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"Curtis, Tony"
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Phosphorus and Nitrogen in Runoff after Phosphorus‐ or Nitrogen‐based Manure Applications
Application of beef cattle (Bos taurus) manure based on nitrogen (N) requirements of crops has resulted in elevated concentrations of soil test phosphorus (P) in surface soils, and runoff from this cropland can contribute to eutrophication of surface waters. We conducted a 3‐yr field study (2005–2007) on a Lethbridge loam soil cropped to dryland barley (Hordeum vulgare) in southern Alberta, Canada to evaluate the effect of annual and triennial P‐based and annual N‐based feedlot manure on P and N in runoff. The manure was spring applied and incorporated. There was one unamended control plot. A portable rainfall simulator was used to generate runoff in the spring of each year after recent manure incorporation, and the runoff was analyzed for total P, total dissolved P, total particulate P, dissolved reactive P, total N, total dissolved N, total particulate N, NO3–N, and NH4–N. Annual or triennial P‐based application resulted in significantly (p ≤ 0.05) lower (by 50 to 94%) concentrations or loads of mainly dissolved P fractions in runoff for some years compared with annual N‐based application, and this was related to lower rates of annual manure P applied. For example, mean dissolved reactive P concentrations in 2006 and 2007 were significantly lower for the annual P‐based (0.12–0.20 mg L‐1) than for the annual N‐based application (0.24–0.48 mg L‐1), and mean values were significantly lower for the triennial P‐based (0.06–0.13 mg L‐1) than for the annual N‐based application. In contrast, other P fractions in runoff were unaffected by annual P‐based application. Our findings suggested no environmental benefit of annual P‐based application over triennial P‐based application with respect to P and N in runoff. Similar concentrations and loads of N fractions in runoff for the P‐ and N‐based applications indicated that shifting to a P‐based application would not significantly influence N in runoff.
Journal Article
\To Go to Nature's Manufactory\: The Material Ecology of Slavery in Antebellum Maryland
This dissertation examines the environmental history of slavery in Maryland and attends specifically to the ways enslaved people’s relationship to their environment manifested in their everyday lives. In this project, I advance an ecological analysis that foregrounds networks of relation between slaves, slaveholders, soils, plants, animals, and cold weather. Grounding my analysis in the everyday world of slavery, my dissertation employs a framework I call material ecology, which utilizes object-oriented analysis as a means of thinking through, unpacking, and rendering the ecology of slavery in Maryland. Using this approach, I organize each of my chapters around a class of objects that materialize different ecological relations. As the points at which such relations converge, cast-iron plows, enslaved people’s shoes, slave-made charms, as well as stews and similar one-pot meals disclose distinctive interactions between the enslaved and their environment. From my analysis of the relationships that cohere around these objects, I argue that in antebellum Maryland slaves and slaveholders differently mobilized elements of their environment against one another in their multiform contests over power. Examining the ecological networks informing these contests illustrates the extent to which the environment in enslaved people’s lives was simultaneously antagonistic and empowering.
Dissertation
Physical and Chemical Properties of Feedlot Pen Surfaces Located on Moderately Coarse- and Moderately Fine-Textured Soils in Southern Alberta
Southern Alberta has the highest density of feedlot cattle in Canada, and there is a concern that leaching of water and contaminants may be greater for feedlots located on coarser-textured than finer-textured soils. Our objective was to determine if infiltration and leaching were greater for a 4-yr-old feedlot located on a moderately coarse-textured (MC) soil compared with two feedlots located on moderately fine-textured (MF) soils (5- and 52-yr-old pens). Various soil physical properties of feedlot pen surfaces were measured, including field-saturated hydraulic conductivity (Kfs) and near-saturated hydraulic conductivity at -0.9 and -3.9 cm water potential. Selected chemical properties of feedlot soil layers were measured, as well as the chloride content of the soil profile (0-100 cm). Mean Kfs, K(-0.9), and K(-3.9) values were not significantly (P > 0.10) greater at the MC site than the two MF sites, indicating no evidence of greater infiltration on coarser-textured soils. In addition, mean Kfs, K(-0.9), and K(-3.9) values of soils within feedlot pens at all three sites were significantly (P 0.10) reduced by 46 to 78% compared with soil outside the pens. Depth of chloride accumulation was greatest at the 52-yr-old feedlot on MF soil (60-70 cm), followed by 4-yr-old feedlot on MC soil (40-50 cm) and 5-yr-old feedlot on MF soil (30-40 cm). Visual inspection determined that the black interface layer formed within 2 mo of cattle stocking at all three sites.
Journal Article
A Further Study of Linux Kernel Hugepages on A64FX with FLASH, an Astrophysical Simulation Code
We present an expanded study of the performance of FLASH when using Linux Kernel Hugepages on Ookami, an HPE Apollo 80 A64FX platform. FLASH is a multi-scale, multi-physics simulation code written principally in modern Fortran and makes use of the PARAMESH library to manage a block-structured adaptive mesh. Our initial study used only the Fujitsu compiler to utilize standard hugepages (hp), but further investigation allowed us to utilize hp for multiple compilers by linking to the Fujitsu library libmpg and transparent hugepages (thp) by enabling it at the node level. By comparing the results of hardware counters and in-code timers, we found that hp and thp do not significantly impact the runtime performance of FLASH. Interestingly, there is a significant reduction in the TLB misses, differences in cache and memory access counters, and strange behavior is observed when using thp.
Paper
Benchmarking with Supernovae: A Performance Study of the FLASH Code
Astrophysical simulations are computation, memory, and thus energy intensive, thereby requiring new hardware advances for progress. Stony Brook University recently expanded its computing cluster \"SeaWulf\" with an addition of 94 new nodes featuring Intel Sapphire Rapids Xeon Max series CPUs. We present a performance and power efficiency study of this hardware performed with FLASH: a multi-scale, multi-physics, adaptive mesh-based software instrument. We extend this study to compare performance to that of Stony Brook's Ookami testbed which features ARM-based A64FX-700 processors, and SeaWulf's AMD EPYC Milan and Intel Skylake nodes. Our application is a stellar explosion known as a thermonuclear (Type Ia) supernova and for this 3D problem, FLASH includes operators for hydrodynamics, gravity, and nuclear burning, in addition to routines for the material equation of state. We perform a strong-scaling study with a 220 GB problem size to explore both single- and multi-node performance. Our study explores the performance of different MPI mappings and the distribution of processors across nodes. From these tests, we determined the optimal configuration to balance runtime and energy consumption for our application.
Paper
Against All Odds: The Story of Four High-Achieving African-American Males (An Ethno-Case Study)
African-American students, particularly males, achieve at levels below their White and Asian-American counterparts as measured on traditional academic indices (e.g., standardized test scores, high school completion rates, grade point averages, and college entrance and completion rates), which—naturally, impact their life outcomes. Yet, against all odds—including enrollment in one of the lowest performing high schools in one of the nation's largest school districts—many African-American high school-level boys prove to be high achieving on these same traditional indices. This project is an attempt to capture the school and home-life stories of four such students, capturing that which promotes their high academic engagement and achievement as to contribute to the conversation about narrowing said academic achievement and life outcome disparities. The theories that the engagement of student narratives and voices is paramount to closing the aforesaid disparities and the working assumption that socio-political forces greatly influence the academic achievement and engagement of African-American male high school students serve as the theoretical framings of this project. Feminist and youth participatory action research traditions inform the research collection design, while ethno-case study is the employed methodology. Findings suggest that a couple of in-school dynamics (i.e., climate in school and peer relationships) greatly influence the students' academic achievements, while extracurricular influence is minimal. With respect to out-of-school dynamics, only family has largely influenced said students' academic achievements, while church and community influences are marginal. And, finally, a sense of self-efficacy, however nurtured, bears significant influence on the students' academic achievements. Such findings can contribute to this ever-important conversation about improving the academic achievements of African-American males and, in doing so, improving their life outcomes.
Dissertation
Comparing the behavior of OpenMP Implementations with various Applications on two different Fujitsu A64FX platforms
The development of the A64FX processor by Fujitsu has been a massive innovation in vectorized processors and led to Fugaku: the current world's fastest supercomputer. We use a variety of tools to analyze the behavior and performance of several OpenMP applications with different compilers, and how these applications scale on the different A64FX processors on clusters at Stony Brook University and RIKEN.
Paper
