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The substellar population in Corona Australis
No full textFunding: KM and AdB-dV acknowledges support from the Fundação para a Ciência e a Tecnologia (FCT) through the CEEC-individual contract 2022.03809.CEECIND (DOI 10.54499/2022.03809.CEECIND/CP1722/CT0001), and the project 2023.01915.BD (DOI 10.54499/2023.01915.BD). KM also acknowledges support from the Scientific Visitor Programme of the European Southern Observatory (ESO) in Chile. BD and AS acknowledge support from the UKRI Science and Technology Facilities Council through grant ST/Y001419/1/. VA-A acknowledges support from the INAF grant 1.05.12.05.03.Context . The substellar initial mass function (IMF) and the formation mechanisms of brown dwarfs (BDs) remain key open questions in star formation theory. A detailed census and characterization of the IMF in a large number of star-forming regions are essential for constraining these processes. Aims . We identify and spectroscopically confirm very low-mass members of the Corona Australis (CrA) star-forming region to refine its substellar census, determine its low-mass IMF, and compare it to other clusters. Methods . Using deep I-band photometry from Suprime-Cam/Subaru and data from the VISTA Hemisphere Survey (VHS), we identified low-mass BD candidates in CrA. We subsequently conducted near-infrared spectroscopic follow-up of 173 of these candidates with KMOS/VLT, and we also obtained optical spectra for eight kinematic candidate members identified via Gaia data using FLOYDS/LCO. Results . The kinematic candidates observed with optical spectroscopy are confirmed as low-mass stellar members with spectral types M1 to M5. In contrast, all 173 BD candidates observed with KMOS are identified as contaminants. Although the follow-up yielded no new substellar members, it places strong constraints on the number of undetected substellar objects in the region. Combined with literature data, this enables us to derive the substellar IMF, which is consistent with a single power-law slope of α = 0.95 ± 0.06 in the range 0.01–1 M⊙ or α = 0.33 ± 0.19 in the range 0.01–0.1 M⊙. The star-to-BD ratio in CrA is ∼2. We also provide updated IMFs and star-to-BD ratios for Lupus 3 and Cha I from the SONYC survey, reflecting revised distances from Gaia. Finally, we estimate surface densities and median far-ultraviolet fluxes for six star-forming regions and clusters to characterize their environments and compare their substellar populations as a function of environmental properties. Conclusions . The IMF and star-to-BD ratio show no clear dependence on stellar density or ionizing flux from the massive stars. A combined effect in which one factor enhances and the other suppresses BD formation also appears unlikely.Peer reviewe
A search for transit-timing variations in the transiting hot-Jupiter systems HIP 65, NGTS-6, NGTS-10, and WASP-173
No full textFunding: JS acknowledges support from STFC under grant no. ST/Y002563/1. FA, MA, and UGJ acknowledge funding from the Novo Nordisk Foundation Interdisciplinary Synergy Programme grant no. NNF19OC0057374. VB and PR are supported by PRIN 2022 CUP D53D23002590006. RFJ acknowledges the support provided by the GEMINI/ANID project under grant no. 32240028, by ANID’s Millennium Science Initiative through grant ICN12_009, awarded to the Millennium Institute of Astrophysics (MAS), and by ANID’s Basal project FB210003. EK is supported by the National Research Foundation of Korea 2021M3F7A1082056. LM acknowledges the financial contribution from PRIN MUR 2022 project 2022J4H55R.Hot 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.Peer reviewe
Longest common subsequence with gap constraints
No full textFunding: The work on the current article was partly supported by the German Research Foundation (DFG) [project numbers 389613931 (research grant); 466789228 (Heisenberg grant)]. Open Access funding enabled and organized by Projekt DEAL.We consider the longest common subsequence problem in the context of subsequences with gap constraints. In particular, following Day et al. (2022), we consider the setting when the distance (i. e., the gap) between two consecutive symbols of the subsequence has to be between a lower and an upper bound (which may depend on the position of those symbols in the subsequence or on the symbols bordering the gap) as well as the case where the entire subsequence is found in a bounded range (defined by a single upper bound), considered by Kosche et al. (2022). In all these cases, we present efficient algorithms for determining the length of the longest common constrained subsequence between two given strings, and discuss lower bounds for the respective problems.Peer reviewe
Variability in SSTc2d J163134.1-240100, a brown dwarf with quasi-spherical mass loss
No full textFunding: AS acknowledges support from the UKRI Science and Technology Facilities Council through grant ST/Y001419/1/. KM acknowledges support from the Fundação para a Ciência e a Tecnologia (FCT) through the CEEC individual contract 2022.03809.CEECIND and research grants UIDB/04434/2020 and UIDP/04434/2020.We report on a search for variability in the young brown dwarf SST1624 (∼M7 spectral type, M ∼ 0.05 M⊙), previously found to feature an expanding gaseous shell and to undergo quasi-spherical mass loss. We find no variability on timescales of 1-6 hours. Specifically, on these timescales, we rule out the presence of a period with amplitude > 1%. A photometric period in that range would have been evidence for either pulsation powered by Deuterium burning or rotation near breakup. However, we see a 3% decrease in the K-band magnitude between two consecutive observing nights (a 10 σ result). There is also clear evidence for variations in the WISE lightcurves at 3.6 and 4.5 µm on timescales of days, with a tentative period of about 6 d (with a plausible range between 3 and 7 d). The best explanation for the variations over days is rotational modulation due to spots. These results disfavour centrifugal winds driven by fast rotation as mechanism for the mass loss, which, in turn, makes the alternative scenario – a thermal pulse due to Deuterium burning – more plausible.Peer reviewe
Chimpanzees’ working memory is not affected by the presence and activity of zoo visitors
No full textFunding: Leverhulme Trust (ECF-2023-573); Templeton World Charity Foundation (TWCF-2021-20648).Cognitive research in non-human primates is increasingly conducted in zoos, where zoo visitors are likely to be present and observe the testing sessions. Previous zoo research has shown that such presence can modulate cognitive performance in monkeys, but similar investigations on great apes are still lacking. Here, we investigated the influence of the presence and activity level of zoo visitors on eight chimpanzees (Pan troglodytes) while they completed a working memory task with various difficulty levels. We also recorded whether their conspecifics were present or not in the testing area, and their approximate physical distance. We found that the presence and activity level of the visitors had no effect on chimpanzees’ working memory, regardless of the cognitive demands of the task. Similarly, the presence of conspecifics and how far they were from the individual being tested was not found to significantly influence performance either. These non-significant effects were supported by Bayesian analyses giving support for the null hypotheses. These results suggest that zoo-living chimpanzees are not distracted by visitors when completing a cognitive task. We suggest new directions to further explore social presence effects in great apes.Peer reviewe
Behavioral responses of goose-beaked whales (Ziphius cavirostris) to simulated military sonar
No full textFunding: US Fleet Forces Command Marine Species Monitoring Program; Naval Facilities Engineering Command Southeast, Grant/Award Numbers: N62470-10-D-3011, N62470-15-D-8006.We report direct measurements of changes in diving and movement behavior for 53 goose-beaked whales (Ziphius cavirostris) in relation to experimentally controlled mid-frequency (3–4 kHz) active sonar (MFAS) signals. These signals simulate powerful Navy sources that have been associated with multiple mortal stranding events for this species. We deployed a multi-scale combination of tags to monitor individual whales, including 50 long-duration (weeks), coarse-resolution satellite-transmitting tags and 3 short-duration (hours), high-resolution archival depth, orientation, and acoustic tags. We evaluated behavioral responses during 13 experimental trials (9 MFAS; 4 no-MFAS controls), resulting in 72 exposure events; some individuals were exposed in multiple trials. Whales were exposed at known and modeled horizontal ranges from ~2 to >200 km and from below ambient noise levels to received levels (RLs) up to ~142 dB re: 1μPa (root-mean-square [RMS]). We investigated changes in diving and movement behavior separately, with a suite of metrics, descriptive evaluations, and statistical tests. We observed similar patterns and probabilities of behavioral changes for control trials and the lowest RL conditions (<100 dB). Above 100 dB RLs, increasingly prevalent and consistent responses occurred, including extended deep dives, prolonged periods between deep dives, directed spatial movement away from the source, and cessation of echolocation. Aspects of these cryptic responses typically persisted for hours following exposure but did not result in broad-scale habitat abandonment. Our study builds upon experimental and observational studies conducted on sonar testing ranges and expands our understanding of the response of this species to MFAS in a region where operational sonar use occurs far less commonly than on Navy testing ranges. These data are directly applicable in the conservation and effective management of this sensitive, protected species.Peer reviewe
Syntheses, characterization, Hirshfeld analysis, and antioxidant activity of Co(II) and Ag(I) complexes based on oxadiazole ligand
No full textFunding: This work was supported by “the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research, King Faisal University, for financial support under the annual funding track [KFU254518]”.The antioxidant activities of [Co(L)2Cl2]·0.25H2O and [Ag2(L)2]n(ClO4)2n complexes with 2-(5-(pyridin-2-yl)-1,2,4-oxadiazol-3-yl)aniline ( L ) are reported to explore their molecular, supramolecular and antioxidant characteristics. Their molecular structures were examined using FTIR and other spectroscopic techniques, and single crystal X-ray diffraction. The Co(II) complex shows a discrete octahedral structure, while the Ag(I) complex is a 1D coordination polymer. Both complexes were evaluated for their antioxidant activities utilizing 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitric oxide, and superoxide anion scavenging assays. The Ag(I) complex consistently demonstrated the highest antioxidant activity across all the three assays (DPPH; IC50 = 52.07 ± 1.22 µM), (nitric oxide; IC50 = 29.14 ± 1.04 µM), and (superoxide; IC50 = 8.74 ± 1.85 µM), particularly excelling in superoxide anion scavenging. The Co(II) complex also showed enhanced activity compared to L especially in the nitric oxide (IC50= 24.70±1.65 µM), and superoxide anion assays (IC50 = 20.78 ± 2.85 µM). These findings reveal how metal-ligand systems can be tuned to enhance antioxidant efficiency, providing insight for the design of bioactive metal complexes as antioxidants.Peer reviewe
A2A adenosine receptor agonists with last-step enzymatic 18F-labelling potential (fluorinase) for positron emission tomography (PET)
No full textFunding: This study was supported by Engineering and Physical Sciences Research Council (EP/X038904/1).New agonists of the A2A receptor are reported with 18F-labelling potential for positron emission tomography (PET). These were designed by exploiting common binding interactions of substrates for the fluorinase and agonists of the human A2A adenosine receptor. Target compounds were structurally inspired by the selective A2A receptor agonist CGS21680 . The new agonists were synthesised and their affinities for the human A2A receptor evaluated through radioligand displacement assays. 18F-Labelled analogues of the new agonists for potential PET radiotracer applications are now accessible through last-step radiosynthesis using the fluorinase enzyme and [18F]fluoride.Peer reviewe
Raman shifting of XeCl laser radiation
Get PDFA XeCl excimer laser system whose output characteristics are suitable for stimulated Raman wavelength shifting, has been developed and used in single-pass conversion experiments in CH₄ and H₂. The overall system, comprising the laser, Raman focusing optics and Raman cell, has been designed with simplicity and system compactness in mind, suitable for a transportable lidar application.
The XeCl laser is a fast discharge pumped device, driven by a C C transfer circuit with a N₂ filled spark gap switch. Various ultraviolet preionisation schemes and cavity component arrangements, employed during the laser development, are described and compared. A general overview of the basic spark preionisation techniques commonly used in rare gas halide lasers is also presented. Over the course of the development, the available laser output power has been increased by a factor of 100, by methods described. Laser output characteristics relevant to stimulated Raman scattering (SRS), are the emission wavelength (308 nm), the output pulse energy (>100 mJ), pulse duration (~6.5 ns FWHM), peak pulse power (>10⁷ W) and the output beam divergence (4 × 15 mrad). The design for a new laser, using a low inductance cavity geometry and an ‘automatic-integral’ preionisation scheme is described.
The problems of poor laser beam quality and focusability which are inherent in rare gas halide lasers, are overcome by the use of an unstable optical resonator. Experiments with a range of ‘continuously coupled’ unstable resonators, in which the laser output coupler is a simple planoconvex lens, are reported. They show that pulse duration, energy and beam divergence are systematically reduced as the round trip resonator magnification M is increased, with the result that the focal spot area can be up to 2000 times smaller than obtainable with conventional stable cavity optics. Furthermore, these output characteristics are shown to depend not simply on the overall value of M, but also on the individual one way magnifications M₁₂ and M₂₁ in the resonator, between mirrors 1 and 2. The dependence has produced significant experimental differences in resonators with very similar values of M. This new observation is attributed, in part, to the shortness of the laser pulse duration in this device.
Experiments have been performed in high pressure CH₄ and H₂ to find the pumping geometries necessary to achieve SRS. The most unstable of the range of resonators studied, having the least divergent output and the highest beam quality, is shown to be the best configuration for the application. In addition, it is found that pump focal power densities greater than 10¹⁰ W/cm² do not automatically guarantee coherent scattering if they have been produced as a result of tight focusing, and that a relatively long Raman focusing length (≥50 cm) is a more fundamental experimental requirement.
Raman scattering in CH₄ has generated output lines from the first anti Stokes (AS₁) to the fourth Stokes (S₄) order, at wavelengths of 283nm, 338nm, 375nm, 421nm and 480nm. The higher Raman gain in H₂ has produced a wider range of Raman shifted orders, extending from the ultraviolet into the infrared, at wavelengths given by 245nm (AS₂), 273nm, 353nm, 414nm, 500nm, 631nm and 855nm (S₅). The relative abundance of the competing SRS and four wave mixing processes in the Raman cell, which determine the range and distribution of energy within the Raman spectrum, has been varied by reducing the feasibility of angular phase matching in the medium. Increasing the pump beam focal length and the Raman cell pressure has enabled the overall energy conversion efficiency into the S₁ order to be optimised at ~29% in H₂, for a corresponding pump depletion of ~32%. For the most intense region of the XeCl laser pump beam only, these values were measured to be 56% and 60% respectively
Dexterous destriers : the literal and figurative horse as educator in Early Modern France, 1500-1625
No full textThis thesis assesses the role of the horse and horsemanship in the education of the nobility in sixteenth- and early seventeenth-century France through a parallel examination of didactic texts on the topic of horsemanship and its literary representations in contemporaneous canonical texts. Where most studies to date have focused either on actual practice or literary representations, this thesis brings these spheres into dialogue to reveal the extent to which they evolved in tandem, ultimately arguing that this interaction led to horsemanship being viewed as a practice with both physical and intellectual benefits. Chapter 1 focusses on childhood education, situating horsemanship as a fundamental part of noble education through the example of Rabelais’s Gargantua and his wooden horses, where Rabelais portrays horsemanship as a means of exploring physical and linguistic creativity. Chapter 2 transitions to adolescence as it examines Ronsard’s poetry in praise of his riding master, François de Carnavalet, in which the poet draws on the myth of Pegasus and Bellerophon to establish a connection between horsemanship and the poetic arts. Chapter 3 assesses how the same mythical pairing became a literal emblem of equestrian print culture as the printer’s mark of Charles Perier, an image which fuses a literary significance with the physical practice of horsemanship. Chapter 4 examines how the emergent genre of didactic riding manuals, specifically those of Federico Grisone, Salomon de La Broue and Antoine de Pluvinel, employs a narrative approach to riding that solidifies the development of horse and rider as a partnership and encourages self-improvement through discipline. Finally, Chapter 5 reflects on a lifetime of practice through the example of Montaigne, assessing his praise of horsemanship as an aid to improving physical mobility and proposing a kinesic reading of the Essais to explore his conception of riding as an aid to cognition and literary creation
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