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M K Lamvik

Publications and source records attributed to M K Lamvik.

5 recordsLinked to original sources
PubMed1991

Temperature directly affects the rate of irradiation-induced mass loss from phosphatidylcholine multilayers.

We monitored the mass thickness of egg yolk phosphatidylcholine multilayers at several temperatures during electron irradiation. The rate of irradiation-induced mass loss was reduced substantially when this specimen was cooled to liquid nitrogen temperature from room temperature. Additional cooling to liquid helium temperature caused an additional reduction of mass-loss rate. The characteristic doses D(1/e), which are the slopes of the logarithm of the differential mass thickness against dose, were approximately 7 x 10(3) e/nm2 at 290 K, 8 x 10(4) e/nm2 at 130 K, and 1.4 x 10(5) e/nm2 at less than 10 K. The fractions of the original mass thickness that remained after arbitrarily high doses were about 69% at 290 K, 72% at 130 K, and 77% at less than 10 K.

Animals↗
PubMed1976

Electronmicroscopic mass determination using photographic isodensity techniques.

Using Agfacontour, Kodalith, or similar films, it is possible to convert an electron micrograph into a map of regions of equal photographic density (isodensitites) by simple copying procedures. If images of polystyrene spheres and a calibrated density wedge are included in the copies, it is possible to quantitatively calibrate the isodensities in terms of mass per unit area of the specimen. In this way, electronmicroscopic mass determination may be accomplished without the need of densitometers or other photometric equipment.

Animals↗
PubMed1976

Minimization of dose as a criterion for the selection of imaging modes in electron microscopy of amorphous specimens.

A fundamental limitation in electron microscopy of organic specimens is radiation damage by the electron beam. To minimize damage it is necessary to have maximum information collection for a given dose. Various modes of operation of conventional and scanning transmission microscopes are compared with respect to their ability to detect small changes in specimen thickness or density with a given signal to noise ratio. Incoherent imaging is assumed, and this is expected to apply to amorphous specimens under a variety of microscope conditions. For either very thin or very thick specimens, the scanning transmission microscope is found to require nearly 10 times less dose than a conventional microscope for the same signal to noise ratio in the image. For specimens of intermediate thickness, scanning and conventional transmission electron microscopes are roughly equivalent.

Electrons↗
PubMed1975

High resolution scanning electron microscopy at the subcellular level.

Recently developed scanning electron microscopes provide sufficient resolution to allow useful observation of subcellular biological objects. Preparation methods for such objects need not be limited to the traditional coating and mounting procedures. Many methods developed for transmission electron microscopy are immediately adaptable to scanning electron microscopy. We show that a number of techniques are available to the microscopist which yield adequate contrast and high resolution. As examples we show skeletal muscle myofibrils dispersed to reveal thick filaments, uncoated on a thin carbon film; a tropomyosin tactoid, negatively stained with uranyl acetate; oncornavirus, conventionally coated; and T4 bacteriophage on an aluminium substrate.

Animals↗