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A carbon, nitrogen, and multi-isotope study of basalt glasses near 14°N on the Mid-Atlantic Ridge. Part A: Degassing processes
No full text14°N on the Mid-Atlantic ridge (MAR) is one of only a few locations worldwide where volatile-saturated, geochemically enriched mid-ocean ridge basalts (E-MORBs) have been recovered. These basaltic glasses are so gas-rich that CO2-filled bubbles may “pop” when brought to the surface, due to the pressure and temperature change. Although these “popping rocks” have long been regarded as representative samples of un-degassed magmas sourced from the upper mantle, uncertainties regarding both their generation mechanism(s) and the potential effects of gas loss/accumulation processes have hampered unambiguous quantification of the upper mantle volatile element (water, carbon, nitrogen, noble gas) inventory. Fortunately, the extent and consequences of gas loss/accumulation processes can be tested by studying characteristic changes in volatile elements compositions, including 4He/40Ar* (where 40Ar* is 40Ar corrected for atmospheric contamination). To document the mechanism of popping rock generation and potential effects of degassing and gas accumulation processes on MORB volatile systematics, we present a comprehensive volatile characterization (carbon, nitrogen and noble gas systematics) of popping rocks and associated MORBs (n = 19) recently sampled at 14°N on the MAR, including 2 normal MORBs (N-MORB) from an oceanic core complex (OCC) and 17 E-MORBs. In line with previous studies, we find that PR exhibit the lowest 4He/40Ar* (1.08 ± 0.04) among all MORB samples, lower than the conventional mantle production ratio of 3 ± 1. Such low 4He/40Ar* could either (i) derive from accumulation of first-generated bubbles originating from open-system degassing of underlying magmas, or (ii) represent the actual upper mantle production ratio. We summarize the arguments in favor of each of these two scenarios (including the required accumulation times for radiogenic noble gases accumulation, the K/U and 232Th/238U of the upper mantle, popping rock vesicle size distributions, and physical considerations for vesicle growth and upwelling through a basaltic magma), and discuss their implications for the volatile composition of un-degassed magmas from the upper mantle. We find homogenous N isotope compositions (average δ15N of −4.49 ± 1.40 ‰ at 14°N) but variable δ13C (from −11 ‰ to −3.4 ‰), potentially compatible with the expectations for residual dissolved gas after Rayleigh fractionation. However, explaining the light δ13C signatures of PR via this process appears incompatible with any of the two scenarios proposed for explaining their low 4He/40Ar*, which would predict (i) 13C-enrichements and (ii) no fractionation relative to an initial composition at δ13C ∼ -5 ‰, respectively. After correction for solubility-controlled degassing fractionation and potential gas accumulation processes using 4He/40Ar* systematics, we find relatively homogeneous C/3He ((2.65 ± 0.51) × 109) but variable C/N (from 125 up to 4578), whose potential origins are discussed as part of a companion paper (Part B: Source effects)
Contaminant Back Diffusion from Low-Conductivity Matrices: Case Studies of Remedial Strategies
No full textRecalcitrant groundwater contamination is a common problem at hazardous waste sites worldwide. Groundwater contamination persists despite decades of remediation efforts at many sites because contaminants sorbed or dissolved within low-conductivity zones can back diffuse into high-conductivity zones, and therefore act as a continuing source of contamination to flowing groundwater. A review of the available literature on remediation of plume persistence due to back diffusion was conducted, and four sites were selected as case studies. Remediation at the sites included pump and treat, enhanced bioremediation, and thermal treatment. Our review highlights that a relatively small number of sites have been studied in sufficient detail to fully evaluate remediation of back diffusion; however, three general conclusions can be made based on the review. First, it is difficult to assess the significance of back diffusion without sufficient data to distinguish between multiple factors contributing to contaminant rebound and plume persistence. Second, high-resolution vertical samples are decidedly valuable for back diffusion assessment but are generally lacking in post-treatment assessments. Third, complete contaminant mass removal from back diffusion sources may not always be possible. Partial contaminant mass removal may nonetheless have potential benefits, similar to partial mass removal from primary DNAPL source zones
Sustainable Water Treatment with Induced Bank Filtration
No full textThis study demonstrates that an induced bank filter (IBF) system can treat raw water polluted with Escherichia coli (E. coli) bacteria. Similar to riverbank filtration (RBF), induced or reversed bank filtration relies on natural processes to clean water, including filtration through layers of allochthone alluvial sediments and a bioactive layer that forms on top of the filter after a ripening period. At the study site, located in Southwestern India, villagers rely on a mountain spring for their water supply. Although of generally high quality, the spring water contains E. coli bacteria (up to ~2000 MPN/100 mL). Raw water diverted from this spring was gravity-fed into the IBF system, which consisted of a (1) flow regulator, (2) pre-filter and (3) the actual IBF filter. Designed and constructed based on pilot testing of prototype filters, a full-scale filter (5 m by 7 m by 2 m) was built and its performance and maintenance requirements were studied during both the monsoon season and the dry season. The data show that the IBF significantly improved the water quality. Turbidity and E. coli concentrations were reduced to or below the detection limit (approximately 2.5 log unit reduction). During the peak of the monsoon season (August), E. coli was present in the IBF effluent after a storm destroyed the cover of the IBF tank. The IBF construction and maintenance costs were documented. Extrapolated over a 10-year period, the cost of IBF water was 3 and 10 times lower than reverse osmosis or water supplied by truck, respectively. This study demonstrates that IBF can be part of an affordable water supply system for rural villages in mountainous terrain where conventional RBF systems cannot be installed or where other water treatment technologies are out of financial reach
Integrating experiments, finite element analysis, and interpretable machine learning to evaluate the auxetic response of 3D printed re-entrant metamaterials
No full textMetamaterials have received extensive attention in fundamental and applied research over the past two decades due to their unique mechanical behavior. This paper presents an interpretable machine learning (ML) approach for efficient response prediction of three-dimensional (3D)-printed metamaterials. However, developing such an ML-based model requires a large consistent, representative, balanced, and complete dataset. To this extent, an experimentally validated finite element analysis (FEA) approach is implemented to generate 8096 non-self-intersecting re-entrant honeycomb structures by varying the mesoscale geometrical features to obtain the corresponding Poisson\u27s ratios. This dataset is leveraged to develop a feed-forward multilayer perceptron-based predictive model. The developed ML model shows excellent predictive efficacy on the unseen test dataset. Shapely additive explanation (SHAP) is then used for model interpretation. SHAP results show that the slant cell length is the dominant input feature dictating the model output whereas cell angle and vertical cell length show mixed trends signifying that other input features influence their effect on the model output. Moreover, cell thickness does not significantly influence the model output when compared to other input features. Overall, the integrated numerical simulation-experiment-interpretable ML-based predictive approach presented here can be leveraged to design and develop metamaterials for a wide range of engineering applications
Development and Evaluation of High-Density SNP Arrays for the Eastern Oyster Crassostrea virginica
No full textThe eastern oyster Crassostrea virginica is a major aquaculture species for the USA. The sustainable development of eastern oyster aquaculture depends upon the continued improvement of cultured stocks through advanced breeding technologies. The Eastern Oyster Breeding Consortium (EOBC) was formed to advance the genetics and breeding of the eastern oyster. To facilitate efficient genotyping needed for genomic studies and selection, the consortium developed two single-nucleotide polymorphism (SNP) arrays for the eastern oyster: one screening array with 566K SNPs and one breeders’ array with 66K SNPs. The 566K screening array was developed based on whole-genome resequencing data from 292 oysters from Atlantic and Gulf of Mexico populations; it contains 566,262 SNPs including 47K from protein-coding genes with a marker conversion rate of 48.34%. The 66K array was developed using best-performing SNPs from the screening array, which contained 65,893 oyster SNPs including 22,984 genic markers with a calling rate of 99.34%, a concordance rate of 99.81%, and a much-improved marker conversion rate of 92.04%. Null alleles attributable to large indels were found in 13.1% of the SNPs, suggesting that copy number variation is pervasive. Both arrays provided easy identification and separation of selected stocks from wild progenitor populations. The arrays contain 31 mitochondrial SNPs that allowed unambiguous identification of Gulf mitochondrial genotypes in some Atlantic populations. The arrays also contain 756 probes from 13 oyster and human pathogens for possible detection. Our results show that marker conversion rate is low in high polymorphism species and that the two-step process of array development can greatly improve array performance. The two arrays will advance genomic research and accelerate genetic improvement of the eastern oyster by delineating genetic architecture of production traits and enabling genomic selection. The arrays also may be used to monitor pedigree and inbreeding, identify selected stocks and their introgression into wild populations, and assess the success of oyster restoration
Design of Positioning Device for Measurement of Gamma Radiation Damage
Get PDFMaterials must be hoisted and lowered into a 30 foot hollow test tube at Rhode Island Nuclear Science Center (RINSC) nuclear reactor. The materials will be experiencing high levels of gamma radiation. The task at hand is to design and redesign from last year\u27s design concept a hoisting mechanism for test materials that will be experiencing high levels of gamma radiation.
To suit the needs of General Dynamics Electric Boat (GDEB), this hoisting and lowering system must be able to withstand ½ lb to 5 lbs of test materials in a bucket that will be lowered 30 feet down in a hollow test tube, have a factor of safety of 1.5, have a speed controller that can lower the test materials at a rate of greater than 1 foot per second, eliminate slippage on all pulleys that the hoisting line comes in contact with, and redesigning a clamping mechanism to the rails around the test pool at RINSC. These are the design requirements that the customer has presented the team to complete in the 2022-2023 academic year. By the process of design concepts, Pugh analysis, and QFD analysis, there are a total of one hundred twenty concept ideas that have been generated amongst the team (thirty for each team member). After careful consideration the team has narrowed down one hundred twenty concepts into three concepts that will be pursued. These concepts are as follows; upgrading the display feature into a 7” LCD screen, integrating knob screws as a method of clamping the device to the rails surrounding the pool, and implementing a two phase incremental encoder.
The process of communication between the team, the company sponsor, and the faculty advisor has aided the team in a detailed product design, location of certain parts, and dimension requirements of the design. A bill of materials was constructed to get the teams required parts, with a total expenditure of 1500. In the spring semester, the sponsor would like for the team to complete the design with enough time to be able to test the product at the nuclear reactor at RINSC before the end of the spring semester. The team will continue to improve the design throughout the entirety of the spring semester while building the product and observing what process will work most efficiently for the product to be the best that can be presented to the customer
CNTR Design and Proof of Concept for Liquid Metal Rotating Fuel Tubes
Get PDFModern chemical engine technology is insufficient to fulfill humanity\u27s aspiration to explore deep space. The 900 s Isp that Nuclear Thermal Propulsion (NTP) engines can achieve is sufficient to enable missions like manned missions to Mars. When employing a storable propellant like hydrogen, methane, ammonia, etc., extravagant missions like this call for a specific impulse of at least 900s to be successful. Consequently, High-Performance Nuclear Thermal Propulsion (HP-NTP) is necessary for space travel for it to take an acceptable length of time. A human voyage to Mars that lasts less than 15 months will be possible thanks to HP-capacity NTP\u27s to generate a precise impulse between 1300 and 1800 seconds. The established perception of the Centrifugal Nuclear Thermal Rocket (CNTR) uses liquid uranium fuel at a temperature near 5000K to directly heat a propellant while spinning around its axis at 5000-7000 RPM. The uranium is intended to adhere to the wall as a result of centrifugal force, leaving a space for the propellant to flow through, heat up, and produce the required thrust.
Several additional engineering teams and universities in the nuclear propulsion sector are presently investigating the viability of employing HP-NTP within a CNTR. This subdivision\u27s scope is primarily concerned with demonstrating the idea of liquid in a rotating fuel tube.
As uranium is not a realistic material to facilitate at this stage, the team focused their studies on the design as if the fuel were water. For the duration of the Fall semester, the primary work of the team consisted of the design and construction of the testing apparatus. Listed in the report are 150 concept designs developed by the team. Just before the start of the Spring semester, the apparatus was built and ready to be tested. The team spent many hours developing a motor controller to properly control and monitor the apparatus. This motor controller allowed for the data collection of the revolutions per minute at which the apparatus was spinning. When all was up and running with water in the apparatus, it was clear that the water climbed the walls of the spinning tube, creating a void region in the center. This proved the concept of the CNTR, that when a liquid is spinning in a tube at a high RPM, a void region develops for a potential propellant to pass through.
There is still much work to be done for this project that the team would strive to achieve. First, aerating the spinning tube would be satisfactory to simulate the propellant passing through the tube and would most likely be the next step. Continuously, casting an ice structure and placing it in the tube to facilitate a phase change is necessary to simulate the solid state of the uranium before start up. While only a small sliver of the CNTR was experimented with throughout this project, the work from Team 1 was of high quality and success to enable future work to be done
Radiation Detection Drone
Get PDFTeam 14 has been assigned the task of designing and developing a radiation detection drone for open-area radiation detection in collaboration with General Dynamics Electric Boat. The project’s primary objective was to create an efficient solution for measuring and mapping radiation in a specified area and producing a ‘heat map’ of the radiation. Sponsored by General Dynamics Electric Boat, the project was guided by a predefined structure that emphasized the exploration of drone technology. Extensive research, including both general and market-oriented studies, was conducted, and the team designed various concepts, comparing them using Pugh analysis to identify the most effective approach.
The chosen solution involves the use of a commercially available aerial drone fastened with a handheld radiation detector, coupled with a Raspberry Pi and Arduino Nano for data acquisition. The design process focused on meeting specified parameters, including a $4000 budget, lift capacity, survey area, flight duration, safety distance, and dimensions based on the given radiation detector. These parameters were identified through research and informative meetings with the sponsors and professor, providing a comprehensive framework for the project.
During the academic year, the team achieved significant milestones. All necessary components, including the drone, radiation detector, Raspberry Pi, and Arduino Nano, were acquired from the college of engineering. The team demonstrated the drone’s capability to fly undisturbed by the attached radiation detection components, confirming the feasibility of the chosen design. Moreover, the successful acquisition of data and heat map production through the Raspberry Pi validated the effectiveness of the selected technology.
Team 14’s project successfully completed the challenge of designing a radiation detection drone. The objectives were met through a comprehensive design process, incorporating research, conceptualization, and practical testing