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611.
612.
Given an edge-weighted tree T and an integer p1, the minmax p-traveling salesmen problem on a tree T asks to find p tours such that the union of the p tours covers all the vertices. The objective is to minimize the maximum of length of the p tours. It is known that the problem is NP-hard and has a (2−2/(p+1))-approximation algorithm which runs in O(pp−1np−1) time for a tree with n vertices. In this paper, we consider an extension of the problem in which the set of vertices to be covered now can be chosen as a subset S of vertices and weights to process vertices in S are also introduced in the tour length. For the problem, we give an approximation algorithm that has the same performance guarantee, but runs in O((p−1)!·n) time. 相似文献
613.
Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS
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Prof. Yohei Uemura Daiki Kido Dr. Yuki Wakisaka Dr. Hiromitsu Uehara Dr. Tadashi Ohba M.Sc. Yasuhiro Niwa Dr. Shunsuke Nozawa Dr. Tokushi Sato Dr. Kohei Ichiyanagi Dr. Ryo Fukaya Prof. Shin‐ichi Adachi Dr. Tetsuo Katayama Dr. Tadashi Togashi Dr. Sigeki Owada Dr. Kanade Ogawa Dr. Makina Yabashi Dr. Keisuke Hatada Prof. Satoru Takakusagi Prof. Toshihiko Yokoyama Prof. Bunsho Ohtani Prof. Kiyotaka Asakura 《Angewandte Chemie (International ed. in English)》2016,55(4):1364-1367
The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time‐resolved X‐ray absorption fine structure (XAFS) spectroscopy using an X‐ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation. 相似文献
614.
Electrostatic Interaction and Reaction Behavior of a 1, 2,4‐Triazole Mixture with Dinitrobenzene
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The electrostatic interactions between gas generating agent and organic electron withdrawing additives were studied to understand how the interaction affects the reactions of their thermal behavior. To explore the electronic interaction and its effect, the thermal behavior of a mixture of dinitrobenzene isomers [p‐dinitrobenzene (pDNB) and m‐dinitrobenzene (mDNB)] and 1, 2,4‐triazole (TA) was analyzed. Density functional calculations and electron density analysis proved that both pDNB and mDNB in a 1:1 ratio withdraw electrons from TA. The analysis of pyrolysis behavior showed that TA and dinitrobenzene mixtures (TA/pDNB or TA/mDNB) react at lower temperatures than each precursor. Gas chromatography mass analysis and UV/Vis spectroscopy showed reasonable results that suggested that pDNB and TA make condensed products in the initial stage of the reaction according to the differential scanning calorimetry measurement. When the mixtures were ignited under pressurized conditions, TA/pDNB burned easily while TA/mDNB burned only partially. These results suggested that the interaction between triazole and dinitrobenzene affects the pyrolysis and combustion behavior of a TA/dinitrobenzene mixture. 相似文献
615.
Stereoselective Synthesis and Reactions of Secondary Alkyllithium Reagents Functionalized at the 3‐Position
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Kohei Moriya Dr. Dorian Didier Meike Simon Jeffrey M. Hammann Dr. Guillaume Berionni Prof. Dr. Konstantin Karaghiosoff Prof. Hendrik Zipse Prof. Dr. Herbert Mayr Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2015,54(9):2754-2757
Secondary alkyllithium reagents bearing an OTBS group (TBS=tert‐butyldimethylsilyl) at the 3‐position can be prepared stereoconvergently through an I/Li exchange from a diastereomeric mixture of the corresponding secondary alkyl iodides. These lithium reagents react with a range of electrophiles, including carbon electrophiles, with retention of configuration to yield various 1,3‐difunctionalized derivatives with good diastereoselectivities. Kinetic studies show that the 3‐siloxy group strongly accelerates the epimerization at the lithium‐substituted carbon atom. This method offers a new way to construct chiral open‐chain molecules with excellent stereoselectivity. 相似文献
616.
Described herein is that a new approach to a one-pot two-step conversion of aromatic carboxylic acids/esters to aromatic aldehydes, in which indium(III) iodide effectively catalyzes both the first reductive thioacetalization of carboxylic acids and a subsequent desulfurization of the in-situ formed thioacetal intermediates leading to aldehydes. 相似文献
617.
A Mechanochromic Luminescent Dye Exhibiting On/Off Switching by Crystalline–Amorphous Transitions
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A mechanochromic luminescent dye based on a simple aminomaleimide skeleton was readily synthesized in a one‐pot process. It exhibited an on/off mechanochromic luminescent switching property dependent on external stimuli, unlike a traditional mechanochromic color change. The green emission was turned on by grinding in a mortar and turned off by heating or treatment with dichloromethane. In the crystalline state, two molecules were stacked by cofacial π–π interactions, which caused concentration self‐quenching. The crystalline‐to‐amorphous transition induced by grinding removed cofacial π–π stacking, which led to intensive emission. Crystallizing processes recovered the cofacial π–π stacking, resulting in elimination of the emission. Theoretical calculations and X‐ray diffraction analyses revealed that the dye molecule was distorted in the crystalline state; thus even a mechanical stimulus caused the crystalline‐to‐amorphous transition. 相似文献
618.
Formation of Discrete Ladders and a Macroporous Xerogel Film by the Zipperlike Dimerization of Meso–Meso‐Linked Zinc(II) Porphyrin Arrays with Di(pyrid‐3‐yl)acetylene
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Kohei Kose Dr. Jin Motoyanagi Prof. Dr. Takahiro Kusukawa Prof. Dr. Atsuhiro Osuka Prof. Dr. Akihiko Tsuda 《Angewandte Chemie (International ed. in English)》2015,54(30):8673-8678
Metal porphyrins assemble to form a supramolecular architecture with a characteristic structure and characteristic properties and functions upon complexation with appropriate ligands. However, there are few applications of these assembly processes to the construction of polymeric porphyrin arrays with useful functionalities. In this study, we found that meso–meso‐linked ZnII porphyrin arrays underwent zipperlike dimerization upon complexation with di(pyrid‐3‐yl)acetylene (DPA) in chloroform to form discrete double‐stranded porphyrin ladders. Similarly, the assembly of poly(zinc(II) porphyrinylene) with DPA gave a thermoresponsive gel, whose three‐dimensional network structure was so strong that a macroporous xerogel film was obtained. 相似文献
619.
Kohei Kawasaki Takahiro Sakurai Eiji Ohmichi Susumu Okubo Hitoshi Ohta Kazuyuki Matsubayashi Yoshiya Uwatoko 《Applied magnetic resonance》2015,46(9):987-992
We have developed the high-pressure electron spin resonance (ESR) system using a micro-coil in the frequency region up to around 2 GHz and potentially 10 GHz. The hybrid-type piston-cylinder pressure cell whose maximum pressure reaches 4 GPa was used. In this study, we obtained ESR spectra at 2.3 GPa successfully, which can never be obtained by the single-layer piston-cylinder pressure cell. The minimum detectable spin number was estimated to be the order of 1012 spins/G. Moreover, it is shown that the sensitivity can be improved by two orders of magnitude using the field modulation technique. This high-pressure ESR technique is a promising one to achieve the sensitivity and the high pressure simultaneously. 相似文献
620.