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Biomedical subjects

R E Burge

Publications and source records attributed to R E Burge.

At least 19 recordsLinked to original sources
PubMed1993

The effect of soft X-radiation on myofibrils.

Myofibrils, the contractile organelles from striated muscles, have been examined in the X-ray microscope to determine the effect of radiation on their function and structure. Using X-rays of energy 350-385 eV in the water window we find that after an exposure to 7.5 x 10(5) photons/micron2 (calculated to give an absorbed dose of 20,000 Gy) the myofibrils will no longer contract. The use of the free radical scavenging agent, DMSO, gives some protection to the fibrils. It has also been found that after this much irradiation the fibrils lose up to 20% of their mass. Further substantial mass loss occurs on subsequent irradiation. After 25 times the loss-of-function exposure only 30% of the mass remains. Analysis of a series of images of the same myofibril covering this range of exposures shows that the mass is preferentially lost in some areas of the structure and consequently significant structural changes occur.

Animals↗
PubMed1988

Towards a digital model for an electron-microscope image.

An image model is defined based on the boundaries between image regions with different textures and series of descriptions of those textures. Six models of texture are studied under the categories of pixel-based and region-based models. Several techniques for the determination of the unit-cell of textures are presented. The model is applied to the consideration of (a) image correction, (b) the classification of image texture, (c) image enhancement including averaging of detail in periodic specimens, and (d) image data compression. A floating point format, which provides a significant simplification for the Huffman code, is also introduced.

Algorithms↗
PubMed1987

X-ray microscopy and X-ray imaging.

Within a framework of an overview of the current status and potential of X-ray microscopy, a description is given of the development of the King's College scanning instrument which produced its first images in September, 1986. The instrument was mounted on the newly-built undulator beam line at the UK Science and Engineering Research Council's SRS synchrotron. There are consequently three sites worldwide where high-resolution X-ray microscopes with zone-plate optics are in operation. The other sites are BESSY-Berlin and NSLS-Brookhaven.

Animals↗
PubMed1982

Multiple signals in STEM.

A brief description is given of the eight image signals that can be simultaneously recorded in digital form using an appropriate data recording system and high resolution STEM; this involves a set of detectors covering bright and dark field. Details are provided of the collection and manipulation of image data for STEM, including on-line estimation of off-focus distance, on-line assessment of astigmatism, on-line signal to noise ratio in any or all detectors; examples of all three procedures are given. The use of the data recording system is discussed together with some aspects of image display, including the use of colour. A method is introduced of providing, using the appropriate hardware, a prescribed colour map (image intensity converted to colour) using replaceable PROMS. Two off-line procedures are considered. One is the Karhunen-Loeve transform and its application to bringing together the information contained within the multiple signals, and the other is the discrete cosine transform by which the storage problem for digital image storage may be reduced, according to the image, by between 15 and 30 times.

Animals↗
PubMed1979

An X-ray study of the cytoplasmic membranes of two gram-positive bacteria.

X-ray diffraction diagrams of partially disordered one-dimensional lattices of isolated bacterial cytoplasmic membranes are described and they provide a basis for suggesting possible molecular structures of bacterial membranes. Biochemical and electron microscope evidence points towards a lipid bilayer with a high degree of fluidity. The protein molecules are in a disordered configuration in the membrane.

Bacillus↗
PubMed1977

Optical and digital image processing in high-resolution electron microscopy.

A comparison is made of the deblurring by digital and optical processing of a single conventional bright field electron image of ferritin particles distributed on a carbon supporting film. The deblurring functions include the effects of the partial temporal and partial spatial coherence of the electron beam, the phase contrast transfer function of the objective lens and Weiner signal to noise optimisation. Practical aspects of the similar results achieved by the two methods are discussed. The relative advantages and disadvantages of the batch and interactive computer modes for picture processing are considered in an Appendix.

Computers↗
PubMed1973

Tuberculin activity of mycobacterial fractions obtained by chromatography.

Commercial purified protein derivatives (PPD), old tuberculin (OT), the bacillary extract, and the culture filtrate of Mycobacterium tuberculosis H37Ra were submitted to Sephadex G-25 and diethylaminoethyl (DEAE)-cellulose chromatography. The ability of the fractions obtained to elicit delayed dermal hypersensitivity in M. tuberculosis H37Ra-infected guinea pigs was studied. Skin tests with Sephadex fractions in M. tuberculosis H37Ra-infected guinea pigs showed that the tuberculin activity was localized in the first fraction. All other Sephadex fractions were nonessential and nonspecifically irritating. Fractions from chromatography of Sephadex G-25 fraction 1 on DEAE-cellulose columns showed that all but the first were able to elicit delayed hypersensitivity reactions. There was a variability in the capacity to elicit the tuberculin reaction according to the fraction injected and the stage of tuberculous infection in guinea pigs. Compared to the others, the seven lots of commercial PPD were variable in composition and content. They contained both essential and nonessential materials for the tuberculin reaction. Sephadex fraction 1 would appear to be a better tuberculin as it excludes nonessential nonspecifically irritating elements and contains the complement able to elicit the tuberculin reaction. Its methodological simplicity would be economically advantageous.

Animals↗