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Search Results: 1 - 10 of 6855 matches for " Mary Beth Leigh "
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Biodegradation of Dispersed Oil in Arctic Seawater at -1°C
Kelly M. McFarlin, Roger C. Prince, Robert Perkins, Mary Beth Leigh
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084297
Abstract: As offshore oil and gas exploration expands in the Arctic, it is important to expand the scientific understanding of arctic ecology and environmental impact to mitigate operational risks. Understanding the fate of oil in arctic seawater is a key factor for consideration. Here we report the chemical loss due to the biodegradation of Alaska North Slope (ANS) crude oil that would occur in the water column following the successful dispersion of a surface oil slick. Primary biodegradation and mineralization were measured in mesocosms containing Arctic seawater collected from the Chukchi Sea, Alaska, incubated at ?1°C. Indigenous microorganisms degraded both fresh and weathered oil, in both the presence and absence of Corexit 9500, with oil losses ranging from 46?61% and up to 11% mineralization over 60 days. When tested alone, 14% of 50 ppm Corexit 9500 was mineralized within 60 days. Our study reveals that microorganisms indigenous to Arctic seawater are capable of performing extensive biodegradation of chemically and physically dispersed oil at an environmentally relevant temperature (?1°C) without any additional nutrients.
Snapshot of the Eukaryotic Gene Expression in Muskoxen Rumen—A Metatranscriptomic Approach
Meng Qi, Pan Wang, Nicholas O'Toole, Perry S. Barboza, Emilio Ungerfeld, Mary Beth Leigh, L. Brent Selinger, Greg Butler, Adrian Tsang, Tim A. McAllister, Robert J. Forster
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0020521
Abstract: Background Herbivores rely on digestive tract lignocellulolytic microorganisms, including bacteria, fungi and protozoa, to derive energy and carbon from plant cell wall polysaccharides. Culture independent metagenomic studies have been used to reveal the genetic content of the bacterial species within gut microbiomes. However, the nature of the genes encoded by eukaryotic protozoa and fungi within these environments has not been explored using metagenomic or metatranscriptomic approaches. Methodology/Principal Findings In this study, a metatranscriptomic approach was used to investigate the functional diversity of the eukaryotic microorganisms within the rumen of muskoxen (Ovibos moschatus), with a focus on plant cell wall degrading enzymes. Polyadenylated RNA (mRNA) was sequenced on the Illumina Genome Analyzer II system and 2.8 gigabases of sequences were obtained and 59129 contigs assembled. Plant cell wall degrading enzyme modules including glycoside hydrolases, carbohydrate esterases and polysaccharide lyases were identified from over 2500 contigs. These included a number of glycoside hydrolase family 6 (GH6), GH48 and swollenin modules, which have rarely been described in previous gut metagenomic studies. Conclusions/Significance The muskoxen rumen metatranscriptome demonstrates a much higher percentage of cellulase enzyme discovery and an 8.7x higher rate of total carbohydrate active enzyme discovery per gigabase of sequence than previous rumen metagenomes. This study provides a snapshot of eukaryotic gene expression in the muskoxen rumen, and identifies a number of candidate genes coding for potentially valuable lignocellulolytic enzymes.
Methodological challenges in carbohydrate analyses
Hall, Mary Beth;
Revista Brasileira de Zootecnia , 2007, DOI: 10.1590/S1516-35982007001000032
Abstract: carbohydrates can provide up to 80% of the dry matter in animal diets, yet their specific evaluation for research and diet formulation is only now becoming a focus in the animal sciences. partitioning of dietary carbohydrates for nutritional purposes should reflect differences in digestion and fermentation characteristics and effects on animal performance. key challenges to designating nutritionally important carbohydrate fractions include classifying the carbohydrates in terms of nutritional characteristics, and selecting analytical methods that describe the desired fraction. the relative lack of information on digestion characteristics of various carbohydrates and their interactions with other fractions in diets means that fractions will not soon be perfectly established. developing a system of carbohydrate analysis that could be used across animal species could enhance the utility of analyses and amount of data we can obtain on dietary effects of carbohydrates. based on quantities present in diets and apparent effects on animal performance, some nutritionally important classes of carbohydrates that may be valuable to measure include sugars, starch, fructans, insoluble fiber, and soluble fiber. essential to selection of methods for these fractions is agreement on precisely what carbohydrates should be included in each. each of these fractions has analyses that could potentially be used to measure them, but most of the available methods have weaknesses that must be evaluated to see if they are fatal and the assay is unusable, or if the assay still may be made workable. factors we must consider as we seek to analyze carbohydrates to describe diets: does the assay accurately measure the desired fraction? is the assay for research, regulatory, or field use (affects considerations of acceptable costs and throughput)? what are acceptable accuracy and variability of measures? is the assay robust (enhances accuracy of values)? for some carbohydrates, we may have to accept
Some Open Problems in Quantum Information Theory
Mary Beth Ruskai
Physics , 2007,
Abstract: Some open questions in quantum information theory (QIT) are described. Most of them were presented in Banff during the BIRS workshop on Operator Structures in QIT 11-16 February 2007. New material has been added in view of the recent counter-examples to p-norm multiplicativity.
Qubit Entanglement Breaking Channels
Mary Beth Ruskai
Physics , 2003, DOI: 10.1142/S0129055X03001710
Abstract: This paper continues the study of stochastic maps, or channels, which break entanglement. We give a detailed description of entanglement-breaking qubit channels, and show that such maps are precisely the convex hull of those known as classical-quantum channels. We also review the complete positivity conditions in a canonical parameterization and show how they lead to entanglement-breaking conditions.
Some Bipartite States do not Arise from Channels
Mary Beth Ruskai
Physics , 2003,
Abstract: It is well-known that the action of a quantum channel on a state can be represented, using an auxiliary space, as the partial trace of an associated bipartite state. Recently, it was observed that for the bipartite state associated with the optimal average input of the channel, the entanglement of formation is simply the entropy of the reduced density matrix minus the Holevo capacity. It is natural to ask if every bipartite state can be associated with some channel in this way. We show that the answer is negative.
Another Short and Elementary Proof of Strong Subadditivity of Quantum Entropy
Mary Beth Ruskai
Physics , 2006, DOI: 10.1016/S0034-4877(07)00019-5
Abstract: A short and elementary proof of the joint convexity of relative entropy is presented, using nothing beyond linear algebra. The key ingredients are an easily verified integral representation and the strategy used to prove the Cauchy-Schwarz inequality in elementary courses. Several consequences are proved in a way which allow an elementary proof of strong subadditivity in a few more lines. Some expository material on Schwarz inequalities for operators and the Holevo bound for partial measurements is also included.
Pauli Exchange Errors in Quantum Computation
Mary Beth Ruskai
Physics , 1999, DOI: 10.1103/PhysRevLett.85.194
Abstract: In many physically realistic models of quantum computation, Pauli exchange interactions cause a subset of two-qubit errors to occur as a first order effect of couplings within the computer, even in the absence of interactions with the computer's environment. We give an explicit 9-qubit code that corrects both Pauli exchange errors and all one-qubit errors.
Connecting N-representability to Weyl's problem: The one particle density matrix for N = 3 and R = 6
Mary Beth Ruskai
Physics , 2007, DOI: 10.1088/1751-8113/40/45/F01
Abstract: An analytic proof is given of the necessity of the Borland-Dennis conditions for 3-representability of a one particle density matrix with rank 6. This may shed some light on Klyachko's recent use of Schubert calculus to find general conditions for N-representability.
Remarks on on Kim's Strong Subadditivity Matrix Inequality: Extensions and Equality Conditions
Mary Beth Ruskai
Physics , 2012, DOI: 10.1063/1.4823581
Abstract: We describe recent work of Kim in arXiv:1210.5190 to show that operator convex functions associated with quasi-entropies can be used to prove a large class of new matrix inequalities in the tri-partite and bi-partite setting by taking a judiciously chosen partial trace over all but one of the spaces. We give some additional examples in both settings. Furthermore, we observe that the equality conditions for all the new inequalities are essentially the same as those for strong subadditivity.
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