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991.
Yoram S. Papir Sudhir Kapur Charles E. Rogers Eric Baer 《Journal of Polymer Science.Polymer Physics》1972,10(7):1305-1319
The relaxation behavior of nylon 6 from 4.2 to 300°K was investigated as a function of orientation, anisotropy and moisture content by using an inverted free-oscillating torsion pendulum. Three new relaxations, δ at 53°K, ? below 4.2°K, and ζ at 20°K, were discovered. The characteristics of these new relaxations strongly depend on the orientation anisotropy, and concentration of adsorbed water in the specimens. The results suggest that the mechanism of the γ process is associated with the motions of both the polar and methylene units. The mechanism of the β relaxation is postulated to originate with motions of both non-hydrogen-bonded polar groups and polymer—water complex units. The behavior of the α peak is consistent with the hypothesis that it originates with the rupture of interchain hydrogen bonding due to the motions of long-chain segments in the amorphous regions. Finally, the data strongly support the proposition that two types of water, tightly bound and loosely bound, exist in nylon 6. 相似文献
992.
993.
We consider a two-body potential which has only periodic ground states and prove that it can be perturbed, by an arbitrarily small perturbation, so as to have only aperiodic ground states.Research supported in part by NSF grant MCS 78-01520-A01. 相似文献
994.
(S)-Citramalic acid, a readily available microbial metabolite has been efficiently transformed into (2S)-2-methyl-2-hydroxy-1-hexanol (), an important chiral synthon for the synthesis of 15-deoxy-16(S)-hydroxy-16-methylprostaglandins. 相似文献
995.
Charles D. LeCroix R.F. Curl Peter M. McKinney Rollie J. Myers 《Journal of Molecular Spectroscopy》1974,53(2):250-272
The microwave spectra of silyl methyl ether, SiH3OCH3, and its isotopic modifications, SiH3OCD3, SiD3OCH3, and SiD3OCD3, have been observed and assigned. Large splittings arising from the internal rotation of the methyl top and somewhat smaller splittings arising from the internal rotation of the silyl top are observed. The “effective barrier” to internal rotation of the methyl top is approximately 550 cal/mole. The effective barrier to internal rotation of the silyl top is approximately 1100 cal/mole. The internal rotation of the two tops is strongly coupled, but no values for the potential coupling constants have been obtained. The dipole moment has been determined to be 1.15 ± 0.02 D (|μa| = 0.647 ± 0.01 and |μb| = 0.95 ± 0.02 D) from measurements of the Stark effect. 相似文献
996.
The dissociation of N2O/Ar mixtures, with and withoutadded CO, has been studied by monitoring both infrared and ultraviolet emissions behind reflected shock waves. Initial temperatures ranged from 1850 to 2535°K, and the total concentrations were 1.94–2.40 × 1018 molecule/cm3. The infrared emission, corrected if necessary for CO, was observed to decay exponentially, and an apparent rate constant Kapp was obtained. Addition of CO had no effect upon kapp and all the data can be described by the followingArrhenius parameters (in units of cm3/molecule.sec): log A=?9.31±0.12 and EA=219.1±5.2 kJ/mole. Ultraviolet emission data, in runs with added CO, indicate that the atomic oxygen concentration reached a constant value at t < 600 μsec for T0 > 2050°K. Numerical integration of the mechanism allowed comparison of calculated and observed parameters relating to both infrared and ultraviolet data. A consistent fit to these data was obtained with k1=1.3×10?9 exp (?238 kJ/RT) and k2=k3=1.91×10?11 exp(?105 kJ/RT). The concentration of atomic oxygen produced by N2O dissociation is shown to be a sensitive function of k1 through k3. Upper limits are also set for the rate constants of the following reactions: 相似文献
997.
998.
999.
A method is presented for evaluating management programmes in which the dischargers are divided into groups. Analogous non-linear mathematical formulations are presented for direct regulation and effluent charge programmes, and a non-linear branch-and-bound solution procedure is described. A detailed algorithm is described for the effluent charge case; it is shown to be very practical in an application to data for the Delaware estuary. 相似文献
1000.