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The energy distribution in an electron beam transmitted by a thin aluminum film was studied by a retarding potential method in which the energy analysis could be made as a function of the polar angle and azimuth of scattering. The results indicated that the transmitted beam contained electrons which had lost essentially zero energy and groups of electrons which had suffered losses of approximately15 ev and 25 ev and possib1y 75 ev. In addition there appeared to be a continuous background of energy losses over the range studied (from 0 to 80 ev). The resolution of the energy analyser was limited by the separation of the data points and was not adequate to observe the dependence of the 15 ev energy loss (plasma loss) on the polar angle of scattering. This study demonstrated the feasibility of this method of energy analysis as well as the short-comings of the apparatus. Suggestions for future improvements are made.

<p> This work is concerned with the calculation by means of many-particle perturbation theory of the lowest order corrections to the Random Phase Approximation (RPA) description of an interacting electron gas in its ground state. Expressions in terms of the dynamically screened coulomb interaction are obtained for the electron proper self-energy, the electron momentum distribution function, and the screening function. Techniques, which reduce computational labour to a manageable level, are developed for the practical evaluation of the required corrections. The numerical results are not conclusive but they indicate that when all corrections of the same order (in the screened interaction) are included, the expansion converges sufficiently rapidly that the results are valid in the range of metallic densities.</p> / Thesis / Doctor of Philosophy (PhD)

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Call number: LD2668 .T4 1939 G81 / Master of Science

An atomic force microscope is an instrument that is capable of imaging magnetic, electric and van der Waals forces with a very high resolution. In this thesis, different methods for detecting the displacement of the force sensing lever in such an atomic force microscope are discussed. Special emphasis is given to optical detection methods that are used in conjunction with a vibrating lever. The three optical systems that are discussed are based on (1) the heterodyne interferometer, (2) the homodyne interferometer, and (3) a new design that utilizes feedback into a laser diode. Images of a hard disk drive head and of domains in a TbFeCo thin film sample that were obtained with the heterodyne system are presented. Also presented are images of domains in a different TbFeCo sample and of interdigital fingers that were collected with the novel laser diode system.

This work is based upon a series of quantitative morphological studies of the parathyroid glands of Mongolian gerbils and rats. Standard stereological methods were used on light and electron microscopical levels. Subclassification of the chief cells based on the staining affinity and electron density of the cytoplasm was not correlated with contents (volume and surface densities) of organelles. Compared to fixation by immersion, fixation by perfusion caused a remarkable reduction in the number of light chief cells and atrophic cells, indicating that the occurrence of those kind of cells is dependent on factors of artifactual nature. The early response of the parathyroid gland to altered concentrations of extracellular calcium was studied in vitro. At six hours of "incubation, enlargement of the Golgi zone (Golgi complex and presecretory granules), but unaltered endoplasmic reticulum, was seen in glands incubated in low (0,5 mM) compared to those incubated in high (3,0 mM) calcium concentrations. Prolonged hypocalcemia induced in vivo by intraperitoneal injections of ethylenediaminetetraacetate and calcium deficient diet for eight days, did not give rise to any major quantitative morphological changes in the individual parathyroid cell, and furthermore, the quantitative morphology of the parathyroid cell was unchanged in experimentally induced hyperparathyroidism (calcium deficient diet for 16 weeks). The morphological data do not support the opinion of a functional cycle in the parathyroid chief cell, but suggest that the early response of this cell to altered extracellular calcium may be funtional activities associated with the Golgi zone. / <p>S. 1-48: sammanfattning, s. 49-170: 5 uppsatser</p> / digitalisering@umu

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No description available.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy