bluuebunny/crossref_metadata_2025 huggingface dataset:
A Dynamic Model for the Performance of Carving Skis
Authors: Bruck F , Lugner P , Schretter H
Published: April 2008

To analyze the behavior and the local force transfer condition by simulation techniques, the ski was modeled with 18 segments and an additional shovel segment. The elastic and damping properties of the ski were concentrated to the joints between the segments representing the bending and torsional characteristics according to measurements. The ski-snow contact comprises forces due to penetration, cutting properties of the edge and friction; new measurements were used for essential data. Since the experimental verification of the simulation results was essential, a special ski-sledge was used instead of a skier.

The results on the one hand show good agreement between measured trajectories for a half turn and their simulated counterparts. On the other hand, by the simulation the discrepancy between carving radii of the deformed skis and the traveled radius became obvious — and consequently starting points for improvements. Moreover, the local force transfer along the edge shows the vertical force distribution and the positions where lateral skidding is relevant.

Further utilization of the dynamic simulation, including local force distribution, should lead to more optimal design of skis and binding plates — as local stiffening of the structure — thereby enhancing sports performance and reducing the effort for recreational skiers.
Release Bindings for Skiboards?
Authors: Senner V , Lehner S , Schaff P
Published: April 2008

Skiboards are defined as skis between 70 and 130 cm in length. Until now they are typically not sold with release bindings. Several studies have shown that when using skiboards,tibia fractures and shoulder injuries occur at a significantly higher rate than with traditional length skis. This paper analyzes the effects the reduced length and the lack of a release binding may have on specific kinematic and dynamic parameters in a typical fall situation. This is done by both an experimental and a theoretical approach, the latter using a computer simulation. The results show that (1) a twist release seems to be necessary (2) a skier using a skiboard is prone to suffer highly dynamic forward falls, (3) a conventional release binding may not be able to prevent the skier from getting injured in this specific situation and (4) a new type of skibinding should be considered. As for the moment no appropriate technical solutions are available, it is concluded that the (novice) skiboarder has to be aware of the fact that there are some inherent risks due to the new equipment.
Ski Injury Epidemiology: A Two Year Epidemiology Study of Injuries With Skiboards
Authors: Greenwald RM , Nesshoever M , Boynton MD
Published: April 2008

A two season epidemiology study of skiing injuries at a large Eastern ski resort was conducted for the 1998–2000 seasons to compare injury rates and injury severity for various mountain sports including Alpine skiing, snowboarding, and particularly, the new sport of skiboarding. Ski patrol reports and follow-up medical injury diagnosis data at the mountain clinic were compiled along with demographic information about the injured skier and their equipment. The population at risk for each sport was determined by collecting parking lot surveys of typical skiers using previously published methodologies. The overall injury rate for all sports at the mountain was consistent with rates reported in the literature at other ski resorts. Injury rates for skiboards represented 1% of the total injury population, while participation in this sport was 2% of the entire mountain population. Skiboard users were on average 10 years younger than skiers and were predominantly male. Lower leg fractures and shoulder injuries represented 26% and 28% of the total skiboard injuries (n=54), respectively. Tibia fractures occurred much more frequently in the skiboard population than in the Alpine skiing population, while knee sprains were significantly lower in the skiboard population.
A Method for Comparing Alpine Skiing Injuries Among Studies
Authors: Johnson RJ , Ettlinger CF , Shealy JE
Published: April 2008

This study compares regional differences in the risk of skiing injury using readily available data. A simple system compares skiing injury data from unrelated studies in several countries using the frequency of ACL sprains as a base for comparison with the frequency of a target injury group, in this case tibia shaft fractures. Prior studies involving the authors' 29-year case-control study at a medium-sized Vermont ski area serve as a basis for this analysis.

For the period from 1992–93 to 1999–2000 the number of total skiing injuries, tibia shaft fractures, and ACL sprains were obtained from widely disbursed sources in 5 countries. The 8-year study involved 5382 tibia fractures and 26,331 ACL sprains.

The ratio of ACL sprains to tibia fractures was computed by dividing the number of ACL sprains by the number of tibia fractures from each source for each year. The authors expected the relationship of ACL injuries to tibia shaft fractures, expressed by this ratio, to reflect differences in the quality of ski binding release function among regions.

Over the 8-year study, the ratio for the authors Vermont study averaged 9.0 while the ratio for the five regions surveyed were from 2.0, 2.1, 2.3, 5.6, and 10.5. The authors propose that low ratios be regarded as an indication of a low standard of ski equipment care in the region. However, high ratios, the authors believe are an indication of a high standard of ski equipment care or comparatively poor snow conditions in the region.

The study shows that the standard of equipment care varies greatly throughout the world. The authors plan to expand the survey to investigate both snow conditions and equipment factors more completely.
The Effect of Ski Shape on Injury Occurrence in Downhill Skiing
Authors: Merkur A , Whelan KM , Kuah D , Choo P
Published: April 2008

Downhill ski design has undergone significant change in recent years. The rapid introduction of shaped skis into the market has meant there have been few research studies into their effect on skier injury. The purpose of this study was to investigate the types and severity of downhill skiing injuries influenced by ski shape at the Perisher Blue Ski Resort, NSW, Australia, during the 2000 ski season. Data collection was via questionnaire at the Perisher Blue Medical Centre. Two hundred and fifty-one questionnaires were completed. Of the 197 questionnaires suitable for analysis, 74 skiers used conventional skis and 123 used shaped skis. Ski shape was found to influence the location, type and severity of downhill skiing injuries.
Femur and Tibial Plateau Fractures in Alpine Skiing
Authors: Shealy JE , Johnson RJ , Ettlinger CF
Published: April 2008

For the past 29 ski seasons, the authors have prospectively tracked skiing injuries at the Sugarbush resort in northern Vermont. This study updates two previous papers on femur and tibial plateau fracture (TPF) injuries in alpine skiing. We examined the etiology and biomechanics of the femur and tibial plateau fracture injury groups, and the demographics of the population at risk. Total skier visits equals 5 912 735, the total number of injuries equals 16 790; femur fractures equals 67, tibial plateau fractures equals 88.

Femur fractures: There has been no significant change in MDBI (Mean Days Between Injury) for femur fractures. No significant changes were found in skier demographics, or injury mechanism, from our previous study. Collisions with trees or other objects remain the principal mechanism of injury. Femur fractures are predominantly male injuries. Femur injured skiers are younger and lighter than the population at risk. Femur-injured skiers reported that they skied faster at the time of injury than those in the “all-other-injury” category.

Tibial plateau fractures: The exponentially regressed MDBI rate has significantly changed over time from 216 800 to 38 500, but this change coincides with a very significant increase in the age of the population at risk. At the same time, the mean age for this injury has not significantly changed. Tibial plateau injured skiers have the oldest mean ages for any injury group in our study. This is a predominantly female injury. The TPF injured person is heavier than those in the all-other-injury group in spite of being predominantly female but not significantly taller. Eighty-nine percent of these injuries involve the lateral aspect of the plateau. The most common mechanism is a crushing injury to the lateral aspect of the tibial plateau via valgus bending, where the lateral femoral condyle presses against the lateral aspect of the tibial plateau.
The Prevalence of Previous Serious Knee Injuries in Freestyle World Championship Skiers
Authors: Heir S , Krosshaug T , Ekeland A
Published: April 2008

Previous major knee injuries among the participants in the FIS Freestyle World Championship 2001 in Whistler/Blackomb, Canada were recorded. Ninety-five skiers answered the questionnaire (response rate: 63%). Forty-seven percent of the skiers reported mean 1.6 previous serious knee injuries (range 1–5), female skiers with a significant higher prevalence than males. Thirty percent of the women and 24% of the men (p = 0.49) had suffered 1–3 ruptures of the anterior cruciate ligament (ACL) of the knee. There was no significant difference between the disciplines (mogul and aerial skiing) in the prevalence of any type of knee injury.

In conclusion, nearly half of the responding FIS freestyle World Championship skiers had previously sustained one or more major knee injuries and still returned to such a high level of athletic performance. One fourth of the skiers had sustained one or more former ACL ruptures. The prevalence of previous serious knee injuries over all was significantly higher among female than among male skiers.
Surface Topology and Fatigue in Si MEMS Structures
Authors: Allameh SM , Gally B , Brown S , Soboyejo WO
Published: April 2008

This paper presents the results of an experimental study of surface topology evolution that leads to crack nucleation and propagation in silicon MEMS structures. Following an initial description of the unactuated surface topology and nanoscale microstructure of polysilicon, the micromechanisms of crack nucleation and propagation are elucidated via in situ atomic force microscopy examination of cyclically actuated comb-drive structures fabricated from polysilicon. It is found that the surface of the polycrystalline silicon MEMS undergoes topological changes that lead to elongation of surface features at the highest tensile point on the surface. A smoothing trend is also observed after a critical stress level is reached.
Cross Comparison of Direct Strength Testing Techniques on Polysilicon Films
Authors: LaVan DA , Tsuchiya T , Coles G , Knauss WG , Chasiotis I , Read D
Published: April 2008

Several direct and indirect testing techniques to characterize the strength and distribution in strength of structural thin films have been developed with widely varying results appearing in the literature (roughly 1 to 4 GPa for polysilicon). Much of the variation between authors has been explained in terms of microstructural differences, sample size effects, and release techniques. Five laboratories participated in a cross comparison of direct tensile testing techniques in an effort to study these variations; all samples were fabricated and released simultaneously at Sandia National Labs to eliminate material variations. Sample lengths ranged from 15 to 1000 μm long. All the samples were fabricated with a thickness of 2.5 μm. The distributions in strength are reported along with a tabulation of mean, standard deviation, and Weibull modulus of fracture strength for each lab.
Influence of the Film Thickness on Texture, Residual Stresses and Cracking Behavior of PVD Tungsten Coatings Deposited on a Ductile Substrate
Authors: Ganne T , Farges G , Crépin J , Pradeilles-Duval R-M , Zaoui A
Published: April 2008

Tungsten coatings are deposited on a steel substrate by magnetron sputtering. for coatings deposited under identical processing conditions, a (111) texture develops with the increase of the coating thickness and the decrease of the residual stress. No gradient stress has been observed in the diffracted volume and the residual stress state is isotropic and plane. Tensile and four-point bending tests are performed in a SEM chamber in order to study the cracking kinetics. Taking account of the residual stresses, an intrinsic cracking stress can be determined. Cracking kinetics are found to depend on the coating thickness and the substrate yield stress. No debonding was observed at the interface despite the large plastic deformation of the substrate at the crack tips. This corresponding strain localization has a strong influence on the crack density and the cracking kinetics.
Derivation of Elastic Properties of Thin Films from Measured Acoustic Velocities
Authors: Pastorelli R , Tarantola S , Beghi MG , Bottani CE , Saltelli A
Published: April 2008

The dispersion relations of surface acoustic waves (SAWs) of layered structures can be measured by quantitative acoustic microscopy, laser acoustic methods, and surface Brillouin scattering. Since methods are available to compute SAW dispersion relations as functions of material properties (direct problem), material properties can be derived fitting the computed velocities to the measured ones (inverse problem). The stability and robustness of the inverse problem solution for an isotropic supported thin film is studied with an appropriate sensitivity analysis. The elastic constants that mainly determine each branch of the dispersion relations are pinpointed: the constants that are more reliably determined in each range of film properties are thus identified. Simulations allow one to estimate the level of experimental errors, either in SAW velocities or in film density and thickness, which still allow a meaningful solution of the inverse problem.
Side-by-Side Comparison of Passive MEMS Strain Test Structures under Residual Compression
Authors: Masters ND , de Boer MP , Jensen BD , Baker MS , Koester D
Published: April 2008

Knowledge and control of residual strain is critical for device design in MEMS, and therefore it is important to establish standards for residual strain measurement. In this study, pointer, microring, bent-beam, and fixed-fixed beam test structures are used to evaluate residual strain both theoretically and experimentally. An equation that enables easier evaluation of bent-beam structures is derived. Also, a finite difference model that incorporates the non-idealities of fixed-fixed beams and determines an optimum fit to the measured deflection curve is presented. The model allows accurate residual strain evaluation of each buckled fixed-fixed beam. Experimentally, pointer structures were found to be susceptible to adhesion. Microrings, intended for residual tension assessment, also could not be evaluated because the residual strain was compressive. Bent-beam and fixed-fixed beams could both be evaluated. The main criterion for test structure effectiveness was taken to be the repeatability of residual strain on structures in close proximity; each should exhibit the same value. Using optical microscopy, the residual strain of bent-beams was determined with ± 13 με repeatability based on standard deviation of adjacent structures of similar design. Using optical interferometry, the residual strain of fixed-fixed beams was determined with ± 2 με repeatability based on standard deviation for adjacent beams of different lengths. The strain values obtained from the two structures are in reasonably good agreement. Cantilevers were also evaluated to obtain film curvature values.
Mechanical Tests of Free-Standing Aluminum Microbeams for MEMS Application
Authors: Zhang P , Lee H-J , Bravman JC
Published: April 2008

We studied mechanical properties and alloy effects of free-standing aluminum microbeams (50 × 500 × 2 μm) in a piezo-actuator-driven test apparatus with a load resolution of ±0.2 mN and a displacement resolution of ±10 nm. Pure Al and Al-2%Ti microbeams were fabricated using micromachining techniques. In tensile tests, we found the yield strength to be approximately 120 MPa for the pure Al beams, and approximately 75% higher for the alloyed beams. We examined the results with respect to those of bulk materials and thin films adhered to substrates. In stress relaxation tests, we observed a load drop of 56% over 10 min for the pure Al beams. We attributed this to grain boundary sliding and the nature of a free-standing thin film, i.e., the absence of a substrate. For the alloyed beams, the load drop was only 16%. We believed the difference was due to Al3Ti precipitates formed at grain boundaries, which hindered dislocation movements. We used TEM to reveal the microstructural features of the microbeams.
Tensile Testing of Thin Films Using Electrostatic Force Grip
Authors: Tsuchiya T , Sakata J
Published: April 2008

Thin film tensile testers using an electrostatic force grip system were developed to enable increased reliability in MEMS devices. This grip system uses electrostatic force to chuck a thin film specimen. The chucking force is easily controlled and the damage to the specimen during testing can be minimized. With these testers, silicon, silicon-dioxide, and silicon-nitride thin films fabricated with surface micromachining were tensile-tested in a vacuum and in air. The specimens were 2 to 10 μim wide, 30 to 300 μm long, and 0.7 to 2.0 μm thick. We compare the strength of these films and discuss the fracture properties of the films and the effect of the environment.
Ductile Thin Foils of Ni3Al
Authors: Demura M , Kishida K , Umezawa O , George EP , Hirano T
Published: April 2008

Ni3Al thin foils with 315 to 357 μm thickness were successfully fabricated by cold rolling. X-ray pole figures showed the formation of {110} rolling textures with various rolling directions in the foils cold rolled over 83% reduction. The deformation microstructure consists of fine slip traces and coarse and wavy shear bands. Banded deformation structure was observed in some foils. In the foils cold rolled to 83% reduction, the Vickers hardness number reached over 600 and the ultimate tensile strength over 1.7 GPa, irrespective of rolling texture and deformation microstructure. The cold rolled foils showed no tensile elongation, but it was possible to bend the foils. The foils recrystallized at temperatures over 1273 K had some tensile ductility (3.0 to 14.6%), though the polycrystalline Ni3Al is known to be brittle due to severe grain boundary fracture. Electron backscatter diffraction measurements revealed that the large amount of total grain boundary area consists of low angle (LAB) and ∑3 coincidence lattice boundaries. This large fraction is probably a chief cause of the observed ductility.
Clays as Biological Carriers
Authors: Goss GR , Baldwin HM , Riepl RG
Published: April 2008

Clays are widely used as agricultural chemical carriers, but often, little thought is given to their use as biological carriers. Water activity is of the utmost importance in biological carriers. Clays have great ability to mediate water activity and are often the most important factor in a soil moisture profile. Commercial clays of relatively wide mineral composition are available and can be modified to meet the needs of a particular microbe. Due primarily to their large surface area, clays can act as a desiccant providing good storage stability for dried or biologically inactive formulations. U.S. patents 3,168,796 and 5,695,541 describe using a dried clay/bacterial powder for legume inoculants. U.S. patent 5,849,284 describes a dry clay/nematode formulation. At higher moistures, clay can be used as a relative humidity moderator for semi-active microbial formulations due to surface area and pore size distribution. U.S. patent 5,042,427 describes storage of entomopathogenic nematodes in a clay mediated 60% relative humidity environment. At still higher moistures, due to an absorbent clay's surface area, pore size distribution and total porosity, water activity can be controlled to provide a moist environment for biologically active formulations. U.S. patent 5,288,296 describes growing and delivering inoculants in this manner. At still higher levels of water, clay can act as a substrate for growth. U.S. patent 4,327,181 uses clay as a support for ectomycorrhizae and U.S. patent 4,620,929 uses clay as a fixed growth support in filtration. Microbes colonize the clay surface in a fixed column to remove proteins and nitrates from water. Finally, the clay can be used merely as a granular carrier. U.S. patent 5,358,863 describes granular carriers for bacteria, fungi and nematodes. The organism is formulated in a liquid and applied to the granule. This paper discusses the theory and practice of using clays as biological carriers.
A Systematic Study of Wetting as Influenced by Hydrocarbon Fluid Type
Authors: Frisch PD , Kuo KK
Published: April 2008

Hydrocarbon fluids and oils are commonly used as adjuvants to improve the wetting and spreading properties of a pesticide formulation. An improvement in wetting leads to an increase in the area of contact of a pesticide on a target and usually, although there are exceptions, translates to an increase in efficacy. Target coverage (area per drop) is controlled by a variety of physical and chemical properties of the fluid or oil; these include surface tension, viscosity, and specific gravity. In this study, the influence of these physical factors as well as the composition of the hydrocarbon fluids on the wetting of Sorghum halepense (johnsongrass) and other model substrates has been investigated.

The wetting properties, as measured by contact angle, of four different series of hydrocarbon fluids (normal paraffins, isoparaffins, mixed aliphatics containing iso-, cyclo- and normal paraffins, and aromatics) have been systematically examined on a variety of surfaces (johnsongrass, extracted johnsongrass wax, paraffin wax, Parafilm® and wax paper). It has been shown that hydrocarbon fluids are very good wetters (θ< 30°) of these substrates. Attempts to correlate contact angle measurements with the physical properties of hydrocarbon fluids were unsuccessful until the compositions of the fluids were considered. When the type of hydrocarbon fluid is taken into account, very good correlations are achieved for normal paraffinic, isoparaffinic and aromatic fluids. Mixed aliphatic fluids, as expected, show poorer correlations.
Physical Properties of Alkylene Carbonate Solvents and Their Use in Agricultural Formulations
Authors: Elsik CM , Stridde HM , Machac JR
Published: April 2008

Alkylene carbonates are a solvent chemistry that has been used in application areas outside of agriculture for over fifty years. They are environmentally friendly, biodegradable, have low Volatile Organic Content (VOC), and are powerful solvents. Blending products with different molecular weights is a technique that can be used to control the polarity of the overall solvent system.

Alkylene carbonates are currently being evaluated as solvents and co-solvents in gricultural formulations. They can add to the effectiveness of pesticide formulations and adjuvants due to their high solvency and low VOC. These are just some of the characteristics of alkylene carbonates that can combine to produce better penetration and sticking of the active ingredient. Higher molecular weight carbonates can be incorporated into formulations to improve rain-fastness and solubility of all formulation components.

In this work we provide background information on alkylene carbonates and present heir physical chemistry. We then present phytotoxicity characteristics and the results of an adjuvancy study with glyphosate. We then provide example formulations that contain alkylene carbonates as part of the solvent system. These formulations include both emulsifiable concentrates (EC) and a microemulsifiable concentrate (MEC).
Application Study of Alkylether Citrate Surfactants in 2,4-D IOE Herbicide Concentrated Emulsion Formulations
Authors: Hazen JL , Lei Y
Published: April 2008

Concentrated emulsion (EW) formulations containing iso-octyl 2,4-dichlorophenoxy acetate (2,4-D IOE) were prepared with alkylether citrate (AEC) surfactants and evaluated in greenhouse tests. The results demonstrate that 2,4-D EW formulations deliver equal or better weed control when compared to commercial emulsifiable concentrate (EC) formulations. The degree of weed control increased as the amount of AEC increased in the formulation for some broadleaf species. Increasing the amount of AEC surfactants has the benefit of reduced 2,4-D loading in the EW formulations while maintaining the same broadleaf control. Overall, AEC surfactants are found to act as excellent emulsifiers and adjuvants for 2,4-D herbicide EW formulations. This presents an attractive option for formulating economical, solvent-free, and environmentally friendly agricultural products.
Formulation of Phenoxy Ester Herbicide EW Concentrates with Alkylether Citrate Ester Surfactants
Authors: Lei Y , Hazen JL
Published: April 2008

Robust and efficacious iso-octyl 2,4-dichlorophenoxyacetate (2,4-D IOE) emulsion concentrates (EW) have been formulated using alkylether citrate ester (AEC) emulsifiers. Focused Beam Reflectance Measurement (FBRM) has been employed to monitor the in-situ formation of concentrated emulsions and to determine the particle size distributions at steady state. The optimal formulation had a median particle size of 3.3 μm with a narrow distribution. The measured peak width at half maximum (PWHM) was 4.0 μm. The optimal EW formulation displayed viscoelastic behavior as determined by rheological measurement and had excellent dilution characteristics in 34, 342, and 1000 ppm water. Glasshouse tests demonstrated that the 2,4-D IOE EW was as efficacious as the commercial 2,4-D LV EC formulation.
Understanding the Performance Characteristics of Air Inclusion Nozzle Technology
Authors: Hall KJ
Published: April 2008

Commercial air inclusion and standard flat fan nozzles were used to examine some solutions containing either blank formulation components or adjuvants. Droplet-size (Dv0.5) measurements and corresponding retention and field studies were made.

In-flight temporal sampling revealed that the physico-chemical properties of the spray solution had a substantial effect on the Dv0.5 values produced by both standard flat fan and air inclusion nozzles. Applications containing adjuvants and formulants applied through standard fan nozzles confirmed previous findings: water-soluble additives reduced Dv0.5 while emulsions increased Dv0.5 values compared with water alone. However, Dv0.5 values of corresponding sprays produced by air inclusion nozzles behaved differently. Generally, emulsions decreased Dv0.5 values while those containing water-soluble additives increased droplet size. Corresponding retention studies revealed that adjuvant inclusion enhanced the performance of standard fan sprays; the performance of air-included sprays was more variable.

Nevertheless, field trials failed to confirm that these differences significantly affected herbicide performance.
Application of Abscission Sprays for Mechanical Harvesting of Hamlin Orange
Authors: Salyani M , Whitney JD , Farooq M
Published: April 2008

The success of technologies for mechanical harvesting of Florida citrus, in part, depends on the efficacy of abscission sprays that are applied to reduce fruit detachment force. The objective of this research was to determine the effects of sprayer type, sprayer airflow rate, and spray volume rate on deposition and abscission efficacy of CMN-Pyrazole, in mechanical harvesting of oranges.

Two experiments were conducted in February 2001, using air-blast and air-curtain tower sprayers. The sprayers were equipped with an axial-flow fan/ hydraulic nozzles and cross-flow fans/ rotary atomizers, respectively. Both sprayers discharged the spray uniformly, along the sprayer tower height, to 5.5–6.5 m high ‘Hamlin’ orange trees. Spray mixtures, containing CMN-Pyrazole, adjuvant Kinetic, and a fluorescent tracer (Pyranine 10G), were applied at 1,170 and 2,340 L/ha. Leaf samples were collected from different canopy locations and spray deposition was quantified by fluorometry. Four days after the applications, fruit detachment force was measured at different canopy heights and dropped fruit was counted. The trees were shaken with a trunk shaker and percentage of fruit removal was determined. Spray deposition and the relationship between deposition and mechanical harvesting parameters were determined for different modes of spray application.
Microencapsulated Medicines for Beneficial Insects
Authors: Kevan SD , Nasr ME , Kevan PG , Trevino JD
Published: April 2008

Few veterinary medicines are used for treating invertebrate micro-livestock. We made and tested a specially designed microcapsulated medicament that disguised antifeedant properties of active ingredients and were of appropriate, ingestable sizes to enter the alimentary tracts where the active ingredient was liberated. Menthol is a fumigant used to suppress populations of parasitic tracheal mites in honeybee hives. Mentholated microcapsules, similar in size to pollen, were designed to deliver and liberate menthol into the bees' ventriculus (mid-gut) where it would be transported to the hemolymph (blood) and circulated. MEM (menthol doubly-microencapsulated with zein and stearic acid) was fed in sugar-candy patties to honeybees without the menthol having its usual anti-feedant and irritant effects. In the laboratory, honeybees fed MEM ad libitum in sugar candy patties at menthol concentrations of 5 to 40 mg/g for two days showed about 40% higher mite mortality than did controls (fed sugar candy patty alone). In a commercially operated apiary, feeding a dose of 40 and 80 mg/g MEM in candy patties to colonies 4 times over 1.5 months, kept tracheal mite prevalence significantly below that in controls for at least 4 months. Our technology probably has wider applicability for disease treatment in microlivestock used directly for food or fiber, and possibly in biocontrol.
History of Isola-VSP Fatigue Testing Results with Correlation to Clinical Implant Failures
Authors: Carson WL , Asher MA , Boachie-Adjei O , Akbarnia B , Dzioba R , Lebwohl NH
Published: April 2008

The objective was to compare the history of Isola-VSP in vitro fatigue testing results with clinical implant failures from a five-center retrospective survey of 2499 cases to determine if the appropriate types of tests had been performed. To determine the effect of bending iron marks, bends, and connectors on 1/4" rod fatigue, 4-point bend fatigue tests were conducted. To characterize bone anchor-connector-rod assemblies, unilateral construct flexion fatigue tests were conducted. Clinically 111 components failed: 41 screws, 57 rods, nine transverse connectors, two interbody graft/cages, one extended slotted connector, and one at unreported location. The screw, rod, and connector clinical data correlate to the lower to higher relative fatigue strength respectively of original integral nut screws; rods at bending iron marks, connectors and lordotic bends; original slotted connector, current slotted connector, and straight rods with unblemished surface. In vitro and clinical failure locations also correlated. The transverse connector cross member failed near the longitudinal rod in 8/9 instances. This implies a lateral bending profile similar to that produced by the H construct used to test them in reversed lateral bending. Recommendations relative to ASTM standards/guides include: incorporation of an H construct to test transverse connectors in lateral bending, replacement of fixed-fixed end with fixed-free end assembly in F 1798-97, and replacement of constrained fixtures in F 1717-01 with unconstrained.
Gauge Length and Mobility of Test Blocks Strongly Affect the Strength and Stiffness of Posterior Occipito-Cervico-Thoracic Corpectomy Constructs
Authors: Slivka MA , Serhan H , Selvitelli DM , Torres K
Published: April 2008

This study was conducted to investigate the effect of test block mobility and gauge length on the strength and stiffness of rod-based posterior occipito-cervical-thoracic corpectomy constructs. The influence of inferior test block mobility was studied by evaluating both pivoting and clamped boundary conditions. Gauge length was varied from 55 mm, the shortest possible length, to 196 mm, simulating the connection of the occipital plate down to T3. Static compression bending and torsion tests were performed in general accordance with ASTM Test Methods for Static and Fatigue for Spinal Implant Constructs in a Corpectomy Model (F 1717-96) to determine the strength and stiffness of the various configurations. Additionally, dynamic compression bending tests were performed to determine the fatigue strength of two types of constructs: 1) 76 mm gauge length with pivoting inferior (and superior) blocks, and 2) longest 196 mm gauge length with clamped inferior block (superior block pivoting). As expected, the stiffness and 2% offset yield load of the constructs in static compression bending decreased with increasing gauge length and clamping the inferior test block caused a dramatic increase in both. The torsional stiffness increased when the gauge length was increased from 55 mm to 116 mm due to the addition of cross-connectors, but then decreased with gauge lengths higher than 116 mm despite adding more cross-connectors. Without adding cross-connectors, the stiffness decreased with increasing gauge length. In dynamic compression bending, the endurance limit nearly doubled for the construct with almost three times longer gauge length simply due to clamping the inferior test block.
Spinal Implant Transverse Rod Connectors: A Delicate Balance Between Stability and Fatigue Performance
Authors: Serhan H , Slivka M
Published: April 2008

Transverse rod connectors have been shown to significantly increase the torsional stability of rod-based posterior spinal implant systems, which may improve clinical fusion outcomes. This study was conducted to determine the effect of number and positioning of transverse rod connectors on the torsional stiffness and compression bending fatigue strength of ISOLA spinal corpectomy test constructs. Results from static torsion testing indicated that the addition of one and two transverse rod connectors between the pedicle screws greatly increased the torsional stiffness of the constructs (45% and 63%, respectively). When placed above and below the pedicle screws, the increase was less pronounced. Placement of one or two transverse rod connectors between the pedicle screws decreased the fatigue life of constructs in dynamic compression bending. Placement of two rod connectors above and below the upper and lower pedicle screws, respectively, did not reduce the fatigue performance of the constructs. Therefore, there is a delicate balance between torsional stiffness and fatigue performance of spinal constructs when transverse rod connectors are used.
Interconnection Strength Testing and its Value in Evaluating Clinical Performance
Authors: Jensen LM , Springer SS , Campbell SF , Gray E
Published: April 2008

ASTM standard F1798-97 provides guidelines for evaluating the strength of interconnection mechanisms used in pedicle screws and hooks. A literature search indicates the following as common significant clinical complications: fractured pedicle screws; fractured rods; disconnection between the rods, bolts, nuts and screws; screw loosening; loss of correction; inaccurate screw placement; broken pedicles; dural leaks; infection; transient and permanent neural injury. The tests outlined in ASTM standard F1798-97 may correspond to disconnection between the rods and screws or loss of correction. The standard does not correspond to any other known causes of the common complications. Therefore, interconnection strength tests may not have any bearing on the clinical outcomes of patients since there is no direct evidence that they sufficiently test for relevant device failures.
Clinical Relevance of Pull-out Strength Testing of Pedicle Screws
Authors: Dawson JM , Boschert P , Macenski MM , Rand N
Published: April 2008

Pull-out strength testing is described in many published manuscripts and is specially treated in ASTM F1692-96, “Standard Test Method for Determining Axial Pull-Out Strength of Medical Bone Screws.” Extensive biomechanics are reported on the importance of variables like hole preparation and cement augmentation. In this study, the pull-out strengths of variously-shaped, titanium pedicle screws were tested and the literature was searched for cited incidences of pull-out. The screws were extracted from polyurethane foam that modeled weak, moderate, and strong cancellous bone. Testing revealed significantly different pull-out strengths depending upon screw design and substrate strength. However, the literature search yielded few citations of screw pull-out. Screw loosening and hardware failure are sometimes mentioned in clinical reports but rarely is pull-out documented as a failure mechanism. Standardized testing is useful in comparing various designs but may have little relationship to in vivo performance.
The Influence of In Vitro Testing Method on Measured Intervertebral Disc Characteristics
Authors: Huber G , Linke B , Morlock MM , Ito K
Published: April 2008

Time-dependent behavior of functional spinal units, especially the anterior column, may interact with experimental methods when measuring their mechanical properties. Since they are tested using different load cycles, the comparison of results is difficult. The goal of this study was to determine the response of anterior column spinal units (body-disc-body units) to load cycles varying in waveform and cycle duration using an experimentally based mathematical model.

Specimen specific transfer function models were formulated for seven ovine lumbar anterior column units by fitting high order exponential functions to axial stress-relaxation measurements. Using axial load cycles with different waveforms and cycle durations, nine simulations in the time domain with each transfer function model were performed. For each simulation, the neutral zone, peak to peak, and hysteresis were evaluated.

The neutral zone and hysteresis were significantly dependent on the waveform of the load cycle. The differences of peak to peak for sinusoidal and triangular waveforms were low. All these characteristics were significantly dependent on the cycle duration. For example, comparison of 1 s to 20 s cycle durations exhibited neutral zone and hysteresis differences of 61–69% and 100%, respectively. Consequently, loading protocols should be chosen carefully and should be clearly reported.
Testing of Human Cadaveric Functional Spinal Units to the ASTM Draft Standard, “Standard Test Methods for Static and Dynamic Characterization of Spinal Artificial Discs”
Authors: Spenciner DB , Paiva JA , Crisco JJ
Published: April 2008

The development of replacement intervertebral discs has recently received significant attention in the new product arena. Presently, ASTM International is considering a standard for the evaluation of artificial discs. The purpose of this study was to evaluate human functional spinal units (FSUs) and intervertebral discs using the methods and equipment in the proposed standard and then to compare the results with existing literature.

FSUs and intervertebral discs were tested in axial rotation, anterior and posterior compressive shear, and axial compression. The stiffness values of the intervertebral discs were 1.8 ± 1.1 N. m/° in axial rotation, 368.2 ± 98.6 N/mm in anterior compressive shear, 483.5 ± 62.9 N/mm in posterior compressive shear, and 1287.5 ± 271.3 N/mm in axial compression. These results are reasonable in comparison with the existing literature but there are notable differences. We conclude that the mechanical properties of the intervertebral disc are not sufficiently defined and further testing is warranted.
Mechanical Analogue Model of the Human Lumbar Spine: Development and Initial Evaluation
Authors: Friis EA , Pence CD , Graber CD , Montoya JA
Published: April 2008

Mechanical testing of spinal instrumentation on cadaveric spine segments can be challenging. In this study, a mechanical analogue lumbar spine model was developed to be similar in rigidity to that of cadaveric spine segments. Three models of an adult human lumbar spine were built from composite vertebrae, ligaments and discs created individually to reproduce the nonlinear mechanical properties of human components. These models and three calf lumbar spines were loaded in a biaxial mechanical test system in axial compression, torsion, right and left lateral bending, flexion and extension. Rigidities were calculated in the secondary linear load-displacement region. Load-displacement behavior was nonlinear for both analogue and calf spines. There was good reproducibility between the models. Average axial rigidity of the analogue spines was 86 N/mm versus 231 N/mm for the calf spines, possibly due to the calf flat-back. In the remaining loading modes, the analogue spine was 26–65% more rigid than young calf spines. Comparisons to human cadaveric spine segments are underway.
Transverse Connectors: Clinical Objectives, Biomechanical Parameters Involved in Their Achievement, and Summary of Current and Needed In Vitro Tests
Authors: Carson WL , Asher MA , Boachie-Adjai O , Akbarnia B
Published: April 2008

The clinical objectives for using transverse connectors (TCs) on different implant constructs are compiled. Results from a survey of 2499 clinical cases, hand held-loaded models, linkage analysis, and finite element analysis were used to identify the important biomechanical characteristics and parameters of constructs affecting the need for a TC and of the TC itself that are involved in achieving the clinical objectives. These were compared to those tested in ASTM standards to evaluate existing and needed TC tests. Axial and torsional gripping characteristics of TC interconnections are adequately tested with ASTM F 1798-97. ASTM F 1717-01 axial test protocol can reveal the effect of TCs on the flexion fatigue life of longitudinal members, however the torsional test protocol results have questionable clinical relevance due to fixtures constraining 3 of 6 construct relative degrees-of-freedom. A substitute gimbal-gimbal or gimbal- pushrod fixture is proposed. The following are proposed to test TC characteristics that are not tested with current ASTM standards: an H construct for testing TC lateral bending characteristics, an unconstrained 3D test for transfixed thoracolumbar constructs having different combinations of hook-claw-wire and screw foundations, and a fixture to test torsional characteristics of constructs having sacroiliac foundations.
An Evaluation of the Influence of UHMWPE Test Block Design on the Mechanical Performance of Bilateral Lumbar Corpectomy Constructs
Authors: Dunbar WL , Cesarone D , Serhan H
Published: April 2008

The purpose of this study was to investigate how the design of corpectomy test blocks influences key strength parameters in bilateral lumbar construct testing. Two different test block designs were used with components from DePuy AcroMed's Stainless Steel ISOLA™ Spinal System in the evaluation. Both test block designs were made to approximate the bending moment and pedicle screw angle in the lower lumbar spine. The first block type was fixed to the test frame by a pin that passed through the block as recommended in ASTM Fl717-97. The second block type had a spherical indentation that mated with a spherical ball fixture (ball-socket connection). A battery of static and dynamic compression bending was performed for each block type. Static compression bending tests for the bilateral constructs yielded statistically different values (p<0.05) for the yield strength, stiffness, and ultimate strength for the two test block types. Dynamic compression bending results showed a difference in runout load of 5.27 Nm between the two block types. The failure modes in static and dynamic compression testing were the same for each block type.
X 15 T.N™ : A new Martensitic Stainless Steel for Surgical Instruments
Authors: Perot N , Moraux JY , Dichtel JP , Boucher B
Published: April 2008

The edge retention and wear resistance of steels are dependant upon hardness nd structure. Until now, two main principles have been adopted to increase the hardness of martensitic stainless steels: 1.Either through the introduction of a structural hardening mechanism into low carbon martensitic grades such as, AISI 630 and XM 16, 2.Or by increasing the carbon content of the martensite and subsequently strengthening it through the presence of primary carbides.

The first option has not allowed to date, the mass production of steels with hardness levels greater than 52/54 HRC. Furthermore, the absence of carbides deleteriously affects cutting quality. The second option has two distinct disadvantages directly linked to the presence of large carbides, which render the steel brittle and reduce corrosion resistance, through chromium depletion of the matrix in the immediate vicinity of the carbides. In X 15 T.N™, (UNS S 42025) nitrogen is used as a partial substitute for carbon, causing hardening by interstitial insertion as well as by the formation of fine nitrides and carbonitrides. In this way, a hardness level (58/60 HRC) is obtained equivalent to a high carbon martensitic steel without chromium depletion, thereby giving a substantial improvement in corrosion resistance, i.e. equivalent or superior to AISI 630 and XM 16.
Quality Aspects of High-Nitrogen Stainless Steel for Surgical Implants
Authors: Windler M , Steger R , Winters GL
Published: April 2008

High-nitrogen stainless steel has been used in orthopedic implants because of its high strength, good corrosion resistance and biocompatibility. In this study six annealed wrought high-nitrogen stainless steel sample bars from five different manufacturers were characterized in terms of chemical composition, mechanical properties, hardness, metallurgical structure and corrosion resistance. The metallurgical investigation, which determined the microstructure, grain size and inclusion content, was made with a light microscope, image analysis and SEM with EDX. The potentio-dynamic corrosion behaviour in the cross-sectional plane was measured at pH 4 and 40°C. No major differences were found in the chemical compositions, mechanical properties, hardness or metallurgies of the six sample materials. The only difference between the materials was established in the corrosion test, where the breakdown potential varied between -150 and +900 mV(SCE). However, no correlation could be established between the corrosion results and chemical composition, microstructure, or type / number of the inclusions. Additional heat treatment improved the material with low breakdown potential. It is recommended that minimum requirements should be established for the breakdown potential and incorporated in the current material standards.