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Development Of Structured Regression Hypotheses Interactive/Descriptive Geometry Through Five Dimensions, United States Department Of Agriculture, Forest Service

Miscellaney

Regression hypotheses admitted to statistical evaluation should, of course, be germain to relations between the variables considered. This constraint is easily violated with the screening of arbitrarily adopted sets of hypotheses. Sequential polynomials in additive models, for example, may include components that are not commensurate with expectation (prior knowledge) and may not include those that are (e.g., unique interaction terms) and, since the analytical results from the screening of meaningless hypotheses may themselves be meaningless, there is substantial incentive for serious preanalysis consideration of the hypotheses to be evaluated.

Ab Initio Comparison Of H Bonds And Li Bonds. Complexes Of Lif, Licl, Hf, And Hcl With Nh3, Z. Latajka, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Ab initio calculations are carried out on the complexes H₃N–LiF, H₃N–LiCl and their analogs H₃N–HF and H₃N–HCl as well as the isolated subunits. Double‐zeta basis sets, augmented by two sets of polarization functions, are used in conjunction with second‐order Moller–Plesset perturbation theory (MP2) for evaluation of electron correlation effects. The Li bonds are found to be substantially stronger than their H‐bonding counterparts, due in large measure to the greater dipole moments of the LiX subunits. Correlation has a large effect on the geometry and energetics of …

Electrostatic And Magnetic Imaging Without Image Rotation, Zhou Li-Wei, Ni Guo-Qiang, Fang Er-Lun

Scanning Electron Microscopy

A method is discussed for designing electrostatic and magnetic imaging systems without image rotation. Tsukkerman's condition for an imaging system free of rotation does not appear to be applicable to practical designs. We have modified his theory to obtain two other conditions for the normalized axial electric potential V(z), the normalized axial magnetic induction G(z), and a lens strength parameter 𝞴 which can be interpreted as an eigen-value. Some analytical examples and numerical results are given.

The Influence Of Sample And Detector Angles Upon Auger Electron Signal, Robert L. Gerlach

Scanning Electron Microscopy

The effects of the sample to incident electron beam angle and of the detector. angle on the Auger electron signal are important for quantitative Auger analysis, particularly for Auger mapping and line scans. A first approximation, single scattering, mean free path model is employed to simulate the Auger signal resulting from a range of sample and detector angles. The model is single scattering in the sense that the excitation path is taken to be a straight line into the solid. A second model approximates multiple scattering by a normal distribution of ionizing flux angles about the incident beam direction.

Since …

Various Attempts To Reduce The Dimensions Of Magnetic Electron Lenses Used For High Voltage Microscopes, J. L. Balladore, R. Murillo, J. Trinquier

Scanning Electron Microscopy

Magnetic fields are used in electron microscopy for a variety of purposes: image formation, energy analysis and correction of astigmatism, for example.

We are interested in the problems of designing short focal length lenses to be used for focusing high energy electrons in the energy range 1-3 MeV.

These lenses are generally very large and we have tried to reduce their dimensions to simplify their construction and use. From this point of view, it is necessary to diminish the magnetic coil and the magnetic circuit iron.

Several solutions have been proposed in the case of the coil. We have obtained …

A Comparison Of Lanthanum Hexaboride, Cold Field Emission And Thermal Field Emission Electron Guns For Low Voltage Scanning Electron Microscopy, J. Orloff

Scanning Electron Microscopy

A comparison of lanthanum hexaboride, cold W(310) field emission and Zr/W thermal field emission cathodes was made by calculating the current-spot size relationship for each, using comparable lenses, to determine which would be suitable for high current operation at 1 keV beam energy, with a focused beam diameter < 0.05 μm. On the criteria of highest current, reasonable operating conditions for the gun for low noise operation and long term cathode stability it was found that the lanthanum hexaboride and cold field emission cathodes are inadequate or marginal and that the best performance is obtainable from the thermal field emission cathode.

Electron Detectors Used For Imaging In The Scanning Electron Microscope, V. N. E. Robinson

Scanning Electron Microscopy

Electron detectors used for imaging in the scanning electron microscope include those which detect secondary electrons, various portions of the backscattered electron signal, and the residual specimen current. The use of a different detector will often produce a different image of the same specimen. The information contained in these images depends upon the signal detected and the properties of the detector used. The choice of detector to be used depends upon the information desired.

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 …

Ab Initio Study Of Fh–Ph3 And Clh–Ph3 Including The Effects Of Electron Correlation, Z. Latajka, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Ab initio calculations are carried out for FH–PH₃ and ClH–PH₃ using a basis set including two sets of polarization functions. Electron correlation is incorporated via Møller–Plesset perturbation theory to second and (in part) to third orders. The basis set is tested and found to produce satisfactory treatments of subsystem properties including geometries and dipole moments as well as the proton affinity and inversion barrier of PH₃. Electron correlation is observed to markedly enhance the interaction between PH₃ and the hydrogen halides. Its contribution to the complexation energy is 30% …

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 …

Food Microstructure

Food Structure

No abstract provided.

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 …