Phase transitions of the first kind as radiation processes

Crystallization and vapor condensation are considered as the processes of sequential penetration of single atoms/molecules into condensate. In the course of these transitions the transitive radiation must be generated, which would carry away the liberated latent heat by photons of characteristic frequencies. The transient radiation is examined by the general Ginzburg-Frank theory. The emission of defined frequencies determined by the values of liberated latent heat is confirmed by analyses of several experiments of authors and other researchers.     

Exchange repulsion between effective fragment potentials and ab initio molecules

The exchange repulsion energy and the Fock operator for systems that contain both effective fragment potentials and ab initio molecules have been derived, implemented, and tested on six mixed dimers of common solvent molecules. The implementation requires a balance between accuracy and computational efficiency. The gradient of the exchange repulsion has also been derived. Computational timings and the current challenges facing the implementation of the gradient are discussed.     

Use of high-temperature differential scanning calorimetry to investigate the β–α transition in calcium pyrophosphate

High-temperature differential scanning calorimetry was used to investigate the thermodynamic parameters of the γ–β and β–α transitions in calcium pyrophosphate (Ca₂P₂O₇). The measured enthalpy of transition compared well with previous results when higher heating rates (≥20 K min^?1) were used. Recommendations for optimal use of HTDSC in high-temperature phase transition measurements are presented.     

trans‐Decahydronaphthalene (decalin) from powder diffraction data

The title compound, C₁₀H₁₈, a decalin stereoisomer, crystallizes with Z′ = 0.5 in the space group P2₁/n. The trans‐decalin molecule is located on an inversion centre with both rings in a chair conformation, making for a quasi‐flat overall shape. Despite the absence of hydrogen bonds, it crystallizes easily. In this work the unknown crystal structure of trans‐decalin has been solved and refined using X‐ray powder diffraction data.     

On the role of the microporous layer in PEMFC operation

The condition of liquid water breakthrough at the cathode of polymer electrolyte fuel cells (PEMFC) is studied experimentally and data on corresponding water saturation and capillary pressure are provided for gas diffusion layers (GDL) with and without a microporous layer (MPL). The data demonstrate that the GDL saturation at water breakthrough is drastically reduced from ca. 25% to ca. 5% in the presence of MPL. This observation is consistent with considerations of invasion percolation in finite-size lattices and suggests an explanation for the role of MPL in improving PEMFC performance at high current densities.     

Asymptotic Behavior of One-Parameter Semigroups and Rigidity of Holomorphic Generators

We study the asymptotic behavior of one-parameter continuous semigroups of holomorphic mappings. We present angular characteristics of their trajectories at their Denjoy–Wolff points, as well as at their regular repelling points (whenever they exist). This enables us to establish new rigidity properties of holomorphic generators via the asymptotic behavior of the semigroups they generate. Received: May 11, 2007. Accepted: July 22, 2007.