1,038 research outputs found

    The Pairwise Peculiar Velocity Dispersion of Galaxies: Effects of the Infall

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    We study the reliability of the reconstruction method which uses a modelling of the redshift distortions of the two-point correlation function to estimate the pairwise peculiar velocity dispersion of galaxies. In particular, the dependence of this quantity on different models for the infall velocity is examined for the Las Campanas Redshift Survey. We make extensive use of numerical simulations and of mock catalogs derived from them to discuss the effect of a self-similar infall model, of zero infall, and of the real infall taken from the simulation. The implications for two recent discrepant determinations of the pairwise velocity dispersion for this survey are discussed.Comment: minor changes in the discussion; accepted for publication in ApJ; 8 pages with 2 figures include

    Significance of DSMC Computed Aerothermal Environments in the Rarefied Regime for Atmospheric Entry Material Response

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    During Mars atmospheric entry, the Mars Science Laboratory (MSL) was protected by a 4.5 meters diameter ablative heatshield assembled in 113 tiles. The heatshield was made of NASA's flagship ablative material, the Phenolic Impregnated Carbon Ablator (PICA). Prior work compared the traditional one-dimensional and three-dimensional material response models at different locations in the heatshield. It was observed that the flow was basically one-dimensional in the nose and flank regions, but three-dimensional flow effects were observed in the outer flank. The objective of this work is to study the effects of the aerothermal environment on the material response. We extend prior work by computing aerothermal environments using the direct simulation Monte Carlo (DSMC) code SPARTA and the CFD code Data Parallel Line Relaxation (DPLR). SPARTA is used to compute environment in the rarefied regime prior to 48.4s of entry where the Knudsen number is such that the Navier-Stokes equations can be inaccurate. Similarly to previous work, the DPLR software is used to compute the hypersonic environment for laminar then turbulent boundary layer assumptions from 48.4 s up to 100 s after Entry Interface (EI) along the MSL 08-TPS-02/01a trajectory. We observe that extending the aerothermal environments to times prior to 48.4 s modifies the thermal response of the heat shield at the surface and in-depth; however the effects on the recession are minimal. Additionally, using the assumption of a turbulent boundary layer versus a laminar one leads to higher surface and in-depth temperatures, larger recession, and a displacement of the peak heating and peak recession location

    Full-Scale MSL Heatshield Material Response Using DSMC and CFD to Compute the Aerothermal Environments

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    During Mars atmospheric entry, the Mars Science Laboratory (MSL) was protected by a 4.5 meters diameter ablative heatshield assembled in 113 tiles [1]. The heatshield was made of NASA's flagship ablative material, the Phenolic Impregnated Carbon Ablator (PICA) [2]. Prior work [3] compared the traditional one-dimensional and three-dimensional material response models at different locations in the heatshield. It was observed that the flow was basically one-dimensional in the nose and flank regions, but three-dimensional flow effects were observed in the outer flank. Additionally, the effects of tiled versus monolithic heatshield models were also investigated. It was observed that the 3D tiled and 3D monolithic configurations yielded relative differences for in-depth material temperature up to 18% and 28%, respectively, when compared to the a 1D model

    Towards cost-effective watershed management in the Brazilian Atlantic Forest: valuing forest ecosystem services related to water quality in the Guapi-Macacu watershed.

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    The Brazilian Atlantic forest is considered a global biodiversity hotspot, harbouring a large number of endemic species, and providing essential watershed services to millions of urban water users. However, agricultural expansion and urban development have reduced the forest area to less than 8% of its original size. Multiple pressures on the Atlantic forest ecosystem continue. Payments for ecosystem services (PES) schemes are increasingly proposed by local initiatives and supported by international cooperation to manage the trade‐offs among agricultural uses and watershed services in a cost‐effective manner. Studying the provision costs of as well as the demand for watershed services can help decision makers to evaluate the scope and economic feasibility of PES and alternative management options. The Guapi‐Macacu watershed in the state of Rio de Janeiro supplies water to 2.5 million inhabitants within five municipalities. Water resources are of utmost importance for agriculture and industries, such water bottle companies, breweries and the biggest Brazilian petrochemical complex COMPERJ. Our study concentrates on valuing watershed services in terms of controlling nutrient and sediment loads under different land use systems. Nutrient loads include Nitrogen and Phosphorus found in surface water, whereas sediment loads are measured in terms of turbidity and total solids. Replacement and avoided cost methods are applied focusing on the local water treatment facility to estimate demand for service maintenance and improvement. To provide empirical evidence of the link between land use/land cover and water quality indicators, we rely on water quality modelling and monitoring specifically adapted to this area. This takes place within the framework of the multi‐disciplinary German‐Brazilian cooperation project DINARIO/MP2. Spatial conservation opportunity cost analysis is used to study the costs of watershed services maintenance and improvement and derive implication for cost‐effective management on the basis of scenario analyses

    Adjuvant therapy after excision and radiation of isolated postmastectomy locoregional breast cancer recurrence: definitive results of a phase III randomized trial (SAKK 23/82) comparing tamoxifen with observation

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    Background: Adjuvant systemic treatment for patients with isolated locoregional recurrence (ILRR) of breast cancer is based on a single reported randomized trial. The trial, conducted by the Swiss Group for Clinical Cancer Research, compared tamoxifen (TAM) with observation after complete excision of the ILRR and proper radiotherapy. We performed a definitive analysis of treatment outcome at >11 years of follow-up, after the majority of the patients had a subsequent event of interest. Patient and methods One hundred and sixty-seven patients with ‘good-risk' characteristics of disease were randomized. ‘Good-risk' was defined as estrogen receptor expression in the ILRR, or having a disease-free interval of >12 months and a recurrence consisting of three or less tumor nodules, each ≀3 cm in diameter. Seventy-nine percent of the patients were postmenopausal at randomization. Results: The median follow-up time of the surviving patients was 11.6 years. The median post ILRR disease-free survival (DFS) was 6.5 years with TAM and 2.7 years with observation (P = 0.053). The difference was mainly due to reduction of further local relapses (P = 0.011). In postmenopausal patients, TAM led to an increase of DFS from 33% to 61% (P = 0.006). In premenopausal women, 5-year DFS was 60%, independent of TAM medication. For the whole study population, the median post-recurrence overall survival (OS) was 11.2 and 11.5 years in the observation and the TAM group, respectively; premenopausal patients experienced a 5-year OS of 90% for observation compared with 67% for TAM (P = 0.175), while the respective figures for postmenopausal patients were both 75%. Conclusions: These definitive results confirmed that TAM significantly improves the post-recurrence DFS of patients after local treatment for ILRR. This beneficial effect does not translate into a detectable OS advantag

    Spatial correlation functions and the pairwise peculiar velocity dispersion of galaxies in the PSCz survey: implications for the galaxy biasing in cold dark matter models

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    We report on the measurement of the two-point correlation function, and the pairwise peculiar velocity of galaxies in the IRAS PSCz survey. We compute these statistics first in redshift space, and then obtain the projected functions which have simple relations to the real-space correlation functions on the basis of the method developed earlier in analyzing the Las Campanas Redshift Survey (LCRS) by Jing, Mo, & B\"orner (1998). We find that the real space two-point correlation function can be fitted to a power law Ο(r)=(r0/r)Îł\xi(r) = (r_0/r)^{\gamma} with Îł=1.69\gamma=1.69 and r_0=3.70 \mpc. The pairwise peculiar velocity dispersion σ12(rp)\sigma_{12}(r_p) is close to 400 \kms at r_p=3\mpc and decreases to about 150 \kms at r_p \approx 0.2 \mpc. These values are significantly lower than those obtained from the LCRS. In order to understand the implications of those measurements on the galaxy biasing, we construct mock samples for a low density spatially-flat cold dark matter model (Ω0=0.3\Omega_0 = 0.3, λ0=0.7\lambda_0=0.7, Γ=0.2\Gamma=0.2, σ8=1\sigma_8=1) using a set of high-resolution N-body simulations. Applying a stronger cluster-underweight biasing (∝M−0.25\propto M^{-0.25}) than for the LCRS (∝M−0.08\propto M^{-0.08}), we are able to reproduce these observational data, except for the strong decrease of the pairwise peculiar velocity at small separations. This is qualitatively ascribed to the different morphological mixture of galaxies in the two catalogues. Disk-dominated galaxy samples drawn from the theoretically constructed GIF catalog yield results rather similar to our mock samples with the simple cluster-underweight biasing.Comment: accepted for publication in ApJ; 24 pages with 9 figure

    Scaling properties of the redshift power spectrum: theoretical models

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    We report the results of an analysis of the redshift power spectrum PS(k,ÎŒ)P^S(k,\mu) in three typical Cold Dark Matter (CDM) cosmological models, where ÎŒ\mu is the cosine of the angle between the wave vector and the line-of-sight. Two distinct biased tracers derived from the primordial density peaks of Bardeen et al. and the cluster-underweight model of Jing, Mo, & B\"orner are considered in addition to the pure dark matter models. Based on a large set of high resolution simulations, we have measured the redshift power spectrum for the three tracers from the linear to the nonlinear regime. We investigate the validity of the relation - guessed from linear theory - in the nonlinear regime PS(k,ÎŒ)=PR(k)[1+ÎČÎŒ2]2D(k,ÎŒ,σ12(k)), P^S(k,\mu)=P^R(k)[1+\beta\mu^2]^2D(k,\mu,\sigma_{12}(k)), where PR(k)P^R(k) is the real space power spectrum, and ÎČ\beta equals Ω00.6/bl\Omega_0^{0.6}/b_l. The damping function DD which should generally depend on kk, ÎŒ\mu, and σ12(k)\sigma_{12}(k), is found to be a function of only one variable kΌσ12(k)k\mu\sigma_{12}(k). This scaling behavior extends into the nonlinear regime, while DD can be accurately expressed as a Lorentz function - well known from linear theory - for values D>0.1D > 0.1. The difference between σ12(k)\sigma_{12}(k) and the pairwise velocity dispersion defined by the 3-D peculiar velocity of the simulations (taking r=1/kr=1/k) is about 15%. Therefore σ12(k)\sigma_{12}(k) is a good indicator of the pairwise velocity dispersion. The exact functional form of DD depends on the cosmological model and on the bias scheme. We have given an accurate fitting formula for the functional form of DD for the models studied.Comment: accepted for publication in ApJ;24 pages with 7 figures include

    Orientation of native versus translocated juvenile lesser spotted eagles <i>(Clanga pomarina)</i> on the first autumn migration

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    The ontogeny of migration routines used by wild birds remains unresolved. Here we investigated the migratory orientation of juvenile lesser spotted eagles (LSE; Clanga pomarina) based on translocation and satellite tracking. Between 2004 and 2016, 85 second-hatched juveniles (Abels) were reared in captivity for release into the declining German population, including 50 birds that were translocated 940 km from Latvia. In 2009, we tracked 12 translocated juveniles, as well as eight native juveniles and nine native adults, to determine how inexperienced birds come to use strategic migration routes. Native juveniles departed around the same time as the adults and six of eight used the eastern flyway around the Mediterranean, which was used by all adults. In contrast, translocated juveniles departed on average 6 days before native LSEs, and five travelled southward and died in the central Mediterranean region. Consequently, fewer translocated juveniles (4/12) than native juveniles (7/8) reached Africa. We conclude that juvenile LSEs have a much better chance of learning the strategic southeastern flyway if they leave at an appropriate time to connect with experienced elders upon departure. It is not clear why translocated juveniles departed so early. Regardless, by the end of the year, most juveniles had perished, whether they were translocated (10/12) or not (6/8). The small number of surviving translocated juveniles thus still represents a significant increase in the annual productivity of the German LSE population in 2009

    Effects related to spacetime foam in particle physics

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    It is found that the existence of spacetime foam leads to a situation in which the number of fundamental quantum bosonic fields is a variable quantity. The general aspects of an exact theory that allows for a variable number of fields are discussed, and the simplest observable effects generated by the foam are estimated. It is shown that in the absence of processes related to variations in the topology of space, the concept of an effective field can be reintroduced and standard field theory can be restored. However, in the complete theory the ground state is characterized by a nonvanishing particle number density. From the effective-field standpoint, such particles are "dark". It is assumed that they comprise dark matter of the universe. The properties of this dark matter are discussed, and so is the possibility of measuring the quantum fluctuation in the field potentials.Comment: 18 pages, minor corrections added to the published varian
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