4,419 research outputs found

    Propagation of Exchange Bias in CoFe/FeMn/CoFe Trilayers

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    CoFe/FeMn, FeMn/CoFe bilayers and CoFe/FeMn/CoFe trilayers were grown in magnetic field and at room temperature. The exchange bias field HebH_{eb} depends strongly on the order of depositions and is much higher at CoFe/FeMn than at FeMn/CoFe interfaces. By combining the two bilayer structures into symmetric CoFe/FeMn(tFeMnt_\mathrm{FeMn})/CoFe trilayers, HebtH_{eb}^t and HebbH_{eb}^b of the top and bottom CoFe layers, respectively, are both enhanced. Reducing tFeMnt_\mathrm{FeMn} of the trilayers also results in enhancements of both HebbH_{eb}^b and HebtH_{eb}^t. These results evidence the propagation of exchange bias between the two CoFe/FeMn and FeMn/CoFe interfaces mediated by the FeMn antiferromagnetic order

    The floristics of Sand Forest in northern KwaZulu-Natal, South Africa

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    We use multivariate analyses (ordination and classification) to assess both the floristic uniqueness of the woody vegeation of Sand Forest in relation to a range of other forest types in the region, and the range of variation within Sand Forest. Two broad Sand Forest subtypes and related Ecotonal Forests are described and grouped under the term Tropical Dry Forest, distinct from all evergreen forests in South Africa. Sand Forest, a dry semi-deciduous type in northeastern KwaZulu-Natals defined by the presence of the canopy dominant Cleistanthus schlechteri as well as Hymenocardia ulmoides, Psydrax fragrantissima, Croton pseudopulchellus and  Drypetes arguta. Sand Forests form a cohesive group in both DCA and TWINSPAN analyses, with similar composition of canopy dominants at sampled sites. This implies that ecological funcioning is similar across the geographical range in northeastern KwaZulu-Natal. However, turnover of subdominant species between recognisable Sand Forest types emphasizes the need to conserve the full range of extant forests

    FRESHWATER POND USE BY WHOOPING CRANES DURING A WET WINTER IN COASTAL TEXAS

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    Wintering whooping cranes (Grus americana) in the Aransas-Wood Buffalo Population have a restricted range along coastal Texas, and they rely on coastal salt marshes and tidal ponds for feeding and roosting habitat as well as upland freshwater ponds for dietary drinking water during drought periods. These upland ponds were used extensively by wintering whooping cranes during a multi-year drought (2011-2014), and use terminated when frequent localized rainfall events occurred across the wintering range. Despite optimum bay salinities that occurred during this study (February-March 2016) in a 6-week winter period, whooping cranes continued to use at least 1 of the 3 upland ponds when tidal pond salinities were \u3e23 ppt, suggesting that need for dietary water is influenced by tidal pond salinities rather than bay salinities

    Multiple Components in Narrow Planetary Rings

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    The phase-space volume of regions of regular or trapped motion, for bounded or scattering systems with two degrees of freedom respectively, displays universal properties. In particular, drastic reductions in the volume (gaps) are observed at specific values of a control parameter. Using the stability resonances we show that they, and not the mean-motion resonances, account for the position of these gaps. For more degrees of freedom, exciting these resonances divides the regions of trapped motion. For planetary rings, we demonstrate that this mechanism yields rings with multiple components.Comment: 4 pages, 7 figures (some in colors

    Complete genome sequence of a highly divergent astrovirus isolated from a child with acute diarrhea

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    <p>Abstract</p> <p>Background</p> <p>Astroviruses infect a variety of mammals and birds and are causative agents of diarrhea in humans and other animal hosts. We have previously described the identification of several sequence fragments with limited sequence identity to known astroviruses in a stool specimen obtained from a child with acute diarrhea, suggesting that a novel virus was present.</p> <p>Results</p> <p>In this study, the complete genome of this novel virus isolate was sequenced and analyzed. The overall genome organization of this virus paralleled that of known astroviruses, with 3 open reading frames identified. Phylogenetic analysis of the ORFs indicated that this virus is highly divergent from all previously described animal and human astroviruses. Molecular features that are highly conserved in human serotypes 1–8, such as a 3'NTR stem-loop structure and conserved nucleotide motifs present in the 5'NTR and ORF1b/2 junction, were either absent or only partially conserved in this novel virus.</p> <p>Conclusion</p> <p>Based on the analyses described herein, we propose that this newly discovered virus represents a novel species in the family Astroviridae. It has tentatively been named Astrovirus MLB1.</p

    Field theoretic description of charge regulation interaction

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    In order to find the exact form of the electrostatic interaction between two proteins with dissociable charge groups in aqueous solution, we have studied a model system composed of two macroscopic surfaces with charge dissociation sites immersed in a counterion-only ionic solution. Field-theoretic representation of the grand canonical partition function is derived and evaluated within the mean-field approximation, giving the Poisson-Boltzmann theory with the Ninham-Parsegian boundary condition. Gaussian fluctuations around the mean-field are then analyzed in the lowest order correction that we calculate analytically and exactly, using the path integral representation for the partition function of a harmonic oscillator with time-dependent frequency. The first order (one loop) free energy correction gives the interaction free energy that reduces to the zero-frequency van der Waals form in the appropriate limit but in general gives rise to a mono-polar fluctuation term due to charge fluctuation at the dissociation sites. Our formulation opens up the possibility to investigate the Kirkwood-Shumaker interaction in more general contexts where their original derivation fails.Comment: 12 pages, 9 figures, submitted to EPJ

    Elimination of the Conduct Requirement in Government Monopolization Cases

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    On July 12, 1978, Professor John Flynn of the University of Utah Law School urged the National Commission for the Review of Antitrust Laws and Procedures (National Commission or NCRALP) to consider recommending that Congress amend section 2 of the Sherman Act to permit the government to challenge persistent and substantial monopoly power without showing that the monopoly power was acquired or maintained through objectionable conduct. In Professor Flynn\u27s view, eliminating the prevailing conduct requirement in certain government monopolization cases would expedite litigation and produce more effective remedies, two of the National Commission\u27s central objectives. First, this article explains that a no-conduct standard would lead to faster, more efficient proceedings. Second, the article maintains that eliminating the conduct requirement should produce more effective remedies. In the remainder of the article the authors present in greater detail the reasons underlying these two particular conclusions, and in the process address the key issues highlighted by the National Commission

    Automatic analysis of Pole Mounted Auto-Recloser data for fault diagnosis and prognosis

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    Fault diagnosis is a key part of a control and protection engineer’s role to ensure the effective and stable performance of electrical power networks. One challenge is to support the analysis and application of expert judgement to the, often, large data sets generated. To assist engineers with this task and improve network reliability, this research focuses on analysing previous fault activity in order to obtain an early-warning report to assist fault diagnosis and fault prognosis. This paper details the design of an integrated system with a fault diagnosis algorithm utilising available Supervisory Control And Data Acquisition (SCADA) alarm data and 11kV distribution network data captured from Pole Mounted Auto-Reclosers (PMARs) (provided by a leading UK network operator). The developed system will be capable of diagnosing the nature of a circuit’s previous fault activity, underlying circuit activity and evolving fault activity and the risk of future fault activity. This will provide prognostic decision support for network operators and maintenance staff
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