Ribotyping and a study of transmission of Staphylococcus aureus collected from food preparation facilities

Food poisoning from Staphylococcus aureus is sometimes caused by improper handling of food items in food preparation facilities. Prevention of contamination by employees is particularly important in facilities where a significant amount of food preparation is performed by hand. Some experiments have been performed to describe bacterial cross-contamination in the food preparation process, but there have been few studies of cross-contamination in actual food preparation facilities. Aiming to shed light on the transmission of S. aureus in food preparation facilities, this study collected samples of 66 strains of this bacterium from the fingers of food preparation staff, foodstuffs, prepared foods, cooking utensils, and cooking equipment and typed them with the ribotyping method. S. aureus from the same ribogroup was detected on the hands of a study participant, a faucet, knife, frying pan, and a salad, indicating that bacteria found on the hands of the study participant was transmitted to cooking utensils and prepared foods. Transmission (from a faucet to a frying pan handle) of bacteria by another person, a third party, was also detected.     

Epitaxially grown free-standing diamond platelet

We obtained an epitaxially grown free-standing diamond platelet utilizing epitaxial diamond film formed on a {100} iridium surface using a d.c. plasma CVD process. Iridium was selected as a suitable substrate material for the heteroepitaxy of diamond based on original criteria. Confocal Raman spectroscopy revealed that the diamond platelet contained little or no non-diamond carbon. The obtained diamond platelet is transparent to visible light and cleavable along the 110 direction on the surface. The angles between the top surface and the cross-sectional surfaces are approximately 55°, almost equal to the theoretical angle of 54.74° between {100} and {111} planes in cubic crystals. Therefore, the cross-sectional surfaces would be {111} planes of a typical facet for single-crystalline diamond. This means that the diamond platelet we have formed has relatively good crystallinity.     

Studies on relationship between activity and electron density on carbonyl oxygen in sex pheromone mimics of the American cockroach,part XI

From the relationship between structures of the 2-substituents of verbanyl analogs and their sex pheromone activities to the American cockroach, electron density of the carbonyl oxygen atom in the substituent, as estimated by the [¹⁷O]NMR chemical shift, was estimated to be an important factor which influenced the activity, in addition to length of the substituent and the position of the carbonyl group. (+)-Verbanyl methylcarbonate (XX), possessing the highest electron density on the carbonyl oxygen atom, showed the strongest activity among the analogs.For Part X, see Manabe et al., 1983. J. Chem. Ecol. 9:533–549.     

添加合金元素对奥氏体不锈钢等离子渗氮和渗碳的影响

奥氏体不锈钢众所周知有良好的耐蚀性,但是在工业上没有用于承受摩擦的工件上,因为它的硬度低,摩擦磨损性能差。奥氏体不锈钢经低温等离子体渗氮或渗碳能生成一层特殊的氮化物或碳化物层,称为S相,它具有高的硬度和优良的耐蚀性。这项研究中各种奥氏体不锈钢都经低温等离子体渗氮或渗碳,用各种分析技术研究了添加合金元素对S相特性的影响,用了光学显微镜和电子显微镜观察,做了X射线衍射分析,在5%H2SO4溶液中测量阳极极化,用球对平面摩擦装置做摩擦磨损测试。氮化物或碳化物层厚度随处理温度增加而加厚,AISI316钢上生成的渗层厚度是所有的基体钢材中最厚的。超过临界温度,由于氮化铬工碳化铬沉淀使耐蚀性降低。临界温度由渗氮的基材决定。另一方面,在渗碳层中临界温度不随基材变化。大部分样品上S相层的耐蚀性比没有处理的不锈钢的低。但是,AISI316和JIS-SUS304J3钢在400℃渗碳后都有和未处理钢一样优良的耐蚀性。每种不锈钢经渗氮或渗碳后耐磨性都有明显的改进。     

Mechanical and physical characteristics of cellulose‐fiber‐filled polyacetal composites

We investigated the mechanical and physical characteristics of composites composed of polyacetal [alternatively called polyoxymethylene (POM)] and cellulose fiber (CelF) derived from wood pulp [10–52 wt % (9.3–50.1 vol %)] without any fiber surface treatment. The modulus, deflection temperature under load, and thermal conduction coefficient of the POM/CelF composites were effectively enhanced with increasing CelF content, and the composites had an advantage of specific modulus compared to glass fiber (GF)‐filled POM. The flexural modulus of POM/CelF 40 wt % (38.2 vol %) was measured to be about 6 GPa, which was comparable to that of POM/GF 20 wt % (12.1 vol %). In the composites, the CelFs were distributed randomly as monofilaments, and the debonding of the interface between the fibers and POM matrices in the fracture faces was confirmed as less by scanning electron microscopy observation. The POM/CelF composites possessed lower specific wear rates than the POM/GF composites, and they had damping behaviors near that of neat POM. No clear dependence of the melt flow index of the base POM on these characteristics was observed, except on Charpy impact strength. The composites studied here were unique in their performance and ability to be designed in accordance with specific demands, and they could be potential replacements for mineral‐filled and GF‐filled POM composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrochemical behavior of copper current collector in imidazolium-based ionic liquid electrolytes

The electrochemical behaviors of copper current collector in 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ionic liquid electrolytes were investigated and compared with that in ethylene carbonate/dimethyl carbonate solutions. Cyclic voltammetry results showed that large oxidation–reduction current of the copper foil appeared in ethylene carbonate/dimethyl carbonate solutions, while a much smaller current in the room temperature ionic liquid electrolytes decreased gradually, indicating that the copper foil was anodically stable. Further study by X-ray photoelectron spectroscopy analysis showed that an unstable product was composed mainly of the carbonate and carbonyl species on the surface of the copper foil after the electrochemical measurement in ethylene carbonate/dimethyl carbonate solutions, leading to the dissolution of the copper foil. While a better passivating film from the reduction of the anions in the room temperature ionic liquid electrolytes covered the surface of copper foil and protected the copper foil from being oxidized even in a higher potential. These results indicate that the use of room temperature ionic liquid electrolytes can improve the stability of copper current collector in the advanced lithium ion batteries.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 4. Preparation parameters and impact index

The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13 wt% MoO₃/Al₂O₃ extrudate catalyst. The Al₂O₃ support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO₃ was marginally small. It was found that the dispersion of Mo oxide species increased as the volume of the impregnation solution increased, gradually approaching a maximum value. The increase in pH (2–8) of the impregnation solution was found to reduce the dispersion of Mo oxide species. The Mo dispersion increased slightly for the impregnation catalysts as the calcination temperature increased (673–873 K), whereas it decreased for the equilibrium adsorption catalysts. The effects of the calcination atmosphere (with or without flowing air, or with flowing humid air) were very small on the dispersion of Mo oxide species under the present preparation conditions. On the other hand, the methanol oxidation activity of MoO₃/Al₂O₃ was sensitive to the preparation parameters examined here. It was demonstrated by means of EPMA and XPS that a considerable migration of Mo took place during the calcination.

In the present study on the preparation of a 13 wt% MoO₃/Al₂O₃ catalyst, an impact index is proposed to measure the magnitude of the effects of the respective parameter(s) on the physicochemical and catalytic properties. With the Mo dispersion, the effects of the preparation parameter decreased in the order, surface area of the support >> drying process > volume of the impregnation solution > pH, calcination temperature and atmosphere. The size of the impact index for the dispersion of Mo sulfide species is 70–75% of that for the Mo oxide species. The HDS activity of the catalyst was less affected by the preparation parameters than the Mo sulfide dispersion. The preparation parameters affected the segregation of Mo on the outer surface of extrudates in a decreasing order: drying process > volume of the impregnation solution > pH, calcination conditions. It was found that the oxidation of methanol was affected most intensely by the drying procedures. The volume of the impregnation solution, calcination conditions and pH of the impregnation solution also strongly affected the oxidation activity. The impact index suggests that the sensitivity to the preparation variables of the physicochemical and catalytic properties of MoO₃/Al₂O₃ decreases in the order, methanol oxidation activity > surface Mo segregation > Mo oxide dispersion > Mo sulfide dispersion > HDS activity.     

Improvement of Pt/ZrO2 by CeO2 for high pressure CH4/CO2 reforming

CH₄/CO₂ reforming over Pt/ZrO₂, Pt/CeO₂ and Pt/ZrO₂ with CeO₂ was investigated at 2 MPa. Pt/ZrO₂, which shows stable activity under 0.1 MPa, and Pt/CeO₂ showed gradual deactivation with time at the high pressure. The deactivation was suppressed drastically on Pt/ZrO₂ with CeO₂ prepared by different impregnation order (co-impregnation of Pt and CeO₂ on ZrO₂, and consecutive impregnation of Pt and CeO₂ on ZrO₂). The amount of coke deposition was found insignificant and similar among all the catalysts (including Pt/ZrO₂ and Pt/CeO₂). Catalytic activity after the reaction for 24 h was in agreement with Pt particle size after the reaction for same period, indicating that the difference of the catalytic stability is mainly dependent on the extent of Pt aggregation through catalyst preparation, H₂ reduction, and the CH₄/CO₂ reforming. Pt aggregation and the amount of coke deposition were least pronounced on (Pt–Ce)/ZrO₂ prepared by impregnation of CeO₂ on Pt/ZrO₂ and the catalyst showed highest stability.