IR nebulae around bright massive stars as indicators for binary interactions

Recent studies show that more than 70% of massive stars do not evolve as effectively single stars, but as members of interacting binary systems. The evolution of these stars is thus strongly altered compared to similar but isolated objects. We investigate the occurrence of parsec-scale mid-infrared nebulae around early-type stars. If they exist over a wide range of stellar properties, one possible overarching explanation is non-conservative mass transfer in binary interactions, or stellar mergers. For ~3850 stars (all OBA stars in the Bright Star Catalogue [BSC], Be stars, BeXRBs, and Be+sdO systems), we visually inspect WISE 22 $\mu$m images. Based on nebular shape and relative position, we distinguish five categories: offset bow shocks structurally aligned with the stellar space velocity, unaligned offset bow shocks, and centered, unresolved, and not classified nebulae. In the BSC, we find that 28%, 13%, and 0.4% of all O, B, and A stars, respectively, possess associated infrared (IR) nebulae. Additionally, 34/234 Be stars, 4/72 BeXRBs, and 3/17 Be+sdO systems are associated with IR nebulae. Aligned or unaligned bow shocks result from high relative velocities between star and interstellar medium (ISM) that are dominated by the star or the ISM, respectively. About 13% of the centered nebulae could be bow shocks seen head- or tail-on. For the rest, the data disfavor explanations as remains of parental disks, supernova remnants of a previous companion, and dust production in stellar winds. The existence of centered nebulae also at high Galactic latitudes strongly limits the global risk of coincidental alignments with condensations in the ISM. Mass loss during binary evolution seems a viable mechanism for the formation of at least some of these nebulae. In total, about 29% of the IR nebulae (2% of all OBA stars in the BSC) may find their explanation in the context of binary evolution.Comment: 21 pages, 5 tables, 6 figures, accepted for publication in A&

Eye Contact and Social Anxiety Disorder

The psychoevolutionary theory of social anxiety disorder (SAD) predicts that individuals with SAD will avoid eye contact to communicate submissiveness. However, direct testing of gaze avoidance in individuals with higher social anxiety through behavioral observation or measurement has produced mixed findings. The goals of this dissertation are to test one of the components of the psychoevolutionary theory, namely, that gaze avoidance is employed by people with SAD, as well as to test whether positive affect may play a role in regulating gaze avoidance. Specifically, based on prior research supporting the role of positive affect in regulating exploratory behavior, I hypothesized that positive affect would mediate the relationship between diagnosis and eye contact. A sample of community participants who either met criteria for generalized social anxiety disorder (GSADs; n = 65) or showed no signs of the disorder (NOSADs; n = 50) completed conversation tasks with a friend in which they took turns discussing a personal characteristic to change (social support conversations). In between the two social support conversations, participants also completed a conversation in which they discussed something that the primary participant wanted the friend to change (conflict conversation). The conversations were recorded and coded for amount of eye contact. Diagnosis significantly predicted eye contact in two out of the three conversations such that participants with GSAD made less eye contact than participants with NOSAD, ps \u3c .012. This effect was especially apparent for GSAD participants who were randomly assigned to discuss something they would like to change after the conflict conversation. Against expectation, positive affect did not significantly mediate the relationship between diagnosis and eye contact, p = .188. The current study’s finding of higher gaze avoidance in individuals with GSAD is the first behavioral observation study to find such a difference in a diagnosed sample. It appears that the effect was strongest during the conflict conversation and the second social support conversation. I theorize that gaze avoidance increased once fears of rejection were activated and that this influence continued into the final conversation, particularly for GSAD participants assigned to discuss a personal characteristic to change in this conversation

Connection and disconnection as predictors of mental health and wellbeing

Despite the established literature on connection to others, and burgeoning research on self-connection, researchers have paid little attention to the equivalent experiences of disconnection that people can experience in their everyday lives. The current research examined connection and disconnection from oneself and others. Specifically, across two studies, participants listed up to twenty words or phrases that they experienced related to each form of (dis)connection. Study 1 focused on how these affected participants’ mental health (i.e. anxiety and depression), while study 2 examined positive forms of wellbeing (i.e., flourishing and life satisfaction). Results suggested that increased mental health was most strongly related to a greater experience of connection to others. Flourishing also increased as one’s experience of other-connection increased. By contrast, poorer wellbeing was related to a greater experience of disconnection from others. Finally, life satisfaction decreased when participants experienced greater self-disconnection. In all, these findings provide an initial test of and support for the continued examination of various forms of both connection and disconnection

Towards representing thermokarst processes in land surface models

Large-scale Earth system and land surface models often lack an adequate representation of subgrid-scale processes in permafrost landscapes. Small-scale processes such as thermokarst formation might, however, considerably impact the energy and carbon budgets in way which is not resolved within large-scale models. Since a spatially high-resolved simulation of such processes is not feasible, novel techniques for up-scaling subgrid processes are demanded. Within this work a one-dimensional model of the ground thermal regime of land surfaces, CryoGrid 3, is employed to conceptually represent small-scale features of permafrost landscapes, particularly those related to thermokarst. For example, the model has been shown to adequately describe the degradation of permafrost underneath waterbodies in a warming climate. Using tiling approaches such point-wise realizations can be up-scaled in a statistical way in order to represent larger land surface units. The model development is closely linked to field campaigns to the Lena River Delta in Siberia which offers very diverse land surface features such as polygonal tundra and thermos-erosional valleys. These features are related to the region’s diverse soil stratigraphies, in particular the occurrence of ice-rich ground. Combining field measurements with modelling ultimately allows an improvement in the qualitative and quantitative understanding of the typical geomorphological processes in permafrost landscapes and their representation in large-scale models

Plankton in an acidifying ocean : from individual responses to community changes and the potential of adaptation

Ocean acidification has strong direct (decreased seawater pH) and indirect (altered food regimes) effects on the performance of marine organisms, their trophic interactions and, consequently, whole ecosystems. Therefore, the aim of this thesis was to investigate potential direct and indirect effects of elevated pCO2 on marine planktonic organisms and their community composition, with a main emphasise on copepods and their adaptational potential. The development of high throughput sequencing technologies has provided scientists with an efficient tool to assess the biodiversity of marine communities, particularly with the recent advances in community barcoding technologies using universal primers. Another aim of this thesis was therefore, to test whether community barcoding is suitable for the assessment of marine planktonic communities, and allows the detection of compositional changes, which would probably remain unnoticed using classical morphological approaches

Borehole temperature reconstructions reveal differences in past surface temperature trends for the permafrost in the Laptev Sea region, Russian Arctic

In central Siberia, past temperature changes have been driving permafrost warming in a region with large organic carbon reserves stored in the perennially frozen ground. However, local arctic temperature histories in the ice-rich permafrost areas of the remote Russian Arctic are sparsely known or based on proxy data with potential seasonal biases and underrepresented in circum-Arctic reconstructions. This study employed two inversion schemes (particle swarm optimization and a least-square method) to reconstruct temperature histories for the past 200–300 years in the Laptev Sea region from two permafrost borehole temperature records. These data were evaluated against larger scale reconstructions from the region. Distinct differences between the western Laptev Sea and the Lena Delta sites were recognized, such as a transition to warmer temperatures a century later in the western Laptev Sea as well as a peak in warming 3 decades later. The local permafrost surface temperature history at Sardakh Island in the Lena Delta was reminiscent of the circum-Arctic regional average trends. However, Mamontov Klyk in the western Laptev Sea was consistent to Arctic trends only in the most recent decade and was more similar to northern hemispheric mean trends. Both sites are consistent with a rapid recent warming that is of synoptic scale. Different environmental influences such as synoptic atmospheric circulation and sea ice may be responsible for differences between the sites. The shallow permafrost boreholes provide missing well-resolved short-scale temperature information in the coastal permafrost tundra of the Arctic. As local differences from circum-Arctic reconstructions, such as later warming and higher warming magnitude, were shown to exist in this region, our results provide a basis for local surface temperature record parameterization of climate models, and in particular of permafrost models