3,741 research outputs found

    Negative Refraction of Excitations in the Bose-Hubbard Model

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    Ultracold atoms in optical lattices provide a unique opportunity to study Bose- Hubbard physics. In this work we show that by considering a spatially varying onsite interaction it is possible to manipulate the motion of excitations above the Mott phase in a Bose-Hubbard system. Specifically, we show that it is possible to "engineer" regimes where excitations will negatively refract, facilitating the construction of a flat lens.Comment: 6 pages, 4 figure

    Domain structures in quantum graphity

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    Quantum graphity offers the intriguing notion that space emerges in the low-energy states of the spatial degrees of freedom of a dynamical lattice. Here we investigate metastable domain structures which are likely to exist in the low-energy phase of lattice evolution. Through an annealing process we explore the formation of metastable defects at domain boundaries and the effects of domain structures on the propagation of bosons. We show that these structures should have observable background-independent consequences including scattering, double imaging, and gravitational lensing-like effects

    The vulnerability of shrimp farming income to climate change events

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    Purpose This paper aims to investigate shrimp income losses of farmers in the four farming systems in the research areas of Ca Mau, Vietnam, and determine the vulnerability of shrimp farming income to climate change events. Design/methodology/approach Field research interviews were conducted with 100 randomly selected households across the four farming systems to access shrimp income status and vulnerability levels to climate change events. Four focus groups, each aligned to a particular farming system, were surveyed to categorise likelihood and consequences of climate change effects based on a risk matrix worksheet to derive levels of risk, adaptive capacity and vulnerability levels. Findings Shrimp farmers in the study areas have been facing shrimp income reduction recently and shrimp farming income is vulnerable to climate change events. There are some differences between farmers’ perspectives on vulnerability levels, but some linkages are evident among shrimp farmer characteristics, ramifications for each farming system, shrimp income losses and shrimp farmers’ perspectives on vulnerability levels of shrimp incomes. From an income perspective, farmers operating in intensive shrimp farming systems appear to be less vulnerable to existing and expected climate change effects relative to those in mixed production or lower density systems. Originality/value Having identified the vulnerability level of shrimp farming income to climate change events in different farming systems based on shrimp farmers’ perspectives, the paper adds new knowledge to existing research on vulnerability of the aquaculture sector to climate change. The research findings have implications for policymakers who may choose to encourage intensive shrimp farming to enhance shrimp farmer resilience to the effects of climate change as well as improving cultivation techniques for shrimp farmers. The findings could thus guide local government decision-making on climate change responses and residents of Ca Mau as well as within the wider Mekong Delta in developing suitable practical adaption measures

    Rheumatoid Arthritis Naive T Cells Share Hypermethylation Sites With Synoviocytes.

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    ObjectiveTo determine whether differentially methylated CpGs in synovium-derived fibroblast-like synoviocytes (FLS) of patients with rheumatoid arthritis (RA) were also differentially methylated in RA peripheral blood (PB) samples.MethodsFor this study, 371 genome-wide DNA methylation profiles were measured using Illumina HumanMethylation450 BeadChips in PB samples from 63 patients with RA and 31 unaffected control subjects, specifically in the cell subsets of CD14+ monocytes, CD19+ B cells, CD4+ memory T cells, and CD4+ naive T cells.ResultsOf 5,532 hypermethylated FLS candidate CpGs, 1,056 were hypermethylated in CD4+ naive T cells from RA PB compared to control PB. In analyses of a second set of CpG candidates based on single-nucleotide polymorphisms from a genome-wide association study of RA, 1 significantly hypermethylated CpG in CD4+ memory T cells and 18 significant CpGs (6 hypomethylated, 12 hypermethylated) in CD4+ naive T cells were found. A prediction score based on the hypermethylated FLS candidates had an area under the curve of 0.73 for association with RA case status, which compared favorably to the association of RA with the HLA-DRB1 shared epitope risk allele and with a validated RA genetic risk score.ConclusionFLS-representative DNA methylation signatures derived from the PB may prove to be valuable biomarkers for the risk of RA or for disease status

    Negotiating Public and Legal Spaces: The Emergence of an LGBT Movement in Vietnam

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    Vietnam’s laws, policies and decrees do not explicitly discriminate against lesbian, gay, bisexual and transgender (LGBT) individuals but their rights are not legally protected and they are socially marginalised. The state promotes a model of a married heterosexual couple with two children in the media and through its public policy campaigns. Families that comply are able to obtain membership of the Communist Party and run for office; women are eligible for micro-credit programmes. Same-sex couples cannot marry and are thus ineligible for the benefits that married couples enjoy. Family laws, with regard to child custody, inheritance and property, do not protect same-sex couples. In order to understand how LGBT civil society organisations can affect legal and social change with regard to the laws that regulate sexual norms and unions, this empirical study explores the following two examples of collective action in Vietnam: 1. The mobilisation strategies of civil society organisations to hold gay pride events. 2. Collective action to legalise same-sex ceremonies and marriages.UK Department for International Developmen

    Reconfigurable quantum metamaterials

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    By coupling controllable quantum systems into larger structures we introduce the concept of a quantum metamaterial. Conventional metamaterials represent one of the most important frontiers in optical design, with applications in diverse fields ranging from medicine to aerospace. Up until now however, metamaterials have themselves been classical structures and interact only with the classical properties of light. Here we describe a class of dynamic metamaterials, based on the quantum properties of coupled atom-cavity arrays, which are intrinsically lossless, reconfigurable, and operate fundamentally at the quantum level. We show how this new class of metamaterial could be used to create a reconfigurable quantum superlens possessing a negative index gradient for single photon imaging. With the inherent features of quantum superposition and entanglement of metamaterial properties, this new class of dynamic quantum metamaterial, opens a new vista for quantum science and technolog
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