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HIDDEN STEWARDS OF THE SOIL : FREE-LIVING NEMATODES AS SENTINELS OF ECOSYSTEM FUNCTIONING
Full text linkThesis (Ph.D.)--Michigan State University. Crop and Soil Sciences- Doctor of Philosophy, 2025Soil biodiversity is instrumental for ecosystem functions such as nutrient cycling and carbon (C) storage. However, as anthropogenic disturbance places soil biodiversity at risk, we may witness disruptions in these essential ecosystem services. Despite its significance, understanding and quantifying shifts in soil biodiversity and their impacts on ecosystem functioning remains challenging. My dissertation addresses three knowledge gaps regarding the use of free-living nematodes as bioindicators of soil biodiversity and function in agroecosystems. First, I assess the relationship between nematode community assemblage and soil C pools and assess how these dynamics shift through time in contrasting agroecosystems. Regenerative agriculture can enhance soil food web structure through improved soil health; however, we have yet to understand if this is true over a long-term period. In chapter 1, I assess the effects of long-term regenerative agriculture practices on soil food web structure through quantifying free-living nematodes in 1991 and 2021 at the W.K. Kellogg Biological Station Long-term Ecological Research site. I found that after 20-years, nematode communities shifted from bacterivore to fungivore dominance in perennial systems. Soil C accumulation was also four times greater after 20-years but only in the early successional and a mown grassland systems. This decadal study demonstrates that the long-term maintenance of perenniality and diversity alters soil food web structure and drives soil C accumulation in agricultural systems. Second, I explore resistance and resilience of soil food webs to drought in a perennial vs. annual row crop. The impact that drought duration has on the soil food webs is seldom investigated, and even less is known regarding the role that agricultural management has on soil food web resistance and resilience to drought. In chapter 2, I aim to 1) understand how management intensity impacts the resistance of nematode communities to drought and 2) assess how the immediate alleviation of drought impacts soil food web resilience in contrasting agroecosystems. This study was conducted at the W.K. Kellogg Biological Station Long-term Ecological Research Site, where three rainfall manipulations (drought, variable, and control) were induced in two systems (early successional and no-till row-crop). Sampling for nematode communities was conducted before drought was imposed (pre-drought), six-weeks after drought was induced (peak-drought), and two days after rewetting (post-drought). I found that nematode communities in early successional systems were both resistant and resilient to drought. However, no-till systems were less resistant to drought stress, whereby fungivore r and K strategist nematode abundances declined under increased drought stress. Additionally, the alleviation of drought indicated that while early successional systems remained resilient to drought, no-till systems were slow to recover post-drought. Overall, this chapter demonstrates that reduced management intensity within agroecosystems is a valuable option for fostering soil food webs that are resistant to drought. Third, I assess how trophic level interactions within the soil food web influence N cycling. Bacterivore nematodes play a vital role in the nitrogen (N) cycle through their trophic interactions with bacterial communities, and their direct excretion of plant available ammonium. Here I 1) explore how the presence and absence of dominant bacterivore nematodes with different life-history strategies impact soil N pools and plant N use, and 2) assess how bacterial trophic channels interact with soil nitrogen use efficiency under the presence of varying bacterivore nematode species. This greenhouse microcosm experiment was conducted using soil collected from an organic farm that was defaunated. Microcosms were treated with four different nematode inoculums: Acrobeloides nanus (A.nanus), Rhabditid intermedia (R,intermedia), a co-inoculation of both species, and no nematodes. A.nanus and R.intermedia vary in their life-history strategies. The results from this study demonstrate that nematode diversity through co-inoculation can significantly increase organic nitrogen pools and soil nitrate. Additionally, co-inoculum treatments drove significant relationships between total nematode abundance and root N, aboveground biomass, and root biomass. I also found that co-inoculations of bacterivore nematodes enhance nitrogen use efficiency (NUE) and impact \uf061-diversity metrics of bacteria. Overall, results indicate that a diversity of bacterivore nematodes, which vary in life-history traits, is essential for overall N cycling and NUE. Taken together, these results indicate that free-living nematodes are highly connected to sustained ecosystem functioning and serve as valuable bioindicators of climatic disturbance and shifts in agricultural management practices. Moreover, this work supplies evidence that the conservation of soil biodiversity is essential for maintaining soil health and ecological function.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
THE PHYSICAL PROPERTIES OF IRON-NITROGEN-CARBON ALLOYS WITHIN PLANETARY CORES
No full textThesis (Ph.D.)--Michigan State University. Earth and Environmental Sciences \u2013 Doctor of Philosophy, 2025Within this thesis we investigate the physical properties of iron-carbon-nitrogen alloys with implications for planetary cores. We employ high pressure mineral physics techniques to determine the Raman Scattering of Rhenium for Secondary Pressure Calibration, investigate the Strength, plasticity, and spin transition of Fe-N compounds in planetary cores, investigate the liquid Structure of iron-nitrogen-carbon alloys within the cores of small terrestrial bodies, and measure the Physical Properties of Transition-Metal Enriched Davemaoite in the Earth's lower mantle. Terrestrial planetary cores consist of Fe-Ni alloys enriched in light elements. Nitrogen and carbon are considered potential core constituents due to their highly siderophile nature and their high Poisson\u2019s ratio when alloyed with iron. These light-element-bearing alloys can be studied experimentally using various high-pressure devices, including the Paris-Edinburgh press and the diamond anvil cell. Accurate pressure calibration is critical for successful high-pressure experiments. Previous studies have shown that different calibrations of the same material can deviate by more than 10% in the multi-megabar regime\u2014a significant uncertainty given that Earth\u2019s core spans 1.3 to 3.6 Mbar. In chapter two, we review various pressure calibrations and develop a secondary pressure scale based on the Raman scattering of Re, a common gasket material in diamond anvil cell experiments. This equation of state can be used to validate pressure conditions, monitor pressure gradients across the sample chamber, and predict diamond failure. In chapters three and four, we investigate the physical properties of Fe-light element alloys. In chapter three, we examine the strength, plasticity, and a transition in the electronic spin (i.e spin transition) of solid Fe-N compounds up to 60 GPa and 300 K using the diamond anvil cell. We find that nonhydrostatic stress broadens pressure range of the spin transition, Fe-N alloys develop unique textures and lattice preferred orientation, and nitrogen strengthens Fe at high pressures. These findings, combined with elasticity measurements, can be used to model the seismic properties of planetary cores in bodies such as Mars, Mercury, and the Moon. In chapter four, we explore the liquid structure of molten iron-nitrogen-carbon alloys under high pressure using the Paris-Edinburgh press, reaching up to 7 GPa and 1900 \ub0C. We observe that increasing nitrogen and carbon content expands the liquid volume by increasing Fe-Fe bond distances, which we model using a modified Birch-Murnaghan equation of state. From these results, we infer that nitrogen and carbon incorporation in liquid iron could contribute to the density deficit observed in the cores of terrestrial bodies. In chapter five, we shift focus to investigating the thermal equation of state of Mn- and Fe-bearing davemaoite. Davemaoite is one of the primary minerals in the lower mantle and was recently found to form a partial solid solution with MnSiO3. We measure the thermal properties of davemaoite under lower mantle conditions and determine that Mn and Fe systematically influence its thermal behavior. Specifically, Fe and Mn shift the tetragonal-to-cubic phase transition to higher temperatures. However, given the realistic abundances of Fe and Mn dissolved in davemaoite, their presence would not make it seismically distinguishable from pure CaSiO3 in the lower mantle.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
In pursuit of wholeness : Curricular perspectives of Black American Muslims in Medina Baye, Senegal
Full text linkThesis (Ph.D.)--Michigan State University. Curriculum, Instruction, and Teacher Education - Doctor of Philosophy, 2025This dissertation examines the curricular perspectives of Black American Muslims in Medina Baye, Senegal. Over a period of three months, I conducted interviews with community members in Medina Baye and led a 10-week Black history program with students at the African American Islamic Institute Legacy Academy (AAIILA). Analysis of interviews and student produced artifacts resulted in three major findings. First, the community\u2019s curricular perspectives are situated in the intellectual traditions of African centered education, yet Islam is their main source of sense-making. Second, the perspectives of Black American Muslims in Medina Baye are connected to the Islamic principle of interconnectedness. Third, youth at the AAIILA expressed their perspectives on their purposes, dreams and goals, and thoughts on freedom through multiple modes in their journal entries. Drawing on Black Critical Theory (BlackCrit), this study examines the orientations of a community of Black American Muslims who migrated to Medina Baye. This study contributes to existing scholarship on curriculum studies, particularly Black curricular perspectives.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
The K2 & TESS Synergy : Uniting NASA's Planet Hunters
No full textThesis (Ph.D.)--Michigan State University. Astrophysics and Astronomy - Doctor of Philosophy, 2025We have entered an era of studying the atmospheres of exoplanets in unprecedented detail,particularly through transmission spectroscopy of transiting planets using the James Webb Space Telescope (JWST). However, most of the 4300+ confirmed transiting planets are not currently accessible to JWST during its mission lifetime. This widespread problem is due mostly to ephemeris degradation: while the transit time and period of the planet may be known to a precision of minutes at discovery, the uncertainties compound with each successive transit, which can culminate in the projected time of future transits being off by hours to days when follow-up observations are being made years later. This costly problem can be alleviated by reobserving transits to greatly narrow down the future transit window before scheduling observations for characterization. Fortunately, NASA\u2019s Transiting Exoplanet Survey Satellite (TESS) mission is observing most of the sky for transit signals, providing an efficient and timely avenue for refreshing the ephemerides of hundreds of planets. With this in mind, the K2 & TESS Synergy is a large scale effort to reanalyze planets originally discovered by NASA\u2019s K2 mission with new observations from the ongoing TESS mission.We combine light curves obtained by both NASA missions along with archival radial velocities,Gaia parallaxes, and spectral energy distributions in global fits using EXOFASTv2, which not only allows us to update the ephemerides, but also build a self-consistent catalog of parameters for the planets and host stars. We present a reanalysis of 26 single-planet systems reobserved by TESS during its prime mission. For half of the planets, we improve the average 3? uncertainties by 2030 from the order of tens of hours down to under one hour. As a result of the faintness of some systems, 13 planets do not have transits detectable by TESS. In those cases, we exclude the TESS photometry from the global fits, resulting in a corresponding ephemeris improvement of 43.2 to 35.6 hours.This systematic approach also provides opportunity to amend ephemerides that were originallyincorrect due to problems such as false positive transits in additional photometry used at discovery. We address one such case, that of K2\u2019s first planet discovery, K2-2 b, where the period was 28.8 minutes ( 3c40?) away from the true value at the time of discovery. In addition to the K2 and TESS light curves, we use a variety of other space- and ground-based photometry to hunt for the transit of K2-2 b. We successfully caught multiple transits of K2-2 b, allowing us to correct and refine the ephemeris such that the transit time uncertainty will be known to within <13 minutes by 2030. We continue the broader reanalysis to the top 50 planets for atmospheric characterization in the K2 catalog to ensure that JWST can be used to obtain transmission spectra for these planets. Seven of the planets in this sample have been part of the previous K2 & TESS Synergy analyses. Most planets in this sample are equally suitable for atmospheric characterization using JWST as other current targets. There are also many targets that would be useful for understanding the formation and evolution processes of sub-Neptunes and giant planets. We have completed analysis for 34 of these planets, with their average ephemeris uncertainties by 2030 improved from 17.4 hours to 16 minutes, enabling future targeted observations be scheduled.The culmination of the work in this thesis is updated global parameters for 54 planets and theirhosts. Efforts like the K2 and TESS Synergy will ensure the accessibility of transiting planets for future characterization while leading to a self-consistent catalog of stellar and planetary parameters for future population efforts.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
H\uc9RITAGE DE LA N\uc9GRITUDE ET D\uc9FIS D\u2019INT\uc9GRATION SOCIALE EN FRANCE DANS NOIRE N\u2019EST PAS MON M\uc9TIER (2018) DE A\ucfSSA MA\ucfGA
No full textThesis (M.A.)--Michigan State University. French and Francophone Studies \u2013 Master of Arts, 2025Dans l\u2019ouvrage Noire n\u2019est pas mon m\ue9tier, A\uefssa Maiga avec quinze actrices noires fran\ue7aises mettent en sc\ue8ne les exp\ue9riences qu\u2019elles ont v\ue9cues dans le milieu cin\ue9matographique fran\ue7ais, des exp\ue9riences marqu\ue9es par un racisme syst\ue9mique et une invisibilisation de leurs images. Entre pute, femme de m\ue9nage, femme sans papiers ou m\ueame la dame \ue0 l\u2019accent africain, ce t\ue9moignage collectif nous plonge au c\u153ur des pr\ue9jug\ue9s dans l\u2019attribution des r\uf4les dans le cin\ue9ma fran\ue7ais. L\u2019ouvrage souligne des th\ue8mes tels que l\u2019int\ue9gration des groupes minoritaires de France, l\u2019invisibilisation, et le racisme syst\ue9mique contre les personnes noires dans le cin\ue9ma fran\ue7ais. Faisant \ue9chos aux combats des grands penseurs de la n\ue9gritude, l\u2019un des premiers mouvements de revendication des causes noires en France, ces actrices d\ue9voilent leur ferme volont\ue9 de rompre avec les s\ue9gr\ue9gations et les st\ue9r\ue9otypes d\u2019ordre raciste dans la cin\ue9matographie fran\ue7aise. Elles sont entre autres Nad\ue8ge Beausson-Diagne, Mata Gabin, Ma\uefmouna Gueye, Eye Haidara, Rachel Khan, A\uefssa Ma\uefga, Sara Martins, Marie-Philom\ue8ne Nga, Sabine Pakora, Firmine Richard, Sonia Rolland, Magaajyia Silberfeld, Shirley Souagnon, Assa Sylla, Karidja Tour\ue9, et France Zobda \ue0 t\ue9moigner de la mani\ue8re dont la racialisation de la vie sociale, n\ue9e avec l\u2019histoire coloniale et l\u2019esclavage persistent dans leur v\ue9cu contemporain et porte atteinte \ue0 leur libert\ue9. Un si\ue8cle apr\ue8s la naissance de la N\ue9gritude, cette \ue9tude vise \ue0 analyser le racisme syst\ue9mique dans l\u2019univers cin\ue9matographique fran\ue7ais tout en mettant en avant les diff\ue9rentes voies que les seize actrices construisent empruntent vers la libert\ue9.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
IMPACT OF SEASONAL CHANGES IN PASTURE-RAISING SYSTEMS ON EGG NUTRITION
Full text linkThesis (M.S.)--Michigan State University. Food Science - Master of Science, 2025Pasture-raised egg production is gaining attention for its potential alignment with regenerative agriculture principles, emphasizing biodiversity, soil health, and ethical animal husbandry. These systems allow laying hens to forage on diverse plant species and insects, which can significantly improve the nutrient composition of eggs compared to conventional grain-based systems. However, the nutrient profile of pasture-raised eggs may fluctuate due to seasonal variation in forage availability, quality, and environmental conditions.This study aimed to evaluate how seasonal changes, specifically late spring through early winter, affect the nutrient density of eggs produced in a pasture-based system in Southern Ohio. Monthly collections of forage, soil, and eggs were conducted from May to December 2022. Nutrient composition of egg yolks was assessed using gas chromatography\u2013mass spectrometry (GC-MS), liquid chromatography, spectrophotometry, and inductively coupled plasma optical emission spectroscopy (ICP-OES). Nutrients analyzed included carotenoids, vitamins A and E, total phenolics, and fatty acids. Findings revealed that forage quality, as measured by total digestible nutrients (TDN), peaked in October, aligning with increased deposition of omega-3 fatty acids and fat-soluble antioxidants in egg yolks during fall months. Vitamin E levels were highest in late fall, while vitamin A concentrations peaked in late summer. Carotenoid content followed a bimodal pattern, with elevated levels in midsummer and late autumn. Principal component and random forest analyses identified September to November as the separated time period yielding the most nutrient-dense eggs.These findings provide novel insight into how seasonal dynamics in regenerative pasture systems influence egg quality. This research supports the role of pasture-raised systems in delivering nutrient-rich animal products and highlights the need for seasonal considerations in both consumer education and on-farm management strategies.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
UNDERSTANDING DRIVER BEHAVIOR IN NAVIGATING TURBO ROUNDABOUTS
No full textThesis (M.S.)--Michigan State University. Civil Engineering - Master of Science, 2025Turbo roundabouts minimize weaving conflicts by introducing raised lane separators within the circulating lanes compared to conventional multi-lane roundabouts. Although widely used in Europe, turbo roundabouts are relatively new in the US. The California Department of Transportation (Caltrans) installed a rotor turbo roundabout in San Benito County in 2024. This research aimed to analyze driver behavior and evaluate safety performance at this newly built turbo roundabout by performing descriptive analysis and statistical modeling. Approximately 5% of vehicles made prohibited lane changes within circular lanes, particularly during left-turn movements. The lane-change model revealed that lower vehicle speeds on circular lanes, light vehicle types, and more significant headways between vehicles contributed to lane-change events. The speed choice model revealed that lower approach speeds, heavy vehicle types, left-turn movements, and smaller circular lane radii all resulted in reduced vehicle speeds on circular lanes. Observed critical gaps (4.4 to 5.8 seconds) were higher than in traditional multi-lane roundabouts (4.5 to 5.3 seconds). Follow-up time (3.7 to 4.7 seconds) was also higher than that of traditional multi-lane roundabouts, as drivers merged more cautiously in the circulating lanes due to the raised lane dividers within the circular lanes. Drivers on the turbo roundabout's inner lane exhibited longer critical gaps than those on the outer lanes due to relatively complex merging events on the inner lanes, such as crossing multiple lanes to merge into the inner circulating lane. An early traffic analysis applying the Extreme Value Theory (EVT) captured the relationship between conflict estimates and observed crashes. Based on average post-encroachment time (PET), extreme conflicts were primarily caused by improper lane changes and failure to yield. The turbo roundabout substantially lowered crash severity and eliminated speeding-related crashes. Seventy-six percent (76%) of post-installation crashes were attributed to unfamiliarity and right-of-way violations, while 22% were due to navigational errors. These findings underscore the need for improved dissemination of proper turbo roundabout driving information and appropriate signage to facilitate safe lane selection and prevent prohibited lane changes within circulating lanes. This research contributes to a broader understanding of turbo roundabout performance in the US. Findings can be used to refine design, capacity, operational, and safety analyses based on driver behavior in the US.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references
Implementation of an evidence-based wellness program for student registered nurse anesthetists
No full textStudent Registered Nurse Anesthetists (SRNAs) face many challenges throughout their rigorous 36-month educational program. Many students report increasing levels of stress and a reduction in overall wellbeing. While the American Association of Nurse Anesthetists provides supportive resources in the form of webinars, support groups and hotlines, program specific wellness initiatives remain the safety net for most SRNAs. In the Michigan State University Nurse Anesthesia Program, wellness education and activities are dispersed throughout the 36 months. However, an evidence-based, intentional approach to wellness is lacking. The purpose of this project is to restructure the current wellness program to include the development and implementation of a mindfulness-based stress reduction course.Thesis (D.N.P.)--Michigan State University. Nurse anesthesiology, 2025Includes bibliographical reference
Advancing Microphysiological Systems : Development of a Scalable Platform for Modeling Developmental and Reproductive Toxicity
No full textThesis (Ph.D.)--Michigan State University. Biomedical Engineering - Doctor of Philosophy, 2025Human birth defects including cleft lip and cleft palate (collectively orofacial clefts, OFCs) arise from complex, multifactorial causes, including poorly understood environmental exposures that can disrupt critical developmental pathways. As the number of chemicals in the environment continues to grow, there is an urgent need for innovative approaches to identify hazardous exposures and improve our understanding of the etiology of human birth defects. This dissertation presents multiple new approach methodologies (NAMs) designed to advance the study of OFCs. To contextualize current knowledge, identify regulatory data gaps, and align with an established regulatory framework, a network of adverse outcome pathways is developed, linking disruption of the Sonic Hedgehog (SHH) signaling pathway to OFC formation. In parallel, digital manufacturing techniques\u2014such as computer numerical control (CNC) machining and laser welding\u2014are explored and applied to fabricate custom microplate-based microphysiological models. These contributions to digital manufacturing aim to support the broader adoption of NAMs in developmental toxicity testing by providing a cost-effective, tractable method well suited to create custom throughput compatible models. These technologies are further leveraged to refine an in vitro model of orofacial development, enabling the study of SHH signaling in a format compatible with high-throughput screening. Additionally, a retrospective in silico analysis of existing in vivo and in vitro data is conducted to evaluate the feasibility of repurposing current assays and existing data for predicting developmental toxicity associated with OFCs. Collectively, this work introduces and integrates multiple NAMs to enhance the mechanistic understanding and predictive assessment of environmental contributors to OFC etiology.Description based on online resource. Title from PDF t.p. (Michigan State University Fedora Repository, viewed ).Includes bibliographical references