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91.
Circular autocorrelation of stationary circular Markov processes 总被引:1,自引:0,他引:1
Toshihiro Abe Hiroaki Ogata Takayuki Shiohama Hiroyuki Taniai 《Statistical Inference for Stochastic Processes》2017,20(3):275-290
The stationary Markov process is considered and its circular autocorrelation function is investigated. More specifically, the transition density of the stationary Markov circular process is defined by two circular distributions, and we elucidate the structure of the circular autocorrelation when one of these distributions is uniform and the other is arbitrary. The asymptotic properties of the natural estimator of the circular autocorrelation function are derived. Furthermore, we consider the bivariate process of trigonometric functions and provide the explicit form of its spectral density matrix. The validity of the model was assessed by applying it to a series of wind direction data. 相似文献
92.
Derek Yiren Ong Zhihao Yen Asami Yoshii Julia RevilloImbernon Ryo Takita Shunsuke Chiba 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5046-5051
New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH‐ZnI2 system delivers alcohols and NaH‐ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines. 相似文献
93.
Simon Rohrbach Andrew J. Smith Jia Hao Pang Darren L. Poole Tell Tuttle Shunsuke Chiba John A. Murphy 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16518-16540
Jüngste Entwicklungen in der experimentellen und theoretischen Chemie haben zur Identifizierung einer schnell wachsenden Klasse von nukleophilen aromatischen Substitutionsreaktionen geführt, die einem konzertierten Mechanismus (cSNAr) folgen, und nicht dem klassischen, zweistufigen SNAr‐Mechanismus. Während klassische SNAr‐Reaktionen auf die substantielle Aktivierung des aromatischen Ringes durch elektronenziehende Substituenten angewiesen sind, ist eine solche Aktivierung für den konzertierten Reaktionsverlauf nicht zwingend nötig. 相似文献
94.
Membrane transporters are expressed in various bodily tissues and play essential roles in the homeostasis of endogenous substances and the absortion, distribution and/or excretion of xenobiotics. For transporter assays, radioisotope‐labeled compounds have been mainly used. However, commercially available radioisotope‐labeled compounds are limited in number and relatively expensive. Chromatographic analyses such as high‐performance liquid chromatography with ultraviolet absorptiometry and liquid chromatography with tandem mass spectrometry have also been applied for transport assays. To elucidate the transport properties of endogenous substrates, although there is no difficulty in performing assays using radioisotope‐labeled probes, the endogenous background and the metabolism of the compound after its translocation across cell membranes must be considered when the intact compound is assayed. In this review, the current state of knowledge about the transport of endogenous substrates via membrane transporters as determined by chromatographic techniques is summarized. Chromatographic techniques have contributed to our understanding of the transport of endogenous substances including amino acids, catecholamines, bile acids, prostanoids and uremic toxins via membrane transporters. 相似文献
95.
Naoki Haga Hiroaki Takayanagi Haruo Ogura Yasunao Kuriyama Katsumi Tokumaru 《Photochemistry and photobiology》1995,61(6):557-562
The mechanism of photocycloaddition of 2′-deoxyuridine (1a) and thymidine (1b) to 2,3-dimethyl-2-butene (Bu) in acetonitrile by UV irradiation has been studied. The reciprocal quantum yield for the cycloaddition increased linearly with reciprocal concentrations of Bu in acetonitrile to give limiting quantum yields at infinite concentration of Bu as 0.030 and 0.0096 for 1a and 1b , respectively. This shows that the cycloaddition proceeds in a two-step mechanism between the triplet state of 1 and Bu through biradical intermediates. Addition of cis-1,3-pentadiene quenched the reaction obeying the Stern–Volmer equation. The above quenching experiments and laser transient spectroscopy revealed that the triplet state of 1a reacts with Bu with much larger rate constant (1.3–1.6 × 109 M?1 s?1) than that of 1b (4–5 × 107 M?1 s?1) reflecting larger steric hindrance exerted in the reaction of 1b than that of 1a . 相似文献
96.
Haruki Inoue Dr. Shin-ichi Naya Atsunobu Akita Dr. Hisashi Sugime Prof. Dr. Hiroaki Tada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(46):e202201653
Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (dAu) at 5.3 nm≤dAu≤8.2 nm. Light irradiation (λex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs. 相似文献
97.
Rapid QM/MM approach for biomolecular systems under periodic boundary conditions: Combination of the density‐functional tight‐binding theory and particle mesh Ewald method 下载免费PDF全文
A quantum mechanical/molecular mechanical (QM/MM) approach based on the density‐functional tight‐binding (DFTB) theory is a useful tool for analyzing chemical reaction systems in detail. In this study, an efficient QM/MM method is developed by the combination of the DFTB/MM and particle mesh Ewald (PME) methods. Because the Fock matrix, which is required in the DFTB calculation, is analytically obtained by the PME method, the Coulomb energy is accurately and rapidly computed. For assessing the performance of this method, DFTB/MM calculations and molecular dynamics simulation are conducted for a system consisting of two amyloid‐β(1‐16) peptides and a zinc ion in explicit water under periodic boundary conditions. As compared with that of the conventional Ewald summation method, the computational cost of the Coulomb energy by utilizing the present approach is drastically reduced, i.e., 166.5 times faster. Furthermore, the deviation of the electronic energy is less than . © 2016 Wiley Periodicals, Inc. 相似文献
98.
Size‐Dependence of the Activity of Gold Nanoparticle‐Loaded Titanium(IV) Oxide Plasmonic Photocatalyst for Water Oxidation 下载免费PDF全文
Miwako Teranishi Masataka Wada Dr. Shin‐ichi Naya Prof. Hiroaki Tada 《Chemphyschem》2016,17(18):2813-2817
Mesoporous TiO2 nanocrystalline film was formed on fluorine‐doped tin oxide electrode (TiO2/FTO) and gold nanoparticles (NPs) of different sizes were loaded onto the surface with the loading amount kept constant (Au/TiO2/FTO). Visible‐light irradiation (λ>430 nm) of the Au/TiO2/FTO photoanode in a photoelectrochemical cell with the structure of photoanode|0.1 m NaClO4 aqueous solution|Ag/AgCl (reference electrode)|glassy carbon (cathode) leads to the oxidation of water to oxygen (O2). We show that the visible‐light activity of the Au/TiO2/FTO anode increases with a decrease in Au particle size (d) at 2.9≤d≤11.9 nm due to the enhancement of the charge separation and increasing photoelectrocatalytic activity. 相似文献
99.
Direct Observation of Ordered High‐Spin–Low‐Spin Intermediate States of an Iron(III) Three‐Step Spin‐Crossover Complex 下载免费PDF全文
Dr. Zhao‐Yang Li Dr. Hiroyoshi Ohtsu Dr. Tatsuhiro Kojima Dr. Jing‐Wei Dai Takefumi Yoshida Dr. Brian K. Breedlove Dr. Wei‐Xiong Zhang Dr. Hiroaki Iguchi Prof. Osamu Sato Prof. Masaki Kawano Prof. Masahiro Yamashita 《Angewandte Chemie (International ed. in English)》2016,55(17):5184-5189
A neutral mononuclear FeIII complex [FeIII(H‐5‐Br‐thsa‐Me)(5‐Br‐thsa‐Me)]?H2O ( 1 ; H2‐5‐Br‐thsa‐Me=5‐bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three‐step spin‐crossover (SCO) with symmetry breaking and a 14 K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS–2LS and 2HS–4LS, which exhibited reentrant phase‐transition behavior. This study provides a new platform for examining multistability in SCO complexes. 相似文献
100.
Summary A set of hydrophilicity parameters in a normal-phase liquid chromatography of peptides is presented in order to clarify the
contribution of individual amino acid residues to peptide retention and to predict retention times. The retention of 100 peptides
was studied using normal-phase liquid chromatography on amide, diol and silica columns. An acetonitrile-water mixed solution
containing 0.2% trifluoroacetic acid +0.2% triethylamine was used as the mobile phase in a linear gradient elution system.
The contribution of each residue upon retention was calculated by linear multiple regression analysis. This paper described
the contribution values as “hydrophilicity retention coefficients”. Using these hydrophilicity retention coefficients, retention
times could be predicted for peptides of known amino acid content and sequence. A set of hydrophilicity retention coefficients
on each column was successfully explained by contributions to the degree of retention. 相似文献