bluuebunny/crossref_metadata_2025 huggingface dataset:
An Estimation of Life in Fretting Fatigue Using an Initiation-Propagation Model
Authors: Navarro C , García M , Domínguez J
Published: April 2008

This paper proposes a method for estimating the total fatigue life in fretting fatigue. It compares the fatigue life of some specimens obtained in various series of fretting fatigue tests with the estimates of total fatigue life using a model that separately takes into account the initiation and propagation of the crack. The experimental tests used a spherical contact and were conducted on an aluminum alloy (Al 7075-T6). The initiation of the crack is considered using the multiaxial fatigue criterion of McDiarmid together with the theoretical distribution of stresses for the given loads applied in each test. The propagation of the crack is considered using two different laws of propagation, Paris law and a curve given by Lankford that would represent the upper limit for the crack propagation velocity (lower limit for fatigue life) when the crack is short. These two estimates are an upper and lower bound respectively of the fatigue life of the specimen; the actual life lies in between.
A Theoretical and Experimental Procedure for Predicting the Fretting Fatigue Strength of Complete Contacts
Authors: Mugadu A , Hills DA , Limmer L
Published: April 2008

An asymptotic approach to the complete fretting contact problem is presented, with a view to elucidating the crack nucleation process. It is suggested that the characteristic stress state at the edge of the prototypical contact can be matched to a test having the same local contact angle and coefficient of friction. A generalized stress intensity factor is then defined, to scale both fields, hence matching the magnitudes of the stress state. Experimental investigations of this approach has prompted the need for some modifications to our original test apparatus, in order to accommodate complete contacts, and these are briefly outlined. Last, the limitations of this approach are discussed.
Effect of Contact Pressure on Fretting Fatigue in Type 316L Stainless Steel
Authors: Nakazawa K , Maruyama N , Hanawa T
Published: April 2008

The effect of contact pressure on fretting fatigue in solution-treated austenitic stainless steel was studied under load control at a stress amplitude of 180 MPa and a stress ratio of 0.1. With an increase in contact pressure, fretting fatigue life was almost unchanged at contact pressures between 15 and 45 MPa, but it decreased drastically at contact pressures beyond 60 MPa. Frictional stress amplitude at the fretted area increased smoothly with contact pressure. It was impossible to explain the contact pressure dependence of life by the change in frictional stress amplitude. At low contact pressures, stress concentration due to fretting damage occurred at the middle portion of fretted area and the main crack responsible for failure was initiated there. At high contact pressures, deep concavity associated with plastic deformation of the specimen under the contact of fretting pad was formed without accompanying heavy wear. The main crack was initiated at the outer edge corner of the concavity which probably acted as a notch. It was suggested that the stress concentration at the concavity edge corner played an important role in fretting fatigue at high contact pressures.
Local Fretting Regime Influences on Crack Initiation and Early Growth
Authors: Dubourg M-C
Published: April 2008

An investigation of fatigue crack initiation and propagation under fretting conditions is described in which both experimental and theoretical approaches are used. Fretting tests were conducted on an aerospace aluminium alloy. The approach presented here aims to describe the propagation of a fretting crack through a step-by-step understanding of the different stages of its life (1) Stage I crack initiation, i.e., sites, growth directions and fracture mode, (2) Stage I-to-Stage II transition as a result of the competition between failure modes, i.e the branching depth and the growth direction after branching. This methodology was successfully applied to fretting fatigue data obtained under the Partial Slip Regime (PSR). Pertinent parameters were proposed to deal with items (1) and (2) depending on the ranges of shear and tensile stresses and their respective roles in crack growth. This step-by-step methodology is used here to analyze the influence on crack initiation and propagation of the local fretting regime and the associated mechanical stress-strain state.
Effect of Contact Pad Geometry on Fretting Fatigue Behavior of High Strength Steel
Authors: Ochi Y , Kido Y , Akiyama T , Matsumura T
Published: April 2008

The effect of contact pad geometry on fretting fatigue behavior of high strength steel was examined by using the clamping double bridge pads system. In order to investigate the effects of bridge pad shapes, the fretting fatigue tests were carried out by using four types of bridge pad with different leg height h*. The fretting fatigue strength decreased with decreasing in the h*. Also, the stick area increased as increasing of the h*. The contact pressure distribution was measured by strain gauge and calculated by using a finite element method in order to investigate the effect of the pads leg height h*. The contact pressure concentrated in the inside on the contact surface where the main crack initiated. Two-stage tests were carried out in order to investigate the fretting fatigue damage. The two-stage test was performed to a certain cycles under fretting condition and then plain tests without fretting as removing the pads were continued.
Effect of Lubricating Anodic Film on Fretting Fatigue Strength of Aluminum Alloy
Authors: Nishida T , Mizutani J , Mutoh Y , Maejima M
Published: April 2008

Wear, scratch, plain fatigue and fretting fatigue tests were carried out using aluminum alloy JIS 6063-T5 specimens with anodic film and lubricating anodic film. Though the surface hardness of lubricating anodic film was lower than that of anodic film, lubricating anodic film had excellent wear resistance and crack resistance compared to anodic film. Plain fatigue strength of the specimen with anodic film was lower than that of the specimen with lubricating anodic film, which almost coincided with that of the specimen without film. The low fatigue strength of the specimen with anodic film may result from the brittleness and tensile residual stress of the anodic film, which attribute to the cracking at lower applied stress, Cracking of the lubricating anodic film during fatigue tests hardly occurred due to its ductile nature and low residual stress and consequently the fatigue strength was not degraded. Fretting fatigue strength of the specimen with lubricating anodic film was higher than that of the specimen with anodic film, which was higher than that of the specimen without film. The lubricating anodic film had the lowest coefficient of friction and a higher cracking resistance, which contributed to the retardation crack initiation and the low crack growth rates. The anodic film also had low coefficient of friction compared to the specimen without film and prevented meta-to-metal contact, which may result in higher fatigue strength compared to the specimen without film. The lubricating anodic film is of significant benefit to fretting fatigue strength without degradation of plain fatigue strength.
Fretting Fatigue Properties of WC-Co Thermal Sprayed NiCrMo Steel
Authors: Okane M , Shiozawa K , Hiki M , Suzuki K
Published: April 2008

Fretting fatigue tests of NiCrMo steel (JIS SNCM439) sprayed with ungsten carbide with additive of 12% cobalt (WC-Co) by HVOF (High Velocity Oxygen Fuel) were carried out to study the effect of WC-Co coating on fretting fatigue behavior. Since the fatigue strength of the present alloy steel was reduced to about 27% by the effect of fretting, fretting fatigue strength was improved by approximately 30% by WC-Co spraying onto the specimen. The tangential force coefficient, which is tangential force measured during the fretting fatigue tests divided by contact load, behaviors of WC-Co sprayed specimen were different form those of the non-sprayed specimen. Especially, the tangential force of WC-Co specimen in an early stage of the test indicated significant low value compared with that of non-sprayed specimen and this was caused from good wear resistance of WC-Co layer. Therefore, the initiation of a fretting crack in case of WC-Co sprayed specimen delayed, and crack propagation rate was lower than that of non-sprayed specimen. These were main reasons for the improvement of fretting fatigue strength by WC-Co spray.
Fretting Wear and Fatigue in Overhead Electrical Conductor Cables
Authors: Lindley TC
Published: April 2008

Fretting wear and fatigue damage induced by wind vibration in overhead power conductors has been investigated by metallographic and fractographic examination. It has been concluded that wear, corrosion and fatigue can each play a role in the degradation of cable, sometimes leading to complete failure.
Effect of Restricted Zone on Permanent Deformation of Dense-Graded Superpave Mixtures
Authors: Kandhal PS , Cooley LA
Published: April 2008

The recommended aggregate properties for Superpave hot mix asphalt (HMA) mixtures include a restricted zone which lies along the maximum density gradation between the intermediate size (either 4.75 or 2.36 mm, depending on the nominal maximum size of the aggregate) and the 300 μm size; it forms a band through which gradations were not recommended to pass. The restricted zone requirement was adopted to help reduce the incidence of tender or rut-prone HMA mixes. Although recommended as a guideline and not a required specification, the restricted zone is commonly interpreted as being based on experience and appropriate to use, if at all possible, for producing acceptable HMA mixes.

According to many paving engineers, compliance with the restricted zone criteria may not be desirable or necessary in every instance to produce paving mixes that give good performance. Some highway agencies and suppliers can provide examples of aggregate gradations that pass through the restricted zone, but produce paving mixes that are performing well. Research has supported this position.

This research project was undertaken to evaluate the effect of the Superpave restricted zone on permanent deformation of dense-graded HMA mixtures. The following factor-level combinations were evaluated: two coarse aggregates, ten fine aggregates, five 9.5 mm nominal maximum aggregate size gradations, and one compactive effort. Of the five gradations used, three pass through the restricted zone and two fall outside the restricted zone (control). Permanent deformation characteristics of mixes meeting Superpave volumetric requirements were evaluated by two different types of tests: empirical and fundamental. For the empirical test, the Asphalt Pavement Analyzer (APA) was used. The Superpave shear tester (SST) and a repeated load confined creep test were utilized as fundamental tests. Test results from the three mechanical tests were analyzed statistically to evaluate the effect of the five gradations on permanent deformation of the HMA mixtures. Based upon the analysis of data, mixes having gradations passing through the restricted zone did not necessarily have lower rut resistance compared to mixes having gradations outside the restricted zone.
Polish Resistance of Tennessee Bituminous Surface Aggregates
Authors: Crouch LK , Sauter HJ , Duncan GM , Goodwin WA
Published: April 2008

In 1992, the Tennessee Department of Transportation (TDOT) initiated a project to pair aggregate performance with pavement functional needs so that all Tennessee aggregate sources could be used efficiently. The principal result of the project was a new pre-evaluation procedure for aggregate polish resistance called the Tennessee Terminal Textural Condition Method (T3CM). The T3CM uses an up-scaled version of the AASHTO T 304 device to monitor an aggregate's ability to retain angularity and texture through a simulated aging process.

In the fourth phase of the study, twenty-three coarse aggregates, sampled at the cold feed stockpile, are subjected to T3CM, T3CM with sand aging, X-ray diffraction, British Pendulum, Loss-on-Ignition, and chemical percent silica techniques. By comparing skid performance versus traffic (ADT, passes, and ESALs) with laboratory test results, aggregate performance and aggregate source variability may be categorized for effective use. Preliminary results indicate that the correlation between T3CM and skid performance (R2 = 0.74) is far superior to the correlations between ASTM C 25 percent silica (R = 0.38), percent silica by X-ray diffraction (R2 = 0.36), and BPN 9 (R2 = 0.0004) with skid performance.
On the Use of Spatiotemporal Techniques for the Assessment of Flash Flood Warning
Authors: García SG
Published: April 2008

In this paper spatial analysis tools are presented which allow the simulation and prediction of flash flooding in semiarid basins. Real-time data from automatic hydrological information systems, the SAIH system, in Spain are integrated in a Geographical Information System (GIS) environment. Making intensive use of the Digital Elevation Model (DEM), the parameters of the developed distributed hydrological models are estimated. The proposed operational environment, Shyska, is applied to the management of flash floods in real time in the basins of the southeast of Spain. This system constitutes a support tool for decision taking, based on spatial analysis, when a flood event occurs.
The Need for Regular Remote Sensing Observations of Global Soil Moisture
Authors: Owe M , De Jeu RAM
Published: April 2008

Soil moisture is an important component of the water and energy balance of the Earth's surface, and as such, is essential to many Earth science disciplines. Regular and accurate estimates of soil moisture are an important input to the study of climate change, numerical weather prediction models, drought forecasts, and agricultural predictions. Soil moisture has been identified as a parameter of significant potential for improving the accuracy of large-scale land surface-atmosphere interaction models. However, accurate estimates of surface soil moisture are often difficult to make, especially at large spatial scales. Soil moisture is a highly variable land surface parameter, and while point measurements are usually accurate, they are typically representative only of the immediate sample location, and simple averaging of point values, in order to obtain large-area spatial means, often leads to substantial errors. In addition, ground sampling is labor intensive and costly, and consequently highly impractical for long-term and/or large-scale monitoring. Since satellite remote sensing observations are already a spatially averaged value, they are ideally suited for easuring land surface parameters such as soil moisture. Passive microwave remote sensing presents the greatest potential for providing regular spatially representative estimates of surface soil moisture at global scales. But, while the optimum wavelength for soil moisture sensing is in the L-band (1.4 GHz or λ = 21 cm), such a sensor has yet to be deployed operationally. However, new and highly improved microwave retrieval techniques are being developed that maximize the information that can be obtained from less optimum sensors, such as C-band and even X-band. Progress from one such study is presented, along with preliminary results of some validation studies and plans to develop a 20-year retrospective global database of surface soil moisture. This data product will be made available to the general public through the Goddard Space Flight Center Distributed Active Archive Center (DAAC). Improved real-time estimates of surface soil moisture should greatly improve the performance of real-time models, while the development of historical data sets will provide necessary information for simulation and validation of long-term climate and global change studies.
A Detailing Method for Improving Leakage Prevention of Exterior Wall Weatherproofing
Authors: Bateman R
Published: April 2008

As generally or often practiced, building design and construction detailing of weatherproofing exterior building walls relies on two-dimensional (2-D) graphic representations of building components to indicate materials used for weatherproofing. However, these details which serve a variety of purposes for different users do not show all the relevant materials needed to construct a weatherproof exterior wall. The various users of construction details, e.g., contractors, builders and material installers, utilize these 2-D drawings as visual instruction guides for constructing and installing building components. Common construction details are intended to show various components that serve a variety of purposes, such as structural support, fire-resistance, energy control, acoustic control, aesthetic appearance and incidentally weatherproofing. Different contractors during construction will review the same detail to obtain information relevant to the purposes of their particular trade. Construction details usually identify a material or component by name and not by the trade that constructs it or the purpose it serves.

Construction details, in addition to traditional uses, need to focus and emphasize weatherproofing materials and assemblies. Three-dimensional details should be used to show the junctures of exterior wall construction where weatherproofing installation is critical. Sequence (Step-by-Step) views should be used to show the layering of weather barriers and flashings in the proper order of installation. Enlarged cross-section details should be used to identify and show what weatherproofing materials are required and where they are installed.
A New Protocol for the Inspection and Testing of Building Envelope Air Barrier Systems
Authors: Knight KD , Boyle BJ , Phillips BG
Published: April 2008

Premature building failures and increased heating and cooling loads have made building envelope air leakage a growing concern in North America. In Canada, the National Air Barrier Association has made the inspection and testing of air barrier systems a mandatory requirement within its Quality Assurance Program. In the United States, Massachusetts is the first of what is expected to be many states introducing revised Energy Codes making air barriers mandatory in new construction. The Air Barrier Association of America has recently formed and will adopt a similar quality assurance program. Utilizing existing ASTM standards, this paper proposes a protocol for the inspection and testing of air barrier systems to be performed before construction begins, during installation, and post-construction. Studies show that even routine testing of the air barrier system will dramatically improve a building's air permeance.
Variability in Oxygen Consumption Calorimetry Tests
Authors: Janssens ML
Published: April 2008

Oxygen consumption calorimetry has been used for more than twenty years to determine the heat release rate from experimental fires. Several investigators have quantified the theoretical uncertainty of heat release rate measurements. Estimates of the precision of heat release tests based on round robin results suggest that in practice the uncertainty may be much greater, in particular for intermediate and large-scale tests. The objectives of this paper are to examine the reasons for this discrepancy, and to propose actions that will improve the precision of heat release rate measurements to an acceptable level without raising costs beyond the reach of commercial fire testing laboratories. The proposed actions include the establishment of a proficiency program to obtain a realistic measure of the uncertainty of heat release rate measurements in fire tests.
Fatigue and Fracture in Membranes for MEMS Power Generation
Authors: Bahr DF , Crozier BT , Richards CD , Richards RF
Published: April 2008

Bulk micromachined membranes containing PZT thin films deposited via sol-gel processing have been tested for fatigue and fracture using a dynamic bulge testing apparatus. These membranes, consisting of silicon, titanium, platinum, PZT, and gold, were pressurized monotonically until failure to determine an average failure pressure and then cyclically pressurized to examine fatigue behavior. Membranes containing PZT show significant degradation of strength as compared to membranes of just silicon or the metallic layers. This is discussed in terms of the residual stresses and defects present in the PZT thin film due to thermal processing. Fractography of the failed membranes shows that delamination does occur at the metal-silicon interface during both types of loading, suggesting both through- thickness and interfacial cracking are possible failure mechanisms in this system.
Effects of Microstructure on the Strength and Fracture Toughness of Polysilicon: A Wafer Level Testing Approach
Authors: Ballarini R , Kahn H , Tayebi N , Heuer AH
Published: April 2008

Specimens have been developed to measure the strength and fracture toughness, of polycrystalline silicon and silicon carbide at the micron scale. The specimens have been fabricated using standard microelectromechanical systems (MEMS) processing techniques, and so have characteristic dimensions comparable to typical MEMS devices (notches, cracks and uncracked ligaments of several microns). They are fully integrated with simultaneously fabricated electrostatic actuators that are capable of providing sufficient force to ensure failure under monotonic loading. Thus the entire experiment takes place on-chip, eliminating the difficulties associated with attaching the specimen to an external loading source. Polycrystalline specimens containing cracks formed by indentation were associated with a microstructure independent average fracture toughness of 1.0 MPa√m. The strength of specimens containing micromachined blunt notches demonstrated a strong dependence on processing procedures and resulting surface roughness. Fractographic investigation suggests that this dependence is related to the size of processing-related flaws on the side surfaces of the films.
Novel Polymeric Dispersants for Aqueous Suspension Concentrate Formulations
Authors: Herbert RM
Published: April 2008

Styrene-acrylic copolymer surfactants demonstrate significant dispersant erformance advantages in suspension concentrate formulations versus current industry standards. The formulation requirement of dispersant to maintain the active ingredient in suspension upon dilution was significantly lower with styrene-acrylic dispersants Atlox® Metasperse 100L or Atlox® Metasperse 500L than with other commercially available anionic surfactants.

When blended with Atlas® G5000 and Synperonic® A7 nonionic surfactants, low viscosity suspension concentrate formulations can be developed using either Atlox® Metasperse 100L or Atlox® Metasperse 500L. Equally important is the use of experimental design techniques to monitor how subtle changes in surfactant ratio can affect formulation performance and aid the formulation chemist in selecting the optimum performing surfactant system.
Improved Efficacy of Lignosulfonate Dispersants Through a Novel Combination
Authors: Winowiski T , Brzezinski J , Lebo S
Published: April 2008

This investigation describes the effect of a combination of lignosulfonate (LS) originating from the sulfite process with an unsulfonated kraft lignin (KL), such that the LS portion provides solubility while the KL provides a hydrophobic region that will strongly adsorb onto the substrate. For reference purposes, previous technologies for the preparation of agricultural dispersants have been included, namely, LS modified by oxidative desulfonation (LS-Ox) and by mild depolymerization/desulfonation (LS-U), as well as commercially available sulfonated kraft lignin (SKL).

Studies were conducted in several formulations including atrazine wettable powder (WP), copper oxychloride (COC) WP, COC extruded water dispersible granules (WDG), and sulfur suspension concentrate. The lignosulfonate/kraft combination (LS-KL) showed a unique ability to maintain suspensibility in extra hard water where the other sulfonated lignins failed. For example, suspensibilities achieved with 2% dispersant in COC WP in extra-hard water at 22 °C were as follows: LS, 40%; SKL, 59%; and LS-KL, 84%.
Adjuvants Influence the Activity of Diuron and Norflurazon
Authors: Singh M , Tan S , Sharma SD
Published: April 2008

Adjuvant effects on weed control by diuron (N'-3,4-dichlorophenyl)-N,N-dimethylurea) and norflurazon [4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3(2H)-pyridazinone] were studied to explore the potential of adjuvants in enhancing activity of soil-applied herbicides and to examine the effect of a leaching-inhibiting adjuvant on herbicide efficacy. Several adjuvants at 5 mL L-1 significantly enhanced the control of barnyardgrass (Echinochloa crus-galli (L.) Beauv.) by diuron. Organosilicone based adjuvants were more effective than other adjuvants with Kinetic being the most effective. Kinetic in the soil also significantly enhanced norflurazon activity on yellow foxtail (Setaria glauca (L.) Beauv.), and the effect increased as Kinetic concentrations increased. Use of Kinetic with norflurazon allowed a 50% herbicide rate reduction to equal performance of the standard herbicide without adjuvant. Monazoline C had no effect on norflurazon efficacy regardless of the concentrations.
Relative 3 Dimensional Motions between End Vertebrae in a Bi-level Construct, the Effect of Fixture Constraints on Test Results
Authors: Carson WL
Published: April 2008

Bilevel spinal implant constructs are 3 dimensional with 6 degrees-of-freedom of superior relative to inferior vertebra motion. ASTM F 1717-01 pinned fixtures constrain 3 degrees-of-freedom, which for posterior constructs are: lateral translation, PA axis rotation, and axial rotation to be about axis through the center of each vertebral body mounting pin. Also, F 1717-01 only illustrates testing of rectangular constructs that are symmetrical about a mid plane. Clinical examples, unconstrained finite element models, and hand held-loaded models are used to illustrate that in general some of the primary components of construct displacement and modes of failure are those constrained by the fixtures in F 1717-01; with one exception being the axial loading of rectangular constructs that remain symmetrical in geometry and biomechanical characteristics of components and interconnections. This raises two questions: the possibility of some clinical modes of failure being obscured by F 1717-01, and the clinical relevance of some numerical test results. Gimbal-gimbal or pushrod-gimbal fixtures for unconstrained axial and torsional load, static and fatigue testing, unsymmetrical as well as symmetrical constructs is proposed as a replacement for the current pinned fixtures.
A Comparison of Two Strength-Testing Methodologies for Interbody Structural Allografts for Spinal Fusion
Authors: Dawson JM , Griffith SL
Published: April 2008

To maintain an intervertebral disc space during fusion, a structural allograft, typically utilizing dense cortical bone, must sustain functional loads. Difficulty with surgical placement of structural allografts has resulted in reports of intraoperative graft fracture but no data have been generated to quantify insertional loads. In this study, simulated intraoperative and immediate postoperative strengths of allograft femoral rings were quantified. Three types of processed allograft were used: Tutoplast® processed bone, frozen-thawed and freeze-dried. To replicate postoperative in vivo functional loading, axial compressive strengths were evaluated by crushing femoral rings between flat platens under displacement control. To replicate surgical placement into an intervertebral space, samples were oriented so that the ring would be loaded transversely and an “insertion” displacement was imposed at 1m/sec. In axial compression, all three allograft types sustained loads far greater than estimated in vivo spinal loads. In insertion loading, all allograft types yielded substantially smaller strengths. Because intraoperative insertional loads are unknown and subjective to individual surgeon technique, the adequacy or inadequacy of any group is unclear. Testing guidlelines should be developed upon both anticipated in vivo loading and intraoperative demands.
Development of a Platinum-Enhanced Radiopaque Stainless Steel (PERSS®)
Authors: Craig CH , Radisch HR , Trozera TA , Turner PC , Govier RD , Vesely EJ , Gokcen NA , Friend CM , Edwards MR
Published: April 2008

Balloon-expandable coronary stents may be made of stainless steel conforming to ASTM or ISO specifications, referred to by ASTM as UNS S31673 alloys. A need exists for an alloy with enhanced radiopacity to make stents more visible radiographically and more effective clinically. A research program was initiated with the objectives of enhancing fluoroscopic radiopacity while maintaining adherence to the ASTM and ISO specifications. These objectives were ultimately achieved by adding a noble metal, platinum, to UNS S31673 by vacuum induction melting a commercially-available alloy. Freedom of the resulting microstructure from formation of harmful topologically close packed phases was ensured by use of phase computation methodology (New PHACOMP), and confirmed by X-ray diffraction and transmission electron microscopy. Platinum was chosen since it is over twice as dense as nickel and, with approximately half its effect as an austenitizer, allows nickel content to be reduced to a minimum level.
Comparative Electrochemical Studies of F 1586-95 and F 138-92 Stainless Steels in Sodium Chloride, pH = 4.0 Medium
Authors: Villamil RFV , de Andrade AHP , Barbosa CA , Sokolowski A , Agostinho SML
Published: April 2008

In this work, ASTM F 1586-95 stainless steel used for surgical implants is studied in 0.9 % NaCl aqueous solution, pH = 4.0 at 40 °C, using potentiodynamic polarization curves and optical surface analysis techniques and its performance is compared to F 138 stainless steel. F 1586-95 remains passivated until transpassivation potential above, which shows only generalized corrosion. F 138-92 presents breakdown potentials of 370 mV / SCE, with the presence of pitting corrosion. The presence of 0.40 % Nb in F 1586-95 promotes passivation currents one order of magnitude higher than that observed for F 1586-95 containing 0.28 % Nb.
Investigation Into Wear-Induced Corrosion of Orthopaedic Implant Materials
Authors: Windler M , MacDougall JE , Schenk R
Published: April 2008

The purpose of this study was to compare the corrosion behaviour under sliding wear of four materials commonly used for surgical implants: Ti-6Al-7Nb, Co-28Cr-6Mo, and two stainless steels, high-nitrogen stainless steel (Fe22Cr10NiN) and AISI 316L. A machine was constructed to simulate sliding wear, and the current density was measured to compare the response of each material to wear and to study the effect of pH (varied from 1 to 6). The results indicate that titanium exhibits higher current densities during wear than other materials tested over the pH range of 2.5 to 6. Additionally, pH has a greater effect on the corrosion behaviour of the two stainless steels than on the titanium or cobalt alloys.
Results of in Vitro Studies about the Mechanism of Wear in the Stem-Cement Interface of THR
Authors: Wirz D , Zurfluh B , Göpfert B , Li F , Frick W , Morscher EW
Published: April 2008

Experiments were performed in a wear machine especially constructed to simulate the natural in vivo process of wear in a de-bonded metal-cement interface. Four different bone cements were fretted against S-30 stainless steel with mat surface finish. The validation of the metal surfaces of the in vitro experiments revealed excellent correspondence to examined retrieved hip stems. No scratches or fretting orientation was noted on the polished surfaces. ZrO2 particles did not play a decisive role in the wear mechanism. PMMA as a softer material than S-30 steel did not mechanically abrade the metallic surface. Further no steel particles could be found within the wear debris. Metal is removed by dissolution in a process of fretting and crevice corrosion. Fretting corrosion causes the formation of debris in the form of a mixture of particles of metallic oxides (but not metallic particles!), polymer and serum.
Corrosion Products Generated from Mechanically Assisted Crevice Corrosion of Stainless Steel Orthopaedic Implants
Authors: Urban RM , Jacobs JJ , Gilbert JL , Skipor AK , Hallab NJ , Mikecz K , Glant TT , Marsh JL , Galante JO
Published: April 2008

Accelerated corrosion of metallic implants in vivo can generate both soluble and insoluble products that can be detected locally and systemically. Retrieved stainless steel implants for trauma fixation or spinal instrumentation demonstrate iron and chromium-containing solid products of corrosion deposited around corroded modular junctions and as phagocytosable particles in the adjacent tissues. In some cases, the resulting adverse local tissue reaction has been associated with pain, inflammation and osteolysis, requiring removal of the implant. In vitro cell and organ culture studies confirm that corrosion products such as particles of chromium phosphate can elicit proinflammatory cytokine secretion from macrophages and promote macrophage-mediated bone resorption. Systemically, soluble corrosion products of chromium can be detected in the serum of selected patients with accelerated corrosion of chromium-containing implants. Metal-protein binding studies indicate that the high molecular weight serum proteins including immunoglobulins have the highest affinity for chromium. These findings stress the importance of the design of modular junctions to minimize corrosion of stainless steels used in orthopaedic appliances.
The History and Development of FETAX (ASTM Standard Guide, E-1439 on Conducting the Frog Embryo Teratogenesis Assay-Xenopus)
Authors: Dumont JN , Bantle JA , Linder G
Published: April 2008

The energy crisis of the 1970's and 1980's prompted the search for alternative sources of fuel. With development of alternate sources of energy, concerns for biological resources potentially adversely impacted by these alternative technologies also heightened. For example, few biological tests were available at the time to study toxic effects of effluents on surface waters likely to serve as receiving streams for energyproduction facilities; hence, we began to use Xenopus laevis embryos as test organisms to examine potential toxic effects associated with these effluents upon entering aquatic systems. As studies focused on potential adverse effects on aquatic systems continued, a test procedure was developed that led to the initial standardization of FETAX. Other than a limited number of aquatic toxicity tests that used fathead minnows and cold-water fishes such as rainbow trout, X. laevis represented the only other aquatic vertebrate test system readily available to evaluate complex effluents. With numerous laboratories collaborating, the test with X. laevis was refined, improved, and developed as ASTM E-1439, Standard Guide for the Conducting Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Collabrative work in the 1990s yielded procedural enhancements, for example, development of standard test solutions and exposure methods to handle volatile organics and hydrophobic compounds. As part of the ASTM process, a collaborative interlaboratory study was performed to determine the repeatability and reliability of FETAX. Parallel to these efforts, methods were also developed to test sediments and soils, and in situ test methods were developed to address “lab-to-field extrapolation errors” that could influence the method's use in ecological risk assessments. Additionally, a metabolic activation system composed of rat liver microsomes was developed which made FETAX more relevant to mammalian studies.
The FETAX of Today — and Tomorrow
Authors: Fort DJ , McLaughlin DW , Burkhart JG
Published: April 2008

Frog Embryo Teratogenesis Assay — Xenopus (FETAX) — was originally developed in the mid-1980s as a developmental toxicity screening test for pure chemicals and complex mixtures in the laboratory. The longevity and success of the FETAX model can be attributed to several factors including the overall reliability of the assay, method standardization, and the versatility of the model system. Until recently, the versatility of the FETAX model had not been exploited. Today, however, developmental toxicity screening is one of many different applications of the FETAX model. This model is now used to evaluate modes of biotransformation, detoxification, and understand mechanisms of actions; as a model for studying limb development; a model for evaluating endocrine disrupting chemicals, including those acting on the thyroid axis; more advanced ecotoxicological evaluation including the use of alternative species; in situ monitoring; impacts of multiple stressors, and more complicated lab-to-field extrapolations; as a model for studying nutritional essentiality and nutritional toxicology; as a system for evaluating mixtures, mixture interactions, and developing structure-activity relationships; and as a model for evaluating reproductive toxicity. Several of these applications of the FETAX model now include a multiple endpoint approach utilizing a combination of whole embryo-larval morphological endpoints with suborganismal and molecular markers with the goal of obtaining more substantive mechanistic information. For example, a tail resorption and limb emergence assay morphologically marking thyroid activity coupled with thyroid hormone and thyroid receptor binding assays are being used to evaluate toxicological impact on the thyroid axis. Most recently, development of new partial lifecycle methods and a new full lifecycle test protocol was developed.
Interaction Between Perchlorate and Iodine in the Metamorphosis ofHyla versicolor
Authors: Sparling D , Harvey G , Nzengung V
Published: April 2008

Perchlorate (ClO4-) is a water-soluble, inorganic anion that is often combined with ammonium, potassium or other cations for use in industry and agriculture. Ammonium perchlorate, for example, is a potent oxidizer and is used in various military applications including rocket fuel. It has also been found in an historically widely used fertilizer, Chilean nitrate and in other fertilizers. It has been found in ground and surface waters of over 30 states and is considered a human health risk. Because of its similar atomic radius and volume, perchlorate competes with iodide for thyroid uptake and storage and thereby inhibits production of thyroid hormones. Amphibians may be particularly affected by perchlorate because they rely on the thyroid for metamorphosis. This study exposed early larval Hyla versicolor to concentrations of perchlorate ranging from 2.2 to 50 ppm to determine the effects of perchlorate on a native amphibian. In addition, three controls, 0 perchlorate, 0 perchlorate with 0.10 ppm iodide (C + I) and 50 ppm perchlorate + 0.10 ppm iodide (50 + I) were tested. Mortality (< 11% with all treatments) and growth appeared to be unaffected by perchlorate. Inhibition of development started with 2.2 ppm perchlorate and little or no development occurred at 22.9 ppm and above. This inhibition was particularly apparent at the latter stages of development including hindlimb formation and metamorphosis. The estimated EC50 for total inhibition of metamorphosis at 70 days of treatment was 3.63 ppm. There was no evidence of inhibition of development with the 50 + I, C + I, or controls, indicating that the presence of small concentrations of iodide could counter the effects of perchlorate. When tadpoles that had been inhibited by perchlorate were subsequently treated with iodide, development through prometamorphosis progressed but mortality was very high.
Multiple Causes for the Malformed Frog Phenomenon
Authors: Lannoo MJ , Sutherland DR , Jones P , Rosenberry D , Klaver RW , Hoppe DM , Johnson PTJ , Lunde KB , Facemire C , Kapfer JM
Published: April 2008

Progress has been made in understanding the malformed frog problem, yet we still cannot identify with assurance specific causes of malformations at particular locations. To address this problem we assembled a team of specialists and present here results on geographic distribution, water quality, parasite infection, and morphological patterns from Minnesota malformed frog sites and reference sites. Malformed frog hotspots (> 5% malformed animals) tend to occur in a broad line from northwest to southeast across Minnesota associated with the North Central Hardwoods and Driftless Area ecoregions, and are less associated with Lake Agassiz Plain, Northern Glaciated Plain, and Western Corn Belt Plain ecoregions. Few hotspots occur in the southwestern grassland and northeastern boreal forested portions of the state. There is a tendency for hotspots to occur at ecoregion junctions. No single water quality feature correlates with hotspots. Heavy Ribeiroia infections always indicate hotspots, but lesser Ribeiroia infections may or may not. Conversely, certain hotspots show no evidence of the presence of Ribeiroia. Among reference sites, two have no evidence of 5 Ribeiroia. The most common hindlimb malformation type was ectromelia, followed by micromelia and the presence of spongiform bone. Limb hyperextension, amelia, and polymelia were the least common malformation types. Malformed frog hotspots are typically associated with altered wetlands and any solution to the malformed frog problem must include restoring these sites.
Influence of Trisiloxane Alkoxylate Polarity on Spreading of Methylated Oil Based Adjuvants
Authors: Pigeon M , Policello G , Sun S , Paccione MA , Koczo K
Published: April 2008

The carbon chain length of the fatty acid methyl esters appears to play an important role in the spreading process of organosilicone adjuvant aqueous dispersions (80/20 blends of Methyl Ester / Silicone). Overall, spreading increases with an increase in the methyl ester chain length ranging from C9 – C18. However other factors, such as degree of saturation and emulsification properties, must be considered for their overall contribution to spreading.

Additionally, spreading is strongly influenced by the polarity of the organosilicone adjuvant (Polarity Index as measured by HPLC). The higher the polarity, the greater the degree of spreading. Likewise, similar effects are observed with the degree of partitioning for the organosilicone adjuvant in the aqueous phase. Highly polar organosilicone adjuvants have higher partitioning in the aqueous phase, while less polar organosilicone adjuvants tend to remain predominantly in the oil phase, which makes them unavailable for spreading.
Enhancing the Biological Activity of Nicosulfuron with Silicone Adjuvants and pH Adjusters
Authors: Green JM , Cahill WR
Published: April 2008

Adjuvants that increased the pH of the spray solution and rapidly solubilized nicosulfuron particles enhanced herbicidal activity with silicone adjuvants under specific conditions. These conditions included high nicosulfuron rates on difficult to control weeds, low spray volumes, and initially acidic spray mixtures. For example, all pH adjusters tested enhanced the activity of nicosulfuron in a spray volume of 140 L/ha with 0.1% w/w silicone surfactant blend on common cocklebur (Xanthium strumarium L.) and large crabgrass [Digitaria sanguinalis (L.) Scop.]. Generally, the most effective pH adjuster was tribasic potassium phosphate followed by triethanolamine. The high pH conditions rapidly dissolved the nicosulfuron particles and usually increased biological activity. However, increasing pH did not always increase biological activity. For example, the silicone-based surfactant and methylated seed oil blend was the most effective silicone adjuvant when applied as the only adjuvant, but the addition of sodium carbonate reduced its activity with on large crabgrass. A possible reason for this difference might be that the silicone surfactant and oil blend would be expected to enhance nicosulfuron uptake through both hydrophilic and lipophilic pathways into the leaf while the increased solubilization caused by the pH adjuster might only increase uptake through hydrophilic pathways. High pH conditions are known to increase silicone surfactant degradation and this could require users to spray silicone adjuvant and pH adjuster mixtures more rapidly than usual. These results generally support the concept that solubilization is necessary but not sufficient for foliarly applied herbicides to express maximum activity.
Biologically Active In-Tank Formulation of Acid Herbicides
Authors: Penner D , Michael J , Brown WG , Sikkema P
Published: April 2008

The hypothesis tested in this research is that with the addition of a suitable adjuvant to the spray solution the acid form of weakly acidic herbicides can be directly added to the spray tank without first making the salt yet obtaining the desired weed control activity. This eliminates the formulation steps of making the salt. Greenhouse studies were focused on applying the adjuvant RI with glyphosate acid to velvetleaf, common lambsquarters, and giant foxtail. Weed control in the presence or absence of additional diammonium sulfate was equivalent to control obtained with the RU formulation of the isopropylamine salt of glyphosate with or without additional diammonium sulfate in the spray solution. The RI adjuvant was also evaluated and found effective in increasing biological activity of generic isopropylamine formulations of glyphosate containing less than 15% adjuvant in the formulations. In field trials the adjuvant RI applied with glyphosate acid performed as effectively as it had in greenhouse trials. In field trials the adjuvant RI applied with dicamba acid was much more effective than the commercial formulation of dicamba. Benefits from this technology include the potential for less off-site movement of dicamba vapors due to greater foliar absorption, less transport of water, elimination of the need to make salts of the herbicide acid, and reduced need for container disposal.
Cotton Insecticide and Defoliant Efficacy as Influenced by Spray Application Parameters
Authors: McMullan PM , Thomas JM
Published: April 2008

Research was conducted in 2002 to evaluate the effect of various spray application parameters on the efficacy of the insecticides indoxacarb and spinosad and the cotton defoliants ethephon/cyclanilide and carfentrazone-ethyl. Laboratory results indicated that an adjuvant was required for air entrapment in sprays from venturi-type nozzles and that defoamer present in the surfactant formulation only slightly reduced the amount of air entrapped in the spray. The amount of air entrapped in the spray differed among the various nozzles, with the ITR80-01 nozzle entrapping the most air and the ULD120-015 nozzle entrapping the least. With both insecticides, the adjuvants HM8802-A or AB0201 decreased the amount of leaf eaten by larvae (leaf damage) compared to leaf damage when insecticides were applied with the hollow cone nozzle. All venturi-type nozzles reduced the amount of leaf damage compared to the hollow cone nozzle. The amount of air entrapped did not appear to be related to efficacy. The drop-nozzle system typically had the least amount of leaf damage of all the spraying systems evaluated. With both defoliants, all of the adjuvants enhanced cotton defoliation when applied using hollow cone nozzles. Ethephon/cyclanilide-enhanced defoliation of cotton was greater when applied through venturi-type nozzles than through hollow cone nozzles at the final evaluation. Carfentrazone-ethyl-enhanced defoliation of cotton was similar when applied through venturi-type nozzles or hollow cone nozzles. The drop-nozzle system enhanced cotton defoliation similar to that from venturi-type nozzles.