Scientific Publications 2007
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2007. "Validation of Potential Models for Li2O in Classical Molecular Dynamics Simulation." Journal of Nuclear Materials 367-370:263-268. doi:10.1016/j.jnucmat.2007.03.139 Abstract Four Buckingham-type pairwise potential models for Li2O were assessed by molecular static and dynamics simulations. In the static simulation, all models afforded acceptable agreement with experimental values and ab initio calculation results for the crystalline properties. Moreover, the superionic phase transition was realized in the dynamics simulation. However, the Li diffusivity and the lattice expansion were not adequately reproduced at the same time by any model. When using these models in future radiation simulation, these features should be taken into account, in order to reduce the model dependency of the results.
2007. "Cyanobacterial NADPH dehydrogenase complexes." Photosynthesis Research 93(1-3):69-77. doi:10.1007/s11120-006-9128-y Abstract Cyanobacteria possess functionally distinct multiple NADPH dehydrogenase (NDH-1) complexes that are essential to CO2 uptake, photosystem-1 cyclic electron transport and respiration. The unique nature of cyanobacterial NDH-1 complexes is the presence of subunits involved in CO2 uptake. Other than CO2 uptake, chloroplastic NDH-1 complex has similar role as cyanobacterial NDH-1 complexes in photosystem-1 cyclic electron transport and respiration (chlororespiration). In this mini-review we focus on the structure and function of cyanobacterial NDH-1 complexes and their phylogeny. The function of chloroplastic NDH-1 complex and characteristics of plants defective in NDH-1 are also described forcomparison.
2007. "A Review of Multidimensional, Multifluid Intermediate-scale Experiments: Flow Behavior, Saturation Imaging, and Tracer Detection and Quantification ." Vadose Zone Journal 6(3):610-637. doi:10.2136/vzj2006.0178 Abstract A review is presented of original multidimensional, intermediate-scale experiments involving non-aqueous phase liquid (NAPL) flow behavior, imaging, and detection/quantification with solute tracers. In a companion paper (Oostrom, M., J.H. Dane, and T.W. Wietsma. 2006. A review of multidimensional, multifluid intermediate-scale experiments: Nonaqueous phase dissolution and enhanced remediation. Vadose Zone Journal 5:570-598) experiments related to aqueous dissolution and enhanced remediation were discussed. The experiments investigating flow behavior include infiltration and redistribution experiments with both light and dense NAPLs in homogeneous and heterogeneous porous medium systems. The techniques used for NAPL saturation mapping for intermediate-scale experiments include photon-attenuation methods such as gamma and X-ray techniques, and photographic methods such as the light reflection, light transmission, and multispectral image analysis techniques. Solute tracer methods used for detection and quantification of NAPL in the subsurface are primarily limited to variations of techniques comparing the behavior of conservative and partitioning tracers. Besides a discussion of the experimental efforts, recommendations for future research at this laboratory scale are provided.
2007. "Three-Dimensional Multifluid Flow and Transport at the Brooklawn Site near Baton Rouge, LA: A Case Study." Soil & Sediment Contamination 16(2):109-141. Abstract Disposal quantities of organic wastes at the Brooklawn Site in Louisiana are suspected to equal nearly 160 Ktons, making this site one of the most contaminated DNAPL sites in the world. Remedial activities at the site include groundwater and dense nonaqueous phase liquid (DNAPL) extraction from recovery wells. DNAPL recovery has markedly declined in recent years, with many of the peripheral wells showing negligible recovery of organic liquids. Three-dimensional simulations of DNAPL movement in the subsurface were conducted using the STOMP simulator, including a new coupled well model. The objectives of this modeling effort were to (1) determine the fate and transport of infiltrated DNAPL, and (2) measure the effects of active recovery through DNAPL pumping. A detailed three-dimensional geologic model of the Brooklawn primary DNAPL disposal area was developed and used as the framework for DNAPL simulations. Additionally, site-specific data were obtained to obtain the most important hydraulic properties of the subsurface related to DNAPL movement and formation of entrapped DNAPL in the laboratory. Besides a simulation using the best available subsurface information, several sensitivity simulations were conducted to assess the effects on DNAPL migration. These simulations include DNAPL pumping, well screen extension, an alternative geology, increased DNAPL density, lower DNAPL viscosity, and more-permeable sand and silt deposits. Results of the simulations were compared to field data that define the extent of DNAPL movement based on where DNAPL has been extracted in the site recovery wells. The model simulations predict no significant reduction in the extent of the DNAPL as a result of pumping. Pumping returns diminish rapidly due to the limited radius of influence of the wells and movement of the DNAPL out of the zone of influence of the wells with a maximum radius of influence of about 6 m. The numerical analysis also demonstrates that it is impractical to extend existing wells or install new wells to retrieve enough DNAPL to affect the overall extent of DNAPL movement.
2007. "Carbon Tetrachloride Flow and Transport in the Subsurface of the 216-Z-9 Trench at the Hanford Site." Vadose Zone Journal 6(4):971-984. doi:10.2136/vzj2006.0166 Abstract Carbon tetrachloride (CT) was discharged to waste sites at the Hanford 200 West Area. Three-dimensional modeling was conducted to enhance the conceptual model of CT distribution in the vertical and lateral direction beneath the 216-Z-9 trench and to investigate the effects of soil vapor extraction. Simulations focused on migration of dense, nonaqueous phase liquid (DNAPL) consisting of carbon tetrachloride and co-disposed organics as a function of the properties and distribution of subsurface sediments and of the properties and disposal history of the waste. The simulations of CT migration were conducted using the Subsurface Transport Over Multiple Phases (STOMP) simulator. Simulation results support a conceptual model for CT distribution where CT in the DNAPL phase is expected to have migrated primarily in a vertical direction below the disposal trench. Results also show that the Cold Creek low permeability units retain more CT DNAPL within the vadose zone than other hydrologic unit during during soil vapor extraction. Additional characterization of the Cold Creek units would provide valuable information about the quantity of CT DNAPL remaining in the vadose zone. A significant amount of the disposed CT DNAPL may have partitioned to the vapor and subsequently water and sorbed phases. Any continued migration of CT from the vadose zone to the groundwater is likely through interaction of vapor phase CT with the groundwater and not through continued DNAPL migration. Additional effort is needed to enhance the understanding of rate-limited volatilization to improve simulation of the SVE process and to provide a basis for refining the design and operation of SVE systems.
2007. "Zero-valent Iron Emplacement in Permeable Porous Media Using Polymer Additions." Ground Water Monitoring and Remediation 27(1):122-130. Abstract At the Hanford Site in Washington, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. One possible cause for premature chromate breakthrough is associated with the presence of high-permeability zones in the aquifer. The potential emplacement of zero-valent iron (Fe0) into high-permeability Hanford sediments to enhance the barrier’s reductive capacity using shear-thinning fluids containing polymers was investigated in three-dimensional wedge-shaped aquifer models. Porous media were packed in the wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone between two low-permeability zones or a high-permeability channel surrounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments. The flow cell experiments indicated that iron concentration enhancements of at least 0.6% (w/w) could be obtained using moderate flow rates and injection of 30 pore volumes. The aqueous pressure increased by a maximum of 25 KPa during infiltration, but a decrease in permeability was not observed. Under optimal conditions, the 0.6% amended Fe0 concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced Fe (II) in the ISRM barrier.
2007. "Submicron and Nanoscale Inorganic Particles Exploit the Actin Machinery to be Propelled Along Microvillilike Structures into Alveolar Cells." ACS Nano 1(5):463-475. doi:10.1021/nn700149r Abstract The growing commerce in micro- and nanotechnology is expected to increase our exposure to submicron and nanoscale particles. One of the main targets of this exposure are the cells that line the respiratory tract, among them are the alveolar type II epithelial cells that have microvilli at their exposed apical surface. Here we show a pathway by which positively charged inorganic submicron and nanoscale particles take advantage of the actin turnover machinery within filopodia and microvilli-like structures to guide and advance their way into these cells. Our observations bring a new view of how submicron and nanoscale inorganic matter can be assimilated into the cellular environment and take advantage of its machinery. While the pathway that we describe can be exploited for a targeted drug delivery, it also points to properties of submicron or nanoscale particles that should be avoided in order to reduce particle internalization and possible toxicity.
2007. "Upconversion Luminescence of Colloidal CdS and ZnCdS Semiconductor Quantum Dots." Journal of Physical Chemistry C 111(44):16261-16266. doi:10.1021/jp074416b Abstract Strong upconversion luminescence is observed from colloidal CdS and CdZnS quantum dots dispersed in hexanes. The nanocrystals were synthesized via non-hot-injection approaches at relatively low temperature, exhibiting cubic crystal structures and narrow size distribution. The upconversion luminescence emission spectra of these binary and ternary nanocrystal ensembles studied are similar in both peak shape and position compared to their corresponding photoluminescence emission spectra. The upconversion luminescence exhibits a near quadratic laser power dependence. Furthermore, the upconversion and photoluminescence show similar decay dynamics. Accordingly, our study indicates that the upconversion luminescence is due to two-photon excitation.
2007. "Use of a Novel Fluidics Microbead Trap/Flow-cell Enhances Speed and Sensitivity of Bead-Based Bioassays." JALA. Journal of the Association for Laboratory Automation 12(5):303-310. doi:10.1016/j.jala.2007.05.002 Abstract Automated devices and methods for biological sample preparation often utilize surface functionalized microbeads (superparamagnetic or non-magnetic) to allow capture, purification and pre-concentration of trace amounts of proteins, cells, or nucleic acids (DNA/RNA) from complex samples. We have developed unique methods and hardware for trapping either magnetic or non-magnetic functionalized beads that allow samples and reagents to be efficiently perfused over a micro-column of beads. This approach yields enhanced mass transport and up to 5-fold improvements in assay sensitivity or speed, dramatically improving assay capability relative to assays conducted in more traditional “batch modes” (i.e., in tubes or microplate wells). Summary results are given that highlight the analytical performance improvements obtained for automated microbead processing systems utilizing novel microbead trap/flow-cells for various applications, including: 1) simultaneous capture of multiple cytokines using an antibody-coupled polystyrene bead assay with subsequent flow cytometry detection; 2) capture of nucleic acids using oligonucleotide coupled polystyrene beads with flow cytometry detection; and 3) capture of Escherichia coli 0157:H7 (E. coli) from 50 mL sample volumes using antibody-coupled superparamagnetic microbeads with subsequent culturing to assess capture efficiency.
