Regiospecific Analysis of Mono- and Diglycerides in Glycerolysis Products by GC × GC-TOF-MS

Comprehensive bidimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOF-MS) was used for the characterization of regiospecific mono- and diglycerides (MG-DG) content in the glycerolysis products derived from five different lipids included lard (LA), sun flower seed oil (SF), corn oil (CO), butter (BU), and palm oil (PA). The combination of fast and high temperature non-orthogonal column set namely DB17ht (6 m × 0.10 mm × 0.10 μm) as the primary column and SLB-5 ms (60 cm × 0.10 mm × 0.10 μm) as the secondary column was applied in this work. System configuration involved high oven ramp temperature to obtain precise mass spectral identification and highest effluent’s resolution. 3-Monopalmitoyl-sn-glycerol (MG 3-C16) was the highest concentration in LA, BU and PA while monostearoyl-sn-glycerol (MG C18) in CO and 1,3-dilinoleol-rac-glycerol (DG C18:2c) in SF. Principal component analysis accounted 82% of variance using combination of PC1 and PC2. The presence of monostearoyl-sn-glycerol (MG C18), 3-Monopalmitoyl-sn-glycerol (MG 3-C16), 1,3-dilinoleol-rac-glycerol (DG C18:2c), 1,3-dipalmitoyl-glycerol (DG 1,3-C16), and 1,3-dielaidin (DG C18:1t) caused differentiation of the samples tested.     

Specific Heat of Olive Oil to 356 MPa

We measured the velocity of sound in olive oil under pressure with the Brillouin light scattering technique. Using the values for the density and the thermal conductivity that have only recently been reported, we calculated the adiabatic compressibility and the isobaric specific heat up to 356 MPa and the thermal diffusivity up to 200 MPa. The specific heat displays a maximum at 124 MPa, suggesting a possible phase transition around this pressure. Apart from the theoretical and practical importance of these results for the food industry and beyond, this work shows that Brillouin light scattering and macroscopic methods are complementary and can be employed to measure thermophysical parameters of food liquids under pressure.     

Laboratory measurements of light scattering properties of kaolinite dust at 532 nm

Light scattering by kaolinite dust samples at 532 nm is studied using a newly developed laboratory apparatus. During the experiments, dust samples are suspended in water, aerosolized by a nebulizer, and then injected into the scattering zone, with or without going through a diffusion drier, to generate either dried dust particles or water droplets with dust inclusions. The light source is a dual wavelength (532 and 1064 nm) diode-pumped solid state laser. Light scattered by an ensemble of particles is collected by a charge-coupled device (CCD) camera, which is mounted on the rotating arm of a stepper motor. The stepper motor rotates the CCD to cover the scattering angle range from 3° to 177°. Polarized scattering light is measured for the horizontally and vertically polarized incident light. The apparatus is calibrated, using pure water droplets as the scattering media. The response function with respect to the scattering angle is obtained by comparing the measurements with Lorenz–Mie calculations and then used in the later data analysis. Measurements show that the backward scattering features of the water droplets are smoothened due to their dust inclusions. Numerical simulations and measurements are extensively compared and discussed. It is found that the Lorenz–Mie theory is inadequate to reproduce the scattering phase functions of either dust particles or water droplets with dust inclusions. A nonspherical aggregate model is applied to simulate the scattering phase functions. The simulation is able to reproduce the overall scattering features; however, substantial discrepancies still exist due to uncertainties in particle shape and refractive index.

Copyright © 2018 American Association for Aerosol Research     

Investigation of vehicle exhaust sub-23 nm particle emissions

A solid particle number limit was applied to the European legislation for diesel vehicles in 2011. Extension to gasoline direct injection vehicles raised concerns because many studies found particles below the lower size limit of the method (23 nm). Here we investigated experimentally the feasibility of lowering this size. A nano condensation nucleus counter system (nCNC) (d_50% = 1.3 nm) was used in parallel with condensation particle counters (CPCs) (d_50% = 3 nm, 10 nm and 23 nm) at various sampling systems based on ejector or rotating disk diluters and having thermal pre-treatment systems consisting of evaporation tubes or catalytic strippers. An engine exhaust particle sizer (EEPS) measured the particle size distributions. Depending on the losses and thermal pre-treatment of the sampling system, differences of up to 150% could be seen on the final detected particle concentrations when including the particles smaller than 23 nm in diameter. A volatile artefact as particles with diameters below 10 nm was at times observed during the cold start measurements of a 2-stroke moped. The diesel vehicles equipped with the Diesel Particulate Filter (DPF) had a low solid sub-23 nm particles fraction (<20%), the gasoline with direct injection vehicles had higher (35–50%), the gasoline vehicles with port fuel injection and the two mopeds (two and four-stroke) had the majority of particles below 23 nm. The size distributions peaked at 60–80 nm for the DPF equipped vehicles, at 40–90 nm for the gasoline vehicles with a separate nucleation mode peak at approximately 10 nm sometimes. Mopeds peaked at sizes below 50 nm when their aerosol was thermally pre-treated.

© 2017 American Association for Aerosol Research     

Piperazine derivatives as inhibitors of the corrosion of mild steel in 3.9 M HCl

The inhibitory action of two piperazine derivatives, 1-benzyl piperazine (P1) and bis(1-benzylpiperazine) thiuram disulfide (P2) on the corrosion of mild steel in 3.9 M HCl at different concentrations has been investigated in the temperature domain 298–333 K. Both weight loss measurements and potentiodynamic polarization methods showed that P2 was the best inhibitor and that its inhibition efficiency increased with concentration to a value >92% at 10⁻³ M. Potentiodynamic polarization studies clearly revealed that P2 acts as cathodic-type inhibitor. The activation energy for the corrosion rates was evaluated in the temperature range 298–333 K. Adsorption of P2 on the mild steel surface in 3.9 M HCl followed a Langmuir isotherm model. A physical adsorption phenomenon is proposed.     

Comparison of textural information from argon(87 K) and nitrogen(77 K) physisorption

Argon(87 K) and nitrogen(77 K) adsorption of three types of porous samples (microporous, microporous-mesoporous and mesoporous) was evaluated. The shapes of isotherms, specific surface areas, mesopore-, micropore- and net pore volumes, pore-size distributions (PSD) and positions of micropore and mesopore PSD’s maxima were compared to ascertain the credibility of individual adsorbates for the texture information estimation. The shapes of adsorption isotherms for Ar and N₂ of all samples are similar and the adsorbed amounts at relative pressure x = 0.975 differ slightly. For mesoporous samples some differences are observed between specific mesopore surface areas derived from nitrogen and argon isotherms. Radii of pore size maxima from Ar(87 K) PSD’s are on average systematically lower than from N₂(77 K) for all samples. The Saito-Foley approach for ZSM-5 samples gives consistently lower mean pore radius from N₂(77 K) adsorbate than from Ar(87 K). This difference probably arises from the multiplication factor, Ω, in the Saito-Foley equation which includes physical properties (magnetic susceptibility, polarizability etc. at 77 and 87 K) and is not easy to obtain with sufficient precision. The use of both adsorbates Ar(87 K) and N₂(77 K) possesses some advantages as well some disadvantages and the comparison of textural properties of individual samples must be evaluated with respect to adsorbate.     

A study of compressive strength between zirconia framework and veneering ceramic as a function of thermal expansion coefficient using Shell–Nielsen test method

This study investigated the adhesion between zirconia framework and four veneering ceramic (VC) materials with varying coefficients of thermal expansions (CTE). Zirconia rods (N?=?40) (ICE Zirkon) (diameter: 4 mm, height: 20 mm) were milled and sintered. After firing, the zirconia rods were air-abraded and cleaned. They were randomly assigned to receive four VCs (n?=?10/group), namely (a) Vita VM9 (VZ; 9–9.2?×?10^?6? K^?1), (b) Cerabien ZR (CZ; 9.1?×?10^?6 K^?1), (c) Matchmaker ZR (MM; 9.4?×?10^?6?K^?1), and (d) Ice Zirconia Ceramic (IZ; 9.6?×?10^?6?K^?1). The VCs were then fired onto zirconia rods (height: 2 mm, thickness: 2 mm) circumferentially and were thermocycled for 6000 times (5/55 °C, dwell time: 30?s). Specimens were loaded from the top of the zirconia rods (0.5 mm/min) in a universal testing machine until debonding. Shell–Nielsen bond strength values were calculated (MPa). Failure types were evaluated under SEM. The data were statistically analyzed (one-way ANOVA, Tukey’s; α?=?0.05). Weibull distribution values including the Weibull modulus (m) (0.05) was calculated. The highest mean bond strength (MPa) was obtained for CZ (42.08?±?4.08), followed by VZ (41.77?±?4.92), MM (40.7?±?3.64), and IZ (40.05?±?5.78). While mean bond strength for VZ, MM, and IZ were not significantly different (p?>?0.05), CZ was significantly higher than that of IZ (p?<?0.05). The lowest shape value was for VZ (m?=?16.94) and the highest for MM (m?=?20.16). Mainly, adhesive failures followed by mixed failures were observed. VCs with a greater mismatch of CTE with the zirconia framework exhibited similar Shell–Nielsen bond strength to those with fewer mismatches. CTE mismatch did not affect the results of CZ (9.1?×?10^?6 K^?1) and IZ (9.6?×?10^?6 K^?1).     

Mobility Analysis of 2 nm to 11 nm Aerosol Particles with an Aspirating Drift Tube Ion Mobility Spectrometer

We describe the performance of a drift tube-ion mobility spectrometry (DT-IMS) instrument for the measurement of aerosol particles. In DT-IMS, the electrical mobility of a measured particle is inferred directly from the time required for the particle to traverse a drift region, with motion driven by an electrostatic field. Electrical mobility distributions are hence linked to arrival time distributions (ATDs) for particles reaching a detector downstream of the drift region. The developed instrument addresses two obstacles that have limited DT-IMS use for aerosol measurement previously: (1) conventional drift tubes cannot efficiently sample charged particles at ground potential and (2) the sensitivities of commonly used Faraday plate detectors are too low for most aerosols. Obstacle (1) is circumvented by creating a “sample volume” of aerosol for measurement, defined by the streamlines of fluid flow. Obstacle (2) is bypassed by interfacing the end of the drift region with a condensation particle counter. The DT-IMS prototype shows high linearity for arrival time versus inverse electrical mobility (R ² > 0.99) over the size range tested (2.2–11.1 nm), and measurements compare well with both analytical and numerical models of device performance. A dimensionless calibration curve linking drift time to inverse electrical mobility is developed. In less than 5 s, it is possible to measure 11.1 nm particles, while 2.2 nm particles are analyzable on a subsecond scale. The transmission efficiency is found to be dependent upon electrostatic deposition for short drift times and upon advective losses for long drift times.

Copyright 2014 American Association for Aerosol Research     

Preparation and characterisation of a lamellar hydroxyapatite/polylactic acid composite

ABSTRACT

In this study, laminated hydroxyapatite/polylactic acid (HAp/PLA) composites were synthesized through solution intercalation method. The phase composition and micro morphology of the prepared HAp/PLA composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The obtained data revealed that intercalated and exfoliated structures were obtained by different HAp contents. Computed tomography result showed that the HAp lamellae distributed well in the PLA matrix and no air-bubble existed in the interface of HAp and PLA. Differential scanning calorimetry and mechanical performance test revealed that the thermal stability and tensile strength were all improved by intercalating of HAp lamellae. Moreover, the degradation experiment confirmed that the 10HAp/PLA showed the slowest degradation rate attributing to the molecular barrier effect of HAp lamellae. Besides that, MTT assay suggested that HAp/PLA composite exhibit excellent biocompatibility, indicating that it may become a promising material for biomedical applications.     

Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Radiative properties of numerically generated fractal soot aggregates of different fractal dimensions were studied using the numerically accurate generalized Mie-solution method (GMM) and the Rayleigh-Debye-Gans (RDG) approximate theory. Fractal aggregates of identical prefactor but different fractal dimensions, namely, 1.4, 1.78, and 2.1, were generated numerically using a tunable algorithm of cluster–cluster aggregation for aggregates containing up to 800 primary particles. Radiative properties of these aggregates were calculated at a wavelength of 532 nm assuming a soot refractive index of 1.6 + 0.6i. Four commonly used structure factors in the RDG approximation were used to investigate the effect of structure factor on the differential and total scattering cross-sections and the asymmetry factor. The differential and total scattering properties calculated using the RDG approximation become increasingly sensitive to the structure factor with increasing the fractal dimension. Primary particle interactions are the fundamental mechanism for the aggregate absorption enhancement for small aggregates and the shielding effect for larger aggregates. The extent of these two competing factors is dependent on the fractal dimension and aggregate size. RDG reasonably predicts the effect of fractal dimension on the scattering properties, but fails to account for the effect of aggregation or fractal morphology on the absorption property of fractal soot aggregates, though the error is in general less than 15%.

Copyright 2013 American Association for Aerosol Research     

Synthesis and Surface Properties of Dicephalic Surfactants with a 1,3-Dioxane Ring

A new group of surface active dicephalic derivatives of 1,3-dioxane, i.e., 2-alkyl-5,5-bis{[3-(N,N-dimethylamino)propyl]amido}-1,3-dioxane-di-N-oxides, were synthesized with high yields by the reaction of an appropriate 2-alkyl-5,5-bis-(carboxyethyl)-1,3-dioxane with an excess of N,N-dimethyl-1,3-propanediamine followed by oxidation with an aqueous solution of hydrogen peroxide. Structures and purity of all intermediates and final di-N-oxides were confirmed by means of ¹H-NMR and ESI-MS spectroscopy. Synthesized compounds showed high surface activity with low values of critical micelle concentration and high effectiveness of surface tension reduction (γ _CMC). However, only derivative with the longest 2-alkyl substituent showed good foaming and moderate emulsifying properties.

Facile preparation and good performance of nano-Ag/metallocene polyethylene antibacterial coatings

Metallocene polyethylene/nano-silver coatings were prepared by a facile air-spray method on polymer films. Different from the prevailing strategy to endow polyethylene with antibacterial performance, we used metallocene polyethylene sol and nano-silver as a precursor to deposit coatings on polymers at a relatively low operating temperature. Antibacterial coatings with excellent mechanical properties, water resistance, and low silver release were achieved. The composite coatings were examined in terms of surface characteristics, mechanical properties, and antibacterial activity against two representative bacterial strains including Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The composite coatings exhibited favorable microstructure, good mechanical properties, and suitable crystallinity. The antimicrobial tests indicated that the fabricated composite coatings showed promising antibacterial activity against E. coli and S. aureus. Furthermore, Ag ions released by the composite coating after 30 days were under 1.2 ppb. These results indicated a promising prospect of the composite coating for wide antibacterial applications.     

The Characteristics and Reactivity of Acid-Labile Aryl Ether Units in Wood Lignin

Wood lignin contains significant amounts of acid-labile aryl ether units, which play a significant role in lignin modification or delignification processes. We have evaluated the rate and reaction kinetics on the acid-catalyzed cleavages of aryl ether structures for wood lignin in situ based on the formation of phenolic hydroxyl groups. The content of acid-labile aryl ether units was quite uniform for a variety of softwood wood lignins (～4% per C₉ unit) and it varied appreciably among hardwood species, ranging from 4% for aspen to 9% for beech wood lignin. These variations, however, appear to be related to the content of syringyl units in wood lignin. The reactivity of these reactive aryl ether structures was noticeably higher for the spruce than for the aspen wood lignin. This difference in reactivity, based on the behavior of lignin model compound reactions, can be attributed to the influence of syringyl moieties in aspen wood lignin. It appears that most of the acid-labile aryl ether units in hardwood were associated with the syringy moiety being present as a benzyl unit, which is much less reactive than the corresponding guaiacyl moiety.     

In Situ Preparation of Functional Heterogeneous Organotin Catalyst Tethered on SBA-15

A stable heterogeneous organotin catalyst has been prepared by in situ tethering organotin compounds on SBA-15. This was verified by XRD, TEM, N₂ adsorption/desorption at −196 °C, FTIR and diffuse reflectance UV–vis spectral techniques. This material was much more active than the sample prepared by the grafting method for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO₂ despite that its catalytic activity was dependent on the organotin amount. This could be attributed to the formation of organotin clusters with different structures and the larger surface area. After immobilization on the SBA-15 mesoporous material, the six-coordinated organotin clusters showed higher activity, compared to the tetrahedral Sn species. With increasing reaction temperature and CO₂ pressure, the catalytic activity considerably increased.     

Engineering Data of Diameter Change during Air Drying of Milk Droplets with 40 wt% Initial Solids Content

Spray drying of liquid food droplets is one of the primary means of manufacturing food powders today. Modeling this process requires single-droplet drying modeling, and droplet size change during drying is one part of such modeling. Some experimental data of milk droplet diameter change at 20 and 30 wt% are reported in literature.^{[ 1} Lin , S.X.Q. ; Chen , X.D. Changes in milk droplet diameter during drying under constant drying conditions investigated using the glass-filament method . Trans IChemE, Part C 2004 , 82 ( C3 ), 213 – 218 . [Google Scholar] ^] Data are not available at higher solid contents, which are of interest to the industry. We now report the experimental results of the effects of drying conditions on milk droplet size change (using projected area diameter as the parameter) using the glass filament technique, complimented by video imaging analysis software. Under the constant drying air conditions for solids content of 40 wt%, and for both skim and whole milk, the droplet diameter changes were correlated using the previous model of Lin and Chen.^{[ 1} Lin , S.X.Q. ; Chen , X.D. Changes in milk droplet diameter during drying under constant drying conditions investigated using the glass-filament method . Trans IChemE, Part C 2004 , 82 ( C3 ), 213 – 218 . [Google Scholar] ^] With previous data together, the shrinkage coefficients were correlated against solids content.     

Absence of any effect of the electric charging state of particles below 10 nm on their penetration through a metal grid

The effect of image force on the penetration of nanometer particles through metal grids remains a controversial issue. Experimental evidence of the existence and of the absence of such effect have both been reported in the past. A careful experimental work to measure penetration of particles in the mobility equivalent diameter range between 3.4 and 10 nm has been carried out. The possible particle size change between the aerosol generator and the filter has been considered, as well as the possible effect of particle number concentration on the filtration efficiency. The geometric dimensions of the filter allowed attainment of the fully developed parabolic flow velocity profile upstream the grid. Measurements were done at two values of the fiber Reynolds number, 0.09 and 0.12, much smaller than 1, as demanded by the currently accepted filtration theory. Penetration of charged particles, measured in three alternative ways, has been compared with penetration of uncharged and neutral particles (the latter consisting of a mixture of positive, negative, and uncharged particles). Two main conclusions have been reached: (1) the charging state of the particles does not affect their penetration through the metal grid and (2) the experimentally measured penetrations are fairly well predicted by the fan filter model of Cheng and Yeh.

Copyright © 2018 American Association for Aerosol Research     

Comparison of In vitro Nanoparticles Uptake in Various Cell Lines and In vivo Pulmonary Cellular Transport in Intratracheally Dosed Rat Model

In present study, the potential drug delivery of nanoformulations was validated via the comparison of cellular uptake of nanoparticles in various cell lines and in vivo pulmonary cellular uptake in intratracheally (IT) dosed rat model. Nanoparticles were prepared by a bench scale wet milling device and incubated with a series of cell lines, including Caco-2, RAW, MDCK and MDCK transfected MDR1 cells. IT dosed rats were examined for the pulmonary cellular uptake of nanoparticles. The processes of nanoparticle preparation did not alter the crystalline state of the material. The uptake of nanoparticles was observed most extensively in RAW cells and the least in Caco-2 cells. Efflux transporter P-gp did not prevent cell from nanoparticles uptake. The cellular uptake of nanoparticles was also confirmed in bronchoalveolar lavage (BAL) fluid cells and in bronchiolar epithelial cells, type II alveolar epithelial cells in the intratracheally administrated rats. The nanoparticles uptake in MDCK, RAW cells and in vivo lung epithelial cells indicated the potential applications of nanoformulation for poorly soluble compounds. The observed limited direct uptake of nanoparticles in Caco-2 cells suggests that the improvement in oral bioavailability by particle size reduction is via increased dissolution rate rather than direct uptake.     

Extension of the Smoluchowski Theory to Transitions from Dilute to Dense Regime of Brownian Coagulation: Triple Collisions

In order to study the transition from dilute (controlled by binary collisions) to dense (controlled by multiple collisions) regime of coagulation of colloidal or aerosol suspensions, the Smoluchowski equation is generalized by consideration of triple collisions in the kinetic approach, recently proposed by the authors for coagulation of comparable size particles. A good agreement of the new model predictions with more general results of the direct numerical simulations by Langevin dynamics (from the literature) is attained in a relatively wide range of the fractional volume, corresponding to the transition from dilute to dense regime of coagulation dynamics, in which multiple collisions among more than three particles can be neglected.

Copyright 2014 American Association for Aerosol Research     

Penetration of Sub-50 nm Nanoparticles Through Electret HVAC Filters Used in Residence

Pleated electret HVAC filters are often used in residence to mitigate the particles that originate both indoors and outdoors. These filters are usually tested with particles larger than 300 nm. However, residential particles can contain a significant amount of nanoparticles with size below 50 nm due to cooking, smoking, cleaning, wood burning, and outdoor infiltration. In order to characterize the nanoparticle removal by electret HVAC filters, penetrations of 3–50 nm silver nanoparticles through five different flat sheet electret media used in commercial residential HVAC filters were tested with face velocities of 0.05, 0.5, and 1.0 m s^–1. Experimental results showed that all media had significantly high penetrations with 0.35–0.8 at the most penetrating particle sizes (MPPSs) for all three velocities, which were in the sizes of 10–30 nm. A model based on single fiber theory for particle penetration predictions was used and compared with the experimental data. Results showed that the model predicted the nanoparticle penetrations very well for all media and all face velocities tested. According to the model, for enhancing the nanoparticle efficiency of the current commercial HVAC filters, the fiber diameter should be reduced or the number of pleats should be increased. However, by doing these, pressure drop and cost may be largely increased. On the other hand, this study found the existing commercial mechanical HVAC filters were much capable for sub–50 nm nanoparticle removal when their minimum efficiency reporting values (MERVs) were larger than 13 and it is concluded mechanical HVAC filters can do a better job than electret ones. However, the quality factor analysis showed electret filters could be regarded as the best filter media for removing particles smaller than 300 nm.

Copyright 2015 American Association for Aerosol Research     

The Ultrasonic Investigation of Phase Transition in Olive Oil up to 0.7 GPa

This paper presents measurements of sound velocity and attenuation in olive oil, with known chemical composition, as a function of pressure, within the range of pressure up to 0.7 GPa. Dependencies of sound velocity, relative ultrasonic wave attenuation, volume, and adiabatic compressibility on pressure show discontinuities. This proves the existence of the first order phase transition in olive oil (liquid to solid-like phase transition). Rapid and large changes in relative attenuation testify to the existence of a phase transition in olive oil. Moreover, the kinetics of phase transition was also investigated. Measurement of acoustic wave velocity and relative attenuation in olive oil during the phase transition and in the high-pressure phase is a novelty. The results obtained can be useful in the development of new methods in food (edible oils) control, processing, and preservation.