Number Of Reaction Products Research Articles

Ice-grain impact on a rough amorphous silica surface

Using molecular dynamics simulation, we analyze the collision between a water-ice grain and a silica surface. Both a flat and porous surfaces are studied. We find that the presence of pores in the silica sample and the induced roughness of the silica surface significantly influence the collision outcome. The presence of pores on the surface increases the contact area of the colliding grain with the silica sample, and consequently also the number of reaction products, i.e., water dissociation products and silanol groups formed at the silica surface. The effect is maximum if the pore size is of the order of the grain radius. In addition, the presence of pores on the surface allows for the penetration of water molecules under the surface, molecule ejection from the colliding ice grain is enhanced, and dissipation of the collision energy into the sample is hindered.

Partial purification of linoleic acid isomerase enzyme from Lactobacillus paracasei bacteria isolated from milk.

Conjugated Linoleic Acid (CLA) has attracted the attention of many researchers, especially that of microbial origin due to its biological importance to the consumer. The current study aims to extract LA Isomerase enzyme from Lactobacillus paracasei bacteria from milk and to use the enzyme in the production of CLA. Selective media, including MRS and MRS-Dagatose, were used in isolating local strains. The selected bacterial isolates were tested for their ability to produce LA-Isomerase enzyme. The isolate with high enzymatic activity was selected. After extraction and partial purification of the enzyme, the optimal conditions for the production of conjugated fatty acid were studied, and the reaction products were diagnosed using GC-MS technology. It was found that 11 isolates have the ability to produce CLA at different concentrations, H1 isolate showed the highest production of conjugated fatty acid at a concentration of 120.45 g.ml-1, this isolate was selected as the source for enzyme extraction. The enzymatic activity of the crude extract and partially purified with ammonium sulfate was estimated using color methods at wavelength of 233 nm. The effect of the optimum conditions (pH, temperature, linoleic acid concentration and enzyme concentration) on the CLA product was studied using the partially purified LA Isomerase enzyme, the optimum conditions for production were 6.5, 45 °C, 100 μg.ml-1 and 0.7 ml, respectively. The GC-MS technique showed the presence of a number of reaction products that are isomers of conjugated linoleic acid (C9T11, T9T12, T10C12) with different concentrations.

Molecular Dynamics Simulation of Silicon Dioxide Etching by Hydrogen Fluoride Using the Reactive Force Field.

In this study, we develop a reactive force field (ReaxFF) for a Si/O/H/F system to perform etching simulations of SiO2 with an HF etchant. Quantum mechanical (QM) training sets from density functional theory calculations, which contain structures of reactant/product and energies with bond dissociation, valence angle distortions, and reactions between SiO2 clusters and SiO2 slab with HF gases, are used to optimize the ReaxFF parameters. Structures and energies calculated using the ReaxFF match well with the QM training sets. Using the optimized ReaxFF, we conduct molecular dynamics simulations of the etching process of SiO2 substrates with active HF molecules. The etching yield and number of reaction products with different incident energies of the HF etchant are investigated. These simulations show that the developed ReaxFF offers insights into the atomistic surface reaction of the SiO2 etching process.

ToF‐SIMS characterization of glyoxal surface oxidation products by hydrogen peroxide: A comparison between dry and liquid samples

As one of the simplest volatile organic compounds, glyoxal and its oxidation products were considered to be important precursors to aqueous secondary organic aerosol formation. Herein, we analyzed products from glyoxal oxidation by hydrogen peroxide in dry and liquid samples using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). ToF‐SIMS spectra and spectral principal component analysis (PCA) were used to investigate surface oxidation products. Dry samples were prepared on clean silicon wafers. Liquid samples consisting of glyoxal and hydrogen peroxide (H2O2) were introduced to a vacuum compatible microfluidic reactor prior to UV illumination or dark aging followed by in situ liquid SIMS analysis. A number of reaction products were observed in both dry and liquid samples; different oligomers and carboxylic acids could be formed depending on reaction conditions. In addition, hydrolyzed products were observed in the liquid samples, but not in the dry samples. Although dry samples reveal some products of the aqueous process, they are not fully representative as results from those of the aqueous samples. Our findings suggest that the ability to characterize the liquid surface reaction products provides more realistic information of the reaction products associated with aqueous secondary organic aerosol formation in the atmosphere. Meanwhile, the high mass resolution spectra from the dry sample SIMS measurement are helpful to identify oxidation products in the liquid samples.

Corrosion Behavior of Al2O3‐C Refractories with Casting Mould Meniscus Slags at 1 550 °C

The degradation behavior of alumina (10–20 wt%) carbon refractories was investigated during high temperature (1 550 °C) contact with a ternary casting mould meniscus slag containing 50% MnO, 25% SiO2, and 25% Al2O3 and a binary slag containing 40% MnO and 60% SiO2. Using the sessile drop approach, the transient progress of corrosion reactions was investigated as a function of time and refractory composition. An in‐depth characterization and analysis of reacted assemblies was carried out using optical and scanning electron microscopy (SEM). Optical micrographs showed a significant penetration of both slags within the refractory substrate, with very little slag remaining behind after 15 min of contact. The depth of penetration of ternary slag was found to increase with carbon concentration in the refractory. An all‐round corrosion was observed with extensive refractory degradation over a period of time. Corrosion was determined to a great extent by dissolution reactions in the interfacial region; alumina dissolution from the refractory resulted in the formation of needle‐like corundum crystallites which transformed to a cohesive network of faceted corundum crystals on extended contact. A number of reaction products containing Mn and Si were also observed.

On the Use of the SiC(100)-c(2×2) Surface as a Substrate for the Creation of Ordered Organic–Semiconductor Interfaces

The creation of ordered organic–semiconductor interfaces on many commonly used semiconductor surfaces poses a significant challenge due to the large number of reaction products that can be formed with small conjugated molecules on these surfaces. In this Letter, we employ ab initio molecular dynamics simulations to investigate the reaction between the SiC(100)-c(2×2) surface and 1,3-cyclohexadiene. By generating detailed free-energy profiles for different possible reaction channels, we find that one of the products, a [4+2] intradimer adduct, is thermodynamically highly favored over other adducts that could potentially form on this surface, suggesting that this product state could form the basis of an ordered interfacial structure. Further investigation of an example of such an ordered structure, again using ab initio molecular dynamics, reveals that this structure is stable at room temperature.

Immunoelectron Microscopic Study of Podoplanin Localization in Mouse Salivary Gland Myoepithelium

We have recently reported that salivary gland cells express the lymphatic endothelial cell marker podoplanin. The present study was aimed to immunohistochemically investigate the expression of the myoepithelial cell marker α-smooth muscle actin (SMA) on podoplanin-positive cells in mouse parotid and sublingual glands, and to elucidate podoplanin localization in salivary gland myoepithelial cells by immunoelectron microscopic study. The distribution of myoepithelial cells expressing podoplanin and α-SMA was examined by immunofluorescent staining, and the localization of reaction products of anti-podoplanin antibody was investigated by pre-embedded immunoelectron microscopic method. In immunohistochemistry, the surfaces of both the mucous acini terminal portion and ducts were covered by a number of extensive myoepithelial cellular processes expressing podoplanin, and the immunostaining level with anti-podoplanin antibody to myoepithelial cells completely coincided with the immunostaining level with anti-α-SMA antibody. These findings suggest that podoplanin is a salivary gland myoepithelial cell antigen, and that the detection level directly reflects the myoepithelial cell distribution. In immunoelectron microscopic study, a number of reaction products with anti-podoplanin antibody were found at the Golgi apparatus binding to the endoplasmic reticulum in the cytoplasm of myoepithelial cells between sublingual gland acinar cells, and were also found at the myoepithelial cell membrane. These findings suggest that salivary gland myoepithelial cells constantly produce podoplanin and glycosylate at the Golgi apparatus, and transport them to the cell membrane. Podoplanin may be involved in maintaining the homeostasis of myoepithelial cells through its characteristic as a mucin-type transmembrane glycoprotein.

The cost and capacity of signaling in the Escherichia coli protein reaction network

In systems biology new ways are required to analyze the large amount of existing data onregulation of cellular processes. Recent work can be roughly classified into either dynamicalmodels of well-described subsystems, or coarse-grained descriptions of the topology of themolecular networks at the scale of the whole organism. In order to bridge these twodisparate approaches one needs to develop simplified descriptions of dynamics andtopological measures which address the propagation of signals in molecular networks.Transmission of a signal across a reaction node depends on the presence of other reactants.It will typically be more demanding to transmit a signal across a reaction node with moreinput links. Sending signals along a path with several subsequent reaction nodesalso increases the constraints on the presence of other proteins in the overallnetwork. Therefore counting in and out links along reactions of a potential pathwaycan give insight into the signaling properties of a particular molecular network.Here, we consider the directed network of protein regulation in E. coli, characterizing itsmodularity in terms of its potential to transmit signals. We demonstrate that the simplestmeasure based on identifying subnetworks of strong components, within which each nodecould send a signal to every other node, does indeed partition the network into functionalmodules. We suggest that the total number of reactants needed to send a signalbetween two nodes in the network can be considered as the cost associated withtransmitting this signal. Similarly we define spread as the number of reactionproducts that could be influenced by transmission of a successful signal. Ourconsiderations open for a new class of network measures that implicitly utilize theconstrained repertoire of chemical modifications of any biological molecule. Thecounting of cost and spread connects the topology of networks to the specificity ofsignaling across the network. Thereby, we address the signaling specificity within andbetween modules, and show that in the regulation of E. coli there is a systematicreduction of the cost and spread for signals traveling over more than two intermediatereactions.

Spectrophotometric study of zirconocene/polymethylalumoxane catalytic systems: principal component analysis and parametric modeling

Transformation of electronic absorption spectra of zirconocene catalytic systems Ph2CCpFluZrCl2-polymethylalumoxane (MAO) and rac-Me2Si(2-Me,4-PhInd)2ZrCl2-MAO (Flu is fluorenyl, Ind is indenyl) in toluene was studied upon a change in the ratio of reactants AlMAO/Zr from 0 to 3000 mol mol−1. Analysis of the spectroscopic data using statistical methods determined the number of reaction products in each system. A reaction model including three equilibria and being common for the both systems was proposed. Effective equilibrium constants and absorption spectra of individual reaction products were determined by parametric self-modeling of the experimental spectra.

Co-oxidation effects of methanol and benzene on the decomposition of 4-chlorobiphenyl in supercritical water

The decomposition reactions of 4-chlorobiphenyl (4CB) are investigated at 25 MPa and 773 K in supercritical water (SCW) in the presence of methanol and then benzene both without and with oxygen (from H 2O 2/H 2O solutions) to understand the co-oxidation effects on PCB conversion and reaction products. The reactions of 4CB, delivered to a tubular reactor as solutions in methanol and benzene (3 g/L), are conducted isothermally under plug-flow regime, and GC–FID/TCD/MSD chromatographic methods are employed for product analysis. At similar oxygen/organic equivalence ratios ( Φ I = 1.2 and Φ II = 1.3), global conversions of this simple PCB congener vary from 79 to 97% when delivered in methanol (I) and from 61 to 88% when benzene (II) has been used as co-solvent (2–24.5 s reaction time). Under the same initial oxygen concentration (0.144 mol/L; Φ I = 1.2 and Φ II = 0.5), molar conversions of 4CB in the latter system are even lower (48–72%). These results show the important role of methanol as reaction rate enhancer compared to benzene. Moreover, the identified reaction products of 4CB/MeOH and 4CB/C 6H 6 differ significantly in these systems, showing different reaction pathways. A dramatic increase in the number of reaction products has been observed in the presence of benzene compared to 4CB/MeOH reactions. Further, the more toxic dibenzofuran has been produced in the largest amount in the 4CB/C 6H 6 system and significant oligomerization of benzene/biphenyl also occurs. Even the most toxic dibenzo- p-dioxin was detected in amounts at the level of unreacted 4CB. These results clearly show the significance of the co-oxidation effects on PCB reaction rates, pathways, and products in SCW.

Gaseous and Particulate Oxidation Products Analysis of a Mixture of α-pinene + β-pinene/O3/Air in the Absence of Light and α-pinene + β-pinene/NOx/Air in the Presence of Natural Sunlight

The gas and particle phase reaction products of a mixture of the atmospherically important terpenes α-pinene and β-pinene with the atmospheric oxidants O3 and OH/NOx were investigated using both gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) for identification and quantification of reaction products. The nighttime oxidation of a mixture of α-pinene and β-pinene in the presence of O3/air, and the daytime oxidation of a mixture of α-pinene + β-pinene with NOx air in the presence of natural sunlight were carried out in the University of North Carolina's large outdoor smog chamber (190 m3) located in Chatham County, North Carolina. Mass balances for gaseous and aerosol reaction products are reported over the course of the reaction. More than twenty-nine products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for ∼74 to ∼80% of the reacted α-pinen/β-pinene mixture carbon. Measurements show that a number of reaction products were found in both O3 and NOx system [pinonaldehyde, pinic acid, pinonic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxy-nopinone, 3-hydroxy-nopinone, and nopinone]. Pinonic acid, pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, and 10-hydroxypinonic acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols.

Mass Balance of Gaseous and Particulate Products from β-Pinene/O3/Air in the Absence of Light and β-Pinene/NOx/Air in the Presence of Natural Sunlight

The gas and particle phase products from the reaction of β-pinene with the atmospheric oxidants O3 and OH radicals in the presence of NOx were investigated using both gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) for identification and quantification of reaction products. The nighttime oxidation of β-pinene in the presence of O3/air and the daytime oxidation of β-pinene in the presence of NOx/air and natural sunlight were carried out in the University of North Carolina large outdoor smog chamber (190 m3) located in Chatham County, North Carolina. A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study the secondary organic aerosol (SOA) formation, and a filter pack/denuder sampling system was used for simultaneously collecting gas and particle phase products for analysis. A gas chromatograph coupled to a mass spectrometer (GC-EIMS or GC-CIMS) was used for the identification and quantification of gas and aerosol products. A HPLC method was used for the measurement of small carbonyl compounds (aldehydes and ketones) as their 2,4-dinitrophenylhydrazones (DNPH) derivatives. Mass balances for gaseous and aerosol reaction products were reported over the course of the reaction. More than sixteen products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for ∼57 to ∼71% of the reacted β-pinene carbon. Measurements showed that a number of reaction products were found in both O3 and NOx systems (pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxynopinone, 3-hydroxynopinone, and nopinone). Pinic acid, pinalic-3-acid, and 4-hydroxypinalic-3-acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols. Detailed reaction schemes are presented to account for most of the observed reaction products.

Gas and Particulate Products Distribution from the Photooxidation of α-Humulene in the Presence of NOx, Natural Atmospheric Air and Sunlight

The photooxidation of α-humulene in the presence of NOx, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for ∼ 44% of the reacted α-humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco-α-humulone aldehyde, 7-seco-α-humulone aldehyde, α-humulal aldehyde, α-humulene 3-oxide or α-humulene 7-oxide, α-humulaic/alic acid isomers, and 3-seco-α-14-hydroxyhumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.

Gas and Particle Products Distribution from the Reaction of β-Caryophyllene with Ozone

Gas and particulate reaction products from the ozonolysis of β -caryophyllene (I) in the presence of atmospheric air were investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study secondary organic aerosol formation. The nighttime oxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported over the course of the reaction. On average, measured gas and particle phase products accounted for ∼64% of the reacted β -caryophyllene (I) carbon. Measurements show that a number of reaction products with low vapor pressure (e.g., β-caryophyllone aldehyde (IV), β-norcaryophyllone aldehyde (V), β-caryophyllonic acid (VIII), β-14-hydroxycaryophyllonic acid (XIV)) were found in the sample taken during the first 20 min of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.

A fast programmable trigger system for the WASA experiment

A programmable fast trigger system for the WASA experiment at The Svedberg Laboratory, Uppsala, Sweden is presented. For minimum signal delay times the hardware architecture is divided into two levels. The first level mainly handles fast signals from about 350 plastic scintillating detectors forming hit cluster multiplicity decision, restricting the total number of reaction products. Track alignment checks, coplanarity and deposited energy checks put further restrictions on the acquired events. The first level incorporates 40 generic trigger modules, prescalers, scalers, and pattern units. To minimize dead-time losses the first level is working in a feed-through mode with no external strobe signals required, the total delay amounts to 120 ns. The second level utilizes a fast cluster finding algorithm implemented in 40 trigger modules operating on signals from an array of 24/spl times/48 CsI crystals. Background is filtered away by restricting the spatial distribution and the number of reaction products. The output from the cluster analyzing second level is provided within 115 ns. The trigger utilizes programmable logic devices and. is fully reconfigurable. An I/sup 2/C-based slow control system is provided for setting discriminator thresholds, pulse duration, channel masking, signal delay, and setup of logic conditions.

Gas-Phase Reactions of Nopinone, 3-Isopropenyl-6-oxo-heptanal, and 5-Methyl-5-vinyltetrahydrofuran-2-ol with OH, NO3, and Ozone

In the troposphere, α-pinene, β-pinene, limonene, and linalool are mainly oxidized to pinonaldehyde, nopinone, 3-isopropenyl-6-oxoheptanal (IPOH), and 5-methyl-5-vinyltetrahydrofuran-2-ol (MVT), respectively. The rate constant of the reactions of nopinone, IPOH, and MVT with OH, NO3, and O3 were determined by long path FT-IR spectroscopy, and the oxidation products from the reactions between the OH radical and pinonaldehyde, nopinone, IPOH, and MVT were investigated using GC−MS and HPLC. The reaction rate constants (k) for the reactions have been determined at 740 ± 5 Torr and 298 ± 5 K, and a number of reaction products were identified. The rate constants obtained for the reactions with nopinone were kOH = (1.7 ± 0.2) × 10-11, kNO3 < 2 × 10-15, and kO3 < 5 × 10-21; for the reactions with IPOH were kOH = (1.1 ± 0.3) × 10-10, kNO3 = (2.6 ± 0.8) × 10-13, and kO3 = (8.3 ± 2.2) × 10-18; and for the reactions with MVT were kOH = (7.4 ± 0.9) × 10-11, kNO3 = (2.0 ± 0.9) × 10-14, and kO3 = (3.8 ± 0.8) × 10-18 (all units are in cm3 molecule-1 s-1, and uncertainties are given as two σ on the experimental data). From the results obtained in this investigation and previous studies, it was concluded that a typical atmospheric lifetime with respect to chemical reactions was only a few hours for pinonaldehyde, IPOH, and MVT but was much longer for nopinone with a lifetime of about 10 h.

Heterogeneous Catalytic Oxidation of Acrolein to Acrylic Acid: Mechanism and Catalysts

Abstract Partial oxidation of acrolein is a commercially important reaction, its product—acrylic acid—being widely used industrially for producing resins, dyes, glues, nonwoven fabrics, etc. Partial oxidation of acrolein is also a convenient model reaction because: (1) the number of reaction products is moderate (CO, CO2, acrylic acid) and (2) their difference in acid-base properties from the starting material makes it possible to select desirable catalysts by applying directly and efficiently Boreskov's concept of intermediate chemical interaction of a catalyst with reaction mixture components. According to this concept [1], the transformation of surface intermediates (SI) formed in the interaction of reactants with a catalyst's surface is determined by the structure and bond energy of these SI. The study of the reaction mechanism includes determination of structures and energy characteristics of the surface intermediates and the elucidation of their connection with catalyst chemical composition and reaction routes to particular products. This reliable information helps us to understand the nature of catalyst action and to elaborate the theory of catalyst selection. We have used this method to approach the problem of the systematic selection of catalysts for the oxidation of acrolein to acrylic acid. The review summarizes the research done in the lnstitute of Catalysis of the Siberian Branch of the Russian Academy of Sciences during recent years.

Aqueous ozonation of a quaternary ammonium surfactant

The reactivity of a mixture of saturated and unsaturated quaternary ammonium surfactants towards ozone was examined at a total substrate concentration of 500 μg l −1. Saturated components were unreactive; unsaturated components of the surfactant were reactive towards ozone. A number of reaction products or their methylated derivatives were identified by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and fast atom bombardment-mass spectrometry (FAB-MS). The reaction products identified were consistent with a 1,3-dipolar cycloaddition of ozone to a carbon-carbon double bond.

Aqueous Ozonation Of Fatty Acids

Abstract The reactivity of a series of fatty acids toward ozone was examined in aqueous solution at low substrate concentration (μg.L−1 range). Saturated fatty acids were unreactive, unsaturated fatty acids were readily consumed. A number of reaction products or their methylated derivatives were identified by gas chromatography and gas chromatography-mass spectrometry. The products identified are consistent with a 1,3-dipolar cyclo-addotion reaction.

Chemical effects of ion implantation on solid benzene

N + 2, CO + and Ar + at keV energy have been implanted on solid benzene. A number of reaction products were found. The most abundant are: biphenyl, 5-phenyl-1,3-cyclohexadiene, 3-phenyl-1,4-cyclohexadiene and phenylacetylene. The experiment shows that the nature of the projectile does not influence the chemical composition of the main products formed in the implantation phenomena. A mechanism explaining the formation of these products is proposed.