The structure of demersal assemblages off Namibia in relation to abiotic factors

Groundfish surveys carried out between October 1992 and October 1996 were used to describe the demersal assemblages of the northern Benguela along the Namibian coast. Multivariate analyses indicated a clear separation between shelf and slope habitats, which were divided into three and two assemblages respectively. These divisions were distinct, with clear distributional boundaries separating them. Species determining the structure of these divisions and subdivisions and their relative abundances were identified. Depth, bottom temperature, bottom salinity and dissolved oxygen were all significantly correlated with the spatial distribution of the assemblages. Minor changes or shifts in the distribution of assemblages were observed over the study period, although patterns of species associations remained relatively constant.Keywords: community, demersal, environment, fishery, Namibia, trawlingAfrican Journal of Marine Science 2001, 23: 397–41

The Influence of Large Animal Diversity in Grazed Ecosystems

Field observations in the Serengeti National Park, Tanzania have revealed several modes of grazing system, including migration, sustained-yield grazing and grazing succession which contribute on the one hand to ecological separation of herbivores by habitat choice, but on the other hand to positive association of species on wet season pastures known as hot spots. Drawing from results of experimental field studies, we consider what is known about resource competition and facilitation, the two key ecological processes underlying these grazing systems, and specify the shape of the relationship between species richness and pasture height that is predicted depending on which process is dominating in the grazing system. We test between these alternatives by analysing for the first time data on herbivore distributions and vegetation condition from a series of 33 survey flights over the entire Serengeti ecosystem. Our preliminary results strongly support the importance of facilitation as a process structuring the herbivore community of the Serengeti Plains in the wet season. Resource competition may limit use of the shortest swards

Speech, communication and use of augmentative communication in young people with cerebral palsy: the SH&PE population study.

BACKGROUND: Communication is frequently impaired in young people (YP) with bilateral cerebral palsy (CP). Important factors include motoric speech problems (dysarthria) and intellectual disability. Augmentative and Alternative Communication (AAC) techniques are often employed. The aim was to describe the speech problems in bilateral CP, factors associated with speech problems, current AAC provision and use, and to explore the views of both the parent/carer and young person about communication. METHODS: A total population of children with bilateral CP (n = 346) from four consecutive years of births (1989-1992 inclusive) with onset of CP before 15 months were reassessed at age 16-18 years. Motor skills and speech were directly assessed and both parent/carer and the young person asked about communication and satisfaction with it. RESULTS: Sixty had died, eight had other conditions, 243 consented and speech was assessed in 224 of whom 141 (63%) had impaired speech. Fifty-two (23% of total YP) were mainly intelligible to unfamiliar people, 22 (10%) were mostly unintelligible to unfamiliar people, 67 (30%) were mostly or wholly unintelligible even to familiar adults. However, 89% of parent/carers said that they could communicate 1:1 with their young person. Of the 128 YP who could independently complete the questions, 107 (83.6%) were happy with their communication, nine (7%) neither happy nor unhappy and 12 (9.4%) unhappy. A total of 72 of 224 (32%) were provided with one or more types of AAC but in a significant number (75% of 52 recorded) AAC was not used at home, only in school. Factors associated with speech impairment were severity of physical impairment, as measured by Gross Motor Function Scale level and manipulation in the best hand, intellectual disability and current epilepsy. CONCLUSIONS: In a population representative group of YP, aged 16-18 years, with bilateral CP, 63% had impaired speech of varying severity, most had been provided with AAC but few used it at home for communication

Modeling the Effects of Climate Variability and Climate Change on a Pastoral Farming System

A simulation model was used to investigate the pasture and animal production and gross margins of a typical all sheep permanent pasture farm in South Canterbury, New Zealand, using 60 years of current climate data, and also a climate change scenario. The model was run on a fixed management system at different stocking rates with and without destocking during feed shortages. Mean annual pasture production was 8060 kg/ha, with a coefficient of variation of 22%. Destocking enabled more stock to be carried on average, with higher, but rh.ore variable, returns. A climate change scenario of a 75% increase in CO2\u27 1.8°C rise in mean temperature, a 5% decrease in rainfall and an 8% increase in solar radiation produced 46% higher but more variable pasture yields, resulting in optimum stocking rates, costs1 returns and gross margins all being increased 25-50%

Flux penetration in slab shaped Type-I superconductors

We study the problem of flux penetration into type--I superconductors with high demagnetization factor (slab geometry).Assuming that the interface between the normal and superconducting regions is sharp, that flux diffuses rapidly in the normal regions, and that thermal effects are negligible, we analyze the process by which flux invades the sample as the applied field is increased slowly from zero.We find that flux does not penetrate gradually.Rather there is an instability in the process and the flux penetrates from the boundary in a series of bursts, accompanied by the formation of isolated droplets of the normal phase, leading to a multiply connected flux domain structure similar to that seen in experiments.Comment: 4 pages, 2 figures, Fig 2.(b) available upon request from the authors, email - [email protected]