Biological Effects of Dispersants and Dispersed Oil in Surface and Deep Ocean Species

Beginning with the use of industrial-strength detergents, dispersing agents have been employed in spill response for decades. The Corexit series of agents in common use today generally consist of non-ionic and/or anionic surfactants in a solvent base designed to enhance miscibility under varying temperature and salinity conditions; cationic surfactants tend to be too toxic for use. While dispersants generally serve to decrease the interfacial surface tension of oil, thus facilitating its weathering under low-energy conditions, their surface-active nature also causes their interaction with cell surfaces – those of single-celled organisms as well as the gills of vertebrates and invertebrates

A note on the effect of supplementation with microbial phytase and organic acids on feed intake and growth performance of growing pigs

peer-reviewedThis experiment was designed to investigate the effects of supplementation with phytase, either alone or in combination with organic acids, on feed intake and growth of pigs from 8 to 89 kg live weight. Some 240 pigs were used in four experimental treatments comprising: (1) control, (2) control plus phytase, (3) control plus phytase plus liquid organic acids (formic, propionic), and (4) control plus phytase plus powdered organic acids (formic, fumaric, propionic). Feed intake and growth rate in the weaner stage were increased (P < 0.05) by phytase supplementation, with some additional benefits from organic acid inclusion. Interval to slaughter was reduced (P < 0.05) by phytase supplementation

The ROSAT Deep Cluster Survey: the X-ray Luminosity Function out to z=0.8

We present the X-ray Luminosity Function (XLF) of the ROSAT Deep Cluster Survey (RDCS) sample over the redshift range 0.05-0.8. Our results are derived from a complete flux-limited subsample of 70 galaxy clusters, representing the brightest half of the total sample, which have been spectroscopically identified down to the flux limit of 4*10^{-14} erg/cm^2/s (0.5-2.0 keV) and have been selected via a serendipitous search in ROSAT-PSPC pointed observations. The redshift baseline is large enough that evolutionary effects can be studied within the sample. The local XLF (z < 0.25) is found to be in excellent agreement with previous determinations using the ROSAT All-Sky Survey data. The XLF at higher redshifts, when combined with the deepest number counts constructed to date (f>2*10^{-14} arg/cm^2/s), reveal no significant evolution at least out to z=0.8, over a luminosity range 2*10^{42}-3*10^{44} erg/s in the [0.5-2 keV] band. These findings extend the study of cluster evolution to the highest redshifts and the faintest fluxes probed so far in X-ray surveys. They complement and do not necessarily conflict with those of the Einstein Extended Medium Sensitivity Survey, leaving the possibility of negative evolution of the brightest end of the XLF at high redshifts.Comment: 12 pages, 4 figures, LaTeX (aasms4.sty). To appear in ApJ Letter

Welfare-maximizing monetary policy under parameter uncertainty

This paper examines welfare-maximizing monetary policy in an estimated micro-founded general equilibrium model of the U.S. economy where the policymaker faces uncertainty about model parameters. Uncertainty about parameters describing preferences and technology implies not only uncertainty about the dynamics of the economy. It also implies uncertainty about the model's utility-based welfare criterion and about the economy's natural rate measures of interest and output. We analyze the characteristics and performance of alternative monetary policy rules given the estimated uncertainty regarding parameter estimates. We find that the natural rates of interest and output are imprecisely estimated. We then show that, relative to the case of known parameters, optimal policy under parameter uncertainty responds less to natural-rate terms and more to other variables, such as price and wage inflation and measures of tightness or slack that do not depend on natural rates.Monetary policy

Response-to-noise studies of some aircraft and spacecraft structures

Fatigue and response to noise of aircraft and spacecraft viscoelastic panels, shell structure, and payload

Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795

Using the X-ray data from \ASCA, spectral and spatial properties of the intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a radial distance of $\sim 12'$ ($\sim 1.3$ $h_{50}^{-1}$ kpc). The ICM temperature and abundance are spatially rather constant, although the cool emission component is reconfirmed in the central region. The azimuthally- averaged radial X-ray surface brightness profiles are very similar between soft (0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with a single-$\beta$ model due to a strong data excess within $\sim5'$ of the cluster center. In contrast, double-$\beta$ models can successfully reproduce the overall brightness profiles both in the soft and hard energy bands, as well as that derived with the \ROSAT PSPC. Properties of the central excess brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT and \ASCA. Thus, the excess X-ray emission from the core region of this cluster is confirmed for the first time in hard X-rays above 3 keV. This indicates that the shape of the gravitational potential becomes deeper than the King-type one towards the cluster center. Radial profiles of the total gravitating matter, calculated using the double-$\beta$ model, reveal an excess mass of $\sim 3 \times 10^{13}~ M_{\odot}$ within $\sim 150 h^{-1}_{50}$ kpc of the cluster center. This suggests a hierarchy in the gravitational potential corresponding to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998

The Beta Problem: A Study of Abell 262

We present an investigation of the dynamical state of the cluster A262. Existing optical line of sight velocities for select cluster galaxies have been augmented by new data obtained with the Automated Multi-Object Spectrograph at Lick Observatory. We find evidence for a virialized early-type population distinct from a late-type population infalling from the Pisces-Perseus supercluster ridge. We also report on a tertiary population of low luminosity galaxies whose velocity dispersion distinguishes them from both the early and late-type galaxies. We supplement our investigation with an analysis of archival X-ray data. A temperature is determined using ASCA GIS data and a gas profile is derived from ROSAT HRI data. The increased statistics of our sample results in a picture of A262 with significant differences from earlier work. A previously proposed solution to the "beta-problem" in A262 in which the gas temperature is significantly higher than the galaxy temperature is shown to result from using too low a velocity dispersion for the early-type galaxies. Our data present a consistent picture of A262 in which there is no "beta-problem", and the gas and galaxy temperature are roughly comparable. There is no longer any requirement for extensive galaxy-gas feedback to drastically overheat the gas with respect to the galaxies. We also demonstrate that entropy-floor models can explain the recent discovery that the beta values determined by cluster gas and the cluster core radii are correlated.Comment: 31 pages, 14 figures, AAS LaTeX v5.0, Encapsulated Postscript figures, to be published in The Astrophysical Journa

Discovery of a Large-scale Wall in the Direction of Abell 22

We report on the discovery of a large-scale wall in the direction of Abell 22. Using photometric and spectroscopic data from the Las Campanas Observatory and Anglo-Australian Telescope Rich Cluster Survey, Abell 22 is found to exhibit a highly unusual and striking redshift distribution. We show that Abell 22 exhibits a foreground wall-like structure by examining the galaxy distributions in both redshift space and on the colour-magnitude plane. A search for other galaxies and clusters in the nearby region using the 2dF Galaxy Redshift Survey database suggests that the wall-like structure is a significant large-scale, non-virialized filament which runs between two other Abell clusters either side of Abell 22. The filament stretches over at least >40 Mpc in length and 10 Mpc in width at the redshift of Abell 22.Comment: 6 pages, 4 figures, accepted for publication in MNRAS letter