Magnetically induced termination of giant planet formation

Here a physical model for terminating giant planet formation is outlined and compared to other methods of late-stage giant planet formation. As has been pointed out before, gas accreting into a gap and onto the planet will encounter the planetary dynamo-generated magnetic field. The planetary magnetic field produces an effective cross section through which gas is accreted. Gas outside this cross section is recycled into the protoplanetary disk, hence only a fraction of mass that is accreted into the gap remains bound to the planet. This cross section inversely scales with the planetary mass, which naturally leads to stalled planetary growth late in the formation process. We show that this method naturally leads to Jupiter-mass planets and does not invoke any artificial truncation of gas accretion, as has been done in some previous population synthesis models. The mass accretion rate depends on the radius of the growing planet after the gap has opened, and we show that so-called hot-start planets tend to become more massive than cold-start planets. When this result is combined with population synthesis models, it might show observable signatures of cold-start versus hot-start planets in the exoplanet population.Comment: 8 pages, 3 figures, accepted for publication in Astronomy & Astrophysic

The Complex Demographic History and Evolutionary Origin of the Western Honey Bee, Apis Mellifera.

The western honey bee, Apis mellifera, provides critical pollination services to agricultural crops worldwide. However, despite substantial interest and prior investigation, the early evolution and subsequent diversification of this important pollinator remain uncertain. The primary hypotheses place the origin of A. mellifera in either Asia or Africa, with subsequent radiations proceeding from one of these regions. Here, we use two publicly available whole-genome data sets plus newly sequenced genomes and apply multiple population genetic analysis methods to investigate the patterns of ancestry and admixture in native honey bee populations from Europe, Africa, and the Middle East. The combination of these data sets is critical to the analyses, as each contributes samples from geographic locations lacking in the other, thereby producing the most complete set of honey bee populations available to date. We find evidence supporting an origin of A. mellifera in the Middle East or North Eastern Africa, with the A and Y lineages representing the earliest branching lineages. This finding has similarities with multiple contradictory hypotheses and represents a disentangling of genetic relationships, geographic proximity, and secondary contact to produce a more accurate picture of the origins of A. mellifera. We also investigate how previous studies came to their various conclusions based on incomplete sampling of populations, and illustrate the importance of complete sampling in understanding evolutionary processes. These results provide fundamental knowledge about genetic diversity within Old World honey bee populations and offer insight into the complex history of an important pollinator

The lived experiences of adolescents with autism spectrum disorder: a personal constructivist and family systems approach

Individuals with Autism Spectrum Disorder (ASD) experience persistent and significant social communicative impairments, as well as restricted and repetitive behaviours and/or interests. There is currently a dearth of literature investigating the experiences of adolescents with ASD, despite research findings indicating adolescence is a particularly challenging period for these individuals. In addition to the significant influence of ASD on the individual, having a family member with the condition can have chronic and pervasive effects on individual family members and the family unit as a whole. However, research investigating the experiences of families who have an adolescent member with ASD is scarce. The overall aim of this thesis is to investigate the lived experiences of adolescents with ASD and their families. More specifically, the studies explore the positive and challenging aspects of adolescence; the coping strategies used by family members; and the distribution of roles and responsibilities within the family and their impact on individual and family functioning. A qualitative approach was used to interview multiple family members, including adolescents with ASD, mothers, fathers, and adolescent siblings. The thesis is informed by Family Systems and Personal Constructivist frameworks. Chapters 2 and 3 examine these frameworks in relation to understanding adolescents with ASD and their families. Conceptual and methodological components of these frameworks were used to guide subsequent qualitative investigations, which are presented in Chapters 4-7. More specifically, Chapters 4 and 5 focus on the experiences of adolescent boys and girls with ASD, respectively; Chapter 6 investigates the experiences of parents; and Chapter 7 identifies issues pertinent to adolescent neurotypically developing siblings. The findings of these qualitative investigations highlight a range of adolescent-specific issues, covering physical, cognitive, emotional, social, and sexual domains, which may provide guidance to clinicians, researchers, and family members supporting adolescents with ASD and their families. Chapter 8 utilises Personal Constructivist methodology to investigate the dependency patterns of adolescents with ASD. Findings indicate that the adolescents had various ways of dispersing their dependencies amongst resources and differed in the types of support most utilised. Additionally, by including family members, the study was able to investigate family awareness of the adolescents’ preferences. The findings presented in this chapter offer a novel approach to understanding the experiences of families living with ASD, given the adoption of the combined Family Systems and Personal Constructivist framework. The thesis concludes with a synthesis of the key findings of the conceptual and qualitative investigations. It considers research limitations of the studies conducted and discusses implications for future research and clinical practice. Overall, the thesis findings address an important gap in literature and have the potential to make significant contributions to the field of clinical psychology by directly informing clinical interventions for adolescents with ASD and their families

The Adaptive Significance of Natural Genetic Variation in the DNA Damage Response of Drosophila melanogaster.

Despite decades of work, our understanding of the distribution of fitness effects of segregating genetic variants in natural populations remains largely incomplete. One form of selection that can maintain genetic variation is spatially varying selection, such as that leading to latitudinal clines. While the introduction of population genomic approaches to understanding spatially varying selection has generated much excitement, little successful effort has been devoted to moving beyond genome scans for selection to experimental analysis of the relevant biology and the development of experimentally motivated hypotheses regarding the agents of selection; it remains an interesting question as to whether the vast majority of population genomic work will lead to satisfying biological insights. Here, motivated by population genomic results, we investigate how spatially varying selection in the genetic model system, Drosophila melanogaster, has led to genetic differences between populations in several components of the DNA damage response. UVB incidence, which is negatively correlated with latitude, is an important agent of DNA damage. We show that sensitivity of early embryos to UVB exposure is strongly correlated with latitude such that low latitude populations show much lower sensitivity to UVB. We then show that lines with lower embryo UVB sensitivity also exhibit increased capacity for repair of damaged sperm DNA by the oocyte. A comparison of the early embryo transcriptome in high and low latitude embryos provides evidence that one mechanism of adaptive DNA repair differences between populations is the greater abundance of DNA repair transcripts in the eggs of low latitude females. Finally, we use population genomic comparisons of high and low latitude samples to reveal evidence that multiple components of the DNA damage response and both coding and non-coding variation likely contribute to adaptive differences in DNA repair between populations

Receptor simulation and the shape of the concentration-response curve and its congeners

We have investigated the utility of curves used to represent concentration (or dose) plotted against response (or effect). We applied crude survival data from our laboratory to demonstrate that a known hyperbolic curve compares favourably with the conventionally used sigmoidal regression in robustness, while avoiding problems associated with the use of transforms

Composition of Early Planetary Atmospheres II: Coupled Dust and Chemical Evolution in Protoplanetary Disks

We present the next step in a series of papers devoted to connecting the composition of the atmospheres of forming planets with the chemistry of their natal evolving protoplanetary disks. The model presented here computes the coupled chemical and dust evolution of the disk and the formation of three planets per disk model. Our three canonical planet traps produce a Jupiter near 1 AU, a Hot Jupiter and a Super-Earth. We study the dependency of the final orbital radius, mass, and atmospheric chemistry of planets forming in disk models with initial disk masses that vary by 0.02 $M_\odot$ above and below our fiducial model ($M_{disk,0} = 0.1 ~M_\odot$). We compute C/O and C/N for the atmospheres formed in our 3 models and find that C/O$_{\rm planet}\sim$ C/O$_{\rm disk}$, which does not vary strongly between different planets formed in our model. The nitrogen content of atmospheres can vary in planets that grow in different disk models. These differences are related to the formation history of the planet, the time and location that the planet accretes its atmosphere, and are encoded in the bulk abundance of NH$_3$. These results suggest that future observations of atmospheric NH$_3$ and an estimation of the planetary C/O and C/N can inform the formation history of particular planetary systems.Comment: Accepted for publication in MNRA