Study of the growth parameters involved in synthesizing boron carbide filaments Second quarterly report

Growth parameters in synthesis of boron carbide whisker

Effects of Heavy Metals (Cadmium, Copper, and Mercury) on Reproduction, Growth, and Survival of Brine Shrimp (\u3cem\u3eArtemia salina\u3c/em\u3e) from the Great Salt Lake

The purpose of this paper is to report findings concerning the effects of cadmium , copper, and mercury on the brine shrimp Artemia Salina, of the Great Salt Lake. Metal toxicity was observed in relation to acute susceptibility, growth, reproduction, and hatching of the brine shrimp. Heavy metal concentrations such as cadmium, copper, and mercury are known to be considerably higher in the Great Salt Lake than those in both freshwater and seawater. No published study has been concerned with heavy metal effects on organisms in salinities greater than seawater (35 grams per liter total dissolved solids). The experiments reported in this paper were carried out in salinities approximating the Great Salt Lake (150-320 grams per liter total dissolved solids). Results of this study indicate that cadmium, copper, and mercury toxicities to the brine shrimp may not be comparable at varying salinities. Findings of acute toxicity experiments were compared to other heavy metal studies on marine organisms. The brine shrimp was found to be very resistant to cadmium and copper poisoning and moderately resistant to mercury. Neither cadmium nor copper inhibited hatching of the brine shrimp eggs although mercury caused severe inhibition at concentrations of 0.3 milligrams per liter. Only cadmium at concentrations between 1.0 and 33 milligrams per liter significantly suppressed growth rate and reproduction. Mercury and copper were not found to affect growth and reproduction below concentrations causing acute poisoning. Mercury was found to be the most lethal to the adult brine shrimp with a range of times to 50 percent mortality from 126 to 8.5 hours at mercury concentrations of 0.01 to 100 milligrams per liter respectively. Copper caused mortalities at concentrations of 1 to 67 milligrams per liter with respective times to 50 percent mortality of 124 and 12 hours. Copper was shown to precipitate out at concentrations near 12 milligrams per liter, Cadmium was found to be the least lethal with a range of times to 50 percent mortality from 94 to 320 hours with respective cadmium concentrations of 100 and 3.3 milligrams per liter

Dynamical Measurements of Black Hole Masses in Four Brightest Cluster Galaxies at 100 Mpc

We present stellar kinematics and orbit superposition models for the central regions of four Brightest Cluster Galaxies (BCGs), based upon integral-field spectroscopy at Gemini, Keck, and McDonald Observatories. Our integral-field data span radii from < 100 pc to tens of kpc. We report black hole masses, M_BH, of 2.1 +/- 1.6 x 10^10 M_Sun for NGC 4889, 9.7 + 3.0 - 2.6 x 10^9 M_Sun for NGC 3842, and 1.3 + 0.5 - 0.4 x 10^9 M_Sun for NGC 7768. For NGC 2832 we report an upper limit of M_BH < 9 x 10^9 M_Sun. Stellar orbits near the center of each galaxy are tangentially biased, on comparable spatial scales to the galaxies' photometric cores. We find possible photometric and kinematic evidence for an eccentric torus of stars in NGC 4889, with a radius of nearly 1 kpc. We compare our measurements of M_BH to the predicted black hole masses from various fits to the relations between M_BH and stellar velocity dispersion, luminosity, or stellar mass. The black holes in NGC 4889 and NGC 3842 are significantly more massive than all dispersion-based predictions and most luminosity-based predictions. The black hole in NGC 7768 is consistent with a broader range of predictions.Comment: 24 pages, 18 figures. Accepted for publication in Ap

Investigation of the reinforcement of ductile metals with strong, high modulus discontinuous brittle fibers Quarterly report

Factors affecting reinforcement of aluminum with boron carbide whisker

Hydrostatic Gas Constraints On Supermassive Black Hole Masses: Implications For Hydrostatic Equilibrium And Dynamical Modeling In A Sample Of Early-Type Galaxies

We present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M(BH)) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGC4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with MBH measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than similar to 10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M(bondi)), finding that the two galaxies with the highest M(bondi) exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.NASA NAS5-26555, NNG04GE76G, G07-8083XAstronom

Soil micromorphological evidence of early agriculture in north-west Europe

International audienceThe study of early agricultural soils using micromorphology is outlined. The effects of tillage due to modern agriculture are reviewed and the results from four experiments in ‘prehistoric cultivation’ are presented. These are used in the interpretation of prehistoric agricultural practices, based on a study of soils from various archaeological sites in north‐west Europe. It is suggested that microfabric features, varying according to soil texture, can be diagnostic of tillage. Microfabric type, textural features (e.g. coatings) and structure are, taken together, better indicators of ancient tillage than single features