Impressions

Publication for alumni and friends of Boston University Henry M. Goldman School of Dental Medicin

Impressions, Winter 2017

Magazine for alumni and friends of the Boston University Dental School

Understanding the Development of a Logic Model in a Multi-Agency Resource Centre

In response to social and economic decline in the downtown area of Sault Ste Marie, Ontario, over thirty diverse community organizations collaborate to deliver services out of the Neighbourhood Resource Centre (NRC). This study seeks to uncover how the objectives of the NRC are being interpreted and enacted by community organizations, and how the organizations navigate diverse desired outcomes to create a logic model. Through participatory action research, the study sought to answer the research questions through field observation, semi-structured interviews, and focus groups. An analysis of the data yields that, through collaboration and engagement the NRC has strengthened the neighbourhood while promoting belonging, as well as, the NRC enacts continuous evaluation, which allows participants to overcome barriers and get on the same page. This study belongs to a growing body of literature that seeks to understand how logic models are developed across diverse collaborations and will contribute to future research on collaborative planning and evaluation

Demonstrator for Selectively Compliant Morphing Systems with Multi-stable Structures

The field of morphing wings presents significant potential for increasing the efficiency of aircraft. Conventional designs used in the industry limit the adaptability of aerodynamic surfaces to address an engineering trade-off between load-carrying and compliance. This same trade-off remains a factor in morphing wings, which must also balance weight considerations while attempting to remain competitive with conventional designs. The current state-of-the-art in morphing wings is briefly described in this work. This is followed by an investigation into a new application of the principle of selective stiffness, by which local changes in stiffness may be applied to affect the global structural characteristics. In this manner, this trade-off is addressed by providing the ability to allow a deformation mode when undergoing shape change and restrict it when sustained load-carrying is required. This principle has previously been explored using pre-stressed composite laminates to produce a bi-stable structure with unique curvature in each stable state. Geometrically bi-stable structures are explored for the same purpose in this research. Three types of bi-stable element are explored and presented. The last of these is then embedded in a simple airfoil concept. The placement and geometry of this element are optimized, and a physical model is produced using additive manufacturing. This physical model is finally mechanically tested to assess the stiffness in each stable state of the embedded element

An examination of the Geochemical properties of late devensian glacigenic sediments in Eastern England

Onshore advance of the North Sea lobe of the Late Devensian British Ice Sheet the last glaciation resulted in the deposition of thick multiple till sequences along the coasts of east Yorkshire and north Lincolnshire. Despite an abundance of sedimentological and stratigraphical data, the origin of these tills remains controversial, and their correlation along the coast is poorly understood. These multiple till sequences provide an excellent opportunity to test models of large-scale subglacial sediment transport and deposition beneath soft-bed ice sheets using geochemistry. Such geochemical analysis has been used extensively in other formerly glaciated areas, notably Canada, to identify till characteristics and dispersal patterns. However, to date it has not been applied in any detail to glacial sediments in the UK and its potential as a tool for till correlation and understanding till genesis remains relatively undeveloped. A detailed sampling method was employed at seven sites in eastern England; Filey, Skipsea, Dimlington, South Ferriby, Kirmington, Welton-Le-Wold and Morston; to investigate vertical and lateral changes in till geochemistry in this region. Particle size analysis of the till matrix was used as an additional tool to provide extra sedimentological data. Complete linkage and Ward's method cluster analysis was used to establish groups of geochemically similar diamicton samples. Geochemical results suggest that there are vertical changes in till geochemistry, which are likely to be related to a change in provenance from local to more distal sources. Geochemistry and particle size results were also unable to precisely differentiate between the Basement, Skipsea and Withernsea till types. Instead, the repeated nature of the geochemical signature at larger sites, such as Dimlington, and the lateral discontinuity of some geochemical groups suggests that the till sequences at Filey, Dimlington, and Skipsea are comprised of a number of lithologically distinct rafts which have been tectonically stacked or elevated to higher levels in the sediment pile. At Dimlington the production of a glacitectonically folded and stacked moraine is proposed as a mechanism to explain the remarkably thick sequence of Withemsea Till and the repeated nature of the geochemical signature at this site. This research therefore provides new evidence for our understanding of glacial stratigraphy and former ice dynamics in eastern England, suggesting that till composition and the mechanics behind its production are more complex than the traditional stratigraphic division allows

The Eagle Ford Formation

Geological Science

The First Anionic Thia-Fries Rearrangement at the Cobaltocenium Cation

While the chemistry of ferrocene is rich and widely explored, this is not the case for the isoelectronic cobaltocenium cation. Here we report the first syntheses of triflate substituted cobaltocenium cations based on respective (cyclopentadienone)(cylopentadienyl)cobalt(I) complexes, which have first been reported by Vollhardt et al. ca. forty years ago. Reaction with triflic anhydride affords the triflate substituted cobaltocenium cations, which upon treatment with lithium diisopropylamide undergo the first anionic thia-Fries rearrangements of cobaltocenium complexes. To our knowledge, this is, in addition, the first case of a deprotonation of a cobaltocenium complex by a lithium base. Alternatively, desilylation of silyl derivatives with cesium fluoride caused anion formation leading to the rearrangement products in higher yields. The 2-(trifluoromethylsulfonyl)(cyclopentadienone) complexes obtained were fully characterized including a crystal structure analysis. As with ferrocene, respective mesylates or tosylates do not undergo the rearrangement

Humphrey Center News: Spring/Summer 1986 v. 2, no. 2

Newsletter of the Hubert H. Humphrey Cancer Research Center at Boston University School of Medicine

Sulfur reduction in sediments of marine and evaporite environments

Transformations of sulfur in sediments of ponds ranging in salinities from that of normal seawater to those of brines saturated with sodium chloride were examined. The chemistry of the sediment and pore waters were focused on with emphasis on the fate of sulfate reduction. The effects of increasing salinity on both forms of sulfur and microbial activity were determined. A unique set of chemical profiles and sulfate-reducing activity was found for the sediments of each of the sites examined. The quantity of organic matter in the salt pond sediments was significantly greater than that occurring in the adjacent intertidal site. The total quantitative and qualitative distribution of volatile fatty acids was also greater in the salt ponds. Volatile fatty acids increased with salinity

Fluorosulfonylferrocene, (Trifluoromethylsulfonyl)ferrocene and New Ferrocenyl Sulfonates: Directed ortho Lithiation and New Anionic Thia-Fries Rearrangements at Ferrocene

Ferrocenyl triflates are known to undergo anionic thia-Fries rearrangements at low temperature in high yields. In order to expand the scope of this reaction, ferrocenyl sulfonates and sulfonylferrocenes were prepared and their reactivity investigated. Treatment of ferrocenyl fluorosulfonate with lithium 2,2,6,6-tetramethylpiperidide gave rise to a new anionic thia-Fries rearrangement at ferrocene. The formation of a rare oxathiine was observed with ferrocenyl (pentafluorophenyl)sulfonate as a result of an ortho lithiation and a subsequent intramolecular nucleophilic aromatic substitution. In contrast to fluorinated ferrocenyl sulfonates, fluorosulfonylferrocene as well as (trifluoromethylsulfonyl)ferrocene underwent ortho lithiation under comparable reaction conditions