9,230 research outputs found

    A novel CMB polarization likelihood package for large angular scales built from combined WMAP and Planck LFI legacy maps

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    We present a CMB large-scale polarization dataset obtained by combining WMAP Ka, Q and V with Planck 70 GHz maps. We employ the legacy frequency maps released by the WMAP and Planck collaborations and perform our own Galactic foreground mitigation technique, which relies on Planck 353 GHz for polarized dust and on Planck 30 GHz and WMAP K for polarized synchrotron. We derive a single, optimally-noise-weighted, low-residual-foreground map and the accompanying noise covariance matrix. These are shown, through χ2\chi^2 analysis, to be robust over an ample collection of Galactic masks. We use this dataset, along with the Planck legacy Commander temperature solution, to build a pixel-based low-resolution CMB likelihood package, whose robustness we test extensively with the aid of simulations, finding excellent consistency. Using this likelihood package alone, we constrain the optical depth to reionazation τ=0.069−0.012+0.011\tau=0.069^{+0.011}_{-0.012} at 68%68\% C.L., on 54\% of the sky. Adding the Planck high-ℓ\ell temperature and polarization legacy likelihood, the Planck lensing likelihood and BAO observations we find τ=0.0714−0.0096+0.0087\tau=0.0714_{-0.0096}^{+0.0087} in a full Λ\LambdaCDM exploration. The latter bounds are slightly less constraining than those obtained employing \Planck\ HFI CMB data for large angle polarization, that only include EE correlations. Our bounds are based on a largely independent dataset that does include also TE correlations. They are generally well compatible with Planck HFI preferring slightly higher values of τ\tau. We make the low-resolution Planck and WMAP joint dataset publicly available along with the accompanying likelihood code.Comment: The WMAP+LFI likelihood module is available on \http://www.fe.infn.it/u/pagano/low_ell_datasets/wmap_lfi_legacy

    An experimental investigation of the independent effect of suction and degree of saturation on very small-strain stiffness of unsaturated sand

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    The paper presents an experimental investigation of very small strain stiffness of unsaturated sand. A triaxial test apparatus was equipped with bender elements and compression discs in order to assess the stiffness at very small strains by measuring the velocity of propagation of shear and compression waves through an unsaturated sample. The negative water column method was adopted to apply suction at the base of the sample. The experiments were designed to investigate the independent effect of suction and degree of saturation on the wave propagation velocities. This was achieved by testing the sand sample on both the drying and wetting path

    Asymmetric Twisting of Coronal Loops

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    The bright solar corona entirely consists of closed magnetic loops rooted in the photosphere. Photospheric motions are important drivers of magnetic stressing, which eventually leads to energy release into heat. These motions are chaotic and obviously different from one footpoint to the other, and in fact, there is strong evidence that loops are finely stranded. One may also expect strong transient variations along the field lines, but at a glance, coronal loops ever appear more or less uniformly bright from one footpoint to the other. We aim to understand how much coronal loops can preserve their own symmetry against asymmetric boundary motions that are expected to occur at loop footpoints. We investigate this issue by time-dependent 2.5D MHD modelling of a coronal loop, including its rooting and beta-variation in the photosphere. We assume that the magnetic flux tube is stressed by footpoint rotation but also that the rotation has a different pattern from one footpoint to the other. In this way, we force strong asymmetries because we expect independent evolution along different magnetic strands. We found that until the Alfven crossing-travel time relative to the entire loop length is much lower than the twisting period, the loop's evolution depends only on the relative velocity between the boundaries, and the symmetry is efficiently preserved. We conclude that the very high Alfven velocities that characterise the coronal environment can explain why coronal loops can maintain a very high degree of symmetry even when they are subjected to asymmetric photospheric motions for a long time

    Non-thermalization in trapped atomic ion spin chains

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    Linear arrays of trapped and laser cooled atomic ions are a versatile platform for studying emergent phenomena in strongly-interacting many-body systems. Effective spins are encoded in long-lived electronic levels of each ion and made to interact through laser mediated optical dipole forces. The advantages of experiments with cold trapped ions, including high spatiotemporal resolution, decoupling from the external environment, and control over the system Hamiltonian, are used to measure quantum effects not always accessible in natural condensed matter samples. In this review we highlight recent work using trapped ions to explore a variety of non-ergodic phenomena in long-range interacting spin-models which are heralded by memory of out-of-equilibrium initial conditions. We observe long-lived memory in static magnetizations for quenched many-body localization and prethermalization, while memory is preserved in the periodic oscillations of a driven discrete time crystal state.Comment: 14 pages, 5 figures, submitted for edition of Phil. Trans. R. Soc. A on "Breakdown of ergodicity in quantum systems

    Encyclopedia of Case Study Research

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    Michael Pagano is a contributing author Healthcare Practice Guidelines and Case Studies . Book description: The Encyclopedia of Case Study Research provides a compendium on the important methodological issues in conducting case study research and explores both the strengths and weaknesses of different paradigmatic approaches. These two volumes focus on the distinctive characteristics of case study research and its place within and alongside other research methodologies.https://digitalcommons.fairfield.edu/communications-books/1008/thumbnail.jp

    transsphenoidal surgery for secreting pituitary microadenomas: results with intraoperative application of absolute alcohol

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    ABSTRACT Background: Pituitary adenomas represent a quite frequent neurosurgical disease. Secreting pituitary adenomas are represented by PRL, GH, ACTH and TSH tumours; the rate of postoperative hormonal recurrence is not ineligible. Methods: We present 106 patients affected by secreting pituitary microadenomas operated through transsphenoidal approach from 1998 through to 2008; in 54 (group 1) patients, intraoperative absolute alcohol was applied, while in the other 52 (group 2) it was not employed. The indications and the intraoperative technique of absolute alcohol application are presented. Hormonal recurrence was treated by hypofractionated stereotactic radiotherapy and/or medical therapy. Results: Postoperative hormonal and clinical remission was achieved in 50 and 47 patients respectively of group one and group two. At the first follow-up control, after 3 months from surgery, no patient of both groups presented hormonal/clinical recurrence. Six months after surgery, no patient of group one presented hormonal recurrence, while two patients of group 2 presented hormonal recurrence. After 2 years from surgery, two patients of group 1 and 4 patients of group 2 presented hormonal recurrence. Three years after operation, hormonal hypersecretion recurred in three patients of group one and in six patients of group 2. At 5 years follow-up, six patients of group one and 8 of group two presented hormonal recurrence. Conclusions: Intraoperative application of absolute alcohol, in selected cases, resulted useful to achieve better results in secreting pituitary microadenomas concerning both postoperative hormonal recurrence and hormonal persistence

    Thermodynamical features of multifragmentation in peripheral Au + Au Collisions at 35 A.MeV

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    The distribution of fragments produced in events involving the multifragmentation of excited sources is studied for peripheral Au + Au reactions at 35 A.MeV. The Quasi-Projectile has been reconstructed from its de-excitation products. An isotropic emission in its rest frame has been observed, indicating that an equilibrated system has been formed. The excitation energy of the Quasi-Projectile has been determined via calorimetry. A new event by event effective thermometer is proposed based on the energy balance. A peak in the energy fluctuations is observed related to the heat capacity, suggesting that the system undergoes a liquid-gas type phase transition at an excitation energy about 5 A.MeV and a temperature 4 - 6 MeV, dependent on the freeze-out hypothesis. By analyzing different regions of the Campi-plot, the events associated with the liquid and gas phases as well as the critical region are thermodynamically characterized. The critical exponents, tau, beta,gamma, extracted from the high moments of the charge distribution are consistent with a liquid-gas type phase transition.Comment: 44 pages, 16 Postscript figures, Fig14_nucl-ex.eps in colors, to be published in Nucl.Phys.A (1999

    Uncertainty, sensitivity analysis and the role of data based mechanistic modeling in hydrology

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    International audienceIn this paper, we discuss the problem of calibration and uncertainty estimation for hydrologic systems from two points of view: a bottom-up, reductionist approach; and a top-down, data-based mechanistic (DBM) approach. The two approaches are applied to the modelling of the River Hodder catchment in North-West England. The bottom-up approach is developed using the TOPMODEL, whose structure is evaluated by global sensitivity analysis (GSA) in order to specify the most sensitive and important parameters; and the subsequent exercises in calibration and validation are carried out in the light of this sensitivity analysis. GSA helps to improve the calibration of hydrological models, making their properties more transparent and highlighting mis-specification problems. The DBM model provides a quick and efficient analysis of the rainfall-flow data, revealing important characteristics of the catchment-scale response, such as the nature of the effective rainfall nonlinearity and the partitioning of the effective rainfall into different flow pathways. TOPMODEL calibration takes more time and it explains the flow data a little less well than the DBM model. The main differences in the modelling results are in the nature of the models and the flow decomposition they suggest. The "quick'' (63%) and "slow'' (37%) components of the decomposed flow identified in the DBM model show a clear partitioning of the flow, with the quick component apparently accounting for the effects of surface and near surface processes; and the slow component arising from the displacement of groundwater into the river channel (base flow). On the other hand, the two output flow components in TOPMODEL have a different physical interpretation, with a single flow component (95%) accounting for both slow (subsurface) and fast (surface) dynamics, while the other, very small component (5%) is interpreted as an instantaneous surface runoff generated by rainfall falling on areas of saturated soil. The results of the exercise show that the two modelling methodologies have good synergy; combining well to produce a complete modelling approach that has the kinds of checks-and-balances required in practical data-based modelling of rainfall-flow systems. Such a combined approach also produces models that are suitable for different kinds of application. As such, the DBM model can provides an immediate vehicle for flow and flood forecasting; while TOPMODEL, suitably calibrated (and perhaps modified) in the light of the DBM and GSA results, immediately provides a simulation model with a variety of potential applications, in areas such as catchment management and planning
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