We use molecular dynamics simulations to study the structure, dynamics, and transport properties of nano-confined water between parallel graphite plates with separation distances (H) from 7 to 20 Å ...at different water densities with an emphasis on anisotropies generated by confinement. The behavior of the confined water phase is compared to non-confined bulk water under similar pressure and temperature conditions. Our simulations show anisotropic structure and dynamics of the confined water phase in directions parallel and perpendicular to the graphite plate. The magnitude of these anisotropies depends on the slit width H. Confined water shows "solid-like" structure and slow dynamics for the water layers near the plates. The mean square displacements (MSDs) and velocity autocorrelation functions (VACFs) for directions parallel and perpendicular to the graphite plates are calculated. By increasing the confinement distance from H = 7 Å to H = 20 Å, the MSD increases and the behavior of the VACF indicates that the confined water changes from solid-like to liquid-like dynamics. If the initial density of the water phase is set up using geometric criteria (i.e., distance between the graphite plates), large pressures (in the order of ~10 katm), and large pressure anisotropies are established within the water. By decreasing the density of the water between the confined plates to about 0.9 g cm(-3), bubble formation and restructuring of the water layers are observed.
Systematic molecular dynamics simulations are used to study the structure, dynamics and transport properties of the ionic liquids composed of the tetra-butylphosphonium (TBP(+), or P(C(4)H(9))(4)(+)) ...cation with six amino acid (AA(-)) anions. The structural features of these ionic liquids were characterized by calculating the partial site-site radial distribution functions, g(r), and computing the dihedral angle distribution of n-butyl side chains in the TBP(+) cations. The dynamics of the ionic liquids are described by studying the velocity autocorrelation function (VACF) and the mean-square displacement (MSD) for the centers of mass of the ions at different temperatures. The ionic diffusion coefficients and the electrical conductivities were evaluated from both the Einstein and Green-Kubo methods. The cross-correlation terms in the electric-current autocorrelation functions, which are an indication of the ion pair correlations, are investigated. The cationic transference numbers were also estimated to study the contributions of the anions and cations to the transport of charge in these ionic liquids. We determined the role of the amino acid anion structures on the dynamical behavior and the transport coefficients of this family of ionic liquids. In general, the MSD and self-diffusion coefficients of the relatively heavier non-planar TBP(+) cations are smaller than those of the lighter amino acid anions. Introducing polar functional groups (acid or amide) in the side chain of AA(-) decreases the diffusion coefficient and electrical conductivity of AAILs. The major factors for determining the magnitude of the transport coefficients are the chemical functionality and the length of the alkyl side chain of the AA(-) anion of these TBPAA ionic liquids.
The dynamical and structural properties of hydrogen (H2) guest gas inside nanoporous Li-LSX zeolite were studied by molecular dynamics (MD) simulation for different loadings (8, 12, 16, and 20) of H2 ...per unit cell at temperatures of 200, 298, 400, and 500 K. Three equal mean-square displacement (MSD) components (in the x, y, and z-directions) for the center of mass of H2 guest molecules show that the translational motion of H2 in this zeolite medium is isotropic due to the high symmetry of the zeolite framework. At these conditions, H2 guest molecules freely move without blocking each other's path into the supercages and channels of the Li-LSX zeolite. The order of calculated self-diffusion coefficient of H2 guest molecules at different temperatures, in the range of 10−9 up to 10−7 m2 s−1, and corresponding activation energy, ∼2 kcal mol−1, followed using the Arrhenius equation is in good agreement with the pores size of Li-LSX zeolite (7.4–12 Å) and compatible with inter-region of well-known Knudsen and Configurational diffusion. The H2 self-diffusion coefficients increase with temperature, while showing no quantifiable changes with loading within this loading range. A further study with a broader guest loading range would be appropriate to fully understand the loading effect on the self-diffusion of H2 guest molecules in the Li-LSX zeolite as the H2 storage candidate. In addition to determining the temperature and loading effects on the H2 guest behavior, current simulations also show that the Li-III cations are specific H2 sorption sites and the structural correlation, dynamics, self-diffusion coefficient, and adsorption of H2 molecules are strongly dependent on the mobility or immobility of the key extraframework Li-III cationic sites of Li-LSX zeolite. The results of the simulation help in the choice of favorable structure, best design, and operative manufacture of zeolites or other microporous materials for similar applications.
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•Current simulations show that the Li-III cations are specific H2 sorption sites.•The diffusion increases with T, while showing no quantifiable changes with loading.•Three equal x, y, and z-components of MSDs show an isotropic diffusion in the zeolite.•The magnitude of H2 diffusion lies between Knudsen and Configurational diffusion.•H2 molecules move without blocking each other's path into the Li-LSX zeolite.
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•Electrochemical analysis of effectiveness of an amino acid-derived ionic liquid inhibitor.•Quantum chemical analysis of effectiveness of an amino acid-derived ionic liquid ...inhibitor.•Finding correlation between electrochemical analysis and quantum chemical analysis.
In this study, an amino acid-derived ionic liquid inhibitor, namely tetra-n-butyl ammonium methioninate, was synthesized and the role this inhibitor for corrosion protection of mild steel exposed to 1.0M HCl was investigated using electrochemical, quantum and surface analysis. By taking advantage of potentiodynamic polarization, the inhibitory action of tetra-n-butyl ammonium methioninate was found to be mainly mixed-type with dominant anodic inhibition. The effectiveness of the inhibitor was also indicated using electrochemical impedance spectroscopy (EIS). Moreover, to provide further insight into the mechanism of inhibition, electrochemical noise (EN) and quantum chemical calculations of the inhibitor were performed.
Efficient synthesis of 2,4,5-triarylimidazole derivatives with simple workup is described using benzil, different aldehydes, and ammonium acetate in presence of fluorinated graphene oxide (A-MFGO) as ...effective catalyst that can be easily recovered and reused for several times without significant loss in activity. The simple preparation of the catalyst, short reaction time, mild conditions, high yield, and low cost make this procedure economically attractive and highly suitable for synthesis of 2,4,5-triarylimidazole derivatives.
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This article reports an efficient method with a simple workup for the facile synthesis of benzimidazole derivatives using an acidic ionic liquid covalently supported on graphene sheets. The catalyst ...was efficiently synthesized and characterized using FTIR, scanning electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. The catalytic organic reaction was performed in different conditions. Among the various catalysts, A-FGO is an excellent catalyst in the reaction. A wide variety of aldehydes were used under optimal reaction conditions to synthesis benzimidazole derivatives. The reaction conditions are mild and the workup method is simple as well as giving high yields. All synthesised products were characterised using melting point, FTIR,
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H NMR,
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C NMR and CHN techniques. At the end of the reaction, the catalyst was recovered by a simple filtration, washed with dichloromethane, dried and then reused in successive reactions. Products were obtained at the same purity as in the initial runs. Shorter reaction times, high yields, safer reaction condition, the eco-friendly nature and possible reuse of the catalyst make these methods an efficient contribution to the current processes within the field of benzimidazole derivatives synthesis.
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Abrasive slurry jet micro-machining (ASJM) can etch micro-features such as holes and channels in virtually any material. Holes, and to a lesser extent, channels machined in brittle materials using ...ASJM typically suffer from substantial edge rounding near the opening. This study investigated the erosive mechanism responsible for the rounding in borosilicate glass and sintered zirconium tin titanate targets, and determined the process parameters capable of minimizing the effect. Computational fluid dynamics (CFD) showed that the rounding that occurred during ASJM with a water-based slurry was due to the impact of particles accelerated by the formation and collapse of cavitation bubbles in regions where local pressures were below the vapor pressure of water. Further evidence of this was obtained by comparing the micro-topography in these regions with that produced by an ultrasonic cavitation apparatus in a water-particle slurry. Cavitation-enhanced erosion in ASJM was minimized using liquids such as mineral or soybean oil that have relatively low vapor pressures, resulting in blind and through-holes having sharp entrance and exit holes in glass and sintered zirconium tin titanate. The increased viscosity of the test fluids also altered the particle trajectories observed in the CFD models, causing the cross-sectional shape of the holes to have flatter bottoms and steeper sidewalls. In ductile targets such as copper, edge rounding due to cavitation-enhanced erosion was found to be much smaller than in brittle targets. In glass channels, the use of a soybean oil-based slurry eliminated the edge rounding and resulted in flatter bottoms, but increased the width by approximately 20%.
•Identified abrasive-enhanced cavitation as the mechanism for edge rounding in slurry jet micro-machining.•Used computational fluid dynamics to model vapor formation.•Used an ultrasonic apparatus to demonstrate abrasive-enhanced cavitation damage.•Eliminated edge rounding using fluids with low vapor pressures.
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Magnetic functional graphene oxide (MFGO) has been synthesized in this work using FeCl4− magnetic anion paired with 1-methyl imidazolium cation. Hybrid poly ortho aminophenol ...(POAP)/MFGO films have then been prepared via POAP electropolymerization in the presence of MFGO nanosheets, serving as active electrodes for electrochemical supercapacitors. The FeCl4- functional group in MFGO plays a major part in atomic scale charge/energy transfer and consequently intramolecular electrochemical phenomena in MFGO systems, as shown by the theoretical results. POAP/MFGO composite films have been characterized by surface and electrochemical analyses. The performance of the system has been investigated by various electrochemical methods such as galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy. Novel nanocomposite compounds have been developed in this work for electrochemical redox capacitors. The advantages of these compounds include simple synthesis method, high active surface area and stability in aqueous electrolytes.
The wide implementation of electronic health record (EHR) systems facilitates the collection of large-scale health data from real clinical settings. Despite the significant increase in adoption of ...EHR systems, these data remain largely unexplored, but present a rich data source for knowledge discovery from patient health histories in tasks, such as understanding disease correlations and predicting health outcomes. However, the heterogeneity, sparsity, noise, and bias in these data present many complex challenges. This complexity makes it difficult to translate potentially relevant information into machine learning algorithms. In this paper, we propose a computational framework, Patient2Vec , to learn an interpretable deep representation of longitudinal EHR data, which is personalized for each patient. To evaluate this approach, we apply it to the prediction of future hospitalizations using real EHR data and compare its predictive performance with baseline methods. Patient2Vec produces a vector space with meaningful structure, and it achieves an area under curve around 0.799, outperforming baseline methods. In the end, the learned feature importance can be visualized and interpreted at both the individual and population levels to bring clinical insights.
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This study demonstrates a method for improving supercapacitive performance of electrochemically synthesized conductive polymer. In this regards, 1-Butyl-3-methyl imidazolium ...hexafluorophosphate (BI) as a new high efficient ionic liquid was synthesized using chemical approach and then fabricated POAP/BI films by electro-polymerization of POAP in the presence of BI to serve as the active electrode for electrochemical supercapacitor. Theoretical study (AIM) and electrochemical analysis have been used for characterization of ionic liquid and POAP/BI composite film. Different electrochemical methods including galvanostatic charge–discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new most efficient materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte.
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