PITS: An Intelligent Transportation System in pandemic times.

The control of the pandemic caused by SARS-CoV-2 is a challenge for governments all around the globe. To manage this situation, countries have adopted a bundle of measures, including restrictions to population mobility. As a consequence, drivers face with the problem of obtaining fast routes to reach their destinations. In this context, some recent works combine Intelligent Transportation Systems (ITS) with big data processing technologies taking the traffic information into account. However, there are no proposals able to gather the COVID-19 health information, assist in the decision-making process, and compute fast routes in an all-in-one solution. In this paper, we propose a Pandemic Intelligent Transportation System (PITS) based on Complex Event Processing (CEP), Fuzzy Logic (FL) and Colored Petri Nets (CPN). CEP is used to process the COVID-19 health indicators and FL to provide recommendations about city areas that should not be crossed. CPNs are then used to create map models of health areas with the mobility restriction information and obtain fast routes for drivers to reach their destinations. The application of PITS to Madrid region (Spain) demonstrates that this system provides support for authorities in the decision-making process about mobility restrictions and obtain fast routes for drivers. PITS is a versatile proposal which can easily be adapted to other scenarios in order to tackle different emergency situations.

Modeling the ascorbate-glutathione cycle in chloroplasts under light/dark conditions.

BACKGROUND: Light/dark cycles are probably the most important environmental signals that regulate plant development. Light is essential for photosynthesis, but an excess, in combination with the unavoidable presence of atmospheric oxygen inside the chloroplast, leads to excessive reactive oxygen species production. Among the defense mechanisms that activate plants to cope with environmental stress situations, it is worth noting the ascorbate-glutathione cycle, a complex metabolic pathway in which a variety of photochemical, chemical and enzymatic steps are involved. RESULTS: We herein studied the dynamic behavior of this pathway under light/dark conditions and for several consecutive days. For this purpose, a mathematical model was developed including a variable electron source with a rate law proportional to the intensity of solar irradiance during the photoperiod, and which is continuously turned off at night and on again the next day. The model is defined by a nonlinear system of ordinary differential equations with an on/off time-dependent input, including a parameter to simulate the fact that the photoperiod length is not constant throughout the year, and which takes into account the particular experimental kinetics of each enzyme involved in the pathway. Unlike previous models, which have only provided steady-state solutions, the present model is able to simulate diurnal fluctuations in the metabolite concentrations, fluxes and enzymatic rates involved in the network. CONCLUSIONS: The obtained results are broadly consistent with experimental observations and highlight the key role played by ascorbate recycling for plants to adapt to their surrounding environment. This approach provides a new strategy to in vivo studies to analyze plant defense mechanisms against oxidative stress induced by external changes, which can also be extrapolated to other complex metabolic pathways to constitute a useful tool to the scientific community in general.

Catalase-like activity of human methemoglobin: a kinetic and mechanistic study.

Hydrogen peroxide triggers a redox cycle between methemoglobin and ferrylhemoglobin, leading to protein inactivation and oxygen evolution. In the present paper, the catalase-like oxygen production by human methemoglobin in the presence of H(2)O(2) was kinetically characterized with a Clark-type electrode. Progress curves showed a pseudo-steady state in the first minutes of the reaction, while double-reciprocal plots were upwardly concave, indicating positive co-operativity dependent upon protein concentration, which is a very unusual kinetic behavior. Addition of superoxide radical scavengers slightly increased activity, suggesting that most oxygen was produced biocatalytically. By considering all the experimental data obtained, a possible mechanism was proposed, including: (a) competition between the one-electron and the two-electron reductions of the oxoferryl free radical species of hemoglobin, giving rise to ferrylhemoglobin and methemoglobin, respectively; (b) competition between the superoxide-dependent inactivation of the protein and its reduction back to the met state. Computer simulations of that model have been performed by numerically integrating the differential equations set describing the mechanism, which was seen to yield predictions of the kinetic parameters variation consistently with the kinetic behavior experimentally observed. We suggest that the catalase-like activity of methemoglobin must predominantly be a biocatalytic reaction that protects the protein against H(2)O(2)-induced suicide inactivation.

Computer simulation of the dynamic behavior of the glutathione-ascorbate redox cycle in chloroplasts.

The glutathione-ascorbate redox pathway in chloroplasts is a complex network of spontaneous, photochemical, and enzymatic reactions for detoxifying hydrogen peroxide. This article presents a comprehensive sensitivity analysis of the system. A model has been constructed to simulate oxidative stress conditions, enabling steady-state concentrations of the metabolites involved in the pathway and photochemical and enzymatic fluxes to be calculated. The model includes an electron source whose flux is distributed among three competitive routes (photogeneration of O2-, photoreduction of NADP+ to NADPH, and photoreduction of monodehydroascorbate to ascorbate) and that allows the simulation of variations in NADPH concentration with time. Each enzyme considered is introduced in the model, taking into account its particular catalytic mechanism, including the inactivation of ascorbate peroxidase in the presence of low-ascorbate concentrations. Computer simulations pointed to the great sensitivity of the system to the ratio among fluxes corresponding to ascorbate and NADPH photoproduction and NADPH consumption by the Calvin cycle. Under oxidative stress conditions, the model shows a sequential depletion of antioxidant power in chloroplasts in the order NADPH, glutathione, ascorbate and their recovery in the reverse order. Decreasing levels of glutathione reductase, ascorbate peroxidase, and superoxide dismutase led to the irreversible photoinactivation of ascorbate peroxidase and the subsequent increase in hydrogen peroxide concentration, preceded by a maximum in dehydroascorbate reductase activity.