Modelling the dynamics of turbulent floods

Consider the dynamics of turbulent flow in rivers, estuaries and floods. Based on the widely used k-epsilon model for turbulence, we use the techniques of centre manifold theory to derive dynamical models for the evolution of the water depth and of vertically averaged flow velocity and turbulent parameters. This new model for the shallow water dynamics of turbulent flow: resolves the vertical structure of the flow and the turbulence; includes interaction between turbulence and long waves; and gives a rational alternative to classical models for turbulent environmental flows

Synthetic Mudscapes: Human Interventions in Deltaic Land Building

In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are denied by traditional inhabitation. Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The social, economic, and ecological evolution of the region are defended by an expanded web of growing land

Deep MMT Transit Survey of the Open Cluster M37 IV: Limit on the Fraction of Stars With Planets as Small as 0.3 R_J

We present the results of a deep (15 ~< r ~< 23), 20 night survey for transiting planets in the intermediate age open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m MMT. We do not detect any transiting planets among the ~1450 observed cluster members. We do, however, identify a ~ 1 R_J candidate planet transiting a ~ 0.8 Msun Galactic field star with a period of 0.77 days. The source is faint (V = 19.85 mag) and has an expected velocity semi-amplitude of K ~ 220 m/s (M/M_J). We conduct Monte Carlo transit injection and recovery simulations to calculate the 95% confidence upper limit on the fraction of cluster members and field stars with planets as a function of planetary radius and orbital period. Assuming a uniform logarithmic distribution in orbital period, we find that < 1.1%, < 2.7% and < 8.3% of cluster members have 1.0 R_J planets within Extremely Hot Jupiter (EHJ, 0.4 < T < 1.0 day), Very Hot Jupiter (VHJ, 1.0 < T < 3.0 days) and Hot Jupiter (HJ, 3.0 < T < 5.0 days) period ranges respectively. For 0.5 R_J planets the limits are < 3.2%, and < 21% for EHJ and VHJ period ranges, while for 0.35 R_J planets we can only place an upper limit of < 25% on the EHJ period range. For a sample of 7814 Galactic field stars, consisting primarily of FGKM dwarfs, we place 95% upper limits of < 0.3%, < 0.8% and < 2.7% on the fraction of stars with 1.0 R_J EHJ, VHJ and HJ assuming the candidate planet is not genuine. If the candidate is genuine, the frequency of ~ 1.0 R_J planets in the EHJ period range is 0.002% < f_EHJ < 0.5% with 95% confidence. We place limits of < 1.4%, < 8.8% and < 47% for 0.5 R_J planets, and a limit of < 16% on 0.3 R_J planets in the EHJ period range. This is the first transit survey to place limits on the fraction of stars with planets as small as Neptune.Comment: 61 pages, 19 figures, 5 tables, replaced with the version accepted for publication in Ap

An R- and I-Band Photometric Variability Survey of the Cygnus OB2 Association

We present a catalog of photometrically variable stars discovered within two 21'.3 X 21'.3 fields centered on the Cygnus OB2 association. There have hitherto been no deep optical variability studies of Cyg OB2 despite it being replete with early-type massive stars, perhaps due to the high and variable extinction (up to A_V ~ 20) that permeates much of the region. Here we provide results of the first variability study with this combination of spatial coverage (~ 0.5 deg) and photometric depth (R ~ 21 mag). We find 121 stars to be variable in both R- and I-band, 116 of them newly discovered. Of the 121 variables, we identify 27 eclipsing binaries (EBs) and eclipsing binary candidates, 20 potential Herbig Ae/Be stars, and 52 pulsating variables. Confirming both the status and the cluster membership of the Herbig Ae/Be stars would address the uncertainty regarding the age and star formation history of Cyg OB2. We match our catalog to known variables and binaries in the region, 2MASS near-IR (NIR) data, and Chandra X-ray observations to find counterparts to new variables in other wavelengths.Comment: 34 pages, 12 figures, submitted to Ap