Longer Heating Time Research Articles

Taurocholate-induced dimerization of bovine cholesterol esterase in sodium dodecylsulfate

Purified bovine cholesterol esterase (CE) showed one major band with an apparent molecular mass of 58 kDa on sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS–PAGE). In the presence of taurocholate another major band with an apparent molecular mass of 116 kDa, corresponding to the dimer, appeared. Longer heating times and higher concentrations of CE in SDS–sample buffer increased the relative amount of the dimer. Higher SDS concentration in the sample buffer reduced the amount of dimer. Mercaptoethanol concentration had no effect. The dimer did not contain taurocholate and readily reverted to the monomer. It is concluded that taurocholate mediates the dimerization of CE in SDS by facilitating the formation of hydrophobic interactions between monomeric subunits.

Effect of Aging on Ignition Delay Times of a Composite Solid Propellant Under CO2 Laser Heating

In this paper, the effect of aging on the ignitibility and reproducibility of a composite solid propellant was investigated. Ignition delay times of solid propellant samples undergone different degrees of aging were determined under various levels of incident CO2 laser energy fluxes. Micrographs obtained from an Environmental Scanning Electron Microscope (ESEM) showed that the surfaces of the aged samples exhibited fiber-like structure as compared to the heterogeneous structure of the as-machined sample. The porosity of the fiber-like structure increased with the degree of aging. Based upon the results of experiments, it was observed that aged propellant samples require much longer heating time to reach self-sustained combustion condition than the as-machined sample at lower energy fluxes (around 50 W/cm2). However, at higher energy fluxes (around 150 W/cm2), the effect of aging on the ignition delay times became smaller.

Effect of Longer Heating Time on Depolymerization of Low Moisturized Starches

AbstractLow moisturized potato, sweet potato, corn and wheat starches were treated with a flow tester under heated and heated‐sheared conditions. The starches depolymerized into lower molecule by longer heating time at 150°C. With an increase in heating time, the cold water solubility of starches increased and the degree of depolymerization progressed. Comparing heated treatment with longer heating time and heated‐sheared treatment, 60—120min heating was necessary for heated specimens to obtain similar cold water solubility and degree of depolymerization of heated‐sheared specimens. These results conducted that heated‐sheared treatment strongly promoted the depolymerization of low moist starches under high temperature as compared with heated treatment only. From the results of λmax of iodine‐polysaccharide complex, there was almost same molecular state between heated for longer time and heated‐sheared treatment. Both amylose and amylopectin depolymerized into lower molecule by both treatments.

Effect of pH of the recovery medium on the apparent heat resistance of three strains of Bacillus cereus

The influence of pH of the recovery medium, in the range 7.6–5.4, on the apparent heat resistance of three strains of Bacillus cereus (ATCC 4342, 7004 and 9818) has been investigated. The highest counts of heat-injured spores were obtained at pH near neutral, decreasing markedly as pH was reduced, especially with longer heating times. When the media were acidified, the apparent D-values tended to decrease, although some exceptions related to the strain and the nature of the medium were observed, z-Values determined were not affected by the pH of the medium.

Synchrotron x-ray scattering measurements of bulk structural properties in superconducting (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes

The structural properties of superconducting (Bi,Pb)2Sr2Ca2Cu3O10–Ag (2223) tapes have been measured using synchrotron x-ray scattering techniques. The x-ray photon energy was tuned just below the silver K absorption edge so the penetration depth was large, which allowed the measurements to be performed in a transmission geometry without removing the silver cladding. Analysis of the peaks in 2θ scans indicates that residual (Bi,Pb)2Sr2CaCu2O8 (2212) superconductor starting material is present in all samples studied. The amount of 2212 varied widely among the tapes, and was not homogeneous along the length of each individual tape. Residual 2212 content increased near the ends of most samples, suggesting that 2223 phase development is sensitive to whether the superconducting material is encased in silver or not. The bulk c-axis alignment was measured in ∼100 mono- and multifilament samples, and correlations between c-axis alignment and current carrying capacity at 77 K were found. Multifilament samples generally had better alignment than monofilament samples. The c-axis alignment along the length of the tapes was uniform, and the superconducting material within ∼1 μm of the Ag was better textured than the bulk of the sample. Intermediate pressings were directly shown to have an adverse affect on c-axis alignment. Finally, the evolution of texture and phase development was examined in a series of samples annealed for varying times. The 2212 starting material acquired the final c-axis alignment state after brief heating times, and only after much longer heating times did the 2212 transform into the 2223 phase. These results and their implications for improving processing procedures are discussed.

Geosynthesis of organic compounds: III. Formation of alkyltoluenes and alkylxylenes in sediments

Heating ortho-undecyltoluene with an acidic clay catalyst and hexamethylbenzene as a methylating agent resulted in the formation of hydrocarbon mixtures containing undecyltoluenes and dimethylundecylbenzenes. At short heating times, methylation at ring positions 4 and 5 forming 2,4- and 2,5-dimethylundecylbenzenes occurred predominantly, while at longer heating times, methylation and isomerization/transalkylation reactions resulted in higher concentrations of more stable alkylxylene isomers. The distributions of undecyltoluenes and dimethylundecylbenzenes in two mature crude oils were also compared to those formed in the laboratory heating experiments. One crude oil derived from carbonate sediments was shown to have a predominance of ortho-undecyltoluene and 2,4- and 2,5-dimethylundecylbenzenes, similar to the reaction products formed from short-term laboratory heating experiments. The other crude oil, derived from clastic sediments containing abundant clays, was shown to contain a mixture of the undecyltoluenes and dimethylundecylbenzenes similar to the reaction products generated from longer-term heating experiments. These observations suggest that alkylxylenes in crude oils result from sedimentary methylation of ortho-alkyltoluenes, as the ortho-alkyltoluenes isomers are often the most abundant isomers in low maturity sediments. The initial products formed under kinetic control then undergo clay-catalyzed isomerization/transalkylation reactions to yield mixtures with higher abundances of the more thermodynamically stable isomers.

Novel diagnosis of thermal deterioration for organic insulating resins by optical loss analysis

AbstractWe propose an “optical loss analysis” as a novel nondestructive diagnosis for the thermal deterioration of insulating resins. Using an alkyd resin film, the optical absorptin loss per unit optical path length and the glass transition temperature (Tg, DMA) by dynamic mechanical analysis were measured during heating tests. At longer heating times, values of the optical absorption loss and the Tg, DMA increased concurrently. By rescaling the heating time as a reduced time as a reduced time, a master curve of the deterioration for the resin was obtained. Consequently, when thermal stress is the main cause of the deterioration, one can estimate the degree of deterioration and theoretically the residual lives of resins using this optical loss analysis.

Stepdown hyperthermia in human melanoma cells

Human melanoma cells have been used to evaluate whether stepdown heating (SDH) could increase the effectiveness of long-duration mild hyperthermia (LDMH). The effects of these treatments were also evaluated on cell survival and DNA polymerase inactivation. Short treatments (30 min) at 43 degrees C did not result in much SDH effect for subsequent protracted heating at 40 degrees C. The effect on DNA polymerases was also very small. However, heating at 44 degrees C for 30 min had a large SDH heating effect on subsequent heating at 40 degrees C and 41 degrees C. The SDH effect occurred mainly in the first 5-10 h of subsequent LDMH and, at longer heating times, the rate of cell killing was reduced. The 44 degrees C SDH effect was also observed on DNA polymerase inactivation. Comparing the degree of cell killing and polymerase inactivation showed a good correlation for the various SDH protocols.

Spin coating of viscoelastic and nonvolatile fluids over a planar disk

Spin coating of two commercially used polymer solutions is studied both theoretically and experimentally. Physical and rheological characterization of these solutions indicates that under the spinning conditions currently used they behave as nonvolatile, viscoelastic fluids with constant viscosity and elasticity. The corresponding Reynolds (Re) and Deborah (De) numbers are up to order unity. The theoretical analysis demonstrates and explains why, at very short times after the inception of impulsive spinning, the velocity and stress fields in such fluids develop in an oscillatory manner. The amplitude of these oscillations increases with the ratio of the retardation parameter to the Deborah number, whereas their damping rate gets smaller as De increases. Since these oscillations dissipate very rapidly, and before substantial thinning of the film takes place, the thinning rate, velocity, and shear stress components do not deviate eventually from those of a Newtonian fluid. Such a complete explanation of similar experimental findings has not been offered before. The radial normal stress component does increase considerably over its Newtonian value, and this explains certain ‘‘experimental practices.’’ Similar oscillatory development early on occurs even at higher Re, as long as Re∼De, but it is dissipated again, this time because of the abrupt thinning of the film. The theoretical results are in good agreement with experimental measurements of ‘‘dry film’’ thickness and with dynamical measurements of ‘‘wet film’’ thickness during spinning, which are reported herein for the first time. Care must be taken in reporting ‘‘dry film’’ thickness because the commercial solutions under study retain part of the solvent after ‘‘soft baking’’ over a hotplate. Complete solvent removal produces dry films, but requires treatment in a vacuum oven, higher temperatures, and longer heating times.

Synthesis, characterization, and properties of photosensitive silicon‐containing copolyimides

AbstractCopolyimides with siloxane moieties in the main chain were synthesized by solution polycondensation of 1,3‐bis(3‐aminopropyl) tetramethyldisiloxane (APMS), oxydianiline (ODA) with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) in N‐methyl‐2‐pyrrolidone (NMP). The adhesion properties between copolyimides and silicon wafer were improved significantly with incorporation of siloxane moiety into polymer chain.Photosensitive copolyimide precursor was obtained by further reaction of silicon‐containing copolyamic acid with 2‐isocyanatoethyl methacrylate (IEM). The insoluble fraction of photosensitive copolyimide precursor reached 90% after 10 min of irradiation with UV light. In comparison, the thermal imidization of irradiated photosensitive copolyimide precursor was more difficult than that of silicon‐containing copolyamic acid. A longer heating time or higher imidization temperature was required.

Behavior of the Electroless Composite Films Plated from a Ni‐P Bath with Metallic Dispersion of Zr and Nb Powders

An electroless Ni‐Zr‐P composite film and a Ni‐Nb‐P composite film were plated and their heat‐treating behaviors were investigated. The addition of 20g dm−3 of metallic powder resulted in a composite film that contained 21.2 weight percent (w/o) of Zr, [13.8 atom percent (a/o)], or 4.8 w/o of Nb, (2.9 a/o), respectively. Both metallic powders were dispersed uniformly throughout the films. The metallic Ni formed by the crystallization of the Ni‐P matrix diffused into the metallic powders, and the amorphous Ni‐Zr and Ni‐Nb phases were formed by heat‐treatment at 500° or 300°C. Some parts of the amorphous Ni‐Zr phases and the metallic Ni phases combined to form intermetallic compounds by heat‐treatment at 600°C. The nickel‐rich parts of the amorphous Ni‐Nb phase were converted into a metastable Ni‐Nb phase (ζ phase) or a Ni‐Nb solid solution by heat‐treatment at 700°C. The longer heating time at 400°C increased the amount of the Ni‐Zr amorphous phase: however, it decreased the reactivity of the amorphous Ni‐Zr phase. The same heat‐treatment of 400°C did not give the considerable change on the amorphous Ni‐Nb phase.

Phosphorylated sugars. Part 25. Synthesis and behaviour in acidic media of 2-acetamido-2-deoxy-D-glucose 4- and 6-phosphates and of a ‘Lipid A’ analogue

With the aid of 2-acetamido-2-deoxy-D-glucose 4- and 6-phosphates and of 2-amino-2-deoxy-D-glucose-6-phosphate, for all of which new and efficient syntheses are described, it has been shown that during treatment of 2-acetamido-2-deoxy-D-glucose 4-phosphate and of the model 2-hydroxyethyl 2-deoxy-2-[(3R)-3-hydroxytetradecanamido]-β-D-glucopyranoside 4-phosphate (which has also been synthesised) under conditions of acidic hydrolysis used in the determination of the structure of ‘Lipid A’ preparations from bacterial endotoxins, migration of the phosphate group from position 4 to position 6 takes place. Conditions are described in which the N-acetyl group is completely removed whilst the extent of phosphate migration is very small. Longer heating times in the same conditions are required to effect almost complete removal of the N-(3R)-3-hydroxytetradecanoyl group from the glucoside, but again very little phosphate migration occurs. The amount of inorganic phosphate formed after removal of the amide-bound substituent from the two 4-phosphates (7.5 and 15.4% respectively) was superior to that formed from N-acetylglucosamine 6-phosphate (2.4%).

Transient Experimental Technique for the Determination of the Thermal Diffusivity of Fibrous Insulation

The current investigation is an attempt to develop a transient technique that will circumvent these long experiment times. The present technique is fundamentally different from the hot-wire and hot-strip techniques, currently the only practical (but limited) transient techniques available for determining the thermal conductivity of insulators. In 1983, a step heat technique involving planar geometry was presented (Bittle, 1983; Bittle and Taylor, 1984; Bittle and Taylor, 1985) that allowed for the measurement of large-grained and nonfibrous insulators up to 400-500C. The technique is an extension of the flash technique in that it allows for larger sample sizes and longer heating times. It was found that the step heat technique is inappropriate for fibrous insulators because of boundary condition violations. At the front face of the sample, the assumption of constant heat flux into the surface of a semi-infinite medium being heated with irradiation is invalid for radiant fluxes and time durations typical in measuring poorly conducting materials. In addition, at the rear of the sample where the temperature rise is monitored, the assumption of no heat loss is violated; this is especially true for insulators at elevated temperatures. While the apparatus for the present technique and the step heat techniquemore » are similar, the present technique involves the substitution of measured values for mathematical approximations and thus is marked departure from previous practices.« less

Transformation of Trace Element-Substituted Maghemite to Hematite

AbstractX-ray powder diffraction (XRD), transmission electron microscopy, infrared spectroscopy, differential thermal analysis, and surface area (BET) measurements were employed to investigate the transformation of microcrystalline maghemite to hematite. At 500°C pure maghemite was completely altered to hematite in 3 hr, whereas maghemites containing small amounts (≤1%) of Co, Ni, Zn, Cu, Mn, Al, V, and Cr required much longer heating times. The maghemite-to-hematite transformation temperature varied from 540° to 650°C. XRD line widths suggest that each particle of maghemite and hematite may have been a mosaic of many independent, coherently diffracting crystals. The transformation of maghemite to hematite at 650°C was accompanied by a reduction in surface area due to sintering of particles.

Effects of ultraviolet irradiation on the thermal gelation of fish meat pastes.

The effects of ultraviolet (UV) irradiation upon the thermal gelation of meat pastes from sardine, hake muscles were examined by means of heating temperature-jelly strength curves (30, 40, 50, 60, 70, and 80°C). The UV irra diation (5000μW/cm2, 15min) applied to the raw meat pastes revealed an enhanced effect on the jelly strength value of the paste after heat treatment. While the jelly strength of the pastes obtained by UV irra diation appeared to decrease with longer heating time at 60°C for sardine, and at 40°, 50°, and 60°C for Alaska pollack and Chile an hake, the values were always higher than those of the non-irradiated pastes. From the UV intensity-the thermal gelation cur ves, it was found that the jelly strength at 70°C rapidly increased in the range of about 3000 to 6000μW/cm2 UV for sardine, and in that of 4000 to 7000μW/cm2 UV for Alaska pollack.

Properties and microstructure of thin LiNbO3 films prepared by a sol-gel process

Thin LiNbO3 films were prepared from polymerized sol-gel precursor solutions having various concentrations and water:alkoxide ratios in an effort to investigate the effects of these and other processing variables on the resultant film properties and microstructure. Films deposted on silicon substrates were mostly amorphous when pyrolyzed at 435°C for 30 min. Randomly oriented polycrystalline films having distinctive microstnietures were produced using longer heating times or higher temperatures. All of the films exhibited low refractive indices due to porosity, which was attributed to the low level of hydrolysis water required to produce stable polymeric precursor solutions. When single-crystal LiNbO4 was used as the substrate, epitaxial growth of the film resulted. This ideal case establishes the feasibility of producing epitaxial films via sol-gel processing. All films were characterized by transmission electron microscopy (TEM) and thin-film x-ray diffraction patterns.

Ion-sensitive microelectrode measurements of free intracellular chloride and potassium concentrations in hyperthermia-treated neuroblastoma cells.

Murine NG108-15 neuroblastoma cells were heated for times of 5-40 min at 45.5 degrees C, and survival ranged from 0.7-0.0015, respectively. Ion-sensitive microelectrodes (ISM) were used to measure the free intracellular concentrations of Cl- and K+ immediately after heating and up to 30 hr later. The free intracellular Cl- and K+ concentrations, [Cl-]i and [K+]i respectively, of the heated cells remained identical to those of the controls for the first 10 hr after heating. At later times, some cells had increased [Cl-]i values and decreased [K+]i values identical to those of the extracellular medium. These cells had a mottled morphology, no longer excluded the vital stain trypan blue, and had no membrane potential. The number of these dye-including, physiologically dead cells increased with time, and was always greater following longer heating times. No changes in mean cellular volume were observed until 25 hr after heating. All trypan-blue-excluding, physiologically live cells had the same [Cl-]i and [K+]i as the control cells, even when the majority of them were destined for clonogenic death.

Antibacterial characteristics of fish protamines. V. Combined effect of heat treatment and protamine on the growth and heat resistance of Bacillus spores.

Combined effects of heat treatment and clupeine sulfate on the growth from the spores of Bacillus subtilis and Bacillus licheniformis were studied. The effectiveness of protamine in pre-venting the growth from the spores was considerably influenced by heat treatment at 95°C. In general, increasing the length of heating time at 95°C, decreased the required protamine level in the prevention of growth from the spores or the presence of higher level of protamine decreased the heating time. In nutritionally rich media with higher concentration of organic substances, higher level of protamine and longer heating time was necessary for the prevention of growth. D value for the thermal death of B. subtilis heated at 90°C were 17 and 14.5 min for control and with 200μg pratamine/ml respectively. This meant a 15% decrease in the D value of the spores when heated along with protamine.

Production of a Bicyclophosphate Neurotoxic Agent During Pyrolysis of Synthetic Lubricant Oil

The formation of 4-ethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2.]octane-1-oxide ("trimethylolpropane phosphate"; "TMPP"; "EPTBO") from the thermal decomposition of a synthetic aircraft engine lubricant has been observed in yields ranging from 100 μg/g to over 9,000 μg/g oil. Although the exact composi tion of the oil studied is proprietary, two ingredients typically used in synthetic lubricants of this type, trimethylolpropane esters of carboxylic acids, and tricresylphosphate, are probable precursors. The production was a linear func tion of temperature over the range of 400 to 645 °C for one test system used, and showed a dramatic increase for a second set of pyrolysis conditions that in cluded higher pressure and longer heating time. Formation of decomposition products was rapid once decomposition temperatures were reached, with some TMPP production occurring within 2 minutes. The relative volatility of this syn thetic lubricant formulation compared with previously studied sources of TMPP (polyurethane foams) requires specific pyrolysis system modifications to carry out controlled decomposition studies. Worst-case conditions for decomposition and TMPP yield are discussed.

Adsorption and desorption of tritium on material for secondary electron multiplier.

As a first step toward solving the problem of contamination by tritium affecting secondary electron multipliers, the material used in a marketed multiplier was studied in respect of adsorption and desorption behavior, with application of thermal desorption spectroscopy. It was found that the tritium adsorbed on the material was desorbed in large part in the form of tritiated water, generated by chemical reaction that combined adsorbed tritium with excess oxygen present on the material and in small part in the form of tritiated hydrocarbons produced by exchange reactions taking place between the tritium and hydrocarbons also found adsorbed on the material surface. It was further indicated that tritium desorption took place from two distinct kinds of adsorption/desorption sites. Effective removal from the material was obtained of the adsorbed tritium by heating in inert gas flow at 500°C for 6 h. If a longer heating time can be allowed, a lower heating temperature should be suffice for decontamination.