Effect of Humic Acid on Adsorption of Polychlorinated Biphenyls onto Organoclay

Mitigation of risks stemming from contaminated sediments in freshwater and estuarine environments remains an important challenge to the field of environmental science and engineering. Capping sediments with reactive materials is one approach that has recently been the subject of research and development. This research evaluated the use of organoclay as a sorbent in a reactive cap for in situ remediation of contaminated sediments, and provides an original contribution by presenting the sorption characteristics of individual polychlorinated biphenyls (PCB) congeners in the presence of high concentrations of humic acids typical of sediment porewater environments. Sorption of coplanar and noncoplanar PCBs on three commercially available organoclays was studied in this work. Studies were conducted to evaluate the kinetics of adsorption of PCBs on organoclay and to determine the effect of humic acid on the kinetics of adsorption. Isotherm studies were conducted to determine the adsorption affinity of PCBs for organoclays in the presence and absence of humic acid. Studies showed a 45 to 96% reduction in the sorption affinity for organoclays after preloading with high concentrations of humic acid, depending both on the congener and the composition of organoclay. Desorption of PCBs upon addition of humic acid after PCBs were equilibrated with organoclay was statistically significant, although the magnitude of the effect was much smaller than that observed from preloading of humic acid

Evaluation of Activated Carbon as a Reactive Cap Sorbent for Sequestration of PCBs in Presence of Humic Acid

This study investigated the interferences caused by high humic acid concentrations on the adsorption of coplanar and noncoplanar polychlorinated biphenyls (PCBs) on coconut shell activated carbon. In particular, the research focuses on the application of activated carbon as a reactive cap for contaminated sediment sites, a possible intervention to reduce contaminant flux through pore water, and to organisms in aquatic environments. Kinetic and equilibrium studies were conducted using activated carbon as a sorbent for individual PCB congeners including BZ 1, 52, 77, 153, and 169, respectively, in the presence and absence of humic acid. Results showed that preloading of activated carbon with humic acid significantly reduced the adsorption affinity for all selected PCB congeners. Experiments conducted without preloading of activated carbon demonstrated that desorption upon subsequent spiking with humic acid (simulating long-term exposure to pore water that contains high humic acid concentrations) was not found to be statistically significant, and varied with coplanarity of PCBs. Results provide important information for the design of reactive caps in sediments where high concentrations of dissolved organic carbon are found, and highlight the importance of considering site conditions when designing effective reactive caps

The Computer for Charting and Monitoring

book chapterBiomedical Informatic

A new hardware architecture for genomic and proteomic sequence alignment

Los Alamitos, US

DASH: localising dynamic programming for order of magnitude faster, accurate sequence alignment

Los Alamitos, US

Restricting mutualistic partners to enforce trade reliance

Mutualisms are cooperative interactions between members of different species, often involving the trade of resources. Here, we suggest that otherwise- cooperative mutualists might be able to gain a benefit from actively restricting their partners’ ability to obtain resources directly, hampering the ability of the restricted partner to survive and/or reproduce without the help of the restricting mutualist. We show that: (i) restriction can be favoured when restricting individuals increase their comparative advantage and thus receive more favourable terms of trade; (ii) restriction maintains cooperation in conditions where cooperative behaviour would otherwise collapse; and (iii) restriction can lead to either an increase or decrease in a restricted individual’s fitness. We discuss the applicability of this scenario to mutualisms such as those between plants and mycorrhizal fungi. These results identify a novel conflict in mutualisms as well as several public goods dilemmas, but also demonstrate how conflict can help maintain cooperation.Publisher PDFPeer reviewe

Centerline Curbing Treatment at Railroad Crossings for Improved Safety

The objectives of this research were to study unsafe actions of motor vehicle drivers at railroadhighway grade crossings, to evaluate centerline barriers in reducing those unsafe driver actions, and to note any maintenance or other issues with the barriers. Driver actions were observed at two railroad crossings before and after installation of centerline barriers. A comparison of observed driver actions in the pre- and post-barrier periods provided information on the effectiveness of the barriers in reducing unsafe driver actions while periodic inspection of the centerline barriers provided information on maintenance needs. A major concern of the Nebraska Department of Roads is the potential for crashes at railroad-highway grade crossings resulting from unsafe actions of motorists such as, rushing the gates to beat an oncoming train or playing “chicken” with an approaching train, among others. Playing “chicken” refers to intentional standing of a motor vehicle on railroad tracks and only moving when the train hits the brakes. Crashes at railroad-highway crossings may not necessarily involve trains as some driver actions (e.g., backing up, and U-turns) may result in crashes involving motor vehicles only. In this research the crossing at North 141st Street in the City of Waverly, NE and the crossing at “M” Street in the City of Fremont, NE were monitored with the help of day and night vision cameras and digital video recorders. Motor vehicle driver actions were observed whenever the gates were down and instances of unsafe actions noted. In an effort to reduce gate rushing and other unsafe motorist actions, the researchers installed flexible rubber and plastic barriers on both sides of the crossings along roadway centerlines to prevent motorists from going around the gates. The actions of motor vehicle drivers were monitored in the post-barrier period and compared to the pre-install period using appropriate statistical tools. Results of the comparison show that fewer unsafe driver actions were observed after installation of the centerline barriers. In particular, installation of centerline barriers significantly reduced instances of gate rushing at the two study sites. Centerline barriers are recommended for use at railroad crossings where unsafe driver actions (e.g., gate rushes) are a concern. Damage to the barriers as a result of abuse from roadway vehicles was noted while no snowplowing issues came to the attention of the researchers during the study period. The amount of damage was a function of traffic volume, percentage of trucks, and if sharp turns were involved. Finally, this study revealed instances of pedestrians and bicyclists engaged in unsafe actions at railroad crossings, which are recommended for investigation in a future study

Effect of Green Tea on Streptococcus mutans Metabolic Activity, Planktonic Growth, and Biofilm Activity in the Presence of Nicotine

poster abstractStreptococcus mutans is the main bacterial cause of dental caries, and it has been proven by previous research that its growth is affected by various concentrations of nicotine and other agents. The amount of S. mutans in the mouth is directly proportional to the number of dental cavities. Studies have shown that smokers have an increased amount of caries, much of which is due to the low concentrations of nicotine the mouth is exposed to. It is known that S. mutans thrives in low-moderate concentrations of nicotine, and that nicotine is a promoting agent for S. mutans. S. mutans has also been proven as a contributor to atherosclerosis, resulting from dental plaque entering the bloodstream. Green Tea is a commonly consumed beverage, which has been known to reduce the number of dental cavities. Previous research has concluded that green tea contains polyphenols, which have antimicrobial effects, including an inhibitory effect on S. mutans. The objective of this research is to observe how green tea affects S. mutans metabolic activity, as well as biofilm and planktonic growth, in the presence of nicotine. The experiments compared S. mutans treated with nicotine concentrations (0-8 mg/ml), and S. mutans treated with a 2.5 g/200 mL concentration of Sencha Jade Reserve Japanese green tea in conjunction with the various nicotine concentrations. The assays were performed in a microtiter plate; the XTT and biofilm assays measured absorbance, and the planktonic assay measured kinetic growth. The experiments conclude that green tea has an inhibitory effect on nicotine-treated S. mutans metabolic activity and planktonic growth, with higher concentrations of green tea inhibiting more effectively. It was also concluded that green tea increases biofilm formation. These conclusions provide evidence of the inhibitory effect green tea has on nicotine-treated S. mutans, and may indicate a way to reduce the incidence of caries and atherosclerosis

Mars habitat

The objective of this study is to develop a conceptual design for a permanently manned, self-sustaining Martian facility, to accommodate a crew of 20 people. The goal is to incorporate the major functions required for long term habitation in the isolation of a barren planet into a thriving ecosystem. These functions include living, working, service, and medical facilities as well as a green house. The main design task was to focus on the internal layout while investigating the appropriate structure, materials, and construction techniques. The general concept was to create a comfortable, safe living environment for the crew members for a stay of six to twelve months on Mars. Two different concepts were investigated, a modular assembly reusable structure (MARS) designated Lavapolis, and a prefabricated space frame structure called Hexamars. Both models take into account factors such as future expansion, radiation shielding, and ease of assembly

A stability index for detonation waves in Majda's model for reacting flow

Using Evans function techniques, we develop a stability index for weak and strong detonation waves analogous to that developed for shock waves in [GZ,BSZ], yielding useful necessary conditions for stability. Here, we carry out the analysis in the context of the Majda model, a simplified model for reacting flow; the method is extended to the full Navier-Stokes equations of reacting flow in [Ly,LyZ]. The resulting stability condition is satisfied for all nondegenerate, i.e., spatially exponentially decaying, weak and strong detonations of the Majda model in agreement with numerical experiments of [CMR] and analytical results of [Sz,LY] for a related model of Majda and Rosales. We discuss also the role in the ZND limit of degenerate, subalgebraically decaying weak detonation and (for a modified, ``bump-type'' ignition function) deflagration profiles, as discussed in [GS.1-2] for the full equations.Comment: 36 pages, 3 figure