Thermal inactivation, growth, and survival studies of Listeria monocytogenes strains belonging to three distinct genotypic lineages

Twenty-one Listeria monocytogenes strains belonging to three different genotypic lineages were evaluated for differences between lineages and between individual strains with respect to thermal inactivation, growth, and survival. Three sets of heat inactivation conditions (60 degrees C, pH 6.0, and 0.5 M lactate; 55 degrees C, pH 6.0, and 0.5 M lactate; and 50 degrees C, pH 4.0, and 0.5 M lactate) were used on strains grown in modified brain heart infusion (BHI) broth with and without glucose. Two sets of growth conditions (35 degrees C, pH 6.5, and 0.1 M lactate and 5 degrees C, pH 6.5, and 0.1 M lactate) were used with modified BHI broths to determine lag phases and exponential growth rates. Two sets of conditions (28 degrees C, pH 4.0, and 1 M lactate and 28 degrees C, pH 4.5, and 0.5 M lactate) were used with modified BHI broth to determine survival times (D-values). Thermal inactivation D-values were consistently lowest for lineage III, but differences were not significant for any set of conditions tested. Some significant differences were observed between lineages with respect to some of the growth and survival conditions tested. Extensive strain-to-strain variation was observed for all parameters tested. Average coefficients of variation for the thermal inactivation, growth, and survival studies were 0.31, 0.18, and 0.26, respectively. Strain-to-strain variations were approximately equal to the uncertainties associated with the analytical procedures. The results obtained indicate a diversity among strains encountered in food processing that must be accounted for in process calculations and risk assessments.     

Localization of the human NMDAR2D receptor subunit gene (GRIN2D) to 19q13.1-qter, the NMDAR2A subunit gene to 16p13.2 (GRIN2A), and the NMDAR2C subunit gene (GRIN2C) to 17q24-q25 using somatic cell hybrid and radiation hybrid mapping panels

1. Three hundred 4-week-old commercial Hibrow broiler chicks were fed ad libitum, 85% and 70% of ad libitum or ad libitum for 5 d per week with 3rd and 5th days of food withdrawal for 28 d to examine the effects of food restriction on liveweight, growth rate, food conversion efficiency, dressing percentage, abdominal fat and mortality. 2. Quantitative food reduction to 85% and 70% of ad libitum, and reduction in feeding time by 2 d/week significantly reduced final body weight and rate of growth. 3. Food restriction (to 70% ad libitum) resulted in lower abdominal fat than ad libitum feeding, 15% food restriction or reduction in feeding time by 2 d/week. 4. There were no significant differences between the effects of 15% food restriction and 2-d reduction in feeding time per week on final body weight, growth rate and abdominal fat. 5. Reduction in feeding time by 2 d/week resulted in the same food efficiency as ad libitum feeding and quantitative food restriction by 15% and a significantly better food efficiency than 30% quantitative food reduction. 6. Reducing feeding time by 2 d/week seemed to have less severe effects on the birds than quantitatively reducing food supply by 30%.     

Efficient bit-serial multiplication and the discrete-timeWiener-Hopf equation over finite fields

Discrete-time Wiener-Hopf equations (DTWHEs) over finite fields are considered. It is shown that solving the DTWHE is equivalent to performing division over finite fields. The proof provides a new interpretation of the relationship between bit-serial multiplication and DTWHEs. The interpretation enables bit-serial multiplication over GF(2 ^m) to be understood more easily. As an example, bit-serial multiplication methods for multiplying any two elements that can be done without performing any transformation, or with only a simple transformation of the bases, are presented     

Speed discrimination of stereoscopic (cyclopean) motion

This study investigated the degree to which speed of stereoscopic translational motion (i.e. moving binocular disparity information) can be discriminated in a display that minimizes position information. Observers viewed dynamic random-element stereograms depicting arrays of randomly positioned stereoscopic dots that moved bidirectionally. Two tasks were performed: a speed discrimination task and a displacement discrimination task. Across a range of conditions, speed could be discriminated under conditions in which displacement could not. Thus, speed of stereoscopic motion can be discriminated when position information is minimal. This result indicates that stereoscopic motion is sensed in a way that cannot be explained by feature tracking or by inferring the motion from memory of position and time.     

Ethanol, flunitrazepam, and pentobarbital modulation of GABAA receptors expressed in mammalian cells and Xenopus oocytes

GABAA receptors composed of human alpha 1 beta 2 gamma 2L, alpha 1 beta 2 gamma 2S, alpha 1 beta 3 gamma 2S, alpha 6 beta 3 gamma 2S, and alpha 5 beta 3 gamma 3 subunits as well as bovine alpha 1 beta 1 gamma 2L and alpha 1 beta 1 subunits were stably expressed in mammalian L(tk-) cells and transiently expressed in Xenopus oocytes. Effects of muscimol, ethanol, flunitrazepam, and pentobarbital on receptor function were compared for the two expression systems using a 36Cl- flux assay for cells and an electrophysiological assay for oocytes. Muscimol activated all receptors in both expression systems but was more potent for L(tk-) cells than oocytes; this difference ranged from 2.6-to 26-fold, depending upon subunit composition. The most pronounced differences between receptors and expression systems were found for ethanol. In L(tk-) cells, low (5-50 mM) concentrations of ethanol potentiated muscimol responses only with receptors containing the gamma 2L subunit. In oocytes, concentrations of 30-100 mM produced small enhancements for most subunit combinations. Flunitrazepam enhanced muscimol responses for all receptors except alpha 6 beta 3 gamma 2S and alpha 1 beta 1, and this enhancement was similar for both expression systems. Pentobarbital also enhanced muscimol responses for all receptors, and this enhancement was similar for L(tk-) cells and oocytes, except for alpha 6 beta 3 gamma 2S where the pentobarbital enhancement was much greater in oocytes than cells. The alpha 6 beta 3 gamma 2S receptors were also distinct in that pentobarbital produced direct activation of chloride channels in both expression systems. Thus, the type of expression/assay system markedly affects the actions of ethanol on GABAA receptors and also influences the actions of muscimol and pentobarbital on this receptor. Differences between these expression systems may reflect posttranslational modifications of receptor subunits.     

ACETIFICATION IN CIDERS AND PERRIES

Acetic acid is formed by many different micro-organisms at various stages in the manufacture and storage of ciders and perries. These include the action of “wild” yeasts, fermenting yeasts, lactic and acetic acid bacteria. Formerly acetification resulted mainly from access of air but recently anaerobic processes have been found which lead to acetic acid formation. The biochemical pathways by which this product is formed from sugars and organic acids are described. Methods of minimizing acetic acid formation are suggested.     

Estimation of the monomeric phenolics of ciders

A method is described for the separation and quantitative determination of the monomeric phenolics of ciders. These are fractionally eluted from a silica-gel column with 2-methylpropan-2-ol/chloroform mixtures of increasing 2-methylpropan-2-ol content. The u.v. spectrum of each fraction is obtained in the range 250-400 nm. Fractions containing hydroxycinnamic acid esters of quinic acid are first irradiated with u.v. light to equilibrate cis and trans forms. The concentration of each of the phenolics is calculated from extinctions at appropriate wavelengths. Ciders from some cider-apple cultivars contained in order of decreasing concentration 5-chlorogenic acid, 4-p-coumarylquinic acid, catechins, phloridzin and phloretin xyloglucoside. In one cultivar catechins were undetectable while in others they exceeded the p-coumarylquinic acid. The contribution of the phenolics to the tannin content is discussed.     

On the state and parameter estimation for maneuvering reentry vehicles

This paper examines several versions of the extended Kalman filter which can be used to estimate the position, velocity, and other key parameters associated with maneuvering reentry vehicles. These filters are discussed in terms of the fundamental problems of modeling accuracy, filter sophistication, and the real-time computational requirements. Techniques which adaptively increase the process noise to compensate for modeling errors during the maneuvers are examined.