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Structural origins of dielectric anomalies in the filled tetragonal tungsten bronze, Sr2NaNb5O15
Get PDFThe tetragonal tungsten bronze, Sr2NaNb5O15, shows promise for application in high-temperature high-efficiency capacitors vital for the sustainable energy revolution. Previously, the structural complexity of this and related materials has obscured the mechanisms underpinning two large anomalies in relative permittivity (εr) which give rise to their exceptionally broad dielectric response. We comprehensively investigate the structural evolution from −173 to 627 °C, combining electron, X-ray and neutron diffraction, electron microscopy, and first principles electronic structure calculations to unambiguously identify the structural origins of both anomalies. The peak in εr at 305 °C is associated with a polar-nonpolar phase transition, wherein cations displace along the c-axis. Guided by DFT, we identify a further transition upon cooling, associated with the second peak at −14 °C, linked to the softening of an in-plane polar distortion with a correlation length limited by ferroelastic nano-domains arising from rigid-unit-like tilting of NbO6 octahedra at high temperature, imparting relaxor-like behaviour. Thus, the two dielectric anomalies in Sr2NaNb5O15 are associated with two distinct crystallographic phase transitions and their interplay with a microstructure that arises from a third, non-polar structural distortion. Chemical control of these will enable development of tuneable materials with dielectric properties suitable for high-temperature energy storage applications
Extreme fluctuations in ambient salinity select for bacteria with a hybrid “salt-in”/”salt-out” osmoregulation strategy
No full textAbundant microbial biofilms inhabit underwater freshwater springs of the Dead Sea. Unlike the harsh (i.e., over 35% total dissolved salts) yet stable environment of the basin, the flow rate of the springs changes with random amplitude and duration, resulting in drastic shifts in salinity, pH, and oxygen concentrations. This requires the organisms to continuously adapt to new environmental conditions. Osmotic regulation is energetically expensive; therefore, the response of the biofilm organisms to rapid and drastic changes in salinity is interesting. For this purpose, we studied the metagenome of an enrichment culture obtained from a green biofilm-covered rock positioned in a spring. We obtained metagenome-assembled genomes (MAGs) of Prosthecochloris sp. (Chlorobiales), Flexistipes sp. (Deferribacterales), Izemoplasma (Izemoplasmatales), Halomonas sp. (Oceanospirillales), and Halanaerobium (Halanaerobiales). The MAGs contain genes for both the energetically cheaper “salt-in” and more expensive “salt-out” strategies. We suggest that the dynamic response of these bacteria utilizes both osmoregulation strategies, similar to halophilic archaea. We hypothesize that the frequent, abrupt, and variable-in-intensity shifts in salinity, typical of the Dead Sea spring system, select for microorganisms with scalable adaptation strategies
Attitudes toward proactive topical corticosteroid use among women with vulval lichen sclerosus
No full textObjectives:
Some practitioners are adopting proactive topical corticosteroid (TCS) therapy for vulval lichen sclerosus (VLS). We sought to understand patient attitudes toward proactive TCS therapy for VLS in a context in which proactive therapy is adopted.
Methods:
Four online focus group discussions with 12 participants. Data analysis was informed by social constructionist grounded theory.
Results:
All participants had accepted a proactive regimen. Three themes were developed from the analysis: “Coming to accept proactive therapy,” “Motivators to maintaining a proactive regimen,” and “The importance of a routine that fits me.” Within each theme are subthemes illustrating different dimensions of the theme.
Conclusions:
Accepting proactive TCS therapy for VLS requires incorporating regular TCS use into a patient's identity, unlearning previous understandings regarding the safety of long-term TCS use, and adopting a regimen that fits within patients' lives and minimizes the loss of autonomy
Natural disasters and local government finance : evidence from Typhoon Haiyan
Get PDFThis paper examines how natural disasters affect local public finances and their interplay with intergovernmental transfers and external resources. Exploiting the randomized nature of the 2013 Typhoon Haiyan, one of the most devastating natural disasters in recent history, we document its causal effect on the local government fiscal dynamics. Combining data on local government finance with reports on the level of damages and using difference-in-differences with instrumental variable to analyze the data, we show that local public revenue and expenditures remain largely unaffected, except for debt payments. However, we find important heterogeneity in local revenue responses: poorer municipalities raised comparatively lower revenue in the aftermath of the Typhoon. We also provide evidence that external funding did not lead to lower tax collection efforts, but instead leads to higher local expenditures, suggesting that disaster aid does not cause a moral hazard problem in local governments' spending decisions
A circular economy approach for recycling electric motors in the end-of-life vehicles : a literature review
Get PDFIncreasing concerns over climate change have led to global decarbonisation efforts, in the form of new legislation, to phase out the sale of internal combustion engine (ICE) vehicles. As a result, the transition to electrified powertrain vehicles as the mode of transportation has never been greater. Electric motors (EMs), serving as the pivotal component of e-mobility, have gained much attention by policy makers and economic experts concerning the supply chain of raw materials needed for manufacturing. Permanent magnets (PMs), including rare earth elements (REEs), account for 40 to 60 % of the total EM cost. Given the importance of these materials to the e-mobility efforts, there has been a great impetus by leading economies to mitigate supply chain instability and mining operation constraints, by identifying and establishing a sustainable supply source through circular economy strategies. Although extensive studies on REEs recovery, via various techniques, have been undertaken by the research community, there remain underlying concerns over feed source, quality and technical challenges surrounding the retrieval of PM via a functional disassembly approach, all of which are yet to be elucidated. The present study serves to highlight state-of-the-art recycling of EMs from EoL electrified vehicles using a circular economy approach
Photonic ferroelectric vortex lattice
No full textThe recent discovery of polar vortex textures revealed a new fascinating facet of nanoscale ferroelectric materials with prospects for new interaction pathways with chiral, topological, and photonic materials. Here, we demonstrate how the subterahertz collective response of the ferroelectric vortex lattice enables a coupling to electric and magnetic fields resulting in a novel type of photonic vortex lattice with particular dispersion that we analyze for a wide class of ferroelectric/paraelectric layered heterostructures. General arguments supported by full, material-specific numerics evidence the appearance of polarization-dependent optoelectronic modes and band gaps. The ferroelectric-photonic vorticity coupling renders photonic elements amenable to elastic, electric, and magnetic probes with far-reaching implications for new multifunctional optoelectronics
LSGraph : a locality-centric high-performance streaming graph engine
Get PDFStreaming graph has been broadly employed across various application domains. It involves updating edges to the graph and then performing analytics on the updated graph. However, existing solutions either suffer from poor data locality and high computation complexity for streaming graph analytics, or need high overhead to search and move graph data to ensure ordered neighbors during streaming graph update. This paper presents a novel locality-centric streaming graph engine, called LSGraph, to enable effcient both graph analytics and graph update. The main novelty of this engine is a differentiated hierarchical indexed streaming graph representation approach to achieve effcient data search and movement for graph update and also maintain data locality and ordered neighbors for effcient graph analytics simultaneously. Besides, a locality-aware streaming graph data update mechanism is also proposed to effciently regulate the distance of data movement, minimizing the overhead of memory access during graph update. We have implemented LSGraph and conducted a systematic evaluation on both real-world and synthetic datasets. Compared with three cutting-edge streaming graph engines, i.e., Terrace, Aspen, and PaC-tree, LSGraph achieves 2.98×-81.08×, 1.46×-12.56×, and 1.26×-10.31× speedups during graph update, while obtaining 1.02×-4.28×, 1.58×-3.55×, and 1.20×-2.72× speedups during graph analytics, respectively
The compressed conjugacy problem in relatively hyperbolic groups
Get PDFWe prove that the compressed conjugacy problem in a group that is hyperbolic relative to a collection of free abelian subgroups is solvable in polynomial time
Seismic behaviour of Exterior RC beam-column joints repaired and strengthened using post-tensioned metal straps
Get PDFExterior beam-column joints are the most vulnerable part of substandard reinforced concrete (RC) buildings and are often the first to be damaged during earthquakes. This article presents an experimental and numerical investigation into the behaviour of exterior RC beam-column joints repaired and strengthened using Post-Tensioned Metal Straps (PTMS) for active confinement. The study focused on full-scale beam-column joints with an inadequate core zone detailing, thus emulating the deficiencies found in existing substandard RC buildings. Initially, four “bare” joints were subjected to cyclic tests to induce substantial damage within the core zone. Subsequently, the damaged core of the joints was repaired and recast with new concrete, and PTMS were applied to strengthen the joints, followed by another round of cyclic testing. The experimental findings were compared with predictions generated through established models from existing literature. The results revealed that ASCE/SEI 41–17 guidelines accurately predict the shear capacity of the bare joints. It is shown that recasting the core with new concrete significantly increased the joint’s shear capacity by up to 42% compared their bare counterparts. The use of PTMS strengthening further enhanced the capacity by up to 25%. A “scissors model” was employed for numerical simulations of both bare and PTMS-strengthened joints using DRAIN-2DX, which proved effective at predicting their nonlinear load-displacement envelope response. This article contributes towards the development of new cost-effective post-earthquake strengthening techniques for beam-column joints, with the potential to reduce the vulnerability of substandard RC buildings in developing countries
