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The hybrid films composed of V2O5 nanoparticles and single-walled carbon nanotubes (V2O5/SWNT) with mesoporous structure are prepared using a simple floating CVD method followed by controllably hydrolytic deposition of V2O5 nanoparticles. The hybrid films as cathodes for lithium ion batteries exhibit a high-rate capacity of 548mAhg−1 at the discharge rate of 300mAg−1 (∼1C); 342mAhg−1 and 171mAhg−1 at higher discharge rates of 1200mAg−1 (∼4C) and 2400mAg−1 (∼8C), which is attributed to the chemical interaction between the V2O5 nanoparticle and the functional groups on the surface of SWNTs evidenced by the HRTEM and XPS results. It is also conclusively elucidated with detailed electrochemicl analysis that SWNTs can improve Li+ diffusivity by 2 to 4 orders of magnitude to significantly facilitate lithium-ion transport, achieving an excellent electrochemical performance of the hybrid cathode system.
Due to the need for in vivo photo-genotoxicity tests, the in vivo photo-comet assay was established in epidermal cells of the SKH-1 mouse. Groups of 10 male SKH-1 mice each were treated once orally with vehicle only, with three fluoroquinolones (25mg/kg clinafloxacin, 20mg/kg lomefloxacin, 200mg/kg ciprofloxacin) or with 200mg/kg 8-methoxypsoralene (8-MOP). Thirty minutes after treatment half of the mice in each group were exposed to 23.8J/cm2 UVA. Thereafter the mice were killed and their epidermal cells tested in the alkaline (pH >13) comet assay; at the same time after administration, compound-treated, non-irradiated mice were killed and analysed. A negative control group of ten male SKH-1 mice received the vehicle only; half of these animals were exposed to UVA, half were not. The comet tail lengths of epidermal cells of the mice were statistically significantly increased for all three fluoroquinolones (FQ) tested in combination with UV irradiation. Treatment with 8-methoxypsoralene+UV induced a significant reduction of comet tail length. Tail intensity and tail moment gave essentially the same results after combined exposure (compound+UV). Without irradiation, the tail lengths of controls and compound-treated mice were comparable under the conditions of this study. In contrast, tail intensity and tail moment were increased for all test compounds (including 8-MOP), without irradiation. Irradiated controls had a tail length comparable to non-irradiated controls, while tail intensity and tail moment were clearly increased in irradiated controls. In conclusion: under the present experimental conditions the in vivo photo-comet assay is able to detect photo-chemically induced DNA strand breaks as well as photo-chemically induced DNA cross-links.
We synthesize a series of cobalt species combined with carbon nanotubes loaded onto graphene-like titanium carbide (CoOx-NC/TiO2C), which are derived from bimetallic CoZn-based zeolitic imidazolite framework and Ti3C2Tx MXene composite (CoZn-ZIF/Ti3C2Tx). The as-result CoOx-NC/TiO2C composites are further explored as the trifunctional electrocatalysts for hydrogen evolution reaction, oxygen reduction reaction, and oxygen evolution reaction. Among composites containing different Ti3C2Tx dosages, the CoOx-NC/TiO2C(22.7%) exhibits the most excellent electrochemical conductivity. When CoOx-NC/TiO2C(22.7%) is used as the electrocatalyst for water splitting, a current density of 10 mA cm−2 (E j = 10) is achieved at a low cell voltage of 1.45 V. Meanwhile, the overall oxygen activity of the CoOx-NC/TiO2C(22.7%) shows a small potential difference (0.72 V) between the E j = 10 for oxygen evolution reaction and the half-wave potential for oxygen reduction reaction. The outstanding catalytic performances are mainly attributed to the synergistic effect among the different components of the CoOx-NC/TiO2C composite, such as carbon nanotube content that is in favour of electronic mobility, hierarchical porosity that facilitates mass transport, and uniformly dispersed cobalt, cobalt oxide, and titanium dioxide active sites in the carbon framework. Consequently, the present work will shed light on the application of other metal-organic framework- and carbon-based electrocatalysts for energy conversion.
Strontium cobalt-based perovskites display high electrochemical activity but poor stability for solid oxide electrolysis cells (SOECs). Here, we evaluate the stability of three strontium cobalt-based materials, i.e. SrCo0.8Nb0.2O3-δ (SCN), SrCo0.8Ta0.2O3-δ (SCT) and SrCo0.8Nb0.1Ta0.1O3-δ (SCNT) as air electrodes for SOECs. The electrochemical results show that the area-specific resistance (ASR) for SCN and SCNT cells decreases and then becomes almost constant whereas the ASR of the SCT cell continuously increases, during the 240 h SOEC test. The improved performance of SCN and SCNT cells is ascribed to the lower energy barrier required for the oxide ion movement in the presence of niobium and the less concentration of undesired phases formed during SOEC operation. SCN is further tested under reversible solid oxide cell (RSOC) conditions with 16 h solid oxide fuel cell (SOFC) and 7 h SOEC cycles. The cell presents excellent stability as its impedance increases only slightly from 0.188 to 0.193 Ω cm2 after 114 h RSOC test. A single cell with NiO-SSZ/SSZ/SDC/SCN configuration shows high electrolysis current densities of 0.51, 0.42 and 0.34 A cm−2 at 800, 750 and 700 °C, respectively, in 10% H2O/90% H2 and 0.79 A cm−2 at 800 °C in 50% H2O/50% H2 at 1.3 V.
Thymosin β4 (Tβ4) is a developmentally expressed 43-amino acid peptide that inhibits organization of the actin-cytoskeleton by sequestration of G-actin monomers. Tβ4 improves cardiac function after myocardial infarction in adult mice and promotes healing properties in both dermal and corneal wounds. We tested the hypothesis that Tβ4 improves functional neurological outcome in a rat model of embolic stroke. Experimental Procedures: Male Wistar rats (n=18) were subjected to embolic middle cerebral artery occlusion (MCAo). Tβ4 (6 mg/kg, IP) was administered 24 h after MCAo and then every 3 days for four additional doses (n=9). Rats treated with saline were used as a control (n=9). The adhesive-removal test (ART) and modified Neurological Severity Score (mNSS) were performed to measure functional outcome. Rats were sacrificed 56 days after MCAo. Immunostaining was performed with antibodies against NG-2 (chondroitin sulfate proteoglycan), CNPase (2”, 3”-cyclic nucleotide 3'-phosphodiesterase) to detect immature and mature oligodendrocytes. Neurofilament-H (NF-H) antibodies were used to detect axons while myelinated axons were identified with Bielschowsky/Luxol (B/L) Blue staining. EBA (endothelial barrier antigen) was used for detection of mature vessels. Results: Ischemic rats treated with Tβ4 demonstrated a significant overall improvement (P<0.01) in the ART and the mNSS when compared to controls. Significant improvement was observed beginning at 14 and 35 days, respectively. Lesion volumes showed no significant differences between the two groups. Treatment with Tβ4 increased myelinated axons and increased vessel density in the ischemic boundary (P<0.05) and augmented remyelination which was associated with an increase of oligodendrocyte progenitor cells (OPCs) and myelinating oligodendrocytes (P<0.05). Conclusions: The present study suggests that Tβ4 improves neurological functional outcome after embolic stroke in rats. Axonal remodeling from mobilization of OPCs is proposed as contributing to Tβ4 induced functional improvement.
In this work, we analyzed the thermal stability of polycarbonate: lithium trifluoromethane sulphonylimide (LiTFSI) systems. Polyethylene carbonate (PEC) and polypropylene carbonate (PPC) undergo depolymerization to ethylene carbonate (EC) and propylene carbonate (PC), respectively, in the presence of Li salt under annealing treatment. The decomposition reaction can explain the surprising high ionic conductivity recently reported for solid polymer electrolyte (SPE) polycarbonate-based systems. Because this phenomenon can strongly impact the results of SPE research, it is essential to control the depolymerization of polymers to avoid inaccurate electrochemical performance. In addition, we observed that the standard drying procedure for the preparation of high-salt-concentration polymer (polymer-in-salt) SPEs traps a high amount of residual solvent, e.g., acetonitrile (ACN), due to the strong bond between the solvent and ionic species. This finding represents another factor influencing the remarkably high ionic conductivity.
Solvent method was used to recover LiCoO2 scrap materials, and the effects of heat treatment on the scrap materials for Li-ion battery were investigated in detail. SEM results showed that heat treatment could slightly reduce the degree agglomeration of the scrap materials. XRD results showed that the layer structure of LiCoO2 was partly destroyed during the recovery process. Low temperature heat treatment could contribute to restore the original layer structure of LiCoO2, however, high temperature heat treatment could lead to the further damage of the layer structure. Compared with the unheat-treated scrap materials, the discharge capacity and the cycle life of the pristine scrap materials heat-treated at 200 °C, 250 °C and 300 °C were obviously improved, Especially after heat-treated at 250 °C, the discharge capacity could reach about 154.6 mAh g−1 and the capacity retention rate still remained at 92.0% after 360 cycles. Particle size distribution, tap density and recovery rate of scrap materials were also investigated.
A novel VO2(B)-multiwall carbon nanotube (MWCNT) composite with a sheet-like morphology was synthesized by a simple in situ hydrothermal process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). FE-SEM observations demonstrated that the nanosheets are frequently grown together in the form of bundles composed of numerous nanosheets, each with a smooth surface and a typical length of 300–500nm, width of 50–150nm, and thickness of 10–50nm. Electrochemical measurements were carried out using different discharge cut-off voltages. Electrochemical tests show that the VO2(B)–MWCNT composite cathode features long-term cycling stability and high discharge capacity (177mAhg−1) in the voltage range of 2.0–3.25V at 1C with a capacity retention of 92% after 100 cycles. The electrochemical impedance spectra (EIS) indicate that the VO2(B)–MWCNT composite electrode has very low charge-transfer resistance compared with pure VO2(B), indicating the enhanced ionic conductivity of the VO2(B)–MWCNT composite. The enhanced cycling stability is attributed to the fact that the VO2(B)–MWCNT composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact. We strongly believe that the VO2(B)–MWCNT composite can be considered as a potential cathode material for lithium-ion batteries.
The formation of metallic lithium on the negative graphite electrode in a lithium-ion (Li-ion) battery, also known as lithium plating, leads to severe performance degradation and may also affect the cell safety. This study is focused on the nondestructive characterization of the aging behavior during long-term cycling at plating conditions, i.e. low temperature and high charge rate. A commercial graphite/LiFePO4 Li-ion battery is investigated in order to elucidate the aging effects of lithium plating for real-world purposes. It is shown that lithium plating can be observed as a loss of cyclable lithium which affects the capacity balance of the electrodes. In this way, lithium plating counteracts its own occurrence during prolonged cycling. The capacity losses due to lithium plating are therefore decreasing at higher cycle numbers and the capacity retention curve exhibits an inflection point. It is further shown that the observed capacity fade is partly reversible. Electrochemical impedance spectroscopy (EIS) reveals a significant increase of the ohmic cell resistance due to electrolyte consumption during surface film formation on the plated lithium. Additional cell opening provides important quantitative information regarding the thickness of the lithium layer and the corresponding mass of the plated lithium.
Absorbency testing is used to determine the percentage of ZnCl2 or NH4Cl solution absorbed by a hydroponics gel (HPG). It is found that the absorbency of ZnCl2 or NH4Cl solution decreases with increasing solution concentration. The conductivity of ZnCl2- and NH4Cl-HPG electrolytes is dependent on the solution concentration. A mixture of salt solution with HPG yields excellent gel polymer electrolytes with conductivities of 0.026 and 0.104Scm−1 at 3M ZnCl2 and 7M NH4Cl, respectively. These gel electrolytes are then used to produce zinc–carbon cells. The fabricated cells give capacities of 8.8 and 10.0mAh, have an internal resistance of 25.4 and 19.8Ω, a maximum power density of 12.7 and 12.2mWcm−2, and a short-circuit current density of 29.1 and 33.9mAcm−2 for ZnCl2- and NH4Cl-HPG electrolytes, respectively.
Renewable systems are especially suited for electricity generation in remote areas but, where high reliability of the electricity supply is required, a hybrid system including electricity storage could be the only solution to avoid the lack of feasibility in single renewable systems. In this paper a hybrid system composed by photovoltaic panels, a biomass gasifier and a battery bank is presented. The system was designed and constructed at the Distributed Energy Resources Laboratory (LabDER) in order to supply electricity to a laboratory complex in the Institut Supérieur des Techniques Appliquées, Democratic Republic of Congo (ISTA-DRC). System behavior was also tested in LabDER prior being installed and operated in the final place. Design characteristics and commissioning results are presented together with the experimental verification of the capability to fulfill the demand with very low fluctuations in the generated electricity supply.
Fe-substituted Li2MnO3 (Li1+x (Fe y Mn1−y )1−x O2, 0≤ x ≤1/3, 0.3≤ y ≤0.7) was synthesized using a combination of coprecipitation, hydrothermal, and heat-treatment methods. It exhibits high initial specific capacity greater than 200mAhg−1 and small capacity, which fades up to the 50th cycle (>150mAhg−1 at the 50th cycle) under electrochemical cycle testing at 60°C. The attractive electrode properties appeared by controlling the chemical composition (x >0.05, 0.3≤ y ≤0.5) and high specific surface area (>20m2 g−1). The Fe-substituted Li2MnO3 is an attractive candidate as a novel 3V-class positive electrode material.
The increasing adoption of mobile devices as the preferred tool to access the Internet imposes to deepen the investigation of security aspects. In parallel, their power constrained nature must be explicitly considered in order to analyze security in an effective and comprehensive manner. This aspect, which is often neglected in the literature, allows investigating two important behaviors of mobile devices: (i) evaluate if all the layers accounting for privacy and security can be re-engineered or optimized to save power, and (ii) understand the effectiveness of draining energy to conduct attacks. In this perspective, this paper surveys and highlights the most recent work on energy-awareness and security. Also, it summarizes the current state of the art on general techniques to save energy, as well as tools to perform measurements. The major contributions of this survey are, thus, a review of past work aimed at minimizing the energy footprint of security mechanisms, and the identification of promising research trends, such as detecting attacks via anomalous power consumption.
We report studies on thin films of a salt doped polymer electrolyte model system. Films of poly(ethylene oxide) with thickness near 1400 Å, doped with lithium triflate salt at salt concentrations ranging from 0 to 40% by weight, were characterised. The high surface to volume ratio of the thin film samples makes them ideal for the study of interfacial effects on the physical properties. The lateral morphology of the system was studied with optical and atomic force microscopy, revealing strong similarities to the bulk system. The composition depth profiles of the ionic species were measured directly using dynamic secondary ion mass spectroscopy (d-SIMS) as well as X-ray photo-electron spectroscopy (XPS) accompanied with ion sputtering. The results are discussed in terms of the possible implications of interfacial effects on practical ionically conducting systems.
Silicon hollow nanostructure has been considered as one of the most promising material for commercial application in lithium-ion batteries due to its significant improvement of cycling stability. The fabricated hybrid structures, carbon-coated silicon nanotube arrays on carbon cloth substrate, with a high surface area and short electron collection pathway have been directly used as anode electrodes without any additional binder. The electrodes exhibit high capacity, excellent rate capability and good cycling stability. The discharge capacity of the hybrid electrode (the deposition time of silicon shell: 5 min) keeps stable, and after 100 cycles, the discharge capacities still remain 3654 mAh g−1 at the rate of 0.5 C.
High performance lithium iron phosphate (LFP) cathode materials were synthesized using amorphous carbon, carbon nanotubes (CNTs), and graphene (G) as conductive materials via sand milling and spray drying processes and followed by calcination. The structural characterizations indicated that CNTs and G can well connected with LFP nanoparticles (NPs), which was coated with a thin layer of amorphous carbon, benefiting the construction of three-dimensional efficient conductive network. The electrochemical measurements confirmed that the introduction of CNTs and G can obviously decrease the charge transfer impedance of lithium ion battery and increase the discharge special capacity. The initial discharge special capacity increases in the order of LFP/C (150.3 mAh/g) < LFP/C/CNTs (155.7 mAh/g) < LFP/C/G (159.7 mAh/g) < LFP/C/G/CNTs (164.5 mAh/g) at 0.1 C. LFP/C/G/CNTs also exhibited considerable discharge special capacity (99.5 mAh/g) at high current of 5 C. Compared with LFP/C (248 Ω), LFP/C/G/CNTs (50 Ω) showed obviously decreased charge transfer impedance. Cycle performance test indicated that the specific capacity retention for LFP/C/G/CNTs was 99% after 200 cycles, displaying good cycle stability. The superior electrochemical performance of LFP/C/G/CNTs is attributed to the significantly synergistic effect of CNTs and G on decreasing charge transfer impedance by constructing highly three-dimensional conductive network. Besides, the effect of G to CNTs mass ratio and the calcination temperature on the electrochemical performance of LIBs were also discussed.
Wireless sensor networks (WSNs) consist of many sensor nodes (SNs) which may be deployed at different geographical locations to perform multiple tasks such as monitoring, data aggregation, and data processing. During all these operations, energy of the SNs continuously depleted which results in the creation of energy holes in some regions. As SNs are battery operated and it is difficult to replace the battery of the SNs each time, so energy conservation is a paramount concern to increase the lifetime of the WSNs. It has been proved in the literature that clustering of SNs can be used for energy saving during various operations in WSNs. Keeping in view of the above issues, in this paper, we propose a new learning automata-based energy efficient heterogeneous selective clustering (LA-EEHSC) scheme for WSNs. Automaton is assumed to be located on each SN with two types of SNs, namely, normal and advanced are considered in the proposed scheme. Based upon the weighted election probability (WEP) of each group of SNs, Cluster Heads (CHs) are selected among the group of SNs by the automaton. Automaton at each SN receives reward or penalty from the environment based upon WEP of different SNs. An efficient learning automata-based energy efficient clustering algorithm is also proposed. Finally, first node die (FND) and last node alive (LNA) are selected as the key parameters for the measurement of lifetime of network field. Using these parameters, we have evaluated the performance of the proposed scheme in different network scenarios in comparison with the well-known existing protocols such as LEACH, LEACH-SC and SEP. The results obtained show that proposed scheme yields 5.89% improvement in lifetime and 21.14% improvement in stability in comparison to LEACH, LEACH-SC, and SEP.
For the first time, we successfully synthesize a self-supported Na0.7CoO2 nanosheet arrays via the facile “sodiation and post-calcination” method. Different from the traditional high temperature solid-state technique, this facile strategy can easily maintain the novel construction of the precursor. A mass loading as high as 8 mg cm−2 is achieved for the Na0.7CoO2 electrode with an initial capacity of 145.2 mAh g−1 at 1 C. Most importantly, the corresponding areal capacity for the Na0.7CoO2 electrode is calculated to be 1.16 mAh cm−2. This superb areal capacity is higher than that of the previously reported cathode materials. This special “sodiation and post-calcination” protocol mentioned in this article guarantees the high mass loading of Na0.7CoO2 on Ni foam, providing a straightforward direction for engineering high-areal-capacity cathode materials.
Particulate matter (PM) collected from mainstream tobacco smoke is a test article commonly used for in vitro genotoxicity and cytotoxicity testing of combustible tobacco products. However, little published data exists concerning the stability of PM. We completed a 2year study to quantify the effect of PM storage at −80°C, on the genotoxicity and cytotoxicity of PM generated from 3R4F and M4A reference cigarettes. The Ames test, Micronucleus assay (MNvit), Mouse Lymphoma assay (MLA) and the Neutral Red Uptake assay (NRU) were used. The majority of M4A and 3R4F PMs were genotoxic and cytotoxic at the timepoints tested. Some minor but statistically significant differences were observed for stored versus freshly prepared PM, but the magnitude of changes were within the variability observed for repeat testing.
The structure and electrochemical properties of a cobalt-free hydrogen storage electrode alloy LaNi4.05−x Al0.45Mn0.5Fe x (0≤ x ≤0.5) have been investigated with different additions of Fe in replacement of Ni. With the increase of Fe content the maximum discharge capacity gradually decreases from 334.8mAhg−1 to 292.8mAhg−1, however the cycle stability is improved correspondingly. The capacity decay can remain 28.6% (x =0.5) after 300 charge/discharge cycles. The high rate discharge (HRD) ability of the alloys (x ≤0.5) is improved with the increase of Fe content. It is found that all of the alloys are single CaCu5 phase structure disclosed by XRD pattern. However, small amount of the La2O3 phase, observed from SEM photographs, exists on the matrix of all the alloys and when x =0.5, some web-like LaNi2.28 phase is segregated out along the crystal boundary.