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911.
Yano K 《SAR and QSAR in environmental research》2001,12(5):417-434
This paper presents a new research method of structure-activity relationships (SAR) based on the concept of substructural balance. By using antiallergic activity (PCA, rat, iv) of a non-congeneric set of 267 structures, the structural feature of active group is expressed in terms of substructural balance. Each structure was expressed with 100 new substructures and the number of each substructure in a molecule was counted. The substructural balance was expressed as their ratio. Structures were classified into three groups based on their potencies (ED50), active (44), median (33) and inactive (190) group. Using two substructural ratios, 80.53% of inactive and 57.58% of median structures were excluded from those that were active. Common features of active structures were shown as a zone indicating the optimal ranges of two substructural ratios. Two substructural ratios were determined out of 4950 substructural ratios, all possible combinations of 100 substructures (100C2), by selecting the greatest discriminatory power of inactive from active structures. The substructures used in this work include: the number of bonds comprising of the longest conjugate system, the number of skeletal atoms and the numbers of electron-donor pairs at certain distances in the molecule. 相似文献
912.
913.
Shoichi Kutsumizu Koushi Morita Tatsuya Ichikawa Shinichi Yano Shuichi Nojima Takanari Yamaguchi 《Liquid crystals》2002,29(11):1447-1458
The structure of the thermotropic cubic phases of 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acids (ANBC-n, where n indicates the number of carbon atoms in the alkoxy group) was studied by X-ray diffraction. For the homologues with n = 15, 16, 17, and 18, the cubic phase was of an Ia3d type, whereas the homologues with n = 19, 20, and 21 exhibited an Im3m cubic structure; for these seven homologues the same type of cubic structure was observed both on heating and cooling. Further lengthening of the alkoxy chain to n = 22 and 26, however, gave two types of cubic structure in the cubic phase region on heating, one with Im3m symmetry in the low temperature region and the other with Ia3d symmetry in the high temperature region. On cooling, the two homologues exhibited the Ia3d cubic structure only. This is the first example in the cubic phase region of a series of homologues containing two types of structure, dependent on temperature and n. Such a complicated phase diagram in the cubic region is clearly understood qualitatively in terms of Gibbs free energy-temperature diagrams. The dependence of structural parameters such as the cubic lattice constant on the alkoxy chain length n are also presented and discussed. 相似文献
914.
915.
Stripe domains with walls perpendicular to the AC demagnetizing field (PACD) are observed in atomically ordered, ferromagnetic NiMn with slightly more than 25 at.% Mn. Based on Lorentz microscopy and magnetic measurements. PACD is explained in terms of an inhomogeneity in the magnetic phase and coherent rotation of the magnetization in the domain. 相似文献
916.
Color constancy is an important feature of the human visual system. Our visual system adapts almost instantly to new illumination and we can perceive the color of objects in a new space correctly whatever color the illumination may be. This feature is not solely that of a commercially available camera. The difference between the human visual system and a camera raises a problem in our observation of pictures. We cannot see the exact color that a photographer intended to show us through a picture. Some color modification must be made to the picture to resolve this. In the present paper, the degree of modification was determined for various color combinations of illumination for taking a picture, FLL and observing the picture, FLo. An entire experiment was carried out in an actual room based on the belief that color appearance of objects is determined in relation to the recognized visual space of illumination (RVSI). A subject observed the color of a room lit by FLL and pictures of the room lit by various colors of FLL were taken. The pictures were displayed in another room lit by FLo and the subject chose the picture that gave him/her the same color impression as the room of FLL. In the case of picture slide, the color of the picture must be modified as if it were taken with the illumination inbetween the color of FLL and FLo. In the case of picture print, a similar modification was needed for reddish FLL and white FLO, but it was not needed for white FLL and reddish FLo. 相似文献
917.
The phase behaviour of the binary systems 4'-n-tetradecyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-14)-n-alkane (n-tetradecane or n-hexadecane) was investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The phase behaviour was a function of temperature (T) and the effective carbon number of the system (n*), where n* involves carbon atoms both from the alkoxy group of ANBC-14 and from the n-alkane added. ANBC-14 shows no cubic phase, but the addition of n-alkane induced cubic phases when n*≧c. 15. An interesting point is that the type of cubic phase is Ia3d for 15≦n*≦17, while an Im3m type is formed for 18≦n*≦20. Furthermore, for n* = 22, two types of cubic phase, one with Im3m symmetry in the low temperature region and the other with Ia3d in the high temperature region, were observed both on heating and cooling. The phase diagram with respect to T and n* is very similar to that of pure one-component ANBC-n, which is a function of T and the number of carbon atoms in the alkoxy group n. 相似文献
918.
K. Baba I. Endo H. Fukuma K. Inoue T. Kawamoto T. Ohsugi Y. Sumi T. Takeshita S. Uehara Y. Yano T. Maki 《Nuclear Physics A》1984,415(3):462-476
Momentum spectra of protons emitted at three lab angles 23°, 55° and 130° in high-energy photoreactions of 9Be and 12C are studied by using tagged photons in the energy range between 360 and 600 MeV. At 23° and 55°, we observe a structure which may be ascribed to protons from quasifree production of a single pion and those from quasideuteron photodisintegration, while at 130°, the spectra are predominantly due to protons resulting from intranuclear multiple scattering. The results of an intranuclear cascade calculation are compared with the data. 相似文献
919.
920.
Suzuki D Nobe Y Watai Y Tanaka R Takayama Y Sato F Urabe H 《Journal of the American Chemical Society》2005,127(20):7474-7479
Coupling of acetylene, nitrile, and a titanium reagent, Ti(O-i-Pr)(4)/2 i-PrMgCl, generated new azatitanacyclopentadienes in a highly regioselective manner. Their subsequent reaction with sulfonylacetylene afforded pyridyltitanium compounds, which, upon reaction with electrophiles, gave substituted pyridines virtually as a single isomer. When optically active nitriles were used in this reaction, chiral pyridines were obtained without loss of the enantiopurity. Alternatively, the azatitanacyclopentadiene prepared from an unsymmetrical acetylene reacted with an aldehyde or another nitrile to give furans or pyrroles having four different substituents again in a regioselective manner. 相似文献