Balancing the demands of two tasks: an investigation of cognitive–motor dual-tasking in relapsing remitting multiple sclerosis

Background: People with relapsing remitting multiple sclerosis (PwRRMS) suffer disproportionate decrements in gait under dual-task conditions, when walking and a cognitive task are combined. There has been much less investigation of the impact of cognitive demands on balance. Objectives: This study investigated whether: (1) PwRRMS show disproportionate decrements in postural stability under dual-task conditions compared to healthy controls, and (2) dual-task decrements are associated with everyday dual-tasking difficulties. The impact of mood, fatigue, and disease severity on dual-tasking was also examined. Methods: A total of 34 PwRRMS and 34 matched controls completed cognitive (digit span) and balance (movement of center of pressure on Biosway on stable and unstable surfaces) tasks under single- and dual-task conditions. Everyday dual-tasking was measured using the Dual-Tasking Questionnaire. Mood was measured by the Hospital Anxiety & Depression Scale. Fatigue was measured via the Modified Fatigue Index Scale. Results: No differences in age, gender, years of education, estimated pre-morbid IQ, or baseline digit span between groups. Compared with controls, PwRRMS showed significantly greater decrement in postural stability under dual-task conditions on an unstable surface (p=.007), but not a stable surface (p=.679). Balance decrement scores were not correlated with everyday dual-tasking difficulties or fatigue. Stable surface balance decrement scores were significantly associated with levels of anxiety (rho=0.527; p=.001) and depression (rho=0.451; p=.007). Conclusions: RRMS causes dual-tasking difficulties, impacting balance under challenging conditions, which may contribute to increased risk of gait difficulties and falls. The relationship between anxiety/depression and dual-task decrement suggests that emotional factors may be contributing to dual-task difficulties

Economies of scale and locational pattern of wool villages in the South Island of New Zealand

This study investigates wool marketing costs in the South Island of New Zealand. The objectives are (1) to determine the extent of economies of scale in wool villages and (2) to investigate a locational pattern of wool villages such that total assembly, processing and distribution costs are minimized. A wool village is defined as a single level store in which brokers combine in the receival, binning, classing, showing, dumping and despatch of wool. Economic theory surrounding returns to scale, the causes of increasing and decreasing returns to scale and methods of recognising scale responses is discussed (Chapter III. A). The LRAC curve is used to recognise the effect of an increase in scale on per unit processing costs. Cost curve theory is reviewed and cost curve development methods suggested (Chapter III. B and C). Synthetic LRAC curves for wool processing within wool villages at each of the four South Island Wool Selling Centres (i.e. Christchurch, Timaru, Dunedin and Invercargill), given the existing industry's conventions and traditions, including locational differences, are developed (Chapter IV). Four LRAC curves are developed for each centre, one for each of the wool processing technologies considered, that is: traditional sale/wagon packing of containers, traditional sale/ground packing of containers, sale by sample/wagon packing of containers, sale by sample/ground packing of containers. Significant economies of scale are indicated within wool villages located at Christchurch and Timaru. At Dunedin and Invercargill economies of scale are displayed for throughputs up to 400,000 bales, thereafter constant returns to scale (approx.) are exhibited. Otago and Southland wools require less in store handling than do Canterbury wools, thus as throughputs rise at Invercargill (say), wool is drawn from Canterbury (requiring more handling). Processing costs rise nullifying any scale economies. The opposite is true for large throughputs at Christchurch or Timaru. In Chapter V location theory is reviewed. The locational pattern of wool villages is determined using a budgetary approach. It is assumed that wool villages can only be located at existing centres. The optimal locational pattern for each processing technology is the two villages, 300,000 bale Christchurch and 400,000 bale Dunedin locational pattern. However the least expensive three village locational pattern and single village location, for each processing technology, is not significantly more expensive than the optimal locational pattern. This suggests in the event of wool villages being established, criteria other than least-cost (e.g. regional considerations) should be considered. These criteria are briefly discussed (Chapter VI)

The co-construction of couplehood in dementia.

Much research has investigated the impact of dementia on spousal relationships. Most often this is from the point of view of the spouse, but occasionally people with dementia are interviewed independently or in parallel. The current study was novel in its aim to understand ‘couplehood’ as it is co-constructed by the couple when one partner has dementia and employed an innovative design that involved interviewing couples together about their relationship. Using grounded theory methodology, the study identified the changing identities within couplehood and the strategies couples employ to maintain their relationship, including normalizing, externalizing, sharing the experience and reframing the experience in light of the past. These findings are discussed in relation to other relevant research and suggest that co-constructed accounts of couplehood are valuable not only when researching the experiences of couples with dementia but also in their clinical assessment and treatment

Generic ecological impact assessments of alien species in Norway: a semi-quantitative set of criteria

The ecological impact assessment scheme that has been developed to classify alien species in Norway is presented. The underlying set of criteria enables a generic and semi-quantitative impact assessment of alien species. The criteria produce a classification of alien species that is testable, transparent and easily adjustable to novel evidence or environmental change. This gives a high scientific and political legitimacy to the end product and enables an effective prioritization of management efforts, while at the same time paying attention to the precautionary principle. The criteria chosen are applicable to all species regardless of taxonomic position. This makes the assessment scheme comparable to the Red List criteria used to classify threatened species. The impact of alien species is expressed along two independent axes, one measuring invasion potential, the other ecological effects. Using this two-dimensional approach, the categorization captures the ecological impact of alien species, which is the product rather than the sum of spread and effect. Invasion potential is assessed using three criteria, including expected population lifetime and expansion rate. Ecological effects are evaluated using six criteria, including interactions with native species, changes in landscape types, and the potential to transmit genes or parasites. Effects on threatened species or landscape types receive greater weightings