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71.
We present the first real-space analysis on a single-particle level of the dipolar chains and branched clusters self-assembling in magnetic fluids in zero field. Spatial correlations and chain-length distributions directly obtained from tracked particle positions in vitrified films of synthetic magnetic (Fe3O4) dispersions provide a quantitative test for simulations and theory of dipolar fluids. A pertinent example is the cluster-size distribution that can be analyzed with a one-dimensional aggregation model to yield a dipolar attraction energy that agrees well with the dipole moment found from independent magnetization measurements. 相似文献
72.
Z-Continuous Posets and Their Topological Manifestation 总被引:3,自引:0,他引:3
Marcel Erné 《Applied Categorical Structures》1999,7(1-2):31-70
A subset selection Z assigns to each partially ordered set P a certain collection Z P of subsets. The theory of topological and of algebraic (i.e. finitary) closure spaces extends to the general Z-level, by replacing finite or directed sets, respectively, with arbitrary Z-sets. This leads to a theory of Z-union completeness, Z-arity, Z-soberness etc. Order-theoretical notions such as complete distributivity and continuity of lattices or posets extend to the general Z-setting as well. For example, we characterize Z-distributive posets and Z-continuous posets by certain homomorphism properties and adjunctions. It turns out that for arbitrary subset selections Z, a poset P is strongly Z-continuous iff its Z-join ideal completion Z P is Z-ary and completely distributive. Using that characterization, we show that the category of strongly Z-continuous posets (with interpolation) is concretely isomorphic to the category of Z-ary Z-complete core spaces. For suitable subset selections Y and Z, these are precisely the Y-sober core spaces. 相似文献
73.
Ern? Müller Rita Skoda-Földes Eszter Takács George Kokotos László Kollár 《Tetrahedron》2005,61(4):797-802
Amino acid methyl esters were used as amine nucleophiles in palladium catalysed aminocarbonylation of iodobenzene and iodoalkenes (1-iodo-cyclohexene and 17-iodo-androst-16-ene). 2-Oxo-carboxamide type derivatives can be isolated as a result of double CO insertion by using iodobenzene as a substrate at elevated carbon monoxide pressure. On the contrary, carboxamides of expected structure were obtained exclusively in excellent yields in the whole pressure range by using iodoalkenes. The aminocarbonylation of 17-iodo-androst-16-ene in [bmim][PF6] or [bmim][BF4] (where bmim=1-butyl-3-methyl-imidazolium cation) ionic liquids was also carried out and the ionic liquid-catalyst mixtures have been reused several times with only a small loss of activity. 相似文献
74.
Csaba Várhelyi Magda Somay Antal Koch Ernő Grünwald 《Monatshefte für Chemie / Chemical Monthly》1978,109(6):1311-1320
Some new ligand exchange reactions of [Co(diph·H)2Cl(H2O)] and [Co(diph·H)2(SO3)(H2O)]– complexes with N3
–, S2O3
2– and with aromatic and heterocyclic amines were carried out. A series of derivatives of the types [Co(diph·H)2(SO3)X]
n–
(X=N3
–, S2O3
2– oramine) and [Co(diph·H)2(S2O3)2]3– were described and characterized. Some structural problems are resolved and discussed on the basis of UV and IR spectral data. 相似文献
75.
A. Ern J.‐L. Guermond L. Quartapelle 《Mathematical Methods in the Applied Sciences》1999,22(6):531-546
This work studies the three‐dimensional Stokes problem expressed in terms of vorticity and velocity variables. We make general assumptions on the regularity and the topological structure of the flow domain: the boundary is Lipschitz and possibly non‐connected and the flow domain may be multiply connected. Upon introducing a new variational space for the vorticity, five weak formulations of the Stokes problem are obtained. All the formulations are shown to lead to well‐posed problems and to be equivalent to the primitive variable formulation. The various formulations are discussed by interpreting the test functions for the vorticity (resp. velocity) equation as vector potentials for the velocity (resp. vorticity). Of the five sets of boundary conditions derived in the paper, three are already known, but only for domains with a trivial topological structure, while the remaining two are new. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
76.
Using Mössbauer spectroscopy and X-ray diffraction as analytical tools, an "anomalous" α-γ phase transformation observed previously in steels was studied. It was shown in this work that this phase transformation is a feature of the Fe-12Cr-4Ni ternary alloy, and the ageing-time dependence of the γ-phase formation follows Avrami kinetics representing a diffusion controlled process. The activation energy of the process was also determined. The equilibrium composition of the samples could be interpreted in terms of calculated phase diagrams of the Fe-Cr-Ni system. On the basis of the hyperfine-field distributions derived from the spectra it was shown that two processes take place in the ferromagnetic α-phase during the ageing at different rates in which the slower one is in accordance with a decrease of the chromium concentration in the α-phase owing to the γ-phase formation. 相似文献
77.
JPC – Journal of Planar Chromatography – Modern TLC - The shiitake mushroom is well known for its health-beneficial effects. In this study we examined its antimicrobial activity by use... 相似文献
78.
Epitaxial silicon carbide thin films grown on a silicon substrate were examined by short wavelength ( 0.71 A from a molybdenum anode) x-ray diffraction to study their atomic distortion and internal layer roughness. Up to 5 order Bragg peaks along (100) were measured and crystallographic structure factors were obtained. Electron density distributions along the surface normal were reconstructed via Fourier transform. In comparing to the ideal situation, it was found that, due to the lattice mismatch, the silicon atoms are no longer fixed on the same atomic plane, thus the corresponding electron distribution maxima were broadened. Also, the maxima for carbon atoms are flattened, indicating the randomized locations. 相似文献
79.
80.
M.G. Albrow A. Bagchus D.P. Barber A. Bogaerts B. Bošnjaković J.R. Brooks A.B. Clegg F.C. Erné C.N.P. Gee D.H. Locke F.K. Loebinger P.G. Murphy A. Rudge J.C. Sens 《Nuclear Physics B》1974,73(1):40-56
Cross sections for the production of positive pions, kaons and protons in proton-proton collisions at the CERN ISR have been measured. These measurements extend to transverse momenta pT of 2.5 GeV and span the range in between 0.3 and 0.8 For transverse momenta larger than ~ 1 GeV the cross sections show an increase relative to low-energy data, but are consistent with scaling within the energy range measured here, . 相似文献