A pyroxene-oldhamite clast in Bustee: Igneous aubritic oldhamite and a mechanism for the Ti enrichment in aubritic troilite

A pyroxene-oldhamite clast in the Bustee aubrite contains major enstatite and minor diopside and forsterite as the silicate host, with abundant (∿30vol%), included 1-5mm spherules of oldhamite. Within the oldhamite (∿5vol% of the oldhamite) are a variety of phases, including osbornite (TiN), titanoan troilite (17.2-25.2wt% Ti), heideite (28.7-29.4wt% Ti), niningerite, daubreelite, forsterite, and Fe metal. This clast represents only the second occurrence of an oldhamite-rich lithology in aubrites. An igneous origin for oldhamite within the Bustee pyroxene-oldhamite clast is suggested by its large size, rounded shapes, presence of included phases formed from multiple, immiscible sulfides, and inclusion of phases unknown from enstatite chondrites. The Bustee clast contains a variety of Ti-rich phases. This work suggests Ti-rich troilite observed in aubrites formed by co-crystallization with or exsolution from Ti-poor sulfides (e.g., oldhamite). In the Bustee case, the undetectably low Ti concentrations in oldhamite and experimental Ti partition coefficient between FeS and CaS approaching infinity support such a suggestion. This mechanism solves the long-standing problem of enriching aubritic troilite in Ti and weakens arguments against a direct derivation of aubrites from known enstatite chondrites

Crystallization of the Zagami Shergottite: An Experimental Study

Spherulites are usually rounded or spherical objects found in rhyolitic obsidian. They usually comprise acicular crystals of alkali feldspar that radiate from a single point. The radiating array of crystalline fibers typically have a similar crystallographic orientation such that a branch fiber departs slightly but appreciably from that of its parent fiber. Individual fibers range from 1 to several micrometers in diameter. The spherulites most likely form by heterogeneous nucleation on microscopic seed crystals, bubbles, or some other surface at high degrees of supercooling. They grow very rapidly stabilizing their fibrous habit and typically range in size from microscopic to a few cm in diameter

Thermosyphon-cooled axial gap electric motors for ship propulsion applications

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995.Includes bibliographical references.by Timothy John McCoy.Ph.D

Phenothiazine normalizes the NADH/NAD+ ratio, maintains mitochondrial integrity and protects the nigrostriatal dopamine system in a chronic rotenone model of Parkinson's disease

Producción CientíficaImpaired mitochondrial function has been associated with the etiopathogenesis of Parkinson's disease (PD). Sustained inhibition of complex I produces mitochondrial dysfunction, which is related to oxidative injury and nigrostriatal dopamine (DA) neurodegeneration. This study aimed to identify disease-modifying treatments for PD. Unsubstituted phenothiazine (PTZ) is a small and uncharged aromatic imine that readily crosses the blood-brain barrier. PTZ lacks significant DA receptor-binding activity and, in the nanomolar range, exhibits protective effects via its potent free radical scavenging and anti-inflammatory activities. Given that DAergic neurons are highly vulnerable to oxidative damage and inflammation, we hypothesized that administration of PTZ might confer neuroprotection in different experimental models of PD. Our findings showed that PTZ rescues rotenone (ROT) toxicity in primary ventral midbrain neuronal cultures by preserving neuronal integrity and reducing protein thiol oxidation. Long-term treatment with PTZ improved animal weight, survival rate, and behavioral deficits in ROT-lesioned rats. PTZ protected DA content and fiber density in the striatum and DA neurons in the SN against the deleterious effects of ROT. Mitochondrial dysfunction, axonal impairment, oxidative insult, and inflammatory response were attenuated with PTZ therapy. Furthermore, we have provided a new insight into the molecular mechanism underlying the neuroprotective effects of PTZ

Natural convection from a horizontal cylinder parallel to a heated vertical wall

Heat transfer measurements have been made from a long (L/D = 15) horizontal cylinder in water parallel to a heated vertical wall. The cylinder and wall boundary conditions were isothermal, and they were maintained at equal temperatures. The investigation covered Rayleigh numbers based on cylinder diameter from 400,000 to 10,000,000. The cylinder height above the wall leading edge was set at height to diameter ratios, H/D, of 2.07, 7.44, and 15.50. The horizontal space between the cylinder and wall spanned the range 0.05 < S/D < 0.62. It was found that heat transfer was degraded as much as 46% for close spacings and enhanced as much as 15% at moderate spacings. The lowest position (H/D = 2.07) showed the greatest overall enhancement, while the highest position (H/D = 15.5) showed overall degradation

Deriving asteroid mineralogies from reflectance spectra: Implications for the MUSES-C target asteroid

In an effort to both bolster the spectral database on ordinary chondrites and constrain our ability to deconvolve modal, mineral chemistry and bulk chemical composition information from ordinary chondrites, we have initiated a spectral study of samples with known bulk compositions from the Smithsonian Institution\u27s Analyzed Meteorite Powder collection. In this paper, we focus on deriving a better formula for determining asteroid mineralogies from reflectance spectra. The MUSES-C mission to asteroid 25143 1998 SF36 will allow any derived mineralogies to be tested with a returned sample

Bulk element compositions of meteorites: A guide for interpreting remote-sensing geochemical measurements of planets and asteroids

We report a large database of bulk meteorite elemental abundances, compiled to aid in the interpretation of elemental abundance data determined by remote-sensing instrumentation on planetary missions. A custom user interface was developed for easy access and manipulation of the abundance data. The database contains almost 3000 individual analyses of more than 1000 individual meteorites. Most major and minor elements are included, as well as small number of trace elements measurable by remote-sensing gamma-ray spectroscopy (notably Th and U). All meteorite classes show variability in bulk compositions between individual analyses. Some of this spread is intrinsic to the parent bodies of the meteorites. However, some variability is undoubtedly due to systematic uncertainties, caused by inter-laboratory bias, misclassification, effect of weathering, and unrepresentative sampling. We use the database here to investigate both how well different meteorite groups can be distinguished on the basis of bulk compositions and how bulk compositions can be related to the cosmochemical and geological processes that produced them. The major elements measurable by X-ray and gamma-ray remote-sensing-oxygen, magnesium, aluminum, silicon, sulfur, calcium and iron-reflect to differing degrees nebular elemental fractionations and parent-body igneous processes and can be used together to distinguish most classes and sub-classes of meteorites. Potassium is potentially useful as a tracer of thermal processes in the early solar system. Thorium and uranium abundances could be used to trace igneous processes on differentiated asteroids

Pulmonary Inflammation Induced by Incomplete or Inactivated Adenoviral Particles

Overview summary The amount of pulmonary inflammation induced in mice by intratracheal administration of high doses of adenoviral vectors was compared to that induced by viral particles that lack the ability to express the genes that they contain. The number of inflammatory cells infiltrating the lung 6 days after particle administration was similar between animals receiving normal versus defective adenoviral particles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63169/1/hum.1995.6.12-1553.pd

Neutral Solar Wind Generated by Lunar Exospheric Dust at the Terminator

We calculate the flux of neutral solar wind observed on the lunar surface at the terminator due to solar wind protons penetrating exospheric dust grains with (1) radii greater than 0.1 microns and (2) radii greater than 0.01 microns. For grains with radii larger than 0.1 microns, the ratio of the neutral solar wind flux produced by exospheric dust to the incident ionized solar wind flux is estimated to be about 10^-4-10^-3 for solar wind speeds in excess of 800 km/s, but much lower (less than 10^-5) at average to slow solar wind speeds. However, when the smaller grain sizes are considered, this ratio is estimated to be greater than 10^-5 at all speeds, and at speeds in excess of 700 km/s reaches about 10^-3. These neutral solar wind fluxes are easily measurable with current low energy neutral atom instrumentation. Observations of neutral solar wind from the surface of the Moon would provide independent information on the distribution of very small dust grains in the lunar exosphere that would complement and constrain optical measurements at ultraviolet and visible wavelengths.Comment: in press in J. Geophys. Re