Biokinetics of dietaryRRR-α-tocopherol in the male guinea pig at three dietary levels of vitamin C and two levels of vitamin E. Evidence that vitamin C does not “spare” vitamin Ein vivo

The net rates of uptake of “new” and loss of “old”2R,4′ R,8′ R-α-tocopherol (RRR-α-TOH, which is natural vitamin E) have been measured in the blood and in nine tissues of male guinea pigs over an eight week period by feeding diets containing deuterium-labelled α-tocopheryl acetate (d ₆-RRR-α-TOAc). There was an initial two week “lead-in” period during which 24 animals [the “high” vitamin E (HE) group] received diets containing 36 mg of unlabelled (d ₀)RRR-α-TOAc and 250 mg of ascorbic acid per kg diet, while another 24 animals [the “low” vitamin E (LE) group] received diets containing 5 mgd ₀-RRR-α-TOAc and 250 mg ascorbic acid per kg diet. The HE group was then tivided into three equal subgroups, which were fed diets containing 36 mgd ₆-RRR-α-TOAc and 5000 mg [the “high” vitamin C (HEHC) subgroup], 250 mg [the “normal” vitamin C (HENC) subgroup] and 50 mg [the “low” vitamin C (HELC) subgroup] ascorbic acid per kg diet. One animal from each group was sacrificed each week and the blood and tissues were analyzed ford ₀- andd ₆-RRR-α-TOH by gas chromatography-mass spectrometry. The LE group was similarly divided into three equal subgroups with animals receiving diets containing 5 mgd ₆-RRR-α-TOAc and 5,000 mg (LEHC), 250 mg (LENC) and 50 mg (LELC) ascorbic acid per kg diet with a similar protocol being followed for sacrifice and analyses. In the HE group the totald ₀-+d ₆-)RRR-α-TOH concentrations in blood and tissues remained essentially constant over the eight week experiment, whereas in the LE group the totalRRR-α-TOH concentrations declined noticeably (except in the brain, an organ with a particularly slow turnover of vitamin E). There were no significant differences in the concentrations of “old”d ₀-RRR-α-TOH nor in the concentrations of “new”d ₆-RRR-α-TOH found in any tissue at a particular time between the HEHC, HENC and HELC subgroups, nor between the LEHC, LENC and LELC subgroups. We conclude that the long-postulated “spring” action of vitamin C on vitamin E, which is well documentedin vitro, is of negligible importancein vivo in guinea pigs that are not oxidatively stressed in comparison with the normal metabolic processes which consume vitamin E (e.g., by oxidizing it irreversibly) or elminate it from the body. This is true both for guinea pigs with an adequate, well-maintained vitamin E status and for guinea pigs which are receiving insufficient vitamin E to maintain their body stores. The biokinetics of vitamin E uptake and loss in the HE guinea pigs are compared with analogous data for rats reported previously (Lipids 22, 163–172, 1987). For most guinea pig tissues the uptake of vitamin E under “steadystate” conditions was faster than for the comparable rat tissues. However, the brain was an exception with the turnover of vitamin E occurring at only one-third of the rate for the rat. NRCC Publication No. 30775.     

Micellization of an anionic gemini surfactant having <Emphasis Type="Italic">N,N</Emphasis>-dialkylamide,carboxyl, and carboxylate groups in aqueous NaCl solutions

The micellization of an anionic gemini surfactant, (CH₂)₂[N(COC₁₁H₂₃)CH(CO₂H)CH₂(CO₂H)]₂·2NaOH, abbreviated as GA, having N,N-dialkylamide, carboxyl, and carboxylate groups, in aqueous solutions of NaCl at pH 5.0 was investigated by means of surface tension and of fluorescence, using pyrene as a probe. The l ₁/l ₃ vs. log surfactant molar concentration (C) plots showed two values of critical micelle concentration (cmc). Of the two values, the higher cmc value was close to that measured by the surface tension method, meaning that the lower cmc value may be caused by the formation of small, non-surface-active soluble premicellar aggregates. Evidence for the existence of these premicellar aggregates includes the fact that the lower of the two cmc values for GA was not observed in the l ₁/l ₃ vs. log C plots for (CH₂)₂[N(COC₁₁H₂₃)CH₂CH₂CO₂Na]₂, abbreviated as 212, in 0.001–0.3 M NaCl at pH 11.0, since the only cmc value obtained was close to that from surface tension data. Plots of log molar concentration of Na⁺ in the solutions vs. log cmc, or Corrin-Harkins plots, revealed that the lower cmc values decrease with an increase in Na⁺ concentration, and when [Na+]=1 M, the values reach the decreasing higher cmc value. This means two mechanisms of GA aggregation occured in at the same aqueous solutions of NaCl. In the first one, “monomeric form” → “micelle I” → “micelle II,” and in the second, “monomeric form” → premicelle → micelle II.” The degree of micelle ionization, or β, for the higher cmc values is 0.97 at 10⁻² M≦[Na⁺]≦0.1 M. This large β value indicates that the GA molecules, as a result of the structural characteristic attributable to the simultaneous presence of N,N-dialkylamide and carboxylate groups in the molecule, may be almost fully dissociated even at the cmc. The β value for the lower cmc is 0.75. This indicates that the existence of a non-monomeric state at concentrations below the cmc determined from surface tension data, which is additional evidence for the premicellar aggregation.     

Syndiospecific Polymerization of Styrene Using Half-Titanocene Catalyst Covalently Supported on MgCl<Subscript>2</Subscript>/AlEt<Subscript>n</Subscript>(OEt)<Subscript>3-n</Subscript>

The novel half-titanocene catalyst bearing reactive functional amino group, η⁵-pentamethylcyclopentadienyltri(p-amino-phenoxyl) titanium [Cp^∗Ti(p-OC₆H₄NH₂)₃], was easily synthesized by the reaction of η⁵-pentamethylcyclopentadienyltrichloride titanium (Cp^∗TiCl₃) with p-amino phenol in the presence of triethyl amine (NEt₃). Cp^∗Ti(p-OC₆H₄NH₂)₃ covalently anchored on MgCl₂/AlEt_n(OEt)_3-n support obtained from the reaction of triethylaluminium (AlEt₃) with the adduct of magnesium chloride (MgCl₂) and ethanol (EtOH), has been investigated and used to catalyze syndiospecific polymerization of styrene. Influences of the support structure, cocatalyst, and the molar ratio of Al in methylaluminoxane (MAO) and Ti (Al_MAO/Ti) on catalytic activity, syndiotacticity and molecular weight of the resultant polystyrene were investigated. Compared with the corresponding Cp^∗Ti(p-OC₆H₄NH₂)₃ homogeneous catalyst, a considerable increase in activity and molecular weight of syndiotactic polystyrene (sPS) was observed for the Cp^∗Ti(p-OC₆H₄NH₂)₃-MgCl₂/AlEt_n(OEt)_3-n supported catalyst even at a relatively low Al_MAO/Ti ratio of 50, and the kinetics of polymerization was stable during the reaction process.     

Preparation and thermo-oxidative degradation of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)-grafted SiO<Subscript>2</Subscript> nanocomposites

Poly(l-lactic acid)/poly(l-lactic acid)-grafted SiO₂ nanocomposites were prepared by in situ melt polycondensation, in which “free” poly(l-lactic acid) and poly(l-lactic acid)-grafted SiO₂ nanoparticles were formed simultaneously. The maximum values of grafting ratio and grafting efficiency of poly(l-lactic acid) were up to 37.67% and 26.60%, respectively. In the polycondensation system, SiO₂ content was a critical parameter of getting nanocomposites with uniformly dispersed SiO₂ nanoparticles. At lower SiO₂ content, Mn of grafted poly(l-lactic acid) was close to that of “free” poly(l-lactic acid), and poly(l-lactic acid)-grafted SiO₂ nanoparticles could be well dispersed in poly(l-lactic acid) matrix. While at higher SiO₂ content, Mn of “free” poly(l-lactic acid) and grafted poly(l-lactic acid) decreased seriously, especially GPC curves of “free” poly(l-lactic acid) exhibited two peaks due to the aggregation of SiO₂ nanoparticles during the polycondensation process. The grafting ratio and SiO₂ content exhibited a clear effect on the thermo-oxidative degradation of nanocomposites. The existence of poly(l-lactic acid)-grafted SiO₂ nanoparticles dramatically improved the thermo-oxidative stability of poly(l-lactic acid). Compared with that of pure poly(l-lactic acid), T _g, T _c, and T _m of nanocomposites varied slightly.     

On the acidity of liquid and solid acid catalysts: Part 1. A thermodynamic point of view

The protonation equilibria of weak bases (B) in solid acids (HClO₄/SiO₂, CF₃SO₃H/SiO₂, H₂SO₄/SiO₂) were studied by UV spectroscopy and the results were compared to those obtained for analogous compounds in concentrated aqueous solutions of strong acids (HClO₄, CF₃SO₃H, H₂SO₄). The behaviour of B in liquid (L) and solid (S) phase was analysed by titration curves, log[BH⁺]/[B] ratios and thermodynamic pK _BH+ values. It has been shown that the proton transfer process acid → base (i.e., from (H+A^-)_(L,S) to (BH+A^-)_(L,S)} can be described by the relationship observed between the activity coefficient terms that are to be taken into account for acid–base equilibria occurring in nonideal systems ( – log(f _B f _B+/f _BH+)_(L,S)= -n _BA log(f _A–f _H+/f _HA)_(L,S)) and can be estimated by the n _BA values. Two “activity coefficient functions” (i.e., Mc(B) = – log(f _B f _B+/f _BH+)and Mc(s) = – log(f _A–f _H+/f _HA)) were used to describe, respectively, the equilibria of B and the equilibria of the acids in concentrated aqueous solutions and the meaning of terms “activity coefficient function” and “protonating ability of an acid” were discussed. The difference between “acidity functions”, determined for solutes (Ac(i)) and solvents (Ac(s)) in aqueous acids, and the H_x acidity functions, the latter developed for solutes in analogous media by the Hammett procedure, was also shown. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polymorphism of cocoa butter

Largely by x-ray diffraction six crystalline states, I–VI, in order of increasing melting point, have been identified for cocoa butter. Of these states II, IV, V and VI are pure and identifiable with previously (or presently) identified polymorphs of 2-oleoylpalmitoyl stearin (POS), namelyα-2,β′-2,β-3 (“V”) andβ-3 (“VI”); V and VI representing distinct but very closely related crystalline structures. State I is a definite but fleeting and not readily characterized subα state and may be a phase mixture, as state III may be also. Melting points, heats of fusion and dilatometric data are reported for all states to the extent that their stability permits. The normal state of cocoa butter in chocolate is apparently V, certainlyβ-3. While it is true that “bloom” has not been observed for pure V nor observed to exist in the absence of VI, it is premature to say that VI is specifically the phase of chocolate “bloom”.     

Synthesis, characterization, thermal degradation, and comparative chain dynamics studies of weak-link polysulfide polymers

Synthesis, spectroscopic and thermal characterization of two new classes of polysulfide polymers: poly[1-(phenoxymethyl) ethylene polysulfide] (PPMEP), and poly[1-(phenoxy) ethylene polysulfide] (PPEP) is presented. The direct pyrolysis mass spectrometry (DP-MS) technique, used to study the thermal degradation behavior of these polysulfide polymers, indicated that the polymers underwent degradation through the weak-links scission. The thermal stability of the polysulfide polymers decreased as the “rank” (number of sulfur atoms in the polysulfide linkage; n = 1, 2, 4) increased. The main-chain flexibility of these polysulfide polymers in terms of their ¹³C NMR spin-lattice relaxation time (T ₁ ) measurements on the backbone methine (-CH-) and methylene (-CH₂-) carbons are reported here for the first time. A comparative study of the solution chain dynamics indicated that it increased as “rank” of the polysulfide linkages decreased as well as by introducing side chain spacers such as, ether (-O-) or methyleneoxy (-CH₂O-) groups.     

Amphiphilic networks. XIV

Summary The synthesis and characterization of novel amphiphilic networks based on dimethylacrylamide and crosslinked by methacrylate telechelic three-arm star polyisobutylene (?(PIB-MA)₃) are reported. The networks are characterized by two M _c's and possess “homogeneous” and “heterogeneous” crosslinks. The networks swell both in water and n-heptane which indicates a cocontinuous hydrophobic-hydrophilic microarchitecture. Water-swollen networks exhibit higher tensile strengths and elongations, than those made previously with linear MA-PIB-MA's of similar overall compositions (i.e., ∼1.0 versus ∼0.5 Mpa, and ∼300% versus ∼200%, respectively). The enhanced mechanical properties of the new networks are being exploited in biomedical applications. Received: 28 July 1999/Revised version: 25 October 1999/Accepted: 27 October 1999     

Fullerene lipids: Synthesis of novel nitrogen-bridged [60]fullerene fatty ester derivatives

Reactions of methyl 6-azido-hexanoate, 8-azido-octanoate, and 12-azido-dodecanoate with [60]fullerene (1) gave the corresponding aza-[60]fullerene ester derivatives (2a-2c, 22–35% based on the amount of [60]fullerene reacted). The nitrogen atom is bonded to the [60]fullerene cage to yield a “[5,6]-open” type aza substructure. This was confirmed by the appearance of 30–31 sp ² signals at δ_C 133–147 in the carbon nuclear magnetic resonance spectra. Reaction of methyl 11-azido-7-undecynoate with [60]fullerene furnished a mixture of aza-[60]fullerene (2d, 53%) and aziridine-[60]fullerene (2e, 38%) ester derivatives. Compound 2e was identified as the “[6,6]-closed” type aziridine-[60]fullerene derivative, which displayed 10 sp ² signals in the region δ_C 140–145 and one signal at δ_C 85.05 for the sp ³ carbons of the cage. Refluxing a solution of compound 2d in toluene for 50 h gave about 50% yield of compound 2e, but not vice versa.     

Heat Treatment Improves Olive Oil Extraction

To determine the effect of hot water pre-treatment on olive oil extraction, six cultivars of olive fruit (Olea europaea L. cvs. “Arbequina”, “Hojiblanca”, “Lechín”, “Manzanilla”, “Picual”, and “Verdial”) were heated at 50, 55, and 60 °C prior to laboratory scale oil extraction. Heat treatment resulted in higher oil extraction than unheated control samples. Quality parameters of the oils were not significantly (P < 0.05) affected by these treatments; however, oil stability and bitterness intensity were reduced and pigment content was increased through pre-heat treatment. This process may be incorporated economically into olive oil processing.     

Reaction mechanism of the direct carboxylation of methanol to dimethylcarbonate: experimental and theoretical studies

The formation of dimethylcarbonate (DMC) from MeOH and CO₂ under [Nb(OMe)₅]₂ catalysis follows a different route (“acid-plus-base activation” of methanol) with respect to other known catalytic systems such as Sn(IV) and dicyclohexylcarbodiimide (DCC) that promote a “double-base activation”. The reaction intermediates and related transition states obtained from density functional (DFT) calculations are presented. Experimental data also feature a different reaction mechanism.     

Structural interpretation on the concentration dependence of molar volume in ternary aluminosilicate glasses containing oxides of the first and second groups of the periodic system

The concentration dependence of the molar volume of ternary aluminosilicate glasses, in which the content of R₂O (or RO) exceeds the Al₂O₃ content, is determined by the degree of depolymerization of the glass structural lattice. The molar volume in glasses with an equimolar content of R₂O (or RO) and Al₂O₃ is additive and depends on the partial values of the molar volume of the “silica” and “aluminate” components in the structural lattice. Translated from Steklo i Keramika, No. 5, pp. 8–11, May, 2000.     

Formation of a liquid film of AgNO3 on a silver surface

The behavior of a AgNO₃/Ag₂O/Ag “sandwich” upon heating in vacuum was studied by in situ X‐ray photoelectron spectroscopy (XPS) and ex situ scanning electron microscopy (SEM). The AgNO₃/Ag₂O/Ag “sandwich” was prepared by exposure of a silver foil to a NO : O₂ mixture. The upper layer of the “sandwich” consists of AgNO₃ crystals of a mean size between 0.1 and 0.4 μm. Heating at 550 K in vacuum results in melting of the AgNO₃ crystals. A liquid film of AgNO₃, readily wetting the silver, covers the surface. Cooling below the melting point of AgNO₃ leads to the agglomeration of silver nitrate to long islands with a size reaching a few tens of micrometers (μm). The possible effects of AgNO₃ liquid‐phase formation on surface processes are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pd-Decorated CNT-Promoted Pd-Ga2O3 Catalyst for Hydrogenation of CO2 to Methanol

Abstract  

A type of Pd-decorated CNT-promoted Pd-Ga catalysts was developed. The catalyst displayed excellent performance for CO₂ hydrogenation to methanol. Under the reaction conditions of 5.0 MPa and 523 K, the observed specific reaction rate of CO₂ hydrogenation reached 2.23 μmol s⁻¹ (m²-Pd)⁻¹, which was 1.39 times that (1.60 μmol s⁻¹ (m²-Pd)⁻¹) of the non-promoted Pd-Ga host. The addition of a small amount of the Pd-decorated CNTs to the Pd-Ga host catalyst did not cause a marked change in the E _a of the CO₂ hydrogenation reaction. The function of the CNT-promoter was mainly in increasing the molar percentage of the catalytically active Pd⁰-species in the total Pd-amount at the surface of the functioning catalyst, and in improving the capability of the catalyst to adsorb and activate H₂ (one of the reactants). Compared to the “Herringbone-type” CNTs, the “Parallel-type” CNTs possess less active surface (with less dangling bonds), and thus, lower capacity for adsorbing H₂, resulting in the rather limited promoter effect.     

Effects of Thickness,Deformation Rate and Energy Partitioning on the Work of Fracture Parameters of uPVC Films

Summary Unplasticised poly(vinyl chloride) (uPVC) films have been tested using the essential work of fracture (EWF) method. Influence of loading rate and film thickness on the tensile properties and work of fracture parameters was evaluated. In addition, energy partition analyses were carried out applying two different approaches (“yielding” and “initiation”), which differ in the treatment of the stored elastic energy. Results showed less effect of the film thickness and deformation rate (<l00 mm/min) on the EWF terms. On the other hand, the specific essential work of fracture (w _e) at high load rate (1.2 m/s) approached the yielding-related term (w _e,y) obtained at static loading rates (<l00 mm/min). Received: 16 July 2002/Revised version: 31 March 2003/Accepted: 29 April 2003 Correspondence to M. Ll. Maspoch     

High activity TiO2 Photocatalysts Prepared by a Modified Sol–gel Method: Characterization and their Photocatalytic Activity for the Degradation of XRG and X-GL

A simple method for preparing high photocatalytic activity TiO₂ has been developed by controlled the hydrolysis of titanium butoxide with water generated “in situ” using an esterification reaction between the acetic acid and ethanol. The photocatalytic activity of the samples prepared was higher than that of the reference Degussa P25 TiO₂ for the liquid phase photocatatlytic degradation of active yellow XRG dye and cationic golden X-GL dye.     

13C nuclear magnetic resonance spectroscopic analysis of the triacylglycerol composition of some margarines

The triacylglycerol fraction of three samples of margarine, namely “Flora” (Holland), “Kaliakra” (Bulgaria), and “Corona” (Holland), were studied by¹³C nuclear magnetic resonance spectroscopy. By examining the various carbon chemical shifts of the saturated and unsaturated carbon nuclei, “Flora” margarine was shown to contain a mixture of hydrogenated and unhydrogenated vegetable oils. This technique allowed all major acyl groups (saturated, oleate, linoleate, and linolenate) and minor acyl components [different positional isomers of long-chain (E)- and (Z)-monoenoic moieties, arising as by-products during catalytic hydrogenation] to be identified. The amount of each fatty acid present in the margarine was also estimated from the relative intensities of the corresponding signals. “Kaliakra” margarine consisted of a blend of unhydrogenated natural fats and oils that contained saturated fatty acids, oleate, and linoleate. There were no signs in the spectrum of “Kaliakra” of any (E)-isomers, nor signals associated with positional unsaturated acyl groups (other than oleate and linoleate). The sample of “Corona” margarine consisted of a mixture of hydrogenated and unhydrogenated vegetable oils and butter (1.3%). The presence of butter in this sample was identified by the characteristic carbon shifts of the C-1 to C-4 carbon atoms of butyrate. The distribution of the fatty acids on the glycerol “backbone” also was estimated by this technique.     

Site requirements in the kinetics of alkane transformations catalysed by metals

Hydrogen pressure is often found to cause an inhibiting effect on the kinetics of alkane reactions on metal surfaces. The most common interpretation of such results is focussed on the degree of dehydrogenation of the active surface intermediate following a dissociative mechanism. A series of arguments will be given in favour of an associative mechanism in which the hydrocarbon reacts with an adsorbed hydrogen atom. In this mechanism, the adsorption site or “landing site” is composed of a chemisorbed hydrogen atom associated with an ensemble of “Z” potential sites. These sites are associated with the hydrogen chemisorption site. The validity of H₂ adsorption to determine the metallic dispersion will be also discussed. Contribution in honour of Dr. Alfred Frennet     

Isolation of two isomeric 2, 6-nonadienals and two isomeric 4-heptenals from beef and mutton tallow

By the use of mainly chromatographic and UV spectrophotometric techniques, 4cis- and 4trans-heptenal (with a “green” odor, characterized in high dilution as tallowy, creamy, butterscotch-like) and 2trans,6cis- and 2trans,6trans-nonadienal (with a “green”-cucumber-like and a tallowy odor) were isolated from reverted beef and mutton tallow. Presented in part by G. Hoffmann at the 7th ISF-Congress, Hamburg, October 1964.