Biology Commons^™

Equations Of Charge Distribution In The Environmental Scanning Electron Microscope (Esem), G. D. Danilatos

Scanning Microscopy

In the environmental scanning electron microscope (ESEM), the electron beam together with various signals emanating from the beam-specimen interaction ionize the gaseous medium in the specimen chamber. A detailed derivation of equations describing the charge density and current flow in the system is presented. It is shown that the various causes of ionization operate over distinct regions, which can be separated out by suitable electrode configuration. The electron probe retains a fraction of electrons with the original charge distribution; this is surrounded by a widespread electron skirt, which, in turn, is surrounded by charge created by the secondary electrons, beyond …

Cryo-Preparation And Planar Magnetron Sputtering For Low Temperature Scanning Electron Microscopy, T. Müller, P. Walther, C. Scheidegger, R. Reichelt, S. Müller, R. Guggenheim

Scanning Microscopy

Cryo-preparation is a reliable technique for the structural investigation of food products in low temperature scanning electron microscopy (SEM). Artifacts, such as, the segregation of water/non-water ingredients, occur during the freezing process by the crystallization of ice; they can be helpful for correct interpretation of visualized details, e.g., the detection of water containing compartments. The size of the segregation structures depends on water concentration and specimen thickness. The condensation of water vapor (ice contamination) is influenced by the specimen temperature and the partial pressure of the water inside the vacuum system. Furthermore, the evaporation (sublimation, etching) of specimen water can …

The Morphology Of Synovial Lining Of Various Structures In Several Species As Observed With Scanning Electron Microscopy, Peter J. Steinberg, Kees C. Hodde

Scanning Microscopy

Data concerning surface morphology of synovial lining of tendons, tendon sheaths, cruciate ligaments, infra-patellar fat pads and peripatellar synovial ridges in various species (rat, rabbit, dwarf goat, sheep, pig, dog, human) are reported on. Supportive studies with transmission electron microscopy (TEM) and light microscopy were performed.

Three principal morphological appearances of the synovium are evident. On structures with a dense fibrous architecture like tendons, tendon sheaths and cruciate ligaments the intimal cells and processes are mostly slender and may tend to orientation in the length-axis of the structure. On the peri- and infrapatellar adipose tissues two principal 'extremes' are seen: …

The Microvasculature Of The Guinea Pig Ureter. A Scanning Electron Microscopic Investigation, S. Aharinejad, A. Lametschwandtner, W. Höltl, W. Firbas

Scanning Microscopy

In 24 albinotic guinea pigs (Cavia porcellus) the gross vasculature and the microvascular architecture of the ureter were studied by light microscopy of tissue blocks and by scanning electron microscopy of vascular casts. The guinea pig ureter is supplied by the renal artery proximally, by the aorta and the internal iliac artery in its mid-segment, and by the uterine and prostatic as well as by the vesical arteries distally. The main arterial trunks run alongside the ureter before they branch to send perforating arterioles to the muscular coat and the mucosal lining. The draining venules are found on …

Immunological Effects Of Ketoconazole, Itraconazole And Fluconazole On Lymphocyte Cell Proliferation And Natural Killer Cell Activity In Immune-Normal, Cyclosporine-Compromised And Cyclophosphamide-Compromised Mouse Models, Jeffrey Tullis Mitchell

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Over the past several years there has been a steady increase in the incidence of immunologically compromised patients. This has been the result of both chemical agents, such as those used in cancer chemotherapy, and biological agents such as HIV, the cause of Acquired lmmunodefeciency Syndrome (AIDS). The increase in immune-suppressed patients has lead to an increase in life-threatening mycoses requiring treatment with antifungal agents. Pharmaceutical companies have increased research for the development of new antifungal agents which are more effective and less toxic than those that are currently used. Several researchers have reported on antifungal agents that demonstrate both …

Approximate Solutions Of The Boltzmann Equation For Secondary Electron Emission: Results And Comparisons To Experiments, A. Dubus, J. Devooght, J. C. Dehaes

Scanning Microscopy

The aim of the present paper is to survey the theoretical work performed in Brussels about secondary electron emission (SEE). Two new approximate solutions of the Boltzmann equation for internal secondary electrons are applied to both electron and ion induced SEE. Using a realistic set of interaction cross sections, most calculated characteristics of electron emission compare fairly well to experiments.

The "improved age-diffusion" model can be used to calculate the electron yield, the energy and angular spectrum and also the depth and radial distributions of outgoing electrons for incident electrons and ions.

The "transport-albedo" model assumes an uniform internal electron …

Multielement Analysis Of Biological Materials By Particle-Induced X-Ray Emission (Pixe), Willy Maenhaut

Scanning Microscopy

An analytical particle-induced X-ray emission (PIXE) procedure for the multielement analysis of biological materials consists of various stages. These include sample and specimen preparation, specimen bombardment, spectral data processing, quantification and correction for matrix effects. Critical aspects of the procedure are contamination and/or losses during sample and specimen preparation and the danger of radiation or heat-induced losses during specimen bombardment. With optimized PIXE procedures precisions of 1-2% and an accuracy of better than 5% are obtainable, whereas the detection limits are down to 0.1 μg/g. Because of its inherent characteristics, PIXE offers great potential for trace element analysis in the …

Scanning Electron Microscope Study Of Wohlfahrtia Magnifica (Schiner, 1862) (Diptera: Sarcophagidae) I. Structures With Parasitic And Possible Taxonomic Meaning, I. Ruíz-Martínez, M. D. Soler-Cruz, R. Benítez-Rodríguez, J. M. Pérez-Jiménez, C. Adalid-Fuentes, M. Díaz-López

Scanning Microscopy

The larval development of Wohlfahrtia magnifica (the most important dipteran causing sheep myiasis in the Palearctic region) has been studied by means of scanning electron microscopy. The ultrastructure of mouth-hooks, oral ridges, labial lobes, body spines and anterior and posterior peritremes is described for the first time. Their possible adaptations to a parasitic lifeway are also discussed. Thus, the use of new structures in the Sarcophagidae taxonomy is proposed from the point of view of their ultrastructure and adaptative morphology.

Responses Of Astrocytes In Culture After Low Dose Laser Irradiation, David T. Yew, D. R. Zheng, C. Au, W. W. Y. Li

Scanning Microscopy

The effect of Helium-Neon low dose laser on astrocytes was investigated in cultures of isolated astrocytes from albino neonatal rats. The laser appeared to inhibit the growth of astrocytes as exemplified by the smaller sizes of the cells and the decreased leucine uptake in each cell after treatment. Temporary decrease in the number of mitoses was also observed, but this trend was reversed soon after. Electron microscopic studies revealed an increase in buddings from cell bodies and processes (branches) after irradiation.

Detector Arrays In Confocal Scanning Microscopes, T. Wilson

Scanning Microscopy

We consider the use of detector arrays in scanning microscopes and show that confocal operation may be achieved in a variety of ways. We base our analysis on a consideration of the form of the optical transfer function or transmission cross coefficient. This reveals that the Fourier transform of the detector sensitivity function is the function of importance. It is not necessary that this function be constant over the whole space and hence a variety of detector sensitivity functions will give fully confocal imaging. The traditional method of a limiting point-like detector is a special case, but one which has …

Crystal Growth Of Calcium Oxalate Monohydrate And Calcium Carbonate From Dilute Solutions, Sergio Deganello, Livia Di Franco

Scanning Microscopy

By controlling evaporation, calcium carbonate (calcite) is precipitated together with calcium oxalate monohydrate from equimolar (1 x 10^-5 M) solutions of calcium chloride and sodium oxalate under decreasing (37.5° - 32.7°C) and increasing temperature (22°-42°, 22°-45°, 22°-50°C), and initial pH's of 6.6 and 6, respectively. If, however, the pH of the solutions is, respectively, 8 and 8.5 and the temperature is 32°C, oxalate breaks down to carbonate and calcium precipitates solely as calcite. This process materializes as the pH of both solutions initially adjusts to about 7.5. Both the quality and the size of the crystals of calcite and …

Particle Induced X-Ray Emission Elemental Analysis: Sample Preparation For A Versatile Instrumental Method, N. F. Mangelson, M. W. Hill

Scanning Microscopy

Particle induced X-ray emission (PIXE) has found extensive application as a multi-element analysis tool. The energetic nature of both the incident particle beam and the emitted characteristic X-rays has lead to considerable versatility in regard to samples which may be analyzed by the PIXE technique. This paper does not deal with the theory, equipment, or data analysis for PIXE, but it should bring to the reader a broad perspective of methods for sample preparation and should point the way into the literature where more complete details are given. Both physical and chemical processes for sample preparation are outlined. Preparation often …

Evidence That A Major Portion Of Cellular Potassium Is "Bound", Ivan L. Cameron, W. Elaine Hardman, Keithley E. Hunter, Christine Haskin, Nancy K. R. Smith, Gary D. Fullerton

Scanning Microscopy

In this report we briefly review recent evidence which shows that a substantial proportion of intracellular K⁺ is "bound" or perturbed from the physicochemical properties expected in dilute aqueous solutions. In addition, we present evidence from electron probe x-ray microanalysis of thin cryosections of cells which indicates that the binding of K⁺ to anionic groups either carboxyl groups (HCO₂) on proteins or to phosphate groups in creatine phosphate (CrP) , in adenosine triphosphate, (ATP), in protein and in nucleic acids, are the main determinants of the maintenance of (as differentiated from the generated of) the well …

Composition Depth Profiles Of High Temperature Superconducting Materials By Energetic Elastic Backscattering, C. R. Gossett

Scanning Microscopy

A review is given of the application of high energy elastic backscattering spectrometry techniques for profiling high-temperature superconducting (HTSC) materials in thin film form. The use of higher bombarding ion energies provides most of the advantages of the more common lower energy or Rutherford backscattering (RBS) but additionally allows profiling to a greater thickness and, by a much larger sensitivity for light elements, permits profiling carbon and oxygen in the presence of heavier substrates. Examples for HTSC materials are given.

Studies Of Irritant Reactions On Epidermis: The Application Of Energy Dispersive X-Ray Microanalysis, Magnus Lindberg

Scanning Microscopy

Modern man is exposed to an increasing amount of chemicals in the environment. The skin is a complex tissue with regards to both structure and function. Contact with external stimuli can lead to various responses in the skin depending on the type of stimuli, the dose and time of exposure and the status of the exposed individual. The electron probe microanalytic technique can be used to obtain information on physiological alterations within the skin and especially the epidermis when the normal homeostasis is disturbed by contact with external stimuli. The present paper presents a review of some aspects of contact …

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.