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in creator/contributor: "Wilkins, M."

open access

Analysis of biostimulated microbial communities from two field experiments reveals temporal and spatial differences in proteome profiles

Stimulated by an acetate-amendment field experiment conducted in 2007, anaerobic microbial populations in the aquifer at the Rifle Integrated Field Research Challenge site in Colorado reduced mobile U(VI) to insoluble U(IV). During this experiment, planktonic biomass was sampled at various time points to quantitatively evaluate proteomes. In 2008, an acetate-amended field experiment was again conducted in a similar manner to the 2007 experiment. As there was no comprehensive metagenome sequence… more

Date: July 15, 2010

Creator: Callister, S. J.; Wilkins, M. J.; Nicora, C. D.; Williams, K. H.; Banfield, J. F.; VerBerkmoes, N. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Composition, stability, and measurement of reduced uranium phases for groundwater bioremediation at Old Rifle, CO

Reductive biostimulation is currently being explored as a possible remediation strategy for uranium (U) contaminated groundwater, and is currently being investigated at a field site in Rifle, CO, USA. The long-term stability of the resulting U(IV) phases is a key component of the overall performance and depends upon a variety of factors, including rate and mechanism of reduction, mineral associations in the subsurface, and propensity for oxidation. To address these factors, several approaches w… more

Date: October 15, 2011

Creator: Campbell, K. M.; Davis, J. A.; Bargar, J.; Giammar, D.; Bernier-Latmani, R.; Kukkadapu, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Impact studies of five ceramic materials and pyrex

We measured the ballistic performance of five ceramic materials (alumina, silicon carbide, boron carbide, aluminum nitride, and titanium diboride) and Pyrex, when they are backed by thick steel plates. The projectile for all tests was a right-circular cylinder of tungsten sinter-alloy W2 with length 25.4 mm and diameter 6.35 mm, fired at velocities from 1.35 to 2.65 km/s. For this threat we determined the minimum areal density of each material that is needed to keep the projectile from penetrat… more

Date: May 22, 1998

Creator: Cunningham, B. J.; Holt, A. C.; Hord, B. L.; Kusubov, A. S.; Reaugh, J. E. & Wilkins, M. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Expression of acetate permease-like (apl) genes in subsurface communities of Geobacter species under fluctuating acetate concentrations

The addition of acetate to uranium-contaminated aquifers in order to stimulate the growth and activity of Geobacter species that reduce uranium is a promising in situ bioremediation option. Optimizing this bioremediation strategy requires that sufficient acetate be added to promote Geobacter species growth. We hypothesized that under acetate-limiting conditions, subsurface Geobacter species would increase the expression of either putative acetate symporters genes (aplI and aplII). Acetate was a… more

Date: March 1, 2010

Creator: Elifantz, H.; N'Guessan, L. A.; Mouser, P. J.; Williams, K. H.; Wilkins, M. J.; Risso, C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mineral transformation and biomass accumulation associated with uranium bioremediation at Rifle, Colorado

Injection of organic carbon into the subsurface as an electron donor for bioremediation of redox-sensitive contaminants like uranium often leads to mineral transformation and biomass accumulation, both of which can alter the flow field and potentially bioremediation efficacy. This work combines reactive transport modeling with a column experiment and field measurements to understand the biogeochemical processes and to quantify the biomass and mineral transformation/accumulation during a bioreme… more

Date: April 20, 2009

Creator: Li, L.; Steefel, C. I.; Williams, K. H.; Wilkins, M. J. & Hubbard, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Influence of heterogeneous ammonium availability on bacterial community structure and the expression of nitrogen fixation and ammonium transporter genes during in situ bioremediation of uranium-contaminated groundwater

The impact of ammonium availability on microbial community structure and the physiological status and activity of Geobacter species during in situ bioremediation of uranium-contaminated groundwater was evaluated. Ammonium concentrations varied by as much as two orders of magnitude (<4 to 400 {micro}M) across the study site. Analysis of 16S rRNA gene sequences suggested that ammonium influenced the composition of the microbial community prior to acetate addition with Rhodoferax species predom… more

Date: April 1, 2009

Creator: Mouser, P. J.; N'Guessan, A. L.; Elifantz, H.; Holmes, D. E.; Williams, K. H.; Wilkins, M. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

Nutrient limitation is an environmental stress that may reduce the effectiveness of bioremediation strategies, especially when the contaminants are organic compounds or when organic compounds are added to promote microbial activities such as metal reduction. Genes indicative of phosphate-limitation were identified via microarray analysis of chemostat cultures of Geobacter sulfureducens. This analysis revealed that genes in the pst-pho operon, which is associated with a high affinity phosphate u… more

Date: September 1, 2009

Creator: N'Guessan, L. A.; Elifantz, H.; Nevin, K. P.; Mouser, P. J.; Methe, B.; Woodard, T. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

"SHARP"--A ONE-DIMENSIONAL HYDRODYNAMICS CODE FOR THE IBM 704

The SHARP code designed to handle calculations of hydrodynamic motion in one-dimensional form, including provision for the disruption of the sample by spallation, is described. The code was prepared by means of the IBM logical coding scheme, FORTRAN. Generation of SHARP requires a set of initial conditions which define an established pressure pulse in the front portion of the sample. The code was developed to investigate the motion of the pressure pulse and the corresponding effects. The input … more

Date: April 1, 1958

Creator: Nance, O.; Wilkins, M.; Blandford, I. & Smith, H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Long-rod projectiles against oblique targets: analysis and design recommendations

Computer calculations provide an understanding of impact phenomena associated with long rod penetrators striking targets at oblique angles. The rod and target material behaviors are described by elastic-plastic work-hardening constitutive models. Ductile fracture is simulated by setting all tensile and shear stresses to zero when the calculated plastic deformation reaches a critical value. The important penetration material properties to defeat a given target are identified. There is no single … more

Date: April 16, 1976

Creator: Norris, D. M.; McMaster, W. H. & Wilkins, M. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Fundamental study of crack initiation and propagation. [Computer model of ductile fracture]

Objective is to determine the fracture toughness of A533B-1 steel by computer modeling Charpy V-notch tests. A computer model of ductile fracture was developed that predicts fracture initiation. The model contains a set of material-dependent parameters obtained by computer simulations of small specimen tests. The computer calculations give detailed stress and strain histories up to the time of fracture, which are used to determine the model parameter values. The calibrated fracture model, that … more

Date: December 21, 1977

Creator: Norris, D.M. Jr.; Reaugh, J.E.; Moran, B.; Quinones, D.F. & Wilkins, M.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Predicting environmental restoration activities through static simulation

This paper discusses a static simulation model that predicts several performance measures of environmental restoration activities over different remedial strategies. Basic model operation consists of manipulating and processing waste streams via selecting and applying remedial technologies according to the strategy. Performance measure prediction is possible for contaminated soil, solid waste, surface water, groundwater, storage tank, and facility sites. Simulations are performed for the U.S. D… more

Date: December 1, 1994

Creator: Ross, T. L.; King, D. A.; Wilkins, M. L. & Forward, M. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Generalized shaped charge design. Final report, October 1975--October 1976

A series of shaped charge devices were designed and tested. The tests showed that by combining detailed Lagrange calculations of liner collapse with simplified incompressible flow models, the explosive and liner contours of the charge can be tailored to yield either constant velocity jets, stretching jets, or converging jets. Measured liner velocity was within 10 percent of theory, except for details near the apex and close to slide planes. It was found that the effects of liner convergence and… more

Date: February 2, 1977

Creator: Van Thiel, M.; Godfrey, C. S. & Wilkins, M. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Automated remedial assessment methodology software system

The Automated Remedial Analysis Methodology (ARAM) software system has been developed by the Pacific Northwest Laboratory to assist the U.S. Department of Energy (DOE) in evaluating cleanup options for over 10,000 contaminated sites across the DOE complex. The automated methodology comprises modules for decision logic diagrams, technology applicability and effectiveness rules, mass balance equations, cost and labor estimating factors and equations, and contaminant stream routing. ARAM is used t… more

Date: November 1, 1994

Creator: Whiting, M.; Wilkins, M. & Stiles, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Proteogenomic monitoring of Geobacter physiology during stimulated uranium bioremediation

Implementation of uranium bioremediation requires methods for monitoring the membership and activities of the subsurface microbial communities that are responsible for reduction of soluble U(VI) to insoluble U(IV). Here, we report a proteomics-based approach for simultaneously documenting the strain membership and microbial physiology of the dominant Geobacter community members during in situ acetate amendment of the U-contaminated Rifle, CO, aquifer. Three planktonic Geobacter-dominated sample… more

Date: August 1, 2009

Creator: Wilkins, M. J.; VerBerkmoes, N. C.; Williams, K. H.; Callister, S. J.; Mouser, P. J.; Elifantz, H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Computer simulations of high pressure systems

Numerical methods are capable of solving very difficult problems in solid mechanics and gas dynamics. In the design of engineering structures, critical decisions are possible if the behavior of materials is correctly described in the calculation. Problems of current interest require accurate analysis of stress-strain fields that range from very small elastic displacement to very large plastic deformation. A finite difference program is described that solves problems over this range and in two a… more

Date: July 18, 1977

Creator: Wilkins, M. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Introduction to Hydrodynamics

Various aspects of hydrodynamics and elastic--plastic flow are introduced for the purpose of defining hydrodynamic terms and explaining what some of the important hydrodynamic concepts are. The first part covers hydrodynamic theory; and discussed fundamental hydrodynamic equations, discontinuities, and shock, detonation, and elastic--plastic waves. The second part deals with applications of hydrodynamic theory to material equations of state, spall, Taylor instabilities, and detonation pressure … more

Date: January 9, 1979

Creator: Wilkins, M. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Plane stress calculations with a two dimensional elastic-plastic computer program. [HEMP]

In the study of ductile fracture it is useful to simulate fracture on the computer under plane stress conditions. In general, this is a three dimensional problem. Presented here is a method for adapting a two dimensional elastic-plastic computer program to calculate problems in plane stress as well as plane strain geometry. A simulation of a tension test of a flat aluminum plate pulled to failure is calculated with the modified two dimensional program. The results are compared with a fully thre… more

Date: April 5, 1976

Creator: Wilkins, M. L. & Guinan, M. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Computer simulation of ductile fracture

Finite difference computer simulation programs are capable of very accurate solutions to problems in plasticity with large deformations and rotation. This opens the possibility of developing models of ductile fracture by correlating experiments with equivalent computer simulations. Selected experiments were done to emphasize different aspects of the model. A difficult problem is the establishment of a fracture-size effect. This paper is a study of the strain field around notched tensile specime… more

Date: January 1, 1979

Creator: Wilkins, M. L. & Streit, R. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fourth Progress Report of Light Armor Program.

No Description Available.

Date: January 1, 1969

Creator: Wilkins, M. L.; Cline, C. F. & Honodel, C. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Cumulative-strain-damage model of ductile fracture: simulation and prediction of engineering fracture tests

A cumulative-strain-damage criterion is used to predict the initiation and propagation of fracture in ductile materials. The model is consistent with a model of ductile rupture that involves void growth and coalescence. Two- and three-dimensional finite difference computer codes, which use incremental-plasticity theory to describe large strains with rotation, are used to trace the history of damage in a material due to external forces. Fracture begins when the damage exceeds a critical value ov… more

Date: October 3, 1980

Creator: Wilkins, M. L.; Streit, R. D. & Reaugh, J. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

A Computer Program for Calculating One-Dimensional Hydrodynamic Flow: KO Code

A computer program is described for the solution of shock, detonation, and spall problems for one-dimensional linear, cylindrical, or spherical hydrodynamic flow. The Flume option is used for calculating flow- through arbitrary cross sections. (R.J.S.)

Date: July 2, 1962

Creator: Wilkins, M.; French, J. & Giroux, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department