Understanding the Sensitivity of Detachment location to External Control on JET

In this thesis, comparisons of predictions of detachment front location sensitivity model (‘DLS model') were made in one L-mode (no N2-seeding), and three H-mode detached discharges (N2-seeding). Although the DLS model and experiment are qualitatively in agreement the model overestimates the sensitivity of the movement along a field line for a given amount of change in two control variables – upstream density, nu and the power entering the scrape-off layer, PSOL. The quantitative mismatch between the DLS model and experiment is not unexpected given the simplicity of the DLS model. Under the assumption that the exponents of nu & PSOL in the DLS model could be incorrect, new exponents were derived for both control variables from the L-mode experimental data in periods of the L-mode case where first only nu, and then both nu & PSOL were varied. The new `empirical' exponents were reduced from the DLS predictions by a factor of approximately 2.5. Those `empirical' exponents in the DLS model were then applied to the prediction of divertor impurity concentration, fz for two H-mode cases which had divertor N2-seeding show reasonable consistency with the variation in core Zeff and variations in PSOL. As part of this work, a measure for the detachment front location was developed based on the transition of the ratio of Dgamma/Dalpha emissivities from high (recombination-dominated) to low (excitation-dominated). The detachment extent along a field line, $\hat{z}$, was found to be inversely proportional to the outer divertor total ion current which may lead to new insights to the relationship between detachment and target ion current loss. The quality of this relationship was unexpected due to many nonlinear divertor processes that could have affected it

Los REA en la práctica: el cambio organizativo mediante el bootstrapping

En aquest treball investiguem un plantejament de canvi institucional encaminat a establir pràctiques educatives obertes (PEO) en una universitat i inculcar l'ús de recursos educatius oberts (REO) com a part del seu treball curricular i la seva pràctica educativa. Les pràctiques tradicionals, consistents a proporcionar recursos d'aprenentatge per a un ensenyament individualitzat en mòduls acadèmics semestrals, s'adapten cada vegada pitjor als requisits d'un panorama educatiu dinàmic i global. Els REO ofereixen una alternativa sostenible i equitativa a aquestes pràctiques tancades, i tenen la capacitat de satisfer la demanda emergent en entorns d'aprenentatge distribuït. No obstant això, canviar les pràctiques educatives continua essent un repte formidable, i l'adopció dels REO comporta una ruptura radical pel que fa a les pràctiques institucionals heretades. En aquest treball ens centrem en el punt de partida per a integrar els REO en el treball curricular i les pràctiques educatives. A la Universitat La Trobe (Austràlia) investiguem aquest canvi més per mitjà d'iniciatives emergents que d'un programa dissenyat jeràrquicament des de dalt: ens plantegem quines són les connexions necessàries per a implantar pràctiques obertes en una universitat. Descrivim tres casos de PEO que, junts, generen capacitats de REA en una universitat. Aprofitem l'estratègia de bootstrapping plantejada per Bardini com a procés d'aprenentatge iteratiu i coadaptatiu que connecta les bones pràctiques in situ amb les estructures institucionals a fi d'establir les bases de treball per al canvi emergent. Aquests casos demostren com uns processos innovadors tan dispars es poden connectar i modificar per a crear una xarxa de PEO incipient. In this paper, we investigate an approach to institutional change that aims to establish open educational practices (OEP) in a university and inculcate the use of open education resources (OER) as part of its curriculum work and teaching practice. Traditional practices that involve delivering knowledge resources for individualised learning within semester-length units of study are becoming increasingly ill-adapted to the demands of a dynamic and global educational landscape. OER offers a sustainable and equitable alternative to such closed arrangements, with the potential to meet the emerging demands of distributed learning settings. Nevertheless, changing educational practice remains a formidable challenge, and adopting OER is a radical break from legacy institutional practices. Our focus in this paper is on the starting point for embedding OER in curriculum work and teaching practice. We investigate change through emergent initiatives rather than a top-down program at La Trobe University in Australia: we ask what connections are necessary to establish open practices in a university. We trace three instances of OEP in one university that together build capacity in OER. We draw on Bardini’s strategy of bootstrapping, as an iterative and co-adaptive learning process that connects good practices in situ with institutional structures in order to build the groundwork for emergent change. These cases demonstrate how disparate innovations can be connected and re-purposed to establish a network of nascent OEP. En este trabajo investigamos un planteamiento de cambio institucional encaminado a establecer prácticas educativas abiertas (PEA) en una universidad e inculcar el uso de recursos educativos abiertos (REA) como parte de su trabajo curricular y su práctica educativa. Las prácticas tradicionales, consistentes en proporcionar recursos de aprendizaje para una enseñanza individualizada en módulos académicos semestrales, se adaptan cada vez peor a los requisitos de un panorama educativo dinámico y global. Los REA ofrecen una alternativa sostenible y equitativa a estas prácticas cerradas, y tienen la capacidad de satisfacer la demanda emergente en entornos de aprendizaje distribuido. No obstante, cambiar las prácticas educativas sigue siendo un reto formidable, y la adopción de los REA supone una ruptura radical con respecto a las prácticas institucionales heredadas. En el presente trabajo nos centramos en el punto de partida para integrar los REA en el trabajo curricular y las prácticas educativas. En la Universidad La Trobe (Australia) investigamos este cambio más a través de iniciativas emergentes que de un programa diseñado jerárquicamente desde arriba: nos planteamos cuáles son las conexiones necesarias para implantar prácticas abiertas en una universidad. Describimos tres casos de PEA que, juntos, generan capacidades de REA en una universidad. Aprovechamos la estrategia de bootstrapping planteada por Bardini como proceso de aprendizaje iterativo y coadaptativo que conecta las buenas prácticas in situ con las estructuras institucionales a fin de sentar las bases de trabajo para el cambio emergente. Estos casos demuestran cómo unos procesos innovadores tan dispares se pueden conectar y modificar para crear una red de PEA incipiente.

Altered Na/Ca exchange distribution and activity in ventricular myocytes from failing hearts

In mammalian cardiac ventricular myocytes, Ca efflux via Na/Ca exchange (NCX) occurs predominantly at T tubules. Heart failure is associated with disrupted t-tubular structure, but its effect on t-tubular function is less clear. We therefore investigated t-tubular NCX activity in ventricular myocytes isolated from rat hearts ∼18 wk after coronary artery ligation (CAL) or corresponding sham operation (Sham). NCX current (I(NCX)) and l-type Ca current (I(Ca)) were recorded using the whole cell, voltage-clamp technique in intact and detubulated (DT) myocytes; intracellular free Ca concentration ([Ca](i)) was monitored simultaneously using fluo-4. I(NCX) was activated and measured during application of caffeine to release Ca from sarcoplasmic reticulum (SR). Whole cell I(NCX) was not significantly different in Sham and CAL myocytes and occurred predominantly in the T tubules in Sham myocytes. CAL was associated with redistribution of I(NCX) and I(Ca) away from the T tubules to the cell surface and an increase in t-tubular I(NCX)/I(Ca) density from 0.12 in Sham to 0.30 in CAL myocytes. The decrease in t-tubular I(NCX) in CAL myocytes was accompanied by an increase in the fraction of Ca sequestered by SR. However, SR Ca content was not significantly different in Sham, Sham DT, and CAL myocytes but was significantly increased by DT of CAL myocytes. In Sham myocytes, there was hysteresis between I(NCX) and [Ca](i), which was absent in DT Sham but present in CAL and DT CAL myocytes. These data suggest altered distribution of NCX in CAL myocytes

Development and simulation of multi-diagnostic Bayesian analysis for 2D inference of divertor plasma characteristics

We present results of the design, implementation and testing of a Bayesian multi-diagnostic inference system which combines various divertor diagnostics to infer the 2D fields of electron temperature T e, density n e and deuterium neutral density n 0 in the divertor. The system was tested using synthetic diagnostic measurements derived from SOLPS-ITER fluid code predictions of the MAST-U Super-X divertor which include appropriate added noise. Two SOLPS-ITER simulations in different states of detachment, taken from a scan of the nitrogen seeding rate, were used as test-cases. Taken across both test-cases, the median absolute fractional errors in the inferred electron temperature and density estimates were 10.3% and 10.1% respectively. Differences between the inferred fields and the test-cases were well explained by solution uncertainty estimates derived from posterior sampling. This work represents a step toward a larger goal of obtaining a quantitative, 2D description of the divertor plasma state directly from experimental data, which could be used to gain better understanding of divertor physics phenomena

Sarcolemmal distribution of ICa and INCX and Ca autoregulation in mouse ventricular myocytes

The balance of Ca2+ influx and efflux regulates the Ca2+ load of cardiac myocytes, a process known as autoregulation. Previous work has shown that Ca2+ influx, via L-type Ca2+ current ( ICa), and efflux, via the Na+/Ca2+ exchanger (NCX), occur predominantly at t-tubules; however, the role of t-tubules in autoregulation is unknown. Therefore, we investigated the sarcolemmal distribution of ICa and NCX current ( INCX), and autoregulation, in mouse ventricular myocytes using whole cell voltage-clamp and simultaneous Ca2+ measurements in intact and detubulated (DT) cells. In contrast to the rat, INCX was located predominantly at the surface membrane, and the hysteresis between INCX and Ca2+ observed in intact myocytes was preserved after detubulation. Immunostaining showed both NCX and ryanodine receptors (RyRs) at the t-tubules and surface membrane, consistent with colocalization of NCX and RyRs at both sites. Unlike INCX, ICa was found predominantly in the t-tubules. Recovery of the Ca2+ transient amplitude to steady state (autoregulation) after application of 200 µM or 10 mM caffeine was slower in DT cells than in intact cells. However, during application of 200 µM caffeine to increase sarcoplasmic reticulum (SR) Ca2+ release, DT and intact cells recovered at the same rate. It appears likely that this asymmetric response to changes in SR Ca2+ release is a consequence of the distribution of ICa, which is reduced in DT cells and is required to refill the SR after depletion, and NCX, which is little affected by detubulation, remaining available to remove Ca2+ when SR Ca2+ release is increased. NEW &amp; NOTEWORTHY This study shows that in contrast to the rat, mouse ventricular Na+/Ca2+ exchange current density is lower in the t-tubules than in the surface sarcolemma and Ca2+ current is predominantly located in the t-tubules. As a consequence, the t-tubules play a role in recovery (autoregulation) from reduced, but not increased, sarcoplasmic reticulum Ca2+ release. </jats:p

Reduced density and altered regulation of rat atrial L-type Ca²⁺ current in heart failure

Constitutive regulation by PKA has recently been shown to contribute to L-type Ca2+current ( ICaL) at the ventricular t-tubule in heart failure. Conversely, reduction in constitutive regulation by PKA has been proposed to underlie the downregulation of atrial ICaLin heart failure. The hypothesis that downregulation of atrial ICaLin heart failure involves reduced channel phosphorylation was examined. Anesthetized adult male Wistar rats underwent surgical coronary artery ligation (CAL, N=10) or equivalent sham-operation (Sham, N=12). Left atrial myocytes were isolated ~18 wk postsurgery and whole cell currents recorded (holding potential=-80 mV). ICaLactivated by depolarizing pulses to voltages from -40 to +50 mV were normalized to cell capacitance and current density-voltage relations plotted. CAL cell capacitances were ~1.67-fold greater than Sham ( P ≤ 0.0001). Maximal ICaLconductance ( Gmax) was downregulated more than 2-fold in CAL vs. Sham myocytes ( P &lt; 0.0001). Norepinephrine (1 μmol/l) increased Gmax&gt;50% more effectively in CAL than in Sham so that differences in ICaLdensity were abolished. Differences between CAL and Sham Gmaxwere not abolished by calyculin A (100 nmol/l), suggesting that increased protein dephosphorylation did not account for ICaLdownregulation. Treatment with either H-89 (10 μmol/l) or AIP (5 μmol/l) had no effect on basal currents in Sham or CAL myocytes, indicating that, in contrast to ventricular myocytes, neither PKA nor CaMKII regulated basal ICaL. Expression of the L-type α1C-subunit, protein phosphatases 1 and 2A, and inhibitor-1 proteins was unchanged. In conclusion, reduction in PKA-dependent regulation did not contribute to downregulation of atrial ICaLin heart failure.NEW &amp; NOTEWORTHY Whole cell recording of L-type Ca2+currents in atrial myocytes from rat hearts subjected to coronary artery ligation compared with those from sham-operated controls reveals marked reduction in current density in heart failure without change in channel subunit expression and associated with altered phosphorylation independent of protein kinase A.</jats:p

Improving response rates using a monetary incentive for patient completion of questionnaires: an observational study

Background: Poor response rates to postal questionnaires can introduce bias and reduce the statistical power of a study. To improve response rates in our trial in primary care we tested the effect of introducing an unconditional direct payment of 5 pound for the completion of postal questionnaires. Methods: We recruited patients in general practice with knee problems from sites across the United Kingdom. An evidence-based strategy was used to follow-up patients at twelve months with postal questionnaires. This included an unconditional direct payment of 5 pound to patients for the completion and return of questionnaires. The first 105 patients did not receive the 5 pound incentive, but the subsequent 442 patients did. We used logistic regression to analyse the effect of introducing a monetary incentive to increase the response to postal questionnaires. Results: The response rate following reminders for the historical controls was 78.1% ( 82 of 105) compared with 88.0% ( 389 of 442) for those patients who received the 5 pound payment (diff = 9.9%, 95% CI 2.3% to 19.1%). Direct payments significantly increased the odds of response ( adjusted odds ratio = 2.2, 95% CI 1.2 to 4.0, P = 0.009) with only 12 of 442 patients declining the payment. The incentive did not save costs to the trial - the extra cost per additional respondent was almost 50 pound. Conclusion: The direct payment of 5 pound significantly increased the completion of postal questionnaires at negligible increase in cost for an adequately powered study