Biology Commons^™

Changes In Rat And Mouse Salivary Glands And Pancreas After Chronic Treatment With Diuretics: A Potential Animal Model For Cystic Fibrosis, Samuel Sagström, Edward B. Mcmillan, Monique Marijianowski, Helmy Mulders, Godfried M. Roomans

Scanning Microscopy

Defective transepithelial chloride and water transport is thought to be the cellular basis of the disease cystic fibrosis (CF). Therefore, it was attempted to develop an animal model for this disease by chronically inhibiting transepithelial chloride transport in experimental animals by long term treatment with high doses of diuretics. In the present study, changes in the salivary glands and pancreas after such treatment were investigated by X-ray microanalysis and electron microscopy.

Treatment of rats for one month with diuretics caused a significant decrease in chloride and an increase in calcium in the acinar cells of the submandibular gland. This increase …

Correlative Light, Transmission, And High Resolution (Se-I) Scanning Electron Microscopy Studies Of Rhesus Adrenocortical Vascular Morphology, R. P. Apkarian, N. L. L' Hernault

Scanning Microscopy

A detailed correlative morphologic description using light microscopy (LM), transmission electron microscopy (TEM) and high resolution SE-I scanning electron microscopy (SEM) was conducted on the capillary endothelium of the zona-fasciculata (Z-F) in juvenile male rhesus monkeys. The glucocorticoid synthesis and release phenomena, associated with stress stimulated release of adrenocorticotropic hormone (ACTH) via the hypothalamic-pituitary axis, intimately involves capillaries of the Z-F. A comprehensive study of all the ultrastructural features implicated in the transendothelial uptake of steroidogenic precursors and release of glucocorticoids in perfused rhesus adrenals has not previously been made. This report presents correlative images of transendothelial openings that include …

Surface Corrections To Bulk Energy Losses In Scanning Transmission Electron Microscopy Of Spheres, A. Rivacoba, P. M. Echenique

Scanning Microscopy

The interaction of a fast electron penetrating a spherical target is studied, in the frame of the classical dielectric theory. Expressions for ω the Fourier component of the induced scalar field and energy loss probability are obtained. The reduction in the bulk loss probability due to the surface boundary correction is calculated to all orders in a multipole expansion. The dependence of this correction on the impact parameter and on the radius of the sphere is also studied and compared with the results for films.

Azimuthal Variations Of Sensitivity In The Coaxial Scanning Auger Microprobe, L. Frank

Scanning Microscopy

Experiments with the PHI 595 Multiprobe have revealed a pronounced asymmetry of the energy filtered image (the shape of the line-scan curve) obtained with an isolated sphere lying on a flat surface. The effect is explained as a consequence of transmission efficiency variations along the circumference of the ring-shaped detector assembly, and is probably caused by deviations from coaxiality of the adjustable parts of the entrance annular aperture controlling the energy resolution. A quantitative model provides realistic results and has indicated the emission anisotropy of Auger electrons as being much larger than that of the energy filtered background emission at …

Comparative Analysis Of The Proliferative Response Of The Rat Urinary Bladder To Sodium Saccharin By Light And Scanning Electron Microscopy And Autoradiography, Samuel M. Cohen, Maria J. Fisher, Takao Sakata, Martin Cano, Gerald P. Schoenig, Clifford I. Chappel, Emily M. Garland

Scanning Microscopy

Three methods used to detect proliferative changes in the rat urothelium, light microscopy, scanning electron microscopy, and autoradiography, were compared for their sensitivity in detecting changes produced by administration of sodium saccharin. Weanling male F344 rats were fed sodium saccharin as 0, 3, 5, or 7.5% of the diet, and the bladders were evaluated after 4, 7, and 10 wks of feeding. Light microscopic changes and an increase in labeling index were seen at all time points in rats fed 7.5 % sodium saccharin, but not at the lower doses. A slight increase in labeling index was also observed at …

Scattering From Atoms And Molecules In The Free State By Electrons With Energies Below 10 Kev., Russell A. Bonham

Scanning Microscopy

A survey of electron scattering from a free atom or molecule by incident electrons with energies below 10 keV is best accomplished by viewing a Bethe surface. This surface presents a global picture of nearly all observable phenomena obtained from the investigation of the angular and energy dependence of scattered electrons. An absolute, comprehensive and accurate surface for molecular nitrogen, obtained from electron energy loss spectroscopic experiments, illustrates the major points to be made. Two general uses of such scattering information are: (i) the inference of various aspects of the electronic structure of the target through the observation of spectral …

Monte Carlo Calculations Of Secondary Electron Emission, Suichu Luo, David C. Joy

Scanning Microscopy

Monte Carlo calculations of secondary electron (SE) generation have been performed using a hybrid model of the exponential decay law and cascade multiplication process. The contributions of both valence and core electron excitations, and the production of secondaries by the volume plasmon decay, have been included. The calculation has been extended to include SE's with energies up to half the incident beam energy. The SE yield δ_SE1 component due to excitation by primary electrons, the SE yield δ_SE2 due to excitation by backscattered electrons, and the β coefficient are estimated using this model. Calculated SE yields, energy distributions, …

Murphy's Law And The Uncertainty Of Electron Probes, Linn W. Hobbs

Scanning Microscopy

The electron microscope has brought over the last fifty years a wealth of information about the structure of solids, from surface topography to the details of atomic arrangements. Like any probe, however, the electron beam is subject to the epistomological constraint that the investigator inevitably perturbs what is being investigated, and from its beginnings questions were raised about the integrity of the ·images generated in the microscope from a specimen which was subjected to such an aggressive probe. A fast electron is about as likely to be scattered inelastically as elastically from a collection of atoms, and the density of …

Extracting Chemical Information From Auger Line Shapes, David E. Ramaker

Scanning Microscopy

We have developed a generally applicable, semi-empirical approach for quantitatively interpreting Auger line shapes. Detailed information on hybridization, electron delocalization and correlation, screening effects, bonding, and covalency can be obtained from the line shape. Methods for extracting the Auger line shape from the experimental data are briefly described. We summarize our recent results from the C KVV Auger line shapes of five different gas phase hydrocarbons (methane, ethane, cyclo-hexane, benzene, and ethylene), three solids (polyethylene, diamond, and graphite), and a molecularly chemisorbed system (ethylene/ Ni). The normal kvv component accounts for only about half of the total experimental KVV intensity …

Secondary Electron Emission From Solids. Ii. Theoretical Descriptions, Michel Cailler, Jean-Pierre Ganachaud

Scanning Microscopy

A primary beam impinging on a solid target suffers elastic and inelastic collisions with the components of the solid. These collisions can be incorporated into a Monte-Carlo simulation model if all the cross sections associated with the various types of collisions are known.

Elastic diffusion effects are mainly related to the interactions of the particles with the real potential V(r) surrounding each ionic core. An essential simplification of the inelastic interactions is to consider that the solid reacts as a whole to an external probe, which is the incident electron beam. The linear response of the solid to an external …

Slowing Down Of Positrons And Applications To Solid Surfaces, Peter J. Schultz, L. R. Logan, W. N. Lennard, G. R. Massoumi

Scanning Microscopy

When monoenergetic positrons enter a solid they scatter and lose energy via processes similar to those for electrons. Theoretical details of these processes have been well established for decades, but experimental results using low energy positron beams are only now becoming available for comparison. We review the theoretical results for elastic and inelastic scattering of positrons and the predictions that follow for backscattering, inner-shell ionization, energy loss and stopping profiles. In this presentation, emphasis is given to specific comparisons with calculations for electrons. We discuss recent experimental results in each of these areas, and conclude with two examples of applications …

Angular And Energy Distributions Of Electrons Emitted From Gases And Thin Foils During Light Ion Bombardment, L. H. Toburen

Scanning Microscopy

The energy and angular distributions of electrons ejected by fast charged particles in ionizing collisions provide detailed information regarding the effects of atomic, molecular, and condensed-phase structure on the energy loss process. Analysis of the wide range of available data has lead to several general conclusions. For ionization of atomic and molecular targets by protons having energies above a few hundred keV, the cross sections for electron production have been found to scale as the number of loosely bound target electrons. The more subtle features of the ejected electron energy spectra are, however, dependent on the electronic structure of the …

Electron Stimulated Surface Chemistry, Miles J. Dresser

Scanning Microscopy

When an electron beam of less than 1000 eV interacts with a surface layer a variety of phenomena may occur. In this paper I will discuss those interactions that lead to either chemical changes on the surface and/or desorption of species or fragments from the surface. Theoretical models of electron stimulated desorption, (ESD) will be presented, specifically the Menzel, Gomer, and Redhead model, the Knotek, Feibelman model and the Ramaker, White and Murday model. Experiments that display the angular distribution of the desorbing ionic or metastable fragments, (referred to as ESDIAD for Electron Stimulated Desorption: Ion Angular Distributions) are the …

Physical Sputtering Of Metallic Systems By Charged-Particle Impact, Nghi Q. Lam

Scanning Microscopy

The present paper provides a brief overview of our current understanding of physical sputtering by charged-particle impact, with the emphasis on sputtering of metals and alloys under bombardment with particles that produce knock-on collisions. Fundamental aspects of ion-solid interactions, and recent developments in the study of sputtering of elemental targets and preferential sputtering in multicomponent materials are reviewed. We concentrate only on a few specific topics of sputter emission, including the various properties of the sputtered flux and depth of origin, and on connections between sputtering and other radiation-induced and -enhanced phenomena that modify the near-surface composition of the target. …

Ion-Induced Electron Emission From Solids, Wolfgang O. Hofer

Scanning Microscopy

A review of ion-induced electron emission is presented which concentrates on the mechanisms relevant to imaging, analysis, and processing of surfaces by ion beams. In this field of applications, the main interest in electron emission lies in kinetic emission by heavy, i.e. multi-electron (Z > 2) ions of energy ≤ 100 keV.

Interband Transitions In Electron Energy Loss Spectrometry, P. Schattschneider, P. Pongratz

Scanning Microscopy

Electron energy loss spectrometry (EELS) allows one to experimentally obtain the dielectric permittivity 𝜀:(ω, q) as a function of frequency ω and wave vector if. From 𝜀 information on inter band transitions in the probed medium can be drawn. In EELS, inter band transitions are screened by the movement of the loosely bound valence or conduction electrons. The screening effect may enhance or attenuate the strength of transitions, and tends to shift the frequencies of resonant oscillations. Another aspect of screening is the occurrence of longitudinal modes in the spectrum. So, great care has to be taken in interpreting …

Compton Scattering In Electron Energy Loss Spectrometry, P. Schattschneider, P. Pongratz, H. Hohenegger

Scanning Microscopy

It is well known that the distribution of electron momenta (electron density in momentum representation) of gases can be probed by Compton scattering of either photons (γ-rays or X-rays) or electrons. Recently it has been shown that Compton scattering of electrons is suited to the study of the electron momentum densities of solids on a microscopic scale. This technique, known as ECOSS, Electron Compton Scattering from Solids can be done in the electron microscope by electron energy loss spectrometry (EELS).

After a discussion of inherent approximations and the introduction of the reciprocal form factor a method is proposed in order …

Spatially Sensitive Electron Energy Loss Spectroscopy, Helmut Kohl

Scanning Microscopy

Over the last decade electron energy loss spectroscopy has been increasingly used as a microanalytical technique. Under favorable conditions a spatial resolution better than 1 nm has been achieved. It is therefore possible to obtain spectroscopic information at an atomic scale. Such a spectrum can be used for the investigation of

- the elemental composition

- defect levels

- surface excitations

- the fine structure.

The spatial sensitivity of such experiments implies, that the initial or the final state of the scattered electrons must have a spatial structure. The theory for the scattering of wave packets will be discussed, focussing …

Secondary Electron Emission From Solids. I. Secondary Electron Spectroscopy, Michel Cailler, Jean-Pierre Ganachaud

Scanning Microscopy

The secondary electron emission spectroscopy can provide useful information about the transitions in the electronic structure from solids and deals with the detection of fine structures superimposed on the true secondary peak, in the kinetic energy range of the true secondary electrons.

Several mechanisms have been proposed for the creation of these fine structures: diffraction phenomena, plasmon decay, interband transitions to unoccupied levels, Auger transitions and more recently, autoionization emission. Some features could not be explained as being due to any bulk effect and were considered as indicative of a need to include surface wave-matching arguments in the analysis of …

Monte Carlo Simulation Of Secondary Electrons In Solids And Its Application For Scanning Electron Microscopy, M. Kotera, T. Kishida, H. Suga

Scanning Microscopy

A new Monte Carlo calculation model is introduced to simulate not only the primary electron behavior but also the secondary electron cascade in a specimen bombarded with an electron beam. Either the primary or the generated electron in a specimen having energy greater than 0.1 keV is defined as a fast electron and the single scattering model is used in the simulation which employs the Mott elastic scattering cross section and the Rao Sahib-Wittry energy loss equation. The electron having energy smaller than 0.1 keV is defined as a slow electron and the cascade model is used which takes into …

Channelling And Related Effects In Electron Microscopy: The Current Status, Kannan M. Krishnan

Scanning Microscopy

The channelling or Borrmann effect in electron diffraction has been developed into a versatile, high spatial resolution, crystallographic technique with demonstrated applicability in solving a variety of materials problems. In general, either the characteristic x-ray emissions or the electron energy-loss intensities are monitored as a function of the orientation of the incident beam. The technique, as formulated in the planar geometry has found wide applications in specific site occupancy and valence measurements, determination of small atomic displacements and crystal polarity studies. For site occupancy studies, the appropriate orientations in most cases can be determined by inspection and the analysis carried …

Electron Beam Nano-Etching In Oxides, Fluorides, Metals And Semiconductors, C. J. Humphreys, T. J. Bullough, R. W. Devenish, D. M. Maher, P. S. Turner

Scanning Microscopy

Etching, lithography, hole formation, surface restructuring and external machining can all be performed on a nanometre scale using an intense electron beam. Results are presented for a range of different materials which demonstrate the variety of mechanisms by which electron beam nano-etching can occur. For example, in crystalline 13-alumina hole formation occurs by surface indentations growing inwards to join up and form a nanometre diameter hole. In amorphous alumina, on the other hand, hole formation is from the inside-out: oxygen gas bubbles form under the electron beam, coalesce, and burst to leave a well defined nanometre diameter hole. In MgO …

Slowing Down And Scattering Of Ions In Solids, W. Heiland, H. Derks, T. Bremer

Scanning Microscopy

The interaction of particle beams with solids yields three parts, i.e. reflected particles, penetrating particles and trapped particles. At very low energies particle reflection is dominant, at very high energies penetration is the most important effect. Trapped particles are the result of energy loss processes, which on the other hand cause radiation damage in the solid. In the energy range discussed here, i.e. above energies where quantum effects, diffraction etc. are important and below energies where nuclear reactions, relativistic effects etc. may occur, the particle trajectories are classical. The energy loss process can be treated separately as nuclear and electronic …

Energy Loss Of Electrons Below 10 Kev, Hans Bichsel

Scanning Microscopy

Monte Carlo calculations are used to obtain the energy loss and spatial distribution of electrons penetrating matter. For this purpose, reliable cross section for the inelastic collisions must be known. As an approximation valid for large energy losses, the Coulomb cross section can be used. It can be modified in a simple way to account for the binding of electrons and for the exchange effect. In the Gryzinski model, collisions with moving electrons are assumed. In the quantum mechanical Bethe approximation, σ is closely related to the dipole oscillator strength (DOS), and its extension to finite momentum transfers, the generalized …

Plasmons In Scanning Transmission Electron Microscopy Electron Spectra, R. H. Ritchie, A. Howie, P. M. Echenique, G. J. Basbas, T. L. Ferrell, J. C. Ashley

Scanning Microscopy

A general self-energy formulation of the interaction between an electron in a scanning transmission electron microscope (STEM) and a localized target is given. We prove a theorem relating the probability of energy transfer to that calculated classically. Local dielectric theory of target excitation for various geometries is discussed. The problem of localization of initially unlocalized excitations in the valence band of solids is treated by transforming cross sections differential in momentum transfer into dependence on an impact parameter variable. We are thereby able to account for experimental data in scanning electron microscopy (SEM) that show high spatial resolution.

Quantitative Evaluation Of Scanning Electron Microscopy-Examined Ciliary Morphological Changes In Control And Noise Exposed Guinea Pig Cochleas, S. Rydmarker, P. Nilsson, D. E. Dunn, C. Lindqvist

Scanning Microscopy

Many investigations of noise-induced hearing loss have demonstrated a poor correlation between hearing threshold and hair cell loss. One reason for this is that more subtle changes in the hair cell, such as detailed morphological changes of stereocilia, have not been evaluated. However, examining such changes increases the problem of distinguishing experimental pathological changes from artefacts. Preparation of the specimen for scanning electron microscopy (SEM) may result in too many artefacts for an adequate quantification of defects due to noise exposure.

One problem with some earlier studies seems to be lack of controls and/or statistical analysis for the purpose of …

Calcium Pyrophosphate Crystal Deposition: A Kinetic Study Using A Type I Collagen Gel Model, Gretchen S. Mandel, Paul B. Halverson, Melisa Rathburn, Neil S. Mandel

Scanning Microscopy

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is characterized by deposits of triclinic (t) and monoclinic (m) CPPD crystals in articular and fibrocartilage. Many investigators have attempted to model CPPD crystal growth using both solution and a variety of gel systems. We have investigated the effect of type I collagen fibrils on CPPD crystal nucleation and growth using an ionic diffusion model. Collagen was isolated from porcine menisci using a pepsin solubilization procedure and gelled in three layers, with one containing 10 mM pyrophosphate (PPi) plus physiologic ions, the middle containing only the ions, while the third contained 25 mM …

The Secondary Blood Vessel System Of Segmental Arteries And Dorsal Aorta In Blennius Pavo And Zosterisessor Ophiocephalus. Histology, Fine Structure And Sem Of Vascular Corrosion Casts., F. Lahnsteiner, A. Lametschwandtner, R. A. Patzner

Scanning Microscopy

The secondary blood vessel system of the segmental arteries and of the dorsal aorta of the teleost fish Blennius pavo and Zosterisessor ophiocephalus are examined by light microscopy, transmission electron microscopy and by scanning electron microscopy of appropriately processed tissue and of vascular corrosion casts. Dorsal, lateral and ventral segmental arteries and the caudal portions of the dorsal aorta have a secondary vessel system. The secondary vessels are formed by capillaries which arise from the proximal portions of the segmental arteries and from the caudal parts of the dorsal aorta. In Z. ophiocephalus these capillaries are strongly dilated at their …

Backscattered Electron Imaging Of Partially-Demineralized Enamel, D. G. A. Nelson

Scanning Microscopy

Backscattered electron (BE) microscopy is being used increasingly as a technique to study the dissolution of dental enamel because of its high resolution and relatively easy sample preparation. Subsurface details such as striae of Retzius, cross-striations and prism microstructure have been observed with a resolution better than 0.1 micrometers using this technique. Since BE images of demineralized enamel appear very similar to microradiography images, it is tempting to interpret them in a similar fashion. We attempt to show that the interpretation of BE images is not straightforward because enamel is not a homogeneous one-phase material, but a two-component composite material …

Binding Of Ions To Nuclear Chromatin, Thomas Von Zglinicki, Heiko Ziervogel, Martina Bimmler

Scanning Microscopy

Ion concentrations in isolated lymphocyte nuclei subjected to KCl or MgCl₂ media of varying ionic strength were measured by X-ray microanalysis. Values were corrected for the contribution of free ions by estimating the volume fraction of the water space morphometrically. The amount of bound cations and Cl was constant and independent of the widely varying free ion concentration.

It is concluded that the mechanism of binding is counterion condensation but with limited cooperativity. In contrast to classical counterion condensation theory, the binding of ions occurs at oppositely charged clusters at the surface of the chromatin. Therefore, both cations and …