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IVAKIN, A. A., M. V. KRUCHININA, and O. V. KORYAKOVA. "ChemInform Abstract: A Novel Iron(III) Vanadate with Mixed Vanadium(IV,V) Oxidation Number." ChemInform 22, no. 4 (August 23, 2010): no. http://dx.doi.org/10.1002/chin.199104021.
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Muronetz, Vladimir I., Aleksandra K. Melnikova, Luciano Saso, and Elena V. Schmalhausen. "Influence of Oxidative Stress on Catalytic and Non-glycolytic Functions of Glyceraldehyde-3-phosphate Dehydrogenase." Current Medicinal Chemistry 27, no. 13 (April 24, 2020): 2040–58. http://dx.doi.org/10.2174/0929867325666180530101057.
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Background: Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH) is a unique enzyme that, besides its main function in glycolysis (catalysis of glyceraldehyde-3-phosphate oxidation), possesses a number of non-glycolytic activities. The present review summarizes information on the role of oxidative stress in the regulation of the enzymatic activity as well as non-glycolytic functions of GAPDH. Methods: Based on the analysis of literature data and the results obtained in our research group, mechanisms of the regulation of GAPDH functions through the oxidation of the sulfhydryl groups in the active site of the enzyme have been suggested. Results: Mechanism of GAPDH oxidation includes consecutive oxidation of the catalytic Cysteine (Cys150) into sulfenic, sulfinic, and sulfonic acid derivatives, resulting in the complete inactivation of the enzyme. The cysteine sulfenic acid reacts with reduced glutathione (GSH) to form a mixed disulfide (S-glutathionylated GAPDH) that further reacts with Cys154 yielding the disulfide bond in the active site of the enzyme. In contrast to the sulfinic and sulfonic acids, the mixed disulfide and the intramolecular disulfide bond are reversible oxidation products that can be reduced in the presence of GSH or thioredoxin. Conclusion: Oxidation of sulfhydryl groups in the active site of GAPDH is unavoidable due to the enhanced reactivity of Cys150. The irreversible oxidation of Cys150 is prevented by Sglutathionylation and disulfide bonding with Cys154. The oxidation/reduction of the sulfhydryl groups in the active site of GAPDH can be used for regulation of glycolysis and numerous side activities of this enzyme including the induction of apoptosis.
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Chomiak, M., J. Trawczyński, and M. Zawadzki. "Effect of cobalt (nickel) oxide on the properties of zinc–titanium sorbents for high temperature desulphurization of model coal gas." Brazilian Journal of Chemical Engineering 38, no. 3 (July 6, 2021): 605–16. http://dx.doi.org/10.1007/s43153-021-00129-y.
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AbstractZn–Ti–Co(Ni) sorbents for H2S removal from model hot coal were prepared and characterized. Effects of cobalt (Co) and nickel (Ni) on the sorbents texture, structure, H2S sorption capacity and regeneration properties were determined. TiO2 formed mixed metal oxides with CoO and NiO in the fresh sorbents, while TiO2 and nanocrystalline sulfides of Zn, Co, Ni were found in sulphided ones. The oxidative regeneration of sulphided sorbents re-formed mixed oxides. Sorption capacity of studied materials increased along with an increase of the amount of added Co (Ni) and also with the number of work cycles. Co-doped Zn–Ti materials adsorbed up to 244% more sulfur than these of Zn–Ti, while Ni-doped materials adsorbed ca. twice more H2S than the corresponding Co-doped sorbents. The addition of Co (Ni) decreased the temperature of ZnS oxidation. The catalytic effect of the Co (Ni) oxides on the oxidation of ZnS was suggested.
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Laishley, E. J., R. D. Bryant, B. W. Kobryn, and J. B. Hyne. "Microcrystalline structure and surface area of elemental sulphur as factors influencing its oxidation by Thiobacillus albertis." Canadian Journal of Microbiology 32, no. 3 (March 1, 1986): 237–42. http://dx.doi.org/10.1139/m86-047.
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The effect of particle size, surface area per unit weight, and molecular composition of S0 on the rate of S0 oxidation by Thiobacillus albertis was studied. Spherical S0 prills varying in size and surface areas were prepared and added as the sulphur source to synthetic salts medium. The rate of S0 oxidation by T. albertis was found to be a function of surface area/unit weight of sulphur. In all these experiments [Formula: see text] was produced in a linear manner with time indicating sterically favorable cell–sulphur oxidation binding sites for bacterial growth. Different powdered forms of S0 (high-purity orthohombic, high-purity polymeric, and mixed molecular sulphur) were oxidized at a significantly faster rate than the prilled S0. Also the initial oxidation was exponential up to 3 days at which point [Formula: see text] production from mixed molecular sulphur utilization fell off substantially with time as compared with similar [Formula: see text] rate curves obtained with high-purity orthorhombic and high-purity polymeric oxidation. It was implied that the increased Sx content in mixed molecular sulphur was responsible for the slower oxidation rate by altering the sulphur crystal lattice formation which affected the number of sterically favorable oxidation binding sites for T. albertis growth. Thiobacillus albertis was shown to colonize S0 surfaces as microcolonies. It was concluded that particle size, surface area/unit weight, and the crystal microstructure of S0 affects the oxidation rate of S0 by T. albertis.
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Mikulová, Zuzana, Květuše Jirátová, Jan Klempa, and František Kovanda. "Modification of Co-Mn-Al Mixed Oxide with Promoters and Their Effect on Properties and Activity in VOC Total Oxidation." Collection of Czechoslovak Chemical Communications 73, no. 8-9 (2008): 1000–1014. http://dx.doi.org/10.1135/cccc20081000.
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The activity and selectivity of the Co-Mn-Al mixed oxide catalyst modified with promoters (Pt, Pd, K and La) in total oxidation of volatile organic compounds (toluene and ethanol) were studied. The promoters were introduced at the stage of coprecipitation of a layered double hydroxide (LDH) precursor or impregnation of the mixed oxide obtained by LDH precursor calcination. In total oxidation of toluene, the most active Co-Mn-Al catalysts were those containing low amounts of potassium regardless of the mode of modification, while in total oxidation of ethanol the catalyst impregnated with a higher potassium concentration (3 wt.%) was the most active. Introduction of Pt and Pd in an amount of 0.5 or 0.1 wt.% into the Co-Mn-Al mixed oxide did not improve its catalytic activity. The impregnation method appears to be a more effective mode for preparation of active catalysts than the method using an addition of promoters at the stage of coprecipitation of the LDH precursor. Undesirable reaction intermediate (benzene) was formed when toluene oxidation was carried out over lanthanum- or palladium-containing catalysts. In total oxidation of ethanol, a number of reaction intermediates were produced acetaldehyde being the main one. The catalysts modified at the stage of LDH precursor coprecipitation exhibited a better selectivity (i.e., a lower acetaldehyde formation) than those modified by impregnation. The best results were obtained with the Co-Mn-Al mixed oxide catalyst modified with potassium.
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Filatov, D. A., M. A. Kopytov, V. S. Ovsyannikova, and E. A. Elchaninova. "Oxidation of a Mixture of Polyaromatic Hydrocarbons by a Mixed Culture of Hydrocarbon-Oxidizing Microorganisms." Eurasian Chemico-Technological Journal 23, no. 1 (March 25, 2021): 59. http://dx.doi.org/10.18321/ectj1034.
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The possibility of biochemical oxidation of polyaromatic hydrocarbon mixtures (PAHs) by the mixed culture of hydrocarbon-oxidizing microorganisms (HOM) in a liquid medium and soil was investigated. The mixed HOM culture was represented by Pseudomonas stutzeri, Pseudomonas putida, Bacillus cereus, and Arthrobacter globiformis genera. It was shown that during HOM cultivation of the microorganisms under study in the liquid medium their number increases from 0.25·104 to 11·108 CFU/ml, which is accompanied by an increase in their oxygenase activity. All PAHs identified were subjected to oxidation from 11.3 to 100%. The results of experiments on biodegradation of PAHs under natural conditions have shown that for 60 days the total utilization of oil products in soils was on the average 65% of the initial contamination. This suggests the prospects for the use of the mixed HOM culture under study for effective biodegradation of PAHs polluting soil and waste waters.
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Giri, R. R., H. Ozaki, Y. Takayanagi, S. Taniguchi, and R. Takanami. "Efficacy of ultraviolet radiation and hydrogen peroxide oxidation to eliminate large number of pharmaceutical compounds in mixed solution." International Journal of Environmental Science & Technology 8, no. 1 (December 1, 2010): 19–30. http://dx.doi.org/10.1007/bf03326192.
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NAKAGAWA, Kiyomasa, Yasumasa SAIKI, Kouichi OKABE, and Etsuhide YAMAMOTO. "Studies on the mechanism of oral mixed infections. Relation between the oxidation-reduction potential and number of viable cells." Japanese Journal of Oral & Maxillofacial Surgery 39, no. 10 (1993): 1035–42. http://dx.doi.org/10.5794/jjoms.39.1035.
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Kaplin, Igor Yu, Ekaterina S. Lokteva, Elena V. Golubina, and Valery V. Lunin. "Template Synthesis of Porous Ceria-Based Catalysts for Environmental Application." Molecules 25, no. 18 (September 16, 2020): 4242. http://dx.doi.org/10.3390/molecules25184242.
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Porous oxide materials are widely used in environmental catalysis owing to their outstanding properties such as high specific surface area, enhanced mass transport and diffusion, and accessibility of active sites. Oxides of metals with variable oxidation state such as ceria and double oxides based on ceria also provide high oxygen storage capacity which is important in a huge number of oxidation processes. The outstanding progress in the development of hierarchically organized porous oxide catalysts relates to the use of template synthetic methods. Single and mixed oxides with enhanced porous structure can serve both as supports for the catalysts of different nature and active components for catalytic oxidation of volatile organic compounds, soot particles and other environmentally dangerous components of exhaust gases, in hydrocarbons reforming, water gas shift reaction and photocatalytic transformations. This review highlights the recent progress in synthetic strategies using different types of templates (artificial and biological, hard and soft), including combined ones, in the preparation of single and mixed oxide catalysts based on ceria, and provides examples of their application in the main areas of environmental catalysis.
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Zatovsky, Igor V., Nikolay S. Slobodyanik, Denis A. Stratiychuk, Konstantin V. Domasevitch, Joachim Sieler, and Eduard B. Rusanov. "A Novel Convenient Synthesis of Mixed-Valence TiIII/TiIV Double Phosphates Starting with Titanium Nitride TiN." Zeitschrift für Naturforschung B 55, no. 3-4 (April 1, 2000): 291–98. http://dx.doi.org/10.1515/znb-2000-3-411.
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Abstract A new synthetic approach for the low- and mixed-valence double titanium phosphates starting with titanium nitride, TiN, and based on the controlled oxidation of a low-valent metal in the phosphate melt is presented. The reaction of the system MI2O - P2O5 - TiN (MI = Na, K) in air (800-1050 °C) leads to loss of nitrogen, N2, and results in the formation of a number of double phosphates: KTiP2O7, K2TiniTiIV(PO4)3, KTiOPO4, NaTiP2O7, NaTi2(PO4)3 and a new mixed-valent diphosphate, NaTiIIITiIV(P2O7)2. The mixed-valent species K2TiIIITiIV(PO4)3 and NaTiIIITiIV(P2O7)2 were characterized by single crystal X-ray diffraction. The described synthetic procedure is proposed as a simple and convenient method for the preparation of lowand mixed-valent phosphate materials
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Ali, Md Eaqub, Md Motiar Rahman, and Sharifah Bee Abd Hamid. "Nanoclustered Gold: A Promising Green Catalysts for the Oxidation of Alkyl Substituted Benzenes." Advanced Materials Research 925 (April 2014): 38–42. http://dx.doi.org/10.4028/www.scientific.net/amr.925.38.
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Catalytic oxidation of alkyl substituted benzenes is an essential route for the synthesis of a number of important chemicals, perfumes, drugs and pharmaceuticals. The oxidation products of ethyl benzene are important precursors for a wide range of pharmaceuticals and synthetic materials. Acetophenone and 1-phenylethanol are two oxidation products of ethyl benzene which are the precursors of optically active alcohol, benzalacetophanones, hydrazones and so on. However, the oxidations of alkyl substituted benzenes have been remaining a challenging task. This is because of the limitations of an appropriate catalyst and requirement of corrosive chemical treatments (potassium permanganate/dichromate and ammonium cerium nitrate) which are hazardous and environmentally unfriendly. The current industrial practice in the oxidation of ethyl benzene unfortunately involves high temperature thermal autoxidation in the absence of catalysts. Although few catalysts have been tested for the oxidation of ethyl benzene, many of them found to be inefficient. For example, cobalt (II) oxide-immobilized on mesoporous silica (Co/SBA-15) was used to catalyze oxidation of alkyl benzene at high temperature (125-150°C) but only 70% conversion was obtained after prolong treatment at 150°C. Additionally, the catalyst formed mixed uncontrolled oxidation products like 1-phenylethyl hydro peroxide, benzoic acid, acetophenone and phenyl ethanol. Carbon/silica/metal oxide supported nanoporous gold is a promising green catalyst for heterogenous molecular transformation. This is because of their three dimensional open pore network structures, high surface to volume ratio, high reusability, distinct optolectronic and physio-chemical properties. Mesoporous carbon/silica/metal oxide thin film supports provide increase dispersion of metal nanocatalysts and facilitate transport of molecules, ions or electrons through the nanopores/nanochannels, enhancing product yields with minimum cost and time. This paper has reviewed various gold-skeleton green catalysts and their preparation and mechanistic schemes for the selective oxidation of alkyl substituted benzenes.
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Selifonov, Sergey A., Peter J. Chapman, Simon B. Akkerman, Jerome E. Gurst, Jacqueline M. Bortiatynski, Mark A. Nanny, and Patrick G. Hatcher. "Use of 13C Nuclear Magnetic Resonance To Assess Fossil Fuel Biodegradation: Fate of [1-13C]Acenaphthene in Creosote Polycyclic Aromatic Compound Mixtures Degraded by Bacteria." Applied and Environmental Microbiology 64, no. 4 (April 1, 1998): 1447–53. http://dx.doi.org/10.1128/aem.64.4.1447-1453.1998.
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ABSTRACT [1-13C]acenaphthene, a tracer compound with a nuclear magnetic resonance (NMR)-active nucleus at the C-1 position, has been employed in conjunction with a standard broad-band-decoupled13C-NMR spectroscopy technique to study the biodegradation of acenaphthene by various bacterial cultures degrading aromatic hydrocarbons of creosote. Site-specific labeling at the benzylic position of acenaphthene allows 13C-NMR detection of chemical changes due to initial oxidations catalyzed by bacterial enzymes of aromatic hydrocarbon catabolism. Biodegradation of [1-13C]acenaphthene in the presence of naphthalene or creosote polycyclic aromatic compounds (PACs) was examined with an undefined mixed bacterial culture (established by enrichment on creosote PACs) and with isolates of individual naphthalene- and phenanthrene-degrading strains from this culture. From13C-NMR spectra of extractable materials obtained in time course biodegradation experiments under optimized conditions, a number of signals were assigned to accumulated products such as 1-acenaphthenol, 1-acenaphthenone, acenaphthene-1,2-diol and naphthalene 1,8-dicarboxylic acid, formed by benzylic oxidation of acenaphthene and subsequent reactions. Limited degradation of acenaphthene could be attributed to its oxidation by naphthalene 1,2-dioxygenase or related dioxygenases, indicative of certain limitations of the undefined mixed culture with respect to acenaphthene catabolism. Coinoculation of the mixed culture with cells of acenaphthene-grown strain Pseudomonas sp. strain A2279 mitigated the accumulation of partial transformation products and resulted in more complete degradation of acenaphthene. This study demonstrates the value of the stable isotope labeling approach and its ability to reveal incomplete mineralization even when as little as 2 to 3% of the substrate is incompletely oxidized, yielding products of partial transformation. The approach outlined may prove useful in assessing bioremediation performance.
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Ab Ghani, Sharin, Zulkarnain Ahmad Noorden, Nor Asiah Muhamad, Hidayat Zainuddin, Muhammad Ilman Hakimi Chua Abdullah, and Imran Sutan Chairul. "Dielectric Strength Improvement of Natural Ester Insulation Oil via Mixed Antioxidants: Taguchi Approach." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 2 (April 1, 2017): 650. http://dx.doi.org/10.11591/ijece.v7i2.pp650-658.
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<span lang="EN-US">Recently, natural ester insulation (NEI) oils are found to be the best candidates to replace mineral-based insulation oils for oil-immersed transformer applications. However, NEI oils are prone to oxidation due to their poor oxidative stability which can be improved by adding antioxidants into the oils. Latest studies have also shown that the use of selected antioxidants improves the AC breakdown voltage (BdV) of NEI oils. However, the experiments in previous studies were designed using the conventional one-factor-at-a-time (OFAT) method, which requires a large number of samples to be tested in order to determine the optimum response. Thus, a Taguchi-based designed experiment is introduced in this study in replacement of the OFAT method. It is found that this method is capable of determining the optimum concentrations of propyl gallate (PG) and citric acid (CA) which will maximize the AC BdV and improve the oxidative stability of the NEI oil. An AC breakdown voltage test is conducted in accordance with the ASTM D1816 standard using Megger OTS60PB portable oil tester, in which the electrode gap distance is kept fixed at 1 mm. The results indicate that the addition of PG and CA antioxidants increases the AC BdV of the rapeseed-based NEI oil. It is found that the optimum concentrations of PG and CA antioxidant is 0.05 and 0.25 wt.%, respectively. Lastly, the model developed in this study is analysed using analysis of variance (ANOVA). Validation test is also conducted on the optimized NEI oil to determine its dielectric strength and oxidative stability.</span>
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Horikoshi, Tetsuo, Kenya Kubo, and Hiroshi Nishihara. "Dependence of intervalence-transfer bands for mixed-valence oligo(1,1′-dihexylferrocenylene)s on the oxidation number and the number of ferrocene units from two to six." Journal of the Chemical Society, Dalton Transactions, no. 19 (1999): 3355–60. http://dx.doi.org/10.1039/a904953c.
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Peng, Yao Li, Jie Lv, Jing Hui Lv, and Guang Yuan Xie. "Distribution of Alkylene Bridge Bonds in Shenfu Coal." Advanced Materials Research 236-238 (May 2011): 715–18. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.715.
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To understand the distribution of the alkylene bridge bonds which connect aromatic moieties and utilize coal effectively, Shenfu coal (SFC), its solvent extraction fractions and carbon disulfide (CS2)/tetrahydrofuran (THF) inextractable matter (RE) were subject to ruthenium ion-catalyzed oxidation (RICO). The results suggest that the carbon number of the alkylene bridge bonds range from C0 to C30 and that dominant alkylene linkage are C2 and C3 in SFC, a,w-diarylalkanes are soluble in a CS2/THF mixed solvent, whereas highly condensed aromatic species in SFC show poor solubility in the CS2/THF mixed solvent.
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Beltran, Claudia, Rosario Pardo, Diana Bou-Teen, Marisol Ruiz-Meana, Josep A. Villena, Ignacio Ferreira-González, and Ignasi Barba. "Enhancing Glycolysis Protects against Ischemia-Reperfusion Injury by Reducing ROS Production." Metabolites 10, no. 4 (March 30, 2020): 132. http://dx.doi.org/10.3390/metabo10040132.
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After myocardial ischemia-reperfusion, fatty acid oxidation shows fast recovery while glucose oxidation rates remain depressed. A metabolic shift aimed at increasing glucose oxidation has shown to be beneficial in models of myocardial ischemia-reperfusion. However, strategies aimed at increasing glucose consumption in the clinic have provided mixed results and have not yet reached routine clinical practice. A better understanding of the mechanisms underlying the protection afforded by increased glucose oxidation may facilitate the transfer to the clinic. The purpose of this study was to evaluate if the modulation of reactive oxygen species (ROS) was involved in the protection afforded by increased glucose oxidation. Firstly, we characterized an H9C2 cellular model in which the use of glucose or galactose as substrates can modulate glycolysis and oxidative phosphorylation pathways. In this model, there were no differences in morphology, cell number, or ATP and PCr levels. However, galactose-grown cells consumed more oxygen and had an increased Krebs cycle turnover, while cells grown in glucose had increased aerobic glycolysis rate as demonstrated by higher lactate and alanine production. Increased aerobic glycolysis was associated with reduced ROS levels and protected the cells against simulated ischemia-reperfusion injury. Furthermore, ROS scavenger N-acetyl cysteine (NAC) was able to reduce the amount of ROS and to prevent cell death. Lastly, cells grown in galactose showed higher activation of mTOR/Akt signaling pathways. In conclusion, our results provide evidence indicating that metabolic shift towards increased glycolysis reduces mitochondrial ROS production and prevents cell death during ischemia-reperfusion injury.
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Shah, Parag M., Joseph W. H. Burnett, David J. Morgan, Thomas E. Davies, and Stuart H. Taylor. "Ceria–Zirconia Mixed Metal Oxides Prepared via Mechanochemical Grinding of Carbonates for the Total Oxidation of Propane and Naphthalene." Catalysts 9, no. 5 (May 22, 2019): 475. http://dx.doi.org/10.3390/catal9050475.
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A series of ceria–zirconia mixed metal oxides with varying metal ratios were prepared by the calcination of precursors synthesized by mechanochemical grinding of the metal carbonates, and tested for catalytic naphthalene and propane total combustion. The mechanically-mixed metal oxides were more active for both propane and naphthalene total oxidation compared to the parent metal oxides. Ce0.95Zr0.05Ox was the most active catalyst for the total combustion of propane and naphthalene. Catalysts were characterized by x-ray diffraction, BET surface area, laser Raman spectroscopy, temperature programmed reduction, scanning electron microscopy with energy dispersive x-ray analysis and x-ray photoelectron spectroscopy techniques. Formation of ceria–zirconia solid solutions was observed for catalysts with a zirconia content of 10% or lower, whereas ceria and zirconia phase separation was observed when zirconia content was above 25%. Surface area increased when ceria and zirconia were mixed, and the reduction temperature of the bulk shifted to lower temperatures upon increasing zirconia content. Incorporation of zirconia was found to increase the relative concentration of surface oxygen defects compared to pure ceria, with low amounts of zirconia showing the greatest increase. The concentration of oxygen defects correlates with propane and naphthalene total oxidation activity. The enhanced total oxidation activity occurs as a result of the increased number of oxygen defects and the higher surface area. The results demonstrate that mechanochemical preparation from carbonate precursors was an effective route to make active catalysts.
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Soriano-López, Joaquín, Rory Elliott, Amal C. Kathalikkattil, Ayuk M. Ako, and Wolfgang Schmitt. "Tuning the Catalytic Water Oxidation Activity through Structural Modifications of High-Nuclearity Mn-oxo Clusters [Mn18M] (M = Sr2+, Mn2+)." Water 13, no. 15 (July 27, 2021): 2042. http://dx.doi.org/10.3390/w13152042.
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The water oxidation half-reaction is considered the bottleneck in the development of technological advances to replace fossil fuels with sustainable and economically affordable energy sources. In natural photosynthesis, water oxidation occurs in the oxygen evolving complex (OEC), a manganese-oxo cluster {Mn4CaO5} with a cubane-like topology that is embedded within a redox-active protein environment located in photosystem II (PS II). Therefore, the preparation of biomimetic manganese-based compounds is appealing for the development of efficient and inexpensive water oxidation catalysts. Here, we present the water oxidation catalytic activity of a high-nuclearity mixed-metal manganese-strontium cluster, [MnIII12MnII6Sr(μ4-O8)(μ3-Cl)8(HLMe)12(MeCN)6]Cl2∙15MeOH (Mn18Sr) (HLMe = 2,6-bis(hydroxymethyl)-p-cresol), in neutral media. This biomimetic mixed-valence cluster features different cubane-like motifs and it is stabilized by redox-active, quinone-like organic ligands. The complex displays a low onset overpotential of 192 mV and overpotentials of 284 and 550 mV at current densities of 1 mA cm−2 and 10 mA cm−2, respectively. Direct O2 evolution measurements under visible light-driven water oxidation conditions demonstrate the catalytic capabilities of this cluster, which exhibits a turnover frequency of 0.48 s−1 and a turnover number of 21.6. This result allows for a direct comparison to be made with the structurally analogous Mn-oxo cluster [MnIII12MnII7(µ4-O)8(µ3-OCH3)2(µ3-Br)6(HLMe)12(MeOH)5(MeCN)]Br2·9MeCN·MeOH (Mn19), the water oxidation catalytic activity of which was recently reported by us. This work highlights the potential of this series of compounds towards the water oxidation reaction and their amenability to induce structural changes that modify their reactivity.
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Lefroy, Rod D. B., Sholeh, and Graeme Blair. "Influence of sulfur and phosphorus placement, and sulfur particle size, on elemental sulfur oxidation and the growth response of maize (Zea mays)." Australian Journal of Agricultural Research 48, no. 4 (1997): 485. http://dx.doi.org/10.1071/a95054.
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The oxidation rate of elemental sulfur (S) can be manipulated by a number of controllable factors to match formation of sulfate to plant demand. Two of these factors are particle size and the presence of adequate nutrients for the oxidising bacteria. A factorial experiment was conducted in a glasshouse consisting of 3 combinations of S and phosphorus (P) placements × 2 S particle sizes [ 35S-labelled 50–150 µm (fine sulfur, Sf) and 150–250 µm (coarse sulfur, Sc)] × 2 harvesting times of maize (Zea mays) (28 and 56 days). In the 3 fertiliser placement treatments, all of the S was evenly mixed with the soil in the front compartment of a split-root box. The treatments differed in the placement of the P fertiliser: (i) all of the P was applied in the front compartment with the S (SPF); (ii) the P was applied evenly throughout the soil in both compartments (SPFB); and (iii) all of the P was applied in the back compartment (SPB). A high P- and S-sorbing basaltic soil (Haplohumult) from Walcha, New South Wales, was used in the split-root boxes. Plant dry weight and fertiliser S uptake were increased when P was mixed with elemental S. Elemental S oxidation after 28 days was higher when mixed with P than when separated from P, and higher with Sf than with Sc. Root proliferation occurred in direct response to the placement of P. There were significant linear relationships between the amount of applied P in the front compartment and root length and root surface area of the front compartment roots. This study shows that the increase in S uptake by the plant from elemental S when it was mixed with P was due to the combined effect of P on elemental S oxidation and on root proliferation.
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Kumar, Ravi, Amit Saxena, and Muniappan Sankar. "Mixed β-bromo/cyano tetrasubstituted-meso-tetraphenylporphyrin Cu(II) complexes: Synthesis and electrochemical studies." Journal of Porphyrins and Phthalocyanines 20, no. 12 (December 2016): 1420–25. http://dx.doi.org/10.1142/s1088424616501169.
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Mixed substituted [Formula: see text]-bromo and cyano Cu(II) porphyrins (CuTPPBr[Formula: see text](CN)[Formula: see text] ([Formula: see text] = 0–4)) were synthesized from CuTPPBr4 by nucleophilic substitution with excess CuCN in quinoline under argon atmosphere for the first time. These porphyrins exhibited a gradual red-shift both in Soret and Q-bands with increase in number of cyano groups. CuTPPBr[Formula: see text](CN)[Formula: see text] ([Formula: see text] 0–4) exhibited anodic shift in their first ring oxidation potential ([Formula: see text] [Formula: see text] = 120–460 mV) and in first reduction potential ([Formula: see text] [Formula: see text] = 450–940 mV) as compared to CuTPP due to electron withdrawing nature of cyano and bromo substituents.
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Cheng, Lei, Bin Sun, Chongyang Du, Wei Gao, and Guangming Cao. "High-Temperature Oxidation Behavior of Fe–10Cr Steel under Different Atmospheres." Materials 14, no. 13 (June 22, 2021): 3453. http://dx.doi.org/10.3390/ma14133453.
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Using a thermogravimetric analyzer (TGA), Fe–10Cr steel was oxidized in dry air and in a mixed atmosphere of air and water vapor at a relative humidity of 50% and a temperature of 800–1200 °C for 1 h. The oxidation weight gain curves under the two atmospheres were drawn, the oxidation activation energy was calculated, and the phase and cross-sectional morphology of the iron oxide scales were analyzed and observed by X-ray diffractometry (XRD) and optical microscopy (OM). The results showed that when the oxidation temperature was 800 °C, the spheroidization of Fe–10Cr steel occurred, and the oxidation kinetics conformed to the linear law. At 900–1200 °C, the oxidation kinetics followed a linear law in the preliminary stage and a parabolic law in the middle and late stages. In an air atmosphere, when the oxidation temperature reached 1200 °C, Cr2O3 in the inner oxide layer was partially ruptured. In an atmosphere with a water vapor content of 50%, Cr2O3 at the interface reacted with H2O to generate volatile CrO2(OH)2, resulting in a large consumption of Cr at the interface. At the same time, a large number of voids and microcracks appeared in the iron oxide layer, which accelerated the entry of water molecules into the substrate, as well as the oxidation of Fe–10Cr steel, and caused the iron oxide scales to fall off. Due to the volatilization of Cr2O3 and the conversion from internal oxidation to external oxidation, the internal oxidation zone (IOZ) of Fe–10Cr steel under water vapor atmosphere decreased or even disappeared.
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Vydrina, Valentina Afanasievna, Marina Petrovna Yakovleva, Aleksey Aleksandrovich Kravchenko, Rasul' Rustemovich Sayakhov, and Gumer Yusupovich Ishmuratov. "HYDROBORATION-OXIDATION OF GLYCIRRETHIC ACID’S DERIVATIVES." chemistry of plant raw material, no. 2 (June 10, 2020): 101–9. http://dx.doi.org/10.14258/jcprm.2020025468.
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The hydroboration-oxidation reaction is widely used in the chemistry of terpenoids both for proving the structure of new compounds isolated from natural raw materials and for the directed synthesis of low molecular weight bioregulators. Moreover, most of the known examples affect mono- and sesquiterpenes, a much smaller number - for di- and triterpenoids: most are represented by hydroboration-oxidation of localized double bonds, examples for conjugated dienes are limited only by hydroboration-oxidation of cis-eudesma-6,11-diene, abietic acid and its methyl ester.
We found that the reduction of the pentacyclic triterpenoid – glycyrrhetate methyl ester – diisobutylaluminium hydride in methylene chloride at -78 ° С and subsequent hydrolysis in the presence of ammonium chloride proceeds with the formation of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene with a yield of 90%. It was shown that the hydroboration of the 1,3-diene system in it with a 3.3 molar excess of diborane in tetrahydrofuran is accompanied by the restoration of the carboxyl function, and after oxidation with the hydrogen peroxide-sodium acetate system of the organoboranes formed, three alcohols are mixed (2 : 1 : 1): 3β,11,30-trihydroxy-18βH-olean-12(13)-ene, 3β,12,30-trihydroxy-18βH-olean-9(11)-ene and 3β,9,30-trihydroxy-18βH-olean-12 (13)-ene, respectively. A similar mixture of triols was also obtained by hydroboration-oxidation of 3β-hydroxy-18βH-olean-9(11),12(13)-diene-30-oic acid. The hydroboration-oxidation reactions of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene or the corresponding 30th acid proceed as monoprocesses predominantly at 9(11) double bonds.
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Gimferrer, Martí, Gerard Comas-Vilà, and Pedro Salvador. "Can We Safely Obtain Formal Oxidation States from Centroids of Localized Orbitals?" Molecules 25, no. 1 (January 6, 2020): 234. http://dx.doi.org/10.3390/molecules25010234.
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The use of centroids of localized orbitals as a method to derive oxidation states (OS) from first-principles is critically analyzed. We explore the performance of the closest-atom distance criterion to assign electrons for a number of challenging systems, including high-valent transition metal compounds, π-adducts, and transition metal (TM) carbenes. Here, we also introduce a mixed approach that combines the position of the centroids with Bader’s atomic basins as an alternative criterion for electron assignment. The closest-atom criterion performs reasonably well for the challenging systems, but wrongly considers O-H and N-H bonds as hydrides. The new criterion fixes this problem, but underperforms in the case of TM carbenes. Moreover, the OS assignment in dubious cases exhibit undesirable dependence on the particular choice for orbital localization.
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Stutz, Timothy C., Alfonso Landeros, Jason Xu, Janet S. Sinsheimer, Mary Sehl, and Kenneth Lange. "Stochastic simulation algorithms for Interacting Particle Systems." PLOS ONE 16, no. 3 (March 2, 2021): e0247046. http://dx.doi.org/10.1371/journal.pone.0247046.
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Interacting Particle Systems (IPSs) are used to model spatio-temporal stochastic systems in many disparate areas of science. We design an algorithmic framework that reduces IPS simulation to simulation of well-mixed Chemical Reaction Networks (CRNs). This framework minimizes the number of associated reaction channels and decouples the computational cost of the simulations from the size of the lattice. Decoupling allows our software to make use of a wide class of techniques typically reserved for well-mixed CRNs. We implement the direct stochastic simulation algorithm in the open source programming language Julia. We also apply our algorithms to several complex spatial stochastic phenomena. including a rock-paper-scissors game, cancer growth in response to immunotherapy, and lipid oxidation dynamics. Our approach aids in standardizing mathematical models and in generating hypotheses based on concrete mechanistic behavior across a wide range of observed spatial phenomena.
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Kourtchev, Ivan, Ricardo H. M. Godoi, Sarah Connors, James G. Levine, Alex T. Archibald, Ana F. L. Godoi, Sarah L. Paralovo, et al. "Molecular composition of organic aerosols in central Amazonia: an ultra-high-resolution mass spectrometry study." Atmospheric Chemistry and Physics 16, no. 18 (September 23, 2016): 11899–913. http://dx.doi.org/10.5194/acp-16-11899-2016.
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Abstract. The Amazon Basin plays key role in atmospheric chemistry, biodiversity and climate change. In this study we applied nanoelectrospray (nanoESI) ultra-high-resolution mass spectrometry (UHRMS) for the analysis of the organic fraction of PM2.5 aerosol samples collected during dry and wet seasons at a site in central Amazonia receiving background air masses, biomass burning and urban pollution. Comprehensive mass spectral data evaluation methods (e.g. Kendrick mass defect, Van Krevelen diagrams, carbon oxidation state and aromaticity equivalent) were used to identify compound classes and mass distributions of the detected species. Nitrogen- and/or sulfur-containing organic species contributed up to 60 % of the total identified number of formulae. A large number of molecular formulae in organic aerosol (OA) were attributed to later-generation nitrogen- and sulfur-containing oxidation products, suggesting that OA composition is affected by biomass burning and other, potentially anthropogenic, sources. Isoprene-derived organosulfate (IEPOX-OS) was found to be the most dominant ion in most of the analysed samples and strongly followed the concentration trends of the gas-phase anthropogenic tracers confirming its mixed anthropogenic–biogenic origin. The presence of oxidised aromatic and nitro-aromatic compounds in the samples suggested a strong influence from biomass burning especially during the dry period. Aerosol samples from the dry period and under enhanced biomass burning conditions contained a large number of molecules with high carbon oxidation state and an increased number of aromatic compounds compared to that from the wet period. The results of this work demonstrate that the studied site is influenced not only by biogenic emissions from the forest but also by biomass burning and potentially other anthropogenic emissions from the neighbouring urban environments.
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Xu, Lin, Cong Wu, Xiao Jing Xu, Bo Quan Li, Xiao Ya Niu, Zhen Huang, and Jian Ning Ding. "The Influences of Frequency on the Fabrication and Structural Studies of Micro-Arc Oxidization Ceramic Films Formed on Pure Titanium." Key Engineering Materials 727 (January 2017): 977–84. http://dx.doi.org/10.4028/www.scientific.net/kem.727.977.
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The porous oxide TiO2 ceramic film containing Ca and P is fabricated on the surface of pure titanium in the electrolyte of C4H6CaO4-NaH2PO4 by micro-arc oxidation (MAO) method. The microscopic structure, elemental composition and phase components of Ceramic Film are studied with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), 3D profilometer and etc. Results indicate that the ceramic film on pure titanium by micro-arc oxidation is a porous mixed crystal structure which contains anatase TiO2 and rutile TiO2, and that the film is mainly composed of such elements as Ti, O, Ca and P. With frequency increasing, the number of micropores increases, the hole is decreased in diameter, porosity and roughness,and the surface is more smooth. The increase of frequencies makes the ratio of Ca/P decrease, the relative content of anatase TiO2 increase and rutile TiO2 decrease.
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Ksepko, Ewelina, and Rafal Lysowski. "Stable Mixed Fe-Mn Oxides Supported on ZrO2 Oxygen Carriers for Practical Utilization in CLC Processes." Catalysts 11, no. 9 (August 29, 2021): 1047. http://dx.doi.org/10.3390/catal11091047.
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The objective of the research was to prepare Fe-based materials for use as oxygen carriers (OCs) and investigate their reactivity in terms of their applicability to energy systems. The performance of ZrO2 supported Fe-Mn oxide oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was analyzed. The influence of manganese addition (15–30 wt.%) on reactivity and other physical properties of oxygen carriers was discussed. Thermogravimetric analyses (TGA) were conducted to evaluate their performance. Multi-cycle tests were conducted in TGA with oxygen carriers utilizing gaseous fuel. The effect of redox cycle number and temperature on stability and oxygen transport capacity and redox reaction rate were also evaluated. Physical-chemical analysis such as phase composition was investigated by XRD, while morphology by SEM-EDS and surface area analyses were investigated by the BET method. For screening purposes, the reduction and oxidation were carried out from 800 °C to 1000 °C. Three-cycle TGA tests at the selected temperature range indicated that all novel oxygen carriers exhibited stable chemical looping combustion performance, apart from the reference material, i.e., Fe/Zr oxide. A stable reactivity of bimetallic OCs, together with complete H2 combustion without signs of FeMn/Zr oxide agglomeration, were proved. Oxidation reaction was significantly faster than the reduction reaction for all oxygen carriers. Furthermore, the obtained data indicated that the materials have a low cost of production, with superior reactivity towards hydrogen and air, making them perfect matching carriers for industrial applications for power generation.
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Velde, B. "Possible chemical controls of illite/smectite composition during diagenesis." Mineralogical Magazine 49, no. 352 (June 1985): 387–91. http://dx.doi.org/10.1180/minmag.1985.049.352.09.
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AbstractRe-interpretation of the significance of phase assemblages present in two sequences of rocks having experienced similar burial diagenesis allows one to establish that the change of oxidation state of iron in sediments could have the effect of changing the smectite content of the mixed layer mineral. This is used to explain an almost isothermal change in the composition of a sequence while others do not show such a rapid change. An indicator of the reaction is seen in the composition of the chlorite present in the rocks which is iron-rich and alumina-poor compared to chlorites in rocks showing a slower rate of change in the smectite content of the mixed-layered mineral. In order to reveal such a relation, one must make an analysis of the clay mineral assemblage, especially in the number of phases present during the course of diagenesis.
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Panasyugin, A. S., L. P. Dolgiy, I. L. Kulinich, A. A. Gerasikova, A. V. Mikishko, N. P. Masherova, and A. R. Tsyganov. "Trends in the use of bentonite clays." Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), no. 4 (December 16, 2020): 78–89. http://dx.doi.org/10.21122/1683-6065-2020-4-78-89.
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The paper gives a general description of the areas of application of bentonite clays. A number of deposits were evaluated in terms of their use in various technological processes. Analysis of directions of application of bentonite clays in foundry was carried out.Using the methods of X-ray and gas chromatographic analysis, scanning electron microscopy, thermogravimetry and direct adsorption-structural measurements, it is shown that materials obtained from montmorillonite and heteronuclear hydroxo complexes Cr-Cu have greater thermal stability and better sorption characteristics compared to montmorillonite fixed by mononuclear hydroxo complexesUsing montmorillonite modified with heteronuclear hydroxo complexes Cr-Cu with the best adsorption-structural parameters and zeolite NCVM, a laboratory batch of mixed adsorbent catalysts has been developed.This material has been studied in deep vapor oxidation processes of low concentrated organic substances such as acetone, toluene, ethyl acetate, ethanol, butanol and butyl acetate.The conversion rate on the mixed adsorbent catalysts for the studied adsorbates was found to be 94.9–97.7 (average 96.2 %).
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Slade, J. H., R. Thalman, J. Wang, and D. A. Knopf. "Chemical aging of single and multicomponent biomass burning aerosol surrogate particles by OH: implications for cloud condensation nucleus activity." Atmospheric Chemistry and Physics 15, no. 17 (September 14, 2015): 10183–201. http://dx.doi.org/10.5194/acp-15-10183-2015.
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Abstract. Multiphase OH and O3 oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low-soluble single-component OA by OH and O3 can increase their water solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate particles exposed to OH and O3 is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type, mixing state, and OH and O3 exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O3 exposure. Following exposure to OH, κ of MNC was enhanced by an order of magnitude, from 0.009 to ~ 0.1, indicating that chemically aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in κ was observed for pure LEV particles following OH exposure. κ of the internally mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH-exposed MNC-coated KS particles is similar to the OH unexposed atomized 1 : 1 by mass MNC : KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions, chemical aging has no significant impact on OA hygroscopicity. The organic compounds exhibiting low solubility behave as if they are infinitely soluble when mixed with a sufficient number of water-soluble compounds. At and beyond this point, the particles' CCN activity is governed entirely by the water-soluble fraction and is not influenced by the oxidized organic fraction. Our results have important implications for heterogeneous oxidation and its impact on cloud formation given that atmospheric aerosol is a complex mixture of organic and inorganic compounds exhibiting a wide range of solubilities.
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Emanuelsson, E. U., M. Hallquist, K. Kristensen, M. Glasius, B. Bohn, H. Fuchs, B. Kammer, et al. "Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties." Atmospheric Chemistry and Physics Discussions 12, no. 8 (August 14, 2012): 20311–50. http://dx.doi.org/10.5194/acpd-12-20311-2012.
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Abstract. Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. Several experiments with exclusively anthropogenic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m−3. The yields (0.5–9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for anthropogenic SOA enabled application of a simplified model to calculate the chemical turnover of the anthropogenic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining at 343 K: 0.86–0.94). The anthropogenic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of anthropogenic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. This change in volatility under dark conditions is likely due to chemical or morphological changes not affecting O/C.
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Laaksonen, A., M. Kulmala, C. D. O'Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K. E. J. Lehtinen, et al. "The role of VOC oxidation products in continental new particle formation." Atmospheric Chemistry and Physics 8, no. 10 (May 20, 2008): 2657–65. http://dx.doi.org/10.5194/acp-8-2657-2008.
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Abstract. Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.
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Laaksonen, A., M. Kulmala, C. D. O'Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K. E. J. Lehtinen, et al. "The role of VOC oxidation products in continental new particle formation." Atmospheric Chemistry and Physics Discussions 7, no. 3 (June 4, 2007): 7819–41. http://dx.doi.org/10.5194/acpd-7-7819-2007.
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Abstract. Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April, 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.
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Draper, D. C., D. K. Farmer, Y. Desyaterik, and J. L. Fry. "A comparison of secondary organic aerosol (SOA) yields and composition from ozonolysis of monoterpenes at varying concentrations of NO<sub>2</sub>." Atmospheric Chemistry and Physics Discussions 15, no. 10 (May 28, 2015): 14923–60. http://dx.doi.org/10.5194/acpd-15-14923-2015.
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Abstract. The effect of NO2 on secondary organic aerosol (SOA) formation from ozonolysis of α-pinene, β-pinene, Δ3-carene, and limonene was investigated using a dark flow-through reaction chamber. SOA mass yields were calculated for each monoterpene from ozonolysis with varying NO2 concentrations. Kinetics modeling of the first generation gas-phase chemistry suggests that differences in observed aerosol yields for different NO2 concentrations are consistent with NO3 formation and subsequent competition between O3 and NO3 to oxidize each monoterpene. α-pinene was the only monoterpene studied that showed a systematic decrease in both aerosol number concentration and mass concentration with increasing [NO2]. β-pinene and Δ3-carene produced fewer particles at higher [NO2], but both retained moderate mass yields. Limonene exhibited both higher number concentrations and greater mass concentrations at higher [NO2]. SOA from each experiment was collected and analyzed by HPLC-ESI-MS, enabling comparisons between product distributions for each system. In general, the systems influenced by NO3 oxidation contained more high molecular weight products (MW >400 amu), suggesting the importance of oligomerization mechanisms in NO3-initiated SOA formation. α-pinene, which showed anomalously low aerosol mass yields in the presence of NO2, showed no increase in these oligomer peaks, suggesting that lack of oligomer formation is a likely cause of α-pinene's near 0% yields with NO3. Through direct comparisons of mixed-oxidant systems, this work suggests that NO3 is likely to dominate nighttime oxidation pathways in most regions with both biogenic and anthropogenic influences. Therefore, accurately constraining SOA yields from NO3 oxidation, which vary substantially with the VOC precursor, is essential in predicting nighttime aerosol production.
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Draper, D. C., D. K. Farmer, Y. Desyaterik, and J. L. Fry. "A qualitative comparison of secondary organic aerosol yields and composition from ozonolysis of monoterpenes at varying concentrations of NO<sub>2</sub>." Atmospheric Chemistry and Physics 15, no. 21 (November 5, 2015): 12267–81. http://dx.doi.org/10.5194/acp-15-12267-2015.
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Abstract. The effect of NO2 on secondary organic aerosol (SOA) formation from ozonolysis of α-pinene, β-pinene, Δ3-carene, and limonene was investigated using a dark flow-through reaction chamber. SOA mass yields were calculated for each monoterpene from ozonolysis with varying NO2 concentrations. Kinetics modeling of the first-generation gas-phase chemistry suggests that differences in observed aerosol yields for different NO2 concentrations are consistent with NO3 formation and subsequent competition between O3 and NO3 to oxidize each monoterpene. α-Pinene was the only monoterpene studied that showed a systematic decrease in both aerosol number concentration and mass concentration with increasing [NO2]. β-Pinene and Δ3-carene produced fewer particles at higher [NO2], but both retained moderate mass yields. Limonene exhibited both higher number concentrations and greater mass concentrations at higher [NO2]. SOA from each experiment was collected and analyzed by HPLC-ESI-MS, enabling comparisons between product distributions for each system. In general, the systems influenced by NO3 oxidation contained more high molecular weight products (MW > 400 amu), suggesting the importance of oligomerization mechanisms in NO3-initiated SOA formation. α-Pinene, which showed anomalously low aerosol mass yields in the presence of NO2, showed no increase in these oligomer peaks, suggesting that lack of oligomer formation is a likely cause of α-pinene's near 0 % yields with NO3. Through direct comparisons of mixed-oxidant systems, this work suggests that NO3 is likely to dominate nighttime oxidation pathways in most regions with both biogenic and anthropogenic influences. Therefore, accurately constraining SOA yields from NO3 oxidation, which vary substantially with the volatile organic compound precursor, is essential in predicting nighttime aerosol production.
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Vesterinen, M., H. Korhonen, J. Joutsensaari, P. Yli-Pirilä, A. Laaksonen, and K. E. J. Lehtinen. "An aerosol dynamics model for simulating particle formation and growth in a mixed flow chamber." Geoscientific Model Development Discussions 4, no. 1 (February 15, 2011): 385–417. http://dx.doi.org/10.5194/gmdd-4-385-2011.
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Abstract. In this work we model the aerosol size distribution dynamics in a mixed flow chamber in which new particles are formed via nucleation and subsequent condensation of oxidation products of VOCs emitted from Norway spruce seedlings. The microphysical processes included in the model are nucleation, condensation, deposition and coagulation. The aerosol dynamics in the chamber is a competition between aerosol growth and scavenging/deposition which results in a cyclic particle formation process. With a simple 1-product model, in which the formed gas is able to both condense to the particles and nucleate, we are able to catch both the oscillatory features of the particle formation process and the evolution of the number concentration in a reasonable way. The gas-phase chemistry was adjusted using pre-estimated reaction rate constant in the simulations and the particle deposition rate as a function of size was determined experimentally. Despite this, some of the essential features of the physical properties of the aerosol population could still be captured and investigated without the detailed knowledge of the physical processes underlying the problem by using the constructed model. The size dependency of the wall loss coefficient was investigated using a slightly modified measurement set-up.
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Liu, Y., S. M. Li, and J. Liggio. "Technical Note: Application of positive matrix factor analysis in heterogeneous kinetics studies utilizing the mixed-phase relative rates technique." Atmospheric Chemistry and Physics 14, no. 17 (September 8, 2014): 9201–11. http://dx.doi.org/10.5194/acp-14-9201-2014.
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Abstract. The mixed-phase relative rates approach for determining aerosol particle organic heterogeneous reaction kinetics is often performed utilizing mass spectral tracers as a proxy for particle-phase reactant concentration. However, this approach may be influenced by signal contamination from oxidation products during the experiment. In the current study, the mixed-phase relative rates technique has been improved by combining a positive matrix factor (PMF) analysis with electron ionization aerosol mass spectrometry (unit-mass resolution), thereby removing the influence of m / z fragments from reaction products on the reactant signals. To demonstrate the advantages of this approach, the heterogeneous reaction between OH radicals and citric acid (CA) was investigated using a photochemical flow tube coupled to a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS). The measured heterogeneous rate constant (k2) of citric acid toward OH was (3.31 ± 0.29) × 10−12 cm3 molecule−1 s−1 at 298 K and (30 ± 3)% relative humidity (RH) and was several times greater than the results utilizing individual m / z fragments. This phenomenon was further evaluated for particulate-phase organophosphates (triphenyl phosphate (TPhP), tris-1,3-dichloro-2-propyl phosphate (TDCPP) and tris-2-ethylhexyl phosphate (TEHP)), leading to k2 values significantly larger than previously reported. The results suggest that heterogeneous kinetics can be significantly underestimated when the structure of the products is highly similar to the reactant and when a non-molecular tracer is measured with a unit-mass resolution aerosol mass spectrometer. The results also suggest that the heterogeneous lifetime of organic aerosol in models can be overestimated due to underestimated OH uptake coefficients. Finally, a comparison of reported rate constants implies that the heterogeneous oxidation of aerosols will be dependent upon a number of factors related to the reaction system, and that a single rate constant for one system cannot be universally applied under all conditions.
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Ng, Nga Lee, Steven S. Brown, Alexander T. Archibald, Elliot Atlas, Ronald C. Cohen, John N. Crowley, Douglas A. Day, et al. "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol." Atmospheric Chemistry and Physics 17, no. 3 (February 13, 2017): 2103–62. http://dx.doi.org/10.5194/acp-17-2103-2017.
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Abstract. Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models. This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.
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Ballerstedt, Hendrik, Eva Pakostova, D. Barrie Johnson, and Axel Schippers. "Approaches for Eliminating Bacteria Introduced during In Situ Bioleaching of Fractured Sulfidic Ores in Deep Subsurface." Solid State Phenomena 262 (August 2017): 70–74. http://dx.doi.org/10.4028/www.scientific.net/ssp.262.70.
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The major objective of the EU Horizon 2020 project “BioMOre” is the technical realization of indirect in situ leaching of Kupferschiefer sandstone and black shale ore by a ferric iron lixiviant generated by a mixed culture of autotrophic, acidophilic, iron-oxidizing bacteria and archaea in a ferric iron-generating bioreactor (FIGB). These organisms could colonize the deeply buried geological formations even under anaerobic conditions as most are able to grow by coupling the reduction of ferric iron to the oxidation of reduced sulfur compounds in the absence of oxygen. Development of an inhibition protocol to eliminate these allochthonous microbial bioreactor populations subsequent to the completion of in situ bioleaching was therefore investigated. Column bioleaching experiments using a laboratory-scale FIGB confirmed not only that metals were solubilised from both the sandstone and shale ores, but also that significant numbers of bacteria were released from the FIGB. The efficacy of 13 different chemical compounds in inhibiting microbial iron oxidation has been tested at different concentrations in shake flask and FIGB-coupled columns. Iron-oxidation activity, microcalorimetrically-determined activity and ATP measurements, in combination with microscopic cell counts and biomolecular analysis (T-RFLP, qPCR), plate counts and most-probable-number (MPN), were used to monitor the inhibiting effects on the acidophiles. Complete inhibition of metabolic activity of iron-oxidizing acidophiles was achieved in the presence of 0.4 mM formate, 300 mM chloride, 100 mM nitrate, 10 mM of primary C6 to C8 alcohols, 100 mM 1-butanol, 100 mM 1-pentanol, 0.1 mM SDS or 0.35 mM benzoic acid. No inhibition was found for 0.6 mM acetic acid and 200 mM methanol. Based on these results a recipe for the chemical composition of the “decommissioning solution” is proposed.
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Hidajat, Marcel Jonathan, Wantaek Jo, Hyeonhyo Kim, and Jongho Noh. "Effective Droplet Size Reduction and Excellent Stability of Limonene Nanoemulsion Formed by High-Pressure Homogenizer." Colloids and Interfaces 4, no. 1 (January 10, 2020): 5. http://dx.doi.org/10.3390/colloids4010005.
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Limonene as an interesting bioactive material that has great benefits due to its antimicrobial and anti-carcinogen properties. However, it has several limitations such as its oxidative and oily nature. In order to overcome these limitations, a high-pressure homogenizer (HPH) was utilized to produce limonene nanoemulsion, which enhances its dispersibility while preventing oxidation with great stability. Limonene was pre-mixed with soybean oil as carrier oil prior to emulsification. The effect of soybean oil to limonene ratio, number of pass, homogenization pressure, emulsifier concentration and homogenization method were observed. A stability test was also conducted for 28 days at room temperature. The result revealed that soybean oil and limonene demonstrated a certain ratio to produce the most stable nanoemulsion. Meanwhile, emulsion size could be reduced from 327.8 nm to 55.5 nm in five passes at 1000 bar. Increasing the emulsifier concentration could reduce the droplet size to 40 nm. A comparison with other emulsification method showed that HPH was the best emulsification technique due to its intense emulsification power resulted from shear, cavitation, and droplet impacts. This study reveals that HPH is a great and simple way to produce stable limonene nanoemulsion for the cosmetic, pharmaceutical, and food industries.
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Asih, Retno, Rosana Martina Dhari, Malik Anjelh Baqiya, Fahmi Astuti, Heru Harsono, Chatree Saiyasombat, Takayuki Kawamata, et al. "Effects of Mn Substitution on Magnetic Properties of ZnO Nanoparticles." Key Engineering Materials 855 (July 2020): 166–71. http://dx.doi.org/10.4028/www.scientific.net/kem.855.166.
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Effects of Mn-substitution on magnetic properties of Zn1-xMnxO (MZO) nanoparticles with x= 0.00, 0.03, 0.05 and 0.07 have been investigated along with their local structure. Study on Mn K-edge XANES spectra of MZO reveals that the oxidation state increases by Mn-substitution, which further implies that MZO exhibits a mixed valence state of Mn3+/Mn4+. The local structure analysis on Mn K-edge EXAFS spectra shows that the coordination number (CN) of Mn reduces by increasing Mn concentration, thus the amount of oxygen vacancy (VO) increases by Mn-substitution. Interestingly, the magnetization of MZO also tend to increase as the Mn concentration increases. The M(H) curves exhibit a linear (paramagnetic) behavior, showing no evidence of room-temperature ferromagnetism. Our results show that magnetism of MZO is related to the correlation between Mn magnetic moment and VO.
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Levett, Alan, Emma J. Gagen, Yitian Zhao, Paulo M. Vasconcelos, and Gordon Southam. "Biocement stabilization of an experimental-scale artificial slope and the reformation of iron-rich crusts." Proceedings of the National Academy of Sciences 117, no. 31 (July 21, 2020): 18347–54. http://dx.doi.org/10.1073/pnas.2001740117.
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Novel biotechnologies are required to remediate iron ore mines and address the increasing number of tailings (mine waste) dam collapses worldwide. In this study, we aimed to accelerate iron reduction and oxidation to stabilize an artificial slope. An open-air bioreactor was inoculated with a mixed consortium of microorganisms capable of reducing iron. Fluid from the bioreactor was allowed to overflow onto the artificial slope. Carbon sources from the bioreactor fluid promoted the growth of a surface biofilm within the artificial slope, which naturally aggregated the crushed grains. The biofilms provided an organic framework for the nucleation of iron oxide minerals. Iron-rich biocements stabilized the artificial slope and were significantly more resistant to physical deformation compared with the control experiment. These biotechnologies highlight the potential to develop strategies for mine remediation and waste stabilization by accelerating the biogeochemical cycling of iron.
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Emanuelsson, E. U., M. Hallquist, K. Kristensen, M. Glasius, B. Bohn, H. Fuchs, B. Kammer, et al. "Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties." Atmospheric Chemistry and Physics 13, no. 5 (March 11, 2013): 2837–55. http://dx.doi.org/10.5194/acp-13-2837-2013.
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Abstract. Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of α-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m−3. The yields (0.5 to 9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (&approx;8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86–0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. The SOA yields, O/C, and f44 (the mass fraction of CO2+ ions in the mass spectra which can be considered as a measure of carboxylic groups) in the mixed photo-chemical experiments could be described as linear combinations of the corresponding properties of the pure systems. For VFR there was in addition an enhancement effect, making the mixed aerosol significantly less volatile than what could be predicted from the pure systems. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. Thus, this change in volatility under dark conditions as well as the anthropogenic enhancement is due to chemical or morphological changes not affecting O/C.
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Hall, James M., and Brian E. Fisher. "The Iceland Research Drilling Project crustal section: stable remagnetization below 3 km crustal depth." Canadian Journal of Earth Sciences 25, no. 8 (August 1, 1988): 1304–15. http://dx.doi.org/10.1139/e88-125.
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A section at below 3.1 km depth in Icelandic crust, sampled in the 1978 Icelandic Research Drilling Project drill hole, contains a number of subaerially deposited lava flows showing both downwards and probably original upwards inclinations of cleaned, stable remanent magnetization. Such "mixed polarities" are inconsistent with an initial cooling thermoremanent origin for the magnetization. An attempt is made to identify the factors involved in producing these mixed polarities and to consider the possible wider importance of the results. The mixed-polarity flows have experienced intense hydrothermal alteration, followed by the widespread deposition of secondary magnetite. Secondary magnetite, which is formed in relatively anhydrous conditions associated with dike intrusion, dominates primary magnetite volumetrically where dike density locally exceeds about 30%.Where secondary magnetite is very dominant or is the only type of magnetite present, directional remagnetization appears to be uniform and complete. Where secondary and primary magnetite are both important, relatively high remanence and saturation magnetizations, total magnetite and primary magnetite grain size, and low deuteric oxidation state of primary magnetite are all associated with downwards directional remagnetization. It appears that a complex balance of the properties and history of primary and secondary magnetite, in addition to the relative abundances of these phases, controls the final stable polarity of samples.If the narrow transition zones between little-altered extrusives, greenschist-facies flows and dikes of the Troodos (Cyprus) ophiolite, and DSDP hole 504B are typical of oceanic crust, a narrow ~0.2 km interval of mixed polarities may be underlain in some locations by an intermediate crustal layer in polarity opposition with the uppermost, little-altered, extrusive layer.
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Debellefontaine, H., F. X. Cammas, G. Deiber, J. N. Foussard, and P. Reilhac. "Wet air oxidation: kinetics of reaction, carbon dioxide equilibrium and reactor design - an overview." Water Science and Technology 35, no. 4 (February 1, 1997): 111–18. http://dx.doi.org/10.2166/wst.1997.0098.
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Aqueous wastes containing organic pollutants can be efficiently treated by wet air oxidation (WAO), i.e. oxidation by molecular oxygen in the liquid phase, under high temperature (200 to 325°C) and pressure (up to 150 bar). In western Europe, only an handful of industrial plants are in operation. Most of them were designed by extrapolating results from pilot plants. Only a very few studies have been devoted to the scientific design of such reactors (bubble columns). This paper discusses what needs to be known for this scientific design. The usual design methods assume that the column is divided into a number of cells. Each cell is a perfectly mixed reactor connected with the contiguous cells. Reliable data and models are available for hydrodynamics (axial dispersion, gas hold up) and mass transfer. Data are also needed for the kinetics of chemical reactions and are available from numerous sources, but have not yet been generalised. The thermodynamics (fugacities and enthalpy) of the gas phase can be determined with the Peng Robinson equation of state, and the Henry law for the solubility of gases in water describes the equilibrium conditions. But additional data are needed for water solutions containing salts. This paper describes a method that allows such a determination to be made by establishing rigorous balances on a batch autoclave. At present, these data are being used to implement a computer program aimed at determining the performance of a wet air oxidation reactor depending on the various operating parameters. Some typical profiles within the reactor are presented, establishing that the pH of the solution is a very important parameter.
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El-Shobaky, G. A., A. M. Ghozza, and S. Hammad. "Effect of Na2O Doping on the Surface and Catalytic Properties of the Mn2O3/Al2O3 System." Adsorption Science & Technology 12, no. 2 (June 1995): 119–28. http://dx.doi.org/10.1177/026361749501200204.
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Manganese/aluminium mixed oxide solids having the formula 0.2MnCO3/Al2O3 were prepared by mechanical mixing of a known weight of finely powdered manganese carbonate and aluminium hydroxide. The solids obtained were treated with NaNO3 (0.75–6 mol%) solution and dried at 110°C, then calcined in air at 500°C and 800°C for 6 h. The phases produced were identified by XRD analysis. The surface properties (SBET, Vp and r̄) of the pure and doped solids were studied by using N2 adsorption at – 196°C and their catalytic activities were determined by studying the oxidation of CO by O2at 125–300°C. The results obtained reveal that pure and doped mixed solids preheated in air at 500°C and 800°C consist of Mn2O3 (partridgite) and a poorly crystalline γ-alumina. Doping with sodium oxide at 500°C and 800°C resulted in a small decrease (14–19%) in the SBET value of the treated solids. However, this treatment brought about a significant modification in the catalytic activity of the doped solids. Doping with 0.75% Na2O at 500°C led to an increase of about 30–50% in the specific catalytic activity which was found to decrease on increasing the percentage of Na2O above this limit, falling to values smaller than that measured for the undoped catalyst. Doping at 800°C led to a progressive decrease in the activity of the treated solid to an extent proportional to the amount of dopant present. The doping process at 500°C and 800°C did not modify the mechanism of the catalytic reaction but altered the number of catalytically-active sites contributing in the catalysis of CO oxidation by O2 without changing their energetic nature.
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Weil, Matthias, Berthold Stöger, Annemarie L. Wessels, and Wolfgang Jeitschko. "Synthesis and Crystal Structure of Hg2V8O20 – the First Ternary Mercury Vanadate with Mixed-valent Vanadium (IV/V)." Zeitschrift für Naturforschung B 62, no. 11 (November 1, 2007): 1390–96. http://dx.doi.org/10.1515/znb-2007-1107.
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Black needle-shaped single crystals of Hg2V8O20 were obtained by heating amorphous precipitates resulting from mixing aqueous solutions of HgNO3OH and NH4VO3 (Hg :V ratios between 1 : 2.0 and 1 : 2.5) in evacuated silica ampoules at 450 °C for two weeks. Their crystal structure was determined from single crystal diffractometer data [C2/m, Z = 2, a = 22.375(1), b = 3.6312(2), c = 9.6113(4) Å, β = 91.708(5)°, R[F2 ≥ 2σ (F2)] = 0.0681, 807 F2 values, 61 variable parameters]. Two of the four independent vanadium atoms are surrounded by six close oxygen atoms whereas the other two have five oxygen neighbors. These coordination polyhedra share edges and corners resulting in puckered layers with an overall composition [V4O10]− extending parallel to (100). The layers are linked by Hg22+ dumbbells (d(Hg-Hg) = 2.510(2) Å) with a short Hg-O distance of 2.13(2) Å(∠(O9−Hg-Hg) = 173.8(5)°). Although Hg2V8O20 crystallizes in a new structure type, it resembles the structures of other layered vanadium oxides with open frameworks and can be classified as being of the Q-UD-type. The near-neighbor environments of the four vanadium positions of this reduced vanadate with an average oxidation number of +4.75 of the vanadium atoms are similar with respect to V-V bonding and it is suggested that the vanadium atoms have delocalized V-V bonding with intermediate valence.
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Huang, Ying, Yan Xiong, Zhong Bin Ye, and Zhu Jun Zhang. "Flow Injection on Line Oxidizing Fluorometry Coupled to Microdialysis Sampling for Studying Phentolamine-Bovine Serum Albumin Interaction." Advanced Materials Research 554-556 (July 2012): 2093–97. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.2093.
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Determination of phentolamine-bovine serum albumin (BSA) interaction based on a flow-injection microdialysis sampling fluorescence system (FI-MD-FL) was proposed. The analytical procedure was based on the oxidation of phentolamine by acidic Ce(IV) and monitoring of the fluorescence intensity of the formed Ce(III). The drug of phentolamine and BSA were mixed in different molar ratios in Ringer’s solution and incubated in a water bath. The microdialysate samples were on-line merged with acidic Ce(IV) solution by putting a microdialysis probe into the mixed solution and perfused with Ringer’s solution at 10 μL min-1. Then the sample was reached the flow cell, excited and monitored at 256/355nm (λex/λem). The dialytic efficiency under the experimental conditions was 38.8±2.2% (n=3). The data obtained was analyzed with Scatchard analysis and Klotz plot. The estimated association constant (K) and the number of the binding site (n) on one molecule of BSA by Scatchard analysis were 1.78×105 L mol-1 and 0.69, respectively. The proposed method has been applied to the study of the binding of phentolamine to bovine serum albumin (BSA) in vitro. The method provided a fast and simple technique for the study of drug-protein interactions.
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Panasyugin, A. S., N. P. Masherova, A. R. Tsyganov, and N. D. Pavlovsky. "Neutralization of solvent vapors of brand 646 by the adsorption-catalytic method." Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), no. 1 (March 26, 2021): 130–36. http://dx.doi.org/10.21122/1683-6065-2021-1-130-136.
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The aim of the paper is investigation of neutralization of solvent vapors of the brand 646 by an adsorption-catalytic method. The adsorption-catalytic method includes the following stages: adsorption of the solvent components by adsorbent, thermal desorption and periodic flameless catalytic oxidation of organic substances to carbon dioxide and water. Synthetic zeolite of the NaX brand was used as a sorbent, catalyst was porous Al2O3/SiO2 ceramic foam material with an active catalytic phase. Solvent contains aceton, toluene, butylacetate, ethanol, ethyl cellosolve, n-butanol. It is shown that the value of the sorption volume of zeolite for each class of compounds depends on the certain factors: the length and structure of the carbon skeleton, the position of the hydroxyl group (for alcohols and esters), number of methyl groups in the molecules (for benzene derivatives). The conversion of the mixed solvent components was 65.4–90.1 %.
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Li, Chunlin, Quanfu He, Julian Schade, Johannes Passig, Ralf Zimmermann, Daphne Meidan, Alexander Laskin, and Yinon Rudich. "Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging." Atmospheric Chemistry and Physics 19, no. 1 (January 4, 2019): 139–63. http://dx.doi.org/10.5194/acp-19-139-2019.
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Abstract. Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in NOx-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is 1.661+0.020i and 1.635+0.003i for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of NOx diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (N2O) was used to simulate NOx-dependent photochemical aging of tar balls in the OFR. Under high-NOx conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.