No description available.

No description available.

No description available.

No description available.

In the global fight against antibiotic resistance, the need for alternatives is more pressing than ever. Antimicrobial peptides (AMPs), short oligopeptides usually produced as part of the immune system of a host, have shown great promise against resistant bacteria, biofilms and even cancer cells. Engineering AMPs that are both specific to a set of bacteria and stable is among the main challenges of the field. Herein, we propose two separate tools to support these efforts. The first one is an AMP SECretion system based in E. coli, dubbed AMPSEC, that can be used to produce active AMPs with specific targets (i.e., gram-positive bacteria or any specific specie). This recombinant protein system uses surface display technologies coupled with specific protease activity to express, export, and release functional AMPs that could readily affect neighbouring target bacteria. The AMPSEC would be ideal to screen AMP libraries, removing the need for purification or chemical synthesis in order to observe toxicity. It could also be used for AMP production, where the secreted AMPs would be purified from the growth medium by HPLC. Finally, if the recombinant system is inserted in a probiotic host, it might even be useful to deliver AMPs in the gut to treat dysbiosis. Herein, we explored six surface display apparatuses for their applicability for AMPSEC and found three out of the six being fully functional in transporting the cargo although the cleaving activity needs to be coordinated better with its localization at the outer membrane. A robust proof-of-concept workflow has also been established and used to evaluate the performance of those six display apparatuses. The second is a bioinformatics approach to highlighting the relationship between the primary structure and the microbial target specificity of AMPs. Our method first clusters sequences from the DRAMP AMP repository using the Linclust algorithm. De novo motif discovery tools can then extract AMP sequence motifs relating to target specificity. These motifs could guide randomized sequence AMP library creation and decrease the number of inactive sequences generated. Clustering AMPs, however, proved to be rather challenging due to the large sequence length variation in the databases, the small sample size and their overall short lengths. It would then be necessary to design an algorithm suited to handle this specific kind of proteomics dataset. A library eventually created using the discovered motifs could then be used with AMPSEC. Combined, these two tools will further improve our ability to design stable AMPs targeting specific bacteria.

Stereographic virtual environments display data in such a way that a user perceives objects within the displayed environment to be separated in depth from the display itself. The effectiveness of stereographic virtual environments as learning tools has been evaluated relative to factors such as multidimensional cues, user interaction, and learner characteristics. This study has examined the relationship between two evaluative factors: the presence of stereographic depth cues and field dependence, a learner characteristic associated with performance on visual tasks. Adult learners were identified on a field dependence continuum based on scores on the Group Embedded Figures Test. Each student received instruction related to the heart using stereographic materials or nonstereographic materials, depending on assignment to treatment group. All participants were given two tests, identification and terminology, following this instruction. The scores on the combination of these tests, denoted as the Modified Total Criterion Test (MTCT), represented the level of visual recall relative to the instructional materials reviewed. Analyses of variance revealed an interaction effect between the level of field dependence and the presence of stereographic depth cues within a virtual environment such that field independent participants scored higher on tests of visual recall within stereographic conditions versus nonstereographic conditions and field dependent participants scored lower within stereographic conditions versus nonstereographic conditions. / Ph. D.

An increasing number of students are learning in classrooms that employ electronic presentations designed in PowerPoint and other similar software programs. The design of the slides in such electronic presentations has an impact upon student learning, and ample recommendations are made within the literature as to specific strategies that serve as presumed best practices for the design of those slides that will best facilitate learning. While most of such recommended strategies are well supported by cognitive theory – they are considered to positively impact learning by contributing to decreased cognitive load, leveraged dual coding, and facilitated active processing, for example – many of them are not supported by empirical evidence that they do in fact enhance learning. Some of the recommended best practice strategies unsupported by empirical evidence include the use of progressive disclosure, dimming, and highlighting of text instead of full disclosure of text. Through the development and use of four separate electronic presentations, each of which was designed to employ one of these specific strategies (full disclosure, progressive disclosure, dimming, and highlighting), this study examined the impact of such strategies on student learning. The findings of this study indicate that significant differences are not evident in learning among the four different strategies. As such, this initial foray into the examination of the effectiveness of these four strategies indicates that any of the four strategies may be used with equal impact in the design of electronic presentations by instructors who want to help foster student learning. / Doctor of Philosophy / An increasing number of students are learning in classrooms that employ electronic presentations designed in PowerPoint and other similar software programs. The design of the slides in such electronic presentations has an impact upon student learning, and ample recommendations are made within the literature as to specific strategies that serve as presumed best practices for the design of those slides that will best facilitate learning. While most of such recommended strategies are well supported by cognitive theory, many of them are not supported by empirical evidence that they do in fact enhance learning. Some of the recommended best practice strategies unsupported by empirical evidence include the use of progressive disclosure, dimming, and highlighting of text instead of full disclosure of text. Through the development and use of four separate electronic presentations, each of which was designed to employ one of these specific strategies (full disclosure, progressive disclosure, dimming, and highlighting), this study examined the impact of such strategies on student learning. The findings of this study indicate that significant differences are not evident in learning among the four different strategies. As such, this initial foray into the examination of the effectiveness of these four strategies indicates that any of the four strategies may be used with equal impact in the design of electronic presentations by instructors who want to help foster student learning.

The field of synthetic biology has leveraged engineering tools such as molecular cloning to create new biological components, networks, and processes. While many of these components and networks have been deployed in the cytosol, there is a shortage of systems that utilize the surface of the cell. In order to address this shortcoming, we have created a synthetic, surface-displayed substrate anchor for bacteria. This approach allows us to engineer surface-based synthetic biological systems as a complement to existing intracellular approaches. We leveraged the tools of synthetic biology to display a catalytically active enzyme that covalently bonds itself to benzylguanine (BG) groups. We created a fusion protein allowing us to place human O6-alkylguanine DNA alkyltransferase (hAGT), also known as SNAP, on the surface of a bacterial cell. Initially, we used this synthetic component as a tool for spatially segregating orthogonal synthetic gene outputs by visualizing an extracellular synthetic green fluorescent reporter, SNAP-Cell® 505-Star, simultaneously with an intracellular red fluorescent protein, mCherry. Moreover, we have shown that our construct enables cells to selectively bond to BG-conjugated magnetic beads. As a result, we have demonstrated that surface displayed SNAP facilitates engineering a direct channel between intracellular gene expression and extracellular material capture. In the near future, we believe this magnetic capture can be expanded as a sortable reporter for synthetic biology as a direct extension of this work. Moreover, our work serves as an enabling technology, paving the way for extracellular synthetic biological systems that may coexist orthogonally to intracellular processes. / Master of Science

A broad range of element size, element shape, and interelement spacing/element size ratio combinations at high and low ambient illuminance levels was used to determine optimal combinations for a 5 X 7 dot matrix visual display. Three tasks - a reading test, a random search task, and a structured (menu) search task - were used to enhance the utility of the research. All tasks were displayed on a CRT display 1.02 m from the subject. There were different overall results for the reading and the search tasks, as shown by an analysis of variance. The smaller elements (0.76 and 1.14 mm) and the 0.5 space/size ratio produced the shortest reading times, while the shortest search times came from the larger elements (1.14 and 1.52 rum). The square shape and low illuminance level (5.4 lux) had the shortest times for all three tasks. For a general purpose display, the combination of a square 1.14 rum dot, with 0.57 mm edge-to-edge spacing is recommended, to be used with the lowest practical ambient illuminance. / Master of Science

Large, high resolution displays combine high pixel density with ample physical dimensions. Combination of these two factors creates a multi-scale workspace where object targeting requires both high speed and high accuracy for nearby and far apart targeting. Modern operating systems support dynamic control-display gain adjustment (i.e. cursor acceleration) that helps to maintain both speed and accuracy. However, very large high resolution displays require broad range of control-display gain ratios. Current interaction techniques attempt to solve the problem by utilizing multiple modes of interaction, where different modes provide different levels of pointer precision. We are investigating the question of the value of allowing users to dynamically choose granularity levels for continuous pointing within single mode of interaction via multiple acceleration curves. Our solution offers different cursor acceleration curves depending on the targeting conditions, thus broadening the range of control-display ratios. Our approach utilizes a consumer multitouch touchpad that allows fast and accurate detection of multiple fingers. A user can choose three different acceleration curves based on how many fingers are used for cursor positioning. Our goal is to investigate the effects of such multi-scale interaction and to compare it against standard single curve interaction. / Master of Science