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Whale Baleen To Monitor Per- and Polyfluoroalkyl Substances (PFAS) in Marine Environments
Get PDFPer- and polyfluoroalkyl substances (PFAS) comprise \u3e10 000 synthetic compounds that are globally distributed and highly persistent but remain challenging to monitor. Here we assess the utility of baleen─an accreting, keratinaceous tissue that baleen whales use for filter-feeding─to track PFAS dynamics in marine food webs. In six species investigated, PFAS were detected in all baleen tested (n = 18 plates, 220 samples, ∑10PFAS range of 0.02–60.5 ng/g of dry weight), at levels higher than those of other tissue types besides liver. Three of the species in our data set had not been tested for PFAS contamination previously, and two of those species (blue whale and North Atlantic right whale) are internationally endangered species. Apparent links were observed between PFAS and life-history events by testing successive subsamples along the growth axis of the baleen plates. These results establish baleen as a viable sample matrix for assessing PFAS contamination in marine ecosystems by enabling multiyear time-series analyses through single-tissue sampling with seasonal resolution
Biomass burning is a source of modern black carbon to equatorial Atlantic Ocean sediments
Get PDFBlack carbon is a refractory form of organic carbon formed from the incomplete combustion of fossil fuels and biomass. Riverine transport is considered the dominant pathway of black carbon to the coastal oceans. However, the provenance and pathways of black carbon to the open ocean remain unknown. Here we use both stable and radiogenic isotopes of carbon to show that sedimentary black carbon across the equatorial Atlantic Ocean is aeolian and primarily derived from biomass burning of C4-plants. Fluxes of surface sedimentary black carbon measured along an equatorial Atlantic Ocean transect using chemothermal oxidation at 375 °C were relatively consistent across the Atlantic, ranging from 0.10–0.35 mg cm−2 kyr−1. Carbon isotope values near Africa suggest the black carbon was mostly young and derived from C4 plants, whereas offshore South America, the black carbon was older and dominated by C3 plants. The black carbon radiocarbon values were similar to the reservoir corrected total organic carbon near Africa, implying little pre-aging on land and increased westwards. These findings highlight the influence of C4-biomass burning in the tropical Atlantic and the importance of aeolian deposition as a black carbon source within the global carbon cycle
Assessing the Hydrologic Response of a Major Drinking Water Reservoir to Extreme Flood Events and Climate Change Using SWAT and OASIS
No full textExtreme flood events present a significant challenge for operators and managers of large drinking water reservoirs. Detailed flood response analysis can predict the hydrology response of a reservoir to changing climate conditions and can aid in managing the reservoir in anticipation of extreme events. Herein, the Soil and Water Assessment Tool (SWAT), a watershed model, was used in conjunction with a reservoir management model, the Operational Analysis and Simulation of Integrated Systems (OASIS) model, to evaluate extreme flood events across a set of initial reservoir storage capacities across various CMIP6 climate scenarios. The SWAT model was calibrated and validated with PRISM climate data in conjunction with land and soil cover data and multi-site gauged stream discharges. The validated model demonstrated satisfactory performance (NSE = 0.55 and R2 = 0.56) for total reservoir inflow. The resulting inflow values from SWAT were utilized to set up a calibrated/validated OASIS model (NSE = 0.55 and R2 = 0.68). OASIS was then used to assess alternative operating rules for the reservoir under varying climate scenarios (RCP4.5 and RCP8.5) and extreme events (synthetic hurricanes). Focusing on a major reservoir in the Northeastern United States, the analysis of the reservoir response was based on (1) reservoir volume–elevation curve, (2) daily reservoir inflow, (3) daily precipitation, (4) spillway flow, and (5) reservoir evaporation. Projected future scenarios indicate a \u3e20% increase in precipitation in April compared to historical records, coupled with likely reduced runoff from November to March. With extreme conditions most likely in the month of April, RCP4.5 and RCP8.5 projections suggest that most scenarios result in a 10–15% increase in the mean of 3D30Y runoff volumes, and a 150% increase under the most extreme conditions. For 7D30Y runoff volumes in April, the RCP4.5 and RCP8.5 analyses reveal an increased likelihood of the reservoir elevation reaching overspill flow levels during the latter half of the simulation period (2020 to 2080). Our findings indicate that simulations with SWAT coupled with OASIS can assist reservoir managers in regulating water levels in anticipation of extreme precipitation events
The contraction of freshwater lenses in barrier island: A combined geophysical and numerical analysis
No full textCoastal aquifers, vital for supplying freshwater to over one billion people worldwide, often face saltwater intrusion, with barrier island aquifers playing a crucial role in this coastal system. Despite the proliferation of studies exploring the impacts of sea-level rise, storm surges, and over-pumping, the effect of droughts on barrier island aquifers salinization remains largely under-investigated. This lack of attention is particularly concerning given the heightened vulnerability of barrier island aquifers; most ultimately rely solely on aerial recharge compared to continental coastal aquifers. An in-depth understanding of recharge and salinization processes is important for sustainably managing these islands\u27 marginal freshwater resources, especially considering climate change impacts. This study presents an evaluation approach for the response of a freshwater lens (FWL) to drought conditions, incorporating in-situ observations, geophysical measurements, and numerical modeling. The study examines the response of a shallow unconfined aquifer on an Atlantic coast barrier island to the 2020 Northeast extreme hydrological drought. It encompasses a density-driven flow model informed by time-lapse electrical resistivity imaging and in-situ measurements, including groundwater head and salinity collected from monitoring wells. Results from our approach indicate that FWL volume is reduced by 11% during the drought, but it returns to its previous volume over the following spring season, indicating that the net volume of the FWL remains unchanged on an annual scale. The mean groundwater residence time on the island is approximately a year, indicating that the barrier island aquifer is a hydrodynamically active coastal zone. These findings highlight the vulnerability and resilience of shallow unconfined barrier island aquifers to droughts and climate change
Wavelet Analysis of Noninvasive EEG Signals Discriminates Complex and Natural Grasp Types
No full textThis research aims to decode hand grasps from Electroencephalograms (EEGs) for dexterous neuroprosthetic development and Brain-Computer Interface (BCI) applications, especially for patients with motor disorders. Particularly, it focuses on distinguishing two complex natural power and precision grasps in addition to a neutral condition as a no-movement condition using a new EEG-based BCI platform and wavelet signal processing. Wavelet analysis involved generating time-frequency and topographic maps from wavelet power coefficients. Then, by using machine learning techniques with novel wavelet features, we achieved high average accuracies: 85.16% for multiclass, 95.37% for No-Movement vs Power, 95.40% for No-Movement vs Precision, and 88.07% for Power vs Precision, demonstrating the effectiveness of these features in EEG-based grasp differentiation. In contrast to previous studies, a critical part of our study was permutation feature importance analysis, which highlighted key features for grasp classification. It revealed that the most crucial brain activities during grasping occur in the motor cortex, within the alpha and beta frequency bands. These insights demonstrate the potential of wavelet features in real-time neuroprosthetic technology and BCI applications
Dynamics of Nanoparticles in Solutions of Semiflexible Ring Polymers
No full textWe use hybrid molecular dynamics-multiparticle collision dynamics (MD-MPCD) simulations to investigate the influence of chain stiffness on the transport of nanoparticles (NPs) through solutions of semiflexible ring polymers. The NPs exhibit subdiffusive dynamics on short time scales before transitioning to normal diffusion at longer times. The terminal NP diffusivity decreases with increasing ring stiffness, similar to the behavior observed in solutions of semiflexible linear chains. The NP subdiffusive exponent is found to be strongly correlated with that of the polymer center of mass (COM) for the range of chain stiffnesses examined, which is at odds with the pronounced decoupling of the NP and polymer COM motions previously observed upon increasing the stiffness of linear chains. Our analysis indicates that these marked differences in the intermediate dynamics are rooted in distinct structural changes that emerge with increasing bending stiffness: Stiffer ring polymers adopt increasingly circular conformations and stack into transient tubes. The void space created near the ring centers is occupied by NPs and other polymers, resulting in strong dynamic coupling on short time scales
Elucidating the role of physicochemical interactions on gel rheology
No full textSoft materials are characterized by their intricate interplay of structure, dynamics, and rheological properties. This complexity makes it challenging to accurately predict their response to shear stress. Here, we investigate how the nature of bonds - electrostatic attractions, physical entanglements, physical repulsion, and covalent bonds - affects the linear and nonlinear rheology of gels. Specifically, we determine the critical roles these bonds play in the yield transition and thixotropic recovery of gel properties through a combination of linear oscillatory deformations, serial creep divergence measurements, and time-resolved flow sweeps. Different classes of gels are prepared with nearly identical linear rheology but significantly different yield transitions and nonlinear properties post-yielding. These differences are directly related to the kinetics by which the underlying elastic networks rebuild after flow. Gels which exhibit thixotropic hysteresis are able to fully recover their yield stress over time while non-thixotropic gels possess time-independent yielding metrics. This direct comparison between thixotropy and yielding reveals the intimate relationship between these phenomena and their controlling physical mechanisms within soft, amorphous materials
Community Awareness of Domestic Violence in Arumeru District, Arusha, Tanzania
Get PDFDomestic violence continues to be prominent among many communities worldwide despite different efforts and strategies geared towards eradicating it. Women and girls are among the main victims of this violence. Lack of or limited awareness of the problem perpetuates the problem. However, much of the levels of awareness of the problem are lacking. This study aimed to establish community awareness of domestic violence and the levels of awareness and determine the association between respondents\u27 characteristics and the level of awareness of gender-based violence. The study employed both probability and non-probability sampling techniques to acquire the respondents. One hundred women and men respondents were surveyed using simple random sampling. Data collection tools for this study included a questionnaire and an interview. The research study found that more than half (56.0%) of the total respondents were not aware of domestic violence practices. Twenty-six percent of the respondents had low awareness, 11% had moderate awareness, and only 9% of the respondents had high awareness of domestic violence. After the respondents\u27 awareness levels were determined, the study investigated whether there was an association between the sex, age, and education level of the respondents and their awareness level. The findings showed that it is evident that sex, age, and education level were significant influences on the level of awareness of domestic violence among the respondents. There was an association between sex (ꭓ²=14.07, p\u3c0.007), age ((ꭓ²=27.32, p\u3c0.043) and education ((ꭓ²=34.72, p\u3c0.001) on community awareness of domestic violence. Respondents have limited awareness of domestic violence despite government and stakeholder efforts to combat the violence