Rutherford backscattering spectrometry (RBS) is shown to be an elegant, powerful tool for the chemical characterization of optical coatings. RBS studies of several thin film materials are presented to illustrate the technique's unique abilities, and to show how RBS is best exploited in investigations of thin film stoichiometry and diffusion. The text begins with an introduction to optical coatings and the practical problems encountered in their implementation. The basic principles of RBS are discussed, and the technique is compared to other popular surface analysis tools. The introductory material concludes with a chapter devoted to specific techniques for RBS data and error analysis, including the derivation of a simple formula for determining the optimum thickness of multi-element samples. The accurate stoichiometric measurements provided by RBS give new insights into the chemical structure of ion-bombarded MgF₂ coatings. The analysis shows that lightly-bombarded coatings contain a small oxygen fraction (< 6%), and the absence of this oxygen in opaque, heavily-bombarded samples implies the oxygen compensates for fluorine deficiencies and is therefore an essential ingredient for transparent films. This beneficial oxygen appears to diffuse into the coatings along columnar voids, and the implied compromise between packing density and transparency is discussed. The final chapter takes advantage of the nondestructive depth-profiles provided by RBS. We present the first direct experimental verification of the interfacial oxide layer responsible for the superior adhesion of aluminum to glass, and show that contrary to popular belief, the layer is not an artifact of oxygen adsorbed during the aluminum's evaporation. We then discuss the diffusion of copper through silver films, and show that the migration is enhanced by exposure to the RBS probe beam. Finally, we consider the diffusion of carbon, from graphite substrates, into the voids of porous coatings during the RBS measurements. This effect, like the enhanced copper diffusion, is consistent with a low temperature, measurement-induced anneal; however, we show that the migrant carbon does not alter the chemical structure of the coatings, but instead serves as a convenient, non-intrusive indicator of film porosity.

Estelle Liebling (1880-1970) was a phenomenally successful voice teacher who occupies a place in the chain of succession of voice teachers devoted to the ideals of the bel canto. Turning out over seventy-five Metropolitan Opera stars over the fifty-plus year span of her teaching career, she was regarded during her lifetime as one of the most distinguished voice teachers in America. Her editions, compositions, and pedagogical writings exerted an influence on the world far exceeding the boundaries of the New York professional musical sphere in which she operated. Despite this, almost nothing has been written to date that documents her contribution to the world of singing. Much of Liebling's pedagogical outlook was derived from that of her immediate predecessor, Mathilde Marchesi, and direct comparison of Liebling's Vocal Course to Marchesi's Theoretical and Practical Vocal Method shows this relationship. Liebling herself acknowledged Marchesi's influence, but the pedagogy she espoused was by no means a carbon copy of that of Marchesi. Important differences exist, distinguishing Liebling's pedagogy as separate and individualized, a legitimate successor to the Marchesi Method. Liebling's legacy consists not only of her teaching and pedagogical writings, however. The tremendous body of vocal literature which she edited, arranged, and composed, mostly for coloratura soprano, is enough in of itself to justify her place in music history. Additionally, her catalogue work of cadenzas and ornamentation for coloratura soprano literature still stands today as the monumental work on the subject.

The research work presented here deals with problems associated with finite element analysis of laminated composite thin-shell structures. The specific objective was to develop a thin shell finite element to model the linear elastic behavior of these shells, which would be efficient and simple to use by the practicing engineer. A detailed discussion of the issues associated with the development of thin shell finite element has been presented. It has been pointed out that the problems encountered with formulation of these elements stem from the need for satisfaction of the interelement normal slope continuity and the rigid body displacement condition by the assumed displacement functions. These difficulties have been surmounted by recourse to the discrete Kirchhoff theory approach and an isoparametric representation of the shell middle surface. A detailed derivation of the strain energy density in a thin laminated composite shell, based on a linear shear deformation theory formulated in a general curvilinear coordinate system, has been presented. The strain-displacement relations are initially derived in terms of the displacement and rotation vectors of the shell middle surface, and are subsequently expressed in terms of the cartesian components of these vectors to enable an isoparametric representation of the shell geometry. A three-node curved triangular element with the tangent and normal displacement components and their first-order derivatives as the final nodal degrees of freedom has been developed. The element formulation, however, starts with the independent interpolation of cartesian components of the displacement and rotation vectors using complete cubic and quadratic polynomials, respectively. The rigid-body displacement condition is satisifed by isoparametric interpolation of the shell geometry within an element. A convergence to the thin shell solution is achieved by enforcement of the Kirchhoff hypothesis at a discrete number of points in the element. A detailed numerical evaluation through a number of standard problems has been carried out. Results of application of the "patch test solutions" to spherical shells demonstrate a satisfactory performance of the element under limiting states of deformation. It is concluded that the DKT approach in conjunction with isoparametric representation results in a simple and efficient thin shell element.

A facile method for the synthesis of highly enriched ¹⁸O labeled pyrimidine ribonucleosides is described. The ribonucleoside may be labelled specifically in the base, the sugar, or both moieties with one or two oxygen-18 atoms. The isotopic purity of the products as well as the location of the oxygen-18 labels have been unambiguously determined by mass spectrometry. Stable isotope labeled analogs have been employed to determine the composition of several clinically significant nucleoside dialdehydes by mass spectrometry. Formation of the trimethylsilyl derivatives permits the gas chromatographic separation of the major components present in the equilibrium mixture. In addition to the expected hemiacetals and hydrates, a substantial amount of the dialdehydes exist in polymeric form. Fast atom bombardment mass spectrometry enabled observation of dimeric and trimeric species from the polymeric material present in the mixture.

Many determinations have been made of the dielectric constant of water, and of its variations caused by temperature and frequency. The dielectric constant of water has a relatively high value as compared with those of many other substances with which water is commonly associated. Consequently, measurements of the dielectric constant (or of the electrical capacitance) of materials such as soil, cereal and grain have been used as indications of their moisture contents. This study was undertaken to determine whether or not a capacitance method can be used to measure sediment concentrations in water. Laboratory measurements were made of varying concentrations of several individual artificial sediments, natural sediments, and pure salts in distilled water. A flow-through-type conductivity cell was used in which the capacitor plates are fixed in relation to each other. The equation for capacitance of the flow through cell can be written as C = kD where C capacitance in farads, k = a constant determined by the physical configuration of the cell, D = dielectric constant, and it is seen that C varies directly as D. Typical values of salt and sediment concentrations existing in natural streams in the United States were determined from the literature. Conclusions of the study are summarized as follows: 1. The capacitance method of measuring concentrations of sediment in natural streams is not practical for the following reasons. The presence of even small quantities of conducting and/or magnetic sediments in the measured samples invalidates the measurements. Concentrations of sediments in most streams in the United States are too low during most of the year to be sensed by the capacitance method. Concentrations of dissolved solids in many streams in the United States are high enough during at least part of the year to render capacitance measurements inaccurate. The surface chemistry of clay-size particles prevents their being reliably measured with the capacitance method. 2. The capacitance method of measurement may be applicable for particular or specialized uses, such as the determination in the laboratory of concentrations of mixtures of known nonconducting and nonmagnetic particulate matter. Such measurements are not noticeably affected by the salts used in this study until their concentrations exceed about 10 meq/l. It is recommended that further efforts to adapt the capacitance method to the measurement of stream sediments be discontinued.

This work contains the analysis and redesign of a translinear circuit. This circuit appeared in the article by Robert Blauschild. The Blauschild circuit was analyzed on H-SPICE, a VAX computer circuit analysis program, with Burr-Brown Integrated Circuit Process 30 models. Circuit improvement to input voltage to current converter stage and circuit simplification of the output stage were implemented and simulated in the redesign. The results of the two simulations were compared, which showed that the improvements were valid and useful. Going through this redesign cycle of circuit analysis, computer simulation and bread-boarding served as an actual design engineering application with a real problem, solution, and result scenarios.

No description available.

No description available.

Our research purpose is to build up new and efficient methods to quantitate amounts of air-borne asbestos. A basic idea behind the methods is the use of a FT-IR instrument to measure the asbestos absorbances. Karen McCune, an ex-coworker in our group, developed three procedures to eliminate background absorbances from the filters on which the asbestos is collected. These procedures included the spectral subtraction, the chemical digestion, and the ashing of cellulose ester filters.My research has ultilized and expanded on the ashing procedure. First, the detection limits and linearity of the aforementioned transmission method were determined. Using amosite asbestos, we developed a standard curve from 40 tg to 2 µg which agreed well with Beer's Law. We determined that the detection limit of this method resulted from minutely contaminated salt and not from instrumental limitations. Even using highly pure KBr, CsCl, or KC1, similar detection limits were obtained.Second, the use of diffuse reflection to measure the asbestos absorbances was investigated. The method, much simpler than the transmission technique, consists of pouring the recovered asbestos-salt mixture into a small cup and obtaining the diffuse reflectance spectrum using a special accessory. A standard curve of amosite ranging from 40 p.g to 1 .tg was produced. One important observation was that when KCl adsorbed water from the air while a background spectrum was collected, the water absorption band contributed negatively to the area under the Si-O stretching region. This contribution prohibits the detection of smaller amounts of amosite. A standard curve of chrysotile asbestos ranging from 40 µg to 5 µg was also produced.Another goal of our research is to investigate the quantitation and identification capabilities when asbestos is present as mixtures of amosite, chrysotile, or other closely related silicates such as, kaolin. In conjunction with the diffuse reflection method, a curve fitting program was used to analyze the amount of each component in a mixture. First mixtures of amosite and chrysotile were studied. Then mixtures of amosite, chrysotile, and kaolin, mixtures which resemble the real world's environment, were studied.Overall, the FT-IR spectroscopic methods are more efficient and applicable than the traditional fiber-counting methods. Our methods not only objectively quantitate the amount of asbestos but also identify the type. / Department of Chemistry

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / Real-time high-volume telemetry data analysts have needs which require access to ever-increasing amounts of data, which must be processed in a seamless and coherent manner. BBN has developed a data analysis software architecture for use in distributed- and parallel-processing environments which is particularly well-suited for telemetry streams. BBN is currently using this software at two Navy sites to do realtime data analysis. The architecture provides data-source management, data-stream fusion, and data extraction all in a modular, scalable framework. Because of the scalable nature of the software, it can easily accommodate high data rates.