Asymptotically cylindrical 7-manifolds of holonomy G_2 with applications to compact irreducible G_2-manifolds

We construct examples of exponentially asymptotically cylindrical Riemannian 7-manifolds with holonomy group equal to G_2. To our knowledge, these are the first such examples. We also obtain exponentially asymptotically cylindrical coassociative calibrated submanifolds. Finally, we apply our results to show that one of the compact G_2-manifolds constructed by Joyce by desingularisation of a flat orbifold T^7/\Gamma can be deformed to one of the compact G_2-manifolds obtainable as a generalized connected sum of two exponentially asymptotically cylindrical SU(3)-manifolds via the method given by the first author (math.DG/0012189).Comment: 36 pages; v2: corrected trivial typos; v3: some arguments corrected and improved; v4: a number of improvements on presentation, paritularly in sections 4 and 6, including an added picture

Economic Impact of Withdrawing Specific Agricultural Pesticides in the Lower Rio Grande Valley

The Air, Pesticides, and Toxics Division of the Environmental Protection Agency (EPA) has encouraged all states to develop a plan to manage the use of pesticides to prevent application that would result in unreasonable risks to human health and the environment from contamination of ground water. In February, 1988, EPA proposed a strategy where by they would regulate certain pesticides by prohibiting their use in areas vulnerable to leaching unless a state develops and implements a management plan acceptable to EPA. However, banning the use of a pesticide in a region is the worst case scenario available to the TWC for managing water quality. The Texas Water Commission (TWC) assessed the State for areas vulnerable to leaching and found the Lower Rio Grande Valley (LRGV) to be a highly vulnerable area. This study examines three pesticides (atrazine, dicrotophos, and aldicarb) currently used in the LRGV that were identified by the TWC as potential contaminants of ground water. Alternative methods of controlling pests in this region were identified, and the economic impacts of withdrawing one or all three of these pesticides from the study area were estimated. Regional impacts on gross receipts (sales), variable costs, and net returns were determined. If atrazine use were banned in the LRGV, corn and sorghum sales would decrease by approximately $1 million, variable costs to produce corn, sorghum, and sugarcane would increase by almost$2 million dollars, leaving farmers in the region with a $3 million dollar 1088 in net income per year. If dicrotophos use were prohibited in the LRGV, variable cost to produce cotton would increase by over$600,000 for the region as a whole. Banning aldicarb use in the study area would reduce citrus sales by almost $3 million, increase variable costs to produce citrus by over$200,000, and reduce farmer net income by over $3 million annually

Type IIA Orientifold Limit of M-Theory on Compact Joyce 8-Manifold of Spin(7)-Holonomy

We show that M-theory compactified on a compact Joyce 8-manifold of $Spin(7)$-holonomy, which yields an effective theory in $D = 3$ with $\N$ = 1 supersymmetry, admits at some special points in it moduli space a description in terms of type IIA theory on an orientifold of compact Joyce 7-manifold of $G_2$-holonomy. We find the evidence in favour of this duality by computing the massless spectra on both M-thory side and type IIA side. For the latter, we compute the massless spectra by going to the orbifold limit of the Joyce 7-manifold.Comment: 26 pages, 2 eps figures, Latex file, two references and one footnote added, corrected some typo

The art of Patient and Public Involvement : Exploring ways to research and reduce air pollution through art-based community workshops - a reflective paper

In this reflective paper we outline and discuss our art-based Patient and Public Involvement (PPI) approach. This exercise held two broad objectives. Firstly, to assist policy makers in understanding the types of interventions communities will find acceptable to address the problem of poor air quality, and secondly, to ascertain community views about our research plans to explore the impact of the planned interventions on neighbourhoods. We reflect on both our approach and the emergent conversations from the PPI activity. Attendees contributed to the process and stressed the importance of not burdening poor neighbourhoods with costly charges as that would ameliorate one health problem but generate others as a consequence of additional financial burden. Equally, they stressed the need to conduct research on matters which they could connect with such as the impact of clean air plans on young children and how information about air pollution is disseminated in their neighbourhoods as and when research findings emerge. This paper offers a conceptual analysis of the art-based PPI method and uniquely draws a connection to the philosophical traditions of Ludwig Wittgenstein. Specifically, we demonstrate how art is conducive to creating a dialogue which is specifically helpful for PPI purposes for both researchers and implementers, and conversely, why traditional conversational approaches may have fallen short of the adequacy mark in this regard

Composite Fermion Description of Correlated Electrons in Quantum Dots: Low Zeeman Energy Limit

We study the applicability of composite fermion theory to electrons in two-dimensional parabolically-confined quantum dots in a strong perpendicular magnetic field in the limit of low Zeeman energy. The non-interacting composite fermion spectrum correctly specifies the primary features of this system. Additional features are relatively small, indicating that the residual interaction between the composite fermions is weak. \footnote{Published in Phys. Rev. B {\bf 52}, 2798 (1995).}Comment: 15 pages, 7 postscript figure

Economic Impact of Withdrawing Specific Agricultural Pesticides in the Lower Rio Grande Valley

The Air, Pesticides, and Toxics Division of the Environmental Protection Agency (EPA) has encouraged all states to develop a plan to manage the use of pesticides to prevent application that would result in unreasonable risks to human health and the environment from contamination of ground water. In February, 1988, EPA proposed a strategy where by they would regulate certain pesticides by prohibiting their use in areas vulnerable to leaching unless a state develops and implements a management plan acceptable to EPA. However, banning the use of a pesticide in a region is the worst case scenario available to the TWC for managing water quality. The Texas Water Commission (TWC) assessed the State for areas vulnerable to leaching and found the Lower Rio Grande Valley (LRGV) to be a highly vulnerable area. This study examines three pesticides (atrazine, dicrotophos, and aldicarb) currently used in the LRGV that were identified by the TWC as potential contaminants of ground water. Alternative methods of controlling pests in this region were identified, and the economic impacts of withdrawing one or all three of these pesticides from the study area were estimated. Regional impacts on gross receipts (sales), variable costs, and net returns were determined. If atrazine use were banned in the LRGV, corn and sorghum sales would decrease by approximately $1 million, variable costs to produce corn, sorghum, and sugarcane would increase by almost$2 million dollars, leaving farmers in the region with a $3 million dollar 1088 in net income per year. If dicrotophos use were prohibited in the LRGV, variable cost to produce cotton would increase by over$600,000 for the region as a whole. Banning aldicarb use in the study area would reduce citrus sales by almost $3 million, increase variable costs to produce citrus by over$200,000, and reduce farmer net income by over $3 million annually

Differences in public's perception of air quality and acceptability of a clean air zone : A mixed-methods cross sectional study

Background: Air pollution is a major cause of morbidity and mortality. Clean Air Zones (CAZs) which restrict the entry of polluting vehicles in targeted areas have been identified as potentially effective in improving health and reducing air pollution; however, their implementation can be controversial. Methods: A cross-sectional survey was completed by 1949 respondents who lived or worked in Bradford, a multi-cultural deprived city in England, between April and December 2021. Of these, 1137 were recruited from the longitudinal Born in Bradford (BiB) family cohort (families with children born in the city during 2007–2011) and 812 were from the general public. Bradford is the seventh largest metropolitan district in England and Wales with a population of over half a million mainly white British and Pakistani origin. The BiB families cohort and the general public respondents were used for descriptive analysis of perception of air quality and acceptability of CAZ, then the relationship between participants responses with demographic characteristics were investigated using the BiB families cohort. Outcomes included perceptions of air quality and acceptability of the CAZ supplemented by free-text questions. Thematic analysis was used to code free-text data. Descriptive analyses were performed on the entire sample. Latent class analysis was used to characterise participants was performed in the BiB dataset for whom detailed existing socio-demographic data were available. Results: The majority of participants (67%) considered improving air quality in Bradford as extremely important; 70% supported implementation of the CAZ. Three latent classes were identified within the BiB sample: deprived white British families (25%), more affluent white British families (32%) and deprived Pakistani-origin families (43%). Deprived white British (OR = 0.54, 95% CI: 0.34 to 0.84) and more affluent white British families (OR = 0.53, 95% CI: 0.36 to 0.79) were less likely to say the air quality was good/excellent when compared with deprived Pakistani-origin families. Affluent White British families were more likely to support the CAZ compared with deprived white British families (OR = 2.24; 95% CI: 1.55. to 3.25) and deprived Pakistani-origin families (OR = 2.06, 95% CI: 1.50 to 2.85). Qualitative analysis suggested that a perceived lack of cohesion in the policy and concerns about financial impacts drove negative attitudes. Conclusion: Families in Bradford were generally supportive of the planned CAZ and efforts to reduce pollution; however, support was weaker in more deprived communities. Pakistani-origin communities living in deprived areas perceived air quality as better than other groups. Tailored approaches to communicate about the proposed benefits of policies such as CAZ prior to implementation may be an important way to increase acceptability amongst vulnerable groups

Electronic structure of rectangular quantum dots

We study the ground state properties of rectangular quantum dots by using the spin-density-functional theory and quantum Monte Carlo methods. The dot geometry is determined by an infinite hard-wall potential to enable comparison to manufactured, rectangular-shaped quantum dots. We show that the electronic structure is very sensitive to the deformation, and at realistic sizes the non-interacting picture determines the general behavior. However, close to the degenerate points where Hund's rule applies, we find spin-density-wave-like solutions bracketing the partially polarized states. In the quasi-one-dimensional limit we find permanent charge-density waves, and at a sufficiently large deformation or low density, there are strongly localized stable states with a broken spin-symmetry.Comment: 8 pages, 9 figures, submitted to PR

Spin interactions and switching in vertically tunnel-coupled quantum dots

We determine the spin exchange coupling J between two electrons located in two vertically tunnel-coupled quantum dots, and its variation when magnetic (B) and electric (E) fields (both in-plane and perpendicular) are applied. We predict a strong decrease of J as the in-plane B field is increased, mainly due to orbital compression. Combined with the Zeeman splitting, this leads to a singlet-triplet crossing, which can be observed as a pronounced jump in the magnetization at in-plane fields of a few Tesla, and perpendicular fields of the order of 10 Tesla for typical self-assembled dots. We use harmonic potentials to model the confining of electrons, and calculate the exchange J using the Heitler-London and Hund-Mulliken technique, including the long-range Coulomb interaction. With our results we provide experimental criteria for the distinction of singlet and triplet states and therefore for microscopic spin measurements. In the case where dots of different sizes are coupled, we present a simple method to switch on and off the spin coupling with exponential sensitivity using an in-plane electric field. Switching the spin coupling is essential for quantum computation using electronic spins as qubits.Comment: 13 pages, 9 figure

Maternal psychological distress in primary care and association with child behavioural outcomes at age three

Observational studies indicate children whose mothers have poor mental health are at increased risk of socio-emotional behavioural difficulties, but it is unknown whether these outcomes vary by the mothers’ mental health recognition and treatment status. To examine this question, we analysed linked longitudinal primary care and research data from 1078 women enrolled in the Born in Bradford cohort. A latent class analysis of treatment status and self-reported distress broadly categorised women as (a) not having a common mental disorder (CMD) that persisted through pregnancy and the first 2 years after delivery (N = 756, 70.1 %), (b) treated for CMD (N = 67, 6.2 %), or (c) untreated (N = 255, 23.7 %). Compared to children of mothers without CMD, 3-year-old children with mothers classified as having untreated CMD had higher standardised factor scores on the Strengths and Difficulties Questionnaire (d = 0.32), as did children with mothers classified as having treated CMD (d = 0.27). Results were only slightly attenuated in adjusted analyses. Children of mothers with CMD may be at risk for socio-emotional and behavioural difficulties. The development of effective treatments for CMD needs to be balanced by greater attempts to identify and treat women. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00787-015-0777-2) contains supplementary material, which is available to authorized users