bluuebunny/crossref_metadata_2025 huggingface dataset:
Oregon's Superpave Implementation
Authors: Leahy RB , Cramer SB , Thompson GO
Published: March 2009

Oregon Department of Transportation (ODOT) has specified performance-based asphalts (PBAs) since 1991. Developed by the Pacific Coast Conference on Asphalt Specifications (PCCAS) in 1990, the PBA concept uses conventional test methods for classification and facilitates binder selection based on climatic conditions. The Conference plan was to use the PBA concept and conventional tests as an interim approach which would eventually be replaced with the Strategic Highway Research Program performance grade (SHRP-PG) specification and supporting tests. As a first step in the SHRP implementation/validation effort ODOT has evaluated its commonly used PBA grades in terms of the SHRP (now called Superpave) protocols. The limited binder evaluation to date suggests the following equivalencies:

Using the Superpave weather database, nomographs were developed to illustrate the recommended binder grades. Because of Oregon's climatic diversity, as many as 14 binder grades could be used. Practical constraints and realistic measures such as state-maintained road-miles associated with the various PG binders, however, suggest that 4 PG binders may suffice. Additionally, preliminary economic analysis suggests that implementation of the PG system could provide substantial savings. Because of Oregon's extensive use of open-graded friction courses, additional work must be done to determine what effects, if any, the PG classification might have on this mix type in terms of field performance.
An Evaluation of the Suitability of the Superpave System to the Design of Limestone Rock Asphalt (LRA) Mixes
Authors: Jackson NM , Dukatz EL
Published: March 2009

Superpave is a volumetric asphalt mix design system which was originally intended for hot mix asphalt (HMA) and low traffic levels. However, it is believed that the concepts behind the Superpave volumetric mix design system can be applied to specific cold mixes with only minor modifications.

An evaluation of the suitability of the Superpave volumetric system to the design of a specific type of cold mix has been conducted at the Vulcan Materials Company, R&D Technical Center. The objective of this study was to subject several Texas Limestone Rock Asphalt (LRA) mixes to the volumetric Superpave system.

The results of this study demonstrate that LRA mixes can be successfully compacted with the SHRP gyratory compactor and evaluated with the Superpave volumetric mix design system. Recommended modifications to the HMA Superpave design criteria are presented with respect to the Texas LRA mixes.
Comparison Between the Aging Processes for Asphalt Mixtures and Those for Asphalt Binders
Authors: Lee M-G , Tia M , Ruth BE , Page GC
Published: March 2009

The Strategic Highway Research Program (SHRP) has proposed a short-term oven aging (STOA) process to simulate the aging effects of hot mixing and construction process on asphalt mixtures, and a long-term oven aging (LTOA) process to simulate the effects of additional aging of asphalt mixtures in service for 5 to 10 years. In the SHRP Superpave Binder Specifications, the conventional Rolling Thin Film Oven (RTFO) Test is used to simulate the effects of the hot-mix process on a binder, and the Pressure Aging Vessel (PAV) is used to simulate additional aging of the binder in service. This study evaluated the effects of the SHRP STOA and LTOA by comparing their effects on the asphalt binders with those produced by the RTFOT and the PAV processes.
Evaluation of Long-Term Oven Aging of Asphalt Mixtures (AASHTO PP2-95) on Superpave Thermal Cracking Performance Predictions
Authors: Romero P , Roque R
Published: March 2009

A study was conducted to determine the effects of long term oven aging of asphalt mixtures (AASHTO PP2-95) on the thermal cracking performance evaluation of mixtures using the SUPERPAVE Indirect Tensile Test (IDT). Asphalt mixtures were aged according to the procedures developed by the Strategic Highway Research Program (SHRP) and tested using the SUPERPAVE Indirect Tensile Test after short- and long-term oven aging. The results were used to make thermal cracking performance predictions using the Penn State Thermal Cracking Model, which is a part of the SUPERPAVE mixture analysis system. The analyses indicated that: 1) long-term oven aging of mixtures produced changes in mixture compliance that led to differences in thermal cracking performance predictions, 2) long-term oven aging can produce excessive aging which results in erroneous (unconservative) performance predictions and 3) the relative ranking of thermal cracking performance of short-term oven-aged mixtures is, for most cases, the same as that of long-term oven aged mixtures. In other words, the system distinguished between mixtures with significantly different performance levels regardless of whether the mixtures were tested after short-term oven aging or long-term oven aging. This finding implies that long-term oven aging may not be justified for mixture specification purposes when the SUPERPAVE low temperature performance evaluations are used.
Driving Rain and Masonry Veneer
Authors: Straube JF , Burnett EFP
Published: March 2009

Wetting, in particular rain wetting, of walls with a masonry veneer is an important performance consideration for reasons of aesthetics, durability, and utility. Over the past four years, a variety of full-scale clay brick veneer wall systems have been tested in the BEGHUT field test facility. These long-term investigations of the response of wall systems to the southwestern Ontario climate have involved observation of both the exterior and interior environments as well as the performance of the brick veneer.

Standard and non-standard air and rain penetration testing has been conducted. Temperature, vapor pressure, air pressures, and brickwork moisture content have been measured. The contribution of vents of various kinds and the flow characteristics (both air and water) of the region behind the screen has been studied. In the latest project, two weather stations are used to monitor the sun, wind, rain, and driving rain. There are also 14 driving rain gauges mounted on the walls of the facility.

The objective of this paper is to propose a probabilistic model relating the wind, rain, and rain penetration. Driving rain, wetting, and surface drainage are discussed in some detail. Some of the more significant preliminary results of this research and its application to wall performance and rain penetration testing, especially for brick veneers, are presented and discussed.
Progress in Through-Hardening Bearing Steels: User's Experience
Authors: Furumura K , Abe T , Murakami Y
Published: March 2009

This paper introduces a material technology relating to longer life bearings made of through-hardening steel.

Efforts to improve steel cleanliness led to the development of a more reliable through-hardening steel (SAE 52100). As the fruit, we have succeeded in mass-producing extremely purified steel (EP steel) in collaboration with a steel maker.

Among the rolling contact fatigue (RCF) life tests under clean lubrication conditions, only one bearing had accidentally failed substantially earlier than all the rest. This earlier failure was at about 1/20 of the L10 life, so that it introduced a large deviation into the Weibull distribution. It was not due to surface originated flaking from a small dent. This extremely earlier failure was believed to be subsurface originated flaking from a large non-metallic inclusion. Under clean lubrication conditions, the large non-metallic inclusions exert a more harmful impact on RCF life than small indentations. Therefore, original evaluation methods of non-metallic inclusions for practical bearing applications, especially from the view point of particle size distribution, have been developed.

Since Japanese bearing manufactures have moved forward with overseas local production due to the recent economic situation, it has been necessary to define the lower limits of permissible bearing steels. Therefore, the permissible limits about cleanliness for bearing steels were studied. Consequently, successful local procurement of almost all bearing steels has been achieved.

By changing the chemical composition of SAE 52100, a new low cost through-hardening steel was developed. This steel was a non-soaking steel which was produced by controlling the primary large carbides and the heat-treatment condition of spheroidized annealing. The performance of bearings made of this steel is equivalent to that of the conventional bearing steel.
New Steels and Methods for Induction Hardening of Bearing Rings and Rollers
Authors: Ouchakov BK , Shepeljakovsky KZ
Published: March 2009

The new method of through-surface hardening (TSH) of bearing rings and rollers was developed and used in Russia and former USSR. The principles of the method include the use of special steels of low or controlled hardenability, through-the-section induction or furnace heating and intense quenching of the parts by water stream in special devices. Due to the low hardenability of applied steels, the bearing rings and rollers have high-strength martensitic surface layer, combined with a core strengthened with a troostite and sorbite structure. High compressive residual stresses are formed in the martensitic surface layers. For a long time TSH has been successfully used for inner rings of bearings for railway car boxes, large rings and rollers of bearings for cement furnaces and rolling mills. Recently TSH was used for hollow rollers of railway bearings. For bearing rings made of SAE 52100 type high-carbon, chromium-alloyed steel a new method of low-deformation hardening was developed. The method is based on self-calibration of the rings during the quenching process and is intended for through hardening by induction heating and quenching by rapidly moved water stream.
The History and Future of Aircraft Turbine Engine Bearing Steels
Authors: Pearson PK
Published: March 2009

The history of aircraft turbine engine bearings is one of great improvements in reliability and performance. Progress in steel has followed two parallel paths. One is in steel composition from low alloys to high speed, fracture tough, and corrosion resistant compositions. The other is in steel quality, from electric furnace to vacuum and remelting methods, and forging and inspection techniques to prevent stress raising flaws. In many ways the developments for turbine engines have led the way for the bearing industry. In this paper the history and future will be reviewed with emphasis on the important lessons we have learned that can be applied wherever rolling contact bearings are used.
Interactive Effects of Pesticide Mixtures on the Neurobehavioral Responses and Ache Levels of Planaria
Authors: Feldhaus JM , Feldhaus AJ , Ace LN , Pope CN
Published: March 2009

The exposure of non-target aquatic organisms to sublethal levels of combinations of environmental pollutants may result in synergistic, antagonistic or additive effects. Short-term exposures of planaria to sublethal concentrations of malathion, carbaryl and 2,4-D alone, and in combination, resulted in alterations in both neurobehavior and acetylcholinesterase (AChE) levels. Both interactive and individual effects of the pesticides were concentration dependent. Pesticide mixtures produced varied interactive effects. At very low levels, all pesticide mixtures produced significant (p < 0.01) synergistic responses in the neurobehavior of planaria and resulted in a greater number of responses than predicted additive values. Responses obtained from exposure to low levels of the pesticide mixtures showed a less than additive increase. Malathion and carbaryl exposure resulted in 5–45% decreases in AChE activity. AChE levels increased 6–34% after 2,4-D exposure. Evaluation of planarian neurobehavior responses provided a simple, sensitive method for biomonitoring the interactive sublethal toxicity associated with pesticide mixtures.
Comparison of Two Reference Toxicants and Their Effect upon the Growth and Development ofMyriophyllum Sibiricumin Axenic Culture
Authors: Roshon RD , Stephenson GR
Published: March 2009

A static, 14 day laboratory bioassay using axenic Myriophyllum sibiricum Komarov was developed and utilized to determine the effects of two reference toxicants [zinc chloride (ZnCl2) and phenol] upon the morphological and physiological development of this species. For ZnCl2 the highest “no observable effect concentration” (NOEC) was 4.26 mg/L for root length. Based upon IC50 values, the most sensitive endpoint parameter for ZnCl2 was root length (range = 8.2–17.8 mg/L), followed by fresh weight (range = 13.2 – 32.4 mg/L) and root number (range = 13.3 – 38.6 mg/L). For phenol, the NOEC was 11.76 mg/L for three endpoint parameters (root number, total root length and fresh weight). Based upon IC50 values for phenol, the most sensitive endpoint parameter was root length (32.6 – 40.0 mg/L), followed by root number (45.8 – 57.0 mg/L) and fresh weight (48.2 – 75.9 mg/L). For both reference toxicants, the results were repeatable over time. As tested in this axenic culturing system, the ZnCl2 was slightly more toxic to the M. sibiricum than the phenol.
Risk Assessment of Human and Animal Health Drugs in the Environment: A Chemical Fate-and Environmental Effects-Approach
Authors: Velagaleti RR , Winberry MW
Published: March 2009

In the United States, the assessment of risk to the environment of manufacture, use and distribution of human and animal health drugs is required under the National Environmental Policy Act of 1969. Such assessments are required by the U.S. Food and Drug Administration (FDA) and in Europe by member countries of the European Union as a requirement for the approval of new drug applications (NDAs) or supplements. The environmental risk assessment methodologies published by these agencies are discussed with an assessment of current knowledge of the regulatory status. The environmental exposure pathways of human and animal health drugs are described. The current understanding of fate and effects of human and animal health drugs in the environment and the author's view of risk assessment from a fate and effects approach are also discussed.
Mathematical Methods for Comparing Structures of Ecological Communities: A Survey for Ecotoxicologists
Authors: Steele C , Skinner C
Published: March 2009

Analyses of experimental data in ecotoxicology often involve making comparisons between or among the structures of different ecological communities. Not surprisingly, many methods have been developed for defining and comparing community structure: species richness, diversity indices, similarity indices, biotic indices. Most were developed for use in detecting environmental stress in aquatic ecosystems, but many perform equally well for terrestrial communities. This brief review examines the most frequently used and/or useful of these methods in order to explore differing approaches to the problems of quantifying community structure and comparing one community with another. The species richness method, S, is discussed. Diversity indices surveyed include: Shannon's H', Simpson's D, Brillouin's H, McIntosh's M, Cairns' Sequential Comparison Index, SCI, Hurlbert's “encounter” Index, PIE, and, Keefe and Bergersen's TU. Five similarity indices are reviewed: Jaccard's Index, Percentage Similarity Index, PSC, Bray-Curtis Index, Euclidean (or “ecological”) distance, and, Pinkham and Pearson's Index, B. Biotic indices covered are Beck's Biotic Index, Chandler's Biotic Score (CBS), Chutter's Index, and the Index of Biotic Integrity.
Modeling the Effect of Toxicants on the Parameters of Dynamic Energy Budget Models
Authors: Muller EB , Nisbet RM
Published: March 2009

Toxicants negatively affect the rates of growth and reproduction of organisms. Dynamic energy budget models offer a convenient mathematical framework to describe growth and reproduction by individuals. Since these models take into account the lipid content of an animal, the accumulation of toxicants is easily incorporated. This paper deals with the subsequent effects of toxicants on growth and reproduction. We argue that the concept of non-competitive inhibition is applicable for toxicants that increase maintenance demands and reduce assimilation. In this way, energy investment in growth and reproduction are indirectly reduced.
Ecotoxicity of Nitroaromatics to Aquatic and Terrestrial Species at Army Superfund Sites
Authors: Hovatter PS , Talmage SS , Opresko DM , Ross RH
Published: March 2009

Nitroaromatic compounds, including 2,4,6-trinitrotoluene, RDX, HMX, tetryl, and associated degradation products, are released into the environment during the manufacturing, loading, packing, and assembling of munitions at U.S. Army Ammunition Plants. With the exception of 2A46DNT, nitroaromatic compounds are more toxic to fresh-water fishes (LC50s ranging from 0.4–32 mg/L) than to freshwater invertebrates (EC50s ranging from 3–100 mg/L). Rainbow trout are the most sensitive test species with LC50 values ranging from 0.43 to 6.4 mg/L for TNT, RDX, and HMX. These compounds produce negative effects on reproductive endpoints in terrestrial mammals at doses >1 mg/kg/day. Limited data indicate that nitroaromatics are not toxic to terrestrial plants (LOECs ranging from 25–100 νg/g in soil) and soil invertebrates (LOEC of 200 νg/g). Additional studies need to be undertaken to completely characterize the toxicity of these compounds; however, the criteria and screening benchmarks presented in this paper can be used to assess the risks to indigenous flora and fauna at Army Superfund sites.
Reference Toxicants for Toxicity Testing Using Caenorhabditis Elegans in Aquatic Media
Authors: Cressman CP , Williams PL
Published: March 2009

Caenorhabditis elegans aquatic toxicity assays were standardized with five common reference toxicants: CdCl2, NaCl, KCl, sodium lauryl sulfate (SLS), and sodium pentachlorophenate (PCP). Aquatic toxicity testing was conducted in 3 media: a standard C. elegans medium; EPA moderately hard reconstituted water; and EPA moderately hard mineral water. Test duration in each medium was 24h without a food source, and 24h and 48h with Escherichia coli strain OP50 as a food source. Each test was replicated three times with each replicate having 6 wells per concentration, 10 worms per well. LC50 values were calculated using probit analysis. The average LC50s for each set of replications were compared to assess sensitivity and reproducibility of the data, identifying expected variation between replicate tests. These reference toxicants increase the database for C. elegans and provide a benchmark for further application.
Thermal Behavior of Mixtures of Perlite and Phase Change Material in a Simulated Climate
Authors: Petrie TW , Childs KW , Childs PW , Christian JE , Shramo DJ
Published: March 2009

A new concept for use of phase change material (PCM) in building envelopes has been investigated. The concept is called a RCR system in analogy to an electrical circuit with a capacitor between two resistors. Here, the thermal capacitance of the PCM is sandwiched between the thermal resistance of conventional insulation. The PCM used was hydrated calcium chloride dispersed in perlite and contained in watertight test cells. One cell had a PCM/perlite ratio of 2:1 by weight; the other had a 6:1 mixture. Extruded polystyrene (XPS) was the insulation below and above the PCM. Heat-flux transducers on the top and bottom of each cell as well as thermocouples from the top to the bottom of each cell allowed us to follow closely the progression of freezing and melting in the PCM as we subjected the cells to both steady and diurnally varying simulated outside temperatures. Computer modeling with a transient heat conduction program was successful in proving that we understood the relevant energy transfer mechanisms and thermophysical properties. For the diurnal cycles, with twice the amount of XPS below as above the PCM, much of the energy stored during daytime by melting PCM flowed to the outside at night when it froze again. Comparisons were made to the behavior of conventional insulation. With PCM, the total daily energy flow into the conditioned space below the test cells was lower and the peak flow rate was delayed in time and decreased in magnitude.
The Measurement of the Morphology of Closed Cell Foams Which Control the Overall Thermal Conductivity
Authors: Glicksman LR , Stewart J
Published: March 2009

Means to characterize and measure morphology which affects the solid and radiative contributions in closed cell foams have been developed. From measured two-dimensional intercept area distributions, the actual cell size distribution is calculated. For each of the smallcelled polyurethane foams examined, the distribution is narrow, close to the mean cell diameter. From numerical analysis of extreme cell segregation, less than 13% error in the extinction coefficient and the radiative contribution calculated from the mean cell diameter is expected due to cell size distribution. A means to measure the fraction of solid in the strut from strut cross sectional areas is derived. for the small-celled foams analyzed, the fraction of solid in the strut decreases from 0.67 to 0.34 as mean cell diameter decreases from 0.363 mm to 0.109 mm. Smaller celled foams which show a redistribution of polymer from the struts to the cell walls as cell size decreases will exhibit a larger solid conductivity which may counterbalance the decrease in radiation which accompanies the small cell size.
The Colorado Snowboarding Injury Study: Eight Year Results
Authors: Janes PC , Abbott P
Published: March 2009

Snowboarding has witnessed an enormous growth in popularity and participation in the last decade. A prospective study was instituted to ascertain the injuries suffered during snowboarding. From 1988 through 1996 questionnaires were collected from 47 medical facilities within the state of Colorado. Four thousand three hundred and ninety physician-diagnosed injuries were obtained and analyzed utilizing an SPSS computer statistical package.

There were 1929 (44%) upper extremity, 1650 (38%) lower extremity, and 811 (18%) other injuries. The mean age of the injured snowboarder was 23 years (7 to 71). There were 3241 males (74%) and 1137 females (26%).

Wrist injuries numbered 869 (20%), and only 5% of injured snowboarders wore some form of wrist protection. Closed head injuries numbered 86 (2.3%) with head contusions, facial fractures, scalp and facial lacerations contributing an additional 2.4%. Only 1.3% of injured snowboarders wore helmets, and 32% of injured participants admitted to a previous snowboarding injury. Spine injuries were fractures 47 (1.2%), sprain/strain 125 (2.8%), and contusions 39 (1.0%).

Beginner snowboarders suffered more MCL injuries, while experts had more of the ACL injuries. There was no correlation between had shell boots and ACL disruption, and 82% of ACL injuries occurred in males. Knee injuries from snowboarding (15%) remain less than one half of the rate suffered by alpine skiers.

Fractures of the anterolateral process of the talus numbered 110 (2.5%) and often required a CT scan for definitive diagnosis. Operative intervention is suggested for all but nondisplaced fractures.

Snowboarding injury patterns are quite distinct, and further research and education should now concentrate on preventative measures.
Alpine Skiing and Spinal Cord Injuries: View From a National Database
Authors: Meyers AR , Misra B
Published: March 2009

Objectives: This study was designed to compare the demographic backgrounds and health care experiences of people with spinal cord injuries (SCIs) injured as a consequence of skiing with three other groups: those injured in other winter sports; those injured in other sports, and those injured as a result of other causes. Methods: Data are derived from the U.S. National Collaborative SCI Database, which includes cross-sectional and some longitudinal data on more than 22 000 people with SCIs who have received acute hospital and rehabilitation care at 21 National Model SCI Systems throughout the United States since 1973. Results: In general, those who sustain their SCIs skiing are more likely to be white, somewhat better educated, though younger than their counterparts. They have fewer acute hospital days and lower acute and rehabilitation care costs. They also report fewer in-patient pressure sores. There are considerable differences between those whose injuries are the result of skiing and those whose are the result of other kinds of sports. Conclusion: Data suggest that those with ski- related SCIs have more favorable prospects of rehabilitation.
Clean Steel Technology - Fundamental to the Development of High Performance Steels
Authors: Wilson AD
Published: March 2009

The use of clean steel technology (low sulfur with calcium treatment for inclusion shape control) is a fundamental building block in the development of high performance plate steels. A brief review will be presented of the benefits of calcium treatment and its effect on non-metallic inclusions (sulfides and oxides) and reducing sulfur levels. During the past thirty years the requirements for low sulfur levels have been reduced from 0.010% maximum to 0.001% maximum. The effects of clean steel practices on specific properties will be reviewed including tensile ductility, Charpy V-notch and fracture toughness, fatigue crack propagation and hydrogen-induced-cracking resistance. Traditional low sulfur plate steel applications have included pressure vessels, offshore platforms, plastic injection molds and line-pipe skelp. More recent applications will be discussed including bridge steels, high strength structural steels to 130 ksi (897 MPa) minimum yield strength, 9% nickel steels for cryogenic applications, and military armor.
Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes: 3rd Volume
Authors: Gilliam TM , Wiles CC
Published: March 2009

Description

Stabilization and solidification (S/S) technologies have been used for decades as a final treatment step prior to the disposal of radioactive and chemically hazardous wastes. STP 1240 provides you with the latest technical exchange of S/S information available from both of these scientific communities.

The majority of papers addresses leachability and durability, the two principal issues associated with long-term containment prospects of waste treated with this technology. 47 papers in 7 sections cover: Basic Considerations in the Application of Vitrification Technologies • Organic Wastes • Mechanisms of Containment • Process Technology Development and Evaluation (Parts I and II) • Emerging Technologies • Field Application and Full-Scale Testing.

For remedial cleanup contractors, hazardous waste treatment and cleaning consultants, professors and researchers of hazardous waste.
Masonry: Esthetics, Engineering, and Economy
Authors: Taubert DH , Conway T
Published: March 2009

Description

Provides new data and additional information to further the knowledge of masons, architects, and engineers. 13 peer-reviewed papers in three sections:

Esthetics,

Engineering,

and Economy.
Environmental Toxicology and Risk Assessment: Fourth Volume
Authors: La Point TW , Price FT , Little EE
Published: March 2009

Description

The most current information available on the international aspects of pollution and its impact on the environment. This comprehensive text includes state of the art research from Canada, Mexico, the Netherlands and the United States.

Featured topics among 15 peer-reviewed papers include: Transboundary pollution issues across international borders • Laboratory and field estimation of exposure and effects • Risk assessment and human health • Generic industrial cleanup criteria in Canada and the U.S. • Aquatic toxicology • Bioindicators International approaches to sediment toxicity assessment.
Multiaxial Fatigue and Deformation Testing Techniques
Authors: Kalluri S , Bonacuse PJ
Published: March 2009

Description

Focuses on state-of-the-art testing techniques for characterizing the multiaxial fatigue and deformation behaviors of monolithic and composite materials. 14 peer-reviewed papers deal with both experimental and theoretical aspects of the multiaxial fatigue and deformation behaviors of structural materials. In 4 sections: Multiaxial Testing Facilities; • Multiaxial Deformation; • Multiaxial Fatigue; and • Structural Failure and Crack Propagation Under Multiaxial Loading.
Recent Developments in Geotextile Filters and Prefabricated Drainage Geocomposites
Authors: Bhatia SK , Suits LD
Published: March 2009

Description

The first publication of its kind featuring innovative approaches to geosynthetic filtration and drainage applications.

15 comprehensive, peer-reviewed papers address the following geotextile filter and prefabricated geocomposite issues:

• Pore Size Characterization and Permeability

• Applications

• and Case Histories.
A New Screening Method Designed for Wear Analysis of Bearing Surfaces Used in Total Hip Arthroplasty
Authors: Wimmer MA , Nassut R , Lampe F , Schneider E , Morlock MM
Published: March 2009

New technologies of surface treatment are speculated to reduce or prevent the generation of polyethylene particles. These new (spherical) bearing surfaces need to be evaluated with an appropriate testing method. Results from testing of flat surfaces are -in general- difficult to interpret.

A bi-axial “pin-on-ball“ device utilising commercially available components of artificial joints has been developed. The contact zone kinematics in hip joints according to in-vivo conditions are approximated. First results are promising: a phase shift between the pin and ball oscillations produced quasi-elliptical displacement trajectories, similar to the ones which are reported to take place during gait. The “pin-on-ball” set-up allowed to identify subtle characteristics of friction and generated a wear pattern which matched the features known from retrieval studies. Therefore, this new testing device might be an interesting alternative to common screening devices.
A Review of The Effects of Design, Contact Stress, and Materials on The Wear of Metal-On-Metal Hip Prostheses
Authors: Poggie RA
Published: March 2009

The clinical and tribological history of metal-on-metal (MOM) hip bearings indicates mixed clinical performance. Low wear and excellent twenty-year clinical performance is reported, as is early loosening and high wear. Contemporary tribological studies of MOM hip implants combined with improved Co-Cr-Mo materials has led to more predicable wear performance, and provided an understanding of the dichotomy in historical clinical performance. Historical failures of MOM bearings can be attributed to one or more of the following: poor control of sphericity and radial clearances greater than 200 μm (high wear), poor implant design and/or cementing technique, inadequate radial clearance via matched head-cup pairs (seizing and high friction), and unpredictable Co-Cr-Mo microstructure and large carbides (two and three body wear). And conversely to these failure modes, the success of contemporary MOM bearings can be attributed to the following: modern machine tools are capable of reliably manufacturing MOM bearings with sphericity of +/- 3 to 5 μm, linear head penetration wear rates of about 5 to 20 μm per year (million cycles) are reliably achieved, and contemporary high carbon (0.25% C) wrought Co-Cr-Mo alloys possess homogenous microstructures with carbides less than 5 μm in size. Furthermore, contemporary radial clearances of 35 to 50 μm result in maximum Hertzian contact stresses of about 25 to 50 MPa, which is 50 times less than the compressive yield strength of Co-Cr-Mo (2700 MPa) or about 20 times less than the tensile yield strength. Therefore, mechanical damage due to excessive contact stress probably does not contribute to bearing failure. Rather, the optimum radial clearance is related to an optimized balance between maintenance of fluid film lubrication and avoidance of bearing seizure due to interference of opposing asperities and/or entrapment of third-body particles. The literature suggests 25 to 45 μm as the optimum radial clearance for 28 and 32 mm diameter head-cup components.
Simulator Wear of Some Commercially Available Metal-on-Metal Hip Implants
Authors: Medley JB , Dowling JM , Poggie RA , Krygier JJ , Bobyn JD
Published: March 2009

Simulator wear tests were conducted for 1.5 million cycles on second generation metal-on-metal hip implants fabricated from cobalt-based alloy (ASTM F 1537-94) to compare their performance with each other and with both custom-made implants and retrieval studies published in the literature. In addition, factors controlling wear were explored. Six commercially available implants were tested (2 low carbon and 4 high carbon) for 1.5 million cycles in a MATCO™ hip simulator following previously established protocols. Volumetric wear was in the same range for all of the implants tested and much less than would be expected in comparable tests with conventional polyethylene cups. The wear of the commercial implants used in the present study was very similar to custom-made hip implants of similar diameter, clearance and surface roughness. Three of the high carbon implants of the present study had somewhat lower wear than expected when their surface roughness was taken into account but, in general, clearance, roughness and lambda (a ratio of lubricant film thickness to combined surface roughness) were factors controlling wear. The simulator wear of the present study showed some agreement with the in vivo wear estimated in retrieval studies in the literature.
Numerical Analysis of Time-Varying Fluid Film Thickness in Metal-Metal Hip Implants in Simulator Tests
Authors: Chan FW , Medley JB , Bobyn JD , Krygier JJ
Published: March 2009

In vitro testing of metal-metal hip implants has shown that metal-metal wear can be up to two orders of magnitude less than the wear of conventional metal- polyethylene articulations. This low wear may be related, in part, to fluid film lubrication at the bearing surfaces. A transient, elastohydrodynamic lubrication model incorporating both squeeze and entraining actions in the hip was developed to predict fluid film thickness for metal-metal hip implants during simulator testing. For a typical case, the model showed that cyclic steady state, with film thickness variations from 38 to 70 nm, was reached in about 3 cycles. Decreased diametral clearance, increased lubricant viscosity, and increased cycle frequency resulted in increased film thicknesses. However, film thickness did not change markedly for different load magnitudes. In all cases, steady state film thickness values calculated using the average load during the cycle corresponded to minimum cyclic steady state values, indicating that this may be a simplified method to predict minimum film thickness. Lambda ratio (ratio of fluid film thickness to combined surface roughness of articulating components) decreased as surface roughness increased, indicating a transition from full fluid film lubrication to boundary lubrication. Steady state lambda ratios were related to the total wear of simulator-tested implants with wear decreasing significantly with increasing lambda ratio. With proper selection of low clearance and low surface roughness values, lambda ratios that predict full fluid film lubrication and possibly further improved wear performance can be obtained, making lambda ratio a potentially useful tool in the design of metal-metal hip implants.
Wear Behavior of Ceramic Pairs Compared on Different Testing Configurations
Authors: Cales B , Chevalier J
Published: March 2009

The wear properties of ceramic pairs including a biomedical grade zirconia ceramic (PROZYR®) were studied. In a simple disk-on-disk wear test in synthetic serum, the best wear behavior was observed with alumina-zirconia pairing. These tests also showed that the zirconia-zirconia combination can be considered for hip joint applications because it demonstrates wear behavior close to the classic alumina-alumina pairing. Hip simulator tests up to 10 million cycles for zirconia-alumina combinations confirm the previous experiments. It is clearly shown, if zirconia ceramic material and convenient wear test procedures are used, that the wear behavior of zirconia ceramic in ceramic-ceramic pairing is outstanding. The wear performance of zirconia was similar to, if not better than, that of alumina. Furthermore, tensile stresses in heads and cups, determined using finite element analysis, were found to be significantly higher in ceramic-on-ceramic bearings than in conventional ceramic-on-polyethylene couplings. This may influence the incidence of ceramic component fractures in ceramic-on ceramic bearings and may have implications concerning ceramic material selection for this application.
Adherent Alumina Coatings by Ion Beam Synthesis
Authors: Armini AJ , Bunker SN , Huntington DM
Published: March 2009

The lower wear rate obtained with bulk alumina femoral hip balls compared to cobalt-chromium alloy balls on ultra-high molecular weight polyethylene is well documented in clinical studies. An alumina coating on a cobalt-chrome component would produce the superior surface properties of the ceramic combined with the desirable bulk properties of the metal. A new technique for forming a blended interface between the alumina coating and cobalt-chrome has been developed. The process uses a high energy ion beam of aluminum impinging on a cobalt-chrome substrate in an oxygen ambient gas to grow the alumina from beneath the metal's surface. Interface thicknesses up to 1200 Angstroms thick have been observed. To date, flat coupons and hip balls, have been coated with coatings 1 micron thick. The coatings were evaluated for polyethylene wear using a laboratory screening tribometer which has been designed to simulate non-linear tracking of the femoral ball on the UHMW polyethylene. The adhesion was measured using a diamond point scratch tester.
Self-Reinforced Composite Polyethylene (SRC-PE): A Novel Material for Orthopedic Applications
Authors: Megremis SJ , Duray S , Gilbert JL
Published: March 2009

An approach to fabricating high fiber volume fraction UHMWPE composites where the reinforcing phase and the matrix phase are of identical composition, and the matrix derives directly from the fiber is characterized. The processing method utilizes a hot compaction technique. During hot compaction, UHMWPE fibers are heated in a constrained mold under pressure to allow diffusion bonding of adjacent fibers. Thus, a composite results where the matrix comes from the fibers; however, the fibers themselves retain much of their original mechanical properties. This material is referred to as self-reinforced composite polyethylene (SCR-PE). Preliminary processing methods are described, and the morphology of the unidirectional SRC-PE composites are examined along with their thermal and mechanical properties. SEM micrographs of etched cross-sections of the composites exhibit fully consolidated specimens in which the fibers are still easily distinguishable and areas of fiber-fiber bonding are revealed. DSC plots show that the composites have very similar thermal properties to the original fibers. The composites also exhibit substantial unidirectional strength in the fiber direction with an approximately ten fold increase in modulus (9.99 ± 1.06 GPa) and strength (506 ± 139 MPa) in tension as compared to reference UHMWPE. However, wide variations in mechanical properties with the type of loading (tension, compression, or bending) were observed. For instance, when compression tests were performed in the fiber direction, the unidirectional specimens exhibited low modulus (1.74 ± 0.46 GPa) and strength (33.8 ± 4.8 MPa), relative to tension and bending, which may be beneficial in orthopedic load bearing applications by allowing for more deformation during contact resulting in a lowering of contact stresses. However, the high tensile and bending strengths in the fiber direction can be advantageous in providing resistance to microfracture events associated with debris generation.
Construction and Performance of Ultrathin Asphalt Friction Course
Authors: Kandhal PS , Lockett L
Published: March 2009

The Novachip process, also known as ultrathin friction course, was developed in France in 1986. The process utilizes a single piece of equipment to place a thin, gap-graded hot mix asphalt (HMA) onto a relatively thick layer of polymer modified asphalt emulsion tack coat. Two Novachip projects were constructed in Alabama in 1992 to achieve the following objectives: (a) Document the materials and the construction procedures utilized in the construction of the Novachip surface course, and (b) monitor and evaluate the performance of the Novachip test sections at regular intervals for a period of three years.

This paper gives the construction details and performance of Novachip after 4 1/2 years in service. Since this was the first Novachip project in the U.S. with the machine imported from France, some equipment related problems were encountered. The surface texture of Novachip is very similar to that of a typical open-graded friction course. No significant raveling was observed on the two-projects after about 4 1/2 years' service, which indicates very good bond between Novachip and underlying surface. Novachip surface has significantly higher pavement surface friction numbers compared to dense graded HMA wearing course. It appears to be a potential alternate for chip seals, micro surfacing, and open-graded friction course.
Quality Management of Hot Mix Asphalt
Authors: Decker DS
Published: March 2009

Description

Provides real-world examples of how quality management systems can and do operate.

10 peer-viewed papers include

• Performance Based Field Quality Control/Quality Assurance for Asphalt-Aggregate Mixtures

• Evaluation and Modification of a Statistical Specification for Hot Mix

• and Quality Management in Asphalt Pavement Construction.

For asphalt contractors, state DOT highway contruction, testing and inspection personnel.
Environmental Toxicology and Risk Assessment: Biomarkers and Risk Assessment: Fifth Volume
Authors: Henshel DS , Bengtson DA
Published: March 2009

Description

Features the most up-to-date research on the diversity of biological measures of environmental stress exposure in every strata of living organisms.

30 peer-reviewed papers from the world's leading experts in the field cover two key areas:

Biomarkers --Comprehensive information on the various classes of biomarkers currently being researched and the types of vertebrates and invertebrates in which these techniques can be evaluated is presented in seventeen papers. Issues covered include: environmental estrogen impact; • chromosome translocation measurement; • mainstream and sidestream smoke exposure; • alterations in chicken embryo development; • and gross brain asymmetry evaluation.

Aquatic and Sediment Toxicology, Behavior and Risk Assessment--A broad spectrum of information on the current issues in environmental toxicology and risk assessment is covered in 13 papers. Topics examined include: the sub lethal impact of toxicants as seen in behavior and functional effect; • quality assurance and toxicity identification in the context of laboratory toxicity testing; • and engineering challenges associated with volatile organic compounds (VOC).
Corrosion Activity of Steel in Cementitious Controlled Low-Strength Materials vs. That in Soil
Authors: Abelleira A , Berke NS , Pickering DG
Published: March 2009

Controlled Low-Strength Materials (CLSM) are high performance fills produced and delivered by ready mix suppliers. CLSM places faster than conventional compacted fill, requires less jobsite equipment, increases jobsite safety, and minimizes future settlement problems. Consequently, the use of CLSM as backfill material is a very attractive option. However, there are numerous factors that influence soil corrosion on buried structures, such as the electrical resistivity of the backfill material along with its pH and drainage characteristics. Corrosion experiments in which steel coupons were placed in simulated soil or covered with cement-based CLSM then placed in simulated soil are discussed.
Bedding Factors and E' Values for Buried Pipe Installations Backfilled with Air-Modified CLSM
Authors: McGrath TJ , Hoopes RJ
Published: March 2009

The use of controlled low strength material (CLSM) as a pipe bedding and backfill material requires characterization in terms of traditional design parameters such as bedding factors for rigid pipe and modulus of soil reaction, or E', values for flexible pipe. Triaxial compression and one-dimensional consolidation tests were conducted on two mixes of air-modified CLSM to establish parameters for use in finite element analyses of buried pipe installations. Both trial mixes contained 25 to 30% entrained air to provide flowability. The tests were conducted at ages of 16 hours, 7 days and 28 days to evaluate the change in strength and stiffness with time.

Results of the tests were analyzed to fit parameters to the Duncan hyperbolic soil model with the Selig bulk modulus model. These parameters were then used in analyses of flexible and rigid pipe installations, backfilled with CLSM, to determine traditional installation design parameters.

The finite element analyses indicate that bedding factors for rigid pipe installations range from 1.8, for trench installations backfilled at an age of 16 hours, to 2.5 for trench installations backfilled at an age of 28 days. Bedding factors for embankment installations of rigid pipe range from 2.5 to 4.8 for ages from 16 hours to 28 days, respectively. Values for the modulus of soil reaction (E') for installation of flexible pipe range from 7 MPa to 21 MPa (1,000 psi to 3,000 psi) for ages from 16 hours to 28 days respectively.
Composite Interlaminar Shear Fracture Toughness, GIIc: Shear Measurement or Sheer Myth?
Authors: O'Brien TK
Published: March 2009

The concept of GIIc as a measure of the interlaminar shear fracture toughness of a composite material is critically examined. In particular, it is argued that the apparent GIIc as typically measured is inconsistent with the original definition of shear fracture. It is shown that interlaminar shear failure actually consists of tension failures in the resin-rich layers between plies followed by the coalescence of ligaments created by these failures and not the sliding of two planes relative to one another that is assumed in fracture mechanics theory. Several strain energy release rate solutions are reviewed for delamination in composite laminates and structural components where failures have been experimentally documented. Failures typically occur at a location where the Mode I component accounts for at least one half of the total G at failure. Hence, it is the Mode I and mixed-mode interlaminar fracture toughness data that will be most useful in predicting delamination failure in composite components in service. Although apparent GIIc measurements may prove useful for completeness of generating mixed-mode criteria, the accuracy of these measurements may have very little influence on the prediction of mixed-mode failures in most structural components.
Evaluation of In-Service Thermoplastic Olefin (TPO) Roofing Membranes
Authors: Simmons TR , Paroli RM , Liu KKY , Delgado AH , Irwin JD
Published: March 2009

As part of a five-year investigation, mechanical (strength and elongation) and chemical (thermogravimetry and dynamic mechanical analysis) methods of evaluation are used in this paper to characterize in-service thermoplastic olefin (TPO) roof membranes. All the non-reinforced membranes meet the minimum thickness and tensile strength requirement as specified in the proposed ASTM standard. The polyester scrim reinforced membranes had higher tensile strength and elongation values than those reinforced with random mat of short glass fibers. The standard should consider defining the breaking strength in terms of “stress” instead of load and incorporating strain energy requirements at 23 °C and -40 °C. The term TPO is confusing and very vague and the standard should consider differentiating between the different types of TPOs. Based on thermogravimetry, at least four different types of TPOs are currently in service. Lastly, the standard should consider using the glass transition temperature to monitor changes in membranes due to aging/weathering.