Generating non-axisymmetric substructure in ringed protoplanetary discs

Recent observations of protoplanetary discs have unveiled their wealth of substructure, the origins and implications of which are yet to be fully understood. Of particular interest is whether they promote planet formation, whether they indicate that planet formation is already underway, and what role they play in setting the architecture of planetary systems. In this thesis I present my investigations into physical processes that can give rise to large-scale, non-axisymmetric substructure. I discuss our current understanding of substructure in protoplanetary discs, and provide an overview of the key processes involved in planet formation. I present the theoretical basis for vortex generation by an accreting planetary embryo. Through hydrodynamics simulations, I show that in massive, axisymmetric dust traps, the growth of a planetary core via pebble accretion produces strong thermal feedback on the disc, making it unstable to vortex formation. I demonstrate how this can further enhance the accretion rate onto the planetary core as well as produce observable non-axisymmetric substructure. I investigate how this process varies with the mass of dust in the ring as well as the local background gas temperature, and show that the thermal feedback always acts to increase the planet’s mass. I establish that the required dust masses lie towards the extreme end of those inferred from observations, otherwise the background temperature must be sufficiently low to emphasize the thermal feedback from the embryo’s accretion luminosity. I also investigate how warped and twisted regions of protoplanetary discs cast shadows across the disc, and how this manifests in observations, giving the appearance of non-axisymmetric substructure. I show that this can be used to constrain the geometry of discs in which there is evidence for strong misalignments between their inner and outer regions.Open Acces

A Cross-Cultural Negotiation Role-Play for Sales Classes

Purpose of the Study: International sales jobs are plentiful; yet many marketing students do not pursue them. This study describes an international negotiation teaching innovation that improved student awareness of both the challenges and rewards of a career in international sales. Method Design and Sample: The use of a cross-cultural negotiation exercise in sales classes from two countries is tested to provide an experiential learning opportunity in a computer-supported, collaborative learning setting. Prior research has shown that the use of web-based technology can enhance collaboration and construction of knowledge (Comeaux and McKenna-Byington, 2003). Students first engaged in a virtual ‘get-to-know you’ exercise. Following lectures on cultural differences and team negotiations, they followed guidelines of a fictional cultural briefing to conduct a cross-cultural negotiation exercise. Throughout the experience, students completed surveys and maintained journals. Results: The innovation increased student knowledge of sales and negotiations while simultaneously improving attitudes toward, and confidence in, international collaboration. Students reported higher intent to pursue international sales careers over the control group. Value to Marketing Educators: Business schools and sales students can increase job market competitiveness through intercultural skill development (Kurpis and Hunter, 2017; Delpechitre and Baker, 2017). Despite progress in sales course offerings, international exposure is still lacking. Soft skills, such as cultural literacy, are considered key to success in the job market (Tuleja, 2014). This negotiation exercise between classes is a realistic way to enhance intercultural skill development within the sales curriculum

Fast-food, everyday life and health: A qualitative study of 'chicken shops' in East London.

The higher prevalence of fast food outlets in deprived areas has been associated with the production and maintenance of geographical inequalities in diet. In the UK one type of fast food outlet - the 'chicken shop' - has been the focus of intense public health and media interest. Despite ongoing concerns and initiatives around regulating these establishments, the 'chicken shop' is both a commercially successful and ubiquitous feature of disadvantaged urban neighbourhoods. However, little is known about how they are perceived by local residents. We report data from a qualitative study of neighbourhood perceptions in a low SES urban setting. Narrative family interviews, go-along interviews and school video focus group workshops with 66 residents of East London were conducted over two waves. The topic of chicken shops was a prolific theme and a narrative analysis of these accounts revealed that local perceptions of chicken shops are complex and contradictory. Chicken shops were depicted as both potentially damaging for the health of local residents and, at the same time, as valued community spaces. This contradiction was discursively addressed in narrative via a series of rhetorical rebuttals that negated their potential to damage health on the grounds of concepts such as trust, choice, balance, food hygiene and compensatory physical activity. In some instances, chicken shops were described as 'healthy' and patronising them constructed as part of a healthy lifestyle. Chicken shops are embedded in the social fabric of neighbourhoods. Successful strategies to improve diet therefore requires context-sensitive environmental interventions

Uptake of one and two molecules of CO2 by the molybdate dianion: a soluble, molecular oxide model system for carbon dioxide fixation

Tetrahedral [MoO4][superscript 2−] readily binds CO[subscript 2] at room temperature to produce a robust monocarbonate complex, [MoO[subscript 3](κ[superscript 2]-CO[subscript 3])][superscript 2−], that does not release CO[subscript 2] even at modestly elevated temperatures (up to 56 °C in solution and 70 °C in the solid state). In the presence of excess carbon dioxide, a second molecule of CO[subscript 2] binds to afford a pseudo-octahedral dioxo dicarbonate complex, [MoO[subscript 2](κ[superscript 2]-CO[subscript 3])[subscript 2][superscript 2−], the first structurally characterized transition-metal dicarbonate complex derived from CO[subscript 2]. The monocarbonate [MoO[subscript 3](κ[superscript 2]-CO[subscript 3])][superscript 2−] reacts with triethylsilane in acetonitrile under an atmosphere of CO[subscript 2] to produce formate (69% isolated yield) together with silylated molybdate (quantitative conversion to [MoO[subscript 3](OSiEt[subscript 3])][superscript −], 50% isolated yield) after 22 hours at 85 °C. This system thus illustrates both the reversible binding of CO[subscript 2] by a simple transition-metal oxoanion and the ability of the latter molecular metal oxide to facilitate chemical CO[subscript 2] reduction.Saudi Basic Industries CorporationSpain. Ministerio de Educación, Cultura y DeporteSpain. Ministerio de Economía y Competitividad (CTQ2012-36966)National Science Foundation (U.S.) (CHE-1111357)National Science Foundation (U.S.) (CHE- 0946721

Longitudinal associations between perceptions of the neighbourhood environment and physical activity in adolescents: evidence from the Olympic Regeneration in East London (ORiEL) study.

BACKGROUND: Most UK adolescents do not achieve recommended levels of physical activity. Previous studies suggested that perceptions of the neighbourhood environment could contribute to explain differences in physical activity behaviours. We aimed to examine whether five measures of perceptions - perceived bus stop proximity, traffic safety, street connectivity, enjoyment of the neighbourhood for walking/cycling, and personal safety - were longitudinally associated with common forms of physical activity, namely walking to school, walking for leisure, and a composite measure of outdoor physical activity. We further aimed to investigate the moderating role of gender. METHODS: We used longitudinal data from the Olympic Regeneration in East London (ORiEL) study, a prospective cohort study. In 2012, 3106 adolescents aged 11 to 12 were recruited from 25 schools in 4 deprived boroughs of East London. Adolescents were followed-up in 2013 and 2014. The final sample includes 2260 adolescents surveyed at three occasions. We estimated logistic regression models using Generalised Estimating Equations to test the plausibility of hypotheses on the nature of the longitudinal associations (general association, cumulative effect, co-varying trajectories), adjusting for potential confounders. Item non-response was handled using multiple imputation. RESULTS: Longitudinal analyses indicate little evidence that perceptions of the neighbourhood are important predictors of younger adolescent physical activity. There was weak evidence that greater perceived proximity to bus stops is associated with a small decrease in the probability of walking for leisure. Results also indicate that poorer perception of personal safety decreases the probability of walking for leisure. There was some indication that better perception of street connectivity is associated with more outdoor physical activity. Finally, we found very little evidence that the associations between perceptions of the neighbourhood and physical activity differed by gender. CONCLUSIONS: This study suggests that younger adolescents' perceptions of their neighbourhood environment, and changes in these perceptions, did not consistently predict physical activity in a deprived and ethnically diverse urban population. Future studies should use situation-specific measures of the neighbourhood environment and physical activity to better capture the hypothesised processes and explore the relative roles of the objective environment, parental and adolescents' perceptions in examining differences in types of physical activity

The effects of environmental enrichment on nicotine sensitization in a rodent model of schizophrenia

Environmental enrichment, for more than fifty years, has shown to increase learning in behaviors and to alter some brain structures (Renner and Rosenzweig). Some brain changes that occur when environmental enrichment is implemented include the following: increases in cortical thickness, especially the occipital cortex, increases in size of neuronal cell bodies, number of dendrites and dendritic spines, increases in astrocyte branching, increases in the number of brain blood capillaries, and increases in mitochondria (an indication of higher metabolic activity) (Stairs and Bard). It has been shown in research studies that rats in the environmental enrichment group are less sensitive to nicotine effects, both repeated and acute, than rats in isolated situations (Green et al). This is so because enrichment changes the intensity of the acute administration of drugs of abuse. Rats are stimulated by the environment, rather than a particular stimulant

Facile synthesis of mononuclear early transition-metal complexes of κ3cyclo-tetrametaphosphate ([P4O12]4−) and cyclo-trimetaphosphate ([P3O9]3−)

We herein report the preparation of several mononuclear-metaphosphate complexes using simple techniques and mild conditions with yields ranging from 56% to 78%. Treatment of cyclo-tetrametaphosphate ([TBA]4[P4O12]·5H2O, TBA = tetra-n-butylammonium) with various metal sources including (CH3CN)3Mo(CO)3, (CH3CN)2Mo(CO)2(η3-C3H5)Cl, MoO2Cl2(OSMe2)2, and VOF3, leads to the clean and rapid formation of [TBA]4[(P4O12)Mo(CO)3]·2H2O, [TBA]3[(P4O12)Mo(CO)2(η3-C3H5)], [TBA]3[(P4O12)MoO2Cl] and [TBA]3[(P4O12)VOF2]·Et2O salts in isolated yields of 69, 56, 68, and 56% respectively. NMR spectroscopy, NMR simulations and single crystal X-ray studies reveal that the [P4O12]4− anion behaves as a tridentate ligand wherein one of the metaphosphate groups is not directly bound to the metal. cyclo-Trimetaphosphate-metal complexes were prepared using a similar procedure i.e., treatment of [PPN]3[P3O9]·H2O (PPN = bis(triphenylphosphine)iminium) with the metal sources (CH3CN)2Mo(CO)2(η3-C3H5)Cl, MoO2Cl2(OSMe2)2, MoOCl3, VOF3, WOCl4, and WO2Cl2(CH3CN)2 to produce the corresponding salts, [PPN]2[(P3O9)Mo(CO)2(η3-C3H5)], [PPN]2[(P3O9)MoO2Cl], [PPN]2[(P3O9)MoOCl2], [PPN]2[(P3O9)VOF2]·2CH2Cl2, and [PPN]2[(P3O9)WO2Cl] in isolated yields of 78, 56, 75, 59, and 77% respectively. NMR spectroscopy, NMR simulations and single-crystal X-ray studies indicate that the trianionic ligand [P3O9]3− in these complexes also has κ3 connectivity.Eni S.p.A. (Firm)Eni-MIT Solar Frontiers Center (Program