William Robert Dunn

The Jovian system is a treasure trove of X-ray sources: diverse and dynamic atmospheric and auroral emissions, diffuse radiation belt and Io torus emissions, and plasma-surface interactions with Jupiter's moons. The system is a rich natural laboratory for astronomical X-rays with each region showcasing its own X-ray production processes: scattering and fluorescence of solar corona emissions; charge exchange emissions from energetic ions; Inverse-Compton, thermal and non-thermal bremsstrahlung emissions from relativistic electrons; and fingerprint fluorescence lines indicative of elemental composition and the potential for life on the Galilean satellites. For the high energy astrophysics domain, perhaps Jupiter's greatest attribute is the opportunity to connect observed X-ray emissions with in-situ plasma and magnetic field measurements of the precise physical processes that lead to them - irreplaceable ground truths for systems that cannot be visited in-situ. Such simultaneous studies have revealed that Jupiter's spectacular soft X-ray flares and pulsations are produced by wave-particle interactions, while the bremsstrahlung aurorae vary with magnetodisk reconnection and dipolarisation. While many remote signatures remain to be linked with their source processes, the future is bright, with synergistic Chandra, NuSTAR, XMM-Newton and Juno in-situ measurements continuing to provide revolutionary insights in the coming years, while JUICE and Europa missions with ATHENA and possibly Lynx will enable a new legacy. However, to truly characterise some emissions (e.g. mapping Galilean satellite elemental composition) in-situ X-ray instrumentation is a necessity. Recent advances enable compact, lightweight, X-ray instrumentation perfectly suited for Jupiter science. The chapter closes by reviewing feasible, low-risk concepts that would paradigm-shift our understanding of the system.

Universal Design for Learning (UDL) and Blended Learning (BL) formats, are widely adopted across K–12 learning environments. Upon graduation, preservice teachers may be expected to implement UDL and BL practices. The present study was motivated by the need to provide preservice teachers with live modeling of UDL and BL concepts. Learning analytics data from 197 preservice teachers was examined for engagement with UDL/BL Access features (location, day-of-the-week, time-of-day, and regularity), Content features (screencasts and quizzes), and to determine if there was a relationship between engagement and achievement. Examination of the learning management system login data revealed regular access to the digital content across differing locations, week days, and time of day. Associations were significant between academic performance and all features. Designing the BL digital course components following UDL principles appears to have served as a self-regulation enabler for preservice teachers themselves while providing exemplars to adopt in their future practice.

Aim: Hypoxia causes vasodilatation of coronary arteries which protects the heart from ischaemic damage through mechanisms including the generation of hydrogen sulphide (H₂S), but the influence of the perivascular adipose tissue (PVAT) and myocardium is incompletely understood. This study aimed to determine whether PVAT and the myocardium modulate the coronary artery hypoxic response and whether this involves hydrogen sulphide.Methods: Porcine left circumflex coronary arteries were prepared as cleaned segments and with PVAT intact, myocardium intact or both PVAT and myocardium intact, and contractility investigated using isometric tension recording. Immunoblotting was used to measure levels of H₂S‐synthesizing enzymes: cystathionine‐β‐synthase (CBS), cystathionine γ‐lyase (CSE) and 3‐mercaptopyruvate sulphurtransferase (MPST).Results: All three H₂S‐synthesizing enzymes were detected in the artery and myocardium, but only CBS and MPST were detected in PVAT. Hypoxia elicited a biphasic response in cleaned artery segments consisting of transient contraction followed by prolonged relaxation. In arteries with PVAT intact, hypoxic contraction was attenuated and relaxation augmented. In arteries with myocardium intact, hypoxic contraction was attenuated, but relaxation was unaffected. In replacement experiments, replacement of dissected PVAT and myocardium attenuated artery contraction and augmented relaxation to hypoxia, mimicking the effect of in situ PVAT and indicating involvement of a diffusible factor(s). In arteries with intact PVAT, augmentation of hypoxic relaxation was reversed by amino‐oxyacetate (CBS inhibitor), but not DL‐propargylglycine (CSE inhibitor) or aspartate (inhibits MPST pathway).Conclusion: PVAT augments hypoxic relaxation of coronary arteries through a mechanism involving H₂S and CBS, pointing to an important role in regulation of coronary blood flow during hypoxia.

Electrical field stimulation (EFS) elicits robust sensory neurogenic relaxation responses in the rat isolated mesenteric arterial bed but these responses are absent or difficult to demonstrate in isolated arteries. We believe that this mismatch is due to the absence of perivascular adipose tissue (PVAT) as it is conventionally removed in studies on isolated vessels. We aimed to determine whether sensory nerves are expressed in PVAT, their physiological roles and their possible interactions with PVAT-derived adipokines. Using confocal imaging, enzyme immunoassay (EIA), myography, vascular perfusion, and multiplex analysis of rat mesenteric arteries, we show that PVAT is crucial for the roles of sensory nerves in control of vasomotor tone and adipokine release. Immunofluorescence double staining showed co-expression of calcitonin gene-related peptide (CGRP; sensory neurotransmitter) and PGP9.5 (neuronal marker) in PVAT of mesenteric arteries. CGRP release from dissected PVAT, measured using EIA, was increased by capsaicin which activates sensory nerves. EFS in both mesenteric arteries and perfused mesenteric arterial beds, with and without PVAT, demonstrated neurogenic relaxation in the presence of PVAT, which was greatly attenuated in preparations without PVAT. Neurogenic relaxation due to EFS was associated with release of leptin in PVAT-intact mesenteric arterial beds, which was abolished in preparations without PVAT. Exposure to low oxygen was associated with an attenuated leptin and adiponectin release, but an increase in IL-6 release, from mesenteric arterial beds. Exogenous leptin augmented relaxation to CGRP in mesenteric arteries. These data show, for the first time, expression of sensory nerves within PVAT and that PVAT is crucial for sensory neurogenic vasorelaxation and crosstalk with adipocytes leading to leptin release, which may augment CGRP-mediated relaxation; leptin release is abolished after exposure to conditions of reduced oxygenation.

The present study examined the hypothesis that potassium ions act as an endothelium-derived hyperpolarizing factor (EDHF) released in response to ACh in small mesenteric arteries displaying myogenic tone. Small mesenteric arteries isolated from rats were set up in a pressure myograph at either 60 or 90 mmHg. After developing myogenic tone, responses to raising extracellular potassium were compared to those obtained with ACh (in the presence of nitric oxide synthase and cyclo-oxygenase inhibitors). The effects of barium and oubain, or capsaicin, on responses to raised extracellular potassium or ACh were also determined. The effects of raised extracellular potassium levels and ACh on membrane potential, were measured using sharp microelectrodes in pressurised arteries. Rat small mesenteric arteries developed myogenic tone when pressurised. On the background of vascular tone set by a physiological stimulus (i.e pressure), ACh fully dilated the small arteries in a concentration-dependent manner. This response was relatively insensitive to the combination of barium and ouabain, and insensitive to capsaicin. Raising extracellular potassium produced a more inconsistent and modest vasodilator response in pressurised small mesenteric arteries. Responses to raising extracellular potassium were sensitive to capsaicin, and the combination of barium and ouabain. ACh caused a substantial hyperpolarisation in pressurized arteries, while raising extracellular potassium did not. These data indicate that K⁺ is not the EDHF released in response to ACh in myogenically active rat mesenteric small arteries. Since the hyperpolarization produced by ACh was sensitive to carbenoxolone, gap junctions are the likely mediator of EDH responses under physiological conditions.

The relative importance of ATP as a functional sympathetic neurotransmitter in blood vessels has been shown to be increased when the level of preexisting vascular tone or pressure is increased, in studies carried out in rat mesenteric arteries. The aim of the present study was to determine whether tone influences the involvement of ATP as a sympathetic cotransmitter with noradrenaline in another species. We used the porcine perfused mesenteric arterial bed and porcine mesenteric large, medium and small arteries mounted for isometric tension recording, because purinergic cotransmission can vary depending on the size of the blood vessel. In the perfused mesenteric bed at basal tone, sympathetic neurogenic vasocontractile responses were abolished by prazosin, an α₁-adrenoceptor antagonist, but there was no significant effect of α,β-methylene ATP, a P2X receptor-desensitizing agent. Submaximal precontraction of the mesenteric arterial bed with U46619, a thromboxane A₂ mimetic, augmented the sympathetic neurogenic vasocontractile responses; under these conditions, both α,β-methylene ATP and prazosin attenuated the neurogenic responses. In the mesenteric large, medium and small arteries, prazosin attenuated the sympathetic neurogenic contractile responses under conditions of both basal and U46619-raised tone. α,β-Methylene ATP was effective in all of these arteries only under conditions of U46619-induced tone, causing a similar inhibition in all arteries, but had no significant effect on sympathetic neurogenic contractions at basal tone. These data show that ATP is a cotransmitter with noradrenaline in porcine mesenteric arteries; the purinergic component was revealed under conditions of partial precontraction, which is more relevant to physiological conditions.