Islands contribute disproportionately high amounts of evolutionary diversity in passerine birds

Island systems generally have fewer species than continental areas due to their small size and geographical isolation. Low island diversity reduces the possibility of exportation of island lineages and island systems are not thought to have a major influence on the build-up of continental diversity. However, the view that islands represent the end of the colonization road has recently been challenged and islands do represent the origin of some specific continental lineages. Here we assess the net contribution of island systems to global diversity patterns of passerine birds, using a complete phylogeny (5,949 species), biogeographical regionalization and null-model comparisons. We show that, in contrast to major continental regions, island regions export relatively more evolutionary lineages than would be expected based on current distributional patterns. This result challenges a central paradigm in island biogeography and changes our perception of the relative importance of islands for the build-up of global diversity

Radiant Emission Characteristics of Diffuse Conical Cavities

Radiant-energy emission of diffuse conical cavitie

The Spectrum of the Loop Transfer Matrix on Finite Lattice

We consider the model of random surfaces with extrinsic curvature term embedded into 3d Euclidean lattice $Z^3$. On a 3d Euclidean lattice it has equivalent representation in terms of transfer matrix $K(Q_{i},Q_{f})$, which describes the propagation of loops $Q$. We study the spectrum of the transfer matrix $K(Q_{i},Q_{f})$ on finite dimensional lattices. The renormalisation group technique is used to investigate phase structure of the model and its critical behaviour.Comment: 10 pages, 5 figures, Latex, psfi

Three-dimensional gonihedric spin system

We perform Monte Carlo simulations of a three-dimensional spin system with a Hamiltonian which contains only four-spin interaction term. This system describes random surfaces with extrinsic curvature - gonihedric action. We study the anisotropic model when the coupling constants $\beta_S$ for the space-like plaquettes and $\beta_T$ for the transverse-like plaquettes are different. In the two limits $\beta_S=0$ and $\beta_T=0$ the system has been solved exactly and the main interest is to see what happens when we move away from these points towards the isotropic point, where we recover the original model. We find that the phase transition is of first order for $\beta_T = \beta_S \approx 0.25,$ while away from this point it becomes weaker and eventually turns to a crossover. The conclusion which can be drown from this result is that the exact solution at the point $\beta_S =0$ in terms of 2d-Ising model should be considered as a good zero order approximation in the description of the system also at the isotropic point $\beta_S =\beta_T$ and clearly confirms the earlier findings that at the isotropic point the original model shows a first order phase transition.Comment: 11 pages, 10 figures, shortened versio

Thermal Radiation Absorption in Rectangular-Groove Cavities

Thermal radiation absorption in rectangular-groove cavitie

Absorption and Emission Characteristics of Diffuse Spherical Enclosures

The thermal radiation characteristics of spherical cavities are of practical interest in connection with the absorption of radiant energy for both space-vehicle and terrestrial applications. Also, spherical cavities are of potential use as sources of black-body energy. The purpose of this brief paper is to determine both the absorption and emission characteristics of spherical cavities which are diffuse reflectors and emitters