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Abstract We have investigated crystalline AlGaAs/GaAs optical coatings with three ultra-stable cavities operating at 4 K, 16 K, 124 K and 297 K. The response of the cavities’ resonance frequencies to variations in optical power indicates non-thermal effects beyond the photo-thermo-optic effect observed in dielectric coatings. These effects are strongly dependent on the intensity of the intracavity light at 1.5 μm. When the rear side of the mirrors is illuminated with external light, we observe a prominent photo-modified birefringence for photon energies above the GaAs bandgap, which points to a possible mechanism relating our observations to the semiconductor properties of the coatings. Separately, we also present a low maintenance evolution of our 124 K silicon cavity system where the liquid nitrogen based cooling system is replaced with closed cycle cooling from a pulse-tube cryo-cooler. 

Bacteria subjected to antiseptic or antibiotic stress often develop tolerance, a trait that can lead to permanent resistance. To determine whether photodynamic agents could be used to counter tolerance, we evaluated three non-iron hemin analogs (M-PpIX; M = Al, Ga, In) as targeted photosensitizers for antimicrobial photodynamic inactivation (aPDI) following exposure to sublethal H2O2. Al-PpIX is an active producer of ROS whereas Ga- and In-PpIX are more efficient at generating singlet oxygen. Al- and Ga-PpIX are highly potent aPDI agents against S. aureus and methicillin-resistant strains (MRSA) with antimicrobial activity (3-log reduction in colony-forming units) at nanomolar concentrations. The aPDI activities of Al- and Ga-PpIX against S. aureus were tested in the presence of 1 mM H2O2 added at different stages of growth. Bacteria exposed to H2O2 during log-phase growth were less susceptible to aPDI but bacteria treated with H2O2 in their postgrowth phase exhibited aPDI hypersensitivity, with no detectable colony growth after treatment with 15 nM Ga-PpIX. 

THz-pulse driven scanning tunneling microscopy (THz-STM) enables access to the ultrafast quantum dynamics of low-dimensional material systems at simultaneous ultrafast temporal and atomic spatial resolution. State-selective tunneling requires precise amplitude and phase control of the THz pulses combined with quantitative near-field waveform characterization. Here, we employ our state-of-the-art THz-STM with multi-MHz repetition rates, efficient THz generation, and precisely tunable THz waveforms to investigate a single sulfur vacancy in monolayer MoS2. We demonstrate that 2D transition metal dichalcogenides (TMDs) are an ideal platform for near-field waveform sampling by THz cross-correlation. Furthermore, we determine the THz voltage via QEV scans, which measure the THz rectified charge Q as a function of THz field amplitude E and dc bias Vdc. Mapping the complex energy landscape of localized states with a resolution down to 0.01 electrons per pulse facilitates state-selective tunneling to the HOMO and LUMO orbitals of a charged sulfur vacancy. 

Transition metal dichalcogenide (TMD) twisted homobilayers have been established as an ideal platform for studying strong correlation phenomena, as exemplified by the recent discovery of fractional Chern insulator (FCI) states in twisted MoTe21–4 and Chern insulators (CI)5 and unconventional superconductivity6,7 in twisted WSe2. In these systems, nontrivial topology in the strongly layer-hybridized regime can arise from a spatial patterning of interlayer tunneling amplitudes and layer-dependent potentials that yields a lattice of layer skyrmions. Here we report the direct observation of skyrmion textures in the layer degree of freedom of Rhombohedralstacked (R-stacked) twisted WSe2 homobilayers. This observation is based on scanning tunneling spectroscopy that separately resolves the G-valley and K-valley moiré electronic states. We show that G-valley states are subjected to a moiré potential with an amplitude of ~ 120 meV. At ~150 meV above the G-valley, the K-valley states are subjected to a weaker moiré potential of ~30 meV. Most significantly, we reveal opposite layer polarization of the K-valley at the MX and XM sites within the moiré unit cell, confirming the theoretically predicted skyrmion layer-texture. The dI/dV mappings allow the parameters that enter the continuum model for the description of moiré bands in twisted TMD bilayers to be determined experimentally, further establishing a direct correlation between the shape of LDOS profile in real space and topology of topmost moiré band. 

Despite the intent to advance engineering education with NGSS, teachers across all grades lack self-efficacy in engineering pedagogy. Instructional shifts envisioned by NGSS, especially with inclusion of engineering, require substantial learning by teachers. For rural schools, due to geographic location and smaller collegial networks, there are challenges in providing content-specific professional learning. This project gathered researchers from four states to provide PL aligned to NGSS and delivered remotely to 150 rural teachers. In summer 2023, experts led a five-day workshop which modeled shifts called for by NGSS (e.g., equitable, discourse-rich, phenomena-based) and provided opportunities to experience next-generation teaching and learning. Likert scale surveys were collected before and after the workshop to gauge self-efficacy regarding teaching science and engineering. We found that science-focused PL, with engineering embedded rather than as stand-alone component, afforded growth in self-efficacy for teaching engineering. Pre-workshop surveys showed that teachers had higher self-efficacy towards teaching science than teaching engineering (Wilcoxon signed-rank; p<.001). Positive attitudes toward teaching science were leveraged to provide PL and pre-workshop to post-workshop analysis showed growth in self-efficacy towards teaching engineering (p<.001). Results are important for professional learning around teaching engineering, for professional learning with rural teachers, and for remote access to professional learning. 

Our work in progress draws from an ongoing investigation of the needs of elementary teachers in small, rural school districts. Due to geographic location, rural schools often struggle to provide content-specific professional learning (PL). Smaller networks of science in these settings may also be barriers. We are exploring how targeted instructional supports that take rural teachers’ contexts into consideration can be sustained through the implementation of cost-effective modest supports. Our research examines the immediate impacts of PL, sustainability of PL outcomes when coupled with modest supports, specific impacts on engineering instruction, and student learning impacts. The intervention started with an online PL to introduce teachers to the NGSS and provide them with a foothold for three-dimensional teaching. This PL was designed for rural teachers using online platforms and resources. The program’s conceptual framework leverages a suite of modest supports previously identified to sustain PL outcomes. These supports are designed to scaffold teachers’ professional growth, provide steady encouragement, and foster community. Approximately 160 teachers across four states were recruited to participate in a 1-year online program, which started with a 5-day PL focused on NGSS-aligned science and engineering instruction. Some modest supports that have since followed, such as professional learning community (PLC) sessions and dedicated electronic supports (e.g., Google Site, shared resources, etc.). These sessions have been tailored to support teachers in these rural settings. Since the project began, we have collected responses from participating teachers about supports they believe would aid their understanding of science and engineering instructional strategies. We are continuing to collect data as teachers are planning science and engineering learning experiences for their classrooms. Our presentation will share details about teachers’ needs and rural contexts, and findings about the immediate impacts of the intervention. 

Oftentimes engineering design tasks are thought of as acultural and devoid of community inclusion and values. However, engineering design is inherently a cultural endeavor. Problems needing engineering solutions or design thinking are situated in a specific community and need community solutions. This work in progress paper describes initial efforts from a project to help elementary and middle school teachers create culturally relevant engineering design tasks for implementation in their classrooms. To integrate best practices for culturally relevant pedagogy, the engineering design framework developed by UTeach Engineering was adapted to specifically address community needs and cultural values. Changes to the framework also include culturally relevant instructional strategies for classroom implementation. To situate the engineering design steps within a culturally relevant framework questions involving communities and students’ cultural needs, values, and expectations were posed in each stage of the design process. A water filtration engineering design task was situated in the cultural concept of “Mni Wiconi” (Water is life in the Dakota language). This was taught in a summer professional development workshop for a cohort of elementary and middle school teachers, in rural North Dakota, with school districts comprised of large Native American student populations. Teachers adapted this design task for their individual classrooms and content areas (science, math, social studies, ELA) and implemented it in their classrooms in the fall of 2021. Additional support for teachers was provided with fall workshop days aimed at helping them with the facilitation of a culturally relevant engineering task. To integrate culturally relevant teaching and good engineering design tasks, the North Dakota Department of Public Instruction’s Native American Essential Understandings Teachings of our Elder’s website was used. This allowed teachers and students to have firsthand knowledge of how various science and engineering concepts are framed within the indigenous community. Professional development focused on how to situate culturally responsive teaching in engineering design. For example, in one of the school districts the water filtration task was related to increased pollution of a nearby lake which holds significant importance for the local Tribal Nation. In addition to being able to visibly witness the demand for cleaner water, the book “We are Water Protectors” written by Carole Lindstrom, was used to provide cultural grounding for the Identify and Describe stages of the engineering design framework. Case studies of how teachers incorporated the water filtration design task into their lesson plans are presented along with their suggestions on how to improve classroom implementation. Future work in the program includes teachers and their students developing engineering design tasks situated in their own communities and cultures. 

Technologies that are appropriate, affordable, and sustainable are needed to increase incomes and resilience among sub-Saharan African smallholder farmers. A combination of thermization and low-cost evaporative cooling, termed Evakuuling, was developed to enable rural smallholder dairy farmers to preserve their evening milk in the absence of grid-electricity. The “EvaKuula” was configured to be powered by biogas. Biogas is used for the thermization process of the system. The evaporative cooling component is powered by wind. Use of biogas from domestic biogas plants add circularity value to smallholder farms. However, domestic biogas plant set-ups are relatively high capital investments and as such, a financial barrier to co-adoption with the EvaKuula. To lower this barrier, other energy sources have been considered. The purpose of this study was to assess alternative energy sources to power the thermization component of the EvaKuula. The list of energy sources considered included biogas, butane, kerosene, charcoal, and firewood. These energy sources were assessed with respect to the sum of the social and market costs. The product of a unit of fuel cost and the units consumed represented the “market cost.” The product of the long-term social carbon cost and total carbon dioxide emission equivalence represented the “social cost.” Regular and improved stoves were included in the charcoal and firewood analysis. As expected, biogas ranked on top of the list, followed by butane and kerosene. However, butane and kerosene are not easily accessible in rural setting. Approximated 76% of farmers in rural sub-Saharan Africa rely on firewood to meet domestic needs like cooking. Butane and kerosene are the fuel sources predominantly used in urban and peri-urban areas, due to accessibility and affordability. Incomes are typically higher among urban dwellers. Therefore, with butane and kerosene not readily available to the target EvaKuula users, the next best option was firewood, provided it is combusted in improved efficient stoves such as Lorena type. Key words: alternative energy, evaporative cooling, sustainable development, food security, circularity, smallholder farmers 

This qualitative study explores teachers’ perceptions of culturally relevant engineering design (CRED) through professional development (PD) that is the first phase of Project ExCEED (Exploring Culturally Relevant Engineering Education Design). The data were collected from nine participants from three public schools in North Dakota. The findings shed light on participants’ understandings of CRED, Next Generation Science Standards (NGSS), the engineering design cycle and determine how PD influences their views about CRED tasks. The findings suggest that the teachers perceive CRED tasks as authentic, sensitive to students’ needs, and modifiable to cross-curricular contents. The results of this study suggest that PD has a positive influence on participants’ culture-specific and engineering design knowledge, participants’ confidence with regards to implementing CRED and thinking beyond the classroom.