bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Affecting the Bioavailability of Hexachlorobiphenyls to Benthic Organisms
Authors: McElroy AE , Means JC
Published: February 2009

The purpose of this study was to simultaneously evaluate several key factors which potentially affect the accumulation of hydrophobic pollutant compounds in sediment by benthic organisms. These factors were: (1) organic carbon content of the sediment; (2) equilibration time of the pollutant with the sediment; and (3) feeding strategies of the organism. [14C-U]2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) was equilibrated with sediments from Narragansett Bay, RI containing either 4 or 2% total organic carbon for periods of either one or four weeks. Biological availability of the compound was assessed by following the kinetics of HCBP uptake into either the omnivorous deposit feeding polychaete Nephtys incisa or the deposit feeding bivalve Yoldia limatula exposed to bedded sediment.

In an attempt to normalize bioaccumulation data for differences in the lipophilic reservoirs between sediment and organism, an apparent preference factor (APF) was calculated comparing body burdens normalized to % lipid with sediment concentrations normalized to % total organic carbon (TOC) APF = (HCBPs/$TOC)/(HCBPo/%lipid) For both organisms, APF reached a constant value within 20 days. Length of isotope incubation with sediment had no observable effect on either the rate of approach to a constant APF or the value of APF reached. Even after normalizing with the preference factor calculation, significant differences were still evident between bioaccumulation from the two sediment types and between bioaccumulation from the same sediment by Yoldia and Nephtys. These data indicate that in addition to the influence of sediment TOC and lipid content of the organism, intrinsic properties of sediment and biological properties of the organism influence the transfer and bioaccumulation of hydrophobic compounds.
A Review of Inter- and Intralaboratory Effluent Toxicity Test Method Variability
Authors: Rue WJ , Fava JA , Grothe DR
Published: February 2009

Due to the increased emphasis on the use of aquatic toxicity tests to evaluate the quality of complex effluents, there is a need to objectively evaluate the precision of effluent toxicity test methods. Based upon an extensive search of the published and unpublished literature (available through April 1985), the intralaboratory and interlaboratory precision of effluent toxicity test methods was evaluated.

Most of the inter- and intralaboratory studies obtained address the acute toxicity of effluents to three standard test organisms: Daphnia spp. (water fleas); Salmo gairdneri (rainbow trout); and the marine bacterium Photobacterium phosphoreum (Microtox). Only limited data exist for Pimephales promelas (fathead minnows); Mysidopsis bahia (opposum shrimp); and Cyprinodon variegatus (sheepshead minnows). Based on LC50 or EC50 values for 141 effluents for which interlaboratory data were available, 81.6% had coefficients of variation ≤40%, and 74.5% had coefficients of variation ≤30%. For 46 effluents for which intralaboratory data were available, 89.2% had coefficients of variation ≤40%, and 89.2% also had coefficients of variation ≤30%. To put this variability in perspective, coefficients of variation for these replicated toxicity tests with effluents are compared to published precision estimates for analytical chemistry methods.
Techniques for Environmental Modeling of the Fate and Effects of Complex Chemical Mixtures: A Case Study
Authors: Vigon BW , Wickramanayake GB , Cooney JD , Durell GS , Pollack AJ , Shook T , Frauenthal M
Published: February 2009

A mathematical model along with physical models were used to determine the fate of complex chemical mixtures released to the multimedia environment. Transport and transformation of phosphorus compounds generated during munition testing were studied by employing the Environmental Protection Agency's (EPA) TOX-SCREEN model. The species modeled were phosphine and a representative linear condensed polyphosphate (LCP). The model predicted that a significant fraction of phosphine was volatilized. The fate of LCP is mainly governed by the sorption capacity of soils. The data gaps identified during the preliminary modeling phase included estimates of polyphosphate sorption capacity onto soil.

Laboratory experiments indicated that the adsorption of total phosphorus onto sand was well represented by Freundlich isotherms. Batch and column studies indicated that sand enhances the oxidation of burn products to orthophosphate in the aqueous environment. The leachate generated from the combustion residue was highly toxic to Daphnia magna. Passage of the leachate through a sand/gravel column removed the toxic compounds and/or transformed them to less toxic products.

A combination of mathematical and physical modeling and toxicity monitoring proved highly effective in evaluating and mitigating potential environmental impacts of phosphorus obscurant smokes.
Field Verification of Multispecies Microcosms of Marine Macroinvertebrates
Authors: Livingston RJ
Published: February 2009

A five-year study was carried out to determine the feasibility of using multispecies microcosms of infaunal macroinvertebrates to predict the responses of estuarine systems to toxic substances. Criteria were developed to evaluate the field validation of laboratory microcosms. Experiments carried out in the Apalachicola Bay system in Florida demonstrated that infaunal macroinvertebrates can be established for short periods (five to six weeks) and that the microcosms can be used to simulate certain features of natural field assemblages.

Water quality in the microcosms essentially paralleled that in the field, although variation of certain water features and sediment characteristics was noted. These laboratory artifacts were apparently caused by the isolation of the microcosms from natural phenomena of the estuarine environment that were not replicable in the laboratory. Physical habitat features and biological responses in the study area were extremely complex and highly variable in space and time. Factors such as water and sediment quality, predator-prey relationships, recruitment, and dominance relationships among infaunal populations, influenced the community structure of benthic organisms in the laboratory and the field. The relative influence of physical and biological factors varied considerably between habitats and through time. Consequently, the extent to which the laboratory microcosms paralleled field conditions depended to a considerable degree on the time of testing and dominance/recruitment features of the system in the source area. Species richness in the laboratory microcosms appeared to be a good indicator of field conditions. Multispecies tests have certain advantages over single-species tests in terms of the expanded scope of evaluation. However, results from such experiments should be interpreted within established limits of natural environmental variation. Each microcosm should undergo a thorough calibration with field conditions to qualify the influence of laboratory artifacts and to identify the potential problems associated with isolation from key controlling factors in the field.
A Toxicity Assessment of Tar Sands Tailings
Authors: Yong RN , Ludwig RD
Published: February 2009

Toxicity assessment was conducted on the liquid fractions of waste tailings generated from the hot water extraction process employed in recovering oil from the Athabasca tar sands. Indices of toxicity employed included a mixed culture of microorganisms indigenous to a major river flowing in the vicinity of containment ponds used to store the waste tailings. Toxicity assessment employing the mixed culture of microorganisms was conducted by monitoring the growth of microbial suspensions through turbidity measurements. Other indices of toxicity employed were the freshwater green alga Selenastrum capricornutum and the bacterium resembling Photobacterium phosphoreum. The liquid fractions considered for toxicity assessment included those of both fresh tailings and aged tailings. In addition, toxicity assessment was conducted on the fluid emanating from accumulated sludge in the containment ponds.

Fresh tailings were observed to be highly toxic to all indices of toxicity employed. At a concentration of 40% by volume, fresh tailings were observed to support on average less than 38% of the growth observed in controls for the mixed culture of river microorganisms, while at a concentration of 25% by volume the fresh tailings brought about an average light emission reduction of greater than 65% in the bacterium resembling Photobacterium phosphoreum. Toxicity assessment with Selenastrum capricornutum gave an interpolated EC50 value of 24% by volume.

Aged tailings were observed to exhibit only slight toxicity to Selenastrum capricornutum and the bacterium resembling Photobacterium phosphoreum and no toxicity to the mixed culture of river microorganisms. In fact, aged tailings at a concentration of 40% by volume appeared to stimulate growth in the mixed culture of river microorganisms over that observed in the controls. At 100% concentration by volume, an average light emission reduction of 16% was observed for the bacterium resembling Photobacterium phosphoreum, and an average 33% inhibition of growth relative to controls was observed for Selenastrum capricornutum.

Emanated sludge fluid was observed to be highly toxic only to the alga Selenastrum capricornutum with an interpolated EC50 value of 29% by volume. At a concentration of 40% by volume, the emanated sludge fluid was observed to apparently stimulate growth in the mixed culture of river microorganisms over that observed in the controls. At a concentration of 100% by volume, an average light emission reduction of only 13% was observed for the bacterium resembling Photobacterium phosphoreum.

The results suggest that, although initially very toxic, the waste tailings undergo a self-detoxification process with time. This may have important implications with regard to measures which might be implemented in the containment and treatment of the tailings.
Effects of Metals from Mine Tailings on the Microflora of a Marsh Treatment System
Authors: Desjardins RM , Bradbury NC , Seyfried PL
Published: February 2009

Bacteria isolated from a freshwater marsh treatment system on the site of a mine tailings basin were assessed for heavy metal and antibiotic resistance. All isolates were found to be multiply antibiotic and heavy metal resistant. Klebsiella and Pseudomonas spp. demonstrated the highest levels of resistance to the antibiotics and metals tested. The fecal coliform group displayed similar resistance patterns, suggesting the presence of a common plasmid. Examination of the K. oxytoca marsh system isolate for the presence of plasmid deoxyribonucleic acid (DNA) revealed six plasmids, ranging in size from 3 × 106 to 50 × 106 daltons (Da). The results of this study suggest that the presence of mine tailings in an aquatic environment may promote the development of antibiotic and heavy metal resistance among the microbial flora.
Development of Effective Ground-Water Sampling Protocols
Authors: Barcelona MJ , Gibb JP
Published: February 2009

The demand for representative ground-water quality samples has been driven by the realization that our water resources are vulnerable to a variety of surface contaminant sources. The techniques by which samples are collected will materially affect the reliability of the analytical data. In this paper, the need for the progressive refinement of sampling and related techniques into sampling protocols is emphasized over the standardization of monitoring network designs or the drilling, sampling, and analytical protocols which are elements of the design. The most effective sampling protocol for a particular investigation must be tailored to the actual site conditions and the information needs of the program. Essential elements of a comprehensive sampling protocol are identified and an example which should prove useful for designing reliable ground-water quality investigations is provided. The example network design is developed by a series of decision trees which allow one to weigh various factors and conditions in a direct manner so as to document how decisions are made. The best model for an effective ground-water sampling protocol is one that is flexible and permits refinement as conditions at a site become better understood.
Availability and Access to Ground-Water-Related Information and Data
Authors: Tockstein CD , Dorwart BC
Published: February 2009

For many years it has been apparent that the ever-increasing volume of information and data accumulated in all fields of human experience is far outpacing the individual's capacity to absorb even a small part of it. It is, in fact, impossible to keep current in one's own field of expertise without a systematic approach to screening, cataloging, and retrieving pertinent information. In recent years, the use of computer technology to create automated systems has provided a means to at least partially mitigate the problem.

ASTM Subcommittee D18.95 on Information Retrieval and Data Automation has, as part of its scope of responsibilities, the charge to keep current on the status of such systems and report this information to the geotechnical community. This paper is a means of fulfilling that charge by reporting the availability and accessibility of ground-water information known to the subcommittee.

Information available to the subcommittee shows that a well-coordinated program of water-data collection and dissemination is currently ongoing under the auspices of the U.S. Geological Survey's Office of Water Data Coordination. The interests of the ground-water community can best be served by encouraging the continued and expanded use of this program to provide a means for all to benefit from the collective experience and knowledge available.
Integrating Geophysical and Hydrogeological Data: An Efficient Approach to Remedial Investigations of Contaminated Ground Water
Authors: DJ Stierman , LC Ruedisili
Published: February 2009

Geophysical methods have been proven a cost-effective tool for investigating ground-water contamination near some landfills and hazardous waste disposal sites. Establishing standard methods or practices for geophysical investigations is made difficult, however, by the many geophysical tools available and the broad range of site conditions encountered by the geophysicist and hydrogeologist. The case histories reported here illustrate, first, that electromagnetic conductivity surveys are less cost-effective than d-c resistivity in detecting and mapping contaminated ground water. Second, they demonstrate the value of employing geophysical measurements as an integral component of a remedial investigation. Geophysical investigations must be planned and data must be interpreted in light of available geologic and hydrologic data. Geophysical, geological, and hydrologic observations must all be used to develop the overall conceptual model. Preliminary analysis of geophysical measurements should be made in the field so that the investigator can adjust his strategy to site-specific conditions. New data that are collected should be compared with predictions made based on the overall conceptual model, and the degree to which new data conform to such predictions serves as an indicator of the reliability of the model and the adequacy of the data. Finally, there is a need to standardize units and data presentations so that information developed by different investigators can be easily compared and fully exploited.
The Use of Controlled Source Audio Magnetotellurics (CSAMT) to Delineate Zones of Ground-Water Contamination—A Case History
Authors: Tinlin RM , Hughes LJ , Roger Anzzolin A
Published: February 2009

A significant potential for the pollution of fresh-water aquifers exists due to oilfield waterflood operations. The sources of potential pollution are surface spills, a lack of mechanical integrity of injection wells, and improperly plugged wells which are in communication with the injection zone. Surface spills are relatively easy to detect and control. Procedures for checking the mechanical integrity of a properly constructed injection well are available. Making a determination in the absence of good records as to whether or not a well is improperly plugged, providing a conduit for the vertical migration of formation brines from the production zone to shallower fresh-water aquifers, is very difficult.

Electrical surface geophysical methods offer considerable promise in detecting the movement of formation brines into fresh-water aquifers, through improperly abandoned or plugged wells.

An electrical surface geophysical technique, Controlled Source Audio-Frequency Magnetotellurics (CSAMT) has been applied to locate the presence of anomalies resulting from the upward movement of formation brines through improperly plugged wells. The primary objective in a CSAMT survey is to provide apparent resistivity and the phase angle between the electric and magnetic fields over a prospect area. CSAMT has the advantages of excellent lateral resolution, good depth penetration (a kilometre or more) and is relatively inexpensive. The frequency and resistivity of the subsurface control the depth of penetration. The lower the frequency, the deeper the penetration.

A CSAMT survey was run in an oil-producing field in east central Oklahoma, which is currently on waterflood and has many abandoned and apparently improperly plugged wells. The water in the Vamoosa aquifer underlying the study area has a high chloride content. The objective of running the CSAMT survey was to locate suspected low-resistivity anomalies due to formation brines in the vicinity of improperly plugged wells and to attempt to map their extent.
Monitoring Well Construction, and Recommended Procedures for Direct Ground-Water Flow Measurements Using a Heat-Pulsing Flowmeter
Authors: WB Kerfoot
Published: February 2009

Direct flow measurements using heat-pulsing techniques provide an accurate and economic method of determining direction of ground-water flow. The use of this method requires that care be taken in choice of well screen, methods of installation, measurement procedure, and method of data handling. The influence of well slot number, slot size, and screen configuration is explained. Drilling without using drilling fluid additives is recommended for installation. The use of coarse and instead of gravel packing for the annular region also improves readings. Hydraulic conductivity and field porosity variation in annular packing versus the natural stratum is dealt with by a new calibration procedure. The use of vector analysis for this data handling is recommended. A procedure involving convergence of down-gradient direction and mean vector sum for direct flow measurement is offered to provide answers to the old question of whether enough wells have been installed for understanding flow in the natural stratum.
Determining Whether Wells and Piezometers Give Water Levels or Piezometric Levels
Authors: RP Chapuis
Published: February 2009

A method is proposed to verify whether wells and piezometers have been adequately sealed into the ground to avoid vertical communication between aquifers and thus prevent misleading results of both piezometric levels and contamination degrees. The method makes use of variable-head permeability tests that are not interpreted by the common graph of ln H versus t, but by the more fundamental graph of the water velocity versus the total head difference. Both presentations are mathematically equivalent. If there is some error in the “measured” piezometric level, it will be hidden in the common logarithmic diagram, but it can be easily detected with the proposed velocity diagram. The method is illustrated by typical examples of velocity diagrams and their interpretation. According to the author's experience, the practice of partial seals along piezometer pipes should be discouraged and a full-length seal is preferred.
Adsorption of Selected Organic Contaminants onto Possible Well Casing Materials
Authors: JN Jones , GD Miller
Published: February 2009

In order to assess and monitor the impact of man's activities on ground-water quality, the nature, concentration, and behavior of pollutants in the subsurface must be determined. To do this, it is necessary to collect representative samples of water from the subsurface environment. Ideally, the material chosen as a well casing for monitoring wells should not add or remove constituents from the ground-water sample collected.

The objective of this study was to determine if specific trace organics adsorb and subsequently leach from various well casing materials upon exposure to those specific pollutants for specified periods of time. The types of well casings studied included thermoplastics, stainless steel and fluoroplastics. Of the pollutants studied, only 4-nitrophenol and 2,4,6-trichlorophenol showed appreciable adsorption for all well casing materials. Subsequent leaching of pollutants was not observed in any measurable quantities.
Recent Development of Downhole Water Samplers for Trace Organics
Authors: Ficken JH
Published: February 2009

Studies concerning the movement and fate of organic chemicals, including hazardous substances, in ground water have underscored the need to use boreholes to obtain samples of ground water that are neither contaminated with foreign materials nor diluted with water from other sources. Additionally, the water samples need to be taken in a manner that prevents the escape of volatile substances. The samples need to be kept close to the original state while in shipment to the water quality laboratory and at the laboratory where the water must be removed from the sample holders without the escape of volatiles or reaction with the air. Within the past year the U.S. Geological Survey has identified its needs for data concerning organics in ground water, and established design criteria for the development of prototype samplers. Certain essential sampler design criteria are: The sampler must go down a 5.1-cm (2 in.) diameter well; the practical sampling depth is at least 61 m (200 ft); the sample holder must be flushed before a sample is taken; and the sample must be kept at the same hydrostatic pressure as when collected.

The Survey is developing prototype samplers using the designated design criteria—a piston sampler operating from a well-logging head, a pumping sampler using a commercial downhole gear pump, a hand-pump sampler, and two electric motor-driven samplers using logging heads. These samplers flush a sample cartridge with the water to be sampled and finally seal the sample prior to being brought to the surface. Later, a design criterion was added that all flush water be removed from the well. New design schemes were drafted that accomplished that requirement. One of the design schemes was a manual sampler which uses a downhole reservoir to collect the flush water. Other design schemes have been envisioned but were found not to be practical. A special sample cartridge that will fit these samplers has been developed to allow removal of the water under pressure. This design helps prevent the escape of volatile substances from the water sample. Fabrication materials include stainless steels, fluoroelastomers, and other fluorinated plastics.
Long-Term Permeability Tests Using Leachate on a Compacted Clayey Liner Material
Authors: Fang H-Y , Evans JC
Published: February 2009

This paper presents the results of laboratory tests on a compacted clayey liner material using landfill leachate. Laboratory permeability tests were conducted with continuous permeation for a period from three to to six months in duration in specially designed traxial cell permeameters. The soil samples were obtained from a borrow pit in eastern Pennsylvania and proposed for use as a compacted liner material. Routine soil tests, including Atterberg Limits, gradation, compressive strength, and compaction tests were conducted on samples exposed to both tap water and leachate. Limited tests were conducted on bentonite-clay mixtures to illustrate the behavioral difference between high-swelling and non-high-swelling clays.

It was found that permeation of the clayey liner material with landfill leachate did not significantly alter permeability of the material. Further, the physical properties remained relatively unchanged. In contrast, test results conducted on bentonite-clay mixtures resulted in more significant changes. It is concluded that leachate permeation of natural silty clays of low activity, such as the material investigated herein, can result in inconsequential change in engineering properties. In contrast, leachate permeation of a high-swelling sodium montmorillonitic soil could result in significant changes in physical and engineering properties of the soil.
A Geologic and Flow-System-Based Rationale for Ground-Water Sampling
Authors: Urban JB , Gburek WJ
Published: February 2009

Representative measurements of ground water require a sampling protocol based on the physical and hydraulic properties of the geologic materials. Measurements must be made within the context of the site and areal ground-water flow systems. A multizone geologic system in east-central Pennsylvania is used as an example of instrumentation by geologic and hydrologic criteria. Geology is that of a weathered, fractured, sedimentary rock mantle overlying deeper, less fractured, sedimentary rock strata.

The focus of this paper is on describing the domain of and controls on ground-water flow within the shallow (<15 m) and deep (15 to 100 m) fracture systems. A systematic approach, using commonly available information, identifies the areal extent, depth, hydraulic conductivity distribution, and paths of ground-water flow in the two systems. This approach was tested within a 7.4-km2 watershed and at stream-valley cross sections. The findings indicate that ground-water quality distribution is accurately portrayed in both settings if the sampling scheme is based on geologic and flow system controls. Ground-water sampling wells must be located, and their data interpreted, by grouping according to geology and the ground-water flow system elements of recharge, lateral flow, and discharge zones.
Basic Questions in Fatigue: Volume I
Authors: Fong JT , Wei RP , Fields RJ , Gangloff RP
Published: February 2009

Description

Volume I contains introductory remarks and addresses the questions of nucleation of fatigue damage in single crystals and polycrystals, with principal emphasis on the observation of damage at the microstructural level. Other sections deal primarily with the role of mechanical variables on fatigue crack growth in ferrous and nonferrous alloys, and focus attention at the continuum level.

Volume II contains 3 sections on more complicated topics of research where the state of knowledge is in the formative stage. The first section considers complex interactions associated with combined fatigue and creep damage. The next section deals with the questions of environmental effects. The last section contains the only papers that address fatigue of nonmetals.
Testing Technology of Metal Matrix Composites
Authors: Adsit NR , DiGiovanni PR
Published: February 2009

Description

Twenty-eight papers cover material systems from the continuous silicon carbon/titanium system to the particulate reinforced aluminum systems. Focuses on the need to obtain accurate and reliable test data. Current testing methodologies are defined and described.
Composite Materials: Testing and Design (Eighth Conference)
Authors: Whitcomb JD
Published: February 2009

Description

This volume continues to document progress in composite materials testing. Twenty-seven papers represent the following areas: Analysis; Impact and Compression; Materials Characterization; Failure Mechanisms; Nondestructive Evaluation; and Filament Wound and Woven Composites.
Adhesively Bonded Joints: Testing, Analysis, and Design
Authors: Johnson WS
Published: February 2009

Description

Twenty-one papers present the latest advances in the understanding of mechanical behavior of adhesives. Their focus is on aircraft and naval applications. The mechanical testing section discusses techniques and specimen designs for determining tensile, shear, and mixed-mode properties of adhesives. Papers on stress analysis consider both analytical and experimental methods to analyze the stress in an adhesively bonded joint. In the section on failure mechanisms examples are presented for several types of adherents and specimen geometries. The final section considers design and durability of bonded joints.
Mathematical Modeling of Fires
Authors: Mehaffey JR
Published: February 2009

Description

Nine papers are featured. Two review the role of ASTM in fire modeling and describe ASTM E 906. Other papers present: a new simple model of fire growth in a compartment; a model of hydrogen chloride and decay; a fire loss modeling code for industrial facilities; characteristic times for describing forced-ventilation enclosure fires; optical and gravimetric soot measuring techniques for the cone calorimeter; a computer model for the heat release rate of wood; and a benchmark compartment fire model computer code.
Performance of Protective Clothing: Second Symposium
Authors: Mansdorf SZ , Sager R , Neilsen AP
Published: February 2009

Description

Papers concern protective quality of various types of apparel for protection against chemical and thermal hazards. Topics include human factors, user attitudes, new materials, thermal protection, industrial chemical stresses, and protection from pesticides.
Standardization of Technical Terminology: Principles and Practices (Second Volume)
Authors: Strehlow RA
Published: February 2009

Description

The purpose of this book is to provide a better understanding of the underlying principles in technical terminology, term formation, definition writing, and glossary compilation. In addition, STP 806 addresses the problems encountered when terminology standards are inadeguintely written.
Mechanical Relaxation of Residual Stresses
Authors: Mordfin L
Published: February 2009

Description

Addresses the relaxation of residual stresses by mechanical means. STP 993 is covers intentional relaxation of undesirable residual stresses and unintentional relaxation of residual stress by cyclic stresses.
Current Trends in Protective Packaging of Computers and Electronic Components
Authors: Peache RJ , O'Sullivan D
Published: February 2009

Description

A collection of 6 papers by packaging experts on contemporary methods for protective packaging of electronic components subject to damage by shock and vibration and/or electrostatic discharge.
Nonlinear Fracture Mechanics: Volume II Elastic-Plastic Fracture
Authors: Landes JD , Saxena A , Merkle JG
Published: February 2009

Description

Two volume set: Volume 1 — Nonlinear Fracture Mechanics: Time Dependent Fracture. Volume 2 — Nonlinear Fracture Mechanics: Elastic-Plastic Fracture

STP 995 contains recent work on traditional elastic plastic fracture mechanics as well newer areas, such as time dependent fracture mechanics and dynamic fracture. Papers discuss analytical considerations, experimental methods, and applications. Third in a series of ASTM books on nonlinear fracture mechanics.
Electrical Insulating Oils
Authors: Erdman HG
Published: February 2009

Description

This symposium was organized to update information on the important role of petroleum-based oil as an insulating and heat transfer agent in electrical apparatus.
Terahertz Ellipsometry Using Electron-Beam Based Sources
Authors: Hofmann Tino , Herzinger Craig M. , Schade Ulrich , Mross Michael , Woollam John A. , Schubert Mathias
Published: February 2009

The precise determination of materials' optical constants in the THz frequency domain is an important new challenge in basic research and is crucial for novel technological applications. Spectroscopic ellipsometry is known as a vital tool for the determination of the materials' dielectric function including its anisotropy. However, ellipsometric measurements at very long wavelengths are difficult due to the lack of reliable sources of sufficient intensity and brilliance. Here we report on our recent advances to use ellipsometry in combination with different electron beam based sources in order to in investigate condensed matter samples in the frequency range from 0.1 to 8 THz. We successfully employ terahertz radiation emitted from two different tunable desktop sources (Smith-Purcell-effect source and a backward wave oscillator) in a polarizer-sample-analyzer ellipsometer scheme. We discuss and present THz range physical material properties due to bound and unbound charge resonances in semiconducting materials. This research will provide important understanding of optical properties for novel materials, inspire new designs, and accelerate development of optical Terahertz devices.
Low Resistance Ohmic Contacts Formation and Mechanism of Current Transport Through p-GaN and p-AlGaN
Authors: Chary Indra , Borisov Boris , Kuryatkov Vladimir , Kudryavtsev Yuriy , Asomoza R , Nikishin Sergey A , Holtz Mark
Published: February 2009

We report the influence of surface treatment, annealing temperature and metal bilayer thickness on the specific contact resistance (ρc) of Au/Ni ohmic contacts to p-GaN and p-AlGaN. Ohmic contact on p-GaN with a hole concentration of 6.5 x 1017 cm-3, shows the lowest ρc of ˜9.2 x 10-6 Ω cm2, when GaN was treated in HCl:H2O (3:1) solution before metal deposition and annealed at 500°C for 10 minutes in 90% N2 and 0% O2 atmosphere. Similar procedure applied on p-AlxGa1-xN (x = 5-7%), with a hole concentration of 2.3 x 1017 cm-3, yields a ρc of 1.8 x 10-4 Ω cm2. An increase is observed in ρc when Mg doping exceeds 4 x 1019 cm-3 in both p-GaN and p-AlGaN. This is attributed to Mg self compensation. This increase is more pronounced in AlGaN which we attribute to the presence of residual native aluminum oxides.
Nucleation and Stochiometry Dependence of Rutile-TiO2(001)/GaN(0001) Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy
Authors: Constantin Costel , sun kai , Feenstra Randall M
Published: February 2009

In this work we explore both the initial nucleation and the stoichiometry of rutile-TiO2(001) grown on wurtzite GaN(0001) by radio-frequency O2-plasma molecular beam epitaxy. Two studies are performed; in the first, the dependence of the growth on stoichiometry (Ti-rich and O-rich) is observed using reflection high energy electron diffraction and high resolution transmission electron microscopy. In the second study we examine the effect of different initial nucleation surfaces (i.e. Ga-terminated and excess Ga-terminated) and compare the interfaces and bulk crystallinity of the TiO2(001) films grown on top of these surfaces. High-resolution transmission electron microscopy and x-ray diffraction measurements show a better interface for TiO2(001)/Ga-terminated - GaN(0001) as compared to the TiO2(001)/excess Ga-terminated- GaN(0001).
Magnetic Resonance Study of Non-Equivalent Centers Created by 4f-Ions in Congruent and Stoichiometric Lithium Niobate
Authors: Malovichko Galina , Grachev Valentin , Jorgensen Jonathan , Meyer Martin , Munro Mark , Todt Benjamin , Vrable Ian , Kokanyan Edward , Bratus Viktor , Okulov Sergei
Published: February 2009

Lithium Niobate doped with 4f-ions is of great interest for both fundamental science and advanced applications including high efficiency lasers with frequency conversion, elements for an all-optical telecommunication network and quantum cryptography. Our study has shown that 4f-ions create an unexpected variety of completely different non-equivalent centers in both stoichiometric and lithium deficient congruent crystals. Dominant Nd1 and Yb1 centers have C3 point symmetry (axial center), whereas all Er and most other Nd and Yb centers have the lowest C1 symmetry. Distant defects create small distortions of the crystal field at the impurity site, which cause line broadening, but do not change the C3 symmetry of observed EPR spectra. Defects in the near neighborhood can lower center symmetry from C3 to C1. We concluded that Nd1 has distant charge compensation, whereas the charge excess in low-symmetry Nd(Li) centers is compensated by near lithium or niobium vacancies. Since no axial centers were found for Er, models with cation vacancies can not describe our experimental data. The dominant axial Yb1 center has no defects in its surrounding. One axial and one low-symmetry Yb centers are self compensating Yb(Li)-Yb(Nb) pairs. Six other centers are different complexes of Yb3+ and intrinsic defects. Obtained data can be used for defect engineering for tailoring properties of photonic materials.
Optical Materials for Medical Applications: an Overview of Ultrafast Emitting Oxidic Pr3+ Scintillating Materials
Authors: Ronda Cees , Gondek Joanna , Goirand Emilie , Jüstel Thomas , Bettinelli Marco , Meijerink Andries
Published: February 2009

This paper describes an investigation towards very fast emitting oxidic luminescent materials doped with Pr3+. Such materials have the potential to be applied as scintillators in Positron Emission Tomography.
Low Temperature Transparent Nanoplatelet Hybrid Gas Barrier Coating Materials via Sol-gel Process
Authors: Asuka Masahiro , Sigmund Wolfgang Michael
Published: February 2009

A novel hybrid coating based on a combination of nanoparticles, sol-gel and organic chemistry is reported. It can be applied to a large variety of surfaces even at low processing temperatures, and it cures below 150°C. Furthermore, fabrication of the hybrid films on polymer sheets can be done under ambient conditions. No vacuum techniques are required. Boehmite nanoplatelet composite hybrid organic/inorganic coating materials have been successfully prepared via this approach. The coating process involves the dispersion of boehmite nanoparticles that are suspended without significant agglomeration. 3-glycidoxy propyl trimethoxy silane (GPTMS) was adopted as dispersant for the nanoplatelets and functions also as a network former. This induces flexibility in the hybrid film due to the organic functional groups. Transparent cured coatings from flexible to brittle were obtained from a single coating step with thicknesses in excess of 10 μm depending on the ratio of the inorganic/organic reagents and their concentrations. Barrier coatings with more than 60wt% ceramic nanoplatelets were achieved, yet they still display transparency of more than 95% to visible light with no cracks or other discernable defects. Several substrates have been successfully tested including poly (ethylene terephthalate) (PET). Moreover water permeability for cured coated PET films is reduced to less than 0.01 g/m2/d. Excellent mechanical properties such as flexibility and hardness are demonstrated by nanoindentation and scratch tests.
Electrical Response of Polycrystalline Silicon Thin Film Transistor on Steel Foil under Mechanical Strain
Authors: Kuo Po-Chin , Jamshidi-Roudbari Abbas , Hatalis Miltiadis K
Published: February 2009

This work investigates the effects of mechanical strain on electrical characteristics of polycrystalline thin film transistors (poly-Si TFTs). Poly-Si TFTs were fabricated on steel foil substrate and characterized under the strain ranging from -1.2% to 1.1% induced by bending. The electron mobility increased under tensile and decreased under compressive strain while that of the hole exhibited an opposite trend. For p-channel TFTs the normalized threshold voltage and subthreshold slope were a function of strain. In both n- and p-channel TFTs the off current decreased under tensile while it increased under compressive strain. The observed mobility trends in poly-Si TFTs are similar to those reported in single crystalline silicon devices.
A Thermodynamic Approach on the Effect of Salt Concentration on Swelling Pressure of Water-saturated Bentonite
Authors: Sato Haruo
Published: February 2009

The effect of salt concentration on swelling pressure of water-saturated bentonite was modelled based on the thermodynamic data of water at montmorillonite surface and of water in solutions of various salinities coming in contact with the montmorillonite. Activities of water at montmorillonite surface were obtained as a function of water content and temperature at montmorillonite densities of 0.6 and 0.9Mg/m3 by a vapor pressure method, and the relative partial molar Gibbs free energies (dGw) were determined. Water affected from the montmorillonite surface was estimated to be almost all interlayer water. Swelling pressure vs. montmorillonite partial density was estimated for solutions of various salinities and compared to data measured for various montmorillonite contents and different silica sand contents of bentonites. The calculated swelling pressure clearly decreased with increasing salinity. The effect of salinity on swelling pressure was not clear in the measured data and was within the range of the scattering in the measured data. This cause is presumed to be due to the increase of the ionic strength of porewater by dissolution of soluble minerals in the bentonite.
Migration Behavior of Bentonite Colloids through a Fractured Rock
Authors: Kuno Yoshio , Sasamoto Hiroshi
Published: February 2009

Bentonite colloids released into groundwater from the buffer in a geological repository for high-level radioactive waste may influence the migration of radioactive elements in fractures of the host rock. In the present study, column experiments were carried out to investigate the migration behavior of bentonite colloids in artificially fractured granite. The objective of the study is to determine whether the colloids are filtered by the fracture, considering the effects of the fracture length and the ionic strength of transporting solutions. Results indicate that bentonite colloids are not filtered if the transporting solution is dilute (i.e., distilled water or 10-4 M NaCl solution). This is evidenced by the observed tendency for normalized colloid concentrations in the column effluent (C/C0) to rapidly approach 1. An initial increase in the breakthrough curves is also observed at early stages of migration experiments involving more concentrated solutions (10-3 M NaCl solution), but the curves later evolve to an approximate steady state with C/C0 < 1. The amount of filtered colloids tends to increase with increasing fracture length. These results suggest that bentonite colloids can be filtered by interactions between the colloids and fracture surfaces, and that these interactions are affected by the ionic strength of the transporting solution. This migration behavior is simulated by a model of colloid migration, taking into consideration the effects of colloid filtration by fracture surfaces. The information on the filtration of bentonite colloids would contribute to a more realistic assessment of colloid effects on radionuclide migration.
Cement Based Encapsulation Experiments for Low-radioactive Phosphate Effluent
Authors: Sugaya Atsushi , Horiguchi Kenichi , Tanaka Kenji , Akutsu Shigeru
Published: February 2009

Development work has been carried out for several years on the cementation of phosphate waste from the Tokai Reprocessing Plant Solvent Waste Treatment Facility. The phosphate waste consists of mainly NaH2PO4 at a concentration of approximately 440g/ℓ, and has a pH of approximately 4. During attempts to encapsulate this waste in cement the phosphate species interfere with the hydration reaction and retard the setting of the cement and reduce the strength of the wasteform. To mitigate these detrimental effects, pretreatment of the phosphate waste with Ca(OH)2 prior to cementation has been investigated at small scale.
The effect of pre-treating the waste with various amounts of Ca(OH)2, specified by the Ca(OH)2/ NaH2PO4 molar ratio, was investigated under a range of mixing conditions. The viscosity of the pre-treated waste simulant was recorded and an optical microscope was used to identify the presence of small crystals formed during pre-treated. Cementation of pre-treated phosphate waste simulant was also investigated using various conditions to assess the effects of changing the waste loading, mixing temperature and water/cement ratio. The dimensional stability and strength of the resulting cemented waste was assessed up to 28 days.
Results from the trials show that pre-treatment of the waste simulant with Ca(OH)2 is particularly sensitive to the Ca(OH)2/ NaH2PO4 molar ratio and mixing temperature. These two factors strongly affect the rheology of the pre-treated waste and the acceptability for subsequent cementation. An optimum Ca(OH)2/ NaH2PO4 molar ratio was found to exist and the importance of controlling the waste temperature during pre-treatment was explained.
Cementation trials were performed using the pre-treated phosphate waste simulant and slag cement. It has been shown that pre-treated phosphate waste may be encapsulated in slag cement where the wasteform achieved compressive strengths exceeding 10 MPa after 28 days curing at waste loadings exceeding 13wt% (given as a % weight of cement wasteform represented by the NaH2PO4 in the untreated waste).
Demonstration trials of pre-treatment and encapsulation will be executed at full scale in the future.
Analysis of Electrochemical Performance of Single Step Co-fired Solid Oxide Fuel Cell (SOFC) Analyzed Using Polarization Model and Impedance Spectroscopy
Authors: Yoon Kyung Joong , Gopalan Srikanth , Pal Uday B.
Published: February 2009

Anode-supported planar solid oxide fuel cell (SOFC) was successfully fabricated by a single step co-firing process. The cell comprised of a porous Ni + yittria-stabilized zirconia (YSZ) anode support, a porous and fine-grained Ni + YSZ anode active layer, a dense YSZ electrolyte, a fine-grained porous Ca-doped LaMnO3 (LCM) + YSZ composite cathode active layer, and a porous LCM cathode current collector layer. The cell was tested between 700˜800oC with humidified hydrogen (97% H2+3% H2O) as fuel and air as oxidant. The measured maximum power densities were 1.42W/cm2 at 800°C, 1.20W/cm2 at 750°C, and 0.87W/cm2 at 700°C. The cell was also tested at 800oC with various compositions of oxidant, and cell parameters including the area specific ohmic resistance, exchange current density, and anodic and cathodic limiting current densities were determined using the polarization model and impedance spectroscopy.
Transport Through Electrophoretically Deposited CuMn1.8O4 Spinel Coatings on Crofer Interconnects
Authors: Huang Wenhua , Gopalan Srikanth , Pal Uday B. , Basu Soumendra
Published: February 2009

Dense and well-adhered CuMn1.8O4 spinel oxide coatings were successfully deposited on Crofer 22 APU stainless steel substrates by a cost effective electrophoretic deposition technique. Coated and uncoated Crofer substrates were oxidized for 120 hours in air at 800°C. A diffusion model was developed for the oxidation of the coated alloys, which predicted para-linear oxidation kinetics. The effective diffusivities in the coating and in the thermally grown oxide were calculated to be 2×10-15 cm2/s and 2.5×10-16 cm2/s respectively, at 800°C. Area specific resistances (ASR) of thermally cycled samples at 800°C did not show a significant difference compared to the isothermally oxidized sample for the same total oxidation time, suggesting good coating adherence. The ASR of the coated alloys is projected to be around 3.8×10-2Ωcm2 after 50000 at 800°C in air, making them excellent candidates for interconnect applications for solid oxide fuel cells operated at 800°C or lower.