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Using a recently established BaTiO3 potential model specifically designed for the calculation of defect energetics, atomistic simulations have been carried out on the intrinsic defect chemistry and Rare Earth (RE3+) doping of hexagonal barium titanate (h-BaTiO3). Five charge compensation schemes have been considered as well as potential cluster binding energies. The results show that ion size arguments are obeyed. In the dilute concentration limit, large RE3+ cations dope at the Ba-site via a titanium vacancy mechanism and mid sized RE3+ cations dope at the Ba and Ti sites simultaneously via a self compensation mechanism. In contrast, small RE3+ cations dope exclusively on the Ti-site via an oxygen vacancy compensation scheme. Comparisons between the hexagonal and cubic phases of BaTiO3 have also been drawn. It is suggested that Ba-site doping is less favorable and that Ti-site doping is considerably more favorable in h-BaTiO3 and that different defect configurations have a significant effect on the binding energies between such defects, leading to some mechanisms becoming more or less energetically favorable as a result. [ABSTRACT FROM AUTHOR]

Metadynamics is employed to sample the configurations available to calcium carbonate nanoparticles in water, and to map an approximate free energy as a function of crystalline order. These data are used to investigate the validity of bulk and ideal surface energies in predicting structure at the nanoscale. Results indicate that such predictions can determine the structure and morphology of particles as small as 3-4 nm in diameter. Comparisons are made to earlier results on 2 nm particles under constant volume conditions which support nanoconfinement as a mechanism for enhancing the stability of amorphous calcium carbonate. Our results indicate that crystalline calcitelike structure is thermodynamically preferred for nanoparticles as small as 2 nm in the absence of nanoconfinement. [ABSTRACT FROM AUTHOR]

A method of simulating complex deformational changes of magnetoelastic systems has been developed. This involves incorporation of the complete Cauchy stress matrix tensor into a finite element micromagnetic code. Finite element modeling was used to precompute the stress on each mesh-element in the studied model. This stress-map is then imported into a finite element micromagnetic code to solve the resultant changes in magnetization. The veracity of this method is demonstrated by comparing simulations of the Villari effect and a hybrid piezoelectric-piezomagnetic system to experimental observations. [ABSTRACT FROM AUTHOR]

We show that recent developments in the application of metadynamics methods to direct simulations of crystallization make it possible to predict the orientation of crystals grown on self-assembled monolayers. In contrast to previous studies, the method allows for dynamic treatment of the organic component and the inclusion of explicit surface water without the need for computationally intensive interfacial energy calculations or prior knowledge of the interfacial structure. The method is applied to calcite crystallization on carboxylate terminated alkanethiols arrayed on Au (111). We demonstrate that a dynamic treatment of the monolayer is sufficient to reproduce the experimental results without the need to impose epitaxial constraints on the system. We also observe an odd-even effect in the variation of selectivity with organic chain length, reproducing experimentally observed orientations in both cases. Analysis of the ordering process in our simulations suggests a cycle of mutual control in which both the organic and mineral components induce complementary local order across the interface, leading to the formation of a critical crystalline region. The influence of pH, together with some factors that might affect the range of applicability of our method, is discussed. [ABSTRACT FROM AUTHOR]

Body size estimation was studied in 22 patients with bulimia and 20 normal controls. Two methods of body size estimation were used, a distorting television image method (DTIM) and the image marking method (IMM). The subjects estimated body size of a dummy as well as their own body on the DTIM. When estimating body size on the DTIM the bulimics overestimated and the controls underestimated, there being a significant difference between the two groups. There was no difference between the groups when estimating the size of the dummy. On the IMM a significant difference was found between the bulimic and control groups, the bulimics overestimating body size and the controls being more accurate. Marked directional effects were found with the DTIM. The two methods of body size estimation are compared. [ABSTRACT FROM AUTHOR]

This report describes the cytologic features of molluscum contagiosum presenting clinically as a left thigh abscess in a 29-yr-old male with AIDS. The fine-needle aspiration findings are correlated with the histologic and ultrastructural findings. Molluscum contagiosum's clinical presentation, natural course, and induction of host immune responses in immunocompetent and immunosuppressed individuals as identified by light microscopy, immunocytochemically and ultrastructurally are reviewed. Molluscum contagiosum presenting clinically and cytologically as an abscess is unusual. In this report, we emphasize the inclusion of molluscum contagiosum in a differential diagnosis of an abscess, particularly in immunosuppressed patients, and discuss the cytologic differential diagnoses.