The Development of Microfabricated Microbial Fuel Cell Array as a High Throughput Screening Platform for Electrochemically Active Microbes

Microbial fuel cells (MFCs) are novel green technologies that convert chemical energy stored in biomass into electricity through microbial metabolisms. Both fossil fuel depletion and environmental concern have fostered significant interest in MFCs for both wastewater treatment and electricity generation. However, MFCs have not yet been used for practical applications due to their low power outputs and challenges associated with scale-up. High throughput screening devices for parallel studies are highly necessary to significantly improve and optimize MFC working conditions for future practical applications. Here in this research, microfabricated platforms of microbial fuel cell array as high throughput screening devices for MFC parallel studies have been developed. Their utilities were described with environmental sample screening to uncover electricigens with higher electrochemical activities. The first version of the MFC arrays is a batch-mode miniaturized 24-well MFC array using ferricyanide as catholyte. Several environmental species that showed higher electricity generation capabilities than Shewanella oneidensis MR-1 (SO) were uncovered using the developed MFC array, with one environmental electricigen, Shewanella sp. Hac353 (dq307734.1)(7Ca), showing 2.3-fold higher power output than SO. The second MFC array platform developed is an air-cathode MFC array using oxygen in air as electron acceptor, which is sustainable compared to ferricyanide that depletes over time. Environmental electricigen screenings were also conducted, showing parallel comparison capabilities of the developed array. The third MFC array platform is a microfluidic-cathode MFC array that enables long-term operations of miniature MFC arrays with improved power generation abilities. The capability of the microfluidic-cathode MFC array to support long-term parallel analysis was demonstrated by characterizing power generation of SO and 7Ca, proving extended operation time and improved power outputs compared to batch-mode MFC array. The fourth MFC array platform enables both catholyte and anolyte replenishments for long-term characterization of various carbon substrate performances. Finally, the 24-well microfluidic MFC array was further scaled up to 96 wells, which greatly increased the throughput of MFC parallel studies. The developed MFC arrays as high throughput screening platforms are expected to greatly impact how current MFC studies are conducted and ultimately lead to significant improvement in MFC power output

Micropatterning of Poly (N-isopropylacrylamide) (PNIPAAm) Hydrogels: Effects on Thermosensitivity and Cell Release Behavior

The thermally driven, reversible change in the surface properties of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels from a hydrophilic (water-swollen) state to a hydrophobic (deswollen) state when heated above the volume phase transition temperature (VPTT, ~35 oC) makes them useful in inducing controlled cell release. To improve the kinetics of swelling and deswelling, we have prepared microstructured (i.e., micropillared) thermoresponsive surfaces comprising pure PNIPAAm hydrogel and nanocomposite PNIPAAm hydrogel embedded with polysiloxane colloidal nanoparticles (~220 nm diameter, 1 wt%) via photopolymerization. The thermosensitivity (i.e., degree and rate of swelling/deswelling) of these surfaces and how it can be regulated using different micropillar sizes and densities were characterized by measuring the dynamic size changes in micropillar dimensions in response to thermal activation. Our results show that the dynamic thermal response rate can be increased by more than twofold when the micropillar size is reduced from 200 to 100 μm. The temperature-controlled cell release behaviors of pure PNIPAAm and nanocomposite PNIPAAm micropatterned surfaces were successfully characterized using mesenchymal progenitor cells (10T1/2). This study demonstrates that the thermosensitivity of PNIPAAm surfaces can be regulated by introducing micropillars of different sizes and densities, while maintaining good temperature-controlled cell release behavior

Evaluation of scaling invariance embedded in short time series.

Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length ~10(2). Calculations with specified Hurst exponent values of 0.2,0.3,...,0.9 show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias (≤0.03) and sharp confidential interval (standard deviation ≤0.05). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records

Low-carbon demand response strategy of buildings considering load rebound

With the carbon emission ratio of buildings increasing, including buildings in the carbon market, an inevitable trend of social development is created. Buildings are characterized by their strong seasonality, high simultaneity rate, and large load, which is not only the main factor leading to the peak load of a power grid but also an important resource for load control. Under the guidance of dynamic carbon emission prices and real-time electricity prices, it is worth considering how best to balance the peak response ability of buildings and the cause of the secondary peak leading to load rebound. Therefore, this paper proposes a low-carbon demand response strategy for buildings considering load rebound. First, a building load is classified based on how schedulable the load remains, and a building demand response model which considers how the load schedulability is constructed. Second, according to the different rebounds of different building loads, a load rebound optimization model based on linear attenuation was built, and the rebound parameters of various loads were designed. Then, the real-time carbon emission factor, load fluctuation reward, punishment factor, and real-time electricity price are introduced. Thus, the lowest running cost of the building load is taken as the objective function needed to construct a building demand response optimization model while also considering load rebound. Finally, an example analysis is used to verify the effectiveness of the proposed model in reducing the comprehensive operation cost of buildings. The proposed model not only effectively reduces the comprehensive operation cost of buildings, but also reduces carbon emissions and load fluctuations under the premise of satisfying the actual building load, which provides a new idea for the research of a low-carbon demand response strategy of buildings with load rebound

Microstructural Characteristics and Mechanical Properties of Friction Stir Spot Welded 2A12-T4 Aluminum Alloy

2A12-T4 aluminum alloy was friction stir spot welded, and the microstructural characteristics and mechanical properties of the joints were investigated. A softened microstructural region existed in the joint, and it consisted of stir zone (SZ), thermal mechanically affected zone (TMAZ), and heat affected zone (HAZ). The minimum hardness was located in TMAZ, and the average hardness value in SZ can be improved by appropriately increasing welding heat input. The area of complete bonding region at the interface increased with increasing welding heat input because more interface metals were mixed. In a certain range of FSSW parameters, the tensile shear failure load of the joint increased with increasing rotation speed, but it decreased with increasing plunge rate or decreasing shoulder plunging depth. Two kinds of failure modes, that is, shear fracture mode and tensile-shear mixed fracture mode, can be observed in the tensile shear tests, and the joint that failed in the tensile-shear mixed fracture mode possessed a high carrying capability

Research on the Impregnation Process and Mechanism of Silica Sol/Phenolic Resin Modified Poplar Wood

Phenolic resin-modified materials partially reduce the toughness of the wood. In this study, organic–inorganic composite modifiers were used to modify the wood. Silica sol/phenolic resin was prepared through in-situ polymerization, and poplar wood was modified using a vacuum pressure impregnation process, enhancing its toughness. Orthogonal experiments were conducted, and the impact toughness of the modified poplar wood was used as the evaluation index. Through orthogonal experiments, using the impact toughness of modified poplar as the evaluation indicator, it was found that when the average particle size of the silica sol is 8–15 nm, the pressure is 1.2 MPa, and the pressurization time is 3 h, the impregnation-modified poplar’s impact toughness reaches its optimum, improving by 84.1% and 135.4% compared to the raw material and phenolic resin impregnated wood, respectively. The Fourier Transform Infrared Spectroscopy (FT-IR) results indicated that the characteristic absorption peak of Si-O-Si appears in the poplar wood after impregnation, confirming the formation of new silicon-oxygen (Si-O) chemical bonds. X-ray Photoelectron Spectroscopy (XPS) analysis revealed that a chemical reaction occurs between the impregnation liquid and the wood, generating Si-O-C. Subsequently, through Dynamic Mechanical Analysis (DMA) and Thermogravimetric (TGA) analysis, it was understood that this chemical reaction significantly enhances the thermal stability and toughness of the impregnated material, making it superior to the original poplar material. The TGA further unveiled that, compared to untreated poplar, the thermal stability of the impregnated material has been notably improved. Lastly, Scanning Electron Microscopy (SEM) analysis demonstrated that the composite impregnation liquid successfully permeates and fills the interior of the poplar cells

Knowledge Mapping of the Rural Teacher Development Policy in China: A Bibliometric Analysis on Web of Science

The rural teacher development policy plays a key role in cultivating high-quality and sufficient rural teachers in China. This study aims to apply a bibliometric analysis to explore the rural teacher development policy in China’s current education system. The advanced retrieval function of Web of Science (WoS) is used for the literature data, the core collection of Web of Science is selected for the database, and the time span of literature retrieval is consistent with the selected literature. We apply Citespace to analyze the spatial dimension, research paradigm and research method, research theme, research hotspots and co-occurrence of keywords, the evolution process of research hotspots and content of rural teacher development policy in China. It is found that with the deepening of the reform and development of rural elementary education, scholars not only pay attention to the exploration of the deep mechanism of rural teacher policy, but also to data-oriented diversified empirical research

Novel event analysis for human-machine collaborative underwater exploration

One of the main task for deep sea submersible is for human-machine collaborative scientific exploration, e.g., human ourselves drive the submersible and monitor cameras around the submersible to observe new species fish or strange topography in a tedious way. In this paper, by defining novel marine animals or any extreme events as novel events, we design a new deep sea novel visual event analysis framework to improve the efficiency of human-machine collaboration and improve the accuracy simultaneously. Specifically, our visual framework concerns diverse functions than most state-of-the-arts, including novel event detection, tracking and summarization. Due to the power and computation resource limitation of the submersible, we design an efficient deep learning based visual saliency method for novel event detection and propose an online object tracking strategy as well. All the experiments are depending on Chinese Jiaolong, the manned deep sea submersible, which mounts several PanCtiltCzoom (PTZ) camera and static cameras. We build a new novel deep sea event dataset and the results justify that our human-machine collaborative visual observation framework can automatically detect, track and summarize the novel deep sea event. (C) 2019 Elsevier Ltd. All rights reserved

A heat dissipation enhancing method for the high-speed spindle based on heat conductive paths

High-speed spindle systems could generate sufficient heat when they are operating and would cause thermal deformation that influences spindle accuracy. Heat dissipation is a common and effective way to remove the generated heat. In this paper, heat conductive paths were created on the bearing seat and the spindle housing along the radial direction. Along these paths, the heat was transferred directly from heat sources inside the spindle system to outside and the heat dissipation was enhanced. To limit the heat transferred along the axial direction, the inner wall of the path was coated with a thermal insulation material. Based on an annular plate model, the influences of the affecting parameters of paths on the heat transfer performance were studied. The temperature distributions of the models with and without heat conductive paths were numerically and experimentally investigated. It was found that after using heat conductive paths, the heat dissipation enhanced significantly. Moreover, it is found that as the number and diameter of paths increases, the temperature of internal parts decreases and the gap between the highest and the lowest temperature is narrowed