Direct ELlSAs for Sulfathiazole in Milk and Honey with Special Emphasis on Enzyme Conjugate Preparation

Direct competitive enzyme-linked immunosorbent assays (ELISAs) were developed for sulfathiazole (ST) analysis. Polyclonal antibody rabbit serum adsorption to polystyrene microtiter plates was enhanced using a 1 μg/mL Protein A precoating solution. Detection limits (20% reduction in maximum enzyme signal) for ST in milk and honey were 12.0 and 34.7 ppb (ng/L), respectively. ST-horseradish peroxidase (HRP) conjugates prepared by linking the N⁴-amino group of ST to periodate-treated HRP were more efficient than those prepared using a more conventional two-step glutaraldehyde method. This represents a new method of preparing sulfonamide conjugates for use in ELlSAs.     

Enzymatic Browning Control in Minimally Processed Mushrooms

Treatments to control discoloration of minimally processed mushrooms were investigated. Whole or sliced mushrooms were immersed in browning inhibitor solutions and evaluated for color change during storage. Browning was more intense in first break mushrooms than in second, and in unwashed mushrooms compared to washed. However, washing sometimes induced purple discolorations, associated with bacterial lesions. Other discolorations were induced by hypochlorite, 4-hexylresor-cinol, and acidic dips. The most effective treatment was a combination of sodium erythorbate, cysteine, and EDTA at pH 5.5. Addition of preservatives to browning inhibitor dips did not improve storage life. However, dipping in 5% hydrogen peroxide prior to application of browning inhibitors significantly increased shelf-life.     

THE IMPACT OF NEW HOUSING CONSTRUCTION UPON ATTITUDES OF INNER-CITY RESIDENTS: A RESEARCH NOTE

This paper examines the impact of new housing construction upon attitudes of inner-city residents toward their home and neighborhood in eight low income neighborhoods of a midwestern city. Effects are estimated with a quasi-experimental a posteriori design. Data were collected by survey technique from four types of homeowners, three of which served as constructed control groups. Weighted least squares (WLS) regression was used to analyze the data, controlling on race, income, and age. Findings indicate that the housing had an effect upon both neighborhood satisfaction and satisfaction with the home, but the effect upon desire to move was less clear. Since the design can be considered relatively weak on internal validity, a number of threats to the internal validity of the results are systematically examined.     

Nomilin Acetyl-Lyase, a Bacterial Enzyme for Nomilin Debittering of Citrus Juices

Nomilin acetyl-lyase, an enzyme responsible for the conversion of bitter nomilin to nonbitter obacunone was purified from cell-free extracts of Corynebacterium fuscians by (NH₄)₂SO₄ precipitation, followed by HPLC gel filtration and ion exchange chromatography. The electrophoretically pure preparation represented a 1050-fold increase in specific activity with a recovery of 38%. The enzyme, (MW 90,000) required sulfhydryl groups for its catalysis, had a pH optimum of 8.5, a K_m of 38.1 PM, and a V_max of 4.83 μmoles/min. Obacunone A-ring lactone hydrolase, which catalyzes the conversion of obacunone to obacunoate, was also purified from the extract by HPLC gel filtration.     

Effect of ZrO2 Inclusions on the Sinterability of Al2O3

The sinterability of Al₂O₃/ZrO₂ composite powder compacts containing 2 and 10 vol% ZrO₂ was compared to the sinterability of their single-phase constituents through constant-heating-rate experiments. The ZrO₂ inclusion phase delayed the initiation of bulk shrinkage and the temperature of maximum strain rate by 100°C. The ZrO₂ inclusion phase also significantly inhibited grain growth. These results, discussed with regard to the thermodynamics of pore disappearance, suggest that phenomena inhibiting grain growth may also inhibit densification.     

METHODS FOR THE DETECTION OF FOODBORNE LISTERIA MONOCYTOGENES IN THE U.S.

A review of methods for the isolation and detection of Listeria monocytogenes used in the United States is presented. Methods reviewed include the cold enrichment technique, the FDA Method, the USDA Method, and two rapid techniques, the Listeria-Tek enzyme-linked immunosorbent assay and the Gene-Trak Listeria Assay. Comparisons of new rapid biochemical test kits, the MICRO-ID LISTERIA System, API Listeria, and the Rosco system vs. conventional tests of identification are also reviewed. Contemporary isolation methods detect all Listeria species so confirmation of L. monocytogenes is still necessary after isolation. The USDA method is the most practical of the cultural methods due to the rapid reporting of negative samples. Rapid methods (Listeria-Tek and the Gene-Trak Listeria Assay) are faster and more objective than cultural procedures but still depend on sample enrichment for detection of Listeria. These rapid techniques are best utilized when screening large numbers of food samples. All the rapid biochemical test kits reviewed provide fast reliable identification of Listeria species when compared to classical techniques. However, the API Listeria system identifies the test strains without a complementary CAMP test. Refinements are still needed in both cultural and rapid methods. Future Listeria methodology must emphasize molecular techniques not requiring enrichment which would be both rapid and specific for L. monocytogenes.     

High-Temperature Thermal Expansion Behavior of Refractory Materials: I, Selected Monocarbides and Binary Carbides

An apparatus for absolute thermal expansion measurements has been developed and operated to 2843°C. Thermal expansion characteristics have been measured for niobium carbide, zirconium carbide, tantalum carbide, and the carbide solutions 8TaC·ZrC, 4TaC·ZrC, TaC·ZrC, and TaC·4ZrC. Supporting evidence for a high temperature inversion in the monocarbides of zirconium and tantalum has been observed. Evidence of analogous behavior for other carbides is also reported.     

Effects of Interfacial Films on Thermal Stresses in Whisker-Reinforced Ceramics

Toughening of whisker-reinforced (or fiber-reinforced) ceramics by whisker pullout requires debonding at the whisker/matrix interface. Compressive clamping stresses, which would inhibit interface debonding and/or pullout, are expected in composites where the matrix has a higher thermal expansion coefficient than the whisker. Because such mismatch in thermomechanical properties can result in brittle composites, it is important to explore approaches to modify the thermal stresses in composites. As a result, the effects of a film at the whisker/matrix interface on the stresses due to thermal contraction mismatch upon cooling are considered in this study. Analysis of various properties of the film are considered for the whisker/matrix systems, in particular for SiC/Al₂O₃, SiC/cordierite, and SiC/mullite composites. Reduction of thermomechanical stresses is shown to occur when the interfacial film has a low Young's modulus. Also, when the whisker has a lower thermal expansion coefficient than the matrix (e.g., SiC/Al₂O₃), the interfacial stresses generated during cooling decrease as the thermal expansion coefficient of the film increases.     

Liquid Immiscibility in the System Na2O-ZnO-B2O3-SiO2

The limits of miscibility within a portion of the system Na₂O-ZnO-B₂O₃-SiO₂ were determined at 650°, 800°, and 950°C. The miscibility gap at 800° and 950°C is a low dome, adjoining the zinc borosilicate miscibility gap. Below 755°C the dome intersects the Na2O-B₂O₃-SiO₂ face of the phase diagram. The locus of this intersection is in agreement with literature data on the sodium borosilicate system. Estimated tie-line placement in the ZnO-B₂O₃-SiO₂ miscibility gap at 1300°C resembles those reported for the corresponding CaO and SrO systems. The microscopic morphology of glasses with the weight composition xNa₂O-18ZnO-18B₂O₃-64SiO₂ with 0≤×≤12 is described in detail.     

A theory of cross-validation error

Abstract

This paper presents a theory of error in cross-validation testing of algorithms for predicting real-valued attributes. The theory justifies the claim that predicting real-valued attributes requires balancing the conflicting demands of simplicity and accuracy. Furthermore, the theory indicates precisely how these conflicting demands must be balanced, in order to minimize cross-validation error. A general theory is presented, then it is developed in detail for linear regression and instance-based learning