Abstract  Fossil stromatolites may reveal information about their hydrochemical palaeoenvironment, provided that assignment to a specific microbial community and a corresponding biogeochemical mechanism of formation can be made. Tithonian stromatolites of the Munder Formation at Thuste, north Germany, have traditionally been considered as formed by intertidal cyanobacterial communities. However, thin sections of the stromatolites show elongated angular traces of former gypsum crystals in a dense arrangement, but no algal or cyanobacterial filament traces. Moreover, high Fe(2+) and Mn(2+) contents, oxygen-isotope and sulphur-isotope ratios of carbonate-bound sulphates, and sulphurized hydrocarbon biomarkers of the stromatolitic carbonate indicate that CaCO(3) precipitation occurred near the oxic-anoxic interface as a result of intensive bacterial sulphur cycling rather than photosynthetic activity. Furthermore, anaerobic oxidation of methane by Archaea may have driven CaCO(3) precipitation in deeper parts of the biofilm community, as reflected by high concentrations of squalane with a strongly negative delta(13)C in conjunction with evaporite pseudomorphs showing extremely low delta(13)C(Carb) ratios. Consequently, the Thuste stromatolites are now interpreted as having initially formed by gypsum impregnation of biofilms. Subsequently, early Mg-calcitic calcitization within the biofilms occurred because of combined bacterial iron, manganese and sulphate reduction, with an increasing contribution of anaerobic oxidation of methane with depth. This model plausibly explains the prominent preservation of signals derived from oxygen-independent metabolic pathways, whereas virtually no geochemical record exists for an aerobic community that may, nevertheless, have prevailed at the stromatolite surface. Photic-zone stromatolites with a prominent signal of anaerobic oxidation of methane may be common in, and indicative of, oxygen-depleted sulphate-bearing environments with high rates of methane production, conditions that possibly were fulfilled at the Archaean to Proterozoic transition.

Abstract  The dynamics of the gas-liquid interfacial reaction of the first electronically excited state of the oxygen atom, O((1)D), with the surface of a liquid hydrocarbon, squalane (C(30)H(62); 2,6,10,15,19,23-hexamethyltetracosane) has been studied experimentally. Translationally hot O((1)D) atoms were generated by 193 nm photolysis of a low pressure (nominally 1 mTorr) of N(2)O a short distance (mean = 6 mm) above a continually refreshed liquid squalane surface. Nascent OH (X(2)Π, v' = 0) reaction products were detected by laser-induced fluorescence (LIF) on the OH A(2)Σ(+)-X(2)Π (1,0) band at the same distance above the surface. The speed distribution of the recoiling OH was characterized by measuring the appearance profiles as a function of photolysis-probe delay for selected rotational levels, N'. The rotational (and, partially, fine-structure) state distributions were also measured by recording LIF excitation spectra at selected photolysis-probe delays. The OH v' = 0 rotational distribution is bimodal and can be empirically decomposed into near thermal (~300 K) and much hotter (~6000 K) Boltzmann-temperature components. There is a strong positive correlation between rotational excitation and translation energy. However, the colder rotational component still represents a significant fraction (~30%) of the fastest products, which have substantially superthermal speeds. We estimate an approximate upper limit of 3% for the quantum yield of OH per O((1)D) atom that collides with the surface. By comparison with established mechanisms for the corresponding reactions in the gas phase, we conclude that the rotationally and translationally hot products are formed via a nonstatistical insertion mechanism. The rotationally cold but translationally hot component is most likely produced by direct abstraction. Secondary collisions at the liquid surface of products of either of the previous two mechanisms are most likely responsible for the rotationally and translationally cold products. We do not think it likely, a priori, that they could be produced in the observed significant yield via a statistical insertion mechanism for a molecule the size of squalane embedded in a surrounding liquid surface.

Abstract  The residual fractions remaining after microbial degradation of diesel fuel, different deparaffinized raffinates and extracts from long-term contaminated soils were analyzed by liquid chromatography, gas chromatography, infrared spectrometry and mass spectrometry. The quantity of saturated hydrocarbons decreased after the microbial treatment, whereas the portion of polar compounds increased. The total content of aromatics changed only insignificantly. n-Paraffins < C26 were found to be no longer present in mineral oils degraded to exhaustion. Infrared spectrometry revealed oxygen compounds in the residues, mainly ketones, fatty acids and esters. Elementary analysis confirms the presence of nitrogen, oxygen and sulphur compounds in the degraded products. The gas chromatograms of high boiling oils, as well as of residues and extracts, consist mainly of a large base "envelope" (about 95% of the total area); thus gc/ms coupling reaches the limits of its applicability. However, mass spectrometry with direct inlet gives valuable information regarding hydrocarbon type analysis. The results revealed the preferable degradation of alkanes, 1-ring aliphatics and benzenes and an enrichment of condensed cycloaliphatics and aromatics. The latter compounds are known to be resistant to microbial attack.

Abstract  A biochemical method was employed to study the response of rabbit skin to isopropyl myristate, squalane, and decane. The results showed that decane damaged the skin so severely that the biosyntheses of lipids, RNA and DNA were reduced markedly for the first 3 days after application, but increased rapidly after that due to the repair. The effect of squalane was found to be weaker than that of isopropyl myristate, though both oils induced the stimulation of biosynthese in the epidermis. The magnitude of the biochemical effects of the 3 oils on the skin was increased in the order of squalane, isopropyl myristate and decane, which was consistent with the results of macroscopic and histological observations. From the profiles of the effects, it is postulated that the repairing processes are controlled by some feedback mechanisms.

Abstract  Different adjuvants were assessed for their role in conferring protection against the rodent malarial parasite P. berghei and compared with the classical Freund's complete adjuvant (FCA). Pretreatment of mice with trehalose dimycolate (TDM) mixed with antigen (Ag), sulpholipids (SL) mixed with Ag, muramyl dipeptide (MDP) alone, liposomes containing Ag and phosphomannoinositides (PIM) mixed with Ag were ineffective in conferring protection. However, MDP given with squalane (Sq) and Ag, MDP with incomplete Freund's adjuvant (IFA) and Ag, palmitoyl-MDP with Sq and Ag, aluminium hydroxide adsorbed Ag, and FCA with Ag were effective in conferring varying degrees of protection to mice. Complete protection in rats was obtained with MDP mixed with Sq and Ag, and FCA mixed with Ag, and a partial protection with liposomes containing Ag.

Abstract  Symmetrical peaks, with sample size independent retention times, are obtained when alkanols are chromatographed in columns packed with alkane stationary phases coated on a deactivated solid obtained by coating Chromosorb W with Carbowax 20M, followed by thermal treatment in inert atmosphere and exhaustive extraction with methanol. Adsorption on the solid support/alkane interface is precluded by this deactivation method, but adsorption on the gas/alkane interface persists as a non-negligible contribution to solute retention. Retention volumes of ten alkanols with three to five carbon atoms were measured at five temperatures within the 30-50 degrees C interval in columns containing between 2 and 12 wt.% of squalane or of n-octadecane on the deactivated support. Partition and adsorption coefficients were obtained from the dependence of retention volumes on wt.% of stationary phase. Alkanols infinite dilution activity coefficients were calculated from partition coefficients; it is demonstrated that important errors are introduced on neglecting adsorption contributions. An indirect proof of consistency between calculated adsorption and partition parameters is given by comparing results obtained with both stationary phases. It is furthermore demonstrated that non-combinatorial contributions to the activity coefficients are independent of the alkane solvent.

Abstract  We have used a squalane adsorbed C-18 phase as presumably a bulk-like stationary phase to secure a simple partition mechanism for solute retention in reversed phase liquid chromatography, and have evaluated the nondispersive (specific) functional group-solvent interaction separately by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20 (v/v%) methanol/water eluents at 25,30,35,40,45, and 50 degrees C. We have found that the absolute magnitude of the carbonyl group (in acetophenone)-mobile phase specific interaction enthalpy is much greater than that of the hydroxyl group (in phenol)-mobile phase specific interaction enthalpy. If we consider the overall differential solute transfer free energy for a pair of polar and nonpolar solutes of the same size, the entropic contribution is dominant for the BT/phenol pair, and the enthalpic contribution, for the ethylbenzene/acetophenone pair. On the other hand, for a pair of nonpolar solutes, the entropic contribution to the differential free energy of solute transfer is much lower than the enthalpic contribution, and the variation in the differential entropy of solute transfer with respect to mobile phase composition is much smaller than the variation in the differential enthalpy, too.

Abstract  The kinetics of the three-phase methanol synthesis over a commercial Cu-Zn-Al2O3 catalyst were studied in an apolar solvent, squalane and a polar solvent, tetraethylene glycol dimethylether (TEGDME). Experimental conditions were varied as follows: P = 3.0-5.3 MPa, T = 488-533 K and Phi(vG)/w =7.5 x 10(-3)-8 x 10(-3) Nm(3) s(-1) kg(cat)(-1). The nature of the slurry-liquid influences the activation energy and the kinetic rate constant by interaction between adsorbed species and solvent and by competitive adsorption of the solvent on the catalyst surface. The rate of reaction to methanol observed in TEGDME appeared to be about 10 times lower than in squalane. TEGDME reduces the reaction rate, which is a disadvantage for its use as a solvent. (C) 1999 Elsevier Science B.V. All rights reserved.

Abstract  Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 degrees C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Using a data set for 39 base oils, formulated oil products and pure compounds it was demonstrated that there was a good positive relationship between biodegradation in CEC L-33-T-82 and mineralisation to CO2 in the modified Sturm test. A mathematical model was developed which described this correlation for most of the materials tested. One outlier from the model was di-iso tridecyl adipate (DITA), the well-degradable calibration oil for the CEC test. The measured mineralisation of DITA was much lower than that predicted by the model based on the compound's high biodegradability in the CEC test. A possible reason for this is given and the implications of this result discussed.

Abstract  In the 1980s long-lived radical species were identified in cigarette tar. Since then, environmentally persistent free radicals (EPFRs) have been observed in ambient particulate matter, and have been generated in particulate matter generated from internal combustion engines. For the first time, we measure in situ the formation and decay of EPFRs through the heterogeneous reaction of ozone and several polycyclic aromatic compounds (PAC). Solid anthracene (ANT), pyrene (PY), benzo[a]pyrene (BAP), benzo[ghi]perylene (BGHIP), 1,4-naphthoquinone (1,4NQ), and 9,10-anthraquinone (AQ) were reacted with gas-phase ozone in a flow system placed in the active cavity of an electron paramagnetic resonance (EPR) spectrometer, and the formation of radicals was measured on the timescale of tens of minutes at ambient levels of ozone down to 30 ppb. For most substrates the net radical production is initially rapid, slows at intermediate times, and is followed by a slow decay. For oxidized solid BAP, radical signal persists for many days in the absence of ozone. To evaluate the effect of substrate phase, the solid PAHs were also dissolved in squalane, an organic oil inert to ozone, which yielded a much higher maximum radical concentration and faster radical decay when exposed to ozone. With higher mobility, reactants were apparently able to more easily diffuse and react with each other, yielding the higher radical concentrations. The EPR spectra exhibit three radicals types, two of which have been assigned to semiquinone species and one to a PAH-derived, carbon-centered radical. Although our system uses levels of PAC not typically found in the environment it is worth noting that the amounts of radical formed, on the order of 10(18) radicals per g, are comparable to those observed in ambient particulate matter.

Abstract  An accurate description of the evolution of organic aerosol in the Earth's atmosphere is essential for climate models. However, the complexity of multiphase chemical and physical transformations has been challenging to describe at the level required to predict aerosol lifetimes and changes in chemical composition. In this work a model is presented that reproduces experimental data for the early stages of oxidative aging of squalane aerosol by hydroxyl radical (OH), a process governed by reactive uptake of gas phase species onto the particle surface. Simulations coupling free radical reactions and Fickian diffusion are used to elucidate how the measured uptake coefficient reflects the elementary steps of sticking of OH to the aerosol as a result of a gas-surface collision, followed by very rapid abstraction of hydrogen and subsequent free radical reactions. It is found that the uptake coefficient is not equivalent to a sticking coefficient or an accommodation coefficient: it is an intrinsically emergent process that depends upon particle size, viscosity, and OH concentration. An expression is derived to examine how these factors control reactive uptake over a broad range of atmospheric and laboratory conditions, and is shown to be consistent with simulation results. Well-mixed, liquid behavior is found to depend on the reaction conditions in addition to the nature of the organic species in the aerosol particle.

Abstract  Whether driven by external mechanical stresses (shear flow) or induced by membrane-active peptides and/or proteins, the collective growth of tubules in membranous fluids has seldom been reported. The pearling destabilization of these membranous tubules which requires an activation of the shape distortion, often induced by optical tweezers, membrane-active biomolecules or an electrical field, has also rarely been observed under mild experimental conditions. Here we report such events of collective tubulation and pearling destabilization in sessile drops of a didodecyl-dimethylammonium bromide (DDAB) vesicular solution that are confined by a surrounding oil medium. Based on the wetting dynamics and the features of the tubulation process, we show that the growth of the tubules here relies on a mechanism of "pinning-induced pulling" from the retracting drop, rather than the classical hydrodynamic fingering instability. We show that the whole tubulation process is driven by a strong coupling between the bulk properties of the ternary (DAAB/water/oil) system and the dynamics of wetting. Finally, we discuss the pearling destabilization of these tubules under vanishing static interface tension and quite mild tensile force arising from their pulling. We show that under those mild conditions, shape disturbances readily grow, either as pearling waves moving toward the drop-reservoir or as Rayleigh-type peristaltic modulations. Besides revealing singular non-Rayleigh pearling modes, this work also brings new insights into the flow dynamics in membranous tubules anchored to an infinite reservoir.

Abstract  We propose a new theoretical model of dynamic wetting for systems comprising two immiscible liquids, in which one liquid displaces another from the surface of a solid. Such systems are important in many industrial processes and the natural world. The new model is an extension of the molecular-kinetic theory of wetting and offers a way to predict the dynamics of a two-liquid system from the individual wetting dynamics of its parent liquids. We also present the results of large-scale molecular dynamics simulations for one- and two-liquid systems and show them to be in good agreement with the new model. Finally, we show that the new model is consistent with the limited data currently available from experiment.

Abstract  We demonstrate the first capture and analysis of secondary organic aerosol (SOA) on a droplet suspended in an aerosol optical tweezers (AOT). We examine three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ∼75% relative humidity. For each system we added α-pinene SOA-generated directly in the AOT chamber-to the trapped droplet. The resulting morphology was always observed to be a core of the original droplet phase surrounded by a shell of the added SOA. We also observed a stable emulsion of SOA particles when added to an aqueous NaCl core phase, in addition to the shell of SOA. The persistence of the emulsified SOA particles suspended in the aqueous core suggests that this metastable state may persist for a significant fraction of the aerosol lifecycle for mixed SOA/aqueous particle systems. We conclude that the α-pinene SOA shell creates no major diffusion limitations for water, glycerol, and squalane core phases under humid conditions. These experimental results support the current prompt-partitioning framework used to describe organic aerosol in most atmospheric chemical transport models and highlight the prominence of core-shell morphologies for SOA on a range of core chemical phases.

Abstract  The factors influencing the separation of monosubstituted phenols on silicone oil, poly(ethylene glycol) (1500), Apiezon L + Bentone 34, squalane, Versamide and diethylhexyl sebacate are discussed. Specific retention volumes, height equivalent to a theoretical plate and thermodynamic quantities are reported. Diethylhexyl sebacate and Versamide are selective for quantitative separation of all the isomers studied.

Abstract  The calculation of retention times, retention indices, and partition constants is a long sought-after goal for theoretical studies in gas chromatography. Although advances in computational chemistry have improved our understanding of molecular interactions, little attention has been focused on chromatography, let alone calculations of retention properties. Configurational-bias Monte Carlo simulations in the Gibbs ensemble have been used to calculate single and multi-component phase diagrams for a variety of hydrocarbon systems. Transferable force fields for linear and branched alkanes have been derived from these simulations. Using calculations for helium/n-heptane/n-pentane systems, it is demonstrated that this approach yields very precise partition constants and free energies of transfer. Thereafter, the partitioning of linear and branched alkane solutes (with five to eight carbon atoms) between a squalane liquid phase and a helium vapor phase is investigated. The Kovats retention indices of the solutes are calculated directly from the partition constants.

Abstract  In an attempt to elucidate the molecular basis for concentration (isotherm) effects on retention in gas-liquid chromatography, configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to investigate changes in analyte partitioning caused by overloading a model chromatographic system with either an alkane or an alcohol. Squalane was used as the stationary-phase material, and the analytes included n-pentane, n-hexane, n-heptane, 1 -butanol, and 1-pentanol. Three systems were studied that differed in the mobile-phase composition: (i) a helium vapor, (ii) a n-hexane vapor, and (iii) a 1-pentanol-saturated helium vapor. While the amount of helium that partitions into the stationary phase is very small, both n-hexane and 1-pentanol partition strongly into and thereby swell the stationary phase. Although the swelling of the stationary phase leads to a reduction in the partition coefficients for the alkane solutes for both the n-hexane- and 1-pentanol-swollen stationary phases, the effects on the alcohol solutes differ markedly. Whereas saturation by n-hexane causes a decrease of the alcohol partition contants (to an extent similar to that for the alkane solutes), the saturation by 1-pentanol causes a dramatic increase of the alcohol partition coefficients; e.g., the Kovats index of 1-butanol increases by more than 150 Kovats units. The formation of hydrogen-bonded alcohol aggregates in the liquid phase is the microscopic origin for the dramatic effect of 1-pentanol saturation on the retention of alcohols.

Abstract  The gel relaxation times of two different poly[styrene-b-(ethylene-altpropylene)-b-styrene] (SEPS) ABA triblock copolymers in squalane at various concentrations has been measured by Theology. These relaxation times were compared with the results of previous time-resolved small-angle neutron scattering (TR-SANS) experiments, which measured chain exchange kinetics in SEP diblock and SEPS triblock micelles in squalane. The gels relaxed up to four orders of magnitude faster than expected based on the chain exchange measurements of equivalent diblock polymers. By accounting for two factors a bias toward shorter end-block lengths in the gel relaxation, and a reduction in the energy barrier to chain pullout caused by the triblock architecture a model is constructed that reconciles the surprisingly short gel relaxation times with the chain exchange times measured via TR-SANS.

Abstract  The exchange of copolymer chains between 1 vol % PS-PEP (poly(styrene-b-ethylene-alt-propylene)) di-block copolymer micelles in squalane (selective for PEP) is investigated using time-resolved small-angle neutron scattering (TR-SANS) as a function of added PEP homopolymer. The solvent squalane, C30H62, is substituted in part or completely with PEP homopolymers that are the same molecular weight as the corona blocks. Polymer solutions/mixtures (1 vol % PS-PEP, plus 2, 7, or 15 vol % PEP in squalane, and 1 vol % PS-PEP in PEP) were separately prepared using normal (h-PS) or deuterated equivalent (d-PS) PS-PEP diblock copolymers. The solvent was contrast matched to a 50/50 mixed h-/d-PS micelle core, so that the scattering intensity decays with the mixing of h- and d-PS-PEP chains undergoing exchange between micelles. The chain exchange rate can therefore be assessed quantitatively. As the concentration of added homopolymer in solution increases above the overlap concentration of PEP chains, the chain exchange rate drops significantly. The results are compared to an earlier study of chain exchange between PS-PEP micelles in a 15% solution in squalane, which was also found to be significantly slower than when the solution is dilute. The primary factor in this slowing down of chain exchange is an increased screening of excluded volume interactions among the corona blocks. The role of increasing micelle aggregation number with PEP concentration is found not to be the dominant effect up to 15% added PEP but may play an increasingly important role in the PEP melt matrix, where no chain exchange could be detected in these experiments.

Abstract  Compatibility between oligomers and polymers was systematically assessed using differential scanning calorimetry (DSC) and was correlated with similarity in saturation and solubility parameter. These measurements enabled validation of detailed volume of mixing calculations using Statistical Association Fluid Theory (SAFT-γ Mie) and molecular dynamics (MD) simulations, which can be used to predict behaviour beyond the experimentally accessible conditions. These simulations confirmed that squalane is somewhat more compatible with poly(isoprene), "PI" than poly(butadiene), "PB", and further enabled prediction of the temperature dependence of compatibility. Surface and interfacial segregation of a series of deuterated oligomers was quantified in rubbery polymer films: PI, PB and hydrogenated poly(isoprene) "hPI". A striking correlation was established between surface wetting transition and mixtures of low compatibility, such as oligo-dIB in PB or PI. Segregation was quantified normal to the surface by ion beam analysis and neutron reflectometry and in some cases lateral segregation was observable by AFM. While surface segregation is driven by disparity in molecular weight in highly compatible systems this trend reverses as critical point is approached, and surface segregation increases with increasing oligomer molecular weight.

Abstract  Mannosylerythritol lipids (MELs) are secreted by yeasts and are promising glycolipid biosurfactants. In our study on the non-aqueous phase behaviors of MEL homologues, we found that MEL-D (4-O-[2',3'-di-O-alka(e)noyl-β-D-mannopyranosyl]-(2R,3S)-erythritol) forms aggregates in decane. The microscopic observation and the X-ray scattering measurement of these aggregates revealed that they are reverse vesicles that consist of bilayers whose hydrophilic domains are located in the interior of the bilayers. In addition, MEL-D formed reverse vesicles without co-surfactants and co-solvents in various oily solutions, such as n-alkanes, cyclohexane, squalane, squalene, and silicone oils at a concentration below 10 mM. This is the first report on the reverse vesicle formation from biosurfactants.

Abstract  An optical ice microscope apparatus equipped with a sealed cooling stage and a CCD camera was used to examine contact freezing events between a water droplet and ice nucleating particles (INP) containing organic hydrocarbons including octacosane, squalane, and squalene. Sample viscosities were measured with a capillary viscometer and compositions were characterized using Fourier transfer infrared spectroscopy with horizontal attenuated total reflectance and Raman microspectroscopy. All of the samples proved to be moderately efficient ice nuclei that induced freezing between -23 and -26 °C, regardless of whether the INP was solid or liquid. At their ice nucleating temperatures, the viscosity of the liquid samples (squalane and squalene) was 0.6 P or greater. Oxidation increased the viscosity of squalene to over 1330 P, but decreased the viscosity of squalane to 0.07 P at room temperature. Most importantly, our results demonstrate that even moderately viscous liquids in contact with water droplets can act to catalyze freezing, plausibly by providing a flexible template which decreases the energy barrier to ice nucleation. The simple soccer ball model of nucleation theory was used to derive the probability of freezing and nucleation rate coefficients as a function of temperature for each type of INP.

Abstract  In the present study, the applicability of high-performance liquid chromatography hyphenated with highly sophisticated mass spectrometric detection (HPLC-MS) for analysis of hindered amine light stabilizers (HALS), thiosynergists and their conversion products is demonstrated. Degradation pathways as well as interactions between these stabilizer groups were successfully studied by analytical evaluation of model formulations after accelerated aging in the polymer-mimicking solvent squalane. Binary mixtures including HALS and thiosynergist as well as three component systems additionally including a phenolic antioxidant were investigated. Results showed that transformation pathways of HALS are highly influenced by the presence of sulfur-containing compounds and no aminoxyl radicals (typical reactive intermediates of HALS) were observed in these mixtures. To get an understanding of the effect of this altered stabilization mechanism on the protection of the polymer, rating of stabilization efficacies was performed by comparing the amount of degradation products derived from squalane using different formulations. (C) 2014 Published by Elsevier Ltd.

Abstract  Inelastic scattering of OH radicals from liquid surfaces has been investigated experimentally. An initially translationally and rotationally hot distribution of OH was generated by 193 nm photolysis of allyl alcohol. These radicals were scattered from an inert reference liquid, perfluorinated polyether (PFPE), and from the potentially reactive hydrocarbon liquids squalane (C30H62, 2,6,10,15,19,23-hexamethyltetracosane) and squalene (C30H50, trans-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene). The scattered OH v = 0 products were detected by laser-induced fluorescence. Strong correlations were observed between the translational and rotational energies of the products. The high-N levels are translationally hot, consistent with a predominantly direct, impulsive scattering mechanism. Impulsive scattering also populates the lower-N levels, but a component of translationally relaxed OH, with thermal-desorption characteristics, can also be seen clearly for all three liquids. More of this translationally and rotationally relaxed OH survives from squalane than from squalene. Realistic molecular dynamics simulations confirm that double-bond sites are accessible at the squalene surface. This supports the proposition that relaxed OH may be lost on squalene via an addition mechanism.