637 research outputs found
Reconciling sovereignties, reconciling peoples: Should the Canadian Charter of Rights and Freedoms apply to inherent-right Aboriginal governments?
Should the Canadian Charter of Rights and Freedoms apply to constrain the actions of Aboriginal governments in Canada exercising the âinherent rightâ of self-government? Is the Charterâs application to these governments necessary to secure the human rights of those they govern, or would it amount to a violation of aboriginal sovereignty that, in any case, would do undue violence to the cultural practices and traditions of Aboriginal communities? This article seeks to contribute to the larger debate over how to balance the rights of individuals with the rights of groups by laying out a methodical, clear-eyed analysis of the strengths and weaknesses of the major arguments found in the literature for and against the Charterâs application. I argue that while the Charterâs application to inherent-right governments would amount to a limit on Aboriginal sovereignty, this is justifiable, in light of the fact that Aboriginal sovereignty should not be construed as absolute, and given the Supreme Court of Canadaâs assertion that the purpose of the Canadian Constitutionâs recognition of Aboriginal rights is reconciliation. I claim that requiring that the right of Aboriginal self-government be exercised in accordance with the Charter would further the goal of reconciliation, whereas allowing the right to be exercised irrespective of the requirements of the Charter would impede it. I thus conclude that the Charter should apply to inherent-right governments, although I stress that it should be applied in a flexible manner, in recognition of the fact that the proper safeguarding of rights can occur in different ways in different cultural contexts
Testing the Expert Based Weights Used in the UKâs Index of Multiple Deprivation (IMD) Against Three Preference-Based Methods
The paper has benefitted from helpful comments and suggestions from Koen Decancq, Rainer Schulz, and participants at the Weighting in Multidimensional Measures workshop at OPHI, Oxford, the Overseas Development Workshop at ODI, London, seminar participants at Universiteit Antwerpen, and conference participants at New Directions in Welfare III, Paris. Any errors or omissions, of course, remain the responsibility of the authors. The project was funded by the Department of the Communities and Local Government. The Chief Scientist Office of the Scottish Government Health and Social Care Directorates funds HERU. The views expressed in this paper are those of the authors only and not those of the funding bodies.Peer reviewedPostprin
In situ investigation of perovskite solar cellsâ efficiency and stability in a mimic stratospheric environment for high-altitude pseudo-satellites
Perovskite solar cells with high power-per-weight have great potential to be used for aerospace applications such as satellites or high-altitude pseudo-satellites. The latter are unmanned aircraft exclusively powered by solar energy, typically flying in the stratosphere where the conditions of pressure, temperature and illumination are critically different from that on the earth's surface. In this work, we evaluate the performance and stability of high efficiency perovskite solar cells under a mimic stratospheric environment. In situ measurements under controlled conditions of pressure, temperature and illumination were developed. We show that the cells can operate efficiently in a large range of temperature from â50 °C to +20 °C, with a maximum power conversion efficiency at â20 °C, which is ideal for use in the stratosphere. Besides, performances are maintained after a number of temperature cycles down to â85 °C, representative of temperature variations due to diurnal cycles. An efficient encapsulation is developed, which could be critical to avoid the accelerated degradation of the cells under vacuum. Finally, a promising stability for 25 days of dayânight cycles was demonstrated, which suggests that perovskite solar cells could be used to power high altitude pseudo-satellites
Nematic order and the superconducting gap in FeSe
The intense scrutiny of the electronic structure of FeSe over the last few years has been motivated
by the opportunity to distil the essential physics of both the nematic and superconducting phases,
and their interplay. Here I will address the evolution of the electronic structure in the nematic phase,
below Ts = 90 K using high-resolution ARPES. The hole pocket undergoes elliptical distortions,
but most dramatically, our `detwinnedâ ARPES results show spectral weight on only one peanutshaped
electron pocket. This unexpected result is also observed in the nematic phase of NaFeAs,
and I will argue that this effect, rather than the 10-20 meV band shifts and distortions, is the critical
ingredient of the electronic structure in the nematic phase. I will also present measurements of the
highly anisotropic superconducting gap on both the hole and electron pockets of FeSe. The results
are consistent with results from quasiparticle interference, but by considering the matrix element
effects in ARPES we are explicitly able to show a scaling of the superconducting gap with the dyz
orbital character. Furthermore we show that such a gap structure arises naturally from the solution
to the linearized gap equation, starting from a tight-binding model with accuracy on both the band
dispersions and their orbital characters, if we also take into account the one-peanut effect as observed
in the nematic phase
Near Infrared Radiation as a Rapid Heating Technique for TiO2Films on Glass Mounted Dye-Sensitized Solar Cells
Near infrared radiation (NIR) has been used to enable the sintering of TiO2 films
on fluorine-doped tin oxide (FTO) glass in 12.5âs. The 9â”m thick TiO2 films
were constructed into working electrodes for dye-sensitized solar cells (DSCs)
achieving similar photovoltaic performance to TiO2 films prepared by heating
for 30âmin in a convection oven. The ability of the FTO glass to heat upon 12.5âs
exposure of NIR radiation was measured using an IR camera and demonstrated
a peak temperature of 680°C; glass without the 600ânm FTO layer reached
350°C under identical conditions. In a typical DSC heating step, a TiO2 based
paste is heated until the polymeric binder is removed leaving a mesoporous film.
The weight loss associated with this step, as measured using thermogravimetric
analysis, has been used to assess the efficacy of the FTO glass to heat sufficiently. Heat induced interparticle connectivity in the TiO2 film has also been
assessed using optoelectronic transient measurements that can identify electron
lifetime through the TiO2 film. An NIR treated device produced in 12.5 seconds
shows comparable binder removal, electron lifetime, and efficiency to a device
manufactured over 30 minutes in a conventional oven
Sources of Pb(0) artefacts during XPS analysis of lead halide perovskites
X-Ray Photoelectron spectroscopy (XPS) spectra of methyl ammonium lead halide perovskite films typically show the presence of lead as Pb(II), but Pb(0) is also often observed, potentially influencing the interpretation of the device physics. In this article the reproducible evolution of Pb(0) peaks which are likely artefacts generated under typical XPS analytical conditions are demonstrated from methyl ammonium lead halide films that contain no Pb(0) initially. The evolution of Pb(0) occurs via (1) X-ray photolysis under typical analytical conditions and (2) alongside other chemical changes as a result of film aging in air. In both cases we note the presence of PbI2 as a common factor contributing to in situ reactions to generate Pb(0) artefacts. Hence the observation of Pb(0) should be treated with extreme caution and here we recommend simple precautions to ensure materials analysis of these films gives reliable information when analyzed under UHV conditions
GPS Rates of Vertical Bedrock Motion Suggest Late Holocene Ice-Sheet Readvance in a Critical Sector of East Antarctica
We investigate present-day bedrock vertical motion using new GPS timeseries from the Totten-Denman glacier region of East Antarctica (âŒ77-120°E) where models of glacial isostatic adjustment (GIA) disagree, glaciers are likely losing mass, and few data constraints on GIA exist. We show that varying surface mass balance loading (SMBL) is a dominant signal, contributing random-walk-like noise to GPS timeseries across Antarctica. In the study region, it induces site velocity biases of up to âŒ+1 mm/yr over 2010-2020. After correcting for SMBL displacement and GPS common mode error, subsidence is evident at all sites aside from the Totten Glacier region where uplift is âŒ1.5 mm/yr. Uplift near the Totten Glacier is consistent with late Holocene ice retreat while the widespread subsidence further west suggests possible late Holocene readvance of the regionâs ice sheet, in broad agreement with limited glacial geological data and highlighting the need for sampling beneath the current ice sheet
Investigating spatial macroscopic metastability of perovskite solar cells with voltage dependent photoluminescence imaging
Metastability is a characteristic feature of perovskite solar cell (PSC) devices that affects powerrating measurements and general electrical behaviour. In this work the metastability of differenttypes of PSC devices is investigated through currentâvoltage (IâV) testing and voltage dependentphotoluminescence (PL-V) imaging. We show that advanced IâV parameter acquisition methodsneed to be applied for accurate PSC performance evaluation, and that misleading results can beobtained when using simple fast IâV curves, which can lead to incorrect estimation of cellefficiency. The method, as applied in this work, can also distinguish between metastability anddegradation, which is a crucial step towards reporting stabilised efficiencies of PSC devices. PL-V isthen used to investigate temporal and spatial PL response at different voltage steps. In addition tothe impact on current response, metastability effects are clearly observed in the spatial PL responseof different types of PSCs. The results imply that a high density of local defects andnon-uniformities leads to increased lateral metastability visible in PL-V measurements, which isdirectly linked to electrical metastability. This work indicates that existing quantitative PL imagingmethods and point-based PL measurements of PSC devices may need to be revisited, asassumptions such as the absence of lateral currents or uniform voltage bias across a cell area maynot be valid
A Comparison of Different Textured and Non-Textured Anti-Reflective Coatings for Planar Monolithic Silicon-Perovskite Tandem Solar Cells
Multijunction solar cells offer a route to exceed the ShockleyâQueisser limit for single-junction devices. In a few short years, silicon-perovskite tandems have significantly passed the efficiency of the best silicon single-junction cells. For scalable solution processing of silicon-perovskite tandem devices, with the avoidance of vacuum processing steps, a flat silicon sub-cell is normally required. This results in a flat top surface that can lead to higher optical reflection losses than conformal deposition on textured silicon bottom cells. To overcome this, textured anti-reflective coatings (ARCs) can be used on top of the finished cell, with textured polydimethylsiloxane (PDMS), a promising candidate. In this work, we vary the texture geometry and film thickness of PDMS anti-reflective foils to understand the effect of these parameters on reflectance of the foil. The best film is selected, and anti-reflective performance is compared with two common planar ARCsâlithium fluoride (LiF) and magnesium fluoride (MgF2) showing considerable reduction in reflectance for a non-textured silicon-perovskite tandem cell. The application of a PDMS film is shown to give a 3â5% increase in integrated JSC in each sub-cell of a silicon-perovskite tandem structure
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