Effect of Pyrolysis on the Removal of Antibiotic Resistance Genes and Class I Integrons from Municipal Wastewater Biosolids

Wastewater biosolids represent a significant reservoir of antibiotic resistance genes (ARGs). While current biosolids treatment technologies can reduce ARG levels in residual wastewater biosolids, observed removal rates vary substantially. Pyrolysis is an anoxic thermal degradation process that can be used to convert biosolids into energy rich products including py-gas and py-oil, and a beneficial soil amendment, biochar. Batch pyrolysis experiments conducted on municipal biosolids revealed that the 16S rRNA gene, the ARGs erm(B), sul1, tet(L), tet(O), and the integrase gene of class 1 integrons (intI1) were significantly reduced at pyrolysis temperatures ranging from 300–700 °C, as determined by quantitative polymerase chain reaction (qPCR). Pyrolysis of biosolids at 500 °C and higher resulted in approximately 6-log removal of the bacterial 16S rRNA gene. ARGs with the highest observed removals were sul1 and tet(O), which had observed reductions of 4.62 and 4.04-log, respectively. Pyrolysis reaction time had a significant impact on 16S rRNA, ARG and intI1 levels. A pyrolysis residence time of 5 minutes at 500 °C reduced all genes to below detection limits. These results demonstrate that pyrolysis could be implemented as a biosolids polishing treatment technology to substantially decrease the abundance of total bacteria (i.e., 16S rRNA), ARGs and intI1 prior to land application of municipal biosolids

Time-Series Ensemble Photometry and the Search for Variable Stars in the Open Cluster M11

This work presents the first large-scale photometric variability survey of the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over two observing seasons were analyzed (using crowded field and ensemble photometry techniques) to obtain high relative precision photometry. In this study we focus on the detection of candidate member variable stars for follow-up studies. A total of 39 variable stars were detected and can be categorized as follows: 1 irregular (probably pulsating) variable, 6 delta Scuti variables, 14 detached eclipsing binary systems, 17 W UMa variables, and 1 unidentified/candidate variable. While previous proper motion studies allow for cluster membership determination for the brightest stars, we find that membership determination is significantly hampered below V=15,R=15.5 by the large population of field stars overlapping the cluster MS. Of the brightest detected variables that have a high likelihood of cluster membership, we find five systems where further work could help constrain theoretical stellar models, including one potential W UMa member of this young cluster.Comment: 38 pages, 13 figures, accepted for December 2005 AJ, high-resolution version available upon reques

The Manipulation and Examination of \u3cem\u3eWolbachia\u3c/em\u3e in Medically Important Mosquitoes

Mosquitoes are a major vector of human disease and result in massive costs to public health in affected regions. It has been suggested that Wolbachia pipientis could be used for mosquito population reduction. Wolbachia is a maternally-transmitted endosymbiont of arthropods and nematodes that infects the cytoplasm of host cells. In mosquitoes, Wolbachia manipulates reproduction through Cytoplasmic Incompatibility (CI), which is characterized by a cessation of embryonic development in certain crossing-types. However, the relationship between Wolbachia and its host is complex and not fully understood. The crossing relationships between naturally-infected and aposymbiotic populations of Culex pipiens pipiens and Culex pipiens molestus were examined in order to better understand the effects of CI on life history traits such as egg production and egg hatch. Hatch consistent with a unidirectional incompatibility relationship was observed. However, low egg production was also observed in some crossing-types, implying that Wolbachia may manipulate its host in unknown ways. In addition, uninfected mosquito eggs were injected with cytoplasm from infected eggs to generate artificially infected Culex lines. While no transinfected lines were successfully generated, several observations were made that may prove useful in future microinjection research

QUASI-EXPERIMENTAL DESIGNS FOR MEASURING IMPACTS OF DEVELOPMENTAL HIGHWAYS IN RURAL AREAS

Quasi-experimental techniques were developed to provide decision-making tools for documenting the impacts of developmental highways in rural areas. Regression discontinuity analysis (RDA) with limited observations was used to compare economic changes in highway counties to those in adjacent and non-adjacent control counties. The RDA models found statistically significant changes in population, per capita income, and taxable sales related to highway development. The study found that some counties benefited from developmental highways, some were unchanged, while some experienced economic decline. RDA models with adjacent controls had better explanatory powers while those with non-adjacent controls were more sensitive to highway-related changes in economic activity. When significant non-highway activities were present, adjacent control models may have understated highway-related impacts, while non-adjacent control models may have overstated these impacts. Arguments for using adjacent and non-adjacent experimental designs are discussed.Community/Rural/Urban Development,

Homogeneous cooling of rough, dissipative particles: Theory and simulations

We investigate freely cooling systems of rough spheres in two and three dimensions. Simulations using an event driven algorithm are compared with results of an approximate kinetic theory, based on the assumption of a generalized homogeneous cooling state. For short times $t$, translational and rotational energy are found to change linearly with $t$. For large times both energies decay like $t^{-2}$ with a ratio independent of time, but not corresponding to equipartition. Good agreement is found between theory and simulations, as long as no clustering instability is observed. System parameters, i.e. density, particle size, and particle mass can be absorbed in a rescaled time, so that the decay of translational and rotational energy is solely determined by normal restitution and surface roughness.Comment: 10 pages, 10 eps-figure

TAP reactor investigation of methane coupling over samarium oxide catalysts

The adsorption and reaction characteristics of a Ba/Sr/Sm2O3 catalyst for methane coupling has been investigated using the TAP (Temporal Analysis of Products) reactor system. Pulsed adsorption experiments using methane, oxygen and krypton at temperatures ranging from 17°C to 800°C show that the transient response of methane is similar to that of Kr and is either not adsorbed, or weakly adsorbed on the catalyst. By contrast, oxygen is strongly adsorbed at temperatures above 500°C which suggests incorporation into the lattice with possible formation of surface anions. Pump-probe experiments in which methane and oxygen are introduced over the catalyst were also performed to investigate the effect of lifetimes of suspected surface intermediates on the relative yields of ethane and ethene. It is shown that the relative yields of both species increase with increasing values of the pulse valve time delay between introduction of the oxygen and methane. An explanation of these results using current knowledge and reasonable speculation of the mechanism is provided

Measurement of Indeterminacy in Packings of Perfectly Rigid Disks

Static packings of perfectly rigid particles are investigated theoretically and numerically. The problem of finding the contact forces in such packings is formulated mathematically. Letting the values of the contact forces define a vector in a high-dimensional space enable us to show that the set of all possible contact forces is convex, facilitating its numerical exploration. It is also found that the boundary of the set is connected with the presence of sliding contacts, suggesting that a stable packing should not have more than 2M-3N sliding contacts in two dimensions, where M is the number of contacts and N is the number of particles. These results were used to analyze packings generated in different ways by either molecular dynamics or contact dynamics simulations. The dimension of the set of possible forces and the number of sliding contacts agrees with the theoretical expectations. The indeterminacy of each component of the contact forces are found, as well as the an estimate for the diameter of the set of possible contact forces. We also show that contacts with high indeterminacy are located on force chains. The question of whether the simulation methods can represent a packing's memory of its formation is addressed.Comment: 12 pages, 13 figures, submitted to Phys Rev

Triclocarban Influences Antibiotic Resistance and Alters Anaerobic Digester Microbial Community Structure

Triclocarban (TCC) is one of the most abundant organic micropollutants detected in biosolids. Lab-scale anaerobic digesters were amended with TCC at concentrations ranging from the background concentration of seed biosolids (30 mg/kg) to toxic concentrations of 850 mg/kg to determine the effect on methane production, relative abundance of antibiotic resistance genes, and microbial community structure. Additionally, the TCC addition rate was varied to determine the impacts of acclimation time. At environmentally relevant TCC concentrations (max detect = 440 mg/kg), digesters maintained function. Digesters receiving 450 mg/kg of TCC maintained function under gradual TCC addition, but volatile fatty acid concentrations increased, pH decreased, and methane production ceased when immediately fed this concentration. The concentrations of the mexB gene (encoding for a multidrug efflux pump) were higher with all concentrations of TCC compared to a control, but higher TCC concentrations did not correlate with increased mexB abundance. The relative abundance of the gene tet(L) was greater in the digesters that no longer produced methane, and no effect on the relative abundance of the class 1 integron integrase encoding gene (intI1) was observed. Illumina sequencing revealed substantial community shifts in digesters that functionally failed from increased levels of TCC. More subtle, yet significant, community shifts were observed in digesters amended with TCC levels that did not inhibit function. This research demonstrates that TCC can select for a multidrug resistance encoding gene in mixed community anaerobic environments, and this selection occurs at concentrations (30 mg/kg) that can be found in full-scale anaerobic digesters (U.S. median concentration = 22 mg/kg, mean = 39 mg/kg)