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Aledo, J. A., Goles, E., Montalva-Medel, M., Montealegre, P., & Valverde, J. C. (2023). Symmetrizable Boolean networks. Inf. Sci., 626, 787–804.
Abstract: In this work, we provide a procedure that allows us to transform certain kinds of deterministic Boolean networks on minterm or maxterm functions into symmetric ones, so inferring that such symmetrizable networks can present only periodic points of periods 1 or 2. In particular, we deal with generalized parallel (or synchronous) dynamical systems (GPDS) over undirected graphs, i. e., discrete parallel dynamical systems over undirected graphs where some of the self-loops may not appear. We also study the class of anti-symmetric GPDS (which are non-symmetrizable), proving that their periodic orbits have period 4. In addition, we introduce a class of non-symmetrizable systems which admit periodic orbits with arbitrary large periods.
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Alfaro, J., Rubio, C., & San Martin, M. (2023). Cosmological Fluctuations in Delta Gravity. Universe, 9(7), 315.
Abstract: About 70% of the Universe is Dark Energy, but the physics community still does not know what it is. Delta gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. Previously, we studied the Universe's accelerated expansion, where DG was able to explain the SNe-Ia data successfully. In this work, we computed the cosmological fluctuations in DG that give rise to the CMB through a hydrodynamic approximation. We calculated the gauge transformations for the metric and the perfect fluid to present the equations of the evolution of cosmological fluctuations. This provided the necessary equations to solve the scalar TT power spectrum in a semi-analytical way. These equations are useful for comparing the DG theory with astronomical observations and thus being able to constrain the DG cosmology.
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Alvarez-Miranda, E., Chace, S., & Pereira, J. (2021). Assembly line balancing with parallel workstations. Int. J. Prod. Res., 59(21), 6486–6506.
Abstract: The simple assembly line balancing problem (SALBP) considers work division among different workstations of a serially arranged assembly process to maximise its efficiency under workload (cumulative) and technological (precedence) constraints. In this work, we consider a variant of the SALBP which allows parallel workstations. To study the effect of parallel stations, we propose a new problem (the parallel station assembly line balancing problem or PSALBP) in which the objective is to minimise the number of parallel stations required to obtain the maximum theoretical efficiency of the assembly process. We study the complexity of the problem and identify a polynomially solvable case. This result is then used as a building block for the development of a heuristic solution procedure. Finally, we carry out a computational experiment to identify the characteristics of assembly lines that may benefit from station paralleling and to evaluate the performance of the proposed heuristic.
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Alves, P. N., Melo, I. C., Santos, R. D., da Rocha, F. V., & Caixeta, J. V. (2022). How did COVID-19 affect green-fuel supply chain? – A performance analysis of Brazilian ethanol sector. Res. Transp. Econ., 93, 101137.
Abstract: The COVID-19 pandemic affected many supply chains worldwide, including the Brazilian green-fuel ethanol supply chain. Our analysis considered sustainability variables (social, environmental, and economic) to investigate the pandemic's effects on the ethanol industries of 15 ethanol producing Brazilian states, comparing data from 2020 to 2019 and applying a novel Data Envelopment Analysis (DEA): the Double Frontier Slack-Based Measure Malmquist Productivity Index (DF-SBM MPI). The findings show that all states suffered negative impacts from the pandemic and some incurred a risk of collapsing it. The least negatively impacted states were Sao Paulo and Mato Grosso. Sao Paulo's ethanol sector is a benchmark for income derived from trade in carbon-credits by RenovaBio certified mills, while Mato Grosso's sector is able to take advantage of the largest spread between ethanol and gasoline prices, certainly a competitive advantage for ethanol producers. We recommend the implementation of public policies to support, mainly, the most affected states by assisting their mills to become environmentally certified participants to take advantage of income opportunities available in the carbon-credit trading market. We recommend, among other actions, a temporary ethanol sales tax reduction, an extension of debt repayment schedules, and stimulating an increase in the fleet of flex-fuel vehicles.
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Aquea, F., Timmermann, T., & Herrera-Vasquez, A. (2017). Chemical inhibition of the histone acetyltransferase activity in Arabidopsis thaliana. Biochem. Biophys. Res. Commun., 483(1), 664–668.
Abstract: Chemical inhibition of chromatin regulators provides an effective approach to investigate the roles of chromatin modifications in plant and animals. In this work, chemical inhibition of the Arabidopsis histone acetyltransferase activity by gamma-butyrolactone (MB-3), the inhibitor of the catalytic activity of mammalian GENERAL CONTROL NON-REPRESSIBLE 5 (GCN5) is evaluated. Arabidopsis seedlings were germinated in LS medium supplemented with different concentrations of MB-3, and inhibition in the root length and yellowed leaves were observed. The yellowed leaves phenotype of the plants grown in 100 μM of MB-3 was reverted when plants were additionally treated with 1 μM of TSA, a histone deacetylase inhibitor. Using an immunoblot assay with specific antibodies revealed a reduction of H3K14 acetylation levels at 3 and 24 h post-treatment. At 24 h post-treatment a reduction of H3K9 acetylation levels was observed. Targets of GCN5 related to stress were downregulated at 3 h post-treatment but no change was observed in target genes related to developmental transition. Our results indicate that MB-3 is a chemical inhibitor of the histone acetyltransferase in Arabidopsis and suggest that this inhibitor could function in other plants species. (C) 2016 Elsevier Inc. All rights reserved.
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Aracena, J., Demongeot, J., Fanchon, E., & Montalva, M. (2013). On the number of different dynamics in Boolean networks with deterministic update schedules. Math. Biosci., 242(2), 188–194.
Abstract: Deterministic Boolean networks are a type of discrete dynamical systems widely used in the modeling of genetic networks. The dynamics of such systems is characterized by the local activation functions and the update schedule, i.e., the order in which the nodes are updated. In this paper, we address the problem of knowing the different dynamics of a Boolean network when the update schedule is changed. We begin by proving that the problem of the existence of a pair of update schedules with different dynamics is NP-complete. However, we show that certain structural properties of the interaction digraph are sufficient for guaranteeing distinct dynamics of a network. In [1] the authors define equivalence classes which have the property that all the update schedules of a given class yield the same dynamics. In order to determine the dynamics associated to a network, we develop an algorithm to efficiently enumerate the above equivalence classes by selecting a representative update schedule for each class with a minimum number of blocks. Finally, we run this algorithm on the well known Arabidopsis thaliana network to determine the full spectrum of its different dynamics. (C) 2013 Elsevier Inc. All rights reserved.
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Aracena, J., Goles, E., Moreira, A., & Salinas, L. (2009). On the robustness of update schedules in Boolean networks. Biosystems, 97(1), 1–8.
Abstract: Deterministic Boolean networks have been used as models of gene regulation and other biological networks. One key element in these models is the update schedule, which indicates the order in which states are to be updated. We study the robustness of the dynamical behavior of a Boolean network with respect to different update schedules (synchronous, block-sequential, sequential), which can provide modelers with a better understanding of the consequences of changes in this aspect of the model. For a given Boolean network, we define equivalence classes of update schedules with the same dynamical behavior, introducing a labeled graph which helps to understand the dependence of the dynamics with respect to the update, and to identify interactions whose timing may be crucial for the presence of a particular attractor of the system. Several other results on the robustness of update schedules and of dynamical cycles with respect to update schedules are presented. Finally, we prove that our equivalence classes generalize those found in sequential dynamical systems. (C) 2009 Elsevier Ireland Ltd. All rights reserved.
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Araneda, A. A., & Villena, M. J. (2021). Computing the CEV option pricing formula using the semiclassical approximation of path integral. J. Comput. Appl. Math., 388, 113244.
Abstract: The CEV model allows volatility to change with the underlying price, capturing a basic empirical regularity very relevant for option pricing, such as the volatility smile. Nevertheless, the standard CEV solution, using the non-central chi-square approach, still presents high computational times. In this paper, the CEV option pricing formula is computed using the semiclassical approximation of Feynman's path integral. Our simulations show that the method is quite efficient and accurate compared to the standard CEV solution considering the pricing of European call options. (C) 2020 Elsevier B.V. All rights reserved.
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Araya-Letelier, G., Concha-Riedel, J., Antico, F. C., & Sandoval, C. (2019). Experimental mechanical-damage assessment of earthen mixes reinforced with micro polypropylene fibers. Constr. Build. Mater., 198, 762–776.
Abstract: The addition of engineered polypropylene fibers to earthen materials offers new opportunities to control their damage evolution and mechanical properties that altogether provides more reliability and extends the life span of these materials. The latter is of special interest considering that earthen materials are still widely used in the form of adobe blocks for earthen masonry, cob, rammed earth or even earthen mortars for new construction and conservation of historic buildings. In this work, the effect of dosage of micro polypropylene fibers (MPPF) in the damage-mechanical performance of earthen mixes is studied experimentally. Part of the experiments includes two different tests to assess distributed and localized cracking of reinforced earth subject to restrained drying shrinkage. In addition, the experimental results showed that the incorporation of MPPF increases up to 83 times the impact strength and 11 times the flexural toughness of earthen mixes. Other mechanical properties such as compressive and flexural strength are not statistically affected by the incorporation of MPPF. (C) 2018 Elsevier Ltd. All rights reserved.
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Araya-Letelier, G., Parra, P. F., Lopez-Garcia, D., Garcia-Valdes, A., Candia, G., & Lagos, R. (2019). Collapse risk assessment of a Chilean dual wall-frame reinforced concrete office building. Eng. Struct., 183, 770–779.
Abstract: Several code-conforming reinforced concrete buildings were severely damaged during the 2010 moment magnitude (M-w) 8.8 Chile earthquake, raising concerns about their real collapse margin. Although critical updates were introduced into the Chilean design codes after 2010, guidelines for collapse risk assessment of Chilean buildings remain insufficient. This study evaluates the collapse potential of a typical dual system (shear walls and moment frames) office building in Santiago. Collapse fragility functions were obtained through incremental dynamic analyses using a state-of-the-art finite element model of the building. Site-specific seismic hazard curves were developed, which explicitly incorporated epistemic uncertainty, and combined with the collapse fragility functions to estimate the mean annual frequency of collapse (lambda(c)) values and probabilities of collapse in 50-years (P-c(50)). Computed values of lambda(c) and P-c(50) were on the order of 10(-5)-10(-4), and 0.1-0.7%, respectively, consistent with similar studies developed for buildings in the US. The results also showed that the deaggregation of lambda(c) was controlled by small to medium earthquake intensities and that different models of the collapse fragility functions and hazard curves had a non-negligible effect on lambda(c) and P-c(50), and thus, propagation of uncertainty in risk assessment problems must be adequately taken into account.
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Asenjo, F. A., & Mahajan, S. M. (2015). Relativistic quantum vorticity of the quadratic form of the Dirac equation. Phys. Scr., 90(1), 4 pp.
Abstract: We explore the fluid version of the quadratic form of the Dirac equation, sometimes called the Feynman-Gell-Mann equation. The dynamics of the quantum spinor field is represented by equations of motion for the fluid density, the velocity field, and the spin field. In analogy with classical relativistic and non-relativistic quantum theories, the fully relativistic fluid formulation of this equation allows a vortex dynamics. The vortical form is described by a total tensor field that is the weighted combination of the inertial, electromagnetic and quantum forces. The dynamics contrives the quadratic form of the Dirac equation as a total vorticity free system.
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Ashina, C., Pugazhenthiran, N., Sathishkumar, P., Selvaraj, M., Assiri, M. A., Rajasekaran, C., et al. (2023). Ultra-small Ni@NiFe2O4/TiO2 magnetic nanocomposites activated peroxymonosulphate for solar light-driven photocatalytic mineralization of Simazine. J. Environ. Chem. Eng., 11(6), 111342.
Abstract: In the heterogeneous photocatalytic degradation of environmental contaminants the recovery, reuse of employed nanocatalyst was crucial and it is essentially required for the scale up applications. Besides, designing a magnetic material with heterojunction that can effectively oxidize the toxic organic contaminants to non-toxic substance under different reaction conditions including direct solar light irradiation remains a challenge. Considering the above facts, herein, we tailored heterojunction between the magnetic materials and non-magnetic materials with ultra-small Ni nanoparticles modified NiFe2O4/TiO2 nanostructures (Ni@NiFe2O4/TiO2 magnetic nanocomposites) through a simple sonochemical route. The Raman phonons at similar to 540 cm(-1) consistent to nickel metal nanoparticles and the spinel ferrites crystal structure confirmed the formation of Ni@NiFe2O4/TiO2 magnetic nanocomposites. The reduced optical bandgap of the resulting nanocomposites indicated the effective absorption of direct solar light irradiation when compared to the bare TiO2. Thus in-turn, enhanced the photocatalytic efficiency of simazine degradation in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k= 11.0 x 10(-4) s(-1)) and augmented the activation of peroxymonosulphate (PMS) in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k= 32.5 x 10(-4) s(-1)). Ni@NiFe2O4/TiO2 +PMS exhibited 3 folds enhanced efficiency in the presence of sunlight. The as-prepared NiFe2O4/TiO2 magnetic nanocatalysts were more stable and the efficiency of simazine oxidation was approximately same for the continuous five cycles at the optimized experimental conditions. The Ni@NiFe2O4/TiO2 magnetic nanocomposites preparation and the activation of PMS may promise the applications in an efficient wastewater treatment.
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Attard, M., & Balbontin, C. (2024). Workshop 6 report: Micromobility movement in urban transport. Res. Transp. Econ., 103, 101399.
Abstract: The theme of micromobility was introduced for the first time in Thredbo 17 as the growth of shared and privately-owned e-scooters, bicycles and e-bicycles continue to affect the nature and structure of urban transport systems worldwide. And whilst in some cases they challenge the priority afforded to the private car, in others they complement already existing and well-established greener transport modes such as cycling and walking. The discussion in this workshop focused on a number of questions looking at the benefits of micromobility and discussing the main incentives for their use as an urban mode of transport, questioning the role of government and describing the potential threats, if any, to public transport systems, in what we expect for the future of micromobility. Five papers showcased evidence on the use of micromobility, from e-scooters in Norway and Australia, to public bicycles in South Korea and The Netherlands. Each of the questions discussed in the workshop is reported in this paper. The need for multimodal integration is evident and remains essential to ensure complementarity across transport in cities. However, other concerns such as the need for regulation, education/ enforcement structures, stronger business models and more effective tendering procedures have been identified and discussed. A long list of future research topics in the area of micromobility is provided and some themes for Thredbo 18 are recommended.
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Ayala, F., Saez, E., & Magna-Verdugo, C. (2022). Computational modelling of dynamic soil-structure interaction in shear wall buildings with basements in medium stiffness sandy soils using a subdomain spectral element approach calibrated by micro-vibrations. Eng. Struct., 252, 113668.
Abstract: This paper presents a strategy for modelling dynamic soil-structure interaction (DSSI) using the spectral element method (SEM) with a Discontinuous Galerkin approach, calibrated by micro-vibrations. The proposed methodology allows not only to adjust the vibration frequencies of the structure but also the observed vibration modes. First, models of two structural shear wall buildings with basements in medium dense sandy soils are developed to estimate empirical modal characteristics and calibrate the structural subdomain and low-strain site properties. Convenient 3D arrays of multiple seismic sensors are used to obtain the environmental vibrations measurements. Afterwards, an optimization process is conducted to calibrate volumetric models of structures. This optimization is performed by preserving the most relevant modal frequencies and shapes to achieve an equivalent dynamic response. Finally, structural models are placed into a neighbouring soil model (soil subdomain), approximating nonlinear soil behaviour by an equivalent linear strategy. Using this complete soil-structure interaction model, relevant engineering performance parameters are assessed via simulations of buildings subjected to a plane wave excitation. The results show the significant effect DSSI have in shear-wall buildings with basements and the importance of considering the flexibility of the foundation in the interpretation of the results. In general, results indicate that DSSI effects are strongly dependent on the input frequency content, which might cause a reduction of the inter-story drifts. Furthermore, a significant period lengthening of the studied structures up to 47% is found, as well as a considerable decrease in story shear up to 220% and a maximum lateral roof displacement reduction of 34% when compared against fixed base referential responses.
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Baler, R. V., Wijnhoven, I. B., del Valle, V. I., Giovanetti, C. M., & Vivanco, J. F. (2019). Microporosity Clustering Assessment in Calcium Phosphate Bioceramic Particles. Front. Bioeng. Biotechnol., 7(281), 7 pp.
Abstract: There has been an increase in the application of different biomaterials to repair hard tissues. Within these biomaterials, calcium phosphate (CaP) bioceramics are suitable candidates, since they can be biocompatible, biodegradable, osteoinductive, and osteoconductive. Moreover, during sintering, bioceramic materials are prone to form micropores and undergo changes in their surface topographical features, which influence cellular physiology and bone ingrowth. In this study, five geometrical properties from the surface of CaP bioceramic particles and their micropores were analyzed by data mining techniques, driven by the research question: what are the geometrical properties of individual micropores in a CaP bioceramic, and how do they relate to each other? The analysis not only shows that it is feasible to determine the existence of micropore clusters, but also to quantify their geometrical properties. As a result, these CaP bioceramic particles present three groups of micropore clusters distinctive by their geometrical properties. Consequently, this new methodological clustering assessment can be applied to advance the knowledge about CaP bioceramics and their role in bone tissue engineering.
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Beltran, J. F., Zamorano, M., Belen, L. H., Risopatron, J., Valdebenito, I., Norambuena, J. A., et al. (2021). A differential proteomic study reveals the downregulation of several plasma membrane Ca2+-binding proteins in the sperm of Atlantic salmon (Salmo salar) following cold storage. Aquaculture, 545, 737211.
Abstract: Sperm motility is a key event in fertilization, which is regulated by different factors. Among the factors that most affect sperm motility in fish are the external concentrations of Ca2+, the influence of which is highly regulated by various plasma membrane Ca2+-binding proteins. Concentrations of this cation have also been shown to be one of the most important factors affecting motility in cold-stored sperm cells. Taking into account the aforementioned aspects, we carried out a differential proteomic study on Salmo salar sperm stored at 4 degrees C with the aim of evaluating the protein profile on day 0 and day 14. The results of our study showed that 401 proteins were significantly downregulated (p < 0.05) on day 14, where four of them are key in the sperm motility of Salmo salar. The results of this study will allow a better understanding of the sperm activation mechanisms of Salmo salar, which will be of great importance in the design of future cold storage strategies for sperm preservation.
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Benitez-Llambay, P., Krapp, L., Ramos, X. S., & Kratter, K. M. (2023). RAM: Rapid Advection Algorithm on Arbitrary Meshes. Astron. J., 952(2), 106.
Abstract: The study of many astrophysical flows requires computational algorithms that can capture high Mach number flows, while resolving a large dynamic range in spatial and density scales. In this paper we present a novel method, RAM: Rapid Advection Algorithm on Arbitrary Meshes. RAM is a time-explicit method to solve the advection equation in problems with large bulk velocity on arbitrary computational grids. In comparison with standard upwind algorithms, RAM enables advection with larger time steps and lower truncation errors. Our method is based on the operator splitting technique and conservative interpolation. Depending on the bulk velocity and resolution, RAM can decrease the numerical cost of hydrodynamics by more than one order of magnitude. To quantify the truncation errors and speed-up with RAM, we perform one- and two-dimensional hydrodynamics tests. We find that the order of our method is given by the order of the conservative interpolation and that the effective speed-up is in agreement with the relative increment in time step. RAM will be especially useful for numerical studies of disk-satellite interaction, characterized by high bulk orbital velocities and nontrivial geometries. Our method dramatically lowers the computational cost of simulations that simultaneously resolve the global disk and potential well inside the Hill radius of the secondary companion.
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Bitran, E., Rivera, P., & Villena, M. J. (2014). Water management problems in the Copiapo Basin, Chile: markets, severe scarcity and the regulator. Water Policy, 16(5), 844–863.
Abstract: This research focuses on the determination of the factors that led to the failure of water management in the Copiapo Basin in Chile. Interestingly, the existence of full private ownership and free tradability of water rights has not prevented the overexploitation of groundwater resources. In the paper, firstly, water regulation and the role of the regulator in Chile are briefly discussed. Secondly, the evolution of water resources in the Copiapo region is characterized and analyzed, and the granting of water use rights in the basin in the last 30 years is concisely described. Thirdly, we examine and analyze prices and quantities traded in the water market of the Copiapo region. We will argue that this crisis is a consequence first of failure in regulatory implementation and second of an extremely rigid regulatory framework that leaves limited room for adjustment to changing conditions, especially regarding the emergence of new information concerning water availability. We believe this investigation is not only relevant for this case in particular, but also for other regions and countries where water markets are in place.
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Bitran, G., & Mondschein, S. (2015). Why individualized contact policies are critical in the mass affluent market. Acad.-Rev. Latinoam. Adm., 28(2), 251–272.
Abstract: Purpose – The purpose of this paper is to study the optimal contact policies for customers that belong to the mass affluent market. Design/methodology/approach – The authors formulate a stochastic dynamic programming model to determine the optimal frequency of contacts in order to maximize the expected return of the company. Findings – The authors show that personalized marketing strategies provide a competitive advantage to companies that contact their customers directly through, for example, phone calls or meetings. The authors show that a threshold policy is only optimal for customers with increasing sensitivity to contact. In all other cases, optimal policies might have a less intuitive structure. The authors also study the importance of the size of the customer database and determine the optimal maximum recency when maintenance costs are present. Practical implications – Contact policies should be tailored for each company/industry individually, due to their sensitivity to customers' purchasing behavior.
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Bonassa, G., Bolsan, A. C., Hollas, C. E., Venturin, B., Candido, D., Chini, A., et al. (2021). Organic carbon bioavailability: Is it a good driver to choose the best biological nitrogen removal process? Sci. Total Environ., 786, 147390.
Abstract: Organic carbon can affect the biological nitrogen removal process since the Anammox, heterotrophic and denitrifying bacteria have different affinities and feedback in relation to carbon/nitrogen ratio. Therefore, we reviewed the wastewater carbon concentration, its biodegradability and bioavailability to choose the appropriate nitrogen removal process between conventional (nitrification-denitrification) and Anammox-based process (i.e. integrated with the partial nitritation, nitritation, simultaneous partial nitrification and denitrification or partial-denitrification). This review will cover: (i) strategies to choose the best nitrogen removal route according to the wastewater characteristics in relation to the organic matter bioavailability and biodegradability; (ii) strategies to efficiently remove nitrogen and the remaining carbon from effluent in anammox-based process and its operating cost; (iii) an economic analysis to determine the operational costs of two-units Anammox-based process when compared with the commonly applied one-unit Anammox system (partial-nitritation-Anammox). On this re-view, a list of alternatives are summarized and explained for different nitrogen and biodegradable organic carbon concentrations, which are the main factors to determine the best treatment process, based on operational and economic terms. In summary, it depends on the wastewater carbon biodegradability, which implies in the wastewater treatment cost. Thus, to apply the conventional nitrification/denitrification process a CODb/N ratio higher than 3.5 is required to achieve full nitrogen removal efficiency. For an economic point of view, according to the analysis the minimum CODb/gN for successful nitrogen removal by nitrification/denitrification is 5.8 g. If ratios lower than 3.5 are applied, for successfully higher nitrogen removal rates and the economic feasibility of the treatment, Anammox-based routes can be applied to the wastewater treatment plant.
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