Gradient silver nanoparticle layers in absorbing coatings--experimental study

Metal island films show a characteristic absorption peak related to the surface plasmon resonance of free electrons. This kind of film can be used in absorbing coatings, together with dielectric layers. Such absorbing multilayer coatings, with and without the gradient of the silver mass thickness in metal island films throughout the coating, have been deposited by electron beam evaporation. It is shown experimentally that coatings with a gradient in the mass thickness of silver nanoparticles have higher absorption than equivalent nongradient coatings with the same total mass thickness of silver nanoparticles.     

Use of gold island films in design of reflectors with high luminosity

We describe the optical properties of gold island films embedded between SiO2 and/or TiO2 layers. Plasmonic properties of gold films have been characterized using spectrometry and variable angle spectroscopic ellipsometry for various combinations of the embedding media. The obtained refractive indices of embedded gold island films have been used in the design of several types of multilayer reflectors.     

Oceanic biogeochemical controls on global dynamics of persistent organic pollutants

Understanding and quantifying the global dynamics and sinks of persistent organic pollutants (POPs) is important to assess their environmental impact and fate. Air-surface exchange processes, where temperature plays a central role in controlling volatilization and deposition, are of key importance in controlling global POP dynamics. The present study is an assessment of the role of oceanic biogeochemical processes, notably phytoplankton uptake and vertical fluxes of particles, on the global dynamics of POPs. Field measurements of atmospheric polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and furans (PCDFs) are combined with remote sensing estimations of oceanic temperature, wind speed, and chlorophyll, to model the interactions between air-water exchange, phytoplankton uptake, and export of organic matter and POPs out of the mixed surface ocean layer. Deposition is enhanced in the mid-high latitudes and is driven by sinking marine particulate matter, rather than by a cold condensation effect. However, the relative contribution of the biological pump is a function of the physical-chemical properties of POPs. It is concluded that oceanic biogeochemical processes play a critical role in controlling the global dynamics and the ultimate sink of POPs.     

Comparison between conventional and qPCR methods for enumerating Campylobacter jejuni in a poultry processing plant

Campylobacter jejuni is worldwide recognized as a human foodborne pathogen. It is widely present in poultry meat and slaughterhouses, but little is known about its fate during the processing of poultry meat preparations. In stress conditions, this pathogen can enter into a viable but non-culturable state, where quantitative PCR (qPCR) becomes more convenient for its detection. In this study, two different pairs of primers, targeting the rpoB and the hipO genes, were compared for its detection and quantification by PCR. Two calibration curves were prepared: one for the meat samples and the other for the environmental samples. rpoB primers showed higher sensitivity with a quantification limit of 1 log cfu/g or ml. Microbial Assessment Scheme (MAS) was used to select the Critical Sampling Locations (CSLs) along the poultry processing line. Forty-six out of 48 samples were positive by qPCR after enrichment (t = 48 ) while only 6 samples were positive by ISO 10272-1:2006. Forty-three samples showed positive signal without enrichment (t = 0 h), however only 16 samples could be quantified. These results showed the high prevalence of C. jejuni in the poultry industry and the need for new, rapid and sensitive techniques, such as qPCR, for the detection and quantification of C. jejuni in meat and environmental samples.     

Novel system for controlled investigation of environmental partitioning of hydrophobic compounds in water

Partitioning behavior of hydrophobic and semivolatile chemicals (such as many POPs and PAHs) in water is key in controlling their environmental distribution and fate. A new equilibrium method is presented here which allows determination of the equilibrium partition coefficient of hexachlorobenzene with suspended particle (K(SPM)≈ 337 L gOC(-1)) in a complex bulk water sample by correcting for a number of sampling artifacts and for the presence of dissolved matter. The method provides simultaneous experimental determination of the fraction of chemical truly dissolved in water (representing in this case about 54% of the bulk water concentration) and that associated to DM (21%). The Henry's law constant was also experimentally determined during the K(SPM) measurements, providing information on the occurrence of partitioning equilibrium in the system for each single observation. Results showed that the high level of quality control and accuracy provided confidence intervals for the K(SPM) estimates within 1 order of magnitude.     

Effect of modified atmosphere packaging on the microbiological and sensory quality on a dry cured beef product: "Cecina de león"

The aim of this study was to investigate the shelf-life of commercial “Cecina de León” (CL) packaged in vacuum (VP) and in CO₂/N₂ atmospheres (20/80% CO₂/N₂ and 80/20% CO₂/N₂). Packaged product was stored at 6 °C, measuring microbiological, physico-chemical and sensory parameters during 210 days. The values obtained for mesophilic aerobic, anaerobic and psychrotrophic counts did not vary in both the vacuum and the gas packaged samples after 210 days of storage. Enterobacteria and enterococci were always below the detection limit, and in the gas-packaged CL, pseudomonad numbers were significantly inhibited. No changes were observed in the counts of the typical microflora of CL (Lactic Acid Bacteria, yeasts and moulds and Micrococcaceae) up to 210 days and no differences (p > 0.05) were found between the counts in the VP and in the gas-packaged samples. A pronounced initial fading was observed in redness (a^∗) within the first 15 days in the VP samples and within the second month in the gas-packaged samples attributed to the presence of white film on surface of CL portions. No differences were observed (p > 0.05) in texture parameters evaluated between packaging methods during storage, and the values found are within the range for CL not packaged. The sensory properties of CL stored in 20/80% CO₂/N₂ were slightly less acceptable than the samples packed under vacuum and under 80/20% CO₂/N₂ at 210 days of storage. It is concluded that no clear advantage of the gas packaging was observed compared to the VP of “Cecina de León”.     

Improving wind turbine drivetrain designs to minimize the impacts of non‐torque loads

Non‐torque loads induced by the wind turbine rotor overhang weight and aerodynamic forces can greatly affect drivetrain loads and responses. If not addressed properly, these loads can result in a decrease in gearbox component life. This work uses analytical modeling, computational modeling and experimental approaches to evaluate two distinct drivetrain designs that minimize the effects of non‐torque loads on gearbox reliability: a modified three‐point suspension drivetrain studied by the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) and the Pure Torque® drivetrain developed by Alstom. In the original GRC drivetrain, the unequal planetary load distribution and sharing were present and they can lead to gear tooth pitting and reduce the lives of the planet bearings. The NREL GRC team modified the original design of its drivetrain by changing the rolling element bearings in the planetary gear stage. In this modified design, gearbox bearings in the planetary gear stage are anticipated to transmit non‐torque loads directly to the gearbox housing rather than the gears. Alstom's Pure Torque drivetrain has a hub support configuration that transmits non‐torque loads directly into the tower rather than through the gearbox as in other design approaches. An analytical model of Alstom's Pure Torque drivetrain provides insight into the relationships among turbine component weights, aerodynamic forces and the resulting drivetrain loads. In Alstom's Pure Torque drivetrain, main shaft bending loads are orders of magnitude lower than the rated torque and hardly affected by wind speed, gusts or turbine operations. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of UV irradiation on enzymatic activities and physicochemical properties of apple juices from different varieties

The influence of ultraviolet irradiation (UV) on some quality attributes (colour, pH, soluble solids content, formol index, total phenolics, sugars and vitamin C) and enzymatic activities (polyphenol oxidase, peroxidase and pectinolytic enzymes) of fresh apple juice was investigated. Apple juices made from four different varieties (Golden, Starking, Fuji and King David) were irradiated during 120 min with a high-pressure mercury lamp of 400 W that emits in a range between 250 and 740 nm with a resulting incident energy of 3.88·10⁻⁷ E·min⁻¹. The treatment was effective in the inactivation of the assayed enzymes. Polyphenol oxidase was inactivated in 100 min, while peroxidase was completely destroyed in only 15 min in all the four varieties. No variations were observed in pH, soluble solids content, formol index, total phenolics and sugars. The colour of the juice made from King David was unvariable during all the experiment. In the ones made from Golden, Starking and Fuji, UV radiation impaired some of the pigments present in the juice, either initially present or the ones formed later. This fact can be especially observed in the increase of the CIELab parameter L*, which increased from 23.2 to 24.6 in Fuji juice. The content of vitamin C in juices from Golden, Starking and Fuji slightly changed during the experiment, decreasing a 4.0% in Fuji juice, 5.7% in Golden one and 5.6% in Starking one. Meanwhile, in the juice from King David the loss was 70.0%. This significant difference can be attributed to the lack of pigmentation of this juice.