Scattering of the low-mode internal tide at the Line Islands Ridge

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2015The scattering of low-mode internal tides by ocean-floor topography is extensively studied through analytical models and field observations at the Line Islands Ridge (LIR). An existing Green function method is utilized to examine the generation of internal tides by idealized topographic shapes as well as realistic transects of the LIR. The method is also applied to examine the scattering of a mode-1 internal tide at these topographies to determine the relative high mode energy flux due to generated and scattered internal tides at the realistic transects. A method of determining the modal content of an internal wave field is advanced to account for arbitrary stratification and rotation. It is then adjusted to allow for image loss as is common to oceanographic studies. Its performance is compared to the existing regression method widely used by oceanographers to determine the modal content of internal tides. The results from this comparison are used to inform the analysis of the field observations. This thesis concludes by examining the modal content of the LIR as determined from measurements taken during the 150-day EXperiment on Internal Tide Scattering (EXITS) NSF field study. Motivated by satellite altimetry data and three-dimensional numerical model studies, the EXITS cruise sought to observe the internal tide scattering process in the ocean for the first time. The data from three moorings equipped with moored profilers, spanning total depths of 3000-5000 m is analyzed to determine the modal content of the southward propagating internal tide before and after it encounters the ridge for evidence of topographic scattering

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

An offshore solution to cobalt shortages via adsorption-based harvesting from seawater

The predicted dominance of electric vehicles and the need for grid-scale energy storage have heightened concerns that cobalt, a key constituent of lithium-ion batteries, could become a critical limiting factor. With limited terrestrial resources and over half the global production coming from politically challenging regions increasing risk, a shortage of cobalt could be experienced by the early 2020s. Fortunately, the oceans contain about 70 times more cobalt than on land and can be harvested sustainably with passive adsorption technologies; and a symbiotic system using existing offshore structures to harvest cobalt could enhance the economic feasibility of seawater cobalt harvesting. Our study finds that retrofitting just 76 unused oil platforms in the Gulf of Mexico could extract an average of 27.3% of the nation's 2017 cobalt consumption. New Offshore Opportunity for Underwater Cobalt Harvesting has the potential to reduce the cobalt supply pinch point in lithium-ion battery production

Results of an Ocean Trial of the Symbiotic Machine for Ocean Uranium Extraction

Amidoxime-based adsorbents have become highly promising for seawater uranium extraction. However, current deployment schemes are stand-alone, intermittent operation systems that have significant practical and economic challenges. This paper presents two 1:10 scale prototypes of a Symbiotic Machine for Ocean uRanium Extraction (SMORE) which pairs with an existing offshore structure. This pairing reduces mooring and deployment costs while enabling continuous, autonomous uranium extraction. Utilizing a shell enclosure to decouple the mechanical and chemical requirements of the adsorbent, one design concept prototyped continuously moves the shells through the water while the other keeps them stationary. Water flow in the shells on each prototype was determined using the measurement of radium adsorbed by MnO 2 impregnated acrylic fibers contained within each enclosure. The results from a nine-week ocean trial show that while movement of the shells through the water may not have an effect on uranium adsorption by the fibers encased, it could help reduce biofouling if above a certain threshold speed (resulting in increased uptake), while also allowing for the incorporation of design elements to further mitigate biofouling such as bristle brushes and UV lamps. The trace metal uptake by the AI8 adsorbents in this trial also varied greatly from previous marine deployments, suggesting that uranium uptake may depend greatly upon the seawater concentrations of other elements such as vanadium and copper. The results from this study will be used to inform future work on the seawater uranium production cost from a full-scale SMORE system.U.S. Department of Energy Office of Nuclear Energy (Contracts DE-NE0008268 and DE-NE000731

A symbiotic approach to the design of offshore wind turbines with other energy harvesting systems

The capital cost of a 5 MW floating wind turbine (FWT) runs as high as $20.7 million, leading to an energy cost of$0.20/kWh, four times that of natural gas (Myhr et al., 2014). Although a single type of energy harvesting device may be too expensive to deploy, if it can operate symbiotically with others, the combined cost of energy might be acceptable. In this study, we show that attaching a wave energy converter (WEC) to the FWT may simultaneously produce an average of 240 kW wave power, reduce the WEC levelized cost of energy by 14% by eliminating redundant components, and reduce the FWT tower lifetime equivalent fatigue stress by 23% by reducing platform motion. Furthermore, the offshore wind turbine may also serve as a structure for the harvesting of valuable elements from seawater, such as uranium, lithium, and cobalt. The major cost drivers for the harvesting of uranium from seawater have been identified to be those associated with the mooring and deployment of the metal adsorbing polymers (Schneider and Sachde, 2013; Byers and Schneider, 2016). In the case of uranium, a symbiotic system coupled with an offshore wind turbine was found to reduce the seawater uranium production cost by at least 11% and up to 30% (Byers et al., 2016, 2018; Haji, 2017). Keywords: Wave energy; Offshore wind turbine; Uranium; Nuclear power; Symbiotic systemNational Science Foundation (U.S.) (Grant 1122374)Naval Engineering Education Center (Grant 3002883706)United States. Department of Energy (Grant DE-NE0008268

Design and testing of auv docking modules for a renewably powered offshore auv servicing platform

© 2020 American Society of Mechanical Engineers (ASME). All rights reserved. Autonomous Underwater Vehicle (AUV) missions are limited in range and duration by the vehicle's battery capacity, and sensor payloads are limited by the processing power onboard which is also restricted by the vehicle's battery capacity. Furthermore, the power consumption of a vehicle's acoustic system limits the possibility of substantial data transmission, requiring the AUV be retrieved to download most data. The Platform for Expanding AUV exploRation to Longer ranges (PEARL), described in this paper, aims to extend the range and endurance of AUVs while reducing data latency and operating costs. PEARL is an integrated autonomous floating servicing station that utilizes renewable energy to simultaneously provide AUV battery recharging and data uplink via new generation high-bandwidth low-Earth orbit satel-lite constellations. This paper details the design and testing of two potential AUV docking modules of the PEARL system. The modules are uniquely located near the ocean surface, an energetic environment that presents a particular set of challenges for AUV docking. The results will be used to inform the design of a prototype system to be tested in an ocean setting

Experimental Investigation of Hydrodynamic Response of an Ocean Uranium Extraction Machine Attached to a Floating Wind Turbine

With conventional sources of uranium forecasted to be depleted within a century, developing methods to cost-effectively harvest uranium from seawater, which is estimated to contain 1,000 times more uranium than land does, is crucial to the continued viability of nuclear power generation. Studies have shown that coupling a uranium harvester system with an existing offshore structure, such as a floating wind turbine (FWT), could greatly reduce the cost of harvesting uranium from seawater as it eliminates the need for dedicated moorings and increases the overall energy-gathering ability of the offshore wind farm. This paper explores the hydrodynamic effects of adding a uranium harvester to an offshore FWT. The experimentally determined hydrodynamic responses of two designs of a symbiotic machine for ocean uranium extraction (SMORE) are compared with that of an unmodified FWT. Both SMORE designs utilize adsorbent filament that is enclosed in a hard permeable shell to decouple the mechanical and chemical requirements of the device. It was found that neither SMORE design significantly shifted the resonant peaks of the FWT.United States. Department of Energy (Grant DE-NE0008268)National Science Foundation (Grant 112237

Effects of Protective Shell Enclosures on Uranium Adsorbing Polymers

This study aims to evaluate the impact of shell enclosures on the uranium uptake of amidoxime-based polymeric adsorbents contained within. Researchers have observed that the tensile strength of the adsorbent's polyethylene backbone is degraded after γ-irradiation to induce grafting of the amidoxime ligand. A two-part system was developed to decouple the mechanical and chemical requirements of the adsorbent by encapsulating them in a hard, permeable shell. The water flow in six shell designs and an unenclosed adsorbent for control in a recirculating flume was analyzed via a novel method developed using the measurement of radium extracted onto MnO2 impregnated acrylic fibers. Although the water flow was found to vary with enclosure design, orientation to the flow, and placement within the flume, little to no difference was observed in the uranium adsorption rate between all enclosures. The results of this study will be used to design a large-scale ocean deployment of a uranium harvesting system.U.S. Department of Energy (Contracts DE-NE0008268 and DE-NE000731