Biomedical subjects

R Kilaas

Publications and source records attributed to R Kilaas.

5 recordsLinked to original sources

PubMed2005

EDM 1.0: electron direct methods.

A computer program designed to provide a number of quantitative analysis tools for high-resolution imaging and electron diffraction data is described. The program includes basic image manipulation, both real space and reciprocal space image processing, Wiener-filtering, symmetry averaging, methods for quantification of electron diffraction patterns and two-dimensional direct methods. The program consists of a number of sub-programs written in a combination of C++, C and Fortran. It can be downloaded either as GNU source code or as binaries and has been compiled and verified on a wide range of platforms, both Unix based and PC's. Elements of the design philosophy as well as future possible extensions are described.

Image Processing, Computer-Assisted↗

PubMed2005

Nonlinear imaging using annular dark field TEM.

Annular dark field TEM images exhibit a dominant mass-thickness contrast that can be quantified to extract single atom scattering cross sections. On top of this incoherent background, additional lattice fringes appear with a nonlinear information limit of 1.2A at 150 kV. The formation of these fringes is described by coherent nonlinear imaging theory and good agreement is found between experimental and simulated images. Calculations furthermore predict that the use of aberration corrected microscopes will improve the image quality dramatically.

Journal Article↗

PubMed2002

Nickel accumulation and nickel oxalate precipitation by Aspergillus niger.

A strain of Aspergillus niger isolated from a metal-contaminated soil was able to grow in the presence of cadmium, chromium, cobalt, copper, and unusually high levels of nickel on solid (8.0 mM) and in liquid (6.5 mM) media. This fungus removed >98% of the nickel from liquid medium after 100 h of growth but did not remove the other metals, as determined by inductively coupled plasma spectroscopy. Experiments with non-growing, live fungal biomass showed that nickel removal was not due to biosorption alone, as little nickel was bound to the biomass at the pH values tested. Furthermore, when the protonophore carbonyl cyanide p-(trifluoremetoxy) phenyl hydrazone (FCCP) was added to the actively growing fungus nickel removal was inhibited, supporting the hypothesis that energy metabolism is essential for metal removal. Analytical electron microscopy of thin-sectioned fungal biomass revealed that metal removed from the broth was localized in the form of small rectangular crystals associated with the cell walls and also inside the cell. X-ray and electron diffraction analysis showed that these crystals were nickel oxalate dihydrate.

Aspergillus niger↗

PubMed2001

Structure determination and structure refinement of Al2CuMg precipitates by quantitative high-resolution electron microscopy.

The structure of the S-phase (Al2CuMg) precipitate in an Al matrix has been determined by using a combination of image processing, quantitative image comparison, and automatic refinement of imaging and structural parameters. A method for comparing images with unknown origin relationship while quickly estimating a possible translation of the origin is outlined. The optimization algorithm used in the structure determination utilizes space group symmetry, which is deduced from the crystal-zone axis and reduces the number of free parameters.

Journal Article↗

PubMed2001

Imaging columns of the light elements carbon, nitrogen and oxygen with sub Angstrom resolution.

It is reported that lattice imaging with a 300 kV field emission microscope in combination with numerical reconstruction procedures can be used to reach an interpretable resolution of about 80 pm for the first time. A retrieval of the electron exit wave from focal series allows for the resolution of single atomic columns of the light elements carbon, nitrogen, and oxygen at a projected nearest neighbor spacing down to 85 pm. Lens aberrations are corrected on-line during the experiment and by hardware such that resulting image distortions are below 80 pm. Consequently, the imaging can be aberration-free to this extent. The resolution enhancement results from increased electrical and mechanical stability of the instrument coupled with a low spherical aberration coefficient of 0.595 + 0.005 mm.

Journal Article↗