Fast computation by block permanents of cumulative distribution functions of order statistics from several populations

The joint cumulative distribution function for order statistics arising from several different populations is given in terms of the distribution function of the populations. The computational cost of the formula in the case of two populations is still exponential in the worst case, but it is a dramatic improvement compared to the general formula by Bapat and Beg. In the case when only the joint distribution function of a subset of the order statistics of fixed size is needed, the complexity is polynomial, for the case of two populations.Comment: 21 pages, 3 figure

Identifying leverage points to transition dysfunctional irrigation schemes towards complex adaptive systems

This article explores the value of Ostrom’s socio-ecological systems framework and Meadows’s leverage point hierarchy, as structured diagnostics, to define systemic problems and avoid approaches based on linear thinking. These frameworks were applied as an ex post analysis of an irrigation scheme in Zimbabwe, drawing on the scheme’s baseline condition and the intervention outcomes. Strong leverage points, particularly those driving feedback mechanisms and institutional design, interacted with other intervention points, initiating systemic change. This analysis suggests that dysfunctional schemes can be transitioned towards complex adaptive systems by using agricultural innovation platforms to identify systemic challenges and intervention points

The dynamics between irrigation frequency and soil nutrient management: transitioning smallholder irrigation towards more profitable and sustainable systems in Zimbabwe

Successful irrigated agriculture is underpinned by answering two critical questions: when and how much to irrigate. This article quantifies the role of the Chameleon and the Wetting Front Detector, monitoring tools facilitating decision-making and learning about soilwater- nutrient dynamics. Farmers retained nutrients in the root zone by reducing irrigation frequency, number of siphons, and event duration. Water productivity increased by more than 100% for farmers both with and without monitoring tools. Transitioning smallholder irrigation systems into profitable and sustainable schemes requires investment in technology, farmers and institutions. Importantly, technologies need embedding in a learning environment that fosters critical feedback mechanisms, such as market constraints

Quantifying Timing Leaks and Cost Optimisation

We develop a new notion of security against timing attacks where the attacker is able to simultaneously observe the execution time of a program and the probability of the values of low variables. We then show how to measure the security of a program with respect to this notion via a computable estimate of the timing leakage and use this estimate for cost optimisation.Comment: 16 pages, 2 figures, 4 tables. A shorter version is included in the proceedings of ICICS'08 - 10th International Conference on Information and Communications Security, 20-22 October, 2008 Birmingham, U

The role of soil water monitoring tools and agricultural innovation platforms in improving food security and income of farmers in smallholder irrigation schemes in Tanzania

Smallholder irrigation is an important pathway towards better livelihoods and food security in sub-Saharan Africa. This article assesses the contribution of farmer-friendly soil and water monitoring tools, and agricultural innovation platforms, towards household income and food security in two small-scale irrigation schemes in Tanzania. Quantitative and qualitative data from farmer’s field books, household surveys and focus groups were used to assess the impacts of the two interventions. The two interventions together contributed to enhancing smallholders’ food security and household income in the two schemes, as did the agricultural innovation platform on its own

Communal irrigation systems in South-Eastern Africa: findings on productivity and profitability

Significant expansion of irrigated agriculture is planned in Africa, though existing smallholder schemes perform poorly. Research at six schemes in Mozambique, Tanzania and Zimbabwe shows that a range of problems are exacerbated by poor management, with limited market linkages leading to underutilization and a lack of profit. Improving sustainability of these complex systems will require: multiple interventions at different scales; investing in people and institutions as much as hardware; clarity in governments’ objectives for their smallholder irrigation schemes; appropriate business models to enable farmers; and better market linkages

Using realist review to inform intervention development: Methodological illustration and conceptual platform for collaborative care in offender mental health

BackgroundThis paper reports how we used a realist review, as part of a wider project to improve collaborative mental health care for prisoners with common mental health problems, to develop a conceptual platform. The importance of offenders gaining support for their mental health, and the need for practitioners across the health service, the criminal justice system, and the third sector to work together to achieve this is recognised internationally. However, the literature does not provide coherent analyses of how these ambitions can be achieved. This paper demonstrates how a realist review can be applied to inform complex intervention development that spans different locations, organisations, professions, and care sectors.MethodsWe applied and developed a realist review for the purposes of intervention development, using a three-stage process. (1) An iterative database search strategy (extending beyond criminal justice and offender health) and groups of academics, practitioners, and people with lived experience were used to identify explanatory accounts (n = 347). (2) From these accounts, we developed consolidated explanatory accounts (n = 75). (3) The identified interactions between practitioners and offenders (within their organisational, social, and cultural contexts) were specified in a conceptual platform. We also specify, step by step, how these explanatory accounts were documented, consolidated, and built into a conceptual platform. This addresses an important methodological gap for social scientists and intervention developers about how to develop and articulate programme and implementation theory underpinning complex interventions.ResultsAn integrated person-centred system is proposed to improve collaborative mental health care for offenders with common mental health problems (near to and after release) by achieving consistency between the goals of different sectors and practitioners, enabling practitioners to apply scientific and experiential knowledge in working judiciously and reflectively, and building systems and aligning resources that are centred on offenders’ health and social care needs.ConclusionsAs part of a broader programme of work, a realist review can make an important contribution to the specification of theoretically informed interventions that have the potential to improve health outcomes. Our conceptual platform has potential application in related systems of health and social care where integrated, and person-centred care is a goal

Theory and application of Agricultural Innovation Platforms for improved irrigation scheme management in Southern Africa

Many small-scale irrigation systems are characterized by low yields and deteriorating infrastructure. Interventions often erroneously focus on increasing yields and rehabilitating infrastructure. Small-scale irrigation systems have many of the characteristics of complex socio-ecological systems, with many different actors and numerous interconnected subsystems. However, the limited interaction between the different subsystems and their agents prevents learning and the emergence of more beneficial outcomes. This article reports on using Agricultural Innovation Platforms to create an environment in which irrigation scheme actors can engage, experiment, learn and build adaptive capacity to increase market-related offtake and move out of poverty

Do agricultural innovation platforms and soil moisture and nutrient monitoring tools improve the production and livelihood of smallholder irrigators in Mozambique?

Over four years, a research-for-development project was implemented at the 25 de Setembro irrigation scheme in Mozambique. The project introduced agricultural innovation platforms to overcome barriers to production such as input and output supply chains and poorly maintained irrigation canals. Soil moisture and nutrient monitoring tools were provided so that farmers could improve their irrigation and fertilizer management. The farmers increased their crop production through the use of the tools and better irrigation infrastructure, and increased their income and overall well-being through better links to markets and new information sources facilitated by the agricultural innovation platforms