Regional Magma Plumbing and emplacement mechanisms of the Faroe-Shetland Sill Complex : Implications for magma transport and petroleum systems within sedimentary basins

Peer reviewed

Regional Magma Plumbing and emplacement mechanisms of the Faroe-Shetland Sill Complex : Implications for magma transport and petroleum systems within sedimentary basins

Peer reviewed

Upstream mechanisms responsible for H₂O₂-induced activation of MAPK and PKB in vascular smooth muscle cells

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Neural Mechanisms of Young Adult Sexual Decision-Making and Risk Behavior

Sexual risk behavior among young adults is a serious public health concern; 50% will contract a sexually transmitted infection (STI) before the age of 25. The current study collected self-report personality and sexual history data, as well as neuroimaging, experimental behavioral (e.g., real-time hypothetical sexual decision making data), and self-report sexual arousal data from 120 heterosexual young adults ages 18-26. In addition, longitudinal changes in self-reported sexual behavior were collected from a subset (n = 70) of the participants. The primary aims of the study were (1) to predict differences in self-report sexual behavior and hypothetical sexual decision-making (in response to sexually explicit audio-visual cues) as a function of ventral striatum (VS) and amygdala activity, (2) test whether the association between sexual behavior/decision-making and brain function is moderated by gender, self-reported sexual arousal, and/or trait-level personality factors (i.e., self-control, impulsivity, and sensation seeking) and (3) to examine how the main effects of neural function and interaction effects predict sexual risk behavior over time. Our hypotheses were mostly supported across the sexual behavior and decision-making outcome variables, such that neural risk phenotypes (heightened reward-related ventral striatum activity coupled with decreased threat-related amygdala activity) were associated with greater lifetime sexual partners at baseline measured and over time (longitudinal analyses). Impulsivity moderated the relationship between neural function and self-reported number of sexual partners at baseline and follow up measures, as well as experimental condom use decision-making. Sexual arousal and sensation seeking moderated the relationship between neural function and baseline and follow up self-reports of number of sexual partners. Finally, unique gender differences were observed in the relationship between threat and reward-related neural reactivity and self-reported sexual risk behavior. The results of this study provide initial evidence for the potential role for neurobiological approaches to understanding sexual decision-making and risk behavior. With continued research, establishing biomarkers for sexual risk behavior could help inform the development of novel and more effective individually tailored sexual health prevention and intervention efforts.

Molecular Mechanisms of Airway Epithelial Progenitor Cell Maintenance and Repair.

The lungs are vital organs whose airways are lined with a continuous layer of epithelial cells. Epithelial cells in the distal most part of the lung, the alveolar space, are specialized to facilitate gas exchange. Proximal to the alveoli is the airway epithelium, which provides an essential barrier and is the first line of defense against inhaled toxicants, pollutants, and pathogens. Although the postnatal lung is a quiescent organ, it has an inherent ability to regenerate in response to injury. Proper balance between maintaining quiescence and undergoing repair is crucial, with imbalances in these processes leading to fibrosis or tumor development. Stem and progenitor cells are central to maintaining balance, given that they proliferate and renew both themselves and the various differentiated cells of the lung. However, the precise mechanisms regulating quiescence and repair in the lungs are largely unknown. In this dissertation, ionizing radiation is used as a physiologically relevant injury model to better understand the repair process of the airway epithelium. We use in vitro and in vivo mouse models to study the response of a secretory progenitor, the club cell, to various doses and qualities of ionizing radiation. Exposure to radiation found in space environments and in some types of radiotherapy caused clonal expansion of club cells specifically in the most distal branches of the airway epithelium, indicating that the progenitors residing in the terminal bronchioles are radiosensitive. This clonal expansion is due to an increase in p53-dependent apoptosis, senescence, and mitotic defects. Through the course of this work, we discovered that p53 is not only involved in radiation response, but is also a novel regulator of airway epithelial homeostasis. p53 acts in a gene dose-dependent manner to regulate the composition of airway epithelium by maintaining quiescence and regulating differentiation of club progenitor cells in the steady-state lung. The work presented in this dissertation represents an advance in our understanding of the molecular mechanisms underlying maintenance of airway epithelial progenitor cells as well as their repair following ionizing radiation exposure.

Experimental and Theoretical Models to Probe Mechanisms of Biological Charge Flow

Nature is challenged to move charge efficiently over many length scales. From sub-nm to μm distances, electron-transfer proteins orchestrate energy conversion, storage, and release both inside and outside the cell. Uncovering the detailed mechanisms of biological electron-transfer reactions, which are often coupled to bond-breaking and bond-making events, is essential to designing durable, artificial energy conversion systems that mimic the specificity and efficiency of their natural counterparts. Here, we use theoretical modeling of long-distance charge hopping (Chapter 3), synthetic donor-bridge-acceptor molecules (Chapters 4, 5, and 6), and de novo protein design (Chapters 5 and 6) to investigate general principles that govern light-driven and electrochemically driven electron-transfer reactions in biology. We show that fast, μm-distance charge hopping along bacterial nanowires requires closely packed charge carriers with low reorganization energies (Chapter 3); singlet excited-state electronic polarization of supermolecular electron donors can attenuate intersystem crossing yields to lower-energy, oppositely polarized, donor triplet states (Chapter 4); the effective static dielectric constant of a small (~100 residue) de novo designed 4-helical protein bundle can change upon phototriggering an electron transfer event in the protein interior, providing a means to slow the charge-recombination reaction (Chapter 5); and a tightly-packed de novo designed 4-helix protein bundle can drastically alter charge-transfer driving forces of photo-induced amino acid radical formation in the bundle interior, effectively turning off a light-driven oxidation reaction that occurs in organic solvent (Chapter 6). This work leverages unique insights gleaned from proteins designed from scratch that bind synthetic donor-bridge-acceptor molecules that can also be studied in organic solvents, opening new avenues of exploration into the factors critical for protein control of charge flow in biology.

Neural mechanisms of negative reinforcement in children and adolescents with autism spectrum disorders.

BACKGROUND: Previous research has found accumulating evidence for atypical reward processing in autism spectrum disorders (ASD), particularly in the context of social rewards. Yet, this line of research has focused largely on positive social reinforcement, while little is known about the processing of negative reinforcement in individuals with ASD. METHODS: The present study examined neural responses to social negative reinforcement (a face displaying negative affect) and non-social negative reinforcement (monetary loss) in children with ASD relative to typically developing children, using functional magnetic resonance imaging (fMRI). RESULTS: We found that children with ASD demonstrated hypoactivation of the right caudate nucleus while anticipating non-social negative reinforcement and hypoactivation of a network of frontostriatal regions (including the nucleus accumbens, caudate nucleus, and putamen) while anticipating social negative reinforcement. In addition, activation of the right caudate nucleus during non-social negative reinforcement was associated with individual differences in social motivation. CONCLUSIONS: These results suggest that atypical responding to negative reinforcement in children with ASD may contribute to social motivational deficits in this population.

Upstream mechanisms responsible for H₂O₂-induced activation of MAPK and PKB in vascular smooth muscle cells

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Seawater carbonate chemistry and impacts of calcium and carbonate ion concentration on Mg and Sr incorporation in cultured benthic foraminifera (Ammonia tepida and Heterostegina depressa), 2011

Laboratory culture experiments were conducted to determine effects of seawater carbonate ion concentration ([CO32-]), and thereby calcite saturation state, on Mg and Sr incorporation into calcite of two species of shallow-water benthic foraminifera: Ammonia tepida and Heterostegina depressa. Impact on Mg and Sr incorporation by increased seawater [CO32-] and thereby higher calcite saturation state, is absent in either species. Comparison to results from a similar culturing experiment, in which calcite saturation state was varied as a function of [Ca2+], reveals that saturation state affects incorporation of Mg and Sr through calcium- rather than carbonate availability. The similarity in response by both species is surprising since the average Mg/Ca ratio is ~ 70 times higher in H. depressa than in A. tepida. Furthermore, these results suggest that the ions involved in biomineralization (i.e. Ca2+ and DIC) are processed by separate cellular transport mechanisms. The similar response of Mg and Sr incorporation in this study suggests that only differences in the Ca2+ transport mechanism affect divalent cation partitioning.

Perspectives of Teachers Regarding the Integration of Mathematics and Science at the Secondary School Level

The integration of mathematics and science in secondary schools in the 21st century continues to be an important topic of practice and research. The purpose of my research study, which builds on studies by Frykholm and Glasson (2005) and Berlin and White (2010), is to explore the potential constraints and benefits of integrating mathematics and science in Ontario secondary schools based on the perspectives of in-service and pre-service teachers with various math and/or science backgrounds. A qualitative and quantitative research design with an exploratory approach was used. The qualitative data was collected from a sample of 12 in-service teachers with various math and/or science backgrounds recruited from two school boards in Eastern Ontario. The quantitative and some qualitative data was collected from a sample of 81 pre-service teachers from the Queen’s University Bachelor of Education (B.Ed) program. Semi-structured interviews were conducted with the in-service teachers while a survey and a focus group was conducted with the pre-service teachers. Once the data was collected, the qualitative data were abductively analyzed. For the quantitative data, descriptive and inferential statistics (one-way ANOVAs and Pearson Chi Square analyses) were calculated to examine perspectives of teachers regardless of teaching background and to compare groups of teachers based on teaching background. The findings of this study suggest that in-service and pre-service teachers have a positive attitude towards the integration of math and science and view it as valuable to student learning and success. The pre-service teachers viewed the integration as easy and did not express concerns to this integration. On the other hand, the in-service teachers highlighted concerns and challenges such as resources, scheduling, and time constraints. My results illustrate when teachers perceive it is valuable to integrate math and science and which aspects of the classroom benefit best from the integration. Furthermore, the results highlight barriers and possible solutions to better the integration of math and science. In addition to the benefits and constraints of integration, my results illustrate why some teachers may opt out of integrating math and science and the different strategies teachers have incorporated to integrate math and science in their classroom.

Microtubule attachment and regulation mechanisms of the budding yeast kinetochore

Thesis (Master's)--University of Washington, 2016-08

Integration of learning and practice as part of the educational system development in Eritrea. "School Management" - a distance learning program by technical university of Kaiserslautern

The distance learning program "School Management" supports decision makers at the school and ministerial levels in the shaping of formal and informal learning processes at different levels in schools and curricula in Eritrea. This paper examines how the distance learning program is interconnected to educational system development. (DIPF/Orig.)

Kinetics and coverage dependent reaction mechanisms of the copper atomic layer deposition from copper dimethylamino-2-propoxide and diethylzinc

Atomic layer deposition (ALD) has been recognized as a promising method to deposit conformal and uniform thin film of copper for future electronic devices. However, many aspects of the reaction mechanism and the surface chemistry of copper ALD remain unclear. In this paper, we employ plane wave density functional theory (DFT) to study the transmetalation ALD reaction of copper dimethylamino-2-propoxide [Cu(dmap)2] and diethylzinc [Et2Zn] that was realized experimentally by Lee et al. [ Angew. Chem., Int. Ed. 2009, 48, 4536−4539]. We find that the Cu(dmap)2 molecule adsorbs and dissociates through the scission of one or two Cu–O bonds into surface-bound dmap and Cu(dmap) fragments during the copper pulse. As Et2Zn adsorbs on the surface covered with Cu(dmap) and dmap fragments, butane formation and desorption was found to be facilitated by the surrounding ligands, which leads to one reaction mechanism, while the migration of ethyl groups to the surface leads to another reaction mechanism. During both reaction mechanisms, ligand diffusion and reordering are generally endothermic processes, which may result in residual ligands blocking the surface sites at the end of the Et2Zn pulse, and in residual Zn being reduced and incorporated as an impurity. We also find that the nearby ligands play a cooperative role in lowering the activation energy for formation and desorption of byproducts, which explains the advantage of using organometallic precursors and reducing agents in Cu ALD. The ALD growth rate estimated for the mechanism is consistent with the experimental value of 0.2 Å/cycle. The proposed reaction mechanisms provide insight into ALD processes for copper and other transition metals.