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Revisiting the interaction between Antarctic Sea ice and Southern Ocean cyclones
Get PDFThe seasonal cycle of Antarctic sea ice—characterized by slow advance and rapid retreat—does not align with the seasonal north-south shift of Southern Ocean storm tracks. This misalignment introduces spatial and temporal complexity into cyclone-sea ice interactions. To gain deeper insights, we apply cyclone tracking to identify cyclones near the sea ice edge and examine both their characteristics and the sea ice's response. Our analysis reveals a significant increase in the frequency of these cyclones across most subregions of the Southern Ocean. To quantify their impact, we introduce an exposure index that encompasses cyclone intensity, local sea ice concentration (SIC), and interaction duration to identify key seasons and regions of cyclone-ice interactions. Furthermore, categorizing cyclones by SIC anomalies reveals that cyclone strength and moving direction are primary drivers of SIC variability. In particular, composite analyses highlight surface temperature advection and sensible heat flux as critical mechanisms linking cyclone circulation to SIC anomalies. These findings highlight the role of cyclones in driving short-term sea ice variability, offering new insights into Antarctic climate system feedbacks
Using aircraft observations and modelling to improve understanding of mineral dust transport and deposition processes
Get PDFWith more than 400-3000 Mt of mineral dust lofted into the atmosphere annually,
dust affects the Earth’s radiation budget, hydrological and carbon cycles, human
health, energy production, aviation and more. Recent observations revealed that
coarse (5-10 µm) and super-coarse (10-62.5 µm) dust particles are more abundant
after long-range transport than expected. Having different impacts on the Earth
system than fine particles, it is vital that we understand how these particles travel
so far to fully comprehend the impacts of dust globally. In this thesis, I analyse the
dust size distribution evolution from the Sahara to the western Caribbean in aircraft
observations and compare to a climate model, then use the model to understand the
sensitivity of coarse particle lifetime to transport and deposition processes. I show
that the model deposits coarse particles too quickly, resulting in an underestimation
of dust mass of increasing orders of magnitude with westwards transport. Processes
in the model which may increase coarse transport are tested. Coarse dust is shown to
be most sensitive to sedimentation, with reductions in sedimentation beyond 80%
increasing the volume size distribution by up to 7 orders of magnitude, bringing
the model into agreement with observations. Convective and turbulent mixing,
impaction scavenging, and shortwave absorption are found to have minimal impact
on long-range transport of coarse particles. Raising the dust in the model to 5km
at the Sahara with the hope to increase long-range transport is shown to increase
particle lifetime, though the coarsest dust is still deposited within 24 hours. Findings
in this thesis suggest the presence and importance of processes not in the model
which could counteract sedimentation, such as asphericity and electric charging, and
suggest that explicit convection representation could improve model transport. This
work demonstrates the need for thorough research of these undetermined processes
to accurately model size distribution evolution
Climate, vegetation, people: disentangling the controls of fire at different timescales
Get PDFHuman activities have a major impact on fire regimes. Human activities that cause landscape fragmentation, such as creating roads and other infrastructure or converting areas to agriculture, tend to restrict, rather than promote, fire. The human influence is complex, however, and the impact of fragmentation on the fire regime depends on climate and vegetation conditions. Climate-induced changes in vegetation and fuel loads also affect the natural fire regime in ways independent of human influence. Disentangling the controls of fire regimes is challenging because of the multiple interactions between climate, vegetation, people and fire, and the different timescales over which they operate. We explore these relationships, drawing on statistical and modelling analyses of palaeoenvironmental, historical and recent observations at regional to global scales. We show how these relationships have changed through time and how they vary spatially as a function of environmental and biotic gradients. Specifically, we show that climate and climate-driven changes in vegetation have been the most important drivers of changing fire regimes at least until the Industrial Revolution. Statistical and modelling analyses show no discernible impact of hunter–gatherer communities, and even the time-transgressive introduction of agriculture during the Neolithic had no impact on fire regimes at a regional scale. The post-industrial expansion of agriculture was an important influence on fires, but since the late 19th century, the overwhelming influence of humans has been to reduce fire through progressive landscape fragmentation rather than through influencing ignitions. Model projections suggest that the reduction of fire through fragmentation will be outweighed by climatically driven increases by the end of the 21st century
Multi-hypothesis prediction for portfolio optimization: a structured ensemble learning approach to risk diversification
Get PDFThis work proposes a unified framework for portfolio allocation, covering both asset selection and optimization, based on a multiple-hypothesis predict-then-optimize approach. The portfolio is modeled as a structured ensemble, where each predictor corresponds to a specific asset or hypothesis. Structured ensembles formally link predictors’ diversity, captured via ensemble loss decomposition, to out-of-sample risk diversification. A structured data set of predictor output is constructed with a parametric diversity control, which influences both the training process and the diversification outcomes. This data set is used as input for a supervised ensemble model, the target portfolio of which must align with the ensemble combiner rule implied by the loss. For squared loss, the arithmetic mean applies, yielding the equal-weighted portfolio as the optimal target. For asset selection, a novel method is introduced which prioritizes assets from more diverse predictor sets, even at the expense of lower average predicted returns, through a diversity–quality trade-off. This form of diversity is applied before the portfolio optimization stage and is compatible with a wide range of allocation techniques. Experiments conducted on the full S&P 500 universe and a data set of 1,300 global bonds of various types over more than two decades validate the theoretical framework. Results show that both sources of diversity effectively extend the boundaries of achievable portfolio diversification, delivering strong performance across both one-step and multi-step allocation tasks
Political equality of EU citizens and their right to vote beyond Delvigne
No full textEuropean Parliamentary (EP) elections are central to ‘the democratic life of the Union’ in which ‘every citizen shall have a right to participate’ (TEU Art 10(3)). Members of the EP ‘shall be elected by direct universal suffrage’ (CFR Art 39(2)) and ‘[e]very person holding the nationality of a Member State shall be a citizen of the Union’ (TFEU Art 20). This paper explores the right to vote in EP elections and sets out four critiques of its current (legal) state which results in divergent eligibility criteria across member states. To address these shortcomings, the paper makes four propositions, arguing that eligibility criteria for EP elections should be uniform across member states and thus harmonised. The paper draws an analogy with existing uniform eligibility criteria in national elections held in federal member states and seeks to take into account the nature of EP elections and the fact that member states are acting on behalf of the Union when they administer and regulate such elections. Critically appraising Parliament's 2022 reform proposal, it calls on EU institutions to address divergent eligibility criteria ahead of the next EP elections
Essays on tax compliance determinants: social norms, politician gender, and participatory budgeting
Get PDFWhy do people pay their taxes when it seems as though cheating would go unnoticed?
Perhaps the reasons stem from unselfish motivations to improve one’s own community.
Perhaps people feel that submitting timely tax payments gives them a greater sense
of moral and ethical utility than evasion. Taxpayers may be motivated by fair and
trustworthy leaders or by a deep appreciation for the challenging process of governmental
budgeting.
In many developed countries, tax compliance is mandatory. However, the extremely low
probability of detection and low penalties can make tax compliance appear more like a
choice to many taxpayers. Each year in countries such as the US and the UK, taxpayers
choose how honest their tax calculations and remittances will be. In both the US and
the UK, variations in the taxpayer demographics may indicate how likely they are to
comply with income and property taxes. Outside influences, such as the demographic
characteristics of the local and national-level political leaders or increases in citizens’
civic engagement, may also serve as important factors.
These essays explore determinants that may have a strong impact on tax compliance,
which may lead to a greater understanding of how people make tax compliance decisions.
These essays examine determinants such as tax compliance norms, politician gender, and
participatory governance to analyze whether changes in these elements lead to increases
in compliance rates
Comparison of MRS acquisition methods for separation of overlapping signals at 3 T
Get PDFBackground: Proton magnetic resonance spectroscopy (MRS) can be used to quantify multiple neurometabolites. However, due to the difficulty of separating overlapping signals at the commonly used field strength of 3 T, the quantified values are often composites of metabolically related chemicals. This can complicate interpretation and mask effects of interest. Therefore, it is important to determine the ability to accurately separate these signals at 3 T. Data acquired at 7 T can provide a benchmark, as higher field strength facilitates spectral resolution and reduces the signal overlap. New Methods: This study assessed the ability of multiple 3 T MRS sequences to separate the commonly acquired neurochemicals (Glutamate (Glu) and Glutamine (Gln); N-Acetyl aspartate (NAA) and N-acetylaspartylglutamate (NAAG); Creatine (Cr) and Phosphocreatine (PCr); Choline (Cho), Phosphocholine (PC) and Glycer- ophosphocholine (GPC)). We compared metabolites quantified at 3 T from 6 acquisitions (PRESS, TE= 20, 30, 40, 80 ms, semi-LASER, TE=28 ms and STEAM TE=6 ms) with those quantified at 7 T using STEAM (TE=8 ms). Results: Sequences with short echo times (STEAM-6, PRESS-20) generally performed better at separating most metabolites when using correlative and difference analyses with 7 T reference data. The exceptions were NAAG, which was best quantified with PRESS-80, and Cr and PCr, which were not well separated by any sequence. Comparison with existing methods and conclusion: When wanting to specifically separate composite metabolite signals using single voxel MRS, shorter echo times generally perform better. Researchers should be mindful of the effects of acquisition parameters on the metabolite measures
Bunting's Monosyllables
Get PDF‘Bunting’s Monosyllables’ begins with praise the poet has received for the distinctive economy of presentation in his insistence on the use of simple, concrete Anglo-Saxon-based language in ‘Briggflatts’. Attending to the intonational tunes used in English to give a meaningful rhythmic contour to collocated monosyllables, the essay questions Bunting’s habitual and polemical insistence on the regionally distinct music of his poetry as sole source of its significance. The conclusion considers how these monosyllabic priorities fair towards his long poem’s close when it attempts to resolve into a life-and-art-justifying shape the loss of the childhood love narrated in its opening section
Teaching vocabulary through listening: an experimental study with Saudi visually impaired EFL learners
Get PDFThere is a dearth of rigorous empirical research focusing on improving the academic
achievement of visually impaired (VI) learners in all curricular areas (Cooney et al., 2015) despite
the inferiority of their educational outcomes compared to sighted (SI) learners (WHO, 2019). The
paucity of research appears to be particularly prevalent in the field of foreign language learning
(Schultz & Savaiano, 2023). Research with VI learners has mainly examined methodologies for
teaching a second or foreign language (L2) rather than investigating the effects of these
methodologies on learning (e.g., Carpenter, 2020; Guinan, 1997; Nehari, 2017; Nikolic, 1987;
Topor & Rosenblum, 2013). Understanding the impact of teaching is especially important in
relation to vocabulary, in view of its centrality for all aspects of language learning and also because
of its challenges for VI learners.
This thesis investigated how different modes of vocabulary instruction through listening
impacted 32 VI and SI female upper-secondary school learners of English as a Foreign Language
(EFL) in Saudi Arabia (SA). Given that listening is the primary channel through which VI learners
obtain information (Barclay & Staples, 2012; Jedynak, 2023). The study investigated two modes
of vocabulary instruction paired with aural input, adopting a mixed within-and between-subjects
counterbalanced design. Mode 1 was codeswitching (CS), in which Arabic (L1) was used to
explain the meaning of target English words. Mode 2 was aural input manipulation followed by
CS (AIMCS), whereby the target item was emphasised within an example sentence through
increased volume. The current study also explored whether and how the effect of the instruction
was moderated by learners’ listening proficiency and their existing vocabulary size. The effects of
repetition on the retention of the target vocabulary items were also considered. In addition,
learners’ responses to the two modes of instruction, both in terms of the strategies it prompted and
their perceptions of its helpfulness or otherwise, were investigated through stimulated recall
interviews with 16 students.
The data collection procedure was over two academic terms, with three intervention
sessions each term. Learners completed a pre-listening test and aural vocabulary pre-, post-, and
delayed post-tests. The 32 participants in the study comprised 16 Saudi VI upper secondary school
students of English alongside a comparison group of 16 SI learners. Codeswitching was selected
as one teaching mode because of the importance of having a correct mental representation in the
L1 before the L2 version can be learnt (Jedynak, 2016). AIMCS was selected because of VI
individuals’ greater pitch sensitivity than SI individuals (Gougoux et al., 2004; Sepúlveda-Palomo
et al., 2024; Smeds, 2015). It was paired with codeswitching to more clearly isolate the effect of
each type of instruction, i.e. CS alone or CS plus AIM.
Before the intervention, learners completed two baseline tests assessing their listening
comprehension and vocabulary knowledge. They then listened to six English passages over six
teaching sessions and received oral explanations for 60 target vocabulary items. The two teaching
modes were counterbalanced in each session, so that learners in both groups experienced both
modes. A vocabulary post-test was employed at the end of each session to measure the learners’
knowledge of target lexical items. Two weeks after each session, a delayed post-test was
administered to assess longer-term retention. Towards the end of each intervention session, a
review activity took place to revise the selected taught lexical items. After the last delayed post-test, stimulated recall interview sessions were conducted with 16 learners —eight from the
experimental group and eight from the comparison group. Lastly, five weeks after the intervention,
a final delayed post-test was administered to explore the impact of repetition on vocabulary gains.
Generalised linear mixed effects models showed that for short-term learning, learners’ pre-listening proficiency significantly moderated the effect of Group and Instruction on vocabulary
learning. While SI learners benefited equally from the intervention, VI learners with higher levels
of listening proficiency showed greater improvement in vocabulary learning than their peers with
lower levels of listening proficiency. In addition, although both types of instruction showed
positive effects on learning, the AIMCS approach seemed more useful for more proficient
listeners, whereas the CS approach showed a similar effect regardless of learners’ pre-listening
proficiency. Such moderation effects, however, disappeared for longer-term vocabulary learning.
More proficient listeners retained significantly more vocabulary at delayed post-test regardless of
Group and the type of instruction received. Concerning the effects of number of repetitions, final
delayed post-test findings indicated no significant effect of repetition on the target lexical items’
retention. Overall, these results suggest that AIMCS was the most beneficial teaching method for
both groups, particularly VI learners, although the effects were primarily short-term. Listening
proficiency also moderated the outcomes, with the greatest benefits observed in learners with
higher listening proficiency.
Qualitative analysis of the students’ stimulated recall interviews revealed that higher and
lower proficiency learners used similar strategies to comprehend the teacher’s explanations (e.g.,
visualisation and selective attention on CS). However, higher proficiency learners seemed to use
these strategies in combination with a broader range of other strategies compared to lower
proficiency learners. The findings also indicated that vision deficit impacted VI higher and lower
proficiency learners’ strategy use (i.e., their use of visualisation lacked visual elements).
Additionally, the analysis of learners’ perceptions regarding the helpfulness of the two modes of
vocabulary instruction indicated that the majority, albeit mainly VI learners, deemed AIMCS to
be a better approach than CS alone. VI learners affirmed that AIMCS catered for their vision
deficits by exploiting their auditory skills by pairing AIM with CS, which elevated both attention,
comprehension, and retention.
This study provides both theoretical insights and pedagogical recommendations for L2
vocabulary instruction tailored to VI learners. It highlights the vital role of listening proficiency in
both developing vocabulary knowledge and influencing the effectiveness of CS and AIMCS
instructional methods. Moreover, the study sheds light on how we can better design inclusive
teaching approaches that leverage the auditory strengths and unique strategy use of VI learners.
This, in turn, can support improved vocabulary acquisition and retention, contributing to a more
equitable and accessible language learning experience for learners with visual impairments
The evolutionary history and timeline of mites in ancient soils
Get PDFAcariform mites play a crucial role as primary soil decomposers, impacting the carbon cycle. However, the timing of their diversification is uncertain, with estimated dates ranging from the Precambrian (no land plants) to the Carboniferous (diverse terrestrial ecosystems). One factor affecting these time estimates is an uncertain phylogenetic position of the earliest unequivocal fossil mites from the Devonian Rhynie Chert, which have been classified in five modern families and three suborders. Here, we thoroughly examine these specimens, assign them to a single species Protacarus crani (family Protoacaridae, fam. nov., suborder Endeostigmata) and integrate this information into a time-calibrated phylogenetic analysis. Our phylogeny suggests a Cambrian basal divergence of Acariformes (508–486 Ma), coinciding with the land colonization by bryophytes. At this time, the mites’ ecological niches were probably diversified beyond the upper soil. Our study provides temporal context, improves the accuracy of fossil dating, and underscores the importance of mites’ diverse habitats and their potential roles in soil food webs