97 research outputs found
Spatial and Dynamical Biases in Velocity Statistics of Galaxies
We present velocity statistics of galaxies and their biases inferred from the
statistics of the underlying dark matter using a cosmological hydrodynamic
simulation of galaxy formation in low-density and spatially flat cold dark
matter cosmogony. We find that the pairwise velocity dispersion (PVD) of all
galaxies is significantly lower than that of the dark matter particles, and
that the PVD of the young galaxies is lower than that of the old types, and
even of all galaxies together, especially at small separations. These results
are in reasonable agreement with the recent measurements of PVDs in the Las
Campanas redshift survey, the PSCz catalogue and the SDSS data. We also find
that the low PVD of young galaxies is due to the effects of dynamical friction
as well as the different spatial distribution. We also consider the mean infall
velocity and the POTENT density reconstruction that are often used to measure
the cosmological parameters, and investigate the effects of spatial bias and
dynamical friction. In our simulation, the mean infall velocity of young
galaxies is significantly lower than that of all the galaxies or of the old
galaxies, and the dynamical bias becomes important on scales less than 3Mpc/h.
The mass density field reconstructed from the velocity field of young galaxies
using the POTENT-style method suffers in accuracy both from the spatial bias
and the dynamical friction on the smoothing scale of R_s=8Mpc/h. On the other
hand, in the case of R_s=12Mpc/h, which is typically adopted in the actual
POTENT analysis, the density reconstruction based on various tracers of
galaxies is reasonably accurate.Comment: 29 pages, 11 figures, accepted for publication in the Ap
SIGNAL: A Ka-band Digital Beam-Forming SAR System Concept to Monitor Topography Variations of Ice Caps and Glaciers
This paper discusses the implementation of an endto-
end simulator for the BIOMASS mission. An overview of
the system architecture is provided along with a functional
description of the modules that comprise the simulator
Age of the Universe: Influence of the Inhomogeneities on the global Expansion-Factor
For the first time we calculate quantitatively the influence of
inhomogeneities on the global expansion factor by averaging the Friedmann
equation. In the framework of the relativistic second-order
Zel'dovich-approximation scheme for irrotational dust we use observational
results in form of the normalisation constant fixed by the COBE results and we
check different power spectra, namely for adiabatic CDM, isocurvature CDM, HDM,
WDM, Strings and Textures. We find that the influence of the inhomogeneities on
the global expansion factor is very small. So the error in determining the age
of the universe using the Hubble constant in the usual way is negligible. This
does not imply that the effect is negligible for local astronomical
measurements of the Hubble constant. Locally the determination of the
redshift-distance relation can be strongly influenced by the peculiar velocity
fields due to inhomogeneities. Our calculation does not consider such effects,
but is contrained to comparing globally homogeneous and averaged inhomogeneous
matter distributions. In addition we relate our work to previous treatments.Comment: 10 pages, version accepted by Phys. Rev.
Lipid-DNAs as Solubilizers of mTHPC
Hydrophobic drug candidates require innovative
formulation agents. We designed and synthesized lipidDNA polymers containing varying numbers of hydrophobic alkyl chains. The hydrophobicity of these amphiphiles
is easily tunable by introducing a defined number of alkyl
chain-modified nucleotides during standard solid-phase
synthesis of DNA using an automated DNA synthesizer.
We observed that the resulting self-assembled micelles
solubilize the poorly water-soluble drug, meta-tetra-hydroxyphenyl-chlorin (mTHPC) used in photodynamic therapy (PDT) with high loading concentrations and loading
capacities. A cell viability study showed that mTHPCloaded micelles exhibit good biocompatibility without irradiation, and high PDT efficacy upon irradiation. LipidDNAs provide a novel class of drug-delivery vehicle, and
hybridization of DNA offers a potentially facile route for
further functionalization of the drug-delivery system with,
for instance, targeting or imaging moieties
The Zel'dovich-type approximation for an inhomogeneous universe in general relativity: second-order solutions
The gravitational instability of inhomogeneities in the expanding universe is
studied by the relativistic second-order approximation. Using the tetrad
formalism we consider irrotational dust universes and get equations very
similar to those given in the Lagrangian perturbation theory in Newtonian
cosmology. Neglecting the cosmological constant and assuming a flat background
model we give the solutions of the nonlinear dynamics of cosmological
perturbations. We present the complete second-order solutions, which extend and
improve earlier works.Comment: 20 pages, LaTeX, no figure
The dependence of clustering on galaxy properties
(abridged)We use a sample of ~200,000 galaxies drawn from the Sloan Digital
Sky Survey to study how clustering depends on properties such as stellar mass
(M*), colour (g-r), 4000A break strength (D4000), concentration index (C), and
stellar surface mass density (\mu_*). We find that more massive galaxies
cluster more strongly than less massive galaxies, with the difference
increasing above the characteristic stellar mass of the Schechter mass
function. When divided by physical quantities, galaxies with redder colours,
larger D4000, higher C and larger \mu_* cluster more strongly. The clustering
differences are largest on small scales and for low mass galaxies. At fixed
stellar mass,the dependences of clustering on colour and 4000A break strength
are similar. Different results are obtained when galaxies are split by
concentration or surface density. The dependence of w(r_p) on g-r and D4000
extends out to physical scales that are significantly larger than those of
individual dark matter haloes (> 5 Mpc/h). This large-scale clustering
dependence is not seen for the parameters C or \mu_*. On small scales (< 1
Mpc/h), the amplitude of the correlation function is constant for ``young''
galaxies with 1.1 < D4000< 1.5 and a steeply rising function of age for
``older'' galaxies with D4000>1.5. In contrast, the dependence of the amplitude
of w(r_p) on concentration on scales less than 1 Mpc/h is strongest for
disk-dominated galaxies with C<2.6. This demonstrates that different processes
are required to explain environmental trends in the structure and in star
formation history of galaxies.Comment: 17 pages, 14 figures; reference updated and text slightly changed to
match the published version; Tables 5 and 6 are available at
http://www.mpa-garching.mpg.de/~leech/papers/clustering
Preliminary Results for the Multi-Robot, Multi-Partner, Multi-Mission, Planetary Exploration Analogue Campaign on Mount Etna
This paper was initially intended to report on the outcome of the twice postponed demonstration mission of the ARCHES project. Due to the global COVID pandemic, it has been postponed from 2020, then 2021, to 2022. Nevertheless, the development of our concepts and integration has progressed rapidly, and some of the preliminary
results are worthwhile to share with the community to drive the dialog on robotics planetary exploration strategies. This paper includes an overview of the planned 4-week campaign, as well as the vision and relevance of the missiontowards the planned official space missions. Furthermore, the cooperative aspect of the robotic teams, the scientific motivation, the sub task achievements are summarised
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