Getting informed in a risky world

Predation ultimately affects the fitness of individuals. In nest building species like birds, the predation of dependent offspring is the most important source of reproductive failure, favouring the selection of parental adaptations to enhance offspring survival. However, environmental heterogeneity hampers individuals of having an accurate knowledge of perceived current risks. Consequently, individuals have to acquire information about their environment to optimise their nest site selection, antipredation responses, and parental investment decisions. Thus, individual reproductive decisions should be dynamic and depend on the availability and reliability of environmental information, as well as a species life-history strategy. This thesis examines the effect of individual risk assessment and antipredation strategies on parental investment in brown thornbills Acantiza pusilla, as well as the reliability of landscape features in predicting nest predation patterns in northern wheatears Oenanthe oenanthe. During incubation brown thornbill females used dynamic risk assessment to evaluate the risk different predators posed. Decreased environmental information via greater nest concealment increased female vigilance, with greater vigilance tending to increase brood survival. Within the breeding season, parental risk sensitivity increased and decreased for consecutive breeding attempts. Feeding rates in the presence of a predator of adults and a brood predator decreased, while risk taking increased by approaching predators more closely. When facing predators, brown thornbills used two alarm vocalisations, with alarm call rate denoting the degree of danger a predator posed to the adult birds. Parental alarm calls only silenced nesting begging over short time periods. In northern wheatears, predation increased for birds breeding closer to agricultural field and woodland habitat interfaces. This was only the case during incubation but not during nestling feeding, indicating that seasonal changes in ground vegetation structure and a change in predator composition can result in highly variable predation patterns. Overall, this thesis shows that antipredation responses and predation patterns can be dynamic and change within time and space, and thus influence the breeding success of bird species in general

Magnetic White Dwarfs from the SDSS II. The Second and Third Data Releases

Fifty-two magnetic white dwarfs have been identified in spectroscopic observations from the Sloan Digital Sky Survey (SDSS) obtained between mid-2002 and the end of 2004, including Data Releases 2 and 3. Though not as numerous nor as diverse as the discoveries from the first Data Release, the collection exhibits polar field strengths ranging from 1.5MG to ~1000MG, and includes two new unusual atomic DQA examples, a molecular DQ, and five stars that show hydrogen in fields above 500MG. The highest-field example, SDSSJ2346+3853, may be the most strongly magnetic white dwarf yet discovered. Analysis of the photometric data indicates that the magnetic sample spans the same temperature range as for nonmagnetic white dwarfs from the SDSS, and support is found for previous claims that magnetic white dwarfs tend to have larger masses than their nonmagnetic counterparts. A glaring exception to this trend is the apparently low-gravity object SDSSJ0933+1022, which may have a history involving a close binary companion.Comment: 20 pages, 4 figures Accepted for publication in the Astronomical Journa

Flares, Rotation, Activity Cycles and a Magnetic Star-Planet Interaction Hypothesis for the Far Ultraviolet Emission of GJ 436

Variability in the far ultraviolet (FUV) emission produced by stellar activity affects photochemistry and heating in orbiting planetary atmospheres. We present a comprehensive analysis of the FUV variability of GJ 436, a field-age, M2.5V star ($P_\mathrm{rot}\approx44$ d) orbited by a warm, Neptune-size planet ($M \approx 25\ M_\oplus$, $R \approx 4.1\ R_\oplus$, $P_\mathrm{orb}\approx2.6$ d). Observations at three epochs from 2012 to 2018 span nearly a full activity cycle, sample two rotations of the star and two orbital periods of the planet, and reveal a multitude of brief flares. Over 2012-2018, the star's $7.75\pm0.10$ yr activity cycle produced the largest observed variations, $38\pm3$% in the summed flux of major FUV emission lines. In 2018, variability due to rotation was $8\pm2$%. An additional $11\pm1$% scatter at 10 min cadence, treated as white noise in fits, likely has both instrumental and astrophysical origins. Flares increased time-averaged emission by 15% over the 0.88 d of cumulative exposure, peaking as high as 25$\times$ quiescence. We interpret these flare values as lower limits given that flares too weak or too infrequent to have been observed likely exist. GJ 436's flare frequency distribution (FFD) at FUV wavelengths is unusual compared to other field-age M dwarfs, exhibiting a statistically-significant dearth of high energy ($>4\times 10^{28}$ erg) events that we hypothesize to be the result of a magnetic star-planet interaction (SPI) triggering premature flares. If an SPI is present, GJ 436 b's magnetic field strength must be $\lesssim$100 G to explain the statistically insignificant increase in orbit-phased FUV emission.Comment: 18 pages, 9 figures, accepted to the Astronomical Journa

Sub-types of insomnia in adolescents: insights from a quantitative/ molecular twin study

Background: Insomnia with short sleep duration has been postulated as more severe than that accompanied by normal/long sleep length. While the short duration subtype is considered to have greater genetic influence than the other subtype, no studies have addressed this question. This study aimed to compare these subtypes in terms of: 1) the heritability of insomnia symptoms; 2) polygenic scores (PGS) for insomnia symptoms and sleep duration; 3) the associations between insomnia symptoms and a wide variety of traits/disorders. Methods: The sample comprised 4,000 pairs of twins aged 16 from the Twins Early Development Study. Twin models were fitted to estimate the heritability of insomnia in both groups. PGS were calculated for self-reported insomnia and sleep duration and compared among participants with short and normal/long sleep duration. Results: Heritability was not significantly different in the short sleep duration group (A=0.13 [95%CI=0.01, 0.32]) and the normal/long sleep duration group (A=0.35 [95%CI=0.29, 0.40]). Shared environmental factors accounted for a substantial proportion of the variance in the short sleep duration group (C=0.19 [95%CI= 0.05, 0.32]) but not in the normal/long sleep duration group (C=0.00 [95%CI=0.00, 0.04]). PGS did not differ significantly between groups although results were in the direction expected by the theory. Our results also showed that insomnia with short (as compared to normal/long) sleep duration had a stronger association with anxiety and depression (p<.05) - although not once adjusting for multiple testing. Conclusions: We found mixed results in relation to the expected differences between the insomnia subtypes in adolescents. Future research needs to further establish cut-offs for ‘short’ sleep at different developmental stages and employ objective measures of sleep

Us and the virus: understanding the COVID-19 pandemic through a social psychological lens

From a social psychological perspective, the COVID-19 pandemic and its associated protective measures affected individuals’ social relations and their basic psychological needs. We aim to identify sources of need frustration (stressors) and possibilities to bolster need satisfaction (buffers). Particularly, we highlight emerging empirical research in areas in which social psychological theorizing can contribute to our understanding of the pandemic’s social consequences: Loneliness, social networks, role conflicts, social identity, compliance, trust, reactance, and conspiracy beliefs. We highlight directions for future social psychological research as the pandemic continues

A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

We present a catalog of 9316 spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey Data Release 4. We have selected the stars through photometric cuts and spectroscopic modeling, backed up by a set of visual inspections. Roughly 6000 of the stars are new discoveries, roughly doubling the number of spectroscopically confirmed white dwarfs. We analyze the stars by performing temperature and surface gravity fits to grids of pure hydrogen and helium atmospheres. Among the rare outliers are a set of presumed helium-core DA white dwarfs with estimated masses below 0.3 Msun, including two candidates that may be the lowest masses yet found. We also present a list of 928 hot subdwarfs.Comment: Accepted by the Astrophysical Journal Supplements, 25 pages, 24 figures, LaTeX. The electronic catalog, as well as diagnostic figures and links to the spectra, is available at http://das.sdss.org/wdcat/dr4

Probing UV-Sensitive Pathways for CN and HCN Formation in Protoplanetary Disks with the Hubble Space Telescope

The UV radiation field is a critical regulator of gas-phase chemistry in surface layers of disks around young stars. In an effort to understand the relationship between photocatalyzing UV radiation fields and gas emission observed at infrared and sub-mm wavelengths, we present an analysis of new and archival HST, Spitzer, ALMA, IRAM, and SMA data for five targets in the Lupus cloud complex and 14 systems in Taurus-Auriga. The HST spectra were used to measure LyA and FUV continuum fluxes reaching the disk surface, which are responsible for dissociating relevant molecular species (e.g. HCN, N2). Semi-forbidden C II] 2325 and UV-fluorescent H2 emission were also measured to constrain inner disk populations of C+ and vibrationally excited H2. We find a significant positive correlation between 14 micron HCN emission and fluxes from the FUV continuum and C II] 2325, consistent with model predictions requiring N2 photodissociation and carbon ionization to trigger the main CN/HCN formation pathways. We also report significant negative correlations between sub-mm CN emission and both C II] and FUV continuum fluxes, implying that CN is also more readily dissociated in disks with stronger FUV irradiation. No clear relationships are detected between either CN or HCN and LyA or UV-H2 emission. This is attributed to the spatial stratification of the various molecular species, which span several vertical layers and radii across the inner and outer disk. We expect that future observations with JWST will build on this work by enabling more sensitive IR surveys than were possible with Spitzer.Comment: Accepted for publication in A