32151 research outputs found
Sort by
Quantifying Breslow intermediate reactivity in intermolecular Stetter reactions
No full textFunding: We thank the EPSRC (JZ and CMY, EP/S020713/1 and EP/S019359/1), the CSC St Andrews PhD scholarship scheme (ZD), the EaSI-CAT centre for Doctoral Training (ASG) and the EU (Marie-Curie Fellowship to PKM) for funding.Quantification of the reactivity of the archetypal Breslow intermediate in NHC-mediated transformations has not been achievable to date and is regarded as a significant challenge due to multiple competitive pathways and their deconvolution. This manuscript describes the development of a kinetic approach to this challenge that avoids the influence of the competitive benzoin reaction and allows quantification of the reactivity of a Breslow intermediate derived from 2-pyridine carboxaldehyde and an in situ generated N-pentafluorophenyl substituted triazolinylidene NHC with a diverse range of Michael acceptors in the intermolecular Stetter reaction. Using this approach the pseudo first-order rate constants of >40 Michael acceptors, primarily derived from (E)-chalcones but also including a nitroolefin and malonic esters, were measured. Notably, incorporating electron-withdrawing substituents within the C(1)-aryl group of (E)-chalcones leads to a substantial enhancement in reactivity, with Hammett and Swain–Lupton analysis used to understand these observations. In addition, an unexpected additive substituent effect associated with the 4,4′-disubstitution of chalcones was observed, with DFT analysis offering insights into this intriguing phenomenon.Peer reviewe
The earliest English almanac? Types of information in early calendrical texts
Get PDFNot all early English texts with calendrical details fit the current genre definitions of the liturgical calendar. There seem to be many divergent examples of texts which could be seen as calendars in the sense that they have a calendrical element, but which in terms of their more varied content and functionality have a greater resemblance with martyrologies, miscellanies, and even later medieval and early modern almanacs. If seen as part of this larger and more varied genre of calendrical Gebrauchsliteratur ('functional literature'), these early medieval English texts can be linked to a characteristic set of generic traits and can benefit from a comparative approach across periods.Peer reviewe
The old world and the intellectual history of American slavery
Get PDFA series of recent books examining the intellectual history of American slavery points to the continuing influence of European ideas not only on the practice of enslavement and subsequent justifications of it, but also on the post-Civil War historiography of the phenomenon. In The Intellectual Origins of American Slavery, John Harpham points to the importance of Roman law categories and arguments in justifying the initial practice by which certain individuals – not for reasons of their race, but because they had been made captive in war or as punishment for crimes – found themselves enslaved. The presumption of Roman law favoured freedom, but explained why, in certain instances, this could be lost. Keidrick Roy in American Dark Age points to a fascination in the antebellum South with Europe's medieval past, whereby comparisons of the plantation system with feudalism and the paternalism it supposedly engendered served to soften perceptions of the exploitative character of slavery. Scott Spillman in Making Sense of Slavery reviews the intellectual history of American slavery between the mid-eighteenth century and the present, first as a contested presence in American life and then after the Civil War as the subject of historical investigation.Peer reviewe
Sandwich-structured GaIn(Zn)P/ZnSeS@ZnS quantum dots-Ag@Fe3O4@SiO2 magnetoplasmonic nanosensor with simulation-driven design for influenza A(H1N1) virus biosensing
Get PDFFunding: OA and KOA acknowledge financial support from the Royal Society of Chemistry (RSC) through E22-7965264821, The Royal Society through RG\R2\232243, and the Engineering and Physical Sciences Research Council (EPSRC) through EP/X029956/1. O.J.A. gratefully acknowledges financial support from the Royal Society through grant numbers RG\R2\232090 & ICAO/R1/231012 (Research Grant & International Science Partnership Fund (ISPF) – International Collaboration Awards).Developing next-generation ultrasensitive bioanalytical sensing systems requires multifunctional nanoarchitectures that integrate engineered photophysics with highly selective biorecognition interfaces. We report on a multifunctional, simulation-guided design of a fluorescence nanosensor for ultrasensitive detection of Influenza A (H1N1) virus in human saliva, integrating heavy-metal-free GaIn(Zn)P/ZnSeS@ZnS quantum dots (QDs) with magnetoplasmonic molecularly imprinted silica shell (Ag@Fe3O4@SiO₂-MIBs) interface. The QDs, engineered with a compositionally graded ZnSeS inner shell and ZnS outer shell, exhibit strong red emission (λemi = 652 nm) and high photoluminescence quantum yield (QY = 78 ± 1.4 %) in aqueous media following ligand exchange with thioglycolic acid (TGA). Self-consistent field (SCF) simulations revealed that TGA capping significantly stabilised the QDs surface and induced distinct magnetic properties, confirming favourable surface energetics for biosensing applications. The TGA-GaIn(Zn)P/ZnSeS@ZnS QDs were conjugated to H1N1-specific DNA aptamers and incorporated with graphene oxide (GO), forming a Förster resonance energy transfer (FRET)-based nanoprobe that switches from an “off” to “on” state upon viral recognition. Target-induced aptamer folding disrupted the QD-GO interaction, thereby restoring the QDs fluorescence. To amplify the fluorescence signal and enable selective enrichment, virus-imprinted Ag@Fe3O4@SiO₂-MIBs were employed. Finite-difference time-domain (FDTD) simulations demonstrated strong plasmon-exciton coupling between QDs and the Ag core, yielding approximately an 18-fold local field enhancement at a 5 nm spacing. The combined effect of molecular imprinting, magnetic separation, and plasmonic amplification enabled a detection limit of 0.15 pg/mL with high specificity against non-target viruses. This study presented a computationally guided design of hybrid nanomaterials for next-generation, point-of-care viral diagnostics with enhanced optical and molecular recognition performance.Peer reviewe
A minimal model to diagnose the contribution of the stratosphere to tropospheric forecast skill
Get PDFFunding: Simon H. Lee is supported by NERC via the SCENARIO Doctoral Training Partnership (NE/L002566/1). Isla R Simpson was supported by the National Center for Atmospheric Research, which is a major facility sponsored by the National Science Foundation under the Cooperative Agreement 1852977.Many recent studies have confirmed that variability in the stratosphere is a significant source of surface sub-seasonal prediction skill during Northern Hemisphere winter. It may be beneficial, therefore, to think about times in which there might be windows-of-opportunity for skillful sub-seasonal predictions based on the initial or predicted state of the stratosphere. In this study, we propose a simple, minimal model that can be used to understand the impact of the stratosphere on tropospheric predictability. Our model purposefully excludes state dependent predictability in either the stratosphere or troposphere or in the coupling between the two. Model parameters are set up to broadly represent current sub-seasonal prediction systems by comparison with four dynamical models from the Sub-Seasonal to Seasonal Prediction Project database. The model can reproduce the increases in correlation skill in sub-sets of forecasts for weak and strong lower stratospheric polar vortex states over neutral states despite the lack of dependence of coupling or predictability on the stratospheric state. We demonstrate why different forecast skill diagnostics can give a very different impression of the relative skill in the three sub-sets. Forecasts with large stratospheric signals and low amounts of noise are demonstrated to also be windows-of-opportunity for skillful tropospheric forecasts, but we show that these windows can be obscured by the presence of unrelated tropospheric signals.Peer reviewe
A questionnaire exploring how third sector alcohol support organisations in Scotland meet the needs of people with intellectual disabilities
Get PDFBackground: Previous research has investigated how staff from National Health Service Substance Use Disorder (SUD)services feel about supporting people with intellectual disabilities but has not explored the third (voluntary) sector, usually the main support provider in Scotland for nondependent SUD. Methods: A questionnaire sent to third sector alcohol support agencies explored: awareness of the needs of people with intellectual disabilities, awareness of other services who can support when working with this group, whether training/adaptations were made to improve accessibility and whether staff hold people with intellectual disabilities in the same regard as people without. Results: Nineteen participants responded. Most knew what intellectual disabilities were and had supported people with intellectual disabilities. However, other findings suggested the need for more training/input with only 16% having been trained about intellectual disabilities by their organisation, a lack of awareness of potential support from intellectual disabilities services and limited knowledge about tailoring approaches to these people. Only 47% felt their services could adequately support this group. There was not strong evidence of a difference in regard towards people with an alcohol problem with intellectual disabilities compared with those without. Conclusions: Improved joint working is needed between intellectual disability and alcohol services to support this group.Peer reviewe
Porphyry copper formation driven by water-fluxed crustal melting during flat-slab subduction
Get PDFFunding: This work was supported by BHP grant ‘Squeeze and Trigger’ (F.J.C.), U–Th–Pb geochronology was supported by NERC National Environmental Isotope Facility grant 2582.1022 (F.J.C.), Rb–Sr geochronology was supported by BHP grant ‘High Grade Hypogene Porphyry Research’ (D.B. and T.E.) and ECR Adv 885531 NONUNE (D.B. and T.E.). M.A.L. and J.J.W. acknowledge BHP grant ‘High Grade Hypogene Zircons’.The prevailing view of the formation of porphyry copper deposits along convergent plate boundaries involves deep crustal differentiation of metal-bearing juvenile magmas derived from the mantle wedge above a subduction zone. However, many major porphyry districts formed during periods of flat-slab subduction when the mantle wedge would have been reduced or absent, leaving the source of the ore-forming magmas unclear. Here we use geochronology and thermobarometry to investigate deep crustal processes during the genesis of the Late Cretaceous–Palaeocene Laramide Porphyry Province in Arizona, which formed during flat-slab subduction of the Farallon Plate beneath North America. We show that the isotopic signatures of Laramide granitic rocks are consistent with a Proterozoic crustal source that was potentially pre-enriched in copper. This source underwent water-fluxed melting between 73 and 60 Ma, coincident with the peak of granitic magmatism (78–50 Ma), porphyry genesis (73–56 Ma) and flat-slab subduction (70–40 Ma). To explain the formation of the Laramide Porphyry Province, we propose that volatiles derived from the leading edge of the Farallon flat slab promoted melting of both mafic and felsic pre-enriched lower crust, without requiring extensive magmatic or metallogenic input from the mantle wedge. Other convergent plate boundaries with flat-slab regimes may undergo a similar mechanism of volatile-mediated lower-crustal melting.Peer reviewe
Continuous-wave, intracavity optical parametric oscillators
No full textThis thesis describes original, theoretical and experimental studies of continuous-wave (cw) intracavity, singly-resonant optical parametric oscillators (ICSRO's). These devices are based on cw solid-state lasers, in which an optical parametric oscillator (OPO) is pumped at an intracavity focus. The OPO efficiently generates two new optical fields, that may be broadly tuned in wavelength. This novel arrangement exploits the intense light fields that circulate inside the laser cavity, allowing a singly resonant OPO geometry to be realised.
Coupled rate-equations describing the dynamics of the ICSRO, are devised, for the first time, for a multi-frequency pump laser. These are solved to find the steady-state behaviour, and conditions for optimising signal and idler output powers. Power characteristics are confirmed experimentally, using an ICSRO based on a KTiOAsO₄ crystal pumped by a Ti:sapphire laser. The OPO down-converts up to 90% of the extractable laser output, in line with theoretical predictions, and generates tunable, Watt-level powers in the 1 to 3μm spectral range.
The stability of the steady-state solutions is tested using a Liapunov analysis. This predicts that, unlike other intracavity frequency-mixing processes, the ICSRO is stable at all pumping levels. This result is confirmed experimentally at pump rates up to ~4.5 times OPO threshold.
Relaxation oscillations in the ICSRO are also investigated theoretically. The intracavity OPO adds a second coupled oscillator to the basic laser system, causing the frequencies and damping times of the dynamics to increase with external pump power. A comprehensive experimental study, using a periodically-poled LiNbO₃ ICSRO which is pumped by a Nd:YVO₄ laser, shows dynamics in broad agreement with theory.
Two quasi-phase-matched nonlinear materials, periodically-poled LiNbO₃ and KTiOPO₄, are assessed for their application to cw ICSRO's. The first is demonstrated in a Ti:sapphire ICSRO, which shows broad spectral coverage from 2.3 to 3.3μm, with a flexibility for setting integral frequency ratios. The second is found to show useful spectral tuning with temperature using a difference-frequency-mixing experiment
Identifying magnetohydrodynamic wave modes in the solar atmosphere
No full textWaves are ubiquitous in the solar atmosphere and have proved to be an important part of solar research. These plasma waves are used in coronal seismology to deduce properties of the solar atmosphere that are not directly observable. They are also thought to play a key role in heating the corona.
In a plasma with constant density and a uniform, homogenous magnetic field, there are three magnetohydrodynamic (MHD) wave modes: Alfvén, fast, and slow. Instead, if the magnetic field or density of the plasma is non-uniform, these wave modes are no longer distinct and have mixed properties, changing energy transport and dissipation properties. As such, a scheme to identify the MHD wave modes in the solar atmosphere is important to better understand the solar atmosphere, including for advancing coronal seismology and assessing how waves contribute to coronal heating.
In this thesis, I have investigated a wave mode identification (WMI) scheme to identify MHD wave modes in the solar atmosphere. In the first paper, we present a proof-of-concept for how this scheme can be used in synthetic observations to isolate properties of the Alfvén wave mode. In Paper II, we recreate the 2D wave experiments in Bogdan et al. (2003), and use their in-depth wave analysis to understand better the information we can deduce from the WMI scheme. We show that the WMI scheme is equivalent to the scheme used in the original article, with the added advantage of being naturally expandable to 3D. In Paper III, we expand the 2D experiments to 3D and analyse how the WMI scheme functions with different wave drivers and magnetic field strengths. We conclude that the scheme isolates the 3D MHD wave modes and that we can deduce several physical properties of the waves from the scheme, like location, period and steepening
Chimpanzee drumming shows rhythmicity and subspecies variation
Get PDFFunding: The authors received funding from the European Union’s 8th Framework Programme, Horizon 2020, grant no. 802719 (V.E. and C.H.); from the Austrian Science Fund (FWF) grant no. W1262-B29 (10.55776/W1262) (V.E. and A. Stoeger); from the Swiss National Science Foundation grant no. 501100001711-166458 (A. Soldati and K.Z.); from a SNSF Eccellenza Professorial Fellowship grant no. PCEFP3 186967 (K.K.); from Homerton College and Newnham College, the A.H. Schultz Foundation, and the Jane Goodall Institute Schweiz (K.K.) and MEXT grants to T. Matsuzawa (K.K. and M.F.); from the Max Plank Society grant no. M.IF.NEPF8103 and M.IF.EVAN8103 (C.C. and R.M.W.); and from the European Union ERC, TOHR, grant no. 101041885 (J.v.d.W. and A.R.). The Center for Music in the Brain is funded by the Danish National Research Foundation no. DNRF117.Rhythmic percussion is present across human cultures and has been proposed as one of the earliest evolved forms of musical expression.1 Key features of human rhythmic percussion include individual and regional variation, as well as structural features widespread across musical cultures, such as the use of non-random timing and isochrony (i.e., evenly spaced note onsets).2,3,4,5 Comparative studies of drumming in our ape relatives contribute to understanding the evolutionary origins of human rhythmic percussion. In this context, large, diverse datasets allow testing for species-level universals and regional variation. Chimpanzees and bonobos, like humans, drum on instrumental substrates.2,6,7,8,9 Wild chimpanzees drum on resonant tree buttresses, showing individual variation during traveling and resting contexts, and often integrate drumming into their long-distance pant-hoot vocalizations.6,7,8 But whether wild chimpanzee drumming shows structural musical features and regional variation in rhythm or in its integration within pant-hoots remains unknown. We show that wild chimpanzees drum with non-random timing and isochrony, providing evidence that rhythmic drumming on instrumental substrates may have been present in our last common ancestor.2 Furthermore, we found subspecies-level regional rhythmic variation, showing that western chimpanzees drum isochronously, while eastern chimpanzees drum by alternating shorter and longer inter-hit intervals. Western chimpanzees also produce more drumming hits, drum at a faster tempo, and integrate drumming earlier in the pant-hoot vocalization, typically during the rhythmic build-up phase. Chimpanzee buttress drumming shows both species-level structural features of human musicality and stable subspecies regional differences across diverse ecologies.Peer reviewe
Access Repository Dashboard
Do you manage St Andrews Research Repository? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!