bluuebunny/crossref_metadata_2025 huggingface dataset:
A Soil Bioassay Using the Nematode Caenorhabditis elegans
Authors: Freeman MN , Peredney CL , Williams PL
Published: March 2009

Caenorhabditis elegans is a free-living soil nematode that is commonly used as a biological model. Recently, much work has been done using the nematode as a toxicological model as well. Much of the work involving C. elegans has been performed in aquatic media, since it lives in the interstitial water of soil. However, testing in soil would be expected to more accurately reproduce the organism's normal environment and may take into consideration other factors not available in an aquatic test, i.e., toxicant availability effects due to sorption, various chemical interactions, etc. This study used a modification of a previous experimental protocol to determine 24h LC50 values for Cu in a Cecil series soil mixture, and examined the use of CuCl2 as a reference toxicant for soil toxicity testing with C. elegans. Three different methods of determining percent lethality were used, each dependent on how the number of worms missing after the recovery process was used in the lethality calculations. Only tests having ⩾80% worm recovery and ⩾90% control survival were used in determining the LC50s, by Probit analysis. The replicate LC 50 values generated a control chart for each method of calculating percent lethality. The coefficient of variation (CV) for each of the three methods was ⩽14%. The control charts and the protocol outlined in this study are intended to be used to assess test organism health and to monitor precision of future soil toxicity tests with C. elegans.
Population Growth Kinetics of Tetrahymena pyriformis Exposed to Selected Electrophiles
Authors: Bearden AP , Sinks GD , Schultz TW
Published: March 2009

This study describes the effects of two selected electrophilic chemicals on the population growth kinetics of the freshwater ciliate Tetrahymena pyriformis (strain GL). The two chemicals selected, 3-butyn-2-one and trans-2-nonenal, each have a polarized, α,β-unsaturated moiety, which is associated with the electrophilic mechanism of Michael-type addition. T. pyriformis populations exposed to both electrophiles exhibited concentration dependent death of the initial inoculum within 1 to 2 h. Three-butyn-2-one which has a low 1-octanol-water partition coefficient (log Kow = -0.89) exhibited greater toxicity with death observed at 0.068 mg/L. Death was first observed in the morehydrophobic, trans-2-nonenal (log Kow = 3.16) at 4.21 mg/L. Death was followed by recovery of the population at the growth rates similar to control populations without chemical exposure.
Development of a Mitochondrial Respiratory Electron Transport Bioindicator for Assessment of Aromatic Hydrocarbon Toxicity
Authors: Tripuranthakam S , Duxbury CL , Babu TS , Greenberg BM
Published: March 2009

Polycyclic aromatic hydrocarbons (PAHs) are phototoxic to animals and plants. To monitor the toxicity of PAHs and understand their mechanism(s) of action, it is important to develop rapid and accurate bioindicators of effect. In this study, we have analyzed the impact of the anthracene photooxidation product, 1,2- dihydroxyanthraquinone (1,2-dhATQ), on mitochondrial electron transport using a preparation of beef heart mitochondria. Employing both NADH and succinate as electron donors, it was found that 1,2-dhATQ inhibited respiratory electron transport to cytochrome c. Using reduced DCPIP (2,6 dichlorophenolindophenol) as an electron donor, it was found that electron transfer was also inhibited. This indicated that inhibition was specific to cytochrome bc1 (ubiquinone-cytochrome c oxidoreductase). Inhibition of cytochrome c oxidase was very weak, indicating that 1,2-dhATQ primarily targets the cytochrome bc1 complex. Thus, analysis of the respiratory electron transport revealed a specific site of impact for 1,2-dhATQ, and a potential mechanistic basis for toxicity of this compound.
Effects of Sublethal Exposure to Cadmium on Shelter-Seeking Behavior of Juvenile Orconectes rusticus (Girard) Crayfish
Authors: Alberstadt P , Steele C , Misra K , Skinner C , Wilson B , Robaskiewicz S
Published: March 2009

Sublethal behavioral effects of heavy metals on crayfishes may adversely affect their survival in the environment. They may experience increased predation due to changes in their ability to remain in or under shelter. The effect of sublethal cadmium exposure on the ability of juvenile Orconectes rusticus crayfish to remain in shelter was evaluated. Four different treatment groups were used (N=12 juveniles each): a control group not exposed to cadmium, and three experimental groups exposed to 1, 2, or 3 mg Cd/L for 7 days. Crayfish were placed, individually, into small glass aquaria containing 3L of laboratory water, with continuous aeration. Each crayfish was provided with a dark, thigmotactic shelter. Cadmium was introduced into the aquaria on days 1 and 4 to establish and maintain the nominal concentrations. On days 5 through 7, observations were taken on each crayfish five times per day, with a minimum of 30 minutes between observations (15 observations per crayfish). The locations of the animals were recorded as in cover or in the open area of an aquarium. Repeated measures ANOVA was used to examine the effects of sublethal exposure to cadmium on shelter use by the juveniles. Juveniles in the control groups were in the shelters for 92.7% of the observations. Results from the experimental groups indicate a significant decrease in shelter use compared to the control group, suggesting hyperactivity induced by the cadmium exposure. Over the 3 days of observations, those in the 1,2, and 3 mg Cd/L exposure groups used the shelters 57.7%, 56.3%, and 32.0%, respectively, indicating hyperactivity induced by cadmium exposure. Looking at the daily results, those juveniles in the 1 mg Cd/L group increased shelter use from 52.0% to 64.0%, then decreased to 57.0%, while those in the 2 mg Cd/L group increased shelter use from 45.0% to 79.0% of the observations by day 3 of the observations indicating some habituation to the cadmium or recovery from the cadmium exposure. Those in the 3 mg Cd/L group spent progressively less time in shelter over the 3 days of observation, from 39.0% to 25.0% then to 32.0% by the third day, indicating sustained hyperactivity due to the sublethal cadmium exposure.
Quality Control in the Application of Flow Cytometry to Studies of Environmentally-Induced Genetic Damage
Authors: McCreedy CD , Robinson JP , Dallas CE , Jagoe CH
Published: March 2009

Flow cytometry (FCM) has been used to demonstrate altered DNA content in fish, reptiles, birds and mammals exposed to radionuclides, PAHs and other contaminants. However, artifacts resulting from sample preparation, handling, variations in instrument parameters or other factors may confound such measurements. Some artifacts resemble genotoxic responses and so could lead to erroneous positive conclusions. As part of ongoing studies of effects of various pollutants on DNA content in fishes, we tested sample handling and preparation methods for the induction of artifacts. We describe QA/QC methods, including control of staining conditions, doublet discrimination by comparison of peak versus integral fluorescence, internal DNA standards, and the use of time versus fluorescence plots. Consistent application of these practices is essential to obtain valid measurements of DNA content in environmental samples, and neglect of these can result in poor quality data and the acceptance of incorrect hypotheses.
Use of Implantable Pellets to Administer Low Levels of Methyl Mercury to Fish
Authors: Arnold BS , Jagoe CH , Gross TS
Published: March 2009

Implantable pellets of methyl mercury chloride were tested in Nile Tilapia (Oreochromis niloticus) to appraise the effectiveness of the method for chronic studies of mercury. Two dosing regimes of 15 and 1.5 grams/CH3HgCl pellet (test 1) and 1 and 0.1 grams/pellet (tests 2–3) of methyl mercury chloride were used in three tests. Additional pellets containing only matrix were used as controls. The pellets were inserted into the peritoneal cavity along with a microchip for identification. Three methods of incision closure: sutures and two types of surgical glue, were tested. Pellets used in test one released the dose too fast, resulting in premature death of the fish. Results from tests 2 and 3 show blood mercury concentrations over time and tissue levels at necropsy consistent with dose suggesting that this is a viable method of dosing fish.
Ecotoxicological Assessment of Bluegill Sunfish Inhabiting a Selenium-Enriched Fly Ash Stream
Authors: Reash RJ , Lohner TW , Wood KV , Willet VE
Published: March 2009

Little Scary Creek (LSC), a 2nd-order tributary of the Kanawha River in West Virginia, receives treated fly ash produced during coal combustion. Selenium and other trace metals were determined in water column and sediment samples, caddisflies, and bluegill sunfish liver and gonads during 1995–96 to estimate pathways of selenium exposure and assess the likelihood of toxic effects. Selenium levels in LSC water and sediment samples, and in caddisflies were elevated compared to reference sites. Mean dry weight selenium concentrations in bluegill liver (53 μg/g), ovary (23 μg/g), and testes (25 μg/g) tissue equaled or exceeded published toxic thresholds. Other trace metals were significantly higher in LSC bluegill. Leukopenia, elevated serum salts, and lowered liver weight were found in LSC bluegill. Fewer older bluegill were found in LSC. Sunfish in LSC are experiencing various kinds of sublethal stress, presumably due to metals exposure. However, major toxic effects that would be predicted to occur based on tissue selenium levels (complete reproductive failure or mortality) have not been observed in this population.
Harmonization of Ecological Effects Test Methods Between the US EPA (OPPTS) and the Organization for Economic Cooperation and Development (OECD): Description, Results and Current Activities
Authors: Smrchek JC , Morcock RE
Published: March 2009

In 1990, the senior management of the US Environmental Protection Agency, Office of Pesticide Programs and Toxic Substances (now called the Office of Prevention, Pesticides and Toxic Substances, or OPPTS) directed the two offices forming OPPTS to “harmonize” their human health, environmental/ecological effects, environmental fate, and physical chemistry testing methods into a single set of test guidelines. These two offices, the Office of Toxic Substances, now the Office of Pollution Prevention and Toxics (OPPT) and the Office of Pesticide Programs (OPP), assess risks posed by industrial chemicals and pesticides, respectively. Each office had developed separate testing guidance and methods. Under the Toxic Substances Control Act of 1976, OPPT developed and published an extensive set of environmental effects test guidelines and technical support documents on testing requirements. In a similar manner, OPP published data requirements for registration of pesticides and developed Standard Evaluation Procedures (SEPs) to explain the procedures used to evaluate submitted ecological effects data. Harmonization of OPPT and OPP guidelines is advantageous because it avoids unnecessary testing, conserves resources, and avoids duplicative testing of chemicals being reviewed by more than one office. Also, there is better coordination of test reviews between each office and greater consistency in test interpretation. Harmonization results in increased guideline uniformity between offices, and a more efficient means of revising and updating the OPPTS guidelines. The Organization for Economic Cooperation and Development (OECD) was similarly engaged in guideline development in the 1970s, and published a set of biotic effects test guidelines in 1981 (second addendum was published in 1984). EPA intends to harmonize OPPTS guidelines with those of the OECD to avoid unnecessary testing of chemicals in international commerce, increase efficiency in reviewing chemicals, use fewer test animals, and reduce nontariff trade barriers. Efforts to date by OPPTS have resulted in developing drafts of ecological effects test guidelines (the “850” harmonized guidelines). These were available as public drafts in 1996; the OPP Scientific Advisory Panel commented on them at that time. Currently the guidelines are being revised and will be available as part 850 in volume 40 of the US Code of Federal Regulations. Examples are discussed of how the harmonized test guideline process between OPPTS and OECD operates and the progress achieved to date. These include development of a revised OECD daphnid chronic test, a new harmonized fish early life stage test, a new OECD aquatic macrophyte toxicity test (Lemna [duckweed] growth inhibition test), and OECD activities in chironomid sediment testing and terrestrial plant toxicity testing. Important harmonization limitations, possible problems, challenges, and future activities are discussed.
Assessing Chemical Data Quality for Risk Assessment Through Data Validation
Authors: Vitale RJ
Published: March 2009

The chemical analytical data that are generated as part of every Superfund investigation are vital for the decisions that will be made regarding selection of a remedy and, ultimately, the future use of a site. Data validation is a process whereby laboratory data (and, to a limited extent, field data) are rigorously qualitatively and quantitatively scrutinized to determine the correctness of the results and to determine if the specified data quality objectives (DQOs) have been achieved. Data quality indicators are used as a gauge to determine if the quality of the data is adequate for the intended use.

Although data validation has become recognized as an important aspect in assessing data quality, a tendency has evolved to turn the validation process into a “checklist” exercise. A case study provides compelling evidence to avoid such approaches, which “short circuit” rigorous data validation. In the case study, rigorous validation of raw instrument output revealed analytical problems that had a significant impact on the risk assessment. These analytical problems were not identified during the initial checklist data validation approach.
Data Quality Objectives for Two Risk Assessments at Hanford
Authors: Lane NK , Clark SW , Tranbarger RK , Roeck FV
Published: March 2009

The opportunity for innovative thinking prevails at the U.S. Department of Energy's Hanford Site in southeastern Washington state. Two projects, in particular, challenged risk assessment staff. They are: 1. A combined Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)/Resource Conservation and Recovery Act (RCRA) risk assessment 2. Developing a risk assessment for a mixed-waste disposal facility.

The combined CERCLA/RCRA risk assessment involved establishing data quality objectives (DQO) either to meet clean closure for a RCRA treatment, storage and/or disposal facility (TSD) or (if the former was not possible) to conform to goals established for industrial land use for Hanford Past-Practice Strategy (HPPS) sites. Radionuclide analysis was reduced by 60 percent through the DQO process.

Developing a risk assessment for the RCRA TSD facility raised several issues. What is the source of information for the contaminants of concern? What are the scenarios for exposure? How will the short-term and long-term impacts be evaluated?
Evaluation of the Use of Substitution Methods to Represent Nondetect Data
Authors: Floit SB , Mahoney LA , Batey JC , Petroff DM
Published: March 2009

One of the issues in quantitative human health risk assessments is the handling of nondetect data. Typically nondetect data are reported by the analytical laboratory as sample quantitation limits (SQLs) and qualified to indicate that the values were nondetect. Nondetect values, however, could actually fall anywhere within the range of zero to the SQL.

Four substitution methods for handling nondetect data were applied to a database of soil concentrations from a site to evaluate the impact on resulting constituent-specific 95 percent upper confidence limits (UCLs). The four methods utilized were: (1) one-half the SQL; (2) one-fifth the contract required quantitation limit (CRQL) (3) zero; and (4) the use of a random number generator to represent nondetect data with values ranging between zero and the SQL.

At low frequency of detections, the currently recommended USEPA Superfund approach of representing nondetect data with one-half the SQL was the least conservative method. As the frequency of detection increased, the resulting 95 percent UCLs for this method became more conservative (larger).
An Evaluation of the Effect of Some Soil Properties on Root Uptake of Four Metals
Authors: Hattemer-Frey HA , Krieger GR , Lau V
Published: March 2009

Although EPA [1] recommends that exposures associated with the consumption of home-grown produce be evaluated in human health risk assessments, the Agency does not provide specific guidance for quantitatively assessing inorganic uptake by plants. In the absence of site-specific data, risk assessors are forced to rely on the use of various predictive methods to quantitatively evaluate the contribution of produce ingestion to total daily intake. The concentration of metals in plants is typically estimated by multiplying the total concentration of metal in soil by a metal-specific soil-to-root uptake factor (RUF). Metal-specific RUFs were calculated using measured soil and plant data collected during the remedial investigation for the Globe Plant (a smelter) in Colorado. These RUFs are compared to values reported by Baes et al. [2]. Results show that RUFs reported by Baes et al. [2] may underestimate the concentration of As, Cd, and Pb in garden crops. Using the concentration of metal in soil to predict the concentration of metal in plants does not account for various soil properties, such as pH, organic matter content, and cation exchange capacity, that are known to influence root uptake of metals. Multiple linear regression analyses were used to develop simple, predictive models for estimating the concentration of metals in home-grown vegetables. This paper presents preliminary predictive equations for estimating root uptake of As, Cd, Cu, and Zn in fruiting and root vegetables to draw attention to this issue, so that the importance of this pathway and subsequent influence on human exposure can be more accurately assessed. Results show that by using data on additional soil parameters (other than relying solely on the concentration of metal in soil), the concentration of metals in fruiting and root vegetables can be more confidently predicted.
Estimating Risk to Ecological Receptors from Contaminated Soil at Superfund Sites
Authors: Burns TP , Cornaby BW , Hadden CT
Published: March 2009

Risks to non-human receptors from contaminated soil at three Superfund sites in New York and New Jersey are assessed using new techniques for screening contaminants of potential concern (COPCs) and characterizing risk. Contaminants were screened as ecological COPCs by comparing toxicity, mobility, and persistence thresholds to values for contaminants obtained from reference texts and electronic databases. Published “no effect levels”, chronic, and acute test endpoints were used to establish conservative toxicity thresholds. Risks to groups of organisms with similar exposures were compared by deriving exposure factors for major exposure pathways. These factors multiplied by the contaminant concentration in the soil and divided by the appropriate toxicity threshold give risk quotients. These methods are consistent with EPA's Framework for Ecological Risk Assessment (ERA) and are flexible enough to incorporate the limited data available for many hazardous waste sites. Results of the ERAs are compared, and the affect on risk management decisions at the three Superfund sites are considered.
A Novel Method to Determine Mass Median Diameter and In-Flight Evaporation of Aerially Sprayed Droplets Deposited on Artificial Samplers at Ground Level
Authors: Sundaram A , Sundaram KMS
Published: March 2009

An aqueous emulsion of permethrin containing a water-soluble red dye was applied at a dosage rate of 70 g of the active ingredient in 4.0 L per ha, using a Cessna 188B aircraft (equipped with 4 × AU3000 Micronair® atomizers), over a 400 m × 400 m spray block in Thessalon in northern Ontario, Canada. Spray mass recovery was assessed on glass plates at ground level and droplets were collected on Kromekote® cards. The stain sizes were grouped into different categories. The area containing the stains were excised and permethrin was extracted. The mass of permethrin present in the extract was determined by gas-liquid chromatography (GLC). The average mass per droplet in each size category was calculated. The mass (of permethrin) median diameter (DM.5) and volume median diameter (DV.5) at the spray release height were computed. The present method showed, for the first time in literature, the advantage of not having to use the conventional tedious procedures to determine spread factors to arrive at the DM.5 and DV.5 values.

The DM.5 was 113 μm both at spray release height and at ground level, and was identical to the volume median diameter (DV.5) at spray release height. The present study provided a method to determine the DV.5 at spray release height for that fraction of the spray cloud that deposited on the Kromekote cards at ground level.

The present study also provided information, for the first time, on the percentage decrease in droplet volume and droplet diameter due to evaporation in-flight. When the emitted droplet sizes increased gradually from 33 to 185 μm, evaporation in-flight decreased progressively resulting in droplet sizes of 16 to 181 μm at ground level. The percent decrease in droplet volume was 88.4 for the smallest droplet and 5% for the largest one. Correspondingly, the droplet diameter decreased from 51 to 1.7%, indicating that the small droplets evaporated to a greater extent than the large ones because of their large surface area to mass ratio.
The Influence of Cosurfactant and Role of Spreading in Stomatal Infiltration by Organosilicone
Authors: Policello GA , Stevens PJG , Forster WA , Gaskin RE
Published: March 2009

Stomatal infiltration, the benefits it can provide, and the major factors influencing it are reviewed. Evidence of a role for spreading in the infiltration process is presented. The spreading and equilibrium surface tension of Silwet L-773 organosilicone surfactant (TSE8M; CAS Registry Number 27306-78-1) + cosurfactant blends have been measured and are compared with the levels of infiltration they achieve. It is shown that, in addition to requiring a low surface tension, stomatal infiltration requires a good spreading ability. Some other unknown factor(s) are also involved, and specific interactions with cosurfactants, and their ratios in blends, suggest those may be the nature of the surfactant aggregates in the solution. It is demonstrated that the infiltration of TSE8M can be extended by blending with select cosurfactants at an optimum ratio of 1 + 1, provided at least 0.2% TSE8M is used. By so doing, certain blends of 0.2% TSE8M + 0.2% cosurfactant are able to provide levels of infiltration comparable with those attained using 0.4% TSE8M.
Photolytic Degradation of Formulated Avermectins: Effect of P-Aminobenzoic Acid (PABA)
Authors: Peterson RF , Alvarez MD , Mookerjee PK
Published: March 2009

A distinctive feature of the foliarly-applied avermectin insecticides is the relative ease with which they decompose under photolytic conditions. From a product perspective it would be an advantage, in certain cases, to extend slightly the “window” of control after application. Consequently, a formulation study was undertaken to characterize the degradation kinetics of two averraectins; emamectin benzoate, and abamectin, in the presence of potential photostabilizers. Interestingly, the use of PABA (p-aminobenzoic acid) in this study did not show the stabilizing effect that was expected from this widely used and effective sunscreen. This report describes the kinetic study involving PABA and discusses possible reasons why some traditional sunscreens may not be the materials of choice for improving the photostability of crop protection products.
An Overview on the Development of Wettable Powder Formulations
Authors: Siegel M
Published: March 2009

The relevant factors that determine which formulation is chosen for commercialization are discussed as well as the advantages and disadvantages of the wettable powder (WP) formulation. The active ingredient properties essential for WP development and the inert ingredients used are summarized along with the physical and chemical tests used to determine the suitability of the formulation.
Water Dispersible Granule Formulation Techniques
Authors: Collins HM , Newsome EE , Turpin KL
Published: March 2009

This paper demonstrates a simple method of screening wetting and dispersing surfactants for Water Dispersible Granule formulations. The method is intended to reduce the number of dry mill trials needed to establish a suitable combination of wetting and dispersing ingredients. Using this method, it is possible to quickly screen a large number of additives eliminating those that do not promote a well dispersed and highly suspensible formulation. The technical is slurried in water with various combinations of wetting and dispersing agents and wet milled. Dilutions of the slurry are visually evaluated to determine if flocculation occurs. Potential candidates are determined based on the wetting and dispersing agents that produce a uniform suspension, free of flocculation. These candidates are further optimized using the traditional dry mill and agglomeration trials.
Superior Multipurpose Adjuvant System for Rainfastness and UV Protection
Authors: Narayanan KS , Ianniello RM
Published: March 2009

Many pesticides of both synthetic and biological origin undergo UV-induced photodegradation, resulting in reduced efficacy. Efficacy can also be reduced by rain washoff of the active ingredient. A tank mix additive (adjuvant) which functions as a UV protectant and rainfast agent would provide improved pest control for problematic a.i.'s. Adjuvant systems which could be directly incorporated into the formulated pesticide, will provide a superior, value added product. Agrimax™ 33 (International Specialty Products) is a proprietary, multipurpose adjuvant composition designed to offer rainfastness for pesticides. It is composed of pyrrolidone-based solvents, surfactants, and water insoluble polymers microdispersed in aqueous medium. The composition can be diluted in all proportions without phase separation. A number of water insoluble UV protectants (Table 1) have been solubilized in Agrimax 3 at levels approaching 30% (w/w). Some of these systems produced stable emulsions on dilution with water, with particle size in the 0.02 μm – 2.0 μm range. Such systems can be used for UV protection. These adjuvants have been successfully incorporated into several active pesticides via lyophilization to yield a rainfast product. In the UV protecting adjuvants described here, Agrimax 3 acts as a carrier for the hydrophobic UV protecting molecules. The spectral data for the UV protectants, the stability of the adjuvant compositions are discussed. A physico-chemical model for the total adjuvant system is presented.
Evaluation of the Rain Fastness of Pesticide Formulations Using Simulated Leaf Surfaces with a Visual Rating System
Authors: Lopez HB , Hua TQ
Published: March 2009

Rain tenacity of formulations of contact fungicides is an important property and should be evaluated during early stages of formulation development. The rain tenacity of these formulations on foliar and fruit surfaces can affect their overall performance (efficacy) and the number of spray applications required for effective season long disease control. A test procedure has been developed which is useful for screening formulation candidates quickly and accurately to select the most effective candidate to advance to greenhouse or field evaluation. The method consists of applying and drying test formulations on small panels which simulated leaf surfaces. The panels are visually rated after subjecting them to a simulated rain. The presented test procedure was validated using a suspension concentrate standard and an experimental formulation of chlorothalonil. The visual ratings were corroborated with gas chromatographic analyses to determine the amount of residue remaining on the panels and banana leaf segments. There was a high degree of correlation between residues retained on the simulated leaf surfaces and the banana leaf segments with both formulations. There was also a strong correlation between residue ratings based on visual observations and actual residue retained as determined by solvent extraction and gas chromatography analysis. It was concluded that this test procedure provides a quick and inexpensive means for obtaining accurate and reliable data on the foliar rain fastness of formulations which form solid suspensions upon dilution with water.
A Comparison of Different Sealant Butt Joint Shapes
Authors: Myers JC
Published: March 2009

This paper reviews the evolution of the butt sealant joint from the deep rectangular joints used in early highway seals to the hourglass shapes used presently in building seals. The paper compares the relative performance of several types of butt sealant joints, including square, rectangular, and hourglass. The performance measures include tensile and cyclic laboratory tests and finite element analyses. The paper compares the performance of hourglass joints in recent tests to the performance of butt joints with other shapes presented in previous publications. These data can assist ASTM Committee C-24 in evaluating the effect of joint shape on the performance of specimens in tensile adhesion or cyclic tests.
Case Study of Sealant Reversion
Authors: Kenney RJ , Piper RS
Published: March 2009

Numerous failures of building seals and sealants have logical and, in most cases, simple explanations as to why the seal or sealant failed to function as intended. This paper focuses on a failure mechanism that is not as apparent or simple to explain; failure caused by improper mixing of two part sealant or the reversion of cured sealant. On two separate buildings with the same sealant, the authors encountered a varied mode of failure. This paper documents the investigation of one of these projects and discuses the failure phenomena in relation to the orientation of the sealant joints and the analysis of physical properties of seals exposed to varied conditions of ultraviolet radiation and elevated temperatures. It is concluded that reversion in certain types of polyurethane sealants compounded with benzoate based plasticizer is more likely when exposed to conditions of high levels of ultraviolet radiation and elevated temperatures.
Structural Silicone in Curtain Walls
Authors: Gutowski VWS , Lalas P , Cerra AP
Published: March 2009

Modern building facades are frequently constructed using Structural Silicone Glazing (SSG) technology. In the USA and South-East Asia, 45 and 65% of facades, respectively, are erected with the use of this technique, in which external cladding panels are attached to the facade framing by an elastomeric silicone adhesive (sealant). The chemical structure of silicone sealants assures chemical bonding across the sealant/substrate interface. Therefore, the bond integrity should be assured for at least the life of the building. The reliance of the facade integrity on adhesive bonding, however, and the relatively young age of the technology require caution and a thorough understanding of material performance and the influence of the service environment on the material properties. Often, hydro-thermal and loading factors are inadequately considered in the facade design, construction and maintenance. Also, the influence of the sealant joint geometry on the material performance is neglected. This paper addresses major issues concerning the above factors, as related to the structural design and maintenance of structurally glazed buildings.
Structural Behavior of Silicone Bonded Glass Block Panels
Authors: Chang KF , Sandberg LB
Published: March 2009

Silicone sealant was substituted for mortar in bonding glass blocks. The sealant's tensile and shear strengths and stiffnesses were determined. Joints bonding two glass blocks were tested for stiffness and strength in tension, bending, out-of-plane shear, and in-plane shear. Bending tests were done on specimens one block wide and four blocks long to evaluate one-way bending behavior. A six block by six block panel, supported on all four sides, was built and tested under simulated wind load. An analytical model with material nonlinearity in the joints was developed for the one-way bending case. It gave good comparisons with the experimental data to load levels approaching failure. A more complex analytical model was developed for the two-way panel. It was only valid for lower load levels, in the range of potential allowable design loads, but compared well with test results. Silicone bonded glass block panels have potential for meeting the wind load requirements necessary for exterior use.
Effects of Weatherproofing Sealants on Building Aesthetics — Part II
Authors: O'Neil VK , Wolf AT
Published: March 2009

The paper describes several sealant related phenomena which can contribute to building aesthetic problems. These include sealant dirt pick-up, fluid streaking on a substrate (staining), and fluid migration into porous substrates. The paper postulates mechanisms for these phenomena and suggests appropriate test methods to assess them. The paper also presents long-term weathering results obtained on 12 weatherproofing sealants selected from the following generic types: plasticized silicones, unplasticized silicones, unplasticized surface-modified silicones, plasticized polyurethanes, unplasticized polyurethanes and plasticized silicon modified polyethers. In order to address the influence of local environment and exposure conditions, sealants are exposed at a rural site in Georgia and an industrial site in Michigan.
Improvement of Initial Adhesion to Aluminum of Insulating Glass Polyurethane Sealants Using a Tertiary Amine Based Curing System
Authors: Hubin-Eschger PJ
Published: March 2009

Hydroxylated polybutadiene based insulated glass sealants are well known to have a very low moisture vapor transmission rate and an excellent adhesion to glass and aluminum. Since the beginning of their industrial development, the best and most known and effective curing system for these sealants has been an organomercuric ester based catalyst.

The current and future pressure regarding ecological and toxicological issues will make this type of product increasingly difficult to use. This paper presents the results of work to develop other catalytic systems, which were obtained with the tertiary amine dimethylbenzylamine. The final improvement of initial adhesion to aluminum is obtained with the use of phenolic derivatives of coumarone indene.
The Effect of Artificial Weathering and Movement Accommodation Testing on Building Sealants
Authors: Beasley JL , Jenkins MR
Published: March 2009

This paper describes the effect of an ultra violet radiation, heat and condensation artificial ageing procedure on the ability of a range of building sealants to survive a movement accommodation test based on the ISO 9047 test method. Sealants stored under standard laboratory conditions were also subjected to the movement accommodation test.

It is shown that sealants which initially pass the movement accommodation test will continue to pass after up to 24 weeks of exposure to the artificial weathering, or storage in standard conditions. Sealants that initially do not survive the movement test can improve their performance after exposure to artificial weathering or storage in standard conditions.

Tensile tests were carried out on sealants that survived the movement test and on static control specimens. It has been found that the movement test, and to a lesser extent the artificial weathering, can reduce the width of the test samples. It has also been found that the movement test can decrease the force produced by most one part sealants when extended to a width of 15mm, nominally 25% strain.

No relationship between changes in sample width or force at 15mm width and the ability to survive the movement test has been found.
Evaluation of Cyclic Fatigue as a Means of Assessing the Performance of Construction Joint Sealants: Polyurethane Sealants
Authors: Lacasse MA , Bryce JE , Margeson JC
Published: March 2009

Polyurethane based high performance construction sealants were subjected to cyclical movements using manually adjusted vices until rupture of the specimens occurred. Sealant fatigue behavior was compared with the fatigue behavior of elastomers and rubbers in order to gain a more quantitative understanding of sealants subjected to fatigue testing. Furthermore, failure of these sealant specimens during cyclic fatigue testing allowed for a comparison with previously reported results obtained from tests on both silicone and polysulfide sealants. The methods described in this paper provide a basis from which to assess the long-term performance of different types of sealants.
Low-Amplitude Fretting of Hard Coatings of TiN, Diamond-Like Carbon, and Polycrystalline Diamond
Authors: Vingsbo O , Venkatachalam M , Sundquist M , Schouterden K
Published: March 2009

Three different hard surface coatings, that is, TiN, so-called diamond-like carbon (DLC) on steel substrates, and polycrystalline diamond on cemented carbide substrates, have been tested and compared under conditions of low-amplitude fretting. The displacement amplitudes were chosen to cover the partial slip regime and the lower part of the gross slip regime, with some emphasis on identifying the critical conditions for incipient gross slip (IGS). A giantmagnetostrictive actuator has been used, allowing extremely well-controlled testing conditions, typical of the partial-slip fretting regime. The relative displacement between the vibrating specimens was measured with an optical technique, capable of a resolution of 2 nm. The displacement and the tangential forces active in the contact surface were recorded as functions of time. Based on these data, post-experiment off-line computation was used for identifying IGS parameter values. Two- and three-dimensional fretting maps were constructed. The fretting scar morphology was studied by scanning electron microscopy. Fretting mechanisms were clarified by comparisons between the recorded test data and the structural damage revealed by the surface studies.
Friction and Wear Mechanisms on CVD Diamond and PVD TiN Coatings under Fretting Conditions
Authors: Mohrbacher H , Blanpain B , Celis J-P
Published: March 2009

Laboratory fretting testing is an appropriate method to investigate the friction and wear behaviors of hard coating materials in vibrating contacts under specified conditions. Such testing can help to select the most suitable coating for a specific application. Furthermore, it can assist in optimizing the coating deposition process. A conceptual framework for modeling laboratory fretting testing is presented together with test equipment and experimental methods for on-line mechanical analysis and off-line material degradation analysis. The application of these concepts is demonstrated for two hard coating types, namely, physical vapor deposition (PVD) TiN and chemical vapor deposition (CVD) diamond coatings. The influence of the fretting conditions on the mechanical contact response as well as on the materials modification induced in the contact is analyzed. The effect of third bodies, tribochemical reactions, and residual stress on the friction and wear behavior of these hard coatings is discussed.
Absorption of Organic Compounds and Organometallics on Ceramic Substrates for Wear Reduction
Authors: Kennedy PJ , Agarwala VS
Published: March 2009

The concept of employing thermally stable compounds (that is, metal oxides) as high temperature vapor phase ceramic lubricants was investigated. A major part of this study was devoted to the development of various calorimetric and tribological techniques that could be used to determine interfacial reactions between thermally stable compounds and ceramic substrates such as zirconia and alumina. This interaction is pivotal in understanding the mechanism of high temperature lubricity. The approach consisted of selecting low sublimation temperature materials and measuring their thermodynamic interactions as vapors with the ceramic substrates. The materials studied included two easily sublimable organic compounds (that is, naphthalene and salicylic acid) and several organometallics (for example, copper phthalocyanine). Thermodynamic data such as heat of adsorption, packing density, and reversibility of the adsorption were obtained on some of these compounds and were related to wear characteristics. All of these compounds provided effective lubrication at room temperature. Copper phthalocyanine was an effective lubricant at temperatures up to 400°C.
Studies on the Characterization and Tribological Behavior of Self-Propagating High-Temperature Synthesis (SHS) Coatings of Chromium Cermet
Authors: Li L , Qunji X
Published: March 2009

A chromium cermet coating, about 150 μm thick, was formed on carbon steel with the gas transport self-propagating high-temperature synthesis (SHS) coating process. The present paper is concerned with the preparation method, property evaluation, and abrasive wear behavior of the SHS coatings. The experiment reveals that there is excellent adhesion between the coating and the substrate, with less matrix damage and good abrasive wear resistance compared with chemical vapor deposition (CVD)-Cr7C3 coatings. Investigations indicated that an intense metallurgical interaction, gradient composition distribution, and unique forming process are the major reasons for the superior performance of the SHS coatings. It is analytically shown that there is a relationship between the size of the abrasive, the coating thickness, and the abrasive wear resistance.
Importance of Stationarity for Geostatistical Assessment of Enviromental Contamination
Authors: Dagdelen K , Turner AK
Published: March 2009

This paper describes a geostatistical case study to assess TCE contamination from multiple point sources that is migrating through the geologically complex conditions with several aquifers. The paper highlights the importance of the stationarity assumption by demonstrating how biased assessments of TCE contamination result when ordinary kriging of the data that violates stationarity assumptions. Division of the data set into more homogeneous geologic and hydrologic zones improves the accuracy of the estimates. Indicator kriging offers an alternate method for providing a stochastic model that is more appropriate for the data. Further improvement in the estimates results when indicator kriging is applied to individual subregional data sets that are based on geological considerations. This further enhances the data homogeneity and makes use of stationary model more appropriate. By combining geological and geostatistical evaluations, more realistic maps may be produced that reflect the hydrogeological environment and provide a sound basis for future investigations and remediation.
Stochastic Simulation of Space-Time Series: Application to a River Water Quality Modelling
Authors: Soares AO , Patinha PJ , Pereira MJ
Published: March 2009

This study aims to develop a methodology to simulate the joint behaviour, in space and time, of some water quality indicators of a river, resulting from a mine effluent discharge, in order to enable the prediction of extreme scenarios for the entire system. Considering one pollutant characteristic measured in N monitoring stations along the time T, a random function X(e,t), e=1,…,N, t=1,…,T, can be defined. The proposed methodology, a data driven approach, intends to simulate the realisation of a variable located in station e in time t, based on values located before e and t, and using a sequential algorithm. To simulate one value from the cumulative distribution F{X(e,t)∣X(e-1,t),…,X(1,t),X(e,t-1),…,X(e,1)}, the basic idea of the proposed methodology is to replace the e.t conditioning values by a linear combination of those: [X(e,t)]*=∑α=1e−1aα⁢X(α,t)+∑β=1t−1bβ⁢X(e,β) which allows the values to be drawn sequentially from bidistributions. The final simulated time series of pH and dissolved oxygen reproduce the basic statistics and the experimental time and spatial covariances calculated from historical data recorded over 15 months at a selected number of monitoring stations on a river with an effluent discharge of a copper mine located in the south of Portugal.
Revisiting the Characterization of Seismic Hazard Using Geostatistics: A Perspective after the 1994 Northridge, California Earthquake
Authors: Carr JR
Published: March 2009

An indicator kriging model of seismic hazard for southern California, based on the time period 1930 – 1971, is developed. This hazard assessment is evaluated in light of the occurrence of more recent, moderate earthquakes: the 1987 Whittier Narrows, the 1990 Upland, and the 1994 Northridge earthquakes. The hazard map shows relatively poor spatial correlation between regions of high hazard and known, active faults. A hypothesis is developed, however, suggesting that high seismic hazard in southern California is a function of spatial proximity to all active faults, not to any one active fault.
Geostatistical Joint Modeling and Probabilistic Stability Analysis for Excavations
Authors: Young DS
Published: March 2009

Two geostatistical interpolation methods were studied for rock joint modeling; ordinary kriging and indicator kriging. Geostatistics was extended to improve the spatial interpretation of joint parameters, especially for pole vectors, which was kriged on the sphere. A matrix approach was introduced for probabilistic block failure analysis, and applied to study the stability of pit slopes and subway tunnels. The localized structural stability was achieved in probabilistic terms based on the geostatistical joint model.
A Fatigue Damage Model for Crack Propagation
Authors: Chow CL , Wei Y
Published: March 2009

This paper presents a fatigue damage model for crack propagation in characterizing the fatigue crack growth behavior of cracked structures. Special emphasis is placed on the numerical simulation of cyclic loading and the dependence of the numerical results on the finite element mesh discretization. A practical method for predicting fatigue crack propagation in engineering structures is proposed. The predicted results are compared favorably with those measured experimentally from fatigue testing a center cracked panel of 2024-T3(Alclad) aluminum plates.