Micromorphological characterization of zinc/silver particle composite coatings

The aim of this study was to evaluate the three‐dimensional (3D) surface micromorphology of zinc/silver particles (Zn/AgPs) composite coatings with antibacterial activity prepared using an electrodeposition technique. These 3D nanostructures were investigated over square areas of 5 μm × 5 μm by atomic force microscopy (AFM), fractal, and wavelet analysis. The fractal analysis of 3D surface roughness revealed that (Zn/AgPs) composite coatings have fractal geometry. Triangulation method, based on the linear interpolation type, applied for AFM data was employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The surface fractal dimension D_f, as well as height values distribution have been determined for the 3D nanostructure surfaces. Microsc. Res. Tech. 78:1082–1089, 2015. © 2015 The Authors published by Wiley Periodicals, Inc.     

Small‐Scale Thermal Studies of Volatile Homemade Explosives

Several homemade or improvised explosive mixtures that either contained volatile components or produced volatile products were examined using standard small‐scale safety and thermal (SSST) testing that employed differential scanning calorimetry (DSC) techniques (constant heating rate and standard sample holders). KClO₃ and KClO₄ mixtures with dodecane exhibited different enthalpy behavior when using a vented sample holder in contrast to a sealed sample holder. The standard configuration produced profiles that exhibited only endothermic transitions. The sealed system produced profiles that exhibited additional exothermic transitions absent in the standard configuration produced profiles. When H₂O₂/fuel mixtures were examined, the volatilization of the peroxide (endothermic) dominated the profiles. When a sealed sample holder was used, the energetic releases of the mixture could be clearly observed. For AN and AN mixtures, the high temperature decomposition appears as an intense endothermic event. Using a nominally sealed sample holder also did not adequately contain the system. Only when a high‐pressure rated sample holder was used the high temperature decomposition of the AN could be detected as an exothermic release. The testing was conducted during a proficiency (or round‐robin type) test that included three U.S. Department of Energy and two U.S. Department of Defense laboratories. In the course of this proficiency test, certain HMEs exhibited thermal behavior that was not adequately accounted for by standard techniques. Further examination of this atypical behavior highlighted issues that may have not been recognized previously because some of these materials are not routinely tested. More importantly, if not recognized, the SSST testing results could lead to inaccurate safety assessments. This study provides examples, where standard techniques can be applied, and results can be obtained, but these results may be misleading in establishing thermal properties.     

Small‐Scale Safety Testing of Ammonium Nitrate and Mixtures

Ammonium nitrate (AN), gunpowder (GP), and an ammonium nitrate gunpowder mixture (AN/GP) were studied for impact sensitivity by four laboratories using the drop hammer apparatus. Bruceton and Neyer methods were used as experimental protocols and for data reduction. The results are presented as 50 % probability of reaction (DH₅₀). For AN, the DH₅₀ values are widely varied among the participants, from sensitive to completely insensitive (limit of the equipment), with no real correlation among results. GP and the AN/GP mixture exhibited much more sensitivity overall and were in some cases within statistical values extrapolated from previous studies of RDX. The variability in results for the AN data is attributed to the difficulty in determining a positive reaction event for AN, as detailed by Neyer experiments and photography during positive reactions. Variability in results for the GP and AN/GP mixtures is attributed to equipment environment and detection criteria. This work was performed by the Integrated Data Collection Analysis (IDCA) program, a multi‐laboratory effort to standardize safety testing of improvised or homemade explosives funded by the Department of Homeland Security.     

Role of predation by zooplankton in transport and fate of protozoan (oo)cysts in granular activated carbon filtration

The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 μm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain™) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water.     

Pile burning of cutting debris in stands of hazel (Corylus avellana): An experimental study of smouldering combustion towards the validation of a burning protocol

Smouldering combustion in burning piles was experimentally investigated by studying temperature changes in six piles of 2 m of diameter of cutting debris of hazel (Corylus avellana) for three days after extinction. The piles were monitored using an IR camera and K-type thermocouples. The experiment was designed in order to study how the maximum temperature of the charcoal might be influenced by the individual and interaction effects of both the quality of extinction and the elapsed time until the start of extinction of the piles. The piles that were properly extinguished (i.e. using a high-pressure, homogeneously distributed water flow of 50 l/min for 4 min) had a uniform temperature profile and did not have significant hot spots. The temperature reached equilibrium with the environment in less than 10 h after extinction. In contrast, a smouldering front moved throughout the poorly extinguished piles, which had a wide temperature distribution and hot spots of up to 700 °C. A simulation of windy conditions after three days of experiments on a poorly extinguished pile showed that the reactivation of charcoal combustion was possible. It gave a high-risk scenario to cause a wildfire, with hot smouldering embers being transported by wind flow. The results are of interest to improve pile burning protocols so that the number of wildfires caused by such practices may be reduced.     

Antimicrobial activity of nisin against Oenococcus oeni and other wine bacteria

Nisin is a bacteriocin used against food spoilage bacteria. Sulphur dioxide is a potent antioxidant as well as an antimicrobial agent widely used in the wine industry. In this study we describe the effect of these important antibacterial agents on the growth of a collection of 64 lactic acid bacteria (23 Oenococcus, 29 Lactobacillus, 3 Leuconostoc and 9 Pediococcus), 23 acetic acid bacteria and 20 yeast isolates, most of them recovered from wine. Minimal inhibitory concentrations (MIC) and minimal bactericide concentrations of nisin, potassium metabisulphite and ethanol were determined. Nisin MIC(50) values for the tested isolates were as follows: 0.024, 12.5, 200 and > or micro for oenococci, lactobacilli-pediococci-leuconostoc, acetic acid bacteria and yeasts, respectively. Synergistic effects on bacterial growth inhibition were observed, and potassium metabisulphite MIC(50) values decreased from one to three orders of dilution when it was combined with subinhibitory concentrations of nisin in the growth media. This effect was observed in all lactic acid bacteria species of our study. Significant differences in nisin sensitivity were observed between Gram-positive and Gram-negative bacteria, and between Oenococcus oeni and other species of lactic acid bacteria. It is concluded that appropriate combinations of nisin and metabisulphite could control the growth of spoilage bacteria in wine and therefore allow a decrease in the levels of sulphur dioxide currently used by the wine industry.     

Kinetic study of the effects of extracts from Vicia faba var. equina on intestinal sugar absorption

Alcoholic and water extracts from seed-coats of Vicia faba var. equina were prepared and their effects on in-vivo intestinal sugar absorption across the rat small intestine were investigated. Both extracts significantly (P<0.001) inhibited sugar absorption. The higher and more stable inhibition was induced by the water extract. Pretreatment of the extracts with polyamide significantly (P<0.001) reduced their inhibitory potency but did not abolish it, suggesting the presence in the extracts of some other intestinal sugar absorption inhibitor, different from polyphenols. Although both extracts inhibited intestinal sugar active transport, only the water extract was able to reduce sugar diffusion across the small intestine. These differences in behaviour seem to be related to the polyphenolic content of each extract.     

在数字调制系统中进行精确的非线性测量

随着日益增加的智能手机和无线互联网3G覆盖范围以及4G系统即将引入带来的持续压力，数字通信射频组件的设计活动越来越丰富。设计活动的前沿在于功率放大器（PA）的开发。PA设计工程师面对的首要问题是功率所增加的效率（PAE）。高PAE意味着：