batterydata/paper-abstracts huggingface dataset:
The electrochemical properties of substituted LiNi0.5Mn1.5−x M x O4 spinels at high potential (>4V vs Li+/Li) have been investigated for M=Ti and Ru, in order to determine the role of the tetravalent cation in such systems where nickel is a priori the only electroactive species. These systems are found to form extended solid solutions (up to x =1.3 and x =1.0 for Ti and Ru, respectively) that were characterized by X-ray diffraction and Raman spectroscopy. Titanium substitution induces a drastic decrease in high potential electrochemical capacity, whereas the capacity is maintained and the kinetics are even improved in the presence of ruthenium. These results are completed by new results on the Li4−2x Ni3x Ti5−x O12 spinel system, which shows not any high potential activity in spite of the presence of up to 0.5 Ni2+ per spinel formula unit on the octahedral site. Taking into account previous data on LiNi0.5Ge1.5O4, we clearly show that even if the tetravalent cation does not participate in the overall redox reaction, electrochemical activity is only possible when nickel is surrounded by tetravalent cations able to accept a local variation of valence (Mn, Ru), whereas full-shell cations such as Ti4+ and Ge4+ block the necessary electron transfer pathways in the spinel oxide electrode.
Manganese (Mn) oxide was prepared by anodizing metallic Mn film that was electrodeposited in n-butylmethylpyrrolidinium bis(trifluoromethylsulfony)imide (BMP–NTf2) ionic liquid. Different anodization courses, namely potentiostatic and cyclic voltammetric methods, led to variations in physical and chemical characteristics of the Mn oxides, and therefore in their pseudocapacitive performance. Evolution of the microstructure, residual weight, and chemical state of the Mn oxides with the charge–discharge cycling number was studied using a scanning electron microscope (SEM), an atomic absorption spectroscope, and an X-ray photoelectron spectroscope, respectively. The analytical results indicate that the electrochemical stability of Mn oxide is mainly determined by its microstructure; the more fibrous (or porous) oxide had a greater durability against cyclic charge–discharge. Moreover, the chemically hydrous state was found to be the most crucial factor that governed the mass specific capacitance of Mn oxide.
Carbon-coated TiO2 one-dimensional nanostructures are synthesized by hydrothermal reaction followed by post-calcination at various temperatures. Post-calcination induces crystallization of TiO2 and the complete crystallization of anatase phase is observed at 600°C of the calcination temperature. Carbon-coated TiO2 nanostructures show relatively poor crystallinity as compared with the pristine counterparts, but their lithiation capacity and high rate capability are improved throughout all calcination temperatures. The coated carbon suppresses severe agglomeration of TiO2 nanotubes which allows easy access of Li-ions and electrons to the whole surface of primary nanotubes, leading to the better lithiation performance. Higher calcination temperatures cause excessive growth of nanotube walls, leading to the collapse of tubular morphology and deterioration of lithiation performance. At 700°C of the calcination temperature, the enhanced electronic conductivity from the graphitization of the coated carbon seems to be the main reason for the improved capacity of TiO2 nanowires.
The detection of biologically important metal ions such as Cu(II) and Pb(II) ions using an electrochemical approach at sensitive level is gaining great attention to reveal the health conditions of patients with serious diseases such as rickets, bone deterioration, and heart disease that are associated with these metal ions as well as environmental hazards. Thus, rapid and efficient detection methods for these metal ions are in great demand. In this study, we developed an ideal protocol using silver metal–organic framework (Ag@MOF) nanoparticles for the detection of Cu(II) and Pb(II) metal ions. Ag@MOF was synthesized by a reflux method, and the working electrode was prepared by coating Ag@MOF onto ITO glass. Compared with the bare ITO electrode, the Ag@MOF/ITO working electrode exhibited a more sensitive electrochemical performance for the detection of Cu(II) and Pb(II) metal ions through the complexation between the inner core hydroxyl groups of Ag@MOF and the metal ions. The crystallographic and structural analyses of Ag@MOF were carried out by X-ray diffraction analysis and Fourier transform infrared spectroscopy, while morphological analysis was performed by high-resolution transmission electron microscopy and field-emission scanning electron microscopy. X-ray photoelectron spectroscopy was performed to investigate the surface electronic states of silver in Ag@MOF. The cyclic voltammetry results showed that Cu(II) and Pb(II) metal ions can be detected using the Ag@MOF working electrode, which exhibited a more sensitive performance compared with the bare ITO working electrode. Our study shows that the developed electrochemical sensor is ideal for the detection of various metal ions.
Urokinase-type plasminogen activator (uPA), a serine protease, converts plasminogen to plasmin. Activation of plasmin leads to degradation of the extracellular matrix, which is critical for tissue recovery, angiogenesis, cell migration, and axonal and synaptic plasticity. We hypothesized that uPA deficiency would cause an abnormal neurophenotype and would lead to exacerbated epileptogenesis after brain injury. Wild-type (Wt) and uPA−/− mice underwent a battery of neurologic behavioral tests evaluating general reactivity, spontaneous exploratory activity, motor coordination, pain threshold, fear and anxiety, and memory. We placed particular emphasis on the effect of uPA deficiency on seizure susceptibility, including the response to convulsants (pentylenetetrazol, kainate, or pilocarpine) and kainate-induced epileptogenesis and epilepsy. The uPA−/− mice showed no motor or sensory impairment compared with the Wt mice. Hippocampus-dependent spatial memory also remained intact. The uPA−/− mice, however, exhibited reduced exploratory activity and an enhanced response to a tone stimulus (p<0.05 compared with the Wt mice). The urokinase-type plasminogen activator deficient mice showed no increase in spontaneous or evoked epileptiform electrographic activity. Rather, the response to pilocarpine administration was reduced compared with the Wt mice (p<0.05). Also, the epileptogenesis and the epilepsy phenotype after intrahippocampal kainate injection were similar to those in the Wt mice. Taken together, uPA deficiency led to diminished interest in the environmental surroundings and enhanced emotional reactivity to unexpected aversive stimuli. Urokinase-type plasminogen activator deficiency was not associated with enhanced seizure susceptibility or worsened poststatus epilepticus epilepsy phenotype.
Sensor drifts and modelling mismatches are key factors that influence the accuracy of state of charge (SOC) estimation for LiFePO4 batteries. In this study, an observer robust to these factors is proposed. First, the causes of SOC errors, for example, modelling error and uncertain initial error, are studied. Second, a geometry classifier is designed to categorize these errors into different groups using the information of voltage error between model and measurements. Third, with the classifier, different types of errors are treated differently by switching the gains of the observer. Finally, the method is tested in comparison to the existing methods for both new and aged cells. The test results show that the proposed method can correctly categorize the error causes and take the corresponding countermeasures. The common problems encountered in SOC estimations, such as local model inaccuracy, current sensor drifting and data saturation, could be overcome. The computation time of the proposed method is close to that of the Luenberger observer, making it suitable for real embedded applications.
Findings of both material- and hemisphere-specific influence on memory performance in children with epilepsy are inconsistent. Verbal memory of 80 children with focal epilepsy, aged 7 to 16, was assessed and compared with verbal memory of 80 healthy schoolchildren. The Verbal Selective Reminding test was used to distinguish between patients with left-sided (N =38) and patients with right-sided (N =42) electroencephalographic focal abnormalities. In addition, groups with temporal (N =36) and extratemporal (N =44) focal epilepsy were compared. Effects of seizure-related variables were also assessed. Children with focal epilepsy scored significantly lower on tests when compared with the healthy group. Lateralization of the EEG focus was not found to significantly affect verbal memory performance. Only the CLTR component of the Verbal Selective Reminding test was susceptible to lateralization and localization effects. Differences between the group with left and the group with right temporal epilepsy (P <0.03) and between the group with temporal and the group with extratemporal epilepsy (P <0.01) reached statistical significance.
An effective approach of alcoholysis is employed to prepare hollow CoS2@C hybrid nanosheets aggregates as anode materials for Li-ion batteries. Amorphous carbon can be loaded on the CoS2 nanoparticles uniformly in the solvothermal alcoholysis process, and the subsequent calcination results of the formation of hollow structures. The capacity of the sample can remain stable as high as 720 mAhg−1 after 200 cycles, and it also exhibits good rate capacity. The nano-scaled characteristics of CoS2 nanosheets embedded in the aggregates ensure the electrode having a high capacity and the fast Li-ion diffusion in the electrode. The in-situ introduction of carbon renders the electrode having a good electronic conductivity and can effectively prevent the formation of polysulfide anions. The unique hollow structures can shorten the length of Li-ion diffusion, which is benefit for the rate performance. The hollow structure also offers a sufficient void space, which sufficiently alleviates the mechanical stress caused by volume change. Therefore, the prepared hierarchical hollow CoS2@C materials constructed by nanosheets exhibit outstanding electrochemical performance.
In a world that is becoming more multilingual, bilingual aphasia is a clinical problem with a major clinical impact. However, at present we lack causal explanations of the many features of recovery patterns and there is no consensus about the language in which the patient should receive speech therapy. Further advance requires an understanding of the dynamics of recovery. In a novel longitudinal, single-case study, we combine fMRI and dynamic causal modeling to examine the effects of specific language treatment for picture naming on the representation and control of language areas during the course of recovery. Improved performance in the treated language was associated with increased activation in language areas. Consistent with theoretical expectations, causal modeling indicated increased connectedness of the control and language networks for the treated language. This functional approach holds great promise for investigating recovery patterns and the effects of specific language treatment in bilingual aphasic patients.
Lithium manganate spinel is extensively studied as a positive electrode in lithium ion rechargeable batteries. Growth of nano-size cathode particles is proposed to improve the rate capabilities of these cathode materials. It remains controversial if the particle size in the nano-range (as compared to the conventional micrometer size particles of these materials) has any appreciable influence on the discharge capacity, rate capabilities, and cycleability of these materials. In the 4V range, especially at slightly elevated temperature, lithium manganate exhibits capacity fading though the underlying mechanism for such fading is not yet clear. In the present work, we have successfully prepared nano-crystalline lithium manganate spinel powder by an acetate base solution route. Though the discharge capacity of these nano-crystalline cathodes was equivalent to their microcrystalline counterpart, these exhibited capacity fading in the 4V range. Through a combined X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses, we correlated the observed capacity fading with the onset of Jahn–Teller (J–T) distortion toward the end of the discharge in the cut-off limit between 4.2 and 3.4V. It was postulated that if J–T distortion is the dominant fading mechanism of these nano-crystalline cathodes then by increasing the average oxidation state of the Mn ions in a virgin lithium manganate cathode, the onset of such distortion towards the end of the discharge could be delayed, and therefore, the cycleability of these cathodes could be improved. By synthesizing lithium and aluminum ion co-doped lithium manganate particles, we could increase the average oxidation state of the Mn ions in the virgin electrodes. Indeed, the cycleability of these co-doped cathodes was dramatically improved which supports our postulation. The doping contents of lithium and aluminum, however, should be further optimized to further increase the discharge capacity of these modified cathodes.
Using synchrotron-based in situ X-ray diffraction, the structural changes of LiCoO2, LiCo0.5Ni0.5O2, and LiNi0.65Co0.25Mg0.05Ti0.05O2 cathode materials during charge in the voltage range of 3.5 to 5.2V have been studied. When a LiCoO2 cathode was charged above 4.5V, a new intermediate phase O1a was observed, before the terminal phase O1 was formed around 4.8V. In the X-ray diffraction spectra for LiCo0.5Ni0.5O2 and LiNi0.65Co0.25Mg0.05Ti0.05O2 cathode materials, Bragg peaks representing the O1 structure were also observed. The amounts of O1 structure formed at the end of charge (5.2V for LiNi0.65Co0.25Mg0.05Ti0.05O2 and 5.0V for LiCo0.5Ni0.5O2) were increased with increasing Co content.
The discovery of deep-sea hydrothermal vents on the late 1970's has led to many hypotheses concerning chemical evolution in the prebiotic ocean and the early evolution of energy metabolism in ancient Earth. Such studies stand on the quest for the bioenergetic evolution to utilize reducing chemicals such as H2 for CO2 reduction and carbon assimilation. In addition to the direct reaction of H2 and CO2, the electrical current passing across a bisulfide-bearing chimney structure has pointed to the possible electrocatalytic CO2 reduction at the cold ocean-vent interface (R. Nakamura, et al. Angew. Chem. Int. Ed. 2010, 49, 7692−7694). To confirm the validity of this hypothesis, here, we examined the energetics of electrocatalytic CO2 reduction by iron sulfide (FeS) deposits at slightly acidic pH. Although FeS deposits inefficiently reduced CO2, the efficiency of the reaction was substantially improved by the substitution of Fe with Ni to form FeNi2S4 (violarite), of which surface was further modified with amine compounds. The potential-dependent activity of CO2 reduction demonstrated that CO2 reduction by H2 in hydrothermal fluids was involved in a strong endergonic electron transfer reaction, suggesting that a naturally occurring proton-motive force (PMF) as high as 200mV would be established across the hydrothermal vent chimney wall. However, in the chimney structures, H2 generation competes with CO2 reduction for electrical current, resulting in rapid consumption of the PMF. Therefore, to maintain the PMF and the electrosynthesis of organic compounds in hydrothermal vent mineral deposits, we propose a homeostatic pH regulation mechanism of FeS deposits, in which elemental hydrogen stored in the hydrothermal mineral deposits is used to balance the consumption of the electrochemical gradient by H2 generation.
Nano-porous silicon composite incorporated with graphite and pyrolyzed carbon was synthesized and investigated as a promising anode material for lithium-ion batteries. The nano-porous Si/graphite composite was prepared via two-step ball-milling followed by etching process. Then carbon was incorporated by using different approaches. The nano-porous Si/graphite/C composite exhibits a reversible capacity of about 700mAh/g with no capacity loss up to the 120th cycle at a constant current density of 0.2mA/cm2. The superior electrochemical characteristics are attributed to the nanosized pores in Si particles, which suppress the volume effect, and buffering action as well as excellent electronic and ionic conductivity of carbon materials.
The properties of the Li/LiCoO2 cell containing several RTILs with three different anions were investigated. Introducing the asymmetric nature to anionic species using amide improved the viscosity and conductivity of the RTIL, however, the rate properties of the cell was not enhanced very much. Declined cathodic stability seems to be responsible for the result. In the case of the stable system consisting of quaternary ammonium cation and imide anion, both of cycling properties and Coulombic efficiency during the cycling were satisfactory and the viscosity dominated the rate properties of the cell. The performance of the Li/LiCoO2 cell in this study was almost consistent with the stability of Li-electrolyte interface evaluated by ac impedance measurement.
Ternary host–guest nanocomposite based on vanadium oxide and two polymers with different types of conductivity (ionic and electronic) – polypyrrole (PPy) and polyethylene oxide (PEO) – is prepared by solventless mechanochemical synthesis. The nanocomposite can be reversibly cycled with a specific capacity of ∼200mAhg−1 for at least one hundred cycles of full charge–discharge as the active component of the positive electrode of lithium batteries. Electrochemical performance of ternary PPy0.1PEO0.15V2O5 is compared with two-component analog PPy0.1V2O5. The presence of macromolecules of an ion-conducting polymer in the composition of the ternary nanocomposite PPy0.1PEO0.15V2O5 promotes interfacial transfer of lithium ions and also facilitates faster transport inside the particles of the nanocomposite.
Jel codes: J24, D24
The international community has long recognized the important role of the small and medium enterprise sector (SMEs) in the economies of the developing world. Policymakers around the world worry about how to foster productivity and growth among this group of firms. In a modern economy, the investment in human capital is crucial to foster technological adoption and, thus ultimately, achieve higher productivity growth. This paper explores a large firm level survey across 99 countries to document the differences in the job training provided by employers across firms of different sizes. Our findings show that a strong and positive correlation across the investment in job training and firm size is a robust empirical finding within and across countries with different institutions and income levels. Furthermore, proxies for some market imperfections and institutional failures impeding SME development do not explain most of the differences in the training intensity across small and large firms. It is thus a very robust finding that large firms conduct more on the job training. Unfortunately, with our data, we cannot fully disentangle correlation from causality. It is possible that size is not driving training and that on-the-job training is productive and itself drives firm productivity and growth. We highlight that more and better data sets are needed to rigorously tackle this identification problem and thus shed more light on this important policy question in developing countries.
Li-ion battery cells are temperature sensitive devices. Their performance and cycle life are compromised under extreme ambient environment. Efficient regulation of cell temperature is, therefore, a pre-requisite for safe and reliable battery operation. In addition, modularity-in-design of battery packs is required to offset high manufacturing costs of electric vehicles (EVs). However, modularity of battery packs is restricted by flexibility of traditionally used battery thermal management systems. For example, scalability of liquid cooled battery packs is limited by plumbing or piping and the auxiliary equipment used in the system. An alternative thermal management system is, therefore, required for modular EV battery packs. In this paper, state-of-the-art developed to control battery temperature near a pre-specified state is qualitatively reviewed with the intent to identify potential candidate for implementation in a modular architecture. Some of the novel techniques that provide high-scalability in addition to appreciable cost and energy-savings over traditional methods are also evaluated while considering the development state and associated technical risks. It is found that only a hybrid system can meet technical requirements imposed by modular design. Based on the current state, phase change materials and thermoelectric devices are more likely to be part of this next generation thermal management system.
Around 20% of the electrical power generated on the planet is consumed inefficiently in lighting application. With the running out of the fossil fuels; lighting utilization will seriously contribute to the worldwide energy problem in the approaching future. Hence measures are to be taken right from this instant in order to conquer the power shortage problem by efficiently utilizing the available power. White organic light-emitting diodes (WOLEDs) and displays represent the next generation energy-saving light source to alleviate the energy crisis. Within the last decade OLEDs have become an internationally highly recognized unique area light source, which has immense potential for the recent display applications and paves a novel path to create white light. This paper reflects the recent advances in the OLED materials and the critical tactics employed in designing the anatomy of OLED devices for energy-saving solid-state lighting (SSL) towards lighting revolution. Novel transparency electrodes for flexible OLEDs, the stability of OLEDs, topical progress regarding various materials used for different layers to fabricate eco friendly and energy efficient OLEDs by innovative fabrication techniques and the necessity of encapsulation are also discussed. In addition, the ongoing challenges and future perspectives of this research frontier with certain measures that can be employed to reduce the driving voltage, minimize the degradation issues and augmentation of their life time are illustrated. Once we accomplish the said challenges, OLEDs can be considered as next generation flat panel displays and solid state lighting sources, which would proffer a world of expanding opportunities in the field of lighting.