1,037 research outputs found
The Pairwise Peculiar Velocity Dispersion of Galaxies: Effects of the Infall
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
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
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
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
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
Orientation of native versus translocated juvenile lesser spotted eagles <i>(Clanga pomarina)</i> on the first autumn migration
Scaling properties of the redshift power spectrum: theoretical models
We report the results of an analysis of the redshift power spectrum
in three typical Cold Dark Matter (CDM) cosmological models, where
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
where
is the real space power spectrum, and equals . The
damping function which should generally depend on , , and
, is found to be a function of only one variable
. This scaling behavior extends into the nonlinear regime,
while can be accurately expressed as a Lorentz function - well known from
linear theory - for values . The difference between
and the pairwise velocity dispersion defined by the 3-D peculiar velocity of
the simulations (taking ) is about 15%. Therefore is a
good indicator of the pairwise velocity dispersion. The exact functional form
of depends on the cosmological model and on the bias scheme. We have given
an accurate fitting formula for the functional form of for the models
studied.Comment: accepted for publication in ApJ;24 pages with 7 figures include
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
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 with and r_0=3.70 \mpc. The pairwise peculiar
velocity dispersion 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 (, , , ) using a set of
high-resolution N-body simulations. Applying a stronger cluster-underweight
biasing () than for the LCRS (), 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
Orientation of native versus translocated juvenile lesser spotted eagles <i>(Clanga pomarina)</i> on the first autumn migration
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
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
Heatshield Entry Modeling Using a Design, Analysis, and Optimization Toolbox
The Mars Science Laboratory (MSL) was protected during its Mars atmospheric entry by an instrumented heatshield that used NASA's Phenolic Impregnated Carbon Ablator (PICA). PICA is a lightweight carbon fiber/polymeric resin material that offers excellent performances for protecting probes during planetary entry. The Mars Entry Descent and Landing Instrument (MEDLI) suite on MSL offers unique in-flight validation data for models of atmospheric entry and material response. MEDLI recorded, among others, time-resolved in-depth temperature data of PICA using thermocouple sensors assembled in the MEDLI Integrated Sensor Plugs (MISP). The objective of this work is to showcase the capability of the Design, Analysis, and Optimization of Thermal Protection Materials (DAOTPM) software. DAO-TPM is a Python based framework that works as a link between mission design, aerothermal and radiative environment computation, Thermal Protection Systems (TPS) microstructure analysis, material response and optimization tools. The toolbox has a Graphical User Interface (GUI) that allows the user to build as well as run the various software and utilities used to design, analyze and optimize a heatshield during atmospheric entry
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