Cluster Winds Blow along Supercluster Axes

Within Abell galaxy clusters containing wide-angle tailed radio sources, there is evidence of a ``prevailing wind'' which directs the WAT jets. We study the alignment of WAT jets and nearby clusters to test the idea that this wind may be a fossil of drainage along large-scale supercluster axes. We also test this idea with a study of the alignment of WAT jets and supercluster axes. Statistical test neighbours indicate no alignment of WAT jets towards nearest clusters, but do indicate approximately 98% confidence in alignment with the long axis of the supercluster in which the cluster lies. We find a preferred scale for such superclusters of order 25 Mpc $h^{-1}$.Comment: Latex, 5 pages, with 5 postscript figures. To be published in MNRAS. Slight revisions to coincide with journal text. Linked to color image at http://kusmos.phsx.ukans.edu/~melott/images/A2634SUW.jp

Launch Vehicle Propulsion Design with Multiple Selection Criteria

The approach and techniques described herein define an optimization and evaluation approach for a liquid hydrogen/liquid oxygen single-stage-to-orbit system. The method uses Monte Carlo simulations, genetic algorithm solvers, a propulsion thermo-chemical code, power series regression curves for historical data, and statistical models in order to optimize a vehicle system. The system, including parameters for engine chamber pressure, area ratio, and oxidizer/fuel ratio, was modeled and optimized to determine the best design for seven separate design weight and cost cases by varying design and technology parameters. Significant model results show that a 53% increase in Design, Development, Test and Evaluation cost results in a 67% reduction in Gross Liftoff Weight. Other key findings show the sensitivity of propulsion parameters, technology factors, and cost factors and how these parameters differ when cost and weight are optimized separately. Each of the three key propulsion parameters; chamber pressure, area ratio, and oxidizer/fuel ratio, are optimized in the seven design cases and results are plotted to show impacts to engine mass and overall vehicle mass

Characteristic QSO Accretion Disk Temperatures from Spectroscopic Continuum Variability

Using Sloan Digital Sky Survey (SDSS) quasar spectra taken at multiple epochs, we find that the composite flux density differences in the rest frame wavelength range 1300-6000 AA can be fit by a standard thermal accretion disk model where the accretion rate has changed from one epoch to the next (without considering additional continuum emission components). The fit to the composite residual has two free parameters: a normalizing constant and the average characteristic temperature $\bar{T}^*$. In turn the characteristic temperature is dependent on the ratio of the mass accretion rate to the square of the black hole mass. We therefore conclude that most of the UV/optical variability may be due to processes involving the disk, and thus that a significant fraction of the UV/optical spectrum may come directly from the disk.Comment: 31 pages, 8 figure

The Strategic Exploitation of Limited Information and Opportunity in Networked Markets

This paper studies the effect of constraining interactions within a market. A model is analysed in which boundedly rational agents trade with and gather information from their neighbours within a trade network. It is demonstrated that a trader’s ability to profit and to identify the equilibrium price is positively correlated with its degree of connectivity within the market. Where traders differ in their number of potential trading partners, well-connected traders are found to benefit from aggressive trading behaviour.Where information propagation is constrained by the topology of the trade network, connectedness affects the nature of the strategies employed

Digital dissection and three-dimensional interactive models of limb musculature in the Australian estuarine crocodile (Crocodylus porosus)

Digital dissection is a relatively new technique that has enabled scientists to gain a better understanding of vertebrate anatomy. It can be used to rapidly disseminate detailed, threedimensional information in an easily accessible manner that reduces the need for destructive, traditional dissections. Here we present the results of a digital dissection on the appendicular musculature of the Australian estuarine crocodile (Crocodylus porosus). A better understanding of this until now poorly known system in C. porosus is important, not only because it will expand research into crocodilian locomotion, but because of its potential to inform muscle reconstructions in dinosaur taxa. Muscles of the forelimb and hindlimb are described and three-dimensional interactive models are included based on CT and MRI scans as well as fresh-tissue dissections. Differences in the arrangement of musculature between C. porosus and other groups within the Crocodylia were found. In the forelimb, differences are restricted to a single tendon of origin for triceps longus medialis. For the hindlimb, a reduction in the number of heads of ambiens was noted as well as changes to the location of origin and insertion for iliofibularis and gastrocnemius externus

Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGN to be composed mainly of stellar light and non-variable on the time-scales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multi-epoch data in the Sloan Digital Sky Survey (SDSS) Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ~700 days) covering a wavelength range of 3900-8900 angstrom. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of two. From these data we find no obvious continuum and emission-line variability in the narrow-line AGNs on average -- the spectroscopic variability of the continuum is 0.07+/-0.26 mag in the g band and, for the emission-line ratios log10([NII]/Halpha) and log10([OIII]/Hbeta), the variability is 0.02+/-0.03 dex and 0.06+/-0.08 dex, respectively. From the continuum variability measurement we set an upper limit on the ratio between the flux of varying spectral component, presumably related to AGN activities, and that of host galaxy to be ~30%. We provide the corresponding upper limits for other spectral classes, including those from the BPT diagram, eClass galaxy classification, stars and quasars.Comment: AJ accepte

Thrombopoietin: A Novel Bone Healing Agent

poster abstractCritical-size defects in bones do not heal spontaneously and usually require the use of grafts. Unfortunately, grafts have several limitations. To improve bone formation, many clinicians now use bone morphogenetic proteins (BMP), particularly in spinal fusion, fracture healing, and in critical-size defect regeneration. However, multiple side effects of BMP treatment have been uncovered including increased incidence of cancer. Thus, there is great interest in alternatives that allow for safe and effective bone regeneration. Here we show the ability of thrombopoietin (TPO), the main megakaryocyte growth factor, to heal critical-size femoral defects rodents. 5mm or 4mm segmental defects were created in the femur of Long Evans rats or C57BL/6 mice, respectively. The defects were filled with a novel bioabsorbable scaffold which was loaded with recombinant human TPO, BMP-2, or saline, and held stable by a retrograde 1.6 mm intramedullary Kirschner wire (rats) or 23G needle (mice). Xrays were taken every 3 weeks in rats and weekly in mice. Animal were sacrificed at 15 weeks, at which time micro-computed tomography (μCT) and histological analyses were performed. The results observed in mice and rats were similar. The saline control group did not show bridging callus at any time. Both the BMP-2 and TPO groups healed the defect, although bridging callus was evident at earlier times in the BMP-2 groups. However, the TPO groups showed a much more remodeled and physiologic contour on both Xray and μCT. μCT and histological analysis confirms that compared to BMP-2, TPO-treated specimens have a thicker cortex but smaller diameter and smoother contour. TPO appears to restore the original bone contour by stimulating osteoblastogenesis, allowing for periosteal bridging and stabilization to occur, while simultaneously stimulating osteoclast formation. Thus, TPO may serve as a novel bone healing agent