation time of TPU2 was 4.2 × 108 s at 100 °C. Copolyurea was uniaxially drawn in ratios of 1.5 and 2.0. The average molecular angles ΦX , ΦY , and ΦZ in three laboratory frames were evaluated from the refractive indices. ΦY decreased and ΦX and ΦZ increased with an increasing draw ratio. The dependence of the second‐order harmonic intensity on the incidence angle, that is, the Maker fringe pattern, was fitted with two independent tensor components, d33 and d31, for undrawn film and five independent tensor components, d33, d32, d31, d15, and d24, for drawn films. For drawn films, Kleinman symmetry was not satisfied: d31 ≠ d15 and d32 ≠ d24. An increase in the draw ratio gave rise to a large increase in the tensor component d33. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 247–255, 2001 相似文献
96.
Kazuyuki Takata Hiroyuki Kimura Daijiro Yanagisawa Koki Harada Kaneyasu Nishimura Yoshihisa Kitamura Shun Shimohama Ikuo Tooyama 《Molecules (Basel, Switzerland)》2022,27(9)
Amyloid-β (Aβ) accumulation and tauopathy are considered the pathological hallmarks of Alzheimer’s disease (AD), but attenuation in choline signaling, including decreased nicotinic acetylcholine receptors (nAChRs), is evident in the early phase of AD. Currently, there are no drugs that can suppress the progression of AD due to a limited understanding of AD pathophysiology. For this, diagnostic methods that can assess disease progression non-invasively before the onset of AD symptoms are essential, and it would be valuable to incorporate the concept of neurotheranostics, which simultaneously enables diagnosis and treatment. The neuroprotective pathways activated by nAChRs are attractive targets as these receptors may regulate microglial-mediated neuroinflammation. Microglia exhibit both pro- and anti-inflammatory functions that could be modulated to mitigate AD pathogenesis. Currently, single-cell analysis is identifying microglial subpopulations that may have specific functions in different stages of AD pathologies. Thus, the ability to image nAChRs and microglia in AD according to the stage of the disease in the living brain may lead to the development of new diagnostic and therapeutic methods. In this review, we summarize and discuss the recent findings on the nAChRs and microglia, as well as their methods for live imaging in the context of diagnosis, prophylaxis, and therapy for AD. 相似文献
97.
The authors consider various procedures for testing the hypotheses of independence of two sets of variables and certain regression coefficients are zero under multivariate regression model. Various properties of these procedures and the asymptotic distributions associated with these procedures are also considered. 相似文献
98.
Prof. Dr. Masaya Nakajima Sho Nagasawa Koki Matsumoto Takahito Kuribara Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Prof. Dr. Tetsuhiro Nemoto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6914-6919
According to the Grotthuss–Draper law, light must be absorbed by a substrate to initiate a photoreaction. There have been several reports, however, on the promotion of photoreactions using hypervalent iodine during irradiation with light from a non-absorbing region. This contradiction gave rise to a mystery regarding photoreactions involving hypervalent iodine. We demonstrated that the photoactivation of hypervalent iodine with light from the apparently non-absorbing region proceeds via a direct S0→Tn transition, which has been considered a forbidden process. Spectroscopic, computational, and synthetic experimental results support this conclusion. Moreover, the photoactivation mode could be extended to monovalent iodine and bromine, as well as bismuth(III)-containing molecules, providing new possibilities for studying photoreactions that involve heavy-atom-containing molecules. 相似文献
99.
Organic structure-directing agents (OSDAs) are often employed for synthesis of zeolites with desired frameworks. A priori prediction of such OSDAs has mainly relied on the interaction energies between OSDAs and zeolite frameworks, without cost considerations. For practical purposes, the cost of OSDAs becomes a critical issue. Therefore, the development of a computational de novo prediction methodology that can speed up the trial-and-error cycle in the search for less expensive OSDAs is desired. This study utilized a nature-inspired ant colony optimization method to predict physicochemically and/or economically preferable OSDAs, while also taking molecular similarity and heuristics of zeolite synthesis into consideration. The prediction results included experimentally known OSDAs, candidates having structures closely related to known OSDAs, and novel ones, suggesting the applicability of this approach.Inspired by the exploratory methods of ant colonies, adaptive optimization was employed to explore the chemical space for organic molecules that guide zeolite crystallization, giving both physicochemically and economically promising molecules. 相似文献
100.
Koki Matsumoto Dr. Masaru Kato Prof. Ichizo Yagi Siqi Xie Prof. Kiyotaka Asakura Prof. Shin-ichiro Noro Prof. Norimitsu Tohnai Dr. Stéphane Campidelli Prof. Takashi Hayashi Prof. Akira Onoda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(5):e202103545
Fe/N/C single-atom catalysts containing Fe−Nx sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N4 sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N4 sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe−N4 sites catalyzing ORR with a TOF value of 0.21 e site−1 s−1 at 0.8 V vs. RHE. This indicates that the formation of Fe−N4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor. 相似文献