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In this work, we fabricated gold nanoparticles (AuNPs) capped with both polyvinyl pyrrolidone (PVP) and iodine (I2) to act as efficient chemiluminescent coreactants for luminol. AuNPs synthesis was based on the direct chemical reduction of Au3+ with NaBH4 in the presence of PVP-I2 complex. The successful synthesis of PVP-I2@AuNPs was confirmed with scanning electron microscopy (SEM) and UV-vis spectrophotometry. Chemiluminescence (CL) intensity of luminol was greatly enhanced, upon its chemical reaction with chemisorbed I2 on AuNPs surfaces owing to the excellent catalytic activity of AuNPs. The PVP-I2@AuNPs/luminol CL sensing system was successfully applied for determination of Hg2+ ions and the results displayed linearity in a wide range from 0.5 to 2000 nM and an ultrasensitive response to 1.0 nM Hg2+. The detection limit of Hg2+ ions was 0.1 nM, which was 100 times lower than the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. This ultrasensitive luminogenic system for Hg2+ detection also exhibited excellent selectivity among 13 types of metals, suggesting that the luminol/PVP-I2@AuNPs system is a promising sensor for real-time detection of Hg2+. [ABSTRACT FROM AUTHOR]

While temporal considerations are of prime importance for chemical reactions, as well as for molecular stability, most chemical concepts (outside of the field of chemical kinetics) are not explicitly formulated on a diachronic basis (Earley in Found Chem 14:235, 2012). It will be argued here that a formulation explicitly incorporating temporal and epistemological considerations enables us to treat chemical reactions and chemical substances on ontologically equivalent terms, instead of assigning a more fundamental status to the latter. After all, in collision theory, a chemical substance is just a collision complex (a "resonance") that takes too long. How long qualifies as "too long", and "too long" in relation to what, are crucial questions that distinguish chemical substances from chemical reactions, and reversible reactions from irreversible ones, thereby introducing anthropocentric considerations into these distinctions. Too long for a lab chemist is very different from too long for an astrochemist studying chemical reactions between chemical substances in inter-stellar space on cosmological timescales. Examining several physical and chemical properties on the basis of which chemical substances are distinguished from one another, the role of temporal and anthropocentric considerations in defining molecular properties is emphasized. I conclude with some observations on the much-debated reduction of chemistry to other disciplines, arguing that such reduction depends on our aesthetic choices as to what kinds of observations demand explanation, and what kinds of explanation are acceptable. [ABSTRACT FROM AUTHOR]

In this paper, silver nanoparticles (Ag NPs) were successfully prepared in situ by chemical pulp fiber (CPF) without any additional reductants. In the green synthesis of Ag NPs, CPF acted as both a weak reductant and a stable carrier. The effect of different synthesis conditions was investigated, and the Ag NP load rate was up to 28.12 wt%. The size of the Ag NPs followed a standard Gaussian distribution, ranging from 10 to 50 nm, and a face-centered cubic structure was identified by XRD and TEM. In addition, the AgNPs/CPF composites exhibited good thermostability below 280 °C according to TG analysis. Owing to the high load rate and large specific surface area of Ag NPs, AgNPs/CPF composites exhibited excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. The conversion rate was up to 95.91% after recycling 50 times, and the catalyst was easily separated from the reaction system. Based on the advantages of high conversion rate, excellent catalytic activity and reusability, AgNPs/CPF composites hold tremendous potential in eliminating nitrophenol and its derivatives from industrial pollution. [ABSTRACT FROM AUTHOR]

The formation of N2O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt-Ba/Al2O3 and Pt/Al2O3 catalysts with H2 and/or C3H6 as reductants. This allows to provide further insights on the mechanistic aspects of N2O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N2O evolution is observed at both lean-to-rich (primary N2O) and rich-to-lean (secondary N2O) transitions. The production of both primary and secondary N2O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N2O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al2O3 catalyst. These results suggest that: (i) primary N2O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N2O originates from reaction between adsorbed NH3 and residual NOx at the beginning of the lean phase. Moreover, N2O reduction was studied performing temperature programming temperature experiments with H2, NH3 and C3H6 as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt-Ba/Al2O3 catalyst, while lower temperatures are detected for Pt/Al2O3 catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H2 a high reactivity in the reduction of N2O, it could react with N2O when the regeneration front is developing. Moreover, also ammonia present downstream to the H2 front could react with N2O, even if the reaction with stored NOx seems more efficient. [ABSTRACT FROM AUTHOR]

Using the effects of chemical polarization of nuclei, mechanism and elementary stages of photochemical reduction of 2,6-diphenyl-1,4-benzoquinone with thiols have been elucidated. The studied quinone is reduced with ethanethiol in two stages (transfer of electron followed by proton transfer). The final photolysis product is a derivative of dibenzofuran. [ABSTRACT FROM AUTHOR]

At present, air cooling and water quenching are traditional treatment methods for molten copper slag. However, the waste heat and valuable metals cannot be recovered efficiently by these methods. Exergy efficiency (EE) of this method is only 21.0%. This paper describes a feasibility of waste heat recovery and direct reduction of copper slag. To investigate the feasibility of this new thermal energy recovery and direct reduction system (TER-DR), thermodynamic compass method was applied. Based on physical and chemical recovery methods, TER-DR1 and TER-DR2 systems are put forward. TER-DR1 system decreases the exergy loss (EXL) and improves the EE to 57.3%, and 0.489 t DRI is acquired for every ton of copper slag. Exergy of six kinds of typical endothermic chemical reactions was analyzed. The exergy of reforming reaction of CH4 by CO2 is the highest and suitable for TER-DR system. Combined with chemical method, TER-DR2 system decreases EXL further and improves the EE to 61.3%. Steam, synthesis gas and DRI are produced by this method. By TER-DR2, for every ton of copper slag, 0.489 t DRI, 67.3 m3 CO and 67.3 m3 H2 are acquired. [ABSTRACT FROM AUTHOR]

Silver nanoparticle-decorated graphene oxide was prepared using a simple green chemical reduction method, and its performance being used for surface-enhanced Raman scattering detection and optical limiting was studied. TEM images, photoluminescence quenching effect and the characteristic absorption peaks of GO and silver nanoparticles confirm the successful preparation of GO-Ag nanocomposite. The Raman spectra results show that the vibration fingerprints of RhB and R6G moleculars are detected only on the GO-Ag substrate, revealing good potential of being used as surface-enhanced Raman scattering substrate for detecting organic molecules. Additionally, nonlinear optical absorption of GO-Ag was measured using z-scan technique with a nanosecond laser operating at the wavelength of 532 nm. The z-scan results show that the transmittance of GO-Ag aqueous suspension has a large decline of 90%, and the nonlinear optical absorption onset input fluence of GO-Ag dispersed PVA film is as low as 1.3 J/cm, indicating that GO-Ag is a good potential optical limiting material for the commonly used high-power 532 nm nanosecond pulsed laser. [ABSTRACT FROM AUTHOR]

We have investigated the preparation of molybdenum powders by reducing the oxide compounds MoO, MgMoO, and CaMoO with magnesium vapor at residual argon pressures in the range 5-20 kPa and temperatures in the range 700-800°C. Using the MgMoO and CaMoO compounds as precursors, we have obtained molybdenum powders with specific surface areas of up to 20 m/g. The powders have a mesoporous structure. The reduction of the molybdenum compounds under such conditions was accompanied by separation of the reaction products due to the removal of magnesium oxide from the reaction zone. [ABSTRACT FROM AUTHOR]

In this work, the reduction and oxidation of hydrogen peroxide on Au single crystals is studied in weakly adsorbing electrolytes. Results are discussed in terms of the potential of zero charge and the adsorption strength of different anions, which in turn depend on the crystallographic orientation of the electrode. Close to the reaction onset, both reactions follow the same activity trend with Au(100) and Au(111) being the most and the least active surface planes, respectively. At high potentials, gold oxides inhibit the oxidation of HO, which seems to be controlled by a surface process. [ABSTRACT FROM AUTHOR]

Proceeding from TeCl and 1-octene a regioselective method was developed of the synthesis of trichloro(2-chlorooctyl)tellane. At adding methanol to this compound chlorine was easily replaced at room temperature by a methoxy group affording trichloro(2-methoxyoctyl)tellane. The reaction of TeBr with 1-octene in methanol resulted in tribromo(2-methoxyoctyl)tellane. A reduction of trichloro- and tribromo(2-methoxyoctyl)tellanes occurs the most selectively in the system NaBH4-water-THF giving 1,2-bis(2-methoxyoctyl)ditellane. The reactions are characterized by a high selectivity and quantitative yields of the products. [ABSTRACT FROM AUTHOR]

The authors describe a method for the fabrication of graphene micro-aerogels (GMA) using a multiple emulsion as a soft template. A mixed surfactant consisting of polymannitol oleate ester and polyoxyethylene castor oil was dissolved in toluene. An aqueous dispersion of graphene oxide was dropped into the above solution to produce a water-in-oil-in-water multiple emulsion. Hydrazine was used to reduce the graphene oxide. The partly reduced sheets of graphene oxide diffuse into the oil phase due to their low polarity. This induces the self-assembly of graphene sheets at the oil-water interface to finally form GMA. Following freeze drying and thermal annealing at 900 °C under Ar/H, GMA is obtained which possesses a microcapsule-like structure, high electrical conductivity (3250 S m), a large specific surface (1253 m g) and a well-defined porous structure. A glassy carbon electrode modified with the GMA shows ultrahigh sensitivity for the electrochemical detection of p-acetamidophenol. The differential pulse voltammetric peak current increases linearly over the 1 × 10 to 8.0 × 10 M p-acetamidophenol concentration range, and the detection limit is 5.7 × 10 M (at an S/N ratio of 3). The sensitivity is much better than that of sensors based on the use of graphene, graphene aerogel, or high density graphene aerogel. The method was successfully applied to the determination of p-acetamidophenol in tablets. The study also provides promising prospects in terms of graphene aerogel materials with improved electrochemical performance in electrocatalysis, supercapacitors and lithium ion batteries. [ABSTRACT FROM AUTHOR]

Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV-Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold-silver bimetallic nanoparticles. [ABSTRACT FROM AUTHOR]

Tellurium tetrabromide readily reacted with 2-allylphenol at room temperature in acetonitrile to give previously unknown tribromo(2,3-dihydro-1-benzofuran-2-ylmethyl)-λ4-tellane in quantitative yield. The reduction of the product afforded bis(2,3-dihydro-1-benzofuran-2-ylmethyl)ditellane and benzyl(2,3-dihydro-1-benzofuran-2-ylmethyl)tellane. [ABSTRACT FROM AUTHOR]

The W-AlO system at T = 2400 K and standard pressure (controlled Ar + H atmosphere) has been calculated by stochastic simulation. It is shown that the presence of hydrogen leads to the formation of aluminum hydrides, hydrogen oxides, and aluminum hydroxides; the compounds from the two latter groups (except for water) can interact directly with tungsten. The main chemical reactions occurring in the system are determined, based on which a conclusion about the cyclic character of the processes is drawn. Some recommendations on the composition and pressure of controlled atmosphere for growing sapphire crystals are given. [ABSTRACT FROM AUTHOR]

In methanol, FeCl reacted readily with L1H ( L1H = bis(1-isoquinolylcarbonyl)amide) and afforded a complex having the formula [Fe( L2)Cl] ( 1) { L2 = N-((1-isoquinolyl)(methoxy)methyl)isoquinoline-1-carboxamide ion}. This reaction involves reduction of one of the two carbonyl groups present in L1H to (methoxy)methyl group. A plausible mechanism for the conversion of L1H to L2 has been proposed. Determination of molecular structure of 1 confirmed this conversion. Fe(III) ion is surrounded by three nitrogen atoms of the ligand and two chloride ions, imparting a rare distorted trigonal bipyramidal NCl coordination environment. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, the results of the study of the reduction of basic lead sulphate with a gas (CO + CO) mixture are presented. This is a secondary reaction during the reduction of lead sulphate. The change in the both lead and PbS content in the reaction products, depending on the process temperature and the composition of the gaseous phase, was established. The comparison of the rate of the reduction reaction of lead sulphate and basic lead sulphate shows that the process proceeding with a higher output is the reduction of basic lead sulphate. [ABSTRACT FROM AUTHOR]

The mechanism of reducing silver(I) oxide particles to silver metals was studied using myristyl alcohol as a reducing agent. The reduction temperature of silver oxide with myristyl alcohol decreased to 150 °C from the temperature of silver oxide in air, 400 °C. The reduction temperature was decreased by myristyl alcohol reacting with silver oxide, which was confirmed by our reaction equation model obtained by gas chromatography determination, pyrolysis gas chromatography-mass spectrometry, and Karl Fischer titration. An endothermic of 153.7 kJ mol in the reduction of silver oxide with myristyl alcohol calculated from the reaction model using Hess's law was coincident with that obtained experimentally by differential scanning calorimetry measurements. [ABSTRACT FROM AUTHOR]

Anhydrous ytterbium chloride was obtained via solid-phase reaction from YbO with AlCl as a chlorination agent. The electrochemical behavior of the chloridized YbO was investigated on W electrodes in LiCl-KCl and LiCl-KCl-AlCl melts by cyclic voltammetry and square wave voltammetry. The results showed that the reduction/reoxidation of Yb(III)/Yb(II) was reversible and controlled by diffusion. The signals related to the formation of two Al-Yb intermetallic compounds were detected in LiCl-KCl-AlCl melt. Potentiostatic electrolysis was carried out in LiCl-KCl-AlCl-YbCl melt on W electrodes at 943 K at different potentials and AlYb, AlYb, AlLi and AlLi phases were detected in deposits. Then, the extraction of ytterbium was performed. The currents evolution was recorded by square wave voltammetry and the extraction efficiency was evaluated via inductive coupled plasma atomic emission spectrometer analysis during electrolysis. The initial extraction rate is much higher than that at longer times. The extraction efficiency was about 98.0 % for Yb(III) after potentiostatic electrolysis for 60 h at −1.84 V in LiCl-KCl-AlCl-YbCl melt. [ABSTRACT FROM AUTHOR]

A method for synthesis of radiolabelled silver nanoparticles is reported. The method is based on proton activation of silver metal powder, enriched in 107Ag, with a 30.7 MeV proton beam. At this proton energy 105gAg is efficiently created, mainly via the 107Ag(p,3n) 105Cd →  105gAg reaction. 105gAg has a half-life of 41.29 days and emits easily detectable gamma radiation on decay to 105Pd. This makes it very useful as a tracing radionuclide for experiments over several weeks or months. Following activation and a period to allow short-lived radionuclides to decay, the powder was dissolved in concentrated nitric acid in order to form silver nitrate (AgNO 3), which was used to synthesise radiolabelled silver nanoparticles via the process of sodium borohydride reduction. For comparison, non-radioactive silver nanoparticles were synthesised using commercially supplied AgNO 3 in order to check if the use of irradiated Ag powder as a starting material would alter in any way the final nanoparticle characteristics. Both nanoparticle types were characterised using dynamic light scattering, zeta-potential and X-ray diffraction measurements, while additionally the non-radioactive samples were analysed by transmission electron microscopy and UV–Vis spectrometry. A hydrodynamic diameter of about 16 nm was determined for both radiolabelled and non-radioactive nanoparticles, while the electron microscopy on the non-radioactive samples indicated that the physical size of the metal NPs was (7.3 ± 1.4) nm. [ABSTRACT FROM AUTHOR]

ZrB-AlO nanocomposite powder was produced by aluminothermic reduction in Al/ZrO/BO system. In this research, high energy ball milling was used to produce the necessary conditions to induce a mechanically induced self-sustaining reaction. The ignition time of the composite formation was found to be about 13 min. The synthesis mechanism in this system was investigated by examining the corresponding sub-reactions as well as changing the stoichiometry of reactants. Thermal behavior of the system was also studied. [ABSTRACT FROM AUTHOR]

In the present article, various nanometric FeNi alloys were synthesized by chemical reduction of the corresponding metal ions, with hydrazine in an aqueous solution. Process variables of reaction temperature, pH of the hydrazine solution and concentration of metal ions were varied in order to determine the optimum synthesis conditions regarding quality, productivity and cost. It is found that pH of hydrazine solution, at low concentration of metal ions, is the most crucial variable affecting the reaction rate, average crystallite and particle sizes of the synthesized nanometric FeNi alloy, followed by the total concentration of metal ions. Thus, increase of pH of hydrazine solution acts as an efficient stabilizer in reducing the particle size. On the contrary, at high concentration of metal ions, the structural characteristics of the nanometric FeNi alloy are almost insensitive to reaction temperature and pH of hydrazine solution, but the reduction rate is remarkably sensitive to reaction temperature. Based on these results, it is decided that a reaction temperature of 80 °C, pH of the hydrazine solution of 12·5 and concentration of metal ions of 0·6 M represent the optimum synthesis conditions. The role of pH of hydrazine solution in reducing the alloy's average particle size as well as efficient stabilizer confirms tremendous effect of synthesis conditions on the alloy structure and therefore, the importance of this study for industrial production of nanometric FeNi alloy. [ABSTRACT FROM AUTHOR]

COREX is the primary process in the current smelting reduction method. The process has strict coal quality standards. Combustion processes of coal used in the COREX operating system were analyzed using a synchronous thermogravimetric analyzer combined with a mass spectrometer. The microcosmic structure and macerals were observed by an electronic scanning microscope. The qualitative and quantitative determinations of oxygen functional groups, such as phenolic hydroxyl, carboxyl, carbonyl, and methoxy groups were detected by the Fourier Transform Infrared spectrometer (FT-IR) and through chemical analysis methods. In addition, the evolution of the chemical structure and transformation mechanism of organic oxygen functional groups during COREX coal combustion have been thoroughly investigated. This study proposes a new coal-requirement index system and coal blending method, which will increase the expansion of coal selection and decrease the overall usage of coal during COREX. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC) is an important material mostly used for cutting-tool applications. The reduction of WO to WC is realized by using several techniques. The existing chemical processes involved in its reduction are long and energy consuming. In our work, we make efforts to reduce WO to WC by the reflux reaction technique. The composite obtained after the reflux reaction is analyzed to check the feasibility of conversion of WO to WC. The preliminary study demonstrates the feasibility of this conversion. The proposed technique seems to be promising and cost-effective for the low-temperature synthesis of ultrafine WC particles. The synthesized powders are studied with the help of X-ray diffraction, scanning electron microscope, energy dispersive X-rays, and transmission electron microscopy for the phase identification and microstructural analyses. [ABSTRACT FROM AUTHOR]

Role of carotenoid end groups on their chain-breaking potency against lipid peroxidation was explored using density functional theory. Hydrogen abstraction and addition of the peroxide and O of the resultant radicals were investigated. The protective potency of CARs is exhibited by their faster reactions with the peroxide radical than fatty acid, and by the much reduced reactivity of the initiated radical toward O. 3,3′-Dihydroxyisorenieratene (DHIR), which consists of hydroxyaryl (3-hydroxy-ϕ) end groups, is by far the most efficient chain-breaking antioxidant. The quinone form of DHIR is also an effective antioxidant. 4-Oxo functional group in β-ring enhances the antioxidative potency of carotenoids, while 3-hydroxyl functional group in β-ring does not have a noticeable effect. [ABSTRACT FROM AUTHOR]

The detailed reaction mechanism of Di-Air, which showed the unprecedented high deNO performance at high temperature conditions, was studied in this work. Since the Di-Air phenomenon occurs with continuous short pulse injections of hydrocarbons over NSR (NO storage and reduction) catalyst, this study focused on the specific function of HC as an effective reductant for NO reduction reaction. As a first step, the deNO performance was compared with three different reductant gases including CO, H and CH in a modified synthetic gas bench equipped with a gas injector which enables continuous small amount of injections. At inlet gas temperature of 450 °C CH showed the best deNO performance whereas H was the best at 150 °C. Moreover the result of temperature programmed desorption showed that intermediate species represented by -NCO (isocyanates) produced from CH was thermally more stable than that produced from CO. These results confirmed that the injected HC reacts with adsorbed NO on NSR catalyst generating thermally stable intermediates, which could contribute the high deNO performance at high temperature conditions. [ABSTRACT FROM AUTHOR]

This study is devoted to an operando study of Pt-Rh/AlO-BaO lean-NO trap catalyst during the regeneration with H/CO reaction mixture. Particular attention was paid to the influence of CO coexisting with H during the regeneration that can simulate the regeneration step by using reformate composed of CO and H. In rich H mixture ammonia predominantly forms. As expected, strongly chemisorbed CO molecules over noble metals lower the efficiency of the trap at 150 °C. Successive hydrogenation of N atoms to ammonia predominates in our conditions. However, the comparison of the outlet gas composition with infrared spectral features also suggests a minor participation of isocyanate species (NCO) as possible intermediates in the production of ammonia especially for long regeneration duration in the absence of water. Interestingly, ammonia formation as reducing agent for the selective reduction of NO can stimulate practical applications for further coupling lean-NO trap with SCR catalysts. [ABSTRACT FROM AUTHOR]

This paper characterizes the integrated activity of fresh and used catalysts on the selective catalytic reduction of NO x using CH. The synthesised K-Ag/AlO catalysts exhibited a promotional effect on deNO x activity in the presence of SO. In addition, 130 h of time-on-stream reactions demonstrated the thermal and mechanical stability of the synthesised materials. A TEM analysis and diffraction patterns demonstrated the sintering of finely dispersed particles to ~0.5 micron size clusters by sulphation. Furthermore, under reaction conditions, the de-sulphation initiated the re-dispersion of the Ag clusters to different sized particles. The TPD studied demonstrated the strong adsorption sites for methane and formation of R-SO x compounds. This surface modification in the SO feed stream is considered to be the reason for the promotional effect on the deNO x reaction. [ABSTRACT FROM AUTHOR]

Chemoselective synthesis of 2-nitroalkanols catalyzed by electro-generated base (EGBs) in the presence of acetonitrile and lithium perchlorate has been studied by cyclic voltammetry and controlled potential electrolysis techniques. Cathodic reduction of nitromethane at platinum cathode produces organic anion which acts as EGBs and undergoes condensation with carbonyl group of substituted aldehydic substrate to produce 2-nitroalkanols in 75-85 % yields. The controlled nucleophilicity of EGBs in organic solvent during electrochemical reaction makes it chemoselective which is a unique feature of this work. [ABSTRACT FROM AUTHOR]

In this study, iron-mediated activator generated by electron transfer for atom transfer radical polymerization of methyl methacrylate was carried out using two different types of salts, acidic hydroxylamine hydrochloride and basic sodium bisulfite as the reducing agents, ethyl 2-bromoisobutyrate as an initiator, FeCl·6HO as a catalyst and triphenylphosphine (PPh) as a ligand. The polymerization could be carried out in the presence of a limited amount of oxygen (air) and showed highly efficient catalyst activity. The living features were confirmed by the polymerization kinetics, analysis of chain end, and chain-extension experiment. [ABSTRACT FROM AUTHOR]

An efficient synthesis of N-mono-substituted β-amino tertiary thiols by reductive ring-opening of 3-thiazolines, obtained by use of the Asinger reaction, is described. This synthesis be regarded as a complementary approach for aminolytic ring-opening of thiiranes. [ABSTRACT FROM AUTHOR]

Feasibility of multidimensional hydrodynamic modeling depends critically on the availability of accurate reduced kinetic mechanisms of physical and chemical processes taking place in the system. Such mechanisms should describe the processes under consideration within a specified error tolerance in the range of initial conditions of interest while keeping the number of species and reactions as small as possible. We have developed an advanced tool for reduction of detailed kinetic mechanisms with a minimal human effort. The tool includes 10 reduction and 2 analysis methods which are based on the results of zero-dimensional modeling. The methods can be combined and applied in sequence. The reduction tool has been implemented as a part the Chemical Workbench computational package and has been tested for a number of large kinetic mechanisms of gas-phase processes. Using this tool, we reduced the mechanism of tar gasification from 177 species and 879 reversible reactions to only 83 species and 278 reactions, while the mechanism of methane combustion initially involving 127 species and 1,206 reactions was reduced to 42 species and 173 reactions. [ABSTRACT FROM AUTHOR]

Polarographic behavior of 2,4-dinitrobenzene and products of its reduction, 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline, is studied: it is shown that formation of the corresponding chloronitroanilines in the case of polarographic reduction of 2,4-dinitrochlorobenzene is rather problematic. 0.1 M NaOH is recommended as the supporting solution for analytical control of conversion of 2,4-dinitrochlorobenzene and a mixture of 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline in reaction solutions obtained by preparative electroreduction of 2,4-dinitrochlorobenzene. [ABSTRACT FROM AUTHOR]

Results are provided for an experimental study of an improvement in periclase-carbon torcrete-mix slag resistance by a reduction in molten slag corrosiveness and modification of refractory composite microstructure. Combination of the refractory microstructure modification obtained and slag with changed chemical composition makes it possible to improve torcrete-mix properties considerably and increase its corrosion slag resistance. [ABSTRACT FROM AUTHOR]

Results are reported from a study of the dependence of the reduction in the thickness of strip on the main process parameters as the strip is bent in the rolls of a roll-forming machine. The study was performed with the use of the theory of experiment planning. [ABSTRACT FROM AUTHOR]

In EDTA solutions with pH ∼5 at 25°C, Am(V) in a concentration of 5 × 10−3 × 10 M slowly transforms into Am(III). The Am(V) reduction and Am(III) accumulation follow the zero-order rate law. In the range 60-80°C, the reaction is faster. In some cases, an induction period is observed, disappearing in acetate buffer solutions. In the range pH 3-7, the rate somewhat increases with pH. In an acetate buffer solution, an increase in [EDTA] accelerates the process. The activation energy is 47 kJ mol. Zero reaction order with respect to [Am(V)] is observed in solutions of ascorbic and tartaric acids, of LiSO (pH > 3), and of hydrazine. The process starts with the reaction of Am(V) with the reductant. The Am(III) ion formed in the reaction is in the excited state, *Am(III). On collision of *Am(III) with Am(V), the excitation is transferred to Am(V), and it reacts with the reductant: *Am(V) + reductant → Am(IV) + R and then Am(IV) + reductant → *Am(III) + R, Am(V) + R → Am(IV) + R. A branched chain reaction arises. The decay of radicals in side reactions keeps the system in the steady state; therefore, zero reaction order is observed. [ABSTRACT FROM AUTHOR]

The effect of the acidity (p K) of the source of protons on the rate and selectivity of acetylene reduction has been investigated in order to elucidate the mechanism of protonation of substrate molecules coordinated to the reduced FeMoco cluster. A number of compounds whose p K in DMF varies between 6 and 20 have been examined as protonating agents. The rate of the reaction is almost independent of the acidity of the proton donor in a wide p K range. This can be explained in terms of the specific features of substrate protonation catalyzed by iron-sulfur clusters. Active protonating agents in the system are those which react with the catalyst to form hydrogen-bonded association species or those which are ligands reversibly binding to the cluster and are capable of donating protons, likely with simultaneous electron transfer. [ABSTRACT FROM AUTHOR]

Hyperhomocysteinemia (HHcy) is a risk factor for vascular disease, but the underlying mechanisms remain incompletely defined. Reduced bioavailability of nitric oxide (NO) is a principal manifestation of underlying endothelial dysfunction, which is an initial event in vascular disease. Inhibition of cellular methylation reactions by S-adenosylhomocysteine (AdoHcy), which accumulates during HHcy, has been suggested to contribute to vascular dysfunction. However, thus far, the effect of intracellular AdoHcy accumulation on NO bioavailability has not yet been fully substantiated by experimental evidence. The present study was carried out to evaluate whether disturbances in cellular methylation status affect NO production by cultured human endothelial cells. Here, we show that a hypomethylating environment, induced by the accumulation of AdoHcy, impairs NO production. Consistent with this finding, we observed decreased eNOS expression and activity, but, by contrast, enhanced NOS3 transcription. Taken together, our data support the existence of regulatory post-transcriptional mechanisms modulated by cellular methylation potential leading to impaired NO production by cultured human endothelial cells. As such, our conclusions may have implications for the HHcy-mediated reductions in NO bioavailability and endothelial dysfunction. [ABSTRACT FROM AUTHOR]

The potential energy surface for the reaction of a typical molecular system composed of N atoms is defined uniquely by 3 N-6 coordinates. These coordinates can be defined by the Cartesian coordinates of the atomic centers (minus overall translation and rotation), or a set of internally defined coordinates such as bond stretches, angle bends, and torsions. By applying principal component analysis to the geometries along a reaction path, a reduced set of coordinates, d ≪ 3 N-6, can be obtained. This reduced set of coordinates can reproduce the changes in geometry along the reaction path with chemical accuracy and may help improve the efficiency of reaction path optimization algorithms. [ABSTRACT FROM AUTHOR]

The activity of 0.25-5% Ag/AlO catalysts in the selective catalytic reduction of nitrogen oxides with n-hexane under the conditions of promotion with a small amount of H was studied. It was found that, upon the introduction of ∼1000 ppm of H into the reaction mixture, the Ag/AlO samples containing 1-2% Ag exhibited optimum activity and selectivity. It was established that, in the presence of 1000 ppm of H, the rate of the selective catalytic reduction of NO was higher by a factor of 10-13, and the onset temperature of the reaction was lower by approximately 100°C. It was found by X-ray photoelectron spectroscopy, temperature-programmed reduction, and UV spectroscopy that the high activity of 1-2% Ag/AlO catalysts was due to the presence of small Ag and Ag clusters on their surface. A decrease in the concentration of Ag below the optimum value resulted in the predominance of an inactive ionic form on the catalyst surfaces. As the concentration of Ag was increased (>2%), large particles of AgO and Ag, which facilitate the oxidation of n-CH, were formed to lead to a decrease in selectivity and in the degree of reduction of nitrogen oxides. [ABSTRACT FROM AUTHOR]

In this paper we re-examine the commonly accepted meaning of the two kinetic constants characterizing any enzymatic reaction, according to Michaelis-Menten kinetics. Expanding in terms of exponentials the solutions of the ODEs governing the reaction, we determine a new constant, which corrects some misinterpretations of current biochemical literature. [ABSTRACT FROM AUTHOR]

The method of self-propagating high-temperature synthesis (SHS) was used to synthesize spinel ceramic pigments. Producing aluminum-nickel and aluminum-cobalt pigments in a finely dispersed state is a complex stepwise (combined) process involving a reduction stage and simultaneous natural air filtration. In the case of small-diameter samples, a flat combustion front is observed and in large samples, the front is formed of many hot spots. The dependence of combustion rate on porosity is presented. The maximum combustion rate of these systems are recorded for porosity of 50-60%. Powdered SHS pigments were obtained for the first time. [ABSTRACT FROM AUTHOR]

It is shown that palladium-cobalt oxide-cerium catalyst deposited on cordierite catalyzes the reduction of nitrogen(II) oxide with carbon monoxide, and cobalt-iron catalysts in simultaneous reduction of NO + NO with C-C alkanes retained high activity in the presence of water vapor and sulfur dioxide. The Pd-CoO/cordierite catalyst exceeds the Pt-CoO/codierite catalyst in the conversion of NO and CO in the reaction mixture CO + NO + O + HO + SO. Modification of the Pd-CoO/cordierite with cerium oxide considerably increases its sulfur resistance. [ABSTRACT FROM AUTHOR]

A spatially nonuniform system in which a first-order chemical reaction occurs is considered. Both the diffusion coefficient and the kinetic coefficient of the reaction are assumed to be dependent on spatial coordinates. An asymptotically valid method is proposed for reducing a diffusion equation (under the described conditions) in the presence of a source (a reaction) to a simple kinetic equation containing a constant kinetic coefficient. A functional is derived that makes it possible to use variational methods for determining the kinetic coefficient. [ABSTRACT FROM AUTHOR]

A(PO)(OH) (A = Ca and Sr)-supported Pt catalysts were prepared and their catalytic activity in NO reduction were investigated. The Sr(PO)(OH)-supported catalyst had high catalytic activity in the CH-NO-O reaction; the activity was higher than that of the γ-AlO-supported catalyst at 300 °C. The basicity of the apatite supports would affect the chemical state of Pt on catalyst, resulting in promotion of NO reduction. [ABSTRACT FROM AUTHOR]

The properties of isoviolanthrone (V1) and its corresponding dihydro form (V1–H2) in argon-saturated 1-phenylethanol in the presence of acetophenone were examined by photophysical and photochemical methods. Upon photolysis of the sensitizer, a radical-induced reduction of V1to V1–H2occurs. The quantum yield of this reduction is close to unity. The fluorescence of V1has a quantum yield of 0.08, for V1–H2Φfis strongly enhanced and the emission maximum is blue-shifted. The ketyl radical, the semiquinone radical and V1–H2were observed in this sequence by flash photolysis. V1–H2is unstable and undergoes oxidation to V1on admission of oxygen. [ABSTRACT FROM AUTHOR]

Published data on the stability of Pu(VI) and Pu(V) in solutions of mineral and organic acids and their salts are analyzed. The hypothesis that Pu(VI) in acid solutions disappears owing to the disproportionation to Pu(VII) and Pu(V) cannot be accepted because of high redox potential of the Pu(VII)/(VI) couple. Plutonium( VI) is reduced owing to radiation-chemical reactions induced by its α-radiation and to the formation of a dimer (so-called excimer) by an excited Pu(VI) ion with an unexcited Pu(VI) ion, which rapidly decomposes to Pu(V) and HO. Plutonium(V) disappears owing to disproportionation and radiation-chemical processes. [ABSTRACT FROM AUTHOR]

Tin and titanium dioxides and their compositions were studied as catalysts for the reaction of complete oxidation of methane. The catalytic activity of the test samples was compared in terms of first-order reaction rate constants with reference to the unit surface area of a catalyst. The crystal structures and specific surface areas of the obtained compositions were characterized. The thermal stability of SnO was investigated. Data on the temperature-programmed reduction of SnO and the composition SnTiO in hydrogen were given. [ABSTRACT FROM AUTHOR]

Differential voltammetry as well as UV-vis spectrophotometry and impedance spectroscopy were used to show that polyaniline doped with polystyrenesulfonic acid mediates the reduction of oxygen and hydrogen peroxide in aqueous media by facilitating the formation of hydroxyl radicals and increasing the sensitivity of the electrochemical method for determining the antioxidant activity of sulfur-containing amino acids. [ABSTRACT FROM AUTHOR]

Titanium diboride powders were prepared through a sol-gel and boron carbide reduction route by using TTIP and BC as titanium and boron sources. The influence of TTIP concentration, reaction temperature and molar ratio of precursors on the synthesis of titanium diboride was investigated. Three different concentrations of TTIP solution, 0.033/0.05/0.1, were prepared and the molar ratio of BC to TTIP varied from 1.3 to 2.5. The results indicated that as the TTIP concentration had an important role in gel formation, the reaction temperature and BC to TTIP molar ratio showed obvious effects on the formation of TiB. Pure TiB was prepared using molar composition of Ti: BC = 1: 2.3 and the optimum synthesis temperature was 1200°C. [ABSTRACT FROM AUTHOR]

The price of iridium currently trends at about half the cost of platinum, the latter being a typical reduction promoter for Co/AlO Fischer-Tropsch (FT) synthesis catalysts in gas-to-liquids (GTL) technology. In the current contribution, both fixed-bed catalytic FT and TPR-EXAFS/XANES experiments were carried out over 0.1% iridium-doped 25% Co/AlO catalysts in order to (1) assess the effectiveness of Ir as a promoter of cobalt oxide reduction and (2) evaluate the effectiveness of the incipient wetness impregnation (IWI) technique for adding the Ir precursor by comparing a catalyst prepared by IWI to one prepared by atomic layer deposition (ALD). Ir was demonstrated to be an effective promoter for facilitating the second step of cobalt oxide reduction, CoO to Co, and the IWI method was found to be superior to ALD. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]