6,958 research outputs found
Representation of the transfer functions of given structures by their eigen-vibrations, taking into consideration any arbitrary excitation
Eigen-vibration representation of transfer functions for structures by considering arbitrary excitation
A new metric for probability distributions
We introduce a metric for probability distributions, which is bounded, information-theoretically motivated, and has a natural Bayesian interpretation. The square root of the well-known chi(2) distance is an asymptotic approximation to it. Moreover, it is a close relative of the capacitory discrimination and Jensen-Shannon divergence.Publisher PDFPeer reviewe
Candidate amino acids involved in H+ gating of acid-sensing ion channel 1a
Acid-sensing ion channels are ligand-gated cation channels, gated by extracellular H+. H+ is the simplest ligand possible, and whereas for larger ligands that gate ion channels complex binding sites in the three-dimensional structure of the proteins have to be assumed, H+ could in principle gate a channel by titration of a single amino acid. Experimental evidence suggests a more complex situation, however. For example, it has been shown that extracellular Ca2+ ions compete with H+; probably Ca2+ ions bound to the extracellular loop of ASICs stabilize the closed state of the channel and have to be displaced before the channel can open. In such a scheme, amino acids contributing to Ca2+ binding would also be candidates contributing to H+ gating. In this study we systematically screened more than 40 conserved, charged amino acids in the extracellular region of ASIC1a for a possible contribution to H+ gating. We identified four amino acids where substitution strongly affects H+ gating: Glu63, His72/His73, and Asp78. These amino acids are highly conserved among H+-sensitive ASICs and are candidates for the “H+ sensor” of ASICs
Quantum to classical crossover in the 2D easy-plane XXZ model
Ground-state and thermodynamical properties of the spin-1/2 two-dimensional
easy-plane XXZ model are investigated by both a Green's-function approach and
by Lanczos diagonalizations on lattices with up to 36 sites. We calculate the
spatial and temperature dependences of various spin correlation functions, as
well as the wave-vector dependence of the spin susceptibility for all
anisotropy parameters . In the easy--plane ferromagnetic region , the longitudinal correlators of spins at distance change sign
at a finite temperature . This transition, observed in
the 2D case for the first time, can be interpreted as a quantum to classical
crossover.Comment: 4 pages, 6 figures, Contribution to the Ising Centennial Colloquium,
ICM2000, Belo Horizonte, Brazil, August 200
OpenSPIM - an open access platform for light sheet microscopy
Light sheet microscopy promises to revolutionize developmental biology by
enabling live in toto imaging of entire embryos with minimal phototoxicity. We
present detailed instructions for building a compact and customizable Selective
Plane Illumination Microscopy (SPIM) system. The integrated OpenSPIM hardware
and software platform is shared with the scientific community through a public
website, thereby making light sheet microscopy accessible for widespread use
and optimization to various applications.Comment: 7 pages, 3 figures, 6 supplementary videos, submitted to Nature
Methods, associated public website http://openspim.or
Theory of short-range magnetic order for the t-J model
We present a self-consistent theory of magnetic short-range order based on a
spin-rotation-invariant slave-boson representation of the 2D t-J model. In the
functional-integral scheme, at the nearest-neighbour pair-approximation level,
the bosonized t-J Lagrangian is transformed to a classical Heisenberg model
with an effective (doping-dependent) exchange interaction which takes into
account the interrelation of ``itinerant'' and ``localized'' magnetic
behaviour. Evaluating the theory in the saddle-point approximation, we find a
suppression of antiferromagnetic and incommensurate spiral long-range-ordered
phases in the favour of a paramagnetic phase with pronounced antiferromagnetic
short-range correlations.Comment: 2 pages, 1 Postscript figure, LTpaper.sty, Proc. XXI Int. Conf. on
Low Temp. Phys. Prague 9
On space vehicle attitude stabilization by passive control moment gyros
Equations of motion for passive control moment gyro stabilization of space vehicle attitud
ImageJ2: ImageJ for the next generation of scientific image data
ImageJ is an image analysis program extensively used in the biological
sciences and beyond. Due to its ease of use, recordable macro language, and
extensible plug-in architecture, ImageJ enjoys contributions from
non-programmers, amateur programmers, and professional developers alike.
Enabling such a diversity of contributors has resulted in a large community
that spans the biological and physical sciences. However, a rapidly growing
user base, diverging plugin suites, and technical limitations have revealed a
clear need for a concerted software engineering effort to support emerging
imaging paradigms, to ensure the software's ability to handle the requirements
of modern science. Due to these new and emerging challenges in scientific
imaging, ImageJ is at a critical development crossroads.
We present ImageJ2, a total redesign of ImageJ offering a host of new
functionality. It separates concerns, fully decoupling the data model from the
user interface. It emphasizes integration with external applications to
maximize interoperability. Its robust new plugin framework allows everything
from image formats, to scripting languages, to visualization to be extended by
the community. The redesigned data model supports arbitrarily large,
N-dimensional datasets, which are increasingly common in modern image
acquisition. Despite the scope of these changes, backwards compatibility is
maintained such that this new functionality can be seamlessly integrated with
the classic ImageJ interface, allowing users and developers to migrate to these
new methods at their own pace. ImageJ2 provides a framework engineered for
flexibility, intended to support these requirements as well as accommodate
future needs
Green's-function theory of the Heisenberg ferromagnet in a magnetic field
We present a second-order Green's-function theory of the one- and
two-dimensional S=1/2 ferromagnet in a magnetic field based on a decoupling of
three-spin operator products, where vertex parameters are introduced and
determined by exact relations. The transverse and longitudinal spin correlation
functions and thermodynamic properties (magnetization, isothermal magnetic
susceptibility, specific heat) are calculated self-consistently at arbitrary
temperatures and fields. In addition, exact diagonalizations on finite lattices
and, in the one-dimensional case, exact calculations by the Bethe-ansatz method
for the quantum transfer matrix are performed. A good agreement of the
Green's-function theory with the exact data, with recent quantum Monte Carlo
results, and with the spin polarization of a quantum Hall ferromagnet
is obtained. The field dependences of the position and height of the maximum in
the temperature dependence of the susceptibility are found to fit well to power
laws, which are critically analyzed in relation to the recently discussed
behavior in Landau's theory. As revealed by the spin correlation functions and
the specific heat at low fields, our theory provides an improved description of
magnetic short-range order as compared with the random phase approximation. In
one dimension and at very low fields, two maxima in the temperature dependence
of the specific heat are found. The Bethe-ansatz data for the field dependences
of the position and height of the low-temperature maximum are described by
power laws. At higher fields in one and two dimensions, the temperature of the
specific heat maximum linearly increases with the field.Comment: 9 pages, 9 figure
- …