The Types of Click Beetles Described by Otto Schwarz from Mexico, Guatemala and Panama (Coleoptera: Elateridae).

The type specimens of Elateridae described by Otto Schwarz from Mesoamerica are redescribed, reassessed and lectotypes designated. Acanthathous championi (Schwarz), Smiliceroides quadrilineatus (Schwarz), Anoplischiopsis divisus Schwarz, Anoplischius dorsalis Schwarz, Atractosomus nigerrimus Schwarz, and Anchastomorphus minutus Schwarz are retained in their current status. Monocrepidius restinctus Schwarz is reduced to synonymy under Monocrepidius rugicollis Champion. Aeolus mediofasciatus Schwarz is transferred to Monocrepidius Eschscholtz. Tomicephalus bilineatus Schwarz is transferred to Anchastus LeConte, renamed Anchastus lapsus Fuller, and reduced to synonymy under Anchastus seminiger Champion. Crepidius blepharipes Schwarz is restricted to the lectotype and retained in its current status; the other syntypes are unidentified species of Dipropus Germar. Anchastus championi Schwarz is reduced to synonymy under Anchastus tenuistriatus Champion; one syntype is an unidentified species of Dipropus Germar. New country records are documented for A. dorsalis, A. nigerrimus and A. minutus (Guatemala), and A. tenuistriatus (United States).

Phase Transformations in the High-Tc Superconducting Compounds, Ba2RCu3O7-δ (R = Nd, Sm, Gd, Y, Ho, and Er).

The phase transformation between the orthorhombic and tetragonal structures of six high-T c superconductors, Ba2RCu3O7- δ , where R = Nd, Sm, Gd, Y, Ho, and Er, and δ = 0 to 1, has been investigated using techniques of x-ray diffraction, differential thermal analysis/thermogravimetric analysis (DTA/TGA) and electron diffraction. The transformation from the oxygen-rich orthorhombic phase to the oxygen-deficient tetragonal phase involves two orthorhombic phases. A superlattice cell caused by oxygen ordering, with a' = 2a, was observed for materials with smaller ionic radius (Y, Ho, and Er). For the larger lanthanide samples (Nd, Sm, and Gd), the a' = 2a type superlattice cell was not observed. The structural phase transition temperatures, oxygen stoichiometry and characteristics of the T c plateaus appear to correlate with the ionic radius, which varies based on the number of f electrons. Lanthanide elements with a smaller ionic radius stabilize the orthorhombic phase to higher temperatures and lower oxygen content. Also, the superconducting temperature is less sensitive to the oxygen content for materials with smaller ionic radius. The trend of dependence of the phase transformation temperature on ionic radius across the lanthanide series can be explained using a quasi-chemical approximation (QCA) whereby the strain effect plays an important role on the order-disorder transition due to the effect of oxygen content on the CuO chain sites.

An Isoparametric Finite Element Model for Large-Strain Elastostatics.

This paper describes a simple finite element model for large-strain elastostatics. The realization of the model in a small-scale computer-code is described. The purpose of the model is to produce test problems for research on the application of penalty techniques in nonlinear elasticity. For this reason the code must balance the requirements of reasonable flexibility with those of computational economy. The current code employs multilinear isoparametric elements. The model is capable of generalization to a variety of element types. The solution method employed is that of incremental loading combined with the Newton-Raphson method. Symmetric, banded systems of equations are produced which are solved in-core. Two- and three-dimensional symmetric bodies which are isoparametric images of a reference "brick" may be modeled. An example comparing two- and three-dimensional models of a "dogbone"-shaped A.S.T.M. rubber tensile-test specimen is presented. The results shed some light on the nature of stress-concentrations which occur in specimens of this geometry.

Microstructural Characterization of Ceramic Materials by Small Angle Neutron Scattering Techniques.

The use of small angle neutron scattering (SANS) techniques for ceramic materials is discussed. Two areas are emphasized: 1) diffraction for microstructural phenomena of less than 100 nm, and 2) beam broadening for microstructural phenomena greater than 90 nm.

Characterization of Creep Damage in Metals Using Small Angle Neutron Scattering.

Creep damage in polycrystalline metallic materials can be attributed to cavitation and cracking along the grain interfaces. Theories of creep cavitation that have been developed in recent years are reviewed. Further evaluation and/or refinement of these theories has been retarded by a lack of an experimental counterpart. Small angle neutron scattering studies (SANS) provide one experimental tool which is complementary to others. SANS done at NBS and elsewhere have shown that this technique is suitable for studying nucleation and early stage of growth of creep cavities. This would provide the impetus to further progress in this area.