Pyroxene reflectance spectra: Minor absorption bands and effects of elemental substitutions

Reflectance spectra of a suite of compositionally diverse pyroxenes exhibit variable spectral properties which are associated with various elemental substitutions. Those associated with transition series elements, such as Cr, Ti, V, and Mn, give rise to a number of minor absorption bands in the visible spectral region and, in some cases (e.g., Mn), at longer wavelengths. Substitutions by other cations, such as Li and Zr, do not result in distinct absorption bands. The spectra of these pyroxenes are dominated by the transition series elements that may be present in the samples. The visible wavelength region of low-calcium pyroxene reflectance spectra exhibit a number of absorption bands which are attributable to Fe2+ spin-forbidden crystal field transitions. Fe2+-Fe3+ intervalence charge transfer absorption bands near 0.77 μm are common in terrestrial pyroxenes which contain both ferrous and ferric iron. Collectively, these results indicate that the presence of various transition series elements can be detected in reflectance spectra and that their oxidation states and site occupancies can also be determined on the basis of unique spectral characteristics present in their reflectance spectra, thereby greatly increasing the range of compositional information which can be derived from analysis of their reflectance spectra.This study was supported by grants-in-aid of research from the Natural Sciences and Engineering Research Council of Canada (NSERC), Sigma Xi, The Scientific Research Society, the Geological Society of America, a research contract from the Canadian Space Agency, and a start-up grant from the University of Winnipeg.This study was supported by grants-in-aid of research from the Natural Sciences and Engineering Research Council of Canada (NSERC), Sigma Xi, The Scientific Research Society, the Geological Society of America, a research contract from the Canadian Space Agency, and a start-up grant from the University of Winnipeg.https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2001JE00159

The comet Halley dust and gas environment

Quantitative descriptions of environments near the nucleus of comet P /Halley have been developed to support spacecraft and mission design for the flyby encounters in March, 1986. To summarize these models as they exist just before the encounters, we review the relevant data from prior Halley apparitions and from recent cometary research. Orbital elements, visual magnitudes, and parameter values and analysis for the nucleus, gas and dust are combined to predict Halley's position, production rates, gas and dust distributions, and electromagnetic radiation field for the current perihelion passage. The predicted numerical results have been useful for estimating likely spacecraft effects, such as impact damage and attitude perturbation. Sample applications are cited, including design of a dust shield for spacecraft structure, and threshold and dynamic range selection for flight experiments. We expect that the comet's activity may be more irregular than these smoothly varying models predict, and that comparison with the flyby data will be instructive.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43774/1/11214_2004_Article_BF00175326.pd

Notes on the wall paintings of Mart Shmuni

Cruikshank Dodd Erica. Notes on the wall paintings of Mart Shmuni. In: Archéologie au Levant. Recueil à la mémoire de R. Saidah. Lyon : Maison de l'Orient et de la Méditerranée Jean Pouilloux, 1982. pp. 451-462. (Collection de la Maison de l'Orient méditerranéen. Série archéologique, 12

The Image of the world: notes on the religious iconography of Islam.

Donated by Klaus KreiserReprinted from : Berytus. Archeological Studies 18, 1969

Clinical characteristics and management of bipolar disorder in women across the life span

Though prevalent in both genders, specific consideration needs to be given when treating a woman suffering from bipolar disorder over her lifetime. Bipolar disorder is a serious and incapacitating illness affecting an estimated 5% of women. The first episode of illness in women is usually a depressive episode. Female gender has been associated with greater axis-one comorbidity, more depressive episodes, rapid cycling and mixed affective states. Special consideration is required for the treatment of bipolar disorder during reproductive events. More studies are required to better understand the course, outcome and gender-specific treatment strategies of this disorder.<br /