Standard Oven Research Articles

Influence of aging on the evolution of structure, morphology and rheology of base and SBS modified bitumen

The influence of aging on the evolution of structure, morphology and rheology of base bitumen and SBS modified binders was investigated by Fourier transform infrared (FTIR), atomic force microscopy (AFM) and dynamic shear rheometer (DSR), respectively. Two laboratory simulation aging methods, named standard rolling thin film oven (RTFO) test and pressure aging vessel (PAV) test were applied in this study. The aging temperature of PAV was selected at 60 °C, which is considered to be consistent with the real high temperature within an asphalt pavement in the field. After aging, it was found that more carbonyl and sulphoxide groups but less chain segments of butadiene were available. With the oxidation of base bitumen and the degradation of SBS segments, obvious asphaltene micelles appeared in both binders, consistent with the changes of softening point and rheology of base bitumen and SBS modified binders.

Killing bacteria present on surfaces in films or in droplets using microwave UV lamps

The killing of bacteria on surfaces by two types of UV sources generated by microwave radiation is described. In both cases, UV radiation is produced by gas-discharge electrodeless lamps (Ar/Hg) excited by microwaves generated by a power supply from a standard domestic microwave oven. For UV lamp excitation, one of these sources makes use of a coaxial line with a truncated outer electrode that allows the excitation of gases and gaseous mixtures over a wide range of pressures at a comparatively low microwave power. In the second source, UV lamps are placed inside a microwave oven. Ultraviolet generated by the two sources was used to destroy vegetative Escherichia coli bacteria dispersed in thin films and in droplets on surfaces. Two types of UV lamps were used in the study. The first was constructed of quartz that filtered UV below 200 nm preventing the dissociation of oxygen in air and, hence, ozone production. The second type of tube was transparent to UV below 200 nm facilitating ozone production in air surrounding it. It was shown that bacterial cells dispersed in films on surfaces are killed more rapidly than cells present in droplets when using the lamps producing ozone and UV radiation. The UV sources described can effect rapid killing and constitute a cost-effective treatment of food and other surfaces, and, the destruction of airborne viruses and bacteria. The lamps can also be utilised for the rapid eradication of microorganisms in liquids.

RF Impedance Method for Estimating Moisture Content in Small Samples of In-Shell Peanuts

Control of moisture content (MC) in peanuts is important in preserving quality and preventing spoilage in postharvest peanuts. Rapid means of MC determination is therefore necessary during the drying of freshly harvested peanuts and, thereafter, during storage, marketing, and processing. Current practice requires the shelling and cleaning of peanut samples for moisture measurements on kernels in commercial moisture meters. New research has shown that MC can be determined nondestructively by RF impedance measurements on a parallel-plate capacitor containing small samples (seven or eight pods), thus rapidly providing results within 1% MC of the reference standard oven MC on 70%-100% of the pods over the moisture range from 5% to 23% MC. Moisture contents are predicted by computer calculation from capacitance and phase angle measurements at three frequencies of 1, 5, and 9 MHz, with an equation relating MC to differences in capacitance and phase angle at the three frequencies and empirically determined calibration constants. A practical instrument using these principles would be useful in drying, storage, marketing, and processing of peanuts

Determination of moisture content of in-shell peanuts by parallel-plate impedance measurements in cylindrical sample holder

This paper describes a method to determine the moisture content of in-shell peanuts with a parallel-plate electrode system fitted inside a cylinder by using impedance measurements made on the system. Two parallel-plate electrodes were mounted inside a cylinder, made of acrylic material, and the space between the plates was filled with in-shell peanuts (80–100 g). The impedance measurements were made on the parallel-plate system at 1 and 9 MHz, and the average moisture content (MC) of the peanut pods (in-shell peanuts) was determined from a semi-empirical equation. The calculated MC values were compared with standard oven-determined values and were within 1% of the standard oven values for 90% of the samples tested in the moisture range between 6% and 19%. Two parallel-plate sensors with different plate separations and peanuts from the 2004 and 2005 harvests, were used in these measurements. The method, being rapid and nondestructive, is suitable for the development of a practical instrument for measurement of moisture content in in-shell peanuts.

Performance Comparison of RF Impedance and DC Conductance Measurements for Single Peanut Kernel Moisture Determination

Two methods for rapidly determining the moisture content of single peanut kernels (Arachis hypogaea L.), were compared with a standard forced-air oven method to evaluate their performance. One method was based on estimating the moisture content from the measurement of capacitance and phase angle of a parallel-plate capacitor with a single peanut held between the plates. These measurements were made at two frequencies (1.0 and 4.5 MHz). The other method was a DC conductance measurement on a single peanut as it passed between two crushing-roller electrodes. This method is used in a commercial instrument presently available. Moisture content was determined by these two methods and by the standard oven method on 30 individual peanut kernels randomly selected from each of six sample lots with moisture contents ranging from 6% to 16%, wet basis. Moisture content measurements obtained using the capacitance and the conductance methods were in agreement with the standard oven values to an acceptable accuracy for over 80% of the samples tested. A distinct advantage of the capacitance method is that it is nondestructive.

Survivability of Salmonella cells in popcorn after microwave oven and conventional cooking

The survivability of Salmonella cells in popcorn preparation was determined for two distinct cooking methods. The first method used a standard microwave oven. The second method used conventional cooking in a pan. Prior to thermal processing in independent experiments, 12 suspensions in a range between 1x10(3) and 8x10(6) colony-forming units (CFU) per gram of Salmonella cells were inoculated in both raw microwave popcorn and conventional corn kernels. The influence of the initial concentration of Salmonella cells in the raw products and the lethal effects on Salmonella by thermal treatments for cooking were studied. Survival of Salmonella cells was determined in the thermally processed material by pre-enrichment and enrichment in selective medium, in accordance with the legislation for expanded cereals and cereals in flakes. Viable experimental contaminants were recovered from the conventionally cooked popcorn with initial inoculation concentrations of 9x10(4)cells/g or greater. Salmonella cell viability was significantly reduced after microwave oven treatment, with recoveries only from initial concentrations of 2x10(6)cells/g or superior.

The Detection of 9-Tetrahydrocannabinol (THC) and 11-nor-9-Carboxy- 9-Tetrahydrocannabinol (THCA) in Whole Blood Using Two-Dimensional Gas Chromatography and El-Mass Spectrometry

A method is described for the simultaneous analysis of Delta(9)-tetrahydrocannabinol (THC) and its carboxylic acid metabolite, 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THCA) as their trimethylsiyl derivatives using 2-dimensional chromatography and electron ionization-mass spectrometric detection. The addition of a Deans switch to a standard GC oven allows the use of two chromatographic columns of differing stationary phase to greatly reduce matrix interference. The analytes are extracted from 1 mL of whole blood by first precipitating the blood proteins with the addition of acetonitrile followed by solid-phase extraction. The limit of quantitation for both THC and THCA was determined to be 1.0 ng/mL. The between-run precision at 1.0 ng/mL (N = 30) was 7.7% and 7.4% for THC and THCA, respectively. The method is linear from 1 to 100 ng/mL.

Ignition studies of cerium nitrate treated towels

This study evaluated the ignitability of cotton towel material saturated with all oxidizer solution of 0.5 N cerium nitrate in 2N nitric acid. Four types of ignition testing were performed in this work: self-heating oven tests, hot object ignition tests, radiative smoldering ignition tests, and piloted flaming ignition/burning rate tests. Results indicate that cerium nitrate significantly enhances the ignitability of the towels. Self-heating properties of cerium nitrate treated towels were measured using. the standard constant temperature oven method described by Bowes. Based upon these self-heating properties.. self-heating is not a hazard for storage scenarios other than bulk storage (depths of several meters) of cerium nitrate treated towels at room temperature. Surface ignition of hot objects was observed for object temperatures as low as 250 degrees C placed upon room temperature cerium nitrate treated towels. Ignition for hot objects buried within a pile of towels occurred for object temperatures as low as 230 degrees C. Radiant 2 heating tests of cerium nitrate treated towels showed initiation of smolder at heat fluxes as low as 3 kW/m(2) at surface temperatures as low as 175 degrees C. This compares with ordinary cellulosic materials that require 7-8 kW/m(2) heat fluxes and temperatures of 250 degrees C. All four scenarios demonstrate enhanced ignitability and burning rates of cerium nitrate treated towels.

Self-heating properties of styrene-butadiene rubber

Rubbers, including styrene-butadiene rubber (SBR), are well known to be susceptible to self-heating. SBR is used in a wide range of applications and is often produced in the form of a crumb which is then used to form the final product. The crumb may be transported and stored in large quantities. Self-heating properties of a SBR crumb have been determined using standard oven methods. The results indicate that self-heating is a real hazard for SBR crumb. The results are generally consistent with recent measurements by Clothier and Prichard (Combust. Flame 2003; 133:207–210) for rubber tyre crumb. Copyright © 2005 John Wiley & Sons, Ltd.

Evaluation of the Single Kernel Characterization System (SKCS) for Measurement of Sorghum Grain Attributes

ABSTRACTThe single kernel characterization system (SKCS) has been widely used in the wheat industry, and SKCS parameters have been linked to end‐use quality in wheat. The SKCS has promise as a tool for evaluating sorghum grain quality. However, the SKCS was designed to analyze wheat, which has a different kernel structure from sorghum. To gain a better understanding of the meaning of SKCS predictions for grain sorghum, individual sorghum grains were measured for length, width, thickness (diameter), and weight by laboratory methods and by the SKCS. SKCS predictions for kernel weight and thickness were highly correlated to laboratory measurements. However, SKCS predictions for kernel thickness were underestimated by ≈20%. The SKCS moisture prediction for sorghum was evaluated by tempering seven samples with varying hardness values to four moisture levels. The moisture contents predicted by SKCS were compared with a standard oven method and, while correlated, SKCS moisture predictions were less than moisture measured by air oven, especially at low moisture content. Finally, SKCS hardness values were compared with hardness measured by abrasive decortication. A moderate (r = 0.67, P < 0.001) correlation was observed between the hardness measurements. The SKCS predictions of kernel weight and diameter were highly correlated with laboratory measurement. Moisture prediction, however, was substantially lower by the SKCS than as measured by an air oven method. The SKCS should be suitable for measuring sorghum grain attributes. Further research is needed to determine how SKCS hardness predictions are correlated to milling properties of sorghum grain.

Complex permittivity and moisture measurements of oil palm fruits using an open-ended coaxial sensor

An open-ended coaxial sensor for the determination of complex permittivity and moisture content of oil palm fruits is presented in this paper. The measurement system consisting of the sensor and a PC-controlled vector network analyzer have been tested successfully on a range of oil palm fruits of various degrees of ripeness. The initial values of the complex permittivity were estimated using the admittance model of the sensor. The amount of moisture content was found by matching the values of permittivity from the quasistatic model with the permittivity of a dielectric mixture model using the moisture content values obtained from the standard oven drying method.

Transient Radiative Heat Transfer from a Plasma Produced by a Capillary Discharge

The objective of this work is to develop a better understanding of the transient behavior of radiative heat transfer from a plasma. The plasma generation occurred within a 3.2-mm-diam and 26-mm-long polyethylene capillary. Because of its high temperature and high pressure, the plasma evolved from the capillary into an ambient air environment as an underexpanded supersonic jet that interacted with a stagnation plate. Various diagnostic techniques were used. They include heat flux and pressure gauges mounted on the stagnation plate, heat flux gauges and silicon photodiodes mounted below the plasma jet, as well as current transducers interfaced with the electrical circuit. The heat flux gauges were manufactured via sputtering and calibrated using a standard convection oven. A fused-silica window, placed about 1 mm above the gauges, ensured that only the radiative heat flux transmitted by the window was deduced. The row of heat flux gauges mounted below the plasma provided an assessment of the fraction of the radiative heat flux transmitted by the fused-silica window. The results show that the peak of emitted radiant flux occurs immediately after the peak of the discharge of electrical energy, which usually occurred a relatively long time prior to arrival of the precursor shock on the stagnation plate.

Validation and cross‐comparison of MRI temperature mapping against fibre optic thermometry for microwave heating of foods

SummaryThe heating of a 5% starch gel in a standard domestic microwave oven has been measured using a combination of magnetic resonance imaging (MRI) ‘offline’, and fibre optic thermometry ‘online’. MRI was used to locate potential hot and cold spots for optimal placement of the fibre optic probes used to measure temperatures both during microwave heating and for the subsequent 100 s which is the time required for transfer of the sample to the magnet (38–48 s) and the acquisition of the 32 × 32 × 128 pixel MRI temperature map (52 s). The MRI data have a systematic offset because of the finite transferral time and duration of the MRI scan, but not to the detriment of high spatial resolution which is necessary to resolve the high temperature gradients induced. It is believed that 3D MRI temperature mapping will be invaluable to further studies of microwave heating as optimized placement of fibre optic thermometry probes is difficult, and the spatial distribution of microwave absorption is highly variable.

New Method to Determine the True Water Content of Organic Soils

Abstract The true water content of organic soils is overestimated when the standard oven drying temperature of 110 ± 5°C is used due to some oxidation of the solids, and underestimated when the recommended oven drying temperature of 60°C is used due to some residual pore water remaining in the voids. A new method is presented to identify the precise oven drying temperature for which the mass of the residual pore water exactly balances the loss in the mass of solids due to oxidation. The true water content is calculated on the basis of the specimen dry mass recorded for this oven drying temperature. A larger error arose when the water content of the test soil (70% organic content) was determined using the specimen dry mass recorded at 60°C rather than the standard drying temperature of 110 ± 5°C. Longer drying times were also required for the dry mass to equilibrate, making it more inconvenient from a practical standpoint. Some oxidation of the organic solids occurred for oven specimen drying above 80°C. The true value of the water content corresponded to an oven drying temperature of 86°C.

Fast and Accurate Technique for Determination of Moisture Content in Oil Palm Fruits using Open-Ended Coaxial Sensor

A simple, fast and accurate technique employing an open-ended coaxial sensor for the determination of the moisture content in oil palm fruit is presented. For this technique, a calibration equation has been developed based on the relationship between the measured moisture content obtained by the oven drying method and the phase of the reflection coefficient of the sensor for 21 fruits. The moisture content predicted by the sensor was in good agreement with that obtained using the standard oven drying method within ±5% accuracy when tested on 145 different fruits samples.

Oven-Drying Characteristics of Soils of Different Origins

The accurate measurement of the moisture content of a soil is an important step in characterizing its engineering behavior. However, the oven-drying method can cause some chemical reaction (oxidation or loss of water of crystallization) to occur in certain soil types. The level of oxidation of the solid particles was studied over the drying temperature range of 60 to 140°C for different soils. The period of oven drying necessary for the specimen mass to equilibrate was also examined. The standard practice of oven drying the soil specimens at 110 ± 5°C or 105±5°C over a period of 24 h was confirmed as giving accurate moisture content values for inorganic soils. Oven drying of peat and other highly organic soils over a period of 24 h at 80°C produced similar levels of accuracy in the moisture content measurements as that for inorganic soils at the standard oven drying temperatures of 105 or 110°C. Some oxidation of the organic fraction commenced at between 80 and 90°C.

Determination of hereditary mutations in the BRCA1 gene using archived serum samples and capillary electrophoresis.

Analysis of DNA variation in biological samples most frequently utilizes the polymerase chain reaction (PCR) performed on extracted genomic DNA, followed by visualization of alleles using various methodologies. Few reports have demonstrated that amplification of DNA from plasma and serum samples is possible. We have performed DNA amplification on a large set of serum samples (n = 2955). Here, we report that known hereditary mutations in the BRCA gene can efficiently be analyzed in serum samples collected and stored over several decades. Fragments were PCR-amplified following a short initial denaturation of the serum sample in a standard microwave oven. Fragment analysis was subsequently performed using a DNA capillary-sequencing instrument. The PCR success rates were fragment- and size-dependent ranging from 83.2% to 97.9%. Of the 11,820 polymerase chain reactions performed, the overall PCR success rate was 91.3% (10,796/11,820), which is comparable to PCR performed on genomic DNA. The advantage of the method described herein is its ability to utilize archival material stored in serum biobanks for long periods of time.

1, 2, 4‐Triazine N‐oxide Derivatives: Studies as Potential Hypoxic Cytotoxins. Part II.

New 1, 2, 4-Triazine N-oxide and N, N'-dioxide derivatives were synthesized in order to obtain compounds as selective hypoxic cell cytotoxins. The starting heterocycles have been prepared using a standard microwave oven in a clean and good-yielded process. The reactivity of methyl-1, 2, 4-triazine N(4)-oxide and N(1), N(4)-dioxide with different electrophilic agents has been studied. The desired products were obtained only when iminium electrophiles were employed. The regioselectivity of this process has been studied by means of experimental and theoretical (at ab initio level) procedures. Theoretically was expected that the most stable intermediates where the benzylic-like anion from position 5. A fact which agreed with the experimental observed regioselectivity. The new compounds were tested for their cytotoxicity in oxia and hypoxia. Some of them proved to be less active in hypoxic conditions than tirapazamine, 3-amino-benzo[1, 2-e]1, 2, 4-triazine N(1), N(4)-dioxide. Derivative 19, 6-methyl-5-[2-(5-nitrothienyl)ethenyl)-1, 2, 4-triazine N(4)-oxide, was the most cytotoxic compound, but it was non-selective.

Source apportionment of sediment PAHs in Lake Calumet, Chicago: application of factor analysis with nonnegative constraints.

A factor analysis model with nonnegative constraints (FA) was used to apportion the sources of PAHs found in sediments of Lake Calumet and surrounding wetlands in southeast Chicago. Source profiles and contributions, with uncertainties, are determined with no prior knowledge of sources. The model includes scaling and backscaling of data with average PAH concentrations without sample normalization. This work is a follow-up to a study that used a chemical mass balance (CMB8.2) model to apportion sources to the same data set. Literature source profiles, modified based on gas/particle partitioning of individual PAHs, from eight PAH sources were considered for comparison. FA results for a two-source solution indicate coke oven (45%) and traffic (55%) are the primary PAH sources to Lake Calumet sediments. A six-source FA solution indicates that coke oven (47%) and traffic (45%) related sources are major PAH sources and wood burning-coal residential (2.3%) is a minor PAH source. From the six-source solution, two coke oven profiles are observed, a standard coke oven profile (33%), and a degraded or second coke oven profile (14%) low in phenanthrene and pyrene. Observed traffic related sources include gasoline engine (36%) exhaust and traffic tunnel air (9.3%). This work supports the previous study of Lake Calumet PAHs by CMB model. In addition, FA provides new insights since wood burning and secondary coke oven profiles were not recognized in the CMB model.

Microwave Mischief and Madness

We briefly describe the general function of standard commercial microwave ovens, together with instructions and photos of several amusing, sometimes pyrotechnic demonstrations.