Trennung von Fetten und Seifen

Ohne Zusammenfassung     

Ising models on the pentagon lattice

We solve inhomogeneous Ising models on the pentagon lattice using the transfer matrix formalism. As two special cases we study the ferromagnetic and the fully frustrated antiferromagnetic model on this lattice. The ferromagnet shows a phase transition at someT _c>0 with the usual Ising behaviour. In the frustrated case no transition occurs at any temperature due to frustration. Frustration also causes a nonvanishing rest entropy. We also calculate the spin-spin-correlation for large distance in both cases. In the ferromagnetic model we thus get the magnetization and the expected algebraic (exponential) decay of the correlations at (above)T _c. The correlations of the frustrated model decay exponentially for all temperatures, includingT=0, indicating that evenT=0 belongs to the disordered high temperature phase. Superimposed to the exponential decay the correlation shows an interesting oscillatory behaviour with temperature dependent wave number, i.e. an incommensurate structure.Work performed within the research program of the Sonderforschungsbereich 125, Aachen-Jülich-Köln     

On the electric current from electrodes in a magnetized semiconductor film

The problem on the electric current from electrodes in a magnetizedsemiconductor film is reduced to the skew derivative problemfor the Laplace equation outside cuts in a plane. The problemfor the Laplace equation is studied under different conditionsat infinity, which have a certain physical meaning. With thehelp of potential theory, the skew derivative problem is reducedto a Fredholm integral equation of the second kind, which isuniquely solvable. The Neumann problem for the Laplace equationin the exterior of cuts in a plane is a particular case of ourproblem.     

阻抗谱法确定扩散系数

给出了阻抗谱法确定扩散系数的理论和方法;以钒酸盐阴极材料Na_(1+x)V_3O_(?)(L.T.)为例,应用本方法计算给出了Li~+在阴极中的扩散系数为10~(?)-10~(-9)cm~2·s~(-1);最后还对误差来源进行了讨论. 关键词：     

Structure analysis of naturally occurring alkyl porphyrins by hydrogen chemical ionisation mass spectrometry

Chemical ionisation (CI) mass spectrometry with H₂ as reagent gas has been used to obtain spectra of a number of demetallated alkyl porphyrins from an oil shale and a bitumen. The spectra give more structural informa- tion than the electron impact spectra, by way of odd electron dipyrrolic fragment ions. Thus, the structural possibilities for a novel /c30 aetio porphyrin have been narrowed to two, although¹HNMR only reduced the possibilities to six. The spectra of four types of components containing a five, six, seven or methyl-substituted six membered exocyclic ring show, for example, that three out of four C₃₂ isomers can be distinguished. The technique offers promise as a tool in structural elucidation of other novel naturally occurring porphyrins.     

Rheological and photorheological effects in aqueous solutions of cetyltrimethylammonium bromide containing 9-anthrylalkanols

Viscosities, flow properties, and static low-angle light scattering of dilute (250 mmol/dm³) aqueous micellar solutions of cetyltrimethylammonium bromide were measured in the presence of various amounts of 9-anthrylmethanol (AM), 2,2,2-trifluoro-1-(9-anthryl)ethanol (TFAE), 1-(9-anthryl)ethanol (AE), 9-methylanthracene (MA), and 9-ethylanthracene (EA). At room temperature the solubilization of AM induces an increase of viscosity and a rise in aggregation numbers (as determined from low-angle light scattering). Both features are reverted upon in in situ photodimerization of AM. After lowering the temperaure, non-Newtonian flow is detected by means of a rotating viscometer. The solubilization of AE and EA, respectively, leads to analogous observations, while no viscoelastic features were obtained with solubilized MA. TFAE containing systems at room temperature show non-Newtonian flow accompanied by viscoelasticity which can be ascribed to the formation of long rod-like micelles. Raising the temperature as well as photodimerization diminish the lengths of the micelles and the non-Newtonian features.