bluuebunny/crossref_metadata_2025 huggingface dataset:
Satellite Based Standardized Terrain Maps: A Case Study
Authors: Singhroy VH , Barnett PJ
Published: April 2008

The Ontario Geological Survey and the Canada Centre for Remote Sensing are currently preparing a series of satellite based terrain maps for a 250 000 square kilometer area of the boreal forest region in Northwest Ontario. The purpose of this provincial and federal mapping program is to produce a series of 1:100 000 standardized, satellite based engineering-terrain maps that will be published as a provincial map series. The terrain maps are being used to plan forestry roads and other civil engineering works in support of forest harvesting programs in the region. They are also used to verify forest productivity models in the boreal forest. This paper presents the interpretation methodologies and examples of the satellite based standardized terrain maps. Our results show that image maps produced from a combination of DEM and TM can provide a base on which to interpret and overlay engineering terrain units at a scale of 1:100 000 for large areas of the boreal forest regions in northern Canada. This method will result in considerable savings in time and cost when compared to traditional air photo methods.
Wind Load Design and Performance Testing of Exterior Walls: Current Standards and Future Considerations
Authors: Prevatt DO
Published: April 2008

Although the main structural systems of fully engineered buildings perform adequately during extreme wind events, costly losses happen to buildings once the components of the exterior walls and claddings fail. In response to these failures, new design methods have been developed that result in higher design wind loads applied to components, and prescribe additional tests on cladding to determine the structural resistance of exterior wall elements.

This paper discusses some recent changes to the wind load design provisions of the American Society of Civil Engineers (ASCE) Standard, ASCE 7-98, that apply to exterior building walls. ASCE 7-98 includes new concepts for cladding design that consider impact resistance and topographic effects on overall wind loads. Examples compare the wind design loads obtained using ASCE 7-98 with loads obtained with 7–95 and 7–88 for regular-shaped buildings. The changes may eventually influence the exterior wall design throughout the U.S. because the recently published International Building Code (IBC-2000), formed under a partnership agreement of the three existing model building codes, has adopted ASCE 7-98.

Improving the wind performance of exterior walls depends equally on improved wind design codes as well as on improved test procedures that determine the structural capacity of installed cladding systems. The current state-of-the-art in full-scale testing of building components is discussed, and a summary of current full-scale tests is presented. The author proposes that the current fragmented design process for different cladding materials and the reliance on materials-specific performance tests is too complex and needs to be streamlined in order to improve the overall performance of building envelope systems.
The Importance of Studying Exemplars when Designing Stone Facades
Authors: McDonald WH , Lewis MD
Published: April 2008

The facades of contemporary buildings clad with dimension stone buildings all too often perform poorly, compared with the walls of much older buildings; despite they're being developed with computers and assembled using space-age parts. At the same time, structures using centuries-old methods often serve their occupants better than buildings many decades younger. Many facades built recently as architects' masterpieces now need major restoration simply to continue service. Their leaks, drafts, and dilapidated states shorten their useful lives.

Problems occur in new facades because their designers rarely understand the complex natural forces acting upon them. Earlier builders observed the performance of successful buildings, exemplars, and borrowed from them to suit their needs. In this way, the solid wall of antiquity evolved into a high architectural and structural art that has endured for centuries. The solid wall changed over the last hundred years to become cladding covering a separate structural skeleton. Although this concept offered aesthetic freedom and factory-expediency, a comparatively small portion of the last century's building inventory remains as healthy exemplars. Few of them have escaped major restoration efforts. And in the past fifty years, new material combinations spawned unprecedented problems. Leaks progressively attacked their concealed supports, inevitably damaging cladding and spiraling damage claims.

Contemporary builders repeat mistakes, partly because structural theory insists this procedure works, even as similarly constructed buildings fail. Poorly-performing exemplars are duplicated because their poor performance is ignored. Meanwhile, many existing older buildings, time-proven examples of sensible construction procedures and systems that perform well, continue to serve. In engineering's evolution from an empirical process to a theoretical one, stone façade construction has changed dramatically. Unfortunately, contemporary builders often ignore exemplars in a continuing but failed effort to fashion new images. To reduce expensive failures, successful builders study past performance. This paper examines the melding of empirical wisdom with new philosophies in producing useful buildings.
When Does it Become a Leak? A Case Study
Authors: Keranen TM
Published: April 2008

This paper explores the basic legal theories under which an owner could seek relief for a leak condition in a legal proceeding; the various standards that could be employed to support the forensic evaluation of the claim, and to “prove” the condition. A case study is used to illustrate the application of these concepts. The paper concludes by making observations and recommendations concerning the process of evaluating and proving a leak condition in a legal proceeding.
A Verification Method for Prevention of Penetration of Moisture to Prove Compliance of Performance-Based Building Codes
Authors: Benge C
Published: April 2008

The New Zealand building code is performance-based, and to facilitate proof of compliance the Building Industry Authority publishes Approved Documents that provide tests or calculation methods (Verification Methods) and “cookbook” solutions (Acceptable Solutions).

Currently the Acceptable Solution for the prevention of penetration of moisture into a building that will cause undue dampness or damage to the building deals only with generic materials such as timber weather boards, brick veneer and stucco on light timber framing.

The Verification Method contains test methods to be carried out in a laboratory. Not only can such tests be costly, but they may also not take account of site conditions or of the protection provided by the layout and orientation of a building.

This paper will examine the possibility of an additional Verification Method that will show compliance with the performance based building code by dealing with the adequacy of the building envelope in terms of such issues as its materials and systems, the joints within and with other claddings, any secondary defense methods, disposal of moisture that does penetrate, and exposure and durability considerations.

It is hoped that the result of this and further studies will be a Verification Method for the building envelope useful for manufacturers to predict that their product will comply with the code and for designers who are dealing with unique situations to prove compliance without costly testing.
Suggestions Towards Improved Reliability of Thermocouple Temperature Measurement in Combustion Tests
Authors: Jones JC
Published: April 2008

Two common forms of combustion testing—oven heating tests for spontaneous combustion propensity of coals and carbons, and temperature measurements in ‘simulated room fires’—are discussed in terms of thermocouple uncertainty. For oven heating tests, radiation effects on thermocouple accuracy are examined and examples, from the recent research literature, of unjustifiable claims of thermocouple accuracy in such tests are given and discussed. For simulated room fires, very detailed calculations based on heat balance at the thermocouple tip are performed, and it is shown how unsuspected radiation effects can entail significant errors. Means of eliminating, or at least of significantly reducing, these errors is given in detail. The approach is applicable to steady or to non-steady conditions.
Calibration of a Heat Flux Sensor up to 200 kW/m2 in a Spherical Blackbody Cavity
Authors: Murthy AV , Tsai BK , Saunders RD
Published: April 2008

This paper presents the results of a comparative study of narrow view-angle and wide view-angle calibrations of a water-cooled Schmidt-Boelter heat-flux sensor. The narrow view-angle calibration, up to a heat flux level of 50 kW/m2, was conducted using the 25 mm Variable Temperature Blackbody (VTBB) facility. An electrical substitution standard was used as a transfer standard to determine the flux level at the sensor plane. The wide view-angle calibration was conducted by placing the sensor inside the radiating cavity of a spherical blackbody. The calibration in the spherical blackbody is based on the heat-flux derived from the Stefan-Boltzmann equation using the blackbody temperature measured from a type-S thermocouple. The calibration covered an extended range from 50 kW/m2 to 200 kW/m2. Results of the calibration of the heat-flux sensor using the two different techniques are presented. A discussion of the problems associated with calibrating sensors at high heat-flux levels by inserting the sensor inside a blackbody cavity is also presented.
Angular Sensitivity of Heat Flux Gages
Authors: Alpert RL , Orloff L , de Ris JL
Published: April 2008

The response of a heat flux gage depends on both the angular distribution of the source radiant flux and the angular sensitivity of the coating on a gage's heat-sensing element. The issue becomes important for the calibration of apparatuses designed to test the response of materials subjected to a known level of incident thermal radiation. In this study, the angular sensitivity of several different gage coatings are measured by rotating the gage sensing surface in front of a black body source. Ideally, gage output is proportional to the cosine of the angle of incidence with respect to the normal, known as Lambertian behavior. Some commercial black coatings become non-Lambertian for angles above 60° from the surface normal, but other coatings maintain a Lambertian response beyond 70°. The impact of these differences on the calibration of the Fire Propagation Apparatus and the Cone Calorimeter is evaluated.
Sandia Heat Flux Gauge Thermal Response and Uncertainty Models
Authors: Blanchat T , Humphries L , Gill W
Published: April 2008

The Sandia Heat Flux Gauge (HFG) was developed as a rugged, cost-effective technique for performing steady state heat flux measurements in the pool fire environment. The technique involves reducing the time-temperature history of a thin metal plate to an incident heat flux via a dynamic thermal model, even though the gauge is intended for use at steady state. In this report, the construction of the gauge is reviewed. The thermal model that describes the dynamic response of the gauge to the fire environment is then advanced and it is shown how the heat flux is determined from the temperature readings. This response model is based on first principles with no empirically adjusted constants. A validation experiment is presented where the gauge was exposed to a step input of radiant heat flux. Comparison of the incident flux, determined from the thermal response model, with the known flux input shows that the gauge exhibits an noticeable time lag. The uncertainty of the measurement is analyzed, and an uncertainty model is put forth using the data obtained from the experiment. The uncertainty model contains contributions from 17 separate sources loosely categorized as being either from uncontrolled variability, missing physics, or simplifying assumptions. As part of the missing physics, an empirical constant is found that compensates for the gauge time lag. Because this compensation is incorporated into the uncertainty model instead of the response model, this information can be used to advantage in analyzing pool fire data by causing large uncertainties in non-steady state situations. A short general discussion on the uncertainty of the instrument is presented along with some suggested design changes that would facilitate the determination and reduction of the measurement uncertainty.
The Difference Between Measured and Stored Minimum Ignition Energies of Dimethyl Sulfoxide Spray at Elevated Temperatures
Authors: Staggs KJ , Alvares NJ , Greenwood DW
Published: April 2008

The use of sprayed flammable fluids as solvents in dissolution and cleaning processes demands a detailed understanding of ignition and fire hazards associated with these applications. When it is not feasible to inert the atmosphere in which the spraying process takes place, then all possible ignition sources must be eliminated. If operators are involved in the process, the potential for human static build-up and ultimate discharge is finite, and nearly impossible to eliminate.
Where Do We Go From Here?
Authors: Ettlinger CF , Johnson RJ , Shealy JE
Published: April 2008

This analysis is the second paper of a two-part review “What Do We Know and Where Do We Go From Here?”[1]. This paper recommends policies, practices, and products which could quickly and effectively reduce the risk of the most common of the serious injuries sustained by alpine skiers. Injury rates cited in this review are based upon a 29-year case-control study by the authors at a medium-sized Vermont ski area. Release binding performance under simulated skiing loads was evaluated using a device defined by ASTM standard test method for measuring the quasi-static release moments of Alpine ski bindings (F 504-00). A description of the test method can be found in Section 15 of the Annual Book of ASTM Standards.The use of this device as a research tool is described by Ettlinger and Bahniuk in the Spring 1980 edition of the Journal of Safety Research [2].
Why the Ski Binding International Standards have been Modified in 2001
Authors: Laporte J-D , Binet M-H , Bally A
Published: April 2008

Skiing is very popular in France, although people have basically been poorly informed on the standards of setting bindings and the necessity of their application. For the past ten years the results of the MDM epidemiological network have put forward beyond doubt that the number of knee injuries has increased, especially in the female population. These findings have motivated a work group of the AFNOR to suggest an improvement of the ISO norm 11088 for binding adjustments; a documentation leaflet was published under the number FD S 52-748. Because in France the actual international standards were badly applied or simply unknown, a large information campaign was launched aiming skiers and ski equipment renters. For the mass public campaign: A television spot of 30 seconds and 1 000 000 documentation leaflets were distributed. A specific information campaign was aimed at the ski equipment renters. The desire to lower the great number of ACL njuries, particularly in women, by distributing these modern adjustment tables has put forward the lack of awareness of the ISO standards. Only 4,4 % [9 of 204 interviewees] were able to give the 4 fundamental criteria of the AFNOR standards. A control group was studied. The survey consisted of 2203 interviews on the slopes using a randomised survey of 1597 alpine skiers. 204 interviews of ski renters were performed by telephone. 42,6% of the control group had heard of the campaign binding adjustment. Most people interviewed (90,1%) heard about the publicity campaign on ski accident risks. It is impossible to establish a link between the effects of the campaign and the small positive result found.
Integrated Platform for Testing MEMS Mechanical Properties at the Wafer Scale by the IMaP Methodology
Authors: de Boer MP , Smith NF , Masters ND , Sinclair MB , Pryputniewicz EJ
Published: April 2008

A new instrument to accurately and verifiably measure mechanical properties across an entire MEMS wafer is under development. We have modified the optics on a conventional microelectronics probe station to enable three-dimensional imaging while maintaining the full working distance of a long working distance objective. This allows standard probes or probe cards to be used. We have proceeded to map out mechanical properties of polycrystalline silicon along a wafer column by the Interferometry for Material Property Measurement (IMaP) methodology. From interferograms of simple actuated cantilevers, out-of-plane deflection profiles at the nanometer scale are obtained. These are analyzed by integrated software routines that extract basic mechanical properties such as cantilever curvature and Young's modulus. Non-idealities such as support post compliance and beam take off angle are simultaneously quantified. Curvature and residual stress are found to depend on wafer position. Although deflections of cantilevers varied across the wafer, Young's modulus E ∼ 161 GPa is independent of wafer position as expected. This result is achieved because the non-idealities have been taken into account.
Effect of Nitrogen Feedgas Addition on the Mechanical Properties of Nano-Structured Carbon Coatings
Authors: Catledge SA , Vohra YK
Published: April 2008

Chemical vapor deposition was employed to grow nano-structured carbon films on a titanium alloy (Ti-6Al-4V) using different N2/CH4 feedgas ratios in a balance of H2. Of particular interest is a determination of how the film hardness changes with N2/CH4 feedgas ratio and how this measurement correlates with the film structure as determined using micro-Raman spectroscopy, X-ray diffraction, and atomic force microscopy. We find that the broad Raman peak at 1550 cm-1 (attributed predominantly to tetrahedral amorphous carbon) becomes more intense and sharp with increasing N2/CH4 ratio and that the relative concentrations of CH4 and N2 are critically linked to the hardness of the film. The combination of high film hardness, low surface roughness, and good toughness is highly desirable (especially for deposition on metals) and these properties can be optimized by manipulation of the N2 and CH4 feedgas concentrations.
Microstructural and Mechanical Characterization of Electrodeposited Gold Films4
Authors: Long GS , Read DT , McColskey JD , Crago K
Published: April 2008

The effects of temperature and duration of thermal treatments on the microstructure and mechanical properties of electrodeposited gold films were evaluated. Specimens were synthesized by electrodeposition of gold on copper foil substrates followed by application of novel photolithographic and microetching techniques so as to produce a series of free-standing gold thin-films of dimensions 2.5 by 200 by 800 μm supported by copper foil frames. Seven different heat treatments, spanning temperatures from 25 to 300°C and up to 8 h in duration, were studied. In each case, thermal annealing of the samples was carried out in an inert atmosphere after the copper foil substrate beneath the tensile coupons had been removed by CuCl2 etchants. X-ray diffraction was used to assess the microstructures. The crystalline texture of the films changed from predominantly <111> (perpendicular to the plane) to strongly <100>, and then back toward <111> with heat treatment. No evidence for grain growth was seen in the X-ray diffraction results. Tensile-strength analyses were performed using a piezo-actuated microtensile testing system. The properties of the heat-treated specimens varied significantly from those of the nontreated material. Tensile strength generally decreased with longer heat treatment. Cyclic fluctuations in the elongation-to-failure, strikingly similar to those in the ratio of <200> to <111> diffracted X-ray intensities, were observed as a function of increasing heattreatment temperature.
The Effects of Radiation on the Mechanical Properties of Polysilicon and Polydiamond Thin Films
Authors: Newton RL , Davidson JL
Published: April 2008

Due to its many excellent properties, diamond is being explored as a material for MicroElectroMechanical Systems (MEMS). However, as is true in the case of silicon, a large amount of basic material characterization issues still warrant investigation. This paper presents preliminary results from charged particle irradiation of Chemical Vapor Deposited (CVD) polycrystalline diamond films. The films were simultaneously dosed to a level of 9.4 × 10th particles/cm2 using 700 keV protons and 1 MeV electrons. The samples were then subject to cross-sectional nanoindention analysts and Raman spectroscopy. Polycrystalline silicon was also investigated for comparison purposes. The diamond was unaffected by the irradiation. However, the silicon did indicate a slight decrease in Young's modulus.
Using Pollinators to Deliver Biological Control Agents Against Crop Pests
Authors: Kevan PG , Al-mazra'awi MS , Sutton JC , Tam L , Boland G , Broadbent B , Thomson SV , Brewer GJ
Published: April 2008

Both honey bees and bumble bees have been shown to be excellent vectors of biological control agents that suppress pests on various crops. Honey bee and bumble bee hives can be fitted with special dispensers that contain inocula of biological control agents (bacteria, fungi and viruses) that are antagonistic to microbial and fungal plant pathogens and to pest insects. The technology has been used successfully against grey mold on soft and tender fruit (strawberries and raspberries), fire blight on pome fruit (pears and apples), and potentially against sclerotinia on oil seeds (canola). Similarly, viral, bacterial, and fungal pathogens of pest insects, such as corn earworm, pollen beetles, banded sunflower moths, and tarnished plant bugs on alfalfa, canola, and sunflower can be delivered to flowers to help protect the crop while improving yields and crop quality through pollination and reduced chemical pesticide load. The development of the technology requires that the biological control agent be effective against the pest, not harm the pollinating vector, and be environmentally acceptable. This new technology is reviewed and its successes noted.
Sulfosulfuron and Glyphosate Efficacy with Various Humectants
Authors: Woznica Z , deVilliers BL , Nalewaja JD , Messersmith CG
Published: April 2008

Research was conducted in the greenhouse and growth chambers to determine the effect of selected humectants on sulfosulfuron {1-(4,6-dimethoxypyrimidin-2-yl)-3-[(2-ethanesulfonyl-imidazo[1,2-a]pyridine-3-yl)] sulfonylurea}and glyphosate {N-(phosphonomethyl)glycine} efficacy and sulfosulfuron spray deposit characteristics. Humectants were glycerol, sorbitol, ethylene glycol, propylene glycol, various polyethylene glycols, sodium lactate, and calcium nitrate. Sulfosulfuron was applied to green foxtail and glyphosate to wheat, with and without nonionic surfactants, and with and without humectant in distilled water. None of the humectants substantially increased glyphosate efficacy, and sodium lactate and calcium nitrate were antagonistic. In the presence of nonionic surfactant, sodium lactate and calcium nitrate caused the greatest increase in sulfosulfuron efficacy and overcame the reduced sulfosulfuron efficacy associated with low humidity. Sodium lactate and calcium nitrate enhanced sulfosulfuron efficacy regardless of spray mixture pH, but the increase appeared greater at low pH (4.3–5) than at high pH (7.7–8.2). Scanning electron micrographs showed that spray deposits at low pH contained dry crystals, presumably sulfosulfuron. Sodium lactate gave a liquid-appearing (presumably water) spray deposit. Water retained in sulfosulfuron spray mixture deposits measured on watch glasses was greater with calcium nitrate and sodium lactate than with glycerol, sorbitol, propylene glycol or polyethylene glycol humectants. These data demonstrate the potential for enhancing efficacy of sulfosulfuron by using selected humectants as components of an adjuvant.
Corrosion on Spinal Implant Constructs: Should Standards Be Revised?
Authors: Kirkpatrick JS , Venugolopalan R , Bibbs M , Lemons JE , Beck P
Published: April 2008

Corrosion is known to occur on modular spinal implants but design features such and material, surface finish, and interconnection characteristics have not been related to corrosion. Literature review was combined with retrieval analysis of thirty-three constructs to identify which design features were associated with corrosion. Corrosion was found consistently on implants where stainless steel components with differing surface finishes (Matte and polished) were designed with rigid interconnections. No clear direction for new standards activity was identified.
Effect of Transverse Connector Design on Development of Late Operative Site Pain: Preliminary Clinical Findings
Authors: Cook S , Asher MA , Carson WL , Lai SM
Published: April 2008

A leading cause for reoperation in patients with idiopathic scoliosis receiving posterior instrumentation and arthrodesis is Late Operative Site Pain (LOSP), with corrosion at the transverse connection site being a common observation. Clinically, a consecutive series of 55 adolescent idiopathic scoliosis patients with Isola Drop Entry Transverse Rod Connector's (DETCs) was compared with an earlier consecutive series of 97 having Isola Threaded Transverse Rod Connectors (TRCs). Both groups were less than 21 years of age, with TRC average follow-up 87 months and DETC 32 months. Kaplan-Meier survivorship analysis, utilizing implant removal for LOSP, was performed on both groups. Biomechanically, axial and torsional gripping capacity tests were performed on the DETC and TRC interconnections to the longitudinal rod. The axial gripping capacity was 1164 and 1191 N for the two DETC connector components versus 363 N for the TRC connector component. Correspondingly the torsional gripping capacity was 4.1 and 4.7 Nm compared to 1.3 Nm. The Kaplan-Meier probability of reoperation for LOSP by 60 months was 4.7% in the TRC group compared to 0% for DETC (p = 0.3993). Seven TRC patients underwent removal for LOSP versus zero for DETC (p = 0.0504). The stronger DETC interconnections possibly correlate with a decreased incidence of LOSP.
Extrusion of Interbody Fusion Devices—Clinical Examples
Authors: Theiss SM
Published: April 2008

Extrusion of lumbar interbody fusion devices is a rare, though well-described, complication. Extrusion has been seen with a variety of interbody devices and surgical techniques. It is most commonly seen when implants are placed using a posterior approach. Extrusion results from instability of the final construct following implantation, or misplacement of the device. Instability can result from placement of an undersized implant or excessive resection of the facet joints. In each case, an error in surgical technique can be identified which leads to the extrusion. A design flaw of the implant is generally not the cause for the extrusion.
Is Push-out Testing of Cage Devices Worthwhile in Evaluating Clinical Performance?
Authors: Springer SS , Campbell SF , Houfburg RL , Pavlovic J , Shinbrot A
Published: April 2008

Interbody cages are successfully used clinically to support the spine's anterior column to facilitate fusion of the motion segment. A standard, “Static Push-Out Test Method for Intervertebral Body Fusion Devices,” is under consideration by ASTM. The objective of this testing was to determine the loads required to extract interbody fusion cages from a simulated spinal motion segment (Grade 20 polyurethane foam model). The results obtained using the foam model were compared to results done using intact cadaver spinal motion segments (thoracic and lumbar). These data are contrasted with incidences of cage expulsion mentioned in the literature. Testing revealed a difference in the expulsion strength between the foam and cadaveric models. Differences between the 13 × 20 mm and the 9 × 20 mm cages were also found. The literature search revealed that posteriorly implanted cages may retropulse into the spinal canal due inadequate annular tension, undersized cages, and destabilization from laminectomy and partial facetectomy. The danger of retropulsion may be alleviated by the addition of posterior instrumentation (rods and screws). Standardized testing is a valuable tool in differentiating among designs but does not represent clinical failures.
Durability Test Method for a Prosthetic Nucleus (PN)
Authors: Hudgins RG , Bao QB
Published: April 2008

Durability is critical for permanent spinal implants. Proposed test methods suggest that prosthetic intervertebral discs (PIDs) having fixation plates for vertebral attachment should be tested at a 45° angle to create combined compression-shear loads. Generally, a prosthetic nucleus (PN) does not have fixation plates and does not transmit shear loads as high as PIDs; thus, loading PNs through fixation plates would not mimic physiological conditions. Currently, most PNs are fatigue tested using compression only. A test method and fixture are proposed for testing a PN in a saline bath at 37 °C under combined compression-flexion-extension loading simulating physiological conditions. A multi-station test fixture, mounted in a servo-pneumatic test frame, was used to conduct the tests under load control. The fixture has a top platen to apply a controlled compression load and a bottom test bed that rotates on a horizontal axis at a set frequency creating a flexion/extension motion. Compression loads were monitored for each station, and the rotation and moment were monitored for the test bed. A software control algorithm coordinated the compression stroke of the test frame with the test bed rotation so that the maximum compression load occurred near the peak rotation angle. The PN compression load range was approximately 200 N–550 N applied at 1.5 Hz, and the test bed rotation was -3.6° to +2.3° to simulate lumbar flexion/extension motion during vigorous walking. The peak compression stress component was approximately 1 MPa, and the peak flexion/extension component was approximately 1 MPa giving a maximum combined stress on the implant edge of 2.0 MPa. Specimens were examined and photographed with magnification, and masses were monitored to assess implant wear. No cracks were observed on any of 6 implants tested to 12.7 million cycles, and the average total mass loss was approximately 6.9 mg (stdev = 4 mg). Testing continues.
An Improved Biomechanical Testing Protocol For Evaluating Multilevel Cervical Instrumentation In A Human Cadaveric Corpectomy Model
Authors: DiAngelo DJ , Foley KT
Published: April 2008

Spinal instrumentation is commonly used to stabilize the multi-level strut- grafted cervical spine. There are no standard tissue-based testing protocols for evaluating spinal devices. An improved biomechanical testing protocol was developed to study the strut-graft mechanics of the instrumented cervical spine in flexion and extension. The biomechanical stability of two different anterior cervical plating systems were evaluated and compared to the harvested condition. A force sensing strut-graft (fssg) was used to measure the axial compressive load. Parameters of stiffness, segmental vertebral motion, and strut-graft loads were statistically compared with a one-way anova (p<0.05) to determine differences between the spine conditions. Applying a bending moment distribution across the cervical spine resulted in a motion response that closely matched the in vivo case. Fssg loads were affected by plate application and specific plate design features. The testing protocol has been used to study the biomechanical stability of various multi-level strut-graft cervical instrumentation. Information of strut-graft loads aided in better understanding graft-plate load-sharing mechanics and clinically-observed multi-level instrumentation failure mechanisms.
Influence of Preload in Flexibility Testing of Native and Instrumented Lumbar Spine Specimens
Authors: Linke B , Meyer G , Knöller S , Schneider E
Published: April 2008

In-vitro investigations on spine specimens are usually performed to evaluate the biomechanical behavior of the native spine, or to determine the stabilizing effects of different types of implants. These investigations are currently performed by the application of pure moments in the anatomic directions. The inclusion of an additional preload is heavily discussed, but seldom used in the experiments. Investigators often mention that different preloads have an influence on the results, but a detailed analysis of the influence on specific outcome parameters is still missing. The aim of this study was to show the effects of preload on the load-displacement behavior of spine specimens and to give basic data upon which investigators of future studies may decide on the necessity of its inclusion, depending on their specific question. A six degree-of-freedom loading device has been developed and was used to load the specimens. It has a parallel architecture and is equipped with a hybrid position/force controller. Sixteen human lumbar spine specimens L1-L3 were investigated. The spines were tested native and in two stabilized corpectomy situations. An anterior stabilization with VentroFix and SynEx was used with and without posterior USS fixation. Compressive preloads of ON - 400N were applied and the flexibility tests carried out. The orientation of the preload was changing in accordance to the movement of the specimen.

A general reduction of the range of motion (ROM) of up to 40% due to 400 N of preload was observed. It could be shown, that this is not a general stiffening effect in the case of a strong sigmoid shape of the hysteresis curve. Whenever the low-stiffness (LS) is considerably lower than the high-stiffness (HS), HS is not affected by preload, but LS is strongly increased (50– 80% in native case). With increasing rigidity of additional instrumentation the stiffening effect is reduced on LS and increased on HS. The stiffness-ratio (SR = HS/LS) is reduced to about 50% due to 400 N preload in the native case. If implants are evaluated by an instrumented-to-native (I/N) comparison, the effect of preload on the I/N ratio of the characteristic parameters is only minimal and specific to the instrumentation used.
Vertebral Bone Density—A Critical Element in the Performance of Spinal Implants
Authors: Tan JS , Kwon BK , Samarasekera D , Dvorak MF , Fisher CG , Oxland TR
Published: April 2008

The effectiveness of spinal implants in fixation is dependent upon the bone-implant interface, and thus on vertebral bone density. Current ASTM assessment methods use synthetic elements as vertebral surrogates and therefore, by definition, do not address important in vivo performance and failure characteristics. The purpose of this study is to contrast the mechanical behaviour of pedicle screws in cadaveric vertebrae versus synthetic surrogates. Short-term physiologic axial compression and bending moment were cyclically applied to pedicle screws inserted in lumbar vertebrae and UHMWPE. Kinematics of the pedicle screws in bone and in UHMWPE were significantly different in terms of the range of motion and pivoting and bending points on the screws. For the vertebral fixation, there was a trend towards a more rigid screw-bone interface with increasing bone mineral density. Devices tested using ASTM and ISO test standards may give clinicians and regulatory bodies a false sense of security with respect to implant performance due to their limited scope.
Characterization of Sandvik Bioline High-N — A Comparison of Standard Grades F1314 and F1586
Authors: Haraldsson C , Cowen S
Published: April 2008

ASTM standard grades for surgical implants F1314 and F1586 are both N-strengthened austenitic stainless steels with high resistance to pitting corrosion. The latter is generally used in Europe while the former is preferred in the United States. In the present study, Sandvik grade Bioline High-N, conforming to ASTM F1586, has been characterized with respect to microstructure, mechanical properties, corrosion resistance and inclusion content and compared with ASTM F1314-material.

In the present comparison it has been shown that Bioline High-N3 compared to ASTM F1314 material has similar or slightly superior mechanical properties, pitting corrosion resistance and nonmetallic inclusion content. All these properties are of critical importance for medical implant material.
Mechanical and Corrosion Properties of Forged Hip Stems made of High-NitrogenStainless Steel
Authors: Windler M , Steger R
Published: April 2008

The purpose of the study was to determine the mechanical and corrosion roperties of forged, commercially available, femoral hip stems. Two different stem designs were selected (the MS-30, sizes 6 and 16, and the MUELLER straight stem, sizes 7.5 and 15.0). They were made of high-nitrogen stainless steel according to ISO 5832-9 and ASTM F1586. The samples for determining the mechanical properties were taken from the proximal part of the prostheses. The metallurgical and the potentio-dynamic corrosion behaviours were investigated in three different transverse cross-sectional planes. The mechanical properties in the forged condition were as follows: Yield strength 1051 – 1172 MPa, tensile strength 1138 – 1238 MPa and elongation 15 – 19%. Vickers hardness values of between 354 and 393 HV were measured. The breakdown potential fell from +1000 mV(SCE) (wrought bar) to +600 to +950 mV(SCE) (forged hip stems) for pH 4 and 37°C. The rotational bending fatigue value for 10 million cycles was 587 MPa.
Metallurgical and Mechanical Evaluation of 316L Stainless Steel Orthopaedic Cable
Authors: Disegi JA , Zardiackas LD
Published: April 2008

Stainless steel cable systems have been designed for a multitude of orthopaedic implant applications. Various implant fixation, cerclage, and tension banding techniques may be used with cable constructs to stabilize a variety of simple and complex bone fractures. Multifilament cable products, however, can pose special challenges regarding metallurgical evaluation and mechanical property testing. The present project investigated the metallurgical and mechanical properties of a new 316L stainless steel cable system designed for general trauma surgery. Important cable attributes such as strand configuration, cable construction, and finishing options are discussed. The advantages of inductively coupled plasma spectroscopy analysis are presented for the compositional verification of solid cable specimens. Metallographic methods for the examination of nonmetallic inclusion limits and grain size are described for a cable construct composed of 75 fine wires. The microstructure associated with laser remelted cable ends is documented via light microscopy. Unique tension test methods are described for the determination of failure load and elongation of 1.1 and 1.7 mm diameter cable sizes. Test results are compared with generalized requirements compiled in ASTM F 2180 Standard Specification for Metallic Implantable Strands and Cables.
MRI Safety and Compatibility of Implants and Medical Devices
Authors: Woods TO
Published: April 2008

Since MRI (magnetic resonance imaging) scanners became available in the 1980's, they have rapidly become one of the most common clinical imaging tools. The MR environment produces unique safety and compatibility issues for materials used in implants and medical devices. The principal issues for MR safety and compatibility are magnetically induced displacement force and torque, radio frequency (RF) heating, and image artifact. This paper defines and discusses the potential hazards produced by implants and devices in the MR environment, with an emphasis on stainless steels. It also describes MR safety and compatibility test methods developed by ASTM and summarizes ongoing MR standards development work.
Fatigue Behavior and In-Vitro Biocompatibility of the Ni-Free Austenitic High-Nitrogen Steel X13CrMnMoN18-14-3
Authors: Tikhovski I , Brauer H , Mölders M , Wiemann M , Bingmann D , Fischer A
Published: April 2008

Austenitic stainless steels generally have a favorable combination of strength and ductility as well as a sufficient resistance against corrosion. This and the reported biocompatibility lead to the use of 304- and later 316 L-type steels in medical applications. Especially in orthopedics these steels were applied as implants for e.g. fracture fixation as bone plates, intermedullary nails, and screws. But these steels contain a high amount of Ni, which was attributed to cause Ni-allergies for an growing amount of patients. Thus, alternatives were needed and — beside the already known CoCrMo-alloys — implants of Ti and its alloys emerged increasingly into the medical market. The aim of this paper is to introduce a new austenitic Ni-free CrMnMo-steel X13CrMnMoN18-14-3 (Material No.: 1.4452, brand name: P2000), which makes use of about 1 % N in order to gain a combination of high strength, high ductility, and a superior corrosion resistance.

In a first step the cyclic fatigue behavior in air and in Ringer solution in the solution annealed state is investigated. This is accompanied by electrochemical testing in Ringer solution as well as in-vitro cytotoxicity tests against MC3T3 cells in bovine serum.

The tests revealed that the solution annealed X13CrMnMoN18-14-3 at 5 Hz has an 50 % endurance limit of 346 MPa in air and of 302 MPa in Ringer solution, which is markedly higher compared to solution annealed CrNiMo-steels. In addition it was found that the CrMnMoN-steel shows no distinct susceptibility to stress-corrosion cracking in the entire region of finite life between stress amplitudes of 400 to 550 MPa. The pitting potential in Ringer solution was measured to be 1.1 V, which is in the range of common Ni-containing high-Nitrogen steels as well as of CoCr20Mo6 alloys. No reduction of MC3T3 cell adhesion could be observed.

Thus, the Ni-free CrMnMoN-steels might be a promising alternative to the CrNiMo- steels in medical applications.
Ammonium Perchlorate Disruption of Thyroid Function in Natural Amphibian Populations: Assessment and Potential Impact
Authors: Carr JA , Urquidi LJ , Goleman WL , Hu F , Smith PN , Theodorakis CW
Published: April 2008

We examined indices of thyroid development in tadpoles from ammonium perchlorate (AP)-exposed sites. Bullfrog (Rana catesbeiana) tadpoles collected from a reference site exhibited normal developmental features, with many completing metamorphoses. In contrast, tadpoles collected from the AP contaminated site exhibited a 5-fold lower hindlimb/snout-vent length ratio than tadpoles from the reference site. The volume of the thyroid gland was 2.5-fold larger in the tadpoles from the reference site, presumably because they had progressed to late prometamorphosis and early metamorphic climax. Premetamorphic western chorus frog tadpoles (Pseudacris triseriata) inhabiting an ephemeral pond contaminated with AP exhibited gross morphological abnormalities of the thyroid including colloid depletion and follicle cell hypertrophy. We conclude that tadpoles exposed to AP-contaminated pond water early in larval life exhibit delayed development of thyroid-hormone sensitive structures. Additionally, there are abnormalities in the developing thyroid gland that seem to depend upon the window of AP exposure. The potential impact of thyroid disruption on development and reproduction in amphibian populations will be discussed.
Using Semipermeable Membrane Devices (SPMDs) to Assess the Toxicity and Teratogenicity of Aquatic Amphibian Habitats
Authors: Bridges CM , Little EE
Published: April 2008

Environmental contamination has been suspected of being partially responsible for recent declines in amphibian populations. It is often not feasible to identify all of the compounds in an environment, nor the concentrations in which they are present. SPMDs are passive sampling devices that uptake lipophilic compounds from the environment in a manner similar to aquatic organisms. The extracts from the SPMDs, therefore, contain a composite sample of the compounds that are present in the environment. In this paper, we outline the methods from studies in which we have used extracts from SPMDs in toxicity tests on amphibian larvae. Using SPMD extracts makes it possible to establish potential links between amphibian deformities and declines and environmental contamination by lipophilic compounds.
Methods for Testing the Combined Effects of Contamination and Hibernation on Terrestrial Amphibians
Authors: James SM
Published: April 2008

Much work needs to be done to improve and develop techniques for contaminant studies with post-metamorphic, terrestrial amphibians. Evaluations also should be made of the impacts of multiple Stressors, because single-factor studies may underestimate environmental stress. Habitat contamination is one of the proposed causes of the global decline of amphibians. Hibernation is an annual period of natural stress when mortality can be very high. This paper describes methods for testing the combined effects of contamination and hibernation on terrestrial amphibians, and includes model species selection, culture practices, hibernation conditions, soil exposures, and food chain exposures. The guidelines provided are based on what works well with American toads (Bufo americanus), but should be useful for other amphibian species.
Integrated Field and Laboratory Tests to Evaluate Effects of Metals-Impacted Wetlands on Amphibians: A Case Study from Montana
Authors: Linder G
Published: April 2008

Mining activities frequently impact wildlife habitats, and a wide range of habitats may require evaluations of the linkages between wildlife and environmental stressors common to mining activities (e.g., physical alteration of habitat, releases of chemicals such as metals and other inorganic constituents as part of the mining operation). Wetlands, for example, are frequently impacted by mining activities. Within an ecological assessment for a wetland, toxicity evaluations for representative species may be advantageous to the site evaluation, since these species could be exposed to complex chemical mixtures potentially released from the site. Amphibian species common to these transition zones between terrestrial and aquatic habitats are one key biological indicator of exposure, and integrated approaches which involve both field and laboratory methods focused on amphibians are critical to the assessment process. The laboratory and field evaluations of a wetland in western Montana illustrates the integrated approach to risk assessment and causal analysis. Here, amphibians were used to evaluate the potential toxicity associated with heavy metal-laden sediments deposited in a reservoir. Field and laboratory methods were applied to a toxicity assessment for metals characteristic of mine tailings to reduce potential “lab to field” extrapolation errors and provide adaptive management programs with critical site-specific information targeted on remediation.