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991.
N Cameron J.M.G CowieR Ferguson J.L Gómez RibellesJ Más Estellés 《European Polymer Journal》2002,38(3):597-605
The glass transition and the structural relaxation processes have been studied in blends of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt.% blend of PMMA with the SAN copolymer containing 30 wt.% of AN is immiscible, while blends with copolymers containing between 13 and 26 wt.% of AN are miscible. Thus the upper limit of miscibility is between 26 and 30 wt.% of AN. The temperature dependence of the relaxation times of the conformational rearrangements of polymer chains around the glass transition have been determined in the blends and pure components by modelling DSC thermograms obtained after different thermal histories in each sample. The slope in the Arrhenius diagram logτ vs 1/T around the glass transition temperature is significantly smaller in the blend which is closer to the upper limit of miscibility than in the other miscible blends in which SAN copolymer contains less AN. The change of slope can be ascribed to a distribution in the glass transition temperatures of the different rearranging regions, reflecting the appearance of a microheterogeneity in the blend that cannot be detected as a double glass transition in the blend. 相似文献
992.
Rapid methods for characterizing soy proteins and their hydrolysates by free-zone capillary electrophoresis were developed. The 7S- and 11S-rich protein fractions were separated by capillary electrophoresis (CE). The relationships between degrees of hydrolysis and electropherograms were established. Protein hydrolysates were separated in less than 6 min. Data showed that the CE method can be used effectively for monitoring protein hydrolysis during processing and for fingerprinting various types of protein products. 相似文献
993.
Leigh WJ Harrington CR Vargas-Baca I 《Journal of the American Chemical Society》2004,126(49):16105-16116
Diphenylgermylene (Ph2Ge) and its Ge=Ge doubly bonded dimer, tetraphenyldigermene (6a), have been characterized directly in solution for the first time by laser flash photolysis methods. The germylene is formed via (formal) cheletropic photocycloreversion of 3,4-dimethyl-1,1-diphenylgermacyclopent-3-ene (4a), which is shown to proceed in high chemical (>95%) and quantum yield (phi = 0.62) by steady-state trapping experiments with methanol, acetic acid, isoprene, and triethylsilane. Flash photolysis of 4a in dry deoxygenated hexane at 23 degrees C leads to the prompt formation of a transient assigned to Ph2Ge (lambda(max) = 500 nm; epsilon(max) = 1650 M(-1) cm(-1)), which decays with second-order kinetics (tau approximately 3 micros), with the concomitant growth of a second transient species that is assigned to digermene 6a (tau approximately 40 micros; lambda(max) = 440 nm). Analogous results are obtained from 1,1-dimesityl- and 1,1-dimethyl-3,4-dimethylgermacyclopent-3-ene (4b and 4c, respectively), which afford Mes2Ge (tau approximately 20 micros; lambda(max) = 560 nm) and Me2Ge (tau approximately 2 micros; lambda(max) = 480 nm), respectively, as well as the corresponding digermenes, tetramesityl- (6b; lambda(max) = 410 nm) and tetramethyldigermene (6c; lambda(max) = 370 nm). The results for the mesityl compound are compared to the analogous ones from laser flash photolysis of the known Mes2Ge/6b precursor, hexamesitylcyclotrigermane. The spectra of the three germylenes and two of the digermenes are in excellent agreement with calculated spectra, derived from time-dependent DFT calculations. Absolute rate constants for dimerization of Ph2Ge and Mes2Ge and for their reaction with n-butylamine and acetic acid in hexane at 23 degrees C are also reported. 相似文献
994.
[reaction: see text] Bis(dipyrromethene)s with relatively long spacers (>5 atoms) form helical monomeric complexes as the two binding units of the bis(dipyrromethene) chelate around the same tetrahedrally coordinated metal ion. Herein we report the first highly diastereoselective mononuclear helicate-forming complexation reactions of bis(dipyrromethene)s using homochiral binol and tartrate motifs which serve as both linkers and asymmetric templates. 相似文献
995.
Condo GT Handler T Shimony J Abe K Austern M Armenteros R Bacon TC Ballam J Bingham HH Brau JE Braune K Brick D Bugg WM Butler JM Cameron W Cohn HO Colley DC Dado S Diamond R Dingus P Erickson R Falicov A Field RC Fortney LR Franek B Fujiwara N Glanzman T Godfrey IM Goldberg JJ Goshaw AT Hall G Hancock ER Hargis HJ Hart EL Harwin MJ Hasegawa K Hulsizer RI Jobes M Kafka T Kalmus GE Kelsey DP Kent J Kitagaki T Levy A Lucas PW Mann WA McCrory ES Merenyi R Milburn R Milstene C Moffeit KC Napier A 《Physical review D: Particles and fields》1990,41(11):3317-3323
996.
Condo GT Handler T Shimony J Abe K Armenteros R Austern M Bacon TC Ballam J Bingham HH Brau JE Braune K Brick D Bugg WM Butler JM Cameron W Cohn HO Colley DC Dado S Diamond R Dingus P Erickson R Falicov A Field RC Fortney LR Franek B Fujiwara N Glanzman T Godfrey IM Goldberg JJ Goshaw AT Hall G Hancock ER Hargis HJ Hart EL Harwin MJ Hasegawa K Hulsizer RI Jobes M Kafka T Kalmus GE Kelsey DP Kent J Kitagaki T Levy A Lucas PW Mann WA McCrory ES Merenyi R Milburn R Milstene C Moffeit KC Napier A 《Physical review D: Particles and fields》1991,43(9):2787-2791
997.
The compound (Ph3P)32N,+BEt4
- is readily prepared from (Ph3P)2N+Cl– and LiBHEt3. The NMR spectrum (1H, 13C. 11B, 33P) are reported. C44H50NBP2
M = 665.64, Triclinic, P (#2), a = 11.530(4), b = 15.397(9), c = 11.497(9) Å, = 102.94(6), = 102.87(4), = 89.34(4)°, V = 1938(4) Å3, and Z= 2. 相似文献
998.
999.
1000.
In the present work plasma actuators were applied in a flat-plate boundary layer with an adverse pressure gradient to influence
the transition of the boundary layer. The first actuator downstream of the leading edge is operated in pulsed mode to introduce
perturbations into the boundary layer to promote transition. Two steady operating actuators further downstream damp the perturbations
significantly, which results in transition delay. 相似文献