Efficient and Accurate Methods for the Computation of Thermodynamic and Transport Properties of Multitemperature Thermal Plasma. Part I: Thermodynamic and Heavy Particle Transport Properties

In this paper we present numerical efficient methods for the computation ofthermodynamic and transport properties of nonequilibrium thermalplasmas. Thermodynamic properties of mono- and diatomic speciesare calculated directly from partition functions. The evaluation oftransport properties is based on the kinetic theory using the classicalChapman–Enskog approach to solve the heavy particle Boltzmannequation. A multitemperature model is used to consider thermalnonequilibrium.     

PROMOT: A Modeling Tool for Chemical Processes

The novel process modeling tool PROMOT supports the object-oriented modeling of chemical processes for the simulation environment DIVA. In PROMOT, differential-algebraic process models can be built by aggregating structural and behavioral modeling entities that represent the topological structure or the dynamic and steady-state behavior, respectively, of the investigated chemical processes. Process models and their modeling entities may be defined either in an object-oriented modeling language or with a graphical user interface. This paper discusses the modeling concept, the modeling language, the knowledge representation aspects, and the implementation of PROMOT.     

Formation Entropy of Schottky Defects and Free Formation Enthalpy of Vacancy Pairs in Alkali Halide Crystals

The melting of alkali halides occurs probably at a critical mole fraction x_c = 3.2 · 10⁻⁴ of thermally created vacancies (Schottky defects). Using this value the formation entropy of Schottky defects is found to be s_S = (962.1 K mol/kJ L/T_m – 16.1) k (L, T_m heat and temperature of fusion, respectively). As to the free association enthalpy g_A = h_A – T_sA of (impurity-vacancy) complexes it is s_A = (10.8 h_A/eV – 2.56) k. Using this relation the concentration vacancy pairs is found to be smaller than that of isolated vacancies up to the melting point.     

Distribution coefficient of foreign ions in ionic crystals-A function of the ionic radius

The distribution coefficient k of foreign ions in melt-grown crystals is found to be proportional to R^−B and R^+B in the case of large and small ionic radii R, respectively. As to alkali halides and alkaline-earth fluorides the exponent B corresponds to the number of nearest neighboured or charge-compensator ion sites in the case of homovalent and heterovalent foreign ions, respectively.     

Twisting DNA: single molecule studies

Over the past 10 years a number of new techniques have emerged that allow the manipulation of single DNA molecules and other biopolymers (RNA, proteins, etc.). These experiments have permitted the measurement of the DNA stretching and twisting elasticity and have consequently revealed the essential role played by the DNA mechanical properties in its interactions with proteins. We shall first describe the different methods used to stretch and twist single DNA molecules. We will then focus on its behaviour under torsion, especially by discussing the different methods used to estimate its torsional modulus.     

Herstellung und Eigenschaften von geformtem Aluminiumoxid. II. Einfluß der mechanischen Zerkleinerung gefällten Böhmithydrogels auf die Porenstruktur und die Abriebfestigkeit des geformten Aluminumoxids

Preparation and Properties of Formed Aluminium Oxide. II. Influence of the Mechanical Comminution of Precipitated Boehmite Hydrogel on the Pore Structure and Abrasion Resistance of the Aluminium Oxide A report is given on the physical-chemical characteristics of formed aluminium oxide on the basis of boehmite which had been continuously precipitated with nitric acid from sodium aluminate solution, subsequently filtrated, dried at 110°C and ground prior to moulding. In double dependence on the grinding intensity (type of mill, grinding time) and on the precipitation conditions (pH value, temperature) the changes of the morphology and the texture of the boehmite hydrogel are investigated. According to the particles constituting the precipitated boehmite hydrogel is made in two stages. In dependence on the grinding intensity a maximum correlation is observed for the abrasion resistance.     

Stoichiometry and point defects in lithium niobate crystals

Investigations of the OH⁻ ion incorporation into LiNbO₃ crystals and the comparison of calculated and measured densities show that undoped congruent lithium niobate crystals contain Li⁺ and O^{− −} ion vavancies O and Li⁺. If really present, stacking faults are of inferior importance. The good agreement of the absorption edges of stoichiometric and of 2.7 mol% MgO containing congruent lithium niobate crystals is explained by the occupance of all oxygen sites within these crystals.     

Anomalous decay of electronically stabilized lead mesas on Ni(111)

With their low surface free energy, lead films tend to wet surfaces. However, quantum size effects (QSE) often lead to islands with distinct preferred heights. We study thin lead films on Ni(111) using low energy electron microscopy and selected area low energy electron diffraction. Indeed, the grown lead mesas show distinct evidence for QSE's. At about 526 K metastable mesas reshape into hemispheres within milliseconds, driven by a huge reduction in interfacial free energy. The underlying diffusion rate is many orders of magnitude faster than expected for lead on bulk lead.     

Electric conductivity and lattice disorder of PbMoO4 crystals

From differential thermal analysis (DTA), thermal etching, perfectly reversable redox treatments and electric conductivity it is concluded that the Pb/Mo ratio of the PbMoO₄ crystals is always 1 and that phase transitions do not occur. Pb³⁺ ions detectable by an absorption band at 435 nm cause a p-conductivity due to the reaction Pb³⁺ ⇌ Pb⁺⁺ + e⁺. At elevated temperatures the p-conductivity increases with increasing oxygen partial pressure of the surrounding atmosphere. The influence of foreign ions on the concentration of ionic and electronic defects in PbMoO₄, CaMoO₄, PbO, and PbTiO₃ can be explained by an anti-Frenkel disorder of the oxygen ion sublattice. For PbMoO₄ crystals the mobility O⁻ ion vacancies and the free formation enthalpy of anti-Frenkel defects are found to be v_v = \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop - \limits_T^{9160} $\end{document} exp (−1.15 eV/kT) cm² K/Vs and g_AF = 3.6kT −2.2 eV, respectively.