Thermodynamic and structural analyses of the solid phases in multi-alkane mixtures similar to petroleum cuts at ambient temperature

Structural analyses were carried out by X-ray diffraction, at ambient temperature, on multi-alkane samples whose mole fraction distribution shows a shape of the ‘exponential decreasing’ type, as observed in petroleum cuts. Nine samples, whose normal-alkane number varies from 15 to 23, have been studied with mole fraction continuous distributions of normal-alkanes going from C₂₂-C₃₆ to C₁₄-C₃₆: each mixture differs from the previous sample by the addition of a lighter n-alkane. At the solid state, the multi-alkane solid samples C₂₂-C₃₆ and C₂₁-C₃₆ are two-phase, C₂₀-C₃₆ to C₁₅-C₃₆, three-phase, and the broader distribution C₁₄-C₃₆, four-phase. In these polyphase solid systems, whose heaviest n-alkane is always C₃₆, the average composition of the heavy and middle phases are constant and their structure are isostructural to the β′ ordered intermediate solid solution, observed in n-alkane binary or ternary molecular alloys; the mean carbon atom number of the light phase decreases as the global average carbon atom number of the synthetic mixtures in relation to the addition of light n-alkanes and its structure simultaneously evolves from the β′ ordered intermediate solid solution towards the β-RI(Fmmm) and the disordered solid solutions, observed in pure n-alkanes: the light n-alkane added between each distribution intercalates itself into the structure whose molecule stacking period (thickness) is compatible with its own carbon chain length, in order to reduce the molecular gaps.     

Screening and Profiling of Hydrocarbon Components and Squalene in Developing Tunisian Cultivars and Wild Arachis hypogaea L. Species

Total hydrocarbon composition and content of whole peanuts from three Tunisian varieties of peanut (two cultivars: AraC (Virginia type), AraT (Valencia type) and a wild one: AraA) were investigated during maturation. The results show that 30 hydrocarbons were identified from the wild AraA species, while only 27 hydrocarbon were detected in the cultivar ones. The hydrocarbon fraction is essentially composed of squalene, n-alkenes especially nC₁₄₌, nC₁₆₌, nC₁₈₌, nC₂₀₌ and nC₂₂₌, n-alkanes such as nC₁₆, nC₁₇, nC₁₈, nC₂₅, nC₂₆ and nC₂₇, and branched saturated hydrocarbon noted (HC₁, HC₂ and HC₃). Among the hydrocarbon components, generally the wild variety AraA presents the highest content of phytochemical squalene during maturation, whereas a maximum was detected from cultivar AraT at 12 days after podding (815.45 mg/100 g of oil). At maturity, the maximum level is reached at about 346.74 mg/100 g of oil for AraA. During maturity, wild AraA is considered to be an excellent source of squalene like olive and pumpkin oil.     

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.     

The Effects of Insect Extracts and Some Insect-Derived Compounds on the Settling Behavior of Liposcelis bostrychophila

Extracts of whole booklice (Liposcelis bostrychophila)—sequentially extracted in hexane and aqueous 80% methanol (80%MeOH)—repel conspecifics. A methanol-soluble fraction (MFr) of the 80% methanol extract was more repellent than either its corresponding water fraction (WFr) or the hexane extract. The repellent effect of the MFr was repeatable across extracts prepared on different occasions over a 1 month period. Gas chromatography, mass-spectrometry (GC-MS) analyses showed that saturated (C₁₆; C₁₈) monoenoic (C_16:1; C_18:1) and a dienoic fatty acid (C_18:2) and the corresponding methyl esters of all but C_16:1 and C₁₈ constituted approximately 95% and 30%, of the detected compounds in the methanol fractions and the hexane extract, respectively. Qualitative thin layer chromatography showed that cholesterol was present in methanol fractions and the hexane extract, and also enabled tentative identification of triacylglycerols and phospholipids in the methanol fractions. Extracts of wheatgerm, dried skimmed milk powder, active yeast, and wholemeal flour—L. bostrychophila dietary components—were analyzed by GC-MS, and C₁₆, C_18:1 and C_18:2 were detected, indicating that C₁₈ and the methyl esters were not directly extractable and/or that they were products of booklice metabolism. A fatty acid amide (stearamide) previously identified in cuticular extracts of L. bostrychophila was not detected, and therefore was not responsible for the observed biological activity. Pure fatty acids and fatty acid methyl esters repelled settling of L. bostrychophila at 10 mM, with the exception of palmitic and stearic acids, indicating, among other things, a difference between the efficacy of saturated and unsaturated fatty acids. The effect of concentrations <10 mM was less significant, although palmiteoleic acid appeared to be attractive to L. bostrychophila at 0.1 mM. Fatty acids and fatty acid methyl esters were at a much lower concentration than 10 mM in the repellent methanol fractions, indicating that an interaction between known and as yet unidentified compounds is likely. The significance of fatty acids in relation to the biology and behavior of L. bostrychophila and their potential for use in traps and monitoring are discussed.     

Isolation and enzymatic characterization of the first reported hyaluronidase from Yak (Bos grunniens) testis

A novel hyaluronidase (BgHya1) from Yak Bos grunniens testis was isolated and shown to have comparatively high activity on sodium hyaluronate. However, surveys on BgHya1 are still limited. The enzyme was purified through gel filtration on Sephacryl S-100 and cation-exchange on SP Sepharose fast flow; the purity was confirmed by a reverse phase FPLC Shodex C₄ column. The specific activity of the purified BgHya1 was 20.4 U/mg assayed by the colorimetric method against 0.85 U/mg for the crude enzyme, representing a 24-fold purification. It was a monomeric protein of 55 kDa estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Sephacryl S-200. It exhibited maximum activity in the presence of 0.15 M NaCl at 37 °C, pH 3.8, and a specificity to sodium hyaluronate higher than that of chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan. The K _m value for BgHya1, using sodium hyaluronate as substrate, was 0.106 mg/mL. Activity of BgHya1 was inhibited mildly by Ca²⁺ and Fe²⁺, and significantly by Fe³⁺, Mg²⁺, EDTA, urea, heparin, and 0.5 M NaCl. It was not affected by Cu²⁺, Zn²⁺, Co²⁺, ascorbic acid, PMSF, DTT, glutathione (reduced), or L-cysteine. BgHya1 was shown to be heat unstable in the range of 4–45 °C. In terms of storage stability, 92% of the activity was retained after four weeks at 4 °C, and 58% at room temperature. In addition, adding BSA (1.0 mg/mL) to the enzyme sample prior to freezing resulted in complete retention of enzyme activity. This work yielded a high purity hyaluronidase, the first one isolated from Bos grunniens by-product.     

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.     

Synthesis and Physicochemical Investigation of Novel Quaternary Ammonium Salt Cationic Gemini Surfactant Derived from Cyanuric Chloride

Three novel quaternary ammonium salt cationic gemini surfactants (QAS C _n ?C2?CC _n where n represents the hydrocarbon chain lengths of aliphatic amine, i.e., 6, 8, 12) were synthesized from 2,4,6?Ctrichloro?C1,3,5?Ctriazine, ethylenediamine, N,N?Cdimethylpropane?C1, 3?Cdiamine and benzyl chloride. ¹H-NMR, ¹³C-NMR, ESI?CMS spectra and elemental analysis were used to confirm the chemical structures of the prepared compounds. Their critical micelle concentrations (CMC) in the aqueous solutions were determined by surface?Ctension, electrical conductivity and steady?Cstate fluorescence methods respectively. With the increasing length of the hydrophobic chain, the values of their CMC decreased. The values of CMC, ?? _CMC, pC ₂₀, ??_max, and A _min were derived from surface tension measurements, while the thermodynamic parameters of micellization (?G _mic ^° and ?G _ads ^° ) were determined by electrical conductivity. These properties are significantly influenced by the hydrophobic chain length.     

Mutagenic potential of ammonia-related aflatoxin reaction products in cottonseed meal

In a joint research effort, the Food and Drug Administration, the National Toxicology Program and the US Department of Agriculture studied the mutagenic potential of aflatoxin reaction products following ammoniation of contaminated cottonseed meal under conditions approximating those approved for commercial ammoniation of nonaflatoxin-contaminated meal. Uniformly ring-labeled¹⁴C-aflatoxin B₁ was added to cottonseed meal that contained ca. 4000 μg naturally incurred aflatoxin B₁/kg. Distribution of the radiolabeled compound was used to trace the modification of aflatoxin B₁ after treatment with ammonia. The radioactivity-to-weight ratio of the fractions isolated by solvent extractions and chemical and enzymic treatments was used to measure the relative concentration of an aflatoxin decontamination product. All extract fractions having a radioactivity-to-weight ratio ≥1 were tested for mutagenic activity using theSalmonella/microsome mutagenicity test (Ames test). Purified aflatoxin B₁ was mutagenic at a concentration of ca. 0.005 μg/plate. The methylene chloride extract of the ammoniated meal after Pronase digestion exhibited a similar response when 180 μg of this fraction was applied to each plate. This fraction represented 0.16% of the original added radioactivity. The other fractions produced no detectable mutagenic response at the concentrations tested (10–1000 μg/plate) onSalmonella tester strain TA100. Ammonia treatment of aflatoxin-contaminated cottonseed meal significantly decreased aflatoxin levels, and the aflatoxin decontamination products formed by the treatment had little or no mutagenic potential.     

Characterization of the Solvent Properties of Glycerol Using Inverse Gas Chromatography and Solubility Parameters

The production of glycerol from the synthesis of biodiesel has led to a market surplus of this polyhydric alcohol and additional research to find new applications for this versatile chemical. This study involves the use of inverse gas chromatography (IGC) to characterize the solute–solvent interactions between glycerol and a homologous series of aliphatic alcohols, in which the latter components are at infinite dilution in the glycerol, which is the stationary phase contained in a packed GC column. The IGC experiments were conducted between 51.5 and 111 °C for the n-alcohols ranging from methanol to n-butanol. All of the n-alcohol homologs exhibited positive deviations from Raoult’s law as based on mole fraction activity coefficients values ranging from 1.86 to 14.4. The measured mole fraction activity coefficients of the alcoholic solutes in glycerol showed good agreement with literature values, and in some cases with those predicted using existing theoretical models. The mole fraction activity coefficients increased going from methanol to n-butanol, reflecting the change in the alcohol’s cohesive energy densities relative to that for glycerol. The total solubility parameter of glycerol calculated from IGC data was found to be 34.8 MPa^1/2 which is in good agreement with that obtained using Hansen solubility parameter approach (31.6 MPa^1/2). This data can be used to characterize the solvent properties of glycerol as well as to provide thermodynamic data for the removal of the alcoholic solutes from glycerol.     

“Anisotactic” polypropylenes produced with a zirconocene-methylalumoxane catalyst: solid state properties and microstructure

Summary Propene was polymerized with ethylene bis(-1-indenyl)-dichlorozirconium (Et(Ind)₂ZrCl₂) and methylalumoxane (MAO) at 70°C. The polymer was fractionated by solvent extraction; there was no hexane insoluble material. The pentane insoluble, hexane soluble (C_5iC_6s) fraction contains 67% mmmm pentads. It has x-ray crystallinity of 59% comprised of 93% -phase, and no NMR detectable misinsertions. However, 1,3-insertion was found in the more soluble fractions.     

Preparation of high-temperature stable SiBCN fibers from tailored single source polyborosilazanes

Bulk SiBCN ceramics derived from polyborosilazanes of the type [B(C₂H₄SiRNH)₃]_n (1a, R = CH₃; 2a, R = H; C₂H₄ = CHCH₃, CH₂CH₂) exhibit an exceptional structural stability at high temperature. Therefore, such quaternary systems are of great scientific and technical interest as fibrous reinforcements intended for high-temperature applications. In this context, the design of novel polyborosilazanes, which display properties tailored for the preparation of SiBCN fibers, is studied. Boron-modified polysilazanes of the type [B(C₂H₄SiRNCH₃)₃]_n (1b, R = CH₃; 2b, R = H) are prepared via aminolysis of the tris(dichlorosilylethyl)boranes B(C₂H₄SiRCl₂)₃ (1, R = CH₃; 2, R = H). It is shown that the functionalisation of the precursors with NCH₃ units improves their processability (i.e. solubility) compared to that of their ammonolysed analogs [B(C₂H₄SiRNH)₃]_n (1a, R = CH₃; 2a, R = H). In addition to the influence of the NCH₃ units, the presence of the SiCH₃ functions in such polymers offers the best potential for the preparation of fibers by melt-spinning. As-spun fibers are then converted under controlled atmosphere into high-temperature stable SiBCN fibers according to the polymer-derived ceramic route.     

Determination of trace C6C8 aromatics in Iraqi natural gasoline by gas-liquid chromatography

The content of C₆C₈ aromatics in Iraqi natural gasoline and a benzene-free hexane fraction was determined quantitatively by gas-liquid chromatography using a 3 m column packed with 30% 1,2,3-tris(2-cyanoethoxy) propane on Diatomite S at 140 °C. The method employed gave more accurate results than standard methods for the samples used, as a result of the separation of the benzene peak after n-tridecane.     

Isotope scrambling in the formation of cyanopolyynes by laser ablation of carbon particles in liquid acetonitrile

Cyanopolyynes, H(CC)_nCN (n = 3–6), were formed by laser ablation of carbon particles in liquid acetonitrile. The molecules were separated according to the size n and characterized by UV absorption spectroscopy, mass spectroscopy in combination with gas-chromatographic separation, and nuclear magnetic resonance (NMR) spectroscopy. For the study of nascent carbon cluster distribution during the growth of the long carbon chain molecules, isotopomer distribution was analyzed by NMR spectroscopy for the product molecules. Two cyanopolyynes of HC₇N and HC₉N were isolated from solutions after laser ablation of isotope-enriched carbon powder (99% ¹³C) in liquid acetonitrile, CH₃CN, of natural isotopic abundance (1.1% ¹³C). With the observed chemical shift, δ, and spin–spin coupling constants, J_CH and J_CC, spectral simulation was made to determine relative abundance of possible isotopomeric forms for HC₉N. We found that the isotope of ¹²C, mostly from solvent molecules, contributes substantially for the part of carbon in the cyano group, –CN, in HC₉N. The isotopomer distribution observed for the sequence of H–CC–CC– was fairly explainable by a binomial, random distribution of the two carbon isotopes of ¹²C and ¹³C, reducing the concentration of ¹³C to 76–55%.     

Copolymerization of ethene with norbornene using palladium(II) α-diimine catalysts: Influence of feed composition, polymerization temperature, and ligand structure on copolymer properties and microstructure

Four cationic palladium(II) α-diimine complexes, [{ArNC(R)-C(R)NAr}Pd(Me)(CH₃CN)] (1, R=H, Ar=2,6-Me₂C₆H₃, =B[3,5-C₆H₃(CF₃)₂]₄; 2, R=CH₃, Ar=2,6-iPr₂C₆H₃; 3, R=CH₃, Ar=2-tBuC₆H₄; 4, R,R=An, Ar=2,6-iPr₂C₆H₃) were used for the copolymerization of ethene with norbornene. The copolymerization behavior of the catalysts and the influence of the polymerization temperature were investigated. The copolymers were characterized using ¹³C NMR spectroscopy, differential scanning calorimetry, and gel permeation chromatography techniques. Sterically demanding ortho -N-aryl substituents and rigid bulky bridge units increase the copolymer molar masses, while the incorporation level of norbornene is decreased. Microstructures with isolated norbornene units and alternating sequences are predominant. Less bulky substituted catalysts yield copolymers with higher norbornene contents and lower molar masses. Norbornene diblock sequences are dominant which are exclusively racemic connected, indicating that the insertion proceeds under chain end control. Optimal polymerization results are achieved at temperatures between 10 and 30 °C, while temperatures below 0 °C result in lower polymerization rates and molar masses. Above 30 °C, activities, molar masses, and norbornene incorporation decreases due to catalyst decomposition.     

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.     

Comparison of the Composition and Structural Parameters of W/O Microemulsions Containing Gemini Imidazoliums with Those Containing Monomeric Analogues

The composition and structural parameters of W/O microemulsions containing the gemini surfactant 1,4‐bis(3‐alkylimidazolium‐1‐yl) butane bromide [(C_n‐4‐C_n)Br₂, n = 12, 14, 16] + pentan‐1‐ol + octane + water and W/O microemulsions containing the ionic liquid surfactant 1‐alkyl‐3‐methylimidazolium (C_nmimBr, n = 12, 14, 16) + pentan‐1‐ol + octane + water were studied and compared. The mole fractions of the n‐alkyl alcohol at the interfacial layer in (C_n‐4‐C_n)Br₂ based microemulsion systems are always larger than those in C_nmimBr based microemulsion systems. However, the mole fractions of the n‐alkyl alcohol in the oil phase are nearly the same for both the microemulsion systems. The (C_n‐4‐C_n)Br₂ based microemulsion systems have greater absolute values of the free enthalpy values than that for C_nmimBr based systems. In the (C_n‐4‐C_n)Br₂ based microemulsion systems, a large number of cosurfactants at the interfacial layer is conducive to the formation of a smaller droplet W/O microemulsion. The effects of n‐alkyl alcohols, alkanes, salinity and temperature on the composition and structural parameters of the (C_n‐4‐C_n)Br₂ based and C_nmimBr based microemulsion systems were also investigated and discussed.     

The effect of bubble column diameter on gas holdup in fiber suspensions

Three bubble column diameters (D=10.2, 15.2, and 32.1 cm) are employed to study the scale-up effect on gas holdup in air-water and air-water-cellulose fiber (hardwood, softwood, and BCTMP) systems. The effect of column diameter depends on flow regime and fiber mass fraction. When , gas holdup decreases with increasing column diameter for the transitional and heterogeneous flow regime, and column diameter effects are negligible in the homogeneous flow regime. When , gas holdup is only affected by column diameter in the transitional flow regime for an air-water system and low fiber mass fraction suspensions (C?0.25%); column diameter effects disappear at medium fiber mass fractions (e.g., C=0.8%) but are significant at high fiber mass fractions (e.g., C=1.4%).     

Chemicals Used for Host Recognition by the Granary Weevil Parasitoid Lariophagus distinguendus

In order to develop methods for mass rearing of the parasitic wasp Lariophagus distinguendus, we characterized and identified chemicals used by this parasitoid to recognize wheat grains infested by its host, larvae of the granary weevil, Sitophilus granarius, a major pest of stored grain worldwide. Bioassays revealed that drumming and drilling behavior of the parasitoids on grain models of filter paper treated with host feces was as intense as on host-infested grains. Thus, chemicals from feces are highly important to recognize infested grains. Extracts of the feces with hexane or dichloromethane applied on grain models were able to provoke drumming and drilling activity. Hexane extract of feces was as active as infested grain itself. Subsequent fractionation of the hexane extract by adsorption chromatography revealed that highest activity was recovered in the dichloromethane fraction. This fraction was characterized by the presence of -tocopherol, -tocopherol, -tocotrienol, cholesterol, ergostenol, and -sitosterol. Synthetic chemicals in proportions found in the active dichloromethane fraction stimulated drumming behavior in bioassays. The significance of these results with respect to the mass propagation of L. distinguendus as natural enemies for the control of the granary weevil is discussed.