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941.
The structure and hydrogen bonding of water in aqueous solutions of various surfactants were analyzed using the contours of the O-H stretching in the polarized Raman spectra. From the relative intensity of the collective band (C value) corresponding to a long-range coupling of the O-H stretching in the aqueous surfactant solutions, the number of hydrogen bonds disrupted due to the presence of one surfactant molecule (N(corr) value) was evaluated. The N(corr) value for decylsulfobetaine was slightly negative, whereas those for ordinary ionic surfactants such as sodium dodecylsulfate and dodecyltrimethylammonium chloride were large positive values. Furthermore, the N(corr) for carboxybetaine surfactant was a small positive value. These results suggest that zwitterionic surfactants do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostriction effect by the proximity between the anionic and cationic groups. 相似文献
942.
The reaction of 3,5-di-O-benzyl-2-deoxy-d-ribofuranose with various alkynyllithium reagents afforded diastereomeric mixtures of the corresponding ring-opened alkynyldiols. The resulting diastereomeric mixtures were successively treated with Co(2)(CO)(8), a catalytic amount of TfOH, Et(3)N, and iodine in one pot to give alkynyl C-3,5-di-O-benzyl-2-deoxy-beta-d-ribofuranosides with high beta-selectivities. The cobalt-mediated cyclization (intramolecular Nicholas reaction) is reversible; thus, thermodynamically more stable beta-anomers were obtained preferentially. The alkynyl C-deoxyribofuranosides were converted to a variety of C-deoxyribofuranoside derivatives. 相似文献
943.
We studied the image deformation due to the surface inclination of objects in photon scanning tunneling microscopes (PSTM). A novel collection mode PSTM with two light sources is proposed to reduce the deformation and experimental results show that the PSTM system is effective. 相似文献
944.
The world of catalysis has grown and broadened greatly. The necessity of catalytic technology in solving the contemporary environmental and industrial problems is obvious. Catalysis will be even more important in the next century in relation to global preservation and the supply of energy and resources. What we now need are truly innovative and useful catalysts and what we lack is the methodology of how to make those catalysts. We may have to admit that, in spite of a large number of published papers, there are many mere trial-and-error type repetitions and very few new and significant findings or concepts. This is due to the very complex nature of catalysts, industrial catalysts in particular. It is not easy to find the right way to proceed. One positive step to assist in finding the right way may be to promote a close and quick exchange of information and new concepts worldwide. We now start a new journal from Japan affiliated with the Catalysis Society of Japan: Catalysis Surveys from Japan. The main aim of this new journal is to disseminate as early as possible the important findings or movements from Japan which possibly lead to new concepts for the design of useful catalysts. Rapid, invited, short reviews or accounts from academia and industry will constitute the major part of Catalysis Surveys from Japan. Surveys of recent progress and activities in catalytic science and technology and related areas in Japan will be covered regularly as well. The journal will be issued twice a year. We would appreciate it if colleagues around the world who read the articles in Catalysis Surveys from Japan would send us critical comments. If requested and deemed appropriate, the comments will be included in the journal. We will be very happy if this small, new journal stimulates global communication between scientists and engineers in the world of catalysis, and assists in the development of innovative useful catalysts. 相似文献
945.
The propagation of light rays in a slab-waveguide whose dielectric constant varies radially with a quadratic law but has fourth and sixth order terms in it is described. Exact solutions consisting of Jacobi elliptic functions are shown. The exact ray trajectory and delay time of an optical pulse, therefore, can be obtained. The results show that the optimum fourth-order and sixth-order coefficients are near 2/3 and 17/45, respectively. 相似文献
946.
Ichiro Noda Toshiaki Kitano Mitsuru Nagasawa 《Journal of Polymer Science.Polymer Physics》1977,15(7):1129-1142
The effect of molecular weight heterogeneity on the second virial coefficient A2 in good solvents is studied for binary mixtures of monodisperse poly(α-methylstyrenes). It is concluded that A2 for polymer mixtures passes through a maximum with variation of the mixing ration. From comparison with the data, it is concluded that no available theory quantitatively explains both the molecular weight dependence of A2 of monodisperse polymer and the variation of A2 of mixtures with the mixing ratio. The interpenetration function for two polymer coils with different molecular weights is discussed on the assumption that the thermodynamic interaction between two polymer coils in good solvents can be approximated by a hard-sphere model. 相似文献
947.
An experimental study of the dynamic shear flow properties of polyethylene melts filled with glass fibers and vinylon fibers was carried out and comparison with the steady shear flow properties was made. The effects of loading level and the characteristics of the fibers on the rheological properties of the fiber-filled systems is discussed. The rigidity and complex viscosity of the fiber-filled systems is sensitive not only to the quantity of fibers but also to their length, distribution and properties. The Cox-Merz empirical law for complex viscosity and steady shear viscosity, and Roscoe's empirical relation for estimating the normal-stress coefficients are both able to be applied to pure polymer melts but not to fiber-filled systems. 相似文献
948.
Tomoyuki Sekine Kunimitsu Uchinokura Haruo Iimura Ryozo Yoshizaki Etsuyuki Matsuura 《Solid State Communications》1984,51(4):187-189
The successive phase transitions of the cubic spinel structure CuV2S4 have been studied by the electrical resistivity and the specific heat. In the resistivity and the specific heat two anomalies have been observed at T1~91 K and T3≈55 K. The specific heat indicates that the phase transition at T1 is in the vicinity of a tricritical point, where the resistivity has a small sharp peak. On the other hand, the specific heat shows a step at T3, where a hysteresis of the resistivity indicates the existence of the first-order phase transition. 相似文献
949.
A gradient-index rod lens was fabricated by the new ion-exchange technique, in which another dopant was added to the fused salt. It was found that this dopant remained only in the merginal region of the glass rod and modified the improper refractive index distribution in this region. The lens has high numerical aperture of 0.6 and gives good results in the light focusing system and the light source coupling system. 相似文献
950.
Tomoyuki Shirai 《Transactions of the American Mathematical Society》2000,352(1):115-132
Let be an infinite -regular graph and its line graph. We consider discrete Laplacians on and , and show the exact relation between the spectrum of and that of . Our method is also applicable to -semiregular graphs, subdivision graphs and para-line graphs.