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Microelectromechanical Systems (MEMS) energy harvesters have been extensively investigated over the past decade, but increasing power density and long-term reliability under high acceleration and low frequency are still major concerns. This study focused on the development of a low-frequency lead zirconate titanate (PZT) based energy harvester capable of operating at high acceleration >4 g with high power density performance. This study investigates the performance effects of altering the electrode configuration and poling configuration to maximize power density. The study investigated using four different types of electrode configuration consisting of long and short interdigitated electrodes (IDE) to operate in d 33 mode, and traditional parallel plate configuration to operate in d 31 mode. The results were numerically and experimentally validated. The results illustrate that the d 33 mode configuration was able to generate >3200 μW mm -3 with good reliability of up to 4 g. 

The El Niño Southern Oscillation (ENSO) is a climate variation that occurs in the Eastern Equatorial Pacific (EEP) ocean, which influences the position of the thermocline today. The ENSO cycle is split into three states: a normal state, an El Niño state, and a La Niña state. Each one is marked by different sea surface temperatures (SST). Under normal conditions, the trade winds push warm water westward, away from the coast of South America. This allows cool water to upwell the east and creates a zonal SST gradient. Every few years, the trade winds slow, preventing the flow of warm water. This increases the SST in the EEP and produces an El Niño. The winds can also strengthen and move more warm water westward. The heightened zonal SST gradient forms a La Niña. This project investigates past conditions in the EEP by reconstructing the mean position of the thermocline: a layer in the ocean where temperature rapidly changes with depth. In the modern ocean, the thermocline is shallower in the east, where SSTs are cool, and deeper in the west, where SSTs are warm. The more uniform SST gradient during an El Niño event flattens the zonal slope thermocline; the stronger gradient during a La Niña steepens it. The temperature proxy used to determine past thermocline positions is the isotopic composition of oxygen in foraminifera (δ18O). Foraminiferal δ18O increases with depth in the water column, as temperature decreases and density increases. Two species with contrasting depth-habitats were analyzed; Globigerinoides ruber, which lives near the surface above the thermocline, and Neogloboquadrina dutertrei, which lives in the lower thermocline. When the thermocline shifts, it changes their difference in δ18O. A smaller difference indicates a deeper thermocline and an El Niño-like state; a greater difference indicates a shallower thermocline and a La Niña-like state. The forams were collected from two deep-sea sediment cores. The first was Ocean Drilling Program (ODP) Leg 202 Site 1239 (0.67˚S, 82.08˚W, 1414 m) drilled in the east near the coast of Ecuador. The second was ODP Leg 138 Site 849 (0.10˚S, 110.31˚W, 3858 m) toward the west. Rather than identifying specific ENSO events, this method provides insight into the position of the thermocline and therefore the mean state of the EEP during the Holocene and last glacial period. 

Sea star wasting disease (SSWD) refers to a suite of gross signs affecting Asteroidea species. These include epidermal lesions, everted viscera, arm autotomy, and ultimately, full body disintegration leading to mortality. The common sea starAsterias rubensis a keystone species in the coastal Northeast Atlantic and may be susceptible to the disease. While the precise aetiology of SSWD remains poorly understood, environmental instability, including rising sea temperatures, has been linked to SSWD outbreaks. To investigate this connection, an experiment was conducted to quantify disease sign expression inA. rubensunder elevated temperature. We exposed sea stars to either elevated temperature (18°C) or a control treatment (12°C) for a 14 d period. We quantified the presence of disease signs associated with SSWD, the progression of signs, and survival of individuals. Elevated temperature induced a greater number of signs consistent with SSWD and also resulted in mortality for some of those animals. Furthermore, larger individuals were more likely to show increased signs of disease. Our results provide evidence that signs associated with SSWD increase with elevated temperature.

 

Viruses that infect phytoplankton are abundant in all regions of the global ocean. Despite their ubiquity, little is understood regarding how biotic interactions can alter virus infection success as well as the fate of phytoplankton hosts. In previous work, the bacterially derived compound 2-heptyl-4-quinolone (HHQ) has been shown to protect the cosmopolitan coccolithophoreEmiliania huxleyifrom virus-induced mortality. The present study explores the potential mechanisms through which protection is conferred. Using a suite of transmission electron microscopy and physiological diagnostic staining techniques, we show that whenE. huxleyiis exposed to HHQ, viruses can gain entry into cells but viral replication and release is inhibited. These findings are supported by a smaller burst size, as well as lower infectious and total virus production when the host is treated with nanomolar concentrations of HHQ. Additionally, diagnostic staining results indicate that programmed cell death markers commonly associated with viral infection are not activated when infectedE. huxleyiare exposed to HHQ. Together, these results suggest that the ability of HHQ to inhibit infectious viral production protects the alga not from getting infected, but from cell lysis. This work identifies a new mechanistic role of bacterial quorum sensing molecules in mediating viral infections in marine microbial systems.

 

Trabecular bone is a spongy bone tissue that serves as a scaffolding-like support inside many skeletal elements. Previous research found allometric variation in some aspects of trabecular bone architecture (TBA) and bone microstructure, whereas others scale isometrically. However, most of these studies examined very wide size and phylogenetic ranges or focused exclusively on primates or lab mice. We examined the impact of body size on TBA across a smaller size range in the mammalian clade Xenarthra (sloths, armadillos, and anteaters). We µCT-scanned the last six presacral vertebrae of 23 xenarthran specimens (body mass 120 g–35 kg). We collected ten gross-morphology measurements and seven TBA metrics and analyzed them using phylogenetic and nonphylogenetic methods. Most metrics had similar allometries to previous work. However, because ecology and phylogeny align closely in Xenarthra, the phylogenetic methods likely removed some covariance due to ecology; clarifying the impact of ecology on TBA in xenarthrans requires further work. Regressions for Folivora had high P-values and low R-squared values, indicating that the extant sloth sample either is too limited to determine patterns or that the unique way sloths load their vertebral columns causes unusually high TBA variation. The southern three-banded armadillo sits far below the regression lines, which may be related to its ability to roll into a ball. Body size, phylogeny, and ecology impact xenarthran TBA, but parsing these effects is highly complex.

 

The association between student motivation and learning, and changes in motivation across a course, were evaluated for students enrolled in one-semester foundation-level inorganic chemistry courses at multiple postsecondary institutions across the United States. The Academic Motivation Scale for Chemistry (AMS-Chemistry) and the Foundations of Inorganic Chemistry American Chemical Society Exam (i.e., a content knowledge measure) were used in this study. Evidence of validity, reliability, and longitudinal measurement invariance for data obtained from the AMS-Chemistry instrument with this population were found using methodologies appropriate for ordinal, non-parametric data. Positive and significant associations between intrinsic motivation measures and academic performance corroborate theoretical and empirical investigations; however, a lack of pre/post changes in motivation suggest that motivation may be less malleable in courses primarily populated by chemistry majors. Implications for inorganic chemistry instructors include paths for incorporating engaging pedagogies known to promote intrinsic motivation and methods for incorporating affect measures into assessment practices. Implications for researchers include a need for more work that disaggregates chemistry majors when evaluating relationships between affect and learning, and when making pre/post comparisons. Additionally, this work provides an example of how to implement more appropriate methods for treating data in studies using Likert-type responses and nested data. 

The effects of total ionizing dose (TID) on SRAM physical unclonable functions (PUF) are studied through x-ray and proton irradiation of commercially available SRAM. Negative shifts in the Fractional Hamming Weight (FHW) were measured with increasing TID, indicating a migration of bistable cells towards logic low. Additionally, positive shifts in the intra-die Fractional Hamming Distance (FHD) were measured and indicate changes to the virtual fingerprint of an SRAM PUF with TID, especially in devices that were dosed while holding data. Shifts in inter-die FHD were negligible, allowing individual SRAMs still to be easily identified based on the FHD between a known and unknown sample even after moderate amounts of TID. In some cases, SRAMs could still be identified by their PUFs after the devices had failed. In all cases, the irradiated SRAM devices retain their virtual fingerprint after recovery through annealing. 

Chlorophyll (Chl) is widely taken as a proxy for phytoplankton biomass, despite well-known variations in Chl:C:biomass ratios as an acclimative response to changing environmental conditions. For the sake of simplicity and computational efficiency, many large scale biogeochemical models ignore this flexibility, compromising their ability to capture phytoplankton dynamics. Here we evaluate modelling approaches of differing complexity for phytoplankton growth response: fixed stoichiometry, fixed stoichiometry with photoacclimation, classical variable-composition with photoacclimation, and Instantaneous Acclimation with optimal resource allocation. Model performance is evaluated against biogeochemical observations from time-series sites BATS and ALOHA, where phytoplankton composition varies substantially. We analyse the sensitivity of each model variant to the affinity parameters for light and nutrient, respectively. Models with fixed stoichiometry are more sensitive to parameter perturbations, but the inclusion of photoacclimation in the fixed-stoichiometry model generally captures Chl observations better than other variants when individually tuned for each site and when using similar parameter sets for both sites. Compared to the fixed stoichiometry model including photoacclimation, models with variable C:N ratio perform better in cross-validation experiments using model-specific parameter sets tuned for the other site; i.e., they are more portable. Compared to typical variable composition approaches, instantaneous acclimation, which requires fewer state variables, generally yields better performance but somewhat lower portability than the fully dynamic variant. Further assessments using objective optimisation and more contrasting stations are suggested.