4,439 research outputs found
Thermodynamic Limit for Spin Glasses. Beyond the Annealed Bound
Using a correlation inequality of Contucci and Lebowitz for spin glasses, we
demonstrate existence of the thermodynamic limit for short-ranged spin glasses,
under weaker hypotheses than previously available, namely without the
assumption of the annealed bound.Comment: 8 page
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
SkyDOT (Sky Database for Objects in the Time Domain): A Virtual Observatory for Variability Studies at LANL
The mining of Virtual Observatories (VOs) is becoming a powerful new method
for discovery in astronomy. Here we report on the development of SkyDOT (Sky
Database for Objects in the Time domain), a new Virtual Observatory, which is
dedicated to the study of sky variability. The site will confederate a number
of massive variability surveys and enable exploration of the time domain in
astronomy. We discuss the architecture of the database and the functionality of
the user interface. An important aspect of SkyDOT is that it is continuously
updated in near real time so that users can access new observations in a timely
manner. The site will also utilize high level machine learning tools that will
allow sophisticated mining of the archive. Another key feature is the real time
data stream provided by RAPTOR (RAPid Telescopes for Optical Response), a new
sky monitoring experiment under construction at Los Alamos National Laboratory
(LANL).Comment: to appear in SPIE proceedings vol. 4846, 11 pages, 5 figure
Noncompete Agreements in the U.S. Labor Force
Using nationally representative survey data on 11,505 labor force participants, we examine the use and implementation of noncompete agreements and the employee outcomes associated with these provisions. Approximately 18 percent of labor force participants are bound by noncompetes, with 38 percent having agreed to at least one in the past. Noncompetes are more likely to be found in high-skill, high-paying jobs, but they are also common in low-skill, low-paying jobs and in states where noncompetes are unenforceable. Only 10 percent of employees negotiate over their noncompetes, and about one-third of employees are presented with noncompetes after having already accepted job offers. Early-notice noncompetes are associated with better employee outcomes, while employees who agree to late-notice noncompetes are comparatively worse off. Regardless of noncompete timing, however, wages are relatively lower where noncompetes are easier to enforce. We discuss these findings in light of competing theories of the economic value of noncompetes
Potential Energy Landscape of the Apparent First-Order Phase Transition between Low-Density and High-Density Amorphous Ice
The potential energy landscape (PEL) formalism is a valuable approach within
statistical mechanics for describing supercooled liquids and glasses. Here we
use the PEL formalism and computer simulations to study the pressure-induced
transformations between low-density amorphous ice (LDA) and high-density
amorphous ice (HDA) at different temperatures. We employ the ST2 water model
for which the LDA-HDA transformations are remarkably sharp, similar to what is
observed in experiments, and reminiscent of a first-order phase transition. Our
results are consistent with the view that LDA and HDA configurations are
associated with two distinct regions (megabasins) of the PEL that are separated
by a potential energy barrier. At higher temperature, we find that low-density
liquid (LDL) configurations are located in the same megabasin as LDA, and that
high-density liquid (HDL) configurations are located in the same megabasin as
HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations
occur along paths that interconnect these two megabasins, but that the path
followed by the liquid is different than the path followed by the amorphous
solid. At higher pressure, we also study the liquid-to-ice-VII first-order
phase transition, and find that the behavior of the PEL properties across this
transition are qualitatively similar to the changes found during the LDA-HDA
transformation. This similarity supports the interpretation that the LDA-HDA
transformation is a first-order-like phase transition between
out-of-equilibrium states.Comment: 29 pages, 8 figure
Competition of the connectivity with the local and the global order in polymer melts and crystals
The competition between the connectivity and the local or global order in
model fully-flexible chain molecules is investigated by molecular-dynamics
simulations. States with both missing (melts) and high (crystal) global order
are considered. Local order is characterized within the first coordination
shell (FCS) of a tagged monomer and found to be lower than in atomic systems in
both melt and crystal. The role played by the bonds linking the tagged monomer
to FCS monomers (radial bonds), and the bonds linking two FCS monomers (shell
bonds) is investigated. The detailed analysis in terms of Steinhardt's
orientation order parameters Q_l (l = 2 - 10) reveals that increasing the
number of shell bonds decreases the FCS order in both melt and crystal.
Differently, the FCS arrangements organize the radial bonds. Even if the
molecular chains are fully flexible, the distribution of the angle formed by
adjacent radial bonds exhibits sharp contributions at the characteristic angles
{\theta} = 70{\deg}, 122{\deg}, 180{\deg}. The fractions of adjacent radial
bonds with {\theta} = 122{\deg}, 180{\deg} are enhanced by the global order of
the crystal, whereas the fraction with 70{\deg} < {\theta} < 110{\deg} is
nearly unaffected by the crystallization. Kink defects, i.e. large lateral
displacements of the chains, are evidenced in the crystalline state.Comment: J. Chem. Phys. in pres
Thermodynamics, Structure, and Dynamics of Water Confined between Hydrophobic Plates
We perform molecular dynamics simulations of 512 water-like molecules that
interact via the TIP5P potential and are confined between two smooth
hydrophobic plates that are separated by 1.10 nm. We find that the anomalous
thermodynamic properties of water are shifted to lower temperatures relative to
the bulk by K. The dynamics and structure of the confined water
resemble bulk water at higher temperatures, consistent with the shift of
thermodynamic anomalies to lower temperature. Due to this shift, our
confined water simulations (down to K) do not reach sufficiently low
temperature to observe a liquid-liquid phase transition found for bulk water at
K using the TIP5P potential. We find that the different
crystalline structures that can form for two different separations of the
plates, 0.7 nm and 1.10 nm, have no counterparts in the bulk system, and
discuss the relevance to experiments on confined water.Comment: 31 pages, 14 figure
Convergence of the waste and water sectors: risks, opportunities and future trends – discussion paper
The aim of this discussion paper is to bring to light the increasing convergence of the water and waste sectors and the associated risks, benefits, and future trends already on the horizon. Current examples of convergence in managing coal seam gas (CSG), food waste, fats, oils and grease (FOG) and biosolids, provide insights into not only the risks to public and environmental health of waste streams that cross sectoral boundaries but also potential opportunities for the water and waste sectors to seize as business opportunities. What is clear is that convergence between these sectors is already happening and in some cases there are adverse environmental consequences and associated health impacts. A key message from this research is the need to take an integrated and coordinated approach to planning and regulating the convergence of the water and waste sectors. Key recommendations to manage the risks associated with cross sector convergence of the water and waste sectors include facilitating: (1) increased engagement between regulators of each sector, (2) greater communication across sectors (3) a co-ordinated approach and plan to managing waste streams, (4) the development of monitoring and evaluation frameworks that cross sectors and (5) a coordinated approach to the assessment of research needs
Fast Ray Tracing of Lunar Digital Elevation Models
Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment
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