8,664 research outputs found
The GSC-II-based survey of ancient cool white dwarfs I. The sample of spectroscopically confirmed WDs
The GSC-II white dwarf survey was designed to identify faint and high proper
motion objects, which we used to define a new and independent sample of cool
white dwarfs. With this survey we aim to derive new constraints on the halo
white dwarf space density. Also, these data can provide information on the age
of thick disk and halo through the analysis of the luminosity function. On the
basis of astrometric and photometric parameters, we selected candidates with mu
> 0.28 as/yr and R_F > 16 in an area of 1150 square degrees. Then, we separated
white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper
motion diagram. Finally, spectroscopic follow-up observations were carried out
to confirm the white dwarf nature of the selected candidates. We found 41 white
dwarfs of which 24 are new discoveries. Here we present the full sample and for
each object provide positions, absolute proper motions, photometry, and
spectroscopy.Comment: 14 pages, 7 figures, submitted to A&
‘RE/TRS’ is a Girl’s Subject: Talking about Gender and the Discourse of ‘Religion’ in UK Educational Spaces
This article addresses what appears to be a retrenchment into narrower forms of identification and an increased suspicion of difference in the context of educational policy in the UK – especially in relation to ‘Religious Education’. The adoption of standardized management protocols – ‘managerialism’ – across most if not all policy contexts including public educational spaces reduces spaces for encountering or addressing genuine difference and for discovering something new and different. A theory of the ‘feminization of religion’ associated historically with Barbara Welter, provides some useful insights as to why this might be, suggesting that those in British society who would prefer to see greater separation from ‘religion’ in ‘secular’ schools may well also be caught up in forms of gender stereotyping
Hunting for brown dwarf binaries and testing atmospheric models with X-Shooter
The determination of the brown dwarf binary fraction may contribute to the
understanding of the substellar formation mechanisms. Unresolved brown dwarf
binaries may be revealed through their peculiar spectra or the discrepancy
between optical and near-infrared spectral type classification.
We obtained medium-resolution spectra of 22 brown dwarfs with these
characteristics using the X-Shooter spectrograph at the VLT.
We aimed to identify brown dwarf binary candidates, and to test if the
BT-Settl 2014 atmospheric models reproduce their observed spectra.
To find binaries spanning the L-T boundary, we used spectral indices and
compared the spectra of the selected candidates to single spectra and synthetic
binary spectra. We used synthetic binary spectra with components of same
spectral type to determine as well the sensitivity of the method to this class
of binaries.
We identified three candidates to be combination of L plus T brown dwarfs. We
are not able to identify binaries with components of similar spectral type. In
our sample, we measured minimum binary fraction of .
From the best fit of the BT-Settl models 2014 to the observed spectra, we
derived the atmospheric parameters for the single objects. The BT-Settl models
were able to reproduce the majority of the SEDs from our objects, and the
variation of the equivalent width of the RbI (794.8 nm) and CsI (852.0 nm)
lines with the spectral type. Nonetheless, these models did not reproduce the
evolution of the equivalent widths of the NaI (818.3 nm and 819.5 nm) and KI
(1253 nm) lines with the spectral type.Comment: Accepted for publication in MNRA
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Imaging stress and magnetism at high pressures using a nanoscale quantum sensor.
Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven [Formula: see text] phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures
Modelling and simulation of operation and maintenance strategy for offshore wind farms based on multiagent system
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Maintenance of offshore wind turbines is a complex and costly undertaking which acts as a barrier to the development of this source of energy. Factors such as the size of the turbines, the size of the wind farms, their distance from the coast and meteorological conditions make it difficult for the stakeholders to select the optimal maintenance strategy. With the objective of reducing costs and duration of such operations it is important that new maintenance techniques are investigated. In this paper we propose a hybrid model of maintenance that is based on multi-agent systems; this allows for the modelling of systems with dynamic interactions between multiple parts. A multi-criteria decision algorithm has been developed to allow analysis and selection of different maintenance strategies. A cost model that includes maintenance action cost, energy loss and installation of monitoring system cost has been presented. For the purposes of this research we have developed a simulator using NetLogo software and have provided experimental results. The results show that employing the proposed hybrid maintenance strategy could increase wind farm productivity and reduce maintenance cost.Acknowledgement is made to European Union for the support of this research through the
European Program INTERREG IVA France-Channel-UK by funding project entitled MER
Innovate
Frailty exists in younger adults admitted as surgical emergency leading to adverse outcomes
Background: Frailty is prevalent in the older adult population (≥65 years of age) and results in adverse outcomes in the emergency general surgical population.
Objective: To determine whether frailty exists in the younger adult emergency surgical population (<65 years) and what influence frailty may have on patient related outcomes. Design: Prospective observational cohort study. Setting: Emergency general surgical admissions. Participants: All patients ≥40 years divided into 2 groups: younger adults (40-64.9 years) and older adult comparative group (≥65).
Measurements: Over a 6-month time frame the following data was collected: demographics; Scottish Index of Multiple Deprivation (SIMD); blood markers; multi-morbidities, polypharmacy and cognition. Frailty was assessed by completion of the Canadian Study of Health and Ageing (CSHA). Each patient was followed up for 90 days to allow determination of length of stay, re-admission and mortality.
Results: 82 young adults were included and the prevalence of frailty was 16% (versus older adults 38%; p=0.001) and associated with: multi-morbidity; poly-pharmacy; cognitive impairment; and deprivation. Frailty in older adults was only significantly associated with increasing age.
Conclusions: This novel study has found that frailty exists in 16% of younger adults admitted to emergency general surgical units, potentially leading to adverse short and long-term outcomes. Strategies need to be developed that identify and treat frailty in this vulnerable younger adult population
Blockchain-Based Distributed Marketplace
Developments in Blockchain technology have enabled the creation of smart contracts; i.e., self-executing code that is stored and executed on the Blockchain. This has led to the creation of distributed, decentralised applications, along with frameworks for developing and deploying them easily. This paper describes a proof-of-concept system that implements a distributed online marketplace using the Ethereum framework, where buyers and sellers can engage in e-commerce transactions without the need of a large central entity coordinating the process. The performance of the system was measured in terms of cost of use through the concept of ‘gas usage’. It was determined that such costs are significantly less than that of Amazon and eBay for high volume users. The findings generally support the ability to use Ethereum to create a distributed on-chain market, however, there are still areas that require
further research and development
Imaging stress and magnetism at high pressures using a nanoscale quantum sensor
Pressure alters the physical, chemical and electronic properties of matter.
The development of the diamond anvil cell (DAC) enables tabletop experiments to
investigate a diverse landscape of high-pressure phenomena ranging from the
properties of planetary interiors to transitions between quantum mechanical
phases. In this work, we introduce and utilize a novel nanoscale sensing
platform, which integrates nitrogen-vacancy (NV) color centers directly into
the culet (tip) of diamond anvils. We demonstrate the versatility of this
platform by performing diffraction-limited imaging (~600 nm) of both stress
fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from
25-340 K. For the former, we quantify all six (normal and shear) stress
components with accuracy GPa, offering unique new capabilities for
characterizing the strength and effective viscosity of solids and fluids under
pressure. For the latter, we demonstrate vector magnetic field imaging with
dipole accuracy emu, enabling us to measure the pressure-driven
phase transition in iron as well as the complex
pressure-temperature phase diagram of gadolinium. In addition to DC vector
magnetometry, we highlight a complementary NV-sensing modality using T1 noise
spectroscopy; crucially, this demonstrates our ability to characterize phase
transitions even in the absence of static magnetic signatures. By integrating
an atomic-scale sensor directly into DACs, our platform enables the in situ
imaging of elastic, electric and magnetic phenomena at high pressures.Comment: 18 + 50 pages, 4 + 19 figure
Parallaxes of Five L Dwarfs with a Robotic Telescope
We report the parallax and proper motion of five L dwarfs obtained with observations from the robotic Liverpool Telescope. Our derived proper motions are consistent with published values and have considerably smaller errors. Based on our spectral type versus absolute magnitude diagram, we do not find any evidence for binaries among our sampleor, at least no comparable mass binaries. Their space velocities locate them within the thin disk, and based on the model comparisons, they have solar-like abundances. For all five objects, we derived effective temperature, luminosity, radius, gravity, and mass from an evolutionary model (CBA00) and our measured parallax; moreover, we derived their effective temperature by integrating observed optical and near-infrared spectra and model spectra (BSH06 or BT-Dusty) at longer wavelengths to obtain bolometric flux using the classical Stefan-Boltzmann law. Generally, the three temperatures for one object derived using two different methods with three models are consistent, although at lower temperature (e.g., for L4) the differences among the three temperatures are slightly larger than those at higher temperature (e.g., for L1).Peer reviewe
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