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Both endogenous and synthetic (e.g. drugs) quinones are essential functional moieties in various biological systems and their activity is mainly governed by their electrochemical properties. In recent years they are also more readily applied in novel energy storage devices, such as batteries and solar cells. In this work, the redox behaviour of 1-aminoanthraquinone (AQ), and 2,3-dichloro-1,4-naphthoquinone (NQ) is studied at a three-phase junction formed by n-octyl-2-pyrrolidone and aqueous electrolyte solution on a glassy carbon working electrode. We show that the two quinones behave quite differently when undergoing reduction at the three-phase junction. AQ underwent a 1-step, 2-electron reduction resulting in transfer of cations from the aqueous phase, while reduction of NQ occurred in two steps, the first of which was accompanied by a transfer of the NQ•− radical to the interface with the reduction potential dependent on the anion present in the aqueous phase due to salting out effects. After that, the quinone was able to undergo a second reduction process forming a dianion which similarly to AQ resulted in a transfer of cations from the aqueous phase. Importantly, the cation transfer potential is determined by ion-pair formation with the quinone, rather than the solvation energy of cation in the pure organic solvent.
As a result, the thickness of the coating needs to be checked regularly both after a change of colour or component and also during the normal application process. Otherwise, there is the risk of producing components that are not fully coated, where the amount of powder is too small, or of incurring unnecessarily high costs, where too much powder is used. It is particularly important to measure the coating before it is cured, in particular in corners and on edges, because any areas that have not been adequately coated can easily be rectified at this early stage.The thickness of powder coatings can now be measured easily, even on complex parts.© TQC
Distinct lines of research demonstrated that patients with amnestic mild cognitive impairment (aMCI), a potential precursor of Alzheimer disease (AD), are particularly impaired in remembering relations between items and that the use of emotional targets can facilitate memory in patients with AD. We link these findings by examining learning through positive and negative feedback in patients with aMCI, and explore its anatomic underpinnings with diffusion tensor imaging and tractography. Compared to healthy controls, patients with single-domain aMCI were impaired in learning from positive feedback, while learning from negative outcomes was preserved. Among pathways within the brain circuit involved in feedback learning, abnormal white matter microstructure was observed in tracts, which connect left-hemispheric amygdala with hippocampus and entorhinal cortex. In all participants, reduced white matter integrity in this left fiber tract was specifically associated with learning from positive outcomes. Microstructure of right-hemispheric tracts between amygdala and entorhinal cortex was related to learning from negative feedback, and was not compromised in aMCI patients. Our results provide new insight into how anatomical connections might contribute to impaired and preserved aspects of learning behaviors in the early AD process and indicate potential compensatory mechanisms.
Membrane electrode assemblies (MEAs) with PtRu/C and Pt/C as both sides electrocatalysts have been fabricated and used in a mixed-reactant alkaline fuel cell without bipolar plate. It has been found that the reactant selectivity of the electrocatalyst is tunable by changing the electrode hydrophobicity. The measurement on a three-cell stack with MEAs using a more hydrophobic PtRu/C electrode and a more hydrophilic Pt/C electrode in an ethanol/oxygen mixed solution shows that the PtRu/C electrode serves as a cathode and Pt/C electrode performs as an anode. The steady-state power density of 31mWcm−2 is achieved in an ethanol solution by continuously bubbling oxygen at ambient temperature and atmosphere pressure.
Redox flow batteries attract ever growing interest over the past decades in stationary energy storage. Iron and zinc species have been widely studied as active species for redox flow batteries. In this paper, the redox behavior of iron species has been tested in aqueous ionic liquid solutions. 1-butyl-3-methylimidazolium chloride (BMImCl) is found to be most effective to regulate the redox activity of iron species. While in the anolyte, the standard rate constant of zinc plating/stripping can be promoted by one order up to 1.44 × 10−4 cm s−1, when aqueous NH4Cl is used as supporting electrolyte. Kinetic analysis is further conducted on the iron and zinc species in the corresponding supporting electrolytes. By using an anion exchange membrane, an aqueous Zn–Fe hybrid flow battery showed a high energy efficiency of 80% at 20 mA cm−2, making it an alternative for flow battery application.
This investigation answers and amplifies calls to model the transdiagnostic structure of psychopathology in clinical samples of early adolescents and using stringent psychometric criteria. In 162 clinically referred, clinically evaluated 11–13-year-olds, we compared a correlated two-factor model, containing latent internalizing and externalizing factors, to a bifactor model, which added a transdiagnostic general factor. We also evaluated the bifactor model psychometrically, including criterion validity with broad indicators of psychosocial functioning. In doing so, we compared alternative approaches to defining and interpreting criterion validity: a recently proposed incremental definition based on amounts of variance in criterion factors explained, and the more typical definition based on the presence of conceptually meaningful relationships. While traditional fit statistics favored the bifactor model as expected, psychometric analyses added important nuance. Despite moderate reliability, the general factor was not fully transdiagnostic (i.e., was not informed by several externalizing scores), and was partially redundant with internalizing scores. Approaches to criterion validity yielded opposing results. Compared to the correlated two-factor model, the bifactor model redistributed, without incrementally increasing, the total variance explained in criterion indicators of psychosocial functioning. Yet, the bifactor model did improve the precision of clinically important relationships to psychosocial functioning, raising questions about meaningful tests of bifactor psychopathology models.
The electrochemical reduction of molten Li–Na–K carbonates at the eutectic composition was (43.5/31.5/25mol%) performed in the range 450–700°C. The analysis of the electrochemical mechanism was done by cyclic voltammetry with an inert vitreous carbon electrode. “Quasi-spherical” carbonaceous particles were obtained with average diameter comprised between 30 and 50nm. The specific surface area as well as the crystallinity and morphology of the powders were strongly influenced by the operating conditions, i.e. potential deposition, temperature of the molten carbonates, temperature of the drying process after washing. The carbon prepared in our experimental conditions contains micro-, meso- and macroporisty. The proportion of each one is strongly dependent on the operating deposition conditions. The highest specific surface area value (1315m2 g−1) was obtained with carbon powder deposited at 450°C for an applied potential of −6V and dried at 600°C under vacuum after washing.
Graphene oxide, an intermediate during graphene synthesis by a modified Hummers's method, exhibits higher capacitance, up to 189 F g−1, than graphene due to an additional pseudo-capacitance effect of attached oxygen-containing functional groups on its basal planes. Taking its higher capacitance, lower cost and shorter processing time into consideration, graphene oxide may be a better choice than graphene as an electrode material for supercapacitors.
In this work, an innovative 3D-frame structure ultrathin NiO nanosheets/carbon nanotubes (CNTs) composite as anode for lithium-ion batteries (LIBs) was successfully fabricated via a facile, effective strategy. Our 3D-frame structure NiO@CNTscompositebasedanodeforLIBsalsoshowsultrahighcapacity (*), rate, cycle and Coulombic efficiency performance for the ultrafast charge slow discharge. When using 100mAg−1 to charge and 2000mAg−1 to discharge (half-cell), the charge and discharge capacity of the NiO@CNTs composites reached 763 and 1000mAhg−1 at the first cycle, respectively. From the 2nd cycle the Coulombic efficiency is higher than 95%, and after 100 cycles the capacity maintained 122.7% based on capacity of the second cycle.
The nanocomposites Ce doped SnS2 (CeSnS2) have been synthesized by a hydrothermal route. The CeSnS2 composites exhibit 3D flowerlike structures. The particle sizes of each petal are in the range from 100 to 200nm with clear lattice fringes. The electrode cycling performance and rate retention ability of CeSnS2 are better than those of SnS2 as anode electrodes materials for lithium ion batteries. The CeSnS2 compound (Ce of 5mol%) shows the best reversible capacities and cycling performance among the synthesized CeSnS2 compounds. The reason is that the part of large-radius cerium ions (much larger than that of Sn4+) can be the substitutes for Sn4+ in the SnS2 lattice. The expansion of the crystal lattice can provide more lattice space for lithium intercalation and de-intercalation, and further improves the cycling performance of CeSnS2.
Tuberculosis (TB) remains the most common cause of infectious disease deaths worldwide. What is perhaps less appreciated is that the caseload of tuberculosis patients in South Asia is staggering.
The development of new overcharge protection compounds for 4V-class lithium cells with LiCoO2 cathodes was attempted in order to protect the cells from the hazards of ignition and/or explosion when overcharged. At least two requirements must be met as regards overcharge protection compounds. They must have an oxidation potential (E ox) in the 4.6–4.8V range versus Li/Li+ and they must not adversely influence the lithium cycling efficiency (Eff). The overcharge protection compounds were used by adding them to the electrolyte solution, which was LiClO4/propylene carbonate. First, this study involved a basic examination of the relationships among the E ox values of arenes including polyacenes, naphthalene derivatives and methylbenzenes, their chemical structure, the aromatic ring size and the effects of substituent functional groups. Next, the E ox and Eff values of cycloalkanes including cyclohexane, decaline, adamantane and norbornane were examined. Based on these examination results, various adamantane derivatives were synthesized and their electrochemical properties were investigated. Finally, four aryladamantanes (1-(p-tolyl)adamantane, 1-(m-tolyl)adamantane, 1-(o-tolyl)adamantane, 1-(4-ethylphenyl)adamantane) were found to exhibit better E ox and Eff values than those of biphenyl, which is already used in commercial cells as an overcharge protection additive.
Si/graphite composite materials embedded with polymer microsphere as an elastic inactive phase were prepared by high-energy mechanical milling and investigated as a high capacity anode material for lithium rechargeable battery. Improved capacity retention was achieved with the composite. In situ measurement of the electrode thickness revealed that the swelling of the electrode became smaller with the increase of polymer microsphere content. It is believed that polymer microsphere played a buffering role of accommodating the mechanical strains induced by silicon expansion during lithiation, resulting in the suppression of the volume expansion of the electrode, which improved the cycle performance of the electrode.
Spherical LiNi0.5Mn1.5O4 (LNMO) cathode material gradient-doped with Mg is successfully synthesized via a co-precipitation method. The average Mg doping concentration in the LNMO is 2 mol% with 10 mol% on the particle surface and a gradual reduction to 0% in the core. The Mg gradient-doped (GD) LNMO shows an improved electrochemical performance with discharge capacities of 121.5 and 91.4 mAh g−1 at discharging rates of 0.1 and 4.0C, respectively. The corresponding values for a pristine LNMO sample are 125.7 and 80.8 mAh g−1. After 80 charge/discharge cycles at room temperature, the Mg(GD)-LNMO retains 92% of the initial capacity, compared with a retention rate of 80% for the pristine LNMO. A high-temperature (55°C) cycling test shows that the Mg(GD)-LNMO has a lower loss of capacity (8%) compared with the pristine LNMO (24%) after 20 cycles. Electrochemical impedance spectroscopy (EIS) reveals that the Mg-rich surface of Mg(GD)-LNMO suppresses the reaction of the electrolyte with the LNMO and decreases the total resistance. In addition, gradient-doping LNMO with Mg can also improve Li ion diffusion based on results of the potentiostatic intermittent titration technique (PITT). Finally, differential scanning calorimetry (DSC) analysis shows that the exothermic peak of the Mg(GD)-LNMO is shifted at higher temperatures and that the amount of heat is decreased by comparison with the values for pristine LNMO.
Hierarchical (bimodal) porous copper (Cu) materials with micro- and nano-sized pores are desired for a wide variety of important applications. This study proposes an annealing-electrochemical dealloying approach for the creation of bulk bimodal porous Cu materials from an as-cast hypereutectic Al75Cu25 (at.%) precursor alloy, which consists of pre-eutectic CuAl2 and lamellar eutectic α-Al(Cu)-CuAl2. Annealing of the precursor alloy plays a critical role in the subsequent electrochemical dealloying for the creation of bimodal porous Cu. It decouples the lamellar eutectic structure and substantially increases the size of the α-Al(Cu) phase which determines the size of the subsequently produced micropores. In addition, it reduces the solubility of Cu in α-Al(Cu) and noticeably decreases the critical potential of the Al75Cu25 alloy thereby enabling more flexible electrochemical dealloying. A variety of bimodal porous Cu structures were produced using the proposed approach. The most homogeneous bimodal porous Cu structure with the average ligament width of 52nm was produced by electrochemical dealloying of the annealed Al75Cu25 alloy at the applied potential of -0.5V, which is above the critical potential of the α-Al(Cu) but below that of the CuAl2 phase. The influence of annealing on the microstructure and the subsequent electrochemical dealloying behaviours of the Al75Cu25 alloy was characterised and discussed in detail.
Novel vanadium nitride/nitrogen-doped graphene (VN/NG) composite was fabricated and used as stable high performance anode materials for supercapacitors. The VN/NG composite anode material exhibited excellent rate capability, outstanding cycling stability, and superior performance. FE-SEM and TEM studies of VN/NG composite revealed that ultra-thin VN nanostructures were homogeneously distributed on flexible NG nanosheets. The NG provided a highly conductive network to boost the charge transport involved during the capacitance generation and also aided the dispersion of nanostructured VN within the NG network. The synergetic VN/NG composite exhibited an ultra-high specific capacitance of 445 F g−1 at 1 Ag−1 with a wide operation window (−1.2 to 0 V) and showed outstanding rate capability (98.66% capacity retention after 10,000 cycles at 10 Ag−1). The VN/NG electrode offered a maximum energy density (∼81.73 Wh kg−1) and an ultra-high power density (∼28.82 kW kg−1 at 51.24 Wh kg−1). The cycling performance of the VN/NG composite was superior to that of pure VN nanostructure. These finding open a new path way to the designated fabrication of VN/NG composite as anode materials in the development of high performance energy storage devices.
Social support and coping are reliably associated with wellbeing during adolescence, but it is unclear whether relationships between these constructs and affect are inter-related or independent. Emotional intelligence (EI) also correlates with greater wellbeing, but the key processes supporting the association are likewise uncertain. This study aimed to compare support and coping as predictors of wellbeing and stress using structural equation modeling to test alternate latent factor models. It also aimed to test how EI, measured as an ability, might influence the constructs. Data were collected from 203 Israeli high-school students. Modeling suggested that social support was a stronger influence than coping style on wellbeing, although avoidance coping made a unique contribution to lower wellbeing. EI was associated with social support, but not coping or outcome. It is concluded that social support is critical for wellbeing, over and above coping, consistent with theoretical perspectives that emphasize the importance of social engagement in adolescence. Ability EI appears to have only a modest influence on emotional functioning during adolescence.
An alkaline microfluidic fuel cell is demonstrated employing an alkaline version of a formic acid anode and a sodium hypochlorite cathode. Both sodium formate fuel and sodium hypochlorite oxidant are available and stable as highly concentrated solutions, thereby facilitating fuel cell systems with high overall energy density. Sodium hypochlorite is commonly available as hypochlorite bleach. The alkaline anodic half-cell produces carbonate rather than the less-desirable gaseous CO2, while sustaining the rapid kinetics associated with formic acid oxidation in acidic media. Both half-cells provide high current densities at relatively low overpotentials and are free of gaseous products that may otherwise limit microfluidic fuel cell performance. The microfluidic fuel cell takes advantage of a recently developed membraneless architecture with flow-through porous electrodes. Power densities up to 52mWcm−2 and overall energy conversion efficiencies up to 30% per single pass are demonstrated at room temperature using 1.2M formate fuel and 0.67M hypochlorite oxidant. The alkaline formate/hypochlorite fuel and oxidant combination demonstrated here, or either one of its individual half-cells, may also be useful in conventional membrane-based fuel cell designs.
The garnet-type lithium ion conductor, nominal Li7La3Zr2O12 (LLZO) has received a lot of interest as they are considered usable as solid electrolytes in lithium battery. The Li+ migration bottleneck size of garnet-type Li7La3Zr2O12 (LLZO) solid electrolyte are posed significant effect on Li+ transportation property. However, the regulation mechanism of the bottleneck size on the Li+ migration activation energy is not clear. In the study, equivalent substitution of tetravalent M4+ (M4+ = Ge4+, Ti4+, Sn4+, Hf4+ and Te4+) ions on Zr site of Li7La3M0.25Zr1.75O12 is designed to regulate the bottleneck size. X-ray absorption fine structure (XAFS) is applied to detect the quantitative structural information of M-doped LLZO. Experimental and calculations results show that the M4+ substitution regulate the Li+ migration bottleneck size via changing M–O bond length. The M–O bond length increases with the increase of M4+ doping ion radius which results in the increase of the bottleneck size. However, larger bottleneck size is not necessarily favorable for Li+ migration. Ge4+ and Ti4+ doped LLZO have smaller bottleneck size than the un-doped LLZO, which is more suitable for Li+ migration (corresponds to lower Ea of 0.28 eV, 0.29 eV, respectively). This study is of great significance for obtaining optimum lithium ion migration channel size for LLZO, and the regulation mechanism is universality for crystal ion conductors.
A study is conducted on the electrical and electrochemical properties of nanocomposite polymer electrolytes based on intercalation of poly(vinylidene fluoride) (PVdF) polymer into the galleries of organically modified montmorillonite (MMT) clay. A solution intercalation technique is employed for nanocomposite formation with varying clay loading from 0 to 4wt.%. X-ray diffraction results show the β phase formation of PVdF on intercalation. Transmission electron microscopy reveals the formation of partially exfoliated nanocomposites. The nanocomposites are soaked with 1M LiClO4 in a 1:1 (v/v) solution of propylene carbonate (PC) and diethyl carbonate (DEC) to obtain the required gel electrolytes. The structural conformation of the nanocomposite electrolytes is examined by Fourier transform infrared spectroscopy analysis. Examination with a.c. impedance spectroscopy reveals that the ionic conductivity of the nanocomposite gel polymer electrolytes increases with increase in clay loading and attains a maximum value of 2.3×10−3 Scm−1 for a 4wt.% clay loading at room temperature. The same composition exhibits enhancement in the electrochemical and interfacial properties as compared with that of a clay-free electrolyte system.
A series of composite proton-exchange membranes have been prepared via sol-gel modification of commercial Nafion membranes with [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane. The structure and physico-chemical properties (water uptake, ion-exchange capacity, vanadyl ion permeability, and proton conductivity) of the prepared composite membranes have been studied as a function of the precursor loading (degree of the membrane modification). If the amount of the precursor is below 0.4/1 M ratio of the amino groups of the precursor to the sulfonic groups of Nafion, the composite membranes exhibit decreased vanadium ion permeability while having relatively high proton conductivity. With respect to the use of a non-modified Nafion membrane, the performance of the composite membrane with an optimum precursor loading in a single-cell vanadium redox flow battery demonstrates enhanced energy efficiency in 20–80 mA cm−2 current density range. The maximum efficiency increase of 8% is observed at low current densities.
Textual representation of graphene in Sweden’s most circulated newspapers is analyzed in 229 articles from 2004 to 2018. What is and is not said about graphene is explored through systematically identifying the lexical and grammatical patterns of sentences using the word “graphene.” Graphene is said to be a super material with certain properties, to be an object of research, commercialization, and application, and to have societal significance. Given frequent classifications of graphene as a nanomaterial in scientific discourse, there is notably limited reference to graphene as “nano” in the newspapers and only marginal reference to risk. This paper discusses the findings regarding this Swedish newspaper discourse on graphene in relation to its intertextuality, i.e., how texts draw upon and recontextualize other texts: the Swedish newspaper discourse on graphene echoes discourses of promise formulated elsewhere in society; it is not very diversified in terms of themes; it is dominated by positive and neutral representations rather than by risk; and it makes limited reference to the nano-discourse, even though, according to most definitions, graphene is a nanomaterial.