Stable Decomposition Products Research Articles

Revealing the Effect of Sulfur Compounds for Low-Temperature Synthesis of Boron Nitride Nanotubes from Boron Minerals

Boron nitride nanotubes (BNNTs), the structural analogues to carbon nanotubes (CNTs), attracted considerable attention due to their excellent properties. However, the synthesis of BNNTs suffers from high-temperature requirement, which increases the cost and adds complexity to instruments (arc-discharge, plasma-assisted CVD, etc.), preventing further exploration of BNNTs and use of harmful chemicals (catalytic chemical vapor deposition) resulting in unwanted byproducts. Here, we demonstrate sulfur-containing compound-assisted synthesis of BNNTs at a relatively low temperature of 1050 °C from colemanite via a chemical vapor deposition (CVD) method. Comparison between thiophene, l-cystine, and l-methionine revealed that thiophene is the most effective sulfur compound with more stable decomposition products and low vapor pressure. Moreover, we have evaluated ulexite and etidot-67 as an alternative to colemanite. We believe that our findings can offer solutions to commonly encountered problems of BNNT synthesis in terms of high energy consumption and precursor cost, leading to broader use of BNNTs in various applications.

Synthesis of Deuterated Methylphosphonic Acid Derivatives for Use as Standard Compounds in the Analysis of Toxic Chemicals

One of the ways to ensure high reliability of detection, identification and accuracy of quantitative determination of toxic chemicals (TC) in environmental and biomedical samples by gas and liquid chromatography-mass spectrometry methods is to use internal standards (IS) as additives to the analyzed sample, which, in contrast from target TC, contain stable isotopes such as D, 13 C, 15 N, 18 O. In this case, preference is given to the most accessible stable deuterated compounds. IS labeled with stable isotopes are widely used in numerous studies to develop methods for the analysis of various toxic chemicals, in particular, alkylphosphonic acids. For the prompt and high-quality performance of the tasks assigned to the assigned laboratory, it seems necessary to have a physical bank of samples labeled with stable IS isotopes, corresponding to those TC, the appearance of which in the analyzed samples is most likely. These include, first of all, stable decomposition products of such as sarin, soman, cyclosarin, VX, VR, CVX, namely, methylphosphonic acid, its ethyl, isopropyl, butyl, isobutyl, pinacolyl and cyclohexyl esters, as well as the corresponding symmetric diesters . In accordance with the objectives of the article, we have synthesized the IS composition of deuteromethylphosphonic acid and its derivatives: acid chlorides of O-alkyl esters of deuteromethylphosphonic acids, acid O-alkyl esters of deuteromethylphosphonic acids, O, O-dialkyl esters of deuteromethylphosphonic acids, and also adducts of tyrosine and tripeptide Tyr-Thr-Lys with chlorides of O-isopropyl and O-cyclohexyl esters of deuteromethylphosphonic acid. NMR 2 Н, 31 Р, GC-MS and HPLC-MS spectral characteristics of the synthesized substances were studied

Local Solvation Modulates Activity of Covalent C−F Bonds in Fluorinated Electrolyte Additives

Fluorinated reactants that enable fluoride bond cleavage, either in electrolytes or cathodes, are receiving increased research attention because of the formation of highly stable decomposition products (e.g. LiF), which also allows large Gibbs free energy change. Electrolytes using fluorinated solvents or additives (e.g. fluoroethylene carbonate (FEC), methyl 2,2,2-trifluoroethyl carbonate (FEMC), and liquefied CH3F) were shown to be able to effectively increase Li cyclability by forming LiF rich solid electrolyte interphase (SEI) on Li. In addition, conversion type Li battery cathodes, such as transition-metal fluorides (MFy, M=Fe, Co, Ni, Cu, y=2, 3) and CFx, can deliver high energy densities through fluoride bond reduction reactions. However, the strong electronegativity of fluorine making most of the fluoride bonds highly stable (i.e. hard to break), which limits their applications in electrochemical systems. Therefore, fundamental understanding of how to modulate fluoride bond strength to unlock activity is of vital importance. Herein, we use perfluoroalkyl group (RF)-containing liquid reactants as model systems to demonstrate that the covalent C−F bonds in RF, which were generally believed to be extremely difficult to reduce, can be unlocked through combined reactant-electrolyte design, with the electrolyte playing a central role in governing activity. The interaction between solvent and fluorinated reactants, such as solvation effects and formation of hydrogen bonds, can alter the electron density distribution along the carbon-fluorine skeleton and weaken fluoride bond strengths as indicated by nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations. As a result, the reduction potential (from galvanostatic measurements for Li cells) can be dramatically increased from < 2.0 V to > 2.9 V vs. Li/Li+ through modulation of the solvent. In addition to activating electrochemically-active pathways, solvent molecules also need to exhibit proper polarities to allow both high miscibility (requiring low polarity), and Li salt solubility (requiring high polarity). Other electrolyte design aspects that can direct the reduction activity of highly fluorinated reactants will also be discussed, including fluoridation of solvent molecules, Li salt dissociation energy, and reactant/salt ratio. These understandings on tuning fluoride bond strength via electrolyte−reactant interactions will open up new design opportunities for fluorinated electrolyte components, either solvents or additives, for Li cells with high cycle stabilities, as well as high-energy Li primary battery with liquid cathodes.

Nitroderivatives of N-pyrazolyltetrazoles: Thermal decomposition and combustion

Thermal decomposition and combustion of a series of novel promising nitro and amino substituted energetic pyrazolyltetrazoles were studied using a number of complementary experimental (thermogravimetry, differential scanning calorimetry, manometry, microthermocouple measurements in a combustion wave, and HPLC) and theoretical (quantum chemical calculations) techniques. According to the DSC and manometry data, the N-(pyrazolyl)tetrazoles turned out to be less thermally stable than the C-(pyrazolyl)tetrazole: the activation energies of their melt-phase decomposition are 117–127 and 140 kJ mol−1, respectively. The kinetics of decomposition in the solid phase is more complicated due to a strong influence of the effect of sub-melting and possible azido-tetrazole isomerization. The reliable CCSD(T)-F12 quantum chemical calculations provided mechanistic insight into the thermolysis of the compounds studied. All species decompose via the ring-opening reaction yielding a transient azide intermediate followed by the N2 elimination. The effective activation barriers of the latter reactions are in reasonable agreement with the melt-phase experiments for N-pyrazolyltetrazoles. On the basis of the HPLC detected products, we also outlined the reactions leading to the stable decomposition products observed. All compounds studied showed a self-sustained fast-burning character. Their typical burning rates are 70−80 mm s−1 at 10 MPa, which is as much as two times higher than the burning rate of a powerful explosive CL-20 under the same conditions. Using the pressure dependence of the surface temperature, we also determined the vapor pressures of (nitropyrazolyl)tetrazoles studied. The boiling points of the latter species are higher than the boiling point of hexogen. The melt-phase kinetic parameters also agree well with the condensed-phase-controlled burning rate model. The low activation energies of the leading combustion reactions are responsible for low pressure exponents of these compounds varying in the range of 0.5 – 0.75.

Clarifying the relationship between redox activity and electrochemical stability in solid electrolytes.

All-solid-state Li-ion batteries promise safer electrochemical energy storage with larger volumetric and gravimetric energy densities. A major concern is the limited electrochemical stability of solid electrolytes and related detrimental electrochemical reactions, especially because of our restricted understanding. Here we demonstrate for the argyrodite-, garnet- and NASICON-type solid electrolytes that the favourable decomposition pathway is indirect rather than direct, via (de)lithiated states of the solid electrolyte, into the thermodynamically stable decomposition products. The consequence is that the electrochemical stability window of the solid electrolyte is notably larger than predicted for direct decomposition, rationalizing the observed stability window. The observed argyrodite metastable (de)lithiated solid electrolyte phases contribute to the (ir)reversible cycling capacity of all-solid-state batteries, in addition to the contribution of the decomposition products, comprehensively explaining solid electrolyte redox activity. The fundamental nature of the proposed mechanism suggests this is a key aspect for solid electrolytes in general, guiding interface and material design for all-solid-state batteries.

β-Bond Scission and the Yields of H and CH3 in the Decomposition of Isobutyl Radicals.

The relative rates of C-C and C-H β-scission reactions of isobutyl radicals (2-methylprop-1-yl, C4H9) were investigated with shock tube experiments at temperatures of (950 to 1250) K and pressures of (200 to 400) kPa. We produced isobutyl radicals from the decomposition of dilute mixtures of isopentylbenzene and observed the stable decomposition products, propene and isobutene. These alkenes are characteristic of C-C and C-H bond scission, respectively. Propene was the main product, approximately 30 times more abundant than isobutene, indicating that C-C β-scission is the primary pathway. Uncertainty in the ratio of [isobutene]/[propene] from isobutyl decomposition is mainly due to a small amount of side chemistry, which we account for using a kinetics model based on JetSurF 2.0. Our data are well-described after adding chemistry specific to our system and adjusting some rate constants. We compare our data to other commonly used kinetics models: JetSurF 2.0, AramcoMech 2.0, and multiple models from Lawrence Livermore National Laboratory (LLNL). With the kinetics model, we have determined an upper limit of 3.0% on the branching fraction for C-H β-scission in the isobutyl radical for the temperatures and pressures of our experiments. While this agrees with previous high quality experimental results, many combustion kinetics models assume C-H branching values above this upper limit, possibly leading to large systematic inaccuracies in model predictions. Some kinetics models additionally assume contributions from 1,2-H shift reactions-which for isobutyl would produce the same products as C-H β-scission-and our upper limit includes possible involvement of such reactions. We suggest kinetics models should be updated to better reflect current experimental measurements.

Structure formation and surface chemistry of ionic liquids on model electrode surfaces-Model studies for the electrode electrolyte interface in Li-ion batteries.

Ionic liquids (ILs) are considered as attractive electrolyte solvents in modern battery concepts such as Li-ion batteries. Here we present a comprehensive review of the results of previous model studies on the interaction of the battery relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) with a series of structurally and chemically well-defined model electrode surfaces, which are increasingly complex and relevant for battery applications [Ag(111), Au(111), Cu(111), pristine and lithiated highly oriented pyrolytic graphite (HOPG), and rutile TiO2(110)]. Combining surface science techniques such as high resolution scanning tunneling microscopy and X-ray photoelectron spectroscopy for characterizing surface structure and chemical composition in deposited (sub-)monolayer adlayers with dispersion corrected density functional theory based calculations, this work aims at a molecular scale understanding of the fundamental processes at the electrode | electrolyte interface, which are crucial for the development of the so-called solid electrolyte interphase (SEI) layer in batteries. Performed under idealized conditions, in an ultrahigh vacuum environment, these model studies provide detailed insights on the structure formation in the adlayer, the substrate-adsorbate and adsorbate-adsorbate interactions responsible for this, and the tendency for chemically induced decomposition of the IL. To mimic the situation in an electrolyte, we also investigated the interaction of adsorbed IL (sub-)monolayers with coadsorbed lithium. Even at 80 K, postdeposited Li is found to react with the IL, leading to decomposition products such as LiF, Li3N, Li2S, LixSOy, and Li2O. In the absence of a [BMP]+[TFSI]- adlayer, it tends to adsorb, dissolve, or intercalate into the substrate (metals, HOPG) or to react with the substrate (TiO2) above a critical temperature, forming LiOx and Ti3+ species in the latter case. Finally, the formation of stable decomposition products was found to sensitively change the equilibrium between surface Li and Li+ intercalated in the bulk, leading to a deintercalation from lithiated HOPG in the presence of an adsorbed IL adlayer at >230 K. Overall, these results provide detailed insights into the surface chemistry at the solid | electrolyte interface and the initial stages of SEI formation at electrode surfaces in the absence of an applied potential, which is essential for the further improvement of future Li-ion batteries.

Reductive Decomposition Mechanism of Prop-1-ene-1,3-sultone in the Formation of a Solid–Electrolyte Interphase on the Anode of a Lithium-Ion Battery

A novel electrolyte additive, prop-1-ene-1,3-sultone (PES), has recently attracted great attention due to its formation of effective solid–electrolyte interphase (SEI) films and remarkable cell performance in lithium-ion batteries. Herein, the reductive decomposition of PES is investigated through density functional calculations combined with a self-consistent reaction field method, in which the bulk solvent effect is accounted for by the geometry optimization and transition-state search. We examine three ring-opening pathways, namely, O–C, S–C, and S–O bond-breaking processes. Our calculations reveal that the Li+ ion plays a pivotal role in the reductive decomposition of PES. While the most kinetically favored process—the S–O bond breaking—is effectively blocked via the formation of an intermediate structure, namely, the Li+-participated seven-membered ring, the other decomposition processes via O–C and S–C bond breaking lead to stable decomposition products. The constituents of SEI observed in previous ...

Calculated rate constants of the chemical reactions involving the main byproducts SO2F, SOF2, SO2F2 of SF6 decomposition in power equipment

SF6 is widely used in electrical equipment as an insulating gas. In the presence of an electric arc, partial discharge (PD) or spark, SF6 dissociation products (such as SF2, SF3 and SF4) react with the unavoidable gas impurities (such as water vapor and oxygen), electrodes and surrounding solid insulation materials, forming several toxic and corrosive byproducts. The main stable decomposition products are SO2F, SO2F2 and SOF2, which have been confirmed experimentally to have a direct relationship with discharge faults, and are thus expected to be useful in the fault diagnosis of power equipment. Various studies have been performed of the main SF6 decomposition species and their concentrations under different types of faults. However, most of the experiments focused on the qualitative analysis of the relationship between the stable products and discharge faults. Although some theoretical research on the formation of main SF6 derivatives have been carried out using chemical kinetics models, the basic data (chemical reactions and their rate constants) adopted in the model are inaccurate and incomplete. The complex chemical reactions of SF6 with the impurities are ignored in most cases. The rate constants of some reactions obtained at ambient temperature or in a narrow temperature range are adopted in the models over a far greater range, for example up to 12 000 K, due to the difficulty in the experimental measurement and theoretical estimation of rate coefficients, particularly at high temperatures. Therefore, improved theoretical models require not only the consideration of additional SF6 decomposition reactions in the presence of impurities but also on improved values of rate constants. This paper is devoted to determining the rate constants of the chemical reactions relating to the main byproducts of SF6 decomposition in SF6 gas-insulated power equipment: SO2F, SOF2 and SO2F2. Quantum chemistry calculations with density functional theory, conventional transition state theory and Wigner’s tunneling effect correction are employed to estimate the rate constants of four important chemical reactions: F + SO2F → SO2F2, F2 + SO2 → SO2F2, SO2F + SF5 → SF6 + SO2 and SOF3 + SF3 → SF4 + SOF2. The results are derived for a large temperature range, from 300 to 12 000 K, and finally fitted by a three-parameter Arrhenius equation. This work lays a basis for the further study of the SF6 decomposition mechanism by means of chemical kinetics modelling.

Prediction of electronically nonadiabatic decomposition mechanisms of isolated gas phase nitrogen-rich energetic salt: Guanidium-triazolate

Electronically nonadiabatic decomposition pathways of guanidium triazolate are explored theoretically. Nonadiabatically coupled potential energy surfaces are explored at the complete active space self-consistent field (CASSCF) level of theory. For better estimation of energies complete active space second order perturbation theories (CASPT2 and CASMP2) are also employed. Density functional theory (DFT) with B3LYP functional and MP2 level of theory are used to explore subsequent ground state decomposition pathways. In comparison with all possible stable decomposition products (such as, N2, NH3, HNC, HCN, NH2CN and CH3NC), only NH3 (with NH2CN) and N2 are predicted to be energetically most accessible initial decomposition products. Furthermore, different conical intersections between the S1 and S0 surfaces, which are computed at the CASSCF(14,10)/6-31G(d) level of theory, are found to play an essential role in the excited state deactivation process of guanidium triazolate. This is the first report on the electronically nonadiabatic decomposition mechanisms of isolated guanidium triazolate salt.

First-Principles Thermochemistry for the Thermal Decomposition of Titanium Tetraisopropoxide.

The thermal decomposition of titanium tetraisopropoxide (TTIP) is investigated using quantum chemistry, statistical thermodynamics, and equilibrium composition analysis. A set of 981 Ti-containing candidate species are proposed systematically on the basis of the thermal breakage of bonds within a TTIP molecule. The ground state geometry, vibrational frequencies and hindrance potentials are calculated for each species at the B97-1/6-311+G(d,p) level of theory. Thermochemical data are computed by applying statistical thermodynamics and, if unknown, the standard enthalpy of formation is estimated using balanced reactions. Equilibrium composition calculations are performed under typical combustion conditions for premixed flames. The thermodynamically stable decomposition products for different fuel mixtures are identified. A strong positive correlation is found between the mole fractions of Ti species containing carbon and the TTIP precursor concentration.

Decomposition processes of diborane and borazane (ammonia-borane complex) on hot wire surfaces

The decomposition efficiencies of B2H6 and H3NBH3 activated on hot wire surfaces were measured mass spectrometrically. The decomposition efficiency of B2H6 increased with the residence time of gases in the chamber, and decreased with total pressure when He was added. Decomposition efficiency was still high even under collision-free conditions. These results suggest that the decomposition is not thermal but catalytic, at least at low pressures, although the wire-material dependence of the decomposition efficiency was minor. The decomposition efficiency of H3NBH3 vapor was higher than that of B2H6 and increased with the addition of H2. H2, NH3, and N2 as well as H2NBH2 were identified as stable decomposition products. These results indicate H3NBH3 is a viable candidate as a safe dopant precursor for B-atom doping.

Neuroprotective effect of 3-morpholinosydnonimine against Zn2+-induced PC12 cell death

Excessive intracellular accumulation of zinc (Zn2+) is neurotoxic and contributes to a number of neuropathological conditions. Here, we investigated the protective effect of 3-morpholinosydnonimine (SIN-1) against Zn2+-induced neuronal cell death in differentiated PC12 cells. We found that Zn2+-induced PC12 cell death was reduced in a concentration-dependent manner by pretreatment with SIN-1. The intracellular accumulation of Zn2+ was not affected by pretreatment with SIN-1, indicating that SIN-1-induced neuroprotection was not attributable to reduced influx of Zn2+ into cells. SIN-1C, the stable decomposition product of SIN-1, failed to prevent Zn2+-induced cell death. Furthermore, the protective effect of SIN-1 against Zn2+-induced PC12 cell death was almost completely abolished by uric acid, a free radical scavenger, suggesting that reactive oxygen and nitrogen species generated by SIN-1 may contribute to the protective effect. SIN-1 prevented the inactivation of glutathione reductase (GR) and the increase in the ratio of oxidized glutathione/total glutathione (GSSG/total GSH) induced by Zn2+. Addition of membrane permeable GSH ethyl ester (GSH-EE) to PC12 cells prior to Zn2+ treatment significantly increased cell viability. We therefore conclude that SIN-1 may exert neuroprotective effect against Zn2+-induced cell death in differentiated PC12 cells by preventing inhibition of GR and increase in GSSG/total GSH ratio.

Partial discharge early-warning through ultraviolet spectroscopic detection of SO2

Surveillance of SF6 decomposition products is significant for detection of partial discharge (PD) in gas insulation switchgear (GIS). As a basis in on-site detection and diagnosis, PD early-warning aims to quickly find the abnormalities using a simple and cheap device. In this paper, SO2 is chosen as a feature product and detected through ultraviolet spectroscopy. The derivative method is employed for baseline correction and spectral enhancement. The standard gases of the main decomposition products are qualitatively and quantitatively detected. Then decomposition experiments with different defects are designed to further verify the feasibility. As a stable decomposition product under PD, SO2 is proved to be applicable for PD early-warning in the field. By selecting the appropriate wavelength range, namely 290–310 nm, ultraviolet derivative spectroscopy is sensitive enough to the trace SO2 in the decomposed gas and the interference of other products can be avoided. Fast Fourier transform could be used for feature extraction in qualitative detection. Concentrations of SO2 and other by-products increase with increasing discharge time and could be affected by the discharge energy and PD type. Ultraviolet detection based on SO2 is effective for PD early-warning but the threshold should still be carefully selected in practice.

Bacillus anthracis co-opts nitric oxide and host serum albumin for pathogenicity in hypoxic conditions

Bacillus anthracis is a dangerous pathogen of humans and many animal species. Its virulence has been mainly attributed to the production of Lethal and Edema toxins as well as the antiphagocytic capsule. Recent data indicate that the nitric oxide (NO) synthase (baNOS) plays an important pathogenic role at the early stage of disease by protecting bacteria from the host reactive species and S-nytrosylating the mitochondrial proteins in macrophages. In this study we for the first time present evidence that bacteria-derived NO participates in the generation of highly reactive oxidizing species which could be abolished by the NOS inhibitor L - NAME, free thiols, and superoxide dismutase but not catalase. The formation of toxicants is likely a result of the simultaneous formation of NO and superoxide leading to a labile peroxynitrite and its stable decomposition product, nitrogen dioxide. The toxicity of bacteria could be potentiated in the presence of bovine serum albumin. This effect is consistent with the property of serum albumin to serves as a trap of a volatile NO accelerating its reactions. Our data suggest that during infection in the hypoxic environment of pre-mortal host the accumulated NO is expected to have a broad toxic impact on host cell functions.

Serum nitric oxide status in patients with type 2 diabetes mellitus in Sikkim.

Background:Serum nitric oxide (NO) has emerged as a fundamental signal associated with the endothelial dysfunction in type 2 diabetes.Aims:To compare serum nitric oxide level among type 2 diabetic patients along with other biochemical parameters and to compare it with that of normal population in Sikkim.Settings and Design:This prospective study was carried out in the Biochemistry Department in a tertiary care teaching hospital in Sikkim on 50 type 2 diabetics compared to 100 non-diabetics.Materials and Methods:The un-hemolyzed blood sample was collected for estimation of biochemical parameters. Griess reaction was used for indirect assay of stable decomposition products in serum(serum nitrite and nitrate levels) as an index of NO generation. The comparison of different parameters between cases and control was done by using Student's t-test.Results:There was significant difference when age- and sex-matched cases and controls were compared in regard to waist circumference and body mass index. The values of fasting and postprandial serum glucose, and lipid profile between study group and control group differed significantly. The mean serum level of NO in the study and control group was 43.83 ± 11.3 μmoles/L and 58.85 ± 12.8 μmoles/L respectively, and this difference was statistically significant.Conclusion:To sum up, serum NO was observed significantly low in diabetic participants as compared to control, along with difference in other biochemical parameters.

The influence of sucrose on the crystallization behaviour in the system CaO–SiO 2–C 12H 22O 11–H 2O under hydrothermal conditions

Hydrothermal synthesis in the presence of sucrose has been carried out at 200 °C and autogeneous pressure in the system CaO–SiO 2–C 12H 22O 11–H 2O to investigate the influence of C 12H 22O 11 on phase formation and the crystal habit of calcium silicate hydrates (CSH-phases). A sucrose/lime ratio of 0.5 was utilized in all experiments and the reactivity of the SiO 2 source was varied using educts of different grain size of ∼40 mesh and >230 mesh. CaO/SiO 2 concentration ratios of 0.5 and 0.8 have been selected, the latter with respect to the composition of the important CSH-phase 11 Å tobermorite. The results were compared with experiments under similar but sucrose-free conditions. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX-analysis) as well as Fourier transform infrared spectroscopy (FTIR-spectroscopy) have been applied for analyses. A retarding effect of sucrose on CSH-phase formation has been observed. Only minor amount of CSH without regular morphology was observed instead of typically fibrous 11 Å tobermorite formed in the sucrose-free system. Sucrose altered the reaction mechanism in the CSH-system and hydrothermal process started with rapid reaction of sucrose and lime. The further course of crystallization was dominated by an extended precipitation of calcium carbonate and small amounts of calcium oxalate hydrate. Formation of these stable hydrothermal decomposition products of saccharated lime is strongly suppressing the CSH-crystallization.

Transition metal ion-modified polyurethanes: Spectroscopic and thermal studies on polyesterurethane/chromium metallopolymers

Polyesterurethane/chromium(III) metallopolymers (PUCr) having chromium contents below 1% were prepared by using different initial molar ratios urethane groups/chromium ions. PUCr were characterized in comparison with the parent polyurethane (PU) by AAS, UV–Vis absorption spectroscopy, FTIR spectroscopy, DSC, DMA and TGA. Chromium ions form coordination complexes with the urethane nitrogen atoms, the intermolecular complexation bringing about the crosslinking of the hard segments. As a result, disturbance of the hydrogen bonding and modifications in the crystallinity of the hard-segment domains take place. PUCr exhibit higher values of soft-segment glass transition and storage modulus than PU, revealing the reinforcing effect of chromium ions on the polyurethane matrix. As compared with PU, PUCr present lower initial thermal stability, a strongly catalyzed final stage of the thermal decomposition process and more thermally stable intermediate decomposition products.

Decomposition of Ethane in Atmospheric-Pressure Dielectric-Barrier Discharges: Experiments

It is well known that electric fields can influence combustion processes. When the magnitude of an external applied electric field exceeds the breakdown field of the fuel gas or fuel/oxidizer mixture, plasma effects dominate. The earlier work in the field of plasma-assisted combustion has demonstrated that dielectric-barrier-discharge (DBD)-driven nonthermal plasmas (NTPs) can increase flame speed and extend the combustion of hydrocarbon fuel gases into very lean-burn regimes. In this paper, results on the decomposition of ethane (C2H6) by DBDs at atmospheric pressure will be presented. The authors have chosen ethane for this paper because its gaseous electronics properties (electron-impact dissociation cross sections, drift velocity) are available in the literature. A subsequent paper will present results on the calculated yield of DBD-driven plasma decomposition products of ethane, as predicted by plasma-chemistry modeling. In this paper, results on experiments carried out to determine the decomposition products of ethane, as measured by gas chromatography are presented. An atmospheric-pressure DBD reactor processed a flowing gas stream of chemically pure ethane in the regime of plasma specific energy ranging from 1200 to 2400 J/std lit. The major stable decomposition products were H2, CH4, C2H2, and C2H4. These results are important in assessing the possibility of using NTPs to enhance the combustion of hydrocarbons

Novel SIN-1 reactive intermediates modulate chloride secretion across murine airway cells.

We examined the effects of reactive oxygen-nitrogen intermediates on chloride (Cl-) currents across murine tracheal epithelial (MTE) cells isolated from CD-1 mice. MTE cells were cultured on permeable supports until they formed water-tight monolayers with transepithelial resistances (Rt)>500 Omega/cm2 and then were mounted in Ussing chambers. Baseline short-circuit current (ISC) values, prior to and following the addition of 10 microM amiloride (an inhibitor of sodium-transport pathways) into the apical side, were 65 +/- 1.9 microA/cm2 and 7.6 +/- 0.51 microA/cm2, respectively (X +/- 1 SE, n=32). The addition of 3-morpholinosydnominine (SIN-1, 1 mM), which generates both superoxide and nitric oxide anions, to amiloride-treated monolayers resulted in a transient increase of ISC to a peak value of 35 +/- 1.3 microA/cm2 (X +/- SE, n=14) within the next 30-60 min. After this, the ISC decreased gradually and returned to its pre-SIN-1 value. These changes were blocked by glibenclamide (200 microM), an inhibitor of cystic fibrosis transmembrane regulator, or reduced by glutathione (GSH, 5 mM), a scavenger of peroxynitrite. Forskolin (10 microM) augmented the SIN-1 effect when added at the peak of the SIN-1 response but not when ISC had returned to its baseline value. Perfusion of MTE cells with SIN-1 also increased whole cell Cl- currents 4-fold and the open probability of CFTR-type single-channel currents from 0.041 to 0.92 in a transient fashion. Decomposed SIN-1, but not pure SIN-1c (the stable decomposition product of SIN-1), also increased ISC with an EC50 of 5 microM. Electrospray mass spectroscopy revealed several unique and uncharacterized compounds formed during the decomposition of SIN-1 as well as the reaction of SIN-1c with peroxynitrite. Formation of these compounds was inhibited by GSH. We conclude that compounds formed by the reaction of peroxynitrite with by-products of SIN-1, rather than reactive oxygen-nitrogen species per se, were responsible for the modulation of Cl- secretion across primary cultures of MTE cells.