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The influence of electrode length on performance is investigated in an air-breathing alkaline direct methanol laminar flow fuel cell (LFFC). Depletion of methanol at the electrode surface along the direction of flow hinders reaction kinetics and consequently also cell performance. Reducing the electrode length can decrease the influence of boundary layer depletion, and thereby, improve both the current and power densities. Here, the effect of boundary layer depletion was found to play a significant effect on performance within the first 18 mm of an electrode length. To further utilize the increased power densities provided by shorter electrode lengths, alternative electrode aspect ratios (electrode length-to-width) and electrode arrangements were explored experimentally. Furthermore, by fitting an empirical model based on experimentally obtained data, we demonstrate that a configuration comprised of a series of short electrodes and operated at low flow rates can achieve higher current and power outputs. The analysis of optimal electrode aspect ratio and electrode arrangements can also be applied to other microfluidic reactor designs in which reaction depletion boundary layers occur due to surface reactions.
We fabricated all-solid-state lithium secondary batteries consisting of LiCoO2 thin films prepared by electron cyclotron resonance (ECR) sputtering LiPON and metallic lithium films, and investigated the influence of the sputtering target composition on the performance of the batteries and LiCoO2 films. We found that the LiCoO2 film sputtered with a stoichiometric LiCoO2 target included many impurities (mainly Co3O4) and these impurities were eliminated by adding an excess of Li source to the sputtering target to achieve a Li/Co atomic ratio of 2.0 elsewhere. The LiCoO2 film sputtered with a Li2.0 target exhibited a larger discharge capacity and a high performance level for large current operation. However, the capacity of a battery employing LiCoO2 film sputtered with a Li2.0 target decreased more rapidly than that with a Li1.0 or Li1.7 target in a charge–discharge cycle test. We also investigated the cycle performance of LiCoO2 films in an ordinary liquid electrolyte by using beaker type cells. We found that the decrease in capacity during the cycle tests was caused by the deterioration of the LiCoO2 film, because the dependence of the target composition on the cycle performance in the beaker type cells was similar to that in the all-solid-state cells. We consider the capacity decrease to be caused by the deterioration in the crystallinity of the LiCoO2 film when using the Li2.0 target and caused by the formation of a Co3O4 layer on the surface of the LiCoO2 film when using a Li1.7 target on basis of the results of X-ray diffraction analysis and Raman spectroscopy.
In this study, graphene oxide (GO) was modified with dopamine to create a matrix for enzyme immobilization. Dopamine can self-polymerize to get polydopamine (PDA) and coated on GO surface. At the same time, GO was reduced to get PDA/rGO biocomposite. The PDA/rGO may offer adherent surface for enzyme immobilization. Glucose oxidase (GOD), an oxidoreductase, was chosen as model enzyme and can be easily immobilized on PDA/rGO. Experimental results indicated that the thermal and pH stability as well as the storage stability and resistance toward the denaturing agents of GOD were significantly improved after immobilization. The Michaelis constant (Km) of the immobilized GOD was very close to that of the free GOD. This study offers a versatile approach for deposition of biopolymer on GO and provides a way for enzyme immobilization. Hopefully, the immobilized GOD may be further applied for biosensor and biofuel cell applications.
3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (DMC) in presence of lithium tetrafluoroborate (LiBF4) or lithium hexafluorophosphate (LiPF6) for use as electrolyte in lithium batteries. The optimized electrolytes in term of conductivity and viscosity are MeOx:EC, x(MeOx)=0.5 and MeOx:DMC, x(MeOx)=0.4 in presence of LiBF4 (1M) or LiPF6 (1M). MeOx:EC electrolytes have a better thermal stability than MeOx:DMC electrolytes but the low wettability of the Celgard separator by MeOx:EC prevents its use in lithium batteries. No lithium insertion–deinsertion occurs when LiPF6 is used as salt in MeOx-based electrolytes. MeOx:DMC, x(MeOx)=0.4+LiBF4 (1M) exhibits a good cycling ability at a graphite electrode but all the investigated electrolytes containing MeOx have a low stability in oxidation at a lithium cobalt oxide electrode (Li x CoO2).
Li[Ni x Li(1/3−2x/3)Mn(2/3−x/3)]O2 (x=0.17, 0.25, 0.33, 0.5) compounds have been prepared by a simple combustion method. Compared with the mixed hydroxide or sol–gel method, the combustion method is very simple, and will therefore reduce the manufacturing cost of the cathode material. The structural and electrochemical properties of the samples were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge–discharge method. Rietvelt analysis of the XRD patterns shows that these compounds can be classified as α-NaFeO2 structure type.Compounds with high Ni content (x=0.25–0.5 in Li[Ni x Li(1/3−2x/3)Mn(2/3−x/3)]O2) appear to be composed of two phases, namely Ni-rich and Ni-deficient phases with the same α-NaFeO2 structure. By contrast, the Li[Ni0.17Li0.22Mn0.61]O2 compound with a low Ni content has good phase integrity with only a single phase. The initial charge–discharge and irreversible capacity become larger as x in Li[Ni x Li(1/3−2x/3)Mn(2/3−x/3)]O2 decreases. The Li[Ni0.50Mn0.50]O2 compound has a relatively low initial discharge capacity of 200mAhg−1 and exhibits a large loss in capacity during cycling. On the other hand, Li[Ni0.17Li0.22Mn0.61]O2 and Li[Ni0.25Li0.17Mn0.58]O2 compounds give high initial discharge capacities of over 245mAhg−1 and a stable cycle performance in the voltage range 4.8–2.0V. The XRD and electrochemical results suggest that the simple combustion method is more appropriate for synthesizing Li[Ni x Li(1/3−2x/3)Mn(2/3−x/3)]O2 compounds with low Ni content.
In this paper, a real time energy management strategy (EMS) is proposed for a dual-mode power-split hybrid electric vehicle in order to improve the fuel economy and maintain proper battery’s state of charge (SOC) while satisfying all the constraints and the driving demands. The EMS employs a cascaded control concept which includes a velocity predictor, a master controller and a slave controller. The short term vehicle velocity predictor is developed to improve the controller performance based on radial basis function neural network. The master controller based on nonlinear model predictive control is developed with slow sampling time to sustain SOC and to reduce fuel consumption. Forward dynamic programming is employed here to solve the optimal problem. And the PID-based slave controller is developed with fast sampling time to coordinate the engine and the two motors. Simulation and testbed experiments are performed to verify it and the results demonstrate the effectiveness of the proposed approach compared with other methods.
The rapid development of portable electronics requires miniaturized and flexible electrochemical capacitors (ECs) with ultrafast frequency response and/or integrated high capacitive performance. Herein, we report such ECs based on the highly conductive films of reduced graphene oxide (rGO) and commercially available poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) prepared by blade coating or filtration. The typical EC with ultrathin film electrodes exhibited a high-rate frequency response (phase angle = −81.4°) at 120 Hz. On the other hand, ECs with freestanding thick film electrodes exhibited outstanding capacitive performance with a wide range linear relationship between areal capacitance and mass loading. Particularly, an ultrathick film electrode with mass loading up to 33 mg cm−2 delivered ultrahigh areal (5365 mF cm−2) and volumetric (203 F cm−3) specific capacitances at 1 A g−1 (33 mA cm−2). The introduced wet-processing method perfectly integrates thin-film ECs for alternating current (AC) line-filtering and thick-film ECs for compact energy storage in one system, which is promising for practical applications.
A functionalized carbon nanotubes paste electrode modified with cross-linked chitosan for the determination of trace amounts of cadmium(II) and mercury(II) by linear anodic stripping voltammetry is described. Under optimal experimental conditions, the peak current was linear in the Cd(II) concentration range from 5.9×10−8 to 1.5×10−6 molL−1 with a detection limit of 9.8×10−9 molL−1 and, for Hg(II) from 6.7×10−9 to 8.3×10−8 molL−1with a detection limit of 2.4×10−9 molL−1. The proposed method was successfully applied for the determination of Hg(II) in natural and industrial wastewater samples, and Cd(II) in sediments, human urine, natural, and industrial wastewater samples.
The electrochemical performance of non-graphitized petroleum cokes has been improved by mild oxidation using hydrogen peroxide, a procedure used for the first time in these materials. For this purpose, various carbonisation temperatures and H2O2 treatments were tested. For low sulfur content cokes, the aqueous oxidative treatment significantly increases the capacity values above 372mAh/g during the first cycles. In contrast, cokes with a sulfur content of ca. 5%, did not shown a real improvement. The former results have been interpreted in terms of an effective oxidation of the particles surface, which removes unorganized carbon, where lithium can be irreversibly trapped. Moreover, a stable and less resistive passivating layer grows during the first discharge of lithium, as revealed by impedance spectroscopy. Therefore, chemical procedures, as mild oxidation, open an interesting field of research for the improvement of disordered carbons as anode materials in lithium ion batteries.
In this study, we report for the first time a simple method that directly converts heat into electrical energy at sub-zero ambient temperatures. The thermo-electrochemical cell was constructed with negative temperature coefficient (NTC) carbon nanotube-vanadium oxide (CNT-VOx) self-heating cathode, which provided thermal energy through an induced Joule effect. The electrical energy was obtained by creating in situ temperature difference between the electrodes (ΔT) and with subsequent redox reactions. A decrease in the cell resistance with an increase in the ΔT, and enhanced electrical energy conversion through a charge-transfer mechanism (i.e., Faradaic redox reaction) was observed. In addition, the advantage of using NTC CNT-VOx cathode as a self-heating source at various ΔT (i.e., without the support of any external source) in a thermo-electrochemical system for sub-zero temperature energy conversion is presented.
Executive functions (EF) reached full maturity during the transition from adolescence to adulthood. Human studies provide important information about adolescent developmental trajectories; however, little remains known about the neural circuits underlying the acquisition of mature EF. Ethical and technical considerations with human subjects limit opportunities to design experimental studies that allows for an in-depth understanding of developmental changes in neural circuits that regulate cognitive maturation. Preclinical models can offer solutions to this problem. Unfortunately, current rodent models of adolescent development have inherent flaws that limit their translational value. For instance, females are often omitted from studies, preventing the assessment of potential sex-specific developmental trajectories. Furthermore, it remains unclear whether cognitive developmental changes in rodents are similar to those observed in humans. Here, we tested adolescent and adult male and female mice in a neurocognitive battery of assays. Based on this approach, we assessed mice performances within distinct subdomains of EF, and observed similarities with human developmental trajectories. Furthermore, the sex-specific cognitive changes we observed were paralleled by molecular and neural activity changes demonstrating that our approach can be used in future research to assess the contribution of precise neural circuits to adolescent cognitive maturation.
We describe a new watermarking scheme based on intelligent shaping of a digital watermark using Genetic Programming (GP). The proposed method, in addition to achieving a superior tradeoff between watermark robustness and imperceptibility, is also able to structure the watermark in accordance with an anticipated attack. This has been achieved by simultaneously hiding the watermark as well as spreading and fusing it in such a way to resist the conceivable attack. Robustness versus imperceptibility tradeoff and increase in bit correct ratio after attack, have been employed as the optimization criteria in the GP search. The concept of bonus fitness has been used to implement multi-objective fitness based GP evolution. Experiments on standard images indicate that such watermark shaping functions could be developed that are cover image independent and enhance imperceptibility. They offer high resistance against removal and interference attacks of Checkmark benchmark.
A low-temperature electro-thermal coupled model, which is based on the electrochemical mechanism, is developed to accurately capture both electrical and thermal behaviors of batteries. Activation energies reveal that temperature dependence of resistances is greater than that of capacitances. The influence of frequency on polarization voltage and irreversible heat is discussed, and frequency dependence of polarization resistance and capacitance is obtained. Based on the frequency-dependent equation, a reduced low-temperature electro-thermal coupled model is proposed and experimentally validated under different temperature, frequency and amplitude conditions. Simulation results exhibit good agreement with experimental data, where the maximum relative voltage error and temperature error are below 2.65% and 1.79°C, respectively. The reduced model is demonstrated to have almost the same accuracy as the original model and require a lower computational effort. The effectiveness and adaptability of the proposed methodology for model reduction is verified using batteries with three different cathode materials from different manufacturers. The reduced model, thanks to its high accuracy and simplicity, provides a promising candidate for development of rapid internal heating and optimal charging strategies at low temperature, and for evaluation of the state of battery health in on-board battery management system.
The suitability of various dimensionally stable anodes (DSAs®) was investigated in comparison to the conventional lead alloy anodes in the electrowinning of copper. DSA® plate and mesh specimens of composition Ti–(70%) IrO2/(30%) Ta2O5 and lead–(6%) antimony were evaluated. The electrochemical behaviour of these anodes was studied by carrying out open circuit potential measurements, galvanostatic chronopotentiometry, cyclic voltammetry and chronoamperometry. Physical characterisation was done using a scanning electron microscope. It was observed that the DSA® plate anode exhibited the highest corrosion resistance followed by the DSA® mesh and lead anodes, respectively. The results also showed that during copper electrowinning using lead anodes, dissolution of the anode occurs while for both DSAs® marginal loss of coating was observed. The lead anode had the highest anode potential followed by the DSA® plate and mesh anodes, respectively. Overall, it was demonstrated that the DSA® plate anode is the most suitable anode for copper electrowinning.
Advanced anode materials for lithium ion batteries are central to the area of electrical energy storage devices. Herein, we have developed a two-step strategy for synthesizing MoS2@polypyrrole (MoS2@PPY) core-shell microspheres. In such a novel architecture, the MoS2 microspheres are homogeneously wrapped by conductive polypyrrole coating forming core-shell microspheres. As a preliminary test, the obtained MoS2@PPY microspheres exhibit greatly enhanced electrochemical performances for lithium storage compared with un-modified MoS2 microspheres. The MoS2@PPY microsphere electrode displays a high specific capacity of 1012 mAh g−1 after 200 cycles at 200 mA g−1 and high rate performance (600 mAh g−1 at 4000 mA g−1). The superior electrochemical performances are attributed to the advantageous combination of hierarchical microsphere structure and conductive PPY coating.
New complexes of the type [{M x M′1−x (dadb)} n ·yH2O] {where dadbH2 =2,5-diamino-3,6-dichloro-1,4-benzoquinone (1); M=Cu(II); M′=Zn(II); x =1 (2), 0.5 (4), 0.0625 (5), 0 (3); y =0–2 and n =degree of polymerization} were synthesized and characterized. Distinct identities of heterobimetallic complexes are revealed from nature and position of their PXRD lines. Complexes under present study are hygroscopic in the temperature range RT–60°C. The TGA, DTA and DSC thermograms suggest that complexes first lose water molecules followed by loss of HCl molecules under 2nd step of thermal degradation which is catalyzed by Cu(II) ions, whereas elimination of CO under 3rd step is catalyzed by air. Residue from 2 and 3 corresponds to 1/2 mole of metallic copper and zinc, respectively, under nitrogen atmosphere, whereas, one mole of CuO and half mole of ZnO, respectively under air. Thermal degradation pattern of the ligand moiety around Cu(II) have been observed to be different than that around Zn(II) ion.
Defects in DNA repair have been extensively linked to neurodegenerative diseases, but the exact mechanisms remain poorly understood. We found that FUS, an RNA/DNA-binding protein that has been linked to amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration, is important for the DNA damage response (DDR). The function of FUS in DDR involved a direct interaction with histone deacetylase 1 (HDAC1), and the recruitment of FUS to double-stranded break sites was important for proper DDR signaling. Notably, FUS proteins carrying familial ALS mutations were defective in DDR and DNA repair and showed a diminished interaction with HDAC1. Moreover, we observed increased DNA damage in human ALS patients harboring FUS mutations. Our findings suggest that an impaired DDR and DNA repair may contribute to the pathogenesis of neurodegenerative diseases linked to FUS mutations.
This paper reports the synthesis of various molar concentrations of manganese (Mn)-doped Sn4P3 nanoparticles and and their efficient use as anode materials for rechargeable lithium-ion batteries (LIBs). The nanoparticles were synthesized via a novel and facile ultrasonic assisted hydrothermal method and characterized in detail by various analytical techniques. The XRD, SEM, and TEM results showed that Mn ion was successfully substituted on the Sn4P3 layered structure without any structure changes. The long cycle stability of the as-prepared Mn-doped Sn4P3 nanoparticles have been tested as an anode material for lithium ion batteries at the different current density. By detailed experimental results exhibited that the Mn dopant content crucially determines the electrochemical performances of Sn4P3 nanoparticles. Electrochemical measurements show that the Sn4P3 nanoparticles with 0.10 mol% molar concentration of Mn dopant give the best cycling performances. They deliver a discharge capacity of 488mAhg−1 after 150 cycles at the current density of 100mAg−1. Even after 150 cycles at a current density of 200mAg−1, the specific capacity still could be remained at 420mAhg−1. Further increasing the current density to 1000mAg−1, it could still maintain 255mAhg−1 after 200 cycles. It is confirmed that Mn substitution in the Sn-Mn-P structure is an important pole to improve the structure stability and electrochemical properties.
The mineralogy of anodic portions of spent alkaline batteries from a leading brand (Duracell) that had been equilibrated in ambient air for approximately 4 months was investigated to determine if material generated from this low energy process may be suitable stock material for recycling. Powder X-ray diffraction (XRD) identified the bulk of the ambient air oxidized anodic material as zincite (ZnO). Scanning electron microscopy investigation indicates a variety of textures of zincite are present with euhedral hexagonal prisms being the most common crystal form. Energy dispersive spectroscopy (EDS) analysis indicates that there are no minor amounts of Mn within the zincite. Transmission electron microscopy investigation indicates a variety of textures exist in the <2μm size fraction including near euhedral prismatic crystals, crystals with step-fashion terminations and indentations, heavily corroded zincite and near amorphous aggregates of anastomozing zinc oxide. Impurities in the <2μm size fraction include minor amounts of unidentified mixed sulfate materials and are interpreted as dominantly occurring as thin coatings on zincite particles. Discrete submicrometer-sized spherical and rhomboid particles of Zn–Mn oxides are also common impurities in the <2μm size fraction but occurr at abundance of <1% by volume. This study provides new baseline information that can be used to develop large scale recycling of zincite from spent alkaline batteries. A promising applications of zincite are numerous, including the development of new solar cell materials. The spent alkaline battery waste stream may serve as promising resource for driving further development of this sector of the economy.
Diary excerpts chronicle the experiences of a nurse-midwife on assignment in Kosovo with Doctors of the World, USA, during the winter of 2000.
We developed and tested a comprehensive method for measuring the three-dimensional distribution of tubeworm colonies using an autonomous underwater vehicle (AUV). We derived volumetric measurements such as the volume, area, average height, and number of tubes for colonies of Lamellibrachia satsuma, the world's shallowest-dwelling vestimentiferan tubeworm discovered at a depth of 82m, at the Haorimushi site in Kagoshima Bay, Japan, by processing geometric and visual data obtained through low-altitude surveys using the AUV Tri-Dog 1. According to the results, the tubeworm colonies cover an area of 151.9m2, accounting for 5.8% of the observed area (2600m2). The total number of tubes was estimated to be 99,500. Morphological parameters such as area, volume, and average height were estimated for each colony. On the basis of average height, colonies could be clearly separated into two groups, short (0.1–0.3m) and tall (0.6–0.7m), independent of the area.
Herein, a ternary vanadium bronze compound, NaV6O15 was synthesized via a low temperature thermal oxidization of sodium-intercalated V2CTx, which exhibited a higher specific capacity than the precursor V2CTx when used as the anode material for lithium-ion batteries (LIBs). The characterization results showed that the NaV6O15 nanorods spontaneously grew in the interlayers and directly damaged the layered structure of MXene. Moreover, the charge–discharge result demonstrated an initial specific discharge capacity of 350mAhg−1 under a current density of 50mAg−1 was achieved and, in particular, a specific capacity of 120mAhg−1 and a Coulombic efficiency of 100% were maintained after as many as 200 cycles at 1000mAg−1 without the lattice expansion and deformation of NaV6O15 during the lithium-ion insertion/de-insertion process. According to these results, it is therefore expected that optimizing the process further to oxidize other metal cations intercalated-MXene will exploit other nanostructures employed as the electrode in LIBs and demonstrate immeasurable performance.