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The effect of the inner particle structure on Li insertion activity and electronic structure of the nano-crystalline Li–Ti–O spinels was studied on materials prepared by solid state and solvothermal synthesis. The high temperature prepared materials of composition corresponding to Li4Ti5O12 feature particles with characteristic size of ca. 200nm with randomly distributed defects. The products of solvothermal synthesis with composition Li1.1Ti1.9O4+δ , feature cubic particles of characteristic dimension of ca. 50nm; the characteristic particle size differs from that of the coherent domain determined by X-ray diffraction. The reduction of the solvothermal and high temperature synthesized nano-crystalline spinels in Li containing solutions leads according to 6Li MAS NMR spectra to Li insertion into tetrahedral 8b and octahedral 16c position, respectively. Additional broad NMR signal attributable to a Knight shift was observed in spectra of partially reduced high temperature spinels. In the case of solvothermal spinels is the Knight shift signal less pronounced and appears only in spectra of samples in which the phase transition occurs on the local level. The UV–vis–NIR spectra of the partially reduced Li–Ti–O spinel samples correspond to expected semiconductor character of Li–Ti–O spinels. Both types of materials are characterized by band gap of 3.8eV (high temperature spinel) and 3.5eV (solvothermal material). Partial reduction accompanied with Li insertion causes additional optical transition in the visible to near infrared region, which can be attributed to formation of trivalent Ti, character of which changes with degree of reduction. The behavior observed for partially reduced high temperature spinels is similar to that reported for TiO2 (anatase). The spectral behavior of the partially reduced solvothermal spinels is more complex and reflects suppressed phase transition.
Cyanide based ionic liquid derived nitrogen-doped-carbons (N-C) has been demonstrated to be fascinating conductive coating agents to improve the performance of lithium ion battery electrodes. To explore its role in electrodes of sodium ion batteries (SIBs), SnS nanoparticles interpenetrated with a high concentration of such N-C ((hN-C@SnS)) are synthesized and comprehensively investigated as anodes for SIBs. We demonstrate that hN-C@SnS electrode can exhibit a remarkable cycling stability as well as a promising rate capability. Especially, the role of cyanide based ionic liquid derived N-C in a sodium ion battery electrode is systematically investigated for the first time by a series of characterization techniques, concluding that the superior cell performance are mainly benefiting from the homogeneous interpenetration of N-C as effective conductive network, rather than its advantageous role in Na+ storage and electron transport. In addition, ex situ XPS measurements strongly suggest that the conversion step of SnS is irreversible, while the alloying process to NaxSn is mostly reversible, which is in strong contrast with previous reports.
Little is known about combining work with caring for a person with advanced illness. This is important given the increasing number of women in the workforce and current policy seeking to increase care in the community. The aim of this paper was to explore the meaning of work for women caring for a husband with an advanced illness and the consequences of combining these two roles.
Alien species experience both costs and benefits in invaded environments, through naiveté of potential prey species, but also predation pressure from native predators. The question of whether alien prey recognise and respond to native predators has been relatively understudied, despite the hypothesised potential for native predators to provide biotic resistance to invasion. There are two main hypotheses about whether exotic prey should recognise native and exotic predators in their new ranges: (1) naiveté—predicting recognition of evolutionarily familiar predators only, and (2) pre-adaptation—predicting recognition of all predators through a generalist recognition template. With regards to antipredator responses, (3) naïveté theory presumes that exotic prey will respond to the predators they recognise, but we suggest that (4) a bold behavioural syndrome, and/or a high marginal value of food in invaded environments might result in weak or absent responses, even to recognised predators. Here we combine the giving-up density framework with behavioural analysis of remote camera footage to experimentally test these ideas in a disturbed, peri-urban, Australian ecosystem, where alien black rats are predated on by alien dogs, foxes, cats, and native quolls. Black rats recognised dogs and foxes, but appear naïve towards quolls. However, they showed no antipredator responses at all, consistent with a bold behavioural syndrome, elevated predation risk, and/or a high marginal value of food in invaded environments.
Numerical simulations using the lattice Boltzmann method (LBM) are developed to elucidate the dynamic behavior of condensed water and gas flow in a polymer electrolyte membrane (PEM) fuel cell. Here, the calculation process of the LBM simulation is improved to extend the simulation to a porous medium like a gas diffusion layer (GDL), and a stable and reliable simulation of two-phase flow with large density differences in the porous medium is established. It is shown that dynamic capillary fingering can be simulated at low migration speeds of liquid water in a modified GDL, and the LBM simulation reported here, which considers the actual physical properties of the system, has significant advantages in evaluating phenomena affected by the interaction between liquid water and air flows. Two-phase flows with the interaction of the phases in the two-dimensional simulations are demonstrated. The simulation of water behavior in a gas flow channel with air flow and a simplified GDL shows that the wettability of the channel has a strong effect on the two-phase flow. The simulation of the porous separator also indicates the possibility of controlling two-phase distribution for better oxygen supply to the catalyst layer by gradient wettability design of the porous separator.
Chronic non-specific low back pain is a major socioeconomic public health issue worldwide and, despite the volume of research in the area, it is still a difficult-to-treat condition. The conservative analgesic therapy usually comprises a variety of pharmacological and non-pharmacological strategies, such as transcutaneous electrical nerve stimulation. The neuromatrix pain model and the new findings on the process of chronicity of pain point to a higher effectiveness of treatments that address central rather than peripheral structures. The transcranial direct current stimulation is a noninvasive technique of neuromodulation that has made recent advances in the treatment of chronic pain. The simultaneous combination of these two electrostimulation techniques (cerebral and peripheral) can provide an analgesic effect superior to isolated interventions. However, all the evidence on the analgesic efficacy of these techniques, alone or combined, is still fragmented. This is a protocol for a randomized clinical trial to investigate whether cerebral electrical stimulation combined with peripheral electrical stimulation is more effective in relieving pain than the isolated application of electrical stimulations in patients with chronic nonspecific low back pain.
LiMn1.5Ni0.5O4 with spinel type of structure was synthesized by sol-gel method and doped by different rare-earth elements (Nd, Gd and Dy). It was found that the inclusion of rare-earth element preserves the cubic spinel structure, leads to smaller particle size and improves the cyclic performance of the produced batteries. The best battery performance was obtained after doping the spinel structure by Gd. Among the used rare-earth elements Gd is the only one with stable oxidation state of 3 + which leads to stabilization of the Mn dissolution. Thus, the improvements observed in battery performance (rate performance and cycle life) are due to the superior structural stability of the doped active materials. It is concluded that the LiMn1.48Ni0.5Gd0.02O4 sample is the one with the best overall performance to act as active material for cathodes in rechargeable lithium-ion batteries.
To satisfy the hot water demand of any building, a suitable thermal storage device must be added to a Photovoltaic thermal system (PVT) to address the time lag between the supply and demand of thermal energy. In this study, a nanofluid-cooled photovoltaic/thermal system retrofitted with a phase change material (PCM)-based thermal battery is designed to meet a portion of the electrical and thermal demands of a residential building for the climate of Dhahran, Saudi Arabia. Daily and yearly performance evaluation of the system is analytically performed through Engineering Equation Solver (EES) software and compared with the performances of a nanofluid-cooled PVT system without thermal storage and an uncooled PV system together with an economic assessment of the proposed system. A comparison of systems with and without thermal storage shows that the introduction of a PCM-thermal battery has made it possible to meet some of the building's thermal load but at the cost of reduction in the system's electrical and thermal outputs. The proposed system, however, shows an 11.7% improvement in its electrical performance over an uncooled PV system. The addition of thermal storage has made it possible to cover up to 27.3% of the residential thermal load along with 77% of the residential electrical load.
In this study, the electrochemical behavior of the Ce(III)/Ce(IV) redox couple in sulfuric acid medium with various concentrations and the influence of the operating temperature were investigated. A change of the concentration of sulfuric acid mainly produced the following two results. (1) With an increase of the concentration of sulfuric acid the redox peak currents decreased. (2) The peak potential separation for the redox reactions increased with rising concentration of sulfuric acid from 0.1 to 2 M and then decreased with further increase of the concentration. Elevated temperature was electrochemically favorable for Ce(III)/Ce(IV) couple, which caused an increase of the peak currents for the redox reactions and a decrease of the peak potentials separation. Constant-current electrolysis shows that the current efficiency was 73% for the oxidation process of Ce(III) and 78% for the reduction process at 298 K, and could be improved by elevating the temperature. The open-circuit voltage of the Ce–V cell, after full charging, remained constant at 1.870±0.005 V for more than 48 h, and is about 29% higher than that of the all-vanadium batteries. The coulombic efficiency was approximately 87%, showing that self-discharge of the Ce–V battery was small. The preliminary exploration shows that the Ce(III)/Ce(IV) couple is electrochemically promising for redox flow battery (RFB) application.
Combined cooling, heating, and power (CCHP) is an economic and eco-friendly technology to mitigate energy issues with remarkable energy efficiency improvement. This study formulates a mixed integer nonlinear programming (MINLP) model for a combined CCHP system coupled with renewable energy, i.e. RCCHP system, which is applied in five different buildings to evaluate the economic and environmental performance under two optimization modes. Net present value (NPV), internal rate of return (IRR) and dynamic payback period (DPP) are introduced as economic indexes, while CO2 emission reduction rate (CER) is considered as the environmental indicator to determine the optimal combination, capacity, and operation strategies for energy technologies. Results indicate that a combination of electricity purchased at valley period during night with power generated by the combined heating and power (CHP) unit coupled with wind turbine in peak period during daytime is cost-optimal which also enables higher energy efficiency. Meanwhile, the feed-in tariff as well as the uncoordinated electrical and thermal loads both show a significant impact on real-time operation strategies. Compared with the reference separate production (SP) system, the combined system shows better performance when applied to shopping mall under both optimization modes, e.g., with NPV up to 67.65 and 46.61 million RMB, IRR up to 20.70% and 25.10%, and the minimum DPP is 5.49 and 4.82 years under NPV and IRR maximization, respectively.
DNA damage and cell viability of human leukocytes cells were examined as simple tests for screening the potential toxicity of organoselenium compounds. Leukocytes were incubated with different organoselenium compounds at 4, 10, 40 and 100μM or vehicle (DMSO) for 3h at 37°C before of in vitro assays. Cell viability was determined by Trypan blue exclusion. DNA damage was assessed using the alkaline comet assay with silver staining. The exposure of leukocytes to (S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate, (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate, (S)-2-amino-1-diselenide-3-methylpropanyl, (S)-2-amino-1-diselenide-3-phenylpropanyl, 3′,3-ditrifluoromethyl diphenyl diselenide, 4′,4-dimethoxy diphenyl diselenide, 4′,4-dichloro diphenyl diselenide and 2′,2,4′,4,6′,6-hexamethyl diphenyl diselenide, in the range of 10–100μM, induced a significant increase in Damage Index (DI). The genotoxic effect of all compounds was associated with high frequencies of cells with damage level 4 and all compounds caused a decrease in cell viability. Our results suggest that the selenium compounds tested were genotoxic and cytotoxic to human leukocytes cells in vitro and that the organoselenium amino acid derivatives ((S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate, (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate, (S)-2-amino-1-diselenide-3-methylpropanyl and (S)-2-amino-1-diselenide-3-phenylpropanyl) were more genotoxic than aromatic derivatives (3′,3-ditrifluoromethyl diphenyl diselenide, 4′,4-dimethoxy diphenyl diselenide, 4′,4-dichloro diphenyl diselenide and 2′,2,4′,4,6′,6-hexamethyl diphenyl diselenide). These effects may be linked to the pro-oxidant activity exhibited by selenium compounds when used in relatively high concentrations.
Spinel-based LiMn2O4 is the most attractive cathode for Li-ion battery due to high voltage, low cost, and non-toxicity. The cycle life of the spinel cathodes could be improved by replacing Mn4+ with Ti4+ leading to the formation of new spinel cathode, LiMnTiO4. However, its application is restricted due to the associated loss in the specific capacity. In this work, spinel-layered Li1+z MnTiO4+δ (z =0, 0.5, and 1.0; δ is the value to reflect the composite character of the material) cathodes were fabricated to achieve long cycle life, without compromising on the specific capacity. Cathodes with excess Li (z =0.5 and 1.0) formed a spinel-layered composite structure with notation (1-a)LiMn2-x Ti x O4.aLi2Mn y Ti1-y O3 [y =0.5–((1/a −1)(1− x))]. These cathodes exhibited an enhanced specific capacity of ∼218mAhg−1 (20% higher), with a capacity retention of 94% after 60 cycles. The structural and electrochemical properties of these cathodes were investigated using X-ray diffraction, galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique to understand the mechanisms underlying the enhanced capacity and cycle stability. The effect of the Li-rich layered phase on the electrochemical performance of the Li1+z MnTiO4+δ cathodes was also investigated.
This paper explores the load shaping ability of microgrid power systems coupled with flexible operation of HVAC systems for commercial customers. In the proposed framework, this integrated system is treated as a dispatchable power source/sink in order to mitigate the uncertainty and variability imposed on the external utility company. The load shaping required is enabled by the natural flexibility in space heating and cooling, along with dispatchable microgrid resources such as batteries. A hierarchical control approach is formulated for the scheduling and supervisory control of the flexible loads and dispatchable energy units within the microgrid. Stochastic optimization is used for scheduling at the slow time scale to ensure forecasting errors in renewable availability and energy demands can be rejected. Deterministic optimization is used at the fast time scale to update dispatch decisions in response to realized conditions. A case study demonstrates that this proposed control approach is able to substantially reduce the uncertainty and variability in energy exchange with the external utility across a variety of commercial load types and in different seasons.
Visual processing difficulties are often present in Alzheimer’s disease (AD), even in its pre-dementia phase (i.e. in mild cognitive impairment, MCI). The default mode network (DMN) modulates the brain connectivity depending on the specific cognitive demand, including visual processes. The aim of the present study was to analyze specific changes in connectivity of the posterior DMN node (i.e. the posterior cingulate cortex and precuneus, PCC/P) associated with visual processing in 17 MCI patients and 15 AD patients as compared to 18 healthy controls (HC) using functional magnetic resonance imaging. We used psychophysiological interaction (PPI) analysis to detect specific alterations in PCC connectivity associated with visual processing while controlling for brain atrophy. In the HC group, we observed physiological changes in PCC connectivity in ventral visual stream areas and with PCC/P during the visual task, reflecting the successful involvement of these regions in visual processing. In the MCI group, the PCC connectivity changes were disturbed and remained significant only with the anterior precuneus. In between-group comparison, we observed significant PPI effects in the right superior temporal gyrus in both MCI and AD as compared to HC. This change in connectivity may reflect ineffective “compensatory” mechanism present in the early pre-dementia stages of AD or abnormal modulation of brain connectivity due to the disease pathology. With the disease progression, these changes become more evident but less efficient in terms of compensation. This approach can separate the MCI from HC with 77% sensitivity and 89% specificity.
Toothed whales produce short, ultrasonic clicks of high directionality and source level to probe their environment acoustically. This process, termed echolocation, is to a large part governed by the properties of the emitted clicks. Therefore derivation of click source parameters from free-ranging animals is of increasing importance to understand both how toothed whales use echolocation in the wild and how they may be monitored acoustically. This paper addresses how source parameters can be derived from free-ranging toothed whales in the wild using calibrated multi-hydrophone arrays and digital recorders. We outline the properties required of hydrophones, amplifiers and analog to digital converters, and discuss the problems of recording echolocation clicks on the axis of a directional sound beam. For accurate localization the hydrophone array apertures must be adapted and scaled to the behavior of, and the range to, the clicking animal, and precise information on hydrophone locations is critical. We provide examples of localization routines and outline sources of error that lead to uncertainties in localizing clicking animals in time and space. Furthermore we explore approaches to time series analysis of discrete versions of toothed whale clicks that are meaningful in a biosonar context.
The effect of quaternary ammonium-based ionic liquids (ILs) including tetraethylammonium hydrogen sulfate (NEt4HSO4) and tetrabutylammonium hydrogen sulfate (NBu4HSO4) on copper electrodeposition from acidic sulfate electrolyte was investigated by cyclic voltammetry and chronoamperometric measurements. These ILs were found to have a blocking effect on the copper electroreduction and induced the formation of more leveled and fine-grained cathodic deposits. Analysis of the dimensionless current–time transients indicated that the electrodeposition of copper was involved with instantaneous three-dimensional nucleation with diffusion-controlled growth. The addition of ILs induced the instantaneous nucleation to more progressive one. Data obtained from X-ray diffraction spectra revealed that the presence of these ILs strongly affected the crystallographic orientation of the electrodeposited copper with a (220) preferential orientation.
The electric performances of direct borohydride fuel cells (DBFCs) are evaluated in terms of power density and life time with respect to the NaBH4 concentration. A DBFC constituted of an anionic membrane, a 0.6mgPt cm−2 anode and a commercial non-platinum based cathode led to performances as high as 200mWcm−2 at room temperature and with natural convection of air. Electrochemical life time test at 0.55mAcm−2 with a 5M NaBH4/1M NaOH solution shows a voltage diminution of 1mVh−1 and a drastic drop of performances after 250h. The life time is twice longer with 2M NaBH4/1M NaOH solution (450h) and the voltage decrease is 0.5mVh−1. Analyses of the components after life time tests indicate that voltage loss is mainly due to the degradation of the cathode performance. Crystallisation of carbonate and borate is observed at the cathode side, although the anionic membrane displays low permeability to borohydride.
Objective The aim of the present study was to investigate the cardiovascular autonomic control in clinically definite multiple sclerosis (MS) patients with a standardised battery of cardiovascular tests and to correlate these findings with the brain magnetic resonance imaging (MRI) lesion load. Methods Fifty-one patients with MS and 50 healthy controls were studied. Brain MRI was performed in all patients showing typical MS lesions. The cardiovascular tests were carried out using a standardised battery. Results Heart rate (HR) responses to deep breathing (P<0.05) and tilt table testing (P<0.001) were significantly decreased in MS patients when compared to those of the controls. Blood pressure (BP) responses in the tilt table test were also impaired in MS patients (diastolic P<0.001, systolic P<0.05). Of the different brain areas investigated the total volume of the midbrain MRI lesions (P<0.05) was the one most clearly associated with the impaired BP responses. Conclusions MS results in both reduced HR variation and decreased BP reactions indicating disturbed cardiovascular regulation. In particular, the midbrain lesions found in MS are associated with cardiovascular dysfunction.
Metal-doped spinel lithium manganese oxides were successfully synthesized via co-precipitation. The synthesized Li1.05M0.05Mn1.9O4 (M=Ni, Mg, Al) had highly crystalline cubic spinel phase with the space group Fd3m, as confirmed by X-ray diffraction study. From scanning electron microscopic observation, it was found that the prepared materials had spherical morphology with high tap-density. The Li1.05M0.05Mn1.9O4 (M=Ni, Mg, Al) electrode exhibited improved cycling performance at elevated temperature. Especially, the Li1.05Al0.05Mn1.9O4 showed capacity retention of 91.5% during 100 cycles at elevated temperature (55°C). Also the thermal stability of the Li1.05M0.05Mn1.9O4 (M=Ni, Mg, Al) was also significantly improved.