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 U(1)U(1) Lattice Gauge Theory

We calculate the heavy quark potential from the magnetic current due to monopoles in four dimensional $U(1)$ 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 $24^4$ 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