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Purpose: To investigate the influence of implant geometry on primary stability and on peri-implant bone loss in an in vitro model using the Periotest and Osstell devices., Materials and Methods: Screw-type implants of various diameters and lengths were inserted into bovine bone blocks of different densities, and the primary insertion stability was recorded. To study the influence of implant geometry on implant stability with different levels of peri-implant bone loss, implants were inserted into acrylic resin blocks to mimic osseointegration, and different amounts of the peri-implant acrylic resin were removed. Measurements with both devices at each millimeter step yielded the threshold for the least detectable attachment loss., Results: The predominant factors influencing implant stability were bone quality and attachment loss. Implant type and length exerted some influence on implant stability values, while variations in implant diameter produced only minor alterations in the measurements. In simulations of peri-implant attachment loss, implant stability decreased more dramatically for the shorter and narrower implants. The inclusion of more variables in the analyses resulted in less focused measurements., Conclusions: The results of this study clearly show that the outcome of implant stability assessment depends on environmental factors such as bone quality and implant geometry. While the authors do not recommend the use of the Periotest or Osstell devices for a comparison of the stability of two individual implants, both should be useful to monitor the state of an individual implant over time.

Transmission electron microscopy (TEM), atomic force microscopy (AFM), and EDX methods were used to study morphology and chemical composition of SiGe/Si(001) islands grown at 700 degrees C and covered at 550 degrees C and 700 degrees C by Si layers of different thickness. The samples were grown in ultra high vacuum chemical vapor deposition process (UHVCVD) controlled with in situ reflection of high-energy electron diffraction (RHEED). The islands transformed from initial pyramid and dome shapes to lens shape for 1.4 nm and 3.7 nm cap layer thickness at 550 degrees C and 700 degrees C, respectively. An increase of lateral to vertical ratio was observed during the transformation. For the higher depositing temperature the ratio was bigger and was increasing continuously with cap layer thickness. Also, with increasing Si cap layer thickness, the Ge concentration was decreasing, which was more observable for higher capping temperature.

Strain mapping is defined as a numerical image-processing technique that measures the local shifts of image details around a crystal defect with respect to the ideal, defect-free, positions in the bulk. Algorithms to map elastic strains from high-resolution transmission electron microscopy (HRTEM) images may be classified into two categories: those based on the detection of peaks of intensity in real space and the Geometric Phase approach, calculated in Fourier space. In this paper, we discuss both categories and propose an alternative real space algorithm (Peak Pairs) based on the detection of pairs of intensity maxima in an affine transformed space dependent on the reference area. In spite of the fact that it is a real space approach, the Peak Pairs algorithm exhibits good behaviour at heavily distorted defect cores, e.g. interfaces and dislocations. Quantitative results are reported from experiments to determine local strain in different types of semiconductor heterostructures.

Objective: We compared the performance of damping capacity assessment (Periotest device) to resonance frequency analysis (Osstell device) in the assessment of peri-implant bone loss in an in vitro experiment., Material and Methods: Screw-type oral implants were polymerized into acrylic blocks. Peri-implant bone loss was simulated by successively removing defined portions of material surrounding the implants in millimeter increments. Measurement values of both devices were compared by assessing the associated measurement errors, by calculating correlation analyses and drawing scatterplots, and by means of regression analysis referring to increasing bone loss., Results: Both devices produced comparable results suggesting agreement of the measured implant stability values to the actual loss of peri-implant resin. There was a noticeable correlation of the Periotest and Osstell implant stability values., Conclusion: The results of this experiment suggest agreement in predicting the actual implant stability with both the instruments with the Osstell instrument being the more precise device.

Previous studies of the structure of core nanocrystals of ferritin (Ft) in the brains of patients with Alzheimer's disease (AD) have shown differences in the mineral compound in comparison with physiological Ft. Both Ft cores have a polyphasic composition but whereas the major phase in physiological Ft is hexagonal ferric iron oxide (ferrihydrite), the major phases in brain AD Ft are two cubic mixed ferric-ferrous iron oxides (magnetite and wüstite). One of these (wüstite) is similar to what is detected in hemosiderin (Hm) cores in primary hemochromatosis (Quintana, C., Cowley, J.M, Marhic, C., 2004. Electron nanodiffraction and high resolution electron microscopy studies of the structure and composition of physiological and pathological ferritin. J. Struct. Biol. 147, 166-178). We have studied, herein, the distribution of iron, Ft, and Hm in sections of AD hippocampus using analytical microscopy. Iron present in Ft cores was directly mapped in a nanoSIMS microscope and the iron distribution has been correlated with the constituent elements N, P, and S. Ft and Hm cores were visualized at an ultrastructural level in an analytical transmission electron microscope. In senile plaques, Ft was observed in the coronal region associated with a non-beta-amyloid component and in the periphery of plaques, together with Hm, in sulfur-rich dense bodies of dystrophic neurites. Hm was also found in lysosomes and siderosomes of glial cells. Ft was observed in the cytoplasm and nucleus of oligodendrocytes. Ft was particularly abundant in myelinated axons in association with oligodendrocyte processes. These findings provide new arguments to support the hypothesis of a dysfunction of Ft (with eventual degradation to Hm) in AD resulting in an increase of toxic brain ferrous ions that may contribute to the production of free radicals that induce both cellular oxidative stress and aged-related myelin breakdown associated with cognitive decline and AD (Bartzokis, G., 2004. Age-related myelin breakdown: a developmental model of cognitive decline and Alzheimer's disease. Neurobiol. Aging 25, 5-18).

The continuous displacement field within elastically relaxed GaInAs islands was calculated from digitized HREM images of [110] cross sections of In0.35Ga0.65As layers grown on GaAs by molecular beam epitaxy. Experimental maps of the deformations parallel to the interface (epsilonx) and along the growth direction (epsilonz) were drawn and compared with the ones calculated via the finite element method. It was found that epsilonx exp was systematically higher than epsilonx calc and the significant maximum observed for epsilonz exp within the island could not be found for epsilonz calc. These discrepancies were attributed to a variation of the chemical composition in the island. The maps showing the indium concentration gradient drawn from HREM and FE calculations were compared to quantitative profiles for indium concentration obtained by nanometric X-ray microanalysis in TEM. The measured gradient within the island backs our assumption.