21,399 research outputs found
Spherical Orbifolds for Cosmic Topology
Harmonic analysis is a tool to infer cosmic topology from the measured
astrophysical cosmic microwave background CMB radiation. For overall positive
curvature, Platonic spherical manifolds are candidates for this analysis. We
combine the specific point symmetry of the Platonic manifolds with their deck
transformations. This analysis in topology leads from manifolds to orbifolds.
We discuss the deck transformations of the orbifolds and give eigenmodes for
the harmonic analysis as linear combinations of Wigner polynomials on the
3-sphere. These provide new tools for detecting cosmic topology from the CMB
radiation.Comment: 17 pages, 9 figures. arXiv admin note: substantial text overlap with
arXiv:1011.427
X-Ray Emission-Line Profile Modeling Of O Stars: Fitting A Spherically Symmetric Analytic Wind-Shock Model To The Chandra Spectrum Of Zeta Puppis
X-ray emission-line profiles provide the most direct insight into the dynamics and spatial distribution of the hot, X-ray-emitting plasma above the surfaces of OB stars. The O supergiant zeta Puppis shows broad, blueshifted, and asymmetric line profiles, generally consistent with the wind-shock picture of OB star X-ray production. We model the profiles of eight lines in the Chandra HETGS spectrum of this prototypical hot star. The fitted lines indicate that the plasma is distributed throughout the wind starting close to the photosphere, that there is significantly less attenuation of the X-rays by the overlying wind than is generally supposed, and that there is not a strong trend in wind absorption with wavelength
Overlapping Unit Cells in 3d Quasicrystal Structure
A 3-dimensional quasiperiodic lattice, with overlapping unit cells and
periodic in one direction, is constructed using grid and projection methods
pioneered by de Bruijn. Each unit cell consists of 26 points, of which 22 are
the vertices of a convex polytope P, and 4 are interior points also shared with
other neighboring unit cells. Using Kronecker's theorem the frequencies of all
possible types of overlapping are found.Comment: LaTeX2e, 11 pages, 5 figures (8 eps files), uses iopart.class. Final
versio
Modulation of plant growth in vivo and identification of kinase substrates using an analog-sensitive variant of CYCLIN-DEPENDENT KINASE A;1
BACKGROUND: Modulation of protein activity by phosphorylation through kinases and subsequent de-phosphorylation by phosphatases is one of the most prominent cellular control mechanisms. Thus, identification of kinase substrates is pivotal for the understanding of many – if not all – molecular biological processes. Equally, the possibility to deliberately tune kinase activity is of great value to analyze the biological process controlled by a particular kinase. RESULTS: Here we have applied a chemical genetic approach and generated an analog-sensitive version of CDKA;1, the central cell-cycle regulator in Arabidopsis and homolog of the yeast Cdc2/CDC28 kinases. This variant could largely rescue a cdka;1 mutant and is biochemically active, albeit less than the wild type. Applying bulky kinase inhibitors allowed the reduction of kinase activity in an organismic context in vivo and the modulation of plant growth. To isolate CDK substrates, we have adopted a two-dimensional differential gel electrophoresis strategy, and searched for proteins that showed mobility changes in fluorescently labeled extracts from plants expressing the analog-sensitive version of CDKA;1 with and without adding a bulky ATP variant. A pilot set of five proteins involved in a range of different processes could be confirmed in independent kinase assays to be phosphorylated by CDKA;1 approving the applicability of the here-developed method to identify substrates. CONCLUSION: The here presented generation of an analog-sensitive CDKA;1 version is functional and represent a novel tool to modulate kinase activity in vivo and identify kinase substrates. Our here performed pilot screen led to the identification of CDK targets that link cell proliferation control to sugar metabolism, proline proteolysis, and glucosinolate production providing a hint how cell proliferation and growth are integrated with plant development and physiology. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-016-0900-7) contains supplementary material, which is available to authorized users
Quasicrystals: Atomic coverings and windows are dual projects
In the window approach to quasicrystals, the atomic position space E_parallel
is embedded into a space E^n = E_parallel + E_perp. Windows are attached to
points of a lattice Lambda \in E^n. For standard 5fold and icosahedral tiling
models, the windows are perpendicular projections of dual Voronoi and Delone
cells from Lambda. Their cuts by the position space E_parallel mark tiles and
atomic positions. In the alternative covering approach, the position space is
covered by overlapping copies of a quasi-unit cell which carries a fixed atomic
configuration. The covering and window approach to quasicrystals are shown to
be dual projects: D- and V- clusters are defined as projections to position
space E_parallel of Delone or Voronoi cells. Decagonal V-clusters in the
Penrose tiling, related to the decagon covering, and two types of pentagonal
D-clusters in the triangle tiling of 5fold point symmetry with their windows
are analyzed. They are linked, cover position space and have definite windows.
For functions compatible with the tilings they form domains of definition. For
icosahedral tilings the V-clusters are Kepler triacontahedra, the D-clusters
are two icosahedra and one dodecahedron.Comment: 15 pages, 7 figures, see also
http://homepages.uni-tuebingen.de/peter.kramer/ corrections, appendix A,B ne
Long term monitoring of mode switching for PSR B0329+54
The mode switching phenomenon of PSR B0329+54 is investigated based on the
long-term monitoring from September 2003 to April 2009 made with the Urumqi 25m
radio telescope at 1540 MHz. At that frequency, the change of relative
intensity between the leading and trailing components is the predominant
feature of mode switching. The intensity ratios between the leading and
trailing components are measured for the individual profiles averaged over a
few minutes. It is found that the ratios follow normal distributions, where the
abnormal mode has a wider typical width than the normal mode, indicating that
the abnormal mode is less stable than the normal mode. Our data show that 84.9%
of the time for PSR B0329+54 was in the normal mode and 15.1% was in the
abnormal mode. From the two passages of eight-day quasi-continuous observations
in 2004, and supplemented by the daily data observed with 15 m telescope at 610
MHz at Jodrell Bank Observatory, the intrinsic distributions of mode timescales
are constrained with the Bayesian inference method. It is found that the gamma
distribution with the shape parameter slightly smaller than 1 is favored over
the normal, lognormal and Pareto distributions. The optimal scale parameters of
the gamma distribution is 31.5 minutes for the abnormal mode and 154 minutes
for the normal mode. The shape parameters have very similar values, i.e.
0.75^{+0.22}_{-0.17} for the normal mode and 0.84^{+0.28}_{-0.22} for the
abnormal mode, indicating the physical mechanisms in both modes may be the
same. No long-term modulation of the relative intensity ratios was found for
both the modes, suggesting that the mode switching was stable. The intrinsic
timescale distributions, for the first time constrained for this pulsar,
provide valuable information to understand the physics of mode switching.Comment: 31 pages,12 figures, Accepted by the Ap
Preparation Of Gas Separation Membranes By Plasma Polymerization With Fluoro Compounds
Plasma polymerization coatings were applied for the preparation of gas separation membranes. Mainly fluoro compounds were used as coating materials. The membranes showed good separation characteristics with high flux for gaseous systems. The plasma polymerization composite parameter given by W/FM plays an important role in obtaining excellent separation characteristics. The correlation between the conversion rate DR/FM, where DR is the deposition rate of plasma polymer, and W/FM is useful to consider the plasma polymer character under the different plasma polymerization conditions (discharge power W and monomer flow rate F). The proper conditions for membrane preparation lie in the intermediate region between the region in which the monomer flow rate is deficient and that in which the discharge power is deficient. Furthermore, the plasma polymerization coatings with the higher molecular weight monomer gave the higher separation characteristics. Plasma polymer composite membranes in this study showed superiority for the molecular sieve type of separation over the solution-diffusion type of separation. © 1984
Mixed Symmetry Solutions of Generalized Three-Particle Bargmann-Wigner Equations in the Strong-Coupling Limit
Starting from a nonlinear isospinor-spinor field equation, generalized
three-particle Bargmann-Wigner equations are derived. In the strong-coupling
limit, a special class of spin 1/2 bound-states are calculated. These solutions
which are antisymmetric with respect to all indices, have mixed symmetries in
isospin-superspin space and in spin orbit space. As a consequence of this mixed
symmetry, we get three solution manifolds. In appendix \ref{b}, table 2, these
solution manifolds are interpreted as the three generations of leptons and
quarks. This interpretation will be justified in a forthcoming paper.Comment: 17 page
A Quasi-Spherical Gravitational Wave Solution in Kaluza-Klein Theory
An exact solution of the source-free Kaluza-Klein field equations is
presented. It is a 5D generalization of the Robinson-Trautman quasi-spherical
gravitational wave with a cosmological constant. The properties of the 5D
solution are briefly described.Comment: 10 pages Latex, Revtex, submitted to GR
Single Top Quark Production and Decay at Next-to-leading Order in Hadron Collision
We present a calculation of the next-to-leading order QCD corrections, with
one-scale phase space slicing method, to single top quark production and decay
process at hadron colliders.
Using the helicity amplitude method, the angular correlation of the final state
partons and the spin correlation of the top quark are preserved. The effect of
the top quark width is also examined.Comment: 47 pages, 9 figure
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