Tectono-magmatic evolution of the younger Gardar southern rift, South Greenland

The 1300–1140 Ma Gardar period in South Greenland involved continental rifting, sedimentation and alkaline magmatism. The latest magmatism was located along two parallel rift zones, Isortoq–Nunarsuit in the north and the Tuttutooq–Ilimmaasaq–Narsarsuaq zone in the south addressed here. The intrusive rocks crystallised at a depth of troctolitic gabbros. These relatively reduced magmas evolved through marked iron enrichment to alkaline salic differentiates. In the Older giant dyke complex, undersaturated augite syenites grade into sodalite foyaite. The larger, c. 1163 Ma Younger giant dyke complex (YGDC) mainly consists of structureless troctolite with localised developments of layered cumulates. A layered pluton (Klokken) is considered to be coeval and presumably comagmatic with the YGDC. At the unconformity between the Ketilidian basement and Gardar rift deposits, the YGDC expanded into a gabbroic lopolith. Its magma may represent a sample from a great, underplated mafic magma reservoir, parental to all the salic alkaline rocks in the southern rift. The bulk of these are silica undersaturated; oversaturated differentiates are probably products of combined fractional crystallisation and crustal assimilation. A major dyke swarm 1–15 km broad was intruded during declining crustal extension, with decreasing dyke widths and increasing differentiation over time. Intersection of the dyke swarm and E–W-trending sinistral faults controlled the emplacement of at least three central complexes (Narssaq, South Qôroq and early Igdlerfigssalik). Three post-extensional complexes (Tugtutôq, Ilímaussaq and late Igdlerfigssalik) along the former rift mark the end of magmatism at c. 1140 Ma. The latter two complexes have oblate plans reflecting ductile, fault-related strain. The Tugtutôq complex comprises quartz syenites and alkali granites. The Ilímaussaq complex mainly consists of nepheline syenite crystallised from highly reduced, Fe-rich phonolitic peralkaline (agpaitic) magma, and resulted in rocks with very high incompatible element concentrations. Abundant anorthositic xenoliths in the mafic and intermediate intrusions point to a large anorthosite protolith at depth which is considered of critical importance in the petrogenesis of the salic rocks. Small intrusions of aillikite and carbonatite may represent remobilised mantle metasomites. The petrological similarity between Older and Younger Gardar suites implies strong lithospheric control of their petrogenesis. The parental magmas are inferred to have been derived from restitic Ketilidian lithospheric mantle, metasomatised by melts from subducting Ketilidian oceanic crust and by small-scale melt fractions associated with Gardar rifting. There are numerous analogies between the southern Gardar rift and the Palaeogene East African rift

Development of a Measure of Craving Suppression

While there is evidence to support the efficacy of mindfulness-based treatment for substance use, the mechanisms through which they lead to therapeutic outcomes have received less attention. A growing body of literature suggests that the ways in which people respond to cravings may be an important mediator of change. Individuals with substance use problems may use them to cope with or avoid negative experiences, which could include the experience of craving itself. Thought suppression in particular has been investigated as a specific form of experiential avoidance, and findings suggest that thought suppression strategies may interfere with attempts to quit using substances. While mindfulness training should be expected to reduce the tendency to suppress or avoid cravings, evidence to support this expectation is limited, largely because no measures yet exist that assess the suppression of craving. Therefore, the purpose of the present study was to develop a self-report measure of the suppression of craving. Existing measures of other types of thought suppression and experiential avoidance were examined to identify items that could be adapted for use in the Craving Suppression Scale (CSS). To assist with the item development process, a focus group was also conducted at a local residential treatment facility. Participants were asked to discuss what they do when they are experiencing cravings and what thoughts go through their minds when cravings come up. Their responses were used to guide content development for the CSS items. Items were developed for two sub-scales: suppression of craving and beliefs about craving. Items were administered to a sample of inpatients in substance use treatment and an online sample of individuals reporting current or previous substance use problems (total N = 208). Factor analysis of the remaining items supported a two-factor structure for the CSS as hypothesized. Relationships were examined between the CSS and other measures of other forms of experiential avoidance/suppression, craving, and emotional distress. The CSS scales correlated well with other measures of suppression but had mixed relationships with other constructs of interest. Evidence for the validity and potential utility of the CSS are discussed along with theoretical and treatment implications

RUMINATIVE THOUGHT IN INDIVIDUALS WITH BORDERLINE PERSONALITY FEATURES

Borderline personality disorder (BPD) is characterized by patterns of intense negative affect, interpersonal difficulties, and maladaptive impulsive behaviors, and is associated with impairments in social and occupational functioning. Rumination is a maladaptive form of repetitive thought that maintains and intensifies emotional disturbance and is associated with behavioral dysregulation. This study tested several hypotheses about relationships between rumination and borderline personality features. This study included 117 college student participants, 88 female students and 29 male students, most of whom (84%) identified themselves as Caucasian. Participants completed a series of measures which included a writing sample to sample repetitive thought. Findings consistently suggested that rumination accounts for significant incremental variance in BPD features after controlling for various facets of neuroticism, which suggests that individuals with BPD features are probably engaging in high levels of multiple types of rumination. However, scores derived from the On Your Mind writing sample did not predict severity of borderline features after controlling for the NEO-neuroticism domain. Implications for these findings and limitations to this study are also discussed

Essays on incentives, economic conditions, and educational choices

In this dissertation, I offer two independent studies that each contribute to the literature on the college choices. The first paper examines the impact of Arizona’s merit based scholarship on college enrollment decisions. I find that both enrollment and tuition and fees increased at Arizona’s three large public institutions after the implementation of the AIMS scholarship. Enrollment effects are strongest among black and hispanic students. The second paper examines the impact of the recent 2009 housing crisis on college enrollment decisions. I find that large reductions in housing wealth lead to increases in public school enrollment and decreases in private school enrollment. Similarly, I find that increases in foreclosures in a metro area are associated with decreases in private school enrollment and increases in public school enrollment

α7 Nicotinic Receptor Modulation Alters Glutamate Release: Implications for Cognitive Deficits in Schizophrenia

2nd Place in Health Professions - Laboratory Cellular Research at Denman Forum (Ohio State University)Symposium Distinction - 3rd Annual Neuroscience Undergraduate Research Forum (Ohio State University)Cognitive deficits in schizophrenia are thought to be caused, in part, by disrupted prefrontal cholinergic and glutamatergic transmission. Activation of the α7 nicotinic acetylcholine receptor (α7nAChR) has been shown to increase prefrontal glutamate as well as rescue failing performance in cognitive tasks in rodents and primates. Intra-accumbens stimulation with NMDA dose-dependently increases prefrontal acetylcholine, which in turn increases prefrontal glutamate via α7nAChR activity. Using NMDA stimulation as an assay to examine the potentiation of glutamate release as a function of the amount of acetylcholine released in the PFC, the potentiation profiles of two α7nAChR positive allosteric modulators (PAMs), AVL-3288 and PNU-120596, were assessed at varying levels of PAM and stimulation. Second-by-second measurements with a glutamate-sensitive microelectrode in the PFC in awake rats reveal that only an appropriate combination of the dose of NMDA and dose of PAM consistently potentiates prefrontal glutamate release. However, at other concentrations of NMDA and PAM, the effect on mesolimbic stimulation varied greatly from significant potentiation to a reduction of glutamate release. Furthermore, the potentiation profile for the type I and type II PAMs differed significantly, possibly due to differences in receptor desensitization in the presence of these two drugs. Overall, these results demonstrate the importance of dose of α7nAChR PAMs in modulating neurotransmitter systems, and PAMs as a potential therapeutic in treating cognitive deficits of schizophrenia as effects were dependent on activity of the orthosteric ligand.URO Summer FellowshipAcademic Enrichment GrantNo embargoAcademic Major: Neuroscienc

Microbial community structure and functions differ between native and novel (exotic-dominated) grassland ecosystems in an 8-year experiment

A Grasslands dominated by non-native (exotic) spe- cies have replaced purely native-dominated areas in many parts of the world forming ‘novel’ ecosystems. Altered precipitation patterns are predicted to exacerbate this trend. It is still poorly understood how soil microbial communities and their functions differ between high diversity native- and low diversity exotic-dominated sites and how altered precipitation will impact this difference. Methods We sampled 64 experimental grassland plots in central Texas with plant species mixtures of either all native or all exotic species; half with summer irrigation. We tested how native vs. exotic plant species mixtures and summer irrigation affected bacterial and fungal community composition and structure, the influence of niche vs. neutral processes for microbial phylotype co- occurrence (C-score analysis), and rates of phosphorus and nitrogen mineralization across an 8-year experiment. Results Native and exotic-dominated plots had sig- nificantly different fungal community composition and structure, but not diversity, throughout the length of the study, while changes in bacterial communities were limited to certain wet and cool years. Nitrogen and phosphorus mineralization rates were higher un- der native plant mixtures and correlated with the abundance of particular fungal species. Microbial communities were more structured in exotic than native grassland plots, especially for the fungal community. Conclusions The results indicate that conversion of native to exotic C4 dominated grasslands will more strongly impact fungal than bacterial community structure. Further- more, these impacts can alter ecosystem functioning be- lowground via changes in nitrogen and phosphorus cycling

Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: implications for melting and metasomatism beneath Northern Scotland

Bulk rock geochemistry and major- and trace-element compositions of clinopyroxene have been determined for three suites of peridotitic mantle xenoliths from the North Atlantic Craton (NAC) in northern Scotland, to establish the magmatic and metasomatic history of subcontinental lithospheric mantle (SCLM) below this region. Spinel lherzolites from the southernmost locality (Streap Com'laidh) have non-NAC mantle compositions, while the two northern xenolith suites (Loch Roag and Rinibar) are derived from the thinned NAC marginal keel. Clinopyroxene compositions have characteristic trace-element signatures which show both 'primary' and 'metasomatic' origins. We use Zr and Hf abundances to identify ancient cryptic refertilization in 'primary' clinopyroxenes. We suggest that Loch Roag and Rinibar peridotite xenoliths represent an ancient Archaean-Palaeoproterozoic SCLM with original depleted cratonic signatures which were overprinted by metasomatism around the time of intrusion of the Scourie Dyke Swarm (∼2.4 Ga). This SCLM keel was preserved during Caledonian orogenesis, although some addition of material and/or metasomatism probably also occurred, as recorded by Rinibar xenoliths. Rinibar and Streap xenoliths were entrained in Permo-Carboniferous magmas and thus were isolated from the SCLM ∼200 Ma before Loch Roag xenoliths (in an Eocene dyke). Crucially, despite their geographical location, lithospheric mantle peridotite samples from Loch Roag show no evidence of recent melting or refertilization during the Palaeogene opening of the Atlantic

Soil depth and grassland origin cooperatively shape microbial community co‐occurrence and function

Many soils are deep, yet soil below 20 cm remains largely unexplored. Exotic plants can have shallower roots than native species, so their impact on microorganisms is anticipated to change with depth. Using environmental DNA and extracellular enzymatic activities, we studied fungal and bacterial community composition, diversity, function, and co-occurrence networks between native and exotic grasslands at soil depths up to 1 m. We hypothesized (1) the composition and network structure of both fungal and bacterial communities will change with increasing depth, and diversity and enzymatic function will decrease; (2) microbial enzymatic function and network connectedness will be lower in exotic grasslands; and (3) irrigation will alter microbial networks, increasing the overall connectedness. Microbial diversity decreased with depth, and community composition was distinctly different between shallow and deeper soil depths with higher numbers of unknown taxa in lower soil depths. Fungal communities differed between native and exotic plant communities. Microbial community networks were strongly shaped by biotic and abiotic factors concurrently and were the only microbial measurement affected by irrigation. In general, fungal communities were more connected in native plant communities than exotic, especially below 10 cm. Fungal networks were also more connected at lower soil depths albeit with fewer nodes. Bacterial communities demonstrated higher complexity, and greater connectedness and nodes, at lower soil depths for native plant communities. Exotic plant communities’ bacterial network connectedness altered at lower soil depths dependent on irrigation treatments. Microbial extracellular enzyme activity for carbon cycling enzymes significantly declined with soil depth, but enzymes associated with nitrogen and phosphorus cycling continued to have similar activities up to 1 m deep. Our results indicate that native and exotic grasslands have significantly different fungal communities in depths up to 1 m and that both fungal and bacterial networks are strongly shaped jointly by plant communities and abiotic factors. Soil depth is independently a major determinant of both fungal and bacterial community structures, functions, and co-occurrence networks and demonstrates further the importance of including soil itself when investigating plant–microbe interactions