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61.
Yoshito Ohtake Yoshimasa Yamamoto Mio Gonokami Tsutomu Nakamura Hiroyuki Ishii Seiichi Kawahara 《Polymer Degradation and Stability》2013
The degradation of an ethylene–propylene-diene (EPDM) rubber seal used in a water supply system was investigated using focused ion beam-scanning electron microscopy (FIB-SEM). The EPDM rubber seal was used for 3 years within the temperature range 20–40 °C in a city water system. The accretions present on the surface of the EPDM seal after use were observed by SEM and were found to consist of iron and oxygen atoms based on energy dispersive X-ray spectroscopy (EDS) analysis. A cross-sectional depth image of the EPDM rubber was obtained by FIB-SEM, after slicing the EPDM rubber with a focused Gallium ion beam. Iron and oxygen atoms in the cross-section of the EPDM rubber were detected through EDS. The distribution of iron was comparable to that of oxygen derived from the carbonyl groups generated by the degradation of EPDM, suggesting that iron ions may promote the degradation of natural rubber through catalytic effects. 相似文献
62.
63.
Masao Kishida Chihiro Mio Kiyoshi Imamura Akira Kondo Akikazu Kaga Manohar Lal Shrestha 《International journal of environmental analytical chemistry》2013,93(2):67-82
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM) with a diameter <10 µm (PM10, 50% cut off) were investigated in the Kathmandu Valley, Nepal, during 2003. In order to understand the dynamics of atmospheric PAHs in winter, the PAH concentrations in total PM and in the gaseous phase were investigated in the valley in December 2005. Total of 45 PAH compounds (∑45PAHs) were analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In 2003, the ∑45PAH concentrations in PM10 ranged between 4.3 and 89 ng m?3 (annual average; 27 ± 24 ng m?3). The average concentrations of ∑45PAHs in December 2005 were 210 ± 33 ng m?3 in total PM and 430 ± 90 ng m?3 in the gaseous phase. The ∑45PAH concentration in PM accounted for more than 30% of the sum of their particulate and gaseous forms. Phenanthrene (Ph) was the most predominant compound in the gaseous phase, whereas four- to seven-ring PAHs were predominant in total PM. The highest values of ∑45PAHs occurred in the winter and spring. Estimates of emission sources based on diagnostic molecular ratios showed that atmospheric PAHs in the Kathmandu Valley mainly originated from the exhaust gas of diesel engine. In the winter and spring, PAH pollution would be accelerated by the operations of brick kilns and the frequent formation of an atmospherically stable layer in the valley. 相似文献
64.
Masami Fukushima Ken FurubayashiNaotaka Fujisawa Mio TakeuchiTakeshi Komai Keishi OtsukaMitsuo Yamamoto Yasunari KawabeShigekazu Horiya 《Journal of Analytical and Applied Pyrolysis》2011,91(2):323-331
The structural features of humic acids (HAs) isolated from sediments on the bottom of dam reservoirs that can affect their binding capacities for Fe(II) were investigated by pyrolysis-gas chromatography/mass spectroscopy using tetramethylammonium hydroxide (TMAH-py-GC/MS). The binding capacities for Fe(II) increased with increasing O/C molar ratio, suggesting that the oxygen-containing functional group content plays a role in the binding of Fe(II). However, it was not possible to identify specific binding-sites for Fe(II) by TMAH-py-GC/MS analysis. Although C16:1ω7, iso-C15:0 and anteiso-C17:0 fatty acids, which serve as molecular markers of anaerobic microbial activity, were detected in all of the HA samples, the contents of these acids were not correlated with binding capacities for Fe(II). However, the ratio of C16:0 to C16:1ω7 fatty acids, which is used as an index of anaerobic bacterial activity, increased with increasing Fe(II) binding capacities of the HAs. It thus appears likely that the activities of anaerobic bacteria on the bottom of dam reservoirs contribute to alterations in the structural features for HAs, and that this process results in increased binding capacities for Fe(II). 相似文献
65.
Atsuya Yaguchi Prof. Hirotsugu Hiramatsu Atsuya Ishida Dr. Mio Oshikawa Prof. Itsuki Ajioka Prof. Takahiro Muraoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9295-9301
Amphiphilic peptides bearing terminal alkyl tails form supramolecular nanofibers that are increasingly used as biomaterials with multiple functionalities. Insertion of alkylene chains in peptides can be designed as another type of amphiphilic peptide, yet the influence of the internal alkylene chains on self-assembly and biological properties remains poorly defined. Unlike the terminal alkyl tails, the internal alkylene chains can affect not only the hydrophobicity but also the flexibility and packing of the peptides. Herein, we demonstrate the supramolecular and biological effects of the central alkylene chain length inserted in a peptide. Insertion of the alkylene chain at the center of the peptide allowed for strengthened β-sheet hydrogen bonds and modulation of the packing order, and consequently the amphiphilic peptide bearing C2 alkylene chain formed a hydrogel with the highest stiffness. Interestingly, the amphiphilic peptides bearing internal alkylene chains longer than C2 showed a diminished cell-adhesive property. This study offers a novel molecular design to tune mechanical and biological properties of peptide materials. 相似文献
66.
Zhe Sun Tatsuru Mio Tomohiko Okada Taisuke Matsuno Sota Sato Hirohiko Kono Hiroyuki Isobe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(7):2062-2066
In the design of machinery such as steel bearings, a fundamental understanding of material characteristics provides an indispensable basis for the design. Although hydrocarbon cycloarylenes have started to be used for providing unique supramolecular bearings with anomalous dynamic behaviors, their fundamental understanding is immature. A unique property of the cycloarylene host is now reported: the cyclic host is so pliable that it tracks the orientational changes of the ellipsoidal guest, that is, C70 fullerene. Unique structures of the complex were revealed by spectroscopic and crystallographic analyses, and additional theoretical investigations deepened our understanding by revealing the structural changes associated with unbiased rotational motions. 相似文献
67.
<正>Photoreaction of 9-vinylcarbazole in acetonitrile in the presence of titanium dioxide and a catalytic amount of magnesium perchlorate gave 3,6-di(9-carbazolyl)-1,2-dioxane as a photooxygenated product via photodimerization of 9-vinylcarbazole.The photoreaction proceeds via an electron transfer mechanism,where magnesium perchlorate accelerated formation of the photo-oxygenated product. 相似文献
68.
69.
Mano N Kamota M Inohana Y Yamaguchi S Goto J 《Analytical and bioanalytical chemistry》2006,386(3):682-688
Ion trap/time-of-flight hybrid mass spectrometers are powerful tools for the detailed structural analysis of modified peptides. We have analyzed Met-Lys-bradykinin modified with deoxycholate at the amino-terminus or the epsilon-amino group as model peptides. These two modified peptides produced fragment ions with the same nominal but different exact masses in tandem mass spectrometry with low-energy collision-induced dissociation. Accurate high-resolution analysis coupled with MS(3) allowed us to distinguish the deoxycholate modification sites in the modified peptides. 相似文献
70.
Tatsuru Mio Koki Ikemoto Sota Sato Hiroyuki Isobe 《Angewandte Chemie (International ed. in English)》2020,59(16):6567-6571
A synthetic strategy to construct large geodesic structures of phenine (1,3,5‐trisubstituted benzene) was devised. In this strategy, five pentagons were assembled on an omphalos pentagon, and bridging peripheral pentagons furnished five additional hexagons. Thirty phenine units were synthetically assembled to afford a large C220H180 molecule with a phenine framework isoreticular to a hemispherical, bisected segment of C60. Although a hemispherical structure of the phenine framework was suggested by solution‐phase NMR spectra, crystallographic analysis revealed an oval‐like deformation of the molecular shape. In‐depth structural analyses, including theoretical calculations, showed that structural fluctuations observed as variations in the biaryl torsion angles allowed structural deformations and, at the same time, that the dynamic fluctuations resulted in the spectroscopic observation of a hemisphere as a time‐averaged structure. 相似文献