Composition of the lipids of the sphagnum and cotton grass peats in the forest steppe and southern and middle taigas of West Siberia

The composition of the organic components of the lipids of sphagnum and cotton grass peats deposited in West Siberia in the limits of different natural climatic zones was studied by chromatography–mass spectrometry. A decrease in the temperature and an increase in the humidity of the environment northwards from the forest steppe to the middle taiga was accompanied by an increase in the concentration of steroids, tocopherols, and pentacyclic triterpenoids in sphagnum peats and by a decrease in the fraction of n-alkanes, n-alkan-2-ones, and carboxylic acids. The relative concentration of carboxylic acids and their methyl esters and also the fraction of n-aldehydes and steroids, in particular, sitosterol, in cotton grass peats were maximal in the zone of a reduced temperature and an excess humidity of air; the relative alkanone content was simultaneously lowered. In general, the peats of the forest-steppe zone were characterized by the decreased concentrations of all of the identified components of lipids other than n-aldehydes and n-alkan-2-ones; the peats of the southern taiga zone were enriched in branched acyclic structures, carboxylic acids and their esters, tocopherols, and cyclic sesqui- and diterpenoids, whereas the peats of the middle taiga zone were enriched in steroids and pentacyclic triterpenoids.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Changes in the composition of the bituminous components of valley peat under stimulated microbial action

The stimulated microbial oxidation of valley peat by aboriginal microflora was experimentally studied for evaluating the participation of microflora in the conversion of organic matter in present-day swamp deposits. The esters of n-carboxylic acids, triphenyl phosphates, C₁₄–C₃₁ n-alkanes, squalene, methyldehydroabietate, steroids, and pentacyclic terpenoids with the predominance of unsaturated structures mainly with the alcohol groups were identified in the composition of the bituminous components of microflora. It was found that the absolute concentrations of all of the identified groups of organic compounds in peat considerably decreased as a result of biodegradation. The relative concentrations of high-molecularweight (C₂₇–C₃₄) homologues and C₁₆–C₂₀ homologues predominant in bacteria in the composition of peat n-alkanes increased. Steroids and pentacyclic triterpenoids were enriched in unsaturated structures and compounds with the alcohol groups. Aldehydes disappeared from the composition of acyclic compounds. The fractions of palmitic acid derivatives in methyl ethers and isoprenoid structures in alkanones sharply increased.     

Mixed Micellization Study of Alkyltrimethylammonium and Alkyltriphenylphosphonium Bromides in Aqueous Solution

Mixed micellization study of cationic surfactants viz. alkyltrimethylammonium bromides (C_nTAB) and alkyltriphenylphosphonium bromides (C_nTPPB) with similar hydrophobic groups (C₁₂-, C₁₄-, and C₁₆-) was performed using tensiometry and UV–visible light spectrophotometry techniques. Critical micelle concentration (CMC) values of the single and binary surfactant mixtures were obtained from a plot of surface tension versus the logarithm of surfactant concentration (C _s). The degree of synergy and various mixed micelle parameters like interaction parameter (β), activity coefficients (f ^m ) and interfacial parameters like surface pressure (π _CMC), packing parameter (P), surface excess concentration (Г _max), surface tension at the CMC (γ _CMC), and minimum area per molecule (A _min) were evaluated using the regular solution theory (RST). Thermodynamic parameters were calculated using several proposed models which suggest the mixed micellar system to be more thermodynamically stable than their respective individual components. In addition, a dye solubilization study was performed using a spectrophotometric method to validate the CMC data obtained from tensiometric method. Conductometric measurements were also carried out for the mixture of C₁₂TAB + C₁₂TPPB only as it showed a more negative β, indicating a higher degree of synergism.     

Search of high-capacity cathode materials based on lithium–iron silicate compounds

The crystal structures of 197 lithium–silicate compounds have been analyzed using the method of crystal chemistry analysis (TOPOS software package). The compounds whose structures are characterized with a combination of high values of such parameters as the channel radius, stability, gravimetric capacity, and capacity per volume unit have been revealed: LiFeSiO₄ (R3?), Li₄Fe₂Si₃O₁₀ (C2/c), Li₂FeSiO₄ (Pc2₁ n), and Li₂FeSiO₄ (C222₁). It has been demonstrated that lithium–iron silicates of the monoclinic syngony have high values of the capacity per volume unit, as compared to those of the rhombic syngony. The structural stability of the Li₂FeSiO₄ (Pc2₁ n) framework has been corroborated using the method of computer simulation within the scopes of the electron density functional theory. The obtained information could facilitate creation of novel cathode materials of high capacity and specific accumulated energy.     

Purification,Surface Tensions,and Miscibility Gaps of Alkyldimethyl and Alkyldiethylphosphine Oxides

Alkyldimethyl (C _n DMPO) with chain lengths of n = 8 (octyl), 10 (decyl), 12 (dodecyl), and 14 (tetradecyl) as well as alkyldiethyl (C _n DEPO) phosphine oxides with chain lengths of n = 10, 12, and 14 were synthesized and purified to study how the adsorption properties and the location of the miscibility gap of these surfactants depend on the size of the head group and on the length of the alkyl chain. After surfactant purification, the surface tension isotherms were determined from which the cmc, the minimum surface tension σ_cmc, the maximum surface concentration Γ_max, and the minimum surface area A _min were obtained. As expected, for one homologous series, a decrease in the cmc and an increase in Γ_max was observed with increasing alkyl chain length. For two surfactants of the same alkyl chain length, the cmc values of the C _n DEPO surfactants are approximately two times lower than those of the C _n DMPO surfactants. However, the Γ_max values of C _n DEPO are lower than those of C _n DMPO as two ethyl chains are sterically more demanding than two methyl chains. In addition to the adsorption properties, the location of the miscibility gap as a function of the alkyl chain length and the head group size was studied. Its location depends on the total number of carbon atoms and not primarily on the length of the main alkyl chain. This observation reflects the decreasing water solubility which can be tuned by increasing the length of either the main alkyl chain or of the shorter head group chains.     

Mixed Stability and Antimicrobial Properties of Gluconamide-Type Cationic Surfactants

The stability of anionic-cationic surfactant solutions and the antimicrobial properties of novel N,N-dimethyl-N-[3-(gluconamide/lactobionamide)]propyl-N-alkylammonium bromides (CnDGPB and CnDLPB), N-methyl-N-hydroxyethyl group-N-[3-(gluconamide)-propyl]-N-alkylammonium bromide (CnMHGPB) and star-shaped gluconamide-type cationic surfactants N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-N-alkylammonium bromide (CnDBGB) were investigated. Mixed stability in combination with sodium n-alkylbenzenesulfonate (LAS) was determined via transmittance; stability is achieved when percent transmittance was greater than 90 %. Transmittance results suggest that these cationic surfactants can form stable solutions with anionic surfactants over a broad concentration range. The inhibition activity of C _n DBGB is the best among the three kinds of glucocationic surfactants. Antimicrobial activity of C₁₂ surfactants was the best, C₁₄ was the second and C₁₀ was the worst. Moreover, antibacterial activity of glucose-based cationic surfactants was greater than lactose-based cationic surfactants.     

The role of molecular structure on impact resistance and bending strength of photocured urethane-dimethacrylate polymer networks

The objective of this study was to investigate the influence of molecular structure on impact resistance (a _n) and bending strength (σ) of photocured urethane-dimethacrylate polymer networks. Urethane-dimethacrylate (UDMA) monomers were synthesized through reaction of oligoethylene glycol monomethacrylate (OEGMMA) with diisocyanate (DI). OEGMMA varied within the length of the oligooxyethylene chain, which consisted of one to four oxyethylene units. DI varied in chemical character: aliphatic, cycloaliphatic or aromatic. The molecular structure of UDMA polymers was characterized by X-ray powder diffraction, which allowed the calculation of the d-spacing (d) and dimensions of microgel agglomerates (D). The measurements of the polymerization shrinkage were used for the determination of the degree of conversion (DC), whereas the concentration of double bonds was used as a measure of the crosslink density (q). It was found that all structural parameters depend on the UDMA chemical structure. The increasing length of the oligooxyethylene chains caused the decrease in d and q, in contrast to the increase in D and DC. The DI chemical character caused the increase in the DC and q accordingly: symmetrical cycloaliphatic or aromatic < asymmetrical cycloaliphatic and aromatic < substituted aliphatic < linear aliphatic. The compact packing and high DC in polymers derived from aliphatic DIs gave rise to the decrease in d and the increase in D. The non-planar conformation of cycloaliphatic DIs emerged in high d as well as D. The planar conformation of aromatic DIs resulted in the decrease in d as well as D. The study indicated that mechanical behavior of UDMA polymer networks can be explained in terms of the structural parameters. DC and q appeared to be the main factors determining both mechanical properties of poly(UDMA)s. The a _n was also shown to be affected by d. Particularly high linear correlations were found on a semi-logarithmic scale for the DC and d with a _n. a _n increased as the DC increased, whereas d decreased.     

Dielectric study of side-chain liquid crystalline polyazomethine/fullerene C<Subscript>60</Subscript> nanocomposite

For side-chain liquid crystalline polyazomethine/fullerene C₆₀ nanocomposite (C₆₀ loading is 0.25 wt%), both real and imaginary components of the dielectric permittivity were investigated in wide regions of temperature and frequency. Analysis of frequency dependent permittivity allowed finding three relaxations (α, β ₁ and β ₂) in the nanocomposite. They were attributed to specific modes of molecular mobility. β-relaxations were described with the Arrhenius equation, whereas α-relaxation was described with the Vogel-Fulcher-Tammann equation. Anti-plasticization effect of the C₆₀ doping was shown to be manifested as an increase of the glass transition temperature of the nanocomposite as compared with that of the neat polymer.     

Maxima of the Specific Heat at Constant Pressure of the <Emphasis Type="Italic">n</Emphasis>-Alkanes C<Subscript>7</Subscript>-C<Subscript>9</Subscript> in the Supercritical Region

Precision measurements of the specific heat at constant pressure, C _p , of high-purity samples of the normal alkanes C₇-C₉ in the supercritical region of state parameters are carried out using an adiabatic flow calorimeter equipped with a calorimetric flowmeter. Currently, this is the most accurate method. The coordinates of maxima of C _p on isobars are determined. A generalized equation for the line of the maxima of C _p in reduced coordinates π-τ and an equation for C _p along this line in corresponding states for the homologous series are obtained in terms of thermodynamic similarity theory using the most reliable published data. Existing experimental methods for determining the critical parameters of individual substances are analyzed.     

Temperature and Pressure Dependence of Elastic Constants and Related Parameters for InP Semiconductor

Based on the empirical pseudo-potential method (EPM), the symmetric and anti-symmetric pseudo-potential form factors have been adjusted to match the calculated energy gaps of InP with the corresponding experimental values. The adjusted symmetrical and anti-symmetrical form factors at G(1,1,1) have been used to calculate the polarity of the considered material. The elastic constants C ₁₁, C ₁₂ and C ₄₄ of InP have been obtained. The knowledge of these constants helps us to determine their related elastic parameters such as bulk (B _u ), shear (C _s ) and Young’s (Y ₀) moduli. Other important parameters such as Poisson’s ratio (σ ), linear compressibility (C ₀ ), Cauchy ratio (C _a ) , Born ratio (B ₀), isotropy factor (A ), bond stretching (α ), bond binding force (β ) and internal strain parameter (ζ ) for InP have also been calculated. The variation of all studied quantities with temperature and pressure has been investigated. Our results show a good agreement with the available experimental data. Most of our data may be taken as references especially for high values of temperature and pressure.     

Prediction of biodiesel properties and its characterization using fatty acid profiles

Biodiesel, the mono-alkyl esters of vegetable oils or animal fats, is an eco-friendly alternative to petrodiesel. The molecular structures of biodiesels, fatty acid methyl esters were applied to predict the characteristics of biodiesel fuels. Based on the structural similarity of biodiesel and petroleum fractions, molecular weight of biodiesel was correlated with other characteristics including boiling point, viscosity and specific-gravity in the form of three equations. For 24 different kinds of biodiesel, the minimum average relative deviation (ARD) of these correlations was calculated to be 0.68%. Moreover, two correlations were developed to predict viscosity and flash point of biodiesel as a function of weighted-average number of carbon atoms (N _C ) and weighted-average number of double bonds (N _DB ) with ARD 3.72% and 4.24% respectively. Also, a high degree of correlation was shown by the logarithmic function with ARD 0.30% between specific gravity and viscosity of biodiesel. Proposed predictive models were verified by experimental data.     

Structure of an <Emphasis Type="Italic">n</Emphasis>-heptane/toluene flame: Molecular beam mass spectrometry and computer simulation investigations

Molecular beam mass spectrometry was used to measure mole fraction profiles of the reactants, major reaction products and intermediates, including precursors of polycyclic aromatic hydrocarbons, in a premixed fuel-rich (equivalence ratio of 1.75) n-heptane/toluene/O₂/Ar flame stabilized on a flat burner at atmospheric pressure. The ratio of the liquid volumes in the n-heptane/toluene mixture was 7: 3. The chemical structure of the flame was modeled using a detailed mechanism of chemical reactions tested against experimental data of other authors on n-heptane/toluene flames and comprising the reactions of formation of polycyclic aromatic hydrocarbons. The mechanism was extended with cross-reactions involving derivatives of n-heptane and toluene. Overall, the new experimental data are in satisfactory agreement with the numerical simulation results; however, there are differences between the measured and calculated mole fraction profiles of some species. Analysis shows that in the n-heptane/toluene flame, the main reactions leading to the formation of low-aromatic compounds (benzene and phenyl) are reactions typical of the pure toluene flame.     

Solvent recovery in solvent deasphalting process for economical vacuum residue upgrading

The solvent deasphalting (SDA) process is a heavy oil upgrading process and used to separate asphaltene, the heaviest and most polar fraction of vacuum residue (VR) of heavy oil, by using density differences, to obtain deasphalted oil (DAO). The SDA process consists of two main stages: asphaltene separation and solvent recovery. Solvent recovery is a key procedure for determining the operating cost of the SDA process, because it uses a considerable amount of costly solvent, the recovery of which consumes huge amounts of energy. In this study, the SDA process was numerically simulated by using three different solvents, propane, n-butane, and isobutane, to examine their effect on the DAO extraction and the effect of the operating temperature and pressure on solvent recovery. The process was designed to contain one extractor, two flash drums, and two steam strippers. The VR was characterized by identifying 15 pseudo-components based on the boiling point distribution, obtained by performing a SIMDIS analysis, and the API gravity of the components. When n-butane was used, the yield of DAO was higher than in the other cases, whereas isobutane showed a similar extraction performance as propane. Solvent recovery was found to increase with temperature and decrease with pressure for all the solvents that were tested and the best results were obtained for propane.     

Partition of <Emphasis Type="Italic">n</Emphasis>-Butanol Among Phases and Solubilization Ability of Winsor type III Microemulsions

The partition of n-butanol in Winsor type III (W-III) microemulsions was investigated in this work. Three kinds of anionic surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (DSS), and sodium dodecyl benzene sulfonate (SDBS)) and two kinds of anionic/cationic surfactant mixtures (SDS/octadecyl trimethyl ammonium chloride (OTAC) mixtures and DSS/OTAC mixtures) were studied. Internal standard gas chromatography was employed in n-butanol content analysis. The results showed that no water exists in the excess oil (EO) phase and no oil exists in the excess water (EW) phase. For the W-III microemulsions obtained by salinity scanning, relatively constant n-butanol content in the EO (11–12 v%) and EW (1–4 v%) was found under different salinities. Accurate measurement of n-butanol content in each phase is important for those systems having low solubilization ability. For the W-III microemulsions prepared using SDS/OTAC surfactant mixture, the percentage of n-butanol distributed into the interfacial layer decreased while the fraction of n-butanol in the interfacial layer first increased sharply and then tended to be stable with the addition of n-butanol. For the different optimum W-III microemulsion systems tested, most of the surfactant-to-alcohol molar ratio data are near 1:3, but obvious deviation could be observed for some data. On the basis of the accurate measurement of n-butanol content in the EO and EW phases, the standard free energy, ΔG _o→in ^* (T = 298.15 K) of n-butanol transferring from the EO phase to the interfacial region was calculated. The results show negative ΔG _o→in ^* values. For microemulsions with the same components, n-butanol content is an important factor influencing the ΔG _o→in ^* value, and a high absolute value of ΔG _o→in ^* leads to high solubilization ability.     

Synthesis,Surface Activities and Toluene Solubilization by Amine-oxide Gemini Surfactants

A series of amine-oxide gemini surfactants featuring amide groups [N, N’-dimethyl-N, N’-bis(2-alkylamideethyl)-ethylenediamine oxide (alkyl = C₁₁H₂₃, C₁₃H₂₇, C₁₅H₃₁, C₁₇H₃₅)] have been synthesized via a three-step synthetic route, and their chemical structures were confirmed by mass spectra, FTIR and ¹H-NMR spectra. The surface activities of these compounds have been measured. The results show that these synthesized amine-oxide gemini surfactants reduced the surface tension of water to a minimum value of approximately 26.91 mN m^?1 at a concentration of 2.92 × 10^?5mol L^?1. Furthermore, their critical micelle concentration (CMC) values and solubilization of toluene decrease with an increase of the hydrophobic chain length from 12 to 18. Isoelectric point measurements revealed that their pI values range from 4.0 to 10.5.     

Optimization of controlled ring-opening polymerization of <Emphasis Type="SmallCaps">l</Emphasis>-lactide to hydroxyl terminated polylactides using zinc acetate catalyst

Hydroxyl terminated polylactide polymers with number of average molecular weights (M _n ) varying from 1625 to 3459 g mol^?1 were synthesized by ring opening bulk polymerization of lactide in the presence of zinc acetate being a potent catalyst. The use of 1,4 butanediol (BDO) initiator leads to hydroxyl terminated polylactides, thus excellent precursors for shape-memory biodegradable polyurethanes. Different reaction conditions employed for the synthesis of hydroxyl terminated polylactide polymers via activated monomer mechanism may result in differences in M _n , percentage mass conversion and percentage degree of crystallinity (%χ _c ) of the product. Influence of process parameters, i.e. catalyst concentration, initiator concentration, reaction temperature and time on characteristics of hydroxyl terminated polylactides was studied. These polymers were characterized by Nuclear Magnetic Resonance (¹H-NMR) spectroscopy, Fourier transforms infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and X-ray diffraction (XRD) techniques. FTIR and ¹H-NMR confirmed the formation of hydroxyl terminated polylactides. M _n was determined by ¹H-NMR, GPC and end group analysis. %χ _c was calculated from XRD spectra. Maximum mass conversion, M _n and %χ _c were observed at 5 mol% SnOct₂ and 5 mol% BDO concentration. At optimum temperature of 145 °C, these characteristics improved linearly with polymerization time up to 6 h and declined thereafter.     

Composition and characteristics of primary combustion products of boron-based propellants

Primary combustion products of boron-based propellants are incomplete combustion products that are emitted from the gas generator of a solid ducted rocket. Studying the composition of primary combustion products provides valuable information about the primary combustion process and also helps to better understand the secondary combustion process. The particle size of the primary combustion products is analyzed by a laser particle size analyzer. The qualitative analysis of the sample composition is performed by using x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetry–differential scanning calorimetry experiments. Based on these results, an integrated quantitative analysis of the sample composition is conducted. The quantitative analysis methods include tube furnace heating, ion chromatography, infrared spectroscopy, and inductively coupled plasma chromatography. In addition, scanning electron microscopy and energy dispersive spectrometry are also used to analyze the micro-morphology and distribution of different components in the sample. The primary combustion products mainly contain B, C, B _m C _n , H₃BO₃, B₂O₃, BN, Mg, MgCl₂, and NH₄Cl. B _m C _n (22–24%), H₃BO₃ (20%), and B (16.8%) are the three major components, while B _m C _n , B, and C (9.8–11.8%) are the three combustible components present in the highest amounts. The oxidant NH₄ClO₄ is completely consumed during the primary combustion, while the metal additive Mg does not show much reactivity. The micro-morphology and distribution of B _m C _n , H₃BO₃ (or B₂O₃), B, Mg, and C in the sample are investigated. Some components in the primary combustion products are found to be agglomerated, while some components are dispersed. Large particles in the sample mainly include B and Mg, while B _m C _n , H₃BO₃ (or B₂O₃), and C particles are small. In general, the combustion completeness of the primary combustion products is rather low. Therefore, better understanding and controlling of the secondary combustion process is very important to improve the performance of B-based propellants.     

SHS under pressure: II. Effect of applied pressure on burning velocity in Ti + C mixtures

For the Ti-C system taken as an example, burning velocity U as a function of applied pressure P was found to be bell-shaped with a clearly pronounced maximum (U _max). The ascending branch of the U(P) function was associated with a pressure-induced increase in the thermal conductivity of starting compacts and suppressed expansion of impurity gases. The descending branch was attributed to a decrease in U due to ever increasing thermal conductivity resulting in a gradually growing heat sink from a burning sample. The annealing of starting compacts in vacuum had little or no influence on U but shifted U _max to lower P.     

Probing the Structural,Electronic, and Magnetic Properties of Ag<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>V (<Emphasis Type="Italic">n</Emphasis> = 1–12) Clusters

The structural, electronic, and magnetic properties of Ag _n V (n?=?1–12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy Ag_nV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag _n?+?1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag _n V (n?=?1–12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag₂ excepted. The most possible dissociation channels are Ag _n V?=?Ag?+?Ag _n???1V for n?=?1 and 4–12 and Ag _n V?=?Ag₂?+?Ag _n???2V for n?=?2 and 3. The energy gap of Ag _n V cluster with odd n is much smaller than that of Ag _n?+?1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag _n V cluster mostly comes from V atom and varies from 1 to 5 μ _B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.