George A. Murgel Copyright (c) 2012 All rights reserved. http://works.bepress.com/george_murgel Recent documents in George A. Murgel en-us Sat, 24 Nov 2012 05:52:34 PST 3600 Pavement Thickness Evaluation by GPR Survey in Idaho http://works.bepress.com/george_murgel/6 http://works.bepress.com/george_murgel/6 Thu, 10 May 2012 15:28:46 PDT In 1995 and 1996, the Idaho Transportation Department (lTD) conducted a series of ground-penetrating radar (GPR) surveys as a nondestructive testing (NDT) method to evaluate the thickness of asphalt and Portland cement concrete (AC/PCC) pavements in Idaho. GPR surveys employed both air-coupled and combination air and ground coupled systems with their associated equipment and software. A total of 30 miles of AC/PCC pavements were evaluated by GPR surveys. The results obtained were correlated with the site-specific ground-truth data from borings.

Knowledge of pavement layer thickness is needed to predict pavement performance, establish load carrying capacities and develop maintenance and rehabilitation priorities. In addition, for new construction, it is important to ensure that the thickness of materials being placed by the contractor is acceptably close to specification. Core sampling and test pits are destructive to the pavement system, expensive, time consuming and intrusive to traffic. The objective of the lTD study was to evaluate, compare and assess the ability of these two GPR systems to accurately measure the thickness of multiple pavement layers, and document the data nondestructively. This paper reviews the findings of these surveys and provides statistically based data for both AC and PCC pavements.

The overall study has shown that reasonably accurate, dependable determination of pavement thickness can be achieved by using GPR survey for conditions encountered in Idaho.

]]> Joseph C. Sener et al. Interactions of Microbial Biofilms with Toxic Trace Metals: 1. Observation and Modeling of Cell Growth, Attachment, and Production of Extracellular Polymer http://works.bepress.com/george_murgel/5 http://works.bepress.com/george_murgel/5 Fri, 04 May 2012 12:51:10 PDT Adsorbent surfaces in natural and engineered systems are frequently modifies by bacterial attachment, growth of a biofilm, and bacterial production of extracellular polymer. Attached cells or sorbed polymers may alter the metal-binding characteristics of the supporting substratum and influence metal partitioning. The interdependent behavior of toxic trace metal partitioning and biofilm development requires description of the interaction between cell growth with its accompanying polymer production and metal speciation. In this article, the first of a two part series, a mechanistic model is developed to describe the growth of a film-forming bacterium which adheres to a substratum through the production of extracellular biopolymers. Each bacterial cell was modeled as a two-component structure consisting of active cell mass and biopolymer. The biopolymer component was further divided into cell-associated and dissolved categories to distinguish which remained naturally bound to cell surfaces from that which did not. Use of this structured model permitted independent description of the dynamics of cell growth, and polymer production, both of which may influence trace metal behavior. Employing parameters obtained from independent experiments as well as published values, the model satisfactorily predicts experimental observations of bacterial growth, attachment and detachment, biopolymer production, and adsorption of polymer onto solid (glass) surfaces. The model stimulated transient and steady-state biofilm systems equally well. In the second article in this series, we describe how this model may be extended and utilized to make predictions of the behavior of transient and steady-state biofilm systems in the presence of a toxic transition metal(Pb).

]]> Ke Ming Hsieh et al. Interactions of Microbial Biofilms with Toxic Trace Metals: 2. Prediction and Verification of an Integrated Computer Model of Lead (II) Distribution in the Presence of Microbial Activity http://works.bepress.com/george_murgel/4 http://works.bepress.com/george_murgel/4 Fri, 04 May 2012 12:51:08 PDT The interfacial interactions of a toxic trace metal, Pb, with a surface modified by a marine film-forming bacterium, Psedomonas atlantica, were predicted by a structured biofilm model used in conjunction with a chemical speciation model. The validity of the integrated model was tested for batch and continuous operations. Dynamic responses of the biophase due to transient lead concentration increases were also stimulated. The reasonable pre dictions achieved by the model demonstrate its utility in describing trace metal distributions in complex systems where the adsorption properties of inorganic surfaces are modified by adherent bacteria production of extracellular polymers.

]]> Ke Ming Hsieh et al. Experimental Apparatus for Selection of Adherent Microorganisms Under Stringent Growth Conditions http://works.bepress.com/george_murgel/3 http://works.bepress.com/george_murgel/3 Fri, 04 May 2012 12:51:06 PDT A bioreactor apparatus is described for studying bacterial attachment. A cyclic, on-off, flow regime was imposed within the apparatus. Model calculations illustrate the utility of this flow pattern in the selection and maintenance of slow-growing, adherent organisms. The apparatus is believed to have general utility in testing bacterial attachment influenced by many types of experimental or environmental constraints, including variations in fluid dynamics, presence of toxic substances (metals or organics), nature of the substratum surface, concentrations of limiting nutrients, and competition between bacterial strains. As an example application, the apparatus was employed to test 14 bacterial strains for surface attachment in a nutrient-limited growth medium. The medium was developed, using the chemical equilibrium program MINEQL, for planned studies of biofilms in a solution with a chemically defined composition that permits calculation of trace metal speciation. The apparatus was used to select organisms with growth and attachment characteristics that could not be evaluated by conventional batch, or chemostat, culture conditions. When supplied with acetate, pyruvate, or succinate as a carbon and energy source, the gram-negative strains Pseudomonas cepacia 17616 and Zoogloea sp. WGO4 showed superior attachment characteristics to glass surfaces in the chemically defined medium but only moderate fluid-phase growth. The gram-positive Arthrobacter sp. strain 9G4D and gram-negative species P. pickettii and Zoogloea sp. WNJ8, when supplied with pyruvate as a carbon and energy source, were capable of superior growth in the fluid phase but formed only a low to moderate biofilm surface coverage.

]]> George A. Murgel et al. Quality of Water and Implications for the Environment and Lifestyles http://works.bepress.com/george_murgel/2 http://works.bepress.com/george_murgel/2 Fri, 04 May 2012 12:51:05 PDT George A. Murgel Teaching a Civil Engineering Senior Capstone Design Course http://works.bepress.com/george_murgel/1 http://works.bepress.com/george_murgel/1 Fri, 04 May 2012 12:51:03 PDT George A. Murgel