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41.
Crystallization of a semi-crystalline polyolefin in the presence of low molecular weight modifiers was quantified by differential scanning calorimetry and optical microscopy. The polyolefin was a commercial grade of isotactic poly(1-butene) (iPB). Two modifiers were used: an oligomeric plasticizer, designated HOAO, which decreased the glass transition temperature (Tg) of the system, and an oligomeric tackifier, designated HOCP, which increased Tg. Binary iPB/modifier blends containing 10% or 20% by weight of HOAO or HOCP were examined to determine how their addition affects Tg, while ternary iPB/HOAO/HOCP blends containing 10% or 20% by weight of total modifier were examined to determine the effects of dilution by using a ratio of HOAO to HOCP that matched the Tg of iPB. The addition of modifier decreased the nucleation rate, spherulitic crystal growth rate, and final crystallinity of each blend. However, only the nucleation rate showed a dependence on the type of modifier, with nucleation retarded more by HOCP than by HOAO. A Hoffman-Weeks analysis of the melting point as a function of crystallization temperature confirmed that the driving force for nucleation was reduced, and that the effect was larger for HOCP. An Avrami analysis of the bulk crystallization kinetics was consistent with these observations, as the Avrami exponents were in the range of 3-4. 相似文献
42.
J. P. Bocquet R. Brissot H. R. Faust M. Fowler J. Wilhelmy M. Asghar M. Djebara 《Zeitschrift für Physik A Hadrons and Nuclei》1990,335(1):41-48
The mass and nuclear charge distributions of fission fragments from229Th(nth, f) have been measured at several kinetic energies with the mass spectrometer Lohengrin (ILL-Grenoble). The average proton e-o effect, which reaches 41%, induces large oscillations in the parameters of the isotopic charge distribution. A comparison of the data from different fissile nuclei shows the importance of the last stage of the process for intrinsic excitations. 相似文献
43.
David B. Redmond Charles M. Quinn Patrick W. Fowler 《Journal of mathematical chemistry》1998,23(3-4):263-276
Some new aspects of qualitative molecular-orbital theory are developed within the context of group theory and a symmetrized
Hückel approximation. Conclusions concerning the eigenvalue sums for sets of eigenfunctions of the same symmetries, the occurrence
of repetitions of symmetry-adapted projections and the relations between eigenvalues of Γg and Γu symmetries are exemplified using the 120 cage structure of Ih point symmetry. The implications of the orbit-by-orbit approach are outlined for larger clusters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
44.
Tian J Ma S Thallapally PK Fowler D McGrail BP Atwood JL 《Chemical communications (Cambridge, England)》2011,47(27):7626-7628
Cucurbit[7]uril (CB[7]), in its amorphous solid state, shows one of the highest CO(2) sorption capacities among known organic porous materials at 298 K and 0.1 and 1 bar. In addition to the highest CO(2) capacity, CB[7] also shows remarkable selectivity of CO(2) over N(2) and CH(4). These properties, along with the existence of readily available precursors, indicate amorphous CB[7] might find applications in recycling CO(2) particularly considering the easy synthesis and potentially low manufacturing costs. 相似文献
45.
G.N. Fowler 《Molecular physics》2013,111(4):383-386
The response of a molecular crystal to electromagnetic radiation is discussed in terms of a response function using the analogy of the electron gas and the results of the previous paper. A qualitative explanation of the phenomenon of hypochromism is suggested according to which the ‘missing’ oscillator strength goes into the photon-exciton modes found by Hopfield. 相似文献
46.
K. J. Moody W. Brüchle M. Brügger H. Gäggeler B. Haefner M. Schädel K. Sümmerer H. Tetzlaff G. Herrmann N. Kaffrell J. V. Kratz J. Rogowski N. Trautmann M. Skålberg G. Skarnemark J. Alstad M. M. Fowler 《Zeitschrift für Physik A Hadrons and Nuclei》1987,328(4):417-422
We have observedγ-rays following the β?-decay of243Np and244Np after chemical isolation of neptunium isotopes from the products of the reaction of 835 MeV136Xe with244Pu. The ground-state of 1.85-min243Np hasJ=5/2. The decay of 2.29-min244Np (probableJ π=7?) populates high-spin members of the ground state rotational band in244Pu. 相似文献
47.
D.P.A. Hardwick S.L. Naylor S. Bujkiewicz T.M. Fromhold D. Fowler A. Patan L. Eaves A.A. Krokhin P.B. Wilkinson M. Henini F.W. Sheard 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):285
We study the effects of inter-miniband electron tunneling and electric field domains on the current–voltage and conductance–voltage curves of biased semiconductor superlattices under the action of a magnetic field that is tilted relative to the plane of the layers. For this geometry, electrons in the superlattice minibands exhibit a unique type of stochastic semiclassical motion. At certain critical values of the electric field within the superlattice layers, the stochastic trajectories change abruptly from fully localized to completely unbounded, and map out an intricate web-like mesh of conduction channels in phase space. Delocalization of the electron paths produces a series of strong resonant peaks in the electron drift velocity versus electric field curves. We use these drift velocity characteristics to make self-consistent drift-diffusion calculations of the current–voltage and differential conductance–voltage curves of the superlattices, which reveal strong resonant features originating from the sudden delocalization of the stochastic single-electron paths. We show that this delocalization has a pronounced effect on the distribution of space charge and electric field domains within the superlattices. Inter-miniband tunneling greatly reduces the amount of space-charge buildup, thus enhancing the domain structure and both the strength and number of the current resonances. 相似文献
48.
A. C. Fowler 《Studies in Applied Mathematics》1985,72(2):161-171
We show how long-term cooling effects in convection can be analyzed in terms of the underlying boundary-layer structure, by a method analogous to averaging in nonlinear oscillations. 相似文献
49.
50.
Journal of Nonlinear Science - 相似文献