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151.
Peter J. Mills Peter F. Green Christopher J. Palmstrm James W. Mayer Edward J. Kramer 《Journal of Polymer Science.Polymer Physics》1986,24(1):1-9
Forward recoil spectrometry is shown to be a useful technique for measuring diffusion of d-polymer chains in h-polymer melts. Concentration profiles of a deuterated diffusing species may be determined with a depth resolution of 80 nm and a sensitivity of 0.1 vol % d-polymer in h-polymer. Consequently diffusion coefficients as small as 10?16 cm2/s can be readily measured. If polymer chains diffuse by a reptation mechanism, the concentration profile ø(x) of diffusing polydisperse polymer should be quite different from øm(x), the Fickian solution, which one obtains for monodisperse polymer. This idea was tested by measuring ø(x) of polydisperse d-polystyrene (d-PS) diffusing into h-PS. The results are in excellent agreement with the ø(x) predicted from the reptation model and the experimentally determined molecular weight distribution. 相似文献
152.
For a fixed integer m ≥ 0, and for n = 1, 2, 3, ..., let λ2m, n(x) denote the Lebesgue function associated with (0, 1,..., 2m) Hermite-Fejér polynomial interpolation at the Chebyshev nodes {cos[(2k−1) π/(2n)]: k=1, 2, ..., n}. We examine the Lebesgue constant Λ2m, n max{λ2m, n(x): −1 ≤ x ≤ 1}, and show that Λ2m, n = λm, n(1), thereby generalising a result of H. Ehlich and K. Zeller for Lagrange interpolation on the Chebyshev nodes. As well, the infinite term in the asymptotic expansion of Λ2m, n) as n → ∞ is obtained, and this result is extended to give a complete asymptotic expansion for Λ2, n. 相似文献
153.
In this work preliminary results are reported on an extensive vibrational analysis of the molecules HCCX and DCCX with X = F and Cl, in which a number of anharmonic resonances are analysed. The importance of quartic anharmonic resonances in these molecular types is reported involving the effective constants K1244 and K1255, and these are related to the corresponding resonances in acetylene and its isotopomers. The correct analysis of Fermi resonances and quartic anharmonic resonances is important not only in reproducing the high overtone energy levels, but also in fitting the observed rotational constants, and in determining the r constants and hence the equilibrium rotational constants. In this paper we revise our recent analysis of the equilibrium structure of HCCF in the light of these effects. 相似文献
154.
155.
156.
A. P. Mills Jr. N. Karl D. M. Zuckerman J. Passner J. Hensel C. D. Beling 《Applied Physics A: Materials Science & Processing》1992,54(1):22-25
We have measured the positron mobility in a sample of scintillation grade anthracene at two temperatures. We obtain at 300 K: =(26.0±0.9±2.6) cm2V–1s–1 and at 77 K: =(33.4±1.1±3.3) cm2V–1s–1, where the first error estimate is statistical and the second is systematic. We have also made preliminary measurements on a highly purified sample that yields =(130±3±20) cm2 V–1 s–1 at 300 K. The data are consistent with the hypothesis that the positron is scattered from both impurities and acoustic phonons in the first sample, and predominantly from photons in the second. It appears that positrons in pure anthracene crystals are delocalized and have a mean free path of about 85 Å at room temperature. 相似文献
157.
An intelligence ink for oxygen 总被引:1,自引:0,他引:1
A generic ink formulation is described, comprising semiconductor photocatalyst particles, a brightly-coloured redox dye, a mild reducing agent, a polymer and a solvent, that creates an irreversible, reusable, UV-light-activated, colorimetric indicator or intelligence ink for oxygen. 相似文献
158.
Under low ionic strength conditions, a linear approximation of the electrostatic potential within the charged polyelectrolyte layer coating the membrane bilayer leads to overestimation of the red cell electrokinetic mobility. Considering the full non linearized Poisson-Boltzmann and Navier-Stokes equations relative to the erythrocyte system, the deviation at low ionic strength between theoretical and experimental values for the cell mobility then almost disappears. A weak glycocalyx expansion may account for the remaining differences. However, this result is in contrast with previously suggested explanations involving an important stretching of the polyelectrolyte chains to interpret the “artificial” erythrocyte aggregation at low ionic strength. Under such conditions cell aggregation is probably induced by haemolysate adsorption onto the erythrocyte membrane and is unlikely to be the consequence of a strong interfacial rearrangement. 相似文献
159.
G.O. Evans W.F. Walter D.R. Mills C.A. Streit 《Journal of organometallic chemistry》1978,144(2):C34-C38
The reactivity of a series of metal carbonyl anions with CO2 has been found to parallel their relative nucleophilicities. The highly nucleophilic species, C5H5Fe(CO)?2, reacts readily to give the dimer, (C5H5Fe(CO)2)2, and carbonate while Co(CO)?4 is unreactive. The reaction of 13CO2 with C5H5Fe(CO)?2 results in the formation of the 13CO enriched dimer. 相似文献
160.