Area factors and suicide: 5-year follow-up of the Northern Ireland population

Background: Suicide rates vary markedly between areas but it is unclear whether this is due to differences in population composition or to contextual factors operating at an area level.
Aims: To determine if area factors are independently related to suicide risk after adjustment for individual and family characteristics.
Method: A 5-year record linkage study was conducted of 1 116 748 non-institutionalised individuals aged 16-74 years, enumerated at the 2001 Northern Ireland census.
Results: The cohort experienced 566 suicides during follow-up. Suicide risks were lowest for women and for those who were married or cohabiting. Indicators of individual and household disadvantage and economic and health status at the time of the census were also strongly related to risk of suicide. The higher rates of suicide in the more deprived and socially fragmented areas disappeared after adjustment for individual and household factors. There was no significant relationship between population density and risk of suicide.
Conclusions: Differences in rates of suicide between areas are predominantly due to population characteristics rather than to area-level factors, which suggests that policies targeted at area-level factors are unlikely to significantly influence suicides rates.

Area-efficient high-speed 3D DWT processor architecture

An area-efficient high-throughput architecture based on distributed arithmetic is proposed for 3D discrete wavelet transform (DWT). The 3D DWT processor was designed in VHDL and mapped to a Xilinx Virtex-E FPGA. The processor runs up to 85 MHz, which can process the five-level DWT analysis of a 128 x 128 x 128 fMRI volume image in 20 ms.

Can traditional harvesting methods for cockles be accommodated in a Special Area of Conservation?

The European Natura 2000 project attempts to balance conservation and exploitation by permitting activities that do not affect the conservation status of designated sites. Given the scale of Natura 2000, guidelines are needed to facilitate the drafting of simple site management plans. This need is particularly acute for traditional harvesting methods for which there is usually strong local opposition to the imposition of controls. These issues were examined in Strangford Lough, a special area of conservation where cockles have traditionally been harvested by hand-raking. Raking was found not to affect the ability of cockles to rebury. There were significant reductions in Zostera biomass when raking was carried out within eelgrass beds (a 90% reduction in biomass available to winter migrant birds from summer raking). Traditional harvesting methods could therefore be accepted in Strangford as long as Zostera beds are avoided. A relatively low intensity of harvesting activity in Strangford Lough probably reflects low cockle densities (average 91.8 m(-2)), with the most economically valuable individuals at some distance from points of access to the shore. An economically feasible management plan could sanction traditional harvesting and result in the implementation of more resource-intensive management only if increases in cockle stocks and market prices stimulate large increases in harvesting activity.

Controls on the contemporary distribution of lake thecamoebians (testate amoebae) in the Greater Toronto Area and their potential as water quality indicators.

Thecamoebians were examined from 71 surface sediment samples collected from 21 lakes and ponds in the Greater Toronto Area to (1) elucidate the controls on faunal distribution in modern lake environments; and (2) to consider the utility of thecamoebians in quantitative studies of water quality change. This area was chosen because it includes a high density of kettle and other lakes which are threatened by urban development and where water quality has deteriorated locally as a result of contaminant inputs, particularly nutrients. Fifty-eight samples yielded statistically significant thecamoebian populations. The most diverse faunas (highest Shannon Diversity Index values) were recorded in lakes beyond the limits of urban development, although the faunas of all lakes showed signs of sub-optimal conditions. The assemblages were divided into five clusters using Q-mode cluster analysis, supported by Detrended Correspondence Analysis. Canonical Correspondence Analysis (CCA) was used to examine species-environment relationships and to explain the observed clusterings. Twenty-four measured environmental variables were considered, including water property attributes (e.g., pH, conductivity, dissolved oxygen), substrate characteristics, sediment-based phosphorus (Olsen P) and 11 environmentally available metals. The thecamoebian assemblages showed a strong association with phosphorus, reflecting the eutrophic status of many of the lakes, and locally to elevated conductivity measurements, which appear to reflect road salt inputs associated with winter de-icing operations. Substrate characteristics, total organic carbon and metal contaminants (particularly Cu and Mg) also influenced the faunas of some samples. A series of partial CCAs show that of the measured variables, sedimentary phosphorus has the largest influence on assemblage distribution, explaining 6.98% (P < 0.002) of the total variance. A transfer function was developed for sedimentary phosphorus (Olsen P) using 58 samples from 15 of the studied lakes. The best performing model was based on weighted averaging with inverse deshrinking (WA Inv, r jack 2= 0.33, RMSEP = 102.65 ppm). This model was applied to a small modern thecamoebian dataset from a eutrophic lake in northern Ontario to predict phosphorus and performed satisfactorily. This preliminary study confirms that thecamoebians have considerable potential as quantitative water quality indicators in urbanising regions, particularly in areas influenced by nutrient inputs and road salts.