scholarly journals Controlling reversible cell differentiation for labor division in microbial consortia

2021 ◽  
Author(s):  
Davide Salzano ◽  
Davide Fiore ◽  
Mario di Bernardo
Keyword(s):  
Control Strategies ◽  
Analytical Framework ◽  
Microbial Consortia ◽  
External Control ◽  
Toggle Switch ◽  
Memory Element ◽  
Control Laws ◽  
Memory Mechanism ◽  
Labor Division ◽  
The Stability

We address the problem of regulating and keeping at a desired balance the relative numbers between cells exhibiting a different phenotype within a monostrain microbial consortium. We propose a strategy based on the use of external control inputs, assuming each cell in the community is endowed with a reversible, bistable memory mechanism. Specifically, we provide a general analytical framework to guide the design of external feedback control strategies aimed at balancing the ratio between cells whose memory is stabilized at either one of two equilibria associated to different cell phenotypes. We demonstrate the stability and robustness properties of the control laws proposed and validate them in silico implementing the memory element via a genetic toggle-switch. The proposed control framework may be used to allow long term coexistence of different populations, with both industrial and biotechnological applications. Examples include consortia where each population produces a compound of interest or where one population supports the growth of the other which has the role of producing a desired molecule. As a representative example we consider the realistic agent-based implementation of our control strategy to enable cooperative bioproduction in microbial consortia.

Stability of a Class of Piezoelectric State-Switching Methods

2000 ◽  
Author(s):  
Andrew J. Kurdila ◽  
William W. Clark ◽  
Weijian Wang ◽  
Dwayne E. McDaniel
Keyword(s):  
Lyapunov Functions ◽  
Closed Loop ◽  
Control Strategies ◽  
Short Circuit ◽  
Open Circuit ◽  
Hybrid Dynamical Systems ◽  
Multiple Lyapunov Functions ◽  
Control Laws ◽  
State Switching ◽  
The Stability

Abstract Experimental and anecdotal evidences have shown that state-switched control strategies for piezoelectric actuators can be advantageous. However, most discussions of the stability of these systems has relied on heuristic, or physically motivated, arguments. In this paper, we show that recent open-circuit/short-circuit state-switching control laws can be viewed as hybrid dynamical systems of Witsenhausen type. Within this framework, the closed-loop stability of OC/SC switching is rigorously established using the method of multiple Lyapunov functions.

scholarly journals Multicellular feedback control of a genetic toggle-switch in microbial consortia

2020 ◽  
Author(s):  
Davide Fiore ◽  
Davide Salzano ◽  
Enric Cristòbal-Cóppulo ◽  
Josep M. Olm ◽  
Mario di Bernardo
Keyword(s):  
Feedback Control ◽  
Microbial Consortium ◽  
Microbial Consortia ◽  
Toggle Switch ◽  
Control Loop ◽  
Bacterial Populations ◽  
Agent Based ◽  
Memory Mechanism ◽  
Two Populations ◽  
Reference Input

AbstractWe describe a multicellular approach to control a target cell population endowed with a bistable toggle-switch. The idea is to engineer a synthetic microbial consortium consisting of three different cell populations. In such a consortium, two populations, the Togglers, responding to some reference input, can induce the switch of a bistable memory mechanism in a third population, the Targets, so as to activate or deactivate some additional functionalities in the cells. Communication among the three populations is established by orthogonal quorum sensing molecules that are used to close a feedback control loop across the populations. The control design is validated via in-silico experiments in BSim, a realistic agent-based simulator of bacterial populations.

Control Strategies for Semi-Active Lorry Suspensions

1996 ◽  
Vol 210 (2) ◽  
pp. 161-178 ◽  
Author(s):  
D Cebon ◽  
F H Besinger ◽  
D J Cole
Keyword(s):  
Linear Models ◽  
Control Strategies ◽  
Power Input ◽  
Optimum Level ◽  
Passive Damping ◽  
Control Laws ◽  
Body Acceleration ◽  
Performance Improvements ◽  
Full State Feedback ◽  
Active Damper

The optimum level of passive damping for minimizing the root mean square (r.m.s.) dynamic tyre force and r.m.s. body acceleration of a heavy vehicle is determined by testing a damper in a ‘hardware-in-the-loop’ (HiL) test rig. Two different control strategies [‘modified skyhook damping’ (MSD), and linear optimal control with full state feedback (FSF)] are investigated theoretically using linear models, and suspension force control laws are derived. These control laws, along with simple ‘on–off’ control, are then tested experimentally using a prototype semi-active damper which is controlled so as to follow the demanded force, except when power input is required. The achievable performance improvements are compared and differences between the linear theory, computer simulations and experimental performance are discussed. It is found that using FSF control, r.m.s. body acceleration and r.m.s. tyre force can be reduced simultaneously by 28 and 21 per cent of their values for optimal passive damping.

Braucht die EU einen flexibleren Stabilitätspakt?

2004 ◽  
Vol 53 (1) ◽  
Author(s):  
Carsten Hefeker ◽  
Friedrich Heinemann ◽  
Klaus F. Zimmermann
Keyword(s):  
Public Awareness ◽  
Time Lag ◽  
Fiscal Rules ◽  
External Control ◽  
Public Expenditures ◽  
Stability And Growth Pact ◽  
Consolidation Process ◽  
Growth Pact ◽  
Long Run ◽  
The Stability

AbstractIn his contribution Carsten Hefeker points out that most of the official arguments concerning the necessity of the Stability and Growth Pact are not convincing. Nevertheless, a mechanism that credibly avoids excessive debts and deficits is needed in most member states. It would be more useful, however, if such rules would focus on overall debt rather than on deficits. In addition, he advocates to create an external control for such fiscal rules, independent from the Commission and ECOFIN. He concludes that the Pact does not need to become more flexible, but more credible.Friedrich Heinemann states that much of the recent reform debate on the Stability Pact is based on a fundamental misconception: The Pact has not been established as a guiding tool for welfare - maximising politicians, but in order to limit detrimental incentives from fiscal short-sightedness. “Stupid” elements like the three-per-cent deficit ceiling have a clear and beneficial strategic function as boundary within the national budgetary process. Furthermore, simple rules are superior to smart ones in increasing the political costs of high deficits in terms of public awareness. The critique on the pact′s missing flexibility is correct mainly regarding its lose logical link to long-run sustainability. Increasing flexibility in a cyclical sense, however, is not a reform priority. Already today the Pact leaves sufficient leeway for responsible politicians. Instead, the reform focus must be on depoliticising the pact in the sense of limiting Council power in the deficit procedure. More flexibility must not come without depoliticising. He recommends that any reform should only be carried into effect with a significant time lag in order to limit the reputation damage which would be the consequence of any quick institutional response to the Pact′s recent crisis.In his paper Klaus F. Zimmermann argues that the Stability and Growth Pact (SGP) has been subject to criticism ever since its inception. He points out that it overlooks business cycle developments within the framework of the consolidation process; it adopts a too short-term view of the stabilisation target which is also hardly under control of policy-makers; and it deals with policy imperfections in a sub-optimal way. Therefore, a reform of the SGP is urgent. The author suggests that the rules must be handled more flexibly. In his opinion, a mediumterm budgetary target and a focus on public expenditures to tackle the pro-cyclical bias is needed. To restore credibility, the task of supervision should be transferred to an independent European institution.

scholarly journals Temporal Stability and Biodiversity of Two Complex Antilisterial Cheese-Ripening Microbial Consortia

2003 ◽  
Vol 69 (7) ◽  
pp. 4012-4018 ◽  
Author(s):  
Ariel Maoz ◽  
Ralf Mayr ◽  
Siegfried Scherer
Keyword(s):  
Species Composition ◽  
Bacterial Species ◽  
Temporal Stability ◽  
Individual Characteristics ◽  
Microbial Consortia ◽  
Cheese Ripening ◽  
Safe Food ◽  
The Stability ◽  
The Individual ◽  
First Time

ABSTRACT The temporal stability and diversity of bacterial species composition as well as the antilisterial potential of two different, complex, and undefined microbial consortia from red-smear soft cheeses were investigated. Samples were collected twice, at 6-month intervals, from each of two food producers, and a total of 400 bacterial isolates were identified by Fourier-transform infrared spectroscopy and 16S ribosomal DNA sequence analysis. Coryneform bacteria represented the majority of the isolates, with certain species being predominant. In addition, Marinolactobacillus psychrotolerans, Halomonas venusta, Halomonas variabilis, Halomonas sp. (106 to 107 CFU per g of smear), and an unknown, gram-positive bacterium (107 to 108 CFU per g of smear) are described for the first time in such a consortium. The species composition of one consortium was quite stable over 6 months, but the other consortium revealed less diversity of coryneform species as well as less stability. While the first consortium had a stable, extraordinarily high antilisterial potential in situ, the antilisterial activity of the second consortium was lower and decreased with time. The cause for the antilisterial activity of the two consortia remained unknown but is not due to the secretion of soluble, inhibitory substances by the individual components of the consortium. Our data indicate that the stability over time and a potential antilisterial activity are individual characteristics of the ripening consortia which can be monitored and used for safe food production without artificial preservatives.

Chaos Control for a Fractional-Order Jerk System via Time Delay Feedback Controller and Mixed Controller

2021 ◽  
Vol 5 (4) ◽  
pp. 257
Author(s):  
Changjin Xu ◽  
Maoxin Liao ◽  
Peiluan Li ◽  
Lingyun Yao ◽  
Qiwen Qin ◽  
...  
Keyword(s):  
Time Delay ◽  
Fractional Order ◽  
Chaos Control ◽  
Chaotic Behavior ◽  
Control Strategies ◽  
Feedback Controller ◽  
Research Approach ◽  
Controlling Chaos ◽  
The Stability ◽  
Jerk System

In this study, we propose a novel fractional-order Jerk system. Experiments show that, under some suitable parameters, the fractional-order Jerk system displays a chaotic phenomenon. In order to suppress the chaotic behavior of the fractional-order Jerk system, we design two control strategies. Firstly, we design an appropriate time delay feedback controller to suppress the chaos of the fractional-order Jerk system. The delay-independent stability and bifurcation conditions are established. Secondly, we design a suitable mixed controller, which includes a time delay feedback controller and a fractional-order PDσ controller, to eliminate the chaos of the fractional-order Jerk system. The sufficient condition ensuring the stability and the creation of Hopf bifurcation for the fractional-order controlled Jerk system is derived. Finally, computer simulations are executed to verify the feasibility of the designed controllers. The derived results of this study are absolutely new and possess potential application value in controlling chaos in physics. Moreover, the research approach also enriches the chaos control theory of fractional-order dynamical system.

Stabilizing Feedback Controls for Nonlinear Hamiltonian Systems and Nonconservative Bilinear Systems in Elasticity

1982 ◽  
Vol 104 (1) ◽  
pp. 27-32 ◽  
Author(s):  
S. N. Singh
Keyword(s):  
Asymptotic Stability ◽  
Hamiltonian Systems ◽  
Attitude Control ◽  
Sufficient Conditions ◽  
Bilinear Systems ◽  
Feedback Controls ◽  
Control Laws ◽  
Nonlinear Maps ◽  
The Stability ◽  
Necessary And Sufficient

Using the invariance principle of LaSalle [1], sufficient conditions for the existence of linear and nonlinear control laws for local and global asymptotic stability of nonlinear Hamiltonian systems are derived. An instability theorem is also presented which identifies the control laws from the given class which cannot achieve asymptotic stability. Some of the stability results are based on certain results for the univalence of nonlinear maps. A similar approach for the stabilization of bilinear systems which include nonconservative systems in elasticity is used and a necessary and sufficient condition for stabilization is obtained. An application to attitude control of a gyrostat Satellite is presented.

scholarly journals Analysis of the stability of multi-mode systems with approximating nonlinear control laws

2021 ◽  
Vol 872 (1) ◽  
pp. 012010
Author(s):  
E A Shakhray ◽  
E V Lubentsova ◽  
V F Lubentsov ◽  
M V Meflekh
Keyword(s):  
Nonlinear Control ◽  
Control Laws ◽  
The Stability ◽  
Multi Mode

scholarly journals The Stability Analysis of a Multi-Port Single-Phase Solid-State Transformer in the Electromagnetic Timescale

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2250 ◽  
Author(s):  
Rui Wang ◽  
Qiuye Sun ◽  
Qifu Cheng ◽  
Dazhong Ma
Keyword(s):  
Stability Analysis ◽  
Solid State ◽  
Single Phase ◽  
Control Strategies ◽  
Current Source ◽  
Practical Stability ◽  
Stability Assessment ◽  
Solid State Transformer ◽  
The Stability ◽  
Signal Sinusoïdal

This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses the stability assessment of the MS3T in detail. First and foremost, the structure of the MS3T and its three stage control strategies are proposed. Furthermore, the stability analysis of each of the MS3T’s subsystems is achieved through the closed loop transfer function of each subsystem, respectively, including an AC-DC front-end side converter, dual active bridge (DAB) with a high-frequency (HF) or medium-frequency (MF) transformer, and back-end side incorporating DC-AC and dc-dc converters. Furthermore, the practical impedance stability criterion in the electromagnetic timescale, which only requires two current sensors and one external high-bandwidth small-signal sinusoidal perturbation current source, is proposed by the Gershgorin theorem and Kirchhoff laws. Finally, the overall stability assessment, based on a modified impedance criterion for the MS3T is investigated. The overall practical stability assessment of the MS3T can be validated through extensive simulation and hardware results.

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