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The etching of ZnO thin films using acetylacetone (Hacac) doses with long exposure times, followed by purging and subsequent exposure to O2 plasma, is studied in a hot-wall reactor using simultaneous in situ spectroscopic ellipsometry and quadrupole mass spectrometry. The static exposure step results in the efficient consumption of Hacac. For each etch cycle, the O2 plasma plays a crucial role in removing unreacted Hacac from the ZnO surface, priming the surface for subsequent Hacac etching. This is confirmed by the production of CO2 during the O2 plasma pulse. The temperature window for etching is established as 220–280 °C with a maximum etch per cycle (EPC) of 0.15 nm/cy. Under these conditions, the Hacac pulse is 2 s long with a 30 s static hold step followed by 5 s O2 plasma step at 300 W power. Statistical analyses of etch data at the granularity level of each cycle reveal the importance of the static hold step in determining EPC. Arrhenius behavior of etching during the hold step reveals a piecewise linear trend with a low temperature (120–200 °C) activation energy (Ea) of 202 meV and a high temperature (200–320 °C) Ea of 32 meV. It is shown that saturation behavior in EPC is pulse time and static hold time dependent. Shorter Hacac pulses (≤1 s) demonstrate saturation behavior for static hold times ∼30 s, longer pulses of Hacac (≥2 s) show no saturation in EPC with static hold times up to 75 s. 

In order to promote justice-centered making in STEAM classrooms, the NASA Landsat-based Science and Technology Education for Land/Life Assessment (STELLA) instrument is proposed as an affordable educational tool for students to collect and analyze data pertaining to vegetation health, surface temperature, and air quality. This instrument can be used to investigate justice-centered, community-based problems and promote civic engagement toward policy change for a healthier world. Our study applies the MakerTPICK theoretical framework to a qualitative study to explore changes in teacher beliefs about the STELLA instrument following three justice-centered STEAM-making activities pertaining to urban heat islands, air quality, and vegetation health. The implications of this research can be used to inform professional development and promote justice-centered learning in the STEAM classroom. 

In this session, we will share our model for K-5 STEM teacher leadership. 

ABSTRACT Spatial organization of pathway enzymes has emerged as a promising tool to address several challenges in metabolic engineering, such as flux imbalances and off-target product formation. Bacterial microcompartments (MCPs) are a spatial organization strategy used natively by many bacteria to encapsulate metabolic pathways that produce toxic, volatile intermediates. Several recent studies have focused on engineering MCPs to encapsulate heterologous pathways of interest, but how this engineering affects MCP assembly and function is poorly understood. In this study, we investigated the role of signal sequences, short domains that target proteins to the MCP core, in the assembly of 1,2-propanediol utilization (Pdu) MCPs. We characterized two novel Pdu signal sequences on the structural proteins PduM and PduB, which constitute the first report of metabolosome signal sequences on structural proteins rather than enzymes. We then explored the role of enzymatic and structural Pdu signal sequences on MCP assembly by deleting their encoding sequences from the genome alone and in combination. Deleting enzymatic signal sequences decreased the MCP formation, but this defect could be recovered in some cases by overexpressing genes encoding the knocked-out signal sequence fused to a heterologous protein. By contrast, deleting structural signal sequences caused similar defects to knocking out the genes encoding the full-length PduM and PduB proteins. Our results contribute to a growing understanding of how MCPs form and function in bacteria and provide strategies to mitigate assembly disruption when encapsulating heterologous pathways in MCPs.IMPORTANCESpatially organizing biosynthetic pathway enzymes is a promising strategy to increase pathway throughput and yield. Bacterial microcompartments (MCPs) are proteinaceous organelles that many bacteria natively use as a spatial organization strategy to encapsulate niche metabolic pathways, providing significant metabolic benefits. Encapsulating heterologous pathways of interest in MCPs could confer these benefits to industrially relevant pathways. Here, we investigate the role of signal sequences, short domains that target proteins for encapsulation in MCPs, in the assembly of 1,2-propanediol utilization (Pdu) MCPs. We characterize two novel signal sequences on structural proteins, constituting the first Pdu signal sequences found on structural proteins rather than enzymes, and perform knockout studies to compare the impacts of enzymatic and structural signal sequences on MCP assembly. Our results demonstrate that enzymatic and structural signal sequences play critical but distinct roles in Pdu MCP assembly and provide design rules for engineering MCPs while minimizing disruption to MCP assembly. 

In depth thermogravimetric analysis and direct comparison of commercial volatile molecular tungsten-based precursors for atomic layer deposition. 

Early to intermediate ontogenetic stages of trees are important in forest regeneration. However, these critical life stages are often overlooked due to survey intensity and impracticality and/or disinterest in characterizing early life stage cohorts. This problem is particularly pervasive in mangrove forests where visibility of smaller stature trees may be limited by tidal flooding and younger cohorts are particularly vulnerable to changing hydrologic and biogeochemical conditions driven by climate change. Lacking data on early life stages in mangrove forests makes it difficult to predict ecosystem degradation and inform habitat resilience and restoration in one of the earth's most valuable blue carbon ecosystems. We identify challenges to collecting empirical data on early to intermediate age classes in mangroves and provide solutions to characterizing these cohorts. We emphasize the importance of gathering these data for improved understanding of forest regeneration dynamics and provide multi-scalar solutions to quantify vegetation structure of mangrove forest. 

Regulation of ion channel expression on the plasma membrane is a major determinant of neuronal excitability, and identifying the underlying mechanisms of this expression is critical to our understanding of neurons. Here, we present two orthogonal strategies to label extracellular sites of the ion channel TRPV1 that minimally perturb its function. We use the amber codon suppression technique to introduce a non-canonical amino acid (ncAA) with tetrazine click chemistry, compatible with a trans-cyclooctene coupled fluorescent dye. Additionally, by inserting the circularly permutated HaloTag (cpHaloTag) in an extracellular loop of TRPV1, we can incorporate a fluorescent dye of our choosing. Optimization of ncAA insertion sites was accomplished by screening residue positions between the S1 and S2 transmembrane domains with elevated missense variants in the human population. We identified T468 as a rapid labeling site (∼5 min) based on functional and biochemical assays in HEK293T/17 cells. Through adapting linker lengths and backbone placement of cpHaloTag on the extracellular side of TRPV1, we generated a fully functional channel construct, TRPV1exCellHalo, with intact wild-type gating properties. We used TRPV1exCellHalo in a single molecule experiment to track TRPV1 on the cell surface and validate studies that show decreased mobility of the channel upon activation. The application of these extracellular label TRPV1 (exCellTRPV1) constructs to track surface localization of the channel will shed significant light on the mechanisms regulating its expression and provide a general scheme to introduce similar modifications to other cell surface receptors.