The Tail of the HI Mass Function

The contribution of extragalactic objects with HI masses below $10^8 M_\odot$ to the HI mass function remains uncertain. Several aspects of the detection of low-mass sources in HI surveys are not always considered, and as a result different analysis techniques yield widely different estimates for their number density. It is suggested at one extreme that the number density of galaxies follows a shallow Schechter power-law slope, and at the other extreme that it follows a steep faint-end rise like that found for field optical sources. Here we examine a variety of selection effects, issues of completeness, and consequences of LSS. We derive results for the large Arecibo Dual Beam Survey which indicate that the field mass function does rise steeply, while within the Virgo Cluster environs, the slope appears to be much shallower. Dependence on the local density of galaxies may partially explain differences between surveys.Comment: 8 pages, presented at Mapping the Hidden Universe: The Universe in HI. eds Kraan-Korteweg, Henning, Andernac

Technological change and productivity growth in the air transport industry

The progress of the civil air transport industry in the United States was examined in the light of a proposal of Enos who, after examining the growth of the petroleum industry, divided that phenomenon into two phases, the alpha and the beta; that is, the invention, first development and production, and the improvement phase. The civil air transport industry developed along similar lines with the technological progress coming in waves; each wave encompassing several new technological advances while retaining the best of the old ones. At the same time the productivity of the transport aircraft as expressed by the product of the aircraft velocity and the passenger capacity increased sufficiently to allow the direct operating cost in cents per passenger mile to continually decrease with each successive aircraft development

Gas and Stars in an HI-Selected Galaxy Sample

We present the results of a J-band study of the HI-selected Arecibo Dual-Beam Survey and Arecibo Slice Survey galaxy samples using the 2 Micron All-Sky Survey data. We find that these galaxies span a wide range of stellar and gas properties. However, despite the diversity within the samples, we find a very tight correlation between luminosity and size in the J-band, similar to that we previously found (Rosenberg & Schneider 2003) between the HI mass and size. We also find that the correlation between the baryonic mass and the J-band diameter is even tighter than between the baryonic mass and the rotational velocity.Comment: AJ in press, 17 pages (including tables and figures) + 6 additional jpg figure

Research on processes for utilization of lunar resources quarterly report, 16 jul. - 15 oct. 1964

Lunar resource utilization - silicate reduction unit and carbon monoxide reduction reacto

Unravelling the Mysteries of the Leo Ring: An Absorption Line Study of an Unusual Gas Cloud

Since the 1980's discovery of the large (2x10^9 Msun) intergalactic cloud known as the Leo Ring, this object has been the center of a lively debate about its origin. Determining the origin of this object is still important as we develop a deeper understanding of the accretion and feedback processes that shape galaxy evolution. We present HST/COS observations of three sightlines near the Ring, two of which penetrate the high column density neutral hydrogen gas visible in 21 cm observations of the object. These observations provide the first direct measurement of the metallicity of the gas in the Ring, an important clue to its origins. Our best estimate of the metallicity of the ring is ~10% Zsun, higher than expected for primordial gas but lower than expected from an interaction. We discuss possible modifications to the interaction and primordial gas scenarios that would be consistent with this metallicity measurement.Comment: 11 pages, 7 figures, accepted Ap

Differential gene expression in the recovery from ischemic renal injury

Differential gene expression in the recovery from ischemic renal injury. Recovery from renal ischemia requires regeneration of damaged tubular epithelium. Previous studies have examined the expression of proto-oncogenes and growth factors after ischemia, but the response of genes coding for structural and functional genes has not been scrutinized. Rats were subjected to 40 minutes of renal artery occlusion and 60 minutes to 96 hours of reperfusion. Total RNA was isolated and mRNA for the structural protein actin, the enzymes superoxide dismutase and renin, the proto-oncogene c-fos, the nuclear protein histone H2b, and the putative marker for cell injury TRPM-2 was quantitated by Northern hybridization. Expression of the proto-oncogene c-fos was seen early but for only short duration. Histone gene expression was not markedly increased until 24 hours after ischemia, but remained increased for several days. Renin mRNA was undetectable one hour after ischemia, but was present in normal amounts at 24 and 48 hours. In contrast, superoxide dismutase mRNA was present in decreased amounts 24, 48, and 96 hours after ischemia. TRPM-2 gene expression was greatly increased 24 to 72 hours after ischemia and began decreasing at 96 hours. This selective sequence of gene expression or repression after renal ischemia might maximize the proliferative repair process. This information will be useful for designing therapies to further enhance recovery from acute renal injury

A comparison of spectral element and finite difference methods using statically refined nonconforming grids for the MHD island coalescence instability problem

A recently developed spectral-element adaptive refinement incompressible magnetohydrodynamic (MHD) code [Rosenberg, Fournier, Fischer, Pouquet, J. Comp. Phys. 215, 59-80 (2006)] is applied to simulate the problem of MHD island coalescence instability (MICI) in two dimensions. MICI is a fundamental MHD process that can produce sharp current layers and subsequent reconnection and heating in a high-Lundquist number plasma such as the solar corona [Ng and Bhattacharjee, Phys. Plasmas, 5, 4028 (1998)]. Due to the formation of thin current layers, it is highly desirable to use adaptively or statically refined grids to resolve them, and to maintain accuracy at the same time. The output of the spectral-element static adaptive refinement simulations are compared with simulations using a finite difference method on the same refinement grids, and both methods are compared to pseudo-spectral simulations with uniform grids as baselines. It is shown that with the statically refined grids roughly scaling linearly with effective resolution, spectral element runs can maintain accuracy significantly higher than that of the finite difference runs, in some cases achieving close to full spectral accuracy.Comment: 19 pages, 17 figures, submitted to Astrophys. J. Supp

Relativistic Lee Model on Riemannian Manifolds

We study the relativistic Lee model on static Riemannian manifolds. The model is constructed nonperturbatively through its resolvent, which is based on the so-called principal operator and the heat kernel techniques. It is shown that making the principal operator well-defined dictates how to renormalize the parameters of the model. The renormalization of the parameters are the same in the light front coordinates as in the instant form. Moreover, the renormalization of the model on Riemannian manifolds agrees with the flat case. The asymptotic behavior of the renormalized principal operator in the large number of bosons limit implies that the ground state energy is positive. In 2+1 dimensions, the model requires only a mass renormalization. We obtain rigorous bounds on the ground state energy for the n-particle sector of 2+1 dimensional model.Comment: 23 pages, added a new section, corrected typos and slightly different titl