Search for: All records

Oyster reef restoration efforts and on-bottom aquaculture are frequently plagued with high predation rates. Oysters are phenotypically plastic, and rearing juvenile oysters, Crassostrea virginica, with predator cues causes them to grow stronger shells that increases survivorship in the field. However, induced defenses (e.g., shell hardening in oysters) are often associated with cost-benefit trade-offs, and the extent the increased shell strength persists into adulthood and alters the growth of somatic and reproductive tissues remains unknown. We raised diploid oysters (used in reef restoration) and triploid oysters (used in aquaculture) with and without predator cues for one month before placing individuals on an oyster farm to grow to market size. Oyster shell characteristics, soft tissue mass, and reproductive investment were measured periodically over one year of culture and compared across treatments. Both diploid and triploid oysters had significantly stronger and smaller shells than controls at the end of their nursery period. However, while diploid shells became 15 % stronger and 17 % smaller than controls, triploid shells became 28 % stronger and 23 % smaller. Additionally, triploid oysters exposed to predator cues returned to the size of controls faster and maintained their shell strength differences longer than diploids. Differences in soft tissue mass between treatments mirrored the patterns exhibited in shell size and weight with greater initial physiological costs and faster recovery for triploid individuals. There was no significant difference in somatic or reproductive tissue mass between induced and control oysters of the same ploidy after seven months in the field. Triploid oysters were 15–110 % larger than diploids depending on the characteristic measured at maturity. Additionally, there was a significant interaction between treatment and ploidy because induced triploids had marginally greater growth than their control counterparts while induced diploids had marginally less growth than controls. These findings demonstrate that physiological costs of oysters reacting to predators in early life stages are minimal by the time individuals reach maturity. Early exposure to predator cues is a promising tool for improving oyster survivorship in restoration and aquaculture operations, especially in regions with high predation pressure. 

Nanohybrids of graphene and colloidal semiconductor quantum dots (QDs/Gr) provide a promising quantum sensing scheme for photodetection. Despite exciting progress made in QDs/Gr photodetectors in broadband from ultraviolet to short-wave infrared, the device performance is limited in middle-wave infrared (MWIR) detection. A fundamental question arises as to whether the thermal noiseinduced dark current and hence poor signal-to-noise ratio in conventional uncooled MWIR photodetectors persist in QDs/ Gr nanohybrids. Herein, we investigated noise, responsivity (R*), and specific detectivity (D*) in HgTe QDs/Gr nanohybrids, revealing that the noise and R* are decoupled in nanohybrids and each can be optimized independently toward its theoretical limit. Specifically, the noise in the QDs/Gr nanohybrids is dominated by that of graphene with a negligible effect from the dark current in HgTe QDs and can be optimized to its intrinsic limit by removing charge doping of adsorbed polar molecules on graphene. Furthermore, the R* is proportional to the photoconductive gain enabled by the strong quantum confinement in QDs and Gr. Achieving high gain in the MWIR spectrum, however, is challenging and requires elimination of charge traps primarily from the surface states of the narrow-bandgap semiconductor HgTe QDs. Using grain-rotation-induced grain-coalescence growth of single-layer and core/shell HgTe QDs, we show the that HgTe QDs surface states caused by Te deficiency can be dramatically suppressed, resulting in high gain up to 4.0 × 107 in the MWIR spectrum. The optimized noise and R* have led to high uncooled MWIR D* up to 2.4 × 1011 Jones, making nanohybrids promising to surpass the fundamental dark-current limit in conventional photodetectors. 

Reverse electrowetting-on-dielectric (REWOD) energy harvesting is an effective energy harvesting method at low frequencies such as the frequencies of human motion. Various REWOD energy harvester designs have been presented in prior works, but these generally use rigid and often expensive substrates and time-consuming and/or costly fabrication methods. To address these challenges, in this work REWOD energy harvesters were fabricated consisting of aluminized polyester sheets as the functional layers and with polycarbonate sheets for added mechanical support. The fabrication of these samples eliminates the need for costly materials, clean room technologies, and high-end equipment. Samples were characterized using a flat arrangement and on a test fixture that simulates the repeated bending that occurs on the back of a bending knee. Without applying any external bias voltage, the maximum voltage and current output for the bending samples were determined to be 25.1 mV and 230 nA, respectively, and the corresponding maximum power is 5.77 nW at a bending frequency of 5 Hz. With an estimated cost of U.S. $ 0.28 for each REWOD harvester (U.S. $ 0.03/cm2), the cost per nanowatt of power is U.S. $ 0.05/nW, which is approximately 380 times lower than the approximately U.S. $ 19/nW of our previous REWOD energy harvesters. Our simple devices provide a low-cost, easily fabricated flexible approach to wearable motion sensing and energy harvesting that can be useful for various healthcare applications. 

Abstract. Sít' Tlein, located in the St. Elias Range, which straddles Alaska's Wrangell–St. Elias National Park and Kluane National Park in the Yukon, is the world's largest piedmont glacier. Sít' Tlein has thinned considerably over 30 years of altimetry, yet its low-elevation piedmont lobe has remained intact in contrast to the glaciers that once filled neighboring Icy and Disenchantment bays. In an effort to forecast changes to Sít' Tlein over decadal to centennial timescales, we take a data-constrained dynamical modeling approach in which we infer the parameters of a higher-order model of ice flow – the bed elevation, basal traction, and surface mass balance – with a diverse but spatiotemporally sparse set of observations including satellite-derived, time-varying velocity fields; radar-derived bed and surface elevation measurements; and in situ and remotely sensed observations of accumulation and ablation. Nonetheless, such data do not uniquely constrain model behavior, so we adopt an approximate Bayesian approach based on the Laplace approximation and facilitated by low-rank parametric representations to quantify uncertainty in the bed, traction, and mass balance fields alongside the induced uncertainty in model-based predictions of glacier change. We find that Sít' Tlein is considerably out of balance with contemporary (and presumably future) climate, and we expect its piedmont lobe to largely disappear over the coming centuries. If warming ceases, and surface mass balance remains at 2023 levels, then by 2073 (2173) we forecast a mass loss (expressed in terms of 95 % credible interval) of 323–444 km3 (546–728 km3). If instead surface mass balance continues to change at the same rate as inferred over the historical period, then we forecast a 2073 (2173) mass loss of 383–505 km3 (740–900 km3). In either case, the resulting retreat and subsequent replacement of glacier ice with a marine embayment or lake will yield a significant modification to the regional landscape and ecosystem. 

A unique method for capturing energy from mechanical electrolyte modulation is known as reverse electrowetting-on-dielectric (REWOD). Prior REWOD studies relied on rigid electrodes which demand a high bias voltage to maximize harvested power, hindering the advancement of self-powered wearable health-monitoring sensors. In addition, the amount of energy harvested via the REWOD technique can be improved to a greater extent with the utilization of a high-dielectric (high-k) metal oxide (HDMO) layer on flexible electrodes. In this study, two distinct sets of electrodes that are flexible are utilized for harvesting energy with the REWOD phenomenon. The samples were coated with HDMO layers, namely, hafnium oxide (HfO2) and manganese dioxide (MnO2), respectively. The material deposition on a polyimide sheet is employed via a sputtering-based physical vapor deposition (PVD). The utilization of MnO2 samples with the proposed flexing REWOD test measurement generated 476.21 μW/cm2 an utmost power density value with an encapsulated electrolyte between electrodes.