Balancing Surface Energy Terms for Stable Growth of Planar Surfaces

We investigate the driving forces that determine the growth mode of heteroepitaxial Ge layers grown from solution on Si substrates with orientations (001), (011) and (111) by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Using liquid phase epitaxy, we can study the influences of strain and surface energy terms independently on effects due to limited surface diffusion. In (001) and (011) orientated layers, {111} faceted islands form (Stranski-Krastanov growth). In contrast, (111) orientated layers grow in a two-dimensional step flow growth mode (Frank-van der Merwe growth). We model these investigations in terms of energy minimisation considering surface energy reduction by formation of faceted islands and elastic strain energy relaxation by island formation. The strain energy relaxation by island formation is calculated by the finite element method. According to our considerations, two-dimensional growth is obtained by selective increase of the free surface energy of the low indices facet planes to a value higher than that of the substrate surface. Formation of faceted islands thus would increase the total surface energy; as a consequence, island formation is suppressed. By choosing the appropriate solvent and temperature in solution growth, we can provide for thermodynamically stable two-dimensional growth

Processing of spatial-frequency altered faces in schizophrenia: Effects of illness phase and duration

Low spatial frequency (SF) processing has been shown to be impaired in people with schizophrenia, but it is not clear how this varies with clinical state or illness chronicity. We compared schizophrenia patients (SCZ, n534), first episode psychosis patients (FEP, n522), and healthy controls (CON, n535) on a gender/facial discrimination task. Images were either unaltered (broadband spatial frequency, BSF), or had high or low SF information removed (LSF and HSF conditions, respectively). The task was performed at hospital admission and discharge for patients, and at corresponding time points for controls. Groups were matched on visual acuity. At admission, compared to their BSF performance, each group was significantly worse with low SF stimuli, and most impaired with high SF stimuli. The level of impairment at each SF did not depend on group. At discharge, the SCZ group performed more poorly in the LSF condition than the other groups, and showed the greatest degree of performance decline collapsed over HSF and LSF conditions, although the latter finding was not significant when controlling for visual acuity. Performance did not change significantly over time for any group. HSF processing was strongly related to visual acuity at both time points for all groups. We conclude the following: 1) SF processing abilities in schizophrenia are relatively stable across clinical state; 2) face processing abnormalities in SCZ are not secondary to problems processing specific SFs, but are due to other known difficulties constructing visual representations from degraded information; and 3) the relationship between HSF processing and visual acuity, along with known SCZ- and medication-related acuity reductions, and the elimination of a SCZ-related impairment after controlling for visual acuity in this study, all raise the possibility that some prior findings of impaired perception in SCZ may be secondary to acuity reductions

Component-Based Design: a Summary and Scheme for Implementation

This paper summarizes the major advantages ofcomponent-based design as a paradigm for handling alldesign and construction information about a buildingat every stage of design. The paper reviews some ofthe current issues that plague the building design andconstruction industry. The component-based paradigmis reviewed as a model that reunites the fragmentedbuilding industry and as a solution for dealing withvast amounts of information that accretes during thedesign-construction process. Based on interviews witharchitects, engineers, contractors and fabricators aswell as on-site documentation of construction wefeature the design and construction of the main stairin the Rosenthal Center for Contemporary Artdesigned by Zaha Hadid as a specific case study toillustrate the viability of component-based design andto highlight the obstacles challenging itsimplementation

Les tourbières du camp militaire de Bitche : mémoire et rôle environnemental

International audienc