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The classification of obsidian artifacts has been receiving considerable attend of changes in obsidian trace element composition can now be identify ancient trade routes. The classification of this glassy volcanic material has been attempted using a variety of elemental analysis technique. The most successful and most widely employed method of non-destructive analysis has been that which employs X-ray fluorescence analysis (XRF); either wavelength dispersive (WDS), or energy dispersive (EDS).
An asymmetrically cut single crystal is, generally, a large flat X-ray monochromating crystal whose principal surface has been cut an angle to the diffracting planes being utilised.
The use of such a crystal was suggested by Stephen and Barnes in 1935 as a means of obtaining a narrow intense beam of monochromatic X-rays. Fankuchen was first to demonstrate this effect experimentally. A number of symmetrically cut mosaic single crystals, including lithium fluoride, was studied by Evans, Hirsch and Kellar and by Gay, Hirsch and Kellar in the beam condensing (beam narrowing) mode only.
As a result of interest in the characterization of materials with large d-spacings and layer periodicities, it has become necessary to develop a low-angle diffraction material which has welldefined diffraction peaks down to very small 2θ angles. The use of silver behenate, CH3(CH2)20COO-Ag, was introduced by one of the authors (TB) at the 1991 International Centre for Diffraction Data (ICDD) Annual Meeting and was shown to have a set of well-defined (001) diffraction peaks down to 1.5° 2θ when using CuKα radiation. The silver behenate diffraction peaks were observed to be slightly asymmetric with relatively long tails at the low angle side of the peaks. The average crystallite size along the c-axis was estimated using the Scherrer equation and was found to be 900 Å.
A task group of the JCPDS-ICJDD Data Collection and Analysis Subcommittee was established with the charge of investigating the use of silver behenate as a possible low-angle calibration material for diffraction applications. Utilizing several data collection and data analysis techniques, d001 long-period spacings in the range of 58.219-58.480 Å were obtained. Using the same collected data and one data analysis refinement calculation method resulted in long-period spacing with a range of 58.303-58.425 Å. Data collected using a silicon internal standard and the same singular data analysis calculation method provided d001 values with a range of 58.363-58.381 Å.
The formation of a full-range 2θ diffraction sample was also investigated. Silver behenate and inorganic powders were mixed with an epoxy binder to form a permanent sample which provides diffraction peaks over the entire 2θ range of a powder diffractometer.
Since the introduction of semiconductor detectors with sufficient energy resolution to resolve K-alpha X-rays from the K-beta X-rays for first row transition metals, there have been several attempts (1,2) to replace traditional detector systems (scintillation detector/graphite monochromator or proportional counter/nickel filter) in X-ray diffraction with semiconductor detectors. The goal of these experiments was to increase the total system detection efficiency by combining the K-beta discrimination and X-ray detection into a single operation. These early attempts showed that the semiconductor detector based system was more efficient, however, the problem of large dead-time losses hampered development in this area.
Not much is known about Claudius Ptolemy's life, beyond what can be deduced from the astronomical observations recorded in his Syntaxis mathematica (better known as the Almagest), made between 127 and 141 CE at Alexandria, and the inscription he seems to have set up at nearby Canopus in 147. Otherwise he remains a nebulous figure, neither filling his own books with colourful anecdotes of his professional life as did the physician Galen, his near contemporary, nor enjoying the post-mortem attribution of fabulous biographical details as did other towering figures of ancient science like Pythagoras or Archimedes. The afterlife of his work was, however, extraordinarily robust. He became the author par excellence in astronomy and harmonics, to the extent that the works of his predecessors were largely obliterated in the wake of Ptolemy and his commentators.
Through the extraordinary breadth of his surviving texts persists a recurrent line of interest in putting the phenomena observed in the world to work in scientific theorisation, most often of a highly quantified kind. In particular, he is persistently interested in the natural and artificial instruments through which we perceive the world, in terms of how the natural ones may be aided and the artificial ones refined so as to provide the most reliable data. Ptolemy's inquiry into the mechanisms through which scientific observations are actually performed might be considered a second-order investigation with respect to the natural systems that are the explicit subjects of his texts. Yet such an investigation is mandatory for the precisely calibrated observational work Ptolemy recommends to his reader.
Far from simply listing the procedures and apparatus of scientific investigation, Ptolemy engages deeply with questions about the kinds of cognitive work they require and in turn perform. The body is presented as a composite of sensory and motor systems together with an array of faculties of judgement, all complexly intertwined and none functioning alone. The eye and ear are not mere relays for sensory data to a separate cognitive faculty, but are themselves an intrinsic part of the process of assessing geometric diagrams, harmonic tones, celestial bodies and other sensible phenomena. The eye may draw as well upon data mediated by computational tables, and Ptolemy describes the eye in action, moving through such tables to seek data or perform calculations.
Leckrone and Adelman have established an IUE observing strategy that has yielded co-added spectra with enhanced S/N ratios for several A and B stars. New observations by Roby and Adelman using the same technique have added two new Hg-Mn stars into this sample. We have begun a long-term study of elemental abundances in this uniform, high-quality set of IUE spectra for 13 stars. We report on the first stages of this project: abundances for N, Cr, Mn, Fe, Co, and Ni. The study of the Fe- peak elements show that our data set can provide accurate abundances and that abundances obtained from UV and optical spectra often are in good agreement. This study provides the groundwork for self-consistent abundance analyses of more exotic elements in our long term project.
Ekphrasis is familiar as a rhetorical tool for inducing enargeia, the vivid sense that a reader or listener is actually in the presence of the objects described. This book focuses on the ekphrastic techniques used in ancient Greek and Roman literature to describe technological artifacts. Since the literary discourse on technology extended beyond technical texts, this book explores 'technical ekphrasis' in a wide range of genres, including history, poetry, and philosophy as well as mechanical, scientific, and mathematical works. Technical authors like Philo of Byzantium, Vitruvius, Hero of Alexandria, and Claudius Ptolemy are put into dialogue with close contemporaries in other genres, like Diodorus Siculus, Cicero, Ovid, and Aelius Theon. The treatment of 'technical ekphrasis' here covers the techniques of description, the interaction of verbal and visual elements, the role of instructions, and the balance between describing the artifact's material qualities and the other bodies of knowledge it evokes.