Inhibitory effects of UV treatment and a combination of UV and dry heat against pathogens on stainless steel and polypropylene surfaces

Abstract: Pathogens that contaminate the surfaces of food utensils may contribute to the occurrence of foodborne disease outbreaks. We investigated the efficacy of UV treatment combined with dry heat (50 °C) for inhibiting 5 foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus) on stainless steel and polypropylene surfaces in this study. We inoculated substrates with each of the 5 foodborne pathogens cultured on agar surface and then UV treatment alone or a combination of both UV and dry heat (50 °C) was applied for 30 min, 1 h, 2 h, and 3 h. The initial populations of the 5 pathogens before treatment were 8.02 to 9.18 and 8.73 to 9.16 log₁₀ CFU/coupon on the surfaces of stainless steel and polypropylene coupons, respectively. UV treatments for 3 h significantly inhibited S. Typhimurium, L. monocytogenes, and S. aureus on the stainless steel by 3.06, 2.18, and 2.70 log₁₀ CFU/coupon, and S. aureus on the polypropylene by 3.11 log₁₀ CFU/coupon, respectively. The inhibitory effects of the combined UV and dry heat treatment (50 °C) increased as treatment time increased, yielding significant reductions in all samples treated for 3 h, with the exception of S. aureus on polypropylene. The reduction level of E. coli O157:H7 treated for 3 h on the surface of stainless steel and polypropylene treated was approximately 6.00 log₁₀ CFU/coupon. These results indicate that combined UV and dry heat (50 °C) treatments may be effective for controlling microbial contamination on utensils and cooking equipment surfaces as well as in other related environments.     

Resistance of pathogenic bacteria on the surface of stainless steel depending on attachment form and efficacy of chemical sanitizers

Various bacteria including food spoilage bacteria and pathogens can form biofilms on different food processing surfaces, leading to potential food contamination or spoilage. Therefore, the survival of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Cronobacter sakazakii) in different forms (adhered cells, biofilm producing in TSB, biofilm producing at RH 100%) on the surface of stainless steel and stored at various relative humidities (RH 23%, 43%, 68%, 85%, and 100%) at room temperature for 5 days was investigated in this study. Additionally, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) on inhibiting various types of biofilms of E. coli O157:H7 and S. aureus on the surface of stainless steel was investigated. The number of pathogens on the surface of stainless steel in TSB stored at 25 °C for 7 days or RH 100% at 25 °C for 7 days was significantly increased and resulted in the increase of 3 log₁₀ CFU/coupon after 1 day, and these levels were maintained for 7 days. When stainless steel coupons were stored at 25 °C for 5 days, the number of pathogens on the surface of stainless steel was significantly reduced after storage at RH 23%, 43%, 68%, and 85%, but not at 100%. When the bacteria formed biofilms on the surface of stainless steel in TSB after 6 days, the results were similar to those of the attached form. However, levels of S. aureus and C. sakazakii biofilms were more slowly reduced after storage at RH 23%, 43%, 68%, and 85% for 5 days than were those of the other pathogens. Formation of biofilms stored at RH 100% for 5 days displayed the highest levels of resistance to inactivation. Treatment with the alcohol sanitizer was very effective at inactivating attached pathogens or biofilms on the surface of stainless steel. Reduction levels of alcohol sanitizer treatment ranged from 1.91 to 4.77 log and from 4.35 to 5.35 log CFU/coupon in E. coli O157:H7 and S. aureus, respectively. From these results, the survival of pathogens contaminating the surfaces of food processing substrates such as stainless steel varied depending on RH and attachment form. Also, alcohol-based sanitizers can be used as a potential method to remove microbial contamination on the surfaces of utensils, cooking equipment, and other related substrates regardless of the microbial attached form.     

Effect of an additional ferromagnetic material on the toroidal magnetic field ripple in the ITER

In the ITER tokamak, the toroidal magnetic field (TF) ripple is estimated with TF coils only, with the installation of ferromagnetic inserts (FIs), and with test blanket modules (TBMs) by using a 2-D code for easy and fast calculation. We assessed the effects of the thickness of the FIs on the TF ripple in order to optimize the FI. And we analyzed how the TBMs distort the TF, and calculated the TF ripple for various amounts of a ferromagnetic material and the positions of the TBMs. Even in the case of moving the TBMs outward up to 60-cm, and reducing the ferromagnetic material to 52%, the TF ripple is not decreased below 0.38%. So we had to adopt ripple correction coils. With a 52% reduced amount of the ferromagnetic material in a TBM, we could reduce the TF ripple to 0.28% at a coil current of 100 kA turn per each coil. And with an outward recess of the TBM up to 60 cm, we could reduce the TF ripple to 0.23% at a coil current of 250 kA turn per each coil. As a combined approach, if we reduce the amount of a ferromagnetic material in a TBM to 30%, and recess the TBM to 15 cm, we can efficiently obtain the TF ripple of 0.25% at a coil current of 150 kA turn per each coil.     

Reconfigurable Beam‐Steering Antenna Using Dipole and Loop Combined Structure for Wearable Applications

This paper proposes a reconfigurable beam‐steering antenna using a bended dipole and a loop. The radiation patterns of the two antennas are cancelled or compensated, and headed towards a specific direction when the dipole and loop antenna are combined at a reasonable ratio. The proposed antenna can steer the beam directions by controlling the operation of two artificial switches. The proposed antenna was manufactured on a PCB (FR‐4) and a flexible PCB (polyimide). In the case of the antenna that was fabricated on a PCB, the maximum beam directions were +50°, 0°, and –50° in the azimuth direction using the two artificial switches, and the antenna gain was 1.96 dBi to 2.48 dBi in the operation bandwidth of 2.47 GHz to 2.53 GHz. Also, the antenna was fabricated on a flexible PCB and measured under various bending conditions for wearable applications.     

Transmission scheduling for wireless mesh network systems equipped with multiple directional antennas

All existing broadcast scheduling algorithms (BSAs) were designed for omnidirectional antenna (OA) packet radio (PR) nodes of a wireless mesh network (WMN). However, when WMN nodes are equipped with multiple directional antennas (DAs), a signal sent from a neighboring node may be received by more than one DA of the receiving node, and some nodes may receive signals from multiple DAs sent from the same node. When existing OA BSAs are used for scheduling transmission time-slots in time division multiple access (TDMA), due to the multiple DA signal detection phenomenon a weak performance in average time delay and channel utilization is obtained. Therefore, a novel transmission scheduling algorithm (TSA) for WMN nodes equipped with multiple DAs is proposed. Simulation results demonstrate that a significant performance gain can be obtained from using the proposed DA-TSA scheme.     

Preparation and characterization of silicone resin nanocomposite containing CdSe/ZnS quantum dots

We report the preparation of the core/shell cadmium selenide/Zinc sulfide quantum dots (CdSe/ZnS QDs)‐silicone resin nanocomposite through the solution‐mixing method, followed by thermal hydrosilylation. After dispersing QDs into Dow Corning two‐component silicone resins (OE6630A and OE6630B at 1:4 mixing ratio by weight), the resins were cured at 150°C for 1.5 h to produce QD‐silicone resin nanocomposites. The curing behavior of the silicone resins resulting from the thermal hydrosilylation was studied using differential scanning calorimetry (DSC). The properties of the QD‐silicone resin nanocomposites were investigated by ultraviolet–visible (UV–vis), fluorescence, confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA) measurements. The QDs that contain trioctylamine (TOA) as the original ligand can poison the Pt catalyst in the resins and inhibit the curing process by increasing the exothermic peak temperature, at which a lower heat of hydrosilylation is observed. Incorporating a small amount of CdSe/ZnS QDs (0.1 wt%) can greatly improve the thermal stability of the silicone resins. Moreover, CdSe/ZnS QDs tend to form clusters that are relatively homogeneously distributed in a cured silicone resin, offering good optical properties of 11.2 lm W⁻¹ luminous efficiency and 14.6% photoluminescence conversion efficiency (PCE) in light emitting device (LED) test. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effects of microwave,UV, and O3 on propylene gas degradation via photocatalytic reaction with CVD TiO2 films

A microwave/UV/ozone/TiO₂ photocatalyst hybrid process system, which is a combination of various propylene gas treatment techniques, is evaluated for use as an advanced, efficient technology for air pollution treatment. TiO₂ photocatalyst balls were prepared using low-pressure metal-organic chemical vapor deposition. The microwave/UV/TiO₂ photocatalyst hybrid process exhibited the higher degradation efficiency than the microwave/UV/alumina ball hybrid system. The degradation efficiency increased almost linearly with increasing ozone dose. The lower the propylene inlet concentration was the higher degradation efficiency. The double bond of propylene is broken by ozone and OH, resulting in production of CH₄ and C₂H₆. These two intermediate products are mineralized into CO₂, H₂O, and CO. C₂H₄ and C₃H₈ may be produced from CH₄, whereas C₂H₆ and C₃H₆ are produced by microwave irradiation.     

Thin film encapsulation for organic light emitting diodes using a multi-barrier composed of MgO prepared by atomic layer deposition and hybrid materials

We demonstrated an organic/inorganic multi-barrier and encapsulation for flexible OLED devices. The multi-barrier consisted of a silica nanoparticle-embedded hybrid nanocomposite, in short, S-H nanocomposite, and MgO, which were used as organic and inorganic materials, respectively. The S-H nanocomposite was spin-coated followed by UV curing. The thickness of the S-H nanocomposite was 200 nm, and 40 nm of MgO was deposited by atomic layer deposition (ALD) using Mg(CpEt)₂ and H₂O at 70 °C. The results of a Ca test showed that the 4.5 dyads of the MgO/S-H nanocomposite had a low water vapor transmission rate (WVTR) of 4.33 × 10^?6 g/m²/day and an optical transmittance of 84%. The normalized luminance degradation of the thin film encapsulated OLED was also identical to that of glass-lid encapsulation after 1000 h of the real operation time. We proposed low temperature ALD as a deposition method to create relatively thin film for OLED passivation without degradation, such as creation of dark spots. The results confirmed that it may be feasible for our multi-barrier to passivate flexible OLEDs devices.