Diversity and noise effects in a model of homeostatic regulation of the sleep-wake cycle

Recent advances in sleep neurobiology have allowed development of physiologically based mathematical models of sleep regulation that account for the neuronal dynamics responsible for the regulation of sleep-wake cycles and allow detailed examination of the underlying mechanisms. Neuronal systems in general, and those involved in sleep regulation in particular, are noisy and heterogeneous by their nature. It has been shown in various systems that certain levels of noise and diversity can significantly improve signal encoding. However, these phenomena, especially the effects of diversity, are rarely considered in the models of sleep regulation. The present paper is focused on a neuron-based physiologically motivated model of sleep-wake cycles that proposes a novel mechanism of the homeostatic regulation of sleep based on the dynamics of a wake-promoting neuropeptide orexin. Here this model is generalized by the introduction of intrinsic diversity and noise in the orexin-producing neurons in order to study the effect of their presence on the sleep-wake cycle. A quantitative measure of the quality of a sleep-wake cycle is introduced and used to systematically study the generalized model for different levels of noise and diversity. The model is shown to exhibit a clear diversity-induced resonance: that is, the best wake-sleep cycle turns out to correspond to an intermediate level of diversity at the synapses of the orexin-producing neurons. On the other hand only a mild evidence of stochastic resonance is found when the level of noise is varied. These results show that disorder, especially in the form of quenched diversity, can be a key-element for an efficient or optimal functioning of the homeostatic regulation of the sleep-wake cycle. Furthermore, this study provides an example of constructive role of diversity in a neuronal system that can be extended beyond the system studied here.Comment: 18 pages, 12 figures, 1 tabl

Constructive effects of diversity in a multi-neuron model of the homeostatic regulation of the sleep-wake cycle

As an instance of diversity-induced resonance and of the constructive role of heterogeneity in complex systems, here we study a generalized version of a physiologically-motivated sleep-wake cycle model taking into account the role of orexin [Patriarca et al. (2012) [16]; Postnova et al. (2009) [9]]. With respect to the versions of the model studied previously, here we consider systems containing both a set of orexin neurons - responsible for the production of orexin - and a set of glutaminergic neurons - representing mental activity or sleep depending on their firing or silent state, respectively - within some basic network topologies. The neurons of one or both types are diversified and it is shown how the interplay between the heterogeneous constituent units produces as an emergent effect the recovering or improving of the sleep-wake cycle. At a general level, the results obtained suggest that also systems with a dynamics driven by a homeostatic mechanism, with a time scale much longer than that of the constituent excitable units, may present diversity-induced resonance.M.P. acknowledges support from the Estonian Science Foundation Grant no. 9462 and the Institutional Research Funding IUT (IUT39-1) of the Estonian Ministry of Education and Research. E.H-G. and R.T. acknowledge support from FEDER and MINECO (Spain) through the project INTENSE@COSYP (FIS2012-30634).Peer Reviewe

Multilevel sampling system for gas analyser in circulating fluidized bed gasification

The main topic of this Master’s Thesis is the development of a multilevel sampling system for gas analysers, in which a single gas analyser can measure the gas composition from gasification or combustion, in three different levels in a riser of a circulating fluidized bed reactor. The two analysers used in this work were the Dx-4000 GASMET gas analyser and the Siemens ULTRAMAT 23 gas analysers. The multilevel sampling system consist of three levels, which are connected to the reactor by steel pipes. There is a computer controlled solenoid valves that controls which level is sampled. In addition, there is an oil scrubber in each level to protect the system from unwanted and dangerous substances such as tar. Heat transfer equations have been used in the process of designing the multilevel system in order to not surpass the maximum allowable temperature of some components. The residence time has also been considered in designing the system, as it is an important parameter, since it had to be as short as possible to avoid some changes in the composition of the gas sampled as well as increasing the acquired amount of reliable measurement data from each test. Finally, the transitional and steady time (residence time) for reliable measurements were calculated for both analysers, obtaining 60 seconds of reliable measurements for GASMET analyser and 40 seconds for ULTRAMAT analyser. One combustion test was done in order to check that the system worked correctly, whose the results were satisfactory

Generalized sampling in U-invariant subspaces

In this work we carry out some results in sampling theory for U-invariant subspaces of a separable Hilbert space H, also called atomic subspaces. These spaces are a generalization of the well-known shift- invariant subspaces in L2 (R); here the space L2 (R) is replaced by H, and the shift operator by U. Having as data the samples of some related operators, we derive frame expansions allowing the recovery of the elements in Aa. Moreover, we include a frame perturbation-type result whenever the samples are affected with a jitter error

Diversity-induced resonance in a system of globally coupled linear oscillators

The purpose of this paper to analyze in some detail the arguably simplest case of diversity-induced reseonance: that of a system of globally-coupled linear oscillators subjected to a periodic forcing. Diversity appears as the parameters characterizing each oscillator, namely its mass, internal frequency and damping coefficient are drawn from a probability distribution. The main ingredients for the diversity-induced-resonance phenomenon are present in this system as the oscillators display a variability in the individual responses but are induced, by the coupling, to synchronize their responses. A steady state solution for this model is obtained. We also determine the conditions under which it is possible to find a resonance effect.Comment: Reported at the XI International Workshop "Instabilities and Nonequilibrium Structures" Vina del Mar (Chile

Modelling the dispersion of non-conservative radionuclides in tidal waters—Part 1: Conceptual and mathematical model

A 2D four-phase model to study the dispersion of non-conservative radionuclides in tidal waters, in conditions of disequilibrium for ionic exchanges, has been developed. At disequilibrium conditions, ionic exchanges cannot be formulated using distribution coefficients kd. Thus, kinetic transfer coefficients have been used. The model includes ionic exchanges among water and the solid phases (suspended matter and two grain size fractions of sediments), the deposition and resuspension of suspended matter and advective plus diffusive transport. In the second part of this work, which is presented in a separate paper, the model is applied to simulate 226Ra dispersion, discharged from a fertilizer processing plant, in an estuarine system in the south-west of Spain.European Union FI3P-CT92-003

Inhibiting crypto‐ransomware on windows platforms through a honeyfile‐based approach with R‐Locker

Ministerio de Economia y Competitividad, Grant/Award Number: TIN2017-83494-RAfter several years, crypto‐ransomware attacks still constitute a principal threat for individuals and organisations worldwide. Despite the fact that a number of solutions are deployed to fight against this plague, one main challenge is that of early reaction, as merely detecting its occurrence can be useless to avoid the pernicious effects of the malware. With this aim, the authors introduced in a previous work a novel antiransomware tool for Unix platforms named R‐Locker. The proposal is supported on a honeyfile‐based approach, where ‘infinite’ trap files are disseminated around the target filesystem for early detection and to effectively block the ransomware action. The authors extend here the tool with three main new contributions. First, R‐Locker is migrated to Windows platforms, where specific differences exist regarding FIFO handling. Second, the global management of the honeyfiles around the target filesystem is now improved to maximise protection. Finally, blocking suspicious ransomware is (semi)automated through the dynamic use of white‐/black‐lists. As in the original work for Unix systems, the new Windows version of R‐Locker shows high effectivity and efficiency in thwarting ransomware action.Spanish Government TIN2017-83494-

Modelling the suspended matter distribution in an estuarine system : Application to the Odiel river in southwest Spain

A numerical model which solves the advective-diffusive dispersion equation for suspended matter and includes the deposition and resuspension is presented. The model requires the simultaneous solution of the hydrodynamic equations under tidal dynamics and atmospheric forcing, using time steps of a few seconds. The model has been applied to the Odiel river (southwest Spain). The hydrodynamic module has been widely validated for neap and medium tides, whereas the dispersion was calibrated against the dissolved 226Ra dispersion pattern. This 226Ra is discharged to the Odiel river from a phosphate fertilizer factory. The model was able to reproduce the observed behaviour of the suspended matter in the estuary. The sedimentation rates have shown that a net, although slow, sedimentation is being produced. Sensitivity tests were inconclusive with respect to parameters describing settling and resuspension, as internal processes within the estuary are overridden by the high influx and efflux of particulate material from the sea.Comisión Interministerial de Ciencia y Tecnología (CICYT) PB89-062

A modeling study of Ra-226 dispersion in an estuarine system in south-west Spain

A numerical model to study 226Ra dispersion in the Odiel River, in which two fertilizer plants release their wastes, has been developed. The hydrodynamic equations have been solved to obtain the instantaneous water state which allows us to describe the advective and diffusive transport of the radionuclides. The hydrodynamic model has been calibrated in order to reproduce field data. Diffusion coefficients have been formulated taking into account the shear effect. Good agreement between calculated and experimentally measured 226Ra concentrations has been achieved. The source term, which was unknown, has been investigated and found to be comparable to that of other fertilizer plants.Comisión Interministerial de Ciencia y Tecnología (CICYT) PB89-062

Torsión testicular: reporte de un caso

ResumenAntecedentesEl escroto agudo es una urgencia y la torsión testicular representa aproximadamente el 25% de las causas. La incidencia anual de torsión testicular es aproximadamente 1/4,000 menores de 25 años, con mayor prevalencia entre los 12 y 18 años de edad. Generalmente ocurre sin causa aparente; sin embargo, se han asociado factores anatómicos, traumáticos, ambientales, entre otros.Caso clínicoAcude al servicio de urgencias un varón de 15 años de edad, sin antecedentes de importancia. Inició su padecimiento al presentar dolor súbito y continuo en testículo izquierdo, progresivo, con irradiación a la región abdominal e inguinal izquierda, acompañado de náuseas y vómitos, con más de 12 h de evolución a su llegada. El ultrasonido doppler reportó cambios sugestivos de torsión testicular, por lo cual, se realizó tratamiento quirúrgico. Los hallazgos fueron un testículo izquierdo necrótico, con rotación del cordón espermático de 360°, por lo cual se realizó orquiectomía izquierda.ConclusiónLa torsión testicular siempre debe ser considerada como una de las causas principales de dolor escrotal agudo. Se deben evitar retrasos en el diagnóstico, ya que el retraso en su atención está directamente relacionado con el porcentaje de salvamento testicular y con su pérdida.AbstractBackgroundThe acute scrotum is an emergency. Testicular torsion represents approximately 25% of the causes. The annual incidence of testicular torsion is approximately 1/4,000 persons under 25 years, with highest prevalence between 12 and 18 years old. It usually occurs without apparent cause, but it has been associated with anatomical, traumatic, and environmental factors, among others.Clinical caseA male 15 year-old male, with no history of importance, was seen in the Emergency Department, presenting with a sudden and continuous pain in the left testicle. It was accompanied by a pain that radiated to the abdomen and left inguinal area, with nausea and vomiting of more than 12h onset. Doppler ultrasound showed changes suggestive of testicular torsion. Surgery was performed that showed findings of a necrotic left testicle with rotation of the spermatic cord of 360°. A left orchiectomy was performed.ConclusionsTesticular torsion should always be considered one of the leading causes of acute scrotal pain. Delays in diagnosis should be avoided as this is directly related to the percentage of testicular salvage or loss