Primary OH Research Articles

Musa Paradaisica and <i>Vitis vinifera</i> Functionalised Ag-NPs: Electrochemical and Optical Detection of <i>Escherichia coli</i> in Seawater

Herein, we demonstrate a simple and inexpensive one-pot green synthesis of silver nanoparticles (Ag-NPs) functionalised with a combination of banana peel (Musa paradisiaca) and grape (Vitis vinifera) fruit extracts. The reaction mixture of aqueous silver nitrate, banana peel and grapefruit extracts revealed a dark brown colour after a reaction time of 18 minutes, which indicates the presence and the successful synthesis of silver nanoparticles. The optical and structural properties of the green synthesised nanoparticles were analysed using UV-Visible spectroscopy (UV-Vis) which confirmed an absorption band at 440 nm. The polydispersity nature and the AgNPs sizes of 30 nm were revealed using small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HR-TEM) techniques. Fourier transform infrared spectroscopy (FT-IR) studies revealed the structure of these nanoparticles which included carbonyl groups, primary amine groups, OH groups and other stabilizing functional groups characteristic of the properties of combined extracts. A simple, quick, less time-consuming surface plasmon resonance (SPR) and electrochemical method in the form of optical and electrochemical sensors have been developed for the detection of Escherichia coli 0157:H7. The obtained limit of detection (LOD) values for SPR and GBPE-Ag-NPs/GCE-based sensor systems were found to be 1 × 102 CFU/mL and 3.5 × 101 CFU/mL, respectively. The obtained values fall within the range for E. coli 0157:H7 in seawater.

Investigating the sources of atmospheric nitrous acid (HONO) in the megacity of Beijing, China

Nitrous acid (HONO) can powerfully influence atmospheric photochemistry by producing hydroxyl radical (OH), which is a crucial oxidant that controls the fate of atmospheric trace species. To deduce HONO formation mechanisms in polluted regions, two field observations were conducted in urban Beijing during the early summer of 2017 and the winter of 2018. These two seasons bore distinguishing pollution characteristics with a higher degree of ageing and heavier aerosol loading in the early summer and more abundant NOx (NOx = NO + NO2) in the winter. Elevated concentrations of HONO were observed during these two seasons, with the mean ± standard deviation (maximum) concentrations of 1.25 ± 0.94 (6.69) ppbv and 1.04 ± 1.27 (9.55) ppbv in early summer and winter, respectively. The observed daytime (08:00–17:00 h, local time) HONO production rate was several times higher in early summer than in winter (4.44 ± 1.93 ppbv h−1 vs. 0.88 ± 0.49 ppbv h−1). Budget analysis revealed distinct daytime HONO formation mechanisms during these two seasons. Photo-induced heterogeneous conversion of NO2 on the ground surface dominated in early summer, and homogeneous reaction of NO + OH was dominant in winter. Photolysis of HONO was the major source of primary OH in both seasons, and thus, played a key role in the regulation of atmospheric oxidising capacity. This study demonstrates the significant seasonal variations in HONO budget and underlines the predominant role of HONO in primary OH production in Beijing. Our findings will be helpful to gain an understanding of the chemical mechanisms underlying the formation of secondary pollution in metropolitan areas.

Immobilized Fe3O4-Polydopamine-Thermomyces lanuginosus Lipase-Catalyzed Acylation of Flavonoid Glycosides and Their Analogs: An Improved Insight Into Enzymic Substrate Recognition.

The conversion of flavonoid glycosides and their analogs to their lipophilic ester derivatives was developed by nanobiocatalysts from immobilizing Thermomyces lanuginosus lipase (TLL) on polydopamine-functionalized magnetic Fe3O4 nanoparticles (Fe3O4-PDA-TLL). The behavior investigation revealed that Fe3O4-PDA-TLL exhibits a preference for long chain length fatty acids (i.e., C10 to C14) with higher reaction rates of 12.6–13.9 mM/h. Regarding the substrate specificity, Fe3O4-PDA-TLL showed good substrate spectrum and favorably functionalized the primary OH groups, suggesting that the steric hindrances impeded the secondary or phenolic hydroxyl groups of substrates into the bonding site of the active region of TLL to afford the product.

Conformations and structures of 1,4-pentadien-3-ol and its water complex characterized by rotational spectroscopy

The 1,4-pentadien-3-ol and its monohydrate have been characterized by microwave spectroscopy in combination with theoretical computations. Experiments and ab initio calculations revealed that the 1,4-pentadien-3-ol monomer prefers a configuration with one vinyl being syn to the hydroxyl oxygen and the hydroxyl hydrogen toward the skew arranged vinyl, which therefore makes possible simultaneous CH···O and OH···π interactions. The observed monohydrate corresponds to the global minimum predicted theoretically, which is stabilized through a primary OH···Ow hydrogen bond together with a much weaker OwH···π hydrogen bond. The NCI analyses, NBO calculation and SAPT method were applied to further elucidate the characteristics of hydrogen bonds in the 1,4-pentadien-3-ol···water complex.

Proton Conductive, Low Methanol Crossover Cellulose-Based Membranes.

This work describes the development of sulfated cellulose (SC) polymer and explores its potential as an electrolyte-membrane for direct methanol fuel cells (DMFC). The fabrication of our membranes was initiated by the preparation of the novel sulfated cellulose solution via controlled acid hydrolysis of microcrystalline cellulose (MCC). Ion-conductive crosslinked SC membranes were prepared following a chemical crosslinking reaction. SC solution was chemically crosslinked with glutaraldehyde (GA) and cured at 30 °C to produce the aforementioned membranes. Effects of GA concentration on methanol permeability, proton conductivity, water uptake and thermal stabilities were investigated. The crosslinking reaction is confirmed by FTIR technique where a bond between the primary OH groups of cellulose and the GA aldehyde groups was achieved, leading to the increased hydrophobic backbone domains in the membrane. The results show that the time of crosslinking reaction highly affects the proton conduction and methanol permeability. The proton conductivity and methanol crossover (3M) of our GA crosslinked SC membranes are 3.7 × 10−2 mS cm−1 and 8.2 × 10−9 cm2 s−1, respectively. Crosslinked sulfated cellulose films have lower ion conductivity than the state-of-the-art Nafion (10.2 mS cm−1); however, the methanol crossover is three orders of magnitude lower than Nafion membranes (1.0 × 10−5 cm2 s−1 at 1 M). Such biofilms with high methanol resistivity address the major hurdle that prevents the widespread applications of direct alcohol fuel cells.

A molecular dynamics study of the effect of functional groups and side chain on adsorption of alcoholic surfactant and interfacial thermal transport

In the present study, we investigated the effect of the number and position of functional groups, and the length of the main chain and side chain in organic surfactant on adsorption behavior and interfacial heat transfer between silica surface and alkane solvent by non-equilibrium molecular dynamics simulation, where the surfactants were primary/secondary alcohol, monohydric/dihydric alcohol, and linear/branched alcohol. The results showed a similar adsorption behavior for all the surfactant types, where hydroxyl functional (OH) groups adsorbed onto the silica surface and alkyl chain was in contact with the solvent, which produced a heat path from silica via surfactant to solvent. The number of adsorbed OH groups did not directly translate to significantly decreased thermal boundary resistance due to the adsorption structure. Coulomb interaction enabled the closer distance between primary terminal OH groups in surfactant and silica surface, which enhanced the solid-surfactant intermolecular heat transfer. However, Coulomb interaction contributed less to shorten the molecular distances between secondary OH groups in surfactant and silica surface, which was connected to less efficient heat transfer from silica to surfactant and thereby did not enhance the interfacial heat transfer as much as surfactants with terminal OH. The increase in terminal OH groups in the surfactant molecules could not significantly reduce thermal boundary resistance, although the adsorption amount of OH was distinctly greater than that of surfactants with single OH. The side chain in surfactant enabled the efficient surfactant-solvent intermolecular heat transfer but related to the desorption of surfactant when decreasing the temperature. Thus branched-chain dihydric alcohol performed better than other surfactants on reducing thermal boundary resistance when the interfacial temperature was high enough to maintain the sufficient adsorption amount. We considered such reverse temperature-sensitive surfactant has a great potential application to fulfill multiple needs for heat dissipation of electronic devices, especially the high temperature operation. The new insights obtained in the present study were a step towards a molecular structure design of surfactant enhancing solid–liquid interfacial heat transfer.

Kinetically Equivalent Functionality and Reactivity of Commonly Used Biocompatible Polyurethane Crosslinking Agents

In this paper, the kinetics of the reaction of phenyl isocyanate with crosslinking agents such as sucrose, sorbitol, and glycerol are reported. Crosslinking agents were used in high molar excess to isocyanate to obtain pseudo-first-order rate dependencies, and the reaction products were separated by high-performance liquid chromatography and detected by UV spectroscopy and mass spectrometry. It was found that the glycerol’s primary hydroxyl groups were approximately four times reactive than the secondary ones. However, in the case of sorbitol, the two primary OH groups were found to be the most reactive, and the reactivity of hydroxyl groups decreased in the order of kOH(6)(8.43) > kOH(1)(6.91) > kOH(5)(1.19) > kOH(2)(0.98) > kOH(3)(0.93) > kOH(4)(0.64), where the numbers in the subscript and in the brackets denote the position of OH groups and the pseudo-first-order rate constants, respectively. The Atomic Polar Tenzor (APT) charges of OH groups and dipole moments of monosubstituted sorbitol derivatives calculated by density functional theory (DFT) also confirmed the experimental results. On the other hand, the reactions of phenyl isocyanate with crosslinking agents were also performed using high excess isocyanate in order to determine the number of OH-groups participating effectively in the crosslinking process. However, due to the huge number of derivatives likely formed in these latter reactions, a simplified reaction scheme was introduced to describe the resulting product versus reaction time distributions detected by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). Based on the results, the kinetically equivalent functionality (fk) of each crosslinking agent was determined and found to be 2.26, 2.6, and 2.96 for glycerol, sorbitol, and sucrose, respectively.

Interference from alkenes in chemiluminescent NO<sub><i>x</i></sub> measurements

Abstract. Nitrogen oxides (NOx=NO+NO2) are critical intermediates in atmospheric chemistry and air pollution. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3 and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants, such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial for air quality monitoring and understanding atmospheric composition. The most commonly used approach for the measurement of NO is the chemiluminescent detection of electronically excited NO2 (NO2∗) formed from the NO + O3 reaction within the NOx analyser. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in conventional instrument background cycles, which also utilises the reaction with ozone, differs from that in the measurement cycle such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed, the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors to a series of alkenes. These NOx monitors range from systems used for routine air quality monitoring to atmospheric research instrumentation. The species-investigated range was from short-chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European PHOtoREactor (EUPHORE) to ensure common calibration and samples for the monitors and to unequivocally confirm the alkene levels present (via Fourier transform infrared spectroscopy – FTIR). The instrument interference responses ranged from negligible levels up to 11 %, depending upon the alkene present and conditions used (e.g. the presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high VOC, low NOx environments such as forests or indoor environments where alkene abundance from personal care and cleaning products may be significant.

Interfacial adhesion of a grafted polymer on a cellulose surface: a first-principles study

This paper presents the first-principles investigation on interfacial adhesive strength between grafted polymer and cellulose. Focusing on maleic anhydride-grafted polypropylene, which is expected to be used in various applications including automobiles, a simple interfacial model was constructed under a local tensile loading condition. Then the stress–strain relation, deformation of molecular structure and breaking process were discussed. From comparison of mechanical responses among three chemically possible bonding configurations, it was clarified that the monoester bond exhibited higher interfacial strength than the diester bond. We also found that controlling the bonding configuration can improve the interface strength by about 50% compared to when primary OH groups react to form ester bonds. It was proved that this first-principles calculation model was effective for the definitive design and development of chemical modification of nanocellulose.

Isolation of Low Dispersity Fractions of Acetone Organosolv Lignins to Understand their Reactivity: Towards Aromatic Building Blocks for Polymers Synthesis.

Two organosolv lignins extracted during pilot runs of the Fabiola process were analyzed, fractionated and chemically modified with ethylene carbonate (EC) to produce building blocks suitable for polymer synthesis. Isolation of low dispersity fractions relied on the partial solubility of the lignins in organic solvents. Lignins solubility was first evaluated and analyzed with Hansen and Kamlet‐Taft solubility parameters, showing a good correlation with the solvents dipolarity/polarizability parameter π*. The results were then used to select a sequence of solvents able to fractionate the lignins into low dispersity fractions of increasing molar masses, which were analyzed by 31P NMR, SEC and DSC. The lignins were then reacted with EC, to convert the phenolic OH groups into primary aliphatic OH groups. The reactivity of the organosolv lignins was high, and milder reaction conditions than previously reported were sufficient to fully convert the phenolic OH groups. A gradual reduction in reactivity with increasing molar mass was evidenced and attributed to reduced solubility of high molar mass fragments in EC. Undesirable crosslinking side reactions were evidenced by SEC, but were efficiently limited thanks to a fine control of the reaction conditions, helping to maximize the benefits of the developed lignin modification with EC.

Statistical relationship between soot volume fraction, temperature, primary particle diameter and OH radicals along transects normal to the local reaction zone in a turbulent flame

We present a new method to extract experimental data from simultaneous planar images in turbulent sooting flames, to derive transects of key species based on local coordinates that are aligned normal to the instantaneous, fluctuating reaction zone. Such statistics represent a milestone in the assessment of turbulent sooting flames, because they are one-dimensional and based on local coordinates conditioned on the distribution of soot sheets, in contrast to previous statistics, which are typically Eulerian and single point in nature. The local coordinate system was determined from instantaneous images of soot volume fraction (fv) based on a varying threshold and the local reaction zone was identified by further referring OH images. Quantitative experimental data of fv, temperature (T) and primary particle diameter (Dp), together with qualitative OH intensities, were extracted along the direction normal to the local reaction zone from simultaneous images of the four parameters. These results were measured in a pre-vaporized toluene diffusion flame (Reynolds number = 10,000) using advanced laser-based techniques. Statistical data were combined together and used to generate the profiles for these four parameters with high accuracy and level of resolution that is not possible using previous statistics methods based on Eulerian coordinates. These new kind results showed that the spatial relationship between fv, T and OH remains broadly similar anywhere in the flame, while the profiles of Dp significantly shift away from those of the other three parameters with the increase in the height of the flame. The mean values of fv, Dp and T also show a clear relationship as a function of the height, even though the trends of mean fv and Dp along the height are different from that of T, also suggesting a strong relationship exists between soot and temperature in the local reaction zone.

The effect of fuel composition and Reynolds number on soot formation processes in turbulent non-premixed toluene jet flames

The soot formation processes in three different turbulent prevaporized non-premixed toluene jet flames stabilized on a jet-in-hot-coflow (JHC) burner were investigated in this study. The jet Reynolds number and the stoichiometric mixture fraction were varied in order to manipulate the flow time scales and the chemistry, respectively. Time-resolved laser-induced incandescence (TiRe-LII), non-linear two-line atomic fluorescence of indium (nTLAF), and OH planar laser induced fluorescence (PLIF) were simultaneously applied to yield spatially resolved and instantaneous fields of soot volume fraction, primary particle size, temperature, and OH. The mean distributions of the detected quantities are used to identify major differences among the flames. The highest soot loading is observed for the low Reynolds number and low stoichiometric mixture fraction flame. However, this flame features also the lowest temperature and primary particle size. Based on these observations, the simultaneously detected data sets and flamelet computations are employed to elucidate differences in the soot formation pathways in the flames. The analyses reveal that the high soot loading causes greater heat losses in the low Reynolds number and low stoichiometric mixture fraction flame. This has a significant impact on the soot formation pathways and causes a reduction in the particle size.

Spatially dependent H-bond dynamics at interfaces of water/biomimetic self-assembled lattice materials

Understanding hydrogen-bond interactions in self-assembled lattice materials is crucial for preparing such materials, but the role of hydrogen bonds (H bonds) remains unclear. To gain insight into H-bond interactions at the materials' intrinsic spatial scale, we investigated ultrafast H-bond dynamics between water and biomimetic self-assembled lattice materials (composed of sodium dodecyl sulfate and β-cyclodextrin) in a spatially resolved manner. To accomplish this, we developed an infrared pump, vibrational sum-frequency generation (VSFG) probe hyperspectral microscope. With this hyperspectral imaging method, we were able to observe that the primary and secondary OH groups of β-cyclodextrin exhibit markedly different dynamics, suggesting distinct H-bond environments, despite being separated by only a few angstroms. We also observed another ultrafast dynamic reflecting a weakening and restoring of H bonds between bound water and the secondary OH of β-cyclodextrin, which exhibited spatial uniformity within self-assembled domains, but heterogeneity between domains. The restoration dynamics further suggest heterogeneous hydration among the self-assembly domains. The ultrafast nature and meso- and microscopic ordering of H-bond dynamics could contribute to the flexibility and crystallinity of the material--two critically important factors for crystalline lattice self-assemblies--shedding light on engineering intermolecular interactions for self-assembled lattice materials.

HONO Budget and Its Role in Nitrate Formation in the Rural North China Plain.

Nitrous acid (HONO) is a major precursor of tropospheric hydroxyl radical (OH) that accelerates the formation of secondary pollutants. The HONO sources, however, are not well understood, especially in polluted areas. Based on a comprehensive winter field campaign conducted at a rural site of the North China Plain, a box model (MCM v3.3.1) was used to simulate the daytime HONO budget and nitrate formation. We found that HONO photolysis acted as the dominant source for primary OH with a contribution of more than 92%. The observed daytime HONO could be well explained by the known sources in the model. The heterogeneous conversion of NO2 on ground surfaces and the homogeneous reaction of NO with OH were the dominant HONO sources with contributions of more than 36 and 34% to daytime HONO, respectively. The contribution from the photolysis of particle nitrate and the reactions of NO2 on aerosol surfaces was found to be negligible in clean periods (2%) and slightly higher during polluted periods (8%). The relatively high OH levels due to fast HONO photolysis at the rural site remarkably accelerated gas-phase reactions, resulting in the fast formation of nitrate as well as other secondary pollutants in the daytime.

Ship emission of nitrous acid (HONO) and its impacts on the marine atmospheric oxidation chemistry

Nitrous acid (HONO) is an important reservoir of the hydroxyl radical (OH) and thus plays a central role in tropospheric chemistry. Exhaust from engines has long been known as a major primary source of HONO, yet most previous studies focused on vehicle emissions on land. In comparison, ship emissions of HONO have been rarely characterized, and their impacts on the tropospheric oxidation chemistry have not been quantified. In this study, we conducted cruise measurements of HONO and related species over the East China Sea. Contrasting air masses from pristine marine background air to highly polluted ship plumes were encountered. The emission ratio of ΔHONO/ΔNOx (0.51 ± 0.18%) was derived from a large number of fresh ship plumes. Using the in-situ measured emission ratio, a global ship emission inventory of HONO was developed based on the international shipping emissions of NOx in the Community Emission Data System inventory. The global shipping voyage emits approximately 63.9 ± 22.2 Gg yr−1 of HONO to the atmosphere. GEOS-Chem modelling with the addition of ship-emitted HONO showed that HONO concentrations could increase up to 40–100% over the navigation areas, leading to about 5–15% increases of primary OH production in the early-morning time. This study elucidates the potentially considerable effects of ship HONO emissions on the marine atmospheric chemistry, and calls for further studies to better characterize the ship emissions of HONO and other reactive species, which should be taken into account by global and regional models.

Development and characterization of swirl-stabilized diffusion mesoscale burner array

A diffusion mesoscale burner array with integrated fuel manifold and injection holes has been developed for compact and efficient propulsion and power systems. Each burner element is equipped with its own fuel injection holes built into its swirl-inducing geometry to improve flame interaction and reduce flame length. The diffusion mesoscale burner array provides comparable performance to a premixed mesoscale burner array under similar operating conditions despite fuel unpremixedness. Overall, diffusion flames on the mesoscale burner array exhibit 7.8% lower global equivalence ratios at lean blow-off conditions compared to premixed flames. Imaging of two primary combustion intermediates, OH and CH2O, is carried out using planar laser induced fluorescence to visualize the post- and pre-combustion zones of diffusion and premixed flames. Simultaneous 10 kHz high-speed OH fluorescence images and pressure measurements are used to study flame response and stability under external acoustic perturbation at a frequency of 200 Hz. OH fluorescence images show higher heat release and flame front fluctuations for diffusion flames. Rayleigh index reveals similar thermo-acoustic stability characteristics between diffusion and premixed flames. However, diffusion mesoscale flames exhibit large flame surface variation under external acoustic perturbation by spectral proper orthogonal decomposition analysis.

Human odour thresholds are tuned to atmospheric chemical lifetimes.

In this study, the odour thresholds (OT) and atmospheric lifetimes (AL) were compared for a suite of volatile organic compounds. It was found that odour threshold, as determined by the triangle bag method, correlated surprisingly well with atmospheric lifetime for a given chemical family. Molecules with short atmospheric lifetimes with respect to the primary atmospheric oxidant OH tend to be more sensitively detected by the human nose. Overall the correlation of odour threshold with atmospheric lifetime was better than with mass and vapour pressure. Several outliers from the correlations for particular chemical families were examined in detail. For example, diacetyl was an outlier in the ketone dataset that fitted the trend when its more important photolysis lifetime was included; and similarly, the relatively low odour threshold of carbonyl sulfide (OCS) was interpreted in terms of uptake by vegetation. The OT/AL relationship suggests that OH rate constants can be used as a first-order estimate for odour thresholds (and vice versa). We speculate that the nose's high sensitivity to chemicals that are reactive in the air is likely an evolved rather than a learned condition. This is based on the lack of dependence on ozone in the aliphatics, that the anthropogenically emitted aromatic compounds had the worst correlation, and that OCS had a much lower than predicted OT. Finally, we use the OT/AL relationships derived to predict odour thresholds and rate constants that have not yet been determined in order to provide a test to this hypothesis.This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.

A Mild Methylation of Whole Leaf Producing Per-O-methyl Cellulo Di-phospho Amino Acid (Dipeptide)

A mild methylation method is detailed in this work. It uses 1N NaOH to deprotonate primary and secondary hydroxyl groups for short time. Excess 1N NH4OH (1.00 ml, pH 11.4) is added, followed by NaHCO3 to make the carbonate esters by nucleophilic substitution of the deprotonated primary and secondary OH groups. The reaction conditions include; ambient temperature and for an appropriate time. Then NaBH4 is added and the reaction conditions are; standing at ambient temperature for at least 4 hours. This converts the carbonate esters to the methyl ethers. Work-up includes transferring the methylated switchgrass leaf section to a vial containing 1N HCl (1.00 ml). The leaf needs to be submerged in the acid. The reaction conditions include; heating the reaction vessel at 72°C, for 4 days. The contents of the vial are reduced in volume to syrup with a stream of air. The mixture dissolves completely in methanol. Mass spectrometry is done on a methanol solution in the negative ion ESI mode. The mass spectral interpretation reveals the presence of methylated glucan amimo acids and glucan dipeptides. The molecules identified were per-O-methylated glucans linked to either serine or asparagine through a di-(hydrido) di-phospho di-hydratephe moeity. It is possible that one ion is derived from a phosphorylated tyrosine linked to either the serine or asparagine linked to an originally di-phospho cellulo-glucan.

The effect of oxygen concentration in the co-flow of laminar ethylene diffusion flames

This paper reports an experimental study of the effects of oxygen concentration (OC) in the oxidant stream on the characteristics of laminar co-flow ethylene diffusion sooting flames. Oxygen concentration was varied from 16.8% to 36.8% (by volume) by either diluting the air co-flow with nitrogen or by adding oxygen. Planar optical measurements were performed, with high spatial resolution, of flame luminosity at 700 nm, soot volume fraction, flame temperature, primary soot particle diameters and OH* chemiluminescence. All measured parameters are found to vary significantly with OC over the investigated range. The soot volume fraction measurements quantify the extent to which soot formation and oxidation are enhanced by increasing OC, revealing that the former effect dominates in the upstream region, while the latter effect dominates the downstream region, close to the flame tip. The changes to flame luminosity, soot volume fraction and flame temperature are strongly correlated with each other, while the primary soot particle diameter correlates well with the soot residence time. In addition, the rate of soot evolution, including its formation and oxidation, correlates with flame temperature along the axis of flames and a second reaction zone emerges in the tip of flames with high OC, as revealed by OH* chemiluminescence. The experimental data are well suited to the development and validation of soot models because of the well-defined boundary conditions, high spatial resolution, systematic nature and combination of the measured scalars.

Mechanism of HF condensive complex plasma modification of polyurethane membrane coatings in the air environment

The mechanism of the high frequency condensive complex plasma modification of polyurethane membrane coatings in air is investigated. The study revealed that after plasma modification in air, oxidation and hydrolysis of polyurethane membrane coatings occurs, which is expressed in an increase in the intensity of absorption bands corresponding to primary OH groups in the range of wave numbers 1005–1070 cm−1, 1310 cm−1 and 1420 cm−1, as well as in partial destruction of polyurethane chains with the formation of urea groups, which corresponds to the vibrations of CO-groups in the range of wave numbers 1590–1690 cm−1.