β-Oxidation of conjugated linoleic acid isomers and linoleic acid in rats

To assess the oxidative metabolism of conjugated linoleic acid (CLA) isomers, rats were force-fed 1.5–2.6 MBq of [1-¹⁴C]-linoleic acid (9c,12c-18∶2),-rumenic acid (9c,11t-18∶2), or-10trans, 12cis-18∶2 (10t, 12c-18∶2), and ¹⁴CO₂ production was monitored for 24 h. The animals were then necropsied and the radioactivity determined in different tissues. Both CLA isomers were oxidized significantly more than linoleic acid. Moreover, less radioactivity was recovered in most tissues after CLA intake than after linoleic acid intake. The substantial oxidation of CLA isomers must be considered when assessing the putative health benefits of CLA supplements.     

Gas chromatography—High resolution selected-ion mass spectrometric identification of trace 21∶0 and 20∶2 fatty acids eluting with conjugated linoleic acid isomers

High-resolution selected-ion recording (SIR) of the exact molecular ion mass was used to confirm unambiguously the presence of conjugated linoleic acid (CLA) derivatives in biological matrices and standard mixtures and to differentiate non-CLA derivatives from CLA derivatives in the CLA region of the gas chromatogram. The success of this method was based on the selectivity of the SIR technique and its sensitivity, which was comparable to that of flame-ionization detection. A minor fatty acid methyl ester (FAME) was identified as methyl heneicosanoate (21∶0), and six isomers of 20∶2 FAME were found to elute in the CLA region. Isomerization of a standard CLA mixture resulted in a non-CLA flame-ionization response eluting in the CLA region of the gas chromatogram. It is therefore recommended that the identification of minor CLA isomers in natural products of biological matrices should include their direct confirmation by mass spectrometry     

Effects of margarine and butter consumption on distribution of trans-18∶1 fatty acid isomers and conjugated linoleic acid in major serum lipid classes in lactating women

Trans FA (TFA) have at least one trans double bond and comprise several isomers and types, including many of the CLA (e.g., c9, t11–18∶2 CLA). Some TFA may have adverse effects (e.g., cardiovascular disease), whereas some are though to have beneficial effects (e.g., anticarcinogenicity). The presence of TFA in human tissues and fluids is related to dietary intake, although this relationship is not completely understood—especially in regard to serum lipid fractions. This study was conducted as part of an investigation designed to test the influence of butter (B), “low TFA” margarine (LT), and regular margarine (RM) on milk fat content. Here we tested the secondary hypothesis that consumption of B, LT, and RM by lactating women would result in differential distribution of TFA and CLA in major serum lipid classes. Breastfeeding women (n=11) participated in this randomized Latinsquare study consisting of five periods: intervention I (5 d), washout I (7 d), intervention II (5 d), washout II (7 d), and intervention III (5 d). Extracted serum lipid was separated into cholesterol ester (CE), TAG, and phospholipid (PL) fractions and analyzed for total and isomeric TFA and CLA concentrations. Data indicate that TAG consistently contained the highest concentration of total t-18∶1. No interaction between treatment and fraction was found for any of the t-18∶1 isomers identified. Absolute concentration of each t-18∶1 isomer was greatest during the RM period, regardless of fraction. On a relative basis, concentrations of t10–18∶1 and t12–18∶1 were most responsive to treatment in the CE fraction. The concentration of c9, t11–18∶2 CLA was highest in the TAG fraction and lowest in the PL fraction, regardless of treatment. In summary, these results indicate (i) that there is a differential distribution of some isomeric TFA and CLA among human serum lipid fractions and (ii) that dietary TFA intake influences absolute and relative concentrations of some of the isomers in selected fractions.     

Preparation, separation, and confirmation of the eight geometrical cis/trans conjugated linoleic acid isomers 8,10-through 11,13–18∶2

Conjugated linoleic acid (CLA) mixtures were isomerized with p-toluenesulfinic acid or I₂ catalyst. The resultant mixtures of the eight cis/trans geometric isomers of 8,10-, 9,11-, 10,12-, and 11,13-octadecadienoic (18∶2) acid methyl esters were separated by silver ion-high-performance liquid chromatography (Ag⁺-HPLC) and gas chromatography (GC). Ag⁺-HPLC allowed the separation of all positional CLA isomers and geometric cis/trans CLA isomers except 10,12–18∶2. However, one of the 8,10 isomers (8cis, 10trans-18∶2) coeluted with the 9trans,11cis18∶2 isomer. There were differences in the elution order of the pairs of geometric CLA isomers resolved by Ag⁺-HPLC. For the 8,10 and 9,11 CLA isomers, cis,trans eluted before trans,cis, whereas the opposite elution pattern was observed for the 11,13–18∶2 geometric isomers (trans,cis before cis,trans). All eight cis/trans CLA isomers were separated by GC on long polar capillary columns only when their relative concentrations were about equal. Large differences in the relative concentration of the CLA isomers found in natural products obscured the resolution and identification of a number of minor CLA isomers. In such cases, GC-mass spectrometry of the dimethyloxazoline derivatives was used to identify and confirm coeluting CLA isomers. For the same positional isomer, the cis,trans consistently eluted before the trans,cis CLA isomers by GC. High resolution mass spectrometry (MS) selected ion recording (SIR) of the molecular ions of the 18∶1 18∶2, and 18∶3 fatty acid methyl esters served as an independent and highly sensitive method to confirm CLA methyl ester peak assignments in GC chromatograms obtained from food samples by flame-ionization detection. The high-resolution MS data were used to correct for the nonselectivity of the flame-ionization detector.     

Modeling and simulation of a commercial graphite–LiFePO<Subscript>4</Subscript> cell in a full range of C-rates

A pseudo two-dimensional model (P2D) was presented to describe the electrochemical behaviour of a commercial 18650 cylindrical cell composed of graphite and LiFePO₄ (LFP) electrodes. Simulations were conducted by COMSOL MULTIPHYSICS 5.2. The model validation was done with experimental data taken from Hydro-Québec for a full range of C-rates (currents). A mosaic model based on a C-rate dependent particle radius in positive and negative electrodes was assumed. The reaction kinetics and diffusion in a solid phase were recognized as cell performance limiting factors in the flat area and in the steep area at the end of discharge of the cell voltage–capacity curve, respectively. Since the diffusion polarization in a solid phase played an important role in the steep area at the end of discharge of the cell voltage–capacity curve, a concentration dependent diffusion coefficient in LFP positive electrode was considered. Based on the fact that activation overpotential was a major polarization in the flat area of the cell voltage–capacity curve in addition to decreasing the particle radius at higher C-rates, a contact resistance between the surface of the particles and the solid matrix was predicted. This contact resistance on the surface of active materials in the positive electrode described the feature of low electronic conductivity in LFP. There was a good agreement between the simulated results with experimental discharge data in a full range of C-rates.

Graphical abstract

Simulated (solid lines) and experimental (symbols) cell voltage-capacity curves for different C-rates.

Open image in new window

     

Inhibitory effect of linoleic acid on chain elongation and desaturation of 18∶2 c,t isomers in lactating and neonatal rats

The previous studies showed that dietary 18∶2 c,t isomers could be chain-elongated and desaturated to produce unusual 20∶4 isomers. The present study was undertaken to determine the minimal amount of 18∶2n−6 required to suppress the chain elongation and desaturation of 18∶2 c,t isomers in the lactating and neonatal rats when animals were fed 15% partially hydrogenated canola oil diet containing 1.72% energy as 18∶2 c,t isomers and varying amounts of free 18∶2n−6. These diets induced marginal essential fatty acid (EFA) deficiency states (0.56% energy 18∶2n−6) to EFA adequacy (2.56% energy 18∶2n−6). After feeding for 50 d, the female animals were mated with males by overnight pairing. After conception, the lactating rats were killed, together with one pup from each dam, at term and day 26 of lactation. Two unusual 20∶4 isomers in both maternal and neonatal liver phospholipids were identified as 20∶4Δ5c,8c,11c,14t and 20∶4Δ5c,8c,11c,15t, which were derived from 18∶2Δ9c,12t, and 18∶2Δ9c,13t, respectively. The results showed that 18∶2n−6 at about 2.0% of total energy in maternal diet was required to block the production of 20∶4Δ5c,8c,11c,14t and 20∶4Δ5c,8c,11c,15t in the maternal liver, whereas 18∶2n−6 at about 2.5% of total energy in maternal diet was required to suppress production of these unusual 20∶4 isomers in the neonatal liver.     

Highly efficient separation of linear and branched C4 isomers with a tailor-made metal–organic framework

Separation of linear and branched isomers is of great commercial significance but still one of the energy-intensive and challenging processes in petrochemical industry. Here, we for the first time report a tailor-made metal–organic framework, ZU-36-Co (also termed GeFSIX-3-Co, GeFSIX = GeF₆²⁻, 3 = pyrazine), for the separation of both C4 linear/branched olefins (n−/iso-C₄H₈) and paraffin isomers (n−/iso-C₄H₁₀). With the pore size ranged between 3.82–5.25 Å, ZU-36-Co traps a large amount of n-C₄H₈ (2.35 mmol/g) and n-C₄H₁₀ (2.20 mmol/g) with iso-C₄H₈ and iso-C₄H₁₀ excluded. The molecular exclusion effect illustrates the significance of tailor-made pore window size for gas separation. To our knowledge, ZU-36-Co exhibits the highest n−/iso-C₄H₈ uptake ratio (13.8) and superior n−/iso-C₄H₁₀ separation performance compared with the state-of-the-art materials and sets a benchmark for the separation of linear and branched C4 isomers. This excellent molecular exclusion effect of ZU-36-Co was further confirmed by mixed gas breakthrough tests.     

Modeling of pressure losses for the slug flow of a gas–liquid mixture in mini- and microchannels

In addition to the previously constructed model of the hydrodynamics of a gas-liquid slug flow, a mathematical model is developed that describes pressure losses taking into account the rearrangement of a velocity profile in liquid slugs and energy losses on the formation and renewal of interfacial area during the motion of bubbles. The contribution of different forms of pressure losses in capillaries is analyzed. It is shown that in microchannels tangential stresses on the surface of a bubble substantially affect the total pressure losses. It is found that the length of bubbles does not affect the rate of surface formation and respective pressure losses if bubbles have the same velocity. The results of modeling are in satisfactory agreement with experimental data of other researchers.     

Hydrodynamics of three-phase fluidization of homogeneous ternary mixture in a conical conduit——Experimental and statistical analysis

Hydrodynamics of conical fluidized bed differ from that of columnar beds by the fact that a velocity gradient exists along the axial direction of the bed.The gas–liquid–solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operations.Such a device is of considerable industrial importance as evident from its wide applications in chemical,refining,petrochemical,biochemical processing,pharmaceutical and food industries.To explore this,a series of experiments have been carried out for homogeneous well-mixed ternary mixtures of dolomite of varying compositions in a three-phase conical fluidized bed.The hydrodynamic characteristics determined included the bed pressure drop,bed fluctuation and bed expansion ratios.The single and combined effects of operating parameters such as superficial gas velocity,superficial liquid velocity,initial static bed height,average particle size and cone angle on the responses have been analyzed using response surface methodology(RSM).A 25 full factorial central composite experimental design has been employed.Analysis of variance(ANOVA) showed a high coefficient of determination value and satisfactory prediction second-order regression models have been derived.Experimental values of bed pressure drop,bed fluctuation and bed expansion ratios have been found to agree well with the developed correlations.     

Microemulsion-mediated hydrothermal growth of pagoda-like Fe3O4 microstructures and their application in a lithium–air battery

This paper reported the growth of novel pagoda-like Fe₃O₄ particles via a facile microemulsion-mediated hydrothermal procedure. The chemical compositions and morphologies of the as-grown Fe₃O₄ particles were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The morphologies of the as-prepared sample evolved from pagoda-like to pinwheel-like to flower-like shapes with increasing reaction time. In addition, the NaOH concentration and polyethylene glycol (PEG)-2000 had key effects on the formation of the final product. The electrocatalytic properties of the prepared pagoda-like micro-Fe₃O₄, as catalytic materials for a lithium–air battery, were further evaluated by galvanostatic charge/discharge cycling and electrochemical impedance spectrometry (EIS). Results showed that the cell displayed an initial discharge capacity of 1429 mA h g⁻¹ at a voltage of 1.5–4.5 V at 100 mA g⁻¹.     

Incorporation and metabolism of trans 20∶5 in endothelial cells. Effect on prostacyclin synthesis

To study the ability of long-chain trans fatty acids (FA) to be incorporated and metabolized into endothelial cells, bovine aortic endothelial cells were incubated with medium enriched eicosapentaenoic acid (EPA) bound to albumin (M2) or one of its geometrical isomers: 20∶5 5c,8c,11t,14c,17c(M3), 20∶5 5c,8c,11c,14c,17t(M4), or 20∶5 5c,8c,11t,14c,17t(M5). After 48 h of incubation, supernatant and cells were harvested and their lipids were analyzed, including prostacyclin synthesis. EPA and 22∶5n−3 of endothelial cells incubated with M2 were, respectively, three and two times higher than in control cells (incubated in M1, without any fatty acid added), whereas 22∶6n−3 increased only in the supernatant, suggesting its release after biosynthesis. However, 18∶2n−6 and 22∶4n−6 decreased (about 30%). Trans 20∶5 isomers represented 4.7, 3.9, and 5.2% of total phospholipid FA in endothelial cells incubated with M3, M4, and M5, respectively. They were elongated into trans 22∶5 and trans 24∶5, as revealed by gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared analysis. In cells incubated with M2, M3, M4, and M5, prostacyclin synthesis was inhibited by 49.0, 62.5, 60.5, and 72.0%, respectively. This effect may be due to less available arachidonic acid in the cells and to a competition between EPA isomers and AA at the level of cyclooxygenase pathway, as it was demonstrated that 20∶5 Δ17t was metabolized by this enzyme.     

Synthesis of various CuO nanostructures via a Na3PO4–assisted hydrothermal route in a CuSO4–NaOH aqueous system and their catalytic performances

Various CuO nanostructures, including spherical, flower-like, cross-like, leaf-like, and elliptical structures, were obtained via a sodium phosphate (Na₃PO₄)–assisted hydrothermal route with CuSO₄ and NaOH as the copper and alkali sources, respectively. The presence of Na₃PO₄ is vital for the formation of various CuO nanostructures. The morphology of the CuO nanostructures is significantly influenced by the feeding concentration of the NaOH solution. The catalytic activity of the CuO products on the thermal decomposition of ammonium perchlorate (AP) was characterized by differential scanning calorimetry (DSC). Results showed that the addition of CuO nanostructures could dramatically decrease the high decomposition temperature of AP, thereby demonstrating their excellent catalytic activity for the thermal decomposition of AP.     

Modelling the coupled transfer of mass and thermal energy in the vapour–liquid region of a nitrogen–oxygen mixture

Current non-equilibrium distillation models do not explicitly include the coupling between thermal and mass fluxes. We present a calculation model for the coupled transfer of mass and thermal energy in the vapour–liquid region of a binary mixture. The region is modelled as a vapour–liquid interface in between two homogeneous films. The entropy production in the vapour–liquid region can be calculated using both irreversible thermodynamics and the entropy balance. The film thickness ratio is found by requiring the entropy production calculated with the two methods to be equal, while keeping the vapour film thickness fixed. Using a nitrogen–oxygen mixture as example, we show that neglecting the coupling between thermal and mass fluxes can have a large impact on the magnitude and direction of the theoretical (net) fluxes. The size of the impact depends on the vapour film thickness, but it is significant for all thicknesses. By increasing the number of control volumes that is used to represent the liquid and vapour films, we also show that the fluxes depend highly on the resistivity profiles in the films. They depend slightly on the interface resistance. A sensitivity analysis of the transport properties shows that accurate values of the Maxwell–Stefan diffusion coefficients in both homogeneous phases and of the liquid phase heat of transfer are most important. Especially the measurable heat flux at the liquid boundary of the system is sensitive to neglect of coupling, to neglect of the interface resistance and to uncertainties in the transfer properties.     

Alteration of 20∶5n−3 and 22∶6n−3 fat contents and liver peroxisomal activities in fenofibrate-treated rainbow trout

Fish easily accumulate n−3 PUFA of exogenous origin, but the underlying mechanisms are not well established in the whole animal. This study was undertaken to investigate whether this feature was physiologically associated with mitochondrial and peroxisomal capacities that differentially affect FA oxidation. For this purpose, peroxisomal FA oxidation was increased by treating rainbow trout with fenofibrate, which strongly stimulates the peroxisome proliferator-activated receptor-α in rodents. Diets containing EPA and DHA, with or without fenofibrate added, were administered to male trout for 12 d. After treatment, neither liver hypertrophy nor accumulation of fat was apparent within the liver and muscle cells. However, fenofibrate treatment decreased the contents of EPA and DHA in the liver, white muscle, and intraperitoneal fat tissue, which represented (per whole body) at least 280 mg less than in controls. Carnitine-dependent palmitate oxidation rates, expressed per gram of liver, were slightly increased by fenofibrate when measured from tissue homogenates and were unchanged when calculated from isolated mitochondria, relative to control fish. The treatment altered neither carnitine palmitoyltransferase I activity rates, expressed per gram of liver, nor the sensitivity of the enzyme to malonyl-CoA inhibition, but did increase the malonyl-CoA content (+45%). Meanwhile, fenofibrate increased (by about 30%) the peroxisome-related activities, i.e, catalase, carnitine-independent palmitate oxidation, acyl-CoA oxidase, and the peroxisomal FA-oxidizing system, relative to the control group. The data strongly suggest that the induction of peroxisomal activities, some of which being able to oxidize very long chain FA, was responsible for the lower contents of EPA and DHA in the body lipids of fenofibrate-treated trout.     

Low-temperature synthesis of BiVO4 crystallites in molten salt medium and their UV–vis absorption

BiVO₄ crystallites were successfully synthesized by a low-temperature molten salt method. XRD analysis and SEM observation showed that the incorporation of salt medium in the preparing process would greatly lower the formation temperature of BiVO₄ phase, and promote their crystallization. UV–vis spectra evidenced their better optical absorption and visible light response than that of TiO₂-P25.     

A detailed anatomy of students’ perception of engagement and their learning a threshold concept in core chemical engineering

An attempt has been made to reveal a detailed anatomy of students’ self-perceived engagement with material in a lecture and their learning of a key course threshold concept. A cohort of 80 students in a third year chemical engineering (64% response rate) course voluntarily recorded their engagement using a Likert-type scale at intervals of 5 min in a (nominally 50 min) lecture, together with written comments. Marks were awarded for a substantial, follow-up summative assignment to test their understanding of the threshold concept. It was found students were highly unaligned in their level of engagement with the lecture. A key reason was that individuals’ engagement varied highly significantly during the lecture. Six engagement styles were identified. Some 33% exhibited Type 1 (engage strongly at the start and slowly disengage) and 23% exhibited Type 2 (remain at a more or less fixed engagement). Significantly, there was no correlation between students’ engagement scores and marks awarded; in particular there was no correlation with specific lecture intervals in which material was identified as most important. Further, there was no correlation between the number of written comments made by an individual and their marks. It is concluded that student self-perceived engagement is not a good predictor of learning as assessed by marks awarded on a summative assignment. It is not known whether student engagement is predicated on particular lecture material and type of lecturer, or other contributing factors. The experimental design could be readily widely applied.     

Properties of Si3N4–TiN composites fabricated by spark plasma sintering by using a mixture of Si3N4 and Ti powders

Si₃N₄–TiN composites were successfully fabricated via planetary ball milling of 70 mass% Si₃N₄ and 30 mass% Ti powders, followed by spark plasma sintering (SPS) at 1250–1350 °C. The sintering mechanism for SPS was a hybrid of dissolution–reprecipitation and viscous flow. The electrical resistivity decreased with increasing sintering temperature up to a minimum at 1250 °C and then increased with the increasing sintering temperature. The composites prepared by SPS at 1250–1350 °C could be easily machined by electrical discharge machining. Composite prepared by SPS at 1300 °C showed a high hardness (17.78 GPa) and a good machinability.     

Laser diffraction characterization of droplet size distributions produced by vibrating mesh nebulization in air and a helium–oxygen mixture

Medical aerosols may be delivered in combination with gases other than air, thus it is of interest to assess the effects of gas properties on the characteristics of the administered aerosol separately from effects on ventilation distribution and particle deposition mechanisms. This work investigated the influence of the supplied gas, either air or a mixture containing 78% helium and 22% oxygen, on droplet sizes produced by a vibrating mesh nebulizer incorporated in a combined gas–aerosol delivery system. Droplet size distributions were measured by laser diffraction. Nebulization was performed using three different meshes, producing droplets with nominal volume median diameters (VMDs) of 3, 4, or 5 μm. Measured VMDs were stable, in that they were in all cases within ±10% of their nominal values, and unaffected by humidity or dilution of the aerosol stream. While VMDs were consistently 5–10% smaller in helium–oxygen than in air, this variation was small compared to the variation between meshes. Accordingly, unlike jet nebulizers, vibrating mesh nebulizers having high output rates can be operated in helium–oxygen with only minor impact on emitted droplet sizes. This will be attractive in the design of controlled clinical studies investigating aerosol delivery in helium–oxygen. In assessing such therapies, it is important to distinguish effects of gas properties on the characteristics of the administered aerosol from effects on particle and fluid mechanics influencing the regional distribution of aerosol in the lung. Use of an aerosol delivery device that is virtually unaffected by changing gas properties, such as that tested in the present study, is a straightforward way to make such a distinction.     

Correct use of the Langmuir–Hinshelwood equation for proving the absence of a synergy effect in the photocatalytic degradation of phenol on a suspended mixture of titania and activated carbon

This study is a critical approach to the widespread use of the first order form of the Langmuir–Hinshelwood (LH) equation for analyzing kinetics in heterogeneous photocatalytic processes. The different kinetic protocols analyzed have been applied to the results, published in the literature, of the photocatalytic degradation of phenol in an aqueous solution by a physical mixture of TiO₂ particles and activated carbon (AC), the impact of which has been enormous over the last decade. It is commonly accepted that there is a strong synergy in this mixture due to the transfer of phenol from the activated carbon particles to TiO₂. However, we found in this study that the apparent synergy between activated carbon and TiO₂ particles arises from the erroneous use of the first order form of the LH equation. When applying the extended form of the LH equation, that includes the inhibitory effect of the phenol concentration, AC/TiO₂ synergy should be disregarded. In this physical mixture the activated carbon merely alleviates the inhibitory effect of the phenol concentration by decreasing its initial value.     

Synthesis of cobalt complexes and their evaluation as an adhesion promoter in a rubber–steel wire system

Cobalt adhesion promoters are considered as one of the most important ingredients in the tyre industry for adhesion between the rubber compound and the brass plated steel cord for manufacturing of steel-belted radial tyres. Most of the commercially available cobalt compounds are either higher fatty acid salts, or cobaltchelate complexes, e.g., cobalt octate, naphthenate, stearate and cobalt-boron complexes. Among all the available cobalt salts, cobalt-boron complexes are the most popular ones and bond well. Considering the availability, economics and performance of the different cobalt salts, an attempt has been made in this study to synthesise different cobalt-chelate complexes and to make a comparative evaluation. In some of the cases the cobalt complexes developed showed better adhesion properties as compared to the control compound.