Biology Commons^™

Approach To A Stable Field Emission Electron Source, H. Adachi

Scanning Electron Microscopy

Field emission occurs at the sharp apex of a metal needle, so that it can be considered as providing a point electron source, which is a desirable feature for a fine focused electron beam. The disadvantage is its low stability. It is shown that the current fluctuations occur mainly due to the interaction with the residual gas in the vacuum; thus reduction of the interaction with the residual gas is essential for a stable field electron source. The stringency of the vacuum requirement has prevented wide application of the field emission electron source. New materials which have low work functions …

Application Of Chelex Standard Beads In Integrated Morphometrical And X-Ray Microanalysis, W. C. De Bruijn, M. I. Cleton-Soeteman

Scanning Electron Microscopy

Chelex ion exchange beads loaded with a known amount (18.3% weight percentage (w/w)) of platinum, have been co-embedded with a mouse peritoneal cell population. To establish the influence of the various deconvolution methods applied, upon the platinum concentration in cytoplasmic granules and erythrocytes these cross-sectioned beads are used as a standard. It is concluded that irrespective of the deconvolution method chosen 1) the Pt concentration inside the particles is identical when the particles and the co-embedded Chelex Pt standard, are analysed strictly under the same instrumental conditions 2) the Pt concentration outside the particle is zero, or virtually zero when …

Development Of Fungal Calcium Oxalate Crystals Associated With The Basidiocarps Of Geastrum Minus (Lycoperdales), H. T. Horner, L. H. Tiffany, A. M. Cody, G. Knaphus

Scanning Electron Microscopy

Calcium oxalate crystals were observed on facing peridial surfaces of developing basidiocarps of Geastrum minus. Five crystal forms were characterized by their outward shapes and X-ray diffraction patterns: Form One, small bipyramids (COD); Form Two, crystals with split tips (COD); Form Three, crystals with oriented overgrowths (COD); Form Four, large bipyramids (COD); and Form Five, rosettes of plate-like crystals (COM). Forms One and Two were first to appear after peridia separated in unopened basidiocarps, whereas Forms Three, Four and Five were present on exposed peridia of opened basidiocarps. Based on time of appearance …

Scanning Electron Microscopy As An Analytical Tool For The Study Of Calcified Intrauterine Contraceptive Devices, S. R. Khan, E. J. Wilkinson

Scanning Electron Microscopy

Within the endometrial cavity intrauterine contraceptive devices (IUDs) become encrusted with cellular, acellular, and fibrillar substances. Scanning electron microscopy was used to study the crust. Cellular material consisted mainly of blood cells and various types of bacteria. The fibrillar material appeared to be fibrin which was omnipresent in the crust and formed a thin layer immediately over the IUD surface. X-ray microanalysis of the acellular component of the crust revealed the presence of calcium. No other major peaks were identified. Near the IUD surface characteristic calcium phosphate crystals were present. Their microanalysis showed peaks for calcium and phosphorus. X-ray diffraction …

The Pleurograms And Seed Surface Patterns Of Some Mimosoideae (Leguminosae) Genera, Randy T. Baker, Terry L. Bridges, Louis H. Bragg

Scanning Electron Microscopy

Seeds of twenty species representing eight mimosoid genera were examined with scanning electron microscopy (SEM) to determine if variations in the pleurograms and seed topographies exist and if these variations might have taxonomic potential. The pleurogram has been previously considered a feature of many mimosoid seeds but has not been adequately described and critically evaluated as to its shape and other features. The pleurogram shapes of the examined seeds can be placed in four general categories: elliptic, ovate, obovate, lanceolate. If the length/width ratio of the pleurogram is considered as well as the extent of the openness of the pleurogram …

Recent Advances In X-Ray Microanalysis In Dermatology, Bo Forslind, Thomas G. Grundin, Magnus Lindberg, Godfried M. Roomans, Ylva Werner

Scanning Electron Microscopy

Electron microprobe and proton microprobe X-ray analysis can be used in several areas of dermatological research. With a proton probe, the distribution of trace elements in human hair can be determined. In contrast to sulfur, which is homogeneously distributed, calcium, iron, and zinc appear to be non-homogeneously distributed over the hair cross-section.

Electron microprobe analysis on freeze-dried cryosections of guinea-pig and human epidermis shows a marked gradient of Na, P and K over the stratum granulosum. In sections of freeze-substituted human skin this gradient is less steep. This difference is likely to be due to a decrease in water content …

Post-Mortem Storage Of Tissue For X-Ray Microanalysis In Pathology, Godfried M. Roomans, Joanna Wroblewski

Scanning Electron Microscopy

Possible alternatives to rapid freezing in liquid nitrogen of tissue for X- ray microanalysis of electrolytes at the cellular level were investigated. These alternatives might be used in cases where tissue becomes available for examination, e.g., at autopsy, but liquid nitrogen is not immediately available. Rat submandibular gland was used as a test tissue. Freezing of pieces of tissue in a conventional freezer at -80°C or even at -20°C retained the elemental distribution at the cellular level, and also retained the difference between a 'normal' and a 'pathological' (mimicked by an inject ion of a high dose of isoproterenol) situation. …

The Application Of Physico-Chemical Procedures In The Analysis Of Urinary Calculi, Allen L. Rodgers

Scanning Electron Microscopy

All physico-chemical techniques used in the analysis of urinary calculi have inherent advantages and limitations. Al though x-ray powder diffraction can identify constituents unambiguously, certain minor components can be missed. Infrared spectroscopy is more sensitive but band assignment at low concentrations is difficult. Scanning electron microscopy together with energy dispersive x-ray analysis permits the simultaneous investigation of morphology and chemical microstructure. However, microanalysis of elements lighter than sodium is not possible and constituents are prone to irradiation damage. With the electron microprobe, minor constituents can be detected but tedious sample preparation procedures are required. Transmission electron microscopy is extremely useful …

The Ballistic Phonon Signal In Low Temperature Scanning Electron Microscopy, R. P. Huebener, W. Metzger

Scanning Electron Microscopy

By scanning the surface of a specimen cooled to liquid-helium temperature with the electron beam, ballistic phonons are generated which can be used for acoustic imaging. The anisotropy of the ballistic phonon propagation caused by the phonon focusing effect has been observed in recent experiments. The simultaneous operation of two or more small-area phonon detectors during the scanning process appears promising for three-dimensional acoustic imaging of structural inhomogeneities even far from the specimen surface. The principles of this scheme for acoustic imaging are discussed and the spatial resolution limits are estimated.

Towards The Ultimate Scanning Electron Microscope, Albert V. Crewe

Scanning Electron Microscopy

An analysis of all the factors which contribute to the electron probe size in a scanning electron microscope and of the correct method of combining those effects to give optimum performance. Assuming perfect specimen preparation the only other factors are the non-local nature of the basic electron interactions and the nature of the display system.

Analysis Of Backscattered Electron Signals For X-Ray Mask Inspection, Michael G. Rosenfield

Scanning Electron Microscopy

A rapid and automated inspection system is a necessity for the detection of defects in x-ray and optical lithography masks. The design of an electron-beam mask inspection system requires a complete understanding of the backscattered electron signal from the various defects which will be encountered. A Monte Carlo simulation program has been used to study the effects of electron-beam size, detector placement, defect type, electron-beam voltage, and absorber thickness on the back-scattered electron signal.

Early Development Of The Vertebrate Limb: An Introduction To Morphogenetic Tissue Interactions Using Scanning Electron Microscopy, Robert O. Kelley

Scanning Electron Microscopy

The developing limbs of most vertebrates serve as a model system for studies of morphogenesis, pattern formation, cell and tissue interactions and cell differentiation. Mesoderm in the flank of the embryo induces overlying ectoderm to form a thickened, stratified or pseudo-stratified epithelium which becomes the highly specialized apical ectodermal ridge. In turn, the apical ridge specifies individual limb parts (first from structures proximal to the body axis, then to more distal components) and is required for those elements to form. If the ridge is removed, subsequent limb development ceases and no further limb parts appear. The series of ectodermal-mesodermal interactions …

Progress In High Resolution Scanning Ion Microscopy And Secondary Ion Mass Spectrometry Imaging Microanalysis, R. Levi-Setti, G. Crow, Y. L. Wang

Scanning Electron Microscopy

The performance of a new high resolution scanning ion microprobe (SIM) is elucidated with regard to imaging capabilities using the ion-induced secondary electron (ISE) or secondary ion (ISI) signals, and the mass-resolved signal from a secondary ion mass spectrometry (SIMS) system. The new instrument focuses a beam extracted from a liquid metal ion source (LMIS) to a range of spot sizes reaching the 20 nm level. The probe current (1.6 pA) available at this level of lateral resolution, which approaches the theoretical resolution limits of the SIMS method, is still adequate to obtain detailed isotopic maps for surfaces rich in …

A Scanning Electron Microscopic Technique For Three-Dimensional Visualization Of The Spatial Arrangement Of Metaphase, Anaphase And Telophase Chromatids, David A. Welter, Lon D. Hodge

Scanning Electron Microscopy

Chromosome and chromatid alignment in mitotic configurations remains a topic of interest because there is little precise information. For example, reconstruction of mitotic configurations from serial sections collected with transmission electron microscopy has proven to be neither practical nor a sensitive method for conceptualizing these arrangements. Similarly light microscopy has been even more unsatisfactory because of its limited resolution and lack of three-dimensional capabilities. These limitations conceivably could be overcome by visualization of mitotic configurations by scanning electron microscopy (SEM). However, SEM has its limitations, of which the most obvious with regard to visualization of mitotic configurations, is that such …

The Use Of The Scanning Electron Microscope In Studying The Heat Treatment Of Prehistoric Lithic Artifacts From The North Florida Weeden Island Period Mckeithen Site, G. Michael Johnson

Scanning Electron Microscopy

In this paper, I discuss a study in which I attempted to determine whether or not the inhabitants of the McKeithen site, a Weeden Island Period mound and village complex in what is today northern Florida, employed heat treatment as part of their lithic reduction technology, and if so, at what point in the reduction sequence it was conducted. I used a scanning electron microscope (SEM) to photograph raw and heat treated control samples of northern Florida chert, then debitage and tools of chert and silicified coral from the McKeithen site which represented the range of colors and luster present …

Analysis Of Minerals Using Specimen Isolated Secondary Ion Mass Spectrometry, J. B. Metson, G. M. Bancroft, H. W. Nesbitt

Scanning Electron Microscopy

Considerably improved suppression of molecular ions in secondary ion mass spectrometry (SIMS) spectra of nonconductor minerals has been obtained using a CAMECA IMS-3f ion microscope with unconventional operating conditions [so-called specimen isolated (SI) conditions]. In a zircon spectrum close to forty elements are positively identified and molecular ions such as oxides and hydrides have very low intensities. Thus, with a ²⁸Si⁺ intensity of 10⁶ cps, the Si⁺/Si0⁺ ratio is 10⁵, and the ³⁰SiH⁺ intensity is low enough to enable quantitative analysis using ³¹P⁺ down to 0.01 wt % …

Microprobe Analysis In Human Pathology, D. Baker, K. G. Kupke, P. Ingram, V. L. Roggli, J. D. Shelburne

Scanning Electron Microscopy

This tutorial paper reviews the literature on the application of microprobe analysis to practical problems in diagnostic human pathology. The goal is to allow the reader ready access to the literature on specific clinical problems. Specimen preparation and commonly encountered artifacts are also considered. It is concluded that energy dispersive x-ray microanalysis and backscattered electron imaging are at present the most generally useful microprobe techniques for clinical work, and are no longer solely research tools. The findings often have diagnostic, therapeutic, and/or legal implications.

Calcium Oxalate Urolithiasis In The Rat: Is It A Model For Human Stone Disease? A Review Of Recent Literature, S. R. Khan, R. L. Hackett

Scanning Electron Microscopy

Calcium oxalate stone disease is the most common human urinary stone disease in the Western Hemisphere. To understand different aspects of the disease, calcium oxalate urolithiasis in the rat is used as a model. Spontaneous calcium oxalate urolithiasis is very rare in rats. Thus the disease is experimentally induced and the rats are generally made hyperoxaluric either by administration of excess oxalate, exposure to the toxin ethylene glycol, or various nutritional manipulations. All the experimental models show renal injury associated with crystal deposition. Calcium oxalate crystals are in most cases intraluminal in renal tubules and often attached to the basal …

Electrical Surface Breakdown: Secondary Electron Emission And Electron Spectroscopy Of Insulators, J. P. Vigouroux, C. Le Gressus, J. P. Duraud

Scanning Electron Microscopy

These results question the usual scheme of flashover. They lead to a different interpretation based on classical concepts in solid state physics which can be verified at every step. An ionizing cascade in the bands, rather than a cascade of electron multiplication on the insulating surface, could explain the flashover, the conditioning and the deconditioning of high voltage generators through the building of a surface charge. As in the usual model the positive charge is responsible for the flashover, in this new model the building of this charge is the basis of the conditioning. The ionizing cascade in the bands …

Summary Of The Results Of Analysis Of Obsidian Artifacts From The Maya Lowlands, F. W. Nelson

Scanning Electron Microscopy

The analytical method of X-ray fluorescence spectrometry has been used to analyze obsidian artifacts from Cerros, Belize and from Yaxchilan, Chiapas, Mexico. The results of these analyses are compared to the results of analysis of obsidian geologic sources using graphical and statistical methods in order to identify the probable source from which the obsidian for the artifacts came. These results are then summarized along with results of analysis by others of obsidian artifacts from several archaeological sites in the Lowland Maya area. Using these data, possible trade routes and how they may have changed through time have been postulated.

Foliar Penetration Of A Fungicide As Detected By Scanning Electron Microscopy And Energy Dispersive X-Ray Analysis, C. R. Krause

Scanning Electron Microscopy

CU II hydroxide, (Cu(OH)₂) a fungicide, produces injury as a result of "chemical burn" or phytotoxicity on some plants. Scanning electron microscopy and energy dispersive X-ray analysis were used to characterize chlorosis on red maple leaves following foliar applications of Cu(OH)₂. Copper was located with X-ray mapping in foliar mesophyll cells of trees sprayed with Cu(OH)₂ but not in leaves of trees sprayed with distilled H₂O.

Computerized Microtomography In Scanning Electron Microscopy, A. Yu. Sasov

Scanning Electron Microscopy

Non-destructive methods of inner object structure reconstruction in the scanning electron microscope (SEM) have been studied. For specimens with a size of about 1 mm a spatial resolution of 10 μm has been achieved. The reconstruction is made from a project ion in X-ray radiation. Algorithms of conventional computerized tomography are used. The application of 3-dimensional reconstruction to different types of microobjects has been shown. As an example, microtomography of organic objects (grass grain, beetle head) and inorganic objects (semiconductor diode) has been carried out.

Geological Applications Of Ionization Lte Model In Laser Probe Mass Spectrometry, J. F. Eloy

Scanning Electron Microscopy

Recently, the laser plasma ionization process of the laser Probe Mass Spectrograph permitted one to obtain quantitative information on the fluid inclusions and trace distributions in ores. Indeed laser ionization provides the physical conditions for a substantial application in the Local Thermodynamical Equilibrium (LTE) model. Other geological information in the case of micro-analysis on the quartz, fluorite, and zircon has also been obtained.

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 …

Scanning Electron Microscope Cytochemistry Of Blood Cells, D. Soligo, E. De Harven, E. Pozzoli, M. T. Nava, N. Polli, G. Lambertenghi-Deliliers

Scanning Electron Microscopy

The backscattered electron imaging (BEI) mode of scanning electron microscopy (SEM) has been applied to study various histo-cytochemical reactions in biological specimens since the early seventies. Due to numerous, recent technical improvements the BEI mode of SEM now belongs to the routine of many SEM laboratories.

For cytochemistry, BEI has been mainly used to: visualize intracellular structures and organelles; recognize the different cell types in heterogeneous populations or tissues; study the correlations between enzymatic activities and cell surface features.

We have evaluated the most relevant results obtained in the study of blood cells and the possible future applications of these …

Structural Changes In Mouse Small Intestinal Villi Following Lower Body Hyperthermia, H. M. H. Kamel, K. E. Carr, S. P. Hume, J. C. L. Marigold

Scanning Electron Microscopy

Heating an exteriorised loop of mouse small intestine resulted in marked changes in the shape of the villi as reported earlier. However, the exteriorisation techniques resulted in non-uniformity in both temperature and effect around circumference of intestine and, in addition, the extent to which handling contributed to the observed damage was not known. The work has therefore been extended using lower-body heating in the temperature range 37.5° - 43.0°C.

Heating in the temperature range 37.5° to 41.0°C produced minimal to moderate structural changes, manifested as scattered, vertically collapsed villi amongst predominantly "normal" villi. No villi showed conical or rudimentary forms …

Integration Of X-Ray Microanalysis And Morphometry Of Biological Material, W. C. De Bruijn

Scanning Electron Microscopy

It was investigated how to extract both morphometrical and X-ray elemental information from scanning electron microscopical (SEM) or scanning transmission electron microscopical (STEM)-images and how to integrate these two information streams either on line or off-line after storage.

Cytochemical reaction products in cell organelles in ultrathin sections are the biological structures of interest. In such organelles four different situations can be met: morphologically the structures are homomorph or heteromorph; chemically the elements are distributed either homogeneously or heterogeneously. A new program has been proposed and described, which permits determination of both the area and the mean net-intensity value of chemical …

Microstructural Matrix-Crystal Interactions In Calcium Oxalate Monohydrate Kidney Stones, J. Stacholy, E. P. Goldberg

Scanning Electron Microscopy

The role of the proteinaceous matrix in the formation of calcium oxalate kidney stones is still not well understood. Simple scanning electron microscopy (SEM) has been of somewhat limited value in visualizing the organic and inorganic microstructure due to difficulties in obtaining detailed structural information for cut or fractured surfaces.

To help clarify matrix-crystal microstructure, serial sections from 10-20 mm calcium oxalate calculi were partially demineralized with ethylenediamine tetraacetic acid (EDTA) and examined by SEM. Sections etched by EDTA showed a radial crystal structure composed of "microcrystal" subunits. Sections simultaneously EDTA etched and fixed with glutaraldehyde to insolubilize all matrix …

Near Edge Fine Structures On Electron Energy Loss Spectroscopy Core Loss Edges, C. Colliex, T. Manoubi, M. Gasgnier, L. M. Brown

Scanning Electron Microscopy

Core edges recorded in Electron Energy Loss Spectroscopy (EELS) display a large variety of profiles. We have investigated several specific aspects concerning Energy Loss Near Edge Structures (ELNES) and emphasize the interest in a careful edge shape analysis to obtain refined microanalytical information, such as local symmetry. After indicating the general impact of EELS fine structures as compared to EDX and Auger spectroscopies we discuss the instrumental conditions required for recording satisfactory spectra and consider the theoretical problems which are involved in data interpretation. The major portion of this paper presents results for selected K, L23, M45 and N45 core …

Relationship Of The Surface Structure Of Metaphase Chromosomes To The Higher Order Organization Of Chromatin Fibers, K. W. Adolph, L. R. Kreisman

Scanning Electron Microscopy

Scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM), has been utilized to determine how the surface structure of mitotic chromosomes is related to the organization of the 30 nm chromosomal fibers. SEM revealed the surfaces of isolated, HeLa cell chromosomes to possess a knobby substructure with chromosomes prepared for EM in buffers containing 0.5-1.5 mM Mg²⁺. These projections had substantially greater widths (65-70 nm) than the underlying chromatin fibers. Reducing the Mg ion concentration to 0.05-0.15 mM resulted in the further expansion of the chromosomes, which flattened the chromosomes for SEM so the fibers became …