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71.
P. Willsau H. Hübel W. Korten F. Azaiez M. A. Deleplanque R. M. Diamond A. O. Macchiavelli F. S. Stephens H. Kluge F. Hannachi J. C. Bacelar J. A. Becker M. J. Brinkman E. A. Henry A. Kuhnert T. F. Wang J. A. Draper E. Rubel 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(3):351-352
Lifetimes of superdeformed states in194Pb were measured by the Doppler-shift attenuation method. Quadrupole moments around 20 eb, that are constant over the observed frequency range, are derived. The results rule out large centrifugal stretching effects. 相似文献
72.
73.
Filled polymeric liquids often exhibit apparent yielding and shear thinning in steady shear flow. Yielding results from non-hydrodynamic particle—particle interactions, while shear thinning results from the non-Newtonian behavior of the polymer melt. A simple equation, based on the linear superposition of two relaxation mechanisms, is proposed to describe the viscosity of filled polymer melts over a wide range of shear rates and filler volume fraction.The viscosity is written as the sum of two generalized Newtonian liquid models. The resulting equation can describe a wide range of shear-thinning viscosity curves, and a hierarchy of equations is obtained by simplifying the general case. Some of the parameters in the equation can be related to the properties of the unfilled liquid and the solid volume fraction. One adjustable parameter, a yield stress, is necessary to describe the viscosity at low rates where non-hydrodynamic particle—particle interaction dominate. At high shear rates, where particle—particle interactions are dominated by interparticle hydrodynamics, no adjustable parameters are necessary. A single equation describes both the high and low shear rate regimes. Predictions of the equation closely fit published viscosity data of filled polymer melts.
n
power-law index
-
n
1,n
2
power-law index of first (second) term
-
shear rate
-
steady shear viscosity
-
0
zero-shear rate viscosity
-
0, 1,
0, 2
zero-shear rate viscosity of first (second) term
-
time constant
-
1,
2
time constant of first (second) term
-
µ
r
relative viscosity of filled Newtonian liquid
-
0
yield stress
-
ø
solid volume fraction
-
ø
m
maximum solid volume fraction 相似文献
74.
Emmanuel Adeniyi Olivia Grounds Zachary Stephens Matthias Zeller Sergiy V. Rosokha 《Molecules (Basel, Switzerland)》2022,27(18)
Similarities and differences of halogen and hydrogen bonding were explored via UV–Vis and 1H NMR measurements, X-ray crystallography and computational analysis of the associations of CHX3 (X=I, Br, Cl) with aromatic (tetramethyl-p-phenylenediamine) and aliphatic (4-diazabicyclo[2,2,2]octane) amines. When the polarization of haloforms was taken into account, the strengths of these complexes followed the same correlation with the electrostatic potentials on the surfaces of the interacting atoms. However, their spectral properties were quite distinct. While the halogen-bonded complexes showed new intense absorption bands in the UV–Vis spectra, the absorptions of their hydrogen-bonded analogues were close to the superposition of the absorption of reactants. Additionally, halogen bonding led to a shift in the NMR signal of haloform protons to lower ppm values compared with the individual haloforms, whereas hydrogen bonding of CHX3 with aliphatic amines resulted in a shift in the opposite direction. The effects of hydrogen bonding with aromatic amines on the NMR spectra of haloforms were ambivalent. Titration of all CHX3 with these nucleophiles produced consistent shifts in their protons’ signals to lower ppm values, whereas calculations of these pairs produced multiple hydrogen-bonded minima with similar structures and energies, but opposite directions of the NMR signals’ shifts. Experimental and computational data were used for the evaluation of formation constants of some halogen- and hydrogen-bonded complexes between haloforms and amines co-existing in solutions. 相似文献
75.
A.M. Rao P.C. Eklund U.D. Venkateswaran J. Tucker M.A. Duncan G.M. Bendele P.W. Stephens J.-L. Hodeau L. Marques M. Núñez-Regueiro I.O. Bashkin E.G. Ponyatovsky A.P. Morovsky 《Applied Physics A: Materials Science & Processing》1997,64(3):231-2239
60 polymers. Pure and mixed phase polymeric samples were synthesized by simultaneously subjecting microcrystalline C60 powder or pellets to various pressures () and temperatures (). The optical spectra of the orthorhombic, tetragonal, and rhombohedral C60 polymer phases are observed to be quite distinct and rich. These spectra exhibit numerous lines and an overall downshift
in frequency relative to C60 is observed, consistent with a loss of double bonds from the fullerene cage. The LDMS spectra of a sample synthesized at
under hydrostatic conditions and , exhibited a succession of clear peaks at mass numbers corresponding to , similar to the LDMS data on the C60 photopolymer. This is taken as further evidence for interfullerene bonds in these high-pressure polymers. The XRD pattern
of this sample indicates the presence of a strong texture in the sample.
Received: 14 November 1996/Accepted: 8 January 1997 相似文献
76.
A Commentary on the paper “Computer simulation studies of anisotropic systems XIX. Mesophases formed by the Gay-Berne model mesogen„, by G.R. Luckhurst, R.A. Stephens and R.W. Phippen. First published in Liquid Crystals, 8, 451-464 (1990). 相似文献
77.
Geoffrey T Crisp Peter D Turner Kim A Stephens 《Journal of organometallic chemistry》1998,570(2):2408
The palladium-catalysed coupling of aryl halides with terminal alkynes can be performed using base, zinc chloride and sodium iodide. This protocol represents a convenient method for the generation of nucleophilic acetylides in situ. 相似文献
78.
Aerosol concentration before atomic-absorption measurement is achieved by use of an electrostatic trapping technique. The effects of various experimental parameters are examined, including those of voltage, trap dimensions, gas flow-rate through the trap and trapping time. It is concluded that the technique offers an inherently clean method of solution preconcentration which is capable of enhancing the signal by an order of magnitude or more. 相似文献
79.
The personality of individuals has been shown to interact with their auditory system in a variety of ways. Subjects with different personalities may differ in their physiological responses to sounds, in their perception of sounds and in the way in which noise influences their performance of a variety of tasks. Severe deafness appears to influence the personality of patients, and fairly characteristic changes are found in specific auditory disorders. The annoyance caused by a variety of noises is influenced by the person's personality and in the past a noise annoyance scale has been used as a measure of neuroticism. 相似文献
80.
H. Hübel R. M. Diamond P. Aguer C. Ellegaard D. B. Fossan H. Kluge C. Schück S. Shih F. S. Stephens U. Smilanski 《Zeitschrift für Physik A Hadrons and Nuclei》1982,304(3):225-230
Average lifetimes of unresolved transitions deexciting very high spin states populated in28Si(136, 129Xe,xn)164? x, 157?xEr reactions have been determined by a Doppler shift attenuation method. We find that the yrast bump region between 1.0 and 1.6 MeV contains a majority of strongly collectiveE2 transitions with very short lifetimes (a few tens of fsec) in the well deformed nuclei around159Er and, with less certainty, almost comparably short lifetimes in the more spherical nuclei around152Er. In the high energy region of 2.0–3.2 MeV we observe transitions which depopulate longer lived states in the nuclei nearN=82 than in the well deformed systems. 相似文献