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Quantifying when and where strong magnetic skew forms in a data-driven global non-potential model of the solar corona I:production and persistence of skew
No full textStrong magnetic skew characterizes several non-potential structures in the solar corona, including filaments, which can erupt, producing major geomagnetic effects. Magnetic skew is thus a useful property in understanding locations of free magnetic energy in, and making forecasts from, global coronal magnetic field models. We develop a new technique for analysing the formation, evolution, and persistence of magnetic skew systematically in such models. This technique is applied to data-constrained magnetofrictional simulations, which include flux emergence in magnetic bipolar regions as observed on the Sun. Magnetic skew in the model is analysed, both globally and within the Earth-bound field of view. The latter is considered as these simulations have an observational bias: magnetogram observations can only be made along the Sun–Earth line. Results show that small patches of strong skew form incrementally, especially around recently emerged bipolar regions. However, large areas of strong skew, of sizes typical of filaments, take approximately two weeks to form after the emergence of new flux. Because of this observational bias in including new bipolar regions, most areas of strong skew in the model form on the far side of the Sun. Once formed, these areas may persist over long periods of time, comparable with the time-scale for solar rotation, and reproduce long-lived solar phenomena. Therefore, most strongly skewed regions in the model on the Earth-facing side of the Sun rotate into the field of view and do not form there. This illustrates a limitation of any global data-driven model that dynamically builds non-potentiality and skew through surface motions and flux emergence, with emergence based solely on observations from the Sun–Earth line
Review - Perfectly Disgraceful: Frank O'Hara's New York School and Mid-Century Mannerism: Perfectly Disgraceful
No full textSpinoza's simplest bodies
No full textIn the entirety of his corpus, Spinoza uses the phrase ‘simplest bodies’ [corporibus simplicissimis] exactly twice and never offers an explanation of what it means. That said, it appears to play a fundamental role in his thought. This paper evaluates two twentieth-century readings of Spinoza in order to present a new original theory of simplest bodies. Ultimately, I present a reading of Spinoza which accepts a nuanced amalgamation of these accounts. I argue that the right understanding of Spinozistic simplest bodies is something like the following: simplest bodies are portions of extension featuring motive homogeneity among their necessarily infinite parts. For Spinoza, simplest bodies thus feature no mereological simplicity at all, but rather only motive simplicity, in that they are properly characterized by a single ratio of motion and rest
Breaking the symmetries of indistinguishable objects
No full textIndistinguishable objects often occur when modelling problems in constraint programming, as well as in other related paradigms. They occur when objects can be viewed as being drawn from a set of unlabelled objects, and the only operation allowed on them is equality testing. For example, the golfers in the social golfer problem are indistinguishable. If we do label the golfers, then any relabelling of the golfers in one solution gives another valid solution. In this paper, we show how we can break the symmetries resulting from indistinguishable objects. We show how these symmetries induce symmetries of types built from indistinguishable objects, for example in a matrix indexed by indistinguishable objects. We then show how the resulting symmetries can be broken correctly and completely. As the method can be prohibitively expensive, we also study methods for breaking the symmetry only partially. In Essence, a high-level modelling language, indistinguishable objects are encapsulated in ‘unnamed types’. We provide an implementation to automatically break symmetries of unnamed types
Theory and modeling of large scale plasmapause surface waves
No full textThe plasmapause in Earth's magnetosphere represents the boundary between the plasma which co-rotates with the Earth (plasmasphere), and the more tenuous plasmatrough outside. The density change across the plasmapause can be large, changing by approximately 1–2 orders of magnitude depending on the prevailing conditions. This would suggest it to be a location where magnetohydrodynamic (MHD) surface waves can form, and indeed, this has been proposed in previous works to explain ultra-low frequency (ULF) wave observations around the plasmapause location. The main question is how such a large scale surface wave on the plasmapause would be excited. In this paper, we propose a model whereby surface waves at the plasmapause are driven by energy input from the magnetopause through solar wind driving. We derive an analytical form for the amplitude of these surface waves with this new driven boundary condition at the magnetopause. The excitation of these waves is then tested in several MHD simulations, where the model geometry, wavenumbers and temporal dependence of the magnetopause driver are varied. We establish that surface waves on the plasmapause can be excited by driving from the magnetopause, and that this still occurs with impulsive and continuous broadband driving. The azimuthal scale of the wave is a critical factor for this excitation, with longer azimuthal scales more favorable for driving larger amplitude surface waves. This mechanism provides new insight for how large scale and large amplitude ULF waves can access the inner magnetosphere, with potential implications for their interaction with radiation belt particles
Artificial worlds and artificial minds:authenticity and language learning in digital lifeworlds
No full textLanguage learning is increasingly being extended into digital and online spaces that have been enhanced by simulated reality and augmented with data and artificial intelligence. While this may expand opportunities for language learning, some critics argue that digital spaces may represent a pastiche or a parody of reality. However, while there are genuine issues, such criticisms may often fall back on naïve or essentialist views of authenticity, in particular by narrowing language learning scenarios to real-life or genuine communication. I argue that research undersocialises authenticity by not taking social relations into sufficient consideration, which denies or elides the ways that authenticity is achieved. In this conceptual paper, I offer a relational account of authenticity, where I conceive digital environments within a stratified ontological framework, where authenticity is not inherent in individuals or texts, but instead emerges from complex social contexts. Authenticity, then, does not refer to authenticity of texts or “being oneself”, but authenticity in relation to others. A stratified ontology provides opportunities to extend relations with others, offering what is described as a “submersion into a temporary agency”, where language learners can experiment with the social order in order to achieve authenticity of themselves in the target language. Finally, I present a relational pedagogy based on responsiveness, where feedback is distributed among disparate human and technical actors which facilitate, problematise or endorse authenticity.<br/
High-speed organic light-emitting diodes based on dinaphthylperylene achieving 4-Gbps communication
No full textOrganic light-emitting diodes (OLEDs) offer advantages for device-integrated transmitters for optical wireless communication because of their simple fabrication, mechanical flexibility, and integration of multiple color devices on a single substrate. However, they are generally considered to be slow due to low charge mobilities. Here, we show they can be made faster by suitable material selection and device design to achieve record-fast transmission by an OLED. We achieve a data rate of 2.9 Gbps in a 10-m data link at a bit error ratio (BER) of 5.54 × 10−3, corresponding to a coded data transmission rate of 2.7 Gbps after accounting for 7.15% overhead. This performance is comparable to the previous record for single-OLED transmitters but over a link 40 times longer. In addition, for a 2-m link, we obtain a record data rate of 4.0 Gbps at a BER of 5.54 × 10−3 (coded data rate of 3.7 Gbps). Our results show that the operational stability of OLEDs is important for high-speed operation. Thus, with synergetic developments in the stability of OLEDs for displays and lighting industries, OLEDs will become increasingly faster, expanding their applications for spectroscopy, communications, and sensing
Isothiourea-catalysed acylative kinetic and dynamic kinetic resolution of planar chiral paracyclophanols
No full textThe development of synthetic methods for the catalytic enantioselective preparation of planar chiral paracyclophane derivatives is of considerable interest to the synthetic community. To date, relatively few successful and effective organocatalytic approaches to this molecular class have been reported. This manuscript describes effective isothiourea catalysed acylative kinetic (KR) and dynamic kinetic resolution (DKR) approaches to the generation of a range of planar chiral paracyclophane macrocycles with excellent levels of enantioselectivity. Effective KR of configurationally stable planar chiral paracyclophanols with 12- and 13-membered ansa-chains is demonstrated (6 examples, s = up to 50) using 5 mol% of the isothiourea (R)-BTM and isobutyric anhydride. Application to configurationally labile macrocyclic phenols with 14 to 18-membered ansa-chains allows their effective acylative DKR, generating the desired products with excellent enantioselectivity (25 examples, up to 95% yield and 98:2 er)
