300 research outputs found
Dualidade de Howe para algumas super álgebras de Lie
No full textOrientador: Prof. Dr. Matheus Batagini BritoTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Matemática. Defesa : Curitiba, 04/08/2023Inclui referênciasResumo: O objetivo deste trabalho é estudar a chamada Dualidade de Howe, que envolve ações comutantes para grupos de Lie clássicos e super álgebras de Lie. Essa teoria foi introduzida em 1976 por Roger Howe (1945-). Dado um super espaço vetorial U = U0 (produto tensorial) U1, Howe definiu a super álgebra A(U), dada por um quociente da álgebra tensorial T(U) pelas relações x (produto tensorial) u (produto tensorial) u (produto tensorial) x e w1 (produto tensorial) w2 + w2 (produto tensorial) w1, para x (produto tensorial) U0, w1, w2 (produto tensorial) U1 e u (produto tensorial) U. Ele considerou U como a representação natural de um grupo de Lie clássico G e A(U) como o G-módulo induzido. Howe também definiu operadores que agem em A(U), e geram a álgebra W(U), conhecida como álgebra de Weyl-Clifford. O foco deste trabalho é estudar a decomposição de A(U) em (G,W(U)G)-módulos. Pode-se identificar o conjunto de geradores de W(U)G com uma base para uma super álgebra de Lie g, explicitamente descrita dependendo de G e U. Em particular, W(U)G é um quociente da álgebra U(g) e (G, g) é chamado de par dual de Howe. Para finalizar, apresentaremos um caso particular da dualidade de Howe para o par dual de Howe (Ok(C), sl2).Abstract: The goal of this work is to study the so-called Howe duality, which involves commuting actions for classical Lie groups and Lie superalgebras. This theory was introduced in 1976, by Roger Howe (1945- ). Given a vector superspace U = U0 (tensorial algebra) U1, Howe defined the superalgebra A(U), defined as a quotient from the tensorial algebra by the relations x (tensorial algebra) u (tensorial algebra) u (tensorial algebra) x and w1 (tensorial algebra) w2 + w2 (tensorial algebra) w1, for x (tensorial algebra) U0, w1, w2 (tensorial algebra) U1 and u (tensorial algebra) U. He regarded U as a natural representation for some classical Lie group G and considered A(U) as the induced G-module. Howe also defined a family of operators that act on A(U) and generate the algebra W(U), known as the Weyl-Clifford algebra. This work focuses on the study of the decomposition of A(U) in (G,W(U)G)-modules. One can also identify the set of generators of W(U)G with a basis for a Lie superalgebra g, explicitly described depending on G and U. In particular, W(U)G is a quotient of U(g) and (G, g) is called a Howe dual pair. To finish our work, we will present a particular case of Howe duality which we considered the Howe dual pair (Ok(C), sl2)
Antimicrobial resistance in integrated agroecosystems: State of the science and future opportunities
No full textAs the Journal of Environmental Quality (JEQ) celebrates 50 years of publication, the division of environmental microbiology is one of the newest additions to the journal. During this time, significant advances in understanding of the interconnected microbial community and impact of the microbiome on natural and designed environmental systems have occurred. In this review, we highlight the intractable challenge of antimicrobial resistance (AMR) on humans, animals, and the environment, with particular emphasis on the role of integrated agroecosystems and by highlighting contributions published in JEQ. From early studies of phenotypic resistance of indicator organisms in waters systems to current calls for integrating AMR assessment across “One Health,” publications in JEQ have advanced our understanding of AMR. As we reflect on the state of the science, we emphasize future opportunities. First, integration of phenotypic and molecular tools for assessing environmental spread of AMR and human health risk continues to be an urgent research need for a one health approach to AMR. Second, monitoring AMR levels in manure is recommended to understand inputs and potential spread through agroecosystems. Third, baseline knowledge of AMR levels is important to realize the impact of manure inputs on water quality and public health risk; this can be achieved through background monitoring or identifying the source-related genes or organisms. And finally, conservation practices designed to meet nutrient reduction goals should be explored for AMR reduction potential.This is the published version of the following article: Howe, Adina C., and Michelle L. Soupir. "Antimicrobial resistance in integrated agroecosystems: State of the science and future opportunities." Journal of Environmental Quality 50, no. 6 (2021): 1255-1265. DOI: 10.1002/jeq2.20289. Copyright 2021 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial. and no modifications or adaptations are made. Posted with permission
Strategies to improve reference databases for soil microbiomes
No full textThis article is published as Choi, Jinlyung, Fan Yang, Ramunas Stepanauskas, Erick Cardenas, Aaron Garoutte, Ryan Williams, Jared Flater, James M Tiedje, Kirsten S Hofmockel, Brian Gelder, and Adina Howe. "Strategies to improve reference databases for soil microbiomes." ISME Journal 11 (2017) 829-834. DOI: 10.1038/ismej.2016.168. Posted with permission.</p
Vibration of Bundled Conductors Following Ice Shedding
No full textThe dynamic behavior of bundled conductors following ice shedding from one subconductor is examined numerically using the finite-element method. An existing model of ice shedding from a single conductor is improved by developing a model of spacers which connect subconductors in the span. The resulting system makes it possible to simulate vibrations following ice shedding from one span of an overhead transmission line with twin, triple, or quad bundles. Vibration characteristics are evaluated as the following parameters are varied: thickness of shed ice, distance between adjacent spacers, and number of subconductors in the bundle. Simulation results will provide information on how the amplitude of vibration and the transient dynamic forces change with the application of spacers. The maximum jump height of the ice-shedding cable, the maximum drop of the loaded cable, and the maximum cable tension are approximated as power functions of ice thickness and the distance between adjacent spacers
Seasonal activities of the phyllosphere microbiome of perennial crops
No full textUnderstanding the interactions between plants and microorganisms can inform microbiome management to enhance crop productivity and resilience to stress. Here, we apply a genome-centric approach to identify ecologically important leaf microbiome members on replicated plots of field-grown switchgrass and miscanthus, and to quantify their activities over two growing seasons for switchgrass. We use metagenome and metatranscriptome sequencing and curate 40 medium- and high-quality metagenome-assembled-genomes (MAGs). We find that classes represented by these MAGs (Actinomycetia, Alpha- and Gamma- Proteobacteria, and Bacteroidota) are active in the late season, and upregulate transcripts for short-chain dehydrogenase, molybdopterin oxidoreductase, and polyketide cyclase. Stress-associated pathways are expressed for most MAGs, suggesting engagement with the host environment. We also detect seasonally activated biosynthetic pathways for terpenes and various non-ribosomal peptide pathways that are poorly annotated. Our findings support that leaf-associated bacterial populations are seasonally dynamic and responsive to host cues.This article is published as Howe, Adina, Nejc Stopnisek, Shane K. Dooley, Fan Yang, Keara L. Grady, and Ashley Shade. "Seasonal activities of the phyllosphere microbiome of perennial crops." Nature Communications 14, no. 1 (2023): 1039.
DOI: 10.1038/s41467-023-36515-y.
Copyright 2023 The Author(s).
Attribution 4.0 International (CC BY 4.0).
Posted with permission
Denitrifying bioreactor microbiome: Understanding pollution swapping and potential for improved performance
No full textDenitrifying woodchip bioreactors are a best management practice to reduce nitrate–nitrogen (NO3–N) loading to surface waters from agricultural subsurface drainage. Their effectiveness has been proven in many studies, although variable results with respect to performance indicators have been observed. This paper serves the purpose of synthesizing the current state of the science in terms of the microbial community, its impact on the consistency of bioreactor performance, and its role in the production of potential harmful by-products including greenhouse gases, sulfate reduction, and methylmercury. Microbial processes other than denitrification have been observed in these bioreactor systems, including dissimilatory nitrate reduction to ammonia (DNRA) and anaerobic ammonium oxidation (anammox). Specific gene targets for denitrification, DNRA, anammox, and the production of harmful by-products are identified from bioreactor studies and other environmentally relevant systems for application in bioreactor studies. Lastly, cellulose depletion has been observed over time via increasing ligno-cellulose indices, therefore, the microbial metabolism of cellulose is an important function for bioreactor performance and management. Future work should draw from the knowledge of soil and wetland ecology to inform the study of bioreactor microbiomes.This is the published version of the following article: Hartfiel, Lindsey, Abby Schaefer, Adina Howe, and Michelle Soupir. "Denitrifying Bioreactor Microbiome: Understanding Pollution Swapping and Potential for Improved Performance." Journal of Environmental Quality (2021). DOI: 10.1002/jeq2.20302. Copyright 2021 The Authors. Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). Posted with permission
Comparison of microbial communities in replicated woodchip bioreactors
No full textDenitrification in woodchip bioreactors is a microbial process, but the effect of variations in bioreactors operation on microbial community structure are not well understood. Here, our goals were to understand hydraulic retention time (HRT) as a factor that influences woodchip bioreactor microbial community variation and structure in replicated field bioreactors and to evaluate relationships between microbial community membership and marker genes for denitrification. We used a combination of qPCR of nirS, nirK, nosZI, and nosZII and 16S rRNA amplicon sequencing to characterize the microbial communities of nine pilot-scale woodchip bioreactors located at Iowa State University. Our results showed dynamic microbial communities but with persistent taxa between two sampling years and three hydraulic retention times (HRTs). Similarities between functional gene copy numbers across sampling year and HRT indicate that the potential for denitrification is conserved despite differences in the microbial communities. These results are evidence that there are specific and persistent taxa within replicated bioreactors. Woodchip bioreactor microbial community membership is recommended to be the focus of future studies to better understand the relationship between microbial community functions and bioreactor management.This is a manuscript version of the following article: Schaefer, Abby, Jaejin Lee, Michelle Soupir, Thomas Moorman, and Adina Howe. Comparison of microbial communities in replicated woodchip bioreactors. Journal of Environmental Quality (2021). DOI: 10.1002/jeq2.20320. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted
Scanning tunneling microscopy and spectroscopy studies of graphene
No full textIn the two-dimensional (2D) lattice of graphene, consisting of carbon atoms arranged in a honeycomb lattice, the charge carriers are described by a Dirac-Weyl Hamiltonian. Seeking to understand their unique nature, this thesis presents results of scanning tunneling microscopy (STM) and spectroscopy (STS) experiments at low temperatures and in magnetic fi eld. These techniques give access, down to atomic scales, to structural information as well as to the electronic properties of graphene. The main findings include the observation of quantized Landau levels (LL) in the presence of magnetic field, their dependence on carrier density and e ffects of charged impurities and other disorder on the LL spectrum. Twisting graphene layers away from the equilibrium Bernal stacking leads to the formation of Moir e patterns that signi ficantly alter the electronic properties of graphene stacks. The second part of the thesis discusses the eff ects of such rotations on the electronic properties as a function of twist angle.Ph. D.Includes bibliographical referencesby Adina Luican-Maye
Microbial linkages to soil biogeochemical processes in a poorly drained agricultural ecosystem
No full textSoil microorganisms mediate biogeochemical processes, but how microbial community composition influences these processes remains contested. We combined monthly sequencing of soil 16S rRNA genes and intensive measurements of nitrogen (N), carbon (C), and iron (Fe) cycling along a topographic gradient in a poorly drained intensive agricultural ecosystem (corn–soybean rotation) in the midwestern United States. Observed microbial composition changed little over time within and among years despite large differences in weather and crop type. Yet, microbial composition varied greatly with topographic location and correlated strongly with moisture, soil organic carbon (SOC), and especially pH. Microbial families, genera, and/or amplicon sequence variants often correlated significantly with measured biogeochemical processes or pools, yet different taxa within the same phylogenetic groups often responded in opposite ways, indicating a lack of ecological coherence among close relatives. Dominant phyla were generally similar across the topographic gradient but specific members showed consistent tradeoffs among locations. Ammonia oxidizing archaea and bacteria sequences varied oppositely with pH across the gradient, but their combined relative abundances remained similar, as did potential nitrification rates. Nitrospira sequences correlated positively with nitrous oxide (N2O) fluxes, suggesting a direct or indirect contribution of nitrification (or possibly comammox) to N2O production. We also found significant linkages between taxonomic groups and redox-sensitive Fe pools, indicating a role for redox variation in structuring microbial communities. Several globally dominant bacteria identified previously correlated significantly with measured biogeochemical variables, providing insights into their possible functional roles. Overall, microbial composition provided a coarse measure of several key biogeochemical functions and implicated taxa that possibly mediate these processes in a widespread agroecosystem of North America.This is a manuscript of an article published as Yu, Wenjuan, Nathaniel C. Lawrence, Thanwalee Sooksa-nguan, Schuyler D. Smith, Carlos Tenesaca, Adina Chuang Howe, and Steven J. Hall. "Microbial linkages to soil biogeochemical processes in a poorly drained agricultural ecosystem." Soil Biology and Biochemistry (2021): 108228. doi:10.1016/j.soilbio.2021.108228. Posted with permission.</p
Diversity of Antibiotic Resistance genes and Transfer Elements-Quantitative Monitoring (DARTE-QM): a method for detection of antimicrobial resistance in environmental samples
No full textEffective monitoring of antibiotic resistance genes and their dissemination in environmental ecosystems has been hindered by the cost and efficiency of methods available for the task. We developed the Diversity of Antibiotic Resistance genes and Transfer Elements-Quantitative Monitoring (DARTE-QM), a method implementing TruSeq high-throughput sequencing to simultaneously sequence thousands of antibiotic resistant gene targets representing a full-spectrum of antibiotic resistance classes common to environmental systems. In this study, we demonstrated DARTE-QM by screening 662 antibiotic resistance genes within complex environmental samples originated from manure, soil, and livestock feces, in addition to a mock-community reference to assess sensitivity and specificity. DARTE-QM offers a new approach to studying antibiotic resistance in environmental microbiomes, showing advantages in efficiency and the ability to scale for many samples. This method provides a means of data acquisition that will alleviate some of the obstacles that many researchers in this area currently face.This article is published as Smith, Schuyler D., Jinlyung Choi, Nicole Ricker, Fan Yang, Shannon Hinsa-Leasure, Michelle L. Soupir, Heather K. Allen, and Adina Howe. "Diversity of Antibiotic Resistance genes and Transfer Elements-Quantitative Monitoring (DARTE-QM): a method for detection of antimicrobial resistance in environmental samples." Communications Biology 5, no. 1 (2022): 216. doi: https://doi.org/10.1038/s42003-022-03155-9. © The Author(s) 2022. Open Access article. This article is licensed under a Creative Commons Attribution 4.0 International
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