A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7μm silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars are characterized by silicate features in emission and Seyfert 1s equally by emission or weak absorption. Seyfert 2s are ...

We present high signal to noise ratio Spitzer Infrared Spectrograph observations of 17 Virgo early-type galaxies. The galaxies were selected from those that define the colour-magnitude relation of the cluster, with the aim of detecting the silicate emission of their dusty, masslosing evolved stars. To flux calibrate these extended sources we have devised a new procedure that allows us to obtain...

The 10μm silicate emission feature and the continuum emission from near infrared to millimeter of the dust in the disk of β Pictoris may be derived by assuming that the dust is continually replenished by comets orbiting close to the star. The basic, initial dust shed by the comets is taken to be the fluffy aggregates of interstellar silicate core-organic refractory mantle dust grains (with an a...

Introduction: Recent work by [1] indicates that the mesoside-rites are isotopically identical to the HEDs, strongly suggesting that they originate from the same parent body. One argument against this theory is the differences between the silicates within the two meteorite groups. Mesosiderite pyroxenes tend to have higher MgO concentrations and lower Fe/Mn ratios, which show a positive correlat...

The zodiacal light is the dominant source of the mid-infrared sky brightness seen from Earth, and exozodiacal light is the dominant emission from planetary and debris systems around other stars. We observed the zodiacal light spectrum with the mid-infrared camera ISOCAM over the wavelength range 5–16 µm and a wide range of orientations relative to the Sun (solar elongations 68 • –113 •) and the...

This experimental study examines the mineral/ melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H2O, and are satur...

The decay of Hf (half life of 9 million years) to W provides a powerful tool to date metal-silicate fractionation in the early solar system. During segregation of metal the siderophile W partitions into the metal phase, whereas the lithophile Hf is preferably incorporated by silicate phases. The formation of iron meteorites during metal-silicate fractionation may have occured during condensatio...

The structural properties of the silicate garnets andradite, Ca(3)Fe(2)Si(3)O(12), uvarovite, Ca(3)Cr(2)Si(3)O(12), knorringite, Mg(3)Cr(2)Si(3)O(12), goldmanite, Ca(3)V(2)Si(3)O(12), blythite, Mn(2+)(3)Mn(3+)(2)Si(3)O(12), skiagite, Fe(2+)(3)Fe(3+)(2)Si(3)O(12), calderite, Mn(2+)(3)Fe(3+)(2)Si(3)O(12), and khoharite, Mg(3)Fe(3+)(2)Si(3)O(12), have been investigated with a quantum-mechanical mo...

A number of root-repair materials have been developed by various manufacturers, including Mineral Trioxide Aggregate (MTA) that has adequate biological and physical properties of a good root repair material [1,2]. MTA has been used for apexification, perforation repair, root resorption, and as a root-end filling material. The main ingredients of MTA are silicate oxide, tricalcium oxide, tricalc...

We propose a new method using coarse-graining and molecular dynamics to calculate structural and mechanical properties for sodium silicate glasses at different scales. Using this method we were able to describe the mechanical behavior of the material, this way a new constitutive model was developed which could be used in continuum calculations.