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21.
The coarse structure magnetic theory presented here is a reformulation of conventional magnetic theory which emphasizes the spin-free (i.e., the coulombic) nature of the electron-electron interaction. We show that the magnetic properties of a system for which fine and hyperfine structure can be neglected depend only on the energy spectrum of a spin-free Hamiltonian. As an example, we treat the Heisenberg linear chain. 相似文献
22.
The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectors are discussed. Interest
is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and
transparent-acrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic
point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic-
and isoclinic-photoelastic data and a finite-difference representation of the planestress equilibrium equations, is used to
compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown. 相似文献
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Particle–hole and pairing relationships are obtained within the framework of the unitary group formulation of the many-electron problem using the concept of particle–hole conjugation. Besides the familiar relationships for alternant hydrocarbons, relationships among various pericyclic reaction paths are obtained. 相似文献
26.
Matsen MW 《The Journal of chemical physics》2004,121(4):1938-1948
The accuracy of strong-stretching theory (SST) is examined against a detailed comparison to self-consistent field theory (SCFT) on dry polymeric brushes with thicknesses of up to approximately 17 times the natural chain extension. The comparison provides the strongest evidence to date that SST represents the exact thick-brush limit of SCFT. More importantly, it allows us to assess the effectiveness of proposed finite-stretching corrections to SST. Including the entropy of the free ends is shown to rectify the most severe inaccuracies in SST. The proximal layer proposed by Likhtman and Semenov provides another significant improvement, and we identify one further effect of similar importance for which there is not yet an accurate treatment. Furthermore, our study provides a valuable means of rejecting mistaken refinements to SST, and indeed one such example is revealed. A proper treatment of finite-stretching corrections is vital to a wide range of phenomena that depend on a small excess free energy, such as autophobic dewetting and the interaction between opposing brushes. 相似文献
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28.
McGraw JD Rowe ID Matsen MW Dalnoki-Veress K 《The European physical journal. E, Soft matter》2011,34(12):131-7
It is known that terraces at the air-polymer interface of lamella-forming diblock copolymers do not make discontinuous jumps
in height. Despite the underlying discretized structure, the height profiles are smoothly varying. The width of a transition
region of a terrace edge in isolation is typically several hundreds of nanometres, resulting from a balance between surface
tension, chain stretching penalties, and the enthalpy of mixing. What is less well known in these systems is what happens
when two transition regions interact with one another. In this study, we investigate the dynamics of the interactions between
copolymer lamellar edges. We find that the data can be well described by a model that assumes a repulsion between adjacent
edges. While the model is simplistic, and does not include molecular level details, its agreement with the data suggests that
some of the the underlying assumptions provide insight into the complex interplay between defects. 相似文献
29.
F. A. Matsen 《International journal of quantum chemistry》1987,32(1):71-86
In the unitary-group formulation of quantum chemistry, the spin-projected, configuration-state spaces of quantum chemistry are realized by the irreducible representation spaces (IRS ) of the freeon unitary group U(n), where n is the number of freeon orbitals. The Pauli-allowed IRS are labeled by the partitions [λ] = [2(N/2)?s, 12S], where N and S are the particle number and the spin, respectively. The generator-state approach (GSA ) to the unitary-group formulation consists of (1) the construction of the overcomplete, nonorthonormal generator basis for each IRS ; (2) the Lie-algebraic computation of matrix elements over generator states; (3) the Moshinsky–Nagel construction of the complete, orthonormal Gel'fand basis in terms of the generator basis; and (4) the computation of matrix elements over Gel'fand states in terms of matrix elements over generator states. 相似文献
30.
Marcie B. Wiggins Mengyu Liu Catherine Matsen Chang Liu Karl S. Booksh 《Molecules (Basel, Switzerland)》2021,26(2)
During conservation of the painted ceiling decoration of Lin’xi Pavilion in the Forbidden City, two distinct paint campaigns were isolated as a unique case study into architectural paint materials during both the Ming and Qing dynasties. Paint samples and cross sections from both paint generations were analyzed with SEM-EDX, time of flight-secondary ion mass spectrometry (ToF-SIMS), XRD, FTIR, and Raman spectroscopies. Similar organic and inorganic materials characteristic of these time periods were identified. The pigments of interest found in both paint generations were botallackite and atacamite polymorphs. This suggests a shift from natural mineral sources to synthetic copper-based pigments for these larger architectural projects. 相似文献