Thermoelektrische Eigenschaften reiner Metalle in der Umgebung der Schmelztemperatur

The thermoelectric power of the face-centered cubic metals copper, silver, gold and aluminium was measured in the vicinity of the melting temperature. For all four metals mentioned a discontinuous change of the absolute Seebeck coefficient towards more positive values was found at the melting point. — Values of the thermoelectric power of liquid metals may be calculated with a model using the correlation function of the ions and their pseudopotentials as proposed byZiman. The results agree, at least qualitatively, with the measured values.     

Anode Spot Instability I. The Homogeneous Short Gap Instability

If the current in a "vacuum arc" surpasses a certain critical value a conspicuous and destructive phenomenon occurs at the anode, the ANODE CONSTRICTION INSTABILITY or ANODE SPOT FORMATION [1 - 10]. This paper will give a quantitative analysis of this phenomenon within the limits of a model which can be characterized by lateral homogenity, collision dominance and small electrode separation. Matching the various model regions results in a differential equation for the anodic spot area which exhibits an anode constriction instability of the "explosive type". A marginal instability criterion is derived and evaluated for various materials. This yields extensive information about the dependence of the constriction instability on the parameters of the experimental set up. The findings are compared with the experimental results and show satisfactory agreement within the limitations of experiments and theory.     

Einfluß der chemischen Bindung auf die Lα1,2− und Lβ1− Röntgenemissionsspektren des Arsens

The As Lα_1,2 and Lβ₁ X-ray emission spectra from metallic arsenic and from the compounds As₂O₃, Na₂HAsO₄·7H₂O, and GaAs were measured with high resolution and fluorescence excitation. The shape of the spectra and correlation between the chemical shifts of the Lα lines (0·1, ? 0·22 and ? 0·05 eV in As₂O₃, Na₂HAsO₄·7H₂O, and GaAs resp.) and atomic charges are discussed.     

Thermal decomposition of ferrocene as a method for production of single-walled carbon nanotubes without additional carbon sources

A new method to grow bulk quantities of single-walled carbon nanotubes (SWCNTs) by a catalytic chemical vapor deposition (CVD) process with the possibility of varying the pressure has been developed and is reported in this paper. Thermal decomposition of ferrocene provides both catalytic particles and carbon sources for SWCNT growth using Ar as a carrier gas. Upon an increase in the pressure, the mean diameter of the SWCNTs decreases. In fact, high abundances of SWCNT with diameters as small as 0.7 nm, which is the limit for stable caps with isolated pentagons, can be obtained. An additional advantage of this method is that as no external carbon sources are required, SWCNT synthesis can be achieved at temperatures as low as 650 degrees C.     

Separating Characters by Blocks

We investigate the problem of finding a set of prime divisorsof the order of a finite group, such that no two irreduciblecharacters are in the same p-block for all primes p in the set.Our main focus is on the simple and quasi-simple groups. Forresults on the alternating and symmetric groups and their doublecovers, some combinatorial results on the cores of partitionsare proved, which may be of independent interest. We also studythe problem for groups of Lie type. The sporadic groups (andtheir relatives) are checked using GAP.     

Probing the dimensions of semi-rigid inner functionalised U-shaped bis-porphyrin cavities

The synthesis of a series of open U-shaped bis-porphyrin cavity molecules is described, with bridged bicyclic backbones to confer rigidity, and a pendant substituted aromatic probe unit suspended on the inside of the cavity. The dimensions and flexibility of the bis-zincporphyrin cavity were probed using several different techniques. Initially the molecular ruler concept was employed, using flexible bidentate ligands as guests with a range of possible linear dimensions. Secondly, NMR methods were employed with rigid bidentate ligand guests of fixed lengths, and thirdly diffusion based NMR methods were utilised. The range of inter-porphyrin distances estimated by these methods suggests that these types of open-cavity systems have a surprising degree of flexibility.     

Determinant Representation for Some Transition Probabilities in the TASEP with Second Class Particles

We study the transition probabilities for the totally asymmetric simple exclusion process (TASEP) on the infinite integer lattice with a finite, but arbitrary number of first and second class particles. Using the Bethe ansatz we present an explicit expression of these quantities in terms of the Bethe wave function. In a next step it is proved rigorously that this expression can be written in a compact determinantal form for the case where the order of the first and second class particles does not change in time. An independent geometrical approach provides insight into these results and enables us to generalize the determinantal solution to the multi-class TASEP.     

Probabilistic clustering via Pareto solutions and significance tests

The present paper proposes a new strategy for probabilistic (often called model-based) clustering. It is well known that local maxima of mixture likelihoods can be used to partition an underlying data set. However, local maxima are rarely unique. Therefore, it remains to select the reasonable solutions, and in particular the desired one. Credible partitions are usually recognized by separation (and cohesion) of their clusters. We use here the p values provided by the classical tests of Wilks, Hotelling, and Behrens–Fisher to single out those solutions that are well separated by location. It has been shown that reasonable solutions to a clustering problem are related to Pareto points in a plot of scale balance vs. model fit of all local maxima. We briefly review this theory and propose as solutions all well-fitting Pareto points in the set of local maxima separated by location in the above sense. We also design a new iterative, parameter-free cutting plane algorithm for the multivariate Behrens–Fisher problem.