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A search for transit-timing variations in the transiting hot-Jupiter systems HIP 65, NGTS-6, NGTS-10, and WASP-173
No full textHot Jupiters are Jupiter-mass planets with orbital periods of less than 10 d. Their short orbital separations make tidal dissipation within the stellar host especially efficient, potentially leading to a measurable evolution of the orbit. One possible manifestation of this is orbital decay, which presents itself observationally through variations in the orbital period and thus times of transit. Here, we select four promising exoplanetary systems for detecting this effect: HIP 65, NGTS-6, NGTS-10, and WASP-173. We present 33 new transit light curves taken with the 1.54 m Danish Telescope, and analyse these alongside photometric data from the Transiting Exoplanet Survey Satellite and transit-timing data from the literature. We construct two ephemeris models for each target: a linear ephemeris and a shrinking orbital period due to tidal decay. The linear ephemeris is preferred for three of the four models – the highest significance for the quadratic ephemeris is over 3σ for WASP-173. We compare these results to theoretical predictions for tidal dissipation of gravity waves in radiation zones, and find that wave breaking is predicted only in WASP-173, making rapid decay plausible in this system but unclear in the other three. The sensitivity of transit timings to orbital decay depends on the square of the time interval covered by available observations, so our results establish a useful baseline against which future measurements can be compared. NGTS-6 and NGTS-10 are important objects for future study as they are in the first field to be observed by the upcoming PLATO mission
The tropical Abel–Prym map
No full textWe prove that, under mild assumptions, the tropical Abel–Prym map Ψ: Γ' → Prym(Γ'/Γ) associated with a free double cover π : Γ' → Γ is harmonic of degree 2 if and only if the source graph Γ' is hyperelliptic. This is in accordance with the already established algebraic result. In this case, the Abel–Prym graph Ψ(Γ') is hyperelliptic of genus gΓ - 1 and its Jacobian is isomorphic, as a pptav, to the Prym variety of the cover. We further show that the Abel–Prym graph coincides with a connected component of the tropical bigonal construction. En route, we count the number of distinct free double covers by hyperelliptic metric graphs
Drawing in the art history classroom:why is it not enough to listen and look?
No full textInspired by the student-centred, experiential, affective and sensory approaches of recent art history, this article discusses the integration of drawing activities in the classroom as an important part of the multimodal art historical pedagogy. It presents as its case study a module on Raphael and His Reception, which incorporates a practice-based seminar entitled ‘Drawing like Raphael’. The discussion considers this pedagogical method in theory and practice and reflects on its benefits, challenges and students’ feedback. Incorporating drawing in the classroom develops students’ sensitivity to the variety of media, grounds and their combinations, giving them an experiential understanding of the meaning of materiality. This article argues that drawing is a creative and fun way to build skills in visual expression and interpretation, but also one that brings affects and emotions to art historical inquiries and encourages students to bring their own thoughts and lived experiences to their art historical studies
Harnessing the orientation of columnar discotic liquid crystals for narrowband blue emission with enhanced out-coupling efficiency toward improvement of SP-OLEDs performance
No full textControlling the supramolecular alignment of columnar mesogens offers a strategy to optimize charge transport and orientation of the transition dipole moment of emissive solution-processed films, ultimately enabling the fabrication of more efficient solution-processable OLEDs. Here, we report the development of multi-resonant thermally activated delayed fluorescent (MR-TADF) discotic liquid crystals (DLCs) containing a diindolocarbazole emissive core that is decorated with four mesogenic groups that are either branched (DICz-DMOC) or linear (DICz-DOD) in nature. DICz-DMOC adopts a columnar mesophase at room temperature, where the neat film shows homeotropic alignment to the substrate surface. Emission is broad and partially quenched as neat films due to the formation of aggregates, while in toluene and as 10 wt.% doped films in mCP, emission originates mainly from monomolecular species. The DLCs align horizontally, which also orients the transition dipole moment of the emitters preferentially horizontally, reflected in an anisotropy factor, a, of 0.22 for the solution-processed neat films. Solution-processed OLEDs (SP-OLEDs) containing DICz-DMOC as the emitter showed a maximum external quantum efficiency (EQEmax) of 10.0% in doped devices and 5.3% in non-doped devices, representing some of the highest device efficiencies using emitters bearing mesogenic groups
Do dogs rationally infer the cases of failed actions?
No full textHumans regularly reason about the causes of events and actions we observe in the world, both to infer the physical properties and mechanisms of objects, and to understand others’ actions. Evidence for causal reasoning in nonhuman animals is mixed, and may be more easily detected in some contexts than others. Dogs, for example, fail at most tests of causal reasoning pertaining to physical cognition, yet possess sophisticated sociocognitive abilities. In this pre-registered study, we test whether dogs are capable of making rational inferences about the causes of failed actions in two analogous experiments, which differed only in the nature of said failures. Dogs observed human agents either succeed or fail to open two gates, in contexts where their failures could be attributed either to the lack of competency of an agent, or the physical properties of a gate. If dogs are capable of making causal inferences equally in social and physical contexts, they should succeed in both experiments. However, if dogs are more likely to make social rather than physical causal inferences, they should find the competency context more interpretable than the physical one. Dogs failed to make rational inferences in either context, raising theoretical and methodological questions for future work
Preparing humanity for the discovery of extra-terrestrial life:the SETI Post Detection Hub
No full textThis paper introduces the SETI Post-Detection Hub, its origins, motivations, and initial undertakings, as well as the rationale for such an endeavour - to explore and develop thorough and integrated approaches in preparation for a potential discovery event in the Search for Extraterrestrial Intelligence (SETI). Officially launched at the University of St Andrews in 2022, it brings together a highly multidisciplinary international team of experts.From the outset, our rationale has been to weave together insights from diverse fields, including governance, impact strategies, analytics, and the humanities, with particular attention to the inclusion of all humanity’s cultural voices – a vital requirement to fully understand our challenge and its solutions. So, in preparation for the discovery of extraterrestrial life, the Hub will endeavour to grow readiness for complex futures by fostering a synergistic environment that encourages imaginative, methodical preparation, to stir transformative interdisciplinary and diverse engagement
Swift heavy ion and UV irradiation of natural cryolite (Na<sub>3</sub>AlF<sub>6</sub>)
No full textThe successful application of fluorides in dosimetry and optics has encouraged study of the optical properties of doped cryolite and cryolite-structure materials. However, natural cryolite (Na3AlF6) has never been described in terms of its defect structure, crucial for optical applications. To address this knowledge gap, we irradiate cryolite with 238U ions and use excitation lifetime photoluminescence to constrain the defect structures formed. Untreated, high-energy ion and UV-irradiated samples are compared in terms of their emission spectra and luminescence lifetimes. Particle irradiation introduces an orange colour to originally black, purple and white cryolite. Untreated cryolite shows blue emissions at ∼2.86 and ∼2.60 eV (435 and 475 nm) and a green emission at 2.27 eV (545 nm). After uranium ion irradiation, the green luminescence intensity is enhanced compared to blue emissions. Subsequent ultraviolet irradiation causes ∼57 % reduction in the dark blue emission intensity and 40–70 % increase in green. All luminescence lifetimes are prolonged by particle irradiation, but stay in the nanosecond range. We infer that a vacancy-related defect is produced by particle and UV irradiation and responsible for the green luminescence. Another defect, presumably electronic, is removed by particle irradiation and UV. The ∼2.27 eV green luminescence centre is interpreted as an F-centre localised on a fluorine vacancy. The blue luminescence centres are interpreted as electron-hole pairs, localised at the AlF6 octahedron normal lattice sites for ∼2.86 eV and octahedral defect sites for ∼2.60 eV. The experiment provides insight into natural defect formation processes in cryolite from the Ivittuut deposit in Southern Greenland
Changes in age-related sexual selection in a humpback whale population recovering from exploitation
No full textWhaling, one of the most extensive and prolonged global commercial hunting operations, pushed many large whales to the brink of extinction. To understand how evolutionary processes may be directly impacted by the consequences of exploitation, we assessed age-dependent population dynamics, reproductive tactics, and reproductive success of 485 male humpback whales (Megaptera novaeangliae) from a recovering breeding ground in New Caledonia. Over 19 years (2000–2018), the population age structure switched from a left-skewed, rapidly increasing low-density population toward a more evenly distributed age structure when abundance was higher in later years. Concurrent with the change in population age structure across time, there was a shift in age-related male mating tactics. Most strikingly, during years of higher abundance, the key reproductive tactics of singing and escorting were over-represented by older age categories when compared with the underlying age structure, suggesting age- and/or density-related tactic choice in males. This behavioral shift corresponded with an increase in the relative reproductive success of the oldest males during periods of higher abundance compared with lower abundance. Overall, our work suggests that at lower population densities, young males were less constrained by age-related restrictions on reproductive success. A reduction of age-related sexual selection could have acted to buffer genetic diversity loss during a time of lower abundance, when this was most critical. Integrating these changes in the pattern of sexual selection with population dynamics provides critical insights into the evolutionary consequences of exploitation and recovery in long-lived species
Emotional responses to state repression predict collective climate action intentions
No full textAs climate activism has expanded, governments have increasingly repressed disruptive but non-violent protests. Yet evidence remains mixed regarding whether repression inhibits or galvanizes activism. In this study, we examine how anticipated and experienced repression predict intentions to engage in normative (rule-conforming) and non-normative (rule- violating) collective climate action, over and above past activism and core psychological antecedents. Survey data from Extinction Rebellion UK mailing-list subscribers (N = 1,375) showed that experienced repression positively predicted non-normative action intentions, and showed a positive indirect predictive effect on non-normative action via reduced fear. Although anticipated repression was not directly associated with either action type, it had positive indirect predictive effects on both action types via anger/outrage, and on non- normative action via contempt. Conversely, it also had a negative indirect predictive effect on non-normative action through heightened fear. These findings predominantly reflect a galvanizing effect of repression on disruptive collective climate action among committed activists
Azobenzene reduction and derivatization and Al–H bond insertion with β-diketiminate gallium(I) complexes
No full textUsing backbone modification of popular β-diketiminate ligands, RDipnacnac = HC(RCNDip)2, with R = Et, iPr (Dip = 2,6-iPr2C6H3), we have prepared the new β-diketiminate gallium(I) complexes [(EtDipnacnac)Ga] 2a and [(iPrDipnacnac)Ga] 2b by salt metathesis/reduction using “GaI” in moderate to good (68%, 2a) and poor (10%, 2b) isolated yields, respectively, highlighting the influence of the ligand backbone substitution on the reaction success. The gallium(I) complexes were converted with azobenzene to the gallium(III) complexes [(RDipnacnac)Ga{(C6H5)NNPh}] 4a (R = Et) and 4b (R = iPr) with reduced former azobenzene fragments showing an N,ortho-C(H)-chelating coordination to the Ga centers. Complex 4a was further converted to its C–H-activated tautomer [(EtDipnacnac)Ga{(C6H4)N(H)NPh}] 5, and reaction with DMSO and benzaldehyde afforded [(EtDipnacnac)Ga(PhNNHPh)(CH2S(O)Me)] 6 after DMSO deprotonation and [(EtDipnacnac)Ga(PhNN(Ph)CH(Ph)O)] 7 from C–N coupling, respectively. Compound 2a also reacted with the aluminum(III) hydride complexes (NHC)AlH3 (NHC = {MeCN(iPr)}2C) and (Me3N)AlH3 to the Ga–Al-bonded complex [(EtDipnacnac)Ga(H)–Al(H2)(NHC)] 8 and [(EtDipnacnac)GaH2] 9, respectively. Gallium(I) complex 2a is a good alternative to commonly used [(MeDipnacnac)Ga] (R = Me) for the study and application of low-oxidation-state gallium complexes
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