Comparison of a real-time PCR method with a culture method for the detection of Salmonella enterica serotype enteritidis in naturally contaminated environmental samples from integrated poultry houses

Conventional culture methods have traditionally been considered the "gold standard" for the isolation and identification of foodborne bacterial pathogens. However, culture methods are labor-intensive and time-consuming. A Salmonella enterica serotype Enteritidis-specific real-time PCR assay that recently received interim approval by the National Poultry Improvement Plan for the detection of Salmonella Enteritidis was evaluated against a culture method that had also received interim National Poultry Improvement Plan approval for the analysis of environmental samples from integrated poultry houses. The method was validated with 422 field samples collected by either the boot sock or drag swab method. The samples were cultured by selective enrichment in tetrathionate broth followed by transfer onto a modified semisolid Rappaport-Vassiliadis medium and then plating onto brilliant green with novobiocin and xylose lysine brilliant Tergitol 4 plates. One-milliliter aliquots of the selective enrichment broths from each sample were collected for DNA extraction by the commercial PrepSEQ nucleic acid extraction assay and analysis by the Salmonella Enteritidis-specific real-time PCR assay. The real-time PCR assay detected no significant differences between the boot sock and drag swab samples. In contrast, the culture method detected a significantly higher number of positive samples from boot socks. The diagnostic sensitivity of the real-time PCR assay for the field samples was significantly higher than that of the culture method. The kappa value obtained was 0.46, indicating moderate agreement between the real-time PCR assay and the culture method. In addition, the real-time PCR method had a turnaround time of 2 days compared with 4 to 8 days for the culture method. The higher sensitivity as well as the reduction in time and labor makes this real-time PCR assay an excellent alternative to conventional culture methods for diagnostic purposes, surveillance, and research studies to improve food safety.     

Discrete element method (DEM) modelling of evolving mill liner profiles due to wear. Part I: DEM validation

Since the early 1990s the discrete element method (DEM) gained considerable success in its ability to predict the power draw and the load behaviour in mills as affected by operating conditions. The DEM can also be used to design milling equipment and predict the breakage of particles. A detailed validation of this method is required in order to produce accurate results. In this paper, we assess the ability of the DEM to predict forces exerted by the mill charge on liners. Data obtained on an experimental two-dimensional mill designed in order to record the normal and tangential forces exerted on an instrumented lifter bar was available. The measured results are compared to the DEM simulated results. Good agreement has been found in terms of amplitude of forces and positions of shoulder and toe at low speed.     

An Overview of Design Fires for Building Compartments

The worldwide trend of moving towards performance-based codes has brought about a need for computational tools, most of which rely on suitably-defined design fires, to adequately predict the impact of fires on buildings and their occupants. This literature review was carried out to determine the range of methods used to characterize design fires. The methods currently available were found to be largely empirical in nature and unsophisticated. The two main quantities used to describe design fires are the heat release rate (pre-flashover scenario) and temperature-time profiles (post-flashover). The most commonly used pre-flashover design fires are t ² fires, whereas a host of empirical correlations are available for post-flashover design fires.     

The testing and evaluation of trial refrigerants: Part 1. System description

This work is a contribution to the discovery and evaluation of new refrigerants. It has been stimulated by the uncertainty created by the Kyoto Protocol over the long‐term availability of the hydroflorocarbons (HFCs) and also by the need for more knowledge of HFC–oil pairings. An economical method for testing refrigerants in terms of coefficient of performance (COP) and evaporative behaviour in a lubricated system is described. Part 1 describes the equipment, its instrumentation and operating procedures. Part 2 discusses the system output for four test refrigerants: two single fluids R134a and R22 and two test non‐azeotropic blends each having a glide of around 9 K. Study of R22 was confined to evaporative behaviour. The ranking of refrigerants by COP and boiling length is given and the generality of use of these rankings is discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Heat release rates of modern residential furnishings during combustion in a room calorimeter

Results are presented from a number of fire experiments that were conducted in a room environment to study the fire characteristics of typical residential furnishings and assist in the design of a subsequent phase of a project involving fully furnished room fire experiments. The experiments were conducted in a 16‐m² test room (with dimensions 3.8 m wide × 4.2 m long × 2.4 m high), which had a 1.5 × 1.5‐m window opening. The furnishings tested included mattresses, bed clothes, bed assemblies, upholstered seating furniture, clothing arrangements, books, plastic audio/video media and storage cases, toys, shoes, and a computer workstation setup. The smoke (gaseous products of combustion) from the room was collected using a hood system in order to measure the heat release rate (HRR) and optical density of the smoke. The test room was instrumented with load cells, heat flux gauges, thermocouples and velocity probes in order to take the following measurements: mass loss, total heat flux on gauge‐installed flush with the internal surfaces (floor, walls, and ceiling), temperatures at numerous locations, and gas velocities in the window opening. Twin‐size mattresses produced peak HRRs of approximately 3800 kW, and the maximum room temperature was approximately 980°C. The HRRs of bed assemblies of various sizes and configurations ranged from 1800 kW for a twin‐size bed to 6250 kW for a bunk bed. The maximum temperature and heat flux recorded in the experiments were 1071°C and 221 kW/m², respectively. Upholstered chairs and sofas had HRRs ranging from 630 kW for an ottoman to 3360 kW for a two‐seat sofa. In tests with clothing, toys, shoes, books, a computer workstation, and CD/DVD media, the peak HRRs ranged from 440 kW for a bookcase to 2045 kW for toys. Furnishings containing a large proportion of rigid thermoplastic plastics, such as shoes and media cases, produced very dense smoke even at low HRRs. The effect of parameters such as bed clothes, mattress type, foundation type, bed assembly and chair size, material composition, and fuel package arrangement was evident in the results. Because the room dimensions and wall lining materials remained constant, temperatures were linearly proportional to the peak HRR (and exposure time) until the ventilation limit (approximately 4100 kW) was reached. Copyright © 2014 John Wiley & Sons, Ltd.     

Discrete element method (DEM) modelling of evolving mill liner profiles due to wear. Part II. Industrial case study

The wear of tumbling mill liners influences the load behaviour and consequently the performance and efficiency of tumbling mills. The ability to accurately predict the evolving mill liner profile due to wear is therefore of great economic significance since it can be used to determine the optimal initial lifter design for a particular operation. In this paper, we use the discrete element method (DEM) to simulate the load behaviour and predict the wear of two different liners used in industrial mills for the grinding of coal in dry conditions. Our simulated results are compared to industrial measurements in both cases. A good agreement is found between those measurements. Moreover a quick empirical equation is derived for a particular lifter in order to predict the wear without using the DEM.     

Unprotected Floor Assemblies and Tenability Conditions in a Test House Under Two Basement Fire Scenarios

A full-scale experimental program was undertaken to study the impact of two basement fire scenarios on the structural integrity of unprotected floor assemblies above a basement and the tenability conditions in a test facility representing a typical two-storey detached single-family house with a basement. The experiments utilized relatively severe, fast-growing fires set in the basement, which had an unprotected (unfinished) ceiling, to challenge the structural integrity of the floor system above the basement, which provides the normal egress route on the first storey for occupants. A range of floor assemblies constructed with various types of engineered floor joists and trusses (including wood I-joists, steel C-joists, metal plate wood trusses and metal web wood trusses) and with solid-wood joists, were used in the experiments with the basement side unprotected (unsheathed). Potential exposure to toxic gases, heat and smoke obscuration under the test conditions was analyzed to estimate the time available for escape. The results help establish the sequence of fire events such as fire initiation, smoke alarm activation, onset of untenable conditions, and structural failure of the floor assembly above the basement to understand how these factors affect the ability of occupants on the upper storeys to escape in the event of a basement fire.     

Modeling the RTD of an industrial overflow ball mill as a function of load volume and slurry concentration

The role of residence time distribution (RTD) in the accuracy of milling simulation is well appreciated in literature. Accordingly, the development of models that can accurately predict the RTD at various mill operating conditions would be of considerable benefit to the milling industry. In this paper, a 3-parameter RTD model has been derived using the concept of serial stirred mixers with a dead zone. The model parameters were optimized by minimizing the error between experimental tracer response data and model predictions using a MATLAB algorithm. Based on the optimum values of the model parameters, the mean residence time of slurry was evaluated and the effects of ball load volume and slurry concentration examined. The results revealed that the mean residence time of slurry inside the mill is affected to a larger extent by slurry concentration than the ball load volume. An empirical correlation was developed to predict the mean residence time as a function of slurry concentration, ball load volume and slurry feed rate. Over the range of conditions investigated, the mean residence time was observed to vary linearly with slurry concentration and ball load volume but inversely with feed flow rate. Lastly, a test case of the simulated mill product size distribution using the predicted RTD is presented displaying a close match with experimental data.     

Deformation of mild steel plates subjected to large-scale explosions

This paper presents the results of two test programmes in which quadrangular mild steel plates are subjected to pressure loads created by exploding charges ranging from 100 to 26,288 kg. The charge consists of different ordnances stacked in different configurations, namely compacted and widespread in a carpet-like form. The effects of the charge configurations on the response of the square mild steel plates are investigated. Simple analytical evaluations of the pressures and impulses are used for the purpose of comparison with the experiments. The correlation shows satisfactory agreement, despite the imperfect terrain and different complex explosive loading arrangement.     

Potassium Sorbate Does Not Increase Control of Listeria monocytogenes when Added to Zein Coatings with Nisin on the Surface of Full Fat Turkey Frankfurter Pieces in a Model System at 4°C

ABSTRACT: The antimicrobial effect of zein coatings containing nisin and potassium sorbate on turkey frankfurters against Listeria monocytogenes strain V7 at 4°C was determined. Our objectives were (1) to determine whether zein coatings with nisin and potassium sorbate alone or in combinations would reduce the growth of L. monocytogenes on turkey frankfurters at 4°C; (2) to determine the effect of zein, nisin, or potassium sorbate on L. monocytogenes after being challenged with high or low initial inoculum counts (log 6 or log 4); and (3) to determine whether potassium sorbate had any synergistic effect on the activity of nisin. Initial counts decreased for all the treatments containing nisin. Over 28 d, the nisin-alone treatment counts were lower than the control by 6.1 logs for the high inoculum. No cells were detected for the low inoculum test by day 21. The solvent controls (ethanol-glycerol or propylene glycol), yielded mean counts similar to those for zein-ethanol-glycerol or zein-propylene-glycol, giving 4 to 5 log lower counts versus the untreated controls at 28 d. Therefore zein per se had no antimicrobial activity. Use of 0.4% potassium sorbate did not significantly inhibit growth compared with the control or solvent-only controls. No significantly lower counts of L. monocytogenes were observed for zein-nisin coating treatments with sorbate versus without sorbate. Therefore, treatments using nisin alone or in combination with zein, ethanol-glycerol, or propylene glycol if approved for use on ready-to-eat foods, show promise for use as barriers against the growth of recontaminating, L. monocytogenes cells on this food substrate at 4°C.