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Bentley, Cameron L., Alan M. Bond i Jie Zhang. "Voltammetric Perspectives on the Acidity Scale and H+/H2 Process in Ionic Liquid Media". Annual Review of Analytical Chemistry 11, nr 1 (12.06.2018): 397–419. http://dx.doi.org/10.1146/annurev-anchem-061417-010022.
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Nonhaloaluminate ionic liquids (ILs) have received considerable attention as alternatives to molecular solvents in diverse applications spanning the fields of physical, chemical, and biological science. One important and often overlooked aspect of the implementation of these designer solvents is how the properties of the IL formulation affect (electro)chemical reactivity. This aspect is emphasized herein, where recent (voltammetric) studies on the energetics of proton (H+) transfer and electrode reaction mechanisms of the H+/H2 process in IL media are highlighted and discussed. The energetics of proton transfer, quantified using the p Ka (minus logarithm of acidity equilibrium constant, Ka) formalism, is strongly governed by the constituent IL anion, and to a lesser extent, the IL cation. The H+/H2 process, a model inner-sphere reaction, also displays electrochemical characteristics that are strongly IL-dependent. Overall, these studies highlight the need to carry out systematic investigations to resolve IL structure and function relationships in order to realize the potential of these diverse and versatile solvents.
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Pichtel, John. "Distribution and Fate of Military Explosives and Propellants in Soil: A Review". Applied and Environmental Soil Science 2012 (2012): 1–33. http://dx.doi.org/10.1155/2012/617236.
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Energetic materials comprise both explosives and propellants. When released to the biosphere, energetics are xenobiotic contaminants which pose toxic hazards to ecosystems, humans, and other biota. Soils worldwide are contaminated by energetic materials from manufacturing operations; military conflict; military training activities at firing and impact ranges; and open burning/open detonation (OB/OD) of obsolete munitions. Energetic materials undergo varying degrees of chemical and biochemical transformation depending on the compounds involved and environmental factors. This paper addresses the occurrence of energetic materials in soils including a discussion of their fates after contact with soil. Emphasis is placed on the explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and the propellant ingredients nitroglycerin (NG), nitroguanidine (NQ), nitrocellulose (NC), 2,4-dinitrotoluene (2,4-DNT), and perchlorate.
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Ivašková, Martina, Martin Lovíšek, Peter Jančovič i Lenka Bukovinová. "Influence of Temperature on the Electrochemical Characteristics of Ti-6Al-4V". Materials Science Forum 811 (grudzień 2014): 77–82. http://dx.doi.org/10.4028/www.scientific.net/msf.811.77.
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Titanium is not only the most widely used biomaterial for medical implants, but with its very good mechanical properties, corrosion resistance and low density is also applicated in many sectors of industry (aerospace, military, aviation, machinery, energetics, chemicals, etc.). In this paper it is described the influence of temperature on the electrochemical characteristics of Ti-6Al-4V alloy. The surface was mechanically grinded and polished by chemical-mechanical process. Basic electrochemical characteristics were determined by potentiodynamic tests in 0.1M NaCl solution at different temperatures. The obtained results were analysed by the Tafel-extrapolation method. Finally, a modified Arrhenius relation was used for determination of activation energy. The activation energy of grinded and chemical-mechanical polished surface is nearly three times higher than activation energy of only grinded surface.
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Leide, B., i P. Stouffs. "Residual Reactivity of Burned Gases in the Early Expansion Process of Future Gas Turbines". Journal of Engineering for Gas Turbines and Power 118, nr 1 (1.01.1996): 54–60. http://dx.doi.org/10.1115/1.2816549.
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The present study investigates the chemical evolution of the burned gases in a first-stage nozzle operated under high inlet temperature and pressure conditions as they are foreseen for next-generation high-efficiency gas turbine machinery. Coupled aerothermochemical simulations are performed up to the extreme case of stoichiometric combustion without ulterior dilution. The intent is to provide an estimation of possible consequences arising from the residual reactivity of gases downstream from the combustor. These consequences might affect the future design of the expansion path in order to render nonstationary chemistry compatible with aerodynamics, energetics, and environmental aspects.
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Böyükata, M., E. Borges, J. C. Belchior i J. P. Braga. "Structures and energetics of CO2–Arn clusters (n = 1–21) based on a non-rigid potential model". Canadian Journal of Chemistry 85, nr 1 (1.01.2007): 47–55. http://dx.doi.org/10.1139/v06-178.
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Energetics and possible stable structures of CO2–Arn (n = 1–21) clusters are investigated by performing molecular-dynamics simulations. The pairwise-additive approximation is tested to construct the potential energy function for describing the non-rigid particle interactions in the system. A potential model by Pariseau et al. (Journal of Chemical Physics, Vol. 42, p. 2335, 1965) is used for the internal motion of the CO2 molecule and the Billing form potential (Chemical Physics, Vol. 185, p. 199, 1994) is used for all other pair interactions. The stable configurations are determined for the ground state of CO2–Arn clusters, and the growing pattern process of the clusters is determined via rearrangement collisions. Ar atoms tend to surround the CO2 molecule, and the clusters prefer to form three-dimensional compact structures. Obtained structures and energetics are in quantitative agreement with previous results (Journal of Chemical Physics, Vol. 109, p. 1343, 1998) that have used split-repulsion and ab initio potentials in which the molecule was treated as rigid.Key words: argon, CO2, cluster, potential energy function, molecular dynamics.
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Ashrafuzzaman, Md, Zahid Khan, Ashwaq Alqarni, Mohammad Alanazi i Mohammad Shahabul Alam. "Cell Surface Binding and Lipid Interactions behind Chemotherapy-Drug-Induced Ion Pore Formation in Membranes". Membranes 11, nr 7 (30.06.2021): 501. http://dx.doi.org/10.3390/membranes11070501.
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Chemotherapy drugs (CDs) disrupt the lipid membrane’s insulation properties by inducing stable ion pores across bilayer membranes. The underlying molecular mechanisms behind pore formation have been revealed in this study using several methods that confirm molecular interactions and detect associated energetics of drugs on the cell surface in general and in lipid bilayers in particular. Liposome adsorption and cell surface binding of CD colchicine has been demonstrated experimentally. Buffer dissolved CDs were considerably adsorbed in the incubated phospholipid liposomes, measured using the patented ‘direct detection method’. The drug adsorption process is regulated by the membrane environment, demonstrated in cholesterol-containing liposomes. We then detailed the phenomenology and energetics of the low nanoscale dimension cell surface (membrane) drug distribution, using atomic force microscopy (AFM) imaging what addresses the surface morphology and measures adhesion force (reducible to adhesive energy). Liposome adsorption and cell surface binding data helped model the cell surface drug distribution. The underlying molecular interactions behind surface binding energetics of drugs have been addressed in silico numerical computations (NCs) utilizing the screened Coulomb interactions among charges in a drug–drug/lipid cluster. Molecular dynamics (MD) simulations of the CD-lipid complexes detected primarily important CD-lipid electrostatic and van der Waals (vdW) interaction energies. From the energetics point of view, both liposome and cell surface membrane adsorption of drugs are therefore obvious findings. Colchicine treated cell surface AFM images provide a few important phenomenological conclusions, such as drugs bind generally with the cell surface, bind independently as well as in clusters of various sizes in random cell surface locations. The related adhesion energy decreases with increasing drug cluster size before saturating for larger clusters. MD simulation detected electrostatic and vdW and NC-derived charge-based interactions explain molecularly of the cause of cell surface binding of drugs. The membrane binding/association of drugs may help create drug–lipid complexes with specific energetics and statistically lead to the creation of ion channels. We reveal here crucial molecular understanding and features of the pore formation inside lipid membranes that may be applied universally for most of the pore-forming existing agents and novel candidate drugs.
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Frey, Nathan C., Eric Van Dornshuld i Charles Edwin Webster. "Benchmarking the Fluxional Processes of Organometallic Piano-Stool Complexes". Molecules 26, nr 8 (16.04.2021): 2310. http://dx.doi.org/10.3390/molecules26082310.
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The correlation consistent Composite Approach for transition metals (ccCA-TM) and density functional theory (DFT) computations have been applied to investigate the fluxional mechanisms of cyclooctatetraene tricarbonyl chromium ((COT)Cr(CO)3) and 1,3,5,7-tetramethylcyclooctatetraene tricarbonyl chromium, molybdenum, and tungsten ((TMCOT)M(CO)3 (M = Cr, Mo, and W)) complexes. The geometries of (COT)Cr(CO)3 were fully characterized with the PBEPBE, PBE0, B3LYP, and B97-1 functionals with various basis set/ECP combinations, while all investigated (TMCOT)M(CO)3 complexes were fully characterized with the PBEPBE, PBE0, and B3LYP methods. The energetics of the fluxional dynamics of (COT)Cr(CO)3 were examined using the correlation consistent Composite Approach for transition metals (ccCA-TM) to provide reliable energy benchmarks for corresponding DFT results. The PBE0/BS1 results are in semiquantitative agreement with the ccCA-TM results. Various transition states were identified for the fluxional processes of (COT)Cr(CO)3. The PBEPBE/BS1 energetics indicate that the 1,2-shift is the lowest energy fluxional process, while the B3LYP/BS1 energetics (where BS1 = H, C, O: 6-31G(d′); M: mod-LANL2DZ(f)-ECP) indicate the 1,3-shift having a lower electronic energy of activation than the 1,2-shift by 2.9 kcal mol−1. Notably, PBE0/BS1 describes the (CO)3 rotation to be the lowest energy process, followed by the 1,3-shift. Six transition states have been identified in the fluxional processes of each of the (TMCOT)M(CO)3 complexes (except for (TMCOT)W(CO)3), two of which are 1,2-shift transition states. The lowest-energy fluxional process of each (TMCOT)M(CO)3 complex (computed with the PBE0 functional) has a ΔG‡ of 12.6, 12.8, and 13.2 kcal mol−1 for Cr, Mo, and W complexes, respectively. Good agreement was observed between the experimental and computed 1H-NMR and 13C-NMR chemical shifts for (TMCOT)Cr(CO)3 and (TMCOT)Mo(CO)3 at three different temperature regimes, with coalescence of chemically equivalent groups at higher temperatures.
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Hijazi, Hadi, i Vladimir Dubrovskii. "Dynamics of Monolayer Growth in Vapor–Liquid–Solid GaAs Nanowires Based on Surface Energy Minimization". Nanomaterials 11, nr 7 (26.06.2021): 1681. http://dx.doi.org/10.3390/nano11071681.
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The vapor–liquid–solid growth of III-V nanowires proceeds via the mononuclear regime, where only one island nucleates in each nanowire monolayer. The expansion of the monolayer is governed by the surface energetics depending on the monolayer size. Here, we study theoretically the role of surface energy in determining the monolayer morphology at a given coverage. The optimal monolayer configuration is obtained by minimizing the surface energy at different coverages for a set of energetic constants relevant for GaAs nanowires. In contrast to what has been assumed so far in the growth modeling of III-V nanowires, we find that the monolayer expansion may not be a continuous process. Rather, some portions of the already formed monolayer may dissolve on one of its sides, with simultaneous growth proceeding on the other side. These results are important for fundamental understanding of vapor–liquid–solid growth at the atomic level and have potential impacts on the statistics within the nanowire ensembles, crystal phase, and doping properties of III-V nanowires.
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Sarkar, Saptarshi, Binod Kumar Oram i Biman Bandyopadhyay. "Ammonolysis as an important loss process of acetaldehyde in the troposphere: energetics and kinetics of water and formic acid catalyzed reactions". Physical Chemistry Chemical Physics 21, nr 29 (2019): 16170–79. http://dx.doi.org/10.1039/c9cp01720h.
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Stamenkovic, Vojislav, Berislav Blizanac, Branimir Grgur i Nenad Markovic. "Electrocatalysis of fuel cells reaction on Pt and Pt-bimetallic anode catalysts: A selective review". Chemical Industry 56, nr 6 (2002): 273–86. http://dx.doi.org/10.2298/hemind0206273s.
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In this review we selectively summarize recent progress, primarily from our laboratory, in the development of interrelationships between the kinetics of the fuel cells reactions and the structure/composition of anode catalysts. The focus is placed on two types of metallic surfaces: platinum single crystals and bimetallic surfaces based on Pt. In the first part it was illustrated that the hydcogen reaction is structure sensitive process, with Pt(110) being an order of magnitude more active than either of the atomically "flatter" (100) and (111) surfaces. The hydrogen reaction on Pt(hkl) modified by pseudomorphic Pd (sub)monolayers shows the "volcano-like" behavior, having the maximum rate on Pt(111) modified by 1 ML of Pd. The Pt(111)-Pd system is used to demonstrate how the energetics of intermediates formed in the hydrogen reaction is affected by interfacial bonding and energetic constraints produced between pseudomorphic Pd films and the Pt(111) substrate. In the second part it was shown that the oxidation of Ha in the presence of CO occurs concurrently with CO oxidation on Pt and Pt bimetallic surfaces. The Pt-Ru system is used to demonstrate that both the bifunctional effect and the ligand effect contribute to the influence of Ru on the CO oxidation rate and for Hz oxidation process in the presence of CO. The knowledge is then used to create the real-life catalyst with the catalytic activities which are, to the greatest extend possible similar to the tailor-made surface.
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Oh, Young-Ho, Sandip S. Shinde i Sungyul Lee. "Nucleophilic Radiofluorination Using Tri-tert-Butanol Ammonium as a Bifunctional Organocatalyst: Mechanism and Energetics". Molecules 27, nr 3 (3.02.2022): 1044. http://dx.doi.org/10.3390/molecules27031044.
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We present a quantum chemical analysis of the 18F-fluorination of 1,3-ditosylpropane, promoted by a quaternary ammonium salt (tri-(tert-butanol)-methylammonium iodide (TBMA-I) with moderate to good radiochemical yields (RCYs), experimentally observed by Shinde et al. We obtained the mechanism of the SN2 process, focusing on the role of the –OH functional groups facilitating the reactions. We found that the counter-cation TBMA+ acts as a bifunctional promoter: the –OH groups function as a bidentate ‘anchor’ bridging the nucleophile [18F]F− and the –OTs leaving group or the third –OH. These electrostatic interactions cooperate for the formation of the transition states of a very compact configuration for facile SN2 18F-fluorination.
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Siekierka, Anna, i Marek Bryjak. "Modified Poly(vinylidene fluoride) by Diethylenetriamine as a Supported Anion Exchange Membrane for Lithium Salt Concentration by Hybrid Capacitive Deionization". Membranes 12, nr 2 (18.01.2022): 103. http://dx.doi.org/10.3390/membranes12020103.
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This paper shows the investigation for the optimal anion exchange membranes (AEM) supporting the desorption step of the HCDI process. The chemical modification of PVDF by diethylene triamine created the AEM. To confirm the ion-exchange character of materials, the chemical analysis with FTIR, SEM, surface energetics, and transportation analysis were applied. Next, the investigated membranes were applied for the sorption and desorption of lithium chloride. The specific sorptive parameters were higher according to the incorporation of the nitrogen groups into polymeric chains. Considering the desorption efficiency, membranes modified by four days were selected for further evaluation. The application in the HCDI process allowed reaching the desorption efficiency at 90%. The system composed of PVDF-DETA4 membrane was suitable for sorption 30 mg/g of salt. By applying the PVDF-DETA4 membrane, it is possible to concentrate LiCl with four factors. The anion exchange character of the developed membrane was confirmed by adsorption kinetics and isotherms of chlorides, nitrates, sodium, and lithium. The prepared membrane could be considered a perspective material suitable for concentration salt with electro-driven technologies for the above reasons.
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Islam, Md Rashedul, Bosong Lin, Yue Yu, Chau-Chyun Chen i Mahdi Malmali. "Comparative Energetics of Various Membrane Distillation Configurations and Guidelines for Design and Operation". Membranes 13, nr 3 (24.02.2023): 273. http://dx.doi.org/10.3390/membranes13030273.
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This paper presents a comparative performance study of single-stage desalination processes with major configurations of membrane distillation (MD) modules. MD modules covered in this study are (a) direct contact MD (DCMD), (b) vacuum MD (VMD), (c) sweeping gas MD (SGMD), and (d) air gap MD (AGMD). MD-based desalination processes are simulated with rigorous theoretical MD models supported by molecular thermodynamic property models for the accurate calculation of performance metrics. The performance metrics considered in MD systems are permeate flux and energy efficiency, i.e., gained output ratio (GOR). A general criterion is established to determine the critical length of these four MDs (at fixed width) for the feasible operation of desalination in a wide range of feed salinities. The length of DCMD and VMD is restricted by the feed salinity and permeate flux, respectively, while relatively large AGMD and SGMD are allowed. The sensitivity of GOR flux with respect to permeate conditions is investigated for different MD configurations. AGMD outperforms other configurations in terms of energy efficiency, while VMD reveals the highest permeate production. With larger MD modules, utilization of thermal energy supplied by the hot feed for evaporation is in the order of VMD > AGMD > SGMD > DCMD. Simulation results highlight that energy efficiency of the overall desalination process relies on the efficient recovery of spent for evaporation, suggesting potential improvement in energy efficiency for VMD-based desalination.
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DEWEY, T. GREGORY. "CHEMICALLY-CONTROLLED REACTION KINETICS ON FRACTALS: APPLICATION TO HYDROGEN EXCHANGE IN LYSOZYME". Fractals 03, nr 02 (czerwiec 1995): 251–67. http://dx.doi.org/10.1142/s0218348x95000217.
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The effect of time-dependent diffusional rate constants on chemically-controlled reactions in solution is considered. A general mechanism is examined that consists of a two step process. First the reactants diffuse together to form an “encounter complex.” This is followed by the collapse of the complex to the final product. The first step is diffusion controlled and the second step is chemically controlled. For reactions in restricted geometries or on fractals the rate constants associated with the diffusive process will scale with time as t−h where h is a constant between 0 and 1. The chemical processes are assumed to have time-independent rate constants. For reactions in which the encounter complex achieves a steady state, the differential equations governing the time course of the reaction can be solved exactly. At short times, the concentration of the reactants decays exponentially, reflecting the time constant of the chemical processes. At longer times, the decreasing diffusive rate constants result in the process being diffusion controlled. A stretched exponential of the form, exp{−kt1−h}, is observed. Approximate solutions for the pre-steady state behavior of the system are also determined using a Liouville transformation and corresponding asymptotic expansions. The short time regime shows power law decays of reactants. These decays will depend both on the dimensionality of the system as well as on the value of the rate constants associated with individual steps in the mechanism. Conditions can exist where a transformation to logarithmic oscillations will occur. Using this theoretical foundation a model is developed to analyze the kinetics of hydrogen isotope exchange kinetics in proteins. The exchange reaction is assume to occur in the boundary volume of the protein. Using the predicted fractal dimension of this boundary volume, scaling exponents are calculated and used as an unadjusted parameter. Highly accurate fits to the experimental data are achieved and activation energies are obtained that reflect the energetics of isotope exchange. This approach allows chemical kinetic behavior to be predicted from X-ray structure information.
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Abdank-Kozubski, Rafal, Andrzej Biborski, Mirosław Kozłowski, Christine Goyhenex, Veronique Pierron-Bohnes, Mebarek Alouani, Marcus Rennhofer i Savko Malinov. "Atomic-Migration-Controlled Processes in Intermetallics". Defect and Diffusion Forum 277 (kwiecień 2008): 113–18. http://dx.doi.org/10.4028/www.scientific.net/ddf.277.113.
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Chemical ordering kinetics in L10- and B2-ordered AB binary intermetallics was simulated by means of Monte Carlo (MC) technique implemented with vacancy mechanism of atomic migration. While vacancy concentration is usually much lower than the antisite defect concentration in L10-ordered systems, triple defects are generated in particular B2–ordered systems. The latter definitely affects the chemical ordering process and requires that full thermal vacancy thermodynamics is involved in B2-ordering simulations. The study on L10-ordered binaries was dedicated to FePt thin layers considered as a material for ultra-high-density magnetic storage media. Metastability of the L10 c-variant with monoatomic planes parallel to the layer surface and off-plane easy magnetization was revealed. Thermal vacancy formation in B2-ordered binaries was modelled by implementing a mean-field Hamiltonian with a specific formalism of phase equilibria in a latticegas composed of atoms and vacancies. It was demonstrated that for particular pair-interaction energetics, equilibrium concentrations of vacancies and antisites result mutually proportional in well-defined temperature ranges. The MC simulations of B2-ordering kinetics involved the modelled equilibrium vacancy concentration and reproduced the experimentally observed low rate of the process.
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Mazur, Ursula, i K. W. Hipps. "Single molecule level studies of reversible ligand binding to metal porphyrins at the solution/solid interface". Journal of Porphyrins and Phthalocyanines 24, nr 08 (sierpień 2020): 993–1002. http://dx.doi.org/10.1142/s1088424620300049.
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Ligands bind reversibly to metal porphyrins in processes such as molecular recognition, electron transport and catalysis. These chemically relevant processes are ubiquitous in biology and are important in technological applications. In this article, we focus on the current advances in ligand binding to metal porphyrin receptors noncovalently bound at the solution/solid interface. In particular, we restrict ourselves to studies at the single molecule level. Dynamics of the binding/dissociation process can be monitored by scanning tunneling microscopy (STM) and can yield both qualitative and quantitative information about ligand binding affinity and the energetics that define a particular ligation reaction. Molecular and time dependent imaging can establish whether the process under study is at equilibrium. Ligand-concentration-dependent studies have been used to determine adsorption isotherms and thermodynamic data for processes occurring at the solution/solid interface. In several binding reactions, the solid support acted as an electron-donating fifth coordination site, thereby significantly changing the metal porphyrin receptor’s affinity for exogenous ligands. Supporting calculations provide insight into the metalloporphyrin/support and ligand–metalloporphyrin/support interactions and their energetics.
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Al-Kalbani, Haitham, Jin Xuan, Susana García i Huizhi Wang. "Comparative energetic assessment of methanol production from CO2: Chemical versus electrochemical process". Applied Energy 165 (marzec 2016): 1–13. http://dx.doi.org/10.1016/j.apenergy.2015.12.027.
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Ananthaneni, Sahithi, Zachery Smith i Rees B. Rankin. "Graphene Supported Tungsten Carbide as Catalyst for Electrochemical Reduction of CO2". Catalysts 9, nr 7 (15.07.2019): 604. http://dx.doi.org/10.3390/catal9070604.
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Electrochemical reduction of CO2 to useful chemical and fuels in an energy efficient way is currently an expensive and inefficient process. Recently, low-cost transition metal-carbides (TMCs) have been proven to exhibit similar electronic structure similarities to Platinum-Group-Metal (PGM) catalysts and hence, can be good substitutes for some important reduction reactions. In this work, we test graphene-supported WC (Tungsten Carbide) nanoclusters as an electrocatalyst for the CO2 reduction reaction. Specifically, we perform density functional theory (DFT) studies to understand various possible reaction mechanisms and determine the lowest thermodynamic energy landscape of CO2 reduction to various products, such as CO, HCOOH, CH3OH, and CH4. This in-depth study of reaction energetics could lead to improvements and development of more efficient electrocatalysts for CO2 reduction.
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Porzuczek, Jan. "Applications of Electrical Capacitance Tomography for Research on Phenomena Occurring in the Fluidised Bed Reactors". Chemical and Process Engineering 35, nr 4 (1.12.2014): 397–408. http://dx.doi.org/10.2478/cpe-2014-0030.
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Abstract The paper presents a review of current achievements in the Electrical Capacitance Tomography (ECT) in relation to its possible applications in the study of phenomena occurring in fluidised bed reactors. Reactors of that kind are being increasingly used in chemical engineering, energetics (fluidised bed boilers) or industrial dryers. However, not all phenomena in the fluidised bed have been thoroughly understood. This results in the need to explore and develop new research methods. Various aspects of ECT operation and data processing are described with their applicability in scientific research. The idea for investigation of temperature distribution in the fluidised bed, using multimodal tomography, is also introduced. Metrological requirements of process tomography such as sensitivity, resolution, and speed of data acquiring are noted.
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Buckley, Steven G., Allen L. Robinson i Larry L. Baxter. "Energetics to energy: Combustion and environmental considerations surrounding the reapplication of energetic materials as boiler fuels". Symposium (International) on Combustion 27, nr 1 (styczeń 1998): 1317–25. http://dx.doi.org/10.1016/s0082-0784(98)80536-5.
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Owens, N. F., D. Gingell i J. Bailey. "Contact-mediated triggering of lamella formation by Dictyostelium amoebae on solid surfaces". Journal of Cell Science 91, nr 3 (1.11.1988): 367–77. http://dx.doi.org/10.1242/jcs.91.3.367.
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Amoebae of the slime mould Dictyostelium discoideum form broad ultrathin cytoplasmic lamellae by a centripetal contractile process soon after they have spread on certain solid surfaces. We have investigated the surface requirements for initial triggering of this contact-mediated signalling system. The lamellar response is not normally evoked by glass, but is seen on glass covalently derivatized with paraffinic chains, as well as on glass covalently derivatized with amine groups and on glass bearing adsorbed polylysine. We have recorded the frequency of the lamellar response on these surfaces as a function of ionic strength and pH, and have measured the electrostatic potentials of the surfaces by the streaming potential method. Using these data we have concluded that the general trigger for the lamellar response is not a ‘simple’ physical or chemical property of the substrata: it is not dependent on specific chemical groups, degree of hydrophobicity, electrostatic potential, or charge density, taken as isolated factors. It seems likely that triggering is dependent on the overall energetics of cell-substratum interaction.
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da Silva, Jéssica Oliveira, Renata Caroline de Farias Gonçalves, Karoline Dantas Brito, Wagner Brandão Ramos i Romildo Pereira Brito. "Rigorous energetic analysis of the pressure-swing distillation process". Chemical Engineering Research and Design 186 (październik 2022): 556–67. http://dx.doi.org/10.1016/j.cherd.2022.08.032.
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Arruda-Silva, Thiago Aurélio, Nahyara Batista Caires Galle, Carlos Caneppele i Niédja Marizze Cezar Alves. "Influence of physical and chemical properties of soybean grains on drying process". Research, Society and Development 9, nr 8 (31.07.2020): e745986504. http://dx.doi.org/10.33448/rsd-v9i8.6504.
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Grain drying can be influenced by many factors and energetic knowledge of this process is essential. The objective was to evaluate the influence of soybean grain properties on drying kinetics and thermodynamic properties. Four soybean cultivars were studied through sphericity, circularity, volume, oil content, total protein and initial moisture in a completely randomized design. Drying was performed at temperatures of 40 and 60 °C, adjusting six mathematical models. By the statistical criteria different models were selected to the cultivars, which were used in the thermodynamic properties’ calculations. The cultivar C with lower volume presented higher drying rate and higher constant k, which presented lower activation energy 23.81 kJ mol-1. The thermodynamic properties of Gibbs enthalpy, entropy and free energy were mainly influenced by volume, being lower for cultivar C.
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Sekiguchi, Osamu, Verena Meyer, Matthias C. Letzel, Dietmar Kuck i Einar Uggerud. "Energetics and Reaction Mechanisms for the Competitive Losses of H2, CH4 and C2H4 from Protonated Methylbenzenes—Implications to the Methanol-to-Hydrocarbons (MTH) Process". European Journal of Mass Spectrometry 15, nr 2 (kwiecień 2009): 167–81. http://dx.doi.org/10.1255/ejms.953.
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We report the unimolecular decomposition following collisional activation of protonated mono-, di- and trimethylbenzenes as a function of collision energy. The resulting energy-resolved mass spectra are then used for the quality control of high-level quantum chemical models of the respective potential energy surfaces. Distinction is made between direct dissociation products (CH4 or H2) and indirect products (alkenes), since formation of the latter requires extensive rearrangement of the molecular skeleton. Very good consistency was found between model and experiment. The models thereby provide a solid foundation for discussing the reaction mechanisms of the industrial methanol-to-hydrocarbon process. The losses of CH4, C2H4 and C3H6 from mesitylenium ions have been studied by 13C and 2H labelling and the alkene losses were found to occur via irreversible isomerisation pathways.
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Cassaignau, Anaïs M. E., Tomasz Włodarski, Sammy H. S. Chan, Lauren F. Woodburn, Ivana V. Bukvin, Julian O. Streit, Lisa D. Cabrita, Christopher A. Waudby i John Christodoulou. "Interactions between nascent proteins and the ribosome surface inhibit co-translational folding". Nature Chemistry 13, nr 12 (14.10.2021): 1214–20. http://dx.doi.org/10.1038/s41557-021-00796-x.
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AbstractMost proteins begin to fold during biosynthesis on the ribosome. It has been suggested that interactions between the emerging polypeptide and the ribosome surface might allow the ribosome itself to modulate co-translational folding. Here we combine protein engineering and NMR spectroscopy to characterize a series of interactions between the ribosome surface and unfolded nascent chains of the immunoglobulin-like FLN5 filamin domain. The strongest interactions are found for a C-terminal segment that is essential for folding, and we demonstrate quantitative agreement between the strength of this interaction and the energetics of the co-translational folding process itself. Mutations in this region that reduce the extent of binding result in a shift in the co-translational folding equilibrium towards the native state. Our results therefore demonstrate that a competition between folding and binding provides a simple, dynamic mechanism for the modulation of co-translational folding by the ribosome.
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Piacentino, A., i E. Cardona. "Advanced energetics of a Multiple-Effects-Evaporation (MEE) desalination plant. Part II: Potential of the cost formation process and prospects for energy saving by process integration". Desalination 259, nr 1-3 (wrzesień 2010): 44–52. http://dx.doi.org/10.1016/j.desal.2010.04.037.
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Hussien, Aseel G. S., i Kyriaki Polychronopoulou. "A Review on the Different Aspects and Challenges of the Dry Reforming of Methane (DRM) Reaction". Nanomaterials 12, nr 19 (28.09.2022): 3400. http://dx.doi.org/10.3390/nano12193400.
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The dry reforming of methane (DRM) reaction is among the most popular catalytic reactions for the production of syngas (H2/CO) with a H2:CO ratio favorable for the Fischer–Tropsch reaction; this makes the DRM reaction important from an industrial perspective, as unlimited possibilities for production of valuable products are presented by the FT process. At the same time, simultaneously tackling two major contributors to the greenhouse effect (CH4 and CO2) is an additional contribution of the DRM reaction. The main players in the DRM arena—Ni-supported catalysts—suffer from both coking and sintering, while the activation of the two reactants (CO2 and CH4) through different approaches merits further exploration, opening new pathways for innovation. In this review, different families of materials are explored and discussed, ranging from metal-supported catalysts, to layered materials, to organic frameworks. DRM catalyst design criteria—such as support basicity and surface area, bimetallic active sites and promoters, and metal–support interaction—are all discussed. To evaluate the reactivity of the surface and understand the energetics of the process, density-functional theory calculations are used as a unique tool.
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Gibot, P., J. Mory, F. Moitrier, L. Vidal, E. Fousson i D. Spitzer. "Miniaturization of micrometric SiC from a detonation process of highly energetic material". Powder Technology 208, nr 2 (marzec 2011): 324–28. http://dx.doi.org/10.1016/j.powtec.2010.08.024.
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Barros, Sâmela Leal, Newton Carlos Santos, Amanda Priscila da Silva Nascimento, Mylena Olga Pessoa Melo, Victor Herbert de Alcântara Ribeiro i Vírginia Mirtes de Alcântara Silva. "Influence of Dehydration in the Physical-Chemical Quality of Commercial Sunflower Almonds". Journal of Agricultural Studies 7, nr 2 (8.08.2019): 82. http://dx.doi.org/10.5296/jas.v7i3.15121.
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Sunflower almonds are widely marketed and have numerous technological applications. Through the drying process occurs the reduction of the water content of the product, a factor that contributes to increase its useful life. However, nutritional losses and physical damage can also occur. In this context, the objective of this study was to evaluate the effect of different temperatures applied in the drying process on the physical-chemical characteristics of commercial sunflower almonds. Convective drying was performed using temperatures of 40, 50, 60 and 80 °C. Afterwards, the samples before and after the drying process were analyzed with respect to the following parameters: moisture, water activity, ash, lipids, proteins, carbohydrates and energetic value to observe the influence of different drying temperatures on these attributes. It was verified that the increase of the temperature of the drying air causes an increase in the ash content, total solids, lipids, carbohydrates and energetic value. However, the reduction of moisture content, water activity and proteins was observed. There was no significant difference between the samples in relation to pH.
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Talukdar, Himansu, Sibaprasad Rudra i Kiron K. Kundu. "Single-ion transfer energetics of some ions using tetraphenylarsonium tetraphenylborate reference electrolyte assumption in aqueous mixtures of urea and glycerol". Canadian Journal of Chemistry 67, nr 2 (1.02.1989): 321–29. http://dx.doi.org/10.1139/v89-053.
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Single-ion transfer free energies [Formula: see text] and entropies [Formula: see text] of some ions from water to aqueous mixtures of urea and glycerol have been determined using the widely used tetraphenylarsonium tetraphenylborate reference electrolyte assumption from solubility and emf measurements of some appropriate electrolytes at five different temperatures (15 to 35 °C). Analysis of [Formula: see text] and [Formula: see text] values of the ions as well as their respective "chemical" effect, [Formula: see text] and [Formula: see text] as obtained after correcting for their cavity and Born-type electrostatic effects, estimated by the scaled particle theory (SPT) and simple Born equation, respectively, show a complex dependence upon solvent composition. Attempts have been made to explain the observed mirror-image entropie behaviour of simple cations and anions in the light of Kundu etal.'s four-step transfer process and to compare the results with those obtained in other aquo-ionic and nonionic systems. Keywords: single ion, transfer energetics, TATB assumption, aqueous glycerol, aqueous urea.
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Chung, Kyungwha, Joonho Bang, Athira Thacharon, Hyun Yong Song, Se Hwang Kang, Woo-Sung Jang, Neha Dhull i in. "Non-oxidized bare copper nanoparticles with surface excess electrons in air". Nature Nanotechnology 17, nr 3 (10.02.2022): 285–91. http://dx.doi.org/10.1038/s41565-021-01070-4.
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AbstractCopper (Cu) nanoparticles (NPs) have received extensive interest owing to their advantageous properties compared with their bulk counterparts. Although the natural oxidation of Cu NPs can be alleviated by passivating the surfaces with additional moieties, obtaining non-oxidized bare Cu NPs in air remains challenging. Here we report that bare Cu NPs with surface excess electrons retain their non-oxidized state over several months in ambient air. Cu NPs grown on an electride support with excellent electron transfer ability are encapsulated by the surface-accumulated excess electrons, exhibiting an ultralow work function of ~3.2 eV. Atomic-scale structural and chemical analyses confirm the absence of Cu oxide moiety at the outermost surface of air-exposed bare Cu NPs. Theoretical energetics clarify that the surface-accumulated excess electrons suppress the oxygen adsorption and consequently prohibit the infiltration of oxygen into the Cu lattice, provoking the endothermic reaction for oxidation process. Our results will further stimulate the practical use of metal NPs in versatile applications.
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Adlakha, Ilaksh, Kuntimaddi Sadananda i Kiran N. Solanki. "Discrete dislocation modeling of stress corrosion cracking in an iron". Corrosion Reviews 33, nr 6 (1.11.2015): 467–75. http://dx.doi.org/10.1515/corrrev-2015-0068.
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AbstractMaterial strengthening and embrittlement are controlled by interactions between dislocations and hydrogen that alter the observed deformation mechanisms. In this work, we used an energetics approach to differentiate two fundamental stress corrosion mechanisms in iron, namely, hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. Considering the small-scale yielding condition, we use a discrete dislocation framework with line dislocations to simulate the crack-tip plastic behavior. The crack growth was modeled using the change in surface energies (cohesive zone laws) due to hydrogen segregation. The changes in the surface energies as a function of hydrogen concentration are computed using atomistic simulations. Results indicate that, when hydrogen concentrations are low, crack growth occurs by alternating mechanisms of cleavage and slip. However, as the hydrogen concentrations increased above some critical value, the crack grows predominately by the cleavage-based decohesion process.
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Kondo, Yohei, i Kunihiko Kaneko. "1P-253 Energetics of a reproducing protocell with chemical reaction process(Nonequilibrium state & Biological rhythm, The 47th Annual Meeting of the Biophysical Society of Japan)". Seibutsu Butsuri 49, supplement (2009): S102. http://dx.doi.org/10.2142/biophys.49.s102_1.
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IRLE, S., G. ZHENG, Z. WANG i K. MOROKUMA. "THEORY–EXPERIMENT RELATIONSHIP OF THE "SHRINKING HOT GIANT" ROAD OF DYNAMIC FULLERENE SELF-ASSEMBLY IN HOT CARBON VAPOR". Nano 02, nr 01 (luty 2007): 21–30. http://dx.doi.org/10.1142/s1793292007000362.
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Though subject to intensive studies, the formation mechanism of buckminsterfullerene C 60 and related higher fullerenes has long evaded discovery. To elucidate their atomistic self-assembly mechanism, we have performed high-temperature quantum chemical molecular dynamics simulations on carbon vapor model systems initially consisting of C 2 molecules. Our simulations reveal a coherent mechanism how highly ordered fullerene cages naturally self-assemble under nonequilibrium conditions, following a series of irreversible processes from the polymerization of C 2 molecules to vibrationally excited giant fullerenes, which then shrink by C 2 evaporation down to the smallest spherical, isolated pentagon rule obeying species C 70 and C 60 as the smallest and kinetically most stable species of the shrinking process. We show that the potential energy surface associated with giant fullerene cage growth, measured by an average cluster curvature, is downhill all the way, and in agreement with high-level energetics from density functional theory. This fullerene formation mechanism is a good example of dynamic self-assembly leading to dissipative structures far from thermodynamic equilibrium, and the "shrinking hot giant" road provides a natural explanation for the observed cage size distributions in a random optimization process consistent with several important experimental observations.
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Rodrigues, Sandra Iara Furtado Costa, José Henrique Stringhini, Márcio Ceccantini, Antonio Mário Penz Júnior, Andrea Machado Leal Ribeiro, Vanessa Peripolli i Concepta Margaret McManus. "CHEMICAL AND ENERGETIC CONTENT OF CORN BEFORE AND AFTER PRE-CLEANING". Ciência Animal Brasileira 16, nr 2 (czerwiec 2015): 158–68. http://dx.doi.org/10.1590/1089-6891v16i217226.
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The poultry industry normally has little control over the raw material that arrives at the processing plant. This experiment aimed to evaluate chemical and energetic quality of corn obtained in a feed mill before and after pre-cleaning. Twenty samples of 30 kg of corn each were taken from trucks delivering corn to the mill. The trucks were then unloaded and the material passed through a pre-cleaning process when another sample was taken. Samples were graded and physical properties evaluated: density (g/L), grain percentages of foreign material, impurities, fragments, broken, soft, insect damaged, fire-burnt, fermented, damaged, cracked and fine particles, as well as chemical composition analysis: Apparent metabolizable energy for poultry (AME), ether extract (EE), crude fiber (CF), starch (STA), water activity (WA), crude protein (CP), digestible and total lysine, methionine, cystine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine and arginine. The experiment was a randomized design with two treatments (before and after pre-cleaning) and twenty replications. Data was analyzed using SAS ® and treatment differences obtained using F test. Correlations and principal components were calculated. There was a decrease in density after the pre-cleaning process, which was probably due to the removal of earth and stones rather than grain and its fractions. Significant increases were found for insect damage, fermented and damaged grain while fire-burn was significantly reduced after the pre-cleaning process. Starch increased after pre-cleaning which is a result of contaminants that normally are poor in this carbohydrate, but fiber levels increased too. Apparent metabolizable energy, aminoacids, digestible (P<0.05) and total (P<0.05) histidine, total lysine and methionine (P<0.1) levels were reduced after pre-cleaning. Density was higher when there were fewer impurities such as straw, husk or small grains. Broken corn was positively correlated (P<0.05) with foreign material (0.63) and fragments (0.76), while proportion of damaged corn was positively correlated with foreign material (0.68), fragments (0.58) and broken corn (0.83). In this study, even in samples classified as excellent quality before pre-cleaning, the pre-cleaning process was effective in reducing humidity and water activity which helps control the growth of fungi or other microorganisms. Starch and fiber levels increased after pre-cleaning while apparent metabolizable energy levels was not improved by pre-cleaning.
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Carlini, M., S. Castellucci i A. Mennuni. "Water hyacinth biomass: chemical and thermal pre-treatment for energetic utilization in anaerobic digestion process". Energy Procedia 148 (sierpień 2018): 431–38. http://dx.doi.org/10.1016/j.egypro.2018.08.106.
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Mihaljević-Jurič, Paula, i Sérgio F. Sousa. "A QM/MM Evaluation of the Missing Step in the Reduction Mechanism of HMG-CoA by Human HMG-CoA Reductase". Processes 9, nr 7 (23.06.2021): 1085. http://dx.doi.org/10.3390/pr9071085.
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Statins are important drugs in the regulation of cholesterol levels in the human body that have as a primary target the enzyme β-hydroxy-β-methylglutaryl-CoA reductase (HMGR). This enzyme plays a crucial role in the mevalonate pathway, catalyzing the four-electron reduction of HMG-CoA to mevalonate. A second reduction step of this reaction mechanism has been the subject of much speculation in the literature, with different conflicting theories persisting to the present day. In this study, the different mechanistic hypotheses were evaluated with atomic-level detail through a combination of molecular dynamics simulations (MD) and quantum mechanics/molecular mechanics (QM/MM) calculations. The obtained Gibbs free activation and Gibbs free reaction energy (15 kcal mol−1 and −40 kcal mol−1) show that this hydride step takes place with the involvement of a cationic His405 and Lys639, and a neutral Glu98, while Asp715 remains in an anionic state. The results provide an atomic-level portrait of this step, clearly demonstrating the nature and protonation state of the amino acid residues involved, the energetics associated, and the structure and charge of the key participating atoms in the several intermediate states, finally elucidating this missing step.
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Akaogi, Masaki, i Makoto Aratono. "Preface". Pure and Applied Chemistry 83, nr 6 (1.01.2011): iv. http://dx.doi.org/10.1351/pac20118306iv.
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The 21st International Conference on Chemical Thermodynamics (ICCT-2010) was held in Tsukuba, Japan, on 1–6 August 2010, by the International Association of Chemical Thermodynamics (IACT) under the sponsorship of IUPAC. The organizing committee was chaired by Prof. T. Atake. The conference attracted more than 600 scientists from 37 different countries. During the conference period, the Rossini lecture and 9 plenary lectures were delivered. Forty invited papers and approximately 200 contributed papers were presented in 7 parallel sessions, together with about 300 poster presentations. The wide variety of fields in chemical thermodynamics is illustrated by the titles of a number of the symposia: “Fluids and fluid mixtures”, “Phase equilibria”, “Foods and pharmaceuticals”, “Biothermodynamics”, “Colloids and interfaces”, “Thermochemistry and molecular energetics”, “Environmental issues”, “Industrial applications, databases and software”, “Theory and simulation”, “Organic materials and polymers”, “Inorganic materials and metals”, “New techniques”, “Education in chemical thermodynamics”, and a special session in honor of Profs. S. Seki and H. Suga. As part of the scientific program, two workshops were also held, the titles of which are: “Energy in subsections on petroleum, coal and alternative sources”, and “Calorimetry with commercial relaxation instruments”.This issue of Pure and Applied Chemistry collects four selected plenary lectures delivered at the conference. The topics include challenges in teaching thermodynamics, new equations-of-state model of fluids and their mixtures, Gibbs energy minimization method in multiphase equilibria, and critical evaluation of thermophysical properties database in chemical process simulation. In these papers, we hope that the readers find the essence of the various aspects of current exciting research in chemical thermodynamics, which were exhibited in a lively manner during this successful conference. Other general papers presented in the symposia and workshops will be published in J. Chem. Thermodynamics, Thermochimica Acta, and Molecular Simulation.The 22nd ICCT is scheduled to be held August 2012 in Búzios, Brazil.Masaki AkaogiMakoto AratonoConference Editors
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Gupta, Prem Kumari. "Effect of temperature and surface area on adsorption of chlorine on different adsorbent carbons". Journal of Applied and Natural Science 4, nr 2 (1.12.2012): 284–87. http://dx.doi.org/10.31018/jans.v4i2.265.
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Chlorine is used in several ways in industry. In such situations, where residual chlorine persists as pollutant, Activated carbons like animal charcoal, carbon black and coconut charcoal can serve as agents to remove residual pollutant “chlorine” by the process of adsorption. Five samples of Carbon black, six samples of active Carbons and two samples of charcoals were treated with a stream of chlorine @0.4 litre/hour at temperature varying from 300 to 1200 C. Chlorine is adsorbed partially physically and partially chemically. Percentage of the chemisorbed increases with rise in the temperature. Maximum percentages of chemisorptions occur at 1200 C while the maximum uptake, physical as well as chemical, takes place at 300 C, which was the lowest temperature. It is seen that activated carbon, carbon blacks and charcoal differ markedly by in their total chlorine uptake at 300 C. Activated carbons associated with high surface were seen to take up maximum chlorine. Fall in surface area is more in active carbons as compared to carbon black due to greater adsorption of chlorine. This probably shows that micro porous carbons are better adsorbent for chlorine adsorption. The unsaturated sites also play far dominant role and provide centres where the adsorption takes place predominantly. Uptake of chlorine is enhanced on evacuating the carbon samples at 6000 C and 10000 C. This is due to the creation of more unsaturated sites. Process of adsorption cum chemisorption takes place through different kinetic stages with different energetics. The activation energies keep on increasing with increasing amounts of chemisorption.
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Stornelli, Giulia, Alberto Maria Gambelli, Andrea Di Schino, Guido Zucca i Federico Rossi. "CIRCULAR ECONOMY APPLIED TO METHANE PRODUCTION FROM NATURAL GAS HYDRATE RESERVOIRS: POTENTIALITIES OF RESIDUAL DUST COMING FROM STEEL PLANTS". Acta Metallurgica Slovaca 28, nr 4 (13.12.2022): 203–7. http://dx.doi.org/10.36547/ams.28.4.1632.
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Natural gas hydrate represents one of the most promising solutions to answer to the constantly increasing energy demand; in addition, the possibility of recover methane via carbon dioxide injection, with a theoretical exchange ratio equal to 1, makes it a potential carbon neutral energy source. Among them, energetical costs associated to practical operations in marine deposits. The use of chemical inhibitors and or promoters to improve the exchange process is gaining increasing interest and researchers are mainly focused on finding less environmental unfriendly additives and on reducing their costs. In that direction, the present work deals with the possible use of waste dust, produced during steel mill processes, as promoter of the CO2/CH4 replacement process. That sand commonly contains a great variety of compounds, such as metal oxides, alumina, salts, and so on. Some of them have a chemical composition close to well-known hydrate inhibitors/promoters. Moreover, that application could be a further energetic cycle for a waste product. In this work, both methane and carbon dioxide hydrate formation were tested in absence and in presence of cupper oxides, with different concentrations. Hydrate formation and dissociation results where then compared among each other and with hydrate equilibrium values for those compounds.
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Figueiró, Clarissa Gusmão, Angélica de Cássia Oliveira Carneiro, Lucas De Freitas Fialho, Carlos Miguel Simões Da Silva i Letícia Costa Peres. "ENERGETIC VALORIZATION OF SAWMILL RESIDUES THROUGH SLOW PYROLISIS PROCESS". FLORESTA 49, nr 1 (17.12.2018): 109. http://dx.doi.org/10.5380/rf.v49i1.57647.
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Brazil is a large producer of sawmill wastes, commonly used to supply boilers and produce energy. In order to reduce unwanted characteristics of the material, thermochemical conversions through carbonization is an alternative. The aim of this study is to characterize the energetic proprieties of raw biomass and pyrolyzed biomass of sawmill residues. In order to analyze the environmental impact in the emission of pyrolysis gases, the behavior of gases during the thermic treatment was determined. Eucalyptus sp. and Pinus sp. residues slow pyrolysis was performed in an electric kiln, whose gases were conducted through a condensable gas recovery system and an online gas analyzer. The charcoal, bio-oil and non-condensable gases yields were estimated. The wood’s and charcoal’s proximate analysis (extractives, lignin, holocellulosis, ash content), higher heating value, equilibrium moisture and density were appraised. The wood’s chemical components were esteemed. Hardwood and softwood’s charcoal presented several differences, especially in yields due to types of lignin. Hardwoods produce a higher amount of acetic acid in slow pyrolysis. This acid was converted, mainly, in carbon dioxide and e a minor extent in methane and carbon monoxide. The gas release was affected by the temperature and wood’s composition. The main gases resulting from the slow pyrolysis of wood are CO2, CO, CH4, H2. The emission of this gases to the atmosphere in addition to increasing the environmental impact caused by the industry is still a waste of energy that could be harnessed more efficiently. Pyrolysis increased the energetic characteristics of sawmill waste. However, in spite of the advantages of carbonization, ways to mitigate the emission of gases emitted in an operational scale should be evaluated.
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Sasaki, Hirokazu, Yuta Yamazaki, Toshitaka Kajino, Motohiko Kusakabe, Takehito Hayakawa, Myung-Ki Cheoun, Heamin Ko i Grant J. Mathews. "Impact of Hypernova νp-process Nucleosynthesis on the Galactic Chemical Evolution of Mo and Ru". Astrophysical Journal 924, nr 1 (1.01.2022): 29. http://dx.doi.org/10.3847/1538-4357/ac34f8.
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Abstract We calculate the Galactic Chemical Evolution of Mo and Ru by taking into account the contribution from ν p-process nucleosynthesis. We estimate yields of p-nuclei such as 92,94Mo and 96,98Ru through the ν p-process in various supernova progenitors based upon recent models. In particular, the ν p-process in energetic hypernovae produces a large amount of p-nuclei compared to the yield in ordinary core-collapse SNe. Because of this, the abundances of 92,94Mo and 96,98Ru in the Galaxy are significantly enhanced at [Fe/H] = 0 by the ν p-process. We find that the ν p-process in hypernovae is the main contributor to the elemental abundance of 92Mo at low metallicity [Fe/H] < −2. Our theoretical prediction of the elemental abundances in metal-poor stars becomes more consistent with observational data when the ν p-process in hypernovae is taken into account.
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Makaryan, Iren A., Eugene A. Salgansky, Vladimir S. Arutyunov i Igor V. Sedov. "Non-Catalytic Partial Oxidation of Hydrocarbon Gases to Syngas and Hydrogen: A Systematic Review". Energies 16, nr 6 (22.03.2023): 2916. http://dx.doi.org/10.3390/en16062916.
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The review contains a comparative analysis of studies on the production of hydrogen and syngas based on the processes of partial oxidation of natural gas and other types of gas feedstock. The results presented in the literature show the high potential of non-catalytic autothermal processes of partial oxidation of hydrocarbons for the development of gas chemistry and energetics. The partial oxidation of hydrocarbons makes it possible to overcome such serious shortcomings of traditional syngas production technologies as technological complexity and high energy and capital intensity. The features of non-catalytic partial oxidation of hydrocarbon gases, the obtained experimental results and the results of kinetic modeling of various options for the implementation of the process, which confirm the adequacy of the kinetic mechanisms used for the analysis, are considered in detail. Examples of industrial implementation of processes based on partial oxidation and proposed alternative options for its organization are considered. Designs of reactors used to ensure stable conversion of rich mixtures of hydrocarbons with an oxidizer are presented. The possibility of obtaining other chemical products by partial oxidation of hydrocarbons is discussed.
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Verevkin, Sergey P., i Aleksandra A. Zhabina. "Platform Chemicals from Ethylene Glycol and Isobutene: Thermodynamics “Pays” for Biomass Valorisation and Acquires “Cashback”". Chemistry 5, nr 2 (9.05.2023): 1171–89. http://dx.doi.org/10.3390/chemistry5020079.
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Ethylene glycol (EG) produced from biomass is a promising candidate for several new applications. In this paper, EG derivatives such as mono- and di-tert-butyl ethers are considered. However, accurate thermodynamic data are essential to optimise the technology of the direct tert-butyl ether EG synthesis reaction or reverse process isobutene release. The aim of this work is to measure the vapour pressures and combustion energies for these ethers and determine the vaporisation enthalpies and enthalpies of formation from these measurements. Methods based on the First and Second Law of Thermodynamics were combined to discover the reliable thermodynamics of ether synthesis reactions. The thermochemical data for ethylene glycol tert-butyl ethers were validated using structure–property correlations and quantum chemical calculations. The literature results of the equilibrium study of alkylation of EG with isobutene were evaluated and the thermodynamic functions of ethylene glycol tert-butyl ethers were derived. The energetics of alkylation determined according to the “First Law” and the “Second Law” methods agree very well. Some interesting aspects related to the entropy of ethylene glycol tert-butyl ethers were also revealed and discussed.
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Nurazizah, Euis Siti, Amalia Rohmah Fajariah, Annisa Aprilia i Lusi Safriani. "Performance Improvement of Dye-Sensitized Solar Cells Using a Combination of TiO<sub>2</sub> and ZnO as Photoanodes". Key Engineering Materials 950 (31.07.2023): 25–30. http://dx.doi.org/10.4028/p-7pijle.
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TiO2 are usually used as photoanode to get high-performance dye-sensitized solar cells (DSSCs). TiO2 has good chemical stability, but still has poor electron mobility so that the DSSC efficiency is low. An alternative semiconductor metal-oxides such as ZnO currently are being explored due to ease of processing, higher electron mobility, interface band energetics, and can be utilized as photoanode also, but the chemical stability is low. Based on these facts, by combining the advantages of TiO2 and ZnO, the TiO2:ZnO composite can be an ideal material as a photoanode in DSSC. In this study, composite of TiO2:ZnO was synthesized using sol-gel method with ratio of TiO2 to ZnO were varied from 80:20, 60:40, 50:50, 40:60, and 20:80 in atomic percent. DSSCs were fabricated by coating the photoanode using screen-printing technique on a FTO-glass substrate. Composite of TiO2:ZnO photoanodes were then sensitized in a solution of N719 dye for several hours. Finally, the DSSCs were assembled and the power conversion efficiency was measured using an I–V measurement system. The highest power conversion efficiency of 2.30% was obtained from the cell fabricated with TiO2:ZnO (50:50) photoanode. This result indicated that the balanced composition allowed to increase Jsc along with reducing recombination process and retaining high dye-loading capability.
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Hofman, Tadeusz. "Preface". Pure and Applied Chemistry 81, nr 10 (1.01.2009): iv. http://dx.doi.org/10.1351/pac20098110iv.
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The 20th International Conference on Chemical Thermodynamics (ICCT 2008) was held in Warsaw, Poland, 3-8 August 2008. It was organized jointly by the Institute of Physical Chemistry of the Polish Academy of Science, both Faculties of Chemistry of the Warsaw University of Technology and the Warsaw University, the Polish Chemical Society, and under the auspices of the International Association of Chemical Thermodynamics (IACT). This conference was significant in a line of traditional meetings gathering biennially chemical thermodynamists from all over the world. Almost 300 participants from 39 countries presented 153 oral presentations and 174 posters, among the former ones 12 plenary and 27 invited lectures were given by distinguished researchers.The culminating event was the Rossini lecture given by Prof. Jürgen Gmehling from the University of Oldenburg in Germany, entitled "Present status and potential of group contribution methods for process development". Prof. Gmehling was awarded the prestigious Frederick D. Rossini Award, which has been given biennially to contemporary chemical thermodynamics for an outstanding contribution.Five 2008 IACT Junior Awards were awarded to young scientists for notable achievements presented during the conference in the form of an oral communication.The conference program was grouped into the following symposia:- Molecular simulations of fluid and statistical thermodynamics- Phase equilibria, supercritical fluids, and separation techniques- Electrolyte solutions and non-electrolyte mixtures including reactive chemical systems- Thermodynamics and properties in the biological, medical, pharmaceutical, agricultural, and food sectors- Nanosystems, nanodevices, and advanced materials- Thermochemistry, calorimetry, and molecular energetics- Ionic liquids- Surface and colloid chemistry- Industrial thermodynamics and databases- Thermodynamics frontiers and education- Modulated and oscillation temperature techniques- Environmental thermodynamicsThis issue of Pure and Applied Chemistry presents 16 papers selected from the plenary and invited lectures delivered at ICCT 2008 with an emphasis on industrial thermodynamics and thermochemistry. We hope that this selection will provide insight into the scientific program of the conference.The 21st International Conference on Chemical Thermodynamics will be held in Tsukuba, Japan, 1-6 August 2010.Tadeusz HofmanConference Editor
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Hansted, Ana Larissa Santiago, Felipe Augusto Santiago Hansted, João Otávio Poletto Tomeleri, Thiago Aguiar Cacuro, Carlos Roberto Sette Jr., Fábio Minoru Yamaji i Vladimir Eliodoro Costa. "Biomass in an industrial boiler: characterizing and reducing waste from the burning process". Research, Society and Development 11, nr 9 (15.07.2022): e45511931948. http://dx.doi.org/10.33448/rsd-v11i9.31948.
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Ashes constitute a waste produced in the heat generation process from bioenergy. This study aimed to improve the biomass energy efficiency used in an industrial boiler. The physicochemical analysis was used to perform improvement in the quality of the biomass for solid fuel. Four biomass types (eucalyptus bark, wood chips, sawdust, and recycled wood waste) were analyzed. The material (ash) was collected every two months over one year. All samples were characterized regarding proximate analysis, chemical composition (macro and micronutrients), morphological characterization (via scanning electron microscopy [SEM] coupled with dispersive energy spectroscopy [EDS]), and particle size distribution. The four biomass types presented significant differences in moisture content and proximate analysis. The bark showed a high percentage of impurities with an ash content of 26.99%. It was possible to reduce the ash content of the biomass inserted into the boiler in half, by separating the bark in the granulometric strata and excluding the smallest particle size (<0.84 mm). The results regarding the ashes showed that chemical composition and physical attributes were similar in all samples over the year. The chemical components were the same, although they varied in quantity. It is possible to improve the biomass energetic performance by excluding the smallest particles prior to the boiler insertion.
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Cichosz, Marcin, Urszula Kiełkowska, Sławomir Łazarski, Łukasz Kiedzik, Marian Szkudlarek, Kazimierz Skowron, Beata Kowalska i Damian Żurawski. "Influence of Ammonia Concentration on Solvay Soda Process Parameters and Associated Environmental and Energetic Effects". Energies 15, nr 22 (9.11.2022): 8370. http://dx.doi.org/10.3390/en15228370.
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Modifying the absorption process in soda production by the Solvay method requires performing many calculations and determining a new equilibrium process. An increase in ammonia concentration in the reaction solution causes kinetic changes in equilibrium. Changes to the Solvay soda production technology were determined using chemical and instrumental analysis methods. A modification of the process in the form of SAB was introduced. Information allowing the design of an additional absorber and its location in the network of technological devices was presented in the form of parameters using typical chemical engineering assumptions. Spectroscopic and electrochemical techniques were used for this purpose. The increase in total alkalinity due to the addition of ammonia to 135 mmol·20 cm−3 resulted in cooling savings of about 152.4 MJ·Mg−1 of soda. The ammonia desorption rate and process energy parameters were determined for the new system. The temperature requirements for the carbonation column were defined, and in particular, a technique was developed to minimize the cooling of the lower part of the reactor, which reduces the consumption of process energy. Emissions of CO2 were reduced from 11.70 to 7.85% and NH3 from 5.52 to 4.89% in exhaust gases from the carbonation column.
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Chebbi, Rachid. "A Model for Oxygen Transport from Blood in Microvessels to Tissue". Applied Sciences 13, nr 6 (16.03.2023): 3805. http://dx.doi.org/10.3390/app13063805.
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Oxygen is vital for cellular energetics and metabolism in the human body. Blood transports oxygen to the tissues with hemoglobin in red blood cells playing a key role in the transportation of oxygen. To account for the Fåhraeus and Fåhraeus–Lindqvist effects, we use Haynes marginal zone concept, which subdivides each microvessel into a cell free layer surrounding a core region of uniform red blood cells concentration. The marginal zone concept is used to develop a steady state model for the transport of oxygen from blood to tissue where chemical reaction of oxygen occurs to produce energy. The approach is based on fundamentals of fluid flow and mass transfer in the two zones while accounting for the role of hemoglobin in the transport process and including mass transfer and chemical reaction in the tissue to produce energy using the Krogh cylinder concept. In contrast to transport modeling of solutes such as glucose, the present model includes the key role of hemoglobin in the transport of oxygen from blood to tissue. The model is analytical and provides analytical expressions for the oxygen level profiles in the blood cell free layer, the core zone, and the Krogh cylinder. The results are found to agree with published results in the literature for oxygen transport from blood in capillary size microvessel to its Krogh tissue cylinder. The model is not restricted to transport from capillaries and includes transport of oxygen from microvessels to tissue in general. Extensions of the model include further investigations in the case where changes in the blood microvessel or red blood cells occur due to pathological conditions.
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Cicic, Dumitru Titi, Corneliu Rontescu, Ana Maria Bogatu, Catalin Gheorghe Amza i Oana Roxana Chivu. "The Influence of the Deposit Parameters on the Medium Chemical Composition of the Welded Joint". Revista de Chimie 68, nr 10 (15.11.2017): 2261–64. http://dx.doi.org/10.37358/rc.17.10.5867.
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Recipient type products from energetic and chemical industry undergo a wide combined process of corrosion and ware, due to working environment. In order to put this products back in use, in a shorter period of time, welding reconditioning procedures are applied which mainly aim to restore the geometrical configuration but also the characteristics growth. Any welding technology applied, involves melting a filler material but also a part of the base material, mixing them, thereby obtaining the welded joint. The paper present the experimental results obtained in determining the optimal parameters for Metal Active Gas welding deposit that are going to be used for the restoration of some components from energetic and chemical industry and that are highlighting the dependence between the deposit parameters and the chemical composition of the juncture.