Investigating thermoregulatory responses of rhabdomys pumilio at high wet-bulb temperatures

As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202

Investigating thermoregulatory responses of rhabdomys pumilio at high wet-bulb temperatures

As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202

C34, a Membrane Fusion Inhibitor, Blocks HIV Infection of Langerhans Cells and Viral Transmission to T Cells

Development of topical microbicides that prevent sexual transmission of HIV is an active area of investigation. The purpose of this study was to test the ability of the potent membrane fusion inhibitor C34, an HIV gp41 antagonist, to block HIV infection of human Langerhans cells (LCs) in an epithelial environment that mimics a major route of HIV infection. We incubated freshly isolated epidermal explants containing LCs with various doses of C34 before, during, and after exposing explants to HIV. Although C34 only partially blocked HIV infection of LCs when pre-incubated with skin, it displayed full, dose-dependent inhibition when present during and after viral exposure. The poor protection from HIV infectivity in pre-incubated samples is consistent with mechanism of C34 inhibition and starkly contrasts to the full protection provided by PSC-RANTES, an entry inhibitor that prevents HIV gp120 interaction with its co-receptor CCR5. Real-time PCR confirmed that C34 blocked HIV infection of LCs before reverse transcription and inhibited LC-mediated transfer of virus to T cells. We conclude that C34, if used topically at susceptible mucosal sites, and if continually present, has the potential to block sexual transmission of HIV

First On-Sky Demonstration of a Scintillation Correction technique using Tomographic Wavefront Sensing

Scintillation noise significantly limits high precision ground-based photometry of bright stars. In this paper we present the first ever on-sky demonstration of scintillation correction. The technique uses tomographic wavefront sensing to estimate the spatial-temporal intensity fluctuations induced by high altitude optical turbulence. With an estimate of the altitudes and relative strengths of the turbulent layers above the telescope, the wavefront sensor data from multiple guide stars can be combined to estimate the phase aberrations of the wavefront at each altitude through the use of a tomographic algorithm. This 3D model of the phase aberrations can then be used to estimate the intensity fluctuations across the telescope pupil via Fresnel propagation. The measured photometric data for a given target within the field of view can then be corrected for the effects of scintillation using this estimate in post-processing. A simple proof-of-concept experiment using a wavefront sensor and a stereo-SCIDAR turbulence profiler attached to the 2.5m Isaac Newton Telescope was performed for a range of exposure times using the Orion Trapezium cluster as the reference stars. The results from this on-sky demonstration as well as simulations estimating the expected performance for a full tomographic AO system with laser guide stars are presented. On-sky the scintillation index was reduced on average by a factor of 1.9, with a peak of 3.4. For a full tomographic system we expect to achieve a maximum reduction in the scintillation index by a factor of ∼25

Olivine-hosted melt inclusions as an archive of redox heterogeneity in magmatic systems

The redox state of volcanic products determines their leverage on the oxidation of Earth's oceans and atmosphere, providing a long-term feedback on oxygen accumulation at the planet's surface. An archive of redox conditions in volcanic plumbing systems from a magma's mantle source, through crustal storage, to eruption, is carried in pockets of melt trapped within crystals. While melt inclusions have long been exploited for their capacity to retain information on a magma's history, their permeability to fast-diffusing elements such as hydrogen is now well documented and their retention of initial oxygen fugacities () could be similarly diffusion-limited. To test this, we have measured Fe3+/ΣFe by micro-XANES spectroscopy in a suite of 65 olivine-hosted melt inclusions and 9 matrix glasses from the AD 1783 Laki eruption, Iceland. This eruption experienced pre-eruptive mixing of chemically diverse magmas, syn-eruptive degassing at the vent, and post-eruptive degassing during lava flow up to 60 km over land, providing an ideal test of whether changes in the of a magma may be communicated through to its cargo of crystal-hosted melt inclusions. Melt inclusions from rapidly quenched tephra samples have Fe3+/ΣFe of (ΔQFM of +0.7 ± 0.1), with no correlation between their and degree of trace element enrichment or differentiation. These inclusions preserve the redox conditions of the mixed pre-eruptive Laki magma. When corrected for fractional crystallisation to 10 wt.% MgO, these inclusions record a parental magma [Fe3+/ΣFe](10) of 0.18 (ΔQFM of +0.4), significantly more oxidised than the Fe3+/ΣFe of 0.10 that is often assumed for Icelandic basalt magmas. Melt inclusions from quenched lava selvages are more reduced than those from the tephra, having Fe3+/ΣFe between 0.133 and 0.177 (ΔQFM from −0.4 to +0.4). These inclusions have approached equilibrium with their carrier lava, which has been reduced by sulfur degassing. The progressive re-equilibration of between inclusions and carrier melts occurs on timescales of hours to days, causing a drop in the sulfur content at sulfide saturation (SCSS) and driving the exsolution of immiscible sulfide globules in the inclusions. Our data demonstrate the roles of magma mixing, progressive re-equilibration, and degassing in redox evolution within magmatic systems, and the open-system nature of melt inclusions to during these processes. Redox heterogeneity present at the time of inclusion trapping may be overprinted by rapid re-equilibration of melt inclusion with the external environment, both in the magma chamber and during slow cooling in lava at the surface. This can decouple the melt inclusion archives of , major and trace element chemistry, and mask associations between , magmatic differentiation and mantle source heterogeneity unless the assembly of diverse magmas is rapidly followed by eruption. Our tools for understanding the redox conditions of magmas are thus limited; however, careful reconstruction of pre- and post-eruptive magmatic history has enabled us to confirm the relatively oxidised nature of ocean island-type mantle compared to that of mid-ocean ridge mantle

Optical sparse telescope arrays and scintillation noise

Fresnel propagation of starlight after it passes through high altitude turbulence in the Earth’s atmosphere results in random fluctuations of the intensity at ground level, known as scintillation. This effect adds random noise to photometric measurements with ground-based optical telescopes. Spatial correlation of the intensity fluctuations means that the fractional photometric noise due to scintillation may be substantially smaller for a sparse array of small aperture telescopes than for a single large aperture of the same total area. Assuming that the photometric noise for each telescope is independent, averaging the light curves measured by N telescopes reduces the noise by a factor of N−−√⁠. For example, for bright stars, the signal-to-noise ratio of a 2.54 m telescope can be achieved for an array of thirty 20 cm telescopes if the scintillation noise measured for each telescope is uncorrelated. In this paper, we present results from simulation and from observations at the Isaac Newton Telescope. These explore the impact that several parameters have on the measured correlation of the scintillation noise between neighbouring telescopes. We show that there is significant correlation between neighbouring telescopes with separations parallel to the wind direction of the dominant high altitude turbulent layer. We find that the telescopes in an array should be separated by at least twice their aperture diameter so that there is negligible correlation of the photometric noise. We discuss additional benefits of using sparse telescope arrays, including reduced cost and increased field of view

Fe-XANES analyses of Reykjanes Ridge basalts: Implications for oceanic crust's role in the solid Earth oxygen cycle

The cycling of material from Earth's surface environment into its interior can couple mantle oxidation state to the evolution of the oceans and atmosphere. A major uncertainty in this exchange is whether altered oceanic crust entering subduction zones can carry the oxidised signal it inherits during alteration at the ridge into the deep mantle for long-term storage. Recycled oceanic crust may be entrained into mantle upwellings and melt under ocean islands, creating the potential for basalt chemistry to constrain solid Earth–hydrosphere redox coupling. Numerous independent observations suggest that Iceland contains a significant recycled oceanic crustal component, making it an ideal locality to investigate links between redox proxies and geochemical indices of enrichment. We have interrogated the elemental, isotope and redox geochemistry of basalts from the Reykjanes Ridge, which forms a 700 km transect of the Iceland plume. Over this distance, geophysical and geochemical tracers of plume influence vary dramatically, with the basalts recording both long- and short-wavelength heterogeneity in the Iceland plume. We present new high-precision Fe-XANES measurements of Fe3+/∑Fe on a suite of 64 basalt glasses from the Reykjanes Ridge. These basalts exhibit positive correlations between Fe3+/∑Fe and trace element and isotopic signals of enrichment, and become progressively oxidised towards Iceland: fractionation-corrected Fe3+/∑Fe increases by ∼0.015 and ΔQFM by ∼0.2 log units. We rule out a role for sulfur degassing in creating this trend, and by considering various redox melting processes and metasomatic source enrichment mechanisms, conclude that an intrinsically oxidised component within the Icelandic mantle is required. Given the previous evidence for entrained oceanic crustal material within the Iceland plume, we consider this the most plausible carrier of the oxidised signal. To determine the ferric iron content of the recycled component ([Fe2O3]source) we project observed liquid compositions to an estimate of Fe2O3 in the pure enriched endmember melt, and then apply simple fractional melting models, considering lherzolitic and pyroxenitic source mineralogies, to estimate [Fe2O3](source) content. Propagating uncertainty through these steps, we obtain a range of [Fe2O3](source) for the enriched melts (0.9–1.4 wt%) that is significantly greater than the ferric iron content of typical upper mantle lherzolites. This range of ferric iron contents is consistent with a hybridised lherzolite–basalt (pyroxenite) mantle component. The oxidised signal in enriched Icelandic basalts is therefore potential evidence for seafloor–hydrosphere interaction having oxidised ancient mid-ocean ridge crust, generating a return flux of oxygen into the deep mantle

Parallel Mapping and Simultaneous Sequencing Reveals Deletions in BCAN and FAM83H Associated with Discrete Inherited Disorders in a Domestic Dog Breed

The domestic dog (Canis familiaris) segregates more naturally-occurring diseases and phenotypic variation than any other species and has become established as an unparalled model with which to study the genetics of inherited traits. We used a genome-wide association study (GWAS) and targeted resequencing of DNA from just five dogs to simultaneously map and identify mutations for two distinct inherited disorders that both affect a single breed, the Cavalier King Charles Spaniel. We investigated episodic falling (EF), a paroxysmal exertion-induced dyskinesia, alongside the phenotypically distinct condition congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID), commonly known as dry eye curly coat syndrome. EF is characterised by episodes of exercise-induced muscular hypertonicity and abnormal posturing, usually occurring after exercise or periods of excitement. CKCSID is a congenital disorder that manifests as a rough coat present at birth, with keratoconjunctivitis sicca apparent on eyelid opening at 10–14 days, followed by hyperkeratinisation of footpads and distortion of nails that develops over the next few months. We undertook a GWAS with 31 EF cases, 23 CKCSID cases, and a common set of 38 controls and identified statistically associated signals for EF and CKCSID on chromosome 7 (Praw 1.9×10−14; Pgenome = 1.0×10−5) and chromosome 13 (Praw 1.2×10−17; Pgenome = 1.0×10−5), respectively. We resequenced both the EF and CKCSID disease-associated regions in just five dogs and identified a 15,724 bp deletion spanning three exons of BCAN associated with EF and a single base-pair exonic deletion in FAM83H associated with CKCSID. Neither BCAN or FAM83H have been associated with equivalent disease phenotypes in any other species, thus demonstrating the ability to use the domestic dog to study the genetic basis of more than one disease simultaneously in a single breed and to identify multiple novel candidate genes in parallel

Models for the Clustering of Far-Infrared and Sub-millimetre selected Galaxies

We discuss and compare two alternative models for the two-point angular correlation function of galaxies detected through the sub-millimetre emission using the Herschel Space Observatory. The first, now-standard Halo Model, which represents the angular correlations as arising from one-halo and two-halo contributions, is flexible but complex and rather unwieldy. The second model is based on a much simpler approach: we incorporate a fitting function method to estimate the matter correlation function with approximate model of the bias inferred from the estimated redshift distribution to find the galaxy angular correlation function. We find that both models give a good account of the shape of the correlation functions obtained from published preliminary studies of the HerMES and H-ATLAS surveys performed using Herschel, and yield consistent estimates of the minimum halo mass within which the sub-millimetre galaxies must reside. We note also that both models predict an inflection in the correlation function at intermediate angular scales, so the presence of the feature in the measured correlation function does not unambiguously indicate the presence of intra-halo correlations. The primary barrier to more detailed interpretation of these clustering measurements lies in the substantial uncertainty surrounding the redshift distribution of the sources.Comment: 5 pages, 6 figures, 1 table, accepted for publication in MNRA