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The infrared luminosity of retired and post-starburst galaxies : a cautionary tale for star formation rate measurements
Get PDFFunding: VW acknowledges Science and Technologies Facilities Council (STFC) grants ST/V000861/1 and ST/Y00275X/1. NVA and VW acknowledge the Royal Society and the Newton Fund via the award of a Royal Society–Newton Advanced Fellowship (grant NAF\R1\180403). NVA acknowledges support from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). KR acknowledges support from NASA grant 80NSSC23K0495.In galaxies with significant ongoing star formation there is an impressively tight correlation between total infrared luminosity (LTIR) and Hα luminosity (LHα), when Hα is properly corrected for stellar absorption and dust attenuation. This long-standing result gives confidence that both measurements provide accurate estimates of a galaxy’s star formation rate (SFR), despite their differing origins. To test the extent to which this holds in galaxies with lower specific SFR (sSFR=SFR/M*, where M* is the stellar mass), we combine optical spectroscopy from the Sloan Digital Sky Survey (SDSS) with multi-wavelength (FUV to FIR) photometric observations from the Galaxy And Mass Assembly survey (GAMA). We find that LTIR/LHα increases steadily with decreasing Hα equivalent width (WHα, a proxy for sSFR), indicating that both luminosities cannot provide a valid measurement of SFR in galaxies below the canonical star-forming sequence. For both ‘retired galaxies’ and ‘post-starburst galaxies’, LTIR/LHα can be up to a factor of 30 larger than for star-forming galaxies. The smooth change in LTIR/LHα, irrespective of star formation history, ionisation or heating source, dust temperature or other properties, suggests that the value of LTIR/LHα is determined by the balance between star-forming regions and ambient interstellar medium contributing to both LTIR and LHα. It is not a result of the differing timescales of star formation that these luminosities probe. While LHα can only be used to estimate the SFR for galaxies with WHα > 3 Å (sSFR ≳ 10-11.5 /yr), we argue that the mid- and far-infrared can only be used to estimate the SFR of galaxies on the star-forming sequence, and in particular only for galaxies with WHα > 10 Å (sSFR≳ 10-10.5 /yr). We find no evidence for dust obscured star-formation in local post-starburst galaxies.Peer reviewe
Janus fluorocyclohexanes as facially polarised motifs for organized supramolecular materials
Get PDFA Janus-face cyclohexane has a single fluorine on each carbon and with all syn configuration, creating a face of fluorines on one side of the ring and hydrogens on the other. This thesis prepares and explores the properties of derivatives of this class of molecule. Chapter 1 introduces organofluorine chemistry, its applications, and an overview of the evolution of Janus fluorocyclohexanes, detailing their initial synthesis and highlighting their unique polar properties. Chapter 2 describes the synthesis of mono-, di-, and tri-alkylated Janus fluorocyclohexane derivatives. In particular the influence of peripheral substituents on supramolecular packing was explored. The tri-alkylated systems adopted columnar discotic stacking. This research suggests that the 2,4,6 tri-alkylated ring systems have potential as a motif for ordered supramolecular assemblies and as they exhibit multiple polymorphs, they offer potential as liquid crystalline materials. Chapter 3 focuses on the synthesis of two novel Janus Organic Framework (JOF) struts, featuring carboxylic acid linkers with either tri- or penta- fluorinated Janus rings. Single crystal X-ray analysis confirmed their structure, and preliminary findings demonstrated increased porosity in first-generation JOF-MOFs compared to isolated JOF struts. Second-generation JOF-MOFs were developed through exchange synthesis with MOF-808, confirming this new class of framework, with initial results showing potential for further porosity enhancements and applications in supramolecular porous materials. Chapter 4 discusses the development of Janus cyclohexanes with a 3,6-dialkyl ether linkage, investigated for their dielectric anisotropic properties and potential use in memory storage devices. These compounds, which possess a long-chain phosphonic acid group for self-assembly on a TiN substrate were designed as potential memory storage molecules. Chapter 5 explores nucleophilic aromatic substitution reactions of pentafluoro aryl ethers, focusing on the para selectivity of these reactions and leading to the generation of Janus 3,6-di alkyl ethers, compounds which displayed significant polymorphism, suggesting potential for liquid crystal applications. In overview this body of work demonstrates new approaches to the synthesis of Janus fluorocyclohexanes and highlights possibilities for their potential applications in supramolecular assembly, liquid crystals, and organic materials science more generally
Rivers of knowledges : Indigenous academics’ experiences in Brazilian universities
Get PDFThis thesis investigates the dialogue between Indigenous knowledges and academic knowledge within Brazilian universities, exploring whether such a dialogue exists and how it is being shaped. It examines the potential for pluri-epistemic dialogue, addressing the extent to which Indigenous epistemologies, voices, and references are present in Brazilian higher education. The research focuses on the challenges faced by Indigenous academics, framed by the concept of luta (struggle) as a legacy of resistance against the coloniality of knowledge. These challenges reflect historical, philosophical, anthropological, and educational processes, contributing to a timely political and democratic discussion of Indigenous rights that extends beyond the implementation of laws and policies. The thesis emphasises the importance of incorporating emotional, spiritual, and experiential knowledge into academic discourse, challenging the dominance of modern knowledge systems. It also highlights how Indigenous academics engage in resistance and re-existence, reaffirming their identities and epistemologies within the university context. Drawing on Paulo Freire’s concept of dialogue, which recognises the oppressed as active agents in their own liberation, I argue that dialogue cannot exist in relations of domination, where a marginalised ‘other’ continues to be oppressed and silenced. This notion is reflected in Indigenous academics’ experiences, where knowledge is communally created and emerges from lived relationships with the land, people, and non-human entities. This perspective contrasts with the often-individualistic nature of academic knowledge production
Lightning-driven pyrite oxidation under Archean atmosphere conditions
Get PDFFunding: This project was financially supported by a NERC Frontiers grant (NE/V010824/1) and a Royal Society research grant (RGS\R1\211184) to EES.Oxidative weathering is a major source of bio-essential micronutrients on Earth today; however, this flux would have been muted on the early Earth or on Mars, where atmospheric O2(g) levels were very low. Here, we explore the hypothesis that nitrogen oxides generated by lightning in an anoxic atmosphere could have elevated pyrite oxidation levels under otherwise anoxic conditions. We performed spark discharge experiments in the presence of pyrite powder and three different gas mixtures, including 80% N2(g) with 20% CO2(g), 95% N2(g) with 5% CO2(g), and modern air. Experiments were run for 30 min, and we tracked the production of NO(g), dissolved nitrate and nitrite, pH, dissolved sulfate, and total dissolved iron. Our results reveal increasing production of nitrogen oxides with increasing CO2(g) and O2(g) levels, which is consistent with previous studies. Dissolved iron and sulfate also increase, indicating that the nitrogen oxides are able to oxidize pyrite abiotically. Extrapolating these data to global conditions suggests that this mechanism was probably insignificant on a global scale on the early Earth; however, in thunderstorm-prone areas, such as in the modern tropics where lightning rates may locally be over 10 times above the global average, lightning could have rivalled abiotic pyrite oxidation by Archean O2 levels. The lightning contribution would have been highest during time periods with elevated CO2(g), which makes it a potentially important contributor to local release of sulphur, iron, and bio-essential micronutrients on prebiotic land surfaces or on other planets with anoxic CO2-rich atmospheres.Peer reviewe
ClickTree : a tree-based method for predicting math students’ performance based on clickstream data
Get PDFThis work was supported by the Medical Research Council [grant number MR/N013166/1].The prediction of student performance and the analysis of students’ learning behaviour play an important role in enhancing online courses. By analysing a massive amount of clickstream data that captures student behaviour, educators can gain valuable insights into the factors that influence students’ academic outcomes and identify areas of improvement in courses. In this study, we developed ClickTree, a treebased methodology, to predict student performance in mathematical problems in end-unit assignments based on students’ clickstream data. Utilising extensive clickstream data, we extracted a novel set of features at three levels, including problem level, assignment-level and student-level, and we trained a CatBoost tree to predict whether a student will successfully answer a problem in an end-unit assignment or not. The developed method achieved an Area under the ROC Curve (AUC) of approximately 79% in the Educational Data Mining Cup 2023 and ranked second in the competition. Our results indicate that students who performed well in end-unit assignment problems engaged more with in-unit assignments and answered more problems correctly, while those who struggled had higher tutoring request rates. We also found that students face more difficulties with “check all that apply” types of problems. Moreover, Algebra II was the most difficult subject for students. The proposed method can be utilised to improve students’ learning experiences, and the insights from this study can be integrated into mathematics courses to enhance students’ learning outcomes. The code and implementation is available at https://www.kaggle.com/code/nargesrohani/clicktree/notebook.Peer reviewe
Commit to your putting stroke : exploring the impact of quiet eye duration and neural activity on golf putting performance
Get PDFFunding: Funding to conduct the research was provided by sportscotland. LC received SINAPSE (www.sinapse.ac.uk) funding as part of a research scheme for ECR to learn MRCPs at University of Rome “Foro Italico.” DD is a member of SINAPSE (www.sinapse.ac.uk) a Scottish Funding Council research pooling initiative.Introduction : There is a growing interest in characterizing the cognitive-motor processes that underlie superior performance in highly skilled athletes. The aim of this study was to explore neural markers of putting performance in highly skilled golfers by recording mobile EEG (electroencephalogram) during the pre-shot period. Methods : Twenty-eight right-handed participants (20 males) with a mean age of 24.2 years (± 6.4) and an average handicap of +1.7 (± 6.4) completed a testing session. Following the warm-up, participants completed 140 putts from a distance of 8ft (2.4m), with putts taken from 5 different positions. While putting, participants wore an eye tracker and a gel-based EEG system with 32 electrodes. Time and frequency domain features of the EEG signals were extracted to characterize Movement-Related Cortical Potentials (MRCP) and rhythmic modulations of neural activity in theta, alpha, sensorimotor and beta frequency bands associated with putting performance. Results : Eye-tracking data demonstrate that mean Quiet Eye durations are not a reliable marker of expertise as the same duration was found for both successful and unsuccessful putts. Following rigorous data processing data from 12 participants (8 males, mean age 21.6 years ± 5.4, average handicap +1.5 ± 4.4) were included in the EEG analysis. MRCP analysis revealed performance-based differences, with unsuccessful putts having a greater negative amplitude in comparison to successful putts. Time frequency analysis of the EEG data revealed that successful putts exhibit distinct neural activity profiles compared to unsuccessful ones. For successful putts, greater suppression of beta was present in the central region prior to the putt. By contrast, increased frontal theta power was present for unsuccessful putts immediately before the putt (consistent with hesitation and the need for motor plan adjustments prior to execution). Discussion : We propose that neural activity may provide plausible insights into the mechanisms behind why identical QE durations can lead to both success and failure. From an applied perspective, this study highlights the merits of a multi-measure approach to gain further insights into performance differences within highly skilled golfers. We discuss considerations for future research and solutions to address the challenges related to the complexities of collecting clean EEG signals within naturalistic sporting contexts.Peer reviewe
Chemospecific heterostructure and heteromaterial assembly of metal–organic framework nanoparticles
Get PDFFunding: AKE, RE, GH and REM acknowledge the European Research Council Advanced Grant (AdG 787073 for funding). ERK, GH and ZZJ acknowledge the U.S. Army Research Office (W911NF-20-1-0233) for financial support. The authors acknowledge the EPSRC Light Element Analysis FacilityGrant (EP/T019298/1) and the EPSRC Strategic Equipment Resource Grant (EP/R023751/1).Nanoparticles of highly porous metal–organic frameworks (MOFs) are some of the most exciting nanomaterials under development, with potential applications that range from biomedicine and catalysis to adsorption technologies. However, our synthetic methodologies to functionalize and manipulate MOF nanoparticles (NPs) are less well developed than they might be. Here we create MOF NPs derivatized with hydrazone units on their exterior, enabling chemospecific reversible dynamic covalent modification of structures on the external surface. Pairwise combinations of nanometer-sized building blocks with complementary dynamic covalent surface units can be used to prepare heterostructure assemblies (i.e., two MOFs with different structures and morphologies) and heteromaterial assemblies (a MOF with a nanoparticle of another kind, in this case gold) in which the directional molecular-level dynamic covalent links demand intimate mixing of the two nanoscale components. Crucially, the defining characteristic of the MOF components─their porosity─is minimally affected by the external functionalization and interparticle linking. The development of atomically precise dynamic covalent functionalization on the external surface of MOF NPs opens up new avenues for programmable frameworks with responsive behaviors and modular assembly of porous materials with precise control over the spatial organization of multiple nanoscale building blocks.Peer reviewe
Conjuring Empire : photography and place during the early years of French colonialism in Indochina (1845–1879)
No full textThis thesis analyses photography’s ties with the French colonial project in Mainland Southeast Asia from the earliest photographs of Vietnam (1845) to the end of naval rule in French Cochinchina (1879).
In Indochina, as in most regions undergoing colonization, photography was increasingly mobilized in support of the French imperial project, to collect intelligence on the landscape and populations, inform decision makers on the progress of expansion and exploitation, contribute to the advancement of colonial sciences, promote prospective action, legitimize structures of domination or boost colonialist sentiment among the metropolitan public.
Acknowledging the performative nature of photographic representation and the importance of historical and sociopolitical contexts, the thesis disentangles existing ties between photographs of Vietnamese and Cambodian lands and the colonial project in four case studies illustrating key moments in the pre- and early colonial periods: the creation and circulation of the first photographs of Việt Nam (1845–53), uses of photography during the Cochinchina Campaign (1858–60), the pivotal role of the Paris Universal Exposition for the dissemination of photographs of Angkor (1866–67) and uses of the camera in Cambodia during the final years of French naval rule (1870s).
Throughout these four chapters, the thesis addresses how photography assisted concrete military, scientific and commercial efforts and examines the processes by which ideologies of power and otherness often infused these images. Considering that visual appropriation often facilitated more tangible forms of control, it proposes a reevaluation of photography’s contribution to French rule in Indochina before 1880
Insights to the formation of Zr-based metal–organic frameworks from in situ powder x-ray diffraction
Get PDFFunding: We gratefully acknowledge Dr Aamod V Desai for fruitful discussions. RE and EEP thank the Fonds der Chemischen Industrie for a Liebig Fellowship. This work was supported by the European Research Council grant ADOR (Advanced Grant 787073). The authors acknowledge the EPSRC Light Element Analysis Facility Grant (EP/T019298/1), the EPSRC Strategic Equipment Resource Grant (EP/R023751/1), the EPSRC Core Equipment Grant (EP/V034138/1) and EP/W034824/1. EALB acknowledges the Allan Handsel Postgraduate Research Scholarship for Chemistry for studentship funding.This study sheds light on the kinetics of crystallisation of two Zr-based metal–organic frameworks (MOFs), namely Zr6-MOF-808 and Zr6-MOF-801, using in situ powder x-ray diffraction (PXRD). Once a room temperature synthesis for the two MOFs was designed for the very small scale, a successful series of in situ PXRD experiments over the range of 10 °C–40 °C yielded high quality quantitative information on the kinetics of crystallisation for both MOFs. These findings indicate the importance of the solubility of the linker and its connectivity: while the rate of nucleation and the resulting particle size of the MOF (Zr6-MOF-801), with the less soluble and lower connected linker, was strongly temperature dependent, the growth and particle size of Zr6-MOF-808 was hardly impacted by an increase in temperature. This work highlights the importance of careful preliminary research and helps to improve future MOF synthesis design to efficiently achieve the desired particle size distribution.Peer reviewe
Palaeoenvironmental reconstruction of a fjord catchment NW Scotland, UK since the Last Glacial Maximum : a multi-geochemical approach
Get PDFFunding: This study was part funded by a Yorkshire Geological Society (YGS) research fund grant (JT) and by the Durham Doctoral Scholarship of Durham University.Loch Sunart, a fjord in NW Scotland, UK records Late Glacial to Holocene sedimentation preserving palaeoenvironmental changes associated with the deglaciation of the British-Irish Ice Sheet (BIIS). This study combines a multi-proxy approach (osmium isotope analysis, carbon, sulphur and nitrogen elemental and isotopic analysis together with X-ray fluorescence, alkenone biomarkers and benthic foraminifera) to contribute to our understanding of the regional nature of BIIS deglaciation and enable the reconstruction of palaeoclimate variations since the last glacial. The observed patterns in the applied proxies collectively suggest that between ~18 and 12.9 cal ka BP as the BIIS retreated Loch Sunart experienced increased glacial meltwater discharge. Throughout this period, 187Os/188Os values are more radiogenic than the contemporaneous open ocean waters (~1.04 – 1.06), which are interpreted to reflect an increase in glacially eroded sediment flux directly associated with glacial retreat following the Last Glacial Maximum. During the Younger Dryas, the fjord experienced a pause in glacially derived sediment reflected by a minimum in 187Os/188Os (~1.1), which was followed by an increase in 187Os/188Os to more radiogenic values (~1.3) at the end of the Younger Dryas. Coincident with changes in 187Os/188Os values, alkenone-based %C37:4 values increase (40-60%), δ13Corg values decrease (-24‰) and foraminifera species indicative of restricted water renewal increased in abundance, suggesting a period of water stratification. A rapid shift in 187Os/188Os values toward a marine signature of ~1 indicates that the basin experienced a breakdown in water stratification and renewed mixing from 5 cal ka BP. This interpretation is further supported by a coincident decrease in %C37:4 to <15%, and by distinct increases in wt% C, wt% N and δ13Corg. This multi-proxy approach, specifically integrating Os, provides additional insight to the BIIS in NW Scotland, in particular how such fjords can respond to glacial readvance during the Younger Dryas, which was not captured by previous studies.Peer reviewe
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