Relating microbiological criteria to food safety objectives and performance objectives

Microbiological criteria, food safety objectives and performance objectives, and the relationship between them are discussed and described in the context of risk-based food safety management. A modified method to quantify the sensitivity of attributes sampling plans is presented to show how sampling plans can be designed to assess a microbiological criterion. Examples presented show that testing of processed foods for confirmation of safety is often not a practical option, because too many samples would need to be analysed. Nonetheless, in such cases the classical “ICMSF cases” and sampling schemes still offer a risk-based approach for examining food lots for regulatory or trade purposes.     

Stabilization of anionic adducts in negative ion electrospray mass spectrometry

Attachment of small anions to neutral molecules is an important ionization mechanism in negative ion electrospray mass spectrometry. In this report, the tendency for different anions to remain attached to selected analyte compound classes has been systematically investigated. A rationale for the formation and stability of preferred anionic adducts is proposed in light of thermodynamic considerations. A series of collision-induced dissociation experiments reveals that the gas-phase basicities of the deprotonated analyte molecule ([M - H]-) and the anion moiety play important roles in determining the stability of anionic adducts. Adducts of the form [M - H]-...H+...[anion]- manifest increased stability when the two anions have similar gas-phase basicities. Within certain limitations, the difference in deltaG degrees values for proton combination with [M - H]- and with [anion]- can be used as a first-order predictor of adduct stability. In addition, stability increases with the rising gas-phase basicities of the two moieties. The specific interaction between a small inorganic anion (bisulfate) and a neutral analyte molecule (alpha-D-glucose) in the form of multiple hydrogen bonding has also been affirmed by computer modeling to contribute to the stability of some anionic adducts. Last, the gas-phase basicity of deprotonated alpha-D-glucose (i.e., the gas-phase acidity of alpha-D-glucose) is determined by a "bracketing method" to be in the range of 1373-1407 kJ/mol.     

Security in storage: a call for participation

The present treatment of stored critical information, especially personal portable storage, provides inadequate protection. Through many means, the IEEE is examining the issue of security in storage and working to make technologies and standards available that advance the interests of society and protect its many critical functions.     

Stress exposure and stress generation in child and adolescent depression: A latent trait-state-error approach to longitudinal analyses.

In 2 longitudinal studies of negative life events and depressive symptoms in adolescents (N = 708) and in children (N = 508), latent trait-state-error structural equation models tested both the stress generation hypothesis and the stress exposure hypothesis. Results strongly suggested that self-reports of depressive symptoms reflect the influence of a perfectly stable trait factor as well as a less stable state factor. Support emerged for both the stress generation model and the stress exposure model. When the state depression factor was modeled as predicting stress, support for the stress generation model appeared to increase with age. When the trait depression factor was modeled as the predictor of stress, support for the stress generation model did not vary with the child's age. In both models, support for the stress exposure remained relatively constant across age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Installation of Horizontal Wells in Landfilled Waste Using Directional Drilling

Leachate levels within a landfill must often be controlled for environmental and/or regulatory reasons by means of pumping from wells. Conventional vertical wells are usually used for this purpose, but there is a perception that they are inefficient. In this paper, the feasibility of using directional drilling to install horizontal wells for leachate control in landfills is investigated with reference to pilot and full scale field trials at Rainham, U.K. The difficulties of well-screen design and installation in a landfilled waste are discussed; the insights gained during trial installation are described; and the effectiveness of three trial wells is assessed with reference to the leachate flow rates and drawdowns achieved, in comparison with conventional vertical wells. It is concluded that the drilling rig used must be sufficiently powerful to cope with the likelihood of at least partial borehole collapse around the well-screen during installation; that the screen slot size can be based on at least the D30 particle size of the waste and a natural filter allowed to develop around the well (provided that the resulting well screen is strong enough); and that as experience with the technology grows, directionally drilled horizontal wells could represent a viable, cost effective alternative to conventional vertical wells for leachate control in landfills.     

Cyclic Lateral Load Behavior of a Pile Cap and Backfill

A series of static cyclic lateral load tests were performed on a full-scale 4×3 pile group driven into a cohesive soil profile. Twelve 324-mm steel pipe piles were attached to a concrete pile cap 5.18×3.05?m in plan and 1.12?m in height. Pile–soil–pile interaction and passive earth pressure provided lateral resistance. Seven lateral load tests were conducted in total; four tests with backfill compacted in front of the pile cap; two tests without backfill; and one test with a narrow trench between the pile cap and backfill soil. The formation of gaps around the piles at larger deflections reduced the pile–soil–pile interaction resulting in a degraded linear load versus deflection response that was very similar for the two tests without backfill and the trenched test. A typical nonlinear backbone curve was observed for the backfill tests. However, for deflections greater than 5 mm, the load-deflection behavior significantly changed from a concave down shape for the first cycle to a concave up shape for the second and subsequent cycles. The concave up shape continued to degrade with additional cycles past the second and typically became relatively constant after five to seven cycles. A gap formed between the backfill soil and the pile cap, which contributed to the load-deflection degradation. Crack patterns and sliding surfaces were consistent with that predicted by the log spiral theory. The results from this study indicate that passive resistance contributes considerably to the lateral resistance. However, with cyclic loading the passive force degrades significantly for deflections greater than 0.5% of the pile cap height.     

Modeling relations between hassles and internalizing and externalizing symptoms in adolescents: A four-year prospective study.

This study examined the relations between hassles and internalizing and externalizing symptoms across 4 years in adolescents who varied with regard to their risk for psychopathology. The sample comprised 240 adolescents assessed in 6th, 7th, 8th, and 9th grades regarding their level of peer and academic hassles and internalizing and externalizing symptoms. Structural equation modeling was used to construct latent variables of hassles and internalizing and externalizing syndromes. Results varied by informant about the teens' symptoms. For adolescent report, the stress exposure model fit the data best for internalizing syndromes; that is, higher levels of stressors predicted significantly higher levels of self-reported symptoms 1 year later. For mother report of adolescents' symptoms, the stress generation model fit the data best for both internalizing and externalizing syndromes; that is, higher levels of adolescents' internalizing and externalizing symptoms, as reported by their mothers, significantly predicted higher levels of hassles 1 year later. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimating the survival of Clostridium botulinum spores during heat treatments

A recently published study of the inactivation of Clostridium botulinum spores at various temperatures in the range of 101 to 121 degrees C and neutral pH revealed that their semilogarithmic survival curves all had considerable upward concavity. This finding indicated that heat inactivation of the spores under these conditions did not follow a first-order kinetics and that meaningful D values could not be calculated. The individual survival curves could be described by the cumulative form of the Weibull distribution, i.e., by log S = -b(T)t(n(T)), where S is the survival ratio and b(T) and n(T) are temperature-dependent coefficients. The fact that at all temperatures in the above range n(T) was smaller than 1 suggested that as time increases sensitive members of the population parish and survivors with increasing resistance remain. If damage accumulation is not a main factor, and the inactivation is path independent, then survival curves under monotonously increasing temperature can be constructed using a relatively simple model, which can be used to calculate the spores' survival in a limiting case. This is demonstrated with computer-simulated heating curves and the experimental constants of the C. botulinum spores, setting the number of decades reduction to 8, 10, and 12 (the current criterion for commercial sterility).     

Survival of bacteria during oxygen limitation

Regulatory mechanisms that enable bacteria associated with food, drinks and the human body to adapt to changes in the availability of oxygen are reviewed. Excess oxygen induces two adaptive responses to oxidative stress. Five or more control circuits enable enteric bacteria to generate energy and grow well in anaerobic environments. Two sets of enzymes catalyse both nitrate and nitrite reduction, and dual two-component regulatory systems sense and respond to the available nitrate and nitrite in the environment. The periplasmic nitrate reductase enables bacteria to scavenge low concentrations of nitrate: similar systems are found in food-borne and other pathogens.