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31.
32.
Abstract A versatile crosslinking agent, tetraallyl piperazinium dichloride (TAP) has been prepared and demonstrated to be useful in copolymerization with water soluble monomers such as acrylic acid and acrylamide. Although the crosslinker itself does not readily homopolymerize in water, it forms transparent rigid hydrogels within a reasonable period of time when copolymerized with acrylic acid. Being nonhydrolysable, the crosslinker presented is superior to other common water soluble crosslinking agents such as methylene or ethylene bis(acrylamides). Since this crosslinker has a low toxicity, it may be used for bioapplications such as gel electrophoresis etc. 相似文献
33.
D. E. Aspnes R. Bhat C. Caneau E. Colas L. T. Florez S. Gregory J. P. Harbison I. Kamiya D. E. Aspnes R. Bhat C. Caneau E. Colas L. T. Florez S. Gregory J. P. Harbison I. Kamiya V. G. Keramidas M. A. Koza M. A. A. Pudensi W. E. Quinn S. A. Schwarz M. C. Tamargo H. Tanaka 《Journal of Crystal Growth》1992,120(1-4):71-77
We provide a perspective on current capabilities for optically monitoring and controlling epitaxial growth, and discuss examples taken from recent work at Bellcore. 相似文献
34.
Bordallo HN Boldyreva EV Buchsteiner A Koza MM Landsgesell S 《The journal of physical chemistry. B》2008,112(29):8748-8759
Incoherent inelastic neutron scattering spectra for the three crystalline polymorphs (alpha- P2(1)/n, beta- P2(1), gamma- P3(1)) of glycine (C2H5NO2) at temperatures between 5 and 300 K (using the time-of-flight (ToF) spectrometer NEAT at HMI) and at pressures from ambient up to 1 GPa (using the ToF spectrometer IN6 at the ILL) were measured. Significant differences in the band positions and their relative intensities in the density of states (DoS) were observed for the three polymorphs, which can be related to the different intermolecular interactions. The mean-squared displacement, (T), dependence reveals a change in dynamic properties at about the same temperature (150 K) for all the three forms, which can be related to the reorientation of the NH3 group. Besides, a dynamic transition in beta-glycine at about 230-250 K on cooling was also observed, supporting previously obtained adiabatic calorimetry data. This behavior is similar to that already observed in amorphous solids, on approaching the glass transition temperatures, as well as in biological systems. It suggests the onset of degrees of freedom most likely related to transitions between slightly different conformational orientations. The DoS obtained as a function of pressure has confirmed the stability of the alpha-form with respect to pressure and also depicted a sign of the previously reported reversible beta-beta' glycine phase transition in between 0.6 and 0.8 GPa. Moreover, a remarkable kinetic effect in the pressure-induced phase transition in gamma-glycine was revealed. After the sample was kept at 0.8 GPa for an hour in the neutron beam, an irreversible transition into a high-pressure form (different from the beta'-form) occurred, although previously in X-Ray diffraction and Raman spectroscopy experiments a gamma- to delta-glycine phase transition was observed above 3.5 GPa only. 相似文献
35.
We hereby report the first preparation of the 3,4-dihydrofuro[3,2-d]pyrimidin-2(1H)-one skeleton formed by two controlled Curtius rearrangements of the corresponding acyl azides, prepared from 2-(2-methoxy-2-oxoethyl)furan-3-carboxylate via the hydrazide. Rearrangement of the acyl azides followed by trapping by nucleophiles and intramolecular trapping provided the target compounds. 相似文献
36.
I. V. Kalinin E. I. Kats M. Koza V. V. Lauter H. Lauter A. V. Puchkov 《Journal of Experimental and Theoretical Physics》2010,111(2):215-219
The results of recent neutron scattering studies of solid helium in silica aerogel are discussed. Previously I.V. Kalinin
et al., Pis’ma Zh. éksp. Teor. Fiz. 87 (1), 743 (2008) [JETP Lett. 87 (1), 645 (2008)], we detected the existence of a superfluid phase in solid helium at a temperature below 0.6 K and a pressure
of 51 bar, although, according to the phase diagram, helium should be in the solid state under these conditions. This work
is a continuation of the above studies whose main goal was to examine the detected phenomenon and to establish basic parameters
of the existence of a superfluid phase. We have determined the temperature of the superfluid transition from solid to superfluid
helium, T
C = 1.3 K, by analyzing experimental data. The superfluid phase excitation parameters (lifetime, intensity, and energy) have
a temperature dependence similar to that of bulk helium. The superfluid phase coexists with the solid phase in the entire
measured temperature range from T = 0.05 K to T
C and is a nonequilibrium one and disappears at T
C. 相似文献
37.
38.
Maths Karlsson Aleksandar Matic Dennis Engberg M?rten E. Bj?rketun Michael M. Koza Istaq Ahmed G?ran Wahnstr?m Lars B?rjesson Sten-G. Eriksson 《Solid State Ionics》2009,180(1):22-28
Proton motions in hydrated proton conducting perovskites BaZr0.90A0.10O2.95 (A = Y and Sc) have been investigated using quasielastic neutron scattering. The results reveal a localized motion on the ps time scale and with an activation energy of ~ 10–30 meV, in both materials. The temperature dependence of the total mean square displacement of the protons shows an onset of this motion at a temperature of about 300 K. The low activation energy, much lower than the activation energy for the macroscopic proton conductivity, suggests that this motion is not the rate-limiting process for the long-range proton diffusion, i.e. it is not linked to the two materials significantly different proton conductivities. In fact, a comparison of the QENS results with density functional theory calculations indicates that for both materials the observed motion may be ascribed to intra-octahedral proton transfers occurring close to a dopant atom. 相似文献
39.
We hereby report the first preparation of the 5,6‐dihydro‐4H‐furo[2,3‐c]pyrrol‐4‐one ( 3 ) and its derivatives starting from methyl 3‐(methoxycarbonyl)furan‐2‐acetate ( 8 ). The ester functionality connected to the methylene group was regiospecifically converted to the desired monohydrazide 9 . Conversion of 9 into the acyl azide 10 followed by Curtius rearrangement gave the corresponding isocyanate derivative 11 (Scheme 2). Reaction of 11 with different nucleophiles produced urethane and urea derivatives (Scheme 3). Intramolecular cyclization reactions provided the target compounds (Scheme 5). Removal of the amine‐protecting group formed the title compound 3 . 相似文献
40.
Sans résumé 相似文献