Synthesis and applications of molybdenum (IV) oxide

Molybdenum dioxide (MoO₂) is a transition metal oxide with unusual metal-like electrical conductivity and high catalytic activity toward reforming hydrocarbons. This review covers the synthesis techniques used to fabricate MoO₂ in a variety of morphologies and particle sizes. Processing from molybdenum ore and reduction from MoO₃ are also covered, with emphasis on reduction mechanisms and kinetic considerations. Discussions of various solution-based and gas phase synthesis techniques shed light on strategies to achieve various unique morphologies, which leads into a brief discussion of nanoscale MoO₂. Nanoscale MoO₂ is of interest for important technological applications including catalysts for partial oxidation of hydrocarbons, solid oxide fuel cell anodes, and high-capacity reversible lithium ion battery anodes.     

Characterizing sources and emissions of volatile organic compounds in a northern California residence using space‐ and time‐resolved measurements

We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single‐family house in California utilizing time‐ and space‐resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during 8 weeks in summer and five in winter. Spatially resolved measurements, along with tracer data, reveal that VOCs in the living space were mainly emitted directly into that space, with minor contributions from the crawlspace, attic, or outdoors. Time‐resolved measurements in the living space exhibited baseline levels far above outdoor levels for most VOCs; many compounds also displayed patterns of intermittent short‐term enhancements (spikes) well above the indoor baseline. Compounds were categorized as “high‐baseline” or “spike‐dominated” based on indoor‐to‐outdoor concentration ratio and indoor mean‐to‐median ratio. Short‐term spikes were associated with occupants and their activities, especially cooking. High‐baseline compounds indicate continuous indoor emissions from building materials and furnishings. Indoor emission rates for high‐baseline species, quantified with 2‐hour resolution, exhibited strong temperature dependence and were affected by air‐change rates. Decomposition of wooden building materials is suggested as a major source for acetic acid, formic acid, and methanol, which together accounted for ~75% of the total continuous indoor emissions of high‐baseline species.     

Indoor emissions of total and fluorescent supermicron particles during HOMEChem

Inhalation of particulate matter is associated with adverse health outcomes. The fluorescent portion of supermicron particulate matter has been used as a proxy for bioaerosols. The sources and emission rates of fluorescent particles in residential environments are not well-understood. Using an ultraviolet aerodynamic particle sizer (UVAPS), emissions of total and fluorescent supermicron particles from common human activities were investigated during the HOMEChem campaign, a test-house investigation of the chemistry of indoor environments. Human occupancy and activities, including cooking and mopping, were found to be considerable sources of indoor supermicron fluorescent particles, which enhanced the indoor particle concentrations by two orders of magnitude above baseline levels. The estimated total (fluorescent) mass emission rates for the activities tested were in the range of 4-30 (1-11) mg per person meal for cooking and 0.1-4.9 (0.05-4.7) mg/h for occupancy and mopping. Model calculations indicate that, once released, the dominant fate of coarse particles (2.5-10 micrometer in diameter) was deposition onto indoor surfaces, allowing for the possibility of subsequent resuspension and consequent exposures over durations much longer than the ventilation time scale. Indoor coarse particle deposition would also contribute to soiling of indoor surfaces.     

Trout‐Skin Gelatin‐Based Edible Films Containing Phenolic Antioxidants: Effect on Physical Properties and Oxidative Stability of Cod‐Liver Oil Model Food

Abstract: Trout‐skin (Oncorhynchus mykiss) gelatin‐based films containing antioxidants (epigallocatechin gallate (EGCG), 50 and 250 ppm w/w) and green tea powder (1% and 20% w/w of gelatin) were tested for tensile strength, elastic modulus, and elongation, and oxygen and water vapor transmission rates, in vitro antioxidant activity using the DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay and effect on stabilizing cod‐liver oil held under mild thermal abuse conditions. Cod‐liver oil overlaid with films was stored at 40 °C for 20 d and analyzed for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Antioxidant activity was retained in films containing green tea powder, but was reduced (P < 0.05) in EGCG films (20 d, 23 °C). Water vapor transmission rate of the films incorporated with antioxidants did not change significantly (P > 0.05), but the oxygen transmission rate for films with 50 ppm EGCG and 20% green tea powder was significant (P < 0.05). Other physical properties varied with antioxidant incorporation. The TBARS and PV of control oil increased from 0.05 ± 0.01 to 4.71 ± 0.30 g MDA/kg oil and from 3.6 ± 0.2 to 178.3 ± 24.5 millieq peroxides/kg oil, respectively, after 20 d. For cod‐liver oil covered with control or antioxidant‐containing films, TBARS remained below 0.37 g MDA/kg oil and PV below 7 millieq peroxides/kg oil. Incorporation of antioxidants to the films did not reduce oil oxidation (P > 0.05) at the levels tested and this was confirmed by activation energy calculations. The rate of oil oxidation was more dependent upon the inherent oxygen barrier property of the films than the presence of antioxidants. Practical Application: This research has the potential to enhance the utilization of fish skins, a valuable food processing by‐product, as edible films with natural antioxidants to extend the shelf life of foods. The film physical properties and barrier to oxygen and water are investigated.     

Eumelanin for nature‐inspired UV‐absorption enhancement of plastics

In the human body, the black‐brown biopigment eumelanin blocks harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV‐absorption properties. We herein report an assessment of the biopigment eumelanin as a nature‐inspired additive for plastics to enhance their UV absorption. Since eumelanin is produced by natural sources and is nontoxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, the eumelanin‐containing films of commercial ethylene–vinyl acetate copolymer, a plastic used for packaging applications, were obtained by melt compounding and compression molding. The biopigment dispersion in the films was improved by means of the melanin free acid treatment. It was observed that eumelanin amounts as low as 0.8 wt% caused an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal stability and photostability of the films: the biopigment proved to be double‐edged, working both as UV‐absorption enhancer and photo‐prooxidant, as thermogravimetric analysis and infrared spectroscopy revealed. © 2019 Society of Chemical Industry     

Mass balance and kinetic analysis of anaerobic microbial dechlorination of pentachlorophenol in a continuous flow column

A mass balance and kinetic investigation of anaerobic dechlorination of pentachlorophenol (PCP) was undertaken using an enriched microbial consortium in a laboratory scale continuous flow column, as a model microbial permeable reactive barrier. The chlorine balance showed that 50 µM PCP was largely dechlorinated to phenol with the formation of a small quantity of 3-chlorophenol as an intermediate metabolite (hydraulic retention time 7.6 days), and the chlorine removal efficiency reached 36 µM d^-1. When the initial PCP concentration was increased to 100 µM the chlorine removal efficiency increased 1.5 times. However, the dechlorination activity disappeared after 7.4 pore volumes (58 days), demonstrating the susceptibility of the dechlorination culture to high concentrations of PCP. Lactate released hydrogen as an electron donor during PCP dechlorination, with acetate, propionate, CO₂ and CH₄ as byproducts. The carbon balance showed that some of the organic carbon source (PCP, lactate) in the influent was converted to gas and utilized for biomass growth in addition to organic metabolites. The kinetic study was conducted in a batch culture and yielded 1.99 mg l^-1 biomass growth per unit of chlorine consumption (µM). The Monod equation was well fitted to the specific growth rate of 1.38 d^-1 and a half saturation constant of 0.29 µM. The organic chlorine removal rate in the batch culture was consistent with the results in the flow column, indicating the feasibility of and potential for in situ estimation and prediction through batch culture studies.     

The House Mouse (Mus musculus L.) Exerts Strong Differential Grain Consumption Preferences among Hard Red and White Spring Wheat (Triticum aestivum L.) Varieties in a Single‐Elimination Tournament Design

Wheat (Triticum aestivum L.) plays a central role in the health and nutrition of humans. Yet, little is known about possible flavor differences among different varieties. We have developed a model system using the house mouse (Mus musculus L.) to determine feeding preferences as a prelude to extending results to human sensory analysis. Here, we examine the application of a single‐elimination tournament design to the analysis of consumption preferences of a set of hard red and hard white spring wheat varieties. A single‐elimination tournament design in this case pairs 2 wheat varieties and only 1 of the 2 is advanced to further tests. Preferred varieties were advanced until an overall “winner” was identified; conversely, less desirable varieties were advanced such that an overall “loser” was identified. Hollis and IDO702 were the winner and loser, respectively, for the hard red varieties, and Clear White 515 and WA8123 were the winner and loser, respectively, for the hard white varieties. When using the more powerful protocol of 14 mice and a 4?d trial, differences in mean daily consumption preferences of 2 varieties were separated at P‐values as small as 2 × 10^?8. The single‐elimination tournament design is an efficient means of identifying the most and least desirable varieties among a larger set of samples. One application for identifying the 2 extremes in preference within a group of varieties would be to use them as parents of a population to identify quantitative trait loci for preference.     

Comparison of two low-hazard organic solvents as individual and cosolvents for the fabrication of polysulfone membranes

Petroleum-derived solvents commonly used in membrane fabrication are often hazardous and toxic, so the investigation of safer alternatives is important. In this study, two low-hazard solvents, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv® PolarClean) and gamma-valerolactone (GVL), were investigated as sole solvents and as cosolvents to cast polysulfone membranes via nonsolvent induced phase inversion. Normalized viscosity was introduced as an indicator of dope solution homogeneity and was used to compare the required time of mixing to achieve full dissolution of the polymer in the different solvents/solvent mixtures. All dope solutions made with low-hazard solvents were found to be more viscous than those made with traditional solvents, which meant additional mixing time was needed, and that fabricated membranes were morphologically different. With respect to operation, membranes cast from dope solutions containing equal amounts of PolarClean and GVL displayed the most similar flux curves and solute rejection to those made using the traditional solvent tested.     

Modified Atmosphere Packaging Technology of Fresh and Fresh-cut Produce and the Microbial Consequences—A Review

Modified atmosphere packaging (MAP) technology offers the possibility to retard the respiration rate and extend the shelf life of fresh produce, and is increasingly used globally as value adding in the fresh and fresh-cut food industry. However, the outbreaks of foodborne diseases and emergence of resistant foodborne pathogens in MAP have heightened public interest on the effects of MAP technology on the survival and growth of pathogenic organisms. This paper critically reviews the effects of MAP on the microbiological safety of fresh or fresh-cut produce, including the role of innovative tools such as the use of pressurised inert/noble gases, predictive microbiology and intelligent packaging in the advancement of MAP safety. The integration of Hazard Analysis and Critical Control Points-based programs to ensure fresh food quality and microbial safety in packaging technology is highlighted.