Rhythmic firing patterns in SCN: The role of circuit interactions

The suprachiasmatic nucleus (SCN) is believed to contain the main generator of circadian rhythmicity in mammals. In order to obtain further functional details of this, electrophysiological extracellular measurements in vitro were made. By means of an interspike interval distribution analysis, it is shown that there is a novel kind of neuronal firing pattern: the harmonic pattern. From these observations, we have developed a theoretical model based on possible filtering processes occurring during synaptic transmission. The model suffices to infer that regular ultradian oscillators could be an emergent property of circuit interactions of cells in the suprachiasmatic nucleus

How to generate pentagonal symmetry using Turing systems

We explore numerically the formation of Turing patterns in a confined circular domain with small aspect ratio. Our results show that stable fivefold patterns are formed over a well defined range of disk sizes, offering a possible mechanism for inducing the fivefold symmetry observed in early development of regular echinoids. Using this pattern as a seed, more complex biological structures can be mimicked, such as the pigmentation pattern of sea urchins and the plate arrangements of the calyxes of primitive camerate crinoids

Kneadings, Symbolic Dynamics and Painting Lorenz Chaos. A Tutorial

A new computational technique based on the symbolic description utilizing kneading invariants is proposed and verified for explorations of dynamical and parametric chaos in a few exemplary systems with the Lorenz attractor. The technique allows for uncovering the stunning complexity and universality of bi-parametric structures and detect their organizing centers - codimension-two T-points and separating saddles in the kneading-based scans of the iconic Lorenz equation from hydrodynamics, a normal model from mathematics, and a laser model from nonlinear optics.Comment: Journal of Bifurcations and Chaos, 201

Diagnosing microscopic pancreatic neuroendocrine tumor using 68-Ga-DOTATATE PET/CT: case series

Neuroendocrine tumors (NETs) are an uncommon diagnosis which often present asymptomatically or with vague symptoms. They can originate from many different organs such as the GI tract, lungs, pancreas and others. 68Gallium DOTATATE positron emission topography/computed topography has been shown to be an effective imaging modality for diagnosing NET and evaluating management options for patients. Here, we present two cases of positive findings in the distal pancreas on the DOTATATE PET/CT scans without any morphological lesion found to be NET in a healthy 48-year-old male and 68-year-old male

Non-linear effects on Turing patterns: time oscillations and chaos.

We show that a model reaction-diffusion system with two species in a monostable regime and over a large region of parameter space, produces Turing patterns coexisting with a limit cycle which cannot be discerned from the linear analysis. As a consequence, Turing patterns oscillate in time, a phenomenon which is expected to occur only in a three morphogen system. When varying a single parameter, a series of bifurcations lead to period doubling, quasi-periodic and chaotic oscillations without modifying the underlying Turing pattern. A Ruelle-Takens-Newhouse route to chaos is identified. We also examined the Turing conditions for obtaining a diffusion driven instability and discovered that the patterns obtained are not necessarily stationary for certain values of the diffusion coefficients. All this results demonstrates the limitations of the linear analysis for reaction-diffusion systems

Economic evaluation of football players through media value

This paper describes an approach based on media value to evaluate sport talent. We then apply this methodology to estimate the theoretical value of transfer fees for professional football players. First, we compute the individual index of media value and e xpressed it with respect to the average of the top 2,500 players included in our data set of more than 5,000 individuals. The media value score is the factor by which the number of news of a player multiplies the news articles of the normal (average) playe r in our sample. Based on individual appraisals, we then work out the media value rank of football teams and leagues. To calculate the theoretical value of football players, we estimate regression models using as dependent variable the transfer fees actu ally paid. Our analyses allow us to conclude that, in determining the theoretical transfer fee of a player, it is necessary to consider a few variables, among which the media value status plays a major role. Other explanatory variables to explain the trans fer fees are: contract duration, economic status of the hiring team, number of years of experience (quadratic form), player's age at the end of the contract, and media value share of the player within his team

How the UEFA Financial Fair Play regulations affect football clubs’ priorities and leagues’ competitive balance?

Institutional and legal reforms applied in the context of sports competitions often provoke structural changes that can be empirically investigated. Using a data set of 560 observations (20 teams per season, from 2009/10 to 2015/16, of teams playing in the Premier League, La Liga, Serie A and Ligue 1), this paper examines how the UEFA Financial Fair Play (FFP) regulations may have altered the football clubs’ decisions concerning their sport and financial priorities. Moreover, based on a simple theoretical description, the paper shows that the increasing financial stability promoted by the FFP rules might actually imply – as an undesired side effect – a declined competitive balance affecting the European football leagues. Finally, the paper discusses some policy issues and recommendations

To comply or not to comply? How a UEFA wage-to-revenue requirement might affect the sport and managerial performance of soccer clubs

This paper evaluates the soccer clubs' compliance with a potential wage-to-revenue requirement by the Union of European Football Associations (UEFA) and studies the effect on sport achievements resulting from sports and managerial skills. The empirical analysis uses data on first division teams of the Premier League, La Liga, Serie A, and Ligue 1, from seasons 2009/2010 to 2018/2019. We measure the teams' quality through the annual wages and use the wage-to-revenue ratio as a proxy measure for financial responsibility. Our results reveal that a more prudent financial performance, which is generally linked to good management practices, implies better sport performance and higher chances of qualifying for UEFA competitions

Modeling the skin pattern of fishes

Complicated patterns showing various spatial scales have been obtained in the past by coupling Turing systems in such a way that the scales of the independent systems resonate. This produces superimposed patterns with different length scales. Here we propose a model consisting of two identical reaction-diffusion systems coupled together in such a way that one of them produces a simple Turing pattern of spots or stripes, and the other traveling wave fronts that eventually become stationary. The basic idea is to assume that one of the systems becomes fixed after some time and serves as a source of morphogens for the other system. This mechanism produces patterns very similar to the pigmentation patterns observed in different species of stingrays and other fishes. The biological mechanisms that support the realization of this model are discussed

Symbolic Toolkit for Chaos Explorations

New computational technique based on the symbolic description utilizing kneading invariants is used for explorations of parametric chaos in a two exemplary systems with the Lorenz attractor: a normal model from mathematics, and a laser model from nonlinear optics. The technique allows for uncovering the stunning complexity and universality of the patterns discovered in the bi-parametric scans of the given models and detects their organizing centers -- codimension-two T-points and separating saddles.Comment: International Conference on Theory and Application in Nonlinear Dynamics (ICAND 2012