A unique talin homologue with a villin headpiece-like domain is required for multicellular morphogenesis in Dictyostelium

AbstractMolecules involved in the interaction between the extracellular matrix, cell membrane and cytoskeleton are of central importance in morphogenesis. Talin is a large cytoskeletal protein with a modular structure consisting of an amino-terminal membrane-interacting domain, with sequence similarities to members of the band 4.1 family, and a carboxy-terminal region containing F-actin-binding and vinculin-binding domains [1,2]. It also interacts with the cytoplasmic tail of β integrins which, on the external face of the membrane, bind to extracellular matrix proteins [3]. The possible roles of talin in multicellular morphogenesis in development remain largely unexplored. In Dictyostelium, a eukaryotic microorganism capable of multicellular morphogenesis, a talin homologue (TALA) has previously been identified and shown to play an important role in cell-to-substrate adhesion and maintenance of normal elastic properties of the cell [4–6]. Here, we describe a second talin homologue (TALB) that is required for multicellular morphogenesis in the development of Dictyostelium. Unlike any other talin characterised to date, it contains an additional carboxy-terminal domain homologous to the villin headpiece

A dipole anisotropy of galaxy distribution: Does the CMB rest-frame exist in the local universe?

The peculiar motion of the Earth causes a dipole anisotropy modulation in the distant galaxy distribution due to the aberration effect. However, the amplitude and angular direction of the effect is not necessarily the same as those of the cosmic microwave background (CMB) dipole anisotropy due to the growth of cosmic structures. In other words exploring the aberration effect may give us a clue to the horizon-scale physics perhaps related to the cosmic acceleration. In this paper we develop a method to explore the dipole angular modulation from the pixelized galaxy data on the sky properly taking into account the covariances due to the shot noise and the intrinsic galaxy clustering contamination as well as the partial sky coverage. We applied the method to the galaxy catalogs constructed from the Sloan Digital Sky Survey (SDSS) Data Release 6 data. After constructing the four galaxy catalogs that are different in the ranges of magnitudes and photometric redshifts to study possible systematics, we found that the most robust sample against systematics indicates no dipole anisotropy in the galaxy distribution. This finding is consistent with the expectation from the concordance Lambda-dominated cold dark matter model. Finally we argue that an almost full-sky galaxy survey such as LSST may allow for a significant detection of the aberration effect of the CMB dipole having the precision of constraining the angular direction to ~ 20 degrees in radius. Assuming a hypothetical LSST galaxy survey, we find that this method can confirm or reject the result implied from a stacked analysis of the kinetic Sunyaev-Zel'dovich effect of X-ray luminous clusters in Kashlinsky et al. (2008,2009) if the implied cosmic bulk flow is not extended out to the horizon.Comment: 20 pages, 11 figures; 24 pages, added a couple of references and 2 figures. Revised version in response to the referee's comments. Resubmitted to Phys. Rev.

Bispectrum and Nonlinear Biasing of Galaxies: Perturbation Analysis, Numerical Simulation and SDSS Galaxy Clustering

We consider nonlinear biasing models of galaxies with particular attention to a correlation between linear and quadratic biasing coefficients, b_1 and b_2. We first derive perturbative expressions for b_1 and b_2 in halo and peak biasing models. Then we compute power spectra and bispectra of dark matter particles and halos using N-body simulation data and of volume-limited subsamples of Sloan Digital Sky Survey (SDSS) galaxies, and determine their b_1 and b_2. We find that the values of those coefficients at linear regimes (k<0.2h/Mpc) are fairly insensitive to the redshift-space distortion and the survey volume shape. The resulting normalized amplitudes of bispectra, Q, for equilateral triangles, are insensitive to the values of b_1 implying that b_2 indeed correlates with b_1. The present results explain the previous finding of Kayo et al. (2004) for the hierarchical relation of three-point correlation functions of SDSS galaxies. While the relations between b_1 and b_2 are quantitatively different for specific biasing models, their approximately similar correlations indicate a fairly generic outcome of the biasing due to the gravity in primordial Gaussian density fields.Comment: 14 pages, 8 figures, accepted for publication in PAS

Error analysis of the photometric redshift tecnique

We present a calculation of the systematic component of the error budget in the photometric redshift technique. We make use of it to describe a simple technique that allows for the assignation of confidence limits to redshift measurements obtained through photometric methods. We show that our technique, through the calculation of a redshift probability function, gives complete information on the probable redshift of an object and its associated confidence intervals. This information can and must be used in the calculation of any observable quantity which makes use of the redshift.Comment: 6 pages, 5 figures, MNRAS style. Accepted for publication in MNRA

Measurements of the Total Reaction Cross Section in 12C, 13C, 14N, 15N, 16O + 28Si Systems

開始ページ、終了ページ: 冊子体のページ付

Worm algorithms for classical statistical models

We show that high-temperature expansions may serve as a basis for the novel approach to efficient Monte Carlo simulations. "Worm" algorithms utilize the idea of updating closed path configurations (produced by high-temperature expansions) through the motion of end points of a disconnected path. An amazing result is that local, Metropolis-type schemes may have dynamical critical exponents close to zero (i.e., their efficiency is comparable to the best cluster methods). We demonstrate this by calculating finite size scaling of the autocorrelation time for various (six) universality classes.Comment: 4 pages, latex, 2 figure

Large-Scale Anisotropic Correlation Function of SDSS Luminous Red Galaxies

We study the large-scale anisotropic two-point correlation function using 46,760 luminous red galaxies at redshifts 0.16 -- 0.47 from the Sloan Digital Sky Survey. We measure the correlation function as a function of separations parallel and perpendicular to the line-of-sight in order to take account of anisotropy of the large-scale structure in redshift space. We find a slight signal of baryonic features in the anisotropic correlation function, i.e., a ``baryon ridge'' which corresponds to a baryon acoustic peak in the spherically averaged correlation function which has already been reported using the same sample. The baryon ridge has primarily a spherical structure with a known radius in comoving coordinates. It enables us to divide the redshift distortion effects into dynamical and geometrical components and provides further constraints on cosmological parameters, including the dark energy equation-of-state. With an assumption of a flat $\Lambda$ cosmology, we find the best-fit values of $\Omega_{\rm m} = 0.218^{+0.047}_{-0.037}$ and $\Omega_{\rm b} = 0.047^{+0.016}_{-0.016}$ (68% C.L.) when we use the overall shape of the anisotropic correlation function of 40 including a scale of baryon acoustic oscillations. When an additional assumption $\Omega_{\rm b}h^2=0.024$ is adopted, we obtain $\Omega_{\rm DE}=0.770^{+0.051}_{-0.040}$ and $w=-0.93^{+0.45}_{-0.35}$. These constraints are estimated only from our data of the anisotropic correlation function, and they agree quite well with values both from the cosmic microwave background (CMB) anisotropies and from other complementary statistics using the LRG sample. With the CMB prior from the 3 year WMAP results, we give stronger constraints on those parameters.Comment: 11 pages, 9 figures, 1 table, typo corrected, references added with respect to published versio