3,296 research outputs found
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Fe isotopes in Martian meteorites: role of water and possibility of life on Mars
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Fe isotopic composition of Martian meteorites
In the present work, we have measured iron isotope compositions of a group of Martian meteorites to establish a baseline Fe-isotope fractionation pattern in the case of high-temperature igneous rocks from Mars
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Fe-Ni Sulphides as Indicators of Alteration in CM Chondrites
This study looks at the sulphide abundance and composition of Fe-Ni sulphide grains in 12 CM chondrites to determine an alteration sequence for these chondrites
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Fe-Ni sulphides in Tagish Lake and CI1 and CM2 carbonaceous chondrites
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Different degrees of aqueous alteration in sulphides within the CI1 chondrites
Sulphides in four different CI1 chondrites were analysed, to evaluate their composition, texture and morphology. The results reinforce the view that CI1 chondrites could be divided into two subgroups, based on their level of aqueous alteration
Free vibrations of delaminated beams
Free vibration of laminated composite beams is studied. The effect of interply delaminations on natural frequencies and mode shapes is evaluated both analytically and experimentally. A generalized vibrational principle is used to formulate the equation of motion and associated boundary conditions for the free vibration of a composite beam with a delamination of arbitrary size and location. The effect of coupling between longitudinal vibration and bending vibration is considered. This coupling effect is shown to significantly affect the calculated natural frequencies and mode shapes of the delaminated beam
2-16 mu m spectroscopy of micron-sized enstatite (Mg,Fe)(2)Si2O6 silicates from primitive chondritic meteorites
We present mid-infrared spectra from individual enstatite silicate grains separated from primitive type 3 chondritic meteorites. The 2-16 mu m transmission spectra were taken with microspectroscopic Fourier-transform infrared (FT-IR) techniques as part of a project to produce a data base of infrared spectra from minerals of primitive meteorites for comparison with astronomical spectra. In general, the wavelength of enstatite bands increases with the proportion of Fe. However, the wavelengths of the strong En(100) bands at 10.67 and 11.67 decrease with increasing Fe content. The 11.67-mu m band exhibits the largest compositional wavelength shift (twice as large as any other). Our fits of the linear dependence of the pyroxene peaks indicate that crystalline silicate peaks in the 10-mu m spectra of Herbig AeBe stars, HD 179218 and 104237, are matched by pyroxenes of En(90-92) and En(78-80), respectively. If these simplistic comparisons with the astronomical grains are correct, then the enstatite pyroxenes seen in these environments are more Fe-rich than are the forsterite (Fo(100)) grains identified in the far-infrared which are found to be Mg end-member grains. This differs from the general composition of type 3 chondritic meteoritic grains in which the pyroxenes are more Mg-rich than are the olivines from the same meteorite
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Fe-Ni Sulphides within a CM1 clast in Tagish Lake
The composition, abundance and mineral associations of Fe-Ni sulphides within a CM1 clast in Tagish Lake are described, and compared with Fe-Ni sulphides in the carbonate-rich and carbonate-poor lithology of Tagish Lake, as well as Fe-Ni sulphides from CI and CM chondrites
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A study of the morphology, composition and mineral associations of Fe-Ni sulphides in CM carbonaceous chondrites
A study of the compositional and textural variations between Fe-Ni sulphides in a suite of pristine to extensively aqueously altered CM chondrites, using SEM and EMP techniques
Practical applications of interactive voice technologies: Some accomplishments and prospects
A technology assessment of the application of computers and electronics to complex systems is presented. Three existing systems which utilize voice technology (speech recognition and speech generation) are described. Future directions in voice technology are also described
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