4,985 research outputs found
Further development of a charged liquid colloid source for electrostatic propulsion Final report
Performance characteristics of charged liquid droplet electrostatic propulsion syste
Universal properties of correlation transfer in integrate-and-fire neurons
One of the fundamental characteristics of a nonlinear system is how it
transfers correlations in its inputs to correlations in its outputs. This is
particularly important in the nervous system, where correlations between
spiking neurons are prominent. Using linear response and asymptotic methods for
pairs of unconnected integrate-and-fire (IF) neurons receiving white noise
inputs, we show that this correlation transfer depends on the output spike
firing rate in a strong, stereotyped manner, and is, surprisingly, almost
independent of the interspike variance. For cells receiving heterogeneous
inputs, we further show that correlation increases with the geometric mean
spiking rate in the same stereotyped manner, greatly extending the generality
of this relationship. We present an immediate consequence of this relationship
for population coding via tuning curves
Transition temperature of Josephson junction arrays with long-range interaction
We report measurements of the dependence on magnetic field and array size of the resistive transition of Josephson junction arrays with long-range interaction. Because every wire in these arrays has a large number of nearest neighbors (9 or 18 in our case), a mean-field theory should provide an excellent description of this system. Our data agree well with this mean-field calculation, which predicts that Tc (the temperature below which the array exhibits macroscopic phase coherence) shows very strong commensurability effects and scales with array size
A point process framework for modeling electrical stimulation of the auditory nerve
Model-based studies of auditory nerve responses to electrical stimulation can
provide insight into the functioning of cochlear implants. Ideally, these
studies can identify limitations in sound processing strategies and lead to
improved methods for providing sound information to cochlear implant users. To
accomplish this, models must accurately describe auditory nerve spiking while
avoiding excessive complexity that would preclude large-scale simulations of
populations of auditory nerve fibers and obscure insight into the mechanisms
that influence neural encoding of sound information. In this spirit, we develop
a point process model of the auditory nerve that provides a compact and
accurate description of neural responses to electric stimulation. Inspired by
the framework of generalized linear models, the proposed model consists of a
cascade of linear and nonlinear stages. We show how each of these stages can be
associated with biophysical mechanisms and related to models of neuronal
dynamics. Moreover, we derive a semi-analytical procedure that uniquely
determines each parameter in the model on the basis of fundamental statistics
from recordings of single fiber responses to electric stimulation, including
threshold, relative spread, jitter, and chronaxie. The model also accounts for
refractory and summation effects that influence the responses of auditory nerve
fibers to high pulse rate stimulation. Throughout, we compare model predictions
to published physiological data and explain differences in auditory nerve
responses to high and low pulse rate stimulation. We close by performing an
ideal observer analysis of simulated spike trains in response to sinusoidally
amplitude modulated stimuli and find that carrier pulse rate does not affect
modulation detection thresholds.Comment: 1 title page, 27 manuscript pages, 14 figures, 1 table, 1 appendi
Fireflies at RPA Natural Area Final Report
Our group worked alongside community partners Shaunna Barnhart and Jim Dunn during the Spring 2024 semester to assist with their annual event Fireflies at RPA Natural Area. RPA Natural Area is a local park in South Williamsport, Pennsylvania that was recently acquired by Southside Recreational Authority. Since taking over the park, the organization has begun hosting an event each July to educate the general public about firefly biology and conservation by showing a film and guiding attendees through a firefly tour through the park. Our goals for this project included creating physical educational materials to be used at the park year-round, creating a promotional campaign to bring awareness to the public about both the park and Fireflies at RPA Natural Area, and preparing the event to be scaled up from 50 to roughly 100 attendees. Over the semester, we have created, distributed, and analyzed results from a community survey aiming to better understand current public knowledge on fireflies, produced trail signage and brochures to be printed and used at the park, and designed social media posts and event invitations
Child relationships in the middle grades
Thesis (Ed.M.)--Boston Universit
A Multicanonical Molecular Dynamics Study on a Simple Bead-Spring Model for Protein Folding
We have performed a multicanonical molecular dynamics simulation on a simple
model protein.We have studied a model protein composed of charged, hydrophobic,
and neutral spherical bead monomers.Since the hydrophobic interaction is
considered to significantly affect protein folding, we particularly focus on
the competition between effects of the Coulomb interaction and the hydrophobic
interaction. We found that the transition which occurs upon decreasing the
temperature is markedly affected by the change in both parameters and forms of
the hydrophobic potential function, and the transition changes from first order
to second order, when the Coulomb interaction becomes weaker.Comment: 7 pages, 6 postscript figures, To appear in J.Phys.Soc.Jpn. Vol.70
No.
Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms
Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical
Journal, January, 200
Damage Analysis Modified TRAC Computer Program (DAMTRAC)
A computer program tailored for EMP damage analysis of solid-state circuitry has been developed by modifying the existing TRAC network analysis program. Modification of the TRAC diode and transistor models to include breakdown parameters and the addition of a semiconductor device parameter library have greatly simplified the analyst\u27s task. An added feature is a subroutine that automatically calculates the amplitude and duration of transient power dissipated in electronic circuit components
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