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791.
Sana Hraiech Anis Jouini Kyoung Jin Kim Yannick Guyot Akira Yoshikawa Georges Boulon 《Radiation measurements》2010,45(3-6):323-327
Yb3+ and M+ monovalent alkali ions (M+ = Li+, Na+, K+)-co-doped CaF2 cubic laser crystals were grown by the micro-pulling-down method (μ-PD) under CF4 atmosphere. Structural and spectroscopic characterizations of Yb3+ in substitution of Ca2+ (absorption, emission and decay curves) were carried out to study the effect of M+ ions as charge compensators. 相似文献
792.
Jan Pejchal Martin Nikl Kentaro Fukuda Noriaki Kawaguchi Takayuki Yanagida Yuui Yokota Akira Yoshikawa Vladimir Babin 《Radiation measurements》2010,45(3-6):265-267
Doubly doped BaY2F8:Er,Nd scintillation crystals were grown by modified micro-pulling-down method. The Er co-doping was chosen to enhance the energy transfer from the host lattice to the Nd3+ luminescence center via the 5d-levels of Er3+, which can be enabled by the overlap of Er3+ 5d-4f emission spectrum with the Nd3+ 4f-5d absorption. The energy transfer was clearly evidenced in the BaY2F8:Er,Nd. The processes are complicated by energy migration to killer centres and/or cross-relaxation processes. The luminescence and energy transfer mechanism are discussed. 相似文献
793.
Syntheses,X‐ray crystal structures,and emission properties of protonated tripyridyltriazines and their ruthenium(II) complexes
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Naokazu Yoshikawa Shoko Yamazaki Hiroko Kimura Nobuko Kanehisa Tsuyoshi Inoue Hiroshi Takashima 《Journal of Physical Organic Chemistry》2018,31(3)
A series of metal‐free compounds, ie, planar triprotonated triazine, triazineH3Cl(PF6)2 ( 1 ), planar triprotonated triazineH3Br(PF6)2 ( 2 ), and nonplanar monoprotonated triazineHPF6 ( 3 ), were prepared. Abbreviations used are triazine = tri‐2‐pyridyltriazine. Ruthenium complexes [RuCl(bpy)(L)](PF6), [RuCl(bpy)(L)](PF6)2, and [Ru(L)2](PF6)2 were also prepared, where bpy is 2,2′‐bipyridine and L's are triazine ( 4 ) and monoprotonated triazine ( 5 ), respectively. Ruthenium complexes [Ru(triazine)2](PF6)2 ( 6 ) were also prepared and crystallized. The X‐ray crystal structures of the 3 compounds 1 , 2 , and 3 and the complex 6 were determined. They were also characterized by electrospray ionization mass spectrometry, UV‐vis spectroscopy, and density functional theory calculations. 相似文献
794.
Dr. Tatsuya Morofuji Yu Matsui Misa Ohno Gun Ikarashi Prof. Naokazu Kano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(22):6713-6718
Herein, a photocatalytic Giese-type reaction with alkylsilicates bearing C,O-bidentate ligands as stable alkyl radical precursors has been reported. The alkylsilicates were prepared in one step from organometallic reagents. Not only primary, secondary, and tertiary alkyl radicals, but also elusive methyl radicals, could be generated by using the present reaction system. The generated radicals were trapped by electron-deficient olefins bearing various functional groups to give the desired alkyl adducts. The silicon byproduct can be recovered after the photoreaction. The radical generation process was investigated by theoretical calculations, which provided an insight into the facile generation of methyl radicals from methylsilicate bearing C,O-bidentate ligands. 相似文献
795.
Yu Kitamura Emi Terado Zechen Zhang Prof. Hirofumi Yoshikawa Dr. Tomoko Inose Prof. Hiroshi Uji-i Prof. Masaharu Tanimizu Prof. Akihiro Inokuchi Dr. Yoshinobu Kamakura Prof. Daisuke Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(66):16347-16353
Novel metal–organic frameworks containing lanthanide double-layer-based secondary building units (KGF-3) were synthesized by using machine learning (ML). Isolating pure KGF-3 was challenging, and the synthesis was not reproducible because impurity phases were frequently obtained under the same synthetic conditions. Thus, dominant factors for the synthesis of KGF-3 were identified, and its synthetic conditions were optimized by using two ML techniques. Cluster analysis was used to classify the obtained powder X-ray diffractometry patterns of the products and thus automatically determine whether the experiments were successful. Decision-tree analysis was used to visualize the experimental results, after extracting factors that mainly affected the synthetic reproducibility. Water-adsorption isotherms revealed that KGF-3 possesses unique hydrophilic pores. Impedance measurements demonstrated good proton conductivities (σ=5.2×10−4 S cm−1 for KGF-3(Y)) at a high temperature (363 K) and relative humidity of 95 % RH. 相似文献
796.
K. Yoshikawa 《Macromolecular Symposia》1996,106(1):367-378
Transition of a single duplex DNA between elongated coil and condensed globule has been studied by the technique of single molecular observation with fluorescence microscopy. It has become clear that individual DNA chains undergo first-order phase transition. We have observed the time-dependent change of the DNA structure accompanied with the phase transition from coil to globule. The speed of the compaction was found to be almost constant along the DNA chain. It is indicated that the coil-globule transition exhibits the phenomenon of “nucleation and growth”. The process of the decollapse of a single DNA has also been observed, the time dependence of the long axis length being described as l ∼ t1.8. 相似文献
797.
Recently, it has been found that individual giant DNA molecules exhibit a discrete transition, or first order phase‐transition, between the compact folded state and the elongated coiled state, i.e., the folding transition. In order to clarify the thermodynamics in the folding transition of single DNA molecules, we have studied the temperature effect on the bimodal distribution of conformation for the ensemble of T4DNA chains (166 kbps) in both poly(ethylene glycol) (PEG) and spermidine (SPD), using single‐chain observation with fluorescence microscopy. From the van't Hoff relationship, the entropy change in the transition from the compact state to the unfolded state is deduced as, ΔS = +11, +38 k/molecule in the aqueous solution of PEG with sodium chloride and potassium chloride, respectively, where k is Boltzmann's constant, whereas, ΔS with SPD is estimated to be −32 k/molecule. The values of ΔS with the transition are discussed in term of the translational entropy of counterions together with the hydration effect. 相似文献
798.
799.
800.
A tetracoordinated sulfurane bearing a 1λ4,2‐dithietane moiety, whose 3‐ and 4‐positions were chiral carbon centers, was synthesized. Its thermolysis gave the corresponding thiirane as a single diastereomer, whose configuration and stereochemistry were determined. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:412–417, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20630 相似文献