Multiple Trophic Levels in Soft-Bottom Communities

In order to assess the general applicability of recent field experiments with predatory infauna, we searched the literature and found 48 well-documented cases of infaunal consumption by such predators. In 63 % of the cases detailed enough to make a determination, the predators ate other predators. Multiple trophic levels within the infauna are probably a common feature of many soft-bottom communities

Ill-posedness of degenerate dispersive equations

In this article we provide numerical and analytical evidence that some degenerate dispersive partial differential equations are ill-posed. Specifically we study the K(2,2) equation $u_t = (u^2)_{xxx} + (u^2)_{x}$ and the "degenerate Airy" equation $u_t = 2 u u_{xxx}$. For K(2,2) our results are computational in nature: we conduct a series of numerical simulations which demonstrate that data which is very small in $H^2$ can be of unit size at a fixed time which is independent of the data's size. For the degenerate Airy equation, our results are fully rigorous: we prove the existence of a compactly supported self-similar solution which, when combined with certain scaling invariances, implies ill-posedness (also in $H^2$)

Calculation of Higher Mass-Dimensional Effective Lagrangians in Quantum Field Theory

A prescription for calculating low-energy one-loop higher-mass dimensional effective Lagrangians for non-Abelian field theories is constructed in the spirit of quasilocal background field method. Basis of Lorentz and gauge-invariant monomials of similar mass-dimensions acting as building blocks are matrix-multiplied in a specified order (usually dictated by a permutation of tensorial indices) generating the much needed invariants. The same set of building blocks is used to generate higher-order corrections for a specific mass-dimension. Though the gauge group, the spacetime dimensions, the order of corrections that can be included, and the mass-dimensions that can be formed are all kept arbitrary in the prescription, we constructed basis invariants from 3 up to 12 mass-dimensions to accommodate higher-order corrections up to fourth-order. With these basis, we pursued solving the zeroth-order corrections leading to invariants from 2 up to 16 mass-dimensions, for first-order from 4 up to 8 mass-dimensions, second and third order corrections from 6 up to 8 mass-dimensions. As a result, we have reproduced the zeroth-order corrections showing dependence on the covariant derivative of the background matrix potential. Previous calculation was done up to 12 mass-dimensions but this dependence was not shown in closed form. For higher-order corrections, the case for 4 up to 6 mass-dimensions are also reproduced. Finally, we calculated the case for 8 mass-dimensions which is reduced only by exploiting the antisymmetry of the fieldstrength tensor and the freedom to throw away total derivatives.Comment: 186 pages, MS Thesi

Influence of residents on the development of a marine soft-bottom community

Field experiments in a Maine estuary were designed to follow community development in newly exposed sediment to determine if resident infauna affect the settlement and survivorship of colonizing infauna and thereby effect changes in community structure. Sets of buckets consisting of control buckets (buckets with previously dried sediment) and two experimental treatments (Nereis virens or Glycera dibranchiata added to dried sediment) were exposed on three dates between June and October 1979 and sampled after 8, 16 and/or 24 weeks. At each sampling, new buckets were established. The index of proportionate similarity comparing the infaunal community of exposure periods with the same starting date was usually greater than the index comparing periods initiated on different dates indicating that assemblages of initial colonizers persisted for the length of the experiment despite the availability of potential colonizers. Large numbers of infauna colonized defaunated sediment, while over the same period of time infaunal density usually declined in sediment which originally contained infauna. Effects of disturbance, drying the sediment, on colonization were controlled by comparing densities in sediment exposed on different dates but after the sediment had been exposed 8 weeks, There was no significant difference in net changes in density between these conditioned sediments despite large differences in the density of their residents. Sediment with low initial density, however, always had a greater net change in density than sediment with high initial density, suggesting that residents had some effect on net changes in density. Highest densities of most infauna were recorded in the Glycera addition treatment and lowest in the Nereis addition treatment. Nereis abundance was reduced in the presence of Glycera, which may account for high densities in the Glycera addition treatment. It is important to know the species composition of resident assemblages before it is possible to make accurate predictions concerning effects of residents on colonization. The apparent response of colonists to disturbance, in this study drying the sediment, needs to be controlled in experiments designed to determine effects of residents on colonization

Development and Analysis of a Software Package to Quantify In Vivo Polyethylene Wear after Total Hip Arthroplasty

Since the first total hip arthroplasty (THA) in 1938, THA evolved and developed into one of the major concentrations of orthopaedic research. The typical hip implant device used today incorporates a femoral and an acetabular component that serve to replicate the anatomical and mechanical functions of the natural hip joint. However, several problems exist that can effect the function of the implant device. Wear in the polyethylene liner of the acetabular component of the total hip replacement device is known as one of the major factors that affects the longevity of total hip replacement devices. Both manual and computer-aided techniques have been developed to measure linear and volumetric polyethylene wear in two and three-dimensional directions. This study aims to develop a software package that will accurately measure in vivo polyethylene wear after total hip arthroplasty and can be applied to determine the factors that lead to polyethylene wear