Tissue engineering and regenerative medicine (TERM) are paving the way to the generation of functional and mature biological tissues that closely emulate cellular, biochemical, and mechanical cues. ...Electrical fields in the human body modulate myriad biological processes, such as synapses, muscle contraction, hearing, and wound healing, which were disregarded in TERM until recently. To preserve and improve tissue electrophysiology, cells can be loaded in electroactive biomaterials and stimulated with exogenous electrical fields. Here, we review how electrical stimulation and electroactive biomaterials can be used to instruct cells to create more mature and functional tissue-engineered constructs. We also highlight the most recent electroactive engineered tissues developed for TERM.
The human body contains endogenous electrical currents due to the flow of ions. Electrical fields generated across cell membranes are involved in cell migration, proliferation, and differentiation, and the repair and regeneration of tissues.Electroactive biomaterials incorporating metals, metalloids, graphene and graphene derivatives, conductive polymers, and piezoelectric polymers have low resistivity. Cell behaviors, such as attachment, migration, proliferation, and differentiation, are enhanced in electroactive biomaterials.The synchronous contractibility of skeletal muscle and cardiac excitable cells can be modulated by applying external electrical fields.Stem cells can be differentiated towards cardiac, skeletal muscle, neurogenic, or osteogenic lineages by applying specific external electrical fields even without the use of differentiation cell culture media.
The purpose of this research was to investigate the potential use of Cu–Ti3AlC2 composites sliding against a Cu–5%Ag alloy as a viable electrical contact couple. Sliding friction and wear tests were ...conducted in the presence of an electric current using a custom-designed block-on-ring wear testing apparatus. The electrical current density was 0–15 A/cm2 along with an apparent contact pressure of 1.25–7.5 N/cm2 and sliding velocities ranging from 2.5 to 15 m/s. The results indicate that friction coefficient, wear rate, and contact voltage drop measured for the sliding couple increases with an increase in the electrical current density. As the apparent contact pressure increases, the contact voltage drop of Cu–Ti3AlC2 composites increases gradually, while friction coefficient and wear rate first decrease and then increase. With an increase in the sliding velocity, the friction coefficient of the sliding pair decreases and the contact voltage drop increases gradually, while wear rate decreases first, then increases. Adhesive wear and arc erosion wear proposed as the main wear modes. A lubricating film was observed to form on the wear surfaces under each test condition, and that film apparently improves the tribological properties of the sliding couples.
•The electrical sliding wear properties of Cu–Ti3AlC2 composites rub against Cu–Ag alloy are studied.•Effect of electrical current density, apparent contact pressure and sliding velocity are studied systematically.•Lubricating films are formed at each contact condition and improve the tribological properties of the material.•Two main mechanisms for electrical sliding wear of Cu–Ti3AlC2 composites are presented.
In this study, we aimed to use ultrasound and low-intensity electrical current practices to make lettuce safer for human health. For this purpose, three electric currents (0.2, 0.8, and 1.4 mA) and ...two ultrasonic processes (24 and 40 kHz), used both separately and simultaneously, were applied to the lettuce leaves at five treatment time (2–10 min). At the first stage, the effects of these processes on the microbiota of the fresh lettuce leaves were investigated. Therefore, the TMAB, the total coliform, the total yeast&mold were determined as 5.94 ± 0.20, 5.65 ± 0.27, and 4.82 ± 0.33 log cfu/g, respectively. After the processes, the maximum inactivation rates were determined as 2.89log, > 3log, and 2.98log, respectively. While there was no dramatic change in physicochemical properties of lettuce; the free chlorine and hydrogen peroxide contents increased with the time in the process water. At the second stage, the effects of these processes on pathogens were investigated. 6 log of E.coli O157:H7, L.monocytogenes and, S.aureus were inoculated to the lettuce samples and was treated by the processes. The pathogenic microorganisms in the lettuce samples were inactivated up to 4.05, 3.12, and 2.84 log cfu/g, respectively. In the model system, the pathogens couldn't be detected after 6, 8 and 4 min, respectively.
-The electrosonication treatments might provide synergistic effect on decontamination.-About 2.8–4.0 log of pathogen decontamination was provided in the model system.-The food matrix prevents the better decontamination as in the model system.-The ultrasonic treatments might reduce the effectiveness of the electrical current.
In this study, a device called a water vapour cell has been successfully fabricated. A water vapour cell consists of patterned silver on the top layer, chitosan film in the middle, titanium in the ...bottom layer and isolator substrate as the cover. Chitosan films utilized as a conversion material which works based on direct chemical interactions between chitosan film surface and water vapour to generate electrical current. The chitosan concentration was varied from 0%, 1%, 2%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25% and 4.5% (w/v), respectively. The energy conversion properties of a water vapour cell were conducted by exposing water vapour into a water vapour cell. The water vapour was represented by a percentage of relative humidity (RH) which varied from 30% - 90% at 27 °C until 24 hours. It was proven that no electrical current was generated by water vapour cell with 0% chitosan film, while the other concentrations generated stable electrical current once exposed to ≤70% RH. However, the electrical current started to increase and achieved a stable state after 13-11 hours when exposed to ≥70% RH. The highest electrical current was generated 15.31 microampere (μA) achieved by 4% chitosan film under 90% RH exposure. The optical band gap and SEM characterization result indicated that the addition of chitosan concentration higher or equal to 4.25% showed the presence of aggregates which decreased chitosan film band gap into 3.22 and 3.53 eV. Therefore, the higher than 4% concentrations of chitosan have an effect on the physical structure which decreasing the band gap and electrical current.
•A laboratory database was compiled to assess the performance of gang saw machines.•Two predictive models using GEP and MLR are proposed for gang saw machines.•The GEP-based model was identified as ...the best model for performance prediction.•The Mohs hardness showed the highest influence on sawing performance.
The process of cutting dimension stones by gang saw machines plays a vital role in the productivity and efficiency of quarries and stone cutting factories. The maximum electrical current (MEC) is a key variable for assessing this process. This paper proposes two new models based on multiple linear regression (MLP) and a robust non-linear algorithm of gene expression programming (GEP) to predict MEC. To do so, the parameters of Mohs hardness (Mh), uniaxial compressive strength (UCS), Schimazek’s F-abrasiveness factor (SF-a), Young’s modulus (YM) and production rate (Pr) were measured as input parameters using laboratory tests. A statistical comparison was made between the developed models and a previous study. The GEP-based model was found to be a reliable and robust modelling approach for predicting MEC. Finally, according to the conducted parametric analysis, Mh was identified as the most influential parameter on MEC prediction.
•Heat transport and humidity is investigated for electrically conducting gel.•The temperature increases nearly quadratically with current.•The humidity increases with temperature.•Applications in ...soft electronics and energy harvesting devices.
With an ever-increasing range of applications found for aqueous electrically conducting gels, it is necessary to not only understand their electrical properties, but also how they dissipate heat and change the surrounding humidity. Here, an experimental setup for simultaneously investigating the electrical properties, the surface temperature and the relative humidity in the vicinity of ionically conducting gelatine is reported. It is found that the sample surface temperature increases quadratically with conducting current until the gel approaches breakdown at sufficiently high temperatures. Simultaneous measurements of the relative humidity indicate that this parameter increases linearly with sample surface temperature in the temperature range investigated. At currents of about 20 mA, the temperature and relative humidity increase approximately 10 °C and 10 %, respectively. Fluctuations in electrical parameters for even larger currents resulted in significant variations in the observed temperature increase and humidity change. The present work provides better insight into mechanisms behind and how electrically conducting biocompatible hydrogels can be used to increase temperature and enhance evaporation.
This study focuses on the wear, friction and electrical characteristics of the newly developed, disc-disc contact design for sliding electrical contacts. Different types of graphite and copper, as ...the material combinations, different contact operating variables and, in particular, different directions of the electrical current, i.e., the disc polarity, were investigated under real contact conditions in a dedicated tribological test rig. The electrographite and polymer-bonded graphite were running in a self-mated contact, against copper and against each other. The polymer-bonded-graphite/polymer-bonded-graphite pair performed the best for almost all the studied parameters, while the mixed, dissimilar, polymer-bonded-graphite/electrographite combination had the worst performance. Moreover, all the pairs containing electrographite material exhibited unstable contact behaviour, and generally gave a worse overall performance. The wear of the self-mated graphite pairs was less than that of the graphite/copper pairs. The effect of the polarity on the graphite/graphite material combinations was negligible, while in the graphite/copper combinations the direction of the electrical current was found to significantly affect the wear of the discs. The wear of the positive graphite disc was up to 30% lower than the negative graphite disc, while the wear of the positive copper disc was up to 8 times more than that of the negative copper disc. Differences in the boundary contact film were observed in the graphite/copper contacts depending on the surface polarity, meaning that sliding contacts with the current flowing from the graphite disc to the copper disc saw less wear than the contacts where the current flows from the copper disc to the graphite disc.
•Novel two-disc design of sliding electrical contact with graphite/graphite and graphite/copper pairs was investigated.•With appropriate graphite/graphite combinations, better tribological and also electrical performances can be achieved.•Current direction has negligible effect at graphite/graphite material pairs.•At graphite/copper pairs, negative graphite disc wear more than positive and positive copper disc more than negative.•Current direction affect conditions in boundary films and thus the wear of contact materials.
Conservation practitioners have long recognized ecological connectivity as a global priority for preserving biodiversity and ecosystem function. In the early years of conservation science, ecologists ...extended principles of island biogeography to assess connectivity based on source patch proximity and other metrics derived from binary maps of habitat. From 2006 to 2008, the late Brad McRae introduced circuit theory as an alternative approach to model gene flow and the dispersal or movement routes of organisms. He posited concepts and metrics from electrical circuit theory as a robust way to quantify movement across multiple possible paths in a landscape, not just a single least‐cost path or corridor. Circuit theory offers many theoretical, conceptual, and practical linkages to conservation science. We reviewed 459 recent studies citing circuit theory or the open‐source software Circuitscape. We focused on applications of circuit theory to the science and practice of connectivity conservation, including topics in landscape and population genetics, movement and dispersal paths of organisms, anthropogenic barriers to connectivity, fire behavior, water flow, and ecosystem services. Circuit theory is likely to have an effect on conservation science and practitioners through improved insights into landscape dynamics, animal movement, and habitat‐use studies and through the development of new software tools for data analysis and visualization. The influence of circuit theory on conservation comes from the theoretical basis and elegance of the approach and the powerful collaborations and active user community that have emerged. Circuit theory provides a springboard for ecological understanding and will remain an important conservation tool for researchers and practitioners around the globe.
Aplicaciones de la Teoría de Circuitos a la Conservación y a la Ciencia de la Conectividad
Resumen
Quienes practican la conservación han reconocido durante mucho tiempo que la conectividad ecológica es una prioridad mundial para la preservación de la biodiversidad y el funcionamiento del ecosistema. Durante los primeros años de la ciencia de la conservación los ecólogos difundieron los principios de la biografía de islas para evaluar la conectividad con base en la proximidad entre el origen y el fragmento, así como otras medidas derivadas de los mapas binarios de los hábitats. Entre 2006 y 2008 el fallecido Brad McRae introdujo la teoría de circuitos como una estrategia alternativa para modelar el flujo génico y la dispersión o las rutas de movimiento de los organismos. McRae propuso conceptos y medidas de la teoría de circuitos eléctricos como una manera robusta para cuantificar el movimiento a lo largo de múltiples caminos posibles en un paisaje, no solamente a lo largo de un camino o corredor de menor costo. La teoría de circuitos ofrece muchos enlaces teóricos, conceptuales y prácticos con la ciencia de la conservación. Revisamos 459 estudios recientes que citan la teoría de circuitos o el software de fuente abierta Circuitscape. Nos enfocamos en las aplicaciones de la teoría de circuitos a la ciencia y a la práctica de la conservación de la conectividad, incluyendo temas como la genética poblacional y del paisaje, movimiento y caminos de dispersión de los organismos, barreras antropogénicas de la conectividad, comportamiento ante incendios, flujo del agua, y servicios ambientales. La teoría de circuitos probablemente tenga un efecto sobre la ciencia de la conservación y quienes la practican por medio de una percepción mejorada de las dinámicas del paisaje, el movimiento animal, y los estudios de uso de hábitat, y por medio del desarrollo de nuevas herramientas de software para el análisis de datos y su visualización. La influencia de la teoría de circuitos sobre la conservación viene de la base teórica y la elegancia de la estrategia y de las colaboraciones fuertes y la comunidad activa de usuarios que han surgido recientemente. La teoría de circuitos proporciona un trampolín para el entendimiento ecológico y seguirá siendo una importante herramienta de conservación para los investigadores y practicantes en todo el mundo.
摘要
保护实践者长期以来一直将生态连接度视为保护生物多样性和生态系统功能的当务之急。在保护科学发展早期, 生态学家将岛屿生物地理学的原理进行扩展, 基于源斑块邻近度和其它来自二元生境图的指标来评估连接度。2006 年到2008 年, 已故的Brad McRae 引入了电路理论, 作为模拟基因流和生物体扩散或移动路径的新方法。他用电路理论中的概念和指标开发了一种稳健的方法来量化景观中多种可能的移动路径, 而这不只是一条最低成本的路径或廊道。电路理论为保护科学提供了许多理论、概念和实践方面的联系。我们综述了近期引用电路理论或是开源软件Circuitscape的459 项研究, 重点关注电路理论在连接度保护科学与实践中的应用, 包括景观和种群遗传学、生物体运动和扩散路径、连接度的人为障碍、火灾、水流和生态系统服务等问题。电路理论通过帮助理解景观动力学、动物移动和生境利用研究, 以及开发新的数据分析和可视化软件工具, 影响着保护科学和实践者。电路理论对保护的影响来自于该方法的理论基础和优雅性, 以及现已出现的强大的合作队伍和活跃的用户群体。电路理论为生态学理解提供了跳板, 并将继续作为全球研究人员和实践者的重要保护工具。翻译: 胡怡思; 审校: 聂永刚
Article impact statement: Uses of circuit theory to understand connectivity have had a durable and global impact on conservation science and practice.
In recent years, the global energy demand, particularly the usage of fossil fuels as motor vehicle propellants such as gasoline and diesel, had steadily increased. This surge in consumption, ...alongside the burgeoning vehicle count, resulted in a depletion of petroleum reserves. Consequently, exploring alternative fuel sources became imperative. Hydrogen gas, derived from water through water electrolysis using an HHO generator, emerged as a promising alternative. This research investigated the impact of diverse copper and stainless-steel electrodes in varied electrolyte solutions and electrical currents for generating HHO gas. Employing an experimental methodology, the study modified an existing HHO generator, reassembling it with different materials based on the experimental design. Subsequent testing and data collection revealed that the highest flow rate of HHO gas, at 0.000807564 m3 /s, occurred using stainless-steel electrodes with an electrical current of 50 A and a 50% NaOH concentration. The study concluded that the size of the electric current and the amount of NaOH significantly influenced the speed of HHO gas flow, indicating a direct relationship between these factors and gas production.
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•Electrically-conductive Pt-coated spacers achieved early pore wetting detection.•The spacers were tested in MD process with gradually developed pore wetting.•A significant ...amplification of the electrical signal was observed in a 1–2 V region.•Permeate flux increased with no adverse coating effect on MD performance.•Effect of spacer design on flux was more pronounced at higher feed temperature.
Membrane distillation (MD) suffers from pore wetting which deteriorates membrane separation properties and causes water protrusion to permeate side. The early detection of pore wetting is a challenge which needs to be addressed to achieve stable MD performance. In this study, electrically-conductive Pt-coated spacers placed inside the feed and coolant channels with a dual purpose of maximizing permeate flux and instantaneous wetting detection once first membrane pores are compromised are proposed. Upon wetting, permeate salt concentration increases thereby initiating redox reactions at two spacer electrodes under the applied electrical potential. As a result, electrical current is produced and measured. The competence of the proposed wetting detection method was explored in MD process in the presence of organic substances with high wetting propensity. An increase in generated electrical current upon wetting development and substantial signal amplification with the voltage increase was demonstrated. The new wetting detection method achieved a faster response comparing to conventional conductivity measurements. Moreover, this method allows to define the wetting onset which can serve as an indication of early membrane impairment. Different spacer geometries and observed no adverse effect of spacer coating on MD performance were further compared. Experimental and numerical simulations accentuated an importance of spacer design by providing specific permeate flux gain for a 1-helical spacer comparing to a spacer with a smooth cylindrical filament. This effect became more evident at higher feed water temperature, condition that favors greater temperature polarization.
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