A note on Mimea infections in Cape Town

No Abstrac

A study of soil moisture controls on stremflow behaviour: results for the OCK basin, United Kingdom

In humid temperate areas ground wetness plays a key role in storm runoff generation, but until recently there have been no instruments capable of providing continuous, reliable, records of changing soil moisture conditions in the field. A new instrument, the IH capacitance probe, can provide continuous measurements of soil water contents. Together with rainfall records these data have been used to study the variations in river flow response of a medium sized (234 km2) rural catchment. Daily flows were simulated, firstly using a standard rainfall runoff model (MACRES) with conventional hydrological and climate data and, secondly, by replacing the net rainfall calculation by a simple functional relationship to the measured soil moisture contents. It was found that incorporating soil moisture measurements in the runoff model: a)Reduced the length of record required for model calibration, b) Improved the simulation of strearnflow

Predicting climate change impacts on maritime Antarctic soils: A space-for-time substitution study

We report a space-for-time substitution study predicting the impacts of climate change on vegetated maritime Antarctic soils. Analyses of soils from under Deschampsia antarctica sampled from three islands along a 2,200 km climatic gradient indicated that those from sub-Antarctica had higher moisture, organic matter and carbon (C) concentrations, more depleted δ13C values, lower concentrations of the fungal biomarker ergosterol and higher concentrations of bacterial PLFA biomarkers and plant wax n-alkane biomarkers than those from maritime Antarctica. Shallow soils (2 cm depth) were wetter, and had higher concentrations of organic matter, ergosterol and bacterial PLFAs, than deeper soils (4 cm and 8 cm depths). Correlative analyses indicated that factors associated with climate change (increased soil moisture, C and organic matter concentrations, and depleted δ13C contents) are likely to give rise to increases in Gram negative bacteria, and decreases in Gram positive bacteria and fungi, in maritime Antarctic soils. Bomb-14C analyses indicated that sub-Antarctic soils at all depths contained significant amounts of modern 14C (C fixed from the atmosphere post c. 1955), whereas modern 14C was restricted to depths of 2 cm and 4 cm in maritime Antarctica. The oldest C (c. 1,745 years BP) was present in the southernmost soil. The higher nitrogen (N) concentrations and δ15N values recorded in the southernmost soil were attributed to N inputs from bird guano. Based on these analyses, we conclude that 5–8 °C rises in air temperature, together with associated increases in precipitation, are likely to have substantial impacts on maritime Antarctic soils, but that, at the rates of climate warming predicted under moderate greenhouse gas emission scenarios, these impacts are likely to take at least a century to manifest themselves

Ferromagnetic phase transition and Bose-Einstein condensation in spinor Bose gases

Phase transitions in spinor Bose gases with ferromagnetic (FM) couplings are studied via mean-field theory. We show that an infinitesimal value of the coupling can induce a FM phase transition at a finite temperature always above the critical temperature of Bose-Einstein condensation. This contrasts sharply with the case of Fermi gases, in which the Stoner coupling $I_s$ can not lead to a FM phase transition unless it is larger than a threshold value $I_0$. The FM coupling also increases the critical temperatures of both the ferromagnetic transition and the Bose-Einstein condensation.Comment: 4 pages, 4 figure

Cosmological Black Holes on Branes

We examined analytically a cosmological black hole domain wall system. Using the C-metric construction we derived the metric for the spacetime describing an infinitely thin domain wall intersecting a cosmological black hole. We studied the behaviour of the scalar field describing a self-interacting cosmological domain wall and find the approximated solution valid for large distances. The thin wall approximation and the back raection problem were elaborated finding that the topological kink solution smoothed out singular behaviour of the zero thickness wall using a core topological and hence thick domain wall. We also analyze the nucleation of cosmological black holes on and in the presence of a domain walls and conclude that the domain wall will nucleate small black holes on it rather than large ones inside.Comment: 13 pages, Revtex, to be published in Phys.Rev. D1

Nariai, Bertotti-Robinson and anti-Nariai solutions in higher dimensions

We find all the higher dimensional solutions of the Einstein-Maxwell theory that are the topological product of two manifolds of constant curvature. These solutions include the higher dimensional Nariai, Bertotti-Robinson and anti-Nariai solutions, and the anti-de Sitter Bertotti-Robinson solutions with toroidal and hyperbolic topology (Plebanski-Hacyan solutions). We give explicit results for any dimension D>3. These solutions are generated from the appropriate extremal limits of the higher dimensional near-extreme black holes in a de Sitter, and anti-de Sitter backgrounds. Thus, we also find the mass and the charge parameters of the higher dimensional extreme black holes as a function of the radius of the degenerate horizon.Comment: 10 pages, 11 figures, RevTeX4. References added. Published versio

Dissipation and noise in adiabatic quantum pumps

We investigate the distribution function, the heat flow and the noise properties of an adiabatic quantum pump for an arbitrary relation of pump frequency $\omega$ and temperature. To achieve this we start with the scattering matrix approach for ac-transport. This approach leads to expressions for the quantities of interest in terms of the side bands of particles exiting the pump. The side bands correspond to particles which have gained or lost a modulation quantum $\hbar \omega$. We find that our results for the pump current, the heat flow and the noise can all be expressed in terms of a parametric emissivity matrix. In particular we find that the current cross-correlations of a multiterminal pump are directly related a to a non-diagonal element of the parametric emissivity matrix. The approach allows a description of the quantum statistical correlation properties (noise) of an adiabatic quantum pump

Presupernova Structure of Massive Stars

Issues concerning the structure and evolution of core collapse progenitor stars are discussed with an emphasis on interior evolution. We describe a program designed to investigate the transport and mixing processes associated with stellar turbulence, arguably the greatest source of uncertainty in progenitor structure, besides mass loss, at the time of core collapse. An effort to use precision observations of stellar parameters to constrain theoretical modeling is also described.Comment: Proceedings for invited talk at High Energy Density Laboratory Astrophysics conference, Caltech, March 2010. Special issue of Astrophysics and Space Science, submitted for peer review: 7 pages, 3 figure