batterydata/paper-abstracts huggingface dataset:
To understand the development of mathematical cognition and to improve instructional practices, it is critical to identify early predictors of difficulty in learning complex mathematical topics such as algebra. Recent work has shown that performance with fractions on a number line estimation task predicts algebra performance, whereas performance with whole numbers on similar estimation tasks does not. We sought to distinguish more specific precursors to algebra by measuring multiple aspects of knowledge about rational numbers. Because fractions are the first numbers that are relational expressions to which students are exposed, we investigated how understanding the relational bipartite format (a/b) of fractions might connect to later algebra performance. We presented middle school students with a battery of tests designed to measure relational understanding of fractions, procedural knowledge of fractions, and placement of fractions, decimals, and whole numbers onto number lines as well as algebra performance. Multiple regression analyses revealed that the best predictors of algebra performance were measures of relational fraction knowledge and ability to place decimals (not fractions or whole numbers) onto number lines. These findings suggest that at least two specific components of knowledge about rational numbers—relational understanding (best captured by fractions) and grasp of unidimensional magnitude (best captured by decimals)—can be linked to early success with algebraic expressions.
This longitudinal study tested the same children at three time points: infancy (10.5months of age), toddlerhood (2.5years of age), and early childhood (4.5years of age). At 10.5months, infants were assessed experimentally with a gaze-following paradigm. At 2.5years, children’s language skills were measured using the MacArthur–Bates Communicative Development Inventories. At 4.5years, children’s explicit theory of mind was assessed with a standard test battery. Analyses revealed that infants with higher gaze-following scores at 10.5months produced significantly more mental-state words at 2.5years and that children with more mental-state words at 2.5years were more successful on the theory-of-mind battery at 4.5years. These predictive longitudinal relationships remained significant after controlling for general language, maternal education, and nonsocial attention. The results illuminate the bridging role that language plays in connecting infants’ social cognition to children’s later understanding of others’ mental states. The obtained specificity in the longitudinal relations informs theories concerning mechanisms of developmental change.
The mechanism of a low temperature wet chemical route for synthesis of LiFePO4 cathode material for Li-ion batteries is presented. Using inorganic salts as precursors and diethylene glycol (DEG) as reaction media, nanosize LiFePO4 powder is obtained. The controversially discussed role of the polyol on this reaction has been clarified by in-situ FT-IR analysis of the gaseous reaction products and a full analysis of solid products. It is observed that DEG does not act as reducing agent for iron(II) salts, nor is it oxidized during the synthesis of LiFePO4. Generally, polyols are used to reduce the oxides and hydroxides into their corresponding metals. The nucleation of Li +, PO 4 3 − and Fe2+-ions in the DEG solvent starts at temperatures 110°C, 130°C and 170°C, respectively. LiFePO4 precipitation from Li-carbonate, Fe(II)-oxalate dihydrate and ammonium dihydrogenphosphate as precursors is driven by thermal decomposition of the salts, intermediate formation and dehydration of amino-ethoxy-ethane, yielding 1,4-dioxane as volatile by-product. With the help of in-situ investigations reaction time and temperature could be minimized. Furthermore, the effect of the concentrations of Li +, Fe2+ and PO 4 3 − ionic moieties on the morphology of LiFePO4 materials obtained by chemical solution deposition and solid state reaction are studied with the help of FT-IR analysis. LiFePO4 platelets morphology exhibited better discharge capacity than LiFePO4 agglomerate morphology. The solid product is characterized by X-ray diffraction, scanning electron microscopy and differential thermogravimetry combined with mass spectrometry and FT-IR.
This investigation elucidates three maleimide (MI)-based aromatic molecules as additives in electrolyte that is used in lithium ion batteries. The 1.1M LiPF6 in ethylene carbonate (EC):propylene carbonate (PC):diethylene carbonate (DEC) (3:2:5 in volume) containing MI-based additives can prompt the formation of a solid electrolyte interface (SEI); and inhibit the entering into the irreversible state during lithium intercalation and co-intercalation. The reduction potential is 0.71–0.98V versus Li/Li+ as determined by cyclic voltammetry (CV). The morphology and element analysis of the positive and negative electrode after the 100th charge–discharge cycle are examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). Moreover, the MI was used in lithium ion batteries and provided 4.9% capacity increase and 16.7% capacity retention increase when cycled at 1C/1C. The MI-based additive also ensures respectable cycle-ability of lithium ion batteries. MI is decomposed electrochemically to form a long winding narrow SEI strip on the graphite surface. This novel SEI strip not only prevents exfoliation on the graphite electrode but also stabilizes the electrolyte. The MI-based additive also ensures respectable cycle-ability of lithium ion batteries.
The results of a wide demonstration test of Off-Grid Radio Base Stations powered with fuel cells and locally available renewable energy sources are presented. The experimental activity has been conducted as part of the FCPoweredRBS project to assess and verify the potential of hydrogen and fuel cells as power and energy sources for the telecom market. For this application, Fuel Cells have been integrated as a programmable power generator with a photovoltaic system and an energy storage system. Both electrochemical batteries and hydrogen produced locally with an electrolyzer have been tested as energy storage solutions. Data collected for a full year have been used to assess the potential of the systems proposed in comparison with diesel generators which are the standard solution for such applications. Results show that the hybrid renewable energy solution may be competitive in terms of energy efficiency and minimum consumption of fossil fuel consumption. Proper sizing and control strategy optimization are key aspects to this aim. Despite the use of FC technology and the integration of many different components, field tests have shown an acceptable level of stability and reliability.
There is a lot of interest in the development of new, safer and more sustainable polar aprotic solvents due to their importance in industrial applications and significant safety issues with the most commonly used examples. One such area of application is in pharmaceutically relevant C–C coupling reactions, where polar aprotic solvents are commonly used for solubility and to stabilise reaction intermediates. Although there are now a number of excellent alternatives in the literature, to date they have not been compared in a single study. This study demonstrates the effectiveness of the green solvents N-butylpyrrolidinone (NBP), γ-valerolactone (GVL), propylene carbonate (PC) and dihydrolevoglucosenone (Cyrene) in Heck and Baylis–Hillman reactions. Good conversions and initial rates were observed in GVL and NBP in Heck reactions. Cyrene exhibited high initial rates of reaction and high yields in the Baylis–Hillman reaction. This demonstrates Cyrene to be a promising alternative polar aprotic solvent for this reaction.
While pressurized irrigation systems can be effectively powered using renewable energy sources, no serious related study is found in Iran in this regard. In the present study, in two different climatic conditions in Iran, development of small-scale solar irrigation were evaluated financially and compared with that of systems powered by the fossil fuel and electricity grid. Financial analysis of systems was provided using life cycle cost (LCC) method. Results showed that in the case of 4.5 and 5.5 kW pumps (for citrus orchard and a vineyard, respectively), photovoltaic irrigation pumps with batteries for energy storage are comparable to the systems in which the electricity used to drive pumps is transmitted through 0.25 km and 1.8 km private lines. It was concluded that, generally, if the required power of irrigation pumps exceeds 3 kW, the electricity supplied by a private power transmission line is more affordable than in-situ generated photovoltaic electricity, if the length of transmission line is less than 2 km. It was also observed that for required power less than 4.5 kW, photovoltaic energy is somewhat comparable to fossil fuel. As Iran is dependent upon its highly subsidized fossil fuels, the financing of solar irrigation projects will not be possible without the help of new policies and laws.
LiNi0.33Co0.33Mn0.33O2 which was synthesized by co-precipitation method has been used to investigate the relationships between crystal/interfacial structures and electrochemical performance of the material in the voltage range of 2.5–4.6V. X-ray diffraction showed that the material maintained high structural stability with charge–discharge cycling. Formation of SEI film was observed by transmission electron microscopy. The chemical compositions of the SEI film were analyzed by X-ray photoelectron spectroscopy, which were mainly composed of some organic compounds such as lithium alkyl carbonate RCH2OCO2Li, as well as some inorganic compounds such as Li x PF y and Li x PO y F z . Transmission electron microscopy showed that the SEI film gradually grew to a thickness of about 40nm after 30 cycles. This caused larger and larger interfacial resistance with charge–discharge cycling, which has been attributed to the continuous capacity fading of LiNi0.33Co0.33Mn0.33O2 in the voltage window of 2.5–4.6V.
Use of highly concentrated methanol fuel is required for direct methanol fuel cells (DMFCs) to compete with the energy density of Li-ion batteries. Because one mole of H2O is needed to oxidize one mole of methanol (CH3OH) in the anode, low water crossover to the cathode or even water back flow from the cathode into the anode is a prerequisite for using highly concentrated methanol. It has previously been demonstrated that low or negative water crossover can be realized by the incorporation of a low-α membrane electrode assembly (MEA), which is essentially an MEA designed for optimal water management, using, e.g. hydrophobic anode and cathode microporous layers (aMPL and cMPL). In this paper we extend the low-α MEA concept to include an anode transport barrier (aTB) between the backing layer and hydrophobic aMPL. The main role of the aTB is to act as a barrier to CH3OH and H2O diffusion between a water-rich anode catalyst layer (aCL) and a methanol-rich fuel feed. The primary role of the hydrophobic aMPL in this MEA is to facilitate a low (or negative) water crossover to the cathode. Using a previously developed 1D, two-phase DMFC model, we show that this novel design yields a cell with low methanol crossover (i.e. high fuel efficiency, ∼80%, at a typical operating current density of ∼80–90% of the cell limiting current density), while directly feeding high concentration methanol fuel into the anode. The physics of how the aTB and aMPL work together to accomplish this is fully elucidated. We further show that a thicker, more hydrophilic, more permeable aTB, and thicker, more hydrophobic, and less permeable aMPL are most effective in accomplishing low CH3OH and H2O crossover.
Thermoelectric transport properties of p-type PbTe:Na, with high hole concentrations of approximately 1020 cm−3, are reinvestigated from room temperature to 750 K. The greatly enhanced Seebeck coefficient at these doping levels can be understood by the presence of a sharp increase in the density of states around the Fermi level. As a result, the thermoelectric figure of merit, zT, reaches ∼1.4 at 750 K. The influence of these heavy hole carriers may contribute to a similarly high zT observed in related p-type PbTe-based systems such as Tl-doped PbTe and nanostructured composite materials.
The hen's egg test for analysis of micronucleus formation (HET-MN) was developed several years ago to provide an alternative test system to the in vivo micronucleus test. In order to assess its applicability and robustness, a study was carried out at the University of Osnabrueck (lab A) and at the laboratories of Henkel AG & Co. KGaA (lab B). Following transfer of the method to lab B, a range of test substances that had been pre-tested at lab A, were tested at Henkel: the genotoxins cyclophosphamide, dimethylbenz(a)anthracene, methotrexate, acrylamide, azorubin, N-nitroso-dimethylamine and the non-genotoxins, orange G and isopropyl myristate. In a second phase, additional compounds with known in vivo properties were examined in both labs: the non-genotoxin, ampicillin, the “irrelevant” positives, isophorone and 2,4-dichlorophenol (“irrelevant” means positive in standard in vitro tests, but negative in vivo), the clastogen p-chloroaniline, and the aneugens carbendazim and vinorelbine. All substances were correctly predicted in both labs with respect to their in vivo genotoxic properties, indicating that the HET-MN may have an improved predictivity compared with current standard in vitro test systems. The results support the promising role of the HET-MN assay as a supplement to existing test batteries.
Teachers are not typically involved as participatory designers in the design of technology-enhanced learning environments. As they have unique and valuable perspectives on the role of technology in education, it is of utmost importance to engage them in a participatory design process. Adopting a case study methodology, we aim to reveal in what ways teachers work as participatory designers and define conditions that support teachers in that. Two initiatives of participatory design in Canada and Singapore were investigated. Design materials, transcripts of design meetings, and interviews with teachers were qualitatively analyzed. Case study 1 (Canada) showed that two teachers participating in software design for an astronomy curriculum contributed by suggesting new design features, introducing pedagogical requirements, and providing feedback on prototypes or design ideas. It appeared essential that teachers feel that their ideas were valued and respected in the entire process. In case study 2 (Singapore), six teachers contributed to the design of a mobile learning trail through: Theorizing and bridging knowledge building principles, collaborative prototyping, contextual inquiry of activity relevance and activity execution, and collaborative evaluation of technology integration. Teachers valued case study discussions with similar cultural contexts and visiting the learning site to design with contextual knowledge. From our case studies, it can be concluded that teachers contribute to the design processes by engaging in theoretical discussion, active participation in a design partnership, reflection about pedagogy and practice, and experimenting with enactment. Conditions that support teachers include support in emergent processes and an atmosphere of trust and inclusion.
Alzheimer’s disease (AD) and Lewy body diseases (LBD), e.g., Parkinson’s disease (PD) dementia and dementia with Lewy bodies (DLB), are common causes of geriatric cognitive impairments. In addition, AD and LBD are often found in the same patients at autopsy; therefore, biomarkers that can detect the presence of both pathologies in living subjects are needed. In this investigation, we report the assessment of α-synuclein (α-syn) in cerebrospinal fluid (CSF) and its association with CSF total tau (t-tau), phosphorylated tau181 (p-tau181), and amyloid beta1-42 (Aβ1-42) in subjects of the Alzheimer’s Disease Neuroimaging Initiative (ADNI; n = 389), with longitudinal clinical assessments. A strong correlation was noted between α-syn and t-tau in controls, as well as in patients with AD and mild cognitive impairment (MCI). However, the correlation is not specific to subjects in the ADNI cohort, as it was also seen in PD patients and controls enrolled in the Parkinson’s Progression Markers Initiative (PPMI; n = 102). A bimodal distribution of CSF α-syn levels was observed in the ADNI cohort, with high levels of α-syn in the subjects with abnormally increased t-tau values. Although a correlation was also noted between α-syn and p-tau181, there was a mismatch (α-syn–p-tau181-Mis), i.e., higher p-tau181 levels accompanied by lower α-syn levels in a subset of ADNI patients. We hypothesize that this α-syn–p-tau181-Mis is a CSF signature of concomitant LBD pathology in AD patients. Hence, we suggest that inclusion of measures of CSF α-syn and calculation of α-syn–p-tau181-Mis improves the diagnostic sensitivity/specificity of classic CSF AD biomarkers and better predicts longitudinal cognitive changes.
Solar energy is a renewable and abundant energy source that has myriad potential applications to be tapped. Energy storage devices often present diminishing performance at lower temperatures, and sometimes they even fail during cold weather; therefore, a renewable technology to spur such sluggish performance not only is important for a sustainable future but also may inspire new-concept devices such as ignition sensors. Here, under solar illumination, the capacitance, energy density and power density of supercapacitors are all largely enhanced owing to the photothermal effect. The supercapacitors employ three-dimensional hierarchical graphene as the electrodes, and show an absorption of >92.88% over the entire solar spectrum, a response time of <200 s, and a surface temperature change of ∼39 °C under 1 solar illumination (1 kW m−2). Under 1 solar illumination, the capacitance of the pseudocapacitor increases by ∼1.5 times, and the capacitance of the electric double-layer capacitor increases by ∼3.7 times. The mechanism is quantitatively analyzed and discussed. This work provides new insights into the applications of solar energy and offers new design options for the development of energy storage devices.
I first show that Kuhn came to have doubts about physics soon after entering college but did not make up his mind to leave the discipline until 1947–1948 when a close association with Harvard’s President James B. Conant convinced him of the desirability of an alternative career in the history of science. I go on to maintain that it was realistic for Kuhn to prepare for such a career in essentially autodidactic ways both because he enjoyed Conant’s patronage and because he could expect that his credentials in physics would be an asset in this relatively young interdisciplinary specialty. I then suggest that it was through his work as a teacher, researcher, and journeyman gatekeeper in the history of science that Kuhn gradually came to identify with the field. Finally, I argue that his training in physics, his teaching of general-education courses, and his hopes of influencing current philosophy of science helped shape his early practice as a historian of science. By way of epilogue, I briefly consider Kuhn’s path from his tenuring at Berkeley in 1958 to the appearance of The Structure of Scientific Revolutions in 1962.
Hybrid of metal oxide and graphene quantum dots may pave one way to improve their electronic, chemical and electrochemical properties. The paper reports one new strategy for synthesis of Co3O4-histidine-functionalized graphene quantum dots (Co3O4-His-GQD). Here, His-GQDs are combined with Co2+ ions to rapidly produce Co-His-GQD complex. Followed by the thermal annealing at 350°C in air to form Co3O4-His-GQD. The resulting nanohybrid offers a well-defined three-dimensional architecture with the rich of porous structures. The regulation of His-GQDs on the release rate of Co2+ ions during the oxidation process of Co2+ make the formed Co3O4 crystals have a small particle size of about 22nm. The in situ synthesis of Co3O4 on the surface of graphene sheets achieves to the intimate chemical and electrical contacts of Co3O4 with His-GQDs. This creates a fast energy and electron transfer between Co3O4 and His-GQDs in the nanohybrid. The sensor based on the Co3O4-His-GQD exhibits an ultrahigh electrochemical response towards hydroquinone. Its differential pulse voltammetric peak current linearly increases with increasing hydroquinone in the range of 2×10−9–8.0×10−4 M with the detection limit 8.2×10−10 M (S/N=3). The sensitivity is better than that of both His-GQDs sensor and Co3O4 sensor. The analytical method provides the advantage of sensitivity, selectivity and stability, it has been successfully applied in the determination of hydroquinone in environmental water samples. The study also provides a promising approach for fabrication of functional graphene quantum dot-based electrode materials with high-performance for sensing, electrocatalysis, supercapacitors and lithium ion batteries.
Magnesium (Mg++) therapy has been shown to be neuroprotective and to facilitate recovery of motor and sensorimotor function in a variety of animal models of traumatic brain injury. However, few studies have investigated the efficacy of Mg++ therapy on cognitive impairments following injury. The present study evaluated the ability of magnesium chloride (MgCl2) to facilitate recovery of function following bilateral anterior medial cortex lesions (bAMC). Rats received electrolytic bAMC lesions or sham surgery and were then treated with 1mmol/kg, i.p. MgCl2, 2mmol/kg, i.p. MgCl2, or 1.0ml/kg, i.p. 0.9% saline. Drug treatment was administered 15min following injury with subsequent injections administered at 24 and 72h. Rats were tested on a battery of behavioral tests that measured both cognitive (reference and working memory in the Morris Water Maze (MWM) and spatial delayed matching-to-sample (DMTS)) and sensorimotor performance (bilateral tactile adhesive removal). The results indicated that bAMC lesions produced significant cognitive impairments in reference memory and working memory in the MWM, DMTS and sensorimotor impairments compared to shams. Mg++ therapy exhibited a dose-dependent effect in facilitating recovery of function. Administration of 2mmol of MgCl2 significantly improved performance on the bilateral adhesive tactile removal test, DMTS and working memory tests. The 1mmol dose of MgCl2 reduced the initial deficit on the tactile adhesive removal test and reduced the working memory impairment on the second day of testing. These results suggest Mg++ therapy improves cognitive performance following injury in a dose-dependent manner.
The hybridization of hydrogen and solar energy technologies is an interesting option to satisfy power demands in locations that are isolated from the electric grid. The main advantage of the photovoltaic (PV)-H2 hybrid system is the possibility of power storage by means of an electrolyzer (EL) which transforms the electricity into hydrogen (H2). The work described here concerns a methodology to design PV-H2 hybrid systems that considers the weather data and the electrical variables of the components to perform energy balances and to assess the system in terms of the load requirements, the levels of energy stored and the resulting costs. Two electrolytic systems (water splitting and ethanol electrochemical reforming) were studied in an attempt to find a best trade-off between the size and voltages of ELs. Ethanol reduced the energy requirements of EL at the expense of reagent consumption and lower current density. The energy supplied by these systems costs 0.28 €/kWh (i.e., roughly the same as power prices paid by domestic customers in Spain), but they have the merit of being autonomous and hydrogen has the capacity for seasonal energy storage ‒ thus avoiding electrification constraints in off-grid locations and limitations of short-term electrical energy storages.