Soil solarization reduces Escherichia coli O157:H7 and total Escherichia coli on cattle feedlot pen surfaces

Feedlot pen soil is a source for transmission of Escherichia coli O157:H7, and therefore a target for preharvest strategies to reduce this pathogen in cattle. The objective of this study was to determine the ability of soil solarization to reduce E. coli O157:H7 in feedlot surface material (FSM). A feedlot pen was identified in which naturally occurring E. coli O157:H7 was prevalent and evenly distributed in the FSM. Forty plots 3 by 3 m were randomly assigned such that five plots of each of the solarization times of 0, 1, 2, 3, 4, 6, 8, and 10 weeks were examined. Temperature loggers were placed 7.5 cm below the surface of each plot, and plots to be solarized were covered with clear 6-mil polyethylene. At each sampling time, five FSM samples were collected from each of five solarized and five unsolarized plots. E. coli concentrations and E. coli O157:H7 presence by immunomagnetic separation and plating were determined for each FSM sample. Initial percentages of E. coli O157:H7-positive samples in control and solarized FSM were 84 and 80%, respectively, and did not differ (P > 0.05). E. coli O157:H7 was no longer detectable by 8 weeks of solarization, but was still detected in unsolarized FSM at 10 weeks. The average initial concentration of E. coli in FSM was 5.56 log CFU/g and did not differ between treatments (P > 0.05). There was a 2.0-log decrease of E. coli after 1 week of solarization, and a >3.0-log reduction of E. coli by week 6 of solarization (P, 0.05). E. coli levels remained unchanged in unsolarized FSM (P > 0.05). Daily peak FSM temperatures were on average 8.7°C higher for solarized FSM compared with unsolarized FSM, and reached temperatures as high as 57°C. Because soil solarization reduces E. coli O157:H7, this technique may be useful for reduction of persistence and transmission of this pathogen in cattle production, in addition to remediation of E. coli O157:H7-contaminated soil used to grow food crops.     

Investigating ozone-induced decomposition of surface-bound permethrin for conditions in aircraft cabins

Abstract  The reaction of ozone with permethrin can potentially form phosgene. Published evidence on ozone levels and permethrin surface concentrations in aircraft cabins indicated that significant phosgene formation might occur in this setting. A derivatization technique was developed to detect phosgene with a lower limit of detection of 2 ppb. Chamber experiments were conducted with permethrin-coated materials (glass, carpet, seat fabric, and plastic) exposed to ozone under cabin-relevant conditions (150 ppb O₃, 4.5/h air exchange rate, <1% relative humidity, 1700 ng/cm² of permethrin). Phosgene was not detected in these experiments. Reaction of ozone with permethrin appears to be hindered by the electron-withdrawing chlorine atoms adjacent to the double bond in permethrin. Experimental results indicate that the upper limit on the reaction probability of ozone with surface-bound permethrin is ∼10⁻⁷. Extrapolation by means of material-balance modeling indicates that the upper limit on the phosgene level in aircraft cabins resulting from this chemistry is ∼1 μg/m³ or ∼0.3 ppb. It was thus determined that phosgene formation, if it occurs in aircraft cabins, is not likely to exceed relevant, health-based phosgene exposure guidelines.  

Practical Implications

Phosgene formation from ozone-initiated oxidation of permethrin in the aircraft cabin environment, if it occurs, is estimated to generate levels below the California Office of Environmental Health Hazard Assessment acute reference exposure level of 4 μg/m³ or ∼1 ppb.     

Spores in dairy – new insights in detection,enumeration and risk assessment

The performance of the ISO method for the ‘Enumeration of the Specially Thermoresistant Spores of Thermophilic Bacteria in Dried Milk’ (ISO/TS27265; 2009) was compared with a more practical method. Both were tested for predictability of spoilage of UHT treated reconstituted milk. The data show that heating for 30 min at 100 °C has the same predictive value as heating for 30 min at 106 °C, provided that specifications are increased 1 log₁₀ and the use of TSA as a cultivation medium is recommended over PCMA. Predictability of spoilage using classical plating methods is furthermore discussed in relation to variation in spore heat resistance of spores commonly present in the dairy industry.     

Ion damage to the specimen in the SEM studied by the EBIC technique

This paper reports ion damage to Si and GaAs diodes during examination in the SEM as revealed by the electron beam induced conductivity (EBIC) technique. Also reported here is the emission of energetic negative ions having a mass-to-charge ratio of 32 from the lanthanum hexaboride electron gun. It is believed that these ions are (O₂)^?, although the possibility that they might be S^? cannot be ruled out. These ions give rise to damaged regions of the specimen which are circular in shape and which have a diameter related to that of the beam-limiting aperture in the SEM final lens. It is presumed that this problem can be avoided, if necessary, by the use of an ion trap at some point in the electron column.     

Experimental and Numerical Study of Micro Deep Drawing of Copper Single Crystal

One of the problems in a micro-forming process is the grain size effect, which means the formed part consists of a single grain or several grains sometimes, so the material shows anisotropic or heterogeneous. Under these conditions, a conventional method, which based on the isotropic and homogeneous material hypothesis, is not suitable. In this paper, Experimental investigations into micro deep drawing of the copper single crystal were carried out and the pattern of the micro-cup and the drawing force were observed. Using crystal plasticity theory, a user material subroutine (VUMAT) was built and linked to ABAQUS, and the micro deep drawing was simulated according to the experimental configuration. The results show that earing occurs at mouth of the micro-cup. The profile, quantity, and location of ears depend on the crystalline orientation in the blank. The simulations are in good agreement with the experiments, which demonstrate that the crystal theory has the rationality and validity in micro-forming simulations.     

Angiogenic Biomaterials to Promote Tissue Vascularization and Integration

Robert Langer’s work with Judah Folkman brought angiogenesis into the spotlight and herein we focus on an offshoot of this work – biomaterial-driven therapeutic angiogenesis. Angiogenic biomaterials are expected to improve vascularization and integration in tissue engineering, wound healing and medical device applications. This review focuses on therapeutic methacrylic acid copolymers, highlighting some new approaches to use these materials. Such copolymers require no biological components (drugs or cells) to promote in vivo vascularization; they are therapeutic polymers.     

Numerical investigation of the multi-pin electrohydrodynamic dryer: Effect of cross-flow air stream

Abstract

This article presents the results of numerical simulation and experimental study of a multi-pin electrohydrodynamic (EHD) dryer. Combined effect of EHD flow and the external air cross-flow on drying performance was investigated with 3-D numerical model, which accounts for electric field, electric charge transport, external air cross-flow and material-gas moisture transport. Effect of cross-flow air stream on drying was positive in the range of low velocities, changing to negative at high velocities due to counteracting with EHD flow. Numerical simulation predicted previously unknown effect of EHD flow on the cross-flow air stream, which was quantified as an increase of airway resistance. This prediction was fully validated by experiments. Both numerical simulation and experiment proved that for given intensity of EHD flow there is an optimum value of the cross-flow, resulting in maximum drying performance. The numerical model can be applied to determine the optimal operating parameters for multi-pin EHD dryer.