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A study for understanding climate-induced crop production risk and relevant climate hazards in a changing environment
Get PDFClimate change poses significant challenges to global agriculture by influencing crop production through various climatic factors such as precipitation, temperature, solar radiation, and atmospheric gases. These factors impact crops during planting, growing, and harvesting seasons, exacerbating risks through extreme events like droughts, heatwaves, and extreme precipitation. Additionally, they shape ecological stressors and agricultural management practices, modulated by large-scale climate oscillations and anthropogenic global warming.
This dissertation employed a multi-faceted approach to understanding climate-induced crop production risks and their relevance to climate hazards in a changing environment. First, we present a current state of knowledge of various climate indicators and extremes that have physiological impacts on crops and their yield. Precipitation and temperature extremes impact crops differently depending on the growth stage. The reproductive stage is susceptible to high temperatures decreasing yields. Solar radiation, atmospheric gas composition, and soil impact growth and nutrient uptake. Humidity, evapotranspiration, and leaf wetness duration can result in environments conducive to pest growth. We define seven large-scale climate oscillations and climate change impacts that influence climate indicators and extremes globally.
Second, utilizing remote sensing-based products and machine learning techniques, we characterized synchronized global crop failures and analyzed their predictability and relationships with agroclimatic conditions. Our findings revealed strong interannual variability in global synchronous crop failures between 1982 and 2016, with extreme events affecting over 40% of global croplands in 2002 and 2012 due to drier and warmer conditions. Machine learning models accurately predicted crop failure events using influential agroclimatic indices such as growing degree days, last spring frost, first fall frost, growing season precipitation, and soil moisture. Soy crop failure was most accurately predicted in both temperate and tropical regions, with maize, wheat, and rice also showing high prediction accuracies. Influential indices exhibited significant trends on over 25% of global croplands, indicating increasing temperatures, earlier spring frosts, later fall frosts, and improving field conditions.
Building on these insights, we further assessed the risk of compound climate extreme events, including simultaneous and sequential combinations of heatwaves, extreme precipitation, and flash droughts, under two climate scenarios (SSP1-2.6 and SSP5-8.5) and eight CMIP6 climate models for early-, mid-, and late-century periods. The analysis of compound climate extreme events revealed that sequential heatwaves and flash droughts under SSP5-8.5 late-century projections led to significant exposure increases. Hotspots of exposure were identified in China, India, and Europe, with population exposure exceeding 50 million person-events. Agriculture land exposures surpassed 90 thousand km2-events in China, South America, and Oceania, while forest land exposures exceeded 120 thousand km2-events in Oceania and South America. Together, findings underscore the heightened risks crop production, human populations, and forest lands face in future climate. Providing valuable insights into the complex interactions between climate hazards and crop production risks, informing food security predictions, weather index selections for crop insurance, and climate adaptation strategies in the face of a changing environment
Seabird Mitigation and the Prevalence of Campylobacter spp. at Oyster Farms in the Northern Gulf of Mexico
No full textOff-bottom oyster farming provides surface area for seabird perching. Regulatory agencies have concerns about bacterial contamination of oysters from seabird excrement and require operational plans aimed at bird mitigation; however, the effectiveness of many bird deterrents have not been validated. An evaluation of the bird populations at an oyster farm and assessment of a simple, inexpensive, non-lethal bird deterrent were conducted alongside an investigation into the prevalence of Campylobacter spp. in farmed oysters and birds interacting with the floating gear. Seabirds, such as pelicans, cormorants, terns, and gulls were abundant year-round but the use of a deterrent reduced bird-cage interactions by 85%. Campylobacter was isolated from 12 of 206 bird fecal samples and from 10 of 66 oyster samples. Isolates shared the highest 16S rDNA sequence identities with C. lari-like species whose pathogenicities are unknown. Strain-level identification is needed to determine their seafood safety risk. Overall, the simple bird deterrent was effective and may be incorporated to meet operational plan requirements, however the risk of oyster contamination with pathogenic Campylobacter species requires further investigation
Synergistic Effects of Surface Roughness & Volumetric Defects on the Mechanical Behavior of Additively Manufactured AlSi10Mg Parts
Get PDFSurface roughness is known to significantly impact the fatigue behavior of additively
manufactured metals. As-printed surface roughness features can have a negative impact on fatigue
life by facilitating crack initiation. Surface treatments can improve the fatigue behavior of
additively manufactured materials by removing as-printed surface roughness and minimizing the
localized stress intensity factors. This study examines the synergistic effect surface roughness and
porosity for five different surface conditions, un-machined, only polished, shallow machined, deep
machined, and machined and polished, on the fatigue behavior of additively manufactured
AlSi10Mg. Tensile properties showed small differences between surface conditions. Surface
condition had little impact on fatigue life due to defects and surface roughness having similar
elastic stress concentration factors and fatigue notch factors. Crack initiation occurred from surface
roughness features in the un-machined conditions. Crack initiation occurred from defects in the
machined conditions, with defect size and aspect ratio playing a role in fatigue life
Strategic Integration of Battery-powered Equipment into Landscape Maintenance Operations
No full textThe landscape maintenance industry has changed drastically due to the legislative
measures that have been taken. The shift is continuously moving toward eco-friendly practices
and equipment, but research into the battery-powered equipment’s (BPE) comparability to gas-
powered equipment (GPE) is lacking. The landscape industry also faces a large disparity in price
between the equipment types. To gain insights into the perceptions, benefits, and challenges of
adopting battery-powered outdoor power equipment, a survey was conducted among landscape
maintenance operators in the US. Professional landscape companies prioritize operation
efficiency factors such as “Reliability,” “Work Capacity,” and equipment “Availability” rather
than the environmental factors such as “Air Pollution” and “Noise Pollution” emphasized in
recent legislative measures. Based on these results, future research should aim to fill the existing
knowledge gap regarding the long-term operational costs and benefits of battery-powered
equipment and gas-powered equipment. The comparison between battery- and gas-powered
equipment requires comprehensive evaluation from multiple perspectives and factors. Laboratory
testing provided insights into energy consumption and runtime without resistance, while field
testing demonstrated the impact of real-world resistance on energy consumption and efficiency.
Notably, field testing revealed an increase in energy consumption compared to laboratory
conditions, highlighting the influence of real-world resistance on equipment performance.
The break-even analysis utilized energy consumption data to determine cost efficiency over time,
assessing whether transitioning to battery-powered equipment would be economically viable.
The findings indicate that a complete transition to battery-powered equipment may not always be
advantageous, as not every tool matches the efficiency of its gas-powered counterpart. Further
research is needed to test a wider variety of equipment, as not all battery- or gas-powered tools
perform equally or achieve the same efficiency. With continuous advancements in technology,
ongoing testing is crucial to ensure up-to-date data on equipment performance
Investigations into Methyl-coenzyme M Reductase Behavior: Expression in a Heterologous Host, Putative Post-Translational Modification Genes, and Molecular Dynamics of MCR Homologues Bound to F430 Variants
Get PDFMethanogens are microorganisms widely found in wetlands and the digestive tracts of animals, which produce methane as a metabolic byproduct. The organism possesses the key methane-forming enzyme methyl-coenzyme M reductase (MCR) which is a dimer of heterotrimers comprised of McrA (α), McrB (β), and McrG (γ) subunits. The enzyme uses a unique nickel-containing coenzyme F430 for activity and contains several unprecedented post-translational modifications (PTMs). The six PTMs located in α subunit of MCR are 2-(S)-methylglutamine, 5-(S)-methylarginine, 3-methylhistidine, S-methylcysteine, didehydroaspartate, and thioglycine residues. Homologues of MCR have been identified in anaerobic methanotrophic archaea (ANME) which operates the anaerobic oxidation of methane (AOM), and in Candidatus Ethanoperedens thermophilum which is an ethane oxidizer. While the MCR homologues share the same structural composition, they differ in the composition of their PTMs, with a 172-methylthio F430 and a 17,172-dimethyl F430 contained in ANME-1 and in Ca E. thermophilum respectively. The exact roles of these PTMs are unknown though several hypotheses have been proposed including their role in improving MCR stability under mesophilic conditions. Processes involved in the maturation and activation of the active enzyme are not yet fully understood. A better understanding of the assembly and activation of MCR may enable its application in natural gas conversion strategies and the development of inhibitors to reduce natural greenhouse gas emissions. Current investigation and progress in some of the PTMs and the expression of MCR in a heterologous, non-methanogenic host is described. Comparative genomics and homology studies were used to identify target genes suspected to be responsible for the PTMs. Putative genes reported (mcmA) and suspected (mm4) to be responsible for the methylcysteine and methylhistidine PTMs respectively, were studied using a combination of computational tools, in vitro and in vivo methods. Molecular dynamics (MD) methods and distance calculations were utilized to investigate the effects of the PTMs on MCR and its homologues. MD simulations were carried out on MCR homologues with and without their PTMs. Results show that MCR exhibits half sites reactivity, and that the PTMs may play a role in coordinating MCR catalytic activity within its two active sites. MCR homologues without PTMs exhibited less dynamism and this could be an indicator that the PTMs evolved as an adaptation of thermophilic proto-MCR to mesophilic growth, enabling proper enzyme dynamics at lower temperature. The requirement of zinc as an accessory factor for the activity of McmA in the methylcysteine modification was inferred from the results. Soluble McrA and McrG proteins were successfully expressed from Escherichia coli cell lines. McrG was coeluted with several coenzyme F430 biosynthetic (Cfb) proteins. Previous work by the Mansoorabadi group showed that CfbE interacts with McrD and could be activated by it. The coelution of McrG with Cfb proteins suggests that the Cfb proteins may form a larger coenzyme F430 synthase complex which interacts with McrG and McrD to coordinate the insertion of coenzyme F430 into the MCR active site. CfbE interaction with McrG indicates that CfbE might be the direct F430 chaperone that delivers the coenzyme to MCR. Considering MCR’s strategic role in methane recycling, understanding these processes are pivotal for the enzyme’s application in strategies for natural gas conversion and reduction
Elucidating an Oxidative Stress Response of Type I Methanotroph through an Integrated Systems Approach
No full textWith the effects of climate instability becoming more and more noticeable, there has been an ever-present need for new ideas for mitigating greenhouse gas emissions. The utilization of methanotrophs has become an apparent choice to help decrease methane emissions because they can uniquely use methane as a carbon source. This work will describe how these microorganisms can efficiently metabolize one of the strongest chemical bonds through a unique enzyme known as methane monooxygenase. It is known that even if a material or, in this case, an organism, can metabolize methane, it still cannot compete with industrial processes already in place in terms of being economically feasible. Literature has now shown a push for these methanotrophs to decrease methane emissions and create a valuable product as a result. It is essential to gain a better understanding of metabolism to exploit it for a higher product yield. This work will mention a robust bacteria - Methylomicrobium buryatense 5GB1 - that has a high growth rate (0.224 h-1) and has shown high uptake rates of methane (6.1 mmol h-1) [1]. Also, a similar species, Methylotuvimicrobium alcaliphilum 20Z, is described as a potential substitute for 5GB1 since they show identical behavior under oxygen-limited conditions and are of the same genus [2]. These Type I methanotrophs are also appealing due to their alkaliphilic nature and preference for medium with large amounts of salt, making contamination more difficult. This work will utilize these unique microbes to investigate a novel oxidative stress phenotype. It will aim to demonstrate the optimal manner in which to obtain this phenotype and how the manipulation of previous conditions can affect future phenotypes. This work will explain methanotrophs' benefits in reducing methane emissions, but it will also describe a novel method to produce organic compounds. Specifically, the organic compound most produced is formate. With the conditions in these experiments, the formate excretion was increased by an order of magnitude from reported values. To better under the metabolic mechanisms in place, transcriptomic data was analyzed. This data depicted a downregulated methane oxidation pathway, except for formate dehydrogenase. Other up-regulated enzymes, such as methyltransferases and superoxide dismutase, indicate that the cell is responding to the oxidative stress conditions. These experiments focus on gaining an understanding of the metabolism of methanotrophs as well as determining their behavior under oxidative stress
Design of Customized Independent Living Environment for Individuals with Mobility Issues
Get PDFSince ancient times, the groups of people with disabilities cannot be ignored, and wars around the world resulting in many amputations in army veterans and civilians have brought disability issues to the world consciousness. Up to now, through the efforts of the people with disabilities and relevant organizations, the rights and interests of the disabled group have been well protected and developed, but even so, the inconvenience of the people with disability in daily life has not been solved. However, while ADA standards for accessible design in 2010 set requirements for public environments and facilities, there are no standard requirements for private living space and furniture. Therefore, the lack of disability-focused rational design of interior and furniture prevents disabled individuals from living barrier-free and independently even at home.
Thus, the purpose of this thesis is to develop a design tool through learning, understanding, and analyzing ergonomics, furniture design, and interior design for users and designers to design independent living environments that can accommodate both the physical and psychological needs of those with mobility issues
Maintaining Meat Quality through the Beef Supply Chain
Get PDFThe studies presented here were designed to evaluate the impacts of increased time periods during two key phases of the beef supply chain: pre-harvest transportation and post-processing storage. In the first study, the objective was to determine the relationship between gut microbial community and pathogen presences in cattle under different levels of transportation stress. Cattle were transported for either 2.5 or 12 hours, with samples collected before and after transportation to evaluate microbial shedding, microbiome, temperature, weight, and exit velocity. Under longer transportation, there was greater weight loss compared with short transportation along with a decrease in microbial diversity, which was associated with an increase in the fecal shedding of Escherichia coli. It is likely that long transportation times are associated with increased risks to food safety due to this dysbiosis.
The second study objective was to determine the impacts of low temperature storage followed by secondary retail storages for long time periods on hamburger patty quality and shelf-life. Hamburger patties we packaged using modified atmosphere packaging and stored using a novel low temperature storage method for either 16, 20, or 30 days, after which they were kept in dark simulated retail storage for either 7, 10, or 14 days. Microbial growth fluctuated depending on storage time, but never exceeded acceptable limits. Similarly, the consensus of panelist’s sensory scores decreased especially under the retail storage time, but never below acceptable limits. Overall, using this storage regimen, the shelf-life of beef hamburger patties can be extended to at least 30 days without freezing. This thesis demonstrates that it is practical and beneficial to extend the storage time in post-processing phases but increasing the time in pre-processing phases may have negative impacts to the beef supply chain
Computational and Experimental Study of Direct-Contact Storage of Thermal Energy Utilizing Phase Change Materials
No full textThis study presents a comprehensive investigation of the dynamic characteristics of the charging process in a direct-contact thermal energy storage (TES) system utilizing phase change materials (PCM). Both numerical and experimental methods are adopted for investigating two distinct cases of a system that consists of a rectangular unit (2D & 3D) that initially contains a solid PCM block.
In the numerical analysis utilizing computational fluid dynamics (CFD), time-dependent continuity, momentum, and energy equations were solved with the aid of a “one-fluid” model for handling three phases, whereas the single-domain enthalpy-porosity approach for modeling phase transition was used. The first idealized no-inlet case concerned a stagnant hot heat transfer fluid (HTF being water) layer resting above a solid cold PCM (n-octadecane) block, with no inlet or outlet ports in the unit. For this case, a slower melting process was observed, with complete melting achieved at 890 seconds. The no-inlet case reached a thermal efficiency of 74.324%, highlighting the potential of the system in energy storage even in stagnant conditions.
For the more realistic second case (inlet case), injection of the HTF at a temperature higher than the PCM’s melting point through three inlet ports at the top of the unit was studied. The impinging HTF spread over the PCM where a thickening hot water layer formed, causing the PCM to melt progressively and concurrently replacing the air at the top of the unit. Shut-off of the HTF flow was applied to realize an equivalent system to the first case in terms of storage capacity. The inlet case exhibited a faster melting process, with complete melting achieved at 785 seconds, an 11.8% improvement over the no-inlet case. The system's thermal efficiency reached 73.79%. Initiation of the Rayleigh-Taylor instability phenomenon (due to density difference between the solid PCM and water) and its progression for both cases were observed, leading to detachment and rise of molten PCM droplets from peaks (humps) of the evolving wavy PCM/HTF interface. Propagation of any density-driven waviness at the HTF/PCM interface was verified through established analytical expressions involving surface tension effects.
The rise of droplets through the HTF was analyzed in detail using a process called binarization, whereby instantaneous contours of the PCM liquid phase fraction being 0.5 were digitized and image processing of a pixelized domain was conducted. Instantaneous droplet shape evolution was evaluated in terms of the number of droplets, area, hydraulic diameter, center of gravity, velocity, and the droplet Reynolds number. As many as three simultaneously rising droplets within the continuous phase were observed for both cases. The inlet case exhibited a faster, more dynamic droplet formation process due to the initial active flow of HTF, whereas for the no-inlet case, with initial stagnant HTF and an air layer above the PCM, droplet formation was slower and more gradual. A total of 304 droplets were generated for the no-inlet case, while for the inlet case, 261 droplets were formed after 46 seconds of HTF injection. Wavelengths of the water/PCM interface ranged between 24 and 80 mm.
To investigate the effect of the longitudinal dimension on the Rayleigh-Taylor instability of the PCM/HTF interface, three unit lengths were simulated. The findings confirmed that the observed instabilities are inherent to the system, and the evaluated wavelengths remained generally independent of the longitudinal length of the TES system. This result indicates that the longitudinal dimension does not play a role in the current simulations.
In the experimental set-up, with its dimensions exactly matching those of computational domain, solid olive oil was used as PCM to replicate conditions from the CFD simulations. For the first experimental case, the HTF was simply placed above the solid PCM without any inlets or outlets, resulting in a slower melting process. This experiment ran continuously for 146.92 minutes until complete melting. In the second experimental case, hot HTF (water) was injected for 71.5 seconds, with the experiment running for 161.12 minutes until complete melting of the olive oil. Results of both experimental cases validated the numerical models, confirming the physics observed in the simulations. Compared to 445 droplets in the no-inlet case, droplet formation was more frequent in the HTF injection case, with a total of 604 droplets observed. To track temperature variations, eleven T-type thermocouples were installed along the inner surface of the back vertical transparent panel, with an additional thermocouple used to measure ambient temperature. Experimental temperature measurements generally supported the CFD-based monitored temperatures, but their frequency response was limited. Through proper non-dimensionalization of time, the maximum-minimum temperature envelope of both CFD and experimental data exhibited a unified agreement. Additionally, the comparison of observed wavelengths between CFD simulations and experiments showed good agreement, with the simulations accurately capturing the essence of the melting process despite differences in material properties between n-octadecane and olive oil
Guidelines for Designing Recreational Vehicles Functionally and Interior for Selected Culture
Get PDFThe thesis is about creating a guideline to help design recreational vehicles for one specific culture or subculture. It covers a brief history of the birth and development of recreational vehicles, including the predecessor of recreational vehicles, the development of RV camping, significant contributors, and global influence. Moreover, there is discussion about the necessity of culturally oriented design and the cultural influence within the recreational vehicle industry. Recreational vehicle development has primarily occurred in North American and Western regions, but the trend of RV camping is rising outside of these areas. Therefore, a design tool is created to assist recreational vehicle designers in understanding a culture objectively and extracting useful cultural elements that can benefit the design process. Following the tool from three perspectives, cultural, regulatory, and market, designers could have a clear overview of the recreational vehicle industry and market in selected cultures. In order to make the design guideline more reliable, a case study on designing a recreational vehicle considering Japanese cultural influence is demonstrated. Based on the results of the case study, feedback is provided for reference on the effectiveness of the design guideline