Thermogravimetrie von Styrol—Chloranilcopolymeren

The thermal decomposition of styrene-chloranil copolymers is investigated by dynamic thermogravimetry. The decomposition occurs at relatively low temperatures and is correlated to the chemical structure of the polymers.

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Synthesis of single- and multi-wall carbon nanotubes over supported catalysts

The quantities of deposited carbon were measured and the quality of the nanotubes was characterized by means of transmission electron microscopy and scanning tunneling microscopy. The inner and outer diameters of the nanotubes were also measured and the diameter distribution histograms were established. The multi-wall straight and coiled nanotubes were found to be quite regular with an average inner (outer) diameter of 4–7 nm (15–25 nm) and with lengths up to 50 μm. The walls contain concentric cylindrical graphene sheets separated by the graphitic interlayer distance. The single-wall nanotubes were found as bundles of hundreds of aligned straight 1-nm-diameter nanotubes with lengths up to 1-μm. The influence of various parameters such as the method of catalyst preparation, the nature and the pore size of the support, the nature of the metal, the quantity of catalyst active particles, and the reaction conditions on the nanotubes formation were studied. The numbers and dimensions of the catalyst active particles dispersed on the support were found to be of importance in regulating the shape of the produced nanotubes. Following these results, a model of growth mechanism was suggested for the nanotubes obtained by this method. Received: 5 January 1998     

Preparation dependent superconductivity in TlCaBa2Cu3O7.5±d above 100 K

Different heat treatment procedures were applied during sample preparation, which resulted in different superconducting properties in samples of the same nominal composition, TlCaBa₂Cu₃O_7.5±d . This manifests itself in different critical temperatures: 104 K, 107 K and 93 K. The highestT _c belongs to the best-crystallized samples in which the tetragonal Tl₂Ca₁Ba₂Cu₂O_8±d phase is responsible for the superconductivity. The effect of heat treatments is reflected in the structural and magnetic properties as well.     

Thermodynamische Wechselwirkung des Poly(2-hydroxyäthylmethacrylats) mit 2-Methyl-2-propanol

Ohne Zusammenfassung     

Proposal to improve the behaviour of self-energy contributions to the S-matrix

A simple modification of the definition of the S-matrix is proposed. It is expected that the divergences related to nonzero self-energies are considerably milder with the modified definition than with the usual one. This conjecture is verified in a few examples using perturbation theory. The proposed formula is written in terms of the total Hamiltonian operator and a free Hamiltonian operator and is therefore applicable in any case when these Hamiltonian operators are known.     

On approximately monotone and approximately Hölder functions

Periodica Mathematica Hungarica - A real valued function f defined on a real open interval I is called $$\Phi $$ -monotone if, for all $$x,y\in I$$ with $$x\le y$$ it satisfies $$\begin{aligned}...     

Infeasible interior-point method for symmetric optimization using a positive-asymptotic barrier

We propose a new primal-dual infeasible interior-point method for symmetric optimization by using Euclidean Jordan algebras. Different kinds of interior-point methods can be obtained by using search directions based on kernel functions. Some search directions can be also determined by applying an algebraic equivalent transformation on the centering equation of the central path. Using this method we introduce a new search direction, which can not be derived from a usual kernel function. For this reason, we use the new notion of positive-asymptotic kernel function which induces the class of corresponding barriers. In general, the main iterations of the infeasible interior-point methods are composed of one feasibility and several centering steps. We prove that in our algorithm it is enough to take only one centering step in a main iteration in order to obtain a well-defined algorithm. Moreover, we conclude that the algorithm finds solution in polynomial time and has the same complexity as the currently best known infeasible interior-point methods. Finally, we give some numerical results.     

Satisfactory graph partition,variants, and generalizations

The Satisfactory Partition problem asks for deciding if a given graph has a partition of its vertex set into two nonempty parts such that each vertex has at least as many neighbors in its part as in the other part. This problem was introduced by Gerber and Kobler [M. Gerber, D. Kobler, Algorithmic approach to the satisfactory graph partitioning problem, European Journal of Operational Research 125 (2000) 283–291] and studied further by other authors. In this paper we first review some applications and related problems. Then, we survey structural, complexity, and approximation results obtained for Satisfactory Partition and for some of its variants and generalizations. A list of open questions concludes this survey.     

Co-Jacobian for Lipschitzian Maps

The notion of co-Jacobian is introduced for locally Lipschitz functions acting between arbitrary normed spaces. The main results of this paper provide a characterization, calculus rules, a mean value theorem, as well as the computation of the co-Jacobian of piecewise smooth functions. Comparisons with known differentiability notions and Mordukhovich’s co-derivatives are derived.