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5d-4d correspondence in twisted M-theory on a conifold
Get PDFWe study twisted M-theory in a general conifold background, and describe it in terms of a 5d non-commutative Chern-Simons-matter theory, which is equivalent to 5d non-commutative Chern-Simons theory for a supergroup. In an equivalent description as twisted type IIA string theory, the matter degrees of freedom arise from topological strings stretched between stacks of D6-branes. In order to study 5d Chern-Simons-matter theories with a boundary, we first construct and investigate the properties of a 4d non-commutative gauged chiral WZW model. We prove the gauge invariant coupling of this 4d theory to the bulk 5d Chern-Simons theory defined on ℝ+ × ℂ2, and further generalize our results to the 5d Chern-Simons-matter theory. We also investigate the toroidal current algebra of the 4d chiral WZW model that arises from radial quantization along one of the complex planes. Finally, we show that a gauged non-commutative chiral 4d WZW model arises from the partition function for quantum 5d non-commutative Chern-Simons theory with boundaries in the BV-BFV formalism, and further generalize this 5d-4d correspondence to the 5d non-commutative Chern-Simons-matter theory for the case of adjoint matter
Hot leptogenesis
Get PDFWe investigate a class of leptogenesis scenarios in which the sector containing the lightest right-handed neutrino establishes kinetic equilibrium at a temperature TN1 > TSM, where TSM is the temperature of the Standard Model sector. We study the reheating processes which realise this “hot leptogenesis” and the conditions under which kinetic and chemical equilibrium can be maintained. We derive and solve two sets of evolution equations, depending on the presence of chemical equilibrium within the hot sector, and numerically solve these for benchmark scenarios. We compare the viable parameter space of this model with standard leptogenesis scenarios with a thermal initial condition and find that hot leptogenesis resolves the neutrino and Higgs mass fine-tuning problems present in the standard scenario
Understanding teacher supply, challenges, trends and implications: A case study of China
Get PDFThis paper examines teacher supply in China, challenging the notion that the country has no teacher shortages. It is part of a broader international study on teacher supply and retention. While China meets mandated class sizes (which is large by most Western European standards), disparities exist in teacher distribution and quality, particularly in rural areas. Political and demographic factors, including education reforms and the one-child policy, have influenced teacher supply. Funding structures also contribute to regional disparities, with secondary schools in poorer provinces facing larger class sizes. Despite concerns over pay, teaching remains prestigious due to Confucian values emphasising respect for educators. The study highlights that teacher shortages are a matter of definition, shaped by cultural and systemic factors
The Metaphysics of Internal Relations
No full textRoughly speaking, internal relations are those that are necessitated in some way by their relata. Throughout the twentieth century, philosophical work on internal relations ignored important distinctions between different kinds of internal relation. There have been few attempts in contemporary metaphysics to provide a systematic, fine-grained analysis of the different kinds of internal relation, and the aim of this paper is to fill this gap. This project is especially important given the recent trend for thinking that all relations are internal. The paper proposes that the source of some internal relations lies in the essences of their relata while other internal relations arise through metaphysical grounding. After identifying different kinds of essential and grounded relations, a four-category system of internal relations is presented, and it is argued that this system ‘carves nature at its joints’ vis-à-vis internal relations
Journalism and Ethical Praxis: A Thematic Analysis of Journalism Ethics Across Five European Countries
Get PDFThe importance of high-quality, ethically sound journalism in sustaining a healthy democratic and deliberative public sphere is well established. However, recent trends suggest a lack of public trust in journalism (Fink 2019. “The Biggest Challenge Facing Journalism: A Lack of Trust.” Journalism; OECD 2024. Survey on Drivers of Trust in Public Institutions—2024 Results) coupled with a range of online challenges to ethically sourced news warrant a closer look at the role that journalism ethics play in the working lives of journalists. This paper provides a thematic analysis of twenty-seven interviews with journalists in five European countries ranked consistently at the top of media freedom rankings, to explore the role of ethical frameworks and codes in their day-to-day practice. Overall, though ethical frameworks appear to play a role in the background in terms of shaping ethical behaviour, our interviewees signal that they are highly valued in terms of guiding their decisions and enhancing their brand. However, our research also highlights that there is concern about the wider communication environment and declining public trust. We suggest that this is a problem that journalism ethics bodies should address urgently given the widespread penetration of disinformation and misinformation within the news ecology and the concomitant erosion of public faith in mainstream news. The paper concludes by suggesting ways that this might be achieved
How useful is household income as a factor in explaining attainment at school in England? Assessing the Parent Pupil Matched Data (PPMD)
Get PDFThis is a report on the first use of the Pupil Parent Matched Dataset (PPMD) linking household income to the National Pupil Database. Having access to this is very valuable for research, and this report only makes a start in looking at what is possible. The report shows that none of the versions of income available in PPMD (benefits, earned, total and equivalised) is yet completely suitable for substantive analysis. In the linked files, pupils are missing, often in large numbers where adults’ income are not linked, or family structures or second adult incomes are not known. An improved PMMD would be very helpful. It would make the substantive and comparative analyses in this report even clearer and safer. The various versions of income in PPMD are compared, and described in terms of available pupil characteristics. Earned income is deemed the most appropriate to use when considering low incomes and those on benefits. Once benefits, and other forms of unearned income, are added to the total household income, it is less clear who is on low or zero income before benefits (the target of the Pupil Premium policy). Free school meal eligibility is a better predictor of attainment than raw income is, perhaps because the FSM records are more complete. This may also be due to limitations of the income data (see below). However, there is a strong linear (and visual) relationship between income, represented in 20 equal bands, and attainment at school (Key Stages 2 and 4). Thus, income bands appear to be the strongest single predictor of attainment. Using a time series approach it is shown that, with these data, low income pupils have become less clustered in schools since the introduction of Pupil Premium funding in 2011. At KS4, low income pupils have also improved their attainment relative to high income pupils. Both of these outcomes might be the result of Pupil Premium policy, but re probably a little too early. At KS2, low income pupils improved their attainment, but not so clearly relative to high income pupils. To a great extent, the substantive results confirm our earlier analyses based on pupils with long-term disadvantage (but with clear differences between Key Stages). It would be interesting to run these kinds of analysis again if a completer and more accurate version of PPMD could be developed. There is also further work to be done on variations by region and school type, and also further development of the number and type of income bands. Given pupils’ long-term FSM status it would be useful to compare income with indicators of permanent disadvantage
Seismic Imaging of the Reykjanes Peninsula, Iceland: Crustal‐Scale Context of Geothermal Areas and Ongoing Volcano‐Tectonic Unrest
Get PDFVolcanic and seismic unrest on the Reykjanes Peninsula in SW Iceland that started in late 2019 after ∼800 years of quiescence has drawn wide interest to this on‐land extension of the Mid‐Atlantic spreading ridge. Here, we use seismic data collected across the larger Peninsula region, covering six volcanic systems and associated high‐temperature geothermal areas to produce a crustal‐scale shear‐wave velocity model. The model is constructed from receiver functions (RF), and pre‐existing surface wave dispersion measurements from recent studies, supplemented with new inter‐station paths from recent seismic deployments. We compare our velocity model to RF stacks which highlight seismic discontinuity boundaries. Results show local seismicity and geothermal systems are limited to the upper crust, which is split into an upper region of extrusive‐dominated heavily fractured material <3 km and intrusive‐dominated more cohesive material below. The gabbroic lower‐crust is dominated by cumulates beyond 10 km depth, which are particularly high‐velocity west offshore of the Peninsula. Crustal thicknesses increase from 15 to 20 km eastwards, likely reflecting increasing temperature and active‐upwelling toward the center of the Iceland hotspot. Reported magma storage depths, for current and historic eruptions, generally sit within the lower‐crust, but several, including for the 2021 Fagradalsfjall eruption, indicate sub‐Moho storage, sourced from a seismically slow region we observe extending to 25 km, which is interpreted as representing a partially molten crust‐mantle transitional region. Our seismic imaging of the Reykjanes Peninsula crust gives insight into regional crustal structure and tectonic processes, as well as providing large‐scale context for the continuing volcano‐tectonic unrest the region is experiencing
On the impulse approximation in electron Compton scattering
Get PDFElectronic structure measurement via Compton scattering requires the impulse approximation to be satisfied. This states that the inelastic collision time is short, so that the ‘secondary’ electron ejected out of the atom is effectively free of the crystal potential. The robustness of the impulse approximation is tested for boron nitride and aluminium using momentum-resolved electron energy loss spectroscopy. Reliable (with respect to impulse approximation) electronic structure information is obtained for Compton peak energies at ∼250 eV energy loss or higher. These experimental results are validated using a simple Kronig-Penney model of the secondary electron travelling through the crystal. For loosely bound valence electrons the impulse approximation is satisfied when the Compton peak energy is significantly larger than the mean inner potential of the crystal. This criterion provides a straightforward estimate of the experimental conditions required for extracting reliable Compton data from any given material
A “waste” of time?: the synthesis of a magnesium-substituted aluminophosphate from an unconventional source of magnesium
Get PDFMagnesium-substituted microporous aluminophosphates (MgAlPOs) are tuneable framework materials that exhibit strong Brønsted acidity and have found great utility as catalysts for a wide variety of green transformations. Typically, refined magnesium salts, such as magnesium acetate, are the source of magnesium used in the synthesis of MgAlPOs. However, magnesium is classified as a critical raw material, thus finding alternative sources of magnesium remains an important endeavour. Here we demonstrate the use of struvite, a mineral which can form as a problematic waste material, as a viable source of magnesium for the synthesis of MgAlPO-5 (AFI framework). Exploration of synthesis conditions showed that using struvite over magnesium acetate as the Mg source led to increased chabazite (CHA) contamination when triethylamine was employed as the template. The CHA phase impurity could be reduced through synthesis optimisation, though not eliminated when struvite was utilised. Phase pure AFI from struvite and magnesium acetate was formed when N,N-methyldicyclohexylamine was used as a template, and the gel stirred during crystallisation. Electron microscopy revealed that the struvite derived MgAlPO-5 materials exhibit a distinct surface morphology featuring nanorod-like growths, presumably associated with the magnesium source, although the underlying cause remains unclear. Despite this we show that both materials are acidic (DRIFTS and CD3CN adsorption studies) and are active catalysts for the dehydration of ethanol to ethylene in the gas phase under flow conditions. In contrast, unsubstituted AlPO-5 shows limited acidity and negligible catalytic activity, validating the incorporation of magnesium into the framework from both magnesium sources. TEM-EDS maps also support this finding, showing a homogenous distribtution of Al, P and O (and Mg) for all materials synthesised. This work demonstrates that struvite can be used in MgAlPO synthesis, under optimised conditions, showing that repurposing this unconventional magnesium source is far from “a waste of time”
Identifying Key Physical Properties of Simple Organic Drop Cast Films that give Visible to Ultraviolet Light Up‐Conversion
Get PDFWe demonstrate UV‐emitting films of 2,5‐diphenyloxazole (PPO) sensitised by 3,3′‐carbonylbis(7‐diethylaminocoumarin) (CBDAC), prepared by simple drop casting with rapid solvent evaporation, giving up‐converted emission even at low excitation intensities. The mechanisms of up‐conversion and triplet quenching in these films has been studied through time‐resolved and steady‐state spectroscopy. The CBDAC sensitizer aggregates strongly even at low concentrations, with CBDAC phosphorescence being observed in all films, indicating that many triplet excitons do not transfer to the surrounding PPO annihilator. Nonetheless, at very low sensitiser concentrations (1 : 40000 CBDAC : PPO), up‐converted PPO UV emission is observed at room temperature which is critically dependent on the film formation conditions. Only in films cast onto substrates held at 60 °C is dominant TTA‐UC observed. Comparing to similar sensitised films of TIPS‐naphthalene, which are TTA‐inactive, we deduce that π‐stacking of the PPO, prevented by the TIPS side groups in the TIPS‐naphthalene films is crucial for efficient triplet diffusion and up‐conversion
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