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Biomedical subjects

C Dwyer

Publications and source records attributed to C Dwyer.

8 recordsLinked to original sources
PubMed2005

Multislice theory of fast electron scattering incorporating atomic inner-shell ionization.

It is demonstrated how atomic inner-shell ionization can be incorporated into a multislice theory of fast electron scattering. The resulting theory therefore accounts for both inelastic scattering due to inner-shell ionization and dynamical elastic scattering. The theory uses a description of the ionization process based on the angular momentum representation for both the initial and final states of the atomic electron. For energy losses near threshold, only a small number of independent states of the ejected atomic electron need to be considered, reducing demands on computing time, and eliminating the need for tabulated inelastic scattering factors. The theory is used to investigate the influence of the collection aperture size on the spatial origin of the silicon K-shell EELS signal generated by a STEM probe. The validity of a so-called local approximation is also considered.

Journal Article↗
PubMed2003

Scattering of A-scale electron probes in silicon.

We use frozen phonon multislice calculations to examine the scattering behaviour of A-scale electron probes in <001> and <110> silicon. For each crystal orientation, we consider the distribution of scattered intensity in real space as a function of crystal thickness, probe size and probe position. The scattered intensity distribution is found to vary drastically for different probe sizes. For a given probe size, the scattered intensity distribution is also significantly influenced by the crystal orientation. We discuss the implications for the simultaneous acquisition of an annular dark-field image and electron energy loss spectra in the scanning transmission electron microscope, with specific reference to the spatial resolution with which electron energy loss spectra can be related to local atomic structure.

Journal Article↗
PubMed2002

Subacute cutaneous lupus erythematosus associated with phenytoin.

Subacute cutaneous lupus erythematosus is a well recognized subset of systemic lupus erythematosus. It is characterized by a nonscarring, papulosquamous or annular eruption in a photosensitive distribution. Several cases, thought to be caused by drugs, have been reported. We report a case of subacute cutaneous lupus erythematosus caused by phenytoin, which has not previously been associated with this condition.

Aged↗
PubMed1983

Brachyolmia, recessive type (Hobaek): a clinical, radiographic, and histochemical study.

Brachyolmia recessive type (Hobaek) is a rare bone dysplasia characterized by short trunk dwarfism that becomes evident during childhood. The radiographic manifestations are primarily limited to the spine, and consist of universal platyspondyly with lateral extension of the vertebral bodies beyond the pedicles and irregularity of the vertebral end plates. Histologic changes seen on growth plate biopsy permit the diagnosis to be confirmed. The inheritance pattern appears to be autosomal-recessive.

Bone Diseases, Developmental↗
PubMed1983

Immunohistochemistry of types I and II collagen in undecalcified skeletal tissues.

Types I and II collagen were demonstrated in semithin sections of undecalcified human endochondral growth plate, articular cartilage, and subchondral bone. The effects of several different methods for fixation, embedding, exposing of antigenic determinants, and immunoperoxidase staining were examined. Fixation in buffered formalin and paraformaldehyde-lysine-periodate solution gave more intense staining for collagens than fixation in paraformaldehyde-gluaraldehyde or Bouin's solution. Specimens embedded in Spurr epoxy resin yielded intense and uniform staining of areas known to contain the particular collagens after the resin had been removed by sodium ethoxide. The staining was enchanced following enzymatic digestion, especially with protease V (Sigma). Staining sensitivity and specificity were comparable with the indirect conjugate and double peroxidase-antiperoxidase (PAP) techniques; the PAP method was less sensitive. Embedment in methacrylate resins proved unsatisfactory because of exaggerated immunostaining of mineralized sites in comparison to unmineralized areas of the same tissues. In the growth plate specimens, type I collagen was identified in the matrices of bone, periosteum, perichondrium, and in the cytoplasm of hypertrophic and degenerative chondrocytes. Type II collagen was found uniformly throughout the cartilage matrix and in spicules of unresorbed cartilage matrix located in subchondral bone. A similar staining pattern was observed for the articular cartilage, except that type I collagen was not detected in chondrocytes.

Bone and Bones↗