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Departures from standard disc predictions in intensive ground-based monitoring of three AGNs
Get PDFFunding: Research by the UC Irvine group has been supported by NSF grants AST-1412693 and AST-1907290, and by grant HST-GO-15124.001-A from the Space Telescope Science Institute. DHGB acknowledges CONACYT support #319800 and of the researchers program for Mexico. JVHS and KDH acknowledge support from STFC grant ST/R000824/1. MCB gratefully acknowledges support from the NSF through grant AST-2407802. YRL acknowledges financial support from the the National Natural Science Foundation of China (12273041), from the Youth Innovation Promotion Association CAS, and from the China Manned Space Project (CMS-CSST-2025-A07). EDB, EMC, and AP acknowledge the support from MIUR grant PRIN 2017 20173ML3WW-001 and Padua University grants DOR 2022–2024; they are also funded by INAF through grant PRIN 2022 C53D23000850006. EMC acknowledges the support by the MIUR grant PRIN 2022 2022383WFT ‘SUNRISE’ (CUP C53D23000850006). DCL gratefully acknowledges support from the NSF through grant AST-1210311. MK acknowledges the support of the National Research Foundation of Korea (NRF) grant (No. RS-2024-00347548). YK acknowledges support from grant PAPIIT-UNAM IN102023.We present ground-based multiband light curves of the AGN Mrk 509, NGC 4151, and NGC 4593 obtained contemporaneously with Swift monitoring. We measure cross-correlation lags relative to Swift UVW2 (1928 Å) and test the standard prediction for disc reprocessing, which assumes a geometrically thin optically thick accretion disc where continuum interband delays follow the relation τ(λ) ∝ λ4/3. For Mrk 509 the 273-d Swift campaign gives well-defined lags that increase with wavelength as τ (λ) ∝ λ2.17±0.2, steeper than the thin-disc prediction, and the optical lags are a factor of ∼ 5 longer than expected for a simple disc-reprocessing model. This ‘disc-size discrepancy’ as well as excess lags in the u and r bands (which include the Balmer continuum and H α, respectively) suggest a mix of short lags from the disc and longer lags from nebular continuum originating in the broad-line region. The shorter Swift campaigns, 69 d on NGC 4151 and 22 d on NGC 4593, yield less well-defined shorter lags < 2 d. The NGC 4593 lags are consistent with τ(λ) ∝ λ4/3 but with uncertainties too large for a strong test. For NGC 4151 the Swift lags match τ(λ) ∝ λ4/3, with a small U-band excess, but the ground-based lags in the r, i, and z bands are significantly shorter than the B and g lags, and also shorter than expected from the thin-disc prediction. The interpretation of this unusual lag spectrum is unclear. Overall these results indicate significant diversity in the τ–λ relation across the optical/UV/NIR, which differs from the more homogeneous behaviour seen in the Swift bands.Peer reviewe
JWST-TST DREAMS : secondary atmosphere constraints for the habitable zone planet TRAPPIST-1 e
Get PDFFunding: R.J.M. is supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51513.001, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. K.B.S. performed work as part of the Consortium on Habitability and Atmospheres of M-dwarf Planets (CHAMPs) team, supported by the National Aeronautics and Space Administration (NASA) under grant Nos. 80NSSC21K0905 and 80NSSC23K1399 issued through the Interdisciplinary Consortia for Astrobiology Research (ICAR) program. D.R.L. acknowledges support from NASA under award number 80GSFC24M0006. C.I.C. acknowledges support by NASA Headquarters through an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by ORAU through a contract with NASA.The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system. Within the TRAPPIST-1 system, planet e stands out as highly likely to sustain surface liquid water if it possesses an atmosphere. Recently, we reported the first JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e, revealing significant stellar contamination, which varied between the four visits. Here, we assess the range of planetary atmospheres consistent with our transmission spectrum. We explore a wide range of atmospheric scenarios via a hierarchy of forward modeling and retrievals. We do not obtain strong evidence for or against an atmosphere. Our results weakly disfavor CO2-rich atmospheres for pressures corresponding to the surface of Venus and Mars and the cloud tops of Venus at 2σ. We exclude H2-rich atmospheres containing CO2 and CH4 in agreement with past work but find that higher mean molecular weight, N2-rich atmospheres with trace CO2 and CH4 are permitted by the data. Both a bare rock and N2-rich atmospheric scenario provide adequate fits to the data but do not fully explain all features, which may be due to either uncorrected stellar contamination or atmospheric signals. Ongoing JWST observations of TRAPPIST-1 e, exploiting consecutive transits with TRAPPIST-1 b, will offer stronger constraints via a more effective stellar contamination correction. The present work is part of the JWST Telescope Scientist Team Guaranteed Time Observations, which is performing a Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).Peer reviewe
Long-range crossed Andreev reflection in a topological insulator nanowire proximitized by a superconductor
Get PDFFunding: This project received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 741121; Y.A.) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through Germany’s Excellence Strategy–Cluster of Excellence Matter and Light for Quantum Computing (ML4Q) under grant number EXC 2004/1 - 390534769 (Y.A.) and grant number CRC 1238 - 277146847 (Subprojects A04 and B01; Y.A.). H.F.L. acknowledges support from the Georg H. Endress Foundation.Crossed Andreev reflection is a non-local transport phenomenon that creates and detects Cooper pair correlations between distant locations. It is also the basis of Cooper pair splitting to generate remote entanglement. Although crossed Andreev reflection has been extensively studied in semiconductors proximity-coupled to a superconductor, observing it in a topological insulator has been very difficult. Here we report the observation of this effect in a proximitized topological insulator nanowire. We perform local and non-local conductance spectroscopy on mesoscopic devices in which superconducting niobium and metallic contacts are connected to a bulk-insulating nanowire. In our local conductance measurements we detect a hard gap and the appearance of Andreev bound states that can reach zero bias. We also occasionally observe a negative non-local conductance when sweeping the chemical potential, providing evidence of crossed Andreev reflection. This signal is detected even over length scales much longer than the expected superconducting coherence length of either niobium or the proximitized nanowire. We suggest that this long-range effect is due to the intricate role of disorder in proximitized nanowires.Peer reviewe
The original contract in Kant : a contractarian justification
No full textThe aim of this thesis is first to provide a general framework that can account for the detailed applications of the original contract throughout Kant’s work: first, the original contract is a generative idea—one that gives rise to the general will as its effect. This generative process also grounds the legitimacy of subjection to the general will, which in turn constitutes the foundation of the republican constitution—that is, the people is the sovereign; second, the original contract is an idea of reason—regulative and binding. This idea requires sovereign to realize this republican constitution through concrete institutional forms and ways of governance. Then, the most innovative contribution of this thesis is the attempt to situate this framework within concrete legal contexts, thereby fleshing out the otherwise abstract and seemingly empty framework. This attempt remains faithful to Kant’s own contextual use of the original contract, since beyond the general discussion, Kant refers to the original contract at least three additional times in the Doctrine of Right: in relation to the security of property, the legitimacy of punishment, and the issue of revolution and the state. Each of these instances requires close, case-specific analysis and interpretation. Accordingly, this thesis unfolds in line with the above blueprint: Chapter 1 provides an introductory framework that the original contract functions as a generative and regulative idea, while the remaining three chapters correspond to Kant’s three specific mentions of the original contract in the Doctrine of Right. Chapter 2 examines how the original contract contributes to securing property rights; Chapter 3 explores how the original contract helps to establish the legitimacy of punishment; and Chapter 4 investigates how the original contract, as a regulative idea, constrains institutions and way of governance from the perspective of reformism."This thesis is funded by CSC-St Andrews PhD Scholarship and Chongqing University Boya PhD Scholarship."--Fundin
Divergent alternative mating tactics in convergent male reproductive morphs
Get PDFFunding: We gratefully acknowledge funding from the Natural Environment Research Council to N.W.B. (NE/W001616/1, NE/ T000619/1) and from the China Scholarship Council PhD scholarship to R.Z. (202004910423).Alternative reproductive phenotypes involve polymorphic behaviors and forms within sexes. Testing whether behavioral variants such as alternative tactics (eg sneaking or satellite behavior) are initially co-expressed or decoupled from morphological polymorphisms (eg weapon size or color pattern) can provide insight into the origins of reproductive diversity. In Hawaiian field crickets (Teleogryllus oceanicus), an eavesdropping parasitoid fly selected for rapid, parallel evolution of male wing mutations that reduce acoustic signals. Two of these, “flatwing” and “curly-wing”, co-occur in populations alongside ancestral “normal-wing” males that can sing. These convergent alternative morphs may both rely on satellite tactics in which nonsinging males position themselves near calling males to intercept females, rather than attracting mates directly by producing a conspicuous song. Here, we test whether flatwing and curly-wing vary in their tendencies to express satellite behavior using playback experiments with virgin, unmanipulated males simulating natural conditions. Surprisingly, flatwing males were significantly less likely to behave as satellites than normal-wing or curly-wing males. Normal-wing males with poorer body condition were more likely to behave as satellites, consistent with theory and previous findings, but the reduced-sound morphs showed no such condition dependence. Our findings suggest that morph-specific variation in the tendency to adopt satellite behavior may contribute to the maintenance of convergent male reproductive morphs; future work would benefit from testing whether such variation is driven by acoustic self-assessment. A decoupled relationship between behavioral reproductive tactics and morphological reproductive strategies may promote diversification of alternative mating morphs in nature.Peer reviewe
On the order sequence of a group
Get PDFFunding: The second author acknowledges NBHM Post Doctoral Fellowship during the preparation of this work and profusely thanks National Board of Higher Mathematics, Government of India for this funding.This paper provides a bridge between two active areas of research, the spectrum (set of element orders) and the power graph of a finite group. The order sequence of a finite group G is the list of orders of elements of the group, arranged in non-decreasing order. Order sequences of groups of order are ordered by elementwise domination, forming a partially ordered set. We prove a number of results about this poset, among them the following. • M. Amiri recently proved that the poset has a unique maximal element, corresponding to the cyclic group. We show that the product of orders in a cyclic group of order n is at least qφ(n) times as large as the product in any non-cyclic group, where q is the smallest prime divisor of n and φ is Euler's function, with a similar result for the sum. • The poset of order sequences of abelian groups of order pn is naturally isomorphic to the (well-studied) poset of partitions of n with its natural partial order. • If there exists a non-nilpotent group of order n, then there exists such a group whose order sequence is dominated by the order sequence of any nilpotent group of order n. • There is a product operation on finite ordered sequences, defined by forming all products and sorting them into non-decreasing order. The product of order sequences of groups G and H is the order sequence of a group if and only if |G| and |H| are coprime. The paper concludes with a number of open problems.Peer reviewe
Melt pond drainage through Arctic sea ice
Get PDFSea ice is a porous material that covers much of the Arctic ocean and insulates it from the atmosphere. In summer, vast tracts of the ice surface are covered by melt ponds, formed of melted snow and ice, which subsequently drain. Melt ponds reflect less solar radiation than bare or snow-covered ice and so their presence enhances ice melt. The formation and subsequent drainage of melt ponds is heavily dependent on the availability of drainage pathways in the ice interior, which are mostly formed of brine channels. Brine channels can either freeze, allowing for the retention of pond water, or melt, facilitating drainage. Understanding the physical controls on this process is crucial to understanding how melt ponds evolve and hence for representing them effectively in large-scale climate models.
In this thesis, we present a series of models for melt-pond drainage in which we treat the ice as a mushy layer and characterise the critical transition between the freezing and melting of brine channels. First, we consider a 1D radial model, where the effects of drainage through the channel are parameterised. We derive analytic formulae relating a critical channel radius controlling closure, opening and, hence, drainage to the dimensionless parameters of the system. We consider three different parameterisations for the effect of channel drainage, compare fixed- and evolving-salinity models and compare planar and axisymmetric geometries. Second, we use a more physically-representative 2D model to investigate the extent to which 2D results can be understood using our 1D model. We use our model to investigate many aspects of the summer ice evolution related to pond drainage, including desalination. Third, we extend our 2D model to consider how drainage is affected by tributary channels which often attend larger brine channels. Finally, we discuss the implications of our results and avenues for future research
Diversity and abundance of ring nucleases in type III CRISPR-Cas loci
Get PDFFunding: This work was supported by a European Research Council Advanced Grant (Grant REF 101018608 to MFW). HC acknowledges the support of the China Scholarship Council (code 202008420207).Most type III CRISPR-Cas systems facilitate immune responses against invading mobile genetic elements such as phages by generating cyclic oligoadenylates (cOAs). Downstream effectors activated by cOAs are typically non-specific proteins that induce damage to essential cellular components, thereby preventing phage epidemics. Due to these toxic effects, it is crucial that the production and concentration of cOAs remain under tight regulatory control during infection-free periods or when deactivating the immune response after clearing an infection. Type III CRISPR loci often encode enzymes known as ring nucleases (RNs) that bind and degrade specific cOAs, while some effectors are auto-deactivating. Despite the discovery of several classes of RNs, a comprehensive bioinformatic analysis of type III CRISPR-Cas loci in this context is lacking. Here, we examined 38,742 prokaryotic genomes to provide a global overview of type III CRISPR loci, focussing on the known and predicted RNs. The candidate RNs Csx16 and Csx20 are confirmed as active enzymes, joining Crn1-3. Distributions and patterns of co-occurrence of RNs and associated effectors are explored, allowing the conclusion that a sizeable majority of type III CRISPR systems regulate cOA levels by degrading the signalling molecules, which has implications for cell fate following viral infection. This article is part of the discussion meeting issue ‘The ecology and evolution of bacterial immune systems’.Peer reviewe
Bonobos respond aversively to unequal reward distributions
Get PDFFunding: E.J.C.v.L. was funded by the European Union under European Research Council Starting Grant no. 101042961—CULT_ORIGINS.Inequity aversion (IA) is the resistance to unequitable rewards given similar investments and has been postulated as an important mechanism by which human cooperation thrives. To understand the evolutionary origin of human IA and its distribution across the animal kingdom, many species have been tested on IA, with mixed results. Where chimpanzees were originally found to show IA, more recent studies showed that their IA response could be explained by social disappointment. We conducted two studies on IA in bonobos using established paradigms: a token-exchange task and the social disappointment task. Bonobos could exchange tokens for equal or less-preferred food rewards than their partners (Study 1) and were tested with humans and machines to control for social disappointment effects (Study 2). We found that bonobos responded aversively to unequal food distributions in both studies, which was reflected by more refusals to participate when disadvantaged. Notably, and contrary to chimpanzees, this effect could not be explained by social disappointment, although Study 2 was only partially consistent with an IA explanation. Overall, our findings indicate that bonobos possess the sensitivity to recognize and respond to unfair treatment, which supports the notion that IA may have co-evolved as a stabilizing mechanism for cooperation.Peer reviewe
Characterising tropical oyster reefs : invertebrate-environment associations and a newly documented reef building species
Get PDFFunding: We thank The Nature Conservancy and OzFish Unlimited for funding this research.Oyster reefs were once widespread across the global tropics but have often been excluded from global assessments of historical distributions, declines and conservation needs. Consequently, little is known about tropical oyster reefs, including ecological function, which species are reef-building, structural characterisations of remnant reefs, associated biodiversity, and whether conservation actions are needed to ensure their recovery. We compared the characteristics of newly documented tropical oyster reefs across three Australian locations to gain a foundational understanding of their ecology. At each location, structural reef traits were assessed, and associated invertebrate communities were quantified taxonomically and functionally. Location had a strong effect on invertebrate communities, with reefs in Gladstone hosting a greater abundance, and larger, invertebrates, followed by Mapoon, and then Proserpine. Most invertebrates were positively associated with the lower intertidal zone and shelly sediment - we hypothesise that heat stress, interstitial reef spaces, and the proportion of habitat edges could be explanations for these observed patterns, however, further research is needed to confirm this. Reef-building oysters identified using molecular markers at all locations were predominantly Saccostrea lineage B, a species broadly distributed across tropical Australia and the Indo-Pacific. These characterisations provide novel insights into the ecology of tropical oyster reefs and baseline information to inform appropriate conservation strategies.Peer reviewe
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