jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Ken Sahara | Yoshihisa Tsukamoto | Akihisa Ishimaru | Takao Fukuma | Jin Kusaka
Source: SAE technical papers on CD-ROM/SAE technical paper series (article, 2019-12-19)
Field: Materials Science — Materials Chemistry

Analysis of NH&lt;sub&gt;3&lt;/sub&gt; Diffusion Phenomena in a Selective Catalytic Reduction Coated Diesel Particulate Filter Catalyst Using a Simple One-Dimensional Core Model &lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;This paper describes a method for estimating constants related to NH&lt;sub&gt;3&lt;/sub&gt; gas diffusion phenomena to the active sites in a selective catalytic reduction diesel particulate filter (SCR/DPF) catalyst. A simple one-dimensional NH&lt;sub&gt;3&lt;/sub&gt; gas diffusion model based on the pore structure inside the catalyst was developed and used to estimate the intracrystalline diffusion coefficient. It was shown that the estimated value agreed well with experimental data.&lt;/div&gt;&lt;/div&gt; Catalysis ; Particulates ; Selective catalytic reduction ; Diesel particulate filter ; Reduction (mathematics) ; Diffusion ; Simple (philosophy) ; Materials science ; Diesel fuel ; Filter (signal processing) ; Diesel exhaust ; Chemical engineering ; Chemistry ; Thermodynamics ; Physics ; Engineering ; Organic chemistry ; Electrical engineering ; Mathematics Catalytic Processes in Materials Science ; Industrial Gas Emission Control ; Ammonia Synthesis and Nitrogen Reduction
Authors: Zakir Hossine | Md. Kamrujjaman
Source: Journal of Advances in Mathematics and Computer Science (article, 2019-12-14)
Field: Chemistry — Organic Chemistry

On the Interplay of Geometrical Shapes and the Analysis of a Dispersal Model for Pattern Formations A reaction-diffusion model is put forward which is capable of generating chemical maps whose concentration contours are similar to the patterns seen on the flanks of zebras, leopards and other mammals. Initially, this type of reaction diffusion kinetics model was introduced by Turing and later Murray applied it to animal coat patterns. Among many chemical reaction mechanism, we consider Schnackenberg reaction mechanism in details and show that the geometry and scale of the domain, the relevant part of the integument, during the time of laying down plays a crucial role in the structural patterns which result. Patterns which exhibit a limited randomness are obtained for a selection of geometries. Finally the system was solved numerically using finite difference method. Randomness ; Mechanism (biology) ; Turing ; Pattern formation ; Statistical physics ; Reaction–diffusion system ; Diffusion ; Domain (mathematical analysis) ; Biological dispersal ; Integument ; Scale (ratio) ; Computer science ; Mathematics ; Algorithm ; Physics ; Mathematical analysis ; Geology ; Statistics ; Thermodynamics ; Biology ; Geography ; Paleontology ; Cartography Axial and Atropisomeric Chirality Synthesis
Authors: James P. Grinias
Source: Carolina Digital Repository (University of North Carolina at Chapel Hill) (article, 2019-08-13)
Field: Chemistry — Spectroscopy

Characterization and Control of Band Broadening in Ultra-High Pressure Liquid Chromatography Columns Improving column performance remains paramount to advancing liquid chromatography (LC) technology. To that end, a series of experiments was designed to both measure and reduce band broadening in LC columns. The main broadening mechanisms (multiple flow path dispersion, longitudinal molecular diffusion, and resistance to mass transfer) were investigated. Dispersion due to multiple flow paths within a packed bed were studied with a series of columns prepared using different packing conditions. Packed column microstructure was analyzed by confocal laser scanning microscopy (CLSM) to determine bed morphology. Column efficiency was correlated to the bed morphology and the radial particle size distribution. Research on longitudinal molecular diffusion focused on the validity of different stationary phase diffusion models. Evidence was found supporting the recently proposed surface-restricted model of surface diffusion. This result has implications affecting both gradient separations and the calculation of the van Deemter B-term. An attempt to reduce the resistance to mass transfer term in the stagnant mobile phase focused on the implementation of a novel sub-2 μm macroporous silica stationary phase support. Unfortunately, the raw packing material contained a significant number of small mesoporous fines that limited the theoretical benefits of these particles, so a hydrodynamic chromatography (HDC) method was developed to remove the fines and reduce the particle size distribution (PSD). In addition to the classical on-column broadening mechanisms described above, broadening effects due to LC operation were studied, including frictional heating and extracolumn band broadening. When mobile phase flows over particles, frictional heating occurs. This heating can decrease column efficiency in sub-2 μm particle-packed columns larger than 1.0 mm in diameter. Studies of frictional heating effects on columns with different dimensions, particle types, and thermal environments were conducted to determine the impact these effects on performance. The LC instrument can diminish efficiency due to extra-column volumes that increase the measured peak variance. The variance contributions of the injector and connecting tubing on a capillary UHPLC system were measured. A possible coupling effect between the components was found that increases the tau-type (exponential decay) broadening contributions from the injector more than theory predicts. Characterization (materials science) ; Chromatography ; Materials science ; Chemistry ; Analytical Chemistry (journal) ; Nanotechnology Analytical Chemistry and Chromatography
Authors: Maram Abdulhakim Qasem Al-Sayaghi
Source: UND Scholarly Commons (University of North Dakota) (article, 2019-01-01)
Field: Chemistry — Inorganic Chemistry

The Effect Of Different Dianhydride Precursors On The Synthesis, Characterization And Gas Separation Properties Of PI And PBO Derived From BisAPAF The current processes used for natural gas separation and purification are considered energy intensive which could potentially be substituted by membrane technology. Aromatic polyimides are considered one of the most viable types of polymers used for the fabrication of membranes for gas separation mainly due to their outstanding properties. Moreover, aromatic polyimides could be thermally rearranged to form another class of polymers called polybenzoxazoles which are characterized by having enhanced gas separation properties. This research aimed to (1) synthesize and characterize three different aromatic polyimides via polycondensation reaction of a diamine (BisAPAF) with three different dianhydride precursors (PMDA, ODPA, BTDA), (2) fabricate free-standing polyimide membranes, and thermally rearrange them to polybenzoxazoles and (3) compare the gas separation properties (permeabilities and selectivities) of the membranes before and after the thermal rearrangement and compare the results to Robeson upper bounds. The tested gas pairs tested were CO2/CH4, N2/CH4 and CO2/N2. All the objectives of this research were successfully achieved, and it was found that chemical structure of the starting monomers plays a key role in the physicochemical properties of the synthesized polyimides which, consequently affected the gas separation properties. Among the three polyimides, APAF-BTDA showed the superior performance followed by APAF-PMDA and finally APAF-ODPA. This is believed to be due to the stability of the BTDA pendant group which resulted in high conversion and, hence, the best separation performance where they surpassed the Robeson upper bound for all gas pairs. Characterization (materials science) ; Separation (statistics) ; Gas separation ; Chemistry ; Pi ; Materials science ; Nanotechnology ; Mathematics Metal-Organic Frameworks: Synthesis and Applications ; Boron and Carbon Nanomaterials Research ; Membrane Separation and Gas Transport
Authors: Andrew Colburn
Source: UKnowledge (University of Kentucky) (article, 2019-05-02)
Field: Materials Science — General Materials Science

SYNTHESIS, FUNCTIONALIZATION, AND APPLICATION OF NANOFILTRATION AND COMPOSITE MEMBRANES FOR SELECTIVE SEPARATIONS Future nanofiltration (NF) membranes used for selective separations of ions and small organic molecules must maintain performance in environments where high concentrations of total dissolved solvents or foulants are present. These challenges can be addressed through the development of composite membranes, as well as the engineering of enhanced surface properties and operating conditions for existing commercial membranes. In this work, ion transport through commercial thin film composite (TFC) polyamide NF membranes were studied in both lab-prepared salt solutions and industrial wastewater. The dependence of several variables on ion rejection was investigated, including ion radius, ion charge, ionic strength, and temperature. The impact of scaling and increasing ionic concentration on membrane performance during recovery of industrial wastewater was investigated. Fouling of the membrane surface was reduced by enhancing commercial NF membrane surfaces via aqueous-phase esterification of lignin sulfonate. NF membranes were also created utilizing an ionic liquid solvent (1-ethyl-3-methylimidazolium acetate) to integrate composite materials into cellulose. Composite materials such as graphene oxide quantum dots, iron III particles, and lignin have been shown to be interact strongly with cellulose in solution with ionic liquid and bind together cellulose chains via hydrogen bonds following nonsolvent induced phase inversion. Studies suggest the composite materials modify membrane surface chemistry and improve selectivity of small organic molecules (~300 nm) while allowing for the complete passage of ions. Nanofiltration ; Surface modification ; Membrane ; Composite number ; Chemistry ; Chromatography ; Materials science ; Chemical engineering ; Engineering ; Composite material ; Biochemistry Material Properties and Applications
Authors: Danutė Kaušpėdienė | Audronė Gefenienė | Romas Ragauskas | Rima Binkienė
Source: Chemija (article, 2019-04-04)
Field: Chemistry — Organic Chemistry

Regeneration of nonfunctional Macronet MN 200 loaded with metal complex dye using alcohols in batch and column experiments The conditions for reuse of the Macronet MN 200 by removing the metal complex dye Lanasyn Navy M-DNL (LnCr) from water solutions have been investigated. The Macronet MN 200 loaded with the LnCr dye has been regenerated using alcohols (methanol, ethanol and 2-propanol) in batch and column experiments. The FTIR spectrum of the Macronet MN 200 loaded with the LnCr dye confirmed physical interactions between the LnCr anion and Macronet MN 200 involving π–π and electrostatic bonds. In the batch experiments the desorption efficiency of LnCr dye depends on the solid/liquid ratio (S/L, g/mL), molecular mass of alcohol and duration of desorption. The LnCr dye has been desorbed most efficiently after 10 min at S/L = 0.033, while the desorption efficiency decreases with the increase of alcohol molecular weight: methanol &gt; ethanol &gt; 2-propanol. The rates of desorption were quantified using second-order (k2), pore diffusion (D/r2) and intraparticle diffusion (ki) models. The column test results showed that the regeneration efficiency of MN 200 loaded with the LnCr dye (Re) using methanol with repeated adsorption/desorption cycles decreased but seems to be stabilized to 70% after 3 cycles. A very high LnCr dye concentration in methanol (about 4 g/L) has been obtained within the first 2 alcohol bed volumes and the LnCr dye has been completely desorbed back to the solution with 10 alcohol bed volumes. Methanol ; Desorption ; Alcohol ; Chemistry ; Adsorption ; Diffusion ; Ethanol ; Analytical Chemistry (journal) ; Chromatography ; Nuclear chemistry ; Organic chemistry Nanomaterials for catalytic reactions ; Pigment Synthesis and Properties ; Catalysis and Hydrodesulfurization Studies
Authors: L. A. Yousef
Source: Arab Journal of Nuclear Sciences and Applications (article, 2019-07-01)
Field: Chemistry — Inorganic Chemistry

Kinetic &amp; Thermodynamic Studies on Uranium Ions Recovery Using Magnetite- Dowex 50WX8 composite Batch Experiments on synthesized "Magnetite-Dowex 50WX8" composite were conducted to characterize its capability towards uranium adsorption. The effect of pH, contact time, composite dose, initial uranium concentration and temperature on uranium adsorption rate was investigated to optimize operation conditions of the synthesized composite. Thermodynamic and kinetic parameters have been studied. The maximum sorption capacity from Langmuir reached up to 200 mg/g at room temperature, pH 4, 25 mg of composite and 30 min. contact time. Uranium adsorption kinetics is well fitted to pseudo second order kinetic model at 500 mg/L uranium concentration. The change in thermodynamic parameters (ΔG, ΔH and ΔS) indicates that the adsorption process is a spontaneous exothermic random process. Loaded hexavalent uranium ions were stripped from the loaded composite using 0.25M nitric acid. Optimum conditions were applied to purify dissolved uranium content from a leaching solution of a granite sample from El-Missikat area, Central Eastern Desert, Egypt. Magnetite ; Uranium ; Composite number ; Ion ; Kinetic energy ; Chemistry ; Materials science ; Radiochemistry ; Nuclear chemistry ; Metallurgy ; Physics ; Composite material ; Organic chemistry Radioactive element chemistry and processing ; Chemical Synthesis and Characterization ; Extraction and Separation Processes
Authors: Hamid Hamid
Source: Scholar Commons (University of South Carolina) (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Mechanisms of Radium Adsorption on Silica and Barite The use of experimental studies with computer modeling is vital in the development of cost-effective methods for treating radium containing wastewaters. The goal of this dissertation is to develop a multi-scale model to study radium removal mechanisms onto silica and barite, and the effect of water quality parameters on radium removal. The major tasks to be accomplished in this study are: to develop a multi-component isotherm model for radium removal on different ionized silica surfaces; to re-parameterize sulphate force fields to account for metal-sulfate interactions; and to simulate radium removal on barite under different water quality conditions. We conducted molecular dynamics (MD) simulations to investigate radium removal on different ionized silica surfaces. The results indicate that high solution pH results in high radium removal due to increased silica surface negative charge, while high ionic strength results in less radium removal due to complexation and competition mechanisms with ions in the solution. The barite isotherm illustrate that ionic strength results in reduced radium removal due to complexation and competition mechanisms with the anions and cations in the solution but some inconsistencies were observed. The predicted isotherms for silica were consistent with experimental isotherm data. In order to accurately predict the removal of radium by adsorption onto the surface of barite, re-parameterization of the literature sulphate force fields were performed to account for metal-sulfate interactions. Different parameters were calculated using MD and umbrella sampling simulations to evaluate metal-sulfate interactions for different Me2+-SO4 systems. In general, the calculated parameters matched the experimental data, demonstrating that the re-parametrized force fields can accurately simulate the properties of barite and celestite, and will therefore could be effective for predicting the removal of radium by adsorption onto barite. The adsorption of different cations onto three barite surfaces (100, 010, and 001) were also simulated in the presence of different salts. The results show that radium removal decreases significantly with increasing ionic strength due to ions competitions and complexation mechanisms. In the case of CaCl2 and MgCl2 solutions, the isotherm predictions based on the multi-component Langmuir isotherm followed the expected trend while the trend for BaCl2, SrCl2, and NaCl solutions were not consistent with experimental isotherms. The findings in this study can elucidate radium removal mechanisms under different conditions to assist in the development of effective treatment technologies. Radium ; Adsorption ; Mineralogy ; Geology ; Environmental science ; Chemistry ; Geochemistry ; Radiochemistry Graphite, nuclear technology, radiation studies ; Nuclear and radioactivity studies
Authors: Natalia Kruszewska | Piotr Bełdowski | Piotr Weber | Steven Yuvan | Marcin Drechny | Marcin Kośmieja
Source: Energies (article, 2019-09-06)
Field: Chemistry — Spectroscopy

Formation of Protein Networks between Mucins: Molecular Dynamics Study Based on the Interaction Energy of the System Molecular dynamics simulations have been performed for a model aqueous solution of mucin. As mucin is a central part of lubricin, a key component of synovial fluid, we investigate its ability to form cross-linked networks. Such network formation could be of major importance for the viscoelastic properties of the soft-matter system and crucial for understanding the lubrication mechanism in articular cartilage. Thus, the inter- and intra-molecular interaction energies between the residues of mucin are analyzed. The results indicate that the mucin concentration significantly impacts its cross-linking behavior. Between 160 g/L and 214 g/L, there seems to be a critical concentration above which crowding begins to alter intermolecular interactions and their energies. This transition is further supported by the mean squared displacement of the molecules. At a high concentration, the system starts to behave subdiffusively due to network development. We also calculate a sample mean squared displacement and p-variation tests to demonstrate how the statistical nature of the dynamics is likewise altered for different concentrations. Mucin ; Molecular dynamics ; Intermolecular force ; Mean squared displacement ; Viscoelasticity ; Chemical physics ; Chemistry ; Displacement (psychology) ; Molecule ; Aqueous solution ; Intermolecular interaction ; Materials science ; Biophysics ; Computational chemistry ; Thermodynamics ; Physics ; Biochemistry ; Physical chemistry ; Biology ; Organic chemistry Analytical Chemistry and Chromatography ; Lipid Membrane Structure and Behavior ; Blood properties and coagulation
Authors: Gülay Baysal
Source: Environment Protection Engineering (article, 2019-01-01)
Field: Chemistry — Organic Chemistry

Application of surfactant-modified montmorillonite in nitrophenol removal by adsorption Quaternary ammonium salts (QASs) such as 1-methyl-di-nonyl-1 phenyl ammonium iodide (QAS1) and 1-methyl-di-dodecyl-1 phenyl ammonium iodide (QAS2) were newly synthesized by complete alkylation reaction for modification of sodium montmorillonite (Mt). The sodium montmorillonite was modified via an ion-exchange reaction with QAS1 and QAS2, and two organoclays, Mt1 and Mt2, have been obtained. The synthesized quaternary ammonium salts were analyzed by nuclear magnetic resonance spectroscopy (NMR). The organoclays (Mt1 and Mt2) were characterized by a range of methods including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption capacities of the synthesized organo-montmorillonites for the hydrophobic organic pollutant 4-nitrophenol (4-NP) have been evaluated. The distances between the organoclay layers showed a much better opening than that reported in the literature. The results show that the adsorption capacity increased in the order Mt2 > Mt1. The adsorption capacities of Mt1 and Mt2 for 4-NP were 77% and 81%, respectively. Montmorillonite ; Adsorption ; Pulmonary surfactant ; Chemistry ; Nitrophenol ; Chemical engineering ; Organic chemistry ; Catalysis ; Engineering ; Biochemistry Nanomaterials for catalytic reactions ; Adsorption and biosorption for pollutant removal ; Graphene research and applications
Authors: T. A. L. Lima | U. Wahl | Ângelo Costa | V. Augustyns | K. W. Edmonds | B. L. Gallagher | R. P. Campion | João P. Araújo | J. G. Correia | M. R. da Silva | K. Temst | A. Vantomme | L. M. C. Pereira
Source: Physical review. B./Physical review. B (article, 2019-10-07)
Field: Materials Science — Materials Chemistry

Thermal stability of interstitial and substitutional Mn in ferromagnetic (Ga,Mn)As In (Ga,Mn)As, a model dilute magnetic semiconductor, the electric and magnetic properties are strongly influenced by the lattice sites occupied by the Mn atoms. In particular, the highest Curie temperatures are achieved upon thermal annealing in a narrow temperature window around $200{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, by promoting the diffusion of interstitial Mn towards the surface. In this work, we determined the thermal stability of both interstitial and substitutional Mn in ferromagnetic (Ga,Mn)As thin films, using the emission channeling technique. At a higher Mn concentration, the temperatures at which substitutional and interstitial Mn become mobile not only decrease, but also become closer to each other. These findings advance our understanding of self-compensation in (Ga,Mn)As by showing that the strong dependence of the Curie temperature on annealing temperature around $200{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ is a consequence of balance between diffusion of interstitial Mn and segregation of substitutional Mn. Curie temperature ; Materials science ; Ferromagnetism ; Annealing (glass) ; Condensed matter physics ; Magnetic semiconductor ; Interstitial defect ; Lattice (music) ; Curie ; Thermal stability ; Chemistry ; Physics ; Metallurgy ; Doping ZnO doping and properties ; Magnetic properties of thin films ; Semiconductor materials and interfaces
Authors: Shanshan Qin | Dujian Zou | Jun Jiang | Tie-Jun Liu
Source: Purdue e-Pubs (Purdue University) (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Establishment of a Numerical Model for Sulfate Attacked Concrete Considering Multi-factors Sulfate attack is one of the major durability problems of concrete structures, which is manifested by expansive cracks and deterioration of cement paste. In this study, a numerical model is proposed to predict the process of ionic diffusion into concrete under external sulfate attack. The chemical reaction and diffusion processes are considered in this model. Furthermore, the influence of calcium leaching, chemical activity of multi-ions, temperature and changes in porosity are also taken into account. The initial porosity and tortuosity are assumed to be homogeneous in concrete, and the chemical potential gradient is regarded as the driving force for ions migrating in pore solution. The modified Davies equation is employed to quantize interaction effect among different ions in solution. A temperature dependent parameter is introduced in the diffusion process of sulfate ion. The dissolution of solid calcium is divided into two stages referring to solid-liquid equilibrium curve of calcium ion. One is the dissolution of the calcium hydroxide, and the other is the decalcification of the calcium silicate hydrate. The influence of calcium leaching on porosity is further considered in diffusion coefficient. Moreover, changes in porosity due to formation of expansive ettringite are also reflected in the diffusion coefficient. Finally, a new numerical model is established and a comparison of the model prediction with the experimental results has been conducted. It is demonstrated that the established diffusion-reaction model can provide a better deterioration assessment of concrete structures exposed to sulfate attack. Sulfate ; Computer science ; Environmental science ; Materials science Structural mechanics and materials ; Material Properties and Failure Mechanisms ; Concrete and Cement Materials Research