Lambda Calculus in Core Aldwych

Core Aldwych is a simple model for concurrent computation, involving the concept of agents which communicate through shared variables. Each variable will have exactly one agent that can write to it, and its value can never be changed once written, but a value can contain further variables which are written to later. A key aspect is that the reader of a value may become the writer of variables in it. In this paper we show how this model can be used to encode lambda calculus. Individual function applications can be explicitly encoded as lazy or not, as required. We then show how this encoding can be extended to cover functions which manipulate mutable variables, but with the underlying Core Aldwych implementation still using only immutable variables. The ordering of function applications then becomes an issue, with Core Aldwych able to model either the enforcement of an ordering or the retention of indeterminate ordering, which allows parallel execution

Coordination using a Single-Writer Multiple-Reader Concurrent Logic Language

The principle behind concurrent logic programming is a set of processes which co-operate in monotonically constraining a global set of variables to particular values. Each process will have access to only some of the variables, and a process may bind a variable to a tuple containing further variables which may be bound later by other processes. This is a suitable model for a coordination language. In this paper we describe a type system which ensures the co-operation principle is never breached, and which makes clear through syntax the pattern of data flow in a concurrent logic program. This overcomes problems previously associated with the practical use of concurrent logic languages

Development and testing the feasibility of a sports-based mental health promotion intervention in Nepal: a protocol for a pilot cluster-randomised controlled trial

Background: Mental wellbeing encompasses life satisfaction, social connectedness, agency and resilience. In adolescence, mental wellbeing reduces sexual health risk behaviours, substance use and violence; improves educational outcomes; and protects mental health in adulthood. Mental health promotion seeks to improve mental wellbeing and can include activities to engage participants in sport. However, few high-quality trials of mental health promotion interventions have been conducted with adolescents, especially in low- and middle-income countries. We sought to address this gap by testing SMART (Sports-based Mental heAlth pRomotion for adolescenTs) in a pilot cluster-randomised controlled trial (cRCT) in Bardiya, Nepal. // Methods: The objectives of the trial are to assess the acceptability and feasibility of SMART, test trial procedures, explore outcome distributions in intervention and control clusters and calculate the total annual cost of the intervention and unit cost per adolescent. The trial design is a parallel-group, two-arm superiority pilot cRCT with a 1:1 allocation ratio and two cross-sectional census surveys with adolescents aged 12–19, one pre-intervention (baseline) and one post-intervention (endline). The study area is four communities of approximately 1000 population (166 adolescents per community). Each community represents one cluster. SMART comprises twice weekly football, martial arts and dance coaching, open to all adolescents in the community, led by local sports coaches who have received psychosocial training. Sports melas (festivals) and theatre performances will raise community awareness about SMART, mental health and the benefits of sport. Adolescents in control clusters will participate in sport as usual. In baseline and endline surveys, we will measure mental wellbeing, self-esteem, self-efficacy, emotion regulation, social support, depression, anxiety and functional impairment. Using observation checklists, unstructured observation and attendance registers from coaching sessions, and minutes of meetings between coaches and supervisors, we will assess intervention fidelity, exposure and reach. In focus group discussions and interviews with coaches, teachers, caregivers and adolescents, we will explore intervention acceptability and mechanisms of change. Intervention costs will be captured from monthly project accounts, timesheets and discussions with staff members. // Discussion: Findings will identify elements of the intervention and trial procedures requiring revision prior to a full cRCT to evaluate the effectiveness of SMART

Multidimensional responses of grassland stability to eutrophication

Eutrophication usually impacts grassland biodiversity, community composition, and biomass production, but its impact on the stability of these community aspects is unclear. One challenge is that stability has many facets that can be tightly correlated (low dimensionality) or highly disparate (high dimensionality). Using standardized experiments in 55 grassland sites from a globally distributed experiment (NutNet), we quantify the effects of nutrient addition on five facets of stability (temporal invariability, resistance during dry and wet growing seasons, recovery after dry and wet growing seasons), measured on three community aspects (aboveground biomass, community composition, and species richness). Nutrient addition reduces the temporal invariability and resistance of species richness and community composition during dry and wet growing seasons, but does not affect those of biomass. Different stability measures are largely uncorrelated under both ambient and eutrophic conditions, indicating consistently high dimensionality. Harnessing the dimensionality of ecological stability provides insights for predicting grassland responses to global environmental change

Excavating buried memories: mnemonic production in the railways under London and Berlin 1933-2013

In this thesis I explore the production of social memory in the subterranean infrastructural landscapes of the London Underground and the Berlin U- and S-Bahn within a period spanning roughly the last eight decades between 1933 and 2013. To do this I apply an approach that is interdisciplinary in scope, comparative in nature and lies at the nexus of transport and cultural history, historical and cultural geography, and memory, landscape and heritage studies. More specifically this approach necessitates an engagement with the theories and literatures related to landscape, social memory and urban infrastructures in order to create new ways to study the cultural geographic and historic characteristics of urban underground railways, whilst simultaneously problematising the biased application of landscape approaches in non-urban contexts and contributing to the re-theorisation of the relationship of landscape and infrastructure. This is achieved by establishing ‘the social memories of landscape’ as my central focus, and the actors, processes, structures and discourses implicated in the production of a variety of ‘buried memories’ as my main concerns. Thereafter, and upon establishing the main components of this research’s mixed methodological and case-orientated comparative approach, I use a series of empirically grounded comparative excavations to shed light on how social memories are produced in the physical, representational and experiential landscapes of the Underground, U- and S-Bahn as exemplified by their cartographies and toponymies, realised and unrealised memorials, and alternative and creative uses of their ruins and vestiges. These excavations contribute in turn to new understandings of the mnemonic actors, processes, structures and discourses that have particular influence and resonance in these urban underground landscapes, and hence serve to demonstrate how the Underground, U- and S-Bahn’s subterranean transport contexts influence the production of social memory