Bostonia. Volume 28

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Quantifying relationships between phosphorus availability and mycorrhizal associations in wetland plants

Increasing evidence indicates that plant community structure and therefore ecosystem function are mediated by below-ground fungal communities that form intracellular associations with plant roots called mycorrhizal associations. Arbuscular mycorrhizal fungi (AMF) are a type of mycorrhiza that colonize the plant host intracellularly but maintain hyphae outside the root cell for resource acquisition. The importance and function of AMF associations are well-documented in terrestrial ecosystems, but are less understood in aquatic or semi-aquatic systems. Phosphorus availability is the primary factor influencing mycorrhizal colonization and growth in terrestrial soils, with phosphorus-abundant soils leading to a decrease in mycorrhizal growth. However, the relationship between arbuscular mycorrhizal colonization and phosphorus supply in wetland systems is not well understood. Previous studies have examined this relationship, but have been limited by methodology and have indicated the need for studies closely mimicking natural conditions. To address this need, a field-based study was performed examining the mycorrhizal colonization of wetland plants growing in a natural wetland. Since field studies allow for only limited isolation and control of variables, a greenhouse study was also performed to isolate the impacts of phosphorus on mycorrhizal colonization in wetland plants. This study showed that phosphorus concentrations between 10 and 30 µg/L PO4-P are sufficient to alter mycorrhizal colonization in wetland plants, but the responses are species-specific. This variable impact on mycorrhizal colonization could induce species-specific responses in wetland plants, leading to shifts in community composition of wetland vegetation and ecosystem functioning

Mapping a New Socio-Political Landscape: British Columbia, 1871-1874

Historians have generally believed that the provincial legislature in post-Confederation British Columbia divided along “Island vs. Mainland” lines prior to the introduction of political parties. This myth is challenged in a study using political voting records and the computer-based methods of legislative roll-call analysis. A systematic re-examination of a traditional source, nineteenth-century newspapers, further supports a new interpretation: that in the inaugural period of Confederation an “Island vs. Mainland” schism did not exist in the B.C. legislature, but a “Rural vs. Urban” split was evident. The underlying divisive issue was adoption of the Canadian tariff.Les historiens ont cru en général que la législature provinciale de la Colombie- Britannique post-Confédération était partagée par une ligne de démarcation entre les représentants de l’île de Vancouver et ceux de la terre ferme avant l’arrivée des partis politiques. Ce mythe est contesté dans une étude fondée sur les documents électoraux politiques et les méthodes informatiques de l’analyse du vote législatif par appel nominal. Le réexamin systématique d’une source traditionnelle, les journaux du XIXe siècle, appuie également une nouvelle interprétation voulant qu’aucun schisme « île versus terre ferme » n’existait à la législature britannocolombienne durant la période inaugurale de la Confédération, mais qu’on y observait bel et bien une division « milieu rural versus milieu urbain ». La question divisive sous-jacente était l’adoption d’un tarif canadien

Doctor of Philosophy

dissertationThis dissertation defines a new class of climbing robots, steering-plane bipeds, which encompasses a large number of existing climbing robots. Three major levels of motion planning are characterized which are common to this class of robots, namely, path planning, step planning, and gait planning. The unified presentation of related motion planning techniques is more generally applicable and more thorough than related algorithms in other literature, while more explicitly identifying limitations and tradeoffs due to alternate design choices within the class of steering-plane bipeds. A novel spline-based method for generating gaits is presented which uses separate path and time rate controls, and explicitly defined foot approach and departure directions that allows 1) a nominal guarantee of collision-free foot trajectories when close to the desired step configuration, 2) independent control of gait shape and speed, and 3) a unified representation of the four gait families of steering-plane bipeds: flipping, inchworm, step-through, and spinning gaits. This dissertation presents a thorough examination of the variations within each gait family, rather than merely presenting a representative instance of each. Concrete case studies applying the techniques of this dissertation are presented for optimizing the gaits for overall speed, energy efficiency, and minimum gripping force and moment. The results highlight that many common gaits in the literature are far from optimal. Results and general rules of thumb for gait planning are extracted that allow guidance for obtaining good results even if using alternate planning techniques without optimization