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Low Voltage Scanning Electron Microscopy, James B. Pawley

Scanning Electron Microscopy

The scanning electron microscope (SEM) usually operates with a beam voltage, V₀, in the range of 10-30 kV, even though many early workers suggested the use of lower voltages to increase topographic contrast and to reduce specimen charging and beam damage. The chief reason for this contradiction is low instrumental performance when V₀ = 1-3 kV. The problems include low source brightness, greater defocussing due to chromatic aberration, greater sensitivity to internal and external stray fields and difficulty in collecting the secondary electron signal without defocussing the probe. Recently considerable efforts have been made to overcome these …

Determination Of Optical Properties Of A Field Emission Gun Coupled With A Linear Accelerator For High Voltage Microscopy, M. Denizart, S. Roques, F. Sonier, B. Jouffrey

Scanning Electron Microscopy

The electron optical properties of a field emission gun plus a twenty-stage linear accelerator system have been determined in the case where the entrance pupil of the system is defined by one of the electrode apertures.

The first part of the calculation concerns the electrical and geometrical parameters of triode and tetrode field emission guns which can give a fixed location of the source and a small spherical aberration coefficient.

The second part is related to the possibility of placing a tetrode field emission gun at the top of the linear accelerator of the scanning high voltage electron microscope which …

Recent Developments In Numerical Electron Optics, Erwin K. Kasper

Scanning Electron Microscopy

The familiar methods for the numerical calculation of fields in electron optical devices are outlined briefly. for the solution of self- adjoint elliptic differential equations in orthogonal curvilinear coordinate systems a favourable ninepoint discretization is worked out which can be applied favourably e.g. to spherical mesh grids. The field calculation in magnetic deflection systems by means of an integral equation method is also highly advantageous. The methods for the field calculation can be still more improved by means of suitable hybrid procedures.

A second and shorter contribution is concerned with ray tracing and aberrations. Some favourable numerically stable new forms …

Energy Selecting Electron Microscopy, F. P. Ottensmeyer

Scanning Electron Microscopy

One of the major improvements in transmission electron microscopy over the last years is the addition of the capability of producing images with electrons that have specific narrow energy bands out of the total spectrum of energies they possess after having passed through the specimen. Though the idea is not new, the power of this application is only beginning to be recognized. Most simply, selection of elastically scattered electrons permits increased contrast in high resolution i mages in bright field, dark field, and diffraction. The use of combined elastic and inelastic signals adds entirely new contrast mechanisms, partially independent of …

Mississippi’S Softwood Timber Potential: Private Nonindustrial Influences, Steven H. Bullard, G. H. Weaver, Willem W. S. Van Hees

Faculty Publications

Mississippi's long-run softwood timber potential was estimated for three input situations under a common set of economic and biological assumptions. Economic goals for sustained pine production were estimated using the computer program GASPLY with no restrictions, with private nonindustrial upland hardwoods excluded from type conversion and with private nonindustrial lands excluded from active forest management altogether. Estimated price-quantity equilibria ranged from $301 per thousand cubic feet (MCF) and 966 million cubic feet (MMCF) in the unrestricted case, to $1,226/MCF and 479 MMCF in the example with passive private nonindustrial management. Widely diffel'ing potential goals for pine product-ion highlight the degree …

Root Diseases And Blister Rust Associated With Bark Beetles (Coleoptera: Scolytidae) In Western White Pine In Idaho, David Kulhavy, A.D. Partridge, R.W. Stark

Faculty Publications

Root systems of western white pine, Pinus montieola Douglas, were excavated with explosives and examined for pathogens. Data were also recorded on portions of the crown killed by blister rust caused by Cronartium ribieola Fisch. Statistical tests revealed a significant association between the bark beetles Dendroetonus ponderosae Hopkins and Pityogenes fossifrons (LeConte), and the root pathogen Armillariella mellea. (Vah!. ex Fr.) Karst and between beetles and all root diseases. Ninety-two percent of the trees attacked by bark beetles had root diseases, and 97% had either root diseases or blister rust. A discriminant analysis correctly classified 88% of the sample trees …

Southern Oak Woodlands Of The Santa Rosa Plateau, Riverside County, California, Earl W. Lathrop, Henry A. Zuill

Aliso: A Journal of Systematic and Floristic Botany

No abstract provided.

An Analysis Of Microstructural Factors Which Influence The Use Of Muscle As A Food, R. G. Cassens, C. E. Carpenter, T. J. Eddinger

Food Structure

Study of structure of muscle provides information on the location and arrangement of various components and the changes which may be inflicted upon them. The structura l features of muscle have been descr ibed in detail down to the molecular level, but rega rding its use as a food, special interest centers on the connective tissue component and on myofibri llar proteins . Muscle comprises about 1/3 of the live weight of the a ni mal and is not static , but rather is subject to major changes in properties associated with growth, repair and se nescence. It is apparent …

Artefacts In Conventional Scanning Electron Microscopy Of Some Milk Products, Miloslav Kalab

Food Structure

Artefacts develop due to changes in the microstructure of the sample under study because of inappropriate preparatory steps and/or due to distortion of the images of properly prepared samples during operation of the microscope. Of a wide variety of possible artefacts. only those occurring mast frequently have been selected and ilustrated with micrographs. In milk powders, the most common artefacts are the recrystallization of lactose in a humid atmosphere, "1 ine" and "dark-area" charging artefacts, and electron beam damage. In moist milk products, artefacts may arise at any preparatory step, such as sampling, fixation, dehydration and critical-point drying or freezing …

The Role Of Gap Filaments In Muscle And In Meat, R. H. Locker

Food Structure

The neglected "gap filaments" are now beginning to receive close attention in several centers, in terms of organisation, composition and function. The author's model for their connections gave them a role as cores to A-filaments. This review attempts to weigh the implications of such a role, and relevant evidence, old and new. New ideas arising largely from PAGE*and immunochemkal studies on candidate proteins, and from the developing concept of the cytoskeleton, are considered.

The author's theory of meat tenderness, based on G-filaments, has been tested by PAGE studies on changes in the large structural proteins (particularly titin and nebulin) during …

Mineral Migration In The Wheat Kernel During Mill Conditioning, A. Al Saleh, B. Bouchet, D. J. Gallant

Food Structure

The structure and histology of the kernel govern migration of water during conditioning or drying. Studies by the energy dispersive x-ray system under the SEM have shown that during an increase of water content from 11.5 to 16.5 per cent, soluble elements migrated from the peripheral bran, accumulated in the aleurone cells and passed through its walls to the endosperm of the kernel if the water content was above 14.5 per cent. Results of study were compared with analyses of milling fractions obtained under the same conditions.

Ultrastructure Of Quinoa Fruit (Chenopodium Quinoa Willd), E. Varriano-Marston, Alicia Defrancisco

Food Structure

The structure of quinoa (Chenopodium quinoa) fruit before and after germination was studied using electron microscopy. Protective coverings include a perianth consisting of loosely adhering cell s which are readily removed by washing, a pericarp and two seed coat layers. Starch granules fill the perispenn cells and are arranged in 18 to 20 oblong aggregates. Limited hydrolysis of the starch occurs after 24 hrs of germination, with amylolytic erosion of large granules occurring at the hilum and periphery of the granul es. Ungerminated embryo cells contain protein bodies with phosphorus-containing globoid inclusions. Essentially complete hydrolysis of the embryo protein bodies …

Ultrastructural Studies Of Raw And Processed Tissue Of The Major Cultivated Mushroom, Agaricus Bisporus, E. M. Jasinki, B. Stemberger, R. Walsh, A. Kilara

Food Structure

Commercial mushroom processors currently lose approximately 30 percent of the mushroom weight due to shrinkage during processing (blanching and canning) , resulting in substantial economic losses . Microscopy was used to assess the extent and type of chemical and structural changes induced by processing mushrooms and causing shrinkage. Scanning electron microscopy revealed that the processing operations including vacuum hydration , blanching , and thermal treatment do not damage the integrity of the tissue. Light microscopy revealed that the morphology of the tissue, shape and spacing of cells, appear similar for raw and processed mushroom tissue . However, the intra ce …

Computer Programs For Analyzing Certain Classes Of 3-D Electrostatic Fields With Two Planes Of Symmetry, Norm Franzen

Scanning Electron Microscopy

At Tektronix, two classes of non-rotationally symmetric electrostatic lenses which lead to significant three-dimensional-field problems are currently under investigation. Extensive interactive computer programs have been developed to study these lens structures.

The first class is referred to as Klemperer lipped lenses; the accelerating quadrupole being the most important. Klemperer lenses are formed from shaped concentric cylindrical electrodes and employ two or three independent voltages. These lenses are predominantly of quadrupole type, but possess higher multipoles to correct for geometry distortion.

The second class of lenses, referred to as wafer-lenses, consists of lenses formed from spaced sequences of metal wafer electrodes …

Magnetic Electron Lenses, Wolfgang Dieter Riecke

Scanning Electron Microscopy

The electron optical properties of magnetic lenses are determined by the ratio S/D of gap width S to bore diameter D, by the actual size of the gap and by the lens strength NJ√U*. Objective lenses of particularly small aberrations are obtained if the specimen is positioned close to the center of the gap and if the width of the gap is made as small as possible. For projector lenses the best performance results if the lens is employed at its minimum focal length. Another aspect important for high resolution lenses is that a stigmator is available for the correction …

Progress In The Theory Of Electron-Beam Deflection, E. F. Ritz Jr.

Scanning Electron Microscopy

Analysis, simulation, and design of electron-beam-deflection systems are reviewed in light of the current state of theoretical understanding. A brief review of the physical principles is followed by a detailed discussion of electrostatic, magnetostatic, mixed-field, traveling-wave, and scan-expansion systems. Each methodology is examined from a triple perspective: calculation of electromagnetic fields, calculation of electron trajectories, and calculation of the ensemble of trajectories forming the beam. Applications discussed include deflectors for television displays, lithography, scanning microscopes, and CRT oscillography. Developments of the last ten years are stressed, thereby supplementing and updating the author's previous review on this subject.

In field calculation, …

Magnetic Electron Lenses Ii, T. Mulvey

Scanning Electron Microscopy

Conventional magnetic electron lenses have evolved to their present highly developed state under the pressure of meeting the exacting requirements of high resolution electron microscopy. More recently, however, the desire to extract quantitative analytical information from the specimen has led to significant changes in the design of electron optical systems. The introduction of efficient lanthanum hexaboride cathodes and high beam current field-emission sources has strengthened this tendency. In addition, more complex lens systems than previously envisaged are now possible since microprocessors can be employed to assist in the rapid and reliable readjustment of the lens system, including the extensive alignment …

Optimization Of Stroboscopic Electron Deflection Systems, H. Rose, J. Zach

Scanning Electron Microscopy

Highly corrected electron-beam blanking systems (EBBS) are required for analyzing fast periodic processes at submicron spatial resolutions by stroboscopic methods. The deleterious degradation of the probe during the blanking operation can be avoided by a new straight-vision deflection system. Chopping of the beam is performed within this system by deflecting it across a knife edge. Calculations demonstrate that this system should be able to generate almost rectangular beam pulses with rise times of a few picoseconds and spot sizes smaller than 0.5 µm. The proposed EBBS consists of two wedge-shaped plate capacitors located symmetrically about the midplane of a rotationally …

Electron Image Simulation: A Complementary Processing Technique, Michael A. O'Keefe

Scanning Electron Microscopy

At present it is difficult to use direct image processing techniques to determine the specimen structure from electron micrographs obtained under non-linear imaging conditions, and impossible when the effects of dynamical scattering are strong (as in the case of thicker specimens). However, computing techniques are available to simulate high-resolution transmission electron microscope (HRTEM) images of postulated model structures. With these techniques it is possible to confirm the validity of interpretation of recorded micrographs, to help analyze crystal defects, to characterize microscope parameters, and to determine the ranges of validity of commonly used interpretive approximations. Because processed micrographs can lead to …

A Computer Controlled Scanning Transmission Electron Microscope Equipped With An Energy Analyzer For Special Investigations On Electron Diffraction- And Channeling Patterns, W. Hylla, H.-J. Kohl, H. Niedrig, D. Wendtland

Scanning Electron Microscopy

A scanning electron microscope was equipped with a double tilting stage, driven by stepping motors, to investigate electron channeling patterns (ECPs) and large angle convergent beam patterns (LACBPs) of single crystals. Transmitted electrons may be energy-selected by a magnetic sector-field energy analyzer. The recording of experimental data and the experimental arrangement are controlled by a microprocessor system, including a picture storage unit of 512 x 512 pixels of 16 bit. Recorded patterns can be stored on 1 Megabyte floppies.

A set of useful programs allows one to perform calculations with stored patter ns, e.g., contrast enhancement or -inversion, noise reduction, …

Displays: Market And Technologies, Steve Blazo

Scanning Electron Microscopy

Displays provide the essential human interface to virtually all electronics instrumentation. The market is large with new applications appearing every year; sometimes with profound impact. Digital watches with liquid crystal displays appeared in the early 1970s and have virtually wiped out the mechanical timepiece industry. Personal computers with cathode ray tube (CRT) displays are proliferating with diverse applications in the industry and in the home. Work stations with high-resolution color displays are changing the way architects, draftsmen, and IC designers perform their job. The CRT is the dominant technology in today's market, and will, no doubt, continue to be for …

Field Emission Source Optics, L. W. Swanson

Scanning Electron Microscopy

The use of field emission processes as a means of generating high brightness sources of both electrons and ions is becoming of increasing practical use in electron/ion optical systems. A review is given of the source optics and emission characteristics of a zirconium oxide coated, <100> oriented, tungsten (Zr0/W(l00)), thermal field emitter electron (TFE) source and a liquid metal ion source (LMIS). The primary interest at present is the use of these high field sources in microprobe focusing columns where beam sizes of < 0.5 µm and target current densities of ~ 1 to 10 A/cm² (in the case of a LMIS) and 10² to 10⁴ A/cm² (in the case …

Electron Beam Deflection Without Off-Axis Aberrations, H. C. Pfeiffer, M. A. Sturans

Scanning Electron Microscopy

A novel focusing/deflection system for high accuracy, high throughput E-beam lithography, denoted as Variable Axis Immersion Lens (VAIL), has been successfully demonstrated. The main attributes of this system include: l) Perpendicular landing at all points of a deflection field > (10 x 10 mm), 2) Elimination of transverse chromatic aberration, 3) High resolution ( < 0.2μm edge slope) over the entire deflection field, 4) Elimination of eddy current effects in the target area, and 5) Total magnetic shielding of the target from external fields.

Synthesis Of Electron Lenses, M. Szilagyi

Scanning Electron Microscopy

This paper is a review of different approaches to one of the most ambitious goals of Electron and Ion Optics: to produce elements and systems with prescribed first-order properties and minimal aberrations. Synthesis of such elements is usually done in two steps: the first is a search for a field distribution with the given properties and the second is the reconstruction of electrodes (pole pieces) that would produce this field distribution. The first problem can be solved by the use of different techniques: Calculus of Variations, Dynamic Programming or Function Minimization. The second one is more complicated and requires a …

Extracellular Enzyme Production By Rhizopus And Mucor Species On Solid Media, D Thompson, Broderick Eribo

Department of Biology Faculty Publications

Solid media were employed to determine the presence and absence of extracellular enzyme production by two genera of fruit-rot fungi, Rhizopus and Mucor. The results of this investigation revealed that phosphatase was released into the cultural medium by all the fungi examined; however, only R. oryzae, R. tritici, M. mucedo, and M. piriformis showed the possibility of being high producers of the enzyme. Protease, urease, ribonuclease, pectate lyase, and polygalacturonase, at varying levels of activity, were detected, in the majority of the fungi, in the cultural medium.

Iowa Academy Of Science Leadership Directory And Membership Roster, 1984-85, Iowa Academy Of Science

Iowa Academy of Science Documents

Contents:

Board of Directors ... 3
Section Chairs ... 4
Section Vice Chairs ... 7
Committees ... 9
Award Recipients ... 25
Past Presidents ... 27
Membership Roster ... 28
Sprecial Directors ... 38

Ec84-1757 Who's Who In Great Plains Songbirds, Ron J. Johnson

University of Nebraska-Lincoln Extension: Historical Materials

Habitat is where wildlife live. It contains all things needed for survival, such as shelter, food, water, and space. There are different types of habitat, each supporting different kinds of wildlife. Examples of habitat types include woodlands or areas with trees, grasslands, old fields, brushy areas, or wetlands.

This publication describes several favorite birds and includes information on their special habitat needs, unique characteristics, nesting sites, where they are found, and their habits or behavior. If you want to help the feathered wildlife described in this publication - or just about any wildlife for that matter - think habitat. You …

Effect Of Monensin, Estradiol Controlled Release Implants And Supplement On Performance In Grazing Steers, J. F. Wagner, H. Brown, N. W. Bradley, W. Dinusson, W. Dunn, N. Elliston, J. Miyat, D. Mowrey, J. Moreman, L. C. Pendlum, C. Parrott, L. Richardson, Ivan G. Rush, H. Woody

Panhandle Research and Extension Center

Five trials in five locations in the United States involving 512 steers were conducted to evaluate the effect of monensin [200 mg/d in .9 kg of supplement (Rumensin)] and estradiol- controlled release implants (Compudose) administered alone and in combination on average daily gain (ADG) in steers on pasture. The effect of energy supplementation on rate of gain was also evaluated in these same trials. The initial weight of steers averaged 250 kg and the average duration of the five trials was 124 d. Estradiol-controlled release implants increased ADG by 15.6% (.095 kg/d; P<.0001) and monensin increased ADG by 8.1% (.054 kg/d; P<.05). The combination of estradiol-controlled release implant and monensin increased ADG by 27.4% (.I68 kg/d). Treatment responses were additive relative to ADG response, with no interaction observed between the treatments. Nine-tenths kilogram of an energy supplement/d increased ADG by 12.4% (.073 kg/d; P<.Ol).

Discrimination And Generalization Of Leaf Damage By Blue Jays (Cyanocitta Cristata), Pamela G. Real, Ruth Iannazzi, Alan C. Kamil, Bernd Heinrich

Papers in Behavior in Biological Sciences

Blue jays (Cyanocitta cristata) responded to projected black-and-white silhouettes of cherry leaves that were either undamaged or were damaged by either cryptic caterpillars that disguise leaf damage due to their feeding or by noncryptic caterpillars that do not disguise leaf damage due to their feeding. Pecks to the key on which the images were projected were reinforced only if interresponse times fell within specified temporal boundaries. These boundaries were different in the presence of the two types of leaf damage. Following training with one exemplar of each damage type, the jays correctly categorized novel instances of both types. …

An Ultrastructural Study Of Transmitting Tissue Development In The Pistil Of Lilium Leucanthum, Stanley R. Gawlik

Biology Faculty/Staff Publications

A study of developing transmitting tissue of Lilium Leucanthum pistils was undertaken in order to correlate structure with function. Lining the stylar canal are stigmatoid cells which contain a secretory zone consisting of a labyrinth of wall ingrowths characteristic of transfer cells. The functional feature of the labyrinth is a high surface-to-volume ration that facilitates an intensive transmembrane flux of solutes. Stigmatoid cells in various stages of development and maturation have been investigated with the aid of electron and light optics in conjunction with cytochemical techniques. During the development of the secretory zone, vesicles, formed by hypersecretory dictyosomes, fuse with …