Lecithins in oil-continuous emulsions. Fat crystal wetting and interfacial tension

Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals. Several analytical methods have been proposed to characterize lecithins, but they are often inadequate to determine the industrial functionality. The purpose of this study was to find a relationship between the interfacial properties of lecithins (adsorption to oil/water and fat crystal/oil/water interfaces), phospholipid composition and functionality. Results show that all lecithins adsorb to fat crystals at the triglyceride oil/water interface, making their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins, such as soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ∼180°). Less polar lecithins give slow adsorption (some hours) and less polar crystals (contact angle ≤90°). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals. We found a relation between high-fat crystal polarity and poor lecithin functionality in margarine (margarines spatters during frying), and also between high-fat crystal polarity and a high polar to nonpolar phospholipids [Σ(PI + PA + LPC)/ΣPE; PI, phosphatidylinositol; PA, phosphatidic acid; LPC, lysoPC, PE, phosphatidylethanolamine] ratio in lecithin. The correlations might bevia aggregation properties of lecithin in the oil. We found also that monoolein shifted the adsorption kinetics of lecithin (soybean PC) to fat crystals and the hydrophilicity of adsorbed layers probably due to formation of mixed aggregates between monoolein and soybean PC.     

Antioxidant intake,plasma antioxidants and oxidative stress in a randomized,controlled, parallel,Mediterranean dietary intervention study on patients with rheumatoid arthritis

Background  

Previously we have reported that patients with rheumatoid arthritis (RA) obtained a significant reduction in disease activity by adopting a Mediterranean-type diet. The present study was carried out to investigate the antioxidant intake, the plasma levels of antioxidants and a marker of oxidative stress (malondialdehyde) during the study presented earlier.     

The influence of CO2, AlCl3 · 6H2O, MgCl2 · 6H2O, Na2SO4 and NaCl on the atmospheric corrosion of aluminum

The influence of salt deposits on the atmospheric corrosion of high purity Al (99.999%) was studied in the laboratory. Four chloride and sulfate-containing salts, NaCl, Na₂SO₄, AlCl₃ · 6H₂O and MgCl₂ · 6H₂O were investigated. The samples were exposed to purified humid air with careful control of the relative humidity (95%), temperature (22.0 °C), and air flow. The concentration of CO₂ was 350 ppm or <1 ppm and the exposure time was four weeks. Under the experimental conditions all four salts formed aqueous solutions on the metal surface. Mass gain and metal loss results are reported. The corroded surfaces were studied by ESEM, OM, AES and FEG/SEM equipped with EDX. The corrosion products were analyzed by gravimetry, IC and grazing incidence XRD. In the absence of CO₂, the corrosivity of the chloride salts studied increases in the order MgCl₂ · 6H₂O < AlCl₃ · 6H₂O < NaCl. Sodium chloride is very corrosive in this environment because the sodium ion supports the development of high pH in the cathodic areas, resulting in alkaline dissolution of the alumina passive film and rapid general corrosion. The low corrosivity of MgCl₂ · 6H₂O is explained by the inability of Mg²⁺ to support high pH values in the cathodic areas. In the presence of carbon dioxide, the corrosion induced by the salts studied exhibit similar rates. Carbon dioxide strongly inhibits aluminum corrosion in the presence of AlCl₃ · 6H₂O and especially, NaCl, while it is slightly corrosive in the presence of MgCl₂ · 6H₂O. The corrosion effects of CO₂ are explained in terms of its acidic properties and by the precipitation of carbonates. In the absence of CO₂, Na₂SO₄ is less corrosive than NaCl. This is explained by the lower solubility of aluminum hydroxy sulfates in comparison to the chlorides. The average corrosion rate in the presence of CO₂ is the same for both salts. The main difference is that sulfate is less efficient than chloride in causing pitting of aluminum in neutral or acidic media.     

The Effect of H<Subscript>2</Subscript> and H<Subscript>2</Subscript>O on the Oxidation of 304L-Stainless Steel at 600 °C: General Behaviour (Part I)

The effect of p(H₂O) and p(H₂) on the oxidation of 304L stainless steel at 600 °C has been investigated in the present study. The samples were analysed by means of X-ray diffraction, Auger spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy. The results showed that at fixed p(H₂), the corrosion rate increased considerably with increasing p(H₂O). At fixed p(H₂O), the corrosion rate decreased slightly with increasing p(H₂). Duplex oxide scales formed during the exposure in all environments. The outer and inner layer consisted of Fe₃O₄ and (Fe, Cr)₃O₄, respectively. The latter was mainly in the form of internal oxidation. The Cr-rich oxide formation was observed at the initial oxidation process before oxide breakdown. The Auger analysis also suggested the presence of Cr-rich oxide layer just after the breakaway oxidation. The results indicated that the rate-determining step in the corrosion attack is surface controlled or diffusion controlled through an oxide layer with fixed thickness over time.     

Evidence for Chromium Evaporation Influencing the Oxidation of 304L: The Effect of Temperature and Flow Rate

The influence of temperature and flow rate on the oxidation of 304L steel in O₂/H₂O mixtures was investigated. Polished samples were isothermally exposed to dry O₂ and O₂+40% H₂O at 500–800°C at 0.02–13 cm/sec flow velocity, for 168 hr. The samples were analyzed by gravimetry, XRD, ESEM/EDX, and AES depth profiling. The oxidation of 304L in water vapor/oxygen mixtures at 500–800°C is strongly influenced by chromium evaporation. The loss of chromium tends to convert the protective chromia-rich oxide initially formed into a poorly protective, iron-rich oxide. The rate of oxidation depends on flow rate; high flow rates result in an early breakdown of the protective oxide. The most rapid breakdown of the protective oxide occurs at the highest temperature (800°C) and the highest gas flow (4000 ml/min=13 cm/sec). The oxide formed close to grain boundaries in the metal is more protective, while other parts, grain surfaces suffer breakaway corrosion. The protective oxide consists of a Cr-rich 50–200-nm thick M₂O₃ film, while the parts experiencing breakaway corrosion form a 10–30-m thick Fe-rich M₂O₃/M₃O₄ scale. The results show that chromium evaporation is a key process affecting the oxidation resistance of chromia formers and marginal chromia formers in O₂/H₂O mixtures.     

Machinability of ultrafine-grained copper using tungsten carbide and polycrystalline diamond tools

Equal channel angular extrusion (ECAE) is an effective process to produce bulk ultrafine-grained (UFG) materials from regular coarse-grained materials. Such ECAE-processed materials typically excel in strength, wear resistance, ductility, and high strain-rate superplasticity, with promising applications in lightweight transportation and medical industries. Precision machining work is generally indispensable for further applications after bulk materials are produced by ECAE. To effectively and efficiently machine such ECAE-processed materials for further broad applications, machining issues such as machinability and tool material selection should be considered. This study was undertaken to investigate the machinability of ECAE-processed pure copper using both tungsten carbide (WC) and polycrystalline diamond (PCD) cutting tools in order to facilitate broad applications of ECAE-processed UFG coppers. It is found that despite its higher cost, PCD is favored to machine UFG copper based on this study since it has better wear resistance, gives lower cutting forces, yields a better workpiece surface finish, and results in no smearing on the workpiece. In machining UFG copper, depth of cut notching was observed as the wear pattern and abrasion as the wear mechanism for the WC tool, while flank wear was observed as the wear pattern and diffusion as the wear mechanism for the PCD tool.     

The double electrostatic ion ring experiment: a unique cryogenic electrostatic storage ring for merged ion-beams studies

We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate "rings" and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.     

Progression of fretting fatigue damage in Ti–6Al–4V

An investigation was conducted to explore the nature of fretting fatigue damage in the stages prior to crack formation. In the unique experimental apparatus employed in this study, where total slip never occurs, several locations on each test specimen exist where cracks can develop due to local contact conditions. Under the test conditions used, not all of the sites had cracks upon test completion. This study evaluated the condition of non-cracked sites on several fretted specimens in an effort to identify differences between these and sites where small cracks were observed.A single test condition of 620 MPa average applied static clamping stress and 250 MPa applied axial fatigue stress for R=0.5 was selected, which corresponds to a fretting fatigue life of 10⁷ cycles based on prior work. For specimens tested to 10⁶ cycles, or 10% of life, several destructive and non-destructive characterization methods were chosen: scanning electron microscopy (SEM), residual stress measurement and transmission electron microscopy (TEM). Each site at which crack nucleation could be expected was inspected in the SEM and was then characterized using surface X-ray diffraction to quantify the residual stresses field near that location. Then TEM foils were cut from one area on a specimen with tiny cracks and dislocation densities were observed. A novel technique was used which permitted TEM samples to be obtained from regions in close proximity on the original specimen.Comparisons were made between as-received (AR) and stress-relief annealed (SRA) specimens, on which the stress-relief was applied prior to fretting fatigue testing. SEM inspection was useful for qualitative analysis of wear debris and identification of cracks as small as 20 μm, but was unable to provide quantitative data on the level of fretting fatigue damage beyond crack size. Although differences were noted in the residual stresses for the SRA versus the AR specimens, no residual stress peaks were noted in the edge of contact regions where cracks would eventually develop. TEM observations in the vicinity of the crack nucleation region showed that the dislocation structure decayed rapidly into the specimen thickness. The cause of the dislocations was attributed to plastic deformation caused by the clamping stresses.     

Predicting submerged aquatic vegetation cover and occurrence in a Lake Superior estuary

Submerged aquatic vegetation (SAV) provides the biophysical basis for multiple ecosystem services in Great Lakes estuaries. Understanding sources of variation in SAV is necessary for sustainable management of SAV habitat. From data collected using hydroacoustic survey methods, we created predictive models for SAV in the St. Louis River Estuary (SLRE) of western Lake Superior. The dominant SAV species in most areas of the estuary was American wild celery (Vallisneria americana Michx.). Maximum depth of SAV in 2011 was approximately 2.1 m. In regression tree models, most of the variation in SAV cover was explained by an autoregression (lag) term, depth, and a measure of exposure based on fetch. Logistic SAV occurrence models including water depth, exposure, bed slope, substrate fractal dimension, lag term, and interactions predicted the occurrence of SAV in three areas of the St. Louis River with 78–86% accuracy based on cross validation of a holdout dataset. Reduced models, excluding fractal dimension and the lag term, predicted SAV occurrence with 75–82% accuracy based on cross validation and with 68–85% accuracy for an independent SAV dataset collected using a different sampling method. In one area of the estuary, the probability of SAV occurrence was related to the interaction of depth and exposure. At more exposed sites, SAV was more likely to occur in shallow areas than at less exposed sites. Our predictive models show the range of depth, exposure, and bed slope favorable for SAV in the SLRE; information useful for planning shallow-water habitat restoration projects.     

A correlation for predicting smoke layer temperature in a room adjacent to a room involved in a pre‐flashover fire

Advanced fire modelling software have been developed and improved during the last couple of decays and these kinds of software have been shown to be valuable tools for fire safety engineers. However, the advances made have not replaced the need for simple hand‐calculation methods. Simple hand‐calculations methods can be used to obtain a first estimate of, for example, smoke layer temperatures in a performance‐based design or to help an engineer determine if it is necessary to perform a detailed computational fluid dynamics calculation, but the current hand‐calculations methods are limited. The current methods can for example only predict smoke gas temperatures in the fire room. A correlation that could predict temperatures in an adjacent space would be useful in performance‐based design when, for example, evaluating the conditions for evacuees or sensitive equipment in an adjacent space to the room of fire origin. In this paper, a correlation for predicting gas temperatures in a room adjacent to a room involved in a pre‐flashover fire is developed. The correlation is derived from results from computer simulations and the external validity is studied by comparing results from the correlation with full‐scale test data. Copyright © 2012 John Wiley & Sons, Ltd.