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The effect of surface area on the electrochemical properties and thermal stability of Li[Ni0.2Li0.2Mn0.6]O2 powders was characterized using a charge/discharge cycler and DSC (Differential Scanning Calorimeter). The surface area of the samples was successfully controlled from ~4.0 to ~11.7 m2 g−1 by changing the molar ratio of the nitrate/acetate sources and adding an organic solvent such as acetic acid or glucose. The discharge capacity and rate capability was almost linearly increased with increase in surface area of the sample powder. A sample with a large surface area of 9.6–11.7 m2 g−1 delivered a high discharge capacity of ~250 mAh g−1 at a 0.2 C rate and maintained 62–63% of its capacity at a 6 C rate versus a 0.2 C rate. According to the DSC analysis, heat generation by thermal reaction between the charged electrode and electrolyte was not critically dependent on the surface area. Instead, it was closely related to the type of organic solvent employed in the fabrication process of the powder.
Although heme oxygenase-1 (HO-1) is induced in keratinocytes after UV radiation, HO-1 expression during normal epidermal differentiation has not yet been reported. We showed by real-time PCR, western blotting, and ELISA that HO-1 mRNA and protein expression by cultured normal human keratinocytes was upregulated during epidermal differentiation induced by a high-calcium medium. Immunohistochemical staining and in situ hybridization showed the graduated expression of HO-1 in the upper epidermis, which was accompanied by suprabasal HO-1 mRNA expression, and the accumulation of bilirubin (BR) in the stratum corneum. We examined the activation of nuclear factor E2-related factor 2 (Nrf2), which is a pivotal transcription factor for HO-1 expression, by western blotting and by examining the mRNA expression of Nrf2 target genes, and excluded its role in HO-1 expression in epidermal differentiation. Next, we examined the regulation of HO-1 expression by inflammatory cytokines. IL-4 and IL-22 significantly reduced HO-1 mRNA and protein expression, whereas IL-1β, IL-17A, and tumor necrosis factor-α (TNF-α) increased it. Finally, immunohistochemical studies on psoriatic lesional skin showed that HO-1 expression was downregulated in the parakeratotic epidermis, whereas it was retained in the orthokeratotic epidermis. These studies demonstrate that HO-1 is functionally expressed by keratinocytes in parallel with epidermal differentiation and that its expression is independently affected by several cytokines.
Herein, the growth of ultrafine Pt nanoparticles on graphene oxide-dispersed pristine carbon nanotube (G-PCNT) supports has been achieved by a convenient and scalable approach. Remarkably, the resulting Pt/G-PCNT hybrid possesses a series of distinct structural advantages, such as cross-linked porous framework, large specific surface area, low-defect CNT skeletons, uniform Pt dispersion, and excellent electron conductivity, which lead to the strong synergetic coupling effects that are very beneficial for methanol oxidation reaction. As a consequence, exceptional catalytic activity, good electrochemical stability, and strong poison tolerance are observed for the obtained Pt/G-PCNT catalyst, all of which are evidently superior to those for conventional Pt/carbon black, Pt/acid-treated CNTs, and Pt/graphene catalysts.
In this paper, temperature dependence of ionic conductivity, crystallographic structural, morphological and thermal characteristics of polymer blends of PMMA and PVC with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) as a dopant salt are investigated. The study on the temperature dependence of ionic conductivity shows that these polymer blends exhibit Arrhenius behavior. The highest ionic conductivity was achieved when 70wt% of PMMA was blended with 30wt% of PVC. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal the amorphous nature and surface morphology of polymer electrolytes, respectively. In DSC analysis it was found that the glass transition temperature (T g ) and melting temperature (T m ) decreased, whereas the decomposition temperature (T d ) increased. In contrast, the shift towards higher decomposition temperature and decrease in weight loss of polymer electrolytes, in TGA studies, indicates that the thermal stability of polymer electrolytes improved.
Several quaternary ammonium or lithium bis(trifluoromethane sulfone) imide (TFSI) salts were dissolved into N,N,N,N-hexyltrimethyl ammonium TFSI ionic liquid, and the conductivities of the resulting solutions were measured. Some asymmetric quaternary ammonium salts contributed to increase the conductivity of the solution, while cyano-containing quaternary ammonium and lithium salts decreased the conductivity. Based on the results of differential scanning calorimetry (DSC) measurements, such conductivity behaviors appeared to be related to the intrinsic miscibility of the ionic liquid solutions.
This work analyses the economic and technical impact of local reactive power provision in grid-connected microgrids with distributed energy resources. Costs of reactive power provision by photovoltaic systems and battery energy storage systems are explicitly formulated and an objective function incorporating the costs is proposed. The advantage of the proposed objective function is validated by comparing it with other objective functions frequently employed in the literature. From various case studies, the extent of economic and technical benefits of local reactive power provision for the microgrid is established. Subsequently, the technical and economic competitiveness of reactive power provision using inverter-based distributed energy resources are compared against those using switched capacitors. Extensive sensitivity analyses are performed to determine the scenarios in which one technology is more competitive than the other. Inverter efficiency has been identified as the most important parameter for reactive power provision from distributed energy resources while electricity price is the most crucial factor for switched capacitors’ competitiveness in producing reactive power.
Different aqueous-based electrolytes have been tested in order to improve the electrochemical performance of hybrid (asymmetric) carbon/MnO2 electrochemical capacitor (EC). Chloride and bromide aqueous solutions lead to the formation of Cl2 and Br2 respectively upon oxidation of the corresponding salt, thus limiting the useful electrochemical window of the MnO2 electrode and producing gas evolution (in the case of chloride salts) detrimental to the cycling ability of an hybrid device. For sulfate and nitrate salts, MnO2 electrode exhibits a 20% increase in capacitance when lithium is used as the cation compared to sodium or potassium salts, probably due to partial lithium intercalation in the tunnels of α-MnO2 structure. The higher ionic conductivity and solubility of LiNO3 has led to the investigation of this electrolyte in carbon/MnO2 supercapacitor compared to standard hybrid cell using K2SO4. A lower resistance increase was evidenced when the temperature was decreased down to −10°C. Long term cycling ability of carbon/MnO2 supercapacitor was also evidenced with 5M LiNO3 electrolyte.
1D nanostructured manganese oxides are prepared by oxidation reaction of precursor LiMn2−x Cr x O4 microcrystals under hydrothermal condition. The crystal structure and morphology of the obtained manganese oxides are strongly dependent on the reaction condition and the chemical composition of the precursors. The α-MnO2 nanowires are prepared by reaction at 120°C, and their aspect ratios decrease with the Cr content in the precursor. Treating precursors with persulfate ions at 160–180°C yields the β-MnO2 nanorods for the precursors LiMn2−x Cr x O4 with lower Cr content and the α-MnO2 nanowires for the precursors with higher Cr content. The structure dependence of the products on the Cr content in the precursors is related to the high octahedral site stabilization energy of Cr3+ ions and/or to the increase of Mn valence state upon Cr substitution. The increase of Cr content in the precursors degrades the electrode performance for the manganates prepared at 160°C but improves electrode activity for those prepared at 180°C. This observation can be explained by the structural variation and chromium substitution of the hydrothermally treated manganates. We conclude that the use of spinel LiMn2−x Cr x O4 as precursors provides an effective way to synthesize 1D nanostructured manganate with tailored crystal structure and morphology.
The objective of this article is to investigate the technically and economically optimum electricity storage technologies for small, insular, autonomous electrical grids, integrated with Renewable Energy Sources (RES) power plants. Three autonomous Greek islands are investigated as case studies: Symi, Astypalaia and Kastelorizo, with annual peak demand at 4.0 MW, 2.2 MW and 0.9 MW respectively. All three islands exhibit excellent wind and solar potential, with ideal sites for the installation of seawater Pumped Hydro Storage (PHS). Two different approaches are investigated, regarding the electricity storage plants: PHS systems (for the two largest islands) and electrochemical storage, alternatively realized with lead acid or lithium-ion batteries. Wind parks and photovoltaic stations are considered as the potential RES units. Relevant operation algorithms are introduced. The dimensioning of the examined plants is optimized with a common target: the achievement of RES annual penetration percentage higher than 70%, ensuring the investments’ economic feasibility, with electricity selling prices lower than the existing specific production cost. Given the favorable land morphology for PHS installations, it is shown that wind-PHS still remains a competitive alternative for Symi and Astypalaia, despite their relatively small size, while for Kastelorizo, a wind-photovoltaic-batteries features as the optimum option. 100% annual RES penetration can be achieved only with the PHS support. With electrochemical storage systems, the RES annual penetration can be between 80 and 90%. The economic feasibility is ensured with electricity selling prices between 200 and 350 €/kWh. The investments’ payback periods are estimated between 6 and 10 years.
Sleep apnea (SA) is highly prevalent in post-stroke patients. Due to physical disability and relative inaccessibility of polysomnography (PSG) to test for SA, patients with stroke frequently remain undiagnosed and untreated. Portable SA monitoring can facilitate at-home or in-hospital testing for SA. However, portable SA monitoring is not recommended in those with complex medical conditions, such as stroke, due to the lack of validation of portable monitoring in such patients.
Abstract The benefits of SiC devices are demonstrated in different application. Therefore different power and voltage ranges from low voltage to medium voltage are addressed. The power electronic circuits are described and the results are shown. The first example is a 10kVA SiC inverter for an online UPS system. The second example is a 1-MW grid–tied battery inverter. And in the third subchapter, different examples of applications or medium voltage power electronics with SiC devices with blocking voltages above 3.3kV are shown.
In recent years, a large diversity of network-enabled devices have been widely prevalent in home environment. With the prevalence of such devices, wireless home networks enable monitoring and control applications for home user comfort and efficient home management. In the home network, alarm signals must be delivered in real-time to the residents or to the emergency services and some home control applications require the response time to be on the order of a few hundred milliseconds for optimal user experience. Most recently, ZigBee has emerged as one of the most promising technologies for wireless home networking because it is targeted at applications that require a low data rate and long battery life, which are also the features of home network applications. However, its usage in close proximity to Wireless Local Area Networks (WLANs) introduces coexistence problems, resulting in failing to fulfil the response time required by the home control applications. To overcome this problem, we propose to control the WLAN traffic when there exist ongoing ZigBee transmissions and the maximum tolerable delay is not met due to the WLAN interference. We aim to guarantee that the delay experienced by ZigBee sensors (especially, for alarm signals) does not exceed the maximum tolerable delay, while maintaining as high throughput as possible in the WLANs. The simulation results demonstrate that our proposed algorithm can enhance the delay performance of ZigBee networks by mitigating the effect of WLAN interference and improve the throughput in the WLANs.
Flaviviruses are a genre of closely related viral pathogens which emerged in the last decades in Brazil and in the world. Saint (St.) Louis encephalitis virus (SLEV) is a neglected flavivirus that can cause a severe neurological disease that may lead to death or sequelae. St. Louis encephalitis pathogenesis is poorly understood, which hinders the development of specific treatment or vaccine.
Despite the death of the dot-coms, there's no doubt that the digital revolution is reshaping the way we do business and relate to each other. Some would argue that this is happening with precious little thought for the environment or society at large, yet others say it has real potential to benefit both. Over the past year, Forum for the Future's Digital Futures project has examined the sustainability opportunities of e-business and the project's findings are summarised in this article. 1
Nanoscale observation of charge distribution and electric polarization is crucial for understanding and controlling functional materials and devices. In particular, the importance of charge dynamics is well recognized, and direct methods to observe charge generation, transfer, and recombination processes are required. Here, we describe tip-synchronized time-resolved electrostatic force microscopy. Numerical modeling clarifies that the tip-synchronized method provides temporal resolution with the timescale of the cantilever oscillation cycle. This method enables us to resolve sub-microsecond charge migration on the surface. The recombination of photo-excited carriers in a bilayer organic photovoltaic thin film is observed as a movie with a 0.3 µs frame step time resolution. Analysis of the images shows that the carrier lifetime is 2.3 µs near the donor/acceptor interface. The tip-synchronized method increases the range of time-resolved electrostatic force microscopy, paving the way for studies of nanoscale charge dynamics.
Adults with ADHD have problems in everyday multitasking situations presumably because of deficits in executive functions. The present study aims to find out (a) whether adults with ADHD show deficient multitasking performance in a standardized task, (b) how they perceive the multitasking situation, and (c) which task structure might be beneficial for them as compared with adults without ADHD. Therefore, we experimentally compared task performance, mood, and motivation in a group of 45 men with ADHD (M-age = 34.47, SD = 9.95) with a comparison group of 42 men without ADHD (M-age = 31.12, SD = 10.59) in three conditions: (a) a multitasking paradigm, (b) an interleaving condition in which tasks had to be performed without planning or monitoring, and (c) a non-interleaving condition. Our results showed no impaired multitasking performance in adults with ADHD. However, they showed better mood and more motivation in the non-interleaving condition.
The electrical properties of composite polymer electrolyte systems composed of 49% poly(methyl methacrylate) (PMMA) grafted natural rubber (MG49) host polymer, ammonium triflate (NH4CF3SO3) salt, and SiO2 as a filler were investigated by impedance spectroscopy technique. Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectra were also measured and indicated the occurrence of polymer–salt–filler interaction. The conductivity for the composite ammonium triflate-doped MG49 polymer was studied as a function of temperature between 303K and 373K. The conductivity was found to exhibit Arrhenius behavior indicating that it is thermally activated. Viscosity measurements were also carried out and showed that the mechanical properties of the composite polymer gel electrolytes (CPGEs) are improved. The highest electrical conductivity of the composite electrolyte system (∼7.55×10−3 Scm−1) was observed for the sample containing 8.0wt.% SiO2. The viscosity for that material was high (∼69cP) compared with the electrolyte containing no SiO2 (∼10cP).
Polymethyl methacrylate (PMMA), which has the thermal property of unzipping, was used as a pore-forming agent during electrode fabrication to solve the chronic volume expansion problem in silicon (Si) anodes for lithium ion batteries (LIBs). PMMA-treated Si alloy electrodes have low volume expansion resulting in low deformation during lithiation. To maximize the effect of a porous structure, the pore diameter in the electrode was controlled. The best cycling stability was obtained when using 10 μm diameter PMMA. After 100 cycles at the 0.5-C rate a bare electrode retained 39% capacity, whereas an electrode using 10 μm diameter PMMA retained 62%. The outstanding capacity retention obtained from porous electrodes originated from the optimized porous architecture. Furthermore, PMMA-treated electrodes provide the lowest resistance in a cell by facilitating fast electron and ion transport, enhancing battery performance. Hence, for cycle-guaranteed Si-based LIBs these porous electrodes could provide an alternative or supplementary structure to other more complex manufacturing processes.
Conjugated polymer semiconductors offer unique advantages over conventional semiconductors but tend to suffer from electro-optic performance roll-off, mainly due to reduced photofastness. Here, we demonstrate that the commodity nickel chelate nickel(II) dibutyldithiocarbamate, Ni(dtc)2, effectively inhibits photooxidation across a wide range of prototypical π-conjugated polymer semiconductors and blends. The addition of 2–10 wt% of Ni(dtc)2 increases the resilience of otherwise quickly photobleaching semiconducting thin films, even in the presence of detrimental, radical forming processing additives. Using electron spin resonance spectroscopy and sensitive oxygen probes, we found that Ni(dtc)2 acts as a broadband stabilizer that inhibits both the formation of reactive radicals and singlet oxygen. The mechanism of stabilization is of sacrificial nature, but contains non-sacrificial contributions in polymers where singlet oxygen is a key driver of photooxidation. Ultrafast pump–probe spectroscopy reveals quenching of triplet excited states as the central mechanism of non-sacrificial stabilization. When introduced into the active layer of organic photovoltaic devices, Ni(dtc)2 retards the short circuit current loss in air without affecting the sensitive morphology of bulk heterojunctions and without major sacrifices in semiconductor properties. Antioxidants based on nickel complexes thus constitute functional stabilizers for elucidating degradation mechanisms in organic semiconductors and represent a cost-effective route toward organic electronic appliances with extended longevity.
Higher requirements have been put forward for self-powered systems operated with weak energy in the environment. Sensitivity, efficiency and power management design of the energy harvesting module play key roles on the sustainability of the system. In this work, we present an ultrasensitive triboelectric nanogenerator (TENG) with Cu coated fluorinated ethylene propylene films stacked in a unipolar manner and suspended by springs. Triboelectrification and electrostatic induction take place between every adjacent film surfaces, during which transferred charges are increased by at least 50%, leading to an increased efficiency. Also, the reduced framework weight makes soft spring can be adopted for greatly improved sensitivity. Depending on the investigation of mechanical motion in the system, TENG's energy harvesting efficiency is boosted by bringing down the moment of inertia. The linear region characteristic of an n-type junction field-effect transistor is utilized for a low-loss power management design with greatly reduced power consumption and start-up time for superior weak energy harvesting applications. Ultrasensitive and high efficient energy harvester with low-loss power management demonstrated in this work promises an outlook for an effective approach to achieve more powerful and more sustainable self-powered systems working with comprehensive ambient weak mechanical energy fitted in diverse application circumstances.
Yttrium is important rare earths (REs) used in numerous fields, mainly in the phosphor powders for low-energy lighting. The uses of these elements, especially for high-tech products are increased in recent years and combined with the scarcity of the resources and the environmental impact of the technologies to extract them from ores make the recycling waste, that contain Y and other RE, a priority. The present review summarized the main hydrometallurgical technologies to extract Y from ores, contaminated solutions, WEEE and generic wastes. Before to discuss the works about the treatment of wastes, the processes to retrieval Y from ores are discussed, since the processes are similar and derived from those already developed for the extraction from primary sources. Particular attention was given to the recovery of Y from WEEE because the recycle of them is important not only for economical point of view, considering its value, but also for environmental impact that this could be generated if not properly disposal.
New electrode designs are required for electrochemical applications such as batteries or fuel cells. Embroidered 3D Cu porous electrodes with a geometric surface of 100 cm2 are presented and characterised by means of the anthraquinone-1,5-disfulfonic acid (AQDS2−) redox system in alkaline solution. The electrochemical behaviour of the 3D electrode is established by the comparison of cyclic voltammetry responses using a micro cell and a 100 cm2 plane Cu-plate electrode. Dependencies of the peak currents and peak-to-peak potential separation on scan rate and AQDS2− concentration are studied. The AQDS2− characterisation is also performed by means of spectroelectrochemical experiments.
Detailed analysis of alternating current impedance data of LiMn2O4 electrodes measured at several temperatures and potentials was carried out. The Nyquist plots generally consisted of semicircles corresponding to two time constants. However, at low temperatures (−10 to 10 °C) and potential region between 3.90 and 4.20 V, three time constants were present. The third semicircle present at the middle to high frequency range was attributed to electronic resistance of LiMn2O4. Impedance parameters were evaluated using appropriate electrical equivalent circuits. From the temperature dependence of resistive parameters, activation energy values for the corresponding processes were calculated.