Phospholipase D activity in hexane

Phospholipase D converts phosphatidylcholine (PC) to phosphatidic acid (PA) at 65° C in water-saturated hexane. Presumably, the active site of the enzyme remains hydrated in the interior of a lipid micelle. Enzyme activity at elevated temperatures in a nonaqueous medium contrasts sharply with inactivation at high temperature in aqueous solution. Results demonstrate that nonhydratable phospholipids can be produced enzyma-tically under conditions comparable to those during oil extraction in commercial soybean processing. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Photochemical studies of rancidity: Antioxidants vs. green light protection

Conclusion 1. The antioxidants used in this investigation showed antioxygenic activity in delaying the development of rancidity, but they were not so effective as green wrappers which absorb all light except that delimited by 4900–5800 Angstrom units. 2. The use of a protective green container or wrapper alone or in conjunction with an antioxidant increased the period during which the oil or fat remained fresh at room temperature and, incidentally, decreased the rate of peroxide formation. 3. Oils or fats stored at low temperatures and with light excluded remained fresh longer than if treated with an antioxidant or packaged in green and exposed to light at room temperature. 4. Packaging in green or opaque wrappers has a special advantage in that they can be used to protect those oil-bearing food products, such as shelled nuts and ground whole grain, to which it is difficult to add an antioxidant. 5. Protecting oil-bearing foods from rancidity by packaging in green or opaque containers is practical.     

Residual stress,aging, and fatigue fracture in injection molded glassy polymers I. Polystyrene

Fatigue tests have been conducted on polystyrene bars molded at different pressures and having different post-molding thermal histories. Fatigue crack propagation rates were not sensitive to molding or thermal history but in unnotched bars initiation seemed to happen more quickly in bars aged for long periods at room temperature or annealed at elevated temperature. Fractographic studies showed that initiation occurred at favored sites and that the skin/core morphology affected crack growth. Prolonged storage of polystyrene bars at ?85°C promoted significant physical property changes (stiffness and density). These changes appeared to be at least partly reversible with rapid recovery occurring within the first 24 h after restoring to room temperature.     

Studies on Nonmetals During Irradiation: V, Growth and Decay of Color Centers in Barium Aluminoborate Glasses Containing Cerium

The radiation-induced absorption of a group of barium aluminoborate glasses was studied in a new facility for measuring optical absorption during irradiation with γ-rays. The results demonstrate that this technique provides significant new information on the kinetics of the radiation-induced coloring of glasses and suggest that most previous measurements are, at best, suspect. Barium aluminoborate glasses, both with and without Ce, were prepared under normal and reducing conditions. The coloring during irradiation and the decay after irradiation can be characterized by the absorption at 3.0 e V and at 2.25 or 1.90 e V. The Ce-free base glass continued to color as long as irradiated and, at a given dose, the absorption was at least 2 or 3 times that of the other glasses. The totally reduced 1% Ce glass colored to a constant level in the uv, but in the visible the coloring increased to a maximum and then decreased to a constant value. The partially reduced 1% Ce glass also colored to a constant value in the uv, but in the visible the original absorption decreased slightly. All the coloring curves recorded during irradiation are described accurately by expressions that include one or more increasing saturating exponential terms and may contain one linear or one decreasing saturating exponential term. After irradiation the coloring curves decrease and can be resolved accurately into one or more decreasing exponential components. Futhermore, all the observed coloring-curve features were derived from relatively simple kinetics.     

An Investigation into Parameters Affecting Crystal Purity of Urea in a Stirred Tank and an Oscillatory Baffled Crystallizer

Confidential industrial trials showed that higher purity crystals were produced in an oscillatory baffled crystallizer (OBC) compared to a stirred tank crystallizer (STC) when operating at similar conditions. This trend is verified in this work using urea as the test compound that is different from that was employed in industrial tests. We have observed that a higher supersaturation level at nucleation coupled with a lower nucleation temperature was measured in the STC at all investigated conditions compared to that in the OBC. This led to a higher nucleation rate in the STC, consequently producing smaller crystals. Crystal size distributions and imaging analyses suggest that these smaller crystals were more likely to form agglomerates in the STC, trapping either mother liquor or impurity or both and leading to the lower purity observed when compared to that in the OBC.     

Pore Growth in Sintered Thoria

Sintered ThO₂ will sometimes undergo a decrease in density, i.e. become more porous, if held at high temperature for a sufficient time. The bulk density of sol-gel ThO₂ sintered to 99% of theoretical density at 1200°C will decrease steadily at 1800°C in air to <90% of theoretical after ∼ 15 h. Gas-release measurements from such porous ThO₂ specimens annealed in air or in vacuum indicate that some gases move through the material freely at 1800°C. The only gases that could contribute to the decrease in density are the oxides of sulfur and carbon, which, if they exist, could be produced or eliminated rapidly by controlling the annealing environment. However, the density decrease appears to depend on factors that affect grain growth, rather than on the generation or elimination of postulated gases.     

Activation and characterization of Fe---Mn---SO4/ZrO2 catalysts

Changes in Fe---Mn---SO₄²⁻/ZrO₂ catalyst formulations during activation have been observed. In air or an inert gas, the added salt, such as iron and/or manganese nitrate, decomposes over a temperature range of about 200–400°C to produce nitric oxide, oxygen and iron and/or manganese oxide. The crystallization of zirconia occurs at 450°C; when the sample contains sulfate the exothermic event occurs at a temperature that is about 200°C higher. Heating in the presence of hydrogen causes the evolution of nitric oxide to occur over a narrow temperature range and at a lower temperature than when the sample is heated in helium or air. It appears that the nitrate ions associated with Fe, Mn and Zr decompose to produce nitric oxide, and presumably water, at different temperatures when the sample is heated in the presence of hydrogen. Heating samples of sulfated zirconia containing iron and/or manganese in hydrogen causes sulfur evolution at a lower temperature, and a significant fraction of it in the form of H₂S.     

Static and Cyclic Fatigue Behavior of a Sintered Silicon Nitride at Room Temperature

The static and cyclic fatigue behavior of sintered silicon nitride was investigated at room temperature. Flexure specimens, with an indentation-induced flaw at the center, were tested under a static or cyclic load applied by four-point bending. Sintered silicon nitride was shown to be susceptible to static and cyclic fatigue failure. Comparing the static and cyclic fatigue lifetimes at frequencies from 0.01 to 10 H z , it was shown that minimum time to failure was almost the same, in spite of differences in loading mode or frequency. However, cyclic stress decreased the scatter in lifetime by reducing the upper limit. Moreover, the cyclic fatigue limit was significantly lower than the static fatigue limit. High-magnification fractography revealed a fatigue failure dominated by intergranular cracking with partial transgranular failure at perpendicularly elongated crystals. This suggests that the intergranular fatigue crack can be arrested at grain-boundary triplets, and also can be reactivated by subsequent cyclic loading. The crack growth rate, calculated from the fatigue lifetime, showed three characteristic regions having a plateau at 70% to 90% of the fracture toughness, which suggests a possible intergranular stress corrosion cracking mechanism resembling that in glass or alumina.     

Antioxidant and Prooxidant Activity Behavior of Phospholipids in Stripped Soybean Oil-in-Water Emulsions

Phospholipids have been reported to inhibit lipid oxidation in bulk oils, but very little is known about their influence on oxidation in oil-in-water emulsions. In the present study, the impact of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) on lipid oxidation was studied in 1% stripped soybean oil-in-water (O/W) emulsions as a function of DOPC concentration and pH (3 and 7). At pH 7.0, DOPC inhibited lipid oxidation in O/W emulsions, while DOPC was prooxidative at pH 3.0. DOPC did not affect emulsion droplet charge or size at either pH 3.0 or 7.0. The antioxidant activity at pH 7.0 was observed in a series of phospholipids (PL) that varied in fatty acid unsaturation level and chain length as well as type of phosphate head group. Overall, phosphatidylcholine with either oleic or palmitic acid were the most effective at inhibiting lipid hydroperoxide and hexanal formation of all of the PL tested. Antioxidant mechanism of PL could not be ascribed to their ability to decompose lipid hydroperoxides. It might be possible that, at pH 7.0, the PL antioxidant activity is related to their ability to form structures within the lipid phase of the emulsions droplets or to chelate metals.     

Radiation-absorbing hydrogel–melanin blends for ocular devices

Hydrophilic polymers and copolymers of 2-hydroxyethyl methacrylate, with low or high crosslinking density, were synthesized and then treated in aqueous medium with epinephrine (adrenaline) at neutral or acid pH, at room temperature, and in the presence of oxygen and light. During this treatment, a melanin is formed and uniformly dispersed in polymers. The resulting slightly colored hydrogels display radiation-absorbing properties in the ultraviolet and visible regions of the natural spectrum. This enhances significantly their value as materials for ocular devices (contact lenses, intraocular lenses) that should protect the retina of the patients without their natural lens from potential damage induced by ultraviolet and visible (violet and blue) radiation. The incorporation of common ultraviolet absorbers led to transmittances similar to that of the natural human lens, i.e., 30% or less at 450 nm, 40% or less at 500 nm, and no more than 50% at 700 nm. The two-phase morphology of the melanized hydrogels, as investigated by TEM, revealed a very fine structure comprising melanin domains of 1 to 12 nm in size. Although no proof for a network interpenetration could be provided, it is believed that the novel blends are true sequential interpenetrating polymer networks.     

Concentration and heat problem of the theory of thermodiffusiophoresis of a doublet of contacting spheres traveling along the line of their centers in a binary gas mixture

An efficient model of studying heat and mass transfer to the surface of two contacting unequal balls with arbitrary thermal conductivity is presented. The axisymmetric thermodiffusion problem is solved in a quasistationary approximation at small Peclet numbers using three-dimensional Laplace equations with linearized boundary conditions. Solutions that can be obtained using the proposed model for problems that are similar in mathematical formulation to the studied one can be used for designing chemical engineering unit operations dealing with evaporation or condensation, adsorption or desorption, combustion or chemical reactions at the interfaces in a disperse system.     

Pasty Polymers in Cancer Drug Therapy

Injectable polymeric systems suitable for the localized delivery of anticancer agents are reviewed. These polymeric systems include: drug-loaded low melting temperature polymers that are injected at the melting temperature of the polymer, usually below 50 °C, that solidify at body temperature to form an in situ device; polymer solutions in buffer or in N-methyl pyrrolidone, ethanol, or acetate esters which, upon injection in tissue,are absorbed into the tissue and cause precipitation of the polymer at the injection site; in situ crosslinking of polymer solutions to form a polymeric implant; and thermoresponsive polymer solutions that are soluble at room temperature and solidify at body temperature. However, these systems are hydrophilic and suffer from burst release of drug within a few hours post injection. Hydrophobic injectable, pasty, fat-based polymers that gel when injected in tissue have been used for the extended release of paclitaxel, cisplatin, and other agents. This polymer releases the drug in a controlled manner with no burst release. These systems have a potential use as drug carriers for regional or systemic drug delivery.     

FUNDAMENTAL CONDITION OF GLASS FORMATION*

The fundamental condition for glass formation is the existence of strongly bonded large networks or long chains of atoms in the liquid. Such chains or networks prevent or hinder the orderly orientation of atoms in the chains or networks themselves and also that of atoms, not in the networks in the liquid, near the melting point or liquidus temperature. A liquid structure will persist when the liquid is cooled below the melting point or liquidus temperature and will continue until free, long-range movement of atoms becomes impossible. In order to obtain such long chains or large networks, it is necessary that (1) the bond strength of atoms in the chains or networks be very strong; (2) the small ring formation of these strongly bonded atoms be at a minimum; and (3) the relative numbers of various atoms in the chains or networks be such that at least a continuous chain is configuratively and structurally possible; at the same time, the coordination numbers of the glassforming atoms should be as small as possible to keep the bond strong. The general treatment is applied to all kinds of glasses, particularly oxide glasses. The bond strengths of all M—O single-bond linkages in these glasses are calculated and tabulated here for the first time. The bond strength of all the glassformers was found to be greater than 80 kilocalories per Avogadro bond, that of the intermediates between 60 and 80, and that of the modifiers below 60; the transition is continuous, and the division into glassformers, intermediates, and modifiers is arbitrary.     

A model for studying LCAT reaction: In vitro cholesterol esterification in pig ovarian follicular fluid

Phosphatidylcholine acyltransferase (lecithin:cholesterol acyltransferase or LCAT; EC 2.3.1.43) activity was found to be present in pig ovarian follicular fluid (POFF), in addition to pig serum (PS). The cholesterol esterification rate in both POFF and PS is linear with incubation time up to 2 hr. The mean absolute rate of POFF-cholesterol esterification was 8.1±0.4 nmoles per ml per hr approximately one-fourth of that in PS. However, the fractional rate (percent of labeled cholesterol esterified per hr) of POFF-cholesterol esterification was similar to that observed in PS. There was little variation of absolute rate of cholesterol esterification in the fluid obtained from different sizes of follicles. Fatty acid or triacylglycerol did not participate in the reaction of cholesterol esterification in POFF. No appreciable change in enzymatic activity was found from storing POFF at 4 C for periods of time up to 24 hr or at −70 C up to 2 months, but activity was lost thereafter. On the other hand, PS showed a much longer period of stability (5 days at 4 C and 9 months at −70 C). A discrepancy between the fatty acid composition of cholesteryl esters formed by the LCAT reaction and the fatty acid composition at the C-2 position of phosphatidylcholine led us to propose a two-step mechanism for the LCAT reaction. It is concluded that the LCAT of POFF, as well as that of plasma, is specific for individual fatty acids rather than for the fatty acid composition of phosphatidylcholine. The fatty acid concentration of lysophosphatidylcholine decreased during prolonged incubation times (6 to 21 hr) suggesting that the increased lysophosphatidylcholine formed as a product of the LCAT reaction may be reused as substrate for the LCAT reaction or for hydrolysis by lysophosphatidylcholine hydrolase. Presented at the AOCS Meeting, New York, May 1977.     

Formation of NOx and SOx precursors during the pyrolysis of coal and biomass. Part II. Effects of experimental conditions on the yields of NOx and SOx precursors from the pyrolysis of a Victorian brown coal

A Victorian brown coal was pyrolysed in a quartz reactor. The reactor has some features of a drop-tube reactor and of a fixed-bed reactor, capable of operating at fast and slow heating rates. The yield of HCN was found to change with gas flow rate and coal feeding rate, indicating that HCN and/or its precursors could interact significantly with the nascent char to be incorporated into char as soot or to form N₂. Experimental results indicated that HCN does not significantly convert to NH₃, either on the char surface or in the gas phase, at least during the pyrolysis of the brown coal in this study. The yields of HCN and NH₃ were both sensitive to changes in heating rate. The reduction in the yields of HCN and NH₃ with decreasing heating rate is mainly due to the lack of radicals at the slow heating rate, which are required to initiate the opening of the N-containing rings. The carbonisation/condensation reactions also make the N-containing heteroaromatic ring systems increasingly stable during the extended holding at high temperatures at the slow heating rate. Experimental results appear to suggest that there are two types of organic sulphur-containing structures in the brown coal with very different thermal stability. The first type could be converted into H₂S at low temperatures (<600°C). The other type was stable at temperatures up to 1000°C. The changes in heating rate or coal feeding rate did not affect significantly the formation of H₂S.     

Mass transfer around prolate spheroidal drops in an extensional flow

Mass transfer in the continuous phase around a small eccentricity prolate spheroidal drop in an axisymmetric extensional creeping flow and at large Peclet numbers was investigated theoretically. The results show that, at very short times, the total quantity of solute transferred to or from the drop represents, at O(Ca¹), mass transfer by diffusion only around a sphere. For long times, or at steady‐state, the total quantity of solute transferred is, at O(Ca¹), slightly smaller than that of a spherical drop, and it decreases with an increase of the capillary number or the viscosity ratio. © 2012 Canadian Society for Chemical Engineering     

Dyeing and Printing by Solvent-assisted Processes

The background to solvent-assisted methods of dyeing and printing and the uses that have been found for them in practical processes in the U.K. are summarised, with particular reference to the Irga-solvent method. In principle, the addition of a suitable solvent has the same effect as either dyeing at a higher temperature for the same time or dyeing or steaming at the same temperature for a much longer time. Wherever it is more practical to include a solvent in the dye-liquor or printing paste rather than increase the dyeing temperature or prolong the dyeing or steaming time, then solvent-assisted processes should be of interest.     

Photobleachable fluorescent species in wool keratin

The fluorescence from scoured merino wool was examined systematically using excitation wavelengths ranging from 280 to 400 nm. Absorption maxima of various fluorophores, were identified. Irradiation of dry wool in dry air at 325 nm selectively destroyed or bleached the fluorophore absorbing maximally at 335 nm while irradiation of dry wool at 365 nm bleached the two fluorophores absorbing maximally at 335 and 380 nm. Comparison of the fluorescence from wool with that observed from collagen by excitation with UVA radiation suggests that the fluorophores present in wool absorbing above 350 nm are not tyrosine derivatives and are probably tryptophan oxidation or hydrolysis products.     

Electrokinetic potential of kaolinite clay in the presence of polystyrene sulfonate

The determination of the electrokinetic potential of clay is very important in many applications. Therefore, this work was aimed at studying the effect of poly(4‐ sodium styrene sulfonate) on the electrokinetic potential and the sedimentation behavior of kaolinite clays at different pH values and/or in the presence of sodium or calcium chlorides. At pH values lower than the point of zero charge (PZC) of the kaolinite clay, the zeta potential of Na‐ or Ca‐kaolinite in CaCl₂ solutions was higher than that in NaCl solutions at the same concentration. Above the PZC, the zeta potential of Na‐ or Ca‐kaolinite in NaCl solution was higher than that in CaCl₂ at the same electrolyte concentration. These results reflect the ability of calcium cations to compress the double layer of the kaolinite clay better than sodium cations. Also, below the PZC and at low concentrations of poly(4‐sodium styrene sulfonate), the zeta potential of the kaolinite clay suspensions had low value, while the sediment volumes had higher values. On the other hand, above the PZC at increasing polymer concentrations, the zeta potentials increased but the sediment volumes had lower values compared to those produced below the PZC. The data showed the zeta potential of Na‐kaolinite suspensions are higher than Ca‐kaolinite, producing lower sediment volumes of Na‐kaolinite compared to Ca‐kaolinite at the same concentrations of polymer and/or pHs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1705–1711, 2006     

Antioxidant efficacy of amino acids in methyl linoleate at different relative humidities

Antioxidant efficacy of the amino acids methionine, tryptophan, aspartic acid, serine, alanine and arginine in methyl linoleate were compared to a methyl linoleate control at 2,50 or 79% relative humidity (RH) at 37°C. Antioxidant efficacy varied with RH and the individual amino acids. Arginine had the highest antioxidant efficacy at all RH values compared to the control. The efficacy of alanine was equal to that of arginine at RHs of 50 and 79% but was lower at 2% RH. The presence of aliphatic, alkaline amino, hydroxyl or thiol groups in the side chain of the amino acids increased the antioxidant efficacy at high RHs.