Glyceryl Behenate and Its Suitability for Production of Aceclofenac Solid Lipid Nanoparticles

The aim of this study was to explore the use of glyceryl behenate (GB) as a candidate lipid for the production of solid lipid nanoparticles (SLN) using the anti-inflammatory drug, aceclofenac, as an example. SLN were produced using the Gasco microemulsion method with three different lipids, namely GB, glyceryl palmitostearate (GP) and cetyl alcohol (CA). The prepared SLN were subjected to determination of entrapment, zeta potential, particle size, in vitro dissolution, entrapment efficiency and biodistribution. Stable SLN of GB having size 245 ± 5 nm were prepared with a polydispersity index of 0.470. The size range was higher with other lipids i.e., CA and GP. It was found that as the drug lipid molar concentration was raised, particles with a smaller size were obtained irrespective of the nature of the lipid. The surfactant poloxamer 188 gave best results when used at a concentration of 2.5% w/v of dispersion. The study recommends GB as a suitable candidate for the production of SLN.     

Influence of Mixing System Design and Operating Parameters on Dissolution Process

Over recent years, the solid dissolution rate in liquid has been the subject of intense and profitable scientific developments. This work aims to study the influence of hydrodynamics on the dissolution rate of solid in water. The impact of the mixing system design was also investigated. The dissolution process can be followed through several parameters. First, experimental results were validated by kinetic models based on mass transfer coefficients such as the Hixson‐Crowell equation. The Weibull model and n‐order model were also tested. Then, the dissolution time t_d,x% was defined as the time needed to reach a given dissolution degree (X). Finally, the dimensionless dissolution number (N t_d) was defined and correlated with the Reynolds number. This correlation provides a more direct and simple link between operating conditions and process efficiency.     

Plasma Lipid Transfer Enzymes in Non-Diabetic Lean and Obese Men and Women

There are considerable differences in the plasma lipid profile between lean and obese individuals and between men and women. Little, however, is known regarding the effects of obesity and sex on the plasma concentration of enzymes involved in intravascular lipid remodeling. Therefore, we measured the immunoreactive protein mass of lipoprotein lipase (LPL), hepatic lipase (HL), cholesterol-ester transfer protein (CETP) and lecithin-cholesterol acyl transferase (LCAT) in fasting plasma samples from 40 lean and 40 obese non-diabetic men and premenopausal women. Women, compared with men, had ~5% lower plasma LCAT (p < 0.041), ~35% greater LPL (p = 0.001) and ~10% greater CETP (p = 0.085) concentrations. Obese, compared with lean individuals of both sexes, had ~30% greater plasma LCAT (p < 0.001), ~20% greater CETP (p < 0.001) and ~20% greater LPL (p = 0.071) concentrations. Plasma HL concentration was not different in lean men and women. Obesity was associated with increased (by ~50%) plasma HL concentration in men (p = 0.018) but not in women; consequently, plasma HL concentration was lower in obese women than obese men (p = 0.009). In addition, there were direct correlations between plasma lipid transfer enzyme concentrations and lipoprotein particle concentrations and sizes. There are considerable differences in basal plasma lipid transfer enzyme concentrations between lean and obese subjects and between men and women, which may be partly responsible for respective differences in the plasma lipid profile.     

Influence of Polymorphic Transformations on Gelation of Tripalmitin Solid Lipid Nanoparticle Suspensions

Solid lipid nanoparticle (SLN) suspensions, which consist of submicron-sized crystalline lipid particles dispersed within an aqueous medium, can be used to encapsulate, protect and deliver lipophilic functional components. Nevertheless, SLN suspensions are susceptible to particle aggregation and gelation during their preparation and storage, which potentially limits their industrial utilization. In this study, we examined the aggregation and gelation behavior of SLN suspensions composed of 10 wt% tripalmitin particles (r < 150 nm) stabilized by 1.5% Tween 20. The tripalmitin and aqueous surfactant solution were homogenized above the lipid melting temperature and cooled under controlled conditions to initiate SLN formation. The aggregation and gelation of SLN suspensions during storage was then examined by shear rheometry, differential scanning calorimetry (DSC), light scattering and microscopy. Rheology measurements indicated that gelation times decreased with increasing storage temperature, e.g., samples formed weak gels after 62, 23, and 10 min at 1, 5, and 10 °C, respectively. DSC revealed increasingly rapid α- to β-polymorphic transformations in SLN dispersions stored at 1, 5, and 10 °C, respectively. We propose that the observed aggregation and gelation of SLN suspensions are associated with a change in the shape of the nanoparticles from spherical (α-form) to non-spherical (β-form) when they undergo the polymorphic transition. When they change shape there is no longer sufficient surfactant present to completely cover the lipid phase, which promotes particle aggregation through hydrophobic attraction. Our results have important implications for the design and fabrication of stable SLN suspensions.     

Indirect electrochemical epoxidation of hexene in a liquid-liquid electrolyte

Preliminary experiments have been carried out on the mediated electrolytic synthesis of 1,2-epoxyhexane from 1-hexene. The electrochemical cell was an undivided parallel-plate reactor under galvanostatic operation at 25°C and 1 atm. The electro-active Br₂/Br^– couple acted as the mediating species. A dispersion of 1-hexene droplets in aqueous sodium bromide solution was generated by use of a static mixer. Current efficiency for organic species and chemical yield of epoxide were determined in order to investigate qualitatively the dependence of the overall electrolyzer performance upon flow rate, organic volume fraction, dispersed droplet size, and current density. The cell effluent was analyzed by gas chromatography. Epoxide current effciencies around 65% were obtained under operation conditions where the rate of bromine production by anodic reaction was sufficiently high so as to exceed the saturation concentration of hexene. Since the aqueous cell effluent was depleted of hexene, if was concluded that mass transfer from the organic phase into the aqueous phase was not able to replenish the electrolyte effectively.Nomenclature c _c product concentration in aqueous phase (M) - c _d product concentration in organic phase (M) - d diameter of dispersed organic droplets (m) - f organic volume fraction - F Faraday's constant, 96 487 C mol^–1 - I applied current (A) - n number of electrons in electrode reaction - Q total cell flow rate (ls^–1)     

Mass transfer from single bubbles in aqueous solutions of surfactants

The constant volume technique developed by Calderbank has been used to measure mass transfer rates for single carbon dioxide bubbles (0.52 <d_o < 1.02 cm) in distilled water and in aqueous solutions of n-hexanol, n-heptanol and n-octanol.The addition of surfactants to water reduced the mass transfer coefficient. A model to estimate the mass transfer coefficient in aqueous solutions of surfactants has been proposed, where the effect of surfactants has been expressed by introducing the retardation coefficient which indicates the degree of the retardation of surface flow at the gas—liquid interface.     

A new perspective on vegetable oil epoxidation modeling: Reaction and mass transfer in a liquid–liquid–solid system

A rigorous mathematical model was developed for a complex liquid–liquid–solid system in a batch reactor. The approach is general but well applicable for the indirect epoxidation of vegetable oils according to the concept of Nikolaj Prileschajew, implying in situ prepared percarboxylic acids as epoxidation agents. The model considers intra- and interfacial mass transfer effects coupled to reaction kinetics. The liquid phases were described with chemical approach (aqueous phase) and a reaction–diffusion approach (oil phase). The oil droplets were treated as rigid spheres, in which the overall reaction rate is influenced by chemical reactions and molecular diffusion. The model was tested with a generic example, where two reactions proceeded simultaneously in the aqueous and oil phases. The example (i.e., fatty acid epoxidation) illustrated the power of real multiphase model in epoxidation processes. The proposed modeling concept can be used for optimization purposes for applications, which comprise a complex water–oil–solid catalyst system.     

Collection Efficiencies in an Aerodyne Aerosol Mass Spectrometer as a Function of Particle Phase for Laboratory Generated Aerosols

The Aerodyne Aerosol Mass Spectrometer (AMS) is a useful tool to study ambient particles. To be quantitative, the mass or (number) of particles detected by the AMS relative to the mass (or number) of particles sampled by the AMS, or the AMS collection efficiency (CE), must be known. Here we investigated the effect of particulate phase on AMS CE for ammonium nitrate, ammonium sulfate, mixed ammonium nitrate/ammonium sulfate, and ammonium sulfate particles coated with an organic liquid. Dry, solid ammonium sulfate particles were sampled with a CE of 24 ± 3%. Liquid droplets and solid particles that were thickly coated with a liquid organic were collected with a CE of 100%. Mixed phase particles, solid particles thinly coated with liquid organic, and metastable aqueous ammonium sulfate droplets had intermediate CEs. The higher CEs for liquid particles compared with solid particles were attributed to wet or coated particles tending to stick upon impact with the AMS vaporizer, while a significant fraction of solid particles bounced prior to vaporization/detection. The consistency of single particle signals indicated that the phase (and hence CE) of mixed component particles did not affect the AMS sensitivity to a particular chemical species once volatilization occurred. Particle phase might explain a significant fraction of the variable AMS CEs reported in the literature. For example, ambient particles that were liquid (e.g., composition dominated by ammonium nitrate or acidic sulfate) have been reported to be sampled with 100% CE. In contrast, most ambient particle measurements report CEs of < 100% (typically~ 50%).     

Solid Lipid Nanoparticles: Effect of Carrier Oil and Emulsifier Type on Phase Behavior and Physical Stability

The impact of surfactant type and carrier oil type on the phase behavior and physical stability of emulsified tripalmitin was investigated. Solid lipid nanoparticles (SLNs) were prepared by homogenizing lipid and aqueous phases at a temperature (≈80 °C) above the melting point of tripalmitin, and then cooling the resulting oil-in-water emulsion to induce lipid droplet crystallization. When stored at 37 °C, tripalmitin particles had good long-term stability (d < 150 nm) when coated with Tween 20, but were prone to aggregation and gelation when coated with modified starch (MS). Conversely, when stored at ≤20 °C tripalmitin particles coated by MS were more stable to aggregation/gelation than those coated by Tween 20. Blending tripalmitin with low melting point lipids (either medium chain triglycerides or orange oil) prior to homogenization led to a considerable alteration in the SLN phase behavior and stability. DSC measurements indicated that the presence of the carrier oils reduced the crystallization temperature, melting temperature, and melting enthalpy of tripalmitin. In addition, the carrier oils improved the stability of SLNs to particle aggregation and gelation, although some particle coalescence still occurred. These results have important implications for formulating colloidal delivery systems for utilization within the food and other industries.     

Mass transfer effects in emulsion polymerization systems. I. Diffusional behavior of chain transfer agents in the emulsion polymerization of styrene

On the basis of the so-called two-films theory for mass transfer, a mathematical model for transfer of chain transfer agents from monomer droplets to polymer particles, where chain transfer agent molecules are consumed by the chain transfer reaction, is developed for an emulsion polymerization system. It is shown by the model that the concentration of chain transfer agent in the polymer particles during the polymerization is decreased to a value much less than that which would be attained if thermodynamic equilibrium for chain transfer agent were reached between the polymer particles and the monomer droplets, due mainly to the resistance to transfer of chain transfer agent molecules across the diffusion films at the interface between the monomer droplets and the water phase. The validity and utility of the model developed for predicting the diffusion and consumption rates for chain transfer agent are demonstrated experimentally using five normal aliphatic mercaptans from n-C₇ to n-C₁₂ as chain transfer agents in the seeded emulsion polymerization of styrene. © 1994 John Wiley & Sons, Inc.     

Interfacial Composition,Structural and Thermodynamic Parameters of Water/(Surfactant+<Emphasis Type="Italic">n</Emphasis>-Butanol)/<Emphasis Type="Italic">n</Emphasis>-Heptane Water-in-Oil Microemulsion Formation in Relation to the Surfactant Chain Length

Interfacial behavior, structural and thermodynamic parameters of a water/(surfactant+n-butanol)/n-heptane water-in-oil (w/o) microemulsion have been investigated using the dilution technique at different temperatures, and [water]/[surfactant] mole ratios. The cationic surfactants used were alkyltrimethyl ammonium bromides (CnTAB, n = 10, 14 and 16) while the nonionic surfactants were polyoxyethylene (20) sorbitan monoalkanoates (polysorbate), viz., palmitate (PS 40), stearate (PS 60) and oleate (PS 80). The distribution of cosurfactant between the oil–water interface and the bulk oil at the threshold level of stability, and the thermodynamics of transfer of the cosurfactant from the bulk oil to the interface were evaluated. Structural parameters such as the dimensions, population density and effective water pool radius of the dispersed water droplets in the oil phase and the interfacial population of the surfactant and cosurfactant have been evaluated in terms of the surfactant chain length.     

Acceptability and Digestibility of Emulsions in a Rat Model: Effects of Solid Fat Content and Lipid Type

The present study sought to determine if alterations in the chemical nature and form of fat in food would reduce digestibility while maintaining acceptability in rats. Oil-in-water emulsions (d < 1 μm) were prepared with either liquid palm oil, solid hydrogenated palm oil or solid docosane, all stabilized with sodium caseinate. The emulsions were incorporated into a fat-free rodent feed, and each offered over 5 days to separate cohorts of 12 male Sprague–Dawley rats housed in metabolic cages. The feed formulated with solid hydrogenated palm oil was significantly less acceptable than the feeds containing either liquid palm oil or docosane (feed intake 4.9, 26.6 and 32.1 g/animal/day respectively). The proportion of the fat retained (i.e. absorbed) was significantly less in the animals consuming the feed formulated with solid docosane than in the animals consuming either the liquid or solid palm oil (retention 8.7, 99.6, and 97.2%, respectively). The appearance of the feces from the rats fed docosane was different from the rats fed the triacylglycerol samples and thermal analysis revealed many of the solid alkane droplets had not coalesced during passage through the rat’s digestive system. These results indicate that indigestible fats can be packaged into food in a manner that does not compromise the acceptability of the product, and does not produce any apparent intestinal distress.     

Electrodissolution of aluminium thin film microband electrodes

This paper discusses the electrodissolution of aluminium thin films as microband electrodes (length = 5 × 10^–3 m) in terms of mass transfer determined by voltammetry and a.c.-impedance techniques as a function of bandwidth (20 to 2000 nm) in 0.1m NaOH solution. The anodic polarization curves of the aluminium microband electrodes show that current density is enhanced with decreasing bandwidth. The ac impedance response suggests that a steady-state diffusion layer appears the more markedly, the smaller the bandwidth. The anodic polarization curves are analysed on the basis of the combined Butler-Volmer high field approximation and the semi-cylindrical diffusion field approximation. As a result of the analysis, the electrodissolution proceeds by a mixed kinetic-mass transfer controlled reaction. The analysis also makes it possible to distinguish the semi-cylindrical diffusive mass transfer contribution to the electrodissolution from the kinetic contribution, i.e., mass transfer index linearly diminishes with decreasing bandwidth. The increased current density is attributable to the decreased mass transfer contribution, i.e., the more predominant semi-cylindrical diffusive mass transfer as compared to laminar diffusive mass transfer.Nomenclature k _a anodic kinetic constant - k _c cathodic kinetic constant - F Faraday constant - _s kinetic transfer coefficient for anodic reaction - _c kinetic transfer coefficient for cathodic reaction - c ^s surface concentration - V anodic polarization - D diffusion coefficient - d diffusion layer thickness - z number of electrons transferred - l length of microband electrode - w bandwidth of microband electrode - r radius of cylinder     

Amphiphilic maleic acid copolymers as corrosion inhibitors for aluminum pigment

Aluminum pigments react in aqueous alkaline media (e.g., water-borne paints) by the evolution of hydrogen. Maleic acid copolymers, which were synthesized by copolymerization of maleic acid anhydride, styrene, and acrylic esters (ethyl-, n-butyl-, n-hexyl-, n-dodecyl-, and n-octadecyl acrylate) inhibit this corrosion reaction. With the increasing chain length of the ester alcohol of the acrylate monomer, the evolved hydrogen volume decreases (i.e., the corrosion inhibiting effect increases). There seems to be a potential correlation between the number of carbon atoms of the ester alcohol of the copolymers and the evolved hydrogen volumes. With the addition of 0.5 wt % of the copolymers with n-butyl, n-hexyl, n-dodecyl-, and n-octadecyl acrylate no hydrogen evolution was observed at pH 8 within 21 days (complete corrosion inhibition). Conductivity measurements of aqueous copolymer solutions indicate that with an increasing chain length of the ester alcohol, the copolymers possibly associate by hydrophobic bonding. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2169–2174, 1998     

Mass transfer in a reciprocating plate extraction column — effects of mass transfer direction and plate material

The mass transfer performance of 5 cm diameter reciprocating plate column has been measured with the system n-butyric acid/kerosene (dispersed)/water (continuous). In most of the tests, the reciprocating plate stack was made of stainless steel which was preferentially wet by the continuous phase. During the mass transfer process the holdup and in some cases the Sauter mean droplet diameter were measured. The mass transfer effectiveness, expressed as the height of a transfer unit (H_ax) corrected for axial mixing, depended on the phase flow rates, the agitation rate and the direction of mass transfer. For continuous to dispersed phase mass transfer (c → d), the mass transfer was more effective, i.e. H_ax was lower than for d → c mass transfer under the same external conditions. Qualitative and quantitative observations indicated much larger drop sizes in the d → c case due to enhanced coalescence. Although mass transfer was less effective under d → c conditions, the column capacity was increased. The same effects were also observed when the plate stack was modified by inserting some Teflon plates which were partly wet by the dispersed phase.     

Electrocaloric behavior and piezoelectric effect in relaxor NaNbO3-based ceramics

We firstly reported the electrocaloric properties in relaxor (1−x−y)NaNbO₃–yBaTiO₃–xCaZrO₃ ceramics, and high electrocaloric effect (∆T ~0.451 K and∣∆T/∆E∣~0.282 Km/MV) can be realized in the ceramics (x = 0.04 and y = 0.10) under low temperature and low electric field. Relaxor behavior of NaNbO₃ ceramics can be found by doping both BaTiO₃ and CaZrO₃. In addition, optimized piezoelectric effects (d₃₃ ~235 pC/N and d₃₃* ~230 pm/V) can be observed in the ceramics (x = 0.04 and y = 0.10) due to the involved morphotropic phase boundary (MPB). Excellent piezoelectric effect (ie, d₃₃~330 pm/V at 41°C, and d₃₃*~332 pm/V at 60°C) can be found because of the characteristics of MPB. Good temperature reliability of piezoelectric effect can be shown because of both MPB and relaxor behavior. We believe that the ceramics with high electrocaloric effect and good piezoelectric effect can be considered as one of the most promising lead-free materials for piezoelectric devices.     

Influence of the Lime Slurry Droplet Spectrum on the Efficiency of Semi‐Dry Flue Gas Desulfurization

A numerical model based on computational fluid dynamics is presented to predict the efficiency of a semi‐dry flue gas desulfurization process. The Euler‐Lagrange particle tracking method is used to predict both evaporation and mass transfer between the flue gas and the lime slurry droplets. The overall desulfurization process is split into two periods, i.e. the constant‐rate and the falling‐rate period, during which the fundamental chemical reaction between sulfur dioxide and calcium hydroxide is modeled. The absorption efficiency is calculated for different spray characteristics, taking into account different size spectra of the lime slurry droplets characterized by different standard deviations for a constant mass mean diameter d₅₀ of 25 μm. The results are compared with published experiments and show excellent agreement as well as a significant role of the spray characteristics in the FGD efficiency.     

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.     

Studies on processing of layered oxide-bonded porous sic ceramic filter materials

Oxide-bonded porous SiC ceramic filter supports were prepared using SiC powder (d₅₀ = 212 µm), Al₂O₃, and clay as bond forming additives and graphite as pore former following reaction bonding of powder compacts at 1400°C in air. Reaction bonding characteristics, phase composition, porosity, pore size, mechanical strength, and microstructure of porous SiC ceramic supports were investigated. Mullite bond phase formation kinetics was studied following the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model using non-isothermal differential thermal analysis (DTA) data. Compared to porous SiC ceramic filter supports having no needle-like mullite bond phase, materials processed by the mullite bonding technique exhibited higher average strength (22.1%) and elastic modulus (5.4%) at a similar porosity level of ~38%, with upper and lower bounds of their strength, modulus, and porosity being 39.1 MPa, 40.2 GPa, and 36.3% and 34.2 MPa, 31.3 GPa, and 33.0%, respectively. Spray coating method was applied for preparation of oxidation-bonded SiC filtration layer having thickness of ~150 µm and pore size of ~5–20 µm over the porous SiC support compacts using aqueous slurry made of fine SiC powder (d₅₀ = 15 µm) followed by sintering. The layered ceramics thus prepared are potential materials for gas filter applications.     

Direct Crystallization of Sulfate‐Type Layered Hydroxide,Derivation of (Gd,Tb)2O3 Green Phosphor,and Photoluminescence

The sulfate‐type layered hydroxides of (Gd_1?xTb_x)₂(OH)₅(SO₄)_0.5·nH₂O (x = 0.06–0.10) have been directly crystallized via hydrothermal reaction at 120°C and pH ~10.0, without the need of conventional anion exchange. The primary crystallites were found to be thin platelets having lateral sizes of ~450–1000 nm and thicknesses of ~65–85 nm. Combined analysis by DTA/TG, FTIR, and XRD revealed that the layered compounds convert into cubic (Gd_1?xTb_x)₂O₃ solid‐solutions through dehydration, dehydroxylation, and desulfuration up to ~1200°C and via a (Gd_1?xTb_x)₂O_2.5(SO₄)_0.5 intermediate phase. Optical spectroscopies found that the layered compounds and the derived oxides have their strongest 4f⁸→4f⁷5d¹ transition excitations at ~248 and 305 nm and optimal Tb³⁺ contents of 9 at.% (x = 0.09) and 8 at.%, respectively. Both the types of materials exhibit the strongest emission at ~544 nm (the ⁵D₄→⁷F₅ transition of Tb³⁺), but the oxide has an emission intensity ~3 times that of the hydroxide. Fluorescence lifetime of the 544 nm green emission was found to decrease from 2.45 to 2.15 ms along with increasing Tb³⁺ content for the oxide, and smaller values of ~1.55 ms were derived for the layered hydroxides.