2,818 research outputs found
Letter from H. L. Hille to Senator Langer Regarding Construction Bids for the Garrison Dam Project, January 31, 1955
This letter, dated January 31, 1955, from Colonel H. L. Hille of the United States (US) Army Corps of Engineers, Garrison District, to US Senator William Langer, informs Langer of the planned invitation for bids for two components of the the Garrison Dam Project taking place on the Fort Berthold Indian Reservation: lawn construction in New Town, North Dakota, on which bids will be opened on or around March 1, 1955, and the construction of the East Abutment Grout Curtain, on which bids will be opened on or about March 15, 1955.
The letter includes more detailed descriptions of the two projects, and enclosed with it are advance notices for each of the two projects. Advance notices, Hille writes, have been sent to all parties who are known to be interesed in bidding on the work.
See also: Letter from Senator Langer to H. L. Hille Regarding Construction Bids for the Garrison Dam Project, February 8, 1955https://commons.und.edu/langer-papers/1993/thumbnail.jp
Sensing of Fluctuating Nanoscale Magnetic Fields Using NV Centres in Diamond
New magnetometry techniques based on Nitrogen-Vacancy (NV) defects in diamond
allow for the imaging of static (DC) and oscillatory (AC) nanoscopic magnetic
systems. However, these techniques require accurate knowledge and control of
the sample dynamics, and are thus limited in their ability to image fields
arising from rapidly fluctuating (FC) environments. We show here that FC fields
place restrictions on the DC field sensitivity of an NV qubit magnetometer, and
that by probing the dephasing rate of the qubit in a magnetic FC environment,
we are able to measure fluctuation rates and RMS field strengths that would be
otherwise inaccessible with the use of DC and AC magnetometry techniques. FC
sensitivities are shown to be comparable to those of AC fields, whilst
requiring no additional experimental overheads or control over the sample.Comment: 5 pages, 4 figure
Letter from H. L. Hille to Representative Burdick Announcing Invitation of Bids for Lawn Construction on Fort Berthold Reservation, January 31, 1955
This letter dated January 31, 1955, from Colonel H. L. Hille to United States (US) Representative Usher Burdick, informs Burdick that the US Army Corps of Engineers proposes to issue an invitation for bids for lawn construction on the Fort Berthold Reservation. Hille details what the work will entail and where it will take place. Hille notes he has included a copy of the invitation for project bids with this letter.
The included invitation for project bids gives specifics needed for a firm to submit an accurate bid and lists the required components for a submission.https://commons.und.edu/burdick-papers/1382/thumbnail.jp
Focusing in Multiwell Potentials: Applications to Ion Channels
We investigate out of equilibrium stationary distributions induced by a
stochastic dichotomous noise on double and multi-well models for ion channels.
Ion-channel dynamics is analyzed both through over-damped Langevin equations
and master equations. As a consequence of the external stochastic noise, we
prove a non trivial focusing effect, namely the probability distribution is
concentrated only on one state of the multi-well model. We also show that this
focusing effect, which occurs at physiological conditions, cannot be predicted
by a simple master equation approach.Comment: 8 pages, 7 figure
New derivation for the equations of motion for particles in electromagnetism
We present equations of motion for charged particles using balanced
equations, and without introducing explicitly divergent quantities. This
derivation contains as particular cases some well known equations of motion, as
the Lorentz-Dirac equations. An study of our main equations in terms of order
of the interaction with the external field conduces us to the Landau-Lifshitz
equations. We find that the analysis in second order show a special behavior.
We give an explicit presentation up to third order of our main equations, and
expressions for the calculation of general orders.Comment: 11 pages, 2 figures. Minor changes. Closer to published versio
Steady state existence of passive vector fields under the Kraichnan model
The steady state existence problem for Kraichnan advected passive vector
models is considered for isotropic and anisotropic initial values in arbitrary
dimension. The model includes the magnetohydrodynamic (MHD) equations, linear
pressure model (LPM) and linearized Navier-Stokes (LNS) equations. In addition
to reproducing the previously known results for the MHD and linear pressure
model, we obtain the values of the Kraichnan model roughness parameter
for which the LNS steady state exists.Comment: Improved text & figures, added references & other correction
Optimization of the leak conductance in the squid giant axon
We report on a theoretical study showing that the leak conductance density,
\GL, in the squid giant axon appears to be optimal for the action potential
firing frequency. More precisely, the standard assumption that the leak current
is composed of chloride ions leads to the result that the experimental value
for \GL is very close to the optimal value in the Hodgkin-Huxley model which
minimizes the absolute refractory period of the action potential, thereby
maximizing the maximum firing frequency under stimulation by sharp, brief input
current spikes to one end of the axon. The measured value of \GL also appears
to be close to optimal for the frequency of repetitive firing caused by a
constant current input to one end of the axon, especially when temperature
variations are taken into account. If, by contrast, the leak current is assumed
to be composed of separate voltage-independent sodium and potassium currents,
then these optimizations are not observed.Comment: 9 pages; 9 figures; accepted for publication in Physical Review
Biased Brownian motion in extreme corrugated tubes
Biased Brownian motion of point-size particles in a three-dimensional tube
with smoothly varying cross-section is investigated. In the fashion of our
recent work [Martens et al., PRE 83,051135] we employ an asymptotic analysis to
the stationary probability density in a geometric parameter of the tube
geometry. We demonstrate that the leading order term is equivalent to the
Fick-Jacobs approximation. Expression for the higher order corrections to the
probability density are derived. Using this expansion orders we obtain that in
the diffusion dominated regime the average particle current equals the
zeroth-order Fick-Jacobs result corrected by a factor including the corrugation
of the tube geometry. In particular we demonstrate that this estimate is more
accurate for extreme corrugated geometries compared to the common applied
method using the spatially dependent diffusion coefficient D(x,f). The analytic
findings are corroborated with the finite element calculation of a
sinusoidal-shaped tube.Comment: 10 pages, 4 figure
Monte Carlo simulation for statistical mechanics model of ion channel cooperativity in cell membranes
Voltage-gated ion channels are key molecules for the generation and
propagation of electrical signals in excitable cell membranes. The
voltage-dependent switching of these channels between conducting and
nonconducting states is a major factor in controlling the transmembrane
voltage. In this study, a statistical mechanics model of these molecules has
been discussed on the basis of a two-dimensional spin model. A new Hamiltonian
and a new Monte Carlo simulation algorithm are introduced to simulate such a
model. It was shown that the results well match the experimental data obtained
from batrachotoxin-modified sodium channels in the squid giant axon using the
cut-open axon technique.Comment: Paper has been revise
Non-Markovian Stochastic Resonance: three state model of ion channel gating
Stochastic Resonance in single voltage-dependent ion channels is investigated
within a three state non-Markovian modeling of the ion channel conformational
dynamics. In contrast to a two-state description one assumes the presence of an
additional closed state for the ion channel which mimics the manifold of
voltage-independent closed subconformations (inactivated ``state''). The
conformational transition into the open state occurs through a domain of
voltage-dependent closed subconformations (closed ``state''). At distinct
variance with a standard two-state or also three-state Markovian approach, the
inactivated state is characterized by a broad, non-exponential probability
distribution of corresponding residence times. The linear response to a
periodic voltage signal is determined for arbitrary distributions of the
channel's recovery times. Analytical results are obtained for the spectral
amplification of the applied signal and the corresponding signal-to-noise
ratio. Alternatively, these results are also derived by use of a corresponding
two-state non-Markovian theory which is based on driven integral renewal
equations [I. Goychuk and P. Hanggi, Phys. Rev. E 69, 021104 (2004)]. The
non-Markovian features of stochastic resonance are studied for a power law
distribution of the residence time-intervals in the inactivated state which
exhibits a large variance. A comparison with the case of bi-exponentially
distributed residence times possessing the same mean value, i.e. a simplest
non-Markovian two-state description, is also presented
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