Microbial Assessment in School Foodservices and Recommendations for Food Safety Improvement

ABSTRACT:  This study evaluated microbial food safety in school foodservices. Five school foodservices were randomly selected, and samples from water, cooking utensils, tableware, foodservice surroundings, and linen were collected in summer and winter ( N = 420). Tap and drinking water samples were collected, samples of food contact surfaces were collected by swab-kit, and samples for foodservice workers' hands and gloves were prepared by glove juice method. Aerobic plate count (APC) and coliform bacterial populations were enumerated on plate count agar (PCA) and desoxycholate lactose agar, respectively. The presence of Escherichia coli , Salmonella , Listeria monocytogenes , and Staphylococcus aureus was also examined by biochemical identification tests. In addition, PCA agar for APCs and Baird-Parker agar for S . aureus were used to enumerate airborne microorganisms. Higher APCs (< 0 to 5.1 log CFU/mL) than acceptable level were generally observed in water samples, while low coliform counts were found in the samples. High APCs were enumerated in cooking utensils, foodservice workers, tableware, and foodservice surroundings, and coliforms were also found in the samples for both seasons. The presence of Salmonella was found from only 10% of plastic glove samples (summer), and the presence of L . monocytogenes was not observed in all samples. S . aureus was detected in some of water, cooking utensils, tableware, employees, and foodservice surroundings, and E . coli was observed in cooking utensils (10% to 20%; summer). No obvious airborne bacteria were detected. These results showed that sanitation practice in school foodservices should be improved, and the results may be useful in microbial assessment of school foodservices.     

MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers chemiresistor and their application in low molecular weight alcohol vapours sensing

Herein, we fabricated MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by electrospinning and dip coating method. The amount of MWCNT–OH adsorbed to the pure electrospun nylon 6,6 nanofibers was 0.056 wt%. The electrical conductivity of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers was 5.24 × 10^?3 S cm^?1. We also investigated the sensing properties of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by measuring its response upon exposure to low molecular weight alcohol vapours such as methanol, ethanol, 1-propanol, and 1-butanol. The changes of the electrical resistance of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers were demonstrated on the basis of hydrogen bonds among the alcohol vapours and hydroxyl groups (–OH) on MWCNT–OH, and amide groups (–NHCO–) in nylon 6,6. The fabricated sensor showed good reversible and reproducible responses upon the cyclic test.     

Noncontact conveyance of conductive plate using omni-directional magnet wheel

A magnet wheel is chosen as the driving method to transfer a conductive plate without mechanical contact in space, due to its high force density. When permanent magnets (hereafter PMs) constituting the magnet wheel rotate below the conductive plate, not only a repulsive type of normal force but also a traction torque is generated on the plate. To utilize the torque as a thrust force, the magnetic fields from PMs are covered partially using a magnetic shield plate. So, in-plane positions of the conductive plate are controlled by turning the shield plate opened partially. In this paper, the operating principle of the noncontact conveyance system using a magnet wheel is discussed, including experimental verification. Specially, the resulting force from the suggested magnet wheel is AC force with oscillation, but it can be minimized through varying entry or exit shape of the open area of the magnetic shield plate.     

Effects of focused ion beam milling on the compressive behavior of directionally solidified micropillars and the nanoindentation response of an electropolished surface

Focused ion beam (FIB) milling is the typical method used to fabricate micropillars to study small-scale plasticity and size effects in uniaxial compression. However, FIB milling can introduce defects into the milled pillars. To investigate the effects of FIB damage on mechanical behavior, we tested Mo-alloy micropillars that were FIB milled following directional solidification, and compared their compressive response to pillars that were not FIB milled. We also FIB milled at glancing incidence a Mo-alloy single-crystal surface, and compared its nanoindentation response to an electropolished surface of the same crystal. Implications for the interpretation of data obtained from FIB-milled micropillars are discussed.     

Load-adaptive, low switching-noise output buffer

An output buffer is described which employs built-in load monitoring in order to bound the transition time over a wide range of load conditions. The adaptive control of driving current enables the switching-noise to be kept to a minimum value. The experimental chip, which was designed to bound the fall time within 6 ns for loading capacitance up to 100 pF, revealed a reduced switching-noise level, 15-35% of a conventional buffer     

A new polarization-insensitive 1.55-μm InGaAsP-InGaAsPmultiquantum-well electroabsorption modulator using astrain-compensating layer

In a conventional polarization-insensitive multiquantum-well electroabsorption modulator, it is normal to apply tensile and compressive strain on the well and the barrier, respectively. But the main disadvantages of such a structure are a low conduction band offset (0.04-0.06 eV), a high heavy-hole band offset (0.20-0.24 eV), and a relatively large well thickness (110-120 Å). We propose a new method of overcoming these disadvantages by placing a tensile strain on both the well and the barrier and compensating for them with a compressive strained intrinsic layer     

Digital signal processing applied to the detection of partialdischarge: an overview

This article is the first of a four-part series by the authors that treats various aspects of digital signal processing applied to partial discharge detection. It is shown that manufacturers and users of high-voltage apparatus are interested in on-site, off-line and on-line analysis of partial discharge to identify and locate defects in insulation systems     

Preparation of silica-layered multi-walled carbon nanotubes activated by grafting of poly(4-vinylpyridine)

Herein, uniformly silica coated carbon nanotubes (CNTs) were fabricated by step reactions with minimized damage of CNTs during oxidation process. First, hydroxyl groups were generated on the surface of CNTs using KMnO₄ in conjunction with tetrapropyl ammonium bromide (TPABr) as a phase transfer catalyst, followed by the grafting of a vinyl group carrying silane coupling agent, methacryloxypropyl trimethoxy silane (MPTMS). Utilizing terminal vinyl groups in in-situ solution polymerization, poly(4-vinylpyrridine) (P4VP) brush was grown from the CNTs which promotes the acid–base interaction between CNTs and tetraethylorthosilicate (TEOS). By means of well-known ammonia catalyzed sol–gel reaction of TEOS in the presence of P4VP-functionalized CNTs, uniformly silica-coated CNTs were obtained. The thickness of the silica layer could be readily controlled by the amounts of reactants. After calcination of silica-coated CNTs, only outer silica remained which resulted in silica nanotubes.     

A semi-empirical atomic potential for the Fe-Cr binary system

Asemi-empirical atomic potential, the second nearest-neighbor MEAM, has been applied to obtain an atomic potential for the Fe-Cr system, based on the previously developed potentials for pure Fe and Cr. The procedure for the determination of potential parameter values and the performance of the assessed alloy potential were also presented. It was shown that the potential describes the basic thermodynamic property and alloy behavior in the bcc solid solution successfully, as well as many physical properties of pure Fe and Cr. The limit in the applicability of the present potential is also discussed.