Brock University Digital Repository
Brock University's Digital Repository is an online archive showcasing and preserving the Brock community's scholarly output as well as items from the Library's Archives & Special Collections. Researchers can disseminate their work by depositing it in this Open Access repository, which provides free, immediate access to users while also allowing Brock scholars to track downloads and views of their scholarship. The Digital Repository is also the home of the Brock University E-Thesis Portal.
For more information, see the repository's policies and procedures.
Communities in Brock University Digital Repository
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Recent Submissions
Niagara ship papers collection, 1874-1905
(2025-03-25) Cameron, Chantal
The collection contains documents related to three Great Lakes ships that were built in the Niagara area: “Arctic”; “Grimsby”; and “Inez”.
Letter to Mrs. Hill from her niece B.A. Tom, January 1, 1861
(2025-03-25) Cameron, Chantal
A letter to Mrs. Hill, Smithville, Gainsborough, District Niagara, Upper Canada, America, dated at Lank St. Breward [Cornwall, England], January 1, 1861, from her niece B.A. Tom. The letter is 6 pages and contains mostly family news. The author writes a great deal about the health of family members and the deaths of many of them. She also comments on the weather and the harvest. The envelope contains postmarks from Bodmin, London, Hamilton, and Smithville. There is also a stamp that reads “insufficiently stamped”. The postage stamp is six pence.
Welland Canal and Fort George photographs, c. 1930s
(2025-03-25) Cameron, Chantal
Thirteen black and white photographs of the Welland Ship Canal and Fort George, c. 1930s. There are eight photos of the Welland Canal including the Homer Bridge up with a ship passing through, and the ship Burlington in the canal. The remaining five photos are of Fort George. Several of the photos contain one or more women and include buildings and cannons. The photographs are personal family photos.
Optimal Design and Planning for Random Effect Models and Models with Measurement Errors.
SARFO, BRIDGET KONADU
This project addresses optimal design problems for linear mixed models with covariates (mixed ANCOVA models), and linear fixed models with measurement errors. First, we examine ANCOVA mixed models, focusing on efficient treatment allocations. We develop optimal designs using a general framework based on D-optimality, proposing a two-stage design approach to account for unknown parameters. In this approach, variances of random effects across treatment groups are considered distinct. Second, we formulate A-optimal designs for measurement error models, addressing errors in the response alone or in both response and explanatory variables. We propose that optimal designs for models with measurement errors significantly outperform classical designs. Furthermore, our results in A-optimal design for the models with measurement errors in both explanatory and response variables provide significantly greater efficiencies compared to classical designs.
Discovery of a Pseudogap Attributed to Charge Density Wave Order at the β-β′ Phase Transition in As2Te3 and the Influence of Cu and Ge Doping on its Properties
(Brock University) Dion, Jeremy; Reedyk, Maureen; Department of Physics
In this work, the origin and driving mechanism of the β to β' phase transition of As2Te3 is investigated through primarily resistivity, optical reflectance and heat capacity measurements. From optical reflectivity we identify the formation of a pseudogap concomitant to the β-As2Te3 to β'-As2Te3 transition. Based on this observation, in addition to a fourfold modulation of the b-axis as reported in the literature, as well as a resistivity anomaly and corresponding hysteresis associated with the phase transition, we propose that this β-As2Te3 to β'-As2Te3 phase transition is due to charge density wave order.
This charge density wave transition is observed to be tunable with both Ge and Cu doping, with evidence indicating that the increase in the number of charge carriers due to doping drives the transition temperature lower until, with Ge doping, the transition is entirely eliminated. Optical reflectivity was used to determine the plasma frequency (whose square is assumed proportional to the number of charge carriers) as a function of dopant-concentration for both dopants. Copper doping was found to add charge carriers in two regimes, with lower dopings adding more charge carriers proportionally up to around Cu0.1As2Te3 beyond which the increase in charge carriers per dopant added decreases. Ge adds substantially more charge carriers per stoichiometric dopant amount added and thus influences the transition temperature more than copper as doping is increased. Utilizing differential scanning calorimetry and heat capacity measurements, a phase diagram was created for doped β-As2Te3. It was found that at higher germanium doping concentrations, the β-As2Te3 structure could be stabilized, and oriented samples were obtained via slow cooling.
Lastly, properties of the pseudogap as doping was varied were investigated. It was found that the pseudogap exhibits a non-Bardeen Cooper Schrieffer-like behaviour with a sharp onset and weak temperature dependence, with doping increasing the characteristic gap energy despite the associated transition temperature decreasing. Predicated by these results we argue that β-As2Te3 may be a member of a group of short coherence length charge density wave materials.