Development and Monitoring of Revegetation Methods: Connecting Students with Restoration Activities at Awcomin Marsh

Five classes in a local elementary school participated in an effort to grow and plant high marsh and upper border vegetation at a salt marsh restoration site in spring 2005. Seeds of six marsh upper edge species were successfully germinated and grown into seedlings by third graders. The seedlings were planted by the students in late spring 2005, but only switchgrass and quackgrass plants appeared to have established and survived after one year. Mature shoots of three high marsh species planted by the third graders (salt hay, salt grass and black grass) established successfully and continue to proliferate. In addition, we assessed an experiment of cordgrass plantings performed by community volunteers in 2002. The experiment was designed to test the effectiveness of three planting techniques at a salt marsh restored by the excavation of old dredge spoil that had been colonized by common reed. After four growing seasons, Plug, Bare Root Shoot, and Seed Head planting techniques exhibited greater cover of cordgrass and total cover of vascular plants when compared with unplanted areas. Cover of perennial plants (e.g., cordgrass), which contributes directly to belowground soil development in salt marshes, dominated the planted plots. Cover of annual species dominated the unplanted plots. Planting cordgrass in areas where dredge spoils and common reed had been excavated from a historic marsh accelerated the development of native vegetation compared with unplanted areas. Performance and evaluation of the two sets of plantings has provided information about appropriate planting techniques for our region and has involved and educated the local community about the values of salt marsh to promote stewardship. Recommendations included the use of bare root shoot and seed head planting techniques where cordgrass is desired. Outside plots or a greenhouse may be needed for successful propagation of upper edge marsh species from seed, and a planting program that includes mature plants as well as seedlings is recommended to ensure success

Local and Global Casimir Energies for a Semitransparent Cylindrical Shell

The local Casimir energy density and the global Casimir energy for a massless scalar field associated with a $\lambda\delta$-function potential in a 3+1 dimensional circular cylindrical geometry are considered. The global energy is examined for both weak and strong coupling, the latter being the well-studied Dirichlet cylinder case. For weak-coupling,through $\mathcal{O}(\lambda^2)$, the total energy is shown to vanish by both analytic and numerical arguments, based both on Green's-function and zeta-function techniques. Divergences occurring in the calculation are shown to be absorbable by renormalization of physical parameters of the model. The global energy may be obtained by integrating the local energy density only when the latter is supplemented by an energy term residing precisely on the surface of the cylinder. The latter is identified as the integrated local energy density of the cylindrical shell when the latter is physically expanded to have finite thickness. Inside and outside the delta-function shell, the local energy density diverges as the surface of the shell is approached; the divergence is weakest when the conformal stress tensor is used to define the energy density. A real global divergence first occurs in $\mathcal{O}(\lambda^3)$, as anticipated, but the proof is supplied here for the first time; this divergence is entirely associated with the surface energy, and does {\em not} reflect divergences in the local energy density as the surface is approached.Comment: 28 pages, REVTeX, no figures. Appendix added on perturbative divergence

Primary goals, information-giving and men\u27s understanding: A qualitative study of Australian and UK doctors\u27 varied communication about PSA screening

Objectives: (1) To characterise variation in general practitioners’ (GPs’) accounts of communicating with men about prostate cancer screening using the prostate-specific antigen (PSA) test, (2) to characterise GPs’ reasons for communicating as they do and (3) to explain why and under what conditions GP communication approaches vary. Study design and setting: A grounded theory study. We interviewed 69 GPs consulting in primary care practices in Australia (n=40) and the UK (n=29). Results: GPs explained their communication practices in relation to their primary goals. In Australia, three different communication goals were reported: to encourage asymptomatic men to either have a PSA test, or not test, or alternatively, to support men to make their own decision. As well as having different primary goals, GPs aimed to provide different information (from comprehensive to strongly filtered) and to support men to develop different kinds of understanding, from population-level to ‘gist’ understanding. Taking into account these three dimensions (goals, information, understanding) and building on Entwistle et al’s Consider an Offer framework, we derived four overarching approaches to communication: Be screened, Do not be screened, Analyse and choose, and As you wish. We also describe ways in which situational and relational factors influenced GPs’ preferred communication approach. Conclusion: GPs’ reported approach to communicating about prostate cancer screening varies according to three dimensions—their primary goal, information provision preference and understanding sought—and in response to specific practice situations. If GP communication about PSA screening is to become more standardized in Australia, it is likely that each of these dimensions will require attention in policy and practice support interventions

Spectral determinants and zeta functions of Schr\"odinger operators on metric graphs

A derivation of the spectral determinant of the Schr\"odinger operator on a metric graph is presented where the local matching conditions at the vertices are of the general form classified according to the scheme of Kostrykin and Schrader. To formulate the spectral determinant we first derive the spectral zeta function of the Schr\"odinger operator using an appropriate secular equation. The result obtained for the spectral determinant is along the lines of the recent conjecture.Comment: 16 pages, 2 figure

Simplified Vacuum Energy Expressions for Radial Backgrounds and Domain Walls

We extend our previous results of simplified expressions for functional determinants for radial Schr\"odinger operators to the computation of vacuum energy, or mass corrections, for static but spatially radial backgrounds, and for domain wall configurations. Our method is based on the zeta function approach to the Gel'fand-Yaglom theorem, suitably extended to higher dimensional systems on separable manifolds. We find new expressions that are easy to implement numerically, for both zero and nonzero temperature.Comment: 30 page

Elliptic aspects of statistical mechanics on spheres

Our earlier results on the temperature inversion properties and the ellipticisation of the finite temperature internal energy on odd spheres are extended to orbifold factors of odd spheres and then to other thermodynamic quantities, in particular to the specific heat. The behaviour under modular transformations is facilitated by the introduction of a modular covariant derivative and it is shown that the specific heat on any odd sphere can be expressed in terms of just three functions. It is also shown that the free energy on the circle can be written elliptically.Comment: 22 pages. JyTe

Stability and Well-posedness of a Nonlinear Railway Track Model

Railway tracks rest on a foundation known for exhibiting nonlinear viscoelastic behavior. Railway track deflections are modeled by a semilinear partial differential equation. This paper studies the stability of solutions to this equation in presence of an input. With the aid of a suitable Lyapunov function, existence and exponential stability of classical solutions is established for certain inputs. The Lyapunov function is further used to find an a-priori estimate of the solutions, and also to study the input-to-state stability (ISS) of mild solutions