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71.
Kazuyuki Enomoto 《Geometriae Dedicata》1997,65(2):193-201
The total squared curvature of a closed plane curve is minimized by a covering of a circle, if the rotation number of the curve is not zero. We measure the closeness of a closed plane curve to a circle by the difference of its total squared curvature from the minimum. A similar result is obtained for a simple closed curve in the 2-sphere. 相似文献
72.
Masaya Enomoto Noriyuki KidaNorimichi Kojima Isao WatanabeTakao Suzuki Yasuyuki Ishii 《Polyhedron》2011,30(18):3137-3139
We have investigated the magnetic properties of iron mixed-valence complexes, (n-CnH2n+1)4N[FeIIFeIII(dto)3] (dto = C2O2S2, n = 3, 5), in which not only a ferromagnetic transition but also a novel charge transfer phase transition (CTPT) take place [1]. This CTPT can be observed under ambient pressure for n = 3, while it appears abruptly above 0.5 GPa for n = 5 [2]. Recently, we have measured the muon spin relaxation (μSR) for the CTPT of n = 3, which revealed the dynamical process of electron-transfer between FeII and FeIII and its frequency was estimated at about 0.1 MHz [3]. To investigate the pressure induced CTPT for n = 5, we carried out the μSR measurement for n = 5 at 150 K between 0.30 and 0.64 GPa with the 4He gas-operated pressure system. The asymmetry of the muon spin relaxation for n = 5 with Cu-Be pressure cell was almost constant up to 0.55 GPa, while it rapidly decreased with increasing pressure above 0.60 GPa. This result shows that the applied pressure causes the spin fluctuation due to the CTPT, which induces the decrease of the asymmetry of muon spin relaxation. This experiment can correctly decide the phase transition pressure from the absence to the appearance of the CTPT for n = 5. 相似文献
73.
Copper-catalyzed allylic alkylation of ketene silyl acetals proceeded with excellent γ-E-selectivity. Efficient α-to-γ chirality transfer with anti-selectivity occurred in the reaction of enantioenriched secondary allylic phosphates, affording enantioenriched β-branched γ,δ-unsaturated esters. Excellent functional group compatibility was observed. 相似文献
74.
Zaima N Goto-Inoue N Hayasaka T Enomoto H Setou M 《Analytical and bioanalytical chemistry》2011,400(7):1865-1871
It has become necessary to assess the authenticity of beef origin because of concerns regarding human health hazards. In this
study, we used a metabolomic approach involving matrix-assisted laser desorption/ionization imaging mass spectrometry to assess
the authenticity of beef origin. Highly accurate data were obtained for samples of extracted lipids from beef of different
origin; the samples were grouped according to their origin. The analysis of extracted lipids in this study ended within 10 min,
suggesting this approach can be used as a simple authenticity assessment before a definitive identification by isotope analysis. 相似文献
75.
The mammalian tongue is one of the most important organs during food uptake because it is helpful for mastication and swallowing.
In addition, taste receptors are present on the surface of the tongue. Lipids are the second most abundant biomolecules after
water in the tongue. Lipids such as phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) are considered
to play fundamental roles in the mediation of cell signaling. Imaging mass spectrometry (IMS) is powerful tool for determining
and visualizing the distribution of lipids across sections of dissected tissue. In this study, we identified and visualized
the PC, LPC, and SM species in a mouse tongue body section with matrix-assisted laser desorption/ionization (MALDI)-IMS. The
ion image constructed from the peaks revealed that docosahexaenoic acid (DHA)-containing PC, LPC, linoleic acid-containing
PC and SM (d18:1/16:0), and oleic acid-containing PC were mainly distributed in muscle, connective tissue, stratified epithelium,
and the peripheral nerve, respectively. Furthermore, the distribution of SM (d18:1/16:0) corresponded to the distribution
of nerve tissue relating to taste in the stratified epithelium. This study represents the first visualization of PC, LPC and
SM localization in the mouse tongue body. 相似文献
76.
Kidera M Seto Y Takahashi K Enomoto S Kishi S Makita M Nagamatsu T Tanaka T Toda M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(3):1215-1219
We developed a detection technology for vapor forms of chemical warfare agents (CWAs) with an element analysis system using an electron cyclotron resonance ion source. After the vapor sample was introduced directly into the ion source, the molecular material was decomposed into elements using electron cyclotron resonance plasma and ionized. The following CWAs and stimulants were examined: diisopropyl fluorophosphonate (DFP), 2-chloroethylethylsulfide (2CEES), cyanogen chloride (CNCl), and hydrogen cyanide (HCN). The type of chemical warfare agents, specifically, whether it was a nerve agent, blister agent, blood agent, or choking agent, could be determined by measuring the quantities of the monatomic ions or CN(+) using mass spectrometry. It was possible to detect gaseous CWAs that could not be detected by a conventional mass spectrometer. The distribution of electron temperature in the plasma could be closely controlled by adjusting the input power of the microwaves used to generate the electron cyclotron resonance plasma, and the target compounds could be detected as molecular ions or fragment ions, enabling identification of the target agents. 相似文献
77.
Enomoto T Kanematsu S Tsunashima K Matsumoto K Hagiwara R 《Physical chemistry chemical physics : PCCP》2011,13(27):12536-12544
Fluorohydrogenate salts of quaternary phosphonium cations with alkyl and methoxy groups (tetraethylphosphonium (P(2222)(+)), triethyl-n-pentylphosphonium (P(2225)(+)), triethyl-n-octylphosphonium (P(2228)(+)), and triethylmethoxymethylphosphonium (P(222(101))(+))) have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium bromide or chloride precursors. The three salts with asymmetric cations, P(222m)(FH)(2.1)F (m = 5, 8, and 101), are room temperature ionic liquids (ILs) and are characterized by differential scanning calorimetry, density, viscosity, and conductivity measurements. Linear sweep voltammetry using a glassy carbon working electrode shows these phosphonium fluorohydrogenate ILs have wide electrochemical windows (>4.9 V) with the lowest viscosity and highest conductivity in the known phosphonium-based ILs. Thermogravimetry shows their thermal stabilities are also improved compared to previously reported alkylammonium cation-based fluorohydrogenate salts. Differential scanning calorimetry and X-ray diffraction revealed that tetraethylphosphonium fluorohydrogenate salt, P(2222)(FH)(2)F, exhibits two plastic crystal phases. The high temperature phase has a hexagonal lattice, which is the first example of a plastic crystal phase with an inverse nickel arsenide-type structure, and the low-temperature phase has an orthorhombic lattice. The high-temperature plastic crystal phase exhibits a conductivity of 5 mS cm(-1) at 50 °C, which is the highest value for the neat plastic crystals. 相似文献
78.
Toshifumi Inouchi Dr. Takuya Nakashima Dr. Masaya Toba Prof. Tsuyoshi Kawai 《化学:亚洲杂志》2011,6(11):3020-3027
T‐shaped π‐conjugated molecules with an N‐methyl‐benzimidazole junction have been synthesized and their acid‐responsive photophysical properties owing to the change in the π‐conjugation system are discussed. T‐shaped π‐conjugated molecules consist of two orthogonal π‐conjugated systems including a phenyl thiophene extended from the 2‐position and alkyl phenylenes connected through various π‐spacers from the 4,7‐positions of the N‐methyl‐benzimidazole junction. The π‐spacers, such as thiophene, ethyne, and ethane, have an effect on the acid response of photophysical properties in terms of changes in conformation, excited‐state energy and charge‐transfer (CT) characteristics. In particular, the π‐conjugated molecule with ethynyl spacers exhibited a marked redshift in the fluorescence spectrum with a large Stokes shift upon the addition of acid, whereas the other molecules showed substantial quenching. The redshift in emission was studied in detail by temperature‐dependent fluorescence measurements, which indicated the transition to a CT state over the finite activation energy at the excited state. The change in the frontier molecular orbitals upon acid addition was further discussed by means of DFT calculations. 相似文献
79.
Huang S Yee WA Tjiu WC Liu Y Kotaki M Boey YC Ma J Liu T Lu X 《Langmuir : the ACS journal of surfaces and colloids》2008,24(23):13621-13626
Polyvinylidene difluoride (PVDF) solutions containing a very low concentration of single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) of similar surface chemistry, respectively, were electrospun, and the nanofibers formed were collected using a modified rotating disk collector. The polymorphic behavior and crystal orientation of the nanofibers were studied using wide-angle X-ray diffraction and infrared spectroscopy, while the nanotube alignment and interfacial interactions in the nanofibers were probed by transmission electron microscopy and Raman spectroscopy. It is shown that the interfacial interaction between the SWCNTs and PVDF and the extensional force experienced by the nanofibers in the electrospinning and collection processes can work synergistically to induce highly oriented beta-form crystallites extensively. In contrast, the MWCNTs could not be well aligned along the nanofiber axis, which leads to a lower degree of crystal orientation. 相似文献
80.
It is well‐known that every planar graph has a vertex of degree at most five. Kotzig proved that every 3‐connected planar graph has an edge xy such that deg(x) + deg (y) ≤ 13. In this article, considering a similar problem for the case of three or more vertices that induce a connected subgraph, we show that, for a given positive integer t, every 3‐connected planar graph G with |V(G)| ≥ t has a connected subgraph H of order t such that Σx∈V(H) degG(x) ≤ 8t − 1. As a tool for proving this result, we consider decompositions of 3‐connected planar graphs into connected subgraphs of order at least t and at most 2t − 1. © 1999 John Wiley & Sons, Inc. J Graph Theory 30: 191–203, 1999 相似文献