10,680 research outputs found

    Active Carbon and Oxygen Shell Burning Hydrodynamics

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    We have simulated 2.5×103\times10^3 s of the late evolution of a 23M23 \rm M_\odot star with full hydrodynamic behavior. We present the first simulations of a multiple-shell burning epoch, including the concurrent evolution and interaction of an oxygen and carbon burning shell. In addition, we have evolved a 3D model of the oxygen burning shell to sufficiently long times (300 s) to begin to assess the adequacy of the 2D approximation. We summarize striking new results: (1) strong interactions occur between active carbon and oxygen burning shells, (2) hydrodynamic wave motions in nonconvective regions, generated at the convective-radiative boundaries, are energetically important in both 2D and 3D with important consequences for compositional mixing, and (3) a spectrum of mixed p- and g-modes are unambiguously identified with corresponding adiabatic waves in these computational domains. We find that 2D convective motions are exaggerated relative to 3D because of vortex instability in 3D. We discuss the implications for supernova progenitor evolution and symmetry breaking in core collapse.Comment: 5 pages, 4 figures in emulateapj format. Accepted for publication in ApJ Letters. High resolution figure version available at http://spinach.as.arizona.ed

    The calpastatin-derived calpain inhibitor CP1B reduces mRNA expression of matrix metalloproteinase-2 and-9 and invasion by leukemic THP-1 cells

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    The ubiquitous proteases μ- and m-calpain are Ca2+-dependent cysteine endopeptidases. Besides involvement in a variety of physio(patho)logical processes, recent studies suggest a pivotal role of calpains in differentiation of hematopoietic cells and tumor cell invasion. However, the precise actions of calpains and their endogenous inhibitor, calpastatin, in these processes are only partially understood. Here we have studied the role of the calpain/calpastatin system in the invasion of leukemic cells under basal and differentiationstimulating conditions. To further differentiate the human leukaemic cell line THP-1 (monocytic), the cells were treated for 24 hours with the differentiationstimulating reagents phorbol 12-myristate 13-acetate (PMA) and dimethyl sulfoxide (DMSO). Macrophage and granulocytelike differentiation was confirmed by induction of vimentin expression as well as by microscopic and fluorescence assisted cytometric analysis. Extracellular matrix (ECM) invasion of both the basal and differentiation stimulated cells in a Matrigel assay was inhibited by preincubation of the cells with the specific calpain inhibitor CP1B for 24 hours. Inhibition of invasiveness correlated with decreased mRNA expression and secretion of the matrix metalloproteinases MMP-2 and MMP-9. In contrast, addition of CP1B only during the invasion process did neither influence transmigration nor MMP release. This is the first report showing that the calpain/calpastatin system mediates MMPmRNA expression of the leukemic THP-1 cells and as a consequence their invasiveness

    UK Housing Market: Time Series Processes with Independent and Identically Distributed Residuals

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    The paper examines whether a univariate data generating process can be identified which explains the data by having residuals that are independent and identically distributed, as verified by the BDS test. The stationary first differenced natural log quarterly house price index is regressed, initially with a constant variance and then with a conditional variance. The only regression function that produces independent and identically distributed standardised residuals is a mean process based on a pure random walk format with Exponential GARCH in mean for the conditional variance. There is an indication of an asymmetric volatility feedback effect but higher frequency data is required to confirm this. There could be scope for forecasting the index but this is tempered by the reduction in the power of the BDS test if there is a non-linear conditional variance process

    Revisiting a Common Measure of Child Postoperative Recovery: Development of the Post Hospitalization Behavior Questionnaire for Ambulatory Surgery (PHBQ-AS)

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    Background The Post Hospitalization Behavior Questionnaire (PHBQ) was designed for assessing children\u27s posthospitalization and postoperative new‐onset behavioral changes. However, the psychometric properties of the scale have not been re‐evaluated in the past five decades despite substantial changes in the practice of surgery and anesthesia. In this investigation, we examined the psychometric properties of the PHBQ to potentially increase the efficacy and relevance of the instrument in current perioperative settings. Method This study used principal components analysis, a panel of experts, Cronbach\u27s alpha, and correlations to examine the current subscale structure of the PHBQ and eliminate items to create the Post Hospitalization Behavior Questionnaire for Ambulatory Surgery (PHBQ‐AS). Data from previous investigations (N = 1064, Mage = 5.88) which utilized the PHBQ were combined for the purposes of this paper. Results A principal components analysis revealed that the original subscale structure of the PHBQ could not be replicated. Subsequently, a battery reduction, which utilized principal components analysis and a panel of experts, was used to eliminate the subscale structure of the scale and reduce the number of items from 27 to 11, creating the PHBQ‐AS. The PHBQ‐AS demonstrated good internal consistency reliability and concurrent validity with another measure of children\u27s psychosocial and physical functioning. Conclusion Revising the former subscale structure and reducing the number of items in the PHBQ to create the PHBQ‐AS may provide a means for reducing the burden of postoperative behavioral assessment through decreasing time of administration and eliminating redundancy of items and allow for more accurate measurement of child postoperative behavioral changes

    Optimal Renormalization Scale and Scheme for Exclusive Processes

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    We use the BLM method to fix the renormalization scale of the QCD coupling in exclusive hadronic amplitudes such as the pion form factor and the photon-to-pion transition form factor at large momentum transfer. Renormalization-scheme-independent commensurate scale relations are established which connect the hard scattering subprocess amplitudes that control exclusive processes to other QCD observables such as the heavy quark potential and the electron-positron annihilation cross section. The commensurate scale relation connecting the heavy quark potential, as determined from lattice gauge theory, to the photon-to-pion transition form factor is in excellent agreement with γeπ0e\gamma e \to \pi^0 e data assuming that the pion distribution amplitude is close to its asymptotic form 3fπx(1x)\sqrt{3}f_\pi x(1-x). We also reproduce the scaling and normalization of the γγπ+π\gamma \gamma \to \pi^+ \pi^- data at large momentum transfer. Because the renormalization scale is small, we argue that the effective coupling is nearly constant, thus accounting for the nominal scaling behavior of the data. However, the normalization of the space-like pion form factor Fπ(Q2)F_\pi(Q^2) obtained from electroproduction experiments is somewhat higher than that predicted by the corresponding commensurate scale relation. This discrepancy may be due to systematic errors introduced by the extrapolation of the γpπ+n\gamma^* p \to \pi^+ n electroproduction data to the pion pole.Comment: 22 pages, Latex, 7 Latex figures. Several references added, discussion of scale fixing revised for clarity. Final version to appear in Phys. Rev.

    Bayes-optimal inverse halftoning and statistical mechanics of the Q-Ising model

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    On the basis of statistical mechanics of the Q-Ising model, we formulate the Bayesian inference to the problem of inverse halftoning, which is the inverse process of representing gray-scales in images by means of black and white dots. Using Monte Carlo simulations, we investigate statistical properties of the inverse process, especially, we reveal the condition of the Bayes-optimal solution for which the mean-square error takes its minimum. The numerical result is qualitatively confirmed by analysis of the infinite-range model. As demonstrations of our approach, we apply the method to retrieve a grayscale image, such as standard image `Lenna', from the halftoned version. We find that the Bayes-optimal solution gives a fine restored grayscale image which is very close to the original.Comment: 13pages, 12figures, using elsart.cl

    The TIGA technique for detecting gravitational waves with a spherical antenna

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    We report the results of a theoretical and experimental study of a spherical gravitational wave antenna. We show that it is possible to understand the data from a spherical antenna with 6 radial resonant transducers attached to the surface in the truncated icosahedral arrangement. We find that the errors associated with small deviations from the ideal case are small compared to other sources of error, such as a finite signal-to-noise ratio. An in situ measurement technique is developed along with a general algorithm that describes a procedure for determining the direction of an external force acting on the antenna, including the force from a gravitational wave, using a combination of the transducer responses. The practicality of these techniques was verified on a room-temperature prototype antenna.Comment: 15 pages, 14 figures, submitted to Physical Review

    Semi-field evaluation of a volatile transfluthrin-based intervention reveals efficacy as a spatial repellent and evidence of other modes of action

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    Presently, the most common malaria control tools-i.e., long lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS)-are limited to targeting indoor biting and resting behaviors of Anopheles mosquito species. Few interventions are targeted towards malaria control in areas where transmission is driven or persists due to outdoor biting behaviors. This study investigated a volatile pyrethroid-based spatial repellent (VPSR) designed to bridge this gap and provide protection from mosquito bites in outdoor spaces. Southern Province, Zambia, is one such environment where outdoor biting is suspected to contribute to malaria transmission, where people are active in the evening in open-walled outdoor kitchens. This study assessed the VPSR in replica kitchens within a controlled semi-field environment. Endpoints included effects on mosquito host seeking, immediate and delayed mortality, deterrence, blood feeding inhibition, and fertility. Host-seeking was reduced by approximately 40% over the course of nightly releases in chambers containing VPSR devices. Mosquito behavior was not uniform throughout the night, and the modeled effect of the intervention was considerably higher when hourly catch rates were considered. These two observations highlight a limitation of this overnight semi-field design and consideration of mosquito circadian rhythms is recommended for future semi-field studies. Additionally, deterrence and immediate mortality were both observed in treatment chambers, with evidence of delayed mortality and a dose related response. These results demonstrate a primarily personal protective mode of action with possible positive and negative community effects. Further investigation into this primary mode of action will be conducted through a field trial of the same product in nearby communities

    On the shopfloor: exploring the impact of teacher trade unions on school-based industrial relations

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    Teachers are highly unionised workers and their trade unions exert an important influence on the shaping and implementation of educational policy. Despite this importance there is relatively little analysis of the impact of teacher trade unions in educational management literature. Very little empirical research has sought to establish the impact of teacher unions at school level. In an era of devolved management and quasi-markets this omission is significant. New personnel issues continue to emerge at school level and this may well generate increased trade union activity at the workplace. This article explores the extent to which devolved management is drawing school-based union representation into a more prominent role. It argues that whilst there can be significant differences between individual schools, increased school autonomy is raising the profile of trade union activity in the workplace, and this needs to be better reflected in educational management research
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