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31.
Lara Sulcek Ramona Langner Ulrike Werner-Zwanziger Josef W. Zwanziger Charlotte Martineau-Corcos Michael Fechtelkord 《Magnetic resonance in chemistry : MRC》2020,58(11):1099-1108
In the present work, our aim is to decipher the cationic ordering in the octahedral and tetrahedral sheets of two Al-rich synthetic materials, namely, phlogopites of nominal composition K(Mg3-xAlx)[Al1+xSi3-xO10](OH)yF2-y and lepidolites in the system trilithionite–polylithionite with composition K (LixAl3-x)[Al4-2xSi2xO10](OH)yF2-y, by directly probing the aluminium distribution through 27Al and 17O magic-angle spinning, multiple-quantum magic-angle spinning, and 27Al-27Al double-quantum single-quantum nuclear magnetic resonance (NMR) experiments. Notably, 27Al-27Al double-quantum single-quantum magic-angle spinning NMR spectra, recorded at 9.34 and/or 20.00 T, show the spatial proximity or avoidance of the Al species inside or between the sheets. In both studied minerals, the ensemble of NMR data suggests a preference for [4]Al in the tetrahedral sheet to occupy position close to the [6]Al of the octahedral sheets. 相似文献
32.
H. Zwanziger A. Steinführer G. Werner und R. Hofmann 《Fresenius' Journal of Analytical Chemistry》1988,330(6):478-483
Summary Multicomponent analysis often suffers from matrix effects. In the present paper several methods are employed to cope with those effects and to keep experimental expense as low as possible and hence to reduce analysis time. Based on the determination of Na, K, and Ca by flame atomic emission spectroscopy experimental design in combination with multivariate calibration (matrix methods) has been tested for suitability in multicomponent analysis. Good results are achieved by statistically designed experiments. The experimental domain should be kept small to allow for linear models. Comparable results are obtained using the P method. As expected the K approach (Beer model) yields the worst results. 相似文献
33.
B. Daus I. L. Marr H. W. Zwanziger 《Fresenius' Journal of Analytical Chemistry》1995,351(2-3):320-324
Samples of marine sediments collected in the vicinity of and remote from an oil production platform have been analysed for several metals (Cr, Cu, Fe, Mn, Ni, and Pb) and for total hydrocarbons. The same samples have been examined by diffuse reflectance IR spectroscopy (DRIFT) after drying, and an attempt has been made to classify the samples according to the patterns of the metals and the reflectance spectra, and to correlate this classification with that based on the sampling site. It is suggested that DRIFT is a faster technique than the conventional solvent-extraction IR method for total hydrocarbons and — while less sensitive — is adequate for screening such samples for significant levels of hydrocarbon pollution. Classification of the samples according to the metals present also distinguishes between the two groups of samples. 相似文献
34.
It is shown how a contribution to the action from a surface at spatial infinity determines the infrared structure of quantum electrodynamics. 相似文献
35.
We prove the equivalence of stochastic quantization to the Faddeev-Popov ansatz for covariant and axial gauges. A principal ingredient of the proof is a theorem which asserts that, for a certain large class of stochastic processes, the time-dependent distribution relaxes to an equilibrium distribution. 相似文献
36.
Joo CG Bronstein LM Karlinsey RL Zwanziger JW 《Solid state nuclear magnetic resonance》2002,22(2-3):235-246
Solid-state NMR studies of composite polymer electrolytes are reported. The materials consist of polyethylene oxide and an organic inorganic composite, together with a lithium salt, and are candidates for electrolytes in solid-state lithium ion batteries. Silicon and aluminum MAS and multiple quantum MAS are used to characterize the network character of the organic-inorganic composite, and spin diffusion measurements are used to determine the nanostructure of the polymer/composite blending. Multiple quantum spin counting is used to measure the ion aggregation. The NMR results are supported by Raman spectra, calorimetry, and impedance spectroscopy. From these experiments it is concluded that the composite suppresses polymer crystallization without suppressing its local mobility, and also suppresses the tendency for the ions to aggregate. This polymer composite thus appears very promising for application in lithium ion batteries. 相似文献
37.
Zwanziger D 《Physical review letters》2003,90(10):102001
We compare the physical potential V(D)(R) of an external quark-antiquark pair in the representation D of SU(N), to the color-Coulomb potential V(coul)(R) which is the instantaneous part of the 44-component: of the gluon propagator in Coulomb-gauge D44(x-->,t)=V(coul)(|x-->|)delta(t)+(noninstantaneous). We show that if V(D)(R) is confining, lim(V(D)(R)=+ infinity, as is believed to hold in the absence of dynamical quarks, then the inequality V(D)(R)0 is the Casimir in the representation D. This implies that -V(coul)(R) is also confining. 相似文献
38.
A new Monte Carlo method for euclidean lattice field theory is introduced by writing the Boltzmann distribution e?s as a solution of a diffusion type equation and constructing the associated random walk process. It is practically tested for a quantum mechanical model and a non-compact version of lattice QCD. It is explained where the main interest in this algorithm lies: the diffusion process coming from an action that can be generalized to include non-conservative forces. This possibility is exploited in our QCD version to implement gauge fixing without Faddeev-Popov ghosts. 相似文献
39.
Karpukhina NG Werner-Zwanziger U Zwanziger JW Kiprianov AA 《The journal of physical chemistry. B》2007,111(35):10413-10420
For two series of fluoride-containing aluminosilicate glasses of high peralkaline type, we apply 27Al, 19F, 29Si, and 23Na NMR spectroscopy to understand the structural changes introduced by the addition of alkali fluorides. Adding fluoride in concentrations above the solubility limit causes crystallization of different phases in sodium and potassium glasses despite identical composition. However, the NMR spectra reveal that the structural evolution of the precrystallized states is similar in both series. In particular, fluorine coordinates exclusively to alkaline cations and aluminum. No indication of direct bonding with silicon was found from 19F --> 29Si cross-polarization experiments. In contrast to other glass systems, double resonance experiments in these peralkaline systems show that halide addition produces at most a minor fraction of tetrahedral aluminum containing fluorine in its coordination sphere. Instead, the fluorine addition prior to crystallization converts up to about 20% of the initial tetrahedral aluminum (1 mol % in absolute units) to 5- and 6-fold coordinated aluminum. A minor portion of five-coordinated aluminum groups is considered as the intermediate to the growing fraction of octahedral aluminum in the silicate matrix. The initialization of the crystallization process is correlated with the saturation of the silicate matrix by octahedral aluminum clusters segregating out under further doping by fluoride. It is suggested that the formation of the nonframework Al-F bonds is responsible for structural relaxation, reflected by the reduction of the glass transition temperature. 相似文献
40.
Hussein Al‐Mughaid Katherine N. Robertson Ulrike Werner‐Zwanziger Michael D. Lumsden T. Stanley Cameron T. Bruce Grindley 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(2):o60-o63
The 2‐propynyl group in the title compound, C17H22O10, adopts an exoanomeric conformation, with the acetylenic group gauche with respect to position C1. Comparison of 13C NMR chemical shifts from solution and the solid state suggest that the acetylenic group also adopts a conformation anti to C1 in solution. The pyranose ring adopts a 4C1 conformation. Of the three secondary O‐acetyl groups, that on position O4, flanked by two equatorial groups, adopts a syn conformation, in agreement with recent generalizations [González‐Outeiriño, Nasser & Anderson (2005). J. Org. Chem. 70 , 2486–2493]. The acetyl group on position O3 adopts a gauche conformation, also in agreement with the recent generalizations, but that on position O2 adopts a syn conformation, not in agreement with the recent generalizations. 相似文献