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261.
Crystals of morpholine biguanide hydrochloride, C6H13N5O. HC1, belong to the orthorhombic space groupPbca;a = 19·02 Å,b = 9·92 Å,c = 10·34 Å andZ = 8. The structure has been solved by three-dimensional Patterson and heavy-atom Fourier syntheses. The hydrogen positions have been located from a three-dimensional difference Fourier synthesis. The positional coordinates of all the atoms and their temperature factors (anisotropic for non-hydrogen atoms and isotropic for hydrogen atoms) have been refined by three-dimensional least-squares methods. The finalR value is 0·087.The morpholine ring has been found to assume a chair configuration. The contribution of various valence bond structures to the normal state of the morpholine biguanide hydrochloride molecule has been studied with reference to the characters of the C-N bonds in the biguanide part of the molecule. Both the guanidine groups are planar. Of six available hydrogen atoms, only four take part in forming hydrogen bonds of the type N-H···Cl–. The molecules in the crystal are linked by a three-dimensional network of hydrogen bonds.Our thanks are due to the staff of the Computing Centres at IIT, Kharagpur and TIFR, Bombay. 相似文献
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263.
Korrapati. V. V. Prasada Rao Ramesh Dandala Vija Y. K. Handa Anand. G. Kamat Inti. V. Subramanyeswara Rao Ananta Rani Andra Naidu 《Journal of heterocyclic chemistry》2007,44(6):1513-1515
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Unequal spaced channel allocation (USCA) is a technique to reduce Four wave mixing (FWM). In this paper, system performance of 8 channel WDM system considering different optical transmitter formats (RZ, NRZ, Raised cosine and Gaussian) using USCA has been evaluated in terms of Q-factor. The simulation results reveal that four wave mixing is minimum for NRZ format. Also the effect of changing the laser power and increasing the bit rate has been observed. 相似文献
266.
Sato G Kondoh T Itoh H Handa S Yamaguchi K Nakamura T Nagai K Ouchi C Teshima T Setomoto Y Den T 《Optics letters》2011,36(18):3551-3553
A Talbot-Lau interferometer using two-dimensional gratings and a conventional x-ray tube has been used to investigate a phase-contrast imaging technique that is sensitive to phase gradients in two orthogonal directions. Fourier analysis of Moiré fringe patterns was introduced to obtain differential phase images and scattering images from a single exposure. Two-dimensional structures of plastic phantoms and characteristic features of soft tissue were clearly obtained at 17.5 keV. The phase-stepping technique was also examined to investigate the spatial resolution of different phase retrieval methods. In the presented setup we found that the choice of phase retrieval method made little difference in image blur, and a large effective source size was found to give a high intensity in the image plane. 相似文献
267.
Kazuhiro Matsumoto Chao FengSatoshi Handa Takuya Oguma Tsutomu Katsuki 《Tetrahedron》2011,67(35):6474-6478
Titanium(salalen) complex 1 was an effective catalyst for asymmetric epoxidation of enol esters. Although (E)-enol esters were reluctant to proceed, (Z)-enol esters underwent asymmetric epoxidation to give the epoxides in high yields with high enantioselectivity ranging from 86 to >99% ee in the presence of aqueous hydrogen peroxide as the stoichiometric oxidant. Complete enantioselectivity was observed in the reaction of (Z)-3,3-dimethylbut-1-en-1-yl 4-methoxybenzoate. The obtained epoxide was readily transformed into the corresponding 1,2-diol by reduction with lithium borohydride without erosion of the high enantiomeric excess. 相似文献
268.
Moriyuki Sato Kazunori Yamauchi Makoto Handa Kuninobu Kasuga 《Macromolecular rapid communications》2000,21(17):1234-1237
Intramolecular cyclization of precursor polyhydrazides derived from hydrazine and four 2,5‐dialkoxyterephthalic acids by direct polycondensation with Lawesson's reagent afforded new conjugated polymers constituted of 1,3,4‐thiadiazole and 2,5‐dialkoxybenzene units. The polymers emitted bluish green light in solution and green light in solid state in spite of the coexistence of non‐cyclized hydrazide linkage in the backbones, the Stokes shifts being 91–138 nm in the solid state. It was suggested that these polymers have appropriate lengths of conjugation backbones based on the 1,3,4‐thiadiazole moiety. 相似文献