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Spinel-type, lithium manganese oxides, e.g.LiMn2O4, are very appealing electrodes for upgrading lithium batteries in terms of cost and environmental compatibility. Unfortunately, the practical use of these oxides has so far been hindered by some drawbacks, the most serious being the short life associated with the severe capacity fading on cycling, especially experienced at temperatures above ambient. In this work we report a new strategy for tackling this issue. The results reported here demonstrate that our approach, based on innovative core-shell electrode morphology, is very effective in improving the behaviour of lithium manganese spinel electrodes in lithium cells, by ensuring exceptional capacity stability upon cycling in temperature ranges where all the previous manganese based electrode materials inevitably failed. We show that our core-shell electrodes deliver a specific capacity of the order of 85 mAh g−1 in range of 3–4.3 V vs.Li/Li+ with a retention of 97% over 100 cycles at 60 °C . To our knowledge, such high performance levels have not been met so far.
A novel wet method of (NH4)3AlF6 coating was explored to enhance the electrochemical performance of Mn-based solid-solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2. The X-ray powder diffraction patterns show that the coating material is pure-phase (NH4)3AlF6 and both pristine and coated samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3m. The field-emission scanning electron microscope images and the energy dispersive X-ray spectroscopy show that (NH4)3AlF6 is successfully coated on the surface of active particle. The (NH4)3AlF6 coated electrodes exhibit improved electrochemical performance, for instance, the initial charge-discharge efficiency was promoted by 5% (NH4)3AlF6 coating, the 1wt.% and 3wt.% coated electrodes deliver elevated cycling ability which is ascribed to the lower resistance between electrode and electrolyte as indicated by AC impedance measurement at different cycles. In addition, the coated-electrodes also give enhanced rate capability particularly for 1wt.% NAF-coated electrode performing surprising capacity of 143.4 mAh g−1 at 5C higher than that of 109.4 mAh g−1 for pristine electrode. Furthermore, the 1wt.% NAF-coated electrode also shows improved cycle and rate performance at 55°C.
γ-MnS/reduced graphene oxide (γ-MnS/rGO) composite was successfully fabricated via a facile one-pot solvothermal route using graphene oxide (GO), thioacetamide (TAA, CH3CSNH2) and MnCl2·4H2O as reactants. It reveals that TAA plays an important role in reducing GO and sulfurizing γ-MnS. The synthesized composite was characterized via X-ray diffraction and scanning electron microscopy for structural and morphological studies. Electrochemical performance was also investigated through cyclic voltammetry and galvanostatic charge–discharge. As for the application of supercapacitors, the γ-MnS/rGO composite shows a great value of 802.5 F g−1 at a current density of 5 A g−1. Furthermore, the capacitance of γ-MnS/rGO has no decrease of its initial values after 2000 cycles. The galvanostatic charge–discharge curve demonstrates the ideal capacitive behavior of γ-MnS/rGO composite electrodes.
The structural changes of spinel Li1.02Mn2O4 and Li1.02Co0.11Ni0.04Mn1.85O4 cathode materials have been studied by synchrotron powder X-ray diffraction and differential scanning calorimetry (DSC) measurements. The results show that spinel Li1.02Mn2O4 undergoes a phase transition from cubic (Fd3m) to orthorhombic symmetry (Fddd) at T=285K. However, substitution of a small amount of Co3+ and Ni3+ ions suppresses phase transition and the cubic phase is maintained at low temperature due to a decrease in the concentration of Jahn–Teller active Mn3+ ions.
The current development of fuel cell scooters has been reviewed in this paper. Fuel cell scooters, by nature, have zero emissions, and they have the potential to replace current petroleum-propelled engine scooters. First, the fundamentals of fuel cells, including the critical technologies pertaining to fuel cell engines and hydrogen storage, were introduced. Then, the technical feasibility of fuel cell scooters was discussed in parallel with the hydrogen infrastructure model. The accomplishments of fuel cell scooters in Taiwan were presented. Moreover, the contribution of replacing petrol scooters by hydrogen fuel cell scooters to reduction in greenhouse gas (GHG) emission and energy conservation was evaluated. Furthermore, industrial competition with regard to the development of fuel cell scooters was discussed on the basis of a strengths, weaknesses, opportunities, and threats (SWOT) analysis. In conclusion, with mature fuel cell technology together with solid foundation of the scooter industry, Taiwan offers conditions that were conducive for the development of fuel cell scooters. Its social and technical capability will be proved on account of the leading demonstrations of fuel cell scooters in the world. If it can develop a successful business model, Taiwan could enjoy the advantages of tapping the huge global market for zero-emission scooters.
Laguna de Terminos, a wide coastal lagoon system in Campeche, Mexico, was investigated for the contamination by polychlorobiphenyls (PCBs). Distribution of these industrial chemical contaminants along with pesticide residues in the lagoon, as well as their sediment–water partitioning and bioaccumulation by oysters and fish were assessed. Contaminant concentrations in the lagoon were compared with toxicity data for aquatic organisms and the ecotoxicological risks discussed. Current contaminant concentrations generally were several orders of magnitude below acute toxic levels for the most sensitive aquatic species and this seems compatible with the status of nature reserve and functions aimed at Laguna de Terminos. In particular, Penaeidae shrimp species that are the most valuable fisheries resources of Campeche with important populations in the Laguna are not impaired with the current low levels of these contaminants. Nevertheless, due to known environmental persistence, the surveillance of chlorinated contaminant levels in the lagoon ecosystems is recommended.
In this review, we examined the published reports on the heritability of cognitive functioning in old age. Twenty-four papers from five study centers, comprising of participants with a mean age of 65years and above were examined. The comparability of findings from different studies was compromised by the use of different measures for the same cognitive domain, and with large scale twin studies in cognitive aging limited to a few Scandinavian countries. While the results from cross-sectional samples appear to lend support for the notion that heritability of cognitive functions decreases in the elderly, the findings are best considered inconclusive. Longitudinal reports show little evidence for genetic effects, but an increase in unique environmental influences on the rate of cognitive change as age increases. In relation to the two prominent theories of cognitive aging, the genetic influence on processing speed as a major contributor to cognitive aging has been indicated in three reports, whereas the genetic relationship between executive functions and other cognitive functions has not been explored. Only two studies have focused on sex difference and did not find sex-specific genetic influence in cognitive abilities. This review indicates that there are complex relationships between heritability, environmental influence, and cognitive functions in the elderly. It highlights the need for more research, with consistent and appropriate cognitive measures, with data obtained from larger and more geographically and culturally diverse twin samples.
The central nervous system (CNS) responds to diverse neurologic injuries with a vigorous activation of astrocytes. In addition to their role in the maintenance of CNS homeostasis and neuronal function, astrocytes are thought to participate in the regulation of innate and adaptive immune responses in the CNS. Following antigen recognition, reactive astrocytes may participate in the initiation of innate immune responses, and modulate adaptive immune response leading to the recruitment of peripheral immune cells. Among activation, astrocytes undergo morphological changes and express several molecules, e.g., chemokines. Lipocalin 2 (LCN2) is involved in the control of innate immune responses, regulation of excess iron, and reactive oxygen production. Here, we investigated the influence of LCN2 on basic astrocytic functions linked to inflammatory responses. In vitro studies revealed a similar chemokine expression pattern in wild-type and Lcn2-deficient astrocyte cultures after treatment with lipopolysaccharides (LPS). Increased wound closure and morphological changes upon LPS treatment are independent of Lcn2 expression. We conclude that LCN2 is not necessary for basic astrocytic functions in the context of inflammation. However, CNS-derived LCN2 might have a regulatory effect on other cells, e.g., endothelial cells of the blood-brain barrier.
Ti45−x Zr35−x Ni17+2x Cu3 (x =0, 2, 4, 6 and 8) icosahedral quasicrystalline phase (I-phase) alloy powders are synthesized by mechanical alloying and subsequent annealing techniques, and the crystallographic and electrochemical characteristics are investigated. The alloy powders are I-phase, and the quasi-lattice constant decreases with increasing x value. The maximum discharge capacity of the I-phase alloy electrodes first increases and then decreases with increasing x value, and the Ti39Zr26Ni29Cu3 I-phase electrode exhibits the highest discharge capacity of 274mAhg−1. The high-rate dischargeability at the discharge current density of 240mAg−1 increases from 55.31% (x =0) to 74.24% (x =8). Cycling stability also increases with increasing x value. The improvement in electrochemical characteristics may be ascribed to the added nickel, which not only improves the electrochemical activity, but also makes the alloy more resistant to oxidation.
The aim of this study was to investigate route-learning ability in 67 children aged 5 to 11years and to relate route-learning performance to the components of Baddeley’s model of working memory. Children carried out tasks that included measures of verbal and visuospatial short-term memory and executive control and also measures of verbal and visuospatial long-term memory; the route-learning task was conducted using a maze in a virtual environment. In contrast to previous research, correlations were found between both visuospatial and verbal memory tasks—the Corsi task, short-term pattern span, digit span, and visuospatial long-term memory—and route-learning performance. However, further analyses indicated that these relationships were mediated by executive control demands that were common to the tasks, with long-term memory explaining additional unique variance in route learning.
Lithium electrodeposition and -dissolution in a commercial battery electrolyte (1 M LiPF6 in EC:DMC) has been studied in situ by light microscopy and ex situ by scanning electron microscopy (SEM). We describe the transition between lithium filaments, which are most likely whiskers, and lithium moss and report in detail on the growth of mossy lithium structures. In the case of mossy lithium, the deposition can occur at the tips or the base of the growing structure. However, the growth is not limited to these locations, but can also occur by insertion at further growth points distributed inside the mossy Li deposit. We show that two different growth modes have to be distinguished: the unusual non-tip-growth by lithium metal insertion into the metallic moss backbone, and the condition where the deposition at the top of the mossy structure is not possible anymore because it was electrically isolated from the current collector due to a previous lithium dissolution step. After a dissolution period causing insulation of Li (“dead Li”), whole moss remnants can get pushed outside by metal structures growing underneath.
The electrical efficiency of photovoltaic (PV) cell is adversely affected by the significant increase of cell operating temperature during absorption of solar radiation. A hybrid photovoltaic/thermal (PV/T) solar system was designed, fabricated and experimentally investigated in this work. To actively cool the PV cells, a parallel array of ducts with inlet/outlet manifold designed for uniform airflow distribution was attached to the back of the PV panel. Experiments were performed with and without active cooling. A linear trend between the efficiency and temperature was found. Without active cooling, the temperature of the module was high and solar cells can only achieve an efficiency of 8–9%. However, when the module was operated under active cooling condition, the temperature dropped significantly leading to an increase in efficiency of solar cells to between 12% and 14%. A heat transfer simulation model was developed to compare to the actual temperature profile of PV module and good agreement between the simulation and experimental results is obtained.
Uniform Li3VO4 film was successfully grown on porous Ni foam, which shows good electrochemical performance as anode for Li-ion battery due to the improved reaction kinetics. The as-prepared Li3VO4/Ni electrode can deliver discharge and charge capacity of 379 and 378 mAh g−1 after 100 cycles at a charge/discharge rate of 0.3C. After various charge/discharge rates from 0.4 to 15C, the discharge capacity of the Li3VO4/Ni electrode can restore to 404 mAh g−1 when lowering the charge/discharge rate to 0.4C. The reaction kinetics of the Li3VO4/Ni electrode was studied by cyclic voltammetry (CV) measurement at various scan rate and electrochemical impedance spectroscopy (EIS). Linear dependence between anodic/cathodic peak currents and the square root of scan rate suggests a lithium ion diffusion controlled mechanism of Li3VO4/Ni electrode in charge/discharge process, and the symmetrical slope of the two straight lines indicates a highly reversible lithiation/delithiation process. EIS measurements of the Li3VO4/Ni electrode show low and stable contact and charge-transfer resistances in cycling, suggesting highly stable charge transfer process and Li-ion diffusion coefficient.
Inflammation is associated with Aβ pathology in Alzheimer's disease (AD) and transgenic AD models. Previously, it has been demonstrated that chronic stimulation of the immune response induces pro-inflammatory cytokines IL-1β and TNF-α which contribute to neurodegeneration. However, recent evidence has shown that inducing the adaptive immune response reduces Aβ pathology and is neuroprotective. Low concentrations of IFN-γ modulate the adaptive immune response by directing microglia to differentiate to antigen presenting cells. Our objective was to determine if exercise could induce a shift from the immune profile in aged (17–19 months) Tg2576 mice to a response that reduces Aβ pathology.
Composite cathodes have been fabricated based on LiMn2O4 spinel powders, which were synthesized by combustion process and characterized by X-ray diffraction as a pure phase. The electrochemical response of the electrode was analyzed by cyclic voltammetry, chronopotentiometric curves and electrochemical impedance spectroscopy (EIS). Cyclic voltammograms showed two reversible processes, which is the typical response of LiMn2O4. The charge–discharge curves showed two plateaux with the charge density of 107mAhg−1. From the EIS data the Li+ diffusion coefficient was determined.
Major rice growth characteristics and grain yield were compared between inside and outside of a chamber coverage area after a seasonal CH4 and N2O flux measurement using a closed chamber technique. Results show that only grain yield was significantly (P<0.01) reduced by chamber enclosure. There was no significant difference (P>0.05) in plant height, total straw weight, spike length, and average grain weight. Temperature increase during the gas flux measurement was likely the major cause for the observed grain yield decrease by sterilizing rice reproductive organs. Methane flux rates from rice fields were likely overestimated by using closed chamber technique because decreasing grain yield by chamber enclosure may result in more plant photosynthesis products released into soils to enhance CH4 production. Analyzing CH4 and CO2 emission ratio from the rice field, after cutting the above-water part of rice plants, indicated that CH4–C emission accounted for approximately 13% of the total CO2 and CH4–C emission during the major rice growing season.
In this study, Co3O4/Co nanoparticles are synthesized within nitrogen-doped porous carbon/carbon nanotube matrix (Co3O4/Co@NC/CNT) by using ZIF-67 metal-organic frameworks. In comparison with commercial Pt/C catalysts, the composite exhibits better electrocatalytic characteristics for oxygen reduction reactions in alkaline media, such as onset potential, half-wave potential, current density, cycle stability, and methanol tolerance. For instance, onset potential and half-wave potential are positively shifted by 67 mV and 25 mV, respectively. Structural and composition analysis demonstrate that enhanced properties result from the formation of pyridinic nitrogen and Co-N-C active sites within carbon matrix. The findings above indicate that the Co3O4/Co@NC/CNT catalyst can replace expensive Pt/C catalyst for potential applications in fuel cells and metal-air batteries.
Synthetic approaches to new materials are as various as the nature of the materials themselves. Here, we report on one synthetic concept that was used during the recent past to address a variety of different families of compounds from superionic conductors and supersphere cages for molecular trapping to new white-light generators and reactive multimetallic clusters. The use of small binary molecules comprising atoms of two main group elements is the base of all of the presented methodologies, which lead to the named classes of materials according to the choice of the elemental combination and the specific reaction conditions.
Carbon coated Li1.2Mn0.56Ni0.16Co0.08O2 and Li1.2Mn0.6Ni0.2O2 were synthesized as cathode materials for Li-ion batteries by a self-combustion reaction, and were characterized by XRD, SEM, HRTEM and Raman spectroscopy in conjunction with electrochemical measurements. Initial discharge specific capacities of 270 mAh g−1 and 230 mAh g−1 are obtained for Li1.2Mn0.56Ni0.16Co0.08O2 and Li1.2Mn0.6Ni0.2O2, respectively at slow rates (e.g.C/10) in galvanostatic charge-discharge cycling. The cathode material Li1.2Mn0.56Ni0.16Co0.08O2 can provide a discharge capacity of 110 mAh g−1 at 4C rate. The importance of the presence of Co in the structure for obtaining high rate capabilities was proven by comparison with Li1.2Mn0.6Ni0.2O2 electrodes, which can exhibit only 80 mAh g−1 at 2C rate. The electrochemical impedance spectra of Li1.2Mn0.56Ni0.16Co0.08O2 recorded at various potentials during charging indicate that there is a substantial increase in the charge-transfer resistance at voltages higher than 4.4V, indicating that the kinetics of Li+ ions insertion into this material is controlled by charge-transfer rather than by Li+ ions diffusion, at high potentials.
The mechanisms by which gene expression patterns emerge during evolution are poorly understood. The sea urchin spec genes offer a useful means to investigate evolutionary mechanisms. Genes of the spec family from Strongylocentrotus purpuratus and Lytechinus pictus have identical patterns of aboral ectoderm-specific expression but exhibit species-specific differences in copy number, genomic structure, temporal expression, and cis-regulatory architecture. Here, we identify spec genes from a phylogenetic intermediate, Strongylocentrotus franciscanus, to gain insight into the evolution of the spec gene family and its transcriptional regulation. We identified two spec genes in the S. franciscanus genome, sfspec1a and sfspec1b, that were orthologous to spec1 from S. purpuratus. sfspec1b transcripts began to accumulate at the blastula stage and became progressively more abundant; this was reminiscent of spec expression in L. pictus but different from that in S. purpuratus. As expected, sfspec1b expression was restricted to aboral ectoderm cells. The six-exon structure of the sfspec1b genomic locus was identical to that of the S. purpuratus spec genes and was bounded by two repeat–spacer–repeat (RSR) repetitive sequence elements, which are conserved features of S. purpuratus spec genes and function as transcriptional enhancers. The enhancer activity of the sfspec1b RSRs was comparable to that of their S. purpuratus counterparts, although the placement and orientation of crucial cis-regulatory elements within the RSRs differed. We discovered a spec gene in S. franciscanus that was only distantly related to other spec genes but was highly conserved in S. purpuratus. Unexpectedly, this gene was expressed exclusively in endoderm lineages. Our results show that the evolution of spec cis-regulatory elements is highly dynamic and that substantial alterations can occur when maintaining or grossly modifying gene expression patterns.
Quinones with their structural diversity and electrochemical reversibility are among the most promising organic electrode materials. One distinct feature of quinones is their cross-conjugated structure, the importance of which in the design of organic electrode materials is so far overlooked. Here we report the design, synthesis, and characterizations of two cross-conjugated quinone oligomers (PBDTD and PBDTDS) and their nanocomposites with carbon nanotubes as potential low-cost organic electrode materials for Li-ion batteries. We investigate the effect of conjugation structure and molecular conformations (planar vs. helical) on electrochemical properties such as electronic conductivity, ionic conductivity, and electrode kinetics. Both quinones deliver similar specific capacity over 200mAhg–1 at 2.5V versus Li/Li+ with excellent stability over 250 cycles. In particular, the difference in their rate performance is mainly determined by two aspects. First, cross-conjugation of PBDTD becomes electron transport-favorable through-conjugation after reduction, while PBDTDS is always cross-conjugated. Second, the planar conformation of PBDTD facilitates electron-transfer compared with the helical PBDTDS. This work provides insights into the popular yet less understood cross-conjugated quinone-based electrode materials and will stimulate the design of better quinone materials to achieve high-performance organic batteries.
In this study, nanoscale copper(I) sulfide (n-Cu2S) was deposited over networks of single-walled carbon nanotubes (SWCNTs) by atomic layer deposition (ALD). This synthetic route provides a high degree of control for tuning the materials properties. The resulting core–shell SWCNT-n-Cu2S composite structure ensures an intimate contact between the two components while maintaining a high porosity for efficient transport of charges. Indeed, electrochemical testing demonstrates that these nanocomposites are promising as cathodes in lithium-ion batteries (LIBs), exhibiting excellent stability over 200 discharge–charge cycles with a sustainable, high capacity of 260 mAh g−1 (92% of the theoretical value in terms of Cu2S) and >99% Coulombic efficiency. This work establishes a general strategy for developing high-performance nanoscale electrode materials.