1,363 research outputs found
Thermally activated foaming compositions Patent
Storage stable, thermally activated foaming compositions for erecting and rigidizing mechanisms of thin sheet solar collector
Dynamic roughening of the magnetic flux landscape in YBaCuO
We study the magnetic flux landscape in YBaCuO thin films as
a two dimensional rough surface. The vortex density in the superconductor forms
a self-affine structure in both space and time. This is characterized by a
roughness exponent and a growth exponent .
This is due to the structure and distribution of flux avalanches in the
self-organized critical state, which is formed in the superconductor. We also
discuss our results in the context of other roughening systems in the presence
of quenched disorder.Comment: 13 pages, 7 figures, accepted for publication in Physica
The 2+1 Kepler Problem and Its Quantization
We study a system of two pointlike particles coupled to three dimensional
Einstein gravity. The reduced phase space can be considered as a deformed
version of the phase space of two special-relativistic point particles in the
centre of mass frame. When the system is quantized, we find some possibly
general effects of quantum gravity, such as a minimal distances and a foaminess
of the spacetime at the order of the Planck length. We also obtain a
quantization of geometry, which restricts the possible asymptotic geometries of
the universe.Comment: 59 pages, LaTeX2e, 9 eps figure
Panel Discussion - Management of Eurasian watermilfoil in the United States using native insects: State regulatory and management issues
While researchers have evaluated the potential of native
insect herbivores to manage nonindigenous aquatic plant
species such as Eurasian watermilfoil (
Myriophyllum spicatum
L.), the practical matters of regulatory compliance and implementation
have been neglected. A panel of aquatic nuisance
species program managers from three state natural
resource management agencies (Minnesota, Vermont and
Washington) discussed their regulatory and policy concerns.
In addition, one ecological consultant attempting to market
one of the native insects to manage Eurasian watermilfoil
added his perspective on the special challenges of distributing
a native biological control agent for management of Eurasian
watermilfoil
Broad Absorption Line Variability in Radio-Loud Quasars
We investigate C IV broad absorption line (BAL) variability within a sample
of 46 radio-loud quasars (RLQs), selected from SDSS/FIRST data to include both
core-dominated (39) and lobe-dominated (7) objects. The sample consists
primarily of high-ionization BAL quasars, and a substantial fraction have large
BAL velocities or equivalent widths; their radio luminosities and
radio-loudness values span ~2.5 orders of magnitude. We have obtained 34 new
Hobby-Eberly Telescope (HET) spectra of 28 BAL RLQs to compare to earlier SDSS
data, and we also incorporate archival coverage (primarily dual-epoch SDSS) for
a total set of 78 pairs of equivalent width measurements for 46 BAL RLQs,
probing rest-frame timescales of ~80-6000 d (median 500 d). In general, only
modest changes in the depths of segments of absorption troughs are observed,
akin to those seen in prior studies of BAL RQQs. Also similar to previous
findings for RQQs, the RLQs studied here are more likely to display BAL
variability on longer rest-frame timescales. However, typical values of
|Delta_EW| and |Delta_EW|/ are about 40+/-20% lower for BAL RLQs when
compared with those of a timescale-matched sample of BAL RQQs. Optical
continuum variability is of similar amplitude in BAL RLQs and BAL RQQs; for
both RLQs and RQQs, continuum variability tends to be stronger on longer
timescales. BAL variability in RLQs does not obviously depend upon their radio
luminosities or radio-loudness values, but we do find tentative evidence for
greater fractional BAL variability within lobe-dominated RLQs. Enhanced BAL
variability within more edge-on (lobe-dominated) RLQs supports some geometrical
dependence to the outflow structure.Comment: 27 pages, 16 figures, 6 tables, accepted to MNRAS, full Appendix A at
http://www.macalester.edu/~bmille13/balrlqs.htm
Dynamical Synapses Enhance Neural Information Processing: Gracefulness, Accuracy and Mobility
Experimental data have revealed that neuronal connection efficacy exhibits
two forms of short-term plasticity, namely, short-term depression (STD) and
short-term facilitation (STF). They have time constants residing between fast
neural signaling and rapid learning, and may serve as substrates for neural
systems manipulating temporal information on relevant time scales. The present
study investigates the impact of STD and STF on the dynamics of continuous
attractor neural networks (CANNs) and their potential roles in neural
information processing. We find that STD endows the network with slow-decaying
plateau behaviors-the network that is initially being stimulated to an active
state decays to a silent state very slowly on the time scale of STD rather than
on the time scale of neural signaling. This provides a mechanism for neural
systems to hold sensory memory easily and shut off persistent activities
gracefully. With STF, we find that the network can hold a memory trace of
external inputs in the facilitated neuronal interactions, which provides a way
to stabilize the network response to noisy inputs, leading to improved accuracy
in population decoding. Furthermore, we find that STD increases the mobility of
the network states. The increased mobility enhances the tracking performance of
the network in response to time-varying stimuli, leading to anticipative neural
responses. In general, we find that STD and STP tend to have opposite effects
on network dynamics and complementary computational advantages, suggesting that
the brain may employ a strategy of weighting them differentially depending on
the computational purpose.Comment: 40 pages, 17 figure
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