Development of a 5-Layer Passive Organic Dermal (POD) Sampler

A 5-layer passive organic dermal sampler was developed to allow the collection, retention, and recovery of a variety of organic compound classes simultaneously. The 5-layers, from outside in, consisted of polypropylene, polyurethane foam, C-18 solid-phase extraction disk, ethylene tetrafluoroethylene, and activated carbon cloth. The layers were enclosed in aluminum foil and placed in a muslin envelope that had a 40.0 mm diameter opening.

Ten samplers were spiked separately with three levels of diesel oil, a 50/50 diesel oil/asphalt mixture, and asphalt binder. For the diesel oil spikes, recoveries were 69.9, 71.3, 88.8, and 95.4% for 10, 10, 50, and 100 mg of diesel oil. For the 50/50 mixture, recoveries were 105.4, 92.8, and 92.0% for 10, 50, and 100 mg of the 50/50 mixture. For the asphalt binder spikes, recoveries were 104.7, 100.2, and 100.1% for 10, 50, and 100 mg of asphalt binder. For repeatability assessment, 7 samplers were spiked with 50 mg of the 50/50 mixture and recoveries averaged 92.6% (standard deviation 8.6). Samplers tested on asphalt paving workers proved functional, comfortable, flexible, and durable.     

An Experimentally Validated Model for Two-Phase Sudden Contraction Pressure Drop in Microchannel Tube Headers

This paper presents the results of an experimental investigation of two-phase pressure loss of R134a in microchannel headers using various end-cut techniques. Novel experimental techniques and test sections were developed to enable the accurate determination of minor losses without obfuscating the problem with a lengthwise pressure gradient. This technique represents a departure from approaches used by other investigators that have extrapolated minor losses from air-water experiments and the combined effects of expansion, contraction, deceleration, and lengthwise pressure gradients. In this study, pressure losses were recorded over the entire range of qualities, from 100% vapor to 100% liquid. In addition, the tests were conducted for five different refrigerant mass fluxes between 185 kg/m²-s and 785 kg/m²-s using two different end-cut techniques. More than 790 data points were recorded to obtain a comprehensive understanding of the effects of mass flux and quality on minor pressure losses. High accuracy instrumentation such as coriolis mass flow meters, RTDs, pressure transducers, and real-time data analyses were used to ensure accuracy in the results. The results show that many of the commonly used correlations for estimating two-phase pressure losses significantly underpredict the pressure losses found in compact microchannel tube headers. Furthermore, the results show that the end-cut technique can substantially affect the pressure losses in microchannel headers. A new model for estimating the pressure loss in microchannel headers is presented, and a comparison of the end-cut techniques on the minor losses is reported.     

Effect of Gas Atmosphere Packaging on Psychrotrophic Growth and Succession on Steak Surfaces

The influence of gas atmosphere packaging (1) 15% CO₂, 40% 0₂, 45% N₂; (2) 60% CO₂ 40% 0₂ (3) 10% CO₂, 5% 0₂, 85% N₂; (4) film overwrap (control) on the microbial growth and succession on steaks was studied during storage. Treatment 3 was most effective in reducing psychrotrophic growth on steaks. Pseudomonas species dominated the microflora for all packaging treatments during early storage. In all gas atmospheres. Serratia liquefaciens increased with storage time and the 10% CO₂ atmosphere showed the greatest increase. Enterobacter aerogenes appeared late in the storage period in all atmospheres and Yersinia enterocolitica was isolated after 12 days of storage from steaks in atmosphere 1.     

EFFECT OF FILM PERFORATION ON THE QUALITY OF INDIVIDUALLY SEAL PACKAGED TOMATOES

Freshly harvested, ethylene treated, mature green tomatoes (Lycopersicon esculentum Mill. cv. ‘Flora-Dade’) were individually packaged in heat-shrinkable perforated films and stored at 21°C and 55% RH. The degree of film perforation (exposed surface area, A) was varied as 0, 1.4, 4.5, 11 and 100%, with the hole diameter, D, being constant at 8 mm or D was varied as 0.7, 4, 8 and 16 mm, while A was kept constant at 11%. Films with A = 0 or 1.4% drastically reduced weight loss and tissue softening resulting in tomatoes of good eating quality and bright red color. Off-flavor was detected when films with D = 0.7 mm were used. Large size holes (D = 16 mm) allowed free gas exchange between the fruit and the environment. Results indicated that fruits transpire throughout the entire skin surface area, but respire primarily through the stem scar.     

Experimental verification of the effects of friction and residual stress on the analysis of interfacial debonding and toughness in single fiber composites

Single-fiber fragmentation tests were done on AS4 carbon fiber/epoxy and E-glass/epoxy specimens. Using a new interpretation of the photoelasticity fringes around fiber breaks we measured debonds that occurred instantaneously after each fiber break. The new techniques led to measured debond lengths that were longer than in prior studies. An energy balance analysis of the debond size when the breaks are far apart was used to investigate the interfacial fracture toughness. The best analysis was one that accounted for both residual stress effects and interfacial friction. It was not possible to determine all effects by debonding experiments alone and thus the most accurate results for interfacial toughness require supplemental experiments such as Raman spectroscopy or additional fragmentation observations. The best estimate for interfacial toughness was 220 J/m² for carbon-fiber/epoxy and 120 J/m² for glass-fiber/epoxy.     

Effect of Electrical Charge on Attachment of Salmonella typhimurium to Meat Surfaces

Treating tissue with electrical current was found to affect both the initial attachment and total numbers of attached Salmonella typhimurium to meat tissues. When lean tissue was attached to the positive terminal of the power supply operating at 50 volts/125 mA DC, the total number of attached cells increased. There was no effect when the samples were attached to the negative terminal. There was a significant (P<0.05) effect on the percentage of strongly attached bacteria with an increase in treating time. Electrical current was found to increase the percentage of strongly attached cells immediately after the current was applied.     

ESCHERICHIA COLI O157 IN IRISH FEEDLOT CATTLE: A LONGITUDINAL STUDY INVOLVING PREHARVEST AND HARVEST PHASES OF THE FOOD CHAIN

The aim of this study was to investigate fecal shedding and transmission of E. coli O157 in cohorts of cattle within a feedlot, to assess subsequent contamination of carcasses with this pathogen and to identify risk factors associated with fecal shedding of E. coli O157. A cohort of 133 heifers housed infour adjacent pens was examined over a five month period, from entering the feedlot to slaughter. Individual rectal fecal samples and pen environmental samples were taken at monthly intervals. The entire outer and inner surfaces of a carcass side of each animal were swabbed immediately following slaughter.
E. coli O157 was isolated from 136 (23%) of the 600 rectal fecal samples; 96% of which contained virulent markers. One hundred and sixty environmental samples were examined and E. coli O157 was isolated from 46 (29%), all of which contained virulent markers. E. coli O157 was not isolated from any of the dressed carcasses. The prevalence of E. coli O157 fecal shedding may be related to the pen and E. coli O157 contamination of the pen floor feces, water trough and feed.
E. coli O157 should be considered as a pathogen shed in the feces of a substantial proportion of feedlot cattle. However, with good hygienic practice at harvest, a very low level of this pathogen can be achieved on dressed carcasses.