494 research outputs found
The spatial distribution of cold gas in hierarchical galaxy formation models
The distribution of cold gas in dark matter haloes is driven by key processes in galaxy formation: gas cooling, galaxy mergers, star formation and reheating of gas by supernovae. We compare the predictions of four different galaxy formation models for the spatial distribution of cold gas. We find that satellite galaxies make little contribution to the abundance or clustering strength of cold gas selected samples, and are far less important than they are in optically selected samples. The halo occupation distribution function of present-day central galaxies with cold gas mass >109 hâ1 Mâ is peaked around a halo mass of â1011 hâ1 Mâ, a scale that is set by the AGN suppression of gas cooling. The model predictions for the projected correlation function are in good agreement with measurements from the H i Parkes All-Sky Survey. We compare the effective volume of possible surveys with the Square Kilometre Array with those expected for a redshift survey in the near-infrared. Future redshift surveys using neutral hydrogen emission will make possible measurements of the baryonic acoustic oscillations that are competitive with the most ambitious spectroscopic surveys planned in the near-infrared
Characterization and application of two RANK-specific antibodies with different biological activities.
Antibodies play an important role in therapy and investigative biomedical research. The TNF-family member Receptor Activator of NF-ÎșB (RANK) is known for its role in bone homeostasis and is increasingly recognized as a central player in immune regulation and epithelial cell activation. However, the study of RANK biology has been hampered by missing or insufficient characterization of high affinity tools that recognize RANK. Here, we present a careful description and comparison of two antibodies, RANK-02 obtained by phage display (Newa, 2014 [1]) and R12-31 generated by immunization (Kamijo, 2006 [2]). We found that both antibodies recognized mouse RANK with high affinity, while RANK-02 and R12-31 recognized human RANK with high and lower affinities, respectively. Using a cell apoptosis assay based on stimulation of a RANK:Fas fusion protein, and a cellular NF-ÎșB signaling assay, we showed that R12-31 was agonist for both species. R12-31 interfered little or not at all with the binding of RANKL to RANK, in contrast to RANK-02 that efficiently prevented this interaction. Depending on the assay and species, RANK-02 was either a weak agonist or a partial antagonist of RANK. Both antibodies recognized human Langerhans cells, previously shown to express RANK, while dermal dendritic cells were poorly labeled. In vivo R12-31 agonist activity was demonstrated by its ability to induce the formation of intestinal villous microfold cells in mice. This characterization of two monoclonal antibodies should now allow better evaluation of their application as therapeutic reagents and investigative tools
Depth-Resolved Composition and Electronic Structure of Buried Layers and Interfaces in a LaNiO/SrTiO Superlattice from Soft- and Hard- X-ray Standing-Wave Angle-Resolved Photoemission
LaNiO (LNO) is an intriguing member of the rare-earth nickelates in
exhibiting a metal-insulator transition for a critical film thickness of about
4 unit cells [Son et al., Appl. Phys. Lett. 96, 062114 (2010)]; however, such
thin films also show a transition to a metallic state in superlattices with
SrTiO (STO) [Son et al., Appl. Phys. Lett. 97, 202109 (2010)]. In order to
better understand this transition, we have studied a strained LNO/STO
superlattice with 10 repeats of [4 unit-cell LNO/3 unit-cell STO] grown on an
(LaAlO)(SrAlTaO) substrate using soft x-ray
standing-wave-excited angle-resolved photoemission (SWARPES), together with
soft- and hard- x-ray photoemission measurements of core levels and
densities-of-states valence spectra. The experimental results are compared with
state-of-the-art density functional theory (DFT) calculations of band
structures and densities of states. Using core-level rocking curves and x-ray
optical modeling to assess the position of the standing wave, SWARPES
measurements are carried out for various incidence angles and used to determine
interface-specific changes in momentum-resolved electronic structure. We
further show that the momentum-resolved behavior of the Ni 3d eg and t2g states
near the Fermi level, as well as those at the bottom of the valence bands, is
very similar to recently published SWARPES results for a related
LaSrMnO/SrTiO superlattice that was studied using the
same technique (Gray et al., Europhysics Letters 104, 17004 (2013)), which
further validates this experimental approach and our conclusions. Our
conclusions are also supported in several ways by comparison to DFT
calculations for the parent materials and the superlattice, including
layer-resolved density-of-states results
A convenient band-gap interpolation technique and an improved band line-up model for InGaAlAs on InP
The band-gap energy and the band line-up of InGaAlAs quaternary compound material on InP are essential information for the theoretical study of physical properties and the design of optoelectronics devices operating in the long-wavelength communication window. The band-gap interpolation of In1-x-y Ga (x) Al (y) As on InP is known to be a challenging task due to the observed discrepancy of experimental results arising from the bowing effect. Besides, the band line-up results of In1-x-y Ga (x) Al (y) As on InP based on previously reported models have limited success by far. In this work, we propose an interpolation solution using the single-variable surface bowing estimation interpolation method for the fitting of experimentally measured In1-x-y Ga (x) Al (y) As band-gap data with various degree of bowing using the same set of input parameters. The suggested solution provides an easier and more physically interpretable way to determine not only lattice matched, but also strained band-gap energy of In1-x-y Ga (x) Al (y) As on InP based on the experimental results. Interpolated results from this convenient method show a more favourable match to multiple independent experiment data sets measured under different temperature conditions as compared to those obtained from the commonly used weighted-sum approach. On top of that, extended framework of the model-solid theory for the band line-up of In1-x-y Ga (x) Al (y) As/InP heterostructure is proposed. Our model-solid theory band line-up result using the proposed extended framework has shown an improved accuracy over those without the extension. In contrast to some previously reported works, it is worth noting that the band line-up result based on our proposed extended model-solid theory has also shown to be more accurate than those given by Harrison's mode
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Adsorption of mono- and multivalent cat- and anions on DNA molecules
Adsorption of monovalent and multivalent cat- and anions on a deoxyribose
nucleic acid (DNA) molecule from a salt solution is investigated by computer
simulation. The ions are modelled as charged hard spheres, the DNA molecule as
a point charge pattern following the double-helical phosphate strands. The
geometrical shape of the DNA molecules is modelled on different levels ranging
from a simple cylindrical shape to structured models which include the major
and minor grooves between the phosphate strands. The densities of the ions
adsorbed on the phosphate strands, in the major and in the minor grooves are
calculated. First, we find that the adsorption pattern on the DNA surface
depends strongly on its geometrical shape: counterions adsorb preferentially
along the phosphate strands for a cylindrical model shape, but in the minor
groove for a geometrically structured model. Second, we find that an addition
of monovalent salt ions results in an increase of the charge density in the
minor groove while the total charge density of ions adsorbed in the major
groove stays unchanged. The adsorbed ion densities are highly structured along
the minor groove while they are almost smeared along the major groove.
Furthermore, for a fixed amount of added salt, the major groove cationic charge
is independent on the counterion valency. For increasing salt concentration the
major groove is neutralized while the total charge adsorbed in the minor groove
is constant. DNA overcharging is detected for multivalent salt. Simulations for
a larger ion radii, which mimic the effect of the ion hydration, indicate an
increased adsorbtion of cations in the major groove.Comment: 34 pages with 14 figure
Galaxy Bias and non-Linear Structure Formation in General Relativity
Length scales probed by large scale structure surveys are becoming closer to
the horizon scale. Further, it has been recently understood that
non-Gaussianity in the initial conditions could show up in a scale dependence
of the bias of galaxies at the largest distances. It is therefore important to
include General Relativistic effects. Here we provide a General Relativistic
generalization of the bias, valid both for Gaussian and non-Gaussian initial
conditions. The collapse of objects happens on very small scales, while
long-wavelength modes are always in the quasi linear regime. Around every
collapsing region, it is therefore possible to find a reference frame that is
valid for all times and where the space time is almost flat: the Fermi frame.
Here the Newtonian approximation is applicable and the equations of motion are
the ones of the N-body codes. The effects of long-wavelength modes are encoded
in the mapping from the cosmological frame to the local frame. For the linear
bias, the effect of the long-wavelength modes on the dynamics is encoded in the
local curvature of the Universe, which allows us to define a General
Relativistic generalization of the bias in the standard Newtonian setting. We
show that the bias due to this effect goes to zero as the squared ratio of the
physical wavenumber with the Hubble scale for modes longer than the horizon, as
modes longer than the horizon have no dynamical effects. However, the bias due
to non-Gaussianities does not need to vanish for modes longer than the Hubble
scale, and for non-Gaussianities of the local kind it goes to a constant. As a
further application, we show that it is not necessary to perform large N-body
simulations to extract information on long-wavelength modes: N-body simulations
can be done on small scales and long-wavelength modes are encoded simply by
adding curvature to the simulation and rescaling the coordinates.Comment: 48 pages, 4 figures; v2: added references, JCAP published versio
Genetic defects in common variable immunodeficiency
Common variable immunodeficiency (CVID) is the most frequent clinically manifested primary immunodeficiency. According to clinical and laboratory findings, CVID is a heterogeneous group of diseases. Recently, the defects of molecules regulating activation and terminal differentiation of B lymphocytes have been described in some patients with CVID. In this study, we show the overview of deficiencies of inducible costimulator, transmembrane activator and calcium-modulator and cytophilin ligand interactor, CD19 molecules, their genetic basis, pathogenesis and clinical manifestations
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