bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
A Standard for the Intercommunication of Computers in a Flexible Manufacturing System
Authors: McEwen SM 
Published: December 2008

Typically the control architecture of a flexible manufacturing system (FMS), as part of an integrated manufacturing system (IMS), consists of a hierarchical structure of computers, most with differing duties and some with differing responsibility. At the lowest levels of the hierarchy are the FMS work stations or subsystems (machine tools, material handling system, chip handling system, etc.) and above that the FMS control computer (the host) with the general overseeing or management responsibility. The proper functioning of this control hierarchy requires the intercommunication of commands and data between the FMS control computer and the FMS subsystems. The controllers and computers used in FMSs are, however, manufactured by a number of different companies most, if not all, of which employ unique hardware plugs and electrical signal structures for communication of data from machine to machine. It is by way of this discussion that the need to develop and implement an FMS communication standard is justified.
The approach we have taken (and an outline for the paper) includes: (1) a survey of the difficulties in FMS intercommunication, (2) establishing the data that are likely to be transmitted within the FMS, (3) setting forth the framework for a communication standard that addresses points 1 and 2, and (4) describing current FMS industry efforts to design an FMS intercommunication standard.
Some Comments on the Crisis in Engineering and Engineering Technology Education
Authors: Merkel KG 
Published: December 2008

The maintenance of a high-quality technological base in the United States is dependent upon adequately funded engineering programs in American colleges and universities. At the current time, many American engineering educators feel that their academic programs are in a state of crisis with respect to adequacy of resources.
A number of foundations associated with large American companies (Exxon, IBM, Amoco, and others) have provided funds designed to aid engineering education. Funded programs at the national level have been proposed in Congress.
At the present time, the current level of funding is still inadequate. It will take a national technological crisis to improve this situation.
On-Line Ultrasonic Inside-Diameter Control System for Zircaloy Tube Etching
Authors: Tanaka Y , Komatsu M , Fujii N , Kubota H 
Published: December 2008

An ultrasonic inside-diameter (ID) control system was used during the final etching process for producing Zircaloy nuclear fuel cladding tubes. This results in establishing automatic inside-diameter control during etching with an automatic etching system.
In this system, the inside-diameter at the center point in the length of each tube is continuously measured with the ultrasonic inside-diameter measuring equipment during the etching process and the etching is automatically stopped by a signal from the control equipment when the inside-diameter reaches the target value.
This made the final etching process economical and suitable for large-scale production, having an equal or better level at the inside-diameter of tubes etched with this system than those made by a process controlled by an air-micrometer.
Flow Softening and Anneal Hardening in Two-Phase Zr-2.5Nb
Authors: Rizkalla AS , Choubey R , Jonas JJ 
Published: December 2008

The flow properties of Zr-2.5Nb were determined in the (α + β) range at 998 and 1148 K, which corresponds to about 15 and 85 volume % β. The flow stresses were determined in axisymmetric compression at constant true strain rates ranging from 3.1 × 10−5 s−1 to 3.1 × 10−2 s−1.
The flow curves were characterized by a peak stress followed by considerable flow softening and, for strain rates less than 10−3 s−1, the flow stress for the large β-fraction materials dropped by only 25 to 30% of the peak stress as compared with 50 to 70% for the predominantly α-materials. The amount of flow softening also decreased with increasing coarseness of the prior α-plate morphology.
The α-plates rotated from an initially random to a distinctly transverse orientation, and at strain rates less than 10−3 s−1, the α-plate structure broke up to produce an equiaxed grain morphology. The strain rate sensitivity concurrently increased from 0.22 to 0.4.
Significant anneal hardening was observed in the predominantly or fully α-region after a β-heat treatment, the amount of which increased with time of holding in the β-region. The activation energy was approximately 140 kJ/mole, which is similar to that for the diffusion of niobium in β-zirconium. The anneal hardening is ascribed to the formation of niobium-rich clusters in the β-phase. These clusters seem to be retained in the α-phase on cooling. Part of the flow softening in the anneal-hardened material can be ascribed to declustering by deformation.
On the Short-Time Recrystallization of Zircaloy-4 Above 600°C
Authors: Bäro G , Wessjohann HG , Nicoll AR 
Published: December 2008

Cold-worked and stress-relieved Zircaloy-4 with and without recrystallized grains (approximately 3%) was thermally shocked to temperatures between 600 and 800°C for up to 1, 10, 100, and 1000 seconds. The resulting changes in tensile properties at 343°C can be described very well using Hunt and Schulson's equation F=F0×exp{−2.08×1018×t×exp(−41550T)}
where
F = unrecrystallized fraction,
F0 = starting value of F,
t = annealing time, s, and
T = temperature, K.
With respect to in-reactor recrystallization it is argued that the activation energy of the recrystallization process under reactor conditions is as high as for unirradiated material, but that the driving force is altered because of the different defect structure due to the neutron flux. This may be described by introducing a fluence-dependent factor λ (φ) to be multiplied with the time t instead of a constant.
Orientation of Hydrides in Zirconium Alloy Tubes
Authors: Cheadle BA , Coleman CE , Ipohorski M 
Published: December 2008

The effects of crystallographic texture, grain size and shape, and tensile stress on the orientation of hydride platelets in Zircaloy-2, Zr-2.5Nb, and Excel tubes have been studied using transverse ring and longitudinal tension specimens.
When the α grains are equiaxed, the hydride platelets precipitate either at grain boundaries or on the basal plane. A sufficiently high tensile stress perpendicular to the basal plane will precipitate the platelets perpendicular to the stress.
When the grains are thin and elongated, the platelets precipitate along the grain boundaries. When the basal plane normals are close to a longitudinal axis of the grains, a sufficiently high stress will precipitate the platelets perpendicular to the stress and the platelets will cut across the grain boundaries.
Correlation Between Fabrication Parameters, Microstructure, and Texture in Zircaloy Tubing
Authors: Moulin L , Reschke S , Tenckhoff E 
Published: December 2008

Starting from the extrusion billet, different reduction sequences were used to fabricate tubing to the same final dimensions. The fabrication sequences varied in the reductions of area, wall thickness, and diameter and also in the number of rolling steps (five to three), corresponding to area reductions in the range from 38% to 90%. They included common reduction routines as well as experimental reduction procedures.
The microstructural properties and the corresponding textures were measured in each sequential pass for the as-rolled and for the annealed conditions, respectively.
The results show that the reduction parameters of the final step predominantly determine the microstructure and texture in the final tube. The parameters governing the texture development, such as the reductions in wall thickness, diameter, and area as well as the intermediate annealing conditions, are determined after each reduction step. Maximum intensities and spread of basal and prism pole orientations, f-factors, etc., describing the texture are correlated with the microstructural parameters, such as grain size, degree of recrystallization, and hardness.
After the final cold reduction step, different annealing temperatures were applied in order to follow up and correlate the changes in microstructure and texture for The final tube condition. The results of these measurements allow conclusions about the recrystallization kinetics, as a function of cold deformation, annealing temperature, and annealing time. Their correlation with the factors determining the texture, resulting from the investigated reduction parameters, lead to an understanding of the control and improvement of the properties of the final tube.
The Interpretation and Analysis of Upper Shelf Toughness Data
Authors: Ingham T 
Published: December 2008

The paper outlines the problems encountered in attempting to define a self-consistent upper shelf toughness data base for use in a generic study of the integrity of a light water reactor (LWR) pressure vessel. Multiple-specimen resistance curve JR data were examined to provide “best estimates” of static initiation fracture toughness Ki at temperatures corresponding to fully ductile upper shelf behavior. In some cases, this involved reassessment of published data. To provide information that should be typical of current commercial steel making practice, Ki temperature relationships were developed from a statistical analysis of those data for A533B-1 and A508-3 steels containing less than 0.010 weight % sufur.
Relatively few data exist for weld metals, but the available results indicated that the Ki temperature relationships derived for base metals should also be applicable when assessing the significance of defects located in welds of a modern LWR pressure vessel.
Lower bound slopes (dJ/da)LB to the available JR data for A533B-1 and A508-3 steels were also defined. These can be used in conjunction with the Ki temperature relationships to derive post-initiation toughness data for up to 2-mm crack growth. The data base was derived from linear JR analyses, and its relevance to upper shelf initiation toughness data derived from nonlinear (power law) JR analyses is considered. Different methods of estimating initiation toughness are discussed and proposals are made to simplify the interpretation of upper shelf toughness data.
A Test Method for Measuring the Efflorescence Potential of Masonry Mortars
Authors: Isberner AW 
Published: December 2008

Efflorescence of masonry construction is a natural occurrence when masonry is constructed in other than under normal conditions. Early age efflorescence may occur shortly after construction has been completed; late age efflorescence may occur if design and construction considerations and building maintenance are not properly attended. Efflorescence, once understood, is deemed beneficial toward identifying problems associated with building performance and indicating corrective action to be taken to remedy the situation.
An efflorescence test method for masonry mortars has been developed. The method is considered beneficial for isolating contributors toward efflorescence, be it adverse exposure conditions, cement retarders, or contaminated individual materials. The interpretation of test results allows isolation of contributing factors and remedial action. Practically, testing of masonry mortars will not guarantee that efflorescence will not appear on the surface of a structure.
A Study of Glazed Brick Durability Characteristics and Building Applications
Authors: Naish WM 
Published: December 2008

The author's company has been manufacturing glazed brick for more than 50 years. From a review of quality control and independent testing laboratory records, it is evident that this product has consistently met ASTM Specification for Facing Brick (Solid Masonry Units Made from Clay or Shale) (C 216) standards for durability. In early 1981 the author initiated a research study to determine some of the characteristics used by architects and structural engineers in designing the exterior walls of a variety of successful buildings utilizing these glazed brick.
The data gathered demonstrate that glazed brick with durability characteristics such as those reported have been used (1) in exterior building walls having a variety of design criteria, (2) in buildings of differing sizes and end uses, and (3) in severe weather climates. The author goes on to discuss that some wall failures have occurred in buildings other than those reviewed in this study; to comment regarding his observations of some such failures; and to suggest ongoing research aimed at more clearly defining in-service conditions that contribute to wall failures.
A Laboratory Comparison of the Effects of Water and Waste Leachate on the Performance of Soil Liners
Authors: Eklund AG 
Published: December 2008

A study was conducted to determine the performance of two compacted native soils and the soils plus a commercial additive when exposed to specific paper mill waste leachates. Fluids produced from actual paper mill wastes were used in accelerated (high-pressure), anaerobic permeability tests with two disposal site soils and the soils with a beneficient added. Comparison tests measuring hydraulic conductivity were performed to determine behavioral differences of the candidate soil liners with the waste leachate and water. Test results were used to evaluate waste impacts on soil and on the soil plus a commercial additive. Emphasis was placed on identifying fatal flaws in expected field linear performance.
Test results indicated that the two soils tested were effective in containing the paper mill waste leachates. One soil physically contained the waste leachates by providing an impermeable barrier (K = &lt;&lt; 10−7 cm/s). The other soil, while not providing as strong a physical barrier, (K = 10−7 cm/s), did contain the leachate through chemical attenuation of the trace contaminants in the leachate. While the commercial additive improved the impervious barrier characteristics of this soil, it was determined to be optional. Both mechanisms of containment will be effective in providing protection of groundwater resources below a nonhazardous waste landfill.
Road Roughness Effects on Vehicle Dynamics
Authors: Wambold JC 
Published: December 2008

This paper is based on the Kummer Lecture presented in June 1983 to ASTM Committee E-17 on Traveled Surface Characteristics. It is intended to be a tutorial on the effects of road roughness on vehicle dynamics and is aimed primarily at those members of the highway community who generally are not versed in vehicle dynamics.
The paper first presents both a quarter-car and a half-car simulation, from which the various effects of road roughness can be used as input into the simulation to obtain various measures from the dynamic model. In particular, the acceleration of the sprung mass can be used, along with a standard such as the ride quality standard of the International Organization for Standardization (ISO), to establish the effects of a rough road on the ride quality of a vehicle. In a similar manner, the effects of a rough road can be applied to determine the energy loss by looking at the forces on the shock absorbers, while the loads transmitted back down through the tire to the pavement can also be investigated. Another application of the theoretical quarter-car model is that it can be used to determine the effects of vehicle dynamics on a road roughness meter, such as the Mays meter or the Portland Cement Association (PCA) meter. Finally, a quarter-truck model is presented to show the effects of roughness on a truck model, as opposed to the car model presented earlier.