Inoculation of beef with low concentrations of Escherichia coli O157:H7 and examination of factors that interfere with its detection by culture isolation and rapid methods

Currently used industry testing programs require the ability to detect Escherichia coli O157:H7 in samples of beef trim or ground beef at levels as low as 1 CFU/375 g. We present a reliable protocol for generating a control inoculum for verification testing at this low concentration and evaluate its use. Results show that half of all samples received no cells when 1 CFU was the target concentration and that targets greater than 3 CFU were much more reliable. Detection by culture isolation and two commercial assays, Qualicon BAX-MP and BioControl GDS, detected 94% ± 11%, 92% ± 10%, and 92% ± 7% of samples inoculated with 5.4 CFU (range 1 to 9 CFU), respectively. We also examined the effect of background aerobic plate count (APC) bacteria and fat content effects on the detection of E. coli O157:H7. At APC concentrations below 6 log CFU/g, the rapid methods detected all beef trim samples inoculated with 26 CFU of E. coli O157:H7 per 65 g. At an APC of 6.7 log CFU/g, culture, BAX-MP, and GDS detected 100, 75, and 13%, respectively, of inoculated samples. Neither commercial method detected E. coli O157:H7 in the samples when APC was 7.7 log CFU/g, whereas culture was able to detect 63% of E. coli O157:H7 in the samples when APC was at this concentration. Increased fat content correlated with decreasing recovery of immunomagnetic separation beads, but this was not observed to interfere with detection of E. coli O157:H7.     

Evaluation of various antimicrobial interventions for the reduction of Escherichia coli O157:H7 on bovine heads during processing

The effectiveness of electrolyzed oxidizing water, FreshFx, hot water, DL-lactic acid, and ozonated water was determined using a model carcass spray-washing cabinet. A total of 140 beef heads obtained from a commercial processing line were inoculated with Escherichia coli O157:H7 on the cheek areas. Each head was exposed to a simulated preevisceration wash and then had antimicrobial wash treatments. Hot water, lactic acid, and FreshFx treatments reduced E. coli O157:H7 on inoculated beef heads by 1.72, 1.52, and 1.06 log CFU/cm2, respectively, relative to the simulated preevisceration wash. Electrolyzed oxidizing water and ozonated water reduced E. coli O157:H7 less than 0.50 log CFU/cm2. Hot water, lactic acid, and FreshFx could be used as decontamination washes for the reduction of E. coli O157:H7 on bovine head and cheek meat.     

Reasoning Processes in Propositional Logic

We conducted a computer-based psychological experiment in which a random mix of 40 tautologies and 40 non-tautologies were presented to the participants, who were asked to determine which ones of the formulas were tautologies. The participants were eight university students in computer science who had received tuition in propositional logic. The formulas appeared one by one, a time-limit of 45 s applied to each formula and no aids were allowed. For each formula we recorded the proportion of the participants who classified the formula correctly before timeout (accuracy) and the mean response time among those participants (latency). We propose a new proof formalism for modeling propositional reasoning with bounded cognitive resources. It models declarative memory, visual memory, working memory, and procedural memory according to the memory model of Atkinson and Shiffrin and reasoning processes according to the model of Newell and Simon. We also define two particular proof systems, T and NT, for showing propositional formulas to be tautologies and non-tautologies, respectively. The accuracy was found to be higher for non-tautologies than for tautologies (p < .0001). For tautologies the correlation between latency and minimum proof length in T was .89 and for non-tautologies the correlation between latency and minimum proof length in NT was .87.     

National Conference on Postdoctoral Training in Professional Psychology.

The Ann Arbor Conference on postdoctoral training (held in October 1992) was the 1st national conference to focus on the articulation of standards for postdoctoral education and training in professional psychology. Experts in education, practice, and credentialing drafted a policy document addressing the purposes of postdoctural training; entrance requirements; program content, structure, and organization; supervision; faculty–staff; evaluation mechanisms; and recommendations for the promotion of excellence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of boiler control to improve the load-following capability of power-plant units

The capability to perform fast load changes has been an important issue in the power market, and will become increasingly more so due to the increasing commercialization of the European power market. An optimizing control system for improving the loadfollowing capability of power-plant units has therefore been developed. The system is implemented as a complement, producing control signals to be added to those of the existing boiler control system, a concept which has various practical advantages in terms of implementation and commissioning. The optimizing control system takes account of the multivariable and load-dependent nonlinear characteristics of the boiler process, as a scheduled LQG controller with feedforward action is utilized. The LQG controller improves the control of critical process variables, making it possible to increase the load-following capability of a specific plant. Field tests on a 265 MW coal-fired power-plant unit reveals that the maximum allowable load gradient that can be imposed on the plant, can be increased from 4 to 8 MW/min.     

Three-wavelength electronic speckle pattern interferometry with the Fourier-transform method for simultaneous measurement of microstructure-scale deformations in three dimensions

We present the simultaneous measurement of three-dimensional deformations by electronic speckle pattern interferometry using five object beams and three colors. Each color, corresponding to an orthogonal direction of displacement, is separated through dichroic filtering before being recorded by a separate CCD camera. Carrier fringes are introduced by tilting the beam path in one arm of each of the three interferometers. The measured deformation modulates these carrier fringes and is extracted using the Fourier-transform method to achieve high displacement sensitivity. The field of view is on the order of a millimeter, making the system suitable for study of microstructural deformations. We compare experimental results with calculated values to validate out-of-plane and in-plane deformation measurements and demonstrate sensitivity on the order of 10 nm.     

Spreading dynamics of a functionalized polymer latex

Functionalized polymer nanoparticles are used as binders for inorganic materials in everyday technologies such as paper and coatings. However, the functionalization can give rise to two opposing effects: It can promote adhesion via specific interactions to the substrate, but a high degree of functionalization can also hamper spreading on substrates. Here, we studied the spreading kinetics of individual functionalized vinyl acetate-co-ethylene polymer nanoparticles on inorganic substrates by atomic force microscopy (AFM) imaging. We found that the kinetics underwent a transition from a fast initial regime to a slower regime. The transition was independent of functionalization of the particles but depended on the wettability of the substrate. Furthermore, the transition from the fast regime to the slow regime occurred at a size-dependent contact angle, leading to a h ～ a(3/2) scaling dependence between the height (h) and the width (a) of the spreading particles. Thereafter, spreading continued on a slower time scale. In the slow regime, the kinetics was blocked by a high degree of functionalization. We interpret the observations in terms of a nanoscale stick-slip transition occurring at interface stress around 6 kPa. We develop models that describe the scaling relations between the particle height and width on different substrates.     

Evaluating the potential of plastic-containing materials as alternative reducing agents

The amount of discarded plastic-containing materials is increasing, and one option to help with this issue is to use these materials in bath smelting processes. The injection of plastic-containing materials to partially substitute coal in zinc-fuming processes has been studied in an industrial trial at Boliden–Rönnskär smelter. To evaluate the potential of plastic-containing materials, thermodynamic calculations were performed in this study. In the first step, a thermodynamic calculation was performed for trials with only coal injection, and then this calculation was applied to trials with the co-injection of plastic materials. The thermodynamic calculation shows that not all the injected coal participates in the reactions within the slag. Similarly, the calculation with the co-injection of plastic-containing materials shows that different amounts of each plastic material participate in the reactions within the slag bath.     

A hub location problem with fully interconnected backbone and access networks

This paper considers the design of two-layered fully interconnected networks. A two-layered network consists of clusters of nodes, each defining an access network and a backbone network. We consider the integrated problem of determining the access networks and the backbone network simultaneously. A mathematical formulation is presented, but as the linear programming relaxation of the mathematical formulation is weak, a formulation based on the set partitioning model and column generation approach is also developed. The column generation subproblems are solved by solving a series of quadratic knapsack problems. We obtain superior bounds using the column generation approach than with the linear programming relaxation. The column generation method is therefore developed into an exact approach using the branch-and-price framework. With this approach we are able to solve problems consisting of up to 25 nodes in reasonable time. Given the difficulty of the problem, the results are encouraging.