3,212 research outputs found
Towards the Modeling of Neuronal Firing by Gaussian Processes
This paper focuses on the outline of some computational methods for the
approximate solution of the integral equations for the neuronal firing
probability density and an algorithm for the generation of sample-paths in
order to construct histograms estimating the firing densities. Our results
originate from the study of non-Markov stationary Gaussian neuronal models with
the aim to determine the neuron's firing probability density function. A
parallel algorithm has been implemented in order to simulate large numbers of
sample paths of Gaussian processes characterized by damped oscillatory
covariances in the presence of time dependent boundaries. The analysis based on
the simulation procedure provides an alternative research tool when closed-form
results or analytic evaluation of the neuronal firing densities are not
available.Comment: 10 pages, 3 figures, to be published in Scientiae Mathematicae
Japonica
The Cochlear Tuning Curve
The tuning curve of the cochlea measures how large an input is required to
elicit a given output level as a function of the frequency. It is a fundamental
object of auditory theory, for it summarizes how to infer what a sound was on
the basis of the cochlear output. A simple model is presented showing that only
two elements are sufficient for establishing the cochlear tuning curve: a
broadly tuned traveling wave, moving unidirectionally from high to low
frequencies, and a set of mechanosensors poised at the threshold of an
oscillatory (Hopf) instability. These two components suffice to generate the
various frequency-response regimes which are needed for a cochlear tuning curve
with a high slope
Performance Comparison in the "Follicular Neoplasm" Category Between the American, British, Italian, and Japanese Systems for Reporting Thyroid Cytopathology
It is now almost ten years that the United Stated of America, England, Italy and Japan had their own reporting system to classify thyroid lesions. Important confusion and uncertainties dominated the "follicular-patterned lesions", a category also known as the "gray zone". Every cytopathologist was using a personal terminology to describe and call lesions made up of a variable admixture of macro- and microfollicular structures. These personal views varied considerably between cytopathologists and generated a great deal of confusion among patients (the cytological report being almost incomprehensible to them), clinicians and even within the same cytopathology community. With the advent of national reporting systems, things changed in a better way and standardized reporting systems became the standard of practice in thyroid cytology. The outcome of the widespread use of standardized diagnostic categories was the reduction of descriptive diagnoses and the improved communication between pathologists, clinicians and patients. In this article we review the major reporting systems, analyze their similarities and differences in the "indeterminate" or "follicular-patterned" diagnostic categories, and when possible, try to assess their performance
Large Loops of Magnetic Current and Confinement in Four Dimensional Lattice Gauge Theory
We calculate the heavy quark potential from the magnetic current due to
monopoles in four dimensional lattice gauge theory. The magnetic current
is found from link angle configurations using the DeGrand-Toussaint
identification method. The link angle configurations are generated in a cosine
action simulation on a lattice. The magnetic current is resolved into
large loops which wrap around the lattice and simple loops which do not.
Wrapping loops are found only in the confined phase. It is shown that the long
range part of the heavy quark potential, in particular the string tension, can
be calculated solely from the large, wrapping loops of magnetic current.Comment: 15 pages (Latex file plus 3 postscript files appended), Univeristy of
Illinois Preprint ILL-(TH)-93-\#1
Biotechnological Approach To Preserve Fresh Pasta Quality.
Fresh pasta is highly susceptible to microbial contamination because of its high water activity and nutrient content. In this study, a new biopreservation system was examined that consists of an active sodium alginate solution containing Lactobacillus reuteri and glycerol, which was added during the production process of pasta. Our aim was to extend the fresh pasta shelf life by the in situ production of reuterin, thereby avoiding the use of thermal treatments that generally compromise food sensory characteristics. Two experimental studies were carried out with the product packaged under either ordinary or modified atmospheric conditions. Microbiological and sensory quality indices were monitored to determine the effectiveness of biopreservation on product quality during storage. The use of the active solution with L. reuteri and glycerol during the production process of pasta improved both microbial and sensory quality, particularly when combined with modified atmosphere
Decoupled CFD-based optimization of efficiency and cavitation performance of a double-suction pump
In this study the impeller geometry of a double-suction pump ensuring the best
performances in terms of hydraulic efficiency and reluctance of cavitation is determined using
an optimization strategy
, which was driven by means of the modeFRONTIER optimization
platform. The different impeller shapes (designs) are modified according to the optimization
parameters and tested with a computational fluid dynamics (CFD) software, namely ANSYS
CFX. The simulations are performed using a decoupled approach, where only the impeller
domain region is numerically investigated for computational convenience. The flow losses in
the volute are estimated on the base of the velocity distribution at the impeller outlet. The best
designs are then validated considering the computationally more expensive full geometry CFD
model. The overall results show that the proposed approach is suitable for quick impeller shape
optimization
Numerical Prediction of Cavitating Vortex Rope in a Draft Tube of a Francis Turbine with Standard and Calibrated Cavitation Model
Transient simulations of flow in a Francis turbine were performed with a goal to
predict pressure pulsation frequencies and amplitudes caused by rotating vortex rope at part
load operating regime. Simulations were done with the SAS SST turbulence model with
curvature correction on basic and refined computational meshes. Without cavitation modelling
too small values of frequency and amplitudes were obtained. With mesh refinement the
calculated amplitudes were a bit closer to the measured values, while the accuracy of predicted
frequency did not improve at all. Agreement between measured and numerical values was
significantly improved when cavitation was included in simulations. In addition, the predicted
value of the dominant frequency was slightly more accurate when, in the Zwart et al. cavitation
model, the default condensation and evaporation model constants were replaced with
previously calibrated ones
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