1,375 research outputs found

    Compact coalgebras, compact quantum groups and the positive antipode

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    In this article -that has also the intention to survey some known results in the theory of compact quantum groups using methods different from the standard and with a strong algebraic flavor- we consider compact o-coalgebras and Hopf algebras. In the case of a o-Hopf algebra we present a proof of the characterization of the compactness in terms of the existence of a positive definite integral, and use our methods to give an elementary proof of the uniqueness - up to conjugation by an automorphism of Hopf algebras- of the compact involution appearing in [4]. We study the basic properties of the positive square root of the antipode square that is a Hopf algebra automorphism that we call the positive antipode. We use it -as well as the unitary antipode and the Nakayama automorphism- in order to enhance our understanding of the antipode itself

    PARADISE: A Framework for Evaluating Spoken Dialogue Agents

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    This paper presents PARADISE (PARAdigm for DIalogue System Evaluation), a general framework for evaluating spoken dialogue agents. The framework decouples task requirements from an agent's dialogue behaviors, supports comparisons among dialogue strategies, enables the calculation of performance over subdialogues and whole dialogues, specifies the relative contribution of various factors to performance, and makes it possible to compare agents performing different tasks by normalizing for task complexity.Comment: 10 pages, uses aclap, psfig, lingmacros, time

    Pricing Efficiency in Major Cattle Auction Centres in the Philippines

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    The problem of low productivity is the major constraint to the development of the Philippine livestock sector. Contribution from the industry particularly cattle production is considered below potential despite conditions favoring cattle raising in the Philippines. Apart from the technical innovations to encourage cattle raising, an improvement in the marketing system is needed to sustain production. The establishment of livestock auction markets to minimize the defects of the traditional marketing system is believed to be the most feasible short-run modification to effect an efficient marketing of cattle . This study evaluates the pricing efficiency in major cattle auction centres in the Philippines. The univariate residual cross-correlation approach by Haugh (1972 , 1976) and Pierce (1977), and the Sims' (1972) distributed-lag regress ion were used to ascertain Whether the auction centres are integrated in terms of price formation. This was done through the assessment of the nature of causality between prices in the various cattle auctions within and among regions. Time series data an prices consisting of 84 monthly observations were utilized for the purpose. Results showed an inter-dependence among markets, thus, rejecting the null hypothesis of no market integration. The study concludes that government policies geared towards an effective dissemination and monitoring of market information, establishment of more auction markets will enhance the output of the livestock sector

    A New Statistical Image Reconstruction Algorithm for Polyenergetic X-Ray CT

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    This paper presents a new statistical reconstruction algorithm for X-ray CT. The algorithm is based on Poisson statistics and a physical model that accounts for the measurement nonlinearities caused by energy-dependent attenuation. We model each voxel’s attenuation as a mixture of bone and soft tissue by defining density-dependent tissue fractions, maintaining one unknown per voxel avoiding the need of a pre-segmentation. Rather than requiring the entire X-ray spectrum, the method approximates the 2D beam hardening function corresponding to bone and soft tissue with the 1D function corresponding to water and one or two empirical tuning parameters. Results on simulated human data (NCAT phantom) showed a beam hardening reduction similar to conventional post-processing techniques, but with an improved signal to noise ratio.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85932/1/Fessler239.pd

    A simple tool to forecast the natural frequencies of thin-walled cylinders

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    This paper presents an approximate method to predict the natural frequencies of thinwalled cylinders. By taking inspiration from a previous work of one of the authors, the starting point of the proposed approach is a proper construction of reasonable eigenfunctions. However, a new simple tool based on the principle of virtual work has been developed to estimate the natural frequencies and the amplitude of vibration without complex numerical resolution. Moreover, the applicability of the model is extended to all the most common constraint conditions. The identification of the natural frequencies of a continuous cylinder is reduced to an eigenvalue problem based on a matrix whose elements depend only on the geometric characteristics of the cylinder, the mechanical properties of the material and known numerical parameters. The latter are precalculated for given boundary conditions, covering clamped or pinned end constraints. Although the proposed formulation can address any constraints combination, only a pinned-pinned cylinder is analyzed here for brevity. The reliability of the model was tested against FEM analysis results. These comparisons showed that the maximum error versus the exact solutions for the lowest natural frequency is around 2% for all the mode shapes of the pinned-pinned case, offering an excellent trade-off between accuracy and ease of use

    Hypothermia and cardiac arrest: the promise of intra-arrest cooling

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    Over the past several years, the implementation of therapeutic hypothermia has provided an exciting opportunity toward improving survival from out-of-hospital cardiac arrest. There are compelling data to support the prompt use of therapeutic hypothermia for initial survivors from out-of-hospital cardiac arrest, but animal data have suggested that initiation of therapeutic hypothermia during the intra-arrest period may significantly improve outcomes even further. In the first feasibility study in humans, Bruel and colleagues report on the implementation of this intra-arrest approach among patients suffering out-of-hospital cardiac arrest, an exciting prospect that is discussed in the present commentary

    Assessment of microbial community structure changes by amplified ribosomal DNA restriction analysis (ARDRA)

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    Amplified ribosomal DNA restriction analysis (ARDRA) is a simple method based on restriction endonuclease digestion of the amplified bacterial 16S rDNA. In this study we have evaluated the suitability of this method to detect differences in activated sludge bacterial communities fed on domestic or industrial wastewater, and subject to different operational conditions. The ability of ARDRA to detect these differences has been tested in modified Ludzack-Ettinger (MLE) configurations. Samples from three activated sludge wastewater treatment plants (WWTPs) with the MLE configuration were collected for both oxic and anoxic reactors, and ARDRA patterns using double enzyme digestions AluI+MspI were obtained. A matrix of Dice similarity coefficients was calculated and used to compare these restriction patterns. Differences in the community structure due to influent characteristics and temperature could be observed, but not between the oxic and anoxic reactors of each of the three MLE configurations. Other possible applications of ARDRA for detecting and monitoring changes in activated sludge systems are also discussed

    The first Oligocene sea turtle (Pan-Cheloniidae) record of South America

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    The evolution and occurrence of fossil sea turtles at the Pacific margin of South America is poorly known and restricted to Neogene (Miocene/Pliocene) findings from the Pisco Formation, Peru. Here we report and describe the first record of Oligocene (late Oligocene, ~24 Ma) Pan-Cheloniidae sea turtle remains of South America. The fossil material corresponds to a single, isolated and well-preserved costal bone found at the Montañita/Olón locality, Santa Elena Province, Ecuador. Comparisons with other Oligocene and extant representatives allow us to confirm that belongs to a sea turtle characterized by: lack of lateral ossification, allowing the dorsal exposure of the distal end of ribs; dorsal surface of bone sculptured, changing from dense vermiculation at the vertebral scute region to anastomosing pattern of grooves at the most lateral portion of the costal. This fossil finding shows the high potential that the Ecuadorian Oligocene outcrops have in order to explore the evolution and paleobiogeography distribution of sea turtles by the time that the Pacific and the Atlantic oceans were connected via the Panama basin

    New findings of Pleistocene fossil turtles (Geoemydidae, Kinosternidae and Chelydridae) from Santa Elena Province, Ecuador

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    New Pleistocene fossilized turtle remains from five localities of western Ecuador (Santa Elena Province) are described here. All these shell (carapace and plastron) fossil remains come from the Tablazo Formation and belong to three different lineages of cryptodires ("hidden-necked" turtles). The most abundant remains belong to geoemydids, attributed here to the genus Rhinoclemmys (indeterminate species). Less abundant in occurrence are the kinosternidids, attributed to Kinosternon (indeterminate species), and the first fossil record of chelydrids, Chelydra (indeterminate species), in the entirety of Central and South America

    Rapidly Restoring Biological Soil Crusts and Ecosystem Functions in a Severely Disturbed Desert Ecosystem

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    Restoring biological soil crusts (biocrusts) in degraded drylands can contribute to recovery of ecosystem functions that have global implications, including erosion resistance and nutrient cycling. To examine techniques for restoring biocrusts, we conducted a replicated, factorial experiment on recently abandoned road surfaces by applying biocrust inoculation (salvaged and stored dry for two years), salvaged topsoil, an abiotic soil amendment (wood shavings), and planting of a dominant perennial shrub (Ambrosia dumosa). Eighteen months after treatments, we measured biocrust abundance and species composition, soil chlorophyll a content and fertility, and soil resistance to erosion. Biocrust addition significantly accelerated biocrust recovery on disturbed soils, including increasing lichen and moss cover and cyanobacteria colonization. Compared to undisturbed controls, inoculated plots had similar lichen and moss composition, recovered 43% of total cyanobacteria density, had similar soil chlorophyll content, and exhibited recovery of soil fertility and soil stability. Inoculation was the only treatment that generated lichen and moss cover. Topsoil application resulted in partial recovery of the cyanobacteria community and soil properties. Compared to untreated disturbed plots, topsoil application without inoculum increased cyanobacteria density by 186% and moderately improved soil chlorophyll and ammonium content and soil stability. Topsoil application produced 22% and 51% of the cyanobacteria density g−1 soil compared to undisturbed and inoculated plots, respectively. Plots not treated with either topsoil or inoculum had significantly lower cyanobacteria density, soil chlorophyll and ammonium concentrations, and significantly higher soil nitrate concentration. Wood shavings and Ambrosia had no influence on biocrust lichen and moss species recovery but did affect cyanobacteria composition and soil fertility. Inoculation of severely disturbed soil with native biocrusts rapidly restored biocrust communities and soil stability such that restored areas were similar to undisturbed desert within three years. Using salvaged biocrust as inoculum can be an effective tool in ecological restoration because of its efficacy and simple implementation. Although salvaging biocrust material can be technically difficult and potentially costly, utilizing opportunities to salvage material in planned future disturbance can provide additional land management tools
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