8,612 research outputs found
Delineation of a unique protein-protein interaction site on the surface of the estrogen receptor
Recent studies have identified a series of estrogen receptor (ER)interacting peptides that recognize sites that are distinct from the classic coregulator recruitment (AF2) region. Here, we report the structural and functional characterization of an ER alpha-specific peptide that binds to the liganded receptor in an AF2-independent manner. The 2-angstrom crystal structure of the ER/peptide complex reveals a binding site that is centered on a shallow depression on the beta-hairpin face of the ligand-binding domain. The peptide binds in an unusual extended conformation and makes multiple contacts with the ligand-binding domain. The location and architecture of the binding site provides an insight into the peptide's ER subtype specificity and ligand interaction preferences. In vivo, an engineered coactivator containing the peptide motif is able to strongly enhance the transcriptional activity of liganded ER alpha, particularly in the presence of 4-hydroxytamoxifen. Furthermore, disruption of this binding surface alters ER's response to the coregulator TIF2. Together, these results indicate that this previously unknown interaction site represents a bona fide control surface involved in regulating receptor activity
Pressure as a Source of Gravity
The active mass density in Einstein's theory of gravitation in the analog of
Poisson's equation in a local inertial system is proportional to .
Here is the density of energy and its pressure for a perfect fluid.
By using exact solutions of Einstein's field equations in the static case we
study whether the pressure term contributes towards the mass
The search for black hole binaries using a genetic algorithm
In this work we use genetic algorithm to search for the gravitational wave
signal from the inspiralling massive Black Hole binaries in the simulated LISA
data. We consider a single signal in the Gaussian instrumental noise. This is a
first step in preparation for analysis of the third round of the mock LISA data
challenge. We have extended a genetic algorithm utilizing the properties of the
signal and the detector response function. The performance of this method is
comparable, if not better, to already existing algorithms.Comment: 11 pages, 4 figures, proceeding for GWDAW13 (Puerto Rico
Momentum-Resolved Electronic Structure of the High- Superconductor Parent Compound BaBiO
We investigate the band structure of BaBiO, an insulating parent
compound of doped high- superconductors, using \emph{in situ}
angle-resolved photoemission spectroscopy on thin films. The data compare
favorably overall with density functional theory calculations within the local
density approximation, demonstrating that electron correlations are weak. The
bands exhibit Brillouin zone folding consistent with known BiO breathing
distortions. Though the distortions are often thought to coincide with
Bi/Bi charge ordering, core level spectra show that bismuth is
monovalent. We further demonstrate that the bands closest to the Fermi level
are primarily oxygen derived, while the bismuth states mostly contribute
to dispersive bands at deeper binding energy. The results support a model of
Bi-O charge transfer in which hole pairs are localized on combinations of the O
orbitals.Comment: minor changes to text and other figures; includes link to online
Supplemental Material; accepted to Phys. Rev. Let
Ground State Energy of the One-Component Charged Bose Gas
The model considered here is the `jellium' model in which there is a uniform,
fixed background with charge density in a large volume and in
which particles of electric charge and mass move --- the
whole system being neutral. In 1961 Foldy used Bogolubov's 1947 method to
investigate the ground state energy of this system for bosonic particles in the
large limit. He found that the energy per particle is in this limit, where .
Here we prove that this formula is correct, thereby validating, for the first
time, at least one aspect of Bogolubov's pairing theory of the Bose gasComment: 38 pages latex. Typos corrected.Lemma 6.2 change
Intersection of a domains in the c-domain matrix driven by electric field in tetragonal ferroelectric crystal
Domain structures in a tetragonal ferroelectric crystal were examined by transmission electron microscopy(TEM) before and after application of bipolar cyclic electric fields. Prior to the application of the bipolar field, the crystal was poled to an initial domain structure which consisted of a high volume fraction of c domains. Dispersed in the matrix of the c domains were two orthogonal sets of a-domain strips. These two sets of a-domain strips stayed apart to avoid direct contact. Upon application of bipolar cyclic electric fields, intersections of the a domains were observed in the ⟨001⟩-oriented tetragonal ferroelectric crystal. These intersections were formed as one set of the a domains grew under the influence of the in-plane electric field. As a result of the domain wall intersection, segments of the domain wall between two intersecting a domains carried excess electric charges. In the successive TEM examination, domain wall distortion and microcracks were found at these intersections
Quasiperiodic Tip Splitting in Directional Solidification
We report experimental results on the tip splitting dynamics of seaweed
growth in directional solidification of succinonitrile alloys with
poly(ethylene oxide) or acetone as solutes. The seaweed or dense branching
morphology was selected by solidifying grains which are oriented close to the
{111} plane. Despite the random appearance of the growth, a quasiperiodic tip
splitting morphology was observed in which the tip alternately splits to the
left and to the right. The tip splitting frequency f was found to be related to
the growth velocity V as a power law f V^{1.5}. This finding
is consistent with the predictions of a tip splitting model that is also
presented. Small anisotropies are shown to lead to different kinds of seaweed
morphologies.Comment: 4 pages, 7 figures, submitted to Physical Review Letter
A New Scheme for Acoustical Tomography of the Ocean
Award #: N00014-95-F-0046 http://www.etl.noaa.gov LONG-TERM GOAL The long-term purpose is to develop a new scheme of the acoustical tomography of the ocean of mesoto global scales which is based on measurements of horizontal-refraction angle (HRA) related to different acoustic modes rather than travel time along different rays. OBJECTIVES To develop robust inversion scheme for retrieving 3-D ocean inner structure based on measurements of HRA. In spite of its small value HRA angle can be easily measured with the help of pair of moderesolving line vertical arrays situated about 10 km apart (ocean interferometer). As a first approximation adiabaticity of mode propagation should be assumed. Then the scheme should be generalized to the case of non-adiabatic propagation with mode interaction taken into account in a "N 2-D" approximation, and appropriate computer simulations should be performed. Scattering of acoustic signals from internal waves should be also considered, and its effect on the accuracy of sound speed field retrieval should be estimated. APPROACH A low frequency tonal sound source (F = 30-100 Hz) is assumed to be towed by a vessel around the area of interest with typical horizontal scale of the order of 1000 km. The transmitted signal is received by acoustic interferometers located inside or outside the area. Thus, the area is exposed from different directions, and HRA is known as a function of source position. Those data are then used for tomography inversion. In the general case, acoustic mode interaction due to water mass inhomogeneity should be taken into account. This is accomplished with the help of iterations. In the first approximation mode interaction is neglected, and HRA are inverted into sound speed profiles assuming adiabatic propagation. The inversion proceeds in two stages: 1) 2-D tomography which retrieves propagation constants of different modes at the nodes of horizontal rectangular grid covering the area. 2) 1-D tomography which retrieves sound speed profile (in terms of expansion with respect to a set of empirical orthogonal functions) at each node of horizontal grid based on already determined values of propagation constants. Then the contribution to horizontal refraction due to mode interaction are calculated with respect to retrieved inhomogeneous medium using propagation code which takes into account mode interactions in
- …