A revised concept for urban water metabolism （UWM） is presented in this study to address the inadequacies in current research on UWM and the problems associated with the traditional urban water metabolic process. Fe...A revised concept for urban water metabolism （UWM） is presented in this study to address the inadequacies in current research on UWM and the problems associated with the traditional urban water metabolic process. Feedback loops can be analyzed to increase the water environmental carrying capacity （WECC） of the new urban water metabolism system （UWMS） over that of a traditional UWMS. An analysis of the feedback loops of an UWMS was used to construct a system dynamics （SD） model for the system under a WECC restriction. Water metabolic processes were simulated for different scenarios using the Tongzhou District in Beijing as an example. The results for the newly developed UWM case showed that a water environment of Tongzhou District could support a population of 1.1926 × 106, an irrigation area of 375.521 km2, a livestock of 0.7732 × 106, and an industrial value added of ￥193.14 × 109 （i.e. about US$28.285 × 109） in 2020. A sensitivity analysis showed that the WECC could be improved to some extent by constructing new sewage treatment facilities or by expanding the current sewage treatment facilities, using reclaimed water and improving the water circulation system.展开更多
The circadian clock temporally coordinates plant growth and metabolism in close synchronization with the diurnal and seasonal environmental changes. Research over the last decade has identified a number of clock compo...The circadian clock temporally coordinates plant growth and metabolism in close synchronization with the diurnal and seasonal environmental changes. Research over the last decade has identified a number of clock components and a variety of regulatory mechanisms responsible for the rhythmic oscillations in metabolic and physiological activities. At the core of the clock, transcriptional/translational feedback loops modulate the expression of a significant proportion of the genome. In this article, we briefly describe some of the very recent advances that have improved our understanding of clock organization and function in Arabidopsis thaliana. The new studies illustrate the role of clock protein complex for- mation on circadian gating of plant growth and identify alternative splicing as a new regulatory mechanism for clock function. Examination of key clock properties such as temperature compensation has also opened new avenues for func- tional research within the plant clockwork. The emerging connections between the circadian clock and metabolism, hor- mone signaling and response to biotic and abiotic stress also add new layers of complexity to the clock network and underscore the significance of the circadian clock regulating the daily life of plants.展开更多
Positive feedback loops drive immune cell polarization toward a pro-tumor phenotype that accentuates immunosuppression and tumor angiogenesis. This phenotypic switch leads to the escape of cancer cells from immune des...Positive feedback loops drive immune cell polarization toward a pro-tumor phenotype that accentuates immunosuppression and tumor angiogenesis. This phenotypic switch leads to the escape of cancer cells from immune destruction. These positive feedback loops are generated by cytokines such as TGF-β, Interleukin-10 and Interleukin-4, which are responsible for the polarization of monocytes and M1 macrophages into pro-tumor M2 macrophages, and the polarization of naive helper T cells intopro-tumor Th2 cells. In this article, we present a deterministic ordinary differential equation (ODE) model that includes key cellular interactions and cytokine signaling pathways that lead to immune cell polarization in the tumor microenvironment. The model was used to simulate various cancer treatments in silico. We identified combination therapies that consist of M1 macrophages or Th1 helper cells, coupled with an anti-angiogenic treatment, that are robust with respect to immune response strength, initial tumor size and treatment resistance. We also identified IL-4 and IL-10 as the targets that should be neutralized in order to make these combination treatments robust with respect to immune cell polarization. The model simulations confirmed a hypothesis based on published experimental evidence that a polarization into the M1 and Th1 phenotypes to increase the M1-to-M2 and Th1-to-Th2 ratios plays a significant role in treatment success. Our results highlight the importance of immune cell reprogramming as a viable strategy to eradicate a highly vascularized tumor when the strength of the immune response is characteristically weak and cell polarization to the pro-tumor phenotype has occurred.展开更多
We consider queueing networks （QN＇s） with feedback loops roamed by ＂intelligent＂ agents, able to select their routing on the basis of their measured waiting times at the QN nodes. This is an idealized model to di...We consider queueing networks （QN＇s） with feedback loops roamed by ＂intelligent＂ agents, able to select their routing on the basis of their measured waiting times at the QN nodes. This is an idealized model to discuss the dynamics of customers who stay loyal to a service supplier, provided their service time remains below a critical threshold. For these QN＇s, we show that the traffic flows may exhibit collective patterns typically encountered in multi-agent systems. In simple network topologies, the emergent cooperative behaviors manifest themselves via stable macroscopic temporal oscillations, synchronization of the queue contents and stabilization by noise phenomena. For a wide range of control parameters, the underlying presence of the law of large numbers enables us to use deterministic evolution laws to analytically characterize the cooperative evolution of our multi-agent systems. In particular, we study the case where the servers are sporadically subject, to failures altering their ordinary behavior.展开更多
文摘A revised concept for urban water metabolism （UWM） is presented in this study to address the inadequacies in current research on UWM and the problems associated with the traditional urban water metabolic process. Feedback loops can be analyzed to increase the water environmental carrying capacity （WECC） of the new urban water metabolism system （UWMS） over that of a traditional UWMS. An analysis of the feedback loops of an UWMS was used to construct a system dynamics （SD） model for the system under a WECC restriction. Water metabolic processes were simulated for different scenarios using the Tongzhou District in Beijing as an example. The results for the newly developed UWM case showed that a water environment of Tongzhou District could support a population of 1.1926 × 106, an irrigation area of 375.521 km2, a livestock of 0.7732 × 106, and an industrial value added of ￥193.14 × 109 （i.e. about US$28.285 × 109） in 2020. A sensitivity analysis showed that the WECC could be improved to some extent by constructing new sewage treatment facilities or by expanding the current sewage treatment facilities, using reclaimed water and improving the water circulation system.
文摘The circadian clock temporally coordinates plant growth and metabolism in close synchronization with the diurnal and seasonal environmental changes. Research over the last decade has identified a number of clock components and a variety of regulatory mechanisms responsible for the rhythmic oscillations in metabolic and physiological activities. At the core of the clock, transcriptional/translational feedback loops modulate the expression of a significant proportion of the genome. In this article, we briefly describe some of the very recent advances that have improved our understanding of clock organization and function in Arabidopsis thaliana. The new studies illustrate the role of clock protein complex for- mation on circadian gating of plant growth and identify alternative splicing as a new regulatory mechanism for clock function. Examination of key clock properties such as temperature compensation has also opened new avenues for func- tional research within the plant clockwork. The emerging connections between the circadian clock and metabolism, hor- mone signaling and response to biotic and abiotic stress also add new layers of complexity to the clock network and underscore the significance of the circadian clock regulating the daily life of plants.
文摘Positive feedback loops drive immune cell polarization toward a pro-tumor phenotype that accentuates immunosuppression and tumor angiogenesis. This phenotypic switch leads to the escape of cancer cells from immune destruction. These positive feedback loops are generated by cytokines such as TGF-β, Interleukin-10 and Interleukin-4, which are responsible for the polarization of monocytes and M1 macrophages into pro-tumor M2 macrophages, and the polarization of naive helper T cells intopro-tumor Th2 cells. In this article, we present a deterministic ordinary differential equation (ODE) model that includes key cellular interactions and cytokine signaling pathways that lead to immune cell polarization in the tumor microenvironment. The model was used to simulate various cancer treatments in silico. We identified combination therapies that consist of M1 macrophages or Th1 helper cells, coupled with an anti-angiogenic treatment, that are robust with respect to immune response strength, initial tumor size and treatment resistance. We also identified IL-4 and IL-10 as the targets that should be neutralized in order to make these combination treatments robust with respect to immune cell polarization. The model simulations confirmed a hypothesis based on published experimental evidence that a polarization into the M1 and Th1 phenotypes to increase the M1-to-M2 and Th1-to-Th2 ratios plays a significant role in treatment success. Our results highlight the importance of immune cell reprogramming as a viable strategy to eradicate a highly vascularized tumor when the strength of the immune response is characteristically weak and cell polarization to the pro-tumor phenotype has occurred.
基金the Fonds National Suisse de la Recherche Scientifique under Grant No.200021-109191/1the Portuguese Fundaao para a Cinca e a Tecnologica(FCT Bolsa FEDER/POCTI-SFA-1-219)The original version was presented on ICSSSM'06.
文摘We consider queueing networks （QN＇s） with feedback loops roamed by ＂intelligent＂ agents, able to select their routing on the basis of their measured waiting times at the QN nodes. This is an idealized model to discuss the dynamics of customers who stay loyal to a service supplier, provided their service time remains below a critical threshold. For these QN＇s, we show that the traffic flows may exhibit collective patterns typically encountered in multi-agent systems. In simple network topologies, the emergent cooperative behaviors manifest themselves via stable macroscopic temporal oscillations, synchronization of the queue contents and stabilization by noise phenomena. For a wide range of control parameters, the underlying presence of the law of large numbers enables us to use deterministic evolution laws to analytically characterize the cooperative evolution of our multi-agent systems. In particular, we study the case where the servers are sporadically subject, to failures altering their ordinary behavior.
