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Elastic Scattering Of Electrons By Atoms, P. Rez

Scanning Electron Microscopy

Elastic scattering is defined as scattering in which the incident particle or radiation does not give up any of its energy to the scatterer. Electrons are elastically scattered in atoms by both the nucleus and the atomic electrons which screen the nuclear charge. When considering only nuclear scattering the first Born approximation quantum mechanical cross section and the classical Rutherford cross section are identical. The effects of the atomic electrons can be taken into account by a simple screening term or by more exact treatments based on Hartree-Fock or Dirac-Fack wave functions. The partial wave expansion can be used to …

Interaction Of Electron Beam With The Target In Scanning Electron Microscope, Koichi Kanaya, Susumu Ono

Scanning Electron Microscopy

Based on the fundamental potential function of the power and exponential forms, a diffusion model of electron beams penetrating in a target has been proposed to take place throughout a hemisphere with a centre located at the most probable energy dissipation depth, related to the diffusion depth and the maximum energy dissipation depth, which is found to agree well with the empirical data of back-scattering coefficient as a function of the incident energy.

Based on the energy retardation power formula concerning the penetration and the energy loss of an electron probe into solid targets, the secondary electron emission yield has …

Secondary Electron Emission, Hellmut Seiler

Scanning Electron Microscopy

The paper surveys experimental and theoretical work on secondary electrons released by primary electrons with energies greater than 100 eV with regard to electron microscopy and microanalysis. The secondary electron emission is a rather complex phenomenon: 1) The interaction of energetic primary electrons with material and the excitation of electrons of the solid into higher energetic states, 2) The transport of the electrons to the solid-vacuum interface, 3) The emission of secondary electrons over the surface barrier into the vacuum.

For the interpretation of scanning electron micrographs especially the secondary electron yield is important, the escape depth of the secondary …

Direct Monte Carlo Simulation Of Kv Electron Scattering Processes-N(E) Spectra For Aluminum, Ryuichi Shimizu, Shingo Ichimura

Scanning Electron Microscopy

A Monte Carlo simulation of the scattering processes of kV electrons penetrating into aluminum was performed. The simulation is based on the use of different types of differential cross-sections for individual elastic and inelastic scattering: (i) the differential cross-sections derived by the partial wave expansion method for elastic scattering, (ii) Gryzinski's excitation function for inner-shell electron excitation, (iii) Streitwolf's excitation function for conduction electron excitation, (iv) Quinn's mean free path for plasmon excitation.

The main purpose of this work is to see how accurately the present direct Monte Carlo simulation describes the backscattered electrons from Al, which is the most …

Backscattered Electron (Bse) Imaging In The Scanning Electron Microscope (Sem) - Measurement Of Surface Layer Mass-Thickness, Oliver C. Wells, Richard J. Savoy, Phillip J. Bailey

Scanning Electron Microscopy

Sometimes, the sample to be examined in the SEM will consist of a compositionally non-uniform substrate that is covered by an approximately uniform surface layer. With a low enough incident beam energy, only the surface layer can be seen in the SEM image. The underlying structure can be seen in the secondary electron (SE) image if the range of the incident electrons is greater than twice the thickness of the surface film. In the backscattered electron (BSE) image the threshold energy is higher because the BSE detector is insensitive to slow electrons. The information depth in the BSE image was …

Monte Carlo Calculations On Electron Backscattering In Amorphous Or Polycrystalline Targets, G. Soum, H. Ahmed, F. Arnal, B. Jouffrey, P. Verdier

Scanning Electron Microscopy

We propose an application of the Monte Carlo method in the field of backscattering. The results obtained for incident electron energies ranging from 0.3 to 3 MeV and for targets of Al, Cu, Ag and Au are compared with experimental values from several sources.

An electron travelling through matter undergoes successive collisions between which it is assumed to travel in a straight line. In our case, we consider the elementary process of interaction electron-nucleus; we have used analytical models for the scattering cross-sections. In order to follow the electron through the specimen, we divide the real trajectory into elements of …

Gaussian Models For The Energy Distribution Of Excitation In Solids: Applications To X-Ray Microanalysis And Solid State Electronics, David B. Wittry

Scanning Electron Microscopy

Gaussian models for the depth distribution of excitation in a solid bombarded by an electron beam have been successfully applied to the interpretation of data obtained in electron probe x-ray microanalysis (spatial resolution and absorption effects) and to the study of voltage dependence of cathodoluminescence and the voltage dependence of electron beam induced currents at Schottky barriers. In these applications, it was assumed that the distribution of excitation with depth can be scaled in depth according to the range-energy equation: R = CEⁿ_o. The physical basis for this range-energy equation is the Bethe equation for electron energy …

Analytical Models In Electron Backscattering, Heinz Niedrig

Scanning Electron Microscopy

The different aspects of electron backscattering from solid films are calculated in terms of simple analytical models for thin films and bulk targets, for normal and oblique incidence. Well-known models regard only one scattering aspect, e.g.: single Rutherford scattering by Everhart's model, diffusion from a point source by Archard's model, diffusion from sources continuously distributed over the depth of the target by Thümmel's model. A few analytical models have been developed recently regarding single scattering and continuous diffusion, e.g. by Werner and by the author. These models allow us to calculate analytically the backscattering coefficient for bulk targets versus atomic …

The River Of Sorrows: The History Of The Lower Dolores River Valley, U.S. Department Of The Interior

Elusive Documents

No abstract provided.

Correlation Of Microscopic Structure Of Corn Starch Granules With Rheological Properties Of Cooked Pastes, D. D. Christianson, F.L. Baker, A.R. Loffredo, E. B. Bagley

Food Structure

The progressive geometric changes that occur in swelling of corn starch granules during heating throughout the range of gelatinization (63-72°C) and at higher temperatures when substantial amount s of soluble starch are released from the granule were observed by scanning electron microscopy (SEM). Corn starch granules begin to swell radially, then undergo radial contraction and random tangential expansion. They form complex geometrical structures at the midpoint range (67-70°C) unlike the more uniform single-dimensional tangential swelling that occurs with lenticular granules of wheat starch . At higher temperatures, when starch begins to solubilize, corn starch granules lose their distinct ridges and …

Electron Microscopy Of Milk And Milk Products: Problems And Possibilities, D. G. Schmidt

Food Structure

Milk and dairy products have frequently been studied by transmission- and scanning electron microscopy. The specimen preparation procedure may considerably influence the final result, and formation of artefacts is frequently observed. In this respect, formation of ice crystals during cryofixation is a well-known phenomenon. But dehydration, to an extent such as is required for embedding procedures, also appears to be harmful to dairy products. Micrographs of thin sections of plastic- embedded samples of casein submicelles show threadlike material, whereas in freeze-etched specimens only spherical particles are found. Similar observations are made when samples of cheese and of concentrated milk are …

Structure And Properties Of The Particulate Constituents Of Human Milk. A Review., M. Ruegg, B. Blanc

Food Structure

Milk contains different types of colloidal or coarsely dispersed particles, such as casein micelles, membrane fragments, fat globules and cells. The fat globules are composed of subpopulations of differently sized particles. In contrast to COW 1S milk, the overall average diameter (dys), increases with advancing lactation from about 1.8 ~min colostrum to 4.0 ~min mature milk. Membrane materials originating from the milk fat globule membrane, plasma membrane, secretory vesicles and other sources can be found in milk serum. These particles have also been called lipoprotein particles. Their size ranges from about 10 - 400 nm. New results concerning the structure …

Aspects Of Sample Preparation For Freeze-Fracture/Freeze-Etch Studies Of Proteins And Lipids In Food Systems. A Review, Wolfgang Buchheim

Food Structure

To select optimum specimen preparation methods and to correctly interpret freeze-fracture/freezeetch micrographs of food systems a detailed knowledge of the individual steps of preparation -- i.e. chemical fixation of samples, their cryoprotective pretreatment, cryofixation, freeze-fracturing and -etching, and replication -- and of their influence on the appearance of different constituents, especially proteins and lipids, is necessary. Food systems show great variation in composition, structure and especially in their content of water -- e.g. molecular and colloidal solutions, oil-in-water and water-in-oil emulsions, gels suspensions, semi-solid systems such as cheese, dried systems such as milk powders -- thus requiring a careful variation …

Guidelines For Minimizing Salinity Buildup In Groundwaters Of Utah, Edward P. Fisk, Calvin G. Clyde

Reports

In arid Utah practically all of the replenishable surface water supplies are nearly fully developed. At least some groundwater resources are being used in every basin. Groundwater use is expanding throughout the state and in some areas the draft is nearly equal to the sustained yield. Irrigated agriculture is the major water user. Multiple reuse of water is common in many areas, but as salinity increases with each cycle of usage, salinity also is usually the limiting factor for usefulness. Effective control of salinity buildup will permit more efficient and more extensive use of the state’s waters with potentially large …

Reverse Osmosis In The Treatment Of Drinking Water, R. Ryan Dupont, Talbert N. Eisenberg, E. Joe Middlebrooks

Reports

An extensive review of the literature was conducted and results were evaluated for the use of the reverse osmosis process in the treatment of drinking water supplies. All aspects of reverse osmosis technology, including pretreatment requirements; membrane type and configuration; membrane cleaning and maintenance; and reverse osmosis removal of organics, inorganics, and microbial contaminants were incorporated inot the literature evaluation. A survey (Appendix E) of existing full scale reverse osmosis installations was also carried out and results of the survey are discussed. In light of data presented in the literature and results of the survey conducted, the following recommendations were …

Hydraulics And Numerical Solutions Of Steady-State But Spatially Varied Debris Flow, Alfredo A. Deleon, Roland W. Jeppson

Reports

Debris flow is a natural phenomenon triggered by special conditions that combine: high intensity rainfall, material available for transport, slopes steep enough to induce flowage, and insufficient protection of the ground by vegetation and/or other erosion control means. These conditions are very common in semiarid and arid regions in Utah, other Western states and many other parts of the globe. Previously, the two models proposed to solve debris flow are the Bingham plastic model and the dilatants model. Both these models depend upon coefficients that are not easy to obtain. Therefore, they are not very useful in practice. According to …

Defining Stream Fish Microhabitat Requirements For Water Project Planning, William T. Helm

Reports

Brown trout daily activities were divided into two braod categories, resting and feeding, and the population was divided into three size groups (one of which is reported on here), based on the timing and location of these activities. Microhabitat components, measured previously in four rivers at sites occupied by fish, were utilized to develop usable componenet ranges for each size group and activity to illustrate the breadth of component values utilized out of the total range available. Microhabitat is thus described as a range of numerical values for each componenet of a specific set of components. A 90 meter section …

Organizational Alternatives To Achieve Greater Uniformity In State-Wide Water Rights Management In Utah, Daniel H. Hoggan, Kirk R. Kimball, Jay M. Bagley, Frank W. Haws

Reports

In the distribution of water among users in the state of Utah there is lack of organizational uniformity. On some rivers, the state engineer is assisted by river sommissioners who have been appointed to measure and monitor water deliveries. On other rivers there are no comissioners; problems and disputes must be settled on a case by case basis by the state engineer. The responsibilities, arrangements, salaries, and methods of payment for commissioners vary from basin to basin. A more unifed distribution organization composed of state-employed water sommissioners would have several advantages over the existing system of commissioners employed by local …

Further Studies Of A Cache Valley Residence Having A Groundwater Heat Pump, Michael L. Henrie

Reports

The thermal behavior of a 5-ton groundwater heat pump and the wood-frame house in which it is installed (located in Logan, Utah, latitude 44°49’; elevation 4775 ft.) were investigated during two 30 day peak use periods, the first in late summer and the second in mid-winter. Continuous measurements were taken of indoor and outdoor temperatures, groundwater temperatures, supply and return air temperatures, gallons of groundwater cycled, and Btu rejected or absorbed. These measurements were used for 1) determining the instantaneous heat gains and/or heat losses of the house by conduction and infiltration of both periods studied and 2) computing the …

Potential For Acid Snowmelt In The Wasatch Mountains, Jay J. Messer, Lloyd Slezak, Charles I. Liff

Reports

Snowmelt collected from snow cores taken from the 1982 spring snowpack in the Wasatch Mountains of northern Utah lacked mineral acidity and retained enough buffering capacity in the form of calcium and magnesium bicarbonates to titrate additional inputs of strong acid equivalent to the amount apparently already neutralized. While acid anion concentrations were higher than those found in pristine areas, they were much lower than those reported for winter precipitation in other western areas experiencing acidification of precipitation. Snowmelt pH ranged from 5.62 to 6.88 (mean = 6.17), and sulfate was relatively more important than nitrate, showing an average equivalent …

Impacts Of Western Coal, Oil Shale, And Tar Sands Development On Aquatic Environmental Quality: A Technical Information Matrix; Volume 1 Introduction And Instructions, Jay J. Messer, Charles I. Liff, Kurt Gernerd, Frederick J. Post

Reports

Introduction: The Upper Colorado River Basin contains vast deposits of coal, oil shale, and tar sands, which could undergo extensive development should oil prices rise or an international situation restrict oil imports. Naturally, the prospect of development of these alternative fossil fuels resources has led to concern over how extraction and conversion activities will impact environmental quality. A thorough understanding of the nature and magnitude of the resulting envionemental impacts is a necessary prerequisite, if the costs and risks of such activites are to be weighed against the economic benefits. When we set out to evaluated these costs and risks, …

Hydrologic Series Generation From The Spectral Density Function, Ronand V. Canfield

Reports

Computer simulation of hydrologic processes has become an effective analytical tool for analysis of complicated water resource systems. Present methods of generating sequences place practical limits on the ability of the methods to preserve an observed autocorrelation structure. This report explores the use of spectral characteristics in the generation of time series. Because of the correspondence between the spectral density function and the autocorrelation function of a time series, the spectrum can be used to fit any of the empirical autocorrelation structures observed in hydrologic sequences. The problem of maintaining an observed correlation structure in a generated sequence is reduced …

Energy Impacts Of Water Based Recreation, J. Clair Batty, David A. Bell, E. Bruce Godfrey, Craig Howell, J. Paul Riley, Thomas C. Stoddard

Reports

The overall objective of the study reported here was to determine to what extent energy accounting could supplement and/or complement economic benfit/cost analyses of water management projects and to specifically examine the energy impacts of water based recreation. The energy accounting literature was carefully reviewed and an energy accounting methodology applicable to water management was devised. Data pertaining to receation at five reservoirs in Utah were assembled from visitation recoreds and on-site surveys. Energy requirements for site construction, travel to and from the recreation site, and recreation at the site were estimated. It was determined that energy devoted to water …

Predicted Limnology Of The Proposed Ridges Basin Reservoir, Lawrence A. Baker, V. Dean Adams

Reports

A limnological evaluation was conducted for the offstream Ridges Basin Reservoir proposed by the Bureau of Reclamation in southwest Colorado. The study required the determination of existing water quality in the source river and use of the information to predict the algal standing crop, hypolimnetic oxygen deficity, Secchi disk transparency, and retention of metals in the proposed reservoir. A water quality study was conducted between May 1977 and August 1978. Samplse were collected from the Animas River, which will provide the inflow to the proposed reservoir, and from the La Plata River, which will receive discharge from the reservoir. Samples …

Cross Sections For Inelastic Scattering Of Electrons By Atoms - Selected Topics Related To Electron Microscopy, Mitio Inokuti, Steven T. Manson

Scanning Electron Microscopy

We begin with a resume of the Bethe theory, which provides a general framework for discussing the inelastic scattering of fast electrons and leads to powerful criteria for judging the reliability of cross-section data. The central notion of the theory is the generalized oscillator strength as a function of both the energy transfer and the momentum transfer, and is the only non-trivial factor in the inelastic-scattering cross section. Although the Bethe theory was initially conceived for free atoms, its basic ideas apply to solids, with suitable generalizations; in this respect, the notion of the dielectric response function is the most …

Electron Scattering And Energy Losses As A Function Of The Incident Energy: Application To Chemical Analysis, Bernard Jouffrey

Scanning Electron Microscopy

This paper gives a rapid overview on the use of the energy losses suffered by an incident electron beam. General approximations are remembered. Then some recent results on inner shell excitations as a function of energy (in high voltage electron microscopy) are given, and the problem of thick samples is rapidly discussed.

The problem of the observation of sensitive materials in electron microscopy is discussed. A simple model is proposed to determine some orders of magnitude on the inelastic mean free path and the elementary volume of defects created during the irradiation with electrons of different energies. This model can …

Light Microscopy Preparation Techniques For Starch And Lipid Containing Snack Foods, F. Olga Flint

Food Structure

Many processed foods lack the structural integrity associated with biological tissue so that the conventional methods of preparation and staining used in light microscopy may introduce misleading artifacts.

Taking as examples of starch-based processed foods, potato chips (UK potato crisps) and three distinct potato snack foods, methods for preparing and demonstrating the constituents present in cryosections of whole and masticated products are discussed. To show constituents in their true relative locations vapor staining and polarized light are used. Iodine vapor staining indicates the extent of starch gelatinisation in the dry snack and it is also used to show the structural …

In-Situ Measurements Of Wave Electric Fields In The Equatorial Electrojet, R. F. Pfaff, M. C. Kelley, B. G. Fejer, N. C. Maynard, K. D. Baker

Space Dynamics Laboratory Publications

Electric field wave measurements have been performed on two sounding rockets in the equatorial ionosphere. During a daytime flight from Chilca, Peru, intense elecrostatic waves were detected on the upward directec electron density gradient. Duing a nighttime flight from Kwajalein Atoll, similar waves were detected on a downward directed gradien. These results are in agreement with a gradient drift instability explanation of the generation of the waves. The wave amplitudes were as high as 5 mV/m implying pertubation drifts comparable to the driving drift velocities. Power spectra from the turbulent region show a peak at long wavelengths, followed by a …

Non-Random Orientation Of Nest Entrances In Saguaro Cacti, R S. Inouye, Nancy J. Huntly, D W. Inouye

Biology Faculty Publications

No abstract provided.

Møller-Plesset Treatment Of Electron Correlation In (Hohoh)-, M. M. Szczesniak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The effects of electron correlation on the calculated properties of the (HOHOH)⁻ anion are studied using Møller–Plesset (MP) perturbation theory. With this technique, inclusion of corrections up to third order are shown to provide results quite similar to those obtained with an extensive CI approach when equivalent basis sets are used. Barriers to proton transfer between the two oxygen atoms at a fixed R(OO) distance are computed with a number of basis sets ranging from split‐valence 4–31G to triple‐valence with polarization functions on all atoms, 6–311G∗∗. Each successive enlargement of the basis set leads to a greater barrier. …