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981.
Shiro Kobayashi Masashi Ohmae Shun-ichi Fujikawa Hirofumi Ochiai 《Macromolecular Symposia》2005,226(1):147-156
Hyaluronidase (HAase)-catalyzed polymerization was performed to provide synthetic hyaluronan (HA), chondroitin (Ch) and their derivatives. The 2-methyl oxazoline derivatives derived from their repeating disaccharides of N-acetylhyalobiuronate ( 1a ) and N-acetylchondrosine ( 3a ) were effectively polymerized by the enzyme, giving rise to synthetic HA and synthetic Ch in good yields through regio-selective and stereo-controlled ring-opening polyaddition. The oxazoline derivatives of 2-ethyl ( 1b , 3b ), 2-n-propyl ( 1c , 3c ), 2-isopropyl ( 1d , 3d ), 2-phenyl ( 1e , 3e ), 2-vinyl ( 1f , 3f ) and 2-isopropenyl ( 1g ) were synthesized and subjected to the enzymatic reaction. Monomers 1b , 1c , 1f , 3b and 3f were polymerized to corresponding polysaccharides 2b , 2c , 2f , 4b and 4f , all of which are unnatural glycosaminoglycans. Compounds 1d , 3c and 3d were also catalyzed by the enzyme, affording oligomers of 2d , 4c and 4d were produced in trace amounts. Monomers 1e , 1g and 3e were not catalyzed by HAase. 相似文献
982.
Thermal and mechanical properties of poly(diarylsilmethylene)s (PDArSMs) with phenyl, m-tolyl or p-tolyl substituents on Si atoms were investigated. According to the TG-DTA, poly(diphenylsilmethylene) (PDPSM) remained almost unchanged in weight up to about 400°C, and showed two-step weight loss in the temperature range between ca. 400 and 700°C in an air atmosphere. The first decomposition step seems assignable to elimination of aryl groups while the second one is presumably due to oxidative decomposition which is evident from a large exothermic peak in the DTA trace. Thermostability of PDArSMs with tolyl groups were comparable to that of PDPSM when the measurement was conducted under nitrogen, whereas the polymers having tolyl substituents were highly thermally unstable in air compared with PDPSM. These polymers exhibited a gain in weight accompanied with a violent exothermic reaction in the early stage of thermal decomposition in air. This thermal instability of the tolyl-substituted polymers can be explained by high sensitivity of the tolyl groups toward oxidative decomposition. Analysis of pyrolyzed products of PDArSMs suggested that these polymers underwent radical cleavage of Si-aryl bonds to provide network materials which can be precursors for Si-containing ceramics. Mechanical properties of PDPSM are also discussed. © 1996 John Wiley & Sons, Inc. 相似文献
983.
Microbial colonisation of synthetic plastic films is normally slow, which affects the total period of biodegradation. Correlation between the modified surface condition and the ability for microorganisms to colonise low-density polyethylene (LDPE) film was studied. Corona discharge treatment was applied to obtain enriched and activated surface condition of LDPE film. It was found from water contact angle and FTIR spectrum evaluations that surface energy was significantly increased due to production of free radicals. Stabilised oxidised LDPE surface was also obtained by further exposure to the corona which gave more suitable condition for subsequent colonisation. Results were compared with UV irradiated (photo-oxidised) LDPE films. Colonisation of corona discharged and UV treated LDPE films were tested in the laboratory environment using known fungal isolates and in a natural compost environment. More active microbial colonisation was observed in all cases for corona discharged and UV treated LDPE films. Far longer UV exposure was required to have the same physicochemical and biological effect as the corona discharge treatment. 相似文献
984.
The strained InGaAs/AlGaAs layer structures have been grown on GaAs ( 10 0) and (3 1 1)B substrates in a horizontal low-pressure metalorganic vapor-phase epitaxy system at a temperature of 800°C. In the surface observation using a high-resolution scanning electron microscope, we have found that surface deformation phenomena induced by electron-beam irradiation in strained In0.36Ga0.64As,/Al0.3Ga0.7As layers on GaAs (1 0 0) and (3 1 1)B substrates. The change of the surface morphology was observed in real time on the display of SEM with the accelerating voltage of 30 kV and the irradiated time of 60–120 s. The surface deformation through mass transport seems to be the cause of the residual strain relaxation due to electron-beam irradiation. 相似文献
985.
Gennadiy Burlak Svetlana Koshevaya Masashi Hayakawa Edmundo Gutierrez-D Vladimir Grimalsky 《Optical Review》2000,7(4):323-325
It is shown that the deceleration of light pulses down to the velocity of a sound value can be realized in a case of unidirectional parametric interaction of two electromagnetic waves with an acoustic one in the regime of forming three wave acousto-optic solitons. This nonlinear acousto-optic interaction can be realized in long distance systems like fibers. As the result of such an interaction, two types of acousto-optic envelope solitons can propagate in fibers. Modulation of the amplitude of the electromagnetic pump wave can control the soliton velocity. 相似文献
986.
Shingo Taniguchi Masashi Takada Takashi Nakamura 《Radiation Physics and Chemistry》2001,61(3-6):523-526
A multi-moderator spectrometer on which is mounted a pair of 6Li and 7Li glass scintillators has been developed as a new type neutron spectrometer which can measure the neutron spectrum in a mixed field of neutrons, charged particles and gamma-rays realized in space. The particle identification capability was investigated in neutron-gamma-ray and neutron-proton mixed fields and the neutron response functions of the spectrometer were obtained by calculations and experiments up to 200 MeV. 相似文献
987.
Ito F Moriguchi T Yoshitake Y Eto M Yahara S Harano K 《Chemical & pharmaceutical bulletin》2003,51(6):688-696
A series of pairs of stable diastereomeric atropisomers caused by restricted rotation around the Csp3-Csp2 bond of [2-(2-hydroxynaphthalen-1-yl)-3,3-dimethyl-2,3-dihydroindol-1-yl]-(3- or 4-substituted phenyl)-methanone or [2-(2-hydroxynaphthalen-1-yl)-3,3-dimethyl-2,3-dihydroindol-1-yl]-1-alkanone were isolated. The conformational analyses of the atropisomers were performed based on the X-ray crystallographic and (1)H-NMR spectral data. It became clear that rotation about the C2-naphthyl bond is restricted at room temperature, whereas the >NCO-Ar bond rotates freely. 相似文献
988.
989.
Patrick Achenbach Carlos Ayerbe Gayoso Ralph Böhm Olga Borodina Damir Bosnar Vakkas Bozkurt Luka Debenjak Michael O. Distler Anselm Esser Ivica Friščić Yuu Fujii Toshiyuki Gogami Mar Gómez Rodríguez Osamu Hashimoto Satoshi Hirose Hiroki Kanda Masashi Kaneta Eunhee Kim Junichiro Kusaka Amur Margaryan Harald Merkel Ulrich Müller Sho Nagao Satoshi N. Nakamura Josef Pochodzalla Christophe Rappold Joerg Reinhold Takehiko R. Saito Alicia Sanchez Lorente Salvador Sánchez Majos B. Sören Schlimme Matthias Schoth Florian Schulz Concettina Sfienti Simon Širca Liguang Tang Michaela Thiel Kyo Tsukada 《Few-Body Systems》2014,55(8-10):887-892
At the Mainz Microtron MAMI exploratory experiments on the spectroscopy of mesonic weak decays (MWD) of electroproduced Λ-hypernuclei were performed. A unique setup was realized to use the broad momentum-band kaon spectrometer Kaos at zero degree angle with respect to the high-intensity electron beam direction to tag strangeness producing processes. A sample of order 103 MWD from a beryllium target was collected by the coincidence technique with the high-resolution multi-spectrometer facility of the A1 Collaboration. It is conjectured that this sample contains monochromatic two-body decays from stopped hyperfragment decays as well as a wide momentum distribution of quasi-free produced Λ- and Σ-hyperon decays and three-body decays from hyperfragments. Stopped hyperfragments will be identified as monochromatic peaks in the π ? momentum spectrum from which their masses can be extracted with a precision of 50 keV/c 2. 相似文献
990.