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排序方式: 共有105条查询结果,搜索用时 31 毫秒
1.
Yoshinori Nishiwaki Masahiko Shimoyama Toshio Nakanishi Toshio Ninomiya Izumi Nakai 《Analytical sciences》2006,22(10):1297-1300
Total reflection X-ray fluorescence spectrometry (TXRF) has been applied for trace elemental analysis of small glass fragments. A small glass sample (a fragment with weight less than 0.5 mg) was decomposed by 100 microg of HF/HNO3 acid; the material was condensed to 10 microl and was dried on a Si wafer. Since the size of the dried residue on the Si wafer was less than 1 cm in diameter, an incident X-ray beam with about 1 cm in width could effectively excite elemental components in such a small glass fragment. The precision of the present technique was checked by analyzing the glass fragments (<0.5 mg) from NIST SRM612; the relative standard deviations (RSD) of less than 8.1% were achieved for elemental ratios that were normalized by Sr. Fragments (<0.5 mg) obtained from 23 figured sheet glasses were used as samples for estimating the utility of this technique to forensic discrimination. Comparison of five elemental ratios of Ti/Sr, Mn/Sr, Zn/Sr, Rb/Sr, and Pb/Sr calculated from X-ray fluorescence spectra was effective in distinguishing glass fragments that could not be differentiated by their refractive indexes (RI). 相似文献
2.
Resorcinol and 5-methylresorcinol, respectively, react with 3-oxo-2-aryl-4,4,4-trifluorobutyronitrile using zinc chloride as a catalyst in dibutyl ether under the Hoesch reaction conditions to give a low yield of 3-aryl-7-hydoxy-4-trifluoromethyl- or 3-aryl-5-hydroxy-7-methyl-4-trifluoromethyl-2H-l-benzopyran-2-ones. However, the related reaction with m-methoxyphenol was found to produce poor yields of 3-aryl-7-methoxy-4-trifluoromethyl-2H-1-benzopyran-2-one and its 3,4-dihydro-4-hydroxy derivative. 相似文献
3.
We are reporting on a new method of constructing dearomatized compounds from α-substituted aryltriazenes. Deprotonation occurs at C atom α to N3. Nucleophilic attack of generated anion at the ortho-position of aryl group forms a new carbon-carbon bond. A stereoselective reaction was observed when the substituents on the C α to N3 are tied together in either a pyrrolidine or a piperidine. The product of this reaction possessed an interesting dearomatized tetrahydrobenzotriazine framework. 相似文献
4.
Combination of cyanocobalamin (VB12) and ascorbic acid (VC) has been widely seen in pharmaceutical products and dietary supplements. However, VB12 has been reported that its behavior in stability in aqueous solution is quite different when VC is mixed. In the present study, we examined the stabilities of these vitamins in acetate buffer (pH 4.8) using high performance liquid chromatography. Degradation of VB12 was not observed in the absence of VC in the buffer. However, when VC was mixed in the VB12 solution, VB12 concentrations decreased in accordance with VC degradation. VB12 and VC degradations were inhibited by adding sodium halides to acetate buffer at pH 4.8. These stabilization effects were also observed in the range from pH 3.5 to 5.3 and by adding potassium, magnesium, and calcium halides. Furthermore, our data demonstrated that increases in the halide anion concentrations and atomic number (Cl-相似文献
5.
Tetsuji Kametani Kazuo Kigasawa Mineharu Hüragi Nagatoshi Wagatsuma Setsu Saitoh Hideo Sugi 《Journal of heterocyclic chemistry》1973,10(3):313-315
Acid treatment of the alkylated products of (Va, Vb, and VIII) of piperidinols IVa and IVb, and tetrahydropyridine VII with β-bromoethylbenzene, afforded 1,2,3,4,5,6-hexahydro-8-hydroxy-2,6-methano-6,1 1-dimethyl-3-phenethyl-3-benzazocine (la) in good yield. Piperidinols Va and Vb were also obtained from the reaction of N-(3-methyl-3-pentenyl)-β-phenethylamine (IIb) with methyl 3-(4-methoxyphenyl)-2,3-epoxypropionate. 相似文献
6.
Yasumasa Nishiwaki Kazunari Masutani Yoshiharu Kimura Chan-Woo Lee 《Journal of polymer science. Part A, Polymer chemistry》2022,60(14):2043-2054
The ABCBA pentablock copolymers (p-d -l -PPS) comprising poly(d -lactide) (PDLA: A), poly(l -lactide) (PLLA: B) and poly(propylene succinate) (PPS: C) were successfully synthesized by two-step ring-opening polymerization (ROP) of d - and l -lactide using a dihydroxy-terminated PPS as a macro-initiator. The pentablock copolymers revealed the high stereocomplex (sc) crystallinity, thermal stability and elastomeric property in their solution-cast films. It was found that the Tg was found to be proportional to the PPS content, whereas the Tm was proportional to their average block length. The thermal resistivity of the copolymer films was found to be as high as 202°C owing to their sc formation. The copolymers also showed improved stereocomplexibility compared to the enantiomeric mixtures of triblock copolymers (PLLA-PPS-PLLA and PDLA-PPS-PDLA) having similar PLLA and PDLA chain lengths. These pentablock copolymers can afford thermoplastic elastomers or flexible plastic materials having a 100% bio-based content, showing high heat-resistive property. 相似文献
7.
Effects of graded porous structure on local strain distribution under compression in silicone rubber
Keijiro Yoshimura Kazunori Nakano Takeshi Nishiwaki Yuki Iwama Masanobu Murata 《Journal of Polymer Science.Polymer Physics》2019,57(16):1033-1042
Silicone rubber samples with gradually changing pore sizes within the range of 70–610 μm are produced using an improved spacer method. The samples are scanned using an X‐ray computed tomography to evaluate their graded structure as compared to uniform rubber. A compressive test reveals that graded porous silicone rubber has characteristic stress–strain curves whose slope changes within a specific strain range depending on the porous structure. Analysis results of local strain based on a digital image correlation of the graded porous silicone rubber under compression demonstrate that the characteristic stress–strain properties are caused by shifts in the main deformation region in the graded structure. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1033–1042 相似文献
8.
9.
Prof. Dr. Mutsumi Kimura Junya Masuo Yuki Tohata Kazumichi Obuchi Naruhiko Masaki Takurou N. Murakami Nagatoshi Koumura Kojiro Hara Atsushi Fukui Ryohsuke Yamanaka Prof. Dr. Shogo Mori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1028-1034
A series of panchromatic ruthenium sensitizers ( MJ sensitizers) with attached thiophene and phenyl units bearing alkyl chains was synthesized. A new synthetic route was used to examine all possible positions for the alkyl chains. The absorption spectra showed the sum of a ruthenium complex and peripheral organic chromophore units. The hypochromic effect and blueshift of the metal‐to‐ligand charge‐transfer band observed in the modified ruthenium sensitizers were suppressed by changing the positions of the alkyl chains on the attached thiophene ring. Changing only one alkyl chain also influenced the performance of dye‐sensitized solar cells. Ruthenium sensitizer MJ‐10 with bulky substituent harvests visible and near‐infrared light, and solar cells sensitized by MJ‐10 exhibit an efficiency of 9.1 % under 1 sun irradiation. 相似文献
10.
Tomohiro Ichitsuka Ikko Takahashi Nagatoshi Koumura Kazuhiko Sato Shū Kobayashi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16025-16030
Aryl amines are important pharmaceutical intermediates among other numerous applications. Herein, an environmentally benign route and novel approach to aryl amine synthesis using dehydrative amination of phenols with amines and styrene under continuous-flow conditions was developed. Inexpensive and readily available phenols were efficiently converted into the corresponding aryl amines, with small amounts of easily removable co-products (i.e., H2O and alkanes), in multistep continuous-flow reactors in the presence of heterogeneous Pd catalysts. The high product selectivity and functional-group tolerance of this method allowed aryl amines with diverse functional groups to be selectively obtained in high yields over a continuous operation time of one week. 相似文献