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1. Control of a Noncooperative Positive Nonlinear System by Augmented Positive Linear System Regulation

   https://doi.org/10.1109/LCSYS.2024.3522944  

   Liu, Guanyun; Menezes, Amor A (December 2024, IEEE Control Systems Letters)

   Positive systems, which are systems whose states are always non-negative, can have both positive linear and positive nonlinear approximations that are valid dynamical models in a prescribed domain. When a linearization of a nonlinear system in a domain near an operating point is equivalent to another linear system representation, a reference-tracking controller for that linear system should also achieve reference-tracking control of the nonlinear system in that domain. Here, we show that only if a linearized positive nonlinear system (PNS) is a positive system (i.e., the PNS is cooperative) will a reference-tracking controller for an equivalent positive linear system realization achieve similar results on the nonlinear system. For an example noncooperative PNS of human blood coagulation, where a published reference-tracking controller assumed a positive linear plant, we develop feedforward and feedback controllers that augment the prior controller to overcome noncooperativity and similarly control the positive nonlinear model. 

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2. Bilinear Controllability of a Simple Reparable System

   https://doi.org/10.23919/ECC64448.2024.10591269  

   Adu, Daniel Owusu; Hu, Weiwei (June 2024, IEEE)

   Reparable systems are systems that are characterized by their ability to undergo maintenance actions when failures occur. These systems are often described by transport equations, all coupled through an integro-differential equation. In this paper, we address the understudied aspect of the controllability of reparable systems. In particular, we focus on a two-state reparable system and our goal is to design a control strategy that enhances the system availability- the probability of being operational when needed. We establish bilinear controllability, demonstrating that appropriate control actions can manipulate system dynamics to achieve desired availability levels. We provide theoretical foundations and develop control strategies that leverage the bilinear structure of the equations. 

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3. Minimax Persistent Monitoring of a network system

   https://doi.org/10.1016/j.automatica.2022.110808  

   Pinto, Samuel C.; Welikala, Shirantha; Andersson, Sean B.; Hendrickx, Julien M.; Cassandras, Christos G. (March 2023, Automatica)
4. Chemical inhibition of a bacterial immune system

   https://doi.org/10.1101/2025.02.20.638879  

   Zang, Zhiyu; Duncan, Olivia K; Sabonis, Dziugas; Shi, Yun; Miraj, Gause; Fedorova, Iana; Le, Shuai; Deng, Jun; Zhu, Yuhao; Cai, Yanyao; et al (February 2025, bioRxiv)

   Abstract The rise of antibiotic resistance motivates a revived interest in phage therapy. However, bacteria possess dozens of anti-bacteriophage immune systems that confer resistance to therapeutic phages. Chemical inhibitors of these anti-phage immune systems could be employed as adjuvants to overcome resistance in phage-based therapies. Here, we report that anti-phage systems can be selectively inhibited by small molecules, thereby sensitizing phage-resistant bacteria to phages. We discovered a class of chemical inhibitors that inhibit the type II Thoeris anti-phage immune system. These inhibitors block the biosynthesis of a histidine-ADPR intracellular ‘alarm’ signal by ThsB and prevent ThsA from arresting phage replication. These inhibitors promiscuously inhibit type II Thoeris systems from diverse bacteria—including antibiotic-resistant pathogens. Chemical inhibition of the Thoeris defense improved the efficacy of a model phage therapy against a phage-resistant strain ofP. aeruginosain a mouse infection, suggesting a therapeutic potential. Furthermore, these inhibitors may be employed as chemical tools to dissect the importance of the Thoeris system for phage defense in natural microbial communities. 

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5. Magnetic Relaxation of a Voigt–MHD System

   https://doi.org/10.1007/s00220-023-04770-1  

   Constantin, Peter; Pasqualotto, Federico (September 2023, Communications in Mathematical Physics)