Digital Commons Network^™

Energy Dispersive X-Ray Microanalysis Of The Dentin In Rat Molars After Corticosteroid Treatment, Karin Nasstrom, Rolf Odselius, Arne Petersson

Scanning Microscopy

The aim of this study was to investigate whether the calcium (Ca) and phosphorus (P) composition of corticosteroid induced dentin was the same as in normally developed dentin. Seven rats were given corticosteroids intravenously and three rats served as controls. Energy dispersive X-ray microanalysis (EDX) was carried out on the axially sawn roots of the molars. Measurements were made at 20 sites, equally distributed in the buccal, mesial, lingual and distal direction. The results showed that the Ca/P ratio (weight %) was slightly above 2.0 in both the experimental and the control group, indicating that the corticosteroid induced dentin had …

Quantitative Dark-Field Mass Analysis Of Ultrathin Cryosections In The Field-Emission Scanning Transmission Electron Microscope, S. Brian Andrews, Roger A. Buchanan, Richard D. Leapman

Scanning Microscopy

The availability of a cryotransfer stage, highly efficient electron energy loss spectrometers, and ultrathin-window energy-dispersive x-ray spectrometers for the VG Microscopes HB501 field-emission scanning transmission electron microscope (STEM) provides this instrument with the potential for high resolution biological microanalysis. Recent technical advances offer cryosections that are thin enough to take advantage of the analytical capabilities of this microscope. This paper first discusses the quantitative characterization of freeze-dried, ultrathin cryosections of directly frozen liver and brain by low-dose dark-field STEM imaging. Such images reveal high-quality sections with good structural detail, mainly due to reduced preparation artifacts and electron beam damage. These …

Measurement Of Subcellular Ca2+ Redistribution In Cardiac Muscle In Situ: Time Resolved Rapid Freezing And Electron Probe Microanalysis, Meredith Bond, Mark D. Schluchter, Eva Keller, Christine S. Moravec

Scanning Microscopy

To directly assess the physiological roles of sarcoplasmic reticulum (SR) and miitochondria (MT), we have utilized energy dispersive electron probe microanalysis (EPMA) on ultrathin freeze-dried cryosections from isolated papillary muscles, rapidly frozen at precise time points of the contractile cycle. Using this approach, we can detect redistribution of subcellular Ca²⁺ during the cardiac contractile cycle. Changes in Ca²⁺ of less than 1.0 mmol/kg dry wt can be detected. By determining the variability of the Ca²⁺ measurements in preliminary experiments, we have also demonstrated that it is possible to optimize experimental design, i.e., to predict the number of …

Strontium, A Tracer To Study The Transport Of Calcium In Mineralizing Tissues By Electron Probe Microanalysis, Ernst-Rudolf Krefting, Kai Frentzel, Jörg Teßarek, Hans-Jürgen Höhling

Scanning Microscopy

In growth plate cartilage the mineralization starts extracellularly in the lower hypertrophic zone. The mineral formed is the calcium phosphate apatite. Enough calcium and phosphate must be available at the mineralization front as well as in regions with proceeding mineralization. There must be a transport of Ca (and phosphate) to these sites.

Electron probe X-ray microanalysis is a well established method to analyze element concentrations in small volumes, but it cannot discriminate isotopes. Strontium is similar to Ca in its chemical and biological behaviour and is therefore a suitable tracer to investigate the transport of Ca.

Small amounts of Sr …

Computer Aided Phase Determination By Electron Probe Microanalysis, P. Nagy

Scanning Microscopy

A measuring procedure and a computer program have been developed for energy dispersive microanalysis to study segregation properties of various bulk, polished samples (alloys and ceramics). A few hundred sampling points were selected at random or regularly forming a grid pattern on the surface of the sample. Energy dispersive spectra were stored and ZAF corrected, and the obtained concentrations were evaluated statistically. An IBM AT compatible computer was used to calculate concentration distribution functions of the elements present in the sample. In addition to the usual statistical values, several types of concentration distribution functions were calculated. The method was tested …

The Interpretation Of X-Ray And Electron Signals Generated In Thin Or Layered Targets, R. H. Packwood, G. Remond

Scanning Microscopy

This work outlines the development of a comprehensive theory for the electron probe microanalyser and scanning electron microscope or SEM, that is intended to serve as a framework of understanding for those employing electron beam methods and as a basis for improved correction procedures. There is particular emphasis on applications to layered and non-uniform specimens. Starting from a simple Gaussian depth distribution of electrons and making assumptions about the X-ray production, a series of predictions of X-ray and electron signals are made for various target configurations. When compared with experimental measurements a series of interesting discoveries follow, which, taken altogether, …

An Analytical Method Of Determining Thickness Of Multi-Layer Films With Electron Microprobe, Yen-Cai Ho, Jia-Guang Chen, Xin-Lei Wang

Scanning Microscopy

In the previous work we have developed a series of theoretical corrections for calculating the emitted X-ray intensity in multi-layer films. By the use of these theories, along with careful experimental operation of the electron probe microanalysis (EPMA) and Monte Carlo iteration calculation, the thickness of each layer in multi-layer films can be determined.

To test the reliability of this method, the multi-layer film specimens Au/Cu/Si, Cu/Au/Si and Ag/Cr/Si of known thicknesses were analyzed at 20, 25, 30 and 35 keV. The percentage relative errors between the thicknesses determined using the correction procedures and those measured using nuclear backscattering are …

Analytical Description Of X-Ray Peaks: Application To L X-Ray Spectra Processing Of Lanthanide Elements By Means Of The Electron Probe Micro-Analyzer, G. Remond, Ph. Coutures, C. Gilles, D. Massiot

Scanning Microscopy

The shape of Lα X-ray peaks analyzed by means of a LiF (200 plane) monochromator was described by a pseudo-Voigt function:

P(λ) = 0.35 P₁(λ)+ 0.65 P₂(λ)

where P₁(λ) and P₂(λ) are a Gaussian and a Lorentzian distribution centered at the same wavelength, with the same amplitude and half-width and in relative proportion 0.35 and 0.65 respectively. For peaks occurring at wavelength greater than ≃ 0.17 nm, a Gaussian offset was added in order to correct the asymmetry of peaks resulting from the monochromator mounting within the spectrometer.

The effective wavelength resolution …

Bacillus-Shaped Deposits Composed Of Hexahedrally Based Crystals In Human Dental Calculus, T. Kodaka, A. Hirayama, K. Miake, S. Higashi

Scanning Microscopy

In human supra- and subgingival calculus, bacillus-shaped deposits showing various rocky-pile forms composed of hexahedrally based crystals were observed by scanning electron microscopy. The crystal size measured approximately 0.1 - 1.5 μm. The electron probe microanalysis always detected calcium, phosphorous, and magnesium. Their molar ratios resembled those of magnesium-containing whitlockite and moreover the crystals also gave the electron diffraction pattern of whitlockite. The bacillus-shaped deposits happened to coexist with the intracellular calcifying microorganisms, furthermore, oral microorganisms partially replaced by the hexahedrally based crystals were found. The crystal deposits were never seen in the surface layers of calculus exposed to the …

Preparation Of Cultured And Isolated Cells For X-Ray Microanalysis, K. Zierold, D. Schäfer

Scanning Microscopy

Various electron microscopical preparation techniques are compared with regard to the preservation of the intracellular element distribution as determined by X-ray microanalysis in scanning and scanning transmission electron microscopy. By use of chemical agents for fixation and dehydration ions are redistributed and washed out. This is also true for freeze-substitution. Whole cells are prepared by cryofixation followed by freeze-drying. Interference of intracellular measurements by extracellular elements can be avoided by appropriate washing the cells before cryofixation. The washing medium has to be carefully selected in order to avoid distortions of the original intracellular element content. These problems are circumvented by …

Cyclic Deposition Of Calcium Salts During Growth Of Cholesterol Gallstones, Peter F. Malet, Norman E. Weston, Bruce W. Trotman, Roger D. Soloway

Scanning Electron Microscopy

Some cholesterol gallstones contain darkly pigmented centers or peripheral concentric pigmented bands. We examined the cross-sectional surface of three cholesterol gallstones which contained both central and peripheral pigmented areas with electron-probe microanalysis (EPM) and energy dispersive x-ray microanalysis (EDXA) to determine the elemental composition of the pigmented regions. Linear EPM across the cross-sectional surface of the stones demonstrated that most of the pigmented regions of all three stones had high Ca and P signals; the nonpigmented intervening areas had markedly lower or no detectable Ca and P signals. In two of the three stones, high O signals coincided with the …

Cell Volume Regulation Studies With The Electron Microprobe, Mary Jo Ingram, F. Duane Ingram

Scanning Electron Microscopy

Lumbricals from the hind feet of young rats are dissected free, stretched to approximately 125% of resting length, and mounted on individual, simple plastic forms. After recovery in physiological saline, the isolated muscles are incubated for periods of 40 to 60 min. in one of a series of hypertonic bathing solutions. The composition of each bathing solution is identical, except for osmolality which is increased with lactose. At least one muscle from each animal is incubated in a control solution to serve as a control muscle for that particular set of 5 to 8 muscles. Mounted muscles are removed from …

Modeling Of Depth Distribution Of X-Ray Production, J. D. Brown

Scanning Electron Microscopy

Knowledge of X-ray production as a function of depth by electrons (𝜙(𝜚z) curves) is important in quantitative electron probe microanalysis and other electron beam technologies. Extensive measurements of such curves have been made for electron energies between 6 and 30 keV and for many X-ray lines and matrix elements. Two experimental techniques based on measurements on sandwich or wedge shaped specimens have been used.

A number of expressions have been used to model 𝜙(𝜚z) curves from a square function through complicated polynomial expressions. Recently, a Gaussian model has been proposed which accurately reflects the shape of the 𝜙(𝜚z) curves and …

Monte Carlo Calculations For Electron Microscopy, Microanalysis, And Microlithography, David F. Kyser

Scanning Electron Microscopy

The methodology of Monte Carlo simulation for electron scattering and energy dissipation in solid targets is reviewed. The basic concepts of single and multiple elastic scattering models are compared, and the continuous energy loss model for inelastic scattering is discussed. Some new developments in Monte Carlo simulation are reviewed, including improvements in the elastic scattering model and discrete models for inelastic scattering. A variety of practical applications of Monte Carlo calculations in the fields of electron microscopy, electron probe microanalysis, and electron beam lithography are reviewed. The Monte Carlo computer program listings available in the literature are also described.

Monte Carlo Electron Trajectory Calculations Of Electron Interactions In Samples With Special Geometries, Dale E. Newbury, Robert L. Myklebust

Scanning Electron Microscopy

Implementing a Monte Carlo simulation for application to electron sample interactions requires use of accurate treatments of elastic and inelastic scattering. In formulating a Monte Carlo simulation, careful testing must be carried out to ensure that the calculation yields sensible and useful results. A suitable testing procedure includes calculation of (1) electron backscatter coefficients as a function of atomic number, including any necessary adjustment of scattering parameters; (2) backscatter coefficients as a function of specimen tilt; (3) backscatter and transmission coefficients for thin foils; (4) backscattered electron energy distributions; (5) electron spatial distributions; and (6) x-rays, including x-ray depth distributions, …