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71.
The thermal behavior and structure of poly(hexamethylene p,p′-biben-zoate) (BB-6)/poly(tetramethyleneoxide) (PTMO) block copolymers (BB-6/PTMO) were studied using differential scanning calorimetry, polarizing optical microscopy, and wide-angle and small-angle x-ray diffractometry. As the PTMO fraction increases, BB-6 liquid crystallinity decreased and two transition temperatures [Tc→M (crystal-mesophase) and Tm→i (mesophase-isotropic melt)] move to lower temperatures. BB-6/PTMO containing less than 20 mol% of PTMO retains liquid crystallinity. The isotropic melt-mesophase transition exotherm of BB-6/PTMO in the cooling process moves to lower temperature with increasing PTMO. Contrary to the isotropic melt-mesophase transition, the mesophase-crystal transition exotherm moves to higher temperature, indicating that PTMO segments favor the molecular mobility of BB-6 segments. As the mole fraction of BB-6 increases, the texture indicative of the smectic liquid crystal is gradually disorganized. BB-6/PTMO containing more than 30 mol% of PTMO no longer forms the texture indicative of smectic liquid crystals. 相似文献
72.
Sonochemical degradation of dilute aqueous solutions of 2-, 3- and 4-chlorophenol and pentachlorophenol has been investigated under air or argon atmosphere. The degradation follows first-order kinetics in the initial state with rates in the range 4.5-6.6 microM min-1 under air and 6.0-7.2 microM min-1 under argon at a concentration of 100 microM of chlorophenols. The rate of OH radical formation from water is 19.8 microM min-1 under argon and 14.7 microM min-1 under air in the same sonolysis conditions. The sonolysis of chlorophenols is effectively inhibited, but not completely, by the addition of t-BuOH, which is known to be an efficient OH radical scavenger in aqueous sonolysis. This suggests that the main degradation of chlorophenols proceeds via reaction with OH radicals; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fe(II) ions accelerates the degradation. This is probably due to the regeneration of OH radicals from hydrogen peroxide, which would be formed from recombination of OH radicals and which may contribute a little to the degradation. The ability to inhibit bacterial multiplication of pentachlorophenol decreases with ultrasonic irradiation. 相似文献
73.
Kuroda N Torii HA Shibata M Nagata Y Barna D Hori M Horváth D Mohri A Eades J Komaki K Yamazaki Y 《Physical review letters》2008,100(20):203402
We report here the radial compression of a large number of antiprotons ( approximately 5 x 10(5)) in a strong magnetic field under ultrahigh vacuum conditions by applying a rotating electric field. Compression without any resonant structures was demonstrated for a range of frequencies from the sideband frequency of 200 kHz to more than 1000 kHz. The radial compression achieved is a key technique for synthesizing and manipulating antihydrogen atoms and antiprotonic atoms. 相似文献
74.
Atsuki Nagata Shinsuke Hiraoka Dr. Shuichi Suzuki Prof. Dr. Masatoshi Kozaki Prof. Dr. Daisuke Shiomi Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Dr. Rika Tanaka Prof. Dr. Keiji Okada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(14):3166-3172
A triplet ground-state diradical molecule, bis(nitronyl nitroxide)-substituted diphenyldihydrophenazine ( 1 ..), that can be converted into a one-electron oxidized species, 1 … + , in the quartet ground state has been developed. Surprisingly, these species, 1 .. and 1 … + , can be used under ambient conditions because they are reasonably stable under aerobic conditions, even in solution. The temperature-dependent magnetic susceptibilities reveal that 1 .. and 1 … + are in the triplet state, with a weak exchange interaction (J1/kB = +3.1 K) and quartet ground state with a strong exchange interaction (J2/kB = +160 K), respectively. The interconversion between the neutral and one-electron oxidized species can be realized through electrochemical reactions. Significantly different absorption bands in the near-IR region newly appeared in the electronic spectra acquired during electrochemical oxidation/reduction. 相似文献
75.
76.
Nuclear magnetic resonance studies of alkaline earth phosphosilicate and aluminoborosilicate glasses
Hiroshi Yamashita Hidetake Yoshino Keishi Nagata Hyuma Inoue Takeshi Nakajin Takashi Maekawa 《Journal of Non》2000,270(1-3):48-59
The 11B, 27Al, 29Si and 31P magic angle spinning (MAS) NMR spectra of MO–P2O5, MO–SiO2–P2O5 and MO(M′2O)–SiO2–Al2O3–B2O3 (M=Mg, Ca, Sr and Ba, M′=Na) glasses were examined. In binary MO–P2O5 (M=Ca and Mg) glasses, the distributions of the phosphate sites, P(Qn), can be expressed by a theoretical prediction that P2O5 reacts quantitatively with MO. In the ternary 0.30MO–0.05SiO2–0.65P2O5 glasses, the 6-coordinated silicon sites were detected, whose population increases in the order of MgOxCaO–0.05SiO2–(0.95−x)P2O5 glasses, its population increases with an increase in f (=([P2O5]−[MO]−[B2O3]−[Na2O])/[SiO2]) and has maximum at f=9. The signal due to the 5-coordinated silicon atoms is also observed when x is smaller than 0.45. When three network-forming oxides such as SiO2, Al2O3 and B2O3 coexist, Al2O3 reacts preferably with MO. The populations of 4-coordinated boron atoms, N4, are expressed well with r/(1−r), where r=([Na2O]−[Al2O3])/([Na2O]−[Al2O3]+[B2O3]). The correlation of the Raman signal at 1210 and 1350 cm−1 with the NMR signal of Si(Q6) at −215 ppm is also seen. 相似文献
77.
trans-1,4-Diphosphacyclohexanes were successfully synthesized by the stereospecific intramolecular coupling reaction of the optically active bisphosphine. This is a new route for the construction of the trans-1,4-diphosphacyclohexane skeleton. A cis isomer was also prepared along with the trans isomer from a mixture of rac- and meso-bisphosphines. The coordinated boranes were easily removed to afford the corresponding 1,4-diphosphacyclohexanes. 相似文献
78.
The infrared photodissociation spectra of [(CO 2) n (CH 3OH) m ] (-) ( n = 1-4, m = 1, 2) are measured in the 2700-3700 cm (-1) range. The observed spectra consist of an intense broad band characteristic of hydrogen-bonded OH stretching vibrations at approximately 3300 cm (-1) and congested vibrational bands around 2900 cm (-1). No photofragment signal is observed for [(CO 2) 1,2(CH 3OH) 1] (-) in the spectral range studied. Ab initio calculations are performed at the MP2/6-311++G** level to obtain structural information such as optimized structures, stabilization energies, and vibrational frequencies of [(CO 2) n (CH 3OH) m ] (-). Comparison between the experimental and the theoretical results reveals the structural properties of [(CO 2) n (CH 3OH) m ] (-): (1) the incorporated CH 3OH interacts directly with either CO 2 (-) or C 2O 4 (-) core by forming an O-HO linkage; (2) the introduction of CH 3OH promotes charge localization in the clusters via the hydrogen-bond formation, resulting in the predominance of CO 2 (-).(CH 3OH) m (CO 2) n-1 isomeric forms over C 2O 4 (-).(CH 3OH) m (CO 2) n-2 ; (3) the hydroxyl group of CH 3OH provides an additional solvation cite for neutral CO 2 molecules. 相似文献
79.
Nagata M Kondo M Suemori Y Ochiai T Dewa T Ohtsuka T Nango M 《Colloids and surfaces. B, Biointerfaces》2008,64(1):16-21
Dialkyl disulfide-linked naphthoquinone, (NQ-Cn-S)2, and anthraquinone, (AQ-Cn-S)2, derivatives with different spacer alkyl chains (Cn: n = 2, 6, 12) were synthesized and these quinone derivatives were self-assembled on a gold electrode. The formation of self-assembled monolayers (SAMs) of these derivatives on a gold electrode was confirmed by infrared reflection-absorption spectroscopy (IR-RAS). Electron transfer between the derivatives and the gold electrode was studied by cyclic voltammetry. On the cyclic voltammogram a reversible redox reaction between quinone (Q) and hydroquinone (QH2) was clearly observed under an aqueous condition. The formal potentials for NQ and AQ derivatives were −0.48 and −0.58 V, respectively, that did not depend on the spacer length. The oxidation and reduction peak currents were strongly dependent on the spacer alkyl chain length. The redox behavior of quinone derivatives depended on the pH condition of the buffer solution. The pH dependence was in agreement with a theoretical value of E1/2 (mV) = E′ − 59pH for 2H+/2e− process in the pH range 3–11. In the range higher than pH 11, the value was estimated with E1/2 (mV) = E′ − 30pH , which may correspond to H+/2e− process. The tunneling barrier coefficients (β) for NQ and AQ SAMs were determined to be 0.12 and 0.73 per methylene group (CH2), respectively. Comparison of the structures and the alkyl chain length of quinones derivatives on these electron transfers on the electrode is made. 相似文献
80.