3 pp. / Originally published 01/2010. / Invasive plants are plants that have been accidentally or intentionally introduced to an area outside their original range and become problematic in their new environment by interfering with native or desirable species. Landowners can help prevent the spread and assist in controlling these invasive plants. Revised 11/2016. Originally published 01/2010.

Neurosurgical retraction is a procedure that involves displacing brain tissue (i.e., to expose cancerous lesions). Current tools for retraction are mostly made of stainless steel and create localized regions of pressure. These tool-tissue interactions can be harmful and lead to postoperative complications. Research on soft robots is rapidly expanding due to their ability to safely interact with human tissue. Using principles of morphological computation, origami-inspired folding patterns have been developed to control the behavior of soft robots. However, for delicate brain tissue-tool interaction, greater control through the integration of soft sensing is required by surgeons. This work presents a pressure-actuated, origami-inspired soft robot with integrated sensing for measuring force during neurosurgical retraction procedures. The robot employs a circular Miura-origami (Miura-ori) pattern, creating well-defined contraction and expansion ratios. To embed a sensing modality in the robot, individual origami unit cells are modified to become flexible capacitors. These flexible Origami Sensing Modules (OSMs) change in capacitance when force is applied due to the displacement of capacitive plates. Surgeons can therefore monitor the procedure to ensure that dangerous levels of force are not exceeded. The OSM is fabricated using a layering technique that embeds a fluidic stiffening actuator within an elastomer dielectric. Thin copper films, which form the capacitive plates, sandwich this dielectric layer. Three OSMs, connected in series, are integrated into the circular Miura-ori pattern at evenly spaced locations. The force range and sensitivity of the OSMs are analyzed through force and motion characterization experiments which give an indication of the capacitive behavior during force application and actuation of the robot. Finally, an in-vitro setup was developed to model the retraction process in the brain and demonstrate the robot’s ability to retract brain tissue and sense the distributed forces. The development of this sensing mechanism allows for both monitoring and controlling the pressure on brain tissue during robotic retraction, demonstrating the potential of soft robots in neurosurgery. / 2025-08-29T00:00:00Z

Introduced cichlid species are increasingly more common in tropical freshwater systems and expanding in range, often with negative consequences to receiving systems. To better understand, monitor, and manage these populations, improved cichlid sampling protocols are required. The goal of this study was to (1) evaluate diel electrofishing and gill netting sampling catch efficiency, and (2) compare two non-lethal methods for extracting stomach contents from Butterfly Peacock Bass Cichla ocellaris. This study suggests that electrofishing, particularly at night, may be a more appropriate gear for sampling cichlid species in the littoral zone of reservoirs, as gill nets were more time intensive, had more variable catch rates, and exhibited considerable selectivity. Pulsed gastric lavage was more effective than acrylic stomach tubes for extracting stomach contents from Butterfly Peacock Bass and was less injurious, with bruising of the stomach wall the most common injury being observed.

Organismal invasions have repeatedly been cited as both a driving force behind global change and beneficiaries of that change. Although many drivers of these invasions have been well studied, few studies have addressed invasions through the perspective of native symbiont communities. In the Mountain Lake region of Virginia, crayfish host diverse assemblages of obligate cleaning symbionts known as branchiobdellida. This cleaning symbiosis has been found to result in significant fitness benefits for native crayfish. Historical survey work showed that invasive crayfish, known to be intolerant of symbionts, were introduced into the region by the 1960s. I carried out an extensive regional survey to determine how this invasion has progressed and what impacts it is having on the native crayfish-branchiobdellida symbiosis. Survey results show that invasive crayfish have successfully spread throughout the region, resulting in the displacement of native crayfish. Additionally, findings suggest that invasion results in significantly reductions in abundance and richness in native symbiont communities. To determine mechanisms contributing to observed impacts on native symbionts, I carried out a study that simulated displacement of native crayfish by invasive crayfish in a controlled setting. This study found that as native crayfish are increasingly displaced by invasive crayfish, both symbiont dispersal and survival are negatively affected. This potential loss of symbiosis caused by invasion may reduce symbionts on native crayfish below abundances necessary for fitness benefits, exacerbating the negative impacts of invasions and presenting a major conservation issue in invaded systems. / M. S. / Introductions of non-native organisms are widely recognized for the negative impacts they have on native biodiversity. Although ongoing study has been directed at understanding many of the factors contributing to invasions, few studies address invasion through the perspective of native symbionts. In the Mountain Lake region of Virginia, crayfish host multiple species of small worms, known as crayfish worms, that provide cleaning services to their crayfish host. These services have been found to provide health benefits to native crayfish. Historical surveys found that invasive crayfish, known to be intolerant of crayfish worms, were introduced into the region by the 1960s. To determine how far invasive crayfish have spread and what impacts they are having on native organisms, I carried out a survey of the region. This survey found that invasive crayfish are now widespread in the region. Additionally, findings suggest that the introduction of invasive crayfish results in reductions in both the number of worms and worm species present. These reductions may be significant enough to prevent health benefits given to native crayfish from occurring. In addition to this survey, I carried out a study under controlled settings to determine what causes negative impacts on native crayfish worms. This study found that as invasive crayfish displace native crayfish, crayfish worms are increasingly killed due to the intolerance of invasive crayfish to the worms. These findings suggest symbiosis should be included in studies of invaded systems if we are to fully understand the introduction and spread of invasive species.

A major trend in invasion biology is the development of models to accurately predict and define invasive species and the stages of their invasions. These models focus on a given species with an assumed set of traits. By doing so, they fail to consider the potential for differential success among different source populations. This study looked at the inland invasion of Rhithropanopeus harrisii in the context of a current invasion model. This species has been introduced worldwide, but has only invaded freshwater reservoirs within the state of Texas (United States) indicating a potential difference amongst source populations. Previous studies indicate that this species should not be capable of invading inland reservoirs due to physiological constraints in the larvae. A more recent study gives evidence to the contrary. To investigate whether the inland populations are in fact successfully established, I attempted to answer the following questions: Can inland populations successfully reproduce in the inland reservoirs and rivers? If so, what factors in the native environment could have led to the evolution of this ability? What are the impacts of this species in the inland reservoirs and what is its potential spread? I combined a larval developmental study, conspecific and heterospecific crab competition trials, field collections, gut content analysis, shelter competition trials with crayfish, and larval and adult dispersal study to answer these questions. I showed that Rhithropanopeus harrisii is established in the inland reservoirs and capable of spreading. I demonstrated that in the native populations along the Gulf coast of the United States, this species is the least aggressive and is therefore likely excluded into lower salinity waters during reproductive periods. This likely led to a lowered salinity tolerance in the larval stages, which predispose these populations to successful introductions in inland freshwater bodies. I showed that the crabs are capable of outcompeting juvenile crayfish for shelter at high densities and therefore warrant management in order to reduce their effect. This study indicates a need for the invasion models to take the source population into account in order to ensure effective and prudent management strategies.

Thesis (M.S.)--Indiana University, 2008. / Title from screen (viewed on April 23, 2008). Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Gabriel M. Filippelli, Catherine J. Souch, Gary D. Rosenberg. Includes vitae. Includes bibliographical references (leaves 85-87).

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references. Also available in electronic format on the Internet.

Thesis (Ph. D.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 182-194). Also available via the World Wide Web.

Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 55-57). Also available via Humboldt Digital Scholar.

Thesis (M. Sc.)--University of Canterbury, 2009. / Typescript (photocopy). "May 2009." Includes bibliographical references (leaves 98-115). Also available via the World Wide Web.