Regional Sea Level Rise Along the United States Coasts

Over the past several years, there has been several studies focused on reconstructing global mean sea level (GMSL) for the 20th century, along with projecting rates out into the future. Of greater importance for mitigation and adaptation plans, however, is the rate of local or regional sea level (RSL) rise. Ocean dynamics along with changes in Earth’s gravitational field can cause RSL to deviate from the change in GMSL. During the satellite altimeter era covering the past two decades, RSL trends can be four times the global average, with much of this spatial variation due to internal climate variability. Isolating the long-term signal that may be expected to persist into the future, or from which an acceleration can be estimated, is a challenge with the short satellite record. Prior to the satellite altimeter era, tide gauges must be used to study past sea level variability. Tide gauges suffer from sampling challenges that make regional studies difficult, and as a result, there has been relatively little discussion and few comprehensive efforts on reproducing long-term RSL trends. This work aims to determine the 20th century regional pattern of sea level rise by reducing the tide gauge data to a usable subset and taking into account the factors that cause spatial variability in trends on long time-scales. This provides an estimate of secular changes leading to RSL rise associated with anthropogenic affects. Either exacerbating or suppressing these regional trends is natural internal climate variability. By determining the frequency and magnitude of these inter-annual to decadal events, we can determine a baseline of future RSL along the East and West coast of the United states. This is an important step for mitigation and adaptation plans, since high frequency events such as storms and high tides will be coupled with RSL rise, causing increased flooding and inundation. As such, we will determine future nuisance flooding in Norfolk, VA, arising from a combination of sea level contributors from tides to internal climate variability

Diffusivity and Weak Clustering in a Quasi 2D Granular Gas

We present results from a detailed simulation of a quasi-2D dissipative granular gas, kept in a non-condensed steady state via vertical shaking over a rough substrate. This gas shows a weak power-law decay in the tails of its Pair Distribution Functions (PDF's), indicating fractality and therefore a tendency to form clusters over several size scales. This clustering depends monotonically on the dissipation coefficient, and disappears when the sphere-sphere collisions are conservative. Clustering is also sensitive to the packing fraction. This gas also displays the standard nonequilibrium characteristics of similar systems, including non-Maxwellian velocity distributions. The diffusion coefficients are calculated over all the conditions of the simulations, and it is found that diluted gases are more diffusive for smaller restitution coefficients.Comment: 14 pages, 11 figure

Analysis and Assembling of Network Structure in Mutualistic Systems

It has been observed that mutualistic bipartite networks have a nested structure of interactions. In addition, the degree distributions associated with the two guilds involved in such networks (e.g. plants & pollinators or plants & seed dispersers) approximately follow a truncated power law. We show that nestedness and truncated power law distributions are intimately linked, and that any biological reasons for such truncation are superimposed to finite size effects . We further explore the internal organization of bipartite networks by developing a self-organizing network model (SNM) that reproduces empirical observations of pollination systems of widely different sizes. Since the only inputs to the SNM are numbers of plant and animal species, and their interactions (i.e., no data on local abundance of the interacting species are needed), we suggest that the well-known association between species frequency of interaction and species degree is a consequence rather than a cause, of the observed network structure.Comment: J. of. Theor. Biology, in pres

Height Pairing on Higher Cycles and Mixed Hodge Structures

For a smooth, projective complex variety, we introduce several mixed Hodge structures associated to higher algebraic cycles. Most notably, we introduce a mixed Hodge structure for a pair of higher cycles which are in the refined normalized complex and intersect properly. In a special case, this mixed Hodge structure is an oriented biextension, and its height agrees with the higher archimedean height pairing introduced in a previous paper by the first two authors. We also compute a non-trivial example of this height given by Bloch-Wigner dilogarithm function. Finally we study the variation of mixed Hodge structures of Hodge-Tate type, and show that the height extends continuously to degenerate situations

X-ray Spectra of the RIXOS source sample

We present results of an extensive study of the X-ray spectral properties of sources detected in the RIXOS survey, that is nearly complete down to a flux limit of 3e-14 cgs (0.5-2 keV). We show that for X-ray surveys containing sources with low count rate spectral slopes estimated using simple hardness ratios in the ROSAT band can be biased. Instead we analyse three-colour X-ray data using statistical techniques appropriate to the Poisson regime which removes the effects of this bias. We have then applied this technique to the RIXOS survey to study the spectral properties of the sample. For the AGN we find an average energy index of 1.05+-0.05 with no evidence for spectral evolution with redshift. Individual AGN are shown to have a range of properties including soft X-ray excesses and intrinsic absorption. Narrow Emission Line Galaxies also seem to fit to a power-law spectrum, which may indicate a non-thermal origin for their X-ray emission. We infer that most of the clusters in the sample have a bremsstrahlung temperature >3 keV, although some show evidence for a cooling flow. The stars deviate strongly from a power-law model but fit to a thermal model. Finally, we have analysed the whole RIXOS sample containing 1762 sources. We find that the mean spectral slope of the sources hardens at lower fluxes in agreement with results from other samples. However, a study of the individual sources demonstrates that the hardening of the mean is caused by the appearance of a population of very hard sources at the lowest fluxes. This has implications for the nature of the soft X-ray background.Comment: 31,LaTeX file, 2 PS files with Table 2 and 22 PS figures. MNRAS in pres

Investigating poultry trade patterns to guide avian influenza surveillance and control: a case study in Vietnam

Live bird markets are often the focus of surveillance activities monitoring avian influenza viruses (AIV) circulating in poultry. However, in order to ensure a high sensitivity of virus detection and effectiveness of management actions, poultry management practices features influencing AIV dynamics need to be accounted for in the design of surveillance programmes. In order to address this knowledge gap, a cross-sectional survey was conducted through interviews with 791 traders in 18 Vietnamese live bird markets. Markets greatly differed according to the sources from which poultry was obtained, and their connections to other markets through the movements of their traders. These features, which could be informed based on indicators that are easy to measure, suggest that markets could be used as sentinels for monitoring virus strains circulating in specific segments of the poultry production sector. AIV spread within markets was modelled. Due to the high turn-over of poultry, viral amplification was likely to be minimal in most of the largest markets. However, due to the large number of birds being introduced each day, and challenges related to cleaning and disinfection, environmental accumulation of viruses at markets may take place, posing a threat to the poultry production sector and to public health