Highly efficient full-vectorial 3-D BPM modeling of fiber to planarwaveguide couplers

The behavior of a fiber-slab coupler used as a polarization and wavelength tunable filter is studied both experimentally and theoretically. The theoretical model is based on a three-dimensional (3-D) fully vectorial beam propagation method (BPM), whose main features concern its high efficiency from the point of view of memory and central processing unit (CPU) requirements. The device characteristics have been measured and the results of the comparisons among experimental and theoretical two-dimensional (2-D) and 3-D numerical modeling are reported and discussed. They show a very good agreement In the 3-D case where field polarization, coupling terms and z-variant structures are taken into account     

Physical Properties of Pecans Relating to Shelling Efficiency

Inshell pecans of 21 cultivars and numbered trial selections were evaluated for selected physical properties and for their adaptability to be efficiently shelled by existing commercial technology. Processing efficiency was based on yield of unbroken half kernels during shelling. There were highly significant differences among varieties in both selected physical properties and shelling efficiency. Correlations between shelling efficiency and physical properties were determined. Results showed that percent total kernel, inshell length/diameter ratio and shell thickness were the physical properties that appeared to have the greatest effect on shelling efficiency.     

Cotyledon Structure of Resting Peanut (Arachis Hypogaea L. cv. Florunner) Seed Before and After Hydraulic Pressing

The cotyledon structure of resting peanut (Arachis hypogaea L. cv. Florunner) seed before and after hydraulic pressing was investigated with light and scanning electron microscopy. Observations were made of the appearance of cell walls and the major subcellular components: spherosomes (oil reserve bodies), aleurone grains and starch grains. Major findings include previously unreported cell wall damage and surface fissures that may be important to processors who express the oil from peanuts.     

Polyphenol Oxidase System in Red Delicious Apples

The polyphenol oxidase system (E.C. 1.14.18.1) in‘Red Delicious’apples (Malus domestica) was investigated. Polyacrylamide gel electrophoresis (PAGE) revealed two active isoenzymes as detected with pyrocatechol substrate. The crude enzyme extract (acetone powder) was found to have one optimum pH of 6.2 and one optimum temperature for the browning reaction of 30°C with the experimental conditions described. The Michaelis constant (Km) as an average of the two active enzyme forms was 2.2 × 10^?lM pyrocatechol and the average maximum velocity (Vmax) was 4.8 × 10^?l AA390 per minute.     

Establishing Thermal Processes for Products with Straight-Line Heating Curves from Data Taken at Other Retort and Initial Temperatures

Heat penetration data were obtained at high and low retort temperatures (RTs) and at high and low product initial temperatures in two can sizes for food products displaying straight-line heating curves in an agitating retort. The extrapolation of data to other RTs was found to be a safe practice for products heating with conduction or significant induced convection. Extrapolating to lower RTs for intermediate viscosity products slightly underpredicted required processing times. The effect of initial temperature was consistent with that found in a previous study for broken-heating products in a still retort, in that heat penetration tests conducted at different initial temperatures can have a significant influence on process establishment, depending on the product.     

Physicochemical Properties of Ovalbumin and Lysozyme Treated with Oleic Acid

Results from polyacrylamide gel electrophoresis confirmed that proteins were more negatively charged in the presence of oleic acid. The electrophoretic mobility of unmodified and modified lysozyme was of opposite but similar magnitude. Critical micelle concentration (50.0 μ M) of oleic acid suggested that association between the fatty acid and proteins was mostly hydrophobic. Muramidase activity of modified lysozyme and difference spectra of modified ovalbumin suggested that oleic acid was partially or totally surrounding the proteins. Improved freeze-thaw characteristics of treated egg white were attributed to greater negative charge and instability of proteins produced by oleic acid.     

Characterization of HgCdTe Diodes on Si Substrates Using Temperature-Dependent Current-Voltage Measurements and Deep Level Transient Spectroscopy

Reverse current in diodes can be dominated by generation processes, depending exponentially on temperature according to the rate-limiting step in the generation process. In this report, the current-voltage-temperature (IVT) relationship is analyzed for several midwave infrared and long-wave infrared (MWIR x = 0.295, LWIR x = 0.233) Hg_1−x Cd _x Te (MCT) diodes. The energy varied from diode to diode. At high reverse biases, the energy tends toward the band gap energy. Close to zero bias, the energy ranged from 0.06 to 0.1 eV. Deep level transient spectroscopy (DLTS) showed a broad peak centered at 55–80 K for the MWIR MCT. Comparison of the DLTS spectrum to a simulation based on the energy and capture cross section from a rate window analysis shows that the peak is a band of traps. The capacitance transient amplitude increased as the filling pulse increased from 1 μs to 0.1 s, consistent with capture at a dislocation. A shift to lower temperatures for the peak was also observed when the diodes are cooled under forward bias. The shift is reversible, indicating that the traps consist at least partially of a bistable defect.     

KINETIC ANALYLSIS OF THE FORMATION OF NITROSYLMYOGLOBIN

The formation of nitric oxide myoglobin (nitrosylmyoglobin) was followed in buffered solutions in which the concentrations of ascorbate, nitrite, chloride, myoglobin and hydrogen ion were varied systematically to determine their effect on the rate constants. The rate of formation of nitrosylmyoglobin was zero order with respect to the pigment. The orders for the other reactants were determined by plotting the zero order rate constants as functions of varying orders of each reagent to determine which order gave a linear plot. The results were used to develop a mechanism and a mathematical expression for the reaction. Two reaction sequences involving different nitrosating species were involved; 1, direct action of nitrous acid and 2, the formation of nitrosyl chloride. Both species then nitrosated ascorbate and ascorbic acid, by different mechanisms. The nitric oxide for nitrosylmyoglobin formation came from the nitrosated ascorbate.     

Carrot Dehydration—Optimization Process Studies on the Explosion-Puffing Process

A carrot dehydration process that includes the unique continuous explosion-puffing system (CEPS) is described. A drying study included moisture distribution throughout a two-stage pilot scale dryer as well as bed temperature during first stage drying. Shrinkage losses of carrots by two dehydration methods were investigated, and volume differences were obtained. Measurements of dried carrot properties such as bulk density, color, nonenzymatic browning, rehydration, and disintegration were used to determine optimum operating pressure, temperature, and feed moisture for CEPS. Response surfaces developed from these properties were used simultaneously to establish a constrained optimum.     

MULTI-RESIDUE DETERMINATION AND CONFIRMATION OF TEN HETEROCYCLIC AMINES IN COOKED MEATS

Heterocyclic aromatic amines (HAAs) have been identified in various cooked meat products. HAAs are formed from pyrolysis of proteins and amino acids and are of interest because many of these primary arylamines are mutagens and rodent carcinogens. We developed a screening method for ten HAAs using liquid-liquid extraction, reverse-phase HPLC separation, and tandem electrochemical (ECD) and fluorescence (FLU) detectors. This detection system exhibited greater sensitivity (50-100 fold) for HAAs than the HPLC-UV methods. HPLC-FLU has detection limits of 100 pg to 1 ng for six HAAs, and HPLC-ECD detection limits of four HAAs were 250 pg to 1 ng. We also developed a confirmatory procedure for ten HAAs using HPLC coupled to positive ion APCI-MS. This technique has subnanogram detection limits. These methods were used to quantify HAAs in meat products at levels formed by typical Western cooking methods.