bluuebunny/crossref_metadata_2025 huggingface dataset:
Disruption of the Endocrine Control of Final Oocyte Maturation in Teleosts by Xenobiotic Chemicals
Authors: Thomas P
Published: March 2009

Final oocyte maturation (FOM) in fish and other vertebrates is under precise endocrine control and involves changes in hormone secretion at all levels of the hypothalamus-pituitary-gonadal axis. Several potential sites and mechanisms of chemical disruption of the endocrine system controlling FOM by are discussed. Neurotoxic chemicals such as lead and PCBs can alter monoamine neurotransmitter function and xenoestrogens can interfere with steroid feedback mechanisms at the hypothalamus and pituitary to impair the neuroendocrine control of gonadotropin secretion. Chemicals which disrupt calcium homeostasis such as cadmium can interfere with calcium-dependent signal transduction pathways activated by reproductive hormones in the pituitary and gonads. Other xenobiotics may disrupt maturation-inducing steroid (MIS) function by impairing its synthesis or receptor binding. The problems in assessing endocrine disruption of FOM are discussed. The relatively few investigatons reported in the literature on endocrine disruption of FOM in fishes by chemicals indicate that organochlorine and organophosphorus pesticides at concentrations less than one ppb can impair induction of FOM in response to gonadotropin and the MIS. Moreover, evidence is presented that certain organochlorine pesticides block MIS action by binding to the MIS receptor which is localized on the oocyte plasma membrane. Steroid membrane receptor function may be particularly susceptible to interference by hydrophilic chemicals. Finally, an in vitro bioassay capable of screening many chemicals simultaneously for their ability to disrupt the endocrine control of FOM is described.
Ecological Risk Assessment of Substances with Suspected Estrogenic Activity Using Standard Laboratory Fish Tests
Authors: Gimeno S , Bowmer CT
Published: March 2009

The assessment of risks to the aquatic environment in the European Union is generally based on a comparison of Predicted Environmental Concentrations (PEC) with Predicted No Effect Concentrations (PNEC) for surrogate, or “representative”, organisms of the receiving waters. Such risk assessments are required for new and priority existing chemicals, pesticides and, in the near future, biocides; they are dependent on robust in vivo test data. Current strategies for ecological risk assessment were not designed to assess the risk of endocrine disrupters. The selection of suitable fish species and practical in vivo end points for determining endocrine disruption in fish are discussed, including the adaptation of some existing guidelines. This paper is partly based on a series of experiments conducted our laboratory to look at the effects of a model alkyl-phenol (4-tert-pentylphenol), an industrial chemical intermediate, acting as a pseudo-estrogen on an all-male population of the common carp, Cyprinus carpio. Exposure to the test substance occurred at critical life stages for endocrine disruption. Biochemical parameters as well as histological parameters were applied, and their suitability to be used in ecological risk assessment is discussed.
Steroid Hormones as Biomarkers of Endocrine Disruption in Wildlife
Authors: Guillette LJ , Rooney AA , Crain DA , Orlando EF
Published: March 2009

Xenobiotic compounds introduced into the environment by human activity have been shown to adversely affect the endocrine system of wildlife. Various species exhibit abnormalities of (1) plasma sex steroid hormones, (2) altered steroid synthesis form the gonad in vitro and (3) altered steroidogenic enzyme function. These endpoints are sensitive and relatively easy to measure quantitatively with reliability and precision. These observations have led to the conclusion that sex steroid hormones could be markers of exposure to, and altered function from, endocrine disrupting contaminants (EDCs). However, there are serious limitations in the use of steroid hormones as generalized markers of EDC exposure. Steroid hormones exhibit seasonal, ontogenetic, gender and species-specific variation. Moreover, the regulation of sex steroid plasma concentrations is a relatively complex phenomenon capable of shorterm (minutes — hours) alteration due to environmental inputs, such as acute stress -- an activational response. Alterations in steroid synthesis and degradation also can be a response to altered embryonic development due to EDC exposure — an organizational response. If steroid hormones are to be used as biomarkers, then closely controlled, well designed sampling has to be performed. Additionally, an appreciation of the variation possible in endocrine responses among the species to be studied must be obtained.
Preliminary Estimates of Adult Exposure to Bisphenol-a from Dental Materials, Food and Ambient Air
Authors: Richardson GM , Clark KE , Williams DR
Published: March 2009

Bisphenol-a is an estrogenic compound which is a degradation product of the polymer bisphenol-a glycidyl methacrylate (BIS-GMA) used in dental materials. Human exposure to bisphenol-a may also arise from epoxy resins used as coatings in food and beverage cans. Bisphenol-a is an industrial pollutant and has been detected in atmospheric fallout and surface waters, which may also contribute to exposure. Therefore, a study was undertaken to estimate potential exposure from composite resin dental materials, from canned foods and beverages and from ambient air. Applying probabilistic exposure assessment methods, and using available data and information on the release of bisphenol-a from dental composites, on bisphenol-a concentrations in canned foods, canned beverages and ambient air, total adult exposure was estimated for the Canadian population. Calculations indicated that mean total exposure from all sources was about 65 times lower than a tolerable daily intake (TDI) for bisphenol-a derived by Health Canada to address potential estrogenic effects of this compound. Maximum estimated exposure was also less than this TDI. On average, composite resin dental materials and canned foods contributed approximately equally to total exposure whereas canned beer, canned soft drinks and ambient air were relatively insignificant sources of exposure.
The Use of Automated Monitoring to Assess Behavioral Toxicology in Fish: Linking Behavior and Physiology
Authors: Brewer SK , DeLonay AJ , Beauvais SL , Little EE , Jones SB
Published: March 2009

We measured locomotory behaviors (distance traveled, speed, tortuosity of path, and rate of change in direction) with computer-assisted analysis in 30 day posthatch rainbow trout (Oncorhynchus mykiss) exposed to pesticides. We also examined cholinesterase inhibition as a potential endpoint linking physiology and behavior. Sublethal exposure to chemicals often causes changes in swimming behavior, reflecting alterations in sensory and motor systems. Swimming behavior also integrates functions of the nervous system. Rarely are the connections between physiology and behavior made. Although behavior is often suggested as a sensitive, early indicator of toxicity, behavioral toxicology has not been used to its full potential because conventional methods of behavioral assessment have relied on manual techniques, which are often time-consuming and difficult to quantify. This has severely limited the application and utility of behavioral procedures. Swimming behavior is particularly amenable to computerized assessment and automated monitoring. Locomotory responses are sensitive to toxicants and can be easily measured. We briefly discuss the use of behavior in toxicology and automated techniques used in behavioral toxicology. We also describe the system we used to determine locomotory behaviors of fish, and present data demonstrating the system's effectiveness in measuring alterations in response to chemical challenges. Lastly, we correlate behavioral and physiological endpoints.
Use of Behavioral Endpoints to Determine Protective Concentrations of the Insecticide Fonofos for Bluegill (Lepomis Macrochirus)
Authors: Fairchild JF , Little EE
Published: March 2009

This research compared the results of laboratory and mesocosm studies to determine the effectiveness of using behavioral measures of sublethal exposure to define environmental concentration ranges that are protective of free-ranging populations of bluegill (Lepomis macrochirus) exposed to the organophophate insecticide fonofos. Thirty-day laboratory chronic studies were conducted to determine the relative sensitivity of standard (e.g. survival and growth) and non-standard behavioral (e.g. swimming capacity, feeding efficiency, and aggression) endpoints in predicting concentrations of fonofos protective of bluegill growth and survival. The lowest observable effect concentration (LOECs) for the standard measures of survival and growth was 5.6 μg/L. Two behavioral endpoints were of similar sensitivity to the standard measures: swimming capacity, LOEC of 5.6 μg/L; and prey strike frequency, LOEC of 5.6 μg/L. However, aggressive interactions were ten-fold more sensitive than swimming or feeding behavior with a LOEC occurring at 0.6 μg/L. Lab results were compared to an aquatic mesocosm study which exposed adult and juvenile bluegill to a 9.41 μg/L concentration of fonofos. The dissipation half-life of fonofos was 5 days in 0.1 hectare aquatic mesocosms. Significant mortality among caged bluegill occurred within 4 days of exposure at 9.41 μg/L. However, the 9.41 μg/L concentration of fonofos had no statistically significant effects on survival, growth, reproduction, or total biomass of free-ranging populations of bluegill. We conclude from these studies that laboratory data can accurately estimate concentrations that are lethal in the field and that the use of behavioral endpoints can provide ecologically relevant, yet conservative estimates of concentrations that are protective of field populations.
Impact of Sugar-Processing Effluents and Domestic Wastes on the Water Quality of Mingoala River in Mbandjock, Cameroon
Authors: Tchounwou PB
Published: March 2009

A longitudinal study was conducted to assess the impact of pollution by a Sugar-Mill Company, and the effects of domestic wastes on the water quality of the Mingoala River in Mbandjock, Cameroon. Over a period of twelve months, bimonthly field samples were collected and analyzed for a number of physico-chemical and bacteriological parameters. Study results indicated that the Mingoala River is the subject of an industrial pollution which is essentially organic in nature. Except for ammonia-N, chloride, nitrite and temperature, statistical analysis revealed significant differences between the mean values of all physical and chemical parameters studied downstream of the point of confluence between the wastestream and the river, as compared to data collected upstream. Such differences were also recorded in bacteriological assessments, with significantly higher counts of bacteria downstream, indicating a microbial contamination associated with poor sanitary conditions. The consequences of this pollution are numerous and include: 1) Degradation of downstream water quality; 2) Disappearance of fish, and appearance of disease vectors; 3) Public health impact associated with nocuous odor, and waterborne illnesses. In order to prevent future ecological damage, appropriate steps should be taken to treat the plant effluents before their discharge into receiving streams, and to educate the Mbandjock population on the cost-effectiveness of sanitation in disease prevention. In this regard, practical recommendations are made on specific pollution-prevention strategies for this community.
Background Determination of Element and Anthropogenic Compounds in Soils of the Maryland Coastal Plain
Authors: Nemeth GR , Romano DJ , Smegal D , Paul J
Published: March 2009

Background concentrations of elements and anthropogenic compounds in soil were determined for the coastal plain region of the northern Chesapeake Bay in the vicinity of a major military facility. Soils used to establish background are from off-site locations. Lead and octachlorodibenzodioxin were determined to be anthropogenic regional contaminants. The background concentrations of arsenic, beryllium, and manganese exceed Region III Environmental Protection Agency risk based criteria for residential soils.
A Case Study in the Determination of Background Concentrations of Inorganic Analytes for Risk Assessment
Authors: Holder JL , Battey TF , Sklar PL
Published: March 2009

Data were collected to support the ongoing Installation Restoration Program (IRP) Remedial Investigation and Feasibility Study (RI/FS) at Vandenberg AFB, CA. These data were used to illustrate how the determination of inorganic background populations can affect the selection of chemicals of concern for risk assessment and, ultimately, risk management decisions. Four population determination approaches are discussed: 1) single population, 2) subunits, 3) pure statistics and 4) statistics plus project requirements. The same data set was used to determine background populations following each approach. Background threshold values that represent the upper limit of naturally occurring background were then calculated for each population. Background threshold values varied greatly depending on the approach used. Thus, chemicals of concern selected for risk assessment and risk management decisions could potentially differ depending on the approach. For the Vandenberg project, the best approach utilized a combination of statistics plus project requirements.
Estimating the Duration and Frequency of Worker Exposures to Soil at U.S. EPA Region I Superfund Sites—An Assessment of the Current Practice
Authors: Shaw CD
Published: March 2009

This study examines the current practice(s) for estimating the duration and frequency of worker exposures to soil at U.S. Environmental Protection Agency Region I Superfund sites. The objectives of the study were to (1) identify EPA's current policies and procedures for determining how long and how often workers may be exposed to soil, (2) assess whether evaluations of the potential risks for workers exposed to soil at Region I Superfund sites are consistent with EPA policies and guidance (i.e., does the actual practice conform with them), and (3) evaluate the acceptability/workability of the guidance (i.e., is it reasonable and does it meet its intended goals).
Comparison of a Lognormal and Normal Distribution in Calculating Concentrations for a Superfund Risk Assessment
Authors: Mahoney LA , Batey JC , Pintenich JL
Published: March 2009

A baseline risk assessment (RA), was conducted for a Superfund site in the Southeast. The site is a former landfill, with associated localized soil and groundwater contamination. There was concern for the potential for the landfill to contaminate groundwater which is used as the regional drinking water supply source.

During the baseline RA, 95 percent upper confidence limits (UCLs) on the arithmetic mean were calculated for groundwater assuming both a normal and lognormal distribution. The UCLs were then used to estimate potential risks associated with the worst-case exposure scenario.

The purpose of this paper is to illustrate how the assumption of the data distribution can influence the results of the calculation of statistics of measured concentrations, and subsequently, associated risk estimates. Groundwater was the medium which was evaluated for this study, however, the process and results could be applicable to any environmental medium.
Bioassay-Based Risk Assessment of Complex Mixtures
Authors: Donnelly KC , Huebner HJ
Published: March 2009

The baseline risk assessment often plays an integral role in various decision-making processes at Superfund sites. The present study reports on risk characterizations prepared for seven complex mixtures using biological and chemical analysis. Three of the samples (A, B, and C) were complex mixtures of polycyclic aromatic hydrocarbons (PAHs) extracted from coal tar; while four samples (001, 002, 004 and 006) extracted from munitions-contaminated soil contained primarily nitroaromatic hydrocarbons. The chemical-based risk assessment ranked sample C as least toxic, while the risk associated with samples A and B was approximately equal. The microbial bioassay was in general agreement for the coal tar samples. The weighted activity of the coal tar extracts in Salmonella was 4,960 for sample C, and 162,000 and 206,000 for samples A and B, respectively. The bacterial mutagenicity of 2,4,6-trinitrotoluene contaminated soils exhibited an indirect correlation with chemical-based risk assessment. The aqueous extract of sample 004 induced 1,292 net revertants in Salmonella, while the estimated risk to ingestion and dermal adsorption (based on TNT content) was 2E-9. The data indicate that the chemical-based risk assessment accurately predicted the genotoxicity of the PAHs, while the accuracy of the risk assessment for munitions contaminated soils was limited due to the presence of metabolites of TNT degradation. The biological tests used in this research provide a valuable compliment to chemical analysis for characterizing the genotoxic risk of complex mixtures.
Influence of Droplet Sizes of Deposits on Persistence of Bacillus Thuringiensis Applied as an Aqueous Flowable, and Azadirachtin Applied as a Nonaqueous Solution, Onto Oak Foliage
Authors: Sundaram KMS , Sundaram A
Published: March 2009

The effect of droplet sizes of deposits on foliage on persistence of Bacillus thuringiensis var. (BTK) applied as an aqueous flowable (Study I), and of azadirachtin applied as a nonaqueous solution (Study II), was investigated under greenhouse conditions. In Study I, uniform droplets, 42 to 250 μm in diameter, of a BTK formulation, Foray 48B, were applied onto foliage of oak seedlings. Leaves were clipped at different intervals of time after treatment, the toxic protein was extracted, and the extracts were bioassayed using fourth instar gypsy moth larvae. The mean half-lives of BTK inactivation (DT50) in foliage were about 26 h for the largest droplets (250 μ m), and about 12 h for the smallest droplets (42 μm). The DT50's for the 42 and 73 μm droplets were significantly lower than for the 103 and 132 μm droplets, which in turn were lower than for the 160 to 250 μm range. An upper limit in the 130 to 160 μm range was indicated beyond which the rate of inactivation was independent of droplet sizes applied. In Study II, uniform droplets, 95 to 450 μm in diameter, of an azadirachtin formulation, Margosan-O®, containing a tracer dye, were applied onto foliage of oak seedlings. Leaves were clipped at different intervals of time after treatment, azadirachtin was extracted, and the extracts were analyzed by high-performance liquid chromatography. The DT50's ofazadirachtin loss from foliage was about 19 h regardless of the droplet sizes applied.
The Role of Orchex® 796 in Pesticide Applications
Authors: Chambers GV
Published: March 2009

A renewed interest in improving the application of chemical pesticides has prompted additional application research on utilizing spray adjuvants for enhancing ground or aerial pesticide applications. This renewed interest is producing additional findings on the role of Orchex® 796 in pesticide applications, as well as research leads for improving pesticide formulations. This paper reviews these additional findings, primarily from published research.

While Orchex® 796 was initially developed for tree pests, its general surface chemistry and other lipid-like properties provide improved spreadability and coverage on biological surfaces. Further, both plant and insect surfaces are modified in a beneficial manner for the application of many pesticides. In addition to providing a temporary modification of the target surface, other properties improve rainfastness. These features provide a greater benefit in ultra low volume application including nonaqueous application, but still retain benefits when applied with even high rates of water, such as in chemigation. Specific crop and pest examples are presented from both temperate and tropical agriculture. These examples illustrate how Orchex 796 properties can provide a multiple role in the formulation or application of pesticides.
Phosphate Ester Compositions by Design
Authors: Reierson RL
Published: March 2009

A fundamental mechanistic study of the alcohol phosphation process has provided a basis for development of a phosphation system which can be systematically varied to produce alkyl phosphate mixtures of predetermined composition. Conventional phosphation with either polyphosphoric acid or phosphoric anhydride typically produces the compositional extremes in terms of the ratio between the monoalkyl and dialkyl phosphate products. Use of both reagents will produce intermediate products in terms of the monoalkyl to dialkyl phosphate (MAP:DAP) ratio which vary as a function of the process. Parameters can be adjusted to produce MAP : DAP molar ratios from about 50 : 50 to 90 : 10 with low residual phosphoric acid and unreacted alcohol levels.

In this preliminary communication, examples of the range of accessible compositions and limits of the technology are presented.
Granular Pesticide Formulations
Authors: Goss GR , Taylor DR , Kallay WB
Published: March 2009

A granular pesticide formulation is one of the many options a formulator has to deliver the pesticide to the target. Granular formulations were first used for mosquito larviciding in swampy areas where foliage interfered with conventional pesticide formulations reaching the water. Today granular formulation use is widespread and most pesticides are formulated as a granule in addition to other formulations. Granules find use still for mosquito larviciding in addition to subsoil applications, soil surface applications, baits, and even some foliar applications (e.g. corn borer control). Granular carriers can be broadly separated into two categories, mineral and organic. Mineral carriers include sand, limestone, gypsum, kaolin, montmorillonite, attapulgite, diatomite, etc. Organic granular carriers include corn cobs, pecan shells, peanut hulls, recycled paper fiber, etc. In its simplest form, a granular formulation consists of the inert granule and the pesticide. If the pesticide is a liquid, it can simply be sprayed on the granule and distributed in the field. Often though, formulation aids such as solvents, stickers, deactivators and dedusting agents are included in the formulations. Each ingredient performs a specific function. Production methods usually involve spraying the pesticide onto the granules for even distribution while the granules are agitated. ASTM testing procedures for agricultural granules include sieve specifications, sampling procedures, bulk density, particle size distribution, resistance to attrition, particle count and liquid holding capacity. This article is a general introduction to granular formulations and provides specific information on carriers, formulation contents, use patterns, production methods and test procedures.
Suspoemulsions with Improved Stability and Correlation of Long Term Stability with the Zeta Potential
Authors: Memula S , Berger P , Chellappa C
Published: March 2009

The word stability is ambiguous in colloidal science and means different things for different people. In suspoemulsions or concentrates it is possible to identify at least three different physical processes which may lead to instability in a particulate system. For example change in particle size may be due to Ostwald's ripening, particle aggregation and particle sedimentation. Therefore an understanding of behavior of fine particles, and their interactions with the inert ingredients in a suspoemulsion or suspension formulation is necessary to develop a stable formulation. The behavior of these fine particles in aqueous suspoemulsion is a cumulative function of electrostatic, steric and hydrophobic interactions with the inert ingredients and other physical processes.

This paper discusses the processes and techniques involved in the stabilization of suspoemulsion / suspension concentrates. A Model pesticidal formulations was chosen to study the effect of surfactant system on the stability of the formulation and its dilution performance. Further attempts were made to correlate the physical long term stability of the formulation with change in particle size, distribution and Zeta potential measurements.
The Relation of Tallowamine Ethoxylates to Dynamic Surface Tension and Field Performance
Authors: Friloux KM , Berger PD
Published: March 2009

The uptake of active ingredient from sprayed formulations via foliar penetration has been demonstrated to be increased by the use of surfactants. The surfactant may increase the spray solution's ability to wet the leaf surface, or facilitate translocation of the active ingredient through the stomata into the leaf.

It has been shown that the structure of surfactants can influence the ability of the surfactant to promote these mechanisms of transport of the active ingredient. The amount of Ethylene oxide in the hydrophilic portion of the surfactant is one such factor that has been linked to the translocation of the active ingredient.

Various hydrophobes such as fatty alcohol and nonylphenol, ethoxylated to various degrees, have been used to show the effect. Another such hydrophobe, tallowamine, is ethoxylated and used as a surfactant in water soluble herbicides. In this study, a series of tallowamine ethoxylates of varying degrees of ethoxylation from 2 moles of Ethylene oxide to 20 moles of Ethylene oxide were evaluated to determine the effect of the amount of Ethylene oxide on surface properties.

Aqueous solutions of the surfactants were measured at different frequencies for dynamic surface tension using the maximum bubble pressure technique. The reduction of the liquid's surface tension increase wetting and spreading of the liquid onto the foliar surfaces thus facilitating translocation of the active ingredient. By measuring the modification of the surface tension of the liquid versus the Ethylene oxide content of the surfactant, we will support the data previously compiled.

Also included in the study will be measurements of the dynamic contact angle of the aqueous solutions on the surface of a leaf, as well as other surfactant properties.
Solid Adjuvants Based on Urea-Surfactant Adducts
Authors: Davis RI
Published: March 2009

Urea forms solid adducts with a wide range of liquid organic molecules. Many surfactant molecules are the right size and conformation to form adducts. A typical urea adduct can contain 40–60% surfactant and secondary components. Ethoxylated alcohols show great promise because they are good wetting agents and have already proven themselves as adjuvants. These liquid surfactants can be transformed into free-flowing, solid urea complexes which are highly effective in actual field trials.
Dearomatized Tailor-made Hydrocarbon Fluids in Co-Adjuvants or Adjuvants in Tank Mixes
Authors: Frisch PD , Verbelen RA
Published: March 2009

Specific dearomatized hydrocarbon fractions with boiling ranges between 220 and 310°C can significantly increase the performance of active ingredients in certain herbicides, fungicides and insecticides when they are incorporated, in combination with surfactants, in the formulations (co-adjuvants) or used as adjuvants in tank mixes.

With the help of these tailor-made fluids, the biological activity of the active ingredients can be improved or modified. Efficacy is significantly increased and other important physico-chemical characteristics; such as, application properties, volatility versus penetration and mode of action, can be modified. The adjustment of these parameters adds formulation flexibility, increases activity which results in cost savings (less pesticide is required per hectare) and environmental benefits (reduction of undesirable residues).

To demonstrate these benefits, two specific pesticides were selected: an insecticide (new generation of pyrethroid) and an herbicide (diphenyl ether family). These active ingredients were then formulated using these tailor-made dearomatized hydrocarbon fluids, other coformulants and specific surfactants and their performance assessed in green house and field trials. Comparisons with other established adjuvants are included where available.
Surfactant Effects on Aerial Spray Droplet Spectra
Authors: Ledson TM , Huddleston EW , Sanderson R
Published: March 2009

Volumetric droplet size spectra of selected non-ionic surfactants as tank mix additives were evaluated in a wind tunnel. Metsulfuron methyl and paraquat were mixed at recommended rates prior to the addition of the surfactants. Four concentrations, 0.0625, 0.125, 0.250, and 0.500% v/v of six surfactants were atomized in a 58 m/s (131 mph) airstream using a D6-46 nozzle at 45 degrees down and back. Dv0.5, DvO.1 decreased with increasing surfactant concentration and % volume < 150μm increased. Significant differences between surfactants were detected.
Recent Developments in the Design of Sealant Joints for Movement and Other Effects
Authors: O'Connor TF
Published: March 2009

Often, thermal movement and other performance factors are inadequately considered in the design of sealant joints. Performance factors that affect sealant joint design are described, including: thermal movement; moisture movement; live and dead loads; creep, elastic frame shortening, and shrinkage of concrete structures; and material, fabrication, and erection tolerances. Three calculation examples will be described for joints in new construction that accommodate movement: (1) an expansion joint in a masonry wall, (2) a joint between different building systems, and (3) a floor line expansion joint for a multi-story curtain wall and two examples for joints in remedial work: (4) a fillet (triangular) joint between a curtain wall and masonry wall and (5) a bridge joint for a precast concrete panel system..
Building Sealants in Russia
Authors: Berman OY
Published: March 2009

In this paper, the author presents information concerning building sealants in Russia.

The paper includes data of demand and provision of construction industry with sealants, the features of sealants application and comprehensive description of types and application areas of sealant materials.

Technical requirements and physical properties, current experimental data on performance capabilities of some types of sealants in Russia are presented and discussed.

Possibilities of organization of a joint sealants business in Russia are described in the conclusion.
History of Building Joint Sealants
Authors: Scheffler MJ , Connolly JD
Published: March 2009

The use of sealants in facades became more widespread in the 1950s and 1960s with the increasing use of curtain wall construction. While most sealants specified for new construction today are silicone or urethane-based, older buildings may contain polysulfide and acrylic-based sealants.

For investigators trying to identify sealants used on older buildings, it is often useful to know which sealants were in common use when the building was constructed, or when the building was repaired. This paper briefly discusses and reviews the history of the use of commonly used building sealants over the last fifty years, detailing when specific sealant types were first developed, when they came into widespread use, or fell out of favor.

Historically, sealant selection has depended upon many factors such as the type of substrate, movement requirements, prior sealants used, cost and aesthetics. Improvements in performance capabilities of sealants and innovations such as structural glazing are discussed.

Some sealants have been found to contain hazardous substances. For example, some polysulfide sealants applied during the 1960s contain polychlorinated biphenyls (PCBs). Issues related to hazardous materials in sealants will be discussed as well as the performance consequences of the current change to sealant products to make them less harmful to the environment.
An Analysis of the 180° Peel Test for Measuring Sealant Adhesion
Authors: Shephard NE , Wightman JP
Published: March 2009

Sealant adhesion to different substrates is often assessed by using a 180° peel test. It is known that the peel force is a function of the viscoelastic response of the adhesive joint coupled with the intrinsic strength of the interphase. Measurement of the fracture energy as a function of straining rate can yield material properties by separating the bulk effects from the interphase strength. The results of this study highlight some important deficiencies of the ASTM peel test method. In particular, the fracture energy of a silicone sealant to glass and aluminum was measured at different rates, peel thicknesses and sealant moduli using the 180° peel test. It was determined that the sealant failed cohesively when tested on glass. For instances of cohesive failure, a plot of fracture energy vs. strain rate fit a power law model. The rate dependence of the fracture energy was shown to be proportional to the amount of uncrosslinked polymer in the sealant and this suggested an increase in dissipation. It was further shown that as the modulus of the sealant decreases the fracture energy increases. However, at low strain rates, the trend reverses and the high modulus sealant has better adhesion to glass than some of the low modulus sealants. Tests on specimens with aluminum substrates failed in accordance with specific test conditions: adhesive failure was more likely to occur when the strained thickness was small; when the strain rates were slow; or when the modulus was high. This study clearly demonstrated that peel testing at one rate and thickness can not adequately compare one sealant to another.
A Review of Recent Developments and Improvements in Accelerated Outdoor and Indoor Xenon Weathering Devices and Methodologies
Authors: Puttnan WJ , Pekara D , McGreer M
Published: March 2009

Accelerated outdoor weathering has a history which extends back at least 50 years. The advantage of this type of testing is that the sun's natural solar energy spectrum is used to irradiate the specimens under test. Since this is an outdoor method, variations in test conditions occur due to the natural seasonal weather differences. Recent improvements in fresnel concentrator accelerated weathering devices such as day and nighttime temperature control, and new moisture cycles are described that minimize seasonal effects.

Since the development of artificial tests in the early 1900's, many types of artificial light sources have been introduced. Improvements in xenon accelerated weathering chambers have enabled development of new test methods utilizing filters that provide a very close approximation of sunlight especially when compared to fluorescent and carbon arc light sources. This paper will also include a description of an advanced air-cooled xenon arc test apparatus for the accelerated exposure of materials.
Nanoindentation and Instrumented Scratching Measurements on Hard Coatings
Authors: Ruff AW
Published: March 2009

Elastic, plastic, and cracking properties of ZrO2, a ZrO2-metal composite, and a Ni-NiO composite, all plasma-sprayed as coatings on metallic substrates, have been studied. Data comparisons were made with bulk ZrO2, bulk nickel, and single-crystal silicon as reference materials. A nanoindentation and scratching apparatus was used for the measurements. Three different indenter and scratching tool shapes were used: 200 μm radius sphere, Vickers four-sided pyramid, and a 45° wedge with a 0.5-mm radius curved edge. During indentation, over a load range of 10 mN to 1 N, continuous load versus depth data were obtained in each case to permit analysis for material hardness and elastic modulus. The loading curve data are used to calculate hardness, and the unloading curve data are used to calculate elastic modulus. The analytical models used are described and compared. An alternate method for deriving elastic modulus from the initial portion of the loading curve is described. Comparison among the results for different tool shapes will be discussed. During instrumented scratching over a similar load range, values for load, tool depth, and scratch-resisting force were continuously measured. The applied load was either held constant at one or more selected values, or linearly increased during scratching. This load variation permitted identification of critical loads for severe cracking damage of the brittle materials. Scanning electron microscope (SEM) studies were used to characterize the cracking damage. The critical load values depended on tool shape and material microstructure. The studies identified damage mechanisms in the hard coatings, and critical loads for damage initiation. Damage morphology typically involved local surface cracking, edge chipping, and plastic deformation. The relative proportions of cracking and plastic response seemed to vary with tool shape, material, and microstructure.
Geostatistical Characterization of Unsaturated Hydraulic Conductivity Using Field Infiltrometer Data
Authors: Miller SM , Kannengieser AJ
Published: March 2009

Estimation of water infiltration and retention in surficial soils is a critical aspect of many geotechnical and environmental site evaluations. The recent development of field-usable tension infiltrometers now allows insitu measurements of unsaturated hydraulic conductivity (Ku), thus avoiding some uncertainties associated with remolded soil samples tested in the laboratory. Several different geostatistical “mapping” methods can be used to spatially characterize Ku, including ordinary and indicator kriging, as well as spatial simulations that provide realizations (stochastic images) of Ku that exhibit more natural variability than do the smoothed spatial estimations of kriging. Multivariate procedures, such as cokriging and Markov-Bayes simulation, can incorporate information from a secondary attribute (e.g., particle size information) to enhance the spatial characterization of an undersampled Ku field. These geostatistical procedures are demonstrated and compared for a case study at a 700 sq. meter site comprised of coarse soil material. Results indicate that percent-by-weight fractions can be used effectively to enhance insitu spatial characterization of Ku.
Geostatistical Simulation of Rock Quality Designation (RQD) to Support Facilities Design at Yucca Mountain, Nevada
Authors: Cromer MV , Rautman CA , Zelinski WP
Published: March 2009

The conceptual design of the proposed Yucca Mountain nuclear waste repository facility includes shafts and ramps as access to the repository horizon, located 200 to 400 m below ground surface. Geostatistical simulation techniques are being employed to produce numerical models of selected material properties (rock characteristics) in their proper spatial positions. These numerical models will be used to evaluate behavior of various engineered features, the effects of construction and operating practices, and the waste-isolation performance of the overall repository system. The work presented here represents the first attempt to evaluate the spatial character of the rock strength index known as rock quality designation (RQD). Although it is likely that RQD reflects an intrinsic component of the rock matrix, this component becomes difficult to resolve given the frequency and orientation of data made available from vertical core records. The constraints of the two-dimensional study along the axis of an exploratory drift allow bounds to be placed upon the resulting interpretations, while the use of an indicator transformation allows focus to be placed on specific details that may be of interest to design engineers. The analytical process and subsequent development of material property models is anticipated to become one of the principal means of summarizing, integrating, and reconciling the diverse suite of earth-science data acquired through site characterization and of recasting the data in formats specifically designed for use in further modeling of various physical processes.
Methodologies for Predicting the Thermomechanical Fatigue Life of Unidirectional Metal Matrix Composites
Authors: Neu RW , Nicholas T
Published: March 2009

Parameters and models to correlate the cycles to failure of a unidirectional metal matrix composite (SCS-6/Timetal 21S) undergoing thermal and mechanical loading are examined. Three different cycle types are considered: out-of-phase thermomechanical fatigue (TMF), in-phase TMF, and isothermal fatigue. A single parameter based on either the fiber or matrix behavior is shown not to correlate the cycles to failure of all the data. Two prediction methods are presented that assume that life may be dependent on at least two fatigue damage mechanisms and therefore consist of two terms. The first method, the linear life fraction model, shows that by using the response of the constituents, the life of these different cycle types are better correlated using two simple empirical relationships: one describing the fatigue damage in the matrix and the other fiber-dominated damage. The second method, the dominant damage model, is more complex but additionally brings in the effect of the environment. This latter method improves the predictions of the effects of the maximum temperature, temperature range, and frequency, especially under out-of-phase TMF and isothermal fatigue. The steady-state response of the constituents is determined using a 1-D micromechanics model with viscoplasticity. The residual stresses due to the CTE mismatch between the fiber and matrix during processing are included in the analysis.
Evolution of Bridging Fiber Stress in Titanium Metal Matrix Composites at Elevated Temperature
Authors: Tamin MN , Ghonem H
Published: March 2009

This paper deals with the determination of stress evolution in bridging fibers during fatigue crack growth in a SM1240/Timetal-21S composite using the finite element method. Several parameters affecting this evolution were considered, namely, the process-induced residual stress, the creep characteristics of the matrix layer surrounding the fiber, the test temperature, and the loading frequency. In support of these calculations, a series of elevated temperature fatigue crack growth tests was conducted to identify the crack growth behavior of the composite when subjected to different temperatures at both high and low loading frequencies. Results of this numerical/experimental work were then utilized in conjunction with a postulated fiber fracture criterion based on the notion that a competition exists between the increase in the axial fiber stress and the continuous degradation of the fiber strength due to cyclic wear induced by the interface frictional shear stress. The conclusions of this study show that the axial stress in the bridging fibers increases with an increase in temperature and with a decrease in both the loading frequency and the matrix grain size. A combination of high-temperature, low-frequency, and small-matrix grain size would enhance creep deformation of the matrix, thus leading to an increase in the rate of the load transfer from the matrix to the bridging fibers. Furthermore, the presence of a compressive residual stress state in the bridging fibers retards the time-dependent increase of their axial stress. The fatigue strength of the bridging fibers was estimated to range from 720 to 870 MPa within the temperature range of 500 to 650°C. This strength was found to depend on both the temperature and the loading frequency.
Thermomechanical Fatigue of Polymer Matrix Composites
Authors: Strait LH , Koudela KL , Karasek ML , Amateau MF , Runt JP
Published: March 2009

The present research was undertaken to evaluate the effects of mechanical constraint on the response of polymer matrix composites during thermal cycling. Analytical and experimental techniques were used to characterize the response of carbon-fiber-reinforced cyanate ester and bismaleimide composites. Cross-ply laminates were subjected to thermal cycles from 24 to 177°C in the unconstrained, fully constrained, and overconstrained conditions. Laminate response, damage mechanisms, and residual compressive properties were characterized for each material and degree of constraint. The results of this research indicate that the level of constraint can have a significant effect on the response of polymer matrix composites during thermal cycling. However, longer-term testing is required to determine if the observed changes in response will ultimately affect the final failure mode and fatigue endurance of the materials.
Cumulative Fatigue Damage of Angle-Plied Fiber-Reinforced Elastomer Composites and Its Dependence on Minimum Stress
Authors: Liu DS , Lee BL
Published: March 2009

The effects of minimum stress on cumulative damage and fatigue lifetime were assessed for an angle-plied nylon-cord-reinforced elastomer composite that represents the bias aircraft tire carcass. The S-N curves were established under constant minimum stress rather than constant R-ratio. The trends of longer fatigue life at a given stress range and higher fatigue endurance limit of the composite were clearly observed with a higher level of minimum stress. These trends stem from the fact that the stress and strain are not linearly related to each other. The stress-strain curve of the elastomer matrix composite exhibits strain stiffening. As a result, in a stress-controlled fatigue test, a shorter strain range or a smaller amount of strain energy is experienced for the same stress range when the level of minimum stress is raised. However, it should be noted that the levels of minimum stress used in the study happened to be safely below a critical level for the initiation of fiber-matrix debonding under static tension. As in other structural materials, the increase of applied stress level in elastomers can be regarded as an increase of the damage potential. Therefore, when the minimum stress exceeds a critical level, the damage potential effect may become dominant and a shorter fatigue life at a given stress range could be observed with a higher level of minimum stress in S-N curves. In the stress-controlled fatigue tests, the role of damage potential could be assessed more clearly when the fatigue life data were plotted directly against the damage parameters, such as strain range, dynamic creep rate, dissipated strain energy, and stored strain energy. The fatigue life curves based on the damage parameters at midlife showed a clear trend of a shorter fatigue life with a higher level of minimum stress. This trend could be established at a given strain range, dynamic creep rate, or dissipated strain energy. The results are in striking contrast to the trend of the S-N curves. The trend of a shorter fatigue life with a higher level of minimum stress was less obvious at a given stored strain energy. The values of dynamic creep rate, dissipated strain energy, and stored strain energy at midlife were found to have a power law relationship with the fatigue life of aircraft tire carcass composite.