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A polymer system based on oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and cyclic carbonate methacrylate (CCMA) was chosen as matrix to realize high-performance gel polymer electrolytes due to the fact that both monomers are able to interact with the liquid electrolyte, thus, retaining it inside the matrix. Additionally, OEGMA enables high flexibility, while CCMA provides mechanical stability. The polymer displays a high thermal stability up to 200 °C and a glass transition temperature below room temperature (5 °C) allowing an easy handling of the obtained films. By immobilizing the liquid electrolyte 1 M LiPF6 in EC:DMC 1:1 w:w in the polymer host a gel polymer electrolyte with a high conductivity of 2.3 mS cm−1 at 25 °C and a stable cycling behavior with high capacities and efficiencies in Li(Ni1/3Co1/3Mn1/3)O2 (NCM)/graphite full cells is obtained. The investigated gel polymer electrolyte is identified as promising electrolyte for lithium-ion batteries, because it combines good electrochemical properties comparable to that of liquid electrolytes with the safety advantage that no leakage of the flammable electrolyte solvents can occur.
Li-rich layered oxide cathodes suffer from poor rate capability, voltage decay and inferior cycling stability. Herein, we propose a novel synergistic strategy to improve the electrochemical performances of Li-rich Li1.20Ni0.13Co0.13Mn0.54O2 by the co-doping of Na+ and PO4 3−. The co-doping of Na+ for Li and PO4 3− for Mn is simultaneously achieved using Na3PO4 as a dopant. The co-doping of Na+ and PO4 3− not only enhances the high-rate performance (106.4 mAhg−1@10C) and capacity retention (93.8%@1C@100 cycles) but also mitigates the voltage decay owing to the synergistic effect of Na+ and PO4 3− co-doping. The synergistic mechanism is unraveled based on neutron diffraction, aberration-corrected scanning transmission electron microscope, X-ray photoelectron spectroscopy, ex-situ X-ray absorption spectra, ex-situ X-ray diffraction, electrochemical impedance spectroscopy and electrochemical measurements. The co-doping of Na+ and PO4 3− enlarges the interlayer spacing and suppresses Li/Ni mixing which increases Li+ diffusivity and enhances the rate capability. Meanwhile, the co-doping of Na+ and PO4 3− shrinks the thickness of the slabs, weakens the TM-O covalency and alleviates the volume change in the charge/discharge process which improves the layered structure stability and the cycling performances. This study presents some new insights into designing high performance cathode materials through a cooperative modulation of different crystal sites doping.
Rechargeable Lithium ion batteries (LIBs) are commonly used power source in everyday electrical devices. Understanding the real-time atomistic evolution of the electrodes in a LIB is indispensable since the performance of a LIB is governed by electrochemical reactions and possible mechanical degradation of the electrodes during the operation of a battery. With advances in high resolution transmission electron microscopy and microfabrication techniques, it has been possible to investigate the evolution of solid electrolyte interphase, electrolyte decomposition, and the response of the electrode upon lithiation-delithiation at the atomic scale. This article provides a comprehensive review of the current understanding of lithiation-delithiation mechanisms in LIBs.
The aim of this study was to design and construct a non-virulent simulant to replace several pathogenic viruses in the development of detection and identification methods in biodefense. A non-infectious simulant was designed and engineered to include the nucleic acid signature of VEEV (Venezuelan Equine Encephalitis virus), Influenza virus, Rift Valley Fever virus, Machupo virus, Lassa virus, Yellow Fever virus, Ebola virus, Eastern Equine Encephalitis virus, Junin virus, Marburg virus, Dengue virus, and Crimean-Congo virus, all in a single construct. The nucleic acid sequences of all isolates available for each virus species were aligned using ClustalW software in order to obtain conserved regions of the viral genomes. Specific primers were designed to permit the identification and differentiation between viral threat agents. A chimera of 3143 base pairs was engineered to produce 13 PCR amplicons of different sizes. PCR amplification of the simulant with virus-specific primers revealed products of the predicted length, in bands of similar intensity, and without detectable unspecific products by electrophoresis analysis. The simulant described could reduce the need to use infectious viruses in the development of detection and diagnostic methods, and could also be useful as a non-virulent positive control in nucleic acid-based tests against biological threat agents.
The heritability of genetic resistance of radiata pine against Fusarium circinatum was not clear. We demonstrated that there are at least 3 QTLs that could be involved in this resistance/susceptibility.
ABSTRACT The charging of electric vehicles (EVs) impacts the distribution grid, and its cost depends on the price of electricity when charging. An aggregator that is responsible for a large fleet of EVs can use a market-based control algorithm to coordinate the charging of these vehicles, in order to minimize the costs. In such an optimization, the operational parameters of the distribution grid, to which the EVs are connected, are not considered. This can lead to violations of the technical constraints of the grid (e.g., under-voltage, phase unbalances); for example, because many vehicles start charging simultaneously when the price is low. An optimization that simultaneously takes the economic and technical aspects into account is complex, because it has to combine time-driven control at the market level with event-driven control at the operational level. Different case studies investigate under which circumstances the market-based control, which coordinates EV charging, conflicts with the operational constraints of the distribution grid. Especially in weak grids, phase unbalance and voltage issues arise with a high share of EVs. A low-level voltage droop controller at the charging point of the EV can be used to avoid many grid constraint violations, by reducing the charge power if the local voltage is too low. While this action implies a deviation from the cost-optimal operating point, it is shown that this has a very limited impact on the business case of an aggregator, and is able to comply with the technical distribution grid constraints, even in weak distribution grids with many EVs.
One of the most popular techniques of renewable energy generation is the installation of photovoltaic (PV) systems using sunlight to generate electrical power. There are many factors that affecting the operation and efficiency of the PV based electricity generation systems, such as PV cell technology, ambient conditions and selection of required equipment. There is no much study that presents all factors affecting efficiency and operation of the entire PV system, in the literature. This paper provides a detailed review of these factors and also includes suggestions for the design of more efficient systems. The presented detailed overview will be useful to people working on theory, design and/or application of photovoltaic based electricity generation systems.
Reduced graphene oxide (RGO) wrapped metal-organic frameworks (MOFs) derived cobalt doped porous carbon polyhedrons synthesized via a carbonization process, are for the first time used for sulfur immobilizers (RGO/C–Co-S) as cathodes for high performance lithium-sulfur (Li–S) batteries. The RGO/C–Co–S cathode exhibits greatly improved electrochemical performance, showing excellent specific capacity of 949mAh g−1 at 300th cycle at a current density 0.3Ag−1, displaying enhanced rate capability with specific capacity of 772, 704 and 606mAh g−1 at current density of 0.5, 1 and 2Ag−1, respectively. The synergetic effect of MOFs-derived porous carbon, homogeneously distributed Co nanoparticles and RGO nanosheets simultaneously contributes to the confinement of sulfur species. The presence of abundant mesopores and micropores is conducive to immobilize large amounts of S species. The homogenously inlaid ultrafine Co nanoparticles can further immobilize sulfur by chemical interactions between Co and S/polysulfides. The RGO nanosheets tightly wrapped on carbon hosts act as barrier layers to prevent polysulfides from diffusing out of the matrix, further suppressing shuttle effect. The porous structure and the RGO can effectively alleviate the volume changes resulted from charge–discharge process. This design strategy can be inspiring for MOF-derived materials in energy storage applications.
Child development researchers often discuss a “two-word” stage during language acquisition. However, there is still debate over whether the existence of this stage reflects primarily cognitive or linguistic constraints. Analyses of longitudinal data from two Deaf children, Mei and Cal, not exposed to an accessible first language (American Sign Language – ASL) until the age of 6years, suggest that a linguistic constraint is observed when cognition is relatively spared. These older children acquiring a first language after delayed exposure exhibit aspects of a two-word stage of language development. Results from intelligence assessments, achievement tests, drawing tasks, and qualitative cognitive analyses show that Mei and Cal are at least of average intelligence and ability. However, results from language analyses clearly show differences from both age peers and younger native signers in the early two-word stage, providing new insights into the nature of this phase of language development.
Nitrogen and sulfur co-doped graphene aerogel (NS-GA) is prepared by one-pot process. The as-prepared materials are investigated as supercapacitors electrodes in an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) electrolyte. The NS-GA is characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy scanning electron microscopy. The results show that the NS-GA has hierarchical porous structure. Electrochemical performance is investigated by cycle voltammetry and galvanostatic charge-discharge. Notably, the supercapacitor based on the NS-GA-5 possesses a maximum energy density of 100.7 Wh kg−1 at power density of 0.94 kW kg−1. The electrode materials also offer a large specific capacitance of 203.2 F g−1 at a current density of 1 A g−1 and the capacitance retention of NS-GA-5 is 90% after 3000 cycles at a scan rate of 2 A g−1. The NS-GA-5 with numerous advantages including low cost and remarkable electrochemical behaviors can be a promising electrode material for the application of supercapacitors.
One of the main challenges to develop all solid state lithium (Li) metal batteries is the poor contact and thus the high interfacial resistance between electrodes and solid state electrolytes (SSEs). Recently, significant improvements have been made toward effective Li-garnet interfaces however due to the poor conductivity and rigid granular morphology of cathode materials, the cathode-garnet interface is deficient. In this work, we report an effective cathode-garnet interface using a mixed ionic-electronic (MIE) conductor, which enables cycling of all solid state batteries without a liquid or polymer electrolyte interface. The solution-processed two dimensional (2D) layered TiS2 shows MIE conductivity after slow pre-lithiation, resulting in more than 20 times lower interfacial resistance. In addition, solution-processed carbon nanotubes offer a conformal coating for an efficient cathode-current collector interface with enhanced charge transport kinetics. As a result, we demonstrated the first garnet-based truly all solid state battery using solution processed composite cathode. Given the excellent chemical stability of the Li metal anode, garnet SSE, and TiS2 cathode, the all solid state batteries can work at high temperatures from 100 °C to 150 °C for 400 cycles at current densities up to 1 mA/cm2. The demonstrated MIE concept for addressing cathode-electrolyte interface can be further extended to other solid state battery chemistries.
In our contribution we study the long-term durability of two different graphite felt materials serving as negative electrode in vanadium redox flow battery. Both electrodes differ in the precursor material and the way of activation which causes significant differences in relevant properties such as electric conductivity, specific surface area and electrochemical double layer capacitance. The performance stability of the felts within 2000 charge-discharge cycles conducted in lab-scale single-cell is evaluated from 4-point characterization before the cycling and after each 1000 cycles. Significant deterioration of electrocatalytic activity is observed for commercially activated polyacrylonitrile-based negative electrode, whereas the in-house activated rayon-based negative electrode provides stable performance over the whole tested period. A comprehensive post-mortem characterization is performed to identify the causes of different durability of both negative electrodes. X-ray photoelectron spectroscopy analysis reveals very similar changes in surface functionalization by oxygen-containing groups for both felts; however, the decrease of sp2-hybridized carbon and simultaneous increase of sp3-hybridized one is significantly higher for the unstable polyacrylonitrile-based felt. Although the performance deterioration of the polyacrylonitrile-based felt cannot be related to the decrease of the surface area or double-layer capacitance, the high surface area of activated rayon-based felt most probably contributes to its excellent performance stability.
Executive functions is an umbrella term describing a wide range of higher order processes that allow the flexible modification of thought and behaviour in response to changing cognitive or environmental contexts. Impairment of executive functions is common in neurodegenerative disorders such as Alzheimer's disease. These deficits negatively affect everyday activities and hamper the ability to cope with other cognitive or behavioural disorders. In this paper, we propose a synthesis of the knowledge on executive impairments in clinical and preclinical Alzheimer's disease, mostly leaning on the current studies made in this domain. We made some propositions for neuropsychological assessment of executive functions in preclinical and clinical phases of Alzheimer's disease. We hope that this overview will provide a useful insight into an area that is still insufficiently explored in the field of the neuropsychology of Alzheimer's disease.
Flexible lithium ion batteries shows great attention as up-and-coming power source for the development of flexible and wearable electronic devices. However, they lack suitable electrode materials that are capable of withstanding rapid charging/discharging to facilitate high power density lithium ion batteries. In this work, we fabricate three dimensional (3D) nitridated hematite nanorods on a carbon cloth as high-performance anode for flexible lithium ion batteries. Our strategy to modify the surface of Fe2O3 via nitridation is to improve the electrical conductivity of Fe2O3. XPS, Raman spectra and SEM images confirmed the incorporation of nitriated surface. The fabricated device based on the nitridated hematite nanorod anode exhibiting high flexibility and outstanding lithium storage performance with power and energy densities of 24328 W kg−1 and 163 Wh kg−1, respectively at high current density of 10 A g−1. The high power density is due to the nitridation that provide a short lithium ion diffusion length and a high electronic conductivity in the nitridated-hematite nanorods leading to favorable kinetics electrical conductivity and significantly improved its rate capability.
A frequent belief is that the rise of so-called “gig work” has led to the displacement of workers in a wide range of traditional jobs. This paper examines the impacts of the flagship of the gig economy—Uber—on workers employed in conventional taxi services. Our analysis exploits newly collected data on the staggered rollout of Uber across metropolitan areas in the United States and a difference-in-differences design to document that incumbent taxi drivers experienced a relative earnings decline of about 10 percent subsequent to Uber’s entry into a new market, while there are no significant effects on their labor supply. Additional evidence from a battery of placebo tests, event study estimates, and specifications using Google Trends data to capture differences in treatment intensity underlines these findings. A triple-differences design that compares changes among taxi drivers relative to bus, tractor, and truck drivers that were unaffected by the arrival of Uber, provides further supporting evidence that the diffusion of Uber has reduced the earnings potential of incumbent drivers in conventional taxi services in the United States.
The inherently poor dynamic charge-acceptance of the lead–acid battery can be greatly improved by the incorporation of additional carbon to the negative plate. An analysis is undertaken of the various ways by which the carbon may be introduced, and of the proposed mechanisms whereby its presence proves to be beneficial. It is intended that such an investigation should provide a guide to the selection of the optimum carbon inventory.
ABSTRACT A series of seven different hydrocolloids are tested as water-soluble binders for synthetic graphite (SG)-based electrodes of lithium-ion batteries (LIBs) and compared with the standard poly(vinylidene difluoride) (PVDF) binder. The hydrocolloids selected are sodium carboxymethyl cellulose (Na-CMC), sodium alginate (Na-Alg), gum arabic (GA), xanthan gum (XG), guar gam (GG), agar-agar (AA) and carrageenan (CAR), the latter three with no precedents in the literature. They all show thermal and electrochemical stability under the experimental conditions employed. For SG/hydrocolloid electrodes, binder concentrations of 5wt% are found to be optimal, providing outstanding electrochemical performances for electrodes with Na-Alg Na-CMC, XG and GG in galvanostatic cycling experiments at constant (C/10, with C=372mAg−1) and variable (fromC/10 to 2C) current rates, which are comparable, or even superior to those of SG/PVDF electrodes with higher binder content (8wt%). In contrast, SG/GA, SG/CAR and SG/AA electrodes show poorer electrochemical performances, most likely owing to the low adhesion capacity of the binder (GA and CAR), or the formation of films covering the SG particles (CAR and AA).
The effects of etching process on the morphology, structure and electrochemical performance of arc-produced multiwalled carbon nanotubes (CNTs) as anode material for lithium-ion batteries were systematically investigated by TEM and a variety of electrochemical testing techniques. It was found that the etched CNTs exhibited four times higher reversible capacity than that of raw CNTs, and possessed excellent cyclability with almost 100% capacity retention after 30 cycles. The kinetic properties of three kinds of CNTs electrodes involving the pristine (CNTs-1), etched (CNTs-2) as well as etch-carbonized samples (CNTs-3) were characterized via ac impedance measurement. It was indicated that, after 30 cycles the exchange current density i 0 of etched CNTs ((7.6–7.8)×10−3 Acm−2) was higher than that of the raw CNTs (5.9×10−3 Acm−2), suggesting the electrochemical activity of CNTs was enhanced by the etching treatment. The storage characteristics of the CNTs electrodes at room temperature and 50°C were particularly compared. It was found that the film resistance on CNTs electrode generally tended to become large with the elongation of storage time, especially storage at high temperature. In comparison with CNTs-1 and CNTs-3, CNTs-2 exhibited more distinctly increase of film resistance, which is related with the surface properties.
Uniform zinc-cyanide hybrid coordination polymer microspheres were successfully synthesized by a coprecipitation method. Then hierarchical yolk-shell structured and carbon coated ZnO microspheres (YC-ZnO) composed of ZnO@C nanocrystals were prepared by consecutive post annealing processes of these microspheres in argon and air atmosphere. Such micro-nano porous structures have the advantages of large specific surface area, good charge transport kinetics, and large cavity to accommodate the volume change and maintain the mechanical integrity of the electrode material. When evaluated as anode materials of lithium ion batteries, these ZnO yolk-shell spheres exhibited excellent battery performance with a high rate capacity and ultra-stable cycling stability.
Publisher Summary Practicing the best design techniques will not eliminate all the mistakes. No one is smart enough to anticipate every nuance and implication of each design decision on even a simple little 4k 8051 product. When complexity soars to hundreds of thousands of lines of code coupled to complex custom ASICs, one can be sure that bugs will multiply like rabbits. When basic design decisions are being made, it is known beforehand that in weeks or months the grand scheme will go from paper scribbles to hardware and software ready for testing. It behooves users to be quite careful with those initial choices, to be sure that the resulting design isn't an undebuggable mess. An unhappy reality is that one will surely spend lots of time debugging both hardware and firmware. For better or worse, debugging consumes project-months with reckless abandon. It's usually a prime cause of schedule collapse, disgruntled team members, and excess stomach acid. Later this chapter describes tools and techniques used in debugging, the role of PCBs, and the importance of planning in these engineering projects.
A facile reflux method has been developed to prepare porous NiO samples using NaBH4-EG and NaOH-EG as alkaline precipitants, respectively. NaBH4-EG is used as alkaline precipitant for the first time. Precipitants influence the morphology and structure of NiO significantly, further affect their specific capacitances as supercapacitor electrodes. Compared with NaOH, NaBH4-EG as alkaline precipitant shows great superiority on morphology control. NiO synthesized by NaBH4-EG presents spherical spongy shape with high specific surface areas, whereas the sample synthesized by NaOH-EG exhibits agglomerated irregular structure. When being applied as supercapacitor electrodes, the former NiO could achieve an extremely high specific capacitance of 930Fg−1 at a current density of 15Ag−1, significantly higher than that of the latter one (510Fg−1). Moreover, the specific capacitance of the former is as high as 1396Fg−1 after 1000-cycle at 4Ag−1, revealing superb electrochemical characteristics. The impedance measurement discloses that the electrode prepared by the former NiO possesses lower charge-transfer resistance and ion-diffusion resistance, demonstrating the superiority of NaBH4-EG as alkaline precipitant. NaBH4-EG is an excellent precipitant for the synthesis of porous NiO as supercapacitor electrodes.
Three-dimensional porous silicon has been prepared by magnesiothermically reducing diatomaceous earth. BET surface area analysis shows that the specific surface area of the obtained porous silicon is about 96 m2 g−1, much higher than that of the diatomaceous earth (6 m2 g−1). The silicon products after HCl immersion have a porous structure similar to that of the diatomaceous earth, with pore sizes around 200 nm. Galvanostatic cycling tests show that the initial charge and discharge capacities of the porous silicon are 1321 mAh g−1 and 1818 mAh g−1, respectively. A reversible capacity of 633 mAh g−1 is retained after 30 cycles.