Exact rings and semirings

We introduce and study an abstract class of semirings, which we call exact semirings, defined by a Hahn-Banach-type separation property on modules. Our motivation comes from the tropical semiring, and in particular a desire to understand the often surprising extent to which it behaves like a field. The definition of exactness abstracts an elementary property of fields and the tropical semiring, which we believe is fundamental to explaining this similarity. The class of exact semirings turns out to include many other important examples of both rings (proper quotients of principal ideal domains, matrix rings and finite group rings over these and over fields), and semirings (the Boolean semiring, generalisations of the tropical semiring, matrix semirings and group semirings over these).Comment: 17 pages; fixed typos, clarified a few points, changed notation in Example 6.

Interrogating the prevention approach of the Housing (Wales) Act 2014 for people with mental health needs who are homeless

Rates of homelessness and poor mental health present significant challenges across the globe. In this article, we explore how these intersecting issues have been addressed in Wales through Part 2 of the Housing (Wales) Act 2014 through a paradigm shift towards a prevention model. This article reports findings from a study (conducted between 2016 and 2018) which evaluated the processes and impacts of the Act against the backdrop of welfare reform and systemic changes taking place in Wales and the UK. Using new evidence, we offer a critical examination of how homelessness prevention policy operates in practice and how social values and power affect policy implementation. We offer new evidence of the translation of policy into practice through the experiences of two stakeholder groups: people with mental health needs and service providers. In doing so, we offer a critique of how policy and practice could be modified to improve outcomes for homeless people with implications for prevention policy in Wales and in other contexts and different welfare regimes

CO3+1 network formation in ultra-high pressure carbonate liquids

Carbonate liquids are an important class of molten salts, not just for industrial applications, but also in geological processes. Carbonates are generally expected to be simple liquids, in terms of ionic interactions between the molecular carbonate anions and metal cations, and therefore relatively structureless compared to more “polymerized” silicate melts. But there is increasing evidence from phase relations, metal solubility, glass spectroscopy and simulations to suggest the emergence of carbonate “networks” at length scales longer than the component molecular anions. The stability of these emergent structures are known to be sensitive to temperature, but are also predicted to be favoured by pressure. This is important as a recent study suggests that subducted surface carbonate may melt near the Earth’s transition zone (~44 km), representing a barrier to the deep carbon cycle depending on the buoyancy and viscosity of these liquids. In this study we demonstrate a major advance in our understanding of carbonate liquids by combining simulations and high pressure measurements on a carbonate glass, (K2CO3-MgCO3) to pressures in excess of 40 GPa, far higher than any previous in situ study. We show the clear formation of extended low-dimensional carbonate networks of close CO32− pairs and the emergence of a “three plus one” local coordination environment, producing an unexpected increase in viscosity with pressure. Although carbonate melts may still be buoyant in the lower mantle, an increased viscosity by at least three orders of magnitude will restrict the upward mobility, possibly resulting in entrainment by the down-going slab

Aligning Manufacturing Strategies with Complexity Factors in the Aerospace Supply Chain

Aerofirm is a large and vertically-integrated manufacturer providing strong and light materials mainly for commercial aerospace, but also for space, defense and industrial application. They face complexity from varying customer needs, a vast product range and a large network. Complexity at Aerofirm also arises from unsynchronized processes, this paper focuses on aligning the manufacturing strategy process. The approach proposed is to first calculate suitable strategy based on: forecast accuracy, volume variability, relative volume and supply chain depth. The results were then reviewed by key personnel to refine them based on qualitative knowledge, showing a mix of manufacturing strategies is essential

Parental age influences offspring telomere loss

1. The age of the parents at the time of offspring production can influence offspring longevity, but the underlying mechanisms remain poorly understood. The effect of parental age on offspring telomere dynamics (length and loss rate) is one mechanism that could be important in this context. 2. Parental age might influence the telomere length that offspring inherit or age-related differences in the quality of parental care could influence the rate of offspring telomere loss. However, these routes have generally not been disentangled. 3. Here, we investigated whether parental age was related to offspring telomere dynamics using parents ranging in age from 2 to 22 years old in a free-living population of a long-lived seabird, the European shag (Phalacrocorax aristotelis). By measuring the telomere length of offspring at hatching and towards the end of the post-natal growth period, we could assess whether any potential parental age effect was confined to the post-natal rearing period. 4. There was no effect of maternal or paternal age on the initial telomere length of their chicks. However, chicks produced by older mothers and fathers experienced significantly greater telomere loss during the post-natal nestling growth period. We had relatively few nests in which the ages of both parents were known, and individuals in this population mate assortatively with respect to age. Thus, we could not conclusively determine whether the parental age effect was due to maternal age, paternal age, or both; however, it appears that the effect is stronger in mothers. 5. These results demonstrate that in this species, there was no evidence that parental age was related to offspring hatching telomere length. However, telomere loss during nestling growth was reduced in the offspring of older parents. This could be due to an age-related deterioration in the quality of the environment that parents provide, or because parents that invest less in offspring rearing live to an older age

The question-behaviour effect: a theoretical and methodological review and meta-analysis

Research has demonstrated that asking people questions about a behaviour can lead to behaviour change. Despite many, varied studies in different domains, it is only recently that this phenomenon has been studied under the umbrella term of the question-behaviour effect (QBE) and moderators of the effect have been investigated. With a particular focus on our own contributions, this article: (1) provides an overview of QBE research; (2) reviews and offers new evidence concerning three theoretical accounts of the QBE (behavioural simulation and processing fluency; attitude accessibility; cognitive dissonance); (3) reports a new meta-analysis of QBE studies (k = 66, reporting 94 tests) focusing on methodological moderators. The findings of this meta-analysis support a small significant effect of the QBE (g = 0.14, 95% CI = 0.11, 0.18, p < .001) with smaller effect sizes observed in more carefully controlled studies that exhibit less risk of bias and (4) also considers directions for future research on the QBE, especially studies that use designs with low risk of bias and consider desirable and undesirable behaviour separately

Harmonic Analysis of Jazz MIDI Files Using Statistical Parsing

Harmonic analysis involves identifying hierarchical structure, similar to that found in the syntax and semantics of language, in the harmonic progressions underlying tonal melodies. In previous work, we have used grammar-based parsing, with related machine-learning techniques, for automatic harmonic analysis of jazz chord sequences. We now turn to the harder task of harmonic analysis of jazz MIDI performances using similar techniques. First, we evaluate a strict pipeline approach: we use an HMM to perform chord recognition and our previous system to analyze the output. Then, we use the chord recognizer to propose a chord lattice and analyze this using an adaptation of the previous system

Plasmodium falciparum: linkage disequilibrium between loci in chromosomes 7 and 5 and chloroquine selective pressure in Northern Nigeria.

In view of the recent discovery (Molecular Cell 6, 861-871) of a (Lys76Thr) codon change in gene pfcrt on chromosome 7 which determines in vitro chloroquine resistance in Plasmodium falciparum, we have re-examined samples taken before treatment in our study in Zaria, Northern Nigeria (Parasitology, 119, 343-348). Drug resistance was present in 5/5 cases where the pfcrt 76Thr codon change was seen (100% positive predictive value). Drug sensitivity was found in 26/28 cases where the change was absent (93% negative predictive value). Allele pfcrt 76Thr showed strong linkage disequilibrium with pfmdr1 Tyr86 on chromosome 5, more complete than that between pfcrt and cg2 alleles situated between recombination cross-over points on chromosome 7. Physical linkage of cg2 with pfcrt may account for linkage disequilibrium between their alleles but in the case of genes pfmdr1 and pfcrt, on different chromosomes, it is likely that this is maintained epistatically through the selective pressure of chloroquine

Challenges to implementing the new homelessness prevention agenda in Wales

Devolution presented an opportunity for the Welsh Government to introduce changes to housing and homelessness policy, and the subsequent homelessness reforms are seen as one of the best examples to date of the Welsh Government using its powers. However, devolved governments in small countries face a number of challenges in terms of realising their housing policy ambitions. In this article we argue that there is inevitable dissonance between the policy behind the Welsh Government legislation (prevention) and practice (implementation) associated with structural challenges (for example austerity and budget restrictions, Welfare Reform and the availability of affordable accommodation). In response we propose a number of actions the Welsh Government might undertake to attempt to mitigate such structural challenges which also resonate in the English context where welfare retrenchment and homelessness prevention policies operate simultaneously