In this work, biocomposites made of polyhydroxyalkanoates (PHA) with natural fibers were produced via compression molding. In particular, polyhydroxybutyrate (PHB) and ...polyhydroxybutyrate‐co‐hydroxyvalerate (PHBV) were reinforced with 20 wt% of agave fibers. Different compatibilization strategies were investigated to improve the fiber‐matrix interaction: fiber surface treatment in PHA solution, fiber surface treatment in maleated PHA solution, fiber propionylation, and extrusion with maleated PHA. The biocomposites were characterized in terms of morphology, mechanical properties, water absorption, and biodegradability by CO2 production tracking. In general, fiber propionylation was the best strategy for mechanical properties enhancement and water uptake decreasing. Biocomposites with propionylated fibers showed improved flexural strength (170% for PHB and 84% for PHBV). The flexural modulus was also enhanced with propionylated fibers up to 19% and 18% compared to uncompatibilized biocomposites (PHB and PHBV, respectively). Tensile strength increased by 16% (PHB) and 14% (PHBV), and the water absorption was reduced using propionylated fibers going from 6.6% to 4.4% compared with biocomposites with untreated fibers. Most importantly, the impact strength was also improved for all biocomposites by up to 96% compared with the neat PHA matrices. Finally, it was found that the compatibilization did not negatively modify the PHA biodegradability.
This article addresses Mexico’s present situation in the lithium industry and its near future, ceteris paribus. Mexico’s short- and long-term lithium supply will not improve by the exploration and ...exploitation planned by the nationalistic objectives of the current government. This analysis demonstrates that significant changes must be made to Mexico’s energy policy to promote the development of lithium due to five risks: manufacturing capacity, misaligned incentives, industrial policies, geographic concentration, and limited international coordination. Therefore, although the world’s largest lithium mine was found in Sonora in 2019, Mexico’s policy approaches to nationalize lithium exploration and exploitation will not allow the country to capitalize on the boom of this industry, as happened in Bolivia. In the short term, Mexico’s policies will create an exploration deficit due to the country’s lack of know-how and investment. Thus, Mexico will not extract lithium in the long term nor benefit from the demand increase and development of a value chain, especially in North America. Given these risks, this article postulates that Mexico’s lithium policy should be revised to open its market to foreign investment and use this nascent market to a good advantage.
•Mexico should refrain from nationalizing the lithium industry.•Mexico needs private investment and technology to develop lithium.•Mexico should create a lithium value chain with its USMCA partners.•Mexico should seek Chinese investments to avoid dependence on US lithium consumers.•Mexico should adopt a lithium policy that balances nationalism and globalism.
The structure-control design approach of mechatronic systems requires a different design formulation where the mechanical structure and control system are simultaneously designed. Optimization ...problems are commonly stated to confront the structure-control design formulation. Nevertheless, these problems are often very complex with a highly nonlinear dependence between the design variables and performance functions. This fact has made the use of evolutionary algorithms, a feasible alternative to solve the highly nonlinear optimization problem; the method to find the best solution is an open issue in the structure-control design approach. Hence, this paper presents a mechanism to exhaustively exploit the solutions in the differential evolution (DE) algorithm in order to find more non-dominated solutions with uniformly distributed Pareto front and better trade-offs in the structure-control design framework. The proposed approach adopts an external population to retain the non-dominated solutions found during the evolutionary process and includes a mechanism to mutate the individuals in their corresponding external population region. As a study case, the structure-control design of a serial-parallel manipulator with its control system is stated as a dynamic optimization problem and is solved by using the proposed approach. A comparative analysis shows that the multi-objective exhaustive exploitation differential evolution obtained a superior performance in the structure-control design framework than a DE algorithm which did not consider the proposal. Hence, the resulting designs provide better trade-offs between the structure-control performance functions.
Increases in power and frequency of hippocampal theta activity have been related to efficient place learning and memory acquisition in hippocampal-dependent tests. The complex medial septum-diagonal ...band of Broca (MS/DBB) is the pacemaker of hippocampal theta activity, influenced by the ascending synchronizing system, and modulated by serotonergic raphe medial afferents, acting on cholinergic and GABAergic septal neurons. The suppression of hippocampal theta expression and the modulation of hippocampal learning and memory are attributed to serotonin. To simultaneously test these hypotheses, a daily local serotonin increase was induced by citalopram (CIT) infusion (100µM, 0.88µL, 0.2µL/m) 15minutes before training in the Morris water maze. The theta activity was recorded in the MS/DBB, dentate gyrus (DG) and CA1 of one group infused with artificial cerebrospinal liquid (ACL) and the other with CIT on Days 1-6 of training. After a probe trial (Day 7) and one resting day, the treatments were reversed (Days 8-11). The CIT MS/DBB infusion in the first 6 training days reduced the efficiency of spatial learning in association with reduced power in the DG, reduced MS/DBB-DG coherence, increased DG-CA1 coherence, and a lack of a negative correlation between MS/DBB power and swam distances. No effect of the CIT occurred once the information was acquired under ACL training. These results support a role of serotonin, in acting on the MS/DBB in the fine tuning of hippocampal learning and memory efficiency through the modulation of learning-related theta activity power and septohipocampal synchronization.
•MS/DBB citalopram infusion increases serotonin and modulates place learning accuracy.•MS/DBB citalopram infusion does not affect spatial information retrieval.•MS/DBB citalopram infusion reduces absolute theta power of the dentate gyrus.•MS/DBB-dentate gyrus coherence is reduced by MS/DBB citalopram infusion.•CA1-dentate gyrus coherence is increased after MS/DBB citalopram infusion.
The efficient speed regulation of four-bar mechanisms is required for many industrial processes. These mechanisms are hard to control due to the highly nonlinear behavior and the presence of ...uncertainties or disturbances. In this paper, different Pareto-front approximation search approaches in the adaptive controller tuning based on online multiobjective metaheuristic optimization are studied through their application in the four-bar mechanism speed regulation problem. Dominance-based, decomposition-based, metric-driven, and hybrid search approaches included in the algorithms, such as nondominated sorting genetic algorithm II, multiobjective evolutionary algorithm based on decomposition and differential evolution, S-metric selection evolutionary multiobjective algorithm, and nondominated sorting genetic algorithm III, respectively, are considered in this paper. Also, a proposed metric-driven algorithm based on the differential evolution and the hypervolume indicator (HV-MODE) is incorporated into the analysis. The comparative descriptive and nonparametric statistical evidence presented in this paper shows the effectiveness of the adaptive controller tuning based on online multiobjective metaheuristic optimization and reveals the advantages of the metric-driven search approach.
The dc motor is one of the most fundamental electromechanical devices of mechatronic systems, which plays an important role in maintaining the accuracy in the execution of tasks. One of the main ...issues in the accuracy and robustness of dc motor control system is how to optimally tune its parameters. In this paper, a multi-objective online tuning optimization approach is proposed to adaptively tune up the velocity control parameters of the permanent magnet dc motor. This approach simultaneously considers the modeled error and the corresponding sensitivity to choose the best compromise solution in the Pareto dominance-based selection process of solutions to deal the changing optimum solutions in the dynamic environment of the tuning approach based on online optimization method and moreover, the modified differential evolution with induced initial population based on non-dominated solution through a memory is proposed to guide the search into the feasible region, and to promote the exploitation of solutions found in the previous time interval. Simulation results verify that proposed modifications provide higher robustness and better quality in the velocity regulation control of the dc motor under parametric uncertainties, and also under discontinuous dynamic load, than multi-objective differential evolution, particle swarm optimization, and non-dominated sorting genetic algorithm-II.
En este estudio evaluamos las microalgas Chlorella vulgaris y Demodesmus asymmetricus, con el fin de determinar la proporción de microalgas que remueven la mayor concentración de nitrógeno y fósforo ...en aguas residuales de una planta de tratamiento. Se realizó un diseño de mezclas de las microalgas con el agua residual durante 9 días, con fotoperiodo 12:12 h, en un invernadero. Las mayores eficiencias de remoción de nitrógeno (principalmente NO3--N y NO2--N) y fósforo (PO43-) se observaron en los tratamientos con mayor proporción de D. asymmetricus, entre ellos sobresalió el tratamiento T3 (25% C. vulgaris / 75% D. asymmetricus) donde se removió el 100% de nitrógeno y 77.1% de fosforo. De igual manera con el oxígeno disuelto (OD), el T3 obtuvo el mejor resultado alcanzando una media de 10.90 ± 0.60 mg/L. Finalmente, de acuerdo con el análisis del diseño de mezclas, se determinó que la mezcla óptima de microalgas que logra la mayor producción de OD y la mayor remoción, fue la proporción de 6% de C. vulgaris y 94 % de D. asymmetricus en un tiempo de cultivo de 9 días. En conclusión, las microalgas demuestran su capacidad de biorremediación de aguas residuales domésticas.
In this work, a comparative study of different meta-heuristic techniques in the adaptive control for the speed regulation of the DC motor with parameters uncertainties is presented. The adaptive ...control is established as the online solution of a constrained dynamic optimization problem. Several adaptive strategies based on Differential Evolution, Particle Swarm Optimization, Bat Algorithm, Firefly Algorithm, Wolf Search Algorithm and Genetic Algorithm are proposed in order to online tune the parameters of the DC motor control. Simulation results show that proposed adaptive control strategies are a viable alternative to regulate the speed of the motor subject to different operation scenarios. The statistical analysis given in this work shows the features and the differences among strategies, their feasibility to set them up experimentally and also a new hybrid strategy to efficiently solve the problem. In addition, comparative analysis with a robust control approach reveal the advantages of the adaptive strategy based on meta-heuristic techniques in the velocity regulation of the DC motor.
The aim of this study is to conduct a prospective, controlled single-center study to determine the prevalence and types of ureteral stent symptoms in kidney transplant (KTx) recipients and compare ...them with nontransplant subjects.
From December 2012 to June 2019, a total of 102 patients having undergone a KTx and Double-J stent (DJS) placement and 88 patients having undergone endourological lithotripsy and DJS placement were enrolled. The Ureteral Stent Symptom Questionnaire (USSQ) was administered to patients with a median of 25 (KTx) and 31 (urolithiasis) days after stent placement. USSQ scores were used to compare symptoms between the two groups.
Of the 190 patients enrolled, 88 belonged to the lithotripsy group (control group) and 102 to the KTx recipients' group. Mean score for urinary symptoms was 21.42 for KTx patients
27.53 for control patients with statistical significance (
< 0.001, CI -7.792 to -4.433). The visual analog scale, overall bother, pain at voiding, flank pain at voiding, and frequency of painkiller use scores were significantly higher for control patients than for KTx patients (
= 0.024, <0.001, <0.001, <0.001, and 0.014, respectively). Frequency of rest, changes in work duration, work domain score, suspicion of urinary tract infection (UTI), and need for professional assistance scores were significantly lower for KTx patients than the control. There were no significant differences in general health and sexual domains between groups.
KTx recipients have significantly fewer urinary symptoms, pain, work-related disturbances, suspected UTIs, and hospitalizations associated with stent placement than urolithiasis patients.
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To evaluate the diagnostic accuracy of a non-invasive technology based on image processing for the identification of obstructive sleep apnea (OSA) and its severity at patients’ home.
...Observational, prospective, diagnostic accuracy study to evaluate the degree of measure agreement between Sleepwise (SW), in-laboratory attended polysomnography (PSG) and a home sleep apnea test (HSAT). 38 consecutive subjects with suspected OSA referred as outpatients to the sleep unit were recruited from September 2016 to September 2017. All patients underwent in-laboratory attended PSG and image processing with SW simultaneously overnight. Subsequently, a HSAT and image processing with SW were performed simultaneously overnight at patients’ home, and the 2 nights after, patients underwent only image processing with SW consecutively.
In-laboratory polysomnography and SW had a Lin's concordance correlation coefficient of 0.933 and a κ of 0.930. Between HSAT and SW the Lin's concordance correlation coefficient was 0.842 and a κ of 0.571. Agreement between two consecutive nights with SW recording showed a Lin's concordance correlation coefficient of 0.923 and a κ of 0. 837.
SW was highly accurate for non-invasive and automatic diagnosis of OSA in outpatients compared to standard methods for OSA diagnosis either in-laboratory attended PSG or HSAT. SW proved to be a technique with repeatable and concordant results on different nights for the same patient. We conclude SW is a non-invasive, easy-to-use, portable, effective and highly accurate system for the in-home diagnosis of OSA.
Evaluar la precisión diagnóstica de una tecnología no invasiva basada en el procesamiento de imágenes para la identificación de la apnea obstructiva del sueño (AOS) y su gravedad en el domicilio de los pacientes.
Estudio observacional, prospectivo y de precisión diagnóstica para evaluar el grado de concordancia entre las mediciones de Sleepwise (SW), polisomnografía (PSG) asistida en el laboratorio y poligrafía respiratoria domiciliaria (PRD). Se reclutaron 38 sujetos consecutivos con sospecha de AOS, referidos como pacientes ambulatorios a la unidad de sueño entre septiembre de 2016 y septiembre de 2017. Se les realizó a todos una PSG y procesamiento de imagen con SW durante la noche en el laboratorio. Posteriormente, se realizó una PRD y procesamiento de imágenes con SW de forma simultánea durante la noche en su domicilio, y las 2 noches siguientes los pacientes se sometieron solo a procesamiento de imágenes con SW.
La polisomnografía en el laboratorio y el SW mostraron un coeficiente de correlación de concordancia de Lin de 0,933 y un κ de 0,930. Entre la PRD y el SW el coeficiente de correlación de concordancia de Lin fue de 0,842 y un κ de 0,571. La concordancia entre las 2 noches consecutivas de grabación con el SW mostró un coeficiente de correlación de concordancia de Lin de 0,923 y un κ de 0,837.
El SW mostró alta precisión para el diagnóstico no invasivo y automatizado de la AOS en pacientes ambulatorios en comparación con los métodos estándar para el diagnóstico de la AOS, ya sean la PSG asistida en el laboratorio o la PRD. El SW demostró ser una técnica con resultados reproducibles y concordantes en diferentes noches para el mismo paciente. Concluimos que la SW es un sistema no invasivo, fácil de usar, portátil, eficaz y altamente preciso para el diagnóstico domiciliario de la AOS.
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