Calculation of subdominant solutions of linear differential equations

Calculation of subdominant solutions of linear differential equation

Induced magnetosphere of Venus

Solar wind and ionospheric conductivity studied for role in inducing Venus or Mars magnetosphere

Community policing : tentative steps towards true reconciliation : inaugural lecture delivered at Rhodes University

Inaugural lecture delivered at Rhodes UniversityRhodes University Libraries (Digitisation

The floristics of Sand Forest in northern KwaZulu-Natal, South Africa

We use multivariate analyses (ordination and classification) to assess both the floristic uniqueness of the woody vegeation of Sand Forest in relation to a range of other forest types in the region, and the range of variation within Sand Forest. Two broad Sand Forest subtypes and related Ecotonal Forests are described and grouped under the term Tropical Dry Forest, distinct from all evergreen forests in South Africa. Sand Forest, a dry semi-deciduous type in northeastern KwaZulu-Natals defined by the presence of the canopy dominant Cleistanthus schlechteri as well as Hymenocardia ulmoides, Psydrax fragrantissima, Croton pseudopulchellus and  Drypetes arguta. Sand Forests form a cohesive group in both DCA and TWINSPAN analyses, with similar composition of canopy dominants at sampled sites. This implies that ecological funcioning is similar across the geographical range in northeastern KwaZulu-Natal. However, turnover of subdominant species between recognisable Sand Forest types emphasizes the need to conserve the full range of extant forests

No adverse signs of the effect of environmental change on tree biomass in the Knysna forest during the 1990s

We analysed the growth of all trees greater than 10 cm diameter at breast height in 108 plots of 0.04 ha each in an unharvested nature reserve in the Knysna forest for the period 1991-2001. Gross growth rates (in-growth plus growth of survivors) of trees were extremely slow (<1%) and thus the forest is extremely sensitive to changes in mortality of large trees. Over the 10-year study period, total basal area and biomass increased by 2%, in part because overall stem density increased by 1.2%. Rainfall in the 1990s was slightly below the longterm mean for the study area. At this stage, therefore, the Knysna forest biomass is not showing a negative response to environmental change

Asymmetric Gaussian steering: when Alice and Bob disagree

Asymmetric steering is an effect whereby an inseparable bipartite system can be found to be described by either quantum mechanics or local hidden variable theories depending on which one of Alice or Bob makes the required measurements. We show that, even with an inseparable bipartite system, situations can arise where Gaussian measurements on one half are not sufficient to answer the fundamental question of which theory gives an adequate description and the whole system must be considered. This phenomenon is possible because of an asymmetry in the definition of the original Einstein-Podolsky-Rosen paradox and in this article we show theoretically that it may be demonstrated, at least in the case where Alice and Bob can only make Gaussian measurements, using the intracavity nonlinear coupler.Comment: 5 Pages, 4 Figure

Interactions of Jets with Inhomogeneous Cloudy Media

We present two-dimensional slab-jet simulations of jets in inhomogeneous media consisting of a tenuous hot medium populated with a small filling factor by warm, dense clouds. The simulations are relevant to the structure and dynamics of sources such as Gigahertz Peak Spectrum and Compact Steep Spectrum radio galaxies, High Redshift Radio Galaxies and radio galaxies in cooling flows. The jets are disrupted to a degree depending upon the filling factor of the clouds. With a small filling factor, the jet retains some forward momentum but also forms a halo or bubble around the source. At larger filling factors channels are formed in the cloud distribution through which the jet plasma flows and a hierarchical structure consisting of nested lobes and an outer enclosing bubble results. We suggest that the CSS quasar 3C48 is an example of a low filling factor jet - interstellar medium interaction whilst M87 may be an example of the higher filling factor type of interaction. Jet disruption occurs primarily as a result of Kelvin-Helmholtz instabilities driven by turbulence in the radio cocoon not through direct jet-cloud interactions, although there are some examples of these. In all radio galaxies whose morphology may be the result of jet interactions with an inhomogeneous interstellar medium we expect that the dense clouds will be optically observable as a result of radiative shocks driven by the pressure of the radio cocoon. We also expect that the radio galaxies will possess faint haloes of radio emitting material well beyond the observable jet structure.Comment: 21 pages, 16 figures, submitted to MNRAS. A version with full resolution figures is available at: http://www.mssl.ucl.ac.uk/~cjs2/pdf/cloudy_hue.pd