Anticipated synchronization in coupled chaotic maps with delays

We study the synchronization of two chaotic maps with unidirectional (master-slave) coupling. Both maps have an intrinsic delay $n_1$, and coupling acts with a delay $n_2$. Depending on the sign of the difference $n_1-n_2$, the slave map can synchronize to a future or a past state of the master system. The stability properties of the synchronized state are studied analytically, and we find that they are independent of the coupling delay $n_2$. These results are compared with numerical simulations of a delayed map that arises from discretization of the Ikeda delay-differential equation. We show that the critical value of the coupling strength above which synchronization is stable becomes independent of the delay $n_1$ for large delays.Comment: 10 pages, 4 figure

Noise-assisted Multibit Storage Device

In this paper we extend our investigations on noise-assisted storage devices through the experimental study of a loop composed of a single Schmitt trigger and an element that introduces a finite delay. We show that such a system allows the storage of several bits and does so more efficiently for an intermediate range of noise intensities. Finally, we study the probability of erroneous information retrieval as a function of elapsed time and show a way for predicting device performance independently of the number of stored bits.Comment: 5 figure

Recent advances on information transmission and storage assisted by noise

The interplay between nonlinear dynamic systems and noise has proved to be of great relevance in several application areas. In this presentation, we focus on the areas of information transmission and storage. We review some recent results on information transmission through nonlinear channels assisted by noise. We also present recent proposals of memory devices in which noise plays an essential role. Finally, we discuss new results on the influence of noise in memristors.Comment: To be published in "Theory and Applications of Nonlinear Dynamics: Model and Design of Complex Systems", Proceedings of ICAND 2012 (Springer, 2014

Characteristics of a Delayed System with Time-dependent Delay Time

The characteristics of a time-delayed system with time-dependent delay time is investigated. We demonstrate the nonlinearity characteristics of the time-delayed system are significantly changed depending on the properties of time-dependent delay time and especially that the reconstructed phase trajectory of the system is not collapsed into simple manifold, differently from the delayed system with fixed delay time. We discuss the possibility of a phase space reconstruction and its applications.Comment: 4 pages, 6 figures (to be published in Phys. Rev. E

High gravity primary continuous beer fermentation using flocculent yeast biomass

The current work assessed a new immobilized cell reactor system throughout a long-term (54 days) continuous primary fermentation of lager-type wort of high specific gravity. The experiment was performed in a 4 L airlift bioreactor and immobilization of biomass was attained solely by flocculation. Despite the constant liquid agitation and washout of biomass, up to 53 g dry wt/L of yeast remained immobilized in the system. Two types of beer were produced without interrupting the reactor, based on two types of wort: a Pilsener type with high specific gravity of 15.6 ± 0.3°P; and a dark lager wort with specific gravity of 14.4 ± 0.03°P. Even during the inlet of high gravity wort, the desired attenuation was achieved without the need for either recirculation or an auxiliary second stage bioreactor. The specific saccharide consumption rate was kept around 7.9 ± 0.4 g/L/h and ethanol productivity oscillated at 3.36 ± 0.2 g/L/h for nearly a month. During this period the volumetric productivity of the current bioreactor reached 1.6 L beer/L/day. The green beers produced from the Pilsener and dark lager worts met the standards of regular finished primary beer fermentation. The productivity of diacetyl through the entire experiment could be correlated to the free amino nitrogen consumption rate. Copyright © 2014 The Institute of Brewing & DistillingEduardo Pires gratefully acknowledges the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for PhD fellowship support (SFRH/BD/61777/2009). All materials supplied by UNICER Bebidas de Portugal, S.A. (S. Mamede de Infesta, Portugal) as well as the technical support of company members Sonia Meireles and Helena Cunha are acknowledged. The financial contributions of the Grant Agency of the Czech Republic (project GACR P503/12/1424) are also gratefully acknowledged. The authors thank also the Foundation for Science and Technology (FCT-Portugal) for their support through the Strategic Project PEst-OE/EQB/LA0023/2013, also for the PEst-OE/BIA/UI4050/2014; and the Project 'BioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes', ref. NORTE-07-0124-FEDER-000028 Co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER

Maintaining yeast viability in continuous primary beer fermentation

Continuous fermentation is a long known and vastly studied process. The use of immobilized cell technology (ICT) is exploited in a significant number of studies owing to the associated high volumetric productivity, time savings and low capital demand. This work was aimed at solving one of the most relevant obstacles to implementing ICT on a large scale in beer fermentations, namely the control of biomass and the maintenance of cell viability in a gas-lift bioreactor. For this purpose, foam fractionation by skimming was proposed as a tool for control of continuous biomass concentration. The consequences of foaming on lignocellulosic yeast carrier losses were assessed and discussed. A steady consumption of sugars from wort, as well as consistent ethanol production, were achieved. The viability of the suspended cells in the reactor was compared with that of the cell population in the foam using flow cytometry. Results suggest that foam might be used as a promising tool to skim non-viable biomass out of the gas-lift reactor, thus ensuring the maintenance of a cell culture with optimum viability. Copyright © 2014 The Institute of Brewing & DistillingEduardo Pires gratefully acknowledges the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for PhD fellowship support (SFRH/BD/61777/2009) and Cristina Ribeiro from the Centre of Molecular and Environmental Biology/Department of Biology for technical support. This work was also supported by FEDER through POFC - COMPETE and by national funds from FCT through the project PEst-C/BIA/UI4050/2011. The materials supplied by UNICER Bebidas, S.A. (S. Mamede de Infesta, Portugal) are gratefully acknowledged. The financial contributions of the EU FP7 project EcoBioCAP - Ecoefficient Biodegradable Composite Advanced Packaging, grant agreement no. 265669 as well as of the Grant Agency of the Czech Republic (project GACR P503/12/1424) are also gratefully acknowledged

Carrier-free, continuous primary beer fermentation

Developing a sustainable continuous fermentation reactor is one of the most ambitious tasks in brewing science, but it could bring great benefits regarding volumetric productivity to modern breweries. Immobilized cell technology is often applied to reach the large densities of yeast needed in a continuous fermentation process. However, the financial cost associated with the use of carriers for yeast immobilization is one of the major drawbacks in the technology. This work suggests that yeast flocculation could address biomass immobilization in a gas-lift reactor for the continuous primary fermentation of beer. Nearly 25 g dry wt L−1 of yeast was flocculated in the reactor before interruption of the fermentation. Stable sugar consumption and ethanol production (4.5% alcohol by volume) from an 11°P wort was evidenced. The key esters and higher alcohols measured in the young beer met the standards of a finished primary beer fermentation.Eduardo Pires gratefully acknowledges the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for the PhD fellowship support (SFRH/BD/61777/2009) and Marcel Karabin from the Department of Biotechnology of the Institute of Chemical Technology (Prague) for technical support. The financial contributions of the EU FP7 project EcoBioCAP - Ecoefficient Biodegradable Composite Advanced Packaging, grant agreement no. 265669 as well as of the Grant Agency of the Czech Republic (project GACR P503/12/1424) are also gratefully acknowledged

Continuous immobilized yeast reactor system for complete beer fermentation using spent grains and corncobs as carrier materials

Despite extensive research carried out in the last few decades, continuous beer fermentation has not yet managed to outperform the traditional batch technology. An industrial breakthrough in favour of continuous brewing using immobilized yeast could be expected only on achievement of the following process characteristics: simple design, low investment costs, flexible operation, effective process control and good product quality. The application of cheap carrier materials of by-product origin could significantly lower the investment costs of continuous fermentation systems. This work deals with a complete continuous beer fermentation system consisting of a main fermentation reactor (gas-lift) and a maturation reactor (packedbed) containing yeast immobilized on spent grains and corncobs, respectively. The suitability of cheap carrier materials for long-term continuous brewing was proved. It was found that by fine tuning of process parameters (residence time, aeration) it was possible to adjust the flavour profile of the final product. Consumers considered the continuously fermented beer to be of a regular quality. Analytical and sensorial profiles of both continuously and batch fermented beers were compared.(Fundação de Amparo a Pesquisa do Estado de São Paulo, Brazil (FAPESPFundação para a Ciência e a Tecnologia (FC

A review of flavour formation in continuous beer fermentations

The attractive prospect of a continuous beer fermentation system consists mostly of the accelerated transformation of wort into beer. Although continuous beer fermentation has been studied as a promising technology for several decades, the number of industrial applications is still limited. The major obstacle hindering the extensive industrial exploitation of this technology is the difficulty in achieving the correct balance of sensory compounds in the short time typical for continuous systems. This paper offers an integral view on the particularities of continuous systems, which may impart beer a sensorial character distinct from conventionally fermented counterparts. The main groups of flavour active compounds are discussed from the perspective of possible control strategies by means of process parameters and strain selection.Czech Grant Agency; MŠM

Effects of Electrical and Structural Remodeling on Atrial Fibrillation Maintenance: A Simulation Study

Atrial fibrillation, a common cardiac arrhythmia, often progresses unfavourably: in patients with long-term atrial fibrillation, fibrillatory episodes are typically of increased duration and frequency of occurrence relative to healthy controls. This is due to electrical, structural, and contractile remodeling processes. We investigated mechanisms of how electrical and structural remodeling contribute to perpetuation of simulated atrial fibrillation, using a mathematical model of the human atrial action potential incorporated into an anatomically realistic three-dimensional structural model of the human atria. Electrical and structural remodeling both shortened the atrial wavelength - electrical remodeling primarily through a decrease in action potential duration, while structural remodeling primarily slowed conduction. The decrease in wavelength correlates with an increase in the average duration of atrial fibrillation/flutter episodes. The dependence of reentry duration on wavelength was the same for electrical vs. structural remodeling. However, the dynamics during atrial reentry varied between electrical, structural, and combined electrical and structural remodeling in several ways, including: (i) with structural remodeling there were more occurrences of fragmented wavefronts and hence more filaments than during electrical remodeling; (ii) dominant waves anchored around different anatomical obstacles in electrical vs. structural remodeling; (iii) dominant waves were often not anchored in combined electrical and structural remodeling. We conclude that, in simulated atrial fibrillation, the wavelength dependence of reentry duration is similar for electrical and structural remodeling, despite major differences in overall dynamics, including maximal number of filaments, wave fragmentation, restitution properties, and whether dominant waves are anchored to anatomical obstacles or spiralling freely