4,616 research outputs found
TALON - The Telescope Alert Operation Network System: Intelligent Linking of Distributed Autonomous Robotic Telescopes
The internet has brought about great change in the astronomical community,
but this interconnectivity is just starting to be exploited for use in
instrumentation. Utilizing the internet for communicating between distributed
astronomical systems is still in its infancy, but it already shows great
potential. Here we present an example of a distributed network of telescopes
that performs more efficiently in synchronous operation than as individual
instruments. RAPid Telescopes for Optical Response (RAPTOR) is a system of
telescopes at LANL that has intelligent intercommunication, combined with
wide-field optics, temporal monitoring software, and deep-field follow-up
capability all working in closed-loop real-time operation. The Telescope ALert
Operations Network (TALON) is a network server that allows intercommunication
of alert triggers from external and internal resources and controls the
distribution of these to each of the telescopes on the network. TALON is
designed to grow, allowing any number of telescopes to be linked together and
communicate. Coupled with an intelligent alert client at each telescope, it can
analyze and respond to each distributed TALON alert based on the telescopes
needs and schedule.Comment: Presentation at SPIE 2004, Glasgow, Scotland (UK
Interpenetration as a Mechanism for Liquid-Liquid Phase Transitions
We study simple lattice systems to demonstrate the influence of
interpenetrating bond networks on phase behavior. We promote interpenetration
by using a Hamiltonian with a weakly repulsive interaction with nearest
neighbors and an attractive interaction with second-nearest neighbors. In this
way, bond networks will form between second-nearest neighbors, allowing for two
(locally) distinct networks to form. We obtain the phase behavior from analytic
solution in the mean-field approximation and exact solution on the Bethe
lattice. We compare these results with exact numerical results for the phase
behavior from grand canonical Monte Carlo simulations on square, cubic, and
tetrahedral lattices. All results show that these simple systems exhibit rich
phase diagrams with two fluid-fluid critical points and three thermodynamically
distinct phases. We also consider including third-nearest-neighbor
interactions, which give rise to a phase diagram with four critical points and
five thermodynamically distinct phases. Thus the interpenetration mechanism
provides a simple route to generate multiple liquid phases in single-component
systems, such as hypothesized in water and observed in several model and
experimental systems. Additionally, interpenetration of many such networks
appears plausible in a recently considered material made from nanoparticles
functionalized by single strands of DNA.Comment: 12 pages, 9 figures, submitted to Phys. Rev.
Fractional Stokes-Einstein and Debye-Stokes-Einstein relations in a network forming liquid
We study the breakdown of the Stokes-Einstein (SE) and Debye-Stokes-Einstein
(DSE) relations for translational and rotational motion in a prototypical model
of a network-forming liquid, the ST2 model of water. We find that the emergence
of ``fractional'' SE and DSE relations at low temperature is ubiquitous in this
system, with exponents that vary little over a range of distinct physical
regimes. We also show that the same fractional SE relation is obeyed by both
mobile and immobile dynamical heterogeneities of the liquid
Intercomparison of standard resolution and high resolution TOVS soundings with radiosonde, lidar, and surface temperature/humidity data
One objective of the FIRE Cirrus IFO is to characterize relationships between cloud properties inferred from satellite observations at various scales to those obtained directly or inferred from very high resolution measurements. Satellite derived NOAA-9 high and standard resolution Tiros Operational Vertical Sounder (TOVS) soundings are compared with directly measured lidar, surface temperature, humidity, and vertical radiosonde profiles associated with the Ft. McCoy site. The results of this intercomparison should be useful in planning future cloud experiments
Instantaneous Normal Mode Analysis of Supercooled Water
We use the instantaneous normal mode approach to provide a description of the
local curvature of the potential energy surface of a model for water. We focus
on the region of the phase diagram in which the dynamics may be described by
the mode-coupling theory. We find, surprisingly, that the diffusion constant
depends mainly on the fraction of directions in configuration space connecting
different local minima, supporting the conjecture that the dynamics are
controlled by the geometric properties of configuration space. Furthermore, we
find an unexpected relation between the number of basins accessed in
equilibrium and the connectivity between them.Comment: 5 pages, 4 figure
Dynamical Behavior Near a Liquid-Liquid Phase Transition in Simulations of Supercooled Water
We examine the behavior of the diffusion coefficient of the ST2 model of
water over a broad region of the phase diagram via molecular dynamics
simulations. The ST2 model has an accessible liquid-liquid transition between
low-density and high-density phases, making the model an ideal candidate to
explore the impacts of the liquid-liquid transition on dynamics. We locate
characteristic dynamical loci in the phase diagram and compare them with the
previously investigated thermodynamic loci. The low-density liquid phase shows
a crossover from non-Arrhenius to Arrhenius behavior, signaling the onset of a
crossover from fragile-to-strong behavior. We explain this crossover in terms
of the asymptotic approach of the low-density liquid to a random tetrahedral
network, and show that the temperature dependence of the diffusion coefficient
over a wide temperature range can be simply related to the concentration of
defects in the network. Our findings thus confirm that the low-density phase of
ST2 water is a well-defined metastable liquid.Comment: 21 pages, 9 figure
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