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Polyfurfuryl alcohol (PFA) derived activated carbons were prepared by the acid catalysed polymerization of furfuryl alcohol, followed by potassium hydroxide activation. Activated carbons with apparent BET surface areas ranging from 1070 to 2600m2 g−1, and corresponding average micropore sizes between 0.6 and 1.6nm were obtained. The porosity of these carbons can be carefully controlled during activation and their performance as electrode materials in electric double layer capacitors (EDLCs) in a non-aqueous electrolyte (1M Et4NBF4/ACN) is investigated. Carbon materials with a low average pore size (<∼0.6nm) exhibited electrolyte accessibility issues and an associated decrease in capacitance at high charging rates. PFA carbons with larger average pore sizes exhibited greatly improved performance, with specific electrode capacitances of 150Fg−1 at an operating voltage window of 0–2.5V; which corresponds to 32Whkg−1 and 38kWkg−1 on an active material basis. These carbons also displayed an outstanding performance at high current densities delivering up to 100Fg−1 at current densities as high as 250Ag−1. The exceptionally high capacitance and power of this electrode material is attributed to its good electronic conductivity and a highly effective combination of micro- and fine mesoporosity.
Confabulation, the production of statements and actions that are unintentionally incongruous to the subject's history, background, present and future situation, is observed in several conditions affecting the nervous system, but it has never been described in normotensive hydrocephalus. In this article we report on a patient with normotensive hydrocephalus who suffered from an amnesic-confabulatory syndrome. After hydrocephalus shunting, both amnesia and confabulation cleared up abruptly. We discuss this finding in terms of a possible disconnection of the hippocampus, due to transitory white matter damage, which may have recovered after hydrocephalus shunting.
Boron (B) has a high theoretical lithium storage capacity of 3046mAhg−1 for forming Li5B4 phase. Li–B alloy has been used in high temperature thermal lithium batteries. In this work, a new tetragonal boron (B50) thin film with a thickness of 80nm has been deposited on a vanadium coated glass substrate by a pulse laser deposition (PLD) method. It is found that this electrode film shows only a lithium storage capacity of 43mAhg−1 in a nonaqueous electrolyte at room temperature. According to a first-principles calculation, the B50 is a metallic conductor. Therefore, the very poor activity could be related to poor lithium ion diffusion property since the diffusion barrier in this tetragonal B50 lattice is calculated as 2.59eV. This consists well with the fact that the lithium storage capacity in the B50 thin film is improved significantly to 268mAhg−1 at 85°C.
We report on a highly conductive CNT micro-spherical network for high-rate silicon anode materials prepared by one-pot spray drying for lithium-ion batteries. The anode material contains silicon nanoparticles bound to CNTs through a small amount of sucrose-derived carbon. The first charge and discharge capacities of the Si/CNT/C microsphere electrode are measured to be 3152 and 2302 mA h g−1 of the composite, respectively, at 0.1 A g−1. The Si/CNT/C microsphere electrode exhibits an initial capacity of 1989 mA h g−1 at current density of 1.0 A g−1 and retains ∼70% of the initial capacity after 100 cycles. Even at a high current density of 10 A g−1, the Si/CNT/C microsphere electrode exhibits a capacity of 784 mA h g−1 with a stable charge/discharge behavior. The superior rate capability of the Si/CNT/C microsphere composites can be attributable to the unhindered Li-ion transport through the highly conductive CNT buffer matrix, to which Si NPs are strongly bound by the sucrose-derived carbon. These salient results give further impetus to the study of CNTs for use as a buffer matrix to improve the rate capability of high-capacity electrode materials with large volume changes during charge storage.
Silicon-coated carbon nanofibers (CNFs) are a viable method of exploiting silicon's capacity in a battery anode while ameliorating the complications of silicon expansion as it alloys with lithium. Silicon-coated CNFs were fabricated through chemical vapor deposition and deposited onto a carbon fiber mesh. This novel anode material demonstrated a capacity of 954mAhg−1 in the first cycle, but faded to 766mAhg−1 after 20 cycles. Structural characterization of the samples before and after cycling was carried out using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results suggest that a portion of the fade may be due to separation of the silicon coating from the CNFs. Enough silicon remains in contact with the conductive network of CNFs to allow a usable reversible capacity that well exceeds that of graphite. An anode of this material can double the capacity of a lithium-ion battery or allow a 14% weight reduction.
ABSTRACT The peanut shells derived porous hard carbons (PSDHCs) by pyrolysis have been investigated as anodes of lithium/sodium batteries (LIBs/NIBs). Directly from the starting peanut shells, 600°C is found to be the favorable pyrolysis temperature for preparation of the PSDHC sample (PSDHC-600) with the best electrochemical performances for LIB applications. Furthermore, from the activated peanut shells in KOH solution, the produced PSDHC-600A by pyrolysis at 600°C is observed to offer greatly enhanced Li+/Na+ ion storages. For LIB applications, PSDHC-600A delivers a retained capacity of 474mAhg−1 after 400 cycles at 1Ag−1, larger than 314mAhg−1 of PSDHC-600. At a high current rate of 5Ag−1, PSDHC-600A sustains over 10000 cycles with no obvious sign of fade in capacity, and a capacity of 310mAhg−1 is still retained. For NIB applications, a capacity of 193mAh g−1 is retained after 400 cycles at 0.25Ag−1, higher than 130mAhg−1 of PSDHC-600. Even at 1Ag−1, PSDHC-600A can be stably cycled over 3000 cycles, and a capacity of 129mAhg−1 is still retained. In comparison to PSDHC-600, the enhanced electrochemical properties of PSDHC-600A can be attributed to the finer porous structure with the increased percentage of nanoscale pores of diameter less than 2nm and the larger specific surface area.
We fabricated LiCoO2/carbon composites by forming helical carbon nanomaterials (HCNs) from organic liquids as carbon sources on the surface of LiCoO2 particles by chemical vapor deposition (CVD) and estimated their electrochemical properties as cathodes of rechargeable lithium cells. By scanning electron microscopy measurements, we observed HCNs called carbon nanotwists formed on the surface of LiCoO2 particles. X-ray diffraction measurements suggested that acetic acid supplies LiCoO2/HCNs with less decomposition of LiCoO2 than C2H2 does. However, we found that the electrochemical properties of cells containing the composites were not as good as those of cells containing acetylene black (AB).
In this paper, we propose a framework for processing and analysing large-scale spatio-temporal data that uses a battery of machine learning methods based on a meta-data representation of point patterns. Existing spatio-temporal analysis methods do not include a specific mechanism for analysing meta-data (point pattern information). In this work, we extend a spatial point pattern analysis method (the Morisita index) with meta-data analysis, which includes anomaly behaviour detection and unsupervised learning to support spatio-temporal data analysis and demonstrate its practical use. The resulting framework is robust and has the capability to detect anomalies among large-scale spatio-temporal data using meta-data based on point pattern analysis. It returns visualized reports to end users.
Solid electrocatalysts of iron phthalocyanine (FePc) embedded in 3D porous N-doped graphene aerogel (NGA) are designed and applied as cathode catalysts for non-aqueous lithium-oxygen (Li−O2) batteries. Two composites with different axial bonding types between FePc and NGA, including a coordinate covalent bond (FePc/NGA-c) and non-covalent π−π stacking interaction (FePc/NGA-π), are fabricated by reflux and physical mixing methods, respectively. Systematical characterizations confirmed the FePc/NGA-c composite using axial coordination between FePc and NGA substrate via the FeNC bond exhibited more thermal stability and less stack and aggregation of FePc molecules in the composite. Combining the bifunctional catalytic activity of the FePc molecule with oxygen reduction reaction/oxygen evolution reaction (ORR/OER) processes and a flexible porous 3D structure and N-doping in NGA, the electrochemical test demonstrated both FePc anchored on NGA composites display higher activity as bifunctional catalysts for O2 electrodes in Li−O2 batteries. However, the FePc/NGA-c electrode displays better electrochemical performance than the FePc/NGA-π composite due to the axial covalent connection of the FePc catalyst with NGA substrate, leading to higher electrocatalytic activity and exceptional structural durability during cycling for FePc/NGA-c. This work provides new insight into the steric effect of the coordination bond between FePc and NGA on the electrocatalytic activity of O2 electrodes. These results indicate our unique structural design of FePc/NGA-c using solid FePc axially anchored on NGA via covalent bonding is a promising cathode material for high performance of rechargeable LiO2 batteries.
Oxidative stress is closely related to cognitive impairment, and the antioxidant system may be a potential therapeutic target to preserve cognitive function in older adults. Selenium plays an important antioxidant role through selenoproteins. This controlled trial aimed to investigate the antioxidant and cognitive effects of the consumption of Brazil nuts, the best selenium food source.
The focus of this study is the production of electric power in an oil-fired, residential heating system using thermophotovoltaic (TPV) conversion devices. This work uses experimental, computational, and analytical methods to investigate thermal mechanisms that drive electric power production in the TPV systems. An objective of this work is to produce results that will lead to the development of systems that generate enough electricity such that the boiler is self-powering. An important design constraint employed in this investigation is the use of conventional, yellow-flame oil burners, integrated with a typical boiler. The power production target for the systems developed here is 100W – the power requirement for a boiler that uses low-power auxiliary components. The important heat transfer coupling mechanisms that drive power production in the systems studied are discussed. The results of this work may lead to the development of systems that export power to the home electric system.
The aim of this research was to determine the ability level of paralinguistic production and comprehension in adults with intellectual disability (ID) with regard to the level of their intellectual functioning and presence of co-morbid psychiatric conditions or dual diagnosis (DD). The sample consisted of 120 participants of both genders, ranging in age between 20 and 56 years (M =31.82, SD=8.702). Approximately 50% of the sample comprised participants with a co-existing psychiatric condition. Each of these two sub-samples (those with ID only and those with DD) consisted of 25 participants with mild ID and 35 participants with moderate ID. The paralinguistic scale from The Assessment Battery for Communication (ABaCo; Sacco et al., 2008) was used to assess the abilities of comprehension and production of paralinguistic elements. The results showed that the participants with mild ID are more successful than the participants with moderate ID both in paralinguistic comprehension tasks (p =.000) and in paralinguistic production tasks (p =.001). Additionally, the results indicated the presence of separate influences of both ID levels on all of the paralinguistic abilities (F [116]=42.549, p =.000) and the existence of DD (F [116]=18.215, p =.000).
The development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiOx films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeOx–Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highly active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeOx–Au catalyst is further demonstrated in a device context by pairing it with a nickel–molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.
V2O5 thin films were deposited by means of dc-ion beam sputtering. To determine the influence of various deposition parameters, samples were characterized by X-ray diffractometry and transmission electron microscopy. Using electron energy loss spectroscopy, the oxidation state of vanadium was quantified based on the chemical shift of absorption edges. Measurement of in-plane direct current showed that the electronic conductivity varies over several orders of magnitude depending on the preparation conditions. The desired structure suitable for battery applications is achieved by sputtering under partial pressure of oxygen and suitable post-annealing under ambient atmosphere. Reversible intercalation of Li into the produced thin films was demonstrated.
A gel polymer electrolyte (GPE) film of poly(vinylidenefluoride) and magnesium triflate is prepared and studied for application in a solid-state rechargeable magnesium battery. The composition of GPE is optimized in view of minimum liquid components and maximum specific conductivity (σ). The σ of GPE of optimum composition is 2.67×10−3 Scm−1 at 20°C, and it follows a Vogel, Tamman and Fulcher equation with an activation energy of about 0.4kJmol−1. The effect of aging on the Mg/GPE interface is studied. The formation of a passivating film on the Mg surface, which increases in thickness on aging in GPE, is established. Several Mg/GPE/MnO2 cells are assembled and studied for discharge capacity and cyclic-life data. The results reveal that Mg/GPE/MnO2 cells at C/8, C/6 and C/4 discharge rates yield, respectively, capacities of 160, 80 and 50mAhg−1 of MnO2. These values are nearly constant for about 30 cycles. Further cycling of the cells leads to a decrease in capacity, which is attributed to passivation of the magnesium electrode and poor efficiency of the Mg2+ ion insertion into the MnO2 positive electrode.
Nanoscience and nanotechnology can provide tremendous benefits to electrochemical energy storage devices, such as batteries and supercapacitors, by combining new nanoscale properties to realize enhanced energy and power capabilities. A number of published reports on hybrid systems are systematically reviewed in this perspective. Several potential strategies to enhance the energy density above that of generation-I electric double layer capacitors (EDLC: activated carbon/activated carbon) are discussed and some fundamental issues and future directions are identified. We suggest a new hybrid supercapacitor system that is able to meet the energy and power demands for a variety of applications, ranging from microelectronic devices to electrical vehicles, which presents itself as a breakthrough improvement. Two practical hybrid supercapacitor systems, namely, a lithium-ion capacitor (LIC: graphite/activated carbon) and a nanohybrid capacitor (NHC: (nc-Li4Ti5O12/CNF composite)/activated carbon), are featured and compared. The proposed NHC can pave the way toward generation-II supercapacitor systems by taking advantage of a novel, high quality, high efficiency and inexpensive nanomaterial preparation procedure. With such a breakthrough in nanofabrication–nanohybridization technology, the NHC, which utilizes an ultrafast nano-crystalline Li4Ti5O12, is considered to be an alternative for conventional generation-I EDLCs.
A lithium-ion battery featuring graphite anode, LiFePO4-C cathode and an innovative, safe, ionic liquid-based electrolyte, was assembled and characterized in terms of specific energy and power after the USABC-DOE protocol for power-assist hybrid electric vehicle (HEV) application. The test results show that the battery surpasses the energy and power goals stated by USABC-DOE and, hence, this safe lithium-ion battery should be suitable for application in the evolving HEV market.
To alleviate the effect of solar radiation fluctuation on solar thermochemical reaction, phase change material (PCM) is applied in solar-chemical reactor to buffer the temperature vibration induced by solar radiation fluctuation. In order to comprehensively study the effect of PCM on chemical reactor, a two-dimensional model was employed to compare the steady performance of 3 different kinds of solar parabolic trough receiver reactors (SPTRR): without PCM (SPTRR0), with PCM near the outer wall (SPTRR1) and with PCM in the center (SPTRR2). Then, the transient performance of three SPTRRs under continuously pulsed solar radiation and real solar radiation fluctuation are, respectively, analyzed. The results showed that comparable chemical performance can be achieved for all three different SPTRRs although the amount of catalysts in SPTRR1 and SPTRR2 are 13.2% less than that in SPTRR0. When the time interval of cloud presence is 3 min, compared with SPTRR0, the averaged methanol conversions in SPTRR1 and SPTRR2 are, respectively, improved by 10.5 and 9.8% and production selectivity (higher H2/CO) is better. And when under a real solar radiation fluctuation, compared to SPTRR0, the averaged methanol conversions in SPTRR1 and SPTRR2 are relatively improved by about 10.7% and 7.2%. SPTRR1 can more effectively attenuate the effect of solar radiation fluctuation and shows better chemical performance than SPTRR2.
Reactive oxygen species (ROS), formed during normal aerobic metabolism, are involved in signal transduction and cognitive functions, but highly increased ROS concentrations may also have detrimental effects. The aim of the present study was to investigate whether aging and cognitive functions are associated with ROS generation in human neocortex obtained from neurosurgical patients. ROS formation in mitochondria from fresh and re-thawed neocortical specimens was measured by monitoring ROS-mediated conversion of dihydrorhodamine 123 to fluorescent rhodamine 123. The validity of this technique was characterized in rat brain mitochondria. The increase in the concentration–response curve of the complex I inhibitor rotenone on ROS generation, as measured by rhodamine 123 (Rh123) fluorescence, was much more pronounced than that of rotenone on mitochondrial [3H]-choline uptake [which indicates changes in the mitochondrial membrane potential (ΔΨ M)]. Thus, mitochondrial ROS generation can be shown by Rh123 fluorescence although this fluorescence may also reflect changes in ΔΨ M to some extent. ROS formation in human brain mitochondria positively correlated with the age of patients. Moreover, an age-corrected positive correlation of ROS formation with presurgical cognitive performance was observed. Our data suggest a mild increase in ROS formation with aging possibly reflecting a physiological compensation of mitochondrial function. Furthermore, higher cognitive performances in tests of executive functions may be paralleled by slightly increased ROS levels.
This paper and a companion paper present a state-of-the-art review of significant research performed in the area of smart structures. The focus of the review is journal articles published since 1997. This paper reviews articles on active and-semi active control of structures using a variety of systems. Active control systems include active tuned mass dampers, distributed actuators, active tendon systems and active coupled building systems. Semi-active control systems include: magnetorheological (MR) fluid dampers, semi-active stiffness dampers, semi-active tuned liquid column dampers, and piezoelectric dampers. A review of hybrid control systems and control strategies is presented in the companion paper.
Advances in ultrasonic telemetry, including the ability to accurately position a transmitter within an array of hydrophone receivers, have led to increased opportunities to investigate a broad spectrum of ecological questions in aquatic systems. The quality and efficiency of positioning a transmitter relies upon factors controlled by the researcher (for example, geometry of the receiver array) as well as environmental conditions (for example, water quality or environmental noise). While the physics of sound wave propagation are well understood, the high amount of environmental variability in and among aquatic habitats makes it difficult to predict exactly how any given ultrasonic signal will behave. To evaluate variability in system performance across different receiver arrays in diverse environments we present positional records for fixed-location tags recorded with a popular positioning array, the VEMCO Positioning System (VPS). Using these records we evaluate the relationships between system performance, measured as both horizontal positioning error and positioning efficiency, and user-controlled and environmental variables. We used generalized linear mixed models to assess performance at a coastal site, a site in a freshwater tidal estuary, and a riverine site.
A simple method has been employed to prepare pillared layered Li1−2x Ca x CoO2 cathode materials by cationic exchange under hydrothermal conditions. The synthesized materials were characterized by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), field emission scanning electron microscope (FE-SEM) and galvanostatic charge–discharge cycling. The XRD data of the products show that they are single phases and retain the layered α-NaFeO2 type structure. The FE-SEM images of the materials prepared by hydrothermal method show uniform small particles, and the particle size of the materials is about 200nm. The initial discharge specific capacities of layered LiCoO2 and pillared layered Li0.946Ca0.027CoO2 cathode materials calcined at 800°C for 5h within the potential range of 3.0–4.3V (vs. Li+/Li) are 144.6 and 142.3mAhg−1, respectively, and both materials retain good charge–discharge cycling performance. However, with increasing upper cutoff voltage, the pillar effect of Ca2+ in Li1−2x Ca x CoO2 becomes more significant. The pillared layered Li0.946Ca0.027CoO2 has a higher capacity with an initial discharge specific capacity of 177.9 and 215.8mAhg−1 within the potential range of 3.0–4.5 and 4.7V (vs. Li+/Li), respectively, and retains good charge–discharge cycling performance.