Katherine G. Nelson

Selective enrichment yields robust ethene-producing dechlorinating cultures from microcosms stalled at cis-dichloroethene.

Dehalococcoides mccartyi strains are of particular importance for bioremediation due to their unique capability of transforming perchloroethene (PCE) and trichloroethene (TCE) to non-toxic ethene, through the intermediates cis-dichloroethene (cis-DCE) and vinyl chloride (VC). Despite the widespread environmental distribution of Dehalococcoides, biostimulation sometimes fails to promote dechlorination beyond cis-DCE. In our study, microcosms established with garden soil and mangrove sediment also stalled at cis-DCE, albeit Dehalococcoides mccartyi containing the reductive dehalogenase genes tceA, vcrA and bvcA were detected in the soil/sediment inocula. Reductive dechlorination was not promoted beyond cis-DCE, even after multiple biostimulation events with fermentable substrates and a lengthy incubation. However, transfers from microcosms stalled at cis-DCE yielded dechlorination to ethene with subsequent enrichment cultures containing up to 109 Dehalococcoides mccartyi cells mL−1. Proteobacterial classes which dominated the soil/sediment communities became undetectable in the enrichments, and methanogenic activity drastically decreased after the transfers. We hypothesized that biostimulation of Dehalococcoides in the cis-DCE-stalled microcosms was impeded by other microbes present at higher abundances than Dehalococcoides and utilizing terminal electron acceptors from the soil/sediment, hence, outcompeting Dehalococcoides for H2. In support of this hypothesis, we show that garden soil and mangrove sediment microcosms bioaugmented with their respective cultures containing Dehalococcoides in high abundance were able to compete for H2 for reductive dechlorination from one biostimulation event and produced ethene with no obvious stall. Overall, our results provide an alternate explanation to consolidate conflicting observations on the ubiquity of Dehalococcoides mccartyi and occasional stalling of dechlorination at cis-DCE; thus, bringing a new perspective to better assess biological potential of different environments and to understand microbial interactions governing bioremediation.

Work in progress: Evaluation of an online education portal from the user's perspective: An empirical investigation of a photovoltaics (PV) engineering learning portal, pveducation.org

In the last couple of decades, Photovoltaic (PV) solar systems have captured a lot of interest as a clean, renewable energy option. As a result, PV engineering has become an emerging field in engineering education. In order to meet increased learning requirements, new learning resources, an effective curriculum and proper assessment are needed. Pveducation.org is one of the disciplines oldest learning resources, providing PV content for photovoltaic professionals. The purpose of this paper is (1) evaluating the effectiveness of the pveducation.org learning portal from the users perspective, and (2) find a relationship between the effectiveness of the website and users learning gains. This study will conduct a systematic assessment of educational technology by using statistical techniques and data collected through a survey.

Work in progress: Developing engineering systems thinking through the modeling of a complex bioengineering system

Systems thinking is an important habit of mind that should be promoted in K-12 engineering education. This work in progress paper describes how systems thinking was introduced in middle school grades through the modeling of a biological system: the artificial heart. Preliminary qualitative results show that introducing systems thinking through modeling is both feasible and useful. Students demonstrated their knowledge of the heart as a system through the structural, functional, and behavioral components of their models.

Work in progress: Identification of misconceptions governed by emergent phenomena in photovoltaics content using the Delphi Method

With the emphasis and growth of solar energy, there is a rising need to educate students to perform in PV engineering. However, the curriculum for PV Engineering has not been well-articulated-needing both a focus on what that content is, and also what learning challenges students face when they learn it. Misconceptions, primarily those resulting from a limited understanding of emergent phenomena, can act as significant barriers to learning, and as such should be considered in curriculum development. The purpose of this work-in-progress is to use the Delphi Method to identify emergent phenomena in PV that is critical to the understanding of PV, while highlighting the resulting misconceptions that can result when students learn this content.