Behavior of Nonproteolytic Clostridium botulinum Type B and E Spores in Cooked Turkey and Modeling Lag Phase and Probability of Toxigenesis

A spore pool inoculum (I) of 4 each type B and E nonproteolytic C. botulinum was applied at levels of log₁₀-2 to 4 spores per 2–3g sample of cooked turkey (0, 1.47, and 2.2% brine (B), respectively), stored under vacuum at 4, 8, 12, 16, 20, and 30°C up to 180 days. Earliest toxin production at the above temperatures (T) was detected in 0% brine meat after > 180, 8, 4, 1.5, 1.5, and 0.5 days, in the 1.47% brine after 70, 8, 7, 2, 1.5 and 1 days, and in the 2.2% brine after 130, 10, 9, 2.5, 1.5 and 1 days, respectively. Lag phase (LP) was affected significantly by T, I, and Txl (p<0.001) but not B (0.0510 LP = 0.625 + 6.710 (1/T) + 0.0005 (I) X (T) ? 0.033 (T) + 0.102 (B) ? 0.102 (I) with R²= 0.970. More precise sampling plans and augmentation of our dataset will increase confidence in the model.     

Precision of light intensity measurement in biological optical microscopy

Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high‐content screening technology. The proper interpretation of data from high‐content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi‐step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide‐field microscope.     

RHEOLOGICAL AND CHEMICAL PROPERTIES OF MOZZARELLA CHEESE

Dynamic viscoelastic parameters and chemical properties of Mozzarella cheese produced using a "no-brine" cheese making method with 3 different cooking temperatures (38, 41, and 44C) were determined. Samples were stored for 3 weeks at 4C before dynamic mechanical analysis at 22C. G', G" and tan δ were 5.8 – 6.4 × 10⁵ dyne/cm², 1.9 – 2.1 × 10⁵ dyne/cm², and 0.33 – 0.35, respectively, at 1% strain and 10 rad/s. The percentage of intact α_s-casein and β-casein were 38–40% and 33–35% of total protein in the cheese, respectively. The range of cooking temperatures used in this experiment had little effect on dynamic viscoelastic properties or the amount of intact protein for the cheese.     

A MAJOR SOLUBLE GLYCOPROTEIN OF POTATO TUBERS1

The major soluble glycoprotein of potato tubers was isolated by chromatography on DEAE cellulose and Con A Sepharose. It contained about 5% neutral sugar and 1%hexosamine, exhibited a molecular weight of 45,000 by SDS gel electrophoresis, and consisted of 6–10 ionic forms as revealed by isoelectric focusing. This glycoprotein comprised about 20%of the soluble protein in all of the 31 tested potato cultivars.     

THE IMPACT FATIGUE PROPERTIES OF PEARLITIC PLAIN CARBON STEELS

A literature search has revealed that the most extensive study of impact fatigue reported is still that of Stanton and Bairstow (1908) who were the first to work on this topic. Their results, which were on pearlitic plain carbon steels, have been reanalyzed in an attempt to deduce from them the effects of chemical composition on impact fatigue in this class of materials. The results show that when the number of impacts to failure, N_f, is greater than about 10³, N_f and the energy absorbed per impact, E_i, are related by the equation: E_i, =E_o+E_kN_f^?p, where E_o appears to be the impact endurance limit. It is suggested that E_k and p be named respectively the “impact fatigue parameter” and “impact fatigue exponent”. E_k is independent of composition except that it is lower by a factor of about four for two materials which probably failed by an intercrystalline rather than transcrystalline fracture; p has a value of 0.6; and E_o increases monotonically with silicon content but does not vary systematically with the carbon, manganese, sulphur or phorphorus contents. The significance of these results is discussed.     

RACIAL COMPOSITION AND NEIGHBORHOOD EVALUATION

While the negative association between racial composition and neighborhood evaluation for white residents is fairly well established, there is less consensus on what are the precise mechanisms which produce this relationship. This paper examines three possible mechanisms in this regard: status loss, perceived decline in the quality of neighborhood services, and fears about personal safety. A survey of nine neighborhoods with different racial mixes finds evidence for the direct effect of racial composition on white residents' evaluations through status loss and its indirect effect through fears about personal safety, but no support for the notion that the racial composition effect operates through negative perceptions of neighborhood public services. Alternatively, having larger numbers of blacks in a neighborhood has a negative effect on black residents through its association with a perception of lower quality public services: at the same time, higher numbers of blacks in a neighborhood has a positive effect on black residents' evaluations of the area, once the association between racial composition and perception of quality of services is taken into account. This positive effect operates directly and also indirectly, through its association with perceptions of greater safety. The implications of these findings for the future of integrated neighborhoods are discussed.