The strain dependent critical current of high field superconductors for fusion energy applications

All superconductors in high field magnets operating above 12 T are brittle and subjected to large strains because of the differential thermal contraction between component parts on cool-down and the large Lorentz forces produced in operation. The continuous scientific requirement for higher magnetic fields in superconducting energy-efficient magnets, in applications such as fusion, means we must understand and control the high sensitivity of critical current density $J_\mathrm{c}$ to strain $\varepsilon$. This thesis presents detailed $J_\mathrm{c} \left( B,T,\varepsilon,\theta \right)$ transport measurements as a function of field $B$, temperature $T$, strain $\varepsilon$ and angle $\theta$ with respect to the applied magnetic field, on high field superconductors that include the very widely observed inverted parabolic dependence for $J_\mathrm{c} \left( \varepsilon \right)$. It is usually assumed that a coincidence occurs between the Fermi energy and a peak in the density of states in the unstrained state which leads to a peak in the superconducting properties in the unstrained state. The long-standing interpretation of $J_\mathrm{c} \left( \varepsilon \right)$ data attributes the inverted parabolic strain behaviour to the averaged response of the underlying material. Features of the data in this work are identified in both HTS REBCO tape and LTS A15 wires which show that both of these assumptions are incorrect. A new analysis is presented which shows the inverted parabolic nature of $J_\mathrm{c} \left( \varepsilon \right)$ is the result of competition between domains with opposing strain dependencies and successfully accounts for the features of the data incompatible with standard assumptions. It is concluded that the origin of the competing domains in REBCO tape lies in twinned domains and in A15 wires is caused by percolative current flow across grain boundaries orientated in different directions which respond to an applied strain in different manners due to the Poisson effect. This work provides fresh insight into how improvements might be made to high field superconductors under strain

The impact of irrigated biomass plantations on mesoscale climate in coastal arid regions

Large-scale agroforestry in coastal arid and semi-arid regions could provide a geoengineering solution to anthropogenic climate change. Since agroforestry may impact on mesoscale climate in unknown ways, urgent research into potential impacts of large-plantations is needed to fully assess the viability and optimal placement for such schemes. Validated mesoscale simulations provide insights into feedbacks between land surface and atmosphere, particularly with respect to convective processes. Simulations of irrigated Simmondsia chinensis (jojoba) plantations were carried out with the WRF-NOAH atmosphere-land surface model using prescribed land surface and plant parameters. A sub-surface irrigation algorithm was developed based on critical soil moisture stress levels and implemented into the model code. The simulation of desert and plantation land surfaces was validated with field data from two sites in the Negev Desert - an arid desert site and a 400 ha jojoba plantation. For desert and vegetated surfaces, the model output of diurnal meteorological quantities and energy fluxes generally match well with the respective observations. Diurnal 2m-temperatures over the desert and plantation are matched by the model to within ± 0.2 °C and ± 1.5 °C, respectively. Wind speeds for both surfaces match to within 0.5 ms−1 and plantation latent heat is reproduced to within ± 20 Wm−2. Subsequent to validation, larger plantations of 100 km × 100 km were then simulated in two coastal arid regions, Israel and Oman over a period of one month and compared with control runs, without plantations. In Oman, convection and precipitation were triggered or enhanced by the plantation over multiple days whereas in Israel almost no impacts were observed. Two mechanisms were responsible for observed convection initiation: turbulent vertical transport of scalars due to increased surface heating and roughness as well as a low pressure-induced convergence at the canopy leeside. The main contributors to the surface heating effect were reduced albedo and the high water-use efficiency exhibited by specialist desert species. The combination of increased net surface radiation and high stomatal resistances significantly limited transpiration and led to a surplus in sensible heat flux compared with the surrounding soils (> 100 Wm−2). In Oman, convection initiation triggered by the plantation tended to occur on days when a high mid-tropospheric temperature lapse rate and significant surface air humidity were present. Israel exhibits more stable lapse rates during summer and drier conditions aloft, both of which suppressed convection significantly, even with a similar land surface perturbation. The initiation of moist convection at the mesoscale is therefore strongly controlled by prevailing synoptic conditions. A regional climatological analysis of temperature and humidity ECMWF reanalysis data and station precipitation data indicate that the south-west of North America has particularly suitable conditions for impacts. Coastal locations in Baja California and the Sonoran Desert exhibit a seasonal concurrence of monsoonal instability, high surface humidity and integrated column water vapor, but at the same time low precipitation. Therefore plantation impacts on convection there are likely and could be beneficial in terms of higher amounts of precipitation. These findings indicate that mesoscale convective events can be triggered by large plantations within arid and semi-arid regions and that these effects may be controllable via judicious placement of such schemes. Thus arid agroforestry has the potential not only to increase precipitation and reverse desertification within arid and semi-arid regions, but also to mitigate climate change if implemented on very large scales.Großräumige Agrarforstwirtschaft in küstennahen ariden und semiariden Gebieten stellt eine Möglichkeit dar, mittels Geoengineering anthropogenem Klimawandel zu begegnen.Agrarforstwirtschaft wird das mesoskalige Klima jedoch in bisher unbekannter Weise beeinflussen. Daher ist es dringend notwendig, die möglichen Auswirkungen von großräumigen Plantagen in Bezug auf Durchführbarkeit und optimale Ausführung zu erforschen. Dazu geben validierte, mesoskalige Modellsimulationen Einblicke in die Wechselwirkungen zwischen Landoberfläche und Atmosphäre, insbesondere in Bezug auf konvektive Prozesse. Bewässerte Jojobaplantagen wurden mit dem Atmosphären-Landoberflächenmodell WRFNOAH simuliert. Dazu wurden die Landoberfläche und geeignete Pflanzenparameter fest vorgegeben. Ein neuer Algorithmus für die unterirdische Bewässerung wurde entwickelt und in den Modellcode implementiert. Die Simulation von Wüsten und Plantagenflächen wurde dann mittels Vergleich der Ergebnisse mit Feldmessungen von zwei Stationen in der Wüste Negev getestet. Eine Station befand sich an einem Wüsten-Standort und eine in einer 400 ha großen Jojobaplantage. Über den simulierten Wüsten und bewachsenen Flächen stimmen die Modellergebnisse der meteorologischen Größen und der Energieflüsse im Tagesverlauf im Allgemeinen gut mit den entsprechenden Beobachtungen überein. Der Tagesverlauf der 2m-Temperaturen in der Wüste und der Plantage bewegt sich im Bereich von ± 0,2 °C beziehungsweise ± 1,5 °C verglichen mit der Beobachtung. Die Windgeschwindigkeiten bewegen sich im Bereich von ± 0,5 ms−1 um die beobachteten Werte und der latente Wärmefluss zeigt Abweichungen von ± 20 Wm−2. Im Anschluss an die Validierung wurden größere Plantagen von je 100 km × 100 km in zwei repräsentativen ariden Küstengebieten (Israel und Oman) über einen Zeitraum von einem Monat simuliert und mit einem Kontrollexperiment ohne Plantagen verglichen. Im Oman löste die Plantage über mehrere Tage Feuchtekonvektion und Niederschläge aus oder verstärkte diese, während sie in Israel fast keinen Einfluss zeigte. Zwei Mechanismen waren im Wesentlichen verantwortlich für die Entstehung der Feuchtekonvektion im Oman: der turbulente, vertikale Austausch der meteorologischen Größen durch eine stärkere Erwärmung der Landoberfläche und erhöhte Rauigkeit sowie eine durch tieferen Luftdruck ausgelöste Konvergenz auf der Leeseite der Plantage. Wesentlich zur Oberflächenerwärmung tragen die verringerte Albedo sowie die effiziente Wasserverwertung der auf Wüstengebiete spezialisierten Pflanzenarten bei. Die Kombination aus erhöhter Nettostrahlung am Boden und erhöhtem Stomatawiderstand begrenzt die Transpiration erheblich und führt zu einem Anstieg des sensiblen Wärmeflusses von ca. 100 Wm−2 im Vergleich zum umgebenden Boden. Im Oman besteht die Tendenz zu einer Beeinflussung der Konvektion durch die Plantage im Fall von starken Temperaturgradienten in der mittleren Troposphäre und signifikant erhöhter Luftfeuchte an der Erdoberfläche. Israel hat im Sommer eine stabilere atmosphärische Schichtung und ist in höheren Lagen sehr viel trockener. Dies unterdrückt den Einfluss auf die Konvektion signifikant, selbst bei einer Änderung der Landnutzung. Die Auslösung von Feuchtekonvektion auf der Mesoskala wird also stark durch die großräumige Zirkulation bestimmt. Eine auf Temperatur- und Feuchtefeldern der EZMW-Reanalysen sowie Niederschlagsdaten basierenden Analyse der regionalen Klimatologie zeigt, dass der Südwesten Nordamerikas besonders geeignete Bedingungen für eine Beeinflussung der Konvektion durch eine Plantage bietet. In der Monsunzeit zeichnen sich die Küstengebiete der Baja California und der Wüste Sonora durch das Zusammentreffen von instabiler Schichtung, hoher Luftfeuchte am Boden und hohem vertikal integriertem Wasserdampfgehalt aus, haben aber gleichzeitig kaum Niederschlag. Daher kann man einen Einfluss von Plantagen auf Konvektion und somit grössere Niederschlagsmengen erwarten. Die Resultate zeigen zum einen, dass konvektive Niederschläge durch einen geeigneten Aufbau größerer Plantagen ausgelöst und zum anderen bezüglich ihrer Intensität beeinflusst werden können. Dies unterstreicht das große Potential der Agrarforstwirtschaft, nicht nur die Niederschlagsmenge zu erhöhen und die Wüstenbildung rückgängig zu machen, sondern auch dem Klimawandel abzuschwächen sofern die Plantagen groß genug sind

Tycho Brahe's 1572 supernova as a standard type Ia explosion revealed from its light echo spectrum

Type Ia supernovae (SNe Ia) are thermonuclear explosions of white dwarf stars in close binary systems. They play an important role as cosmological distance indicators and have led to the discovery of the accelerated expansion of the Universe. Among the most important unsolved questions are how the explosion actually proceeds and whether accretion occurs from a companion or via the merging of two white dwarfs. Tycho Brahe's supernova of 1572 (SN 1572) is thought to be one of the best candidates for a SN Ia in the Milky Way. The proximity of the SN 1572 remnant has allowed detailed studies, such as the possible identification of the binary companion, and provides a unique opportunity to test theories of the explosion mechanism and the nature of the progenitor. The determination of the yet unknown exact spectroscopic type of SN 1572 is crucial to relate these results to the diverse population of SNe Ia. Here we report an optical spectrum of Tycho Brahe's supernova near maximum brightness, obtained from a scattered-light echo more than four centuries after the direct light of the explosion swept past Earth. We find that SN 1572 belongs to the majority class of normal SNe Ia. The presence of a strong Ca II IR feature at velocities exceeding 20,000 km/s, which is similar to the previously observed polarized features in other SNe Ia, suggests asphericity in SN 1572.Comment: 15 pages, 3 figures - accepted for publication in Natur

Some Gender Implications of the ‘Civilising Mission’ of the Anglican Church for the Acholi Peoples of Northern Uganda

Anglican missionaries arriving in Uganda’s Acholiland in 1903 saw the local peoples as in need not just of Christianisation but also of civilising. This last consisted primarily of inculcating western notions of gender identities for both men and women, with an emphasis on the wearing of gender-appropriate clothing and terminating the practices of polygyny and bride-price payment. The first missionaries considered the Acholi to have high levels of gender equality but they still believed conversion would improve women’s status through domesticating them and instilling the notion of male superiority, despite the fact that local customary rituals did not distinguish on grounds of gender. Over decades, the population gradually converted to various Christian denominations, mainly Anglicanism and Catholicism, but without abandoning their customary rituals, using them as and when required, to ward off evil or ask for rain, for instance. The most significant impact of the civilising process was arguably the institutionalisation of the notion of masculine superiority now legitimised by appeals to what happened in the Garden of Eden. The paper is based on historical documents, both published and from the missionary archives, as well as on ethnographic research into gender in the region today

ACL injuries identifiable for pre-participation imagiological analysis: Risk factors

Identification of pre-participation risk factors for noncontact anterior cruciate ligament (ACL) injuries has been attracting a great deal of interest in the sports medicine and traumatology communities. Appropriate methods that enable predicting which patients could benefit from pre- ventive strategies are most welcome. This would enable athlete-specific training and conditioning or tailored equipment in order to develop appropriate strategies to reduce incidence of injury. In order to accomplish these goals, the ideal system should be able to assess both anatomic and functional features. Complementarily, the screening method must be cost-effective and suited for widespread application. Anatomic study protocol requiring only standard X rays could answer some of such demands. Dynamic MRI/CT evaluation and electronically assisted pivot-shift evaluation can be powerful tools providing complementary information. These upcoming insights, when validated and properly combined, envision changing pre-participation knee examination in the near future. Herein different methods (validated or under research) aiming to improve the capacity to identify persons/athletes with higher risk for ACL injury are overviewed.

The surface-boundary layer connection across spatial scales of irrigation-driven thermal heterogeneity: An integrated data and modeling study of the LIAISE field campaign

Irrigation in semi-arid regions induces thermal heterogeneity across a range of spatial scales that impacts the partitioning of energy at the surface, the development of the atmospheric boundary layer, and the bidirectional interactions between the atmosphere and the surface. In this analysis, we use data from the Land Surface Interactions with the Atmosphere in the Iberian Semi-Arid Environment (LIAISE) experiment combined with a coupled land–atmosphere model to understand the role of the scales of irrigation-induced, thermal heterogeneity on the surface fluxes and consequently, the development of the diurnal convective boundary layer. The surface heterogeneity is characterized by Bowen ratios that range from ∼0.01 in the irrigated areas to ∼30 in the non-irrigated areas; however, the observed boundary-layers dynamics in both locations are similar. In this analysis, we address the questions of how the surface fluxes impact the development of the boundary-layer dynamics and how the boundary layer influences the diurnal cycle of surface fluxes. To interpret the observations, we introduce a heterogeneity scaling scheme where length scales range from local scale (∼100 m) to regional scale (∼10 km) to investigate the role of scale on surface representation in numerical models and to address the discrepancy between surface observations and their representation in weather and climate models. We find that at the surface, both the available energy and its partitioning depend on spatial scale. The observed boundary-layer properties can be explained through the composite of surface fluxes at the regional scale. Surface fluxes at the local scales are unable to replicate the observed boundary layer — even when including large-scale contributions. We find that non-local boundary layer processes like advection are important for partitioning energy at the local scale. We explore the connection between surface fluxes and the development of the boundary layer and the potential non-local effects on boundary-layer development

The Sneeuberg: A new centre of floristic endemism on the Great Escarpment, South Africa

The Sneeuberg mountain complex (Eastern Cape) comprises one of the most prominent sections of the Great Escarpment in southern Africa but until now has remained one of the botanically least known regions. The Sneeuberg is a discrete orographical entity, being delimited in the east by the Great Fish River valley, in the west by the Nelspoort Interval, to the south by the Plains of Camdeboo, and to the north by the Great Karoo pediplain. The highest peaks range from 2278 to 2504 m above sea level, and the summit plateaux range from 1800 to 2100 m. Following extensive literature review and a detailed collecting programme, the Sneeuberg is reported here as having a total flora of 1195 species of which 107 (9%) are alien species, 33 (2.8%) are endemic, and 13 (1.1%) near-endemic. Five species previously reported as Drakensberg Alpine Centre (DAC) endemics are now known to occur in the Sneeuberg (representing range extensions of some 300–500 km). One-hundred-and-five species (8.8%) are DAC near-endemics, with the Sneeuberg being the western limit for most of these. Ten species (0.8%) represent disjunctions across the Karoo Interval from the Cape Floristic Region (CFR) to the Sneeuberg. In all, some 23 significant range extensions, eight new species, and several rediscoveries are recorded. We conclude by recognising the Sneeuberg as a new centre of endemism along the Great Escarpment, with floristic affinities with the Albany Centre and the DAC, and links to the CFR

A Survey of Bayesian Statistical Approaches for Big Data

The modern era is characterised as an era of information or Big Data. This has motivated a huge literature on new methods for extracting information and insights from these data. A natural question is how these approaches differ from those that were available prior to the advent of Big Data. We present a review of published studies that present Bayesian statistical approaches specifically for Big Data and discuss the reported and perceived benefits of these approaches. We conclude by addressing the question of whether focusing only on improving computational algorithms and infrastructure will be enough to face the challenges of Big Data

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016