Phylogenetic relationships and call structure in four African bufonid species

Four species of toads of the genus Bufo, comprising three species endemic to southern Africa and one closely-related species, were examined electrophoretically to infer their phylogenetic relationships. The evolution of advertisement call structure in these species is discussed in relation to this phylogeny. Bufo rangeri and B. gutturalis, two species with very different call structures, are sister taxa. Two pairs of species with very similar call structures, B. partialis and B. gutturalis, and B. rangeri and B. angusticeps, were only distantly related. Our resufts suggest that call parameters are poor characters to use in inferring phylogenies among congeneric species, probably because of selection for optimal audibility in different habitats, and because of the role that they play in premating isolation. The phylogeny derived from allozyme data agrees with evidence on albumin immunological distance, karyotype and morphology

Anuran distribution, diversity and conservation in South Africa, Lesotho and Swaziland

The distributions of 96 anuran species in South Africa were mapped using published locality records, and the collections of the South African and Port Elizabeth museums. Centres of richness, endemism and Red Data Book (RDB) richness were identified, and compared with currently protected areas, using a geographical information system (GIS). Maputaland and the Kwazulu/Natal coast were identified as centres of species richness. Endemic ‘hotspots’ occur in the vicinity of Pietermaritzburg, Durban and Ihe fynbos region of the Western Cape, The Western Cape was also identified as a centre of RDB species richness. A large portion (95,8%) of South African anuran species are found in protected areas. The effective long-term viability of populations of many of these species within these areas, must be assessed. Currently four South African frog species are not found within protected areas. The Karoo biomes were identified as being under-represented, both in the species database and in the proportion of conserved areas. While a large proportion of the fynbos biome is contained in reserve areas, the low-lying fynbos habitats have almost disappeared as a result of urbanization and agriculture. Remnants of the sandy coastal fynbos and renosterveld veld types require urgent conservation. Several areas in the Western and Eastern Cape were identified as requiring additional research and conservation measures. A GIS proves a useful tool in the analysis of species distributions and the prioritization of areas and species for conservation. The importance of accurate collection data, for incorporation into species databases, and the regular publication of reserve species lists is emphasized

The effect of substrate roughness on air entrainment in dip coating

YesDynamic wetting failure was observed in the simple dip coating flow with a series of substrates, which had a rough side and a comparatively smoother side. When we compared the air entrainment speeds on both sides, we found a switch in behaviour at a critical viscosity. At viscosity lower than a critical value, the rough side entrained air at lower speeds than the smooth side. Above the critical viscosity the reverse was observed, the smooth side entraining air at lower speed than the rough side. Only substrates with significant roughness showed this behaviour. Below a critical roughness, the rough side always entrained air at lower speeds than the smooth side. These results have both fundamental and practical merits. They support the hydrodynamic theory of dynamic wetting failure and imply that one can coat viscous fluids at higher speeds than normal by roughening substrates. A mechanism and a model are presented to explain dynamic wetting failure on rough surfaces

Charged particle production in the Pb+Pb system at 158 GeV/c per nucleon

Charged particle multiplicities from high multiplicity central interactions of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the central and far forward projectile spectator regions using emulsion chambers. Multiplicities are significantly lower than predicted by Monte Carlo simulations. We examine the shape of the pseudorapidity distribution and its dependence on centrality in detail.Comment: 17 pages text plus 12 figures in postscript 12/23/99 -- Add TeX version of sourc

Semiclassical theory of potential scattering for massless Dirac fermions

In this paper we study scattering of two-dimensional massless Dirac fermions by a potential that depends on a single Cartesian variable. Depending on the energy of the incoming particle and its angle of incidence, there are three different regimes of scattering. To find the reflection and transmission coefficients in these regimes, we apply the Wentzel-Kramers-Brillouin (WKB), also called semiclassical, approximation. We use the method of comparison equations to extend our prediction to nearly normal incidence, where the conventional WKB method should be modified due to the degeneracy of turning points. We compare our results to numerical calculations and find good agreement.Comment: Minor revision; several references have been adde

"Tomography" of the cluster structure of light nuclei via relativistic dissociation

These lecture notes present the capabilities of relativistic nuclear physics for the development of the physics of nuclear clusters. Nuclear track emulsion continues to be an effective technique for pilot studies that allows one, in particular, to study the cluster dissociation of a wide variety of light relativistic nuclei within a common approach. Despite the fact that the capabilities of the relativistic fragmentation for the study of nuclear clustering were recognized quite a long time ago, electronic experiments have not been able to come closer to an integrated analysis of ensembles of relativistic fragments. The continued pause in the investigation of the "fine" structure of relativistic fragmentation has led to resumption of regular exposures of nuclear emulsions in beams of light nuclei produced for the first time at the Nuclotron of the Joint Institute for Nuclear Research (JINR, Dubna). To date, an analysis of the peripheral interactions of relativistic isotopes of beryllium, boron, carbon and nitrogen, including radioactive ones, with nuclei of the emulsion composition, has been performed, which allows the clustering pattern to be presented for a whole family of light nuclei.Comment: ISBN 978-3-319-01076-2. 55 pages, 28 figure

Measurement of the gamma ray background in the Davis Cavern at the Sanford Underground Research Facility

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4,850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0--3300~keV) varied from 596~Hz to 1355~Hz for unshielded measurements, corresponding to a total flux in the cavern of 1.9±0.4~γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220±60~Bq/kg of 40K, 29±15~Bq/kg of 238U, and 13±3~Bq/kg of 232Th

Operational sex ratios in Bufo rangeri: A test of the active-inactive model

The active-inactive model predicts temporal variation in the operational sex ratio (OSR) throughout a breeding season, as a function of each male's optimal strategy for finding mates. I tested the model using data for the raucous toad, Bufo rangeri, collected nightly over three breeding seasons. The numbers of active males and fertilizable females were correlated in two of the three breeding seasons. The OSR, defined as the average ratio of sexually active males to fertilizable females, decreased throughout each season, except for the first, when it rose to a peak before decreasing. The OSR fluctuated towards the end of the season in two of the three seasons, and rose again at the end in only one. Although the equal-performance assumption was violated, the temporal pattern of the OSR in this species complied largely with that predicted by the active-inactive model. Reasons for deviations from the model's predictions are discussed. Despite the lack of data on mortality rates, this study represents the most comprehensive test of the model yet, as tests on other species have been based on data collected intermittently, as opposed to nightly, over only two breeding seasons.Articl

Nesting success and within-season breeding dispersal in the Orange-breasted Sunbird Anthobaphes violacea

Nest predation is a primary cause of nesting mortality for many bird species, particularly passerines. Nest location can affect predation, and it has also been demonstrated that predation risk can alter nest site selection. Birds can limit predation risk by selecting specific habitat characteristics; by changing nest site characteristics between attempts; and by dispersing between nesting events. Here we report breeding data from a population of Orange-breasted Sunbirds Anthobaphes violacea (L.), for a single breeding season in the Jonkershoek Nature Reserve, South Africa. Neither shrub type nor nest height was found to affect the outcome of a nest. For subsequent breeding attempts, birds were not more likely to change the type of shrub in which they nested after a predation event than when the attempt was successful, nor did they change the height of their nest. However, we found that the distance between a nest and the subsequent one was significantly shorter after a successful nest than after an unsuccessful one. We interpret this as an adaptive strategy to avoid predation. Copyright © NISC Pty Ltd.Articl

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