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Half-cell electrochemical characterizations were conducted on carbon nanotube-vanadium oxide (CNT-VO x ) yarn electrodes in an 8 M LiCl aqueous electrolyte. A supercritical fluid deposition and in-situ oxidation process was utilized to deposit nanoscale coatings of vanadium oxide on carbon nanotube (CNT) surfaces throughout the porous structure of CNT yarns. The high surface area, interconnected pore structure and high electrical conductivity of the CNT yarn enabled extraordinary rate capabilities from the high capacity Li/VO x system. High-rate cyclic voltammetry scans, requiring current densities of hundreds of amperes per gram of electrode mass, produced rectangular voltammograms with distinguishable redox peaks from Li-ion intercalation/deintercalation. Capacitances of over 150 F g−1 were achieved at a scan rate of 5 V s−1 over a 1.2 V potential window resulting in an energy density of >32 Wh kg−1 (>30 Wh L−1) for the yarn electrode. The charge storage also showed good reversibility when cycled over this large potential window, maintaining 90% of the capacitance after 100 cycles at a scan rate of 2 V s−1. Electrochemical impedance spectroscopy shows the frequency dependent behavior is distinctly lacking of the characteristic responses from the rate-limiting processes associated with faradaic charge storage in VO x .
The ability to selectively activate or inhibit gene expression is fundamental to understanding complex cellular systems and developing therapeutics. Recent studies have demonstrated that duplex RNAs complementary to promoters within chromosomal DNA are potent gene silencing agents in mammalian cells. Here we report that chromosome-targeted RNAs also activate gene expression. We have identified multiple duplex RNAs complementary to the progesterone receptor (PR) promoter that increase expression of PR protein and RNA after transfection into cultured T47D or MCF7 human breast cancer cells. Upregulation of PR protein reduced expression of the downstream gene encoding cyclooygenase 2 but did not change concentrations of estrogen receptor, which demonstrates that activating RNAs can predictably manipulate physiologically relevant cellular pathways. Activation decreased over time and was sequence specific. Chromatin immunoprecipitation assays indicated that activation is accompanied by reduced acetylation at histones H3K9 and H3K14 and by increased di- and trimethylation at histone H3K4. These data show that, like proteins, hormones and small molecules, small duplex RNAs interact at promoters and can activate or repress gene expression.
Supercapacitors have shown extraordinary promise for miniaturized electronics and electric vehicles, but are usually limited by electrodes with rather low volumetric performance, which is largely due to the inefficient utilization of pores in charge storage. Herein, we design a freestanding graphene laminate film electrode with highly efficient pore utilization for compact capacitive energy storage. The interlayer spacing of this film can be precisely adjusted, which enables a tunable porosity. By systematically tailoring the pore size for the electrolyte ions, pores are utilized optimally and thereby the volumetric capacitance is maximized. Consequently, the fabricated supercapacitor delivers a stack volumetric energy density of 88.1 Wh l−1 in an ionic liquid electrolyte, representing a critical breakthrough for optimizing the porosity towards compact energy storage. Moreover, the optimized film electrode is assembled into an ionogel-based, all-solid-state, flexible smart device with multiple optional outputs and superior stability, demonstrating enormous potential as a portable power supply in practical applications.
Li-ion batteries are leading candidates for mobility because electric vehicles (EV) are an environmentally friendly mean of transport. With age, Li-ion cells show a more resistive behavior leading to extra heat generation. Another kind of problem called thermal runway arises when the cell is too hot, what happens in case of overcharge or short circuit. In order to evaluate the effect of these defects at the whole battery scale, an air-cooled battery module was built and tested, using electrical heaters instead of real cells for safety reasons. A battery thermal management system based on a phase change material is developed in that study. This passive system is coupled with an active liquid cooling system in order to initialize the battery temperature at the melting of the PCM. This initialization, or PCM solidification, can be performed during a charge for example, in other words when the energy from the network is available.
LiNi1/3Co1/3Mn1/3O2 is prepared by a rheological phase method. Homogeneous precursor derived from this method is calcined at 800°C for 20h in air, which results in the impressive differences in the morphology properties and electrochemical behaviors of LiNi1/3Co1/3Mn1/3O2 in contrast to that obtained by a solid-state method. The microscopic structural features of LiNi1/3Co1/3Mn1/3O2 are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD). The electrochemical properties of LiNi1/3Co1/3Mn1/3O2 are carried out by charge–discharge cycling test. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performances. The obtained results suggest that the rheological phase method may become an effective route to prepare LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium battery.
A new method for the determination of apparent diffusion coefficients of lithium ions in graphite electrodes was developed. In situ colorimetry – a technique relating the color of an electrode to its state of charge – was used to measure the distribution of lithium ions in model battery electrodes with good local and temporal resolution. Diffusion kinetics data are obtained from the rate of equilibration of a deliberately induced heterogeneous lithium distribution. An apparent activation energy of ca. 17kJ/mol was measured for the diffusion of lithium in a porous graphite electrode.
Lithium ion batteries with graphitic carbon anodes and LiCoO2 cathodes are cycled reversibly in electrolytes based on trans-2,3-butylene carbonate (t-BC), even in the absence of ethylene carbonate. While the poor interfacial film (the solid electrolyte interface (SEI)) on the lithium electrode can be readily explained in terms of previous models of its stability, this highly reversible behavior of graphite is hard to account for. To explain this profound difference in the SEI stability of the two electrodes, we have taken into account the influence that the nature of the electrode (lithium metal versus graphite) and the type of the reaction site (basal plane versus edge sites) exert on the solvent reduction pathways.
Effects of rare earth composition on the high-rate capability and low-temperature capacity of AB5-type hydrogen storage alloys have been studied and analyzed with pattern recognition methods. The results show that the increase of Ce and Pr and the decrease of La and Nd concentration improve the high-rate capability and low-temperature capacity of AB5-type hydrogen storage alloys, Ce exhibiting better favorable influences than Pr. The improvement of both high-rate capability and low-temperature capacity are mainly ascribed to the lower stability of the hydride. The alloy with the rare earth composition of La0.1645Ce0.7277Pr0.0234Nd0.0845 shows very good high-rate capability and low-temperature capacity.
MoO2 is synthesized via carbothermal reduction, using pitch, of hydrothermally produced MoO3 nanobelts. X-ray diffraction (XRD) and electron microscopic data indicate that the MoO3 is readily reduced to MnO2 and the smooth surfaces are modified by carbon products after the heat treatment in reduction atmosphere. The produced carbon-coated MoO2 lengthened a few micrometers is ball-milled to reduce the particle size below 100 nm. Electrochemical tests of the milled carbon-coated MoO2 electrode demonstrate a high discharge (reduction) capacity approximately 248 mAh (g-MoO2)−1 at 150 mA g−1 (0.5 C-rate) with an average operation voltage of 1.3 V, and the resulting charge (oxidation) capacity approximates to 208 mAh g−1. The charge capacity is retained about 98.6% upon cycling. The carbon-coated MoO2 electrode is also suitable for high rate charge and discharge, reaching 129 mAh g−1 for charge and 146 mAh g−1 for discharge even at 30 C-rates (9 A g−1), suggesting feasibility of the MoO2 as the anode material suitable for high rate applications.
Inverted perovskite solar cells (IPSCs) have attracted great attention in recent years due to their reliable operational stability, negligible hysteresis and low-temperature fabrication process. To accelerate their commercialization, the focus of research on IPSCs has been to enhance the power conversion efficiency over the past few years. Herein, an overview of efficiency progress in IPSCs is given including the structure design, the fabrication of perovskite films and the modification of charge transport materials. Specifically, the effects of interface passivation on the performance of those devices have been emphasized. Finally, perspectives on the further development and commercialization of IPSCs are proposed, such as developing new electron transport materials and rear electrode materials, and employing field effect passivation materials and inorganic hole transport materials.
This paper starts by discussing research into the effect of background knowledge on English for Academic Purposes (EAP) tests and discusses EAP tests in which the content of at least some of the test components is related to students’ fields of academic study. This section shows how research has demonstrated that students do not necessarily do better if they are given tests in their own academic subject areas and how, because of the difficulties inherent in test-equating, such tests may not be testing the students fairly. The paper suggests, therefore, that for international EAP tests, English for Specific Academic Purposes testing be abandoned. In its second part, the paper discusses what EAP tests might consist of in the future. Instead of EAP proficiency tests, the paper suggests that there should be aptitude tests to find out whether L1 and L2 students would be capable of rapidly acquiring the requisite academic discourse practices once they had embarked on their academic courses. Such tests for L2 students should include a test of specific grammatical skills, so that receiving institutions can be sure that students have the requisite linguistic infrastructure needed to carry out academic work in English.
Carbon-coated SnS2 nanoparticles were prepared by a simple solvothermal route at low temperature. A carbon coating with a thickness of about 5nm was deposited on nano-sized SnS2 particles to serve as the anode in lithium-ion batteries. Both the nanostructure and the morphology of the SnS2 powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The coated samples were used as active anode materials for lithium-ion batteries, and their electrochemical properties were examined by constant current charge–discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The reversible capacity of the carbon-coated SnS2 after 50 cycles was 668mAh/g, which was much higher than that of the uncoated SnS2 (293mAh/g). The carbon-coated SnS2 also had a better rate capability than the uncoated SnS2 in the range of 0.008–1 C. The capacity retention of the carbon-coated SnS2 was improved due to its good conductivity and the effective buffer matrix that alleviated volume expansion during the charge–discharge process.
Fe2O3 anode suffers from drastic volume change during cycling and poor electronic conductivity, resulting in inferior electrochemical performance. To address these problems, the Fe2O3/nitrogen-doped graphene sheets hybridization strategy is proposed by a hydrothermal/annealing process. In this composite, Fe2O3 nanoparticles are tightly confined in graphene sheets matrix and the porous structure is obtained due to the crumpled and cross-like graphene framework, which can alleviate the volume expansion, maintain integrity of the electrode, and improve electrical conductivity and Li+ diffusion. As a result, benefiting from the synergistic effect of N-doped graphene sheets matrix and Fe2O3 nanoparticles, the composite exhibits a reversible capacity up to 952 mAh g−1 at a current density of 100 mA g−1 and excellent rate capability (348 mAh g−1 at a current density 5000 mA g−1).
A germanium/copper germanide/carbon (Ge/Cu3Ge/C) composite is prepared by the Pechini method using GeO2, CuSO4, and citric acid/ethylene glycol as the Ge, Cu and carbon sources, respectively. The microstructure and electrochemical properties of this nano-composite are compared to those of germanium/carbon (Ge/C) that is prepared without the copper precursor. In the latter composite, irregular-shaped submicron-sized (0.4–0.5μm) Ge particles are dispersed inside a carbon matrix. In the former, however, sphere-shaped nano-sized (<100nm) Ge particles are produced, inside of which a Cu3Ge phase is uniformly dispersed in nano-scale. The pure Ge component in both electrodes is lithiated up to Li15Ge4 after a lithiation down to 0.0V at a current density of 100mAg−1. The Cu3Ge-containing electrode gives a superior cycle and rate performance to that of the Cu3Ge-free counterpart. This difference has been ascribed to the favorable roles provided by the nano-sized Cu3Ge phase that is intimately contacted with the nano-sized Ge particles within a sphere. The electrochemical dilatometry study reveals that the electrode swelling is much smaller for the Cu3Ge-containing electrode, illustrating that the electrochemically inactive Cu3Ge phase serves as a buffer against a massive volume change encountered in the Ge component.
5 July 2011 Date filed: 5 February 2007 Inventors: Stinson; Jonathan S. (Minneapolis, MN) Assignee: Boston Scientific Scimed, Inc. (Maple Grove, MN) Endoprostheses including metal matrix composite structures An endoprosthesis that includes a composite having a metal matrix and a plurality of stiffening particles in the matrix. The metal of the metal matrix can include titanium, niobium, tantalum, or alloys thereof. The stiffening particles can include a metal core and a thin surface layer. The thin surface layer can include oxides, carbides, nitrides, or combinations thereof.
The demand for electric vehicles has inspired extensive efforts to develop solid oxide fuel cells (SOFCs) for transportation. However, the high cost of hydrogen fueled SOFC systems and the deactivation of Ni-YSZ anodes in hydrocarbon fuels hinder the progress of SOFCs' development and commercialization. Here, we report a unique multi-functional anode for SOFCs that allows direct utilization of transportation fuels (iso-octane) without co-feeding O2 and CO2, demonstrating a peak power density of ∼0.6W/cm2 at 750°C. The multi-functional anode is derived from a conventional NiO-YSZ anode with BaCO3 modification in the anode support, creating a catalytically active conformal coating of BaZr1−x Y x O3−δ (BZY) on YSZ and nano-islands of BaO on Ni surface, which greatly promote reforming of octane and oxidation of the reformed fuels. Further, the simple and cost-effective modification process can be readily adopted in the fabrication of the state-of-the-art NiO-YSZ supported cells.
Recent studies have shown that frontal and temporal lobe epilepsy, the most common forms of focal epilepsy, may impair theory of mind (ToM) by impacting on key zones of ToM's underlying neural network. Clinical research has characterized the severity and specificity of ToM impairments, as well as model methods of assessment, thereby extending the potential of ToM to expand the scope of the neuropsychology of epilepsy. Theory of mind deficits have been linked to self-rating and coping styles, suggesting a role for ToM in awareness and subjective well-being. The study of ToM in epilepsy is important not only for advancing understanding of its underlying neural network but also for clinical care. A task for the future is to identify patients with and without impaired ToM and the subsequent associations with personality complications and vulnerability to psychiatric comorbidities. Knowledge of the type and direction of the relationship between ToM, personality, and behavior might contribute to characterizing the neurobehavioral consequences of specific epilepsy syndromes as well as planning nonpharmacological treatments for alleviating psychobehavioral distress and social maladjustment.
Solid electrolytes which comprise lithium and magnesium triflate ionic salts in polyacrylonitrile (PAN)-based gels are used to fabricate electrochemical double-layer capacitors in conjunction with ethylene carbonate (EC) and propylene carbonate (PC) as plasticizers and high-density graphite (HDG) as polarizable electrodes. The conductivity of the solid electrolytes is around 10−3 Scm−1 at ambient temperatures. Composites which consist of PAN+EC+PC+electrolyte are electrochemically stable over a wide potential range. Cells of the type: HDG/PAN–EC–PC–Li and Mg-triflate/HDG exhibit single-electrode discharge capacitance values of 480 and 383μFcm−2, respectively, with attractive charge–discharge characteristics.
To meet the requirements for high-rate battery with desirable performance, a self-supported Ni2P@Ni sponge electrode is synthesized via simple steps, in which the Ni sponge substrate is synthesized by a one-pot hydrothermal method and the Ni2P nanosheets grown on the novel substrate are converted from Ni(OH)2 via a phosphorization reaction. This hybrid composite combines the 3D porous structure of Ni sponge and high capacity of Ni2P nanosheets, which exhibits lightweight, flexible and highly-conductive properties, resulting in an excellent specific capacity of 430.3 mAh g−1 at a current density of 1 A g−1 and remaining as high as 77.0% capacity even at 40 A g−1. More importantly, the Ni2P@Ni sponge//C cell exhibits the maximum energy density of 182.1 W h kg−1 at a power density of 205 W kg−1 along with superior capacity retention of 85.2% after 3000 cycles. It is suggested that the Ni2P nanosheet@ Ni sponge composite is a promising electrode material for high-rate batteries.
Nitrogen-containing carbon was prepared from the vapor deposition of acetonitrile at 900 °C over silica- or magnesia-supported Fe, Co, and Ni particles. The byproducts of pyrolysis were monitored by mass spectrometry. The carbon formed from silica precursors was washed with KOH to remove the silica and HCl to remove metal particles, whereas the carbon formed from magnesia samples was washed with HCl to remove the support and the metal. The solid carbon product was characterized with N2 physisorption to measure surface area and pore volume distribution, X-ray diffraction to determine the crystalline phases present, and temperature-programmed oxidation to determine ash and nitrogen content. Magnesia was more readily removed from the carbon compared with silica. A significant amount of metal, encased in carbon, remained in the samples after washing. The Co particles led to a higher content of bulk nitrogen in the carbon, as high as 2.9% based on oxidation measurements. Electron microscopy imaging confirmed that all of the metal particles catalyzed the formation of various types of carbon nanofibers, with the diameter and structure of the fibers varying with different metal–support precursor combinations. A possible application for these fibers is oxygen reduction reaction catalysts for proton-exchange membrane fuel cell cathodes.
Older adults suffering from Parkinson’s disease (PD) frequently present with an additional form of severe neurodegenerative and/or vascular pathology. Findings of differential clinical manifestations of cognitive impairment, depending on presence and nature of such coexisting brain pathology, raise the question for neuropsychological procedures that are capable not only of distinguishing between non-demented PD patients and patients with Parkinson-associated dementia (PDD), but also of detecting other types of cognitive decline, most likely Alzheimer’s disease (AD) or vascular dementia (VD), superimposing PD. The aim of this article is to review the literature on neuropsychological processes at risk in developing PDD, to introduce comorbid causes of cognitive decline in the presence of PD, to discuss the scope of the “cortical versus subcortical dementia”-concept in view of its capability of differentiating dementias, and to scrutinize existing diagnostic criteria concerning the toleration of comorbidity. Additionally, we derive an evidence-based neuropsychological diagnostic procedure for assessing PDD under special consideration of these comorbid aspects.
The diffusion of vanadium ions across the membrane along with side reactions can have a significant impact on the capacity of the vanadium redox flow battery (VFB) over long-term charge–discharge cycling. Differential rates of diffusion of the vanadium ions from one half-cell into the other will facilitate self-discharge reactions, leading to an imbalance between the state-of-charge of the two half-cell electrolytes and a subsequent drop in capacity. Meanwhile side reactions as a result of evolution of hydrogen or air oxidation of V2+ can further affect the capacity of the VFB. In this paper, a dynamic model is developed based on mass balances for each of the four vanadium ions in the VFB electrolytes in conjunction with the Nernst Equation. This model can predict the capacity as a function of time and thus can be used to determine when periodic electrolyte remixing or rebalancing should take place to restore cell capacity. Furthermore, the dynamic model can be potentially incorporated in the control system of the VFB to achieve long term optimal operation. The performance of three different types of membranes is studied on the basis of the above model and the simulation results together with potential operational issues are analysed and discussed.
Na-ion batteries are considered as promising alternatives for Li-ion batteries in electrochemical energy-storage. However, the lack of high performance anode materials severely plagues their practical application. In this work, we synthesized the SnO2@graphene (SnO2@G) nanocomposites through one-pot hydrothermal method, in which the ultrafine SnO2 nanoparticles (∼4 nm) evenly distributed on the graphene sheets surface. The synthesized SnO2@G delivered a Na storage capacity of 343 mAh g−1 at 100 mA g−1 after 100 cycles, with excellent capacity retention. Even at a low temperature of −20 °C, SnO2@G still maintains a specific capacity of 97 mAh g−1 after 100 cycles, making it both available for ambient and low temperature environment. The detailed Na-storage mechanism for SnO2@G is revealed. It is found that both conversion and alloying reaction contribute to sodium storage. The dominating contribution from conversion reaction is attributed to the ultrafine nanoparticles, which triggers the activity of conversion reaction of SnO2 with sodium. The study provides new insights for using SnO2 as the anode materials for Na-ion batteries.
Polyaniline (PANI) is a promising organic cathode material for electrochemical batteries. Its specific capacity is limited by irreversible formation of pernigraniline base, and its energy density is limited by the voltage which could be improved. We present an ab initio study of PANI and PANI functionalized with functional groups which lead to increased voltage and stabilization of the pernigraniline salt. Specifically, the oxidation potential achieved by functionalization with CN on the nitrogen is computed to be 1.3 V higher than that of pristine PANI oligomer, leading to a higher voltage, and the formation of the pernigraniline base is predicted to be simultaneously suppressed, leading to a higher reversible capacity. Therefore, functionalized PANI could be a promising candidate organic cathode for Li-ion batteries.