bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress and Deformation of the Sandwich Panel Having Curved Faceplates Under Pressure Loading
Authors: Akasaka T , Asano K
Published: December 2008

An analytical and experimental study is conducted on the stress and deformation of a pressurized square sandwich panel, simply supported by four corner hinges. This panel is constructed with a pair of curved faceplates of stainless steel and foam plastics core together with a reinforcing side frame. This is expected to be available for a lightweight roof panel of huge frame architecture like a gymnasium by virtue of its prominent ability in withstanding the pressure load due to the shell effect of curved faceplates in addition to the sandwich effect. In this analysis, we used the extremum principle of total potential under the subsidiary conditions of boundary and symmetry for displacement functions. Good agreement is obtained between the theoretical and the experimental results of strains and deflections.
Fabrication of Silicon Carbide Fiber-Reinforced Aluminum Composites
Authors: Kohara S , Muto N
Published: December 2008

A fabrication method for silicon carbide (SiC) fiber-aluminum composites was investigated. An SiC fiber manufactured from an organosilicon polymer was used, and the combination of slurry impregnation and hot pressing was adopted in the present study. The method was improved so as to control the volume fraction of fibers in the fabricated composites. The composites with high fiber content were achieved by means of this method. During the fabrication process, degradation of the SiC fibers was observed. The addition of silicon to the aluminum matrix was effective in reducing the degradation. However, the complete prevention of the degradation of SiC fibers could not be achieved by silicon alloying.
Fiber-Matrix Reaction Zone Growth Kinetics in SiC-Reinforced Ti-6Al-4V as Studied by Transmission Electron Microscopy
Authors: Rhodes CG , Spurling RA
Published: December 2008

Fiber-matrix reaction zone product formation and growth kinetics at 850 and 900°C in silicon carbide (SiC) reinforced Ti-6Al-4V have been studied by thin-foil transmission electron microscopy. The major reaction product is titanium carbide, which is sandwiched between a layer of Ti5Si3 and a fine-grained mixture of titanium carbide and Ti5Si3. The large volume fraction of titanium carbide compared to titanium silicide results from the presence of a carbon-rich layer at the surface of the fibers. Growth of the reaction zone and consumption of the fiber surface layer are nonuniform, with greater reaction occurring where the fiber contacts beta phase in the titanium matrix. During exposure at 850 and 900°C, the reaction products exhibit parabolic growth, with the titanium carbide growing at a faster rate than the titanium silicide. After consumption of the carbon-rich fiber surface layer, however, the titanium silicide growth rate increases over that of titanium carbide. Reaction zone growth rate and fiber surface layer consumption rate are faster at 900°C than at 850°C.
An Experimental and Theoretical Approach to Rock Deformation at Elevated Temperature and Pressure
Authors: Brodsky NS , Getting IC , Spetzler H
Published: December 2008

Specimens of Westerly granite have been tested to failure in triaxial compression during investigations of strain rate and temperature-dependent deformation within the brittle regime. We have used a method of specimen pretreatment that enables more accurate measurement of temperature dependent deformation caused by thermally activated crack growth under applied load. Thermal cycling of Westerly granite before testing to failure modifies the form of the stress-strain curve obtained.

In modelling our experimental results we find stress corrosion and a fracture mechanics approach for evaluating crack-tip stresses adequate to explain time-dependent phenomena. To reasonably predict temperature and confining pressure dependent deformation, we must include additional constraints such as frictional characteristics or perhaps plastic deformation mechanisms.
Measurement of Thermal Conductivity and Thermal Expansion at Elevated Temperatures and Pressures
Authors: Van Buskirk R , Enniss D , Schatz J
Published: December 2008

Laboratory procedures and equipment have been developed to measure thermal response of rock under a simulated in situ environment of overburden stress, pore fluid pressure, and temperature. Routine tests are conducted up to 250°C, with stress levels to 100 MPa, on basalt, shale, tuff, and sandstone. High-pressure high-temperature use of the transient “needle-probe” heat source technique for the measurement of thermal conductivity is discussed. Considerations in the design of the thermal expansion apparatus, which maximize stability and minimize error, are included.

Laboratory procedures used, calibration techniques, and overall accuracy of the testing are reviewed. Thermal conductivity and thermal expansion are measured on equipment calibrated by using fused quartz as a standard. Uncertainty of calibrations caused by some inconsistency in published values for fused quartz is discussed. Methodical specimen preparation, frequent calibrations and computer test control, and data reduction allow accuracy to be maximized and relatively long-term tests to be conducted with a high degree of repeatability.

Where possible, results of the tests are compared with previously published values. A suite of data obtained in support of studies on a potential nuclear waste repository in tuff is examined. Comparisons of theoretical thermal conductivities and expansions, derived from the behavior of the mineral constituents of the rock, and the measured responses are made.

The advantages of these systems lie in the relative ease by which specimens may be tested at elevated temperatures and pressures, and the repeatability of the results. The accuracies (which are dependent upon calibration accuracies) are well within the range of engineering investigations.
Experimental Design Considerations
Authors: O'Neil JJ
Published: December 2008

Consensus protocols, used in common by different research laboratories, have been proposed as a means of making clinical research data across different laboratories directly comparable for purposes of determining the no-effects level of inhalation exposure to air pollutants in man. Such consensus protocols appear attractive to some, and they may be helpful for a limited number of studies, for example, if investigators from several laboratories wished to collaborate on a common research problem requiring a broad-based approach or to provide a means of concentrating differing skills or techniques available at several laboratories to attack a specific question. However, there is a larger body of research that would potentially be inhibited by the imposition of consensus protocols. Mechanistic studies, designed to address questions of how pollutants act, would probably be difficult to design effectively under consensus guidelines since they may require specialized exposure, exercise, or study conditions. Indeed, studies into the mechanism of pollutant action are likely to be of the greatest use to end-users (in this case, program officers and regulators), since studies of this nature provide health effects data and information on the significance of the response to an inhaled pollutant. Hypothesis testing should not be driven by design considerations. On the contrary, experimental and statistical design should be appropriate for and determined by the hypothesis being tested.
Clinical Research Insights into the Pathogenesis of Chronic Lung Disease
Authors: Bromberg PA
Published: December 2008

The problems inherent in studying the pathogenesis of chronic lung disease in human subjects in relation to inhaled air pollutants are discussed. The automatic rejection of findings of reversible airways changes as a significant health effect of acute pollutant inhalation is suggested to be unjustified, and an analogy with cigarette smoke inhalation is discussed. The author suggests that future clinical studies of air pollutant effects should emphasize response parameters, such as inflammation, which have amplifying potential. Recent studies of ozone effects are cited in this connection. The usefulness of nasal epithelium and of cultured human respiratory cells as models is noted. Finally, the hope is expressed that clinical air pollutant research will remain in the mainstream of our understanding of human lung biology.
Statistical Considerations in Designing, Analyzing, and Reporting of Clinical Pulmonary Studies
Authors: Van Ryzin J
Published: December 2008

This paper presents a review of some statistical issues that arise in the design, analysis, and reporting of clinical pulmonary studies which are to be used for ambient air quality standard setting.
A Small-Scale System to Evaluate Anti-Foam Performance
Authors: Frank R , Hazen JL
Published: December 2008

Foaming is a widely observed phenomenon in manufacturing and product-filling and in dilution of agricultural chemicals. Foam generation should be avoided, however, since time and container volume are limited. Antifoam agents are designed to minimize foam-related trouble when used in the formulation as a processing aid or a spray-tank defoamer. This paper describes the design of simple equipment which allows easy laboratory-scale evaluation of defoamers for liquid systems.

The principle is as follows: A calculated amount of water at given pressure is added to a certain volume of formulation through a specially designed nozzle. After generation of foam, its initial volume and decomposition rate are measured versus time. This system allows very simple testing of the influence of defoamers on liquid systems. It requires only a very small amount of material and it quickly yields accurate results relating to real-life conditions.
Evaluation of Plant Growth Regulators
Authors: Armstrong TF
Published: December 2008

In recent years, interest in plant growth retardants (PGRs) for use on turfgrass has been very high. This interest has occurred because of the availability of some new experimental compounds, increases in fuel and labor rates, and the desire for people to have more recreation time. In the past, turfgrass PGRs were primarily foliage-absorbed compounds; however, the identification of root or crown absorbed experimental compounds (such as MON-4620) has created a renewed interest in the evaluation and potential use of a PGR on turfgrass.

This paper presents an overview of Monsanto's development efforts to identify and implement turfgrass PGR evaluation parameters, and it discusses the need to standardize these evaluation parameters with both chemical industry and university researchers.
Development of Toxic Baits for Control of Imported Fire Ants
Authors: Banks WA , Lofgren CS , Williams DF
Published: December 2008

Toxic baits for control of the red and black imported fire ants, Solenopsis invicta Buren and S. richteri Forel, respectively, were developed by incorporating an effective toxicant into a liquid food material and absorbing this into a granular carrier for distribution in the field. Screening tests with worker ants and laboratory colonies showed that of more than 4400 chemicals tested only three primary toxicants and four insect growth regulators demonstrated promise for control of field populations of the fire ants. Effective bait formulations that gave good control of the ants were produced by incorporating the amidinohydrazone toxicant, AC-217300, or the insect growth regulator, Prodrone, into soybean oil and impregnating the oil solution onto pregel defatted corn grits.
An Inexpensive, Multiple-Experiment Monitoring, Recording, and Control System
Authors: Meyn DA , Moore PG , Bayles RA , Denney PE
Published: December 2008

Strip chart recorders and data loggers have numerous shortcomings for monitoring sustained-load cracking (SLC) and fatigue tests, principally because they record at fixed rates. During a long test this affords low resolution during rapidly changing events and creates large amounts of mostly useless data. For over two years the authors have used a personal computer to monitor tests and record data for SLC and fatigue experiments. The computer stores specimen identification and test parameters, converts raw data into usable form, displays current test status, notes and acts on various test status parameters, periodically stores significant data on a floppy disk system, and automatically terminates tests as specified by the operator. The decision-making capability of the computer greatly reduces the amount of nonsignificant data to be stored while permitting more rapid data acquisition when the signals begin to change rapidly. A fast-switching battery-inverter system provides standby power for up to two and a half days in the event of power failure. If both primary and standby power fail, the computer's autostart feature allows it to resume data collection when power resumes.

The use of BASIC permits software to be produced in-house and allows revision as operational needs change. The input routines, start-up, and running of experiments are completely interactive, and designed to prevent omissions and errors by the operator. Presently four experiments can be conducted simultaneously, but a newly acquired 16-channel, 12-bit analog-to-digital converter will allow for considerable expansion. Because system response is inadequate to measure and record fatigue load signals directly, they are filtered to produce an average value which is recorded. The analysis of data stored on disk files is done using another personal computer to avoid interference with data acquisition. A unique feature of the analytical method is the use of the decrease in load with increasing crack length in the stiff, displacement-controlled test configuration to calculate crack lengths, instead of using a clip gage across the notch.
Krak-Gages for Automated Fatigue Crack Growth Rate Testing: A Review
Authors: Liaw PK , Logsdon WA , Roth LD , Hartmann H-R
Published: December 2008

Bondable Krak-gages were utilized to monitor fatigue crack growth rates (FCGR) of various steels in air and salt water at 24°C and in wet hydrogen at 80°C. The FCGR data generated via bondable Krak-gages were consistent with those generated via either the compliance technique or optical measurements. Moreover, Krak-gages were effective in monitoring short crack extension.

Using atomic fusion technology, Krak-gages were sputtered on specimens so as to perform high-temperature (288 and 427°C) FCGR experiments. The FCGR results obtained with the sputtered Krak-gages were in good agreement with those obtained by the compliance method.

The Krak-gages were found to be a valuable addition to fracture mechanics testing. They readily interface with computers for fully automated FCGR experiments.
Evaluation of Thermal Conductance of Liquefied Natural Gas Tank Insulation
Authors: Brendeng E
Published: December 2008

The activities in testing of liquefied natural gas (LNG) insulation of The Division of Refrigeration Engineering at the University in Trondheim were initiated by the need for a satisfactory insulation system for the spherical tank LNG carriers of Moss Rosenberg Verft. A large scale guarded hot plate apparatus has been built, with test area 2 by 3 m2. The temperature on the cold plate may be 0 to –162°C, and on the warm plate 30 to –30°C. Measurements may be made in horizontal convection-free mode, and in vertical convection mode.

A load-bearing evacuated insulation may be a possible solution in the efforts to reduce the boil-off of the tank content. A heat flow meter apparatus for testing evacuated insulations under load has been built, with diameter of the specimen 400 mm, and thickness up to 100 mm.
Use of a Heat Flow Meter Apparatus for Testing Loose-Fill Materials Prepared for Laboratory Testing
Authors: McCaa DJ
Published: December 2008

The use of loose-fill type attic insulation is increasing, and the requirement for manufacturers to test their products has also increased along with production. This paper discusses some of the critical parameters involved in testing loose-fill materials using a heat flow meter apparatus. It is shown, in studies conducted to characterize a material, that many of the sample preparation variables must be fixed.
Recent Developments with the Thin-Heater Thermal Conductivity Apparatus
Authors: Hager NE
Published: December 2008

A thin-foil heating element is employed in a thermal conductivity apparatus that operates in accordance with the basic concept of the guarded hot plate. The metal foil is sufficiently thin that lateral heat flow along the plane of the heater is insignificant, at least in the central region, so there is no need for isolation and separate temperature control of a guard region. This makes the apparatus simple and inexpensive to construct and operate. The resultant low-mass configuration minimizes drift error and usually reaches steady state in less than 30 min with 0.5-cm-thick specimens of nonmetallic solids. Thermal conductivity values are calculated on an absolute basis with an estimated accuracy of ±3%.

Speed and simplicity make the apparatus well suited for product-development and quality-control applications. Because temperature differences within the sample do not exceed a few degrees, uncertainty in mean sample temperature is sharply limited, water-vapor-migration problems are minimized, and thermal conductivity can be measured close to melting points or other critical temperatures. New data obtained with dry calcium silicate give preliminary experimental verification of the validity of the apparatus in the temperature range extending between ambient and 550 K.
Research in Calibration and Application Errors of Heat Flux Sensors
Authors: van der Graaf F
Published: December 2008

The influence of the presence of a built-in heat flux sensor on local heat flux has been studied.

Starting with the definition of a calibration value for the heat flux sensor (the intrinsic calibration value), this influence is described and expressed in measurement errors. The influence is considered to result from two separate and well-recognized effects, namely, the change in thermal resistance and the heat flux deflection. This splitting up has been proved correct by both experiments and calculations. A satisfying agreement between the methods was found.

The importance of a well-dimensioned guard ring, dependent on parameters such as thermal conductivity and dimension, is apparent. Finally, rough guidelines for the design of “low-error” heat flux sensors and a basic calibration method are given.
A New Type of Heat Flowmeter for Application and Study of Insulation and Systems
Authors: Degenne M , Klarsfeld S
Published: December 2008

Greater and greater use is being made of the heat flowmeter for laboratory and in situ measurements of materials and systems. Two new types of flowmeters are described: (1) with junctions arranged in two parallel planes and (2) with coplanar junctions.

Through metallization and photoetching, as employed in printed circuits, it is possible to achieve relatively slim and sensitive “intergrating” heat flowmeters that offer a large surface area and excellent uniformity.
Determining the U-Value of a Wall from Field Measurements of Heat Flux and Surface Temperatures
Authors: Modera MP , Sherman MH , Sonderegger RC
Published: December 2008

Thermal conductances (U-values) and thermal resistances (R-values) are discussed throughout the literature as the appropriate parameters for characterizing heat transfer through walls. Because the quoted numbers are usually determined from handbook values of material properties, they have several drawbacks: (1) they do not take into account degradation effects, (2) they ignore construction irregularities, and (3) they do not take into account multidimensional heat flow. This paper examines the use of field measurements of heat flow and surface temperatures to determine the U-values of walls. The effects of thermal mass on measurements of wall U-values are described in detail, using two data interpretation techniques to estimate the U-values of insulated and uninsulated cavity walls, with and without brick facing. The errors in U-values estimation are determined by comparison with an analytical model of wall thermal performance. For each wall, the error in the U-value determination is plotted as a function of the test length for several typical weather conditions. For walls with low thermal mass, such as fiberglass-insulated cavity wall, it appears that, under favorable test conditions, a 6-h measurement is adequate to measure the U-value within about 10% uncertainty. For masonry walls, the measurement time required is considerably longer than 6 h. It is shown that for masonry walls, and in general, the optimal measurement time is a multiple of 24 h because of the effects of diurnal weather fluctuations.
Microindentations in Metals
Authors: Samuels LE
Published: December 2008

The mechanisms involved when an indentation is made in the surface of a metal by a blunt indenter have received a good deal of attention, but little of this work has appeared in publications that might easily come to the attention of those who actually carry out hardness tests. Even less of the work has been analyzed for its implications in practical hardness testing. The main models of indentation which have been proposed to date are reviewed, with particular attention to the one that most closely relates to the realities of hardness testing. This model, developed by Mulhearn, proposes that indentation occurs by radial compression, the formation of the indentation being likened to the expansion of a hemispherical cavity. The implications of this model to indentation hardness testing, and specifically to microindentation testing, are considered. This involves consideration of the current status of views on the effects of indentation size on the apparent hardness number.
Stress and Load Dependence of Microindentation Hardness
Authors: Vitovec FH
Published: December 2008

The effect of the test load on the sensitivity to stress of the diamond pyramid hardness (DPH) was investigated on a martensitic spring steel, a Type 304 stainless steel, and an aluminum bronze with duplex microstructure. For this purpose, a loading frame and load cell of 1200-N capacity were fitted to the microhardness tester, which provided for application of uniaxial tensile loads to a flat test specimen. The test materials were heat treated differently and had different surface preparations, ranging from polished before vacuum annealing to electropolished following the annealing treatment.

Within the load range of 15 to 500 gf, the hardness increased in most cases to a peak from which it leveled off to a more or less constant value as the test load increased. Applied uniaxial tensile stresses did not change this trend except when plasticity initiated. In general, the hardness decreased linearly with increasing applied tensile stress. The rate of decrease was independent of the load for the hardness measurement. Yielding affected the hardness sensitively, particularly at small loads, thus changing the trend of the effect of applied stress on hardness as well as the hardness-load relation. Surface films or residual stresses do substantially affect the hardness-load relationship and the trend of the stress effect.
Review of Scratch Test Studies of Abrasion Mechanisms
Authors: Kosel TH
Published: December 2008

The use of scratch tests to simulate the material removal mechanisms which occur during abrasion is reviewed. Although useful studies of the effect of the rake angle on material removal have been carried out using diamond tools, closer simulation of the mechanisms of material removal can be obtained using actual irregular individual abrasive particles as scratch tools.

Previous studies are reviewed in which scratch tests have been performed with both conventional scratch test instruments and a specially designed system used for in situ scratch tests in the scanning electron microscope (SEM). Multiple-pass scratch tests over the same scratch path have been shown to create surface features and wear debris particles which are very similar to those produced by low-stress abrasion. Alumina (Al2O3) particles have been shown to produce continuous micromachining chips from the hard, brittle carbide phase of Stellite alloys, establishing direct cutting as the important mechanism of material removal for this type of abrasive. An in situ study of material removal from white cast irons by quartz particles has provided conclusive evidence that carbide removal does not occur by direct cutting but rather always involves microfracture.

Previously unpublished work which has compared scratch tests with crushed quartz and alumina particles is included. Also described is a new scratch test system which controls the depth of cut rather than the scratch load in order to simulate high-stress abrasion, in which abrasive particles are constrained to a fixed depth of cut. Preliminary new results show substantially different carbide fracture behavior under fixed-depth conditions.
Quality Assurance of Flexible Plastic Pipes for Hot-Water Service
Authors: Skarelius J
Published: December 2008

A common way to express the durability of a plastic material is to present a long-term strength diagram for different temperatures for well made straight pipes. In the case of materials for hot-water pipes, the testing time must be longer, and the tests must also be completed with bent and notched pipes, and tests in water completed with additives reducing the surface tension. Examples and test methods are given in the paper. Comparisons between testing with water or air outside the pipes at high temperatures are also made.

A way to measure the thermostability and lifetime of a material or product is to use induction time in differential thermal analysis (DTA) or differential scanning calorimetry (DSC). This method must be used with greatest care and only together with other long-term tests. The use of Arrhenius plots at high temperatures to predict lifetimes of pipes is not helpful. Examples are given in the paper.

DTA or DSC induction tests are however very useful in production control and in, for example, testing of antioxidants resistance to extraction into water. When the type tests mentioned above have secured the possibility of a long service life of the material, the quality control methods (short-term production control tests) shall ensure that production quality is the same as the type tested quality. The correspondence between long- and short-term tests must then be proven. The paper will also deal with these questions.
Studies of Stress-Corrosion Cracking Behavior of Surgical Implant Materials Using a Fracture Mechanics Approach
Authors: Bundy KJ , Desai VH
Published: December 2008

Results of stress-corrosion cracking (SCC) studies of surgical implant materials that have employed a fracture mechanics type of specimen are presented. The behavior of Type 316L stainless steel and Ti-6AI-4V ELI in a number of different environments has been examined. Tests have been performed in boiling 44% magnesium chloride solution (154°C), 5% hydrochloric acid (37°C), and physiological saline solution (37°C). Crack propagation velocity versus stress intensity curves have been obtained. Plateau velocities and threshold stress intensities have been determined. Some specimens were tested under open circuit conditions. Others were potentiostatically polarized with applied potentials similar in magnitude to those that can be generated by bioelectric effects in vivo. Propagation of stress corrosion cracks in Type 316L in physiological saline solution at 37°C was observed in situations where there was a high stress intensity and a passive film that had been disrupted by polarization.
Mechanical Properties and Structure of Ti-6Al-4V with Graded-Porosity Coatings Applied by Plasma Spraying for Use in Orthopedic Implants
Authors: Hahn H , Lare PJ , Rowe RH , Fraker AC , Ordway F
Published: December 2008

The object of this work was to determine mechanical properties of implants with graded porous coatings without reference to the properties of the ingrown bone. Optimum strength of a bone/implant interface consisting of porous metal and ingrown bone requires a gradation from base metal to the original bone. The composite metal-bone interface can be obtained by applying a metal coating of graded porosity, varying from near zero at the substrate surface to more than 50% at the outermost layer, on the original implant. Graded porous coatings of titanium or Ti-6Al-4V were obtained by plasma spraying of selected particle size fractions in three layers of successively decreasing density, the top coat being made with 300 to 850 μm powder. Tensile and shear strengths of the coatings were determined by cementing coated samples face to face with an adhesive resin to simulate ingrown bone. Data from these tests are given. Shear strength values ranged from 5.6 to 9.9 MPa (815 to 1430 psi) and tensile strength values were 5.1 to 25.5 MPa (745 to 3700 psi). Failure occurred within the porous coating and not at the interface between the substrate and the coating. Corrosion fatigue tests in Hanks' solution at 37°C (98.6°F) and a pH of 7.4, with a cyclic, fully reversed, peak torsional shear strain of ±0.01, gave lifetimes comparable to or better than those reported for mill-annealed Ti-6Al-4V, except for the samples that had been sintered.
Ultrastructural Examination of In Vitro and In Vivo Cells Exposed to Elements from Type 316L Stainless Steel
Authors: Lucas LC , Bearden LJ , Lemons JE
Published: December 2008

The ultrastructural features of in vivo and in vitro cells exposed to Type 316L stainless steel corrosion product solutions were examined. The in vivo cells were from fibrous tissue capsules formed around stainless steel rods implanted in the back muscles of New Zealand white rabbits. Aqueous solutions of the stainless steel alloy were injected at the implant-to-capsule interface to increase the concentration of alloy constituents bathing the tissues. The in vitro cells were cultured human gingival fibroblasts also exposed to stainless steel solutions of similar concentration. The ultrastructural features of both in vitro and in vivo cells were examined by transmission electron microscopy.

The following observations were made for both the in vitro and in vivo cells:

1. The severity of the cellular response increased when the concentration of the solutions of stainless steel exposed to the cells increased.

2. As the severity of the cellular response increased, the cells showed a decrease in rough endoplasmic reticulum, an increase in cytoplasmic vacuolation with altered organelles, a more diffuse plasma membrane, and a decrease in cellular organization.
Degradation of Polyester Arterial Prostheses: A Physical or Chemical Mechanism?
Authors: King MW , Guidoin R , Blais P , Garton A , Gunasekera KR
Published: December 2008

Despite earlier claims of biological stability, there is growing evidence from case histories, in vitro testing, and implant retrieval programs that poly(ethylene terephthalate) fibers experience some degradation when implanted in humans as arterial prostheses.

Previously, this was of minor significance when prognoses were of limited duration. Today these devices are being implanted in a wider spectrum of patients with the expectation of longer service lifetimes. There is growing urgency, therefore, to identify the rate and cause of this degradative behavior.

The authors have previously reported a progressive loss in the bursting strength of commercial polyester arterial prostheses with increasing times of implantation in humans. They have suggested that physical factors, such as the changes in the geometry of the knitted and woven structures have contributed to this loss of mechanical performance. This paper reports additional findings from an implant retrieval program. After residency periods from a few hours to 14 years, the chemical properties of the explanted devices have been analyzed. The results are compared with those from unused controls in order to determine the nature and extent of the chemical changes to the polymer during implantation. Losses in bursting strength are accompanied by losses in molecular weight and increases in carboxyl group concentration, suggesting that a chemical mechanism is also responsible for the degradative process. The kinetics of this chain scission reaction approximate a logarithmic decay model rather than that expected from autocatalytic initiation or a simple random or end-group mechanism with or without diffusion control of the initiator. It is estimated that 25% of the initial bursting strength is lost after 162 ± 23 months and 25% of the initial molecular weight is lost after 120 ± 15 months of implantation in humans.
Clean Water Act Update: A New Role for Toxicology
Authors: Wise PL
Published: December 2008

Implementation of the Clean Water Act started with development of water pollution controls using the tools of engineering and mathematical modeling. As implementation of the act has evolved, however, we have come to recognize the importance of toxic pollutants and that we need new and different methods, toxicological methods, to analyze toxic pollution and to set cost-effective toxic effluent controls. To deal with this new challenge, we have over the past year begun to put together an approach for regulating toxic effluents. Although a regulatory policy is now in place, implementation of that policy is just beginning. We have little experience in using toxicological methods and tests for regulating effluents, yet we need to make this new regulatory approach work. We need the help of the scientific community of toxicologists, and we need it now—to develop toxicological tools that can be used in the cost-effective analysis and control of toxic water pollution.
What Industry is Doing to Protect Aquatic Life
Authors: Alexander HC , Quick JA
Published: December 2008

Much of the chemical industry has had long-term environmental involvement and commitment. The hazard evaluation process is being used by industry to evaluate its products, by-products, and waste for potential environmental effects. Fate and effects testing are the core of this process and provide the data for estimating hazards. The adverse environmental impact of wastes is minimized by recycling or reuse, chemical or biological treatment, high-temperature incineration, and secure landfilling. Biomonitoring and field surveys assess the environmental impact of effluents and product applications. Industry is concerned about the proper use, safe handling, and environmental impact from product use and disposal.
Research Needs in Developing Structure Activity Relationships
Authors: Lipnick RL
Published: December 2008

A short historic overview of the development of quantitative structure activity relationships (QSARs) is presented. Applications of QSARs to problems in environmental toxicology and hazard assessment are reviewed. A number of research needs related to QSAR are identified including: (1) research to quantify the effects of metabolism on a bioconcentration QSAR model, (2) research to determine the upper boundaries of linearity for the bioconcentration QSAR for hydrophobic chemicals, (3) research to refine the understanding of the predictive limitations of the QSAR for acute toxicity of simple nonelectrolytes to aquatic organisms, (4) research to identify additional classes of non-electrolytes that exhibit increased toxicity caused by more specific mechanisms of binding to biological receptors, and (5) research involving investigations of fundamental mechanisms of toxicity.
Comparison of QSAR Predictions with Fish Toxicity Screening Data for 110 Phenols
Authors: Lipnick RL , Bickings CK , Johnson DE , Eastmond DA
Published: December 2008

A comparison was made between the predicted 96-h guppy LC50s of 110 phenols based upon QSAR equations of Saarikoski and Viluksela and the data from 936 toxicity screening tests for these chemicals. Test data on up to eight species of freshwater fishes were available per compound. Overall, the experimental toxicity data on these chemicals were consistent with the QSAR predictions. The 110 phenols occupy a considerably larger range of spanned substituent space than the QSAR training set. One compound, 4-aminophenol (14), exhibited lethality at test concentrations of 35 times below that predicted. The increased fish toxicity of this compound is explained in terms of a proelectrophile molecular mechanism, in which the parent compound is metabolically oxidized to a para quinoid structure. The resulting electrophilic metabolite is susceptible to attack by nucleophilic moieties present in biological macromolecules leading to covalent bond formation and inhibition of biochemical processes.
Rapid Aquatic Toxicity Assay Using Incorporation of Tritiated-Thymidine into Sea Urchin, Arbacia punctulata, Embryo: Evaluation of Toxicant Exposure Procedures
Authors: Nacci DE , Jackim E
Published: December 2008

Toxicity of substances in seawater was measured using growth inhibition of embryonic sea urchins during a short period after fertilization. Growth of Arbacia punctulata embryos was monitored by incorporation of tritium-labeled thymidine, a nucleoside incorporated into newly synthesized deoxyribonucleic acid (DNA). Sensitivity and ranking ability of this rapid Arbacia embryo test were judged by comparison of toxicity values for several organic industrial chemicals using this test and two standard acute aquatic toxicity tests. Median effective toxicity values (EC50 values) for early embryos compared favorably to median lethal values (LC50 values) obtained in standard acute toxicity tests using Pimephales promelas (fathead minnow) and Daphnia magna (water flea).

This paper presents a comparison of toxicant exposure procedures using the Arbacia embryo thymidine incorporation test. Toxicant exposure began before, at the time of, or after fertilization and continued for 4 h following fertilization. In addition to the eight organic chemicals tested for comparison to acute toxicity values for other species, several chemicals with embryotoxic potentials (tumor promoters and teratogens) were tested to determine differential sensitivities of exposed life-stages: unfertilized egg, fertilization, and early embryo. EC50 values for any one substance were not significantly changed by exposure modification. Toxicity values for exposures that included fertilization as well as early embryo growth were at least as sensitive as post-fertilization exposure values for all compounds tested except one. Because of technical ease and potential sensitivity, toxicant exposure that includes fertilization as well as early embryo growth (but not unfertilized egg exposure) is recommended for future testing.

Additional development, refinement, and standardization of this fertilization and early embryo test should further increase its utility in toxicity testing. Because this test requires only 4 h to exposure and can be correlated with standard measurements of toxicity, it could be used in early stage hazard evaluation in conjunction with other aquatic bioassays.
Acute and Chronic Toxicity to the Fathead Minnow, Pimephales promelas, of Effluents from a Treatment Plant Receiving Dye and Pigment Processing Wastewater
Authors: Pickering QH , Shaul GM , Dostal KA
Published: December 2008

Ninety-six hour, static acute, and continuous-flow early life-stage (ELS) chronic toxicity tests, using the fathead minnow (Pimephales promelas), were conducted to evaluate the toxicity of effluents from a pilot scale activated sludge (AS) treatment system receiving dye and pigment wastewater. In the first test with a powdered activated carbon (PAC) dosage of 1800 mg/L of influent, survival was the most sensitive measure of effect in the ELS test. The highest effluent concentration tested (10%) was lethal to the embryos and larvae. No adverse effect on survival or growth was observed at lower effluent concentrations (5.0 to 0.63%). The maximum acceptable toxicant (effluent) concentration (MATC) was between 10 and 5%. Ten 96-h median lethal concentration (LC50) values from static acute tests ranged from 12.9 to greater than 80%. In the second test at a PAC dosage of 1000 mg/L of influent, growth was the most sensitive measure of effect in the ELS test. Larval growth was significantly reduced at the highest effluent concentration tested (20%). The MATC was between 20 and 10%. Seven 96-h LC50s from static acute tests ranged from 28.3 to greater than 80%. The effluent from the treatment system receiving the higher PAC dosage of 1800 mg/L was more toxic than the effluent from the treatment system receiving the lower PAC dosage of 1000 mg/L. However, the influent to the treatment system receiving the higher level of PAC also was more acutely toxic.
Electrochemical Impedance Tests for Protective Coatings
Authors: Mansfeld F , Kendig MW
Published: December 2008

The experimental approach for carrying out electrochemical impedance measurements for coated metals is described. Models for the impedance behavior have been developed for different coating systems, and methods for the analysis of experimental impedance diagrams in terms of coating and interface properties and their changes during exposure to corrosive environments are discussed. The systems studied include polybutadiene coatings on bare and conversion coated steel and aluminum alloys, commercial chromate conversion coatings on aluminum alloys and sulfuric acid, or chromic acid anodized aluminum alloys. For the anodized aluminum alloys, suggestions for development of a quality control test are given.
Corrosion Testing in Potable Water
Authors: Nielsen K
Published: December 2008

Corrosion in potable water varies greatly depending upon the water composition. The most important factors are oxygen content, pH value, temporary hardness, chloride, sulfate, and conductivity. To be able to carry out tests of corrosion resistance, thorough knowledge of corrosion processes of the individual metals and alloys in supply water is required. This is important in order to identify the most deleterious combinations of the relevant factors. Testing must take place as a combination of field tests and laboratory tests. Not only methods for testing materials are required in the efforts to prevent corrosion but also methods for testing water types. The actual corrosion also depends on design and performance of the individual parts and the complete pipe system. Where it is not possible to control the corrosion, easy replacement of the pipes must be ensured. An account is given of corrosion and corrosion testing of the commonly used materials galvanized steel, copper, and brass and of soldering metals, also in relation to metal pickup. This paper reviews the use of test methods to control different corrosion types in tap water systems and describes recent developments in this field at the Danish Corrosion Centre.
A Comparison of Actual and Estimated Long-Term Corrosion Rates of Mild Steel in Seawater
Authors: Bogar FD , Peterson MH
Published: December 2008

The linear polarization resistance method of predicting corrosion behavior was compared directly with weight loss measurements on freely corroding specimens. The estimated weight loss was obtained by calculation from the corrosion current and the polarization resistance. The anodic Tafel constant βa was determined from potentiodynamic curves for mild steel in flowing, oxygen containing, natural seawater. The cathodic Tafel constant βc was calculated by substitution of the corrosion current, the anodic Tafel constant, and the polarization resistance into the Stern-Geary relationship. In subsequent experiments, βa = 0.066 V/decade and βc = 0.077 V/decade were used in all calculations. Although an initial agreement between estimated and actual corrosion rates existed for periods of up to 60 days, long-term studies began to produce “anomalous” data in about 120 days. It was observed empirically that the polarization resistance was semilogarithmically related to the scan rate over three orders of magnitude from 0.001 to 1 mV/s.
Vacancy Properties During Irradiation with High Energy Particles
Authors: Schüle W
Published: December 2008

Results of investigations of radiation enhanced diffusion on copper-15at% aluminum alloys are reported where the electron flux, the irradiation temperature, and the thickness d of the specimens are varied. The activation energy of ordering or of diffusion is Qirr = 0.355 eV for an electron current density of 4.25 μA cm−2 almost independent of d. Qirr increases slightly with decreasing flux, and Qirr = 0.377 eV is found for 0.04 μA cm−2 and 0.1-mm-thick specimens. This behavior is in agreement with the assumptions that (1) the migration energy of vacancies EM1V decreases with increasing flux and (2) interstitials have to jump about 30 times more often than vacancies in order to change the degree of order by the same amount. It is further found that small sink concentrations cause an acceleration of the ordering rate rather than a decrease of this quantity through an increase of the mobility of the defects.

In copper-aluminum alloys almost no sinks for point defects are formed during irradiation; thus defects annihilate mainly by pair recombination even at low irradiation temperatures in contrast to results obtained for many other alloys.
Quantitative Study By Field Ion Microscopy of Radiation Damage in Tungsten After Proton and Neutron Irradiation
Authors: Farnum DJ , Sommer WF , Inal OT , Yu J
Published: December 2008

The defects that result from proton and neutron irradiation of tungsten were studied using a field ion microscope. The initial stages of radiation damage can be examined by noting the configuration, density, and type of defect. This study used medium-energy protons as well as a spallation neutron flux for the irradiation.

Annealed tungsten was examined in the field ion microscope in both an unirradiated and irradiated condition. Irradiations were conducted using protons and spallation neutrons at the Los Alamos Meson Physics Facility (LAMPF). Temperature was controlled in the proton irradiations (by water cooling) to less than 323 K. The temperature for the neutron irradiations was measured at 398 K. The concentration of vacancies that survived recombination and were observed with the field ion microscope were 1 to 3% of the calculated displacements per atom (dpa). The remainder are suspected to have undergone vacancy-interstitial recombination resulting from a fluence of 1022 and 1024 protons per square metre was observed to be 2.5 × 10−3 and 8 × 10−3, respectively. The neutron-irradiated samples contained a vacancy concentration of 4 × 10−3 after a fluence of 1023 neutrons per square metre. Depleted zones containing 1000 or more vacant lattice sites along with smaller zones containing from 30 to 300 vacant lattice sites were observed in the irradiated material. The shape of the smaller zones was irregular and elongated in at least one direction while the larger depleted volumes split into “nodes”.

Unirradiated samples of the same stock were examined for artifacts and defects. The calculated equilibrium vacancy concentration at 300 K is 10−50. Only one vacnacy and one small void volume were found in the unirradiated samples examined.

The data indicated that the number of vacancies increases with increasing fluence. The most numerous defect for both the proton and neutron irradiations was the single vacancy. Depleted zones were of two basic sizes, 30 to 300 vacant lattice sites or over 1000 vacant lattice sites.